Ovulation Of Dominant Follicle Research Articles

Kinase pathways in dominant and subordinate ovarian follicles during the first wave of follicular development in sheep

The mechanism by which one or more dominant ovarian follicles continue development while other subordinate follicles regress is not known. The mitogen activated protein kinases (MAPKs) are a group of kinases that are activated by hormonal factors and form a cascade of processes that regulate cell growth, division and differentiation. The aim of the present experiment was to characterise the presence of the MAPKs, Erk 1/Erk 2 and Akt in healthy dominant follicles and regressing subordinate follicles. Following in vivo monitoring of ovarian follicle development, three ewes were ovariectomised and the follicular fluid and follicle wall (theca and granulosa cells) saved from the dominant and largest subordinate follicle. The dissected diameter and follicular fluid oestradiol concentration of the dominant follicle was larger ( P<0.01) than the largest subordinate follicle (6.5±0.0 mm and 41.3±4.9 ng/ml versus 4.7±0.3 mm and 0.6±0.4 ng/ml). Western blot analyses showed that there was more Akt (202.7±6.4 versus 59.6±32.7 units; P<0.05) and Erk 1/Erk 2 (104.5±10.6 versus 0.3±0.2 units; P<0.01) present in follicle wall samples from the dominant compared to the largest subordinate follicles. Phosphorylated forms of Akt and Erk 1/Erk 2 were detected in samples from dominant but not subordinate follicles. We suggest that signal transduction pathways involving Akt and Erk 1/Erk 2 may play an important role in determining the outcome of ovarian follicle growth and development in sheep.

Ultrasonography and hormone profiles of persistent ovarian follicles (cysts) induced with low doses of progesterone in cattle

The aims of this study were to expose dominant ovarian follicles at the end of the oestrous cycle to low progesterone concentrations similar to those that occur during stress, and to examine the effect of a subsequent small increase in progesterone 10 days later. Half a progesterone releasing intravaginal device (0.5 PRID) was administered to 13 heifers from day 15 of the oestrous cycle. In group 1 (n = 7), one 0.5 PRID remained in place until day 40 or until each heifer ovulated. In group 2 (n = 6), the first 0.5 PRID was removed on day 28, and replaced immediately with a second 0.5 PRID. Ultra-sonography and blood collection (10 ml) were conducted each day for 26 days from day 14 and then on alternate days. The largest follicle that emerged during the first 5 days after insertion of the initial 0.5 PRID remained > 10 mm in diameter for 15.3 +/- 1.7 and 11.6 +/- 0.4 days in groups 1 and 2, respectively. This period of dominance, during which no other follicles emerged, was closely correlated with the duration of plasma oestradiol concentrations exceeding 10 pg ml(-1). In four heifers from group 1, the persistent follicle ovulated between days 30 and 37 (sub-group 1a; 0.5 PRID expelled). In three heifers from sub-group 1b (0.5 PRID retained), the dominant follicle secreted oestradiol for 17 +/- 5 days but remained detectable by ultrasonography for a total of 33 +/- 8 days (range 26-52 days). Monitoring continued beyond day 40 in these animals. In group 2, the new 0.5 PRID inserted on day 28 resulted in an increase in plasma progesterone concentration of 0.9 +/- 0.3 ng ml(-1). Simultaneously, oestradiol decreased by 10.1 +/- 3.3 pg ml(-1), and a new follicular wave emerged 5-7 days later. In conclusion, exposure to very low concentrations of progesterone produced persistent follicles that secreted oestradiol for 17 days. This oestradiol production could be disrupted by a second increase of 0.9 ng ml(-1) in peripheral progesterone concentration. In the absence of the second progesterone treatment, some of the persistent follicles remained detectable by ultrasonography for up to 52 days, despite cessation of oestradiol secretion.

The inter-ovarian distribution of dominant follicles is influenced by the location of the corpus luteum of pregnancy.

The objective was to characterise the distribution of dominant ovarian follicles in the early post-partum period in relation to the side of the preceding pregnancy and its relationship with the left and right ovaries. Primiparous cows were enrolled over a 2-year period (n = 33 in Year 1 and n = 28 in Year 2). Ovarian follicles were observed daily by trans-rectal ultrasonography commencing within 9 days of calving. Dominant follicles (DF) were described as occurring on the ovary ipsilateral to the CL of preceding pregnancy (ipsilateral ovary of pregnancy, IOP) or contralateral to the CL of the preceding pregnancy (contralateral ovary of pregnancy, COP), and as occurring on the left or right ovary. Results in Year 1 were analysed for the effect of breed (Friesian n = 15; Jersey n = 18). There was a bias towards the COP for the first DF post-partum in both breeds (DF1; 70%; p<0.05). A breed interaction was observed with the second DF post-partum with a bias towards the COP in the Friesian (93%; p<0.05); but not the Jersey animals (50%). In Year 2, all cows were Friesians, and there was again a biased distribution of the DF1 towards the COP (89%; p<0.05) and for the combined distribution of the first three DF post-partum (76%; p<0.05) as well as the first ovulatory follicle (71%; p<0.05). A comparison of the pooled data for the location of the DF1 from both years showed that only one DF1 was observed on a left ovary in the 29 cases where the preceding pregnancy was also on the left side. This study demonstrated a bias in the distribution of DL in the early post-partum period towards the ovary on the side opposite that of the preceding pregnancy as well as towards the right side.

