• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.624-628
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• 1999

Annual plasma levels of vitellogenin and sex steroids were investigated in relation to the gonadal development for understanding the endocrine control of reproduction in spotted flounder, Verasper variegatus. The plasma vitellogenin level was highest, 6.36 mg/ml, in November when vitellogenesis was most active. The level, thereafter, decreased to 3.81 mg/ml in December with the initiation of spawning. On the other hand, estradiol-17 $\beta$ was highest, 2.7 ng/ml, in December, and rapidly decreased in January when spawning occurred. The decreased level of estradiol-17$\beta$, around 0.2 ng/ml, remained unchanged until May. The profiles of plasma testosterone were similar to those of estradiol-17$\beta$ in the fish, The plasma 17 $\alpha$-hydroxyprogesterone level was relatively low throughout the spawning period, but increased slightly with the initiation of ovarian development, In males, the plasma testosterone and 11-ketotestosterone were highest in December when spermiation actively proceeded, but rapidly decreased during the spawning period (January).

• Development and Reproduction
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• v.13 no.4
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• pp.207-215
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• 2009

Numerous factors can affect the activities of hypothalamus-pituitary-gonad (HPG) hormonal axis, resulting in alteration of reproductive capacity or status such as onset of puberty and menopause. Soon after the finding of leptin, a multifunctional hormone secreted from adipocytes, a close relationship between reproduction and body energy balance have been manifested. Ghrelin, another multifunctional hormone from gastrointestinal tract, is an endogenous ligand of growth hormone secretagogue receptor (GHSR), and is thought to be a counterpart of leptin in the regulation of energy homeostasis. As expected, ghrelin can also modulate the reproductive capacity through the modulation of activities of HPG axis. This paper summarizes the current knowledge on the discovery, gene structures, tissue distribution and roles of ghrelin and GHSRs in mammalian reproduction in particular modulation of reproductive hormone secretion in HPG axis. Like POMC gene expression in pituitary gland, preproghrelin gene can generate a complex repertoire of transcripts which further undergo alternative splicing and posttranslational modifications. Concerning the roles of preproghrelin gene products in the control of body physiology except energy homeostasis, limited knowledge is available so far. Several lines of evidence, however, show the interplay of ghrelin between metabolism and reproduction. In rat and human, the distribution of ghrelin receptor GHSRs (GHSR1a and GHSR1b) has been confirmed not only in the hypothalamus and pituitary which were originally postulated as target of ghrelin but also in the testis and ovary. Expression of the preproghrelin gene in the brain and gonads was also verified, suggesting the local role (s) of ghrelin in HPG axis. Ghrelin might play a negative modulator in the secretions of hypothalamic GnRH, pituitary gonadotropins and gonadal steroids though the action on pituitary is still questionable. Recent studies suggest the involvement of ghrelin in regulation of puberty onset and possibly of menopause entry. It is now evident that ghrelin is a crucial hormomal component in 'brain-gut' axis, and is a strong candidate links between metabolism and reproduction. Opposite to that for leptin, ghrelin signaling is likely representing the 'hunger' state of body energy balance and is necessary to avoid the energy investment into reproduction which has not a top priority in maintaining homeostasis. Further researches are needed to gain a deep insight into the more precise action mechanism and role of ghrelin in reproduction, and to guarantee the successful biomedical applications.

• Animal cells and systems
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• v.5 no.4
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• pp.327-331
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• 2001

There is a critical developmental period during which brain sexual differentiation proceeds irreversibly under the influence of gonadal hormone. Recently, kinesin superfamily-associated protein 3 (KAP3) gene expressed during the 'critical period' of rat brain differentiation was identified by us (Choi and Lee, 1999). KAP3 functions as a microtubule-based motor that transports membranous organelles anterogradely in cells, including neurons (Yamazaki et al., 1996). mRNA level of KAP3 gene markedly increased before the initiation of puberty. Neonatal treatment of estrogen clearly inhibited the prepubertal increase in KAP3 mRNA level (Choi and Lee, 1999). In the present study, we aimed to investigate the effects of polychlorinated biphenyls (PCBs), as endocrine disruptors (EDs) on the expression of KAP3 gene during the 'critical period' of rat brain development. In our data, PCBs significantly decreased the expression of KAP3 gene in the fetal (day 17) and the neonatal (day 6 after birth in) male and female rat brains. The body weight and the breeding ability were significantly decreased in the PCBs-exposed rats compared with the control. These results showed that PCBs affect the transcriptional level of brain sexual differentiation related gene, KAP3, in the fetal and the neonatal rat brains. The maternal exposure to the PCBs may lead to toxic response in embryonic brain sexual differentiation and breeding ability after sexual maturation. This study indicates that KAP3 gene may be useful as a gene marker to analyze the molecular mechanism of toxic response in the animal brain development and sexual maturation exposed to PCBs.

