Acute effects of unilateral ovariectomy on follicular development in the cyclic hamster

Hamsters were hemispayed at 09:00 h on Day 3 of the cycle (Day 1 equal to ovulation) and were killed 1 h after injection of [3H]thymidine at 09:00, 12:00, 17:00 or 22:00 h. Unilateral ovariectomy had no effect on the number of Stage 1 or Stage 2 follicles, but there were significantly fewer Stage 3 follicles between 10:00 and 13:00 h. This decrease was not encountered in intact hamsters and was reflected in an increase in the number of Stage 6 (antral) follicles. At 13:00 h there was no difference in the number of atretic follicles between the experimental and control groups. It is concluded that preantral follicles with 6-7 layers of granulosa cells were recruited within 4 h after unilateral ovariectomy and transformed into antral follicles.     

Effects of unilateral ovariectomy on follicular development and ovulation in cattle

In a study of 4 cyclic dry cows (Trial I) and 6 cyclic puberal heifers (Trial II), unilateral ovariectomy increased the number of ovulatory follicles, did not alter the hormone profile, cycle length or the number of follicular waves. Ovarian follicular development in all 4 cows was monitored daily using transrectal ultrasonography until the day of ovulation, during which period daily blood samples were also taken from the tail vein for determination of plasma FSH, LH and P4 concentrations. Unilateral ovariectomy was performed on the day after ovulation and ovarian activity was again monitored daily (ultrasonography and blood sampling for FSH, LH and P4) for 2 consecutive cycles (8 cycles in all). Estrus in all 6 heifers was synchronized using 2 injections of PGF2 alpha given 12 d apart. Similarly, ovarian activity in the 6 puberal heifers was monitored daily using ultrasonography and blood sampling for 1 complete control cycle. Following estrus and ovulation the left ovary was removed in all the animals, and thereafter 1 complete cycle was followed. Mean cycle length, FSH, LH and P4 concentrations before and after unilateral ovariectomy were compared using paired sample t-test. The results show that unilateral ovariectomy neither altered the cycle length nor the number of follicular waves in the cows, but it increased the number of ovulatory follicles (2 follicles developed and ovulated in 6 of the 8 cycles). The mean diameter of the largest follicle was 16.1 +/- 0.9 mm and the second largest 12.5 +/- 0.9 mm. No significant (P > 0.05) differences were observed in FSH (0.72 +/- 0.09 vs 0.71 +/- 0.07), LH (0.42 +/- 0.1 vs 0.37 +/- 0.07) and P4 (2.8 +/- 0.6 vs 2.6 +/- 0.4) levels before and after unilateral ovariectomy. Of the 6 heifers, 5 had 2 waves and 1 heifer had 3 waves of follicular growth during the control cycle, and this pattern did not change after the procedure. Mean cycle length (20.7 +/- 0.9 vs 21 +/- 0.9) did not differ before and after unilateral ovariectomy, and 4 of the 6 heifers ovulated twin follicles following ovariectomy. The mean diameter of the largest follicle was 14.5 +/- 0.7 mm and second largest measured 12.1 +/- 0.8 mm. No significant (P > 0.05) differences were observed in FSH (0.16 +/- 0.09 vs 0.21 +/- 0.07), LH (0.11 +/- 0.1 vs 0.15 +/- 0.07) and P4 levels (3.6 +/- 0.26 vs 3.8 +/- 0.29) before and after unilateral ovariectomy. Based on these results, we conclude that unilateral ovariectomy is an ideal method for obtaining twin ovulations in cows and heifers.     

Compositional changes in the rat femur following ovariectomy

Ovariectomy has been shown to produce osteoporosis in the femur of the rat. 11-month-old Sprague-Dawley rats were either ovariectomized or given a sham operation. The loss of calcium in the femur of the rats was compared with two indices of osteoporosis, the ponderal index and the femur score. The calcium content was more closely associated with the femur score (r = 0.5, p = 0.0064) than with the ponderal index (r = -0.367, p = 0.05). An accelerated rate of fat deposition in the ovariectomized rat femur reduced the femur weight loss, which resulted in a barely significant association of calcium content with the ponderal index.     

Short- and long-term effects of hypophysectomy and unilateral ovariectomy on ovarian follicular populations in sheep

The effects of hypophysectomy and unilateral ovariectomy on the total number of follicles with greater than 3 layers of granulosa cells were determined at 4 and 70 days following treatment. The population of preantral follicles (less than 0.23 min diam.) was found to be under the control of gonadotrophins but such control was only evident on a long-term basis. At 70 days after unilateral ovariectomy there was a large increase in the number of preantral follicles but at 70 days after hypophysectomy there was a large decrease. The population of antral follicles (greater than 0.23 mm diam.) was under the immediate control of gonadotrophins. By 4 days after hypophysectomy all large antral follicles had become atretic and the number of antral follicles was further decreased at 70 days after treatment. At 70 days after unilateral ovariectomy there was an increase in the number of antral follicles. The follicular growth rates at 70 days following treatment were decreased in hypophysectomized ewes but increased in ewes after unilateral ovariectomy.     

