Showing papers on "Ultraviolet light published in 1985"

Rapid transfer of DNA from agarose gels to nylon membranes.

Abstract: The unique properties of nylon membranes allow for dramatic improvement in the capillary transfer of DNA restriction fragments from agarose gels (Southern blotting). By using 0.4 M NaOH as the transfer solvent following a short pre-treatment of the gel in acid, DNA is depurinated during transfer. Fragments of all sizes are eluted and retained quantitatively by the membrane; furthermore, the alkaline solvent induces covalent fixation of DNA to the membrane. The saving in time and materials afforded by this simple modification is accompanied by a marked improvement in resolution and a ten-fold increase in sensitivity of subsequent hybridization analyses. In addition, we have found that nylon membrane completely retains native (and denatured) DNA in transfer solvents of low ionic strength (including distilled water), although quantitative elution of DNA from the gel is limited to fragments smaller than 4 Kb. This property can be utilized in the direct electrophoretic transfer of native restriction fragments from polyacrylamide gels. Exposure of DNA to ultraviolet light, either in the gel or following transfer to nylon membrane, reduces its ability to hybridize.

High-frequency switching of colony morphology in Candida albicans

Abstract: The pathogenic yeast Candida albicans switches heritably and at high frequency between at least seven general phenotypes identified by colony morphology on agar. Spontaneous conversion from the original smooth to variant phenotypes (star, ring, irregular wrinkle, hat, stipple, and fuzzy) occurs at a combined frequency of 1.4 X 10(-4), but is increased 200 times by a low dose of ultraviolet light that kills less than 10 percent of the cells. After the initial conversion, cells switch spontaneously to other phenotypes at a combined frequency of 2 X 10(-2). Switching is therefore heritable, but also reversible at high frequency. The genetic basis of this newly discovered process and its possible role in Candida pathogenesis are considered.

Method for impressing grating within fiber optics.

Abstract: A method of establishing a dielectric periodic index of refraction phase grating (16) upon the core (19) of an optical waveguide (15) by intense angled application of several tranverse beams (99) of ultraviolet light, enabling the establishment of a distributed, spatially resolving optical fiber strain gauge (13).

Guidance of neurite outgrowth by pathways of substratum-adsorbed laminin.

Abstract: Neurite outgrowth is guided by narrow pathways of bioactive laminin. These pathways are created by ultraviolet light irradiation of laminin-coated coverslips masked with electron microscope grids. Patterned outgrowth of neurites is independent of gross mechanical guidance and guidance caused by substrate limitation. Cells on unirradiated laminin are less readily displaced by shear forces than cells on irradiated laminin. This study suggests that ultraviolet light alters the adhesive properties of laminin and that differential cell-substratum adhesion may guide extending neurites on the purified naturally occurring substance, laminin.

Photoelectric enhanced plasma glow discharge system and method including radiation means

Abstract: Plasma enhancement is achieved in a plasma glow system by increasing the number of photoelectric electrons in the plasma glow by producing photoelectrons from the surface of a target in the system by the use of a radiation source. This is more particularly accomplished by flooding the surface of the target with a UV laser beam during the plasma process where emitted photoelectrons are injected into the plasma to increase the plasma density. The plasma enhancement is used in a sputter etching/deposition system which includes a chamber containing a cathode, a target, a substrate platform containing substrate and a pump. An ultraviolet light source such as a UV laser and focussing optics for focussing the UV radiation onto the target through a UV transmission window are also provided. A plasma region in the chamber is enhanced by photons from the laser striking the target and producing photoelectrons which are injected into the plasma to increase its density.

Ultraviolet light-induced yellowing of dental restorative resins.

Abstract: 6. Craig RG: Restorative Dental Materials, ed 6. St. Louis, 1980, The CV Mosby Co. Council on Dental Materials and Devices: Revised American Dental Association specification No. 19 for non-aqueous, elastomeric dental impression materials. J Am Dent Assoc 94:733, 1977. Webber RL, Ryge G: The determination of tear energy of extensible materials of dental interest. J Biomed Mater Res 2:281, 1968. Keck SC, Douglas WH: Tear energy of non-aqueous impression materials. J Dent Res 63:155, 1984. Yeh CL, Powers JM, Craig RG: Properties of addition-type silicone impression materials. J Am Dent Assoc 101:482, 1980.

