ULTRAVIOLET ACTION SPECTRUM FOR FLUOROGEN PRODUCTION IN THE OCULAR LENS

Abstract— …Previous work has demonstrated that fluorescent material (360nm excitation, 440nm emission), whose concentration normally increases with age in human lenses, can be generated artificially by exposing cultured human or animal lenses to UV radiation. In the present paper we report measurements of the rate of production of this fluorescent material in rat lenses in vitro as a function of UV irradiation wavelength. A plot of the observed rate of fluorogen production normalized to constant photon flux vs irradiation wavelength shows little action at 360 or 320nm, increases sharply at 300nm, remains relatively constant in the range 300–280nm, and then exhibits a further gradual rise from 270–250nm. The results on rat lenses are compared with results reported elsewhere for tryptophan in aqueous solution. The action spectrum for photochemical destruction of tryptophan in solution closely parallels that for fluorogen production in rat lenses. This result and other evidence suggest that photochemical destruction of tryptophan might be the initial event in UV-induced fluorogen production in the ocular lens.     

AN ULTRAVIOLET RADIATION ACTION SPECTRUM FOR IMMEDIATE PIGMENT DARKENING

The wavelength dependence for immediate pigment darkening (IPD) was investigated by exposing the midback skin of volunteers to a series of incremental fluences of narrow waveband radiation isolated by band-pass filters in the310–400 nm region. The threshold IPD fluence for each waveband was determined by visual assessment of the skin responses immediately after each exposure. The action spectrum, constructed from the mean threshold fluences, was broad and extended from 320 nm to 400 nm with a peak at around 340 nm. No IPD could be evoked at 310 nm, even after erythemogenic fluences. The spectrum was similar in each of the three skin types investigated (III, IV, V). The broad nature of the action spectrum within the UVA region suggests that IPD may serve as an alternative endpoint for measuring photoprotection against these wavelengths.     

AN ACTION SPECTRUM FOR ULTRAVIOLET RADIATION-INDUCED MEMBRANE DAMAGE IN Escherichia coli K-12

A wild-type Escherichia coli K-12 strain was irradiated using monochromatic radiation in the range 254 to 405 nm. A measure of the cell membrane damage induced at each wavelength was investigated by comparing cell viability after irradiation on nutrient agar and on minimal medium containing either a low or high inorganic salt concentration. An action spectrum for lethality and for cell membrane damage was then determined. From 254 to 310 nm lethality closely corresponded to the absorption spectrum of DNA, and there was no indication of membrane damage. However, above a wavelength of 310 nm, the direct absorption of radiation by DNA could not account for the sensitivity observed. Moreover, at wavelengths longer than 310 nm, cell membrane damage was induced and by an increasing factor up to a peak at 334 nm. At the longer wavelengths of 365 and 405 nm, there was a gradual decrease from the peak of damage to cell membranes induced by 334 nm radiation. These results indicate that cell membrane damage may contribute significantly to near-UV radiation-induced cell lethality in wild-type E. coli K-12.     

ACTION SPECTRUM FOR SUBLIMINAL LIGHT CONTROL OF ADAPTATION IN Phycomyces PHOTOTROPISM

Abstract -Adaptation processes enable phototropism and other blue light responses of Phycomyces to operate over a 10-decade range of Ruencc rate. Phototropic latency, used routinely to monitor the kinetics of sensitivity recovery after a step down in fluence rate, can be shortened by application of dim light for 35 min during the early part of the latency period. This light is termed subliminal , because it does not elicit phototropism under these experimental conditions; rather, it exerts its influence on the underlying adaptation kinetics. Fluence rate-response data for this latency reduction, obtained at 17 wavelengths of subliminal light from 347 to 742 nm, showed a variety of shapes that could be fit by zero, one, or two sigmoidal components, plus a constant term. At most wavelengths, the fluence-rate threshold for latency reduction by subliminal light tended to be well below the absolute threshold for phototropism, indicating that this effect is highly sensitive. An action spectrum for the sensitivity of the subliminal light effect, derived from the fluence rate-response curves, shows major peaks around 400 and 500 nm and a broad band from 570 to 670 nm, followed by a steep absorption edge. The sensitivity in the near ultraviolet region is relatively very low. The magnitude of the latency reduction also depends strongly on wavelength with a maximum at about 450 nm. The Huence-rate response data and the action spectrum–which is markedly different from that for phototropism and other blue-light responses of Phycornyces – indicate the participation of multiple pigments, or pigment states, in the photocontrol of adaptation.     

