Erina Saita

Gifu University, Gihu, Gifu, Japan

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Publications (9)15.28 Total impact

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    ABSTRACT: Pentachlorophenol (PCP), a component of biocides and a contaminant in diverse tissue samples from humans from various geographic areas, disrupts regulatory effects of thyroid hormones. Here we examined the effects of developmental exposure of rats to PCP on various aspects of brain development, male reproductive function, and adrenal function, all of which are under thyroid hormones regulation. PCP was administered to dams and their offspring via drinking water (6.6 mg l(-1)) during gestation and lactation. Tissue samples were obtained from dams, 3-week-old weanling pups, and 12-week-old pups. Gene expressions of thyroid hormone receptor beta1 and synapsin I, factors that promote brain growth, was increased in the cerebral cortex of PCP-treated weanling females, whereas plasma concentrations of total thyroxine were decreased in dams and weanling pups, and plasma thyroid-stimulating hormone concentrations were higher in PCP-treated weanling males. PCP caused a decrease in plasma corticosterone concentrations in 12-week-old female rats, but not in male rats or weanling females. PCP-treated male pups had significantly increased testis weight at 12 week of age. No overt signs of toxicity were noted throughout this study. Our results show that PCP exposure during development causes thyroid function vulnerability, testicular hypertrophy in adults, and aberrations of brain gene expression.
    No preview · Article · Jan 2009 · Endocrine
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    ABSTRACT: To investigate the effect of hypothyroidism on gonadal and adrenal functions in male Japanese quail (Coturnix japonica), hypothyroidism was induced in male adult Japanese quail by daily administration of 2-Mercapto-1-methylimidazole (methimazole) in their drinking water. Four weeks after methimazole treatment, the Japanese quail were sacrificed, and the plasma concentrations of free triiodothyronine (FT3), free thyroxine (FT4), total T3 (TT3), total T4 (TT4), corticosterone, testosterone, LH and immunoreactive (ir) inhibins were measured by radioimmunoassay, the testes and adrenal glands were removed and weighed and the thyroid glands and testes were fixed in 4% paraformaldehyde for histological observation. The results showed that the hypothyroidism induced by methimazole caused a significant decrease in body and testes weight; the plasma levels of FT3, FT4 and TT4 significantly decreased, and the hypothyroid quail possessed a greater number of small follicles and more follicular epithelial cells in the thyroid gland. In addition, hypothyroidism resulted in a significant decrease in the plasma concentrations of corticosterone, LH, testosterone and ir-inhibin. Furthermore, no spermatogenesis was found in the seminiferous tubules of the methimazole treatment groups. These results clearly demonstrate that hypothyroidism caused both gonadal and adrenal disturbances in the adult male Japanese quail.
    No preview · Article · Jan 2008 · Journal of Reproduction and Development
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    ABSTRACT: Besides lead poisoning of waterfowl, contamination of wild fauna with other toxic elements such as cadmium and thallium has also been reported in recent years. In this study, therefore, contamination with these three heavy metals was surveyed in Japanese black bears, sika deers, Japanese serows, Japanese hares and common cormorants by means of particle-induced X-ray emission (PIXE). Cadmium concentration was high in the kidneys of Japanese black bears and Japanese hares: 27 of 74 bears and five of 16 hares exhibited levels exceeded 10mg-Cd/kg. Lead concentrations were high in Japanese black bears and common cormorants. Five bears exhibited more than 2mg-Pb/kg in the liver, one of the criteria for lead contamination. No cormorants showed levels that exceeded the criterion. Thallium was not detected from any samples examined. These results suggest that cadmium exposure is relatively high in Japanese black bears and Japanese hares, and lead contamination may be occurring sporadically in Japanese black bears.
    Preview · Article · Jan 2007
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    ABSTRACT: Thyroid hormones permit the annual reproductive transition of seasonal breeders. Although, precise function of thyroid hormones in seasonal breeding is not well understood. In the present study, we examined effects of hypothyroidism on the hypothalamus-pituitary-gonadal axis in adult male golden hamsters after transition of the short-day photoperiod (SD; 8 h light: 16 h dark) condition. We confirmed that hypothyroid, which had been induced by administration of thiouracil in drinking water for 4 weeks, did not have direct effects on testes in male hamsters under the long-day photoperiod. Plasma concentrations of free T3 and T4 decreased 15 weeks after transition of SD condition. Plasma concentrations of testosterone in the hypothyroid group decreased earlier than in the control group after the transition from LD to SD. In animals treated with testosterone after castration, plasma concentrations of LH in the hypothyroid group decreased earlier than in the control group after the transition of SD. On the other hand, pituitary response to GnRH for LH release did not change in castrated hamsters as a result of hypothyroidism. These results suggest that thyroid hormones act the hypothalamus and might be required to maintain GnRH secretion in male golden hamsters.
