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Showing papers on "Ultraviolet light published in 1981"


Journal ArticleDOI
TL;DR: The finding that LC surface markers and to a lesser extent the cells themselves are particularly susceptible to UV irradiation has important implications in view of previous findings that LC are potent stimulators of antigen-specific and allogeneic T cell activation.

441 citations


Journal ArticleDOI
TL;DR: It is shown that sewage-borne bacteria were relatively resistant to the bactericidal effect of sunlight when diluted in fresh mountain stream waters, suggesting that the visible rather than the ultraviolet light spectrum of sunlight was primarily responsible for the observed bactericidaleffect.
Abstract: The stability of the natural populations of fecal coliforms and fecal streptococci in raw sewage diluted 1:1,000 in seawater or phosphate-buffered water at 24 +/- 2 degrees C was markedly affected by the absence or presence of sunlight. In the absence of sunlight, these bacteria survived for days, whereas in the presence of sunlight 90% of the fecal coliforms and fecal streptococci were inactivated within 30 to 90 min and 60 to 180 min, respectively. The bactericidal effect of sunlight was shown to penetrate glass, translucent polyethylene, and at least 3.3 m of clear seawater, suggesting that the visible rather than the ultraviolet light spectrum of sunlight was primarily responsible for the observed bactericidal effect. However, these same sewage-borne bacteria were relatively resistant to the bactericidal effect of sunlight when diluted in fresh mountain stream waters. These results indicate that the presence of sunlight is a major factor controlling the survival of fecal coliforms and fecal streptococci in seawater.

323 citations


Journal ArticleDOI
TL;DR: In this chapter, the discussion of general concepts are applicable in broad outline, if not in precise genetic or biochemical detail, to the corresponding cellular responses to ionizing radiation and chemical mutagens.
Abstract: INTRODUCTION Physical and chemical mutagens can produce various kinds of structural defects in yeast DNA. Under appropriate vegetative growth conditions, such changes in DNA may lead to killing (measured as inhibition of macrocolony formation), mutation, or mitotic recombination. Sensitivity to these effects depends on the nature of the mutagen, on the genetic constitution of the cells, and on their physiological state before, during, and after exposure. For reviews of early work in this area see Mortimer (1961), Haynes (1964a, 1975a), James and Werner (1965), and Kilbey (1975). Our knowledge of the mechanisms of DNA repair and its involvement in mutagenesis has come primarily from genetic and biochemical studies on the effects of ultraviolet light (254 nm UV) on microorganisms, including yeast (Haynes et al. 1966; Hanawalt and Setlow 1975; Hanawalt et al. 1978, 1979). Therefore, in this chapter, our discussion of general concepts is based largely on experimental results from the UV photobiology of Saccharomyces cerevisiae. However, most of the ideas are applicable in broad outline, if not in precise genetic or biochemical detail, to the corresponding cellular responses to ionizing radiation and chemical mutagens. For information concerning these latter mutagens, as well as UV, see the recent articles by Kircher et al. (1979), Resnick (1979), Ruhland and Brendel (1979), Lemontt (1980), Prakash and Prakash (1980) and Lawrence (1981). At the observational level in large populations, the genetic effects of UV are randomly distributed, generally independent of one another, and the dose-response relations can be described formally by single-event1 Poisson...

288 citations


Journal ArticleDOI
TL;DR: Both recombinational and nonrecombinational repair mechanisms may function in postReplication repair and most of postreplication repair is error free.
Abstract: Postreplication repair of nuclear DNA was examined in an excision defective haploid strain of yeast lacking mitochondrial DNA (ral ρ0). The size of the DNA synthesized in cells exposed to various fluences of ultraviolet light (UV) corresponds approximately to the average interdimer distance in the parental DNA. Upon further incubation of cells following exposure to 2.5 J/m2, the DNA increases in size; by 4 h, it corresponds to DNA from uniformly labeled cells. The alkaline sucrose sedimentation pattern of DNA pulse labeled at various times after UV irradiation, for up to 4 h, does not change substantially, indicating that dimers continue to block DNA replication. A significant amount of postreplication repair requires de novo protein synthesis, as determined by its inhibition by cycloheximide. The rad6 mutant does not carry out postreplication repair, the rad18 and rad52 mutants show great inhibition while the rev3 mutation does not affect postreplication repair. Both recombinational and nonrecombinational repair mechanisms may function in postreplication repair and most of postreplication repair is error free.

