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排序方式: 共有216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.
The catalytic bimodality of mammalian phosphoglycerate mutase 总被引:1,自引:0,他引:1
Rabbit muscle phosphoglycerate mutase, presumed to manifest an absolute cofactor requirement for activity, has been found to express catalysis (3 +/- 1% of optimum) in the absence of added D-glycerate-2,3-P2. Isotope experiments indicate that this catalysis proceeds through a binary phosphoryl enzyme-glycerate intermediate which dissociates into free enzyme and monophosphoglycerate. 32P-Labeled phosphoglycerate mutase is formed by reaction with either D-32P-glycerate-3-P or D-U32P-glycerate-2,3-P2. In each case, the acid lability and alkali stability of the covalent adduct, phosphoenzyme, is consistent with a phosphohistidyl residue having been formed within the active site. D-[U-14C]Glycerate reacts with phosphoenzyme to generate D-[U-14C]monophosphoglycerate which, in turn, can react further with phosphoenzyme to yield D-[U-14C]glycerate-2,3-P2. The pH profile for the cofactor-independent activity exhibits an optimum at 6.0 as opposed to 7.0 when D-glycerate-2,3-P2 is present in the reaction medium. Bisubstrate kinetics (pH 7.0, 23 degrees C) with D-glycerate-3-P concentration as the variable, yields a family of reciprocal plots which is in accord with a modified ping-pong mechanism when D-glycerate-2,3-P2 concentrations are greater than 10(-1) Km (where Km = 0.33 microM). Progressively diminishing concentrations (much less than Km) of D-glycerate-2,3-P2 produce curvilinear reciprocal plots that approach linearity as a limit in accordance with single substrate kinetics. 相似文献
4.
5.
M Kraus-Filarska J Ma?olepszy R Jankowska W Kope? M Stankiewicz 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1990,45(29-31):605-607
The study included 20 patients (8 males and 12 females) with non-atopic bronchial asthma treated with attenuated vaccines. Circulating immune complexes were assayed with two methods prior to and after the treatment of each patient. No increase in serum circulating immune complexes was produced after the treatment. Clinical improvement was noted in 75% of treated patients. Circulating immune complexes were detected in the blood serum of three patients treated without an effect. 相似文献
6.
M Stankiewicz G Sokolska A Pilarczyk D Sadowska E L Jeska 《The Journal of parasitology》1989,75(4):647-649
Very little is known about the role played by complement in vivo during Trichinella spiralis infections, although previous reports indicate that it binds readily to the surfaces of muscle stages of the parasite in vitro. In order to study the binding of complement to muscle-stage larvae in vivo, larvae were recovered from BALB-c inbred, NFR/N inbred, and Swiss white outbred mice from 20 to 95 days postinfection. The presence of C3 was examined by direct immunofluorescence and leucocyte- and erythrocyte-adherence tests. Complement was found on a few larvae from the outbred strain and only rarely on larvae from the 2 inbred strains. Histological sections prepared from inbred strains and used in immunofluorescence tests to study in situ complement activation and binding were negative. Larvae from all 3 mouse strains bound complement 100% of the time when it was added to the worms in vitro. The results indicate that extrapolation from in vitro to in vivo activation and binding of complement to T. spiralis larvae may not be valid. 相似文献
7.
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
8.
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
9.
The fungicide oxafun decreased the production of antibiotic substances active against Phoma betae, by Bacillus subtillis. This was confirmed by reduced effectiveness of antibiotic substances against Phoma infection in micropot experiment. Besides, the bacterial metabolites effected cell membrane permeability of mycelium and resulted in some relationships of fungicide and antibiotic substances. 相似文献
10.