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41.
S Nakajin S Fujii S Ohno M Shinoda 《The Journal of steroid biochemistry and molecular biology》1992,41(2):179-184
In earlier studies, two distinct molecules, 20 alpha-HSD-I and 20 alpha-HSD-II, responsible for 20 alpha-HSD activity of pig adrenal cytosol were purified to homogeneity and characterized [S. Nakajin et al., J. Steroid Biochem. 33 (1989) 1181-1189]. We report here that the purified 20 alpha-HSD-I, which mainly catalyzes the reduction of 17 alpha-hydroxyprogesterone to 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, catalyzes 3 alpha-hydroxysteroid oxidoreductase activity for 5 alpha (or 5 beta)-androstanes (C19), 5 alpha (or 5 beta)-pregnanes (C21) in the presence of NADPH as the preferred cofactor. The purified enzyme has a preference for the 5 alpha (or 5 beta)-androstane substrates rather than 5 alpha (or 5 beta)-pregnane substrates, and the 5 beta-isomers rather than 5 alpha-isomers, respectively. Kinetic constants in the reduction for 5 alpha-androstanedione (Km; 3.3 microM, Vmax; 69.7 nmol/min/mg) and 5 beta-androstanedione (Km; 7.7 microM, Vmax; 135.7 nmol/min/mg) were demonstrated for comparison with those for 17 alpha-hydroxyprogesterone (Km; 26.2 microM, Vmax; 1.3 nmol/min/mg) which is a substrate for 20 alpha-HSD activity. Regarding oxidation, the apparent Km and Vmax values for 3 alpha-hydroxy-5 alpha-androstan-17-one were 1.7 microM and 43.2 nmol/min/mg, and 1.2 microM and 32.1 nmol/min/mg for 3 alpha-hydroxy-5 beta-androstan-17-one, respectively. 20 alpha-HSD activity in the reduction of 17 alpha-hydroxyprogesterone catalyzed by the purified enzyme was inhibited competitively by addition of 5 alpha-DHT with a Ki value of 2.0 microM. Furthermore, 17 alpha-hydroxyprogesterone inhibited competitively 3 alpha-HSD activity with a Ki value of 150 microM. 相似文献
42.
Tadahiro Fukiage Hiroki Murakami Masao Eura Tsutomu Ikawa Takeru Ishikawa 《Cancer immunology, immunotherapy : CII》1991,33(3):139-145
Summary Peripheral blood lymphocytes were cultured for 5 days with allogeneic tumor cells (allogeneic mixed lymphocyte/tumor cell culture), and subsequently cultured with recombinant interleukin-2 for 12 days. These cultured cells were found to be cytotoxic to autologous tumor cells. Results of two-color analysis using monoclonal antibodies to cell markers showed that more than 80% of their cultured cells were CD3+ cells, and CD4+ cells showed a higher distribution than CD8+ cells. However, CD8+ cells had a much higher killing activity with autologous tumor than did CD4+ cells, when estimated by an elimination study using monoclonal antibodies to T cell phenotypes and complement. The cold-target inhibition test showed that the cytotoxicity of these cells for autologous tumor cells was inhibited by unlabeled autologous tumor cells but not by unlabeled stimulator cells. Furthermore, about 40% of the cytotoxicity was suppressed by blocking of HLA class I antigen with a monoclonal antibody on autologous tumor cells. Thus, cytotoxic activity of lymphocytes to autologous tumor restricted by target cell HLA class I antigen is possibly induced by allogeneic tumor-stimulation. 相似文献
43.
Analysis of bacterial populations in a grassland soil according to rates of development on solid media 总被引:3,自引:0,他引:3
Abstract The process of colony formation by bacteria from grassland soil sampled in April, July and September was simulated by a colony-forming curve (CFC). The CFC was a super-imposition of several component curves (cCFC) given theoretically by the first order reaction (FOR) model [3,6]. The pattern of FOR model curves was not influenced by the time of sampling and four cCFCs were always recognized during an incubation period of 160 h. It was considered that the CFC describes an inherent property of the bacterial population of the field. Bacterial isolates were obtained from colonies produced in each of four cCFCs on agar plates. Isolates corresponding to one cCFC were classified as one group. The bacterial isolates were characterized by morphological and physiological tests and subsequently clustered. Few oligotrophic bacteria were obtained among bacteria which produced visible colonies within 63 h of incubation time. On the other hand, approx. 50% of bacteria which produced v colonies after 63 h were oligotrophic bacteria. The time required for the appearance of the first colony, t r of the FOR model, was very similar in the isolates belonging to one group. A close linear relationship was observed between t r value and doubling time of isolates. 相似文献
44.
