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PubMed2005

Oxygen and photoinactivation of Escherichia coli in UVA and sunlight.

AIMS: To establish the influence of oxygen on Escherichia coli before, during and after exposure to UVA or simulated sunlight. METHODS AND RESULTS: Bacterial suspensions were exposed either to UVA or simulated sunlight. Conventional aerobic plate counts of illuminated cell suspensions were consistently lower than those obtained under conditions where reactive oxygen species (ROS) were neutralized, either (i) by the addition of the peroxide scavenger sodium pyruvate (0.05% w/v) to the medium with subsequent incubation in an anaerobic jar or (ii) by culturing on a prereduced medium within an anaerobic cabinet, indicating that a substantial proportion of such cells are sublethally injured. While the presence of oxygen during the growth period resulted in a greater resistance of aerobically grown cells to simulated sunlight compared with their anaerobic counterparts, the extent of inactivation during illumination was directly related to the dissolved oxygen content of the water. CONCLUSIONS: The results show that, at each stage, oxygen has a marked influence on the observed colony count. SIGNIFICANCE AND IMPACT OF THE STUDY: Overall, the results indicate that future studies of bacteria exposed to UVA or sunlight should consider the effects of oxygen at every stage in the procedure, and especially during enumeration, where the inhibitory effects of ROS must be neutralized in order to obtain a valid count. An investigation of the effects of ROS neutralization on the counts of faecal bacteria under field conditions in natural waters is now required to establish the significance of these finding to solar water treatment.

Anaerobiosis↗
PubMed2003

Evidence that enforced sunlight exposure can cause hyperthermia in cattle ingesting low levels of ergot of rye (Claviceps purpurea), when air temperature and humidity conditions are only moderate.

OBJECTIVE: To determine the rectal temperature response of cattle, following the oral administration of ergot of rye (Claviceps purpurea), under pen conditions of enforced sunlight compared with those of enforced shade. DESIGN AND PROCEDURE: Hereford cross steers were divided into two groups of 18. One group was dosed once, on a Monday morning, with finely ground rye grass ergots at a rate of 180 mg/kg body weight and held in the sun for 7 h each day until Friday afternoon. The other group was not dosed but was similarly held in the sun during the same period. Their rectal temperatures were measured early morning and mid afternoon, from Monday to Friday inclusive. The process was repeated for each group, but this time they were held in the shade. The four treatment options were run concurrently by conducting the experiments over 6 weeks and using 3 animals in each treatment group, each week. RESULTS: The thermic response over all weeks, of the ergot treated, sunlight exposed cattle, was deemed greater than for the other groups, based on the following four parameters. The increase in rectal temperature between early morning and mid afternoon, the size of the mid afternoon rectal temperature rise, the difference between the maximum mid afternoon rectal temperature recorded by an animal in the sun compared with that recorded by the same animal in the shade, and finally the number of animals in a treatment group that recorded rectal temperatures > 40.00 degrees C. The difference in the daily increase in body temperature between the ergot treated, sun exposed cattle and the ergot treated, shaded cattle, was greater than that observed between the sun exposed and shade restricted control cattle. Nine of 18 ergot treated and sun exposed cattle developed hyperthermia; no cattle in the other three groups did. CONCLUSIONS: Some sunlight exposed cattle, dosed with a low amount of ergot of rye, can experience a body temperature elevation above the normal range, even under mild ambient temperature and humidity conditions. Sunlight exposure causes an increase in body temperature in normal cattle that is probably attributable to solar radiant heat. Ergot ingestion causes an increase in body temperature in shaded cattle that is probably attributable to ambient temperature and humidity effects. This response can be increased by sun exposure and this increase is attributable to solar radiant heat effects and possibly also solar radiation. A response to radiant heat is consistent with the known physiological effects of ingested ergot alkaloids, but a response to solar radiation is not.

Animal Feed↗
PubMed1990

Biologically effective doses of sunlight for immune suppression at various latitudes and their relationship to changes in stratospheric ozone.

