PHOTOREACTIVATION OF ICR 2A FROG CELLS EXPOSED TO SOLAR UV WAVELENGTHS

Abstract Exposure of ICR 2A frog cells to photoreactivating light (PRL) following irradiation with a fluorescent sun lamp (FSL) resulted in an enhancement in survival compared with FSL-irradiated cells incubated in the dark. Hence, pyrimidine dimers played a role in the killing of cells exposed to the UV produced by this source. However, when the light was passed through a series of filters to remove increasing segments of the wavelength region shorter than 320 nm, the effect of the PRL progressively decreased, demonstrating that non-dimer photoproducts play an increasingly important role in the killing of cells exposed to wavelengths approaching 320 nm. Cells were also exposed to 313 nm UV produced by a monochromator and it was found, once again, that the effectiveness of the PRL treatment depended on the filter the beam was passed through. These results indicate that for both FSL-produced UV and 313 nm UV emitted by a monochromator, that the critical photoproducts induced within the cell depend on the filter used in conjunction with the UV source.     

REPAIR OF NEAR-VISIBLE- and BLUE-LIGHT-INDUCED DNA SINGLE-STRAND BREAKS BY THE CHO CELL LINES AA8 and EM9

The induction of single-strand breaks (SSB) and the kinetics of SSB repair were measured in two Chinese hamster ovary cell lines irradiated with monochromatic photons of near-visible radiation (405 nm) and blue light (434 nm). The radiosensitive and UV-A-sensitive mutant line EM9 is known to repair SSB induced by ionizing radiation or 365-nm UV-A more slowly than the parent line AA8. At the 10% survival level, EM9 cells were 1.7- and 1.6-fold more sensitive than AA8 cells to 405 and 434 nm radiation, respectively. This sensitivity was not due to differences in induction of SSB because AA8 and EM9 cells accumulated the same number of initial breaks when irradiated at 0.5 degrees C with either 405 nm (5.9 SSB per MJ/m2) or 434 nm (5.1 SSB per MJ/m2), as measured by alkaline elution. When the cells repaired these SSB at 37 degrees C in full culture medium, biphasic repair kinetics were observed for both cell lines. In both phases of repair, EM9 cells repaired breaks induced by both wavelengths more slowly than did AA8 cells. The t1/2 values for the repair phases for 405-nm-induced SSB were 3.8 and 150 min for EM9, and 1.5 and 52 min for AA8; the corresponding values for repair of 434 nm breaks were 3.7 and 39 min for EM9, and 2.0 and 30 min for AA8. Because of this slower repair, EM9 cells left more SSB unrepaired after 90 min than did AA8 cells for both wavelengths.(ABSTRACT TRUNCATED AT 250 WORDS)     

The dose-response relationship for tumourigenesis by UV radiation in the region 311-312 nm

Groups of hairless mice were irradiated daily with Philips TL01 UVB sources. This type of lamp has become available recently and was developed for UVB phototherapy of psoriasis. The TL01 emits radiation in a narrow band around 311-312 nm. Tumours developed on all animals. The dose-response relationship had practically the same shape as that found in a similar experiment with Westinghouse FS40 sunlamps; the tumour induction time appeared to be proportional to the daily dose to a power of -0.58. An additional experiment was performed with a TL01 from which the shorter wavelengths were filtered away. This reduced the carcinogenic effectiveness by a factor of 2.3. The potential of the filtered lamp for phototherapy of psoriasis is discussed.     

DAMAGE BY SOLAR RADIATION AT DEFINED WAVELENGTHS. INVOLVEMENT OF INDUCIBLE REPAIR SYSTEMS

Abstract The susceptibility of bacteriophage damaged by solar-ultraviolet (UV, 290-380 nm) radiations at denned wavelengths and by radiation at a visible wavelength (405 nm) to the Weigle reactivation system induced by far-UV (254 nm) irradiation of the host cell has been studied in a repair competent strain of Escherichia coli . The sector of inducible repair diminishes with wavelength, being very small after 313 nm irradiation and absent after irradiation at longer wavelengths. However, irradiation of bacteria at wavelengths as long as 313 nm induces a bacteriophage reactivation system as effectively as radiation at 254 nm in both the repair competent and an excision deficient host cell. At longer wavelengths pre-irradiation of the repair competent host cell enhances reactivation of 254 nm irradiated bacteriophage but the reactivation is smaller and the process quite distinct from that induced in the 254-313 nm region. We conclude that, with increasing wavelength, damage induced by solar UV radiations becomes increasingly less susceptible to repair systems induced by far-UV (pyrimidine dimers) and that this type of inducible repair system is no longer induced by wavelengths longer than 313 nm.     

