A model for determining baseline morphometrics of skeletal myofibres

The minimum diameter method of morphometry (MDM) is used to measure and detect changes in myofibre diameters (FD). The MDM is used to identify pathology in skeletal muscle. In such studies, an assumption is made that the mean FD in a particular muscle in both limbs is essentially the same. This study explored this premise to determine the accuracy of MDM as a means of morphometric analysis. Muscle biopsies were obtained from the left (G1) and right (G2) tibialis anterior of four vervet monkeys and from the massaged left (G3) and untreated right (G4) tibialis anterior of four animals. Wax sections were prepared for MDM and FD was measured. Three specimens were re-measured on four occasions. The mean FD of each biopsy from G1 and G2 limbs were compared and the number of measurements necessary to produce a meaningful result determined. Repeated measurement showed a difference of < 3.0% in FD means between the first and three subsequent measurements. There was no significant difference of FD means between G1 and G2, whilst the difference between G3 and G4 was 11.2%. When > 175 FD were measured, the difference from the final mean was less than 2.0%. These data show that, (1) FD data derived from a muscle in an untreated limb can be used as a control for experiment mediated changes of FD in the other, (2) MDM is a reliable means of measuring FD and (3) 150-175 FD are needed to provide a dependable result.