Characteristics of peaks in serum concentrations of follicle-stimulating hormone and estradiol, and follicular wave dynamics during the interovulatory interval in cyclic ewes

There are three or four ovarian follicular waves in the interovulatory interval of cyclic ewes. Each follicular wave is preceded by a transient peak in serum follicle-stimulating hormone (FSH) concentrations. Serum concentrations of estradiol also increase concurrent with the growth of follicle(s) in each wave. In the current study, we investigated the patterns of follicular wave development and characteristics of FSH and estradiol peaks in all follicular waves of the interovulatory interval and after induction of a supraphysiologic FSH peak in cyclic ewes (Ovis aris). In Experiment 1, 19 ewes underwent daily ovarian ultrasonography and blood sampling for a complete interovulatory interval. In Experiment 2, seven ewes received two administrations of ovine FSH (oFSH), 8 h apart (1 μg/kg; sc), at the expected time of the endogenous FSH peak preceding the second follicular wave of the interovulatory interval. In Experiment 1, the amplitude of the FSH peaks decreased (up to 50%), whereas basal serum FSH concentrations increased across the interovulatory interval (P < 0.05). Maximum follicular diameter was greater (P < 0.05) for Wave 1 and the Ovulatory wave (6.0 ± 0.3 and 6.1 ± 0.2 mm, respectively) than for Waves 2 and 3 (5.3 ± 0.1 and 5.4 ± 0.3 mm, respectively). Life span was greater for follicles in Wave 1 compared with other waves (P < 0.05). Treatment with oFSH increased the amplitude of an FSH peak by 5- to 6-fold. This treatment increased estradiol production (P < 0.05) but had little effect on other characteristics of the subsequent follicular wave. We concluded that changes in the amplitude and duration of the peaks in serum concentrations of FSH that precede follicular waves across the interovulatory interval do not influence the characteristics of the follicular waves that follow.     

Evaluation of the ultrasound image attributes of developing ovarian follicles in the four follicular waves of the interovulatory interval in ewes

Computer-assisted quantitative echotextural analysis was applied to ultrasound images of antral follicles in the follicular waves of an interovulatory interval in sheep. The ewe has three or four waves per cycle. Seven healthy, cyclic Western White Face ewes (Ovis aris) underwent daily, transrectal, ovarian ultrasonography for an interovulatory interval. Follicles in the third wave of the ovulatory interval had a longer static phase than that of those in Waves 1 and 2 (P < 0.05). The numeric pixel value for the wall of anovulatory follicles emerging in the third wave of the cycle was significantly higher than that for Waves 1 and 2 at the time of emergence (156.7 ± 8.09, 101.6 ± 3.72, and 116.5 ± 13.93, respectively), and it decreased as follicles in Wave 3 reached maximum follicular diameter (P < 0.05). The numeric pixel value of the antrum in the ovulatory follicles decreased as follicular diameter increased to ≥5 mm in diameter (P < 0.05). The pixel heterogeneity of the follicular antrum in Wave 1 increased from the end of the growth phase to the end of the regression phase for follicles in that wave (P < 0.05). The total area for the wall and antrum of the follicles studied were correlated with follicular diameter in all follicular waves (r = 0.938, P < 0.01 and r = 0.941, P < 0.01 for the wall and antrum, respectively). Changes in image attributes of the follicular wall and antrum indicate potential morphologic and functional differences among antral follicles emerging at different stages of the interovulatory interval in cyclic ewes.     

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 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).     

Repeatability of 2-wave and 3-wave patterns of ovarian follicular development during the bovine estrous cycle

