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At least 19 recordsLinked to original sources
PubMed2005

Lactated Ringer's solution and hypertonic saline improve survival in uncontrolled hemorrhagic shock in female rats in metestrus.

BACKGROUND: In the present investigation the effect of fluid treatment in uncontrolled hemorrhagic shock after massive splenic injury (MSI) was comparatively studied in male and female rats. MATERIALS AND METHODS: The anesthetized animals were randomly divided into three groups: in group 1 MSI was induced in males, in group 2 MSI was induced in females in proestrus, in group 3 MSI was induced in females in metestrus. Each group was divided into four subgroups: a) Sham-operated, b) MSI untreated (UT), c) MSI treated with 40 ml/kg lactated Ringer's solution (RL), and d) MSI treated with 5 ml/kg NaCl 7.5% (HTS). RESULTS: Total blood loss (TBL) in groups 1b, 2b, and 3b was 31.7 +/- 3.6%, 33.1 +/- 2.6%, and 36.7 +/- 2.6%, respectively, and mean survival time (MST) was 143.7 +/- 25.3 min, 174.8 +/- 10.4 min, and 67.8 +/- 11.4 min (P < 0.01 versus group 2b), respectively. TBL in groups 1c, 2c, and 3c increased to 52.4 +/- 5.5% (P < 0.02 versus UT), 48.6 +/- 1.6% (P < 0.02 versus UT), and 48.8 +/- 4.1% (P < 0.02 versus UT), respectively, and MST decreased to 126 +/- 19.4 min, (P < 0.05 versus UT), and 136.8 +/- 13.0 min (P < 0.05 versus UT) in groups 1c and 2c, respectively, and increased in group 3c to 120.4 +/- 23.3 min (P < 0.05 versus UT). TBL in groups 1d, 2d, and 3d was 31.3 +/- 4.8%, 38.0 +/- 4.2%, and 40.6 +/- 3.7%, respectively, and MST increased to 198.5 +/- 13.9 min (P < 0.05 versus UT) in group 1d, decreased to 128.4 +/- 17.2 min (P < 0.01) in group 2d, and increased to 102.6 +/- 19.0 min (P < 0.002 versus group 1d) in group 3d. CONCLUSIONS: RL infusion significantly increased blood loss in all three groups, reduced survival time in males and female rats in proestrus, but significantly improved survival in females in metestrus. HTS treatment did not alter blood loss in all three groups, but significantly improved survival in females in metestrus and males.

Animals↗
PubMed2006

Effects of 17beta-estradiol and flutamide on inflammatory response and distant organ damage following trauma-hemorrhage in metestrus females.

We hypothesized that administration of androgen receptors antagonist flutamide following trauma-hemorrhage (T-H) in metestrus females will maintain immune function and reduce remote organ damage under those conditions. Female B57BL/J6 mice (metestrus state, 8-12 weeks old) underwent laparotomy and hemorrhagic shock (35.0+/-5.0 mmHg for 90 min) and then received 17beta-estradiol (E2; 50 microg/25 g), flutamide (625 microg/25 g), or E2 + flutamide. Four hours after resuscitation, plasma cytokine and chemokine (TNF-alpha, IL-6, IL-10, IFN-gamma, and MCP-1) concentrations and their release in vitro by hepatic and pulmonary tissue macrophages (M Phi) were determined by flow cytometry. Organ damage was assessed by edema formation (wet-to-dry weight ratio) and neutrophil infiltration [myeloperoxidase (MPO) activity]. Administration of E2, flutamide, or E2 + flutamide following T-H resulted in a significant decrease in systemic TNF-alpha, IL-6, and MCP-1 concentrations under those conditions. This was accompanied by significantly decreased in vitro TNF-alpha release by Kupffer cells after administration of E2, flutamide, or E2 + flutamide. The in vitro release of proinflammatory cytokines by alveolar M Phi, however, was reduced significantly only by the addition of E2 or E2 + flutamide but not by the addition of flutamide. A significant decrease in pulmonary and hepatic edema formation as well as neutrophil infiltration in the lung was observed after E2, flutamide and E2 + flutamide administration. In contrast, hepatic neutrophil infiltration was only significantly reduced following E2 and E2 + flutamide administration. Thus, although flutamide does not produce synergistic, salutary effects with E2, its administration in females following T-H also produces salutary effects on the immune and organ function, similar to E2 administration under those conditions.

