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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
Clinically, proestrus is defined as the stage when observations of the dog’s behavior or external genitalia signify that estrus is about to occur. Signs include a serosanguinous vaginal discharge and progressive swelling of the vulva. The duration of this phase is variable, ranging from 0 to 27 days, with an average of around 9 days. During this time, FSH levels fall as estrogen levels rise to a peak in line with follicular development in the ovary. Towards the end of proestrus, the estrogen levels decrease and progesterone levels start to rise, related to the luteinization of the preovulatory follicles and replacement of granulosa cells by luteal cells (Concannon et al. 1977). During late proestrus, serum testosterone levels are also elevated, peaking at the time of the LH surge, with levels observed that are similar to those in intact male dogs (Olson et al. 1984; Concannon and Castracane 1985). Approximately 2–3 days before ovulation, there is an LH surge that can last from 24 to 96 hours (Phemister et al. 1973). A temporary increase in FSH is also seen around the time of the LH peak (Olson et al. 1982; Reimers et al. 1978) and increased androstenedione (a steroid precursor to testosterone and estradiol produced by theca cells) also increases during proestrus, peaking around the time of the LH peak, and then decreasing through estrus (Concannon and Castracane 1985).
Female Reproductive Senescence
Published in Richard C. Adelman, George S. Roth, Endocrine and Neuroendocrine Mechanisms of Aging, 2017
Richard W. Steger, William E. Sonntag, Joseph Meites
Under certain specific instances, content of LHRH in the arcuate-median eminence region is directly related to the concentration of gonadal steroids.236 LHRH content fluctuates throughout the estrous cycle, with a major decrease occurring on the day of proestrus.234 In a more detailed study, Kalra and Kalra237 found that MBH-LHRH decreased between 1400 and 1445 hr on proestrus. An LH surge occurred at 1605 hr. Although the decrease in LHRH content was highly correlated with increases in serum LH, changes in LHRH content during estrus or diestrus were not highly correlated with serum LH.237,238 In castrated rats, LHRH content in MBH areas decreased up to 21 days after ovariectomy.234,235 Studies from the authors' laboratory have confirmed the effect of circulating steroids on LHRH content.236 Ovariectomy decreased LHRH content while estrogen reversed this effect. Progesterone acted synergistically with estrogen in increasing LHRH content. Thus, under certain specific circumstances, decreases in LHRH content are correlated with increases in serum LH, suggesting that LHRH was released into the portal vasculature and was responsible for the elevated concentration of LH in serum
Prolactin
Published in Paul V. Malven, Mammalian Neuroendocrinology, 2019
Neuroendocrine events in the reproductive cycle of female rats are highly circadian. For example, discharges of adenohypophysial hormones (notably LH and PRL) occur only at specific times of the day. As will be discussed later in Chapter 12, the preovulatory surge of LH release can only occur in the late afternoon hours. Ovulation and formation of new corpora lutea occur during the nocturnal hours between the days designated, based on vaginal cytology, as proestrus and estrus of the 4–5 day estrous cycle of unmated female rats. The female is sexually receptive during this same nocturnal period. When copulation occurs during this period of female receptivity, the newly formed corpora lutea are activated to secrete more progesterone and to have a functional life span of approximately 12 days during which proestrus/estrus changes are blocked. This period of mating-induced diestrus is called pseudopregnancy. Although pseudopregnancy does not depend on conception, in cases of fertile matings it allows development of the fetoplacental unit to the point where it can provide luteotrophic support of the corpora lutea for maintenance of pregnancy to term at 22 days. As discussed earlier in this chapter, PRL exerts an important luteotrophic function in the rat. In fact, it is the only hormone required for functional maintenance of rat corpora lutea during the early part of pseudopregnancy (Smith et al., 1975). The secretory profiles of adenohypophysial PRL in non-mated and mated female rats are illustrated in Figure 9-2. Non-mated females have a surge of PRL release during the afternoon of proestrus approximately coincident with the preovulatory surge of LH release denoted in Figure 9-2. However, it is possible with experimental means to dissociate the PRL and LH surges on the afternoon of proestrus (Alexander et al., 1989).
Investigation of the embryo-toxicity of the antiviral drug “Ribavirin” in Wistar rats during different gestation periods
Published in Egyptian Journal of Basic and Applied Sciences, 2023
Mohamed Magdy, Abd El Wahab El Ghareeb, Taha M. A. Eldebss, Heba Ali Abd El Rahman
A total of 18 pregnant Wistar rats (Rattus norvegicus) (165–185 g), 11–13 weeks old, and five mature Wistar male rats (170–190 g) were procured from the Central Animal House of Veterinary Faculty Cairo University. The animal handling and experimental work was carried out according to the guidelines of The Institutional Animal Care and Use Committee of the Faculty of Science, Cairo University (Approval no: CUIF/23/20). Animals/experimental groups were kept/housed in (a 12:12 hr LD) illumination cycle at an ambient temperature (of 25 ± 2°C). Animals have free access to food and water ad libitum. Vaginal smears were taken for five days to observe those in the proestrus after one week of residence and inspected under a light microscope [11]. For the mating procedure, each 2 of the 18 female rats with recorded estrus cycles was taken at the proestrus phase and placed with a single male rat all night in a regulated environmental condition of warmth, humidity, and light until all the 18 female rats became pregnant. Day one of gestation was deemed to have begun when sperm were discovered in the vaginal smear the following morning [12]. The weight of the pregnant rats was measured and separated into three groups randomly (six each):
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
The data in this current study confirmed that the estrous cycle and chronic stress are critical factors in mechanical pain and formalin-evoked acute nociception in female rodents. Mechanical hyperalgesia occurred in CUMS rats in proestrus and estrus, but in contrast, increased formalin-evoked acute hyperalgesia was observed in metestrus and diestrus. In addition, positive correlations between mechanical thresholds in von Frey tests and the licking time in phase I of the formalin test were observed. Several studies, however, have reported different conclusions on the effects of the estrous cycle on stress-related nociception (Devall, Santos, & Lovick, 2011; Moloney et al., 2016). Research on rats undergoing maternal separation in early life showed decreased pain thresholds and increased pain behaviors to colorectal distension (visceral pain) across all phases of the estrous cycle (Moloney et al., 2016). Exposure to mild stress induces a decrease in tail-flick latency and hyperalgesia in animals in the late diestrus phase (Devall et al., 2011). These discrepancies in the stress models may be due to stressor diversity and the nature of pain.
Sub-chronic oral cinnamaldehyde treatment prevents scopolamine-induced memory retrieval deficit and hippocampal Akt and MAPK dysregulation in male mice
Published in Neurological Research, 2020
Armaghan Kazerouni, Masoumeh Nazeri, Alireza Karimzadeh, Roksana SoukhakLari, Leila Moezi, Fatema Pirsalami, Maryam Moosavi
Male NMRI mice (aged 50–60 days, weight 20–25 g) were purchased from the animal lab of Shiraz University of Medical Sciences. The mice had access to water and food ad libitum, and were housed under controlled temperature (20 ± 2°C) and lighting (07:00 to 19:00 h) status. Ethical approval was from the local Committee for the Ethics of Scientific Research in Shiraz University of Medical Sciences (approval number: IR.SUMS.REC.1397.946). All animal experiments complied with the ARRIVE guidelines and were carried out in accordance with the National Institutes of Health guide for the care and use of Laboratory animals (NIH Publications No. 8023, revised 1978). In female mice, four stages of estrous cycle (estrus, proestrus, diestrus and metestrus) exist during which the sexual hormones fluctuate. These hormonal changes have been shown to affect memory performance [21]. Then, in this study, only male mice were used.