Miniature ponies: 2. Endocrinology of the oestrous cycle

2008 ◽  
Vol 20 (3) ◽  
pp. 386 ◽  
Author(s):  
O. J. Ginther ◽  
M. A. Beg ◽  
A. P. Neves ◽  
R. C. Mattos ◽  
B. P. L. Petrucci ◽  
...  
Keyword(s):  
Maximum Concentration ◽  
Luteal Phase ◽  
Plasma Concentrations ◽  
Oestrous Cycle ◽  
Slow Increase ◽  
Lh Surge ◽  
Ovulatory Follicle ◽  
The Future ◽  
Three Phases

Plasma concentrations of FSH, LH, oestradiol and progesterone were studied daily during 12 interovulatory intervals and 21 periovulatory periods in nine Miniature ponies. The peak of the FSH surge that was temporally associated with emergence of the future ovulatory follicle occurred when the follicle was ~9 mm, compared with a reported diameter of 13 mm in larger breeds. The ovulatory LH surge involved a slow increase between Days 13 and 18 (ovulation = Day 0; 0.6 ± 0.1 ng day–1), a minimal increase or a plateau on Days 18 to 21 (0.04 ± 0.1 ng day–1), and a rapid increase after Day 21 (2.2 ± 0.4 ng day–1; P < 0.0001). The end of the plateau and the beginning of the rapid increase occurred on the day of maximum concentration in the oestradiol preovulatory surge. An unexpected mean increase and decrease in LH occurred (P < 0.04) on Days 5 to 9. Concentrations of oestradiol and progesterone seemed similar to reported results in larger breeds. Results indicated that in Miniature ponies the peak of the FSH surge associated with emergence of the future ovulatory follicle occurred at a smaller diameter of the future ovulatory follicle than in larger breeds, the ovulatory LH surge increased in three phases, and the ovulatory LH surge was followed by an LH increase and decrease during the early luteal phase.

Studies of the oestrous cycle, oestrus and pregnancy in the koala (Phascolarctos cinereus)

Reproduction ◽  
2000 ◽  
pp. 49-57 ◽  
Author(s):  
SD Johnston ◽  
MR McGowan ◽  
P O'Callaghan ◽  
R Cox ◽  
V Nicolson
Keyword(s):  
Luteal Phase ◽  
Post Partum ◽  
Plasma Concentrations ◽  
External Genitalia ◽  
Oestrous Cycle ◽  
Phascolarctos Cinereus ◽  
Pregnant Females ◽  
Peripheral Plasma ◽  
The Mean ◽  
High Concentrations

As an integral part of the development of an artificial insemination programme in the captive koala, female reproductive physiology and behaviour were studied. The oestrous cycle in non-mated and mated koalas was characterized by means of behavioural oestrus, morphology of external genitalia and changes in the peripheral plasma concentrations of oestradiol and progestogen. The mean (+/- SEM) duration of the non-mated oestrous cycle and duration of oestrus in 12 koalas was 32.9 +/- 1.1 (n = 22) and 10.3 +/- 0.9 (n = 24) days, respectively. Although the commencement of oestrous behaviour was associated with increasing or high concentrations of oestradiol, there were no consistent changes in the morphology or appearance of the clitoris, pericloacal region, pouch or mammary teats that could be used to characterize the non-mated cycle. As progestogen concentrations remained at basal values throughout the interoestrous period, non-mated cycles were considered non-luteal and presumed anovulatory. After mating of the 12 koalas, six females gave birth with a mean (+/- SEM) gestation of 34.8 +/- 0.3 days, whereas the remaining six non-parturient females returned to oestrus 49.5 +/- 1. 0 days later. After mating, oestrous behaviour ceased and the progestogen profile showed a significant increase in both pregnant and non-parturient females, indicating that a luteal phase had been induced by the physical act of mating. Progestogen concentrations throughout the luteal phase of the pregnant females were significantly higher than those of non-parturient females. Parturition was associated with a decreasing concentration of progestogen, which was increased above that of basal concentrations until 7 days post partum.

