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PubMed1987

Action spectra for human skin cells: estimates of the relative cytotoxicity of the middle ultraviolet, near ultraviolet, and violet regions of sunlight on epidermal keratinocytes.

Action spectra for the cytotoxic action of electromagnetic radiation in the solar range 280-434 nm have been determined for human fibroblasts and epidermal keratinocytes derived from the same foreskin biopsy. The spectra for the two cell types are close to identical and coincide with our previously published data for a human lymphoblastoid line indicating that the mechanism of inactivation of the three human cell types is similar at any given wavelength. Using published data for ultraviolet transmission of human skin and sample spectral irradiance data, we have estimated the relative biological effectiveness of the middle ultraviolet (UVB) (290-320 nm), near ultraviolet (UVA) (320-380 nm), and violet (380-434 nm) regions of sunlight for cytotoxicity at the basal layer of the epidermis. We conclude that the UVB component in noon summer sunlight (the most UVB rich spectral conditions tested) may contribute only about 40% of the total cytotoxic effectiveness of sunlight at 290-434 nm. At lower zenith angles, UVA can account for up to 80% of the cytotoxic effectiveness of the combined UVA and UVB regions. Finally, a comparison of published action spectra data for human erythema with cytotoxicity data corrected for ultraviolet transmission to different depths of the human epidermis suggests that UVA erythema could be causally related to cytotoxicity occurring at an average depth of 40-50 micron into the human epidermis.

Cell Line↗
PubMed1999

Effect of simulated sunlight on atrazine and metolachlor toxicity of surface waters.

Atrazine and metolachlor are the two most widely used herbicides in the United States; through non-point-source runoff both herbicides may cause toxicity to aquatic organisms. Toxicity changes were measured for atrazine and metolachlor in surface waters after exposure to simulated sunlight (0, 20, and 40 kJ/m2) using a Xenon Weather-Ometer. A Microtox toxicity test, using the marine luminescent bacterium Vibrio fischeri, was conducted on deionized, river, and bay water samples mixed with atrazine or metolachlor herbicide (12 mg/liter) after exposure to simulated sunlight. Microtox test (EC50%) results demonstrated that the toxicity decreased with increasing light intensity for both herbicides in river and bay water. These results also indicate that the toxicity of the bay water, with high concentrations of organic and suspended matter, was reduced, for both herbicides, compared with the toxicity of the river water, possibly through photodegradation of pesticides.

Acetamides↗
PubMed1976

Alteration of O,O-dimethyl S-[alpha-(carboethoxy)benzyl] phosphorodithioate (phenthoate) in citrus, water, and upon exposure to air and sunlight.

The fate of 32P- and 14C-labeled O,O-dimethyl S-[alpha-(carboethoxy)benzyl] phosphorodithioate (phenthoate) was determined in citrus, water, and upon exposure to air and sunlight. The products recovered from citrus and glass plates exposed to sunlight were unchanged phenthoate, phenthoate oxon, demethyl phenthoate, mandelic acid, bis-[alpha-(carboethoxy)benzyl] disulfide, O,O-dimethyl phosphorothioic and phosphorodithioic acid. Similar products generally were found in citrus leaf and fruit extracts. Phenthoate was fairly stable in phosphate buffered water with a half-life of approximately 12 days at pH 8.0. The major hydrolysis products were phenthoate acid, demethyl phenthoate and demethyl phenthoate oxon.

Air↗
PubMed2000

Sunlight exposure and vitamin D deficiency in Turkish women.

