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Gut microbial features can predict host phenotype response to protein deficiency.
Malnutrition remains a major health problem in low- and middle-income countries. During low protein intake, <0.67 g/kg/day, there is a loss of nitrogen (N2 ) balance, due to the unavailability of amino acid for metabolism and unbalanced protein catabolism results. However, there are individuals, who consume the same low protein intake, and preserve N2 balance for unknown reasons. A novel factor, the gut microbiota, may account for these N2 balance differences. To investigate this, we correlated gut microbial profiles with the growth of four murine strains (C57Bl6/J, CD-1, FVB, and NIH-Swiss) on protein deficient (PD) diet. Results show that a PD diet exerts a strain-dependent impact on growth and N2 balance as determined through analysis of urinary urea, ammonia and creatinine excretion. Bacterial alpha diversity was significantly (P < 0.05, FDR) lower across all strains on a PD diet compared to normal chow (NC). Multi-group analyses of the composition of microbiomes (ANCOM) revealed significantly differential microbial signatures between the four strains independent of diet. However, mice on a PD diet demonstrated differential enrichment of bacterial genera including, Allobaculum (C57Bl6/J), Parabacteroides (CD-1), Turicibacter (FVB), and Mucispirillum (NIH-Swiss) relative to NC. For instance, selective comparison of the CD-1 (gained weight) and C57Bl6/J (did not gain weight) strains on PD diet also demonstrated significant pathway enrichment of dihydroorodate dehydrogenase, rRNA methyltransferases, and RNA splicing ligase in the CD-1 strains compared to C57Bl6/J strains; which might account in their ability to retain growth despite a protein deficient diet. Taken together, these results suggest a potential relationship between the specific gut microbiota, N2 balance and animal response to malnutrition
The obese gut microbiome across the epidemiologic transition
Abstract The obesity epidemic has emerged over the past few decades and is thought to be a result of both genetic and environmental factors. A newly identified factor, the gut microbiota, which is a bacterial ecosystem residing within the gastrointestinal tract of humans, has now been implicated in the obesity epidemic. Importantly, this bacterial community is impacted by external environmental factors through a variety of undefined mechanisms. We focus this review on how the external environment may impact the gut microbiota by considering, the host’s geographic location ‘human geography’, and behavioral factors (diet and physical activity). Moreover, we explore the relationship between the gut microbiota and obesity with these external factors. And finally, we highlight here how an epidemiologic model can be utilized to elucidate causal relationships between the gut microbiota and external environment independently and collectively, and how this will help further define this important new factor in the obesity epidemic
HST Photometry for the Halo Stars in the Leo Elliptical NGC 3377
We have used the ACS camera on HST to obtain (V,I) photometry for 57,000
red-giant stars in the halo of the Leo elliptical NGC 3377. We use this sample
of stars to derive the metallicity distribution function (MDF) for its halo
field stars, and comment on its chemical evolution history compared with both
larger and smaller E galaxies. Our ACS/WFC field spans a radial range extending
from 4 to 18 kpc projected distance from the center of NGC 3377 and thus covers
a significant portion of this galaxy's halo. We find that the MDF is broad,
reaching a peak at [m/H] ~ -0.6. It may, in addition, have relatively few
stars more metal-rich than [m/H] = -0.3$, although interpretation of the
high-metallicity end of the MDF is limited by photometric completeness that
affects the detection of the reddest, most metal-rich stars. NGC 3377 appears
to have an enrichment history intermediate between those of normal dwarf
ellipticals and the much larger giants. As yet, we find no clear evidence that
the halo of NGC 3377 contains a significant population of ``young'' (< 3 Gy)
stars.Comment: 40 pages, 17 figure
The equilibrium condition in gravitational collapse and its application to a cosmological scenario
We discuss the equilibrium conditions of the gravitational collapse of a
spherically symmetric matter cloud. We analyze the spinor structure of a
general collapsing space-time and redefine the equilibrium conditions by using
Cartan scalars. We qualitatively investigate the equilibrium configuration of a
two-fluid system consisting of a dust-like fluid and a fluid with a negative
