Katsuyuki Takahashi

Tohoku University, Japan

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Publications (19)21.39 Total impact

  • Akira Tsuiki · Hiroshi Hoshiai · Katsuyuki Takahashi · Masakuni Suzuki · Kazuhiko Hoshi ·
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    ABSTRACT: Successful in vitro fertilization requires mature oocytes in which the first polar body has been extruded and capacitated sperm capable of penetrating the zona pellucida. In this study we made a time sequential observations on human sperm-egg interactions by SEM in two experimental systems. Human sperm-human zona pellucida interaction: Cytoplasmic processes of corona cell extend around sperm head. Spermatozoa took different angles in attaching or penetrating to the zona pellucida. The head of some spermatozoa bound to the zona were vesiculated, suggesting the progression of the acrosomal reaction. Initially, the anterior part of the sperm head penetrates from the pore of the zona pellucida. Human sperm-zona-free hamster egg interaction: Most spermatozoa lie flat on the vitellus surface covered with numerous microvilli, but a few are oriented perpendicular to the vitellus surface. Most bound sperm had lost their acrosomal caps, because a ridge exists at the leading edge of the equatorial segment. Initially most microvilli appeared to grasp and immobilize the anterior tip of the sperm head. But as gamete interaction proceeded, microvilli were overlying the postacrosomal region and were observed adjacent to the plasma membrane of the postacrosomal region. The postacrosomal region is first incorporated into the ooplasma, the anterior tip of sperm head being the last portion to be incorporated. The microvilli of the oolemmal surface where sperm penetrated did not show major changes in size or in appearance, and the so-called incorporation cone was not observed.
    Archives of Andrology 02/1986; 16(1):35-47. DOI:10.3109/01485018608986921 · 0.89 Impact Factor
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    ABSTRACT: Wistar female rats housed under conditions of 12 hr dark/12 hr light were pinealectomized (PX) or underwent sham-operation (SO) 21 days after ovariectomy, on the 7th or on the 15-17 th day of pregnancy. Serum and pituitary prolactin (PRL) levels in ovariectomized (OVX) rats were determined 9 days after pinealectomy. In the case of OVX rats receiving estrogen and progesterone injections (OVX-EP), PRL levels were determined 48 hr after injection administered 7 day after pinealectomy. PRL levels in pregnant rats were determined on the 20th day of pregnancy and in postpartum rats, on the 3rd day following parturition. As compared with the SO control, pinealectomy resulted in a significant decrease in the serum PRL level in the OVX-EP rats but in a significant increase in that level in the OVX, pregnant and postpartum rats. In OVX-EP rats, exogenous estrogen raised the serum PRL level less in PX than in SO rats, probably because the pineal gland is closely related to the facilitation of PRL secretion by estrogen. The high estrogen level in OVX-EP rats seemed to trigger pineal stimulation of PRL release, but low estrogen levels in OVX and postpartum rats or markedly high levels of progesterone in pregnant rats on the 20th day are thought to cause pineal inhibition.
    The Tohoku Journal of Experimental Medicine 08/1984; 143(3):305-13. DOI:10.1620/tjem.143.305 · 1.35 Impact Factor
  • Katsuyuki Takahashi · Nobuko Ikeno · Hiroshi Hoshiai · Masakuni Suzuki ·
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    ABSTRACT: Each of 20 pregnant women (greater than or equal to 39 weeks) was given an intravenous injection of various doses (50, 100, 200 and 400 mg) of dehydroepiandrosterone sulfate (DHA-S) and each of 5 pregnant women (greater than or equal to 39 weeks) was given glucose solution as a control. After the administration of DHA-S, significant increases in serum estrogen concentration, especially estradiol-17 beta concentration, and in the Bishop score were observed. The maximum increase in the level of estradiol-17 beta was significantly correlated with the doses of 50-200 mg of DHA-S. However, serum levels of estrone or estriol were not dose-dependently increased by DHA-S. Since the rate of conversion of DHA-S to estrogen did not necessarily seem to be dose-dependent, there may be some limitation regarding converted doses of DHA-S. There was a significant correlation between the increase in serum estrogen concentration and the increase in the Bishop score. Two hundred mg DHA-S were administered to 4 subjects pregnant with twins. Serum estrogen concentrations in these subjects were significantly higher than those in singleton pregnancies after the administration.
