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S Kanamura

Publications and source records attributed to S Kanamura.

At least 55 records · Page 3Linked to original sources
PubMed1987

Significance of increase in glucose 6-phosphatase activity in brown adipose cells of cold-exposed and starved mice.

Cytochemical and biochemical glucose 6-phosphatase (G6Pase) activity was examined in brown adipose tissues of normal, cold-exposed, or starved mice. In addition, G6Pase activity in white adipose tissue and hexokinase activity in brown and white adipose tissues were biochemically measured. In normal animals, the reaction product for G6Pase activity was localized in the endoplasmic reticulum and nuclear envelope of brown adipose cells. The amount of the reaction product increased in cold-exposed or starved animals. Biochemical G6Pase activity (259.7 +/- 48.5 ng Pi/min/mg protein) in brown adipose tissues of normal animals was higher when the value was compared with values of other organs. Biochemical G6Pase and hexokinase activities increased rapidly in brown adipose tissues of cold-exposed animals, and a close relation was found between activities of the two enzymes. In brown adipose tissues of animals starved for 3 days, biochemical G6Pase activity increased, but hexokinase activity did not change. In white adipose tissues of normal, cold-exposed, or starved animals, G6Pase activity was very low, although the enzyme activity increased slightly in animals starved for 3 days. The results show that the high G6Pase activity in brown adipose cells probably relates to thermogenesis in cold-exposed animals and may be concerned with glucose release into the blood in starved animals.

Adipose Tissue, Brown↗
PubMed1987

Glucose 6-phosphatase and glycogen phosphorylase activities in chondrocytes in epiphyseal cartilage of growing rats.

Glycogen, glycogen phosphorylase, and glucose 6-phosphatase (G6Pase) activities were examined cytochemically in chondrocytes of femoral epiphyseal cartilages and cartilaginous ribs of 3- and 7-day-old rats. G6Pase activity was also examined biochemically. Glycogen was abundant in chondrocytes of the reserve zone, while it became scarce in the cells of the proliferative zone. From the upper part (adjoining the proliferative zone) to the lower part of the hypertrophic zone, glycogen accumulated in chondrocytes and decreased in the cells of the degenerative zone. Inversely, glycogen phosphorylase a and G6Pase activities were relatively high in chondrocytes of the proliferative zone and upper hypertrophic zone and were low in the cells of the reserve zone, lower hypertrophic zone, and degenerative zone. The reaction product for G6Pase was present in the endoplasmic reticulum and nuclear envelope of all types of chondrocytes composing the cartilages, although the amounts of reaction product varied with the cell types in parallel with the histochemical results. Biochemical G6Pase activity was higher in epiphyseal cartilages than in cartilaginous ribs. The possible mechanism and significance of the accumulation and decrease of glycogen in chondrocytes of the epiphyseal cartilage were discussed.

Animals↗
PubMed1986

Peri- and postnatal development of heterogeneity in the amounts of endoplasmic reticulum in mouse hepatocytes.

The surface density and area per cell of the endoplasmic reticulum (ER) in periportal and perihepatic hepatocytes from male ddY mice, "17-, 18-, and 19-day-old fetuses," "newborn and 1-, 5-, 10-, and 20-day-old animals," and "adult animals" were analyzed by quantitative electron microscopy. The surface density of rough ER was not significantly different between periportal and perihepatic cells in all age groups examined, except for 19-day-old fetuses in which the value was greater in periportal cells than perihepatic cells. The surface density of smooth ER and total (rough and smooth) ER did not significantly differ between the periportal and perihepatic cells from 17-day-old fetuses to 5-day-old animals. In 10- and 20-day-old and adult animals, the values of smooth and total ER were greater in perihepatic cells than in periportal cells. When the data were expressed as area per cell, the patterns of subacinar distributions hardly differed, but age-related changes differed considerably from the patterns seen in the surface density data. The differences were generally caused by the increase in hepatocyte volume between 20 days of age and adulthood, especially in perihepatic cells, and by the changes in volume during the perinatal period. The results show that differences in the surface density and area per cell of smooth and total ER between periportal and perihepatic hepatocytes evident in adult animals are not present in fetal and newborn animals but arise during postnatal development.

Age Factors↗
PubMed1986

Plasma membrane reregionalization in cultured mouse hepatocytes.

