Ovarian follicular and luteal dynamics in wapiti during the estrous cycle

The reproductive tracts of 13 mature hinds were examined daily by transrectal ultrasonography and blood samples were taken daily from October to January to characterize follicular, luteal, and endocrine dynamics in wapiti during the estrous season. Follicle development occurred in waves characterized by regular, synchronous development of a group of follicles in temporal succession to a surge in serum FSH concentration. The mean interovulatory interval was 21.3 +/- 0.1 d, but was shorter in hinds exhibiting two follicular waves than in hinds exhibiting three and four waves (P < 0.05). The interwave interval was similar among waves in two-wave cycles and the first wave of three-wave cycles. All other interwave intervals in three- and four-wave cycles were shorter (P < 0.05). The maximum diameter of the dominant follicle of the first wave was similar among two-, three-, and four-wave cycles. For all other waves in three- and four-wave cycles, the maximum diameter was smaller (P < 0.05). Corpus luteum diameter and plasma progesterone concentrations were similar between two- and three-wave cycles, but the luteal phase was longer (P < 0.05) in four-wave cycles. The dominant follicle emerged at a diameter of 4 mm at 0.4 +/- 0.1 and 0.8 +/- 0.1 d before the largest and second largest subordinate follicles, respectively. The follicle destined to become dominant was larger (P < 0.05) than the largest subordinate follicle one day after emergence, which coincided with the first significant decrease in serum FSH concentration. We concluded that the estrous cycle in wapiti is characterized by two, three, or four waves of follicular development (each preceded by a surge in circulating FSH), that there is a positive relationship between the number of waves and the duration of the cycle, and an inverse relationship between the number of waves and the magnitude of follicular dominance (diameter and duration of the dominant follicle).     

Ovarian follicular dynamics in heifers during early pregnancy

Daily ultrasonic monitoring of individual follicles was used to compare follicular wave characteristics of nonbred (n = 6) and pregnant heifers (n = 6). The dominant follicle of the first wave (Wave 1) did not differ significantly between reproductive statuses for any endpoint. The dominant follicle of Wave 2 was the ovulatory follicle in all nonbred heifers. The maximum diameter of the dominant follicle of Wave 2 was greater (p less than 0.05) for the nonbred heifers (14.8 mm) than for the pregnant heifers (13.0 mm). The dominant follicle of Wave 3 was detected later (p less than 0.003; Day 19.7 vs. Day 17.3) and reached a greater diameter (p less than 0.05; 16.6 mm vs. 12.0 mm) in the nonbred than in the pregnant heifers. On the mean day of onset of luteolysis (Day 15.2) in the nonbred heifers, the dominant follicle was similar in diameter for the two groups. Within a few days, the follicle began to regress in the pregnant heifers but maintained or increased in diameter in the nonbred heifers so that a greater maximum diameter was attained. During Days 0 70 of pregnancy, the interval from emergence of a wave to the emergence of the next wave was constant (not significantly different; mean intervals, 8.5 9.8 days). The mean maximum diameter attained by the dominant follicles differed significantly among the first 6 follicular waves; diameter was greatest for Wave 1 (15.7 mm), smallest for Waves 2 (13.1 mm) and 3 (12.6 mm), and intermediate for Waves 4 (14.0 mm), 5 (13.7 mm), and 6 (14.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovarian follicular dynamics in the llama

Ovarian follicular dynamics were determined in adult llamas by ultrasonography and palpation per rectum and hormone analysis (estradiol-17 beta and estrogen conjugates) of plasma and urine. The relationship of gonadotropin secretion to follicular development was determined by the analysis of plasma FSH and LH concentrations. Progesterone analysis of plasma was used to verify or deny the presence of CL. Final follicular development (from 3 mm) averaged 4.8 days, while the duration of the mature follicle (8-12 mm) averaged 5.0 days; regression of the follicle occurred over about 4 days. The development of a subsequent dominant follicle usually began within 2-3 days after onset of regression of the dominant follicle. While several follicles were present at the time of the demise of the dominant follicle, only one follicle continued to develop. The interval between ovarian follicle waves averaged 11.1 days. Dominant follicle activity alternated between ovaries in 81% of the cycles. The occurrence of dominant follicles was evenly distributed between ovaries. While plasma estradiol and estrogen conjugate concentrations were positively associated (p less than 0.05) with follicular activity, urinary estrogen conjugate concentrations best reflected ovarian follicular dynamics (p less than 0.001). Daily FSH concentrations in plasma were not correlated with follicular activity. LH concentrations in plasma were low in all animals throughout the study, indicating estrogen from developing ovarian follicles does not induce the release of LH. Progesterone values were low during the study, indicating that the llama does not spontaneously ovulate, at least under the conditions of this study. In summary, llamas have overlapping ovarian follicle waves that occur at about 11-day intervals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation between progesterone concentrations during the early luteal phase and follicular dynamics in goats

