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Category: Puberty

Effects of Melengestrol Acetate on Onset of Puberty: DISCUSSION(3)

Although the stimulatory effects of progestins reported in this and other studies are novel, they do not contradict the concept that physiological levels of progesterone organize the estrous cycle via negative feedback action on LH release. It is important to note that the doses of progestins used to enhance onset of puberty are probably much […]

Effects of Melengestrol Acetate on Onset of Puberty: DISCUSSION(2)

Our observation that pulsatile LH secretion is increased following MGA withdrawal is similar to that of Anderson and coworkers, who described an increase in LH pulse frequency in prepubertal heifers after norgestomet withdrawal. Recently, Anderson et al. proposed a mechanism whereby progestins might enhance pulsatile release of LH in prepubertal heifers. According to their hypothesis, […]

Effects of Melengestrol Acetate on Onset of Puberty: DISCUSSION(1)

Administration of MGA to prepubertal heifers for 8 days increased the number of heifers attaining puberty within 10 days after treatment. This effect was associated with an increase in pulsatile LH secretion and growth of the largest ovarian follicle. Our data support the claim that progestin treatment hastens the onset of puberty by enhancing the […]

Effects of Melengestrol Acetate on Onset of Puberty: RESULTS(2)

Analysis of covariance of mean LH concentrations revealed a treatment X time interaction (p = 0.0001). On Days 0 and 7, mean LH was not different (p = 0.071 and 0.112, respectively) between CON animals and MGA-treated animals (Fig. 3). On Day 9, mean LH was higher (p = 0.003) in MGA-treated animals than in […]

Effects of Melengestrol Acetate on Onset of Puberty: RESULTS(1)

Effect of MG A on Puberty Induction Before MGA treatment, corpora lutea or elevated concentrations of progesterone were not detected in any heifers. Within 10 days of MGA withdrawal, all of the MGA-treated heifers had ovulated, whereas only 4 (44%) of the CON heifers had ovulated (p = 0.013). Of the 4 CON heifers that […]

Effects of Melengestrol Acetate on Onset of Puberty: MATERIALS AND METHODS(4)

Approximately 5 ml of blood was drawn for analysis of progesterone concentrations. Each sample was collected into a tube containing 100 |xl of 0.16 M EDTA. Blood was kept on ice until centrifugation (1770 X g) at 4°C for 17 min. Blood plasma was pipetted off and stored at -20°C until assayed for progesterone using […]

Effects of Melengestrol Acetate on Onset of Puberty: MATERIALS AND METHODS(3)

In addition to sequential blood sampling, blood samples were drawn via jugular venipuncture 12 days and 1 day before initiation of MGA and on Mondays, Wednesdays, and Fridays for 3 wk after MGA withdrawal. These samples were used to monitor circulating concentrations of progesterone and thus determine luteal function. asthma inhalers In order to detect […]

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