• Development and Reproduction
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• v.18 no.4
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• pp.301-309
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• 2014

Nesfatin-1, an anorexic nucleobindin-2 (NUCB2)-derived hypothalamic peptide, controls appetite and energy metabolism. Recent studies show that nesfatin-1/NUCB2 is expressed not only in the brain but also in gastric and adipose tissues. Thus, we investigated the distributions of nesfatin-1/NUCB2 in various tissues of male and female mice by real-time PCR, western blotting, and immunohistochemical staining. Real-time PCR analyses showed that NUCB2 mRNA was predominantly expressed in the pituitary and at lower levels in the hypothalamus, spleen, thymus, heart, liver, and muscle of both male and female mice. Expression was much higher in reproductive organs, such as the testis, epididymis, ovary, and uterus, than in the hypothalamus. Western blot analysis of the nesfatin-1 protein level showed similar results to the real-time PCR analyses in both male and female mice. These results suggest that nesfatin-1/NUCB2 have widespread physiological effects in endocrine and non-endocrine organs. In addition, immunohistochemical staining revealed that nesfatin-1 was localized in interstitial cells, including Leydig cells and in the columnar epithelium of the epididymis. Nesfatin-1 was also expressed in theca cells and interstitial cells in the ovary and in epithelial cells of the endometrium and uterine glands in the uterus. These results suggest that nesfatin-1 is a novel potent regulator of steroidogenesis and gonadal function in male and female reproductive organs. Further studies are required to elucidate the functions of nesfatin-1 in various organs of male and female mice.

• The Korean Journal of Malacology
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• v.4 no.1
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• pp.30-41
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• 1988

The gonadal development, the annual reproductive cycle and the first sexual maturity of surf clam, Mactra veneriformis Reeve were studied histologically. Speciemens were monthly collected at the intertidal zone of Naechodo, Chollabuk-do, Korea, for one year from March 1986 to February 1987. Sexuality of the clam is dioecious. The gonads were located between the subregion of mid-intestinal gland in the visceral cavity and the reticular connetive tissues of the foot, The ovary is composed of a number of ovarian sacs, and the testis comprise several testiculat lobules. The undifferentiated mesenchymal tissues and eosinophilic granular cells function as nutritive cells in the early stage. The ripe eggs were about 50-60${\mu}{\textrm}{m}$ in diameter, and they were wurroundedby the gelatinous membranes. The spawing period was from early June to September the main spawning occurred beetween July and August when the water temperature reached above 24$^{\circ}C$. The annual reproductive cycle of this species could be classified into five successive stages: multiplicative(January to March), growing(March to May), mature(April to August), spent(June to September), degenerative and resting(September to February). The monthly changes of fatness coefficient closely correlated with the annual reproductive cycle. Percentages of the first sexual maturity of female and male clams were over 50% among those individals ranging from 2.1 To 2.5cm, and 100% in those over 2.6cm in shell length.

• Environmental Analysis Health and Toxicology
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• v.20 no.1
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• pp.13-21
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• 2005

The purpose of this study was to determine the effects of bisphenol A (BPA), which is known to have estrogenic activity, on the early development of medaka fish (Oryzias latipes). The fertilized eggs of medaka were treated with BPA at different concentrations for 3 weeks. Embryonic growth, deformation, hatching success, and gonadal differentiation were determined to observe the effects of this chemical. Also we tried to measure the estrogenic activity of bisphenol A using ELISA and RT-PCR methods. By using this techniques, we evaluated the induction of vitellogenin, an estrogen-regulated gene from the whole body-homogenates of larvae. At results, a reduced blood circulation was seen in embryos and peritoneal edema and hindrance of yolk-sac absorption were observed in larvae of treated group. However, BPA at the concentrations tested (2～200 ㎍/L) did not have severe adverse effects on the early life-stages. According to the observation of gonadal histology, inter-sex or sex -reversal was not found in all test fish. After the exposure was ended, vitellogenin mRNA and protein levels were measured in larvae and then their levels were found to be increased in treated group with 200㎍/L. These results indicate that BPA can induce the expression of vitellogenin in early life-stages as well as in adult male fish.

