TYPE, DIAMETER AND DISTRIBUTION OF FIBERS IN SOME RESPIRATORY AND ABDOMINAL MUSCLES OF THE GOAT

This study was designed to determine the histochemical properties, siz e and composition of fibres in the diaphragm, intercostal and abdomina l muscles of goats to clarify whether reported similarities in respira tory muscle physiology between goats and humans have a structural basi s. Serial sections (10 mum) of muscular tissue from adult female goats were stained for myosin adenosine triphosphatase and reduced nicotina mide adenine dinucleotide dehydrogenase-tetrazolium reductase activiti es; the fibres were classified into types I, IIA and IIB; and their me an diameter and composition were determined. Abdominal and intercostal muscles contained types I, IIA and IIB fibres in the ratio 1:1:1, and the mean diameter of the fibres ranged from 49.2 to 62.2 mum. In cont rast, the diaphragm contained 58.9% type I and 41.1% type II fibres, a nd the latter could not be differentiated into types IIA and IIB. Diap hragmatic fibres were also smaller (36.9 - 40.9 mum). These findings c ontrast with those in humans, where the diaphragm, intercostal and abd ominal muscles contain >50% type I fibres and have fibres of identical diameter. ne differences in fibre characteristics between the diaphra gm, intercostal and abdominal muscles of goats and the differences bet ween goats and humans need to be taken into consideration in interpret ing the results from studies in respiratory muscle physiology.