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Biomedical subjects

M Okamoto

Publications and source records attributed to M Okamoto.

At least 883 records · Page 49Linked to original sources
PubMed1987

Production of 19-hydroxy-11-deoxycorticosterone and 19-oxo-11-deoxycorticosterone from 11-deoxycorticosterone by cytochrome P-450(11)beta.

Incubation of 11-deoxycorticosterone with a cytochrome P-450(11)beta-reconstituted system yielded, in addition to corticosterone and 18-hydroxy-11-deoxycorticosterone, a new steroid product. The retention time of the new product was identical with that of authentic 19-hydroxy-11-deoxycorticosterone on high performance liquid chromatography (HPLC). The turnover number of 19-hydroxy-11-deoxycorticosterone formation was 7.0 mol/min/mol P-450. When a large amount of cytochrome P-450(11)beta was used for the reaction and the products were analyzed by HPLC, the 19-hydroxy-11-deoxycorticosterone peak disappeared from the chromatogram and concomitantly new unidentified peaks appeared. These results suggest that 19-hydroxy-11-deoxycorticosterone was further metabolized to other steroids by cytochrome P-450(11)beta. Therefore, we next incubated 19-hydroxy-11-deoxycorticosterone with cytochrome P-450(11)beta and analyzed the reaction products by HPLC. The above-mentioned unidentified peaks appeared again in the chromatogram. The retention time of one of the peaks coincided with that of authentic 19-oxo-11-deoxycorticosterone. This peak substance was purified by repeated HPLC and subjected to mass spectrometry and 1H NMR analyses. Its field desorption mass spectrum (FD-MS) showed a M+ peak at m/e 344. The 1H NMR spectrum showed the signal of an aldehyde proton instead of those of hydroxymethyl protons at the C-19 position. These results suggest that cytochrome P-450(11)beta can catalyze the 19-hydroxylation of 11-deoxycorticosterone, and the 19-hydroxy-11-deoxycorticosterone produced is further oxidized at the C-19 position to 19-oxo-11-deoxycorticosterone.

Adrenal Cortex↗
PubMed1987

Aldosterone biosynthesis and cytochrome P-45011 beta: evidence for two different forms of the enzyme in rats.

Whereas cytochrome P-45011 beta has been recently shown to catalyze the two-step conversion of corticosterone to aldosterone in the bovine and porcine adrenal cortex, the identity of the enzyme involved in the two final steps of aldosterone biosynthesis in the rat adrenal cortex is as yet unknown. Mitochondria from capsular adrenals of sodium-deficient, potassium-replete rats converted corticosterone to 18-hydroxycorticosterone and aldosterone at markedly higher rates than mitochondria from capsular adrenals of sodium-replete, potassium-deficient rats. However, the same preparations exhibited no difference in the 11 beta-hydroxylase activity, i.e. the conversion of deoxycorticosterone to corticosterone. Only mitochondria of zona glomerulosa from rats with stimulated aldosterone biosynthesis contained a 49K protein which showed a strong cross-reactivity with a monoclonal antibody raised against purified bovine cytochrome P-45011 beta. By contrast, a crossreactive protein with a molecular weight of 51K was found in mitochondria of zona fasciculata and in mitochondria of zona glomerulosa from rats with a suppressed aldosterone biosynthesis. These findings indicate the existence of two different forms of cytochrome P-45011 beta in the rat adrenal cortex, with only one of them, i.e. the 49K form, being capable of catalyzing the two final steps of aldosterone biosynthesis in situ.

18-Hydroxycorticosterone↗
PubMed1987

Leiomyosarcoma of inferior vena cava.

A case of leiomyosarcoma of the inferior vena cava is presented and pertinent clinical features of 57 reported cases in the English literature are reviewed.

Female↗
PubMed1987

Switching mechanism of a cyclic enzyme system: role as a "chemical diode".

We previously showed with computer simulations that cyclic enzyme systems play a role in metabolic switching events. In the present study, the detailed switching mechanism was investigated by clarifying the relationship between the switching mode and the phase-difference of two sinusoidal inputs to the cyclic enzyme system. The switching time could be predicted theoretically. Half-wave and full-wave rectifications were observed when the phase-difference of two sinusoidal inputs is equal to pi. This result indicates the possibility that this cyclic enzyme system is available for use as a switching circuit (biochip) in a bio-computer.

Computer Simulation↗
PubMed1987

Electron microscopic evidence for epidermal growth factor receptor (EGF-R)-like immunoreactivity associated with the basolateral surface of gastric parietal cells.

Epidermal growth factor (EGF), in addition to its effects on cell growth, has a suppressive effect on gastric hydrochloride secretion. We recently demonstrated EGF-receptor (EGF-R)-like immunoreactivity on human gastric parietal cells by light microscopy. To reveal further the localization of this reaction an immuno-electron microscopical study was performed. 528IgG, an anti-EGF-R murine monoclonal antibody and a polyclonal anti-EGF antibody were employed for immunostaining using the avidin-biotin method. Positive reaction against 528IgG was shown mostly on the outer membrane of parietal cells, except in the apical portion. No reaction was observed on most of the intracytoplasmic membranes including intracellular canaliculi, endoplasmic reticulum and other membranous components. In the basillar portion, the 528IgG-positive parietal cell membrane formed labyrinthine interdigitations. No reaction against anti-EGF was demonstrated in any of the gastric mucosal cells, although a reaction was clearly shown on salivary gland cells. These findings suggest a blood-mediated direct action of EGF on parietal cells.

Cell Membrane↗
PubMed1987

Transfer of granulomatous inflammation with nonviable preparations of schistosome granulomas in naive mice.

