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At least 1,153 records · Page 64Linked to original sources
PubMed1997

Sunscreens prevent local and systemic immunosuppression of contact hypersensitivity in mice exposed to solar-simulated ultraviolet radiation.

Ultraviolet (UV) irradiation causes the immunosuppression of contact hypersensitivity (CH) responses in animals and humans. There are conflicting reports regarding the effectiveness of sunscreens in preventing UV-induced suppression of both local-type CH (induced by the application of the contact sensitizer directly to UV-exposed skin) and systemic-type CH (induced by the application of the contact sensitizer to an unirradiated skin site 3 days after UV exposure). The purposes of this study were as follows: 1. to derive solar simulator UV dose-response curves for the induction of local and systemic CH suppression in C3H mice; 2. to establish minimum immune suppression doses (MISDs) for local and systemic CH; 3. to determine the local and systemic immune protection capacity of two commercial sunscreen lotions with labeled sun protection factors (SPFs) of 4 and 8. Dose-response curves for the induction of local and systemic CH suppression were derived by exposing groups of mice to a range of full-spectrum UV doses (0.37-21.4 kJ m-2) on two consecutive days delivered from a filtered 1000 W xenon arc lamp solar simulator. The MISDs, defined as the lowest dose tested to cause approximately 50% suppression of the normal CH response, were obtained from the dose-response curves. Although the local and systemic immunosuppression dose-response curves were not statistically different, the MISD for local suppression of CH (1.35 kJ m-2) was about fivefold lower than that for systemic CH suppression (6.76 kJ m-2). The MISD was used as the endpoint to determine sunscreen immune protection levels. Both sunscreens, applied at 2 mg cm-2, provided immune protection against the induction of local and systemic CH suppression in mice exposed to an effective UV dose of 1 MISD given through the sunscreen, i.e. 4 MISD to SPF 4 sunscreen-protected mice and 8 MISD to SPF 8 sunscreen-protected mice mounted CH responses that were significantly greater than those elicited in unprotected mice exposed to 1 MISD of solar-simulated UV radiation. The calculated immune protection factors for these sunscreens exceeded the level of protection predicted by their labeled SPFs, i.e. the local immune protection factor of both sunscreens was 15 and the systemic immune protection factors were 8 for the SPF 4 sunscreen and 15 for the SPF 8 sunscreen. Our data show that these two sunscreens provide levels of immune protection which exceed the levels predicted by their labeled SPFs in immunoprotection tests conducted in mice exposed to a relevant MISD of UV radiation from a source emitting a UV power spectrum similar to that of sunlight.

Animals↗
PubMed1989

Coupling of Solar Energy to Hydrogen Peroxide Production in the Cyanobacterium Anacystis nidulans.

Hydrogen peroxide production by blue-green algae (cyanobacteria) under photoautotrophic conditions is of great interest as a model system for the bioconversion of solar energy. Our experimental system was based on the photosynthetic reduction of molecular oxygen with electrons from water by Anacystis nidulans 1402-1 as the biophotocatalyst and methyl viologen as a redox intermediate. It has been demonstrated that the metabolic conditions of the algae in their different growth stages strongly influence the capacity for hydrogen peroxide photoproduction, and so the initial formation rate and net peroxide yield became maximum in the mid-log phase of growth. The overall process can be optimized in the presence of certain metabolic inhibitors such as iodoacetamide and p-hydroxymercuribenzoate, as well as by permeabilization of the cellular membrane after drastic temperature changes and by immobilization of the cells in inert supports such as agar and alginate.

Journal Article↗
PubMed1986

[Photosensitivity in human pathology: mechanisms and clinical aspects].

Photosensitivity diseases are reviewed. The pathogenesis of photodermatoses is not completely elucidated, especially because the photosensitizing agents are rarely identified. In exogenous photosensitization, the chemical agent (chromophore) is most often identified, reaching the skin either via topical contact or by systemic administration (drugs). Concepts of phototoxicity (photochemical reaction) and photo-allergy (photo-immunologic reaction) explain the clinical aspects. Dermatoses with photosensitivity are divided into three groups: photo-aggravated dermatoses (solar herpes, lupus erythematosus), photosensitivity caused by protective system defect (xeroderma pigmentosum), and photosensitivity caused by metabolic defects (porphyrias, pellagra). Idiopathic photodermatoses (unknown chromophore) are triggered by solar exposure (systemic photo-allergens would serve as mediators): 'benign estival polymorphous light eruption', polymorphous light eruptions, persistent light reactor, solar urticaria.

