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Biomedical subjects

Y Takata

Publications and source records attributed to Y Takata.

At least 235 records · Page 13Linked to original sources
PubMed1986

Receptor binding and negative cooperativity of a mutant insulin, [LeuA3]-insulin.

[LeuA3]-insulin, the third mutant insulin, was semisynthesized and was studied for receptor binding and negative cooperative effects. Receptor binding and biological effects of the mutant insulin were 0.3-0.5% of normal, the lowest among three mutant insulins. However, negative cooperative effects of the mutant insulin were almost normal at higher concentration (greater than 10(-6) M). Monoclonal anti-insulin antibody binding studies revealed that carboxyterminal region of B chain was relatively unchanged. These results suggest that N-terminal region of A-chain extending to A3 is important for receptor binding and confirm that A3 does not play an important role for negative cooperativity.

Adipose Tissue↗
PubMed1986

Effect of duration of diabetic state on insulin action in isolated rat soleus muscles.

We studied the effect of the duration of diabetic state on insulin action in skeletal muscle by measuring insulin binding, 2-deoxyglucose uptake, and intracellular glucose metabolism in isolated soleus muscles from streptozotocin-induced diabetic rats. Insulin binding to soleus muscles from diabetic rats was increased over that from controls. Glucose transport activity was determined by measuring the 2-deoxyglucose uptake at the concentration of 1 mmol/L at 25 degrees C. In the rats with diabetes of one week duration, insulin-stimulated 2-deoxyglucose uptake was not impaired, whereas basal 2-deoxyglucose uptake was decreased. However, the diabetic rats with two weeks duration revealed a 35.6% decrease in the insulin-stimulated 2-deoxyglucose uptake. Furthermore, four week duration of diabetic state led to a 60% decrease both in basal and insulin-stimulated 2-deoxyglucose uptake. Total glucose utilization was estimated as the total amount of glucose incorporated into muscle and lactate released into the medium following incubation at 37 degrees C, with 5 mmol/L glucose. The diabetic rats with one week duration did not demonstrate any changes in total glucose utilization both in basal and insulin-stimulated state. However more than two weeks duration of diabetes led to a 30% to 35% decrease both in basal and insulin-stimulated total glucose utilization, similar to the findings in the 2-deoxyglucose uptake study. We concluded that prolonged insulinopenia led to decreased glucose transport and intracellular glucose metabolism and resulted in insulin resistance in skeletal muscles.

Animals↗
PubMed1986

A primary defect in insulin receptor in a young male patient with insulin resistance.

We studied insulin binding to cells from an insulin-resistant patient, a 5-year-old boy with clinical Rabson-Mendenhall syndrome. Decreased insulin binding was observed in three different cells: erythrocytes (37.4% of normal), cultured fibroblasts (53.3% of normal), and transformed lymphocytes (9.8% of normal). Decreased insulin binding in the cultured cells suggested that the patient had a primary defect in insulin receptors. In addition, insulin binding to the transformed lymphocytes from the patient was relatively high at lower pH compared with those in normal subjects. The cultured fibroblasts from the patient showed decreased glucose incorporation at the low insulin concentration with normal maximal stimulation, and the insulin dose response curve was shifted to the right. These results suggested that the defect resided in the receptor binding but not in the postreceptor steps. This was one of the rare cases showing decreased insulin binding clearly demonstrated in three different cells from a young male patient with extreme insulin resistance.

Child↗
PubMed1986

Long-term in vitro effects of insulin on insulin binding and glucose transport.

The long-term in vitro effects of insulin on insulin binding and glucose transport were studied using rat adipocytes in a time-dependent manner. Isolated fat cells were incubated with insulin (100 ng/ml) for 4, 8 and 24 h in a TCM 199 medium, at 37 degrees C, and then insulin binding (37 degrees C, 60 min) and 3-O-methylglucose transport (37 degrees C, 2 s) were determined. Decreased insulin binding was demonstrated in the cells incubated with insulin for 8 h, and Scatchard analysis revealed that receptor number was decreased to 61.7% of that of control cells. Thus, insulin-induced down regulation of receptors was evident after 8 h incubation with insulin. On the other hand, 8 h incubation with insulin resulted in markedly increased basal (i.e., in the absence of insulin) glucose transport up to 246% of control values. In the cells incubated with insulin for 24 h, maximally insulin-stimulated glucose transport was significantly increased up to 248% of control value. Thus, these results suggested that insulin-induced down regulation of receptors appeared to be coupled with increased cell-surface glucose transporters, and that there was a time-lag between down regulation of insulin receptors and increase of available glucose transporters in the plasma membrane.