Vitamin D is an essential steroid involved in bone metabolism, cell growth, differentiation, and regulation of the minerals in the body. The main sources of this vital vitamin are adequate diet and photosynthesis in the skin. The aim of this study was to investigate the efficiency of vitamin D synthesis in 48 premenopausal women (14-44 years) in relation to three different types of dressing in summer. Women in the first group (Group I) dressed in a style which exposed the usual areas of the skin to sunlight; women in the second group (Group II wore traditional clothing with the skin of the hands and face uncovered, while the third group (Group III) dressed in traditional Islamic style, covering the whole body including hands and face. Serum 25OHD levels of Group I, Group II, and Group III were 56+/-41.3 nmol/l, 31.9+/-24.4 nmol/l, 9+/-5.7 nmol/l, respectively (Group I vs Group III, p<0.001; Group II vs Group III, p<0,03; Group I vs Group II, p>0.05). Vitamin D levels were low in 44 percent of the Group I and 60% of the Group II, which suggested that sun exposure of skin areas of hands and face may partially provide vitamin D synthesis, but may not be enough to eliminate vitamin D deficiency. All the patients in group III had vitamin D levels below normal. This study emphasizes the necessity of vitamin D fortification of food even in a sunny country where some people may not be exposed to sunlight because of inappropriate clothing or an indoor-life.

Adolescent↗
PubMed1980

Damage and repair in mammalian cells after exposure to non-ionizing radiations. II. Photoreactivation and killing of rat kangaroo cells (Potorous tridactylus) and Herpes simplex virus-1 by exposure to fluorescent "white" light or sunlight.

Photoreactivation (PR) of ultraviolet (254 nm)-inactivated cornea cells of the potoroo (or rat kangaroo; Potorous tridacylus) has been studied at wavelengths greater than 375 nm from either fluorescent "white" light or sunlight. In both cases the PR kinetics curves pass through maxima, which most likely result from the superposition of concomitant inactivation by the photoreactivating light. The inactivating effect of light was directly demonstrated for non-UV-irradiated cells, permitting correction of the PR curves. Wavelengths greater than 475 nm, and even greater than 560 nm, which do not noticeably damage cells, still photoreactivate, though less effectively than shorter wavelengths. Light treatment of UV-inactivated Herpes simplex Virus-1 (HSV-1) after infection leads to PR effects resembling those observed for cells, while light treatment of unirradiated virus after infection likewise causes inactivation. The "fluence-reduction factor" of PR, which is greater than 3 for the virus, exceeds that for the cells, where it decreases with increasing UV fluence. In vitro tests have indicated that sunlight greater than 375 nm causes photorepairable DNA lesions which are virtually fully repaired by the same light. Thus cell inactivation resulting from these solar wavelengths must be due to non-photorepairable damage.

Animals↗
PubMed1981

Killing and mutagenic action of sunlight upon Bacillus subtilis spores: a dosimetric system.

A method to monitor killing and mutagenic activity of sunlight was established by using wild-type spores (UVR) of Bacillus subtilis and mutant spores (UVS) sensitive to UV radiation. Samples exposed to radiations consisted of the spores spotted and dried on membrane filter. After the exposure, they were recovered as suspensions in water and assayed for colony-forming survival and frequency of reversion of an auxotrophic marker (hisB101). In this system, the UVS spores were inactivated exponentially, and the 37% survival was attained with 2.0 Jm-2 of 254 nm or 2.5 X 10(3) Jm-2 of 313 nm radiation, and with 7 min (August) or 63 min (December) exposure to noon-time sunlight under a clear sky at Tsukiji (latitude 35 degrees 40' N) at sea level in Tokyo. The doubling of the spontaneous mutation frequency of the UVR spores was attained with 3.0 Jm-2 of 254 nm or 2.2 X 10(3) Jm-2 of 313 nm radiation, and with 32 min (August) or 136 min (December) of solar exposure. The results encourage the use of this B. subtilis spore system to determine the gene-damaging activity of the solar-UV radiation under a variety of environmental conditions.

Bacillus subtilis↗
PubMed1987

Sunlight supply and gas exchange systems in the microalgal bioreactor.

The bioreactor with sunlight supply system and gas exchange systems presented here has proved feasible in ground tests and shows much promise for space use as a CELSS device. Our chief conclusions concerning the specification of total system needed for a life support system for a man in a space station are the following. (1) Sunlight supply system: compactness and low electrical consumption. (2) Bioreactor system: high density and growth rate of chlorella. (3) Gas exchange system: enough for O2 production and CO2 assimilation.

