Journal of Reproduction and Development
Online ISSN : 1348-4400
Print ISSN : 0916-8818
ISSN-L : 0916-8818
Volume 47, Issue 5
October
Displaying 1-10 of 10 articles from this issue
Review
  • Horacio MERCHANT-LARIOS
    Article type: scientific monograph
    Subject area: none
    2001 Volume 47 Issue 5 Pages 245-252
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    Considering gamete distribution of sex heteromorphic chromosomes, three groups of vertebrates can be distinguished: i. Heterogametic males with X:Y chromosome pairs; ii. Heterogametic females with Z:W chromosome pairs and, iii. Species without heteromorphic sex chromosomes. Whereas in species with heteromorphic sex chromosomes, sex is determined at fertilization, in the other species sex determination occurs later. Among this group, there are species where temperature may act as sex-determining factor. In turtles, higher temperatures are female-promoting whereas in crocodiles they are male-promoting. Regulation of steroid hormones levels by temperature is suggested as the physiological mechanism of sex determination. Several genes related to sex determination in mammals and birds are also expressed in gonads of reptiles with temperature sex determination (TSD). However, the diverse sequence and timing of their expression indicates that different genetic pathways of sex determination have evolved. Determination of Sertoli cells is a critical stage in developing gonads of vertebrates for sex determination. Sox9 is a Sry-related gene implicated in differentiation of Sertoli cells in reptiles, birds and mammalian embryos. In the present review, Sox9 expression in the sea turtle Lepidochelys olivacea, a species with TSD, is compared with Sox9 expression in other vertebrate species with temperature or genetic sex determination.
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Original Article
  • Miho WATANABE, Korehito YAMANOUCHI
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 253-258
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    To clarify the role of the extrahypothalamic signals to the hypothalamus in regulating ovulation, the effect of interruption of the dorsal inputs of the hypothalamus on delayed ovulation induced by the treatment with pentobarbital (PB) was examined in female rats. A posterior half-circle horizontal cut at the dorsal of the hypothalamus (PDC) was made and spontaneous ovulation or ovulation delayed by PB were observed. When PDC was performed at 10:00-11:30 h on the day of proestrus, ovulation occurred normally the next morning in all rats. Treatment with PB at 16:00h on the day of proestrus, but not at 13:00 h, induced one-day-delayed ovulation in most rats without brain surgery. In contrast, ovulation was seen normally on estrus in 60.0% of PDC females, when treated with PB at 16:00 h. However when PB was injected at 13:00 h, ovulation was delayed one day in 88.9% of PDC females. Twenty days after making PDC, delayed ovulation was not induced by PB at 16:00 h in 54.5% of rats. These results suggest the possibility that PDC advances the effective period in which PB can cause delayed ovulation. Furthermore, the effect of the PDC continues for at least 20 days after the operation. Thus, dorsal inputs to the hypothalamus may be concerned with a control mechanism of the critical period for triggering of ovulation in female rats.
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  • Kazumasa HONDA, Takashi HIGUCHI
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 259-265
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    Release of posterior pituitary hormones is known to be controlled by hemodynamic information in addition to factors related to reproductive function such as suckling stimulus by pups during lactation and afferents from the uterine cervix during parturition. The midbrain parabrachial nucleus, which is one of the major sites for the integration of the autonomic function, sends heavy projections to the hypothalamic supraoptic and paraventricular nuclei which contain oxytocin and vasopressin secreting neurones. The present experiments were undertaken to examine the physiological role of these projections. Electrical stimulation of the parabrachial nucleus increased the excitability of 65% of putative oxytocin neurones, and 60% of putative vasopressin neurones. Electrolytic lesion of the parabrachial nucleus itself did not affect the basal firing rate, which suggests that inputs from the parabrachial nucleus to the supraoptic nucleus are not tonically driven. Although the lesion did not change the responsiveness of neurones to hyperosmotic stimulation, it affected the responsiveness of putative vasopressin neurones to the decrease of blood pressure. In addition to the well-known role of neurosecretory neurones in reproductive functions, these neurones may change their electrical activity in response to inputs driven by the parabrachial nucleus and contribute to the control of body fluid balance.
