Boar pheromone androstenol may affect the ovarian morphology in cycling gilts by humoral pathway

Up to 1999 it was accepted that pheromones act exclusively by stimulation of dendritic receptors of olfactory neurons massed in the olfactory epithelium, but in 1999-2000, the presence of local humoral pathway for transfer of boar pheromone androstenol from the nasal cavity to the hypophysis and brain was demonstrated in gilts. The aim of the present study was to ascertain whether boar pheromone androstenol may affect by humoral pathway the ovarian morphology in gilts. This study demonstrated that intramuscular injections of androstenol in the follicular phase (17-20 day) of the estrous cycle in anosmatic gilts, in which the neural pathway for olfactory function was experimentally blocked, produced lack of the ovulation and changes in the morphology of ovaries. Histological analysis of the ovaries, collected seven days after androstenol injections, revealed the absence of corpora lutea and healthy follicles of a diameter over 6 mm as well as a significant decrease in the number of the follicles up to I mm in diameter (P<0.01). In androstenol-treated gilts, the number of atretic follicles from 1 mm to 6 mm in size was increased (P<0.01-P<0.001) and in one gilt cysts were found. The obtained results provided some evidence that in gilts in addition to acting by standard neural pathway, androstenol as a priming pheromone may affect the ovarian morphology by a humoral pathway.     

Differences in follicular morphology, steroidogenesis and oocyte maturation in naturally cyclic and PMSG/hCG-treated prepubertal gilts

Ovaries were obtained from naturally cyclic pigs on Days 16-17, 18, 19, 20 and 21 of the oestrous cycle and on the basis of observed follicular characteristics were assigned as representative of the early (Group 1), mid- (Groups 2 and 3) or late (after LH; Group 4) follicular phase. Follicular development in cyclic gilts was compared with that in ovaries obtained from late prepubertal gilts 36 (Group 5) or 72 (Group 6) h after treatment with 750 i.u. PMSG alone, or with a combination of 500 i.u. hCG 72 h after PMSG and slaughter 30-40 h later (Group 7). After dissection of all follicles greater than 2 mm diameter, follicular diameter, follicular fluid volume, follicular fluid concentrations of progesterone, oestradiol and testosterone, and the stage of oocyte maturation were determined. Combined PMSG/hCG treatment of immature gilts resulted in a pattern of follicular development different from that in naturally cyclic gilts during the follicular phase. Overall exogenous gonadotrophin treatment also increased (P less than 0.001) the variability in follicular diameter and fluid volume. Comparisons between appropriate groups also established differences in the variability of both morphological (diameter and volume, Group 1 vs Group 5; P less than 0.05) and biochemical development (follicular fluid oestradiol, Group 3 vs Group 6 and Group 4 vs Group 7; both P less than 0.05). Such differences in both morphological and biochemical characteristics between cyclic and PMSG/hCG-treated gilts were particularly evident in the population of larger (greater than 6 mm) follicles. These results indicate that the pattern of follicular development in naturally cyclic and in PMSG/hCG-treated gilts is dissimilar and suggests that the ovaries of gonadotrophin-treated prepubertal gilts are functionally different from the ovaries of mature females.     

