Biomedical subjects

Y Shigeta

Publications and source records attributed to Y Shigeta.

At least 163 records · Page 9Linked to original sources

PubMed1987

The effect of high-glucose condition on insulin binding to IM-9 lymphocytes.

The long-term effect of high-glucose condition on insulin binding to IM-9 cells was studied by incubating the cells in RPMI-1640 medium containing 450 mg/dl of glucose. Insulin binding began to decrease after incubation for 6 days in high-glucose-treated cells, and significantly decreased after 14 days due to the reduction of receptor affinity. The number of binding sites for insulin did not change by the treatment. Thus, high-glucose condition per se does not appear to induce the decrease of the number of insulin receptors on target cells, as observed in diabetic patients.

Cell Line↗

PubMed1987

Thyrotropin-releasing hormone reduces myo-inositol content in rat cerebellum pretreated with lithium.

The effect of thyrotropin-releasing hormone (TRH) and lithium on myo-inositol metabolism has been assessed in rat cerebral cortex, cerebellar cortex, and sciatic nerves. Sprague-Dawley male rats were injected subcutaneously with 10 mEq/kg of LiCl and intraperitoneally with 10 mg/kg of TRH-tartrate, alone or in combination. Either lithium or TRH alone had little effect on the myo-inositol concentration in cerebellar cortex, whereas the combination of lithium and TRH significantly lowered the level. The myo-inositol level of cerebellar cortex reached its nadir (70% of values in untreated control rats) 30 min after addition of TRH and then returned to the control level at 90 min. In cerebral cortex, both lithium alone and lithium plus TRH significantly reduced the myo-inositol level. No effect was seen on the myo-inositol concentration in sciatic nerves with these regimens. These results suggested that the pharmacological dose of TRH activated phosphatidylinositol turnover in rat cerebellar cortex and subsequently reduced the myo-inositol level in the presence of lithium.

Animals↗

PubMed1987

Computerized glucose clamp method for the determination of insulin sensitivity in diabetic subjects.

A new, simplified computerized glucose clamp method was performed for estimation of glucose utilization at the insulin level of postprandial level. The program for the method is based on the mathematical algorithm using values of blood glucose, changes of its concentration and the desired glucose level. The coefficients of variation of the clamped blood glucose values during the last 60 minutes was 6.3 +/- 1.7(%) in normal, 3.7 +/- 0.3(%) in NIDDM, which was within satisfactory limit, and also indicated an attainment of steady state. Glucose infusion curves showed some bumps for the initial 60 min, which did not seriously affect the glucose utilization rate at steady state. In some cases, whose insulin sensitivity was high, CV was not low enough and occasional manual adjustment of K values was required. Average glucose infusion rate was 7.59 +/- 0.85 (mg/kg/min) in normal, and this was significantly lowered in NIDDM (42.3 +/- 3.4) at steady state, indicating a decreased insulin sensitivity for glucose utilization in NIDDM.

Adult↗

PubMed1987

Chronic idiopathic neutropenia with hypergammaglobulinemia.

Chronic idiopathic neutropenia can occur in spite of the normocellular bone marrow in myeloid series with or without anti-neutrophilic antibody. We report a patient with chronic neutropenia and severe polyclonal hypergammaglobulinemia. The patient demonstrated a positive anti-neutrophil antibody by fluorocytometry, although granulocyte-specific anti-nuclear factor and anti-stem cell (CFU-GM) antibody were negative. Thus, neutropenia of this patient appeared to be due to the antibody-mediated destruction of neutrophils. Both neutropenia and hypergammaglobulinemia were normalized by the administration of prednisone.

Aged↗

PubMed1987

Evidence for existence of polyol pathway in cultured rat mesangial cells.

The accumulation of polyols has been previously found in renal glomeruli isolated from streptozocin-induced diabetic (STZ-D) rats, although the intraglomerular polyol pathway has not been exactly localized. Because we have previously observed mesangial cell dysfunction in STZ-D rats, we examined whether the polyol pathway exists in mesangial cells as a possible candidate of the cause of cellular dysfunction. The activities of two polyol pathway enzymes, aldose reductase and sorbitol dehydrogenase, were clearly detected in the crude homogenate of cultured mesangial cells at higher levels than those of whole glomeruli when DL-glyceraldehyde or D-fructose was used as substrate. When cells were incubated in medium containing 55 mM glucose or galactose, a large amount of sorbitol or galactitol was accumulated intracellularly. The accumulation of polyols was effectively blocked by an aldose reductase inhibitor, ICI 128436. These results suggest that the polyol pathway exists in mesangial cells of rat glomeruli and may play a role in the development of mesangial cell dysfunction found in STZ-D rats.