Characteristics predictive of a 2-wave versus 3-wave pattern of ovarian follicular development during the interovulatory interval (IOI) were examined by ultrasonographic monitoring of 91 IOIs from 31 beef heifers. Repeatability of the wave pattern within individuals and the effects of season and age were determined using a subset of 75 IOIs from 15 heifers examined for multiple IOIs. The 2-wave pattern was detected in 62 of 91 (68%) IOIs, and the 3-wave pattern was detected in 29 of 91 (32%) IOIs. The preponderance of the 2-wave versus 3-wave pattern (P < 0.05) was not influenced by season (P = 0.61) but was even greater in the more mature age group (P = 0.02). The majority of IOIs ≤21 d was of the 2-wave pattern (88%; P < 0.05), whereas the majority of IOIs ≥22 d was of the 3-wave pattern (78%; P < 0.05). The proportion of nonalternating patterns (repeatability) was more than twofold greater than the proportion of alternating patterns (70% vs. 30%; P < 0.01). This relationship was consistent among seasons (P < 0.01) and even more marked in the more mature age group (P = 0.01). Emergence and follicular dominance of Wave 2 were delayed (P < 0.01), and the onset of corpus luteum regression was earlier (P < 0.01) in 2-wave versus 3-wave IOI. In conclusion, the duration of the IOI was predictive of the wave pattern, and the pattern was repeatable within individuals. Factors influencing the period of follicular dominance of Wave 1 in 2-wave versus 3-wave IOI may be responsible for regulating the wave pattern and may be associated with heifer maturity or relative nutritional demand during the postpubertal period. The impact of greater follicular attrition recorded in 3-wave versus 2-wave IOI on ovarian depletion and reproductive senescence is worthy of critical evaluation.     

Glucose uptake and lactate production by the autotransplanted ovary of the ewe during the luteal and follicular phases of the oestrous cycle

Two experiments were carried out on ewes with ovarian autotransplants to estimate the ovarian uptake of glucose and production of lactate. The first was carried out in the luteal phase of the oestrous cycle. Samples of carotid arterial, ovarian venous and jugular venous blood were collected simultaneously for glucose analysis. The arterial concentration of glucose (58.0 ± 5.0 mg/dL; Mean ± SEM) was significantly higher than the ovarian venous concentration (42.3 ± 2.4 mg/dL; P < 0.001). Next, a second more complete experiment was carried out in the luteal and follicular phases of the oestrous cycle. The oestrous cycle was synchronised and samples of carotid arterial, ovarian venous and jugular venous blood were collected simultaneously for glucose and lactate analysis. There were significant positive arterio-venous differences in the concentration of glucose in the luteal (5.6 ± 1.2 mg/dL, mean ± SEM; P = 0.001), early (3.1 ± 0.82 mg/d; P = 0.003) and late follicular (6.4 ± 1.3 mg/dL; P = 0.001) phases of the oestrous cycle. There was a significant negative arterio-ovarian venous difference in the concentration of lactate in only the luteal phase (-2.2 ± 0.96 mg/dL; P = 0.043).The results show significant removal of glucose from the arterial circulation during its passage through the ovary in the luteal, early follicular and late follicular phases of the oestrous cycle. Furthermore, there was lactate production in the luteal phase but not in the follicular phase suggesting that in the luteal phase of the oestrous cycle, ovarian metabolism can be anaerobic.     

Effects of low versus physiologic plasma progesterone concentrations on ovarian follicular development and fertility in beef cattle

The objective of this study was to determine the effects of low versus physiologic plasma progesterone concentrations during the ovulatory wave on fertility in cattle. Suckled beef cows (Bos taurus; n = 129) and pubertal heifers (Bos taurus; n = 150) at random stages of the estrous cycle were given a luteolytic dose of prostaglandin F_2α (500 μg cloprostenol; PGF) twice, 11 d apart. Ten days after the second PGF treatment, cattle were given estradiol benzoate im (1.5 and 1.0 mg for cows and heifers, respectively) and a progesterone-releasing intravaginal device (Cue-Mate) with a single pod containing 0.78 g progesterone (Day 0). Cattle in the low-progesterone group (n = 148) received a luteolytic dose of PGF on Day 0, whereas those in the high-progesterone (i.e., physiologic plasma concentrations) group (n = 131) were allowed to retain their corpora lutea. On Day 8, the Cue-Mate was removed, and PGF was given to both groups. Fifty-four hours to 56 h later, cattle received 12.5 mg of porcine LH (pLH) im and were concurrently artificially inseminated. The dominant follicle in the low-progesterone group was larger (P < 0.001) than that in the high-progesterone group on the day of insemination (14.9 ± 0.3 mm vs. 12.7 ± 0.3 mm, mean ± SEM). At 7 d after ovulation, the low-progesterone group had a larger corpus luteum (24.5 ± 0.54 mm vs. 21.9 ± 0.64 mm, P < 0.01) and higher plasma progesterone concentration (4.0 ± 0.3 vs. 3.1 ± 0.2, P < 0.01) than that of the high-progesterone group. However, pregnancy rates did not differ (79 of 148, 53.4%, and 70 of 131, 53.4%) for low- and high-progesterone groups, respectively). In summary, low circulating progesterone concentrations during the growing phase of the ovulatory follicle resulted in a larger dominant follicle and a larger CL that produced more progesterone, with no significant effect on pregnancy rate.     

