• Development and Reproduction
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• v.9 no.1
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• pp.23-31
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• 2005

Vitellogenesis during oogenesis, reproductive cycle and first sexual maturity of the female Neptunea (Barbitonia) arthritica cumingii was investigated by light and electron microscope observations. In the early vitellogenic oocyte, the Golgi complex and mitochondria were involved in the formation of lipid droplets and yolk granules. In late vitellogenic oocytes, the rough endoplasmic reticulum and multivesicular bodies were involved in the formation of proteid yolk granules in the cytoplasm. A mature yolk granule was composed of three components: main body(central core), superficial layer, and the limiting membrane. The spawning season was between May and August and the main spawning occurred between June and July when the seawater temperature rose to approximately $18{\sim}23^{\circ}C$. The female reproductive cycle can be classified into five successive stages: early active stage(September to October), late active stage(November to February), ripe stage(February to June), partially spawned stage(May to August), and recovery stage(June to August). The rate of individuals reaching the first sexual maturity was 53.1% in females of 51.0 to 60.9mm in shell height, and 100% in those over 61.0mm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.167-176
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• 1991

Sexual maturation of the bluespotted mud hopper, Boleophthalmus Pectinirostris(Linnaeus) was investigated histologically on the gonadal development, and studied by gonadosomatic index(GSI), egg diameter composition. Samples were collected in the intertidal zone of Wolyon-ri, Hoihyon-myon, Okku-gun, Chollabuk-do, Korea, from April to October in 1988 and from June to August in 1989. The ovary is a pair of sac-shaped organ. The testis is a pair of tubule-shaped organ and it is connected to the seminal vesicle which is located at the posterior end of the testis. In male and female, GSI began to increase from late May when the water temperature began to increase and reached the maximum value in June and July, respectively. It began to decrease from August, the highest water temperature season. Thereafter, maintained relatively low values until October. The annual reproductive cycle of this species could be classified into four sucessive developmental stages: growing stage$(April{\~}May)$, mature stage$(June{\~}early\;July)$, ripe and spent stage(late lune-early August), degenerative and resting stage$(late\;August{\~}March:\;the wintering\;period)$. According to the frequency distributions of egg diameters in the spawning season, Boleophthalmus Pectinirostris was species to spawn twice or more in the spawning season.

• Journal of Life Science
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• v.13 no.3
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• pp.359-364
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• 2003

The seaweed Porphyra pseudolinearis as a dominant species grows at upper of the intertidal zone of the East Sea from October to March. Vegetative cells have not matured during October when observed with naked eye and microscope. In the middle of November, although it didn't distingush between female and male gametophytes by eye, it showed antheridium and carpogonium when observed vertical section under microscope. From early December, It could be distinguished female and male gametophytes clearly. From Feburary it showed shorted length of thalli by release of spermatangia and carposporangia as maturation. At early March, the colar has been decaeded and side of thalli has been melted, completed of release of spermatia. At the end of December, the average length and width of female thalli were 149.9$\pm$5.6mm and 22.2$\pm$2.3mm, respectively. The length and width of male thalli were 149.9$\pm$9.4mm and 20.7$\pm$1.8mm. At the end of January, the average length and width of female thalli were 94.6$\pm$6.4mm and 29.1mm$\pm$5.1, respcetively. The length and width of male thalli were 107.8$\pm$7.3mm and 25.9$\pm$0.9mm. From this period lengths of female and male thalli have already been shortned by the release of spermatia and carpogonia.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.11
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• pp.1514-1517
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• 2000

