The effect of frozen ovarian autografts on compensatory ovulation and steroid production in unilaterally ovariectomized rats.

In the present study rats were unilaterally ovariectomized (ULO) and the surgically removed ovary was frozen for 13 days. After allowing the remaining ovary to compensate with respect to number of ova shed, the frozen graft was thawed and transplanted subcutaneously to determine the effect on ovulation number, cycle length, uterine weight, ovarian weight and plasma levels of estradiol-17beta (E2) and progesterone. Rats ULO at 45 days of age, which received an autograft 13 days later, had a decrease in the number of eggs shed as compared to control ULO rats (6.4 +/- 0.8 vs. 11.1 +/- 0.9 eggs, respectively) and a decrease in plasma E2 (14.5 +/- 1.7 VS. 21.0 +/- 1.5 PG/ML, respectively). No differences were observed in progesterone concentration, uterine weight, ovarian weight or cycle length. In contrast, rats ULO at 31 days of age, which received an autograft 13 days later, showed no differences in comparison to control ULO rats. Castrates which received ovarian autografts developed cycling vaginal smears and had increased E2 (31.9 +/- 4.3 pg/ml) and decreased progesterone (18.3 +/- 1.9 ng/ml) levels. Since ULO animals with autografts shed fewer ova, the present study demonstrates that the amount of ovarian tissue influences ovulation number either by utilization of gonadotropins or by an, as yet, undefined mechanism.     

Compensatory ovulatory mechanisms operative after first ovulation in rats unilaterally ovariectomized prepubertally

Ovarian steroid contents and serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were measured during the days after first ovulation in rats unilaterally ovariectomized in late prepuberty. In addition, follicle counts were made at second estrus and second metestrus. During the cycle following first ovulation, ovarian estradiol contents in unilaterally ovariectomized (ULO) rats were significantly increased as compared to intact rats on the day of metestrus, on diestrus 1 and on second estrus. Ovarian progesterone was significantly increased on the days of metestrus, on diestrus 1, second proestrus and second estrus, but no differences were seen in ovarian androgen contents. After ULO there was an indication of an augmented FSH surge at the first and the second ovulation. Follicle counts revealed that the total number of healthy as well as of atretic antral follicles on the day of second estrus was significantly increased after ULO, due to increased numbers of the smallest antral follicles. At second metestrus the number of larger antral follicles (350-500 micron 3) and the total number of healthy antral follicles was higher after ULO. It is concluded that the compensatory process after ULO involved increased recruitment of small antral follicles. Activities in the remaining ovary were not simply doubled but a new hormonal balance was established.     

Effect of reduced ovarian tissue on cyclicity, basal hormonal levels and follicular development in old rats

Reduction of the number of growing follicles was proposed to contribute to the decline in reproductive performance with aging (Butcher and Page, 1981). To investigate the effects of a reduced number of follicles, rats which maintained regular estrous cycles at greater than 1 yr of age had either unilateral ovariectomy (ULO) or control surgery. Irregular estrous cycles and periods of constant estrus were more frequent during a period of 90 days after ULO than in controls. Follicle-stimulating hormone (FSH) concentration in plasma collected at 0900-1100 h of the metestrus nearest to 20, 50, and 90 days after surgery was increased by ULO; in both treatment groups, FSH increased between 20 and 90 days. Compensation in ovarian weight and number of corpora lutea had occurred by 90 days after ULO. Estradiol, estrone and luteinizing hormone (LH) concentrations did not change with time or treatment. Numbers of small, medium and large antral follicles per ovary at metestrus were increased by ULO, while the number of follicles per rat was decreased. It was concluded that the reduction in ovarian tissue (which decreased the number of growing follicles) resulted in an elevation of basal FSH followed by irregularity in estrous cycles.     

Unilateral ovariectomy increases loss of primordial follicles and is associated with increased metestrous concentration of follicle-stimulating hormone in old rats.

