scholarly journals The effect of a direct arterial infusion of insulin and glucose on the ovarian secretion rates of androstenedione and oestradiol in ewes with an autotransplanted ovary

1999 ◽  
Vol 163 (3) ◽  
pp. 531-541 ◽  
Author(s):  
JA Downing ◽  
J Joss ◽  
RJ Scaramuzzi
Keyword(s):  
Ovarian Function ◽  
Ovarian Follicle ◽  
Plasma Concentrations ◽  
Ovulation Rate ◽  
Follicle Development ◽  
Short Term ◽  
Arterial Infusion ◽  
Follicle Selection ◽  
Metabolic Hormone ◽  
Secretion Rates

Improving ewe nutrition even for short periods will increase ovulation rate. The increased nutrients must in some way affect the number of follicles that develop to the pre-ovulatory stage. One possible mechanism is that a nutrient or a metabolic hormone that responds to nutrition might act directly on the ovary to influence follicle development and/or follicle selection. In the study described here, insulin and glucose, alone or together, were infused directly into the ovarian artery of ewes with an autotransplanted ovary, for 13.5 h on day 11 of the oestrous cycle. The pattern of androstenedione and oestradiol secretion in response to a GnRH-stimulated LH pulse was measured 2.5 h before and 12.5 h and 24.5 h after the start of the infusion. Glucose or insulin infused alone had no effect on the secretion of androstenedione and oestradiol. However, when infused together, they decreased significantly the secretion of androstenedione and, to a lesser extent, oestradiol. We suggest that the sudden availability of additional glucose and insulin increases insulin-stimulated glucose uptake by the follicle. This leads to an inhibition of LH-stimulated steroidogenesis by the ovarian follicle which occurs in the absence of any detectable changes in circulating plasma concentrations of FSH. These results show that insulin and glucose act together to influence ovarian function directly and suggest that the effects of short-term nutrition on ovulation rate may be mediated by a direct ovarian action of insulin and glucose.

A model for follicle selection and the determination of ovulation rate in the ewe

1993 ◽  
Vol 5 (5) ◽  
pp. 459 ◽  
Author(s):  
RJ Scaramuzzi ◽  
NR Adams ◽  
DT Baird ◽  
BK Campbell ◽  
JA Downing ◽  
...  
Keyword(s):  
Final Section ◽  
Ovarian Follicle ◽  
Ovulation Rate ◽  
Follicle Development ◽  
Anatomical Changes ◽  
Multiple Ovulation ◽  
Molecular Endocrinology ◽  
Further Development ◽  
Follicle Selection

A model for folliculogenesis is proposed that is based as far as possible on a knowledge of physiological, rather than anatomical, changes taking place during follicle development. The model is therefore functional, rather than descriptive, and consists of five classes of follicles that have been defined by their dependency and sensitivity to gonadotrophins. These classes are: primordial, committed, gonadotrophin-responsive, gonadotrophin-dependent and ovulatory. The model is an attempt to encourage discussion and to promote the integration of morphological models of folliculogenesis with recent advances in the molecular endocrinology of the ovarian follicle. Two hypotheses for the mechanisms that determine ovulation rate are developed in light of the model. In the first, multiple ovulation results when the viability of gonadotropin-dependent follicles is enhanced. In the second, multiple ovulation is caused by increasing the number of gonadotrophin-responsive follicles available for further development; this results from the increasing rate of folliculogenesis and the throughput of follicles. The final section of this paper examines how these two hypothetical mechanisms, which are not mutually exclusive, appear to account for most of the known genetical and environmental effects on ovulation rate of sheep. In particular, the effects of nutrition, genotype, exogenous gonadotrophins, immunity to both oestrogens and androgens, and immunity to inhibin are discussed.

scholarly journals Follicle development, endocrine profiles and ovulation rate in adult Merino ewes: effects of early nutrition (pre- and post-natal) and supplementation with lupin grain