Waves of follicle development during the estrous cycle in sheep

The pattern of ovarian follicle development in maiden cyclic lambs was characterized using the definition of a follicle wave as the changes in the number of follicles among the days of the estrous cycle, as originally defined in cattle by Rajakoski in 1960. We also examined the steroid content relationships among follicles on Days 5 (Wave 1) and 14 (Waves 2 and 3) of the estrous cycle. In Experiment 1, the ovaries of 20 cyclic lambs (40 to 45 kg) were examined daily using transrectal ultrasonography for 1 or 2 estrous cycles (n = 31 cycles). The number of small (2 and 3 mm in diameter), medium (4 and 5 mm) and large (> or = 6 mm) follicles were aligned with the beginning and end of the average length estrous cycle and then compared among days. Identified follicles were defined as those that grew to > or = 4 mm and remained at > or = 3 mm for > or = 3 d. The number of identified follicles emerging (retrospectively identified at 2 or 3 mm) per ewe per day was also aligned with the average length estrous cycle. In Experiment 2, ewe lambs were ovariectomized on Day 5 (n = 6) or 14 (n = 5) of the estrous cycle, then follicle diameters and follicular fluid concentrations of estradiol and progesterone were compared among follicles. Data were analyzed by repeated measures ANOVA and compared among days using Fisher's LSD. In Experiment 1, either 2 (n = 10 cycles), 3 (n = 20 cycles) or 4 (n = 1 cycle) periods of emergence of identified follicles occurred during individual cycles, with estrous cycle lengths of 15.6 +/- 1.6, 16.1 +/- 1.1 and 17 d respectively. In animals with 2 or 3 periods of emergence of identified follicles, the total number of small, medium and large follicles differed (P < 0.05) among days of the estrous cycle showing a wave-like pattern. In Experiment 2, a single follicle collected on each of Days 5 and 14 of the cycle (6.2 +/- 0.2 and 3.9 +/- 0.2 mm in diameter) had a higher (P < 0.05) concentration of follicular fluid estradiol (36.2 +/- 4.4 and 50.9 +/- 21.6 ng/mL) than other follicles collected on the same day (next largest follicle: 4.3 +/- 0.3 and 3.5 +/- 0.4 mm; 4.3 +/- 0.9 and 18.2 +/- 6.7 ng/mL estradiol). The results showed that 1) there was a synchronous emergence of follicles associated with fluctuations in the number and size of follicles during the estrous cycle; 2) within a wave there was a hierarchy among follicles for diameter and steroid content; 3) ovarian follicle growth in ewe lambs occurred in 2 or 3 organized waves during the estrous cycle.     

Effects of pregnant mare serum gonadotropin (eCG) on follicle development and granulosa-cell apoptosis in the pig

The effect of eCG on follicular development and granulosa-cell apoptosis in sexually mature and immature gilts and on granulosa-cell apoptosis in vitro were studied. The sexually mature gilts were treated with eCG on Day 11 of the estrous cycle, and effects were analyzed at different times after treatment with untreated animals at corresponding stages of the cycle as controls. Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), hematoxylin and eosin staining, and DNA ladder. The proportion of apoptotic cells in atretic follicles (39%) was significantly higher (P<0.01) than that in healthy follicles (9%). At 24h after eCG treatment in mature gilts, the total number of follicles visible on the ovarian surface (57 per ovary), the number of small (<3mm) follicles (31.5 per ovary) and the number of medium-sized (3-5mm) follicles (23 per ovary) were significantly higher (P<0.05) than those of control animals (28, 20 and 6.5 per ovary, respectively), and declined gradually thereafter to below the level of control animals. The number of large (>or=5mm) follicles began to show a marked increase at 72h after eCG (8.5 versus 2.5, P<0.05). At 24h after eCG treatment, the proportions of apoptotic cells in small (7.2%) and medium-sized follicles (7.4%) were markedly lower (P<0.01) than those in controls (21.5 and 21%, respectively) and increased gradually thereafter to approach the level in controls. The percentage of apoptotic cells in large follicles (10% at 24h post-eCG) did not change significantly. Before eCG treatment, there were markedly fewer follicles of all types on ovaries of immature gilts than of mature gilts (9 versus 25 per ovary) and the proportion of apoptotic cells in small and medium follicles was high (25 and 34%, respectively). After eCG treatment, the changes in follicle number and proportion of apoptotic cells in the immature gilts followed a similar pattern to that of the mature gilts. Equine chorion gonadotropin inhibited apoptosis of granulosa cells cultured either in vitro or in intact follicles in a dose-dependent manner. Thus, follicular atresia in the pig, as in other animals, was characterized by apoptosis of large numbers of granulosa cells, and eCG promoted follicular development by inhibition of granulosa-cell apoptosis.     

