Characterization and analysis of transcriptomes of multiple tissues from estrus and diestrus in pigs

A comprehensive understanding of the complex regulatory mechanisms governing estrus and ovulation across multiple tissues in mammals is imperative to improve the reproductive performance of livestock and mitigate ovulation-related disorders in humans. To comprehensively elucidate the regulatory landscape, we analyzed the transcriptome of protein-coding genes and long intergenic non-coding RNAs (lincRNAs) in 58 samples (including the hypothalamus, pituitary, ovary, vagina, and vulva) derived from European Large White gilts and Chinese Mi gilts during estrus and diestrus. We constructed an intricate regulatory network encompassing 358 hub genes across the five examined tissues. Furthermore, our investigation identified 85 differentially expressed lincRNAs that are predicted to target 230 genes associated with critical functions including behavior, receptors, and apoptosis. Importantly, we found that vital components of estrus and ovulation events involve "Apoptosis" pathway in the hypothalamus, "Autophagy" in the ovary, as well as "Hypoxia" and "Angiogenesis" in the vagina and vulva. We have identified several differentially expressed transcription factors (TFs), such as SPI1 and HES2, which regulate these pathways. SPI1 may suppress transcription in the autophagy pathway, promoting apoptosis and inhibiting the proliferation of ovarian granulosa cells. Our study provides the most comprehensive transcriptional profiling information related to estrus and ovulation events.

The effect of orexin on the hypoxic ventilatory response of female rats is greatest in the active phase during diestrus

We recently showed that in male rats, orexin contributes to the hypoxic ventilatory response (HVR), with a stronger effect in the active phase. The effect of orexin on the HVR in females has not been investigated. As estrogen can inhibit orexin neurons, here we hypothesized that orexin neurons are activated by hypoxia and facilitate the HVR only in diestrus, when estrogen is low. We exposed female rats (n = 10) to near-isocapnic hypoxia ([Formula: see text] from 0.21 to 0.09) over ∼5 min, after vehicle and again after suvorexant (a dual OxR antagonist; 20 mg/kg ip), with ventilation measured using whole body plethysmography. Each rat was tested in proestrus or estrus (p/estrus), and again in diestrus, during both inactive and active phases. We also performed immunohistochemistry (IHC) to determine the proportion of orexin neurons activated by acute hypoxia during diestrus (n = 6) or proestrus/estrus (n = 6) in the active phase. In the inactive phase, the HVR was unaffected by OxR blockade, irrespective of estrus stage. In the active phase, the effect of OxR blockade depended on stage: the slope of the HVR was significantly reduced by OxR blockade only during diestrus. IHC revealed that hypoxia activated more orexin neurons during diestrus compared with p/estrus. We conclude that in females, orexin neurons are activated by hypoxia and contribute to the HVR only in diestrus when estrogen levels are low. Stage of the estrus cycle should be considered when examining the physiological function of orexin neurons in females.NEW & NOTEWORTHY We previously showed that orexin facilitates the hypoxic ventilatory response (HVR) of adult male rats during the active phase. Others have shown that estrogen inhibits orexin neurons. Here we show that orexin neurons are activated by hypoxia and facilitate the HVR of adult female rats during the active phase, but only in diestrus. These data suggest that orexin neurons facilitate the HVR in females when they are free from the inhibitory effects of estrogen.

Triplex doppler ultrasonography to describe the uterine arteries during diestrus and progesterone profile in pregnant and non-pregnant bitches of different sizes

Hemodynamics of uterine vascularization is modified throughout pregnancy to meet the increasing demand of the growing fetuses and triplex doppler ultrasonography is widely used in human medicine to study the uterine arteries and assess the fetal and placental conditions. The aim of our study was to confirm this observation in the bitch, to evaluate differences between bitches of different sizes and to study abnormal pregnancies. Forty-four bitches were monitored during the estrous period to determine ovulation and every 10 days from ovulation to 50 days post-ovulation: the resistivity (RI) and pulsatility (PI) indexes of the right uterine artery were measured as well as usual assessment of fetal development and follow up of the luteal function. Thirty-three out of forty-four bitches were pregnant, including 6 abnormal pregnancies (resorption of more than 10% of the embryos). We also divided them in four weight categories: 8 were small (<10 kg), 13 medium (10-25 kg), 13 large (>25-40 kg) and 10 were giant breeds (>40 kg). We observed that RI and PI decreased over time and were significantly lower for pregnant bitches compared to non-pregnant ones from 30 days post-ovulation. In contrast, RI and PI did not significantly vary with the size of the bitches and we could not determine a significant impact of abnormal pregnancies either. In conclusion, we found no significant difference related to the size of bitches in the RI and PI. The only significant difference between pregnant and non-pregnant bitches was observed from 30 days post-ovulation.

Sex-Specific and Estrous Cycle-Dependent Antidepressant-Like Effects and Hippocampal Akt Signaling of Leptin

Sex differences in the incidence of depression and antidepressant treatment responses are well documented. Depression is twice as common in women as in men. Recent studies indicate that low levels of leptin, an adipocyte-derived hormone, are associated with increased symptoms of depression in women. Leptin has been shown to produce antidepressant-like effects in male rodents. In the present study, we examined sex differences and estrous cycle variations in antidepressant-like responses to leptin. Leptin administration significantly reduced immobility, a putative measure of behavioral despair, in the forced swim test in intact female mice in the proestrus phase but not in the diestrus phase of the estrous cycle. Moreover, leptin administration stimulated Akt phosphorylation in the hippocampus of female mice in proestrus but not in diestrus, in correlation with its differential behavioral effects in these two phases of the cycle. Leptin-induced behavioral responses and stimulation of hippocampal Akt phosphorylation in female mice were abolished by ovariectomy. By contrast, the antidepressant-like effect of leptin in male mice was not affected by gonadectomy (castration). Pretreatment with 17β-estradiol restored sensitivity to the effects of leptin on behavior and hippocampal Akt phosphorylation in ovariectomized female mice. These results suggest leptin regulates depression-like behavior and hippocampal Akt signaling in a sex-specific and estrous cycle-dependent manner.

Sex-related neurogenesis decrease in hippocampal dentate gyrus with depressive-like behaviors in sigma-1 receptor knockout mice

Male sigma-1 receptor knockout (σ1R(-/-)) mice showed depressive-like phenotype with deficit in the survival of newly generated neuronal cells in the hippocampal dentate gyrus (DG), but female σ1R(-/-) mice did not. The level of serum estradiol (E2) at proestrus or diestrus did not differ between female σ1R(-/-) mice and wild-type (WT) mice. Ovariectomized (OVX) female σ1R(-/-) mice, but not WT mice, presented the same depressive-like behaviors and neurogenesis decrease as male σ1R(-/-) mice. Treatment of male σ1R(-/-) mice with E2 could alleviate the depressive-like behaviors and rescue the neurogenesis decrease. In addition, E2 could correct the decline in the density of NMDA-activated current (INMDA) in granular cells of DG and the phosphorylation of NMDA receptor (NMDAr) subtype 2B (NR2B) in male σ1R(-/-) mice, which was associated with the elevation of Src phosphorylation. The neuroprotection and antidepressant effects of E2 in male σ1R(-/-) mice were blocked by the inhibitor of Src or NR2B. The NMDAr agonist showed also the neuroprotection and antidepressant effects in male σ1R(-/-) mice, which were insensitive to the Src inhibitor. On the other hand, either the deprivation of E2 or the inhibition of Src in female σ1R(-/-) mice rather than WT mice led to a distinct decline in INMDA and NR2B phosphorylation. Similarly, the Src inhibitor could cause neurogenesis decrease and depressive-like behaviors in female σ1R(-/-) mice, but not in WT mice. These results indicate that the σ1R deficiency impairs neurogenesis leading to a depressive-like phenotype, which is alleviated by the neuroprotection of E2.

Relationship among insulin resistance, growth hormone, and insulin-like growth factor I concentrations in diestrous Swedish Elkhounds

Background

In the dog, the normal estrous cycle includes a prolonged luteal phase. Progesterone stimulates local canine mammary growth hormone (GH) production, which may act systemically and contribute to insulin resistance. Swedish Elkhounds are predisposed to progesterone‐related diabetes mellitus, and the relationship among insulin resistance, GH, and insulin‐like growth factor I (IGF‐I) is of particular interest.

Objective

To study insulin resistance in relation to GH and IGF‐I in nondiabetic Swedish Elkhounds during diestrus. We also assessed whether alterations in these hormones could predict diestrus‐linked diseases and all‐cause mortality.

Animals

Eighty‐four privately owned female intact Swedish Elkhounds >4 years of age.

Methods

Blood sampling and clinical examination during luteal phase, with a follow‐up questionnaire after 20 months. Insulin resistance was calculated by homeostasis model assessment (HOMA‐IR).

