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Biomedical subjects

F Urbach

Publications and source records attributed to F Urbach.

At least 37 records · Page 2Linked to original sources
PubMed1988

Biologically effective ultraviolet radiation: surface measurements in the United States, 1974 to 1985.

Recent reports of stratospheric ozone depletion have prompted concerns about the levels of solar ultraviolet radiation that reach the earth's surface. Since 1974 a network of ground-level monitoring stations in the United States has tracked measurements of biologically effective ultraviolet radiation (UVB, 290 to 330 nanometers). The fact that no increases of UVB have been detected at ground levels from 1974 to 1985 suggests that meteorological, climatic, and environmental factors in the troposphere may play a greater role in attenuating UVB radiation than was previously suspected.

Humans↗
PubMed1987

Comparative efficacy of two dosage forms of oral methoxsalen in psoralens plus ultraviolet A therapy of psoriasis.

Two alternate oral formulations of 8-methoxypsoralen, one liquid and the other crystalline, were evaluated in a double-blind trial for their comparative efficacy in combination with ultraviolet A (UVA) light in the treatment of severe psoriasis. With the liquid formulation a greater proportion of patients achieved a good clinical result within the 20 treatment sessions than patients receiving the crystalline formulation. This difference is even more striking using a more rigorous criterion of clearance. Among all patients who achieved clearance, no significant differences were seen in either the number of treatments required or in the total UVA energy employed between the two groups. The preceding clinical results are discussed in light of published pharmacokinetic data.

Administration, Oral↗
PubMed1985

Effect of indoor lighting on normal skin.

A small but measurable component of some indoor lighting is ultraviolet radiation (UVR); whether it is sufficient to modify the indoor worker's risk for chronic skin changes is not directly answerable with available technology. A first approach to this question involves a) estimating a range of annual background solar exposure for indoor workers currently at risk; b) determining whether, and at what levels, UVR exposure is a part of specified indoor lighting; and c) calculating the increment in risk implied by a and b. This algorithm predicts that some lighting conditions that meet NIOSH recommended standards would still result in significant increases in the risk of cumulative UVR damage, including skin cancer. More information concerning actual exposure conditions, the relation of spectral effectiveness for luminosity and UVR production, and dose-time reciprocity are required to improve our predictions of long-term cutaneous effects of indoor lighting.

Erythema↗
PubMed1984

An animal model to determine sunscreen protectiveness against both vascular injury and epidermal cell damage.

Sunscreen preparations can reduce the erythemogenic ( sunburning ) effects of solar ultraviolet radiation (UVR). Less is known about the ability of sunscreens to protect against other forms of UVR-induced damage. This study was designed to yield data on epidermal cell damage at UVR doses sufficient to provoke vascular changes (edema and erythema) in hairless mice, and to determine the comparative effectiveness of a commercial sunscreen in protecting against these two criteria of injury. The sunscreen (Piz Buin 12 Sun Protection Cream) was used at full concentration and at three serial dilutions. The dorsa of 144 hairless mice were treated with one of six sunscreen or vehicle preparations and subsequently irradiated with one of six exposures to an appropriately filtered xenon arc solar simulator. Vascular responses were determined by observing the animals for alterations in the gross appearance of the treated and irradiated sites (edema and erythema). Epidermal cell damage was assessed by determining the sunburn cell ( SBC ) indices in the epidermis removed 24 hours after irradiation. Both the vascular responses and SBC indices indicated that the sunscreen provided concentration-dependent protection against radiation damage. Furthermore, SBC indices provided a relatively continuous variable for quantification of sunscreen effectiveness.

Animals↗
PubMed1983

Tinea capitis in Philadelphia.

From 1962 to 1979, there was a dramatic change in tinea capitis infections in children in the Philadelphia area. This has been primarily due to the virtual disappearance of tinea capitis due to Microsporum organisms. This dramatic change in a common, highly infectious childhood disease is most likely due to a sudden change in hair styles, particularly in black boys, which prevents infectious spores from reaching the scalp.

Female↗
PubMed1982

Modification of photocarcinogenesis by chemical agents.

The evidence is long standing and compelling that chemical agents can modify the carcinogenic effects of light. Various types of chemical-light interaction are discussed, and events in chemical photocarcinogenesis, chemically enhanced photocarcinogenesis, and promotion of photocarcinogenesis are described. Specific examples of each type of process are given, and the importance of interaction of various wavelengths of UV radiation for these processes is stressed.

