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  • Author or Editor: Peter B. Hill x
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Objective—To investigate the direct interaction between canine keratinocytes and live Malassezia pachydermatis and thereby determine the role of these organisms in the pathogenesis of epidermal hyperplasia associated with Malassezia dermatitis in dogs.

Sample population—Primary canine keratinocyte cultures established from skin samples obtained from clinically normal dogs.

Procedure—The proliferative response of keratinocytes co-cultured with Malassezia organisms for 1, 2, or 3 days was assessed by use of direct manual counting (to determine the number of keratinocytes in both the monolayer and the medium) and immunohistochemical staining techniques involving antibodies against proliferating cell nuclear antigen (PCNA) and another cellular proliferation marker, Ki-67. The potential cytotoxic effect of Malassezia organisms was investigated by use of an apoptosis detection kit to label keratinocytes co-cultured with M pachydermatis that underwent apoptosis.

Results—No stimulatory effect of Malassezia organisms on canine keratinocyte proliferation was detected via cell counting and immunohistochemical techniques. However, there was a significant increase in dead keratinocytes in the medium with increasing numbers of Malassezia organisms in the co-culture. More apoptotic cells were observed in keratinocyte monolayers co-cultured with high numbers of M pachydermatis than there were in monolayers cultured without Malassezia organisms, and the number increased after prolonged incubation.

Conclusions and Clinical RelevanceM pachydermatis did not stimulate canine keratinocyte proliferation in vitro. The results suggested that the epidermal hyperplasia observed in dogs with Malassezia dermatitis is unlikely to be caused by a direct effect of the organism on the keratinocyte cell cycle, but is likely to involve other mechanisms. Am J Vet Res (2004;65:787–796)

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in American Journal of Veterinary Research


Objective—To compare cytotoxic effects and antiviral efficacy of 9 nucleoside reverse transcriptase inhibitors (NRTIs) against FIV in feline peripheral blood mononuclear cells.

Sample—Peripheral blood mononuclear cells obtained from 3 specific pathogen–free cats.

Procedures—3 of the 9 NRTIs had not been previously assessed in feline cell lines. Cytotoxic effects were determined by colorimetric quantification of a formazan product resulting from bioreduction of a tetrazolium reagent by viable peripheral blood mononuclear cells; uninfected cells from 1 cat were used in these assays. Cells from all 3 cats were infected with a pathogenic clone of FIV, and in vitro antiviral efficacy of each NRTI was assessed with an FIV p24 antigen capture ELISA.

Results—Cytotoxic effects in feline peripheral blood mononuclear cells were observed only at concentrations > 10 μM for all 9 NRTIs. Comparison of the cytotoxic effect at the highest concentration investigated (500μM) revealed that didanosine and amdoxovir were significantly less toxic than abacavir. All drugs induced a dose-dependent reduction of FIV replication. At the highest concentration investigated (10μM), there was no significant difference in antiviral efficacy among the test compounds.

Conclusions and Clinical Relevance—The evaluated NRTIs had low cytotoxicity against feline peripheral blood mononuclear cells and appeared to be safe options for further in vivo evaluation for the treatment of FIV-infected cats. There was no evidence suggesting that the newly evaluated compounds would be superior to the existing NRTIs for reducing FIV burden of infected cats.

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in American Journal of Veterinary Research