Regional distribution of fiber types in developing baboon diaphragm muscles

Publisher Website
Google Scholar
Abstract
Fiber type distribution and mean fiber area were determined for seven sites in diaphragm muscles of premature (140 days gestation), full‐term (180 days gestation), and adult baboons. Within a group, data did not differ significantly amongst the seven sites. The diaphragm of premature animals had a large proportion [56(±2)%] of type IIc fibers, smaller proportions of type I, IIo, and IIh fibers [16(±2), 21(±1), and 7(±2)%, respectively], and no type IIg fibers. Full‐term animals had fewer type IIc [2(±1)%] fibers, greater proportions of type I [46(±2)%], IIh [23(±1)%], and IIg [11(±1)%] fibers, and a similar proportion of type IIo fibers [17(±1)%]. Diaphragm from adult baboons had similar proportions of type I, IIo, IIh, IIg, and IIc fibers in females [39(±4), 20(±2), 1(±1), 41(±5), and 1(±1)%] and males [48(±2), 16(±1), 0(±0), 36(±2), and 3(±2)%]. Fiber area for premature [143(±9), 210(±15), 231(±15), and 156(±16) μm2 for type I, IIo, IIh, and IIc fibers], newborn [317(±32), 374(±36), 468(±42), 498(±43), and 322(±37) μm2 for type I, IIo, IIh, IIg, and IIc fibers], and for type I, IIo, IIg, and IIc fibers from adult female [1,759(±130), 2,365(±284), 5,026(±742), and 1,843(±111) μm2] and adult male [2,513(±221), 3,987(±267), 6,102(±376), and 2,833(±151) μm2] baboons indicated growth which correlated with body weight. Our results also show that metabolic and contractile enzymes develop normally, but growth of respiratory muscle fibers is arrested, during 10 days following premature birth.