Aldehyde Reductase↗

PubMed1986

A suppressive role of c-kinase for the stimulation of hepatic ketogenesis by glucagon and epinephrine.

The regulatory mechanism of hepatic palmitate oxidation into ketone bodies by c-kinase has been studied in isolated hepatocytes. Glucagon and epinephrine stimulated [U-14C]palmitate oxidation to ketone bodies by 60 and 25% as early as at 1 h. The stimulatory effects were almost totally prevented by the simultaneous presence of vasopressin, phorbol 12-tetradecanoate 13-acetate (TPA), or diacylglycerol (1-oleoyl-2-acetylglycerol). When hepatocytes were treated with glucagon or epinephrine, carnitine palmitoyltransferase (CPT), a key regulatory enzyme of palmitate oxidation, was activated. This hormone-induced activation of CPT was not observed in the presence of TPA. These observations suggest that c-kinase inhibits glucagon- or epinephrine-stimulated palmitate oxidation to ketone bodies, and that this inhibition may be mediated through a covalent modification of CPT.

Animals↗

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

Impaired contractile responsiveness of diabetic glomeruli to angiotensin II: a possible indication of mesangial dysfunction in diabetes mellitus.

The contractile function of renal glomerulus was studied in vitro using isolated glomeruli from streptozotocin-diabetic rats. Glomerular contraction was assessed by the reduction of extracellular [3H]inulin space of glomerulus, mostly composing of intracapillary space, produced by angiotensin II. The inulin space was dose-dependently reduced after angiotensin II addition in both diabetic and control rats but the degree of reduction significantly smaller in the former. The radioreceptor assay revealed rather increased angiotensin II receptors in diabetic glomeruli. Since the contractile response of glomerulus to angiotensin II is mediated via mesangial cell contraction, these results suggest the presence of mesangial cell dysfunction in diabetes.

Angiotensin II↗

PubMed1986

Effect of angiotensin II infusion on glomerular angiotensin II receptor in rats.

Previous studies by other investigators have shown that sodium depletion causes down-regulation of angiotensin II receptors in renal glomeruli, which is ascribed to elevation of circulating angiotensin II levels. The present study was designed to determine whether elevation of circulating angiotensin II levels alone can down-regulate its own receptors without changes in the sodium balance. Rats were infused with angiotensin II at 50 ng/min intraperitoneally for 24 h or 7 d, then glomeruli were isolated by a mechanical sieving technique and used in a radioreceptor assay for angiotensin II. Angiotensin II infusion for 24 h and for 7 d both significantly suppressed plasma renin activity, and elevated plasma angiotensin II level (3-fold) but did not affect the plasma sodium and potassium or differences between dietary intake and urinary excretion of these electrolytes. By Scatchard analyses significant down-regulation of angiotensin II receptor number was demonstrated in renal glomeruli derived from rats infused with angiotensin II for either 24 h (32% decrease from the control value) or 7 d (37% decrease). No significant changes in receptor affinity were observed after 24 h of angiotensin II infusion, although the infusion for 7 d slightly but significantly decreased Kd (to 2.57 +/- 0.08 nM from 3.17 +/- 0.19, P less than 0.01). From these results, we conclude that circulating angiotensin II level itself can regulate the number of its own receptors in renal glomeruli even in the absence of changes in the sodium balance.

Angiotensin II↗

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

Development of specific and non-specific somatostatin analogs.