267 citations


Journal ArticleDOI
TL;DR: These studies indicate that adherence of C. albicans is enhanced by a surface component of germinated yeast, probably a surface protein that binds to the epithelial receptor, possibly a glycoprotein.
Abstract: Factors that may influence adherence of Candida albicans to exfoliated human vaginal and buccal epithelial cells were studied in vitro. Factors that enhanced germination enhanced adherence. Heat-killed, germinated Candida organisms demonstrated poorer adherence than viable Candida organisms and no better adherence than nonviable, ungerminated Candida organisms. The difference between adherence of C. albicans to buccal epithelial cells and that to vaginal epithelial cells was significant, as were differences among volunteers. Preincubation in fucose but not mannose, glucose or galactose solutions, preincubation of germinated yeast or of epithelial cells in chymotrypsin or trypsin, a culture supernatant of germinated yeast killed by ultraviolet light, or precoating of epithelial cells with lactobacilli each inhibited adherence. These studies indicate that adherence of C. albicans is enhanced by a surface component of germinated yeast, probably a surface protein that binds to the epithelial receptor, possibly a glycoprotein.

230 citations


Journal ArticleDOI
TL;DR: The simplest model to account for the observations is that sulA and lon participate in a pathway of filamentation independent of that which produces transient filamentation in wild-type strains; sulB product may be the target of sulA action and may play a role in normal cell division.
Abstract: Cells containing the pleiotropic Escherichia coli mutation lon filament extensively and die after exposure to ultraviolet light Outside suppressors of the ultraviolet sensitivity, called sul, have previously been described at two loci; these mutations reverse the ultraviolet sensitivity of lon strains but do not affect the mucoidal or degradation defect of these strains An isogenic set of strains carrying combinations of lon, sulA, and sulI was constructed, and their behavior during normal growth and after ultraviolet treatment was studied sulA mutations had no detectable phenotype in lon+ cells; the lon sulA strains filamented transiently after ultraviolet irradiation, as did lon+ sul+ cells We found that the sulB mutation, which alters cell morphology and slows recovery from transient filamentation after ultraviolet treatment, was epistatic to both lon and sulA Whereas sulA mutations were recessive to the wild-type allele, sulB was partially dominant The simplest model to account for our observations is that sulA and lon participate in a pathway of filamentation independent of that which produces transient filamentation in wild-type strains; sulB product may be the target of sulA action and may play a role in normal cell division Images

228 citations


Journal ArticleDOI
TL;DR: It is concluded that hnRNA is part of a highly organized nuclear structure and by irradiation of intact cells or isolated nuclear matrices with ultraviolet light, proteins tightly associated with hn RNA can be induced to cross-link with the RNA.
Abstract: In this study, DNA-depleted nuclear protein matrices are isolated from HeLa S3 cells. These nuclear matrices consist of peripheral laminae, residual nucleoli, and internal fibrillar structures. High molecular weight, heterogeneous nuclear RNA (hnRNA) is quantitatively associated with these structures and can be released intact only by affecting the integrity of the matrices. It is, therefore, concluded that hnRNA is part of a highly organized nuclear structure. By irradiation of intact cells or isolated nuclear matrices with ultraviolet light, proteins tightly associated with hnRNA can be induced to cross-link with the RNA. Performing the cross-linking in vivo is an extra guarantee that only hnRNA-protein (hnRNP) complexes existing in the intact cell are covalently linked. Such hnRNP complexes were isolated and purified under conditions that completely dissociate nonspecific RNA-protein complexes. By comparison of the hnRNP found in nuclear matrices and the published data on the composition of hnRNP particles, it was found that the so-called hnRNP "packaging" proteins (32,000-38,000 mol wt) were not efficiently cross-linked to hnRNA by UV irradiation. They were, however, present in the matrix preparations, bound to hnRNA, because they were released from nuclear matrices after ribonuclease treatment of these structures. On the other hand, two major hnRNPs (41,500 and 43,000 mol wt) were efficiently cross-linked to hnRNA. These proteins were not released by ribonuclease treatment, which suggests that they are involved in the binding of hnRNA to the nuclear matrix.

