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Biomedical subjects

R Itoh

Publications and source records attributed to R Itoh.

At least 199 records · Page 11Linked to original sources
PubMed1985

Changes in adenylate energy charge and total adenine nucleotide concentration in mouse testis induced by cadmium administration.

Subcutaneous administration of CdCl2 (3 mg/kg body weight) caused a decrease in adenylate energy charge, (ATP + 0.5ADP)/(ATP + ADP + AMP), and a depletion of the adenine nucleotide pool in the testis of mice. This preceded a decrease in LDH-X activity in the testicular extracts. These results biochemically support the hypothesis that the testicular damage induced by cadmium is secondary to anoxia caused by vascular lesion.

Adenine Nucleotides↗
PubMed1984

Arthrographic findings in hemiplegic shoulders.

To discover the influence of hemiplegia on arthrographic changes in hemiplegic shoulders, we compared arthrographic findings from paralyzed and nonparalyzed shoulders in 77 patients with hemiplegia. The correlation between arthrographic changes in paralyzed shoulders and characteristics of the hemiplegic condition was also investigated. Hemiplegic changes were considered to be responsible for adhesive changes in affected shoulders because those changes were found in paralyzed shoulders at a statistically significant higher rate (54.6%) than in the nonparalyzed side (32.5%). The occurrence rate of contrast leakage from capsule tear on the subscapular bursa and the bicipital tendon sleeve was higher on the nonparalyzed side than on the paralyzed side. It is suggested that capsular contracture due to hemiplegia prohibits capsular tear during arthrographic maneuvers. No significant difference was found in the occurrence of rotator cuff tear between the paralyzed and the nonparalyzed shoulder. Those changes on the paralyzed side were not correlated with any characteristics of hemiplegics except for shoulder pain prior to the onset of hemiplegia.

Adult↗
PubMed1983

Effect of oral administration of fructose on purine nucleotide metabolism in rats.

Oral administration of fructose (4 g/kg body wt) accelerated the production of uric acid and allantoin in rat liver. Changes in the concentrations of various metabolites in the liver after the administration of fructose suggested that this was due to the acceleration of AMP degradation induced by the rapid fall in adenylate energy charge resulted from rapid phosphorylation of fructose with ATP.

Adenine Nucleotides↗
PubMed1982

Studies on some molecular properties of cytosol 5'-nucleotidase from rat liver.

A cytosol 5'-nucleotidase was purified from rat liver. It appeared to be homogeneous on the criteria of polyacrylamide gel electrophoresis. We estimated the approximate molecular weight of the enzyme to be 200 000 and concluded that the enzyme most likely exists in the native state as a tetramer. Our results suggest that adenine nucleotides, which are activators of the enzyme, induce its conformational change.

5'-Nucleotidase↗
PubMed1982

[Effects of protizinic acid on the prostaglandins system and the production of oxygen radicals].

Effects of protizinic acid (PRT) on prostaglandins (PG) and the production of oxygen radicals were compared with those of other non-steroidal anti-inflammatory agents. Oral administration of 30 mg/kg of PRT, indomethacin (IM), or ibuprofen (IB) significantly inhibited arachidonic acid-induced erythema in guinea pigs. Although 30 mg/kg of PRT significantly inhibited PGE2-induced erythema, IM and IB did not significantly inhibit it. PRT inhibited phospholipase A2 (PLA2) activity, and the IC50 value was 2.1 X 10-4 M. On the other hand, IM and IB exerted no effect on the PLA2 activity at 3 X 10-4 M. These results suggest that PRT possesses a broader pharmacological activity on the PG system than IM and IB. As for effects on the production of oxygen radicals, in order of relative inhibitory potency was PRT greater than metiazinic acid (MA) = IM greater than IB = phenylbutazone (PB) in the xanthine oxidase assay, PB great than IM greater than PRT greater than MA = IB in the rabbit neutrophil myeloperoxidase assay, and IM greater than PB greater than PRT greater than MA greater than IB in the guinea pig macrophage assay. In the rabbit neutrophil and aggregated IgG-bound micropore filter assay, the order was PRT greater than MA greater than PB greater than IM = IB. Thus, the inhibitory effects of PRT was verified in all experiments on the production of oxygen radicals in contrast to IB. In particular, it could be especially meaningful that PRT showed the most potent activity in the aggregated IgG-bound micropore filter assay which has been reported to be a good model for studying the pathogenesis of inflammatory diseases believed to be caused by immune complexes.

Animals↗
PubMed1981

Regulation of cytosol 5'-nucleotidase by adenylate energy charge.

In the physiological range of the adenylate energy charge in liver (0.7-0.9), th rate of AMP-hydrolysis catalysed by rat liver cytosol 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) increased sharply with decreasing energy charge. In addition, a decrease in the concentration of Pi caused marked acceleration of the AMP-hydrolysing activity over the physiological range of adenylate energy charge. These responses seem to serve to protect the cells against a metabolic stress which could result from sudden utilization of ATP by removal of AMP. The AMP-hydrolysing activity of this enzyme decreased sharply as the size of the adenine nucleotide pool decreased in the physiological range. This effect may be a self-limiting response to prevent excess depletion of the pool. IMP-hydrolysing activity of this enzyme increased with increasing adenylate energy charge. But no marked response to its variation within the physiological range was observed. On the basis of the data obtained in this study, the IMP-hydrolysing activity of the cytosol 5'-nucleotidase in rat liver cells seems to be comparable to that of AMP deaminase reaction, but the AMP-hydrolysing activity was estimated to be less than 10% of AMP deaminase reaction at energy charge value of about 0.7. This strongly suggests that the AMP leads to IMP leads to inosine pathway is more significant that the AMP leads to adenosine leads to inosine pathway in rat liver.

