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PubMed1996

Controlled, reversible suppression of estrous cycles in beef heifers and cows using agonists of gonadotropin-releasing hormone.

Agonists of GnRH were examined for their potential to achieve controlled, reversible suppression of estrous cycles in beef cattle. In Exp. 1, cyclic heifers received two (Group B2) or four (Group B4) buserelin (D-Ser[Bu(t)]6-Pro9-LHRH[1-9] nonapeptide ethylamide) implants and degree of cessation of estrous cycles was monitored. Treatment with buserelin caused estrous cycles to cease, as indicated by basal (.2 ng/mL) concentrations of progesterone, for 48.4 +/- 3.8 d (mean +/- SEM) in Group B2, which was less (P = .6) than the 87.4 +/- 17.4 d in Group B4. In Exp. 2, heifers treated with one (Group D1) or two (Group D2) implants of deslorelin (D-Trp6-Pro9-des-Gly10-LHRH ethylamide) had basal progesterone concentrations for 203 +/- 26 d (Group D1) and 170 +/- 28 d (Group D2; P > .05). In Exp. 3, stage of the estrous cycle was synchronized in cows, and, on d 7 of the ensuing cycle, cows received four deslorelin implants for 28 (Group D28) or 56 d (Group D56). Treatment with deslorelin induced an acute increase in plasma concentrations of immunoactive and bioactive LH, which remained increased over 7 d of observation. Based on profiles of progesterone, cows did not develop a functional corpus luteum during deslorelin treatment. Days to first and second estrus after implant removal were similar for cows in Group D28 (23.6 +/- 2.1 and 40.2 +/- 4.2 d, respectively) and Group D56 (21.5 +/- 3.3 and 44.3 +/- 2.9 d). The findings indicated that GnRH agonists block estrous cycles in cattle. Also, estrous cycles returned after discontinuation of treatment. Furthermore, the consistent and predictable responses detected in cows after implant removal indicated that agonists should be suitable for achieving a controlled, reversible suppression of estrous cycles in cattle.

Animals↗
PubMed1997

Synthesis and messenger ribonucleic acid expression of apolipoproteins E and A-I by the bovine corpus luteum during the estrous cycle and pregnancy.

In an attempt to characterize proteins secreted by the corpus luteum, explant cultures of luteal slices from cows taken on Days 3, 7, 11, 14, 17, and 19 of the estrous cycle, and Days 17, 88, 180, and > 240 of pregnancy were incubated with H-leucine for 24 h. Proteins in luteal-conditioned medium were separated by two-dimensional PAGE, transferred to polyvinylidene fluoride membrane, and subjected to N-terminal amino acid microsequencing. Microsequence analysis revealed that the bovine corpus luteum synthesized and released de novo synthesized apolipoproteins (Apo) E and A-I in culture during the estrous cycle and pregnancy. Release of Apo E was observed only on Day 3 of the estrous cycle. Release of Apo A-I was observed on Days 11, 14, 17, and 19 of the estrous cycle, and on all days of pregnancy examined. To demonstrate the presence of the appropriate mRNA and characterize the temporal relationship for these identified proteins, total RNA was isolated from corpora lutea on Days 2, 3, 7, 16, 17, and 20 of the estrous cycle, and on Days 17, 90, 170, 180, and 272 of pregnancy, and submitted to Northern and dot blot analysis. Apo E mRNA was expressed only on Days 2-3 of the estrous cycle and was not expressed on the other days of the cycle or during pregnancy. A single Apo E mRNA transcript about 1.0 kilobase (kb) in size was observed. Expression of Apo A-I mRNA was detected on all days of the estrous cycle and pregnancy examined. Apo A-I cDNA hybridized with a single mRNA transcript about 1.0 kb in size. Apo A-I mRNA levels did not differ among days of the estrous cycle, although higher levels of Apo A-I mRNA were observed during later stages of pregnancy. Serum concentrations of Apo A-I and progesterone were correlated across the estrous cycle but not during the prepartum period or after parturition. This study demonstrates for the first time that the corpus luteum synthesizes Apo E and Apo A-I and expresses their respective mRNAs. The pattern of expression of Apo E and Apo A-I mRNAs paralleled that of de novo synthesis of their respective proteins after incubation of luteal tissue with [H]leucine. The role of luteal apolipoproteins may involve an autocrine/paracrine function influencing luteal development, tissue remodeling, and steroidogenesis.

