A study of the behavior and mechanism of thermal conduction in the skin under moist and dry heat conditions.

PURPOSE: We analyzed skin heat conduction under moist and dry heat conditions to confirm the influence of moist heat on the skin and subcutaneous region. METHODS: Six healthy subjects placed their forearms in moist and dry heat air chambers, and the thickness of and moisture levels in the stratum corneum were measured. Skin surface temperatures, heat flux, and skin blood flow were measured in 11 healthy subjects. RESULTS: Within 10 min, the stratum corneum in skin exposed to moist heat reached a thickness of about 150%, and water content in the stratum corneum increased to about 200%. In contrast, the thickness of water content in the stratum corneum did not change in the dry heat condition. Skin surface temperatures of skin exposed to moist heat were significantly higher after 0.5 min of exposure (P < 0.01), the skin surface heat flux was greater, and blood flow was significantly higher (P < 0.05) after 10 min than that of skin exposed to dry heat. CONCLUSION: Stratum corneum moisture levels and skin surface heat conductivity were higher in the moist heat condition and skin blood flow was significantly greater than that in skin exposed to dry heat. Therefore, moist heat is more efficient at warming the body than dry heat.

Changes in natural killer activities in experimental secondary amyloidosis.

Natural killer (NK) cell activity in experimental murine amyloidosis was studied. In CBA/J mice, which show a high incidence of amyloidosis, NK activity was significantly decreased after 1 week of casein treatment. In C3H mice, which show a low incidence of amyloidosis, NK activity was not changed by casein treatment. Pretreatment with lipopolysaccharide in vivo enhanced the NK activities in CBA/J and C3H mice. These increases were not observed after casein treatment. The lowered NK activity of cells from CBA/J mice after casein treatment was restored to the normal range by indomethacine in vitro. Depletion of adherent cells from the spleen cells treated with casein had no effect on NK activity. Single-cell assay showed that casein treatment impaired the killing but not the binding of NK cells to target cells. After casein treatment, the splenic serum amyloid A (SAA) level gradually increased in CBA/J mice but remained low in C3H mice. NK activity was suppressed by the addition of serum obtained from CBA/J mice treated with casein but not by normal control serum. And partially purified AA protein obtained from the spleen of CBA/J mice treated with casein also suppressed NK activity in vitro.