Ultrastructure of malpighian and inflammatory cells in epidermal papillomas of white suckers Catostomus commersoni

Abstract

Epidermal papillomas affect many white suckers Catostomus commersonj in the Great Lakes of North America, in particular among populations inhabiting polluted environments. Representative papillomas were examined ultrastructurally for viruses, inflammatory cell infiltrates and malpighian cell morphology. Three distinctive gross morphologies of papillomas all contained malpighian cell hyperplasia with some papilloma formation. Lip papillomas had normal malpighian cells but intercellular spaces were enlarged, desmosomes were aggregated, and increased numbers of all leukocytes, but particularly neutrophils, were evident. Discrete papillomas on the body surface contained normal malpighian cells with no aggregation of desmosomes, but enlarged intercellular spaces were filled with granular debris and a prominent neutrophil infiltrate was common. Diffuse papillomas (plaques) on the body surface contained malipighian cells with aggregated desmosomes. Lymphocytes and neutrophils were extremely abundant. Abnormal desmosome aggregations could alter the growth characteristics of malpighian cells making up lip papillomas and plaques. Inflammatory and immunologic cell infiltrates observed in these papillomas could limit the growth or persistence of these neoplasms. No virus-like inclusions were identified in any preparations. The role of viruses in the epidermal papillomas affecting white suckers in polluted locations of the Great Lakes remains unresolved.