Exogenous insulin and additional energy affect follicular distribution, follicular steroid concentrations, and granulosa cell human chorionic gonadotropin binding in swine

The objective was to determine whether exogenous insulin and dietary energy interact to affect follicular development in gilts. In a 2 x 2 x 2 completely randomized design, main effects were level of dietary energy (5771 or 9960 kcal metabolizable energy/day beginning on Day 12 of the estrous cycle), insulin dosage (0 or 0.4 IU/kg twice daily beginning on Day 15 of the cycle), and day of cycle at ovary removal (Day 17 or Day 19). Percentage of follicles designated small (less than or equal to 3 mm diameter) decreased from Day 17 to Day 19 of the cycle, and the percentage of large follicles (greater than or equal to 7 mm) increased (p less than 0.05). Insulin interacted with day of the cycle (p less than 0.05) to affect distribution of medium (4-6 mm) and macroscopically atretic follicles. Percentage of atretic follicles increased from Day 17 to Day 19 in saline-treated (from 15.5% to 38.2%) but not in insulin-treated animals (6.3% to 10.7%). Percentage of medium (4-6 mm) follicles decreased from Day 17 to Day 19 in saline-treated gilts (from 41.7 to 16.6%) but not in insulin-treated gilts (39.8% to 35.1%). Intrafollicular testosterone and progesterone concentrations were not affected by treatments. In medium follicles, the ratio of estradiol to progesterone was greater (p less than 0.05) for insulin-treated gilts on Day 17 than for the other treatment combinations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Short-term effects of FSH in vitro on granulosa cells of individual sheep follicles

In Romanov ewes at Day 13 or 14 of the cycle, granulosa cells originating from individual follicles were studied in short-term incubations for aromatase activity and thymidine incorporation. The study was performed on 76 follicles of different sizes (2-7 mm diameter) and degree of atresia, as assessed by histological examination of smears of granulosa cells. As atresia progressed, the labelling index and aromatase activity of granulosa cells decreased. In normal follicles, when follicular diameter increased, the labelling index decreased, while aromatase activity of granulosa cells and oestradiol-17 beta concentration in follicular fluid increased. There was a negative relationship between oestradiol concentration in follicular fluid and the labelling index of granulosa cells in vitro (rs = -0.75; P less than 0.01), suggesting an inverse relationship between growth and differentiation of granulosa cells in normal sheep follicles. In normal small and medium-sized follicles (2-6 mm), incubation with FSH (100 ng/ml) for 2 h increased significantly the labelling index of granulosa cells. In normal medium-sized follicles (4-6 mm), incubation with FSH (50 ng/ml) for 1 h decreased the aromatase activity of granulosa cells. From these results, it is suggested that FSH acts mainly on cells in the G1 phase of the cell cycle, which are steroidogenically active, and makes them move into the S phase where their steroidogenic activity is temporarily inhibited.     

Relationship between concentrations of immunoreactive insulin-like growth factor-I in follicular fluid and various biochemical markers of differentiation in bovine antral follicles

Three experiments were conducted to determine the relationship between concentrations of insulin-like growth factor-I (IGF-I) in ovarian follicular fluid and various biochemical markers of follicular differentiation in bovine follicles. In Experiment I, ovaries were removed on Days 7, 14, 28, 42, or 56 after parturition from a total of 21 cows. In Experiment II, ovaries of 31 cows were removed between Days 20 and 30 postpartum after 48 or 96 h of either saline (0.9% NaCl, 5 ml) or luteinizing hormone-releasing hormone (LHRH, 500 ng/5 ml saline) injections given every 2 h via jugular cannulae. In Experiment III, ovaries of six cows were removed 48-50 h after a 35-mg injection of prostaglandin F2 alpha during the midluteal phase of an estrous cycle. In Experiments I and II, all follicles greater than or equal to 8.0 mm in diameter were removed from each ovary (n = 33 and 46, respectively). In Experiment III, fluid from all follicles greater than 4 mm in diameter were removed individually (n = 10), and fluid from follicles 1-4 mm in diameter were pooled for each cow. Follicles for each experiment were further categorized as either estrogen-active (E-A, concentration of estradiol greater than progesterone in follicular fluid) or estrogen-inactive (E-I, concentration of progesterone greater than estradiol in follicular fluid). Measurements of immunoreactive IGF-I (i-IGF-I) were made after separating IGFs from their binding proteins with an acid-ethanol extraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Concentrations of somatotropin and prolactin in the follicular fluid and blood serum of cows in different phases of the estrous cycle