Characteristics of ovarian follicular dynamics throughout the estrous cycle of Egyptian buffaloes

Data of 56 normal and 9 abnormal estrous cycles were collected from 9 Egyptian buffaloes (Bublus bublis) to describe the follicular growth wave pattern. Heat was checked twice daily while, ovaries were scanned daily to monitor the patterns of follicular waves. Day of ovulation was determined when the largest follicle was replaced by corpus haemorrhgicum (CH). Number of waves/cycle, day of emergence of the follicular wave, characteristics of the dominant follicle and corpus luteum (CL) growth features were monitored. Buffaloes displayed mainly two types of follicular waves; two (46.4%) and three (53.6%). In cycles of three wave pattern, time of emergence of the 1st wave post-heat was longer (P < 0.05) and number of recruited follicles/wave were larger (P < 0.05) compared to the corresponding values of the two wave pattern. Number of recruited follicles in early follicular waves (1st or the 2nd) had larger number (P < 0.05) compared to the subsequent ones. Follicles that reached ovulation in both types of estrous cycle had shorter life-span (P < 0.05) than the previous ones. Life-span of CH, growing and regressed CL were 3.6 ± 0.6, 11.2 ± 0.8 and 4.4 ± 0.5 days, respectively with no difference in both types of follicular wave. Three types of ovarian disorders were observed. Follicular waves and CL growth features showed unique pattern for each individual. These results demonstrate that buffaloes display two main types of follicular waves with dominance of three wave type.     

Plasma concentrations of inhibin a and follicle-stimulating hormone differ between cows with two or three waves of ovarian follicular development in a single estrous cycle

Patterns of ovarian follicle development were monitored daily in Holstein-Friesian cows that had two (n = 4) or three (n = 4) waves of ovarian follicle development during a single estrous cycle. The plasma from daily blood samples was used in assays for inhibin A, FSH, progesterone, and estradiol-17beta. Mean cycle lengths for cows with two and three waves were 21.8 and 25.3 days, respectively (P < 0.02). Although the average number of follicles >3-mm diameter on each pair of ovaries was similar for two- and three-wave cows on Days 2, 3, and 4 (Day 0 = day of ovulation; 8.6 vs. 9.6 follicles), there were more follicles >6-mm diameter on the ovaries of cows with two waves on Days 3 and 4. This difference was associated with a shorter interval from wave emergence to peak concentrations of inhibin A during the first wave in two-wave cows (2.0 vs. 3.8 days; P = 0.03) and with higher peak concentrations (474 vs. 332 pg/ml; P = 0.03). Differences in peak FSH concentrations were not significant (1.7 vs. 1.3 ng/ml; P = 0.10) and were inversely related to inhibin A concentrations. The peak concentrations of inhibin A and FSH in the second nonovulatory wave in the three-wave cows were similar to the low concentrations measured in the first wave (292 vs. 332 pg/ml of inhibin A, 1.3 vs. 1.3 ng/ml of FSH; P > 0.20). Average peak concentrations of inhibin A and FSH were similar during the ovulatory wave for cows with either two or three waves in a cycle (432 vs. 464 pg/ml of inhibin A, 2.3 vs. 2.1 ng/ml of FSH; P > 0.3). The lower concentrations of FSH during the emergence of the first follicular wave in cows with three-wave cycles may have reduced the rate of development of some of the follicles and reduced the concentrations of inhibin A. This pattern of lower concentrations of FSH and inhibin A was repeated in the second nonovulatory wave but not in the ovulatory wave. Subtle differences in the concentrations of these two hormones may underlie the mechanism that influences the number of waves of ovarian follicle development that occur during the bovine estrous cycle.     