In chicken, exogenous genes introduced into germinal crescent region (GCR) of the early developmental stage, where primordial germ cells (PGCs) were concentrated, were successfully transferred to the gonads via PGCs. The foreign genes were also confirmed to be successfully incorporated into F1 and F2 generations. We tried to incorporate the exogenous genes into PGCs by lipofection, then the DNA mixture was injected into GCR at stage 3-5 or 9-11 of embryonic development (Hamburger and Hamilton, 1951). The manipulated eggs were incubated, and hatched chicks were reared until sexual maturation. F1 generation was obtained from the DNA-treated chicken (DNA-chicken) mated with normal birds. Furthermore, F2 generation was also obtained from the F1 chicken mated with normal birds. The transfer of introduced foreign genes were confirmed by marker gene detection methods and PCR analysis in the hatched chicks, F1 and F2 generations. However, in our experiments, DNA-chickens showed abnormal characteristics such as low egg production rate, abnormal appearance and decreased number of spermatozoa. In the case of F1 chicken, low egg production and the deterioration of sperm capacity for insemination in male chicken were observed.

• Animal cells and systems
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• v.1 no.1
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• pp.53-61
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• 1997

Seasonal variation of the population structure and the reproductive pattern of the Korean striped field mouse, Apodemus agrarius, were investigated. High capture ratios in juveniles, young adult, and old adult mice were found during the period from October to November, from November to March, and from May to September, respectively, and extremely low capture ratios of old adults during the period from November to February were characteristic. It seemed that the young adults that survived during the winter might become older by summer and have been counted as the old adults. The breeding in the mice began earlier in males (from mid February or early March to late October) than in females (from mid March to late October), having a peak in August and September, and both the male and female mice weighing more than 20 g generally reached sexual maturation in general. In the breeding season, both young and old adult males had large testes with enlarged seminiferous tubules filled with numerous germ and Sertoli cells, and expanded caudal epididymides with a vast number of spermatozoa; the females had many Graafian follicles and corpora lutea in large ovaries, and developed uterine glands in the thick endometria. The lower ratios of the testis weight to the body weight in July and August in 1994 compared to 1995 seemed due to the extreme drought and considerably higher temperature in 1994, but the decrease in the ratio in mid-summer, only in the old mice, in both years might be explained partially by aging.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.3
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• pp.359-366
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• 2010

It was easy to find that children of a skeletal anterior crossbite in the early mixed dentition period showed a stark difference in the dental maturity between their maxillary and mandibular teeth, if they have stronger physical characteristics. If the difference of dental age between maxillary and mandibular teeth which can be identified via panoramic radiographs may serve as an early sign of class III malocclusion, this is considered valuable as a tool of early detection diagnosis. We obtained lateral cephalometric radiographs, panoramic radiographs, working model and clinical images of patients of Hellman dental age IIA and IIC who visited the department of pediatric dentistry, Pusan National University Dental Hospital and examined them to select 50 patents for normal occlusion group and skeletal anterior crossbite group, respectively. Their panoramic radiographs were used for the Demirjian's method to figure out dental ages of maxillary and mandibular teeth of each group and the eruption rate of the first molars. Their differences are as follows: 1. In both groups, the dental ages from Demirjian's method were advanced than the chronological ages. No sexual dimorphism was detected for the chronological or dental age in either group (p>0.05). 2. The difference of dental age of maxillary and mandibular teeth between the normal occlusion group and crossbite group was 0.22 and 0.69 years, respectively, with a higher difference in crossbite group(p<0.05). 3. Compared to the normal occlusion group, the crossbite group showed a higher difference in the eruption rate between maxillary and mandibular first molar(p<0.05).

• Journal of Aquaculture
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• v.17 no.1
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• pp.30-38
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• 2004

