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901.
The role of asialo GM1+ (ASGM1+) cells and exogenous IL-2 in the age-related decline in allospecific CTL activity was evaluated. Primary CTL were generated in mixed leukocyte culture (MLC) [BALB/cANN (H-2d) anti C57BL/6N (H-2b)] and tested for allospecific lytic activity against the EL-4 (H-2b) cell culture line, and for non-MHC-restricted activity against WEHI-3 (H-2d) and YAC-1 (H-2a). Cultures included responder cell populations which had been treated with antibody to ASGM1 plus complement or complement alone, and irradiated stimulator cells, in the presence or absence of rIL-2 or crude IL-2-containing supernatants. The amount of rIL-2 used to accommodate the age-related decline in IL-2 production was determined empirically to be 500 U by assessing IL-2 production in MLCs containing responder cells from young versus old animals. rIL-2 appeared to restore the allospecific CTL activity generated by spleen cells of old mice to the level of that of young. However, treatment with anti-ASGM1 antibody revealed that this restoration was due to an effect of the IL-2 on ASGM1+ cells. The allospecific target cells, EL-4, were not sensitive to lymphokine-activated killer (LAK) cells induced by IL-2 alone under the conditions used. It is suggested that the apparent restoration was due to increased LAK-like (or MHC-nonrestricted) activity mediated by an ASGM1+ cell in the CTL precursor population. 相似文献
902.
Retrovirus-mediated immunosuppression. II. FeLV-UV alters in vitro murine T lymphocyte behavior by reversibly impairing lymphokine secretion 总被引:5,自引:0,他引:5
C G Orosz N E Zinn R G Olsen L E Mathes 《Journal of immunology (Baltimore, Md. : 1950)》1985,135(1):583-590
Murine splenocytes and cloned murine T cells were used to study the in vitro immunosuppressive effects of UV-inactivated feline leukemia virus (FeLV-UV) on lymphokine secretion. FeLV-UV can significantly depress the accumulation of IL 2 in cultures of Con A-stimulated C57BL/6 splenocytes and in cultures containing the alloreactive helper T cell clone B6D/2-2m plus Con A. Inhibition of lymphokine accumulation in these cultures could not be attributed to absorption or inactivation of IL 2 by the FeLV-UV or to the FeLV-UV-induced production of substances which interfere with the IL 2 bioassay. Thus, FeLV-UV appears to block production and/or secretion of IL 2 by a direct inhibitory effect on IL 2-secreting murine T lymphocytes. Additional studies indicate that FeLV-UV impairs IL 2 production only if added very soon after lymphocyte contact with lymphokine-inducing agents and that IL 2 secretion resumes when FeLV-UV is removed from the culture. FeLV-UV also impairs accumulation of MAF (interferon-gamma?) in cultures of Con A-stimulated C57BL/6 splenocytes and in cultures containing the alloreactive cytotoxic T lymphocyte clone B6D/2-7c plus Con A. The latter observation again suggests that FeLV-UV impairs lymphokine secretion by a direct effect on lymphokine-producing T lymphocytes. Furthermore, it suggests that FeLV-UV does not selectively impair production of IL 2 nor does it have selective inhibitory effects on helper T cells. Rather, FeLV-UV appears to have a general inhibitory effect on lymphokine production by T lymphocytes. Finally, concentrations of FeLV-UV which suppress MAF production by the CTL clone have little influence on the cytolysis mediated by the same cloned T cell population. Thus, the immunosuppressive influence of FeLV-UV is selective for phenomena associated with induction of new T lymphocyte functions, such as lymphokine secretion, and spares other immune functions already expressed by the same cells. 相似文献
903.
Inhibitors of DNA synthesis (aphidicolin and araC/HU) prevent the recovery of RNA synthesis after UV-irradiation 总被引:4,自引:0,他引:4
L V Mayne 《Mutation research》1984,131(5-6):187-191
UV-irradiation causes an immediate depression in the rate of RNA synthesis in human skin fibroblasts. RNA synthesis rates recover to greater than or equal to 90% of unirradiated levels within 90 min in normal cells. This recovery can be prevented by incubating the cells after irradiation with araC/HU or aphidicolin, potent inhibitors of DNA replication and excision repair. The effect of these inhibitors on the recovery of RNA synthesis can also be observed in non-dividing cells; it is thus independent of their effects on DNA replication. 相似文献
904.
