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Biomedical subjects

K Fujiyama

Publications and source records attributed to K Fujiyama.

At least 73 records · Page 4Linked to original sources
PubMed1990

Acute effect of thyroid hormone on insulin secretion in rats.

To elucidate the mechanism of thyroid hormone-induced hyperinsulinemia, the acute and direct effect of thyroid hormone administration on insulin secretion was investigated in rats in vivo and in vitro. In the perfused rat pancreas, the addition of thyroxine (10 micrograms/dL) or 3,5,3'-triiodothyronine (150 ng/dL) to the perfusing medium did not affect insulin secretion. The administration of thyroxine (40 micrograms/kg, s.c.) in vivo increased the plasma insulin level from 11 +/- 2 microUnits/mL (mean +/- SD) to 30 +/- 7 microUnits/mL, while blood glucose and plasma glucagon were unchanged. This phenomenon was inhibited completely by the preadministration of oxprenolol hydrochloride (2 mg/kg, s.c.), and inhibited partly by the preadministration of metoprolol tartrate (35 mg/kg, s.c.). These results suggest that thyroid hormone induces hyperinsulinemia via beta-adrenergic stimulation in the rat.

Animals↗
PubMed1990

Genomic DNA structure of two new horseradish-peroxidase-encoding genes.

Genomic DNAs encoding the horseradish peroxidase (HRP) isozymes, prxC2 and prxC3, were cloned and sequenced. By comparing the sequences of the HRP isozyme-encoding genes, prxC1a and prxC1b and their cDNA [Fujiyama et al., Eur. J. Biochem. 173 (1988) 681-687], , it was concluded that prxC2 and prxC3 consisted of four exons and three introns as in the prxC1 gene family. The position of introns in coding regions were the same in all four prx genes. Genes prxC2 and prxC3 coded for 347 and 349 amino acid (aa) residues, respectively, including putative signal sequences at the N termini. In the flanking regions of both genes, putative promoters and polyadenylation signals were found. Nucleotide sequence homology in the coding region was 71% between prxC1a and prxC2, and 66% between prxC1a and prxC3. The aa sequence homologies in plant and microbial peroxidases were compared.

Amino Acid Sequence↗
PubMed1990

Oral and intravenous glucose-induced insulin secretion in hyperthyroid patients.

To elucidate glucose intolerance in hyperthyroidism, insulin response to oral (75 g) and intravenous (IV) (20 g) glucose administration was investigated in 18 hyperthyroid patients and six normal control subjects. In oral glucose tolerance tests (OGTT), plasma insulin and C-peptide levels in hyperthyroid patients were not significantly different from that in controls; however, an impaired blood sugar response was observed in hyperthyroid patients. In IVGTT, blood sugar, plasma insulin, and C-peptide levels were significantly higher in hyperthyroid patients than in controls. Insulin secretion in proportion to blood sugar stimulus (the sum of increment in insulin divided by the sum of increment in blood sugar after glucose load, sigma delta IRI/sigma delta BS) in IVGTT was similar in hyperthyroid patients and controls; however, that in OGTT was significantly lower in hyperthyroid patients. After thyroid function tests had returned to normal by treatment with thiamazole, glucose tolerance and sigma delta IRI/sigma delta BS in OGTT were almost normalized. These results indicate that decreased insulin secretion after oral glucose may have an important role in abnormal oral glucose metabolism in hyperthyroidism.

Administration, Oral↗
PubMed1990

Possible role of the stomach in enteroinsular axis in rats.

To elucidate the possible role of the stomach in enteroinsular axis, rats had both an inflow gastric cannula and an outflow diversion cannula and a duodenal inflow cannula. The effects of intragastric infusion of glucose (1 mL in 10% solution) or mannitol (1 mL in 10% solution) on blood and plasma insulin responses to subsequent intraduodenal glucose (1.5 g/kg in 10% solution) or amino acids (1.0 g/kg in 10% solution) infusion were investigated. Blood glucose and plasma insulin responses to intraduodenal amino acids were not altered by intragastric infusion of glucose or mannitol. However, higher blood glucose and lower plasma insulin responses to intraduodenal glucose were observed in the rat with intragastric infusion of glucose or mannitol compared with controls (intragastric infusion of distilled water). This phenomenon was abolished in the rat with preadministration of phentolamine. These results suggest that intragastric tonicity may suppress glucose-induced insulin secretion, probably through the alpha-adrenergic mechanism in the rat.