The cytochemical localization of alkaline phosphatase (ALPase) activity and the autoradiographic distribution of glucagon receptors were examined in the plasma membrane of cultured mouse hepatocytes. After 24 hours of culture, ALPase activity was exclusively localized on the plasma membrane in areas of cell-cell contact, and glucagon receptors were more numerous in the plasma membrane at the periphery of re-formed cell trabeculae. These results indicate that plasma membrane regionalization of hepatocytes, lost by cell isolation, reappeared during culture. The cells maintained this plasma membrane regionalization until 48 hours of culture. By 72 hours of culture, however, ALPase activity was seen on the external surface of all regions of plasma membrane, and the glucagon receptors decreased markedly in number and became scattered in all regions of plasma membrane. Thus, the re-formed plasma membrane regionalization disappeared in the cells by 72 hours of culture.

Alkaline Phosphatase↗
PubMed1986

Cytochemical and biochemical glucose 6-phosphatase activity in skeletal muscle cells of mice.

Cytochemical and biochemical glucose 6-phosphatase (G6Pase) activity and fiber type composition were studied in soleus (SOL) and gastrocnemius (GC) muscles of mice. The SOL is a red muscle which contains numerous type I fibers (60%) and relatively few type II fibers (40%). The GC is a white muscle which contains numerous type II fibers (90-100%) and very few type I fibers (0-10%). In the SOL and GC, cytochemical G6Pase activity was localized in the sarcoplasmic reticulum, lateral elements of triads, myonuclear envelope, and in the endoplasmic reticulum and nuclear envelope of endothelial cells. Differential centrifugation showed that G6Pase activity was recovered in the 105,000g pellet (microsomal fraction). Histochemical enzyme activity in type II fibers was slightly higher than that in type I fibers. Biochemical G6Pase activity in the GC was significantly higher than that in the SOL. The possible functional significance of G6Pase in skeletal muscles was discussed.

Animals↗
PubMed1986

Glucose 6-phosphatase activity in pregnant and lactating mammary glands of the mouse.

Glucose 6-phosphatase activity was studied in the secretory epithelial cell and other cell types composing alveoli of the mammary gland (cytochemical study) and in the whole mammary gland (biochemical study) of pregnant and lactating mice. The reaction product for the enzyme activity was seen in the endoplasmic reticulum and nuclear envelope in secretory epithelial cells from all animals examined (days 7 and 14 of pregnancy, and days 0, 3, 10, and 20 of lactation. The amounts of the reaction product appeared scarce at day 7 of pregnancy, moderate at day 14 of pregnancy and day 0 of lactation, and abundant at days 3 and 10 of lactation. The reaction product, however, became generally scarce at day 20 of lactation. Biochemical activity was relatively low at days 7 and 14 of pregnancy and days 0 and 20 of lactation, while it was high at days 3 and 10 of lactation. The increased activity is probably related to functions of secretory epithelial cells in the lactating gland.

Animals↗
PubMed1986

Significance of the increase in glucose 6-phosphatase activity in skeletal muscle cells of the mouse by starvation.

The effects of starvation on glucose 6-phosphatase (G6Pase; EC 3.1.3.9., D-glucose 6-phosphate phosphohydrolase) and glycogen phosphorylase (EC 2.4.1.1.) activities, and on glycogen content, were studied in skeletal muscles (m. rectus femoris) of mice. In the muscle cells from fed animals, the cytochemical reaction product for G6Pase activity was observed in moderate amounts in the terminal cisternae of sarcoplasmic reticulum and in small amounts in the nuclear envelope, and was rare or absent in the intermyofibrillar sarcoplasmic reticulum. After 4 days of starvation, however, the reaction product became abundant in all of the terminal cisternae, intermyofibrillar sarcoplasmic reticulum, and nuclear envelope. Biochemical G6Pase and glycogen phosphorylase a (active form) activities were higher in the muscles of starved mice than in those of fed animals. The glycogen content decreased markedly in the muscles of starved mice. The results suggest that the role of the increased G6Pase in skeletal muscle cells of starved mice is to release glucose into the blood by hydrolyzing glucose 6-phosphate produced through the increased phosphorylase activity.

Animals↗
PubMed1986

Intracellular localization of alkaline phosphatase in freshly isolated foetal rat hepatocytes.