Aspiration of a single dominant follicle leads to improved cohort development and pregnancy in a patient with poor response to in vitro fertilization treatment

Objective: To report improved follicular cohort development and a healthy ongoing pregnancy after midcycle aspiration of a single dominant ovarian follicle in a patient with poor response to IVF treatment. Design: Case report. Setting: University-based infertility center. Patient(s): A 39-year-old woman (gravida 1, para 0) with a borderline FSH level and four previous unsuccessful IVF attempts. Intervention(s): A single 27-mm follicular cyst was aspirated after 13 days of treatment, while controlled ovarian hyperstimulation was continued. Main Outcome Measure(s): Number of follicles developed, number of oocytes retrieved, development of a clinical pregnancy. Result(s): In previous attempts, the patient had no more than two dominant follicles and a maximum of three oocytes retrieved. After midcycle aspiration of the single lead follicle, a new cohort of seven follicles developed and seven oocytes were recovered. Six embryos were replaced by tubal ET and an ongoing singleton gestation resulted. Conclusion(s): Midcycle aspiration of a single lead follicle in a patient with poor response to IVF treatment allowed the development of a larger secondary cohort of follicles during the same cycle and ultimately led to a viable pregnancy. This intervention may have future implications for the treatment of poor responders.

Estrus synchronization of beef cattle with a combination of melengestrol acetate and an injection of progesterone and 17beta-estradiol.

Our hypothesis was that estrus synchronization in beef cattle using melengestrol acetate (MGA) and an injection of progesterone (P4) and 17beta-estradiol (E2) to regress dominant ovarian follicles would improve pregnancy rate (number conceived/number in group) to AI compared with feeding only MGA or injecting PGF2alpha. During 2 yr, peripubertal heifers (n = 52) and cows (n = 327) received either 1) MGA for 18 d (d 0 = 1st d of MGA) plus an injection of P4 and E2 in sesame oil (vehicle) on d 11 to regress persistent ovarian follicles (MGA+P4), 2) MGA for 18 d plus vehicle on d 11 (MGA), or 3) two injections of PGF2alpha 10 d apart (d 7 and 17, PG). Concentration of P4 was assessed in blood samples obtained on d 0, 7, and 17 to indicate estrual status (anestrual or estrual) during treatment to induce estrus synchrony. Observations for detection of estrus occurred every 6 h for 180 h following treatment cessation. Females showing estrus were inseminated 6 to 12 h after estrus detection. Conception to AI was determined by ultrasonography 35 to 40 d later. Conception rate was greater (P < .05) in females in the PG than in those in the MGA group but did not differ from conception rate of females in the MGA+P4 group. Among anestrual females, estrus synchrony rates were greatest (P < .10) among females treated with MGA+P4. Among females that were estrual before treatment cessation, estrus synchrony rates were greater (P < .10) among females treated with MGA+P4 or PG than among those given MGA. Pregnancy rates were greater (P < .05) among females that were anestrual before treatment cessation and treated with MGA or MGA+P4 than among those treated with PG. Estrus synchronization using MGA+P4 and E2 differentially improves estrus synchronization and pregnancy rates among anestrual and estrual beef cattle while maintaining conception rates similar to those of PGF2alpha-treated females.

Comparison of three methods of acute administration of progesterone on ovarian follicular development and the timing and synchrony of ovulation in bos indicus heifers

The aim of this study was to induce the formation of a persistent dominant ovarian follicle and to compare the effects of 3 methods of acute administration of P 4 on ovarian follicular development and on the timing and synchrony of ovulation. Stage of the estrous cycle was initially synchronized in Bos indicus heifers with a norgestomet implants (3 mg) for 10 d and with an analogue of PGF 2α (15 mg) on the first and last day of norgestomet treatment. Eight days after removal of the implants, heifers were randomly assigned to 4 groups. All heifers received a norgestomet implant (Day 0), which was removed 17 d later (Day 17); PGF 2α was administered on Days 0 and 4. Heifers in the control group (n =5) received no other treatment. On Day 10 heifers in Group P 4C (n = 5) were treated with a CIDR for 24 h; heifers in Group P 4O (n = 5) were administered 100 mg im of P 4 in oil, while heifers in Group P 4S (n = 5) were administered 100 mg im of P 4 in saline/alcohol. Data were analyzed using bootstrap estimates of location (mean) and spread (standard deviation; SD). Compared with the control heifers, day of emergence of the ovulatory follicle was delayed, and age and duration of dominance of the ovulatory follicle were reduced in the P 4C and P 4O heifers (P < 0.05) but not in the P 4S heifers (P > 0.05). In all groups treated with P 4 both the mean and variability (SD) in the timing of ovulation did not differ with that of the control group (P > 0.05) but there was less variability in the day of emergence, age, duration of dominance and diameter of the ovulatory follicle than in the control group (P < 0.05). Delayed timing and reduced synchrony (SD) of ovulation and greater age of the ovulatory follicle (P < 0.05) occurred in P 4S heifers than in P 4C heifers. We conclude that administration of 100 mg of P 4 in oil is as effective as treatment with a CIDR for synchronizing emergence and ovulation of a newly recruited dominant follicle. However, reduced synchrony of ovulation, greater age of the ovulatory follicle and delayed timing of ovulation occurred following administration 100 mg of P 4 in saline/alcohol compared with the CIDR device.

