Biomedical subjects

I Shibuya

Publications and source records attributed to I Shibuya.

147 records · Page 9Linked to original sources

PubMedDate not supplied

Correlation of regional cerebral blood flow with performance on neuropsychological tests in schizophrenic patients.

Regional cerebral blood flow (rCBF) was determined by the 133Xe inhalation technique (Headtome II: ring detection SPECT) in 53 DSM-III schizophrenic patients. The rCBF values were corrected by using end-tidal carbon dioxide concentration values (PECO2). After rCBF measurement, neuropsychological tests--Word Fluency Test, Maze Test and Wisconsin Card Sorting Test--were performed. There were significant correlations between frontal rCBF and scores on each neuropsychological test. In particular, a moderate correlations between the frontal rCBF and the performance on the Wisconsin Card Sorting Test was noted. It seems likely that decrease of rCBF in prefrontal regions at rest reflects a disturbance of frontal lobe function in schizophrenic patients.

Adult↗

PubMedDate not supplied

Temperature dependence of processes proximal and distal to the glucose-induced [Ca2+]i rise in stimulus-secretion coupling in rat pancreatic islets.

Cooling is known to inhibit glucose-induced insulin secretion from pancreatic islets, but temperature-dependent processes in stimulus-secretion coupling remain unclear. In the present study, we examined the effects of cooling on the glucose-induced increase in cytoplasmic Ca2+ concentration ([Ca2+]i) and concomitant insulin secretion in rat pancreatic islets to analyze the temperature dependence of processes proximal and distal to the Ca2+ signal in stimulus-secretion coupling. Rat pancreatic islets were isolated and perifused. [Ca2+]i was measured using fura-2. Glucose (15 mM) caused a triphasic [Ca2+]i response in single islets at 35 degrees C: an initial decrease and a transient increase followed by a gradual increase, on which series of Ca2+ transients were frequently superimposed. Cooling to 30 and 25 degrees C caused slower and smaller [Ca2+]i responses with a Q10 (temperature coefficient) of 1.8. Glucose caused biphasic insulin secretion at 35 degrees C, which was inhibited by cooling, with a Q10 of 11.6. The ratio of glucose-induced insulin secretion to [Ca2+]i rise (IS/Ca) was calculated to represent the efficiency of Ca2+ to cause exocytosis. The Q10 value of the ratio of IS/Ca was 6.6. The Q10 values of the ratio of IS/Ca in the responses to high K+ (30 mM), carbamylcholine (100 microM) and glibenclamide (2 microM) were 5.6, 3.8, and 13.0, respectively. These values were greater than the Q10 values of corresponding [Ca2+]i responses: 1.2, 1.4, and 1.8, respectively. From these results, we conclude that cooling inhibits not only the glucose-induced [Ca2+]i rise but also Ca(2+)-activated exocytosis, and that the latter is much more sensitive to cooling than the former.

Animals↗

PubMedDate not supplied

Stability of sodium 5,6-benzylidene-L-ascorbate.

The stability of sodium 5,6-benzylidene-L-ascorbate (SBA), consisting of two diastereomers, was investigated by high-performance liquid chromatography. In extensively acidic buffer, the acetal in SBA was immediately cleaved to liberate ascorbic acid and benzaldehyde. At higher pH, the cleavage of SBA was significantly reduced, but the degradation (due to possible opening of the lactone ring) of SBA was stimulated. The degradation rate of SBA was significantly increased with increasing temperature, and was higher than that of ascorbic acid or benzaldehyde. SBA was degraded with incubation time in culture medium, with accompanying loss of its biological activity, but only a marginal concentration of benzaldehyde, but not of ascorbic acid, was produced from SBA. The amount of SBA extracted from the apoptosing leukemic cells by 70% acetonitrile amounted to about 0.04% of that present in the medium fraction. These data suggest that SBA itself, but not contaminating ascorbic acid nor benzaldehyde, is responsible for the antitumor activity of SBA.

Antineoplastic Agents↗