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Biomedical subjects

P Thune

Publications and source records attributed to P Thune.

At least 55 records · Page 3Linked to original sources
PubMed1989

Photocarcinogenesis is retarded by a partly photodegraded solution of para-aminobenzoic acid.

A solution of para-aminobenzoic acid (PABA) was exposed to ultraviolet (UV) radiation emitted from a Philips TL 40 W/12 sunlamp and the degree of photodegradation following an exposure of 27 J/cm2 was estimated to be approximately 40%. The formation of the photoproducts was confirmed by mass spectroscopy and UV spectroscopy. The solution was painted on the backs of hairless light-pigmented mice prior to daily UV irradiation by the above sunlamp, and this procedure was continued for 30 weeks. The preirradiated solution of PABA significantly retarded the tumor induction time and reduced significantly the number of squamous cell carcinomas compared with nonprotected controls. This tumor-retarding ability did not differ significantly from the effect achieved when using nonirradiated PABA.

4-Aminobenzoic Acid↗
PubMed1988

The water barrier function of the skin in relation to the water content of stratum corneum, pH and skin lipids. The effect of alkaline soap and syndet on dry skin in elderly, non-atopic patients.

Clinical dryness of the skin is a common problem among elderly, dermatological patients. In the present investigation, hydration, surface lipids, skin pH and water barrier function as expressed by the transepidermal water loss (TEWL) were studied in both dry and normal skin. Using these parameters, a comparison of the local effects of acid and alkaline cleansing products was made. In non-atopic elderly patients with dry skin, the TEWL values were lower than in the younger control group but higher than in the older controls. Following one week's topical therapy, the TEWL values in the patient group decreased further and approached the lower values of the older control group. At the same time the skin hydration values increased, indicating a beneficial effect on the skin barrier. An inverse relationship was demonstrated between TEWL and skin hydration. The study indicates that high TEWL values are frequently correlated with high pH, low hydration of the stratum corneum and reduced skin surface lipid content. Despite the intensive use of an acid syndet and lotion, the pH-readings increased but were still within the 'confidence limits' of the control groups.

Administration, Cutaneous↗
PubMed1988

The Scandinavian multicenter photopatch study 1980-1985: final report.

At 16 different dermatology clinics in Scandinavia from 1980-1985, photopatch testing was performed on 1993 patients with suspected photodermatosis. The collective results are presented in this article. The most common cause of sun-related dermatosis was polymorphic light eruption (PLE) (38%), while secondary aggravation of pre-existing skin diseases was established in 16% of the patient group. Photocontact dermatitis (11%) and contact dermatitis (10%) were responsible for 274 and 369 positive test reactions (respectively) on photopatch testing using the SPDRG standard series. Musk ambrette and para-aminobenzoic acid were the leading photosensitizers, while perfume mixture, balsam of Peru and lichen mixture were the most frequent causes of contact sensitivity. The principal photoallergens and contact allergens in the PLE, persistent light reaction and actinic reticuloid groups are discussed, together with the problems, risks and possible mechanisms of induction of photosensitization in these patients. The incidence, causes and diagnostic and therapeutic implications of secondary sunscreen sensitivity in these groups are also addressed.

Clinical Trials as Topic↗
PubMed1988

Contact and photocontact allergy to glyceryl para-aminobenzoate.

High-purity glyceryl para-aminobenzoate was produced from a commercial source of the chemical by using a chromatographic technique. Negative test reactions to this purified substance were obtained when it was patch/photopatch-tested on 2 patients with contact and photocontact allergy to a nonpurified batch of glyceryl para-aminobenzoate.

4-Aminobenzoic Acid↗
PubMed1988

Measurements of the photodegradation of PABA and some PABA derivatives.

The photodegradation of 4-aminobenzoic acid, 2-ethylhexyl N,N-dimethyl 4-aminobenzoate (Escalol 507) and 1-glyceryl 4-aminobenzoate (Escalol 106), resulting from irradiation by sun lamps, was examined by UV spectroscopy. 2-ethylhexyl N,N-dimethyl 4-aminobenzoate showed the longest half-life, indicating the highest photostability.

4-Aminobenzoic Acid↗
PubMed1984

Low density lipoprotein receptors in cultured skin fibroblasts from psoriasis patients.

