The gastrointestinal tract of Burmese pythons (Python molurus (L., 1758)) exhibits large morphological and physiological changes in response to feeding and extended periods of fasting. In this study the mucosa of the stomach, small intestine, and colon were examined for changes in structure and cellular proliferation. The mucosa of fasting pythons exhibited low levels of cellular replication, but after feeding, cellular replication was evident as early as 12 h in the small intestine and colon and 24 h in the stomach. Replication peaked 3 days postfeeding for the small intestine and colon, but was still increasing at 6 days postfeeding in the stomach. Interestingly, cell proliferation was still evident after 45 days in the colon. In these tissues, a stock of ''ready-to-use'' primary lysosomes is found in the mucosal cells of fasting animals, whereas profound intracellular recycling is typical of animals that have been fed. These findings indicate that during the postprandial period, the intestinal mucosa undergoes extensive remodelling in anticipation of the next fasting and feeding period. One key adaptive factor for the python's ability to cope with infrequent feeding is a well-prepared digestive system in fasting animals that can quickly start functioning again when food becomes available.Résumé : Le tractus gastro-intestinal du python de Birmanie (Python molurus (L., 1758)) subit d'importants changements morphologiques et physiologiques en réaction à des nourrissages suivis de longues périodes de jeûne. Nous avons examiné les changements de structure et de prolifération cellulaire dans les parois muqueuses de l'estomac, de l'intestin grêle et du colon. Chez les pythons à jeun, tous les organes étudiés ont présentés un très faible niveau de prolifération cellulaire. Cependant, la production de nouvelles cellules a été observée dès 12 h après la réalimentation dans l'intestin grêle et le colon et après 24 h dans l'estomac. Cette prolifération atteint un maximum 3 jours après la réalimentation dans l'intestin grêle et le colon, mais elle augmente toujours dans l'estomac après 6 jours. Curieusement, la prolifération reste toujours détectable dans le colon malgré un jeûne de 45 jours. Dans toutes les cellules épithéliales, un large réservoir de lysosomes primaires « prêts à l'emploi » se retrouve chez les animaux à jeun, tandis qu'un profond recyclage intracellulaire se produit chez les animaux nourris. Ainsi, pendant la période postprandiale, la muqueuse digestive se modifie profondément et anticipe la prochaine période de jeûne et de réalimentation. Un des facteurs adaptatifs clés expliquant la capacité des pythons molures de résister à des réalimentations imprévisibles consiste ainsi à posséder chez les animaux à jeun un système digestif bien préparé et qui peut très rapidement se remettre en fonctionnement lorsque la nourriture est de nouveau disponible.
The morphology of the digestive system in fasting and refed Burmese pythons was determined, as well as the localization of the proton (H(+), K(+)-ATPase) and sodium (Na(+), K(+)-ATPase) pumps. In fasting pythons, oxyntopeptic cells located within the fundic glands are typically non-active, with a thick apical tubulovesicular system and numerous zymogen granules. They become active Immediately after feeding but return to a non-active state 3 days after the Ingestion of the prey. The proton pump, expressed throughout the different fasting/feeding states, is either sequestered in the tubulovesicular system in non-active cells or located along the apical digitations extending within the crypt lumen in active cells. The sodium pump is rapidly upregulated in fed animals and is classically located along the baso-lateral membranes of the gastric oxyntopeptic cells. In the Intestine, it is only expressed along the lateral membranes of the enterocytes, i.e., above the lateral spaces and not along the basal side of the cells. Thus, solute transport within the Intestinal lining is mainly achieved through the apical part of the cells and across the lateral spaces while absorbed fat massively crosses the entire height of the cells and flows into the Intercellular spaces. Therefore, in the Burmese python, the gastrointestinal cellular system quickly upregulates after feeding, due to Inexpensive cellular changes, passive mechanisms, and the progressive activation and synthesis of key enzymes such as the sodium pump. This cell plasticity also allows anticipation of the next fasting and feeding periods.
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