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PubMed2004

Uterine motor alterations and estrous cycle disturbances associated with colonic inflammation in the rat.

The impact of colitis on uterine contractility and estrous cycle was investigated after intracolonic administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in rats. Colitis severity was assessed by macroscopic damage scoring (MDS) 4 days after TNBS, and myeloperoxidase (MPO) activity was measured in both colon and uterus of control and colitic rats. Estrous cycle stages were determined by vaginal smears and histology, and uterine contractility was assessed in vitro on longitudinal and circular strips. In control rats, uterine MPO activity varied markedly during the cycle and peaked around estrus. In rats with moderate colitis [MDS < 5, 3.1 +/- 0.2 (mean +/- SE)], uterine MPO decreased by 61% compared with estrus control, without disruption of the cycle. Frequency of spontaneous contractions was reduced by 32% in circular muscle. Contractile responses to KCl and carbachol were not affected, whereas maximal response to oxytocin decreased by 47% in the longitudinal muscle. In rats with severe colitis (MDS > 5, 6.0 +/- 0.2), uterine MPO was reduced by 96% and estrous cycle was disrupted. Spontaneous contractility was impaired in circular strips, and a 39% decrease in the contraction frequency occurred in the longitudinal strips. Circular strips did not contract to KCl or carbachol; however, longitudinal strips had maximal responses to KCl, carbachol, and oxytocin reduced by 36%, 27%, and 46%, respectively. Estrogen replacement protected the uterine responses to carbachol in colitic rats, whereas oxytocin responses remained depressed. These data indicate that colonic inflammation can influence both spontaneous and evoked uterine contractility, in relation to estrous cycle disturbances, impaired estradiol production, and functional alterations of myometrial cells.

Animals↗
PubMed2004

Effect of increasing levels of undegradable intake protein on metabolic and endocrine factors in estrous cycling beef heifers.

To determine the influence of three levels of undegradable intake protein (UIP) supplementation on metabolic and endocrine factors that influence reproduction, 23 yearling crossbred heifers (body condition score = 4.5 +/- 0.5; initial BW = 362 +/- 12 kg) were stratified by BW and assigned randomly to one of three supplements: 1) low UIP (1,135 g x heifer(-1) x d(-1); 30% CP, 115 g UIP, n = 7); 2) mid UIP (1,135 g x heifer(-1) x d(-1); 38% CP, 216 g UIP, n = 8); or 3) high UIP (1,135 g x heifer(-1) x d(-1); 46% CP, 321 g UIP, n = 8). Heifers were estrually synchronized before initiation of supplementation. Supplement was individually fed daily for 30 to 32 d, at which time heifers were slaughtered (d 12 to 14 of the estrous cycle) and tissues collected. Heifers were fed a basal diet of sudan grass hay (6.0% CP) ad libitum. On d 28 of supplementation (d 10 of the estrous cycle), no differences were observed (P > 0.10) in serum insulin or IGF-I among treatments. At slaughter (d 10 to 12 of the estrous cycle), treatments did not influence corpus luteum weight, cerebral spinal fluid leptin, or IGFBP; serum estradiol-17beta, progesterone, leptin, IGF-I, and IGFBP; or anterior pituitary content of IGFBP (P > 0.10). Follicular fluid IGFBP-2 and IGFBP-4 were greater in high-UIP heifers than low- or mid-UIP heifers on d 12 to 14 of the estrous cycle (P < 0.05). Basal serum LH concentrations and LH area under the curve (every 15 min for 240 min) did not differ (P > 0.10) following 28 d of supplementation (d 10 of the estrous cycle); however, basal serum FSH concentrations were greater (P = 0.06) in low- and mid- vs. high-UIP heifers (5.2 and 5.2 vs. 4.6 ng/mL, respectively), and FSH area under the curve was greater (P = 0.03) in low- vs. high-UIP heifers. At slaughter (d 12 to 14 of the estrous cycle), anterior pituitary LH and FSH content and steady-state mRNA encoding alpha, LHbeta, and GnRH receptor did not differ (P > 0.10) among treatments. However, FSHbeta mRNA was increased approximately twofold (P = 0.03) in mid vs. low UIP. In summary, low and mid levels of UIP supplements fed to estrous cycling beef heifers seemed to enhance pituitary expression and/or secretion of FSH relative to high levels of UIP. Moreover, high-UIP supplementation was associated with increased low-molecular-weight IGFBP compared with supplementation of low and mid levels of UIP. These data suggest that differing levels of UIP supplementation may alter pituitary and ovarian function, thereby influencing reproductive performance in beef heifers.

