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Biomedical subjects

S Hirose

Publications and source records attributed to S Hirose.

At least 865 records · Page 48Linked to original sources
PubMed1978

Mechanism of spermine stimulation of rat-liver isoleucyl-tRNA formation.

The mechanism of spermine stimulation of rat-liver isoleucyl-tRNA formation has been studied by Cleland's method [Biochim. Biophys. Acta, 67, 104--137 & 173--197 (1963)]. It was demonstrated that isoleucyl-tRNA formation proceeded through a ping-pong mechanism in the presence of spermine and magnesium. From a study of the effect of spermine on both the formation of isoleucyl-AMP . enzyme complex and on the subsequent formation of isoleucyl-tRNA from the isoleucyl-AMP . enzyme complex, evidence is presented that the stimulatory effect of spermine functions mainly through the spermine preventing the tRNA inhibition of isoleucyl-AMP . enzyme complex formation.

Adenosine Triphosphate↗
PubMed1978

Morphological observations on the vasculitis in the mucocutaneous lymph node syndrome. A skin biopsy study of 27 patients.

Twenty-seven skin biopsies were obtained from the exanthemata of patients in the acute stage of the mucocutaneous lymph node syndrome (MCLS). The three vascular systems of different caliber size--the intrapapillary capillary loops (ICL), the superficial arteriolar or venular plexus (SAP, SVP) and the small subcutaneous vessels--were examined to investigate the characteristics of the vasculitis in MCLS and differentiate it from infantile polyarteritis nodosa (IPN). Significant papillary edema and dilatation of ICL, SAP and SVP were observed on the 4th day after the onset of the illness, and then gradually decreased. In the subcutaneous regions, vasculitis began with endothelial necrosis, and subendothelial edema and degenerative changes in the muscle cells followed. These changes in the small subcutaneous vessels were observed for a longer period than in the ICL, SAP and SVP. Moderate mononuclear cell infiltrations were observed. Both arteries and veins were affected.

Acute Disease↗
PubMed1978

Relationship between polyamine contents and protease activity in the rat submaxillary gland.

The effect of polyamines on the protease activity in the submaxillary gland of castrated rats has been investigated in vivo. The protease activity, which is increased by testosterone, is also increased to a lesser degree by the subcutaneous administration of spermidine. The administration of putrescine was less effective than that of spermidine. The increase of polyamine contents in the submaxillary gland of the castrated rats administered either testosterone or spermidine was nearly parallel to the increase of the enzymatic activity. The administration of methylglyoxal bis(guanylhydrazone), a potent inhibitor of spermidine synthesis, with testosterone inhibited slightly the increase of the protease activity by testosterone, while the administration of the inhibitor with spermidine had essentially no effect on the increase of the enzymatic activity by spermidine. The administration of testosteorne also caused a slight increase of S-adenosyl-L-menthionine decarboxylase activity. These results suggest that spermidine synthesis may be necessary for the stimulation by testosterone of protease synthesis in the rat submaxillary gland.

Adenosylmethionine Decarboxylase↗
PubMed1978

Effect of polyamines on isoleucyl-tRNA formation by rat-liver isoleucyl-tRNA synthetase.

The effect of polyamines on rat-liver isoelucyl-tRNA formation was studied using isoleucyl-tRNA synthetase purified by column chromatography successively on Sephadex G-200, DEAE-Sephadex A-25, and tRNA-Sepharose 4B. In the presence of 50 mMK+, isoleucyl-tRNA formation was inhibited markedly by 1.5 mM or higher concentrations of Mg2+. However, the addition of spermine to the reaction mixture prevented the inhibitory effect of Mg2+. In the presence of 200 mMK+, the addition of spermine to the reaction mixture stimulated isoleucyl-tRNA formation in the presence of Mg2+ concentrations from 0 to 5 mM. Although the effective concentration was different, spermidine exhibited a similar stimulative effect. The effective concentration of spermine required for stimulation was higher when larger amounts of tRNA were used. The stimulatory effect of isoleucyl-tRNA formation by polyamines was shown to reflect on polypeptide synthesis. When formaldehyde-treated poly(A,U) was used as messenger RNA, polypeptide synthesis from amino acids was stimulated by polyamines, but that from aminoacyl-tRNAs was not stimulated by polyamines.

Amino Acyl-tRNA Synthetases↗
PubMed1978

Definitive evidence for renin in rat brain by affinity chromatographic separation from protease.

1. Angiotensin I-generating activity of rat brain extract was separated into two components by affinity chromatography on a casein-Sepharose gel column. 2. The component without affinity to the gel was identified as true renin on the basis of its sensitivity to anti-renin antibody and the lack of protease activity. 3. The second renin-like component with affinity to the gel was a protease insensitive to the anti-renin antibody. Its renin-like activity examined with sheep substrate was pronounced compared with the rate of angiotensin I generation from the rat substrate. 4. It was concluded that rat brain contains true renin, which can be detected by the use of rat substrate but can be masked when examined with sheep substrate.

Angiotensin I↗
PubMed1978

Effect of double partial hepatectomies at various intervals on [3H]thymidine incorporation into rat liver DNA.

At various intervals after a 34% hepatectomy, another 34% (50% of the remnant) hepatectomy was performed on rats, and the [3H]thymidine incorporation into the DNA of remaining liver cells was measured 24 hr after the first operation. The values of [3H]thymidine incorporation into liver DNA of rats hepatectomized doubly (34% and 34%) at 6, 8 and 10 hr intervals were greater than the sum of the value of rats which received a single 34% hepatectomy at the start and those of rats which received a single 68% hepatectomy at 6, 8 and 10 hr, respectively.

