Biomedical subjects

H Kitai

Publications and source records attributed to H Kitai.

22 records · Page 2Linked to original sources

PubMed1984

Gonadotropin-releasing hormone: effects on the in vitro perfused rabbit ovary.

Gonadotropin-releasing hormone (GnRH) has been shown to inhibit ovulation in gonadotropin-primed hypophysectomized rats and steroid production in cultured rat granulosa cells. To determine if similar effects of GnRH can be observed in another species, the extracorporeal perfused rabbit ovary was utilized. Two groups of rabbit ovaries were exposed to GnRH in a pulsatile fashion at two dose levels (Group I, 2.56 X 10(-8) M; Group II, 2.56 X 10(-7) M). Contralateral ovaries were not perfused with GnRH. Human chorionic gonadotropin (hCG) was added to the perfusate of all ovaries 30 min after the onset of perfusion. Ovulation occurred in all ovaries exposed to hCG in the presence or absence of GnRH. Ovulatory efficiency was similar in both the experimental and control groups. No statistical difference could be determined in the time of ovulation, stage of maturity of oocytes, or percent of degeneration of ovulated or follicular oocytes. Progesterone production was not inhibited in the GnRH-treated ovaries. In contrast to observations in the rat, GnRH does not exhibit a direct inhibitory effect on ovulation or steroid production in the rabbit.

Animals↗

PubMed1984

Influence of calcium and magnesium deprivation on ovulation and ovum maturation in the perfused rabbit ovary.

The role of calcium (Ca++) and magnesium (Mg++) in the ovulation process was studied using in vitro perfused rabbit ovaries. Ovaries were perfused with or without human chorionic gonadotropin (hCG) in Ca++/Mg++-free medium (M199) alone or combined with standard M199 to yield varying concentrations of Ca++ and/or Mg++. In all ovaries perfused with hCG, ovulatory efficiency was similar regardless of the concentration of Ca++ and/or Mg++. In ovaries perfused in Ca++/Mg++-free medium without hCG, ovulatory efficiency was similar to that in ovaries perfused with hCG. As Ca++/Mg++ levels were increased without hCG, ovulatory efficiency declined. Ovulation time was significantly accelerated in ovaries perfused in Ca++/Mg++-free medium with or without hCG. Most ovulated ova from ovaries perfused without hCG were immature. With hCG, degree of ovum maturity was directly related to ovulation time. Ovarian smooth muscle contractions were undetectable in 3 ovaries perfused in Ca++/Mg++-free M199 despite occurrence of ovulation. Smooth muscle contractions were recorded in 2 of 3 ovaries perfused in standard M199 with hCG. These results indicate: 1) Ca++/Mg++ exclusion results in rapid follicle rupture and immature ova; 2) oocyte maturation appears to be gonadotropin-dependent; 3) ovulation occurs in the absence of ovarian smooth muscle contractions during perfusion with Ca++/Mg++-free medium.

Animals↗

PubMed1983

Effect of histamine and histamine blockers on the ovulatory process in the vitro perfused rabbit ovary.

An increase in the content of histamine in the ovary following luteinizing hormone (LH) release and the inhibition of ovulation in the rabbit by antihistamines suggest that histamine may be involved in the ovulatory process. The effects of various doses of histamine and antihistamines on ovulation were investigated using the in vitro perfused rabbit ovary system. Histamine (100 ng/ml) added to the perfusate at hourly intervals induced ovulation, although at a rate below that observed following human chorionic gonadotropin (hCG) administration. Cimetidine (10 micrograms/ml), an H2 blocker, inhibited histamine-induced ovulation, while the H1 blocker, chlorpheniramine (66.7 micrograms/ml), failed to do so. Neither cimetidine nor chlorpheniramine was able to block ovulation following hCG (50 IU). In all experimental groups in which histamine was used to induce ovulation, both extruded ova and follicular oocytes remained in an immature stage and displayed little evidence of degeneration. In contrast, a high percentage of ova exposed to hCG were mature. Ovarian edema was increased in ovaries in which ovulation occurred, regardless of treatment. A linear correlation was noted between ovulatory efficiency and degree of ovarian edema. Histamine may be an intermediary in the mechanism of follicular rupture, but does not support ovum maturation. However, the inability of H1 and H2 antagonists to block hCG-induced ovulation raises questions regarding the role of histamine in the physiologic process of ovulation.

Animals↗

PubMed1981

Ultrastructure and some biologic properties of human oocytes and granulosa cells cultured in vitro.

Of follicular oocytes with germinal vesicles, 79% resumed meiosis within 48 hours in modified Ham's F-10 medium for oocyte culture, and 59% of them reached the second-metaphase stage of meiosis. An increase in cortical granules and tubular aggregates and a decrease in the Golgi apparatus were observed during the maturation process. Scanning electron microscopy of the oocyte surface revealed a decrease in number and length of microvilli. Nuclear DNA contents diminished to approximately one-half, but cytoplasmic protein contents measured by cytofluorometry were unchanged after culture in spite of these structural changes. Insemination with washed spermatozoa resulted in fertilization of 5 of 43 zona-intact cultured oocytes. After removal of the zona, 6 of 17 cultured oocytes showed polyspermic penetration, although immature oocytes were not fertilized even after removal of the zona. Cultured granulosa cells secreted progesterone spontaneously, and its amount was correlated with follicular size. Ultrastructurally, mitochondria with laminar cristae, enlarged nuclei, dispersed Golgi apparatus, smooth endoplasmic reticulum, lipid droplets in the ooplasm, and granular cytoplasmic protrusions were observed on the oocyte surface.

Cell Membrane↗