209 citations


Journal ArticleDOI
TL;DR: In this article, thin strips of Scots pine and lime were irradiated behind filters which transmitted selected regions of the ultraviolet and visible spectrum, and tensile tests on irradiated strips show that ultraviolet light is highly active in degrading wood, but indicate that the visible part of the spectrum also contributes significantly to loss of strength.
Abstract: The photodegradation of wood is essentially a surface phenomenon, and although in practical terms it has no effect on strength properties, it does have serious consequences for the surface technologist. A principal concern is photodegradation of the timber surface underlying clear and lightly-pigmented finishes—a problem which can lead to early failure of the coating and to expensive remedial measures. Recent thinking is directed towards the development of pretreatments which could stabilise the timber surface against photodegradation. However, in the absence of detailed investigations on the wood-degrading capabilities of different regions of the solar spectrum such developments have so far been restricted. In this paper, thin strips of Scots pine and lime were irradiated behind filters which transmitted selected regions of the ultraviolet and visible spectrum. Tensile tests on irradiated strips show that ultraviolet light is highly active in degrading wood, but indicate that the visible part of the spectrum also contributes significantly to loss of strength. Throughout the exposure period, samples were taken for SEM observation. The loss of strip strength is associated with a light-induced depolymerisation of lignin and cell wall constituents, and to the subsequent breakdown of the wood microstructure.

154 citations


Journal ArticleDOI
TL;DR: During 1965 to 1968, 80 workers who had been engaged in the production of 2, 4, 7, 8-tetrachlordibenzo-p-dioxin and butylester of trichlorphenoxyacetate acid became ill, and two patients have died of bronchogenic lung carcinoma; one of liver cirrhosis; and one of a rapidly developed, extremely unusual type of atherosclerosis precipue cerebri.
Abstract: During 1965 to 1968, 80 workers who had been engaged in the production of 2, 4, 5-sodium trichlor-phenoxyacetate and butylester of trichlorphenoxyacetate acid became ill. The cause of the illness was 2, 4, 7, 8-tetra-chlordibenzo-p-dioxin, A 10-yr study has been conducted for 55 exposed individuals. The majority of the patients developed chloracne, and 11 manifested porphyria cutanea tarda. Approximately one-half of the patients suffered from metabolic disturbances, i.e., pathologically elevated lipids with abnormalities In the Sipoprotein spectrum, and two-fifths of the patients had pathoiogical changes in the glucose toierance test. One-third of the patients had bio-chemical deviations indicative of a mild liver lesion. Histo-logical examination revealed light steatosis, or periportal fibrosis, or activation of Kupffer cells. Fluorescence of the liver tissues was present in ultraviolet light. In 17 persons symptoms of nervous system focal damage existed, with predominance of peripheral neuron l...

150 citations


Journal ArticleDOI
TL;DR: In strains containing excision-defective mutations in any of nine genes in combination with the cdc9 mutation, the absence ofLow-molecular-weight DNA at the nonpermissive temperature after ultraviolet treatment suggests that these mutants are incision defective, whereas the presence of low-molescular- Weight DNA indicates that the mutants are defective in a step after incision.
Abstract: cdc9, a temperature-sensitive mutant defective in polynucleotide deoxyribonucleic acid (DNA) ligase activity, accumulates low-molecular-weight DNA fragments (as measured by sedimentation of DNA in alkaline sucrose gradients) at the nonpermissive temperature after irradiation with ultraviolet light. This phenotype of cdc9 is a sensitive indicator of successful incision during excision repair of dimers. In strains containing excision-defective mutations in any of nine genes in combination with the cdc9 mutation, the absence of low-molecular-weight DNA at the nonpermissive temperature after ultraviolet treatment suggests that these mutants are incision defective, whereas the presence of low-molecular-weight DNA indicates that the mutants are defective in a step after incision. With rad1, rad2, rad3, rad4, and rad10 mutants, the molecular weight of the DNA remained unchanged after ultraviolet irradiation and incubation at the restrictive temperature, despite the presence of the cdc9 mutation; these mutants are therefore incision defective. Low-molecular-weight DNA was observed in rad14 cdc9 and rad16 cdc9 strains. With the rad16 strain, the accumulation of low-molecular-weight DNA correlated with the amount of excision taking place, whereas in the rad14 mutant strain, no evidence of dimer removal was obtained. Therefore, rad14 is likely to be defective in a step after incision.

