Quantitation of nexus junctions in the granulosa cell layer of rabbit ovarian follicles during ovulation.

Electron microscopy was used in a semi-quantitative study to determine changes in the abundance and size of surface nexuses and changes in the abundance of interiorized nexuses in growing and mature ovarian follicles during the ovulatory process. Mature follicles contain larger granulosa cells than follicles in the early stage of antral formation. Also, the granulosa cells of mature follicles have a slightly greater number of surface nexuses (without a change in nexus length), and more interiorized nexuses, compared to immature follicles. As a mature follicle approaches rupture, there is an appreciable decrease in the number of surface nexuses per granulosa cell. There is also a slight reduction in the number of interiorized nexuses at this time. It is concluded that this decrease in both surface nexuses and interiorized nexuses may be a consequence of ovulatory changes during which the rate of granulosa cell division is greater than the rate of formation of new nexuses. Additionally, the disruption to cell-to-cell cohesion during the ovulatory process appears to be independent of the interiorization of surface nexuses.

An inexpensive filtration unit and manifold for radioligand binding studies.

An inexpensive filtration manifold for radioligand binding studies is described. The manifold can be for any number of filter units, is inexpensive to produce, and is easy to use. The filter units are produced from Swinnex 25-mm syringe filter units. The radioligand binding curve for [3H] QNB to guinea pig ventricle membrane fraction shows that the unit produces consistent results.

Effects of ovulation on the conduction and contraction velocities in rabbit oviduct: contrasts between longitudinal and circular muscle.

The contraction and electrical conduction velocity of the longitudinal and circular muscle of the oviduct from rabbits in estrus, 24 or 72 h following administration of human chorionic gonadotropin (hCG) or 14 days following castration have been compared. Two populations of conduction and contraction velocities were identified, with the faster velocity being associated with the longitudinal muscle. There was a large overlap between longitudinal and circular contraction, suggesting complex relationships between longitudinal and circular muscle. From the results it appears that during ovum transport the circular velocities increased, with the slowest rates at estrus. The values obtained 72 h following hCG injection most closely resembled those in the castrate group of animals. In the longitudinal orientation, however, the velocities were greater 24 h following hCG injection than at estrus or 72 h following hCG injection, suggesting a complex relationship between both longitudinal and circular muscle of the oviduct following ovulation.

Effect of ovulation on the ionic and water content of rabbit oviduct.

The water content, extracellular space, intracellular water, potassium, sodium and chloride content of oviduct and uterus removed from rabbits in estrus and 24 and 72 h following hCG injection have been determined. Following ovulation, there was an increase in water content of the region of the oviduct corresponding to the ampullary -isthmic junction which, at 24 h, is probably due to increased intracellular water. In the ampullary-isthmic junction, ovulation decreases the potassium content and, at 24 h in the isthmic region of the oviduct, chloride is reduced. The water and ionic content of mucosa and smooth muscle cells has been calculated and mucosa cells have greater intracellular water and chloride and sodium content and less potassium and extracellular space than the smooth muscle cells of the oviduct. The significance of the changes in ionic and water content is discussed.

Role of prostaglandins in contractile activity of the ampulla of the rabbit oviduct.

Contractile activity of the ampulla of rabbit oviducts removed 24 h after an ovulating injection was studied in vitro. Spontaneous activity, field-stimulated activity, and response to phenylephrine were studied in normal, reversed, and scraped (endosalpinx removed) sections of tissues in the presence or absence of inhibitors of prostaglandin synthetase (8 or 51 micrograms/ml indomethacin or 10 or 100 micrograms/ml 5,8,11,14-eicosatetraynoic acid (ETA)). The effects of in vivo treatment with 10 mg/kg of indomethacin on the same responses were examined. Scraped tissues produced more prostaglandin E and F (measured by radioimmunoassay) than did normal tissues, and this production was suppressed by 10 micrograms/ml of indomethacin or 100 micrograms/ml of ETA. Production of prostaglandin by normal tissues was not depressed by these compounds in vitro, but was significantly reduced by pretreatment of the animals with indomethacin in vivo. In the absence of the endosalpinx, the myosalpinx exhibited spontaneous activity and responded to field stimulation and phenylephrine. Scraped and reversed tissues, however, showed a faster decline in response to field stimulation than normal tissues, and this was due to the traumatization. By contrast, traumatization increased the sensitivity of the tissue to respond to phenylephrine. Inhibition of prostaglandin synthetase by low doses of indomethacin or ETA prevented desensitization of the tissue to field stimulation, but this desensitization was little affected by the higher doses of indomethacin in vitro or in vivo. ETA did not affect the phenylephrine dose-response curves and nor did 8 micrograms/ml of indomethacin, whereas the high dose was inhibitory. Spontaneous activity was only affected by the in vivo pretreatment with indomethacin, which prevented the decline in activity of scraped tissue with time.

Effects of tension and transmural stimulation on prostaglandin production by estrous rabbit oviductal isthmus.

The effect of longitudinal and circular stretch on the amounts of Prostaglandin F (PGF) and Prostaglandin E (PGE) found in the fluid bathing rabbit oviductal isthmus has been investigated. It was found that the amounts of PGE and PGF measured in the bathing fluid of longitudinally or circularly stretched tissues were negatively correlated to the maturity of the animal. Prostaglandin E increased with time in the tissues under longitudinal and circular tension. Prostaglandin F also increased with time under longitudinal tension but remained fairly constant under circular tension. Increasing the load from 0.5 to 2.0 g had no significant effect on PGE found under longitudinal or circular tension or on PGF found under longitudinal tension. Under circular tension, PGF found increased. Transmural stimulation at 20 Hz increased PGE 8-fold over control values while PGF increased only 1 to 3-fold. It is suggested that distension of the rabbit oviductal isthmus results in increased PGF production, which could be important in ovum transport.