Animals↗
PubMed1982

Simulated stratospheric ozone depletion and increased ultraviolet radiation: effects on photocarcinogenesis in hairless mice.

Solar ultraviolet radiation at the surface of the earth is a recognized cause of skin cancer. Postulated anthropogenic reductions in the thickness of the ozone layer would lead to an increased amount of ultraviolet radiation and hence would be expected to increase the risk of skin carcinogenesis. This study uses hairless (Skh:HR) mice as an animal model to study this increased risk. The mice were exposed 5 days/week to graded doses of ultraviolet radiation from a xenon arc lamp attenuated by five different thicknesses of Schott glass filters (WG320) to simulate various ozone layer thicknesses. A Robertson-Berger sunburning ultraviolet meter was used as one of the forms of dosimetry. The results of the various exposure treatments are expressed as the percentage of animal with tumors (incidence) versus time after commencing irradiation and as cumulative tumor yield (average number of tumors per survivor) versus time. With any given filter, the time to 50% incidence is inversely related to daily dose in Robertson-Berger meter units. The time to 50% incidence for comparable Robertson-Berger meter doses through different filter thicknesses increases with increasing thickness. These results indicate that the effective dose for skin cancer induction may be estimated from the Robertson-Berger meter dose but that the Robertson-Berger meter response spectrum underestimates the photocarcinogenic effectiveness of the shorter wavelengths. The cumulative tumor yield data are also consistent with these conclusions. Alternate weighting of the source spectra with the acute-response action spectrum for mouse skin edema gave a better correlation between unit dose and time to a tumor response, independent of the source spectral distribution. This suggests that the mouse skin edema action spectrum, indistinguishable from a human skin erythema action spectrum for lambda greater than 295 nm, is similar in shape to the mouse skin photocarcinogenesis action spectrum for lambda greater than 295 nm.

Animals↗
PubMed1980

The relative importance of risk factors in nonmelanoma carcinoma.

The relative importance of risk factors such as solar exposure, complexion, age, and the ability to tan were examined for their relationships to the development of basal and squamous cell carcinoma. Three samples were studied: patients with basal cell carcinoma (N = 366), patients with squamous cell carcinoma (N = 58), and control subjects (N = 294). The technique of logistic regression was used to estimate the relative risk of each type of carcinoma. Solar exposure was the most important risk factor for both basal and squamous cell carcinoma; however, the ability to tan was shown to be of special importance even at low levels of exposure. Given the same level of cumulative lifetime solar exposure, subjects over 60 years of age were shown to be at higher risk for nonmelanoma carcinoma than those at younger ages. Complexion was only shown to be significant for basal cell carcinoma.

Age Factors↗
PubMed1979

Bowen's disease and squamous cell carcinoma. Occurrence in a patient with psoriasis after topical, systemic, and PUVA therapy.

Multiple lesions of Bowen's disease and squamous cell carcinoma on the penis and pubic areas developed in a 32-year-old patient with psoriasis who was undergoing treatment with psoralen and long-wave ultraviolet radiation (PUVA). A cumulative dose of more than 3,700 joules/sq cm of UVA had been administered over a three-year period. This case may be an early warning of possible carcinogenicity of PUVA therapy, alone or as part of sequential therapy with other agents.

Adult↗
PubMed1979

Enhancement of experimental photocarcinogenesis by topical retinoic acid.

Topical application of retinoic acid (RA) solutions greatly enhanced the response of hairless mouse skin to a moderate dose of simulated sunlight. Tumors appeared much earlier, and in much greater numbers, in animals treated daily with 1 or 10 micrograms of RA in methanol immediately after 2 h exposure to a xenon arc filtered through 2 mm of Schott WG 320 glass (approximately equivalent in human erythema effectiveness to 5 min of mid-summer noon solar exposure in northern mid-latitudes), compared to mice treated with light and methanol only. The higher amount of RA, in combination with light, produced moderate epidermal hyperplasia and some scaling and transient erythema, but no gross ulceration or inflammation of skin. The lower amount of RA, though about equally effective in carcinogenesis, produced minimal epidermal hyperplasia compared to the ultraviolet radiation + methanol control.

Administration, Topical↗