141 citations


Journal ArticleDOI
01 May 1981-Plasmid
TL;DR: A simple and rapid method discriminating between covalently closed circular (CCC), open circular (OC), and linear (L) forms of plasmid DNA is presented.

Journal ArticleDOI
TL;DR: The data indicate (i) that between pH 6.2 and 7.8 internal spore pH has little effect on dormant spore properties, (ii) that there is a strong permeability barrier in dormant spores to movement of charged molecules and small uncharged molecules, and (iii) that extremely early in spore germination this permeability barriers are breached, allowing rapid release of internal monovalent cations.
Abstract: Previous investigators using the extent of uptake of the weak base methylamine to measure internal pH have shown that the pH in the core region of dormant spores of Bacillus megaterium is 6.3 to 6.5. Elevation of the internal pH of spores by 1.6 U had no significant effect on their degree of dormancy or their heat or ultraviolet light resistance. Surprisingly, the rate of methylamine uptake into dormant spores was slow (time for half-maximal uptake, 2.5 h at 24 degrees C). Most of the methylamine taken up by dormant spores was rapidly (time for half-maximal uptake, less than 3 min) released during spore germination as the internal pH of spores rose to approximately 7.5. This rise in internal spore pH took place before dipicolinic acid release, was not abolished by inhibition of energy metabolism, and during germination at pH 8.0 was accompanied by a decrease in the pH of the germination medium. Also accompanying the rise in internal spore pH during germination was the release of greater than 80% of the spores K+ and Na+. The K+ was subsequently reabsorbed in an energy-dependent process. These data indicate (i) that between pH 6.2 and 7.8 internal spore pH has little effect on dormant spore properties, (ii) that there is a strong permeability barrier in dormant spores to movement of charged molecules and small uncharged molecules, and (iii) that extremely early in spore germination this permeability barrier is breached, allowing rapid release of internal monovalent cations (H+, Na+, and K+).

Journal ArticleDOI
TL;DR: Analysis of radiation-induced alterations in the steady-state distribution of sizes of pulse-labeled, nascent DNA suggests that normal and repair-deficient human fibroblasts either are able to rapidly bypass certain dimers or these dimers are not recognized by the chain elongation machinery.

Journal Article
TL;DR: Using germicidal lamps and Westinghouse sunlamps with and without filtration, the effectiveness of ultraviolet and near-ultraviolet light in inducing molecular and cellular changes was measured and it was inferred that increasing intensities of short-wavelength ultraviolet light would result in smaller increases in biological action, e.g., skin cancer, compared to current levels of action.
Abstract: Using germicidal lamps and Westinghouse sunlamps with and without filtration, the effectiveness of ultraviolet and nearultraviolet light in inducing molecular and cellular changes was measured. Cell survival and the induction of resistance to 6-thioguanine or to ouabain were measured with V79 Chinese hamster cells, cell survival and neoplastic transformation were measured with C3H mouse 10T½ cells, and the induction of pyrimidine dimers containing thymine was measured in both cell lines. The short-wavelength cutoff of the sunlamp emission was shifted from ∼290 nm (unfiltered) to ∼300 and ∼310 nm by appropriate filters. Although it was found that the efficiency with which all end points were induced progressively decreased as the short-wavelength cutoff was shifted to longer wavelengths, the rates of decrease differed appreciably. For example, doses of near-ultraviolet light longer than ∼300 nm that were effective in mutating or in transforming cells were ineffective in killing them. In respect to pyrimidine dimer induction, several but not all cellular end points were induced by dose ratios of sunlamp light (short-wavelength cutoff, ∼290 nm) to germicidal lamp light (254 nm) in fairly close accord with the doses required to produce equivalent proportions of dimers. However, for near-ultraviolet light having cutoffs at longer wavelengths, the biological action observed was appreciably greater than what would be predicted from the proportion of dimers induced. From the latter observation, it is inferred that increasing intensities of short-wavelength ultraviolet light, as would be expected from reductions in stratospheric ozone around the earth, would result in smaller increases in biological action, e.g. , skin cancer, compared to current levels of action than would be predicted from an action spectrum completely corresponding to that of a pyrimidine dimer induction spectrum in DNA.

