Showing papers on "Ultraviolet light published in 1974"

Photochemotherapy of psoriasis with oral methoxsalen and longwave ultraviolet light.

Abstract: Oral administration of a photoactive drug, 8-methoxypsoralen (methoxsalen), followed by exposure to a high-intensity, longwave ultraviolet-light system resulted in complete clearing of generalized psoriasis in 21 patients. In 16 of these cases, a paired comparison showed methoxsalen followed by longwave ultraviolet light to be more effective than conventional ultraviolet light. 8-Methoxypsoralen followed by exposure to longwave ultraviolet light has previously been shown to inhibit epidermal DNA synthesis; this may be its mechanism of action in psoriasis, a disorder characterized by an accelerated cell cycle and rate of DNA synthesis. The term photochemotherapy is used to emphasize the point that the effect on epidermal proliferation and the therapeutic response require the interaction of light and drug. (N Engl J Med 291:1207–1211, 1974)

The wavelengths in sunlight effective in producing skin cancer: a theoretical analysis.

Abstract: DNA is taken as the target for skin cancer induced by ultraviolet light, and the known data on the sensitivity of DNA as a function of wavelength are summarized. The sun's spectrum at the surface of the earth and the DNA action spectrum are used to calculate the carcinogenic effectiveness as a function of wavelength. The most effective wavelengths at 30°N latitude are <305 nm, and a 1% change in atmospheric ozone results in a 2% change in the effective dose of ultraviolet light. Since both the basic biological and physical data are reasonably precise, the major requirement for a quantitative evaluation of the dose response relation for ultraviolet-induced skin cancer in man is better epidemiological data to compare with data from animal models.

Photochemical reactions initiated by and influencing ozone in unpolluted tropospheric air

Abstract: This paper presents theoretical arguments in favour of OH-concentrations larger than 10 6 molecules cm ?3 in the sunlit lower troposphere even if allowance is made for heterogeneous removal of OH, HO 2 and HNO 3 molecules. The OH-concentrations, presented in this paper, were calculated considering for the first time the photochemical effect of both scattered and direct radiation at ground levels and adopting recent accurate data for the quantum efficiency of O( 1 D) production in the ozone photolysis near 310 nm. The significant role played by OH in the atmospheric carbon, nitrogen and possibly sulphur cycles is discussed. Low background mixing ratios of NOx molecules (< 10 ?9 ) in the unpolluted atmosphere are calculated. The oxidation of NH3, initiated by the reaction with OH, may provide a significant source of tropospheric NOx-molecules, if its rate constant is about 10 ?13 cm 3 s ?1 near the ground. The conversion of NO 2 into HNO 3 , followed by heterogeneous removal of HNO 3 , is the most important tropospheric sink for NO x -molecules. The photodissociation of ozone in ultraviolet light between 300 and 330 nm, which leads to the formation of the excited O( 1 D) atom, “drives” several sequences of reactions treated in this study. Several chains of reactions, involving carbon and nitrogen compounds, lead to large rates of formation and destruction of ozone in the troposphere. These rates partly balance each other. Whether there is a net production or destruction of ozone in the troposphere cannot be determined at present. Ozone is a very active, catalytic component in the tropospheric chemical systems. Globally, the combustion source of CO for the year 1970 is more than 20% of the natural source of CO as provided by the oxidation of biologically produced CH 4 . For middle latitudes of the Northern Hemisphere the combustion source is about equal to the natural source. However, too little is known about homogeneous and heterogeneous reactions affecting the methane oxidation products. DOI: 10.1111/j.2153-3490.1974.tb01951.x

The postnatal development of the human temporomandibular joint.

