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Biomedical subjects

A A Schothorst

Publications and source records attributed to A A Schothorst.

At least 37 records · Page 2Linked to original sources
PubMed1984

Application of controlled high dose rates in UV-B phototherapy for psoriasis.

The use of a cabin fitted with Sylvania UV-21 tubes, which have a very high output of UV-B radiation, made it possible to treat psoriasis patients with a maximal exposure time of 5 minutes per session. An exposure-control unit was used to measure and regulate the applied dose to prevent overdosage. The clinical results obtained with two comparable groups of psoriasis patients treated with Sylvania UV-6 or UV-21 tubes were equal.

Adult↗
PubMed1984

Comparison of phototherapy (UV-B) and photochemotherapy (PUVA) for clearing and maintenance therapy of psoriasis.

One hundred eighty-three patients with psoriasis were treated with UV-B irradiation or oral methoxsalen plus longwave UV light (PUVA). Patients treated with PUVA, in the initial and maintenance period, achieved in general a higher therapeutic score (95% to 100% clearance) than those receiving UV-B therapy. However, taking 80% to 100% improvement as criterion, no difference was found between initial UV-B and PUVA therapy, if less than 50% of the skin surface was affected by psoriasis. If more than 50% of the skin was involved, PUVA was better than UV-B therapy. The maintenance treatment frequency for the UV-B-treated patients for more than a year seemed to be higher than for PUVA-treated patients. A positive correlation was found between response to sunbathing (questionnaire survey) and the response to UV-B phototherapy. An extra UV-B treatment to the leg lesions appeared useless.

Actuarial Analysis↗
PubMed1983

Induction of actinic lichen planus with artificial UV sources.

A fair-complected woman had an episode of actinic lichen planus (ALP) following natural sunlight exposure. The occurrence of ALP in the Netherlands, with its temperate summers, is highly unusual. Phototests with repeated doses of UV-B radiation successfully induced lichen planus-like skin lesions, while UV-A irradiation had no effect. Histologic examination of both the naturally occurring ALP lesions and the artificially induced lesions disclosed features characteristic of lichen planus.

Female↗
PubMed1983

Phototoxicity and mutagenicity of 4,5'-dimethylangelicin and long-wave ultraviolet irradiation in Chinese hamster cells and human skin fibroblasts.

The phototoxicity and mutagenicity of 4,5'-dimethylangelicin (Ang) were assessed in cultures of hamster cells and human skin fibroblasts after long-wave ultraviolet irradiation. To obtain an impression of the clinical usefulness of Ang, we compared the phototoxicity and mutagenicity of this compound with those of 8-methoxypsoralen (8-MOP). To reach the same cell-killing rate in hamster cells and human skin fibroblasts, the concentration of Ang had to be 15 times higher than that of 8-MOP at comparable doses of radiation. Whether we used the same concentrations and an adjusted radiation dose or adjusted concentrations of Ang and 8-MOP at a constant radiation dose, the mutation induction in hamster cells and human skin fibroblasts was much higher after incubation with Ang than with 8-MOP.

Animals↗
PubMed1982

Influence of water and salt solutions on UVB irradiation of normal skin and psoriasis.

The influence of tap-water (TW) and salt solutions on the minimal erythema dose (MED) was investigated for normal human skin and uninvolved skin of psoriasis patients. MED (UVB) determinations on the forearm revealed that: (1) the MED definitely decreases whenever the arm is immersed in TW or NaCl solutions with a low concentration (4%) prior to UVB exposure, whereas almost saturated NaCl solution (26%), as well as locum Dead Sea water (LDSW), do not produce a change in the MED, and (2) the decrease in MED obtained by wetting the skin with TW was no longer present when the skin was allowed to dry for 20 min. A decrease in water uptake by skin (in vivo) and by callus (in vitro) was found as the salt concentration of the external solution increased. It is proposed that water taken up by the skin plays an important role in the sensitivity of the skin to UVB exposure. Bathing in TW or 4% NaCl prior to UVB exposure offered a slight to moderate improvement in psoriasis over UVB irradiation alone. Finally, it was shown that there is no obvious difference in clearance of the psoriatic skin between a bath in TW, 4% NaCl, or LDSW prior to UVB exposure.

Adolescent↗
PubMed1982

Damage and repair of molecular targets of human skin fibroblasts irradiated with fluorescent light (380-420 nm).

Human fibroblast cultures irradiated in phosphate-buffered saline are severely damaged by high doses of fluorescent light (380-420 nm), which have a direct effect on such cells. At a dose of 400 kJ/m2, the colony-forming capacity is decreased by up to 50%. SH groups in the membrane and cytosol are destroyed by irradiation, as determined with 6-6'-dithiodinicotinic acid (DTNA) and 5,5-dithiobis-2-nitrobenzoic acid (DTNB). Another molecular target that is severely damaged is tryptophan (up to 25%). However, peroxidation products of unsaturated fatty acids were not observed in our experiments. Survival improved and molecular damage was repaired to some extent by exposing the cells to optimal growth conditions immediately after irradiation.

Cell Division↗
PubMed1981

Influence of UVA on the erythematogenic and therapeutic effects of UVB irradiation in psoriasis; photoaugmentation effects.

