Mailing muscle biopsy samples for histochemical processing. Conditions and morphometric approach to the alterations induced by storage.

Muscle samples obtained in patients with different neuromuscular diseases were stored at 0 degree C for periods of 6-12h and were subsequently frozen for histochemical processing. Compared to reference samples which had been immediately frozen, the individual test sections displayed different degrees of swelling of the muscle fibres. After 12h of storage the mean diameters had increased by 20% in type-1 and type-2A fibres and by 16% in type-2B fibres. With shorter periods type-2B fibres also showed the smallest amounts of increase in mean fibre diameter. The distribution of fibre diameters, variability coefficients and atrophy and hypertrophy factors showed corresponding changes but rarely fell outside the range defined from the reference sections. The histological, histochemical and cytological quality of the sections remained satisfactory. The decrease in glycogen content during storage appeared to be crucial. Time for mailing samples can be extended up to 27h without essential loss of histo-and cytochemical quality of the sections at the light microscopic level.