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Biomedical subjects

W Westerhof

Publications and source records attributed to W Westerhof.

At least 91 records · Page 5Linked to original sources
PubMed1993

HLA associations in vitiligo patients in the Dutch population.

This study characterizes the HLA class I and class II antigens in a group of patients with vitiligo and a control group, both of Dutch descent. Earlier reports had shown a significant positive association with DR4 and a significant negative association with DR3. We found that, after correction for the broad antigens studied, only Cw7 and DR6 were significantly associated with vitiligo. The significant positive association of DR6 with vitiligo is interesting since vitiligo has an autoimmune component in its pathogenesis and DR6 may be a marker for high immune responsiveness.

HLA Antigens↗
PubMed1992

Production of catecholamines in the human epidermis.

Cell-free extracts from human full thickness skin (i.e., epidermis and dermis), suction blister roofs (i.e., epidermis) and from human keratinocytes express biopterin-dependent tyrosine hydroxylase a well as phenylethanolamine-N-methyl transferase, both representing key enzymes for the biosynthesis of epinephrine. These enzyme activities could not be detected in cell extracts from human melanocytes and human fibroblasts. Since keratinocytes in the human epidermis, and in cell cultures, express a high density of beta-2-adrenoceptors, and this signal transduction system regulates intracellular calcium homeostasis, it can be concluded that epinephrine production in the epidermis activates calcium transport via the beta-2-adrenoceptor system. Our results show for the first time that the human epidermis has the capacity to independently produce epinephrine.

Biopterins↗
PubMed1992

[Exogenous ochronosis, a little-known side effect of hydroquinone-containing ointments].

Two patients with exogenous ochronosis, an unfamiliar side effect of hydroquinone-containing bleaching creams, are presented. This disorder is characterized by progressive darkening of the area to which the cream is applied. Histologically there is deposition of yellow-brown pigment in the dermis, in addition to degeneration of collagen and elastic fibres. The chemical composition of the ochronotic material and the pathogenesis of this paradoxical effect of hydroquinone are unknown. Hydroquinone containing creams should not be used for longer than two years. If there is no improvement within six months, application should be discontinued.

Adult↗
PubMed1992

Cytotoxicity of a selected series of substituted phenols towards cultured melanoma cells.

Substituted phenolic compounds were previously shown to exhibit cytotoxicity towards epithelial cells in the presence of the enzyme tyrosinase as a result of the formation of their quinone products. Seventeen of these compounds were tested for cytotoxic properties towards three different melanoma cell lines. The compounds were split into four groups of phenol derivatives, A; alkoxyethers, including 4-hydroxyanisole (4HA), B; oxyethers derivatized at the acyl side chain, C; oxyethers derivatized at the phenol, and D; acyl thioethers. Toxicity was determined by total cell counts after 3 days exposure to the compounds. Large reductions in cell numbers were observed with 4HA (the methoxy-), ethoxy-, propoxy and iso-butoxyethers of group A and the methyl- and propyl thioethers of phenol of group D. Derivatization of the ethoxy- and propoxy side chains (group B) did not seem to increase the cytotoxic effects, as determined by cell counts. Compounds of group C, which need intracellular esterase activity to release the phenols, showed moderate toxicities. Toxicity of certain compounds was confirmed by LDH release into the culture medium and by increased trypan blue uptake of cells exposed to the compounds. Flow cytometric investigations of cells after exposure for 24 h revealed that most compounds caused an increase in the proportion of cells in G1 phase. A complete accumulation of cells in S-phase was observed after exposure to 4-ethoxyphenol. Inhibition of DNA synthesis was also shown by inhibition of bromodeoxyuridine incorporation. The results presented show that phenolic compounds exhibit cytotoxic properties towards melanoma cells some of which may be mediated by tyrosinase activity. Toxicity of the compounds was shown to be exerted during DNA replication but their toxic action may also be due to membrane damage and inhibition of cell metabolism.

Antineoplastic Agents↗
PubMed1992

Molecular heterogeneity of the fourth component of complement (C4) and its genes in vitiligo.

In view of evidence suggesting vitiligo is an autoimmune disease, we investigated whether vitiligo is associated with inherited deficiencies of the fourth (C4) and second (C2) component of complement and with certain human leukocyte antigens (HLA). Analysis of functional activities of C4 and C2 in sera of patients with vitiligo (n = 42) showed that 17% of them had a heterozygous C4 deficiency and 5% had a heterozygous C2 deficiency. In the normal control group (n = 30), 3% had a heterozygous C4 deficiency and none had a C2 deficiency. C4 typing by Western blot analysis showed the frequency of the C4A*Q0 allele in the vitiligo patient group to be close to normal. However, the frequency of one C4B*Q0 allele was three times higher, and that of two C4B*Q0 alleles five times higher in the vitiligo patient group than the reported frequencies in normal control groups. Southern blot analysis of Taq1 digests of DNA using C4 and 21-hydroxylase probes showed that two patients with two C4B*Q0 alleles had a deletion of a 21-OHA-C4B segment. In the other patients, having one or two C4B*Q0 alleles, these null alleles probably occurred due to a loss of C4 gene expression. HLA analysis did not show any allelic association of C4A*Q0 or C4B*Q0 with any HLA antigen in vitiligo, but confirmed the previous findings of a negative association with HLA-DR3 and a positive association with HLA-DR4. These results suggest that abnormalities of the C4B gene and the above-mentioned associations with HLA antigens may be some of the risk factors in vitiligo.