We studied the relationship between progesterone (P4) concentrations early in the estrus cycle and follicular dynamics in dairy goats. We used seven untreated goats (control group) and six progesterone treated goats (P group) with a controlled internal drug release device from Days 0 to 5 (Day 0: day of ovulation). We performed daily ultrasonograph during the interovulatory interval to determine ovarian change and took daily blood samples to determine serum estradiol 17beta (E2) and P4 concentrations by RIA. We divided the control goats into 3- (n = 4) and 4-wave goats (n = 3), according to the number of follicular waves recorded during the ovulatory cycle. Mean progesterone concentrations between Days I and 5 were higher and mean estradiol concentrations between Days 3 and 5 were lower in 4-wave goats (P4: 3.8+/-0.2 ng/ml; E2: 1.6+/-0.2 pg/ml) than in 3-wave goats (P4: 2.0+/-0.5 ng/ml, P < 0.05; E2: 4.4+/-0.9 pg/ml, P < 0.05). Wave 2 emerged earlier in 4-wave (Day 4.2+/-0.3) than in 3-wave goats (Day 7.3+/-0.3, P < 0.05). Three out of six of the progesterone-treated goats had short cycles (mean 8.0+/-0.0 days) and ovulated from Wave 1. The other three goats had shorter cycles (mean 18.3+/-0.3 days) than the control group (20.0+/-0.2 days; P < 0.05), although they were within the normal range of control cycles (shortened cycles). In the three treated goats with shortened cycles (two with four waves, one with three waves), mean progesterone concentrations between Days I and 5 were higher (4.7+/-0.6 ng/ml) than in the 3-wave control goats. In these goats, Wave 2 emerged at Day 4.3+/-0.3, similar to the time observed in 4-wave goats but earlier (P < or = 0.05) than in 3-wave control goats. Overall results confirm a relationship between the progesterone levels and the follicular wave turnover during the early luteal phase in the goat. Higher progesterone concentrations may accelerate follicular turnover probably by an early decline of the negative feedback action of the largest follicle of Wave 1. This is followed by an early emergence of Wave 2.     

Ovarian follicular dynamics during the estrous cycle in heifers monitored by real-time ultrasonography

It is not clear whether the turnover of ovarian follicles during the estrous cycle in cattle is continuous and independent of the phase of the cycle, or whether waves of follicular growth occur at specific times of the cycle. To clarify this controversy, the pattern of growth and regression of ovarian follicles was characterized during a complete estrous cycle in ten heifers by daily ultrasonographic examinations. Follicles greater than or equal to 5 mm were measured and their relative locations within the ovary were determined in order to follow the sequential development of each individual follicle. Results indicated the presence of either two (n = 2 heifers), three (n = 7), or four (n = 1) waves of follicular growth per cycle. Each wave was characterized by the development of one large (dominant) follicle and a variable number of smaller (non-dominant) follicles. In the most common pattern observed (three waves/cycle), the first, second, and third waves started on Days 1.9 +/- 0.3, 9.4 +/- 0.5, and 16.1 +/- 0.7 (X +/- SEM), respectively. The dominant follicle in the third wave was the ovulatory follicle. The maximal size and the growth rate of the dominant follicle in the second wave were significantly lower than in the other waves, but no significant difference was observed between the first and third waves. For the two heifers that had two follicular waves/cycle, the waves started on Days 2 and 11, whereas in the remaining heifer (four waves/cycle), the waves began on Days 2, 8, 14, and 17, respectively. At 0, 1, 2, 3, and 4 days before estrus, the ovulatory follicle was the largest follicle in the ovaries in 100%, 95%, 74%, 35%, and 25% of follicular phases monitored, respectively. The relative size of the preovulatory follicle at the completion of luteolysis (progesterone less than 1 ng/ml) was negatively correlated (r = -0.90; p less than 0.0001) with the interval of time between the end of luteolysis and the luteinizing hormone surge, suggesting that the length of proestrus is determined by the size of the pre-ovulatory follicle at the beginning of proestrus. In conclusion, this study shows that the development of ovarian follicles greater than or equal to 5 mm in heifers occurs in waves and that the most common pattern is three waves per estrous cycle.     

