EXTERNAL STIMULI AND INTRACELLULAR SIGNALING IN THE MODIFICATION OF THE NEMATODE SURFACE DURING TRANSITION TO THE MAMMALIAN HOST ENVIRONMENT

Previous work has shown that the surface of infective larvae of parasi tic nematodes will not bind the fluorescent lipid analogue 5-N-(octade canoyl)aminofluorescein (AF18) until after exposure of the parasite to mammalian tissue-culture conditions. In this study, culture media whi ch are permissive or non-permissive for the acquisition of lipophilici ty for AF18 were altered in order to examine possible stimuli involved . This showed that external alkaline pH and high sodium ion concentrat ion were highly stimulatory. The internal signalling pathways which ma y be involved in the surface alteration were then examined using agent s which are known to affect intracellular signalling in mammalian cell s. The results indicated that elevation of cGMP levels was stimulatory whereas inhibition of a putative Na+/H+ antiporter or calcium mobiliz ation was inhibitory, and it is argued that high intracellular levels of cAMP may be inhibitory. Whilst the precise effects of the agents us ed on nematode cells remain to be established, these results provide a framework for the examination of the processes involved in the modifi cation of the nematode surface which takes place immediately after the infection event.