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At least 973 records · Page 54Linked to original sources
PubMed2001

Photosynthetic light response of flooded cherrybark oak (Quercus pagoda) seedlings grown in two light regimes.

Two-year-old cherrybark oak (Quercus pagoda Raf.) seedlings raised in full or partial (27%) sunlight were flooded for 30 days to study the effects of light availability and root inundation on photosynthetic light response. Compared with seedlings receiving full sunlight, seedlings receiving partial sunlight developed leaves with 90% greater blade area, 26% less mass per unit volume, and 35% lower nitrogen (N) concentration per unit area, leading to a 15% reduction in leaf photosynthetic capacity when carbon exchange rates were based on blade area. However, when carbon exchange rates were based on leaf mass, leaves acclimated to partial sunlight exhibited a 15% greater photosynthetic capacity realized primarily through an increased initial slope of the photosynthetic light response (A/PPFD) curve and increased net photosynthesis at leaf saturation (Amax). Short-term flooding increased leaf mass per unit area more than 19%, reduced foliar N concentrations per unit dry mass by 19%, and initiated reductions in Amax and apparent quantum yield (phi) of seedlings in both light regimes. Greatest impairment of Amax (56% area basis, 65% mass basis) and phi (40%) were observed in leaves receiving full sunlight, and the declines were concomitant with a 35% decrease in chlorophyll concentration. Flooding also depressed instantaneous photosynthetic N-use efficiency (PPNUE) such that Amax decreased 54%, and the initial slope of PPNUE/PPFD curves decreased 33 and 50% for leaves acclimated to partial and full sunlight, respectively. The A/PPFD patterns indicated that the magnitude of flood-induced inhibition of the photosynthetic mechanism of cherrybark oak seedlings is determined partly by the light environment.

Light↗
PubMed2006

Impact of dietary and lifestyle on vitamin D in healthy student girls aged 11-15 years.

OBJECTIVE: To study daily intake of calcium, phosphorus and vitamin D, to determine the biochemical findings of rickets and the effect of sunlight exposure and vitamin D supplementation in school girls with hypovitaminosis D. METHODS: A cross-sectional study was conducted on school girls aged 11-15 years selected randomly from various areas of Tehran, Iran. Dietary information and amount of sunlight exposure were estimated by a 7 day recalling method using self-reported questionnaire. Hypovitaminosis D defined as low serum 25-hydroxyvitamin D concentration with two or more others abnormal biochemical findings. Girls with hypovitaminoses D were randomly divided into two groups. The faces and hands of girls in group 1 were exposed to sunlight for one hour per day for twenty days, while those in group 2 were administered vitamin D capsules, 50,000 IU per day for the same period. RESULTS: four-hundred fourteen girls evaluated, mean daily calcium intake, sunlight exposure and vitamin D acquirement were 360 mg, 10 minutes and 119 IU, respectively. Mean serum 25-hydroxyvitamin D concentration was 30 ng/ml among all girls whereas in 15 (3.63%) of 414 girls was 7.8 ng/ml. Abnormal biochemical findings in these girls included hypocalcemia (n=4), hypophosphatemia (n=5), raised serum alkaline phosphatase (n=13), and parathyroid hormone (n=15). After intervention, mean serum 25-hydroxyvitamin D concentration in sunlight exposure (n=8) and vitamin D (n=7) supplementation increased to 14.4+/-4 ng/ml and 23+/-4 ng/ml respectively. There was a significant difference between the two groups (p<0.05). CONCLUSION: Vitamin D deficiency developed in rapid growth period of girls without clear clinical rickets in sunny temperate climate city in Iran which vitamin D supplementation improved biochemical findings better than sunlight exposure.

Adolescent↗
PubMed2001

Synergistic effect of solar radiation and solar heating to disinfect drinking water sources.

