Eppig, 1977Eppig, , 1979Bachvarova et al., 1980

No abstract

We have recently demonstrated an alteration in the levels of G-proteins and their correlation with adenylyl cyclase in spontaneously hypertensive rats (SHR). In the present studies we examined if the other models of hypertensive rats, such as DOCA-salt hypertensive rats (HR), also exhibit the similar alterations in G-protein and in adenylyl cyclase activity. We have determined the adenylyl cyclase activity stimulated and inhibited by hormones, as well as the levels of G-proteins using specific antibodies and cDNA probes in the hearts from DOCA-salt HR and their sham-operated controls after 2 and 4 weeks of treatment. Adenylyl cyclase activity stimulated by GTP gamma S, isoproterenol, and glucagon was significantly decreased in heart sarcolemma from DOCA-salt HR as compared to their controls after 2 and 4 weeks of treatment. In addition, the inhibitory hormones inhibited the enzyme activity to a greater extent in hypertensive rats than controls. Furthermore, the levels of Gi alpha-2 and Gi alpha-2 mRNA, as determined by immunoblotting and Northern blotting techniques, respectively, were higher in hearts from DOCA-salt HR. However, the levels of G8 alpha 45 were decreased in these rats. These results indicate that, similar to SHR, the hearts from DOCA-salt HR exhibit the increased expression of Gi, however unlike SHR, the expression of G8 was decreased. It is suggested that the altered expression of G-proteins may partly be responsible for the decreased responsiveness of adenylyl cyclase to hormone stimulation and increased responsiveness to hormone inhibition in DOCA-salt hypertension.

SUMMARYThus, two steps may be considered in complete oocyte maturation : i. The resumption of meiosis by rupture of the inhibitory effect of the granulosa layer. This is not basically dependent on gonadotropins.2 . On the contrary, passage of the male pronucleus growth factor, or its precursor, inside the oocyte is gonadotropic-follicular dependent.These processes are both the necessary prerequisites to normal fertilization, and they can be activated in a pure in vitro system. The follicle constitutes a balanced physiological unit, the oocyte preventing luteinization of the granulosa and theca cells (N>a KO r,A and N A r, BANDOV , 1971 ), and the granulosa, the resumption of oocyte meiosis (F OO TE and Txisaur.T, ig6g

Summary ― In vitro fertilization assays were performed to investigate their validity in evaluating artificial insemination (Al) bull fertility. A total of 1 532 oocytes, collected from ovaries at the abattoir, were subsequently used in a 4 x 6 x 2 factorial design: 4 doses of heparin added into the capacitation and fertilization medium (0; 0.05; 0.1 and 0.2 pg/ml), 6 different bulls with known on-field nonreturn (NR) rates (range: 64.6-75.3%) and 2 different ejaculates for each bull, collected within a approximately 1-month interval. Oocytes were considered fertilized when 2 pronuclei (or more) were seen in the ooplasm. Both the heparin dose and bull exerted a highly significant effect on the in vitro fertilization (IVF) rates which ranged, per oocyte group, from 30-80%; bull x dose of heparin interaction was significant (P < 0.001 The 0.05 pg/ml dose of heparin was optimal for discriminating individual bulls. At that dose, the correlation coefficients between the bulls, NR rates and the IVF rates from each ejaculate (within-bull or the mean of two ejaculates), were highly significant (r = 0.83).