Amino Acid Sequence↗
PubMed2003

Regulation of Akt expression and phosphorylation by 17beta-estradiol in the rat uterus during estrous cycle.

Molecular and intra-cellular mechanisms involved in the regulation of apoptosis processes in endometrial cells are poorly understood and documented. We have investigated the possibility that Akt survival pathway might be involved in the regulation of apoptosis in the uterus during the estrous cycle. Rats with regular estrous cycle (4 days) were killed at different days of estrous cycle (diestrus, proestrus, estrus and metestrus). Uteri were collected and fixed for immunohistochemical staining (IHC) and apoptotic cell death detection by [TdT]-mediated deoxyuridinetriphosphate nick end-labelling (TUNEL) or endometrial protein extracts collected for Western analysis. TUNEL analysis revealed that apoptosis was mainly found at estrus compared to other day of estrous cycle. TUNEL positive cells were apparent in luminal epithelial cells only. No apoptotic cells were observed at proestrus. In contrast, proliferation was maximal at proestrus as confirmed with the expression of CDC47/MCM7 (a cell proliferation marker). Intact form of caspase-3 was maximal at proestrus and was reduced only at estrus. Likewise, presence of a specific cleaved caspase-3 fragment was observed only at estrus and IHC revealed that cleaved caspase-3 signal was found in luminal epithelial cells. PTEN protein, a phosphatase involved in the regulation of Akt phosphorylation, was present at all days of estrous cycle and showed no significant regulation in relation to cycle. Expression of phospho-Akt (the activated form of Akt) was present at metestrus, diestrus, and proestrus but decreased significantly at estrus. Akt protein expression was maximal at estrus. IHC revealed that Akt expression was high in both stromal and epithelial cells at estrus. Further studies using ovariectomized rats demonstrated that 17beta-estradiol increased endometrial cell proliferation which was accompanied by an increase of both Akt expression and phosphorylation. These results suggest that increased Akt expression and activity in response to estradiol may be an important mechanism to protect endometrial cells from apoptotic triggering and to induce endometrial cell proliferation, whereas inhibition of Akt activity leads to caspase-3 activation and apoptosis in endometrial cells.

Animals↗
PubMed1989

Effect of estradiol on secretion of luteinizing hormone during the follicular phase of the bovine estrous cycle.

Mean concentrations of luteinizing hormone (LH) increase during the follicular phase of the estrous cycle in cows. The working hypotheses in the present study were (1) that increasing concentrations of 17 beta-estradiol (E2) during the follicular phase of the estrous cycle cause an increase in mean concentration of LH by increasing amplitude of pulses of LH, and (2) that increasing E2 concentrations during this stage of the estrous cycle decrease frequency of pulses of LH in bovine females. Day of estrus was synchronized in seventeen mature cows. Treatments were initiated on Day 16 of the experimental estrous cycle (Day 0 = estrus). At Hour 0 (on Day 16), 4 cows were lutectomized. Lutectomy of these cows (EE; n = 4) allowed for endogenous secretion of E2. The remaining cows were ovariectomized at Hour 0 and were assigned to one of three E2 treatments: luteal phase E2 (LE, n = 5), increasing then decreasing E2 (DE, n = 5), and no E2 (NE, n = 3). Cows in the group that received LE were administered one E2 implant at Hour 0, which provided low circulating concentrations of E2 similar to those observed during the luteal phase of the estrous cycle. Cows in the group that received DE were administered one E2 implant at Hour 0, and additional implants were administered at 8-h intervals through Hour 40; then, two implants were removed at Hours 48 and 56, and one implant was removed at Hour 64.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Role of LH and prostaglandin F2alpha on the development and regression of corpus luteum in mithun (Bos frontalis) estrous cycle.

