Biomedical subjects

S Kanamura

Publications and source records attributed to S Kanamura.

At least 37 records · Page 2Linked to original sources

PubMed1993

Densities of NADPH-ferrihemoprotein reductase and cytochrome P-450 molecules in the endoplasmic reticulum membrane of rat hepatocytes.

In hepatocytes, NADPH-ferrihemoprotein reductase (reductase) has been hypothesized to exist as aggregates or micelles in endoplasmic reticulum (ER) membrane. However, if the number of reductase molecules per unit area of ER is low, this hypothesis cannot explain how a few reductase molecules efficiently reduce many P-450 molecules. To test this hypothesis, we estimated the numbers of reductase and P-450 molecules per unit ER area (reductase and P-450 densities) by microphotometry of the two enzymes in conjunction with morphometry of ER in periportal, midzonal, and perivenular rat hepatocytes. The reductase density in periportal, midzonal, and perivenular hepatocytes (107-179 molecules/microns 2 of ER) was high enough to efficiently reduce all P-450 molecules in the ER, although the value in perivenular hepatocytes was lowest owing to the relatively greater amount of ER in this region. The pattern of sublobular gradient in the reductase density was similar to that in the P-450 density. Consequently, the molar ratio of P-450 to reductase in ER was similar (about 40:1) in hepatocytes regardless of their positions within the liver lobule.

Animals↗

PubMed1993

Significance of high glucose-6-phosphatase activity in rat oviduct epithelium.

To study the origin of glucose in the oviduct fluid, we cytochemically examined glucose-6-phosphatase (G6Pase) activity in rat oviduct. The activity in the whole oviduct was also assayed biochemically. During proestrous, estrous, and metestrous phases, staining reaction for the activity was moderate in the epithelium of the caudal isthmus (CaI) and uterotubal junction (UJ), whereas it was weak in that of the ampulla (A) and cephalic isthmus (CeI). In the diestrous phase, staining reaction in the epithelium of CaI and UJ became strong although it remained weak in that of A and CeI. Reaction product for the activity was localized in the endoplasmic reticulum and nuclear envelope of all cell types in the epithelium. The amount of reaction product in secretory cells was small to moderate in CaI and UJ, and small in A and CeI during proestrus, estrus, and metestrus. In diestrous the amount became abundant in CaI and UJ and moderate in A and CeI. However, the amount in ciliated cells remained small in the four segments during the four phases. The biochemical activity in diestrous was greater than that in proestrus, estrus, or metestrus. This shows that the activity is high in secretory cells in the epithelium of CaI and UJ in the diestrous phase and suggests that the role of the high activity is to release glucose into the oviduct fluid for use by the embryo passing down the CaI and UJ to the uterus.

Animals↗

PubMed1993

Postnatal development and sublobular distribution of cytochrome P-450 in rat liver: a microphotometric study.

To study the process of expression of cytochrome P-450 (P-450) in hepatocytes during development, we measured microphotometrically the P-450 content in periportal and perivenular hepatocytes of male rats during peri- and postnatal growth. From Day 19 of gestation to Day 5 after birth, P-450 content in both periportal and perivenular hepatocytes increased markedly (periportal 1046%; perivenular 819%). The content in periportal hepatocytes remained unchanged from 5 to 20 days of age, and increased slightly (24%) from 20 to 45 days of age. However, the content in perivenular hepatocytes increased progressively (105%) between 5 and 45 days of age. The difference in P-450 content became apparent between periportal and perivenular hepatocytes after 7 days of age. The content in periportal or perivenular hepatocytes reached the adult level at 45 days of age. Therefore, the perinatal period is the time at which a marked increase in P-450 occurs in hepatocytes throughout the liver lobule. The subsequent period before weaning is the time at which the sublobular heterogeneous distribution of P-450 appears. The period after weaning is the time at which a slight increase in P-450 content in periportal hepatocytes and a marked increase in the enzyme in perivenular hepatocytes takes place.

