• Korean Journal of Ichthyology
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• v.20 no.4
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• pp.255-262
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• 2008

The endemic Korean stumpy bullhead Pseudobagrus brevicorpus is a first-grade endangered wild fish as designated by the Ministry of Environment of Korea. As part of its restoration and proliferation effort, a histological study of this fish was carried out to investigate sex differentiation and gonadal development based on F1 generation individuals obtained by artificial breeding. On days 4~5 after hatching, a pair of genital ridges including clusters of primordial germ cells was observed between the gut and the mesonephric duct. On days 20 after hatching, the ovary began to initially differentiate and contained early oocytes with chromatin-nucleolus and peri-nucleolus stages on days 30~40 after hatching. As yolk material accumulated after day 80 from hatching, the oocytes grew increasingly large and were surrounded by a distinct follicular layer. On days 306 after hatching, the oocytes grew toward a mature ovum. In the males, the testis was distinguished by emergence of spermatogonium cells on 25 days after hatching, and day 40 after hatching it contained a small number of seminal lobes forming cysts. From 173 days after hatching, the testis consisted of numerous enlarged seminal lobes including spermatocytes and spermatids. Over 14 months after hatching, some seminal lumens were filled with spermatozoa.

• Journal of Food Hygiene and Safety
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• v.31 no.2
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• pp.113-118
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• 2016

Proprotein convertase subtilisin/kexin type 9 (PCSK9), is a protein mainly secreted by a liver. The PCSK9 plays an important role in low density lipoprotein (LDL) metabolism acting as a repressor of LDL receptor through transportation of the LDLR to the lysosome for degradation. Thus, the PCSK9 inhibitor suppresses PCSK9-regulated degradation of the LDL receptor as a LDL-lowering medicine. However, little is known about the role of PCSK9 in the reproductive system. Therefore, in the present study, we investigated Pcsk9 expression in male reproductive tracts including penises, prostates and testes using rats in response to their diets between a normal diet and a high-fat diet with cholesterol. Based on our previous study, the high-fat diet elevates concentration of total cholesterol and LDL in serum whereas it reduces the concentration of plasma high density lipoprotein (HDL). In addition, it dramatically affects to morphological changes of the male reproductive organs. Consistent with these results, the expression of Pcsk9 was substantially decreased in the penile tissues (P < 0.001) from rats fed a high fat diet as compared to a normal diet. Moreover, it slightly reduced in the prostate and testes (P < 0.05) of rats in response to a high fat diet. Localization of Pcsk9 was predominantly detected in urethral epithelium of penises, cylinder-shaped cells of prostate glands, and spermatogonia, spermatocytes and spermatid of testes of rats. Collectively, results of current study provide invaluable insights into the Pcsk9 gene with respect to its tissue- and cell-specific expression by a high fat diet with cholesterol.

• Journal of Genetic Medicine
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• v.5 no.2
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• pp.139-144
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• 2008

We report on two cases of pericentric inversion of X chromosome. The cases were found in a 40-year-old man with azoospermia and in a family of a 38-year-old pregnant woman. The first case with 46,Y,inv(X)(p22.1q27) had concentrations of LH, prolactin, estradiol, and testosterone that were within normal ranges; however, FSH levels were elevated. Testis biopsy revealed maturation arrest at the primary and secondary spermatocytes without spermatozoa. There were no microdeletions in the 6 loci of chromosome Y. For the second case, the cytogenetic study of thepregnant woman referring for advanced maternal age and a family history of inversion X chromosome was 46,X,inv(X)(p22.11q27.2). The karyotype of her fetus was 46,X,inv(X)(p22.1q27). Among other family members, the karyotypes of an older sister in pregnancy and her fetus were 46,X,inv(X)(p22.11q27.2), and 46,Y,?inv(X), respectively. The proband's father was 46,Y,inv(X)(p22.11q27.2). All carriers in the family discussed above were fertile and phenotypically normal. In addition, the ratio of inactivation of inv(X) by RBG-banding was discordant between the two sisters, with the older sister having only 4.1% of cells carrying inactivated inv(X) while the proband had a 69.5% incidence of late replicating inv(X). Therefore, we suggest that the cause of azoospermia in the first case might be related to inversion X chromosome with positional effect. Also, the family of the second case showing normal phenotype of the balanced inv(X) might be not affected any positional effect of genes.

