Search PubMed⌕ Search

Biomedical subjects

M Okamoto

Publications and source records attributed to M Okamoto.

At least 847 records · Page 47Linked to original sources
PubMed1988

Decreased autophosphorylation of EGF receptor in insulin-deficient diabetic rats.

We have previously reported that despite an increase in receptor concentration, there is a decrease in autophosphorylation and tyrosine kinase activity of the insulin receptor in insulin-deficient diabetic rats. To determine if other tyrosine kinases might be altered, we have studied the epidermal growth factor (EGF) receptor kinase in wheat germ agglutinin-purified, Triton X-100-solubilized liver membranes from streptozotocin (STZ)-induced diabetic rats and the insulin-deficient BB rat. We find that autophosphorylation of EGF receptor is decreased in proportion to the severity of the diabetic state in STZ rats with a maximal decrease of 67% (P less than 0.01). A similar decrease in autophosphorylation was observed in diabetic BB rats that was partially normalized by insulin treatment. Separation of tryptic phosphopeptides by reverse-phase high-performance liquid chromatography revealed a decrease in labeling at all sites of autophosphorylation. A parallel decrease in EGF receptor phosphorylation was also found by immunoblotting with an anti-phosphotyrosine antibody. EGF receptor concentration, determined by Scatchard analysis of 125I-labeled EGF binding, was decreased by 39% in the STZ rat (P less than 0.05) and 27% in the diabetic BB rat (not significant). Thus autophosphorylation of EGF receptor, like that of the insulin receptor, is decreased in insulin-deficient rat liver. In the case of EGF receptor, this is due in part to a decrease in receptor number and in part to a decrease in the specific activity of the kinase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Intralymphocytic sodium and free calcium and plasma renin in essential hypertension.

Intracellular sodium, potassium, and free calcium concentrations were investigated in lymphocytes of 30 patients with essential hypertension and 30 normotensive controls. All subjects were placed on a diet containing 8 to 10 g of sodium chloride per day. Lymphocyte sodium concentration was higher in hypertensive patients than in normotensive controls (19.8 +/- 1.8 vs 18.4 +/- 1.8 mmol/kg wet weight; p less than 0.01), whereas lymphocyte potassium concentration was similar in both groups. Lymphocyte free calcium concentration was also higher in hypertensive patients than in normotensive controls (134.6 +/- 13.2 vs 120.2 +/- 16.4 nmol/L; p less than 0.01). There was a positive correlation between lymphocyte sodium and free calcium concentrations in normotensive controls, in hypertensive patients, and in the subjects combined (r = 0.59, p less than 0.01; r = 0.71, p less than 0.001; and r = 0.70, p less than 0.001, respectively). Lymphocyte potassium concentration was not related to lymphocyte sodium or free calcium concentration in each group. In patients with essential hypertension, intracellular sodium and free calcium concentrations were negatively correlated with plasma renin activity (r = -0.66, p less than 0.001; r = -0.60, p less than 0.001, plasma norepinephrine concentration. These results suggest that a considerable relationship exists between intracellular sodium and free calcium in lymphocytes and that, in essential hypertension, the alteration in cellular metabolism of sodium and calcium may be linked to the renin system but not to blood pressure, age, or adrenergic activity.

Adult↗
PubMed1988

Defective processing of insulin-receptor precursor in cultured lymphocytes from a patient with extreme insulin resistance.

We have studied a patient with extreme insulin resistance, acanthosis nigricans, and decreased erythrocyte insulin binding. EBV-transformed lymphocytes from this patient exhibited markedly reduced binding of 125I-insulin. Radioiodination of cell surface receptors followed by immunoprecipitation with anti-receptor antibodies revealed the presence of increased amounts of a 210-kD protein but no detectable alpha or beta subunits. Continuous labeling with 2-[3H]mannose revealed the synthesis of a 190-kD precursor and a 210-kD protein. The 210-kD protein was phosphorylated in an insulin-dependent manner at high insulin concentrations. These results suggest that in this patient the biosynthesis of 190-kD receptor precursor, its terminal glycosylation, and intracellular transport to the cell surface proceed normally, while proteolytic maturation to alpha and beta subunits does not occur. We postulate that this defect either results from mutation(s) within the insulin-receptor gene, which render the precursor resistant to cleavage, or from a defect in the receptor processing enzyme.

Acanthosis Nigricans↗
PubMed1988

Effects of alpha-human atrial natriuretic polypeptide, sodium nitroprusside and dibutyryl cyclic GMP on aldosterone production in bovine zona glomerulosa cells.