Animals↗

PubMed1992

Postnatal changes in sublobular distribution of NADPH-cytochrome P-450 reductase in rat liver.

Immunohistochemical distribution of NADPH-cytochrome P-450 reductase (NADPH-ferrihaemoprotein reductase; EC 1.6.2.4.) in the liver lobule was examined during development of the rat. From the 19th day of gestation to 4 days after birth, the enzyme was distributed uniformly throughout the lobule. The immunostaining for the enzyme was weak before birth, and became slightly stronger after birth. A slightly uneven distribution of immunoreactivity, stronger in perivenular zones, appeared at 5 days after birth. Then, the staining intensity in perivenular zones became progressively stronger with age, except for a slight increase between 10 and 20 days of age. The intensity in periportal zones also increased gradually, although it remained weaker than that in perivenular zones. Around 30 days of age, the distribution of the immunostaining, stronger in perivenular than in periportal zones, was similar to that seen in the lobules of adult animals. Thus, heterogeneity among hepatocytes with respect to the enzyme content is not present in fetal and newborn rats but develops gradually during postnatal development; the postnatal growth of the liver is accompanied by a change in the pattern of the distribution of this enzyme within the lobule.

Age Factors↗

PubMed1992

Relation between cytochrome P-450 increase and endoplasmic reticulum proliferation in hepatocytes of mice treated with phenobarbital: a microphotometric and morphometric study.

To obtain detailed information on phenobarbital (PB)-induced cytochrome P-450 (P-450) increase and endoplasmic reticulum (ER) proliferation in hepatocytes, we estimated microphotometrically the amount of P-450 per unit cytoplasmic volume and morphometrically the area of ER per unit cytoplasmic volume in hepatocytes adjacent to the portal area or central venule (1 periportal or 1 perivenular cells) and in the second and third layers from the portal area or central venule (2, 3 periportal or 2, 3 perivenular cells) from mice injected with 35, 50, 100, or 150 mg/kg PB once a day for 3 days. By dividing the P-450 amount by the ER area, the number of P-450 molecules per unit ER area was also calculated. In 1 and 2, 3 perivenular cells, except for 2, 3 perivenular cells after injection of 150 mg/kg PB, the amount of P-450 increased with ER proliferation and the number of P-450 molecules in ER remained unchanged after injection of 50, 100, or 150 mg/kg PB. In 2, 3 periportal cells, however, the P-450 amount and the number of P-450 molecules in ER increased markedly without or with some ER proliferation after injection of 50, 100, or 150 mg/kg PB; the P-450 increase appears to be generally independent of ER proliferation. The 1 periportal cells are probably exceptional hepatocytes that usually did not respond to PB stimulation.

Animals↗

PubMed1992

Quantitative analysis of rough endoplasmic reticulum in chondrocytes of articular and tracheal cartilage of rabbits following the systemic administration of hydrocortisone.

The rough endoplasmic reticulum (RER) in chondrocytes was analysed stereologically in articular cartilage of knee joints and in tracheal cartilage of rabbits injected intramuscularly with 5 mg/kg hydrocortisone daily for 4 wk. In articular cartilage, RER area per unit cytoplasmic volume decreased in chondrocytes in all (superficial, middle and deep) zones, although the volume of glycogen deposits per unit cytoplasmic volume increased in the middle and deep zones. RER area per chondrocyte also decreased in the 3 zones without changes in average chondrocyte volume in the superficial and deep zones. Furthermore, the volume of glycogen deposits per chondrocyte did not alter in the 3 zones. These indicate a reduction of RER area in articular chondrocytes after hydrocortisone administration and suggest a decrease in the protein-synthesising capacity of these cells. In tracheal cartilage in which 2 zones were identifiable, RER area per unit cytoplasmic volume decreased in chondrocytes in both the superficial and main zones without changes in the volume of glycogen deposits per unit cytoplasmic volume. In addition, RER area per chondrocyte decreased in the main zone. The results suggest that the decrease in RER area in chondrocytes after corticosteroid administration is not specific to articular cartilage but is common to cartilage in various organs.