Air Conditioning↗
PubMed1992

Survival, excision repair and inhibition of DNA synthesis in normal human skin fibroblasts exposed to simulated sunlight.

The responses of normal human skin fibroblasts exposed to simulated sunlight produced by a solar simulator were examined. The parameters investigated were cellular survival, excision repair and the inhibition and recovery of DNA synthesis. The latter two effects were examined using the bromodeoxyuridine photolysis assay and the alkaline step elution assay respectively. The results of these experiments are consistent with the conclusion that the lesions induced by simulated sunlight represent a mixture of damage which elicits cellular responses and repair mechanisms similar to those manifested by cells irradiated with UVC and UVA radiation.

Adult↗
PubMed1992

Inactivation and mutation induction in Saccharomyces cerevisiae exposed to simulated sunlight: evaluation of action spectra.

The effectiveness of polychromatic light irradiation was investigated for haploid yeast cells. Inactivation and mutation induction were measured in both a RAD-wildtype strain and an excision-repair defective strain. The behaviour of vegetative "wet" cells was compared to that of dehydrated cells. The aim of the study was to assess the interaction of UVC with other wavelengths in cells of different states of humidity. The irradiation procedure was therefore carried out using a solar simulator either with full spectrum or with a UVC-blocking filter (modified sunlight) added. The results were analysed on the basis of separately determined action spectra. The summation of the efficiency of individual wavelengths was compared to the values obtained from polychromatic irradiation. It is shown that the effects caused by the whole-spectrum irradiation in wet cells can be predicted sufficiently from the calculation, while dried wildtype cells exhibit higher mutation rates. Thus it can be assumed that drying-specific damage leads to lethal and mutagenic lesions which are processed in different ways, causing a synergistic behaviour in mutation induction. Irradiation of vegetative cells with modified sunlight (UVC-) results in less inactivation and lower mutation rates than were calculated. From these results it can be concluded that this antagonistic behaviour is caused by the interaction of near-UV photoproducts.

Dose-Response Relationship, Radiation↗
PubMed1995

The specificity of p53 mutation spectra in sunlight induced human cancers.

Ultraviolet (UV) irradiation emitted by the sun has been clearly implicated as a major carcinogen in the formation of skin cancers in man. Indeed, the high levels of cutaneous tumors in xeroderma pigmentosum patients (XP) who are deficient in repair of UV-induced lesions have confirmed that DNA damage produced by sunlight is directly involved in the cancer development. The tumor suppressor gene, p53, very frequently found modified in human cancers, has proved to be a perfect target gene for correlating mutation spectra with different cancer causing agents as there are nearly 300 potential mutation sites available for analysis. In a comparative analysis of p53 mutations found in internal cancers with those in skin tumours we show here that clear differences exist between the types of spectra obtained. The specificity of UV induced mutations in skin cancers is confirmed when single and tandem mutations are compared. Most of the p53 point mutations found are GC to AT transitions both in skin and internal tumors where in the latter they are located mainly at CpG sequences probably due to the deamination of the unstable 5-MeC. Moreover, mutations are targeted at py-py sequences in over 90% of skin tumors whereas in internal cancers the distribution is proportional to the frequency of bipyrimidine sequences in the p53 gene. Most significantly, all mutations found in XP skin tumors are targeted at py-py sites and more than 50% are tandem CC to TT transitions considered as veritable signatures of UV-induced lesions. Tandem mutations are also relatively common (14%) in skin tumors from normal individuals compared to their very rare occurrence in internal malignancies (0.8%). Finally, nearly all mutations observed in XP skin tumors are due to unrepaired lesions remaining on the coding strand whereas no strand bias is seen in mutation location of internal or skin tumors from normal individuals. In fact the mutation spectrum analysed in XP skin cancers has permitted the first demonstration of the existence of preferential repair in man. In conclusion, using the p53 gene as a probe it is obvious that the mutation spectra from skin tumors are very similar to those observed in UV-treated gene targets in model systems but statistically different from those described in other types of human cancer. This has allowed us to demonstrate, without ambiguity, the major role of UV-induced DNA lesions in sunlight related skin carcinogenesis.

