INACTIVATION BY ULTRAVIOLET RADIATION AT DIFFERENT WAVELENGTHS OF THE RNA ISOLATED FROM POTATO VIRUS X

Abstract— –The action spectra and quantum yields for photoreactivable, non-photoreactivable and total damage caused by u.v. in the RNA isolated from potato virus X differ from those for similar types of damage in the whole virus. The differences result from the virus protein partly protecting the RNA from damage, and the degree of protection depends on the wavelength of u.v. and on the salt concentration of the irradiated solution. The action spectra for the different types of damage in the RNA all resemble the absorption spectrum of the RNA, but do not exactly parallel it. The photoreactivable sectors of the RNA and of the whole virus are greater at 290 nm than at 230 nm but, whereas that of the virus increases rectilinearly, that of the RNA has a pronounced minimum at about 250 nm. At wavelengths longer than 240 nm, the photoreactivable sector of the virus exceeds that of the RNA, because, at these wavelengths, the virus protein protects the RNA more against non-photoreactivable damage than against photoreactivable damage.     

INACTIVATION OF A RHIZOBIUM BACTERIO-PHAGE BY ULTRAVIOLET RADIATION OF DIFFERENT WAVE-LENGTHS

Abstract— The action spectrum for inactivation of a Rhizobiurn bacteriophage by U.V. radiation follows the shape of the absorption spectrum of DNA between the wave-lengths of 240 and 290 mμ (where inactivation probably reflects damage to the nucleic acid only), and deviates sharply upwards at wave-lengths shorter than 240 mμ (where inactivation may depend on damage to both the nucleic acid, and protein of the phage). The rate of inactivation follows first order kinetics approximately at all wave-lengths tested. Infectivity of the phage is halved when each mg of the phage nucleic acid has absorbed about 0 08 J of radiation energy at any wave-length between 240 and 290 mμ.
The bacteriopharge can be photoreactivated after inactivation at any wave-length between 230 and 290 mμ, but less so after inactivation at 230 mμ than at any wave-length above 240 mμ. No evidence was found to suggest that dimerization of thymine residues of the phage-DNA plays any part in the mechanism of inactivation of the bacteriophage by U.V. radiation.     

IN ACTIVATION OF A STRAIN OF TOBACCO NECROSIS VIRUS AND OF THE RNA ISOLATED FROM IT, BY ULTRAVIOLET RADIATION OF DIFFERENT WAVE-LENGTHS

Abstract— A train of tobacco necrosis virus (TNV) and infective nucleic acid isolated from it (TNV-RNA) are equally susceptible to inactivation by U.V. radiation at all wave-lengths tested (230-290 m_μ) and can be photoreactivated to the same extent by exposing inoculated host plants to daylight. The shape of the action spectrum for inactivation by U.V. of TNV and of TNV-RNA follows that of the absorption spectrum of TNV-RNA. Thus, unlike the RNA of tobacco mosaic virus, the RNA of TNV behaves in all these respects in the same way irrespective of whether it is inside or outside the virus particle. To inactivate TNV or TNV-RNA to 50 per cent of their original infectivities, each mg of RNA must absorb about 0.27 joules of radiation energy of any wave-length between 230 and 290 mp, which corresponds to a quantum yield of about 0.65 ×10^-3 at 260 mμ.     

IN VITRO PHOTOREACTIVATION OF ULTRAVIOLET-INACTIVATED RIBONUCLEIC ACID FROM TOBACCO MOSAIC VIRUS

Abstract— Treatment of ultraviolet-inactivated tobacco mosaic virus ribonucleic acid (TMV–RNA) with extracts obtained from the local lesion host, Nicotiana tabacum var. Xanthi , n.c., and simultaneous illumination at 365 nm results in up to a four-fold increase in infectivity over non-illuminated controls. The active material in the extract appears to be associated with protein, based on its inactivation by boiling, precipitation with ammonium sulfate, and exclusion from Bio-Rad P100 polyacrylamide. Partially purified DNA photoreactivating enzyme from yeast or pinto bean has no activity on ultraviolet-irradiated TMV–RNA.     

