Do large motor neurons contain more nuclear DNA than small motor neurons?
Although we showed that the nuclei of normal spinal motor neurons contain diploid amounts of DNA on average , it remained possible that their DNA content might vary somewhat according to cell body size. Because nuclear and cell body size are positively correlated, the size of nuclei obtained from isolated motor neuron cell bodies can be used as an indication of the size of its parent motor neuron. Thus, simultaneous fluorescence activated flow cytometry and light scattering were used to determine the size and DNA content of individual, propidium iodide-stained nuclei obtained from isolated frog spinal motor neurons (Sato et al., 1994). While we found no evidence of polyploidy, there was a slight increase in the amount of propidium iodide-stained DNA in nuclei of increasing size. Whether this small increase represents an actual gain in DNA is not clear, since an equally plausible explanation is that as nuclear size increases, DNA unfolding (but not DNA content) increases, causing more o