Animals↗
PubMed2006

Natural sunlight and sun simulator photolysis studies of tetra- to hexa-brominated diphenyl ethers in water using solid-phase microextraction.

Photo-solid-phase microextraction (photo-SPME) is combined for the first time with natural and simulated sunlight to study the photochemical behaviour of environmental concerning tetra- to hexa-brominated diphenyl ethers. The sunlight photodegradation kinetics of five brominated diphenyl ethers (BDE 47, BDE 100, BDE 99, BDE 154 and BDE 153) has been studied. These BDEs are the most abundant congeners in penta-BDE commercial formulations used as flame-retardants and are considered among the most toxic ones. The five studied BDEs were photolytically labile. The detected photodegradation products include more stable lower brominated diphenyl ethers and polybrominated dibenzofurans (PBDFs). The photoformation and decay kinetics of these photoproducts were also monitorized by photo-SPME. Aqueous photodegradation studies have also been carried out. In this case, SPME is only used as the extraction technique. Obtained results in the aqueous photodegradation experiments were compared with those obtained in photo-SPME experiments.

Ethers↗
PubMedDate not supplied

Sunlight exposure and pathogenesis of uveal melanoma.

Uveal melanoma is the most frequent primary malignant intraocular tumor of adults. Among various non-modifiable risk factors, Caucasian race seems to be the most significant with light skin color, blond hair, and blue eyes being specific risk factors. The racial predisposition to uveal melanoma have been explained on the basis of susceptibility of Caucasian race to oncogenic effects of sunlight. Although there is ample evidence in support of this hypothesis in regard to skin melanoma, the evidence in regard to uveal melanoma is insufficient and contradictory. In the following review, we examine physiologic, epidemiological, and genetic data in order to determine the role of sunlight exposure in the pathogenesis of uveal melanoma.

Environmental Exposure↗
PubMed1972

Photochemical effects of sunlight.

The importance of sunlight in bringing about not only photosynthesis in plants, but also other photochemical effects, is reviewed. More effort should be devoted to photochemical storage of the sun's energy without the living plant. There is no theoretical reason to believe that such reactions are impossible. Ground rules for searching for suitable solar photochemical reactions are given, and a few attempts are described, but nothing successful has yet been found. Future possibilities are suggested. Photogalvanic cells which convert sunlight into electricity deserve further research. Eugene Rabinowitch has been an active pioneer in these fields.

Coloring Agents↗
PubMed2000

Effect of short-term sunlight irradiation on absorbance spectra of chromophoric organic matter dissolved in coastal and riverine water.

Samples of riverine and coastal, filtered (filter pore size 0.2 microm) water were exposed to short-term sunlight irradiation which reduced their absorbance in the UV and visible regions. Absorbance losses in coastal chromophoric dissolved organic matter (CDOM) were up to 10-fold smaller than those in riverine CDOM. Accompanying changes of absorbance spectra shapes (increased slope parameter) were, probably, a result of decrease of the mean molecular size of light absorbing organic matter. The potential of coastal CDOM to photodegradation was smaller and was exhausted during the course of a day-long experiment. A distinctive feature of spectral changes after sunlight exposure was a maximum absorbance decrease which appeared at approximately 300 nm in riverine and at approximately 280 nm in coastal water. That selective absorbance loss has been ascribed in both cases to the disappearance of chromophores of terrestrial origin which, in coastal water, had a lower mean molecular size (due to flocculation and/or prior photodegradation) but, nevertheless, retained their molecular properties.

Environmental Monitoring↗
PubMed2000

Determination of rate constants for the reaction of hydroxyl radicals with some purines and pyrimidines using sunlight.