Control of Ovulation as a Practical Reproductive Management Tool in Cattle

Infertility in cattle is often caused by poor estrus detection which results in insemination timing error. Estrus detection failure is also a major cause of missing heat and delayed start of re-breeding after carving. Synchronization of estrus by using gestagen or prostaglandin (PG) F2α has been extensively used for improving estrus detection efficiency. However, variation in intervals from treatment to estrus was too large for the existing estrus synchronization methods to be of practical value, for a timed artificial insemination after treatment with gestagen or PGF2α results in disappointing conception rates. Recently, a program for synchronization of estrus using GnRH and PGF2α has been developed. GnRH is administered at first irrespective of estrus cycle to induce ovulation of dominant follicle and a follicular wave, and then PGF2α is given 7 days later for luteal regression, followed by second GnRH injection 30 to 48 hours after the PGF2α. Cattle can be inseminated artificially at a fixed time, 16 to 24 hours after the second GnRH, since ovulation is usually synchronized 24 to 32 hours after the second GnRH. Satisfactory pregnancy rates after synchronization of ovulation and timed AI have been reported in north America as well as in Japan. The greatest advantage of the ovulation synchronization and timed AI program is that virtually 100% of the animals can be inseminated within a certain period with a satisfactory pregnancy rate. Moreover, the program does not require estrus detection. Further studies on the synchronization programs and on factors influencing conception rate after timed AI would significantly improve reproductive management of cattle.

Follicular Dominance in Cattle Is Associated With Divergent Patterns of Ovarian Gene Expression for Insulin-Like Growth Factor (IGF)-I, IGF-II, and IGF Binding Protein-2 in Dominant and Subordinate Follicles

A decrease in insulin-like growth factor (IGF) binding protein (BP) amount occurs within the follicular fluid of dominant ovarian follicles. At the same time, concentrations of follicular fluid IGF-I do not change. The mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3 in dominant and subordinate follicles were measured to determine if changes in IGF or IGFBP gene expression are associated with follicular dominance. Heifers were ovariectomized during a follicular wave, either during early-dominance (emerging dominant follicle, 9 mm diameter) or mid-dominance (established dominant follicle, 14–16 mm diameter). Follicles were classified as either dominant (DF), subordinate (SF), or not-recruited (NRF; small antral follicles). mRNA was localized by in situ hybridization and measured by image analyses. The IGF-I mRNA (granulosa cells) was greatest in DF and increased in DF, SF, and NRF from early- to mid-dominance. Likewise, IGF-II mRNA (theca cells) was greatest in DF compared with SF or NRF. The IGFBP-2 mRNA (granulosa cells), however, was nearly undetectable in DF, whereas adjacent SF expressed abundant IGFBP-2 mRNA. The NRF were not uniform in their IGFBP-2 expression because only 5 of 13 NRF had IGFBP-2 mRNA. The IGFBP-3 mRNA (granulosa cells) was found only in two NRF, suggesting that local synthesis is not a predominant source of follicular fluid IGFBP-3. These data show that changes in gene expression for IGFBP-2 are opposite to those for IGF-I or IGF-II. Increased IGF-I and IGF-II mRNA and decreased IGFBP-2 mRNA within the DF may be one mechanism leading to follicular dominance. The opposite pattern of IGFBP-2 gene expression in SF and some NRF may lead to follicular atresia.

Duration of treatment with progesterone and regression of persistent ovarian follicles in cattle.

