Vitamin D status in different subgroups of British Asians.
To assess the effect of religious dietary practices and social customs on the vitamin D status of Asian immigrants, we kept records of the dietary intake and time spent out of doors of 81 Ugandan Asian men, women, and girls (9-19 years old). Sera were analysed for 25-hydroxycholecalciferol (25-OHD3), and 28% of the subjects were found to have levels below the lower limit of normal. The (vegetarian) Hindus had the lowest dietary intakes, least time out of doors, and lowest serum 25-OHD3. The Goan (Roman Catholic) Asians, despite more pigmentation, had 25-OHD3 levels similar to those found among indigenous British people and had the most satisfactory vitamin D intakes. Among Asians, whose exposure to sunlight may be limited, dietary vitamin D becomes the major determinant of serum 25-OHD3. (+info)
Histologic analysis of photochemical lesions produced in rhesus retina by short-wave-length light.
The photopathology of retinal lesions produced by extended exposure (1000 sec) to low corneal power levels (62 microW) of blue light (441 nm) was investigated by light microscopy in 20 rhesus eyes over an interval ranging from 1 hr to 90 days after exposure. Results indicate a nonthermal type of photochemical lesion originating in the retinal pigment epithelium and leading to a histological response with hypopigmentation which requires 48 hr to appear. This type of lesion helps to explain solar retinitis and eclipse blindness and has significance for aging and degenerative changes in the retina. (+info)
Absorption of solar radiation by an ellipsoid sensor simulated the human body.
Assessment of heat gain in man caused by solar radiation is one of the most important problems in research of the human heat balance outdoors. The purpose of the present study was to investigate a new method for estimation of solar heat income. Absorption of short wave radiation (direct, diffuse and reflected) was measured with an ellipsoid sensor representing a simple, physical model of man. Measurements were performed in climatic chamber with the use of an iodide CSI solar lamp. The absorbed quantity of solar radiation varied as a result of sun altitude as well as of a colour and insulation of fabric covering the ellipsoid sensor. The new coefficients derived from our investigations for estimating doses of absorbed solar radiation should be applicable for a standing man. They correlate better with mean skin temperature observed on subjects outdoor than previous results obtained based on a cylinder as an analogue model of man. The ellipsoid sensor covered by a black fabric absorbed about 6 times more of solar radiation than when covered by a white textile. (+info)
Merkel cell carcinoma and melanoma: etiological similarities and differences.
Merkel cell carcinoma (MCC) of the skin and cutaneous malignant melanoma can now be compared epidemiologically through the use of population-based data not previously available for MCC. The results may provide new clues to etiology. In this study, United States data covered by the Surveillance, Epidemiology, and End Results (SEER) Program were from nine areas of the United States (approximately 10% of the population). In 1986-1994, 425 cases of MCC were registered. The annual age-adjusted incidence per 100,000 of MCC was 0.23 for whites and 0.01 for blacks; among whites, the ratio of melanoma to MCC was approximately 65 to 1. Only 5% of MCC occurred before age 50, unlike the lifelong risk of nodular and superficial spreading melanoma. Regional incidence rates of both cancers increased similarly with increasing sun exposure as measured by the UVB solar index. The most sun-exposed anatomical site, the face, was the location of 36% of MCC but only 14% of melanoma. Both cancers increased in frequency and aggressiveness after immunosuppression and organ transplantation (36 cases from the Cincinnati Transplant Tumor registry and 12 from published case reports) and after B-cell neoplasia (5 cases in this study; 13 from case series in the literature). The SEER data contained reports of six patients with both types of cancer; 5 melanomas before the diagnosis of MCC and 1 after diagnosis. MCC and melanoma are similarly related to sun exposure and immunosuppression, but they differ markedly from one another in their distributions by age, race, and anatomical site, especially the face. (+info)
p53 mutations in human cutaneous melanoma correlate with sun exposure but are not always involved in melanomagenesis.
