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Testing for Reproductive Hazards from Dermal Exposure
Published in Francis N. Marzulli, Howard I. Maibach, Dermatotoxicology Methods: The Laboratory Worker’s Vade Mecum, 2019
Estrous cycle length and normality should be evaluated by vaginal smears for all parental rat females during a minimum of 3 weeks prior to mating and throughout cohabitation. (ICH variation: Vaginal smears should be done at least during mating.) Care should be taken to prevent the induction of pseudopregnancy.
Reproductive System and Mammary Gland
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Justin D. Vidal, Charles E. Wood, Karyn Colman, Katharine M. Whitney, Dianne M. Creasy
The histology of the reproductive tract during the estrous cycle is generally similar in normally cycling rats and mice. The histologic features of normal estrous cycle as well as changes during puberty have been previously described in detail (Dixon et al. 2014; Greaves 2007; Li and Davis 2007; Parker and Picut 2016; Picut et al. 2014, 2015; Westwood 2008; Yoshida et al. 2009; Yuan and Carlson 1985; Yuan and Foley 2002). Therefore, the major changes at each stage of the cycle are only briefly summarized here. The key to determining the stage of the cycle using histology is appreciating the predictable and synchronous changes occurring in each of the organs that reflect the hormonal milieu at the time that the samples were obtained (Table 20.3). It should be kept in mind that all features of a specific stage may not be present due to variability in the stage of cycle and/or the plane of histologic section. Because the rodent estrous cycle is entrained to photoperiod, it is also important to recognize that the time of day at which samples are obtained can significantly influence the histologic appearance of the tissues of the reproductive tract (Yuan and Carlson 1985).
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
(oestrus) A noun that defines either the phase of the reproductive ESTROUS cycle during which female sexual behaviour is typically observed, or female sexual behaviour itself, as 'in estrus'. It comes from the Latin word oestrus, meaning 'gadfly', and denotes the abrupt change in behaviour when a cycling female goes into HEAT. The estrous cycle is divided into approximately four phases, DIESTRUS, METESTRUS, PROESTRUS, and ESTRUS, each of which correspond to different hormonal and behavioural patterns. For example, in female rodents the estrous cycle is approximately four to five days in length. Dynamic changes in ESTROGEN and PROGESTERONE secretion by the ovaries, and subsequent binding to specific steroid receptors in the brain, are critical for the induction of the cycle and underlie virtually all of the changes in behaviour observed across the cycle. This creates a system in which the behaviour of the female and her neuroendocrine state are tightly linked: her SEXUAL BEHAVIOUR occurs only when she is in an optimal neuroendocrine state to support pregnancy.
Effects of estrogen deficiency on liver function and uterine development: assessments of Medicago sativa's activities as estrogenic, anti-lipidemic, and antioxidant agents using an ovariectomized mouse model
Published in Archives of Physiology and Biochemistry, 2021
Hajer Jdidi, Fatma Ghorbel Kouba, Nissaf Aoiadni, Raed Abdennabi, Mouna Turki, Fatma Makni-Ayadi, Abdelfattah El Feki
The estrous cycle in mice involves several physiological and morphological changes in the uterus, ovaries, and vagina. In mice, the cycle consists of four phases (estrous, metestrous, diestrous and proestrous) characterized by three types of cells – epithelial (round and nucleated), cornified (without nucleus) and leukocytes (little round ones); recurring at 4–5 day intervals (Cordial et al.2006). The appearance of cornified cells in the cycle is an indicator of estrogenic activity. Smear images of Giemsa stained cells clearly identified proestrous, estrus, metestrus, and diestrus stages of the estrous cycle in control groups and groups treated with 15% alfalfa. Vaginal smear examination of all the mice after ovariectomy prior to the treatment showed the presence of only leucocytes, thus confirming the complete removal of ovaries and absence of endogenous estrogens (Malaivijitnond et al.2006). A similar smear with no signs of cornification of cells was observed in OVX mice for 21 days highlighting the unavailability of estrogenic compounds. The oral administration of Medicago sativa or 17β-estradiol in OVX mice provoked the cornification of epithelial cells after 21 days (Figure 3).
Methyl palmitate reversed estradiol benzoate-induced endometrial hyperplasia in female rats
Published in Toxicology Mechanisms and Methods, 2021
Adeola O. Olowofolahan, Olubukola T. Oyebode, Olufunso O. Olorunsogo
Twenty-four virgin female Wistar strain rats ranging from 150 to 200 g in weight were obtained from the Pre-clinical Animal House, University of Ibadan, Nigeria. The animals were allowed to acclimatize for 14 days in cages in the animal house of the Department of Biochemistry, University of Ibadan. The animals had free access to water and chow ad libitum and were kept under standard conditions of temperature and humidity. The rats used in this study showed regular estrous cycle length (4–5 days). The estrous cycles of the animals were assessed by observing the vaginal smear in the morning according to the procedure described by Solomon et al. (2010). The experiment was conducted according to the guidelines of National Institute of Health (NIH publication 85–23, 1985) for laboratory animal care and use. The work was approved by the Departmental Ethical Review Committee.
Chronic stress influences nociceptive sensitivity of female rats in an estrous cycle-dependent manner
Published in Stress, 2020
Chun-Xiao Yang, Yi Wang, Qi Lu, Yan-Na Lian, Enoch Odame Anto, Ying Zhang, Wei Wang
Rats were randomly assigned into the following two groups: (1) Control rats, n = 15; (2) CUMS rats, n = 24. Control rats were maintained in normal condition, and CUMS rats were exposed to chronic stressors according to the CUMS procedures protocols as described by Liu and Lian (Liu et al., 2014, 2017). The estrous phase was determined by the examination of vaginal changes. Vaginal cytology samples were collected daily in the morning. The phase of the estrous cycle (metestrus, diestrus, proestrus or estrus) was determined by microscopic examination based on the types of cells (leukocytes, nucleated epithelial or cornified epithelial cells) (McLean, Valenzuela, Fai, & Bennett, 2012). According to the phase of the estrous cycle of each rat, Control and CUMS rats were further divided into eight subgroups: (1) control in the proestrus phase (P control rats); (2) control in the estrus phase (E control rats); (3) control in the metestrus phase (M control rats); (4) control in the diestrus phase (D control rats); (5) CUMS in the proestrus phase (P CUMS rats); (6) CUMS in the estrus phase (E CUMS rats); (7) CUMS in the metestrus phase (M CUMS rats); and (8) CUMS in the diestrus phase (D CUMS rats).