Smita Mitra

Mutation induced by vibriophage PS166 infection changes biotype and phage type of Vibrio cholerae.

The effect of a newly isolated vibriophage, PS166, on Vibrio cholerae (E1 Tor) MAK757 was investigated. Two PS166-resistant mutants of strain MAK757 were isolated. These had undergone transition to the classical biotype with concomitant acquisition of new phage sensitivity. However, the parental Ogawa serotype remained unchanged. These mutant strains also showed a unique temperate phage-sensitivity profile, distinct from that of strain MAK757. The possible target of phage PS166 interaction is discussed.

Effect of bioamines on uptake of promastigotes of Leishmania donovani by hamster peritoneal macrophages

Epinephrine and norepinephrine inhibit attachment of Leishmania donovani promastigotes to cultured hamster peritoneal macrophages. The inhibition was significant at catecholamine concentrations of 10(-4) and 10(-5) M and occurred when they were added to the cell mixtures, or after pre-treatment of either macrophages or parasites. Inhibition of attachment after pre-treatment was less marked than when the catecholamines were added to parasite-cell mixtures. Similar results were obtained with dibutyryl cyclic AMP, cholera toxin, theophylline, and cadaverine which raise intracellular cyclic AMP (cAMP). Pretreatment of parasites or macrophages with the bioamines elevated the intracellular cAMP concentration. It is suggested that the inhibitory effect on the host-parasite interaction is mediated through cAMP.