Book ChapterDOI
TL;DR: In this paper, the photochemical behavior of monosilanes has been investigated by mercury-sensitized photolysis, flash-photolysis and vacuum ultraviolet photo-lysis.
Abstract: Publisher Summary This chapter discusses the recent results on the photochemical generation and reactions of the silylenes and silicon–carbon double-bonded intermediates. The photochemical behavior of monosilanes has been investigated by mercury-sensitized photolysis, flash photolysis, vacuum ultraviolet photolysis, and matrix photolysis. All of the cyclic and acyclic permethylpolysilanes with the exception of hexamethyldisilane readily undergo photolysis on irradiation with ultraviolet light to give shorter chain compounds with the concurrent generation of the divalent silicon intermediate, dimethylsilylene. The silylene species generated during photolysis are thought to polymerize in the absence of a trapping agent. The photolysis of branched permethylpolysilanes is of considerable interest, because a novel silylene intermediate––trimethylsilylmethylsilylene––is produced. The photolysis of phenyl-substituted polysilanes also affords a convenient method for the generation of silylene species. The stereochemistry of photochemical generation of dimethylsilylene is reported. Hydrosilanes are one of the most suitable silylene trapping agents and are often used in photolysis. The yields of the silacyclopropanes are highly dependent on the structure of the olefins used. When tetramethylethylene is used as a quencher, only a trace of the methoxysilane is obtained along with small amounts of the silylalkenes.

Journal ArticleDOI
TL;DR: Data indicate a contribution of the delta chain to the binding site(s) of several well-characterized noncompetitive blockers and suggest that other receptor polypeptides may also contribute to this binding.
Abstract: Reversible ligands were attached covalently to membrane-bound acetylcholine receptor from Torpedo marmorata by a method which is generally applicable and does not require the synthesis of specially designed molecules. UV irradiation of the receptor in the presence of [3H]trimethisoquin, [3H]phencyclidine, or [3H]perhydrohistrionicotoxin resulted in the labeling of the binding site(s) for these noncompetitive blockers of the permeability response. The labeling of the delta chain was enhanced by carbamoylcholine, and this increase was blocked by snake alpha-toxins. The effect of carbamoylcholine on [3H]trimethisoquin binding was more pronounced than with the other two noncompetitive blockers; in all instances, the labeling was abolished by unlabeled histrionicotoxin. These three compounds therefore interact with the high-affinity site for noncompetitive blockers. Incorporation of radioactivity also occurred into the alpha chain but either was insensitive to cholinergic effectors or decreased in the presence of carbamoylcholine (or snake alpha-toxin), probably as a result of an interaction with the acetylcholine-binding site. In contrast to the other noncompetitive blockers tested, [3H]chlorpromazine heavily labeled the four receptor polypeptides (alpha, beta, gamma, delta), and this labeling also was enhanced by carbamoylcholine and decreased by histrionicotoxin. These data indicate a contribution of the delta chain to the binding site(s) of several well-characterized noncompetitive blockers and suggest that other receptor polypeptides may also contribute to this binding.

Journal ArticleDOI
27 Mar 1981-Science
TL;DR: Unscheduled DNA synthesis occurred in both male and female pronuclei of the mouse zygote in response to irradiation with ultraviolet light, indicating a capacity for excision repair and damaged DNA can be repaired after the sperm enters the egg cytoplasm.
Abstract: Unscheduled DNA synthesis occurred in both male and female pronuclei of the mouse zygote in response to irradiation with ultraviolet light, indicating a capacity for excision repair. Furthermore, damage to DNA of the male gamete before fertilization can be repaired after the sperm enters the egg cytoplasm.

