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PubMed1996

Partial purification from bovine follicular fluid of a factor of low molecular mass with inhibitory effects on the proliferation of bovine granulosa cells in vitro and on rat follicular development in vivo.

Bovine follicular fluid was aspirated from follicles of 2-20 mm in diameter, charcoal-treated to remove steroids and then separated into low and high molecular mass fractions. The low molecular mass (< 10 kDa) fraction was purified on a Sephadex G-25 chromatography column with formic acid as the eluent. Seven peaks were isolated and assayed for biological activity in cultures of bovine granulosa cells at concentrations of 10, 100 and 1000 ng ml-1. One peak (peak 4) inhibited (P < 0.001) the proliferation of granulosa cells when measured by cell counting and by [3H]thymidine incorporation (33-37% inhibition). This peak inhibited proliferation of granulosa cells from both small (< 2 mm) and medium (2-10 mm) follicles, but not large (> 10 mm) follicles. The inhibitory effect of peak 4 was not due to a toxic effect on cells. Administration of peak 4 to rats did not affect liver or kidney masses but did decrease uterine (25%, P < 0.01) and ovarian (35%, P < 0.01) masses. Peak 4 also caused a reduction in the number of large follicles (65%, P < 0.01) but increased the number of small follicles (55%, P < 0.01). We have named the inhibitory factor associated with peak 4, granulosa cell-inhibitory factor (GCIF). The results presented suggest that GCIF may be a factor secreted by dominant follicles that inhibits the development of subordinate follicles.

Animals↗
PubMed1986

Plasma concentrations of gonadotrophins, preovulatory follicular development and luteal function associated with bovine follicular fluid-induced delay of oestrus in heifers.

In Exp. 1, injections of 10 ml bovine follicular fluid (bFF, i.v. or s.c.), given twice daily for 3 days after injection of a luteolytic dose of PGF-2 alpha, delayed the onset of oestrus in 3 of 6 heifers to 8 or 9 days after PGF-2 alpha, as compared with 2 or 3 days after PGF-2 alpha in control heifers. Mean plasma concentrations of FSH and LH during the injection period were not different from those in saline-injected heifers. In Exp. 2, i.v. injections of 20 ml bFF twice daily for 3 days uniformly delayed oestrus to 8 days after PGF-2 alpha (N = 4) and injections of 20 ml bFF i.v. every 6 h for 24h on the day of PGF-2 alpha injection delayed oestrus to 5.0 +/- 0.6 days after PGF-2 alpha as compared with 2.8 +/- 0.3 days for control heifers. In both treatment groups, plasma concentrations of FSH were suppressed during the injection period and increased transiently after treatment, but plasma concentrations of LH during the injection period were not different from those of control heifers. Plasma levels of oestradiol in heifers given bFF remained basal for 2 or 3 days after treatment, then increased several days before the delayed oestrus, in a manner similar to that in control heifers, and elicited normal preovulatory surges of LH and FSH. Plasma concentrations of progesterone and the length of the next oestrous cycle were normal, indicating formation of functional corpora lutea. Therefore, bFF treatments appear to delay oestrus by selectively suppressing plasma FSH, without affecting LH, and delaying the development of the preovulatory follicle. These results suggest that FSH may be critical to support the growth and development of the preovulatory follicle after luteolysis in cows.

Anestrus↗
PubMed1992

Simultaneous induction of multiple follicular development with gonadotrophins and steroid replacement for in-vitro fertilization.

Simultaneous administration of follicle stimulating hormone, oestradiol valerate and progesterone was employed in a patient with a possible enzymatic deficiency involving low production of oestradiol. The patient became pregnant after in-vitro fertilization. This case demonstrates that this treatment is useful in women with low oestradiol production and subsequent inadequate endometrial development; it also illustrates the role of oestradiol in follicular development and questions the importance of serum oestradiol measurements in the monitoring of ovulation induction.

Adult↗
PubMed1983

Assessment of follicular development by ultrasonography and total serum estrogen in human menopausal gonadotropin-stimulated cycles.