AN ACTION SPECTRUM FOR BLUE AND NEAR ULTRAVIOLET IN ACTIVATION OF Propionibacterium acnes; WITH EMPHASIS ON A POSSIBLE PORPHYRIN PHOTOSENSITIZATION

— Propionibacterium acnes (P. acnes ), grown on Eagles medium with different pH. were irradiated with monochromatic light in the range 320 to 440 nm. Different pH leads to different porphyrin concentrations in the cells. The light sensitivity of the bacteria was estimated from the reduction in their ability to form colonies after radiation. The sensitivity was highest for the lowest wavelength (320 nm). and decreased continuously with increasing wavelength up to 380 nm. In the region between 380 and 440 nm there was a second maximum (at 415 nm) which corresponds to the maximum absorption ol the fluorescing porphyrins in P. acnes . The sensitivity to 415 nm light was found to be dependent on the endogenous porphyrin concentration in the cells. while the sensitivity to 320 nm radiation was independent of the amount of porphyrin present. These results indicate that porphyrins produced by the bacteria are important for the light sensitivity of these bacteria.     

ACTION SPECTRUM FOR ENHANCEMENT OF PHOTOTROPISM BY Arabidopsis thaliana SEEDLINGS

Fluence-response relationships have been measured at wavelengths from 350 to 760 nm for the enhancement of phototropism in Arabidopsis thulium L. (Heynh) strain “Estland” by an irradiation at each of these wavelengths, given 2 h prior to a 450 nm inductive unilateral irradiation. Action spectra have been constructed from these fluence-response relationships based on: (i) the fluence required to obtain a curvature of 25° (corresponding to an enhancement of 15°), (ii) the fluence required to obtain 50% of the maximum enhancement and (iii) the fluence threshold for enhancement by a pre-irradiation. The action spectra exhibit two maxima, one at 669 nm and a second at 378 nm. The height of the maximum at 669 nm is approximately 4 times the height of the maximum at 378 nm. Based on the action spectra, it is concluded that the enhancement of phototropism in A. thaliana is mediated by phytochrome.     

AN INSTRUMENT FOR ACTION SPECTRUM STUDIES IN DERMATOLOGY

Abstract— An instrument designed for convenient determination of action spectra for cutaneous photo-responses in man and experimental animals is described. Light from 450 W Xe lamp is dispersed by a concave holographic grating. The spectrum from 244 to 616 nm is projected as a planar strip (2 times 17 cm) intercepted by a grid with 31 ports. The bandwidth at each port is 12 nm and the size of the port increases from about 4 × 4 mm to 6 × 8 mm from the low to high wavelength limits, respectively. Typical fluence rates in quanta m^-2 s^-1 are 4.0 times 10¹⁹ at 298 nm, 16 times 10¹⁹ at 394nm and 22 times 10¹⁹ at 538 nm. Responses due to delayed erythema in normal skin and to musk ambrette photoallergy and solar urticaria in patients skin have been elicited with this instrument.     

AN ACTION SPECTRUM FOR ULTRAVIOLET-INDUCED SPORULATION IN THE FUNGUS STEMPHYLIUM SOLANI WEBER

Abstract— An action spectrum for conidial (spore) production in the fungus Stemphylium solani Weber is presented. The response is in the far-ultraviolet region (far u.v.). The spectrum shows a single peak at 280 nm, a shoulder at 260 nm, a trough at 250 nm, followed by a rise which is still rising at 230 nm, the shortest wavelength studied. The u.v. induced spore stimulation can be interrupted temporarily by irradiation in the visible region within 4 hr after induction.     

