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Biomedical subjects

B L Diffey

Publications and source records attributed to B L Diffey.

At least 37 records · Page 2Linked to original sources
PubMed1990

Inhibition of photosensitivity in erythropoietic protoporphyria with terfenadine.

The effect of terfenadine on the response to irradiation with blue light was measured in seven patients with erythropoietic protoporphyria. Terfenadine caused significant inhibition of the immediate flare reaction, but did not alter the erythemal response localized to the irradiation sites. Treatment with beta-carotene had no effect on the flare and erythemal responses. However, the flare reaction was still inhibited by terfenadine during treatment with beta-carotene. These results show that histamine release is involved in the mechanism of porphyrin photosensitivity. H1 receptor antagonists may be of use in the treatment of patients with erythropoietic protoporphyria.

Adolescent↗
PubMed1990

Effect of topical solvents on ultraviolet B erythema.

The skin of subjects was pretreated with 3 solvents, normal saline, 95% ethanol and diethylether. No significant difference in erythemal sensitivity to UVB was demonstrated for any of the solvents.

Administration, Cutaneous↗
PubMed1990

Human exposure to ultraviolet radiation.

Although the sun remains the main source of ultraviolet radiation (UVR) exposure in humans, the advent of artificial UVR sources has increased the opportunity for both intentional and unintentional exposure. Intentional exposure is most often to tan the skin. People living in less sunny climates can now maintain a year-round tan by using sunbeds and solaria emitting principally UVA radiation. Another reason for intentional exposure to artificial UVR is treatment of skin diseases, notably psoriasis. Unintentional exposure is normally the result of occupation. Outdoor workers, such as farmers, receive three to four times the annual solar UV exposure of indoor workers. Workers in many industries, eg, photoprinting or hospital phototherapy departments, may be exposed to UVR from artificial sources. One group particularly at risk is electric arc welders, where inadvertent exposure is so common that the terms "arc eye" or "welders flash" are often used to describe photokeratitis. In addition to unavoidable exposure to natural UVR, the general public is exposed to low levels of UVR from sources such as fluorescent lamps used for indoor lighting and shops and restaurants where UVA lamps are often used in traps to attract flying insects.

Environmental Exposure↗
PubMed1990

Exposure to solar ultraviolet radiation in flight.

The ultraviolet radiation (UVR) exposure of airline pilots during flight was measured with ultraviolet-sensitive film badges. The badges were worn by flight crew on the epaulette nearest to the window of either a Boeing 737 or 767 during 18 different flights in 1989. The results showed in every case that the UVR exposure was negligible; a flight lasting several hours resulted in an exposure equivalent to no more than a minute or two outdoors. There is anecdotal evidence that pilots may be at increased risk of developing skin cancer compared with many other occupational groups. The suggestion that this is due to significant exposure to UVR, the main aetiological factor in skin cancer, on the flight deck cannot be sustained.

Aerospace Medicine↗
PubMed1990

Textiles and sun protection.

The spectral transmission of ultraviolet radiation was measured through natural textiles (cotton, wool, silk) and human-made textiles (acrylic, viscose, polyester). Each textile exhibited a characteristic spectral transmission curve, but the protection afforded by a given fabric depended more on the nature of the weave than on the particular type of textile.

Humans↗
PubMed1989

Adverse effects of sunscreens in photosensitive patients.

Experimental and epidemiological evidence shows that the common photosensitive disorder of polymorphic light eruption is caused by the ultraviolet A component of sunlight. Sunscreens protect mainly against ultraviolet B; consequently they reduce sunburn and allow longer periods of exposure to the sun and to greater doses of ultraviolet A than would otherwise be possible. Patients with polymorphic light eruption who intend to obtain a tan by sunbathing should not, therefore, be treated with sunscreens which may worsen their rash, but should be advised to sunbathe without sunscreens for a shorter time.

Disease Susceptibility↗
PubMed1989

Effect of indomethacin on UVB- and UVA-induced erythema in polymorphic light eruption.

The effect of topical indomethacin on the intensity of UVB- and UVA-induced erythema was measured by reflectance spectrophotometry in 23 patients with polymorphic light eruption. Thirteen patients showed a response to indomethacin that was identical to that seen in normal subjects (i.e., inhibition of UVB-induced erythema; no effect on the intensity of UVA-induced erythema). In the remaining 10 patients indomethacin caused abnormal augmentation of UVB- and UVA-induced erythema. These results show for the first time that the term polymorphic light eruption embraces at least two disease states that have different mechanisms of photosensitivity and that can be distinguished on the basis of clinical features and results of photobiologic investigation.

Administration, Topical↗
PubMed1989

The design and evaluation of an automated system for monitoring 133Xe in room air.