Results

In multivariable regression analysis, GH was positively associated with HOMA‐IR (P = .009). An increase in GH of 1 ng/mL was associated with a 12.7% increase in HOMA‐IR. Moreover, C‐peptide was positively associated with IGF‐I (P = .04), and an increase in C‐peptide of 0.1 ng/mL was associated with a 6.9% increase in IGF‐I. Structural equation modeling supported these results. Twenty‐three animals were found to have previously unrecognized mammary masses and had higher GH (P < .0001) and IGF‐I (P = .007) than dogs without mammary masses (n = 61). There was no association between high GH and IGF‐I concentrations at sampling and future mammary masses.

Conclusion

We showed that GH was strongly associated with insulin resistance in older Swedish Elkhounds during diestrus.

Pregnancy is associated with decreased cardiac proteasome activity and oxidative stress in mice

During pregnancy, the heart develops physiological hypertrophy. Proteasomal degradation has been shown to be altered in various models of pathological cardiac hypertrophy. Since the molecular signature of pregnancy-induced heart hypertrophy differs significantly from that of pathological heart hypertrophy, we investigated whether the cardiac proteasomal proteolytic pathway is affected by pregnancy in mice. We measured the proteasome activity, expression of proteasome subunits, ubiquitination levels and reactive oxygen production in the hearts of four groups of female mice: i) non pregnant (NP) at diestrus stage, ii) late pregnant (LP), iii) one day post-partum (PP1) and iv) 7 days post-partum (PP7). The activities of the 26 S proteasome subunits β1 (caspase-like), and β2 (trypsin-like) were significantly decreased in LP (β1∶83.26±1.96%; β2∶74.74±1.7%, normalized to NP) whereas β5 (chymotrypsin-like) activity was not altered by pregnancy but significantly decreased 1 day post-partum. Interestingly, all three proteolytic activities of the proteasome were restored to normal levels 7 days post-partum. The decrease in proteasome activity in LP was not due to the surge of estrogen as estrogen treatment of ovariectomized mice did not alter the 26 S proteasome activity. The transcript and protein levels of RPN2 and RPT4 (subunits of 19 S), β2 and α7 (subunits of 20 S) as well as PA28α and β5i (protein only) were not significantly different among the four groups. High resolution confocal microscopy revealed that nuclear localization of both core (20S) and RPT4 in LP is increased ∼2-fold and is fully reversed in PP7. Pregnancy was also associated with decreased production of reactive oxygen species and ubiquitinated protein levels, while the de-ubiquitination activity was not altered by pregnancy or parturition. These results indicate that late pregnancy is associated with decreased ubiquitin-proteasome proteolytic activity and oxidative stress.

The use of digital infrared thermal imaging to detect estrus in gilts

Yorkshire/Landrace crossbred gilts (N = 32) were evaluated using digital infrared thermal imaging (DITI) to discriminate between estrus and diestrus phases of the porcine estrous cycle. Gilts (N = 32) were part of an ongoing reproductive efficiency study involving the use of raw soybean (RSB; N = 15) versus soybean meal (SBM; N = 17) as a source of dietary protein. Gilts were monitored daily for signs of estrus using a teaser boar. Thermal images of vulva surface temperatures (TEMP) were recorded at standing estrus and diestrus. Measurements for analysis included minimum (MIN), maximum (MAX), mean (AVG), and standard deviation (SD) of temperature gradients. At imaging, ambient (AMB) and rectal temperatures (RT) were recorded, and blood samples taken for serum progesterone (P(4)) concentration analysis (by RIA) to confirm stage of cycle. Mean serum progesterone values at estrus and diestrus were (mean ± SD) 1.0 ± 0.1 and 10.9 ± 0.8 ng/mL, respectively. Vulva MIN, MAX, and AVG thermal images were positively correlated with one another (P < 0.01), and were positively correlated with ambient temperature (P < 0.01). Vulva MAX and AVG thermal temperatures were greater (P < 0.05) at estrus than at diestrus (36.6 ± 0.2 °C and 33.4 ± 0.3 °C vs. 35.6 ± 0.3 °C and 31.8 ± 0.6 °C, respectively), whereas MIN and SD had no differences (P > 0.05) between stages of the cycle. No differences (P > 0.05) in RT were detected between stages and RT was not significantly correlated with vulva thermal images. Diet had no significant effect on RT or vulva temperature.

Vaginal bacterial flora and cytology in proestrous bitches: role on fertility

The study of canine vaginal cytology underwent limited evolution over the years. Presence and significance of inflammatory cells in vaginal smears are little considered aspects in the bitch. Moreover, occurrence of vaginal bacteria in breeding bitches during follicular phase of the reproductive cycle, in absence of clinical signs of infection, involves the difficult question of antibiotics administration. The aim of this study was to relate findings in vaginal cytology (presence of neutrophils, lymphocytes, eosinophils, erytrocytes and bacteria) and microbial environment during proestrus with fertility outcomes (development of pregnancy, uterine infection, resorption, abortion and neonatal mortality). Bacteria sensitivity to antibiotics normally used in small animal practice was also evaluated. Bacteria isolated from vagina, in order of frequency, were Enterococcus faecalis, Streptococcus β-haemolyticus, Pasteurella multocida, E. coli, Klebsiella pneumoniae, Proteus mirabilis, E. coli haemolyticus, Arcanobacterium pyogenes, Streptococcus spp., Staphylococcus spp. and Acinetobacter spp. No mycoplasmas were observed. The present study showed that proestrous cytological aspects do not affect fertility. Eosinophils were never detected, while erythrocytes were always detected. During diestrus, E. coli was found in all pregnant bitches that developed clinical symptoms of uterine disorders (n = 3), resulting in uterine infection, resorption or abortion, but without statistical significance. Vaginal presence of Streptococcus spp. in proestrus was instead negatively associated with development of uterine infections (P = 0.005). Therefore, Streptococcus spp. could have a protective competitive role against more dangerous pathogens affecting fertility of the bitch. Among the 12 antibiotics tested, Gram-negative bacteria showed a significant sensitivity towards the amoxicillin and clavulanic acid association (P = 0.038). However, antibiotic treatment before mating, on the basis of positive culture, yet in the absence of clinical signs, seems to be unnecessary besides harmful leading to imbalance in vaginal commensal flora with adverse effects on fertility. In conclusion, vaginal bacteria, neutrophils, lymphocytes and erytrocytes should be considered as physiological aspect in the bitch during proestrus that does not require antibiotic therapy when asymptomatic.

[D2-type dopaminergic receptors and anxiety-depression-like behavior in female rats]

Results of a comparative study of the effects of chronic administration of the D2-receptor agonist quinperole (0.1 mg/kg, i.p.) and the D2-receptor antagonist sulpiride (10.0 mg/kg, i.p.) for 14 days on anxiety- and depressive-like behavior in key phases of the ovarian cycle in adult female rats are presented. The model of depression in rats was implemented in Porsolt test, while the anxiety level was assessed in the elevated plus maze test. It is established that the chronic administration of quinperole produced an anxiolytic action in female rats during diesrous, estrous and proestrous phases, but failed to modify depression-like behavior during the entire ovarian cycle. Sulpiride administration resulted in anxiogenic effect in all phases of the ovarian cycle. It was also found that sulpiride produced some modulation of depression-like behavior in connection to ovarian cycle phases, which was a prodepressive action at a moderate level of estrogens and an antidepressant effect at a reduced/enhanced level of estrogen. It is suggested that the extent of involvement of D2-receptors in the mechanisms of anxiety-depressive-like behavior can vary depending on alterations of the hormonal balance during the ovarian cycle. The data obtained are indicative of a close interaction between ovarian hormonal and dopaminergic systems of the brain involved in the mechanisms of anxiety and depression.

Luteal and placental function in the bitch: spatio-temporal changes in prolactin receptor (PRLr) expression at dioestrus, pregnancy and normal and induced parturition

BACKGROUND

Endocrine mechanisms governing canine reproductive function remain still obscure. Progesterone (P4) of luteal origin is required for maintenance of pregnancy. Corpora lutea (CL) are gonadotrop-independent during the first third of dioestrus; afterwards prolactin (PRL) is the primary luteotropic factor. Interestingly, the increasing PRL levels are accompanied by decreasing P4 concentrations, thus luteal regression/luteolysis occurs in spite of an increased availability of gonadotropic support. PRL acts through its receptor (PRLr), the expression of which has not yet been thoroughly investigated at the molecular and cellular level in the dog.

