• Journal of Embryo Transfer
• /
• v.5 no.1
• /
• pp.1-20
• /
• 1990

Follicular atresia is a universal and characteristic phenomenon of both non-mammalian and mammalian vertebrates. Generally it is estimated that greater than 99% of follicles become atretic in higher domestic animals and human. The number of selected follicles developing to the preovulatory stage are thus fewer. Follicles can become atretic at any stage of development. The previous studies emphasized on descriptive and retrospect aspects of a limited population of the fully grown preovulatory follicle. The main efforts in ovarian physilogical researches are focused on follicular development culminating in ovulation but recent advances have resulted in a better understanding of atresia. Nowadays, recent studies are concentrated on the induction of atresia in a selected population of follicles and of the associated cellular, endocrine, biochemical and molecular changes. The factors initiating atresia and follicle selections are worthy of investigations. Another intriguing question is whether one can predict when a follicle will become atretic, i.e., what biochemical markers indicate that a follicle is destined for atresia. It is generally agreed that atretic process may vary even in antral follicles at different stages of their differentiations and among species. The dicisive factors are follicular responsiveness and the hormonal milieu. Some generalizations can be made on the basis of experimental induction of atresia. Alteration of the pattern of follicular steroid production is associated with the initiation stage of atretic process. Atresia appears to be a process unfolding gradually and affecting progressively in increasing number of functions and components of the follicle. The oocyte may be the latest to be afflicted in the atretic process. The high steroidogenic activity of atretic follicles lends support to the notion that atresia is not necessarily a degenerative process and that atretic follicles may play an essential role in ovarian physiology. The simultaneous occurence of growth and atretic processes may render the search for regulatory mechanisms involved in atresia difficult extremely. The questions such as how follicles are selected to undergo ovulation rather than atresia or what the mechanism of atresia is remain unanswered. However, the factors regulating or modifying ovarian hormonal milieu for the initiation of follicular growth and maturation or of atresia are being elucidated.

• Korean Journal of Animal Reproduction
• /
• v.16 no.2
• /
• pp.165-173
• /
• 1992

In order to study the mechanism of follicle growth and maturation, and also to supplement the criteria identifying the follicle state of normal of atretic, the histochemical investigation on the ovarian follicles according to the ovarian cycle of mouse, rat and pig has been done. The intercellular space of granulosa cells, especailly Call-Exner body, and follicular fluid in the antrum showed positive to PAS, and blue stain by trichrome dye. The resutls suggest that the mucous polysaccharide was synthesized by the granulosa cells, and secreted into the antrum through Call-Exner body so as to be the components of the follicular fluid as the follicles proceeded to growth and maturation. The further the follicles proceeded to atresia the more densely their theca externa were stained blue by follicles proceeded to atresia the more densely their theca externa were stained blue by trichrome dye, and the more densely the granulosa cells were stained red by oil red 0 dye. Therefore, these staining methods can be applied to the criteria identifying the follicle atresia.

• Clinical and Experimental Reproductive Medicine
• /
• v.18 no.2
• /
• pp.123-131
• /
• 1991

In order to study the growth and maturation of ovarian follicle, the localization and activity of alkaline phosphatase(ALPase) and adenosine triphosphatase(ATPase) of the granulosa cells and theca layer were examined according to the follicle size, the follicle state and the ovarian cyclic phase in pig. Theca interna of the small follicles was more heavyly localized with reaction product by the activites of ALPase and ATPase than that of the large follicles. It is assumed that, as the follicles proceed to growth and maturation, antrum formation is the result of the follicular fluid accumulation by means of active transport by the activities of ALPase and ATPase in theca interna. The activities of ALPase and ATPase in atretic follicles were higher than those of normal follicles. These results imply that the mechanisms of follicle maturation and atresia are different according to the phase of ovarian cycle.

