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排序方式: 共有110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.
Dobbins DE 《Mediators of inflammation》1992,1(4):241-246
Neurokinin A and B are putative inflammatory mediators. We assessed their ability to alter prenodal lymphatic resistance. Intralymphatic neurokinin A (3.0 x 10(-6), 3.0 x 10(-5) and 3.0 x 10(-4) mol l(-1)) significantly constricted lymphatics at the two highest doses. Preliminary experiments suggested that neurokinin B might dilate lymphatics. To test this, lymphatic pressure was increased by norepinephrine (3.1 x 10(-6) mol l(-1)). Neurokinin B (2.7 x 10(-4) mol l(-1)) was then infused intralymphatically during norepinephrine infusion. Norepinephrine increased perfusion pressure from 5.6 +/- 0.6 mmHg to 12.1 +/- 1.4 mmHg. Subsequent infusion of neurokinin B significantly decreased lymphatic perfusion pressure from 11.9 +/- 1.3 mmHg to 9.9 +/- 1.1 mmHg. These data indicate that neurokinin A and B can alter lymphatic resistance and are consistent with the hypothesis that lymph vessel function may be subject to modulation by neurokinins. 相似文献
3.
4.
Substrate and inhibitor specificity of anion exchangers on the brush border membrane of rabbit ileum
Roy G. Knickelbein Peter S. Aronson John W. Dobbins 《The Journal of membrane biology》1985,88(2):199-204
Summary In previous studies we have found that several anions can be transported by an exchange process in rabbit ileal brush border membranes. We demonstrated exchanges of Cl for OH or HCO3, SO4 for OH, oxalate for OH, and oxalate for Cl. The purpose of these studies was to determine the number of distinct carriers mediating these exchanges. We utilized substrate and inhibitor specificity studies to distinguish between different anion exchange transporters. We conclude that SO4OH and oxalate: OH exchange occur on the same carrier because: (i) pH-gradient stimulated transport of both14C-oxalate and35SO4 were equally sensitive tocis-inhibition by unlabeled SO4 or oxalate; and (ii) both were inhibited equally by K. We conclude that oxalate: OH and oxalate: Cl exchanges occur on different carriers because: (i) Cl or SO4 caused unequalcis-inhibition of these two exchanges; and (ii) as compared to oxalate: Cl exchange, oxalate: OH exchange was more sensitive to inhibition by probenecid and K and less sensitive to inhibition by bumetanide. Finally, we conclude that oxalate: Cl exchange and ClHCO3 exchange occur on different carriers because: (i) ClHCO3 exchange was almost completely insensitive tocis-inhibition by oxalate; and (ii) oxalate: Cl exchange was more sensitive to inhibition by DIDS and bumetanide than ClHCO3 exchange. Thus we have found that there are at least three separate anion exchangers on rabbit ileal brush border: (i) a ClHCO3 exchanger; (ii) a SO4OH exchanger, which also transports oxalate; and (iii) an oxalate: Cl exchanger. 相似文献
5.
6.
alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine
proteinase inhibitor superfamily, has a primary role in controlling
neutrophil elastase activity within the mammalian circulation. Several
studies have indicated that the reactive center region of alpha 1-PI, the
amino acid sequence of which is critical to recognition of and binding to
target proteinases, is highly divergent within and among species. This
appears to be a consequence of accelerated rates of evolution that may have
been driven by positive Darwinian selection. In order to examine this and
other features of alpha 1-PI evolution in more detail, we have isolated and
sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus
saxicola and Mus minutoides and have compared these with a number of other
mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent
of nonsynonymous substitution is generally high throughout the alpha 1-PI
mRNA molecule, indicating greater overall rates of amino acid substitution.
Within and among mouse species, the 5'-half of the mRNA, but not the
3'-half, has been homogenized by concerted evolution. Finally, the reactive
center is under diversifying or positive Darwinian selection in murid
rodents (rats, mice) and guinea pigs yet is under purifying selection in
primates and artiodactyls. The significance of these findings to alpha 1-PI
function and the possible selective forces driving evolution of serpins in
general are discussed.
相似文献
7.
