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

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.

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Effects of bovine somatotrophin (bST) on ovarian function in post-partum beef cows

Reproduction Fertility and Development ◽

10.1071/rd9960951 ◽

1996 ◽

Vol 8 (6) ◽

pp. 951 ◽

Cited By ~ 18

Author(s):

LP Andrade ◽

SM Rhind ◽

IA Wright ◽

SR McMillen ◽

PJ Goddard ◽

...

Keyword(s):

Ovarian Function ◽

Post Partum ◽

Ovarian Follicle ◽

Beef Cows ◽

Ovarian Follicle Development ◽

Factor I ◽

Glucose Injection ◽

Igf I ◽

And Function ◽

Bovine Somatotrophin

The effects of bovine somatotrophin (bST) on ovarian follicle development and function and associated gonadotrophin profiles during the first nine weeks post partum were investigated in beef cows. Thirty-two cows (Shorthorn x Galloway) in moderately low body condition (BC) at calving were fed to maintain BC thereafter. At Weeks 2, 4, 6 and 8 post partum, animals were injected with 320 mg bovine somatotrophin (bST) (T, treated; n = 17) or with the carrier oil only (C, control; n = 15). Ovulation occurred in 4 of 17 T cows and 0 of 15 C cows (P = 0.10) by nine week post partum. Treatment with bST did not affect the numbers of small (3-8 mm in diameter) or large (> 8 mm in diameter) follicles or the granulosa cell populations but enhanced the oestradiol (P < 0.05) and insulin-like growth factor-I (IGF-I) content (P < 0.01) of large follicles by nine weeks post partum. It did not significantly affect the testosterone concentrations of large follicles. Circulating concentrations of growth hormone (GH) and IGF-I were higher in T cows than in C cows (P < 0.001) but were unrelated to gonadotrophin profiles or gonadotrophin receptor concentrations in the follicles. At Week 8, plasma insulin concentrations were higher in T cows than in C cows both before (P < 0.05) and after (P < 0.05) glucose injection. It is concluded that GH may play an important role in mediating the effects of nutritional state on ovarian function during the post-partum period, possibly through alteration of intrafollicular IGF-I concentrations.

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An epigenetic switch repressingTet1in gonadotropes activates the reproductive axis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1704393114 ◽

2017 ◽

Vol 114 (38) ◽

pp. 10131-10136 ◽

Cited By ~ 15

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.

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Effect of GnRH pulse infusion on LH profiles and ovarian follicle populations at 7 weeks post-partum in beef cows in different body conditions

Proceedings of the British Society of Animal Production (1972) ◽

10.1017/s0308229600023059 ◽

1992 ◽

Vol 1992 ◽

pp. 196-196

Author(s):

L. Pinto Andrade ◽

S.M. Rhind ◽

L.A. Wright ◽

S.R. McMillen ◽

T.K. Whyte

Keyword(s):

Body Condition ◽

Post Partum ◽

Ovarian Follicle ◽

Follicular Development ◽

Beef Cows ◽

Ovarian Follicles ◽

Normal Process

Previous studies have indicated that low body condition (LBC) at calving increases the duration of the postpartum anoestrous period in suckling beef cows (Henricks et al 1986; Wright et al 1987). The results of recent experiments also suggest that animals in LBC have a reduced incidence of LH pulses (Wright et al 1990) which is associated with a reduction in the incidence of large, oestrogenic, potentially ovulatory ovarian follicles (Prado et al 1990).An experiment was designed to determine a) whether or not the normal process of follicular development can be accelerated in LBC cows by infusion of pulses of GnRH, so that their postpartum anoestrous period was as short as that of cows in HBC and b) the effect of GnRH pulse infusions on associated gonadotropin profiles.

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Ovarian function in ewes made hypogonadal with GnRH antagonist and stimulated with FSH in the presence or absence of low amplitude LH pulses

Journal of Endocrinology ◽

10.1677/joe.0.1560213 ◽

1998 ◽

Vol 156 (1) ◽

pp. 213-222 ◽

Cited By ~ 33

Author(s):

BK Campbell ◽

H Dobson ◽

RJ Scaramuzzi

Keyword(s):

