Publication year: 2012
Source: Mechanisms of Development, Available online 2 February 2012
Michael Stauber, Christine Laclef, Annalisa Vezzaro, Mahalia E. Page, David Ish-Horowicz
Regular production of somites, precursors of the axial skeleton and attached muscles is controlled by a molecular oscillator, thesegmentation clock, which drives cyclic transcription of target genes in the unsegmented presomitic mesoderm (PSM). The clock is based on a negative feedback loop which generates pulses of transcription that oscillate with the same periodicity as somite formation. Mutants in several oscillating genes including the Notch pathway geneLunatic fringe(Lfng) and the Notch targetHes7, result in defective somitogenesis and disorganised axial skeletons. Both genes encode negative regulators of Notch signalling output, but it is not yet clear if they are just secondary clock targets or if they encode components of a primary, pacemaker oscillator.In this paper, we try to identify components in the primary oscillator by manipulating delays in the feedback circuitry. We characterise recombinant mice in whichLfngandHes7introns are lengthened in order to delay mRNA production. Lengthening the thirdHes7intron by 10 or 20 kb disrupts accurate RNA splicing and inactivates the gene.Lfngexpression and activity is normal in mice whoseLfngis lengthened by 10 kb, but no effects on segmentation are evident. We discuss these results in terms of the relative contributions of transcriptional and post-transcriptional delays towards defining the pace of segmentation, and of alternative strategies for manipulating the period of the clock.
Highlights► Test strategy to identify the pacemaker of the vertebrate segmentation clock. ► Lengthened endogenous genes in transgenic mice to alter transcriptional delay. ► Test role for lengthenedLunatic fringein mouse segmentation.
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Modifying transcript lengths of cycling mouse segmentation genes
» Mech Dev -
Intrinsic and Extrinsic Modifiers of the Regulative Capacity of the Developing Liver
» Mech DevPublication year: 2012
Source: Mechanisms of Development, Available online 31 January 2012
Donghun Shin, Gilbert Weidinger, Randall T. Moon, Didier Y.R. Stainier
Zebrafishwnt2bbmutants initially fail to form a liver, but surprisingly the liver eventually forms in a majority of these embryos which then develop into fertile adults. This unexpected result raised the possibility that identifying the mechanisms of liver formation inwnt2bbmutants could provide insights into the poorly understood yet general principle of regulative development, a process by which some cells can change fate in order to compensate for a deficiency. Here, we identify two factors that underlie the regulative capacity of endodermal tissues: an intrinsic factor, Sox32, a transcription factor of the SoxF subfamily, and an extrinsic factor, Fgf10a.sox32is expressed in theextrahepaticductprimordium which is not affected inwnt2bbmutants. Blocking Sox32function prevented liver formation in mostwnt2bbmutants.fgf10a, which is expressed in the mesenchyme surrounding non-hepatic endodermal cells, negatively impactsthe regulative capacity of endodermal tissues. In Wnt/β-catenin signaling deficient embryos, in which the liver completely fails to form, the repression of Fgf10a function allowed liver formation. Altogether, these studies reveal that there is more than one way to form a liver, and provide molecular insights into the phenomenon of tissue plasticity.
Highlights► hhexexpression in the extrahepatic duct is not affected inwnt2bbmutants.► sox17andsox32are expressed in the extrahepatic duct primordium. ► Blocking Sox32 function abolishes liver formation inwnt2bbmutants. ► Fgf10a negatively impacts the regulative capacity of endodermal tissues. -
Regulation of Polycomb Group genesPscandSu(z)2inDrosophila melanogaster
» Mech DevPublication year: 2012
Source: Mechanisms of Development, Available online 24 January 2012
Sung Yeon Park, Yuri B. Schwartz, Tatyana G. Kahn, Dalal Asker, Vincenzo Pirrotta
Certain Polycomb Group (PcG) genes are themselves targets of PcG complexes. Two of these constitute the DrosophilaPsc-Su(z)2locus, a region whose chromatin is enriched for H3K27me3 and contains several putative Polycomb Response Elements (PREs) that bind PcG proteins. To understand how PcG mechanisms regulate this region, the repressive function of the PcG protein binding sites was analyzed using reporter gene constructs. We find that at least two of these are functional PREs that can silence a reporter gene in a PcG-dependent manner. One of these two can also display anti-silencing activity, dependent on the context. A PcG protein binding site near thePscpromoter behaves not as a silencer but as a down-regulation module that is actually stimulated by the Pc gene product but not by other PcG products. Deletion of one of the PREs increases the expression level ofPscandSu(z)2by two-fold at late embryonic stages. We present evidence suggesting that thePsc-Su(z)2locus is flanked by insulator elements that may protect neighboring genes from inappropriate silencing. Deletion of one of these regions results in extension of the domain of H3K27me3 into a region containing other genes, whose expression becomes silenced in the early embryo.
Highlights► Four PcG binding sites were tested for autonomous PRE activity. ► two have classical PRE activity. ► One has an unusual downregulating activity and inverse dependence on PC. ► Deletion of one binding site causes a weak derepression. ► A presumptive insulator prevents silencing of flanking genes. -
Regulation of PP2A activity by Mid1 controls cranial neural crest speed and gangliogenesis
» Mech DevPublication year: 2012
Source: Mechanisms of Development, Available online 20 January 2012
Elizabeth J. Latta, Jon P. Golding
X-linked Opitz syndrome (XLOS), caused by mutation in theMID1gene, is a midline malformation syndrome with obvious craniofacial abnormalities. Because cranial neural crest cells (CNC) play a pivotal role in cranial morphogenesis, we examined the spatio-temporal expression ofcMid1in chick embryos and investigated if alterations in Mid1 protein function, specifically the ability of Mid1 to negatively regulate levels of protein phosphatase 2A (PP2A), affected CNC survival or migration.During the main phase of CNC migration (stage 9- to 11)cMid1is strongly expressed within r2 and a subset of CNC in cranial mesenchyme at the level of r1/2 to the isthmus, but is not expressed in more caudal CNC streams. Inhibiting cMid1 function in r2 elevated PP2A levels. Overexpression of PP2A in r2 slowed CNC migrationin vitroandin ovoand inhibited trigeminal gangliogenesis.Conversely in r4, forced expression ofcMid1, or pharmacological inhibition of PP2A lowered PP2A levels. Inhibition of PP2A in r4 CNCin vitroup-regulated the disintegrin and metalloprotease ADAM10 and selectively increased CNC motility on fibronectin and collagen substrates, but not on laminin.In ovo, inhibiting PP2A activity in r4 increased CNC migration and hastened formation of the geniculate/ vestibuloacoustic ganglion, comprising mostly epibranchial placode neuroblasts. Placodal neuroblast migration into the cranial mesenchyme is known to depend on the presence of r4 CNC and we show that inhibition of PP2A in r4 CNC causes premature breakdown of the epibranchial placode basement membrane and early immigration of placodal neuroblasts. In all cases, CNC proliferation and death were unaffected by altered PP2A levels.We propose that factors capable of altering PP2A activity, such as Mid1, affect CNC motility and matrix remodeling, thereby modulating craniofacial development.
Highlights► cMid1 (expressed in r2 CNC) depletes protein phosphatase 2A (PP2A). ► cMid1 decrease/ PP2A increase slow r2 CNC migration and trigeminal gangliogenesis. ► Ectopic cMid1/ PP2A inhibition increase r4 CNC migration. ► PP2A decrease causes early placode neuroblast migration and facial gangliogenesis. ► PP2A inhibition in r4 CNC increases: ADAM10, migration on fibronectin or collagen. -
CCDC-55 is required for larval development and distal tip cell migration inC. elegans
» Mech DevPublication year: 2012
Source: Mechanisms of Development, Available online 20 January 2012
Ismar Kovacevic, Richard Ho, Erin J. Cram
TheC. elegansdistal tip cells (DTCs) are anin vivomodel for the study of developmentally regulated cell migration. In this study we characterize a novel role for CCDC-55, a conserved coiled-coil domain containing protein, in DTC migration and larval development inC. elegans. Although animals homozygous for a probable null allele,ccdc-55(ok2851), display an early larval arrest, RNAi depletion experiments allow the analysis of later phenotypes and suggest that CCDC-55 is needed within the DTC for migration to cease at the end of larval morphogenesis. Theccdc-55gene is found in an operon withrnf-121andrnf-5, E3 ubiquitin ligases that target cell migration genes such as the β-integrin PAT-3. Genetic interaction studies using RNAi depletion and the deletion allelesrnf-121(ok848)andrnf-5(tm794)indicate that CCDC-55 and the RNF genes act at least partially in parallel to promote termination of cell migration in the adult DTC.
Highlights► The conserved coiled-coil domain protein CCDC-55 is a novel regulator of cell migration. ► CCDC-55 is necessary for larval development inC. elegans.► CCDC-55 likely functions in the distal tip cells.► ccdc-55is found in an operon with the ubiquitin ligasesrnf-121andrnf-5.► CCDC-55, RNF-121 and RNF-5 regulate the final position of the distal tip cells. -
Neucrin, a novel secreted antagonist of canonical Wnt signaling, plays roles in developing neural tissues in zebrafish
» Mech DevPublication year: 2012
Source: Mechanisms of Development, Available online 12 January 2012
Ayumi Miyake, Satoka Nihno, Yuino Murakoshi, Ayano Satsuka, Yoshiaki Nakayama, ...
Wnt signaling plays crucial roles in neural development. We previously identified Neucrin, a neural-specific secreted antagonist of canonical Wnt/β-catenin signalling, in humans and mice. Neucrin has one cysteine-rich domain, in which the positions of 10 cysteine residues are similar to those in the second cysteine-rich domain of Dickkopfs, secreted Wnt antagonists. Here, we have identified zebrafishneucrinto understand its rolesin vivo. Zebrafish Neucrin also has one cysteine-rich domain, which is significantly similar to that of mouse Neucrin. Zebrafishneucrinwas also predominantly expressed in developing neural tissues. To examine roles ofneucrinin neural development, we analyzedneucrinknockdown embryos. Neural development in zebrafish embryos was impaired by the knockdown ofneucrin. The knockdown ofneucrincaused increased expression of the Wnt/β-catenin target genes. In contrast, overexpression ofneucrinreduced the expression of the Wnt/β-catenin target genes. The knockdown ofneucrinaffected specification of dorsal region in the midbrain and hindbrain. The knockdown ofneucrinalso suppressed neuronal differentiation and caused increased cell proliferation and apoptosis in developing neural tissues. Neucrin is a unique secreted Wnt antagonist that is predominantly expressed in developing neural tissues and plays roles in neural development in zebrafish.
Highlights► Zebrafishneucrinwas predominantly expressed in developing neural tissues. ► The knockdown ofneucrincaused overactivation of Wnt/β-catenin signaling. ► Overexpression ofneucrinreduced the expression of the Wnt/β-catenin target genes. ► Neucrin is involved in cell proliferation, survival and differentiation in brain. -
Editorial Board
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Volume 75, Issue 5, 2011, Pages CO2
[No author name available] -
Mouse germ cell clusters form by aggregation as well as clonal divisions
» Mech DevPublication year: 2012
Source: Mechanisms of Development, Available online 5 January 2012
Lindsey Mork, Hao Tang, Iordan Batchvarov, Blanche Capel
After their arrival in the fetal gonad, mammalian germ cells express E-cadherin and are found in large clusters, similar to germ cell cysts inDrosophila. InDrosophila, germ cells in cysts are connected by ring canals. Several molecular components of intercellular bridges in mammalian cells have been identified, including TEX14, a protein required for the stabilization of intercellular bridges, and several associated proteins that are components of the cytokinesis complex. This has led to the hypothesis that germ cell clusters in the mammalian gonad arise through incomplete cell divisions. We tested this hypothesis by generating chimeras between GFP-positive and GFP-negative mice. We show that germ cell clusters in the fetal gonad arise through aggregation as well as cell division. Intercellular bridges, however, are likely restricted to cells of the same genotype.
Highlights► Germ cell clusters arise through aggregation as well as cell division. ► Intercellular bridges are specific to clonally related cells. ► Synchronous cell divisions may require communication through intercellular bridges. -
Fate maps of ventral and dorsal pancreatic progenitor cells in early somite stage mouse embryos
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 29 December 2011
Rika Miki, Tetsu Yoshida, Kazuya Murata, Shinya Oki, Kazuhiko Kume, ...
