Analysis of Compact Fluorescent Lights for Use by Patients with Photosensitive Conditions

Ultraviolet radiation (UVR) is hazardous to patients with photosensitive skin disorders, such as lupus erythematosus, xeroderma pigmentosum and skin cancer. As such, these patients are advised to minimize their exposure to UVR. Classically, this is accomplished through careful avoidance of sun exposure and artificial tanning booths. Indoor light bulbs, however, are generally not considered to pose significant UVR hazard. We sought to test this notion by measuring the UV emissions of 19 different compact fluorescent light bulbs. The ability to induce skin damage was assessed with the CIE erythema action spectrum, ANSI S(λ) generalized UV hazard spectrum and the CIE photocarcinogenesis action spectrum. The results indicate that there is a great deal of variation amongst different bulbs, even within the same class. Although the irradiance of any given bulb is low, the possible daily exposure time is rather lengthy. This results in potential daily UVR doses ranging from 0.1 to 625 mJ cm⁻², including a daily UVB (290–320 nm) dose of 0.01 to 15 mJ cm⁻². Because patients are exposed continually over long time frames, this could lead to significant cumulative damage. It would therefore be prudent for patients to use bulbs with the lowest UV irradiance.     

THE INFLUENCE OF SODIUM PENTOBARBITAL ANESTHESIA ON in vivo PHOTODYNAMIC THERAPY

Abstract The use of sodium pentobarbital anesthesia 50 jig gm⁻¹ during localized photodynamic therapy (PDT) was examined in C57BL/6 mice transplanted with the pigmented B-16 melanoma. A 10 mg kg⁻¹ i.p. injection of Photofrin II was administered 24 h prior to light exposure (630 nm, 150 mW, cm⁻², 300-500 J cm⁻²). Separate groups of mice were utilized to monitor tumour temperature and PDT tumor response. Core tumor temperatures decreased by approx. 10^oC following sodium pentobarbital administration. Tumor responses were determined by documenting the percentage of treated animals without tumor recurrences for a period of 50 days following PDT. Superior PDT induced tumor responses were obtained in control (non-anesthetized) mice following light doses of 400 and 500 J cm⁻². The results of this study indicate that sodium pentobarbital can induce a protective effect on B-16 melanomas treated with PDT.     

COMPARATIVE ANALYSES OF ACTION SPECTRA OF GLYCOLATE EXCRETION ("PHOTORESPIRATION") AND PHOTOSYNTHESIS IN THE BLUE-GREEN ALGA AN ACYSTIS NIDULANS

Abstract. The action spectra were determined by measuring photosynthetic H¹⁴CO^-₃-fixation and ¹⁴C-glycolate excretion to the medium during 15 min exposure to light at 15 different wavelengths in the visible region using interference filters and a 2500 W high pressure Xe lamp at a constant photon flux of about 1.51 × 10¹⁹ quanta m^-2.s^-1 at all wavelengths.
When plotted on relative scales the action spectrum of glycolate excretion lies below that of photosynthesis at all wavelengths shorter than 517 nm. As glycolate excretion had an exponential relationship to photosynthetic rates, different methods were used to analyze for a specific blue light effect which demonstrated that the relative amount of glycolate excretion was depressed by blue light compared with that by green and red. The greatest difference was observed around 460–480 nm. However, on statistical grounds it is not permitted to draw a difference spectrum which might indicate the absorption characteristics of pigment(s) involved.
A hypothesis is discussed assuming that some glycolate is consumed in an oxidation process for supply of electrons to Photosystem I when Photosystem II is poorly excited in the blue region of the spectrum, which was the case for Anacystis used in the present investigation.     