Characterization of ovarian follicular dynamics in dromedary camels (Camelus dromedarius)

Ovarian follicular dynamics was monitored by transrectal ultrasonography, for a period of 60 to 90 days, and its correlation with plasma estradiol-17β (E2) and progesterone (P4) were studied in seventeen, multiparous, non-lactating, 12 to 20-year-old dromedary camels. The average number of follicles recruited (12.77 ± 0.93) in each wave between animals varied (P < 0.001). The number of follicles recruited during different follicular waves was highly repeatable (0.95) within individual animals. The growth and mature phase periods of the dominant follicle (DF) were 6.10 ± 0.15 and 10.20 ± 0.47 days, respectively with a linear growth rate of 1.17 ± 0.02 mm/day between Day 0 and 10 of the follicular wave. There was an inverse relationship between the diameter of the largest DF and number of follicles (r = −0.95, P < 0.001). The DF development did not regularly alternate between the ovaries and the incidence of codominance was 45%. The mean maximum diameter of DF during its mature phase was 27.30 ± 0.78 mm and oversized follicle was 38.43 ± 1.41 mm. In 73.3% waves, the DF continued its growth for a period of 10.64 ± 1.53 days even after losing its dominance and developed into oversized follicle. The duration of the regression phase of DF and oversized follicle were 24.71 ± 3.79 and 18.50 ± 2.23 days. The mean duration of a complete follicular wave was 47.11 ± 2.94 days with an interwave interval (IWI) of 16.36 ± 0.37 days. The IWI within an individual was repeatable (0.88) and between the animals was variable (P < 0.001). Plasma E2 concentration profiles showed a wave like pattern. The peak plasma E2 concentrations were attained approximately 12 days after beginning of the growth phase, when the largest DF grew to a diameter of 18.7 mm. Plasma concentration of P4 was below 1.0 ng/mL in 85% of waves and above 1.0 ng/mL in 15% of the waves for a period of 3 to 6 days in the absence of spontaneous ovulation. It is concluded that ovarian follicular development and plasma E2 concentrations occurs in a wave like pattern in dromedary camels and the IWI and follicle numbers recruited per wave are variable between the animals and repeatable within an individual animal.     

The effect of hormone treatments (hCG and cloprostenol) and season on the incidence of hemorrhagic anovulatory follicles in the mare: A field study

The association between use of hormone treatments to induce estrus and ovulation and the incidence of hemorrhagic anovulatory follicles (HAFs) was studied in a mixed population of mares (Equus caballus) during two breeding seasons in a commercial breeding clinic. Mares treated with cloprostenol (CLO) were more likely to develop HAFs than were mares with spontaneous cycles (P < 0.001) or those treated with human chorionic gonadotropin alone (P = 0.08). There was no significant effect of season on the incidence of HAFs. The mean (±SEM) interval from CLO treatment to beginning of HAF development was 6.1 ± 0.5 d. Age of mares with HAF cycles was not different (12 ± 1.3 yr; P > 0.05) from that of mares with ovulatory cycles (10.5 ± 1.5 yr).     

Hormone concentrations temporally associated with contralateral and ipsilateral relationships between the CL and preovulatory follicle during the third follicular wave in heifers

Concentrations of circulating hormones after Day 14 (Day 0 = ovulation) were determined daily in 87 interovulatory intervals (IOIs) in heifers. The IOIs were grouped into four permutations according to an ipsilateral (Ipsi) or contralateral (Contra) relationship between the CL and the preovulatory follicle and two (2W) or three (3W) follicular waves per IOI. The number of IOIs per group differed (P < 0.005) from equality among the Ipsi-2W (n = 27), Contra-2W (n = 31), Ipsi-3W (n = 9), and Contra-3W (n = 20) groups. A continuous decrease in progesterone (luteolysis) began later (P < 0.05) in the Contra-3W group (Day 18.0 ± 0.4) than in each of the Ipsi-2W (15.4 ± 0.2), Contra-2W (15.6 ± 0.2), and Ipsi-3W (16.2 ± 0.5) groups. Concentrations of LH and estradiol began to increase near the beginning of luteolysis in each group. A minor FSH surge that did not stimulate a major follicular wave developed in about 50% of the IOIs in each group, except that none were detected in the Ipsi-3W group. The minor FSH surge reached a peak about 4 days before ovulation and several days after wave 3 had emerged. The hypothesis that luteolysis begins earliest in two-wave IOIs, intermediate in three-wave IOIs with an ipsilateral CL/follicle relationship, and latest in three-wave IOIs with a contralateral relationship was supported. The hypothesis that a minor FSH surge occurs most frequently in association with three follicular waves was not supported.     

