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Biomedical subjects

L C Harber

Publications and source records attributed to L C Harber.

At least 37 records · Page 2Linked to original sources
PubMed1982

Cutaneous aspects of the porphyrias.

The clinical features of the porphyrias are often characteristic; and all can be definitively diagnosed by appropriate biochemical tests. Many of the cutaneous lesions are thought to be the result of photochemical damage which occurs due to 400 nm radiation exciting abnormally high concentrations of porphyrins in the skin. Others are probably based on hormonal or unidentified systemic factors. The effects of exogenous environmental porphyrinogenic agents have become increasingly well understood in recent years and at present treatment for many of the porphyrias is available. Early diagnosis, aided by recognition of the initial cutaneous signs and symptoms, is crucial for rapid implementation of appropriate therapy.

Coproporphyrins↗
PubMed1982

Current status of predictive animal models for drug photoallergy and their correlation with drug photoallergy in humans.

The number of adverse responses considered to be drug photosensitivity reactions account for only an exceedingly small percentage of the total undesirable effects from environmental chemicals. However, the rising incidence of and severe disability resulting from drug photosensitivity, especially when the photosensitivity is of the persistent light reactor type, indicate that increased photobiologic research and development efforts are required. Predictive tests are an obvious approach to minimize or eliminate those chemicals showing a risk-benefit ratio that is undesirable to society in general or to an unknowing individual in particular. Animal models with predictive value for determining the risk of photoallergic contact dermatitis in humans have undergone considerable modification during the past decade. This study reports an improved experimental guinea pig model for inducing photoallergic contact dermatitis to musk ambrette. In contrast to previously described models that used Freund's adjuvant, this model does not require nuchal stripping with cellophane tape. Control studies for primary irritancy, phototoxicity, allergic contact dermatitis, and "angry back" syndrome were included in the experimental design. Only photoallergic contact dermatitis was observed. Although the technique used to demonstrate this phenomenon is conducive to standardization, additional studies are required to ascertain whether or not other chemicals known to be photoallergic in humans can also be demonstrated with this animal model.

Animals↗
PubMed1981

Photoallergic contact dermatitis to musk ambrette. Histopathologic features of photobiologic reactions observed in a persistent light reactor.

Studies concerning a patient with contact photosensitivity to musk ambrette, a commonly used fragrance, are reported. The patient had a persistent light reaction. The patient's history, clinical appearance, and phototest and photopatch test results are described. The observed patterns of these were identical to those previously noted in patients who had persistent light reactions after exposure to other photosensitizers such as the halogenated salicylanilides. The histopathologic findings in the phototest and photopatch test sites were those of an acute spongiotic dermatitis. No abnormal change was seen with ultraviolet A radiation exposure alone.

Aged↗
PubMed1981

Normal numbers of phenotypic helper, suppressor, and total T cell populations in psoriasis vulgaris: quantitation by monoclonal antibodies.

Previous studies of E rosette-forming cells in the blood of patients with psoriasis vulgaris have demonstrated conflicting results. Availability of a battery of monoclonal antibodies permitted quantitation of individual T cell populations in patients with psoriasis. Peripheral blood mononuclear leukocytes from twelve patients with extensive, active psoriasis and from fifteen normal controls were studied by indirect immunofluorescence. No statistically significant differences from control values were identified (p values were all greater than or equal to 0.4). These monoclonal antibodies provide highly specific reagents, previously not available, for identifying different lymphocyte phenotypes. Analysis of the data indicates that shifts in major T lymphocyte subpopulations are not present in patients with active psoriasis.

Adult↗
PubMed1981

Current status of mammalian and human models for predicting drug photosensitivity.

The status of efforts to develop experimental models for drug photosensitivity reactions in small mammals is reviewed. Tests which are practical and also have a high predictive value in determining photosensitivity hazards to man are the goal of this research. The various animal model systems which have been used are evaluated with respect to these goals.

Animals↗
PubMed1980

Pyrimidine dimer formation and repair in human skin.

Cyclobutyl pyrimidine dimers have been detected in the DNA of human skin following in vivo irradiation with suberythemal doses of ultraviolet (UV) radiation from FS-20 sun lamp fluorescent tubes. Dimers were assayed by treatment of extracted DNA with Micrococcus luteus UV-specific endonuclease, alkaline agarose electrophoresis, and ethidium bromide staining. This technique, in contrast to conventional dimer assays, can be used with nonradioactive DNA and is optimal at low UV light doses. M. luteus endonuclease-sensitive sites were determined after exposure of untanned skin in two volunteers to UV light (0.97, 1.94, or 3.88 X 10(3) J/sq m; lambda, 290 to 360 nm). At 20 min postirradiation (dose, 1.94 X 10(3) J/sq m), fewer M. luteus endonuclease-sensitive sites were found in the DNA than immediately after the irradiation. Even fewer endonuclease-sensitive sites were found at 20 min when the UV-irradiated skin was subsequently irradiated with visible light than when the area was kept in the dark. These data suggest that some dimer disappearance by excision repair occurs within 20 min of UV irradiation and that photoreactivation of dimers can make a contribution to the total repair process.

DNA↗
PubMed1980

Photoallergic contact dermatitis to musk ambrette. Clinical report of two patients with persistent light reactor patterns.

Two male patients with photoallergic contact dermatitis to musk ambrette, 2-methoxy-3,5-dinitro-4-methyl-t-butylbenzene, are reported. Musk ambrette is a synthetic fragrance material commonly used in foods and cosmetics. The clinical distribution of lesions presented by these patients strongly suggested an adverse reaction to light. Over a period of several years no etiology had been determined in these cases despite extensive testing and hospitalization. Photopatch tests to musk ambrette were positive. No other etiology for photosensitivity was found. This report emphasizes that exposure to household or cosmetic products represents a potential source of contact photosensitivity. Patients presenting with dermatoses of unknown origin confined to the light-exposed areas should have fragrances considered as possible etiologic agents.

Aged↗
PubMed1979

PUVA therapy status.

Explore the source record for details and available documents.

Carcinoma, Squamous Cell↗
PubMed1979

Assay of contact photosensitivity to musk ambrette in guinea pigs.

This study reports the induction of contact photodermatitis to musk ambrette, 2-methoxy-3,5-dinitro-4-methyl-t-butylbenzene, in guinea pigs. Photoallergic contact dermatitis was assayed using 2 alternative induction methods. Successful photosensitization was achieved only when the nuchal skin was stripped with scotch tape before application of musk ambrette and ultraviolet radiation. Induction methods utilizing nonstripped nuchal skin which induce photosensitivity to potent photoallergens were ineffective for musk ambrette. Phtotoxicity tests to musk ambrette at concentrations between 1 and 50% and a dose of 10.2 joules/cm2 from "Black Light" fluorescent tubes were all negative. Under identical irradiation conditions, anthracene at 0.9% and 8-methoxypsoralen at 1% were consistently positive. The mechanism of photosensitivity to musk ambrette appears to be photoallergic rather than phototoxic. The requirement for skin abrasion to induce photosensitization parallels the clinical reports of photosensitivity to musk ambrette in man.

Allergens↗