| 1. |
- Piontkewitz, Y, et al.
(author)
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The expression of c-myc during follicular growth and luteal formation in the rat ovary in vivo.
- 1997
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In: The Journal of endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 152:3, s. 395-406
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Journal article (peer-reviewed)abstract
- The processes of folliculogenesis and formation of corpora lutea involve proliferation and differentiation of the follicular cells. The expression of several oncogenes is associated with the proliferative phase in many cell types. The present study examined the expression and hormonal regulation of the c-myc proto-oncogene during follicular development and the luteal phase of pseudopregnancy. Follicular development was initiated by pregnant mare's serum gonadotropin (PMSG) in immature rats followed two days later by the injection of human chorionic gonadotropin (hCG) to induce ovulation and luteal formation. Ovaries were collected at different time points and the content and distribution of c-myc mRNA/protein were examined. C-myc increased rapidly after the administration of both PMSG and hCG, but the effect of PMSG was less pronounced. The increase after PMSG was transient and localized primarily to the granulosa cells of developing follicles. The ovulatory dose of hCG resulted in a rapid and substantial increase of c-myc mRNA and protein with maximal levels at 1 h and 2-4 respectively. At this stage, the c-myc protein was localized to the follicular cells, the surface epithelium and, to some extent, to the interstitial tissue. There was a subsequent decrease prior to ovulation. The luteal phase was characterized by decreasing levels of c-myc with increasing luteal age. In order to examine the involvement of specific hormones in the regulation of c-myc, hypophysectomized, immature rats were injected sequentially with estradiol (E2) and follicle-stimulating hormone (FSH). Hypophysectomy resulted in a decrease of c-myc compared with intact animals. The administration of E2 resulted in an increase of c-myc mRNA and protein. The subsequent treatment with FSH did not result in a further increase and the levels remained at the same level as with E2 only. However, an ovulatory dose of hCG to E2 and FSH primed animals resulted in an additional increase of c-myc mRNA and protein. The levels after E2 and FSH were considerably lower compared with those of untreated ovaries of intact, immature animals, suggesting the involvement of other endocrine and paracrine factors. The presence of proliferating cell nuclear antigen in cell extracts indicated that the expression of c-myc was associated with phases of increased proliferation of follicular cells after hormonal stimulation. The results demonstrate that c-myc is regulated by hormones (E2, gonadotropins) in the rat ovary during follicular development to the preovulatory stage. The pronounced increase prior to ovulation also suggests a role for c-myc in the regulation of proliferative events involved in luteal formation.
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| 2. |
- Sundfeldt, Karin, 1962, et al.
(author)
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E-cadherin-catenin complex in the rat ovary: cell-specific expression during folliculogenesis and luteal formation.
- 2000
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In: Journal of reproduction and fertility. - : Bioscientifica. - 0022-4251. ; 118:2, s. 375-85
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Journal article (peer-reviewed)abstract
- The cadherins and their cytoplasmic counterparts, the catenins, form the adherens junctions, which are of importance for tissue integrity and barrier functions. The development and maturation of the ovarian follicle is characterized by structural changes, which require altered expression or function of the components involved in cell-cell contacts. The present study examined the cell-specific localization and temporal expression of epithelial cadherin (E-cadherin) and alpha- and beta-catenin during follicular development, ovulation and corpus luteum formation in the immature gonadotrophin- and oestrogen-stimulated rat ovary. Immunohistochemistry and immunoblotting demonstrated the expression of E-cadherin in theca and interstitial cells of immature ovaries before and after injection of equine chorionic gonadotrophin (eCG). E-cadherin was not detected in granulosa cells, except in the preantral follicles located to the inner region of the ovary. The content of E-cadherin in theca and interstitial cells decreased after an ovulatory dose of hCG. Granulosa cells of apoptotic follicles did not express E-cadherin. Oestrogen treatment (diethylstilboestrol) of immature rats for up to 3 days did not result in a measurable expression of E-cadherin in granulosa cells. alpha- and beta-catenin were expressed in all ovarian compartments. The concentration of beta-catenin was constant during the follicular phase, whereas the content of alpha-catenin decreased in granulosa cells after treatment with diethylstilboestrol or hCG. The expression of alpha-catenin was also reduced in theca and interstitial cells after hCG. alpha- and beta-catenin were present in most ovarian cells at all stages of folliculogenesis. Therefore, the catenins have the potential to associate with different members of the cadherin family and to participate in the regulation of cytoskeletal structures and intracellular signalling. The restricted expression of E-cadherin in granulosa cells of preantral follicles indicates a role in the recruitment of these follicles to subsequent cycles. The specific decrease of alpha-catenin in granulosa cells and the reduction of both alpha-catenin and E-cadherin in theca cells of ovulatory follicles might reflect some of the molecular changes in cell-cell adhesion associated with ovulation and luteinization.
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