title: Smooth muscle development during postnatal growth of distal bronchioles in infant rhesus monkeys.
abstract: Development of smooth muscle in conducting airways begins early in fetal life. Whereas the pattern and regulation of smooth muscle differentiation are well-defined, the impact of airway growth on the process is not. To evaluate the transformations in organization during postnatal growth, smooth muscle bundle organization (size, abundance, and orientation) was mapped in five generations of distal airways of infant rhesus monkeys (5 days and 1, 2, 3, and 6 mo old). On the basis of direct measurement of the bronchiole proximal to the terminal bronchiole, length increased by 2-fold, diameter by 1.35-fold, and surface area by 2.8-fold between 5 days and 6 mo of age. Smooth muscle bundle size was greater in proximal bronchioles than in respiratory bronchioles and did not change with age. However, relative bundle size decreased in proportion to airway size as the airways grew. Relative bundle abundance was constant regardless of airway generation or age. The distribution of smooth muscle bundle orientation changed with age in each airway generation, and there were significant changes in the terminal and respiratory bronchioles. We conclude that smooth muscle undergoes marked organizational changes as airways grow during postnatal development.
authors.affiliation: Dept. of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: Mai-Uyen T
authors.initials: MU
authors.lastname: Tran
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Weir
authors.forename: Michelle V
authors.initials: MV
authors.lastname: Fanucchi
authors.forename: April E
authors.initials: AE
authors.lastname: Murphy
authors.forename: Laura S
authors.initials: LS
authors.lastname: Van Winkle
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Evans
authors.forename: Suzette M
authors.initials: SM
authors.lastname: Smiley-Jewell
authors.forename: Lisa
authors.initials: L
authors.lastname: Miller
authors.forename: Edward S
authors.initials: ES
authors.lastname: Schelegle
authors.forename: Laurel J
authors.initials: LJ
authors.lastname: Gershwin
authors.forename: Dallas M
authors.initials: DM
authors.lastname: Hyde
authors.forename: Charles G
authors.initials: CG
authors.lastname: Plopper
mesh_terms: D000367:Age Factors; D000818:Animals; D001980:Bronchi / Q000033:anatomy & histology / Q000254:growth & development*; D007091:Image Processing, Computer-Assisted; D008253:Macaca mulatta; D008297:Male; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000254:growth & development*