HELMSTETTER, C; SECOR, S.M*; POPE, R.K.; LIGNOT, J-H; Louis Pasteur University; University of Alabama; Indiana University South Bend; Louis Pasteur University: Postprandial cellular replication and morphological responses of the Burmese python gastrointestinal tract.

Changes in cellular ultrastructure and replication associated with the dramatic digestive regulation of the Burmese python (Python molurus) with fasting and feeding were examined for gastric and intestinal epithelium. In fasted pythons, crypt cells in the gastric fundic area were packed with secretory vesicles and presented an apical tubulo-vesicular system typical of inactive cells. 12 hours post-feeding, crypts were enlarged and cell length was reduced by half due to flushing of secretory granules and formation of microvilli-like digitations within the crypt lumen. 1 day post-feeding, active cells packed with mitochondria and zymogen granules mostly appeared underneath the elongated digitations. 3 days post-feeding, cells were less active as they contained numerous cytoplasmic secretory vesicles, the apical digitations were shorter, and the apical tubulo-vesicular system had reappeared. Replicating cells at the neck region of the fundic glands were typically observed 3 days post-feeding. This was in contrast to intestinal epithelium where cellular replication was evident 1 day postfeeding. Up to 26% of epithelial cells had replicated by day 3 of digestion. Therefore, an adaptive response of pythons in coping with infrequent meals is to maintain a quiescent gut while fasting and to quickly upregulate cell function with feeding. The stomach and intestine employ different upregulatory strategies; gastric cells jump start function as soon as prey has been consumed, with cell renewal occurring later, whereas epithelial cells of the small intestine overlap the upregulation of function with replication.