Showing papers on "Ultraviolet light published in 1979"

Photoprotection by melanin—a comparison of black and Caucasian skin

Abstract: The photoprotective role of melanin was evaluated by comparing the transmission of ultraviolet (UV) radiation through skin samples of blacks and Caucasians, using both biologic and spectroscopic techniques. UVA transmission was measured using fluoranthene, which causes a phototoxic response to UVA wavelengths. UVB was measured by monitoring erythema produced by either a 150-watt xenon arc or FS-20 sunlamps. It was found that on the average, five times as much ultraviolet light (UVB and UVA) reaches the upper dermis of Caucasians as reaches that of blacks. Differences in transmission between the stratum corneum of blacks and of Caucasians were far less striking. The main site of UV filtration in Caucasians is the stratum corneum, whereas in blacks it is the malpighian layers. Melanin acts as a neutral density filter, reducing all wavelengths of light equally. The superior photoprotection of black epidermis is due not only to increased melanin content but also to other factors related to packaging and distribution of melanosomes. Not only are these data consistent with epidemiologic evidence, but they also may indicate why blacks are less disposed to phototoxic drug responses as well as less susceptible to acute and chronic actinic damage.

Metabolic suppressors of trimethoprim and ultraviolet light sensitivities of Saccharomyces cerevisiae rad6 mutants.

Abstract: Dominant mutations at two newly identified loci, designated SRS1 and SRS2, that metabolically suppress the trimethoprim sensitivity of rad6 and rad18 strains, have been isolated from trimethoprim-resistant mutants arising spontaneously in rad6-1 rad18-2 strains of the yeast Saccharomyces cerevisiae. The SRS2 mutations also efficiently suppress the ultraviolet light sensitivity of the parent strains. They do not, however, suppress their sensitivity to ionizing radiation or their deficiency with respect to induced mutagenesis and sporulation. Such observations support the hypothesis that RAD6-dependent activities can be separated into two functionally distinct groups: a group of error-free repair activities that are responsible for a large amount of the radiation resistance of wild-type strains and also for their resistance to trimethoprim, and a group of error-prone activities that are responsible for induced mutagenesis and are also important in sporulation, but which account at best for only a very small amount of wild-type recovery.

Relative contributions of diet and sunlight to vitamin D state in the elderly.

Abstract: In winter the vitamin D state of elderly people may reach levels associated with osteomalacia, although the disease may not be clinically apparent A statistical correlation was observed in a group of elderly subjects during the winter between dietary vitamin D intake and vitamin D state, but the intake was generally too low to make a biologically important contribution to maintaining vitamin D concentrations Ultraviolet light (UVL) is the primary determinant of vitamin D state in summer and winter, in winter owing to the pools of vitamin D built up during the previous summer Plasma concentrations of 25-hydroxy vitamin D (25-OHD) in winter of 150-225 nmol/l (6-9 ng/ml) require that the concentration in the previous summer was over 40 nmol/l (16 ng/ml) To maintain plasma concentrations in the elderly above those associated with osteomalacia a mean dietary vitamin D intake of over 5 microgram/day is required A more physiological approach, however, would be to increase exposure to UVL

Physicochemical properties of kevlar 49 fiber

Abstract: The high-strength, high-modulus Kevlar 49 fiber is widely used today because of its superior properties. The fundamental physicochemical nature of the commerical fiber is discussed. It is an extended chain polymer, poly(p-phenylene terephthalamide), which is highly crystalline. Extensive analysis shows that the material composition is quite consistent from lot to lot and is low in impurities. The fiber absorbs water reversibly; the extent of absorption is related to the ash content. The well-known interaction of the fiber with ultraviolet light is illustrated with spectra, and the thermal stability of the fiber is demonstrated with various thermal analysis techniques.

Functionally distinct classes of complex phosphorus compounds in lake water1

Abstract: Abstmct Complex phosphorus compounds were classified functionally according to the manner by which orthophosphate was released. Filtrable phosphorus compounds in two cutrophic lakes (East and West Twin lakes) and a humic bog (Crazy Eddie Bog) in northeastern Ohio wcrc fractionated by anion-exchange and gel-filtration chromatography. Fractions were analyzed for soluble reactive phosphorus and total dissolved phosphorus; absorbance at 400 nm was used as a measure of filtrable “yellow acids.” The cutrophic lakes contained numerous low molecular weight compounds which were resistant to low-dose ultraviolet irradiation but readily released orthophosphate upon treatment with alkaline phosphatase. Filtrable phosphorus compounds of the humic bog were predominantly high molecular weight, cochromatographed with the yellow acids in each fractionation procedure, and resisted enzyme hydrolysis, but released orthophosphate upon irradiation with low doses of ultraviolet light.