Comparative investigations of somatotropin and prolactin contents in the fluid of antral follicles and blood serum of cows in different phases of the oestrous cycle were performed. The somatotropin concentration in the fluid was shown to rise with increasing the follicle diameters from 3-5 to 6-10 mm in the follicular phase and to decrease in follicles of diameter 11-20 mm in the luteal phase. The prolactin concentration was higher in the fluid of follicles 11-20 mm in diameter than in those of 3-5 mm in diameter in the follicular phase and did not depend on the follicle size in the luteal phase. Concurrently, the prolactin content in follicles 3-5 mm in diameter was higher in the luteal than follicular phase of the cycle. As compared to the follicular phase, an increase in the prolactin concentration in the bovine blood serum during the luteal phase was also found. The data obtained indicate that changes in the somatotropin and prolactin contents in the follicular fluid are related to processes regulating growth and development of antral follicles depending on the phase of oestrous cycle and to changes in the blood hormone concentrations as well.     

Effect of FSH infusion on follicle development in GnRH agonist-treated gilts

The aim was to investigate the effect of infusion of purified FSH alone on follicle development in hypogonadotrophic GnRH agonist-treated gilts. Large-White hybrid gilts (n = 12) were treated during the mid-luteal phase and again after 28 days (day 0) with a potent slow releasing GnRH agonist. On day 3, seven gilts were infused for 168 h with 1.5 S1 units oFSH h-1 (equivalent to 1.5 units of bioactivity of NIH-FSH-S1 standard) and blood samples were collected. Ovaries were then recovered and all follicles > or = 1 mm in diameter were dissected and incubated for 2 h in 1 ml Eagle's minimum essential medium. The ovaries were recovered from the remaining five GnRH agonist-treated gilts on day 10 and also from five cyclic gilts during the late follicular phase (controls). Plasma FSH concentrations in GnRH agonist-treated gilts were lower (P < 0.01) than in follicular phase controls, increased (P < 0.001) after 1 h of FSH infusion and reached a plateau similar (P > 0.1) to that of controls after 8 h. Basal LH concentrations were similar (P > 0.1) between GnRH agonist-treated and control gilts and remained unchanged (P > 0.1) throughout the infusion period. GnRH agonist treatment reduced (P < 0.01) basal oestradiol concentrations compared with control gilts. Infusion with FSH alone increased (P < 0.001) plasma oestradiol concentrations after 96 h compared with those before infusion; when the animals were killed oestradiol concentrations were higher (P < 0.01) in GnRH agonist-treated gilts infused with FSH than in controls. This was also apparent by vulval swelling and behavioural oestrus. There were more follicles > or 1 mm in diameter in the GnRH agonist-treated groups than in the controls (184, 153 and 86 per animal; P < 0.01). Infusion with FSH increased the maximum follicle diameter (GnRH agonist: < 4 mm; FSH infused: < 12 mm; controls: < 10 mm) and tended to increase (P < 0.07) the mean number of follicles > or = 6 mm diameter per animal (FSH infused: 53; controls: 21). Total oestradiol production in vitro by follicles > or = 1 mm was higher (P < 0.01) in GnRH agonist-treated gilts infused with FSH and in follicular phase controls than in animals treated with GnRH agonist alone. However, oestradiol and testosterone secretion in vitro per follicle > or = 6 mm in diameter was lower (P < 0.05) in FSH-infused animals than in controls. In summary, although infusion of FSH alone stimulated the growth of multiple follicles of preovulatory size in GnRH agonist-treated gilts, steroidogenic output by individual follicles was impaired.     

