Potential protection of skin by acute UVA irradiation--from cellular to animal models

The UVA (320-380 nm) component of sunlight has oxidizing properties which may be deleterious to skin cells and tissue but can also lead to the strong up-regulation of the heme-catabolizing enzyme, heme oxygenase-1. This enzyme has well-established antioxidant actions in cells as well as anti-inflammatory properties in mammals. There is also evidence from rodent models that this enzyme is responsible for the UVA-mediated protection against UVB-induced immunosuppression that occurs in skin. The relevance of these findings to acute and chronic effects of sunlight including skin carcinogenesis is currently under investigation as are the potential implications for sunlight protection in humans.     

Some approaches for measuring and modelling riparian shade

The radiation environment of streams is of major ecological importance because it controls stream thermal regime and light availability for photosynthesis. Therefore, methods are needed for measuring stream shade in practical riparian management. The quantity ‘diffuse non-interceptance’ (difn), defined as the proportion of incident lighting received under a sky of uniform brightness and best estimated from fish-eye images, is useful for general specification of light exposure. For routine measurement of difn along stream reaches we recommend using a matched pair of simple light sensors (e.g. photosynthetically available radiation sensors) under conditions of complete overcast (which has almost uniform brightness). Methods are also needed for predicting future light exposure as riparian plantings grow and increasingly shade the stream. A simple model is outlined for predicting difn at the channel centre as a function of channel dimensions (stream width, w) and riparian plant character (foliage density, canopy height, h). The model reproduces the broad empirical trend of increasing shade with increasing h/w ratio. Future model refinement will aim to quantify the increase in shade moving from channel centre to edge under an overhanging canopy.     

Sun exposure, sexual behavior and uterine cervical human papilloma virus

Introduction We have previously observed marked seasonal fluctuations in the frequency of cervical smears positive for human papilloma virus (HPV) in a series of smears obtained in Holland, with a peak in the summer months, especially August. Here, we tested two possible mechanisms that might underlie this summer peak: (1) enhanced transmission of HPV due to increased seasonal sexual activity, or (2) suppression of immunity due to summertime population exposure to solar ultraviolet (UV) radiation. Methods Data derived from a continuous series of >900,000 independent cervical smears obtained from 1983 to 1998 were assessed for histopathologic epithelial changes pathognomonic of HPV. The rate of HPV positivity was then compared to both the rate of sexual activity (using conception frequency as a readily available surrogate) as well as yearly and monthly fluctuations in solar-UV fluency. Results The rate of HPV positivity was found to be twice as high during the summer months, with a peak in August corresponding with maximal UV fluency. Furthermore, over these 16 consecutive years of continuous observation, maximum HPV detection rate and maximum UV fluency are positively correlated (r=0.59, P<0.01); the sunnier the year, the greater the rate of HPV. Likewise, there is a positive correlation of the monthly UV fluency, and monthly HPV discovery rate (r=0.16, P<0.03). In contrast, conception frequency (and, presumably, population sexual HPV transmission) was maximal near the vernal equinox, with relatively modest (<10%) seasonal fluctuation, i.e., not fully explaining this prominent August peak in HPV discovery. Conlusions There is a clear relationship between the detection of HPV-positive cervical smears and sunlight exposure. We speculate that the well-known phenomenon of UV-mediated suppression of immune surveillance may be causally related to this unusual increase in cytologically defined active HPV infections during the summer months in northern countries such as Holland. Confirming this relationship elsewhere may be important, because whatever the risk conferred by sunlight is, in principle, behaviorally avoidable.     

紫外光和日光对噬藻体PP活性的影响

分别研究了实验室条件卜紫外灯照射及不同季节中目光照射对噬藻体PP活性的影响。结果表明紫外光(UV-A和UV-B)对噬藻体PP有较强的致失活作用,并且其致失活作用强弱与波长有关。日光的作用下,夏季时噬藻体PP的日失活率为88．60％,冬季时为58．86％。同时发现不同季节中,尽管在某些时段的目光强度相似,但噬藻体PP失活率的差别却较大,这一现象可能是由于光质不同引起的。上述结果有助于解释淡水环境中噬藻体种群大小的季节性波动。     

Differences in Sleep and Circadian Preference between Eastern and Western German Adolescents

Only a few studies focus on comparisons to reveal differences in sleep and circadian preferences in adolescents. This study used the same instrument to compare adolescents in Eastern and Western Germany. In all, 674 pupils between 11 and 16 yrs participated. The questionnaire asked questions about wake times and bed times (on weekend and weekdays), and the Composite Scale of Morningness (CSM) was completed to assess diurnal preferences. Locality (East/West Germany) had no effect on rise and bed times during the week and on sleep length on the weekend. Western pupils rose later on weekends and went to bed later on weekends. While sleep length on weekdays was shorter in West Germany, weekend oversleep was longer and misalignment was higher. Diurnal preferences (CSM scores) suggested a higher eveningness in West Germany. As interaction effects were insignificant, changes throughout adolescence seem similar in East and West Germany. These data suggest that given similar school start times, Western German pupils are at higher risk because they are later chronotypes. The finding of earlier rise and bed times of the East German pupils is consistent with the hypothesis that sunlight acts as the entrainment for the biological clock of adolescents, as sunrise is earlier in Eastern Germany.     