The present investigation was designed to study the role of LH and prostaglandin F2alpha (PGF2alpha) on the development and regression of corpus luteum (CL) in the mithun estrous cycle. Blood samples were collected from jugular vein and PGF2alpha secretion was evaluated on the basis of peripheral 15-keto-13,14-dihydro-PGF2alpha (PGFM) concentration. The daily variations in plasma LH, PGFM, and progesterone (P4) concentrations throughout the estrous cycle were monitored in morning and evening blood samples. The variations in plasma LH, PGFM, and P4 concentrations during the early luteal phase were monitored in blood samples that were collected every 2 h until 120 h following the onset of estrus (Day 0). The pulsatile secretion patterns of plasma LH, PGFM and P4 during estrus (Day 1), mid-diestrus (Day 10), and luteolysis (Day 14) were assessed in blood samples that were collected every 15 min for 6h. In the estrous cycle, P4 concentration increased above basal level on day 6-7, peaked on day 10-12 and declined thereafter. Following estrus, a significant (P<0.01) gradual increase in P4 concentration was observed. LH concentration was found to be significantly (P<0.01) greater around estrus and it declined gradually (P<0.01) following estrus. In the estrous cycle, PGFM concentration increased above basal level on day 9-11, peaked on day 16-17, and declined thereafter. The frequency of LH pulses and basal LH concentration were found to be significantly (P<0.01) greater on day 1, but significantly (P<0.01) greater amplitude of LH pulses was found on day 10 and 14. The frequency of P4 and PGFM pulses was found to be significantly (P<0.01) greater on day 1. In contrast, the amplitude of P4 and PGFM pulses and basal P4 and PGFM concentrations were found to be significantly (P<0.01) greater on day 10 and 14. The results indicate that probably the early stages of CL development continued until day 5-6 of the estrous cycle and a fully functional CL existed approximately at the mid estrous cycle. Luteolysis probably started since day 11-13 of the cycle and completed before the onset of the next estrus. The elevated basal LH concentration along with frequent low amplitude LH pulses were probably required for the early stages of CL development. In contrast, the high amplitude LH pulses of lower frequency during the mid estrous cycle were either sufficient or not required for maintaining the luteal function. Whereas, PGF2alpha pulses of greater amplitude and elevated basal PGF2alpha concentration during the mid and late estrous cycle were probably responsible for luteolysis.

Animals↗
PubMed1995

Benzodiazepine binding varies with stage of estrous cycle in unwashed membranes from mouse brain.

The influence of the stage of the estrous cycle on binding of [3H]diazepam was examined in membranes from brains of female mice. In order to conserve endogenous factors such as progesterone, other steroids, or GABA, the assay was performed without the extensive washing procedures typically employed in measurements of benzodiazepine binding. Significant variations in the apparent maximal numbers of binding sites (Bmax) were noted during the estrous cycle in both hypothalamus and cortex. The Bmax measured in membranes from proestrus female mice was significantly higher than in membranes from mice at other stages in the estrous cycle. Variations in apparent equilibrium binding dissociation constants (Kd) were not statistically significant by stage of the estrous cycle. The demonstrated variations in binding suggest the existence of a factor which varies with the estrous cycle in female mice and modulates the activity of the GABAA receptor complex.

Animals↗
PubMed1976

Circadian organization of the estrous cycle of the golden hamster.

In constant dim illumination the hamster estrous cycle free-runs with a period that is a quadruple multiple of the concurrently recorded rhythm of wheel-running activity; both activity and estrous cycles are generated by biological clocks. Maintenance of stable phase angle differences between heat onset and running onset before and after treatment with deuterium oxide suggests that a common circadian system generates periodicities in estrus and activity. An organization of the estrous cycle is proposed in which the stimulus for the ovulatory surge of luteinizing hormone is generated by a circadian system that includes the suprachiasmatic nuclei of the hypothalamus. Various possible interactions of estradiol and photoperiod with the neurogenic stimulus for the luteinizing hormone surge are described and implications of different types of circadian organization of the estrous cycle for theories of sexual differentiation are considered.

Animals↗
PubMed2003

The beta1-adrenoceptor site activated by CGP12177 varies in behavior according to the estrous cycle phase and stress.

