Expression of follicle-stimulating hormone and luteinizing hormone receptor messenger ribonucleic acids in bovine follicles during the first follicular wave

The effect of type of vaginal insert and dose of pLH on embryo production, following fixed-time AI in a progestin-based superstimulatory protocol in Nelore cattle

The objective was to analyze and report field data focusing on the effect of type of progesterone-releasing vaginal insert and dose of pLH on embryo production, following a superstimulatory protocol involving fixed-time artificial insemination (FTAI) in Nelore cattle (Bos taurus indicus). Donor heifers and cows (n = 68; 136 superstimulations over 2 years) received an intravaginal, progesterone-releasing insert (CIDR or DIB, with 1.9 or 1.0 g progesterone, respectively) and 3-4 mg of estradiol benzoate (EB) i.m. at random stages of the estrous cycle. Five days later (designated Day 0), cattle were superstimulated with a total of 120-200 mg of pFSH (Folltropin-V), given twice daily in decreasing doses from Days 0 to 3. All cattle received two luteolytic doses of PGF2alpha at 08:00 and 20:00 h on Day 2 and progesterone inserts were removed at 20:00 h on Day 3 (36 h after the first PGF2alpha injection). Ovulation was induced with pLH (Lutropin-V, 12.5 or 25 mg, i.m.) at 08:00 h on Day 4 with FTAI 12, 24 and in several cases, 36 h later. Embryos were recovered on Days 11 or 12, graded and transferred to synchronous recipients. Overall, the mean (+/-S.E.M.) number of total ova/embryos (13.3 +/- 0.8) and viable embryos (9.4 +/- 0.6) and pregnancy rate (43.5%; 528/1213) did not differ among groups, but embryo viability rate (overall, 70.8%) was higher in donors with a DIB (72.3%) than a CIDR (68.3%, P = 0.007). In conclusion, the administration of pLH 12 h after progesterone removal in a progestin-based superstimulatory protocol facilitated fixed-time AI in Nelore donors, with embryo production, embryo viability and pregnancy rates after embryo transfer, comparable to published results where estrus detection and AI was done. Results suggested a possible alternative, which would eliminate the need for estrus detection in donors.

Transcriptional regulation of the FSH receptor: new perspectives

The cell-surface receptor for the gonadotropin follicle-stimulating hormone (FSH) is expressed exclusively on Sertoli cells of the testis and granulosa cells of the ovary. FSH signal transduction through its receptor (Fshr) is critical for the timing and maintenance of normal gametogenesis in the mammalian gonad. In the 13 years since the gene encoding Fshr was first cloned, the mechanisms controlling its transcription have been extensively examined, but a clear understanding of what drives its unique cell-specificity remains elusive. Current knowledge of basal Fshr transcription highlights the role of an E-box in the proximal promoter which is bound by the basic helix-loop-helix transcription factors upstream stimulatory factor 1 (Usf1) and Usf2. Recent studies utilizing knockout mice and chromatin immunoprecipitation validated the importance of Usf to Fshr transcription and demonstrated a sexually dimorphic requirement for the Usf proteins to maintain normal Fshr expression. Studies have also shown that the promoter region itself is insufficient for appropriate Fshr expression in transgenic mice, indicating Fshr transcription depends on regulatory elements that lie outside of the promoter. Identification of such elements has been propelled by recent availability of genome sequence data, which facilitated studies using comparative genomics, DNase I hypersensitivity mapping, and transgenic analysis with large fragments of DNA. This review will focus on the current understanding of transcriptional regulatory processes that control expression of rat Fshr, including recent advances from our laboratory.

Expression of follicle stimulating hormone and luteinizing hormone receptors during follicular growth in the domestic cat ovary

In order to better understand the pituitary regulation of follicular growth in the domestic cat, follicle stimulating hormone (FSH) and luteinizing hormone (LH) receptors (R) were localized and quantified in relation to follicle diameter and atresia using in situ ligand binding on ovarian sections. Expression of FSHR was homogeneous and restricted to follicle granulosa cells from the early antral stage onwards, whereas expression of LHR was heterogeneous on theca cells of all follicles from the early antral stage onward, and homogeneous on granulosa cells of healthy follicles larger than 800 microm in diameter and in corpora lutea. LHR were also widely expressed as heterogeneous aggregates in the ovarian interstitial tissue. Atretic follicles exhibited significantly reduced levels of both FSHR and LHR on granulosa cells, compared with healthy follicles whatever the follicular diameter, whereas levels of LHR on theca cells were lower only for atretic follicles larger than 1,600 microm in diameter. In healthy follicles, levels of FSHR and LHR in all follicular compartments increased significantly with diameter. Although generally comparable to that observed in other mammals, the expression pattern of gonadotropin receptors in the cat ovary is characterized by an early acquisition of LHR on granulosa cells of growing follicles and islets of LH binding sites in the ovarian interstitial tissue.

Expression of LH receptor mRNA splice variants in bovine granulosa cells: changes with follicle size and regulation by FSH in vitro

In cattle, most evidence suggests that granulosa cells express LH receptors (LHR) after (or as) the follicle becomes dominant, however there is some suggestion that granulosa cells from smaller pre-dominant follicles may express several LHR mRNA splice variants. The objective of this study was to measure LHR expression in bovine follicles of defined size and steroidogenic ability, and in granulosa cells from small follicles (<6 mm diameter) undergoing differentiation in vitro. Semiquantitative RT-PCR demonstrated that LHR mRNA was undetectable in granulosa cells of follicles <7 mm diameter (nondominant follicles), and increased with follicle diameter in follicles >7 mm diameter. Splice variants with deletions of exon 10 and part of exon 11 were detected as previously described, and we detected a novel splice variant with a deletion of exon 3. Cultured granulosa cells contained LHR mRNA, but with significantly greater amounts of variants with deletions of exon 10 and/or exon 11 compared with cells from dominant follicles. FSH increased the abundance of some but not all LHR mRNA splice variants in cultured granulosa cells. The addition of LH to cultured cells did not increase progesterone secretion, despite the presence of LHR mRNA. Collectively, these data suggest that granulosa cells do not acquire functional LHR until follicle dominance occurs.

Luteinizing hormone and follicle-stimulating hormone receptors and their transcribed genes (mRNA) are present in the lower urinary tract of intact male and female dogs

In dogs, one of the side effects of neutering is the development of urinary incontinence. The relationship between neutering and urinary incontinence caused by acquired urethral sphincter mechanism incompetence (USMI) has been reported. Recently, GnRH analogue treatment that suppresses elevated plasma gonadotrophin concentrations post-spaying has been successfully used in incontinent bitches. These data and the fact that non-gonadal tissues may contain receptors for LH (LHR) and FSH (FSHR) suggest that there might be a functional relationship between gonadotrophins and the lower urinary tract in dogs. This study aimed to investigate the presence of LHR and FSHR in the lower urinary tract of intact male and female dogs. Four regions of the lower urinary tract, i.e. (i) body of the bladder, (ii) neck of the bladder, (iii) proximal urethra and (iv) distal urethra were collected from 10 healthy dogs (5 males and 5 anoestrous females). In situ hybridization and immunohistochemistry were performed to characterise the presence of receptor mRNA and receptor protein. Staining was rated semi-quantitatively, incorporating both the distribution and intensity of specific staining. The distribution of receptor expression in different tissue layers (epithelium, subepithelial stroma and muscle) in each region was statistically analyzed. Luteinizing hormone receptor and FSHR mRNA and protein were present in all four regions and in three tissue layers of males and females. Irrespective of region and layer, female dogs expressed significantly higher expression for LHR mRNA (P<0.001), LHR protein (P<0.05) and FSHR protein (P<0.001). The expression of LHR and FSHR mRNA and protein was not uniform and depended on region, tissue layer and gender. The expression of LHR mRNA was higher in the bladder, compared to the urethra (P<0.05). The FSHR mRNA significantly increased from the bladder to the urethra. Protein expression for LHR and FSHR was highest in the proximal urethra (P<0.05). The overall expression for LHR and FSHR at both mRNA and protein levels was highest in the epithelium, intermediate to low in the subepithelial stroma and muscle. A significant interaction between region and tissue layer showed that mRNA and protein expression for LHR and FSHR decreased from the bladder to the urethra in the epithelium and subepithelial stroma. In contrast, it gradually increased from the bladder to the urethra in the muscle. In conclusion, the present study showed that both mRNA and protein for LHR and FSHR were expressed in the canine lower urinary tract, and the expression levels varied between genders and among regions and tissue layers. The presence of these receptors suggests that gonadotrophins have a role in the physiology and/or pathology of the lower urinary tract function in the dog.

Optimizing Ovulation to First GnRH Improved Outcomes to Each Hormonal Injection of Ovsynch in Lactating Dairy Cows

Ovulatory response to the first GnRH of Ovsynch is the critical determinant for successful synchronization of ovulation in dairy cows. Our objective in this study was to develop a pre-Ovsynch treatment that increased the percentage of cows that ovulated in response to the first GnRH injection of Ovsynch. To accomplish our goal, we evaluated a hormonal strategy that consisted of PGF2alpha and GnRH before the first GnRH of Ovsynch. Lactating dairy cows (n = 137) were assigned to receive either no treatment before Ovsynch (control) or 25 mg of PGF2alpha (PreP) followed 2 d later by 100 microg of GnRH (PreG), administered 4 (G4G), 5 (G5G), or 6 (G6G) d before initiating the Ovsynch protocol. Transrectal ultrasonography was performed to assess follicular size and resulting ovulation, and blood samples were collected to measure circulating concentrations of progesterone and estradiol immediately before each hormonal injection. Cows were inseminated at a fixed time 16 h after final GnRH of Ovsynch. Pregnancy diagnosis was performed 35 d later by palpation per rectum of uterine contents. Proportion of cows that ovulated to first GnRH of Ovsynch was 56.0, 66.7, 84.6, and 53.8% for G4G, G5G, G6G, and controls, respectively, and was greater for G6G than for control cows. Luteolytic response to PGF2alpha of Ovsynch was greater in all treated than control cows (92.0, 91.7, 96.2, and 69.2% for G4G, G5G, G6G, and control, respectively). Synchronization rate to Ovsynch was greater (92 vs. 69%, respectively) in G6G than in control cows. In addition, cows that ovulated in response to first GnRH of Ovsynch had greater response to PGF2alpha of Ovsynch (92.7 vs. 77.1%, respectively) and greater synchronization rate to the overall protocol (87.9 vs. 62.9%, respectively) than those that did not ovulate. Concentrations of progesterone at PGF2alpha of Ovsynch, and estradiol and follicle size at final GnRH of Ovsynch, were identified as significant predictors of probability of pregnancy 35 d after artificial insemination. In summary, a PGF2alpha-and-GnRH based pre-Ovsynch strategy consisting of a 6-d interval between PreG and first GnRH of Ovsynch resulted in a greater ovulatory and luteolytic response to first GnRH and PGF2alpha of Ovsynch, respectively, compared with control cows. This, in turn, optimized synchronization rate to Ovsynch.

