Hypovolemia and hyperosmolality due to thermal dehydration suppress thermoregulatory responses of sweating and cutaneous vasodilation in humans, resulting in increasing a risk of heat illness. Recently, we found in young and older subjects that an ingestion of carbohydrate-protein supplement immediately after a bout of exercise during training accelerated an increase in plasma volume and an improvement of thermoregulatory responses. These results suggest that change in plasma volume alters cutaneous vasodilation and sweat rate through baroreflexes; however, no electrical signals in the efferent path of the reflex loop have not been identified. We have recently successfully recorded skin sympathetic nerve signal components synchronized and non-synchronized with cardiac cycles, separately, in passively heated young subjects, and found that although both components increased with cutaneous vasodilation and sweat rate in hyperthermia, an increase in synchronized component was suppressed by hypovolemia with suppressed cutaneous vasidilation, while an increase in non-synchronized component was not suppressed as sweat rate. On the other hand, we found that hyperosmolality suppressed the increases of both components with suppressed cutaneous vasodilation and sweat rate. These results suggest that a synchronized component controls cutaneous vasodilation while a non-synchronized component controls sweat rate, and also that beat-by-beat changes in atrial pressure due to a fluctuation of venous return to the heart varies cutaneous vasodilation through baroreflexes but not sweat rate.

Before the introduction of high density barium for contrast studies of the upper gastrointestinal tract, we conducted a survey concerning the adverse reactions to a swallow of barium and barium concentration.
The incidence of side effects rose as the density of barium increased but the effects were transient. There were no cases requiring medical treatment.
Furthermore, the constipation group and the normal group were examined separately.
The ratio of adverse reactions was high in the constipation group even when the barium density was low. In this group stool hardening and delayed excertion were also noticed.
The constancy of barium stool excretion was basically normal, and the barium density had little effect.
The effects of a laxative on the excretion consistency were investigated. The administration of a laxative did not always have a positive affect on excretion. The timing of the administration of the laxative and the amount of water intake should be examined in the future.
We also investigated how the patients feel when they are swallowing barium. We found that whether feel uncomfortable or not depended on the properties of barium rather than its density.
From these results it appears that appropriate guidance is necessary about the use of high density barium, in order to supress the occurrence of side effects, especially in the constipation group.