Adrenal Hyperplasia, Congenital↗
PubMed1991

Grafting of venous leg ulcers. An intraindividual comparison between cultured skin equivalents and full-thickness skin punch grafts.

Skin equivalents that consisted of a noncontracted collagen gel populated with allogeneic fibroblasts and covered with autologous cultured keratinocytes were used for grafting venous leg ulcers. The results were compared in the same patient with those obtained with a routinely used standard method of grafting with autologous full-thickness punch grafts. The skin equivalents and the punch grafts were grafted successfully in four of five patients. The median healing time of ulcers grafted with skin equivalents was 18 days whereas that of ulcers covered with punch grafts was 15 days. The cosmetic appearance of the skin equivalent-grafted ulcers was better than that of the punch-grafted ulcers.

Aged↗
PubMed1991

Evidence for alpha-MSH binding sites on human scalp hair follicles: preliminary results.

Alpha-MSH, considered an important pigmentation hormone, binds to melanocytes and is thought to stimulate melanogenesis through a cyclic-AMP-dependent mechanism. The binding of alpha-MSH to follicular melanocytes has been investigated in human hair of different colors, ranging from black to blond and senile white. Hairs were plucked, the follicles were cut off, and an alpha-MSH binding assay, using a radiolabeled alpha-MSH analogue, was performed on these bulbs. As controls of each assay, fragments of hairs of the same person were used. The results show a dose-response relationship and the assay seems to be specific for alpha-MSH, because other peptides such as ACTH, beta-LPH and beta-endorphins do not compete for binding sites as alpha-MSH does. These binding sites seem to be present only on melanin synthesizing melanocytes, since the controls and follicles of senile white hair, which do not contain active melanocytes, show negative results. All the assays were performed on raw material, i.e., whole plucked hair follicles. This is the first time that binding sites for alpha-MSH have been demonstrated on human scalp hair follicles. In addition, their presence was found to be associated with active melanin production; their absence was demonstrated on senile white hair follicles.

Binding Sites↗
PubMed1990

Determination of catechol O-methyltransferase activity in relation to melanin metabolism using high-performance liquid chromatography with fluorimetric detection.

A new sensitive method for the determination of catechol O-methyltransferase activity has been developed. The method is based on the O-methylation of the indolic intermediates of melanin metabolism. The substrate, 5,6-dihydroxyindole-2-carboxylic acid, is converted by the enzyme to two O-methylated products, which can be separated by high-performance liquid chromatography and measured with fluorimetric detection. The physiological presence of both substrate and products could be detected in crude melanoma cell extracts. The limit of sensitivity for detection of the O-methylated products is less than 0.5 pmol per injection. The method was compared with an earlier described HPLC method which makes use of uv detection of O-methylated products of 3,4-dihydroxybenzoic acid. The described method will be used to study the importance of catechol O-methyltransferase as a protective enzyme in (malignant) melanocytes.

Catechol O-Methyltransferase↗
PubMed1990

The relation between constitutional skin color and photosensitivity estimated from UV-induced erythema and pigmentation dose-response curves.

In 54 healthy volunteers we assessed predictors of sensitivity to ultraviolet (UV) light, including Fitzpatrick's sun reactive skin types and constitutional skin color, and compared these with one another and with responses of the skin to UV irradiation, as determined experimentally by a minimal erythema dose (MED), a minimal melanogenic dose (MMD), and dose-response curves for UV-induced erythema and pigmentation. For these studies, a xenon arc solar simulator was used as the source of UV irradiation, and a chromameter interfaced with a computer for objective measurement of UV-induced erythema and pigmentation was employed. The skin type did not correspond well to the constitutional skin color, as measured by a chromameter prior to UV irradiation. Within each skin type, there were large ranges of MED and MMD values and great variability in the shapes of the dose-response curves. Constitutional skin color was also not a good predictor of the measured MED and MMD values but did appear to correlate with the steepness of the dose-response curves for erythema and for pigmentation. From these studies, we propose that objectively measured constitutional skin color is a better predictor of UV responses of the skin than skin type and that steepness of dose-response curves for erythema is a better measure of the response of the skin to UV irradiation than is a MED measurement.

Adolescent↗
PubMed1990

Prospective randomized study comparing the debriding effect of krill enzymes and a non-enzymatic treatment in venous leg ulcers.