Compensatory responses after unilateral ovariectomy in rabbits

Compensatory ovarian and gonadotropic responses to unilateral ovariectomy (ULO) were examined in the rabbit doe, an induced ovulator. On Days 2, 4, 5, 6, 8, 10, 15 and 20 after ULO, ovaries from 3 hemiovariectomized does and 1 sham-hemiovariectomized doe were examined macro- and microscopically for number, size and signs of atresia of follicles. The number of surface follicles increased initially to 7 or 8 follicles 2 days after ULO, followed by an increase to 10 or more follicles by Day 15 (control ovaries had 5.7 +/- 0.4 follicles). Total numbers of antral follicles and the proportion of follicles which were atretic did not vary relative to day after ULO. However, distributions of antral follicles in classes of 0.2-mm increments were significantly different between sham-ovariectomized and hemiovariectomized does after Day 2 due to shifts of follicles into larger size classes. Peripheral serum concentrations of follicle-stimulating hormone (FSH), but not luteinizing hormone (LH), increased temporarily during the 48 h after ULO. Follicular compensation after ULO in the doe entailed nonlinear increases in numbers of preovulatory follicles, due to increased growth within the antral population of follicles, probably the result of an acute surge of FSH. A period of more than 10 days was necessary to restore the number of preovulatory follicles after ULO. Exogenous human chorionic gonadotropin (hCG) induced ovulation of recruited follicles.     

Acute effects of unilateral ovariectomy in the baboonPapio cynocephalus

The purpose of this study was to determine if steroids secreted by one ovary affected the steroid secretion of the other ovary by direct transportation of the steroids via uterine blood vessels. Either two or three baboons were scheduled for ovariectomy on the day of ovulation and on alternate days from 1–15 days before the expected day of ovulation. Two days before the scheduled ovariectomy, utero-ovarian vein blood from both sides was collected by the use of a laparoscope. Measurement of estradiol (E₂) was carried out in these samples. The ovary with a higher concentration of E₂ was designated the dominant side. At the time of ovariectomy utero-ovarian vein and uterine vein blood from the two sides was again collected. After removal of the dominant side ovary another sample of utero-ovarian and uterine vein blood was collected. The interval between removal of one ovary and blood collection from the contralateral side ranged from 2–15 min. Steroids E₂, progesterone (P), testosterone (T), and androstenedione (A) were measured in the blood plasma. Of the 21 baboons 12, 12, 11, and 10 baboons showed an increase in E₂, P, T, and A values, respectively, on the contralateral side after unilateral ovariectomy. The time elapsed between pre-ovariectomy blood collection and post-ovariectomy blood collection as well as the day of the follicular phase, when these samples were collected had no effect on the increases and decreases on the contralateral side. Statistical analysis, however, showed that the change in utero-ovarian vein or uterine vein hormone levels on the contralateral side after removal of one ovary was not significant for any of the four hormones E₂, P, T, and A. Thus there is no evidence to demonstrate cross circulation of steroids from one ovary to the other via direct vascular channels. This research was supported by NIH grant HD15300 toA. A. Shaikh.     

Ovarian follicular wave characteristics in alpacas

The objectives were to describe in detail ovarian follicular growth characteristics and to establish the interval between successive large follicles in unmated alpacas. The ovarian follicular status of 16 non-pregnant, non-lactating mature alpacas was recorded using ultrasound every second day for between 46 and 100 days. An inverse relationship was observed between the diameter of the largest follicle and the total number of follicles indicating that follicular growth in alpacas occurs in waves. There were 15/38 (39%) inter-wave intervals of 12 days and 12/38 (32%) intervals of 16 days. The maximum follicular diameter in each follicular wave was 8.8±0.3 mm (n=38). Inter-wave intervals of longer duration were associated with a larger maximum follicle diameter (P<0.001). However, the growth rate of dominant follicles was consistent over the first 10 days after emergence. They reached a diameter capable of ovulation by this time, regardless of subsequent inter-wave interval. The latter observation suggested that the optimal time of mating might be predicted in alpacas, provided that the emergence of ovarian follicular waves was controlled.     

Cloprostenol inouced luteal regression in the beef cow. I. Ovarian response and endocrine changes

Forty-two cycling, multiparous beef cows (percentage-Brahman) were given two injections of 500 ug Cloprostenol (CLP) 11 days apart. Cows were randomly allocated to be ovariectomized at 0, 12, 24, 36, 48, 60 or 72 hr after the second CLP injection. Mean CL weight declined within 36 hr after CLP. Mean concentration of P4 in luteal tissue increased between o and 60 hr, while mean P4 content per CL declined by 12 hr after CLP. There was a precipitous decrease in mean serum P4 by 12 hr following CLP injection. Serum E2 was elevated until 24 hr and then declined through 72 hr after CLP. Follicular T concentration increased from 0 to 48 hr and then decreased by 60 hr. We conclude that CLP caused rapid diminution of luteal function which was accompanied by a reduction in P4 content but not in P4 concentration. Futhermore, the concentration of E2 in large follicles decreased by 72 hr post-CLP which is consistent with an alteration of the steroidogenic pathway in the periovulatory follicle.     

