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21.
Danielle S. Bassett Nicholas F. Wymbs M. Puck Rombach Mason A. Porter Peter J. Mucha Scott T. Grafton 《PLoS computational biology》2013,9(9)
As a person learns a new skill, distinct synapses, brain regions, and circuits are engaged and change over time. In this paper, we develop methods to examine patterns of correlated activity across a large set of brain regions. Our goal is to identify properties that enable robust learning of a motor skill. We measure brain activity during motor sequencing and characterize network properties based on coherent activity between brain regions. Using recently developed algorithms to detect time-evolving communities, we find that the complex reconfiguration patterns of the brain''s putative functional modules that control learning can be described parsimoniously by the combined presence of a relatively stiff temporal core that is composed primarily of sensorimotor and visual regions whose connectivity changes little in time and a flexible temporal periphery that is composed primarily of multimodal association regions whose connectivity changes frequently. The separation between temporal core and periphery changes over the course of training and, importantly, is a good predictor of individual differences in learning success. The core of dynamically stiff regions exhibits dense connectivity, which is consistent with notions of core-periphery organization established previously in social networks. Our results demonstrate that core-periphery organization provides an insightful way to understand how putative functional modules are linked. This, in turn, enables the prediction of fundamental human capacities, including the production of complex goal-directed behavior. 相似文献
22.
Risk Factors for Late-Stage HIV Disease Presentation at Initial HIV Diagnosis in Durban,South Africa
Paul K. Drain Elena Losina Gary Parker Janet Giddy Douglas Ross Jeffrey N. Katz Sharon M. Coleman Laura M. Bogart Kenneth A. Freedberg Rochelle P. Walensky Ingrid V. Bassett 《PloS one》2013,8(1)
Background
After observing persistently low CD4 counts at initial HIV diagnosis in South Africa, we sought to determine risk factors for late-stage HIV disease presentation among adults.Methods
We surveyed adults prior to HIV testing at four outpatient clinics in Durban from August 2010 to November 2011. All HIV-infected adults were offered CD4 testing, and late-stage HIV disease was defined as a CD4 count <100 cells/mm3. We used multivariate regression models to determine the effects of sex, emotional health, social support, distance from clinic, employment, perceived barriers to receiving healthcare, and foregoing healthcare to use money for food, clothing, or housing (“competing needs to healthcare”) on presentation with late-stage HIV disease.Results
Among 3,669 adults screened, 830 were enrolled, newly-diagnosed with HIV and obtained a CD4 result. Among those, 279 (33.6%) presented with late-stage HIV disease. In multivariate analyses, participants who lived ≥5 kilometers from the test site [adjusted odds ratio (AOR) 2.8, 95% CI 1.7–4.7], reported competing needs to healthcare (AOR 1.7, 95% CI 1.2–2.4), were male (AOR 1.7, 95% CI 1.2–2.3), worked outside the home (AOR 1.5, 95% CI 1.1–2.1), perceived health service delivery barriers (AOR 1.5, 95% CI 1.1–2.1), and/or had poor emotional health (AOR 1.4, 95% CI 1.0–1.9) had higher odds of late-stage HIV disease presentation.Conclusions
Independent risk factors for late-stage HIV disease presentation were from diverse domains, including geographic, economic, demographic, social, and psychosocial. These findings can inform various interventions, such as mobile testing or financial assistance, to reduce the risk of presentation with late-stage HIV disease. 相似文献23.
24.
SA Carrasco 《New Zealand journal of zoology.》2013,40(1):32-45
This study combined morphological and morphometric information on egg clutches, egg capsules and paralarvae of two sympatric coastal octopuses from New Zealand waters, Octopus huttoni and Pinnoctopus cordiformis, to provide species-specific traits to identify their early life stages obtained from field surveys. Eggs of O. huttoni (2.5 mm length; 1 mm width) were entwined with one another forming strings that ranged from 11 to 25.8 mm in length. Eggs of P. cordiformis (6.4 mm length; 1.5 mm width) were significantly bigger than those of O. huttoni and were grouped in small clusters of about seven eggs. Paralarvae O. huttoni and P. cordiformis differed in hatching size (1.4 mm versus 3.1 mm mantle length), number of suckers per arm (four versus eight), number of lamellae per outer demibranch (five versus ten) and arrangements of chromatophores in the body surface (29 to 59 versus 91 to 179), respectively. The morphological traits described in hatchlings from the laboratory allowed comparisons with field-collected paralarvae, suggesting that such characters were reliable species-specific patterns to enable a consistent differentiation between the early life stages of these two sympatric species, even in the absence of the brooding female. 相似文献
25.
