Ultrastructural localization of gold particles within neural grafts labeled with gold-filled sendai viral envelopes

The ability to discriminate between host and donor cells is required to interpret the organization of neural grafts at the electron microscopic (EM) level. Using light microscopy, Ardizzoni et al. (Ardizzoni, S.C., Michaels A., and Arendash, G.W. [1988] Science 239: 635–637) described a method, using gold‐filled Sendai viral envelopes, for labeling cell suspensions prior to grafting. As the colloidal gold used in this procedure is especially attractive for use with EM, we have examined the ultrastructural distribution and character of this label with transplanted cells. Cell suspensions taken from the nucleus basalis of fetal rats were labeled using gold‐filled Sendai viral envelopes and grafted into the dorsal neocortex of adult host rats with nucleus basalis lesions. After varying survival times ranging from 1 to 14 months, grafts and surrounding host tissue were examined using standard EM techniques. Within the graft site, gold particles ranging from 10–200 nm were found associated with various membranes throughout the cytoplasm of both neurons and glia. Gold particles of similar size were also found within the nuclei of neuronal and non‐neuronal cells. Host cells near the graft site contained some small gold particles (10–40 nm). Control injections of non‐viable, gold‐labeled cells or colloidal gold alone resulted in similar patterns of small gold particles which were readily discriminable from the larger virally inserted gold particles found in viable labeled donor cells. We conclude that this method allows discrimination between closely associated host and donor cells.