Apoptosis is a process by which granulosa cells are thought to be deleted during ovarian follicular atresia. The aims of the present studies, using sheep as the experimental model, were to determine 1) whether morphological changes in cells composing the membrana granulosa during the process of atresia conformed with the general criteria of apoptotic cell death as assessed using tissue sections stained with hematoxylin and eosin; 2) whether cells classified as apoptotic on the basis of their morphology contained fragmented DNA using an in situ 3' end-labeling technique; and 3) the degree of apoptosis and mitosis within the granulosa cell populations of large antral follicles (> or = 3 mm in diameter) during both spontaneous and experimentally induced atresia using stereological methods. The results showed that most degenerate granulosa cells in follicles undergoing atresia display the morphological characteristics of apoptosis, suggesting that this is the most common pathway of cell deletion. Typical features were cells containing nuclei with marginated chromatin; cells with a single small densely staining nucleus (pyknotic appearance); cells with multiple smaller, densely staining nuclear fragments; and densely staining membrane-bound bodies (apoptotic bodies) either singly or in clusters. Cells with morphological features more typical of oncosis or necrosis were sometimes observed, but mainly during the later stages of atresia. All cells classified as apoptotic on the basis of morphological criteria contained fragmented DNA as measured by 3' end-labeling. Apoptotic bodies and/or cells were found in all follicles examined, including those classified as healthy. The overall prevalence of apoptotic cells plus apoptotic bodies expressed as a percentage of the total granulosa cell number per follicle varied from 0.02% to 0.20% in healthy follicles, varied from 0.21% to 2.00% in follicles in early (primary) atresia, and was > 2.0% in follicles in later (secondary) atresia. Percentages of mitotic cells in healthy follicles were > 0.5% in all but one of those examined and were < 1.0% in all follicles classified as atretic. Both morphological and 3' end-labeling results indicated that apoptotic cells were widely disseminated throughout the membrana granulosa, including the cell layer adjacent to the basement membrane. Collectively, these observations indicate that during early atresia, apoptosis occurs randomly and is not limited to specific areas within follicles. Our finding that apoptotic cell death and mitosis occur simultaneously within the same follicle is consistent with the notion that atresia is determined by a dynamic equilibrium between cell division, differentiation, and death.
Horn CC, Still L, Fitzgerald C, Friedman MI. Food restriction, refeeding, and gastric fill fail to affect emesis in musk shrews. Am J Physiol Gastrointest Liver Physiol 298: G25-G30, 2010. First published November 5, 2009 doi:10.1152/ajpgi.00366.2009.-Nausea and emesis are common side effects of gastrointestinal disease. Reports indicate that ghrelin and endocannabinoids, agents that stimulate appetite, also reduce emesis evoked by chemotherapy treatment, which suggests that stimulation of feeding inhibits the emetic system. In the following study we conducted a more direct test of this hypothesis by determining the impact of manipulating the motivation to eat on emesis, using food restriction and refeeding. Emesis was induced in musk shrews, a commonly used animal model for emesis research, using the cancer chemotherapy agent cisplatin (20 mg/kg ip), nicotine (2 mg/kg sc), or motion (1 Hz, horizontal, 4-cm displacement), because these treatments are known to target separate emetic pathways: gut vagal afferents, area postrema, and vestibular pathways, respectively. Twenty-four hours of food restriction was sufficient to stimulate food intake, and 1 h of refeeding filled the stomach. The results indicate that food restriction, refeeding, and gastric fill had no significant effects on the amount of emesis produced by any of the emetic treatments tested here. This suggests that, although activation of the emetic system might have prominent effects on food intake, neural controls for feeding behavior do not significantly affect the neural pathways for emesis. These results may have implications for how we treat patients who experience a constellation of side effects, including nausea and emesis, since stimulating appetite may not necessarily inhibit emetic pathways.
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