The primary objective of these studies was to determine whether unilateral ovariectomy (ULO) would affect rate of loss of primordial follicles. In experiment 1, retired breeder rats, unilaterally ovariectomized and maintained on the experiment for 90 days after surgery, had fewer (p less than 0.01) primordial follicles per ovary than sham-operated controls of the same age. The purpose of experiment 2 was to determine whether time after ULO or age of rats was the critical factor necessary for increased loss of primordial follicles found after ULO in experiment 1. It was found that age was more important than time: when ULO was performed at 30 days of age, the number of primordial follicles did not decrease in ULO rats compared to controls (p greater than 0.05) before 250 days of age. Concentrations of FSH during metestrus were not greater (p greater than 0.05) in ULO rats than in controls until rats were 250 days old. There were also fewer (p less than 0.05) growing follicles per ovary in ULO than in sham-operated rats at 250 days of age. It is concluded that ULO can increase the loss of primordial follicles, but only in old rats (greater than or equal to 250 days of age).     

Interference with the preovulatory luteinizing hormone surge and blockade of ovulation in immature pregnant mare's serum gonadotropin-primed rats with the anti-androgenic drug, hydroxyflutamide

The involvement of androgens in the control of ovulation has been assessed by administration of the androgen antagonist, hydroxyflutamide, to prepubertal rats treated with pregnant mare's serum gonadotropin (PMSG) to induce first estrus and ovulation. Without human chorionic gonadotropin (hCG) injection, only 46% of rats that received six 5-mg, s.c. injections of hydroxyflutamide at 12-h intervals, beginning an hour before s.c. injection of 4 IU PMSG on Day-2 (Day 0 = the day of proestrus), had ovulated a mean of 1.3 +/- 0.4 oocytes per rat when killed on the morning of Day 1, whereas 92% of sesame oil-treated controls had ovulated a mean of 6.9 +/- 0.6 oocytes. After i.p. injection of hCG at 1600 h on Day 0, 92% of hydroxyflutamide-treated rats ovulated a mean of 8.3 +/- 1.2 oocytes compared to 100% of controls, which ovulated 7.3 +/- 0.4 oocytes per rat: these groups were not significantly different from each other, nor from control rats that received no hCG. Thus, exogenous hCG completely overcame the inhibitory effect of hydroxyflutamide on ovulation. Rats treated with PMSG and hydroxyflutamide without hCG were killed either on the morning of Day 0 to determine serum and ovarian steroid levels or on the afternoon of Day 0 to determine serum LH levels. Serum levels of estradiol-17 beta and testosterone in hydroxyflutamide-treated rats were significantly higher (178% and 75%, respectively; p less than 0.01) than levels observed in controls on the morning of Day 0. Ovarian concentrations of the steroids were also elevated in hydroxyflutamide-treated rats (p less than 0.01 for testosterone only).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of unilateral ovariectomy on compensatory ovarian hypertrophy, peripheral concentrations of follicle-stimulating hormone and luteinizing hormone, and ovarian venous concentrations of estradiol-17 beta in prepuberal gilts

A study was designed to characterize the compensatory ovarian response to unilateral ovariectomy (ULO) in prepuberal gilts and to investigate further the mechanisms involved in compensatory ovarian hypertrophy (COH). Forty-eight crossbred gilts were sham ovariectomized (Sham) or unilaterally ovariectomized at 130 days of age (Day 0). Remaining ovaries in ULO gilts were removed and Sham gilts were bilaterally ovariectomized 2, 4 or 8 days later. A peripheral blood sample was taken before surgery and ovarian venous blood samples were taken before removal of each ovary. Serum estradiol-17 beta (E2) concentrations were determined. Mean wet and dry ovarian weights per ovary on Day 2 for ULO and Sham gilts were 3.4 versus 2.8 and 0.26 versus 0.24 g, respectively. Those weights on Days 4 and 8 were greater (P less than 0.01) for ULO than Sham gilts. Follicular fluid weight per ovary was greater (P less than 0.05) for ULO than Sham gilts on Days 2, 4 and 8. Ovarian venous E2 concentrations were greater (P less than 0.01) for ULO than for Sham gilts on Days 2 and 4 but were similar on Day 8. In a second experiment, 42 prepuberal gilts 130 days of-age were subjected to Sham (n = 18), ULO (n = 18) or bilateral ovariectomy (BLO; n = 6) to evaluate follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion immediately after surgical treatment. Release of FSH within the first 24 h was greater for BLO than ULO and for ULO than Sham gilts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Circulating radioimmunoassayable inhibin during periods of transient follicle-stimulating hormone rise: secondary surge and unilateral ovariectomy