Ovarian follicular dynamics during the estrous cycle in buffalo (Bubalus bubalis)

The growth, selection, regression and ovulation of ovarian follicles was ultrasonically monitored in 30 Murrah buffalo throughout a spontaneous estrous cycle during the breeding season (autumn). Examinations revealed that follicular growth during the estrous cycle occurs in waves; the buffalo showed 1-wave (3.3%, n = 1), 2-wave (63.3%, n = 19) or 3-wave (33.3%, n = 10) follicular growth. The first wave began at 1.00, 1.16 +/-0.50 and 1.10 +/- 0.32 d in buffalo with 1, 2 and 3 waves, respectively (ovulation = Day 0). The second wave appeared at 10.83 +/- 1.09 and 9.30 +/- 1.25 d (P < 0.01) for the 2 and 3 wave cycle animals, respectively. The third wave started at 16.80 +/- 1.22 d. Structural persistence of the first dominant follicle was longer in the 2- than 3-wave cycles (20.67 +/- 1.18 vs 17.90 +/- 3.47 d ; P < 0.05). The duration of the growth and static phases of the first dominant follicle differed between the 2 and 3 wave cycles (P < 0.05), whereas there were no differences in linear growth rates (cm/d). Two and three wave cycles differed (P < 0.05) with respect to the maximum diameter of both the first dominant follicle (1.51 +/- 0.24 vs 1.33 +/- 0.18 cm) and the ovulatory follicles (1.55 +/- 0.16 vs 1.34 +/- 0.13 cm). No relationship was found between dominant follicle development and the presence of either a CL or a previous dominant follicle in either ovary. Two and three wave cycles also differed with respect to the mean length of intervals between ovulation (22.27 +/- 0.89 vs 24.50 +/- 1.88 d; P < 0.01) and the mean length of luteal phases (10.40 +/- 2.11 vs 12.66 +/- 2.91 d; P < 0.05). These results demonstrate that buffalo have estrous cycles with 1, 2 or 3 follicular waves; that 2-wave cycles are the most common; and that the number of waves in a cycle is associated with the luteal phase and with estrous cycle length.     

Ovarian follicle development in wapiti (Cervus elaphus) during the anovulatory season

The ovaries of 12 mature wapiti hinds were studied by transrectal ultrasonography during the anovulatory season to characterize follicular dynamics and to test the hypothesis that follicle development occurs in a wave-like fashion. The hinds were examined daily, standing without sedation. Follicle size and numbers were recorded, and individual follicles were identified serially. Follicle development was considered wave-like if periodic changes in follicle numbers could be associated temporally with the development of a dominant follicle. There were non-random changes (P<0.01) in the number of follicles > or =4 mm in diameter detected per day. Each peak in follicle numbers was associated with the development of a single dominant follicle. The dominant follicle of the cohort was larger (P<0.05) than the other follicles 1 day after its emergence. Intervals between successive peaks (6.8 +/- 0.4 day) and troughs (6.8 +/- 0.4 day) in follicle numbers, and emergence of sequential dominant follicles (7.1 +/- 0.5 day) were not different (P=0.86). Results confirmed the hypothesis that ovarian follicles develop in a wave-like fashion in wapiti during the anovulatory season.     