Journal Article
TL;DR: These studies indicate that uv irradiation of EC prior to haptenation not only abrogates their capability of inducing ACS but also induces a state of specific immunologic tolerance, which is in part due to the generation of suppressor T-cells.
Abstract: Ultraviolet (uv) radiation has profound effects on the immune system both in vitro and in vivo. Recent studies, utilizing uv irradiation of intact animals, have focused on the suppressive effect of uv irradiation on the generation of allergic contact sensitization (ACS). To explore the mechanism(s) by which uv affects ACS, we used a recently described technique of sensitizing mice with the subcutaneous (s.c.) injection of haptenated epidermal cells. uv-treated or untreated mouse epidermal cells (EC) were conjugated with 1 mM trinitrobenzene sulfonate and injected s.c. into syngeneic recipients. Six days later the ear was challenged with 20 ..mu..l of 1% trinitrochlorobenzene (TNCB), and 24 h later ear thickness was measured. Our studies indicate that uv irradiation of EC prior to haptenation not only abrogates their capability of inducing ACS but also induces a state of specific immunologic tolerance. These studies indicate that the s.c. injection of trinitrophenyl conjugated (TNP) uv-irradiated (TNP-uv) EC induces a state of specific immunologic hyporesponsiveness, and passive transfer studies showed that this hyporesponsiveness is in part due to the generation of suppressor T-cells.

Journal ArticleDOI
TL;DR: Tn5 insertion mutants and in vitro-generated deletion mutants of the mutagenesis-enhancing plasmid pKM101 have been used to identify several genetic regions on the pKKM 101 map.
Abstract: Tn5 insertion mutants and in vitro-generated deletion mutants of the mutagenesis-enhancing plasmid pKM101 have been used to identify several genetic regions on the pKM101 map. In clockwise order on the pKM101 map are: (i) the bla gene, coding for a beta-lactamase; (ii) the Slo region, responsible for retarding cell growth on minimal medium; (iii) the tra genes, enabling pKM101 to transfer conjugally; (iv) sensitivity to IKe phage (this function[s] maps within the tra region); (v) the muc gene(s), responsible for enhancing ultraviolet light and chemically induced mutagenesis in the cell; and (vi) the Rep region, essential for plasmid replication. The muc gene(s) and the Rep region are contained in a deoxyribonucleic acid region bounded by inverted repeated sequences.

Journal ArticleDOI
TL;DR: The results are consistent with IMR-1E1 containing a regulatory mutation which increased production of the components of the chitinolytic enzyme system and/or with IMG1E2 containing a tandem duplication of theChitinase genes.
Abstract: Genetic modification of Serratia marcescens QMB1466 was undertaken to isolated mutants which produce increased levels of chitinolytic activity. After mutagenesis with ultraviolet light, ethyl methane sulfonate or N-methyl-N'-nitro-N-nitrosoguanidine, 19,940 colonies were screened for production of enlarged zones of clearing (indicative of chitinase activity) on chitin-containing agar plates. Forty-four chitinase high producers were tested further in shake flask cultures. Mutant IMR-1E1 was isolated which, depending on medium composition, produced two to three times more than the wild type of the other components of the chitinolytic enzyme system--a factor involved in the hydrolysis of crystalline chitin and chitobiase. After induction by chitin, endochitinase and chitobiase activity appeared at similar times for both IMR-1E1 and QMB1466, suggesting possible coordinate control of these enzymes. The results are consistent with IMR-1E1 containing a regulatory mutation which increased production of the components of the chitinolytic enzyme system and/or with IMR-1E1 containing a tandem duplication of the chitinase genes. The high rate of reversion of IMR-1E1 to decreased levels of chitinase production suggests that the overproduction of chitinase by IMR-1E1 is due to a tandem gene duplication.

Journal ArticleDOI
TL;DR: Unlike native gene 32 protein, G32P∗I can melt native DNA to equilibrium, which suggests that the kinetic pathways for DNA melting by these two species must differ, since the changes in equilibrium binding parameters measured here are far too small to account for the differences in melting behavior.

Journal ArticleDOI
TL;DR: Novobiocin at sufficiently low concentrations apparently generates a quiescent state (in terms of cellular DNA metabolism) from which recovery is possible, under more drastic conditions of time in contact with cells and concentration, however, novobioc in itself induces mammalian cell killing.