We have measured changes in circulating immunoreactive (ir-) inhibin in male and female rats using an RIA with an antiserum raised against porcine inhibin alpha (1-26)-Gly-Tyr. The same synthetic peptide was used for standards and for the preparation of tracer. Serum ir-inhibin levels were significantly higher in intact female than in intact male rats (p less than 0.001). Immunoreactive inhibin was significantly reduced in both sexes 24 h after bilateral gonadectomy (p less than 0.0001). Unilateral ovariectomy (ULO) of female rats on metestrus caused a transient decrease in serum inhibin 8 h after surgery, but levels were not significantly different from those of sham-operated controls at later times after surgery. Increases in serum FSH and LH were observed for 8-18 h after ULO. Serum ir-inhibin levels were also measured on the early morning of estrus during the secondary FSH surge. At this time, ir-inhibin levels were low, while FSH levels were high and LH levels were low. These results show that serum ir-inhibin levels in rats are decreased at times when serum FSH levels are high.     

Superovulation of immature hypothyroid rdw rats by thyroxine therapy and the development of eggs after in vitro fertilization.

The aim of this study was to examine the effect of thyroxine on ovulation in immature rdw rats and the fertilization and development of the eggs. Serum thyroxine concentrations at 30 days of age were significantly lower in rdw rats than in normal rats (P < 0.001), and greatly increased after thyroxine replacement therapy (P < 0.001). Although few eggs (1-5 +/- 1-2) were obtained from immature rdw rats treated with gonadotrophins alone, females treated with gonadotrophins and thyroxine ovulated significantly more eggs (85 +/- 5). As a control, normal littermates ovulated 21-45 eggs when treated with gonadotrophins alone, and 68 eggs when administered with gonadotrophins and thyroxine. Of the eggs collected from rdw rats treated with gonadotrophins and thyroxine, and inseminated with spermatozoa from mature F1 males, 98% were penetrated and in almost all (99%) of these eggs, male and female pronuclei formed. Forty-seven per cent of the pronuclear eggs developed to the blastocyst stage in vitro. After transfer to recipients, 21% (14/66) of one-cell and 22% (8/37) of two-cell embryos developed to offspring, and 62% (8/13) of pups were of rdw/rdw genotype. The average body weight (6.9 versus 7.8 g) of offspring derived from one-cell embryos was lower than that for two-cell embryos. The morulae and blastocysts did not develop to term, although 41% implanted in the uterine horns of recipients. In conclusion, in immature rdw rats, superovulation was induced by gonadotrophins combined with thyroxine therapy and the superovulated oocytes were fertilized and developed in vitro and developed to term after embryo transfer.     

Dietary fish oil delays puberty in female rats.