Using information on solar irradiance at different latitudes derived from a radiative transfer model and a detailed in vivo action spectrum for immune suppression in a murine system, we report here calculations of the "biologically effective" irradiance of sunlight for immune suppression. From 40 degrees N to 40 degrees S in summer, under normal stratospheric ozone concentrations this value ranged from 0.27 W/m2 (40 degrees N or S) to a peak of 0.33 W/m2 (20 degrees N or S) predicting that 50% immune suppression in the Balb/c mouse would occur after 21-26 min of sunlight exposure within this latitude range. We also found that the most effective wavelengths for immune suppression shift from a peak of 270 nm in the laboratory to near 315 nm in sunlight. Furthermore, using ozone depletion scenarios of 5 to 20%, at latitudes 20 degrees S and 40 degrees N, a 0.6% increase in biologically effective irradiance levels of solar UVB for immune suppression was predicted for each 1% decrease of ozone. This value rose to a nearly 1% increase for each 1% decrease in ozone at 60 degrees N latitude in wintertime. These data indicate that activation of immune suppression, in a murine model, requires relatively low levels of sunlight and that these levels are easily obtainable over most of the populated regions of the world. Since a UVB-activated photoreceptor, urocanic acid, regulates immune suppression in mice and since this same compound exists on other mammalian skin, including human skin, suppression of the mammalian immune system is predicted to increase if substantial stratospheric ozone depletion takes place.

Animals↗
PubMed2006

Effect of natural sunlight on bacterial activity and differential sensitivity of natural bacterioplankton groups in northwestern Mediterranean coastal waters.

We studied the effects of natural sunlight on heterotrophic marine bacterioplankton in short-term experiments. We used a single-cell level approach involving flow cytometry combined with physiological probes and microautoradiography to determine sunlight effects on the activity and integrity of the cells. After 4 h of sunlight exposure, most bacterial cells maintained membrane integrity and viability as assessed by the simultaneous staining with propidium iodide and SYBR green I. In contrast, a significant inhibition of heterotrophic bacterial activity was detected, measured by 5-cyano-2,3 ditolyl tetrazolium chloride reduction and leucine incorporation. We applied microautoradiography combined with catalyzed reporter deposition-fluorescence in situ hybridization to test the sensitivity of the different bacterial groups naturally occurring in the Northwestern Mediterranean to sunlight. Members of the Gammaproteobacteria and Bacteroidetes groups appeared to be highly resistant to solar radiation, with small changes in activity after exposure. On the contrary, Alphaproteobacteria bacteria were more sensitive to radiation as measured by the cell-specific incorporation of labeled amino acids, leucine, and ATP. Within Alphaproteobacteria, bacteria belonging to the Roseobacter group showed higher resistance than members of the SAR11 cluster. The activity of Roseobacter was stimulated by exposure to photosynthetic available radiation compared to the dark treatment. Our results suggest that UV radiation can significantly affect the in situ single-cell activity of bacterioplankton and that naturally dominating phylogenetic bacterial groups have different sensitivity to natural levels of incident solar radiation.

Bacteria↗
PubMed1996

Retention of enteropathogenicity by viable but nonculturable Escherichia coli exposed to seawater and sunlight.

The effect of natural sunlight on culturability and persistence of pathogenicity of Escherichia coli was examined in the field, i.e., in the Morlaix Estuary, France, using an enterotoxigenic strain of Escherichia coli H10407. Results showed that E. coli responds to the estuarine diurnal solar cycle by entering the viable but nonculturable state upon exposure to sunlight. That is, direct counts of viable cells remained stable without significant change, but E. coli cells remained fully culturable only when exposed to seawater in control chambers in the dark, i.e., without solar irradiation. The effect of sunlight on the pathogenicity of E. coli H10407 was studied, using both the rabbit intestinal loop assay and ganglioside-enzyme-linked immunosorbent assay (GM1-ELISA), a sensitive procedure for testing for production of enterotoxin. Results of the GM1-ELISA demonstrated that strains of E. coli, after exposure to sunlight and entering the viable but nonculturable state, as well as culturable E. coli, retained pathogenicity, i.e., produced enterotoxin. The GM1-ELISA is concluded to be more sensitive than the rabbit intestinal loop assay for analysis of enterotoxin in natural water samples.

Animals↗
PubMed1998

Bone mass in prepubertal children: gender differences and the role of physical activity and sunlight exposure.