The aim of this work was to assess whether stress and estrous cycle phases affected the beta1-adrenoceptor (beta1-AR) site activated by CGP12177 in the right atria of rats. The chronotropic response to CGP12177 in the absence or presence of antagonists was determined in atria from rats submitted to one daily foot-shock session for 3 consecutive days. Blood was collected for hormonal assays. The pD2 for CGP12177 in atria from females was lower than in atria from males and was unaltered by stress or the estrous cycle. Propranolol (200 nM) or CGP20712A (3 microM) shifted the concentration-response curves to CGP12177 to the right in control and stressed estrus or control diestrus rats. Atria from stressed diestrus rats were resistant to blockade by propranolol or CGP20712A, indicating that the effect of beta-adrenoceptor antagonists on the response to CGP12177 is influenced by estrous cycle phases. The stress-induced increase in serum corticosterone levels was independent of the estrous cycle or gender, but the estradiol/progesterone ratio was affected differently in the two groups of female rats. In the diestrus group, serum estradiol levels decreased after the first foot-shock session and remained low until the day of sacrifice, whereas in the estrus group the serum levels of estradiol did not decrease after stress and peaked on the second day, which corresponded to proestrus. These data do not indicate whether there is a direct or indirect effect of stress hormones and (or) sex steroids on cardiac beta1-AR sensitivity. However, they do show that the classic and low-affinity binding sites of the beta1-AR are independently regulated and that the beta1-AR atypical site affinity for antagonists depends on the estrous cycle.

Adrenergic beta-1 Receptor Agonists↗
PubMed2006

Anterior pituitary cell renewal during the estrous cycle.

The anterior pituitary gland undergoes a process of cell renewal during the estrous cycle. Although the occurrence of proliferation and death of anterior pituitary cells at specific stages of the estrous cycle is well known, the underlying mechanisms that regulate these processes are still being uncovered. In spite of the recognized proliferative effects of estrogens on lactotropes, recent evidence shows that estrogens can also trigger antiproliferative and apoptotic responses in anterior pituitary cells. In the present review we analyze the actions of gonadal steroids on proliferation and death of anterior pituitary cells during the estrous cycle and the mediators involved in these actions. Estradiol sensitizes anterior pituitary cells not only to mitogenic stimuli but also to apoptotic signals and upregulates local synthesis of tropic growth factors as well as proapoptotic cytokines. Several growth factors and cytokines have been shown to induce estrogen-dependent lactotrope proliferation and death, whereas progesterone antagonizes estrogen-induced effects. These locally synthesized factors may mediate the effects of gonadal steroids in the process of anterior pituitary cell renewal during the estrous cycle.

Animals↗
PubMed2005

[Influences of applying force during the different stages of estrous cycle on orthodontic tooth movement of rats].

OBJECTIVE: To explore the effects of applying force during the different stages of estrous cycle on orthodontic tooth movement of rats, so as to offer an experimental princinple for women's orthodontic treatment. METHODS: 80 female 3-month-old Wistar rats, which had a stable and five-day estrous cycle, were used. They were randomly divided into control groups and loading-force groups. Each group was divided again into 4 sub-groups according to the different stages of the estrous cycle. The loading-force groups received repeated intermittent orthodontic force for four times seperately during the same stage of the estrous cycle. The distance between upper incisor and the first molar on the left was measured. The data were analyzed by One-way ANOVA, S-N-K. RESULTS: There were significant variations in the amount of tooth movement among the groups which received the mechanical force during the different stages of the estrous cycle (P <0.01). There were significant variations in the amount of tooth movement between the groups received force during pre-estrus and estrus (P <0.05). There were not significant variations between the groups received force during metestrus and diestrus (P > 0.05). The largest amount of tooth movement was in estrus group and smallest in pre-estrus one. CONCLUSION: The effect of tooth movement depended on which stage of estrous cycle was chosen to be the time of applying orthodontic force.

Analysis of Variance↗
PubMed1985

Release of progesterone by porcine luteal cells from different days of estrous cycle: effect of LH, PRL and PGF2 alpha.

