A cell division counter exists in the chick embryo myogenic lineage

A computer assisted timelapse video microscopy system was developed to study the behaviour of individual chick embryo myogenic cells in culture. With this system it is possible to monitor and photograph the development of 50-100 myogenic clones simultaneously. Photos were made with a frame grabber and image compressor and were stored in digital form on the computer's hard disc. Colonies derived from 10-day chick embryo myogenic were followed over a period of 3 days. The cultures were then fixed, reacted first with a mouse monoclonal antibody against sarcomeric myosin, then with peroxidase-labelled goat anti-mouse IgG, and stained with diaminobenzidine to detect antibody binding. The dishes were then replaced into the video system and the computer was used to find the originally photographed colonies. Cells which bound the antibody against sarcomeric myosin were identified in the last image stored for each colony. The computer was then used to retrieve the images from each colony in reverse order and to determine the lineage ancestry of every antibody-positive cell in each clone. Several hundred colonies and many hundreds of cell divisions have been examined thus far. In all but one clone, every antibody-positive cell was produced by a symmetrical cell division in which its sister was also antibody-positive (or died). Antibody-positive cells were generated by a sequence of no more than 4 symmetrical cell divisions. Thus, most colonies consisted of 1, 2, 4, 8 or 16 nuclei in terminally differentiated muscle cells. Those colonies in which cell numbers was not a power of 2 were always produced by cell death or detachment.(ABSTRACT TRUNCATED AT 250 WORDS)