Biological activity of six somatostatin analogs has been investigated. In these analogs, disulfide bond is replaced by ethylene bond cyclized with alpha-amino suberic acid. In addition, they contain unique D-configuration in both Trp8 and Cys14 moiety with dicarba substitution. An analog of the short chain length, C omega 7-cyclo (Phe6-Phe7-D-Trp8-Lys9-Thr10-Phe11-D-Asu14) (analog 4) has suppressive effect for GH, but not for other hormones. Analog 6, C omega 9-cyclo(Asn5-Phe6-Phe7-D-Trp8-Lys9-Thr10-Ph e11-Thr12-D-Asu14), has suppressed GH and insulin secretion, but not for gastrin and glucagon. Analog 1, C omega 11-cyclo (Lys4-Asn5-Phe6-Phe7-D-Trp8-Lys9-Thr10-Phe11- Thr12-Ser13-D-Asu14] and 5, C omega 9-cyclo (Lys4-Asn5-Phe6-Phe7-D-Trp8-Lys9-Thr10-Phe11-D-+ ++Asu14) have broad suppressive effect for GH, gastrin, insulin and glucagon release after arginine infusion. The shortest analog, analog 2, C omega 5-cyclo (Phe7-D-Trp8-Lys9-Thr10-D-Asu14) has weak suppressive effect of GH, insulin and glucagon secretion, and it is suggested that Phe6 and Phe11 are necessary for the appearance of suppressive effect of GH. Specific analog, analog 4, may be useful for the future treatment for acromegaly and diabetic retinopathy. Nonspecific analogs, 1 and 5 are candidates for the clinical application of wide variety.

Animals↗

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

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

Biphasic alteration of renin-angiotensin-aldosterone system in streptozotocin-diabetic rats.

The alteration of renin-angiotensin-aldosterone system caused by diabetes mellitus was studied in streptozotocin-diabetic rats. The plasma renin activity (PRA), and plasma levels of angiotensin II (A II) and aldosterone (PAC) were measured in diabetic and age-matched control rats in 1, 2, 4 and 8 weeks after the intravenous injection of streptozotocin (50 mg/kg body weight). Diabetic rats showed the marked hyperglycemia persistently throughout the experimental period. On 1st week PRA, A II and PAC were significantly increased, and A II and PAC were also significantly elevated on 2nd week in diabetic rats compared with control rats. However, on 4th and 8th weeks PRA, A II and PAC in diabetic rats were significantly lower than those of control rats. Hematocrit values in diabetic rats were elevated on 1st week, normalized on 2nd and 4th weeks and then decreased on 8th week. These results may suggest that the hyperglycemia causes a biphasic alteration of renin-angiotensin-aldosterone system, i.e., early stimulated state due to volume depletion and later suppressed state due to volume expansion.

Aldosterone↗

PubMed1986

Low frequency of the large insertion in the human insulin gene in Japanese.

We have studied the restriction fragment-length polymorphism in the 5'-flanking region of the human insulin gene in 47 nondiabetic Japanese subjects and in 52 subjects with non-insulin-dependent diabetes (NIDDM) to elucidate the ethnic variation of the genetic polymorphism and its relationship with NIDDM. Allelic frequencies in the nondiabetic subjects were 0.957 in class 1 (Bgl l fragments of 2800 +/- 300 bp), 0 in class 2 (fragments of 3500 +/- 300 bp), and 0.043 in class 3 (fragments of greater than 3900 bp with a mean of 4500 bp). Corresponding frequencies in the NIDDM subjects were 0.962, 0, and 0.038, respectively. Four subjects with NIDDM who had the class 3 allele did not exhibit any particular clinical characteristics compared with the rest of the patients. Thus, the class 3 allele or the large insertion of the human insulin gene is much less frequent in Japanese than reported in other races, including Caucasians, and this class of allele is not associated with NIDDM in Japanese. Ethnic homogeneity is, thus, important in the analysis and interpretation of the genetic polymorphism.

Adult↗

PubMed1986

New alpha 2-adrenergic blocker (DG-5128) improves insulin secretion and in vivo glucose disposal in NIDDM patients.

Effects of oral administration of DG-5128, a new oral hypoglycemic agent, on glycemic control after a mixed meal and an in vivo glucose disposal were measured in subjects with nonobese non-insulin-dependent diabetes mellitus (NIDDM). Oral administration of DG-5128 significantly (P less than .05) enhanced insulin secretion both 30 and 60 min after a mixed meal (550 kcal), with a concomitant decrease in postprandial plasma glucose levels at 60 and 120 min. Glucose disposal rate between the 2nd and 4th h of a euglycemic insulin clamp, developed through a constant infusion of insulin (0.77 mU X kg-1 X min-1) together with somatostatin (80 ng X kg-1 X min-1), was 2.5-fold higher in a DG-5128-treated group (P less than .01) than in a control group. However, there was no difference between the two groups in either plasma glucose concentration or plasma insulin concentration at either the 2nd or the 4th h. These results indicate that DG-5128 is effective in controlling plasma glucose levels in subjects with NIDDM by stimulation of both insulin secretion and in vivo glucose disposal.

Adrenergic alpha-Antagonists↗