The secretion of progesterone (P4) by porcine luteal cells from 5th, 8th, 14-16th and 17th day of estrous cycle was estimated under basal conditions and after stimulation with LH (0.1 and 1 microgram ml-1), PRL (2 micrograms ml-1) and PGF2 alpha (0.1 and 5 micrograms ml-1). P4 in the medium was estimated by radio-immunological method after 30 min and then after 3, 6, 9 and 15 h of incubation. Luteal cells from 5th, 8th, 13th, 14-16th and 17th day of estrous cycle released on average 140.9 +/- 14.4, 138.9 +/- 12.7, 224.4 +/- 21.3, 62.3 +/- 4.2 ng and 6.4 +/- 0.6 ng P4 per ml-1 medium, respectively. Luteal cells from 5th day of the estrous cycle significantly increased (P less than 0.05) P4 release during first 30 min of incubation in the presence both doses of LH, but the dose of 1 microgram LH significantly stimulated P4 secretion during next 3 h, too. Only the luteal cells from 13th day of the estrous cycle increased (P less than 0.05) P4 production in the presence of 1 microgram LH, and prolactin exerted luteolytic effect also only on luteal cells from 13th day of the estrous cycle. The release of P4 by luteal cells from 5th day of the estrous cycle increased (P less than 0.05) during first 30 min of incubation in the presence of PGF2 alpha. However, PGF2 alpha (5 micrograms) exerted inhibitory effect (P less than 0.05) on P4 release by luteal cells from only 13th day of the estrous cycle. The results showed that the effect of these hormones on P4 secretion by luteal cells depended on the period of estrous cycle and doses used.

Animals↗
PubMed2004

Changes in the content and distribution of microtubule associated protein 2 in the hippocampus of the rat during the estrous cycle.

The molecular mechanisms involved in the regulation of synaptic plasticity in the hippocampus during the estrous cycle of the rat are not completely understood. Because this process implicates changes in neuronal cytoskeleton organization, we analyzed the content of microtubule associated protein 2 (MAP2) and Tau in the hippocampus and the frontal cortex of the rat by Western blot, as well as the hippocampal distribution of MAP2 during the estrous cycle by immunohistochemistry. In the hippocampus the lowest content of MAP2 was found on diestrus day, and it significantly increased at proestrus. This increase was maintained on estrus and metestrus days. In the frontal cortex MAP2 content did not significantly change during the estrous cycle. In contrast, the content of Tau did not vary during the estrous cycle in either the hippocampus or the frontal cortex. The immunohistochemical analysis showed an increase in dendrite thickness and in dendritic branching in the CA1 region on proestrus day, as well as an aggregation of MAP2 in apical dendrites near to pyramidal somata on this day in comparison with diestrus. We suggest that changes in the content and neuronal distribution of MAP2 are involved in the structural changes that occur in the hippocampus of the rat during the estrous cycle, and that these variations are related to changes in estradiol and progesterone levels.

Animals↗
PubMed1998

Sleep homeostasis in the female rat during the estrous cycle.

To investigate whether sleep homeostasis in the female rat is modulated by the estrous cycle, the vigilance states, EEG power spectra and cortical temperature (TCRT) were assessed on the basis of 4-day continuous recordings. A regulatory response was elicited by 6-h sleep deprivation (SD) during the proestrous (PRO) and the estrous (EST) day and compared to the baseline recordings. The vigilance states varied across the estrous cycle. In the PRO dark period the amount of sleep was reduced. The decrease in rapid-eye-movement (REM) sleep was already evident towards the end of the preceding light period, and an increased fragmentation of sleep was present throughout PRO. Compared to the other days of the estrous cycle, slow-wave activity (SWA; EEG power density 0.75-4.75 Hz) in nonREM (NREM) sleep was lower in PRO at the end of the light period and in the beginning of the dark period. High-frequency activity (HFA; EEG power density 10.25-25.0 Hz) was increased in the dark period of PRO. The SD performed during the first 6 h of the light period of PRO and EST enhanced SWA in NREM sleep and reduced sleep fragmentation during the subsequent 6 h. The extent and time course of the response to SD did not differ between the two phases of the estrous cycle. It is concluded that despite the marked baseline variations of the vigilance states and the EEG, homeostatic regulation is little affected by the estrous cycle.

Animals↗
PubMed2003

Glucoprivic regulation of estrous cycles in the rat.