Mitochondrial DNA polymorphisms in subterranean mole-rats of the Spalax ehrenbergi superspecies in Israel, and its peripheral isolates 总被引:1,自引:0,他引:1
Nevo E; Honeycutt RL; Yonekawa H; Nelson K; Hanzawa N 《Molecular biology and evolution》1993,10(3):590-604
Patterns of mitochondrial DNA (mtDNA) variation were examined in 133
mole-rats constituting all four chromosomal species (2n = 52, 2n = 54, 2n =
58, and 2n = 60) of the Spalax ehrenbergi superspecies in Israel, as well
as the peripheral isolates of 2n = 60. In the main range of the complex, a
total of 28 mtDNA haplotypes were found in 64 mole-rats, with most
haplotypes being unique to either a single chromosomal species or
population. mtDNA divergence increased from low to high diploid number in a
north-to-south direction in Israel. Overall levels of mtDNA diversity were
unexpectedly the highest in the 2n = 60, the youngest species of the
complex. The mtDNA haplotypes can be separated into two major groups, 2n =
52-54 and 2n = 58-60, and a phylogenetic analysis for each group revealed
evidence of a few haplotypes not sorted by diploid number. The overall
patterns of mtDNA divergence seen within and among the four chromosomal
species are consistent with the parapatric mode of speciation as suggested
from previous studies of allozyme and DNA hybridization. In a separate data
set the patterns of mtDNA variation were examined across the main
geographic range and across peripheral semi-isolates and isolates of the 2n
= 60 chromosomal species. Fifteen haplotypes were found in 69 mole-rats.
High levels of mtDNA diversity characterized the main range, semi-isolated,
and even some desert isolated populations. The peripheral isolates contain
much mtDNA diversity, including novel haplotypes.
相似文献
8.
The working precisions of the 5.0-ml-capacity Cornwall, the LKB 2075, and the Micromedic model 25000 dispensers were compared, and the bias of the LKB dispenser was contrasted with that of the Micromedic dispenser. Three technologists used six Cornwall dispensers, three LKB units with four different pumps, and three Micromedic units with six different pumps to dispense (in 1.0-ml amounts) sucrose solution adjusted to match the normal viscosity of serum. Under these conditions, the LKB dispenser was approximately 30% more precise than the Micromedic dispenser, which was approximately four times as precise as the Cornwall dispenser. Although the left pump site of the Micromedic was slightly more precise than the LKB, overall the Micromedic was less precise than the LKB. Moreover, the LKB was easier to use than the Micromedic. 相似文献
9.
Reza?Yousefi-NooraieEmail author Maureen?Dobbins Alexandra?Marin Robert?Hanneman Lynne?Lohfeld 《Implementation science : IS》2016,10(1):166
Background
We studied the evolution of information-seeking networks over a 2-year period during which an organization-wide intervention was implemented to promote evidence-informed decision-making (EIDM) in three public health units in Ontario, Canada. We tested whether engagement of staff in the intervention and their EIDM behavior were associated with being chosen as information source and how the trend of inter-divisional communications and the dominance of experts evolved over time.Methods
Local managers at each health unit selected a group of staff to get engage in Knowledge Broker-led workshops and development of evidence summaries to address local public health problems. The staff were invited to answer three online surveys (at baseline and two annual follow-ups) including name generator questions eliciting the list of the staff they would turn to for help integrating research evidence into practice. We used stochastic actor-oriented modeling to study the evolution of networks. We tested the effect of engagement in the intervention, EIDM behavior scores, organizational divisions, and structural dynamics of social networks on the tendency of staff to select information sources, and the change in its trend between year 1 and year 2 of follow-up.Results
In all the three health units, and especially in the two units with higher levels of engagement in the intervention, the network evolved towards a more centralized structure, with an increasing significance of already central staff. The staff showed greater tendencies to seek information from peers with higher EIDM behavior scores. In the public health unit that had highest engagement and stronger leadership support, the engaged staff became more central. In all public health units, the engaged staff showed an increasing tendency towards forming clusters. The staff in the three public health units showed a tendency towards limiting their connections within their divisions.Conclusions
The longitudinal analysis provided us with a means to study the microstructural changes in public health units, clues to the sustainability of the implementation. The hierarchical transformation of networks towards experts and formation of clusters among staff who were engaged in the intervention show how implementing organizational interventions to promote EIDM may affect the knowledge flow and distribution in health care communities, which may lead to unanticipated consequences.10.
Priming is a nonconscious form of memory that involves a change in a person's ability to identify, produce or classify an item as a result of a previous encounter with that item or a related item. One important question relates to the specificity of priming - the extent to which priming reflects the influence of abstract representations or the retention of specific features of a previous episode. Cognitive neuroscience analyses provide evidence for three types of specificity: stimulus, associative and response. We consider empirical, methodological and conceptual issues that relate to each type of specificity, and suggest a theoretical perspective to help in guiding future research. 相似文献