M A Lieberman P Rothenberg D M Raben L Glaser 《Biochemical and biophysical research communications》1980,92(2):696-702
Epidermal growth factor (EGF) induced DNA synthesis in non-confluent, G0-arrested Swiss 3T3 fibroblasts is partially blocked by plasma membranes isolated from the EGF receptor deficient NR-6 Swiss 3T3 cell line. This inhibition could be due to either a steric block of the receptor by the membranes, a membrane induced down regulation of the EGF receptor, or a signal generated by membrane binding which is antagonistic towards the mitogenic signal generated by EGF. Binding measurements utilizing 125I-labeled EGF demonstrated that membranes do not block either the EGF induced down regulation of the receptor or alter the number of receptors on the surface. These results suggest that the membranes exert their inhibitory effect via generation of a signal which is antagonistic to the EGF induced mitogenic signal, with the result expressed as a reduced mitogenic response. 相似文献
905.
At pH greater than 7 the absorption and magnetic circular dichroic spectra of cobalt carboxypeptidase A are insensitive to anions [Latt, S. A., & Vallee, B. L. (1971) Biochemistry 10, 4263-4270], but at pH less than 6 chloride and other anions perturb them in a manner specific for each anion. Lowering of the pH apparently facilitates the entry of an anion into the metal coordination sphere, suggesting that an acidic group normally stabilizes a metal-coordinated water molecule against displacement. The lack of sensitivity to anions at pHs between 7 and 9--when the enzyme is maximally active--and its evident abolition upon protonation of an active-site group are consistent with this interpretation. Selective modification of cobalt carboxypeptidase at Glu-270 using a carbodiimide affinity reagent generates sensitivity to anions at pH 7 very similar to that of the unmodified enzyme at pH approximately 5. This suggests that the group stabilizing the metal-coordinated water is the catalytically essential carboxylate of Glu-270. These and related results provide evidence for a mechanistically important interaction of Glu-270 with a metal-bound water molecule. 相似文献
906.
907.
Slash pine needles and cortex oleoresin have been found to contain a new major diterpene constituent, imbricataloic acid. The closely related imbricatoloic acid, previously reported only in Araucaria imbricata, was found to be present in small amounts in slash pine needle extract. Spectral data are given for an unidentified diterpene alcohol isolated from the cortex oleoresin. 相似文献
908.
Hepatic alcohol dehydrogenase activity and mass content change coordinately during development in male rats. Enzyme activity and mass content increase continuously after birth to 100 and 80% of maximal values within 6 weeks (2.6 ± 0.4 μmole/min/g liver and 92 ± 20 μg/g liver), respectively. When expressed per milligram of soluble proteins, both parameters peak at 3 weeks (0.052 ± 0.002 μmole/min/mg protein and 2.0 ± 0.4 μg/mg protein) and then decrease gradually to plateau levels. These decreases probably arise from a “surge” in soluble liver protein levels that occurs after weaning. Similar developmental patterns also occur in female rats. These findings are the first quantitative measurements of this enzyme in developing animals. 相似文献
909.
L V Loskutova M A Gilinski? 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1987,37(6):1070-1074
Character of conditioned reaction of passive avoidance was analyzed in Wistar line male rats after neurochemical destruction of terminal dopaminergic fields of the amygdalar complex. 6-hydroxydopamine was bilaterally administered to the central nucleus of the amygdalar complex after preliminary treating with desmethylimipramine for selective destruction of dopaminergic terminals. Lowering of dopamine level in the amygdalar complex led to a weakening of reproduction and to prolongation of spontaneous extinction of conditioned reaction. Features of conditioned reaction are highly similar to the effect of latent inhibition connected with attention deficit. It is suggested that activity of terminal fields of the amygdalar complex is one of the mechanisms providing for attention and intensifying selection of information in learning. 相似文献
910.