X-ray microanalysis of single muscle fibres visualized in the scanning- and scanning-transmission mode of electron microscopy has been applied to human muscle biopsies to quantify changes of intracellular elements in different
muscle disorders. To detect elements representing diffusible
ions, cryofixation and cryosectioning was performed and analyses were conducted on freeze-dried cryosections 6 micron thick. Changes in the concentration of elements were found to differentiate certain muscular disorders. A large increase in
sodium (Na) and
chlorine (Cl), and a decrease in
potassium (K) was typical of
myotubular myopathy, while a moderate increase in Na and Cl was found in
central core disease and
nemaline myopathy. The normal elemental spectrum was found in
multicore myopathy and facio- scapulo -humeral muscle dystrophy. In
dystrophia myotonica there was constantly a decrease in K whereas in
myotonia congenita an increase in K was a common finding. In
myotonic dystrophy an increase in Na and Cl seemed to be related to the increase in the ring fibre formation. Experimental
tenotomy of the soleus muscle of the rat is characterized by plasma membrane changes and the formation of core fibres. A marked increase in Na and Cl and a decrease in K was found to be a prominent elemental change in such core fibres. We conclude that changes in the concentration of certain intracellular elements demonstrable by X-ray microanalysis on cryosectioned freeze-dried muscle biopsies seem to be an indication of muscle fibre membrane disturbances.