Waterborne diseases are still common in developing countries as drinking water sources are contaminated and feasible means to reliably treat and disinfect these waters are not available. Many of these developing countries are in the tropical regions of the world where sunlight is plentiful. The objective of this study was to evaluate the effectiveness of combining solar radiation and solar heating to disinfect contaminated water using a modified Family Sol*Saver System (FSP). The non-UV transmittable cover sheet of the former FSP system was replaced with an UV transmittable plastic cover sheet to enable more wavelengths of sunlight to treat the water. Disinfection efficiency of both systems was evaluated based on reduction of the natural populations of faecal coliform, E. coli, enterococci, C. perfringens, total heterotrophic bacteria, hydrogen sulphide producing bacteria and FRNA virus. The results showed that under sunny and partly sunny conditions, water was heated to critical temperature (60 degrees C) in both the FSP systems inactivating more than 3 log (99.9%) of the concentrations of faecal coliform and E. coli to undetectable levels of < 1 CFU/100 mL within 2-5 h exposure to sunlight. However, under cloudy conditions, the two FSP systems did not reduce the concentrations of faecal indicator bacteria to levels of < 1 CFU/100 mL. Nonetheless, sufficient evidence was obtained to show that UV radiation of sunlight plus heat worked synergistically to enhance the inactivation of faecal indicator bacteria. The relative log removal of indicator microorganism in the FSP treated water was total heterotrophic bacteria < C. perfringens < F RNA virus < enterococci < E. coli < faecal coliform. In summary, time of exposure to heat and radiation effects of sunlight were important in disinfecting water by solar units. The data indicated that direct radiation of sunlight worked synergistically with solar heating of the water to disinfect the water. Thus, effective disinfection was observed even when the water temperature did not reach 60 degrees C. Finally, the hydrogen sulphide test is a simple and reliable test that householders can use to determine whether their water had been sufficiently disinfected.

Biomarkers↗
PubMed2003

Photoenhanced toxicity of aqueous phase and chemically dispersed weathered Alaska North Slope crude oil to Pacific herring eggs and larvae.

The photoenhanced toxicity of weathered Alaska North Slope crude oil (ANS) was investigated in the eggs and larvae of Pacific herring (Clupea pallasi) with and without the chemical dispersant Corexit 9527. Oil alone was acutely toxic to larvae at aqueous concentrations below 50 microg/L total polycyclic aromatic hydrocarbons (tPAH), and median lethal (LC50s) and effective concentrations (EC50s) decreased with time after initial oil exposure. Brief exposure to sunlight (approximately 2.5 h/d for 2 d) significantly increased toxicity 1.5- to 48-fold over control lighting. Photoenhanced toxicity only occurred when oil was present in larval tissue and increased with increasing tPAH concentration in tissue. Ultraviolet radiation A (UVA) treatments were less potent than natural sunlight, and UVA + sunlight caused greater toxicity than sunlight alone. The toxicity of chemically dispersed oil was similar to oil alone in control and UVA treatments, but oil + dispersant was significantly more toxic in the sunlight treatments. The chemical dispersant appeared to accelerate PAH dissolution into the aqueous phase, resulting in more rapid toxicity. In oil + dispersant exposures, the 96-h no-observed-effect concentrations in the UVA + sunlight treatment were 0.2 microg/L tPAH and 0.01 microg/g tPAH. Exposure of herring eggs to oil caused yolk sac edema, but eggs were not exposed to sun and UVA treatment did not cause phototoxicity. These results are consistent with the hypothesis that weathered ANS is phototoxic and that UV can be a significant and causative factor in the mortality of early life stages of herring exposed to oil and chemically dispersed oil.

Animals↗
PubMed1994

Changing the risk spectrum of injury and the performance of sunscreen products throughout the day.

Sunscreen products are tested normally against a defined solar simulator spectrum that, in ultraviolet (UVB), closely resembles the noontime spectral composition of summer sunlight. Although such a spectrum may define the product for use in the most adverse sunlight conditions, little attention has been given to how such products perform against other natural sunlight spectra. Outdoor clinical trials suggest that indoor testing of sunscreens may overestimate the performance of many products. In this study we compared the predicted efficacy of specific products to a variety of natural sunlight spectra taken at different solar angles and under different atmospheric conditions. We found that a standard product always provides less protection for a natural sunlight spectrum than its label value would suggest. The deviation from the labeled value is the greatest when the sun is low in the sky, i.e., close to the horizon. The deviation is due to the changing ratio of UVA to UVB radiation in natural sunlight. The deviation can be as large as a factor of 2.0.

