G W Smith

University College Dublin, Dublin, L, Ireland

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Publications (35)102.26 Total impact

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    ABSTRACT: Members of the bone morphogenetic protein (BMP) family regulate follicular development and granulosa cell function. However, changes in expression of BMP2 and its receptors during follicular waves in cattle and ability of BMP2 to modulate bovine granulosa cell estradiol production are not well understood. The objectives of this study were to determine temporal regulation of mRNA for BMP2 and its type I and II receptors (BMPR1A and BMPR2) in bovine follicles collected at specific stages of a follicular wave (predeviation, early dominance, mid dominance, preovulatory), ability of BMP2 to modulate bovine granulosa cell steroidogenesis, and whether effects of BMP2 on granulosa cell estradiol production are influenced by cotreatment with cocaine- and amphetamine-regulated transcript (CART), an intrafollicular regulatory peptide shown to inhibit estradiol production in response to other trophic hormones (FSH and IGF1). Relative abundance of mRNAs for Bmp2 and Bmpr2 was elevated at the mid dominance stage relative to earlier stages of the follicular wave and further increased at the preovulatory stage. Abundance of mRNA for Bmpr1a was lowest at early dominance stage and highest at preovulatory stage relative to other stages of the follicular wave examined. Treatment of bovine granulosa cells in vitro with BMP2 increased estradiol but decreased progesterone concentrations. Co-incubation with CART reduced the BMP2-stimulated increase in granulosa cell estradiol production. Results suggest that BMP2 may play a regulatory role in development of bovine follicles to the preovulatory stage and that CART can inhibit granulosa cell estradiol production in response to multiple hormones/growth factors, including BMP2.
    Domestic animal endocrinology 11/2012; · 1.65 Impact Factor
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    ABSTRACT: Mammals such as cattle, swine, sheep and humans are born with a highly variable number of ovarian follicles and oocytes in the ovaries that dwindle during ageing and are never replenished. This variation in the ovarian reserve is reflected in the numbers of antral follicles in the ovaries at all ages after birth. As numbers of follicles in ovaries are determined during gestation, the role of maternal nutrition and health during gestation (at time of ovarian development in their foetuses) has been investigated as factors that may impact oogonia proliferation and thus follicle numbers post-natally. These studies have found that both nutrition and health impact numbers of follicles in their offspring. The idea that numbers of follicles and oocytes in ovaries impact fertility is a long-held belief in reproductive biology. This has recently been tested in cattle, and it has been shown that cows with a relatively high number of antral follicles in ovaries have higher pregnancy rates, shorter calving to conception intervals and fewer artificial inseminations during the breeding season compared with cows with a lower number of follicles, and similarly, heifers with many follicles had higher pregnancy rates than those with fewer follicles. Studies summarized in this review highlight the importance of the maternal environment during gestation in determining the size of the ovarian reserve in their offspring and also the contribution of the ovarian reserve to subsequent fertility in cattle.
    Reproduction in Domestic Animals 08/2012; 47 Suppl 4:31-7. · 1.39 Impact Factor
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    ABSTRACT: The total number of ovarian follicles ≥ 3mm in diameter (antral follicle count, AFC) during follicular waves varies among cattle of similar age, but AFC is highly repeatable within individuals. We hypothesized that lower AFC could be associated with reduced fertility in cattle. The AFC was assessed by ultrasonography for 2 d consecutively during the first wave of follicular growth of the estrous cycle, 4.6±1.43 d (mean ± SD) after estrus, in 306 Holstein-Friesian dairy cows approximately 70 d postpartum. Cows were classified into 3 groups based on AFC: low (AFC ≤15), intermediate (AFC=16 to 24), and high (AFC ≥25). During the cycle in which AFC was assessed and in subsequent cycles, cows were artificially inseminated (AI) following detection of estrus, and pregnancy status was assessed using ultrasonography. Cows with high AFC had 3.34 times greater odds of being pregnant at the end of the breeding season compared with cows with low AFC; the odds of a successful pregnancy at first service were 1.75 times greater in the intermediate compared with the low group. The predicted probability of a successful pregnancy by the end of the breeding period (length of breeding season was 86±16.3 d) was 94, 88, and 84% for the high, intermediate, and low AFC groups, respectively. No difference was evident among groups in 21-d submission rate (proportion of all cows detected in estrus and submitted for AI in the first 21 d of the breeding season), but the interval from calving to conception was shorter in the high (109.5±5.1 d) versus low (117.1±4 d) group, and animals with intermediate AFC received fewer services during the breeding season (2.3±0.1) compared with animals with low AFC (2.7±0.1). Lactating cows with ≤15 ovarian follicles have lower reproductive performance compared with cows with higher numbers of follicles, but the existence of a positive association between high numbers of ovarian follicles and fertility is yet to be established.
