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Biomedical subjects

R Lavker

Publications and source records attributed to R Lavker.

10 recordsLinked to original sources
PubMed1997

The spectral dependence for UVA-induced cumulative damage in human skin.

The wavelength dependence for UVA-induced cumulative damage was investigated in human skin. Epidermal changes (stratum corneum thickening, viable epidermal thickening sunburn cell production), as well as dermal alterations (lysozyme deposition, inflammation), were used as indices of cumulative photoperturbation. UVA wavelengths between 320 nm and 345 nm were more effective than longer wavelengths (360-400 nm) in inducing viable epidermal thickening. Similarly, the shorter wavelengths (320-345 nm) elicited more sunburn cells, although these differences did not reach statistical significance. All UVA bands were equally effective in inducing the dermal markers. At equal fluences, wavelengths > 400 nm produced no measurable cutaneous alterations. These findings suggest that (i) chronic epidermal and dermal damages have different spectral dependence and (ii) the action spectrum for dermal damage in the UVA is broad, extending up to 400 nm, and is different from the acute erythema spectrum in humans.

Adolescent↗
PubMed1995

Message of nexin 1, a serine protease inhibitor, is accumulated in the follicular papilla during anagen of the hair cycle.

A group of specialized mesenchymal cells located at the root of the mammalian hair follicle, known as the follicular or dermal papillary cells, are involved in regulating the hair cycle, during which keratinocytes of the lower follicle undergo proliferation, degeneration and regrowth. Using the arbitrarily primed-PCR approach, we have identified a 1.3 kb messenger RNA that is present in large quantities in cultured rat follicular papillary cells, but not in skin fibroblasts. This mRNA encodes nexin 1, a potent protease inhibitor that can inactivate several growth-modulating serine proteases including thrombin, urokinase and tissue plasminogen activator. In situ hybridization showed that nexin 1 message is accumulated in the follicular papilla cells of anagen follicles, but is undetectable in keratinocytes or other skin mesenchymal cells. In addition, nexin 1 message level varies widely among several immortalized rat vibrissa papillary cell lines, and these levels correlate well with the reported abilities of these cell lines to support in vivo follicular reconstitution. These results suggest a possible role of nexin 1 in regulating hair follicular growth.

Amyloid beta-Protein Precursor↗
PubMed1991

Urticaria pigmentosa. Systemic evaluation and successful treatment with topical steroids.

Nine patients with adult-onset urticaria pigmentosa were studied for the incidence of extracutaneous mast cell involvement and the efficacy of potent topical corticosteroid therapy for cutaneous lesions. Seven of the nine patients had increased mast cells in the marrow biopsy specimens, and five patients had focal aggregates of mast cells. The bone scan was abnormal in one patient. Liver-spleen scans revealed a shift of colloid uptake from liver to spleen in four patients. No abnormal gastrointestinal tract roentgenograms were obtained. Urinary histamine metabolites correlated with nodular bone marrow involvement, but not with other parameters. Results of the psychoneurologic testing revealed significant deviation from the norm with a verbal memory deficit in all nine patients and abnormalities on the Minnesota Multiphasic Personality Inventory in four patients. All nine patients were treated with 0.05% betamethasone dipropionate ointment under occlusion over half of the body nightly for 6 weeks. Seven of nine patients treated responded with almost complete resolution of their lesions. Hypothalamic pituitary adrenal axis suppression was evaluated with intramuscular cosyntropin stimulation and metyrapone administration during treatment. Only two patients, both of whom used the medication improperly, developed transient abnormalities. Slow return of lesions was noted 6 months after completion of therapy. Remissions could be lengthened with single weekly applications of topical steroids. Systemic involvement is frequent in patients with cutaneous mast cell disease and it is best demonstrated by bone marrow biopsy. Mast cell lesions can be safely and effectively treated with topical steroids in motivated patients.

Administration, Topical↗
PubMed1983

Terbutaline modulation of human allergic skin reactions.

Terbutaline, a preferential beta 2-adrenergic agonist, has been shown to inhibit allergen-induced histamine release in vitro. In contrast, orally administered therapeutic doses of terbutaline do not inhibit antigen-induced wheal and flare reactions. We studied the effects of local terbutaline on antigen-induced whealing response, histamine release, cellular inflammatory response, and ultramicroscopic mast cell changes in antigen-challenged skin sites in ragweed-sensitive subjects. Results showed that ragweed challenge significantly induced increased histamine release in all subjects. In contrast, no such histamine release was observed at sites challenged with antigen in the presence of terbutaline. Thus locally applied terbutaline in nontoxic doses modulates mediator release in certain allergic reactions.

Biopsy↗
PubMed1981

Histamine suppression of in vivo eosinophil accumulation and histamine release in human allergic reactions.

Although it has been shown that histamine inhibits antigen-induced in vitro histamine release from basophils, it is unclear whether histamine inhibits in vivo mediator release in human allergic reactions. We report effects of exogenous histamine on histamine release and inflammatory cell responses in antigen-challenged skin sites in eight ragweed-sensitive individuals. Four heat-suction blisters in each subject were unroofed, and a collection chamber was appended to each blister base. Chamber A contained 1000 PNU/ml ragweed extract; chamber B contained buffered saline (control fluid); chamber C contained 1000 PNU/ml ragweed and 50 ng (5 x 10(-7) M) of histamine; and chamber D contained histamine alone (50 ng). Comparative analyses of chamber histamine levels in individual subjects showed that (1) histamine levels in chamber A were significantly greater than those in chamber B (p less than 0.01) and that histamine levels in chamber C were not significantly different than those in chamber D (p less than 0.5). Likewise, comparison of eosinophils attaching to membrane filters appended to the chamber bases for 2 hr showed that there were significantly more eosinophils in chamber A than in chamber B (p less than 0.01) and that there was no significant difference in eosinophil numbers on filters appended to chamber C vs chamber D. In three of four subjects studied, addition of exogenous histamine (50 ng/ml) to ragweed before intradermal injection inhibited the ultrastructural mast cell alterations seen within 10 min after injection of ragweed alone. In the one subject in which mast cell alterations were not prevented, exogenous histamine also did not inhibit antigen-induced histamine release or subsequent eosinophil accumulation in the skin chambers.

Eosinophils↗