Modulatory action of α-tocopherol on erythrocyte membrane adenosine triphosphatase against radiation damage in oral cancer.

To investigate the possible effects of α-tocopherol on erythrocyte membrane adenosine triphosphatases against radiation damage in oral cancer patients. Adenosine triphosphatase activities were analysed in oral cancer patients before and after radiotherapy (at a dosage of 6000 cGY in five fractions per week for a period of six weeks) and after supplemented with α-tocopherol (400 IU per day for entire period of radiotherapy). The membrane bound enzymes such as Na(+)/K(+)-ATPase, Ca(2+)-ATPase, Mg(2+)-ATPase and some trace elements were altered in oral cancer patients before and after radiotherapy. Supplemented with α-tocopherol modulates the erythrocyte membrane which is damaged by radiotherapy which suggests that α-tocopherol protects the erythrocyte membrane from radiation damage in oral cancer patients.

DNA helicase activity in purified human RECQL4 protein.

Human RECQL4 protein was expressed in insect cells using a baculovirus protein expression system and it was purified to near homogeneity. The protein sedimented at a position between catalase (230 kDa) and ferritin (440 kDa) in glycerol gradient centrifugation, suggesting that it forms homo-multimers. Activity to displace annealed 17-mer oligonucleotide in the presence of ATP was co-sedimented with hRECQL4 protein. In ion-exchange chromatography, both DNA helicase activity and single-stranded DNA-dependent ATPase activity were co-eluted with hRECQL4 protein. The requirements of ATP and Mg for the helicase activity were different from those for the ATPase activity. The data suggest that the helicase migrates on single-stranded DNA in a 3'-5' direction. These results suggest that the hRECQL4 protein exhibits DNA helicase activity.

Dietary selenium levels determine epidermal langerhans cell numbers in mice.

Selenium (Se) is a dietary trace element that is essential for effective immunity and protection from oxidative damage induced by ultraviolet radiation (UVR). Langerhans cells (LC) represent the major antigen-presenting cells resident in the epidermis; a proportion migrate from the skin to the draining lymph nodes in response to UVR. Because it is known that Se deficiency impairs immune function, we determined what effect this has on LC numbers. CH3/HeN mice were weaned at 3 wk and placed on diets containing <0.005 ppm of Se (Se deficient) or 0.1 ppm of Se (Se adequate, control mice). After 5 wk on the diet, the epidermal LC numbers in the Se-adequate group were 966 +/- 51 cells/mm2 and LC counts in the epidermis of the Se-deficient mice were 49% lower (p<0.05). Glutathione peroxidase- I (GPx) activity was measured in the epidermis, lymph nodes, and liver. In the epidermis, the activity of GPx in the Se-deficient mice was only 39% (p<0.01) of that seen in epidermis from Se-adequate mice (1.732 U/mg protein). The mice were then irradiated with one dose of 1440 J/m2 of broadband UVB or mock irradiated. After 24 h, the decrease in LC number after UVB was greater in the Se-adequate mice, (40% decrease) compared to the Se-deficient group (10%). Thus, Se deficiency reduces epidermal LC numbers, an effect that might compromise cutaneous immunity.

The influence of photochemical treatment on immunogenicity and epidermal Langerhans cells of murine skin grafts.

The combined treatment of murine skin grafts with 8-methoxypsoralen and longwave ultraviolet radiation (PUVA) leads to a prolonged survival after transplantation on allogeneic recipients. This may be due to inactivation of intragraft antigen presenting cells like epidermal Langerhans cells. In this study the effects of PUVA or middle range ultraviolet radiation (UVB) on ATPase positive Langerhans cells and immunogenicity of murine skin grafts were compared. Graft immunogenicity is reduced immediately after PUVA treatment, whereas the number of ATPase positive Langerhans cells decreases later, reaching its minimum three days after irradiation. UVB light reduces the number of ATPase positive Langerhans cells to a similar degree but skin graft survival is prolonged only marginally. Obviously, the effects of photochemotherapy on the ATPase activity of Langerhans cells reflect only partially the alterations of skin graft immunogenicity. Other antigen presenting cells like dendritic cells in the dermis may be of importance. Because these cells are located deeper in the graft they are better reached by stronger penetrating longwave ultraviolet radiation (PUVA) than by UVB.