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Reproductive Efficiency in Dairy Cows: Change in Trends!
Published in Juan Carlos Gardón, Katy Satué, Biotechnologies Applied to Animal Reproduction, 2020
Ana Heras-Molina, José Luis Pesantez Pacheco, Susana Astiz
In the beginning of the investigation of estrus protocols, the usefulness of progestins were investigated (Hansel, 1961). Afterwards, different studies confirmed that the utilization of a progesterone intravaginal device such as CIDR, PRID, etc. within the Ovsynch protocol, between the first GnRH and the PGF2α injection could improve the percentage of pregnant cows at day 60 after AI (34.2 vs. 29.6%) (Bisinotto et al., 2015), mainly for cows with scarce Body Condition Scores, with and without a CL at the beginning of the synchronization protocol. Cows benefitting the most from supplemental progesterone are those that are anovular or not in diestrus at the onset of the TAI program, confirming the therapeutical effect of the supplemented progesterone. This dissimilarity could be explained by the difference in amount of progesterone released by CL during diestrus and a single progesterone insert (Stevenson, 2016). The utilization of these devices has been studied in both 7-day and 5-day Ovsynch/Cosynch protocols (Fig. 5.4), with controversial results, that could depend on the initial percentage of noncycling cows. Some authors (Colazo and Ambrose, 2011; Wilson et al., 2010) did not find differences between both, but Bridges et al. (2008) reported an improvement of pregnancy rate when using CIDR for 5 days instead of 7 (60 vs. 70%). Thus, pregnancy rate could be more related to the programming of an adequate TAI taking into account the proestrus rather than the time of CIDR removal (Wilson et al., 2010).
Neurohypophyseal Hormones and Reproductive Hormone Secretion
Published in Craig A. Johnston, Charles D. Barnes, Brain-Gut Peptides and Reproductive Function, 2020
Recently, we have examined more closely the dependence of the OXY influence on plasma LH release on circulating levels of estradiol. The ability of a central injection of OXY to affect plasma LH on proestrus (when plasma levels of estradiol are physiologically high) was compared to the response observed on metestrus or diestrus (when estradiol levels are low). Stainless steel cannulae were placed into the third cerebral ventricle of cycling female rats using a stereotaxic apparatus and the atlas of König and Klippel (1967) as a guide. Rats were then monitored for regularity of cycles by examining the cytology in their daily vaginal lavage. Animals demonstrating two consecutive regular four-day cycles were then utilized for further experiments beginning with the next cycle. On diestrus of the experimental cycle, a cannula was placed in the right external jugular vein as previously described (Harms and Ojeda, 1974). Each animal was then treated on proestrus and either metestrus or diestrus as follows: at 1100 h intravenous cannulae were connected to collecting tubes. OXY (10 μg/5 μl) or vehicle (5 μl saline, saline group) was administered icv at 1500 h and plasma samples were obtained via the chronic jugular cannulae from the unanesthetized, freely moving animals at 10 min before and 5, 15, 30 and 60 min following icv injection. The results of these experiments are shown in Table I.
Hormones
Published in S.J. Mulé, Henry Brill, Chemical and Biological Aspects of Drug Dependence, 2019
Injection of pentobarbital at diestrus does not appear to prevent the release of gonadotropin responsible for estrogen secretion and the delayed ovulation may be due to interference with the normal effects of estrogen on the hypothalamo-hypophyseal system.66
Superior mesenteric ganglion via ovarian plexus nerve involved in the cross-talk between noradrenaline and GnRH in rat ovaries
Published in Systems Biology in Reproductive Medicine, 2023
María Belén Delsouc, Sandra Vallcaneras, Cristina Daneri Becerra, Fabián Heber Mohamed, Marina Fernández, Adriana Soledad Vega Orozco, Marilina Casais
With regard to progesterone, its levels in ovarian medium did not change during the incubation period of the ex vivo system, although they increased during the incubation period of the denervated ovaries (p < 0.001). This result showed correspondence with a lower mRNA expression of Akr1c18 with respect to the ovary of the system (p < 0.01), suggesting that the SMG-OPN pathway has implications for the progesterone steroid in the late luteal phase. In fact, the addition of 10−6 M NA into the SMG compartment decreased the progesterone levels in ovarian medium at 60 and 120 min (p < 0.05), with respect to the control group (Figure 4B). Although noradrenergic stimulation of the ganglion did not alter the Hsd3b3 mRNA expression (Figure 4C), it increased the Akr1c18 mRNA expression in the ovarian tissue (p < 0.05), compared to the control group (Figure 4D). In contrast, the addition of 10−6 M NA into the ovary compartment increased progesterone levels (120 min: p < 0.001), in comparison with the control group (Figure 4B). Furthermore, NA increased the Hsd3b3 mRNA expression (p < 0.05) (Figure 4C) and decreased the Akr1c18 mRNA expression (p < 0.01) (Figure 4D). It seems that the progesterone production is a complexly regulated matter in diestrus II. NA receptors and GnRH receptors are expressed in granulosa cells and luteal cells (essential sources of progesterone), so both would be involved in the regulation of the synthesis of this steroid.
Chronic cholestasis is associated with hypogonadism and premature ovarian failure in adult rats (cholestasis causes ovarian hypogonadism)
Published in Ultrastructural Pathology, 2018
Hisopathology and immunohistochemistry: The ovaries were harvested on diestrus phase. Ovarian sections from the Sham group showed normal structure of a mature ovary. The ovary was covered by surface epithelium. The parenchyma was divided into two poorly demarcated zones: an outer cortical region containing ovarian follicles at different stages of development and an internal medullary region of loose connective tissue with many blood vessels. The ovarian follicles observed at the diestrus phase included primordial, primary, secondary, and antral follicles, besides large corpora lutea from previous cycles (Figure 2a, Table 3). The ovarian surface epithelium consisted of one layer of cuboidal cells. Primordial follicles were located near to the surface epithelium and defined as an oocyte surrounded by a layer of flattened cells. Primary follicles possessed an oocyte surrounded by a single layer of cuboidal granulosa cells. Secondary follicles were surrounded by 2–6 layers of cuboidal granulosa cells, with no visible antrum (Figure 2b). In antral follicles, the oocyte becomes surrounded by six or more layers of cuboidal granulosal cells with a fully formed thecal layer and an antral cavity (Figure 2c). Few atretic follicles were also noted, and were identified by possessing altered shape of the follicle or the oocyte. All follicular cells except those of the atretic follicles showed strong immunoreactivity for PCNA and ER within the cells of the zona granulosa (Figure 3a and 3b, Table 4).
Cyclophosphamide, a cancer chemotherapy drug-induced early onset of reproductive senescence and alterations in reproductive performance and their prevention in mice
Published in Drug and Chemical Toxicology, 2022
Vadakkepurath Raj Athira, Thimmappa Shivanandappa, Hanumant Narasinhacharya Yajurvedi
The mice in all the groups proceeded from regular estrous cycles to irregular estrous cycles. However, at what age this occurred was different in different groups. The irregular cycles were characterized by an increase in the duration of each cycle due to an increase in the length of estrus and/or diestrus stages. This was followed by a state of persistent diestrus, marking the onset of reproductive senescence and anestrous condition. The age at onset of reproductive senescence and reproductive life span were significantly lower in CP treated mice compared to controls, whereas these did not significantly differ from those of the controls in mice treated with DH + CP (Table 1).