Cell body volume of spinal ganglion neurons: estimation by three different methods.

We estimated the mean volumes of two series of nerve cell bodies, one from rabbit and one from rat spinal ganglia by three different methods: a procedure we devised 25 years ago (the circle-fitting method), one of the new stereological methods (the nucleator method) and the method of serial sectioning--the most direct and accurate procedure presently available for estimating cell size. In the case of the rabbit, in which most spinal ganglion neurons have a single nucleolus, the mean volumes estimated by the first two methods are closely similar and deviate by less than 2% from the mean obtained by serial sectioning. In the case of the rat, in which approximately half of the spinal ganglion neurons have more than one nucleolus, the mean volumes estimated by the first two methods are again closely similar, but deviate by about 12% from the mean obtained by serial sectioning. These findings show that: a) both the nucleator method and the circle-fitting procedure are more accurate when applied to neurons with a single nucleolus; b) if certain conditions are respected, not all the methods previously used to estimate cell size give biased results. However, the new stereological procedures are easier and quicker to use than the earlier methods. These findings also show that our previous results obtained by the circle-fitting method are to be considered valid.