AN ACTION SPECTRUM FOR ULTRAVIOLET INDUCED ELASTOSIS IN HAIRLESS MICE: QUANTIFICATION OF ELASTOSIS BY IMAGE ANALYSIS

To determine an action spectrum for ultraviolet (UV)-induced elastosis, four groups of 24 albino hairless mice each were exposed to four different spectra emitted by a xenon arc solar simulator fitted with cut-off filters (Schott WG 320, 335, 345, and 360). These filters progressively removed more of the shorter wavelengths until, in the final spectrum, only long wavelength UVA (greater than 335 nm) remained. Exposures continued up to 62 weeks. A fifth group of mice served as controls. Skin biopsies were taken at pre-determined dose points and were processed for light microscopy. Elastosis was quantified by computerized image analysis, yielding dose-response curves for each spectrum. The total energy required for a 50% increase in elastic tissue compared to controls was determined graphically for each spectrum. These were: WG 320, 65 J/cm2; WG 335, 865 J/cm2; WG 345, 1230 J/cm2; and WG 360, 2000 J/cm2. Our results were tested against published action spectra for erythema, photocarcinogenesis and elastosis. The erythema spectrum was the most predictive for elastosis except that the longer UVA wavelengths were less effective for elastosis than for erythema. Solar simulating radiation (WG 320 filter) with its UVB component was the most effective in inducing elastosis. Full spectrum UVA (WG 345) required 20 times more energy while long wavelength UVA (WG 360) required 30 times more energy to induce equivalent elastosis.     

DETAILED ACTION SPECTRUM FOR THE DELAY SHIFT IN PUPAE EMERGENCE OF DROSOPHILA PSEUDOOBSCURA*

Abstract— Dose-response curves were measured for the delay phase shift of pupae emergence of Drosophila pseudoobscura. From these curves an action spectrum was determined for this process; it suggests a flavin to be the photoreceptor pigment.     

THE ACTION SPECTRUM OF AN IN VITRO DNA PHOTOREACTIVATION SYSTEM

Abstract— The wavelength-dependence of in vitro photoreactivation of transforming DNA by yeast extract has been determined. There is an intensity-dependent lag at the beginning of the biological reaction. There is a similar lag in the splitting of thymine dimers by the yeast extract in the light, a process known to account for most or all of the increase in transforming activity of photoreactivated DNA. The most efficient wavelengths for photoreactivation are around 3550 and 3850 Å. Although the action spectrum is not very similar to flavin absorption, riboflavin at very low concentration inhibits photoreactivation, as it also inhibits a number of flavoenzymes, suggesting that the photoreactivating enzyme might be a flavoprotein.     

PROTEIN-RNA CROSSLINKS IN RIBOSOMES: ULTRAVIOLET ACTION SPECTRA. COMPARISON WITH INACTIVATION ACTION SPECTRUM

Abstract— RNA-protein crosslinking by UV of different wavelengths was studied in 70S E. coli ribosomes by three techniques: sucrose gradient centrifugation in the presence of sodium dodecyl sulfate (SDS), RNA solubilization in LiCI-urea concentrated solutions and RNA adsorption on nitrocellulose filters in the presence of SDS.
The centrifugational technique shows that the crosslinking reaction occurs in two steps, the first one corresponding to the fixation of a few protein molecules on 16 or 23 s RNAs and the second one corresponding to extensive RNA-protein crosslinking so that most protein molecules are no longer released by SDS from 30S and 50S subunits.
The initial rates for the first step of crosslinking were evaluated by the solubilization and adsorption techniques at 7 (or 6) wavelengths of irradiation between 223 and 290 mm. The action spectrum for RNA solubilization in LiCl-urea is perturbed at 223 nm by the breakage of protein chains. The action spectrum for retention on nitrocellulose filters seems to be exempt of this defect. It corresponds at high wavelengths to a nucleic chromophore and at low wavelengths to a proteic one. This means that RNA-protein crosslinking may occur through RNA and protein excitation. The similarity between the action spectrum for RNA retention on nitrocellulose filters and the action spectrum for inactivation of ribosomal synthesis activity suggests that RNA-protein crosslinking may be responsible for inactivation of ribosomes by UV.     

ACTION SPECTRUM STUDIES FOR INDUCTION OF IMMUNOLOGIC UNRESPONSIVENESS TO DINITROFLUOROBENZENE FOLLOWING IN VIVO LOW DOSE ULTRAVIOLET RADIATION

Abstract— Topical application of the contact sensitizer dinitrofluorobenzene to the skin of C3H mice previously exposed in vivo to low doses of UVB radiation from FS20 sun lamps resulted in the acquisition of antigen-specific unresponsiveness to that hapten. When narrow band radiation at various wavelengths between 260 and 320 nm was employed, increasing doses of radiation were found to produce increasing amounts of immunosuppression. Construction of an action spectrum curve revealed that radiation between 260 and 300 nm was most efficient in producing unresponsiveness. Wavelengths above 300 nm were much less efficient than those below 300 nm. These results indicate that there are major differences in the effectiveness of various components of the short and middle wavelength UV spectrum in eliciting immunologic unresponsiveness to a topically administered hapten. Potential chromophores for this UVB-induced immunosuppressive effect include DNA and urocanic acid.     