Hepatic granulomas of euthymic (nu/+) mice infected with Schistosoma mansoni were freeze-dried or freeze-thawed 3 times and transplanted subcutaneously into naive nu/+ and athymic (nu/nu) mice. The grafted sites, studied histologically, showed formation of organized granulomas in nu/+ mice similar to donor granulomas as observed after grafting of freshly isolated granulomas. On the other hand, in nu/nu mice, the nonviable transplants elicited small and disorganized granulomas, like hepatic granulomas in nu/nu mice with schistosomiasis, but different from fresh nu/+ transplants in nu/nu skin. The findings indicate viable cells are not required for transfer of granulomatous reactions, but T cells are needed for full expression.

Animals↗
PubMed1987

Intralymphocytic sodium and free calcium concentration in relation to salt sensitivity in patients with essential hypertension.

In order to clarify the relation between salt sensitivity and changes in intracellular sodium ([Na]i) and free calcium concentration ([Ca2+]i) after salt loading, [Na]i and [Ca2+]i were determined in lymphocytes of twenty patients with essential hypertension under a low salt diet (3 g/day) and a high salt diet (20 g/day) for seven days, respectively. They were classified as "salt-sensitive" (n = 10) or "nonsalt-sensitive" (n = 10) on the basis of the changes in blood pressure after salt loading. Both lymphocytic [Na]i and [Ca2+]i were significantly increased with salt loading in salt-sensitive patients (p less than 0.05 for both), while they were not affected by salt loading in nonsalt-sensitive patients. Lymphocytic [Ca2+]i showed a positive correlation with lymphocytic [Na]i under both low salt diet (r = 0.62, p less than 0.01) and high salt diet (r = 0.70, p less than 0.01) in all patients in both groups. In addition, a close and positive correlation was observed between the changes in lymphocytic [Na]i and those in lymphocytic [Ca2+]i after salt loading in all patients in both groups (r = 0.80, p less than 0.001). These results suggest that the increase in [Ca2+]i, possibly linked with the increase in [Na]i, may be involved in elevation of blood pressure in the salt-sensitive patients after salt loading.

Adult↗
PubMed1987

[Change in the electrical impedance caused by cornification of the epithelial cell layer of the vaginal mucosa in the rat].

The electrical impedance in the vagina (EIV) is significantly high in the proestrus stage compared with other stages of the estrous cycle in rats. Therefore, the EIV can be used to detect the optimum day for mating. The relation between the EIV and the conditions of the epithelial cell layer of vaginal mucosa were investigated. The EIV was at a high level (over 3,000 omega) in vaginas in the proestrus stage in either intact or excised vaginal mucus. But it decreased (under 3,000 omega) after the epithelium of the vaginal mucosa was removed. The EIV of ovariectomized rats was low, but increased after Estradiol administration. The cornification of the epithelial cell layer of the vaginal mucosa occurred concurrently with the high EIV in the proestrus stage and after Estradiol administration. This indicates that the cornification of the epithelial cell layer of the vaginal mucosa may cause the elevation of EIV in the proestrus stage, the optimum day for mating in the rats.

Animals↗
PubMed1987

Inherited hydrocephalus in Csk: Wistar-Imamichi rats; Hyd strain: a new disease model for hydrocephalus.

Hydrocephalic rats were found in a breeding colony of Csk: Wistar-Imamichi strain rats. In males, the hydrocephalus were serious and could be detected from 7 days after birth. Survival was 3-4 weeks. In females, the hydrocephalus was moderate, there was no abnormal external appearance, and the rats were able to mature. Ventricular dilatation was excessive in males but moderate in females. The total frequency of hydrocephalus was 34.3% in both males and females. Breeding data indicated that this disease is heritable and is single dominant and X-linked (symbol, Hyd). The female moderate hydrocephalics could be detected by progeny tests without examining brain sections. No evidence of developmental anomaly was observed in the ventricles. This hydrocephalus was classified as being of the communicating type, and this strain was named the Hyd strain as an animal model for human hydrocephalus.

Animals↗
PubMed1987

[A method for detecting the optimum day for mating during the 4-day estrous cycle in the rat; measuring the value of electrical impedance of the vagina].

A method for detecting the optimum day for mating in the rat was investigated. Cyclic changes of electrical impedance of vagina (EIV) were studied in the rats. EIV indicated high value (over 3,000 omega) only at proestrus, and it was lower (under 3,000 omega) at other stage of estrous cycle. These results apparently indicate that measuring the EIV made to distinguish proestrus from other phases of estrous cycle. The female caged with male showed high copulation rate (88 approximately 96%) when her EIV had been over 3,000 omega.

Animals↗
PubMed1987

[Comparison of chemical and immunological methods in fecal occult blood testing].

Conventional occult blood testing using the chemical method has been compared with newly developed immunological testing methods; the Hemoccult slide II (HEM II) test has been widely accepted as a guaiac test but such recent tests as the Latex agglutination test (Latex) and the Enzyme Immunoassay method (EIA) have also come to be employed. Thirty colorectal cancer patients, 30 gastric cancer patients and 30 healthy persons were subjected the three above described tests during 3 consecutive days while under no restricted diet. False positive rates during this three-day testing period were 26.7% in HEM II, 93.3 in Late and 8.3% in EIA. Although the immunological testing method has the advantage of reducing the false positive rate without the need for a restricted diet it is time-consuming and expensive. Considering these results as well as our previous knowledge accrued from a mass survey, it is suggested that a new flow-chart may be found necessary, in which an initial screening is given by the chemical method and then followed by a secondary screening by the immunological method. This new flow-chart, if routinely employed, would greatly facilitate the mass screening of colorectal cancer.

Hemoglobins↗