    Journal of Dairy Science 05/2012; 95(5):2355-61. · 2.57 Impact Factor
  • COST Action FA0702, Periconceptional Developmental Programming Workshop; 05/2011
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    ABSTRACT: The mechanism whereby the inherently high variation in ovary size and the total number of high-quality oocytes in ovaries (ovarian reserve) impact on ovarian function and fertility, diagnostics to measure the size of the ovarian reserve and the factors that cause variation in the ovarian reserve are unknown. Our results show that cattle can be phenotyped reliably based on the number of antral follicles growing during follicular waves (antral follicle count, AFC). Young adult cattle with a consistently low v. a high AFC have smaller gonads, a markedly diminished ovarian reserve and many other phenotypic characteristics usually associated with ovarian aging and infertility. A powerful new approach based on a single measurement of serum concentration of anti-Müllerian hormone (AMH) is described to test the longstanding hypothesis that the size of the ovarian reserve is positively associated with fertility. Also, new evidence shows that maternal environment has a critical role in regulation of the high variation in the ovarian reserve and perhaps fertility in offspring. These results support the conclusion that the inherently high variation in the ovarian reserve, potentially caused by alterations in the maternal environment, has a negative impact on ovarian function that may result in suboptimal fertility in young adult cattle, and a single AMH measurement can be used reliably in future studies to determine if fertility is suboptimal in young adult cattle with low circulating AMH concentrations and a correspondingly diminished ovarian reserve.
    Reproduction Fertility and Development 01/2011; 23(1):1-14. · 2.58 Impact Factor
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    ABSTRACT: The mechanisms regulating development of a single (dominant) follicle capable of ovulation during each follicular wave in cattle and atresia of remaining follicles (dominant follicle selection) are not well understood. FSH and IGF1 are known regulators of follicle growth and granulosa cell estradiol production during follicular waves. Recent evidence indicates cocaine and amphetamine regulated transcript (CARTPT), with intraovarian expression only in single-ovulating species, is a novel regulator of follicular development. The mature CARTPT peptide (CART) is a potent negative regulator of FSH and IGF1 action on granulosa cells in vitro and can inhibit follicular estradiol production in vivo. Follicular fluid CART concentrations in healthy follicles decrease after dominant follicle selection and CARTPT mRNA is lower in healthy versus atretic follicles collected prior to and early after initiation of follicle dominance, suggestive of a regulatory role in the selection process. The inhibitory actions of CART on FSH signaling and estradiol production are dependent on the G(o/i)-subclass of inhibitory G proteins and linked to multiple components of the FSH signal transduction pathway resulting in reduced CYP19A1 mRNA and estradiol production. Evidence to date supports a potential important functional role for CART in regulation of dominant follicle selection and the species-specific ovulatory quota in monotocous species.
    Society of Reproduction and Fertility supplement. 12/2010; 67:105-17.
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    ABSTRACT: 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.
    Reproduction 11/2010; 140(5):713-20. · 3.56 Impact Factor
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    ABSTRACT: In cattle we have noted that the antral follicle count (AFC, follicles > or = 3 mm in diameter) varies greatly among animals (from 5 to 50), is repeatable within animals, and is highly correlated with the total number of healthy follicles in ovaries. Also, animals with low AFC have higher serum concentrations of FSH and LH, but lower concentrations of Anti-Mullerian Hormone, progesterone and androgens than animals with high AFC. We have investigated the effect of maternal environment during gestation on their offspring AFC by restricting maternal nutrition to 60% of maintenance requirements (compared with 100% in controls) during the first third of gestation. Calves born to nutritionally restricted mothers had 60% lower AFC compared with calves born to mothers fed control diets. In other studies we have evidence to indicate that fertility may be compromised in animals with low AFC due to effects on oocytes, progesterone and the endometrium compared with animals with high AFC. To examine this directly we assessed AFC in post-partum dairy cows and found that cows with a high AFC had higher pregnancy rates, shorter calving to conception intervals and received fewer services during the breeding season compared with cows with a low AFC. In addition, the high variation in follicle numbers in adults may not only be reflective of reproductive disorders and suboptimal fertility, but there is evidence to indicate that it may be associated with alterations in the function of other non-reproductive systems (e.g. cardiovascular) that may have profound effects on the animal's health and welfare.