Low density lipoprotein (LDL) receptor activity, measured as 125I-LDL association and degradation at 37 degrees C, was determined in cultured fibroblasts from involved as well as uninvolved skin obtained from 20 psoriasis patients. The same analyses were conducted in fibroblasts from two reference groups consisting of 19 heterozygotes for familial hypercholesterolemia and 16 normal subjects, respectively. Psoriasis patients had significantly lower LDL receptor activity than normals, and it was comparable to that of the heterozygotes for familial hypercholesterolemia. The reduced LDL receptor activity was not accompanied by an increase in total serum cholesterol. The psoriasis patients had a significant reduction in apo-B concentration, but did not differ from the normals in the other serum lipid or lipoprotein parameters. There was no difference in LDL receptor activity between involved and uninvolved skin from psoriasis patients. These results suggest that there is an abnormal cell membrane in dermal fibroblasts from psoriasis patients. Since their total serum cholesterol is normal, their low LDL receptor activity may be confined to dermal cells, leaving the hepatic lipid metabolism normal. The pathogenetic significance of this finding is unknown.

Apolipoprotein A-I↗
PubMed1984

The Scandinavian multicenter photopatch study. Preliminary results.

The Scandinavian photopatch test procedure has been applied to 745 patients with suspected photodermatoses during the years 1980-1981. Our experience has been encouraging with the recording of several relevant reactions. A total of 132 positive photocontact reactions and 120 ordinary contact reactions were seen. Photocontact reactions to musk ambrette (19 cases) and PABA (19 cases) were surprisingly frequent. The next most common photocontact reactions were to promethazine (24), chlorpromazine (22 cases) and fentichlor (12). Ordinary contact reactions were observed to balsam of Peru (30), PABA (23), lichen mix (21), wood mix (14) and to perfume mix (10).

4-Aminobenzoic Acid↗
PubMed1984

Contact and photocontact allergy in persistent light reactivity.

The patient group consisted of 18 elderly male patients with persistent light reactivity who were subjected to extensive phototesting with different wavelengths, including patch and photopatch testing. All reacted adversely to ultraviolet light and some also to longer wavelengths when tested on normal appearing skin. 17 patients showed contact or photocontact reactions, of which 12 were positive photopatch test reactions and 11 were plain contact reactions. Contact allergy to constituents of oak moss and different lichen compounds was twice as common as allergy to Compositae oleoresins. 72 patients with chronic polymorphic light eruption were used as a control group. 10 of these patients had either a positive photopatch test reaction or a plain contact allergy. Patients with persistent light reactivity are characterized by a particular susceptibility to develop a delayed-type hypersensitivity. They frequently have both photo and plain contact allergy, often to substances used in cosmetics. In 13 of 16 patients in whom a biopsy was carried out, the histology supported the clinical diagnosis. In none of the biopsies was the picture diagnostic in itself. This underlines the inadequacy of light microscopy as the only diagnostic procedure.

Aged↗
PubMed1984

The sensitizing capacity of atranorin.

The allergenic potential of the aromatic lichen substance atranorin has been investigated by means of the guinea pig maximization test of Magnusson & Kligman. Sensitivity was induced in 30% of the animals, which corresponds to a moderate allergenic capacity (grade III). This is in agreement with the clinically-observed frequency of 1.5% among our patients. A modified photoallergy test on the same animals was performed, but irradiation did not increase the number of positive reactions. 4 patients with proven contact sensitivity to atranorin, evernic, usnic or physodic acid, were examined with different dilutions from 0.001 to 0.1%. Irradiation of the test series did not provoke any clear-cut photoallergic reaction.

Adult↗
PubMed1984

Contact and photocontact allergy to sunscreens.

Patch and photopatch test studies in 23 patients with reactions to sunscreen preparations revealed 17 photopatch and 38 patch test-positive reactions. The offending allergens could be traced in 18 of the 23 patients. Allergy to PABA was demonstrated in 11 patients, 5 of whom had photocontact allergy. Photocontact allergy to oxybenzone was seen in 3 patients, while 8 were sensitive to cinnamates, and 2 of these had a photocontact allergy. Six patients were sensitive to the PABA-derivatives octyldimethyl-PABA and amyldimethyl-PABA and the ester glyceryl PABA, 2 of whom had a photocontact allergy. None of the 3 patients with benzocaine sensitivity, including 2 with a photocontact allergy, reacted to the PABA-ester. Eight patients were sensitive to different cinnamates, including 2 cases of photocontact allergy. In one patient sensitivity to two azo-naphthol dyes, contained in a sunscreen preparation, was confirmed. Five other patients had positive skin test reactions to different sunscreen preparations but the offending allergen could not be traced. Thirteen of the 23 patients had chronic light sensitive disorders such as polymorphic light eruption (PMLE) or persistent light reactivity (PLR). Sunscreen sensitivity appears to be more common than previously reported.

4-Aminobenzoic Acid↗