Changes of cyclic AMP levels and phosphodiesterase activities in the rat ovary

Cyclic AMP (cAMP) is a second messenger that plays a critical role in follicular recruitment, development and luteinization in the mammalian ovary. The cellular level of cAMP is largely dependent on the activity of phosphodiesterase (PDE), which degrades cAMP into 5'-AMP. The present study was conducted to investigate the level of cAMP and the activity of cAMP-PDE in postnatal rats; immature rats during gonadotropin-primed follicular development, ovulation and luteinization; adult rats during normal estrous cycling; and aged rats that spontaneously developed persistent estrous (PE) by radioimmunoassay (RIA). All four rat models were confirmed by histological examination of one ovary and assayed using the other ovary by RIA. In the postnatal rats, the ovarian cAMP level was high on day 10 after birth, while ovarian cAMP-PDE activity was highest at 21 days of age. In the immature female rats, both the ovarian cAMP level and cAMP-PDE activity increased remarkably after treatment with equine chorionic gonadotropin (eCG), increased continuously 24 h after injection of human chorionic gonadotropin (hCG) for induction of ovulation and luteinization, and then declined significantly. In the adult rats during the normal estrous cycle, the ovarian cAMP levels were low on the day of estrus, and there were no significant changes in ovarian cAMP-PDE activity throughout the estrous cycle. In the PE rats, the ovarian cAMP levels were similar to those of the adult rats on the day of estrus but were lower than those on the other days of the estrous cycle; ovarian cAMP-PDE activity was lower than that in the adult rats on any day of the estrous cycle. Together, these findings indicate that the ovarian cAMP level and cAMP-PDE activity were regulated in a stage-dependent manner during ovarian follicular development, atresia and luteinization and providing evidences that cAMP and cAMP-specific PDEs are involved in these physiological processes.     

Factors affecting ovarian compensation after unilateral ovariectomy in gilts

Two experiments were conducted to identify the temporal limits of an ovarian compensatory response after unilateral ovariectomy (ULO) in gilts and to examine ovarian and hormonal factors that might be related to this response. In the first study, all eight gilts that were unilaterally ovariectomized on d 12, 14 or 16 of an estrous cycle and two of four ULO on d 18 had a significant compensatory increase in ovulation rate per ovary compared with controls. Ovulatory compensation failed to occur, however, in two of four and four of four gilts ULO on d 18 or 19 of an estrous cycle, respectively. In the second study, blood samples were collected from 26 gilts beginning on d 14 of an estrous cycle, and animals were assigned to sham-surgery or ULO on d 17, 18 or 19. Ovarian compensation occurred after ULO on all 3 d of surgery in the second study, but most follicles failed to ovulate and formed large luteinized cysts. The ability to compensate was related positively to the number of medium-sized follicles on the intact ovary at the time of ULO, to an increase in concentrations of follicle-stimulating hormone 12 to 18 h after ULO and to the interval from ULO to the preovulatory surge of luteinizing hormone. In a third experiment, interruption of the ovulatory mechanism and development of cystic follicles similar to those observed in the second study were induced simply by physical manipulation of the d 19 preovulatory ovary while contralateral untouched ovaries ovulated normally.     

Serous cysts are a benign component of the cyclic ovary in the guinea pig with an incidence dependent upon inhibin bioactivity

Ovaries were collected from normal cycling female guinea pigs on each day of the estrous cycle (n = 5 per day) for histological analysis of ovarian morphology. Three types of ovarian cysts were observed: serous cysts, follicular cysts and parovarian cysts. The most common were serous cysts (cystic rete ovarii), which were present throughout the estrous cycle with an overall incidence of 63.5% (54 out of 85 animals). Follicular cysts occurred in 22.4% of guinea pigs overall (19 out of 85). Only one parovarian cyst (1 out of 85) was observed in the present experiment. Follicular cysts always coincided with serous cysts and were less common during diestrus. The incidence of serous cysts did not vary significantly across the estrous cycle. In a second experiment, cycling female guinea pigs were arrested in a prolonged luteal phase by a progesterone implant in order to achieve ovarian synchrony. They were then treated with inhibin antiserum (0.5 or 1 ml per animal i.v.; n = 6 per group) or normal goat serum (controls; n = 6 per group). There was a dose dependent increase in the incidence of serous ovarian cysts following passive immunization against the inhibin alpha-subunit. These results suggest that serous cysts are a normal component of the cyclic guinea pig ovary and that alterations in the inhibin-follicle-stimulating hormone system appear to modulate the incidence of serous ovarian cysts in this species.     