The debriding potential of a recently discovered potent enzyme preparation derived from Antarctic krill (Euphausia superba) was compared to a routine non-enzymatic treatment in 31 patients with venous leg ulcers. To assure a reliable interpretation of the cleaning effect, computer image analysis was used to measure wound size and the amount of debris day by day. Krill enzyme treatment was significantly (p less than 0.01) better than the non-enzymatic treatment. The necrotic area diminished by 53%, while in the control group no reduction of the necrotic area was observed in 7 days. The median time required to clean the ulcer was 7 days in the krill group and 10 days in the control group. Afterwards the ulcers were grafted with autologous skin biopsies, which yielded similar results in both groups. No side effects were observed. It was concluded that krill enzymes fulfil criteria for effective debridement of venous leg ulcers.

Adult↗
PubMed1989

Increased anthralin irritation response in vitiliginous skin.

The irritation response to anthralin was studied using the chamber-testing technique in 17 patients with vitiligo. Anthralin concentrations of 0.1%, 0.5%, 1%, and 5% in lanette wax were applied to both vitiliginous and adjacent pigmented skin for 24 h. The extent of the erythematous reaction was evaluated on the 2nd day after application. The visual assessment of the paired anthralin patches indicated that the erythema was more intense in pigmented skin than in vitiliginous skin in 15 out of 17 patients. Chromometer readings, however, clearly indicated that the erythematous response was stronger in the vitiliginous skin than in the pigmented skin, confirming the known fact that the human eye is not accurate in the quantitative assessment of complex colors. Immunophenotypification of cellular infiltrates, using the combination of different monoclonal antibodies and the peroxidase technique, showed that inflammatory cell infiltrates caused by the anthralin exposure contained increased numbers of granulocytes and monocytes in vitiliginous skin when compared with normal skin. The percentage of T-cell subsets, Langerhans cells, and mast cells in the same infiltrates of both types of skin were similar. Our results are discussed in accordance with the view that anthralin-induced radical species of the pigmented skin can be neutralized by the scavenging properties of melanin.

Adult↗
PubMed1989

Treatment of bullous pemphigoid with topical clobetasol propionate.

The potent topical corticosteroid clobetasol propionate was evaluated in an open-label study for its safety and efficacy in the treatment of bullous pemphigoid. Ten patients admitted to the hospital with this diagnosis had clobetasol propionate cream applied twice daily to affected skin until all lesions were healed and for 2 weeks thereafter. Complete epithelialization was achieved in every case within 4 to 17 days of treatment. After discharge, patients received decreasingly less potent corticosteroid creams as maintenance therapy for between 5 weeks and 13 months. As of this report, 7 of the 10 patients remain in remission (range 1 to 10 months). In one patient the disease was exacerbated, and therapy with corticosteroids could not be discontinued. No local or systemic side effects were observed during the study, and plasma cortisol levels were within the normal range when measured during the early tapering-off period while patients were receiving less potent topical corticosteroids. We conclude that clobetasol propionate cream produced rapid healing of bullous lesions without adverse effects and that this treatment followed by maintenance therapy with less potent topical corticosteroids was highly effective in patients with bullous pemphigoid.

Administration, Cutaneous↗
PubMed1989

Large-scale cultivation of human melanocytes using collagen-coated Sephadex beads (cytodex 3).

Pure melanocytes were obtained from the epidermis of human foreskin by a modification of a previously described method in which geneticin was added for selective killing of fibroblasts. Purity of the culture was confirmed by light and electron microscopy and by the use of a monoclonal antibody NKI-beteb, which is specific for a vesicular membrane antigen present on melanocytes. Melanocytes were tested for their affinity to several microcarriers. They attached to cytodex 1 and 3 and dorma cell, but they did not attach to glass and gelatin beads. The best results were obtained with cytodex 3. After an almost immediate and total attachment of melanocytes a fourfold to fivefold increase in cell number was achieved on this microcarrier within 3 weeks. With the results obtained, it seems that the collagen-coated cytodex 3 microcarrier surface supports the growth of melanocytes. Preliminary results obtained with a microcarrier cell culture fermenter clearly indicate that the large-scale cultivation of normal human melanocytes in such an automated system is possible.

Cell Adhesion↗
PubMed1989

A comparison of acrivastine versus terfenadine and placebo in the treatment of chronic idiopathic urticaria.

Patients (n = 56) with a diagnosis of chronic idiopathic urticaria were assessed in a fully randomized, double-blind, crossover study to investigate the efficacy of acrivastine at two doses (8 and 4 mg) versus 60 mg terfenadine and placebo administered three times daily. All three active preparations were found to be effective, and significantly better than placebo, in controlling the signs and symptoms of urticaria. No significant differences were found between the active preparations, although in some cases efficacy trends favoured 8 mg acrivastine and terfenadine over 4 mg acrivastine. No significant differences were noted between the active treatments and placebo with regard to reports of drowsiness.

Adult↗