An ultrastructural and histochemical study of fibre types in the pectoralis thoracica and iliotibialis muscles of the fowl (Gallus domesticus)
MacNaughtan, A.F.
Journal of Anatomy 118(Pt 1): 171-186
1974
ISSN/ISBN: 0021-8782 PMID: 4279242 Document Number: 72165
All the fibres in the pectoralis muscle showed high myosin adenosine triphosphatase (myosin ATPase) and glycogen phosphorylase (GPase) activities and low succinate dehydrogenase (SDHase) activity. Two types of fibre could be differentiated in the iliotobialis muscle, one low in myosin ATPase and GPase activities and moderate to high in SDHase activity, the other high in myosin ATPase and GPase activities with a very wide range of SDH activity in different fibres. The ultrastructure of both muscles was typical of vertebrate twitch muscle. The pectoralis fibres had thin Z discs, few mitochondria, a single triad per sarcomere situated at the level of the Z disc and, compared with the iliotibialis, a poorly developed sarcoplasmic reticulum. In the iliotibialis the Z discs were thicker and more variable, and the overall content of the mitochondria was higher than in the pectoralis, but there was wide variation between fibres. There were two triads per sarcomere located near the A-I junction, and the sarcoplasmic reticulum was extensive. A correlation between the histochemical and ultrastructural features of different fibre types was attempted.