Animals↗
PubMed1999

Retention of a functional corpus luteum and peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha following metestrus administration of Syncro-Mate-B.

This study was conducted to examine the effects of metestrus administration of SyncroMate-B (SMB) on PGF2alpha secretion and corpus luteum (CL) development. In a study replicated over 2 yr, cows were observed for spontaneous estrus in yr 1, and cows received an injection of 25 mg of PGF2alpha and were observed for subsequent estrus in yr 2. At standing estrus (estrus = d 1), cows were randomly allotted to receive either the standard SMB regimen (n = 40) on d 3 of the estrous cycle or no treatment (n = 8). Fifty percent (n = 20) of SMB-treated cows were administered PGF2alpha on d 10 of the estrous cycle 48 h prior to implant removal. Twice-daily blood samples were collected in the morning (AM) and evening (PM) from d 2 AM through d 14 AM of the treated estrous cycle and subsequently analyzed for progesterone (P4) and PGF2alpha metabolite (PGFM). Prior to statistical analysis, SMB- and SMB/PGF2alpha-treated cows were sorted according to P4 concentration at d 10 of the treated estrous cycle to either a CL functional group (P4 > or = 1 ng/mL; n = 20) or a CL nonfunctional group (P4 < 1 ng/mL; n = 17). Following d 10 AM administration of PGF2alpha, functional and nonfunctional groups were further subdivided based on treatment. The groups were as follows: untreated control cows (n = 8); SMB-treated cows retaining a functional CL (SMB-F; n = 8); SMB-treated cows with a nonfunctional CL (SMB-N; n = 11); SMB/PGF2alpha-treated cows retaining a functional CL (SMB/PG-F; n = 12); and SMB/PGF2alpha-treated cows with a nonfunctional CL (SMB/PG-N; n = 6). Of all SMB-treated cows, 54% retained a functional CL through d 10 AM of the treated estrous cycle. Mean serum P4 concentrations increased for cows in all groups until d 7, after which P4 concentrations increased for cows in SMB/PG-F, SMB-F, and control groups and decreased for cows in SMB/PG-N and SMB-N groups. Following PGF2alpha administration on d 10, mean serum P4 concentrations remained < 1 ng/mL for cows in SMB/PG-N and SMB-N groups, decreased to < 1 ng/mL for cows in the SMB/ PG-F group, and remained > 1 ng/mL for cows in SMB-F and control groups. Mean serum PGFM concentrations tended (P = .06) to increase in cows with nonfunctional CL compared with control cows on d 8 AM and were greater (P < .05) in cows with functional CL on d 8 PM through d 9 PM. These results indicate that retention of a functional rather than a nonfunctional CL following metestrus administration of SMB is dependent on a premature release of uterine PGF2alpha.

Animals↗
PubMed1997

Late estrus or metestrus insemination after estrual inseminations decreases farrowing rate and litter size in swine.

A study was conducted with 360 gilts and sows from four herds to determine whether fertility was affected when the final of multiple inseminations was performed in late estrus or metestrus (late insemination). Sows and gilts were inseminated at 24-h intervals immediately after the detection of estrus. After receiving a first insemination, females were paired according to parity and estrus status on d 2 of estrus. Each pair set was inseminated with extended semen from the same semen collection(s). Control females were inseminated once on d 1 if they were not in estrus on d 2 (n = 31) or on both days if they were in estrus on d 2 (n = 149). Late inseminated females in each pair were managed and inseminated in the same manner as control females and then inseminated again 24 h later regardless of estrus status. Overall reproductive performance was similar among the four herds. Late insemination caused a drop in farrowing rate in parity 1 and 2 females (23 and 22%; P < .05 and P < .01, respectively) and average litter size decreased by 1.1 pigs per litter (P < .05) regardless of parity. There were no differences in either litter size or farrowing rate between late inseminated females in estrus and those that were in metestrus at the time of their last insemination.