Passive immunization of the pig against gonadotropin releasing hormone during the follicular phase of the estrous cycle

Three experiments were conducted to determine the effects of passively immunizing pigs against gonadotropin releasing hormone (GnRH) during the follicular phase of the estrous cycle. In Experiment 1, sows were given GnRH antibodies at weaning and they lacked estrogen secretion during the five days immediately after weaning and had delayed returns to estrus. In Experiment 2, gilts passively immunized against GnRH on Day 16 or 17 of the estrous cycle (Day 0 = first day of estrus) had lower (P<0.03) concentrations of estradiol-17beta than control gilts, and they did not exhibited estrus at the expected time (Days 18 to 22). When observed three weeks after passive immunization, control gilts had corpora lutea present on their ovaries, whereas GnRH-immunized gilts had follicles and no corpora lutea. The amount of GnRH antiserum given did not alter (P<0.05) serum concentrations of LH or pulsatile release of LH in sows and gilts. In Experiment 3, prepuberal gilts were given 1,000 IU PMSG at 0 h and GnRH antiserum at 72 and 120 h. This treatment lowered the preovulatory surge of LH and FSH, but it did not alter serum estradiol-17beta concentrations, the proportion of pigs exhibiting estrus, or the ovulation rate. These results indicate that passive immunization of pigs against GnRH before initiation of or during the early part of the follicular phase of the estrous cycle retards follicular development, whereas administration of GnRH antibodies during the latter stages of follicular development does not have an affect. Since the concentration of antibodies was not high enough to alter basal or pulsatile LH secretion, the mechanism of action of the GnRH antiserum may involve a direct ovarian action.     

Systemic and intraovarian effects of corpus luteum on follicular dynamics during estrous cycle in hair breed sheep

The present study aimed to determine systemic and local effects of corpora lutea (CL), on follicular dynamics throughout the estrous cycle. All follicles >or=2 mm and CL were assessed by daily transrectal ultrasonography in 12 West African ewes. Blood samples were collected to determine plasma concentration of progesterone. Fifteen estrous cycles were evaluated with a mean interovulatory interval of 16.8+/-0.2 days. Two (13.3%), 10 (66.7%) and 3 (20%) of the estrous cycles had 2, 3 and 4 waves of follicular development, respectively. In sheep with three waves of follicular development, both the length of growing phase and the growth rate of dominant follicles from midluteal wave II were diminished (3.4+/-0.3 days, P<0.0001, and 0.4+/-0.1 mm/day, P<0.01, respectively) when compared to follicles from early luteal phase (wave I, 4.1+/-0.2 days, and 0.7+/-0.1 mm/day) or late luteal phase (wave III, 6.3+/-0.4 mm and 0.6+/-0.1 mm/day). The diameter of the dominant follicle was smaller during the midluteal phase (3.9+/-0.1 mm, P<0.0001) than in the early and late luteal phase (5.0+/-0.2 and 5.7+/-0.2 mm; respectively). The effect of the dominant follicle was less during midluteal phase, because number of accompanying smaller follicles was fewer (P<0.01) in waves I and III (6.3+/-0.9 compared with 3.4+/-0.8 and 2.3+/-0.7). The number of follicles was also different between ovaries that had CL and those that did not. The total number of large follicles during the luteal phase was less in ovaries with CL (0.9+/-0.5 compared with 2.7+/-0.3; P<0.01), as was the mean daily number of both large (0.1+/-0.02 compared with 0.2+/-0.02; P<0.001) and total number of follicles >or=2 mm (2.5+/-0.1 compared with 3.3+/-0.1; P<0.01). Current results indicate that the presence of a functional CL may exert both systemic and local effects on the population of follicles, affecting the dominance exerted by large follicles.     

Pattern of follicular development in high fecundity Olkuska ewes during the estrous cycle