LIGHT INDUCED FLUORESCENCE SPECTRAL CHANGES IN NATIVE PHYTOCHROME FROM Secale cereale L. AT LIQUID NITROGEN TEMPERATURE

Abstract— Fluorescence spectra of native rye phytochrome were determined under different light conditions at liquid nitrogen temperature. Fluorescence spectrum of the red-light-absorbing form (Pr) had a major peak at about 685 nm (14 600 cm⁻¹) and a broad sub-peak at about 515 nm (19 400 cm⁻¹). The peak height at 685 nm was reduced by irradiation with monochromatic light of 640 nm, and a new peak became obvious at about 702 nm (14250 cm⁻¹). This spectral change was almost completely reversed by subsequent irradiation with 700-nm light. Fluorescence spectrum of the photoequilibrium mixture of Pr and far-red-light absorbing form under continuous red light showed a sharp peak at about 685 nm having a peak height ca. 12% of Pr, and a broad sub-peak at about 508 nm (19 700 cm⁻¹). Light of 730 nm did not reduce the peak height at about 685 nm but induced a new shoulder at about 699 nm (14300 cm⁻¹). Monochromatic light of 640 and 700 nm given following the light of 730 nm could not reverse the spectral change at 699 nm induced by the irradiation with 730-nm light. Fluorescence spectrum of Pr in partially degraded phytochrome was similar to that in native phytochrome but the peak position in the red region was shifted by about 5 nm (100 cm⁻¹) to the blue.     

POLARIZED UV-ABSORPTION SPECTRA OF RETINAL ISOMERS-I. MEASUREMENTS IN EXTREMELY THIN MONOCRYSTAL PLATELETS

Abstract Crystals of all- trans retinal and both different forms of 11- cis , 12-s- cis retinal were grown on quartz slides with faces (101), (001) and (101), respectively, forming thin platelets of less than 0.2 μm thickness. Polarized UV absorption spectra at room temperature were measured in the range from 20 to 43 × 10³ cm⁻¹ with a microscope-spectrophotometer. In this spectral range three diffuse absorption bands were observed for all crystal types at similar wave numbers. A main absorption band was found at 25–28 × 10³ cm⁻¹, and two further bands at 32–34 and 38–40 × 10³ cm⁻¹. In case of all- trans retinal the latter band is by far the weakest in this spectral range. Additionally, the crystal spectrum of all- trans retinal shows a shoulder at the low wavenumber side of the main band which cannot be resolved in the corresponding solution spectrum. In the crystal spectra of 11- cis , 12-s- cis retinal, however, only a strong dissymmetry is observed at this side of the main band.     

KINETICS OF BACTERIAL BIOLUMINESCENCE AND THE FLUORESCENT TRANSIENT

Abstract— The addition of FMNH₂ to Vibrio harveyi luciferase at 2°C in the presence of tetradecanal results in the formation of a highly fluorescent transient species with a spectral distribution indistinguishable from that of the bioluminescence. The bioluminescence reaches maximum intensity in 1.5 s and decays in a complex manner with exponential components of 10^-1s^-1, 7 × 10^-3s^-1, and 7 × 10 ⁴s^-1. The fluorescent transient rises exponentially at 7 × 10^-2s^-3 and decays at 3 × 10^-4s^-1. The slowest bioluminescence component, comprising the bulk of the bioluminescence, decays at twice the rate of the fluorescent transient under all variations of reaction conditions: concentration of reactants, temperature 2–20°C, and aldehyde chain length—decanal, dodecanal and tetradecanal. The activation energy for both the slowest bioluminescence decay and the transient fluorescence decay is 80 kJ-mol^-1. An energy transfer scheme is proposed to explain the results where two distinct chemically energized species utilize the fluorescent transient as emitter for the slower bioluminescences, and for the faster process a fluorophore present in the protein preparation. Kinetic observations suggest that typical preparations of V. harveyi luciferase comprise 15% active protein.     