Papulacandin B: an inhibitor of glucan synthesis in yeast spheroplasts.

Abstract: Papulacandin B, the main component of a series of antibiotics produced by the deuteromycete Papularia sphaerosperma, inhibits the growth of yeasts. It is a highly amphophilic substance containing residues of glucose, galactose and two long-chain unsaturated fatty acids. It does not cause the release of potassium ions from yeast cells and therefore differs in its mode of action from the polyene antibiotics. Papulacandin B, at concentrations slightly below the minimal inhibitory concentration, partially but selectively inhibited the incorporation of glucose into cells of Saccharomyces cerevisiae and Candida albicans. A much clearer effect was observed on spheroplasts, obtained by digestion of the yeast cell wall with snail digestive enzyme. Incubation of spheroplasts in a minimal medium stabilised by sorbitol led to the incorporation of glucose into alkali-insoluble glucan, mannan and a fraction containing mainly alkali-soluble 1,3-glucan together with some glycogen. Papulacandin B inhibited the synthesis of the alkali-insoluble fraction, while causing a slight stimulation of glucose incorporation into the other two polysaccharide fractions. The 50% inhibitory concentrations of papulacandin B for glucan synthesis in S. cerevisiae spheroplasts and C. albicans spheroplasts were respectively 0.16 μg/ml and 0.03 μg/ml. C. albicans cells were irradiated with ultraviolet light and selected for maximum resistance to papulacandin B. The 50% inhibitory concentration for glucan synthesis in spheroplasts prepared from this mutant was 2.5 μg/ml. Echinocandin B, a polypeptide antibiotic containing a long-chain fatty acid, also inhibited the synthesis of glucan in spheroplasts. It is concluded that papulacandin B and probably also echinocandin B inhibit glucan synthesis during cell-wall synthesis, and thus cause lysis of cells by osmotic rupture.

Age-related Decrease of Ultraviolet Light-induced DNA Repair Synthesis in Human Peripheral Leukocytes

Abstract: The capacity for ultraviolet light-induced DNA repair synthesis, studied in peripheral leukocytes from 58 healthy subjects 13 to 94 years old, was found to vary greatly between individuals. A negative, statistically significant correlation was obtained between age and this synthesis, indicating a decrease in repair capacity with age. An age-related decrease in DNA repair may increase the susceptibility of cells to agents causing DNA damage, i.e. , carcinogens and certain cytostatic drugs.

Abnormal Kinetics of DNA Synthesis in Ultraviolet Light-irradiated Cells from Patients with Cockayne's Syndrome

Abstract: Cells from patients with the hereditary disorder Cockayne's syndrome and from the sun-sensitive individual, 11961, are sensitive to the lethal effects of ultraviolet light (UV) but have no detectable defect in either excision- or postreplication repair after UV irradiation. In normal cells and in Cockayne heterozygotes, UV causes a depression in the rate of DNA-replicative synthesis followed by a recovery of normal rates 5 to 8 hr after irradiation. In Cockayne and 11961 cells, the initial depression in DNA synthesis is the same as that in normal cells, but no subsequent recovery is observed. The recovery of DNA synthesis in normal cells appears to be unaffected by fluorodeoxyuridine but inhibited by cycloheximide. This suggests a possible requirement for de novo protein synthesis, but there are a number of alternative interpretations of these data.

