Showing papers on "Ultraviolet light published in 1982"

Conversion in different depths of ultraviolet and visible light activated composite materials

Abstract: Studies by means of infrared multiple internal reflection spectroscopy of ultraviolet and visible light polymerized composite resin materials indicated that the degree of conversion below the surface is nearly constant for most of the materials investigated until a depth is reached where the degree of conversion rapidly decreases. The maximum depth of cure has also been measured for some proprietary dental composite resin materials. This investigation has demonstrated that the conversion at different depths and the maximum curing depth are dependent on the composition of the composite filling material, light source, and exposure time. With respect to the activating system it was found that with visible light activated materials larger curing depths were obtained than with ultraviolet light activated materials. Better results with respect to curing depth were also obtained with materials containing conventional inorganic fillers than with those containing so-called microfillers.The limiting factor for tota...

The Role of Solar Ultraviolet Radiation in Marine Ecosystems

Abstract: Atmosphere and Basic Biological Dosimetry.- Preface to Section I.- UV-B Reaching the Surface.- Possible Anthropogenic Influences on Stratospheric Ozone.- Ozone Depletion Calculations.- On the Latitudinal and Seasonal Dependence of Ozone Perturbations.- Middle Ultraviolet Irradiance at the Ocean Surface: Measurements and Models.- The Effect of Perturbation of the Total Ozone Column Due to CFC on the Spectral Distribution of UV Fluxes and the Damaging UV Doses at the Ocean Surface: A Model Study.- Multi-Wavelength Determination of Total Ozone and Ultraviolet Irradiance.- Radiometric Measurements in the UV-B Region of Daylight.- Photobiological Dosimetry of Environmental Ultraviolet Radiation.- Action Spectra.- Some Thoughts on UV Action Spectra.- Action Spectra and Their Role in Solar UV-B Studies.- Action Spectra: Emphasis Mammalian Cells.- Dosage Units for Biologically Effective UV-B: A Recommendation.- Measuring Devices and Dosage Units.- The Sunburn UV Network and its Applicability for Biological Predictions.- Description and Application of a Personal Dosimeter for Measuring Exposure to Natural Ultraviolet Radiation.- Nomograms for Biologically Effective UV.- A Formula for Comparing Annual Damaging Ultraviolet (DUV) Radiation Doses at Tropical and Mid-Latitude Sites.- The Hydrosphere.- Preface to Section II.- Spectral Irradiance Penetration in Natural Waters.- A Method for the Estimation of the Penetration of Biologically Injurious Solar Ultraviolet Radiation into Natural Waters.- Yellow Substance in the Sea.- Note on the Role of Vertical Mixing in Relation to Effects of UV Radiation on the Marine Environment.- Photochemical Transformations Induced by Solar Ultraviolet Radiation in Marine Ecosystems.- Penetration of Solar UV-B into Waters off Iceland.- The Biosphere.- Preface to Section III.- Lethal Effects on Biological Systems Caused by Solar Ultraviolet Light: Molecular Considerations.- DNA Damage of the 5,6-Dihydroxydihydrothymine Type Induced by Solar UV-B in Human Cells.- Mechanisms of Actions of Longwave-UV on Marine Organisms.- Survival of the Brine Shrimp, Artemia Salina, After Exposure to 290-NM Ultraviolet Radiation, with and without Maximum Photoreactivation.- Photoreactivation: Mammalian Cells.- The Amelioration of UV-B Effects on Productivity by Visible Radiation.- Error Prone Repair-Emphasis Weigle Reactivation.- Sensitivity to UV-B Irradiation as Related to Bacterial Life Cycles.- Pigment Dispersion by Light in the Melanophores of the Fiddler Crab.- Yellow Lens Pigment: An Adaptation for Activity in Bright Sunlight.- Photomovement of Aquatic Organisms in Response to Solar UV.- Movement Reactions of Blue-Green Algae in Response to Their Photoenvironment.- Short-Term Responses of Some Planktonic Crustacea Exposed to Enhanced UV-B Radiation.- Review of Literature Concerning the Impact of UV-B Radiation Upon Marine Organisms.- Assessment of Effects of UV Radiation on Marine Fish Larvae.- The Effect of UV-B Irradiation on the Integument of the Marine Flatfish Pleuronectes Platessa L..- Assessment of the Influence of Enhanced UV-B on Marine Primary Productivity.- Modeling Light Loss Versus UV-B Increase for Organisms Which Control Their Vertical Position in the Water Column.- Effects of UV-B Radiation on Thalassiosira Pseudonana: A Preliminary Study.- The Effects of Ultraviolet Irradiation on Photosynthesis by Ruppia Maritima L. (Widgeon Grass).- Effects of UV Radiation on Photosynthesis of Natural Populations of Phytoplankton.- The Effect of High Intensity U.V. Radiation on Benthic Marine Algae.- The Effects of UV-B Irradiation on Higher Plants.- Preliminary Results Regarding the Spectral Efficiency of UV on the Depression of Photosynthesis in Higher Plants.- Possible Errors in Photosynthetic Measurements Arising from the Use of UV-Absorbing Cuvettes: Some Examples in Higher Plants.- Biological Interactions Between Wavelengths in the Solar-UV Range: Implications for the Predictive Value of Action Spectra Measurements.- Does Solar UV Influence the Competitive Relationship in Higher Plants.- A Model to Evaluate the Impact of Cyclically Recurring Hazards on Selected Populations.- Solar UV Radiation as a Selective Force in the Evolution of Terrestrial Plant Life.- Atmospheric Evolution and UV-B Radiation.- Some Considerations on the Ecological and Evolutionary Effects of Solar UV.- The Attenuation of Light by Marine Phytoplankton with Specific Reference to the Absorption of Near-UV Radiation.- Possible Influences of Solar UV Radiation in the Evolution of Marine Zooplankton.- List of Contributors.