The objective of the present study was to determine the duration of elevated concentrations of progesterone necessary to induce atresia of persistent ovarian follicles. Heifers were administered 25 mg of PGF2alpha on d 6 and 7 (d 0 = d of synchronized estrus) and a norgestomet implant from d 6 to 14. Ovaries were monitored by ultrasonography, and blood samples were collected on d 3, 5, 7, 9, 11, and 12 and daily from d 14 until ovulation. On d 12, heifers received either two progesterone-releasing intravaginal devices (PRID) for 6 h (6-h; n = 5), two PRID for 24 h (24-h; n = 5), or no treatment (CON; n = 5). Blood samples were collected at 15-min intervals from h -6 to 30 (PRID insertion = h 0) and analyzed for concentrations of LH. Characteristics of LH secretion were determined for consecutive 6-h periods (Period 0 to 5). Hourly blood samples, collected from h 0 to 29, were analyzed for concentrations of 17beta-estradiol (estradiol) and progesterone. The dominant ovarian follicles present on d 7 increased in size to 15.4+/-.3 mm on d 12 ("persistent follicle"). Following removal of the PRID and norgestomet implants, atresia of persistent follicles and ovulation of new follicles were induced in one of five and in four of five heifers in the 6-h and 24-h treatments, respectively. Persistent follicles ovulated after withdrawal of norgestomet in all other heifers. Concentrations of progesterone were increased from h 1 to 7 in the 6-h and h 1 to 26 in the 24-h treatment. Frequency of LH pulses was reduced (P < .05) during Periods 1 to 2 in the 6-h and Periods 1 to 5 in the 24-h treatment relative to the CON treatment. By h 10, concentrations of estradiol in the 6-h and 24-h treatments were lower (P < . 05) than in the CON treatment. This suppression continued through h 29 in the 24-h treatment (P < .05), whereas concentrations in the 6-h treatment were intermediate to those of the CON and 24-h treatments after h 14. Suppression of pulsatile LH release and estradiol secretion was evident with 6 and 24 h of treatment with progesterone, but only the 24-h treatment induced atresia of persistent follicles in a majority of the heifers.

Gonadotropin secretion and development of ovarian follicles during oestrous cycles in heifers treated with luteinizing hormone releasing hormone antagonist

The hypothesis tested was that reduced LHRH stimulation of the anterior pituitary would lead to attenuated development of ovarian follicles as a result of reduced gonadotropin secretion during oestrous cycles of cattle. Twenty heifers were randomly assigned to be treated ( n = 5/treatment) with an antagonist to LHRH (LHRH-Ant) 1) from Day 2 to 7 (Day 0 = behavioural oestrus), 2) Day 7 to 12, 3) Day 12 to 17, 4) or serve as untreated control animals. LHRH-Ant suppressed LH pulses of heifers in all treatment groups from treatment initiation through Day 17 as compared with untreated control heifers [Peters et al., 1994. Luteinizing hormone has a role in development of fully functional corpora lutea (CL) but is not required to maintain CL function in heifers. Biol. Reprod., 51 (1994) 1248-1254]. Circulating concentration of FSH from Day 8 to 10 of the oestrous cycle did not increase in heifers treated with LHRH-Ant from Day 2 to 7 or Day 7 to 12; however, there was increased (P < 0.05) FSH from Day 8 to 10 of the oestrous cycle in heifers treated with LHRH-Ant from Day 12 to 17 and control heifers. Compared with control heifers, heifers treated with LHRH-Ant from the Day 2 to 7 had suppressed (P < 0.05) size and persistence of the first and second dominant ovarian follicles. Heifers treated with LHRH-Ant from Day 7 to 12 had suppressed size (P < 0.05 and tended (P < 0.10) to have a shorter persistence of the second dominant ovarian follicle compared with control heifers. Heifers treated with LHRH-Ant from Day 12 to 17 had a similar (P > 0.10) size and persistence of dominant ovarian follicles but had reduced (P < 0.10) numbers of large follicles compared with control heifers. Heifers treated with LHRH-Ant from Day 2 to 7 had lower (P < 0.01) concentrations of 17 beta-oestradiol during the treatment period and tended (P < 0.10) to have lower concentrations of 17 beta-oestradiol from Day 7 to 12 of the oestrous cycle compared with control heifers. Heifers treated with LHRH-Ant from Day 7 to 12 or Day 12 to 17 had similar (P > 0.10) circulating LH concentrations of l7 beta-oestradiol compared with control heifers. Reduced LHRH stimulation of the pituitary from Day 2 to 12 of the oestrous cycle and the resulting modulation in circulating LH and FSH led to suppressed ovarian follicular development and oestradiol secretion. After Day 12 of the oestrous cycle, reduced LHRH stimulation of the anterior pituitary did not lead to altered ovarian follicular development to the extent as reduced LHRH stimulation before Day 12 although pulsatile release of LH was similarly suppressed by treatment with the LHRH-Ant.

Selection of the dominant follicle in cattle occurs in the absence of differences in the expression of messenger ribonucleic acid for gonadotropin receptors.

