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Triggering of cytotoxic T lymphocytes and NK cells via the Tp103 pathway is dependent on the expression of the T cell receptor/CD3 complex 总被引:2,自引:0,他引:2
B Fleischer E Sturm J E De Vries H Spits 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(4):1103-1107
The expression and function of the T cell activation molecule Tp103 on human cloned cytotoxic CD3+ and CD3- cells were studied. All in vitro growing CD3+ and CD3- clones expressed Tp103 regardless of their phenotype and the expression of a CD3-associated TCR complex. Whereas the CD2 pathway was functional in all these clones, only CD3-expressing clones could be triggered via Tp103 to kill target cells. In contrast, both CD2 and Tp103 pathways were suppressed after modulation of the TCR complex with anti-CD3 mAb. This indicates that the function of Tp103 but not of CD2 is dependent on the expression of a functional Ag receptor on cytotoxic T cells. Furthermore, modulation of the Ag receptor induces a state of unresponsiveness in cytotoxic T cells that cannot be attributed to just the removal of the CD3/TCR complex from the cell membrane. 相似文献
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G. Emons J. Nill R. Sturm O. Ortmann 《The Journal of steroid biochemistry and molecular biology》1992,42(8):831-839
Acute (0.5–4 h) treatment of estradiol (E)-primed female rat pituitary cells with progesterone (P) augments gonadotropin-releasing hormone (GnRH)-induced LH release, whereas chronic (48 h) P-treatment reduces pituitary responsiveness to the hypothalamic decapeptide. Dispersed E-primed (48 h, 1 nM) rat pituitary cells were cultured for 4 or 48 h in the presence of 100 nM P to assess the effects of the progestagen on GnRH receptors and on gonadotrope responsiveness to the decapeptide. P-treatment (4 h) significantly augmented GnRH-receptor concentrations (4.44 ± 0.6 fmol/106 cells) as compared to cells treated only with E (2.6 ± 0.5fmol/106 cells). Parallel significant changes in GnRH-induced LH secretion were observed. The acute increase in GnRH-receptor number was nearly maximal (180% of receptor number in cells treated with E alone) within 30 min of P addition. Chronic P-treatment (48 h) significantly reduced pituitary responsiveness to GnRH as compared to E-treatment. The GnRH-receptor concentrations (3.9 ± 0.6 fmol/106 cells), however, remained elevated above those in E-primed cells. GnRH-receptor affinity was not influenced by any of the different treatments. These results indicate that the acute facilitatory P-effect on GnRH-induced LH release is at least chronologically closely related to an increase in GnRH-receptor concentration. The chronic negative P-effect on pituitary responsiveness to GnRH, however, shows no relation to changes in available GnRH receptors. 相似文献
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Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
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The study of the orientation of single-stranded DNA in polyacrylamide gels in denaturing conditions has been undertaken by electric birefringence in order to determine the mechanism involved in the electrophoretic transport. The presence of an overshoot in the birefringence signal, when applying the electric field, and the study of the influences of the electric field and of the gel concentration on the dynamics show that a mechanism of reptation with elongation of the molecule occurs in polyacrylamide gels with low T values. Therefore it is suggested that the use of pulsed fields in sequencing electrophoresis is possible and can lead to a large increase of the length of the fragments that can be sequenced in one single run. 相似文献
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Phytohemagglutinin, the lectin of the common bean Phaseolus vulgaris, is a N-linked glycoprotein with one high-mannose-type and one xylose-containing oligosaccharide side chain per polypeptide. The high-mannose-type glycan is attached to Asn12 and the complex-type glycan to Asn60 [Sturm, A. & Chrispeels, M. J. (1986) Plant Physiol. 81, 320-322]. The structures of the oligosaccharides were elucidated from two glycopeptides obtained from the lectin by Pronase digestion, affinity chromatography on concanavalin-A--Sepharose and gel-filtration chromatography on a column of BioGel P-4. The N-linked glycan structures were investigated by 500-MHz 1H-NMR spectroscopy and were established to be: [formula; see text] 相似文献
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