• Development and Reproduction
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• v.17 no.4
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• pp.469-475
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• 2013

In mammals, puberty is a process of acquiring reproductive competence, triggering by activation of hypothalamic kisspeptin (KiSS)-gonadotropin releasing hormone (GnRH) neuronal circuit. During peripubertal period, not only the external genitalia but the internal reproductive organs have to be matured in response to the hormonal signals from hypothalamic-pituitary-gonadal (H-P-G) axis. In the present study, we evaluated the maturation of male rat accessory sex organs during the peripubertal period using tissue weight measurement, histological analysis and RT-PCR assay. Male rats were sacrificed at 25, 30, 35, 40, 45, 50, and 70 postnatal days (PND). The rat accessory sex organs exhibited differential growth patterns compared to those of non-reproductive organs. The growth rate of the accessory sex organs were much higher than the those of non-reproductive organs. Also, the growth spurts occurred differentially even among the accessory sex organs; the order of prepubertal organ growth spurts is testis = epididymis > seminal vesicle = prostate. Histological study revealed that the presence of sperms in seminiferous tubules and epididymal ducts at day 50, indicating the puberty onset. The number of duct and the volume of duct in epididymis and prostate were inversely correlated during the experimental period. Our RT-PCR revealed that the levels of hypothalamic GnRH transcript were increased significantly on PND 40, suggesting the activation of hypothalamic GnRH pulse-generator before puberty onset. Studies on the peripubertal male accessory sex organs will provide useful references on the growth regulation mechanism which is differentially regulated during the period in androgen-sensitive organs. The detailed references will render easier development of endocrine disruption assay.

• Development and Reproduction
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• v.14 no.1
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• pp.35-41
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• 2010

Mammalian reproduction is regulated by a feedback circuit of the key reproductive hormones such as GnRH, gonadotropin and sex steroids on the hypothalamic-pituitary-gonadal axis. In particular, the onset of female puberty is triggered by gain of a pulsatile pattern and increment of GnRH secretion from hypothalamus. Previous studies including our own clearly demonstrated that genistein (GS), a phytoestrogenic isoflavone, altered the timing of puberty onset in female rats. However, the brain-specific actions of GS in female rats has not been explored yet. The present study was performed to examine the changes in the activities of GnRH neurons and their neural circuits by GS in female rats. Concerning the drug delivery route, intracerebroventricular (ICV) injection technique was employed to eliminate the unwanted actions on the extrabrain tissues which can be occurred if the testing drug is systemically administered. Adult female rats (PND 100, 210-230 g BW) were anaesthetized, treated with single dose of GS ($3.4{\mu}g$/animal), and sacrificed at 3 hrs post-injection. To determine the transcriptional changes of reproductive hormone-related genes in hypothalamus, total RNAs were extracted and applied to the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). ICV infusion of GS significantly raised the transcriptional activities of enhanced at puberty1 (EAP-1, p<0.05), glutamic acid decarboxylase (GAD67, p<0.01) which are known to modulate GnRH secretion in the hypothalamus. However, GS infusion could not change the mRNA level of nitric oxide synthase 2 (NOS-2). GS administration significantly increased the mRNA levels of KiSS-1 (p<0.001), GPR54 (p<0.001), and GnRH (p<0.01) in the hypothalami, but decreased the mRNA levels of LH-$\beta$ (p<0.01) and FSH-$\beta$ (p<0.05) in the pituitaries. Taken together, the present study indicated that the acute exposure to GS could directly activate the hypothalamic GnRH modulating system, suggesting the GS's disrupting effects such as the early onset of puberty in immature female rats might be derived from premature activation of key reproduction related genes in hypothalamus-pituitary neuroendocrine circuit.

• Korean Journal of Psychosomatic Medicine
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• v.4 no.1
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• pp.146-154
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• 1996

The impact of stress on immune function is known to be associated with the interactions among the central nervous system(CNS), neuroendocrine system, and immune system. The main pathways between stress and immune system are wiring of lymphoid organs and neuroendocrine system. Immune system also produces neuropeptides, which modulate immune system. Mediators of psychosocial influences on immune function are found to be peptides released by the pituitry, hormones, md autonomic nervous system. Hypothalamus integrates endocrine, neural and immune systems. Particularly, paraventricular nucleus appears to play a central role in this integration. On the other hand, endocrine system receives feedback from the immune system. The major regulatory pathways which pituitary modulates include the hypothalamic-pituitary-adrenal-thymic(HPAT) axis, hypothalamic-pituitary-gonadal-thymic(HPGT) axis, pineal-hypothalamic-pituitary(PHP) axis. Bidirectional pathways such as feedforward and feedback pathways are suggested in the interaction between stress and immune system. It suggests that psychosocial inputs affect immune function, but also that immunological inputs affect psychosocial function. Thus, prospective studies for elucidating the relationship between stress and immune function should incorporate measures of immune function as well as measures of endocrine, autonomic, and brain activities at the same time.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.8
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• pp.1065-1074
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• 2016