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  • Keiichiro TOMINAGA, Yukako HAMADA
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 267-273
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    Recently, new vitrification methods for bovine embryos characterized by ultra-rapid cooling have been reported. The present study was undertaken to determine the availability of gel-loading tips as containers for vitrification of in vitro-produced bovine embryos at various developmental stages. Bovine embryos at Days-1, -2, -3, -4, -5, and -7 (the day of insemination was defined as Day-0) were placed in 0.6~0.7 μl of vitrification solution (20% ethylene glycol, 20% DMSO and 0.6 M sucrose) in a commercially available gel-loading tip, and cooled by immersing in liquid nitrogen. Survival of the vitrified embryos was evaluated by in vitro development into the blastocyst stage. There was no significant difference (P ≥0.05) between the survival rates for fresh and vitrified embryos at Day-1 (70.5 and 58.0%, respectively), Day-2 (75.9 and 68.3%, respectively), Day-3 (75.9 and 57.9%, respectively), Day-4 (80.0 and 67.6%, respectively), Day-5 (82.1 and 60.0%, respectively) and Day-7 (100 and 97.8%, respectively). And no significant differences were found between the total numbers of cells or the proportion of inner cell mass cells of blastocysts developed from fresh versus vitrified embryos. These results demonstrate that the gel-loading tip is applicable as a container for vitrification of in vitro-produced bovine embryos at the 2-cell to blastocyst stages.
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  • Aki OKADA, Toshio ANDOH, Yasutomo MIZUOCHI, Kumiko YOSHII, Naohisa ISH ...
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 275-281
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    This study investigated two different GnRH analogues (fertirelin acetate or buserelin acetate) with two different dosages (Experiment 1: spring) and different injection times at estrus in superovulated ewes (Experiment 2: autumn). Effects on ovarian response and recovered embryo quality were compared among the treated ewes in each season. All ewes were pre-treated with vaginal sponges impregnated with synthetic progesterone for 12 days and were injected intramuscularly with 20 mg pFSH and 250 IU eCG at 2- and 1-day before the sponge removal, respectively. The ewes were observed for estrous behavior from the time of sponge removal every 6 h, and were treated at estrous detection by intramuscular injections as follows: in Experiment 1 (n=34), 1 ml of Conceral (containing 50 μg fertirelin acetate per 1 ml) (Treatment Group 1), 2 ml of Conceral (Treatment Group 2), 1 ml of Estomal (containing 4.2 μg buserelin acetate per 1 ml) (Treatment Group 3), 2 ml of Estomal (Treatment Group 4), and 1 ml of 0.6% NaCl solution (Treatment Group 5; control), and in Experiment 2 (n=27), Treatment Groups 1 and 3 as in Exp. 1. The ewes that had not shown estrous behavior within 24 h after the sponge removal were treated with either Conceral or Estomal at 24 h. The ewes were inseminated intrauterinally with fresh-diluted semen by means of a laparoscope 32 to 36 h after sponge removal and ovarian response was observed. Embryo recovery were performed under surgical operation on the 5th day after the insemination. In Experiment 1, the mean ovulation rate in Treatment Group 3 tended to be higher than in Treatment Groups 2 and 4. The incidence of abnormal corpora lutea (CL) in Treatment Group 2 tended to be higher than in the others. In Experiment 2, the ewes were divided into two groups by the interval between sponge removal and onset of the estrous sign. The mean ovulation rate in the ewes that did not show estrous signs within 24 h after sponge removal and were treated with 1 ml of Estomal was significantly lower than in the others (P<0.05). The present study indicates that the dose of 2 ml of the two GnRH analogues may be over-dosage and has a detrimental effect on ovarian response. It also suggested that the timing of GnRH injection affects the ovulation rate and embryo recovery results.
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  • Masahiko NISHIGAI, Akiko TAKAMURA, Hideo KAMOMAE, Tomomi TANAKA, Yoshi ...