Reproduction ◽  
2014 ◽  
Vol 147 (1) ◽  
pp. 101-110 ◽  
Author(s):  
C Viñoles ◽  
B L Paganoni ◽  
K P McNatty ◽  
D A Heath ◽  
A N Thompson ◽  
...  
Keyword(s):  
Early Life ◽  
Ovarian Function ◽  
Ovulation Rate ◽  
Aromatase Activity ◽  
Follicle Development ◽  
Short Term ◽  
Antral Follicles ◽  
Cell Numbers ◽  
Metabolic Hormones ◽  
The Third

In adult ewes, we tested whether ovarian function, including the response to short-term supplementation, was affected by the nutrition of their mothers during the pre-/post-natal period. A 2×2 factorial design was used with nutrition in early life (low or high) and a 6-day supplement (with or without) as factors. All ewes received three prostaglandin (PG) injections 7 days apart, and the supplement (lupin grain) was fed for 6 days from 2 days after the second until the third PG injection. We measured reproductive and metabolic hormones, studied follicle dynamics (ultrasonography), and evaluated granulosa cell numbers, aromatase activity and oestradiol (E2) concentrations in follicular fluid in healthy follicles at days 3 and 7 of supplementation. Ovulation rate was increased by 25% by exposure to high pre-/post-natal nutrition (1.5 vs 1.2; P<0.05), in association with a small decrease in FSH concentrations (P=0.06) and a small increase in insulin concentrations (P=0.07). The number of healthy antral follicles was not affected. Acute supplementation increased the number of granulosa cells (3.7±0.2 vs 3.0±0.2 million; P<0.05) in the largest follicle, and the circulating concentrations of E2 (4.6±0.3 vs 3.9±0.3 pmol/l; P<0.05) and glucose (3.4±0.03 vs 3.3±0.03 mmol/l; P<0.01). Both early life nutrition and acute supplementation appear to affect ovulation rate through changes in glucose–insulin homoeostasis that alter follicular responsiveness to FSH and therefore E2–FSH balance.

scholarly journals An epigenetic switch repressingTet1in gonadotropes activates the reproductive axis

2017 ◽  
Vol 114 (38) ◽  
pp. 10131-10136 ◽  
Author(s):  
Yahav Yosefzon ◽  
Cfir David ◽  
Anna Tsukerman ◽  
Lilach Pnueli ◽  
Sen Qiao ◽  
...  
Keyword(s):  
Ovarian Function ◽  
Ovarian Follicle ◽  
Gene Promoter ◽  
Follicle Development ◽  
Mrna Levels ◽  
Epigenetic Switch ◽  
Ovarian Follicle Development ◽  
Reproductive Axis ◽  
Poorly Differentiated ◽  
Tet Enzymes

The TET enzymes catalyze conversion of 5-methyl cytosine (5mC) to 5-hydroxymethyl cytosine (5hmC) and play important roles during development. TET1 has been particularly well-studied in pluripotent stem cells, butTet1-KO mice are viable, and the most marked defect is abnormal ovarian follicle development, resulting in impaired fertility. We hypothesized that TET1 might play a role in the central control of reproduction by regulating expression of the gonadotropin hormones, which are responsible for follicle development and maturation and ovarian function. We find that all three TET enzymes are expressed in gonadotrope-precursor cells, butTet1mRNA levels decrease markedly with completion of cell differentiation, corresponding with an increase in expression of the luteinizing hormone gene,Lhb. We demonstrate that poorly differentiated gonadotropes express a TET1 isoform lacking the N-terminal CXXC-domain, which repressesLhbgene expression directly and does not catalyze 5hmC at the gene promoter. We show that this isoform is also expressed in other differentiated tissues, and that it is regulated by an alternative promoter whose activity is repressed by the liganded estrogen and androgen receptors, and by the hypothalamic gonadotropin-releasing hormone through activation of PKA. Its expression is also regulated by DNA methylation, including at an upstream enhancer that is protected by TET2, to allowTet1expression. The down-regulation of TET1 relieves its repression of the methylatedLhbgene promoter, which is then hydroxymethylated and activated by TET2 for full reproductive competence.