Retrospective studies have suggested that the prepubertal years may be an important window of opportunity to increase bone mass, but there have been few direct studies and little exploration of gender differences in this age group. In this study, we report the associations among physical activity measures, sunlight exposure, body composition, and bone mass in 8-yr-old children. We studied 330 children in 1996 (115 girls and 215 boys; response rate, 60%) who had previously taken part in a cohort study of cot death in 1988. They had measurement of anthropometrics (height, weight, and body composition), sunlight exposure (by questionnaire), and physical activity [questionnaire, muscle strength by dynamometry, and bicycle ergometric physical work capacity at a pulse of 170 beats/min (PWC170)]. Bone mineral density (BMD) was assessed at the spine, femoral neck, and total body by a Hologic QDR2000 densitometer. In females only, PWC170 [hip, 2.4%/quartile (95% confidence interval (CI), 0.3-4.5); spine, 1.7%/quartile (95% CI, 0.0-3.4); size adjusted] was associated with BMD, whereas in males only, BMD was associated with both sports participation (hip, 4.2% (95% CI, 1.1-7.3); spine, 4.3% (95% CI, 0.9-7.7)] and muscle strength [hip, 1.7%/quartile (95% CI, 0.0-3.4); but not spine; size adjusted]. Winter sunlight exposure was associated with BMD in girls [hip, 2.9%/category (95% CI, 0.7-5.0); spine, 3.6%/category (95% CI, 1.4-5.8)], but not in boys [hip, 0.3%/category (95% CI, -1.4 to +2.0); spine, 1.4%/category (95% CI, -0.7 to +3.5)]. Males and females were very similar in body size. However, males had higher size-adjusted BMD at the hip (9.6%; 95% CI, 6.9-14), whereas females had higher size-adjusted BMD at the spine (3.2%; 95% CI, 0.8-5.6%). In conclusion, this study has suggested that physical activity and exposure to sunlight are important in the bone mineralization of prepubertal male and female children. The magnitude of both gender and environmental differences in bone mass in this age group is substantial, suggesting that modification at this stage of life may influence peak bone mass and possibly fracture risk in later life.

Body Composition↗
PubMed1993

Effect of intermittent exposure to sunlight on melanoma risk among indoor workers and sun-sensitive individuals.

Intermittent exposure to sunlight is considered to be an important risk factor for melanoma, but the associations reported in most case-control studies are surprisingly weak. The aim of this study was to evaluate whether the incorporation of a subject's background exposure to the sun and pigmentation characteristics (which are assumed to influence a person's susceptibility to sunlight exposure) could produce stronger associations between sunlight exposure and the risk for melanoma. A population-based case-control study was performed in the mid-eastern part of the Netherlands. The study group comprised 141 patients with a histologically verified melanoma and 183 controls with other malignancies who were registered by the same cancer registry. Patients with a lentigo maligna melanoma or an acrolentiginous melanoma were excluded. Information was collected by interviews and physical examination. We categorized subjects as indoor or outdoor workers on the basis of occupational exposure to the sun. Pigmentation characteristics, which are known to be risk indicators for cutaneous melanoma, were summarized as one sun sensitivity score. We used this score to distinguish between sun-sensitive and sun-resistant persons. The odds ratios associated with sunbathing, vacations spent in sunny countries, and sunburns were higher among the indoor workers than among the outdoor workers. After stratification by the sun sensitivity score, the effect of sunbathing, participating in water sports (swimming excluded), vacations to sunny countries, and a history of sunburn was largest for the sun-sensitive persons. The data show a general trend toward higher relative risks among indoor workers and sun-sensitive individuals. The results of this study support the intermittent sunlight hypothesis.

Adolescent↗
PubMed2001

The requirement for natural sunlight to prevent vitamin D deficiency in iguanian lizards.

To investigate possible causes of embryonic and neonatal mortality in a group of captive Fijian iguanas (Brachylophus fasciatus and Brachylophus vitiensis), the vitamin D status of adults in the colony was compared with that of agamid and iguanid lizards either housed in indoor enclosures under artificial ultraviolet light or exposed to natural sunlight (wild-caught or captive animals housed outdoors). Those under artificial lighting had a significantly lower vitamin D status than those housed exclusively outdoors, whereas the vitamin D status of Fijian iguanas that had received intermittent exposure to natural sunlight was intermediate and not significantly different from that of animals housed exclusively outdoors. However, eggs from some of these Fijian iguanas had substantially lower vitamin D content than eggs from outdoor iguanid and agamid animals. Artificial ultraviolet light, therefore, might not be an adequate substitute for natural sunlight to maintain vitamin D status of lizards. This possible inadequacy may be because either artificial ultraviolet light has a lower intensity of the wavelengths that induce vitamin D than does sunlight or the intensity of the artificial lighting is not sufficient.

