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Biomedical subjects

H Kagawa

Publications and source records attributed to H Kagawa.

At least 145 records · Page 8Linked to original sources
PubMed1983

Evidence for a decrease in aromatase activity in the ovarian granulosa cells of amago salmon (Oncorhynchus rhodurus) associated with final oocyte maturation.

Aromatase activity in the isolated granulosa layers of amago salmon (Oncorhynchus rhodurus) ovarian follicles was examined during the course of vitellogenesis and final oocyte maturation and ovulation. Estradiol-17 beta production by isolated granulosa layers incubated with exogenous testosterone increased during the period of vitellogenesis to reach a peak in late vitellogenesis, and then declined rapidly, in association with the ability of the oocyte to mature in response to partially purified salmon gonadotropin (SG-G100). Extremely low levels of estradiol-17 beta were produced by granulosa layers from follicles which had undergone final oocyte maturation in vivo and by post-ovulatory follicles. SG-G100 had no discernible effect on estradiol-17 beta production. These results are discussed in relation to other studies on the endocrine control of steroidogenesis in this species.

Animals↗
PubMed1982

Oocyte maturation in the amago salmon (Oncorhynchus rhodurus): in vitro effects of salmon gonadotropin, steroids, and cyanoketone (an inhibitor of 3 beta-hydroxy-delta 5-steroid dehydrogenase).

The effect of partially purified chinook salmon gonadotropin (SG-G100) and a number of steroids on the induction of germinal vesicle breakdown (GVBD) in amago salmon (Oncorhynchus rhodurus) oocytes (with intact follicle layers) was investigated in vitro. SG-G100 was effective only at the highest concentration tested (1 microgram/ml). 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHprog) was the most potent maturation-inducing steroid tested, followed by 17 alpha-hydroxyprogesterone. Testosterone or deoxycorticosterone (DOC) enhanced the rate of GVBD in response to SG-G100. DOC also enhanced the response to 17 alpha,20 beta-diOHprog but testosterone was without effect, suggesting that DOC has a direct action on the oocyte while testosterone probably acts at the level of the follicle. Estradiol-17 beta had no effect on GVBD in response to SG-G100 or 17 alpha,20 beta-diOHprog. The action of SG-G100 was shown to be dependent on the synthesis of a second delta 4 steroidal mediator of maturation since cyanoketone, a specific inhibitor of 3 beta-hydroxy-delta 5-steroid dehydrogenase, completely abolished the maturational effects of the gonadotropin and pregnenolone but not delta 4 steroids. Radioimmunoassay of media in which oocytes were induced to mature in vitro with SG-G100 revealed significantly elevated levels of progesterone and 17 alpha,20 beta-diOHprog. Estradiol-17 beta levels, high in control media, were only elevated twofold by SG-G100. Levels of the two progestogens were extremely low or nondetectable in media in which oocytes were incubated with cyanoketone, while estradiol-17 beta levels remained high. These results are discussed in relation to other evidence indicating that 17 alpha,20 beta-diOHprog is the naturally occurring maturation-inducing steroid of amago salmon. The role of other steroid hormones, particularly the possible involvement of corticosteroids, in the control of final oocyte maturation in teleosts is explored.

17-alpha-Hydroxyprogesterone↗
PubMed1982

In vitro steroid production in the postovulatory follicles of the amago salmon, Oncorhynchus rhodurus, in response to salmon gonadotropin.

Partially purified chinook salmon gonadotropin (SG-G100) was used to investigate estradiol-17 beta and progesterone production in vitro in the isolated postovulatory follicles of the amago salmon, Oncorhynchus rhodurus, at varying intervals after ovulation. Chinook salmon gonadotropin stimulated progesterone production in vitro in the young postovulatory follicles, but not in the older ones. In contrast, estradiol-17 beta production was not stimulated in either young or older postovulatory follicles. Morphological observations indicate that young postovulatory follicles are more glandular than older ones. Thus, it is concluded that the young postovulatory follicles of the amago salmon are steroidogenic.

Animals↗
PubMed1981

Correlation of plasma estradiol-17 beta and progesterone levels with ultrastructure and histochemistry of ovarian follicles in the white-spotted char, Salvelinus leucomaenis.

Plasma estradiol-17 beta and progesterone profiles were correlated with morphological changes in ovarian follicles during the preovulatory and postovulatory periods in the white-spotted char, Salvelinus leucomaenis, Plasma estradiol levels were highest in September, and were followed by a sharp drop in October; they remained very low throughout the postovulatory period. There was a good correlation between plasma estradiol levels and the gonadosomatic index, thus suggesting that estradiol is responsible for the synthesis of vitellogenic proteins. Plasma progesterone levels were very low in August, began to rise in September and reached a peak soon after ovulation; progesterone remained high for several days after ovulation. A preovulatory rise in plasma progesterone levels was recorded, and this is discussed in relation to the induction of oocyte maturation. In the preovulatory follicles, neither granulosa cells nor special thecal cells (ST cells) showed delta 5, 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity. In the young postovulatory follicles, in contrast, the ST cells showed intense 3 beta-HSD activity with extensive agranular endoplasmic reticulum and numerous large mitochondria, while granulosa cells did not show 3 beta-HSD activity. These results strongly suggest that the ST cells are the major sites of progesterone synthesis during the postovulatory period.