scholarly journals Involvement of miRNAs in equine follicle development

Reproduction ◽  
2013 ◽  
Vol 146 (3) ◽  
pp. 273-282 ◽  
Author(s):  
S N Schauer ◽  
S D Sontakke ◽  
E D Watson ◽  
C L Esteves ◽  
F X Donadeu
Keyword(s):  
Cell Survival ◽  
Granulosa Cells ◽  
Follicular Fluid ◽  
Ovarian Follicle ◽  
Follicle Development ◽  
Previous Evidence ◽  
Ovarian Follicle Development ◽  
Fluid Levels ◽  
Follicle Selection

Previous evidence fromin vitrostudies suggests specific roles for a subset of miRNAs, including miR-21, miR-23a, miR-145, miR-503, miR-224, miR-383, miR-378, miR-132, and miR-212, in regulating ovarian follicle development. The objective of this study was to determine changes in the levels of these miRNAs in relation to follicle selection, maturation, and ovulation in the monovular equine ovary. In Experiment 1, follicular fluid was aspirated during ovulatory cycles from the dominant (DO) and largest subordinate (S) follicles of an ovulatory wave and the dominant (DA) follicle of a mid-cycle anovulatory wave (n=6 mares). Follicular fluid levels of progesterone and estradiol were lower (P<0.01) in S follicles than in DO follicles, whereas mean levels of IGF1 were lower (P<0.01) in S and DA follicles than in DO follicles. Relative to DO and DA follicles, S follicles had higher (P≤0.01) follicular fluid levels of miR-145 and miR-378. In Experiment 2, follicular fluid and granulosa cells were aspirated from dominant follicles before (DO) and 24 h after (L) administration of an ovulatory dose of hCG (n=5 mares/group). Relative to DO follicles, L follicles had higher follicular fluid levels of progesterone (P=0.05) and lower granulosa cell levels ofCYP19A1andLHCGR(P<0.005). Levels of miR-21, miR-132, miR-212, and miR-224 were increased (P<0.05) in L follicles; this was associated with reduced expression of the putative miRNA targets,PTEN,RASA1, andSMAD4. These novel results may indicate a physiological involvement of miR-21, miR-145, miR-224, miR-378, miR-132, and miR-212 in the regulation of cell survival, steroidogenesis, and differentiation during follicle selection and ovulation in the monovular ovary.

scholarly journals Effect of GnRH treatment following a short-term estrous induction protocol on estrus and ovulation in Saanen goats, during the transitional period

2021 ◽  
Vol 71 (4) ◽  
pp. 2569
Author(s):  
I. DOGAN ◽  
M. B. TOKER ◽  
S. ALCAY ◽  
D. UDUM KUCUKSEN
Keyword(s):  
Transition Period ◽  
Plasma Concentrations ◽  
Physiological Saline ◽  
Transitional Period ◽  
Follicle Development ◽  
Estrus Cycle ◽  
Short Term ◽  
Pooled Data ◽  
Buserelin Acetate ◽  
Synchronization Protocol

The objective of this study was to compare the effect on the ovulation time and estrus parameters of a GnRH agonist (buserelin acetate) administered 24 or 36 h following a short-term estrus induction and synchronization treatment in non-lactating Saanen goats during the transitional period. Goats received 20 mg FGA sponges for 6 days plus 300 IU eCG and 125 μg d-cloprostenol 24 h prior to sponge removal. After removal of the sponges, goats were given either 1 ml physiological saline (0.9% NaCI) solution (Group1; n = 9) after 12 h, 0.004 mg GnRH (Group2; n = 10) after 24 h or 0.004 mg GnRH (Group3; n = 10) after 36 h. The follicle development and ovulation in the ovaries were monitored by transrectal ultrasonography starting from the sponge application until the fifth day of the estrus cycle. Blood samples were collected on the same days to determine the plasma concentrations of progesterone (P4) and estradiol (E2). No statistical differences among groups were detected in any synchronization parameters, ultrasonic evaluations and plasma P4 and E2 concentrations. The evaluation of pooled data showed that the response of Saanen goats to treatments was comparable to the results of other published trials. Results of this study indicate that administration of GnRH at 24 h or 36 h after sponge removal, at the end of a short estrus induction and synchronization protocol, does not affect plasma P4 and E2 concentrations, estrus parameters and ovulation time in goats, during the transition period.

