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P. Smith
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W-S. O
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N. L. Hudson
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L. Shaw
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D. A. Heath
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L. Condell
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D. J. Phillips
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K. P. McNatty
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The aim of this study was to determine whether the FecB gene influenced some aspects of fetal development in sheep. Carrier (BB/B+) and non-carrier (++) female fetuses were recovered at specific times of gestation, namely, days 40, 55, 75, 90, 95 and 135. The results showed that the FecB gene influenced litter size, body weight and ovarian development during fetal life. The mean litter sizes were larger (P < 0.05) and body weights were lighter (P < 0.05) at most gestational ages in BB/B+ than in ++ fetuses. Morphometric studies of the ovary showed that the development of the BB/B+ ovaries was retarded: the ++ genotype had more oogonia at day 40 (P < 0.01), more germ cells entering meiosis at day 55, more primordial follicles developing at days 75, 90 and 95 (P < 0.05), a greater loss of germ cells by atresia at day 90 (P < 0.01) and more growing follicles (P < 0.01) and more antral follicles (P < 0.05) at day 135. Differences between the BB/B+ and ++ genotypes in the plasma concentrations of immunoreactive (i) inhibin, i-FSH, bioactive (b)-FSH or (i)-LH were not apparent at any age except for i-LH at day 75 (BB/B+ > ++; P < 0.05). Likewise no differences were noted in the contents of ovarian or adrenal oestradiol or i-inhibin except for i-inhibin in the adrenal at day 75 (++ > BB/B+, P < 0.01). No differences between the genotypes were noted in the i-inhibin contents of the mesonephros at day 40. In mid- to late but not early gestation (i.e. days 40 and 55) significant correlations (i.e. P < 0.05) were noted between litter size and body weight at days 75, 90 and 135, and between litter size and ovary weight, ovary volume, adrenal weight and pituitary weight at day 135. To eliminate the effect of litter size, equal numbers of BB/B+ and ++ embryos were transferred to respective recipient ewes, and fetuses were recovered at the equivalent of days 40 and 90 of gestation. The results showed that the genotypic difference in fetal body weight at day 40 (++ > BB, P < 0.001) and in number of oogonia at day 90 (++ > BB/B+, P < 0.05) were independent of litter size. We hypothesize that many of the differences between the Booroola genotypes in ovarian follicular development and pituitary function in neonatal and adult life may be a consequence of differences in the timing or rate of body weight or organ development in fetal life.

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D B B P Paris Department of Zoology, University of Melbourne, Victoria 3010, Australia and Royal Zoological Society of South Australia, c/o School of Earth and Environmental Science, University of Adelaide, Frome Road, Adelaide, South Australia 5005, Australia

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D A Taggart Department of Zoology, University of Melbourne, Victoria 3010, Australia and Royal Zoological Society of South Australia, c/o School of Earth and Environmental Science, University of Adelaide, Frome Road, Adelaide, South Australia 5005, Australia

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G Shaw Department of Zoology, University of Melbourne, Victoria 3010, Australia and Royal Zoological Society of South Australia, c/o School of Earth and Environmental Science, University of Adelaide, Frome Road, Adelaide, South Australia 5005, Australia

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P D Temple-Smith Department of Zoology, University of Melbourne, Victoria 3010, Australia and Royal Zoological Society of South Australia, c/o School of Earth and Environmental Science, University of Adelaide, Frome Road, Adelaide, South Australia 5005, Australia

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M B Renfree Department of Zoology, University of Melbourne, Victoria 3010, Australia and Royal Zoological Society of South Australia, c/o School of Earth and Environmental Science, University of Adelaide, Frome Road, Adelaide, South Australia 5005, Australia