Folliculogenesis was studied daily in the 18 oestrous cycles in six prolific Olkuska ewes from October to December using transrectal ultrasonography to record the number and size of all ovarian follicles > or =2 mm in diameter. Blood samples were taken once a day and were analyzed for concentrations of FSH, LH, estradiol and progesterone. Follicular and hormonal data were analyzed for associations between different stages of development of the follicular waves and concentrations of FSH and estradiol. The first wave during which at least one follicle reached maximum diameter of > or =4 mm after ovulation, was defined as a wave 1, and the following waves were numbered sequentially. Waves 1, 2, 3, 4 and the ovulatory one emerged on days: -2 to 4, 4 to 8, 6 to 11, 10 to 12 and 11 to 15, respectively. The mean number of follicles per wave that reached diameter of > or =4 mm was 4.15 +/- 1.1 and 16.62 +/- 8.6 follicles per estrous cycle of a total 299 follicles were observed. Significantly more follicles (p> or =0.05) emerged on days 2, 8 and 13 than in other days. Serum FSH concentrations fluctuated from 0.11 ngml(-1) on day 2 to preovulatory maximum 1.81 ngml(-1) on day 17 of the estrous cycle. The emergence of follicular waves was associated with elevations of FSH concentrations in blood serum. The mean increase in FSH concentration was followed by the recruitment of follicles of the next wave. The mean daily FSH concentration and the mean number of follicles emerging each day were negatively correlated. The length of the interwave interval (4.4 +/- 1.6 days) did not differ significantly from the interval between pulses of FSH (4.8 +/- 0.3 days). The mean serum estradiol concentrations showed fluctuations until day 14 and then gradually increased from 5.47 +/- 0.3 pgml(-1) to reach a peak 13.14 +/- 0.2 pgml(-1) on the day before ovulation. To summarize, the growth of ovarian follicles during the estrous cycle in high fecundity Olkuska sheep exhibited a distinct wave-like pattern. Ovarian follicles emerged from the pool of 2 mm follicles. The preovulatory follicles originated from the large follicle population were present in the ovary at the time of luteal regression. The initial stages of the growth of the largest follicles appears to be controlled primarily by increases in FSH secretion.     

Relationship between progesterone and estradiol contents of follicular fluid and the morphological appearance of granulosa cells of follicles coexisting with corpora lutea in bovine ovaries

Bovine ovaries (n=149) bearing follicles (>5 mm) coexisting with mature corpora lutea (CL;>10 mm) were obtained at a local abattoir without regard for the reproductive status of the donor cows. Most corpora lutea were 21 to 25 mm in diameter, and nearly half of the largest follicles were 11 to 15 mm in diameter. When oocytes were aspirated from follicles 16 to 30 mm in diameter, approximately 60% of them proved to be degenerated. Concentrations of progesterone (P4) and estradiol-17beta (E2) in the follicular fluid of 23 follicles (>10 mm) were determined. Progesterone and estradiol-17beta were found to be the major hormone in 16 (69.6%) and 7 (30.4%) of the follicles, respectively. Light-microscope observations of the granulosa cells of the same 23 follicles showed that 7 were deficient in mural granulosa cells, and that 15 of the remaining 16 follicles were atretic or luteinizing. Ultrastructural observations of granulosa cells revealed many lipid droplets in the cytoplasm of follicles coexisting with mature CL, suggesting the initiation of luteinization. These results show that approximately 70% of the follicles were P4-dominant and that more than 95% of them were morphologically degenerated. Thus it is suggested that morphological signs of atresia precede changes in the concentrations of hormones in the follicular fluid of follicles coexisting with corpora lutea (>10 mm) during the middle of the estrous cycle.     

Effect of progesterone administration on the ovarian response to superovulatory treatments in cattle