Adult↗
PubMed2006

Coexposure to benzo[a]pyrene and UVA induces DNA damage: first proof of double-strand breaks in a cell-free system.

DNA damage induced by solar ultraviolet (UV) radiation plays an important role in the induction of skin cancer. Although UVA constitutes the majority of solar UV radiation, it is less damaging to DNA than UVB. The DNA damage produced by UVA radiation, however, can be augmented in the presence of a photosensitizer. We previously used benzo[a]pyrene (BaP), an environmental carcinogenic polycyclic aromatic hydrocarbon, as an exogenous photosensitizer, and demonstrated that combined exposure to BaP and UVA resulted in DNA double-strand breaks (DSBs) in cultured Chinese hamster ovary (CHO-K1) cells. In this study, we investigated whether coexposure to BaP and UVA induces DSBs in a cell-free system and whether reactive oxygen species (ROS) were involved in the generation of the DSBs. DSBs were induced by the coexposure both in the cell-free system (in vitro) and in CHO-K1 cells (in vivo), but not by treatment with BaP or UVA alone. DSB induction in vitro required higher doses of UVA and BaP than were required in vivo, suggesting that the mechanism of DSB induction differed. A similar difference in efficiency also was observed in the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) by coexposure to BaP and UVA in vitro and in vivo. A singlet oxygen ((1)O2) scavenger (NaN3) effectively inhibited the production of DSBs and 8-oxodG, suggesting that (1)O2 is a principal ROS generated by BaP and UVA both in vitro and in vivo. Furthermore, repair-deficient xrs-5 cells were more sensitive to coexposure with BaP and UVA than were CHO-K1 cells, but the two cell lines were equally sensitive to the combined treatment in the presence of NaN3. This result suggested that the cell death produced by coexposure to BaP and UVA was at least partly due to the DSBs generated by (1)O2. Our findings indicate that coexposure to BaP and UVA effectively induced DNA damage, especially DSBs, which results in phototoxicity and possibly photocarcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2006

Geographical clustering of mortality from systemic lupus erythematosus in the United States: contributions of poverty, Hispanic ethnicity and solar radiation.

The objective was to investigate whether spatial variation in poverty, Hispanic ethnicity, and solar radiation explains the strong pattern of geographical clustering of mortality from systemic lupus erythematosus (SLE) in the United States. SLE mortality counts for women and men of black and white race in US counties, 1979-1998, were obtained from the National Center for Health Statistics. County-level poverty rates and proportions of Hispanic residents were drawn from the 1990 national census. The annual cumulative level of ambient ultraviolet 'B' radiation (UVB) was estimated for each county according to latitude, longitude, and elevation. Maps for the full study population and for sex - and race-specific subpopulations showed that the national pattern of geographical variation in SLE mortality primarily reflected the experience of white women. Formal spatial analysis of the data for white women identified 10 statistically significant, multi-county clusters--four with elevated and six with reduced SLE mortality rates. Multivariate regression modeling established that higher levels of poverty, Hispanic ethnicity, and UVB were each associated with elevated local rates of SLE mortality among white women. Statistical adjustment via the regression model was used to remove effects of these factors on local rates. In a re-application of spatial analysis to the adjusted rates, four clusters 'disappeared'. In those clusters, poverty, Hispanic ethnicity and UVB had explained an average of 58.2% of the deviations between local and national SLE mortality rates. In six clusters (including three that disappeared with adjustment), Hispanic ethnicity explained a larger percentage of the deviations between local and national rates than either poverty or UVB. In multivariate models based on data for black women and for men of both races, poverty and UVB had similar effects on SLE mortality rates to those observed among white women. However, Hispanic ethnicity was not a significant predictor of SLE mortality in any of these other groups. The contributions of poverty, Hispanic ethnicity and solar radiation to geographical variation of SLE mortality in the United States are substantial, but these factors do not fully account for the clustering phenomenon.

Black or African American↗
PubMedDate not supplied

Photostabilization of organic UV-absorbing and anti-oxidant cosmetic components in formulations containing micronized manganese-doped titanium oxide.

