• 한국응용곤충학회지
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• 제34권1호
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• pp.20-32
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• 1995

Adult diapause in insects is characterized by suppression of reproductive development. It is induced by environmental cues such as photoperiod, temperature, food availability, and other conditions Diapause-inducing environment is recognized and analyzed by the brain of the insects. The interpreted information is conveyed via endocrine system to target tissues such as ovaries, fat body, and other tissues. From this signal hierarchy of a brain-endocrine-target tissue axis, several factors are involved to express a diapause trait in a quantitative mode, even though the insects show a binomial phenotye between being in diapause or not. Recent works estimated that the number of the factors is relatively small by a series of crossing trials between high and low diapause lines. Heritability of the diapause is quite high (ca. 70%) in some species. Epistasis, sex-linkage, pleiotropism, and other nongenetic components also affect diapause inheritance. Most physiological studies have been focused on control mechanisms of the juvenile hormone (JH) synthesis in corpora allata (CA) because JH level in hemolymph of teneral adults is critical to decide a later developmental mode. Allatostatin, an antagonizer of JH synthesis, has been believed to be a potent brain message to CA for adult diapause induction.

• 한국발생생물학회지:발생과생식
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• 제18권4호
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• pp.321-327
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• 2014

Ultrastructural studies of oocyte degeneration in the oocyte, and the functions of follicle cells during oocyte degeneration are described to clarify the reproductive mechanism on oocyte degeneration of Mactra chinensis using cytological methods. Commonly, the follicle cells are attached to the oocyte. Follicle cells play an important role in oocyte degeneration. In particular, the functions of follicle cells during oocyte degeneration are associated with phagocytosis and the intracellular digestion of products. In this study, morphologically similar degenerated phagosomes (various lysosomes), which were observed in the degenerated oocytes, appeared in the follicle cells. After the spawning of the oocytes, the follicle cells were involved in oocyte degeneration through phagocytosis by phagolysosomes. Therefore, it can be assumed that follicle cells reabsorb phagosomes from degenerated oocytes. In this study, the presence of lipid granules, which occurred from degenerating yolk granules, gradually increased in degenerating oocytes. The function of follicle cells can accumulate reserves of lipid granules and glycogen in the cytoplasm, which can be employed by the vitellogenic oocyte. Based on observations of follicle cells attached to degenerating oocytes after spawning, the follicle cells of this species are involved in the lysosomal induction of oocyte degeneration for the reabsorption of phagosomes (phagolysosomes) in the cytoplasm for nutrient storage, as seen in other bivalves.

• Applied Microscopy
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• 제15권1호
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• pp.86-100
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• 1985

A observation of the ovarian development and oogenesis of Pieris rapae Linne has been carried out during metamorphosis using stereo-microscope, light microscope and electron microscope. The results obtained through this experiment are as follows: 1. The ovarian development and vitellogenesis begin at the 3-day old pupa and the 6-day old pupa respectively, and the adult ovary right after their emergence contains a few mature eggs. 2. The species described above are further observed at six different stages in oogenesis, and the results are summarized as follows. 1) Pieris rapae has polytrophic ovarioles. The cell organelles of the nurse cells are transfered to the oocyte through the ring canal at the early oogenesis. 2) At stage 2, the nuclear envelope of oocyte nucleus is less infolding than that of nurse cell nucleus. In the oocyte cytoplasm a large number of ribosomes are observed. 3) At stage 3 and 4, many micropinocytotic vesicles are observed in the oocyte cytoplasm. These vesicles are fused together to form large proteid yolks. 4) At stage 5, the vitelline membrane is laid down in the intercellular space between the follicle cells and oocyte. 5) At stage 6, the chorion is formed by the follicle cells. 6) A micropyle and a number of aeropyle are observed on the surface of a mature egg.

