Kazuko Hori

On the enzyme system obtained from some mutants of Bacillus brevis deficient in gramicidin S formation

Twenty mutants of Bacillus brevis which were deficient in gramicidin S formation were isolated by N-methyl-N′-nitrosoguanidine treatment. In addition to three groups which have been previously classified, further two groups were established according to their characteristics of amino acid activating enzymes concerned with gramicidin S formation. The fourth group mutants had a phenylalanine activating enzyme, but they had an enzyme complex from which one specific enzyme among proline, valine and leucine activating enzymes was deleted. Some of them also the ability to form d-phenylalanyl-l-prolyl diketpiperazine (DKP) even though they had phenylalanine and proline activating enzymes. The fifth group mutants contained both a phenylalanine activating enzyme and a complex of prodine, valine, ornithine and leucine activating enzymes like as a wild strain, but did not synthesize gramicidin S, and also one of them could not form even DKP. Combination of enzymes from DKP (+) mutants of the fourth or fifth groups with the first group mutant which had an intact proline, valine, ornithine and leucine activating enzyme complex showed gramicidin S formation, but the combination of enzymes from DKP (−) mutants except a proline activating enzyme minus mutant with the first group mutant could not synthesize gramicidin S.

Effect of serotonin on ouabain-sensitive, K+-dependent, p-nitrophenylphosphatase activity in strial marginal cells of normal and reserpinized guinea pigs

Na+,K+-ATPase activity is abundant on the basolateral infoldings of the strial marginal cells and contributes to the maintenance of the characteristic electrolyte composition of the endolymph. However, the stria vascularis of the cochlea is known not to be innervated. In order to clarify its humoral regulation by serotonin, the K+-p-nitrophenylphosphatase activity of strial marginal cells was investigated with a cerium-based method in normal guinea pigs and in guinea pigs treated with reserpine, 5-hydroxytryptamine or reserpine plus 5-hydroxytryptamine. K+-p-nitrophenylphosphatase activity was almost completely depressed 3--20 days after reserpine administration. Ten days after reserpinization, followed by repeated 5-hydroxytryptamine treatment, the enzyme activity was detectable. These results suggest that 5-hydroxytryptamine increases the phosphatase activity. Thus, the function of the stria vascularis in producing cochlear endolymph may be regulated by 5-hydroxytrypt amine.

Zucker obese rats are sensitive to weight-reducing effect and insensitive to orexigenic effect by cold exposure

Abstract Male Wistar and Zucker (lean and obese) rats at 7 weeks of age were divided into three groups: warm-acclimated (25°C for 11 weeks), cold-acclimated (10°C for 11 weeks), and deacclimated (10°C for 9 weeks and 25°C for 2 weeks) groups. The rate of increase in body mass (BM) was lower in obese rats as compared to lean rats. Cold-acclimated Wistar and Zucker lean rats exhibited greater food intake, compared to warm-acclimated rats. Food intake did not increase in obese rats exposed to cold. Obese rats are sensitive to weight-reducing effect and insensitive to the orexigenic effect by cold exposure.

Adaptive changes in brown adipose tissue in Wistar rats, Zucker lean and obese rats

Abstract (1) Male Wistar, and Zucker (lean and obese) rats aged 7 weeks of age were divided into three groups; warm acclimated (25°C for 11 weeks), cold acclimated (10°C for 11 weeks), and deacclimated (10°C for 9 weeks and 25°C for 2 weeks) groups. (2) Density of lipid droplet in brown adipose tissue (BAT) of obese rats was the greatest and that in lean rats was less than that in Wistar rats. (3) Mass of brown adipose tissues (BATM) per body mass (BM) was greater in obese rats than lean rats. (4) Marked weight-reducing effect observed in obese rats during cold acclimation is partly resulted from greater BATM/BM.

Purification and Properties of Ornithine and N-Acetylornithine Aminotransferases from Gramicidin S-Producing Bacillus Brevis

Ornithine and α -N -acetylornithine δ-aminotransferases were purified to a homogeneous state from a gramicidin S-producing strain of Bacillus brevis. Ornithine aminotransferase has a molecular weight of about 90,000 and N -acetylornithine aminotransferase has that of about 80,000 on gel filtration, respectively. Both enzymes were composed of two identical subunits. Ornithine aminotransferase is specific for ornithine, and N -acetylornithine aminotransferase is specific for N -acetylornithine as amino donor. Both enzymes used 2-oxoglutarate as amino acceptor.