Patent
05 Mar 1981
TL;DR: Aromatic substances to be applied to tobacco to improve aroma characteristics are prepared by exposing an alcoholic extract, which contains carotenoids and may additionally contain diterpenes and has been isolated from fresh tobacco plants, to ultraviolet light and oxygen as mentioned in this paper.
Abstract: Aromatic substances to be applied to tobacco to improve aroma characteristics are prepared by exposing an alcoholic extract, which contains carotenoids and may additionally contain diterpenes and has been isolated from fresh tobacco plants, to ultraviolet light and oxygen. Additionally, aromatic substances may be produced from xanthophyll containing plant extracts by the same method.

Journal ArticleDOI
TL;DR: It was found that shortwave ultraviolet light and ultraviolet B increased the density of Ia-bearing cells (Langerhans cells) in the skin, and Psoralens and ultraviolet A (PUVA) depleted the skin of IA- bearing cells, an effect which takes 2 weeks to produce but which persists for several weeks after stopping treatment.

Journal ArticleDOI
25 Apr 1981-BMJ
TL;DR: The concentrations of all three metabolites studied vary according to the season, so to interpret these concentrations in any subject the normal range for the particular season must be referred to.
Abstract: Serum concentrations of 25-hydroxycholecalciferol (25-OHD), 24,25-dihydroxycholecalciferol (24,25-(OH)2D), and 1,25-dihydroxycholecalciferol (1,25-(OH)2D) were measured at monthly intervals throughout the year in eight normal subjects 25-OHD was measured by competitive protein-binding assay after Sephadex LH 20 chromatography, 24,25-(OH)2D by competitive protein-binding assay after Sephadex LH 20 and high-pressure chromatography, and 1,25-(OH)2D by radioimmunoassay after the same separation procedure as for 24,25-(OH)2D A seasonal variation, apparently dependent on exposure to ultraviolet light, was found for all three metabolites A study in six other normal subjects showed that there was no diurnal rhythm in any of the metabolites Oral administration of 2 microgram 1,25-(OH)2D caused a sharp rise in serum concentrations of 1,25-(OH)2D and no change in the concentrations of the two other metabolites, but by 12 hours the 1,25-(OH)2D concentration had returned to the basal value The concentrations of all three metabolites studied vary according to the season Thus to interpret these concentrations in any subject the normal range for the particular season must be referred to

Journal Article
TL;DR: Melphalan resistance developed previously in a human melanoma cell line (MM253) could not be further increased and evidence suggests that the cross-linking events and that developed resistance arises from decreased susceptibility to DNA to this damage.
Abstract: Melphalan resistance developed previously in a human melanoma cell line (MM253) could not be further increased. Cross-resistance was found to nitrogen mustard but not to ultraviolet light radiation. A clone of MM253 had the same drug sensitivity and heterogeneous chromosome complements as did the parent culture. The melphalan-resistant cells (MM253-12M) had 2.6-fold the D0, 1.5-fold the size, 1.3-fold the RNA content, 1.4-fold the protein content, and 2.6-fold the DNA content of the sensitive parent line. There was no evidence for activation or detoxification of melphalan by intact melanoma cells or by mouse liver microsomes competent for the activation of other drugs. Melphalan transport was similar in both cell lines, reaching a steady-state level 3 times the concentration in the medium after 2.5 min. Both lines covalently bound the same total amount of [3H]melphalan per cell, but in MM253-12M a 50% decrease in binding to DNA was almost sufficient to account for the increase in resistance. The level of melphalan-induced DNA interstrand cross-links, which were heat labile but not alkali labile, reached a maximum during the 4-hr treatment period and then declined slowly. The degree of cross-linking in MM253-12M was 50% less than that in MM253. Unlike ultraviolet light, methyl methanesulfonate, and nitrogen mustard, melphalan at equitoxic doses did not damage the DNA sufficiently to immediately inhibit DNA synthesis. Although both lines were proficient for repair of ultraviolet light and methyl methane sulfonate damage, melphalan did not induce significant levels of DNA repair synthesis and had little effect on the rate of DNA chain elongation. In MM253 cells, strand breaks were detected only at high melphalan doses; MM253-12M formed breaks more readily. This evidence suggests that the cross-linking events and that developed resistance arises from decreased susceptibility to DNA to this damage.