AN ACTION SPECTRUM FOR LIGHT AVOIDANCE BY PHYSARUM NUDUM PLASMODIA

Abstract— Plasmodia of the myxomycete Physarum nudum , grown on agar in darkness, avoided a lighted field. The percentage of plasmodia migrating out at the lighted field was found to be dependent on light intensity. An action spectrum for this response has two maxima at 452 and 375 nm.     

AN ACTION SPECTRUM FOR PHOTOTAXIS BY PSEUDOPLASMODIA OF Dictyostelium discoideum

Abstract— The sensitivity of phototactic orientation of pseudoplasmodia (slugs) of the cellular slime mold Dictyosrelium discoideum has been measured for white light and monochromatic light using computer aided directional statistics. The zero threshold for white light was found at about 10^-5 Ix. An action spectrum for positive phototaxis has been calculated from fluence rate-response curves; it shows two major maxima at about 420 and 440 nm and secondary peaks at 560 and 610 nm. This action spectrum is significantly different from the one for phototactic orientation in Dictyostelium amoebae.     

ACTION SPECTRUM FOR THE PHOTOINHIBITION OF BIOLUMINESCENCE IN THE MARINE DINOFLAGELLATE DISSODINIUM LUNULA

Abstract— The fractional photoinhibition of the mechanically stimulable bioluminescence in the vacuolar dinoflagellate Dissodinium lunula is proportional to the logarithm of the exposure. The action spectrum for this photoinhibition has been determined by measuring threshold exposures in absolute units of photons cm⁻². The threshold exposure at the wavelength of maximum sensitivity, 450 nm, was 2 ± 10⁻² photons cm⁻². The action spectrum is consistent with absorption by a blue light receptor pigment shielded by a nonphotoactive pigment which absorbs in the region of the bioluminescence emission spectrum. It is suggested that there may be some selective advantage for this absorbing pigment in the vacuolar dinoflagellates in order to prevent the organisms from being photoinhibited by their own bioluminescence.     

ULTRAVIOLET INACTIVATION OF THE ABILITY OF E. COLI TO SUPPORT THE GROWTH OF PHAGE T7: AN ACTION SPECTRUM

Abstract— Ultraviolet (UV)-irradiated E. coli K-12 wild-type cells were sensitized by a post-irradiation treatment with 10^-2 M 2, 4-dinitrophenol (DNP). This effect was not seen in strains carrying a uvr mutation, suggesting that DN P interferes with the excision repair process. The polA strain was sensitized to the same extent as the wild-type strain, while the exrA strain was not affected by DNP treatment.
Recombination deficient strains ( recA, recB and recA recB ) were protected by DNP treatment after UV irradiation. This protection was abolished by the addition of a uvr mutation (i.e., in strains recA uvrB and recB uvrB ).
Alkaline sucrose gradient sedimentation studies showed that DNP treatment interfered with the rejoining of DNA single-strand breaks induced by the excision repair process. This interference was apparently specific for the exr gene-dependent branch of the uvr gene-dependent excision repair process, since the uvr and exr strains were not sensitized while the wild-type and polA strains were sensitized.     

ACTION SPECTRA FOR ULTRAVIOLET KILLING AND PHOTOREACTIVATION IN THE BLUE-GREEN ALGA AGMENELLUM QUADRUPLICATUM

Abstract— The action spectrum for photoreactivation has been determined in a coccoid blue-green alga, Agmenellum quadruplicatum. The spectrum is rather similar to that recorded for Streptomyces griseus conidia, with some suggestion of a little more structure. The action spectrum suggests possible carotenoid involvement; however, no other evidence for this could be found. The action spectrum for u.v. killing is also broad with some evidence of fine structure. The possible implication of tetrahydropteridines or c -phycocyanin as chromophores in the region 240–300 nm, along with DNA, is pointed out.     

THE ACTION SPECTRUM IN DRUG INDUCED PHOTOSENSITIVITY

Abstract— A new method is proposed for expressing the data obtained from in vivo studies of drug-induced photosensitivity. It is shown that consideration of the underlying normal photobiological responses that occur in the absence of the photosensitising drug can yield much closer agreement between the in vitro absorption spectrum of the drug and the action spectrum obtained in photosensitised skin than is apparent from many published reports.