    The Tohoku Journal of Experimental Medicine 04/1984; 142(3):289-98. DOI:10.1620/tjem.142.289 · 1.35 Impact Factor
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    ABSTRACT: Adult female Wistar rats (in 12 hr light/12 hr dark) were pinealectomized (PX) or sham-operated (SO) either 21 days after ovariectomy or on the 15-17th day of pregnancy. Ovariectomized (OVX) rats were injected with estrogen and progesterone (EP) 48 hr before decapitation. Melatonin, serotonin or arginine vasotocin (AVT; 50, 100 or 200 micrograms) were administered intravenously into OVX-EP rats 9 days after pineal removal. In PX and SO groups, the same study was done 3 days after delivery. Sera and pituitaries were collected 30 min after injection in order to determine prolactin (PRL) levels. Fifty micrograms melatonin significantly suppressed serum PRL levels in PX-OVX-EP rats and PX postpartum rats, but had not significant effect in SO-OVX-EP or PX postpartum rats. After administration of AVT, serum PRL levels markedly rose in PX and SO rats. These results suggest that melatonin may act not only to stimulate but also to inhibit rat PRL secretion and that the stimulatory function would be superior to its inhibitory function when the pineal gland is intact.
    The Tohoku Journal of Experimental Medicine 10/1983; 141(1):107-16. DOI:10.1620/tjem.141.107 · 1.35 Impact Factor
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    ABSTRACT: Serum methanol extracts were obtained from nine women with the galactorrhea-amenorrhea syndrome, 24 pregnant women in the third trimester, and 18 normal men and women. The serum extract released prolactin (PRL) in significant amounts from rat anterior pituitary in vitro. The extracts from patients with galactorrhea-amenorrhea released PRL in large quantities. A significant positive correlation was observed between the PRL-releasing activity and serum PRL levels in individual samples from the pregnant women and normal subjects but not from the patients with galactorrhea-amenorrhea. Bromocriptine therapy suppressed serum PRL levels of five patients without tumors but increased the PRL-releasing activity in three out of five patients after treatment for 1 or 2 months. Apparently hypothalamic regulation of PRL secretion was disrupted in these three patients after bromocriptine therapy.
    American Journal of Obstetrics and Gynecology 06/1983; 146(1):74-9. DOI:10.1016/0002-9378(83)90930-4 · 4.70 Impact Factor
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    ABSTRACT: The variation of cytoplasmic estrogen receptor in the mammary gland during pregnancy and puerperium was studied to determine the role of estrogens in the mechanism of lactation. Cytosol estrogen receptors from rat mammary glands were incubated with 3H-estradiol, and the free estradiol was removed using dextran-coated charcoal. The maximum number of binding sites in the cytosol was estimated from saturation curves and Scatchard analysis. During pregnancy the number of binding sites was relatively low (2.5 to 3.8 pmoles per mg protein), but increased after delivery to 7.8 pmoles per mg protein. The number of estrogen binding sites in the mammary glands of lactating rats five days after delivery was at the same level as on the day of delivery. However, at ten days after delivery the number of binding sites increased markedly to 58.9 pmoles per protein. The number of estrogen-binding sites in the mammary glands of lactating rats was decreased by castration and by the injection of testosterone or 2-bromoergocriptine. There appeared no competition by testosterone, progesterone or cortisol with estrogen receptors in the mammary gland.
    The Tohoku Journal of Experimental Medicine 03/1982; 136(2):195-202. DOI:10.1620/tjem.136.195 · 1.35 Impact Factor
  • Kiyo Muraguchi · Katsuyuki Takahashi · Masakuni Suzuki · Nobuko Ikeno ·
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    ABSTRACT: Simultaneous determinations of unconjugated estradiol (E2), estriol (E3) and 15 alpha-hydroxyestriol (E4) levels in maternal serum were studied serially to ascertain the significance of these estrogens in the feto-placental unit. The samples of serum were collected serially from 25 normal and 44 abnormal pregnancies. In normal pregnancy, these estrogen levels increased throughout pregnancy, especially E3 and E4 nearing the term. In 15 cases of IUGR pregnancy (including 4 cases of perinatal death), E2 levels were mostly low (less than M -- S.D.), E3 was within normal limits (M +/- S.D.) or low, and E4 was either high (greater than M + S.D.) or relatively low, and normal. In 9 cases of twin pregnancy, most E2 levels were within normal limits, while E3 and E4 were remarkedly high. The results signified that E2 indicated placental function, that E3 indicated placental and fetal function, and that E4 indicated fetal function.