Animal Nutritional Physiological Phenomena↗
PubMed1989

Effect of termination of pregnancy or long-term progestogen exposure on subsequent estrous cycle length and concentration of progesterone in plasma of heifers.

An experiment was conducted to determine whether short estrous cycles following abortion of heifers between 70 and 75 d of gestation are due to factors associated with the previous presence of a conceptus or long-term exposure of the uterus and(or) ovaries to a progestogen. Fifty crossbred heifers were randomly allotted at estrus (d 0) to five groups: control (n = 10), pregnant (Preg.; n = 14), progestogen (norgestomet) implant (Norg.; n = 9), progesterone-releasing intravaginal device (PRID; n = 9), or hysterectomy (Hyst.; n = 8). Control heifers were injected during the mid-luteal phase of an estrous cycle with 25 mg prostaglandin F2 alpha (PGF2 alpha) and length of the subsequent estrous cycle was determined. Beginning 6 to 8 d after estrus, heifers in the Norg. or PRID groups were given norgestomet ear implants or intravaginal coils, respectively, every 10 d for 70 d. Heifers were hysterectomized 5 to 8 d after estrus. Seventy to 75 d after conception, progestogen treatment or hysterectomy, heifers were injected (i.m.) with 25 mg PGF2 alpha and the last norgestomet ear implants or PRIDs were removed. Interval from PGF2 alpha injection to first estrus (means +/- SE) ranged from 2.5 +/- .2 to 4.4 +/- .7 d (P greater than .05). Length of the first estrous cycle means +/- SE) following PGF2 alpha-induced luteolysis or progestogen withdrawal was shorter (P less than .01) for the Preg. group (8.2 +/- .4 d) than for the control, Norg. and PRID groups (21.5 +/- .6 d; 19.3 +/- 1.4 d; and 18.2 +/- 1.3 d, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Induced↗
PubMed1988

Effect of feeding tall fescue seed infected with endophytic fungus (Acremonium coenophialium) on the estrous cycle in CD-1 mice.

The objective of this study was to assess the effects of endophyte-infected tall fescue (G1-307) seed (80% infected, by Acremonium coenophialum) on the estrous cycle in CD-1 mice. Twelve 60-day-old CD-1 female mice were randomly allocated to one of two dietary treatments containing 50% laboratory chow and (1) 50% endophyte-free (noninfected) fescue seed; (2) 50% endophyte-infected fescue seed. All mice were fed ad libitum. On day 35 of the study all mice were allowed access to a diet containing 100% laboratory chow for 7 days. Vaginal smears of each female were prepared daily throughout the 42 day trial period. All vaginal smears were stained and evaluated to determine phase of the estrous cycle. The days (+/- SE) to the first abnormal occurrence in the estrous cycle for treatments one and two were 27.0 +/- 5.6 and 16.7 +/- 5.2, respectively. The percent abnormal cycles of the total cycles observed between treatments one and two were 20.5 +/- 6.1 and 39.3 +/- 12.5, respectively. Mice on treatment two exhibited a greater frequency of abnormal sequences of the phases of the estrous cycle and greater cycle length (P less than 0.05). The results suggest that the infected fescue seed had a significant effect on the estrous cycle of the mouse (P less than 0.05).

Acremonium↗
PubMed1997

Central vs. peripheral metabolic control of estrous cycles in Syrian hamsters. I. Lipoprivation.