Secretion patterns of luteinising hormone, follicle-stimulating hormone and 17beta-oestradiol during oestrus and the mid-luteal phase of the oestrous cycle in mithun (Bos frontalis)

The present study reports the pulsatile secretion of gonadotrophins and 17beta-oestradiol (OE2) on the day of oestrus and at the mid-luteal phase of the oestrous cycle in mithun (Bos frontalis). The frequency of luteinising hormone (LH) and follicle-stimulating hormone (FSH) pulses was found to be greater (P < 0.05) on the day of oestrus than at the mid-luteal phase. In contrast, the amplitude of the LH and FSH pulses was greater (P < 0.01) at the mid-luteal phase than on the day of oestrus. A synchronised (P < 0.01) LH and FSH secretion pattern was found only at the mid-luteal phase. A pulsatile secretion pattern for OE2 in the peripheral circulation was evident for both phases of the oestrous cycle. The frequency of the OE2 pulses did not differ significantly in different phases of the oestrous cycle. In contrast, the amplitude of the OE2 pulses and the basal OE2 concentration were found to be greater (P < 0.01) at the mid-luteal phase than on the day of oestrus. A synchronised (P < 0.01) LH and OE2 secretion pattern was observed in both phases of the oestrous cycle. In contrast, a synchronised (P < 0.05) FSH and OE2 secretion pattern was found only on the day of oestrus. In conclusion, a different pattern of LH and FSH secretion was observed in both phases of the oestrous cycle, mainly on the day of oestrus, which indicates a differential regulatory mechanism of LH and FSH release. In addition, as in cattle, OE2 exerts a positive feedback on LH and FSH release on the day of oestrus and on LH release at the mid-luteal phase of the oestrous cycle in mithun. Also, as in cattle, the greater basal plasma OE2 concentration and increased amplitude of OE2 pulses exert a negative feedback on FSH release at the mid-luteal phase of the oestrous cycle.

Involvement of the bone morphogenetic protein/receptor system during follicle development in the bovine ovary: Hormonal regulation of the expression of bone morphogenetic protein 7 (BMP-7) and its receptors (ActRII and ALK-2)

Bone morphogenetic proteins (BMPs) are crucial factors in follicular growth and development. Among the BMP ligands, BMP-7 which use ActRII as their type II receptor, strongly bind to ALK-2 as their type I receptor. However, whether their receptors are expressed and the regulatory mechanisms controlling their expression during the process of bovine follicle development are still unknown. The aim of the present study was to clarify the involvement of the receptor system for BMP-7 in follicular selection by examining the effects of follicle-stimulating hormone (FSH) and estradiol (E2) on the regulation of ActRII and ALK-2 mRNA expression in bovine granulosa cells (GCs). To observe mRNA expression, follicles were obtained from heifers and GCs were classified into two groups: pre-selection follicles (PRF; follicles with an average diameter of 7 mm and low E2) and post-selection follicles (POF; follicles with an average diameter of 15 mm and high E2). The theca cell (TC) layer and GCs were harvested from aspirated follicles. For in vitro studies, GCs were obtained from bovine follicles of 4-7 mm diameter and cultured in Dulbecco's modified Eagle's/F12 (DMEM/F-12) medium with 10% fetal calf serum for 24h. The medium was then replaced with serum-free DMEM/F-12 supplemented with different doses of E2 (1, 10,100 ng/ml), FSH (1, 5, 10 ng/ml) or combinations of 1 ng/ml of E2 with different FSH doses (1, 5, 10 ng/ml). Total RNA was extracted from GCs and the mRNA expression of ActRII and ALK-2 was estimated by the quantitative PCR method using LightCycler. The expression of BMP-7 mRNA in TCs did not differ between the PRF and POF. ActRII and ALK-2 expression was detected in GCs from bovine antral follicles and was higher in the GCs of POF than in those of PRF, while the expression of the ActRII and ALK-2 genes in the TCs was not different between PRF and POF. Treatment of GCs with E2 (10 ng/ml) alone increased the expression of both ActRII and ALK-2 mRNAs, whereas FSH alone had no effect. However, ActRII and ALK-2 mRNA levels were up-regulated by the combination of E2 (1 ng/ml) and FSH (5 ng/ml). The results of the present study provide the first evidence that FSH and E2 regulate the expression of the ActRII and ALK-2 genes in bovine GCs. Thus, our data suggest that the BMP7/ActRII/ALK-2 system may be critically involved in the process of selection of bovine follicles.

Expression of fibroblast growth factor 1 (FGF1) and FGF7 in mature follicles during the periovulatory period after GnRH in the cow

The aim of this study was to evaluate the expression pattern of mRNA for fibroblast growth factor 1 (FGF1), FGF7, and their receptor variants (FGFR2IIIb) in time-defined follicle classes before LH surge, between LH surge and ovulation, and in the early corpus luteum (CL) in the cow. The ovaries were collected by transvaginal ovariectomy (n=5 cows/group), and the follicles (n=5, one follicle/cow) were classified into the following groups: before GnRH administration (before LH surge); 3-5 h after GnRH (during LH surge); 10 h after GnRH; 20 h after GnRH; 25 h after GnRH (periovulation), and early CL (Days 2-3). The mRNA expression was analyzed by quantitative real-time PCR (RotorGene 3000). The mRNA expression of FGF1 showed no significant differences in the follicle groups examined, but increased significantly at the early CL phase. A transient increase in FGF7 mRNA expression was observed 3-5 h after GnRH and again in the early CL phase. In contrast, the expression of FGFR2IIIb was constant throughout the period from the final growth of the follicle to early CL formation. The results of this study suggest that FGF1 and FGF7 may be involved differently in the process of follicle maturation and CL formation, which is strongly dependent on angiogenesis.

GATA-4 Gene Organization and Analysis of Its Promoter

The mouse GATA-4 gene is separated by six introns, and this gene organization is conserved in rodents and man. The transcriptional start site of the GATA-4 gene is essentially the same in rat heart, stomach and testis, and in cultured cells expressing GATA-4 such as TM3, TM4, I-10 and P19.CL6 cells. The 5'-upstream of the GATA-4 gene is also conserved in rodents and man. We examined its promoter activity by means of luciferase reporter gene assay using testis-derived TM3 and TM4 cells. The GC-boxes and E-box located in the several tens of base pairs upstream of the transcriptional start sites of the GATA-4 gene were found to be critical for its promoter activity in these cells, consistent with the mode of transcription characteristics of the TATA-less promoter. P19.CL6 cells differentiate into beating cardiomyocytes upon induction by DMSO, accompanied by stimulation of the transcription of heart-specific genes including GATA-4. Interestingly, they exhibit increased luciferase reporter gene activity upon induction by DMSO. Both proximal tandem GC-boxes and the E-box are also contributed to the reporter gene activity in P19.CL6 cells.

Remodeling of extracellular matrix at ovulation of the bovine ovarian follicle

Using immunohistochemistry and RNA analyses we examined the fate of components of a newly identified matrix that develops between granulosa cells (focimatrix, abbreviated from focal intraepithelial matrix) and of the follicular basal lamina in ovulating bovine ovarian follicles. Pre- and postovulatory follicles were generated by treatment with estradiol (Day 1), progesterone (Days 1-10), and prostaglandin analogue (Day 9) with either no further treatment (Group 1, n = 6) and or with 25 mg porcine LH (Day 11, Group 2, n = 8 or Day 10, Group 3, n = 8) and ovariectomy on Day 12 (12-14 hr post LH in Group 2, 38-40.5 hr in Group 3). In the time frame examined no loss of follicular basal lamina laminin chains beta2 and gamma1 or nidogen 1 was observed. In the follicular basal lamina collagen type IV alpha1 and perlecan were present prior to ovulation; after ovulation collagen type IV alpha1 was discontinuously distributed and perlecan was absent. Versican in the theca interna adjacent to the follicular basal lamina in preovulatory follicles was not observed post ovulation, however, the granulosa cells then showed strong cytoplasmic staining for versican. Expression of versican isoforms V0, V1, and V3 was detected at all stages. Focimatrix was observed in preovulatory follicles. It contained collagen type IV alpha1, laminins beta2 and gamma1, nidogen 1 and perlecan and underwent changes in composition similar to that of the follicular basal lamina. In conclusion focimatrix and the follicular basal lamina are degraded at ovulation. Individual components are lost at different times.