Amino Acids↗
PubMed1990

Effect of long-term administration of insulin and glibenclamide on pancreatic A and B cell function.

To investigate the effects of insulin and sulfonylurea drug administration on islet A and B-cell functions, insulin and glucagon response was studied in normal rats treated with insulin (4 U/day subcutaneously) or glibenclamide (0.03 mg/kg intraperitoneally) for 8 weeks. In intravenous glucose tolerance test (0.5 g/kg), lower insulin response and impaired glucose tolerance were observed in insulin-treated rats and higher insulin response and impaired glucose tolerance were observed in glibenclamide-treated rats. In perfused pancreas, insulin response to glucose and arginine was significantly lower in insulin-treated rats and that was significantly higher in glibenclamide-treated rats. Glucagon response was not altered by insulin or glibenclamide treatment. These results suggest that hyperinsulinisation and glibenclamide administration strongly influence pancreatic B-cell function but not influence pancreatic A-cell function.

Animals↗
PubMed1990

Anaplastic ependymoma of the spinal cord in childhood. A case report.

We report a 6-year-old girl with anaplastic ependymoma probably originating in the region of the conus medullaris and probably spreading retrogradely to the region of the interventricular foramen (Monro) through the cerebrospinal fluid (CSF). Since ependymoma of the spinal cord rarely occurs in children, and retrograde spreading is extremely rare, the histological features and mechanism of metastasis of the tumor are discussed.

Child↗
PubMed1990

Possible role of thyroid hormone in decreased somatomedin-C levels in diabetic and starved rats.

To elucidate the possible role of thyroid hormone in somatomedin-C (SmC)/insulin-like growth factor I regulation in diabetes mellitus and starvation, plasma SmC, liver SmC, and kidney SmC concentrations were measured in streptozotocin-induced (60 mg/kg) diabetic and starved (for 72 h) rats. Triiodothyronine (T3, 5.0 micrograms/kg every 24 h) was subcutaneously injected into diabetic rats for 7 days and into starved rats at 12, 36, and 60 h after starvation. Plasma T3, plasma SmC, liver SmC, and kidney SmC concentrations were significantly decreased in diabetic and starved rats. T3 administration restored plasma T3 levels to the normal value in diabetic and starved rats. Plasma SmC and kidney SmC concentrations were significantly increased in T3-treated starved rats, while they were not increased in T3-treated diabetic rats. These results suggest that thyroid hormone may have some role in SmC regulation during starvation, but may have no role in diabetes mellitus in the rat.

Animals↗
PubMed1990

Effect of intestinal osmolality on insulin secretion to subsequent intravenous glucose or arginine in the rat.

To elucidate the effect of intestinal osmolality on insulin secretion, we investigated insulin response to a subsequent intravenous infusion of glucose or arginine after intragastric or intraduodenal mannitol or NaCl instillation in the rat. After anesthesia with intraperitoneal pentobarbital sodium, mannitol solution (10% or 20%) or 2.7% NaCl was instillated into the stomach or duodenum for 5 min at a flow rate of 0.5 ml/min, and 20% glucose (0.5 g/kg) or 10% L-arginine (0.5 g/kg) was infused bolus into the femoral vein 45 min after intestinal instillation. Insulin response to intravenous glucose was significantly higher in the rat with intragastric or intraduodenal mannitol or NaCl infusion than in control rats with intragastric or intraduodenal instillation of distilled water. Insulin response to intravenous arginine was almost the same in all groups. Subcutaneous preadministration of propranolol (0.4 mg/kg), atropine (1.2 mg/kg), or phentolamine (0.8 mg/kg) did not alter the present phenomenon. These results suggest that intestinal osmolality may enhance insulin release to intravenous glucose, but not to arginine in the rat.

Animals↗
PubMed1989

Effect of thyroid hormone on somatomedin-C release from perfused rat liver.