Ovarian follicular development was assessed by serial ultrasonography in infertile women being treated with human menopausal gonadotropin. Both follicular size and number of follicles correlated with serum estrogen values in most patients, and follicles increased in size 2--3 mm per day. Most patients had serum estrogen values greater than 750 pg/ml when one or more follicles larger than 18 mm were present. A comparison of conception cycles with non-conception cycles did not reveal a significant difference in size or number of follicles, or in the rate of rise or peak value of serum estrogen. When women monitored with ultrasonography were compared with patients treated with gonadotropins prior to the availability of ultrasonography, there was no significant difference in the rates of successful conception, although the number of ampules of pergonal used by the former was significantly reduced, permitting more efficient use of an expensive medication.

Estrogens↗
PubMed1987

Ovarian follicular development in oral contraceptive cycles.

The cyclic changes in serum hormone concentrations, ovarian follicular development, uterine size, and endometrial appearance have been observed in 58 spontaneous ovulatory cycles and compared with 22 initial cycles of oral contraceptive (OC) therapy. A far greater inhibitory effect on the ovary was achieved by starting contraception on day 1 of the cycle rather than on day 5. The relevance of these findings with regard to OC failures is discussed.

Adult↗
PubMed1989

[Follicular development in cattle; changes in their count and size during the ovarian cycle].

Follicular development was examined by transrectal ultrasound scanning in 12 heifers during 51 oestrous cycles. Internal diameters of largest and second largest follicles and the number of smaller ovarian vesicles were determined. Diameters of dominant follicles showed inverse growth pattern to the second largest follicles and numbers of smaller follicles (greater than or equal to 5 mm). There was an increase in diameters of the largest follicles from beginning of dioestrous to day 9 and from time of luteolysis to ovulation, which was coincident which a decrease in diameters of the second largest follicles and numbers of smaller ovarian vesicles. Smaller follicles increased in count and diameter, when the dominant follicle achieved its largest dimension and started to regress. The cyclic corpus luteum had no local influence on diameters of the largest and second largest follicles in the ovary bearing the corpus luteum versus the contralateral ovary. Internal diameters of oestrous follicles measured 14.7 +/- 2.6 mm in heifers and 15.3 +/- 2.9 mm in cows at the day of oestrous (p greater than 0.05; t-test). Dioestrous follicles with similar size were detected during various stages of the oestrous cycle. The diameter of the dominant follicle is not an accurate criterion for determining the stage of the oestrous cycle.

Animals↗
PubMed2002

Involvement of inhibitory nuclear factor-kappaB (NFkappaB)-independent NFkappaB activation in the gonadotropic regulation of X-linked inhibitor of apoptosis expression during ovarian follicular development in vitro.

Increased X-linked inhibitor of apoptosis (XIAP) expression and suppressed follicular apoptosis are important determinants in the regulation of follicular development by FSH. The objective of the present study was to examine the role and regulation of nuclear factor-kappaB (NFkappaB) in the gonadotropic control of granulosa cell XIAP expression and follicular growth in vitro. FSH (100 ng/ml) increased rat granulosa cell XIAP mRNA abundance and protein content. The gonadotropin also induced granulosa cell p65 subunit-containing NFkappaB translocation from cytoplasm to nucleus and increased NFkappaB-DNA binding activity. Supershift EMSA indicated the FSH-activated NFkappaB contained p65 and p50 subunits. Unlike TNFalpha, FSH failed to elicit a significant change in granulosa cell phospho- and total-inhibitory NFkappaB (IkappaB) IkappaB contents in vitro and dominant-negative IkappaB expression was ineffective in blocking the increase in NFkappaB-DNA-binding activity and XIAP protein content induced by the gonadotropin. In contrast, SN50 (a cell permeable inhibitory peptide of NFkappaB translocation, 50-200 ng/ml) suppressed FSH-stimulated NFkappaB-DNA binding, XIAP expression, and follicular growth. FSH also increased granulosa cell phospho-Akt contents, a response sensitive to the PI-3K inhibitor LY294002 (10 microM). In conclusion, the present studies demonstrate that the FSH-induced XIAP expression is mediated through the NFkappaB pathway through activation of phosphatidylinositol 3-kinase rather than the classical IkappaB kinase.

Animals↗
PubMed1986

Morphological and endocrinological studies on follicular development during the human menstrual cycle.