Regulation of apoptosis in the atresia of dominant bovine follicles of the first follicular wave following ovulation

During atresia of bovine follicles, granulosa cells are lost through the controlled form of cell death, apoptosis. The purpose of this study was to characterize the regulation of apoptotic death of granulosa cells in dominant bovine follicles during the first wave of follicular development. Dominant follicles were collected from Holstein heifers on days 4, 6 or 8 of the first follicular wave (n = 5/day). Regulation of apoptosis in granulosa cells was examined by annexin V and propidium iodide staining; measurement of relative levels of mRNA encoding Bcl-2, Bcl-xL and Bax; and activity of caspase-3, -8 and -9. Steady-state levels of mRNA encoding four oxidative stress-response proteins were determined. Compared with day 4, the incidence of apoptotic and nonviable granulosa cells tended to increase on day 6, and numbers of nonviable cells were higher on day 8. The ratios of relative levels of mRNA encoding Bcl-2 to Bax and Bcl-xL to Bax were higher on day 6 than days 4 and 8. Activity of caspases-3 and -9 in granulosa cells did not change among the 3 days, while caspase-8 activity decreased on day 8 compared with days 4 and 6. Amounts of GSHPx, MnSOD and Cu/ZnSOD mRNA in granulosa cells were higher on day 8 than day 6. In theca interna, amounts of Cu/ZnSOD mRNA decreased between days 4 and 6. From the decreased production of estradiol and increased numbers of apoptotic and nonviable granulosa cells, we conclude that atresia of the dominant follicle is initiated between days 4 and 6 of the first follicular wave. However, apoptosis of granulosa cells does not appear to be initiated by changes in expression of oxidative stress-response proteins.

Regulation of nuclear factor-kappaB (NF-kappaB) activity and apoptosis by estradiol in bovine granulosa cells

Although atresia of bovine follicles is associated with apoptosis of granulosa cells, the signals initiating this cell death have not been resolved. NF-kappaB has been implicated as an important regulator of genes controlling apoptosis, and previous studies indicate that estradiol may modulate NF-kappaB activation. We hypothesized that estradiol activates NF-kappaB, and thus, inhibits apoptosis in granulosa cells of dominant follicles. Dominant follicles were collected on Days 4, 6, and 8 of the first follicular wave following ovulation and assayed for NF-kappaB activity. Concentrations of estradiol in follicular fluid decreased on Day 6 compared to Day 4 of the wave. NF-kappaB activity in granulosa cells was lower on Day 8 compared to Days 4 and 6. In vitro, NF-kappaB activity and minimal incidence of apoptosis (<4%), as measured by Annexin V and TUNEL assays, were associated with production of estradiol. However, inhibition of NF-kappaB in vitro led to a suppression of apoptosis. These results indicate that follicular NF-kappaB activation is associated with estradiol production. However, whether NF-kappaB is playing a pro- or anti-apoptotic role in granulosa cells of the dominant bovine follicle remains to be elucidated.

Alterations in follicular IGFBP mRNA expression and follicular fluid IGFBP concentrations during the first follicle wave in beef heifers

The objective was to determine the pattern of IGFBP-2, -3 and -4 gene expression and follicular fluid concentrations of IGFBP-2, -3, -4 and -5 during emergence, selection and dominance of the first follicle wave of the estrous cycle in cattle and during exogenous steroid treatment. Heifers (n = 35) were ovariectomized at 36 (n = 7), 66 (n = 8), 84 (n = 12) and 108 (n = 8) h after the onset of estrus. Heifers in the 84 h ovariectomy group were sub-divided to receive either no treatment (n = 6) or were treated with a progesterone-releasing intravaginal device (n = 6, PRID) and 0.75 mg estradiol benzoate i.m. at the approximate time of ovulation, 30 h post estrus until ovariectomy. Within heifers the four largest follicles recovered following ovariectomy were ranked on size (F1, F2, F3 and F4). At 36 h IGFBP gene expression and follicular fluid IGFBP concentrations were similar in all follicles (F1-F4). Mean diameter of the F1 follicle increased (P < 0.05) between 36 and 84 h with no difference between 84 and 108 h. The F1 follicle had the highest (P < 0.05) concentration of estradiol compared with the F2, F3 and F4 at 84 and 108 h. There was no granulosa cell IGFBP-2 mRNA in F1 follicles at 84 or 108 h. Intrafolliclar IGFBP-2 concentrations were lower (P < 0.05) in the F1 compared with F3 and F4 follicles at 108 h. There was no difference in theca cell IGFBP-4 mRNA expression at 108h, but amounts of follicular fluid IGFBP-4 were lower (P < 0.05) in F1 follicles compared with F3 and F4 follicles at 108 h. IGFBP-3 mRNA was localized in the theca layer of all follicles examined with no difference in expression or follicular fluid concentrations during emergence, selection and dominance of the first follicle wave. IGFBP-5 concentrations were higher (P < 0.05) in follicular fluid of F3 follicles at 108 h compared with the F3 at 36 h. In conclusion follicular dominance was associated with low or decreased follicular fluid concentrations of IGFBP-4 and -5, increased estradiol and differential regulation of IGFBP production.

Formation of mammalian oocytes and their growth, differentiation and maturation within ovarian follicles

The limited knowledge on the regulation of oocyte formation, the different steps of folliculogenesis and the required conditions for oocytes to undergo proper growth, differentiation and maturation are major causes of the failure in obtaining viable offspring from in vitro cultured early oocytes from domestic animals and humans. This review highlights the factors that at present are known to be involved in the formation of mammalian oocytes and their growth, differentiation and maturation within ovarian follicles.

Molecular biology of the 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase gene family

The 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) isoenzymes are responsible for the oxidation and isomerization of Delta(5)-3beta-hydroxysteroid precursors into Delta(4)-ketosteroids, thus catalyzing an essential step in the formation of all classes of active steroid hormones. In humans, expression of the type I isoenzyme accounts for the 3beta-HSD activity found in placenta and peripheral tissues, whereas the type II 3beta-HSD isoenzyme is predominantly expressed in the adrenal gland, ovary, and testis, and its deficiency is responsible for a rare form of congenital adrenal hyperplasia. Phylogeny analyses of the 3beta-HSD gene family strongly suggest that the need for different 3beta-HSD genes occurred very late in mammals, with subsequent evolution in a similar manner in other lineages. Therefore, to a large extent, the 3beta-HSD gene family should have evolved to facilitate differential patterns of tissue- and cell-specific expression and regulation involving multiple signal transduction pathways, which are activated by several growth factors, steroids, and cytokines. Recent studies indicate that HSD3B2 gene regulation involves the orphan nuclear receptors steroidogenic factor-1 and dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Other findings suggest a potential regulatory role for STAT5 and STAT6 in transcriptional activation of HSD3B2 promoter. It was shown that epidermal growth factor (EGF) requires intact STAT5; on the other hand IL-4 induces HSD3B1 gene expression, along with IL-13, through STAT 6 activation. However, evidence suggests that multiple signal transduction pathways are involved in IL-4 mediated HSD3B1 gene expression. Indeed, a better understanding of the transcriptional factors responsible for the fine control of 3beta-HSD gene expression may provide insight into mechanisms involved in the functional cooperation between STATs and nuclear receptors as well as their potential interaction with other signaling transduction pathways such as GATA proteins. Finally, the elucidation of the molecular basis of 3beta-HSD deficiency has highlighted the fact that mutations in the HSD3B2 gene can result in a wide spectrum of molecular repercussions, which are associated with the different phenotypic manifestations of classical 3beta-HSD deficiency and also provide valuable information concerning the structure-function relationships of the 3beta-HSD superfamily. Furthermore, several recent studies using type I and type II purified enzymes have elegantly further characterized structure-function relationships responsible for kinetic differences and coenzyme specificity.

Reproductive Hormones and Follicular Growth During Development of One or Multiple Dominant Follicles in Cattle1

The mechanisms regulating ovulation rate under natural conditions are not yet defined, particularly for monovular species. In the present study, we evaluated ovarian structures (every 12 h by ultrasonography) and circulating hormones (every 6 h) to determine the differences between cows that developed one (single dominant; n = 16), two (double dominant; n = 8), or three (triple dominant; n = 3) dominant follicles. The four largest follicles were tracked retrospectively, and the data were normalized to the time of expected follicular deviation (F1 >/= 8.5 mm; hour 0). Follicular dynamics from emergence to deviation were similar, whereas after deviation, expected subordinate follicles continued to grow at a rate similar to the dominant follicle. Triple dominants had greater FSH than double dominants (hour -24 to hour -12) and single dominants (hour -42 to hour -6), and double dominants had greater FSH than single dominants (hour -24 to hour -12). Increased circulating estradiol but lower inhibin were observed in cows that developed multiple follicles. In addition, double dominants had greater LH than single dominants (hour -42 to hour -24 and hour -6 to hour 0) and lower progesterone than single dominants (hour -12 and hour -6). Luteal volume was similar between groups, but milk production was greater for codominant than for single-dominant cows. Thus, selection of multiple dominant follicles during high milk production is related to a transient increase in circulating FSH and LH during the 24 h before follicular selection, producing continued postdeviation growth of follicles that ordinarily would have regressed. Increased FSH and LH probably result from decreased circulating inhibin and progesterone in cows that develop codominant follicles.

Gene expression for LH receptor, 17α-hydroxylase and StAR in the theca interna of preantral and early antral follicles in the bovine ovary

The onset of gene expression for three proteins that play pivotal roles in theca interna function, namely the LH receptor (LH-R), cytochrome P450 17α-hydroxylase (17αOH) and the steroidogenic acute regulatory protein (StAR), was determined. Ovaries were obtained on day 9 of the oestrus cycle from mature synchronized dairy cows (n= 5) and gene expression in preantral and antral follicles up to 4 mm in diameter was evaluated byin situhybridization. LH-R and 17αOH mRNAs were observed first, in the theca interna of large preantral follicles (type 4), concurrent with its morphological differentiation. StAR mRNA appeared later during follicular growth, in follicles >1 mm in diameter (type 6). LH-R and 17αOH mRNAs were found exclusively in the thecal cells, whereas StAR mRNA appeared in thecal cells, granulosa cells of late atretic follicles and oocytes. In early atresia, thecal cells expressed all three mRNAs, and their expression decreased gradually as atresia progressed. Atresia in granulosa cells was characterized by massive apoptosis of periantral, but not peribasal cells, that differentiated into luteal-like cells expressing StAR.