scholarly journals Effect of bovine somatotropin (growth hormone) treatment on gonadotropin profiles and ovarian follicle populations during the postpartum period in beef cows in low body condition

1993 ◽  
Vol 1993 ◽  
pp. 89-89
Author(s):  
L.P. Andrade ◽  
S.M. Rhind ◽  
I.A. Wright ◽  
S.R. McMillen ◽  
T.K. Whyte
Keyword(s):  
Growth Hormone ◽  
Body Condition ◽  
Growth Hormone Treatment ◽  
Ovarian Function ◽  
Post Partum ◽  
Ovarian Follicle ◽  
Hormone Treatment ◽  
Beef Cows ◽  
Follicle Development ◽  
Ovarian Follicle Development

Cows in low body condition exhibit a prolonged postpartum anoestrous period and a delayed return to normal follicular function (Prado et al 1990). Previous studies have shown that the effects of body condition on gonadotrophin profiles are inconsistent (Wright et al 1990; Rhind et al 1992) indicating that the effects of body condition on ovarian function cannot be explained by changes in gonadotrophin profiles alone. Since nutritional state influences growth hormone profiles which in turn can affect ovarian function (Gong et al 1991), it was postulated that the effects of body condition on the duration of postpartum anoestrus could be mediated through changes in profiles of this hormone.The aim of the present study was to determine the effect of growth hormone on ovarian follicle development and associated gonadotrophin profiles in post-partum beef cows.

Dietary protein intake during the oestrous cycle does not alter the ovulation rate in gilts

2004 ◽  
Vol 16 (6) ◽  
pp. 589 ◽  
Author(s):  
César A. Mejia-Guadarrama ◽  
Armelle Prunier ◽  
Hélène Quesnel
Keyword(s):  
Dietary Protein ◽  
Protein Intake ◽  
Plasma Concentrations ◽  
Prostaglandin F2α ◽  
Protein Restriction ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Short Term ◽  
Nutritional Treatment ◽  
Digestible Energy

The effect of protein intake on ovulation rate was investigated in cross-bred gilts. On Day 14 of the third oestrous cycle, luteolysis was induced by injection of an analogue of prostaglandin F2α. The ovulation rate was recorded when gilts were killed on Day 27. In the first experiment, nutritional treatment was applied from Day 14 to Day 27. Gilts were fed diets providing the same amount of digestible energy, but containing either a low, medium or high amount of dietary protein. Protein restriction linearly decreased plasma concentrations of urea (P < 0.001) and had no effect on plasma concentrations of insulin-like growth factor-I and leptin measured at Day 27 (P > 0.1). Protein restriction did not influence ovulation rate (mean (± s.e.m.) 17.0 ± 0.4; P > 0.1). In the second experiment, the nutritional treatment was applied from Day 5 until Day 27. Gilts received the same amount of digestible energy and either a low or a high amount of protein, as in Experiment 1. A third group of gilts received the high amount of protein and also more digestible energy. The ovulation rate did not differ between the three groups of gilts. These data indicate no effect of short-term dietary protein restriction on ovulation rate in cyclic gilts.

scholarly journals Short-term nutritional supplementation of ewes in low body condition affects follicle development due to an increase in glucose and metabolic hormones