Animals↗

PubMed1991

Measurement of NADPH-ferrihemoprotein reductase content in sections of liver.

We developed a method for measuring the content of NADPH-ferrihemoprotein reductase in sections of liver. First, reductase in sections of rat liver was detected with the indirect immunoperoxidase reaction. Subsequently, specific absorbances were measured in the stained sections by microphotometry. Then, the resulting specific absorbances were converted into the reductase content in the sections using an apparent extinction coefficient obtained from a nitrocellulose binding assay. The average of the reductase content in hepatocytes in periportal, intermediate, and perivenous zones thus measured was consistent with the value in liver homogenates estimated by enzyme-linked immunosorbent assay. Therefore, the present method gave accurate measurement of the reductase content in the sections. Perivenous hepatocytes contained 1.5 times as much reductase (1.15 nmol/g liver, mean for five animals) as that in periportal hepatocytes (0.74 nmol/g liver). The reductase content in hepatocytes in the intermediate zone (0.93 nmol/g liver) was intermediate between values of the periportal and perivenous hepatocytes.

Animals↗

PubMed1991

An improved microphotometry system for measurement of cytochrome P-450 in hepatocyte cytoplasm.

To measure cytochrome P-450 (P-450) content in hepatocyte cytoplasm, we developed a dual monochromator-equipped microphotometry system (KWSP-1). Simultaneous measurements of absorbance at 450 and 490 nm with narrow band width (0.5 nm) and small spot size (2 microns) were accomplished by this system. Corresponding fields in serial sections could be easily and rapidly identified under the Nomarski imaging mode of KWSP-1. Photometric accuracy and repeatability of wavelength setting of KWSP-1 were also satisfactory for measurement of P-450. With this system, it is thus possible to measure the extinction of P-450 from many small measuring areas and to precisely determine P-450 content in the cytoplasm of rat hepatocytes. A microphotometric method was developed using cuvette slides and two serial 10-microns thick sections (mapping method). The intracellular distribution of P-450 in individual hepatocytes could be visualized by the mapping method with KWSP-1. However, this method was not applicable to tissue sections containing hemoglobin larger than 4 microM.

Animals↗

PubMed1991

High glucose-6-phosphatase activity in non-pigmented epithelial cells of rabbit ciliary body.

For study of the origin of glucose in the aqueous humor, glucose-6-phosphatase (G6Pase) and hexokinase activities, and glycogen, were cytochemically examined in the ciliary body (CB) of rabbit. G6Pase activity was also assayed biochemically. The staining reaction for G6Pase activity was strong in the non-pigmented epithelium (NPE) in the pars plana and tips of ciliary processes in the region containing large ciliary pockets within the pars plicata. NPE cells contained abundant reaction product for G6Pase activity in the endoplasmic reticulum (ER) and nuclear envelope. However, NPE in other regions of the CB and pigmented epithelium (PE) of CB, and other areas surrounding the anterior and (PE) of CB, and other areas surrounding the anterior and posterior chambers, showed weak or no G6Pase staining reaction. Biochemical G6Pase activity in the whole ciliary body was relatively high. Both NPE and PE in the pars plana and the tips showed strong staining reaction for hexokinase activity but no staining for glycogen. Furthermore, NPE cells in the tips bore large aggregates of smooth ER and many Golgi apparati. These suggest that the high G6Pase activity in NPE cells in the pars plana and the tips is related to glucose release into the aqueous humor.

Animals↗

PubMed1990

Neuronal regulation of substrate cycle between glucose 6-phosphate and glucose in brown adipose tissues of cold-exposed mice.