Analysis of Variance↗
PubMed1989

Human chorionic gonadotropin affects tissue levels of progesterone and cyclic adenosine 3',5'-monophosphate in the metestrus rat uterus in vitro.

The effect of human chorionic gonadotropin (hCG) on in vitro progesterone (P) level in the uterus was investigated by using short-term incubations of uterine tissue taken from 4-day cyclic rats at different stages of the estrous cycle. Control incubations resulted in a decrease of endogenous P content in uteri removed from rats in proestrus (PRO), estrus (EST), and metestrus (MET): -25% (n = 6), -60% (n = 6), and -45% (n = 8), respectively. The amount of P found after incubation of MET tissue in the presence of hCG was significantly higher (p less than 0.001) than that found after control incubations. The hCG effect was dose-dependent and was not observed with PRO or EST tissue. Although the mean P level found in MET tissue after incubation with 10 IU/ml hCG was not significantly different from the mean level found in unincubated tissue (1562 +/- 341 vs. 1470 +/- 174 pg/mg protein, n = 8), an obvious synthesis was observed in two experiments. It thus seems likely that observed hCG effect would involve a de novo P synthesis rather than a decrease of P catabolism. Furthermore, hCG induced a dose-dependent increase of cyclic adenosine 3', 5'-monophosphate (cAMP) uterine levels in MET tissue. N,O'-dibutyryl cyclic AMP [Bu)2 cAMP) at 5 mM induced a significative increase (p less than 0.01) of P uterine level in EST and MET tissue compared to control incubations, but had no effect on PRO tissue. Our results suggest the progressive maturation throughout the rat estrous cycle of a luteinizing hormone/hCG- and cAMP-dependent process able to regulate uterine P content.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Proestrus and metestrus rat uterus, a rapid and simple in vitro method for detecting histamine H2-receptor antagonism.

The antagonism caused by metiamide and cimetidine on histamine-induced inhibition of spontaneous and electrically stimulated isometric contractions of superfused rat uterine horns from proestrus and metestrus stages was studied in vitro. Histamine depressed smooth muscle "twitch" responses of spontaneously contracting or electrically stimulated uterine preparations of both stages in the same dose-dependent manner. The typical effects of organ relaxation, inhibition of contraction height and reduction of resting tension generated by histamine, could both be antagonized by the histamine H2-receptor blockers metiamide and cimetidine, while both compounds failed to reverse orciprenaline- or isoproterenol-induced inhibition of uterine contractility. Diphenhydramine, a histamine H1-receptor antagonist, was not able to reduce histamine-induced inhibition of uterine contractions, thereby confirming that the histamine receptors of the rat uterine tissue are H2 in type. Furthermore, beta-adrenergic blockers, like propranolol and dichloroisoproterenol, failed to antagonize the decrease in contraction amplitude but prevented fall in resting tension induced by histamine. Tyramine, cAMP or dibutyryl-cAMP produced no inhibition of motility of the isolated uterine tissue. Possible mechanisms of these findings are discussed. The findings show that the isolated non-estrus rat uterus is useful as a rapid method for investigating specific effects of drugs designated for potential histamine H2-receptor antagonism. This preparation offers the additional advantage that no interference with beta-blockers occurs.

Animals↗
PubMed1992

Luteal function and reproductive response in suckled beef cows after metestrus administration of a norgestomet implant and injection of estradiol valerate with various dosages of injectable norgestomet.

In an experiment replicated over 2 yr, 149 suckled beef cows were administered Syncro-Mate-B (SMB), a 6-mg Norgestomet (NOR) ear implant (in situ 9 d) in conjunction with an i.m. injection of 5 mg of estradiol valerate (EV), and either 3.0, 4.5, or 6.0 mg of NOR, 2 d after estrus. All cows were artificially inseminated at 48 h (timed insemination; TI) after implant removal (IR) and cows were reinseminated at any estrus subsequent to 24 h of TI through 30 d. Blood samples collected before treatment, every 3 d through IR, and at TI were assayed for progesterone (P4). At TI, 44, 39, and 12% of cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively, had serum concentrations of P4 greater than 1 ng/mL (3.0 and 4.5 mg vs 6.0 mg, P less than .01). Fifty-eight, 63, and 84% of cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively, exhibited a synchronized (within 5 d of IR) estrus (3.0 and 4.5 mg vs 6.0 mg, P less than .05). Pregnancy rates for the 5-d synchronized period were 38, 45, and 66% for cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively (3.0 and 4.5 mg vs 6.0 mg, P less than .05). First-service pregnancy rates were 66, 71, and 79% for cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Recombinant human inhibin A and recombinant human activin A regulate pituitary and ovarian function in the adult female rat.

