Computer-aided reconstruction from serial sections

Abstract

The development of CARTOS, a system for Computer-Aided Reconstruction by Tracing Serial Sections, has been directed by efforts to investigate some rather specific biological questions. We want to study the detailed structure of simple nerve nets so that the anatomy of individual nerve cells and their fibers can be recorded in three dimensions and the morphologically visible synapses connecting them noted. Furthermore, we would like to carry out these morphological studies as a function of time during embryological development in organisms which reproduce clonally so that, except for mutations, all individuals within a clone have the same genes. The specific questions we have been trying to answer are: a) To what extent is there variation in the morphology of particular cells when they are examined in different but genetically identical animals raised under identical environmental conditions? b) To what extent can morphological variation be induced by changes in the environmental conditions during development? c)Within the same animal how precisely does the anatomy of a particular cell match the mirror image of its bilaterally symmetric mate? d) Mathematically precise bilateral symmetry must break down when fibers cross the midplane of an animal. Is this breaking of symmetry a feature that occurs in the same way in different organisms? e) What is the sequence of development steps leading to the adult structure of the visual nervous system and is this sequence unique and reproducible between animals that have the same genes? f) What clues concerning the mechanism by which particular cells make specific connection can be obtained by following the progress of a particular neuron during; its development?

Supported by a gift from the RGK Foundation and by Public Health Service Facility Grant #RR00442 (04).