METHODS

The expression of PRLr was assessed in CL of non-pregnant dogs during the course of dioestrus (days 5, 15, 25, 35, 45, 65 post ovulation; p.o.) as well as in CL, the utero/placental compartments (Ut/Pl) and interplacental free polar zones (interplacental sites) from pregnant dogs during the pre-implantation, post-implantation and mid-gestation period of pregnancy and during the normal and antigestagen-induced luteolysis. Expression of PRLr was tested by Real Time PCR, immunohistochemistry and in situ hybridization.

RESULTS

In non-pregnant CL the PRLr expression was significantly upregulated at day 15 p.o. and decreased significantly afterwards, towards the end of dioestrus. CL of pregnancy showed elevated PRLr expression until mid gestation while prepartal downregulation was observed. Interestingly, placental but not interplacental expression of PRLr was strongly time-related; a significant upregulation was observed towards mid-gestation. Within the CL PRLr was localized to the luteal cells; in the Ut/Pl it was localized to the fetal trophoblast and epithelial cells of glandular chambers. Moreover, in mid-pregnant animals treated with an antigestagen, both the luteal and placental, but not the uterine PRLr were significantly downregulated.

CONCLUSIONS

The data presented suggest that the luteal provision of P4 in both pregnant and non-pregnant dogs may be regulated at the PRLr level. Furthermore, a role of PRL not only in maintaining the canine CL function but also in regulating the placental function is strongly suggested. A possible functional interrelationship between luteal P4 and placental and luteal PRLr expression also with respect to the prepartal luteolysis is implied.

Activity of hypothalamic dopaminergic neurones during the day of oestrus: involvement in prolactin secretion

A secretory surge of prolactin occurs on the afternoon of oestrus in cycling rats. Pituitary prolactin is inhibited by dopamine. We evaluated the activity of the neuroendocrine dopaminergic neurones during oestrus and dioestrus, as determined by dopaminergic activity in the median eminence and neurointermediate lobe of the pituitary, as well as Fos-related antigen expression in tyrosine hydroxylase (TH)-immunoreactive (ir) neurones of the arcuate nucleus (ARC) and periventricular nucleus (Pe). During oestrus, the 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence decreased at 16.00 h, coinciding with the increase in plasma prolactin levels. Similarly, the expression of Fos-related antigen in TH-ir neurones of Pe and rostral-, dorsomedial- and caudal-ARC also decreased at 16.00 h. On dioestrus, 4-dihydroxyphenylacetic acid/dopamine ratio in the median eminence and Fos-related antigen expression in TH-ir neurones of Pe and rostral-ARC decreased at 18.00 h, whereas prolactin levels were unaltered. No variation in dopaminergic activity was found in the neurointermediate lobe of the pituitary on either oestrus or dioestrus. The number of TH-ir neurones in the ARC and parameters of dopaminergic activity were found to be generally lower on oestrus compared to dioestrus. The transitory decrease in the activity of neuroendocrine dopaminergic neurones temporally associated with the prolactin surge on the afternoon of oestrus suggests a role for dopamine in the generation of the oestrous prolactin surge.

Are endogenous sex hormones related to DNA damage in paradoxically sleep-deprived female rats?

The aim of this investigation was to evaluate overall DNA damage induced by experimental paradoxical sleep deprivation (PSD) in estrous-cycling and ovariectomized female rats to examine possible hormonal involvement during DNA damage. Intact rats in different phases of the estrous cycle (proestrus, estrus, and diestrus) or ovariectomized female Wistar rats were subjected to PSD by the single platform technique for 96 h or were maintained for the equivalent period as controls in home-cages. After this period, peripheral blood and tissues (brain, liver, and heart) were collected to evaluate genetic damage using the single cell gel (comet) assay. The results showed that PSD caused extensive genotoxic effects in brain cells, as evident by increased DNA migration rates in rats exposed to PSD for 96 h when compared to negative control. This was observed for all phases of the estrous cycle indistinctly. In ovariectomized rats, PSD also led to DNA damage in brain cells. No significant statistically differences were detected in peripheral blood, the liver or heart for all groups analyzed. In conclusion, our data are consistent with the notion that genetic damage in the form of DNA breakage in brain cells induced by sleep deprivation overrides the effects related to endogenous female sex hormones.

Characterisation of lymphocyte subsets in the equine oviduct

REASONS FOR PERFORMING STUDY

The equine oviduct is the site of fertilisation and location of embryonic development during the first 5 or 6 days. It therefore has an important influence on mare fertility. Although histopathological changes have been described previously, there is limited information regarding lymphocyte subtypes present in the mucosa of the normal equine oviduct.

OBJECTIVES

To characterise the distribution of CD3+, CD4+, CD8+ and B lymphocytes in the equine oviduct from inseminated mares during oestrus and dioestrus, and from noninseminated mares during the immediate post ovulatory period.

METHODS

Oviductal tissues were collected from noninseminated mares at oestrus (> 30 mm follicle, n = 4), at Day 1 post ovulation (n = 3) and at dioestrus (Day 7 post ovulation; n = 4). Oviducts were also collected from inseminated mares at Days 1, 2, and 3 post ovulation (n = 4 for each period). Cross-sections of tissues from the ampullar-isthmic junction from each oviduct were snap frozen and cryostat sections stained by the immunoperoxidase technique with monoclonal antibodies directed against equine lymphocyte surface markers for B cells as well as CD3+, CD4+ and CD8+ cells.

RESULTS

In all oviductal sections examined, B cells were rare whereas T cells were relatively abundant. The predominant cell type found was the CD8+ phenotype, with a lesser number of CD4+ cells. Among mares, individual variation was large; therefore, although breeding status and stage of oestrous cycle appeared to alter lymphocyte populations, these differences were not significant.

CONCLUSIONS AND POTENTIAL RELEVANCE

A population of CD3+, CD4+ and CD8+ cells exists within the mucosal region of the equine oviduct. The density of these cells is similar to that described in the human oviduct. Their function is not currently known, but they may be involved with modulation of the maternal response to the presence of spermatozoa or the early conceptus within the equine oviduct. As our capacity to differentiate these cell types improves, along with the ability to identify the specific cytokines they produce, their functional significance will become more apparent.

Medial amygdala involvement in discrimination of same-species and closely-related-species male stimuli in estrous female Mesocricetus hamsters

Efficient discrimination between individuals of closely related species is important to maximize reproductive potential. Some studies using males as subjects have indicated that the medial amygdala (MeA) is involved in discrimination between odors of conspecific females and females from distantly related species. The authors investigated the involvement of the MeA in discrimination by females between odors of conspecific males and odors of males of a closely related species. The authors exposed estrous or diestrous female hamsters (Mesocricetus auratus) to saline, conspecific male odors, or heterospecific (M. brandti) male odors and quantified the expression of c-fos-related antigens in the anterior and posterior MeA. They found that estrous (but not diestrous) females investigated conspecific male odors longer than heterospecific male odors. Neural activity in both the anterior and the posterior MeA was higher in estrous than in diestrous females. In the anterior MeA, there were no significant differences in response to odors of conspecific and heterospecific males. In the posterior MeA, however, neural activity was higher when estrous females were exposed to conspecific odors than when they were exposed to heterospecific odors. No such difference was observed in diestrous females.

Female fear: influence of estrus cycle on behavioral response and neuronal activation

Our observation that male rat's innate fear response differed with hormonal status, as well as the higher prevalence of fear and anxiety disorders in human females led to the current investigation of the impact of phases of the estrus cycle on innate fear responding. Female rats in different phases of the cycle were exposed to an innate fear-inducing stimulus (2,5-dihydro-2,4,5-trimethylthiazoline, TMT odor) and monitored for changes in behavior and brain activation. Behavioral data showed freezing responses to TMT were significantly enhanced during estrus as compared to other phases of the cycle. This data was supported by significant increases in pixel intensity in cortical and sub-cortical regions in estrus compared to proestrus and diestrus. Imaging results demonstrated significant increases in brain activation in the somatosensory and insular cortices when comparing estrus to diestrus. There were significant increases in neural activity in the bed nucleus of the stria terminals (BNST) and septum in estrus as compared to proestrus. Additionally, the hippocampus, hypothalamus, olfactory system, and cingulate cortex show significant increases in the estrus phase when compared to both diestrus and proestrus. Taken together, these results suggest that the female's hormonal status may be correlated with alterations in both neuronal and behavioral indices of fear.

Protective influence of spayed and androgen-treated females on oestrous cycle in food-restricted mice

Diet restriction induced disruption of oestrous cycle in regularly cycling female mice. The irregularities in the oestrous cycle in females were directly related to the degree of diet restriction. The presence of spayed and androgen-treated females prevented these irregularities and helped to maintain regular oestrous cycles in underfed females. The ability of androgen-treated females to prevent the irregularities in the oestrous cycle in underfed females was inversely related to the degree of diet restriction. The results suggest that the production of the male-originating pheromone that helps to prevent the underfeeding-induced disruption of oestrous cycles in females is androgen-dependent.