Abstract: Fifty-one temporomandibular joints (24 male, 27 female) obtained at autopsy were used in the study. Forty-four specimens were younger than ten years while others ranged to 21 years. These joints were radiographed, sectioned sagittally or frontally, and slide-mounted as decalcified and undecalcified sections using conventional histologic techniques. The slides were examined microscopically in whole, polarized, and ultraviolet light. Two of the specimens surveyed exhibited fluorescent labeling as a consequence of therapeutic tetra cycline application. Throughout the postnatal developmental period the articular tissue and disc consist of fibrous connective tissue. Cartilage cells were not observed in these structures at any time during the twenty-one year age-span studied. At birth the disc is flat and develops an accentuated S-shaped profile as the articular tubercle develops. The articular tubercle is only a small elevation at birth and is formed by a combination of endochondral, immature, and ordinary intramembranous bone formation. The characteristic profile of the temporal portion of the joint is achieved during the first two or three years of life, after which gradual enlargement and compaction of bony structures occur. While the mandibular condyle grows in a constant posterior, superior, and lateral direction, it does not attain its mature contour until the late mixed dentition age. Condylar growth cartilage is approximately 1.5 mm thick at birth but it thins down in a short time to about 0.5 mm. During the first two years of life the growth cartilage is penetrated by vascularized connective tissue septa whose function appears to be nourishment of the cartilage. The growth cartilage does not show the columnar arrangement of chondrocytes seen in epiphyses, nor are isogenous groups observed. At 16 to 17 years, the growth cartilage becomes thinner and a closing plate of bone is beginning to coalesce below it.

Lack of chemically induced mutation in repair-deficient mutants of yeast.

Abstract: Two genes, rad6 and rad9 , that confer radiation sensitivity in the yeast Saccharomyces cerevisiae also greatly reduce the frequency of chemically-induced reversions of a tester mutant cyc1-131 , which is a chain initiation mutant in the structural gene determining iso-1-cytochrome c . Mutations induced by ethyl methanesulfonate (EMS), diethyl sulfate (DES), methyl methanesulfonate (MMS), dimethyl sulfate (DMS), nitroquinoline oxide (NQO), nitrosoguanidine (NTG), nitrogen mustard (HN2), β-propiolactone, and tritiated uridine, as well as mutations induced by ultraviolet light (UV) and ionizing radiation were greatly diminished in strains homozygous for either the rad6 or rad9 gene. Nitrous acid and nitrosoimidazolidone (NIL), on the other hand, were highly mutagenic in these repair-deficient mutants, and at low doses, these mutagens acted with about the same efficiency as in the normal RAD strain. At high doses of either nitrous acid or NIL, however, reversion frequencies were significantly reduced in the two rad mutants compared to normal strains. Although both rad mutants are immutable to about the same extent, the rad9 strains tend to be less sensitive to the lethal effect of chemical mutagens than rad6 strains. It is concluded that yeast requires a functional repair system for mutation induction by chemical agents.

Preferential DNA repair in human cells.

Abstract: EXCISION repair plays a vital role in the recovery of human cells from ultraviolet irradiation1, but it does not remove all lesions from DNA, even when they are as potent as cyclobutane pyrimidine dimers. In fact, only about 50% to 75% of the dimers produced by low fluences of ultraviolet light are excised and the remainder persist in the DNA for at least 24 to 48 h2–4. We have investigated why some but not all dimers are excised. Our conclusion is that dimers, and possibly other ultraviolet photoproducts, persist in tracts of DNA which are rendered refractory to excision repair by a ‘mask’ of protein.

Aflatoxin-producing strains of Aspergillus flavus detected by fluorescence of agar medium under ultraviolet light.

Abstract: The fluorescence method of detecting aflatoxin-producing strains of Aspergillus flavus and related species utilizes the ultraviolet-induced fluorescence of aflatoxin produced in a modified Czapek's solution agar containing corn steep liquor, HgCl(2), and (NH(4))H(2)PO(4) instead of NaNO(3). The presence of aflatoxin is confirmed by thin-layer chromatography of CHCl(3) extracts of the fluorescing agar.

Isolation and Characterization of an Escherichia coli ruv Mutant Which Forms Nonseptate Filaments After Low Doses of Ultraviolet Light Irradiation