Nutritional status influences reproductive seasonality in Creole goats: 1. Ovarian activity during seasonal reproductive transitions

The objective was to determine the effect of body energy stores, evaluated by a body mass index (BMI), and food intake (FI), on the length of the anovulatory period and ovarian activity during the seasonal reproductive transitions in Creole goats. Non-pregnant, non-lactating Creole goats (n = 28) were fed to induce two different BMI conditions: Greater (GBMI; n = 15), and Lesser (LBMI; n = 13). Each BMI group was divided into two sub-groups, which were either feed restricted (FR) or non-feed restricted (NFR). Goats in the NFR groups received a diet containing 100% of the daily maintenance requirements (basal diet), while restricted goats were subjected to alternated periods, receiving 100% (11 d) and 60% (10 d) of the basal diet, during the entire experimental period. The experiment started after does were treated to synchronize time of estrus. Serum progesterone was determined in samples obtained twice a week, and used as a criterion for determining ovulations. During the transition to the anovulatory period three transrectal ovarian ultrasonographic scans were performed in a sub-group of 12 goats (n = 3 for each treatment combination). The diameter of the largest follicle (LFD) and the total number of antral follicles ≥2 mm (TAF) were recorded. Ultrasonographic ovarian scans were performed at 21, 42 and 63 days after the beginning of the experiment, concurrently with the end of each feed restriction period. The variables of response associated with ovulation were not influenced by BMI or BMI × FI interaction. However, FI influenced length of anovulatory season, as the anovulatory period was 30 d longer (P < 0.05) in the FR group as compared with the NFR group. Independently of treatments, TAF and LFD decreased from the first to the third ultrasonographic ovarian scan (13.2, 10.8 and 4.4 follicles; 3.7, 2.7 and 2.3 mm). Nevertheless, in PER 1 the number of TAF was greater (P < 0.05) in the FR as compared with NFR group and the GBMI group had a larger LFD (P < 0.05) as compared to the LBMI group. It is concluded, that temporal restriction in feed intake could affect the time of cessation and initiation of ovulations during the periods of transition to seasonal anestrus and return to estrous activity, and increase the length of the anovulatory period. In addition, ovarian follicular development during transition into the anovulatory period is differentially influenced by food intake and the status of body energy stores.     

Ovarian follicular populations during early pregnancy in heifers

Ovarian follicles >/=2mm were studied in 14 pregnant and 14 nonpregnant Holstein heifers by daily ultrasound examinations. There were significant differences among days, from Day 0 (day of ovulation) to Day 21, in the diameter of the largest follicle and the diameter of the second largest follicle in pregnant and nonpregnant heifers. There was an interaction of day and reproductive status (P < 0.001) for the diameter of the largest follicle. Significant differences among days were also observed in the numbers of follicles 2 to 3 mm, 4 to 6 mm, 7 to 10 mm, 11 to 13 mm, and >13 mm, and the total number of follicles >/=2 mm. There was a significant main effect of reproductive status for the number of follicles 11 to 13 mm. An interaction of day and reproductive status was observed for the number of follicles >13 mm, but not for any of the other diameter categories. The effect of reproductive status for number of follicles 11 to 13 mm and the interactions for the number of follicles >13 mm and the diameter of the largest follicle seemed due to the selective growth and ovulation of the follicle destined to ovulate in nonpregnant heifers. The differences in ovarian follicular populations between pregnant and nonpregnant heifers were attributed solely to the presence of a physiological mechanism for the selection of an ovulatory follicle in nonpregnant heifers. There were no significant differences among days for any follicular endpoint during Days 22 to 60 in the pregnant heifers.     

Ovarian follicular dynamics in Nelore breed (Bos indicus) cattle

The most common beef cattle raised in Brazil is the Nelore breed (Bos indicus). Information obtained by ultrasonography on follicular growth in Bos taurus cattle has been accumulating rapidly. However, there are few publications to date on follicular development in Bos indicus breeds. The follicular dynamics in Nelore heifers and cows during natural or prostaglandin (PG)-induced estrous cycle were studied. From the detection of estrus onward, all animals were examined daily by ultrasonography for one (n = 35) or two (n = 10) consecutive estrous cycles. The follicular dynamic in Nelore cattle was characterized by the predominance of 2 follicular waves in the cows (83.3%, n = 18, P < 0.05) and 3 waves in the heifers (64.7%, n = 16, P < 0.05). Most of the cattle observed over 2 consecutive estrous cycles presented the same pattern of follicular waves in the first and second cycle, and only 30% showed variation in the number of waves from one cycle to the other. Most of the follicular parameters analyzed were not affected by PG treatment or age but were altered by follicular waves. Consequently, data on cows and heifers were combined according to the number of follicular waves. The ovulatory follicle was larger than the other dominant follicles (P < 0.05), and the ovulatory wave was shorter than the preceding waves (P < 0.05). The interovulatory interval was longer in animals showing 3 waves than those exhibiting 2 waves (P < 0.05). Maximum diameter of the dominant follicle (around 11 mm) and of the corpus luteum (CL, approximately 17 mm) were smaller than those reported for European breeds. In conclusion, the results demonstrate that although the dominant follicle and corpus luteum are smaller than in European breeds, the follicular dynamics in Nelore cattle were similar to those observed in European breeds and were characterized by 2 or 3 follicular waves for cows and heifers, respectively, during the natural or prostaglandin-induced estrous cycle.     

