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Biomedical subjects

J L Hawk

Publications and source records attributed to J L Hawk.

At least 91 records · Page 5Linked to original sources
PubMed1991

Juvenile spring eruption of the ears: a probable variant of polymorphic light eruption.

We report 18 cases in which a pruritic, erythematous, papular and vesicular eruption developed on the ears following sun exposure. Four of these patients had, on other occasions, suffered from typical polymorphic light eruption. The clinical features, histological changes, and results of phototesting suggest that juvenile spring eruption of the ears is a localized form of polymorphic light eruption.

Adolescent↗
PubMed1991

Abnormal erythemal response and elevated T lymphocyte HRPT mutant frequency in Cockayne's syndrome.

In three children with Cockayne's syndrome (CS), skin exposed to ultraviolet radiation responded transiently either with erythematous papules or an exaggerated sunburn-like response, without chronic actinic damage. Irradiation monochromator tests demonstrated an abnormal delay or reduction in the threshold to ultraviolet (UVB) irradiation-induced erythema similar to that of xeroderma pigmentosum (XP). As with XP there was an elevated frequency of mutants resistant to 6-thioguanine in circulating T lymphocytes. The mutant frequency in a single obligate heterozygote was normal. In contrast to XP, in the two CS individuals studied, adaptive cell-mediated immunity and natural killer cell function were normal. Because the risk of skin cancer is very high in XP but not in CS, the normal immune function in CS provides evidence that immune surveillance may be important in UV tumorigenesis.

Child, Preschool↗
PubMed1991

The prevalence of antinuclear antibodies in patients with apparent polymorphic light eruption.

Polymorphic light eruption (PLE) is a very common photosensitive disorder, the most important differential diagnosis of which is lupus erythematosus (LE). One-hundred and forty-two patients with PLE were screened for circulating antinuclear (ANA), Ro and La antibodies over a 2-year period. Results were negative in 66 patients. Sixty-two patients had low-titre ANA of various patterns, ranging from trace to 1/80 without evidence of LE although one later developed subacute cutaneous LE. Fourteen had more significant findings, six with ANA ranging from 1/160 to 1/1280 but no anti-Ro antibodies, four with ANA ranging from 1/160 to 1/1280 and also with anti-Ro antibodies and four patients with anti-Ro antibodies but low-titre ANA, one of whom later developed discoid LE. Three of these 14 patients fulfilled the American Rheumatism Association criteria for the diagnosis of systemic LE, but it was not certain in any of the patients whether the PLE-like rash represented cutaneous LE or coincidental PLE. However the overall 10% incidence of definite or possible LE in patients with suspected PLE suggests that all PLE patients should be screened for LE.

Adult↗
PubMed1991

In-vivo studies of the action spectrum and time course for release of transforming growth factor-alpha by ultraviolet irradiation in man.

Transforming growth factor-alpha (TGF-alpha) is a growth-promoting cytokine which enhances epithelial proliferation and is secreted by a wide variety of tumour cells. It is also present in normal human epidermis and its overproduction may be responsible for epidermal hyperproliferation in psoriasis. Ultraviolet (UV) B irradiation of human skin leads to epidermal damage and significant subsequent hyperplasia after approximately 24 h, whereas UVA irradiation has little such effect and predominantly damages the dermis. The relative efficacies of UVB and UVA in releasing TGF-alpha were studied in 10 subjects of skin types I and II using a skin-chamber technique and a specific TGF-alpha radioimmunoassay. Significantly elevated concentrations of immunoreactive TGF-alpha were detected in samples after 24 h in UVB-irradiated compared with unirradiated skin. Samples at earlier time points from UVB- and UVA-exposed skin contained measurable levels of TGF-alpha but these were not significantly elevated above the levels found in samples from unirradiated areas. These results, which suggest the UVB irradiation increases release of TGF-alpha from human skin at 24 h, indicate that TGF-alpha may be implicated in UVB-induced epidermal hyperplasia.

Cell Division↗
PubMed1991

Sunscreens with low sun protection factor inhibit ultraviolet B and A photoaging in the skin of the hairless albino mouse.