Yi Wang Dianne Edwards Michael Bassett Hong‐He Xu Jiafei Xiao Qing Jiang Xiaole Zhang 《Palaeontology》2013,56(4):679-683
Pinnatiramosus qianensis Geng, 1986, is a plant with a complex, extensive pinnate branching system and pitted tracheids, collected from marine Lower Silurian (Llandovery; c. 430 Ma) rocks in Guizhou Province, China. It challenges long‐held theories on the origin and early evolution of vascular plants in the Silurian and Devonian. However, there is a hypothesis that the fossils were not syngenetic with the entombing rock, but were the rooting systems of much younger plants, probably of Permian age. New sections and collections of P. qianensis have been subjected to detailed analyses, which indicate that P. qianensis belongs to an early Permian (c. 285 Ma) rooting system growing down into lower Silurian rocks. 相似文献
26.
Harriet Bunning Lee Bassett Christina Clowser James Rapkin Kim Jensen Clarissa M. House Catharine R. Archer John Hunt 《Ecology and evolution》2016,6(14):4711-4730
Sexual selection may cause dietary requirements for reproduction to diverge across the sexes and promote the evolution of different foraging strategies in males and females. However, our understanding of how the sexes regulate their nutrition and the effects that this has on sex‐specific fitness is limited. We quantified how protein (P) and carbohydrate (C) intakes affect reproductive traits in male (pheromone expression) and female (clutch size and gestation time) cockroaches (Nauphoeta cinerea). We then determined how the sexes regulate their intake of nutrients when restricted to a single diet and when given dietary choice and how this affected expression of these important reproductive traits. Pheromone levels that improve male attractiveness, female clutch size and gestation time all peaked at a high daily intake of P:C in a 1:8 ratio. This is surprising because female insects typically require more P than males to maximize reproduction. The relatively low P requirement of females may reflect the action of cockroach endosymbionts that help recycle stored nitrogen for protein synthesis. When constrained to a single diet, both sexes prioritized regulating their daily intake of P over C, although this prioritization was stronger in females than males. When given the choice between diets, both sexes actively regulated their intake of nutrients at a 1:4.8 P:C ratio. The P:C ratio did not overlap exactly with the intake of nutrients that optimized reproductive trait expression. Despite this, cockroaches of both sexes that were given dietary choice generally improved the mean and reduced the variance in all reproductive traits we measured relative to animals fed a single diet from the diet choice pair. This pattern was not as strong when compared to the single best diet in our geometric array, suggesting that the relationship between nutrient balancing and reproduction is complex in this species. 相似文献
27.
Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium. 相似文献
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A survey questionnaire regarding perceptions of risk and genetic susceptibility to Alzheimer's disease (AD) was completed by 518 offspring of AD cases from families with multiple affected, ascertained as part of a genetic linkage study of late onset AD. The questionnaire focused on respondents' perceptions of their own risk for AD as well as on the properties of real and hypothetical susceptibility tests, including error rates for false-positive and false-negative test results. Our findings showed that about 20% of the sample would refuse a susceptibility test with zero error rates, about 40% would accept tests with very high error rates in both directions, and the remainder would exercise some discrimination. Acceptance of high test error rates was significantly associated with male gender, low education, and high perceived lifetime risk of AD. In a previous paper related to this work, we showed that physicians caring for these families exercised much more discrimination in judging the acceptability of genetic tests they would offer to these same respondents. The findings show that there is a pressing need to educate the public, particularly those with relatives affected by a complex disease, to expect standards of accuracy for genetic tests comparable to those that prevail in other diagnostic and prognostic testing efforts in the broad field of clinical medicine. 相似文献