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WH2 and proline-rich domains of WASP-family proteins collaborate to accelerate actin filament elongation.
WASP-family proteins are known to promote assembly of branched actin networks by stimulating the filament-nucleating activity of the Arp2/3 complex. Here, we show that WASP-family proteins also function as polymerases that accelerate elongation of uncapped actin filaments. When clustered on a surface, WASP-family proteins can drive branched actin networks to grow much faster than they could by direct incorporation of soluble monomers. This polymerase activity arises from the coordinated action of two regulatory sequences: (i) a WASP homology 2 (WH2) domain that binds actin, and (ii) a proline-rich sequence that binds profilin-actin complexes. In the absence of profilin, WH2 domains are sufficient to accelerate filament elongation, but in the presence of profilin, proline-rich sequences are required to support polymerase activity by (i) bringing polymerization-competent actin monomers in proximity to growing filament ends, and (ii) promoting shuttling of actin monomers from profilin-actin complexes onto nearby WH2 domains. Unoccupied WH2 domains transiently associate with free filament ends, preventing their growth and dynamically tethering the branched actin network to the WASP-family proteins that create it. Collaboration between WH2 and proline-rich sequences thus strikes a balance between filament growth and tethering. Our work expands the number of critical roles that WASP-family proteins play in the assembly of branched actin networks to at least three: (i) promoting dendritic nucleation; (ii) linking actin networks to membranes; and (iii) accelerating filament elongation
Allergic gastroenteritis hospital admission time trends in Australia and New Zealand
AIM: Recent epidemiological studies indicate increases in hospital food allergy-related anaphylaxis admission rates in Australian and New Zealand. The aim of the study was to examine whether non-IgE-mediated food allergy might have increased in parallel. METHODS: We analysed childhood hospital admissions rates by ICD 10 codes for allergic gastroenteritis (AG) and infective gastroenteritis in Australia and New Zealand between June 1998 and July 2014. RESULTS: In Australia, most AG-related admissions (73%) occurred in those aged <1 year and increased by 7.3%/year (95% confidence interval (CI) 5.5-9.3, P < 0.0001) from 6.8 to 26.5/10(5) population. Similar trends were observed for New Zealand; 81% of admissions occurred in those aged <1 year and increased by 9.4%/year (95% CI 5.5-9.3, P < 0.0001) from 7.2 to 30.7/10(5) population. By contrast there were no significant changes in AG-related admission rates in the older patients and infective gastroenteritis admissions fell in both countries in those aged <1 year; Australia by 4.4%/year (95% CI 4.3-4.6, P < 0.0001) and in New Zealand by 5.8%/year (95% CI 5.4-6.2, P < 0.0001). CONCLUSION: We observed a fourfold increase in AG-related admission rates in two countries with known high rates of IgE-mediated food allergy/anaphylaxis. If confirmed by other studies, it will be of interest to determine if factors thought to contribute to the increase in IgE-mediated food allergy might also play a role in non-IgE-mediated gastroenterological food allergy syndromes
Morphological Instability of Steps During Crystal Growth from Solution Flow
It is shown that step moving to meet solution flow can be unstable against
lateral perturbations. The instability of long-wavelength perturbations occurs
at values of the solution flow intensity less than some critical value
depending on the step velocity. At given intensity of the solution flow, the
instability comes at the step velocity exceeding a critical velocity. Decay of
short-wavelength fluctuations is conditioned by the line tension of the step.
The step moving along the solution flow is laterally stable at all values of
the step velocity and the intensity of the solution flow. The overlapping
diffusion field of the neighbour steps suppresses the lateral instability but
it gives an instability of the step train against doubling of the period, i.e.