• 한국패류학회지
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• 제22권1호
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• pp.51-61
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• 2006

Oogenesis and the reproductive cycle in female Ruditapes philippinarum were investigated by cytological and histological observations. R. philippinarum is dioecious and oviparous. During vitellogenesis, the Golgi complex, glycogen particles and mitochondria were involved in the formation of lipid droplets and lipid granules in the cytoplasm of the early vitellogenic oocyte. In the late vitellogenic oocyte, cortical granules, the endoplasmic reticulum, and mitochondria were involved in the formation of proteid yolk granules in the cytoplasm. At this time, exogenous lipid granular substance and glycogen particles in the germinal epithelium passed into the oocyte through the microvilli of the vitelline envelope. The spawning period was once a year between early June and early October, and the main spawning occurred between July and August when seawater temperature was approximately $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (May to October), and spent/inactive stage (August to February). Percentages of female clams at frst sexual maturity of 15.1-20.0 mm in shell length were 52.6% (50% of the rate of group maturity was 17.83 mm in length), and 100% for the clams > 25.1 mm.

• 한국패류학회지
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• 제22권1호
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• pp.1-11
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• 2006

The gonadosomatic index (GSI), oogenesis and reproductive cycle in female Neptunea (Barbitonia) afhritica cumingii were investigated by light and electron microscope observations. In the early vitellogenic oocyte, the Golgi complex and mitochondria were involved in the formation of glycogen, lipid droplets and yolk granules. Late in the vitellogenic oocytes, the rough endoplasmic reticulum and multivesicular bodies were involved in the formation of proteid yolk granules in cytoplasm. In particular, compared with the results of other gastropods, it showed a different result that appearances of cortical granules at the cortical layer and microvilli on the vitelline envelope, which is associated with heterosynthetic vitellogenesis, were not observed in vitellogenic oocytes during oogenesis. A mature yolk granule was composed of three components: main body (central core), superficial layer, and the limiting membrane. Monthly changes in the gonadosomatic index in females studied in 2004 and 2005 were closely associated with ovarian developmental phases. Spawning occurred between May and August in 2004 and 2005 and the main spawning occurred between June and July when the seawater temperature rose to approximately $18-23^{\circ}C$. 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).

• 한국발생생물학회지:발생과생식
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• 제27권3호
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• pp.127-135
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• 2023

Effects of changes in photoperiod on the reproductive events in fish are suggested to be mediated mainly via the action of melatonin (MEL). Changing levels of plasma MEL throughout the day and year are suggested to influence the hypothalamus-pituitary-gonadal axis in fish. Therefore, in this study, we aimed to investigate the effects of MEL on oocyte maturation and germinal vesicle breakdown (GVBD) in the marine fish, Chaenogobius annularis, in vitro. Oocytes at three different stages (pre-, mid-, and late-vitellogenesis) were incubated with (a) only MEL (5, 10, 50, 100, 500, and 1,000 pg/mL) and (b) 50 pg/mL of 17α,20β-dihydroxy-4-pregnen-3-one (17α20βP), maturation-inducing hormone (MIH) of this species, and MEL (4-h incubation before addition of MIH). Any single MEL treatment did not significantly induce GVBD. However, treatment with 50 pg/mL MEL or MIH significantly induced GVBD. These results suggest that preincubation with MEL accelerates the effect of MIH on longchin goby oocyte maturation.

• 한국발생생물학회지:발생과생식
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• 제17권4호
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• pp.421-426
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• 2013

In this study, oocyte steroidogenesis are investigated in relation to oocyte development in the starry flounder, Platichthys stellatus, a marine multiple spawner. Vitellogenic (0.52 and 0.55 mm oocyte diameter) and mature oocytes (0.63, 0.66 and 0.71 mm oocyte diameter) were incubated in vitro in the presence of $[^3H]17{\alpha}$-hydroxyprogesterone ($[^3H]17{\alpha}$-OHP) as a precursor. Steroid metabolites were extracted from the incubated media and oocytes, the extracts were separated and identified by thin-layer chromatography (TLC), high performance liquid chromatography (HPLC) and gas chromatographymass spectrometry (GC-MS). The major metabolites produced from $[^3H]17{\alpha}$-OHP were androgens [androstenedione ($A_4$) and testosterone (T)] and estrogens [$17{\beta}$-estradiol ($E_2$) and estrone ($E_1$)] and progestins [$17{\alpha},20{\alpha}$-dihydroxy-4-pregnen-3-one ($17{\alpha}20{\alpha}P$) and $17{\alpha},20{\beta}$-dihydroxy-4-pregnen-3-one ($17{\alpha}20{\beta}P$)] in vitellogenic and mature oocytes. The results from this study suggest the potential roles of $E_1$ in the oocytes with diameter 0.52-0.71 mm, $17{\alpha}20{\alpha}P$ and $17{\alpha}20{\beta}P$ at the oocytes of 0.63, 0.66 and 0.71 mm.