The effect of thyroid hormone on plasma somatomedin-C (SmC) level and on SmC release from perfused rat liver was investigated. Plasma SmC levels and liver tissue SmC were significantly increased in thyroxine-treated rats. Physiological doses of triiodothyronine increased SmC release and SmC concentration in the perfused rat liver. These results indicate that thyroid hormone directly enhances the synthesis and release of SmC in the rat.

Animals↗
PubMed1989

Glucose tolerance and gastric emptying in thyrotoxic rats.

To clarify the contribution of gastrointestinal function to impaired oral glucose tolerance in hyperthyroidism, gastric emptying rate and portal and peripheral blood glucose responses to intragastric or intraduodenal glucose administration were investigated in experimental thyrotoxic rats. Glucose absorption from perfused intestine of thyrotoxic rats was also examined. Thyrotoxicosis was induced by subcutaneous (SC) thyroxine injection (50 micrograms/kg/d) for seven days. In intragastric glucose tolerance test, although insulin and glucagon responses were not significantly altered, increments in portal and peripheral blood glucose were significantly higher in thyrotoxic rats than in controls at 30 minutes. This phenomenon was almost normalized by the preadministration of phentolamine (2 mg/kg SC). In intraduodenal glucose tolerance test, blood glucose, insulin, and glucagon responses were similar in thyrotoxic and control rats. Gastric emptying rate in thyrotoxic rats was significantly higher than that in controls at 30 minutes, and that was also normalized by phentolamine administration. Absorption of glucose from perfused intestine was similar in thyrotoxic and control rats. These results suggest that an altered glucose tolerance to intragastric glucose load in thyrotoxic rats may primarily be due to rapid gastric emptying induced by increased alpha-adrenoceptor responses, and that glucose absorption from small intestine was not increased in short-term thyrotoxic rats.

Animals↗
PubMed1989

Thyroidal dependence of glucose-induced insulin secretion in starved rats.

To elucidate the possible role of thyroid hormone in insulin secretion during starvation, we investigated the glucose-induced insulin release in T3-administered starved rats. The rats were fasted for 72 hr, and one-half of the starved rats were administered subcutaneous 3,5,3'-triiodothyronine (5.0 micrograms/kg) at 12, 36, and 60 hr. In an intravenous glucose (0.5 g/kg) infusion test, insulin response was significantly lower in starved rats than in fed controls. This decreased insulin was restored by T3 administration. These results suggest the thyroidal dependence of insulin response to glucose in short-term starvation.

Animals↗
PubMed1989

Decreased plasma C-peptide to insulin molar ratio after oral glucose in elderly subjects.

To evaluate the effect of aging on hepatic extraction of insulin, peripheral plasma insulin and C-peptide levels after an oral glucose ingestion were measured in 39 non-obese healthy subjects with normal glucose tolerance test. The subjects were divided into two groups. One age group was below 30 years (n = 17) and another was above 50 years (n = 22). Blood glucose level was significantly higher in elderly subjects than in young at 30 and 60 min, and insulin level was also significantly higher in elderly subjects than in young subjects at 60 min after glucose ingestion. C-peptide response after glucose ingestion was similar in both groups. The molar ratio of C-peptide to insulin after glucose ingestion in elderly subjects was slightly lower than that in young subjects, and the difference between the incremental areas of C-peptide and insulin divided by the incremental area of C-peptide were significantly lower in elderly subjects. These results suggest that hepatic insulin extraction after glucose loading is decreased in elderly subjects and this may partly be responsible for the slightly altered glucose metabolism in elderly subjects with normal glucose tolerance test.

Administration, Oral↗
PubMed1989

Urinary N-acetyl-beta-D-glucosaminidase in the patients with hyperthyroidism.

Urinary N-acetyl-beta-D-glucosaminidase (NAG) was measured in patients with hyperthyroidism. The value of urinary NAG in these patients was higher than that in normal subjects and diabetic patients without diabetic nephropathy. This high level of urinary NAG in patients with hyperthyroidism decreased to the level of normal subjects after treatment of hyperthyroidism. Why urinary NAG increases in the patients with hyperthyroidism remains unknown. On the occasion of estimating the significance of the high level of urinary NAG, however, the possibility of the existence of hyperthyroidism has to be considered in addition to renal damage or hyperglycemia which have already been found to increase urinary NAG.