Animals↗
PubMed2005

Evidence for alteration in chemical and physical properties of water and modulation of its biological functions by sunlight transmitted through color ranges of the visible spectrum-a novel study.

We investigated the changes in the properties of water when exposed to sunlight for 40 days. We hypothesize and prove that solar irradiation to water entraps electromagnetic radiation as potential energy, which becomes kinetic energy in various systems. It is postulated that photochemically-induced energy transfers, associated with individual spectral emission of visible spectrum of solar light, exert diverse influences on biological systems. Bottles of distilled water, individually wrapped in spectral-colored cellophane were exposed to sunlight and compared to an unwrapped bottle to determine chemical and physical changes as well as modifications of biological properties. Each bottle of water was named according to the color of cellophane paper with letter E (stands for exposed) as a prefix with (E-violet, E-indigo, E-blue, E-green, E-yellow, E-orange, and E-red). E-control (without wrap) was exposed to polychromatic sunlight. This study addresses two main issues viz., the chemical and physical changes in E-water and its effect on biological activities. Chemical and physical composition analysis using inductively coupled plasma atomic emission spectrometry; physical conductance by a Wheatstone Bridge type conductivity meter; osmolarity by a vapor pressure osmometer; and, salt solubility profile of 10% sodium bicarbonate were determined. Furthermore, testing the effect of E-waters on human lymphocyte proliferation, mosquito larvae hatching and seed germination determined the functional role of solar radiation through specific spectrum/s of visible light on various biological processes. We found that water exposed to visible spectral emissions of sunlight had an altered elemental composition, electrical conductance, osmolarity and salt-solubility, as well as differences in bio-modulatory effects. A gradual increase in leaching of Boron from E-violet to E-red was noted. E-indigo showed maximal increase in electrical conductance and maximal salt solubility of sodium bicarbonate. E-blue inhibited phyto-hemagglutinin-induced immune cell proliferation and mosquito larvae hatching. E-orange stimulated root elongation in seed germination. We conclude that 40-day exposure of water to specific solar spectrum changes chemical and physical properties and influences on biological activity.

Animals↗
PubMedDate not supplied

Monocular eye closure in sunlight.

Monocular eye closure in sunlight is often noted in patients with intermittent exotropia. Neither the reason for eye closure nor its frequency of occurrence in other populations is known. We questioned 147 consecutive nonoperated patients (and/or their parents) ages 1-45 years, 93 with strabismus with onset prior to 7 years of age and 54 without strabismus, for a history of closing one eye in sunlight. Monocular eye closure in sunlight was reported most frequently by patients with intermittent exotropia but was also reported by those with other forms of strabismus as well as by nonstrabismic normals. Cooperative subjects were studied further to determine the cause for eye closure. Each subject was exposed to a source of intense illumination while fixating a target. All who closed one eye under these conditions reported photalgia associated with the high light intensity, most noting less discomfort after closing one eye. None reported diplopia prior to eye closure. Monocular and binocular photophobia thresholds were then measured for each subject. The mean monocular photophobia threshold was significantly higher than the binocular threshold. In addition, binocular photophobia thresholds were significantly lower in those reporting eye closure compared with those who did not. Monocular eye closure in sunlight is a mechanism used to reduce photophobia and is not related to avoidance of diplopia.

Adolescent↗
PubMed2003

The significance of sunlight for the elimination of indicator bacteria in small-scale bathing ponds in central Europe.