Expression of nerve growth factor (NGF), and its receptors trkA and p75 in ovaries of the cyclic golden hamster (Mesocricetus auratus) and the regulation of their production by luteinizing hormone

In the present study, changes in localization of nerve growth factor (NGF) and its receptors, trkA and p75 in the ovary were investigated during the estrous cycle of the golden hamster. The effect of LH surge on changes in localization of NGF, trkA and p75 in the ovary was also investigated. NGF and its receptors trkA and p75 were localized in oocytes, granulosa cells and theca cells of various stages of follicles throughout the estrous cycle. NGF and its two receptors were also present in numerous interstitial cells and luteal cells. The number of interstitial cells staining positively for NGF and its two receptors was greater in ovaries of day 1 (day 1=day of ovulation) than the other days during the estrous cycle. Treatment with the antiserum against luteinizing hormone releasing hormone (LHRH-AS) at 1100 h on day 4 completely blocked ovulation. There were few positive reactions for NGF and its two receptors in interstitial cells 24 hr after LHRH-AS injection. The effect of LHRH-AS treatment was blocked by a single injection of 10 IU human chorionic gonadotropin. The distinct widespread distribution of NGF and its two receptors in the ovary of golden hamsters suggest that NGF may be an important growth factor for regulation of ovarian function. Furthermore, the LH surge may be an important factor for inducing production of NGF and its two receptors in interstitial cells of the cyclic golden hamster.     

ASAS centennial paper: Contributions in the Journal of Animal Science to the development of protocols for breeding management of cattle through synchronization of estrus and ovulation

American Society of Animal Science members, publishing in Journal of Animal Science (JAS), completed research that resulted in understanding the estrous cycle of cattle, which led to the ability to inseminate cattle on a given day with pregnancy rates similar to those achieved by 21-d breeding by a fertile and sound bull. Research published in JAS led to understanding estrus, ovulation, the estrous cycle, and postpartum interval for cattle (1930s through 1960s) and hormonal factors affecting corpus luteum lifespan of cattle (1950s through 1980s). Research during the 1940s to 1960s, using gonadotropins and progesterone to manage the estrous cycle of cattle, established the concepts for estrous synchronization and stimulated commercial research directed at developing cost-effective progestogen estrous synchronization products, leading to commercially available products from 1967 through today (Repromix, melengestrol acetate, Syncro-Mate-B, controlled internal drug release). Prostaglandin F(2alpha) products were approved for estrous synchronization (1970s, 1980s), and GnRH products were approved for use in cattle to treat ovarian follicular cysts (1970s, 1980s). Research published in JAS was essential for understanding the biology of and potential value of both PGF(2alpha) and GnRH and contributed both to new knowledge and scientific bases for future Food and Drug Administration Center for Veterinary Medicine approval of those products. Research during the1980s through 2000s led to understanding ovarian follicular waves and described the timing of follicular recruitment, selection, dominance, and atresia; this research was essential for the ability to effectively manage follicles to achieve success with timed AI. The knowledge gained through research published in JAS resulted in development of the numerous estrous synchronization and breeding management protocols that are cost-effective and meet the breeding management needs of most beef and dairy enterprises.     

Uterine and ovarian blood flow in a Holstein Friesian cow with aplasia of one uterine horn

The ovarian dynamics and uterine and ovarian blood flows of a 6-year-old (2 parturitions) Holstein Friesian cow with right uterine horn aplasia were observed during two estrous cycles. In one estrous cycle, a corpus luteum (CL) formed in the right ovary, but regression of the CL and subsequent ovulation were not observed. In the other estrous cycle, a CL formed in the left ovary and delayed regression of the CL and subsequent ovulation were observed. The blood velocity of the right uterine artery was lower than that of the left uterine artery throughout both estrous cycles when a CL formed in either the right and left ovary. The blood velocities of the right and left ovarian arteries were unaffected by right uterine horn aplasia and changed depending on the presence of a CL. These results indicated that the blood flow of the right uterine artery was very weak and that aplasia of one uterine horn affects the estrous cycle, especially CL regression.     

Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers

Our objectives were to identify stages of the estrous cycle at which initiation of a timed artificial insemination (Ovsynch/TAI) protocol may reduce pregnancy rates and to monitor ovarian follicle dynamics and corpus luteum development after initiation of the Ovsynch/TAI protocol at different stages of the cycle. Cycling Holstein heifers (n = 24) were injected twice with prostaglandin F2alpha to induce estrus and were scanned by ovarian ultrasonography to determine the day of ovulation (d 0). Heifers were assigned to initiate the Ovsynch/TAI protocol at d 2 (n = 5), 5 (n = 5), 10 (n = 4), 15 (n = 5), or 18 (n = 5) of the cycle. The Ovsynch/TAI was initiated with an injection of gonadotropin-releasing hormone agonist followed 7 d later with an injection of prostaglandin F2alpha. At 36 h after injection of prostaglandin F2alpha, heifers were injected with gonadotropin-releasing hormone agonist and inseminated 16 h later. Heifers were scanned daily during the Ovsynch/TAI protocol and every other day after insemination until 16 d later. Blood samples were collected daily starting at the 1st day heifers were scanned and continued until 16 d after insemination. Initiation of the Ovsynch/TAI protocol at d 15 of the estrous cycle caused heifers to ovulate prior to insemination. A shortened return to estrus (< 16 d) was caused by ovulation failure to the second gonadotropin-releasing hormone injection, by incomplete regression of the corpus luteum, and by short life-span of the induced corpus luteum. Day of the cycle in which the Ovsynch/TAI protocol is initiated affects dynamics of follicular development, plasma progesterone profiles, and occurrence of premature ovulation. Size of the pre-ovulatory follicle was associated positively with subsequent progesterone concentrations following insemination.     

Serous cystadenoma in a normally cyclic mare with high plasma testosterone values

Serous cystadenoma was diagnosed by histologic examination of a large ovary removed from a 16-year-old Thoroughbred mare with normal estrous cycles. Palpation and ultrasound examination per rectum had revealed an excessive number of follicles in the right ovary. The ovulation fossa was palpable on the right ovary, and the left ovary appeared to have normal activity. Plasma testosterone values were high at the time of examination (0.15 ng/ml), but decreased to normal values (0.09 ng/ml) after removal of the cystadenoma.     

Effect of deslorelin acetate on gonadotropin secretion and ovarian follicle development in cycling mares

OBJECTIVE: To evaluate gonadotropin secretion and ovarian function after administration of deslorelin acetate to induce ovulation in mares. DESIGN: Randomized controlled trial. ANIMALS: 16 healthy mares with normal estrous cycles. PROCEDURE: 8 control mares were allowed to ovulate spontaneously, whereas 8 study mares received deslorelin to induce ovulation when an ovarian follicle > 35 mm in diameter was detected. Follicle development and serum concentrations of gonadotropins were monitored daily during 1 estrous cycle. Pituitary responsiveness to administration of gonadotropin-releasing hormone (GnRH) was evaluated 10 days after initial ovulation. RESULTS: Interovulatory intervals of mares treated with deslorelin (mean +/- SD, 25.6 +/- 2.6 days) were longer than those of control mares (22.9 +/- 1.8 days). Diameter of the largest follicle was significantly smaller during 2 days of the diestrous period after ovulation in deslorelin-treated mares than in control mares. Concentrations of follicle-stimulating hormone (FSH) were lower in deslorelin-treated mares on days 5 through 14 than in control mares. Concentrations of luteinizing hormone were not different between groups during most of the cycle. Gonadotropin release in response to administration of GnRH was lower in mares treated with deslorelin acetate than in control mares. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of deslorelin was associated with reduction in circulating concentrations of FSH and gonadotropin response to administration of GnRH during the estrous cycle. Low concentration of FSH in treated mares may lead to delayed follicular development and an increased interovulatory interval.     