In order to clarify the morphological dynamics of follicular development and its correlation with ovarian endocrine activity, the present studies were performed in 45 regularly menstruating women who underwent gynecological surgery. Ovarian venous blood was collected from 35 women during the follicular phase. Thirteen of these 35 women were ovariectomized. In addition, 11 pairs of ovaries were obtained from women during the luteal phase. The ovaries were sectioned serially at 2.5 micron and every 13th stained slice was examined to assess the sizes and numbers of atretic and nonatretic follicles. The follicles were divided into five stages: 0.4 less than or equal to approximately less than 1.0 mm, 1.0 less than or equal to approximately less than 2.0 mm, 2.0 less than or equal to approximately less than 4.0 mm, 4.0 less than or equal to approximately less than 6.0 mm, and 6.0 mm less than or equal to approximately in follicular diameter. Estradiol concentrations in ovarian venous plasma were low on both sides on days 1 and 3 of the cycle, whereas a clear asymmetry was found on day 5 before morphological recognition of the dominant follicle. Thereafter, estradiol increased proportionally to the growth of the dominant follicle, followed by a sudden drop when ovulation was imminent. An asymmetrical rise of progesterone occurred on day 10 and later which was sustained up to ovulation. A dominant follicle was recognized in 8 of 11 women between days 6 and 14. All dominant follicles were invariably associated with higher estradiol concentrations in the ipsilateral ovarian blood. Seven of 8 dominant follicles were on the side contralateral to the preceding corpus luteum. The mean diameters of the largest nonatretic follicles were 5.4 +/- 0.3 (SE) mm during the luteal phase as a whole and 4.7 +/- 0.7 mm during the late luteal phase. The mean diameters of the largest nonatretic follicles were not significantly different between the groups with or without the corpus luteum in the luteal phase. In terms of number and atretic rate, follicles of less than 4.0 mm in diameter did not change throughout the cycle in the presence or absence of the corpus luteum. In contrast, cyclic changes of growth and atresia occurred in the larger antral follicles.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Ovarian follicular development in mink (Mustela vison).

Ovarian follicular dynamics were studied during the breeding season, before and after ovulation in mink. Nulliparous female mink were stimulated to ovulate with an injection of 4 micrograms GnRH. Ovaries from three animals were collected on days 0, 2, 3, 4, 5, 6 and 7 after hormone treatment. A second dose of GnRH was administered on day 8 and ovaries were collected from three animals on day 9. Corpora lutea and follicles were identified in histological sections and follicles were classified by stage of development, healthy versus atretic, and by diameter. Preovulatory follicles (diameter 0.7-1.0 mm) were present in the ovaries of all animals on day 0 and these responded to GnRH treatment by ovulating. A synchronized wave of follicular development occurred following ovulation. Changes in follicle populations indicated that follicles are recruited from the small antral follicle class (0.2-0.4 mm) into the 0.4-0.6 mm class, with the first defined changes occurring between days 2 and 4. From the recruited group, a smaller cohort of follicles is selected to become the dominant follicles between days 4 and 6, and these acquire the ability to respond to a stimulus which induces ovulation at diameters of > 0.7 mm. The ovaries of unmated mink also contained substantial numbers of large, degenerating, luteinized, unruptured follicles. These degenerating, luteinized follicles are considered to represent the demise of large follicles that failed to receive an ovulatory stimulus.

Animals↗
PubMed1982

Plasma and pituitary hormone changes and follicular development after unilateral ovariectomy in cyclic rats.

After unilateral ovariectomy of 4-day-cyclic rats, plasma FSH increased over control values for 6--12 h after the surgery regardless of whether unilateral ovariectomy was performed before or after 08:00 h on the day of dioestrus, after which time compensatory ovulation did not occur at the next oestrus. Pituitary content of FSH also increased from 6 h after unilateral ovariectomy. In contrast, plasma and pituitary levels of LH and prolactin were generally within the range of values of sham-operated rats. Treatment with pentobarbitone between 13:00 and 14:00 h on the day of pro-oestrus in rats unilaterally ovariectomized after 08:00 h on dioestrus delayed the next spontaneous ovulation by 1 day and was accompanied by a rise in plasma FSH concentrations for 24 h and a doubling in the number of ovulations from the remaining ovary. Follicle counts showed an increase in large healthy follicles (greater than or equal to 501 micrometers diam.) and a decrease in atretic follicles in pentobarbitone-treated rats. It is suggested that the FSH rise induces compensatory follicular development and decreases follicular atresia when there is sufficient time for follicles to develop before the LH surge.

Animals↗
PubMed2002

Effects of culture medium, serum type, and various concentrations of follicle-stimulating hormone on porcine preantral follicular development and antrum formation in vitro.