3-Hydroxysteroid Dehydrogenases↗
PubMed1980

In vitro polymerization of polyhook protein from Salmonella SJW880.

Polyhooks were isolated from Salmonella SJW880, a non-flagellated mutant, and purified by cesium chloride density gradient centrifugation. The polyhooks were disintegrated into protein subunits (monomer) by heat in the absence of salt. The monomer was repolymerized in the presence of moderately high concentrations of sodium citrate at neutral pH. Three types of polymer were produced. One type of polymer, produced at room temperature and at citrate concentrations less than 0.3 M, had no regular shape and no definite thickness. Another type of polymer, produced at room temperature and at citrate concentrations greater than 0.4 M, had a straight shape and a similar thickness to that of polyhook but was easily dissociated into monomer in the absence of salt. A third type of polymer was produced at low temperature, independently of the concentration of citrate, and seemed to be a tubular polymer with a thickness similar to that of polyhook but had no helical curvature. However, this type of polymer was shown to have a structure locally the same as that of polyhook by electron microscopic observation, optical diffraction and circular dichroism measurements.

Bacterial Proteins↗
PubMed1980

Diffusion of H-meromyosin in F-actin plus ATP solution at a very low electrolyte concentration.

The translational diffusion coefficient (D) of H-meromyosin in actin (F-actin) and ATP solution was measured under conditions wherein the actin-activated ATPase activity is close to its maximal value at a very low electrolyte concentration. The results were compared with similar data obtained with 0.1 M KCl, where H-meromyosin and actin were almost completely dissociated. With 0.1 M KCl, it was found that there was no dependence of the D of H-meromyosin on actin concentration. On the other hand, at a very low electrolyte concentration, it was found that the D of H-meromyosin did depend on actin concentration; at a rather high actin concentration (and activation of ATPase), it was slightly larger than at low or zero actin concentrations. This behavior of D at a low electrolyte concentration is interpreted on the assumption that even in solution, H-meromyosin molecules can actively slide on actin filaments due to the ATPase activity.

Actins↗
PubMed1980

Ultrastructural localization of delta 5-3 beta-hydroxysteroid dehydrogenase in the interrenal cells of the goldfisch (Carassius auratus).

The ultrastructural localization of the enzyme delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) was studied in the goldfish interrenal cells by using the potassium ferricyanide method. Immersion fixation in a mixture of 1% paraformaldehyde and 0.25% glutaraldehyde results in a consistently good ultrastructural preservation and enzyme localization. A precipitate of copper ferrocyanide indicating the localization of 3 beta-HSD activity was observed in close vicinity to the smooth endoplasmic reticulum or in contact with the outer surface of its membrane. A small number of precipitated grains were also found in the lumen of mitochondrial cristae. Addition of phenazine methosulfate increased the intensity of the reaction without changing the localization of the copper ferrocyanide grains. The findings suggest that the outer surface of the smooth endoplasmic reticulum is the major site of 3 beta-HSD activity in goldfish interrenal cells.

3-Hydroxysteroid Dehydrogenases↗
PubMed1979

Isolation and characterization of bacterial flagellar hook proteins from salmonellae and Escherichia coli.

Flagellar hook proteins from Salmonella and Escherichia coli were dissociated in acid and purified by diethylamino-ethyl-cellulose column chromatography. These two proteins had the same electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels. However, analytical electrofocusing patterns showed that these proteins had different isoelectric points (4.7 for Salmonella typhimurium and 4.4 for E. coli). Immunodiffusion and immuno-electron microscopy carried out with antisera prepared against purified hook proteins from S. typhimurium and E. coli showed that these antisera reacted with both hooks. Affinity chromatography allowed separation of antibodies specific for hook proteins from each bacterial species. These results indicate that the hook proteins share common antigenic determinants as well as specific antigens, although the specificity is not quantitatively resolved. From comparisons of the amino acid composition of the hook proteins and flagellins, it was concluded that the differences between flagellins from S. typhimurium and E. coli were larger than those between hook proteins from these species.

Antibodies, Bacterial↗
PubMed1978

Local migration of myosin in F-actin plus ATP solution on the boundary of a diffusion cell.

The diffusion phenomena of myosin (myosin A, H-meromyosin or subfragment-1) in F-actin plus ATP solutions were investigated. The upper part of the diffusion cell was filled with F-actin plus ATP, and the lower part was filled with F-actin, ATP, and myosin, then both parts were brought into contact so that a boundary of the two solutions was formed and the diffusion of myosin in F-actin plus ATP solutions started. The diffusion pattern was observed with a schlieren lens system. When almost all the ATP in the lower part of the cell had been consumed by actomyosin, a hyper-sharp schlieren pattern appeared near the boundary. On analyzing this pattern, it was found that a local fast migration of proteins was occurring. Simple Brownian motion of myosin molecules could not explain the hyper-sharp phenomenon. This phenomenon occurred in ther pesence of Mg2+ or Ca2+, but very little in the presence of EDTA. Although it is well known that the superprecipitation of myosin B suspension occurs only at physiological ionic strength, this phenomenon occurred over a relatively wide range of ionic strengths. The molecular mechanism of this phenomenon is discussed in relation to the basic mechanism of the interaction between myosin and F-actin.

Adenosine Triphosphate↗