Formation and repair of DNA interstrand cross-links in relation to cytotoxicity and unscheduled DNA synthesis induced in control and mutant human cells treated with cis-diamminedichloroplatinum(II).

Abstract: A comparative study was performed with a variety of human cell lines on the effects of treatments with cis -diamminedichloroplatinum(II) (cisplatin) on cell survival and the induction of unscheduled DNA synthesis. In addition to control fibroblasts (Han, MB), cell lines defective in DNA repair were used [xeroderma pigmentosum, XP(A) and XP(F), and Fanconi9s anemia (FA)], as well as cells deficient in arylsulfatase A (mucolipidosis II, ML1 and ML2). Ultraviolet light and mitomycin C were included in this study as model DNA-damaging agents. Furthermore, induction of DNA interstrand cross-links by cisplatin and their repair were studied. As for survival, only XP cells were abnormally sensitive to ultraviolet light, and only FA cells were abnormally sensitive to mitomycin C. To cisplatin, however, all mutants tested were more sensitive (2 to 5 times) than were normal cells. Unscheduled DNA synthesis induction by ultraviolet light was strong in all but the XP cells; the other two agents did not induce unscheduled DNA synthesis. Induction of DNA interstrand cross-links by cisplatin was linear with dose. Formation continued for up to 18 to 24 h after treatment. During this period, all cells but the ML mutants responded similarly. In ML cells, much fewer cross-links were induced, which were repaired rapidly. In FA cells, accumulation continued for at least 96 h; in the other cells, most of the cross-links had been removed after that period. In the discussion, the cisplatin-induced DNA interstrand cross-links are proposed as an important potentially lethal lesion, in view of their persistence in the highly sensitive FA cells. Furthermore, the possible involvement of certain steps of the long-patch excision repair pathway in the removal of this lesion is considered. The sensitivity of ML cells to cisplatin is attributed to cytoplasmic effects, rather than to chromosomal damage.

Sodium arsenite enhances the cytotoxicity, clastogenicity, and 6-thioguanine-resistant mutagenicity of ultraviolet light in Chinese hamster ovary cells

Abstract: Cytotoxicity, chromosome aberrations, and mutations to 6-thioguanine resistance were synergistically increased by incubating the ultraviolet light (UV)-irradiated Chinese hamster ovary (CHO) cells in medium containing sodium arsenite. However, the frequencies of sister-chromatid exchanges and mutations to ouabain resistance induced by UV were not synergistically increased by sodium arsenite. The synergistic effect of sodium arsenite on UV-induced chromosome aberrations varied with cell-harvesting time and decreased with increasing time intervals between UV and sodium arsenite treatments.

A possible mechanism of psoralen phototoxicity not involving direct interaction with DNA

Abstract: Psoralens in combination with ultraviolet light (UVA; 320-400 nm) are used in the photochemical treatment of a variety of skin diseases including vitiligo, a skin depigmentational disorder, and psoriasis, a disease of accelerated epidermal cell proliferation. Although it is generally assumed that the major site of action of the psoralens is DNA, we have obtained evidence that another site may be the primary target for these compounds. We have identified specific, saturable, high-affinity binding sites for 8-methoxypsoralen on HeLa cells and have detected specific binding of 8-methoxypsoralen to four other human cell lines and five mouse cell lines. In HeLa cells, specific binding is reversible and independent of the ability of the compound to intercalate into DNA. In addition, binding sites become covalently modified by the psoralen after UVA exposure. Specific binding of 8-[methoxy-3H]methoxypsoralen constitutes 79% of the label bound to the cells. Scatchard analysis indicated two classes of psoralen binding sites: high-affinity sites with a Kd of 19 X 10(-9) M (1.8 X 10(5) sites per cell) and low-affinity sites with a Kd of 4 X 10(-6) M (7.1 X 10(6) sites per cell). Four structurally related psoralen analogs block 8-methoxypsoralen binding in a manner that parallels their biological activity. Based on these findings, we hypothesize that specific binding sites for psoralens on mammalian cells mediate, at least in part, psoralen-induced phototoxicity.

