Effect of exogenous human chorionic gonadotropin on ovulation in mice

The implementation of assisted reproductive technologies (ART), hormonal stimulation in particular, may change the quality of ovulated oocytes. The purpose of our work was to study ovulation in CD1 mice after their stimulation with human chorionic gonadotropin (hCG) and to investigate the effects of such hormonal stimulation on the pregnancy duration, fetal losses and the weight of the offspring. No significant differences were found in the total number of ovulated oocytes or in the number of immature (without a polar body) ovulated oocytes; nor were there differences between the groups in the number of oocytes with a developing polar body. However, the number of matured oocytes with a distinct polar body was significantly higher (p < 0.05) in mice stimulated with hCG (experimental group) as compared with the controls (6.2 ± 0.86 and 2.2 ± 0.97, respectively). No significant differences were observed between the experimental and control mice in the duration of pregnancy or in the numbers of term offspring, including the percentage of live and stillborn pups. However, the body weight of the offspring in the experimental group was significantly lower (p < 0.001) as compared with the controls on the fifth day after birth (3.16 ± 0.09 and 3.76 ± 0.07, respectively). Thus, exogenous hCG facilitates the development of mouse oocytes in vivo, which leads to the larger number of their mature forms at ovulation, however, the offspring born after hCG-stimulated pregnancy was characterized by a lower body weight on the fifth day after birth

Effects of a high-fat diet on the lipid profile of oocytes in mice

There are evidences that obese women exhibit a detrimental oocyte quality. However, it remains unclear how this change is associated with obesity, indirectly – or directly through a change in the content and/or composition of lipids in oocytes. The aim of this work was to study effects of a high-fat diet applied to female donor mice on the amount and qualitative composition of lipids of immature and in vivo matured oocytes. A high-fat diet caused larger body weight in female mice compared with the control (p < 0.001; 44.77±1.46 and 35.22±1.57, respectively), and increased the blood levels of cholesterol (p < 0.05; 2.06±0.10 and 1.78±0.10, respectively) and triglycerides (p < 0.05; 2.13±0.23 and 1.49±0.21, respectively). At the same time, this diet does not affect the level of unsaturation of lipids in immature (0.207±0.004 in the experiment and 0.206±0.002 in the control) and matured oocytes (0.212±0.005 in the experiment and 0.211±0.003 in the control). Total lipid content increased during in vivo maturation of mouse oocytes. The amount of lipids was greater in mature oocytes in the experimental group compared to the control (p < 0.01; 8.15±0.37 and 5.83±0.14, respectively). An increase in intracellular lipid amount during oocyte maturation was revealed both after a standard diet (p < 0.05; 4.72±0.48 and 5.83±0.14, respectively) and after a fat-rich diet (p < 0.001; 3.45±0.62 and 8.15±0.37, respectively). Thus, during in vivo oocyte maturation in mice the content of intracellular lipids enhanced, the high-fat diet aggravated this dynamics of lipid increase during in vivo maturation of oocytes