Cutaneous histamine reactivity, histamine content of commercial allergens, and potential for false-positive skin test reactions in dogs.

The cutaneous reactivity of normal and atopic dogs to intradermal injections of histamine phosphate was evaluated. Significant differences were not found in the mean wheal diameters of either group. Commercial allergens used for intradermal skin testing and immunotherapy were determined to contain histamine. To determine whether allergen histamine content was sufficient to cause false-positive skin test results, the cutaneous response of Johnson grass allergic dogs was compared, using commercial Johnson grass allergen and commercial Johnson grass allergen with histamine removed. Significant differences were not noticed between Johnson grass and dehistaminized Johnson grass. Therefore, the histamine content of commercial Johnson grass allergen did not appear to cause false-positive skin test results for this group of Johnson grass allergic dogs.

Cutaneous laser-Doppler velocimetry in nine animal species.

The assessment of cutaneous microcirculation by laser-Doppler velocimetry (LDV) has been primarily limited to human studies. The purpose of this investigation was to establish normal values in various species and anatomic sites for blood flow, velocity, and volume as determined by LDV. Microcirculation was measured with a laser-Doppler velocimeter in 54 animals, 6 healthy animals from each of 9 species. The standard sites used were the buttocks, convex surface of the ear, metacarpal pad, humeroscapular junction, thoracolumbar junction, ventral portion of the abdomen, dorsal metacarpus (hooved animals), and ventral surface of the tail (horse). Significant differences in blood flow, velocity, and volume were measured between species and sites within species. The ventral portion of the abdomen consistently had the highest relative blood flow across all species except the monkey. Measurements in the canine metacarpal pad had a high SD, possibly indicating the stratum corneum and epidermis to be too thick for LDV. Our findings provide baseline data in several species, with application of LDV in comparative dermatologic research.

Skin pustules and nodules caused by Actinomyces viscosus in a horse.

A 12-year-old Arabian stallion was evaluated for a refractory skin problem of 2 years' duration. Skin nodules and pustules, which would rupture, had developed over the right lumbar muscles. Anaerobic culturing from the pustules yielded Actinomyces viscosus, and histologic examination of biopsy specimens revealed globular eosinophilic structures. Concomitant treatment with isoniazid (8 mg/kg of body weight, q 24 h for 8 weeks), trimethoprim-sulfadiazine (30 mg/kg, q 24 h for 8 weeks), and sodium iodide solution (66 mg/kg, every 1, 2, or 4 weeks, for 32 weeks) resolved the condition.

Interspecies and interregional analysis of the comparative histologic thickness and laser Doppler blood flow measurements at five cutaneous sites in nine species.

Studies in dermatology, cutaneous pharmacology, and toxicology utilize skin from different animal species and body sites. However, regional differences exist in topical chemical percutaneous absorption studies in man and in animal. The objective of this study was to compare epidermal thickness and number of cell layers across species and body sites using both formalin-fixed paraffin and frozen sections. Cutaneous blood flow determined by laser Doppler velocimetry (LDV) was compared to histologic data. Six animals of each of the following species were used: monkeys, pigs, dogs, cats, cows, horses, rabbits, rats, and mice. Cutaneous blood flow was determined and 6-mm skin biopsies were taken directly from the following sites: buttocks, ear, humeroscapular joint, thoracolumbar junction, and abdominal area. When the two histologic methods were compared across all species and body sites, the thickness of the epidermis was significantly greater, and the thickness of the stratum corneum significantly less, in paraffin sections versus frozen sections (p less than 0.05). There were no differences in the number of viable cell layers determined by both methods. The values for LDV-determined blood flow did not significantly correlate (p greater than 0.05) to epidermal or stratum corneum thickness. However, regional and species differences were noted in all these parameters. In conclusion, these data indicate that thickness and LDV blood flow are independent and must be evaluated separately when comparisons are made between species and body sites. This work provides a data base for future comparative studies in which a knowledge of skin thickness or blood flow might be important variables.

Localization of the alpha 3 (V) chain of type V collagen in human skin.