In summary, our study suggests that in spite of the presence of 17αOH, a key enzyme in steroidogenesis, the ability to produce steroids by bovine follicles smaller than 1 mm in diameter must be very limited due to the absence of StAR protein. During the early stages of atresia, thecal cells remain morphologically and functionally healthy, and continue to express all three studied mRNAs.

Effect of presynchronization using prostaglandin F2α and a milk-ejection test on pregnancy rate after the timed artificial insemination protocol, Ovsynch

The objective of this research was to determine if PGF2alpha-induced milk letdown (ML) is an accurate indicator of luteolysis, allowing cows to be synchronized to begin the Ovsynch protocol (GnRH-7d-PGF2alpha-2d-GnRH-24h-AI) at the most beneficial time of the estrous cycle (days 5-9), and determine if this would improve pregnancy rate (PR). Lactating Holstein cows between 55 and 70 days in milk were used to evaluate the ML test and PR after the Ovsynch protocol, when initiated on the basis of the test result (PROSYNCH). PROSYNCH cows (n = 60) had one teat cannulated to test for ML and were treated with 500 microg cloprostenol, PGF2alpha analogue (PG). Cows with ML were started on Ovsynch 10 days later, and those without started 3 days later. Cows in the control group (OVSYNCH, n = 64) were injected with physiological saline and observed for ML. This group was started on Ovsynch 10 days after saline treatment. Milk samples were collected thrice weekly to determine progesterone concentrations. ML indicated luteolysis with a sensitivity of 98% and a specificity of 60%. The positive and negative predictive values were 83 and 92%, respectively. Pregnancy rates were 48% for PROSYNCH and 52% for OVSYNCH (P = 0.72). When data from both groups were combined, PR was greater in cows that started the Ovsynch protocol in stage 2 of the estrous cycle (days 5-9, 67%) than all other stages (stage 1: days 1-4, 35%; stage 3: days 10-16, 45%; stage 4: days 17-21, 42%; P < 0.01). The proportion of animals with ovulation after GnRH#1, luteolysis after PGF2alpha, and ovulation after GnRH#2 were all greater in the PROSYNCH group (77% versus 55%, P < 0.02; 83% versus 66%, P < 0.03; 97% versus 84%, P < 0.03, respectively). Therefore, the ML test indicated luteolysis with sufficient precision to time the initiation of the Ovsynch protocol between days 5 and 9 of the cycle, however, this did not alter PR compared to starting the protocol randomly throughout the cycle. Initiating the Ovsynch protocol between days 5 and 9 of the cycle increased PR, and improved the efficacy of each injection.

Immunolocalization of von Willebrand Factor and Vascular Endothelial Growth Factor during Follicular Atresia in the Swamp Buffalo Ovary

The aim of this study was to investigate the distribution pattern of von Willebrand factor (vWF) and vascular endothelial growth factor (VEGF) in the healthy antral and atretic follicles of Philippine swamp buffaloes (SB) in comparison with Holstein-Friesian cows (HF). Paraffin sections of healthy follicles and atretic follicles at various stages were immunostained with vWF antibody and VEGF antibody. The density of vWF-positive capillary vessels in the theca interna significantly increased as atresia progressed in SB, whereas the density significantly decreased in late atretic follicles compared with advanced ones in HF. On the other hand, the area of vWF-positive capillary vessels in the theca interna significantly increased as atresia progressed in both SB and HF. Immunoreactions of VEGF in the granulosa cells (in all follicle types) were observed in both SB and HF. In the granulosa layer, a reduction in the VEGF immunoreaction was noted as follicles progressed from healthy to advanced atretic follicles in both animals. Granulosa cells (in both SB and HF) showed a higher immunopositive staining than theca cells. In the theca interna, VEGF immunostaining diminished as follicles progressed to the late atretic follicles in both animals. These results indicate that during atresia, changes of vWF expression are the opposite of VEGF expression in SB. Both vWF and VEGF are suggested to be associated with follicular atresia in SB.

Expression of Gap Junction Protein Connexin 43 during Follicular Atresia in the Ovary of Swamp Buffaloes

The present study was performed to detect the presence of gap junction protein connexin 43 (Cx43) and describe the changes in its expression during ovarian follicular atresia in the swamp buffalo in comparison with cattle. Ovaries of Philippine swamp buffaloes (Bubalus bubalis; SB) and Holstein-Friesian cows (Bos taurus; HF) were collected from slaughterhouses, fixed in 10% formalin in PBS and embedded in paraffin. Sections of healthy follicles and at various follicular stages of atresia were immunostained with anti-Cx43 antibody. Cx43 appeared as punctate staining between granulosa cells (healthy to advanced atretic follicles), indicating assembled gap junctions, but was absent in the theca interna. In SB as well as in HF, granulosa cells showed a dense, moderate, and sparse immunoreactivity to Cx43 in healthy, early atretic, and advanced atretic follicles, respectively. Cumulus cells (in the advanced atretic follicle) surrounding oocytes and adjacent granulosa layers retain the Cx43 protein, although there was only a sparse expression of Cx43 observed in the granulosa layers distant from oocytes in the same follicles. The results indicate that gap junction protein Cx43 decreases in association with atresia and supports the concept that a loss of gap junctional communication plays a coordinating role in the process of atresia. Furthermore, the schema of Cx43 immunoreactivity in SB granulosa cells is similar to that of HF.

Developmental Pattern of Small Antral Follicles in the Bovine Ovary1

The study was designed to characterize the developmental pattern of 1- to 3-mm follicles and to determine the stage at which the future dominant follicle first attains a size advantage among its cohorts. In experiment 1, heifers (n = 18) were examined every 24 h by transrectal ultrasonography for one interovulatory interval (IOI). In experiment 2, cows (n = 9) were examined every 6 h from 5 to 13 days after ovulation to monitor precisely the diameter changes of individual follicles >/=1 mm during emergence of wave 2. Results revealed a change over days (P < 0.05) in the number of 1- to 3-mm follicles, with a maximum (P < 0.05) 1 or 2 days before wave emergence (conventionally defined as the time when the dominant follicle is first detected at 4 mm), followed 3-4 days later by a maximum (P < 0.05) in the number of >/=4-mm follicles. The profiles of small (1-3 mm) and large (>/=4-mm) follicles were inversely proportional (r = -0.79; P = 0.01). The profile of the number of 1- to 3-mm follicles during wave emergence was similar (P = 0.63) between waves in two-wave IOI, but differed (P < 0.01) among waves in three-wave IOI as a result of a greater number of follicles in the ovulatory wave (P < 0.04). As well, the number of follicles in the ovulatory wave tended to be greater (P < 0.06) in three-wave IOI than in two-wave IOI. The future dominant follicle was first identified at a diameter of 1 mm and emerged 6-12 h earlier than the first subordinate follicle (P < 0.01). After detection of the dominant follicle at 1 mm (0 h), its diameter differed from that of the first and second subordinate follicles at 24 h (P = 0.04) and 12 h (P = 0.01), when the dominant follicle was 2.4 +/- 0.17 mm and 1.7 +/- 0.14 mm, respectively. The growth rate of the dominant follicle differed from that of the first and second subordinate follicles at 120 h (P = 0.03) and 108 h (P = 0.02), when the dominant follicle was 9.5 +/- 0.30 mm and 8.8 +/- 0.49 mm, respectively. Emergence of the future dominant (r = 0.71), first (r = 0.73), and second (r = 0.76) subordinate follicles was temporally associated (P < 0.01) with a rise in circulating concentrations of FSH. Transient, nocturnal elevations in plasma FSH concentration were followed within 6 h by an increase in the growth rate of 1- to 3-mm follicles. We conclude that 1) 1- to 3-mm follicles develop in a wave-like manner in association with surges in plasma concentrations of FSH, 2) 1- to 3-mm follicles are exquisitely responsive to transient elevations in FSH, and 3) selection of the dominant follicle is manifest earlier than previously documented and is characterized by a hierarchical progression over a period encompassing the entire FSH surge (5 days).

Expression of components of the insulin-like growth factor system and gonadotropin receptors in bovine cumulus-oocyte complexes during oocyte maturation

IGF system expression has been largely explored in the bovine follicular wall whereas it remains poorly studied in the COC. Using semi-quantitative RT-PCR and Western blot analysis, we have investigated spatial and temporal expression of IGF-1, IGFR-1, IGFBP-2, IGFBP-4, as well as gonadotropin receptors in bovine COC during oocyte maturation. In addition, we have compared changes in the IGF system and FSHR expression during in vitro maturation in TCM199 alone or in the presence of 10 ng/ml of EGF. The transcripts for IGFR-1 and IGFBP-2 were detected in cumulus and germinal cells whereas IGF-1, IGFBP-4 and FSHR mRNA were restricted to cumulus cells. Topography of the IGF system and gonadotropin receptor expression within COC were unaffected by the maturation step. In contrast, levels of IGFBP-2 and FSHR expression decreased (P < 0.05) in matured COC. Under defined culture conditions, IGFBP-2 and FSHR mRNA expression remained at a high level in TCM199 alone and were significantly reduced (P < 0.05) in the presence of 10 ng/ml EGF after a 24 h period of in vitro maturation. In conclusion, our results demonstrate a cell-specific pattern of IGF system member gene expression within bovine COC suggesting interaction between the somatic and germinal compartments. In addition, synchronized changes in the pattern of COC IGFBP-2 and FSHR expression during oocyte maturation suggest possible synergistic actions between IGF-1 and FSH.