The origins of liver progenitor cells have been extensively studied, but evidence on the origin of pancreatic precursor cells is currently limited.Pancreatic and duodenal homeobox gene 1(Pdx1) is one of the earliest known markers for the pancreas. A transgenic mouse line expressing green fluorescent protein (GFP) under the control of thePdx1promoter showed thatPdx1/GFP expression was first observed in the mid-region of the anterior intestinal portal (AIP) lip at embryonic day (E) 8.5 at the 5–6 somite stage (ss). The liver progenitors were confirmed to originate from separate domains at the lateral endoderm and the inner part of the medial AIP as previously reported (), which turned out to lie caudally to thePdx1/GFP-expressing domain. To confirm if the earlyPdx1/GFP-positive cells give rise to the pancreatic bud, we labeled the cells on the lip of the AIP using the carbocyanine dye CM-DiI and traced their fates in 1-4 ss, 5–6 ss and 7–9 ss E8.5 embryos using anex uterowhole embryo culture method. At 1ss, the ventral pancreas progenitors were observed in the lateral endoderm, not yet being segregated from the liver or gut progenitors. Cells that contributed solely to the ventral pancreas first appeared at the AIP lip from 5 ss. At 5–6 ss, cells from the medial of the AIP lip contributed to the ventral pancreas. The pancreas fate region become narrower as development progresses. At 7–9 ss, the cells contributing to the ventral pancreas resided in a narrow region of the AIP lip. From 5ss, the right flanking region contributes to the posterior gut, and the left flanking region contributes to the anterior gut. Dorsal pancreatic progenitors originate from the dorsal endoderm at the 3–6 somite level at 7–9 ss, though they have not yet diverged from the dorsal gut progenitors at this stage.
Highlights► We constructed a fate map for the ventral and dorsal pancreas in early mouse embryos. ► The ventral pancreas (vp) progenitors reside at the AIP lip, anterior to the liver. ► The left or right AIP flankings contribute to the anterior or posterior gut. ► A conversion of left-right to anterior-posterior asymmetry occurs from 5 ss. ► Dorsal pancreatic progenitors reside at the 3–6 somite level at 7–9 ss. -
A case of plane rotations of an elastic pendulum
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
A.P. Markeyev
The motion of a point mass, suspended on a spring in a uniform gravity field, is investigated. The spring is assumed to be weightless and to possess linear elasticity. Motion occurs in a specified fixed vertical plane. It is shown that a pendulum motion exists in which the angle, made by the axis of the spring and the vertical, varies uniformly with time. The problem of the orbital stability of this motion is solved. -
Non-linear constitutive relations for unstable materials
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
K.A. Agakhi, Yu. G. Basalov, V.N. Kuznetsov
Non-linear constitutive relations to describe the rheological properties of unstable materials in the one-dimensional case are proposed, where the properties of instability, in particular ageing (i.e., the increase in stiffness and toughness of the material with time), are described by experimentally determined “instability functions”, which depend on the “age” of a given batch of material and, possibly, on invariance of the stress or strain tensors, which affect the rate of physical-chemical processes in the materials. Taking into account the instability of the material, a “fast” time is introduced, measured from the beginning of a short-term test with a material of a given age, and a “slow” time, measured from the instant when the material is produced. An exact solution of the problem of identifying the model, i.e., a determination of the material instability functions from experimental data, is constructed. -
Analysis and optimization of the rectilinear motion of a two-body system
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
F.L. Chernous’ko
The rectilinear motion of a system of two interacting bodies when there is a dry friction force acting on both of them is considered. It is assumed that the relative velocity of the bodies can vary practically instantaneously, while the distance between them has upper and lower limits. The periodic motion of the system as a whole is constructed, and the mean velocity of motion and the energy costs per unit of path are determined. The optimum values of the parameters for which the highest mean velocity is reached with the superimposed limitations are obtained. -
Transient vibration of an infinite string bearing a concentrated mass and supported by elastic-viscous suspensions
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
P.M. Belotserkovskii
The transient transverse vibration of a string, bearing a concentrated mass and supported by elastic-viscous suspensions a constant distance apart, is investigated. The vibration is excited either by an instantaneous impulsive force or a constant force suddenly applied to the concentrated mass. In the first case a formal Fourier transformation of the Dirac impulse function is employed. In the second case the action of the constant force is regarded as a succession of actions of instantaneous pulses. -
The scattering of acoustic waves by a cylinder with a non-uniform elastic coating
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
A.G. Romanov, L.A. Tolokonnikov
The problem of the scattering of a plane acoustic wave by a solid cylinder with a radially non-uniform elastic coating is considered. An analytical expression describing the scattered acoustic field is obtained. The equations of motion of the non-uniform elastic cylindrical layer are reduced to a system of ordinary differential equations, the boundary-value problem for which is solved by the power-series method. The results of calculations of the directional pattern of the scattered field are presented. -
A qualitative analysis of the dynamics of a disc on an inclined plane with friction
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
A.V. Karapetyan, A.M. Rusinova
The problem of the motion of a disc on an inclined plane with dry friction is investigated. It is shown that, if the friction coefficient is greater than the slope of the plane, the disk will come to rest after a certain finite time, and its sliding and rotation will cease simultaneously. The limit position of the instantaneous centre of velocities is indicated. The limit motions of the disc in the case when the ratio of the friction coefficient to the slope of the plane is equal to or less than unity: uniform sliding (in the case of a general position) and equiaccelerated sliding (always) of the disc along the line of greatest slope of the plane, respectively, are obtained. The case when the friction coefficient is equal to the slope, while the initial sliding velocity is directed upwards along the line of greatest slope, is an exception. In this case, the disc comes to rest after a finite time, and the sliding velocity and the angular velocity of the disc vanish simultaneously. -
Time-optimal steering of an object moving in a viscous medium to a desired phase state
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
L.D. Akulenko
The two-point problem of the time-optimal attainment of a desired phase state by a multidimensional dynamic object is investigated. The motion occurs in a viscous medium by means of a limited force. The open-loop and/or feedback control laws constructed by numerical-analytical methods for arbitrary initial data. An asymptotically approximate solution of the maximum principle boundary-value problem is presented for short and long time intervals. The singularities of the optimal trajectory are established for the initial and final parts of the motion. The solution obtained of the two-point problem of the optimal control of the motion of a dynamic object in a homogeneous viscous medium by means of a force of bounded modulus is compared with the known solutions in special formulations. -
The three-dimensional problem of a thin inclusion in a composite elastic wedge
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
V.M. Aleksandrov, D.A. Pozharskii
The three-dimensional problem of a thin rigid elliptic inclusion in the middle of a composite elastic wedge is investigated. The wedge consists of three connected wedge-shaped layers connected by a sliding clamp, in which the layer containing the inclusion is incompressible. The outer faces of the composite wedge are also under sliding-clamp conditions. The inclusion is completely bonded to the elastic medium in the contact region. Using Fourier and Kontorovich–Lebedev transformations, a system of integral equations of the problems are derived for the shear contact stresses. A regular asymptotic method is used to solve this system. Calculations are carried out. The results can be used for calculations on the strength of rubber-metal articles and structures having a corner line. -
The resonance stabilization of a class of unstable systems
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
A.L. Kunitsyn
The Lyapunov stability of the trivial solution of a non-linear system, which, in the first approximation, describes a multifrequency oscillatory process, is investigated. It is shown that a system that is unstable when account is taken of non-linear terms can be made asymptotically stable by tuning it to a fourth-order resonance. Sufficient conditions for asymptotic stability are obtained. -
A theory of thin shells with finite displacements and deformations based on a modified Kirchhoff–Love model
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
V.N. Paimushin
A refined classical Kirchhoff–Love theory of thin shells with finite displacements and deformations is given that takes account of deformation in a transverse direction by introducing an additional unknown function to describe it. It is shown that the last of the three equilibrium equations for the moments obtained from the variational equation of the principle of virtual displacements serves to determine it. Constitutive relations are constructed for the internal forces and moments introduced into the treatment based on the introduction of the true Novoshilov stresses and strains into the discussion. The solution of problem of the static stability of a cylindrical shell made of a rubber-like incompressible material inflated by an internal pressure is given using the equations constructed. Chernykh's constitutive relations are used in its formulation. -
The steady motions of gyrostats with equal moments of inertia in a central force field
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
A.A. Burov, A.D. Guerman, R.S. Sulikashvili
The problem of the motion of a gyroscope in a central force field is considered. It is assumed that the principal central moments of inertia of the gyrostat are equal to one another, while the centre of mass moves in a circular orbit in a plane passing through the attracting centre. The steady motions of the gyrostat and their stability are investigated. The case when the mass distribution allows of the symmetry group of a tetrahedron is considered as an example. -
Asymptotic solutions of coupled dynamic problems of thermoelasticity for thin bodies of anisotropic inhomogeneous-in-plan materials
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
L.A. Aghalovyan, R.S. Gevorgyan
Two-dimensional recurrence resolvents for an inhomogeneous thin body (plates of variable thickness and shells) are derived by an asymptotic method based on the three-dimensional equations of the coupled dynamic problem of the thermoelasticity of an anisotropic body, which are solved in the case of anisotropy, having, at each point, one plane of symmetry perpendicular to the transverse axis. Recurrence formulae are derived in a general formulation for determining the components of the stress tensor, the strain vector and the function of the change in the temperature field, when different boundary conditions of dynamic problems of the theory of coupled thermoelasticity and thermal conductivity are given on the end surfaces of a thin body. An algorithm for determining the analytical and numerical (necessary) solutions of these boundary-value problems with an arbitrarily specified accuracy is developed. -
The motion of a ball on a grassy lawn
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
V.G. Vil’ke, D.S. Migunova
The motion of a ball of constant spherical shape on a grassy lawn represented by a set of deformable rods with one end rigidly attached to a plane, while the other end is free and can contact the ball, is investigated. The contact area on the ball surface is represented by a spherical sector, whose dimensions and location on the ball surface depend on the position of the centre of the ball and its orientation. The projection of the contact area onto the plane is a circle, whose centre and radius vary as the centre of the ball moves. When the rods come into contact with the ball, they experience longitudinal and flexural strains, as well as impact actions on the boundary of the contact area. The translational–rotational motion of a ball on a lawn of rods without friction, as well as motion with viscous friction at the points of contact of the ends of the rods with the ball, is considered. -
Shock wave structure in an inviscid heat-conducting locally equilibrium medium of a perfect gas with radiation
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 21 December 2011
A.N. Kraiko
The structure of a shock wave (SW) in an inviscid heat-conducting locally equilibrium medium of a perfect gas with radiation at temperatures up to hundreds of thousands and millions of degrees is analysed in the approximation of non-linear heat conduction. At such temperatures, heat conduction is far more important than viscosity, the medium consists of ions, electrons and radiation, and the electrons and radiation make a decisive contribution to the heat transfer and an appreciable contribution to the thermodynamic functions of the medium. Combinations with the dimensions of all the flow parameters are constructed from the gas density ahead of the SW and the constants appearing in the equations of state of such a medium. If they are taken as the corresponding scales, the equations of state for different media in dimensionless form only differ in the ratio of the specific heat capacities (the adiabatic exponent) of the gas. The SW structure is studied for adiabatic exponents from 1 to 3, dimensionless temperatures ahead of the SW from zero to infinity and any SW velocities exceeding the speed of sound in the unperturbed medium. The following cases are successively considered: 1) when the contribution due to radiation is neglected in the equations of state, 2) when radiation is taken into account and the SW moves through a gas at a zero temperature (through a cold background), and 3) the radiation contribution is allowed for in the case of a warm background. It is ascertained when the SW structure is continuous and when it contains a finite or infinite forerunner and an isothermal shock. The transition from a continuous structure to a structure with an isothermal shock and the intensity of this shock are independent of the form of the formulae for the thermal conductivity in Fourier's law. In the case of adiabatic exponents greater than unity, the structure is continuous for all SW velocities starting from a certain dimensionless background temperature. -
Retinoic acid metabolism links the periodical differentiation of germ cells with the cycle of Sertoli cells in mouse seminiferous epithelium
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 19 December 2011
Ryo Sugimoto, Yo-ichi Nabeshima, Shosei Yoshida
Homeostasis of tissues relies on the regulated differentiation of stem cells. In the epithelium of mouse seminiferous tubules, the differentiation process from undifferentiated spermatogonia (Aundiff), which harbor the stem cell functions, to sperm occurs in a periodical manner, known as the “seminiferous epithelial cycle”. To identify the mechanism underlying this periodic differentiation, we investigated the roles of Sertoli cells (the somatic supporting cells) and retinoic acid (RA) in the seminiferous epithelial cycle. Sertoli cells cyclically change their functions in a coordinated manner with germ cell differentiation and support the entire process of spermatogenesis. RA is known to play essential roles in this periodic differentiation, but its precise mode of action and its regulation remains largely obscure. We showed that an experimental increase in RA signaling was capable of both inducing Aundiff differentiation and resetting the Sertoli cell cycle to the appropriate stage. However, these actions of exogenous RA signaling on Aundiffand Sertoli cells were strongly interfered by the differentiating germ cells of intimate location. Based on the expression of RA metabolism-related genes among multiple cell types—including germ and Sertoli cells—and their regulation by RA signaling, we propose here that differentiating germ cells play a primary role in modulating the local RA metabolism, which results in the timed differentiation of Aundiff and the appropriate cycling of Sertoli cells. Similar regulation by differentiating progeny through the modulation of local environment could also be involved in other stem cell systems.
Highlights► Undifferentiated spermatogonia differentiate periodically in mouse seminiferous tubules. ► Meiotic and haploid germ cells regulate the local retinoic acid (RA) metabolism. ► The increased RA triggers the differentiation of undifferentiated spermatogonia. ► RA also resets the functional cycle of somatic Sertoli cells. ► Thus, RA metabolism links the germ cell differentiation and Sertoli cell cycle. -
Canonical Wnt signaling in the visceral muscle is required for left-right asymmetric development of theDrosophilamidgut
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 17 December 2011
Junpei Kuroda, Mitsutoshi Nakamura, Masashi Yoshida, Haruka Yamamoto, Takaaki Maeda, ...