Intensification of ultraviolet-induced dermal damage by infrared radiation

Abstract: Abnormal dermal deposition of elastic fibers is the earliest and most striking effect of prolonged sun exposure (solar elastosis). The hyperplastic fibers are usually ascribed to ultraviolet (UV) rays. Nonetheless, other portions of the solar spectrum may play contributing roles. Heat, for example, enhances experimental UV tumorigenesis. Heat induces erythema ab igne in which the structural alterations resemble those of actinically damaged skin, including the development of premaligant and malignant lesions. In regions of high insolation, infrared radiation (IR) is a constant companion of UV. To assess the role of IR in actinic damage to the dermis, albino guinea pigs were irradiated for 45 weeks with UV-B and UV-A, with and without IR. Control animals received IR only or no irradiation at all. Unirradiated dermis contains small amounts of elastic fibers in the upper dermis with greater depositions around follicles and sebaceous glands. After irradiation with UV, the fibers became more numerous, thicker, and more twisted; IR alone produced many fine, feathery fibers. The addition of IR to UV resulted in dense matlike elastic fiber depositions that exceeded what was observed with either irradiation alone. In combination or alone UV and IR radiation produced a large increase in ground substance, a finding also seen in actinically damaged human skin. Infrared radiation, in the physiologic range, though pleasant is not innocuous.

Fluorescence of paint and varnish layers (Part II)

Abstract: As part of a study of fluorescence of paint and varnish layers under ultraviolet light, the fluorescence of a number of pigments has been measured with a fluorescence spectrometer. Of the pigments studied, only zinc white, cadmium pigments and genuine madder appear to possess fluorescence of considerable intensity. The physico-chemical background of fluorescence in general and of fluorescence of pigments in particular is discussed.

Some fluorescent counterstains for neuroanatomical studies.