Abstract: Two ultraviolet light (UV)-sensitive mutants have been isolated from Escherichia coli K-12. These mutants, designated RuvA(-) and RuvB(-), were controlled by a gene located close to the his gene on the chromosome map. They were sensitive to UV (10- to 20-fold increase) and slightly sensitive to gamma rays (3-fold increase). Host cell reactivation, UV reactivation and genetic recombination were normal in these mutants. Irradiation of the mutants with UV resulted in the production of single-strand breaks in deoxyribonucleic acid, which was repaired upon incubation in a growth medium. After UV irradiation, these mutants resumed deoxyribonucleic acid synthesis at a normal rate, as did the parent wild-type bacteria, and formed nonseptate, multinucleate filaments. From these results we concluded that the mutants have some defect in cell division after low doses of UV irradiation, similar to the lon(-) or fil(+) mutant of E. coli. The ruv locus was divided further into ruvA and ruvB with respect to nalidixic acid sensitivity and the effect of minimal agar or pantoyl lactone on survival of the UV-irradiated cell. The ruvB(-)mutant was more sensitive to nalidixic acid than were ruvA(-) and the parent strain. There was a great increase in the surviving fraction of the UV-irradiated ruvB(-) mutant when it was plated on minimal agar or L agar containing pantoyl lactone. No such increase in survival was observed in the ruvA(-) mutant.

Properties of R plasmids determining gentamicin resistance by acetylation in Pseudomonas aeruginosa.

Abstract: Two clinical isolates of Pseudomonas aeruginosa, one a pyocin type 5 strain from Atlanta, could transfer gentamicin resistance by conjugation. Donor and recipient strains inactivated gentamicin by acetylation. The R plasmids, pMG1 and pMG2, also determined resistance to sisomicin, another substrate of gentamicin acetyltransferase I, sulfonamides, and streptomycin, but not resistance to kanamycin, neomycin, tobramycin, butirosin, or BB-K 8. They were transmissible to many strains of P. aeruginosa, including a Rec(-) strain, but not to Escherichia coli or other enterobacteriaceae. These R plasmids were compatible with R plasmids transmissible to P. aeruginosa from E. coli, including members of C, N, P, and W incompatibility groups. From a strain carrying pMG1 and a compatible plasmid, pMG1 was transferred independently but transfer of the second plasmid often resulted in cotransfer of pMG1. In contrast, pMG1 and pMG2 were incompatible with pseudomonas R plasmids R931 and R3108, and with R931 they readily formed recombinant plasmids. The four plasmids in this incompatibility group determine additional biological properties, including resistance to inorganic and organic mercury compounds, to ultraviolet light, and to certain deoxyribonucleic acid phages. pMG1 and pMG2 also phenotypically inhibited pyocin production. Consequently such R plasmids alter the phage and pyocin types of their host strains.

Analysis of Interphase Chromosome Damage by Means of Premature Chromosome Condensation after X- and Ultraviolet-Irradiation

Abstract: Sendai virus-mediated fusion between mitotic and interphase mammalian cells causes the rapid condensation of the interphase chromosomes into distinct structures, a process termed premature chromosome condensation. This phenomenon has been used to assess the immediate action of x-rays and ultraviolet light on the chromosomes of HeLa cells irradiated in the G1 phase of the life cycle. X-irradiation produces fragmented chromosomes; but even the most finely chopped fragments retain the condensed morphology characteristic of the premature chromosome condensation of unirradiated G1 cells. For doses up to about 1800 rads, the increase in the number of fragments is linearly related to the dose. One mean lethal dose (about 100 rads) yields a net increase of 10-15 fragments per G1 cell, which is considerably larger than previous estimates based on scoring of mitotic chromosomes. Incubation of irradiated cells produces a rapid (within 2 hr) reduction in the number of fragments, indicative of a rejoining process. The decrease in the number of pieces is not accompanied by unscheduled DNA synthesis detectable by radioautography. G1 chromosomes of cells irradiated with UV light in G1 phase are not appreciably fragmented but are elongated and attenuated so that they resemble the premature-chromosome-condensation chromosomes of unirradiated S-phase cells. Both the degree of “S-like” character attained by the G1 chromosomes in a cell and the percentage of the cell population displaying the G1 → S transition increase with the dose and incubation time after irradiation. Thus, in contrast to the immediate manifestation of damage from x-rays, the maximum induction of the “S-like” state does not occur until about 2 hr after irradiation. The “S-like” chromosomes are capable of unscheduled DNA synthesis. We suggest that the difference in chromosome morphology found after UV- and x-irradiation underlies the reason why the former, but not the latter, induces unscheduled DNA synthesis in G1 cells.