Optical Absorption of Blood Depends on Temperature during a 0.5 ms Laser Pulse at 586 nm

Optical properties are important parameters in port wine stain laser treatment models. In this study we investigated whether changes in blood optical properties occur during a 0.5 ms laser pulse. Blood from three volunteers was irradiated in vitro with laser pulses (radiant exposure 2–12 J cm⁻², wavelength 586 nm, pulse length 0.5 ms). Reflection and transmission coefficients, measured using double integrating spheres, decreased slightly during the first part of the pulse. At 2.9 J cm⁻² radiant exposure, the reflectance increased, independent of total radiant exposure of the pulse. This was caused by blood coagulation. A second sudden increase in reflection and a significant increase in transmission occurred near 6.3 J cm^–2 and was accompanied by a "popping" sound, indicating rapid expansion of bubbles due to blood vaporization. A multilayered model of blood was used to fit calculated transmission coefficient curves to the measurements and determine temperature-dependent optical blood absorption. Heat diffusion was shown to be of minor importance. A 2.5-fold increase in absorption for temperatures increasing from 20 to 100°C, accurately describes transmission coefficients measured up to 2.9 J cm⁻².     

DOES LOW-INTENSITY He-Ne LASER RADIATION PRODUCE A PHOTOBIOLOGICAL GROWTH RESPONSE IN Escherichia coli?

Abstract A photobiological study was camed out on the bacterium Escherichia coli in order to determine whether stimulation of growth occurred after irradiation of an inoculum with coherent red light. No enhancement or inhibition of growth was observed for cultures of the bacterium following irradiation of inocula with a Helium-neon laser (continuous wave, λ= 632.8 nm) at irradiances of 7.7 × 10¹⁵ and 1.8 × 10¹⁶ photons cm⁻² s⁻¹ using fluences of 4.5 × 10^−-1 and 4.5 J cm⁻² at each irradiance. Bacterial growth in irradiated and control cultures was monitored during a growth period of ca 2 h using a viable count technique after inocula in the early exponential phase had been diluted with fresh growth medium. These results do not provide support for the work of Kam et al . (1983, Nuov. Cim . 2D, 1138–1144), and Tiphlova and Karu (1988, Photochem. Photobiol . 48 , 467–471), which appear to show substantial enhancement of E. coli growth under these conditions.     

DESIGN AND PERFORMANCE OF THE OKAZAKI LARGE SPECTROGRAPH FOR PHOTOBIOLOGICAL RESEARCH

A computer-operated spectrograph was recently built at Okazaki, Japan. Different specimens can be placed on a horseshoe-shaped focal curve (10 m long) covering a wavelength range of 250 to 1000 nm so they can be irradiated simultaneously. The linear dispersion is about 0.8 nm/cm. The photon fluence rate on the focal curve is 5 x 10¹⁵. photons x cm^-2 x s^-1 at 300nm and 1 x 10¹⁶ photons x cm^-2 x s^-1 at 600 and at 900 nm. The spectral half width is 5.5 nm or less on the focal curve. The stray light content is about 10^-5 of the main peak at the peak wavelength ± 100 nm. Specimens are set in microcomputer-controlled threshold boxes so that wavelengths, photon fluence rates, photon fluences and timing of irradiations are controlled automatically according to a pre-programmed schedule. An optical fiber system is also provided for remote irradiations.     

PHOTOCHEMICAL REACTION OF 13-CIS-BACTERIORHODOPSIN STUDIED BY LOW TEMPERATURE SPECTROPHOTOMETRY

Abstract— The photoreaction cycle of 13- cis -bacteriorhodopsin (13- cis -bR) was investigated by low temperature spectrophotometry using two different preparations; 13- cis -bR constituted from bacterioopsin and 13- cis -retinal, and dark-adapted bacteriorhodopsin (bR^D), which is an equi-molar mixture of 13- cis -bR and trans -bR.
By irradiation with 500 nm light at — 190°C, 13- cis -bR was converted to its batho-product, batho-13- cis -bR (batho-bR¹³), which is different from batho-product from trans -bR, batho-bR^t. On warming batho-bR¹³ to -5°C in the dark, it completely changed to trans -bR. We estimated the composition of 13- cis -bR and trans -bR in the warmed sample spectrophotometrically and then the absorption spectrum of batho-bR¹³ was calculated. The absorption maximum lies at 608 nm, 1250 cm⁻¹ longer than that of 13- cis -bR; the molar extinction coefficient (ε) is about 74000 M ⁻¹ cm⁻¹, larger than that of 13- cis -bR (52000 M ⁻¹ cm⁻¹).
On the warming the sample containing batho-bR¹³ formed by irradiating 13- cis -bR or bR^D at — 190°C, we could not detect other intermediates such as the lumi- or meta-intermediates seen in trans-bR system.     