Absorption↗
PubMed2004

Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers.

OBJECTIVE: Three phase 1 clinical trials of a superpotent melanotropic peptide, melanotan-1 (MT-1, or [Nle(4)-D-Phe(7)]alpha-melanocyte-stimulating hormone) were performed to demonstrate safety for MT-1 therapy combined with UV-B light or sunlight. DESIGN: Open-label studies at 2 dose levels of MT-1 combined with small doses of UV-B to the neck or buttock or full sunlight to half of the back. SETTING: Dermatology clinics at the Arizona Health Sciences Center, Tucson. INTERVENTIONS: The first study randomized 4 subjects to MT-1 (0.08 mg/kg per day subcutaneously) and 4 subjects to injections of isotonic sodium chloride (9%) solution for 10 days, followed by neck irradiation with 3 times the minimal erythema dose (MED) of UV-B light. In the next study (n = 12), the MT-1 dosage was increased to 0.16 mg/kg per day for 10 days, with UV-B radiation (0.25-0.75 MED) given to a buttock site for 5 days during (n = 7) or after (n = 5) MT-1 administration. A final study randomized 8 subjects to 3 to 5 days of sunlight to half of the back or to sunlight plus 0.16 mg/kg of MT-1 for 5 days per week for 4 weeks. RESULTS: Tanning in the first study was achieved in 3 of 4 subjects receiving MT-1, and these subjects also had 47% fewer sunburn cells at the irradiated neck site. More skin sites darkened with the higher dose of MT-1 in the second study. In the third study, there was significantly enhanced tanning of the back in the MT-1 group, and this was maintained at least 3 weeks longer than the tanning in the sunlight-only controls, who required 50% more sun-exposure time for equivalent tanning. MAIN OUTCOME MEASURE: There were no pathologic findings at any UV-B or sun-exposed sites in any subject. Toxic effects due to MT-1 were minor, consisting of nausea and transient facial flushing. CONCLUSION: Melanotan-1 can be safely combined with UV-B light or sunlight and appears to act synergistically in the tanning response to light.

Adult↗
PubMed2006

Environmental discontinuity hypothesis: Buffer dysfunctions as a source of human disease.

Adaptive physiologic buffers enable organisms to respond to environmental variation with appropriate plasticity. Modern humans have substantially remodeled their environment such that many interactions with the environment have become relatively discontinuous functions compared to the past. Examples include sunlight, temperature, and altitude. We propose that environmental discontinuity represents a Darwinian maladaptation and may promote disease by inducing buffer dysfunctions. Skin pigmentation is an adaptive, dynamic buffer that normalizes sunlight exposure to balance the potential harm of damaging rays with the importance of sunlight in driving systemic biologic functions such as melatonin and vitamin D. Due to lifestyle characteristics such as indoor-outdoor living, well-intended sun-avoidance campaigns, and inhomogeneous use of apparel and sunblock techniques, modern humans increasingly experience sunlight variation as a discontinuous function. The resulting skin pigmentation buffer dysfunction may promote diseases associated with over- or under-exposure to sunlight, the most striking example being melanoma. In addition to promoting discontinuity of sunlight exposure, sun-avoidance campaigns may undermine sun-dependent biologic pathways such as melatonin and vitamin D that appear to protect against cancer. These issues may partly explain the rise in melanoma rates despite the implementation of sun-avoidance campaigns. Also discussed is the potential role that discontinuous temperature variation associated with modern lifestyles plays in diseases such as viral infection, heart failure, and acute coronary syndromes. Acute discontinuous changes in pressure and oxygen levels related to air travel may contribute to autonomic dysfunction, venous thromboembolism, and viral infections. Therapeutic implications are discussed.

Adaptation, Physiological↗
PubMed2003

Animal models of melanoma: an HGF/SF transgenic mouse model may facilitate experimental access to UV initiating events.