    Nippon Naibunpi Gakkai zasshi 08/1981; 57(7):974-82. DOI:10.1507/endocrine1927.57.7_974
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    ABSTRACT: We evaluated the frequency of endometriosis among the patients who underwent laparotomy and studied retrospectively the frequency of endometriosis in Japanese women. The frequency of operation for endometriosis has been about 0.6% of all the new outpatients and 10.8% of patients with laparotomy. We found a higher frequency of endometriosis in the most recent period (1977–1979). The mean age of endometriosis patients was 40.74 + 0.65 (mean + SE) years old. Our results indicated that the frequency of endometriosis in Japanese women has increased during the last two decades.
    Journal of Obstetrics and Gynaecology Research 06/1981; 7(2). DOI:10.1111/j.1447-0756.1981.tb00520.x · 0.93 Impact Factor
  • Atsushi Haneda · Nobuyoshi Sakurada · Katsuyuki Takahashi · Masakuni Suzuki ·
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    ABSTRACT: Purpose : Although it is known that prostaglandin (PG) causes the release of gonadotropin and prolactin (PRL) in rats, its site of action has not yet been elucidated. Consequently, we undertook this study to determine the relationship between various limbic nuclei and the release of gonadotropin and PRL due to PGE2.Methods : Mature, female, Wister rats were castrated and pretreated 3-5 weeks later with estrogen and progesterone. 72 hrs later the following experiments were carried out.Expt : Using the Albe-Fessard brain map, 2μg PGE2 was injected into various intracranial sites with a stereotaxic instrument. 15, 30 and 60 min after the experiment, the rats were sacrificed by decapitation, blood was collected, and the adenohypophysis was excised. Serial sections of the brain were prepared, and the site of injection was confirmed.The gonadotropin and PRL levels in the blood and pituitary were determined by RIA. Results : 1) Following a medial amygdala (m-AMYG) injection, significant changes in the blood and pituitary levels of these hormones were not seen. 2) 30 min following a medial preoptic area (MPO) injection, a significant increase in blood LH content was found, but no change in FSH or PRL was seen. 3) An injection into the third ventricle (IIIV) resulted in a significant increase in blood gonadotropin and PRL levels 15 min later, which correlated with the decrease in pituitary levels. 4) 15 min following an arcuate nucleus (ARC) injection, blood LH content increased significantly to 238.5 ± 80.2ng/ml (as compared to control values of 30.2 ± 9.8ng/ml), correlating with the decrease in pituitary LH. There was also a significant increase in blood PRL after 15 min and a similar tendency for FSH levels.From this investigation of PG injections into various limbic sites, it is concluded that the nuclei in the vicinity of the IIIv are involved in gonadotropin and PRL secretion due to PG. The ARC is particularly involved in LH secretion.
    Nippon Naibunpi Gakkai zasshi 04/1980; 56(3):231-40. DOI:10.1507/endocrine1927.56.3_231
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    ABSTRACT: A serum component with suppressive activity on human lymphocyte responses to phytohemagglutinin was examined in pregnancy serum. No correlation could be found between the elevated level of alpha-2AP glycoprotein and the immunosuppressive activity. The active constituent was isolated by ultracentrifugation, salt fractionation, ion exchange chromatography and gel filtration. The immunosuppressive activity was found to be associated with alpha-globulin which consisted of neither lipoprotein nor alpha-2-AP glycoprotein. In terms of its antigenicity, the active fraction was found to be a mixture of 5 components.
    The Tohoku Journal of Experimental Medicine 02/1980; 130(1):11-23. DOI:10.1620/tjem.130.11 · 1.35 Impact Factor
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    ABSTRACT: A 15-year-old Japanese female with complaints of abdominal tumor and exophthalmos underwent surgery. Histologically, the tumor showed a starry-sky pattern with the macrophages interspersed among undifferentiated lymphoblastoid cells. Considering the clinical aspects, distribution of tumor deposits, and cytological findings, the tumor was diagnosed as Burkitt's tumor. The patient expired on the 42nd day of hospitalization due to general dissemination.
