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Calcium imaging of the entire muscle system of Hydra reveals extensive cellular multifunctionality
Hydra vulgaris is a Cnidarian species with a life cycle containing only a polyp stage, and with a simple body plan in which ectodermal and endodermal epitheliomuscular cells play many roles. These two epithelia generate motion of the polyp by exerting contractile force on myonemes. The function of this musculature was studied on a system scale using whole-animal calcium imaging to measure functional activity in all epitheliomuscular cells simultaneously. This approach maps the diversity of functional activation patterns underlying the behavior of Hydra, and reveals that individual epitheliomuscular cells participate in multiple patterns using at least two different types of calcium signaling that propagate by different mechanisms and at vastly different rates. These studies establish the functional basis for the epithelial muscle systems of Cnidaria, revealing new operational principles and deep evolutionary ties to mechanisms of contractile activity that exist elsewhere in Metazoa
Inhibition of EZH2 Promotes Human Embryonic Stem Cell Differentiation into Mesoderm by Reducing H3K27me3.
Mesoderm derived from human embryonic stem cells (hESCs) is a major source of the mesenchymal stem/stromal cells (MSCs) that can differentiate into osteoblasts and chondrocytes for tissue regeneration. While significant progress has been made in understanding of molecular mechanisms of hESC differentiation into mesodermal cells, little is known about epigenetic factors controlling hESC fate toward mesoderm and MSCs. Identifying potential epigenetic factors that control hESC differentiation will undoubtedly lead to advancements in regenerative medicine. Here, we conducted an epigenome-wide analysis of hESCs and MSCs and uncovered that EZH2 was enriched in hESCs and was downregulated significantly in MSCs. The specific EZH2 inhibitor GSK126 directed hESC differentiation toward mesoderm and generated more MSCs by reducing H3K27me3. Our results provide insights into epigenetic landscapes of hESCs and MSCs and suggest that inhibiting EZH2 promotes mesodermal differentiation of hESCs
Prompt Optical Observations of Gamma-ray Bursts
The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure
simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs).
A search for optical counterparts to six GRBs with localization errors of 1
square degree or better produced no detections. The earliest limiting
sensitivity is m(ROTSE) > 13.1 at 10.85 seconds (5 second exposure) after the
gamma-ray rise, and the best limit is m(ROTSE) > 16.0 at 62 minutes (897 second
exposure). These are the most stringent limits obtained for GRB optical
counterpart brightness in the first hour after the burst. Consideration of the
gamma-ray fluence and peak flux for these bursts and for GRB990123 indicates
that there is not a strong positive correlation between optical flux and
gamma-ray emission.Comment: 4 pages, 3 figures, submitted to ApJ Letter
Cardiovascular Damage in Alzheimer Disease: Autopsy Findings From the Bryan ADRC
Autopsy information on cardiovascular damage was investigated for pathologically confirmed Alzheimer disease (AD) patients (n = 84) and non-AD control patients (n = 60). The 51 relevant items were entered into a grade-of-membership model to describe vascular damage in AD. Five latent groups were identified āI: early-onset AD,ā āII: controls, cancer,ā āIII: controls, extensive atherosclerosis,ā āIV: late-onset AD, male,ā and āV: late-onset AD, female.ā Expectedly, Groups IV and V had elevated APOE Ļµ4 frequency. Unexpectedly, there was limited atherosclerosis and frequent myocardial valve and ventricular damage. The findings do not indicate a strong relationship between atherosclerosis and AD, although both are associated with the APOE Ļµ4. Instead, autopsy findings of extensive atherosclerosis were associated with possible, not probable or definite AD, and premature death. They are consistent with the hypothesis that brain hypoperfusion contributes to dementia, possibly to AD pathogenesis, and raise the possibility that the APOE allele Ļµ4 contributes directly to heart valve and myocardial damage
Correlation energies of inhomogeneous many-electron systems
We generalize the uniform-gas correlation energy formalism of Singwi, Tosi,
Land and Sjolander to the case of an arbitrary inhomogeneous many-particle
system. For jellium slabs of finite thickness with a self-consistent LDA
groundstate Kohn-Sham potential as input, our numerical results for the
correlation energy agree well with diffusion Monte Carlo results. For a helium
atom we also obtain a good correlation energy.Comment: 4 pages,1 figur
Relativistic Treatment of Hypernuclear Decay
We compute for the first time the decay width of lambda-hypernuclei in a
relativistic mean-field approximation to the Walecka model. Due to the small
mass difference between the lambda-hyperon and its decay products---a nucleon
and a pion---the mesonic component of the decay is strongly Pauli blocked in
the nuclear medium. Thus, the in-medium decay becomes dominated by the
non-mesonic, or two-body, component of the decay. For this mode, the
lambda-hyperon decays into a nucleon and a spacelike nuclear excitation. In
this work we concentrate exclusively on the pion-like modes. By relying on the
analytic structure of the nucleon and pion propagators, we express the
non-mesonic component of the decay in terms of the spin-longitudinal response
function. This response has been constrained from precise quasielastic (p,n)
measurements done at LAMPF. We compute the spin-longitudinal response in a
relativistic random-phase-approximation model that reproduces accurately the
quasielastic data. By doing so, we obtain hypernuclear decay widths that are
considerably smaller---by factors of two or three---relative to existing
nonrelativistic calculations.Comment: Revtex: 18 pages and 4 postscript figure
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