Animals↗
PubMed1977

Native form of renin in the kidney.

Renin (EC 3.4.99.19) has been observed to exist in a high molecular weight (Mr greater than 50,000) and a low molecular weight from (Mr approximately 42,000) in various tissues. Little is known concerning the origin and function of the high molecular weight form of renin and its relationship to low molecular weight renin. We have found that the high molecular weight form of renin in the kidney was converted to the low molecular weight form during the extraction process. The conversion is apparenly catalyzed by an agent(s) which requires free sulfhydryl groups since blockers of sulfhydryl groups completely suppress the conversion. This conversion could not be prevented by various specific inhibitors of serine proteases nor by the metal chelator EDTA. By the use of Na-tetrathionate it was possible to preserve the renin activity of hog kidney exclusively in the high molecular weight form. Similarly, using N-ethylmaleimide it was shown that a similar high molecular weight form of renin is the exclusive form present in rat kidney. These results suggest that the high molecular weight form of renin is the native form stored in the kidney and that it is converted by an enzyme or agent requiring sulfhydryl groups to the circulating (low molecular weight) form when it is secreted into blood. Renin activity was increased to approximately 155% of the original level upon conversion.

Animals↗
PubMed1977

Effects of polyamines on the activities of Escherichia coli ribonuclease I and II.

The effects of polyamines on the breakdown of synthetic polynucleotides [poly(A), poly(C), and poly(U)] by E. coli ribonuclease I [ribonucleate 3'-oligonucleotidohydrolase, EC 3.1.4.23] and ribonuclease II [EC 3.1.4.1] have been studied. The degradation of poly(C) by RNase II was stimulated by spermine and spermidine, while that of poly(A) by RNase II was not affected by polyamines. Under our standard experimental conditions, the breakdown of poly(U) by RNase II was inhibited slightly by polyamines. The stimulatory effect of spermine and spermidine on the breakdown of poly(C) occurred in the absence of monovalent cations but not in the absence of divalent cations. When polyamines were used as a stimulant of RNase II, the ratio of poly(C) degradation to poly(U) degradation was greater in the presence of inhibitors such as poly(G) than in their absence. Although the breakdown of all synthetic polynucleotides by RNase I was stimulated by polyamines, the degree of stimulation by polyamines was in the order poly(C)greater than poly(A)(see text)poly(U). However, the difference in degree of stimulation among polynucleotides decreased as monovalent cation concentration was increased.

Endonucleases↗
PubMed1977

Effects of polyamines on the degradation of ribonucleic acids by polynucleotide phosphorylase of Micrococcus luteus.

The effects of polyamines on the breakdown of synthetic polynucleotides [poly(A), poly(C), and poly(U)] by polynucleotide phosphorylase [polyribonucleotide: orthophosphate nucleotidyltransferase, EC 2.7.7.8] from Micrococcus luteus have been studied. Although the breakdown of all the synthetic polynucleotides tested was stimulated by polyamines, the degree of stimulation by polyamines was in the order poly(C) greater than poly(A) greater than poly(U) at pH 7.5. However, the difference in degree of stimulation among polynucleotides decreased as the pH or monovalent cation concentration was increased. In the presence of heparin, an inhibitor of polynucleotide phosphorylase hydrolysis of polynucleotides, spermidine clearly stimulated the breakdown of poly(C) and poly(A), while the breakdown of poly(U) was stimulated only slightly by the addition of spermidine. Although binding of [14C]spermine to polynucleotide phosphorylase was observed by gel filtration, the amount of spermine bound to the enzyme was much less than that to RNA.

Binding Sites↗
PubMed1977

Studies on the restoration of the activities of Ribonucleases by polyamines in the presence of various ribonuclease inhibitors.

The effect of polyamines on ribonucleases in the presence of various inhibitors (poly(G), heparin, and rat liver RNase inhibitor) has been studied. Bovine pancreatic RNas A and a ribonuclease from horse submaxillary gland (RNase HS) were inhibited by the inhibitors, but RNase T1 and RNase M were not inhibited. Polyamines were found to restore the activites of RNase A and RNase HS inhibited by poly(G) or heparin but not those activities inhibited by rat liver RNase inhibitor. When poly(U) and poly(C) were used as substrates, the inhibitory effects of poly(G) and heparin were greater with poly(U) than poly(C) as a substrate. However, when poly(C) was used as a substrate in the presence of either of the above inhibitors, the restoration of RNase activity by sperimine was more efficient. In fact, a stimulatory effect was observed. From the double-reciprocal plots, it was concluded that polyamines restored the activiities of RNases by increasing the availability of the substrate and enzyme to each other. The restoration of enzyme activity by polyamines occurred through the binding of the polyamines to the inhibitor and the subsequent release of enzyme from the inhibitor.

Animals↗
PubMed1977

Base specificity of polyamine binding to synthetic polynucleotides.

The binding of polyamines and magnesium to synthetic polynucleotides has been studied by gel filtration on a Sephadex G-50 column. Among the single-stranded polynucleotides examined [poly(A), poly(C), and poly(U)], polyamines were found to bind to poly(C) and poly(U) preferentially, while the binding of Mg2+ was greatest with poly(A). Spermine bound to poly(U) was displaced completely by NH4+ but incompletely by Mg2+, while Mg2+ bound to poly(A) was displaced completely be spermine but incompletely by NH4+. The optimal pH for the binding of spermine to poly(U) was found to be about 7.9, while Mg2+ could bind to poly(A) over a broad pH range (7.1--8.7).

Chemical Phenomena↗