Research Interests: Endocrinology, Animal Science, Biology, Diet, Lactation, and 15 moreMedicine, Energy Metabolism, Biological Sciences, Growth Hormone, Internal Medicine, Female, Animals, Hormones, Cattle, Luteinizing Hormone, Gonadotropins, Follicle stimulating hormone, Biology Reproduction, Follicular phase, and Medical and Health Sciences
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Studies in cattle assessing changes in number and size of antral follicles, concentrations of estradiol, androgens and progesterone in serum and follicular fluid, and numbers of gonadotropin receptors per follicle during repetitive... more
Studies in cattle assessing changes in number and size of antral follicles, concentrations of estradiol, androgens and progesterone in serum and follicular fluid, and numbers of gonadotropin receptors per follicle during repetitive estrous cycles and postpartum anestrus are reviewed. The rate of growth of small follicles (1 to 3 mm) into larger follicles increases as the estrous cycle progresses from d 1 to 18 (d 0 = estrus). Size of the largest antral follicle present on the ovary also increases with advancement of the estrous cycle. Most large follicles (>10 mm) persist on the ovarian surface for 5 d or more between d 3 and 13 of the bovine estrous cycle. After d 13, most of these large follicles are replaced more frequently by new growing follicles (turnover) with an increased probability' for recruitment of the ovulatory follicle after d 18. More research is needed to determine the time required for growth of bovine follicles from small to lane antral size and evoke recru...
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Negative energy balance associated with the onset of lactation results in hypoinsulinemia, uncoupling of the IGF-somatotropin axis, attenuation of gonadotropin release and delayed first ovulation. Our objectives were to examine the... more
Negative energy balance associated with the onset of lactation results in hypoinsulinemia, uncoupling of the IGF-somatotropin axis, attenuation of gonadotropin release and delayed first ovulation. Our objectives were to examine the effects of elevated insulin during the immediate postpartum period on circulating IGF-I concentrations, ovarian follicular growth, estradiol secretion and LH pulse profiles. Holstein cows (n=14) were subjected to either a hyperinsulinemic-euglycemic clamp (INS) or saline infusion (CTL) for 96 hours starting on day 10 postcalving. Blood samples were taken on days 8-9 to establish baseline glucose values. Insulin was infused continuously (1 μg/kg BW/hr) via a jugular catheter. Blood samples were collected hourly, and euglycemia was maintained by infusion of exogenous glucose. During infusion, insulin concentrations were increased 8-fold in INS cows over those in CTL cows (2.4 ± 0.1 vs. 0.3 ± 0.1 ng/ml; P<0.001), while blood glucose concentrations were no...
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The objective was to determine the effect of dietary intake on follicle and oocyte morphology in unstimulated and superovulated ewes. Fifty-four ewes were fed grass meal at 0.5, 1.0 or 2.0 times maintenance energy requirements (M) for 32... more
The objective was to determine the effect of dietary intake on follicle and oocyte morphology in unstimulated and superovulated ewes. Fifty-four ewes were fed grass meal at 0.5, 1.0 or 2.0 times maintenance energy requirements (M) for 32 days. Oestrous cycles were synchronized using progestagen pessaries and either unstimulated or superovulated with 200 mg pig FSH. The ewes were killed and ovaries were collected either 36 or 12 h before the anticipated LH surge. Serum progesterone concentrations in ewes on day 10 after withdrawal of the pessary were lower in ewes fed 2.0M than in ewes fed 0.5M or 1.0M (P < 0.05). LH pulse frequency tended to be higher in ewes fed 2M than 1M (1.0 +/- 0.3 versus 0.3 +/- 0.2 pulses per 8 h) on day 6 after removal of the pessary but the effect was not significant. In unstimulated ewes, more follicles (>/= 3 mm) were observed when the animals were killed in ewes fed 2.0M (3.5 +/- 0.3) than in ewes fed 0.5M (2.4 +/- 0.3) or 1.0M (2.4 +/- 0.5; P <...
