Patterns of muscle fiber-type disproportion in hypotonic infants.
We studied the histochemical characteristics of muscle in five hypotonic infants. A number of different patterns of disproportion in the sizes and numbers of type 1 and type 2 fibers were found. In three cases, type 1 fibers were smaller than type 2 fibers and type 2b or 2c fibers were largest. In one case, type 2 fibers were smaller than type 1 fibers and were reduced in number, while in a case of Prader-Willi syndrome there was a preponderance of type 2 fibers that were smaller than type 1 fibers. Type 2c fibers were increased in number in all but one case. We postulate that these various patterns of fiber-type disproportion are the result of altered neural influences leading to impaired maturation of type 1 or type 2 motor units.
D000255:Adenosine Triphosphate / Q000378:metabolism; D001706:Biopsy; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009123:Muscle Hypotonia / Q000151:congenital / Q000473:pathology*; D009132:Muscles / Q000201:enzymology / Q000473:pathology*; D011218:Prader-Willi Syndrome / Q000473:pathology
D000255:Adenosine Triphosphate