Sachiko Yoshimoto

Effect of chromium administration on glucose tolerance in stroke-prone spontaneously hypertensive rats with streptozotocin-induced diabetes

The present study was conducted to assess the effect of chromium (Cr) administration on glucose tolerance in insulin-dependent diabetes that accompanies hypertension. Four rat groups were used: stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY) with and without streptozotocin (SZ, 40 mg/kg)-induced diabetes. Each group of rats was subdivided to the Cr-dose group and the control group. The Cr-dose group, which was intraperitoneally administered Cr solution (20 micrograms trivalent chromium/kg body weight/d for 4 weeks), and the control group (saline) were studied for plasma glucose and plasma insulin during intraperitoneal glucose tolerance test (IPGTT) and insulin action by isolated adipocytes. For diabetic SHRSP showing the highest plasma glucose and lowest plasma insulin among the four groups, Cr administration led to the greatest reduction in plasma glucose without a significant effect on plasma insulin during IPGTT. For each diabetic WKY and normal SHRSP and WKY, those given Cr showed lower levels of plasma glucose with lower levels of plasma insulin than the controls. For diabetic SHRSP, glucose uptake by isolated adipocytes in the Cr-dose group was higher than that in the control group. This effect of Cr administration involved enhancement of insulin responsiveness and sensitivity, attributed to enhanced affinity of the insulin receptor. A similar tendency was observed for diabetic WKY. However, for normal SHRSP and WKY, the increase in glucose uptake due to Cr administration coincided only with enhanced insulin responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of age on contractile response to angiotensin II in rat aorta

The effects of aging on contractile response to angiotensin II and tachyphylaxis to it were investigated using aortic strips from rats aged 1.5, 4 and 22 months. Whether the endothelium was present or not, the contractile response to angiotensin II was greater and tachyphylaxis to it was less in 1.5-month-old rats than in 4- and 22-month-old rats. The differences between 4- and 22-month-old rats were not significant. Removal of the endothelium enhanced angiotensin II-induced maximal contraction and depressed the tachyphylaxis, these endothelial effects being greater in 4- rather than in 1.5-month-old rats. When the contractile force of angiotensin II was adjusted to a similar level for 1.5- and 4-month-old rats, the endothelial effect on the tachyphylaxis was greater in the 4-month-old rats, but no significant difference was noted in the endothelial effect on the contractile force. These results suggest that during growth, the contractile response of rat aorta to angiotensin II decreases while the endothelial effect on it increases.

Effects of ethanol on contractile response of gall bladder isolated from guinea pig.

The effects of ethanol treatment in vitro and in vivo on gall bladder contraction were investigated using gall bladder strips isolated from guinea pigs. In vitro pretreatment of the strips with ethanol at a concentration of over 50 mM significantly attenuated the reactivity and sensitivity of contractile responses to KCl, acetylcholine and histamine in a concentration-dependent manner. Indomethacin treatment or removal of extracellular calcium remarkably reduced gall bladder contractile response to acetylcholine. The depressive effect of ethanol in vitro on gall bladder contraction was also noted in the presence of indomethacin or absence of calcium in the medium. The concentration-response curve of calcium-induced contraction in 40 mM KCl-depolarized gall bladder strip shifted to the right on pretreatment with ethanol. In the case of strips following the chronic administration of 3% ethanol solution ad libitum for 4 weeks, contractile responses to KCl, acetylcholine and histamine did not differ, compared to those in the pair-fed group. This chronic ethanol administration induced tolerance to the acute inhibitory effect of ethanol on gall bladder contractile responses to the agonists. Ethanol is thus shown to exert direct inhibitory action on gall bladder contraction by lowering the calcium sensitivity of the contractile apparatus of smooth muscle; it is unlikely that ethanol consumption would affect gall bladder motility in vivo, owing to the tolerance produced toward the acute inhibitory action of ethanol.

An epidemiologic study on the correlation between salt threshold, academic test marks, biochemical data, number of complaints, and personality in women college students.

