Female Sprague-Dawley derived rats were received at 21 days of age and either sham-operated or ad... more Female Sprague-Dawley derived rats were received at 21 days of age and either sham-operated or adrenalectomized on that day. Half of the animals received either 25 IU pregnant mare's serum gonadotrophin (PMS) or 0.9 saline at 9 AM on the next day; the other half were injected at 26 days of age. On the day of expected ovulation (days 24-25 and days 28-29) the rats were killed at 4-hr intervals and the incidence of ovulation determined. Serum progesterone and corticosterone were measured with the intent of comparing the pattern of these steroids with the timing and incidence of ovulation. Twenty-two-day-old rats given PMS ovulated later (at 0400 on day 25) than did the 26-day-old rats (at 2400 on day 28). Adrenalectomized ADRX rats ovulated later than intact controls at both ages (ovulation complete at 1600 on days 25 and 29, respectively). There was a reduced ovarian weight response to PMS in ADRX rats but uterine weights were not consistently different from intact PMS-treated rats. Associated with the different timing of ovulation and organ weight response in the ADRX rats there was a lower serum progesterone response on days 24-25. In intact PMS-treated rats, the rhythm of the serum corticosterone was different in the two age groups. It is concluded that adrenalectomy alters the normal response to PMS resulting in a delay in the time of ovulation. It is possible that the adrenal normally participates in the induction of ovulation after PMS, possibly by acting as an internal priming agent to facilitate gonadotrophin release in the young rat.
ABSTRACT This chapter considers how best to integrate STEM education into the larger context of t... more ABSTRACT This chapter considers how best to integrate STEM education into the larger context of the undergraduate experience to address important national concerns.
24 and 28 day old rats, raised in a 14 h light: 10 h dark (14:10) cycle, showed a clear serum cor... more 24 and 28 day old rats, raised in a 14 h light: 10 h dark (14:10) cycle, showed a clear serum corticosterone (B) peak at the beginning of the dark period (18.00 h) with an amplitude of 25-30 mug%. Other B values during the 24 h period were lower (9-12 mug%). Rats raised in a 8.5:15.5 cycle had a B peak (after onset of the dark period, at 22.00 h). Rats raised in constant light (LL) showed no variation in B throughout the 24 h. Weanling rats raised in a 8.5:15.5 cycle appeared to synchronize more rapidly to a 14:10 cycle than did rats raised in LL. When placed in LL at weaning, rats raised either in 14:10 or 8.5:15.5 had lost their periodicity by day 24. When rats raised in 8.5:15.5 were shifted to LL or 14:10 after weaning age (day 24), the pattern of response was different. One day after the shift, rats placed in a 14:10 cycle displayed a pattern of B synchronized to the normal 14:10 pattern for rats born and raised in that light cycle. This synchrony persisted for at least 3 days. Rats placed in 14:10 at 21 days of age did not show a fully synchronized pattern until day 28. It can be concluded that weanling rats exposed to a light-dark cycle adapt quickly to a new light cycle and that older prepubertal rats shift even more quickly.
Female Sprague-Dawley derived rats were received at 21 days of age and either sham-operated or ad... more Female Sprague-Dawley derived rats were received at 21 days of age and either sham-operated or adrenalectomized on that day. Half of the animals received either 25 IU pregnant mare's serum gonadotrophin (PMS) or 0.9 saline at 9 AM on the next day; the other half were injected at 26 days of age. On the day of expected ovulation (days 24-25 and days 28-29) the rats were killed at 4-hr intervals and the incidence of ovulation determined. Serum progesterone and corticosterone were measured with the intent of comparing the pattern of these steroids with the timing and incidence of ovulation. Twenty-two-day-old rats given PMS ovulated later (at 0400 on day 25) than did the 26-day-old rats (at 2400 on day 28). Adrenalectomized ADRX rats ovulated later than intact controls at both ages (ovulation complete at 1600 on days 25 and 29, respectively). There was a reduced ovarian weight response to PMS in ADRX rats but uterine weights were not consistently different from intact PMS-treated rats. Associated with the different timing of ovulation and organ weight response in the ADRX rats there was a lower serum progesterone response on days 24-25. In intact PMS-treated rats, the rhythm of the serum corticosterone was different in the two age groups. It is concluded that adrenalectomy alters the normal response to PMS resulting in a delay in the time of ovulation. It is possible that the adrenal normally participates in the induction of ovulation after PMS, possibly by acting as an internal priming agent to facilitate gonadotrophin release in the young rat.
ABSTRACT This chapter considers how best to integrate STEM education into the larger context of t... more ABSTRACT This chapter considers how best to integrate STEM education into the larger context of the undergraduate experience to address important national concerns.
24 and 28 day old rats, raised in a 14 h light: 10 h dark (14:10) cycle, showed a clear serum cor... more 24 and 28 day old rats, raised in a 14 h light: 10 h dark (14:10) cycle, showed a clear serum corticosterone (B) peak at the beginning of the dark period (18.00 h) with an amplitude of 25-30 mug%. Other B values during the 24 h period were lower (9-12 mug%). Rats raised in a 8.5:15.5 cycle had a B peak (after onset of the dark period, at 22.00 h). Rats raised in constant light (LL) showed no variation in B throughout the 24 h. Weanling rats raised in a 8.5:15.5 cycle appeared to synchronize more rapidly to a 14:10 cycle than did rats raised in LL. When placed in LL at weaning, rats raised either in 14:10 or 8.5:15.5 had lost their periodicity by day 24. When rats raised in 8.5:15.5 were shifted to LL or 14:10 after weaning age (day 24), the pattern of response was different. One day after the shift, rats placed in a 14:10 cycle displayed a pattern of B synchronized to the normal 14:10 pattern for rats born and raised in that light cycle. This synchrony persisted for at least 3 days. Rats placed in 14:10 at 21 days of age did not show a fully synchronized pattern until day 28. It can be concluded that weanling rats exposed to a light-dark cycle adapt quickly to a new light cycle and that older prepubertal rats shift even more quickly.
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