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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
In both rats and mice, increasing cycle length progresses to the development of estrous cycle irregularities including persistent estrus, persistent diestrus (consistent clinically with repeated pseudopregnancy), and eventually, persistent anestrus late in life (Felicio et al. 1984; Peluso and Gordon 1992; vom Saal et al. 1994). The age at which these senescent changes begin, and the sequence in which they occur, vary and are influenced by species, strain, and husbandry (Felicio 1984; LeFevre and McClintock 1991; vom Saal et al. 1994). Persistent estrus refers to a state that may last for months, in which the vaginal epithelium remains cornified in association with low circulating progesterone, tonic secretion of estradiol, and low or absent LH surges. These endocrine findings reflect the presence of numerous follicular cysts in the ovary, ongoing follicular development, and an absence of corpora lutea (vom Saal et al. 1994). Repeated pseudopregnancy refers to repeated periods of vaginal diestrus, often lasting about 14 days that may be separated by brief intervals of estrus or proestrus. This condition, which occurs when corpora lutea persist in the ovaries of the non-gravid animal, is associated with high levels of circulating progesterone with normal diestrus levels of estradiol and slightly increased prolactin. Persistent corpora lutea in animals exhibiting repeated pseudopregnancy typically lack the basophilia seen during the normal estrous cycle and may contain areas that are hypocellular or acellular (Peluso and Gordon 1992). Persistent anestrus is the final stage of ovarian decline in which cyclical activity is absent, circulating levels of estradiol and progesterone are low and vaginal cytology is dominated by leukocytes. Histologic findings in the reproductive tract at this stage include an absence of corpora lutea with limited or no follicular development and small uteri with atrophic glands (Peluso and Gordon 1992; vom Saal et al. 1994).
Bovine Reproductive Management
Published in Juan Carlos Gardón, Katy Satué, Biotechnologies Applied to Animal Reproduction, 2020
José Javier de la Mata, Gabriel Amilcar Bó
During the postpartum period (Fig. 1.1), negative energy balance (NEB) is generated particularly by deficient nutrition and the presence of the offspring. The reproductive response increases the length of anestrus, decreased fertility and increases early embryo mortality. In cows, BCS at parturition was the most important factor that determines the period to re-conception postpartum (D’Occhio et al., 2019) and cows with high BCS synchronized with progesterone-based treatment protocols for FTAI had higher pregnancy rates than cows with poor BCS (Bó et al., 2002). Resumption of ovarian cyclicity is largely dependent on LH pulse frequency (Crowe et al., 2014) as well as the dominant follicle in the ovary should grow with the stimulation of many growth factors (e.g. IGF 1 family) and nutrients (Meikle et al., 2018). At calving, pituitary LH stores are low, because of high plasma concentration of progesterone in the early and medium gestation, and later estrogen is synthesized by placental tissue. The re-accumulation of pituitary stores of LH takes 2–3 weeks to complete (reviewed by Crowe et al., 2014). In Argentina, a common practice is to wean calves as early as ~ 60 days (early weaning), ~120 days (anticipated weaning) or later at ~150 days (traditional weaning). After the early weaning, calves are feed with high quality hay and a protein supplementation, and management must be done in a dry lot system with an intensive assistance during 40–50 days after weaning. Calf management enable to postpartum cow to return to cyclic stage between 10–20 days post weaning, preventing the maternal-offspring bonding, resulting in cyclic LH pulse frequency and periodic surge that will trigger a subsequent ovulation. First ovulation after parturition is generally silent (without behavioral estrus signs) and the first luteal phase would be, at least in 70% of cases, of short duration (short-live corpus luteum), in which oocyte can become fertilized. However, embryo arrests growing, an early luteolysis undergoes and the embryo dies prior to the maternal-embryo recognition (day 10–14 after ovulation).
Pineal Gland
Published in Paul V. Malven, Mammalian Neuroendocrinology, 2019
Female sheep (ewes) initiate estrous cycles in the autumn and deliver offspring about 5 months later in the spring. Ewes of most breeds then enter a period of anestrus during the remainder of the spring and the early part of the summer. Ovulation does not occur during this period of anestrus, and it has been well established that the secretion of LH is effectively suppressed during anestrus by the low levels of circulating estrogens derived from the otherwise quiescent ovaries (Karsch et al., 1984). This period of anestrus ends with the onset of the breeding season because the inhibitory feedback of estrogen is no longer able to prevent increases in LH secretion. This change in feedback sensitivity to estrogen is synchronized among individual ewes by perceived changes in the duration of daily elevations of melatonin secretion during the dark period (Wayne et al., 1988). The reduced sensitivity to LH-inhibitory feedback of estrogen can also occur spontaneously, but in such cases it is not especially synchronous among individuals (Woodfill et al., 1991). Such spontaneous changes in feedback sensitivity to estrogen appear to result from development of a photorefractory state in which exposure to long days is no longer able to maintain high sensitivity to estrogen suppression of LH. This photorefractory state may have a role in initiating the breeding season under natural conditions because onset of ovulation often occurs when photoperiods have hardly begun to decrease (Thimonier and Mauleon, 1969). Pineal secretion of melatonin was not disrupted in ewes that had become photorefractory since increased serum concentrations of melatonin still faithfully reflected each period of darkness (Karsch et al., 1986). Therefore, unknown components of the hypothalamic-hypophysial system for LH secretion change as a result of photorefractoriness to the melatonin signal of long days (i.e., short duration of elevated nocturnal melatonin), and the resulting increase of LH secretion initiates ovarian follicular development leading to the resumption of ovulatory estrous cycles. In ewes that are not mated, these estrous cycles continue for several months and usually end early in the winter. The termination of ovulatory estrous cycles is caused by an increased sensitivity to estrogen suppression of LH secretion. This resumption of enhanced estrogen feedback appears to be caused by development of photo-refractoriness to short days and the associated nocturnal elevations of melatonin secretion (Malpaux et al., 1988).
