排序方式: 共有35条查询结果,搜索用时 296 毫秒
31.
Eva Bresson Tommy Seaborn Mélissa Côté Geneviève Cormier Pierre R Provost Bruno Piedboeuf Yves Tremblay 《Reproductive biology and endocrinology : RB&E》2010,8(1):2
Background
Accumulating evidences suggest that sex affects lung development. Indeed, a higher incidence of respiratory distress syndrome is observed in male compared to female preterm neonates at comparable developmental stage and experimental studies demonstrated an androgen-related delay in male lung maturation. However, the precise mechanisms underlying these deleterious effects of androgens in lung maturation are only partially understood. 相似文献32.
Emily H. Le Sage Sarah I. Duncan Travis Seaborn Jennifer Cundiff Leslie J. Rissler Erica J. Crespi 《Heredity》2021,126(5):790
Phenotypic variation among populations is thought to be generated from spatial heterogeneity in environments that exert selection pressures that overcome the effects of gene flow and genetic drift. Here, we tested for evidence of isolation by distance or by ecology (i.e., ecological adaptation) to generate variation in early life history traits and phenotypic plasticity among 13 wood frog populations spanning 1200 km and 7° latitude. We conducted a common garden experiment and related trait variation to an ecological gradient derived from an ecological niche model (ENM) validated to account for population density variation. Shorter larval periods, smaller body weight, and relative leg lengths were exhibited by populations with colder mean annual temperatures, greater precipitation, and less seasonality in precipitation and higher population density (high-suitability ENM values). After accounting for neutral genetic variation, the QST–FST analysis supported ecological selection as the key process generating population divergence. Further, the relationship between ecology and traits was dependent upon larval density. Specifically, high-suitability/high-density populations in the northern part of the range were better at coping with greater conspecific competition, evidenced by greater postmetamorphic survival and no difference in body weight when reared under stressful conditions of high larval density. Our results support that both climate and competition selection pressures drive clinal variation in larval and metamorphic traits in this species. Range-wide studies like this one are essential for accurate predictions of population’s responses to ongoing ecological change.Subject terms: Biogeography, Ecological modelling, Evolutionary ecology, Evolution 相似文献
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34.
Travis Seaborn Samantha S. Hauser Lauren Konrade Lisette P. Waits Caren S. Goldberg 《Ecology and evolution》2019,9(9):5063-5078
A critical decision in landscape genetic studies is whether to use individuals or populations as the sampling unit. This decision affects the time and cost of sampling and may affect ecological inference. We analyzed 334 Columbia spotted frogs at 8 microsatellite loci across 40 sites in northern Idaho to determine how inferences from landscape genetic analyses would vary with sampling design. At all sites, we compared a proportion available sampling scheme (PASS), in which all samples were used, to resampled datasets of 2–11 individuals. Additionally, we compared a population sampling scheme (PSS) to an individual sampling scheme (ISS) at 18 sites with sufficient sample size. We applied an information theoretic approach with both restricted maximum likelihood and maximum likelihood estimation to evaluate competing landscape resistance hypotheses. We found that PSS supported low‐density forest when restricted maximum likelihood was used, but a combination model of most variables when maximum likelihood was used. We also saw variations when AIC was used compared to BIC. ISS supported this model as well as additional models when testing hypotheses of land cover types that create the greatest resistance to gene flow for Columbia spotted frogs. Increased sampling density and study extent, seen by comparing PSS to PASS, showed a change in model support. As number of individuals increased, model support converged at 7–9 individuals for ISS to PSS. ISS may be useful to increase study extent and sampling density, but may lack power to provide strong support for the correct model with microsatellite datasets. Our results highlight the importance of additional research on sampling design effects on landscape genetics inference. 相似文献
35.
Effects of germanium and silicon on bone mineralization 总被引:1,自引:0,他引:1
The chemical properties of Ge are similar to Si. This study investigated whether Ge can substitute for, or is antagonistic
to, Si in bone formation. Sixty male weanling Sprague-Dawley rats were randomly assigned to treatment groups of 12 and 6 in
a 2×4 factorially arranged experiment. The independent variables were, per gram fresh diet, Si (as sodium metasilicate) at
0 or 25 μg and Ge (as sodium germanate) at 0, 5, 30 or 60 μg. Results confirmed that Ge does not enhance Si deprivation and
provided evidence that Ge apparently can replace Si in functions that influence bone composition. When Si was lacking in the
diet, calcium and magnesium concentrations of the femur were decreased; this was reversed by feeding either Ge and/or Si.
Similar effects were found for zinc, sodium, iron, manganese, and potassium of vertebra. There were some responses to Si deprivation
that Ge could not reverse: Ge did not increase femur copper, sodium, or phosphorus or decrease molybdenum of vertebra, effects
that were eveked by Si supplementation. Additionally, some findings suggested that 60 μg Ge/g diet could be a toxic intake
for the rat. On the other hand, some responses induced by Ge indicate that this element may be acting physiologically other
than as a substitute for Si. Germanium itself affected bone composition. Germanium supplementation decreased Si and molybdenum
in the femur and increased DNA in tibia. Regardless of the amount of Si fed, animals fed 30 μg Ge/g diet had increased tibial
DNA compared to animals fed 0 or 60 μg Ge; however, tibial DNA of animals fed 30 μg Ge was not statistically different from
those animals fed 5 μg Ge. Thus, Ge may be of nutritional importance. 相似文献