Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.

Alteration of racial differences in melanosome distribution in human epidermis after exposure to ultraviolet light.

Abstract: CAREFUL studies of human epidermis have revealed that there is no significant difference between the number of melanocytes in the various racial groups, although there are regional differences in the population density of DOPA-positive melanocytes in various areas of the body (for example, on the forehead, 2,310 mm−2; abdomen, 800 mm−2; and back, 1,100 mm−2)1. These differences in the number of melanocytes may explain the colour differences in various areas of the body, but the colour of skin in the various races is apparently due to variations in the number of melanin granules, or melanosomes, in the melanocytes and in the epidermal keratinocytes, as well as to the degree of melanization of the individual melanosomes.

Experiences of the first 16 hospitals using copper-silver ionization for Legionella control: implications for the evaluation of other disinfection modalities.

Abstract: Background and Objectives:Hospital-acquired legionnaires' disease can be prevented by disinfection of hospital water systems This study assessed the long-term efficacy of copper-silver ionization as a disinfection method in controlling Legionella in hospital water systems and reducing the incidence of hospital-acquired legionnaires' disease A standardized, evidence-based approach to assist hospitals with decision making concerning the possible purchase of a disinfection system is presentedDesign:The first 16 hospitals to install copper-silver ionization systems for Legionella disinfection were surveyed Surveys conducted in 1995 and 2000 documented the experiences of the hospitals with maintenance of the system, contamination of water with Legionella, and occurrence of hospital-acquired legionnaires' disease All were acute care hospitals with a mean of 435 bedsResults:All 16 hospitals reported cases of hospital-acquired legionnaires' disease prior to installing the copper-silver ionization system Seventy-five percent had previously attempted other disinfection methods including superheat and flush, ultraviolet light, and hyperchlorination By 2000, the ionization systems had been operational from 5 to 11 years Prior to installation, 47% of the hospitals reported that more than 30% of distal water sites yielded Legionella In 1995, after installation, 50% of the hospitals reported 0% positivity, and 43% still reported 0% in 2000 Moreover, no cases of hospital-acquired legionnaires' disease have occurred in any hospital since 1995Conclusions:This study represents the final step in a proposed 4-step evaluation process of disinfection systems that includes (1) demonstrated efficacy of Legionella eradication in vitro using laboratory assays, (2) anecdotal experiences in preventing legionnaires' disease in individual hospitals, (3) controlled studies in individual hospitals, and (4) validation in confirmatory reports from multiple hospitals during a prolonged time (5 to 11 years in this study) Copper-silver ionization is now the only disinfection modality to have fulfilled all four evaluation criteria

Genome sequencing of mucosal melanomas reveals that they are driven by distinct mechanisms from cutaneous melanoma.

Abstract: Mucosal melanoma displays distinct clinical and epidemiological features compared to cutaneous melanoma. Here we used whole genome and whole exome sequencing to characterize the somatic alterations and mutation spectra in the genomes of ten mucosal melanomas. We observed somatic mutation rates that are considerably lower than occur in sun-exposed cutaneous melanoma, but comparable to the rates seen in cancers not associated with exposure to known mutagens. In particular, the mutation signatures are not indicative of ultraviolet light- or tobacco smoke-induced DNA damage. Genes previously reported as mutated in other cancers were also mutated in mucosal melanoma. Notably, there were substantially more copy number and structural variations in mucosal melanoma than have been reported in cutaneous melanoma. Thus, mucosal and cutaneous melanomas are distinct diseases with discrete genetic features. Our data suggest that different mechanisms underlie the genesis of these diseases and that structural variations play a more important role in mucosal than in cutaneous melanomagenesis.

Interaction of Escherichia coli RuvA and RuvB proteins with synthetic Holliday junctions.

Abstract: The RuvA, RuvB, and RuvC proteins of Escherichia coli are required for the recombinational repair of ultraviolet light- or chemical-induced DNA damage. In vitro, RuvC protein interacts with Holliday junctions in DNA and promotes their resolution by endonucleolytic cleavage. In this paper, we investigate the interaction of RuvA and RuvB proteins with model Holliday junctions. Using band-shift assays, we show that RuvA binds synthetic Holliday structures to form specific protein-DNA complexes. Moreover, in the presence of ATP, the RuvA and RuvB proteins act in concert to promote dissociation of the synthetic Holliday structures. The dissociation reaction requires both RuvA and RuvB and a nucleotide cofactor (ATP or dATP) and is rapid (40% of DNA molecules dissociate within 1 min). The reaction does not occur when ATP is replaced by either ADP or the nonhydrolyzable analog of ATP, adenosine 5'-[gamma-thio]triphosphate. We suggest that the RuvA and RuvB proteins play a specific role in the branch migration of Holliday junctions during postreplication repair of DNA damage in E. coli.