Evaluation of ovulation rate and ovarian phenotype in puberal heifers from a cattle population selected for increased ovulation rate

Long-term selection for increased ovulation rate (1984 to 2002) has resulted in a unique ovarian phenotype in the MARC Twinner cattle population. Ovulation rate and frequency of bilateral ovulations were examined by rectal palpation in 29,547 estrous cycles for 3,910 heifers (12 to 18 mo of age) in this population. Bilateral ovulations (one corpus lutuem [CL] on each ovary) were of interest because bilateral twin pregnancies result in decreased dystocia and increased calf survival. Ovulation rate increased linearly at a rate of 0.026 CL per year, and it currently averages 1.48 +/- 0.04 CL per estrous cycle. Concurrent with the increase in ovulation rate, the frequency of triplet ovulations increased from 0% to 2.3 +/- 0.8% (P < 0.001). Ovulation rate of both the right and left ovary increased equally at a rate of 0.013 CL per year, and mean ovulation rate of the right ovary remained greater than mean ovulation rate of the left ovary throughout the study (0.66 vs. 0.55 +/- 0.003 CL per estrous cycle; P < 0.001). Although correlations were low, ovulation rate of one ovary was negatively correlated (P < 0.001; r = -0.07) with ovulation rate of the same ovary in the previous estrous cycle, but positively correlated (P < 0.001; r = 0.13) with the contralateral ovary of the previous estrous cycle. The proportion of bilateral ovulations averaged 55.7 +/- 0.7%, a value greater than the predicted 49.5% (P < 0.001). In addition to dystocia and retained placenta, triplet pregnancies increase the incidence of pregnancies gestating fetuses of opposite sexes and subsequent incidence of freemartins; thus, selection pressure on ovulation rate may need to be adjusted in the MARC Twinner population. The proportion of bilateral ovulations in the population is greater than expected, and this may be an economically important trait, which will respond to selection and be beneficial for improving bovine reproductive efficiency. Understanding factors controlling the increased functional activity of the right ovary and bilateral ovulations may provide further insights into the mechanisms controlling follicle selection and methods to improve reproductive management of cattle.     

Plasma gonadotropins and ovarian hormones during the estrous cycle in high compared to low ovulation rate gilts

Mature gilts classified by low (12 to 16 corpora lutea [CL], n = 6) or high (17 to 26 CL, n = 5) ovulation rate (OR) were compared for plasma follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, estradiol-17beta, and inhibin during an estrous cycle. Gilts were checked for estrus at 8-h intervals beginning on d 18. Blood samples were collected at 8-h intervals beginning on d 18 of the third estrous cycle and continued for one complete estrous cycle. Analysis for FSH and LH was performed on samples collected at 8-h intervals and for ovarian hormones on samples collected at 24-h intervals. The data were standardized to the peak of LH at fourth (d 0) and fifth estrus for the follicular phase and analyzed in discrete periods during the periovulatory (-1, 0, +1 d relative to LH peak), early-luteal (d 1 to 5), mid-luteal (d 6 to 10), late-luteal (11 to 15), periluteolytic (-1, 0, +1 d relative to progesterone decline), and follicular (5 d prior to fifth estrus) phases of the estrous cycle. The number of CL during the sampling estrous cycle was greater (P < 0.005) for the high vs low OR gilts (18.8 vs 14.3) and again (P < 0.001) in the cycle subsequent to hormone measurement (20.9 vs 14.7). For high-OR gilts, FSH was greater during the ovulatory period (P = 0.002), the mid- (P < 0.05) and late-luteal phases (P = 0.01), and tended to be elevated during the early-luteal (P = 0.06), but not the luteolytic or follicular periods. LH was greater in high-OR gilts during the ovulatory period (P < 0.005), but not at other periods during the cycle. In high-OR gilts, progesterone was greater in the mid, late, and ovulatory phases (P < 0.005), but not in the follicular, ovulatory, and early-luteal phases. Concentrations of estradiol-17beta were not different between OR groups during the cycle. Inhibin was greater for the high OR group (P < 0.005) during the early, mid, late, luteolytic, and follicular phases (P < 0.001). The duration of the follicular phase (from last baseline estrogen value to the LH peak) was 6.5 +/- 0.5 d and was not affected by OR group. These results indicate that elevated concentrations of both FSH and LH are associated with increased ovulation rate during the ovulatory phase, but that only elevated FSH during much of the luteal phase is associated with increased ovulation rate. Of the ovarian hormones, both inhibin and progesterone are highly related to greater ovulation rates. These findings could aid in understanding how ovulation rate is controlled in pigs.     