Serum from goats immunized with human type V collagen chains that were cut out of polyacrylamide gels contained an antibody that recognized only type V collagen in an enzyme-linked immunoabsorbent assay and did not label laminin, fibronectin, or types I and IV collagen. Western blot analysis of the antibody showed that its determinant was the alpha 3 (V) chain of type V collagen. Indirect immunofluorescent staining of intact human skin with the antibody produced staining of the dermal blood vessels but not of the dermal-epidermal junction (DEJ). In contrast, both the dermal blood vessels and the DEJ were labeled by the antibody if the skin substrate was first split through the lamina lucida region of the DEJ by incubation in 1 M NaCl solution. Indirect immunoelectron microscopy confirmed the staining pattern found by immunofluorescence and defined the ultrastructural localization of type V collagen in skin. Type V collagen is localized within the DEJ to the lamina lucida region and polar aspects of the basal cell keratinocyte plasma membrane.

Uveitis associated with poliosis and vitiligo in six dogs.

Idiopathic panuveitis with retinal detachment was associated with facial poliosis, vitiligo, and alopecia in 6 dogs; 4 were adult males. Dermatohistologic examination of affected facial sites from all dogs revealed a lichenoid dermatitis and unusual histiocytic cells. Intensive topical and systemic corticosteroid and topical mydriatic/cycloplegic therapy was successful in controlling uveitis in all dogs for variable periods. Three dogs, monitored for 12, 30, and 46 months, retained useful vision despite infrequent recurrence of uveitis. One dog was lost for subsequent examination. Two dogs were euthanatized and necropsied. Ocular histologic examination of these dogs revealed extensive granulomatous iridocyclitis and choroiditis, with retinal detachment and lenticular degeneration.

Noninfectious skin diseases of cattle.

The noninfectious bovine skin disorders can best be summarized by four factors: environmental, nutritional, congenital, and neoplastic. This article has attempted to address the etiology, treatment, and prevention of most of these noninfectious diseases.

Cutaneous diseases of the paw.

Cutaneous disorders of the paw remain a challenging clinical entity. The presenting appearance of the various etiologies is often amazingly similar. However, by using a standardized diagnostic method, one can systemically rule in or out the more common causes and objectively establish a working differential diagnosis. Therapeutic and prognostic considerations are dependent on the etiology. General dermatologic principles apply to the paw as well as to the other areas of the skin; however, because of the known frequency of relapses and therapeutic difficulties, one must approach any case of pododermatitis with a realistic attitude and anticipation of prolonged therapy.

Pitfalls in immunofluorescence testing in canine dermatology.

Indirect immunofluorescence testing for pemphigus-like antibodies was performed on 100 dogs: 50 dogs with various nonpemphigus dermatologic diseases, 25 dogs with various nondermatologic diseases, and 25 normal dogs. One dog (generalized demodicosis) was positive for pemphigus-like antibodies at a titer of 1:10. It was concluded that canine pemphigus-like antibodies are a potential source of misinterpretation and misdiagnosis in indirect immunofluorescence testing. Direct immunofluorescence testing for IgG, IgA, IgM, and C3 was performed on the footpads of 11 normal dogs. Granular deposition of IgM at the basement membrane zone was demonstrated in 5 of the 11 dogs. It was concluded that direct immunofluorescence testing of canine footpads using only polyvalent immunoglobulin antisera or anti-IgM antisera may lead to misinterpretation and misdiagnosis in up to 45% of all dogs tested.

Use of a gold compound for the treatment of pemphigus foliaceus in a foal.

A 4-month-old foal was examined because of generalized exfoliative dermatitis, with thick scales, extensive crusting, and oozing of serum. A diagnosis of pemphigus foliaceus was made by histologic and immunopathologic examinations of skin biopsy specimens. The foal was treated with a gold compound, aurothioglucose (1 mg/kg once weekly for 14 weeks). For the initial 5 weeks, high-dose glucocorticoid treatments also was used. The skin disorder resolved entirely after 12 weeks of treatment.

Observations of the immunopathology and therapy of canine pemphigus and pemphigoid.

Immunopathologic evaluation of 27 dogs with pemphigus and pemphigoid demonstrated that direct immunofluorescence testing was vastly superior to indirect immunofluorescence testing for diagnosis. Therapeutic studies in 31 dogs with pemphigus and pemphigoid demonstrated that glucocorticoids given for systemic effect were unsatisfactory as the sole form of treatment because of lack of efficacy of unacceptable side effects, or both, in over 50% of the cases.