Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sunlight”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1990

Spectral comparison of solar simulators and sunlight.

In evaluating sunscreen efficacy, spectral distribution of the irradiation sources can influence the sun protection factor (SPF). The purpose of this investigation was to examine the uniformity of ultraviolet (UV) spectral irradiance of solar simulators used in various SPF testing laboratories, compare them with natural sunlight UV radiation (UVR), and recommend performance limits to ensure that the variability of radiation sources in the UVB region minimally affects SPF estimates. The critical portion of the solar erythemogenic spectrum was identified as the UVB portion, defined as the region between 280 and 320 nm. The spectral irradiance of 26 solar simulators and other UV sources was measured and compared with a summer noon solar spectrum measured in Albuquerque, NM. Proposed spectral limits were developed as a 6-nm "acceptance band" centered on this standard spectrum normalized at 320 nm. The results indicated that the xenon-arc solar simulators currently used in the United States in testing sunscreens either meet the proposed standard solar spectrum or can be readily modified with available UV filters to meet this standard. The devices that have spectral characteristics not resembling sunlight fail to meet the proposed standard and should not be used for sunscreen SPF testing.

Filtration↗
PubMed1990

[Skin pigmentation, nevi and sunlight as etiologic factors of cutaneous malignant melanoma].

In this review, an attempt is made to provide a status on the current knowledge concerning the connection between skin pigmentation, naevi, sunshine and development of cutaneous malignant melanoma. Our knowledge is based partly on descriptive epidemiological reports, and partly on information obtained from case control investigations. The descriptive investigations have revealed characteristic geographical and ethnic differences in the distribution of the disease. Cancerregistry data have revealed a rapid increase in the incidence among white populations during the past 30-40 years with particularly pronounced increase for the areas of the body normally covered with clothes. Lacking consistency between indicators for cumulative exposure to sunlight and descriptive epidemiological studies have led to the hypothesis that intermittent exposure to sunlight is particularly harmful. Case control investigations have provided further support to this hypothesis and have demonstrated that sunbathing is associated with an increased risk for development of melanoma, particularly during childhood and particularly if it leads to sunburning. In addition, the risk of development of melanoma is increased in persons with a tendency to freckle and/or with many naevi. On this background, certain risk groups may be informed about prophylactic measures with subsequent possibility of reducing the number of new cases of cutaneous melanoma in the future. Finally, it is emphasized that the disease is multifactorial in origin and that the pathogenesis is not fully elucidated.

Humans↗
PubMed1989

Effect of simulated sunlight on Langerhans' cells in malignant melanoma patients.

The effect of artificial sunlight on the number and HLA class II expression of Langerhans' cells was studied in 10 patients with malignant melanoma and 10 control volunteers. The total number of Langerhans' cell decreased in both groups but at 96 h there was a greater and significant decrease (p less than 0.01) in the number of Langerhans' cells in the melanoma group, compared with controls. This decrease persisted and was still greater in the melanoma group (p less than 0.02) at one week post-irradiation. There was a rise in Langerhans' cell count over the following 3 weeks in both groups. Unexpectedly, during this period in the melanoma group-but not controls-there was a significant median peak rise above pre-irradiation levels (p less than 0.001). Alteration in the response of Langerhans' cells to sunlight may play a part in the aetiology of malignant melanoma.

Adult↗
PubMed1989

Ozone depletion and its consequences for the fluence of carcinogenic sunlight.

A slight reduction of the ozone level over the northern hemisphere in the period 1969-1986 has been reported [D. Lindley, Nature (Lond.), 323: 293, 1988]. Ozone measurements performed in Oslo are in agreement with this. However, the ozone level for 1987 and 1988 was above normal, and no negative or positive trend is apparent for the last 10 years. The consequences of an ozone reduction for the fluence rate of carcinogenically effective sunlight was evaluated on the basis of recent action spectra for mutagenesis in cells, carcinogenesis in mice, and erythema induction in humans. Depending on the choice of action spectrum we find amplification factors (defined as percentage increase in yearly fluence of carcinogenically efficient sunlight per percentage reduction of the ozone level) between 1.1 and 1.3 at latitudes between 0 and 20 degrees and between 0.9 and 1.1 for Northern Europe. These estimates are significantly lower than 2.0, which is the value found when the calculations are based on the DNA absorption spectrum (R. B. Setlow, Proc. Natl. Acad. Sci. USA, 71:3363-3366, 1974).

