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排序方式: 共有169条查询结果,搜索用时 15 毫秒
1.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献2.
3.
A rapid method is described for the analysis of mixtures of short-chain acyl coenzyme A thioesters by reversed-phase ion-pair chromatography on LiChrosorb RP-8 and μBondapak C18 columns. The technique is applicable to separation of CoASH, acetyl-CoA propionyl-CoA, and 3-hydroxy-3-methylglutaryl-CoA, as well as dicarboxylic acids and several nucleotides commonly used as cofactors for biosynthetic reactions. The method was utilized on a preparative scale for purification of 3-hydroxy-3-ethylglutaryl-CoA from CoASH and 3-hydroxy-3-ethylglutaric acid. The counterion employed was tetrabutylammonium (phosphate), pH 5.5, in various methanol:water mixtures. Elution profiles and retention values of compounds were influenced by the concentration of counterion and mass of injected sample. Tetrabutylammonium ions could be removed from effluent by ionexchange chromatography on Amberlite IR-120 resin. 相似文献
4.
5.
This paper describes the nature and titre of juvenile hormone at different developmental stages of the Colorado potato beetle, Leptinotarsa decemlineata Say, determined by a selective mass-spectroscopic detection technique, High levels of juvenile hormone III were observed in long-day beetles, whereas low titres occurred in pre-diapause and diapause adults. The level of juvenile hormone III in larvae was low compared with reproductive adults, whereas hardly any juvenile hormone could be detected in pupae. We were not able to detect juvenile hormones I or II. The results agree well with previously reported data using the Galleria bioassay. 相似文献
6.
This study reports the first cases of intersex (abnormal development of both male and female reproductive tissues in a gonad) paddlefish Polyodon spathula, an Acipenseriform species of large rivers in the central U.S. and in aquaculture worldwide. Despite a large, multi-decadal data set in Oklahoma, Montana, and North Dakota, intersex development was not observed until 2019, when two individuals were harvested from the Grand Lake/Neosho River stock in Oklahoma. This suggests that intersex development in mid-water, zooplanktivorous paddlefish is rarer than in bottom-dwelling sturgeons for which intersex development is regularly observed. Although contaminants are implicated in causing intersex development in other Acipenseriformes, more investigation is needed. 相似文献
7.
Abstract
Integration of habitat heterogeneity into spatially realistic metapopulation approaches reveals the potential for key cross-scale
interactions. Broad-scale environmental gradients and land-use practices can create autocorrelation of habitat quality of
suitable patches at intermediate spatial scales. Patch occupancy then depends not only on habitat quality at the patch scale
but also on feedbacks from surrounding neighborhoods of autocorrelated patches. Metapopulation dynamics emerge from how demographic
and dispersal processes interact with relevant habitat heterogeneity. We provide an empirical example from a metapopulation
of round-tailed muskrats (Neofiber
alleni) in which habitat quality of suitable patches was spatially autocorrelated most strongly within 1,000 m, which was within
the expected dispersal range of the species. After controlling for factors typically considered in metapopulation studies—patch
size, local patch quality, patch connectivity—we use a cross-variogram analysis to demonstrate that patch occupancy by muskrats
was correlated with habitat quality across scales ≤1,171 m. We also discuss general consequences of spatial heterogeneity
of habitat quality for metapopulations related to potential cross-scale interactions. We focus on spatially correlated extinctions
and metapopulation persistence, hierarchical scaling of source–sink dynamics, and dispersal decisions by individuals in relation
to information constraints. 相似文献
8.
Luana Leandro Gois Sanjay Mehta Maria Zilma Andrade Rodrigues Robert T Schooley Roberto Badaró Maria Fernanda Rios Grassi 《Memórias do Instituto Oswaldo Cruz》2014,109(1):9-14
The effects of human immunodeficiency virus (HIV) on the immune response in patients
with cutaneous leishmaniasis have not yet been fully delineated. This study
quantified and evaluated the function of memory T-cell subsets in response to soluble
Leishmania antigens (SLA) from patients coinfected with HIV and
Leishmania with tegumentary leishmaniasis (TL). Eight TL/HIV
coinfected subjects and 10 HIV seronegative subjects with TL were evaluated. The
proliferative response of CD4+and CD8+T-cells and naïve, central memory (CM) and
effector memory (EM) CD4+T-cells in response to SLA were quantified using flow
cytometry. The median cell division indices for CD4+and CD8+T-cells of coinfected
patients in response to SLA were significantly lower than those in patients with
Leishmania monoinfection (p < 0.05). The proportions of CM and
EM CD4+T-cells in response to SLA were similar between the coinfected patients and
patients with Leishmania monoinfection. However, the median CM and
EM CD4+T-cell counts from coinfected patients were significantly lower (p < 0.05).
The reduction in the lymphoproliferative response to Leishmania
antigens coincides with the decrease in the absolute numbers of both EM and CM
CD4+T-cells in response to Leishmania antigens in patients
coinfected with HIV/Leishmania. 相似文献
9.
VLJ Whitehall TD Dumenil DM McKeone CE Bond ML Bettington RL Buttenshaw L Bowdler GW Montgomery LF Wockner BA Leggett 《Epigenetics》2014,9(11):1454-1460
The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features. 相似文献
10.
Finding habitat patches and directional connectivity 总被引:12,自引:0,他引:12
For animal species inhabiting patchy environments, the search behavior of individuals and the distance from which they can detect suitable habitat (perceptual range) are key determinants of the functional connectivity of landscapes. We examined the movement behavior and perceptual range of adult cactus bugs ( Chelinidea vittiger ), which are habitat specialists that feed and reproduce on Opuntia cactus. Movement pathways of walking individuals released into unsuitable matrix habitat (30–3000 m from Opuntia ) were highly directional. These results supported predictions of optimal search behavior from published simulation models. A release experiment within natural patch networks indicated that the perceptual range of C. vittiger depended on size of the target patch, matrix structure, and direction of the target patch relative to prevailing winds. A strong effect of wind direction on orientation behavior (and presumed perceptual range) was evident in a release experiment using 'artificial' patches of potted Opuntia . In these two experiments, individuals released 50–100 cm from Opuntia patches were more likely to orientate toward patches located upwind than to those located crosswind or downwind. A reexamination of the pathways of individuals walking in the matrix also revealed a strong bias for movement upwind. Such upwind movement by individuals, both within and outside of patch networks, suggests that C. vittiger uses olfaction to navigate and it complicates our ability to interpret search behavior and to estimate perceptual range. Current techniques for assessing perceptual range have limitations for olfactory-based species. Furthermore, we need to broaden our view of perceptual range and of patch and landscape connectivity. Perceptual range may be anisotropic and connectivity may be directional. An organism-based approach to spatial ecology requires that we consider the dominant senses used by species when navigating around patchy landscapes. 相似文献