Ultraviolet light-induced crosslinking of mRNA to proteins

Abstract: Irradiation of intact or EDTA-dissociated L-cell polyribosomes with 254 nm UV light at doses of 1-2 x 10(5) ergs/mm2 extensively crosslinks mRNA to proteins. The crosslinked mRNA-protein complexes can be isolated on the basis of buoyant density in urea-containing CS2SO4 gradients that dissociate non-covalent complexes. Crosslinking of mRNA can also be assayed by phenolchloroform extraction. mRNA recovered from the crosslinked complexes by digestion with proteinase K has the same electrophoretic mobility in polyacrylamide gels as unirradiated mRNA. Therefore, irradiation does not either crosslink RNA molecules to RNA molecules or break phosphodiester bonds. With these methods it has been found that more than 70% of high molecular weight polydisperse mRNA, but only 25-40% of histone mRNA, can be crosslinked to protein. On the basis of buoyant density the histone mRNA-protein complex had a protein content of 26%, whereas the mean protein content of most non-histone mRNA-protein complexes was 65%. It is concluded that most mRNA in polyribosomes is in close contact with proteins, and that histone mRNA can be crosslinked to many fewer proteins that most other mRNAs.

Induction of mouse epidermal ornithine decarboxylase activity and DNA synthesis by ultraviolet light.

Abstract: Irradiation of hairless mice with ultraviolet light of mainly the sunburn region [region of ultraviolet light with a wavelength of 290 to 320 nm (UVB)] resulted in a dramatic increase in epidermal ornithine decarboxylase activity. A significant increase in enzyme activity was observed as early as 2 hr following UVB exposure. Maximum activity, about 250- to 350-fold above basal level, occurred at about 28 hr and, thereafter, ornithine decarboxylase activity declined steadily but had not returned to the original level even at 48 hr after UVB irradiation. UVB treatment also led to an increased activity of S -adenosyl-l-methionine decarboxylase, a second enzyme in the pathway of polyamine biosynthesis. Enzyme activity was increased at about 6 hr and remained elevated at 48 hr after exposure to UVB. UVB-induced epidermal ornithine decarboxylase activity was depressed by treatment of mice either with cycloheximide, an inhibitor of protein synthesis, or with 5-azacytidine, an inhibitor of RNA synthesis. The half-life of UVB-induced ornithine decarboxylase was found to be about 24 min as determined by the decline of enzyme activity after cycloheximide treatment. Incorporation of tritiated thymidine into epidermal DNA was initially depressed, and a 4-fold increase at 48 hr after UVB exposure was observed. Histological examination of UVB-treated skin revealed epidermal thickening by 48 hr. These studies show that irradiation with UVB, the most carcinogenic region of ultraviolet light, induces mouse epidermal ornithine decarboxylase activity, and the elevated enzyme activity precedes increased epidermal DNA synthesis.

Isolation and characterization of a mutant mouse lymphoma cell sensitive to methyl methanesulfonate and X rays

Abstract: A methyl methanesulfonate-sensitive strain has been isolated from L5178Y mouse lymphoma cells. This mutant, M10, is more sensitive to killing by X rays than the parent wild-type strain. This sensitivity to the alkylating agent and ionizing radiation has not changed for 11 months since the isolation of the mutant. The plating efficiency, doubling time, and sensitivity to ultraviolet light of M10 cells are not appreciably different from those of the wild-type cells.

Postreplication repair: questions of its definition and possible alteration in xeroderma pigmentosum cell strains

Abstract: DNA synthesis in normal cells and in excision-defective and variant xeroderma pigmentosum cells was investigated after irradiation with ultraviolet light. The sizes of DNA synthesized during brief pulses of [3H]thymidine 1-2 hr after irradiation were decreased, the xeroderma pigmentosum variant showing the smallest molecular weight. Once synthesized, however, labeled DNA increased in size at the same rat as control in all cell strains, and the rate was relatively insensitive to caffeine. After 2-3 hr, labeled DNA in each cell type reached a maximum size that was less than that in control cells, indicating the presence of long-lived blocks to DNA chain growth. This kind of experiment (pulse-chase) has in the past been used to investigate a repair process believed to be associated with the bypass of damaged sites in parental DNA: postreplication repair. We present an alternative model that does not involve a specific postreplication repair mechanism, but involve a specific postreplication repair mechanism, but involves normal chain elongation and termination mechanisms in which we conceive that dimers and other damaged sites act as well-or-nothing blocks to the progress of replication forks. No evidence could be found for any inducible process that enhanced the bypass of damaged sites.