Metabolic energy availability has profound effects on reproduction in a wide variety of species. We have been studying the effects of fasting on estrous cycles in Syrian hamsters as a model system for metabolic control of reproduction. In previous experiments, a 48-h period of fasting inhibited estrous cycles in lean, but not fat, hamsters. In fat hamsters the effects of fasting may have been offset by the presence of high circulating levels of free fatty acids mobilized from lipids in adipose tissue. Consistent with this idea fat hamsters treated with the inhibitor of fatty acid oxidation methyl palmoxirate (MP) showed fasting-induced anestrus. Experiment 1 was designed to examine whether vagally transmitted signals are critical for the inhibitory effects of fasting and MP treatment. Lean or fat hamsters that had received bilateral subdiaphragmatic vagotomy or sham surgery were fasted and treated with MP or vehicle. In vagotomized and sham-operated hamsters, estrous cycles were inhibited in lean fasted hamsters and in fat fasted hamsters treated with MP, but not in fat fasted hamsters treated with vehicle. Thus the results of experiment 1 indicated that vagally transmitted signals about peripheral fatty acid availability are not critical for the effects of these particular metabolic challenges on estrous cycles in Syrian hamsters. In experiment 2, hamsters without food were allowed to ingest pure glucose or fructose solutions or vegetable shortening. One-half of each group was treated with an inhibitor of glucose utilization, 2-deoxy-D-glucose (2-DG), or vehicle. If ingestion of fructose or shortening, but not glucose, had protected hamsters from 2-DG-induced anestrus, this might have indicated that peripheral fuel availability is critical for anestrus. On the contrary, 2-DG treatment induced anestrus regardless of the type of fuel ingested. Neither experiment yielded results that implicated changes in peripheral fuel availability as a critical signal in metabolic control of estrous cycles.

Anestrus↗
PubMed1988

Changes in lipid contents and fatty acid compositions in ovine corpora lutea during the estrous cycle and early pregnancy.

Changes in lipid contents and fatty acid compositions of each lipid fraction were examined in corpora lutea from 34 unmated ewes between Days 8 and 16 of the estrous cycle and from 6 ewes at Day 16 of pregnancy. Four patterns were observed during advancement of the estrous cycle. Luteal concentrations of free cholesterol and triglyceride (neutral lipids) increased between Days 14 and 16, during luteal regression, in a manner approximated by exponential functions of time, whereas luteal concentrations of phospholipid (polar lipids) increased and then decreased between Days 8 and 16 in a manner approximated by a sin function of time. Likewise, within the various lipid class component fatty acids, changes in palmitic acid weight percentages were approximated by sin functions of time, whereas arachidonic acid weight percentages increased between Days 14 and 16 in a manner approximated by exponential functions of time. Pregnancy either inhibited or reversed the changes in luteal lipid profiles, especially arachidonic acid percentages, between Days 14 and 16 of the estrous cycle. Luteal lipid profiles of corpora lutea from Day 16 pregnant sheep approximated lipid profiles of corpora lutea recovered from sheep between Days 12 and 14 of the estrous cycle. Comparison of luteal lipid profiles after tissue incubations at either 0 or 37 degrees C for 2 h revealed an effect of reproductive status on fatty acid metabolisms at Day 16. Changes observed in luteal lipid contents and fatty acid compositions during advancement of the estrous cycle represent aspects of lutein cell maturation and impending senescence that can be inhibited or reversed by pregnancy.

Animals↗
PubMed1994

Bioactive follicle-stimulating hormone concentrations in plasma during the estrous cycle of the ewe.

Bioactive FSH (B-FSH) concentrations in plasma were determined during the ovine estrous cycle by means of an in vitro bioassay. The concentrations of B-FSH were elevated during and after the preovulatory LH surge and were significantly (p < 0.05) lower during the late-luteal to mid-follicular phases compared with the mid-luteal phase. A significant (p < 0.05) increase in B-FSH was found about 36 h before the LH surge, at a time when the immunoreactive FSH (I-FSH) concentrations were low and unchanged. The plasma B/I ratio for FSH was relatively constant during the luteal phase; it then increased significantly (p < 0.05) before the LH surge and decreased again at the time of the LH surge itself. Pulsar analysis showed that there were 4 peaks of B-FSH throughout the estrous cycle with 2 during the luteal phase, 1 after the LH surge, and the other either during the follicular phase or associated with the LH surge. For I-FSH there were approximately 8 peaks throughout the cycle with 4 during the luteal phase, 2 after the LH surge, and 1 each during the follicular phase and the preovulatory LH surge. There was a weak negative correlation between I-FSH and immunoreactive inhibin (I-inhibin) during most of the estrous cycle, but B-FSH and the B/I ratio were only correlated (negatively) with I-inhibin in the 24 h before the preovulatory LH surge. These findings suggest that there are significant changes in the circulating isoforms of FSH during the ovine estrous cycle that may affect the growth of antral follicles developing towards ovulation.