Marine oils contain eicosapentaenoic acid, a fatty acid that competes for cyclooxygenase and reduces the synthesis of dienoic prostanoids including prostaglandin E2 (PGE2). Since PGE2 plays an important role in the estrogen-stimulated release of hypothalamic GnRH on proestrus, it was postulated that a diet containing fish oil would delay first ovulation through inhibitory effects on GnRH release. Thirty, 22-day-old female Sprague-Dawley rats were fed a diet containing fish oil ad libitum. Controls were pair-fed an identical diet with the substitution of safflower oil as the dietary fat. All rats were killed on the morning of first metestrus after vaginal opening and the display of an estrous smear(s). Fish oil feeding did not affect growth as indicated by the lack of an observed effect on body weights or femur lengths. On the other hand, pituitary, ovarian, and uterine weights were significantly lower in the rats fed fish oil (p < 0.001). The age at first estrus of the rats fed fish oil was significantly increased compared with the controls (42.9 +/- 1.0 vs. 36.1 +/- 0.3 days; p < 0.001), whereas the number of rats with corpora lutea (CL), as well as the number of CL per ovary (2.3 +/- 0.4 vs 4.8 +/- 0.6 for controls; p < 0.001) was significantly reduced by fish oil feeding. GnRH concentration in the preoptic area/hypothalamus was significantly increased in the fish oil-fed rats (21.4 +/- 4.0 pg/mg vs. 7.6 +/- 2.2 pg/mg for controls; p < 0.01); radioimmunoassable hypothalamic PGE2 was concomitantly reduced (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrasonic transit-time measurement of blood flow in the umbilical arteries and veins in the bovine fetus during stage II of labor

The vitality of the bovine fetus during parturition depends on an intact umbilical circulation to supply adequate amounts of oxygen and nutrients to the fetus. The goal of the present study was to measure the blood flow in the umbilical vessels during stage II of labor and to determine when blood flow ceases in the umbilical cord. In 20 cows, ultrasonographic transducers were placed on one umbilical vein and one umbilical artery after rupture of the allantochorionic sac, and the blood flow volume per unit time was measured. At the same time, a pressure transducer was placed into the uterus to measure uterine pressure. Parturition was spontaneous in all 20 cows. In 20 live calves born, pH, base excess and lactate concentration were measured in the blood immediately after birth. During the last 90 min before birth the mean total umbilical blood flow (artery and vein combined) was 1.186+/-0.028 L/min. Calves with a blood pH> or =7.2 (n=13) had a higher mean total blood flow than calves with a pH<7.2 (n=7; 1.243+/-0.038 versus 1.095+/-0.038 L/min). In calves with a blood pH<7.2, the mean total blood flow decreased from 1.178+/-0.134 at 20 min before birth to 0.959+/-0.126 L/min at the end of stage II of labor. During this time period, the arterial blood flow did not differ between calves with a blood pH> or =7.2 and<7.2, but venous blood flow decreased significantly in calves with a blood pH<7.2. During uterine contractions, the total umbilical blood flow decreased significantly by 0.22 L/min. The blood flow in the umbilical artery and vein ceased before the calves were completely born.     

Inhibin-like activity in ovarian venous serum after unilateral ovariectomy in prepubertal gilts

To examine a role for inhibin in compensatory ovarian hypertrophy after unilateral ovariectomy (ULO) of prepubertal gilts, changes in inhibin activity in ovarian venous blood were estimated by bioassay. Three groups of 130-day-old gilts were unilaterally ovariectomized after collecting blood from an ipsilateral ovarian vein (Day O); blood samples were obtained from the remaining ovary on Day 2, 4, or 8. Coetaneous gilts underwent sham ovariectomy on Day 0, and venous blood was collected from both ovaries on Day 2, 4, or 8. An assay for inhibin activity, which measured inhibition of secretion of follicle-stimulating hormone (rFSH) by rat pituitary cells in culture, was validated for serum samples. Presumptive inhibin activity was always greater in ovarian venous serum than in peripheral serum samples. In the ULO groups, inhibin activity (in terms of a house reference preparation) in ovarian venous serum was 55 +/- 13 micrograms/ml (means +/- SE, n = 13) on Day 0, 251 +/- 79 (n = 5) on Day 2, 275 +/- 111 (n = 4) on Day 4, and 68 +/- 14 micrograms/ml (n = 4) on Day 8. The five-fold increases on Days 2 and 4 were significant (p less than 0.05). In contrast, no significant differences in inhibin activity were detected between ovarian venous serum (within gilts) or between Days 2, 4, and 8: 82 +/- 29, 73 +/- 30, and 99 +/- 48 micrograms/ml (n=4/day) in control groups. These results demonstrate that, in prepubertal gilts, the remaining ovary's response to ULO includes a major increase in release of inhibin-like activity.     

