Search PubMed⌕ Search

Biomedical subjects

H Okamura

Publications and source records attributed to H Okamura.

At least 793 records · Page 44Linked to original sources
PubMed1976

An enzymologic study of corpora lutea in early pregnant rats treated with abortifacient agents.

Luteal metabolism was investigated in corpora lutea of early pregnant rats treated with four abortifacient agents. In corpora lutea of rats treated with prostaglandin F2alpha or of rats 1 day postpartum, glucose-6-phosphate dehydrogenase (G6PDH) activity increased 140 to 170% and 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) was activated to significantly high levels, whereas malic enzyme activity decreased to 29% of control values. In aminoglutethimide-treated rats, the activities of G6PDH and malic enzyme decreased, while 20alpha-HSD activity was maintained at a very low level. With the increased dose, complete abortion was observed. In corpora lutea of these aborted rats, 20alpha-HSD was activated moderately and G6PDH values were slightly higher than control values, whereas malic enzyme activity fell to lower levels. All rats treated with clomiphene citrate aborted within 63 hours after the last injection. The activities of G6PDH, malic enzyme, and ATP citrate lyase in these corpora lutea decreased to 66, 68, and 72% of control levels, respectively; 20alpha-HSD activity was maintained at a very low level, and activities of 3beta-hydroxysteroid dehydrogenase, 6-phosphogluconate dehydrogenase, and pyruvate kinase were not appreciably altered. These findings indicated that, at the beginning of luteolysis and fetal resorption, the activities of steroidogenic enzymes decreased and 20alpha-HSD was not yet activated. Therefore, we could gauge the early changes of luteolysis by measuring the activities of G6PDH, MALIC ENZYME, AND ATP citrate lyase as well as 20alpha-HSD.

ATP Citrate (pro-S)-Lyase↗
PubMed1976

Regulation of tyramine oxidase synthesis in Klebsiella aerogenes.

Tyramine oxidase in Klebsiella aerogenes is highly specific for tyramine, dopamine, octopamine, and norepinephrine, and its synthesis is induced specifically by these compounds. The enzyme is present in a membrane-bound form. The Km value for tyramine is 9 X 10(-4) M. Tyramine oxidase synthesis was subjected to catabolite repression by glucose in the presence of ammonium salts. Addition of cyclic adenosine 3',5'-monophosphate (cAMP) overcame the catabolite repression. A mutant strain, K711, which can produce a high level of beta-galactosidase in the presence of glucose and ammonium chloride, can also synthesize tyramine oxidase and histidase in the presence of inducer in glucose ammonium medium. Catabolite repression of tyramine oxidase synthesis was relieved when the cells were grown under conditions of nitrogen limitation, whereas beta-galactosidase was strongly repressed under these conditions. A cAMP-requiring mutant, MK54, synthesized tyramine oxidase rapidly when tyramine was used as the sole source of nitrogen in the absence of cAMP. However, a glutamine synthetase-constitutive mutant, MK94, failed to synthesize tyramine oxidase in the presence of glucose and ammonium chloride, although it synthesized histidase rapidly under these conditions. These results suggest that catabolite repression of tyramine oxidase synthesis in K. aerogenes is regulated by the intracellular level of cAMP and an unknown cytoplasmic factor that acts independently of cAMP and is formed under conditions of nitrogen limitation.

Amino Acid Oxidoreductases↗
PubMed1976

In vitro steroidogenesis by human corpora lutea of pregnancy. Effects of human chorionic gonadotropin and prostaglandin F2alpha.

Human corpora lutea of pregnancy obtained at 5 to 11 weeks of gestation were incubated in vitro in the presence of various concentrations of human chorionic gonadotropin (hCG) and prostaglandin F2alpha (PGF2alpha). Progesterone (P) and 17beta-estradiol (E2) released into the medium during incubation were measured by radioimmunoassay. Pieces of the corpora lutea were also examined ultrastructurally before and after incubation. Release of P and E2 into the medium was significantly increased by the addition of hCG and PGF2alpha in some cases. However, the response to hCG and PGF2alpha appeared to vary according to the age of the corpus luteum. Ultrastructurally, the lutein cells were well maintained with respect to the appearance of the smooth endoplasmic reticulum and mitochondria after 120-min incubations. On the basis of these observations, the following conclusions have been reached: 1) This incubation system seems to be suitable for investigating the direct effects of chemicals on lutein cells in vitro. 2) Both hCG and PFG2alpha directly stimulate steroidogenesis in the human corpus luteum of pregnancy, demonstrating their luteotropic actions in vitro. 3) Observed variations in P and E2 secretion might have been due to the different activities of aromatizing enzymes at different stages of gestation.

Chorionic Gonadotropin↗
PubMed1976

[Flow of molten metal in denture base in horizontal centrifugal casting procedure. (Part 1) Flow, inflow volume and casting time of molten metal passing through single aprue into disk type mold (author's transl)].

A pyrex glass plate was fitted at the bottom of casting ring, and disk type wax pattern (thickness. 0.43 mm) was put on the plate. Five types of sprueing were applied. Pure tin was casted using holizontal centrifugal casting machine. Flow of molten metal was filmed by the motor drive camera with the method of stroboscope. The results were summarized as follows. 1) When the sprue was attached at the center of the disk type mold vertically, moten metal flowed like a concentric circle at the early stage of casting. It was affected gradually by the direction of gravity and revolution, and it filled the mold from the lower part to the upper part. 2) When the sprue gate was attached to the side edge of the mold, and the sprue gate was placed to the forward and backward direction against the revolution direction, molten metal filled from lower part to the upper part. 3) When the sprue gate was placed against upper edge, molten metal flow was affected by the direction of gravity and revolution. When the sprue gate was placed against lower edge, molten metal filled quietry from the lower part to the upper part. 4) Inflow volume per unit time (inflow rate) was small at the early stage of casting. Inflow rate increased and became constant at the next stage. At the latter stage it became small again. 5) Inflow rate increased with the increase of area of sprue. 6) The time which was necessary to fill the volume of 1 cm (about 80% of the mold volume) became short with the increase of area of sprue. It was also influenced by the type of sprueing.

Dental Casting Technique↗
PubMed1975

Effects of electrical stimulation on human ovarian contractility.

Electrical stimulation was applied to the follicular walls, capsules of corpora lutea, and pieces of atrophic ovaries obtained from 29 human ovaries. The quantitative analysis of contractile capacity in these ovarian strips was performed on the basis of stimulation-response relationships. Only with follicular walls and capsules of corpora lutea was the step linear dose-response relationship similar to that shown by the uterine rube obtained by alternating current stimulation. The basal portions of mature follicular walls showed much more distinct responses to AC-stimulation than the apical portions. This difference further indicates a possible role of contractions by basal follicular walls in the process of follicular rupture at the apex in the human ovulation. The contractile elements of these ovarian strips were electronmicroscopically investigated with the strips which had shown contractions and confirmed to be smooth muscle cells in the ovary.

Adult↗