Journal ArticleDOI
TL;DR: The number of genome equivalents of DNA per cell of M. radiodurans changed from approximately 5 to 10 depending on the media used, but the sensitivity to ultraviolet light or gamma-rays was not different between the cells with different genome multiplicity, suggesting that the efficient repair process for DNA damage expressed in M. Radioduran is not influenced by the multiplicity of genomes in a cell.
Abstract: The number of genome equivalents of DNA per cell of M. radiodurans changed from approximately 5 to 10 depending on the media used. The sensitivity to ultraviolet light or gamma-rays was not different between the cells with different genome multiplicity. This suggests that the efficient repair process for DNA damage expressed in M. radiodurans is not influenced by the multiplicity of genomes in a cell.

Journal ArticleDOI
TL;DR: Because the action spectra for cytotoxicity and transformation are the same as the spectrum for dimer production, DNA is suggested as the target for all these processes.
Abstract: Action spectra were determined for neoplastic transformation, production of pyrimidine dimers, and lethality in Syrian hamster embryo cells Of wavelengths between 240 and 313 nm, the most effective were 265 and 270 The relative sensitivities per quantum for transformation, pyrimidine dimer production, and lethality were essentially the same at each of the wavelengths tested This action spectrum for transformation, which is relevant to carcinogenesis, is similar to spectra obtained previously by measuring other cellular responses in either microbial or mammalian systems Because the action spectra for cytotoxicity and transformation are the same as the spectrum for dimer production, DNA is suggested as the target for all these processes

Journal ArticleDOI
Gary Gardner1
27 Feb 1981-Science
TL;DR: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of chloroplast membranes irradiated in the presence of [(l4)C]-azidoatrazine indicated radioactivity in only one region, corresponding to a protein with a molecular weight of approximately 32,000.
Abstract: Binding of the 4-azido analog of the herbicide atrazine to pea chloroplast membranes was compared with that of atrazine. When [ 14 C ] azidoatrazine was treated with 300-nanometer ultraviolet light in situ, reversibility of binding was lost in proportion to the duration of irradiation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of chloroplast membranes irradiated in the presence of [ l4 C ]- azidoatrazine indicated radioactivity in only one region, corresponding to a protein with a molecular weight of approximately 32,000. Azidoatrazine is a photoaffinity reagent for the triazine binding site in chloroplasts and serves as a label to identify this site, which may be the apoprotein of the secondary electron acceptor in photosystem II.

Journal ArticleDOI
TL;DR: The technique of photoaffinity crosslinking with agents like hydroxysuccinimidyl-p-azidobenzoate provides a rapid, simple method of covalently attaching ligands to their putative receptors.
Abstract: The photoaffinity crosslinker hydroxysuccinimidyl-p-azidobenzoate was used to attach 125I-labeled glucagon covalently to a rat liver membrane protein of Mr ≈ 53,000 Membranes that had been incubated with 125I-labeled glucagon were treated in the dark with hydroxysuccinimidyl-p-azidobenzoate, and a covalent complex was then formed by irradiation with ultraviolet light Characteristics of 125I-labeled glucagon binding and covalent attachment to the Mr 53,000 peptide were consistent with this peptide being a component of the glucagon receptor involved in the activation of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4611] Binding and covalent attachment of 125I-labeled glucagon to the Mr 53,000 peptide were inhibited by glucagon concentrations that were within the dose-response curve for adenylate cyclase activation, and GTP specifically decreased the photoaffinity crosslinking of 125I-labeled glucagon to the Mr 53,000 peptides Insulin did not compete for the photoaffinity crosslinking of 125I-labeled glucagon The same technique of photoaffinity crosslinking that covalently attached 125I-labeled glucagon to the Mr 53,000 peptide with an efficiency of 1-2% can be used to attach 125I-labeled insulin covalently to a Mr 125,000 peptide with an efficiency of approximately 10% This peptide has been shown to be a subunit of the high-affinity insulin-binding site in rat liver membranes The technique of photoaffinity crosslinking with agents like hydroxysuccinimidyl-p-azidobenzoate provides a rapid, simple method of covalently attaching ligands to their putative receptors Photoaffinity crosslinking does not require chemical modification of the labeled ligand and has a less stringent requirement for specific reactive groups than the commonly used bifunctional crosslinking reagents