5'-Nucleotidase↗
PubMed1981

Purification and some properties of cytosol 5'-nucleotidase from rat liver.

A 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) was highly purified from rat liver. The preparation appeared homogeneous on the criteria of disc-gel electrophoresis. A pH optimum at about 6.5 was observed for all substrates tested. The activity of this enzyme was absolutely dependent on the presence of various bivalent metal salts. The highest V value was attained with MgCl2 and the concentration at half-enzyme saturation was lowest with MnCl2. The enzyme had markedly higher affinities for IMP, dIMP, GMP and dGMP than the other 5'-mononucleotides, although V values for all the substrates tested were in the same order of magnitude. The activity of this enzyme was stimulated by various alkali metal salts, some carboxylic acids and adenine nucleotides. When AMP was used as substrate, the substrate-velocity plot was sigmoidal and NaCl, Tris-maleate and ATP stimulated the enzyme by decreasing the sigmoidicity of the plot. When IMP was used as substrate, the substrate-velocity plot was hyperbolic and these three activators stimulated the enzyme by increasing the V and decreasing the Km value. Some of these results provided consistent evidence for the identity of this enzyme and the cytosol 5'-nucleotidase, the presence of which had been reported in crude preparations from rat liver.

5'-Nucleotidase↗
PubMed1981

Effects of trapidil on thromboxane A2-induced aggregation of platelets, ischemic changes in heart and biosynthesis of thromboxane A2.

Trapidil inhibited the aggregation of rat platelets and the contraction of the isolated aortic strip of rabbit mainly caused by thromboxane A2, and the thromboxane A2 biosynthesis in rabbit platelets. The drug also reduced ischemic changes in ECG, the incidence of myocardial infarction, histopathological changes and a decrease in serum high density lipoprotein cholesterol, and inhibited an increase in plasma thromboxane B2 and a decrease in plasma 6-keto-prostaglandin F1 alpha content in the animals with an experimental ischemic heart injury caused by the injection of thromboxane A2 into the coronary artery. These findings suggest that trapidil is a new type of a therapeutic agent for ischemic heart disease which not only dilates the coronary artery but also inhibits the actions and biosynthesis of thromboxane A2 and may promote the biosynthesis of prostaglandin I2.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

Crystallization of water-soluble chlorophyll-proteins from Lepidium virginicum.

Water-soluble chlorophyll-proteins were prepared from leaves of Lepidium virginicum, by means of ammonium sulfate fractionation followed by column chromatography on DEAE-cellulose and Sephacryl S-200. After intensive purification the chlorophyll-proteins were crystallized by dialysis against an ammonium sulfate solution.

Chlorophyll↗
PubMed1980

[Pharmacological properties of trapidil: comparison with other coronary vasodilators (author's transl)].

Effects of trapidil and other coronary vasodilators on retrograde blood flow in acute coronary-ligated dogs, isolated large and small coronary arteries of pig, platelet aggregation, biosynthesis of prostacyclin in isolated aortic rings and hyperlipemia in quails were investigated. Trapidil showed an increase in retrograde blood flow while dipyridamole, nifedipine, diltiazem and dilazep did not. Trapidil and nitroglycerin relaxed large coronary arteries, while dipyridamole, diltiazem, dilazep and adenosine relaxed small arteries. Trapidil, dipyridamole, diltiazem and aspirin protected against the secondary phase of ADP-induced platelet aggregation in guinea-pig platelet rich plasma more effectively than did nifedipine and dilazep. Trapidil and aspirin protected only against rabbit platelet aggregation as induced by arachidonic acid. Moreover, only trapidil protected against platelet aggregation as induced by prostaglandin G2-thromboxane A2 mixture. Trapidil and dipyridamole enhanced the platelet aggregation protection of prostacyclin. Trapidil also facilitated biosynthesis of prostacyclin more markedly than did the other drugs. Trapidil increased serum content of HDL cholesterol and significantly lowered serum content of triglyceride and the ratio of LDL cholesterol to HDL cholesterol in hyperlipemic quails. Dipyridamole, diltiazem, nifedipine and dilazep, however, showed little effect.

Animals↗
PubMed1979

Chicken liver amidophosphoribosyltransferase. Ligand-induced alterations in molecular properties.

A homogeneous amidophosphoribosyltransferase (EC 2.4.2.14) preparation, which was sensitive to purine nucleotide inhibitors, was obtained from chicken liver. From the result of sodium dodecyl sulfate polyacrylamide gel electrophoresis, the subunit weight was estimated to be approximately 58 000. In Tris-HCl buffer, the predominant form of the enzyme had an S20,w of 6.5, Strokes radius of 40 A, and estimated molecular weight of 110 000. Incubation with 5-phosphoribosyl 1-pyrophosphate or Pi resulted in an increase in the S20,w to 9.1--9.5, Strokes radius 50 A, and estimated molecular weight to 200 000. Incubation of the large form with AMP led to a decrease in the molecular wight of the enzyme. It is concluded that chicken liver amidophosphoribosyltransferase is an allosteric protein whose activity is regulated by a series of conformational changes induced by a number of ligands.

Adenosine Monophosphate↗