The radioactive gas 133Xe is widely used for ventilation imaging. This paper describes a system for continuous monitoring of the air concentration of 133Xe. The instrument consisted of a sodium iodide scintillation detector, a scaler/ratemeter and a data logger. The crystal was mounted inside a lead shield and enclosed in a perspex cylinder. A fan at one end of the cylinder drew room air into a shielded active volume via an inlet aperture designed to generate turbulent flow with no stagnant areas. The instrument was rendered relatively insensitive to external radiation by positioning the energy window over the 31 keV peak in the 133Xe spectrum. The detector sensitivity was approximately 2 s-1 per MBq m-3, with a typical background count rate of 0.12 s-1. The system was therefore capable of detecting a concentration of 0.06 MBq m-3 in a one-minute sampling interval. Results collected at five centres demonstrated that the eight-hour time-averaged concentrations were much less than the derived air concentration (DAC) for occupationally exposed persons (mean values 0.4 to 1.5% of the DAC), but that transient concentrations were extremely variable (mean values 7 to 24% of the DAC).

Air Pollutants, Occupational↗
PubMed1989

The normal range in diagnostic phototesting.

The minimal erythema doses (MED) to UVB and UVA radiation were measured in 254 normal subjects. Bivariate correlation analysis applied to the data showed a strong positive correlation between the UVB and UVA MEDs. By calculating the probability that a given combination of UVB and UVA MEDs is likely to occur in normal subjects, it was shown that, in some instances, both the UVB MED and UVA MED observed in a given subject may be within their respective normal ranges, but that the particular combination is more in keeping with abnormal photosensitivity.

Erythema↗
PubMed1989

Treatment of actinic prurigo with PUVA: mechanism of action.

Five patients with actinic prurigo were treated twice weekly with PUVA. One area on the back was shielded from UVA throughout the 15-week treatment period. Before PUVA, all patients had increased erythemal sensitivity to UVA and showed abnormal augmentation of UVB erythema by topical indomethacin. After PUVA, all patients were free of photosensitive symptoms and skin that had been exposed to UVA showed normal erythemal responses. By contrast, the areas of skin that had been protected from UVA showed erythemal responses that were unchanged from pre-PUVA values. Augmentation of UVB erythema by topical indomethacin persisted, both on UVA exposed and UVA protected skin. These results show that, although PUVA is an effective treatment in actinic prurigo, it does not alter the underlying mechanism of photosensitivity. The protective effect is local and is due presumably to an increase in melanin pigmentation and epidermal thickness.

Adult↗
PubMed1989

A double-blind study of ultraviolet phototherapy in the prophylaxis of chilblains.

A randomized, double-blind study was carried out to assess the prophylactic value of ultraviolet irradiation in the autumn as a means of preventing the development of chilblains on the toes and fingers during the course of the winter. Placebo irradiation was achieved by means of an optical filter which absorbed all ultraviolet radiation from the lamps but allowed the visible light component to be transmitted, thus giving patients the impression that both limbs were being treated. Patients were reviewed at monthly intervals during the winter. The response between patients was variable; some patients developed chilblains whilst others remained symptom free. However, in no patient did the ultraviolet treated limb differ from the untreated limb. We conclude that the ultraviolet phototherapy is of no value in the prophylaxis of chilblains.

Chilblains↗
PubMed1989

A comparison of the dose-response relationship for psoralen-UVA erythema and UVB erythema.

Twenty patients with psoriasis were phototested to determine their erythemal responses to UVB and psoralen-UVA (PUVA) (oral 8-methoxypsoralen). The smallest ultraviolet radiation doses to produce erythema (minimal erythema dose and minimal phototoxic dose, respectively) were recorded and dose-response curves were constructed for UVB (24 hours after irradiation) and PUVA (48 hours) using objective measurement. The choice of a 48-hour measurement was validated by phototesting an additional 11 subjects to determine the time course of PUVA erythema. No correlation was demonstrated between minimal erythema dose for UVB, minimal phototoxic dose for PUVA, and sun-reactive skin type. The mean slope of the dose-response curve for UVB erythema was four times steeper than that for PUVA. Psoralen-UVA erythema reached a broad maximum between 48 and 96 hours after irradiation. Using objective methods we have demonstrated that the commonly accepted view of a steep dose-response relationship for PUVA erythema is not valid.

Adult↗
PubMed1989

Phototoxic potential of thiazide diuretics in normal subjects.

Monochromator phototesting has been carried out in 22 subjects before and 2 weeks after therapy with either bendroflumethiazide (bendrofluazide) or hydrochlorothiazide. An increase in erythemal sensitivity was observed in several subjects in those wave bands that are maximally absorbed by the respective drugs in vitro. Both drugs showed similar phototoxic capabilities, yet in clinical practice, reports of photosensitivity caused by hydrochlorothiazide are much more common than those caused by bendroflumethiazide. One possible reason is suggested.

Adult↗