Research Interests: Endocrinology, Physiology, Reproduction, Biology, Medicine, and 15 moreProgesterone, Internal Medicine, Reproduction and human fertility, Female, Animals, Clinical Sciences, Ovarian Follicle, Oocytes, Luteinizing Hormone, Follicular Fluid, Oocyte, Estrous cycle, Follicular phase, Paediatrics and reproductive medicine, and follicle
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Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-β family of proteins that have been implicated in the paracrine regulation of granulosa cell (GC) function, but whether responses to BMPs change with... more
Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-β family of proteins that have been implicated in the paracrine regulation of granulosa cell (GC) function, but whether responses to BMPs change with follicular size or interact with connective tissue growth factor (CTGF) or BMP antagonists (e.g., gremlin [GREM]) to directly affect GC function of cattle is unknown. Therefore, to determine the effects of BMP4 on proliferation and steroidogenesis of GCs and its interaction with GREM or CTGF, experiments were conducted using bovine GC cultures. In vitro, BMP4 (30 ng/mL) inhibited (P < 0.05) follicle-stimulating hormone (FSH) plus insulin-like growth factor 1 (IGF1)-induced progesterone and estradiol production by large- and small-follicle GCs, but the inhibitory effect of BMP4 on estradiol production was much more pronounced in large-follicle GCs. In small-follicle GCs, BMP4 had no effect (P > 0.10) on IGF1-induced proliferation, but GREM inhibited (...
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Changes in numbers of ovarian follicles and coincident secretion of pituitary gonadotropins were characterized in suckled, anovulatory beef cows injected iv with 500 ng of luteinizing hormone-releasing hormone (LHRH) every 2 h for 48 or... more
Changes in numbers of ovarian follicles and coincident secretion of pituitary gonadotropins were characterized in suckled, anovulatory beef cows injected iv with 500 ng of luteinizing hormone-releasing hormone (LHRH) every 2 h for 48 or 96 h, starting 21.4 +/- .4 d after parturition. Two hours after the last injection, all cows were ovariectomized. Compared with saline-injected controls, LHRH had no effect on baseline or overall concentrations of luteinizing hormone (LH) in serum (P greater than .10), but increased (P less than .05) frequency and decreased (P less than .05) amplitude of LH pulses. Luteinizing hormone-releasing hormone increased (P less than .05) baseline concentration of follicle stimulating hormone (FSH) in serum and frequency of FSH pulses, but decreased (P less than .05) pulse amplitude. Overall concentrations of FSH increased 20% (P less than .10). Exogenous LHRH did not affect diameter of the two largest follicles or numbers of follicles 1.0 to 3.9 mm, 4.0 to 7.9 mm or greater than or equal to 8.0 mm in diameter. These data suggest that increasing the frequency of episodic LH and FSH pulses in postpartum cattle by intermittent administration of LHRH did not increase mean circulating levels of LH, or alter size and numbers of ovarian follicles within the 96-h period of injections. Thus, induction of ovulation in anovulatory cows treated with low-dose injections of LHRH cannot be explained on the basis of an increase in mean concentrations of LH or numbers of antral follicles within 96 h after initiation of injections.
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To determine if specific binding of 125I-labeled gonadotropins to granulosa and thecal cells, or concentrations of steroids in ovarian follicles change during the postpartum anovulatory period, 21 suckled beef cows were slaughtered on d... more
To determine if specific binding of 125I-labeled gonadotropins to granulosa and thecal cells, or concentrations of steroids in ovarian follicles change during the postpartum anovulatory period, 21 suckled beef cows were slaughtered on d 7, 14, 28, 42 or 56 after parturition (n = 4 to 6 per d). After slaughter, 10 to 15 follicles were dissected from each pair of ovaries and categorized by diameter: small (1.0 to 3.9 mm), medium (4.0 to 7.9 mm) or large (greater than or equal to 8 mm). Progesterone (221 to 612 ng/ml), androstenedione (48 to 94 ng/ml) and estradiol (2.7 to 23.9 ng/ml) did not change (P greater than .10) in fluid of small or medium follicles from d 7 to 42 to 56 after parturition. Similarly, specific binding of human chorionic gonadotropin (125I-hCG) or follicle stimulating hormone (125I-oFSH) to homogenates of small, medium or large follicles did not change (P greater than .05). In contrast, progesterone in fluid of large follicles increased (P less than .05) 3.4-fold between d 7 and 14, but decreased (P less than .05) 55% between d 14 and 28. Concentrations of androstenedione in fluid of large follicles did not change (P greater than .10) from d 7 to 42 to 56. Concentrations of estradiol in fluid of large follicles remained constant between d 7 and 14, but increased (P less than .05) 4.2-fold between d 14 and 28. We conclude that during the postpartum anovulatory period, there is no change in steroidogenic capabilities of small or medium follicles, both of which predominantly produce progesterone.(ABSTRACT TRUNCATED AT 250 WORDS)