In order to determine the impact of sunlight on the reduction rate of indicator bacteria, bathing waters of different turbidity were artificially contaminated with indicator bacteria and exposed to sunlight. The reduction rates determined for the indicator bacteria showed a significant correlation with radiation intensity and, thus, also the time of day as well as the turbidity of the water. Under conditions of strong radiation intensity and low water turbidity (< 5 FTU), indicator bacteria were eliminated within 1-2 h of contamination with an initial concentration of 10(5) CFU/mL. Moreover, differences between different indicator bacteria were found. Enterococcus faecalis proved to be significantly more resistant to sunlight than the other indicator bacteria tested (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus). The results of the present study, namely the complete elimination of indicator bacteria within a few hours, showed that sunlight, given an appropriate intensity and good water transparency, was the most important factor in the reduction of hygienically-relevant microorganisms in surface waters and, thus, also in small-scale bathing ponds.

Bacteria↗
PubMed1989

The effects of bergapten and sunlight on cutaneous pigmentation.

The effects of bergapten-containing preparations in sunlight-induced skin pigmentation were evaluated. Oil and lotion vehicles with bergapten/UV-B sunscreen or sunscreen alone were applied to the backs of subjects twice weekly for 4 weeks and the subjects were exposed to gradually increasing doses of midday sunlight. The degree of skin darkening was assessed by clinical examination, reflectometry, and light microscopy of skin biopsy specimens. At 5 weeks, 1 week after the last sunlight exposure, the sites treated with either the bergapten/UV-B sunscreen lotion or the lotion vehicle were significantly darker than the sites treated with the sunscreen lotions without bergapten. Oil preparations produced less clearcut results, possibly because of a less potent sunscreen or because the bergapten did not leave the vehicle and absorb into the epidermis. In type I skin, the bergapten/sunscreen and the oil vehicle alone produced the same amount of tanning; both yielded more tanning than the sunscreen in oil by clinical examination. The findings were not confirmed by reflectometry or by light microscopy. Thus, we conclude that bergapten added to a UV-B sunscreen lotion preparation can increase skin pigmentation over the sunscreen alone when one is exposed to sunlight. The bergapten/UV-B sunscreen combination is a potentially useful product since one can develop a psoralen and UV-A-induced tan while being protected from UV-B-induced sunburn by the UV-B sunscreen incorporated into the formulation.

5-Methoxypsoralen↗
PubMed1986

Effects of sunlight exposure on Langerhans cells and melanocytes in human epidermis.

The effects of 12 daily, half-hour exposures to sunlight on epidermal Langerhans cells (LC), and melanocytes were studied in 31 healthy volunteers. Nineteen were of Celtic and 12 of mixed European descent. Sunlight appeared to have both a direct, transient, detrimental effect and an indirect stimulating effect on the LC, and a direct and an indirect stimulating effect on the melanocytes. The mixed Europeans had a somewhat greater increase in the melanocyte population density following exposure to sunlight than the Celts. However, the number of LC fell following sunlight exposure regardless of the melanocyte response. Thus the melanocytes did not appear to provide the LC with immediate protection from ultraviolet light.

Adult↗
PubMed1985

Sunlight suppressing rejection of 280- to 320-nm UV-radiation-induced skin tumors in mice.

Repeated exposure of female C3H/HeNCR- mice to sunlight prevented the normal immunologic rejection of a UV-induced tumor. This systemic immunologic alteration was transferred to syngeneic lethally X-irradiated animals with lymphoid cells from mice exposed to sunlight. The lymphoid cells also were able to suppress the capacity of lymphoid cells from normal animals to reject a UV-induced tumor. The 295- to 320-nm wave band appeared to be responsible for this immunosuppressive effect of sunlight because suppression was prevented by filtration of the radiation through Mylar and by application of a sunscreen containing para-aminobenzoic acid. These observations may have importance in understanding the pathogenesis of sunlight-induced skin cancer in humans.

Animals↗
PubMed1979

Sunlight and human cataracts.

Studies of the cataractous lenses of humans in three different geographic locations indicate that where the ultraviolet components of sunlight are more intense, dark brown cataracts result at a higher frequency than in locations where they are weak. Individuals exposed to sunlight regularly by virtue of their outdoor occupations seemed to develop this dark brown type of cataract much more frequently than those who work indoors. The biochemical characteristics of all brunescent cataracts were found to be very similar, whether derived from individuals exposed to high or low levels of sunlight. These findings support the idea that exposure to sunlight specifically enhances brunescent cataract development in humans.