Successful induction of lactation in a barren thoroughbred mare: growth of a foal raised on induced lactation and the corresponding maternal hormone profiles

The purpose of this study was to demonstrate that a barren parous Thoroughbred mare with lactation induced by hormonal treatment can be introduced to an orphan foal at the same farm and that the mare can become pregnant after the end of the hormonal treatment. An additional purpose was to investigate the changes in the plasma concentrations of prolactin, estradiol-17β, progesterone, follicle-stimulating hormone, and luteinizing hormone before, during, and after hormonal treatment. The difference in body weight between the adopted foal and the control foals, which were at the same farm and raised by their natural mothers, was 17 kg at 24 weeks old, when the foals were weaned. However, the adopted foal and the control foals had almost the same weight at 35 weeks old and later. The first ovulation after hormonal treatment was confirmed 10 days after the end of hormonal treatment and then the normal estrous cycle resumed. Furthermore, the changes in plasma progesterone, estradiol-17β, follicle-stimulating hormone, and luteinizing hormone showed regular patterns after the first ovulation. Conception was confirmed in the fifth ovulation. Meanwhile, another study demonstrated that conception was confirmed in the first ovulation after hormonal treatment. The present study is the first to demonstrate the hormonal profiles during and after induction of lactation in a Thoroughbred mare. This approach is useful for solving the economic and epidemic problems of introducing a nurse mare to an orphan foal.     

Bovine Normal and Abnormal Reproductive and Endocrine Functions during the Postpartum Period: A Review

The results of numerous studies on postpartum uterine involution, ovarian activity and endocrinological changes before, during and after normal and abnormal parturitions, have been reviewed in this article. Most studies have shown that abnormal parturition is the main factor which delays completion of uterine involution and occurrence of the first estrous cycle post partum. The reviewed reports also indicated that any interference (corticosteroid injection, overiectomy, etc.) with normal synchronized hormonal changes of parturition can increase the incidence of retained fetal membrane. Reports on the use of hormonal treatments and their effects on the elimination of bacterial infection, rate of uterine involution and the resumption of ovulation activity are conflicting. It is suggested that the use of natural substances such as lipopolysaccharide of E. coli, serum or hyperimmune serum, extracts of poly morphonuclear leucocytes and/or macrophage-granulocyte Colony Stimulating Factor as treatments of postpartum uterine infection may play an important role in the completion of uterine involution and the commencement of estrous cycle .     

Kisspeptins and the reproductive axis: potential applications to manage reproduction in farm animals

Kisspeptins (Kp) are a family of neuropeptides produced mainly by two hypothalamic neuronal cell populations. They have recently emerged as a major regulator of the gonadotropin axis and their action is located upstream of the gonadotropin-releasing hormone (GnRH) cell population. In less than 10 yr a growing body of literature has demonstrated the involvement of these peptides in most, if not all, aspects of reproductive axis maturation and function. In contrast to these abundant basic research studies, few experiments have evaluated the potential application of Kp as tools to manipulate reproduction in domestic animals. In mammals, exogenous Kp administration potently stimulates gonadotropin secretion. This action is exerted mainly, if not exclusively, through the stimulation of GnRH release. Intravenous, intraperitoneal, or subcutaneous administration of Kp induced a robust and rapid increase in plasma gonadotropins (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]). However, this stimulatory effect is of short duration. Prolonged LH and FSH release over several hours can be achieved only when Kp are given as repeated multiple bolus or as an infusion. Kp administration was used in two experimental models, ewe and pony mare, with the aim of inducing well-timed and synchronized ovulations. During the breeding season, progesterone-synchronized ewes were given an intravenous infusion of Kp starting 30 h after the removal of progesterone implants. An LH surge was induced in all Kp-treated animals within 2 h of infusion onset. In contrast, in pony mares a constant infusion of Kp for 3 d in the the late follicular phase was unable to induce synchronized ovulation. Another set of studies showed that Kp could be used to activate reproductive function in acyclic animals. Pulsatile administration of Kp in prepubertal ewe lambs was shown to activate ovarian function, leading to enhanced ovarian steroidogenesis, stimulation of LH preovulatory surge, and ovulation. In anestrous ewes, an intravenous infusion of a low dose of Kp induced an immediate and sustained release of gonadotropins, followed a few hours later by an LH surge. This hormonal pattern mimicked hormonal changes normally observed during the estrous cycle follicular phase and was associated with a high percentage of ovulating animals (80%). In summary, exogenous administration of Kp appears to be a new tool to manipulate reproduction. However, optimal doses and periods of treatment should be defined for each species, and the development of powerful analogs or long-term release formulations is necessary before large-scale applications in domestic animals could be envisaged.     