The increase in both glucose 6-phosphatase and hexokinase activities in brown adipose tissues of cold-exposed mice probably relates to thermogenesis by the substrate cycle between glucose 6-phosphate and glucose (Watanabe et al.: Anatomical Record 219:39-44, 1987). To clarify the factors causing the simultaneous increase, we examined biochemically the effects of uni- or bilateral surgical denervation of brown adipose tissues, of adrenalectomy, or of streptozotocin injection on the increase in the two activities in the tissues of cold-exposed mice. Further, the effects of denervation on the increase were also examined histochemically. The simultaneous increase in the two activities was inhibited in the denervated tissues of cold-exposed animals in biochemical and histochemical experiments. However, the increase in the activities was not inhibited in the tissues of animals exposed to cold after adrenalectomy or streptozotocin injection. The results suggest strongly that the activation of the substrate cycle in brown adipose tissues of cold-exposed mice is caused by a transmitter released from sympathetic nerve endings, probably norepinephrine.

Adipose Tissue, Brown↗

PubMed1990

Fine structure and function of hepatocytes during development.

This paper reviews the fine structure and function of hepatocytes during fetal and postnatal development. Bile canaliculi develop to a mature appearance during perinatal and early postnatal periods, while bile secretory function is immature at birth and develops during the postnatal period. The rough endoplasmic reticulum is prominent and remains unchanged in amount during development, and the Golgi complex is large from early stages of fetal life. The smooth endoplasmic reticulum (SER) appears shortly before birth and increases in quantity to the adult level after birth. In mouse hepatocytes, Sv (area per unit cytoplasmic volume) of SER increases in perivenular cells between 1 and 10 days of age, although it remains low in periportal cells. Similarly, Sv of total ER increases in both periportal and perivenular cells between 1 and 5 days of age and then becomes greater in perivenular than periportal cells. This suggests that the postnatal increase in the drug-metabolizing capacity occurs predominantly in perivenular hepatocytes. SER proliferates after phenobarbital (PB) administration in both perivenular and periportal cells in 3-, 5-, and 10-day-old mice, and predominantly in perivenular cells in 20-day-old and adult mice. Thus the conspicuous proliferation of SER in perivenular hepatocytes after PB administration, characteristic of adult liver, becomes manifest during postnatal development. In mouse hepatocytes, Vv (volume per unit cytoplasmic volume) of mitochondrial matrix and peroxisomes and Sv of mitochondrial inner membrane and cristae increase in both periportal and perivenular cells between birth and 10 days of age. Then, Vv of mitochondrial matrix remains unchanged in periportal cells but decreases in perivenular cells. In general, the process of postnatal hepatocyte differentiation appears to include several phases of development; cell organelles develop during the early postnatal period, subsequently the cells undergo both functional and structural heterogeneity, and the late postnatal period after weaning is the time for a marked increase in cell size.

Animals↗

PubMed1990

Microphotometric analysis of cytochrome P-450 in periportal, midzonal, and perivenular hepatocytes of mice treated with phenobarbital.

To obtain detailed information on the increase of cytochrome P-450 (P-450) content in periportal, midzonal, and perivenular hepatocytes after phenobarbital (PB) administration, and to study the mechanism of increased P-450 in the endoplasmic reticulum (ER), we estimated microphotometrically the P-450 content and morphometrically the area of ER in hepatocytes of three zones from mice injected with 35, 50, 100, or 150 mg/kg of PB for 3 days. The amount of P-450 per unit cytoplasmic volume and the number of P-450 molecules per unit ER area (P-450 number) were increased by injection of 50, 100, or 150 mg/kg, and the ER area per unit cytoplasmic volume was increased by injection of 100 or 150 mg/kg, in hepatocytes from all three zones. Thus, the amount of P-450 in hepatocytes appeared in general to increase multiplicatively by simultaneous increases in both the P-450 number and the ER area. Furthermore, we could recognize two general types of relationship in the P-450 number and ER area between the patterns of change and the increasing doses: (a) increase in the P-450 number without ER proliferation (active type) in periportal and perivenular hepatocytes after injection of low doses; and (b) increase in ER proliferation without increase in the P-450 number (passive type) in hepatocytes of all three zones after injection of high doses.