Seasonal variation of the ovarian follicular dynamics and luteal functions of sheep in the subtropics

This study was undertaken to describe the development of individual follicles and corpora lutea (CL) in Ossimi ewe lambs at different seasons of the year in the subtropics. Seven ewe lambs underwent daily ultrasonographic examination for 20 interovulatory periods (IOP) during spring, winter and autumn. Ovarian follicles >or=2 mm and corpora lutea were counted and measured. Blood samples were taken for progesterone (P(4)) analysis. All ewe lambs included, but one, were cyclic in all seasons studied. Three (65%) and two (35%) follicular waves were detected per estrous cycle. None of the characteristics of the large follicles was affected by season. Follicles >or=2 mm in diameter were significantly higher in winter. The CL developed slowly in autumn. Serum P(4) level was higher in autumn. Double ovulation was observed only in autumn. The data demonstrated that Ossimi sheep in the subtropics were cyclic in most seasons of the year. Season affected mainly the luteal functions with little influences on the follicular characteristics.     

Glucose kinetics and substrate oxidation during exercise in the follicular and luteal phases.

The purpose of this investigation was to determine whether plasma glucose kinetics and substrate oxidation during exercise are dependent on the phase of the menstrual cycle. Once during the follicular (F) and luteal (L) phases, moderately trained subjects [peak O(2) uptake (V(O(2))) = 48.2 +/- 1.1 ml. min(-1). kg(-1); n = 6] cycled for 25 min at approximately 70% of the V(O(2)) at their respective lactate threshold (70%LT), followed immediately by 25 min at 90%LT. Rates of plasma glucose appearance (R(a)) and disappearance (R(d)) were determined with a primed constant infusion of [6,6-(2)H]glucose, and total carbohydrate (CHO) and fat oxidation were determined with indirect calorimetry. At rest and during exercise at 70%LT, there were no differences in glucose R(a) or R(d) between phases. CHO and fat oxidation were not different between phases at 70%LT. At 90%LT, glucose R(a) (28.8 +/- 4.8 vs. 33.7 +/- 4.5 micromol. min(-1). kg(-1); P < 0.05) and R(d) (28.4 +/- 4.8 vs. 34.0 +/- 4.1 micromol. min(-1). kg(-1); P < 0.05) were lower during the L phase. In addition, at 90%LT, CHO oxidation was lower during the L compared with the F phase (82.0 +/- 12.3 vs. 93.8 +/- 9.7 micromol. min(-1) .kg(-1); P < 0.05). Conversely, total fat oxidation was greater during the L phase at 90%LT (7.46 +/- 1.01 vs. 6.05 +/- 0.89 micromol. min(-1). kg(-1); P < 0.05). Plasma lactate concentration was also lower during the L phase at 90%LT concentrations (2.48 +/- 0.41 vs. 3.08 +/- 0.39 mmol/l; P < 0.05). The lower CHO utilization during the L phase was associated with an elevated resting estradiol (P < 0.05). These results indicate that plasma glucose kinetics and CHO oxidation during moderate-intensity exercise are lower during the L compared with the F phase in women. These differences may have been due to differences in circulating estradiol.     

Ovarian epidermal growth factor-like activity. Concentrations in porcine follicular fluid during follicular enlargement

Numerous data indicate that epidermal growth factor has important effects on cultured granulosa cells. However, most of the few attempts to detect epidermal growth factor in ovarian tissue have been unrevealing. In this study, ovarian epidermal growth factor-like activity was easily detected by a radioreceptor assay based on the A431 cell line but not by an immunoassay for mouse epidermal growth factor. The concentration of this activity in follicular fluid from small porcine ovarian follicles was higher than that in fluid from medium or large follicles or serum (p less than 0.01), but lower than that in salivary gland extracts. Receptor-active epidermal growth factor-like peptides could function as local ovarian regulators.     