To evaluate ovarian response in Angus cows previously treated with progesterone (P4), animals were randomly assigned to two groups: T600 group (n=14), 600 mg of P4/day. P4 was injected from days 3 to 7 of the estrous cycle. On day 7, superovulatory treatments began. The control group (n=12) was given vehicle only. The superovulatory treatments in the control group began on days 7-9 of the estrous cycle. The superovulatory total treatment dose of 400mg NIH FSH P1 was given twice a day over a 4-day period. Ultrasonography of the ovaries was conducted 3 days preceding the initiation of superovulatory treatment, every 24h. In both groups, an additional ultrasonographic evaluation was made at 24h after the end of superovulatory treatment. Blood samples were collected 4 days preceding the initiation of superovulatory treatment, every 24h. Additional samples were taken from the P600 group for 12 day after of initiation of superovulatory treatment every 24h, except on the fifth day after the initiation of superovulatory treatment. In the P600 group, P4 concentrations were greater than in the control group (P<0.01) and remained over 1 ng/ml up to day 11 after beginning of superovulatory treatment. The diameter of the dominant follicle was larger in the animals of the control group (P<0.01). Cows of the P600 group had a greater number of Class I (3-4mm) follicles (P<0.01). A significant day and treatment effect (P<0.01) were observed in Class II (5-9 mm) follicles. Effects due to treatment on the number of Class III follicles (P<0.05) were observed. In the P600 group, no estrous post-superovulatory was observed and there were no ovulations that occurred. Conversely, 100% of the cows of the control group showed estrous. In the P600 group, there were a greater number of Class III follicles (P<0.01) and a lesser number of Class II follicles (P<0.05) at 24h after the end of superovulatory. In the control group, 66.7% of the cows responded to superovulatory treatments. In conclusion, the daily administration of 600 mg of P4, from days 3 to 7 of the estrous cycle, produces an increase of plasma concentrations of this hormone from day 4, resulting in changes in follicular dynamics (absence of follicles greater than 10mm of diameter and an increase of the population of Class I follicles). As to the ovarian stimulation using Folltropin V in animals receiving a daily injection of 600 mg of P4 from days 3 to 7 of the estrous cycle, a greater population of follicles>or=10mm developed by 24h after superovulatory treatments were completed.     

Changes in ovarian function in mature beef cows grazing endophyte infected tall fescue

The objective was to examine follicular and luteal development and function in mature, lactating beef cows grazing endophyte free (E-) or endophyte infected (E+) tall fescue during the early postpartum period. Angus, Hereford, and Angus x Hereford cows were exposed to pasture for 37-39 days before synchronized estrus. Serum concentrations of prolactin were evaluated during the luteal phase before the synchronized estrus. Every Monday, Wednesday, and Friday for one estrous cycle ovaries were monitored by transrectal ultrasonography and blood was collected for determination of serum concentrations of progesterone and estradiol in cows that responded to synchronization. Signs of fescue toxicosis in E+ cows included decreased serum concentrations of prolactin (84.9+/-13.6 pg/ml versus 32.3+/-12.0 pg/ml; P < 0.009) measured during the luteal phase (day 37 of grazing) and decreased body condition of cows and weight of cows and calves (P < 0.001). Neither serum concentrations of progesterone or estradiol, nor diameter of the CL differed between treatments. Diameter of the largest follicle tended to be smaller for cows grazing E+ fescue, especially between days 8 and 12 of the estrous cycle (P < 0.08). Numbers of class 1 (3-5 mm) and class 3 (>10 mm) follicles were similar (P > 0.05) between treatments, but number of class 2 (6-9 mm) follicles was reduced in E+ cows for most of the cycle (days 10 through 20; P < 0.03). Length of synchronized estrous cycle, days open, calving interval, and pregnancy rate at 30, 45, 60, and 90 days post-breeding was similar (P > 0.05) among treatment groups. Even though follicular dynamics (diameter of the largest follicle and number of class 2 follicles) were altered in cows grazing E+ tall fescue, follicular function was apparently not affected by ergot alkaloids.     

Expression of chemerin and its receptors in the ovaries of prepubertal and mature gilts

Recent studies have demonstrated that chemerin participates in the regulation of female reproductive function at the level of the ovaries. Due to the lack of data concerning the presence of the chemerin system (chemerin and its receptors: CMKLR1, GPR1, CCRL2) in the ovaries of pigs, one of the most economically important livestock species, the aim of this study was to investigate the expression and localization of chemerin and its receptors in the ovaries of prepubertal and mature gilts. We also aimed to examine the concentrations of chemerin in the follicular fluid of prepubertal and mature animals. In the present study, we have demonstrated the expression patterns of chemerin system components in the porcine follicles of different sizes of prepubertal and mature animals, as well as in corpora lutea of mature gilts during the estrous cycle and early pregnancy. The obtained results suggest that the expression of chemerin system components is influenced by the reproductive stage, cell type, and the hormonal status of gilts (the estrous cycle/pregnancy). We have also presented the localization of the chemerin system components in various ovarian structures, and also showed changes in the concentration of chemerin in the follicular fluid of pigs. The presented findings not only confirm that chemerin is produced locally in the porcine ovary but they also demonstrate that chemerin directly affects ovarian cells, as confirmed by the presence of chemerin receptors in all ovarian structures. Therefore, chemerin appears to be an important intra‐ovarian factor that could regulate ovary function in pigs.     

