Is the supply of axoplasmic proteins a burden for the cell body? Morphometry of sensory neurons and amino acid incorporation into their cell bodies.

Since the perikaryon is considered to be the source of all axoplasmic proteins, we estimated the amount of protein synthesized in cell bodies and axoplasmic volumes of sensory neurons of two anuran species (Xenopus and Caudiverbera) to detect a correlation between these variables. The range of cell body volumes was 1:28 and 1:38 in Xenopus and Caudiverbera, respectively, while that of axoplasmic volumes was 1:5000-6000. The protein synthesis in glial and neuronal cell bodies was assessed with pulses of labeled amino acids followed by radioautography. No obvious correlation was found between axoplasmic volume and either rate or amount of amino acid incorporated into cell bodies. The rate of amino acid incorporation into glial and neuronal cell bodies was of the same order of magnitude. Results suggest that the maintenance of the axoplasm does not seem to be a burden for the perikaryon.