STUDIES ON THE INACTIVATION OF TOBACCO MOSAIC VIRUS BY ULTRAVIOLET LIGHT*,‡,§

Abstract— The irradiation of TMV with u.v. light of 2537 Å wavelength results in the binding of protein subunits to the RNA. These bound subunits are stable towards warm sodium dodecyl-sulfate; however, the binding is not covalent since the subunits are removed by 66% acetic acid, guanidine hydrochloride, or phenol. Approximately one protein subunit is bound per lethal biological 'hit'. The virus and the nucleic acid extracted from irradiated virus show virtually identical rates of inactivation.     

THE WAVELENGTH DEPENDENCE OF HERPES SIMPLEX VIRUS INACTIVATION BY ULTRAVIOLET RADIATION

The effect of different wavelengths of ultraviolet (UV) radiation on Herpes simplex virus when assayed on mammalian cells (measured by plaque forming ability) was investigated. The wavelength dependence of viral inactivation was obtained for 11 different wavelengths over the region 238–297 nm. The resulting action spectrum does not closely follow the absorption spectrum of either nucleic acid or protein. The most effective wavelengths for viral inactivation are over the region 260–280 nm.     

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.     

PHOTOREACTIVATION ACTION SPECTRUM OF TOBACCO MOSAIC VIRUS-RIBONUCLEIC ACID INACTIVATED BY U.V. RADIATION*

Abstract— Initially photoreactivation of irradiated (2537 Å) nucleic acid on pinto bean increases linearly with time of illumination with white light of 250 ft-c. Maximum amounts of photo-reactivation depend on the quality of light used. The action spectrum shows a peak in the ‘black light’ region, where the greater amount of photoreactivation is found, and a shoulder in the blue light region. Maximum repair is obtained with ‘black light.’ Photoreactivation does not occur at wavelengths above 550 nm. Photoprotection by illumination of leaves prior to inoculation by irradiated RNA was not found. The action spectrum for photoreactivation does not resemble the action spectrum for photosynthesis.     

CLEAVAGES OF TRANSCRIPTS OF TOBACCO MOSAIC VIRUS BY SYNTHETIC RIBOZYMES in vitro

Based upon computer-assisted predictions on the secondary structures of tobacco mosaicvirus (TMV) genomic RNA (both polarities), hammerhead type ribozymes were synthesizedin vitro, which all shared a conserved domain adapted from satellite tobacco ringspot virus(sTobRV)RNA. Ribozymes RZ1, RZ2 and RZ3 were designed to cleave the phosphodiester bondsimmediate to the 3'--end of GUC between the residues 5384-5385 and 6312--6313 on the plusstrand and 1214-1215 on the minus strand, respectively. The in vitro data indicated that RZ1 wasable to cleave completely its substrates BT1(+ ) and BT2(+ ), representing partial sequencesof the plus strand of the TMV MP region at 50, 37 and 30℃ with a molar ratio of ribozymeto the target as low as 1:1. Its two iso-ribozymes RZ1A and RZ1B which were respectivelymodified to contain a CUUCGG sequence in the conserved region and in an additional 3'-ter-minal stem-loop of UUUUUCUUCGGAAAAA were able to cleave BT1(+) and BT2(+) asefficiently as RZ1. Ribozyme RZ3 cleaved, with l     

INHIBITION OF PROTEIN SYNTHESIS IN CULTURED TOBACCO CELLS BY ULTRAVIOLET RADIATION

Abstract— Ultraviolet (254 nm) irradiation of liquid-cultured tobacco cells strongly and quickly inhibited their ability to incorporate labeled amino acids into protein. An incident dose of only 388 J/m² reduced incorporation to 37 per cent of the original rate. The effect on amino acid incorporation did not seem to depend on inhibition of amino acid uptake, inhibition of the supply of nucleoside triphosphates, or inhibition of the supply of messenger RNA to cytoplasmic ribosomes.     