Changes in the gene expression of adiponectin and adiponectin receptors (AdipoR1 and AdipoR2) in ovarian follicular cells of dairy cow at different stages of development

Adiponectin is one of the most important, recently discovered adipocytokines that acts at various levels to control male and female fertility through central effects on the hypothalamus-pituitary axis or through peripheral effects on the ovary, uterus, and embryo. We studied simultaneous changes in the gene expression pattern of adiponectin and adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2) in granulosa and theca cells, cumulus-oocyte complex, and in corpus luteum in healthy bovine (Bos tarus) follicles at different stages of development. The expression levels of adiponectin, AdipoR1, and AdipoR2 mRNA were lower (P < 0.05) in granulosa and cumulus cells in comparison with that in theca cells and oocyte. In contrast with the oocyte, AdipoR1 in granulosa, theca, and luteal cells was expressed (P < 0.05) more than AdipoR2. Adiponectin expression increased (P < 0.05) in granulosa cells and in cumulus-oocyte complex during follicular development from small to large follicles. Opposite results were observed in theca cells. Expression of adiponectin was highest in the late stages of corpus luteum (CL) regression, whereas lower expression was recorded in active CL (P < 0.05). AdipoR1 and AdipoR2 expression increased during the terminal follicular growth in granulosa and theca cells (P < 0.05) and during the luteal phase progress in CL. There was positive correlation between adiponectin mRNA level in granulosa cells from large follicles and follicular fluid estradiol concentration (r = 0.48, P < 0.05) and negative correlation between adiponectin mRNA abundance in theca cells and follicular fluid progesterone concentration (r = -0.44, P < 0.05). In conclusion, we found that the physiologic status of the ovary has significant effects on the natural expression patterns of adiponectin and its receptors in follicular and luteal cells of bovine ovary.     

Ovarian follicular dynamics, follicle deviation, and oocyte yield in Gyr breed (Bos indicus) cows undergoing repeated ovum pick-up

The objective of this study was to evaluate ovarian follicular dynamics during intervals between successive ovum pick-up (OPU) and determine its effects on the number and quality of recovered cumulus-oocyte complexes (COCs) in Zebu cows (Bos indicus). Pluriparous nonlactating Gyr cows (Bos indicus; n = 10) underwent four consecutive OPU sessions at 96-h intervals. The dynamics of ovarian follicular growth between OPU sessions was monitored by twice-daily ultrasonographic examinations. A single dominant follicle (DF) or two codominant (CDF) follicles (>9 mm) were present in 63.3% (19 of 30) of intervals studied, with follicle deviation beginning when the future dominant follicle (F1) achieved a diameter of 6.2 ± 0.3 mm. The phenomenon of codominance was observed in four (13.3%) of the inter-OPU intervals. The remaining intervals (36.6%, 11 of 30) were characterized by a greater follicular population, lower rate of follicular growth, and a smaller diameter F1 (P < 0.0001). There was a tendency (P = 0.08) toward an increase in the number of recovered COCs when dominant follicles were not present (NDF). The quality of COCs was not affected by the presence of a single dominant follicle, but codominant follicles resulted in recovery of a lower proportion of viable embryos (40.0%, 62.1%, and 63.6%; P < 0.05) and higher proportions of degenerate COCs (56.0%, 30.3%, and 28.6%; P < 0.05) for CDF, NDF, and DF respectively. We concluded that, in Zebu cows, (a) repeated follicle aspirations altered ovarian follicular dynamics, perhaps by increasing follicular growth rate; (b) follicular dominance could be established in cows undergoing twice-a-week OPU; and (c) the presence of a dominant follicle during short inter-OPU intervals may not affect COC quality, except when a codominant follicle was present.     