Mechanisms that allow selection of a dominant ovarian follicle from a cohort of growing follicles are unknown. Large healthy, estrogen-active follicles contain more LH receptors than atretic estrogen-inactive follicles, and levels of messenger RNA (mRNA) for LH receptor increase in the granulosa cells of dominant follicles as growth progresses. The aim of the present study was to test the hypothesis that changes in the temporal pattern of expression of mRNA for LH and FSH receptors are associated with selection of dominant follicles in cattle. Based on size, the dominant and two largest subordinate follicles were collected from the ovaries of heifers on days 2 (n = 3) or 3 (n = 3) of a follicular wave. On day 2, the dominant follicle was 1 mm larger than the largest subordinate follicle, but by day 3 of the wave the dominant follicle was 2-4 mm larger than the largest subordinate. Follicular fluid concentrations of estradiol and estradiol secretion in vitro by pieces of follicle wall (granulosa and theca cells) were greatest by the dominant compared with the subordinate follicles (P < 0.05). These data indicate that selection of a dominant follicle had occurred by the second day of the follicular wave. By in situ hybridization, mRNAs for LH and FSH receptors, P450 aromatase and P450 17alpha-hydroxylase (17alpha-OH) were localized in frozen sections from each follicle. The expression of mRNA for LH receptor in granulosa cells was always at or near background and was not different between days or follicle types (P = 0.63). In contrast, the expression of mRNA for LH receptor in theca cells of the same sections was readily detectable; there was no difference between follicle types on the second day of the follicular wave, but by the third day expression in the subordinate follicles had decreased (P < 0.05). The expression of mRNA for FSH receptor was highest in granulosa cells of dominant follicles collected on day 3 of the follicular wave (P < 0.05) and was not different between dominant and subordinate follicles on day 2 of the wave (P > 0.05). The expression of mRNA for aromatase in granulosa cells was similar (P > 0.05) between the dominant follicles on days 2 and 3 and the largest subordinate follicle on day 2 of the follicular wave and was much lower in the remaining follicles (P < 0.01). On day 2 of the wave, the expression of mRNA for 17alpha-OH was not different between the dominant and subordinate follicles, but by day 3 the dominant follicles had more mRNA for 17alpha-OH than the subordinate follicles (P < 0.05). These data show that the dominant follicle had been selected by the second day of the follicular wave (based on diameter and estradiol secretion) and that selection occurred in the absence of detectable levels of mRNA for LH receptor in the granulosa cells or differences between dominant and subordinate follicles in mRNA for LH receptor in theca cells or FSH receptor in granulosa cells. However, the divergent pattern of growth between dominant and subordinate follicles (after follicle selection) was associated with higher levels of mRNA for gonadotropin receptors and steroidogenic enzymes in dominant compared with subordinate follicles. Therefore, selection of the dominant follicle in cattle does not appear to involve the regulation of expression of mRNA for gonadotropin receptors, although such regulation may be important at other stages of differentiation of the dominant follicle.

Use of the GnRH analogue, deslorelin acetate, in a slow-release implant to accelerate ovulation in oestrous mares

In two separate controlled clinical trials, the efficacy and safety of 2.2 mg of the GnRH analogue deslorelin, administered subcutaneously as a short-term implant to normally cycling mares in oestrus...

Will treatment with progesterone, either alone or with oestradiol result in behavioural oestrus and a normal length luteal phase in postpartum beef suckler cows induced to ovulate by calf isolation and once-a-day suckling?

In beef suckler cows, the prolonged interval from calving to first ovulation (post-partum interval, PPI) is due to failure of ovulation of dominant follicles. It appears that a combination of poor body condition, maternal calf-bond and suckling act to suppress the LH pulse frequency necessary for ovulation. A combination of calf isolation and once-a-day suckling can significantly shorten the PPI, but the first ovulation generally occurs without overt oestrus and the subsequent cycle is short (8 to 11 days) due to lack of progesterone priming. The aim of this study was to examine the effects of progesterone or progesterone and oestradiol in conjunction with calf isolation on the interval to first ovulation, incidence of overt oestrus at first ovulation and length of the subsequent interovulatory interval.

Estrus synchronization and fertility after the control of formation and regression of the corpus luteum, and emergence of the ovarian dominant follicle in cattle