Reproduction ◽  
2005 ◽  
Vol 129 (3) ◽  
pp. 299-309 ◽  
Author(s):  
C Viñoles ◽  
M Forsberg ◽  
G B Martin ◽  
C Cajarville ◽  
J Repetto ◽  
...  
Keyword(s):  
Body Condition ◽  
Oestrous Cycle ◽  
Nutritional Supplementation ◽  
Ovulation Rate ◽  
Follicle Development ◽  
Short Term ◽  
Metabolic Hormones ◽  
The Third ◽  
Short Period ◽  
Igf I

This study tested whether the effects of a short period of nutritional supplementation given to ewes during the luteal phase on follicle development and ovulation rate is associated with an increase in circulating concentrations of FSH, glucose or metabolic hormones. Oestrus was synchronised with two prostaglandin injections given 9 days apart and the supplement consisted of corn grain and soybean meal. Corriedale ewes with low body condition were randomly assigned to 2 groups: the control group (C; n = 10) received a maintenance diet while the short-term supplemented group (STS; n = 10) received double the maintenance diet over days 9 to 14 of the oestrous cycle (day 0 = ovulation). Ovaries were examined daily by ultrasound and blood was sampled three times a day during the inter-ovulatory interval for measuring reproductive and metabolic hormones. On days 9, 11 and 14 of the oestrous cycle, half of the ewes from each group (n = 5) were bled intensively to determine the concentrations of glucose, insulin, IGF-I and leptin. Plasma FSH, progesterone, oestradiol and androstenedione concentrations were similar among groups. Dietary supplementation increased plasma insulin concentrations from the first to the sixth day of supplementation and increased glucose concentrations on the third day, compared with control ewes. Plasma leptin concentrations were higher in STS ewes from the second to the fifth day of supplementation. The pattern of IGF-I concentrations was similar among groups. In STS ewes, the nutritional treatment prolonged the lifespan of the last non-ovulatory follicle, so fewer follicular waves developed during the cycle. In STS ewes, increased concentrations of glucose, insulin and leptin one day before ovulatory wave emergence were associated with increased numbers of follicles growing from 2 to 3 mm and with stimulation of the dominant follicle to grow for a longer period. We suggest that the mechanism by which short-term nutritional supplementation affects follicle development does not involve an increase in FSH concentrations, but may involve responses to increased concentrations of glucose, insulin and leptin, acting directly at the ovarian level. This effect is acute, since concentrations of all three substances decrease after reaching peak values on the third day of supplementation. The status of follicle development at the time of maximum concentrations of glucose and metabolic hormones may be one of the factors that determines whether ovulation rate increases or not.

Effects of active immunization against inhibin and androstenedione, separately or together, on hormone profiles, ovarian follicle populations and ovulation rate in heifers

1991 ◽  
Vol 1991 ◽  
pp. 17-17
Author(s):  
S.M. Rhind ◽  
S.R. Schemm ◽  
B.D. Schanbacher
Keyword(s):  
Ovarian Follicle ◽  
Pulse Frequency ◽  
Active Immunization ◽  
Follicular Phase ◽  
Ovulation Rate ◽  
Follicle Development ◽  
Ovarian Follicle Development ◽  
Endocrine Status ◽  
Ovulatory Follicles ◽  
Follicle Maturation

It was postulated that the induction of twin ovulations in cattle may require a combination of two appropriate stimuli. The first putative requirement is an increase in the circulating FSH concentrations and/or a decrease in inhibin concentrations to induce the development of additional potentially ovulatory follicles. The second putative requirement is an increase in LH pulse frequency during the follicular phase of the cycle to enhance the stimulus for follicle maturation and ovulation. On the basis of studies reported in the literature, it was suggested that such stimuli may be provided by immunization against inhibin and against a steroid hormone such as androstenedione, respectively. This experiment was designed to determine the effects of immunization against androstenedione and inhibin, either separately or together on the endocrine status of heifers and on the associated patterns of ovarian follicle development and ovulation rate.

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