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 283-294
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    Proceeding with research into human chorionic gonadotropin (hCG) administration, designed to promote pregnancy rates in embryo transfer, hCG was administered to bovine recipients on the day of ovulation in Holstein cows and the day of selection of recipients, ie., day prior to embryo transfer (5 days after the day of ovulation), and the changes in ovaries and the concentrations of plasma progesterone (P) and estradiol-17β (E2) levels after administration were determined. Changes in the ovaries and functions of blood P and E2 levels after administration were determined in order to investigate the effects of hCG on increase in luteinization and functions of P secretion. Nine Holstein dairy cows were divided into two groups. All 4 cows of one group received an intramuscular injection of saline at a dose of 5 ml on the day of ovulation (Day 0-control group: the day of ovulation was designated as Day 0), which was followed by an injection of hCG at a dose of 1,500 IU on the corresponding day of the next estrous cycle (Day 0-hCG group). In a similar way, 4 cows in the other group received an injection of saline at a dose of 5 ml on day 5 (Day 5-control group), then 3 of the 4 cows and the remaining cow received intramuscular injections of hCG at a dose of 1,500 IU on the corresponding day of the next estrous cycle (Day 5-hCG group). These cattle were examined for changes in ovarian follicles and corpus luteum (CL) every day or every other day by rectal palpation and ultrasonography, and blood samples were collected every day for the P and E2 analysis. The estrous cycle lengths in the hCG groups tended to be slightly longer than those in the control group, though the difference was not significant. In the Day 5-hCG group, ovulation was induced in all cows 1 or 2 days after hCG administration, and was followed by the development of new CL (induced CL). Ultrasonographic observations revealed that the total luteal tissue area of the CL periodicum and the induced CL in the Day 5-hCG group were significantly (P<0.05) wider than those in the Day 5- control group from 3 days after hCG administration onward. Plasma P levels started rising 3 hours after hCG administration in the Day 5-hCG group, and they were significantly (P<0.05) higher than those in the Day 5-control group on days 6, 7, 12, 13 and 14, respectively. Plasma E2 levels decreased rapidly after hCG administration in the Day 5-hCG group, and were lower than those in the Day 5-control group. These results showed enhancement of the luteal activity and a decrease in plasma E2 level by hCG administration 5 days after ovulation, suggesting that the hCG treatment on the day prior to embryo transfer is effective at increasing the pregnancy rate in embryo transfer.
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  • Koh-ichi HAMANO, Katsuhiko SASAKI, Junji MASAKI, Min-Soo KANG, Hiroshi ...
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 295-302
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    The effect of maitotoxin (MTX), the most potent marine toxin produced by dinoflagellate, was investigated by monitoring the penetration ability of spermatozoa into oocytes. Bull spermatozoa were incubated in BO media with or without caffeine and/or calcium with final concentrations of 0.469, 0.938 and 1.875 ng/ml of MTX for 5 or 30 min. After MTX treatment, zona-free hamster oocytes were inseminated with the spermatozoa. When spermatozoa were treated with MTX in the medium without calcium, they failed to undergo the acrosome reaction and did not penetrate the oocytes. Caffeine stimulated the penetration ability of spermatozoa treated with MTX. When spermatozoa were treated with 1.875 ng/ml MTX, their motility was inhibited and they failed to penetrate into oocytes. Penetration of oocytes by spermatozoa treated with 0.938 ng/ml MTX for 5 min was enhanced. MTX treated spermatozoa began to penetrate oocytes within 15 min after insemination and achieved total penetration within 3 h after insemination. These results suggest that MTX may be used as a substance to induce sperm capacitation and to demonstrate a mechanism of acrosome reaction.
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  • Naomi KASHIWAZAKI, Kazuhiro KIKUCHI, Kaoru SUZUKI, Junko NOGUCHI, Taka ...