Cutaneous malignant melanoma, the most lethal of the skin cancers, known for its intractability to current therapies, continues to increase in incidence, providing a significant public health challenge. There is a consensus that skin cancer is initiated by sunlight exposure. For non-melanoma skin cancer there is substantial evidence that chronic exposure to the ultraviolet B radiation (UVB) (280-320 nm) portion of the sunlight spectrum is responsible. Experimentally, UVB is mutagenic and chronic UVB exposure can cause non-melanoma skin cancer in laboratory animals. Non-melanoma tumors in animals and in humans show characteristic UVB signature lesions in the tumor suppressor p53 and/or in the patched (PTCH) gene. An action spectrum or wavelength dependence for squamous cell carcinoma in the mouse shows a major peak of efficacy in the UVB. For malignant melanoma, however, the situation is unclear and the critical direct target(s) of sunlight in initiating melanoma and even the wavelengths responsible are as yet unidentified. This lack of information is in major part a result of a paucity of animal models for melanoma which recapitulate the role of sunlight in initiating this disease. The epidemiology of melanoma differs significantly from non-melanoma skin cancer. Intense sporadic sunlight exposure in childhood, probably exacerbated by additional adult exposure, is associated with elevated melanoma risk. Melanoma is also a disease of gene-environment interactions with underlying genetic factors playing a significant role. These major differences indicate that extrapolation from information for non-melanoma skin cancer to melanoma is unlikely to be useful. We summarize in this review the experimental information available on the role of UV radiation in melanoma and give an overview of animal melanoma models. A new model derived by neonatal UV irradiation of hepatocyte growth factor/scatter factor (HGF/SF) transgenic mice is described which recapitulates the etiology, the histopathology and molecular pathogenesis of human disease. It is anticipated that the HGF/SF transgenic model will provide a means to access the mechanism(s) by which sunlight initiates this lethal disease and provide an appropriate vehicle for derivation of appropriate therapeutic and preventive strategies.

Animals↗
PubMed1999

Two decades of the public health approach to skin cancer control in Australia: why, how and where are we now?

Incidence and mortality rates due to skin cancer are rising in most Western countries. Early detection of these tumours at a stage when they can be easily cured is the primary approach taken by many people wishing to deal with the problem. A primary prevention approach, that is, reduction in sunlight exposure, is being considered by an increasing number of organizations. The public health approach to primary prevention of skin cancer, including melanoma, requires an understanding of the role of sunlight in the production of these tumours. Despite a clear understanding of exactly how sunlight does this, there is enough epidemiological and laboratory evidence to suggest a broad approach to the problem. This includes reduction of sunlight exposure, particularly in childhood and adolescence. It also suggests the need to recommend avoidance of suntanning and particularly the excessive exposures that lead to sunburn. Widespread primary prevention public health programmes have been running in Australia for almost 20 years. The data measuring the effect of these programmes indicate a very large shift in knowledge attitudes and beliefs about sunlight exposure and suntans, and major shifts in behaviour. Suntans are no longer as popular as they were and people are reducing their sunlight exposure by a variety of methods encapsulated in Slip! Slop! Slap! Cohort analysis of the incidence rates for melanoma and non-melanoma skin cancer show that the incidence of these tumours is levelling out in young people and is dropping in some instances. These are the people who were able to be influenced by the public health programmes in recent decades. Finally, following initial dramatic changes in all the behavioural variables related to the programme, a period of consolidation with continuing effort and more specific targeting will be required in the coming decades to maintain the improvement.

Australia↗
PubMed1999

Why do mothers still sun their infants?

OBJECTIVE: To determine the prevalence of maternal beliefs about the therapeutic uses of sunlight in infancy in tropical Australia. METHODOLOGY: Data were collected by interviewing 114 post-partum patients in Townsville (19 degrees 16'S), Queensland. Each woman was asked a series of open-ended and set-response questions about ancestry, pigmentation, residential history, parity, maternal and paternal education, and beliefs regarding the reputed therapeutic uses of sunlight. RESULTS: Half of the women had at least one risky belief about the perceived benefits of sunning their baby. Thirty-six per cent were in favour of using sunlight to treat neonatal jaundice; 20.2% believed it was necessary to intentionally sun their baby to prevent vitamin D deficiency; and 10.5% thought sunlight was a good remedy for nappy rash. Independent predictors of one or more of these beliefs included maternal age and education level, and having another child that had been treated for jaundice. Forty per cent of multiparous women had sunned a child to treat neonatal jaundice. In most cases, advice to mothers to sun their baby had been given by a midwife/nurse (41% or a doctor/paediatrician (28%). CONCLUSIONS: Post-parturient women had a high prevalence of beliefs that may result in their infant being intentionally exposed to sunlight, and which could increase their child's future risk of skin neoplasia. Midwives and doctors, including paediatricians, were identified as the major professional sources of these beliefs. Professional education is needed to change the beliefs of health professionals who recommend therapies involving sunlight.