• 한국수산과학회지
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• 제45권1호
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• pp.17-24
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• 2012

We cloned and sequenced the cDNA encoding the $FSH{\beta}$ and $LH{\beta}$ subunits from the pituitary of the blacktip grouper Epinephelus fasciatus, which regulate vitellogenesis and maturation in vertebrates, to achieve stable and healthy gametes. The full-length cDNAs of $FSH{\beta}$ and $LH{\beta}$ were 571 bp and 617 bp, encoding 120 amino acid (aa) and 147 aa proteins, respectively. The deduced amino acid sequences of $FSH{\beta}$ and $LH{\beta}$ were highly homologous (68-97%) to those of other Perciformes; E. bruneus, Dicentrarchus labrax, Thunnus thynnus, and Pseudolabrus sieboldi. Phylogenetic analysis showed that the deduced $FSH{\beta}$ and $LH{\beta}$ amino acid sequences were categorized as a distinct subunit in the $GTH{\beta}$ family, and are closely related to the teleostei $FSH{\beta}$ and $LH{\beta}$, respectively. $FSH{\beta}$ and $LH{\beta}$ mRNA exhibited high abundance in the pituitary gland and low in other brain areas, but were not present in peripheral tissues, as determined by RT-PCR.

• 한국수산과학회지
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• 제37권3호
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• pp.192-196
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• 2004

The in vitro effect of bisphenol A (BPA) on ovarian steroidogenesis of the longchin goby (Chasmichthys dolichognathus) was investigated. Oocytes taken during the maturing phase (vitellogenic, fully vitellogenic or germinal vesicle breakdown stage) were incubated with BPA (100 ng/mL) in the presence of exogenous precursor $^{3}H-17\alpha\;hydroxyprogesterone\;(^{3}H-17\alphaOHP).$ Steroids were extracted from the media and the isolated oocytes, and the extracts were separated and identified by thin layer chromatography and gas chromatography-mass spectrometry. The identities of the major metabolites were progestogens $[17{\alpha}-hydroxy,20{\alpha}-dihydroprogesterone\;(17{\alpha}20{\alpha}OHP)\;and\;17{\alpha}-hydrxy,20{\beta}-dihydroprogesterone\;(17{\alpha}20{\beta}OHP),$ androgens [androstenedione (A4) and testosterone (T)] and estrogens [estrone $(E_1)\;and\;estradiol-17{\beta}(E_2)].$ BPA treatment inhibited production of estrogens in all the maturing phases and progestogens in the germinal vesicle migrating stage. Percentage yield of estrogens was decreased with increased yield of androgens. In conclusion, BPA had an inhibitory effect on the conversion of $^3H-17\alphaOHP$ to estrogens and progestogens. These results demonstrate that BPA can act either estrogenic or anti-estrogenic effects.

• 한국수산과학회지
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• 제35권2호
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• pp.130-134
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• 2002

볼락의 난소는 낭상형이며, 다수의 난소소엽으로 구성되어 있었다. 난황축적 이전의 난모세포들은 난소소엽의 결체성 조직에 매몰되어 관찰되었다. 난모세포는 성장하면서 난소강으로 돌출되어 난병 유사구조를 가지고 포도송이와 같은 구조를 나타냈다 난소 소엽내에 매몰되어있는 직경 약 20$\mu$m 크기의 초기 난모세포에서 난황과립과 방사대는 관찰되지 않았다 직경 약 80$\mu$m의 초기 난모세포의 난병 유사구조 세포질에서는 전자밀도가 높은 난황과려들이 다수 관찰되었으나, 방사대의 pore canal system에서 음세포작용은 관찰되지 않았다. 이 시기에 난병 유사구조에서는 미세섬유, 발달된 소포체와 미토콘드리아, 전자밀도가 낮은 과립상 물질 그리고 활성화된 multivesicular body들이 관찰되었다. 이러한 결과들은 볼락의 난병 유사구조는 난모세포의 부착과 초기 난모세포의 외재적 난황축적에 관여함을 시사하는 것이라고 할 수 있다.