1,721 research outputs found
Plasma homocysteine, folate and vitamin B(12) compared between rural Gambian and UK adults.
The disease risk indicator plasma total homocysteine (tHcy) is influenced by genetic and environmental factors, including folate and vitamin B(12) status. Little is known about the determinants of tHcy in rural West Africa. We explored the hypothesis that tHcy in rural Gambian adults might vary between the sexes and physiological groups, and/or with folate and vitamin B(12) status. Comparisons were made with a British national survey. Non-pregnant Gambian women (n 158) had tHcy concentrations (geometric mean 9.0 micromol/l) similar to those of non-pregnant UK women (n 449; 9.4 micromol/l), whereas pregnant Gambian women (n 12) had significantly lower values (6.2 micromol/l). Gambian men (n 22) had significantly higher values (14.7 micromol/l) than British men (n 354; 10.8 micromol/l). Gambian lactating women and British men and women exhibited significant inverse relationships between log(e)(tHcy) and folate status; however, only the British subjects exhibited significant inverse relationships between loge(tHcy) and vitamin B(12) status. In the British sample, and in Gambian lactating women, folate and vitamin B(12) status variations together accounted for 20-25 % of the variation in log(e)(tHcy). Within the UK, black-skinned adults had folate and tHcy levels similar to those of their white-skinned counterparts, but significantly higher vitamin B(12) values. We conclude that, whereas folate and vitamin B(12) status are similar between British and rural Gambian populations, tHcy is higher in Gambian men and lower in pregnant Gambian women, and that serum vitamin B(12) values appear to be higher in black-skinned than white-skinned British subjects. Possible reasons are discussed
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Efficient Data Compression Leads to Categorical Bias inPerception and Perceptual Memory
Efficient data compression is essential for capacity-limited sys-tems, such as biological memory. We hypothesize that the needfor efficient data compression shapes biological perception andperceptual memory in many of the same ways that it shapesengineered systems. If true, then the tools that engineers useto analyze and design systems, namely rate-distortion theory(RDT), can profitably be used to understand perception andmemory. To date, researchers have used deep neural networksto approximately implement RDT in high-dimensional spaces,but these implementations have been limited to tasks in whichthe sole goal is compression with respect to reconstruction er-ror. Here, we introduce a new deep neural network architecturethat approximately implements RDT in a task-general manner.An important property of our architecture is that it is trainedâend-to-endâ, operating on raw perceptual input (e.g., pixels)rather than an intermediate level of abstraction, as is the casewith most psychological models. We demonstrate that ourframework can mimick categorical biases in perception andperceptual memory in several ways, and thus generates spe-cific hypotheses that can be tested empirically in future work
The effect of heterogeneity on invasion in spatial epidemics: from theory to experimental evidence in a model system
Heterogeneity in host populations is an important factor affecting the ability of a pathogen to invade, yet the quantitative investigation of its effects on epidemic spread is still an open problem. In this paper, we test recent theoretical results, which extend the established âpercolation paradigmâ to the spread of a pathogen in discrete heterogeneous host populations. In particular, we test the hypothesis that the probability of epidemic invasion decreases when host heterogeneity is increased. We use replicated experimental microcosms, in which the ubiquitous pathogenic fungus Rhizoctonia solani grows through a population of discrete nutrient sites on a lattice, with nutrient sites representing hosts. The degree of host heterogeneity within different populations is adjusted by changing the proportion and the nutrient concentration of nutrient sites. The experimental data are analysed via Bayesian inference methods, estimating pathogen transmission parameters for each individual population. We find a significant, negative correlation between heterogeneity and the probability of pathogen invasion, thereby validating the theory. The value of the correlation is also in remarkably good agreement with the theoretical predictions. We briefly discuss how our results can be exploited in the design and implementation of disease control strategies
Modeling human intuitions about liquid flow with particle-based simulation
Humans can easily describe, imagine, and, crucially, predict a wide variety
of behaviors of liquids--splashing, squirting, gushing, sloshing, soaking,
dripping, draining, trickling, pooling, and pouring--despite tremendous
variability in their material and dynamical properties. Here we propose and
test a computational model of how people perceive and predict these liquid
dynamics, based on coarse approximate simulations of fluids as collections of
interacting particles. Our model is analogous to a "game engine in the head",
drawing on techniques for interactive simulations (as in video games) that
optimize for efficiency and natural appearance rather than physical accuracy.