ON THE MECHANISMS OF PHOTOLYSIS OF COMPOUNDS I AND II OF HORSERADISH PEROXIDASE AT 77 K*

Abstract—When Compounds I and II of horseradish peroxidase in glycerol/water glasses at 77 K were irradiated with the light of a mercury lamp, some changes in optical spectra as well as the development of strong EPR signals of a free-radical type were detected. In case of photolysis of Compound I the light of wavelengths around 400 nm was the most effective, while only short wavelength (≥ 280 nm) light affected Compound II. The results of experiments with thawing and freezing the product of photolysis of Compound I (called Intermediate Y) provide further evidence for the suggestion that the ferric state of the heme iron is generated in the course of the photolysis. The quantum yields of the photolysis of Compound I at different wavelengths of irradiating light were obtained and mechanisms of the photolysis of Compounds I and II are proposed.     

RESTRICTION ENZYME CLEAVAGE OF UV-IRRADIATED DNA: A COMPARISON OF FAR-UV AND MID-UV WAVELENGTHS

UV-irradiated DNA is less susceptible to restriction by Type II endonucleases than unirradiated DNA presumably due to photolesions formed in the recognition sites. Previous reported studies have used 254 nm radiation or 313 nm plus acetophenone, both treatments which introduce pyrimidine dimers in preference to other photolesions. To assess the effect of a longer wavelength, at which the ratio of pyrimidine dimer formation to the formation of other photolesions is reduced, two different DNAs were irradiated with UV of either 254 or 313 nm and restricted with suitable restriction endonucleases. Restriction patterns were analysed for novel fragments resulting from UV-induced alteration of enzyme recognition sites. EcoRI restriction of 254 nm irradiated lambda DNA produced six novel bands, only three of which were observed following restriction of 313 nm irradiated lambda. These three represented the largest fragments resulting from single site blocks. Novel fragments involving adjacent site blocks observed at 254 nm were not found with 313 nm radiation. Comparison of 254 nm irradiated pSV₂gpt to that irradiated at 313 nm, both restricted with Dral, revealed a more complex pattern. Although all sites were singly blocked by radiation of both wavelengths, multiple site blocks produced by 313 nm radiation did not occur in the order predicted by the 254 nm radiation dose response. These data suggest that certain sites in pSV₂gpt may be more refractory to multiple site blocks than others when irradiated at 313 nm.     

Infrared light-emitting diode radiation causes gravitropic and morphological effects in dark-grown oat seedlings

Oat (Avena sativa cv Seger) seedlings were irradiated with IR light-emitting diode (LED) radiation passed through a visible-light-blocking filter. Infrared LED irradiated seedlings exhibited differences in growth and gravitropic response when compared to seedlings grown in darkness at the same temperature. Thus, the oat seedlings in this study were able to detect IR LED radiation. These findings call into question the use of IR LED as a safe-light for some photosensitive plant response experiments. These findings also expand the defined range of wavelengths involved in radiation-gravity (light-gravity) interactions to include wavelengths in the IR region of the spectrum.     

ULTRAVIOLET ENHANCED REACTIVATION OF HERPES SIMPLEX VIRUS INACTIVATED BY DIFFERENT WAVELENGTHS OF UV RADIATION

The degree of ultraviolet enhanced reactivation (UVR) exhibited by mammalian cells when infected with Herpes simplex virus inactivated by different wavelengths of far ultraviolet (UV) radiation was measured. A wavelength dependence for this effect is presented over the wavelength region 238–297 nm. Within the limits of the deviations obtained, the degree of UVR exhibited is similar at each wavelength. This suggests that virus irradiated with different wavelengths of UV radiation received the same type of damage or that cells repaired the different types of viral damage with the same efficiency.     

DNA NICKING BY ULTRAVIOLET RADIATION IS ENHANCED IN THE PRESENCE OF IRON and OF OXYGEN

Double-stranded covalently closed circular supercoiled DNA (ccc DNA) from plasmid pUK 9 was irradiated in vitro at denned wavelengths in the UV region (290, 313 and 365 nm). The nicking was monitored by electrophoresis on agarose gels, ethidium staining and densitometric quantitation of supercoiled and relaxed moieties. At the explored wavelengths, the dose required for introducing one nick per million phosphodiester bonds diminishes with increased concentration of added ferric iron, whereas the effect of cupric iron is practically negligible. Adding metal chelators or bubbling argon prior to the irradiation results in a dramatic increase in the dose required for introducing one nick per million phosphodiester bonds. Taken together, these results seem to indicate that iron and oxygen play a role as cofactors in the UV-induced nicking of ccc DNA in vitro.     

