• Applied Microscopy
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• v.25 no.3
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• pp.63-74
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• 1995

The development of pale chub oocyte from the immature oogonium to mature oocyte was investigated by light and electron microscope. The cytoplasm of pale chub oogonia was acidic and many vesicles were located at inner side of nuclear membrane. In primary oocytes, yolk vesicles were distributed in cytoplasm. Also, fibrous materials and protuberances were distributed on the surface of zona radiata. The nucleus of secondary oocyte was enlarged and yolk vesicles in cytoplasm migrated to zona radiata. In early egg, yolk mass are formed and yolk vesicles were located at inner side of zona radiata. Three-layered zona radiata was about $3{\mu}m$ in thickness. The three layers were an outer fibrous material layer, a middle nurse cell layer in which microvilli of early egg cytoplasm contact with processes of nurse cells, and an inner layer with high electron density. In mature egg, euchromatin and a germinal vesicle were developed, mitochondria, free ribosomes, and yolk mass were distributed in cytoplasm. But, yolk vesicles were disappeared. Specially, zona radiata of matured eggs were better thin than the one of immature eggs In conclusion, it is summerized that the oogenesis of pale chub were the increase of cell size, the formation and accumulation of yolk, the decrease in nucleat electron density, changes of zona radiata, and the development of microvilli.

• Korean Journal of Ichthyology
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• v.13 no.1
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• pp.19-23
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• 2001

The full-grown oocyte envelope of the two spined loaches, Niwaella multifasciata and Kichulchoia brevifasciata, was examined by electron microscopy. The oocyte is surrounded by its envelope, and an external modification (an adhesive structure) in the surface of the envelope is present. The envelope consists of two layers, a zona radiata externa which is the site of the adhesive structure, and a zona radiata interna, which has heterogeneous, electron-dense multi layers. The surface (zona radiata externa) of the envelope in N. multifasciata is equipped with short villuslike protuberances, which have a length of 1.5~2.5 ${\mu}m$ and are separated from each other by a distance of 2~2.5 ${\mu}m$. In contrast, K. brevifasciata has undulating or wave-like structures that extend over the entire oocyte surface. The waves are 1.5~2.5 ${\mu}m$ in length and are separated a distance of 2.5~3.3 ${\mu}m$ from each other.

• The Korean Journal of Zoology
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• v.39 no.4
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• pp.419-425
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• 1996

The five spedes of genus Iksookimia from Korea were investigated by electron microscopes to clarify the adhesive membranes on zona radiata. In the late vitellogenic stage the adhesive membranes could be classified into three form as follows: 1) villous form of Iksookimia koreensis, I pumila, and I. hugowolfeldi, 2) cotton-shaped form of I. longicorpus, and 3) vine-shaped form of I. choii. And although I. koreensis, I pumila, and I. hugowolfeldi possessed the same villous form, It was evident that fine structure of the zona radiata varied according to spedes. The adhesive membranes and fine structures of zona radiata in Iksookimla showed a species specificity related to closely their habitats and spawning properties.

• Korean Journal of Animal Reproduction
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• v.16 no.3
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• pp.247-260
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• 1992

This study was carried out to investigate the histomorphological changes of ovaries obtained from 100 of 1-year-old female Korean loach(misgurnus anguillicaudatus). The light microscopic and ultrastructural changes ofooplasm and follicular membranes of oocytes, were observed by lightand transmission electron microscope during the reproductive cycle. All data were collected from November in 1991 to May in 1992. The results obtained in this study were as follows: The size of the nucleoli and number of the yolk granules increased as the oocytes grown. Yolk granules were loosely deposited in the oocytes as crystalline granules. Due to the presence of large early and late maturing oocytes, their ovaries were enlarged, transparent, granular and yellowish in color. The lattice was broken down at hydration, leaving the egg transparent. As the percentages of fish in LMO and RO stage increased from March to April, mean gonadosomatic index(GSI) values(18.49%) increased. Zona radiata change a squamous into cuboid shape in EMO stage. Processes from the granulosa cells and from the oocyte, microvilli grow and make contact with other in the pore canals of the zona radiata during vitellogenesis, but are withdrawn as the zona radiata becomes more compact and devoid of pore canals during oocyte maturation. Seasonal changes in the microscopic appearance of the ovaries were well correlated with those in both GSI and macroscopic appearance.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.121-129
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• 1997