neighbouring steps are attracted. The equidistant train moving to meet the
solution flow is stable against the period variations.Comment: 22 pages, REVTEX (will be appeared in Journal of Crystal Growth
Nuclear structure of 178Hf related to the spin-16, 31-year isomer
The projected shell model is used to study the multi-quasiparticle and
collective excitations of 178Hf. With an axially symmetric basis, the spin-16
isomer at 2.4 MeV appears to be well separated in energy/spin space from other
configurations. However, projected energy surface calculations suggest that
178Hf has significant softness to axially asymmetric shapes, which can strongly
modify the level distribution. The implications for photodeexitation of the
isomer are discussed.Comment: 8 pages, 4 figure
Renal disease pathophysiology and treatment:contributions from the rat
The rat has classically been the species of choice for pharmacological studies and disease modeling, providing a source of high-quality physiological data on cardiovascular and renal pathophysiology over many decades. Recent developments in genome engineering now allow us to capitalize on the wealth of knowledge acquired over the last century. Here, we review rat models of hypertension, diabetic nephropathy, and acute and chronic kidney disease. These models have made important contributions to our understanding of renal diseases and have revealed key genes, such as Ace and P2rx7, involved in renal pathogenic processes. By targeting these genes of interest, researchers are gaining a better understanding of the etiology of renal pathologies, with the promised potential of slowing disease progression or even reversing the damage caused. Some, but not all, of these target genes have proved to be of clinical relevance. However, it is now possible to generate more sophisticated and appropriate disease models in the rat, which can recapitulate key aspects of human renal pathology. These advances will ultimately be used to identify new treatments and therapeutic targets of much greater clinical relevance
Early stages of ramified growth in quasi-two-dimensional electrochemical deposition
I have measured the early stages of the growth of branched metal aggregates
formed by electrochemical deposition in very thin layers. The growth rate of
spatial Fourier modes is described qualitatively by the results of a linear
stability analysis [D.P. Barkey, R.H. Muller, and C.W. Tobias, J. Electrochem.
Soc. {\bf 136}, 2207 (1989)]. The maximum growth rate is proportional to
where is the current through the electrochemical cell,
the electrolyte concentration, and . Differences
between my results and the theoretical predictions suggest that
electroconvection in the electrolyte has a large influence on the instability
leading to ramified growth.Comment: REVTeX, four ps figure
Growth Models and Models of Turbulence : A Stochastic Quantization Perspective
We consider a class of growth models and models of turbulence based on the
randomly stirred fluid. The similarity between the predictions of these models,
noted a decade earlier, is understood on the basis of a stochastic quantization
scheme.Comment: 3 page
Motion of Contact Line of a Crystal Over the Edge of Solid Mask in Epitaxial Lateral Overgrowth
Mathematical model that allows for direct tracking of the homoepitaxial
crystal growth out of the window etched in the solid, pre-deposited layer on
the substrate is described. The growth is governed by the normal (to the
crystal-vapor interface) flux from the vapor phase and by the interface
diffusion. The model accounts for possibly inhomogeneous energy of the mask
surface and for strong anisotropies of crystal-vapor interfacial energy and
kinetic mobility. Results demonstrate that the motion of the crystal-mask
contact line slows down abruptly as radius of curvature of the mask edge
approaches zero. Numerical procedure is suggested to overcome difficulties
associated with ill-posedness of the evolution problem for the interface with
strong energy anisotropy.
Keywords: Thin films, epitaxy, MOCVD, surface diffusion, interface dynamics,
contact lines, rough surfaces, wetting, regularization of ill-posed evolution
problems.Comment: 21 pages, 11 figures; to appear in Computational Materials Scienc
Growth Kinetics in a Phase Field Model with Continuous Symmetry
We discuss the static and kinetic properties of a Ginzburg-Landau spherically
symmetric model recently introduced (Phys. Rev. Lett. {\bf 75}, 2176,
(1995)) in order to generalize the so called Phase field model of Langer. The
Hamiltonian contains two invariant fields and bilinearly
coupled. The order parameter field evolves according to a non conserved
dynamics, whereas the diffusive field follows a conserved dynamics. In the
limit we obtain an exact solution, which displays an interesting
kinetic behavior characterized by three different growth regimes. In the early
regime the system displays normal scaling and the average domain size grows as
, in the intermediate regime one observes a finite wavevector
instability, which is related to the Mullins-Sekerka instability; finally, in
the late stage the structure function has a multiscaling behavior, while the
domain size grows as .Comment: 9 pages RevTeX, 9 figures included, files packed with uufiles to
appear on Phy. Rev.
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