Developing a culture system for preantral follicles has important biotechnological implications due to the potential to produce large number of oocytes for embryo production and transfer. As an initial step toward accomplishing this long-term goal, a study was conducted to determine the effects of culture medium, serum type, and different concentrations of FSH on preantral follicular development in vitro. Specific endpoints included follicular growth rate, antrum formation, recovery rate of cumulus cell-oocyte complexes (COCs) from follicles, and oocyte meiotic competence. Compared with the North Carolina State University medium 23 (NCSU23), preantral follicles cultured in TCM199 medium for 4 days grew faster (P < 0.02). However, more follicles cultured in NCSU23 differentiated to form an antrum than in TCM199 (P < 0.01). For this reason, NCSU23 was chosen to investigate the role of FSH and serum type in regulating preantral follicular growth. Compared with the 0 mIU/ml FSH control, addition of 2 mIU/ml FSH to the medium stimulated follicular growth and antrum formation and suppressed apoptosis of granulosa cells (P < 0.05), supporting the essential role of FSH in preantral follicular growth and development. Another experiment compared fetal calf serum (FCS) with prepubertal gilt serum (PGS) and studied different concentrations of FSH in the culture medium (0.5, 1, and 2 mIU/ml). The best follicular growth rate was obtained with 2 mIU/ml compared with 0.5 or 1 mIU/ml FSH. Compared with PGS, FCS supplementation increased the cumulative percentage of antral follicles and COC recovery rate (P < 0.04). None of the oocytes recovered from any of these experiments reached metaphase II stage after maturation in vitro. In summary, culture medium, serum type, and FSH concentration in the medium interacted to affect follicular growth and antrum formation in vitro. These results suggest that a longer term culture of preantral follicles (>4 days) may be needed to produce oocytes capable of undergoing meiosis in vitro.

Animals↗
PubMed1990

Follicular development and oocyte maturation after stimulation with gonadotropins versus leuprolide acetate/gonadotropins during in vitro fertilization.

Follicular development and oocyte maturation were compared in 22 patients stimulated with human menopausal gonadotropins/human chorionic gonadotropin (hCG, group I) and in 52 women also treated with the gonadotropin-releasing hormone agonist (GnRH-a) leuprolide acetate (LA, group II). Suppression of endogenous leutinizing hormone (LH) surges by LA allowed delayed hCG administration, resulting in higher peripheral estradiol levels, more retrieved oocyte cumulus corona complexes, and greater numbers of cryopreserved embryos. Reduction in spontaneous LH surges in the GnRH-a cycles may have allowed time for larger follicular fluid (FF) volume accumulation during all phases of oocyte cumulus corona complex maturation, restoring synchrony between FF volume and oocyte cumulus corona complex maturity.

Adult↗
PubMed1990

Suppression of the secondary FSH surge with bovine follicular fluid is associated with delayed ovarian follicular development in heifers.

Holstein heifers were given 5 injections (twice/day) of 10 ml charcoal-extracted bovine follicular fluid (bFF; N = 6) or 10 ml saline (N = 5) beginning 12 h after the onset of oestrus. Blood samples were collected for determination of plasma concentrations of FSH, LH, progesterone and oestradiol-17 beta. Treatment with bFF suppressed the secondary FSH surge (P less than 0.01). Cessation of bFF injections was followed by a rebound period during which FSH was elevated compared with controls (P less than 0.01). Daily ultrasonographic examinations revealed that follicular growth occurred in waves, with 4 of 5 control heifers exhibiting 3 waves and the other 2 waves. In contrast, 5 of 6 bFF-treated animals exhibited 2 waves and the other 3 waves. Appearance of follicles in the first wave was delayed in bFF-treated heifers (Day 3.3 +/- 0.3 compared with Day 1.4 +/- 0.2; P less than 0.0001) and appearance of the dominant follicle of the first wave was delayed (Day 4.5 +/- 0.3 compared with Day 1.8 +/- 0.2; P less than 0.0001). Follicles in the second wave appeared later in animals treated with bFF (Day 12.7 +/- 0.4 compared with Day 10.4 +/- 0.6; P less than 0.01), and the dominant follicle of this wave also appeared later (Day 13.0 +/- 0.5 compared with Day 10.6 +/- 0.5; P less than 0.01). Oestradiol-17 beta increased during the early luteal phase, but this increase occurred later in heifers treated with bFF (peak concentrations on Day 6.3 +/- 0.6 compared with Day 4.2 +/- 0.2; P less than 0.05). LH, progesterone and cycle length were not affected by bFF. Delayed follicular growth associated with suppression of FSH suggests that the secondary FSH surge is important in the initiation of follicular development early in the bovine oestrous cycle, and thus may play a role in the regulation of ovarian follicular dynamics.