Many animals develop left-right (LR) asymmetry in their internal organs. The mechanisms of LR asymmetric development are evolutionarily divergent, and are poorly understood in invertebrates. Therefore, we studied the genetic pathway of LR asymmetric development inDrosophila.Drosophilahas several organs that show directional and stereotypic LR asymmetry, including the embryonic gut, which is the first organ to develop LR asymmetry duringDrosophiladevelopment. In this study, we found that genes encoding components of the Wnt-signaling pathway are required for LR asymmetric development of the anterior part of the embryonic midgut (AMG).frizzled 2(fz2) andWnt4, which encode a receptor and ligand of Wnt signaling, respectively, were required for the LR asymmetric development of the AMG.arrow(arr), an ortholog of the mammalian gene encoding low-density lipoprotein receptor-related protein 5/6, which is a co-receptor of the Wnt-signaling pathway, was also essential for LR asymmetric development of the AMG. These results are the first demonstration that Wnt signaling contributes to LR asymmetric development in invertebrates, as it does in vertebrates. The AMG consists of visceral muscle and an epithelial tube. Our genetic analyses revealed that Wnt signaling in the visceral muscle but not the epithelium of the midgut is required for the AMG to develop its normal laterality. Furthermore,fz2andWnt4were expressed in the visceral muscles of the midgut. Consistent with these results, we observed that the LR asymmetric rearrangement of the visceral muscle cells, the first visible asymmetry of the developing AMG, did not occur in embryos lackingWnt4expression. Our results also suggest that canonical Wnt/β-catenin signaling, but not non-canonical Wnt signaling, is responsible for the LR asymmetric development of the AMG. Canonical Wnt/β-catenin signaling is reported to have important roles in LR asymmetric development in zebrafish. Thus, the contribution of canonical Wnt/β-catenin signaling to LR asymmetric development may be an evolutionarily conserved feature between vertebrates and invertebrates.
Highlights► Canonical Wnt signaling is required for the LR asymmetric development of the midgut. ► Wnt signaling needs to be activated in the visceral muscle for normal gut laterality. ► Wnt signaling in the gut is activated with bilateral LR symmetry. ► Roles of Wnt signaling in LR asymmetric development may be conserved evolutionarily. -
The possibility of a theoretical confirmation of the experimental values of the external critical pressure of thin-walled cylindrical shells
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 December 2011
Ye.A. Lopanitsyn, Ye.A. Matveyev
The problem of the buckling of elastic, isotropic, thin-walled cylindrical shells with small initial shape defects that are under the action of an external pressure is solved in a geometrically non-linear formulation. Equations that are identical to Marguerre's equations for a shallow cylindrical shell are used in formulating the problem. The solution is constructed by the Rayleigh–Ritz method with the points of the middle surface of the shell approximated by double functional sums over trigonometric and beam functions. The system of non-linear equations obtained is solved by arc-length methods. Cases of the clamped and supported shells when loading with a lateral and uniform hydrostatic pressure are considered. Its deflections from the limit points of the postbuckling branches of its loading trajectory are used as the initial imperfections. An inspection of the different forms of the initial imperfections when they have maximum values of up to 30% of the shell thickness made it possible to obtain practically the whole range of experimentally found critical pressures. -
A family of analytic extremals in problems of the optimal control of the rotation of a body
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 December 2011
A.N. Sirotin
The problem of the optimal control of the rotation of an absolutely rigid body about the centre of mass is investigated. The main purpose of the control is to vary the angular velocity vector from its initial value to the required terminal value in a finite time so that the manoeuvre would require the smallest power consumption, which is characterized by an integral quadratic functional. The principal torque produced by the external forces applied to the body serves as the control. The change in orientation is not taken into account, i.e., the problem of the overspeed–braking control of the body, is studied. A new class of analytic extremals based on the use of space-time deformations of the solutions of the dynamical Euler equations for the free rotation of a rigid body is described. Sufficient conditions for the existence of such extremals for all types of symmetries are presented. -
Retraction notice to ‘DrosophilaTen-ais a maternal pair-rule and patterning gene’ [Mech. Dev. 124 (2007) 911–924]
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 11 December 2011
Nadya Rakovitsky, Yosef Buganim, Tomer Swissa, Yael Kinel-Tahan, Shirly Brenner, ... -
p21, an important mediator of quiescence during pituitary tumor formation, is dispensable for normal pituitary development during embryogenesis
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 1 December 2011
Pamela Monahan, Ashley D. Himes, Agata Parfieniuk, Lori T. Raetzman
A delicate balance between proliferation and differentiation must be maintained in the developing pituitary to ensure the formation of the appropriate number of hormone producing cells. In the adult, proliferation is actively restrained to prevent tumor formation. The cyclin dependent kinase inhibitors (CDKIs) of the CIP/KIP family, p21, p27 and p57, mediate cell cycle inhibition. Although p21 is induced in the pituitary upon loss of Notch signaling or initiation of tumor formation to halt cell cycle progression, its role in normal pituitary organogenesis has not been explored. In wildtype pituitaries, expression of p21 is limited to a subset of cells embryonically as well as during the postnatal proliferative phase. Mice lackingp21do not have altered cell proliferation during early embryogenesis, but do show a slight delay in separation of proliferating progenitors from the oral ectoderm. By embryonic day 16.5,p21mutants have an alteration in the spatial distribution of proliferating pituitary progenitors, however there is no overall change in proliferation. At postnatal day 21, there appears to be no change in proliferation, as assessed by cells expressing Ki67 protein. However,p21mutant pituitaries have significantly less mRNA ofMycand the cyclinsCcnb1,Ccnd1,Ccnd2andCcne1than wildtype pituitaries. Interestingly, unlike the redundant role in cell cycle inhibition uncovered inp27/p57double mutants, the pituitary ofp21/p27double mutants has a similar proliferation profile top27single mutants at the time points examined. Taken together, these studies demonstrate that unlike p27 or p57, p21 does not play a major role in control of progenitor proliferation in the developing pituitary. However, p21 may be required to maintain normal levels of cell cycle components.
Highlights► Timely separation of the developing pituitary from the oral ectoderm relies on p21. ► P27 and P21 do not act synergistically to restrain pituitary proliferation. ► P21 is necessary to maintain basal levels of cell cycle machinery components. -
Contents
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Volume 128, Issues 7-10, September-December 2011, Pages iii
[No author name available] -
OBC: Contents
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Volume 128, Issues 7-10, September-December 2011, Pages OBC
[No author name available] -
A lineage specific enhancer drivesOtx2expression in teleost organizer tissues
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 13 November 2011
Daisuke Kurokawa, Tomomi Ohmura, Koji Akasaka, Shinichi Aizawa
In mouseOtx2plays essential roles in anterior–posterior axis formation and head development in anterior visceral endoderm and anterior mesendoderm. TheOtx2expression in these sites is regulated by VE and CM enhancers at the 5’ proximal to the translation start site, and we proposed that these enhancers would have been established in ancestral sarcoptergians after divergence from actinopterigians for the use ofOtx2as the head organizer gene (). This would make doubtful an earlier proposal of ours that a 1.1kb fragment located at +14.4∼+15.5 kb 3’ (3’En) of fuguOtx2agene harbors enhancers phylogenetically and functionally homologous to mouse VE and CM enhancers (). In the present study, we demonstrate that fuguOtx2ais not expressed in the dorsal margin of blastoderm, shield and early anterior mesendoderm, and that the fuguOtx2a3’En do not exhibit activities at these sites of fugu embryos. We conclude that the fuguOtx2a3’En does not harbor an organizer enhancer, but encodes an enhancer for the expression in later anterior mesendodermal tissues. Instead, in fugu embryosOtx2bis expressed in the dorsal margin of blastoderm at blastula stage and shield at 50% epiboly, and this expression is directed by an enhancer, 5’En, located at -1000 to -800bp, which is uniquely conserved among teleostOtx2borthologues.
Highlights► Otx2is essential to head development in visceral endoderm, mouse organizer. ► Enhancer for thisOtx2expression is conserved in tetrapod but not teleost. ► In teleost,Otx2b, but notOtx2a, remains active in organizer tissues. ► The enhancer for thisOtx2bexpression is not homologous to tetrapodOtx2enhancer. -
Real-Time Monitoring of Blood Carbon Dioxide Tension by Fluorosensor
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 4 November 2011
Weizhong Jin, Jinjun Jiang, Yuanlin Song, Chunxue Bai
A new intravascular fluorosensor was developed and validated for inline PCO2monitoring. The PCO2sensor was based on the fluorescent indicator 1-hydroxypyrene-3,6,8-trisulfonate. The PCO2sensor was then immersed in various solutionsin vitroand carotid artery bypass of rabbitsin vivofor testing. Changes of PCO2in solutions and blood were created by bubbling CO2/N2and hyperventilation/hypoventilation, respectively. The changes of fluorescent intensity over PCO2range of 14-150 mmHg was linear. The resolution of the whole sensor system was 1 mmHg, with a bias ± SD of -0.1 ± 2.9 mmHg and precision ± SD of 2.1 ± 1.9 mmHg. The sensor signal has been stable during measurement for at least 25 h and was insensitive to fluctuations of ions concentration and osmosis at pathophysiological limits. The performance of the sensor is in agreement with blood gas analyzer in a wide range of PCO2and it is qualified for continuous intravascular measurement of blood PCO2at various conditions.
Highlights► We developed an optical PCO2sensor to measure PaCO2in real time ► The sensor had a good performance ► It was suitable for continuous PaCO2monitoring in animals -
Plasticity in mast cell responses during bacterial infections
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 4 November 2011
Cheryl Y Chan, Ashley L St. John, Soman N Abraham
Mast cells (MCs) have been implicated in orchestrating the host's early innate immune and adaptive immune responses in several models of acute bacterial infections. Most of this activity results in early clearance of the bacteria and timely resolution of infection. However, during chronic infections because of the prolonged nature of MC–bacterial interactions, the role of the MC in determining the fate of infection is markedly more complex. Depending on the nature of the pathogen, severity of infection, and its association with a preexisting inflammatory disease, MCs may promote rather than contain chronic infections and exacerbate their pathological sequellae.
Highlights► Mast cells directly and indirectly bind bacterial pathogens or secreted products. ► Mast cells can mediate acute and adaptive immune responses upon bacterial infection. ► Immediate and local mast cell activation during acute infection is beneficial. ► Systemic and sustained mast cell activation can exacerbate pathological sequellae. ► Activate/suppressing mast cells can modulate host immunity for therapeutic benefit. -
More than just lysins: peptidoglycan hydrolases tailor the cell wall
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 2 November 2011
Tsuyoshi Uehara, Thomas G Bernhardt
Enzymes that degrade the peptidoglycan (PG) cell wall layer called PG hydrolases or autolysins are often thought of as destructive forces. Phages employ them to lyse their host for the release of virion particles and some bacteria secrete them to eliminate (lyse) their competition. However, bacteria also harness the activity of PG hydrolases for important aspects of growth, division, and development. Of course, using PG hydrolases in this capacity requires that they be tightly regulated. While this has been appreciated for some time, we are only just beginning to understand the mechanisms governing the activities of these ‘tailoring’ enzymes. This review will focus on recent advances in this area with an emphasis on the regulation of PG hydrolases involved in cell division.
Highlights► Cell wall hydrolases play important roles in bacterial growth and division. ► Mechanisms regulating hydrolase activity are beginning to be elucidated. ► Cell wall hydrolases are important for virulence and are potential antibiotic targets. -
Editorial Board
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Volume 75, Issue 4, 2011, Pages CO2
[No author name available] -
Players between the worlds: multifunctional DNA translocases
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 31 October 2011
Christine Kaimer, Peter L Graumann
DNA translocases play important roles during the bacterial cell cycle and in cell differentiation.Escherichia colicells contain a multifunctional translocase, FtsK, which is involved in cell division, late steps of chromosome segregation and dimer resolution. In Gram-positive bacteria, the latter two processes are achieved by two translocases, SftA and SpoIIIE. These two translocases operate in a two step fashion, before and after closure of the division septum. DNA translocases have the remarkable ability to translocate DNA in a vectorial manner, orienting themselves according to polar sequences present in bacterial genomes, and perform various additional roles during the cell cycle. DNA translocases genetically interact with Structural Maintenance of Chromosomes (SMC) proteins in a flexible manner in different species, underlining the high versatility of this class of proteins.