Animals↗
PubMed1989

Epidemiological studies of the influence of sunlight on the skin.

We examined and interviewed 809 randomly selected individuals (56% women and 44% men, mean age 44 years) from 4 Swedish cities; 1.7% had the sun-reactive skin type I, 26.2% type II, 61.3% type III and 10.7% type IV. Some variations in the distribution of skin types were found between the cities. One hundred subjects (12.4%), mostly women (p less than 0.001), had a history of polymorphous light eruption. People with skin type IV had significantly fewer facial skin problems than the rest of the subjects (p less than 0.05). The majority of subjects with atopic eczema, acne vulgaris or seborrheic dermatitis experienced improvement after exposure to sunlight. Individuals with rosacea also experienced improvement more often than impairment from exposure to sunlight. Facial telangiectases occurred in 57% of the subjects, unilaterally in 8.5% of the cases. The occurrence of telangiectases increased with increasing age (p less than 0.001), increasing sunbathing (p less than 0.01) and poor pigmentation ability (p less than 0.05).

Adult↗
PubMed1987

Socioeconomic status, sunlight exposure, and risk of malignant melanoma: the Western Canada Melanoma Study.

In a study of 261 male melanoma patients and age-and sex-matched controls, a strong positive univariate association between socioeconomic status, as determined by usual occupation, and risk of melanoma was detected. This association, however, was substantially explained by host constitutional factors and occupational, recreational, and vacation sunlight exposure. The study demonstrated an increased risk of melanoma in draftsmen and surveyors and a reduced risk of melanoma in construction workers and individuals employed in the finance, insurance, and real estate industry even after control for the effect of host factors and sunlight exposure.

Canada↗
PubMed1986

Relationship of cutaneous malignant melanoma to individual sunlight-exposure habits.

The relationships of different histologic types of cutaneous malignant melanoma to occupational and recreational sunlight exposure, habits of clothing, sunburn histories, and use of sunscreening agents were examined in a case-control study of 507 patients and 507 matched controls in Western Australia. Variations in relationships according to the primary site of melanoma were also examined. An increased incidence rate of superficial spreading melanoma was associated with low total outdoor exposure in early adulthood and frequent participation in boating and fishing. Superficial spreading melanoma of the trunk was also related to frequency of sunbathing at ages 15-24 years and of exposure of the trunk while working outdoors. In women the rate ratio for all types of melanoma occurring on the trunk was estimated at 13.0 (95% confidence interval, 2.0-83.9) in those who wore a bikini or bathed nude at ages 15-24 years compared with those wearing a conservative one-piece bathing suit. There was little evidence that sunbathing or wearing a bikini within 10 years of case diagnosis were risk factors for melanoma of the trunk. After control of confounding due to constitutional factors, only Hutchinson's melanotic freckle melanoma showed a relationship to severe sunburn. For nodular melanoma, sunburn appeared to be protective. Although many of the results supported the hypothesis that melanomas other than the Hutchinson's melanotic freckle type are related to occasional bursts of recreational sun exposure during a susceptible period in early adult life, little support for the hypothesis was obtained when recreational sun exposure was expressed as a proportion of total outdoor exposure, which had been considered a priori to be an index of intermittent sunlight exposure.

Adolescent↗
PubMed1985

Effects of calcium supplementation and sunlight exposure on growing beagle dogs.