Micronized titanium oxide (TiO(2)) and manganese-doped titanium oxide (TiO(2):Mn) particles have been incorporated into a variety of oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions in conjunction with the UV-absorbing organic compounds butyl methoxydibenzoylmethane (BMDM) and octyl methoxycinnamate (OMC) and with the anti-oxidants vitamin E and vitamin C. The retention of the organics under solar exposure has been shown to be significantly enhanced by the addition of TiO(2):Mn to the formulation. In the case of BMDM and OMC, the retention is increased from 20% and 24% to 63% and 83%, respectively, after two hours of solar exposure. In this system, TiO(2) particles are shown to provide only limited protection relative to BMDM and OMC. Vitamin E and vitamin C are actively degraded by the presence of TiO(2) in the emulsion during solar exposure. This effect is reversed with TiO(2):Mn, the use of which can protect >90% of anti-oxidants in both the oil and water phases of the formulation. The absence of reactive oxygen species (ROS) generation and surface scavenging of ROS by TiO(2):Mn is responsible for a significantly reduced ROS load on the organic components and consequent photostabilization of the emulsion.

Antioxidants↗
PubMed1997

An overview of research on the beneficial effects of vegetation in contaminated soil.

Vegetation can enhance in situ bioremediation processes in many applications. Microbial transformations occur in soil and water external to plant roots. Organic contaminants also enter vegetation and are transformed within plants. Research progress is reviewed with emphasis on recent experimental results and mathematical models of contaminant fate in systems where vegetation is present. Plant evapotranspiration provides a solar driven pump-and-treat system which moves contaminants to the rhizosphere and helps to contain them on site. Significant savings have been reported at several field sites where vegetation has been utilized.

Biodegradation, Environmental↗
PubMed2004

Variation of the enhanced biologically damaging solar UV due to clouds.

The variation of the biologically damaging solar UV (UVBE) enhanced by clouds above that of clear sky UVBE has been investigated. This was undertaken for summer through to winter for SZA of 5 to 60 degrees employing an integrated automatic cloud and spectral UV measurement system that recorded the solar UV spectra and the sky images at five minute intervals. The UVBE calculated with action spectra with higher relative effectiveness in the UVA produced the lower percentage of cloud enhanced cases. The DNA UVBE provided the highest percentage of cloud enhanced cases compared to the total number of UV scans with 2.2% cloud enhanced cases. As a comparison, the plant and fish melanoma UVBE provided the lowest percentage of cloud enhanced cases with 0.6 to 0.8% cloud enhanced cases. For the cases of cloud enhanced UVBE, the average ratio of the measured UVBE to calculated cloud free UVBE for the photokeratitis, cataracts, plant, generalized plant damage and fish melanoma action spectra was 1.21 to 1.25. In comparison, the highest value of 1.4 was for the DNA action spectrum.

Animals↗
PubMed1999

Development and characterization of a DNA solar dosimeter.

In this paper, we report the development and characterization of a solar ultraviolet (UV) dosimetry system that can be used as a film badge for radiation monitoring. DNA molecules are coated on a thin nylon membrane as a UV dosimeter. The membrane is sealed in a polyethylene filter envelope with silica gel to keep the humidity low. After exposure to UV or solar light, induced DNA damage is measured by an immunochemical reaction. The intensity of color developed during the immunological reaction can be correlated linearly with the irradiated UV dose delivered by an Oriel solar simulator within a limited dose range. We observe no effects of temperature on the level of damage induction. The membrane is proficient for measuring DNA damage for more than 21 days when stored at either 37 or 4 degrees C. The induced damage remains stable on the membrane for at least 22 days at both 37 and 4 degrees C. In addition to these indoor experiments, we report measurements of solar UV dose in outdoor experiments.

DNA↗
PubMed1998

A single exposure of solar simulated radiation suppresses contact hypersensitivity responses both locally and systemically in humans: quantitative studies with high-frequency ultrasound.

Ultraviolet radiation (UVR)-induced suppression of cutaneous cell-mediated immunity plays an important role in the development of photocarcinogenesis in the mouse and a similar role is suspected in humans. Cell-mediated immunity is readily tested in vivo by measuring the contact hypersensitivity (CHS) response to topically applied haptens. CHS in humans is usually determine clinically, with a subjective scoring system. However, these subjective scores cannot be statistically analysed. This paper compares four methods currently used to quantify CHS elicitation responses in humans. The data show that ultrasound images provide the most accurate and reproducible measurements of the clinically observed CHS response. We also demonstrate that assessment of the primary allergic response is a useful indicator of the magnitude of the elicitation response and can be used to avoid severe CHS reactions in volunteers. There are few human studies investigating the effects of solar simulated radiation (SSR) exposure on immunosuppression. In this study we demonstrate SSR is highly immunosuppressive in all subjects tested. Irradiating a small area of skin with a single exposure to 3MEDs of SSR completely suppressed CHS both locally (12/12 volunteers) and systemically (10/12 volunteers). Our data do not support a role for a genetic susceptibility to UVR-induced immunosuppression in humans.