Effects of treatment with a gonadotrophin-releasing hormone analogue on follicle development in dairy cows fed one of two different diets

2001 ◽  
Vol 26 (2) ◽  
pp. 451-455
Author(s):  
E.C.L. Bleach ◽  
C.L. Moore ◽  
H.J. Zeale ◽  
P.G. Knight
Keyword(s):  
Dairy Cows ◽  
Luteal Phase ◽  
Cycle Length ◽  
Crude Protein ◽  
Oestrous Cycle ◽  
Follicle Development ◽  
Releasing Hormone ◽  
Ovulatory Follicle ◽  
Metabolisable Energy ◽  
Phase Length

AbstractFollicle development occurs in two or three waves during the bovine oestrous cycle. Artificially extending the duration of ovulatory follicle dominance influences pregnancy rates in cattle, as does the interval from emergence to oestrus in dairy cows undergoing spontaneous oestrous cycles. The objectives of the presented study were to determine whether the interval from ovulatory follicle emergence to oestrus might be altered by diet and/or gonadotropin-releasing hormone (GnRH) treatment. Lactating primiparous Holstein/Friesian cows (n=21) were randomly allocated to one of two diets at calving (Diet 1, n=ll, DM 480 g/kg, metabolisable energy 12.0 MJ/kg DM crude protein 178 g/kg DM, oil B 48 g/kg DM, neutral detergent fibre 318 g/kg DM and diet 2, n=10, DM 440 g/kg, metabolisable energy 12.1 MJ/kg DM, crude protein 172 g/kg DM, oil B 40 g/kg DM, neutral detergent fibre 300 g/kg DM). From 10 days after observed oestrus (oestrus 1), ovarian follicular and luteal development was monitored by daily transrectal ultrasonography until the subsequent oestrus and ovulation. A GnRH analogue was injected (i.m.; 10 μg) 12 days after oestrus 1 in 6 cows fed diet 1 and 5 cows fed diet 2. Oestrous cycle length was longer (p<0.05) in control cows fed diet 1 than those fed diet 2. Treatment with GnRH increased (p<0.005) cycle length in cows fed diet 2 but not those fed diet 1. Increases in cycle length observed were associated with longer luteal phase length. Follicular phase length was reduced (p<0.05) by GnRH treatment in cows fed diet 1. Ovulatory follicles emerged later (p<0.05) in control cows fed diet 1 than those fed diet 2. GnRH treatment delayed (p<0.01) the emergence of the ovulatory follicle in cows fed diet 2, this delay was associated with an increase (p<0.05) in the incidence of 3 follicle waves in oestrous cycles following GnRH treatment. The interval from emergence of the ovulatory follicle to the subsequent oestrus was similar among the treatment groups. We conclude that treatment with GnRH during the mid-luteal phase may delay the emergence of the ovulatory follicle. However, the response is dependent on diet fed. Where ovulatory follicle emergence is delayed, the interval from emergence to the subsequent oestrus was unaffected since oestrous cycle length is extended.

scholarly journals Hyaluronan (HA) content, the ratio of HA fragments and the expression of CD44 in the ovine cervix vary with the stage of the oestrous cycle

Reproduction ◽  
2010 ◽  
Vol 140 (1) ◽  
pp. 133-141 ◽  
Author(s):  
K Perry ◽  
W Haresign ◽  
D C Wathes ◽  
M Khalid
Keyword(s):  
Smooth Muscle ◽  
Luteal Phase ◽  
Muscle Layer ◽  
Oestrous Cycle ◽  
The Other ◽  
Water Molecules ◽  
Lh Surge ◽  
Cd44 Expression ◽  
Complex Anatomy ◽  
Phase Group