Acetylglucosaminidase↗
PubMed1989

Insulin extraction and glucose output by the perfused liver of starved rats.

Using the isolated and perfused liver of rats, we investigated the effect of starvation on hepatic glucose output and hepatic insulin extraction. The rats were starved for 72 h. The intestines of fed and starved rats were isolated and perfused, and portal venous effluent (PVE) was collected. The liver of fed and starved rats was perfused with synthetic medium or PVE containing 100 mg/dl glucose and 100 muU/ml insulin. Fractional uptake of insulin and reduction in glucose output by the perfused liver were almost the same in all groups. These results suggest that the removal and action of insulin in the liver were not altered by short-term starvation in rats.

Animals↗
PubMed1988

Structure of the horseradish peroxidase isozyme C genes.

We have isolated, cloned and characterized three cDNAs and two genomic DNAs corresponding to the mRNAs and genes for the horseradish (Armoracia rusticana) peroxidase isoenzyme C (HPR C). The amino acid sequence of HRP C1, deduced from the nucleotide sequence of one of the cDNA clone, pSK1, contained the same primary sequence as that of the purified enzyme established by Welinder [FEBS Lett. 72, 19-23 (1976)] with additional sequences at the N and C terminal. All three inserts in the cDNA clones, pSK1, pSK2 and pSK3, coded the same size of peptide (308 amino acid residues) if these are processed in the same way, and the amino acid sequence were homologous to each other by 91-94%. Functional amino acids, including His40, His170, Tyr185 and Arg183 and S-S-bond-forming Cys, were conserved in the three isozymes, but a few N-glycosylation sites were not the same. Two HRP C isoenzyme genomic genes, prxC1 and prxC2, were tandem on the chromosomal DNA and each gene consisted of four exons and three introns. The positions in the exons interrupted by introns were the same in two genes. We observed a putative promoter sequence 5' upstream and a poly(A) signal 3' downstream in both genes. The gene product of prxC1 might be processed with a signal sequence of 30 amino acid residues at the N terminus and a peptide consisting of 15 amino acid residues at the C terminus.

Amino Acid Sequence↗
PubMed1984

Construction of hybrid genes of 6-aminohexanoic acid-oligomer hydrolase and its analogous enzyme. Estimation of the intramolecular regions important for the enzyme evolution.

Hybrids were constructed of the genes for two homologous enzymes, 6-aminohexanoic acid-oligomer hydrolase (EII, one of the nylon oligomer degradation enzymes), and its probable evolutionary antecedent (EII'). The structural genes of EII (nylB) and EII' (nylB') have 88% similarity in their nucleotide sequences, an open frame encoding a peptide of 392 amino acids, conserved restriction sites, and in vitro recombination between these genes at the corresponding restriction sites generated genes directing various hybrid enzymes. In a comparison of the EII, EII', and the hybrid enzymes, we concluded that one or more of the four amino acid alterations that occurred in the intramolecular region (between amino acids 162-257) of EII' is essential to the adaptation of the enzyme to nylon oligomer degradation, and that its effect is enhanced 20-fold by one or more further alterations in the 258-380 region. Our results also suggest that this technique is useful for improving enzyme characteristics.

Amidohydrolases↗
PubMed1984

Synthesis of a gene for human growth hormone and its expression in Escherichia coli.

A gene coding for human growth hormone, which consists of 192 amino acids, was chemically synthesized. The synthesis entailed ligating 78 deoxyribooligonucleotides, which had been synthesized on polymer supports by the phosphotriester method with frequently occurring amino acid codons of Escherichia coli. The chemically synthesized gene was inserted into an E. coli plasmid downstream from the E. coli trp promoter, with a modified ribosome-binding region carried on pBR322. E. coli cells transformed with this recombinant plasmid synthesized 2.9 X 10(6) molecules per cell of human growth hormone upon induction. The induced polypeptide was identical with natural human growth hormone in size and in immunological properties, as well as in biological activity as examined by the tibial test with hypophysectomized rats.

Amino Acid Sequence↗