Androgen receptor mRNA expression in the bovine ovary

Previous studies have shown that androgen receptor (AR) is expressed in granulosa cells of healthy, growing ovarian follicles in rats and primates. However, AR expression in the bovine ovary has not been examined. Therefore, a 346-base pair segment of the bovine AR was cloned and sequenced. Using a ribonuclease protection assay, AR expression was detected in total RNA from bovine ovarian cortex. Expression (absence or presence) of AR mRNA was detected by in situ hybridization in bovine ovarian cortex. Follicles (n = 32) were classified as follows: type 1 (1 layer of flattened granulosa cells), type 2 (1-1.5 layers of cuboidal granulosa cells), type 3 (2-3 layers of granulosa cells), type 4 (4-6 layers of cuboidal granulosa cells and formation of thecal layer), and type 5 (>6 layers of cuboidal granulosa cells, defined theca layer, and antrum formation). Frequency of AR mRNA expression increased (P < 0.001) as follicles entered the growing pool. Expression of AR mRNA was absent in type 1 follicles (n = 8), but present in the granulosa cells of 41% of type 2 follicles (n = 12). In types 3-5 follicles, AR mRNA expression was present in granulosa cells of 100% of follicles examined (n = 4, 4, and 4, respectively) and was greater than type 1 follicles (P = 0.002). These data provide evidence of AR mRNA expression in bovine follicles and suggest that AR mRNA increases during early follicle development.

Gonadotropin requirements for dominant follicle selection in GnRH agonist-treated cows

A study was conducted to examine the effects of gonadotropins on ovarian follicular development and differentiation in GnRH agonist (GnRHa)-treated cattle. Holstein cows were allotted into two pre-treatment groups: controls (n = 5) and GnRHa-treated (n = 9). Ovaries were removed from control cows on day 5 following a synchronized estrus. Treatment with GnRHa resulted in follicular arrest at <5 mm. Following follicular arrest, GnRHa-treated cows received a constant infusion of FSH for 96 h (GnRHa/FSH), with a randomly selected subset receiving hourly pulses of LH in addition to FSH during the last 48 h of infusion (GnRHa/FSH + LH). At the end of infusion, ovaries were removed, follicles were counted and measured, and follicular fluid samples were collected from large follicles (>10 mm). Differences in expression of mRNA for LH receptor, FSH receptor, cytochrome P450 side-chain cleavage, 3β-hydroxysteroid dehydrogenase, cytochrome P450 17α-hydroxylase (P450c17) and cytochrome P450 aromatase were determined in large follicles using in situ hybridization. The number of large follicles did not differ between GnRHa/FSH-treated and GnRHa/FSH + LH-treated cows (P = 0.64), but was greater than control animals (P ≤ 0.004). Follicular fluid concentrations of estradiol-17β and androstenedione were highest in GnRHa/FSH + LH-treated cows (P ≤ 0.04), intermediate in control cows, and lowest in GnRHa/FSH-treated cows. Hybridization intensity of P450c17 was greater in GnRHa/FSH + LH-treated versus control or GnRHa/FSH-treated cows (P ≤ 0.03). These results indicate that while FSH can support bovine follicular growth >10 mm, LH increases androgen production and expression of P450c17.

Fertility following fixed-time AI in CIDR-treated beef heifers given GnRH or estradiol cypionate and fed diets supplemented with flax seed or sunflower seed

The objectives were to determine pregnancy rates following fixed-time AI (FTAI) in heifers: (1). given GnRH or estradiol cypionate (ECP) to synchronize follicular wave emergence and ovulation in a CIDR-based protocol; and (2). fed diets supplemented with flax or sunflower seeds. At two locations, Angus and crossbred Angus heifers (n=983) were examined ultrasonically to confirm reproductive maturity and randomly allocated to six synchronization groups in a 2 x 3 factorial design. On Day 0 (start of synchronization treatments), heifers received a CIDR and either 100 microg GnRH i.m. (n=492) or 1mg ECP plus 50 mg progesterone i.m. (n=491); in these groups, CIDR removal and PGF treatment were done concurrently on Days 7 and 8.5, respectively. Heifers were re-randomized to receive 0.5 mg ECP i.m. at CIDR removal or 24 h later (with FTAI 58-60 h after CIDR removal in both groups), or 100 microg GnRH i.m. concurrent with FTAI (52-54 h after CIDR removal). The heifers were fed a barley silage-based diet for 50 days (from Day -25 to 25) supplemented with 1kg/heifer per day of flax seed (n=321), sunflower seed (n=324), or no oilseed (n=338). Pregnancy rate to FTAI (overall, 56.2%) was not affected by treatment at CIDR insertion (P = 0.96) but was higher (P < 0.05) in heifers given ECP 24h after CIDR removal (216/330, 65.4%) than in those given either ECP at CIDR removal (168/322, 52.1%) or GnRH at AI (169/331, 51.1%). Overall, there was no effect of diet on pregnancy rates (P = 0.46). In summary, pregnancy rate to FTAI was not significantly affected by treatment at CIDR insertion to synchronize follicular wave emergence, but 0.5mg ECP 24h after CIDR removal (to synchronize ovulation) resulted in the highest pregnancy rate.

Expression of messenger ribonucleic acid encoding for steroidogenic acute regulatory protein and enzymes, and luteinizing hormone receptor during the spring transitional season in equine follicles

The period of spring transition, from the anovulatory to the ovulatory season, is characterized in many mares by cyclical growth and regression of large dominant follicles. These follicles produce only low concentrations of estradiol and it is thought that acquisition of steroidogenic competence by large follicles during spring transition is prerequisite in stimulating LH prior to first ovulation. In situ hybridization was used to localize and quantify expression of factors that play a key role in follicular steroidogenesis: StAR, P450scc (CYP11A1), P450c17 (CYP17), P450arom (CYP19), and LH receptor (LHr). One ovary was obtained from mares on the day after detection of an actively growing 30 mm transitional anovulatory follicle (defined as the transitional follicle), and the remaining ovary was removed at the third estrus of the breeding season on the day after the preovulatory follicle reached 30 mm in diameter (defined as the preovulatory follicle). Messenger RNAs encoding StAR, CYP11A1, and CYP17 were detected only in theca cells and CYP19 mRNA was confined to the granulosa layer. There was significantly lower expression of mRNAs for the steroidogenic enzymes, StAR (P<0.001) and LHr (P<0.05) in transitional follicles than in preovulatory follicles. In conclusion, large equine follicles during spring transition have low levels of mRNA encoding steroidogenic enzymes, StAR and LHr which will contribute to the steroidogenic incompetence of dominant follicles during spring transition and their subsequent regression.

Gene transcription and regulation of oocyte maturation

The developmental potential of an embryo is dependent on the developmental potential of the oocyte from which it originates. The process of oocyte maturation is critical for the efficient application of biotechnologies such as in vitro embryo production and mammalian cloning. However, the overall efficiency of in vitro maturation remains low because oocytes matured in vitro have a lower developmental competence than oocytes matured in vivo. Furthermore, oocytes that have been exposed to gonadotropins have greater developmental competence than oocytes matured in the absence of gonadotropins. By understanding the molecular mechanisms underlying gonadotropin-induced maturation, improvement in oocyte maturation technologies may be expected as procedures to manipulate specific factors involved in signalling for resumption of meiosis are identified. The present review will focus on transcriptional mechanisms underlying the maturation of mammalian oocytes in vitro, as well as on the acquisition of oocyte developmental competence. In addition, a working model for the transcriptional control of mammalian oocyte maturation is proposed.

Xenografting of Bovine Secondary Follicles into Ovariectomized Female Severe Combined Immunodeficient Mice

Xenografting of ovarian tissue into immunodeficient mice has been used as a model to study the dynamics of follicular development and provides an alternative method for the production of mature oocytes. In a previous experiment, we demonstrated that xenografted bovine secondary follicles developed to the antral stage in severe combined immunodeficient (SCID) mice. In the present study, we examined the development of bovine secondary follicles (140-190 microm in diameter) grafted into ovariectomized mice in comparison with intact female mice as a control. At 4 weeks after grafting, several antral follicles ranging from 350 to 550 microm (457.6 +/- 50.8 microm) in diameter were found in the control mice, while a single large (larger than 2.5 mm) antral follicle and other small follicles were observed in every ovariectomized mouse. At 6 weeks after grafting, the mean diameter of morphologically normal follicles had further increased in the control group (591.8 +/- 132.0 microm). In ovariectomized mice, however, the mean diameter of follicles decreased (4 weeks: 864.2 +/- 988.2 microm; 6 weeks: 496.5 +/- 137.6 microm), since the single large antral follicle observed at 4 weeks had degenerated by 6 weeks. In control mice, more than 70% of follicles were morphologically normal and formed an antrum, and most of the follicles contained morphologically normal oocytes which grew to 122.5 +/- 2.2 microm. In ovariectomized mice, morphologically normal oocytes also grew larger than before grafting, but their survival rate was significantly lower than that in control mice. These results suggest that ovariectomy of host mice alters the developmental pattern of xenografted bovine secondary follicles to accelerate a single follicle to develop in the graft.

Cholesterol side-chain cleavage cytochrome P450 and 3beta-hydroxysteroid dehydrogenase expression and the concentrations of steroid hormones in the follicular fluids of different phenotypes of healthy and atretic bovine ovarian follicles

Bovine ovarian antral follicles exhibit either one or the other of two patterns of granulosa cell death in atresia. Death can commence either from the antrum and progress toward the basal lamina (antral atresia) or the converse (basal atresia). In basal atresia, the remaining live antrally situated cells appeared to continue maturing. Beyond that, little is known about these distinct patterns of atresia. Healthy (nonatretic) follicles also exhibit either one or the other of two patterns of granulosa cell shape, follicular basal lamina ultrastructure or location of younger cells within the membrana granulosa. To examine these different phenotypes, the expression of the steroidogenic enzymes cholesterol side-chain cleavage cytochrome P450 (SCC) and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in granulosa cells and concentrations of steroid hormones in follicular fluid were measured in individual histologically classified bovine antral follicles. Healthy follicles first expressed SCC and 3beta-HSD in granulosa cells only when the follicles reached an approximate threshold of 10 mm in diameter. The pattern of expression in antral atretic follicles was the same as healthy follicles. Basal atretic follicles were all <5 mm. In these, the surviving antral granulosa cells expressed SCC and 3beta-HSD. In examining follicles of 3-5 mm, basal atretic follicles were found to have substantially elevated progesterone (P < 0.001) and decreased androstenedione and testosterone compared to healthy and antral atretic follicles. Estradiol was highest in the large healthy follicles, lower in the small healthy follicles, lower still in the antral atretic follicles, and lowest in the basal atretic follicles. Our findings have two major implications. First, the traditional method of identifying atretic follicles by measurement of steroid hormone concentrations may be less valid with small bovine follicles. Second, features of the two forms of follicular atresia are so different as to imply different mechanisms of initiation and regulation.