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Changes in semen quality and morphology of the male reproductive tract were studied throughout the year in the highly promiscuous tammar wallaby. Body size, semen quality and gross morphology of the reproductive organs were assessed in adult males each month from January to November. The mean weight of males was similar in most periods sampled, but males were slightly heavier in the minor (P < 0.05) than the non-breeding season. Since body weight was correlated with weights of the testes, epididymides and accessory sex glands, organ weights were adjusted for body weight in subsequent analyses. In the major breeding season (late January/early February), when most females go through a brief, highly synchronized oestrus, the testes, prostate, Cowper’s glands, crus penis and urethral bulb were heaviest, volume and coagulation of ejaculates were greatest, and sperm motility had increased. Semen samples collected by electroejaculation at this time contained low numbers of spermatozoa, possibly as a result of dilution and entrapment by the seminal coagulum or depletion of epididymal stores during intense multiple mating activity. In the non-breeding season (late May–July), when mating does not normally occur in the wild, there was a significant decrease in the relative weight of nearly all male reproductive organs and a decline in most semen parameters. In the minor breeding season (September–November), when pubertal females undergo their first oestrus and mating, the weights of testes, epididymides and most accessory sex glands had significantly increased similar to those of males in the major breeding season. The total number and motility of ejaculated spermatozoa were highest during this period, but the volume and coagulation of ejaculates and weight of the prostate had only increased to levels that were intermediate between the major and non-breeding seasons. Ejaculate volume was strongly correlated with prostate weight, and % motile spermatozoa was strongly correlated with epididymis weight. Semen quality thus varied seasonally with changes in androgen-dependent reproductive organs in the male tammar wallaby and appeared to be influenced by the seasonal timing of oestrus in females. Semen quality may also improve in response to an increase in the number of available oestrous females.

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D. J. Tisdall
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A. E. Fidler
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P. Smith
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L. D. Quirke
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V. C. Stent
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D. A. Heath
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K. P. McNatty
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The aim of this study was to investigate stem cell factor and c-kit gene expression and protein localization in the mesonephros and ovary of sheep fetuses at different days of gestation, using RNA in situ hybridization and immunohistochemical procedures. At days 24 and 26 of gestation, stem cell factor mRNA and protein were present in cells throughout the developing gonad and mesonephros. From day 28 to day 40 of gestation, stem cell factor mRNA and protein became increasingly localized to the cortical region of the ovary, where most germ cells were present as actively proliferating oogonia. From day 40 to day 90 of gestation, stem cell factor mRNA and protein localization were confined mainly to the ovarian cortex. Moreover, within the cortical region, stem cell factor mRNA was low or absent where follicles were first forming and highest in the outer ovarian cortex, where germ cells were undergoing mitosis or the early stages of meiosis. In contrast, stem cell factor protein was present in newly forming follicles, as well as in mitotic and meiotic germ cells, which is consistent with the presence of both membrane-bound and soluble forms of this ligand. However, by day 90 of gestation, both stem cell factor mRNA and protein were observed in the granulosa cells of most (> 90%) primordial follicles. C-kit mRNA and protein were observed from day 24 of gestation in both germ cells and somatic cells but, with increasing gestational age, preferentially in germ cells (for example, pre-meiotic germ cells and both isolated oocytes and follicle-enclosed oocytes). C-kit protein, but not mRNA, was also observed in germ cells that were undergoing meiosis. The results indicate that the cells containing stem cell factor mRNA within the ovary up to day 90 of gestation originated from the gonadal blastema and from cells that migrated from the mesonephros before day 28 of gestation. Since stem cell factor mRNA was absent in both mesonephric cells migrating after day 28 of gestation and in regions where follicles were first forming, it is suggested that these later migrating mesonephric cells are the progenitors of the granulosa cells in the first forming follicles. In conclusion, during follicle formation, c-kit mRNA is localized to germ cells whereas c-kit, together with stem cell factor protein, is localized to both germ cells and somatic cells, consistent with the hypothesis that the presence of this receptor–ligand pair is essential to prevent apoptosis.

