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排序方式: 共有688条查询结果,搜索用时 31 毫秒
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Repression of the Escherichia coli modABCD (molybdate transport) operon by ModE. 总被引:5,自引:1,他引:4
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A M Grunden R M Ray J K Rosentel F G Healy K T Shanmugam 《Journal of bacteriology》1996,178(3):735-744
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Ovine trophoblast protein-1 (oTP-1), a protein secreted by the sheep conceptus immediately prior to implantation has sequence homology with alpha interferon. We have previously shown that, in parallel with human alpha interferon (IFN), oTP-1 reduces the release of prostaglandins (PG) E and F2 alpha from cultured ovine endometrial cells. Here we have examined the time and dose dependence of these actions and the possible site of action of the peptides. The concentrations of oTP-1 and IFN required for 50% inhibition of PGE release were 92 pg/ml and 0.88 pg/ml and for PGF2 alpha release, 165 pg/ml and 1.12 pg/ml respectively. Significant effects on PG release were not measured before 12 h after addition of peptide to culture dishes. Following removal of the peptides, the cells released less PGs for a further 18 h but then recovered. A large increase in PG synthesis and release occurred from cells cultured with added serum or arachidonic acid (AA) and an interactive effect was demonstrated between them, AA having a greater stimulatory effect on PG released in the presence of serum. However, in all cases oTP-1 and IFN continued to attenuate prostaglandin release. We conclude that the IFNs act directly or indirectly on the prostaglandin synthase enzyme. 相似文献
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A study of functionally active amino acids involved in the interaction of HLA-A2 or HLA-A3 molecules with cytolytic T lymphocytes 总被引:3,自引:0,他引:3
F Healy J Sire E Gomard H Yssel B Jordan J P Levy 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(7):2487-2496
A large series of HLA-A2/HLA-A3 recombinant genes were generated by using the in vivo recombination technique. These genes have each been modified in the last two-thirds of the third exon such that one or several HLA-A2-specific substitutions have been made in the HLA-A3 gene and vice versa. The recombinant genes were transfected into the murine cell line P815 and the transfectants were used as targets for a series of 20 human CTL lines or clones specific for HLA-A2 or HLA-A3, or restricted by HLA-A2 and specific for influenza A. Several patterns of anti-HLA-A2, anti-HLA-A3, and HLA-A2-restricted anti-influenza CTL activity were observed and when uncloned cell lines were studied, a progressive selection of some clones with a similar pattern of activity was regularly found. From the comparison of these different patterns the following conclusions can be drawn: 1) In most but not all cases both domains of the class I molecule were essential for CTL recognition, but residue 152 was critically important for the majority of CTL tested; 2) amino acids 114/116 were also critical in most cases, and their position close to amino acid 152 in the tertiary structure of the molecule may have some functional significance; and 3) amino acid 161, although highly conserved, plays an unexpected but very important role in CTL function. 相似文献
6.
Molecular Analysis of the P-M Gonadal Dysgenesis Cline in Eastern Australian Drosophila Melanogaster
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The latitudinal cline in P-M gonadal dysgenesis potential in eastern Australia has been shown to comprise three regions which are, from north to south respectively, P, Q, and M, with the P-to-Q and Q-to-M transitions occurring over relatively short distances. The P element complements of 30 lines from different regions of the cline were determined by molecular techniques. The total amount of P element-hybridizing DNA was high in all lines, and it did not correlate in any obvious way with the P-M phenotypes of individual lines. The number of potentially full-sized P elements per genome was high in lines from the P regions, but variable or low among lines from the Q and M regions, and thus declined overall from north to south. A particular P element deletion-derivative, the KP element, occurred in all the tested lines. The number of KP elements was low in lines from the P region, much higher in lines from the Q region, and highest among lines from the M region, thus forming a cline reciprocal to that of the full-sized P elements. Another transposable element, hobo, which has been described as causing dysgenic traits similar to those of P-M hybrid dysgenesis, was shown to be present in all lines and to vary among them in number, but not in any latitudinal pattern. The P-M cline in gonadal dysgenesis potential can be inferred to be based on underlying clinal patterns of genomic P element complements. P activity of a line was positively correlated with the number of full-sized P elements in the line, and negatively correlated with the number of KP elements. Among Q and M lines, regulatory ability was not correlated with numbers of KP elements. 相似文献
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We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
10.
Oligochaeta in Spartina stems: the microdistribution of Enchytraeidae and Tubificidae in a salt marsh,Sapelo Island,USA 总被引:1,自引:1,他引:0
The distribution and abundance of Enchytraeidae and Tubificidae in and around Spartina alterniflora plants in a tidal salt marsh on Sapelo Island, Georgia, USA were studied using two different sampling techniques: wet funnel extraction and stem dissection. At least 80% of all worms inhabited leaf sheaths at the bases of S. alterniflora plants, and densities were low in sediment, root and surface debris samples. Oligochaete densities were dependent on the position within the marsh, the height on stems and the stage of sheath decay. Six predominant species were identified and included Marionina appendiculata, Marionina spartinae, Marionina waltersi, Marionina paludis, and Monopylephorus parvus. Individual species were distributed differently on stems and enchytraeids were more common than tubificids on standing-dead and further up S. alterniflora stems. Estimates of oligochaete densities in salt marsh habitats are increased dramatically when the numbers of worms on stems are considered. Possible advantages of the stem microhabitat are discussed in relation to the biology and ecology of oligochaetes. 相似文献