The roles of recombinant human inhibin A (rh-inhibin A) and rh-activin A in regulating the pituitary and ovary of the adult female rat were examined. Serum and pituitary FSH and LH and serum estradiol and progesterone concentrations were evaluated at 1, 2, and 6-12 h after sc hormone administration on metestrus and on proestrus. A second study examined the effect of the hormones 24 h after injection at 1000 h on each day of the cycle. Rh-inhibin A inhibited FSH secretion 60 min after injection on proestrus but did not alter serum FSH concentration on metestrus. FSH remained low for the 12 h examined during the evening of proestrus and on the morning of estrus. Serum LH concentration, pituitary FSH content, and pituitary LH content were not significantly changed under any experimental condition. Rh-inhibin A did not regulate estradiol concentration on metestrus or on proestrus; however, it did cause a rise in serum estradiol in animals treated on metestrus and diestrus and examined 24 h later. This suggests that inhibin may participate in regulating follicular maturation in a subset of developing follicles. Last, after rh-inhibin A treatment, the duration of the proestrus progesterone surge was shortened. Serum FSH concentration rose by 6 h after rh-activin A administration on proestrus and both FSH and LH rose by 6 h after hormone administration on metestrus. Rh-activin A significantly increased serum estradiol through 6 h of treatment on proestrus. Progesterone levels were significantly greater in animals treated on metestrus and killed 24 h later. The increased length of the midcycle progesterone surge may be the result of increased LH on metestrus. These studies suggest that rh-inhibin A and rh-activin A may regulate ovarian and pituitary function in a cycle dependent manner. Specifically, rh-inhibin A can acutely regulate FSH and progesterone on proestrus and estradiol during follicular development. Rh-activin A acutely regulates FSH on both proestrus and metestrus and LH on metestrus. Whether circulating endogenous inhibin or activin participate physiologically in these functions is under investigation.

Activins↗
PubMed1998

Physiologic regulation of postovulatory neutrophil migration into vagina in mice by a C-X-C chemokine(s).

Leukocytes, particularly neutrophils, infiltrate into female genital organs after ovulation in both humans and mice. In mice, a female sexual cycle consists of 5 phases: proestrus, estrus, metestrus-1, metestrus-2, and diestrus. Ovulation occurs at estrus; at metestrus-2, a large number of neutrophils infiltrate into the vaginal epithelium accompanied by an increased neutrophil number in vaginal lavage fluid. Concomitantly, concentrations of a functional IL-8 homologue, murine macrophage inflammatory protein (MIP)-2, were increased significantly in vaginal lavage fluid at metestrus-2 as compared with other phases. On the contrary, MIP-2 was not detected in plasma during the whole course of a sexual cycle. Moreover, immunohistochemical analyses demonstrated that MIP-2 protein expression was prominent at the upper layer of the vaginal epithelium at metestrus-2, in contrast to a marginal staining in the vaginal epithelium at proestrus and estrus. These results suggest that a C-X-C chemokine, MIP-2, was produced physiologically in the vaginal epithelium in a sexual cycle-dependent manner. Furthermore, the administration of neutralizing anti-IL-8R homologue Abs at proestrus abrogated leukocyte infiltration into the vagina at metestrus. However, anti-MIP-2 Abs reduced leukocyte influx at metestrus by approximately 50%. Thus, a murine IL-8 homologue, MIP-2, and its related molecules physiologically regulate neutrophil migration into the vagina in a sexual cycle-dependent manner.

