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排序方式: 共有643条查询结果,搜索用时 15 毫秒
1.
S Kafert S Luther I B?ll K Wagner A Ganser M Eder 《The Journal of biological chemistry》1999,274(46):33064-33071
To analyze the function of each subunit of the receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF), GMR, we previously generated a single-chain chimeric receptor by fusion of the extracellular and transmembrane domain from the alpha-subunit (alpha-GMR) to the intracellular part of the beta-subunit (beta-GMR) introducing an additional glutamate residue at the fusion site (alpha/beta-GMR). We demonstrated the capacity of alpha/beta-GMR to bind GM-CSF with low affinity and to induce GM-CSF-dependent activation of tyrosine kinase activity and proliferation in transfected Ba/F3 cells. To further compare the functions of wild type and chimeric receptors, we now report that this alpha/beta-GMR is sufficient to mediate morphological changes, expression of alpha(4)- and beta(1)-integrin receptor subunits, and serine-phosphorylation of Akt kinase. To analyze the function of the glutamate residue at the fusion region of alpha/beta-GMR various point mutants changing this amino acid and its position were expressed in Ba/F3 cells. None of these mutants was capable of supporting GM-CSF-dependent proliferation; however, when beta-GMR was coexpressed, GM-CSF mediated short and long term proliferation. Interestingly, some mutants but not alpha/beta-GMR can induce proliferation in the presence of an anti-alpha-GMR antibody. These data demonstrate the significance of a glutamate residue in the transmembrane region of alpha/beta-GMR for ligand-induced receptor activation. 相似文献
2.
Jerry F. Downhower Lawrence S. Blumer Luther Brown 《Evolution; international journal of organic evolution》1987,41(6):1386-1394
Seasonal variation in sexual and natural selection in male mottled sculpins (Cottus bairdi) can be evaluated by calculating selection differentials, which measure the magnitude of phenotypic change resulting from selection, and by calculating indices of the opportunity for selection, which indicate the potential for phenotypic selection in a given interval. Selection differentials are high at the beginning of the breeding season and decline throughout the breeding season. The magnitude and direction of selection differentials depend on when spawning occurs and are independent of the size or age of the females that spawn. Annual selection differentials due to differences in mating success (female choice) are nearly constant between years. Annual selection differentials associated with hatching success are variable. Opportunities for selection (I = fitness variance/[mean fitness]2) show clear seasonal patterns. They are highest at the beginning and at the end of the spawning season. However, this variation is dependent on the mean used to calculate I, and hence variation in I values does not indicate a significant change in the variance of male fitness. 相似文献
3.
Rat intestinal UDPgalactose: N-acetylglucosaminyl(beta 1----4)galactosyltransferase activity was studied as to its intestinal and villus-to-crypt distribution, and then purified and characterized. Rapid UDPgalactose hydrolysis was noted in the duodenum and jejunum; little to no breakdown was detected in the distal ileum, cecum and proximal colon. Product analysis suggested that UDPgalactose hydrolysis was due to nucleotide-sugar pyrophosphatase and galactose-1-phosphate phosphatase activities; ileum appeared to have little of the first activity and none of the latter. An aboral gradient of galactosyltransferase activity was noted, activity being 3-4-fold higher in the ileum, cecum and proximal colon. Total homogenate exogenous acceptor galactosyltransferase activities showed no villus-crypt differences but activity measured with intact isolated cells demonstrated higher activity with crypt cells; this was particularly evident in the ileum. Galactosyltransferase activity was purified from ileal-colonic mucosa. An over 4000-fold purification with 75 percent yield was achieved. Only one band of approx. 70-75 kDa was noted on sodium dodecyl sulfate polyacrylamide electrophoresis. As with other eukaryotic galactosyltransferase activities, there was an absolute requirement for Mn2+; the concentration required for half maximal activity was only 2.5 microM and higher concentrations did not inhibit. The Km for UDPgalactose was 30 microM. 相似文献
4.
A Stumpa B T?mová P Luther 《Journal of hygiene, epidemiology, microbiology, and immunology》1988,32(2):173-180
Ten strains of influenza A (H3N2) virus isolated from an outbreak in 1983, and ten strains isolated in 1985 from sporadic cases of infection were included in the study. For characterization of envelope antigens were used the polyclonal and monoclonal antibodies tested in the reaction of haemagglutinin inhibition, neuraminidase inhibition, and by lectin test. The strains but slightly different in the tests with polyclonal antibodies could clearly be classified to 3-4 groups using 5 monoclonal antibodies to H antigen of A/Bangkok 1/79 and A/Philippines 2/82 strains. Strains from the 1983 epidemics represent a more homogeneous group of which only one of ten strains failed to react with monoclonals of the strains A/Bangkok and A/Philippines. Strains from sporadic cases of infection in 1985, except for two strains, did not react at all with the monoclonal discriminating A/Bangkok and A/Philippines. The other strains could be classified to three groups, i.e. whether they agreed with 4, 2 or none of the A/Philippines H antigen epitopes. Alterations of neuraminidase are less apparent, and cannot be defined by means of normal immune sera. With the use of monoclonal antibodies the strains under study do not react any more with the strains of 1968-1973 influenza virus; yet the monoclonals to A/Texas/77 strain still do recognize one or two epitopes of the 1983-1985 strains. 相似文献
5.
6.
P Luther G E Klett S Weber H Pechmann K C Bergmann 《Journal of biological standardization》1983,11(2):115-121
Two methods for the detection of neuraminidase antibodies were compared. The lectin neuraminidase inhibition test (LNI-test) gave results comparable with those provided by the conventional neuraminidase inhibition test (NI-test). Reproducibility and repeatability were better with the LNI-test which used smaller amounts of materials, was less time consuming than the NI-test and was more sensitive. 相似文献
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9.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
10.
Cameron L. Rutt W. Justin Cooper Christian B. Andretti Thiago V. V. Costa Philip C Stouffer Claudeir F. Vargas David A. Luther Mario Cohn-Haft 《Diversity & distributions》2023,29(4):466-477