Characterization of antral follicle populations during the estrous cycle in pigs selected for ovulation rate

The objectives of this study were to characterize and compare ovarian follicular populations in Gene Pool Control (GPC, randomly selected) and Relax Select line (RS, nine generations of selection for high ovulation rate followed by six generations of random selection) gilts during different stages of the estrous cycle. Thirty-five RS and 23 GPC gilts were allotted randomly within litter for ovary recovery on either d 3, 15 or 19 of the estrous cycle. Surface follicles on the ovaries were classified by size (small, less than 3 mm; medium, 3 to 6.9 mm; large, 7 to 12 mm), and counts were recorded for each ovary. Ovarian weight (OW), number of corpora lutea (CL), follicular fluid volume (FFV) from small, medium and large follicles, residual ovarian weight and follicular fluid weight (FFW) also were recorded. Total numbers of small and medium follicles were greatest on d 15, whereas total number of large follicles and FFW were greatest on d 19. The OW, FFW and follicle numbers of all classes were lowest on d 3. The RS gilts expressed longer interestrous intervals (21.9 vs 20.4 d, P less than .05) and higher ovulation rates (18.5 vs 15.3 CL, P less than .01) than GPC gilts. The left ovary of RS gilts was responsible for most of the ovulation rate advantage (10.3 vs 7.4 CL, P less than .01) Overall, GPC gilts had more total small follicles than RS gilts (P less than .01). The advantage was due primarily to higher numbers of small follicles at d 15.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovarian follicular growth, function and turnover in cattle: a review

Studies in cattle assessing changes in number and size of antral follicles, concentrations of estradiol, androgens and progesterone in serum and follicular fluid, and numbers of gonadotropin receptors per follicle during repetitive estrous cycles and postpartum anestrus are reviewed. The rate of growth of small follicles (1 to 3 mm) into larger follicles increases as the estrous cycle progresses from d 1 to 18 (d 0 = estrus). Size of the largest antral follicle present on the ovary also increases with advancement of the estrous cycle. Most large follicles (greater than 10 mm) persist on the ovarian surface for 5 d or more between d 3 and 13 of the bovine estrous cycle. After d 13, most of these large follicles are replaced more frequently by new growing follicles (turnover) with an increased probability for recruitment of the ovulatory follicle after d 18. More research is needed to determine the time required for growth of bovine follicles from small to large antral size and evoke recruitment of the ovulatory follicle. Factors that regulate selection of the ovulatory follicle are unknown but may involve increased frequency of LH pulses in blood, altered blood flow and(or) changes in intrafollicular steroids and proteins. Quantitative evaluation of ovarian follicles indicated occurrence of consistent short-term changes in fluid estradiol and numbers of luteinizing hormone receptors in cells of large follicles only during the pre-ovulatory period. Presumably, low concentrations of follicular estradiol found during most of the estrous cycle are not due to a lack of aromatizable precursor or follicle-stimulating hormone receptors. Follicular fluid concentrations of progesterone increase only near the time of ovulation. Little is known about changes in follicular growth, turnover and function during postpartum anestrus in cattle. However, preliminary data suggest that the steroidogenic capacity of large follicles changes markedly during the postpartum period.     

Granulosa-theca cell tumor associated with an ovulation fossa and normal ovarian stroma in a mare.

A granulosa-theca cell tumor was found in an ovary that had an ovulation fossa and normal ovarian tissue. The ovary was removed from a mare with a history of ovarian enlargement and behavioral changes. The affected ovary had a multicystic appearance on ultrasonographic examination performed before surgery, and an ovulation fossa was not palpable on examination per rectum. However, during surgery, the affected ovary was found to be within normal size limits, with an enlargement on 1 pole, and to contain an ovulation fossa. Atrophy of the infundibulum of the affected ovary helped to confirm the diagnosis of granulosa-theca cell tumor, and the ovary was removed. The mare's testosterone concentrations were normal. Granulosa-theca cell tumors are usually associated with a spherical ovary, attributable to ablation of the ovulation fossa, with no normal ovarian tissue present.     