Animals↗
PubMed1982

Mechanisms of suppression of ovarian follicular development during lactation in the rat.

To determine the mechanisms responsible for the suppression of follicular development in the lactating rat, in vivo and in vitro determinations of steroid and peptide hormones combined with the histological size-distribution of ovarian follicles were compared among three groups of post-parturient rats nursing 0, 2 or 8 pups. From Days 4 to 12 (day of parturition = Day 0 of lactation), in dams nursing 8 pups, follicles larger than 401 microns in diameter were absent, whereas follicles of this size were always present in mothers nursing 0 or 2 pups. The in vitro production rates of estradiol-17 beta (E2) and testosterone (T) by nonluteal ovarian tissues (NLO) were consistently lower in dams nursing 8 pups than in mothers nursing 0 or 2 young, correlating with the histological observations. Serum E2 and 20 alpha-dihydroprogesterone (20 alpha-OHP) in rats with 8 pups were significantly lower, whereas serum progesterone (P) was significantly increased compared to the values in dams nursing 0 or 2 pups. In mothers nursing 8 pups, the corpora lutea (CL) of lactation, formed at postpartum ovulation, produced in vitro significantly greater amounts of P but significantly lesser amount of E2 compared to the other groups. Serum luteinizing hormone (LH) was consistently lower in dams nursing 8 pups than in dams nursing 0 or 2 pups. There was, however, no significant difference in serum follicle-stimulating hormone (FSH) among the 3 types of postparturient rats. Throughout lactation serum values of FSH were within the range of diestrous levels during the estrous cycle. Serum levels of prolactin (Prl) in dams nursing 8 pups were strikingly higher compared to dams nursing 2 pups. The administration of small doses of human chorionic gonadotropin (hCG) or ovine LH twice daily from Days 2 to 5 to lactating rats nursing 8 pups induced the maturation of follicles capable of ovulating. These findings indicate that during the first half of lactation the strong suckling stimulus reduces serum LH directly or indirectly via high levels of serum Prl and P, which in turn inhibit follicular maturation. During the second half of lactation, the suckling stimulus wanes, Prl and P decline and serum LH recovers to basal cyclic values which are reflected in the initiation of follicular maturation.

Animals↗
PubMed1996

Relationship of fertility to patterns of ovarian follicular development and associated hormonal profiles in dairy cows and heifers. Cooperative Regional Research Project.

Ovarian follicular development, hormonal patterns, and fertility were compared for growing and persistent follicles in 98 lactating dairy cows and in 89 heifers. Pregnancy rates were greater in animals that ovulated the first-wave dominant follicle while it was growing (GF) vs persistent (PF; for cows 54.2 vs 14.0%, P < .001; for heifers 62.0 vs 35.9%, P < .05). Follicles were larger in cows than in heifers (P < .05). Preovulatory growth rate (mm/d) for PF in cows was parallel to that of GF in both groups; in heifers, PF grew more slowly. At estrus, PF were larger than GF in cows and overall (P < .001), but not in heifers. Estradiol in plasma was greater (P < .05 in animals with PF than in those with GF before estrus (for 6 d in heifers, 8 d in cows). During d -6 through -2, progesterone in plasma tended to be lower (P = .12) in cows with PF than in heifers with PF. Pulse frequency of LH in plasma increased on d 7 in animals with GF and more frequent LH pulses continued through d 13 and 14 in animals with PF. After AI, progesterone in plasma did not differ between GF and PF, in either cows or heifers. However, among cows with GF, progesterone was greater (P < .01) by d 6 to 7 after estrus in pregnant than in nonpregnant cows. In summary, fertility was lower in animals that ovulated a persistent rather than a growing follicle, especially in lactating cows. Lower fertility in animals with PF was associated with prolonged increases in concentrations of LH and estradiol in plasma before estrus and ovulation.

Animals↗
PubMed1988

Treatment with bovine follicular fluid suppresses follicular development in gonadotrophin-releasing hormone-treated anoestrous ewes.