The cytochemical localization of alkaline phosphatase activity in foetal rat hepatocytes was examined in relation to the pattern of cell to cell attachment during cell isolation and culture. In foetal hepatocytes in vivo, alkaline phosphatase was exclusively localized on the bile canalicular membrane. In freshly isolated foetal hepatocytes, however, the activity was present in the endoplasmic reticulum, nuclear envelope, Golgi apparatus, tubulo-vesicular organelles, and over the entire plasma membrane. In monolayer cells cultured for one or two days, the activity was localized on the reconstituted bile canalicular membrane, plasma membrane sites adjacent to neighbouring cells and on the bottom surface of the monolayer, but was detected in none of the intracellular organelles. Biochemical alkaline phosphatase activity did not change during isolation of the cells. These results suggest that, in foetal hepatocytes, loss of cell-cell contact may induce a temporal disturbance, or dedifferentiation, in their membrane system.

Alkaline Phosphatase↗
PubMed1986

Morphometric analysis of fetal rat hepatocytes cultured in monolayer or following gyratory shaking.

The stereological technique was used to quantify glycogen areas and endoplasmic reticulum in fetal rat hepatocytes cultured for 24 hr in monolayer (monolayer cells) or following shaking by gyratory rotation (shaken cells). The volume density and volume per cell of glycogen areas decreased in order of freshly isolated hepatocytes, monolayer cells, and shaken cells. The surface density and area per cell of smooth endoplasmic reticulum increased in order of freshly isolated cells, monolayer cells, and shaken cells. The results show that the decrease of glycogen areas and proliferation of the smooth endoplasmic reticulum are more prominent in shaken cells than in monolayer cells. Prominent proliferation of the smooth endoplasmic reticulum in shaken cells may be due to the consumption of glycogen for energy release as a result of gyratory rotation.

Animals↗
PubMed1986

High and testosterone-dependent glucose 6-phosphatase activity in epithelium of mouse seminal vesicle.

For study of the mechanism of seminal fructogenesis, glucose 6-phosphatase activity was examined cytochemically (a method modified from that of Wachstein and Meisel) and biochemically (the method of Leskes et al.) in seminal vesicles from normal, castrated, and castrated and testosterone-treated mice. The reaction product for the activity was localized in the endoplasmic reticulum and nuclear envelope of all cell types composing the seminal vesicle. In normal seminal vesicle, the reaction product was apparently more abundant in columnar and basal cells than in other cell types. Ten, 20, and 30 days after castration, the abundant amount of reaction product in columnar and basal cells decreased to the level in other cell types. In animals treated with testosterone after castration, however, the reaction product in columnar and basal cells remained abundant. If fructose 6-phosphate was added to the reaction medium in place of glucose 6-phosphate, the amount and pattern of deposition of the reaction product did not change. Changes in biochemical activity in castrated or castrated and testosterone-treated animals paralleled the cytochemical results. The results show that the high activity in columnar and basal cells is under the control of testosterone, and the role of this enzyme is probably to release fructose into the seminal fluid.

Animals↗
PubMed1985

Quantitative analysis of development of mitochondrial ultrastructure in differentiating mouse hepatocytes during postnatal period.

Between birth and 10 days of age, the volume density (volume/unit cytoplasmic volume) of the matrix, and the surface density (area/unit cytoplasmic volume) of the inner membrane and cristae increased in both periportal and perihepatic hepatocytes, and did not differ significantly between the cells of the two zones. After 10 days of age, however, the volume density of the matrix decreased in perihepatic cells and remained unchanged in periportal cells, and, therefore, it became greater in periportal cells than in perihepatic cells in 20-day-old and adult animals. The surface density of the inner membrane and cristae decreased in the cells of both zones. Further, the hepatocyte volume increased markedly, especially in perihepatic zones between 20 days of age and the adult. The results show that, in postnatally differentiating hepatocytes, mitochondria are likely to develop during early postnatal period, then the structural heterogeneity of mitochondria arises, and hepatocyte volume increases markedly during late postnatal period after weaning. Thus, the process of postnatal hepatocyte differentiation includes such several phases of development.

Aging↗
PubMed1985

Inhibitory effect of colchicine and vinblastine on transport of glucagon receptors to the plasma membrane in cultured rat hepatocytes.