    Society of Reproduction and Fertility supplement. 01/2010; 67:421-9.
  • G. Wee, K. B. Lee, J. J. Ireland, G. W. Smith
    Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2010; 22(1).
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    ABSTRACT: We hypothesised that higher serum FSH concentrations in cattle with low v. high follicle numbers during follicular waves are caused by a different capacity of the pituitary gland to produce gonadotropins. Dairy cows with high (> or = 30; n = 5) and low (< or = 15; n = 5) follicle numbers were selected and serum concentrations of oestradiol and FSH during an oestrous cycle were measured. Cows were ovariectomised at oestrus and bled frequently up to 8 days after ovariectomy. After 33 days, cows were injected with gonadotropin-releasing hormone (GnRH) and bled intensively up to 8 h after GnRH injection. One day later, animals were injected with follicular fluid (FF) from bovine follicles and were bled intensively up to 2 days after the first injection. Serum concentrations of FSH and LH were measured. After 2 days, cows were killed and their pituitary glands collected. Prior to ovariectomy, serum oestradiol concentrations were similar between groups, whereas FSH concentrations were higher in cattle with low v. high numbers of follicles. No differences were detected in serum gonadotropin concentrations after ovariectomy, GnRH injection or FF challenge between groups. The results indicate that the inherent capacity of the pituitary gland to secrete gonadotropins does not differ between cattle with high v. low numbers of follicles during follicular waves.
    Reproduction Fertility and Development 01/2010; 22(3):550-7. · 2.58 Impact Factor
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    ABSTRACT: The annual economic value of livestock and poultry sales in the United States currently exceeds $132 billion (1), yet only about 0.04% ($32.15 million) (2) of the $88 billion Department of Agriculture (USDA) budget in fiscal year 2007 (3) was allocated to its competitive grants program for research that directly involves agriculturally important domestic animals. By contrast, the Department of Health and Human Services (DHHS) apportioned 4.1% ($29.5 billion) of its $716 billion budget in fiscal year 2008 to the National Institutes of Health (NIH) of which ∼80% supported extramural research (4). Whether this direct comparison between USDA and DHHS is appropriate may be debatable; still, it clearly illustrates the huge disparity in total budget available for research grants focused on animal agriculture, about 1/918th that for human health. The private sector does invest in agricultural research and development, but, understandably, such funds are highly focused on commercial interests and not on basic research of the kind we discuss.
    Science 05/2009; 324(5926):468-9. · 31.20 Impact Factor
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    ABSTRACT: Low progesterone concentrations and diminished ovarian reserves (total number of healthy oocytes) during reproductive cycles are linked to infertility in single-ovulating species like cattle. However, the extent and mechanisms whereby the inherently high variation in ovarian reserves may negatively affect progesterone production are unknown. Cattle were chosen to address these questions because the size of their ovarian reserves can be predicted based on an antral follicle count (AFC) during follicular waves. The present study determined if progesterone concentrations, differentiation and function of the corpus luteum (CL), and endometrial thickness differed during reproductive cycles of age-matched healthy young adult cattle with low versus high AFC during follicular waves. The results showed that, despite enhanced LH secretion, progesterone concentrations were lower during estrous cycles for animals with low versus high AFC. Animals with low versus high AFC also had a decreased basal, LH-, and 25-hydroxycholesterol-induced capacity of luteal and granulosal cells to produce progesterone, reduced amounts of STAR and mRNAs for STAR and LH receptor in the CL, and no change in endometrial thickness during estrous cycles. Taken together, these results 1) supported the conclusion that high variation in ovarian reserves of young adults is associated with alterations in differentiation and function of the CL and 2) provided insight into the potential factors that may cause suboptimal luteal function (e.g., heightened LH secretion and desensitization of the LH receptor, diminished LH responsiveness, diminished STAR, inherent deficiency in capacity of granulosal cells to undergo luteinization) and infertility (e.g., low progesterone, poor endometrial growth) in individuals with diminished ovarian reserves.