The complex anatomy of the ovine cervix limits the success of trans-cervical artificial insemination in sheep. However, there is a degree of natural relaxation of cervix at oestrus that is accompanied by an increase in the water content. As hyaluronan (HA) has a high affinity for water molecules, in this study, we tested the hypothesis that the HA content of the cervix, the proportion of different size fragments of HA and expression of its receptor CD44 vary with the stage of the oestrous cycle. Oestrous was synchronized in 25 Welsh mountain ewes, and their cervices were collected either during luteal phase (n=8) or pre-LH (n=8) or post-LH (n=9) surge stage of the oestrous cycle. The pre-LH surge group had the highest HA content (2.96 ng/mg of cervical tissue), which was significantly (P≤0.05) higher than that observed for the post-LH surge (2.04 ng/mg) group. The luteal phase group had a mean HA content intermediate between the pre- and post-LH surge groups, and was significantly different from either. The frequency of cervical samples containing both sizes of HA fragments (small and large) was significantly higher (P≤0.05) in the pre-LH surge group compared with the luteal and the post-LH surge groups, whereas that in post-LH surge group was significantly (P≤0.05) higher than that in the luteal group. The number of cervical samples that contained only small HA fragments was significantly (P≤0.05) higher in the luteal group compared with both the pre- and post-LH surge groups, whereas the number of samples containing only large HA fragments was significantly (P≤0.05) higher in the post-LH surge group compared with the luteal or pre-LH surge groups. Overall mean expression of CD44 in the vaginal and mid regions was significantly (P≤0.001) higher than that in the uterine region, with no difference between the vaginal and mid regions of the cervix. Pattern of CD44 expression depended on the stage of the oestrous cycle. At the luteal stage, CD44 expression did not vary among epithelial, sub-epithelial, circular and longitudinal smooth muscle layers, whereas at the pre- and post-LH surge stages, the expression in the epithelial layer was significantly (P≤0.001) higher than that in the other three layers. In general, CD44 expression in the transverse smooth muscle layer was significantly (P≤0.05) lower than the expression in all the other layers at all the stages of the oestrous cycle. The results indicated that the HA varied with the steroid status. Higher HA values at a time when cervical relaxation is naturally higher may indicate its involvement in remodelling of the cervix at oestrus.

scholarly journals Effect of ram introduction on the oestrous cycle of springbok ewes (Antidorcas marsupialis)

Reproduction ◽  
2002 ◽  
pp. 509-513 ◽  
Author(s):  
DC Skinner ◽  
SD Cilliers ◽  
JD Skinner
Keyword(s):  
Maximum Concentration ◽  
Luteal Phase ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Arid Environments ◽  
Wild Ungulates ◽  
Plasma Progesterone ◽  
Before And After ◽  
Antidorcas Marsupialis

Springbok are aseasonally breeding wild ungulates that inhabit arid environments, and interest has been shown in domesticating them for agricultural purposes. The present study was conducted for husbandry purposes to determine the effect of introducing a vasectomized ram to an isolated herd of springbok ewes (n = 9). Blood was collected from ewes every third day, before and after introduction of a vasectomized ram. Ewes were subjected to the ram for 42 days. Plasma progesterone was measured by radioimmunoassay and was used to establish the stage of the oestrous cycle. After introduction of the ram, the variation in the timing of the follicular phase between ewes was clearly reduced, compressing the spread of oestrus in the springbok ewes from 11 to 3 days. In seven of the nine ewes, the ram was introduced during the luteal phase of the oestrous cycle, causing this cycle to be significantly longer in duration (P < 0.05) and to have a higher maximum concentration of progesterone (P < 0.001) than cycles before and after introduction of the ram. This finding implies that the mechanism of synchronization operates through a luteotrophic effect. These results indicate that rams may be used successfully to synchronize breeding in springbok.

Evidence that the switch from negative to positive feedback at the level of the pituitary gland is an important timing event for the onset of the preovulatory surge in LH in the ewe

1995 ◽  
Vol 145 (2) ◽  
pp. 271-282 ◽  
Author(s):  
I J Clarke
Keyword(s):  
Pituitary Gland ◽  
Negative Feedback ◽  
Luteal Phase ◽  
Bolus Injection ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Lh Surge ◽  
Small Rise ◽  
Lh Secretion