To estimate the spawning period the annual change of gonadosomatic index (GSI) were examined from January 2000 to December 2001. Fecundity, spawning frequency and egg diameter were measured by ocular observation. Germ cell differentiation during gametogenesis, the reproductive cycle and the first sexual maturity of greenling Hexagrammos otakii were observed under light microscopy from January to December, 2000. GSI began to increase in August and reached the maximum in November when ovary was getting mature. The reproductive cycle of H. otakii can be divided into five successive stages in females: early growing stage (July), late growing stage (July to August), mature stage (September to October), ripe and spent stage (September to December), and recovery and resting stage (December to June). Males showed four successive stages : growing (June to August), mature (August to October), ripe and spent (September to December), and recovery and resting stage (December to May). According to the frequency distributions of egg diameter in spawning season, H. otakii could be one of polycyclic species spawning 2 times or more during one spawning season. Number of total eggs and mature eggs in the absolute fecundity were related to the standard length and body weight, respectively. Number of total eggs and mature eggs in relative fecundity were also proportional to the standard length, but rather these numbers decreased with body weight. Percentages of first sexual maturity of females and males in greenling were over 50% from 19.1 to 21.1cm in length, and 100% for fish over 25.1cm in length. Therefore, both sexes are ready to reproduce after one year old.

• The Korean Journal of Malacology
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• v.19 no.2
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• pp.153-153
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• 2003

Reproductive cycle with the ovarian developmental phases, first sexual maturity of the female venus clam, Cyclina sinensis, was investigated by a histological study, and the number of spawned eggs and spawning frequency by artificial spawning induction of the clams were estimated. Samples were collected from the intertidal zone of Simpo, Gimje city, Korea between January and December, 2001. The reproductive cycle of this species can be classified into five successive stages; early active (February to April), late active (March to June), ripe (May to August), spent (July to September), and spent and inactive (September to February). The spawning period was once a year between July and August, a spawning peak was seen in July and August. Percentages of first sexual maturity of female clams of 25.1-30.0 mm in shell length were 64.3%, and 100% for the clams > 40.1 mm. The number of the eggs released from each clam by spawning induction increased as the size of clam in terms of shell length increased. The mean number of the eggs released from the second induction of spawning was 76.87% of the number of the eggs released in the first spawning. Our data indicated that the interval of each spawning was estimated to be approximately 15-17 (average 16.5) days.

• Journal of Marine Life Science
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• v.8 no.1
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• pp.32-42
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• 2023

Fish reproduction is regulated by various neurohormones secreted from the brain and gonadotropic hormones secreted from the pituitary. Reproduction of eel (Anguilla japonica) is also regulated by these hormones. However, how the neurohormones regulate the secretion of pituitary hormones during sexual maturation is not completely understood. Previous studies have shown that neurohormones such as progesterone (P4), melatonin and serotonin (5-HT) are involved in the regulation of reproductive processes in some fish. In this study, the eel pituitary was primary cultured, and stabilized pituitary cells were treated with P4, 17β-estradiol (E2), melatonin, or 5-HT. The effect of these treatments on the expression of FSHβ, LHβ, GH and SL mRNA was, then, investigated. P4 increased the expression of FSHβ and LHβ in pituitary cells, and melatonin increased the expression of GH and SL as well as FSHβ and LHβ. However, 5-HT did not significantly affect the expression of these mRNA. These results suggest that P4 and melatonin may play some important roles in the early sexual maturation of eels.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.4
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• pp.349-356
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• 2006

Gonad development in the sandfish Arctoscopus japonicus was investigated using a histological method. Specimens were collected monthly from April 2003 to March 2004, in the East Sea of Korea. The gonadosomatic index (GSI) of females began to increase in August, reached a maximum in November, and declined sharply in December. By contrast, in males, the GSI began to increase in June and reached a maximum in August. The annual reproductive cycle of A. japonicus can be divided into four successive stages in females: the early growing (January-March), late growing (April-August), ripe and spent (September-November), and recovery (December) stages. Males passed through early growing (January-April), late growing (May-July), ripe and spent (August-November), and recovery (November-December) stages. These results indicate that the spawning season was from October to December. The egg diameter of mature oocytes was 3.12$\pm$0.02 mm. The relationship between fecundity (F$_e$) and body length (BL) was F$_e$=0.4693BL$^{2.6825}$. Fecundity ranged from 483-2,254 eggs in a body length of 14.3-22.9 cm and increased with body length. The body length at 50% maturity was 14.80 cm, which corresponded to an age of 2.40 years.