Vaginal keratinization during the estrous cycle in rats: a model for evaluating retinoid activity

Effect of genistein on the gene and protein expressions of CXCL-12 and EGR-1 in the rat ovary

The effect of genistein (GEN) on the gene expression level of stromal cell-derived factor-1/CXCL-12 and early growth response gene-1 was studied in ovarian tissue of young and initially ageing (early stages in the ageing process) female rats. Forty, young female Sprague Dawley (SD) rats of 2-3 months old (200 ±20 g) and forty, initially ageing female SD rats of 10-12 months (490 ± 20 g) old were selected. According to the weight, rats were divided into control group, low-dose group (L), medium-dose group (M) and a high-dose group (H) and were given 15, 30 and 60 mg/kg GEN respectively. The positive control (Oestrogen) group was given 0.5 mg/kg diethylstilbestrol. The treatment lasted for 30 days. The mRNA expression of C-X-C motif chemokine ligand 12 (CXCL-12) and early growth response factor-1 (EGR-1) was measured by real-time PCR, and protein expression of EGR-1 was detected by Western blot. When compared to the negative control group (NC), the ovary/body weight ratio in the young rats decreased in the GEN group, but the difference was not significant. Similarly, compared with NC, the ovary/body weight ratio in the initially ageing rats also decreased with the increase in GEN concentration, but the decrease was significant in M and H groups (p < .01). The administration of GEN enhanced both the gene and protein expression levels of CXCL-12 and EGR-1 in the ovary. Pearson's correlation analysis showed a synergistic effect between CXCL-12 and EGR-1. Thus, we conclude that the effect of GEN on CXCL-12 and EGR-1 in the initially ageing group was obvious than that in the younger group.

GLP-1 modulates the supramammillary nucleus-lateral hypothalamic neurocircuit to control ingestive and motivated behavior in a sex divergent manner

OBJECTIVE

The supramammillary nucleus (SuM) is nestled between the lateral hypothalamus (LH) and the ventral tegmental area (VTA). This neuroanatomical position is consistent with a potential role of this nucleus to regulate ingestive and motivated behavior. Here neuroanatomical, molecular, and behavior approaches are utilized to determine whether SuM contributes to ingestive and food-motivated behavior control.

METHODS

Through the application of anterograde and retrograde neural tract tracing with novel designer viral vectors, the current findings show that SuM neurons densely innervate the LH in a sex dimorphic fashion. Glucagon-like peptide-1 (GLP-1) is a clinically targeted neuro-intestinal hormone with a well-established role in regulating energy balance and reward behaviors. Here we determine that GLP-1 receptors (GLP-1R) are expressed throughout the SuM of both sexes, and also directly on SuM LH-projecting neurons and investigate the role of SuM GLP-1R in the regulation of ingestive and motivated behavior in male and female rats.

RESULTS

SuM microinjections of the GLP-1 analogue, exendin-4, reduced ad libitum intake of chow, fat, or sugar solution in both male and female rats, while food-motivated behaviors, measured using the sucrose motivated operant conditioning test, was only reduced in male rats. These data contrasted with the results obtained from a neighboring structure well known for its role in motivation and reward, the VTA, where females displayed a more potent response to GLP-1R activation by exendin-4. In order to determine the physiological role of SuM GLP-1R signaling regulation of energy balance, we utilized an adeno-associated viral vector to site-specifically deliver shRNA for the GLP-1R to the SuM. Surprisingly, and in contrast to previous results for the two SuM neighboring sites, LH and VTA, SuM GLP-1R knockdown increased food seeking and adiposity in obese male rats without altering food intake, body weight or food motivation in lean or obese, female or male rats.

CONCLUSION

Taken together, these results indicate that SuM potently contributes to ingestive and motivated behavior control; an effect contingent on sex, diet/homeostatic energy balance state and behavior of interest. These data also extend the map of brain sites directly responsive to GLP-1 agonists, and highlight key differences in the role that GLP-1R play in interconnected and neighboring nuclei.