Sex steroids level in blood plasma and ovarian follicles of the chimeric chicken

The study was performed to determine the hormonal status of mature germline chimeras obtained by blastodermal cell transfer from chicken embryos of a donor breed [Green-legged Partridgelike breed (GP) x Araucana (AR)] to those of a recipient breed [White Leghorn (WL)] being at the same stage of embryonic development. The egg-laying chimeras and WL hens (control) of the same age were used in the experiment. At first, blood samples were taken from each bird at 0.5, 5, 12.5 and 18.5 h following oviposition. Subsequently, the chimeras and the WL hens were decapitated 1-2 h after ovulation. A stroma and the following follicles were isolated from the ovary: white normal (1-4, 4-6 and 6-8 mm), white atretic and yellow preovulatory follicles (F4-F1). Sex hormones, progesterone (P4), testosterone (T) and oestradiol (E2) in blood plasma and ovarian follicles were determined radioimmunologically. The activity of the 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the granulosa and theca layers of the follicles was analysed histochemically. In chimeric chickens, a higher level of T in blood plasma during the ovulatory cycle was noticed. However, in the stroma, white prehierarchical and medium-size preovulatory ovarian follicles the level of T was significantly lower. With respect to E2, its elevated levels were found both in blood and in the ovarian follicles. There were no significant differences in P4 concentrations in blood plasma while in ovarian follicles a higher level was observed only in white 6-8 mm follicles. 3beta-HSD activity in granulosa and theca layers of the ovarian follicles in chimeras was not different from that in the WL hens. In conclusion, the results obtained indicate that germline chimeras exhibit significant alterations in sex hormone levels in the ovary and blood plasma, which in turn may affect their reproductive abilities.     

德州驴发情周期中卵泡动力学和激素变化规律的研究

本研究旨在揭示德州母驴发情季节的卵巢卵泡波变化特点以了解其卵泡的募集、选择、优势化、闭锁或者排卵,为驴人工授精和超数排卵提供可靠依据.本研究在德州驴发情季节(5～8月份)用直肠超声探查法每日检测5头德州母驴的10个排卵间隔的卵泡发育动态.同时每日采血,用放免法(RIA)检测E2、FSH、LH和IGF-1浓度.研究结果发现:(1)驴的排卵间隔平均为(23.22±0.28)d,每个周期中存在2个卵泡波,其中有4个展示主-主卵泡波,有6个展示次-主卵泡波.(2)第1波和第2波开始出现募集的时间分别在排卵后的第1和第(10.2±1.4)天,募集的卵泡数分别为(5.2±1.2)和(4.0±0.3)个,选择的卵泡数分别是(2.3±0.5)和(2.5±0.4)个.第1和第2卵泡波开始优势化的时间分别在排卵后的第(5.8±0.6)和第(18.1±1.4)天.波峰平均出现时间分别为第(7.67±0.24)和第(23.22±0.28)天.波峰时优势卵泡平均最大直径分别为(26.44±2.37)和(40.7±2.45)mm.第1和第2波最大优势卵泡每日平均生长率分别为(2.01±0.5)和(3.15±0.6)mm·d-1.(3)黄体(CL)最大直径平均为(37.61±1.58)mm,CL平均持续时间为(17.30±1.62)d.(4)E2浓度从排卵前3d至排卵后2d的发情期内均很高,平均维持在(46.47±9.53)Pg·mL-1,在排卵前2d达到峰值(62.84±4.89)Pg·mL-1.(5)由于E2的负反馈作用,FSH浓度到优势卵泡最后阶段(即第7天闭锁或第23或24天排卵时)大幅度下降.(6)LH在排卵前几天迅速升高,在排卵后第2天达到峰值(4.69±0.43)mIU·mL-1.(7)IGF-1的升降状况与E2基本相同,在排卵前1d达到峰值(47.9±3.91)ng·mL-1.通过上述卵泡和激素动态学变化,本研究得出下述结论:驴的卵巢卵泡发育是以卵泡波形式进行的,每个发情周期中最常出现的是2个卵泡波;排卵发生于发情结束前2 d;E2和IGF-1调节驴的发情活动;FSH调节小卵泡的募集;LH增高与排卵有关.