Search PubMed⌕ Search

Biomedical subjects

M Okada

Publications and source records attributed to M Okada.

At least 1,639 records · Page 91Linked to original sources
PubMed1982

Carcinogenicity of N-alkyl-N-(acetoxymethyl)nitrosamines after subcutaneous injections in F-344 rats.

As model compounds for metabolically activated N,N-dialkylnitrosamines, five N-alkyl-N-(acetoxymethyl)nitrosamines were synthesized and their carcinogenicity was tested in F-344 rats of both sexes. Compounds used in this study are N-methyl-(MAMN), N-ethyl-(EAMN), N-propyl-(PAMN), N-butyl-(BAMN), and N-isobutyl-N-(acetoxymethyl)nitrosamines (i-BAMN). All chemicals were dissolved in olive oil and rats received 10 weekly subcutaneous injections of these chemicals (10 X 5 mg MAMN or equimolar amounts of other chemicals) at the interscapular region. Subcutaneous tumors were detected in many rats of all groups treated with the chemicals, although no tumor was detected in the control group. Lung and/or thyroid tumors were also observed in many rats in the experimental groups. The incidence of subcutaneous tumors was highest in EAMN, followed in order by MAMN, PAMN, BAMN, and i-BAMN. On the contrary, the incidence of lung and thyroid tumors was highest in MAMN and decreased as the length of the alkyl chain of the chemicals increased. Histologically, almost all subcutaneous tumors were malignant fibrous histiocytomas. The results indicate that the chemicals possess systemic as well as local carcinogenicity in F-344 rats. The potent carcinogenic effects at the injection site of the alpha-acetoxy nitrosamines, coupled with their direct mutagenic activity reported previously, support the notion that these derivatives are useful as models for the ultimate form in the metabolic activation of N,N-dialkylnitrosamines.

Animals↗
PubMed1982

Multiple calcified aneurysms of splenic artery, hypersplenism and concomitant cholelithiasis.

Multiple calcified aneurysms of splenic artery with hypersplenism and concomitant cholelithiasis were found in a 73-year-old Japanese woman. The symptoms and radiological findings were referable to the aneurysms. The predisposing factors are reviewed. Proximal ligation of the splenic artery and splenectomy gave a good postoperative result. Histopathological examination revealed an atherosclerotic origin, nevertheless, specimens from an elderly person may obscure the actual pathology.

Aged↗
PubMed1982

Software system for real-time discrimination of multi-unit nerve impulses.

We have developed a computer program to separate a unit of interest from multi-units of nerve impulses on an on-line, real-time operation basis. This method is divided into two phases: (1) the learning phase; (2) the hunting phase. In the learning phase, the user specifies spike patterns of a random unit from among varied spike trains displayed on CRT. The template for the unit is also constructed. In the hunting phase, the detection of spikes is carried out followed by almost simultaneous template-matching. As soon as a spike is established to be identical with the learned pattern, time information is delivered to the main memory of the computer.

Animals↗
PubMed1982

The relationship of serum uric acid to hypertension and ischemic heart disease in Hisayama population, Japan.

The association of serum uric acid (SUA) with hypertension, ischemic ECG change, diabetes mellitus, and drinking and smoking habits was studied by multivariate analysis among 1871 residents aged 40 and over in Hisayama, Japan. Blood pressure level and history of hypertension did not correlate with an increased level of SUA when other factors such as serum creatinine, obesity, beta-lipoprotein and leucineaminopeptidase were taken into account. Antihypertensive medication was a significant factor influencing SUA. The association of SUA with Minnesota code 4.1-3 (S-T depression) was insignificant in men and significant in women when other factors influencing SUA were taken into account. Glycosuria was negatively correlated with SUA, while alcohol ingestion has positive correlation. There was no correlation between the amount of tobacco smoked and the level of SUA.

Alcohol Drinking↗
PubMed1982

A summary of cytogenetic, morphologic, and clinical data on t(8q - ;21q+) and t(15q + ;17q-) translocation leukemias in Japan.

Cytogenetic, morphologic, and clinical data of 33 acute nonlymphocytic leukemia (ANLL) patients with t(8q - ;21q+) and 19 patients with acute promyelocytic leukemia (APL) were collected from seven laboratories in Japan. The latter class included 18 patients with t(15q + ;17q-) and one with a normal karyotype. The t(8q - ;21q+) and t(15q + ;17q-) translocations were each shown to be associated with a specific type of ANLL, namely, AML-M2 and APL-M3, respectively. No patient with APL had the M3 variant. The t(8q - ;21q+) translocation seems to be more common as an abnormality in ANLL in Japan as compared to findings in other countries. The high incidence of t(15q + ;17q-) among Japanese patients with APL indicated in this study, however, still awaits confirmation.

Acute Disease↗
PubMed1982

Induction of pole cells in sterilized Drosophila embryos by injection of subcellular fraction from eggs.

A subcellular fraction isolated from a homogenate of young Drosophila embryos was shown to be capable of inducing pole cells when injected into UV-sterilized Drosophila embryos. Most of the pole cell-inducing activity was recovered from the precipitate after centrifugation at 27,000 x g. The activity remained in this precipitate (called F-3 fraction hereafter) even after membranous structures were removed from it through centrifugation on a sucrose density gradient. Dialysis, lyophilization, and heating at 80 degrees C for 10 min did not inactivate the F-3 fraction. The pole cells, which were produced when the F-3 fraction was injected at the posterior pole of UV-sterilized embryos, did not develop into germ cells. Furthermore, the F-3 fraction was unable to induce pole cells when injected into the anterior region of the egg. These results can be explained by assuming that (i) pole cell formation and germ cell determination are controlled by different factors, (ii) pole cell formation requires at least two factors, which are normally localized in the posterior-pole cytoplasm, one of which is sensitive and one resistant to the UV dosage we used, and (iii) the subcellular fraction we obtained contains the UV-sensitive factor but not the UV-resistant factor.

