The effects of ageing, cachexia and neoplasms on striated muscle. Quantitative histological and histochemical observations on an autopsy material.

The effects of ageing, cachexia and neoplasms on striated muscle were examined in histological sections of an autopsy material. Paraffin sections were examined from four separate muscles of 30 previously healthy subjects who died suddenly, from eight cases with cachexia and from 16 cases with cachexia and neoplasms. In addition, ATP-ase stained cryostat sections were examined from two muscles from most of the cases. All the sections were evaluated with regard to atrophy, myopathic changes and fibre type grouping. Furthermore, the exact size of 100 fibres of each type was determined in the enzyme stained sections. Myopathic changes were found in a few muscles, mainly in the normal cases. They were considered incidental findings without clinical significance. Fibre type grouping could not be evaluated in the anterior tibial muscle because large clusters of the same fibre type occur normally in this muscle. In the biceps brachii only two normal cases and none of the cachectic cases showed fibre type grouping. A moderate small grouped muscle fibre atrophy was found in normal cases with increasing age. The cases with cachexia showed a marked small grouped atrophy which involved both fibre types. There were only small and uncertain differences between cases with cachexia and tumours and those with cachexia alone. Thus, no changes were observed which could be ascribed to tumours alone. The small grouped atrophy in ageing and cachexia resembled that seen in denervation atrophy but the exact mechanism of the changes remains obscure.