Photochemical aspects of tropospheric iodine behaviour

Abstract: The I-atom sensitised decomposition of ozone in air at 1 atm pressure and ambient temperature has been investigated. Iodine atoms were produced by photolysis of I2 using visible light or of CH3I using ultraviolet light. In both cases, the quantum yield for O3 decomposition was 1.25 (±0.11) per I atom. An important role is proposed for the self-reaction of IO radicals leading to higher oxides of iodine, IO+IO(+M)→I2O2(+M)→higher oxides, which predominated over the bimolecular reaction leading to regeneration of I atoms, IO+IO→2I+O2, with k 2a/k 2b≥4. Simple computer modelling calculations indicate that reaction (2a) may be important in determining the fate of photolabile iodine species in the atmosphere. The consequences for the behaviour of radioiodine releases are also discussed.

Ultraviolet light-induced crosslinking reveals a unique region of local tertiary structure in potato spindle tuber viroid and HeLa 5S RNA

Abstract: The positions of intramolecular crosslinks induced by irradiation with ultraviolet light were mapped into potato spindle tuber viroid RNA and HeLa 5S rRNA. Crosslinking in each of these molecules occurred at a single major site, which was located by RNA fingerprinting and secondary analysis (and additional primer extension studies in the case of the viroid). Various lines of evidence suggest that these crosslinks identify a previously undescribed element of local tertiary structure common to these two widely divergent RNA molecules: (i) both crosslinks occur in an identical eight-base context, with the sequence 5' GGGAA 3' on one side and the sequence 5' UAC 3' on the other; (ii) both crosslinks connect bases that are not thought to be involved in conventional hydrogen bonding, within regions usually depicted as single-stranded loops flanked by short helical segments; and (iii) both crosslinks connect a purine and a pyrimidine residue, and both may generate the same G-U dimer. Furthermore, it is likely that the crosslinking site is of functional significance because it is located within the most highly conserved region of the viroid sequence and involves bases that are essentially invariant among eukaryotic 5S rRNA molecules.

Effect of hematoporphyrin derivative and photodynamic therapy on atherosclerotic rabbits

Abstract: This study was performed to demonstrate selective uptake of hematoporphyrin derivative (HPD) within actively developing atheroma, to localize the site of uptake of HPD within the atheroma, and to determine the potential for photodynamic therapy (PDT) of atherosclerosis in the rabbit model. Fifteen rabbits were rendered atherosclerotic. Five rabbits received neither HPD nor PDT and 2 rabbits received HPD, 10 mg/kg intravenously, without subsequent irradiation. Eight other rabbits received 5 to 20 mg of HPD intravenously and subsequent intravascular 636-nm laser radiation to either the thoracic aorta or the aortic arch. A total of 32 to 288 J of laser energy was delivered through a 300-μ quartz fiber. All rabbits that received in vivo HPD had red fluorescence of their aortas when placed under ultraviolet light. The pattern of fluorescence corresponded precisely to the pattern of atheroma. In segments that received PDT, light microscopic examination revealed an accumulation of smooth muscle cells at the intimal surface. Fluorescence microscopy revealed a diminishing concentration gradient of HPD from intimal surface layers towards the media. Assessment of treated thoracic aortic segments revealed quantitative and qualitative differences compared with control segments. In the arch-treated segments, however, no changes were seen. It is concluded that HPD localizes within rabbit atheroma, can be detected by fluorescence and is deposited in a diminishing concentration gradient from lumen toward media. Irradiation with 636-nm light may induce qualitative and quantitative changes in atheroma.

Preparation of inactivated viral vaccines

Abstract: Vaccines employing inactivated viruses having improved retention of antigenic characteristics are prepared by psoralen-inactivation of the live virus in a non-oxidizing atmosphere. By excluding oxygen and other oxidizing species from the inactivation medium, degradation of the antigen characteristics resulting from irradiation with ultraviolet light is largely prevented. The resulting inactivated viruses are employed in vaccine preparations for the inoculation of susceptible hosts to inhibit viral infection.

Cyclobutane pyrimidine dimers and (6-4) photoproducts block polymerization by DNA polymerase I.

Abstract: Bipyrimidine cyclobutane dimers and 6-4'-(pyrimidin-2'-one)-pyrimidine photoproducts are the major adducts formed in DNA following exposure to ultraviolet light. The relationship between the type and frequency of UV-induced DNA damage and the effects of such damage on DNA replication were investigated. UV-irradiated M13 phage DNA was employed in polymerization reactions with the Kenow fragment of Escherichia coli DNA polymerase I. The locations and frequencies of polymerase termination events occurring within a defined sequence of M13 DNA were compared with measurements of the locations and frequencies of UV-induced DNA damage of the same DNA sequence by using UV-specific enzymatic and chemical methods. The results indicate that both cyclobutane dimers and (6-4) photoproducts quantitatively block polymerization by DNA polymerase I.