Adolescent↗
PubMed1996

Mutagenic specificity of solar UV light in nucleotide excision repair-deficient rodent cells.

To investigate the role of nucleotide excision repair (NER) in the cellular processing of carcinogenic DNA photoproducts induced by defined, environmentally relevant portions of the solar wavelength spectrum, we have determined the mutagenic specificity of simulated sunlight (310-1100 nm), UVA (350-400 nm), and UVB (290-320 nm), as well as of the "nonsolar" model mutagen 254-nm UVC, at the adenine phosphoribosyltransferase (aprt) locus in NER-deficient (ERCC1) Chinese hamster ovary (CHO) cells. The frequency distributions of mutational classes induced by UVB and by simulated sunlight in repair-deficient CHO cells were virtually identical, each showing a marked increase in tandem CC-->TT transitions relative to NER-proficient cells. A striking increase in CC-->TT events was also previously documented for mutated p53 tumor-suppressor genes from nonmelanoma tumors of NER-deficient, skin cancer-prone xeroderma pigmentosum patients, compared to normal individuals. The data therefore indicate that the aprt gene in NER-deficient cultured rodent cells irradiated with artificial solar light generates the same distinctive "fingerprint" for sunlight mutagenesis as the p53 locus in NER-deficient humans exposed to natural sunlight in vivo. Moreover, in strong contrast to the situation for repair-component CHO cells, where a significant role for UVA was previously noted, the mutagenic specificity of simulated sunlight in NER-deficient CHO cells and of natural sunlight in humans afflicted with xeroderma pigmentosum can be entirely accounted for by the UVB portion of the solar wavelength spectrum.

Adenine Phosphoribosyltransferase↗
PubMed2002

An investigation of professional advice advocating therapeutic sun exposure.

OBJECTIVE: To determine the prevalence of inappropriate professional advice advocating therapeutic sun exposure in infancy and the post-partum period. METHODS: Self-administered postal questionnaires were completed by doctors (n=130; 71% response) and nurses (n=285; 58.6% response) responsible for the care of post-parturient women in eight hospitals in metropolitan and regional Queensland (1999/2000). RESULTS: Both groups reported several risky beliefs about the therapeutic benefits of sun exposure including using sunlight to treat: cracked nipples (41.1% nurses, 46.2% doctors); neonatal jaundice (49.5%, 34.9%); nappy rash (23.3%, 19.5%); and acne (12.3%, 20.2%). Approximately 10% of nurses and doctors recommended sunlight to treat sore/cracked nipples from breastfeeding, while 42% recommended sun exposure to treat neonatal jaundice. Relatively few doctors and nurses who recommended therapeutic sun exposure stipulated sunning through a window. Subtropical residence was a significant predictor of recommending sunlight to treat cracked nipples (p=0.002) and nappy rash (p=0.0005) among nursing staff. Midwives were more likely to recommend sunlight for neonatal jaundice than other nurses (p=0.004). Obstetricians (p=0.046), older doctors (p=0.049) and those who qualified earlier (p=0.031) were more likely to recommend sunlight to treat nappy rash. Paediatricians and neonatologists were less likely to recommend sunlight to treat neonatal jaundice than obstetricians and other doctors (p=0.009). CONCLUSIONS AND IMPLICATIONS: An education program is needed to change the practices of health professionals who recommend therapeutic sun exposure and should coincide with a health promotion campaign aimed at reducing the prevalence of related risky beliefs among parents.

