Biomedical subjects
Publications and source records attributed to F Greiter.
Pilot measurements were made of natural UV radiation (UVA and UVB, broad-band and erythemogenic) on the Dead Sea (400 m below sea level) and in Spain at sea level, both at approximately the same geographical latitude. Measurements were made at different times of single days during the 1985/1986 season. The preponderance of UVA over UVB was more pronounced in winter.
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Indomethacin applied after an erythematogenic dose of UVB light suppresses the development of erythema by inhibition of prostaglandin synthesis. In this study indomethacin was tested prior to UV exposure in humans in vivo and was shown to be a potent UVB and UVA filter. Indomethacin thus represents the first topical agent known to prevent and treat sunburn simultaneously. A 2.5% indomethacin solution was applied on test areas 1 h before UVB irradiation. Indomethacin-pretreated skin tolerated 4.3 times more UVB light and indomethacin-protected skin developed significantly less sunburn cells than untreated areas. In order to study its possible UVA screening capacity test areas were irradiated with 2, 4, 6, 8, 10 J/cm2 UVA light (PUVA) after ingestion of 8-methoxypsoralen. Indomethacin-pretreated skin tolerated 2.2 times more UVA than untreated test areas. Immediate pigment darkening induced by UVA doses up to 25 J/cm2 was less pronounced in indomethacin-pretreated skin. To investigate the mode of action of the photoprotective effect observed skin was irradiated with erythematous doses of UVB light transmitted through a quartz glass layer coated with the indomethacin solution. The skin developed no erythema thus indicating that the effect of indomethacin when applied before irradiation is based upon photoabsorption and not upon inhibition of prostaglandin synthesis. This is also confirmed by the fact that the development of sunburn cells can be prevented only when indomethacin is applied before and not after irradiation.
One of the functions of the skin is perception of heat and cold and passing on of information to the regulatory centre of the brain. Variation of blood flow through skin and muscles is the response to the respective air temperature. Whether strong UV radiation has an additional negative effect on the vascular system has not been investigated so far. Exact heat conduction figures of skin, surrounding air and ingredients of a cold air protection cream are of importance for establishing the formulation of an ideal protective product. Cold air protection for the skin is of vital importance for winter sports or at high altitudes. But it can also be of importance for people staying in the water for a long time, or for swimming in very cold water, or for exposure to water and strong wind, e.g. when surfing. Tests show that the skin will lose 20% less heat in cold water when it is greased. Hyperaemising substances should only be used for cold air protection products in well-defined doses (indication of a skin blood supply factor) in order to avoid functional disturbance of the skin. Combined application of a hyperaemising product and a cold air protection cream doubles the duration of the protection and allows for an extension of the warming effect to the muscles. This improves functional capacity and coordination.
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Serum levels of 8-methoxypsoralen (8-MOP) were determined 2 hours after oral administration and found to vary considerably among psoriatic patients. There was no definite correlation between the 8-MOP serum level, the dose of 8-MOP/kg body weight ingested, and the minimal phototoxic UVA dose.
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