Adipose Tissue↗
PubMed1986

Can insulin antibodies of diabetic patients distinguish human insulin from porcine insulin?

We examined antisera from patients treated with bovine-porcine mixture (hereafter referred to as bovine/porcine), porcine or human insulin, and compared their binding affinities to human insulin with those to porcine insulin. Patients treated with bovine/porcine insulin developed antisera with a higher affinity to porcine insulin compared with that to human insulin in five of nineteen cases. Furthermore, three of these five antisera had a comparable affinity to bovine and porcine insulin and appeared to recognize the amino acid residue at B-30. Treatment with porcine or human insulin, on the other hand, did not result in any significant difference in the affinity to porcine and human insulin in twenty-three patients. These results indicate the significant role of B-30 amino acid residue as an antigenic determinant, and suggest that the amino acid sequence of the A chain of bovine insulin may contribute to the development of antibody recognizing B-30 amino acid residue.

Adult↗
PubMed1986

Pressor response to NaCl solution administered intracerebroventricularly or intracisternally to conscious normotensive and spontaneously hypertensive rats.

We examined the central action of NaCl on blood pressure using intracerebroventricular (i.c.v.) and intracisternal (i.c.) injections of hypertonic NaCl solution in conscious, unrestrained spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. The dose-dependent pressor response produced by i.c.v. hypertonic NaCl was greater in SHR than in WKY rats, while the dose-related pressor action produced by i.c. NaCl did not differ between the two strains. The hyperresponsiveness to i.c.v. NaCl in SHR was abolished by pretreatment with an i.c.v. injection of the angiotensin II (ANG II) analogue 1-Sar, 8-IIeu ANG II. Both ANG II and a combination of ANG II and NaCl given by i.c.v. injection had a greater pressor response in SHR than in WKY rats, although both ANG II and phenylephrine given intravenously elevated blood pressure to the same extent in both strains. Furthermore, i.c.v. ANG II both with and without hypertonic NaCl caused dipsogenic behaviour which lasted longer in SHR than in WKY rats. This response to i.c.v. hypertonic NaCl without ANG II was not substantially different between the two strains. Intracisternal hypertonic NaCl did not induce drinking behaviour. These observations suggest that in the SHR, the third ventricle rather than the brain stem is a more sensitive area to NaCl. The brain renin-angiotensin system in the SHR may play an important role in this accelerated pressor response and may be responsible, at least to some extent, for the enhanced reaction to chronic oral salt loading.

Angiotensin II↗
PubMed1986

Number of hits necessary for complement-mediated hemolysis.

The number of hits necessary for the C8 and C9 steps of immune hemolysis was reexamined with a previously unemployed experimental design, in which various numbers of EAC1-7, excess of the supplementary component and a constant amount of the component tested were incubated in a constant volume (Inoue et al. 1976. Infect. Immun. 13: 337). Our results were consistent with previous findings; the steps of guinea pig C8 and C9, the human C8 each followed a one-hit mechanism, while that of human C9 showed ka multi-hit response. When lysis of sensitized erythrocytes (EA) by normal human serum was analysed in a similar way, one-hit curves were obtained. This result, taken together with the above results, suggests that immune hemolysis occurs by a single lesion including a single C8 and multiple C9 in the case of human complement and that normal human serum contains sufficient excess of C9. On the other hand, when C9-deficient human serum was used for lysis of EA, multiple-hit curves were obtained. The mechanism of lysis by C5b-8 may differ from that by C5b-9.

Animals↗
PubMed1986

Effect of diet change on insulin action: difference between muscles and adipocytes.

To investigate the difference of insulin action between skeletal muscle and adipose tissue in response to dietary manipulation, we studied the effect of high-sucrose (HS) and high-fat (HF) diet on insulin action by measuring insulin binding and insulin action both in soleus muscles and adipocytes. HS feeding led to a 14 and 28% decrease, and HF feeding led to a 25 and 36% decrease in insulin binding both to soleus muscles and adipocytes, respectively (P less than 0.01). In HF-fed rats, both rates of glucose uptake and intracellular glucose metabolism were impaired by 30-40% in soleus muscles (P less than 0.01), and adipocyte glucose uptake was also decreased by 30% in the submaximally insulin-stimulated state (P less than 0.05). On the other hand, in HS-fed rats with prominent hyperinsulinemia, glucose uptake was 2.3- to 2.7-fold increased in adipocytes (P less than 0.01). However, both rates of glucose uptake and intracellular glucose metabolism were not increased in soleus muscles from HS-fed rats. Steady-state plasma glucose (SSPG) level was unchanged in HS-fed rats during somatostatin, glucose, and insulin infusion, whereas the SSPG level of HF-fed rats was twice as much as that in controls (P less than 0.01). These results indicate that long-term regulation of glucose metabolism by ambient insulin in skeletal muscle may be different from that in adipocytes and that insulin action in muscle, rather than in adipocyte, may reflect insulin action of whole body.