Follicular and endocrinological turnover associated with GnRH induced follicular wave synchronization in Indian crossbred cows

The goal of this study was to record the hormonal and follicular turnover in Jersey crossbred cows when subjected for follicular wave synchronization using GnRH. Six healthy, non-lactating and regularly cycling Jersey crossbred cows (5-6 y) were used for the study. In the control group, the follicular wave pattern was ultrasonographically investigated in 18 cycles (3 cycles/cow). In the treatment group, GnRH analogue (buserelin acetate 10 μg im) was administered on Day 6 of the cycle and follicular wave pattern was studied in 12 cycles (2 cycles/animal). Follicular population was categorized based on their diameter Class I, ≤5 mm; Class II, >5-<9 mm; Class III, ≥9 mm) and the number of follicles in each category was determined on Day 6, Day 8 and Day 10. Plasma FSH and progesterone concentrations were estimated in both control and treatment groups. Out of 18 estrous cycles studied, 14 cycles (77.8%), three cycles (16.7%) and one cycle (5.6%) exhibited three-, two- and four-follicular waves per cycle, respectively. It was evident that the DF of Wave I established its dominance and was in the growing phase by Day 6 of the estrous cycle in all the normally cycling crossbred cows. The DF ovulated in all the animals (100%) in the mean interval of 27.7 ± 0.2 h after GnRH administration. A synchronized homogenous group of follicles emerged two days after GnRH injection (Day of 8.0 ± 0.0) in all the animals (100%). The combination of LH surge induced ovulation of DF (abrupt termination of Wave I) and FSH surge stimulated homogenous recruitment of Class I follicles, led to a synchronized emergence of follicular wave. All the GnRH treated cows had three follicular waves because of early emergence and short period of dominance of Wave II DF.     

Exercise affects both ovarian follicular dynamics and hormone concentrations in mares

The objectives were to evaluate the effects of exercise on ovarian folliculogenesis and related hormones in mares. Mares (n = 11) were randomly assigned into a control (non-exercised) or treatment (exercised) group. Treatment mares (n = 5) were moderately exercised for 30 min, 6 d/wk. All mares underwent daily transrectal ultrasonographic examinations and ovarian follicles > 6 mm were measured. Blood samples were collected during the first (Cycle 1) and last (Cycle 4) cycle, and serum concentrations of cortisol, LH, and FSH were determined. Mean cortisol concentrations were elevated (P < 0.05) in exercised mares, 6.29 ± 0.22 compared with 5.62 ± 0.16 ng/dL (mean ± SEM), 30 min post exercise. There were no significant differences between groups in mean FSH concentrations; however, exercised mares had lower (17.3 ± 6.4 vs 41.1 ± 5.5 ng/mL; P < 0.05) peak LH concentrations. Furthermore, exercised mares experienced a longer (24.7 ± 0.8 vs 22.2 ± 0.8 d; P < 0.05) mean interovulatory interval for all cycles combined, fewer (P < 0.05) follicles 6 to 20 mm in diameter, and an increased (P < 0.05) number of follicles >20 mm following deviation. The dominant and largest subordinate follicle in exercised mares had a greater (P < 0.05) mean diameter on the day of deviation, suggesting delayed deviation. Exercised mares also tended (P = 0.06) to have an increased number of cycles with at least two dominant follicles compared to control (62 vs 36%, respectively), indicating a decreased ability of the largest follicle to assert dominance. Under the conditions of this study, moderately exercising mares induced higher cortisol concentrations, lowered peak LH concentrations, and altered ovarian follicular dynamics.     

Age-related dynamics of follicles and hormones during an induced ovulatory follicular wave in mares

