Cytoskeleton-mediated, age-dependent lateral topography of lectin-gold-labelled molecules on the plasma membrane of cultured neurons: a statistical view.

In dissociated spinal cord neurons (12-day-old mouse embryo, monolayer culture), an electron microscopic study was carried out to examine quantitatively the rearrangement of wheat-germ agglutinin-gold-labelled molecules on the neuronal somatic surface at two developmental stages (on the fifth and 15th days in vitro), and after cytoskeletal interruptions. In tests, before labelling the cultures were incubated with colchicine or cytochalasin in order to affect microtubules or mostly actin filaments, respectively. Samples of electron micrographs that display soma membrane (profile) fragments were quantified. A set of stochastic geometry approaches was accomplished, which allowed statistical and stereological analysis of labelling. Images that illustrate the lateral (surface) patterns of label were simulated. On the fifth day in vitro, both colchicine and cytochalasin were found to cause an increase in the surface density and aggregation of wheat-germ agglutinin label relative to controls, the effect of cytochalasin being significantly more profound. By the 15th day in vitro, treatment with both drugs led to a similar tendency towards heavy aggregation of wheat-germ agglutinin labels. In contrast, neuron processes showed an opposite tendency of label rearrangement, which suggests lateral migration of labelled molecules, as a result of drug action. Possible molecular mechanisms involved in the phenomena are discussed.