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Induction of surface fluidity in Trichinella spiralis larvae during penetration of the host intestine: simulation by cyclic AMP in vitro

Published online by Cambridge University Press:  01 January 1997

J. MODHA
Affiliation:
Division of Biochemistry and Molecular Biology, The Davidson Building, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
M. C. ROBERTS
Affiliation:
Division of Biochemistry and Molecular Biology, The Davidson Building, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
M. W. KENNEDY
Affiliation:
Wellcome Laboratories for Experimental Parasitology, Division of Infection and Immunity, The Joseph Black Building, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
J. R. KUSEL
Affiliation:
Division of Biochemistry and Molecular Biology, The Davidson Building, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK

Abstract

The lateral diffusion (DL) properties of the fluorescent lipid probe 5-N (octadecanoyl) aminofluorescein (AF18) inserted into the surface of muscle-stage larvae of Trichinella spiralis were investigated by fluorescence recovery after photobleaching. AF18 was not free to diffuse laterally in dormant larvae, and this remained unchanged after larval activation in vitro with trypsin and bile. However, a significant increase in surface fluidity of the probe was demonstrated (%R = 74·5; DL = 11·5 × 10−9 cm2/sec) when larvae invaded intestinal epithelial tissue following oral infection of mice. Membrane-permeant photoactivatable caged cyclic AMP was used to analyse the putative mechanism responsible for this increase in lateral diffusion in the parasite surface. Although incubation of larvae with 1–50 μM caged cAMP had no effect on surface fluidity, incubation with 100 μM caged cAMP induced a substantial increase in the lateral mobility of AF18 (%R = 64·3; DL = 8·3 × 10−11 cm2/sec) immediately following photo-activation of the caged messenger. This induced fluidity, however, was transient and the larval surface reverted to immobility within 15 min. These observations constitute the first reported measurement of the fluid properties of the surface of intracellular parasites, the first demonstration of the parasite surface fluidity altering as a result of host cell invasion and the first indication of a mechanism underlying changes in surface fluidity in parasitic helminths.

Type
Research Article
Copyright
© 1997 Cambridge University Press

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