Research Interests: Endocrinology, Animal Science, Biology, Medicine, Biological Sciences, and 15 morePregnancy, Progesterone, Internal Medicine, Female, Animals, Anovulation, Cattle, Ovarian Follicle, Granulosa Cells, Luteinizing Hormone, Estradiol, Follicle stimulating hormone, Androstenedione, postpartum period, and cattle diseases
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The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers.... more
The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers. Heifers were allotted by BW and age to three treatments with a replication in each of 2 yr: full-fed (n = 13; FF) to gain 1.36 kg/d; limit-fed (n = 12; LF) to gain .68 kg/d; maintenance-full-fed (n = 13; MFF) to gain .23 kg/d for 16 wk, then full-fed to gain 1.36 kg/d. Heifers were slaughtered within 10 d after the onset of puberty. At slaughter, kidney, pelvic, and heart fat (KPH) and udder (UDDER) were separated from carcass, as was fat surrounding viscera (OM). After 48 h at 4 degrees C a carcass side was dissected into subcutaneous fat (SC), intermuscular fat (SEAM), soft tissue (SFT = inseparable lean and fat), LEAN, and BONE. In yr 1, LF heifers (431 d) were older (P &lt; .05) than MFF heifers (371 d) at puberty, but age of FF heifers (389 d) did not differ (P &gt; .10) from that of LF and MFF heifers. In yr 2, FF heifers (351 d) were younger (P &lt; .05) than LF and MFF heifers (398 and 434 d, respectively). The FF heifers had greater (P &lt; .05) BW and a greater (P &lt; .01) percentage of lipid in the carcass at puberty than LF and MFF heifers. During the first 16 wk of treatment, concentrations of NEFA were greater in heifers with slower daily gains (MFF &gt; LF &gt; FF; P &lt; .01). Concentrations of NEFA were lesser and concentrations of IGF-I and insulin were greater in plasma of FF than in that of MFF heifers during the 10 wk before puberty. Treatment significantly altered age, BW, carcass composition, and lipid partitioning at puberty in beef heifers. We conclude that the percentage of body fat is not the sole regulator of puberty, and age may be an important modulator in determining the onset of puberty in beef heifers.
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Research Interests: Animal Science, Biology, Energy Metabolism, Biological Sciences, Growth Hormone, and 15 moreBlood Glucose, Animal, Female, Animals, Anovulation, Cattle, Growth rate, Body Weight, Body Condition Score, Estradiol, Follicle stimulating hormone, Biology Reproduction, Estrous cycle, Endocrine System, and cattle diseases
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The effects of recombinant bovine interleukin-2 (IL-2) on steroidogenesis of bovine ovarian granulosa and thecal cells were evaluated. Granulosa cells were examined from both small (surface diameter ≤ 5 mm) and large (≥ 8 mm) follicles,... more
The effects of recombinant bovine interleukin-2 (IL-2) on steroidogenesis of bovine ovarian granulosa and thecal cells were evaluated. Granulosa cells were examined from both small (surface diameter ≤ 5 mm) and large (≥ 8 mm) follicles, whereas thecal cells from only large follicles were utilized. IL-2 significantly attenuated FSH-induced estradiol production by cells from small but not large follicles. Moreover, IL-2 significantly attenuated FSH-induced progesterone production by granulosa cells from small and large follicles but had no effect on LH-induced progesterone or androstenedione production by thecal cells.
Endothelins (EDN) are a group of vasoactive 21 amino acid peptides reported to play roles in steroidogenesis, folliculogenesis, and ovulation. EDN1, EDN2 and EDN3 have all been shown to affect granulosa cell (GC) function in a variety of... more
Endothelins (EDN) are a group of vasoactive 21 amino acid peptides reported to play roles in steroidogenesis, folliculogenesis, and ovulation. EDN1, EDN2 and EDN3 have all been shown to affect granulosa cell (GC) function in a variety of mammalians species. Herewithin, the role of EDN in regulating steroidogenesis and ovarian follicular development is reviewed, focusing on the localization and function of EDN and their receptors in ovarian follicular function emphasizing species differences. For example, in single ovulating species such as humans and cattle, in the presence of trophic hormones such as FSH and IGF1, EDN1 and EDN2 significantly inhibited GC estradiol production in 2 of 4 studies, while no effect was observed for GC progesterone production in 2 of 4 studies. In contrast, EDN1 exhibited inhibitory effects on progesterone production by GC in 3 of 3 studies in pigs and 3 of 4 studies in rats. Also, EDN1 inhibited GC estradiol production in 4 of 5 studies in rats. Altogether, these results indicate that EDN are produced by ovarian follicles and are involved in the regulation of steroidogenesis of GC of several mammalian species including humans, cattle, pigs and rats, but that these effects may vary with species and culture condition.