We examined the chronic effect of long daily suberythemal, fluorescent solar-stimulated radiation (FSSR; ultraviolet B (UVB)+A(UVA)) and UVA alone on female Skh-1 hairless albino mouse skin. Mice were dorsally irradiated 8 h every weekday for 16 weeks with FSSR or UVA, or 32 weeks with UVA alone. Various topical, low concentration, UVB and/or UVA sunscreens were applied before irradiation. Damage was assessed by skin-fold thickness, histology and biochemically by changes in the proportion of type III collagen. All FSSR-exposed mice showed increased skin thickening, elastic fibre hyperplasia, collagen damage and an increased proportion of type III collagen. Application of the UVB sunscreen (2.00%) resulted in marked protection for all nonbiochemical endpoints. There was no obvious advantage of adding 0.75% UVA sunscreen to the UVB sunscreen, but adding 2.00% UVA sunscreen reduced biochemical changes and connective tissue damage. Sixteen weeks of UVA irradiation caused skin thickening and laxity but the histology and biochemistry were indistinguishable from the controls. The mice irradiated with UVA for 32 weeks showed slight elastic fibre hyperplasia and collagen damage histologically, and increased skin thickening and laxity; these changes were unmodified by the 0.75% UVA sunscreen. These mice showed a significant increase in the proportion of type III collagen against which the UVA sunscreen offered protection. Our data suggest that UVA may be important in photoaging and that the use of low sun protection factor UVB+ UVA sunscreens on a day-to-day basis may offer some protection from solar photoaging.

Administration, Cutaneous↗
PubMed1990

Genetic heterogeneity in erythropoietic protoporphyria: a study of the enzymatic defect in nine affected families.

Erythropoietic protoporphyria (EPP) is associated with a deficiency of protohaem ferrolyase. We have used a novel assay for this enzyme based on its ability to utilize zinc as a substrate to investigate the inheritance of EPP in nine affected families. Zinc chelatase activity was markedly reduced in peripheral blood mononuclear cells from 14 EPP patients (mean, 3.3 nmol Zn protohaem/h/mg protein; range, 0.3-8.0) when compared with 41 controls (16.8 +/- 3.6) p less than 0.01. In three families with parent-to-child transmission of disease, the asymptomatic parent had an enzymatic activity within the normal range. In three pedigrees where the parents were asymptomatic, enzymatic activities were below the 95% confidence limits in both. Zinc chelatase activity was below the mean control value in 17 of the 18 parents in nine affected pedigrees, and six of seven asymptomatic offspring of patients with protoporphyria. The findings suggest that EPP is not transmitted as a simple dominant trait and that inheritance of more than one gene may be required for disease expression.

Adolescent↗
PubMed1990

Immune function, mutant frequency, and cancer risk in the DNA repair defective genodermatoses xeroderma pigmentosum, Cockayne's syndrome, and trichothiodystrophy.

There is evidence for defective DNA repair in xeroderma pigmentosum, Cockayne's syndrome, and trichothiodystrophy, but for increased cancer risk only in xeroderma pigmentosum. Natural and adaptive immune surveillance and mutant frequency to 6-thioguanine resistance in circulating T-lymphocytes were studied in five patients with xeroderma pigmentosum, two with Cockayne's syndrome, and one with trichothiodystrophy. Forty-eight-hour cutaneous hypersensitivity responses to recall antigens excluded anergy and circulating CD3+, CD4+, CD8+, and CD16+ cell numbers were within normal limits in all patients tested, as were proliferative lymphocyte responses to PHA, except in the trichothiodystrophy patient. Proliferative responses to recall antigens (PPD, SKSD, and Candida) showed that all patients responded to one or more antigens. Direct natural killer cytotoxicity measured against the human erythromyeloid leukaemia cell line K562 using a 4-h 51Cr release assay was significantly reduced in xeroderma pigmentosum (specific cytotoxicity less than mean +/- SD greater than 17.4 +/- 9.4 per cent, with effector:target cell ratio of 50:1) compared to normal controls (45.8 +/- 17.8), but normal in Cockayne's syndrome and trichothiodystrophy. Generation of lymphokine activated killer cell activity was normal in the two xeroderma pigmentosum lines tested. The mutant frequency in the xeroderma pigmentosum donors was significantly increased (p less than 0.01) and was elevated in the two Cockayne's syndrome donors, taking age into account. No mutants were observed from the single trichothiodystrophy donor. These findings suggest that reduced natural killer cell activity may contribute to the greatly increased susceptibility to skin cancer in xeroderma pigmentosum.

Antigens, CD↗
PubMed1990

Homozygous variegate porphyria: a case report.

