Genetics and Physiology of Follicle Recruitment and Maturation during Seasonal Anoestrus

Webb, Robert I.; Gauld, I. K.

doi:10.1007/978-94-009-5026-9_4

Cited by 19 publications

(11 citation statements)

References 15 publications

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“…In agreement with results in other breeds of sheep (Webb and Gauld, 1985;Driancourt el al, 1988Driancourt el al, , 1990Webb et al, 1989), the study reported here shows that ewes in Booroola Scottish Blackface populations can be induced to ovulate, during both seasonal anoestrus and the luteal phase of the oestrous cycle, with a single challenge of hCG (750 iu). The number of induced ovulations was generally representative of the genotype and supported our previous hypothesis that the mechanism controlling the number of follicles maturing to the ovulatory stage is operative throughout the year in sheep, including seasonal anoestrus .…”

Section: Introductionsupporting

confidence: 92%

The effect of the Booroola (FecB) gene on peripheral FSH concentrations and ovulation rates during oestrus, seasonal anoestrus and on FSH concentrations following ovariectomy in Scottish Blackface ewes

Boulton

Haley²,

Springbett³

et al. 1995

Reproduction

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Section: Introductionsupporting

confidence: 92%

The effect of the Booroola (FecB) gene on peripheral FSH concentrations and ovulation rates during oestrus, seasonal anoestrus and on FSH concentrations following ovariectomy in Scottish Blackface ewes

Boulton

Haley²,

Springbett³

et al. 1995

Reproduction

Self Cite

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“…The mean of the two perpendicular diameters was used. After dissection, individual follicles were incubated in 1 ml medium (Medium 199 buffered with 20 mmol HEPES/1 and containing Hank's salts, 0-35 g sodium bicarbonate/1 and 2 mmol glutamine/1; Flow Laboratories, Irvine, Strathclyde) at 37°C for 2 h. The steroid production from follicles over this time had been shown to reflect both in-vivo steroid pro¬ duction (Webb & Gauld, 1985) and the steroid con¬ centration in follicular fluid (Webb & Gauld, 1987). Medium was then removed and replaced with medium containing ovine LH (NIADDK-LH-S23; NIH, Bethesda, MD, U.S.A.) and the incubation con¬ tinued for a further 2 h. At the end of the second incu¬ bation period, medium was removed and stored with the first incubation medium at -20°C until assayed for oestradiol and testosterone.…”

Section: Methodsmentioning

confidence: 99%

Effect of gonadotrophin-releasing hormone agonist-induced suppression of LH and FSH on follicle growth and corpus luteum function in the ewe

McNeilly

Fraser²

1987

Journal of Endocrinology

155

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Continuous infusion of a gonadotrophin-releasing hormone (GnRH) agonist (buserelin) by osmotic minipump from day 1 of the luteal phase in five Welsh ewes resulted in a sustained suppression of plasma concentrations of FSH which increased three- to eightfold within 2 days after the end of infusion 29 days later. Plasma concentrations of LH increased three- to eightfold over the first 5 days of infusion and then became basal and non-pulsatile until 1 day after the end of infusion. Duration of the luteal phase and plasma concentrations of progesterone were not significantly different in control and treated ewes. Pulses of LH in control ewes were followed by increases in concentrations of progesterone in samples collected at 10-min intervals for 7 h on days 10 and 14 of the luteal phase. However, progesterone was also released in a pulsatile manner in the absence of LH pulses in both control and GnRH agonist-treated ewes. After natural luteolysis, no ovulation or corpus luteum function occurred in treated ewes up to 15 days after the end of treatment on day 29, even though oestrus, indicating follicular development and oestrogen secretion, had occurred 8-11 days after treatment ended. After 30 days of infusion the ovaries of GnRH agonist-treated ewes contained no follicles greater than 2.5 mm in diameter. In follicles of 1-2 mm in diameter the basal and LH-stimulated production of oestradiol and testosterone in vitro were similar in both control and GnRH agonist-treated ewes, and a similar proportion of these follicles was oestrogenic (greater than 370 mol oestradiol per follicle) in GnRH agonist-treated and control ewes. These results show (1) that progesterone secretion by the corpus luteum of the ewe can be sustained in the presence of basal concentrations but absence of pulsatile secretion of LH, and progesterone is released in a pulsatile manner whether or not LH pulses are present, (2) that follicular development beyond 2.5 mm in diameter in the ewe is dependent upon adequate stimulation by both LH and FSH and (3) that the continuous infusion of GnRH agonist is a simple method for providing reproducible suppression of LH and FSH and follicular development in the ewe to allow the study of gonadotrophin action on the ovary in vivo.