Patterns of follicular growth during the four-day estrous cycle of the rat

Female Sprague-Dawley rats underwent laporatomy during metestrus at 70 to 75 days of age or remained untreated to study the effects of surgical stress on follicular growth. Groups of rats were killed on each day of a 4-day estrous cycle, serial sections of the ovaries were prepared histologically and the number and size of follicles with one or more complete layers of cuboidal granulosa cells were determined. Since no differences due to surgery were found, the data were pooled by day of the estrous cycle (17 or 18 rats/day of cycle) for characterization and comparison of size distribution of follicles on different days of the estrous cycle. Follicles were classified as atretic or healthy and divided into groups by increments of 20 micron of diameter for graphing. Data were analyzed by analysis of variance and least squares means. Significant differences were found in the distribution of both healthy and atretic follicles among days of the estrous cycle. At least 21 follicles/ovary were recruited from less than 260 micron into greater than 260 micron in diameter between proestrus and estrus, and the follicles for ovulation were selected by diestrus. A greater number of growing follicles of 70 to 100 micron in diameter were present at diestrus. From the disappearance of follicles greater than 260 micron between estrus and proestrus, it appears that atresia is a very rapid process.     

Use of high-resolution transrectal ultrasonography to assess changes in numbers of small ovarian antral follicles and their relationships to the emergence of follicular waves in cyclic ewes

Transrectal ovarian ultrasonographic studies have shown that, in cattle, follicular wave emergence is associated with a large increase in the number of small antral follicles (4-6mm in diameter); an analogous association has not been found for small follicles (2-3mm in diameter) in the ewe. In previous studies in ewes, accurate assessment of the number of follicles has been limited to follicles > or =2 or 3mm in size. Newer, high-resolution equipment allowed us to identify follicles > or =0.4mm and to quantify all antral follicles > or =1mm in diameter in seven cyclic Western White Face ewes. This allowed us to expand the small follicle pool examined, from 1 to 4 follicles/day (2-3.5mm in diameter) in earlier studies, to 8-18 follicles/day (1-3mm in diameter). Total number of small follicles (> or =1 and < or =3mm in diameter) increased between Days -1 and 0 (Day 0=day of ovulation), and declined between Days 1 and 3 (P<0.05). There were no significant changes in the number of small or medium (4mm in diameter) follicles around days of follicle wave emergence (+/-2 days). The 1-3 follicles in the 2-3mm size range, which constituted a follicle wave (i.e. grew to > or =5mm in size before regression or ovulation), were the only small follicles to emerge in an orderly succession during the estrous cycle, approximately every 3-5 days. Thus, unlike in cattle, there is no apparent increase in numbers of small follicles at follicle wave emergence in cyclic sheep, and little evidence for selection of recruited follicles and follicular dominance.     

Time of ovarian follicle selection during the porcine estrous cycle

Two experiments were conducted to: 1) determine the time during the procine estrous cycle when compensation in ovulation rate after unilateral ovariectomy (ULO) ceases to be complete, 2) compare the follicle selection process in gilts selected for high ovulation rate with unselected control gilts and 3) determine the number of follicles on the right ovary at various stages of the estrous cycle. Experiment I included 25 crossbred gilts, while Experiment II included 17 gilts selected for high ovulation rate and 16 unselected control gilts. The right ovary was removed via a mid-ventral laparotomy on either day 13, 15, 17 or 19 of the cycle. In Experiment I, compensation in ovulation rate ceased between days 13 and 15; whereas, in Experiment II, cessation occurred between days 15 and 17. Selected and control gilts responded alike to ULO, indicating similarity in the follicle selection process. Follicle numbers in the right ovary showed a general decline, especially between days 17 and 19, indicating that atresia was occurring during the follicular phase. The results indicate that the selection of ovarian follicles for ovulation at the ensuing estrus occurs before day 17 of the porcine estrous cyle.