| Method |
"Junctional morphology in EDL [extensor digitorum longus] muscles was evaluated at several
times during the first 2 postnatal weeks. The morphology of the
postjunctional membrane [pjm] was quantified by measuring the lengths of
total pjm and of thickened pjm, and normalizing these to the length of
the midline of the primary cleft. The resulting ratio of lengths “total
pjm to 1° cleft midline” is a measure of the extent of postjunctional
membrane folding. The ratio “thickened pjm to 1° cleft midline” is a
measure of the relative amount of junctional surface area which is
specialized thickened membrane. By dividing the two ratios, one can
determine the proportion of the total pjm which is specialized at each
age (52 to 58% between days 1 and 7, and gradually falling thereafter to
the adult value of ~30%). For most ages, >800µm length of 1° cleft
were analyzed (from 20 to 50 separate endplates) in these cases, the
table gives the mean and standard error of the ratios obtained for the
several muscle samples. For some ages, fewer total endplates were
analyzed, and only the overall ratio is given without the error." |