Ultraviolet (UV) irradiation is an increasingly used method of water disinfection. UV rays can be classified by wavelength into UVA (320-400 nm), UVB (280-320 nm), and UVC (<280 nm). We previously developed UVA sterilization equipment with a UVA light-emitting diode (LED). The aim of this study was to establish a new water disinfection procedure using the combined irradiation of the UVA-LED and another UV wavelength. An oxidative DNA product, 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased after irradiation by UVA-LED alone, and the level of cyclobutane pyrimidine dimers (CPDs) was increased by UVC alone in Vibrio parahaemolyticus. Although sequential irradiation of UVA-LED and UVC-induced additional bactericidal effects, simultaneous irradiation with UVA-LED and UVC-induced bactericidal synergistic effects. The 8-OHdG and CPDs production showed no differences between sequential and simultaneous irradiation. Interestingly, the recovery of CPDs was delayed by simultaneous irradiation. The synergistic effect was absent in SOS response-deficient mutants, such as the recA and lexA strains. Because recA- and lexA-mediated SOS responses have crucial roles in a DNA repair pathway, the synergistic bactericidal effect produced by the simultaneous irradiation could depend on the suppression of the CPDs repair. The simultaneous irradiation of UVA-LED and UVC is a candidate new procedure for effective water disinfection.
We present autopsy findings in a patient with a dissecting aneurysm of the vertebral artery causing subarachnoid haemorrhage. We sectioned the artery longitudinally and compared it with the angiogram, which showed the "pearl-and-string". Histological examination showed a pseudoaneurysm covered by adventitia alone, forming the "pearl". Internal elastic lamina and media were destroyed, and haematoma extended in the subadventitial space of the wall of the pseudoaneurysm. Media thickened by haematoma caused the "string", narrowing the parent artery. Alcian blue staining showed that stratified internal elastic lamina in the aneurysm and the parent artery, had undergone marked mucoid degeneration, which may have been responsible for the dissection.
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