Hormone-regulated expression and distribution of versican in mouse uterine tissues

BACKGROUND

Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination.

METHODS

Uteri from mice in all phases of the estrous cycle, and animals subjected to ovariectomy and hormone replacement were collected for immunoperoxidase staining for versican, as well as PCR and quantitative Real Time PCR.

RESULTS

In diestrus and proestrus, VER was exclusively expressed in the endometrial stroma. In estrus and metaestrus, VER was present in both endometrial stroma and myometrium. In OVX mice, VER immunoreaction was abolished in all uterine tissues. VER expression was restored by E2, MPA and E2+MPA treatments. Real Time PCR analysis showed that VER expression increases considerably in the MPA-treated group. Analysis of mRNA identified isoforms V0, V1 and V3 in the mouse uterus.

CONCLUSION

These results show that the expression of versican in uterine tissues is modulated by ovarian steroid hormones, in a tissue-specific manner. VER is induced in the myometrium exclusively by E2, whereas MPA induces VER deposition only in the endometrial stroma.

Estradiol increases the Bax/Bcl-2 ratio and induces apoptosis in the anterior pituitary gland

BACKGROUND

Estrogens are recognized as acting as modulators of pituitary cell renewal, sensitizing cells to mitogenic and apoptotic signals, thus participating in anterior pituitary homeostasis during the estrous cycle. The balance of pro- and antiapoptotic proteins of the Bcl-2 family is known to regulate cell survival and apoptosis.

AIMS

In order to understand the mechanisms underlying apoptosis during the estrous cycle, we evaluated the expression of the proapoptotic protein Bax and the antiapoptotic proteins Bcl-2 and Bcl-xL in the anterior pituitary gland in cycling female rats as well as the influence of estradiol on the expression of these proteins in anterior pituitary cells of ovariectomized rats.

METHODS/RESULTS

As determined by Western blot, the expression of Bax was higher in anterior pituitary glands from rats at proestrus than at diestrus I, Bcl-2 protein levels showed no difference and Bcl-xL expression was lower, thus increasing the Bax/Bcl-2 ratio at proestrus. Assessed by annexin V binding and flow cytometry, the percentage of apoptotic anterior pituitary cells was higher in rats at proestrus than at diestrus I. Chronic estrogen treatment in ovariectomized rats enhanced the Bax/Bcl-2 ratio and induced apoptosis. Moreover, incubation of cultured anterior pituitary cells from ovariectomized rats with 17beta-estradiol for 24 h increased the Bax/Bcl-2 ratio, decreased Bcl-xL expression and induced apoptosis.

CONCLUSION

Our results demonstrate that estradiol increases the ratio between proapoptotic and antiapoptotic proteins of the Bcl-2 family. This effect could participate in the sensitizing action of estrogens to proapoptotic stimuli and therefore be involved in the high apoptotic rate observed at proestrus in the anterior pituitary gland.

Molecular imaging provides novel insights on estrogen receptor activity in mouse brain

Estrogen receptors have long been known to be expressed in several brain areas in addition to those directly involved in the control of reproductive functions. Investigations in humans and in animal models suggest a strong influence of estrogens on limbic and motor functions, yet the complexity and heterogeneity of neural tissue have limited our approaches to the full understanding of estrogen activity in the central nervous system. The aim of this study was to examine the transcriptional activity of estrogen receptors in the brain of male and female mice. Exploiting the ERE-Luc reporter mouse, we set up a novel, bioluminescence-based technique to study brain estrogen receptor transcriptional activity. Here we show, for the first time, that estrogen receptors are similarly active in male and female brains and that the estrous cycle affects estrogen receptor activity in regions of the central nervous system not known to be associated with reproductive functions. Because of its reproducibility and sensitivity, this novel bioluminescence application stands as a candidate as an innovative methodology for the study and development of drugs targeting brain estrogen receptors.

The ovary-mediated FSH attenuation of the LH surge in the rat involves a decreased gonadotroph progesterone receptor (PR) action but not PR expression

Hyperstimulation of ovarian function with human FSH (hFSH) attenuates the preovulatory surge of LH. These experiments aimed at investigating the mechanism of ovarian-mediated FSH suppression of the progesterone (P(4)) receptor (PR)-dependent LH surge in the rat. Four-day cycling rats were injected with hFSH, oestradiol benzoate (EB) or vehicle during the dioestrous phase. On pro-oestrus, their pituitaries were studied for PR mRNA and protein expression. Additionally, pro-oestrous pituitaries were incubated in the presence of oestradiol-17beta (E(2)), and primed with P(4) and LH-releasing hormone (LHRH), with or without the antiprogestin RU486. After 1 h of incubation, pituitaries were either challenged or not challenged with LHRH. Measured basal and LHRH-stimulated LH secretions and LHRH self-priming were compared with those exhibited by incubated pituitaries on day 4 from ovariectomized (OVX) rats in metoestrus (day 2) injected with hFSH and/or EB on days 2 and 3. The results showed that: i) hFSH lowered the spontaneous LH surge without affecting basal LH and E(2) levels, gonadotroph PR-A/PR-B mRNA ratio or immunohistochemical protein expression; ii) incubated pro-oestrous pituitaries from hFSH-treated rats did not respond to P(4) or LHRH, and lacked E(2)-augmenting and LHRH self-priming effects and iii) OVX reversed the inhibitory effects of hFSH on LH secretion. It is concluded that under the influence of hFSH, the ovaries produce a non-steroidal factor which suppresses all PR-dependent events of the LH surge elicited by E(2). The action of such a factor seemed to be due to a blockade of gonadotroph PR action rather than to an inhibition of PR expression.

Neuroprotective effects of lactation against kainic acid treatment in the dorsal hippocampus of the rat

Marked hippocampal changes in response to excitatory amino acid agonists occur during pregnancy (e.g. decreased frequency in spontaneous recurrent seizures in rats with KA lesions of the hippocampus) and lactation (e.g. reduced c-Fos expression in response to N-methyl-d,l-aspartic acid but not to kainic acid). In this study, the possibility that lactation protects against the excitotoxic damage induced by KA in hippocampal areas was explored. We compared cell damage induced 24 h after a single systemic administration of KA (5 or 7.5 mg/kg bw) in regions CA1, CA3, and CA4 of the dorsal hippocampus of rats in the final week of lactation to that in diestrus phase. To determine cellular damage in a rostro-caudal segment of the dorsal hippocampus, we used NISSL and Fluorojade staining, immunohistochemistry for active caspase-3 and TUNEL, and we observed that the KA treatment provoked a significant loss of neurons in diestrus rats, principally in the pyramidal cells of CA1 region. In contrast, in lactating rats, pyramidal neurons from CA1, CA3, and CA4 in the dorsal hippocampus were significantly protected against KA-induced neuronal damage, indicating that lactation may be a natural model of neuroprotection.

Recovery rate, morphological quality and nuclear maturity of canine cumulus-oocyte complexes collected from anestrous or diestrous bitches of different ages

Canine cumulus-oocyte complexes (COC) were recovered from ovaries of post-pubertal animals (1-3, 4-6 and 7-10 years old) at different ovarian estrous phases (anestrus and diestrus). The number of COCs, and the number and nuclear maturity of high-quality (grade-1) oocytes were assessed. For all animals, no significant differences were found between the two reproductive phases relatively to the total number of COCs and grade-1 oocytes recovered. However, significant higher numbers of COCs were recovered from young than from elderly animals, and the proportion of grade-1 oocytes was also significantly higher in the younger group than in the other two age-groups. Of 226 grade-1 oocytes, 73% were at the germinal vesicle stage (GV), 10% had resumed meiosis (9% at germinal vesicle breakdown; 1% at metaphase-I) and 17% were degenerated. A significant effect of the reproductive phase on oocyte nuclear maturity was found only for adult animals, with a higher number of GV oocytes being found at anestrous (79%) due to higher rates of meiosis resumption (34%) at diestrous. The high number of grade-1 oocytes with meiosis resumption and fragmented or unidentified nuclear contents, indicates that current criteria for the selection of viable canine COCs are not optimized and need a new definition.

Proliferation and apoptosis in mammary epithelium during the rat oestrous cycle

AIM

During each oestrous cycle, the mammary gland is subject to changes in ovarian hormone levels. It responds with limited proliferation, differentiation and regression. To understand the processes resulting in these changes, particularly the regulation of cell death, we examined protein levels in mammary epithelium during the oestrous cycle of the Sprague-Dawley rat.

METHODS

Studies of serum hormone levels, vaginal smears, uterine weight and morphology, mammary gland morphology, proliferation and apoptotic indices, and protein levels during the stages of the Sprague-Dawley rat oestrous cycle were used to examine the response of mammary epithelium to the oestrous cycle.