Previous research has shown that glucoprivation induced by chronic 2-deoxy-D-glucose (2DG) treatment extends estrous cycle length and disrupts reproductive behaviors in female hamsters, similar to food deprivation. Such treatment also suppresses food intake, which is reversed in male rats by reducing brain histamine levels prior to 2DG treatment. We, therefore, determined if 2DG extends estrous cycles in the female rat and if this is due to elevated brain histamine levels. We measured estrous cycle length during 2DG-induced glucoprivation, in the presence and absence of alpha-fluoromethylhistidine (FMH), a treatment that reduces brain histamine levels. Adult female rats were treated for 72 h with either saline (n = 8), 2DG (200 mg/kg S.C. every 6 h; n = 9), or FMH (100 mg/kg i.p. daily) + 2DG (200 mg/kg; n = 7). An additional group was treated with FMH (100 mg/kg i.p.; n = 5) alone. To determine if 2DG extends estrous cycles due to glucoprivation or to decreased caloric intake, a group of rats (n = 7) received a reduced diet equal to the mean daily food intake of rats receiving 2DG alone. 2DG induced more long estrous cycles compared to rats receiving saline, FMH + 2DG, or FMH alone. In rats treated with FMH + 2DG, the percentage of 4-5-day cycles was similar to that of saline-treated rats, and a high percentage of 4-5-day cycles was also observed in rats receiving a reduced diet. These data suggest that 2DG does not suppress estrous cycles through a decrease in total calorie intake, but rather by inducing glucoprivation. In addition, during 2DG-induced glucoprivation, elevated brain histamine levels contribute to the mechanism that suppresses reproductive function.

Animals↗
PubMed1992

Ultrastructural changes in guinea pig endometrial cells during the estrous cycle.

In the guinea pig, the estrous cycle is characterized by a constant measurable level of plasma progesterone with two peaks: the first one associated with the peak of plasma estradiol-17 beta occurring at proestrus and the second, during diestrus, more pronounced at the time at which the level of estradiol-17 beta is undetectable. The progesterone receptor content is the highest on day 1 and the lowest on day 10 of the estrous cycle, which lasts 16.3 +/- 1.5 days (n = 37; mean +/- SD). There is a positive correlation between the plasma level of estradiol-17 beta and the progesterone receptors detected immunocytochemically in both endometrial epithelial and stromal cells. The general morphology of the endometrium during proestrus and estrus is consistent with an estrogenic stimulation, i.e., a smooth and regular surface of the endometrium and the presence of numerous microvilli on the cell surface. However, a moderate secretory activity also occurs in proestrus and estrus. During postestrus, the glandular cells display an increase in characteristic secretory features which parallels the rise of progesterone in the plasma.

Animals↗
PubMed2002

Uterine and ovarian blood flow during the estrous cycle in mares.

Uterine and ovarian blood flow was investigated in four mares during two consecutive estrous cycles using transrectal color Doppler sonography. The uterine and ovarian arteries of both sides were scanned to obtain waves of blood flow velocity. The pulsatility index (PI) reflected blood flow. There were significant time trends in PI values of all uterine and ovarian blood vessels during the estrous cycle (P < 0.05). PI values did not differ between the uterine arteries ipsi- and contralateral to the corpus luteum or the ovulatory follicle. PI values of the uterine arteries showed a wave shaped profile throughout the estrous cycle. The highest PI values occurred on Days 0 and 1 (Day 0 = ovulation) and around Day 11, and the lowest PI values were measured around Days 5 and -2 of the estrous cycle. During diestrus (Days 0-15) PI values of the ovarian artery ipsilateral to the corpus luteum were significantly lower than PI values of the contralateral ovarian artery (P < 0.0001). No differences (P > 0.05) in resistance to ovarian blood flow occurred between sides during estrus (Days -6 to -1). In this cycle stage PI values decreased in both ovarian vessels (P < 0.05). During diestrus, high PI values of the ovarian artery ipsilateral to the corpus luteum were measured between Days 0 and 2, followed by a decline until Day 6 (P < 0.05). From this time on, the resistance to blood flow increased continuously until Day 15 (P < 0.05). The cyclic blood flow pattern in the contralateral ovarian artery was similar to that in the uterine arteries (r = 0.68; P < 0.0001). No correlations occurred between the diameter of the corpus luteum and the PI values of the ipsilateral ovarian artery (P > 0.05) during diestrus. During estrus, there was a negative relationship between growth of the diameter of the ovulatory follicle and changes in PI values of the dominant ovarian artery (r = -0.41; P < 0.05). PI values of the uterine arteries and of the ovarian artery ipsilateral to the ovulatory follicle were negatively related to estrogen (E) levels in plasma during estrus (uterine arteries: r = -0.21; P < 0.05; dominant ovarian artery: r = -0.35; P < 0.05). In diestrus, PI values of the dominant ovarian artery were negatively related to plasma progesterone levels (r = -0.38; P < 0.0001), but not the PI values of the uterine arteries (P > 0.05). The findings of this study show that there are characteristic changes in blood supply of the uterus and the ovaries throughout the equine estrous cycle. There are negative correlations between resistance to blood flow in the uterine and ovarian arteries and the plasma estrogen levels during estrus. In diestrus, there is a negative relationship between the resistance to ovarian blood flow and the progesterone levels.