Gnrh Antagonist ◽

Ovarian Function ◽

Ovarian Follicle ◽

Venous Blood ◽

Hormone Secretion ◽

Follicle Development ◽

Ovarian Follicle Development ◽

Antral Follicles ◽

Low Amplitude ◽

Experimental Group

This study examined the effect of LH pulses, of similar amplitude and frequency to those found in the luteal phase, on the pattern of hormone secretion and follicle development in GnRH antagonist-suppressed ewes stimulated with exogenous FSH. This experiment was conducted on ewes with ovarian autotransplants in a continuous study. Follicle development was suppressed in 18 ewes by 3 weeks of GnRH antagonist treatment (50 micrograms/kg per 4 days s.c.), and was then stimulated by infusion of ovine (o)FSH (5 micrograms NIADDK-oFSH-16/h i.v.) for 3 days. In addition to FSH, 10 animals received pulses of LH (2.5 micrograms NIADDK-oLH-26 i.v.) every 4 h for the entire period of the FSH infusion. The follicle population was determined by daily ultrasound. Samples of ovarian and jugular venous blood were collected at 4-h intervals over the period of the FSH infusion and there were three periods of intensive blood sampling (15-min intervals for 2.5 h at 24, 48 and 72 h after the start of the FSH infusion) when the steroidogenic capacity of the follicles in all 18 ewes was tested around an LH challenge (2.5 micrograms i.v.). GnRH antagonist treatment resulted in a 57% decrease in FSH concentrations and prevented ovarian follicle development beyond 3 mm in diameter. Infusion of FSH resulted in a 60% increase in FSH concentrations and stimulated the development of large antral follicles and a coincident increase in ovarian androstenedione, inhibin and oestradiol secretion in both experimental groups. In the absence of 4-hourly LH pulses basal steroid secretion was negligible (< 1 ng/min; P < 0.001). Daily LH challenges, however, revealed no difference in the steroidogenic capacity of the follicle population in either experimental group. Similarly, LH pulses had no effect on the growth rate and number of antral follicles stimulated by FSH infusion, or the pattern of ovarian inhibin secretion. In conclusion, these results show that while FSH alone can stimulate the development of ovulatory sized follicles in ewes made hypogonadal with GnRH antagonist, physiological patterns of LH stimulation have no deleterious effects on FSH-stimulated follicle development and are essential for normal steroidogenesis.

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Ovarian follicle populations, steroidogenicity and micromorphology at 5 and 9 weeks post partum in beef cows in two levels of body condition

Animal Science ◽

10.1017/s0003356100005195 ◽

1990 ◽

Vol 51 (1) ◽

pp. 103-108 ◽

Cited By ~ 20

Author(s):

R. Prado ◽

S. M. Rhind ◽

I. A. Wright ◽

A. J. F. Russel ◽

S. R. McMillen ◽

...

Keyword(s):

Body Condition ◽

Post Partum ◽

Ovarian Follicle ◽

Live Weight ◽

Beef Cows ◽

Lower Number ◽

The Body ◽

Lh Pulsatility ◽

Body Condition Scores

ABSTRACTThe effect of body condition at calving on ovarian follicle characteristics during post-partum anoestrus was studied in 38 suckling Blue-Grey cows with mean body-condition scores of 2·80 (s.e. 0·05) (H) or 2·35 (s.e. 0·05) (L) at calving and fed so that they maintained live weight and body condition during lactation. Cows of each level of body condition were ovariectomized at either 5 or 9 weeks after calving and follicles ≥3 mm in diameter were dissected out and incubated in a medium (Medium 199) for 2 h. Follicle incubates were assayed for progesterone, testosterone and oestradiol. L cows had fewer follicles ≥3 mm in diameter than H cows (24·1 v. 44·9; P < 0·05) at 5 weeks post partum due to a lower number of small (3 to 4 mm) follicles (12·9 v. 30·6; P < 0·05). At 9 weeks there was no effect of body condition on mean numbers of follicles (38·1 v. 40·4; P > 0·05). The proportions of healthy, intermediate and atretic follicles in all cows were 0·35, 0·20 and 0·45 respectively; these proportions were not affected by body condition or time of ovariectomy. Body condition did not affect the overall mean capacity of the cultured follicles to produce oestradiol or progesterone in vitro but testosterone production was higher in follicles from H than L cows (6406 v. 5206 pg/h; P < 0·05). However, at 9 weeks post partum a greater proportion of H than L cows had a large (>8 mm), healthy, highly oestrogenic follicle (4/8 v. 1/7; P = 0·18).At 9 weeks post partum, the four large, healthy, oestrogen-active follicles (those secreting >250 pg/h) from H cows were approximately 11-fold more oestrogenic than the single comparable follicle from L cows (7100 v. 635 pg/h; P > 0·05). There was little difference at week 5 post partum: 3288 and 2785 pg/h (P > 0·05) for H and L cows respectively. Oestrogen-active follicles from H cows were significantly more oestrogenic at 9 than 5 weeks post partum (5807 v. 3021 pg/h; P < 0·05). The results suggest that the body condition-related reduction in the number and steroidogenic capacity of large oestrogenic follicles in post-partum cows may be associated with a reduction in LH pulsatility.

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