Animals↗
PubMed1997

Ketanserin and anxiety levels: influence of gender, estrous cycle, ovariectomy and ovarian hormones in female rats.

The influence of gender, estrous cycle, ovariectomy and ovarian hormones on the behavioral effects of the 5-HT2 receptor antagonist, ketanserin (KET), was studied. Intact males, female rats in the four stages of the estrous cycle and ovariectomized (OVX) female rats 14 days after surgery were used. The OVX rats received progesterone [PROG, 25 mg/kg, subcutaneously (SC)] and/or estradiol benzoate (EB, 10 micrograms/kg, SC). KET (3 mg/kg, SC) was injected 30 min before testing. All the animals were subjected to the following behavioral tests: exploration of an elevated plus-maze and retention of a passive-avoidance response. KET enhanced the exploration of the open arms in diestrous female rats but inhibited this behavior during the other stages of the cycle and in OVX rats injected either with oil or EB. This dose of KET was ineffective in males and in OVX rats injected with PROG. Furthermore, KET inhibited the retention of the passive avoidance response in males, in diestrous and metestrous female rats and in OVX rats injected with oil. In estrous females and in OVX rats injected with EB, KET enhanced the passive-avoidance response. These results demonstrate that the sensitivity to KET differs with the gender, estrous cycle and hormonal treatment and suggest that central serotonergic activity is influenced by the hormonal status of the animal.

Animals↗
PubMed2003

The effects of stages of the estrous cycle on pain thresholds in female white rats.

The effects of stages in the estrous cycle on electrical pain thresholds were studied in white rats in conditions of chronic measurement. On recording day 3, females in the diestrus and estrus stages showed sharp increases in shudder and paw-shuffling thresholds. Females in proestrus and metestrus showed no change in thresholds as compared with those in the first days of recording. Starting from day 7, there were progressive decreases in electrical pain thresholds regardless of the stage of the estrous cycle. Data for all animals showed that regular measurement of pain thresholds induces a smooth two-fold increase in body resistance from day 1 to day 7. This was followed by a sharp drop on day 8, with parallel decreases in body resistance and electrical pain thresholds. Thus, chronic measurement of electrical pain thresholds and body resistance changed in a complex fashion, and threshold values depended on the stage of the estrous cycle.

Animals↗
PubMed1984

Changes in NK cell activity during the estrous cycle and pregnancy in mice.

Changes in NK cell activity during the estrous cycle and pregnancy in mice were studied by a 4 h 51Cr-release assay using YAC-1 cells as a target. NK activity both in the spleen and peripheral blood mononuclear cells showed a single fluctuation with a peak at met-estrous-2 during the estrous cycle. Splenic NK activity was suppressed in the early to mid-stages of pregnancy but increased sharply in the late stage. The activity declined thereafter, reaching the estrous level post-partum. NK activity in the peripheral blood showed a decrease throughout the entire pregnancy, but increased on Day 1 post-partum, returning to the estrous level thereafter. To elucidate the mechanisms involved in these variations of NK activity, NK-enriched and non-adherent cells were prepared from the spleens of mice at estrous and met-estrous-2 and those at early and late stages of pregnancy and then examined for NK activity. The results showed that there was no difference in the cytotoxic activity among these purified NK cells. Adherent cells purified from the spleens of mice in the early stage of pregnancy when co-cultured with the non-adherent NK cell fractions suppressed the NK cytotoxicity. These results strongly suggest the possibility that phagocytic and/or adherent cells may be involved in the regulation of splenic NK activity during the estrous cycle and pregnancy.

Animals↗
PubMed2004

Orexin A and B levels in the hypothalamus of female rats: the effects of the estrous cycle and age.