Journal Article↗
PubMed1982

Increase of inactive form of aspartate aminotransferase in pyridoxine-deficient rat liver.

Cytosolic aspartate aminotransferase from rat liver was separated into at least 3 subforms, focused at pH 6.2, 5.9, and 5.7, by isoelectric focusing. Increase of subforms with low pI values was observed in pyridoxine-deficient rat liver. These subforms with low pI values showed low catalytic activities relative to their antigenic activities. The Km values for substrate and optimal pH values of the two main subforms were not significantly different in pyridoxine-deficient and control rat livers. Some conformational change of enzyme in the cytosol of pyridoxine-deficient rat liver was suggested by circular dichroic and fluorescent spectra. The N and C terminals of the enzyme from both pyridoxine-deficient rats and controls were shown to be alanine and glutamine, respectively.

Animals↗
PubMed1982

Effect of pyridoxine-deficiency on the syntheses of aspartate aminotransferase in rat liver and muscle in vivo.

The rates of synthesis of aspartate aminotransferase isozymes in the liver and skeletal muscle in pyridoxine-deficient rats were examined. The rates of synthesis were compared in rats given pyridoxine-deficient diet ad libitum, rats given control diet ad libitum and rats pair-fed with those on the deficient diet. The rates of incorporation of 3H-L-leucine by both cytosolic and mitochondrial enzymes were highest in pair-fed controls. Incorporation of radioactivity into the cytosolic enzyme was higher in deficient rat liver than in that of controls fed ad libitum, but the rate of incorporation into the mitochondrial enzyme was similar in these two groups. In muscle the rates of incorporation of labeled leucine into both isozymes were similar in all groups when expressed relative to total protein synthesis. It was suggested that increase of glucocorticoid receptor might result in increased synthesis of cytosolic aspartate aminotransferase in pyridoxine-deficient rat liver.

Animals↗
PubMed1982

Effect of pyridoxine deficiency on activities and amounts of aspartate aminotransferase isozymes in rat tissues.

The enzyme and antigen activities of aspartate aminotransferase [EC 2.6.1.1] isozymes in several tissues of rats fed on pyridoxine-deficient or control diet for 4 weeks were determined. The enzyme activities in liver (supernate, mitochondria), heart (supernate), brain (mitochondria), and muscle (mitochondria) preparations of the deficient rats were abnormally low, whereas those in other tissue preparations were similar to those of control rats. In liver and heart preparations, the antigen activities of the deficient rats were similar to those in controls, but in brain and muscle mitochondria they were abnormally low. These findings suggest that the activity and the amount of this enzyme are regulated in different ways in different tissues, and suggest that the coenzyme level affects metabolic regulation of the enzyme molecule.

Animals↗
PubMed1982

[Histochemical study of glycosaminoglycan in Wilms tumors of rats and rabbits and fetal kidneys of rats].

Histochemical studies were performed on glycosaminoglycan (GAG) components in Wilms tumors of rats and rabbits and fetal kidneys of rats. 1. Wilms tumors. The interstitial components had an intense stainability with Alcian blue, and digestion test with hyaluronidase and chondroitinase was intensely positive. The epithelial tumor cells, showing a tubular pattern, were also stained with Alcian blue. The enzyme-digestion test was positive in the basal portion of the tumor cells, whereas it was negative in the free surface of the cells. 2. Rat kidneys. In fetal rats, the epithelial cells as well as the interstitial components were stained with Alcian blue, and the enzyme-digestion test was intensely positive. However, in adult rats, Alcian blue-stainability in the free surface of the tubular epithelium was not abolished by treatment with hyaluronidase and chondroitinase. The substance in the free surface seemed to be consisted mainly of heparan sulfate. Although the physiological significance of GAG in the cell surface cannot be deduced, it is quite conceivable that GAG, especially heparan sulfate, plays an important role in fluid absorption and transportation.

Animals↗
PubMed1982

Role of glucose on fatty liver formation in pyridoxine-deficient rats.

Studies were made on whether glucose starvation causes fatty liver in pyridoxine-deficient male Wistar rats. Pyridoxine deficiency resulted in significantly lower levels of liver glucose than in pair-fed controls but no significant change in the serum glucose concentration. In non-starving animals, serum immuno-reactive insulin (IRI) was significantly lower in pyridoxine-deficient rats than in pair- or ad libitum-fed controls. Liver glucokinase activity in pyridoxine-deficient rats was also significantly lower than in ad libitum-fed controls. The extent of insulin deficiency was evaluated by examining the effect of administration of insulin on pyridoxine-deficient rats. Administration of insulin had no effect on the activity of liver glucokinase in pyridoxine-deficient rats, but induced the enzyme in ad libitum-fed controls. In response to a decrease in the activity of liver glucokinase or hexokinase in the deficient group, glycolytic activity, estimated as lactate production from glucose in the liver supernatant spun at 100,000 X g, was reduced to half the control level in pyridoxine-deficient rats. The effects of glucose administration on the liver lipid content, serum insulin and serum glucose were investigated. The serum glucose concentration was not significantly different in pyridoxine-deficient and control rats at any time after the glucose load. The level of serum IRI after the load was similar in the two groups after 30 min but then gradually decreased in the deficient group. The liver lipid content of the deficient rats tended to decrease whereas that of the controls remained unchanged throughout the experiment. Thus glucose starvation in pyridoxine-deficient rats is one factor responsible for fatty liver formation. Possible mechanisms of this phenomenon are discussed.

Animals↗