Studies on Repair of Adenovirus 2 by Human Fibroblasts Using Normal, Xeroderma Pigmentosum, and Xeroderma Pigmentosum Heterozygous Strains

Abstract: Cell strains established from fibroblasts of 10 normal persons, 12 persons afflicted with xeroderma pigmentosum (XP), and 4 XP heterozygotes have been used as hosts in studies on the repair of ultraviolet-irradiated human adenovirus 2. The virus appeared most ultraviolet light sensitive when strains belonging to XP complementation Groups A and D were used as hosts, less sensitive when strains belonging to Groups B and C were used, and least sensitive when normal or heterozygous strains were used. One-hit inactivation of adenovirus 2 required fluences of 7 to 15, 25 to 78, and 222 J/sq m, respectively, in each of these three categories of cell strains. One XP strain, judged by other methods to be capable of normal repair, was found to have a 30% repair defect by the adenovirus repair assay.

Partial purification and characterization of four endodeoxyribonuclease activities from Escherichia coli K-12.

Abstract: Four hitherto undescribed endodeoxyribonucleases, temporarily designated A(1), A(2), A(3), and B, have been isolated from E. coli K-12. Each requires Mg(++) and is not stimulated by ATP or S-adenosylmethionine. A(3) is strongly inhibited by Fe(+++) and weakly inhibited by ATP, S-adenosylmethionine, and DPN, whereas B is inhibited by caffeine. Each can be purified free of exonuclease or DNA-3'-phosphatase. A(1) (molecular weight approximately 72,000) cleaves single-stranded, circular fd DNA to form 3'-hydroxyl termini and introduces nicks and breaks in the closed, double-stranded replicative form DNA of fd (fd RFI). A(2) (molecular weight approximately 46,000) cleaves fd DNA and introduces nicks and breaks in RFI, forming 3'-hydroxyl- and 5'-phosphoryl termini. A(3) (molecular weight approximately 38,000) cleaves fd DNA to form 3'-hydroxyl termini and introduces only nicks in fd RFI. Irradiation of the RFI with ultraviolet light markedly increases the rate of hydrolysis by A(3). B appears to form 3'-phosphoryl termini with fd DNA, but its characterization is highly preliminary due to its instability.

Possible role of DNA synthesis in formation of sister chromatid exchanges

Abstract: As there is now evidence that an eukaryote chromosome is composed of a single molecule of double-stranded DNA1,2, sister chromatid exchanges (SCEs) detectable in mitotic chromosomes of higher organisms can be regarded as a kind of recombination between two homologous DNA duplexes. The SCE formation is readily enhanced by exogenous agents such as ultraviolet light and chemical mutagens and seems to be closely related to post-replicational repair process in mammalian cells3. Precise knowledge about the time and sites of the SCE formation might help greatly to understand the mechanism underlying this phenomenon and its biological significance. Previous attempts3 to pinpoint cellular phases in which this recombination process is initiated have been hampered by the usage of 3H-thymidine which, although indispensable for the demarcation of sister chromatids, would cause strand scissions at any cellular phases.

Effect of ultraviolet light on mengovirus: formation of uracil dimers, instability and degradation of capsid, and covalent linkage of protein to viral RNA.

Abstract: UV irradiation of purified mengovirus resulted in a very rapid inactivation of the infectivity of the virions (D(37) [37% survival dose] = 700 ergs/mm(2)) which correlated in time with the formation of uracil dimers in the viral RNA. During the first 2 min of irradiation, an average of 1.7 uracil dimers were formed per PFU of virus inactivated. Hemagglutination activity of the virions began to decrease only after a lag period of about 5 min and at a much lower rate (D(37) = 84,000 ergs/mm(2)). This decrease coincided in time with the appearance of altered proteins in the capsid and a structural change in the capsid. Although 10- to 20-min irradiated virions appeared intact in the electron microscope and sedimented at 150S in sucrose density gradients, the RNA of the virions became accessible to RNase and extractable by low concentrations of sodium dodecyl sulfate, and the virions broke down upon equilibrium centrifugation in CsCl gradients. During longer periods of irradiation (30 to 60 min), a progressively greater proportion of the virions were converted to 14S protein particles and 80S ribonucleoprotein particles composed of intact viral RNA and about 30% of the capsid proteins, alpha, beta, and gamma. Empty capsids were not detectable at any time during 60 min of irradiation, by which time disruption of the virions was complete. Irradiation of complete virions also resulted in an increased sedimentation rate of the viral RNA and in the covalent linkage to the viral RNA of about 1% of the total capsid protein in the form of heterogeneous low-molecular-weight polypeptides. The two observations seem to be causally related, since irradiation of isolated viral RNA did not result in an increase in sedimentation rate of the RNA, even though uracil dimer formation in viral RNA occurred at about the same rate and to the same extent whether intact virions or viral RNA were irradiated.