Adult↗
PubMed2004

Effect of clothing varieties on solar photosynthesis of previtamin D3: an in vitro study.

BACKGROUND/PURPOSE: Vitamin D3 plays important roles in the absorption of calcium and phosphorus from the gastrointestinal tract and in the treatment of rickets; in addition, it facilitates the deposition of minerals in bones, thus minimizing the possibility of developing osteomalacia. Sunlight naturally induces vitamin D3 photosynthesis. Such a process is affected by a number of factors such as age, geographical location, skin color, sunscreen application and clothing. It is intended in the present investigation to study in vitro the effect of clothing on the solar photoproduction of vitamin D3. METHODS: Fifteen different fabric samples were tested for their effect on the efficiency of the in vitro solar conversion of 7-dehydrocholesterol (7-DHC) to vitamin D3. 7-DHC was dissolved in methanol to give a concentration of 2.6 x 10(-4) M. Solutions were exposed to sunlight in quartz containers for predetermined periods either uncovered or covered with the fabric sample under test. Changes in the concentrations of 7-DHC and the photoproducts were monitored by HPLC. Fabrics were graded as the number of threads per square inch (in(2)), and their sunlight attenuation was determined. RESULTS: 7-DHC is transformed to previtamin D3 upon exposure to sunlight, and the amount generated exhibited an almost linear relationship. When fabric-covered samples of 7-DHC were irradiated, photoproducts were also detected and their concentrations depended on the degree of sunlight attenuation imposed by the fabric. Generally, the higher the number of threads per in(2) the more the light attenuation produced. CONCLUSION: Clothing plays an important role in attenuating sunlight, thus leading to diminished vitamin D3 production to an extent that would require dietary compensation.

Cholecalciferol↗
PubMed1994

Photostability determination of commercially available nifedipine oral dosage formulations.

Nifedipine (NIF), a 1,4-dihydropyridine calcium channel antagonist, undergoes photodegradation to dehydronifedipine (DNIF) upon exposure to ultraviolet (UV) light and to the nitroso analogue of dehydronifedipine (NDNIF) when exposed to sunlight. NIF photodegradation products do not contribute to clinical activity, thus the content of NIF must remain uniform between equipotent formulations. Large differences in light stability between bioequivalent NIF products could potentially result in the therapeutic failure of unstable preparations. Consequently, if large photostability differences do exist between NIF preparations, product substitution may not be warranted. The light stability of 10 intact immediate- or controlled-release oral NIF formulations, obtained from several European and North American manufacturers, was studied using direct continuous artificial sunlight exposure extending over a 12-week period. The content of both NIF and NDNIF for each product was measured to determine the extent of photodecomposition using a specific and sensitive reversed-phase high pressure liquid chromatographic (HPLC) method. In addition, NIF photodegradation was measured using both pure NIF powder and methanolic NIF solution to determine the effectiveness of the artificial sunlight source used in this study. After 12 weeks of artificial sunlight exposure, less than 3% of NDNIF (w/w initial NIF content) was present in each of the 10 tested dosage forms. Photodegradation was greater than 10% (w/w initial NIF content) in approximately 5-10 min (mean t1/2 = 31 min), and in approximately 24 h (mean t1/2 = 7.7 days) of artificial sunlight exposure for methanolic NIF solution and pure NIF powder samples, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemistry, Pharmaceutical↗
PubMed2006

Phototransformation of 2,4,6-trinitrotoluene: sensitized by riboflavin under different irradiation spectral range.

Riboflavin-sensitized phototransformation of 2,4,6-trinitrotoluene (TNT) under natural sunlight was investigated with reverse-phase high performance liquid chromatography/mass spectrometry (HPLC/MS) and gas chromatography/mass spectrometry (GC/MS). The effect of different spectral region of sunlight on TNT phototransformation in the absence or presence of riboflavin was also investigated by using optical filters with cut-off at 400 or 455 nm. The concentration of riboflavin in the phototransformation of TNT was optimized. Concentration of riboflavin and TNT was 1.0 and 50 microM, respectively. The rates of phototransformation of TNT under natural sunlight in the presence or absence of riboflavin were conformed to initial pseudo-first-order rate equation. The photolysis half life of TNT in the presence of riboflavin was 21.87 min, compared to 39 min in the absence of riboflavin under natural sunlight. Two major phototransformation products of TNT, 3,5-dinitroaniline (3,5-DNA) and 1,3,5-trinitrobenzene (1,3,5-TNB), were detected in the samples in the presence of riboflavin receiving irradiation at full wavelength or wavelength >400 nm. The results indicate that riboflavin mediates TNT sensitized-phototransfomation under natural sunlight or near-UV-vis light.