equation of state. We use our results to investigate certain cosmological
scenarios where dark energy can cluster inside the over-dense regions of dark
matter and together reaches a stable configuration. We compare the outcomes of
our work with existing work where the virialization technique is used to
stabilize the two-fluid system.Comment: 20 pages, 7 figure
Two populations among the metal-poor field RR Lyrae stars
We compute the spatial velocity components and the galactic orbital elements
for 209 metal-poor RRLyrae (ab) variable stars in the solar
neighborhood using proper motions, radial velocities, and photometric distances
available in the literature. We observe abrupt changes in the stellar spatial
and kinematical characteristics when the peculiar velocities relative to the
local standard of rest cross the threshold value,
\mbox{km s}. This provides evidence that the general population of
metal-poor RRLyrae stars is not uniform, and includes two spherical subsystems
occupying different volumes in the Galaxy. Based on the agreement between
typical parameters of corresponding subsystems of field RRLyrae stars and of
the globular clusters, studied by us earlier, we conclude that metal-poor stars
and globular clusters can be subdivided into two populations, but using
different criteria for stars and clusters. We suppose that field stars with
fast motion and clusters with redder horizontal branches constitute the
spheroidal subsystem of the accreted outer halo, with is approximately two
times larger in size than the first subsystem. It has absolutely no metallicity
gradients, most of its stars have eccentric orbits, many stars display
retrograde motion in the Galaxy, and their ages are comparatively low,
supporting the hypothesis that the objects in this subsystem have an
extragalactic origin.Comment: Accepted for A&A, 8 pages, 3 figure
G Protein Coupled Receptors in Embryonic Stem Cells: A Role for Gs-Alpha Signaling
Background: Identification of receptor mediated signaling pathways in embryonic stem (ES) cells is needed to facilitate strategies for cell replacement using ES cells. One large receptor family, largely uninvestigated in ES cells, is G protein coupled receptors (GPCRs). An important role for these receptors in embryonic development has been described, but little is known about GPCR expression in ES cells. Methodology/Principal Findings: We have examined the expression profile of 343 different GPCRs in mouse ES cells demonstrating for the first time that a large number of GPCRs are expressed in undifferentiated and differentiating ES cells, and in many cases at high levels. To begin to define a role for GPCR signaling in ES cells, the impact of activating Gs-alpha, one of the major alpha subunits that couples to GPCRs, was investigated. Gs-alpha activation resulted in larger embryoid bodies (EBs), due, in part, to increased cell proliferation and prevented the time-related decline in expression of transcription factors important for maintaining ES cell pluripotency. Significance/Conclusions: These studies suggest that Gs-alpha signaling contributes to ES cell proliferation and pluripotency and provide a framework for further investigation of GPCRs in ES cells
Structural model of a complex between the heterotrimeric G protein, Gsα, and tubulin
AbstractA number of studies have demonstrated interplay between the cytoskeleton and G protein signaling. Many of these studies have determined a specific interaction between tubulin, the building block of microtubules, and G proteins. The α subunits of some heterotrimeric G proteins, including Gsα, have been shown to interact strongly with tubulin. Binding of Gα to tubulin results in increased dynamicity of microtubules due to activation of GTPase of tubulin. Tubulin also activates Gsα via a direct transfer of GTP between these molecules. Structural insight into the interaction between tubulin and Gsα was required, and was determined, in this report, through biochemical and molecular docking techniques. Solid phase peptide arrays suggested that a portion of the amino terminus, α2–β4 (the region between switch II and switch III) and α3–β5 (just distal to the switch III region) domains of Gsα are important for interaction with tubulin. Molecular docking studies revealed the best-fit models based on the biochemical data, showing an interface between the two molecules that includes the adenylyl cyclase/Gβγ interaction regions of Gsα and the exchangeable nucleotide-binding site of tubulin. These structural models explain the ability of tubulin to facilitate GTP exchange on Gα and the ability of Gα to activate tubulin GTPase
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