The effect of elevated temperature on the vasculature of mouse jejunum.

The effect of elevated temperature on mouse jejunal vasculature was investigated. Both local and lower-body heating were employed, using a hot water bath; heating time was kept constant at 1 hour, bath temperatures ranging from 40.0 degrees C to 43.0 degrees C. Animals were sacrificed after heating, the erythrocytes were stained with benzidine and H2O2 and the blood vessels revealed by mounting in a clearing resin. The earliest damage seen was the disappearance of capillaries, followed by loss of progressively larger vessels. Loss is interpreted as destruction, not merely as interruption of blood flow. A gradient of sensitivity occurs from the inner layer of the jejunum to the outer, the threshold heating temperature required to produce vascular damage being lowest at the inside. Neither temperature gradient, nor early release of gastric juice from the stomach, appears responsible for this differential response. The mean length of intact venous tree was employed as a parameter for assessing the damage.