Photolysis↗
PubMed1983

Environmental UVA radiation and eye protection during PUVA therapy.

Experimental and clinical evidence suggests that patients receiving psoralens plus UVA radiation (PUVA) therapy for the treatment of psoriasis or other skin diseases run the risk of developing cataracts. The total exposure to UVA radiation of these patients has been difficult to quantify because they are exposed to UVA radiation in the environment as well as during PUVA therapy. In our studies, the spectral irradiances of possible environmental sources of UVA radiation (sunlight, daylight and cool white fluorescent bulbs, and incandescent bulbs) were measured and compared to the spectral irradiance of a bank of PUVA bulbs. Sunlight and PUVA bulbs were found to have similar irradiances in the UVA waveband. Window glass reduced the UVA irradiance from sunlight. Artificial sources of illumination had a very low UVA irradiance compared with PUVA bulbs and sunlight. These results indicate that patients should protect their eyes from sunlight both outdoors and indoors after ingestion of psoralens; however, protection from incandescent bulbs or cool white and daylight fluorescent bulbs is much less important, and possibly unnecessary.

Cataract↗
PubMed2000

Shoot growth responses to light microenvironment and correlative inhibition in tree seedlings under a forest canopy.

To examine the mechanisms underlying crown development, I investigated the dependence of shoot behavior on light microenvironment in saplings of the evergreen broad-leaved tree species, Litsea acuminata (Bl.) Kurata, growing on a forest floor. The local light environment of individual shoots (shoot irradiance) and plants (plant irradiance, defined as the shoot irradiance of the most sunlit shoot of a plant) were analyzed as factors affecting shoot behavior. Daughter shoots that developed under partially sunlit conditions were longer and less leafy than daughter shoots developed under shaded conditions. Shoot production increased with increasing shoot irradiance. Terminal shoots receiving 5% or less of full sunlight produced 0.67 daughter shoots on average, whereas shoots receiving 10% or more of full sunlight produced 1.72 daughter shoots. In terminal shoots receiving 5% or less of full sunlight, the probability of producing no daughter shoots was about 63% when other shoots on the plant received 10% or more of full sunlight, but was < 35% where the rest of the plant was also shaded. Shoot death was observed only in shoots receiving 5% or less of full sunlight. The mortality of shaded shoots was higher in plants growing in high irradiance than in plants growing in low irradiance. The ecological significance of correlative inhibition (the enhanced mortality and reduced production of new shaded shoots in the presence of partially-sunlit shoots) is discussed.

Environment↗
PubMed1990

Sunglasses: are they necessary in Christchurch?

Concern over potential eye injury from sunlight prompted this study to see if the levels of sunlight in Christchurch posed a particular risk to our population's eyes, whether the populace was aware of any risk and whether effective sunglasses were freely available to the public. While there has been a 4% to 9% increase in UV radiation since 1969 due to global ozone depletion, no firm evidence was found that focal ozone depletion was a particular problem in New Zealand. Christchurch residents were poorly informed about the ocular hazards of sunlight. A questionnaire completed by 200 adults disclosed 32% were unaware of the particular danger of UV light and only 3% knew that snow blindness, eclipse burns and cataracts could all be caused by sunlight. Fifty-four sunglasses were analysed for labelling and for transmission characteristics of their lenses. The standard of labelling of the sunglasses was poor with only 53% making reference to UV transmission characteristics and only three pairs stating that they adhered to the New Zealand Sunglass Standard. Attention is drawn to the need to improve public awareness of the potential for eye injury from sunlight and to improve the standard of labelling of sunglasses.

Adult↗