OBJECTIVE: Orexins have been implicated in the regulation of several physiological functions including reproduction, energy balance and vigilance state. For successful reproduction, the precisely timed hormonal secretions of the estrous cycle must be combined with appropriate nutritional and vigilance states. The steroid- and nutritional state-dependent modulation of LH release by orexins, as well as an increase of vigilance, suggest that orexins may co-ordinate these functions in the course of the estrous cycle. DESIGN: We studied the brain tissue levels of orexins in the course of the estrous cycle in young and middle-aged rats. Young cycling rats (3 months old) and irregularly/non-cycling (7-9 months old) female rats were inspected for vaginal smears and serum hormone levels. METHODS: Tissue concentrations of orexin A and B were measured in the hypothalamus and lateral hypothalamus on different days of the estrous cycle. RESULTS: Orexin A concentration in the hypothalamus of young cycling rats was higher on the day of proestrus 5-6 h after the lights were switched on than on the other days of the estrous cycle at the same circadian time. Orexin B concentration was higher on both the day of proestrus and the day of estrus as compared with the days of diestrus. The hypothalamic concentrations of both orexin A and B in the non-cycling middle-aged rats were lower than those in cycling rats on the days of proestrus and estrus. CONCLUSIONS: We have concluded that the high hypothalamic concentration of orexins on the day of proestrus may contribute to the LH and prolactin surges. High orexin A levels may also contribute to the decreased amount of sleep on the day of proestrus.

Aging↗
PubMed1997

Ovarian follicular dynamics during the estrous cycle in buffalo (Bubalus bubalis).

The growth, selection, regression and ovulation of ovarian follicles was ultrasonically monitored in 30 Murrah buffalo throughout a spontaneous estrous cycle during the breeding season (autumn). Examinations revealed that follicular growth during the estrous cycle occurs in waves; the buffalo showed 1-wave (3.3%, n = 1), 2-wave (63.3%, n = 19) or 3-wave (33.3%, n = 10) follicular growth. The first wave began at 1.00, 1.16 +/-0.50 and 1.10 +/- 0.32 d in buffalo with 1, 2 and 3 waves, respectively (ovulation = Day 0). The second wave appeared at 10.83 +/- 1.09 and 9.30 +/- 1.25 d (P < 0.01) for the 2 and 3 wave cycle animals, respectively. The third wave started at 16.80 +/- 1.22 d. Structural persistence of the first dominant follicle was longer in the 2- than 3-wave cycles (20.67 +/- 1.18 vs 17.90 +/- 3.47 d ; P < 0.05). The duration of the growth and static phases of the first dominant follicle differed between the 2 and 3 wave cycles (P < 0.05), whereas there were no differences in linear growth rates (cm/d). Two and three wave cycles differed (P < 0.05) with respect to the maximum diameter of both the first dominant follicle (1.51 +/- 0.24 vs 1.33 +/- 0.18 cm) and the ovulatory follicles (1.55 +/- 0.16 vs 1.34 +/- 0.13 cm). No relationship was found between dominant follicle development and the presence of either a CL or a previous dominant follicle in either ovary. Two and three wave cycles also differed with respect to the mean length of intervals between ovulation (22.27 +/- 0.89 vs 24.50 +/- 1.88 d; P < 0.01) and the mean length of luteal phases (10.40 +/- 2.11 vs 12.66 +/- 2.91 d; P < 0.05). These results demonstrate that buffalo have estrous cycles with 1, 2 or 3 follicular waves; that 2-wave cycles are the most common; and that the number of waves in a cycle is associated with the luteal phase and with estrous cycle length.

Journal Article↗
PubMed1983

Characteristics of the estrous cycle of the swamp buffalo under temperate conditions.

Estrous cycle, duration of estrus and time of ovulation of eight cyclic buffaloes were examined during a period of one year. Animals were kept under loose-housing conditions and fed according to the Japanese Feeding Standards for dairy cattle. All the animals were observed for the occurrence of estrus twice daily by using a vasectomized bull, and ovarian cycles of each animal were monitored by weekly rectal palpation. Duration of estrus and time of ovulation were determined in 32 estrous periods from eight animals. Animals came in estrus throughout the year. The estrous cycles corresponding to single ovarian cycles ranged from 11 to 38 days with a mode interval of 20 days, averaged 21.5+/-4.7 days. Percentage of the cycles within a range of a mean+/-1 SD (17-26 days) was 79.2%, whereas that of cycles shorter or longer than the expected range was 9.4% and 11.4%, respectively. Estrus took place regardless of the time of day and lasted 9 to 27 hr (19.9+/-4.4 hr). Ovulation occurred 6 to 21 hr (13.9+/-3.4 hr) after the end of estrus, with a mode interval of 12 hr. There were no significant seasonal variations in the estrus characteristics studied.

Journal Article↗
PubMed2003

Plasma gonadotropins and ovarian hormones during the estrous cycle in high compared to low ovulation rate gilts.