Abstract Experiments were performed to test the hypothesis that there is a negative feedback 'clamp' of ovarian hormones on the hypothalamus and pituitary gland during the follicular phase of the oestrous cycle that limits the secretion of GnRH and LH. GnRH secretion was monitored by sampling the hypophysial portal blood of ewes during the luteal phase of the oestrous cycle and either 24 h or 48 h after the induction of luteolysis by the injection of cloprostenol, a prostaglandin analogue. There was an increase in GnRH pulse frequency in the transition from the luteal to the follicular phase of the cycle. A reduction in the amplitude of GnRH pulses did not occur until 48 h after cloprostenol, suggestive of negative feedback at the level of the hypothalamus that is more profound in the latter part of the follicular phase. The responsivity of the pituitary gland to GnRH was monitored in ewes during the luteal phase of the oestrous cycle and 24 h or 48 h after cloprostenol. Injections of 250 ng or 1000 ng GnRH were given (i.v.) to ewes that had been anaesthetised to suppress endogenous secretion of GnRH and LH. Using the lower dose, the responses 48 h after cloprostenol were not significantly different from those in the luteal phase. With the higher dose of GnRH, a significant (P<0·05) increase in mean responsivity was seen 48 h after cloprostenol. There was, however, a marked variation in response, with some ewes showing profound increases in LH secretion in response to GnRH and others showing responses that were similar to those obtained during the luteal phase of the cycle. These data are interpreted to mean that the secretion of LH is 'clamped' during the follicular phase of the oestrous cycle and the 'clamp' is only released near the time of the preovulatory LH surge. To test whether or not a rise in GnRH input to the pituitary gland could over-ride the 'clamp' on the pituitary secretion of LH in the late follicular phase of the cycle, sheep were treated 40 h after cloprostenol with either a bolus injection of 500 ng GnRH or four pulses of 125 ng GnRH given at 10-min intervals. These treatments caused small elevations in LH secretion but did not always cause preovulatory LH surges. In some cases, a small rise in LH secretion was induced by GnRH treatments and levels of LH in plasma returned to baseline with the preovulatory LH surge occurring a few hours later. In one clear case, a bolus injection of GnRH induced an LH surge. The overall data from the GnRH-treated groups, however, indicated a significant delay in the onset of the LH surge which may have been due to perturbation of the subcellular mechanisms in the gonadotrophs. These data were interpreted to mean that the secretion of LH from the pituitary gland is inhibited up to very soon before the onset of the LH surge. The inhibitory factor could be oestrogen but could also be some other pituitary feedback hormone such as gonadotrophin surge-attenuating factor. It is concluded that the increase in the secretion of GnRH at the time of the onset of the LH surge is closely linked to an increase in the responsivity of the gonadotrophs to GnRH. The latter is not caused by the increase in the secretion of GnRH. Journal of Endocrinology (1995) 145, 271–282

scholarly journals Plasma concentrations of prolactin in brushtail possums (Trichosurus vulpecula) in different physiological states

2006 ◽  
Vol 190 (2) ◽  
pp. 295-305 ◽  
Author(s):  
J L Crawford ◽  
B P Thomson ◽  
M F Beaumont ◽  
D C Eckery
Keyword(s):  
Breeding Season ◽  
Post Partum ◽  
Mammalian Species ◽  
Plasma Concentrations ◽  
Oestrous Cycle ◽  
Brushtail Possum ◽  
Blood Samples ◽  
Lh Surge ◽  
Time Determination ◽  
First Time

Prolactin (Prl) has been implicated in reproduction in many mammalian species and is illustrated by the distinctive patterns of secretion during the breeding season, the oestrous cycle and lactation. The recent development of a homologous RIA for measuring the circulating Prl concentrations in brushtail possums has facilitated the reliable measurement of Prl in plasma during different physiological states in this species for the first time. Determination of Prl concentrations during lactation involved the collection of weekly blood samples from eight female possums from the time of parturition through either one or two consecutive lactational cycles. Prl was at baseline levels during early lactation (weeks 0–14 post-partum), and then increased markedly to maximum concentrations at weeks 19–21 before returning to nadir levels at a time coincident with the weaning of pouch young (weeks 23–27). The profile of Prl secretion over the oestrous cycle and in particular at the time of the preovulatory LH surge was obtained from 14 possums during the reproductive cycle, in which preovulatory follicle development and ovulation were monitored by laparoscopy. There was no distinct daily pattern of Prl secretion during the oestrous cycle; however, in 3/4 possums in which a typical preovulatory LH surge was measured, a biphasic preovulatory Prl surge was also observed. The preovulatory Prl surge commenced 2–6 h prior to, and had returned to baseline close to the onset of, the preovulatory LH surge, and a second surge of Prl occurred concomitantly with the delayed preovulatory FSH surge. Seasonality of Prl levels was established from weekly blood samples collected from six barren female possums, and concentrations of Prl were lower during the breeding season compared to the non-breeding season. Additionally, a circadian pattern of Prl secretion was evident in both female and male possums, with Prl levels higher in the morning compared to the afternoon. In conclusion, interpretation of endogenous secretory patterns suggests that Prl may be important during late lactation and at impending ovulation, but the involvement of the circannual rhythm of Prl in the regulation of seasonality in the brushtail possum remains to be determined.