• Journal of Aquaculture
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• v.8 no.1
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• pp.31-46
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• 1995

Gonadal maturation and annual reproductive cycle in ovoviviparous oblong rockfish, Sebastes oblangus on the basis of monthly gonadosomatic indices (GSI), hepatosomatic indices (HSI) and histological observations of gonadal tissues. GSI values of female were in a wide range from $0.l5\pm0.0l\;(July)\;to\;58.54\pm3.86$ (December) and began to increase in August and reached the maxium in December, then decreased rapidly thereafter. Male GSI values were in a range from $0.08\pm0.03$ (July) to $1.55\pm0.27$ (September) and began to increase rapidly in July and reached the maximum in September, then decreased gradually, thereafter. Female HSI was in a range from $0.89\pm0.12$ (December) to $3.73\pm0.15$ (October), and male's was from $2.09\pm0.76$ (October) to $3.62\pm0.48$ (August). HSI reached the maximum values one or two months before GSI reached their maxium values in both sex, and then decreased rapidly thereafter. Mature oocytes began to appear in late October as being oocytes began to mature in August, and the type of oocyte development is categorized in the roup-synchronous oocyte development'. Ovulation and fertilization of ripe oocytes occurred in November, and hatched larvae were born from December to January. Maturation of testis was progressed in short term from August to October and spermatozoa were released in October. Sperm balls consisted of many spermatozoa were preserved in ovarian cavity of female after copulation. These results may suggest that the annual reproductive cycle of oblong rockfish could be divided into the following successive stages: growing (August and September), mature (September and October), gestation (November and December), parturition (December and January) and resting (February to July) in female, and growing (August and September), mature (September and October), copulation (October) and resting (November to July) in male.

• Environmental Analysis Health and Toxicology
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• v.21 no.1 s.52
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• pp.35-43
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• 2006

Reproduction and organ structure of the pale chub, Zacco platypus in Isa stream were investigated by means of histological methods. The results of the study confirmed reproductive abnormality and histopathological features in the pale chub. The gonadosomatic index (GSI) of the fish showed two peak in April and August. In summer season, GSI of the male was about two times of the female's GSI. Monthly variation of the gonadal development was very irregular. From the histological analysis of the organ structure, epidermal atrophy, necrosis and hyperplasia of pigment cell were observed in the skin. Epithelial layer lifting and clubbing of the lamella and bifurcation of the filament were observed in the gill. Also histological changes as congestion, cytoplasmic degeneration of hepatic cell, degeneration of bile duct, glomerular dilatation, degeneration of renal tubule and pycnosis of interstitial cell were identified in the liver and kidney, respectively.

• Journal of Aquaculture
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• v.11 no.2
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• pp.173-182
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• 1998

The study has been conducted to understand gonadal development and the effects of $17^{\alpha}$-methyltestosterone on sex inversion of the red spotted grouper, Epinephelus akaara. Fish were collected from Deukyand bay in the southern coast of Korea in August, 1996 and then they had been cultivated at the indoor tank until August, 1997. Gonad somatic index (GSI) in the females of both treated and control group began to increase from February when water temperature was rainse again, and reached the maximum value in August, whereas it had decreased from September adn thereafter maintained relatively low value until January. Unlike females, GSI in the male or intersex of treated groups decreased after June. Hepatosomatic index (HSI) of the control group tended to show the relatively low around Autumn, whereas it showed relatively highr value in April and June when the ovary was in the growing stage. Although the treated groups showed relatively higher value of the HSI than the control, hte paterns in monthly variation of HSI were similar to the control. Sexual change of the female grouper to the male was attempted by acceleration with oral administration of $17^{\alpha}$-methyltestosterone at the dose of 0.2 and 0.5mg/kg fish for 120days. Transitional hermaphroditic gonads were observed from the various size of groupers ranging 21.0 to 36.1 cm in total length, while the functional males could be induced from th individuals of 28.8 to 33.5cm in total length. This result indicated that larger groupers than 30cm in total length should be used for sex inversion to maleness with $17^{\alpha}$-methyltestosterone.

• Ocean and Polar Research
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• v.38 no.1
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• pp.81-88
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• 2016

In many fish species, including Nile tilapia (Oreochromis niloticus), gonadal development occurs at the expense of stored energy and nutrients. Therefore, reproductive systems are inhibited by limited food supply. It has been well established that reproductive function is highly sensitive to both metabolic status and energy balance. Nothing is known about the possible mediated connection between energy balance and reproduction. Kisspeptin, a neuropeptide product of the Kiss gene has emerged as an essential gatekeeper of reproduction and may be possibly be linked to energy balance and reproduction in non-mammalians. Thus, in this study, the effect of fasting (10 days) on the expression of kisspeptin and the gonadotropin-releasing hormone (GnRH) gene were assessed in Nile tilapia (male and female) using qRT-PCR. In addition, plasma levels of estradiol-$17{\beta}$ ($E_2$) and 11-ketotestosterone (11-KT) in adult tilapia were measured by ELISA. In male tilapia, fasting reduced Kiss2 and GnRH I mRNA expression in the brain and 11-KT level in comparison with the fed tilapia (p < 0.05). In females, however, there were no significant differences in GnRH I mRNA expression and $E_2$ between fish subjected to fasting and those fed (p > 0.05). These data indicate the impact of nutritional states on kisspeptin as a potential regulatory mechanism for the control of reproduction in male Nile tilapia.