    The Tohoku Journal of Experimental Medicine 09/1979; 128(4):359-66. DOI:10.1620/tjem.128.359 · 1.35 Impact Factor
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    ABSTRACT: Female Wistar rats were divided into four groups.Group 1 : The rats were pinealectomized by the Kuszak and Robin modified method or sham-operated 3 weeks after castration. They were injected with estrogen-progesterone 1 week after the pinealectomy and sacrificed by decapitation 48 hours after the injection.Group 2 : The rats were pinealectomized or sham-operated after 1 week of pregnancy and decapitated after 20 days of pregnancy.Group 3 : The rats were pinealectomized or sham-operated after 15-19 days of pregnancy. The litter was separated from the mother immediately after delivery. These non-lactating rats were sacrificed by decapitation 3 days after delivery.Group 4 : Pinealectomy and sham-operation were done by the same method as in group 3. The litter was not separated and allowed to suckle. These lactating rats were decapitated 3 days after delivery.Prolactin levels in the pituitaries and serum were determined by radioimmunoassay.We found that pinealectomy made the serum prolactin level significantly increase in pregnant and puerperal rats, and significantly decrease in castrated rats. The hypophysial prolactin level decreased in all groups, but there was no significant difference apart from group 3.These results indicate that the suckling stimulation made the prolactin secretion significantly increase even though the rats had undergone a pinealectomy. The pineal gland effects the hypothalamus appearing to inhibit PIF and PRF. This would suggest that the prolactin release action of the pineal gland has no relation to the route of the central nervous system concerning suckling stimulation.
    Nippon Naibunpi Gakkai zasshi 03/1979; 55(2):114-21. DOI:10.1507/endocrine1927.55.2_114
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    ABSTRACT: After inserting the Cu-IUD and plastic-IUD into the horn of the uterus of rats, vaginal smears were daily observed for twelve estrus cycles, but no abnormal changes were noted. The female rats with the IUD were exposed to impregnation placing together with male rats. Neither the Cu-IUD nor the plastic-IUD affected copulation, and a complete contraceptive result was obtained in these rats. There were no significant differences in any effect examined between Cu-IUD and plastic-IUD groups. In order to investigate the influence of copper on the penetration of sperm, we placed the rats with the IUD under direct observation and then exposed them to natural copulation. By examining various sites of the reproductive organs 30 min after copulation, the hindrance of sperm migration by the Cu-IUD was confirmed.
    The Tohoku Journal of Experimental Medicine 01/1979; 126(4):325-33. DOI:10.1620/tjem.126.325 · 1.35 Impact Factor
  • Atsushi Haneda · Nobuyoshi Sakurada · Katsuyuki Takahashi · Masakuni Suzuki ·
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    ABSTRACT: Numerous reports concerning the mechanism by which pituitary gonadotropin and prolactin are released by prostaglandins (PG) have been made since the experimental work of Orczyk & Behrman et al (1972). Nonetheless, it is still uncertain whether the location of this effect is in the hypothalamus, higher centers or in the pituitary gland. In this paper the authors report an investigation of the effects of PGE2 on the vaginal smear in rats and observation of central nervous system changes based upon the recording of multiple unit activity (MUA). Furthermore, they have measured the effects of PGE2 on these locations by determining the amounts of gonadotropin and prolactin in the blood and the pituitary gland.
    Nippon Naibunpi Gakkai zasshi 12/1978; 54(11):1238-48. DOI:10.1507/endocrine1927.54.11_1238
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    ABSTRACT: Pregnant rat hypothalamic fragments were extracted with 30 mM Tris-HCl buffer at pH 7.8, subjected to enzymatic digestion, and applied to gel filtration on Sephadex G-25 for purification of the prolactin releasing factor. Effect of the eluted fractions on the release of prolactin were tested by the determination of serum and pituitary prolactin after the injection in lactating rats. Prolactin was estimated by radioimmunoassay. One fraction (tube number 61--73) eluted later than synthetic ACTH enhanced release of prolactin 30 min after injection, but other fractions had no effect on the release of prolactin. Prolactin releasing factor would be quantitatively predominant over prolactin inhibiting factor in pregnant rat.
    The Tohoku Journal of Experimental Medicine 10/1978; 126(1):77-84. DOI:10.1620/tjem.126.77 · 1.35 Impact Factor
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    ABSTRACT: Serum estradiol, progesterone, LH and FSH were concomitantly measured by radioimmunoassay in pre and post menopausal women in an attempt to study hormonal changes occurring in menopause. The level of serum estradiol in post menopausal women was maintained at the same level as in pre menopausal stage within one year after menopause and thereafter began to decrease to the senile minimal level. On the other hand, the mean serum levels of FSH and LH were elevated gradually after menopause. At the conclusion of this study, it was suggested that the key point of the mechanism of menopause may exist not only in the depletion of ovarian function but in the change of the regulatory mechanism of LH and FSH secretion by aging.