RESULTS

Proliferation of mammary epithelium was greater in diestrus and proestrus, while apoptosis was increased in metestrus and diestrus. Growth factor-, hormone- and anchorage-mediated cell survival signalling, indicated by activation of Stat5A, FAK and Akt 1 and expression of anti-apoptotic Bcl-2 family members, was greater in proestrus and reduced in metestrus. In contrast, the levels of pro-apoptotic Bcl-2 family members and proteins associated with apoptosis in mammary epithelium (TGFbeta3, pStat3) were increased during metestrus and diestrus.

CONCLUSION

Decreases in growth factor, hormone and cell attachment survival signals corresponded with increased apoptosis during the second half of the oestrous cycle. The protein levels detected during oestrus suggest parallels to apoptosis in mammary involution.

Sex differences in PPARgamma expressions in rat adipose tissues

Clinical studies had suggested that there were sex differences in pharmacological and side effects of pioglitazone. However, there are few studies on the sex differences of peroxisome proliferator-activated receptor (PPAR) gamma expressions in rat adipose tissues. We investigated the sex differences in peroxisome proliferator-activated receptor (PPAR) gamma expressions in rat adipose tissues. Subcutaneous abdominal adipose tissues and perigonadal adipose tissues were obtained from male and female Wistar rats (12 weeks of age). Expressions of PPARgamma protein were determined by Western blot analysis with anti-PPARgamma antibody. Vaginal smear check was performed in female rats. We obtained adipose tissues from females, according to the different phases of the estrous cycle. Both PPARgamma1 and gamma2 subtypes were expressed in subcutaneous adipose tissues. Expressions of PPARgamma2 in subcutaneous adipose tissues were significantly higher in males than in females. On the other hand, expressions of PPARgamma2 in perigonadal adipose tissues were significantly higher in females than in males. Expressions of PPARgamma2 in perigonadal adipose tissues in females significantly decreased during diestrus. It can be suggested that the sex hormones might affect the expressions of PPARgamma2 in adipose tissues.

Effect of the oestral cycle on respiratory mechanics in the rat

AIM

To assess the effect of the oestral cycle on the respiratory mechanics of the rat.

METHODS

We measured the main mechanical respiratory parameters, namely respiratory system and lung resistances and compliances, by the end-inflation occlusion method on two populations of female rats, during proestrous-oestrous and metaoestrous-diestrous phases.

RESULTS

Inflation-deflation loops of the lungs were found to be statistically higher in rats during metaoestrous-diestrous phase. No other statistically significant difference was found in the measured mechanical respiratory parameters.

CONCLUSION

Our results suggest that the naturally occurring fluctuations in serum sexual hormone levels during the sexual cycle influence the lung's hysteresis but do not influence the respiratory system and lung resistances or static compliances. A possible effect of female sexual hormones on surfactant activity is also suggested.

Reproductive phenotypes in mice with targeted disruption of the 20alpha-hydroxysteroid dehydrogenase gene

In the corpus luteum of rats and mice, 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) catalyzes the conversion of progesterone to a biologically inactive metabolite, 20alpha-dihydroprogesterone (20alpha-OHP). The reduction of progesterone by 20alpha-HSD is believed to be important for functional luteolysis in these rodent species. In addition to the corpus luteum, expression of 20alpha-HSD has been demonstrated in tissues such as the placenta, endometrial epithelia, and fetal skin, although the roles it plays in the latter tissues remain to be determined. To determine the contribution of 20alpha-HSD to functional luteolysis and to the rodent reproductive system more generally, we generated a strain of mice with targeted disruption of the 20alpha-HSD gene. In the 20alpha-HSD-/- mice we obtained, which lacked the genomic region essential for catalytic reaction, neither 20alpha-HSD activity in the corpus luteum nor an increase in the serum concentrations of 20alpha-OHP during pseudopregnancy or pregnancy was detected. The durations of the estrous cycle, pseudopregnancy, and pregnancy were significantly prolonged in the 20alpha-HSD-/- mice, although the serum progesterone levels decreased to levels low enough for delivery of pups at term of pregnancy. In addition, the number of pups, especially live pups, was markedly decreased in the 20alpha-HSD-/- mice. These findings suggest that the role of 20alpha-HSD in functional luteolysis is relatively minor but that it is involved in the survival of newborn mice.

Estrus cycle: influence on cardiac function following trauma-hemorrhage

Since cardiac function is depressed in males but not in proestrus (PE) females following trauma-hemorrhage (T-H), we examined whether different estrus cycles influence cardiac function in female rats under those conditions. We hypothesized that females in the PE cycle only will have normal cardiac function following T-H and resuscitation. Sham operation or T-H was performed in five groups of rats (250–275 g) including PE, estrus (E), metestrus (ME), diestrus (DE), and ovariectomized (OVX) females ( n = 6–7 per group). Cardiac function was determined 2 h after T-H, following which cardiomyocytes were isolated and nuclei extracted. Cardiomyocyte IL-6 and NF-κB expressions were measured using Western blotting. Moreover, plasma IL-6, estradiol, and progesterone levels were measured using ELISA or EIA kits. Results (1-way ANOVA) indicated that following T-H, 1) cardiac function was depressed in DE, E, ME, and OVX groups but maintained in the PE group; 2) the PE group had the highest plasma estrogen level; 3) plasma IL-6 levels increased significantly in DE, E, ME, and OVX groups, but the increase was attenuated in the PE group; 4) cardiomyocyte IL-6 protein level increased significantly in DE, E, ME and OVX groups after TH, but the increase was attenuated in the PE group; and 5) cardiomyocyte NF-κB expression increased significantly but was attenuated in the PE group. These data collectively suggest that the estrus cycle plays an important role in cardiac function following TH. The salutary effect seen in PE following TH is likely due to a decrease in NF-κB-dependent cardiac IL-6 pathway.

Degeneration and apoptosis of endometrial cells in the bitch

The relationships between changes in plasma progesterone concentrations, degeneration of the luminal epithelium, the occurrence of apoptosis of endometrial cells and endometrial leucocyte populations in the bitch were determined. Mature bitches (n = 15) were euthanized and necropsied when in diestrus (Days 7-75, n = 12) or in anestrus (Days 10, 32 and 53). Degeneration of the luminal epithelium was observed in bitches in late diestrus (Days 38-75, n = 5) when plasma progesterone concentrations were decreasing and in anestrus (Days 10 and 32, n = 2) when plasma progesterone concentrations were < 0.5 ng/mL. Endometrial leucocyte populations increased after degeneration of the luminal epithelium (around Day 42 of diestrus). Apoptosis was mainly observed in the basal glandular epithelial cells and endothelial cells of blood capillaries in all except anestrous bitches. Very few apoptotic cells were found in the superficial glandular epithelial cells and stromal cells. Higher apoptotic indices were detected in the basal glandular epithelium on Days 12-42 of diestrus than at other stages. Therefore, apoptosis of glandular basal epithelial cells occurred mainly in early diestrus, degeneration of cells of the luminal epithelium occurred from mid-diestrus to early anestrus, and the increase in leucocyte numbers may have been a consequence and not a cause of luminal epithelial degeneration.

Apoptosis in canine corpus luteum during spontaneous and prostaglandin-induced luteal regression

Spontaneous luteal regression and prostaglandin-induced luteolysis in bitches were evaluated by measuring the apoptotic index for DNA fragmentation and the relative level of Bax gene expression in ovaries removed from nine untreated nonpregnant bitches at selected times during diestrus and in nine pregnant bitches after 1 day of administering abortive doses of a PGF-analog gel formulation given intravaginally at selected times during gestation. Nonpregnant diestrus was divided into three periods (early, mid and late) based on vaginal cytology and plasma progesterone concentration. Pregnant bitches were treated with a PGF-analog gel at corresponding stages of pregnancy (early, mid and late) and evaluated by ultrasound. Another eight pregnant bitches were similarly studied and serum progesterone concentrations were determined after 1, 2, 3 or 4 days of PGF-analog gel. Corpora lutea obtained by ovariohysterectomy were analyzed for apoptotic internucleosomal DNA fragmentation relative to that in a control cell line (U937), using an apoptotic DNA ladder kit and gel electrophoresis and for relative expression of the pro-apoptotic Bax gene by RT-PCR and electrophoresis. In nonpregnant bitches, the DNA fragmentation apoptotic index was greater in late than in early diestrus (P < 0.01). The index after 1 day of PGF-analog gel was higher in early pregnant bitches than in early diestrus bitches (P < 0.05); it was highest in midpregnancy (P < 0.05). The degree of apoptosis was related to the number of times PGF-analog gel was administered. Bax mRNA was detected in the corpus luteum (CL) and Bax expression increased from early to middiestrus in nonpregnant subjects (P < 0.05). Potential elevation in Bax due to PGF-analog gel treatment in pregnancy was only significant in relation to normal diestrus during early pregnancy (P < 0.01). In conclusion, we inferred that the effects of endogenous or exogenous prostaglandin on CL life span in bitches involved increases in apoptotic activity and that increased apoptosis was implicated in normal luteal regression in nonpregnant bitches.