In vitro phosphorylation of NS protein by the L protein of vesicular stomatitis virus.

Abstract: Summary The structural proteins L and NS of vesicular stomatitis virus were obtained from purified viral ribonucleoprotein complex followed by phosphocellulose column chromatography and assayed for protein kinase activity using [γ-32P]ATP as the phosphate donor. The fractions containing purified L protein phosphorylated NS protein in vitro. 8-Azido-ATP, a photoreactive analogue of ATP, was also used as the phosphate donor for phosphorylation of NS protein by the L protein. In the presence of ultraviolet light, only L protein was specifically cross-linked with 8-azido-[γ-32P]ATP. In the absence of u.v. light 8-azido ATP did no inhibit RNA transcription in a reconstituted reaction or substitute ATP for RNA synthesis in vitro. The above results, taken together, suggest that 8-azido-ATP was bound to the kinase site and phosphorylation of NS protein was mediated by th L protein. Exogenous phosphate acceptor proteins such as phosvitin and casein were also phosphorylated by the L protein fraction. However, addition of an excess of phosvitin failed to compete with the phosphorylation of NS by L, indicating that the protein kinase activity possessed higher affinity for NS. The phosphorylation of NS was strongly inhibited by photoreaction of L protein with 8-azido-ATP with concomitant inhibition of transcription in vitro. These results suggest that phosphorylation of NS protein by L may have a role in the regulation of the virus genome transcription in vitro.

The lacI shuttle: rapid analysis of the mutagenic specificity of ultraviolet light in human cells

Abstract: A system has been devised that allows the effect of mutagens acting in human cells to be readily analyzed at the DNA sequence level. The bacterial gene lacI, carried on a shuttle vector, is introduced into human tissue culture cells by transfection and allowed to replicate in the cell nucleus. Twenty-four to 48 hr after transfection, the cells are exposed to a mutagen. After 1-2 days of further replication, vector DNA is purified and transfected back into Escherichia coli for scoring and analysis of mutations in lacI. The nucleotide sequence changes for 53 UV light-induced mutations have been deduced in this way. Most of the mutations are transitions and occur at pyrimidine-pyrimidine sequences. The mutagenic specificity observed closely resembles that of UV light in E. coli, suggesting that human and bacterial cells respond similarly to damage from UV light. Use of the lacI shuttle in this way should permit determination of the mutagenic specificity of a wide range of mutagens and carcinogens in human cells.

Selective absorption of ultraviolet laser energy by human atherosclerotic plaque treated with tetracycline

Abstract: Tetracycline is an antibiotic that absorbs ultraviolet light at 355 nm and preferentially binds to atherosclerotic plaque both in vitro and in vivo. Tetracycline-treated human cadaveric aorta was compared with untreated aorta using several techniques: absorptive spectrophotometry, which demonstrated a distinct absorptive peak at 355 nm in tetracycline-treated plaque that was absent in treated normal vessel; ultraviolet microscopy, which showed that treated atheroma acquired the characteristic fluorescence of tetracycline under ultraviolet light; and tissue uptake of radiolabeled tetracycline, which showed 4-fold greater uptake by atheroma than by normal vessel. In addition, intravenous tetracycline administered to patients undergoing vascular surgery demonstrated characteristic fluorescence in surgically excised diseased arteries. Because of tetracycline's unique properties, we exposed tetracycline-treated and untreated aorta to ultraviolet laser radiation at a wavelength of 355 nm. We found enhanced ablation of tetracycline-treated atheroma compared with untreated atheroma. The plaque ablation caused by ultraviolet laser radiation was twice as extensive in tetracycline-treated vs nontreated plaque (2.2 ± 0.25 mm vs 1.3 ± 0.55 mm, p

Structural determination of the ultraviolet light-induced thymine-cytosine pyrimidine-pyrimidone (6-4) photoproduct.

Abstract: Ultraviolet light induces damage to DNA, with the majority of the damage expressed as the formation of cyclobutane dimers and pyrimidine-pyrimidone (6-4) photoproducts. The (6-4) photoproducts have been implicated as important UV light-induced premutagenic DNA lesions. The most abundant of the (6-4) products is the thymine-cytosine pyrimidine-pyrimidone (6-4) photoproduct, or TC (6-4) product. The structure of the TC (6-4) product was deduced by proton NMR, IR, and fast atom bombardment mass spectroscopy, and the product was found to differ from the previously described photoadduct, Thy(6-4)Pyo, by the presence of an amino group at the 5 position of the 5' pyrimidine. The implications of this structure on DNA base pairing and the induction of ultraviolet light-induced mutations are discussed.