PROPERTIES OF THE ULTRAVIOLET-LIGHT-MEDIATED BINDING OF BOVINE SERUM ALBUMIN TO DNA*

Abstract— The binding of DNA to protein mediated by U V (254 nm) radiation has been investigated using binding of the complex to Millipore membrane filters as an assay technique. The reaction proceeds through an activated protein intermediate which then reacts with the DNA. The activated protein has a half-life of about 75 min at 0°C and about 18 min at 37°C. Short wavelengths are more efficient in forming the complex than wavelengths in the 250–280 nm range. N-ethyl maleimide treatment of protein before irradiation markedly inhibits the reaction.     

The determination of traces of ammonium-nitrogen in aqueous solution by optical emission spectrometry with a high-frequency inductively coupled argon plasma source

A method for the determination of low levels of ammonium ion in solution by optical emission spectrometry with an inductively coupled argon plasma source operated at 27 MHz is presented. The ammonium ion is oxidized with sodium hypobromite in alkaline medium, the evolved nitrogen is passed into the argon plasma, and the NH emission intensity produced in the plasma at 336.0 nm is monitored. A practical detection limit of 0.1 μg N ml^-1 for 5-ml aqueous sample solutions has been obtained. The method has been applied to the determination of the exchangeable ammonium content of soil samples.     

LEAKAGE OF 86Rb+ AFTER ULTRAVIOLET IRRADIATION OF Escherichia coli K-12

Abstract— Stationary phase cultures of a DNA repair proficient Escherichia coli K-12 strain showed a release of intracellular material as assessed by three different methods (260 nm absorption; [methyl-³H]thymidine leakage and ⁸⁶Rb⁺ leakage) after broad-band (Black-Light Blue) near-UV radiation but not after far-UV (254 nm) radiation. As a control response for membrane damage to cells, this leakage of intracellular material was also determined by each method after mild-heat (52°C) treatment of E. coli K-12. An action spectrum for the release of ⁸⁶Rb⁺ from E. coli K-12 after irradiation with monochromatic wavelengths, from 254 to 405 nm, is also presented. The action spectrum for lethality (F₃₇ values) obtained for this strain, shows that leakage of ⁸⁶Rb⁺ occurs at fluences equivalent to or slightly less than fluences causing inactivation at wavelengths above 305 nm. In contrast, at wavelengths below 305 nm, leakage of ⁸⁶Rb⁺ from irradiated cells can be induced but only at fluences significantly greater than was required to cause cell inactivation. These results indicate, therefore, that near-UV radiation can induce a damaging effect on the cell's permeability barrier which may be significant in causing the death of the cell, whereas the effect is not significant in causing the death of cells by far-UV radiation where DNA damage is known to be the main cause of lethality.     

Pathogen control in complex fluids with water-coupled excimer lamps at 282 and 308 nm

Water-coupled excimer lamp systems have been developed to inactivate microorganisms within complex, low-optical quality, fluids. Monochromatic lamps were selected to minimize UV-B and UV-C absorption within the carrier fluids while maximizing deposition within specific chemical targets. Fundamentals, system scaling and power supply design are discussed. This work used two large-surface area excimer lamps as intense sources of near monochromatic radiation at 308 and 282 nm. Data are presented for two distinct fluid systems: flow-through processing of large-volume metalworking fluids used in heavy industry and batch irradiation of human blood plasma and platelet suspensions used in transfusion medicine. In the first, a 200-600 L/min reactor is used to control bacterial concentrations within metalworking fluids used in large-scale metal machining processes. Control is defined as the maintenance of 10(3) to 10(4) CFU/mL in fluids that without treatment would have concentrations over 10(7) CFU/mL. The second is a batch process for viral inactivation in undiluted blood bank products. Samples of fresh frozen plasma and platelet suspensions were spiked with high titers of porcine parvovirus (PPV) and irradiated at 308 and 282 nm. Although both wavelengths were effective at reducing PPV levels, 308 nm light resulted in both higher rates of viral inactivation (greater than 6 log units) and lower rates of fluid degradation.     

Photoreaction of pyrido[2,3-c]furoxan

When pyrido[2,3-c]furoxan 4 was irradiated in acetonitrile containing a little water with a low pressure mercury lamp, 3-nitro-2-pyridone 5 was obtained. When compound 4 was irradiated in the presence of morpholine with a low pressure mercury lamp in an argon atmosphere, 6-morpholinopyridine 2,3-dioxime 6 , 6-morpholinopyrido[2,3-c]furazan 7 , 3-amino-6-morpholino-2-nitropyridine 8 , and 3-amino-4,6-dimorpholino-2-nitropyridine 9 was produced. The results of photoreaction study indicated the only photo-product to be compound 6 . The main difference between these two reactions may be considered due to the behavior of nitrogen in the pyridine ring.     