Ovarian follicular dynamics after cauterization of the dominant follicle in anestrous ewes

An experiment was conducted to ascertain if follicles could reach ovulatory size after the largest follicle (dominant) has been removed at different times during a progestin treatment in anestrous ewes, and secondly to determine if these new follicles could respond to an hCG-induced ovulation and have similar function as corpora lutea. Mature crossbred sheep (n=44) in anestrous were treated with an intravaginal sponge containing 40 mg of FGA (day 0=sponge insertion) for 9 days. Treatments consisted of cauterization of the largest follicle on the experimental day 3 (T1), day 6 (T2) and day 9 (T3); day 12 to ascertain the size of the largest follicle in control ewes. During laparotomies, the diameters of the largest follicle (DF), and those of the second and third largest follicles (SF1 and SF2, respectively) were determined. On day 12, a second laparotomy was performed for those ewes which had their DF cauterized on days 3, 6 and 9, a fourth group was left intact and only laparotomized on day 12. At this time, the size of the new DF, SF1 and SF2 were determined. Immediately after the laparotomy on day 12, all the ewes were treated with 1000 i.u. of hCG to induce ovulation. Blood samples were collected daily from day 0 to 50 and samples were analyzed for progesterone concentrations. The size of the DF at the time of sponge removal was smaller that those observed on day 3 or 6 of sponge suggesting that follicles in ewes treated with this progestin regress and a new wave of follicular development ensues between day 6 and the time of sponge removal. The size of the DF on day 12 was also smaller in ewes that have the largest follicle removed at the time of sponge removal reflecting that these follicles had a shorter period of growth; however, the rate of growth was greater for these follicles than for follicles arising after cauterization on day 3 or 6 after sponge insertion. There were no differences among treatments, in the number of ewes that formed a corpus luteum (CL) in response to hCG. Life span of the corpora lutea did not differ among ewes having their DF removed on day 6 or 9 or those that served as controls, however, ewes that had their DF removed on day 3 developed longer lived CL in a larger proportion of animals. Average progesterone concentration during the life span of the induced corpora lutea was greater in control ewes than in any other experimental group. These observations allow us to conclude that, (a) the follicular dynamics observed in anestrous ewes treated with a progestin intravaginal sponge resembles that observed during the normal estrous cycle in the ewe; (b) the effects of progesterone on life span of the corpus luteum could not be only related to direct effects at the follicle but also involve changes in other components of the uterine-ovarian-hypothalamic axis; (c) the mechanisms controlling luteal life span seem to be different to those mechanisms controlling the function of the induced corpus luteum.     

The effect of subluteal levels of exogenous progesterone on follicular dynamics and endocrine patterns during early luteal phase of the ewe

Nineteen Corriedale ewes were treated with an im dose of a PGF2alpha during the luteal phase to synchronize estrus. After ovulation had been detected by using ultrasonography (Day 0); the ewes were randomly assigned to 2 different groups. In 11 ewes a CIDR, which had previously been used for 10 d, was inserted on the fourth day after ovulation. The ewes then received a dose of PGF2alpha on Day 5 to induce luteolysis. The CIDR remained in place until the end of the experiment (Day 9). Control ewes (n = 8) received no treatment. Blood samples were taken daily for estradiol, progesterone and FSH determinations. In the untreated ewes, 2 follicular waves were detected in all of the animals throughout the monitoring period, with a mean wave interval of 4.5 d. The total number of follicles which were > or =2 mm decreased from Day 0 to Day 4 (8.8+/-1.0 to 5.3+/-0.6; P< or =0.05) and then increased at Day 7 (7.5+/-0.9; P< or =0.05). The growth profiles of both the largest and the second largest follicles of Wave 1 showed significant divergence, while no divergence was observed in Wave 2. Serum estradiol concentrations decreased significantly from the day before to the day of ovulation and then increased again during the growing phase of the largest follicle of Wave 1. Concentrations of FSH were high on the day of emergence of both waves, but while a significant decline was observed after emergence in Wave 1, the levels remained high in Wave 2. In 8 of the 11 treated ewes, the largest follicle of Wave 1 was still present on the ninth day after ovulation (persistent follicle). In the other 3 ewes, the largest follicle of Wave 1 was already regressing on the day that the treatment was administered, and the largest follicle that was present on Day 9 originated from Wave 2 (nonpersistent follicle). In persistent follicle ewes, the largest follicle of Wave 1 prolonged its lifespan significantly, attaining the maximum diameter (Day 8.1+/-0.8) later than in untreated (Day 3.0+/-0.4) and nonpersisted follicle ewes (Day 2.0+/-0.6). The total number of follicles decreased in persistent follicle ewes between Day 0 and Day 4 (7.9+/-1.5 to 4.5+/-0.5, respectively; P< or =0.05) and remained low until the end of the experiment. Progesterone concentrations (nmol/L) between Days 6 and 9 were significantly different between untreated and persistent follicle ewes (12.8+/-1.0 vs. 9.4+/-1.0, P< or =0.02). The present study confirms that the largest follicle of Wave 1 is dominant in the ewe and that subluteal progesterone concentrations can prolong its lifespan and extend this dominance.     