Abstract: Methods for counterstaining neural tissue that contains fluorescent markers have been developed. Acridine orange is useful for localizing cells that are retrogradely labelled with the fluorescent tracers true blue, bisbenzimide, and nuclear yellow because at low concentrations it yields a green Nissl stain when excited with blue, but not with ultraviolet, light; since the tracers fluoresce only when exposed to ultraviolet light, they are not masked by the counterstain. In addition, counterstaining at pH 2 increases bisbenzimide fluorescence considerably. Ethidium bromide is useful for immunohistochemistry (IHC) because it yields a bright red Nissl counterstain when excited by green light, and is only faintly visible when the fluorescein marker is excited with blue light, or when ultraviolet excitation is used. Ethidium bromide is therefore a good counterstain for fluorescent retrograde tracer and for combined IHC-retrograde tracer studies as well. Certain dyes are also useful for studies of the normal morphology of neural tissue. For example, bisbenzimide and nuclear yellow at low concentrations produce a brilliant Nissl stain at pH 2, and stain only nuclei at pH 7.2. The latter procedure may be particularly useful for cell counts. Finally, neutral red, astrazone red, and safranin-O differentially stain cells amd myelinated fibers, producing fluorescence analogs of the Kluver-Barrera stain.

5,6-Saturated thymine lesions in DNA: production by ultraviolet light or hydrogen peroxide

Abstract: Thymine analogs with saturated 5-6 bonds are important types of DNA damage that are recognized by the DNA N-glycosylase activity of E. coli endonuclease III. Seeking agents which could preferentially form 5,6-hydrated thymine residues in duplex DNA both in vivo and in vitro, we exposed purified duplex DNA to 325- or 313-nm light; however, after such exposure pyrimidine dimers greatly predominated over 5,6-hydrated thymine. Hydrogen peroxide, on the other hand, formed significant numbers of endonuclease III-sensitive sites in vitro which were not apurinic/apyrimidinic lesions and thus were likely to be 5,6-hydrated thymines.

Radiation-Sensitive Mutants of CAENORHABDITIS ELEGANS

Abstract: Nine rad (for abnormal radiation sensitivity) mutants hypersensitive to ultraviolet light were isolated in the small nematode Caenorhabditis elegans . The mutations are recessive to their wild-type alleles, map to four of the six linkage groups in C. elegans and define nine new games named rad-1 through rad-9 . Two of the mutants— rad-1 and rad-2 —are very hypersensitive to X rays, and three— rad-2, rad-3 and rad-4 —are hypersensitive to methyl methanesulfonate under particular conditions of exposure. The hypersensitivity of these mutants to more than one DNA-damaging agent suggests that they may be abnormal in DNA repair. One mutant— rad-5 , a temperature-sensitive sterile mutant—shows an elevated frequency of spontaneous mutation at more than one locus; rad-4 , which shows a cold-sensitive embryogenesis, reduces meiotic X-chromosome nondisjunction tenfold and partially suppresses some but not all mutations that increase meiotic X-chromosome nondisjunction; the viability of rad-6 hermaphrodites is half that of rad-6 males at 25°; and newly mature (but not older) rad-8 hermaphrodites produce many inviable embryo progeny. Meiotic recombination frequencies were measured for seven rad mutants and found to be close to normal.

Probing aerosols by photoelectric charging

Abstract: Particles suspended in a gas may emit photoelectrons upon irradiation with ultraviolet light. It is shown that photoemission from small particles involves material and surface dependent physical processes that yield new information, especially on ultrafine particles not accessible to the well‐known diffusion charging. An apparatus is presented for the measurement of the electric mobility and the charge generated on particles in the atmosphere using a monochromatic low‐pressure Hg arc. Particles generated by combustion of organic material, e.g., auto exhaust, are charged with high efficiency. This offers a new way to detect and/or remove such particles from the air. In outside air the concentration of photoelectrically active particles has a diurnal cycle which also depends on the meteorological conditions. Surprisingly, highly mobile particles are detectable even during rainfall.

SINGLE‐STRAND BREAKS INDUCED IN BACILLUS SUBTILIS DNA BY ULTRAVIOLET LIGHT: ACTION SPECTRUM and PROPERTIES

Abstract: — The induction of single-strand breaks (alkali-labile bonds plus frank breaks) in the DNA of Bacillus subtilis irradiated in vivo by monochromatic UV light at wavelengths from 254 to 434 nm was measured. The spectrum consists of a major far-UV (below 320 nm) component and a minor near-UV shoulder. A mutant deficient in DNA polymerase I accumulates breaks caused by near-UV (above 320 nm) wavelengths faster than the wild-type strain proficient in polymerase I. Measurable breaks in extracted DNA are induced at a higher frequency than those induced in vivo. Anoxia, glycerol, and diazobicyclo (2.2.2.) octane inhibit break formation in extracted DNA. Alkali-labile bonds induced by 365-nm UV radiation are largely (78%) covalent bond chain breaks, the remainder consists of true alkali-labile bonds, probably apurinic and apyrimidinic sites.