Animals↗

PubMed1989

A new microphotometric method for measurement of cytochrome P-450 in sections of liver.

We developed a new microphotometric method for measuring the amounts of cytochrome P-450 (P-450) in fresh frozen sections of liver. Four serial frozen sections cut from the liver were separately incubated in 50 mM Tris-HCl buffer (pH 8.0) alone, in buffer containing sodium dithionite, in buffer saturated with carbon monoxide (CO), and in buffer saturated with CO and containing sodium dithionite. The difference between absorbance at 450 nm and that at 490 nm was measured in these sections with a simple microphotometer system. This method yielded precise amounts of P-450 in sections by measuring the true extinction of P-450 and by minimizing the effect of contaminating hemoproteins. Livers of adult rats contained large amounts of P-450, which was greater in perivenular hepatocytes than in periportal hepatocytes. In livers of newborn rats, however, small amounts of the enzyme were distributed evenly throughout the lobule.

Aging↗

PubMed1988

Morphological differences between secretory cells of wet and dry types of human ceruminous glands.

Morphological differences between secretory cells of the wet and dry types of human ceruminous glands were examined. The heights of secretory cells varied from tall and medium to low in both wet- and dry-type glands. The two gland types differed in morphologic features of the tall cells and the cells of medium height. The Golgi apparatus was well developed in the tall cells and fairly well developed in the cells of medium height in the wet-type gland, whereas it was generally small in the corresponding cells of the dry type. Light granules were abundant in the tall cells and in the cells of medium height in the wet-type gland, whereas light granules were rare in these cells in the dry-type gland. Furthermore, the light granules in the wet-type gland cells were observed in close relation to a well-developed Golgi apparatus, and sometimes showed a morphologic appearance suggesting exocytosis. Apical protrusions, probably related to apocrine secretion, were generally large and round and bore "microvilli and light granules" or "very few microvilli and no light granules" in the tall cells of the wet-type gland. However, the protrusions of the tall cells of the dry-type gland were generally large and slender and possessed no microvilli and no granules. The protrusions were not observed in the cells of medium height or in low cells in either type of gland. The results show that eccrine secretion characterizes the wet-type gland, but it is not clearly evident in the dry-type gland. This differences may be related to differences in composition between the wet and dry cerumens.

Adult↗

PubMed1988

High glucose-6-phosphatase activity in osteoblasts in the metaphysis of femur of growing rats.

Glucose-6-phosphatase (G6Pase) activity was examined cytochemically in the metaphysis of femurs of 3- and 7-day-old rats. G6Pase and hexokinase activities were also examined biochemically in the femur and tibia of 3-day-old animals. The reaction product for G6Pase activity was seen in the endoplasmic reticulum and nuclear envelope of all cell types composing the metaphysis. The amount of the reaction product was abundant in osteoblasts, moderate in osteocytes, and moderate to scarce in osteoclasts and capillary endothelial cells. Biochemical G6Pase activity in the bones was higher than that in the brain, submandibular gland, or pancreas of the animals. Hexokinase activity in the bones was not different from that in the submandibular gland, pancreas, or kidney. The activity ratio of G6Pase and hexokinase in the bones (0.603) was greater than that in the submandibular gland, pancreas, or brain and smaller than that in the kidney. Possible physiological significances of the higher G6Pase activity in osteoblasts are discussed.

Animals↗

PubMed1988

Inhibitory effect of phenobarbital on peroxisome biogenesis in mouse hepatocytes.