Follicular oocyte growth and acquisition of developmental competence

At birth the ovaries of mammalian females contain a finite store of primordial follicle oocytes. Each oocyte and its surrounding follicle cells share a communication system, the gap junction network, which facilitates the transfer of signals as well as nutrients in to and out off the oocyte and between follicle cells. The connexin family of proteins form the building blocks of this communication network, their expression is specific to the differentiated state of the granulose cell and the stage of folliculogenesis. Factors such as the c-kit receptor and its ligand, IGF-I, IGF-I receptors and the IGF binding proteins, members of the transforming growth factor beta (TGFbeta) family, in particular, some of the bone morphogenetic proteins, play prominent roles in oogenesis, primordial follicle activation and subsequent follicle/oocyte development culminating in oocyte ovulation. The oocyte undergoes a progressive series of morphological modifications as it grows and proceeds through the different stages of development. These structural rearrangements facilitate the increasing energy and nucleic acid synthesis requirements of the developing oocyte and are a prerequisite to the oocytes achievement of meiotic and embryo developmental competence. Several factors determine the ultimate competence of the oocyte, these have been investigated and attempts made to mimic these conditions in vitro. The complexity of the orchestration of the events that control oocyte growth and ultimate acquisition of developmental competence is under continuous investigation. The present review describes some of the findings to date.

Endocrine regulation of ovarian antral follicle development in cattle

Antral follicle growth in cattle occurs in two distinct phases; the first 'slow' growth phase spans the time from antrum acquisition to a size of approximately 3 mm detectable by transrectal ultrasound, and the second 'fast' phase is gondadotrophin-dependent and includes cohort growth, dominant follicle (DF) selection, and DF growth. This review summarises current concepts of the relative roles FSH and LH, ovarian and metabolic hormones play mainly in the second phase of antral follicle growth in animals of different reproductive and nutritional states. It is proposed that differential FSH response may enable one cohort follicle to become selected, and that follicular secretions, particularly inhibin, suppress FSH and thus are responsible for DF selection and dominance. Acute dependence of the DF on LH pulses will determine DF lifespan, and the LH pulse profile can be influenced by metabolic hormones such as leptin, providing one possible link for nutritional state and reproduction. Direct ovarian effects of acute and chronic changes in growth hormone, insulin and insulin-like growth factor (IGF)-I have been described on cohort follicles, DF oestrogen activity and on DF growth. Influences of metabolic hormones on early antral follicles undergoing their first 'slow' growth phase are less well described, yet metabolic hormones appear to enhance growth into the cohort available for FSH-induced emergence, and may influence subsequent developmental competence of oocytes.

Distribution of cytochrome P450-side chain cleavage in the theca interna layers of bovine small antral and cystic follicles

Cystic follicle is anovulatory follicular structure that is caused by an endocrine imbalance. The activity of cytochrome P450-side chain cleavage (P450scc) is essential for the initiation of steroidogenesis in the follicle. The present study was designed to compare the frequency of cells containing P450scc between healthy and atretic small antral follicles, and among several types (I, II and III, classified based on the presence of granulosa layer) of cystic follicles. Paraffin sections of healthy (2-5 mm in diameter), atretic (2-5 mm) and cystic follicles (>25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine P450scc. The P450scc-positive cells were counted in four different regions of the follicles from the apical to the basal side. In small antral follicles and cystic follicles, P450scc-positive cells were localized in the theca interna layers but not granulosa layers. The P450scc-positive cell populations decreased in the late atretic follicles compared with the early and advanced atretic follicles at all the regions of follicle. Type III cystic follicles showed significantly lower frequencies of P450scc-positive cells than those in the types I and II cystic follicles. These results suggest that in both small and cystic follicles in cows, total loss of granulosa cells may be associated with the reduction of frequency of P450scc-positive cells in theca interna layer.

Human oocytes reversibly arrested in prophase I by phosphodiesterase type 3 inhibitor in vitro

This study addresses the role of cAMP hydrolytic isoenzyme phosphodiesterase type 3 (PDE 3) modulation on human oocyte maturation in vitro. Presence of phosphodiesterase type 3 A (PDE 3A) mRNA was confirmed in human germinal vesicle-stage (GV) oocytes. Making use of a selective PDE 3 inhibitor, Org 9935 (10 microM), oocytes retrieved from immature follicles were arrested in prophase I with a high efficiency for up to 72 h. Cumulus oocyte complexes (COCs) were retrieved in the follicular phase of the cycle before or after exposure to endogenous LH or hCG administration in vivo and randomly distributed into maturation medium with or without the PDE 3 inhibitor. Previous exposure of small follicles to LH activity in vivo had no influence on the arresting capacity of the PDE 3 inhibitor. Reversal from pharmacological arrest leads to a progression through meiosis in a normal time frame with formation of a well-aligned metaphase plate. Ultrastructure analysis of COC derived from follicles between 8 and 12 mm showed that the induced extension of prophase I arrest in vitro resulted in cytoplasm changes but not in apparent nuclear changes during culture.

Temporal relationships between FSH receptor, type 1 insulin-like growth factor receptor, and aromatase expression during FSH-induced differentiation of bovine granulosa cells maintained in serum-free culture

A serum-free culture system has been developed in ruminants that allows gonadotrophin-responsive induction of oestradiol (E2) production by non-differentiated granulosa cells (GC) from small antral follicles. Critical determinants are dose of FSH and insulin-like growth factor (IGF), and the plating density of the GC. Over the first 16 h of culture when cells remained as a dispersed monolayer, expression declined in FSH receptors (FSHr) (P <0.001), IGF type 1 receptor (IGF-1r) (P <0.08) and p450 arom (CYP19, P <0.001). Characteristic GC clusters formed from 16 h and further enlarged between 24 and 48 h, accompanied by marked increases in FSHr (P <0.01), IGF-1r (P <0.05), and p450 arom (P <0.01) expression, and preceded induction and subsequent peak E2 production, at 96 and 144 h, respectively (P <0.01). In conclusion, isolation and dispersion of GC appears to induce reversion to an immature state resulting in loss of receptor expression. Re-establishment of cell-cell communications in the presence of FSH and IGF results in receptor up-regulation and induction of cellular differentiation.

Reproductive adaptations to a large-brained fetus open a vulnerability to anovulation similar to polycystic ovary syndrome

During the ovarian or menstrual cycle, prior to ovulation, many female primates exhibit a relatively prolonged follicular phase and terminate the postovulatory luteal phase with menstrual bleeding. The prolonged follicular phase is a trait that distinguishes primate from nonprimate species. It enables extended estrogen-induced proliferation and growth of the uterine endometrium prior to progesterone-induced maturation during the luteal phase to accommodate a potential pregnancy with a rapidly invading placenta. Progressive development of both an extended duration of estrogen-induced, preimplantation endometrial proliferation and a rapidly invading placenta across the Primate order may well have been necessary to accommodate differentiation and growth of an increasingly large fetal brain. Prolongation of the follicular phase in primates has also led to the isolation of the final stages of follicle selection (growth deviation of the dominant follicle from its contemporaries) solely within the follicular phase and thus outside the protection of luteal phase progesterone inhibition of pituitary luteinizing hormone (LH) secretion. Such primate reproductive characteristics put the latter stages of ovarian follicle selection at risk of exposure to excessive pituitary secretion of LH. Excessive secretion of LH during follicle selection could result not only in impaired follicle development, excessive ovarian androgen secretion, and ovulation failure, but also in excessive estrogenic stimulation of the uterine endometrium without intervening menstrual periods. Such reproductive abnormalities are all found in a single, prevalent infertility syndrome afflicting women in their reproductive years: polycystic ovary syndrome (PCOS). We propose that successful female reproductive adaptations to accommodate the growth demands of large-brained primate fetuses have facilitated a particular vulnerability of higher primates to hypergonadotropic disruption of ovulatory function, as found in PCOS.

Matrix metalloproteinases-2 and -9 activities in bovine follicular fluid of different-sized follicles: relationship to intra-follicular inhibin and steroid concentrations

Matrix metalloproteinases (MMPs) play very important roles in extracellular matrix (ECM) remodeling during ovarian follicular development, ovulation and atresia. The aim of the present study was to determine the content of gelatinases in follicular fluid in various sized bovine follicles. Bovine ovaries were collected from local slaughterhouse and follicular fluid from follicles of 2 to over 25 mm in diameter was collected. Gelatinase activity within the follicular fluid was analyzed by gelatin zymography. The concentration of inhibin in the follicular fluid was also measured by immunoblot analysis. The proMMP-2 and alpha-subunit (alphaN) inhibin was detected in all follicles regardless of their size. The abundance of proMMP-2 varied with follicular size, while alphaN inhibin increased significantly (P<0.01) in follicles of 10-14 and 15-20 mm in size. There was a positive and negative correlation between estradiol (E(2)) and progesterone (P(4)) concentrations with abundance of proMMP-2, respectively. Follicles of diameter over 25 mm had greater proMMP-9 activity than other follicles. These same follicles had significantly (P<0.01) lower inhibin levels than follicles of 10-14 and 15-20 mm in size. In conclusion, these results suggest a significant role of these proteases in growth and development of bovine follicle, particularly proMMP-2 and active MMP-2 activities in the follicular fluid could serve as markers of follicular health while abundance of proMMP-9 may possibly denote a follicular cyst.

lmmunohistochemical Localization of 3.BETA.-Hydroxysteroid Dehydrogenase in the Granulosa and Theca Interna Layers of Bovine Cystic Follicles

The aim of the present study was to determine whether the alteration of population of cells containing 3beta-hydroxysteroid dehydrogenase (3beta-HSD) is responsible for the formation of cystic follicles. Paraffin sections of healthy (2 to 5 mm in diameter), atretic (2 to 5 mm) and cystic follicles (more than 25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine 3beta-HSD. The 3beta-HSD-positive cells were counted in 4 different regions of the follicles from the apical to the basal side. The frequencies of 3beta-HSD-positive granulosa cells in cystic follicles were significantly higher than those in the healthy follicles (P<0.05), although the number of 3beta-HSD-positive granulosa cells in the cystic follicle were fewer than half the cells (30 to 40%) and was much smaller than that in preovulatory follicles (Conley et al., 1995). The frequencies of 3beta-HSD-positive cells were higher in the granulosa layer and lower in the theca interna layer of the cystic follicles than the atretic follicles. These results suggest that the differentiation of granulosa cells to express 3beta-HSD might be insufficient in cystic follicles and accordingly they fail to ovulate. The differences of frequencies of 3beta-HSD-positive cells in the granulosa and theca interna layers between cystic and atretic follicles may be one of the reasons why regression is delayed in cystic follicles.

