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231.
N-Acetylcysteine inactivates Migration Inhibitory Factor and Delayed Hypersensitivity Reactions 总被引:3,自引:0,他引:3
In vitro studies suggest that delayed hypersensitivity follows the production of migration inhibitory factor (MIF) by sensitive lymphocytes in the presence of specific antigen. This factor arrests the migration of macrophages in vitro and in vivo. After attraction, aggregation and activation in vivo, these bystander cells produce toxic substances which induce the local reaction1. When lymphocytes from tuberculin (PPD) sensitized guinea-pigs were incubated with PPD, cell-free supernatant fluids of the cultures contained MIF2. Such migration inhibitory fluids injected intradermally with PPD, into PPD-sensitive animals, enhanced the delayed hypersensitivity reaction3. Concentrated migration inhibitory supernatant fluids injected intradermally into unsensitized animals produced local reactions of induration and erythema within 6 h; reactions reached a maximum after 16 h. Histologically there was an infiltrate of mononuclear cells at the site of injection and neutrophils and eosinophils were also present1. 相似文献
232.
Structure of the Purple Membrane 总被引:34,自引:0,他引:34
IN the preceding article1 it has been shown that a cell membrane fragment, the purple membrane, isolated from Halobacterium halobium2 contains retinal bound in a mole ratio of 1 : 1 to a protein of molecular weight 26,000 which is the only protein present. We now describe the structure of the purple membrane and its localization in the bacterial cell envelope. 相似文献
233.
234.
Virus Specific RNA in Cells transformed by RNA Tumour Viruses 总被引:21,自引:0,他引:21
Virus specific RNA comprises 5% of the nuclear RNA and 0.5–1.0% of the cytoplasmic RNA of cells transformed by murine sarcoma viruses. Even cryptically transformed cells which possess no detectable virus or viral proteins synthesize detectable amounts of viral RNA. 相似文献
235.
236.
Cell-free Studies on the Regulation of the Arabinose Operon 总被引:17,自引:0,他引:17
A DNA directed, cell-free system which synthesized L-ribulokinase coded by the L-arabinose operon ara OIBAD, has been developed. L-arabinose but not the araC gene product is required for the expression of this operon and, in addition, cyclic AMP and guanosine tetraphosphate are needed for optimal synthesis. 相似文献
237.
Inhibitors of the RNA and DNA Dependent Polymerase Activities of RNA Tumour Viruses 总被引:20,自引:0,他引:20
RNA viruses of several animal leukaemias and sarcomas possess what seems so far to be a unique enzyme—an RNA dependent DNA polymerase1–6. Specific inhibitors of the viral enzyme will not only be useful in the analysis of its possible role in neoplasia, but might provide drugs for leukaemia and cancer therapy. 相似文献
238.
Interactions between Marek's Disease Herpesvirus and Avian Leucosis Virus in Tissue Culture 总被引:3,自引:0,他引:3
A GROUP B herpesvirus is important in the aetiology of Marek's disease, a highly contagious lymphoproliferative disease of chickens1,2. Chicks inoculated with enveloped Marek's disease herpesvirus (MDHV), extracted from feather follicle epithelium of chickens with the disease, developed tumour-like aggregates of lymphoid cells in the viscera and frequently in the peripheral nerves3,4. Cultures of chicken embryo fibroblast (CEF) cells infected with MDHV develop discrete foci of altered cells5. Our data show that MDHV infection of cultures of CEF cells, previously infected with an avian leucosis virus (RAV-2), results in both a reduction in the number of MDHV foci and an increase in the complement fixing avian leucosis antigen (COFAL)6 titre. 相似文献
239.
WHEN BHK 21 hamster cells are infected with polyoma virus1, there is no vegetative growth of virus, but stably transformed cells appear. These transformed cells are more easily transplanted than BHK 21 cells; they initiate their growth cycle in otherwise restrictive cultural conditions such as the absence of serum, high density and suspension; they grow with random orientation and have exposed on their surfaces receptor sites for certain glycoprotein agglutinins2–5. The proportion of stably transformed cells is low, even after high doses of virus. But a much higher proportion (sometimes all cells) shows abortive transformation—changes characteristic of transformation, but which last only a few days. In suspension cultures, for example, most of the infected cells grow into small colonies of four to thirty-two cells6. In surface cultures deprived of serum DNA synthesis is initiated and the cells may then divide at least once7: they also temporarily lose the normal parallel orientation and develop the typical random appearance of transformed cells. Moreover, the polyoma nuclear T-antigen and also a surface antigen detected by immunofluorescence, appear temporarily in most polyoma infected BHK 21 cells8, while 3T3 cells exposed to SV40 virus show transient exposure of cell surface sites reacting with conconavalin A (ref. 9). 相似文献
240.
ROBERT LAW 《Nature: New biology》1971,231(23):186-187
AIKEN and Vane have reported1 the independent actions of angiotensin I (AI) and angiotensin II (AII) on various isolated smooth muscle preparations, including rat colon. Tney showed that the apparent contractile action of AI on these preparations depended primarily on its in situ conversion to All by “converting enzyme” and that when the activity of the enzyme was inhibited by a pentapeptide extracted from Bothrops jararaca venom, the residual contractile action, probably due to unchanged AI, was very small. I have investigated the action of synthetic tetradecapeptide renin substrates (TPRS) on rat colon, in the light of the known actions of AI and All. 相似文献