Repair capability and the cellular age response for killing and mutation induction after UV.

Abstract: The cell-cycle response for killing and mutation induction by ultraviolet irradiation was measured in synchronous Chinese hamster ovary cells (CHO wild-type) and in a UV-hypersensitive mutant (43-3B) derived from this line. The CHO 43-3B line shows a greatly enhanced sensitivity to killing ( D 0 of 0.3 as compared to 3.2 J/m 2 for the wild-type), is hypermutable, and deficient in DNA repair. For the wild-type, a characteristic age response is seen for killing by UV, with maximum sensitivity in early-S and resistance increasing through the S-phase. There is also a life-cycle specificity for induction of diphteria-toxin resistance in late-G 1 and early-S. Relatively little variation is seen through the cell cycle for induced 6-thioguanine and ouabain resistance. In contrast, the 43-3B cell line shows a relatively ‘flat’ response to UV throughout the cell cycle, for both killing and mutation induction. Therefore it appears that the characteristic age responses seen in the wild-type CHO are associated with the function of an essentially erro-free repair process. A variation in the ability of this repair process to act in eliminating potentially lethal and mutagenic lesions (either due to a variation in repair enzyme activities through the cell cycle, or in the time available for repair) would account for most of the age response which is seen in the wild-type for killing and mutation induction by ultraviolet light.

Defective removal of DNA cross-links in a repair-deficient mutant of Chinese hamster cells.

Abstract: To further understand the relationships between DNA damage, DNA repair, and cellular end points such as survival and mutation, the repair capacity of a DNA repair-deficient mutant (strain UV-20) of Chinese hamster ovary cells was characterized in response to DNA cross-linking agents. This mutant, previously shown to be hypersensitive to killing by both ultraviolet light and the cross-linking agent mitomycin C, was also found to be extremely sensitive to cis -diamminedichloroplatinum, another DNA cross-linking agent. The efficiency of DNA cross-link removal after treatment with mitomycin C or cis -diamminedichloroplatinum was measured using the technique of alkaline elution and compared in wild-type Chinese hamster ovary cells and strain UV-20. Wild-type cells removed 80 or 95% of the cross-links within 24 hr after treatment with cis -diamminedichloroplatinum or mitomycin C, respectively. In contrast, UV-20 cells, which were equally as susceptible to cross-link damage as were wild-type cells, removed only a small proportion of the cross-links made by either agent. These results emphasize the importance of DNA repair processes in modulating the cytotoxic effects of chemicals that produce DNA cross-link damage and suggest that cross-link repair in Chinese hamster ovary cells is controlled by a pathway that also repairs damage from ultraviolet radiation.

Powder coating composition for automotive topcoat

Abstract: A thermosetting acrylic powder coating composition contains an acrylic copolymer of a methacrylic acid and at least one other monoethylenically unsaturated monomer, a crosslinking agent capable of reacting with carboxylic acid groups, a blend of an ultraviolet light stabilizer and an ultraviolet screener capable of preventing degradation of the coating by ultraviolet light and a flow control agent. Preferably, the composition is nonpigmented and provides a clear, glossy, and durable film useful as the clear coat of a clear coat/color coat automobile finish.

Effects of intake of l-ascorbic acid on the incidence of dermal neoplasms induced in mice by ultraviolet light.