We have presented evidence suggesting that the suprachiasmatic nucleus (SCN) is involved in central regulation of glucose homeostasis. To elucidate this role of the SCN, we examined the effects of its electrical stimulation on glucose metabolism in male Wistar rats. During and shortly after this stimulation, we observed hyperglycemia associated with enhanced hyperglucagonemia but no immediate hyperinsulinemia. In addition, we detected significant increase in liver glycogen phosphorylase alpha activity and significant decrease in the liver glycogen content. These findings suggest that the SCN is important in control of glucose homeostasis through effects on glucagon and insulin secretions and liver glycogen metabolism. 相似文献
45.
Hepatocytes from neonatal rats of 0 to 3 days old grew actively in primary culture without added serum or growth factors. In these culture conditions, growth of hepatocytes decreased progressively with increase in age of the rats from which they were isolated, and hepatocytes from rats of 2 weeks old showed scarcely any growth. Actively growing hepatocytes were found to secrete a growth factor that promoted their growth and that of Swiss 3T3 cells, but not that of adult hepatocytes. This growth factor in conditioned medium of growing hepatocytes was heat- and acid-stable, but sensitive to trypsin, and had a molecular weight of over 10,000. It did not inhibit the binding of [125I]epidermal growth factor to its receptor, and its growth promoting activity was not inhibited by monoclonal antibody against insulin-like growth factor II. Therefore, it seems to be a new growth factor. These results, together with previous findings (Nakamura, T., Nagao, M., & Ichihara, A. (1987) Exp. Cell Res. 169, 1-14) demonstrated a reciprocal relation between growth and maturation of neonatal hepatocytes during development, like that of adult cells, but indicated that unlike growth of the latter, growth of neonatal cells is induced by an autocrine mechanism. 相似文献
46.
An enzyme activity which catalyzes the ring cleavage of the anthraquinone questin to form benzophenone desmethylsulochrin was found in the cell-free extract of Aspergillus terreus, a (+)-geodin producer. The product was identified as desmethylsulochrin by high-resolution mass spectroscopy and chemical carrier dilution analysis. The enzyme showed an absolute requirement of NADPH and molecular oxygen. Therefore, the enzyme, named questin oxygenase, was considered to be classified as a monooxygenase. The optimum pH was around 7.5. The enzyme was very unstable and lost its activity completely after storage overnight at 4 degrees C in 0.05 M phosphate buffer, pH 7.5. The instability of the questin oxygenase was partially overcome by the addition of polyols and the non-ionic detergent Tween 80 to the buffer. By DEAE-cellulose column chromatography, two protein fractions, named DE-I and DE-II, were obtained. Neither fraction reacted with questin by itself. However, the combination of DE-I and DE-II reconstituted the questin oxygenase system to convert questin to desmethylsulochrin. This result suggested that the system is not a simple combination of oxygenase and hydrolase, but requires some additional factor(s) such as electron transfer protein. 相似文献
47.
48.
A major plasma protein, referred to as SP 1, exhibits sex- and stage-specific expression during the larval development of the silkworm, Bombyx mori. We have isolated a plasmid clone bearing a part of mRNA sequence coding for SP 1 and quantitated the amount of SP 1 mRNA by means of RNA blot hybridization using the cDNA probe. The developmental change in the amount of SP 1 mRNA in the fat body closely reflected that of the hemolymph concentration of SP 1, indicating that the biosynthesis of SP 1 is regulated in a sex- and developmental stage-specific fashion at the level of mRNA. 相似文献
49.
50.
Theoretical analysis of a site-specific chemiluminescence reaction and its application to quantitation of lipid hydroperoxides 总被引:1,自引:0,他引:1
K Fukuzawa T Yoshimura T Fujii K Takauchi M Miki H Tamai M Mino 《Chemistry and physics of lipids》1988,48(3-4):197-203
A system was designed for chemiluminescent measurement of lipid hydroperoxides by their site-specific reaction in sodium dodecylsulfate micelles. Ferrous ion-induced decomposition of lipid hydroperoxides in the sodium dodecylsulfate micelles resulted in strong chemiluminescence of the Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (CLA). After addition of ferrous sulfate to the micelles containing lipid hydroperoxide and luciferin, the chemiluminescence intensity reached a maximum rapidly and then decreased. The sequence of this reaction was elucidated by theoretical analysis, which demonstrated that the maximum chemiluminescence intensity is proportional to the initial concentration of hydroperoxide. Good linear relationships were observed between the maximum counts of chemiluminescence and the amounts of hydroperoxides of linoleic acid, phosphatidylcholine, choresterol (5 alpha), cumene and tert-butyl and hydrogen peroxide. This chemiluminescence method was simple and sensitive enough to detect picomole levels of linoleic acid and phosphatidylcholine hydroperoxides. 相似文献