Adipose Tissue↗
PubMed1986

Brain renin angiotensin system contributes to the salt-induced enhancement of hypertension in SHR.

The study was performed to determine whether the brain renin angiotensin system may contribute to the acceleration in hypertension following long-term salt loading in spontaneously hypertensive rats (SHR). Five weeks old SHR and normotensive Wistar-Kyoto (WKY) were given 1% NaCl solution or plain tap water as drinking for 7 weeks. The salt treatment exaggerated the development of hypertension in SHR, but did not change the blood pressure (BP) in WKY. The hypotensive actions of intracerebroventricular (ICV) captopril was greater in SHR treated with salt than in those without treatment, whereas ICV AII increased BP to a similar degree between salt and control SHR. In WKY, the effects of ICV captopril and AII were not altered by the salt loading. The increases in BP induced by ICV hypertonic saline were not different between the rats with and without saline drinking in either SHR or WKY. The intravenous (IV) hexamethonium led to a greater fall in BP in SHR treated with saline than in those without salt, while it tended to produce a smaller decrease in BP in WKY with salt overload than in those without loading. Both duration and magnitude of the depressor effects of IV captopril were reduced by the chronic saline treatment in SHR. The plasma renin concentration (PRC) in both SHR and WKY was significantly suppressed by the salt load. The present results suggest that long-term salt overload may result in the enhanced activity of brain renin angiotensin system, which could be responsible for the exaggerated development of hypertension in SHR. Our observations also provide further evidence that the central renin angiotensin system is independent of the peripheral system.

Angiotensin II↗
PubMed1986

Comparative study on acute antihypertensive effects and pharmacokinetics of nisoldipine, nifedipine, nimodipine and nicardipine administered orally to conscious renal hypertensive dogs.

The acute antihypertensive effects and pharmacokinetics of orally administered nisoldipine (Bay k 5552) were compared with those of nifedipine, nimodipine and nicardipine in conscious renal hypertensive dogs. The antihypertensive effects of hydralazine were also investigated. Nisoldipine as well as nifedipine, nimodipine and nicardipine dose-dependently lowered mean blood pressure, which was significant 0.5 h and reached its peak effect 1 to 2 h after dosing. Significant antihypertensive effects of hydralazine started 1 h and peaked 3 h after dosing. Of the drugs used, nisoldipine showed the most potent and the longest antihypertensive effects. The fall in mean blood pressure by the drugs was accompanied by a significant increase in heart rate. The tachycardia by nisoldipine and nimodipine, but not by nifedipine and nicardipine, was not dose-dependent. The tachycardia by nisoldipine was not significantly different from those by the other four drugs. The plasma nisoldipine concentration was significantly correlated with the fall in mean blood pressure. This was also the case for nifedipine, nimodipine or nicardipine. However, the slope of the regression line for nisoldipine obtained by plotting the antihypertensive effects against plasma concentrations was greater than those for the other 1,4-dihydropyridines examined. Nisoldipine had the lowest maximum plasma concentration and the longest elimination half-life among the four 1,4-dihydropyridines, resulting in no significant difference in the area under the plasma concentration-time curve. These results suggest that of the drugs examined, nisoldipine is the most potent, has the longest duration of action making it useful for long-term treatment of hypertension.

Administration, Oral↗
PubMed1985

[A case of leprechaunism with extreme insulin resistance due to a primary defect in insulin receptors].

This report describes a 3-month-old female infant with the typical physical features of leprechaunism. The patient demonstrated glucose intolerance and marked hyperinsulinemia (4600 microU/ml). Since an intravenous insulin injection (actrapid insulin: 0.15 U/kg) caused no significant decrease in the blood glucose level, the presence of insulin resistance was suggested. Neither insulin antibodies nor insulin receptor antibodies were were found in the patient's plasma, and other circulating insulin antagonists such as glucagon, growth hormone, and cortisol were within normal limits. [125I]Insulin binding to the erythrocytes from the patient was as low as 1.02% (control infants: 4.89 +/- 1.08% [mean +/- SD]). [125I]Insulin binding to the cultured transformed lymphocytes from the patient was similarly reduced to 3.58% (control: 20.9 +/- 2.71% [mean +/- SD]). From these findings we concluded that the insulin resistance was due to a primary defect in insulin receptors. Interestingly, transient remissions of the patient's glucose intolerance and hyperinsulinemia were observed during a year of follow-up study. The insulin tolerance test which was performed at the remission period showed an improvement in insulin resistance. However, the insulin binding defect to erythrocytes remained unchanged even at the remission period. The exact cause of these remissions was not clear and remained to be elucidated.