One hundred nine 19-year-old female students were surveyed as to academic test marks; salt detection and recognition thresholds; serum cholesterol, serum uric acid, serum cortisol, and other biochemical indices in serum; urinary sodium/creatinine and potassium/creatinine, as well as number of complaints based on the Cornell Medical Index (CMI) and personality based on the Yatabe-Guilford (Y-G) test. The salt recognition threshold showed a high negative correlation with serum uric acid concentration and a slight correlation with CMI complaint number, academic test marks, blood pressure, obesity, and serum cholesterol. The subjects with high salt thresholds had relatively passive personalities. Cholesterol, uric acid, hemoglobin, ferritin, and glucose levels in the serum were higher in the group with higher academic marks. These students also had fewer complaints and more of them were type B individuals based on the Y-G test. They also seemed to be under greater stress. In regression analysis, the partial regression coefficient between academic test marks and serum cholesterol was 60 percent higher than that between academic test marks and serum uric acid. Students who lived on campus had 24.8 milligrams per deciliter (15.7 percent) more serum cholesterol and 3.8 micrograms per deciliter (37.7 percent) more serum cortisol than those who commuted from home.

Potentiating effect of NH4Cl on vasoconstriction in rat aorta

The effect on the vasocontractile response of pretreatment with NH4Cl at a concentration (10 mM) that made almost no change in the resting tension was investigated using aortic strips from rats. NH4Cl pretreatment for 10 min significantly potentiated strip contractions induced by KCl (less than or equal to 30 mM), BAY K 8644 (0.1 microM) and phenylephrine (0.01 microM). This potentiating action of NH4Cl was eliminated in presence of nifedipine (1 microM). KCl (14.7 mM)-stimulated 45Ca uptake in rat aorta was significantly potentiated by pretreatment with NH4Cl (10 mM) for 10 min, but this NH4Cl effect was also eliminated in the presence of nifedipine. These results suggest that NH4Cl potentiates contractions induced by KCl and agonists in rat aorta by facilitating calcium influx through the nifedipine-sensitive calcium channel.

Relation of Serum and Erythrocyte Magnesium Levels to Blood Pressure and a Family History of Hypertension A Follow‐up Study in Japanese Children, 12‐14 Years Old

Abstract. Serum and erythrocyte magnesium concentrations (S‐Mg, E‐Mg) were measured in 122 junior high school students followed up for two years from 12 to 14 years of age, and the relationship to blood pressure and a family history of hypertension were investigated. The subjects who had high S‐Mg and E‐Mg levels at the first examination two years prior tended to show high levels after this follow‐up. There were significant positive correlations between two intraindividual values of S‐Mg and E‐Mg. A similar tendency was found for blood pressure. Tracking phenomena were observed with these measures. The subjects who had high E‐Mg levels at the first examination showed no blood pressure elevation during the two‐ year period. The subjects with a family history of hypertension [FH(+)] showed a higher degree of blood pressure rise during two years than those with no family history [FH(‐)], with a significant difference in systolic blood pressure at the age of 14. E‐Mg tended to be lower in the FH(+) group than in the FH(‐) group with a significant difference in 14‐year‐old girls. These results suggest that a hereditary predisposition to hypertension is related to magnesium metabolism and that intracellular magnesium deficiency may influence blood pressure elevation in the FH(+) children.

An epidemiological study of plasma renin activity in schoolchildren in Japan: distribution and its relation with family history of hypertension

Plasma renin activity (PRA) was determined in a group of 610 Japanese schoolchildren aged 10-14 years in order to investigate the relationship between PRA distribution and a family history of hypertension. Plasma renin activity was higher in the subjects with a family history of hypertension (FH+) than in those without a family history of hypertension (FH-). Systolic blood pressure (SBP) was also higher in the FH+ group than in the FH- group. The FH- group showed a significant negative correlation between PRA and SBP (boys, r = -0.254, P less than 0.01; girls, r = -0.225, P less than 0.01), whereas the FH+ group showed no correlation between PRA and blood pressure. These results suggested that schoolchildren with a family history of hypertension might have an enhanced renin-aldosterone (R-A) system, resulting in elevation of blood pressure.

