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141.
The effect of pre- and posttreatment incubation of UV-irradiated and ethyl methanesulphonate (EMS) treated cells with non-toxic concentrations of inhibitors of de novo purine synthesis (dnPS) on expression of potentially lethal and premutational damage at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 cells has been examined. The concentrations of inhibitors used were shown to profoundly perturb de novo DNA synthesis, by measurements of [14C]formate uptake, and cell cycle progression by flow cytofluorimetry. Postincubation in 6-methyl mercaptopurine ribonucleoside (MMPR) usually but not invariably potentiated the cytotoxic effects of UV and EMS but azaserine (AZS) and methotrexate (MTX) were without effect. No effects on mutant frequencies were observed on posttreatment with any of these agents. Caffeine produced the least effect on dnPS, but invariably potentiated lethal damage. This potentiation of lethal damage is not mediated by dnPS inhibition as has been suggested for Chinese hamster ovary (CHO) cells. 相似文献
142.
H. Stam H. Jansen W.C. Hülsmann 《Biochemical and biophysical research communications》1980,96(2):899-906
Chylomicron degradation by hearts from fed and fasted rats was studied using a perfusion technique, which allows the separate collection of coronary (Qrv) and interstitial effluent (Qi). Upon perfusion with [3H]-cholesterol-containing chylomicrons the tissue recovery of label was highest in the fasted state, while label recovered in Qi was highest in the fed state. Density gradient centrifugation of Qi indicated that the label was recovered in lipoproteins with higher densities: low density lipoproteins (1.019<d<1.050), high density lipoproteins (1.050<d<1.21) and a fraction of d>1.21. These particles probably represent chylomicron degradation products (remnants and “surface fragments”). Our results indicate that tissue cholesterol uptake during chylomicron degradation may be inhibited in the fed state. Furthermore, the role of the myocyte (or interstitial) lipoprotein lipase in chylomicron degradation is discussed. 相似文献
143.
144.
Y D Karkhanis R L Anderson J Y Zeltner R Z Maigetter D J Carlo T H Stoudt 《Biochemical and biophysical research communications》1979,89(2):750-758
An antigenic subunit of molecular weight 66,000 daltons has been isolated from the antigenic complex of the Melvin strain of . Incubation of the complex in 8M urea at room temperature for four hours resulted in the dissociation of the subunit from the complex. It was separated from the complex by chromatography of the incubation mixture on a Sepharose 6B column in 50 mM ammonium bicarbonate pH 8.5 without 8M urea and further purified by affinity chromatography. This communication reports on a newly isolated antigenic protein devoid of LPS present in the bacteria. 相似文献
145.
Enzymatic inactivation of human alpha-1-proteinase inhibitor by neutrophil myeloperoxidase. 总被引:13,自引:0,他引:13
N R Matheson P S Wong J Travis 《Biochemical and biophysical research communications》1979,88(2):402-409
Peanut agglutinin was acylated with a new heterobifunctional, cleavable photosensitive crosslinking reagent, N-[4-(p-azidophenylazo)benzoyl]-3-aminopropyl-N′-oxysuccinimide ester. The lectin derivative binds specifically and reversibly to neuraminidase-treated human erythrocyte ghosts and upon irradiation covalent attachment of over 35% of the bound lectin occurs. The affinity-crosslinked ghosts were solublized in deoxycholate, immunoprecipitated with anti-peanut agglutinin antiserum, and analyzed by sodium dodecylsulfate polyacrylamine gel electrophoresis. Bands containing both peanut agglutinin and membrane glycoproteins were detected with apparent molecular weights of 58 000, 85 000, 110 000 and 135 000. Upon subsequent cleavage with sodium dithionite, asialoglycophorin A (apparent M.W. 41 000 and 85 000) and a second glycoprotein (apparent M.W. 58 000 – 61 000) were tentatively identified as the receptors for peanut agglutinin in the intact membrane. 相似文献
146.
Stereospecific binding of human β-endorphin to rat membrane preparations is described for the first time using as the ligand. The binding is time dependent and saturable with respect to βh-endorphin with an apparent dissociation constant of 0.3 nM. Sodium ion (100 mM) elevates this value to 2.5 nM but has no effect on the total number of binding sites present in the membrane preparation. The ability of certain β-endorphin analogs, opiate agonists as well as antagonists to inhibit the binding of βh-endorphin, is presented. 相似文献
147.
148.
A simple procedure for the isolation of cathepsin-B from bovine pancreas employing ammonium sulphate fractionation, DEAE cellulose
chromatography and Sephadex G-200 gel filtration is described. The purified enzyme gave a single band on polyacrylamide gel
electrophoresis. The molecular weight as determined by gel filtration of the enzyme was 26,850. ItsK
m andV
max values were 12.8 mM and 0.303 Μmol/min/mg, respectively. TheK
i for iodoacetamide was 0.16 mM. 相似文献
149.
150.