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Research Interests: Biology, Regulation, Medicine, Humans, Female, and 6 moreAnimals, Androgens, Biological activity, Ovary, Catecholamines, and Estradiol
2-Hydroxyestradiol (2-OH-E2) stimulates progestin secretion by granulosa cells, but the intracellular locus of the stimulatory effect has not been clarified. The objectives of the present studies were to 1) determine the role of de novo... more
2-Hydroxyestradiol (2-OH-E2) stimulates progestin secretion by granulosa cells, but the intracellular locus of the stimulatory effect has not been clarified. The objectives of the present studies were to 1) determine the role of de novo sterol synthesis in the effect of 2-OH-E2 on progestin biosynthesis, and 2) examine the effects of 2-OH-E2 on cholesterol side-chain cleavage (SCC) activity and the level of messenger RNA (mRNA) for P450scc. Inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase with lovastatin (5 micrograms/ml) or mevinolin (5 micrograms/ml) reduced FSH- and 2-OH-E2-stimulated (but not E2-stimulated) progesterone production. Mevalonate (20 mM) enhanced basal progesterone production and reversed the inhibitory effect of lovastatin but did not affect progesterone biosynthesis in the presence of 2-OH-E2. As an index of the activity of cholesterol SCC enzyme, granulosa cells were exposed to 25-hydroxycholesterol (10 micrograms/ml) for 24 h and progesterone secretion monitored. Conversion of 25-hydroxycholesterol into progesterone was stimulated 2- to 3-fold by maximally effective concentrations of 2-OH-E2, E2, and FSH. 2-OH-E2 and/or E2 further enhanced 25-hydroxycholesterol conversion in the presence of FSH, LH, and epinephrine. Aminoglutethimide, an inhibitor of SCC, reduced 2-OH-E2- and 2-OH-E2 plus FSH-stimulated progesterone production by 97% and 95%, respectively. 2-OH-E2 also increased basal (by 2 to 3-fold) and FSH-stimulated (to 3.5-fold of FSH-treated controls) levels of mRNA for cytochrome P450scc. Collectively, our studies support the hypothesis that 2-OH-E2-enhanced progesterone biosynthesis by porcine granulosa cells is dependent on de novo cholesterol synthesis and is associated with increased levels of the mRNA encoding cytochrome P-450scc, which leads to increases in basal and gonadotropin-induced SCC activity.
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Changes in numbers of ovarian follicles and coincident secretion of pituitary gonadotropins were characterized in suckled, anovulatory beef cows injected iv with 500 ng of luteinizing hormone-releasing hormone (LHRH) every 2 h for 48 or... more
Changes in numbers of ovarian follicles and coincident secretion of pituitary gonadotropins were characterized in suckled, anovulatory beef cows injected iv with 500 ng of luteinizing hormone-releasing hormone (LHRH) every 2 h for 48 or 96 h, starting 21.4 +_ .4 d after parturition. Two hours after the last injection, all cows were ovariectomized. Compared with saline-injected controls, LHRH had no effect on baseline or overall concentrations of luteinizing hormone (LH) in serum (P> A0), but increased (P<.05) frequency and decreased (P<.05) amplitude of LH pulses. Luteinizing hormone-releasing hormone increased (P<.05) baseline concentration of follicle stimulating hormone (FSH) in serum and frequency of FSH pulses, but decreased (P<.05) pulse amplitude. Overall concentrations of FSH increased 20% (P<. 10). Exogenous LHRH did not affect diameter of the two largest follicles or numbers of follicles 1.0 to 3.9 mm, 4.0 to 7.9 mm or > 8.0 mm in diameter. These data ...