    Biology of Reproduction 03/2009; 80(6):1272-81. · 4.03 Impact Factor
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    ABSTRACT: The mechanisms whereby the high variation in numbers of morphologically healthy oocytes and follicles in ovaries (ovarian reserve) may have an impact onovarian function, oocyte quality, and fertility are poorly understood. The objective was to determine whether previously validated biomarkers for follicular differentiation and function, as well as oocyte quality differed between cattle with low versus a high antral follicle count (AFC). Ovaries were removed (n = 5 per group) near the beginning of the nonovulatory follicular wave, before follicles could be identified via ultrasonography as being dominant, from heifers with high versus a low AFC. The F1, F2, and F3 follicles were dissected and diameters determined. Follicular fluid and thecal, granulosal, and cumulus cells and the oocyte were isolated and subjected to biomarker analyses. Although the size and numerous biomarkers of differentiation, such as mRNAs for the gonadotropin receptors, were similar, intrafollicular concentrations of estradiol and the abundance of mRNAs for CYP19A1 in granulosal cells and ESR1, ESR2, and CTSB in cumulus cells were greater, whereas mRNAs for AMH in granulosal cells and TBC1D1 in thecal cells were lower for animals with low versus a high AFC during follicle waves. Hence, variation in the ovarian reserve may have an impact on follicular function and oocyte quality via alterations in intrafollicular estradiol production and expression of key genes involved in follicle-stimulating hormone action (AMH) and estradiol (CYP19A1) production by granulosal cells, function and survival of thecal cells (TBC1D1), responsiveness of cumulus cells to estradiol (ESR1, ESR2), and cumulus cell determinants of oocyte quality (CTSB).
    Biology of Reproduction 02/2009; 80(5):954-64. · 4.03 Impact Factor
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    ABSTRACT: Methods to predict numbers of healthy oocytes in the ovaries of young adults could have important diagnostic relevance in family planning and animal agriculture. We have observed that peak antral follicle count (AFC) determined by serial ovarian ultrasonography during follicular waves is very highly reproducible within individual young adult cattle, despite 7-fold variation among animals. Herein, we tested the hypothesis that AFC is positively associated with the number of morphologically healthy oocytes and follicles in ovaries and with serum concentrations of anti-Müllerian hormone (AMH), an indirect marker for number of healthy follicles and oocytes in ovaries. In the present study, age-matched young adult cattle (12-18 mo old) were subjected to serial ultrasonography to identify animals with a consistently high (> or =25 follicles that were > or =3 mm in diameter) or low (< or =15 follicles) AFC during follicular waves. Differences in serum AMH concentrations, ovary weight, and number of morphologically healthy and atretic follicles and oocytes were determined. The phenotypic classifications of cattle based on AFC during follicular waves or AMH concentrations both predict reliably the relative number of morphologically healthy follicles and oocytes in ovaries of age-matched young adult cattle.
    Biology of Reproduction 09/2008; 79(6):1219-25. · 4.03 Impact Factor
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    ABSTRACT: Transcription factors inhibit or assist RNA polymerases in the initiation and maintenance of transcription; however, the cell specific expression and roles of transcription factors within bovine ovarian follicles during development are unknown. The aim of present study was to determine if the expression of transcription factors in theca and granulosa cells differ between the dominant and the largest subordinate follicles at different stages of the follicle wave. We used a bovine cDNA microarray to screen granulosa and theca cells from dominant and subordinate follicles for differential expression of genes coding for transcription factors. Expression was confirmed using reverse transcription polymerase chain reaction and differences in mRNA abundance further examined at Emergence, Selection and Dominance stages of the follicle wave. We have identified five genes encoding for transcription factors that have not been previously described in developing follicles with greater mRNA abundance in subordinate compared to dominant follicles. The genes (and their putative roles) are CEBP-beta (responsible for luteinization), SRF (cell survival), FKHRL1 (stimulates apoptosis), NCOR1 (modulation of the actions of the oestradiol receptor) and Midnolin (control of development via regulation of mRNA transport in cells).