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“…However, in the luteal phase significantly (P < 0.05) more of these follicles were oestrogenic (FFE2 concentration > 10 µg/l) and potentially ovulatory (FFE2 concentration > 50 µg/l; Webb & Gauld 1985). In the follicular phase there were also more oestro¬ genic and potentially ovulatory follicles in the high than low condition ewes but this just failed to reach significance (P = 0.06).…”

Section: Follicles 3= 4 MMmentioning

confidence: 50%

“…After dissection, all follicles < 4 mm were incubated in 1 ml of medium (Medium 199 buffered with 20 mmol/1 Hepes (N-2-hydroxy ethylpiperazine-N'-2-ethanesulphonic acid) and containing Hank's salts, 0.35 g sodium bicarbonate/ 1, and 2 mmol/1 glutamine; Flow Laboratories, Irvine, UK) at 37°C for 2 h ). The steroid production from follicles over this time has been shown to reflect steroid production in vivo (Webb & Gauld 1985). Medium was then removed and stored at -20°C until assayed for oestradiol and testosterone.…”

Section: Follicle Incubationsmentioning

confidence: 99%

Reduced ovarian follicular development as a consequence of low body condition in ewes

McNeilly

Jonassen

Rhind³

1987

Acta Endocrinologica

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The effect of body condition on ovarian follicular development was investigated in Scottish Blackface ewes in high and low body condition. Follicles were dissected from ovaries on days 11 and 12 of the luteal phase and 24 h after prostaglandin-induced luteal regression. Ewes in low body condition had a lower ovulation rate (low: 0.9; high: 1.8 P < 0.05) and lower mean plasma levels of FSH during both the luteal (low: 54; high: 72 \g=m\g/l ) and follicular (low: 34; high: 43 \g=m\g/l)phases of the cycle. Low body condition was associated with a reduced number of large ([2A7E]4 mm) follicles in both the luteal and follicular phases, and in low condition a lower proportion of these follicles was oestrogenic and potentially ovulatory as assessed by follicular fluid levels of oestradiol. However, within the different oestrogenic classifications of these large follicles there were no significant differences in the steroidogenic capacity as assessed by the concentrations of either oestradiol or testosterone in follicular fluid, basal and hCG-stimulated testosterone production, thecal 125I hCG binding or basal and testosterone-stimulated oestradiol production by granulosa cells in relation to body condition. These results suggest that body condition influences ovulation rate by altering the concentration of FSH in blood, which in turn affects the number of potentially ovulatory follicles growing beyond 4 mm.Ovulation rate in the ewe is influenced by both body condition and the food intake at mating. Low body condition in hill and upland sheep is associated with a decreased ovulation rate (Gunn 1982). The endocrine mechanisms responsible for this are still unclear since previous studies have not indicated any specific difference in gonado¬ tropin levels either within (Rhind et al. 1984) or between (Land 1976; Cahill et al. 1981) breeds of ewe. More recently we have shown that ewes in low body condition have significantly lower plasma levels of both follicle-stimulating hormone (FSH) and prolactin than high body condition ewes, whereas neither the basal nor the pulsatile secretion of luteinizing hormone (LH) was differ¬ ent (Rhind & McNeilly 1986). The decrease in FSH was associated with fewer large follicles in ewes in low body condition.The present paper describes a detailed analysis of the steroidogenic capacity and LH receptor binding of ovarian follicles from low and high condition ewes to determine the functional capa¬ city of these follicles and then relate this to the difference in ovulation rate in the two body condi¬ tions. Materials and MethodsThe management of the ewes has been described in detail previously (Rhind & McNeilly 1986). Briefly, 22Scottish Blackface ewes were divided into 11 blocks of two similar ewes on the basis of body condition score (degree of fatness) and liveweight. One ewe from each block was assigned a high (target) condition score at random and the other a low (target) score. The ewes were then differently fed on hay and dried grass pellets to achieve their target condition scores (Rüssel...

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Genetics and Physiology of Follicle Recruitment and Maturation during Seasonal Anoestrus

Cited by 19 publications

References 15 publications

The effect of the Booroola (FecB) gene on peripheral FSH concentrations and ovulation rates during oestrus, seasonal anoestrus and on FSH concentrations following ovariectomy in Scottish Blackface ewes

The effect of the Booroola (FecB) gene on peripheral FSH concentrations and ovulation rates during oestrus, seasonal anoestrus and on FSH concentrations following ovariectomy in Scottish Blackface ewes

Effect of gonadotrophin-releasing hormone agonist-induced suppression of LH and FSH on follicle growth and corpus luteum function in the ewe

Reduced ovarian follicular development as a consequence of low body condition in ewes

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