Monte Carlo Model of Stricture Formation in Photodynamic Therapy of Normal Pig Esophagus

Photodynamic therapy (PDT) is FDA-approved for use in patients with Barrett's esophagus using porfimer sodium (2 mg per kg) and a recommended light dose of 130 J cm⁻¹ for high grade dysplasia. Despite uniform drug and light doses, the clinical outcome of PDT is variable. A significant number of PDT cases result in esophageal strictures, a side effect related to excessive energy absorption. The purpose of this project was to model esophageal stricture formation with a Monte Carlo simulation. An original multilayer Monte Carlo computer simulation was developed for esophageal PDT. Optical absorption and scattering coefficients were derived for mucosal and muscle layers of normal porcine esophagus. Porfimer sodium was added to each layer by increasing the absorption coefficient by the appropriate amount. A threshold-absorbed light dose was assumed to be required for stricture formation and ablation. The simulation predicted irreversible damage to the mucosa with a 160 J cm⁻¹ light dose and damage to the muscle layer with an additional 160 J cm⁻¹ light dose for a tissue porfimer sodium content of 3.5 mg kg⁻¹. The simulation accurately modeled photodynamic stricture formation in normal pig in vivo esophageal tissue. This preliminary work suggests that the absorbed light threshold for stricture formation may be between 2 and 4 J per gram of tissue.     

SOME SPECTRAL CHARACTERISTICS OF THE LIGHT EMITTING SYSTEM OF THE POLYNOID WORMS

Abstract— The bioluminescence emission spectrum of the light emitted from the elytra of certain poly-noid worms is similar to the fluorescence of the scales and to the fluorescence of flavins. In extracts the fluorescence is confined to the particulate fraction. Stimulation of bioluminescence from such particles was observed upon the addition of Fe²⁺ ions.     

LIGHT-INDUCED FOURIER TRANSFORM INFRARED SPECTROSCOPIC INVESTIGATIONS OF THE INTERMEDIARY ELECTRON ACCEPTOR REDUTION IN BACTERIAL PHOTOSYNTHESIS

Abstract— Molecular changes associated with the light-induced reduction of the intermediary electron acceptor I (bacteriopheophytin, BPh) in bacterial photosynthesis were studied by means of Fourier transform infrared (FTIR) difference spectroscopy. Chromatophore membranes and reconstituted reaction centers (RCs) of Rhodopseudomonas viridis were prereduced with sodium dithionite and illuminated in order to trap photochemically the state I⁻. Fourier transform infrared spectra of these samples were recorded before, during and after illumination, with an accuracy better than 10⁻³ absorbance units. Difference spectra of I⁻ in chromatophores and in RCs closely correspond to each other. In the carbonyl stretching frequency region between 1640 and 1750 cm⁻¹, bands are tentatively attributed to a shift (from 1713 to 1683 cm⁻¹) of a keto carbonyl group, a change of an acetyl carbonyl grou at 1656 cm⁻¹ and a decrease in absorbance strength of ester carbonyl groups (at 1746 and 1732 cm⁻P) after reduction of I. These groups likely belong to the BPh molecule, although at least one of the ester carbonyls could be assigned to an amino acid side chain. The absence of strong bands in the amide I and amide II region excludes large protein conformational changes associated with I reduction.     