Adult↗
PubMed1995

Sunlight exposure, pigmentary factors, and risk of nonmelanocytic skin cancer. I. Basal cell carcinoma.

BACKGROUND AND DESIGN: Basal cell carcinoma (BCC) of the skin is the most common neoplasm in white populations, and solar radiation is generally accepted to be the dominant environmental risk factor for this disease. However, little information is available on the nature of the relationship between BCC and sunlight. The purpose of this study was to evaluate the nature of the relationship between sunlight exposure, pigmentary factors, and BCC of the skin. A population-based case-control study of 226 male patients with BCC diagnosed from January 1, 1983, through December 31, 1984, and 406 randomly selected male control subjects was conducted in Alberta, Canada. The study was conducted using a standardized questionnaire, administered in person by trained interviewers. Data were analyzed using conditional logistic regression methods. RESULTS: After controlling for other host and pigmentary factors, the risk of BCC was increased in subjects with light skin color and those who freckled in childhood. A history of severe sunburn in childhood also increased risk. Subjects of southern European ethnic origin were at significantly lower risk of BCC. Surprisingly, no association was seen between mean annual cumulative summer sunlight exposure and risk of BCC. A significantly increased risk of BCC was seen in subjects with increased recreational sunlight exposure in adolescence and childhood (age, 0 to 19 years), although an inverse relationship was seen with lifetime recreation exposure. The relationship with childhood sun exposure was most pronounced among sun-sensitive subjects whose skin tended to burn rather than tan in the sun. CONCLUSIONS: The lack of association between cumulative sun exposure and BCC contradicts conventional wisdom about the cause of this tumor, and the increased risk with sun exposure at age 0 to 19 years suggests that childhood and adolescence may be critical periods for establishing adult risk for BCC.

Adult↗
PubMed1996

Effect of inactivation by sunlight on the larvicidal activities of mosquitocidal Bacillus thuringiensis H-14 isolates from Nigerian soils.

Bacillus thuringiensis H-14 is a well recognized bioinsecticide against mosquitoes. This study investigates the inactivation effect of sunlight on the larvicidal activities of four Nigerian isolates of B. thuringiensis H-14, code-named OBG1, OBG8, GSC3 and GNA13 as compared with a standard mosquito larvicide, B. thuringiensis var. israelensis (BTI). A 0.125 mg/1 suspension of spore-delta-endotoxin powder of each isolate was exposed to direct sunlight for 7 h on a concrete roof (ca. 13 m high). After exposure, the toxicity of each bacterial suspension to Aedes aegypti larvae was determined by bioassay. Three of the isolates, OBG8, OBG1 and GSC3 exhibited higher larvicidal activities than B.T.I. against A. aegypti larvae after exposure to sunlight. The resistance of Nigerian isolates to inactivation effects of sunlight advocates their potential in biocontrol of mosquitoes.

Animals↗
PubMed1997

Serum concentrations of melatonin in prepubertal or postpubertal gilts exposed to artificial lighting or sunlight.

To determine if the type of environmental lighting or reproductive status influences secretory patterns of serum melatonin, gilts were exposed to artificial light or full sunlight during the summer months. In Experiment 1, eight prepubertal and eight postpubertal gilts (Hampshire x Yorkshire x Duroc) were exposed to light intensity of 700 lux in an environmentally controlled room from 0730 to 1900 h daily. An additional eight prepubertal and eight postpubertal gilts were reared outdoors in an open modified-front gestation building and fed on a concrete apron outdoors where light intensity approached 50,000 lux in full sunlight. After 2 mo of acclimating to these environmental conditions, blood samples were drawn from each gilt at 2-h intervals from 1000 to 0200 h. Serum concentrations of melatonin were assayed utilizing Guildhay antisera. The experiment was repeated during the same months of the following year utilizing different gilts (Experiment 2). During both replications, neither light intensity nor reproductive status affected the secretory patterns of melatonin during the sampling period (P >0.05). In both prepubertal and postpubertal gilts, serum concentrations of melatonin were not reduced (P >0.05) by exposure to direct sunlight. Since baseline concentrations of serum melatonin were not reduced by sunlight during the day, the incidence of nocturnal rises of melatonin was not increased (P >0.05) in either prepubertal or postpubertal gilts.

Journal Article↗