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 303-310
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    The objective of the present study was to evaluate the development to the blastocyst stage in vivo and in vitro of porcine oocytes matured and fertilized in vitro (IVM/IVF). When IVM/IVF oocytes had been transferred to oviducts of synchronized recipients just after IVF, more than 70% of blastocysts recovered after 6 days of transfer had developed to the hatched blastocyst stage with a mean cell number of 181.5 per blastocyst. In contrast, when IVM/IVF oocytes were cultured in vitro for 2 days and then transferred to the oviducts of recipients, or cultured in vitro for 6 days without transfer to oviducts, most recovered blastocysts were still enclosed by zona pellucidae. Mean cell numbers of blastocysts obtained from IVM/IVF oocytes cultured for 2 days in vitro plus 4 days in the oviducts and for 6 days in vitro decreased significantly (P<0.01) to 58.2 and 38.4, respectively, compared with that of blastocysts obtained from IVM/IVF oocytes cultured in oviducts for 6 days. These results suggest that porcine IVM/IVF oocytes have a high potential for developing to the blastocyst stage equal to that of in vivo matured oocytes and that the in vitro culture conditions used for IVM/IVF oocytes in the present study were suboptimal.
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  • Tetsuma MURASE, Koji MUKOHJIMA, Shin-ichi SAKAGUCHI, Tsuyoshi OHTANI, ...
    Article type: technical report
    Subject area: none
    2001 Volume 47 Issue 5 Pages 311-316
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    This study investigated the activation of phosphoinositidase C (PIC) and phosphatidylcholine-specific phospholipase C (PLC) during the acrosome reaction of spermatozoa induced by Ca2+ and Ca2+ ionophore A23187 in a subfertile Japanese black bull. Sperm motility, viability, morphology and penetration of cervical mucus by spermatozoa in a subfertile bull were comparable to those in a fertile bull. When frozen-thawed spermatozoa were stimulated with 3 mM Ca2+ and 1 μM A23187, both bulls' spermatozoa showed a time-dependent increase in percent acrosome reactions, but the increase was more rapid and higher in spermatozoa from the fertile bull. The amounts of 1,2-diacylglycerol (DAG) mass, a product of PIC and PLC, peaked at 1 min after a similar treatment with a gradual decline towards 10 min in both bulls' spermatozoa but were significantly higher throughout stimulation for the subfertile bull. These results suggest that active PIC/PLC may be present in spermatozoa of the subfertile bull, and that other mechanisms were possibly associated with the lowered induction of the acrosome reaction. However, it remains unclear whether the high levels of 1,2-DAG mass were responsible.
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Research Note
  • Sueo NIIMURA, Ryoko WAKASA
    Article type: Introduction
    Subject area: none
    2001 Volume 47 Issue 5 Pages 317-323
    Published: 2001
    Released on J-STAGE: November 07, 2001
    JOURNAL FREE ACCESS
    The role of actin filaments and contractions in hatching was determined by time-lapse videomicrography in mouse blastocysts whose hatching ability had been suppressed by cytochalasin B (CB), an inhibitor of polymerization of actin filaments. The hatching rate of blastocysts developed from morulae in a medium containing CB at a concentration of 0.4 μg/ml (CB-treated blastocysts) was 4.3%, which was significantly lower than the 63.3% of blastocysts developed from morulae in a medium without CB (non-treated blastocysts). The rate of blastocysts with protrusion of trophectoderm cells from a small hole in the zona pellucida and that of blastocysts with a slit in the zona pellucida by enlarging the protrusion of trophectoderm cells were significantly lower in CB-treated blastocysts (66.7 and 33.3%) than in non-treated blastocysts (93.5 and 80.6%). Such a CB-treated blastocyst took a significantly longer time for the protrusion of trophectoderm cells after blastocoel formation than non-treated blastocysts. Over the span of 32 h after blastocoel formation, the number of weak contractions was similar in CB-treated and non-treated blastocysts, but the number of strong contractions (more than 20% volume reduction) was significantly larger in CB-treated blastocysts (3.43 times) than in non-treated blastocysts (1.13 times). These results suggest that actin filament-mediated movements of trophectoderm cells contribute to the hatching by facilitating the protrusion of trophectoderm cells from a small hole in the zona pellucida and also by enlarging the protrusion. In addition, it is suggested that the low ability of hatching in blastocysts is related to strong contractions with high frequency.
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