In two behavioral experiments, we found that the model accurately captured
people's predictions about how liquids flow among complex solid obstacles, and
was significantly better than two alternatives based on simple heuristics and
deep neural networks. Our model was also able to explain how people's
predictions varied as a function of the liquids' properties (e.g., viscosity
and stickiness). Together, the model and empirical results extend the recent
proposal that human physical scene understanding for the dynamics of rigid,
solid objects can be supported by approximate probabilistic simulation, to the
more complex and unexplored domain of fluid dynamics.Comment: Under review at PLOS Computational Biolog
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Structure, stability, and reorganization of 0.5 L0 topography in block copolymer thin films
The structure, stability, and reorganization of lamella-forming block copolymer thin film surface topography (âislandsâ and âholesâ) were studied under boundary conditions driving the formation of 0.5 L0 thick structures at short thermal annealing times. Self-consistent field theory predicts that the presence of one perfectly neutral surface renders 0.5 L0 topography thermodynamically stable relative to 1 L0 thick features, in agreement with previous experimental observations. The calculated through-film structures match cross-sectional scanning electron micrographs, collectively demonstrating the pinning of edge dislocations at the neutral surface. Remarkably, near-neutral surface compositions exhibit 0.5 L0 topography metastability upon extended thermal treatment, slowly transitioning to 1 L0 islands or holes as evidenced by optical and atomic force microscopy. Surface restructuring is rationalized by invoking commensurability effects imposed by slightly preferential surfaces. The results described herein clarify the impact of interfacial interactions on block copolymer self-assembly and solidify an understanding of 0.5 L0 topography, which is frequently used to determine neutral surface compositions of considerable importance to contemporary technological applications
Casein kinase iδ mutations in familial migraine and advanced sleep phase.
Migraine is a common disabling disorder with a significant genetic component, characterized by severe headache and often accompanied by nausea, vomiting, and light sensitivity. We identified two families, each with a distinct missense mutation in the gene encoding casein kinase Iδ (CKIδ), in which the mutation cosegregated with both the presence of migraine and advanced sleep phase. The resulting alterations (T44A and H46R) occurred in the conserved catalytic domain of CKIδ, where they caused reduced enzyme activity. Mice engineered to carry the CKIδ-T44A allele were more sensitive to pain after treatment with the migraine trigger nitroglycerin. CKIδ-T44A mice also exhibited a reduced threshold for cortical spreading depression (believed to be the physiological analog of migraine aura) and greater arterial dilation during cortical spreading depression. Astrocytes from CKIδ-T44A mice showed increased spontaneous and evoked calcium signaling. These genetic, cellular, physiological, and behavioral analyses suggest that decreases in CKIδ activity can contribute to the pathogenesis of migraine
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Anhydride copolymer top coats for orientation control of thin film block copolymers
The concepts described herein involve the use of random copolymer top coats that can be spin coated onto block copolymer thin films and used to control the interfacial energy of the top coat-block copolymer interface. The top coats are soluble in aqueous weak base and can change surface energy once they are deposited onto the block copolymer thin film. The use of self-assembled block copolymers to produce advanced lithographic patterns relies on their orientation control in thin films. Top coats potentially allow for the facile orientation control of block copolymers which would otherwise be quite challenging.Board of Regents, University of Texas Syste
Vascular endothelial growth factor-A165b restores normal glomerular water permeability in a diphtheria-toxin mouse model of glomerular injury
BACKGROUND/AIMS:Genetic cell ablation using the human diphtheria toxin receptor (hDTR) is a new strategy used for analysing cellular function. Diphtheria toxin (DT) is a cytotoxic protein that leaves mouse cells relatively unaffected, but upon binding to hDTR it ultimately leads to cell death. We used a podocyte-specific hDTR expressing (Pod-DTR) mouse to assess the anti-permeability and cyto-protective effects of the splice isoform vascular endothelial growth factor (VEGF-A165b).
METHODS:The Pod-DTR mouse was crossed with a mouse that over-expressed VEGF-A165b specifically in the podocytes (Neph-VEGF-A165b). Wild type (WT), Pod-DTR, Neph-VEGF-A165b and Pod-DTR X Neph-VEGF-A165b mice were treated with several doses of DT (1, 5, 100, and 1,000 ng/g bodyweight). Urine was collected and the glomerular water permeability (LpA/Vi) was measured ex vivo after 14 days. Structural analysis and podocyte marker expression were also assessed.
RESULTS: Pod-DTR mice developed an increased glomerular LpA/Vi 14 days after administration of DT (all doses), which was prevented when the mice over-expressed VEGF-A165b. No major structural abnormalities, podocyte ablation or albuminuria was observed in Pod-DTR mice, indicating this to be a mild model of podocyte disease. However, a change in expression and localisation of nephrin within the podocytes was observed, indicating disruption of the slit diaphragm in the Pod-DTR mice. This was prevented in the Pod-DTR X Neph-VEGF-A165b mice.
CONCLUSION: Although only a mild model of podocyte injury, over-expression of the anti-permeability VEGF-A165b isoform in the podocytes of Pod-DTR mice had a protective effect. Therefore, this study further highlights the therapeutic potential of VEGF-A165b in glomerular disease
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