The Response of the Toad Intestine to Prolonged Starvation: A Morphological, Functional and Metabolic Study*

Abstract

Abstract. 1. Toads were kept without solid nourishment for four months or more, and the morphological and functional characteristics of their intestines were compared with those of freshly captured animals. 2. The intestinal mucosa is one of the organs that is specifically and preferentially consumed during the process of autophagy. Histological sections reveal that a substantial loss of villous architecture is incurred. The epithelial cells covering the mucosal surface are interspersed with frequent vacuoles, the significance of which is as yet unclear. 3. The absorptive capacity of intestinal slices excised from autophagous toads, determined by their ability to accumulate radioactive phenylalanine, is lower than that of normal animals, but this difference can be ascribed to the distinct tissue composition of the intestinal slices. 4. Intestinal slices of autophagous toads have a lower respiration rate but higher glucose consumption than those of normal animals.

Effect of Starvation on Small Intestinal Enzyme Activity in Germ-Free Rats

“…In the present study the term specific activity was used for enzyme activity referring to the wet or dry weight of intestinal mucosa or to its protein and DNA content. The decrease in mucosal dry weight, protein and DNA is explained by the findings of smaller and less cellular villi and crypts (2,5,6,12,18,19,22). Assuming that DNA most closely reflects the cell number (1, 3, 7) a probably occurring loss of DNA in the course of starvation overnight is too small to be detected by this method.…”

“…There were striking differences in the response to starvation between the proximal, mid and distal third of the small intestine. The importance of the proper reference system was discussed.There is an increasing amount of literature on the effect of starvation on small intestinal epithelium (2, 4, 5, 8,(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(24)(25)(26). Most of the work has been done in conventional animals and mostly only one defined segment of gut was investigated.…”

Maintenance of Distal Intestinal Structure in the Face of Prolonged Fasting: A Comparative Examination of Species From Five Vertebrate Classes

“…The reduction in the surface area of the proximal intestine is concomitantly accompanied by decreases in membrane‐bound enzyme activities (e.g., aminopeptidase, maltase) and nutrient transport rates (Secor et al, ; Ott and Secor, ; German et al, ). Although the mechanism of change varies among endothermic and ectothermic taxa, the general patterns of reduced activity and surface area in the proximal intestine in response to fasting are common among vertebrates having been documented in fishes (Gas and Noailliac‐Depeyre, ; German et al, ; Zaldua and Naya, ), amphibians (Perez‐Gonzalez and Robinson, ; Cramp and Franklin, ; Cramp et al, ), reptiles (Secor and Diamond, ; Starck and Beese, ; Secor and Lignot, ), birds (Hume and Biebach, ; Karasov et al, ; Smirnov et al, ), and mammals (Dunel‐Erb et al, ; Habold et al, ; Habold et al, ).…”