Fibroblast growth factor 9 (FGF9) protein affects granulosa cell (GC) function but is mostly localized to theca cell (TC) and stromal cell of rat ovaries. The objectives of this study were to determine the 1) effects of FGF9 on TC... more
Fibroblast growth factor 9 (FGF9) protein affects granulosa cell (GC) function but is mostly localized to theca cell (TC) and stromal cell of rat ovaries. The objectives of this study were to determine the 1) effects of FGF9 on TC steroidogenesis, gene expression, and cell proliferation; 2) mechanism of action of FGF9 on TCs; and 3) hormonal control ofFGF9mRNA expression in TCs. Bovine ovaries were collected from a local slaughterhouse and TCs were collected from large (8–22 mm) follicles and treated with various hormones in serum-free medium for 24 or 48 h. FGF9 caused a dose-dependent inhibition (P<0.05) of LH- and LH+IGF1-induced androstenedione and progesterone production. Also, FGF9 inhibited (P<0.05) LH+IGF1-induced expression ofLHCGR,CYP11A1, andCYP17A1mRNA (via real-time RT-PCR) in TCs. FGF9 had no effect (P>0.10) onSTARmRNA abundance. Furthermore, FGF9 inhibited dibutyryl cAMP-induced progesterone and androstenedione production in LH+IGF1-treated TCs. By contrast, ...
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Previously, we determined that a primary cause of proportional stunted growth in a line of Brahman cattle was related to an apparent refractoriness in metabolic response to GH in young animals. The objective of this study was to determine... more
Previously, we determined that a primary cause of proportional stunted growth in a line of Brahman cattle was related to an apparent refractoriness in metabolic response to GH in young animals. The objective of this study was to determine the effect of administration of GH, insulin (INS), and GH plus INS to mature miniature Brahman cows (n = 6; 9.7 ± 2.06 y; 391 ± 48.6 kg) and bulls (n = 8; 9.4 ± 2.00 y; 441 ± 54.0 kg) on circulating concentrations of metabolic hormones and metabolites, primarily IGF-I and IGF-I binding proteins. We hypothesized that IGF-I secretion could be enhanced by concomitant administration of exogenous GH and INS, and neither alone would be effective. Animals were allotted to a modified crossover design that included four treatments: control (CON), GH, INS, and GH + INS. At the start of the study, one-half of the cattle were administered GH (Posilac; 14-d slow release) and the other one-half served as CON for 7 d. Beginning on day 8, and for 7 d, INS (Novolin L) was administered (0.125 IU/kg BW) twice daily (7:00 AM and 7:00 PM) to all animals; hence, the INS and GH + INS treatments. Cattle were rested for 14 d and then were switched to the reciprocal crossover treatments. Blood samples were collected at 12-hour intervals during the study. Compared with CON, GH treatment increased (P &lt; 0.01) mean plasma concentrations of GH (11.1 vs 15.7 ± 0.94 ng/mL), INS (0.48 vs 1.00 ± 0.081 ng/mL), IGF-I (191.3 vs 319.3 ± 29.59 ng/mL), and glucose (73.9 vs 83.4 ± 2.12 mg/dL) but decreased (P &lt; 0.05) plasma urea nitrogen (14.2 vs 11.5 ± 0.75 mg/dL). Compared with INS, GH + INS treatment increased (P &lt; 0.05) mean plasma concentration of INS (0.71 vs 0.96 ± 0.081 ng/mL), IGF-I (228.7 vs 392.3 ± 29.74 ng/mL), and glucose (48.1 vs 66.7 ± 2.12 mg/dL), decreased (P &lt; 0.01) plasma urea nitrogen (13.6 vs 10.4 ± 0.76 mg/dL), and did not affect GH (13.5 vs 12.7 ± 0.95 ng/mL). In the miniature Brahman model, both the GH and GH + INS treatments dramatically increased circulating concentrations of IGF-I in mature cattle, suggesting that this line of Brahman cattle is capable of responding to bioactive GH.
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The objective of the present study was to determine the interactions among bST, insulin, and gonadotropins on steroid production by granulosa and thecal cells from bovine follicles. Basal production of estradiol by granulosa cells from... more
The objective of the present study was to determine the interactions among bST, insulin, and gonadotropins on steroid production by granulosa and thecal cells from bovine follicles. Basal production of estradiol by granulosa cells from small (1 to 5 mm) and large (&gt; or = 8 mm) follicles (expressed as picograms of estradiol per 10(5) cells per 24 h) was not affected by 50 or 300 ng/ml of bST, but 300 ng/ml of bST inhibited estradiol production that was induced by FSH plus insulin in cells from small and large follicles. Progesterone production and proliferation by granulosa cells from large follicles were not affected by 3 to 100 ng/ml of bST. In cultures of thecal cells that exhibited a &gt; 3-fold increase in androstenedione production induced by LH, 3 to 30 ng/ml of bST further increased androstenedione production by 29 to 42%, but cell proliferation and progesterone production were unaffected by bST. In cultures of thecal cells that exhibited a &lt; 2-fold increase in androstenedione production induced by LH, 3 to 30 ng/ml of bST inhibited androstenedione production by 32 to 33% and inhibited cell proliferation by 9 to 13%, but progesterone was unaffected by bST. In summary, only pharmacologic doses of bST inhibited estradiol production by granulosa cells, but physiologic doses of bST altered androstenedione production by thecal cells, which indicated that bST might not have an important role in granulosa cell function but might play a role in thecal cell function in cattle.