PHOTOREACTIVATION OF DNA-CONTAINING CAULIFLOWER MOSAIC VIRUS AND TOBACCO MOSAIC VIRUS RNA ON DATURA

Abstract— Datura stramonium L. is a local lesion host for TMV-RNA and DNA-containing cauliflower mosaic virus (CAMV). Datura can photorepair UV-damaged TMV-RNA and CAMV, giving photoreac-tivation sectors of 0.40 and 0. 33 , respectively. Dose response curves for photoreactivation of TMV-RNA and CAMV show that 4540 min of cool white light (15 W.m^-2) is required for maximum photoreactivation. Blue light and near UV are equally effective in photoreactivating UV-irradiated TMV-RNA, whereas near UV is initially more effective than blue light for the photorepair of UV-inactivated CAMV. Higher doses of near UV apparently inactivate the CAMV photorepair system. In the case of CAMV, photoreactivating light must be applied immediately after inoculation with the virus. Two to three hours of incubation in the dark after inoculation results in complete loss of response to photoreactivating irradiation. In contrast, limited photoreactivation of TMV-RNA occurs even after 4 h of dark incubation after inoculation, although photoreactivating irradiation is most effective when applied immediately after inoculation. Light is required for the maintenance of photoreactivation for both TMV-RNA and CAMV. Daturas placed in the dark for six days lose their ability to photoreacti-vate. Recovery of the TMV-RNA photorepair system is rapid; complete recovery attained with 90 or more min of white light (15 W m-'). Recovery of CAMV photorepair system is slow; 90% recovery attained after only 20 h of light. However, full recovery can be induced by as little as 6h of light when CAMV is inoculated 24 h after the onset of illumination. These results suggest two photorepair systems are present in Datura .     

VIRUS RESISTANCE OF TRANSGENIC TOBACCO PLANTS EXPRESSING TOBACCO MOSAIC VIRUS COAT PROTEIN GENE

An intermediate expressing vector carrying the tobacco mosaic virus (TMV, Chinese common strain) coat protein (CP) gene was constructed by recombinant DNA techniques. The TMV-CP gene was transferred into the tobacco genome via Ti plasmid and a large number of regenerated plants, including both systemic and local lesion hosts for TMV, were obtained. Southern blot analysis revealed that 1-5 copies of the CP gene were integrated into the tobacco genome. RNA and protein analysis demonstrated that the TMV-CP gene was correctly expressed in the transgenic plants. The abundance of TMV-CP mRNA in total leaf RNA accounted for 0.005-0.01%, while the amount of coat proteins reached 0.05-0.2% of the total leaf soluble proteins. Virus challenge experiments showed that the symptom development of virus infection was markedly delayed and the replication as well as the spread of the virus was significantly inhibited in the transgenic plants expressing the TMV-CP gene. Three of these plants were completely protected afte     

ANNUAL EXPOSURES TO CARCINOGENIC RADIATION FROM THE SUN AT DIFFERENT LATITUDES and AMPLIFICATION FACTORS RELATED TO OZONE DEPLETION. THE USE OF DIFFERENT GEOMETRICAL REPRESENTATIONS OF THE SKIN SURFACE RECEIVING THE ULTRAVIOLET RADIATION

In most calculations of annual fluences of carcinogenic light as well as of the radiation amplification factor and of biological amplification factors associated with ozone depletions, the radiation is assumed to fall on a horizontally oriented plane surface. This is obviously a bad approximation of the surface of the human body. In order to evaluate the importance of using a realistic geometric representation of the surface of the human body we here present calculations of the flux of carcinogenically effective radiation falling on three different bodies: a vertically standing cylinder, a sphere and a horizontally oriented surface. The exposure to carcinogenic radiation depends strongly on the surface geometry. However we find that the radiation amplification factors are almost independent of the surface geometry chosen. The biological amplification factors for the three geometrical representations are also similar to within 20%. The total amplification factor for the increase in the incidence of non-melanoma skin cancer related to ozone depletion is about 17% larger when a cylindrical representation is used compared to when a plane horizontal surface is considered.     