Metabolomic profiling of ovary in mice treated with FSH using ultra performance liquid chromatography/mass spectrometry

The growth and development of follicles are a very complex physiological process that is regulated by endocrine, autocrine and paracrine mechanisms. The effect of small molecules in follicular microenvironment on follicular growth and development has not been clearly analyzed. In the present study, the metabolic changes in ovaries of FSH-stimulated mice were investigated. Metabolomic profiling of ovary stimulated by FSH were analyzed by ultra-performance liquid chromatography/mass spectrometry and characterized by principal components analysis and orthogonal partial least squares discriminant analysis. Multivariate statistical analysis identified 21 differentially metabolites in positive ion mode and 12 in negative ion mode in the FSH-treated mice compared with the control mice. These results indicated that various types of phosphatidylcholine were changed. Furthermore, the levels of L-Glutamyl 5-phosphate, N-Acetyl-L-aspartic acid, 4-fumarylacetoacetic acid, adenylylselenate and 5′-Methylthioadenosine in the ovaries of the FSH-stimulated mice were decreased. However, the levels of 19-hydroxytestosterone and 5,10-methenyltetrahydrofolic acid were significantly increased in the positive ion mode and negative ion mode, respectively. Thirty-three differential metabolites including fatty acid metabolism, amino acid metabolism and lipid metabolism in the ovaries of mice were affected by FSH injection. The findings of our study provide a new insight into understanding the follicular development.

Estradiol is a critical regulator of food-reward behavior

Food intake is reduced by estrogenic hormones, levels of which vary throughout life and fluctuate throughout the ovarian cycle in females. However, estrogens have also been shown to increase reward derived from drugs of abuse, where motivational properties of drugs and progression to addiction are potentiated by estrogens. Whether reward derived from food, and specifically motivational properties of food, are altered by estrogens remains unknown. Here we investigated the effect of the estrous cycle on food reward behavior and show estrous cycle dictated variability in food motivation, measured by progressive ratio operant conditioning, in female rats. Reward behavior was lowest on days associated with high estrogen signaling. We therefore also examined the actions of subcutaneously administered β-estradiol on food reward and found that β-estradiol reduced food reward behavior. The ventral tegmental area (VTA) is a crucial node of the neurocircuitry underlying motivated behavior and estrogen receptors are expressed in this nucleus. Thus, we examined whether the effects of estrogens on reward were exerted directly at the level of the VTA. Intra-VTA microinjection of β-estradiol led to a significant reduction in food-motivated behavior. Interestingly, this effect was not accompanied by a reduction in chow intake or body weight, nor did it alter locomotor activity. Importantly, removal of the ovaries produced a potent and lasting elevation in food reward and food-seeking behavior, suggesting that ovarian sex steroids are critical for maintenance of normal food reward behavior. These data reveal a novel role for estrogens in the control of food reward behavior.​.

Comparison of the vaginal environment of Macaca mulatta and Macaca nemestrina throughout the menstrual cycle

PROBLEM

Pigtail macaques, Macaca nemestrina (PT), are more susceptible to vaginal transmission of simian immunodeficiency virus (SIV) and other sexually transmitted diseases (STD) than rhesus macaques (RM). However, comparative studies to explore the reasons for these differences are lacking.

METHOD OF STUDY

Here, we compared differences in hormone levels and vaginal mucosal anatomy and thickness of RM and PT through different stages of the menstrual cycle. Concentrations of plasma estradiol (E2) and progesterone (P4) were determined weekly, and vaginal biopsies examined at days 0 and 14 of the menstrual cycle.

RESULTS

Consistent changes in vaginal epithelial thickness occurred at different stages of the menstrual cycle. In both species, the vaginal epithelium was significantly thicker in the follicular than in luteal phase. Keratinized epithelium was strikingly much more prominent in RM, especially during the luteal phase. Further, the vaginal epithelium was significantly thinner, and the P4:E2 ratio was higher in PT during luteal phase than RM.

CONCLUSIONS

Striking anatomic differences in the vaginal epithelium between rhesus and pigtail macaques combined with differences in P4:E2 ratio support the hypothesis that thinning and less keratinization of the vaginal epithelium may be involved in the greater susceptibility of pigtail macaques to vaginal transmission of SIV or other STD.