Homozygous variegate porphyria is described in a 14-year-old girl with a unique clinical presentation of photosensitivity from the second year of life, mental retardation, clinodactyly, and normal growth rate. The erythrocyte protoporphyrin concentration was raised with the protoporphyrin being predominantly zinc-chelated, which appears to be characteristic for all homozygous hepatic porphyrias. Protoporphyrinogen oxidase activity in lymphoblasts was decreased in both patient and parents despite the latter having normal porphyrin excretion.

Adolescent↗
PubMed1990

Photosensitivity in the elderly.

Photosensitivity to drugs and chemicals in the elderly is more prevalent due to more frequent use of medications. Phototoxic reactions to common, orally administered drugs such as diuretics, cardiac agents and antidiabetics may occur and the reactions may be remedied by discontinuing drug therapy. Photocontact dermatitis due to the ingredients in sunscreens or other agents, such as perfumes, may also arise. Diagnosis is often confirmed by photopatch testing and subsequent avoidance of these agents leads to gradual resolution. Idiopathic photodermatoses, such as sunlight-induced polymorphic light eruption or solar urticaria, may occur and persist from an early age and, in elderly subjects, they can cause mild to marked disability. The most disturbing disorder of this type is the severe, widespread eczematous chronic actinic dermatitis, which can be difficult to diagnose. Porphyrias, such as variegate porphyria or erythropoietic protoporphyria, may persist from an early age, whereas porphyria cutanea tarda generally begins in later life. Porphyrias all have specific clinical and biochemical features and, apart from variegate porphyria, usually respond well to treatment following diagnosis. Exposure of elderly skin to sunlight may also cause deterioration of many ordinary dermatoses, particularly seborrhoeic eczema, which generally respond to protection from UV exposure and to treatment of the underlying abnormality. Progress in identifying the underlying causes, the availability of increasingly sophisticated diagnostic techniques, and improvements in sunscreen preparations and therapeutic medications will probably significantly reduce abnormal photosensitivity in the elderly in the near future.

Adult↗
PubMed1990

Polymorphic light eruption.

Polymorphic light eruption (PLE) describes a broad clinical spectrum including a number of different yet overlapping clinical subgroups. In the absence of an understanding of pathogenic mechanisms it remains unclear whether these subdivisions are appropriate. The action spectrum for PLE usually includes the ultraviolet A (UVA) spectrum, but a proportion of patients respond principally to UVB. This diversity in action spectra remains unexplained, as does the difficulty in artificial induction of lesions, particularly when physiologically relevant doses of UV radiation are employed. Models for the pathogenesis of PLE must explain several characteristic features of the condition, including nonuniform susceptibility of exposed skin areas, higher incidence in temperature climates, particularly in spring, and progressive tolerance during the summer months in some patients. Although unproven, an immunological mechanism is consistent with such features and is supported by immunohistological changes and keratinocyte ICAM-1 expression, similar to known type IV hypersensitivity reactions, and clinical response of severe cases to immunosuppression with azathioprine. Other recently proposed mechanisms include an abnormality in cutaneous arachidonic acid metabolism in response to UV irradiation, and excessive leukotriene B4 release by circulating leukocytes following UVA irradiation.

Child↗
PubMed1990

The acute idiopathic photodermatoses.

The acute idiopathic photodermatoses are more common in females and comprise polymorphic light eruption, actinic prurigo, hydroa vacciniforme, and solar urticaria. Polymorphic light eruption occurs considerably more frequently than the others and while precise pathogenic mechanisms are still unclear, increasing evidence suggests an immunological basis for this condition. Although clinically distinct, actinic prurigo may be a variant of polymorphic light eruption, whereas solar urticaria and possibly hydroa vacciniforme are distinct entities, the former representing a type I hypersensitivity response. Polymorphic light eruption is characterized by a recurrent cutaneous reaction to ultraviolet (UV) exposure occurring after a delay of several hours that consists of pruritic erythematous papules, vesicles, or plaques on usually only some exposed sites and resolves without scarring over about a week. Actinic prurigo is differentiated from polymorphic light eruption by childhood onset and more persistent and excoriated lesions present both on sun-exposed and, to a lesser extent, non-exposed sites. Hydroa vacciniform is a rare disorder that also begins in childhood, and is characterized by recurrent crops of vesicles on sun-exposed skin and subsequent vacciniforme scarring. Solar urticaria is an uncommon condition that usually begins in the third or fourth decade and is differentiated from the other acute idiopathic photodermatoses by rapid onset of urticarial lesions within minutes of UV exposure and resolution within 1 to 2 hours.

Humans↗