PHOTOCHEMISTRY OF A MACROMOLECULE: TOBACCO MOSAIC VIRUS

Abstract— A history of the photochemistry of the first known virus is presented. Hollaender and Duggar recognized that the virus contains nucleic acid because of the shape of their action spectrum for photoinactivation. An analysis of this spectrum in detail presents a challenge to photochemists because of the combined role of protein and nucleic acid in determining rates of inactivation. At present these rates can not be explained simply on the basis of the photochemistry of each of the constituents; that is, the photochemistry of free infectious nucleic acid differs in several respects from that exhibited by nucleic acid irradiated in intact virus. At present it is believed that pyrimidine hydrate and dimer formations are important, but an explicit solution to the problem is not in sight.     

ACTION SPECTRUM FOR INACTIVATION OF THE INFECTIVITY OF POTATO VIRUS X BY U.V. RADIATION

Abstract— Quantum yields for inactivation of infectivity of potato virus X by monochromatic ultraviolet radiation of wavelengths ranging from 230 to 290 nm, were measured with reference to energy absorbed by (a) the whole virus and (b) the virus RNA. The yields depended on the wavelength, but those with reference to energy absorbed by the RNA varied much less (with extreme values of 10^-3 and 1.9 ± 10^-3 than those with reference to whole virus. Consequently the action spectrum for inactivation of a dilute solution of the virus resembled the shape of the absorption spectrum of the RNA, but not closely enough to allow coincidence by adjusting the scales. The amount of photoreactivation increased as the wavelength increased and also as the year progressed from May to July; the extreme values of the photoreactivable sector were 0.43 and 0.86.     

THE OCULAR DOSE OF ULTRAVIOLET RADIATION FROM SUNLIGHT EXPOSURE

Abstract— The ocular toxicity of ultraviolet radiation has been demonstrated in acute photokeratitis and is suspected of contributing to cataractogenesis and senile macular degeneration. While previous studies have emphasized photochemical and epidemiologic aspects of ocular UV-B irradiation, little is known about the extent of such exposure in human subjects. To determine levels of ocular UV-B exposure from sunlight, four mannikin headforms were fitted with UV-B sensitive film (polysulphone) and exposed on an unobstructed rooftop (Baltimore, Md.: latitude = 39.5 degrees) to four hours of sunlight (11 am-3 pm local time) over a three month period (June-August). Simultaneous measurements of ocular and ambient exposure revealed a ratio of 19.5 ± 2.9% that was independent of ambient level (P < 0.05). Measurements performed during earlier hours (8 am-11 am) revealed a similar ratio. Mannikin headforms fitted with brimmed baseball caps showed a22–95% reduction in ocular exposure, depending on the angle of the hat brim to the forehead. Three sets of spectacles substantially reduced ocular UV-B exposure,62–94% dependent on the absorption properties of the spectacle lenses. These anthropomorphic measurements indicate that a substantial percentage of ambient UV-B light is incident upon the cornea and that personal factors, such as wearing a hat or spectacles, can markedly affect UV-B exposure.     

SOLAR ULTRAVIOLET RADIATION AT THE EARTH'S SURFACE

The biologically effective ultraviolet irradiance at the earth's surface varies with the elevation of the sun, the atmospheric ozone amount, and with the abundance of scatterers and absorbers of natural and anthropogenic origin. Taken alone, the reported decrease in column ozone over the Northern Hemisphere between 1969 and 1986 implies an increase in erythemal irradiance at the ground of four percent or less during summer. However, an increase in tropospheric absorption, arising from polluting gases or particulates over localized areas, could more than offset the predicted enhancement in radiation. Any such extra absorption is likely to be highly regional in nature and does not imply that a decrease in erythemal radiation has occurred on a global basis. The Antarctic 'ozone hole' represents a special case in which a portion of the earth has experienced ultraviolet radiation levels during spring that are far in excess of those which prevailed prior to the present decade.