Effect of gonadotrophin dose on oocyte retrieval in superovulated BALB/c mice.

Mice are commonly used animal models in reproductive and developmental research. In order to get satisfying results from such experiments, large numbers of ova must be available and this can be achieved by using various ovulation induction protocols. To obtain an optimal response from these stimulation protocols, parameters such as breeding-housing conditions of the animal strains, the best age for superovulation, and type and dose of gonadotrophins must be optimized. The aim of this study was to investigate the impact of exogenous stimulation with increasing amounts of gonadotrophins on the number and quality of oocytes/pre-embryos recovered from outbred BALB/c mice. A dose-response analysis was performed by stimulating prepubescent (21- to 25-day-old) and sexually mature (6 to 8 weeks old) female mice with hMG, which contains equal amounts of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The stimulation dose contained 5, 10, 15, 20, 25 or 30 IU of FSH/LH. The effect of increasing stimulation was assessed by monitoring the number and maturity of ova recovered from the tubes. The data were analyzed by using a one-way Anova test and student t-test. Increasing stimulation doses in the prepubescent females resulted in an increased number of ova. A maximum of 55 ova per mouse was reached when stimulating with 20 IU of FSH/LH; higher stimulation doses showed no further increase in oocyte recovery. In the prepubescent group, a maximal number of recovered mature ova was reached with 15 IU of FSH/LH. In the sexually mature female group, 20 IU of FSH/LH gave the best quantitative and qualitative results. Positive effects of copulation on the number and maturity of oocytes in all induction doses were more evident in the prepubescent females and these parameters were significantly more improved (P < 0.05) in this group when compared to the pubertal females. Our findings led to the conclusion that ovulation induction of prepubescent outbred BALB/c mice with 15 IU FSH/LH and sexually mature ones with 20 IU FSH/LH give the best results in terms of oocyte number and maturity.

The ionic basis of membrane potential changes from before fertilization through the first cleavage in the egg of the frog Rana cameranoi.

Experiments were performed to identify the ionic basis of membrane potential changes in the Rana cameranoi egg, from prior to fertilization through the first cleavage. The membrane potential was monitored continuously during this period. Ten per cent Ringer was used as the recording solution in the control group. The effects of Na+ or Ca2+ conductances were observed by altering external concentrations of these ions. K+ and Cl- conductances were tested by adding channel blockers of these ions (TEA and SITS, respectively) to the extracellular medium. The resting potential of the unfertilized egg is mainly affected by K+ conductance. Chloride conductance is responsible for the depolarization phase of the fertilization potential evoked by sperm entry, and K+ conductance is responsible for the repolarization phase of this potential. We suggest that Na+ permeability does not directly contribute to the fertilization potential; however fertilization potential peak is significantly reduced upon a reduction of extracellular sodium. The fertilization potential is not significantly influenced by extracellular Ca2+, and eggs fertilized in calcium-free solutions maintain their normal development; these results suggest that extracellular Ca2+ does not significantly contribute to the electrical and mechanical blocks that prevent polyspermy. The membrane potential of the fertilized egg does not alter significantly until the first cleavage. Potassium conductance contributes to hyperpolarization generated upon the first cleavage, whereas sodium is the basic ion responsible for the phase which follows peak hyperpolarization, and which plays a role in the return of the post-cleavage membrane potential to a steady level. Cl- conductance, which is important as the ionic basis of the fertilization potential, does not significantly influence any parameter of the cleavage cycle.

Effects of static magnetic field on specific adenosine-5'- triphosphatase activities and bioelectrical and biomechanical properties in the rat diaphragm muscle.

In this study, we aimed to clarify the effects of chronically applied static magnetic field (200 Gauss) on specific ATPase activities and bioelectrical and biomechanical responses in isolated rat diaphragm muscle. The mean activities of Na(+)-K+ ATPase and Ca2+ ATPase determined from the diaphragm homogenates were significantly higher in the magnetic field exposed group (n = 20), but that of Mg2+ ATPase was nonsignificantly lower compared to the control group (n = 13). Resting membrane potential, amplitude of muscle action potential, and overshoot values (mean +/- SE) in the control group were found to be -76.5 +/- 0.6, 100 +/- 0.8, and 23.5 +/- 0.6 mV, respectively; these values were determined to be -72.8 +/- 0.4, 90.3 +/- 0.5, and 17.2 +/- 0.4 mV in the magnetic field-exposed group, respectively. The latency was determined to increase in the experimental group, and all the above-mentioned bioelectrical differences between the groups were significant statistically. Force of muscle twitch was found to decrease significantly in the magnetic field-exposed group, and this finding was attributed to the augmenting effect of magnetic field on Ca2+ ATPase activity. These results suggest that magnetic field exposure changes specific ATPase activities and, thence, bioelectrical and biomechanical properties in the rat diaphragm muscle.

Endogenous digoxin-immunoreactive substance in normal and preeclamptic pregnancies.

AIMS: To determine the potential use of a digoxin-immunoreactive substance in the prediction of preeclampsia, to study the relationship between serum levels of this substance and gestational age, and to evaluate the correlation between this substance and blood pressure findings in preeclamptic pregnancies. METHODS: Serum digoxin-immunoreactive substance concentrations were measured by RIA (double antibody radioimmunoassay) in normotensive (n = 14) and preeclamptic (n = 17) pregnant women in their third trimesters. Statistical evaluation was performed with the Mann-Whitney U-test and correlation-regression analysis. RESULTS: The mean (+/- S.E.) digoxin-immunoreactive substance levels in the normal and preeclamptic patients were 0.29 +/- 0.06 and 0.31 +/- 0.05 ng/ml, respectively, the slightly higher level in the hypertensive group being statistically non-significant. Serum digoxin-immunoreactive substance levels did not demonstrate good correlation with gestational age and systolic blood pressure in preeclamptic pregnancies. CONCLUSIONS: An endogenous digoxin-immunoreactive substance is present in the sera of third trimester pregnant women, but it does not contribute to the pathogenesis or prediction of preeclampsia.