Concentration of receptors for estradiol and progesterone in canine endometrium during estrus and diestrus

Receptors for estrogen and progesterone were measured in cytosols prepared from specimens of canine endometrium obtained at late proestrus, day 4 of estrus, day 2 of diestrus, and at 10 day intervals from days 10 through 80 of diestrus. Twenty nine adult bitches were used, with 2 to 4 dogs used at each time point. Concentrations of estradiol receptors measured in endometrial cytosols from late proestrus through day 10 of diestrus were similar (mean +/- SEM: 9.9 +/- 2.2, 10.5 +/- 1.2, 16.3 +/- 1.6, and 16.2 +/- 2.9 pmol/g of tissue at proestrus, day 4 of estrus, days 2 and 10 of diestrus, respectively). As serum concentrations of progesterone increased during early diestrus, the concentration of estradiol receptors decreased and were significantly (P less than 0.05) lower on days 30 (4.9 +/- 1.3 pmol/g of tissue) and 40 (3.7 +/- 0.6 pmol/g of tissue) of diestrus. After day 40 of diestrus, when serum concentrations of progesterone were approaching basal concentrations, the concentration of estradiol receptors increased and remained significantly (P less than 0.05) higher from days 60 to 80 of diestrus (day 60, 13.4 +/- 2.9; day 70, 15.7 +/- 1.7; day 80, 19.8 +/- 2.4 pmol/g of tissue). As observed for estrogen receptors, the concentration of endometrial receptors for progesterone also gradually increased from late proestrus (4.9 +/- 1.3 pmol/g of tissue) to day 2 of diestrus (6.4 +/- 0.3 pmol/g of tissue).(ABSTRACT TRUNCATED AT 250 WORDS)     

Testosterone administration to mares during estrus: duration of estrus and diestrus and concentrations of LH and FSH in plasma

To study the possible role of ovarian androgens in regulation of follicle stimulating hormone (FSH) secretion in the cycling mare, five mature, intact mares were treated with testosterone (20 micrograms/kg of body weight) daily during estrus; five control mares received safflower oil on the same schedule. Mares were teased for estrus and samples of jugular blood were drawn daily through one full estrous cycle. Concentrations of FSH in plasma were measured by a newly developed radioimmunoassay based on anti-ovine FSH serum and radioiodinated equine FSH. Testosterone treatment during estrus had no effect on duration of estrus, diestrus or the total cycle. Concentrations of FSH in plasma during estrus were unaffected by testosterone treatment. However, FSH concentrations in testosterone-treated mares were elevated (P less than .05) compared with controls during mid-diestrus (d 6 through 11). The magnitude and timing of the LH peaks were unaffected by treatment, as was the day on which the first elevated progesterone concentration occurred. These data are consistent with a model of FSH secretion in which ovarian androgens cause an accumulation of FSH in the pituitary during estrus in preparation for the surges that occur in FSH secretion during diestrus.     

Concentrations of testosterone in canine serum during late anestrus, proestrus, estrus, and early diestrus

Serum testosterone concentrations in samples collected daily from 6 bitches for at least 60 days before the onset of diestrus were determined by radioimmunoassay. Mean serum concentrations (+/- SEM) of testosterone ranged from 31 +/- 11 to 141 +/- 63 pg/ml during late anestrus. Mean testosterone concentrations during proestrus ranged from 106 +/- 29 to 239 +/- 113 pg/ml, with the highest concentration (526 +/- 225 pg/ml) occurring the day of the preovulatory surge of luteinizing hormone. Although the ovaries may be sites of production during late anestrus, proestrus, estrus, and early diestrus, further investigation is necessary to determine whether testosterone has an important physiologic or endocrinologic function in the bitch (ie, sexual behavior, vaginal hypertrophy, and luteinizing hormone surge).     

Efficacy of synovex-S implants in suppression of estrus in the mare

The objective of this study was to determine if administration of Synovex-S^® implants, approved for use in cattle to promote weight gain and feed efficiency, would suppress the expression of behavioral estrus and/or alter follicular development and ovulation in the mare. Twenty-four clinically normal adult horses were randomly assigned to one of four treatment groups (6 mares per group) which received a total of 0, 8, 32 or 80 Synovex-S^® pellets 5 days after ovulation. An implant dose of 8 Synovex-S^® pellets contained a total of 200 mg of progesterone and 20 mg of estradiol benzoate. Mares were monitored daily by teasing and ultrasonography of the reproductive tract per rectum for 45 days. A blood sample was collected daily for progesterone analysis. All mares receiving Synovex-S^® implants returned to estrus at the predicted time. No differences were noted in duration of estrus, interovulatory interval or ovulation rate. In conclusion, subcutaneous administration of 8, 32 or 80 Synovex-S^® pellets did not suppress the expression of behavioral estrus or block ovulation in mares.     