Mature gilts classified by low (12 to 16 corpora lutea [CL], n = 6) or high (17 to 26 CL, n = 5) ovulation rate (OR) were compared for plasma follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, estradiol-17beta, and inhibin during an estrous cycle. Gilts were checked for estrus at 8-h intervals beginning on d 18. Blood samples were collected at 8-h intervals beginning on d 18 of the third estrous cycle and continued for one complete estrous cycle. Analysis for FSH and LH was performed on samples collected at 8-h intervals and for ovarian hormones on samples collected at 24-h intervals. The data were standardized to the peak of LH at fourth (d 0) and fifth estrus for the follicular phase and analyzed in discrete periods during the periovulatory (-1, 0, +1 d relative to LH peak), early-luteal (d 1 to 5), mid-luteal (d 6 to 10), late-luteal (11 to 15), periluteolytic (-1, 0, +1 d relative to progesterone decline), and follicular (5 d prior to fifth estrus) phases of the estrous cycle. The number of CL during the sampling estrous cycle was greater (P < 0.005) for the high vs low OR gilts (18.8 vs 14.3) and again (P < 0.001) in the cycle subsequent to hormone measurement (20.9 vs 14.7). For high-OR gilts, FSH was greater during the ovulatory period (P = 0.002), the mid- (P < 0.05) and late-luteal phases (P = 0.01), and tended to be elevated during the early-luteal (P = 0.06), but not the luteolytic or follicular periods. LH was greater in high-OR gilts during the ovulatory period (P < 0.005), but not at other periods during the cycle. In high-OR gilts, progesterone was greater in the mid, late, and ovulatory phases (P < 0.005), but not in the follicular, ovulatory, and early-luteal phases. Concentrations of estradiol-17beta were not different between OR groups during the cycle. Inhibin was greater for the high OR group (P < 0.005) during the early, mid, late, luteolytic, and follicular phases (P < 0.001). The duration of the follicular phase (from last baseline estrogen value to the LH peak) was 6.5 +/- 0.5 d and was not affected by OR group. These results indicate that elevated concentrations of both FSH and LH are associated with increased ovulation rate during the ovulatory phase, but that only elevated FSH during much of the luteal phase is associated with increased ovulation rate. Of the ovarian hormones, both inhibin and progesterone are highly related to greater ovulation rates. These findings could aid in understanding how ovulation rate is controlled in pigs.

Animals↗
PubMed1982

Altered pituitary responsiveness to gonadotropin- releasing hormone in middle-aged rats with 4-day estrous cycles.

We employed a perifusion system to compare the GnRH responsiveness of pituitaries removed from young (3-6 months old) and middle-age (10-14 months old) female rats with 4-day estrous cycles in order to determine whether changes at this locus may contribute to alterations in LH secretion which precede a loss of regular estrous cycles. Pituitaries were removed and halved on each day of the 4-day cycle; one hemipituitary was retained for measurement (by RIA) of LH content. The second half was perifused for 2.5 h with medium 199 plus BSA, then stimulated for 6 h with 10(-7) M GnRH in medium 199 plus BSA. Results were as follows. 1) Within young and middle-aged groups, the magnitude of GnRH-stimulated LH release varied with stage of the estrous cycle (proestrus, diestrous day 2 greater than estrus, diestrous day 1). General patterns of LH release were similar between age groups; however, pituitaries removed from middle-aged females released significantly less LH on proestrus and diestrous day 1 than did those removed from young females. 2) The time required to reach maximal response to GnRH also varied with the estrous stage; response times were shortest on proestrus and estrus in both age groups. The time to maximal response was significantly longer in the middle-aged vs. the young group on all days of the estrous cycle except diestrous day 2. 3) Within age groups, pituitary LH content varied with the estrous cycle in a pattern similar to that of GnRH responsiveness. Between groups, LH content in middle-age females was equivalent to or greater than that in young females on all days of the cycle. These results indicate that reduced pituitary responsiveness to GnRH may contribute to the delayed attenuated proestrous LH surge that precedes reproductive senescence in the female rat.

Aging↗
PubMed1992

In vitro metabolism of glucose by bovine reproductive tissues obtained during the estrous cycle and after calving.

