Decrease in the nucleo-cytoplasmic volume ratio of rabbit spinal ganglion neurons with age.

Nuclear and perikaryal volumes, as well as the mean percentage of perikaryal volume occupied by lipofuscin, were estimated in spinal ganglion neurons of 12, 42 and 79 month-old rabbits. The volume ratio between nucleus and perikaryal cytoplasm (N/C volume ratio) decreased progressively and significantly with increasing age. This was not a consequence of the perikaryal enlargement due to the age-related lipofuscin accumulation since the same result was obtained when the volume occupied by lipofuscin was subtracted from the perikaryal volume. The decrease in the N/C volume ratio may depend on an age-related loss of DNA, a cytoplasmic influence on nuclear size, or other unknown causes.