Nine 7-week-old Beagle dogs were given 2.3 g of dietary calcium supplementation once a day and were exposed to sunlight to permit endogenous vitamin D formation. After 70 days, the serum calcium and phosphorus concentrations, thyroid morphometry, and bone density and composition were compared with those values in a similar group of 10 dogs not given calcium supplementation and maintained in restricted, artificial light. Lower serum calcium and phosphorus concentrations in the supplement-fed dogs may be attributed to hypercalcitonism, which was assumed to be present because of increased proportions of C cells and decreased proportions of thyroid follicles. They also had significantly more trabecular bone of a lower specific gravity containing more water and less combustible matter. The findings indicate that the high dietary calcium intake and sunlight exposure induced C-cell hyperplasia during a relatively short period of 70 days. It is possible that Beagles maintained through maturity on a diet high in calcium concentration and in outdoor runs may develop chronic C-cell hyperplasia. The possible contribution of high calcium intake and chronic C-cell hyperplasia to reduced thyroid function and skeletal changes is not yet clear.

Animals↗
PubMed1982

Genotoxic effects of sunlight-activated waste water in cultured mammalian cells.

Cultured Chinese hamster ovary cells were incubated with dilutions of an oil shale retort process water and exposed to nautral sunlight. An enhancement of sevenfold to ninefold was seen in photoinduced cytotoxicity (by a colony-forming assay) and mutagenicity [at the hypoxanthine phosphoribosyltransferase (HPRT) locus] for cells pretreated with the process water compared to effects seen in cells exposed to sunlight only. Significant photoinduced cytotoxicity was also observed in cultured human skin fibroblasts when exposed to the process water before being exposed to near UV (NUV) radiation. The mutation frequencies (determined for the HPRT locus) induced by the process water and NUV radiation were as great as those frequencies seen for far UV light alone. Increases in genotoxicity were observed in excision repair-deficient xeroderma pigmentosum skin fibroblasts when compared to the responses seen in normal cells. Risks to health resulting from the phototransformation of these oil shale retort process waste waters are unassessed at this time.

Animals↗
PubMed1978

The correlation of indoor solar simulator and natural sunlight: testing of a sunscreen preparation.

To determine the equivalence of xenon arc solar simulator and natural sunlight test results, the sun protection factor (SPF) for an experimental sunscreen preparation was determined using each light source. The minimal erythemal doses (MEDs) were shown to be equivalent on unprotected skin. It was necessary to supply additional heat to the treated skin prior to solar simulator exposures to obtain comparable SPFs. By careful control of the subjects' environment, natural sunlight effects can be duplicated with a solar simulator.

Dermatology↗
PubMed1994

Effects of gamma rays, ultraviolet radiation, sunlight, microwaves and electromagnetic fields on gene expression mediated by human immunodeficiency virus promoter.

Previous work by our group and others has shown the modulation of human immunodeficiency virus (HIV) promoter or long terminal repeat (LTR) after exposure to neutrons and ultraviolet radiations. Using HeLa cells stably transfected with a construct containing the chloramphenicol acetyl transferase (CAT) gene, the transcription of which is mediated by the HIV-LTR, we designed experiments to examine the effects of exposure to different types of radiation (such as gamma rays, ultraviolet and sunlight irradiations, electromagnetic fields and microwaves) on HIV-LTR-driven expression of CAT. These results demonstrated ultraviolet-light-induced transcription from the HIV promoter, as has been shown by others. Exposure to other DNA-damaging agents such as gamma rays and sunlight (with limited exposures) had no significant effect on transcription mediated by HIV-LTR, suggesting that induction of HIV is not mediated by just any type of DNA damage but rather may require specific types of DNA damage. Microwaves did not cause cell killing when cells in culture were exposed in high volumes of medium, and the same cells showed no changes in expression. When microwave exposure was carried out in low volumes of medium (so that excessive heat was generated) induction of HIV-LTR transcription (as assayed by CAT activity) was evident. Electromagnetic field exposures had no effect on expression of HIV-LTR. These results demonstrate that not all types of radiation and not all DNA-damaging agents are capable of inducing HIV. We hypothesize that induction of HIV transcription may be mediated by several different signals after exposure to radiation.