Can maternal treatment with metformin during gestation and lactation cause metabolic and cardiovascular disorders in rat offspring?
Published in Archives of Physiology and Biochemistry, 2020
Daniella R. B. S. Novi, Camila B. Vidigal, Bruno V. D. Marques, Simone Forcato, Hiviny A. Raquel, Dimas A. M. Zaia, Cássia T. B. V. Zaia, Marli C. Martins-Pinge, Daniela C. C. Gerardin, Graziela S. Ceravolo
The dose of metformin used was based in previous studies from our group (Forcato et al.2017, Novi et al.2017, Vidigal et al.2018) and others (Lobato et al.2012, Salomäki et al.2013). Dams’ weights were obtained every three days during all pregnancy and lactation for dose adjusting, and to evaluate weight gain during pregnancy it was described as weight gain variation (Δ = PND1 − GD0) and lactation (Δ = PND21 − PND1). The food consumption of dams was evaluated weekly. The day of birth was denominated post-natal day (PND) 0. At PDN 1 the pups were identified by sex and at PND 4 were culled to ten pups and, whenever possible, a number of six males and four females were kept. Pups were weaned and housed in groups (five animals per cage) at PDN 21. Male and female offspring were evaluated at PND 75–80 (adulthood). Different littermates from each litter were used for each evaluation conducted. For adult females, vaginal smears were collected every morning starting at PND 75 and they were evaluated in the day of the diagnosis of physiological oestrus cycle. All animals had free access to water and regular laboratory chow (Nuvital, Curitiba, Brazil). They were maintained at 21 ± 2 °C on a 12:12 h light–dark cycle (lights on at 06:00 AM). At the end of it protocol the rats were euthanized by overdose of anaesthetic (sodium thiopental, 60 mg/kg, ip). All experimental protocols were approved by the State University of Londrina Ethics Committee for Animal Research (CEUA/UEL: 6996.2015.02).
Differential expression of BMP/SMAD signaling and ovarian-associated genes in the granulosa cells of FecB introgressed GMM sheep
Published in Systems Biology in Reproductive Medicine, 2020
Satish Kumar, Pradeep Kumar Rajput, Sangharatna V. Bahire, Basanti Jyotsana, Vijay Kumar, Davendra Kumar
A total of 28 GMM and Malpura ewes of 3–6 years of age were selected for oestrus synchronization. Nine homozygous carrier GMM (FecBBB), 10 non-carrier GMM (FecB++) and 9 non-carrier Malpura (FecB++) ewes were synchronized with progesterone impregnated sponges (Avikesil-S@350mg per ewe) as per the protocol followed at Avikanagar (De et al. 2015). Progesterone sponges were inserted into the vagina for 12 days in a major breeding season (July-August). Sponges were removed on day 12 and oestrus response of each ewe was recorded. To culture the granulosa cells, ovariectomy was performed to retrieve the single ovary from each synchronized animal during the follicular phase of the oestrus cycle. All procedures were conducted as per the guidelines of the Institute Animal Ethics Committee.
Role of preovulatory concentrations of estradiol on timing of conception and regulation of the uterine environment in beef cattle
Published in Systems Biology in Reproductive Medicine, 2020
George A. Perry, Robert A. Cushman, Brandi L. Perry, Amanda K. Schiefelbein, Emmalee J. Northrop, Jerica J.J. Rich, Stephanie D. Perkins
Proenkephalin-A is the precursor of several individual enkephalins (Marx 1983). Transcript abundance of proenkephalin-A has been reported to increase fourfold during pregnancy in the rat uterus (Jin et al. 1988), and was increased by exposure to progesterone and decreased by exposure to RU486 (Cheon et al. 2002). Similarly, Jin and co-workers (1988) reported that expression in the rat uterus was greatest at metestrus and diestrus. In the current study, proenkephalin-A mRNA was not detected on Day 0 and was not different between treatments. However, expression increased from Day 5 to Day 10, then decreased to Day 16 of the cycle. This again supports the hypothesis that the uterus in the non-estrus animals may not be functioning properly to support proper embryo development and survival, even among proteins that are regulated by progesterone.