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Research Interests: Dairy Science, Animal Production, Energy Metabolism, Dexamethasone, Blood Glucose, and 15 moreInsulin, Cholesterol, Female, Animals, Leptin, Dairy, Cattle, Ovarian Follicle, Food Sciences, Luteinizing Hormone, Glucocorticoids, Estradiol, Follicle stimulating hormone, Corpus Luteum, and Estrus Synchronization
The effects of estradiol, insulin, and gonadotropins on levels of insulin-like growth factor binding protein (IGFBP)-2, -3, -4, and -5 mRNA levels in bovine granulosa and theca cells were evaluated in vitro using serum-free medium... more
The effects of estradiol, insulin, and gonadotropins on levels of insulin-like growth factor binding protein (IGFBP)-2, -3, -4, and -5 mRNA levels in bovine granulosa and theca cells were evaluated in vitro using serum-free medium containing various hormone treatments arranged in four ...
Research Interests: Gene expression, Animal Production, Real-time RT-PCR, real time PCR, Insulin, and 12 moreFemale, Animals, Cattle, Ovarian Follicle, Veterinary Sciences, Granulosa Cells, Luteinizing Hormone, Estradiol, Follicle stimulating hormone, Gene Expression Regulation, reverse transcriptase polymerase chain reaction, and Domestic animal
Research Interests: Physiology, Reproduction, Gene expression, Signal Transduction, Progesterone, and 15 moreHumans, Insulin, Mice, G protein-coupled receptors, Female, Animals, Clinical Sciences, Cattle, Rats, Luteinizing Hormone, Androstenedione, Signaling pathway, reverse transcriptase polymerase chain reaction, G Protein Coupled Receptors, and Paediatrics and reproductive medicine
Since its discovery in 1994, leptin, a protein hormone synthesized and secreted by adipose tissue, has been shown to regulate feed intake in several species including sheep and pigs. Although a nimiety of information exists regarding the... more
Since its discovery in 1994, leptin, a protein hormone synthesized and secreted by adipose tissue, has been shown to regulate feed intake in several species including sheep and pigs. Although a nimiety of information exists regarding the physiological role of leptin in ...
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Prepubertal gilts of obese (n = 241 or lean (n = 241 genetic lines were injected (s.c.1 daily with 0, 2, or 4 mg of porcine somatotropin (pST1 for 6 wk starting at 160 d of age to determine whether pST affects follicular function. Blood... more
Prepubertal gilts of obese (n = 241 or lean (n = 241 genetic lines were injected (s.c.1 daily with 0, 2, or 4 mg of porcine somatotropin (pST1 for 6 wk starting at 160 d of age to determine whether pST affects follicular function. Blood and ovaries were collected at slaughter 24 h after the last injection. Surface follicles 2
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Fibroblast growth factor 9 (FGF9) has been suggested to act as a dedifferentiation factor during bovine folliculogenesis, reducing steroidogenesis and increasing cell proliferation in granulosa (GC) and theca (TC) cells, but whether... more
Fibroblast growth factor 9 (FGF9) has been suggested to act as a dedifferentiation factor during bovine folliculogenesis, reducing steroidogenesis and increasing cell proliferation in granulosa (GC) and theca (TC) cells, but whether endogenous GC production of FGF9 change during bovine folliculogenesis and atresia/apoptosis is unknown. The objective of these studies was to investigate the relationship between FGF9 mRNA, follicle size, and health status of follicles. Ovaries (n = 10 cows) from a local abattoir classified visually as in midcycle phase (i.e. presence of corpus luteum and large follicles) were collected and categorized as small (1–5 mm), medium (5.1–8 mm) or large (8.1–22 mm) in size (Experiment 1). Follicular fluid (FFL) was aspirated for measurement of oestradiol (E2) and progesterone (P4) via radioimmunoassay and GC collected for RNA extraction. Abundance of mRNA for FGF9 and Caspase-3 (CASP3), an effector of apoptosis, were measured by real-time PCR (qPCR). Data wer...