Three experiments were conducted with the aim of improving estrus synchronization and conception rates to AI after progestogen-based estrus synchronization. In Experiment 1, stage of the estrous cycle was synchronized in heifers, and on Day 6 of the ensuing cycle (Day 0 of treatment) heifers (n = 14) received a norgestomet implant with prostaglandin (PG) administered on Days 0 and 1. This resulted in an increase in pulsatile secretion of LH and continued growth of the dominant follicle. On Day 4, groups of heifers received 500 (n = 4), 1,000 (n = 4), 1,500 (n = 3) or 3,000 (n = 3) IU hCG, which induced the dominant follicle to ovulate. This was followed within 48 h by the emergence of a newly-recruited dominant follicle that ovulated after the removal of norgestomet and injection of PG on Day 10. The dose of 500 IU hCG was sufficient to ovulate the dominant follicle on Day 4, and this dose was used in subsequent experiments. In Experiment 2, stage of the estrous cycle was synchronized in cows, and on Day 6 of the ensuing cycle (Day 0 of treatment) the cows were given PG and a single norgestomet implant On Day 4 of treatment cows were divided into 2 groups: Group 2A (n = 17), injection of PG; Group 2B (n = 13), injection of PG plus 500 IU hCG. Norgestomet implants were removed on Day 10, coinciding with an additional injection of PG. Cows were inseminated 12 h after estrus. Cows that received hCG (ovulated a newly-recruited dominant follicle) had a higher (P < 0.05) pregnancy rate than control cows (ovulated a persistent dominant follicle; 61 and 23%, respectively). In Experiment 3, heifers at different stages of the estrous cycle were given PG and a norgestomet implant on Day 0, and a second injection of PG plus 500 IU hCG on Day 4. The heifers were divided into 2 groups and those in Group 3A (n = 9) were given PG on Day 10, with the norgestomet implant removed on Day 11. Heifers in Group 3B (n = 9) were given PG at implant removal on Day 11. Injection of PG 24 h before norgestomet implant removal induced an earlier onset of estrus and tended to improve the closeness of estrus synchrony, but pregnancy rates (89%) were the same for both groups of heifers. The norgestomet/hCG regimen allows tor control of the development and regression of the corpus luteum (CL), together with ovulation of a newly-recruited dominant follicle. This protocol can be further developed for estrus synchronization programs to consistently achieve close synchrony of estrus and high fertility in cattle.

Blood flow changes in the ovarian and uterine arteries during the normal menstrual cycle

OBJECTIVE: Our purpose was to study the hemodynamic changes in the uterine and intraovarian vessels during the normal menstrual cycle and to relate the vascular changes to hormonal index values. STUDY DESIGN: Seven women who had bilateral tubal patency, a normal pelvis on laparoscopy, and regular ovulatory cycles underwent serial transvaginal ultrasonography on menstrual cycle day 2, daily from estimated day of ovulation –6, hourly from estimated day of ovulation –2, or when the mean follicular diameter was >16 mm (whichever was earlier) until 6 hours after follicular rupture and once 7 days after follicular rupture. At each scan uterine and intraovarian blood flow was assessed with transvaginal color Doppler ultrasonography and serum concentrations of follicle-stimulating hormone, luteinizing hormone, estradiol, and progesterone assessed by fluoroimmunoassay. RESULTS: In one case there was evidence of a luteinized unruptured follicle and the patient was therefore excluded from analysis. In the other six women there was spontaneous ovulation at a mean of 39 hours after the onset of the luteinizing hormone surge. On the side with the dominant follicle, follicular and ovarian stromal peak systolic blood flow velocity rose significantly during the menstrual cycle with no significant change in pulsatility index. The changes in blood flow velocity correlated significantly with changes in serum follicle-stimulating hormone, luteinizing hormone and progesterone concentrations. There were no significant changes in either blood flow velocity or pulsatility index in the contralateral ovary. Uterine artery time-averaged maximum velocity on the side of the developing ovarian follicle increased during the menstrual cycle with no significant change in the contralateral vessel. Uterine artery pulsatility index on the side of the developing follicle declined during the midluteal phase and was significantly lower than on the contralateral side. The changes in time-averaged maximum velocity correlated with the changes in serum estradiol and progesterone concentrations. CONCLUSION: The vascular changes in the wall of the dominant ovarian follicle and ovarian stroma during the menstrual cycle are consistent with activity of angiogenic-like factors. The decline in uterine artery resistance during the midluteal phase may reflect optimal vascularity for implantation of the blastocyst. (Am J Obstet Gynecol 1996;175:625-31.)

Ovarian follicular development and the follicular fluid hormones and growth factors in normal women of advanced reproductive age.