Peroxisomes in hepatocytes from mice administered 35, 50, or 100 mg/kg of phenobarbital (PB) were analyzed by quantitative electron microscopy. In perivenular hepatocytes, the volume of peroxisomes per unit cytoplasmic volume decreased to 78 or 57% of that of control animals by administration of 50 or 100 mg/kg. Their average volume also decreased to 78 or 64% of that in control animals in animals injected with 35 or 50 mg/kg. Further, cytochemical catalase activity appeared decreased in peroxisomes of hepatocytes of this zone after administration of 50 or 100 mg/kg. These suggest an inhibitory action of PB administration of biogenesis of peroxisomes in perivenular hepatocytes. In periportal hepatocytes, however, the volume density, average volume, and cytochemical catalase activity of peroxisomes did not change by administration of any doses of PB. Thus, PB administration appears to produce no inhibitory effect on the peroxisome biogenesis in periportal hepatocytes. On the other hand, the number of peroxisomes per unit cytoplasmic volume increased in both periportal and perivenular hepatocytes in animals injected with 50 mg/kg, although it returned to the level of control animals by injection of 100 mg/kg. The inhibitory effect of PB on the peroxisome neogenesis in perivenular hepatocytes may be related to the marked smooth endoplasmic reticulum proliferation by administration of this drug.

Animals↗

PubMed1988

Glucagon receptors in endothelial and Kupffer cells of mouse liver.

To determine whether hepatic sinusoidal cells contain glucagon receptors and, if so, to study the significance of the receptors in the cells, binding of [125I]-glucagon to nonparenchymal cells (mainly endothelial cells and Kupffer cells) isolated from mouse liver was examined by quantitative autoradiography and biochemical methods. Furthermore, the pathway of intracellular transport of colloidal gold-labeled glucagon (AuG) was examined in vivo. Autoradiographic and biochemical results demonstrated many glucagon receptors in both endothelial cells and Kupffer cells, and more receptors being present in endothelial cells than in Kupffer cells. In vivo, endothelial cells internalized AuG particles into coated vesicles via coated pits and transported the particles to endosomes, lysosomes, and abluminal plasma membrane. Therefore, receptor-mediated transcytosis of AuG occurs in endothelial cells. The number of particles present on the abluminal plasma membrane was constant if the amount of injected AuG increased. Therefore, the magnitude of receptor-mediated transcytosis of AuG appears to be regulated by endothelial cells. Kupffer cells internalized the ligand into cytoplasmic tubular structures via plasma membrane invaginations and transported the ligand exclusively to endosomes and lysosomes, suggesting that the ligand is degraded by Kupffer cells.

Animals↗

PubMed1987

Physiological role of skeletal muscle glycogen in starved mice.

To study the physiological role of skeletal muscle glycogen in starved animals, effects of starvation on glycogen and glycogen phosphorylase (EC 2.4.1.1.) activity were studied in muscle fibers (morphologic study) and in whole muscles (biochemical study) of the rectus femoris muscle of mouse. Glycogen content in the liver of the starved animals was also measured. PAS reaction, strong in muscle fibers of fed animals, became weak predominantly in type IIB fibers after 2 days and almost disappeared after 4 days of starvation. Glycogen particles, numerous in the sarcoplasm between myofibrils of muscle fibers, decreased markedly predominantly in type IIB fibers after 2 days and almost disappeared after 4 days. Phosphorylase a activity, undetected in fibers of fed mice, appeared weak in type IIB fibers and very weak in type IIA fibers after 2 days and became moderate in type IIB fibers and weak in type IIA fibers after 4 days. Muscle glycogen content did not differ by 16 hours from the values of corresponding fed animals. However, liver glycogen content had already decreased after 8 hours and markedly so after 12 hours. The results support our hypothesis-"skeletal muscle glycogen is used for maintaining the blood glucose level in starved mice" (Hirose et al.: Anat. Rec., 216:133-138, 1986)-and show that type IIB fibers play a main role in maintaining the glucose level and that muscle glycogen is utilized after depletion of liver glycogen.

Animals↗