The effects of cervical dilation on plasma PGFM, progesterone and the duration of luteal function in diestrous mares.

Transcervical diagnostic techniques may alter the length of the equine estrous cycle and affect subsequent luteal function. Therefore, nine mares were used to determine the effect of cervical dilation on plasma 13, 14-dihydro, 15-keto-prostaglandin F(2) (PGFM), progesterone (P(4)) and posttreatment duration of luteal function. Mares were given a daily score of 0 to 4 based on sexual receptivity. Five days following the end of receptivity, mares were randomly assigned to one of three, 3 x 3 latin squares. Control mares received no cervical dilation. Cervically stimulated mares recieved cervical dilation for 60 sec. Cervically stimulated plus inhibitor mares were dilated similarly to cervically stimulated mares, but received a prostaglandin synthetase inhibitor 30 min prior to treatment. Each mare completed all three treatments in three consecutive estrous cycles. Plasma PGFM and P(4) were determined by RIA. Plasma PGFM was lower (P<0.05) in cervically stimulated plus inhibitor than control and cervically stimulated mares. In addition, plasma P(4) was lower (P<0.10) in cervically stimulated plus inhibitor than in control and cervically stimulated mares. Luteal function following treatments did not differ. These data indicate that neither plasma PGFM and P(4) nor the duration of luteal function were affected by cervical dilation. However, administration of a prostaglandin synthetase inhibitor prior to cervical dilation decreased plasma PGFM and P(4) concentrations.

Relationship of plasma beta-carotene and vitamin A to luteal function in postpartum cattle.

The influence of plasma concentrations of beta-carotene and vitamin A on in vivo progesterone production by bovine corpora lutea after gonadotropin-releasing hormone-induced LH release was assessed in 39 postpartum dairy cows. Thirty Holsteins and nine Jerseys were given 100 micrograms gonadotropin-releasing hormone on d 12 of an estrous cycle, which began from 30 to 49 d postpartum. Concentrations of beta-carotene and vitamin A in plasma and progesterone and LH in serum were determined prior to gonadotropin-releasing hormone injection (0 h); serum progesterone and LH concentrations were also determined 1, 2, and 3 h after injection of gonadotropin-releasing hormone. Serum concentrations of progesterone and LH were increased by gonadotropin-releasing hormone. Incremental progesterone production in an analysis of covariance was influenced by breed as well as the interactions of breed with vitamin A, of season with beta-carotene, and of season with vitamin A. The regression coefficients were positive for beta-carotene and negative for vitamin A in all cases. In conclusion, luteal function in the postpartum cow appears to be related to plasma concentrations of beta-carotene and vitamin A.

Protein S and thrombosis.

Thrombosis is a serious problem in the United States. Activated protein C is a vitamin K-dependent serine protease that seems to be an important regulator of the hemostatic process. Protein S is another vitamin K-dependent protein that is essential for the expression of the anticoagulant activity of activated protein C. Evidence suggests that defects in either of these proteins may be related to the development of thrombosis. Therefore, the accurate measurement of these proteins is important in the study and in the treatment of thrombosis. Sixty percent of the protein S found in human plasma is bound to the complement component C4b-binding protein, and when in this complex, protein S is inactive. The remaining 40 percent is the free, functional form of protein S. This paper describes the measurement of both free and total protein S by two types of assays. The first assay involves immunoelectrophoresis, also known as the Laurell Rocket method. The second assay is a capture enzyme linked immunosorbent assay (ELISA). The two assays are compared as to relative ease and cost.

Effect of beta-carotene and vitamin A on progesterone production by bovine luteal cells.

The relationship between concentrations of plasma vitamin A and c-carotene and corpora lutea was studied using 52 Holstein cows. Bovine luteinizing hormone was added to incubation tubes in doses of 0, 10, or 100 ng/ml. Regression of progesterone secretion by luteal cells in vitro on plasma beta-carotene was positive and significant for corpora lutea collected during the winter months when plasma beta-carotene was low. The two were unrelated during the summer months when beta-carotene was higher. Similar regressions for in vitro progesterone production and vitamin A were not significant in either season. These results suggest that in vivo beta-carotene status is related to bovine luteal function in vitro.