Adolescent↗
PubMed2005

Optical performance at the thermodynamic limit with tailored imaging designs.

Ultracompact concentrators and illuminators that approach the thermodynamic limit to optical performance can be realized with purely imaging strategies. We explore two-stage reflector systems where each optical surface is tailored to eliminate one order of aberration--the so-called aplanatic designs. The contours are monotonic functions that can be expressed analytically, which are important for the facilitation of optimization studies and practical fabrication. The radiative performance of the devices presented is competitive with, and even superior to, that of high-flux nonimaging systems. Sample results of practical value in solar concentration and light collimation are presented for systems that cover a wide range of numerical aperture.

Journal Article↗
PubMed1986

Application of hydrogenase for photoinduced hydrogen evolution.

Various attempts have been made to develop suitable redox systems for the photochemical utilization of solar energy. Recent work has shown that the three component systems containing a photosensitizer, an electron donor, and an electron acceptor can be used to evolve hydrogen when a suitable catalyst is present. The reactions are quite general and have been demonstrated for a wide range of photosensitizers and electron carriers. Hydrogenase or colloidal platinum are widely used as catalysts, for they can catalyze the reduction of protons in the presence of a suitable electron donating agent such as reduced methylviologen. Some properties of these components and the efficiency of the photoinduced hydrogen evolution are discussed.

Chemical Phenomena↗
PubMedDate not supplied

[Psychosomatic status and quality of work of pilots in years of the quiet and the active sun years].

The study indicated that with an increased solar activity the body systems of highly anxious (HA) flight-operators as compared to low anxious (LA) operators reach a new, more intensive level of functioning. Such a condition of the physiological status in HA operators goes together with a sharp rise of pilot mishandling in flying technique, a decrease in working capacity which along with other characteristics are indicative of a fall in the central nervous system functioning during active versus quiet sun year. The LA operators capacity to maintain the homeostasis during active sun year at a level of the quiet one affects positively flying longevity and less pronounced, as compared to HA operators, increase of pilot mishandling in flying technique during the active sun year.

Adult↗
PubMed1991

A study of elastic tissue and actinic radiation in "aging," temporal arteritis, polymyalgia rheumatica, and atherosclerosis. The actinic storm in the modern world.

Solar radiation provokes a lifelong series of destructive changes in the supporting elastic tissues of "exposed" skin. Called actinic elastosis/lysis (or actinic "aging"), the sequence begins in early life as simple elastic hyperplasia, converts in middle life to progressive actinic elastotic degeneration, and, in late life, typically ends with a stage of resorption (elastolysis) and atrophy ("aged" skin). Superficial "exposed" arteries such as the temporal artery participate in the same sequence of degenerative elastotic changes, which, as in the skin, may provoke granulomatous responses in a few of the many subjects affected. In the case of the temporal artery, a contingent outcome may be giant cell (temporal) arteritis and its recognized systemic vascular expression, polymyalgia rheumatica. Actinic commotion at the surface of the body is often massive in degree and extent and may be expected to exert a deleterious autoimmune impact on the essential elastic tissues of the arterial system. For this reason, solar radiation should be recognized as a risk factor for other elastic-related vascular diseases, including atherosclerosis and aneurysms. Man-made radiations may be exacerbating the effects of predominant solar radiation. Of the many radiant bands that make up the actinic (electromagnetic) spectrum, little is known for certain about the identity of those that cause these prevalent disorders of elastic tissue. Until this void is filled, more care should be taken with solar and the other "safe" radiations.

Arteriosclerosis↗
PubMed1981

[Autonomic reactions in patients with infantile cerebral palsy].

The authors examined the neurovegetative reactions in 20 children aged 2 to 5 years suffering from infantile cerebral paralysis. The children examined had suffered perinatal hypoxia and natal intracranial injuries. Combined examinations of the cardiovascular, respiratory, and thermoregulatory systems were carried out in standard conditions in a microclimate chamber. Various types of the response of the above systems to the orthostatic, solar, and oculocardiac loads were revealed. The disturbances of the homeostatic functions of the central and peripheral genesis on the one hand, and mode-rate hypertensive-hydrocephalic syndrome on the other were found to be in parallel. On the basis of the data of their experimental study the authors conclude that in the children examined the higher vegetative centres responsible for the body homeostasis have suffered a hypoxic damage.

Animals↗