The five species of genus Cobitis from Korea were investigated by electron microscopes to clarify the adhesive membranes on zona radiata. In the late vitellogenic stage the adhesive membranes could be classified into two form as follows: 1) granular form of Cobitis lutheri, C. striata, C. sinensis, and C. sinensis-longicorpus, 2) villous form of C. melanoleuca. Although C. lutheri, C. striata, C. sinensis, and C. sinensis-longicorpus possessed the same granular form, it was evident that fine structure of the zona radiata varied according to species. The adhesive membranes and fine structures of zona radiata in Cobitis showed a species specificity closely related to their habitats and spawning properties.

• Korean Journal of Ichthyology
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• v.11 no.2
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• pp.126-133
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• 1999

Ultrastructure of the zona radiata and the micropyle of ripe eggs in the rainbow trout (Oncorhynchus mykiss), catfish (Silurus asotus) and loach (Misgurnus anguillicaudatus) were examined by light, scanning and transmission microscopes. The egg micropyle of rainbow trout and catfish consists of a funnel-shaped vestibule and a tapered canal transversing the zona radiata. The micropyle of rainbow trout and catfish showed the similar structure with flat pit and long canal. The micropylar wall showed the clockwise spiral structure in rainbow trout. The micropyle of the loach showed the type with a hollow pit leading into a short canal and the micropylar wall showed the counterclockwise spiral structure. There are numerous and various size pores at the surface area around the opening in every experimented fish. Interconnecting ridges were observed in the unfertilized eggs of every fish.

• Applied Microscopy
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• v.28 no.4
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• pp.447-463
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• 1998

This study was carried out to investigate the histomorphological changes and the electrophoretic patterns of egg components, obtained from 100 of 2-year-old female catfishes (Silurus asotus). Female Korean catfishes collected in the vicinity of Chollabukdo have synchronous ovaries which discontinously ovulate eggs during the breeding season (from late May until early July). The fishes were killed by severing the spinal cord just posterior to the head after immobilization with tricaine methanesulfonate (MS 222). Especially, the light microscopic and ultrastructural changes of ooplasm and follicular membranes of oocytes, were examined by means of light and transmission electron microscopy. The size of the nucleoli and number of the yolk granules increased as the oocyte groved. Yolk granules were deposited in the oocyte as fluid Due to tile presence of large early and late maturing oocytes, their ovaries were enlarged, transparent, granular and greenish in color. As the percentages of fish in late maturing oocyte (LMO) and ripe oocyte (RO) stage increased from March to April, mean gonadosomatic index (GSI) values (19.95%) increased. Zona radiata changed from squamous into cuboid in shape in the early maturing oocyte (EMO) stage. Processes, microvilli, from the zona radiata and from the oocyte grow, and make contact with each other in the pore canals of the zona radiata during vitellogenesis, but are withdrawn as the zona radials becomes more compact and devoid of pore canals during oocyte maturation. Seasonal changes in the microscopic appearance of the ovaries were well correlated with those in both gonadosomatic index and macroscopic appearance. The main cytological changes such as increase in size of cell, nucleus, nucleolus, and increase in number of nucleoli and mitochondria demonstrated with electron microscopy in the previtellogenic oocytes of Korean catfish, provided evidences for important synthetic processes in an early preparatory phase of oocyte development. The electrophoretic pattern of major band in mature stage was much thicker (24 k, 66 k, 90-110k dalton) than that in previtellogenic phase.