Mobilization of LH secretory granules in gonadotrophs in relation to gene expression, synthesis and secretion of LH during the preovulatory phase of the sheep oestrous cycle

1995 ◽  
Vol 147 (2) ◽  
pp. 259-270 ◽  
Author(s):  
R J W Currie ◽  
A S McNeilly
Keyword(s):  
Electron Microscopy ◽  
Luteal Phase ◽  
Secretory Granules ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Single Type ◽  
Maximum Diameter ◽  
Northern Analysis ◽  
Mrna Levels ◽  
Lh Surge

Abstract Changes in LH secretory granules in pituitary gonadotrophs throughout the sheep oestrous cycle were determined by immunogold localisation of LH at ultrastructural level by electron microscopy. Oestrous cycles in Welsh Mountain ewes were initially synchronised with progestagen sponges and studies carried out in the subsequent cycle. Animals were allocated at random to six groups each of five animals, one killed on day 12 of the luteal phase and the other groups after prostaglandin (PG)-induced luteal regression at PG plus 18 h (early follicular phase), oestrus (PG plus 33·6±1·0 h), oestrus plus 9 h just before the preovulatory LH surge, 1 h after GnRH agonist-induced LH surge at PG plus 48 h (mid-LH surge) and oestrus plus 24 h, after the preovulatory LH surge. Blood samples collected throughout confirmed the pulsatile secretion of LH before and the timing in relation to the preovulatory LH surge. Pituitaries were dissected and processed for transmission electron microscopy and frozen for later extraction of mRNA. Only a single type of LH cell was present in the sheep pituitary. In the luteal phase, LHimmunopositive secretory granules were distributed throughout the cytoplasm in 80% of cells while in 20% of cells granules were polarised to the region of the cell next to a vascular sinusoid. The percentage of polarised cells increased during the follicular phase to 45% at oestrus, 75% at oestrus plus 9 h just before the LH surge and 90% in mid-LH surge. Cell size increased in parallel with polarisation. Gonadotrophs after the LH surge were almost totally devoid of LH granules but prominent LHβ immunoreactivity was observed in the rough endoplasmic reticulum. Analysis of granule diameters revealed a single class of granules with a maximum diameter of 300 nm. Polarised cells had significantly fewer 130–150 nm granules than non-polarised cells, suggesting preferential exocytosis of LH-containing granules of this size from polarised cells. Northern analysis showed that LHβ mRNA levels decreased from luteal through the follicular phase. These results suggest that the preovulatory LH surge in sheep is not related to a change in synthesis of LH but to a progressive recruitment of gonadotrophs into a releasing state, priming, as indicated by polarisation of secretory granules to the region of the cell next to the vascular system. Journal of Endocrinology (1995) 147, 259–270

PLASMA CONCENTRATIONS OF OVARIAN HORMONES DURING THE OESTROUS CYCLE OF THE SHEEP AND COW

1979 ◽  
Vol 81 (1) ◽  
pp. 61-64 ◽  
Author(s):  
I. D. HERRIMAN ◽  
D. J. HARWOOD ◽  
C. B. MALLINSON ◽  
R. J. HEITZMAN
Keyword(s):  
Maximum Concentration ◽  
Peak Concentration ◽  
Plasma Concentrations ◽  
Ovarian Hormones ◽  
Oestrous Cycle

