[Skeletal muscle ultrastructure of untrained humans and animals after physical loading]

In non-trained mice subjected to a single and repeated swimming up to complete wearness, fibres in the skeletal muscles demonstrated certain ultrastructural alterations in their nuclei. Twenty-four and 48 h after a single swimming many muscular nuclei have only non-condensed chromatin. After repeated swimming large clumps of condensed chromatin appear in most of the muscular fibre nuclei. These nuclear changes are accompanied by segregation of separate fibrillar areas containing nuclei. Similar phenomena are also noticed in muscular fibres of non-trained people after a single physical loading. Ultrastructural changes in skeletal muscular fibres of volunteers, nonsportsmen are of individual character and depend on the degree of wearness resulting from the loading. In people subjected to the experiment and having severe fatigue (disability to work) significant shifts in submicroscopical structure of the fibrillar components were observed: in mitochondria, sarcoplasmic reticulum, T-system, contractile apparatus, etc. In this case, matrix becomes clear, lysis in mitochondrial crysts, dilatation of terminal cysterns of the sarcoplasmic reticulum and T-system tubes, destructive and regenerative processes in the contractile apparatus are observed. The data obtained demonstrate varied changes in ultrastructure of different components composing skeletal muscles of the non-trained organism subjected to physical loading.