Ultrasonographic imaging of the reproductive tract and surgical recovery of oocytes in Cebus apella (capuchin monkeys)

Two-dimensional real-time and Doppler ultrasonography are valuable non-invasive methods to assess reproductive anatomy and physiology. In adult, postpubertal female Cebus apella (capuchin monkeys), the objectives were to determine (1) uterine and ovarian dimensions, ovarian follicular dynamics, day of ovulation, and arterial blood flow of uterus and utero-ovarian ligament during the follicular phase of the menstrual cycle and (2) the number of oocytes aspirated from antral follicles at laparotomy. Based on two-dimensional, transabdominal B-mode ultrasonography, mean (+/- S.E.M.) length, height, width, and volume of the uterus were 17.9+/-0.4, 12.4+/-0.3, 13.6+/-0.3 mm, and 1.55+/-0.08 mL, respectively, and of the ovary were 13.4+/-0.2, 8.2+/-0.1, 7.7+/-0.1 mm, and 4.5+/-0.2 mL. Ovarian follicles were monitored for 6 days before ovulation, which occurred on day 9.3+/-0.5 (range, days 7-11; day 1=start of menses), with 10 of 12 ovulations in the right ovary. Diameter and volume of the preovulatory follicle were 10.1+/-0.2 mm and 0.55+/-0.03 mL (on the estimated day of ovulation) and of the CL were 8.1+/-0.4 mm and 0.3+/-0.05 mL. Resistivity and pulsatility indices were 0.86+/-0.02 and 2.15+/-0.11 for uterine arteries, and were 0.69+/-0.04 and 1.63+/-0.15 for the utero-ovarian ligament (UOL) artery; just prior to ovulation, both indices peaked (P<0.05) in the uterine artery ipsilateral to the side of ovulation, but both reached a nadir (P<0.05) in the UOL artery. In the absence of ovarian stimulation, 31 oocytes (diameter, 137+/-10 microm) were aspirated (average of 2 oocytes/(female attempt)) on days 5, 7, and 9. In conclusion, transabdominal ultrasonography facilitated assessment of reproductive anatomy and physiology in C. apella adult females. Resistance and pulsatility indices of uterine and UOL arteries changed near the time of ovulation. Dominant follicles were easiest to aspirate at 8-9 mm in diameter ( approximately day 9), with intact cumulus-oocyte complexes recovered from ovarian follicles 2-9 mm in diameter.     

Season determines timing of first ovulation in rhesus monkeys (Macaca mulatta) housed outdoors

In order to determine the relative importance of age and season on the occurrence of first ovulation in rhesus monkeys, the timing of puberty in spring-born females (Group S, N = 13) was compared to that of fall (N = 3) and winter-born (N = 5) females (Group W). All females were housed outdoors and were studied from 12 months of age through first ovulation. Menarche occurred at a similar age but significantly earlier in the year for Group W (31.2 +/- 0.7 months; 25 August +/- 19.5 days) than for Group S females (31.2 +/- 0.7 months; 14 November +/- 17.1 days). First ovulation, as assessed from twice weekly serum progesterone determinations, occurred exclusively in the fall or winter in a bimodal age distribution for all females. For Group W females, 6/8 ovulated during the 3rd year at 35.8 +/- 0.7 months while 2/8 ovulated during the 4th year at 45.3 +/- 0.1 months. In contrast, only 3/13 Group S females ovulated during the 3rd year and at a significantly younger age of 31.4 +/- 0.4 months compared to Group W. The remaining Group S females (10/13) ovulated the following autumn at 43.2 +/- 0.2 months, significantly younger than the later ovulating Group W females. In addition to this pattern of first ovulation, serum concentrations of prolactin varied seasonally, rather than with age, in both groups of females with higher levels in the summer and low levels in the winter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estrogen status affects sensitivity to focal cerebral ischemia in stroke-prone spontaneously hypertensive rats

