Ichitomo Miwa

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Glucokinase (Gck) functions as a glucose sensor for insulin secretion, and in mice fed standard chow, haploinsufficiency of beta cell-specific Gck (Gck(+/-)) causes impaired insulin secretion to glucose, although the animals have a normal beta cell mass. When fed a high-fat (HF) diet, wild-type mice showed marked beta cell hyperplasia, whereas Gck(+/-) mice(More)
D-mannose is an essential monosaccharide constituent of glycoproteins and glycolipids. However, it is unknown how plasma mannose is supplied. The aim of this study was to explore the source of plasma mannose. Oral administration of glucose resulted in a significant decrease of plasma mannose concentration after 20 min in fasted normal rats. However, in(More)
Rat liver is known to contain a regulatory protein (RP) that inhibits glucokinase competitively with respect to glucose. By an immunohistochemical technique and by cell fractionation in glycerol, we investigated the distribution of RP in rat liver and its changes in response to high glucose. RP was detected almost exclusively in the nuclei of the(More)
Lipid peroxidation due to oxidative stress is accelerated under hyperglycemic conditions such as diabetes mellitus. The effect of 4-hydroxy-2-nonenal (HNE) and other lipid peroxidation products on the ability of isolated rat pancreatic islets to secrete insulin was examined in this study. HNE concentration- and time-dependently deteriorated glucose-induced(More)
Pancreatic glucokinase (GK) is considered an important element of the glucose-sensing unit in pancreatic beta-cells. It is possible that the brain uses similar glucose-sensing units, and we employed GK immunohistochemistry and confocal microscopy to examine the anatomical distribution of GK-like immunoreactivities in the rat brain. We found strong GK-like(More)
Subcellular distribution of glucokinase was studied in rat liver. With an immunohistochemical procedure, glucokinase immunoreactivity was clearly shown in the nucleus of parenchymal cells of rat liver, but faintly in the cytoplasm. Nuclei, cytosol (extranuclear fraction in the strict sense), and homogenate prepared in nonaqueous medium, i.e. glycerol, were(More)
We examined the cytotoxicity of troglitazone toward cultured rat hepatocytes. The drug concentration- and time-dependently decreased cell viability and increased lactate dehydrogenase leakage from the cells. Troglitazone-induced cell death was characterized by "DNA ladders", condensation of nuclei, and a positive reaction to in situ nick-end labeling. The(More)
Human erythrocytes were loaded with homogeneous rat liver glucokinase by an encapsulation method based on hypotonic hemolysis and isotonic resealing. As assayed at 10 mM glucose, glucokinase and hexokinase activities in glucokinase-loaded erythrocytes were 218 and 384 nmol/min/gHb, respectively; whereas hexokinase activity in both intact and unloaded red(More)
The distribution of glucokinase in rat liver under both normal feeding and fasting-refeeding conditions was investigated immunohistochemically. Under normal feeding conditions, glucokinase immunoreactivity was observed in both nuclei and cytoplasm of parenchymal cells. The nuclei were stained intensely and evenly, whereas the cytoplasm showed weak(More)