Uterine estrogen receptor alpha and progesterone receptor during the follicular and luteal phase in llamas

Estrogen receptor-alpha (ERalpha) and progesterone receptor (PR) were characterized in different endometrial cell types as luminal and glandular epithelium and stroma during the follicular (FP) and the luteal phase (LP) in llamas. Animals were examined daily by transrectal ultrasonography for the determination of the presence of an ovulatory follicle and ovulation was immediately induced by a GnRH injection (Day 0). Endometrial samples were obtained by transcervical biopsies from the left uterine horn on Day 0 (FP) and 9 days after the GnRH injection (Day 9, LP). Blood samples were collected on these days for estradiol 17beta and progesterone determination by RIA. An immunohistochemical technique was used to visualize ERalpha and PR immunostaining which was then analyzed by two independent observers. Total positive area and average staining for ERalpha were affected by the phase of the ovarian activity: in the three cell types there was more positive area and intense staining during the FP than during the LP. Similar findings were observed for PR, more positive stained areas were found during the FP than during the LP in the epithelia. In addition, the three cell types had more intense staining during the FP than during the LP. An effect of the cell type for ERalpha and PR was observed; epithelia (luminal and glandular) had more positive stained areas and greater intensity than stromal cells. In conclusion, the results of the present study suggest that in llamas, like in other ruminants, estradiol has a stimulatory effect while progesterone downregulates the ERalpha and PR and that the receptor is cell type specific.     

Ovarian antral follicular dynamics in sheep revisited: Comparison among estrous cycles with three or four follicular waves

In this study, the characteristics of ovarian follicular waves and patterns of serum concentrations of follicle-stimulating hormone (FSH), estradiol, and progesterone were compared between cycles with three (n = 9) or four (n = 10) follicular waves in Western White Face (WWF) ewes (Ovis aries). Transrectal ultrasonography and blood sampling were performed daily during one cycle. Estrous cycles were 17.11 ± 0.3 and 17.20 ± 0.2 d long in cycles with three and four waves, respectively (P > 0.05). The first interwave interval and the interval from the emergence of the final wave to the day of ovulation were longer in cycles with three waves compared with those in cycles with four waves (P < 0.05). The growth phase (5.1 ± 0.5 vs. 3.1 ± 0.4 d) and life span (5.67 ± 0.3 vs. 4.3 ± 0.3 d) of the largest follicle growing in the last or ovulatory wave was longer in cycles with three waves compared with that in cycles with four waves (P < 0.05). The maximum diameter of the largest follicle was greater in the first wave and the ovulatory wave compared with that in other waves of the cycle (P < 0.05). The regression phase of the largest follicle growing in the first wave was longer in cycles with three waves compared with that in cycles with four waves (4.44 ± 0.4 vs. 3.4 ± 0.4 d; P < 0.05). The length of the life span, regression phase, and, although not significant in every case, FSH peak concentration and amplitude decreased across the cycle (P < 0.05). We concluded that estrous cycles with three or four follicular waves were confined within the same length of cycle in WWF ewes. In this study, there were no apparent endocrine or follicular characteristics that could explain the regulation of the different number of follicular waves (three vs. four) during cycles of similar length.