Reproductive aging in women (a physiological decline in the function of the hypothalamic-pituitary-ovarian axis) is an infrequently investigated and poorly understood biological phenomenon. Although menstrual irregularity and anovulation are known to precede the menopause, normal women in their fifth decade experience a profound decrease in fertility while still experiencing regular menstrual cycles. To further our understanding of the physiological changes associated with reproductive aging, this study examined the spontaneous development and function of ovarian follicles in normal women, aged 40-45 yr. The subjects were women (n = 21), aged 40-45 yr, who had regular 25- to 35-day ovulatory menstrual cycles, were not infertile, had no medical problems, and met specific criteria for weight, diet, and exercise. The controls were normal women (n = 20), age 20-25 yr, who met the same criteria. The subjects were monitored with daily hormone measurements [LH, FSH, estradiol (E), progesterone (P), and inhibin] and pelvic sonograms from day 1 of their study cycle until the dominant ovarian follicle reached a mean diameter of 15 mm and/or a serum E level of 550 pmol/L or higher was attained. At that time, 10,000 U hCG were given, and a transvaginal sonographic follicle aspiration was performed 32 h later. The follicular fluid (FF) was collected, stored frozen at -70 C, and later analyzed for E, P, testosterone (T), androstenedione, inhibin, insulin-like growth factor I (IGF-I), and IGF-II. The number of cycle days to aspiration was lower (11.6 vs. 15.6 days; P < 0.001) and the early follicular phase mean FSH and mean E levels were higher (9.3 vs. 6.6 mIU/mL and 305 vs. 160 pmol/L; P < 0.01) in the older (O) group compared to the younger group. There was a strong trend toward higher FF mean E (2280 vs. 1931 nmol/L) and lower FF mean T (978 vs. 2361 pmol/L) levels in group O. The E/T ratio was significantly higher (5253 vs. 2408; P < 0.03) in group O. In group O, the mean FF P levels were increased as well (25.1 vs. 18.8 micromol/L; P < 0.01). The serum mean IGF-I (153 vs. 226 ng/mL; P < 0.001) and FF mean IGF-I (113 vs. 158 ng/mL; P < 0.02) levels were significantly decreased in group O. There were no differences between groups in serum or FF IGF-II or inhibin levels. Whether reproductive aging is an intrinsic ovarian process or the ovary is simply responding to exogenous influences, the ovary in general and its follicles in particular are the primary site of the effects of aging. Ovarian follicles in older ovulatory women have some unique features: 1) the follicles are the same size as those in younger women, but form more rapidly; 2) secretion of E and inhibin is not compromised; 3) the concentrations of steroids in the FF are indicative of a healthier follicle, i.e. increased P levels and higher estrogen to androgen ratio; and 4) serum and FF levels of IGF-I are decreased, but there are no differences in IGF-II levels.

Nutrition and reproduction

Through their influence on embryonic and early fetal development dietary nutrients affect the size, vigour and viability of the newborn and, in the case of sheep, adult ovulation rates. Nutritional regimens that impair post-natal growth reduce ovarian follicular development and delay puberty but have little, if any, effect on either N-methyl-D-aspartate stimulated GnRH release or the pituitary content of gonadotrophins. Nutritional effects on ovulation rate in ewes are not always accompanied by shifts in circulating FSH concentrations. Instead they may operate through altered ovarian hormone feedback mechanisms that influence the duration of exposure of the gonadotrophin-dependent follicles to FSH or through threshold-reducing actions of specific nutrients and dietary-induced metabolites on the amount of FSH needed to support the gonadotrophin-dependent follicles. Recent results suggest that the enhanced faecal excretion of oestradiol by well-fed ewes may increase ovulation rate by reducing ovarian oestradiol feedback. In the post-partum period, the key hypothalamic and pituitary secretions for successful ovulation develop normally despite undernutrition but ovulation is prevented by failure of GnRH release with, in the case of suckler beef cows, a delay in oestrus arising from the repeated development and atresia of dominant ovarian follicles. This effect is accentuated in cows that are in poor body condition at calving. Alleviating the energy deficits of high-yielding dairy cows in early lactation by giving supplements of dietary fat can reduce the interval to first oestrus but subsequent fertility can be impaired. Loss of body protein delays oestrous cyclicity; paradoxically attempts to correct this loss in ruminants by feeding diets high in rumen undegradable protein can stimulate body fat mobilization and milk production with detrimental effects on rebreeding. Excess rumen degradable protein and high feeding levels reduce embryo survival, the latter by suppressing circulating progesterone concentrations. In superovulated ewes diet-induced reductions in progesterone concentrations during oocyte maturation can impart a legacy of developmental retardation leading to decreased embryo survival. In late pregnancy, undernutrition decreases uterine blood flow, fetal insulin and IGF-1 concentrations and impairs growth and development. In the newborn, low insulin and a low selenium and iodine status inhibit thermogenesis from brown adipose tissue. Insulin may also be important in conveying information on nutritional status to the GnRH neurones thereby initiating the cascade of events that is required for successful reproduction in both sexes.

Development of persistent ovarian follicles during synchronization of estrus influences the superovulatory response to FSH treatment in cattle