Abnormalities, Multiple↗
PubMed1985

Chemical modification of S-adenosylhomocysteinase by a water-soluble carbodiimide.

S-Adenosylhomocysteinase (EC 3.3.1.1) from rat liver is inactivated by 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate (CMC) in a pseudo-first-order fashion. The rate of inactivation is linearly related to the concentration of the reagent, and a second-order rate constant of 4.94 +/- 0.27 M-1 min-1 is obtained at pH 5.5 and 25 degrees C. The inactivation does not involve change in the quaternary structure of the enzyme nor modification or release of the enzyme-bound NAD. Lack of modification at tyrosine, serine, cysteine, histidine, and lysine residues and the fact that the inactivation is favored at low pH suggest that the inactivation is caused by the modification of a carboxyl group. Statistical analysis of the relationship between the residual enzyme activity and the extent of modification, and comparison of the number of residues modified in the presence and absence of the substrate adenosine show that, among four reactive residues per enzyme subunit, only one residue which reacts more rapidly with the reagent than the rest is critical for activity. The CMC-modified enzyme binds adenosine and S-adenosylhomocysteine and is able to oxidize the 3' hydroxyl of these substrates, but apparently fails to catalyze the abstraction of the 4' proton of adenosine.

Adenosylhomocysteinase↗
PubMed1985

Inhibition of down regulation by chloroquine in cultured lymphocytes (RPMI-1788 line).

We studied the effect of chronic exposure to insulin on insulin receptors of cultured lymphocytes (RPMI-1788 line). The cells treated with insulin (2 micrograms/ml) at 37 degrees C for 12 h, showed a 36.5% decrease in the number of binding sites. Solubilized extract from the cells treated with insulin showed a 35.9% decrease of binding capacity, suggesting that insulin exposure induced the loss of total (cell surface and intracellular) receptors. Insulin-induced loss of receptors was blocked by chloroquine, suggesting that receptor loss is mediated by a chloroquine sensitive pathway. Bacitracin, which inhibited the insulin degradation, had no effect on insulin-induced receptor loss in this cell line. We also found that vitamin K5, one of the insulin mimickers, induced a 31.5% loss of insulin receptors. Therefore, the post-receptor process appeared to mediate down regulation. In cultured lymphocytes, insulin exposure caused a significant loss of total receptors, suggesting that insulin-induced receptor loss may be due to receptor degradation. Insulin-induced receptor loss is mediated by a chloroquine sensitive pathway, and is related to the post-binding process stimulated by vitamin K5.

Bacitracin↗
PubMed1985

Prolonged disappearance rate of a structurally abnormal mutant insulin from the circulation in humans.

The first mutant insulin, [LeuB25]insulin, was semisynthesized, and its disappearance rate from the circulation was measured. Three micrograms of normal human or [LeuB25] insulin per kg were administered to three normal subjects. The half-lives of normal insulin and the mutant insulin were 4.5 and 24 min, respectively. The decrement in blood glucose levels after injection of mutant insulin was 22.6% that after injection of normal insulin. The blood glucose-lowering effect of the mutant insulin, evaluated by the time required to reach the nadir, was slightly prolonged (30 vs. 45 min). These results indicate that hyperinsulinemia in patients with abnormal insulin is due to prolonged disappearance because of decreased receptor binding.

Adipose Tissue↗
PubMed1985

Effects of Ca antagonists on the norepinephrine release and contractile responses of isolated canine saphenous veins to high KCl.