Growth factors play an important role during early ovarian development and folliculogenesis, since they regulate the migration of germ cells to the gonadal ridge. They also act on follicle recruitment, proliferation/atresia of granulosa cells and theca, steroidogenesis, oocyte maturation, ovulation and luteinization. Among the growth factors, the growth differentiation factor 9 (GDF9) and the bone morphogenetic protein 15 (BMP15), belong to the transforming growth factor beta (TGF-${\beta}$) superfamily, have been implicated as essential for follicular development. The GDF9 and BMP15 participate in the evolution of the primordial follicle to primary follicle and play an important role in the later stages of follicular development and maturation, increasing the steroidogenic acute regulatory protein expression, plasminogen activator and luteinizing hormone receptor (LHR). These factors are also involved in the interconnections between the oocyte and surrounding cumulus cells, where they regulate absorption of amino acids, glycolysis and biosynthesis of cholesterol cumulus cells. Even though the mode of action has not been fully established, in vitro observations indicate that the factors GDF9 and BMP15 stimulate the growth of ovarian follicles and proliferation of cumulus cells through the induction of mitosis in cells and granulosa and theca expression of genes linked to follicular maturation. Thus, seeking greater understanding of the action of these growth factors on the development of oocytes, the role of GDF9 and BMP15 in ovarian function is summarized in this brief review.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.701-708
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• 2011

The aim of the present study was to analyze the reductive cycle of the red marbled rockfish Sebastiscus tertius. The analysis was based on annual changes in the gonadosomatic index (GSI), the hepatosomatic index (HSI), histology of the gonadal structure, and plasma sex steroid hormone levels of adult fish from April 1997 to April 1998. GSI of females began to increase in February and peaked ($10.8{\pm}2.72$) in May. HIS levels ($3.41{\pm}0.49$) peaked in February and elevated plasma steroid hormones ($1.47{\pm}0.75$ ng/mL for estradiol-$17{\beta}$ ($E_2$) and $230.7{\pm}27.6$ pg/mL for testosterone (T)) were observed in April. However, in male fish, GSI levels started to increase in August and remained high until November ($0.21{\pm}0.05$). T levels were was also elevated in August and peaked in October ($188.1{\pm}43.5$ pg/mL) and November ($186.8{\pm}28.0$ pg/mL), but started to decline 1 month than the GSI. These results suggest that female ovoviviparious periods span from April to June and amle mating periods occur from November to February.

• Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.115-121
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• 2014

Eyestalk ablation (ESA) is commonly used in aquaculture to stimulate ovarian maturation in crustaceans, and methyl farnesoate (MF) affects crustacean molting and reproduction. To investigate the physiological effects of ESA and MF treatments on the shrimp Litopenaeus vannamei, we compared the effects of single eyestalk removal and MF injections. The ESA group had the lowest survival rate (50%), and individuals in the $0.1{\mu}g$ and $1.0{\mu}g$ MF-treated groups had survival rates of 80 and 73.3%, respectively. Conversely, molting numbers were highest in the ESA group, and similar to those of the 1.0-${\mu}g$ MF group. To investigate shrimp growth, we measured body weight during the experimental period and found that individuals in the ESA and $1.0{\mu}g$ MF groups showed significant increases in body weight. Furthermore, to investigate the effects of ESA and MF treatments on gonadal maturation, the gonad somatic index (GSI) was calculated after the experiment. All treated groups (ESA and MF) had higher GSI values than the control group, but the ESA and $1.0{\mu}g$ MF groups were not significantly different. Using histological ovary analysis, we determined that all treated groups showed indications of the previtellogenic stage, unlike the control group (immature stage). These results suggest that the high-MF-concentration treatment produced effects similar to those of ESA with respect to molting number, growth, and ovarian maturation.

• Clinical and Experimental Reproductive Medicine
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• v.26 no.2
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• pp.281-285
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• 1999

Kallmann's syndrome has both a general and specific connotation in describing general condition of gonadotropin-releasing hormone (GnRH) deficiency or a particular cluster of anomalies associated with primary eunuchoidism. The familial occurrence of hypogonadotropic hypogonadism associated with anosmia, color blindness, synkinesia, and mental defect is the classic Kallmann's syndrome. Interestingly, anosmia, or lack of smell, was not found in the absence of gonadal deficiency in the original study of this disorder. This disorder was found on both sexes, but the male to female ratio was 11:1, and Kallmann's syndrome is more often listed under disorders of male hypogonadism for this reason. Gross anatomy has shown disorders of the olfactory bulbs associated with Kallmann's syndrome and it was demonstrated a failure of GnRH-containing cells to migrate from the olfactory placode to the hypothalamus and preoptic area. We have experienced a case of Kallmann's syndrome which showed a hypoplasia of olfactory bulb in MRI during the workup of primary amenorrheic patient. So we report this case with a brief review of literatures.