    Molecular Reproduction and Development 06/2008; 75(5):904-14. · 2.81 Impact Factor
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    ABSTRACT: Ovarian follicles develop in groups yet individual follicles follow different growth trajectories. This growth and development are regulated by endocrine and locally produced growth factors that use a myriad of receptors and signal transduction pathways to exert their effects on theca and granulosa cells. We hypothesize that differential growth may be due to differences in hormonal responsiveness that is partially mediated by differences in expression of genes involved in signal transduction. We used the bovine dominant follicle model, microarrays, quantitative real-time PCR and RNA interference to examine this. We identified 83 genes coding for signal transduction molecules and validated a subset of them associated with different stages of the follicle wave. We suggest important roles for CAM kinase-1 and EphA4 in theca cells and BCAR1 in granulosa cells for the development of dominant follicles and for betaglycan and FIBP in granulosa cells of regressing subordinate follicles. Inhibition of genes for betaglycan and FIBP in granulosa cells in vitro suggests that they inhibit estradiol production in regressing subordinate follicles.
    Physiological Genomics 05/2008; 33(2):193-204. · 2.81 Impact Factor
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    ABSTRACT: We have previously demonstrated a positive association of follistatin mRNA abundance with bovine oocyte competence. Furthermore, exogenous follistatin supplementation during the early stages of in vitro bovine embryo development (before embryonic genome activation) can reduce time to first cleavage, increase proportion of embryos developing to the blastocyst stage, and increase trophectoderm cell numbers, suggesting a potential role for follistatin in bovine early embryonic development. However, the requirement of endogenous follistatin for early embryogenesis in cattle has not been directly tested. Thus, the aim of the present study was to determine the requirement of follistatin for early embryonic development using small interfering RNA (siRNA)- based knockdown procedures. Small interfering RNA corresponding to exons 2 (siRNA 2) and 3 (siRNA 3) of the bovine follistatin gene were synthesized, and the optimal dose of each siRNA resulting in maximal reduction in follistatin mRNA (at the 4-cell stage) following microinjection into presumptive zygotes was determined. Injection of follistatin siRNA 2 or siRNA 3 resulted in a >80% decrease in follistatin mRNA abundance in 4-cell embryos, but mRNA abundance for 5 housekeeping genes and the oocyte-specific gene JY-1 was not affected. Effects of follistatin siRNA injection on follistatin protein abundance were evaluated by immunofluorescence staining of 16-cell embryos. Follistatin immunoreactivity was dramatically reduced in siRNA-treated v. uninjected embryos. Upon validation, the effects of follistatin siRNA on early embryonic development were investigated. Cumulus–oocyte complexes were harvested from ovaries obtained from a local abattoir, matured and fertilized in vitro. Sixteen to 18 h following fertilization, denuded presumptive zygotes (25–30 per treatment, n = 4 replicates) were microinjected with (1) follistatin siRNA 2, (2) negative control (nonspecific) siRNA, (3) sham (water), or (4) served as uninjected controls. After injections, embryos were cultured in KSOM medium supplemented with 0.3% BSA. Proportions of embryos reaching the 2-cell stage within 30 h (early cleaving), 30–36 h (late cleaving), and within 48 h post-fertilization (total cleavage rate) were recorded. Number of embryos reaching the 8–16-cell stage was recorded 72 h after fertilization, and embryos were cultured in fresh KSOM medium supplemented with 0.3% BSA and 10% fetal bovine serum until day 7. Injection of follistatin siRNA 2 did not affect proportion of early and late cleaving embryos (21 v. 19% and 41 v. 37%) and total cleavage rate (80 v. 81%). However, injection of follistatin siRNA 2 decreased the proportion of embryos reaching the 8–16-cell stage (41 v. 59%) and percentage blastocyst development (12 v. 27%, P < 0.05). Experiments were repeated, and effects of follistatin siRNA 3 determined (25–30 embryos per treatment, n = 4 replicates). Similar results were obtained as for follistatin siRNA 2 injection. Results support a requirement of endogenous follistatin for bovine early embryogenesis.
    Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2008; 20(1).
