The relation between the Nissl and Sudan black pictures of the motor neurones of the spinal cord of the adult horse, with special reference to the cytoplasmic inclusions

Abstract

ABSTRACT The motor neurones of the spinal cord of the horse, fixed in neutral formaldehydecalcium, embedded in paraffin, and sectioned, are easily coloured with Sudan black dissolved in propylene glycol or in tertiary butanol. No procedure for ‘unmasking’ lipids is necessary. Any effect due to electropolar bonds are excluded by blocking and extraction procedures. The true lysochrome effect is confirmed by the removal of the colour by lipid solvents and the absence of stable sudanophilia and of background colouring. No brown colour suggestive of decomposition products is seen, and this is further confirmed by absorption spectra of the Sudan black solutions. The structures revealed are in the main identical with those of ordinary Nissl preparations made, for instance, by Einarson’s chromalum/gallocyanin stain. In addition, however, structures closely similar to ordinary Nissl bodies are seen in the axon hillock and in the axon. This suggests that in these situations Sudan black colours corpuscles that are lacking in ribonucleic acid (presumably endoplasmic reticulum devoid of ribosomes). The nature of the lipids revealed by Sudan black in these cells has not been determined histochemically. Extraction in pyridine either before or after fixation had no definite effect on the colouring of the Nissl bodies or of the nucleus. The histochemical recognition of lipids in the cytoplasmic network of neurones has recently been reported by David and Brown (1961). The present paper supports the findings of these authors. Different material and methods were used, but the colouring agents were the same.