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D Corcoran School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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T Fair School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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S Park School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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D Rizos School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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O V Patel School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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G W Smith School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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P M Coussens School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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J J Ireland School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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M P Boland School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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A C O Evans School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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P Lonergan School of Agriculture, Food Science and Veterinary Medicine and Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland and Department of Animal Science and Center for Animal Functional Genomics Michigan State University, East Lansing, Michigan 48824, USA

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In vivo-derived bovine embryos are of higher quality than those derived in vitro. Many of the differences in quality can be related to culture environment-induced changes in mRNA abundance. The aim of this study was to identify a range of mRNA transcripts that are differentially expressed between bovine blastocysts derived from in vitro versus in vivo culture. Microarray (BOTL5) comparison between in vivo- and in vitro-cultured bovine blastocysts identified 384 genes and expressed sequence tags (ESTs) that were differentially expressed; 85% of these were down-regulated in in vitro cultured blastocysts, showing a much reduced overall level of mRNA expression in in vitro- compared with in vivo-cultured blastocysts. Relative expression of 16 out of 23 (70%) differentially expressed genes (according to P value) were verified in new pools of in vivo- and in vitro-cultured blastocysts, using quantitative real-time PCR. Most (10 out of 16) are involved in transcription and translation events, suggesting that the reason why in vitro-derived embryos are of inferior quality compared with in vivo-derived embryos is due to a deficiency of the machinery associated with transcription and translation.

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E. Soloy
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V. Sršeň
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A. Pavlok
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P. Hyttel
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P. D. Thomsen
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S. D. Smith
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R. Procházka
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M. Kubelka
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R. Høier
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P. Booth
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J. Motlík
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T. Greve
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The ability of a single electric pulse to mimic a block against sperm penetration in bovine oocytes matured in vitro was investigated. Confocal laser scanning microscopy detected a global loss of spots, presumed to be cortical granules, stained with Lens culinaris agglutinin, in pulsed oocytes. Transmission electron microscopy revealed that cortical granule exocytosis occurred within 1 min of stimulation and the number of remaining cortical granules was significantly reduced in all pulsed oocytes. The ability of pulsed oocytes to undergo fertilization in vitro was also affected, as only 31% of the pulsed oocytes were penetrated compared with 87% in the control group. Since incidences of penetration in pulsed oocytes (31%), and of polyspermy in control oocytes (18%) did not differ and were highly correlated (P = 0.009) among trials (n = 15), the induced block is considered to be comparable with the natural block triggered by a spermatozoon. The increased resistance of the zona pellucida to pronase E observed in pulsed oocytes suggests that the induced block depends, at least partly, on modifications of zona pellucida glycoproteins. Finally, the majority (66%) of pulsed, penetrated oocytes did not form male pronuclei, probably as a consequence of asynchrony between the formation of female pronucleus and sperm penetration. The reduced ability of the cytoplasm to induce the formation of a male pronucleus was accompanied by a fall in histone H1 kinase activity to basal values by 3 h after stimulation. These results demonstrate that a single electric pulse can induce a block against sperm penetration similar to that of the spermatozoon itself.

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K P McNatty AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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L G Moore AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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N L Hudson AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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L D Quirke AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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S B Lawrence AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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K Reader AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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J P Hanrahan AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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P Smith AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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N P Groome AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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M Laitinen AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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O Ritvos AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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J L Juengel AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand, Teagasc, Athenry Research Centre, Athenry, Ireland,School of BMS, Oxford Brookes University, Gipsy Lane, Headington, Oxford X3 OBP, UK and Biomedicum Helsinki, PO Box 63 (Haartmaninkatu 8), FIN-00014, University of Helsinki, Helsinki, Finland