Estrogen treatment has been shown to reduce ischemic brain damage. Because endogenous estrogen levels fluctuate markedly during the estrous cycle, we investigated the effect of stage of estrous cycle on ischemic brain damage. Halothane anesthetized 3- to 5-mo-old female Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) in proestrus (high estradiol levels) or metestrus (low estradiol levels) underwent permanent middle cerebral artery occlusion. In SHRSP, infarct volume at 24 h postocclusion was 24% smaller in proestrus compared with metestrus [208.6 +/- 9.5 mm(3) (n = 7) vs. 272.7 +/- 23.8 mm(3) (n = 7), respectively, means +/- SE; P = 0.0278, unpaired t-test]. In WKY, infarct volumes were similar in proestrus and metestrus [157.0 +/- 5.4 mm(3) (n = 5) and 131.5 +/- 16.5 mm(3) (n = 8), respectively; P = not significant (NS)]. Brain swelling (ipsilateral minus contralateral hemispheric volumes) was similar in proestrus and metestrus for SHRSP [138 +/- 9 mm(3) (n = 6) and 136 +/- 10 mm(3) (n = 7), respectively] and for WKY [103 +/- 15 mm(3) (n = 5) and 90 +/- 11 mm(3) (n = 8), respectively]. Thus the reduction in infarct size in SHRSP is caused by a true attenuation of the infarct volume and not simply by a reduction in brain edema.     

Leukocyte supplementation increases the luteinizing hormone-induced ovulation rate in the in vitro-perfused rat ovary

Ovaries from eCG-primed (20 IU s.c. on Day 28) rats were perfused from the morning of Day 30 of age in a recirculating system initially containing a buffered blood cell-free medium (M199 + 4% BSA) for periods of up to 21 h. The addition of ovine LH (0.1 micrograms/ml) at 0 h of perfusion resulted in ovulations in all 6 ovaries perfused (3.2 +/- 0.7 ovulations per treated ovary; mean +/- SEM), whereas none of the 6 control ovaries ovulated. Rat leukocytes (50 x 10(6)), added at 7 h of perfusion significantly increased the number of LH-induced ovulations (7.8 +/- 0.5; p less than 0.05). All ovulated oocytes showed resumption of meiosis as judged from the presence of germinal vesicle breakdown. Ovaries perfused with leukocytes but without LH did not ovulate. Histological examination of ovaries 14 h after leukocyte administration showed a considerable number of perifollicular extravasated white blood cells. These findings indicate that leukocytes participate in the normal ovulatory process as part of an inflammation-like reaction.     

Ovarian features contributing to the variability of PMSG-induced ovulation rate in sheep

In Exp. 1, ovulation rate was measured in three groups of Romanov ewes given two injections of 600 i.u. PMSG 3 weeks apart with the ewes intact (Group I, N = 8), a similar treatment with the ewes intact at the first injection and unilaterally ovariectomized at the second (Group II, N = 8), or unstimulated ewes which were hemispayed at the same time as Group II ewes (Group III, N = 6). In Exp. 2, the follicular population of one ovary was correlated with the number of ovulations induced by 600 i.u. PMSG in the contralateral ovary (10 Romanov ewes). From 8.4 +/- 1.8 (Group I) and 8.2 +/- 3.3 (Group II) CL at the first injection, PMSG-induced ovulation rate at the second injection decreased to 3.9 +/- 1.8 and 3.7 +/- 1.2 in Groups I and II respectively, a value similar for ewes with 1 or 2 ovaries. Furthermore, despite no major changes in the number of antral follicles after the first injection, there was no correlation (r = -0.09) between the response to the two successive injections in intact ewes. Comparison of the ovarian status of the ovary removed before the PMSG injection (Group II ewes of Exp. 1, ewes of Exp. 2) to the number of CL found in the remaining ovary demonstrated that PMSG-induced ovulation rate was not correlated with the overall antral follicle population (r = 0.62 in Exp. 1, r = 0.49 in Exp. 2).(ABSTRACT TRUNCATED AT 250 WORDS)     

Transport of uterine PGF2 alpha to the ovaries by systemic circulation and local lymphovenous-arterial diffusion during luteolysis in sheep.