• Journal of Radiation Protection and Research
• /
• v.37 no.4
• /
• pp.208-212
• /
• 2012

In previous studies, ovarian follicle in rat has been used a higher radiation dose than that for cancer radiotherapy in clinical practice. The aim of this study was to evaluate the effect of radiation dose used for cancer radiotherapy on ovarian follicle atresia in rat. Mice of 4-week-old female were whole body irradiated with 2 cGy or 2 Gy (Mevatron 67, Siemens, Germany) and sacrificed by cervical dislocation. Ovaries were collected at 24 hours after irradiation to observe the degree of follicular atresia. Ovaries were fixed in neutral formaldehyde solution for 24 hours and embedded with paraffin. Cutted in $5{\mu}m$ thickness with microtome and stained with hematoxylin and eosin (H&E) and TUNEL immunohistochemical stain, and examined histologically under a light microscope. All data were presented as mean ${\pm}SD$, calculating the ratio of normal or atretic follicles to total ovarian follicles. Statistical analysis was performed by the Mann Whitney test using the SPSS ver 19.0. Ratio of atretic to total follicles of 2 Gy group was significantly higher than control or 2 cGy groups (p<0.05). Ratio of normal to total follicles of 2 Gy group was significantly lower than control group in preantral follicle (64.0 vs. 87.7, p=0.027). Ratio of normal to total follicles of 2 cGy group was significantly increased more than control or 2 Gy groups in antral follicle, and there were no significant difference between control and 2 Gy groups (p=0.522). Radiation dose of 2 Gy for cancer radiotherapy have a significant effect on ovarian follicle atresia in rat.

• Development and Reproduction
• /
• v.4 no.1
• /
• pp.13-17
• /
• 2000

Follicle stimulating hormone (FSH) stimulates follicle growth, and inhibits the follicle atresia in the immature rodent ovaries. The present study was carried out to know the histological changes of ovarian follicles after FSH treatment in the prepubertal mice. Ten i.u. of recombinant FSH was i.p. injected on 3 weeks old mice. After the treatment, at 1, 2 and 3 days, left ovaries were collected for the histological study. The atretic ratio of preantral follicles increased with time after FSH treatment. However, in the case of antral follicles, there was no significant change in the ratio. The degenerating follicles contained apoptotic granulosa cells, macrophage, and polymorphonuclear leukocytes in the follicular cavity. The present results suggest that follicular degeneration caused by FSH hyperstimulation could be mediated by apoptosis as well as the acute inflammation.

• Clinical and Experimental Reproductive Medicine
• /
• v.25 no.2
• /
• pp.179-187
• /
• 1998

In mammal, lots of follicles start simultaneously their growth but only a few oocytes are ovulated in every sexual cycles. Most of matured and grown oocytes are destined to degenerate by atresia. However, the molecular and physiological mechanisms are not elucidated yet. The present study was designed to establish an induction method of follicular atresia with ketamine or pentobarbitone and evaluate the effect of these anesthetics on oocyte maturation and granulosa cell apoptosis of the mouse ovarian follicle. The percentages of degenerated oocyte and apoptotic granulosa cell in ketamine treated groups were significantly higher than that in controls (58.9% vs 33.5%, p<0.01, degeneration; 44.9% vs 26.6%, p<0.01, apotosis). Futhermore, it was revealed that the concentrations of progesterone in both groups were markedly higher than that in control. In cunclusion, it is considered that ketamine induce an atresia as pentobarbitone, and may be useful for inducing follicular atresia.

• Nuclear Engineering and Technology
• /
• v.33 no.3
• /
• pp.255-260
• /
• 2001

In mammals, most of the follicles can not be ovulated, and instead, are degenerated throughout the entire reproductive period. However, the precise mechanism of follicle atresia is unknown. Three weeks old female mice (ICR strain) were ${\gamma}$-irradiated with a dose of LD$^{50}$ . Before irradiation (day 0) and at day 1, 2, and 3 after irradiation, the normal and atretic preantral and antral follicles of the left ovaries were morphologically observed. Atretic follicles at 2 days after irradiation had numerous cell debris, apoptotic cells and bodies, and polymorphonuclear leukocytes in the antral cavity. In severely atretic follicles, numerous polymorphonuclear leukocytes infiltrated into the follicle. The frequencies of atretic antral (58.0 $\pm$8.6) and preantral follicles (27.3$\pm$11.2) induced by ${\gamma}$-radiation increased to 94.0$\pm$3.4 and 86.9$\pm$7.6, respectively at 2 days after irradiation (p<0.05). The number of follicles with one or more neutrophils in the largest cross sections at 2 and 3 days after irradiation significantly increased (p<0.05). It can be concluded that ${\gamma}$-radiation triggers the recruitment of neutrophils into the follicles during degeneration. The ovarian follicles can make a role of informative biological end-point useful for disaster-prevention.