When bovine adrenal zona glomerulosa cells were incubated with alpha-human atrial natriuretic polypeptide (alpha-hANP), the basal aldosterone production in the cells was hardly affected, although the angiotensin II- or K+-stimulated production was completely inhibited. alpha-hANP was found to cause the generation of cyclic GMP in the cells. When the cells were incubated with sodium nitroprusside, the drug inhibited the angiotensin II- or K+-stimulated aldosterone production, and also generated cyclic GMP in the cells. In contrast, dibutyryl cyclic GMP was found to be a stimulator of the aldosterone response rather than an inhibitor. The results obtained in this study cast doubt on the role of cyclic GMP as an intracellular second messenger for the action of ANP on aldosterone secretion.

Aldosterone↗
PubMed1988

Premature opening of the pulmonary valve in endomyocardial fibrosis.

Two-dimensional and Doppler echocardiographic findings in a 67-year-old man with endomyocardial fibrosis (EMF) are described. The two-dimensional echocardiogram showed typical features of EMF, right ventricular endomyocardial calcification, a thickened right ventricular wall, obliteration of the apex of the right ventricle and marked dilatation of the right atrium. In addition, premature opening of the pulmonary valve was observed during late diastole. The Doppler echocardiogram revealed forward flow from the right ventricle to the pulmonary artery, indicating the conduit state of the right ventricle. These findings were supported by cardiac catheterization and autopsy. Thus, two-dimensional and Doppler echocardiography are useful not only in making the diagnosis, but also in understanding the hemodynamic condition in EMF.

Aged↗
PubMed1988

[rdw rats, a new hereditary dwarf model in the rat].

A new hereditary dwarf mutation was found in Csk: Wistar-Imamichi rat breeding colony. The mutant rats and control normal rats were studied with clinical, genetical and histological examination. The result showed that the present mutation was inherited in autosomal recessive trait (gene symbol; rdw) and was provoked with the hypoplasia of pars distalis (anterior pituitary), in particular the secretory cells of GH, PRL and TSH. The characteristics of the present mutant (rdw) was very similar to dw mouse, and was usefull for endocrinological research as an animal model of human pituitary dwarfism.

Animals↗
PubMed1988

[Establishment of a new hereditary-cataract mouse (CSM) strain derived from SENCAR mouse].

A mouse representing a new hereditary cataract strain was found in a mouse colony and a new line was established strain CSM. These mice were investigated genetically, histologically and biochemically. The results suggested that this cataract was apparently inherited through two recessive autosomal genes. Histologically the denucleation process of lens fibers was abnormal and small vacuoles appeared in the equatorial region of the lens cortex at 12 days. Biochemically, insoluble protein and sodium increased in the lens with age.

Animals↗
PubMed1988

Regulation of glucose-transporter gene expression by insulin in cultured human fibroblasts.

To clarify the effect of insulin on glucose-transporter (GT) biosynthesis, we determined GT mRNA levels in human cultured skin fibroblasts, using HepG2 GT cDNA as a probe. Insulin specifically increased the GT mRNA level in a time- and dose-dependent manner. Time-course study demonstrated that the mRNA level peaked within 3 h of insulin (1 x 10(-7) M) addition. After remaining elevated for several hours, mRNA decreased and returned to the basal level after 24 h. In the cell strains from seven normal subjects, the mean (+/- SE) GT mRNA level determined after 3 h of treatment with 1 x 10(-7) M insulin was 164.3 +/- 8.5% of the level found in untreated control cells. The insulin dose-response curve of GT mRNA levels showed that the maximum stimulation was elicited at 1 x 10(-7) M, and the half-maximum stimulation occurred at approximately 5 x 10(-10) M. Degradation rates of GT mRNA determined in the presence of actinomycin D were not different between insulin-treated and untreated cells. These results suggest that insulin increases GT gene expression in cultured human fibroblasts.

Cells, Cultured↗
PubMed1988

[Pulmonary tuberculosis in patients with oral cancer].

During an 11 year period, from 1976 to 1986, 33 (10.1%) out of 328 patients with oral cancer treated at our clinic had either a scarred pulmonary tuberculosis (TB) or active TB. Four of these 33 patients developed active TB. In two of these cases TB occurred before the therapy of oral cancer commenced and in the other two, after the operation for oral cancer. In one of the 4 cases, a recrudescence of the TB was suspected. Five cases that were suspected of having TB on analysis of their chest X-rays were administered prophylactic anti-tuberculous chemotherapy, after which no recrudescence or onset of TB.

Adult↗
PubMed1988

Erythrocyte antioxidant enzymes are reduced in patients with rheumatoid arthritis.

Superoxide dismutase, catalase, and glutathione peroxidase activities were determined in erythrocytes isolated from 17 patients with rheumatoid arthritis (RA) and from 19 with osteoarthritis of the knee joints as controls. In a comparison of the 2 groups, it was found that the activities of these 3 antioxidant enzymes were significantly decreased in patients with RA. This indicates that erythrocytes in patients with RA might be injured more easily by oxy radicals which are endogenously generated in red blood cells.

Aged↗