The theory of countercurrent vascular transfer of PGF2 alpha during luteolysis was examined. In the first experiment, pulmonary clearance of PGF2 alpha was determined to re-examine whether the total amount of PGF2 alpha was degraded in the lungs after one passage. Cardiac output was measured by the Fick method and PGF2 alpha by radio-immunoassay before and after vascular lung supply, using pulmonary catheterization and the interventional radiology method in ten anaesthetized ewes on day 16 of the oestrous cycle. Cardiac output remained stable (7156 +/- 439 ml min-1). Infusion of 5 iu oxytocin resulted in an increase in plasma PGF2 alpha concentrations at 30 min in the uterine vein and the pulmonary and femoral arteries (3811 +/- 806, 224 +/- 55 and 18 +/- 4 pg ml-1, respectively). The PGF2 alpha concentrations decreased exponentially and the half-time decreases were 27 (r = 0.99), 16 (r = 0.99) and 18 (r = 0.98) min, respectively. Pulmonary clearance of PGF2 alpha was estimated at 6338 +/- 451 ml min-1. In a second experiment, an arterio-arterial gradient of plasma PGF2 alpha concentrations was analysed between the proximal and distal segments of the ovarian artery to verify whether the total amount of PGF2 alpha flowing to the ovary was from the local venous-arterial countercurrent pathway. Surgical catheterization techniques were performed on 11 ewes on day 16 of the oestrous cycle. The ovarian arterial blood flow was measured by the implantable Doppler method (8 +/- 1 ml min-1). The maximum plasma PGF2 alpha concentrations in the femoral and distal ovarian arteries were 23 +/- 6 and 42 +/- 11 pg ml-1 (P < 0.05), respectively. Plasma PGF2 alpha decreased exponentially in the femoral artery and the half-time decrease was 26 min (r = 0.98), and in the distal ovarian artery close to the ovary PGF2 alpha decreased linearly and the half-time decrease was 108 min (r = 0.96). Consequently, the arterio-arterial diffusion gradient of PGF2 alpha concentrations was extended to 3 h. These experiments showed that the PGF2 alpha flow rate in the pulmonary artery was 42.275 +/- 10.793 micrograms per 150 min (n = 10) and the systemic arterial PGF2 alpha flow rate was 5.359 +/- 1.658 micrograms per 150 min (n = 10). Therefore, 12% of the PGF2 alpha was not oxidized by the lungs. The proximal ovarian PGF2 alpha flow rate was 6.909 +/- 2.341 ng per 150 min, while the distal flow rate was 21.003 +/- 5.703 ng per 150 min (n = 11). Thus, 33% of the PGF2 alpha was transported rapidly to the ovary via the systemic route, while 67% was transported by slow local countercurrent diffusion, which extended the duration of luteolytic activity to four times that of the PGF2 alpha surge. These results indicate both rapid systemic transport of PGF2 alpha to the ovaries and a slower buffer mechanism involving a local diffusion pathway, rather than a direct countercurrent system.     

Endothelial vasodilator production by uterine and systemic arteries. IV. Cyclooxygenase isoform expression during the ovarian cycle and pregnancy in sheep

