Nicolás Bianco

Stage-specific activity of potential antimalarial compounds measured in vitro by flow cytometry in comparison to optical microscopy and hypoxanthine uptake

The evaluation of new antimalarial agents using older methods of monitoring sensitivity to antimalarial drugs are laborious and poorly suited to discriminate stage-specific activity. We used flow cytometry to study the effect of established antimalarial compounds, cysteine protease inhibitors, and a quinolone against asexual stages of Plasmodium falciparum. Cultured P. falciparum parasites were treated for 48 h with different drug concentrations and the parasitemia was determined by flow cytometry methods after DNA staining with propidium iodide. P. falciparum erythrocytic life cycle stages were readily distinguished by flow cytometry. Activities of established and new antimalarial compounds measured by flow cytometry were equivalent to results obtained with microscopy and metabolite uptake assays. The antimalarial activity of all compounds was higher against P. falciparum trophozoite stages. Advantages of flow cytometry analysis over traditional assays included higher throughput for data collection, insight into the stage-specificity of antimalarial activity avoiding use of radioactive isotopes.

Effects of intra-articular corticosteroids in vivo on synovial fluid variables in rheumatoid synovitis.

Intra-articular instillation of corticosteroids in patients with rheumatoid arthritis (RA) is often followed by transient relief of symptoms and signs of local synovitis (Hollander, Brown, Jessar, and Brown, 1951; Ziff, Scull, Ford, McEwen, and Bunim, 1952). The basis for this clinical improvement is not known and has not been comprehensively correlated with changes in the characteristic synovial fluid (SF) abnormalities of RA. Decreases in the SF acid phosphatase level and leucocyte count (Ziff and others, 1952; Lemperg, Beckman, and Beckman, 1971) and transient decreases in SF haemolytic complement (CH50) level (Hunder and McDuffie, 1972) have been reported after the intra-articular administration of a corticosteroid. The theoretical bases for these alterations include the ability of corticoids to suppress immune inflammation in vivo (Gell, 1955), to inhibit leucocyte chemotaxis (Ward, 1966) and other leucocyte functions (Packer and Greendyke, 1960) in vitro, and to stabilize leucocyte and other cell lysosomal membranes (Weissmann and Dingle, 1961). We therefore investigated the concomitants of the beneficial clinical effect of intraarticular corticosteroids in patients with RA, using serial SF leucocyte counts and acid phosphatase levels as a measure of inflammation. SF rheumatoid factor (RF) titres and complement levels were determined to assess local immune abnormalities.