Abstract: We have carried out a study of large malignant skin tumors (squamous cell carcinomas) and other lesions in hairless mice (groups of 38-45) intermittently exposed to ultraviolet light over a period of 15 weeks, beginning when the mice were about 10 weeks old. The several groups were given a standard diet with 0%, 0.3%, 5%, and 10% added L-ascorbic acid (vitamin C) throughout the study. No lesions developed in unirradiated control groups. The lesions were counted every 14 days for 4 months, beginning 4 weeks before the end of the period of irradiation. The observed incidence of lesions of several sizes during successive time periods was analyzed by the statistical method recommended by a committee of the International Agency for Research on Cancer. A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of the malignant lesions was observed with high statistical significance.

DNA repair in Escherichia coli: identification of the uvrD gene product.

Abstract: A 2.9-kilobase (kb) Pvu II DNA fragment that contains the uvrD gene of Escherichia coli K-12 has been cloned in both low-copy and multiple-copy plasmid vehicles. The low-copy uvrD plasmid (pVMK49) complements a variety of uvrD, uvrE, and recL mutations. In contrast, the same strains carrying the 2.9-kb fragment in a multiple-copy plasmid (pVMK45) remain sensitive to ultraviolet light (UV). Additionally, pVMK45 transformants of wild-type E. coli are sensitive to UV and methyl methanesulfonate and appear to be recombination deficient. The cloned uvrD gene does not complement the dominant uvrD3 allele. The 2.9-kb Pvu II insert in these plasmids encodes a single 76,000-dalton protein, which, on the basis of insertional inactivation experiments with the Tn1000 transposon, must be the uvrD gene product. These data confirm earlier genetic analysis which suggested that recL, uvrE, and uvrD were all allelic. The direction of transcription of the uvrD gene has also been determined.

Ultraviolet Action Spectrum for Anthocyanin Formation in Broom Sorghum First Internodes

Abstract: An action spectrum for anthocyanin formation in dark-grown broom sorghum (Sorghum bicolor Moench, cv Acme Broomcorn and cv Sekishokuzairai Fukuyama Broomcorn) seedlings was determined over the wavelength range from 260 to 735 nanometers. The action peaks were at 290, 650, 385, and 480 nanometers in descending order of height. The action of the 290-nanometer peak was not affected by subsequently given far red light, whereas those of the other three action peaks were nullified completely. The nullification of the 385-nanometer peak action by far red light was reversible. When an irradiation at these action peaks was followed by a phytochrome-saturating fluence of red light irradiation, the action of the 290-nanometer peak remained, whereas that of the 385-nanometer peak as well as those of the 650- and 480-nanometer peaks was masked by the action of the second irradiation. These findings suggested that the 290- and 385-nanometer action peaks involved different photoreceptors, the latter being phytochrome. The blue light-absorbing photoreceptor as reported to be a prerequisite for phytochrome action in milo sorghum was not found to exist in the broom sorghums.The action spectrum deprived of the involvement of phytochrome was determined in the ultraviolet region by irradiating with far red light following monochromatic ultraviolet light. The spectrum had a single intense peak at 290 nanometers and no action at all at wavelengths longer than 350 nanometers.

Photodegradation and Photoprotection of Wood Surfaces

Abstract: Photodegradation of southern yellow pine and its protection have been studied. Scanning electron micrographs showed that most of the cell walls on exposed transverse surfaces were separated at the middle lamella region after only 500 h of ultraviolet light irradiation. Fibers at the surface were degraded severely after 1,000 h of irradiation. Half-bordered pits and bordered pits on exposed radial surfaces were severely damaged by ultraviolet light. Enlargement of pit apertures as well as loss of pit domes was observed. However, wood irradiated on tangential surfaces was quite resistant to UV irradiation; only microchecks were observed. The photodegradative effect on wood surfaces can be mitigated by treating with aqueous solutions of chromic acid or ferric chloride. Only relatively small amounts of these chemicals are needed for effective protection. Possible chemistry and mechanisms of degradation and protection are discussed.

Ultraviolet light: photosensitivity and other effects on the visual system.

Abstract: It is generally stated in elementary lectures on sensory systems that the limits of the visible spectrum are 400 nm (violet) and 700 nm (red), although there are several exceptions to this generalization. Recently, the properties of ultraviolet (UV) vision in invertebrates, as well as vertebrates, have been better characterized, and it is worthwhile to examine visual phenomena in the UV region of the spectrum. The purpose of this review is to integrate what is known about UV vision in invertebrates, which have been particularly well studied, with a growing literature on UV sensitivity and UV effects in the visual systems of humans and other vertebrates.