Sunlight and Protection Against Influenza

Recent medical literature suggests that vitamin D supplementation protects against acute respiratory tract infection. Humans exposed to sunlight produce vitamin D directly. This paper investigates how differences in sunlight, as measured over several years across states and during the same calendar week, affect influenza incidence. We find that sunlight strongly protects against getting influenza. This relationship is driven almost entirely by the severe H1N1 epidemic in fall 2009. A 10% increase in relative sunlight decreases the influenza index in September or October by 1.1 points on a 10-point scale. A second, complementary study employs a separate data set to study flu incidence in counties in New York State. The results are strongly in accord.     

Reintroduction of a classic vitamin D ultraviolet source

As early as 1930 sunlamps claiming to provide ultraviolet (UV) exposure to make vitamin D were sold to the public in the US and Canada for home use. Today even with dietary supplementation of vitamin D many people do not get enough solar UV exposure to maintain sufficient vitamin D levels. There is growing interest in the availability of sunlamps for this purpose. The original Sperti Sunlamp, with label claiming vitamin D benefit was approved by the American Medical Association in 1940 as a sunlamp. This intermediate pressure mercury lamps ultraviolet B emission lines, at 297, 302, and 313 nm are able to convert 7-dehydrocholesterol in the skin to vitamin pre-D3 initiating the natural process of vitamin D formation. Today's KBD Vitamin D lamp, an updated model of the earlier type source. In order to comply with modern safety guidance, the source is filtered to remove unnecessary UVC radiation and is equipped with a timer to control the dose administered. The 5 min timer provides an exposure, at 20 in. from the user's skin, of one standard erythemal dose (SED). The SED represents a suberythemal dose for even the most sensitive skin type I individual.     

紫外光和日光对噬藻体PP活性的影响

分别研究了实验室条件下紫外灯照射及不同季节中日光照射对噬藻体PP活性的影响.结果表明紫外光(UV-A和UV-B)对噬藻体PP有较强的致失活作用,并且其致失活作用强弱与波长有关.日光的作用下,夏季时噬藻体PP的日失活率为88.60%,冬季时为58.86%.同时发现不同季节中,尽管在某些时段的日光强度相似,但噬藻体PP失活率的差别却较大,这一现象可能是由于光质不同引起的.上述结果有助于解释淡水环境中噬藻体种群大小的季节性波动.     

日光温室渗灌效果研究

对日光温室渗灌和沟灌的土壤环境,室内空气环境,作物生育及病毒状况,水分利用效率等进行了研究,结果表明,与沟灌相比,渗灌可增加土壤水稳定性团粒81．4％,降低土壤容重21．2％,增加土壤孔隙度29．0％,提高土壤温度1．1－1．7℃,降低空气湿度13．4％,节约灌溉用水36．7％,而且能促使作物早熟,提高作物产量,减少作物病害,降低生产成本,是目前日光温室理想的灌溉技术。     

Adverse effects of ultraviolet radiation: a brief review

Solar ultraviolet radiation (UVR) has always been part of the environment of man. UVB is required for the conversion of 7-deoxycholesterol to vitamin D, which is critically important in the maintenance of healthy bones and research is making clear that it has other potential roles in maintenance of human health. Exposure to UVR, whether of solar or artificial origin, also carries potential risks to human health. UVR is a known carcinogen and excessive exposure-at least to solar radiation in sunlight-increases risk of cancer of the lip, basal cell, and squamous cell carcinoma of the skin and cutaneous melanoma, particularly in fair skin populations. There is also evidence that solar UVR increases risk of several diseases of the eye, including cortical cataract, some conjunctival neoplasms, and perhaps ocular melanoma. Solar UVR may also be involved in autoimmune and viral diseases although more research is needed in these areas. Artificial UVR from tanning beds, welding torches, and other sources, may contribute to the burden of disease from UVR. This brief review will assess the human evidence for adverse health effects from solar and artificial UVR and will attempt to assign a degree of certainty to the major disease-exposure relationships based on the weight of available scientific evidence.