Sunlight mediated hydroxyl radical production from aqueous ferric perchlorate at low pH has been investigated using deoxyribose-thiobarbituric acid assay. The rate of production of hydroxyl radical was found to be dependent on the time of irradiation. Hydroxyl radical scavengers can compete with deoxyribose for hydroxyl radicals produced in the system leading to a decreased yield of thiobarbituric acid chromogen. The second-order rate constants of the added scavengers can be determined using a simple competition kinetic method. The rate constants for the reaction of hydroxyl radical with a number of purine and pyrimidine derivatives were determined using this method. The rate constants obtained (1-7 x 10(9) dm(3) mol(-1) s(-1)) were found to be in good agreement with those reported using pulse radiolysis technique. The rate constants of dimethyluracil, xanthosine, amino and methyl substituted pyrimidines, cytidine monophosphate and uridine monophosphate were also determined by this method. It is proposed that sunlight mediated production of hydroxyl radical coupled with deoxyribose-thiobarbituric acid assay is a simple and efficient method for the determination of rate constants for the reaction of hydroxyl radical with a wide range of biomolecules.

Chemistry, Organic↗
PubMed1997

Sunlight and the onset of skin cancer.

The photons of sunlight precipitate a series of genetic events in skin leading to cancer. These events involve somatic mutations as well as inherited alleles. Competition between cell populations ensues, as a single mutated cell expands into a clone. Thus cancer involves both a single-cell problem and a many-cell problem; in skin cancer, sunlight appears to drive both.

Apoptosis↗
PubMed1983

Photobiology of melanin pigmentation: dose/response of skin to sunlight and its contents.

A randomized double-blind clinical trial involving twenty-two volunteers was conducted in two locations (Orlando, FL, and St. Paul, MN) to test the efficacy of the newly designed ultraviolet monitor badges (Sun Timers), described in another paper by us in this issue of the Journal, 1 and to establish the relationship between spectral band exposure dose and the biologic responses of erythema and pigmentation. Individuals with skin types II, III, and IV, exhibiting differences in reactivity to solar radiation, were exposed to varying doses of full-spectrum sunlight through templates mounted on the lower portion of the back. Simultaneously, on the upper portion of the back, the same volunteers were exposed through two different types of polyester filters that transmitted ultraviolet A (UVA) and visible radiation. Using templates with windows, exposures to full-spectrum sunlight, UVA, and visible radiation were carried out to 1, 2, 3, 6, and 9 sunburn units (approximately 30-270 millijoules/cm2 between 10:30 A.M. and 3:30 P.M. daylight time in mid summer), measured with the aid of a Robertson-Berger meter and an IL700 International Light radiometer. Erythema and pigmentation resulting from these exposures were graded (double-blind) immediately after exposure, at 24 hours, and after 5 days. Numerical skin response ratings at each exposure dose for different spectral bands were then averaged and plotted. It was found that the UVB monitor response was predictive of a 24-hour erythema response and 5-day pigmentation response within 30% of the biologic average for skin types II, III, and IV. UVA radiation stimulated melanogenesis. The minimal melanogenic dose (MMD) for skin type II was the same as the minimal erythemogenic dose (MED). The MMD for individuals of skin types III and IV was distinctly less than their MED. Thus, melanogenesis can be stimulated with a suberythemal dose of UVB or UVA radiation. The sun protection factor values of melanin for melanized skin have been estimated to vary from 1.0 (skin type II) to 4.3 (skin types V and VI).

Clinical Trials as Topic↗
PubMed2001

Is it possible to develop a QSPR model for direct photolysis half-lives of PAHs under irradiation of sunlight?

By the use of the partial least squares method and 11 fundamental quantum chemical descriptors computed from the PM3 Hamiltonian, a Quantitative Structure-Property Relationship model was obtained for direct photolysis half-lives of selected polycyclic aromatic hydrocarbons (PAHs) under irradiation of sunlight. Direct photolysis half-lives for some other PAHs without reported values were predicted. It was concluded from the model that the main factors affecting photolysis half-lives of PAHs under irradiation of sunlight are PAH absolute hardness and electronegativity, which are related to the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, (Elumo - Ehomo) and (Elumo + Ehomo), respectively. Increasing Ehomo and the average molecular polarizability (alpha) values of the PAHs leads to decrease of photolysis half-lives. Increasing (Elumo - Ehomo) and Elumo values of the PAHs leads to an increase of the PAH photolysis half-lives.

Environmental Pollutants↗