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    ABSTRACT: The significance of the high variation in numbers of follicles produced during reproductive cycles in humans and cattle is unknown. We selected beef heifers with high (> or =25) or low (< or =15) numbers of ovarian follicles and determined the association with alterations in FSH and estradiol concentrations, as well as responsiveness to superstimulation and embryo quality. The variation in follicle numbers was also compared with oocyte quality in natural cycles using IVF and abattoir-sourced bovine ovaries. Results show that: (i) FSH was lower (P < 0.03) in animals with high compared with low follicle numbers per follicle wave; (ii) after superovulation, in the high versus low follicle number group, the number of oocytes/embryos recovered after insemination (10.6 +/- 2.7 versus 4.7 +/- 0.7) and the number of transferable embryos (5.4 +/- 1.3 versus 3.8 +/- 0.8) per animal were greater (P < 0.05), whereas the proportion of transferable embryos (50.7% versus 79.8%) was lower (P < 0.05); (iii) in unstimulated animals, the numbers of high-quality oocytes harvested and in-vitro fertilized oocytes developing into blastocysts were up to 4-fold greater (P < 0.05) for ovaries with high versus low numbers of follicles, but the proportions of oocytes developing into blastocysts were similar in the two groups. Phenotypic classification based on numbers of follicles may be useful to improve superovulation procedures. The lower proportion of transferable embryos following superovulation of ovaries with high numbers of follicles is probably not the result of differences in the quality of oocytes before superovulation.
    Human Reproduction 07/2007; 22(6):1687-95. · 4.67 Impact Factor
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    ABSTRACT: The cellular form of the prion protein (PrPC) has been detected in many tissues including reproductive tissues. While its function is unclear, it has been suggested to act as a receptor for an unidentified ligand and/or as an antioxidant agent. We tested the hypothesis that PrPC is differentially expressed in dominant, growing, compared to subordinate bovine ovarian follicles. Using both microarray analysis and quantitative real-time PCR, the level of prion protein mRNA (Prnp) in both theca and granulosa cells was measured. We found that levels of Prnp were significantly higher in the theca cells of dominant compared to subordinate follicles but similar among granulosa cells from different follicles. This difference was apparent immediately after selection of the dominant follicle and continued to the dominance stage of the follicle wave. Levels of the protein for PrPC were also higher (P < 0.05) in theca cells of dominant compared to subordinate follicles. In conclusion, elevated PrPC was associated with ovarian follicle growth and development and we suggest that it may play a role in the success of follicle development. Mol. Reprod. Dev. 75: 243–249, 2008. © 2007 Wiley-Liss, Inc.
    Molecular Reproduction and Development 06/2007; 75(2):243 - 249. · 2.81 Impact Factor
  • G W Smith, G J M Rosa
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    ABSTRACT: The recent development of tools for expression profiling in livestock has availed reproductive biologists of new opportunities to examine global changes in gene expression during key developmental events, in response to hormonal or other treatments, and as a tool for phenotyping or predicting developmental potential. Such experiments often yield lists of tens to thousands of modulated genes, transcripts of interest, or both. Some argue that such technological advances signal a move from hypothesis-driven research to descriptive discovery research, resulting in information overload at the expense of biological significance. One can easily spend hours staring into the abyss, wondering if the results are real and what they mean. However, microarrays can be more than a high throughput and expensive screening tool. Many factors contribute to the success of expression profiling experiments and the yield of interpretable data, including the nature of the hypothesis or objective of the study, the microarray platform, the complexity of the tissue of interest, the experimental design, and the incorporation of the best available strategies for data analysis and interpretation of the biological themes. Although challenging due to the lack of extensive annotation or ontology classification for genes in livestock species, functional categories of coregulated genes and gene pathways can be determined, and hypotheses about common regulatory elements or the functional significance can be formulated. We have applied cDNA microarray technology to studies of follicular growth, oocyte quality, and the periovulatory period in cattle. Lessons learned from such experiments and a review of the available literature form the basis for the strategies described to facilitate successful application of microarray technology to studies of reproductive biology of livestock species.
    Journal of Animal Science 04/2007; 85(13 Suppl):E20-3. · 2.09 Impact Factor

Publication Stats

477 Citations
102.26 Total Impact Points

Institutions

  • 2004–2012
    • University College Dublin
      • • School of Agriculture & Food Science
      • • College of Agriculture, Food Science and Veterinary Medicine
      • • Conway Institute of Biomolecular & Biomedical Research
      Dublin, L, Ireland
  • 2002–2012
    • Michigan State University
      • • Department of Animal Science
      • • Department of Physiology
      East Lansing, Michigan, United States
  • 2009
    • University of Missouri
      • Division of Animal Sciences
      Columbia, MO, United States
  • 2006
    • University of Glasgow
      • School of Veterinary Medicine
      Glasgow, SCT, United Kingdom