Changes in rabbit corpus luteum progesterone secretion and cellular morphology following unilateral luteectomy or ovariectomy.

The objective of this study was to determine whether removal of corpora lutea (CL) from one ovary (unilateral luteectomy; ULL) or removal of the entire ovary (unilateral ovariectomy; ULO) of pseudopregnant rabbits would cause compensatory growth and progesterone production by the contralateral ovary. Pseudopregnancy was induced in rabbits with hCG (Day 0). On the first day of pseudopregnancy, one group of rabbits received a sham operation (controls), another group underwent ULL, and a third group underwent ULO. On Day 11 of pseudopregnancy, each rabbit underwent laparotomy, the ovarian artery and vein were cannulated, and the ovary(ies) was removed and perfused in vitro for 6 h. The mean CL weight increased by 33% in the ULL group and by 28% in the ULO group as compared to sham-operated controls. Peripheral estradiol and progesterone levels in sham-operated control, ULL, and ULO groups were similar. Ovarian venous estradiol levels were similar in the control and ULL groups, but were significantly increased in the remaining ovary of the ULO group. Both ovarian venous progesterone in vivo and progesterone secretion in vitro increased significantly in contralateral ovaries from ULL and ULO rabbits as compared to sham-operated controls. Progesterone secretion by ovaries perfused in vitro increased significantly in the contralateral ovary of the ULL and ULO groups. Mean number of luteal cells per CL increased significantly in the ULL group, but not in the ULO group. In contrast, luteal cell volume increased significantly in the ULO, but not in the ULL group. The stimuli responsible for increased progesterone production following ULL and ULO result in morphological changes in the remaining CL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovarian follicular population changes with the advance of the breeding season in intact and unilaterally ovariectomized ewes

In ewes at the 1st, 2nd or 4th oestrous cycle after unilateral ovariectomy, the ovulation rate remained constant at 1.5 in the control (sham-operated) ewes, but increased from 1.3 to 2.0 in unilaterally ovariectomized ewes. In control ewes, the proportion of preantral follicles declined significantly (P less than 0.05) with each oestrous cycle while the antral follicles increased as the breeding season progressed (P less than 0.05). In contrast, after unilateral ovariectomy, the proportion of preantral and antral follicles remained constant throughout the cycles studied. The rate of atresia of antral follicles, especially those from small size classes, decreased significantly after one cycle of unilateral ovariectomy (P less than 0.05). Larger antral follicles had a different rate of atresia as the breeding season advanced. It is concluded that unilateral ovariectomy acutely decreased the rate of atresia and maintained the within-ovary equilibrium between preantral and antral follicles which otherwise would have decreased due to the depletion of preantral follicles with the advance of the breeding season.     

Ovarian follicular development following administration of progesterone or aspiration of ovarian follicles in Holstein cows

The objective of this study was to compare the effects of administration of a single injection of progesterone (P4) and follicle aspiration on Day 7 of the estrous cycle on the timing and synchrony of follicular wave emergence, time of ovulation, and concentrations of P4, estradiol and FSH in Holstein cows. Twenty cows were assigned to 4 groups (n=5 cows per group) in a 2 by 2 factorial arrangement. Cows were treated on Day 7 (Day 0 = estrus) of the estrous cycle with either sham follicular aspiration and an oil vehicle administered intramuscularly (control), aspiration of ovarian follicles (aspiration), 200 mg of P4 im, or aspiration and 200 mg of P4 im (aspiration + P4). On Day 11, PGF(2alpha)(25mg) was administered to all groups. Synchrony of ovulation was less variable in each of the treatment groups compared with the control group (P<0.05), whereas ovulation was delayed in cows in the P4 group (P<0.05). Day of follicular wave emergence was delayed in the cows of the P4 group compared with cows in the aspiration and aspiration + P4 groups (P<0.01), whereas variability in wave emergence was less among both groups of aspirated cows compared with the cows in the control group (P<0.01). More follicles 4 to 7 mm in diameter were detected in the 2 aspiration groups compared with the cows in the control and P4 group (P<0.05). No difference was detected among groups in the maximum concentration of FSH associated with follicular wave emergence. We conclude that both the administration of P4 and the aspiration of follicles on Day 7 of the estrous cycle improves the synchrony of ovulation when luteolysis is induced on Day 11 and results in similar concentrations of FSH at the time of follicular wave emergence, but the timing of wave emergence and the number of follicles post-emergence differ.