Photocatalyst system and ultraviolet light curable coating compositions containing the same

Abstract: The oxygen inhibition of the photopolymerization of acrylic resins is reduced by employing a photocatalyst system containing an aromatic ketone and/or aromatic aldehyde photosensitizer having a triplet energy in the range of from about 54 kilocalories per mole to about 72 kilocalories per mole and which promotes polymerization through bimolecular photochemical reactions of the energy donor type and an aromatic ketone photoinitiator which generates a radical pair by way of unimolecular homolysis resulting from photoexcitation An exemplary photocatalyst system is benzophenone and isobutyl benzoin ether

MoO3 layers — optical properties, colour centres, and holographic recording

Abstract: The spectral variations of optical absorption and refractive index are reported for thin layers of molybdenum trioxide prepared by evaporation in vacuum. These layers can be coloured by ultraviolet light and the absorption spectra of coloured layers show a single broad absorption band centred at 850 nm. The appearance of the colour centre absorption and the associated changes in the intrinsic edge have been used to record stable ‘thin’ holograms. A short discussion is given of the electronic structure of MoO3 and of the defects responsible for coloration. Le spectre d'absorption et l'indice de refraction ont ete mesure pour les couches minces de MoO3. Les couches minces ont ete colorees par UV et le spectre d'absorption des couches minces colorees a une bande d'absorption a la longeur d'onde λ = 850 nm. Le developpement de l'absorption des centres colores et le changement pres de l'absorption fondamentale ont ete utilises pour l'enregistrement holographique.

Slow excision repair in an mfd mutant of Escherichia coli B/r.

Abstract: A mutant of Escherichia coli B/r designated mfd is very deficient in the ability to exhibit “mutation frequency decline”, the characteristic loss of potential suppressor mutations which occurs when protein synthesis is briefly inhibited after irradiation with ultraviolet light (UV). This mutant is known to excise pyrimidine dimers at an abnormally slow rate, although it is as UV-resistant as its mfd+ B/r parent strain. We have found that the mfd mutant performs the initial incision step of excision repair normally, but repairs the resulting single-strand breaks much more slowly than the mfd+ strain. We conclude that the mfd mutant performs the excision step of pyrimidine dimer excision inefficiently, but our data do not rule out the possibility that one or more subsequent steps of repair may also be slow. In spite of the slow dimer excision in the mfd mutant, single-strand DNA breaks do not accumulate during post-irradiation incubation, implying that incision and excision are well coordinated. The prolonged post-irradiation lag in cell division and DNA synthesis which accompany slow excision in the mfd strain indicates that resumption of these processes at optimal rates is linked to the timing of excision repair. The normal UV-resistance of the mfd mutant also suggests such coordination and shows that the rate of excision repair is independent of its ultimate efficiency.

The fate of pyrimidine dimers in the DNA of ultraviolet-irradiated Chinese hamster cells.

Abstract: —As an aid to understanding the relationship between dimer repair and cellular recovery, we have studied dimer removal and replication of dimer-containing DNA in Chinese hamster ovary (CHO) cells irradiated with ultraviolet light (254 nm). These investigations demonstrated that (1) dimers are not excised as polynucleotides of less than 500,000 mol. wt, (2) fractionation of the ultraviolet dose does not enhance dimer excision, (3) dimer-containing DNA is replicated in ultraviolet-irradiated CHO cells, and (4) the dimers are conserved in the replicated DNA. These findings support the proposed mechanism of bypass of photoproducts during DNA replication in mammalian cells.

Photoreactivation of sister chromatid exchanges induced by ultraviolet irradiation.