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.107-111
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• 2007

Sex differentiation of the brown croaker Miichthys miiuy (Basilewsky) is described from hatching to the 120th day post-hatching (dph) (water temperature $24^{\circ}C$). Primordial germ cells (PGCs) were observed on the 20th dph (10.4 mm total length (TL), 0.14 g body weight (BW), and began to protrude into the peritoneal cavity from the 40th dph (19.4 mm TL, 0.39 g BW). On the 65th dph (31.3 mm TL, 0.93 g BW, $1,560D^{\circ}$ (degree-days)), initial ovarian differentiation was identified by the PGCs with condensed chromatin, and their transformation into meiotic oocytes. By the 120th dph (4.60 mm TL, 1.38 g BW, $2,880D^{\circ}$), the oocytes were in the perinucleolus stage and had increased from 20 to $40{\mu}m$ in diameter. While ovaries gradually grew after sex was differentiated, testes continued to multiply from the 65th dph. On the 80th dph (37.9 mm TL, 1.39 g BW, $1,920D^{\circ}$), the beginning of testis lobule formation was indicated by the occurrence of spermatogonial cysts enveloped by somatic cells in some of the testes. On the 120th dph, the testis lobules of some of the fish contained all germ cell stages through to the spermatocytes. Therefore, the sex differentiation type of the brown croaker is identified as gonochoristic.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.241-250
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• 1982

The structure of gonads, gametogenesis and reproductive cycle of the cockle, Fulvia mutice, were studied mainly by histological observation. The materials were monthly sampled in the southern area of Yeosu from October 1980 to September 1981. F. mutica was monoecious. The gonads were situated between the liver tissues and the outer fibronuscular layers compacted by the connective tissue fibers and muscle fibers beneath the outermost layer of simple cuboidal epithelium. The gonad was composed of a number of the ovarian sacs and the testicular tubules which form the tubular structure. Testicular tubules in the mature stage sometimes contained 'testis-ova' The undifferentiated mesenchymal tissues and the eosinophilic cells were abundantly distributed on the germinal epithelium in the early development stage. With the further development of the ovary and testis, these tissues and cells gradually disapprared. The undifferentiated mesenchymal tissues and the eosinophilic cells are related to the growing of the oocytes and spermatocytes . Early multiplicating oogonium was about $10{\mu}m$ in diameter. As the oocytes grow to $27-34\times50-58{\mu}m$ by increasing cytoplasm, the oocytes connected to the basement membrane by their egg-stalks. The ripe eggs were about $60{\mu}m$ in diameter and they were surrounded by gelatinous membrane. Most male germ cells in mature stage were transformed into the spermatozoa and they formed the sperm bundles. After spawning, undischarged ripe eggs and spermatozoa remained in the ovarian sac and the testicular tubule respectively for some time, then they finally degenerated. Especially the early spent ovarian sacs in May did not contract significantly and then they took part in the secondary maturation within two or three months during the summer season. The monthly changes of the fatness well agreed with the reproductive cycle. The reproductive cycle of F. mutica could be classified into six successive stages : multiplicative, growing, mature, spent, degenerative and recovery stage. It seems that the spawning season is closely rotated to the water temperature, and the spawning occurs from May to October at about $20^{\circ}C$ in water temperature. The peak spawning seasons appeared twice a year between June and July and in September. Acknowledgement The authors wish to express their gratitude to Dr. Kim, In Bae, Dr. Chun, Seh Kyu and Dr. Yoo, Sung Kyoo of National Fisheries University of Busan and Mr. Min, Byoung Seo of National fisheries Research and Development Agency for their critical reading of the manu script.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.6
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• pp.563-574
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• 1986