Multiple cancers. Tumor burden permits the outgrowth of other cancers.

Abstract: We demonstrate that tumor-bearing hosts permit the outgrowth of "potentially malignant" cells that are located at a different site. These second cancers continued to grow and kill their hosts even though they retain the "premalignant" phenotype, even after removal of the original malignancy. The potentially malignant cells used in these experiments were ultraviolet light- or methylcholanthrene-induced regressor tumor cells that are rejected regularly by normal mice at any testable dose, and only form progressive tumors in immunosuppressed individuals. The immunological rejection of these highly immunogenic, potentially malignant cells was suppressed by Thy-1+, Ly-2-, nonadherent, radio-sensitive suppressor cells in the tumor-bearing mice. These suppressor cells were absent in nude tumor-bearing mice. Unlike helper and cytolytic T cell-mediated responses, which are exquisitely tumor specific, the suppression caused by a progressively growing tumor was crossreactive among many syngeneic, independently derived tumors induced by different carcinogens. However, T cell-mediated immune responses to alloantigens, allogeneic tumors, certain syngeneic tumors, and humoral responses to xenogeneic red blood cells were normal in these mice. The immune suppression in the tumor-bearing animals closely simulated that induced by ultraviolet light irradiation, and both types of suppression might therefore share common mechanisms. Our findings may contribute to understanding the growth, development, and possible control of multicentric malignancies and add a precaution to the potential use of strongly immunogenic tumor variants for active immunotherapy in hosts bearing less immunogenic tumors.

Filter apparatus for use with an x-ray source

Abstract: Filter apparatus for use in x-ray equipment including a repetitively pulsed x-ray source, a window for transmitting x-rays generated by the source to an object to be irradiated, and a vacuum chamber containing the x-ray source and the filter apparatus. The filter apparatus includes a baffle for diffusing hot gases and directing them away from the window. The filter apparatus further includes an ultraviolet light absorber which overlies the window with respect to the x-ray source whereby undesirable components generated with the x-rays by the x-ray source are substantially eliminated prior to reaching the window. Also disclosed is a method of eliminating undesirable by-products of x-ray generation.

Polyhalogenated hydrocarbon refrigerants and refrigerant oils colored with fluorescent dyes and method for their use as leak detectors

Abstract: A leak detectable refrigeration composition including a polyhalogenated hydrocarbon refrigerant, a refrigeration oil, or a mixture of the two having a fluorescent dye dissolved therein, is prepared for use in refrigeration systems in automobile air conditioning systems, commercial refrigeration systems, and the like. Upon exposure to ultraviolet light, there is sufficient fluoresence by the refrigeration liquid to allow one to visually detect a leak in the system due to the presence of the dye at the source of the leak. Small leaks which were previously nondetectable with dye coloring systems detectable in normal light may now be detected due to the greater visibility of the flourescent dye under an ultraviolet light.

Stabilizer compositions for synthetic resins imparting improved light stability

Abstract: Stabilizer compositions for synthetic resins are provided, improving the resistance of the resin to deterioration when exposed to ultraviolet light, comprising a 2,2,6,6-tetramethylpiperidyl compound and an alkylidene-bis-(benzotriazolyl phenol) having the formula: ##STR1## wherein: R 1 is hydrogen or alkyl having from one to about twelve carbon atoms; R 2 is alkyl having from one to about twelve carbon atoms or arylalkyl having from seven to about sixteen carbon atoms; X is selected from the group consisting of hydrogen, halogen, alkyl having from one to about twelve carbon atoms, aryl having from six to ten carbon atoms, arylalkyl having from seven to about sixteen carbon atoms, alkoxy having from one to about twelve carbon atoms, aryloxy having from six to ten carbon atoms; and arylalkoxy having from seven to about sixteen carbon atoms; as well as synthetic resin compositions containing such stabilizers.

Photochemical generation and deposition of copper from a gas phase precursor

Abstract: The photochemical generation and deposition of copper metal from a volatile copper coordination complex are described. Pulsed and cw ultraviolet light sources were used to induce deposition. The chemical compositions of the films are compared for all methods.