Animals↗
PubMed1997

Effect of prostaglandin F2 alpha treatment before norgestomet and estradiol valerate treatment on regression, formation, and function of corpora lutea in beef heifers.

Two experiments were conducted to determine if corpus luteum regression, formation, and function were associated with the decreased calving rate observed in beef females administered PGF2 alpha 5 days before Syncro-Mate B (SMB) treatment. Experiment 1 included 31 beef heifers 11 to 13 months old and experiment 2 included 31 beef heifers 19 to 21 months old. Heifers were randomly assigned to 1 of 2 groups (control and PGF2 alpha 5 days before SMB treatment). Heifers were bled 10 days before PGF2 alpha treatment, immediately before PGF2 alpha and SMB treatments, at the time of implant removal, and twice weekly after implant removal. Heifers in experiment 2 were observed twice daily for estrus for 5 days after PGF2 alpha treatment and for 3 days after norgestomet implant removal. Based on the blood samples collected before SMB treatment, 15 heifers in experiment 1 and every heifer in experiment 2 were with estrous cycles. All heifers in experiment 1 had progesterone concentrations < 0.5 ng/ml 2 days after implant removal. However, progesterone concentrations during the luteal phase in control heifers with estrous cycles were higher (P < 0.05) than in PGF2 alpha treated heifers with estrous cycles and in heifers previously without estrous cycles. In experiment 2, based on the occurrence of estrus and progesterone concentrations, heifers were also classified as metestrus or diestrus at the time of SMB treatment. The data were analyzed as a 2 x 2 factorial with treatment (control or PGF2 alpha) and stage of the cycle (metestrus and diestrus) as main effects. More metestrus heifers (40%) had progesterone concentrations > 1.0 ng/ml 2 days after implant removal than diestrus heifers (0%). In addition, progesterone concentrations during the luteal phase in metestrus heifers were lower (P < 0.05) than in diestrus heifers. PGF2 alpha treatment had no effect (P > 0.25) on the number of heifers with > 1.0 ng/ml progesterone 2 days after implant removal and progesterone concentrations during the luteal phase. There was no treatment by stage of the estrous cycle interactions. In summary, the administration of PGF2 alpha 5 days before SMB decreased the calving rate by causing more heifers to be metestrus at SMB treatment. Fewer metestrus heifers (than diestrus heifers) were synchronized (with < 1.0 ng/ml of progesterone 2 days after implant removal) to SMB treatment and those synchronized had lower progesterone concentrations during the luteal phase.

Animals↗
PubMed2003

Cyclic changes of the canine endometrial surface: an electron-microscopic study.

The endometrial surface morphology of 38 dogs during different stages of the estrous cycle was investigated with scanning electron microscopy. The cell surface altered from convex in proestrus and estrus to very variable in early metestrus, flattened in late metestrus and became completely plane in anestrus. Microvilli were numerous and long in proestrus and in estrus, became short and variable in number in early metestrus, decreased further in length in late metestrus and became very short and rare in anestrus. The variable appearance in early metestrus was not influenced by changing the osmolarity of the fixative and might be a physiological process. The number of glandular openings showed little variability throughout the estrous cycle. Ciliated cells were rare but present in all cycle stages except in late metestrus. However, in the latter cycle stage and in anestrus rare single strands were noted. Transmission electron microscopy was used to determine the inner structure of these strands. Microtubuli were detected in transversal and longitudinal sections but without the 9 + 2 arrangement which is characteristic for cilia. The nature and function of these structures remain unclear.

Animals↗
PubMed2002

The hormonal responses of lipoprotein lipase activity and lipolysis in adipose tissue differ depending on the stage of the estrous cycle in female rats.