Effects of verapamil, diltiazem and nicardipine on tritium overflow and contraction evoked by 40 mM KCl were evaluated using canine saphenous vein strips preloaded with [3H]norepinephrine. Phentolamine, 10(-6) M, almost completely inhibited the contraction induced by KCl, while it significantly enhanced the evoked tritium overflow. These responses to KCl were dependent on external Ca2+. All Ca antagonists tested significantly increased the spontaneous tritium overflow in a concentration-dependent manner without any changes in basal tension. Verapamil at 10(-6) M significantly inhibited the contraction with no significant effect on the evoked overflow; and at concentrations above 10(-5) M, it inhibited the contraction much more strongly than the evoked tritium overflow. Diltiazem and nicardipine at concentrations above 3 X 10(-6) M significantly inhibited both tritium overflow and contraction evoked by KCl. A significant correlation between inhibitions of both responses to KCl by the three Ca antagonists was observed, although the y-intercept and slope of the regression line for verapamil obtained by plotting the inhibition of the KCl-evoked contraction as a function of the inhibition of the evoked tritium overflow were greater than those for the other two antagonists. The inhibitory effects of verapamil and diltiazem on the tritium overflow and contraction evoked by KCl were not related to their local anesthetic activities. Neither the increase in the spontaneous tritium overflow nor inhibitions of the evoked tritium overflow and contraction by nicardipine were related to its phosphodiesterase inhibiting activity. These results suggest that diltiazem and nicardipine may inhibit the KCl-evoked contraction mainly by inhibiting Ca2+-dependent transmitter release from the nerve endings, while verapamil may inhibit it by acting on the postsynaptic sites and at the relatively higher concentrations used, by further inhibition of transmitter release.

1-Methyl-3-isobutylxanthine↗
PubMed1985

In vivo and in vitro effect of p-chlorophenoxyisobutyrate on insulin binding and glucose transport in isolated rat adipocytes.

We studied the in vivo and in vitro effect of p-chlorophenoxyisobutyrate (CPIB) on insulin binding and glucose transport in isolated rat adipocytes. In the in vitro study, adipocytes were incubated with 1mM of CPIB for 2 h at 37 degrees C, pH 7.4, and then insulin binding (37 degrees C, 60 min) and 3-0-methylglucose transport (37 degrees C, 2s) were measured. Incubation with CPIB did not affect either insulin binding or glucose transport in the cells. The addition of insulin (10 ng/ml) with CPIB to the incubation media also did not affect the following insulin binding and glucose transport. In the in vivo study, rats were fed a high sucrose-diet containing 0.25% CPIB for 7 days. Serum cholesterol, plasma free fatty acid, and insulin levels were significantly decreased in the CPIB-treated rats. The treated rats demonstrated an almost 2 fold increased maximal binding capacity for insulin (189,000 sites/cell for treated vs 123,000 sites/cell for control cells). Basal glucose transport (glucose transport in the absence of insulin) significantly decreased in the CPIB-treated rats, although insulin-stimulated glucose transport was comparable in treated and control cells. Thus, CPIB might have no direct effect on glucose transport and insulin binding, as determined by the in vitro studies. Furthermore, a relatively short-term in vivo treatment with CPIB, such as 7 days, did not stimulate glucose transport.

3-O-Methylglucose↗
PubMed1985

Decreased biologic activity and degradation of human [SerB24]-insulin, a second mutant insulin.

A second mutant insulin, identified as [SerB24]-insulin, has a highly hydrophilic character. To determine the biologic activity and the degradation of this mutant insulin, human [SerB24]- and [SerB25]-insulin analogues were semisynthesized from porcine insulin by an enzyme-assisted coupling method. All of the following studies on isolated rat adipocytes were performed at 37 degrees C to directly correlate the binding potency and the biologic activity. The ability of these insulins to displace 125I-porcine insulin bound to adipocytes was 0.5-2% and 1-4%, respectively, of porcine insulin. When the ability of these insulins to stimulate glucose transport and glucose oxidation was measured, both analogues had full activity at high concentrations (250 ng/ml). However, ED50 of the porcine, [SerB24]-, and [SerB25]-insulins to stimulate glucose transport was 0.37 +/- 0.05, 46.3 +/- 5.4, and 23.3 +/- 5.5 ng/ml, respectively. Similarly, for glucose oxidation, ED50 was 0.38 +/- 0.06, 33.8 +/- 3.6, and 16.6 +/- 3.4 ng/ml, respectively. Thus, the biologic activity of [SerB24]- and [SerB25]-insulins was reduced to 0.5-2% and 1-4% of that of porcine insulin, which was compatible with our previous studies under different conditions. No antagonistic effects were observed for either analogue. Degradation of 125I-labeled [SerB24]- and [SerB25]-insulins was also decreased to 62.8% and 55.8%, respectively, of 125I-porcine insulin. These results confirm the importance of the hydrophobic residues at B24 and B25 in the biologic activity of insulin; the patient having this hydrophilic insulin was considered to be in an insulinopenic state despite the hyperinsulinemia due to decreased degradation of the mutant insulin.

Adipose Tissue↗