In melanoma, the relationship between sun exposure and the origin of mutations in either the N-ras oncogene or the p53 tumour-suppressor gene is not as clear as in other types of skin cancer. We have previously shown that mutations in the N-ras gene occur more frequently in melanomas originating from sun-exposed body sites, indicating that these mutations are UV induced. To investigate whether sun exposure also affects p53 in melanoma, we analysed 81 melanoma specimens for mutations in the p53 gene. The mutation frequency is higher than thus far reported: 17 specimens (21%) harbour one or more p53 mutations. Strikingly, 17 out of 22 mutations in p53 are of the C:G to TA or CC:GG to TT:AA transitional type, strongly suggesting an aetiology involving UV exposure. Interestingly, the p53 mutation frequency in metastases was much lower than in primary tumours. In the case of metastases, a role for sun exposure was indicated by the finding that the mutations are present exclusively in skin metastases and not in internal metastases. Together with a relatively frequent occurrence of silent third-base pair mutations in primary melanomas, this indicates that the p53 mutations, at least in these tumours, have not contributed to melanomagenesis and may have originated after establishment of the primary tumour. (+info)
In situ repair of cyclobutane pyrimidine dimers and 6-4 photoproducts in human skin exposed to solar simulating radiation.
DNA repair is crucial to the integrity of the human genome. The ultraviolet radiation portion of solar radiation is responsible for the rising incidence of skin cancer, one of the most common types of cancer in humans. We applied a recently developed 32P-postlabeling technique to measure the in situ DNA repair efficiency of solar-simulated radiation induced cyclobutane pyrimidine dimers and 6-4 photoproducts in the skin of nine healthy volunteers with skin type II. Our results show about 6-fold interindividual variations in the level of DNA damage after exposure to an equal biologic dose - 2 minimal erythema doses. The kinetics of DNA repair indicated a base sequence dependence of the repair process. The DNA repair efficiency showed a 20-fold difference in volunteers. An age-related decrease of DNA repair capacity was observed; however, the data are limited due to a small number of subjects and a narrow age range. The variable response in DNA damage levels and individual differences in DNA repair efficiency suggest a susceptible subgroup of people probably with a higher skin cancer risk. (+info)
Is sunlight an aetiological agent in the genesis of retinoblastoma?
The incidence of unilateral, but not bilateral, retinoblastoma in human populations at different geographical locations increases significantly with ambient erythemal dose of ultraviolet B radiation from sunlight. This supports the hypothesis that sunlight plays a role in retinoblastoma formation. (+info)
Ineffective vitamin D synthesis in cats is reversed by an inhibitor of 7-dehydrocholestrol-delta7-reductase.
Changes in plasma 25-hydroxyvitamin D (25-OHD) were used as an index of vitamin D status of cats. Plasma 25-OHD concentration of kittens given a purified vitamin D-free diet and exposed to direct summer sun for 15 h/wk declined at a similar rate as kittens given the same diet kept indoors. Similarly, plasma 25-OHD of kittens exposed to ultraviolet (UV) lamps declined at a similar rate as kittens not exposed, and these kittens developed clinical signs of vitamin D deficiency. Eight weaned kittens were given the vitamin D-free purified diet until their plasma concentrations of 25-OHD were < 5 nmol/L. They then had the hair on their backs clipped at weekly intervals and were paired on the basis of skin color and exposed to UV light for 2 h/d. One member of each pair was given an inhibitor of 7-dehydrocholesterol (5, 7-cholestradien-3beta-ol)-delta7-reductase (EC 18.104.22.168) in the diet. Cats receiving the inhibitor had a progressive increase in 25-OHD concentration of plasma with time to 91 +/- 22 nmol/L (mean +/- SEM), whereas cats not receiving the inhibitor had plasma 25-OHD concentrations that were not detectable (P < 0.001). Biopsy samples of skin from cats receiving the inhibitor had more than five times the concentration of 7-dehydrocholesterol (P < 0.001) than the skin of control cats. Low concentration of 7-dehydrocholesterol (presumably due to high activity of the reductase) in the skin of cats is the major impediment to effective vitamin D synthesis. Analysis of wild caught potential prey of cats indicated that these animals could supply adequate vitamin D to meet the requirement of growing kittens. (+info)