Canine corpus luteum regression: Apoptosis and caspase-3 activity

The present study evaluated the occurrence of apoptosis and caspase-3 activity in the canine corpus luteum during the period of luteal regression in eight pregnant and nine nonpregnant diestrus bitches. Intact luteal cells were obtained from corpora lutea in both peripartum pregnant bitches and nonpregnant diestrus bitches at approximately 65 d (range 63-68) after estrus, but not at days 75 and 85 in nonpregnant bitches. In all bitches, apoptotic cells were rarely detected and when present, those cells were more easily detected using the hematoxylin and eosin technique than using the critical electrolyte concentration technique. The luteal structures at 75 and 85 d of diestrus had histological characteristics similar to a corpus albicans. Caspase-3 activity was detected in morphologically normal corpora lutea from both pregnant and diestrus bitches around day 65, and also in the later structures considered corpus albicans tissue. These results suggested that apoptosis may not be the major mechanism involved in canine functional luteal regression, and that caspase-3 participated in both functional and morphological luteolysis and in the tissue reorganization involved in corpus albicans formation.

A preliminary study on the induction of dioestrous ovulation in the mare--a possible method for inducing prolonged luteal phase

Background

Strong oestrous symptoms in the mare can cause problems with racing, training and handling. Since long-acting progesterone treatment is not permitted in mares at competition (e.g. according to FEI rules), there is a need for methods to suppress unwanted cyclicity. Spontaneous dioestrous ovulations in the late luteal phase may cause a prolongation of the luteal phase in mares.

Methods

In this preliminary study, in an attempt to induce ovulation during the luteal phase, human chorionic gonadotropin (hCG) (3000 IU) was injected intramuscularly in four mares (experimental group) in the luteal phase when a dioestrous follicle ≥ 30 mm was detected. A fifth mare included in this group was not treated due to no detectable dioestrous follicles ≥ 30 mm. Four control mares were similarly injected with saline. The mares were followed with ultrasound for 72 hours post injection or until ovulation. Blood samples for progesterone analysis were obtained twice weekly for one month and thereafter once weekly for another two to four months.

Results

Three of the hCG-treated mares ovulated within 72 hours after treatment and developed prolonged luteal phases of 58, 68 and 82 days respectively. One treated mare never ovulated after the hCG injection and progesterone levels fell below 3 nmol/l nine days post treatment. Progesterone levels in the control mares were below 3 nmol/l within nine days after saline injection, except for one mare, which developed a spontaneously prolonged luteal phase of 72 days.

Conclusion

HCG treatment may be a method to induce prolonged luteal phases in the mare provided there is a dioestrous follicle ≥ 30 mm that ovulates post-treatment. However, the method needs to be tested on a larger number of mares to be able to draw conclusions regarding its effectiveness.

Ovarian blood flow responses to electroacupuncture stimulation depend on estrous cycle and on site and frequency of stimulation in anesthetized rats

Electroacupuncture (EA) applied to the abdomen and hindlimb modulates the ovarian blood flow (OBF) response. The present study aimed to further elucidate the role of the site and the frequency of short-term EA stimulation and the influence of the estrous cycle on the OBF response using anesthetized rats. EA stimulation was applied to the abdominal or the hindlimb muscles at three different frequencies (2, 10, and 80 Hz) during the estrus or diestrus phase. Involvement of spinal and supraspinal reflexes in OBF responses to EA stimulation was investigated by spinal cord transection. Abdominal EA stimulation at 10 Hz increased the OBF response, whereas hindlimb EA stimulation at 10 Hz and abdominal and hindlimb stimulation at 80 Hz decreased the OBF response; 2-Hz EA caused no OBF response. The OBF response to abdominal EA was more pronounced in the estrus than the diestrus phase. The OBF response to abdominal and hindlimb EA stimulation at both 10 and 80 Hz was almost abolished, both after severance of the sympathetic nerves and after spinal cord transection. In conclusion, the OBF response to both abdominal and hindlimb EA stimulation was mediated as a reflex response via the ovarian sympathetic nerves, and the response was controlled via supraspinal pathways. Furthermore, the OBF response to segmental abdominal EA stimulation was frequency dependent and amplified in the estrous phase.

Oestrogen receptor-immunoreactive neurons in the trigeminal sensory system of male and cycling female rats

Many common craniofacial pain conditions are more prevalent in women than men and may be related to the phase of the menstrual cycle. Long-term effects of oestrogen in the nervous system are produced by receptor-mediated [oestrogen receptor alpha (ERalpha) and beta (ERbeta) isoforms] mechanisms; however, it is not known if the distribution of ER-positive neurons in the trigeminal system is similar in males and females. Quantitative immunocytochemistry was used to compare the distribution of ERalpha-labelled neurons in the trigeminal brainstem complex (TBC) and ganglion of male and female rats at different stages of the oestrous cycle. A high density of ERalpha-labelled neurons was seen in the superficial laminae (I-III) throughout the trigeminal subnucleus caudalis (Vc) and the upper cervical dorsal horn. Counts of ERalpha-positive neurons in laminae I-III were similar for prooestrous and dioestrous females, while males had fewer cells. The deeper laminae (IV-V) of the Vc and the cervical dorsal horn had few ERalpha-positive neurons in all groups. At the region surrounding the central canal at caudal levels of the Vc, prooestrous females had more ERalpha-positive neurons than dioestrous females or males. Few labelled cells were seen rostral to the trigeminal subnucleus interpolaris/caudalis transition region (Vi/Vc) in any group. In the trigeminal ganglion, prooestrous and dioestrous females had a moderate (8-10%) number of nuclear-labelled small or medium-sized neurons, while males had fewer labelled cells (4.5%). Qualitatively, the pattern of staining for ERbeta was similar, although weaker, than for ERalpha in the trigeminal dorsal horn or ganglion. These results were consistent with the hypothesis that oestrogen acts through trigeminal ganglion cells and caudal portions of the Vc to modulate sensory and autonomic aspects of craniofacial pain in a sex-related manner.

The use of deslorelin implants for the synchronization of estrous in diestrous bitches

A novel approach to estrous induction in diestrous bitches is described. Twelve spontaneously cycling anestrous bitches served as controls. Thirteen anestrous and 15 diestrous bitches were induced to come into synchronous estrous using prostaglandin (diestrous bitches only) and deslorelin implants (Ovuplant). Implants contained either 2.1 or 1.05 mg deslorelin and were administered beneath the vestibular submucosa. All treated bitches came into estrous, regardless of implant size. Whereas all anestrous bitches ovulated, one of six diestrous bitches treated with the larger implant and three of nine treated with the smaller implant failed to ovulate. Induced bitches generally produced fewer corpora lutea than controls. Sixty-seven percent of control bitches became pregnant, with 0.63 fetuses per corpus luteum, whereas the pregnancy rate and fetuses per corpus luteum were 67 and 70% and 0.42 and 0.55 in the anestrous bitches induced with 1.05 and 2.1 mg deslorelin implants, respectively (not different from controls). Only 2 of 15 induced diestrous bitches conceived a detectable pregnancy, one of which was resorbed. In conclusion, although ovulatory estrous can be induced in bitches that had their most recent ovulation 40-100 days ago, these bitches are very unlikely to become pregnant during the induced estrous. The reason for the poor fertility in these diestrous bitches requires further study.

Meiotic Competence of Canine Oocytes Embedded in Collagen Gel

The present study was conducted to examine the meiotic competence of canine oocytes embedded in collagen gel, and to investigate the effects of timed exposure of the oocytes embedded in collagen gel to gonadotrophins during maturation culture, on their nuclear maturation. Cumulus-oocyte complexes (COCs) were collected from bitches at the anoestrous and dioestrous stages of the reproductive cycle. In the first experiment, half of the COCs were embedded in collagen gels. The COCs with or without collagen-gel embedding were cultured in a TCM-199 medium supplemented with 0.1 IU/ml human menopausal gonadotropin (hMG) and 10 IU/ml human chorionic gonadotropin (hCG) for 72 h. In the second experiment, the COCs embedded in collagen gels were cultured in TCM-199 medium with gonadotrophins (hMG and hCG) for various periods (0, 24, 48 and 72 h) and then cultured in the medium without gonadotrophins until reaching total culture period (72 h). The percentage of the oocytes reaching metaphase I and metaphase II (MI/MII) was significantly higher (p < 0.05) in COCs with collagen-gel embedding than in COCs without collagen-gel embedding. The percentage of oocytes that were arrested at the germinal vesicle stage was significantly lower (p < 0.05) in oocytes cultured with gonadotrophins than in oocytes cultured without gonadotrophins. However, there were no significant differences in the percentages of oocytes that reached each stage of meiosis among the groups, irrespective of the duration of exposure to gonadotrophins. These observations indicate that embedding of COCs by collagen gel enhances the meiotic competence of canine oocytes, but removal of hormone supplement from maturation medium does not improve the ability of the oocytes to reach MII stage.