The role of microtubules in the regulation of glucagon receptors on cultured rat hepatocytes was studied. Antimicrotubular reagents, colchicine and vinblastine, did not affect the binding of 125I-labelled glucagon to hepatocytes at 4 degrees C. At 20 and 37 degrees C, however, the reagents reduced the binding after 60 or 90 min of incubation. Scatchard analysis indicated that the reduction in the binding was due to loss of glucagon-receptor populations. If hepatocytes were preincubated with both unlabelled glucagon and the reagents at 37 degrees C, the binding of the ligand to the cells decreased markedly after a certain delay. The reagents did not inhibit the internalization of the ligand in the cells until 30 min of incubation at 37 degrees C. The results suggest that the microtubule system plays a role in the transport of glucagon receptors to the plasma membrane, which is followed by their internalization.

Animals↗
PubMed1984

Development of morphologic heterogeneity of hepatocyte mitochondria in the mouse.

The ultrastructure of mitochondria in periportal and perihepatic hepatocytes from newborn, 5-, 10-, and 20-day-old, and adult male ddY mice was analyzed by quantitative electron microscopy. In newborn and 5- and 10-day-old animals, the axial ratio (length per diameter), surface to volume ratio (area of the outer membrane per unit mitochondrial volume), and volume density were not significantly different between periportal and perihepatic cells. In 20-day-old and adult animals, the surface to volume ratio was greater in perihepatic cells than periportal cells, and the volume density was greater in periportal cells than perihepatic cells. The axial ratio became greater in perihepatic cells than periportal cells in adult animals. However, there were no differences in the surface density of the outer membrane, and of the inner membrane and cristae between the cells of both zones in all age groups examined. When the data were expressed as volume and area per cell, the patterns of subacinar distribution and age-related changes differed from the patterns seen in the volume and surface density data mainly in adult animals. This difference was generally caused by the marked increase in hepatocyte volume between 20 days of age and adulthood, especially in perihepatic cells. The results show that differences between mitochondria in periportal cells and those in perihepatic cells in the shape (the axial and surface to volume ratios), volume density, and area of the outer membrane per cell, evident in adult animals, are not present in newborn animals but arise during postnatal development.

Animals↗
PubMed1984

Receptor-mediated endocytosis of glucagon in isolated mouse hepatocytes.

The binding of glucagon to the cell surface and the pathway of intracellular transport of the hormone in isolated mouse hepatocytes were studied by autoradiography, colloidal gold-labeled glucagon (Au-glucagon), and biochemical methods. In cells incubated with 1251-glucagon at 4 degrees C, the label was mainly localized to the plasma membrane even after 60 min of incubation. At 20 degrees C, the labeled ligand was internalized by the cells and the amount of internalized ligand increased with time of incubation. At 37 degrees C, the ligand was rapidly internalized and found to be associated with coated or uncoated vesicles. Au-glucagon experiments revealed clearly the process of internalization of glucagon. Au-glucagon bound to the plasma membrane was transported to coated regions and then internalized into vesicles via coated pits. Biochemical results supported these findings from autoradiography and Au-glucagon experiments. Thus, glucagon is internalized by hepatocytes via receptor-mediated endocytosis.

Animals↗
PubMed1984

Quantitative analysis of smooth endoplasmic reticulum proliferation in hepatocytes of early postnatal and adult mice treated with phenobarbital.

The smooth endoplasmic reticulum in hepatocytes of early postnatal and adult ddY male mice injected with phenobarbital was analyzed stereologically. The animals received daily intraperitoneal injections of phenobarbital and were killed about 24 h after the last injection. In early postnatal animals (injected with 35 mg/kg of the drug at days 1 and 2 after birth, or injected with 35 mg/kg at day 2 and with 50 mg/kg at days 3 and 4 after birth), the smooth endoplasmic reticulum proliferated both in perivenular and periportal hepatocytes; there was no significant difference in amount of smooth endoplasmic reticulum between the cells of the two zones. In adult animals, however, proliferation occurred only in perivenular cells after the administration of 35 mg/kg of phenobarbital for 2 days, and predominantly in perivenular cells even after the administration of 150 mg/kg of the drug for 7 days. These results suggest that the conspicuous proliferation of the smooth endoplasmic reticulum in perivenular hepatocytes in response to phenobarbital administration, which is characteristic of adult liver, does not occur in early postnatal mice but becomes manifest during postnatal development.

Aging↗