Highlights► DNA translocases share a conserved domain for fast, directional transport of DNA. ► The direction of translocation is determined by short polar sequences on the DNA. ► DNA translocases act at different stages of the cell cycle and during differentiation. ► They are versatile in their function and can differ in their mode of action. -
Central chemoreflex ventilatory responses in humans following passive heat acclimation
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 29 October 2011
Andrew E. Beaudin, Michael L. Walsh, Matthew D. White
Since there is temperature dependence of pulmonary ventilation () in response to the normal modulators (i.e. PCO2/pH, PO2), it was asked in this study if passive heat acclimation (HA) modifies the human central chemoreflex ventilatory response to CO2. Nine males performed normothermic- and hyperthermic modified Read re-breathing tests before and after HA. HA consisted of 2 h/day exposures to 50 °C and 20% RH that elevated rectal temperature to between 38.5 and 39.0 °C for 10 consecutive days. Ventilatory recruitment thresholds (VRT) and central chemosensitivity were assessed before and after HA during normothermia oesophageal temperature (Tes) of ∼37 °C and in hyperthermia when Teswas 38.5-39.0 °C. Results showed VRT and central chemosensitivities were unaltered by HA (p≥0.375) and hyperthermia increased pre- (p = 0.010) but not post-acclimation (p = 0.332) central chemosensitivity. Additionally, during hyperthermia became progressively greater (p = 0.027) relative to corresponding normothermic values in the re-breathing tests. In conclusion, the ventilatory response to CO2was unaltered by HA and, irrespective of acclimation state.
Highlights► heat acclimation ► hyperoxic CO2 rebreathing ► pulmonary ventilation ► passive hyperthermia -
HYPOCAPNIA-DEPENDENT FACILITATION OF AUGMENTED BREATHS: OBSERVATIONS IN AWAKE VS. ANESTHETIZED RATS
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 29 October 2011
J. Moore, P. Haouzi, A. Van de Louw, H.J. Bell
Highlights► Injectable anesthetics alter the regulation of augmented breaths (ABs) in rats ► Urethane prevents their production in normoxic breathing ► Ketamine/xylazine blunts their facilitation during exposure to hypoxia ► Under anesthesia hypocapnia remains an essential factor in their facilitationAbstractWe investigated whether commonly used injectable laboratory anesthetics alter the regulation of augmented breaths (ABs) in different respiratory backgrounds. Male rats were studied on three separate experimental days, receiving one of three injections in randomized order: ethyl carbamate (‘urethane’; 1.2 mg·kg), ketamine/xylazine (ket/zyl; 80/10 mg·kg), or normal saline. Following each of the three interventions, breathing was monitored during 15 minute exposures to normoxia (room air), hypoxia (10% O2) and hypoxia + CO2(10% O2, 5% CO2). Urethane anesthesia completely eliminated ABs from the breathing rhythm in room air conditions (P < 0.001), and decreased the hypocapnia-dependent component of this response (p < 0.001). Ket/xyl left the normal incidence of ABs in room air breathing intact but significantly suppressed the hypoxia-induced facilitation of ABs (p = 0.0015). These results provide the first clear evidence that laboratory anesthesia can profoundly alter the regulation of ABs including the hypocapnia-dependent component of their facilitation. -
Age and sex differences in the ventilatory response to hypoxia and hypercapnia in awake neonatal, pre-pubertal and young adult rats.
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 29 October 2011
Heidi S. Holley, Mary Behan, Julie M. Wenninger
There is evidence for a “sensitive period” in respiratory development in rats around postnatal age (P) 12-13d. Little is known about sex differences during that time. The purpose of this study was to assess the effect of sex on breathing development, specifically around the “sensitive period”. We used whole-body plethysmography to study breathing in normoxic, hypoxic and hypercapnic gases in non-anesthetized male and female neonatal rats from P10-P15, juvenile (P30) and young adult (P90) rats. Compared to other neonatal ages, P12-13 male rats had significantly lower ventilation during normoxia, hypoxia, and hypercapnia. Compared to age-matched females, P12-13 male rats had lower ventilation in normoxia and hypoxia and a lower O2saturation during hypoxia. Circulating estradiol was greater in P12-13 male vs. female rats. Estradiol and ventilatory responses to hypoxia and hypercapnia were negatively correlated in neonatal male, but not female, rats. Our results suggest that P10-P15 includes a critical developmental period in male but not female rats.
Highlights► We examined sex differences in breathing in rats during postnatal days 10-15. >In hypoxia, P12-13 male rats had lower ventilation and O2 saturation vs female rats. >At P12-13, male rats had higher estradiol concentration vs. female rats. >In male rats, estradiol and hypoxic ventilation had a strong negative correlation. >P12-13 is a sensitive period of breathing development in male but not in female rats. -
Evolution of sex and mating loci: An expanded view from Volvocine algae
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 27 October 2011
James G Umen
Sexual reproduction in Volvocine algae coevolved with the acquisition of multicellularity. Unicellular genera such asChlamydomonasand small colonial genera from this group have classical mating types with equal-sized gametes, while larger multicellular genera such asVolvoxhave differentiated males and females that produce sperm and eggs respectively. Newly available sequence from theVolvoxandChlamydomonasgenomes and mating loci open up the potential to investigate how sex-determining regions co-evolve with major changes in development and sexual reproduction. The expanded size and sequence divergence between the male and female haplotypes of theVolvoxmating locus (MT) not only provide insights into how the colonial Volvocine algae might have evolved sexual dimorphism, but also raise questions about why the putative ancestral-likeMTlocus inChlamydomonasshows less divergence between haplotypes than expected.
Highlights► Volvocine algae include unicellularChlamydomonasand multicellularVolvox. ►Chlamydomonasis isogamous whileVolvoxis oogamous. ► TheVolvoxmating locus (MT) is expanded relative toChlamydomonas MT. ► A model forMTexpansion driven by sexual selection is presented. ► Models for unexpectedly low divergence ofChlamydomonas MThaplotypes are presented. -
A fungal sexual revolution:AspergillusandPenicilliumshow the way
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 25 October 2011
Paul S Dyer, Céline M O’Gorman
Fungi have some of the most diverse sex lives in nature, ranging from self-fertility to obligate outcrossing systems with several thousand different sexes, although at least 20% of fungal species have no known sexual stage. However, recent evidence suggests that many supposed ‘asexual’ species do indeed have the potential to undergo sexual reproduction. Using experimental and genomic findings fromAspergillusandPenicilliumspecies as examples, it is argued that evidence such as the presence and expression of apparently functional sex-related genes, the distribution of mating-type genes, detection of recombination from population genetic analyses, and the discovery of extant sexual cycles reveal an on-going revolution in the understanding of fungal asexuality.
Highlights► Recent evidence suggests that many supposed ‘asexual’ fungal species have the potential to undergo sexual reproduction. ► Experimental and genomic findings show that certain criteria or ‘sex tests’ can provide evidence for cryptic sexuality. ► Criteria include the distribution of mating-type genes and the detection of recombination from population genetic analyses. ► Recent discoveries of extant sexual cycles in previously considered asexualAspergillusandPenicilliumspecies are listed. ► The taxonomic implications and arguments for an ongoing revolution in the understanding of fungal asexuality are discussed. -
Structure-Activity Relationships in Rodent Diaphragm Muscle Fibers vs. Neuromuscular Junctions
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 25 October 2011
Dylan C. Sieck, Wen-Zhi Zhan, Yun-Hua Fang, Leonid G. Ermilov, Gary C. Sieck, ...
The diaphragm muscle (DIAm) is a highly active muscle of mixed fiber type composition. We hypothesized that consistent with greater activation history and proportion of fatigue-resistant fibers, neuromuscular transmission failure is lower in the mouse compared to the rat DIAm, and that neuromuscular junction (NMJ) morphology will match their different functional demands. Minute ventilation and duty cycle were higher in the mouse than in the rat. The proportion of fatigue-resistant fibers was similar in the rat and mouse; however the contribution of fatigue-resistant fibers to total DIAm mass was higher in the mouse. Neuromuscular transmission failure was less in mice than in rats. Motor end-plate area differed across fibers in rat but not in mouse DIAm, where NMJs displayed greater complexity overall. Thus, differences across species in activation history and susceptibility to neuromuscular transmission failure are reflected in the relative contribution of fatigue resistant muscle fibers to total DIAm mass, but not in type-dependent morphological differences at the NMJ.
Highlights► >Diaphragm muscle in mice has a greater activation history than rats. >Susceptibility to neuromuscular transmission failure is less in mice than rats. ► Fatigue-resistant fibers contribute to a greater fraction of muscle mass in mice. ► Rats, but not mice, show fiber type differences in neuromuscular junction morphology. ► Functional differences across species are not reflected in neuromuscular morphology. -
Motors in fungal morphogenesis: cooperation versus competition
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 24 October 2011
Gero Steinberg
Fungal tip growth underlies substrate invasion and is essential for fungal virulence. It requires the activity of molecular motors that deliver secretory vesicles to the growth region or which mediate bi-directional motility of early endosomes. Visualizing motors and their cargo in living fungal cells revealed unexpected cooperation between motors in membrane trafficking: (1) Class V chitin synthase, which has a class 17 myosin motor domain, moves bi-directionally, with myosin-5 and kinesin-1 cooperating in delivery to the growth region, and dynein taking it back to the cell centre. The myosin-17 motor domain competes with dynein by tethering the chitin synthase to the plasma membrane before exocytosis; (2) Long-range endosome motility is based on a cooperation of kinesin-3 and dynein, but towards the microtubule plus-end dynein competes with kinesin-3 to prevent the organelles from ‘falling off the track’. These results reveal a fine-balanced network of cooperative and competitive motor activity, required for fungal morphogenesis.
Highlights► Motor cooperation occurs between the same motor type on a single early endosome to increase the run-length. ► Actin- and microtubule-dependent motors cooperate by transporting the same cargo along different cytoskeletal fibres. ► Motors can cooperate by recycling each other to opposite poles of microtubules. -
Salmonella, the host and its microbiota
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 24 October 2011
Parameth Thiennimitr, Sebastian E Winter, Andreas J Bäumler
The intestine is host to a diverse bacterial community whose structure, at the phylum level, is maintained through unknown mechanisms. Acute inflammation triggered by enteric pathogens, such asSalmonella entericaserotype Typhimurium (S.Typhimurium), is accompanied by changes in the bacterial community structure marked by an outgrowth of the pathogen. Recent studies show thatS.Typhimurium can harness benefit from the host response to edge out the beneficial bacterial species that dominate in the healthy gut. The elucidation of howS.Typhimurium alters the bacterial community structure during gastroenteritis is beginning to provide insights into mechanisms that dictate the balance between the host and its microbiota.
Highlights► Non-typhoidalSalmonellaserotypes use their virulence factors to trigger intestinal inflammation. ► The response againstSalmonellaconsists of macrophage activation, neutrophil recruitment and the epithelial release of antimicrobials. ► Neutrophil transepithelial migration and the epithelial release of antimicrobials enableSalmonellato edge out competing microbes. ► The deployment of virulence factors could be seen as an attempt to create a niche that favors growth of the pathogen. -
Hypothyroidism Stimulates D2Receptor-mediated Breathing in Response to Acute Hypoxia and alters D2Receptors Levels in Carotid Bodies & Brain
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 25 October 2011
Evelyn H. Schlenker, Harold D. Schultz
Hypothyroidism can depress breathing and alter dopamine D2 receptor expression and function. We hypothesized that relative to euthyroid hamsters (EH), hypothyroid hamsters (HH) contain increased D2 receptors in brain regions associated with breathing and carotid bodies (CB), and that stimulation of D2 receptors would decease ventilation more in the HH compared to the EH. Hamsters were treated with vehicle, carmoxirile (peripherally acting D2 receptor agonist), or bromocriptine (central and peripherally acting D2 receptor agonist) and breathing was evaluated during exposure to air, hypoxia, and then air. HH exhibited increased D2 receptor protein levels in the striatum and CB's, but decreased levels in the paraventricular hypothalamic nucleus. Relative to vehicle, carmoxirole and bromocriptine stimulated ventilation in the HH during and following exposure to hypoxia. Only bromocriptine depressed ventilation in the EH during and after exposure to hypoxia. Thus, hypothyroidism impacts the expression of D2 receptors in the carotid body, PVN and striatum, and D2 stimulation affects ventilation remarkably differently than in EH.