An ovulatory follicular wave was induced by ablation of follicles ≥6 mm and treatment with prostaglandin F2α (PGF) on Day 10 (ovulation = Day 0). Follicle and hormone dynamics of the induced waves were compared among three age groups: young (5-6 y, n = 14 waves), intermediate (10-14 y, n = 16), and old (≥18 y, n = 15). During the common-growth phase of the induced wave (Days 12-17), diameter of the future ovulatory follicle was not different among ages, but the young group had more (P < 0.05) follicles that reached ≥10 mm. The number was correlated (r = +0.7; P < 0.0001) within mares between consecutive interovulatory intervals, indicating repeatability. Concentrations of LH increased in all age groups during Days 12-17, but were greatest (P < 0.002) in the young group and continued to be greater (P < 0.0001) throughout the ovulatory LH surge. During several days before Day −1, there were no age-related effects on systemic estradiol concentrations, diameter of the preovulatory follicle, or B-mode echo texture or color-Doppler signals of blood flow in the follicle wall. Interpretations were: (1) greater number of follicles in the young group reflected a greater follicle reserve, (2) greater LH concentrations throughout the ovulatory surge in the young group reflected a more positive response to an extraovarian/environmental influence after removal of the negative effect of progesterone, and (3) lower LH concentrations in the older groups were adequate for the preovulatory changes in the follicle.     

Antioxidant capacity of follicular fluid in relation to follicular size and stage of estrous cycle in buffaloes

The present study was designed to evaluate the changes in the concentrations of different antioxidants, such as glutathione (GSH), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT), in the follicular fluid collected from different follicular size categories in relation to stage of estrous cycle in buffaloes. In addition, malondialdehyde (MDA) as an indicator for lipid peroxidation was also estimated. Fifty pairs of buffalo ovaries were collected from a local slaughterhouse. Based on ovarian structures, the cycle was divided into follicular and luteal phase. The follicles on each pair were classified into three groups; small (≤3 mm), medium (4-9 mm) and large (≥10 mm). The concentrations of SOD, CAT, GSH, and GR in the follicular fluid of each group as well as MDA were estimated. Results indicated that there was a significant decrease (P < 0.05) in the average numbers of small follicles obtained at the follicular phase than those obtained at the luteal phase of the cycle. However, the mean numbers of the large sized follicles was significantly increased (P < 0.05) in the follicular phase than in the luteal phase. Large follicles obtained at the luteal phase had a significantly higher (P < 0.05) concentration of GSH than that obtained from small ones. A significant (P < 0.05) effect of follicular size on GR concentrations was observed. The concentration of SOD tended to be higher in large follicles obtained at the follicular phase than that collected at the luteal phase (56.7 ± 3.7 vs. 28.1 ± 6.7 U/mL, respectively). On the contrary, a significantly higher concentration (P < 0.05) of SOD was recorded in small follicles as compared with medium and large follicles collected at the luteal phase. CAT concentrations did not significantly differ among different follicular sizes between follicular and luteal phases as well as within each phase. Malondialdehyde concentration was significantly decreased (P < 0.05) in the follicular fluid obtained from small follicles collected at the follicular phase compared with those obtained at the luteal phase. In conclusion, the present study showed that the concentrations of enzymatic antioxidants except for CAT vary according to the follicle size and the stage of the estrous cycle suggesting their possible role in the process of follicular development during estrous cycle in buffaloes.     

Characterization of ovarian follicular wave dynamics in women

A wave phenomenon of ovarian follicular development in women has recently been documented in our laboratory. The objective of the present study was to characterize follicular waves to determine whether women exhibit major and minor wave patterns of follicle development during the interovulatory interval (IOI). The ovaries of 50 women with clinically normal menstrual cycles were examined daily using transvaginal ultrasonography for one IOI. Profiles of the diameters of all follicles >or=4 mm and the numbers of follicles >or=5 mm were graphed during the IOI. Major waves were defined as those in which one follicle grew to >or=10 mm and exceeded all other follicles by >or=2 mm. Minor waves were defined as those in which follicles developed to a diameter of <10 mm and follicle dominance was not manifest. Blood samples were drawn to measure serum concentrations of estradiol-17beta, LH, and FSH. Women exhibited major and minor patterns of follicular wave dynamics during the IOI. Of the 50 women evaluated, 29/34 women with two follicle waves (85.3%) exhibited a minor-major wave pattern of follicle development and 5 women (14.7%) exhibited a major-major wave pattern. Ten of the 16 women with three follicle waves (62.5%) exhibited a minor-minor-major wave pattern, 3 women (18.8%) exhibited a minor-major-major wave pattern, and 3 women (18.8%) exhibited a major-major-major wave pattern. Documentation of major and minor follicular waves during the menstrual cycle challenges the traditional theory that a single cohort of antral follicles grows only during the follicular phase of the menstrual cycle.     

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.