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Maternal heat stress reduces oocyte competence for fertilization and post-fertilization development, but the mechanism is unknown. The present experiment investigated two potential mechanisms: (1) reduced oxygen delivery to the... more
Maternal heat stress reduces oocyte competence for fertilization and post-fertilization development, but the mechanism is unknown. The present experiment investigated two potential mechanisms: (1) reduced oxygen delivery to the preovulatory follicle (due to increased thermoregulatory vascular perfusion of skin and respiratory tract); (2) reduced follicular steroid synthesis. These hypotheses were tested by measuring the fractional concentration of oxygen and concentrations of estradiol-17beta and progesterone in follicular fluid of the preovulatory follicle of lactating Holstein cows. Estrous cycles were synchronized using GnRH on Day -9 and PGF(2alpha) on Day -2. On Day 0, all cows without a CL and with a large preovulatory follicle were assigned to control or heat stress treatments for 1d (beginning at 1030 h). Between 4 and 6 h after treatment (1430-1630 h), follicular fluid was aspirated by transvaginal puncture, and fractional oxygen concentration in follicular fluid of the dominant follicle was determined with a fluorometric fiber-optic oxygen sensor. There was no significant effect of heat stress on follicular fluid P(O2) or concentrations of estradiol-17beta or progesterone among cows that had follicular fluid steroid concentrations considered typical of a preovulatory follicle. Follicular oxygen concentration was 6.9+/-0.4% for control cows and 7.3+/-0.3% for heat-stressed cows. Oxygen concentration tended to be inversely correlated to follicular diameter (P=0.09). In conclusion, it was unlikely that reduced oocyte competence due to acute heat stress was caused by reductions in follicular concentrations of oxygen, estradiol-17beta, or progesterone.
Research Interests: Lactation, Biological Sciences, Pregnancy, Progesterone, Female, and 15 moreAnimals, Body Temperature, Cattle, Ovarian Follicle, Oxygen, Heat stress, Fiber Optic, Dairying, Follicular Fluid, Estradiol, Estrous cycle, Acute Disease, Follicular phase, Dominant follicle, and Medical and Health Sciences
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Postnatal development of the ovine uterus primarily involves uterine gland morphogenesis or adenogenesis. Adenogenesis involves the budding differentiation of the glandular epithelium (GE) from the luminal epithelium (LE) and then GE... more
Postnatal development of the ovine uterus primarily involves uterine gland morphogenesis or adenogenesis. Adenogenesis involves the budding differentiation of the glandular epithelium (GE) from the luminal epithelium (LE) and then GE proliferation and coiling/branching morphogenetic development within the stroma between birth (postnatal day or PND 0) and PND 56. Insulin-like growth factor (IGF)-I and IGF-II mRNAs were previously found to be expressed only in the endometrial stroma, whereas the IGF receptor (IGF-1R) mRNA was most abundant in epithelia and in stroma, suggesting that an intrinsic IGF system regulates postnatal development of the uterus. Given that the biological activities of IGFs are modulated by a family of six IGF binding proteins (IGFBPs) and specific proteases, the objective was to determine the effects of age and estrogen disruption on expression of IGFs, IGFBPs and pregnancy-associated plasma protein A (PAPP-A or IGFBP-4 protease) in the ovine uterus. In Study O...
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Leptin, a recently-discovered hormonal product of the obese gene, circulates in the blood at levels paralleling those of fat reserves and regulates satiety and improves reproductive performance if injected into mice lacking circulating... more
Leptin, a recently-discovered hormonal product of the obese gene, circulates in the blood at levels paralleling those of fat reserves and regulates satiety and improves reproductive performance if injected into mice lacking circulating leptin. Therefore, we tested the hypothesis that ...