Measurements were made of the plasma concentrations of testosterone, progesterone and oestradiol-17β during the oestrous cycle of the ewe, and of the plasma concentrations of testosterone and progesterone during the oestrous cycle of the heifer. The maximum concentration of progesterone in the heifer was nearly twice that in the ewe. The maximum concentration of testosterone was similar in both species and occurred at the onset of luteolysis; in the ewe the peak concentration of 19·5 pg/ml plasma was significantly greater (P < 0·05) than the concentrations of testosterone measured during the remainder of the oestrous cycle.

scholarly journals Hormonal Levels and Follicular Dynamics in Relation to the Oestrous Cycle in Barb and Arabian Mares, Algeria

2021 ◽  
Vol 65 (2) ◽  
pp. 1-8
Author(s):  
H. Houssou ◽  
F. Bouzebda-Afri ◽  
Z. Bouzebda ◽  
Z. Haddouche
Keyword(s):  
Luteal Phase ◽  
Follicle Stimulating Hormone ◽  
Oestrous Cycle ◽  
Follicular Growth ◽  
Reliable Criterion ◽  
Serum Progesterone ◽  
Maximal Diameter ◽  
Ovulatory Follicle ◽  
Hormonal Levels ◽  
Follicular Dynamics

Abstract This current study is an effort to understand the hormonal and follicular growth in the Barb and Arabian mares during the oestrous cycle; as mares are unique creatures. A total of 53 mares with 97 oestrous cycles were studied. The mares with a mean age of 10.38 ± 4.55 were examined by ultrasonography every day during their breeding season (2017). Two blood samples from each mare (n = 24) were obtained for progesterone (P4), oestrogen (oestradiol-17 beta) and follicle-stimulating hormone (FSH) determinations. The data revealed that the duration of the oestrous cycle was between 19 to 22 days. The pre-ovulatory follicle grew (3.02 ± 1.04) millimetre per day. The rate of cycles exploited in the mare (Arabian versus Barb) for conception was significantly different (P < 0.001). The maximal diameter of the follicle was 50.00 millimetre. The serum progesterone levels (P < 0.01) in mares were significantly higher in the luteal phase than those recorded during the time of oestrous. However, the levels of oestradiol and for FSH did not significantly change during the oestrous cycle in the mares. Determining the association between the size of the follicle and the hormone profiles were the most reliable criterion in the prediction of ovulation.

Changes in plasma LRH during the normal menstrual cycle in women

1980 ◽  
Vol 93 (3) ◽  
pp. 257-263 ◽  
Author(s):  
A. Miyake ◽  
Y. Kawamura ◽  
T. Aono ◽  
K. Kurachi
Keyword(s):  
Menstrual Cycle ◽  
Luteal Phase ◽  
Plasma Concentrations ◽  
Mean Value ◽  
Lh Surge ◽  
Double Antibody ◽  
Normal Menstrual Cycle ◽  
The Mean ◽  
Plasma Oestradiol

Abstract. The plasma concentrations of immunoreactive LRH, LH, FSH, oestradiol and progesterone were measured daily by a sensitive double antibody radioimmunoassay during 12 cycles of 8 normal cyclic women. The mean (± se) immunoreactive LRH levels in the follicular and luteal phase except the immunoreactive LRH peaks during normal cycles were 4.18 ± 0.38 pg/ml and 4.50 ± 0.45 pg/ml, respectively. The immunoreactive LRH peaks were observed in 11 of 12 cycles, appearing on day −4 to −1 from the LH surge in 9 cycles and on day +1 and +2 in 2 cycles. The mean value of immunoreactice LRH peaks was 42.0 ± 11.4 pg/ml with range of 12 to 154 pg/ml. The immunoreactive LRH peak lasted for one day in 10 cycles and for 4 days in one cycle. The immunoreactive LRH peaks in different cycles of the same women did not occur on the same day relative to the LH peak. The plasma immunoreactive LRH levels measured every 10 min for 40 min periods every day in normal cyclic women during the ovulatory phase showed slight, but not significant fluctuations. Plasma oestradiol levels began to increase on day −6, reaching a peak on day − 1, and were followed by peaks of LH and FSH. These data indicate that increase in serum oestradiol was followed by release of LRH from the hypothalamus and pre-ovulatory discharge of gonadotrophins from the pituitary.

Sign in / Sign up

Export Citation Format

Share Document