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Ovulation rate in mammals is determined by a complex exchange of hormonal signals between the pituitary gland and the ovary and by a localised exchange of hormones within ovarian follicles between the oocyte and its adjacent somatic cells. From examination of inherited patterns of ovulation rate in sheep, point mutations have been identified in two oocyte-expressed genes, BMP15 (GDF9B) and GDF9. Animals heterozygous for any of these mutations have higher ovulation rates (that is, + 0.8–3) than wild-type contemporaries, whereas those homozygous for each of these mutations are sterile with ovarian follicular development disrupted during the preantral growth stages. Both GDF9 and BMP15 proteins are present in follicular fluid, indicating that they are secreted products. In vitro studies show that granulosa and/or cumulus cells are an important target for both growth factors. Multiple immunisations of sheep with BMP15 or GDF9 peptide protein conjugates show that both growth factors are essential for normal follicular growth and the maturation of preovulatory follicles. Short-term (that is, primary and booster) immunisation with a GDF9 or BMP15 peptide-protein conjugate has been shown to enhance ovulation rate and lamb production. In summary, recent studies of genetic mutations in sheep highlight the importance of oocyte-secreted factors in regulating ovulation rate, and these discoveries may help to explain why some mammals have a predisposition to produce two or more offspring rather than one.

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K. P. McNatty
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K. M. Henderson
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S. Lun
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D. A. Heath
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K. Ball
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N. L. Hudson
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J. Fannin
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M. Gibb
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L. E. Kieboom
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P. Smith
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Summary. A marked difference in both the function and composition of individual ovarian follicles was noted in Booroola × Romney ewes (6–7 years of age) which had previously been segregated on at least one ovulation rate record of 3–4 (F+ ewes, N = 21) or <3 (++ ewes, N = 21).

Follicles in F+ ewes produced oestradiol and reached maturity at a smaller diameter than in ++ ewes. In F+ ewes (N = 3), the presumptive preovulatory follicles were 4·4 ± 0·5 (s.e.m.) mm in diameter and contained 2·1 ± 0·3 × 106 (s.e.m.) granulosa cells, whereas in ++ ewes (N = 3), such follicles were 7·3 ± 0·3 mm in diameter and contained 6·5 ± 0·8 × 106 cells. During a prostaglandin (PG)-induced follicular phase, the secretion rate of oestradiol from ovaries containing 3 presumptive preovulatory follicles in F + ewes was similar to that from ovaries with only one such follicle in ++ ewes.

We suggest that the putative 'gene effect' in F+ ewes is manifested during early follicular development and that it may be mediated via an enhanced sensitivity of granulosa cells to pituitary hormones. As a consequence, the development of 3 preovulatory follicles in F+ ewes may be necessary to provide a cell mass capable of producing the same quantity of oestradiol as that from one preovulatory follicle in ++ ewes.

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D. A. Redmer
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Y. Dai
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J. Li
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D. S. Charnock-Jones
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S. K. Smith
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L. P. Reynolds
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R. M. Moor
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The corpus luteum undergoes tremendous growth, development and regression each oestrous or menstrual cycle. These changes are reflected by equally impressive growth and regression of the luteal vasculature. We have previously shown that angiogenic factors from corpora lutea are primarily heparin binding and that one of these factors is similar to vascular endothelial growth factor (VEGF). In an effort to identify this factor, and to define its role in luteal vascular development, the cDNA for the coding region of ovine VEGF was sequenced and a sensitive RNase protection assay was developed to quantitate mRNA encoding VEGF in luteal tissues from ewes in the early (days 2–4), mid- (day 8) and late (days 14–15) stages of the oestrous cycle. In addition, an N-terminal peptide was synthesized from the translated ovine cDNA sequence for VEGF and an antiserum was raised against this peptide for use in western immunoblotting procedures. Nested reverse transcriptase (RT)-PCR of RNA from ovine corpora lutea resulted in three products that correspond in size to the alternatively spliced variants of VEGF VEGF120, VEGF164, and VEGF188) predicted from other species. The RNase protection assay revealed that the proportion of mRNA encoding VEGF was 2- to 3-fold greater on days 2–4 than on day 8 or days 14–15. Densitometric analysis of gels from the RNase protection assay showed that VEGF120 represented approximately one third of the total mRNA encoding VEGF in the corpus luteum and that this proportion did not vary with stage of the oestrous cycle. SDS-PAGE and western immunoblot analysis of a homogenate from corpora lutea showed a single 18 kDa protein. These data demonstrate that VEGF is expressed in luteal tissue throughout the ovine oestrous cycle and that expression of mRNA encoding VEGF is upregulated during the period of rapid luteal development, when luteal vascular growth is at its maximum.

