Cytotoxic activity of LPS from Pseudomonas fluorescens MF37 treated with cyclic nucleotide analogs. Effect of treatment of P. fluorescens MF37 with dibutyryl cyclic AMP (dbcAMP) and 8-bromo cyclic GMP (8BcGMP) on the apoptotic (A) and necrotic (B) activity of its LPS. The apoptotic effect of the LPS was determined by measurement of the accumulation of NO2- in the medium resulting from the activation of inducible NO synthase activity in glial cells. The necrotic action of the LPS was assessed by measurement of the accumulation of lactate dehydrogenase (LDH) in the medium resulting from rupture of the cytoplasmic membrane of glial cells. Values are expressed as mean concentrations of NO2- or LDH in the culture medium after 24 h of incubation with untreated (n = 9) or treated (n = 11 for dbcAMP, and n = 11 for 8BcGMP) LPS (500 ng.ml-1). Data are means for three independent experiments. * : Significantly different (P < 0.05). NS: Not significantly different.