Structural Changes in Mouse Small Intestinal Villi Following Lower Body Hyperthermia

Heating an exteriorised loop of mouse small intestine resulted in marked changes in the shape of the villi as reported earlier. However, the exteriorisation techniques resulted in non-uniformity in both temperature and effect around circumference of intestine and, in addition, the extent to which handling contributed to the observed damage was not known. The work has therefore been extended using lower-body heating in the temperature range 37.5 degrees - 43.0 degrees C. Heating in the temperature range 37.5 degrees C to 41.0 degrees C produced minimal to moderate structural changes, manifested as scattered, vertically collapsed villi amongst predominantly "normal" villi. No villi showed conical or rudimentary forms of collapse. Such villi were, however, seen after heating at 41.5 degrees C and were greatly increased in number after heating at 42.0 degrees C. The most severe damage was observed after heating at 43.0 degrees C. Although the lower body heating method gave information which was less complicated by technical considerations, the hyperthermic damage observed was qualitatively similar to that previously seen following local administration of hyperthermia to an exteriorised loop of intestine. Direct quantitative comparisons between the two methods of heating are difficult because of differences in equilibration time and temperature. However, using a comparable heating time, less damage was scored following the exteriorisation technique compared with in situ heating.