Purification of water through the use of ozone and ultraviolet light

Abstract: Water may be treated so as to oxidize organic contaminants and so as to kill microbiological contaminants through the utilization of ultraviolet light and ozone so as to obtain some residual ozone in the water treated by passing a mixture of water and air or air and ozone through a nozzle which concurrently compresses the mixture and breaks up any gas bubbles within the mixture into what may be loosely referred to as a radiation housing or chamber. The housing is a hollow, cylindrical chamber located around an elongated tubular lamp for producing actinic light such as ultraviolet light. The mixture is introduced into this chamber in a substantially tangential manner so as to swirl around the interior chamber in passing from the inlet of the chamber where the nozzle is located to the outlet of the chamber at the other end of the chamber.

Inhibition of ultraviolet light-induced erythema by antioxidants

Abstract: In spite of numerous papers devoted to the erythema produced by UV irradiation [1, 15], the photochemical basis of this phenomenon is still an open question. It is not even known whether the erythemogenic photochemical process is an oxidative reaction or relates to some other type of phototransformations. Under UV irradiation photoperoxidation of the chains of unsaturated fatty acids is induced in the skin and in the surface lipids [3, 5, 6, 11, 16]. The opinion, based on this fact, was put forward that UV-induced erythema is caused by photoperoxidation of lipids [3]. Lipid photoperoxidation in the membrane structures of cells [8, 10, 14] and some other photoxidation reactions of biomolecules [7, 8] are inhibited by antioxidants. Therefore, one of the possible approaches to the elucidation of the photoxidation role in the UV-induced erythema may be the study of antioxidants' action. Recently, De Rios et al. [2] have found out in experiments with albino hairless mice that the antioxidant BHT (2,6di-t-butyl-4-methyl phenol), when administered systemically or topically applied before the exposure to UV radiation, reduced its erythemic action considerably. However, the connection of this antioxidant effect with possible inhibition of photoxidation reactions remains obscure. In the present paper the effect of antioxidants c~-tocopherol, BHT, and phospholipid phosphatidylcholine (which readily undergoes photoperoxidation under UV irradiation [14]) on the UV lightmediated erythema of rabbit skin was studied. D,L-c~-Tocopherol and c~-tocopheryl acetate prepared by synthesis, were a gift of Dr. I. K. Sarytcheva of Moscow Institute of Fine Chemical Technology. Commercial BHT was three times recrystallized from hot ethanol. Phosphatidylcholine was isolated from hen's-egg yolk by thin-layer chromatography on silica gel [12]. The samples of phosphatidylcholine used were stored not longer than 72 h under argon at 1 0 ~ C.

Ultraviolet light induction of diphtheria toxin-resistant mutants of normal and xeroderma pigmentosum human fibroblasts

Abstract: The UV induction of diphtheria toxin-resistant (DTr) mutants in normal and xeroderma pigmentosum human fibroblasts has been quantitatively characterized. A concentration of diphtheria toxin at which DTr cells are cross-resistant to Pseudomonas aeruginosa exotoxin A was determined and used in the selection of resistant mutants. Recovery of mutants was not influenced by the presence of wild-type cell densities of 1-8 x 10(5) per 9-cm plate, indicating no metabolic cooperation exists, in contrast to what is seen in the selection of some other variant phenotypes. Expression periods for UV-induced mutations differed with the severity of mutagen treatment and cell strain used. A relatively long (10-15 days after UV treatment) expression period was required for the maximum recovery of DTr mutants. Maximum recovery was followed by a decrease in mutation frequency on subsequent days evaluated. An apparent linear dose response within the dose range used was observed for UV-induced mutations in both normal and xeroderma pigmentosum fibroblasts. Our results indicate that xeroderma pigmentosum fibroblasts have higher UV-induced mutation frequencies per unit UV dose but similar frequencies per unit survival compared to normal cells within the range of UV doses tested.

Ultraviolet-mediated cytotoxic activity of phenylheptatriyne from Bidens pilosa L.

Abstract: The tropical weed Bidens pilosa L. (Asteraceae) contains a number of polyacetylenes which are phototoxic to bacteria, fungi, and human fibroblast cells in the presence of sunlight, artificial sources of long-wave ultraviolet light, or cool-white fluorescent light. The principle photoactive compound in the leaf, phenylheptatriyne, is present in the cuticle as well as in the underlying cells. Experiments with calf thymus DNA indicate that, unlike photoactive furanocoumarins, phenylheptatriyne does not form interstrand cross linkages with DNA in ultraviolet light.