Involvement of phytochrome and a blue light photoreceptor in UV-B induced flavonoid synthesis in parsley (Petroselinum hortense Hoffm.) cell suspension cultures.

Abstract: Flavonoid synthesis in cell suspension cultures of parsley (Petroselinum hortense Hoffm.) occurs only after irradiation with ultraviolet light (UV), mainly from the UV-B (280–320 nm) spectral range. However, it is also controlled by phytochrome. A Pfr/Ptot ratio of approximately 20% is sufficient for a maximum phytochrome response as induced by pulse irradiation. Continuous red and far red light, as well as blue light, given after UV, are more effective than pulse irradiations. The response to blue light is considerably greater than that to red and far red light. Continuous red and blue light treatments can be substituted for by multiple pulses and can thus probably be ascribed to a multible induction effect. Continuous irradiations with red, far red and blue light also increase the UV-induced flavonoid synthesis if given before UV. The data indicate that besides phytochrome a separate blue light photoreceptor is involved in the regulation of the UV-induced flavonoid synthesis. This blue light receptor seems to require the presence of Pfr in order to be fully effective.

The effect of ultraviolet light on the mechanical properties of polyethylene and polypropylene films

Abstract: Measurements were made of dynamic mechanical response spectra and stress–strain properties at room temperature on films of isotactic polypropylene and low-density polyethylene prior and after ultraviolet irradiation in a Xenotest 450 apparatus. The period of irradiation that caused a deep deterioration of ultimate mechanical properties influenced the dynamic mechanical properties only insignificantly. This is attributed to the heterogeneous nature of the photo-oxidative degradation process which is concentrated in a finite number of sites, thus forming crack precursors rather than changing the material properties in bulk. For a biaxially oriented tubular film of low-density polyethylene, anisotropic embrittlement after exposure in Xenotest 450 was observed. This even reversed the order of strain-at-break values in the two main directions of the film. This is remarkably similar to the effect of artificial incisions introduced into the specimens.

Photolysis of pyridinoline, a cross-linking amino acid of collagen, by ultraviolet light.

Abstract: Pyridinoline, a cross-linking amino acid of collagen, was degraded by irradiation of ultraviolet light. The decomposition rate varied with pH of the solution and wavelength of irradiation light. The maximum of the degradation rate at individual pH coincides with the ultraviolet absorption maximum. Namely, it was maximally degraded by irradiation at 295 nm in acidic solution and at 325 nm in neutral and alkaline solution. At the optimum wavelength, the photolysis occurred more rapidly in neutral and alkaline solution than in acidic solution. The quantum yield in neutral solution was approximately 0.11 and independent of wavelength. One of the photolysis products was identified as hydroxylysine on an amino acid analyser, indicating that the cleavage of the pyridinium ring occurred.

Simultaneous detection of changes in chromosome number, gene conversion and intergenic recombination during mitosis of Saccharomyces cerevisiae: spontaneous and ultraviolet light induced events.

Abstract: We have employed a hyperhaploid strain of Saccharomyces cerevisiae disomic for chromosome VII to monitor spontaneous and ultraviolet light induced restitution of haploidy (chromosomal loss and/or nondisjunction), mitotic gene conversion and mitotic intergenic recombination. The disomic chromosomal pair incorporates six heterozygous markers, including cyh2r, distributed on both sides of the centromere. Cycloheximide resistant segregants of spontaneous origin were analyzed to calculate the spontaneous mitotic rates of restitution of haploidy, intergenic recombination and gene conversion that result in expression of the cyh2r mutation. Restitution of haploidy was found to be the most common source of spontaneously arising cycloheximide resistant segregants. In contrast, those induced by ultraviolet light resulted most frequently from gene conversion of CYH2s to cyh2r. The chromosome VII hyperhaploid system provides a sensitive method to detect the aneugenic and recombinagenic effects of suspect chemical and physical agents.