Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sequence of events within the ovary during the process of ovulation discussed in this review is schematically represented in Fig. 1. It is obvious that LH, perhaps with some contribution from FSH, is the normal physiological trigger for the ovulatory sequence of events, and it appears from the available information that the effects of LH are mainly mediated via adenylate cyclase and increased cAMP levels. The cAMP in turn, via cAMP-dependent protein kinase, influences at least three distinct steps in the ovulatory process which seem to be of crucial importance, namely 1) the stimulation of steroidogenesis; 2) the stimulation of cyclooxygenase/lipooxygenase leading to increased prostaglandin/leukotriene synthesis; and 3) the stimulation of plasminogen activator which catalyzes the conversion of plasminogen to plasmin. A fourth crucial step in the ovulatory mechanism is the LH-induced increase in latent collagenase, but it remains to be determined if this step is mediated via cAMP. Concomitant with the increase in latent collagenase, there also appears to be an LH-dependent increase in collagenase inhibitors. The latent collagenase is then activated, and it appears that leukotrienes and prostaglandins, as well as plasmin, may be involved in this process. The active collagenase causes a digestion of the collagen in the follicle wall, and plasmin, as well as possibly other proteolytic enzymes such as proteoglycanases, may cause a further dissociation of the follicular wall. These processes of digestion of collagen and dissociation of the collagen fibers result in an opening in the follicular wall with the formation of the stigma and rupture. While the weakening of the follicular wall takes place throughout the entire wall, rupture remains for the most part a localized process at the apex of the follicle. This localization of the rupture may be explained on the basis of mechanical factors operating when the follicle wall thins and weakens. While it is clear that prostaglandins and leukotrienes can influence smooth muscle by causing contractions and that these compounds can cause vascular changes such as increased permeability, vasodilation, and vasoconstriction, it is not clear what the exact role of these latter processes are in ovulation. It appears that progesterone and not estrogen play an important role in the mechanism of LH-induced follicular rupture, but the locus of action of progesterone and its mechanism of action remains to be determined.(ABSTRACT TRUNCATED AT 400 WORDS)
Steroids 1989 Nov
PMID:Mechanism of mammalian ovulation. 255 97

Surface cell changes at the apices of preovulatory follicles and ovulations were documented in isolated perfused ovaries from immature rats treated with pregnant mare serum gonadotropin (20 IU) and 48 h later with human chorionic gonadotropin (hCG) (10 IU). A video camera coupled to an inverted microscope and a video recorder captured the preovulatory and ovulatory events at a cellular level. At around 8 h post-hCG, the follicular apex changed from a smooth and optically homogeneous appearance into a rough surface with bleb formation and extrusions of single cells through minute perforations (early stigma formation). At approximately 10 h, a sticky material formed a basketlike structure with trapped cells (late stigma formation). At 12 to 15 h, ovulation took place at a constant speed and with no contractions of the follicular wall. This indicates that ovulation can occur with no visible circumfollicular muscular activity. Furthermore, the observations of a leakage of cells over an extended period of time indicates that the follicular wall is partly digested several hours before ovulation occurs.
Steroids 1989 Nov
PMID:Ovulation in the isolated perfused rat ovary as documented by intravital microscopy. 261 44