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Ultraviolet light

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


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Book ChapterDOI
TL;DR: The remarkable susceptibility of SCEs to ultraviolet light or chemicals having similar modes of action, and the simplicity of scoring this event with the aid of the BUdR-labeling method, make SCE a new assay system for hazardous effects of various environmental mutagens and carcinogens.
Abstract: Publisher Summary This chapter discusses the spontaneous and induced sister chromatid exchanges (SCE) as revealed by the 5-bromo-2’-deoxyuridine (BUdR)-labeling method. The elaboration of techniques for labeling chromosomes efficiently in vivo and a comparison of the incidence of SCEs in cells from various tissues or organs of animals, especially immunocompetent cells, germ line cells, and embryonic cells, would provide important clues in determining the existence of spontaneous SCEs and their biological significance which has long remained an enigma. Recently an attempt has been made to explain the evolution of multiple gene families in eukaryotic genomes such as rRNA and immunoglobulin V-gene families in terms of the consecutive occurrence of unequal SCEs. It has been shown that many eukaryotic genomes contain a large (over 70%) DNA fraction in which middle repetitive sequences of about 300 nucleotides are interspersed between single-copy DNA sequences averaging 3000 nucleotides or less in length. A correspondence between the middle repetitive sequences and the sites of meiotic crossing-over has been suggested in liliaceous plants. Strand exchange involving the pairing of these sequences may well have a chance to undergo unequal recombination without affecting the array of structural genes in the chromosome. The remarkable susceptibility of SCEs to ultraviolet light or chemicals having similar modes of action, and the simplicity of scoring this event with the aid of the BUdR-labeling method, make SCE a new assay system for hazardous effects of various environmental mutagens and carcinogens.

211 citations

Journal Article
TL;DR: Primary tumors from the albino strain were the least antigenic as a group, whereas the C3H- tumors exhibited the greatest degree of antigenicity, which was comparable among the three strains.
Abstract: The carcinogenic effects of chronic exposure to ultraviolet radiation were compared in three inbred mouse strains with different coat colors. Albino mice (BALB/cAnN) developed tumors earlier than agouti [C3H/HeN (mammary tumor virus negative) hereafter called C3H-] or black (C57BL/6N) mice, and a large proportion of the tumors in the albino strain arose on the ears, in contrast to the other strains) in which dorsal tumors predominated. The most common histological types of tumor observed were fibrosarcomas, followed by squamous cell carcinomas. The types and frequency of types were comparable among the three strains. On the basis of a comparison of tumor growth in normal and immunosuppressed syngeneic recipients, primary tumors from the albino strain were the least antigenic as a group, whereas the C3H- tumors exhibited the greatest degree of antigenicity. In BALB/cAnN mice 33% of the ultravioletinduced tumors tested failed to grow in normal syngeneic mice although they grew in immunosuppressed recipients. In C57BL/6N mice 54% and C3H- mice 75% of the tumors tested were not transplantable in normal syngeneic recipients and grew only in immunologically deficient hosts.

210 citations

Journal ArticleDOI
TL;DR: In this article, the paramagnetic resonance spectra of free radicals in liquids have been studied during the course of intense irradiation with ultraviolet light, in which the liquid sample flows through the microwave cavity of the spectrometer and is photolyzed as it passes the sensitive region of the cavity.
Abstract: Paramagnetic resonance spectra of free radicals in liquids have been studied during the course of intense irradiation with ultraviolet light. Equipment is described in which the liquid sample flows through the microwave cavity of the spectrometer and is photolyzed as it passes the sensitive region of the cavity. In this way the steady‐state concentration of short‐lived radicals have been observed. Temperatures from about −70° to 60°C have been used. A number of alcohols containing up to 1% H2O2 have been studied. In the absence of dissolved oxygen the main products are the radicals formed by abstraction of a hydrogen from the position alpha to the hydroxyl group. The radicals RĊHOH where R is H, CH3, C2H5, C3H7, (CH3)2CH, and C6H5 have values of aα near room temperature ranging from 14.7 to 17.4 G and g values ranging from 2.00298 to 2.00334. Those radicals with beta hydrogens have values of aβ ranging from 20.0 to 22.2 G. The ring protons of C6H5ĊHOH are inequivalent. When the alpha hydrogen is abstracted from allyl alcohol two radicals are formed that are geometric isomers with the relative abundances depending on temperature. Coupling values for all hydrogens in each isomer are given. All couplings are also given for the radicals formed from ethylene glycol and isopropyl alcohol. In many cases couplings have been measured at several temperatures. Values for hydrogens in hydroxyl groups are strongly temperature dependent and in some cases become zero. Alpha and beta coupling constants are less temperature dependent. The various results are discussed. In the presence of dissolved oxygen, peroxy radicals are formed and their spectra are discussed. Their linewidths are strongly dependent on temperature and on concentration of dissolved oxygen. Radicals have been seen in photolyzed hydrogen peroxide solutions for concentrations ranging from 10% to 45%. In the presence of acid a single absorption line is observed. Without the acid the spectra are complex. These results are also discussed.