Interactions between the Oocyte and Surrounding Somatic Cells in Follicular Development: Lessons from In Vitro Culture

Mammalian oogenesis occurs concomitantly with folliculogenesis in a coordinated manner in the ovaries. In vitro growth (IVG) culture systems of the oocytes have been developed as a new technology for utilizing incompetent oocytes in the ovary as a source of mature oocytes as well as for studying oogenesis, folliculogenesis, and oocyte-somatic cell interactions. The results of IVG experiments have suggested that direct association of oocytes and surrounding granulosa cells supports oocyte viability and growth through the gap junctions, which are efficient conduits for low molecular weight substances. It has been revealed that granulosa cells metabolize some molecules which are in turn transported into the oocytes. IVG systems have also provided evidence that FSH promotes the development of follicles at secondary or later stages by its stimulation of proliferation and differentiation of granulosa cells, and perhaps by its anti-apoptotic effects. In addition, interactions between granulosa cell-derived KIT ligands and oocyte KIT receptors have been suggested as initiating oocyte growth and follicular development. Furthermore, recent findings suggest there are growth factors derived from oocytes such as GDF-9 and BMP-15. With such factors, oocytes participate in follicular development by regulating the differentiation of surrounding somatic cells. These bidirectional communications between oocytes and somatic cells are important for oocyte growth and follicular development. IVG systems should provide further information regarding oogenesis and folliculogenesis in the ovary.

Differential requirement for pulsatile LH during the follicular phase and exposure to the preovulatory LH surge for oocyte fertilization and embryo development in cattle

The requirement for pulsatile LH and the LH surge for the acquisition of oocyte fertilizing potential and embryo developmental competency was examined in Zebu heifers. Follicular growth was superstimulated using the GnRH agonist-LH protocol in which pulsatile LH and the preovulatory LH surge are blocked. In experiment 1, heifers were assigned on Day 7 of the estrous cycle to receive: group 1A (n = 5), 1.5 mg norgestomet (NOR) implant; group 1B (n = 5), GnRH agonist implant. Follicular growth was superstimulated with 2x daily injections of FSH from Day 10 (a.m.) to Day 13 (p.m.), with PGF2alpha injection on Day 12 (a.m.). Heifers were ovariectomized on Day 15 (a.m.) and oocytes were placed immediately into fertilization, without 24 h maturation. Respective cleavage and blastocyst development rates were: group 1A, 0/64 oocytes (0%) and 0/64 (0%); group 1B, 34/70 oocytes (48.6%) and 2/70 (2.9%). In experiment 2, heifers were assigned on Day 7 of the estrous cycle to receive: group 2A (n = 10), 1.5 mg NOR implant; group 2B (n = 10), GnRH agonist implant; group 2C (n = 10), GnRH agonist implant. Follicular growth was superstimulated as in experiment 1 above. Heifers in groups 2A and 2B received an injection of 25 mg LH on Day 14 (p.m.) and all heifers were ovariectomized on Day 15 (a.m.); oocytes were placed immediately into fertilization without 24 h maturation. Cleavage rates were similar for heifers in group 2A (84/175 oocytes, 48.0%), group 2B (61/112 oocytes, 54.5%) and group 2C (69/163, 42.3%). Blastocyst development rates were similar for heifers in group 2A (22/175 oocytes, 12.6%) and group 2B (25/112 oocytes, 22.3%) and lower (P < 0.05) for heifers in group 2C (9/163 oocytes, 5.5%). Oocytes obtained from heifers treated with GnRH agonist, without injection of exogenous LH, underwent cleavage indicating that neither pulsatile LH nor the preovulatory LH surge are obligatory for nuclear maturation in cattle oocytes. Exposure to a surge-like increase in plasma LH increased embryo developmental competency indicating that the preovulatory LH surge promotes cytoplasmic maturation. The findings have important implications for controlling the in vivo maturation of oocytes before in vitro procedures including nuclear transfer.

Fertility of lactating dairy cows treated with Ovsynch after presynchronization injections of PGF2 alpha and GnRH

Synchronization of ovulation (Ovsynch) using GnRH and PGF2 alpha allows control of follicle growth, corpus luteum regression, and ovulation, but resulting pregnancy rates vary. This study examined whether presynchronization to allow initiation of Ovsynch during diestrus would improve pregnancy rates at timed artificial insemination (AI). Lactating dairy cows (n = 427), 69 to 75 d postpartum, were randomly assigned to two groups by parity. Control cows received Ovsynch (GnRH, d 0; PGF2 alpha, d 7; GnRH, d 9; timed AI 16 h after second GnRH). Treated cows received presynchronization injections of PGF2 alpha and GnRH, 10 and 7 d, respectively, before starting Ovsynch. Pregnancy diagnoses were performed 36 d after AI. Progesterone (P4) concentrations from a subset of cows (n = 84) were determined in serum samples collected on d 0, 3, and 7 of Ovsynch. Presynchronization increased the percentages of cows with > or = 1 ng/ml serum P4 compared with control cows at first injection of GnRH (d 0; 93 vs. 56%) and on d 3 (90.7 vs. 51.2%) during Ovsynch. On day of PGF2 alpha, d 7 during Ovsynch, percentages of cows with > or = 1 ng/ml serum P4 were similar (95.3%, treated vs. 82.9%, control) but more treated cows had > or = 2 ng/ml serum P4 (95.3 vs. 63.4%). However, pregnancy to timed AI was similar between treated (41.5%) and control cows (38.3%). Cows with above-average milk production had greater pregnancy rate (45.8 vs. 33.8%) compared with lower producing cows. Although presynchrony increased the proportion of cows with luteal function at onset of Ovsynch, pregnancy rate to timed AI was not improved. Cows with above-average milk production had greater fertility at timed AI than herdmates with lower milk production.

Follicle wave growth in cattle

Ovarian follicle growth in cattle culminates in the selection of a single dominant follicle which attains the ability for final maturation and ovulation once or twice during the luteal phase and at the end of the oestrous cycle, as well as during other reproductive states. This review will describe in detail the first follicle wave of the cycle leading to selection of the first wave dominant follicle, indicating the specific gonadotrophin dependencies of cohort and dominant follicles, and relating follicle fate to steroidogenesis. As a differential gonadotrophin response of growing antral follicles during the follies-stimulating hormone (FSH) decline may determine which follicle becomes selected, first wave follicles are also characterized in relation to intrafollicular growth factors, which may modify the gonadotrophin response, such as inhibins and members of the insulin-like growth factor (IGF) family. Subsequently, the follicular control of the transient FSH rise and decline so crucial to dominant follicle selection will be discussed. It is concluded that successful hormonal manipulation of follicle wave growth and dominant follicle selection will depend on our detailed understanding of the gonadotrophin requirements of differentiating wave follicles.

Activin A, estradiol, and free insulin-like growth factor I in follicular fluid preceding the experimental assumption of follicle dominance in cattle

In cattle, the two largest follicles of a wave (F1, F2) begin to deviate into a dominant follicle and a subordinate follicle when F1 is a mean of 8.5 mm in diameter. After the beginning of deviation, F1 and F2 are diameter-defined dominant and subordinate follicles. Changes associated with the conversion of F2 into a future dominant follicle were studied by ablating F1 at the expected beginning of deviation (F1, 8.5 mm; Hour 0) and assessing the follicular-fluid factors in F2. Follicles were designated F1C and F2C in controls and F2A in F1-ablated heifers. Follicular-fluid collections were made at Hours 0, 4, 8, or 12 (n = 7 heifers per hour; fluid from F1C, F2C, and F2A; experiment 1) or at Hours 4, 6, 8, 10, or 12 (n = 9 heifers per hour; fluid from F2A; experiment 2). Postablation concentrations of circulating FSH increased (P < 0.05) between Hours 2 and 6. Diameter of F2A increased (P < 0.05) after Hour 8 in both experiments so that the diameter of F2A at Hours 10 or 12 was not different (P > 0.1) from the diameter of F1 at Hour 0. A transient elevation (P < 0.05) in follicular-fluid activin A occurred in F2A at Hour 8 in both experiments. Concentrations of estradiol (P < 0.05) and insulin-like growth factor I (IGF-I; P < 0.1) decreased in F2C by Hour 8. In F2A, the concentrations of both factors began to increase (P < 0.05) after Hours 4 or 8 so that there was no difference (P > 0.1) between F1C and F2A at Hour 12. Concentrations of IGF-I and IGF binding protein 2 (IGFBP-2) in F2A changed in opposite directions at the same hours. No differences between follicles were found for concentrations of progesterone, androstenedione, inhibin A, and inhibin B. The order of events in the conversion of a future subordinate follicle to a future dominant follicle was an increase in systemic FSH, a transient elevation in follicular-fluid activin A, and a simultaneous increase in follicular-fluid estradiol and restoration of an apparent growth-compatible balance of free IGF-I and IGFBP-2.

