Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0277787 (stigma)
 13,352 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The connective tissue matrix of the wall of ovarian follicles is degraded and remodeled during ovulatory rupture and formation of the corpus luteum. Ovarian surface epithelial cells in close contact with the apical wall of preovulatory ovine follicles secrete a urokinase-type plasminogen activator in response to surge levels of gonadotropins. Urokinase activates latent collagenases and stimulates release of tumor necrosis factor alpha from thecal endothelium. Tumor necrosis factor alpha progressively induces matrix metalloproteinase gene expression, apoptosis, and inflammatory necrosis. Collagenolysis and cellular death are a prelude to stigma formation and ovarian rupture. Ovulation is blocked by intrafollicular injection of TNFalpha or MMP-2 antisera. Unruptured follicles luteinize but are deficient in collagenous/vascularized trabeculae, and produce less progesterone than their control luteal counterparts. It appears that TNFalpha, via MMP-2 induction, contributes to the reorganization of an ovulatory follicle into a fully competent corpus luteum.
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PMID:Proteolytic mechanisms in the ovulatory folliculo-luteal transformation. 1294 4

The ovulatory process is extraordinary in that it constitutes a hormone-induced injury. Gonadotropin delivered via the follicular vascular wreath stimulates secretion of plasminogen activator by contiguous ovarian surface epithelial cells. A consequent elevation in interstitial plasmin activates collagenases and cleaves tumor necrosis factor alpha from its anchors on endothelium. Collagen fibril degradation and cellular death at the apex of the preovulatory follicle are hallmarks of impending ovulation. Follicular contractions rupture the weakened fabric at the apex, and the ovum, which has been disconnected from the underlying granulosa, is expelled; these components of the cascade are prostaglandin-mediated. Ovulation is required for fertility; unfortunately, it imparts a cancer risk to the ovarian surface epithelium. DNA-damaging reactive oxygen species are generated by inflammatory cells attracted into the vicinity of the ovulatory stigma. An ischemia-reperfusion flux coincident with ovulation and wound repair also contributes to genotoxicity. Potentially mutagenic lesions in DNA are normally reconciled by TP53 tumor suppressor-dependent cell-cycle arrest and base excision repair mechanisms; it is a unifocal escape that could be problematic. Epithelial ovarian cancer is a deadly insidious disease because it typically remains asymptomatic until it has metastasized to vital abdominal organs.
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PMID:Mechanisms and pathobiology of ovulation. 2175 73