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41.
The probable effect of increasing levels of ammonium nitrogen on the growth, efficiency of nitrogen fixation, and main cellular constituents of Azotobacter vinelandii was studied under shaking and static culture conditions. The presence of NH4+-N up to 50 mgl-1 level has no harmful effect on the multiplication as well as the yield efficiency ratio of the tested organism. A. vinelandii was able to fix dinitrogen in the presence of NH4+-N when both nitrogen sources were available in the culturing medium. The efficiency of nitrogen fixation was affected by the initial presence of NH4+-N in the medium, it was quite low at the highest level. The crude protein efficiency ratio was correlated inversely with the initial NH4+-N concentration, whereas the total carbohydrate efficiency ratio as well as the total lipid efficiency ratio were positively correlated with the NH4+-N concentration. The presence of NH4+-N in the culturing medium has no essential influence on the qualitative composition of the amino acids in the Azotobacter cells. 相似文献
42.
The irreversible binding of [2,3-14C]acrylonitrile (VCN) to proteins, RNA and DNA of various tissues of male Sprague-Dawley rats after a single oral dose of 46.5 mg/kg (0.5 LD50) has been studied. Proteins were isolated by chloroform-isoamyl alcohol-phenol extraction. RNA and DNA were separated by hydroxyapatite chromatography. Binding of VCN to proteins was extensive and was time dependent. Radioactivity in nucleic acids was registered in the liver and the target organs, stomach and brain. DNA alkylation, which increased by time, was significantly higher in the target organs, brain and stomach (119 and 81 pmol/mg, respectively, at 24 h) than that in the liver. The covalent binding indices for the liver, stomach and brain at 24 h after dosing were, 5.9, 51.9 and 65.3, respectively. These results suggest that VCN is able to act as a multipotent carcinogen by alkylation of DNA in the extrahepatic target tissues, stomach and brain. 相似文献
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Water-soluble chromatin from rat submandibular gland nuclei was isolated, and had a DNA: RNA:protein ratio of 8:1:20. The spectral properties of this preparation were similar to those described for chromatins from other tissues. The rat submandibular gland chromatin possessed protein phosphokinase activity. It was able to incorporate 32P from [γ-32P]-ATP into chromatin proteins, and into dephospho-phosvitin. The chromatin-associated protein phosphokinase activity (measured with dephospho-phosvitin as substrate) required Mg2+, Na+ or K+ and dithiothreitol for optimal activity. A single injection of isoproterenol influenced the activity of this enzyme system, so that it was decreased at 2 h, showed a transient increase at 4 h, and a large increase at 10–16 h after the injection. This event appears to precede the increase in ribosomal RNA induced by Ipr [13]. By 48 h the chromatin-associated protein kinase returned to the normal control levels. These changes appeared to be commensurate with the corresponding alterations in the non-histone acidic protein complement of these chromatins. Actinomycin D or cycloheximide, when administered 30 min prior to isoproterenol, blocked the increase in chromatin-associated protein kinase at 4 as well as 10 h after the injection of isoproterenol. Injection of pilocarpine did not influence the chromatin-associated protein phosphokinase activity. Dichloroisoproterenol appeared to be antagonistic to the influence of isoproterenol in mediating changes in chromatin-associated protein kinase. The results suggest that the isoproterenol-induced increase in chromatin-bound protein phosphokinase which precedes the increase in RNA synthesis is related to the eventual onset of DNA synthesis in rat submandibular gland stimulated by isoproterenol. The chromatin-bound protein phosphokinase activity (or activities) may have a regulatory role on gene action, mediated through the control of phosphorylation of nuclear non-histone acidic proteins [26]. 相似文献
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Khalid Ahmed Peter H. van der Meide John L. Turk 《Cancer immunology, immunotherapy : CII》1989,30(4):213-218
Summary Some conventional and experimental anticancer drugs were tested for their effect on concanavalin-A-induced interferon release from rat splenocytes in vitro. When 2.5 × 106 rat splenocytes/ml, stimulated with 1 µg/ml concanavalin A, were incubated with various non-cytotoxic doses of the vinca alkaloid vincristine, there was an inhibition of the release of interferon in culture supernatants. The antitumour antibiotics bleomycin and Adriamycin, alkylating agents 4-hydroperoxycyclophosphamide and mafosfamide, and the immunoactive peptides FK 156 and FK565 did not affect the release of interferon under similar conditions. However, cyclosporin A, in similar experiments, markedly inhibited the release of interferon . 相似文献
50.
A new bacterial alcohol dehydrogenase active on degraded lignin and several low molecular weight aromatic compounds 总被引:1,自引:0,他引:1
Jean Pelmont Catherine Tournesac Ahmed Mliki Michel Barrelle Claude Beguin 《FEMS microbiology letters》1989,57(1):109-114
A new intracellular bacterial dehydrogenase has been purified. It was active in the reversible reduction by NADH of conjugated carbonyl groups in partially degraded lignin. It was also active on various aromatic aldehydes such as vanillin, syringaldehyde and cinnamaldehyde, but had no effect on acetovanillone and lignin models carrying a conjugated ketone. It is proposed that this enzyme functions as a broadly specific lignin dehydrogenase at the level of aldehydic groups that are present in the lignin preparations. 相似文献