The final stages of dominant follicle selection in cattle

The final stages of ovarian follicle growth in cattle are typically characterized by the ultrasound-detectable emergence of a cohort of small (3-5mm in diameter) antral follicles, followed by a selection process during which the number of follicles continuing to grow decreases. Finally, only one follicle (the dominant follicle; DF) shows an enhanced growth rate and estradiol synthesis when it attains 8.5mm compared to its closest competitor (the largest subordinate follicle; SF). Cohort emergence is caused by a transient FSH rise, while DF selection occurs during declining FSH indicating differential FSH dependence of DF and SF. In order to elucidate the mechanisms underlying DF survival or SF atresia, this review aims to (i) describe follicular changes in the local production and regulation of members of the inhibin family of proteins and the insulin-like growth factor (IGF) system in relation to FSH deprivation leading to DF selection, and (ii) develop a model for DF selection outlining the putative involvement of inhibins, activin and follistatin on the one hand, and bioavailable IGFs regulated by IGF binding proteins (IGFBPs) and IGFBP proteases on the other hand. It is concluded, that the first indications of differential FSH dependence are seen within 33h of the FSH peak, and high amounts of precursor forms of inhibin and free activin, and low amounts of the lower molecular weight (MW) IGFBPs are related to follicle survival in terms of enhanced growth and estradiol synthesis, and suppression of granulosa cell apoptosis. In addition, maintenance of low amounts of intrafollicular IGFBP4 may constitute an important mechanism in the future DF to attain FSH independence.

Follicle-stimulating hormone receptors in oocytes?

The regulatory mechanisms of oocyte maturation remain poorly understood. Although gonadotropins play a major role in these processes, they have generally been considered to act on somatic supportive cells, but not directly on germ cells. We have raised high affinity monoclonal antibodies against LH and FSH receptors. When using the latter to study receptor distribution in human and pig ovaries we have observed the presence of FSH (but not LH) receptors in the oocytes. FSH receptors appeared in the oocytes of primary follicles during follicular development and persisted up to the preovulatory stage. In denuded human preovulatory oocytes, FSH receptor mRNA was detected at a concentration per cell exceeding by about 20-fold that present in granulosa cells. Saturable binding of [(125)I]FSH to the membrane of oocytes was demonstrated by autoradiography. When incubated with FSH, denuded oocytes responded by a mobilization of Ca(2+). These observations concur to demonstrate the presence of functional FSH receptors in oocytes and raise the possibility of direct control of oocyte development by FSH.

Embryo recovery and pregnancy rates after the delay of ovulation and fixed time insemination in superstimulated beef cows

The aim of this study was to evaluate the effect of delaying ovulation subsequent to superstimulation of follicular growth in beef cows (Bos indicus) on embryo recovery rates and the capacity of embryos to establish pregnancies. Ovulation was delayed by three treatments using either progesterone (CIDR-B) or a GnRH agonist (deslorelin). Multiparous Nelore cows (n = 24) received three of four superstimulation treatments in an incomplete block design (n = 18 per group). Cows in Groups CTRL, P48 and P60 were treated with a CIDR-B device plus estradiol benzoate (EB, 4 mg, i.m.) on Day-5, while cows in Group D60 were implanted with deslorelin on Day-7. Cows were superstimulated with FSH (Folltropin-V, 200 mg), from Day 0 to 3, using twice daily injections in decreasing amounts. All cows were treated with a luteolytic dose of prostaglandin on Day 2 (08:00 h). CIDR-B devices were removed as follows: Group CTRL, Day 2 (20:00 h); Group P48, Day 4 (08:00 h); Group P60, Day 4 (20:00 h). Cows in Group CTRL were inseminated at 10, 20 and 30 h after first detected estrus. Ovulation was induced for cows in Group P48 (Day 4, 08:00 h) and Groups P60 and D60 (Day 4, 20:00 h) by injection of LH (Lutropin, 25 mg, i.m.), and these cows were inseminated 10 and 20 h after treatment with LH. Embryos were recovered on Days 11 or 12, graded and transferred to synchronized recipients. Pregnancies were determined by ultrasonography around Day 100. Data were analyzed by mixed procedure, Kruskal-Wallis and Chi-square tests. The number of ova/embryos, transferable embryos (mean +/- SEM) and pregnancy rates (%) were as follows, respectively: Group CTRL (10.8+/-1.8, 6.1+/-1.3, 51.5), P48 (12.6+/-1.9, 7.1+/-1.0, 52.3), P60 (10.5+/-1.6, 5.7+/-1.3, 40.0) and D60 (10.3+/-1.7, 5.0+/-1.2, 50.0). There were no significant differences among the groups (P > 0.05). It was concluded that fixed time AI in association with induced ovulation did not influence embryo recovery. Furthermore, pregnancy rates in embryos recovered from cows with delayed ovulation were similar to those in embryos obtained from cows treated with a conventional superstimulation protocol.

Comparison of two Ovsynch protocols (GnRH versus LH) for fixed timed insemination in buffalo (Bubalus bubalis)

We evaluated the efficiency of replacing GnRH with LH in the ovulation synchronization protocol in buffaloes. Buffaloes received GnRH on Day 0, (Buserelin; Conceptal, 20 microg), PGF2alpha (Luprostiol; Prosolvin, 15 mg) on Day 7 and GnRH (Buserelin; Conceptal, 10 microg; Group 1) or porcine LH (LH; Lutropin-V, 12.5 mg; Group 2) on Day 9. In Experiment 1, we studied the follicular dynamics of 30 buffaloes (Group 1, n = 15 and Group 2, n = 15). We performed ultrasonography every 12 h from Days 0 to 2, then on Day 7 and then every 6 h from the time of GnRH or LH treatment (Day 9) until the time of ovulation. All females not ovulating by 48 h after the second GnRH or LH injection were considered as nonresponders. In Experiment 2, we evaluated 305 buffaloes (Group 1, n = 154; Group 2, n = 151), using the same two treatments studied in Experiment 1. We also recorded and evaluated aspects like parity, lactational status, the presence of mucus, and uterine tone at the time of artificial insemination (Al). In Experiment 1, ovulation rate after the first GnRH was 86.6% (26/30). Ovulation rates were 93.3% (14/15; Group 1) after the second dose of GnRH and 93.3% (14/15) after LH (Group 2). Ovulation occurred 36.4+/-10.4 h after the first GnRH. The interval for treatment to ovulation was 26.5+/-9.6 h for buffaloes treated with GnRH (Group 1) and 24.4+/-7.9 h for buffaloes treated with LH (Group 2); the time of ovulation did not differ statistically between the two groups (GnRH versus LH; P > 0.05). In Experiment 2, conception rates of the animals AI in the field were 56.5% (Group 1) and 64.2% (Group 2), respectively (P = 0.08). The response to the treatment with LH was not different to the treatment with GnRH; however, multiparous buffaloes had higher conception rates than the primiparous buffaloes in both groups (P > 0.05). Buffaloes with mucus at the time of AI in Group 2 had higher conception rates than the buffaloes that had mucus in Group 1 (P < 0.05). Uterine tone and lactational status did not influence conception rates (P > 0.05). In summary, the results showed that both treatments resulted in synchronization of ovulation and acceptable conception rates. Therefore, the exogenous injection of LH can substitute the GnRH injections in the Ovsynch program in buffaloes.

In vitro culture and in vitro maturation of mouse preantral follicles with recombinant gonadotropins

OBJECTIVE

To develop an effective method for in vitro maturation of preantral follicles isolated from mice ovarian tissue.

DESIGN

Isolated preantral follicles were randomly allocated to designed experimental groups for study.

SETTING

University-based research lab.

PATIENT(S)

Healthy, normal mice.

INTERVENTION(S)

Superovulation with pregnant mare serum gonadotropin and hCG.

MAIN OUTCOME MEASURE(S)

Morphological changes and E(2) production were assessed.

RESULT(S)

To obtain competent oocytes, preantral follicles must be cultured with medium containing insulin and recombinant gonadotropins (i.e., recombinant FSH and recombinant LH), with a change of medium daily. A high initial recombinant LH or recombinant FSH facilitates E(2) secretion, enhances granulosa cell outgrowth, and has earlier antral formation. However, prolonged culture in high-recombinant LH or recombinant FSH triggers early differentiation and luteinization of granulosa cells, which results in low metaphase II oocyte and blastocyst formation.

CONCLUSION(S)

We have developed a culture system that allows the successful maturation of preantral follicles in vitro. The matured follicles are a physiologically functional unit that not only secrete E(2) but also generate competent oocytes. In a special condition, 90% of the cultured follicles survived, 53.5% of them produced MII oocytes, and 50% of the derived MII oocytes were fertilized and reached the blastocyst stage after culture in vitro.

Physiological classification of anovulatory conditions in cattle

Evaluation of follicular growth patterns by ultrasound combined with measurement of circulating reproductive hormones has allowed designation of three functionally critical follicular sizes during the final stages of follicular growth: emergence (-4 mm), deviation (-9 mm), and ovulation (variable from 10 to 20 mm). Classification of anovulatory conditions on the basis of these three critical points is logical and provides for rational diagnosis and treatment of the underlying physiological condition. In extreme undernutrition, there is growth of follicles to emergence but not to deviation; however, the underlying pathophysiology is not defined because of relatively few scientific investigations of this condition. Anovulatory conditions with growth of follicles to deviation but not to ovulatory size have been extensively studied. Undernutrition and/or suckling can cause this anovulatory condition. It is characterized by a greater negative feedback effect of estradiol on GnRH/LH pulses than found in normally cycling cows. Another anovulatory condition that is common in high producing lactaing dairy cows is characterized by growth of follicles to larger than ovulatory size, such as is observed in cows with follicular cysts. This condition is characterized by an insensitivity of the hypothalamus to the positive feedback effects of estradiol. Thus, these last two common anovulatory conditions appear to be primarily due to changes in the responsiveness of the hypothalamus to estradiol. Treatments that increase circulating progesterone concentrations can help in the treatment of these two conditions by potentially altering GnRH/LH pulses and allowing the final stages of follicular growth or resetting the hypothalamic responsiveness to the positive feedback effects of estradiol.