POLARIZED UV-ABSORPTION SPECTRA OF RETINAL ISOMERS—II. ON THE ASSIGNMENT OF THE LOW AND HIGH ENERGY ABSORPTION BANDS

Abstract The polarized UV-absorption spectra of all- trans retinal and both crystal forms of 11- cis , 12-s- cis retinal (presented in the previous paper, Part I) are analyzed using Lowry-Hudson functions to describe the band profiles. The polarization ratios of the polarized bands is used to determine the direction of the corresponding transition moments. For all- trans retinal the polarization spectra show that the absorption between 23 and 36 X 10³ cm⁻¹ is caused by three overlapping bands labeled S, A and B. For 11- cis retinal the B-band is also clearly resolved whereas the S and A bands are separated with much less certainty than for all- trans retinal.
Comparing these bands with the excited state manifold resulting from semiempirical CI-calculations including double excitations, the S-band could be assigned to the ¹A_g⁻→¹A_g-* and the A-band to the ¹A_g⁻→¹B_u+* transition. However, no transition is found in this manifold which could positively be assigned to the B-band because the transitions predicted in this spectral region have negligible oscillator strengths. In all the crystal spectra a further band C is observed around 39 X 10³ cm⁻¹ which is particularly pronounced in the case of 11- cis retinal. For this band an assignment to the ¹A_g⁻→¹A_g+*-transition is proposed.     

ULTRASTRUCTURAL STUDIES ON THE MECHANISM OF THE PHOTODYNAMIC THERAPY OF TUMORS

Abstract Balb/c mice bearing a transplanted MS-2 fibrosarcoma were injected with 2.5 mg kg ¹ of either tetra(4-sulfonatophenyl/porphine (TPPS) in phosphate-buffered saline or 0.5 mg kg⁻¹ of Zn²⁺-phthalocyanine (Zn-Pc) incorporated into unilamellar liposomes of dipalmitoyl-phosphatidylcholine. Chromatographic studies showed that TPPS is mainly transported in the serum by globulins and albumin, while Zn-Pc is specifically bound by lipoproteins. Exposure of the injected mice to red light (300 J cm⁻²) caused extensive tumor necrosis. The ultrastructural analysis of tumor specimens taken from mice at 15 h after PDT showed that TPPS photoinduces a preferential necrosis of the neoplastic cells, while Zn-Pc causes severe photodamage to both the vascular system and the neoplastic cells. The different modes of tumor photosensitization by TPPS and Zn-Pc are discussed on the basis of the transport mechanism of the two dyes.     

In vitro photodynamic eradication of Pseudomonas aeruginosa in planktonic and biofilm culture

Photodynamic disinfection (PDD) is a nonantibiotic approach to treating drug-resistant bacterial infections. Pseudomonas aeruginosa , an opportunistic pathogen, is problematic because of its propensity to develop antibiotic resistance and its ability to secrete a protective biofilm matrix. This study examined the ability of PDD to eradicate planktonic and biofilm cultures of P. aeruginosa in vitro . Planktonic P. aeruginosa cultures were briefly exposed to a methylene blue-based photosensitizer formulation and subjected to energy doses ranging from 1.7 to 20.6 J cm⁻² using a 670 nm nonthermal diode laser. Biofilms were grown for 24 and 48 h and exposed to photosensitizer for 30 s before illumination with 13.2 or 26.4 J of energy. A single exposure of planktonic P. aeruginosa to photosensitizer at >15.5 J cm⁻² resulted in 100% eradication (>7 log₁₀ reduction from control), an effect that could be decreased significantly in the presence of the singlet oxygen quenchers l -tryptophan and sodium azide. Decreasing the energy dose below this threshold by varying both power density and illumination duration resulted in a dose-dependent decrease in bacterial kill. In addition, 24 h biofilm viability was reduced by 99% with single exposure and 99.9% with double exposure, while 48 h biofilm viability was reduced by >99.999% with both single and double exposures. This study shows that PDD is effective in eradicating planktonic and biofilm cultures of P. aeruginosa, supporting the concept that translation into clinical practice for indications such as otitis externa and wound disinfection is a viable option.     