210 citations

Journal ArticleDOI
TL;DR: The V79-4 Chinese hamster line was mutagenized and surviving clones screened for X-ray sensitivity using a replica microwell technique, and 3 clearly sensitive clones were isolated from approximately 5000 screened, and designated irs 1 to irs 4.
Abstract: The V79-4 Chinese hamster line was mutagenized and surviving clones screened for X-ray sensitivity using a replica microwell technique. One slightly sensitive clone and 3 clearly sensitive clones were isolated from approximately 5000 screened, and designated irs 1 to irs 4. The 3 more sensitive clones showed different responses to the genotoxic agents mitomycin C (MMC), ethyl methanesulphonate (EMS) and ultraviolet light (UV). irs 1 showed considerable sensitivity to all the agents tested, in the order MMC much greater than EMS greater than UV. irs 2 and irs 3 had similar sensitivities to EMS and to UV (EMS greater than UV) but irs 3 was more sensitive than irs 2 to MMC. None of these mutants is identical in phenotype to previously published mutants.

210 citations

Journal ArticleDOI
TL;DR: In this article, the authors present and discuss the Hubble Space Telescope (HST) (WFPC2 and FOC) images and ultraviolet (GHRS) spectra plus ground-based optical spectra of three Seyfert 2 nuclei (NGC 7130, NGC 5135 and IC 3639).
Abstract: We present and discuss Hubble Space Telescope (HST) (WFPC2 and FOC) images and ultraviolet (GHRS) spectra plus ground-based optical spectra of three Seyfert 2 nuclei (NGC 7130, NGC 5135 and IC 3639). These galaxies, together with Mrk 477 (Heckman et al.), were selected on the basis of ultraviolet brightness from a bigger sample that comprises the 20 brightest Seyfert 2 nuclei, with the goal of studying the starburst-active galactic nucleus (AGN) connection and the origin of the so-called featureless continuum in Seyfert 2 nuclei. The data provide direct evidence of the existence of nuclear starbursts that dominate the ultraviolet light and that are responsible for the featureless continuum in these type 2 Seyfert nuclei. The GHRS spectra show absorption features formed in the photospheres (S V λ1501, C III λλ1426, 1428, Si III λ1417, and Si III + P III λ1341-1344) and in the stellar winds (C IV λ1550, Si IV λ1400, and N V λ1240) of massive stars. Signatures of massive stars are also clearly detected in their optical and near-UV spectra where the high-order Balmer series and He I lines are observed in absorption. These lines are formed in the photospheres of O and B stars, and thus they also provide strong independent evidence of the presence of massive stars in the nuclei of these Seyfert 2 nuclei. Interstellar absorption lines similar to those formed in the interstellar medium of starbursts are also observed. They are blueshifted by a few hundred km s-1 with respect to the systemic velocity, indicating that the interstellar gas is outflowing. These outflows are most likely driven by the nuclear starburst. These starbursts are dusty, compact, and powerful. They have sizes ranging from less than 100 pc to a few hundred parsecs (much smaller than that seen in the prototype Seyfert 2 galaxy NGC 1068). Their UV colors imply that they are heavily reddened (by 2 to 3 mag in the UV), and the implied bolometric luminosities are of order 1010 L☉. The bolometric luminosities of these starbursts are similar to the estimated bolometric luminosities of their obscured Seyfert 1 nuclei. The data on this small sample suggest that more powerful AGNs may be related to more powerful central starbursts. Comparing the HST spectra to IUE spectra obtained through apertures with projected sizes of 3-11 kpc (and to IRAS far-IR data) we estimate that the nuclear starbursts account for 6%-25% of the total intrinsic UV luminosity of the entire galaxy.

210 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202346
2022181
20211,101
20201,978
20192,639
20182,772