Advances in synchronizing estrus and ovulations in the mare: A mini review

Synchronization of estrus (SE) in mares has been achieved, but not of ovulation (SO). Progestins followed by PGF_2a are useful for SE only. In the two studies reviewed here, SE and SO were attempted by using CIDR-B, an intravaginal (itv) progesterone (1.9 g) releasing device, alone (study 1) or accompanied by estradiol (10 mg) given also itv (study 2). In both studies, Ovuplant™ (OT), an implant containing 2.1 mg of the GnRH analog deslorelin was used for the control of ovulation. Eighty cycling Hanoverian mares, 40 each in studies 1 and 2, received CIDR-B itv for 12 days, with PGF_2a given once at CIDR-B removal. In study 1, 15 mares each received OT when the lead follicle had reached 40 mm (A) or on Day 3 of estrus (B); 10 controls received no OT (C). In study 2, E2 was used in addition on Day 0 (CIDR-B insertion) (10 mares; group II), or on Days 0 and 7 (10; group III) or not (20; groups I and IV). Mares in groups I to III received OT as in study 1 (A); group IV (10) remained untreated. Ovaries were examined and blood samples were taken in studies 1 and 2 from all mares in 1, 2 or 4-day intervals, respectively, and concentrations of FSH, LH, progesterone and estradiol were determined by RIA. In study 1, CIDR-B treatment achieved SE, but not SO as shown by a wide spread of days on which follicles were reaching 40 mm; OT treatment assured ovulations in 48 hours in 93.3% of treated mares vs. 44.4% in controls (P<0.05. In study 2, SE was achieved and SO, but only when estradiol was given once (itv) on Day 0 (group II) but not twice on Days 0 and 7 (group III). In both studies, CIDR-B prevented estrus but stimulated follicle growth: 8 mares in study 1 ovulated with CIDR-Bs in place and 2 in trial 2, respectively. Only when estradiol was used together with CIDR-B, follicle growth was retarded (group II) or suppressed (group III: P<0.05 vs. groups I and IV). The pregnancy rate in study 2 from a single breeding at the first estrus was 52.8% with no significant differences between groups. FSH rose until Day 4 or 8 and had dropped sharply at Day 12; after CIDR-B removal FSH rose most quickly in group II, study 2. LH declined slightly until Day 12 and rose thereafter, reaching peak levels by Day 18 or 20, respectively. In both studies, estradiol had dropped slightly by Day 4 but increase steadily thereafter until ovulation had occurred. Preovulatory rise and postovulatory drop was seen earlier in group II, study 2. Values for progesterone had risen uniformly by Day 4, had declined slowly by Day 12 and precipitously in response to PGF_2a by Day 14. Treatment of cyclic mares with CIDR-B for 12 days, followed by PGF_2a at the day of CIDR-B removal and by Ovuplant™ a deslorelin implant when a follicle had reached 40 mm, resulted in synchronization of estrus. Adding to this scheme a single dose of estradiol (10 mg, intravaginal) on Day 0 resulted also in synchronization of ovulation.     

Electrocoagulative removal of endometrial cysts in the mare

Six mares had endometrial cysts removed by endoscopic electrocoagulative surgery. These mares exhibited poor reproductive histories and endometrial cysts were the only detectable abnormalities. In each case, at least two cysts greater than 2.5cm were present. One mare subsequently produced a live foal; two are presently in foal; one conceived but absorbed; one formed more cysts after surgery; and one has not yet been bred. Histologically, the walls of the cysts contained entire lamina propria, relatively normal endometrial glands, and small cystic spaces.     

The electrosurgical treatment of endometrial cysts in the mare

A minimally invasive technique for the removal of endometrial cysts is described. Intraluminal cysts hinder the migration of the embryo through the uterus in early pregnancy and in a later stage hinder placenta development and hence diminish the chance of successful pregnancy. Cysts can also give rise to false-positive results in early pregnancy tests. Endometrial cysts located in the lumen can be removed surgically from the standing mare. After placement of the endoscope, a wire is placed, via the biopsy channel, around the base of cyst, which is then cut through by cauterization. The cyst is removed with the help of forceps. Five barren mares with multiple cysts were treated in this way during the anoestrous period for October to February. Three of these mares became pregnant during the next oestrus period.     

Technique and interpretation of cervical and endometrial cytology in the mare

This paper illustrates and describes the findings obtained from cervical and uterine cytology smears in the mare. Cervical/endometrial cytology is a simple technique that provides valuable information to the clinician regarding the existence of an acute or active endometritis. The most frequent observation is the presence of neutrophils. Chronically infected/inflamed mares with some degree of inflammatory cellular infiltration can also be identified on the cytology smear by the presence of neutrophils, macrophages and lymphocytes. Microorganisms are sometimes found with either acute or chronic endometritis.

This technique is not a substitute for uterine culture and biopsy. The correct identification of bacteria should be based on the cultural characteristics of the microorganisms.     

Behavioural modifications of bitches during diestrus and anestrus

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