Highlights► Hypothyroidism affects expression of D2 receptors in the PVN, stratum and CB. ► D2 receptor stimulation and hypoxia depressed breathing in normal hamsters ► D2 receptor stimulation and hypoxia stimulated breathing in hypothyroid hamsters ► Carotid body and CNS D2 modulation of breathing are altered in hypothyroidism. -
Corrigendum to ‘Dynamic vs. fixed bag filling: impact on cardiac output rebreathing protocol’ [Respir. Physiol. Neurobiol. 171 (2010) 22–30]
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 25 October 2011
Gerald S. Zavorsky, Kenneth C. Beck, Lauren M. Cass, Raul Artal, Peter D. Wagner
A purpose of this study was to compare the repeatability (2.77 multiplied by the within-subject SD) between two different rebreathing protocols on cardiac output (), pulmonary diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO), and pulmonary capillary blood volume (Vc). This study compared two bag volume protocols [Fixed Bag Volume (FBV) = bag volume fixed at 60% of forced vital capacity; Dynamic Bag Volume (DBV) = bag volume matched to tidal volume at each stage of exercise]. Ten females (age = 27 ± 8 yrs;had measurements at rest (12%), 52%, 88%, and 100% ofon two study days. Neither the slope nor intercept ofvs.were different between either bag volume protocols. The slope of DLCO vs.was the same but the intercept was higher for the FBV protocol. The bag volume affected the slope and the intercept between DLNO vs.(p < 0.05). The mean repeatability was similar between both protocols for(2.0 vs. 2.3 L/min) and DLCO (3.8 vs. 5.9 mL/min/mmHg), regardless of exercise intensity. Increasing exercise intensity made the measurement error worse for Vc and DLNO (p ≤ 0.06). Measurement error was lower for Vc when using the FBV protocol (p = 0.02). Also, the pattern of bag volume used during rebreathing maneuvers affected the relation between DLNO vs.more than it affected DLCO vs., or Vc vs.. Additionally, the FBV protocol provided less measurement error for Vc compared to the DBV protocol. -
Extracellular signaling and multicellularity inBacillus subtilis
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 23 October 2011
Elizabeth Anne Shank, Roberto Kolter
Bacillus subtilisregulates its ability to differentiate into distinct, co-existing cell types in response to extracellular signaling molecules produced either by itself, or present in its environment. The production of molecules byB. subtiliscells, as well as their response to these signals, is not uniform across the population. There is specificity and heterogeneity both within genetically identical populations as well as at the strain-level and species-level. This review will discuss how extracellular signaling compounds influenceB. subtilismulticellularity with regard to matrix-producing cannibal differentiation, germination, and swarming behavior, as well as the specificity of the quorum-sensing peptides ComX and CSF. It will also highlight how imaging mass spectrometry can aid in identifying signaling compounds and contribute to our understanding of the functional relationship between such compounds and multicellular behavior.
Highlights►Bacillus subtilisexists in multicellular communities composed of various cell types. ► The formation of these cell types can be regulated by extracellular compounds. ► We summarize recent results about how extracellular signals affect development. -
Social parasites
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 21 October 2011
Miguel A Lopez, HoangKim T Nguyen, Michael Oberholzer, Kent L Hill
Protozoan parasites cause tremendous human suffering worldwide, but strategies for therapeutic intervention are limited. Recent studies illustrate that the paradigm of microbes as social organisms can be brought to bear on questions about parasite biology, transmission and pathogenesis. This review discusses recent work demonstrating adaptation of social behaviors by parasitic protozoa that cause African sleeping sickness and malaria. The recognition of social behavior and cell–cell communication as a ubiquitous property of bacteria has transformed our view of microbiology, but protozoan parasites have not generally been considered in this context. Works discussed illustrate the potential for concepts of sociomicrobiology to provide insight into parasite biology and should stimulate new approaches for thinking about parasites and parasite–host interactions.
Highlights► Protozoan parasites cause tremendous human suffering worldwide, but strategies for therapeutic intervention are limited. ► The recognition of social behavior and cell-cell communication in bacteria has transformed our view of microbiology. ► The paradigm of social behavior has not generally been applied to protozoan parasites. ► Here, we discuss recent work demonstrating adaptation of social behaviors by protozoa that cause African sleeping sickness and malaria. ► Works discussed illustrate the potential for concepts of sociomicrobiology to provide insight into parasite biology, transmission and pathogenesis. ► These findings should stimulate new approaches for thinking about parasites and parasite-host interactions. -
Glial activation in the spinal ventral horn caudal to cervical injury.
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 20 October 2011
James A. Windelborn, Gordon S. Mitchell
Microglia and astrocytes play complex roles following spinal cord injury (SCI), contributing to inflammatory processes that both exacerbate injury and promote functional recovery by supporting neuro-protection and neuroplasticity. The crossed phrenic phenomenon (CPP) is an example of respiratory plasticity in which C2cervical hemisection (C2HS) strengthens crossed-spinal synaptic pathways to phrenic motor neurons ipsilateral to injury. We hypothesized that microglia and astrocytes are activated in the phrenic motor nucleus caudal and ipsilateral to C2HS, suggesting their potential for involvement in the CPP. To test this hypothesis, an incomplete cervical spinal hemisection (C2lateral injury; C2LI) was performed, and rats were allowed to recover for 1, 3, 14 or 28 days before collecting perfused spinal tissues. Microglia (via OX42) and astrocytes (via GFAP) were visualized with immunofluorescence microscopy in the C4-C5ventral horn, the region encompassing most of the phrenic motor nucleus. OX42-occupied fractional area ipsilateral to injury increased with C2LI (vs. sham) at 1 (12.5 + - 1.8%, p < 0.001), 3 (29.0 + - 1.9%, p < 0.001), 14 (26.1 + - 3.1%, p < 0.001) and 28 (19.2 + - 2.0%, p < 0.001) days post-C2LI. GFAP-occupied fractional area also increased with C2LI at 3 (24.4 + - 3.2%, p < 0.001) and 14 (16.8 + - 8.3%, p = 0.012) days, but not at 1 (6.2 + - 3.9%, p = 0.262) or 28 (10.6 + - 3.9%, p = 0.059) days post-C2LI. Thus, microglia and astrocytes are activated in the phrenic motor nucleus caudal to C2LI, suggesting that they play a role in functional deficits and/or recovery following spinal injury.
Highlights► We examined microglia and astrocyte activation in the phrenic motor nucleus after C2 hemisection ► Microglia activation was measured by OX42 immunofluorescence ► Astrocytic activation was measured by GFAP immunofluorescence ► Microglial activation increased at 1-28 days after injury ► Astrocytic activation increased at 1-28 days after injury. -
Self-assembling enzymes and the origins of the cytoskeleton
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 18 October 2011
Rachael M. Barry, Zemer Gitai
The bacterial cytoskeleton is composed of a complex and diverse group of proteins that self-assemble into linear filaments. These filaments support and organize cellular architecture and provide a dynamic network controlling transport and localization within the cell. Here, we review recent discoveries related to a newly appreciated class of self-assembling proteins that expand our view of the bacterial cytoskeleton and provide potential explanations for its evolutionary origins. Specifically, several types of metabolic enzymes can form structures similar to established cytoskeletal filaments and, in some cases, these structures have been repurposed for structural uses independent of their normal roles. The behaviors of these enzymes suggest that some modern cytoskeletal proteins may have evolved from dual-role proteins with catalytic and structural functions.
Highlights► The list of proteins forming bacterial cytoskeletal structures is expanding. ► Some enzymes self-assemble into higher-order structures such as filaments. ► Assembly may regulate activity and be repurposed for structural roles. ► Dual-role filaments may have been the origin of the cytoskeleton. -
Naloxone Pro-drug Rescues Morphine Induced Respiratory Depression in Sprague-Dawley Rats
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 19 October 2011
Michael Wallisch, Nehad M. El Rody, Baohua Huang, Dennis R. Koop, James R. Baker, ...
Respiratory depression is the main obstacle for the safe administration of morphine for acute pain after injury. Due to this complication, new delivery methods are needed to insure that safe and effective doses of opioid analgesics are administered during emergencies. A depot formulation containing a naloxone pro-drug was designed to release the antidote when morphine causes dangerous hypoxic conditions in the blood. The aim of this work was to test the naloxone releasein vivoin response to a severe overdose of morphine in the Sprague-Dawley rat model. Non-invasive two-chamber plethysmography was used to monitor and record respiration and to test the capability of the naloxone pro-drug to respond to and rescue morphine-induced respiratory depression in the animal. We show that the pro-drug formulation can both prevent and reverse severe morphine induced respiratory depression. The animal model demonstrates that co-administration of the naloxone pro-drug reliably antagonizes profound respiratory depressive effects of morphine.
Highlights► Newly synthesized naloxone pro-drug is examinedin vivoin the rat. ► Morphine induced respiratory depression is studied using plethysmography. ► Naloxone pro-drug releases naloxone in response to morphine overdose. ► Naloxone pro-drug rescues respiratory depression from morphine overdose. -
Exhaled nitric oxide is associated with acute mountain sickness susceptibility during exposure to normobaric hypoxia
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 19 October 2011
M.J. MacInnis, E.A. Carter, M.S. Koehle, J.L. Rupert
Nitric oxide is a gaseous signaling molecule that participates in a large variety of physiological functions and may have a role in the pathology of altitude illnesses, such as acute mountain sickness (AMS). The effect of normobaric hypoxia on the fraction of exhaled NO (FENO) is a controversial area of high altitude physiology, with the effect varying widely across studies. We exposed 19 male subjects to normobaric hypoxia for 6 hours and measured FENOand AMS (via Lake Louise Score) each hour. For data analysis, subjects were divided into AMS-positive and AMS-negative groups based on their Lake Louise Scores during exposure. Eighteen subjects completed the study, and the incidence of AMS was 50%. Mean FENOwas unchanged at hour 1 but was significantly elevated above baseline for the remainder of the normobaric hypoxia exposure (p < 0.001). Subjects who developed AMS had a significantly lower mean FENOat baseline compared to resistant subjects (p = 0.013). Further investigations are warranted to confirm our results and to understand the physiological basis of this association.
Highlights► The fraction of exhaled nitric oxide (FeNO) increased during 6 hours of normobaric hypoxia exposure. ► Subjects who developed acute mountain sickness had lower FeNO at baseline compared to subjects who did not develop the condition. ► Innate nitric oxide production could contribute to acute mountain sickness susceptibility. -
Candida albicansdevelopmental regulation: adenylyl cyclase as a coincidence detector of parallel signals
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 17 October 2011
Deborah A Hogan, Fritz A Muhlschlegel
In the healthy individual,Candida albicansis frequently found as a harmless commensal residing in the gastrointestinal tract. However, in the compromised patient,C. albicansmay invade the body and cause disease that is associated with poor prognosis and high mortality. TheC. albicansadenylyl cyclase, Cyr1, which is required for virulence in animal models, regulates three developmental programs, including invasive filamentous growth, phenotypic switching to a mating-competent cell type, and biofilm formation. Evidence suggests that Cyr1 controls these phenotypes in response to various environmental cues that are present within microbial populations. Additionally,C. albicanssecretes an autoregulatory molecule, farnesol, which was recently shown to directly inhibit Cyr1 activity. Below, we summarize recent advances in our understanding of Cyr1-regulated development and discuss the multiple inputs known to positively and negatively regulate cAMP synthesis. We discuss the possibility that Cyr1 acts as a coincidence detector that tightly regulates fungal development in response to parallel environmental stimuli, and highlight ways in which this might occur.
Highlights► Adenylyl cyclase (Cyr1) regulates developmental processes such as hyphal growth, biofilm formation, and phenotypic switching. ► Cyr1 activity is stimulated directly by regulatory proteins (Ras1 and Gpa2), peptidoglycan fragments and carbon dioxide. ► Farnesol, an autoregulatory molecule secreted by C. albicans, inhibits Cyr1 activity. -
Pre-junctional muscarinic autoreceptors in bovine airways
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 15 October 2011
Michele Baroffio, Emanuele Crimi, Lorenzo Brichetto, Lucia Zappi, Kai Rehder, ...
We searched for pre-junctional inhibitory muscarinic receptors in isolated bovine trachealis strips and bronchial rings. Electric stimulation (ES)-induced tritiated acetylcholine ([H]ACh)-release and isometric contractions were determined in muscles incubated with the non-selective muscarinic agonist pilocarpine, the non-selective muscarinic antagonist atropine, the selective M2-receptor antagonists methoctramine and gallamine, or the selective M4-receptor antagonist PD102807. Electric field stimulation (EFS)-induced isometric contractile responses were assessed in trachealis strips and bronchial rings treated with 10-10M methoctramine, gallamine or PD102807. Pilocarpine (10and 10M) and atropine (10M) significantly decreased and increased ES-evoked [H]ACh-release, respectively. The enhancing effect of atropine on [H]ACh-release prevailed over the inhibitory effect of pilocarpine. M2- and M4-receptor antagonists did not increase EFS-induced contraction or ES-induced [H]-ACh-release. However, 10M methoctramine, gallamine or PD102807 significantly attenuated the inhibitory effects of pilocarpine 10M on ES-induced [H]-ACh-release. Conclusions: muscarinic autoregulation is present in bovine airways but is not fully accounted for by M2- and M4-receptor subtypes.
Highlights► We searched for pre-junctional muscarinic autoreceptors in isolated bovine airways. ► Pilocarpine decreased electrically-evoked ACh release and atropine increased it. ► The enhancing effect of atropine prevailed over the inhibitory effect of pilocarpine. ► M2- and M4-antagonists partially attenuated the effect of pilocarpine. ► Muscarinic autoreceptors in addition to M2and M4may exist in bovine airways. -
Lubricating effect of sialomucin and hyaluronan on pleural mesothelium
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 15 October 2011
Francesca Bodega, Matteo Pecchiari, Chiara Sironi, Cristina Porta, Francesca Arnaboldi, ...
