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Publications (3)1.84 Total impact

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    ABSTRACT: To evaluate selective effects of ultraviolet (UV) irradiation on spontaneous and induced apoptosis in freshly extracted mice thymocytes. Cells were exposed to UV radiation with emission peaks of 365 nm (UVA) exposures of 1620-10200 J m(-2), of 312 nm (UVB) exposures of 34-1620 J m(-2) or of 254 nm (UVC) exposures of 1.5-1620 J m(-2), and incubated for 5.5 h with or without hydrocortisone, phorbol-12-myristate-13-acetate or anti-Fas antibody. Additionally, cells were irradiated with gamma-rays (5 Gy) before UVB exposure (408 J m(-2)) at different times. Apoptosis was quantified by DNA fragmentation. Up to an irradiation of 5000 J m(-2), UVA exposure did not show any effect on thymocyte apoptosis, while at 10200 J m(-2) irradiation, considerable DNA fragmentation was observed. In contrast, UVB and UVC irradiation clearly inhibited natural and cortisone-induced apoptosis. Moreover, UVB inhibited apoptosis triggered by phorbol-12-myristate-13-acetate and gamma-irradiation, but not by anti-Fas antibody. The response of mouse thymocytes in culture to UV irradiation strongly depends on the wavelength used. It is suggested that either a survival or an apoptotic pathway occurs depending on the physiological state of the cell, spectral composition of the UV light and cell type. The possible involvement of extracellular signal-regulated kinase and stress-activated protein kinase/c-Jun N-terminal kinase in the apoptotic pathway is discussed.
    International Journal of Radiation Biology 07/2004; 80(6):445-50. · 1.84 Impact Factor
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    ABSTRACT: The spectral composition of the underwater light field was examined in two hypertrophic South African impoundments (Hartbeespoort and Roodeplaat Dams) under a range of inorganic turbidities and chlorophyll a concentrations. The data indicated that inorganic turbidity and gilvin were dominant to chlorophyll in regulating underwater light attenuation during the present study. Under all conditions the wavelengths between 405 and 510 nm were attenuated more rapidly than near UV and the wavelengths above 510 nm and the 623 nm component penetrated deepest. Under low turbidities the 546 nm wavelength was the next most penetrating component, but its attenuation increased with increasing turbidity. This characteristic of the underwater light field may be important to the cyanobacteria which dominate in these hypertrophic lakes.
    01/1985;
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    ABSTRACT: The spectral composition of the underwater light field was examined in two hypertrophic South African Impoundments (Hartbeespoort and Roodeplaat Dams) under a range of inorganic turbidities and chlorophyll α concentrations. The data indicated that inorganic turbidity and gilvin were dominant to chlorophyll in regulating underwater light attenuation during the present study. Under all conditions the wavelengths between 405 and 510 nm were attenuated more rapidly than near UV and the wavelengths above 510 nm and the 623 nm component penetrated deepest. Under low turbidities the 546 nm wavelength was the next most penetrating component, but its attenuation increased with increasing turbidity. This characteristic of the underwater light field may be important to the cyanobacteria which dominate in these hypertrophic lakes.