Abstract: IN contrast to the inefficiency of ionising radiations in the induction of sister chromatid exchanges (SCEs)1,2, ultraviolet lignt can cause a striking increase in the SCE frequency in mammalian chromosomes3,4. It has been shown in Chinese hamster cells that the SCE formation requires postirradiation DNA synthesis, and that a single ultraviolet irradiation can induce SCE repeatedly for several cell cycles4. As pyrimidine dimers are the major DNA lesions caused by ultraviolet light and as Chinese hamster cells have a poor ability to excise them5, the delayed formation of SCE seems to be due to unexcised pyrimidine dimers. This possibility was tested here with the use of a rat kangaroo cell line possessing a photoreactivating enzyme6–8 to see if the frequency of ultraviolet-induced SCE was actually reduced when cells were post-treated with visible light.

Segregation and recombination of non-mendelian genes in chlamydomonas

Abstract: Non-Mendelian genes in Chamydomonas reinhardtii are inherited in a uniparental (UP) fashion. Most zygotes and their progeny receive UP genes only from the mt(+) or maternal parent. However, a few exceptional zygotes are also found in which the mt(-) or paternal UP genome is transmitted. Most of the exceptional zygotes are biparental in that their progeny segregate UP genes transmitted by both parents. As a result, biparental zygotes have been extensively used to study the rules governing UP inheritance. The frequency of biparental zygotes can be greatly increased if the maternal parent is irradiated with ultraviolet light prior to mating. Based principally on studies with ultraviolet-induced biparental zygotes, Sager has argued that a vegetative cell contains two copies of the UP genome and that the progeny of a biparental zygote receive a copy derived from each parent. Results reported in this paper with spontaneous and ultraviolet-induced biparental zygotes do not support the two copy model, but argue for a mulitple copy model with most of the copies normally being transmitted by the maternal parent. A multiple copy model which accounts for both Sager's results and ours is presented.

Sedimentation of DNA from Human Fibroblasts Irradiated with Ultraviolet Light: Possible Detection of Excision Breaks in Normal and Repair-Deficient Xeroderma Pigmentosum Cells

Abstract: Usual alkaline sucrose techniques, which produce single-stranded DNA from unirradiated mammalian cells of $2-5\times 10^{8}$ daltons (120-165 S) prove inadequate for resolution of strand breaks transiently present during excision repair of ultraviolet (uv) damage. These breaks seem to be relatively few in number and sedimentation changes are at the limit of resolution. Using a simple modification employing brief lysis in alkali, DNA with sedimentation coefficients up to 350 S have been obtained from human fibroblasts. 350-S DNA from unirradiated fibroblasts consists of complementary strands cosedimenting with choline-labeled material originating in the cytoplasm, in a conformation that allows renaturation to double-stranded DNA on neutralization after gradient fractionation. Large changes in sedimentation coefficient occur immediately after irradiation of normal fibroblasts with doses as low as $5-10\ {\rm ergs}/{\rm mm}^{2}$ , but not xeroderma pigmentosum (XP) fi...

Homologous Interference Induced by Sindbis Virus

Abstract: Homologous interference during Sindbis virus infection has been investigated. Prior infection of either chicken embryo fibroblast or BHK21 cell cultures results in reduced yields of progeny virions of the superinfecting genotype. This reduction in yield results from a reduction in the number of cells in the cultures capable of producing the superinfecting genotype. The development of interference parallels the attachment kinetics of Sindbis virus. Interference requires an active viral genome since the activity is sensitive to inactivation by ultraviolet light, and an RNA− mutant, ts-24, fails to induce interference under nonpermissive conditions. However, ts-6, an RNA− mutant belonging to a different complementation group, and the RNA+ mutants, ts-2 and ts-20, interfere at both permissive and nonpermissive temperatures.

On the Mechanism of the Changes in Phenylalanine Ammonia-lyase Activity Induced by Ultraviolet and Blue Light in Gherkin Hypocotyls

Abstract: Irradiation with ultraviolet light causes in the hypocotyl of dark-grown gherkin seedlings the partial conversion of trans-hydroxycinnamic acids to the cis-isomers. The trans-hydroxycinnamic acids inhibit the development of phenylalanine ammonia-lyase activity, and the transformation of these compounds to the much less inhibitory cis-isomers forms a ready explanation for the increase in phenylalanine ammonia-lyase activity in the hypocotyl of gherkin seedlings irradiated with ultraviolet light. Arguments are advanced that the increase in phenylalanine ammonia-lyase activity caused by irradiation with blue light is also (at least in part) initiated by trans-cis isomerisation of the hydroxycinnamic acids.