Coefficient of kinetic friction (μ) between rabbit visceral and parietal pleura, sliding in vitro at physiological velocities and load, increases markedly after blotting mesothelial surface with filter paper; this increase is only partially reduced by wetting blotted mesothelium with Ringer solution. Given that mesothelial surface is covered by a thick coat with sialomucin and hyaluronan, we tested whether addition of sialomucin or hyaluronan solution after blotting lowers μ more than Ringer alone. Actually, these macromolecules lowered μ more than Ringer, so that μ was no longer significantly higher than its preblotting value. Moreover, Ringer addition, after washout of macromolecule solution, increased μ, in line with their dilution. These findings indicate that mesothelial blotting removes part of these molecules from the coat covering mesothelial surface, and their relevance for pleural lubrication. Transmission electron micrographs of pleural specimens after mesothelial blotting showed that microvilli were partially or largely removed from mesothelium, consistent with a substantial loss of macromolecules normally entrapped among them. -
Comments on L.D. Akulenko and S.V. Nesterov's paper “The stability of the equilibrium of a pendulum of variable length”,Prikl Mat Mekh2009;73(6); 893–901
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 October 2011
A.O. Belyakov, A.P. Seyranian -
The bending of a circular membrane on a linearly deformed foundation
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 October 2011
V.M. Aleksandrov, V.Yu. Salamatova
The axisymmetric problem of the bending of a circular transversely-loaded membrane (i.e., a thin plate having no flexural stiffness), which lies without friction on a linearly deformed foundation, where there is contact over the whole area of the membrane, is considered. The problem is reduced to the combined investigation of a differential equation for the bending of the membrane and an integral equation of the first kind with an irregular kernel in the unknown contact pressure. The method of special orthonormalized polynomials and the regular asymptotic “large λ” method are used to solve the problem. -
Invariant properties of systems of equations of the mechanics of inhomogeneous fluids
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 October 2011
V.G. Baydulov, Yu.D. Chashechkin
The invariant properties of the fundamental system of equations of the mechanics of inhomogeneous fluids and its widely used approximations are analysed by the methods of continuous group theory. Simplifying assumptions significantly alter the invariant properties of the systems of equations. Both extending and contracting the admissible symmetry group can occur and provide evidence of the violation of the conditions of equivalence between the original and derived systems. For example, the use of the incompressibility and Boussinesq approximations leads to extension of the concept of an inertial reference frame to all frames moving relative to one another with arbitrary linear acceleration. -
The linear stability of inviscid shear flow of a vibrationally excited diatomic gas
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 October 2011
Yu. N. Grigor’ev, I.V. Yershov
The problem of the linear stability of plane-parallel shear flows of a vibrationally excited compressible diatomic gas is investigated using a two-temperature gas dynamics model. The necessary and sufficient conditions for stability of the flows considered are obtained using the energy integrals of the corresponding linearized system for the perturbations. It is proved that thermal relaxation produces an additional dissipation factor, which enhances the flow stability. A region of eigenvalues of unstable perturbations is distinguished in the upper complex half-plane. Numerical calculations of the eigenvalues and eigenfunctions of the unstable inviscid modes are carried out. The dependence on the Mach number of the carrier stream, the vibrational relaxation time τ and the degree of non-equilibrium of the vibrational mode is analysed. The most unstable modes with maximum growth rate are obtained. It is shown that in the limit there is a continuous transition to well-known results for an ideal fluid as the Mach number and τ approach zero and for an ideal gas when τ → 0. -
Simulation of seepage flows from channels
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 15 October 2011
E.N. Bereslavskii
Plane steady-state seepage in a homogeneous isotropic ground from channels through a layer of soil with an underlying highly permeable pressurized water-bearing layer when the ground possesses capillarity and there is evaporation from the free surface is considered in a hydrodynamic formulation. To investigate it, a mixed multiparametric boundary-value problem of the theory of analytical functions is formulated, which is solved using the Polubarinova-Kochina method and conformal mapping of the regions of a special form, typical of problems of underground hydromechanics. On the basis of this model, an algorithm for calculating the capillary spreading of water and seepage flow is developed in situations when the ground capillarity is taken into account in the seepage of water from channels, as well as evaporation from the free surface of the ground waters, and also backwater of the underlying highly permeable stratum. Using the exact analytical relations obtained and numerical calculations, a hydrodynamic analysis of the structure and characteristic features of the simulated process, and also of the effect of all the physical parameters of the system on the seepage characteristics, is carried out. Limit and special cases, related to the absence of one or two of the three factors, characterizing the simulated process are considered: the ground capillarity, evaporation from the free surface, and also backwater of the underlying highly permeable water-bearing layer. The results of the calculations are compared with similar seepage characteristics with a similar scheme, but in which the flow region is underlaid by an impenetrable base. -
Expression of Brain-derived Neurotrophic factor and TrkB receptor in the Sudden Infant Death Syndrome brainstem
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 14 October 2011
Samantha Tang, Rita Machaalani, Karen A. Waters
This study compared the expression of BDNF (proBDNF and rhBDNF forms) and its receptor TrkB, in the medulla of Sudden Infant Death Syndrome (SIDS) infants and infants who died from known causes (non-SIDS). This study also evaluated these markers in association with SIDS clinical risk factors including, sleep position, cigarette smoke exposure and gender. Brainstem tissue was immunohistochemically stained and quantitative analyses were made for eight nuclei of the caudal and rostral medulla. Compared to non-SIDS, SIDS infants had lower rhBDNF in the caudal nucleus of the solitary tract and higher TrkB in the caudal dorsal motor nucleus of the vagus. Within the SIDS cohort, prone sleep position was associated with lower rhBDNF in the caudal arcuate nucleus, and cigarette smoke exposure was associated with lower rhBDNF and TrkB in the inferior olivary nucleus. Abnormal expression of BDNF and TrkB suggests that neuroprotective functions of the BDNF/TrkB system may be reduced in respiratory-related nuclei of SIDS infants.
Highlights► SIDS infants have lower rhBDNF in the caudal nucleus of the solitary tract and higher TrkB receptor in the caudal dorsal motor nucleus of the vagus. ► Prone sleeping position amongst SIDS is associated with lower rhBDNF in the caudal arcuate nucleus. ► Cigarette smoke exposure amongst SIDS is associated with lower rhBDNF and TrkB in the inferior olivary nucleus. ► A significant gender by diagnosis interaction is evident for proBDNF and TrkB in the DMNV. -
Experimental Approaches To The Study Of The Mechanics Of Breathing During Exercise
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 14 October 2011
Paolo B. Dominelli, A. William Sheel
This review describes the methodology and analysis of respiratory mechanics as it pertains to dynamic exercise. Underlying physical principles governing respiratory mechanics and commonly used measuring instruments will be discussed. We explain the physiological basis behind respiration, along with the dynamics of pulmonary ventilation. This review will outline the theoretical framework behind several forms of analysis along with their specific pitfalls, advantages and assumptions. Particular attention will be given to the techniques used to estimate the mechanical work of breathing. Specifically, we detail the different styles of work of breathing analysis and their inherent limitations as well as common sources of error often encountered. Finally, recent technological advancements that contribute to the understanding of respiratory mechanics are explained. -
The method of successive approximations for solving the problem of the decay of a discontinuity and its application to the equations of two-layer shallow water theory
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 14 October 2011
P.Ye. Karabut, V.V. Ostapenko
The method of successive approximations for solving the problem of the decay of a small amplitude discontinuity is proposed for hyperbolic systems of conservation laws. In the linear approximation, a Cauchy problem for a linear hyperbolic system is obtained. Its solution represents lines of discontinuity separating the regions in which the solution is constant. Most attention is paid to the first and second approximations, within the limits of which the discontinuities obtained in the first approximation decay into stable shock waves and rarefaction waves. An analysis of the qualitatively different flow conditions that arise when solving the problem of the failure of a dam for a two-layer shallow water model with a free boundary is presented as an example. -
Two formulations of elastoplastic problems and the theoretical determination of the location of neck formation in samples under tension
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 14 October 2011
D.V. Berezhnoi, V.N. Paimushin
Two formulations of elastoplastic problems in the mechanics of deformable solids with finite displacements and deformations are investigated. The first of these is formulated starting from the classical geometrically non-linear equations of the theory of elasticity and plasticity, in which the components of the Cauchy–Green strain tensor, associated with the components of the conditional stress tensor by physically non-linear relations according to flow theory in the simplest version of their representation, are taken as a measure of the deformations. The second formulation is based on the introduction of the true tensile and shear strains which, according to Novoshilov, are associated with the components of the true stresses by physical relations of the above-mentioned form. It is shown that, in the second version of the formulation of the problem, the use of the corresponding equations, complied taking account of the elastoplastic properties of the material with correct modelling of the ends of cylindrical samples and the method of loading (stretching) them, enables the location of the formation of a neck to be determined theoretically and enables the initial stage of its formation to be described without making any assumptions regarding the existence of initial irregularities in the geometry of the samples. -
Two types of interface defects
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 14 October 2011
M.A. Grekov
The solution of a plane problem in the theory of elasticity for a two-component body with an interface, a finite part of which is either weakly distorted or is a weakly curved crack is constructed using the perturbation method. In the first case, it is assumed that the discontinuities in the forces and displacements at the interface are known, and, in the second case, the non-equilibrium nature of the load in the crack is taken into account. General quadrature formulae are derived for the complex potentials, which enable any approximation to be obtained in terms of elementary functions in many important practical cases. An algorithm is indicated for calculating each approximation. Families of defects are studied, the form of which is determined by power functions. The effect of the amplitude of the distortion and the shape of the interface crack on the Cherepanov–Rice integral as well as the shape of the distorted part of the interface on the stress concentration is investigated in the first approximation. An analysis of the applicability of the oscillating solution for a distorted interface crack is carried out. The results of the calculations are shown in the form of graphical relations. -
The effective characteristics and electroelastic state of active composite elements
» Mech DevPublication year: 2011
Source: Journal of Applied Mathematics and Mechanics, Available online 13 October 2011
A.V. Vasilenko, N.N. Rogacheva
For rods in which the piezoelectric and elastic layers are perpendicular to the rod axis and the lamination has a periodic structure, formulae for the effective characteristics of inhomogeneous material are obtained and the equations that describe the electroelastic state are constructed by the asymptotic method of homogenization. Such active composite elements are known as stacks. As an example, the electroelastic state of stacks executing forced harmonic vibrations under the action of an electrical load is calculated, the effective characteristics of material are found, and both the slowly varying state described by the rod theory and the rapidly varying state caused by the inhomogeneity of the layered structure are calculated. The effect of the thickness of weak adhesive layers on the electromechanical coupling coefficient, characterizing the stacks as energy convertors, is investigated. -
Editorial Board
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Volume 14, Issue 5, October 2011, Pages i
[No author name available] -
Contents
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Volume 14, Issue 5, October 2011, Pages iii
[No author name available] -
Next Issue of This Journal
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Volume 14, Issue 5, October 2011, Pages iv
[No author name available] -
Effects of Malnutrition with or without Eicosapentaenoic Acid on Proteolytic Pathways in Diaphragm
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 12 October 2011
Joanne M. Bando, Mario Fournier, Xiaoyu Da, Michael I. Lewis
Attenuation of muscle wasting has been reported with eicosapentaenoic acid (EPA) use in cachectic states. Pathways mediating muscle proteolysis with severe short-term nutritional deprivation (ND) ± EPA were evaluated, including diaphragm fiber-specific cross-sectional areas, mRNA (real-time PCR) and protein expression (Western blot). Rats were divided into 3 groups: 1) free-eating controls, 2) ND and 3) ND + EPA. ND significantly influenced multiple proteolytic pathways. EPA significantly reduced mRNA abundances for most genes to control levels with ND. However, discordant muscle protein expression of many genes was noted with the use of EPA, as protein levels failed to fall. EPA had no impact on diaphragm muscle atrophy, despite the impressive mRNA and some protein results. We conclude that EPA does not attenuate diaphragm muscle atrophy with severe levels of ND. Postulated mechanisms include reduction in muscle protein synthesis and persistent ongoing stimuli for proteolysis. Our study provides unique data on proteolytic signals with ND and has important implications for future studies using epa
Highlights► Proteolytic pathways were studied in the malnourished (ND) diaphragm ± EPA treatment ► EPA significantly reduced mRNA abundances for most genes to control levels with ND ► Muscle protein levels failed to fall with the use of EPA despite robust mRNA changes ► EPA had no impact on individual diaphragm muscle fiber atrophy ► Reduced protein synthesis and persistent proteolytic stimuli are likely explanations -
Isolatedin vitrobrainstem-spinal cord preparations remain important tools in respiratory neurobiology
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 12 October 2011
Stephen M. Johnson, Sara M. Turner, Adrianne G. Huxtable, Faiza Ben-Mabrouk
Isolatedin vitrobrainstem-spinal cord preparations are used extensively in respiratory neurobiology because the respiratory network in the pons and medulla is intact, monosynaptic descending inputs to spinal motoneurons can be activated, brainstem and spinal cord tissue can be bathed with different solutions, and the responses of cervical, thoracic, and lumbar spinal motoneurons to experimental perturbations can be compared. The caveats and limitations ofin vitrobrainstem-spinal cord preparations are well-documented. However, isolated brainstem-spinal cords are still valuable experimental preparations that can be used to study neuronal connectivity within the brainstem, development of motor networks with lethal genetic mutations, deleterious effects of pathological drugs and conditions, respiratory spinal motor plasticity, and interactions with other motor behaviors. Our goal is to show how isolated brainstem-spinal cord preparations still have a lot to offer scientifically and experimentally to address questions within and outside the field of respiratory neurobiology
Highlights► In vitro brainstem-spinal cords are used extensively in respiratory neurobiology. ► These preparations have several experimental advantages despite their limitations. ► This review describes these advantages and highlights examples in the literature. -
Respiratory Mechanics and Lung Tissue Remodeling in a Hepatopulmonary Syndrome Rat Model
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 8 October 2011
César Augusto Melo-Silva, Eduardo Gaio, José E. Trevizoli, Caio S. Souza, Alessandra S. Gonçalves, ...