Temporal association of serum progesterone concentrations and vaginal cytology in walruses (Odobenus rosmarus)

Concentrations of serum estradiol-17β and progesterone were monitored in six female walruses using an enzyme immunoassay. Progesterone concentrations increased from March to May in females aged 6 y or older, and subsequently declined (October). No significant elevation of estradiol-17β concentration was detected before an elevation of progesterone concentration. Vaginal smears from four females were examined with Papanicolaou staining. In all females, most epithelial cells were basophilic intermediate-superficial cells; no color change from basophilic to eosinophilic of the cells was detected. Meanwhile, the percentage of anucleate cells in vaginal smears reached its highest value before the elevation of progesterone concentration, followed by an increase in the percentage of leukocytes. We inferred that the change in populations of anucleate cells and leukocytes in vaginal smears reflected ovarian status and CL formation in female walruses.

A quantitative method for assessing stages of the rat estrous cycle

The impact of gender and/or hormone variations on a wide variety of neural functions makes the choice between studying males or females (or both) of a given species difficult. Although female rats are widely used experimentally, few studies control for the stage of estrus. More detailed information about how to distinguish the various stages of the estrous cycle is needed. For the present study, vaginal smears were obtained once a day and stained using an adaptation of the Papanicolaou (PAP) procedure. Images are provided of unstained "wet" samples and the corresponding PAP stained smears illustrating the cellular profile for each stage of the cycle as well as post-ovariectomy. The different cell populations across the cycle were quantified and ratios determined to show trends between the predominant and other cell types in each stage of the estrous cycle. Both stained and unstained images and cell quantification data provide valuable guidelines for distinguishing the stages of the estrous cycle.

Determination of Oestrous Cycle of the Rats by Direct Examination: How Reliable?

For determination of the oestrous cycle in rats classical Papanicolaou technique has long been used successfully. Instead of using many stains in Papanicolaou, staining the vaginal secretions with only methylene blue has also been defined. Recently a new technique in which vaginal samples are directly examined under light microscope has been introduced. The aim of this study was to assess the reliability of this new technique by comparing it with the classical staining techniques. From 20 Wistar rats 60 vaginal samples were collected with a micropipette, three from each. Briefly, the vagina was flushed two to three times then the fluid was placed onto a glass slide. The fluid was equally distributed onto three glass slides. The glass slides were coded. Two samples were stained with Papanicolaou and methylene blue while the other one was examined directly. Determination of the phases of the oestrous cycle was made by the same histologist who was blinded to the groups and coding system. After determination of the oestrous phase in all samples, the results were compared and it was found that the results were matching. In conclusion, the same results can be obtained with the direct examination technique and this technique is reliable, so there is no need to use relatively time-consuming, less practical and more expensive techniques such as Papanicolaou or methylene blue.

Four weeks of oral isotretinoin treatment causes few signs of general toxicity in male and female Sprague–Dawley rats

Despite widespread use of isotretinoin for its anti-acne effects and its current evaluation in clinical trials as a cancer treatment, little is known about its general toxicity in adult nonpregnant animals, particularly after oral administration which mimics the human route. Here, adult male and female Sprague-Dawley rats were gavaged daily with 0 (soy oil), 7.5, or 15 mg/kg isotretinoin for 28 days during which time body weight, food/water intake, and estrous phase were measured. At sacrifice, organ weights were collected and concentrations of dopamine (DA), serotonin and metabolites were measured in frontal cortex, striatum, hippocampus, and diencephalon. Food intake was mildly decreased in both treated groups (approximately 15% in males and 7% in females); however, body weight and water consumption were unaffected. The estrous cycle appeared slightly affected (i.e., lengthened by 15 mg/kg, and both treated groups appeared to have less time in diestrus and more time in estrus). Kidney/body weight ratio was decreased by 7.5 and 15 mg/kg isotretinoin and spleen/body weight ratio was increased in the 7.5 mg/kg group. Males of the 7.5 mg/kg group exhibited significantly higher gonad/body weight ratios than did same-sex controls. Concentrations of monoamine and metabolites in the frontal cortex and diencephalon were unaffected. Nor were striatal DA and DOPAC concentrations affected; however, there were isolated effects on striatal HVA and 5-HIAA. Hippocampal DA concentrations were marginally increased. These data indicate mild effects resulting from oral isotretinoin treatment at doses which likely produce serum levels within the range of humans.