A Resonance Raman Study Of the C=C Stretch Modes in Bovine and Octopus Visual Pigments with Isotopically Labeled Retinal Chromophores

Abstract— Previous resonance Raman spectroscopic studies of bovine and octopus rhodopsin and bathorhodopsin in the C–C stretch fingerprint region have shown drastically different spectral patterns, which suggest different chromophore-protein interactions. We have extended our resonance Raman studies of bovine and octopus pigments to the C=C stretch region in order to reveal a more detailed picture about the difference in retinal-protein interactions between these two pigments. The C=C stretch motions of the protonated retinal Schiff base are strongly coupled to form highly delocalized ethylenic modes located in the 1500 to 1650 cm⁻¹ spectral region. In order to decouple these vibrations, a series of 11,12-D₂-labeled retinals, with additional 13C labeling at C₈, C₁₀, C₁₁ and C₁₄, respectively, are used to determine the difference of specific C=C stretch modes between bovine and octopus pigments. Our results show that the C₉=C₁₀ and C₁₃=C₁₄ stretch mode are about 20 cm⁻¹ lower in the Raman spectrum of octopus bathorhodopsin than in bovine bathorhodopsin, while the other C=C stretch modes in these two bathorhodopsins are similar. In contrast, only the C₉=C₁₀ stretch mode in octopus rhodopsin is about 10 cm⁻¹ lower than in bovine rhodopsin, while other C=C stretches are similar.     

CAFFEINE-ENHANCED PHOTOMOVEMENT IN THE CILIATE, STENTOR COERULEUS

The effects of caffeine, ionophores and calcium flux blockers on the step-up photophobic response, phototactic orientation and the intracellularly recorded, light-induced electrical action potential were studied in the ciliate, Stentor coeruleus . Caffeine alters the absorption and CD spectra and enhances the fluorescence of the photoreceptor pigment, stentorin. Independent of its effects on the spectroscopic properties of the photoreceptor pigment, caffeine shortens the photophobic response time by enhancing the Ca²⁺ conductivity of membranes, while Ca²⁺ flux blockers (LaCI₃ or ruthenium red) prolong it; both effects cancel each other. Evidence is presented that phototactic orientation is brought about by repetitive photophobic responses, since a change in the phobic response time results in a decreased accuracy of phototaxis.     

THE ROLE OF HEMOGLOBIN IN THE PHOTOTAXIS OF THE NEMATODE Mermis nigrescens

Abstract A dense zone of crystalline hemoglobin in the head has been presumed to be involved in the photosensitivity of Mermis. With the aim of identifying its role, we have studied the wavelength dependence of the phototaxis. Measuring phototaxic efficiency at constant photon fluence rate (intensity), we find that the spectral response curve is approximately fiat from 350–540 nm and falls to an insignificant level by 580 nm. This is unlike the absorptance (fraction absorbed) spectrum of the hemoglobin pigmentation. Also, fluence-rate/response curves at 420 and 500 nm occur at the same fluence rates even though these wavelengths correspond to a maximum and a minimum of hemoglobin absorption. These results prove that the hemoglobin cannot be functioning as the visual pigment in phototaxis but, for reasons discussed, they neither confirm nor rule out a role as a shadowing pigment. The results are consistent with a shadowing role in the presence of contrast enhancement by the nervous system.
A steep fluence-rate dependence suggests that contrast enhancement does occur in Mermis phototaxis. The 420 or 500 nm fluence rate for half-maximal response is 6 times 10 photons s^-1 cm^-2 (about equivalent in effectiveness to pre-dawn twilight). The wide range of sensitivity, 350–560 nm, has interesting implications as to the nature of the visual pigment.
†NATO reaearch collaborator a n leave from the Department of Biophysics. Laboratorium voor Algemene Natuurkunde, Rijksuniversiteit Groningen, Westersin-gel 34. 9718 CM Groningen, The Netherlands.