An in vitro study on spontaneous myometrial contractility in the mare during estrus and diestrus

Uterine smooth muscle specimens were collected from euthanatized mares in estrus and diestrus. Longitudinal and circular specimens were mounted in organ baths and the signals transcribed to a Grass polygraph. After equilibration time and 2 g preload, their physiologic isometric contractility was recorded for a continuous 2.0 h. Area under the curve, frequency and time occupied by contractions were studied. Differences between cycle phases, between muscle layers, and over the recorded time periods were statistically evaluated using linear mixed-effect models. In the mare, physiologic contractility of the uterus decreased significantly over time for all variables evaluated (time as covariate on a continuous scale). For area under the curve, there was a significant effect of muscle layer (longitudinal > circular). For frequency, higher values were recorded in estrus for circular smooth muscle layer, whereas higher values were seen in longitudinal smooth muscle layers during diestrus. In longitudinal layer and in diestrus, more time was occupied by contractions than in circular layer, and in estrus. This study is describing physiologic myometrial motility in the organ bath depending on cycle phase.

Distribution of Eosinophils and Mast Cells in the Cervical Tissue of Non-Gravid Mares during Dioestrus

Little is known about the local cellular immune system of the equine cervix. In this study we characterize the distribution of eosinophilic granulocytes and mast cells in the cervical tissue of non-gravid mares during dioestrus. For this purpose cervices of 10 mares were histologically examined after Sirius red and Toluidine blue staining. Both cell types could be found in the lamina propria mucosae. In the tunica muscularis the two cell populations were only rarely detected. No cells could be found in the epithelium mucosae. There was a decreasing cell density from the vaginal to uterine side of the cervix (p < 0.01). Therefore, eosinophils might be a part of the local cellular immune system of the equine cervix during dioestrus, unlike in animals studied so far as cows and rats.

Rat estrous cycle influences the sexual diergism of HPA axis stimulation by nicotine

We previously reported that female rats had significantly greater hypothalamic-pituitary-adrenal (HPA) axis responses to cholinergic stimulation by nicotine (NIC) than did male rats. Females in defined estrous cycle stages, however, were not studied because of sample size limitations. We further explored this finding by determining HPA axis responses to two doses of NIC in female rats (N = 101) during different estrous cycle stages, and in males (N = 69). NIC doses were: 0.3 mg/kg, which provided the greatest female-male difference in the earlier study, and 0.5 mg/kg, which stimulated the HPA axis similarly in the two sexes. Plasma AVP, ACTH, and corticosterone were measured. Proestrous and estrous females had higher ACTH responses to NIC (0.3 mg/kg) compared to metestrous and diestrous females, and compared to males. ACTH responses to NIC (0.5 mg/kg) were similar, regardless of estrous cycle stage or sex. Males had higher AVP responses to both NIC doses compared to females in all estrous cycle stages. Corticosterone responses followed the ACTH responses, except that females in all estrous stages started from a higher corticosterone baseline compared to males. These results are similar to our earlier findings across the estrous cycle with non-specific cholinergic stimulation by physostigmine and suggest that the nicotinic system contributes to the differential HPA axis responses to cholinergic challenge across the estrous cycle.

Mifepristone (RU486) inhibits lateral perforant path long‐term potentiation in hippocampal slices from prenatally morphine‐exposed female rats

In brain slices from prenatally saline-exposed female rats during proestrus and diestrus, long-term potentiation (LTP) can be induced in the lateral perforant pathway (LPP). Prenatal morphine exposure suppresses LTP induction in the LPP during proestrus. Here we studied synaptic plasticity in the LPP in slices from female rats prenatally exposed to morphine. Two additional factors were investigated: the role of the estrous cycle and role of glucocorticoid receptors. Hippocampal slices were prepared from adult, prenatally saline- or morphine-exposed female rats. One hour prior to decapitation, vaginal smears were obtained and the rats either in proestrus or diestrus were treated with a non-specific glucocorticoid receptor antagonist mifepristone (RU486) or with a vehicle. LPP was stimulated with high-frequency stimulation. Short-tem plasticity (STP) and the induction and maintenance of long-term potentiation (LTP) were assessed. In all groups of prenatally saline-exposed rats, LTP was induced and maintained with the exception of RU486-treated rats during proestrus where the LTP was induced but not maintained. In prenatally morphine-exposed females in diestrus, both STP and LTP were induced after postnatal vehicle treatment. In morphine-exposed, proestrous females, neither STP nor LTP were induced irrespective of the postnatal treatment. Thus, prenatal morphine exposure suppresses the induction of LTP in the LPP, except during diestrus. Data indicate that the induction and maintenance of LTP in the LPP in hippocampal slices from female rats is multifactorial: ovarian steroids and functionality of glucocorticoid receptors cooperation are necessary for induction and maintenance of the LTP, prenatal morphine exposure interferes with this process possibly by its long-term effects on synaptic plasticity.

Effect of oestrous-cycle stage on the response of mares in a novel object test and isolation test

In various species, sex, hormonal treatments and oestrous-cycle stage have been shown to affect the animal's response in behavioural tests. Few such studies have been performed in the horse. The main aim of the present study was to investigate whether oestrous-cycle stage affects mares' response to a novel object test and isolation test and, in part, to study whether mares, assumed to suffer from oestrous-related behavioural problems, respond differently in these tests when compared with controls. Twelve mares were tested twice, in oestrus and dioestrus, in a crossover design. Seven behavioural and two heart rate variables were measured for the novel object test and two heart rate variables for the isolation test. Oestrous-cycle stage and whether a mare was classified as a 'problem' mare did not affect the mare's response. However, test order, i.e. the cycle stage a mare was tested in first, affected its reaction. This effect could partly be explained by significant differences between test occasions 1 and 2 in three behavioural variables and one heart rate variable (p < 0.05) in the novel object test. The mares explored the novel object more and had a higher mean heart rate in the first test. Exploring the novel object more could largely be attributed to those mares tested in dioestrus first, perhaps indicating that the mares in oestrus were less receptive to the novel object. The reason for the differences between test occasions could be an effect of learning or habituation.

Ovarian steroids regulate neuropeptides in the trigeminal ganglion

Women are more than three times as likely as men to experience migraine headaches and temporomandibular joint pain, and painful episodes are often linked to the menstrual cycle. To understand how hormone levels may influence head and face pain, we assessed expression of pain-associated neuropeptides and estrogen receptor alpha (ERalpha) during the natural estrous cycle in mice. Gene expression was analyzed in the trigeminal ganglia of cycling female mice at proestrus, estrus and diestrus using RT-PCR. Peptide/protein expression in trigeminal neurons was analyzed using immunohistochemistry. ERalpha mRNA was present at all stages and highest at estrus. ERalpha protein was present in the cytoplasm of medium-sized and small trigeminal neurons. ERalpha immunoreactive neurons were most common at diestrus. CGRP and ANP mRNAs did not change across the estrous cycle, while expression of galanin and NPY mRNAs were strongly linked to the estrous cycle. Galanin mRNA levels peaked at proestrus, when expression was 8.7-fold higher than the diestrus levels. Galanin immunoreactivity also peaked at proestrus. At proestrus, 7.5% of trigeminal neurons contained galanin, while at estrus, 6.2% of trigeminal neurons contained galanin, and at diestrus, 4.9% of trigeminal neurons contained galanin. NPY mRNA peaked at estrus, when levels were 4.7-fold higher than at diestrus. Our findings suggest that estrogen receptors in trigeminal neurons modulate nociceptive responses through effects on galanin and NPY. Variations in neuropeptide content in trigeminal neurons across the natural estrous cycle may contribute to increases in painful episodes at particular phases of the menstrual cycle.