Chloramphenicol O-Acetyltransferase↗
PubMed1994

Chromametric quantification of pigmentary changes in the solar lentigo after sunlight exposure.

The purpose of this study is to compare by chromametric analysis the changes seen in normal skin and solar lentigos after exposure to sunlight. The color measurements were made with a Minolta CR200 chromameter and expressed in the L*a*b* system, which allows a color to be quantified according to 3 axes: white-black (L*), red-green (a*) and yellow-blue (b*). In order to better assess the sensitivity of physiological mechanisms involved in this pigmentation, we chose the weakest conditions of sunlight: the first series of measurements were made at the end of the winter (March) on areas rarely exposed for several months, and the second measurement was made 2 months later before the first intense summer solar exposure. Solar lentigos underwent a significant change in pigmentation, with a darkening of these lesions and an increase in the red and yellow color components. The pigmentation of healthy skin adjacent to these lentigos remained unchanged.

Adult↗
PubMed1977

Skin cancer: comparison of aggressive potentials of sunlight-induced and x-ray-induced tumors.

Differences in clinical behavior between sunlight- and x-ray-induced skin cancer have been shown. The frequency of occurrence of multiple lesions is greater in those induced by x-ray than in the solar or nevoid type. Recurrence and major surgical sequelae appear to be greater with x-ray-induced lesions. The electron microscopic pictures of sunlight-induced and x-ray-induced basal cell carcinoma are different.

Adolescent↗
PubMed1996

The effect of season and latitude on in vitro vitamin D formation by sunlight in South Africa.

AIMS: To assess the effect of season and latitude on the in vitro formation of previtamin D3 and vitamin D3 from 7-dehydrocholesterol (7-DHC) by sunlight in two cities in South Africa, Cape Town and Johannesburg. METHODS: An in vitro study utilising vials containing 7-DHC, which were exposed to sunlight for a period of 1 hour between 8:00 and 17:00 on 1 day a month for a year. Previtamin D3 and vitamin D3 were separated from 7-DHC by high-performance liquid chromatography, and the amounts formed were calculated with the use of external standards. RESULTS: A marked seasonal variation in vitamin D3 production was noted in Cape Town, with very little being formed during the winter months of April through September. In Johannesburg, in vitro formation changed little throughout the year, and was similar to that found in Cape Town during the summer. During sunlit hours, vitamin D3 production was maximal at midday and small quantities were still being formed between 8:00 and 9:00, and between 16:00 and 17:00 during the summer. During winter in Cape Town, peak formation at midday was less than one-third of that in Johannesburg, and negligible amounts were formed before 10:00 and after 15:00. CONCLUSIONS: The previously documented seasonal variation in serum 25-hydroxyvitamin D recorded in patients in Johannesburg is probably a consequence of the increased clothing worn and the decreased time spent out of doors during winter, rather than decreased ultraviolet radiation reaching the earth. The limited in vitro formation of vitamin D3 during winter in Cape Town may have clinical implications insofar as the management of metabolic bone diseases like rickets and osteoporosis is concerned. Breast-fed infants resident in the area are likely to suffer from vitamin D deficiency rickets unless vitamin D supplements are provided, or the mothers are encouraged to take their children out of doors.

Breast Feeding↗
PubMed2001

Heteroflocculation of Sulfate Polystyrene Latex and Anticarsia gemmatalis Nucleopolyhedrovirus as a Model System for Studying Sunlight Protection.

Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus widely used as a pest control agent. Data on field persistence of this microbial insecticide reveal that sunlight is the most destructive of the environmental factors. The introduction of a physical barrier to protect the baculovirus from sunlight has been proposed. In the present work we report on the coating of a baculovirus surface with a uniform layer of smaller particles. The coating was carried out at pH 3, a condition where the baculovirus surface becomes positively charged and can be covered by sulfate polystyrene latex particles. The heteroflocculation was assessed by isotherm measurements and scanning electron microscopy. High-affinity isotherms were obtained for the two sizes of latex used, and the number of latex particles bound per baculovirus was not affected when pH was changed back to neutral range (5<pH<7). Two cycles of centrifugation and washing with deionized water did not wash the sulfate polystyrene from the polyhedron surface. Copyright 2001 Academic Press.