The effect of repeated exposure to an additive dose of long ultraviolet (UVA) radiation on the erythemogenic and therapeutic effects of middle ultraviolet (UVB) irradiation was investigated in 8 patients with psoriasis. The surface of the backs of these patients was divided into 2 parts, 1 of which received only UVB irradiation 4 times a week and the other UVA + UVB. UVB was provided by Philips TL-12 lamps and UVA by glass-filtered Philips TL-09 lamps. UVA was held constantly at 10 J/cm2, whereas UVB was increased. The erythemogenic effects of UVA + UVB and UVB alone were evaluated by 4 tests during the treatment to determine the minimal erythema dose (MED). Test I (at the start of the therapy) showed a photoaugmentative effect which was no longer apparent in test III (third week). Test III showed a reversal of the ratios of the MEDs of the sites irradiated with UVA + UVB and UVB (MED A + B/MED B). This is ascribed to the marked pigmentation which appeared after repeated irradiation with the UVA + UVB combination. Comparison showed for the improvement of the psoriasis no distinct differences between UVA + UVB irradiation and UVB alone, but the former had the cosmetic advantage of giving pleasing tan.

Adult↗
PubMed1980

Photochemical damage to skin fibroblasts caused by protoporphyrin and violet light.

Foreskin fibroblasts cultured in a medium containing protoporphyrin and exposed to violet light lose the capacity to proliferate. This phenomenon can be assessed on the basis of the ability of the irradiated cells to form colonies. Potentially lethal injuries can, however, be repaired during postirradiation incubation under optimal growth conditions. We investigated the photodynamically induced transformations of certain molecular targets in the irradiated cells. Biochemical analysis showed that only traces of unsaturated fatty acids were oxidized, but SH groups of both the membranes and the cytosol appeared to be very sensitive targets. Of the tryptophan content, 20% was damaged during irradiation. Recovery was observed during post-irradiation incubation. The tryptophan content and the SH groups recovered to some extent, and these results showed a good correlation with the regeneration of surviving cells.

Cell Survival↗
PubMed1980

UV-B phototherapy of psoriasis.

The effect of ultraviolet-B light provided by TL-12 fluorescent lamps was investigated in 45 patients with psoriasis vulgaris. 33 (73.3%) of the 45 patients showed considerable and rapid improvement during UV-B therapy. The initial (clearing) phase (4 irradiations a week) required an average of 23 irradiations (range: 9-33). During maintenance treatment, irradiation once every 1-5 weeks proved adequate in 64.4% of the patients.

Adolescent↗
PubMed1980

Erythropoietic protoporphyria. Photoactivation of the complement system.

The complement system was analysed in 14 asymptomatic patients with erythropoietic protoporphyria. In the majority of the sera studied the levels of complement components C1, C4, C2, and C3 were within the normal range. Upon ultraviolet light (330--460 nm) irradiation of the serum samples in vitro, a marked decrease in total hemolytic activity accompanied by reduction of C1, C4, C2, and C3 levels was observed. The loss of total hemolytic activity can be directly correlated with the levels of protoporphyrin (PP) and similar changes can be obtained in normal serum upon addition of PP followedf by ultraviolet light irradiation. It is postulated that after irradiation the excited PP develops the capacity to activate the complement sequence with the production of cleavage products, which may contribute to the skin changes observed in these patients upon sun exposure.

Complement Activation↗
PubMed1979

[Solaria].

Explore the source record for details and available documents.

Cholecalciferol↗
PubMed1977

In vitro studies on the protoporphyrin uptake and photosensitivity of normal skin fibroblasts and fibroblasts from patients with erythropoietic protoporphyria.

Fibroblasts derived from patients with erythropoietic protoporphyria (EPP) are not sensitive to violet light and do not contain an excess of protoporphyrin (PP). Fibroblasts from both normal individuals and patients with EPP can take up very low concentrations of PP from culture medium. Cells grown in PP-containing medium showed a gradually increasing but limited uptake of PP and also an increased sensitivity to light. A sensitive scanning microfluorometric method has made it possible to demonstrate that the PP is mainly localized in the perinuclear granules. After exposure to violet light, cells photosensitized by PP in a culture medium showed increased membrane permeability as well as reduced reproductive capacity. Both of these photodamage effects can be repaired during postirradiation incubation in culture medium at 37 degrees C.

Cell Division↗
PubMed1977

The role of oxygen in the photodamaging effect on erythrocytes of some photoallergic and phototoxic compounds.

Red blood cells irradiated with longwave ultraviolet light in the presence of a number of photoallergic or phototoxic compounds showed a marked loss of K+ ions. This process was strongly restricted by anaerobic conditions. During irradiation, oxygen was consumed. Since pre-irradiated photosensitizers were not toxic to erythrocytes, it is concluded that during irradiation, oxidative processes take place in the erythrocyte. The concentrations of the investigated photoallergic compounds required to induce photohaemolysis, were several times higher than those required for the phototoxic compound protoporphyrin. These findings indicate that photoallergic compounds, like the photodynamic compounds, also have photo-oxidative capacities, but to a much lower degree.

Erythrocytes↗