OBJECTIVE: This study was designed to elucidate whether there were differences in the hormonal responses of the parameters involving triacylglycerol (TG) deposition and mobilization in adipose tissue among the stages of the estrous cycle in female rats. MEASUREMENTS: Adipose tissue was obtained from the parametrial region in female rats at each stage of the estrous cycle. Lipoprotein lipase (LPL) activity in the extracts of acetone/ether powders of the tissues was measured as a parameter for TG deposition. Norepinephrine-stimulated lipolysis in isolated fat cells was measured as a parameter for TG mobilization. RESULTS: LPL activity changed periodically during the estrous cycle; the activity level was highest at diestrus, began to decrease at proestrus, reached a minimum at estrus, began to increase again at metestrus-1, and increased further at metestrus-2. At diestrus and proestrus, LPL activity was increased with an increase in plasma insulin levels, suggesting that plasma insulin was the predominant up-regulator of LPL. But at estrus, metestrus-1 and metestrus-2, LPL activity remained low even when plasma insulin levels were high, indicating that it was not up-regulated by plasma insulin. Norepinephrine-stimulated lipolysis in fat cells was high at estrus and metestrus-1 and low at diestrus. CONCLUSION: The hormonal responses of LPL activity and lipolysis in adipose tissue differed depending on the stage of the estrous cycle.

Adipose Tissue↗
PubMed1997

Apoptotic cell death during the estrous cycle in the rat uterus and vagina.

BACKGROUND: Rodent uterus and vagina show marked histological changes during the estrous cycle. Apoptotic cell death has been demonstrated in hamster and rat uterine epithelium during the estrous cycle by electron microscopy: numerous epithelial cells undergo apoptosis at estrus. We examined cell death and cell proliferation in rat uterus and vagina during estrous cycle. METHODS: To examine the rate of proliferation in uterine and vaginal cells at each estrous stage, the numbers of cells at metaphase were counted separately in epithelial and stromal cells. We identified the apoptotic cells in uterus and vagina at each estrous stage by using DNA fragmentation, in situ DNA 3'-end labeling, and electron microscopy. RESULTS: Mitotic rates in uterine luminal and glandular epithelial cells were low at metestrus and estrus, respectively. Intense fragmentation was found in the uterus at metestrus and in the vagina at proestrus and metestrus. In uterine luminal and glandular epithelial cells, apoptotic index showed peaks at metestrus and estrus, respectively. In vaginal epithelial cells, many apoptotic cells were encountered in the superficial layer at proestrus, which may contribute to keratinization. In the middle and basal layer of vaginal epithelial cells, apoptotic index was high at metestrus, when mitotic rate was low. Electron microscopy confirmed the results of the labeling studies. CONCLUSIONS: Apoptotic cell death was encountered in the uterus and vagina during estrous cycle in rats. There is an inverse correlation between cell death and cell proliferation in rat uterine and vaginal epithelial cells during the estrous cycle.

Animals↗
PubMed1976

Autonomic innervation and plasma estradiol-17beta and progesterone levels in rats with subcutaneous ovarian autografts.

Ovaries were removed from female rats and immediately autografted into a subcutaneous pouch in the flank in order to quantitate the relationship of graft re-innervation, steroid secretion and vaginal smear pattern. Animals were killed at thre time periods: three days after grafting, on the first day a cornified vaginal smear appeared and at the first metestrus. In addition, control animals were killed at metestrus. Plasma samples were obtained from all rats and analyzed for estradiol-17beta and progesterone concentration by radioimmunoassay. At the first day of vaginal cornification after grafting, plasma estradiol-17beta (45.8+/-4.0 pg/ml) was elevated in comparison to controls at metestrus (24.0+/-2.6 pg/ml), but plasma progesterone (21.5+/-4.0 ng/ml) was not different (30.6+/-1.7 ng/ml). Subsequently, at the first metestrus following grafting, plasma estradiol-17beta (23.0+/-3.5 pg/ml) was comparable to control values. In contrast, progesterone was decreased (17.5+/-1.9 ng/ml). A definite correlation was detected between the vaginal smear and plasma levels of steroid hormones in the castrated female rat with subcutaneous ovarian autographs Histochemical techniques were used to study the adrenergic and cholinergic innervations of grafts three days after grafting, at the first day of vaginal cornification, and at the first metestrus. No correlation was shown between density of adrenergic or cholinergic innervation and plasma levels of estradiol-17beta and progesterone or onset of a cycling vaginal smear.

Acetylcholinesterase↗
PubMed1978

Changes in catecholamine content in discrete brain nuclei during the estrous cycle of the rat.