Journal Article↗
PubMed2000

The DNA damage spectrum produced by simulated sunlight.

The mutagenic effects of ultraviolet and solar irradiation are thought to be due to the formation of DNA photoproducts, most notably cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). Experimental systems for determining the levels and sequence dependence of photoproduct formation in DNA have often used high doses of short-wave (UVC) irradiation. We have re-assessed this issue by using DNA sequencing technologies and different doses of UVC as well as more physiologically relevant doses of solar irradiation emitted from a solar UV simulator. It has been questioned whether hot alkali treatment can detect (6-4)PPs at all sequence positions. With high UVC doses, the sequence distribution of (6-4)PPs was virtually identical when hot alkali or UV damage endonuclease (UVDE) were used for detection, which appears to validate both methods. The (6-4)PPs form at 5'-TpC and 5'CpC sequences but very low levels are seen at all other dipyrimidines including 5'-TpT. Contrary to expectation, we find that (6-4) photoproducts form at almost undetectable levels under conditions of irradiation for up to five hours with the solar UV simulator. The same treatment produces high levels of CPDs. In addition, DNA glycosylases, which recognize oxidized and ring-opened bases, did not produce significant cleavage of sunlight-irradiated DNA. From these data, we conclude that cyclobutane pyrimidine dimers are at least 20 to 40 times more frequent than any other DNA photoproduct when DNA or cells are irradiated with simulated sunlight.

Alkalies↗
PubMed1987

Transient induction of photolyase activity in arrested frog cells in response to a short-wave ultraviolet segment of simulated "sunlight".

Induction of photolyase activity was studied in cultured frog cells using clonogenic assays. Exposure of arrested cells to a pre-irradiation (90% survival) of 254 nm ultraviolet light resulted in a transient enhancement of photolyase activity. Cells expressed a decreased level of photolyase activity in response to an equitoxic fluence of simulated "sunlight" wavelengths 280-310 nm. However, no significant increase of enzyme activity was detected in cells following treatment with "sunlight" wavelengths 310-330 nm. In addition, this process depends on newly biosynthesized protein(s).

Animals↗
PubMed2001

Modeling aerosol formation from alpha-pinene + NOx in the presence of natural sunlight using gas-phase kinetics and gas-particle partitioning theory.

A kinetic mechanism was used to link and model the gas-phase reactions and aerosol accumulation resulting from alpha-pinene reactions in the presence of sunlight, ozone (O3), and oxides of nitrogen (NOx). Reaction products and aerosol formation from the kinetic model were compared to outdoor smog chamber experiments conducted under natural sunlight in the presence of NOx and in the dark in the presence of O3. The gas-particle partitioning of semivolatile organics generated in the gas phase was treated as an equilibrium process between particle absorption and desorption. Models vs experimental aerosol yields illustrate that reasonable predictions of secondary aerosol formation are possible from both dark ozone and light NOx/alpha-pinene systems over a variety of different outdoor conditions. On average, measured gas- and particle-phase products accounted for approximately 54-72% of the reacted alpha-pinene carbon. Model predictions suggest that organic nitrates account for another approximately 25% of the reacted carbon, and most of this is in the gas phase. Measured particle-phase products accounted for 60-100% of the particle filter mass, with pinic acid and pinonic acid being the primary aerosol-phase products. In the gas phase, pinonaldehyde and pinonic acid are major products. Model simulations of these and other products show generally reasonable fits to the experimental data from the perspective of timing and concentrations. These results are very encouraging for a compound such as pinonaldehyde, since it is being formed from OH attack on alpha-pinene and is also simultaneously photolyzed and reacted with OH.

Aerosols↗