Research Interests: Endocrinology, Obesity, Cell Division, Biological Sciences, Progesterone, and 15 moreInsulin, Female, Animals, Leptin, Proteins, Cattle, Ovary, Granulosa Cells, Estradiol, Follicle stimulating hormone, Radioimmunoassay, Reproductive Performance, aromatase, Cell count, and Medical and Health Sciences
Endothelins are a group of vasoactive 21 amino acid peptides reported to play roles in steroidogenesis, folliculogenesis, and ovulation (Bridges et al. 2012 Life Sci. 91, 501–506). Nevertheless, the role of endothelins in regulating... more
Endothelins are a group of vasoactive 21 amino acid peptides reported to play roles in steroidogenesis, folliculogenesis, and ovulation (Bridges et al. 2012 Life Sci. 91, 501–506). Nevertheless, the role of endothelins in regulating steroidogenesis in the bovine species requires further investigation. Thus, the objective of this study was to investigate the effects of endothelin 1 (ET-1) and endothelin 2 (ET-2) on bovine granulosa cell (GC) steroidogenesis. Bovine ovaries were obtained from a local abattoir. Follicular fluid was aspirated from small (1–5 mm) follicles and GC were isolated and exposed to various treatments (ET-1, ET-2, or ET-1 plus ET-2 with FSH and with or without insulin-like growth factor-1). In replicated experiments, culture medium was removed and analysed for steroid production via radioimmunoassay. Granulosa cells were either harvested with trypsin and counted using a Coulter Counter or collected with Trizol for RNA extraction and quantification via real-time ...
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To determine whether the hormonal regulation of IGF-I production differs between granulosa and thecal cells in cattle, granulosa and thecal cells from bovine follicles were collected, cultured for 2 d in medium containing 10% fetal calf... more
To determine whether the hormonal regulation of IGF-I production differs between granulosa and thecal cells in cattle, granulosa and thecal cells from bovine follicles were collected, cultured for 2 d in medium containing 10% fetal calf serum, washed, and then treated for an additional 24 h in serum-free medium with various hormones. In Exp. 1, granulosa cells were treated with 0 or 100 ng/mL of insulin and(or) 50 ng/mL of follicle-stimulating hormone (FSH), insulin plus 10 ng/mL of epidermal growth factor, or insulin plus 10 ng/mL of basic fibroblast growth factor. In Exp. 2, thecal cells were treated as described in Exp. 1 except that 100 ng/mL of luteinizing hormone (LH) was used instead of 50 ng/mL of FSH. In Exp. 3, granulosa and thecal cells were treated with 0 or 30 ng/mL of cortisol with or without 100 ng/mL of insulin, 300 pg/mL of glucagon, or glucagon plus insulin. In Exp. 4, granulosa and thecal cells were treated with 0 or 300 ng/mL of estradiol with or without 100 ng/m...
Research Interests:
Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected... more
Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PGF2alpha on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PGF2alpha. Jugular vein blood was collected from each animal at PGF2alpha injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small (< or = 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large (> or = 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone ref...
Research Interests:
Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five... more
Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) x 1/2 F (B x F), 1/2 F x 1/2 C (F x C), 1/2 B x 1/2 C (B x C). Composite III ewes were a Columbia x Suffolk x Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), B x F (n = 6), F x C (n = 3), and B x C (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large (> or = 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in B x C and B x F ewes than in C or F x C ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three...
Research Interests: Animal Science, Biological Sciences, Progesterone, Animal, Female, and 15 moreOvulation, Animals, Hormones, Ovarian Follicle, Base Sequence, Ovary, Luteinizing Hormone, Follicular Fluid, Estradiol, Follicle stimulating hormone, Ovulation rate, Radioimmunoassay, Insulin Like Growth Factor, Molecular Sequence Data, and Follicular phase
Studies in cattle assessing changes in number and size of antral follicles, concentrations of estradiol, androgens and progesterone in serum and follicular fluid, and numbers of gonadotropin receptors per follicle during repetitive... more
Studies in cattle assessing changes in number and size of antral follicles, concentrations of estradiol, androgens and progesterone in serum and follicular fluid, and numbers of gonadotropin receptors per follicle during repetitive estrous cycles and postpartum anestrus are reviewed. The rate of growth of small follicles (1 to 3 mm) into larger follicles increases as the estrous cycle progresses from d 1 to 18 (d 0 = estrus). Size of the largest antral follicle present on the ovary also increases with advancement of the estrous cycle. Most large follicles (greater than 10 mm) persist on the ovarian surface for 5 d or more between d 3 and 13 of the bovine estrous cycle. After d 13, most of these large follicles are replaced more frequently by new growing follicles (turnover) with an increased probability for recruitment of the ovulatory follicle after d 18. More research is needed to determine the time required for growth of bovine follicles from small to large antral size and evoke ...