• Nuclear Engineering and Technology
• /
• v.31 no.4
• /
• pp.385-390
• /
• 1999

Ovarian follicles are faced with one of two fates, atresia or development. Up to 99% of follicles become degenerated rather than ovulated in female life span. Thus, atresia occurs at all stages of follicle development in mammalian ovaries. In the present experiment, the effect of ${\gamma}$-radiation on primordial follicles was morphologically analyzed in a mouse ovary. Thirty-seven percent of the primordial follicles in the non-irradiated control mice ovaries were abnormal. At day 8 post irradiation, most of primordial follicles became atretic. They lost their integrity of architecture in the follicular shape. Then, all the oocytes disappeared from the follicles. And only 3 to 4 granulosa cells lay down onto the basement membrane. Disappearance of granulosa cells or oocytes resulted from the radiation-induced apoptotic process. It is definitely clear that ${\gamma}$-radiation induces rapid apoptotic degeneration of the primordial follicles. The morphological degeneration induced by radiation in the primordial follicles can be used as an experimental model to draw out a deeper insight for radioprotectant researches.

• Journal of Animal Reproduction and Biotechnology
• /
• v.35 no.4
• /
• pp.329-337
• /
• 2020

Cytochrome P450 1A2 (CYP1A2) is a member of the cytochrome P450 superfamily enzymes in mammals and plays a major role in metabolizing endogenous hormones in the liver. In recent days, CYP1A2 expression has been found in not only the liver but also other tissues including the pancreas and lung. However, little information is available regarding the expression of CYP1A2 in the ovary, in spite of the facts that the ovarian follicle growth and atresia are tightly associated with controls of endocrine hormonal networks. Therefore, the expression of CYP1A2 in the ovaries of prepubertal and pubertal rats was investigated to assess its expression pattern and puberty-related alteration. It was demonstrated that the expression level of CYP1A2 was significantly (p < 0.01) higher in the pubertal ovaries than prepubertal counterparts. At the ovarian follicle level in both groups, whereas CYP1A2 expression was less detectable in the primordial, primary and secondary follicles, the strongly positive expression of CYP1A2 was localized in the granulosa cell layers in the antral and pre-ovulatory follicles. However, the ratio of CYP1A2-positive ovarian follicle was significantly (p < 0.01) higher in the ovary of pubertal group (73.1 ± 3.1%) than prepubertal one (41.0 ± 10.5%). During the Immunofluorescence, expression of CYP1A2 was mainly localized in Fas-positive follicles, indicating the atretic follicles. In conclusion, these results suggested that CYP1A2 expression was mainly localized at the atretic follicular cells and affected by the onset of puberty. Further study is still necessary but we hypothesize that CYP1A2 expresses in the atretic follicles to metabolize residue of the reproductive hormones. These findings may have important implications for the fields of reproductive biology of animals.

• Development and Reproduction
• /
• v.4 no.2
• /
• pp.137-145
• /
• 2000

The regulatory mechanisms of the initiation and the formation of ovarian follicles during fetal stage of mammals are largely unknown. In addition to the gonadotropins secreted from pituitary, various growth factors, and steroid hormones are believed to be involved in the differentiation and initiation of growth of primordial follicles consisting of primordial germ cells migrated from yolk sac and streamed cells from mesonephric somatic cells. In human, primordial follicles that have already initiated differentiation at fetal stage undergo either folliculogenesis to ovulate or atresia after growth. Some of primordial follicles remain without growth for 50 years or longer. The objective of this paper is to review the mechanism of the formation, growth arrest, and initiation of primordial follicles in human fetal and neonatal ovaries.