Intrapulmonary vasodilation is a hallmark of the hepatopulmonary syndrome (HPS). However, its effects on respiratory mechanical properties and lung morphology are unknown. To determine these effects, 28 rats were randomly divided to control and experimental HPS groups (eHPS). The spontaneous breathing pattern, gas exchange, respiratory system mechanical properties, and lung and liver morphology of the rats were evaluated. Tidal volume, minute ventilation and mean inspiratory flow were significantly reduced in the eHPS group. Chest wall pressure dissipation against the resistive and viscoelastic components and elastic elastance were increased in the eHPS group. The lung resistive pressure dissipation was lower but the viscoelastic pressure was higher in the eHPS group. The airway volume proportion of collagen and elastic fibers was increased in the eHPS animals (16% and 51.7%;P < 0.05 andP < 0.001, respectively). The proportion of collagen volume in the vasculature increased 29% in the eHPS animals (P < 0.01). HPS presents with respiratory system mechanical disarray as well as airway and vascular remodeling. -
Innexin2 gap junctions in somatic support cells are required for cyst formation and for egg chamber formation inDrosophila
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 4 October 2011
Masanori Mukai, Hirotaka Kato, Seiji Hira, Katsuhiro Nakamura, Hiroaki Kita, ...
Germ cells require intimate associations with surrounding somatic cells during gametogenesis. During oogenesis, gap junctions mediate communication between germ cells and somatic support cells. However, the molecular mechanisms by which gap junctions regulate the developmental processes during oogenesis are poorly understood. We have identified a female sterile allele ofinnexin2(inx2),which encodes a gap junction protein inDrosophila. In females bearing thisinx2allele, cyst formation and egg chamber formation are impaired. In wild-type germaria, Inx2 is strongly expressed in escort cells and follicle cells, both of which make close contact with germline cells. We show thatinx2function in germarial somatic cells is required for the survival of early germ cells and promotes cyst formation, probably downstream of EGFR pathway, and thatinx2function in follicle cells promotes egg chamber formation through the regulation of DE-cadherin and Bazooka (Baz) at the boundary between germ cells and follicle cells. Furthermore, genetic experiments demonstrate thatinx2interacts with thezero population growth(zpg)gene, which encodes a germline-specific gap junction protein. These results indicate a multifunctional role for Inx2 gap junctions in somatic support cells in the regulation of early germ cell survival, cyst formation and egg chamber formation. Inx2 gap junctions may mediate the transfer of nutrients and signal molecules between germ cells and somatic support cells, as well as play a role in the regulation of cell adhesion.
Highlights► We identify a female sterile allele ofinnexin2gene. ► Inx2 in escort cells promotes cyst formation probably with EGFR pathway. ► Inx2 in follicle cells promotes egg chamber formation by DE-cadherin regulation. ► Inx2 gap junctions play crucial roles during early oogenesis. -
New(s) to the (Z-)ring
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 5 October 2011
Clare L Kirkpatrick, Patrick H Viollier
Cytokinesis in bacteria is mediated by a macromolecular machine known as the divisome, consisting of an assembly of FtsZ polymers around the cylindrical axis of the cell and the downstream regulators of division that are subsequently recruited to it. FtsZ polymerizes into filaments in a GTP-dependent manner, similarly to its eukaryotic structural homolog tubulin. The initial placement of the FtsZ polymerization site is tightly regulated by multiple mechanisms, as are the subsequent polymer reshaping and force generation that separate the two daughter cells from each other. New factors have been recently discovered that contribute to this regulation, notably affecting FtsZ polymer shaping, and modulating FtsZ polymerization in response to the metabolic or redox state of the cell.
Highlights► Shapers of FtsZ structures identified. ► Redox and metabolic signals described. ► Insight into the mechanism of nucleoid occlusion obtained. ► Structural basis of the Min oscillator elucidated. -
Hypoxia-induced arterial chemoreceptor stimulation and Hydrogen sulfide: Too much or too little?
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 5 October 2011
Philippe Haouzi, Harold Bell, Andry Van de Louw
This brief review presents and discusses some of the important issues surrounding the theory which asserts that endogenous hydrogen sulfide (H2S) is the mediator of, or at least an important contributor to, hypoxia-induced arterial chemorereceptor stimulation. The view presented here is that before H2S can seriously be considered as a candidate for transducing the O2-signal in the carotid bodies (CB), fundamental contradictions need to be resolved. One of these major contradictions is certainly the discrepancy between the levels of H2S endogenously present in the CB during hypoxia compared to the levels required to stimulate the arterial chemoreceptorsin vitro. Very small amounts of H2S are thought to be produced endogenously during a given level of hypoxia, yet the partial pressure of tissue H2S which is needed to produce an effect commensurate with that of hypoxia is thousands to millions of times higher. This review discusses this and other contradictions in light of what is known about H2S concentration and production in various tissues, the lessons we have learnt from the response to exogenous sulfide and the ability of the blood and the mitochondria to oxidize very large amounts of sulfide. These considerations suggest that the increased production of H2S in hypoxia and exogenous sulfide cannot produce the same effect on the carotid bodies and breathing. While the effects of the endogenous H2S on breathing remains to be established, the effects exogenous sulfide can be accounted for by its long established toxicity on cytochrome C oxidase.
Highlights► Hydrogen sulfide is a gas which has been proposed to play an important role in various physiological functions, including the stimulation of breathing induced by hypoxia. ► This review discusses the limits of this hypothesis. -
Effects of cigarette smoke and chronic hypoxia on airways remodeling and resistance. Clinical significance
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 3 October 2011
Elena Olea, Elisabet Ferrer, Jesus Prieto-Lloret, Carmen Gonzalez-Martin, Victoria Vega-Agapito, ...
Previously we have reported that association of cigarette smoke (CS) and chronic hypoxia (CH) interact positively to physiopathologically remodel pulmonary circulation. In present study we have exposed guinea pigs to CS smoke (four cigarettes/day; 3 months; CS) and to chronic hypoxia (12% O2, 15 days; CH) alone or in combination (CSCH animals) and evaluated airways remodeling and resistance assessed as Penh (enhance pause). We measured Penh while animals breathe air, 10% O2and 5% CO2and found that CS and CH animals have higher Penh than controls; Penh was even larger in CSCH animals. A rough parallelism between Penh and thickness of bronchiolar wall and muscular layer and Goblet cell number was noticed. We conclude that CS and CH association accelerates CS-induced respiratory system damage, evidenced by augmented airway resistance, bronchial wall thickness and muscularization and Goblet cell number. Our findings would suggest that appearance of hypoxia would aggravate any preexisting pulmonary pathology by increasing airways resistance and reactivity.
Highlights► We used a model of smoking guinea pig with/without exposure to sustained hypoxia. ► Each stressor separately increased airways resistance ► Concomitant alterations in bronchiolar structure were observed ► Association of both stressors worsens all the above parameters in an additive manner ► Appearance of hypoxia in the lung ill patients asks for a prompt intervention -
The Drosophila Hem/Kette/Nap1 protein regulates asymmetric division of neural precursor cells by regulating localization of Inscuteable and Numb
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 2 October 2011
Zengrong Zhu, Krishna Moorthi Bhat
The Hem/Kette/Nap1 protein is involved in many biological processes. We have recently reported that Hem is required for the normal migration of neurons in the Drosophila embryo.In this paper, we report that Hem regulates the asymmetric division of neural precursor cells. We find that a well-studiedHem/Kettemutant allele produces at least twomain, but possibly more, phenotypic classes of mutant embryos, and these phenotypes correlatewith variable levels of maternalwild type Hem protein in the developing embryo. While the weaker class exhibits weak axon guidance defect and the mis-migration of neurons, the stronger class causes severe axon guidance defects, mis-migration of neurons and symmetric division of ganglion mother cells (GMC) of the RP2/sib lineage.We also show that the basis for the loss of asymmetric division is due to non-localization of Inscuteable and Numb in GMC-1. A non-asymmetric Numb segregates to both daughter cells of GMC-1, which then prevents Notch signaling from specifying a sib fate. This causes both cells to adopt an RP2 fate. Furthermore, loss of function for Abelson tyrosine kinase also causes loss of asymmetric localization of Inscuteable and Numb and symmetric division of GMC-1, the loss of function for WAVE has a very weakly penetrant loss of asymmetry defect. These results define another role forHem/Kette/Nap1 in a neural precursor cell during neurogenesis.
Highlights► We show that the mutant alleles ofHemshow significant phenotypic variability. ► The variability correlates with the amount of maternal Hem ► We show that the Hem pathway regulates asymmetric division of neural precursors. ► Hem regulates asymmetric localization of determinants. -
Origin of neomuscularized vessels in mice exposed to chronic hypoxia
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 1 October 2011
Slaven Crnkovic, Andelko Hrzenjak, Leigh M. Marsh, Andrea Olschewski, Grazyna Kwapiszewska
Exposure of mice to chronic hypoxia is one of the most often used animal models to study pulmonary hypertension. Hypoxia exposure leads to vascular remodeling and muscularization of the small parenchymal vessels in the lung. Due to the anatomical differences between mice and humans, it is not possible to determine whether the remodeled vessels originate from the arterial or venous side of the vasculature. By applying antibodies against specific marker molecules expressed by arterial (ephrinB2) and venous (EphB4) endothelial cells, we could show that remodeled parenchymal vessels in hypoxia-exposed mice are mostly of arterial origin with slight venous involvement. Using these tools, it is possible to further characterize remodeled vessels in other small animal models, such as transgenic or knockout mice. Particularly useful applications would include selection of parenchymal vessels for laser microdissection studies.
Highlights► ephrinB2 and EphB4 are specific arterial and venous markers. ► origin of remodeled parenchymal vessels in mice can be determined. ► remodeling affects predominantly arterioles under hypoxia. ► slight venous remodeling can also be detected in the hypoxic mice lung. -
Lipopolysaccharide-Induced Lung Injury: Role of P2X7 Receptor
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 1 October 2011
Leonardo C. Monção-Ribeiro, Viviane R. Cagido, Graziela Lima-Murat, Patricia Teixeira Santana, Douglas R. Riva, ...
RATIONALE: P2X7 receptors have been involved in inflammatory and immunological responses, and their activation modulates pro-inflammatory cytokines production by LPS-challenged macrophages. OBJECTIVES: To determine the role of P2X7R in LPS-induced acute lung injury in mice. METHODS: wild-type (C57BL/6) and P2X7 knockout mice received intratracheal injection of saline orE. coliLPS (60 μg). After 24 h, changes in lung mechanics were determined by the end-inflation occlusion method. Bronchoalveolar lavage was performed, and lungs were harvested for measurement of morphometry, fibers content, inflammatory cells and cytokine expression by histochemistry and immunochemistry. RESULTS: Compared with saline, LPS increased lung mechanical parameters, mast cell, collagen and fibronectin deposition in lung parenchyma, as well as nitric oxide and lactate dehydrogenase release into bronchoalveolar fluid in wild-type, but not in P2X7R knockout mice. Alveolar collapse, lung influx of polymorphonuclear and CD14cells, as well as TGF-β, MMP-2, and IL-1β release were higher in wild-type than knockout LPS-challenged mice, while MMP-9 release where similar between the two genotypes. LPS increased macrophage immunoreactivity in lung tissue in both genotypes, but macrophages were not activated in the P2X7R knockout mice. Furthermore, LPS administration increased P2X7R immunoexpression in lung parenchyma in wild-type mice, and TLR4 in both wild-type and P2X7R knockout mice. CONCLUSION: P2X7 receptors are implicated in the pathophysiology of LPS-induced lung injury, modulating lung inflammatory and functional changes.