    No preview · Article · May 2005 · Journal of Reproduction and Development
  • E Saita · S Hayama · H Kajigaya · K Yoneda · G Watanabe · K Taya
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    ABSTRACT: We compared morphologic changes in thyroid glands of great cormorants (Phalacrocorax carbo) from the Tokyo Bay and Lake Biwa areas in Japan with presence of residues of polychlorinated dibenzo-dioxins (PCDDs), polychlorinated dibenzo-furans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs). Prominent morphologic changes in thyroid glands included increased density of small follicles and increased number of epithelial cells surrounding follicular lumens. The extent of morphologic changes in the thyroid gland was higher in cormorants captured from Tokyo Bay than in those captured from Lake Biwa. Increased thyroid change in cormorants from the Tokyo Bay area was associated with significantly higher levels of PCDFs and Co-PCBs. Thus, we suggest that morphologic changes in thyroid glands from the cormorants are associated with increased levels of dioxin contamination in Japan.
    No preview · Article · Nov 2004 · Journal of wildlife diseases
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    ABSTRACT: Gonadal function in the male golden hamster (Mesocricetus auratus) was investigated during exposure to a short photoperiod condition. Within 3 weeks of exposure to the short photoperiod condition, FSH and testosterone in the plasma significantly decreased, and subsequently immunoreactive (ir)-inhibin significantly decreased. Testicular contents of ir-inhibin and testosterone, and pituitary contents of LH and FSH also significantly decreased by 3 weeks with regression of weight of testes, epididymis and seminal vesicles and sperm head count. Circulating LH varied but not significantly. Thereafter, all reproductive parameters and secretion of LH, FSH, ir-inhibin and testosterone gradually recovered after 17 weeks of exposure even though animals continued to be subjected to the short photoperiod condition. Plasma concentrations of inhibin B and inhibin pro-alphaC were detectable and were significantly decreased after 15 weeks of exposure to the short photoperiod, but their levels were still detectable. Immunopositive reaction of inhibin alpha and betaB subunits was found in Sertoli cells and Leydig cells in the regressed testes of animals subjected to short photoperiod as was also seen in animals before exposure to the short photoperiod. Although the spermatogenic cycle was suppressed like prepubertal animals, the present study showed that the testicular recovery, so-called refractoriness, is functionally different from the developing stage of immature animals, especially with regard to inhibin secretion. The present results showed that changes in FSH preceded changes in inhibin during the regression and recovery phases, indicating that FSH is a major regulatory factor of inhibin secretion in male golden hamsters. The present study also demonstrated that regressed testes still secrete a small amount of bioactive inhibin during exposure to a short-photoperiod condition.
    No preview · Article · Mar 2003 · Journal of Reproduction and Development
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    ABSTRACT: In the present study, to clarify whether inhibin affects follicle-stimulating hormone (FSH) secretion in the recrudescence of the male golden hamster, we used a recently developed specific enzyme-linked immunosorbent assay (ELISA) in order to measure 2 forms of inhibin molecules: inhibin B and inhibin pro-alphaC. In addition, we used the radioimmunoassay (RIA) to measure immunoreactive (ir-)inhibin, FSH, luteinizing hormone (LH), and testosterone. And finally, we used the proliferating cell nuclear antigen (PCNA) and computer-assisted sperm motion analysis (CASA) methods to ascertain how well spermatogenesis and sperm motility recover from the photoinhibition caused by exposure to a short-day (SD; 10-hour light: 14-hour dark) photoperiod. Animals were exposed to SD for 15 weeks, and then their testes were checked carefully and found to be completely regressed. Thereafter, those animals were transported to a long-day (LD; 14-hour light: 10-hour dark) photoperiod. Sampling was carried out at weeks 0 (exposed SD 15 weeks), 1, 2, 4, 6, 8, and 10. Plasma FSH rapidly increased and reached peak levels 2 weeks after transferral to the LD photoperiod and then declined to normal LD levels at week 6. Circulating ir-inhibin, inhibin B, and inhibin pro-alphaC rose to normal LD levels by week 4. A highly significant inverse correlation was observed between plasma FSH and inhibin B but not between FSH and either ir-inhibin or inhibin pro-alphaC. Plasma testosterone recovered to normal LD levels within 1 week. Sperm motility parameters were low until week 2 and recovered to normal LD levels from weeks 4 to 10. PCNA-labeled cells were confined to the spermatogenic cells of the seminiferous tubules, though Leydig and Sertoli cell nuclei were never stained for PCNA during the period studied. The number of pachytene spermatocytes and the diameter of seminiferous tubules increased in a time-dependent manner after transferral from SD to LD. In conclusion, these results suggest that 1) secretion of inhibin B may be stimulated by an early rise in FSH; 2) inhibin B suppresses FSH secretion from weeks 2 to 10, after transferral to the LD photoperiod; and 3) testes recrudescence is based on the increase in the number of sperm cells instead of the increase in the number of Sertoli and Leydig cells of the male golden hamster.