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F Mossa
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F Jimenez-Krassel School of Agriculture Food Science and Veterinary Medicine, Molecular Reproductive Endocrinology Laboratory, Laboratory of Mammalian Reproductive Biology and Genomics, and Conway Institute of Biomedical and Biomolecular Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland

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J K Folger School of Agriculture Food Science and Veterinary Medicine, Molecular Reproductive Endocrinology Laboratory, Laboratory of Mammalian Reproductive Biology and Genomics, and Conway Institute of Biomedical and Biomolecular Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland

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J L H Ireland School of Agriculture Food Science and Veterinary Medicine, Molecular Reproductive Endocrinology Laboratory, Laboratory of Mammalian Reproductive Biology and Genomics, and Conway Institute of Biomedical and Biomolecular Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland

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G W Smith School of Agriculture Food Science and Veterinary Medicine, Molecular Reproductive Endocrinology Laboratory, Laboratory of Mammalian Reproductive Biology and Genomics, and Conway Institute of Biomedical and Biomolecular Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland

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P Lonergan
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A C O Evans
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J J Ireland School of Agriculture Food Science and Veterinary Medicine, Molecular Reproductive Endocrinology Laboratory, Laboratory of Mammalian Reproductive Biology and Genomics, and Conway Institute of Biomedical and Biomolecular Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland
School of Agriculture Food Science and Veterinary Medicine, Molecular Reproductive Endocrinology Laboratory, Laboratory of Mammalian Reproductive Biology and Genomics, and Conway Institute of Biomedical and Biomolecular Research, College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland

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Androgens have an important role in ovarian follicular growth and function, but circulating androgen concentrations are also associated with ovarian dysfunction, cardiovascular disease, and metabolic disorders in women. The extent and causes of the variation in androgen production in individuals, however, are unknown. Because thecal cells of follicles synthesize androstenedione and testosterone, variation in production of these androgens is hypothesized to be directly related to the inherently high variation in number of healthy growing follicles in ovaries of individuals. To test this hypothesis, we determined whether thecal CYP17A1 mRNA (codes for a cytochrome P450 enzyme involved in androgen synthesis), LH-induced thecal androstenedione production, androstenedione concentrations in follicular fluid, and circulating testosterone concentrations were lower in cattle with relatively low versus high number of follicles growing during follicular waves and whether ovariectomy reduced serum testosterone concentrations. Results demonstrated that cattle with a low follicle number had lower (P<0.05) abundance of CYP17A1 mRNA in thecal cells, reduced (P<0.01) capacity of thecal cells to produce androstenedione in response to LH, lower (P<0.01) androstenedione concentrations in ovulatory follicles, and lower (P<0.02) circulating testosterone concentrations during estrous cycles compared with animals with high follicle number. Also, serum testosterone in cattle with low or high follicle number was reduced by 63 and 70%, respectively, following ovariectomy. In conclusion, circulating androgen concentrations are lower in cattle with low versus high number of follicles growing during follicular waves, possibly because of a reduced responsiveness of thecal cells to LH.

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K. M. Smith
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P. C. W. Lai
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H. A. Robertson
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R. B. Church
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F. L. Lorscheider
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Summary. Maximal concentrations of AFP, measured by RIA, were obtained in fetal plasma and amniotic and allantoic fluid between the 3rd and 4th month of gestation, with levels declining thereafter until term. AFP values in maternal plasma were unchanged. Throughout gestation, AFP values were higher in allantoic than in amniotic fluid and the ratio of allantoic fluid/amniotic fluid AFP was significantly correlated with gestational age.

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