The structure of gonads, gametogenesis and reproductive cycle of the jackknife clams, Solen strictus and Solen gordonis were investigated mainly by histological observation. The first species used were monthly sampled at the coastal area of Dadaepo, Pusan, Korea and Naechodo, Kunsan, Korea for one year from February 1982 to January 1983. The second species were monthly sampled at the sand beach of Dadaepo, Pusan, Korea, from February 1982 to January 1983. Sexualities of Solen strictus and Solen gordonis are dioecious, and these species are oviparous. The gonads are irregularly arranged from the subregion of mid-intestinal gland in visceral cavity to reticular connective tissue of foot. The ovary was composed of a number of small ovarian sacs and the testis was composed of several testicular lobuli which from the tubular structure. Early multiplicating oogonium was about $10{\mu}m$ in diamater. Nucleus and nucleolus, at that time, were distinct in appearance. Each of the early growing oocytes made an egg-stalk, connected to the germinal epithelium of the ovarian sac. A great number of undifferentiated mesenchymal tissue and eosinophilic granular cells are abundantly distributed in the ovarian sacs in the early development stages. With the further development of gonad, these tissue and cells gradually disappeared. Then the undifferentiated mesenchymal tissue and eosinophilic granular cells function as nutritive cells in the formation and development of the early stage germ cells. Mature oocytes were free in the lumen of ovarian sacs and gradually become round or oval. Ripe oocyte was about 80 to $90{\mu}m$ in diameter. With the further development of testis, each of the testicular lobuli formed stratified layers composed of spermatogonia, spermatocytes, spermatids and spermatozoa in groups on the germinal epithelium. After spawning, the gonad gradually degenerated, and disorganized completely. Then new differentiated tissues were rearranged next year. The annual reproductive cycle of those species could be classified into five stages; multiplicative, growing, mature, spent, degenerative and resting stage. It seems that the spawning season is closely related to the water temperature, and the spawning of Solen strictus occurs from June to July at above $20^{\circ}C$ in water temperature. The peak spawning season appeared in June at Dadaepo and in July at Kunsan, The spawning of Solen gordonis occurs from May to June with the peak spawning season in June. Percentages of the first maturity in female of Solen strictus ranging from 5.1-6.0 cm and 7.1-8.0 cm in shell length were $50\%$ and $100\%$, respectively.

• Korean Journal of Ichthyology
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• v.6 no.2
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• pp.237-243
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• 1994

This work was conducted to study sex differentiation in the black sea bream, Acanthopagrus schlegeli (Bleeker), using a histological method for the appearance of primordial germ cell, formation of primitive gonads, differentiation of female and male from newly hatched larva to the ovotestis stage of fish. The 3~4 primordial germ cells of $6.8{\sim}7.2\;{\mu}m$ in size, which were buried under fibrous mesenchymal tissue between gut duct and notochord of pre-larva with a total length (T.L.) of 2.4 mm at 3 days after hatching. The proto-gonial cells were located in the epithelium of the coelom attached with pigment cells of juvenile with 6.4 mm in T.L. at 21 days after hatching. In juvenile of 20.8 mm in T.L. at 59 days after hatching, the proto-gonial cells were migrated to the retro-peritoneum through the lineshaped primitive gonad composed of fibrous mesenchymal tissue. In juvenile of 7.8 em in T.L. at 186 days after hatching, the mitotic division of proto-gonial cell appeared in the lineshaped primitive gonad having many eosinophilic granule cells and abundant fibrous connective tissue. In juvenile of 9.5 em in T.L. at 254 days after hatching, the gonad was occupied by abundant fibrous connective tissue, bundles of spermatocyte and spermatid. In juvenile of 10.5 cm in T.L. at 13 months after hatching, the gonad was divided into cortical layer and medullary layer. The former was composed of bundles of a few spermatocytes and proto-gonial cells, the latter was filled with the fibrous mesenchymal tissue and a few proto-gonial cells. In juvenile of 14.7 em in T.L. at 16 months after hatching, the gonad was separated into ovarian part and testicular part by the fibrous connective tissue. The ovarian part is consisted of ovarian cavity and oocytes of perinucleolus stage. The testicular part was occupied by spermatogonia in the cyst.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.629-636
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• 1999

Gonadal development, gametogenesis, reproductive cycle, egg-diameter and composition, condition factor, and the first sexual maturity of the clam, Potamocorbula amurensis were investigated by histological observation. Samples were collected monthly from the tidal flat of Moonpo, Puan-gun, Chollabuk-do, west coast of Korea from November 1996 to October 1997. P. amurensis is dioecious and oviparous. The gonads were composed of a number of gametogenic follicles. The oogonia and fully ripe oocytes were $9\~12\mu$m and $50\~60\mu$m in diameter, respectively. Each of the spermatogenic follicle formed stratified layers composed of spermatogonia, spermatocytes spermatids, and spermatozoa in groups on the follicular wall. The reproductive cycle of P. amurensis could be classified into five successive stages: early active, late active, ripe, partially spawned, and recovery. Spawning occurred twice a year from May to July and from September to October, the main spawning seasons also appeared twice a year between May and June, and in October when the water temperatures reached above $18^{\circ}C$. The monthly changes in the condition factor were closely related with the reproductive cycle. Minimum size for the sexual maturation of female and male were 8.1 mm in shell length. There were two patterns for the gametogenesis: 1. After spawning, the undischarged ripe oocytes and spermatozoa in the follicles were degenerated and absorbed, but in part, the existing follicles were not contracted significantly and then they took part in new gametogenesis within one or two months (especially, in summer). 2. After spawning, each follicle was contracted, thereafter gametogenesis again occurred in newly formed follicles.