Determination of the estrous cycle phases of rats: some helpful considerations

The short length of the estrous cycle of rats makes them ideal for investigation of changes occurring during the reproductive cycle. The estrous cycle lasts four days and is characterized as: proestrus, estrus, metestrus and diestrus, which may be determined according to the cell types observed in the vaginal smear. Since the collection of vaginal secretion and the use of stained material generally takes some time, the aim of the present work was to provide researchers with some helpful considerations about the determination of the rat estrous cycle phases in a fast and practical way. Vaginal secretion of thirty female rats was collected every morning during a month and unstained native material was observed using the microscope without the aid of the condenser lens. Using the 10 x objective lens, it was easier to analyze the proportion among the three cellular types, which are present in the vaginal smear. Using the 40 x objective lens, it is easier to recognize each one of these cellular types. The collection of vaginal lavage from the animals, the observation of the material, in the microscope, and the determination of the estrous cycle phase of all the thirty female rats took 15-20 minutes.

Female sex hormones as regulatory factors in the vaginal immune compartment

Sexually transmitted diseases (STD) are now considered to be among the most common human infections. The incidence of STD is on the rise, which is partly due to frequent transmission during the asymptomatic phase of infection. The compounded cost of STD just in the United States is estimated to exceed $10 billion annually. STD are particularly prevalent in teenagers and young adults and the health problems caused by these diseases tend to be more severe and more frequent in woman than in men. Despite considerable efforts, a vaccine that provides protective immunity against sexually transmitted diseases in humans has not been developed. Nonetheless, research in animal models indicates that strong local and regional immune responses can influence the outcome of vaginal challenge with microbial pathogens. Vaginal immunity is an area of basic immunology that has received relatively little attention, but it is already clear that the mucosal and regional immunology of the vagina has unique features. The present review summarizes some of the anatomical, physiological and immunological features of the vagina and uterus that distinguish humans, non-human primates, rats and mice. These interspecies differences need to be taken into account in laboratory efforts to develop effective vaccines for STD in humans.

Changes in the activity of alcohol dehydrogenase isoenzymes during the estrus cycle in the vagina of the rat

In rodents, the vaginal epithelium undergoes cyclical changes with an alternating pattern of keratinization and mucification. It has been known for decades that vitamin A and its active form retinoic acid are responsible for normal epithelial homeostasis. However, it has not so far been certain which enzymes catalyze the first and rate-limiting step in retinoic acid synthesis. By means of microdissection and ultrathin-layer gel electrophoresis, alcohol dehydrogenase isoenzyme activity was determined quantitatively in the various layers of the vaginal mucous membrane. It was found that, in the rat, only alcohol dehydrogenase 3 and 4 are expressed. Marked cyclical changes of alcohol dehydrogenase 4 activity in the stratum germinativum of the vaginal epithelium strongly support the assumption that this isoenzyme is responsible for retinoic acid synthesis, and that it is essential for the changes accompanying keratinization and mucification.

Retinoid receptors in rat vaginal and uterine epithelia: changes with ovarian steroids

In rats, vaginal epithelium shows cyclic changes with an alternating pattern of keratinization under estrogen control and mucification under progesterone control. Since retinoids suppress keratinizing differentiation, in this paper we studied the expression of the major retinoid receptors normally present in keratinizing squamous epithelia: RAR alpha, RAR gamma and RXR alpha. In cyclic rats and steroid-treated ovariectomized rats, RXR alpha and RAR gamma were detected in basal and suprabasal cells while RAR alpha was mainly localized in suprabasal cells. No changes in RAR gamma expression were observed in correlation with ovarian steroids. During diestrus and in ovariectomized rats, the superficial cuboid cells expressed the three receptors. In the uterine epithelium, RAR alpha, RAR gamma and RXR alpha expression was induced by estrogens. Retinoic acid treatment did not modify retinoid receptor expression in vaginal and uterine epithelia. These data suggest specific roles for the different receptors in the complex process of vaginal epithelium proliferation and differentiation under estrogens and retinoic acid control.