    Full-text · Article · Nov 2002 · Journal of Andrology
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    ABSTRACT: We studied developmental reproduction of male golden hamsters (Mesocricetus auratus) by determining hormone secretion, observing morphological changes including distribution of immunoexpression of inhibin α subunit, 3β-hydroxysteroid dehydrogenase (HSD), and investigating sperm head count from birth to adulthood. Immunoexpression of inhibin α subunit was found in interstitial cells of not well organized testes of neonatal animals, and positive staining was also found in Sertoli cells in developing animals. However, the intensity of immunostaining in Sertoli cells varied when the spematogenic cycle of the seminiferous epithelium began. Testosterone levels in the plasma and testicular contents of testosterone and immunoreactive (ir)-inhibin increased from around 25 days of age, about 10 days before the presence of the first sperm in the testis. On the other hand, plasma concentrations of ir-inhibin progressively increased from birth to 10 days of age, when it reached peak levels. A reciprocal pattern of change between plasma concentrations of ir-inhibin and FSH was found from 10 days of age. Plasma concentrations and pituitary contents of LH increased from 15 days of age and reached adult levels about 40 days of age. The present results suggest that inhibin is an important factor in the regulation of FSH secretion even in infant male golden hamsters, and the regulated FSH may control the increasing the number of germ cells. Inhibin might be not the only endocrine factor as the regulator of FSH secretion, but also a paracrine or autocrine factor which is involved in spermatogenesis in the golden hamster.
    No preview · Article · Jan 2002 · Journal of Reproduction and Development
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    ABSTRACT: To investigate physiological roles of basal levels of circulating LH on follicular development during the second half of pregnancy in golden hamsters, we treated animals with anti-luteinizing hormone (A/LH) or normal horse serum (control serum) at 1100 h on day 12 of pregnancy (day 0 of pregnancy=sperm positive in vaginal smear). Thereafter, changes in plasma concentrations of immunoreactive (ir)-inhibin, estradiol-17β, progesterone and testosterone were determined until 48 h after the treatment; ovaries were also examined immunohistochemically. Furthermore, pregnant golden hamsters were injected with human chorionic gonadotropin (hCG) to determine the effects of immunoneutralization of LH on follicular activity. Plasma concentrations of ir-inhibin and estradiol-17β decreased significantly within 24 h after A/LH treatment, while plasma concentrations of progesterone and testosterone were unchanged. The number of follicles ovulating in response to hCG in the A/LH treated groups (7.0 ± 3.4, n=3) was significantly lower than in the control serum treated group (34.6 ± 4.8, n=5) at 24 h after the treatment. Immunostaining of inhibin α subunit was observed in granulosa cells of healthy and atretic large follicles at 24 h after A/LH treatment, whereas immunopositive reaction of aromatase was not observed in atretic follicles. Positive immunoreaction of 17α-hydroxylase/C17, 20-lyase (CYP17) was observed in theca cells of healthy follicles but not in atretic follicles. These results clearly demonstrate that basal levels of circulating LH are important for maturation of antral follicles and secretion of ir-inhibin and estradiol-17β, but not for progesterone during the second half of pregnancy in the golden hamster.
    No preview · Article · Jan 2002 · Journal of Reproduction and Development