Animals↗
PubMed2003

Concentrations of progesterone, follistatin, and follicle-stimulating hormone in peripheral plasma across the estrous cycle and pregnancy in merino ewes that are homozygous or noncarriers of the Booroola gene.

The circulating concentrations of progesterone, FSH, and follistatin across the estrous cycle and gestation were compared in Australian merino sheep that were homozygous for the Booroola gene, FecB, or were noncarriers. The Booroola phenotype is due to a point mutation in the bone morphogenetic protein receptor 1B. Progesterone concentrations began to rise earlier and were higher in the Booroola ewes than in the noncarriers on most days of the luteal phase but not during the follicular phase of the cycle. Follistatin concentrations remained unchanged across the estrous cycle in both groups of ewes, with no differences between genotypes. FSH concentrations were higher in Booroola ewes than in noncarrier ewes on most days of the estrous cycle, with a significantly higher and broader peak of FSH around the time of estrus. Progesterone concentrations were significantly higher in early and midgestation in Booroola ewes but were lower toward the end of gestation than those in noncarriers. FSH declined in both groups across gestation, with lower concentrations of FSH in Booroola ewes during midgestation. Follistatin remained unchanged across gestation in Booroola ewes and noncarrier ewes with a twin pregnancy but declined across gestation in noncarrier ewes with a singleton pregnancy. These results suggest that follistatin concentration is not regulated by the FecB gene during the estrous cycle and pregnancy but is influenced by the number of fetuses. However, the FecB gene appears to positively affect both progesterone and FSH during the estrous cycle and across pregnancy, which suggests that bone morphogenetic proteins play an important role in the regulation of both hormones.

Animals↗
PubMed2003

Evidence for the regulation of glycosylation of golden hamster (Mesocricetus auratus) oviductin during the estrous cycle.

The oviduct contributes to the reproductive environment by secreting various factors, including a family of glycoproteins termed oviductins. Although many studies have demonstrated that ovarian hormones modulate oviductin gene expression in several mammalian species, there has been controversy surrounding the regulation of golden hamster oviductin. The current study was undertaken to investigate the transcriptional and translational modifications of hamster oviductin during the estrous cycle. First, we verified that hamster oviductin mRNA expression remains constant throughout the estrous cycle by semiquantitative reverse transcription polymerase chain reaction. We then developed a polyclonal antibody against recombinant hamster oviductin (rhaOvm). The anti-rhaOvm antibody was subsequently used in conjunction with quantitative immunocytochemistry to investigate the oviductin levels in the hamster oviduct during the estrous cycle. Quantification of immunolabeling revealed a high, consistent level of glycoprotein throughout the estrous cycle. Therefore, it appears that the production of oviductin is not regulated differentially during the estrous cycle. Size variations in hamster oviductin expression were also investigated by Western blot analysis. The oviduct contains several forms of oviductin at each stage of the estrous cycle, the native glycosylated form(s) of 160-350 kDa, and several precursor forms of 70-100 kDa. Although variations in the intensities of the polydispersed band were not evident during the estrous cycle, additional bands ranging from 90 to 100 kDa were detected in the estrus, metestrus, and diestrus 1 stages. The results from the present investigations suggest that whereas ovarian hormones do not appear to influence the hamster oviductin mRNA and protein expressions, glycosylation of hamster oviductin appears to be differentially regulated during the estrous cycle.

Animals↗