Ultraviolet mutagenesis of normal and xeroderma pigmentosum variant human fibroblasts

Abstract: The mutabilities of normal and xeroderma pigmentosum variant (XP4BE) human fibroblasts by ultraviolet light (UV) were compared under conditions of maximum expression of the 6-thioguanine resistance (TGr) phenotype. Selection was with 20 μg TG/ml on populations reseeded at various times after irradiation. Approx. 6–12 days (4–8 population doublings), depending on the UV dose, were necessary for complete expression. The induced mutation frequencies were linear functions of the UV dose but the slope of the line for normal cells extrapolated to zero induced mutants at 3 J/m2. The postreplication repair-defective XP4BE cells showed a higher frequency of TGr colonies than normal fibroblasts when compared at equal UV doses or at equitoxic treatments. The induced frequency of TGr colonies was not a linear function of the logarithm of survival for either cell type. Instead, the initial slope decreased to a constant slope for survivals less than about 50%. The UV doses and induced mutation frequencies corresponding to 37% survival of cloning abilities were 6.7 J/m2 and 6.2 × 10−5, respectively, for normal cells and 3.75 J/m2 and 17.3 × 10−5 for the XP4BE cells. The lack of an observable increase in the mutant frequency for normal fibroblasts exposed to slightly lethal UV doses suggests that normal postreplication repair of UV-induced lesions is error-free (or nearly so) until a threshold dose is exceeded.

Method for mounting parts on circuit boards

Abstract: One or more parts having terminals can be mounted on a circuit board by coating an ultraviolet-curing and thermosetting resin composition comprising an ultraviolet-curing resin, an addition polymerizable monomer, a photosensitizer and a heat polymerization initiator, on the circuit board by screen printing with a prescribed pattern, mounting the parts on the printed resin composition, curing the resin composition by simultaneous irradiation of ultraviolet light and heat rays so as to bond the parts to the circuit board, and soldering the parts onto the circuit board.

Ultraviolet phototherapy of uremic pruritus.

Abstract: Repeated exposure to mid-range ultraviolet light (UVB) can dramatically relieve the pruritus associated with uremia. The efficacy of UVB phototherapy in uremic pruritus has been established in a controlled trial; experience with 38 patients suggests that 80 to 90% of those receiving 6 to 8 exposures respond favorably within the treatment period (2 to 5 weeks). Treatment frequency appears not to influence the remission rate, although patients on more intensive schedules experience relief sooner than those treated once weekly. Remissions are long-lasting in many patients, sometimes longer than 2 years. Patients with recurrent pruritus respond to phototherapy at least as well as previously untreated patients and tend to improve more rapidly. UVB phototherapy appears to exert its beneficial effect systemically rather than locally, but its mechanism of action is otherwise unknown.

Recovery of DNA synthesis after ultraviolet irradiation of xeroderma pigmentosum cells depends on excision repair and is blocked by caffeine

Abstract: Normal human and xeroderma pigmentosum (XP, excision-defective group A) cells (both SV40-transformed) pulse-labeled with [(3)H]thymidine at various times after irradiation with ultraviolet light showed a decline and recovery of both the molecular weights of newly synthesized DNA and the rates of synthesis per cell. At the same ultraviolet dose, both molecular weights and rates of synthesis were inhibited more in XP than in normal cells. This indicates that excision repair plays a role in minimizing the inhibition of chain growth, possibly by excision of dimers ahead of the growing point. The ability to synthesize normal-sized DNA recovered more rapidly than rates of synthesis in normal cells, but both parameters recovered in phase in XP cells. During recovery in normal cells there are therefore fewer actively replicating clusters of replicons because the single-strand breaks involved in the excision of dimers inhibit replicon initiation. XP cells have few excision repair events and therefore fewer breaks to interfere with initiation, but chain growth is blocked by unexcised dimers. In both cell types recovery of the ability to synthesize normal-sized DNA was prevented by growing cells in caffeine after irradiation, possibly because of competition between the DNA binding properties of caffeine and replication proteins. Our observations imply that excision repair and semiconservative replication interact strongly in irradiated cells to produce a complex spectrum of changes in DNA replication which may be confused with parts of alternative systems such as post-replication repair.