Physical methods for the study of the dynamics of axonal transport

Currently used techniques for the study of the dynamics of axonal transport are reviewed. Emphasis is placed on those nonstructural and nonbiochemical methods which are most useful in the investigation of the dynamics of the mechanisms that underline the transport process. The methods by which the transport of specified materials may be assessed are divided into two broad groups: those which involve the collection, or accumulation, of transported materials at a region where transport is slowed or arrested, and those methods in which the distribution of a marker of the transported material is assayed in a series of nerve segments. Potential problems and sources of error associated with these techniques are considered as is their applicability to particular biological preparations. Recently introduced methods for concentrating and labeling transported material are described. New methods for conducting segment analysis of transported material by the use of position-sensitive detectors of radiation are considered. Optical methods of detecting axonal transport are reviewed with emphasis being placed on recently introduced methods and on the means by which the motion of optically detected organelles may be analyzed. In addition, biological preparations which are particularly suited to the optical approach are described.