Highlights► P2X7 receptors are involved in inflammatory responses. ► This receptors modulate cytokine production by LPS-challenged macrophages. ► P2X7 receptors modulate lung inflammation and remodeling in vivo LPS-induced lung injury. -
HYPERTONICITY ACTIVATES PULMONARY VAGAL AFFERENTS INDEPENDENTLY OF VASOCONSTRICTION
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 1 October 2011
N. Song, A.M. Roberts, J. Yul
Injecting hypertonic saline into the lung periphery causes a vagally-mediated neural hyperpnea and tachypnea (the excitatory lung reflex, ELR). In the present study, we tested the hypothesis that hypertonic saline activates lung afferents mainly by increasing fluid flux from pulmonary vessels into the alveoli. If our hypothesis is correct, reducing perfusion of the vagal sensory region will reduce the fluid flux and attenuate the ELR. In anesthetized, open chest and mechanically ventilated rabbits, using intravital video microscopy, we confirmed that topical KCl (100 mM) constricted sub-pleural blood vessels and limited blood flow significantly, as indicated by a 43.3 ± 9% decrease in arteriolar diameters (p < 0.005), sluggish microvascular flow and paleness of alveolar walls. Then, we compared respiratory responses (assessed from phrenic nerve activity) to injections of hypertonic saline (8.1%, 0.1 ml) into the lung periphery before and after locally injecting KCl to limit fluid flux. The respiratory responses were the same with or without vasoconstriction. However, the responses were significantly decreased (from 22 ± 5% to 1 ± 2% for phrenic amplitude and from 75 ± 9% to 13 ± 6% for phrenic burst rate; n = 14, p < 0.02) after local injection of 2% lidocaine to block sensory endings. Since the ELR was not attenuated by vasoconstriction, increased transvascular fluid flux does not appear to be a major mechanism for hypertonic saline induced ELR.
Highlights► This study explored the underlying mechanism for activation of the excitatory lung reflex (ELR) by testing the hypothesis that hypertonic saline activates lung afferents mainly by increasing fluid flux from pulmonary vessels into the alveoli. ► Our data showed that vasoconstriction around the sensory ending did not alter the ELR. ► Thus, increased transvascular fluid flux does not appear to be a major mechanism for hypertonic saline induced ELR. -
Drosophilaspoonbillencodes a dual-specificity A-kinase Anchor Protein essential for oogenesis
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 1 October 2011
Meytal Hadad, Tali Bresler-Musikant, F. Shira Neuman-Silberberg
spoonbillis aDrosophilafemale-sterile mutation, which interferes with normal egg patterning during oogenesis. Previous analyses linked the mutation to a number of seemingly unrelated pathways, including GRK/EGFR and DPP, two major pathways essential forDrosophilaand vertebrate development. Further work suggested thatspoonbillmay also function in actin polymerization and border-cell migration. Here we describe the molecular cloning of thespoonbillgene and characterize new mutant alleles, further demonstrating thatspoonbill’s function is essential during oogenesis. We foundspoonbillto be allelic to CG3249 (also known asyu), which encodes the only known dual-specificity A-kinase anchor protein inDrosophila. Our data indicate that similar to mammalian AKAPs, Spoonbill protein contains a number of potential kinase and phosphatase binding motifs, and is targeted, in the ovary, to mitochondria and Golgi. Finally, we address some ofspoonbill’s mutant phenotypes from the perspective of the published data on the AKAP protein family.
Highlights► spoonbillis allelic to CG3249 (yu), the onlyDrosophiladual-specificity AKAP. ► Characterization of new alleles provesspoonbillis essential during oogenesis. ► Like mammalian AKAPs, Spoonbill contains kinase and phosphatase binding motifs. ► In the ovary Spoonbill is primarily targeted to mitochondria and Golgi. -
A conserved regulatory role for antisense RNA in meiotic gene expression in yeast
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 29 September 2011
Huei-Mei Chen, Aaron M Neiman
A significant fraction of the eukaryotic genome is transcribed into RNAs that do not encode proteins, termed non-coding RNA (ncRNA). One class of ncRNA that is of particular interest is antisense RNAs, which are complementary to protein coding transcripts (mRNAs). In this article, we summarize recent studies using different yeasts that reveal a conserved pattern in which meiotically expressed genes have antisense transcripts in vegetative cells. These antisense transcripts repress the basal transcription of the mRNA during vegetative growth and are diminished as cells enter meiosis. While the mechanism(s) by which these antisense RNAs interfere with production of sense transcripts is not yet understood, the effects appear to be independent of the canonical RNAi machinery.
Highlights► Antisense RNAs are common in the yeast transcriptome. ► Antisense RNAs are enriched at meiotically induced genes during mitotic growth. ► The antisense RNAs interfere with basal expression of these genes. ► This is a conserved regulatory strategy for meiotic genes in budding and fission yeasts. -
ParA ATPases can move and position DNA and subcellular structures
» Mech DevPublication year: 2011
Source: Current Opinion in Microbiology, Available online 29 September 2011
Florian Szardenings, David Guymer, Kenn Gerdes
Prokaryotic chromosomes and plasmids can be actively segregated by partitioning (par) loci. The common ParA-encodingparloci segregate plasmids by arranging them in regular arrays over the nucleoid by an unknown mechanism. Recent observations indicate that ParA moves plasmids and chromosomes by a pulling mechanism. Even though ParAs form filamentsin vitroit is not known whether similar structures are presentin vivo. ParA of P1 forms filamentsin vitroat very high concentrations only and filament-like structures have not been observedin vivo. Consequently, a ‘diffusion-ratchet’ mechanism was suggested to explain plasmid movement by ParA of P1. We compare this mechanism with our previously proposed filament model for plasmid movement by ParA. Remarkably, ParA homologues have been discovered to arrange subcellular structures such as carboxysomes and chemotaxis sensory receptors in a regular manner very similar to those of the plasmid arrays.
Highlights► In this review, we discuss how Type Iparloci segregate plasmids and chromosomes. ► ParA tethers plasmids in regular arrays on the nucleoid. ► ParA can also generate regular arrays of subcellular structures such as carboxysomes. ► Chromosomes are segregated by a pulling mechanism. -
Abnormal ventilatory control in Parkinson's disease–further evidence for non-motor dysfunction.
» Mech DevPublication year: 2011
Source: Respiratory Physiology & Neurobiology, Available online 29 September 2011
Leigh M. Seccombe, Hugh L. Giddings, Peter G. Rogers, Alastair J. Corbett, Michael W. Hayes, ...
There has been increasing recognition of pre-motor manifestations of Parkinson's disease (PD) resulting from early brainstem involvement. We sought to determine whether ventilatory control is abnormal.Patients with PD without respiratory disease were recruited. Spirometry, lung volumes, diffusing capacity and respiratory muscle strength were assessed. Occlusion pressure and ventilation were measured with increasing CO2. Arterial blood gases were taken at rest and following 20mins exposure to 15%O2. A linear correlation assessed associations between respiratory function and indices of PD severity.19 subjects (17 males) with mild-moderate PD were studied (mean (SD) age 66 (8) years). Respiratory flows and volumes were normal in 16/19. Maximum inspiratory and expiratory pressures were below LLN in 13/19 and 15/19 respectively. 7/15 had a reduced ventilatory response to hypercapnia and 11/15 had an abnormal occlusion pressure. There was no correlation between impairment of ventilatory response and reduction in respiratory muscle strength. Response to mild hypoxia was normal and there were no associations between disease severity and respiratory function.Our findings suggest that patients with mild-moderate PD have abnormal ventilatory control despite normal lung volumes and flows. -
Editorial Board
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A1
[No author name available] -
Sponsoring Organizations and Liaisons
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A2
[No author name available] -
Table of Contents
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A3-A4
[No author name available] -
Display Ad
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A5
[No author name available] -
Information for Authors
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A6-A7
Carol A. Lefebvre -
Information for Readers
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A8-A9
[No author name available] -
Display Ad
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages A10
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Management of misangulated implants for a maxillary overdenture with spherical abutments: A clinical report
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 209-213
Avinash S. Bidra, John R. Agar
Misangulated and malpositioned implants pose a significant challenge for the prosthodontic treatment of edentulous patients. Most reports of maxillary overdenture patients have described the use of a bar to splint malaligned implants, followed by successful fabrication of the prosthesis. Few reports have discussed the use of individual abutments in such situations. This clinical report describes the successful use of spherical/ball abutments for the management of 4 malaligned implants in the edentulous maxilla for an overdenture. The rationale and technique for the use of spherical abutments for overdenture fabrication in such situations are described. -
Nonrigid connection of tooth with implants in the esthetic zone with a ceramic restoration: A clinical report
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 214-218
Panagiota-Eirini Spyropoulou, Michael E Razzoog, Dimitrios Chronaios
Restoring edentulous areas with fixed prostheses can be challenging, especially when key abutment teeth are missing and implant placement is not an option. Sometimes, clinicians are faced with situations where teeth have to be connected with implants even though long-term prognosis of those connections may be questionable. This clinical report presents a connection of 2 implants with 1 tooth in the esthetic zone with a nonrigid connection. Two zirconia custom abutments and 1 zirconia coping definitively cemented on the tooth were used. A zirconia superstructure, veneered with porcelain, was cemented with provisional cement on the abutments and the coping. -
Severe and rapid erosion of dental enamel from swimming: A clinical report
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 219-223
Leila Jahangiri, Steven Pigliacelli, A. Ross Kerr
The diagnosis and treatment of a patient with excessive and rapid erosion of enamel is presented. Although the Center for Disease Control and the dental literature have reported on dental enamel erosion resulting from swimming pool chlorination, the awareness of such etiology among dental professionals may be limited. Common findings in these reports include cold sensitivity, a distinctive appearance resembling laminate veneer preparations of the facial surfaces of anterior teeth, occurrence of diastemas, and at times, a rough or gritty texture of the remaining tooth structure. Clinical presentations of erosive lesions can be diagnosed and the best course of treatment determined. -
Annual review of selected scientific literature: Report of the committee on scientific investigation of the American Academy of Restorative Dentistry
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 224-265
Terence E. Donovan, Maxwell Anderson, William Becker, David R. Cagna, Thomas J. Hilton, ... -
Photoelastic stress analysis of external versus internal implant-abutment connections
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 266-271
Pattapon Asvanund, Steven M. Morgano
Statement of problemCommon complications of implant restorations are abutment screw loosening and screw fracture. The geometry of the implant-abutment connection may affect stresses generated from loading, and these stresses may have a role in screw loosening or fracture.PurposeThis study compared the load transfer characteristics of a complete-arch restoration supported by 4 implants with external and internal implant-abutment connections. Loads were applied to the prostheses in 3 positions.Material and methodsTwo-dimensional photoelastic models were used to simulate bone. Two types of implants (ReplaceSelect Internal-Interface Tapered Implants and ReplaceSelect External-Interface Tapered Implants) were placed in the photoelastic models. Complete-arch metal frameworks were fabricated on the abutments. Artificial teeth were arranged on the framework, and the prosthesis was screwed onto the abutments. The specimens were analyzed at 2 levels (implant-abutment level and apical to the implant level) with 3 loading conditions (4-point load; 2-point anterior load; and 2-point lateral load). The numbers of fringe orders were recorded and compared.ResultsWith the 4-point load, no stress differences occurred between the external-implant abutment connection and internal-implant abutment connection at the connection level and at the apical level. With the 2-point anterior load, the internal-implant abutment connection resulted in lower stresses at the connection level both in the loaded and non-loaded areas. With the 2-point lateral load, the internal-implant abutment connection resulted in lower stresses at the connection level at the non-loaded area.ConclusionsWhen loaded off-center, the internal-implant abutment connection produced less stress when compared with the external-implant abutment connection. -
A segmented implant surgical guide connected with magnets
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 272-276
Junping Ma, James S. Brudvik
The 2-piece surgical guide introduced in this article is designed for guiding implant placement in the edentulous arch. With the aid of embedded magnets, this guide can be easily and quickly assembled and disassembled during the surgical procedure without losing the predetermined guidance for the implant placement. -
News and Notes
» Mech DevPublication year: 2011
Source: The Journal of Prosthetic Dentistry, Volume 106, Issue 4, October 2011, Pages 277-278
[No author name available] -
Interaction between NF-κB signaling and Notch signaling in gliogenesis of mouse mesencephalic neural crest cells
» Mech DevPublication year: 2011
Source: Mechanisms of Development, Available online 29 September 2011
Kyohei Fujita, Saki Yasui, Takeshi Shinohara, Kazuo Ito
In the present study, we elucidated that nuclear factor-κB (NF-κB) participates in the gliogenic specification of mouse mesencephalic neural crest cells. Whereas transfection of the NF-κB expression vector stimulated gliogenesis, treatment with the dominant negative NF-κB expression vector orNF-κBsmall interfering RNA suppressed the promotion of gliogenic specification by FGF treatment or Notch activation. This suppression was recovered by the treatment with Deltex-1 expression vector or mammalian hairy and enhancer of split homologues expression vectors. Furthermore, transfection of the inhibitor of κB (IκB) expression vector inhibited gliogenesis. In addition, treatment with the NF-κB expression vector promoted the expression of Deltex-1. These data suggest that NF-κB signaling is implicated in the gliogenesis through the interaction with Notch signaling. Moreover, cells that contain Sox10 expressed NF-κB and Deltex-1 in the presumptive trigeminal ganglia of embryonic day 9.0-9.5 mouse embryos. This observation supports our notion that the interaction between NF-κB signaling and Notch signaling plays an important role in the gliogenic specification of mouse mesencephalic neural crest cells.
Highlights► NF-κB signaling is implicated in gliogenesis. ► The interaction between NF-κB and Notch plays an important role in gliogenesis. ► There are cells expressing SOX10, Deltex-1, and NF-κB in mouse trigeminal ganglia.