PHOTOCHEMICAL DEGRADATION OF KERATINS

Abstract— Twenty-nine samples of fur, hair. wool and feathers have been irradiated with a Sunlamp (Λ max. 310 nm) and with a 2 kW mercury vapour lamp emitting mixed U.V. and visible radiation resembling sunlight. Photodegradation is accompanied by progressive yellowing when irradiated with the Sunlamp. It is accompanied by bleaching followed by yellowing, or by bleaching throughout irradiation if the initial yellowness is high, when exposed to the 2 kW lamp. A group of nine fur and hair samples, representing four different orders of mammals, are the most sensitive to yellowing, followed by a group of ten wool and hair samples from the Artiodactyla and finally by the feather keratins which are less susceptible than the α-keratins. Amino acid analysis of the keratins before and after Sunlamp irradiation shows strong correlation of yellowing both with the initial concentration of tryptophan and with its destruction during irradiation. Similar correlations of yellowing with destruction of other amino acids are less significant. Preliminary washing with non-ionic detergent increases susceptibility to u.v. yellowing.     

Photodecomposition of polymethylsiloxane

Infrared spectroscopy studies were undertaken to determine the effects of ultraviolet light radiation on a methylsiloxane resin. The results indicate that SiCH₂Si linkages were formed as a result of irradiation at wavelengths above 281 mμ from a xenon are lamp; on the other hand, Si? OH and SiCH₂CH₂Si linkages were formed instead when the resin was exposed to the lower wavelengths emitted from a mercury vapor lamp. The different effects on the resin induced by the two ultraviolet light sources are attributed to the fact that only the energies from the mercury vapor lamp radiation are sufficient to cause the excitation of oxygen molecules in the air surrounding the irradiated polymer. The excited oxygen molecules prevented the formation of SiCH₂Si structures by interacting with active %tbond;Si units that were formed as a result of Si? C bond rupture to produce Si? OH; SiCH₂CH₂Si linkages were formed as the result of a secondary reaction.     

CELL SURFACE DAMAGE IN CULTURED MAMMALIAN CELLS WITH SYNCHROTRON RADIATION AT 160 nm

Cultured mammalian cells (HeLa) were allowed to attach onto a membrane filter and were irradiated with 160 nm synchrotron radiation. The cells then were rinsed with medium, fixed, and stained. Some of the cells became detached from the membrane filter during irradiation before post-irradiation incubation at 37°C. The cells remaining attached to the membrane filter were released by trypsinization, collected and examined for dye-exclusion ability with eosin Y. The number of stained cells was increased when the cells were irradiated at 160 nm, while no such increase was observed in cells irradiated with synchrotron radiation at 220 nm, with a low pressure Hg lamp (predominantly 254 nm), or with gamma-rays of ⁶⁰Co. These results indicated that the cell surface was injured by irradiation with synchrotron radiation at 160 nm.     

Photooxidation of PVC

Pure and peroxided PVC films were irradiated under monochromatic ultraviolet light between 300 and 400 nm. The degradation state of PVC is measured by means of carbonyl absorption in the infrared spectra and polyene content by UV spectroscopy. The initial rate of carbonyl formation depends on the wavelengths and oxidized impurities content. Peroxided PVC is oxidized faster than pure PVC with wavelengths above 320 nm. Two hazardous ranges of wavelengths have been detected: 300–320 and 350–370 nm. Good protection of PVC against UV radiation can be assured by the exclusion of wavelengths under 380 nm.     

ALPHA POLYMERASE INVOLVEMENT IN EXCISION REPAIR OF DAMAGE INDUCED BY SOLAR RADIATION AT DEFINED WAVELENGTHS IN HUMAN FIBROBLASTS

Abstract Cultured fibroblasts derived from normal human skin have been irradiated at a series of monochromatic wavelengths throughout the ultraviolet region and exposed to the specific α polymerase inhibitor, aphidicolin (1 μg/m l , 2 days) prior to assay for colony forming ability. Repair of 75-80% of the lethal damage induced by UVC (254 nm) or UVB (302 nm, 313 nm) radiation is inhibited by aphidicolin suggesting that such damage is repaired by a common α polymerase dependent pathway. Exposure to aphidicolin after irradiation at longer UVA (334 nm, 365 nm) or a visible (405 nm) wavelength leads to slight protection from inactivation implying that the processing of damage induced in this wavelength region is quite distinct from that occurring at the shorter wavelengths and does not involve α polymerase.     

KONSTRUKTION UND ERPROBUNG EINER LICHT-BOGENTEMPERIERBAREN QUECKSILBERNIEDERDRUCKLAMPE

Abstract— A new low pressure mercury lamp was constructed and described in detail. The silica-lamp surrounds the analytical vessel and has two water-cooled circuits. The first one for cooling the mercury electrodes and the second one for cooling of the arc. The temperature dependence of the arc intensity was studied and discussed.
The lamp was calibrated for two wavelengths (253·7 nm and 365 nm) by using an u.v.-standard lamp. The effective intensity within the analytical cell has a value of 6·7 × 10^-6 Einstein cm^-2 min^-l.