The role of FSH in gonadotrophin-releasing hormone (GnRH)-induced follicular development in anoestrous ewes was investigated using injections of bovine follicular fluid (bFF) to reduce plasma FSH levels. Groups of five animals were treated for 12 h with GnRH (250 ng at 2-h intervals) alone, GnRH plus bFF or saline alone, or for 36 h with GnRH alone, GnRH plus bFF or bFF alone. The administration of bFF (1.5 ml s.c. at 8-h intervals) significantly (P less than 0.05) reduced mean plasma FSH levels, but with the exception of animals treated with bFF alone, had no effect on LH levels. Treatment with bFF alone for 36 h resulted in a significant (P less than 0.05) increase in LH concentrations. There was considerable variation in the number of follicles greater than or equal to 2 mm in diameter in the treatment groups. The mean diameter, oestradiol secretion and number of 'oestrogenic' follicles were significantly (P less than 0.01) reduced in ewes treated with GnRH plus bFF or bFF alone for 36 h compared with those treated with GnRH alone. Testosterone secretion by the follicles was not affected by treatment. These results confirm previous findings that treatment with bFF decreases circulating FSH levels in anoestrous ewes and, moreover, that concurrent administration of bFF and GnRH inhibits the follicular maturation that is induced by treatment with GnRH alone, suggesting that FSH as well as LH is required for follicular maturation in the ewe.

Anestrus↗
PubMed2005

Expression of plexin-B1 in the mouse ovary and its possible role in follicular development.

OBJECTIVE: To study the expression of plexin-B1 in the mouse ovary and its possible role in follicular development. DESIGN: Controlled laboratory study. SETTING: Research laboratory, Ha'Emek Medical Center. PATIENT(S): ICR female mice (n = 36) were studied. MAIN OUTCOME MEASURE(S): Plexin-B1 expression by immunohistochemistry, Western blot analysis, and reverse transcriptase-polymerase chain reaction. Microscopic morphometric and morphologic analysis for the evaluation of mouse follicular growth and E2, P, and T secretion from the developed follicles. RESULT(S): Plexin-B1 was expressed in the mouse ovary mostly in the granulosa cells. Plexin-B1 gene expression increased significantly by 126.8% +/- 38% in the pregnant mare serum gonadotropin-treated group and increased by 98.7% +/- 15.2 and 262.2% +/- 65.4% in the hCG-treated group 6 h and 24 h after injection, respectively (ANOVA; P < .05). Comparison of the maximum diameters of the control and study groups on day 9 of the culture period revealed a significant difference between the two groups (P < .001). In the control group, the mean maximum diameter was 191 +/- 2.6 microm compared with 136 +/- 5.13 microm in the presence of neutralizing antibodies against plexin-B1. Neutralizing antibody against plexin-B1 decreases E2 and P secretion. CONCLUSION(S): This study shows for the first time the expression of plexin-B1 in the mouse ovary. A possible role for plexin-B1 in follicular growth and steroidogenesis, most likely via the granulosa cells, is suggested.

Animals↗
PubMed1995

Effect of heat stress on follicular development during the estrous cycle in lactating dairy cattle.

In this study we examined, in two experiments, patterns of follicular development and dominance under conditions of heat stress. Estrous cycles were programmed to include two follicular waves (wave 1 and 2). On Day 1 of the estrous cycle (Day 0 = estrus), cows were assigned randomly to cooled (C; n = 6) or heat-stressed (H; n = 6) groups. In experiment 1, on Day 12 prostaglandin (PG) F2 alpha was injected and a controlled intravaginal drug release device (1.9 g progesterone) was inserted (this was removed on Day 17). In experiment 2, PGF 2 alpha was injected on Day 14. Ovarian structures were examined daily by ultrasonography, and blood samples were collected at each scanning. Cycle lengths were 20 and 17 days in experiments 1 and 2, respectively. Mean maximal body temperatures were higher (p < 0.01) in H (40.3 degrees C) than in C (38.8 degrees C) cows. In experiment 1, the rate of increase in number of large follicles (> or = 10 mm) was greater in H than in C cows (p < 0.01), resulting in 53% more large follicles in H cows during wave 1; this was associated with a lower (p < 0.05) number of medium-sized (6-9 mm) follicles between Days 7 and 10 of the cycle. Heat stress hastened (p < 0.02) the decrease in size of the first-wave dominant follicle and hastened (p < 0.01) the emergence of the second dominant (preovulatory) follicle by 2 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