The synchronization of estrus with synthetic progestins or progesterone (P 4) results in the development of a large, persistent ovarian follicle. The objectives of the present study were to determine if development of a persistent ovarian follicle during synchronization of estrus suppresses recruitment of additional follicles during FSH treatment. On Day 5 of the estrous cycle (estrus = Day 0), beef cows were treated with 0.5 or 2.0 P 4 releasing intravaginal devices (PRIDs) for 8 d (Experiment 1, n = 20), 5 or 2 d (Experiment 2, n = 44) before initiation of FSH treatment. Prostaglandin F 2α (25 mg) was administered on Days 5 and 6. Superovulation was induced with 24 mg of recombinant bovine FSH (rbFSH, Experiment 1) or 28 mg of FSH-P (Experiment 2) over a 3- or 4-d period, respectively. The PRIDs were removed concurrently with the 5th injection of rbFSH or FSH-P. There was a treatment-by-day interaction (P < 0.001) for the concentration of 17β-estradiol in cows treated for 8, 5 or 2 d before FSH treatment. In Experiment 1, FSH treatment initiated 8 d after insertion of a 0.5 PRID did not affect the number of CL (6.9 ± 1.4 vs 6.7 ± 1.6), ova/embryos (3.7 ±1.3 vs 3.0 ± 1.3) and transferable embryos (2.4 ± 0.9 vs 3.0 ± 0.9) compared with that of the 2.0 PRIDs. In Experiment 2, FSH treatment initiated 5 d after insertion of a 0.5 PRID decreased the number of CL (4.0 ± 0.5 vs 8.3 ± 0.8; P < 0.001), ova/embryos (3.0 ± 0.6 vs 5.9 ± 1.2; P < 0.03) and transferable embryos (2.3 ± 0.6 vs 5.1 ± 1.0; P < 0.03) compared with that of a 2.0 PRID, respectively. Initiation of FSH treatment 2 d after insertion of a 0.5 PRID compared with a 2.0 PRID had no affect on the number of CL (8.0 ± 2.1 vs 8.7 ± 1.2), total ova (4.8 ± 1.4 vs 6.9 ± 1.4) and transferable embryos (2.9 ± 1.2 vs 6.1 ± 1.7). In conclusion, treatment with low doses of P 4 (0.5 PRID) for 5 d but not for 2 or 8 d before initiation of FSH treatment results in the development of a dominant ovarian follicle, which reduces recruitment of ovarian follicles, and the number of CL, total ova and transferable embryos.

Acceleration and Timing of Fertile Ovulation in Cyclic Mares with a Deslorelin Implant

In a blinded trial, the effectiveness and safety of 2.2 mg of the GnRH analog deslorelin acetate, administered in a short-term implant (STI) to normally cycling mares in estrus with a dominant ovarian follicle of 30 mm in diameter or larger, were evaluated, using a placebo implant as a negative control. A total of 39 mares received treatments at admittance with pre-randomized implants containing either 2.2 mg or 0 mg deslorelin. Mares were teased daily and examined rectally with ultrasound at 24 h intervals to determine time to ovulation and duration of estrus. The number of breedings and the pregnancy rate at 18 (+/- 3) and 38 (+/- 3) days were recorded, as were systemic side effects and local reactions at the implantation sites. Pregnancies resulting from breedings during the treatment estrus and/or from breedings during the next estrus were followed and the early and late pregnancy loss rate, the number of pregnancies going to term and of live-born foals was recorded. Mean follicle diameter at treatment was not significantly different between the deslorelin and placebo treatment group with 41.6 mm and 40.8 mm, respectively. Treatment with deslorelin STI reduced the time interval to ovulation significantly from 69.5 +/- 25.48 h to 42.7 +/- 12.35 h (p < 0.001). The percentage of mares having ovulated within 48 h rose from 26.3% to 95.0%, respectively, for placebo and deslorelin STI (p < 0.001). As a consequence, the duration of estrus in days and the percent of animals requiring more than 1 breeding were significantly reduced in deslorelin treated animals from 5.4 days to 4.6 days, and from 55.6% to 5.0%, respectively (p = 0.009 and = 0.001). The percent of mares pregnant from breedings at the treatment estrus (65.0% versus 44.4%) or the next estrus (83.3% versus 92.3%) was satisfactory and similar for deslorelin and placebo treated mares (p > 0.005), and in 70.0% and 66.7% of these once or twice bred mares did pregnancies go to term and live foals were born.

Hormone concentrations in the caudal vena cava during the first ovarian follicular wave of the oestrous cycle in heifers.

Changes in pulsatile secretion of LH, FSH, oestradiol and progesterone were related to the growth phase, early plateau phase and regression phase of the first ovarian dominant follicle of the oestrous cycle in Bos indicus heifers. Relationships between these hormones during the three phases were also investigated. Accurate measurements of episodic ovarian steroid secretion were obtained by catheterizing the caudal vena cava via the lateral saphenous vein; the tip of the catheter was positioned just cranial to the ovarian vein using transrectal ultrasonography. Pulsatile secretion of oestradiol was increased only during the growth phase of the dominant follicle and was associated with high frequency release of LH pulses. However, mean concentrations of oestradiol were reduced when the dominant follicle attained its maximum diameter. Between the growth and plateau phases, as the amount of progesterone released increased and oestradiol released decreased, LH pulse frequency and mean concentration of LH decreased. Pulses of LH released were followed within 15 min by increases in mean concentrations of oestradiol (P < 0.001); however, there was no apparent relationship between LH and progesterone release (P = 0.19). Although there was little evidence of pulsatile release of FSH, mean concentrations of FSH were increased by 0.2 ng ml-1 (P = 0.04) during the plateau phase, which was on average 2.1 days before the day of emergence of the second dominant follicle of the oestrous cycle. This increase in FSH, in conjunction with the decrease in secretion of oestradiol, may be an indication of the loss of functional dominance by the first dominant follicle of the oestrous cycle.