• Korean Journal of Ichthyology
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• v.23 no.3
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• pp.179-186
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• 2011

Slime flounder, Microstomus achne is distributed in the coastal waters of Korea, west sea of Japan, BoHai, Yellow sea and East china sea. They are mainly caught by bottom trawl net during winter, from December to March. Sexual maturation of slime flounder were investigated using samples collected from commercial catch in the southern coast of Korea from November, 2006 to March, 2007. The ovary of the slime flounder is a conical bag in shape and is bilateral structure develops lengthily from the posterior of the abdomen to the end of the anal fin. The testis also is bilateral in structure, usually located in small size in the abdomen. In females, the gonadosomatic index (GSI) were peaked in January (12.46), then decreased rapidly thereafter. Female GSI values plummeted to 2.72 in March just after spawning. Male GSI values were peaked in December (2.46) before in the spawning season, then decreased slowly thereafter. The reproductive cycle would be classified into three successive developmental stages : maturation stage (November to January), ripe and spawning stage (December to February), degenerative and resting stage (February to March). Relationships between the fish sizes in total length (TL) and the number of ovarian eggs (F), the body weights (BW) and the number of ovarian eggs were indicated by the exponential equation respectively: F=29.027TL-767.8 (r$^2$=0.7686), F=0.3998BW+24.288 (r$^2$=0.8919).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.5
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• pp.309-315
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• 2005

Changes of sex steroid hormones in the plasma of yellowfin goby, Acanthogobius flavimanus were investigated in relation to the gonadosomatic index (GSI), the hepatosomatic index (HSI) and gonadal development. The GSI in females rose rapidly in November and remained high from December to May $(7.26\pm0.89­6.62\pm0.02)$. The Male's GSI also increased gradually from November and was highest in May $(0.16\pm0.08)$. The HSI in both sexes was in reverse correlation with the GSI, and the HSI was low during the spawning season (February-May). In females, the $estradiol-17{\beta}\;(E_2)$ level increased during vitellogenesis (November and December) and reached its maximum $(8.13\pm2.87 ng/mL)$ at the maturing period, in January. $17{\alpha},\;20{\beta}$-dihydroxy-4-pregnen-3-one$(17{\alpha}20{\beta}OHP)$ gradually increased from October $(0.063{\pm}0.02ng/mL)$ to March $(0.16{\pm}0.02ng/mL)$ and increased rapidly in May. The level of testosterone (T) showed a similar tendency of $E_2$. In males, T increased gradually during spermatogenesis from September to December $(0.14{\pm}0.06­0.26{\pm}0.10ng/mL)$ and peaked in January $(0.36{\pm}0.29 ng/mL)$ when the spermatozoa filled the testis. 11-KT also rose markedly in January and then decreased. On the other hand, $17{\alpha}29{\beta}OHP$ in males did not show any clear tendencies.

• The Korean Journal of Malacology
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• v.22 no.2
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• pp.115-124
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• 2006

Gonad index, spermatogenesis and the reproductive cycle of Meretrix petechialis were investigated by cytological, histological observations. Monthly changes in the gonad index coincides the gonadal development. The morphology of the spermatozoon had a primitive type and is similar to that of other bivalves having a short mid-piece with five to six mitochondria surrounding the centrioles. The morphology of the sperm nucleus type and the acrosome shape of this species were cylindrical type and cap-like shape, respectively. The spermatozoon was approximately 40-45 ${\mu}m$ in length including the sperm nucleus length (about 1.50 ${\mu}m$), acrosome length (0.60 ${\mu}m$) and tail flagellum. The axoneme of the tail flagellum consisted of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail showed 9 + 2 microtubular arrangement. The spawning period was from June to September and the main spawning occurred from July to August when seawater temperatures were higher than $20^{\circ}C$. The reproductive cycle of this species could be categorized into five successive stages: early active stage (February to March), late active stage (February to May), ripe stage (April to July), partially spawned stage (June to September), and spent/inactive stage (September to February).