Two experiments were conducted to determine the effect of physiological state (stage of the estrous cycle or time after calving) on the in vitro metabolism of glucose by reproductive tissues. In Exp. 1, the corpus luteum and ipsilateral uterine horn were collected at surgery from 15 cows at early (d 6 to 7), middle (d 10 to 13), or late (d 17 to 19) stages of the estrous cycle. Luteal or endometrial tissues (45 mg) were incubated (4 h, 37 degrees C) in metabolic flasks containing Nutrient Mixture F-10 (3 mL), increasing concentrations of glucose (1, 2, 5, 10, or 15 mM), and 1 microCi of [U-14C]glucose. Luteal tissue collected at the middle stage of the estrous cycle had greater (P less than .04) rates of glucose uptake (17.8 vs 12.1 ng/mg of wet tissue per min) and oxidation (138.6 vs 67.7 pg/mg of wet tissue per min) and a lower (P less than .02) rate of metabolism of glucose to lactate (10.5 vs 13.3 ng/mg of wet tissue per min) than tissue collected at the late stage. Compared to tissue collected at early and late stages, endometrial tissue collected at the middle stage of the estrous cycle had a similar (P greater than .5) rate of glucose uptake (29.6 vs 27.8 and 26.1 ng/mg of wet tissue per min), a lower (P less than .02) rate of metabolism of glucose to lactate (13.8 vs 16.6 and 16.4 ng/mg of wet tissue per min), and a greater (P less than .1) rate of oxidation of glucose (84.1 vs 65.8 and 72.3 pg/mg of wet tissue per min). In Exp. 2, the previously gravid uterine horn was collected at surgery on d 20 (n = 8) or 30 (n = 7) after calving, or the uterine horn ipsilateral to the preovulatory follicle was collected at first observed estrus after calving (n = 8). Uterine tissue obtained at first estrus after calving had a greater (P less than .003) rate of glucose uptake and oxidation (88.8 vs 77.3 and 75.5 pg/mg of tissue per min) than d-20 or d-30 endometrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Variations of synaptotagmin I, synaptotagmin IV, and synaptophysin mRNA levels in rat hippocampus during the estrous cycle.

Periodic changes in ovarian steroid levels during fertility cycles affect learning both in humans and in rats in parallel with electrophysiological and morphological fluctuations in selective neuronal populations. In particular, during the estrous cycle of the female rat, hippocampal CA1 region undergoes cyclic modifications in synaptic density. To investigate the molecular mechanisms involved in synaptic remodeling during the estrous cycle, we analyzed the expression of three presynaptic markers, synaptotagmin I, synaptotagmin IV, and synaptophysin, in the female adult rat brain by in situ hybridization. Relative abundance in mRNA for these three markers was quantified at four phases of the estrous cycle: diestrus, proestrus (AM and PM), and estrus. mRNA levels for syt1 exhibited cyclic variations in pyramidal neurons of the CA3 region of hippocampus during the estrous cycle, while mRNA levels for syt4 and SYN were relatively invariant in this or other regions of the hippocampus. Because CA3 pyramidal neurons make synaptic contacts in CA1, modulation of syt1 expression in CA3 may participate in the changes in synaptic density observed in CA1 during the estrous cycle. Furthermore, both syt1 and SYN mRNA varied cyclically in layer II, but not in layer III of entorhinal cortex, while syt4 remained unchanged throughout the cycle. These data suggest that regular variations in steroid hormone levels during fertility cycles may alter the properties of several networks involved in information processing and learning and memory through altered levels of presynaptic proteins.

Animals↗
PubMed2005

Examination of the failure properties of the anterior cruciate ligament during the estrous cycle.

The purpose of this study was to determine whether the mechanical properties of the rat anterior cruciate ligament (ACL) vary when tested in vitro at different stages of the estrous cycle. Sixty female rats were allocated to four groups according to their stage of the estrous cycle: diestrus (n=16), proestrus (n=17), estrus (n=13) and metestrus (n=14). Right hindlimbs were harvested for mechanical testing and left hindlimbs were harvested for immunohistochemical staining to confirm the presence of the estrogen receptor. Results from the first relaxation test showed a significant difference between the estrus and proestrus stage, which was not observed in a second subsequent relaxation test. Likewise, no significant differences were found when comparing failure load and stiffness between the different stages of the estrous cycle. These results suggest that normal physiological fluctuations in estrogen during the estrous cycle did not alter the failure properties of the rat ACL.

Animals↗