    The Tohoku Journal of Experimental Medicine 01/1977; 121(3):231-238. DOI:10.1620/tjem.121.231 · 1.35 Impact Factor
  • Katsuyuki Takahashi · Masaharu Saito · Teiko Wakai · Hiroshi Hoshiai · Yuichi Wada ·
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    ABSTRACT: The present study attempted to elucidate stimulatory factor(s) in the rat hypothalamus which controls prolactin secretion from the anterior pituitary. Rat serum prolactin was elevated so much in late pregnancy that we prepared the hypothalamic extract of late pregnant rats. Prolactin levels in serum and pituitary by radioimmunoassay. After injection of this extract into a lactating rat 48-60 hr after delivery, the serum prolactin level was elevated significantly one to four hr later and the pituitary prolactin level declined two hr later. On the other hand, the hypothalamic extract of normal female rats prepared in a similar manner inhibited prolactin secretion from the anterior pituitary in the lactating rat as described by other authors. These data indicate that the prolactin releasing factor may consist in the hypothalamus of late pregnant rat, and be predominant over the prolactin inhibiting factor during late pregnancy. Prolactin secretion was also investigated in lactating and non-lactating puerperium rats. Prolactin in serum and pituitary declined with days after delivery in non-lactating rats, but not in lactating rats. The presumed factor for such prolactin release in lactating rats is considered to be the prolactin releasing factor.
    The Tohoku Journal of Experimental Medicine 12/1976; 120(3):231-7. DOI:10.1620/tjem.120.231 · 1.35 Impact Factor
  • Nobuaki Furuhashi · Tetsuro Abe · Masakuni Suzuki · Yoshihiro Yamaya · Katsuyuki Takahashi ·
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    ABSTRACT: The serum levels of estradiol, progesterone, LH and FSH were determined by radioimmunoassay in post-menopausal and castrated women and the data obtained at the same periods after menopause and castration were compared. The serum levels of estradiol and progesterone in post-menopausal women within 1 year after menopause were higher than those of castrated women. The result suggested that ovarian function was indeed depressed in the post-menopausal women but was still preserved for 1 to 2 years after menopause. In the post-menopausal women, the levels of serum LH and FSH rose gradually to reach a peak at 1 to 3 years after menopause, when the production of ovarian sex steroid hormones presumably ceased. On the contrary, the serum LH and FSH levels of castrated women began to decrease gradually 4 to 9 years after castration. It is highly suggestive from these findings that a negative feedback mechanism is elicited by ageing.
    The Tohoku Journal of Experimental Medicine 10/1976; 120(1):19-24. DOI:10.1620/tjem.120.19 · 1.35 Impact Factor
  • Katsuyuki Takahashi · Teiko Wakai · Kimio Nakagawa · Hiroshi Hoshiai · Yuichi Wada ·
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    ABSTRACT: Regulation of prolactin secretion in pituitary is considered to be mostly carried with the action of prolactin inhibiting factor in hypothalamus. We have investigated on the subject of prolactin releasing factor in the hypothalamus of rats in last stage of pregnancy using puerperal and ovariectomized rats as recipients. After prepared the cell-free system of pregnant rat hypothalamus with sonic oscillator, supernatant was produced by ultracentrifuge (25,000 X g, 30 min.) and utilized for the experiments. When the extract was injected intramuscularly to puerperal rats (48-60 hours after delivery), serum prolactin values increased gradually to 3 times of control values, but pituitary prolactin values showed the variation with decrease and recovery. The control values were obtained by determination after injection of cerebral cortical extract to puerperal rats. After administration of a extract of non-pregnant rat hypothalamus to puerperal rats, serum prolactin values decreased and pituitary prolactin values increased antagonistically. In the ovariectomized rats pretreated with estradiol and progesterone, serum prolactin values increased in 1 hour after administration of the extract of pregnant rat hypothalamus, but pituitary prolactin values did not show any variation. The present experiment suggests that the prolactin secretion promoting factor exists in the hypothalamus of pregnant rats and predominates over as compared with PIF in last stage of pregnancy.
    Nippon Naibunpi Gakkai zasshi 01/1976; 51(12):1015-23. DOI:10.1507/endocrine1927.51.12_1015