Norepinephrine (NE) and dopomine (DA) concentrations were measured in discrete brain nuclei in female rats at different stages of the 4-day estrous cycle. In the medial preoptic and paraventricular nuclei, NE levels were reduced on the days of proestrus and estrus as compared to metestrus-diestrus. NE levels sharply increased between estrus and metestrus in the lateral septal nucleus but did not vary significantly at other times. In the mesencephalic central gray catecholamine area, NE levels were elevated on metestrus as compared to all other days of the cycle. DA concentrations also varied in certain nuclei during the estrous cycle. In the lateral septum, DA levels were highest during diestrus, and in the nucleus of the tractus diagonalis, DA levels were highest on metestrus. The DA concentration of the caudate nucleus decreased between proestrus and estrus and remained low through metestrus. DA in the medial preoptic nucleus showed a similar pattern of change as did NE. In the median eminence DA levels increased significantly from proestrus afternoon to estrus, but did not vary on the other days. It is concluded that cyclic activity of catecholamines in a few discrete areas of the brain may be related to the fluctuations of the gonadotropins and ovarian hormones to influence ovulation and mating behavior.

Animals↗
PubMed1993

Inhibition of estrus and corpora lutea function with Norgestomet.

Forty-five nonpregnant, nonlactating, Angus and Brangus cows were utilized to determine how long a Norgestomet ear implant would inhibit estrus when administered at various stages of an estrous cycle. All cows completed a nontreated estrous cycle to ensure normal cyclicity. At the second observed estrus (estrus = Day 1), cows were randomly allotted to be treated at metestrus (Day 3 or Day 4, n = 15); at diestrus (Day 9 or Day 10, n = 14); or at proestrus (Day 15 or Day 16, n = 16). All cows received a 2-ml intramuscular injection of 3 mg of Norgestomet accompanied by a 6-mg Norgestomet ear implant, which remained in situ for 21 days, or until individual cows were observed in estrus. Estrus was inhibited for a mean (+/- SEM) of 18.7 +/- 0.7, 19.9 +/- 0.8, and 17.0 +/- 0.8 days, respectively, when cows were treated at metestrus, diestrus, and proestrus (metestrus and diestrus vs proestrus; P < 0.05). Estrus was inhibited for an entire 21-day implantation period in 27, 50, and 38% of cows treated at metestrus, diestrus, and proestrus, respectively (P > 0.10). Norgestomet inhibited estrus in all cows for 11, 17, and 11 days after implantation when treatment was initiated at metestrus, diestrus, and proestrus, respectively (P > 0.10). These data indicate that a 6-mg Norgestomet ear implant effectively inhibits estrus in all cows for a maximum of 11 days, with some cows exhibiting estrus by Day 12 with the Norgestomet implant in situ.

Journal Article↗
PubMed1984

Cell proliferation in the principal target organs of the dog (beagle) ovary during various periods of the estrous cycle.

Cell proliferation in the principal target organs of the ovary was studied in 7 beagle dogs during proestrus, early estrus, secretory and regressive metestrus. Pulse labelling with (3H)-thymidine and autoradiography were applied and labelling indices were determined. Organs with squamous and with glandular epithelium except the mammary gland showed a proliferation peak during early proestrus, the incidence of labelling being higher in organs with squamous epithelium. During early proestrus the intensity of labelling decreased in organs with squamous epithelium in the following order: vulva, vagina, portio vaginalis, and portio supravaginalis. At this time cell replication was higher in the superficial glands of the cervix and corpus uteri as well as the circular layer of the myometrium compared with values from the basal glands or the longitudinal layer. The steepest decline of the proliferative activity occurred between the proestrous period. While some labelled cells were observed during secretory metestrus, labelling was almost absent during regressive metestrus. By contrast, the mammary gland began to develop at the periovulatory period and was at the height of its proliferative activity during secretory metestrus. It is concluded for species with a long estrous cycle that: (1) the rate of cell replication in the vulva, vagina, uterus and oviduct is at its peak at the beginning of the estrous cycle and declines during proestrus; (2) as compared to observations in species with short estrous cycles, cell proliferation is very low during metestrus.

Animals↗