Leishmania major: in vitro ultrastructural study of the paraxial rod of promastigotes.

The flagellum of Leishmania major promastigotes has an intraflagellar structure known as the paraxial rod (PAR) which extends from a point halfway in the flagellar pocket to the tip of the flagellum, lying opposite the axonemal microtubule doublets 4-7. An expansion of the axonemal plasma membrane envelops the PAR and may provide desmosomal attachment at the orifice of the flagellar pocket. The complex organization of the 4-6 nm thick filaments in the PAR was studied by us in cross, oblique, longitudinal and tangential sections by electron microscope.