Investigations on the expression of cytokines in the canine corpus luteum in relation to dioestrus

Control of luteal regression in the dog is still poorly understood. Unlike other domestic animal species, luteolysis is not prevented by hysterectomy. Indications that PGF(2alpha) may act as an endogenous luteolytic agent have been found only in pregnant animals during the prepartal decline of progesterone. Evidence from several species indicates that the immune system plays an important role in corpus luteum (Cl) function, possibly by the release of cytokines from immigrant immune cells. Hence, in the present experiment we attempted to examine the expression of cytokines in the canine Cl during the course of dioestrus (formation and regression of the Cl), using RT-PCR. Groups of 4-5 bitches were ovario-hysterectomised on days 5, 15, 25, 35, 45 and 60-80 after ovulation. Canine-specific primers for IL-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, TNFalpha, IFNgamma and TGFbeta1 were used. Positive and negative controls were included in all tests. Adequate expression was confirmed by sequencing selective samples of positive PCR products. The expression of mRNA for IL-8, IL-10, IL-12, TNF-alpha and TGF-beta1 was detected in all samples at each stage of dioestrus, without any obvious variations indicating a likely modulatory function of these cytokines in differentiation, maintenance or regression of the canine Cl. All tests for the expression of mRNA for IL-4, IL-1beta and IL-2 were negative. More negative than positive results were obtained when testing for the expression of mRNA for IL-6 and IFN-gamma, leading to the conclusion that expression of these two cytokines is at a low level, and no conclusion can be drawn as to their involvement in control of Cl function.

Acute effect of ethanol on IgA immunoreactive cells in the intestine-associated immune system

The purpose of this study was to investigate the acute effect of ethanol on mucosa-associated lymphoid tissue at the level of Peyer's patches and the intestinal lamina propria in female rats and to determine whether this action of ethanol is modulated during the estrous cycle. Adult female rats showing proestrus or diestrus day 1 were treated intraperitoneally (ip) with ethanol (4 g/kg). Untreated and saline-injected rats were used as controls. The animals were sacrificed by decapitation 0.5 h after ethanol administration. Immunoglobulin A (IgA) immunoreactive cells were analyzed by indirect immunohistochemistry using mouse anti-rat IgA and a Dako LSAB+ kit. The number of IgA-immunoreactive cells in Peyer's patches was unaltered by ethanol treatment at both phases of the estrous cycle. However, stereological analysis revealed a significant increase in the number of IgA-immunoreactive cells (p < 0.01) in the intestinal lamina propria following acute ethanol administration at proestrus and on diestrus day 1. The results indicate that the intestinal lamina propria, the effector site of the mucosal immune system, can be affected by a single dose of ethanol at both phases of the estrous cycle.

Stability of hippocampal place cell activity across the rat estrous cycle

Findings from both in vitro and in vivo studies have shown that estrogen exerts pronounced effects on hippocampal morphology and physiology. The degree to which these molecular findings influence hippocampal processing in freely behaving animals is unclear. The present study assessed the effect of the estrous cycle on hippocampal place cells in naturally cycling rats during two behavioral states. Female Sprague-Dawley rats were trained to alternate on a U-shaped runway for food reinforcement. Single-unit recordings of hippocampal CA1 cells were conducted under two conditions: (1) at rest on a holder, and (2) running on the maze. Spatial firing characteristics of the cells were examined at different stages of the estrous cycle (i.e., diestrus, proestrus, and estrus). Specifically, information was collected on (1) mean firing rates; (2) basic place field parameters; and (3) changes in the firing dynamics of these cells (e.g., burst properties). The findings showed a decrease in mean firing rate on the maze during proestrus. However, other basic measures of spatial tuning and burst properties were unchanged. The current study suggests that there is relative stability of hippocampal place cells across the estrous cycle during a well-trained task.

Guanylin-immunoreactive cells in the female and male rat adenohypophysis and their changes under various physiological and experimental conditions

The peptide guanylin, first isolated from rat small intestine, is involved in the regulation of water-electrolyte transport between the intracellular and extracellular compartments of the epithelia. The main sites of guanylin expression are the intestinal, airway, or exocrine gland ductal epithelia where guanylin acts in a paracrine/luminocrine fashion. Because guanylin also circulates in the blood, sources of this peptide were sought in endocrine glands. Our group has already demonstrated the presence of guanylin-immunoreactive cells in the pars tuberalis of male rat adenohypophysis. In this study, we investigated whether guanylin-immunoreactive cells exist also in the adenohypophysial pars distalis and whether their appearance or distribution correlates with various physiological conditions in female rats or alters after gonadectomy in both sexes. These studies revealed that the rat pars distalis contains two guanylin-immunoreactive cell types, gonadotrophic cells, whose number varied notably during the estrous cycle, reached a peak in the proestrous phase, and increased consistently during pregnancy, in lactating animals, and after gonadectomy, and folliculo-stellate cells, a discrete number of which were found only in female rats at the estrous phase. These findings suggest that guanylin is involved in regulating gonadotrophic cell function. They also add important information on the controversially discussed functions of folliculo-stellate cells.

Sexual behavior of female rats in a multiple-partner preference test

In this study, sexually experienced female rats were tested in a multiple-partner preference test (MPPT) in which they were allowed to pace their sexual contacts with four sexually active males. Four cylinders, with a small hole through which only the female could move freely from one cylinder to another, were assembled forming in the center an empty compartment. An intact female was placed in the central compartment and a sexually active male in each cylinder. Female sexual behavior was analyzed throughout the estrus cycle in four consecutive days. Each daily test lasted 15 min. The percentage of exits after intromission or ejaculation was significantly higher than the percentage of exits after each mount. The female spent significantly longer time with one of the males. We designated this male as the preferred male (PM). Although in each of the 4 days studied, females spent significantly longer time with the PM, however, the male selected was not the same throughout the estrus cycle. The number of entries into the compartment of the PM was significantly higher and increased around proestrus. Compared to previous studies, pacing behavior was notably lower in the conditions of the MPPT. No significant differences were observed during the estrous cycle concerning the other parameters recorded. The present results suggest that the MPPT could be a good model to study partner preference in the female rat.

Expression of Messenger RNA Coding for 5-HT Receptor, Alpha and Beta Adrenoreceptor (Subtypes) during Oestrus and Dioestrus in the Bovine Uterus

Serotoninergic and adrenergic receptors (5-HTR and AR) are involved in the regulation of uterine contractility. The objective of this study was to compare mRNA levels of 5-HTR(1A), 5-HTR(1B), 5-HTR(1D), 5-HTR(1F), 5-HTR(2A), 5-HTR(2B), 5-HTR(2C), 5-HTR(4) and alpha(1A), alpha(1B), alpha(1D), alpha(2AD), alpha(2B), alpha(2C), and beta(1), beta(2), beta(3)-AR in oestrus and dioestrus, and at three uterine locations (tip, middle and base) using quantitative real-time polymerase chain reaction. Uterine specimens consisting of endometrium and myometrium including vessels and serosa were collected from cows in oestrus (n = 10) and dioestrus (n = 15) respectively. Levels of 5-HTR and AR mRNA were expressed relative to the geometric mean of ribosomal RNA (18S), ubiquitin and glyceraldehyde phosphate dehydrogenase by the mean values of geNorm algorithm. 5-HTR(1A), 5-HTR(2C) and beta(3)-AR mRNA could not be detected in uterine tissues. The mRNA levels of 5-HTR(1F) and 5-HTR(2B) were lower (P < 0.05), but of 5-HTR(4) were higher (P < 0.05) in oestrus than in dioestrus. The mRNA levels of alpha(1A)-AR, alpha(2AD)-AR, alpha(2B)-AR were lower (P < 0.05), but of alpha(2C)-AR and beta(2)-AR were higher (P < 0.05) in oestrus than dioestrus. The mRNA levels of 5-HTR(1B) and 5-HTR(1D) (oestrus) and of alpha(2AD)-AR (dioestrus) differed among uterine locations (base > middle > tip; P < 0.05). The mRNA expression of 5-HTR and AR (subtypes) in bovine uterus was associated with cycle activity and varied according to uterine location. Additional studies on protein level will be carried out in order to elucidate the role of these receptor families on uterine contractility, which may then help to clarify clinical relevance.

Effect of PACAP on LH release studied by cell immunoblot assay depends on the gender, on the time of day and in female rats on the day of the estrous cycle

We have previously demonstrated that pituitary adenylate cyclase activating polypeptide (PACAP) can be released from cultured rat anterior pituitary cells and when added to the medium in physiological concentration it releases LH from individual gonadotropes. In the present work, we studied whether the release of PACAP and the responsiveness of LH cells to PACAP depend on the gender, on the time of day when the animals were sacrificed, and in females on the stage of the estrous cycle. Anterior pituitary cells were cultured on nitrocellulose membrane. We found that the number of PACAP releasing cells was higher in proestrous than in diestrous female or in male rats and their number was always higher in the evening than at the other times. The effect of PACAP on LH cells was stimulatory in the morning of proestrus and diestrus. In proestrous rats, PACAP did not influence LH release in the afternoon or the evening, but in diestrous rats it decreased it in the afternoon and the evening. In males, there was a decrease of LH due to PACAP treatment at 10 and 20 h; however, PACAP did not influence LH at 16 h. It was concluded that in vivo PACAP might be involved in the circadian and episodic release of LH at pituitary level.