Inhibitory Effects of Daunorubicin on Endothelium‐dependent Vasorelaxing Response to Acetylcholine of Rat Aorta

Abstract— The effect of daunorubicin on the endothelium‐dependent vasorelaxing response to acetylcholine was investigated using rat isolated aorta and compared with the effect of aclarubicin. Treatment of aortic strips with daunorubicin (20 μM) significantly attenuated the relaxing response to acetylcholine in the absence of tetraethylammonium, but not in its presence. Pretreatment with daunorubicin at a higher concentration (50 μM) or with aclarubicin (20 μM) strongly attenuated the relaxing response to acetylcholine; this attenuation was unaffected by the presence of tetraethylammonium. The increase in aortic cGMP in response to acetylcholine was also significantly suppressed by pretreatment with 50 μM daunorubicin or 20 μM aclarubicin, but not by treatment with 20 μM daunorubicin. The inhibitory effect of 20 μM aclarubicin on the acetylcholine‐induced responses was stronger than that of 50 μM daunorubicin. Even in strips pretreated with both 50 μM daunorubicin and 20 μM aclarubicin, relaxation induced by 0·1 μM sodium nitroprusside was retained. These results suggest that daunorubicin at 20 μM inhibits the endothelium‐dependent vasorelaxing response to acetylcholine via a mechanism other than the nitric oxide‐mediated pathway, whilst at 50 μM, it inhibits the nitric oxide‐mediated vasorelaxation.

Effect of diethyldithiocarbamate on diabetogenic action of alloxan in rats.

To determine whether alloxan action is mediated by hydroxyl radicals in vivo, we assayed methane sulfinic acid (MSA), a product of the trapping reaction of dimethyl sulfoxide (DMSO) with hydroxyl radicals. In DMSO-treated rats, the plasma levels of MSA were increased after injection of alloxan (75 mg/kg). This supports the hypothesis that the diabetogenic action of alloxan is mediated by hydroxyl radicals in vivo. The role of cytosolic superoxide dismutase (SOD) in protecting B cells against chemically induced diabetes was studied in rats injected intraperitoneally with diethyldithiocarbamate (DDC). When rats were injected intraperitoneally with DDC (750 mg/kg), the SOD activity at 2.5 h was decreased by 44% in the whole pancreas. The decreased SOD activity was affected by DDC but not by alloxan. Intraperitoneal injection of rats with DDC (750 mg/kg) increased diabetogenic susceptibility to a nondiabetogenic dose of alloxan (20 mg/kg). Subcutaneous injection of vitamin E, prior to administration of both DDC and alloxan, provided partial protection to the rats against the diabetogenic action. These findings suggest that the susceptibility to diabetogenic action of alloxan in B cells is augmented when the cellular SOD activity is inhibited. Thus, cellular SOD may play an important role in the maintenance of B cell function.

Changes of HDL subfractions by eicosapentaenoic acid intake and physical load in 20- to 25-year-old men.

The effects of daily eicosapentaenoic acid (EPA) intake and physical activity on high-density lipoprotein (HDL) subfraction, which may be an index of health status, were examined. The HDL subfraction, triglyceride and T-chol levels in the serum of 10 male volunteers aged 20–25 were examined before, immediately after and 1 h after being subjected to a physical load by bicycle ergometer at 90 W for 20 min. Subjects were then given 1.25 g EPA/day for 2 weeks, and the above test was repeated. By EPA intake, the distribution of HDL3b and 3c decreased significantly by 16.8 and 15.3%, respectively, and that of 2b increased significantly by 17.9%. The rate of change of subfraction of the 29th part (2b) of 30 parts in the total range of HDL increased by 67%, and decreased by 47% in 7th part (3c). By physical load, the distribution of HDL2a increased significantly by 15.4%, while 3b tended to decrease. By physical load after EPA intake, the distribution of 2a decreased significantly by 9.7%, and those of 3b and 3c increased significantly by 20.5 and 5.4%, respectively, and that of the 7th part (3c) increased by 37%. Thus, the physical load after EPA intake is effective to prevent arteriosclerosis as increasing the rate of change of HDL3c and as showing the longevity pattern of the HDL subfraction. Concentration of TG in a modal HDL pattern group increased by 95% after EPA intake, but that of a bimodal group did not show any change. HDL-cholesterol level in the bimodal group was higher than that in the modal group, especially after EPA intake. Two type III subjects changed to type IV by the load and the EPA intake, respectively. Thus, it seemed that the transformation from a modal pattern to a bimodal pattern by a certain lifestyle, especially regular physical activity and proper food intake, is a very important trial for the prevention of cerebrovascular diseases.