Uterine artery endothelial production of the potent vasodilator, prostacyclin, is greater in pregnant versus nonpregnant sheep and in whole uterine artery from intact versus ovariectomized ewes. We hypothesized that uterine artery cyclooxygenase (COX)-1 and/or COX-2 expression would be elevated during pregnancy (high estrogen and progesterone) and the follicular phase of the ovarian cycle (high estrogen/low progesterone) as compared to that in luteal phase (low estrogen/high progesterone) or in ovariectomized (low estrogen and progesterone) ewes. Uterine and systemic (omental) arteries were obtained from nonpregnant luteal-phase (LUT; n = 10), follicular-phase (FOL; n = 11), and ovariectomized (OVEX; n = 10) sheep, as well as from pregnant sheep (110-130 days gestation; term = 145 +/- 3 days; n = 12). Endothelial and vascular smooth muscle (VSM) COX-1 protein levels and uterine artery endothelial cell COX-1 mRNA levels were compared. Using immunohistochemistry and Western analysis, the primary location of COX-1 protein was the endothelium; that is, we observed 2.2-fold higher COX-1 protein levels in intact versus endothelium-denuded uterine artery and a 6.1-fold higher expression in the endothelium versus VSM (P < 0.05). COX-2 protein expression was not detectable in either uterine artery endothelium or VSM. COX-1 protein levels were observed to be higher (1.5-fold those of LUT) in uterine artery endothelium from FOL versus either OVEX or LUT nonpregnant ewes (P < 0.05), with substantially higher COX-1 levels seen in pregnancy (4.8-fold those of LUT). Increases in uterine artery endothelial COX-1 protein were highly correlated to increases in the level of COX-1 mRNA (r(2) = 0.66; P < 0.01) for all treatment groups (n = 6-8 per group), suggesting that increased COX-1 protein levels are regulated at the level of increased COX-1 mRNA. No change in COX-1 expression was observed between groups in a systemic (omental) artery. In conclusion, COX-1 expression is specifically up-regulated in the uterine artery endothelium during high uterine blood flow states such as the follicular phase and, in particular, pregnancy.     

Estrous cycle stage-independent treatment of PMSG and hCG can induce superovulation in adult Wistar-Imamichi rats.

The estrous cycle influence on the number of ovulated eggs after injection of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) was investigated in 12, 18, and 24 weeks old adult female Wistar-Imamichi (WI) rats. PMSG (150 IU/kg) was injected at metestrus, diestrus, proestrus, or estrus, followed by hCG (75 IU/kg) 55 h later. Ovulation was induced at all ages and stages of the estrous cycle. The number of ovulated eggs was not affected by stage for similarly aged rats, however, the number of ovulated eggs obtained after treatment decreased with age. These results demonstrate that the PMSG/hCG treatment can induce ovulation at any stage of estrous cycle in WI rats and efficient superovulation at 12 weeks of age.     

Sprint training attenuates the deficits of force and dynamic stiffness in rat soleus muscle caused by eccentric contractions

We investigated whether sprint training attenuates the deficits in force and dynamic stiffness caused by eccentric contractions to the soleus muscles of Wistar rats. Two groups of male rats were analyzed: sedentary (C, n=8) and trained (T, n=8). T rats were sprint trained for 10 weeks. Subsequently, the right soleus muscles of rats were freed under anesthesia, leaving the bone insertion and blood supply intact. Eccentric contractions were induced by lengthening muscles during tetanic contractions. Force and dynamic stiffness were tested before and after 20 rounds of eccentric contractions. Tension decline was analyzed using a two-state model (first-order kinetics) in the context of Kramer's theory. Training improved the twitch tension (C, 6.44+/-0.6N/cm(2); T, 10.90+/-0.8N/cm(2)), tetanic force (C, 61.74+/-0.6N/cm(2); T, 85.62+/-0.8N/cm(2)), and increased the dynamic stiffness (C, 41.28+/-1.0N/cm(2); T, 49.56+/-3.2N/cm(2)). Twitch tension after eccentric contractions declined to 73% and 75% in C and T groups, respectively, while tetanic tension decreased to 60% and 36% in C and T groups, respectively. After eccentric contractions, dynamic stiffness decreases were smaller in T rats (from 49.56+/-3.2 to 36.09+/-2.1N/cm(2)) than in C rats (from 41.28+/-1.0 to 20.73+/-1.8N/cm(2)). Sprint training increased the dynamic stiffness and tetanic tension of the soleus muscle and protected against the attenuation induced by eccentric contractions. Finally, the two-state model provided evidence that the number of force-generating cross-bridges increases in trained muscle.