• Applied Microscopy
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• v.31 no.1
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• pp.19-35
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• 2001

Outlines for plasma $estradiol-17\beta$, components, electrophoretic patterns, and ultrastructural changes were obtained in female rainbow trout (Oncorhynchus mykiss) during the seasonal reproductive cycles. Plasma $estradiol-17\beta$ under the natural conditions, exhibited distinct seasonal variation, peaking very late in vitellogenic season during September, decreasing gradually the halt of spawning in December, and ultimately falling during the early stages of seasonal ovarian recrudescence in February and March. This change in $estradiol-17\beta$ appeared to stimulate vitellogenin production as evidenced by increases in plasma calcium, phosphorus, glucose, albumin and total protein levels. The electrophoretic patterns of late maturing or spawning oocytes were stained more intensively than those of late perinucleolus oocytes (molecular weights of approximately 70,000 and 200,000). Two protein bands were found in the SDS-PAGE separation, coincident with the $estradiol-17\beta$ hormone peak. Gonadosomatic indices (GSI) significantly increased from October to January, and showed the highest peak in January, coinciding with the numerically abrupt increase of ripe ova in female. A positive correlation (r=0.701, p<0.01) was established between plasma $estradiol-17\beta$ levels and the gonadosomatic index during the prespawning. The highest level of hepatosomatic index (HSI) observed in December. During the breeding season (December), the gonadotropes were large and filled with GTH-containing inclusions such as granules and globules. The vitellogenic phase began as late perinurleolus oocytes became transformed into early maturing oocytes through the accumulation of yolk, and oocytes reached the late maturing stages as the ooplasm was completely packed with yolk. Marked ultrastructural changed in the granulosa cells during nuclear migration involve the dilation of the rough endoplasmic reticulum and the appearance of the rod-shaped mitochondria with tubular cristae. Microvilli (finger-like projections), from the zona radiata and from the oocyte grew, and made contact with each other in the pore canals of the zona radials during vitellogenesis, but were withdrawn as the zona radiata became more compact and devoid of pore canals during oocyte maturation. The zona radiata grew to a tripartite structure such as an outer thin homogeneous layer, and two inner thick helicoidal layers (zona radials interna and zona radiata externa). Under the normal conditions, the ovarian follicle influenced the histological development and periodical secretion of the hormones , sufficient for a oogenesis and gonadal steroid production.

• Korean Journal of Animal Reproduction
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• v.19 no.2
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• pp.105-117
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• 1995

This study was carried out to investigate the histomorphological changes and the electrophoretic patterns of egg components, obtained from 100 of 1-year-old female catfish(Silurus asotus). Especially, the light microscopic and ultrastructural changes of ooplasm and follicular membranes of oocytes, were observed by light and transmission electron microscope. All data were collected from October in 1992 to May in 1993. The size of the nucleoli and number of the yolk granules increased as the oocyte grew. Yolk granules were deposited in the oocyte as fluid. Due to the presence of large early and late maturing oocytes, their ovaries were large, transparent, granular, and greenish in color. As the percentages of fish in LMO and RO stage increased from March to April, mean of GSI values(19.95%) increased. Follicle cells such as granulosa cell and thecal cell change a squamous into cuboid shape in LPO and EMO stage. Processes, microvilli, from the granulosa cells and from the oocyte grow and make contact with each other in the pore canals of the zona radiata during vitellogenesis, but are withdrawn as the zona radiate becomes more compact and devoid of pore canals during oocyte maturation. The electrophoretic pattern of major band in mature stage was much thicker(21k, 24k, 32k, 45k, 67∼110k, 170k dalton) than that in previtellogenic phase.

• Korean Journal of Ichthyology
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• v.13 no.4
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• pp.254-260
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• 2001

In the goby Micropercops swinhonis, the follicular layer of full-grown oocytes consists of an outer layer (theca cell) and an inner layer (granulosa cell). As the oocyte grows, columnar cells of inner granulosa layer secrete mucin to their cytoplasm and then surround the oocyte. Such granulosa cells appear to be cuboidal cells in the early vitellogenesis, yolk vesicle stage, to be replaced by columnar cell secreting mucins (adhesive materials) in the middle vitellogenesis, yolk granule stage. The enveloping layer of the oocyte has a muco- follicle layer filled with mucins. The mucins are an amorphous and electron-dense substance. Interestingly, the oocyte enveloping layer becomes thickened towards the animal pole as vitelogenesis proceeds. A zona radiata of about $7.8{\sim}11.5\;{\mu}m$ thick is present below the muco-follicle layer. The zona radiata is composed of an one-layered electron-dense externa and a three to five-layered electron-less interna.