title: Three-dimensional reconstruction of tubular myelin.
abstract: The lipid and protein components of pulmonary surfactant are synthesized by alveolar type II cells and stored in their secretory granules, the lamellar bodies. Tubular myelin is a highly ordered surfactant structure that is lung specific and produced in the alveolar airspace. Recent work identified Ca2+, surfactant apoproteins A and B, and saturated phospholipids as necessary for tubular myelin structure and function. We have used serial ultrathin sections from fetal rat lungs and reconstructed the three-dimensional structure of tubular myelin. The spheres of tubular myelin we viewed were 2-3 microns in diameter and were surrounded by up to 20 lamellar bodies, each apparently simultaneously contributing material to the tubules. We measured a long-range symmetry of the tubules, which were folded about a central axis and showed a repeated crossing of individual tubes from one side to the other of the large structure. The tubes appeared closed on their outer edges and there was a delay in the penetration of tubules by cationic ferritin added to tissue slices containing the tubular myelin, although within a few minutes tracer appeared in the lumina and on the walls of the tubules. The three-dimensional images were compatible with existing views of tubular myelin.
authors.affiliation: Department of Medicine, Durham VA Medical Center, North Carolina 27705.
authors.forename: S L
authors.initials: SL
authors.lastname: Young
authors.forename: E K
authors.initials: EK
authors.lastname: Fram
authors.forename: E W
authors.initials: EW
authors.lastname: Larson
mesh_terms: D000818:Animals; D001688:Biological Products; D005260:Female; D007091:Image Processing, Computer-Assisted; D009186:Myelin Sheath; D011506:Proteins; D011663:Pulmonary Surfactants / Q000648:ultrastructure*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001688:Biological Products; D011506:Proteins; D011663:Pulmonary Surfactants; C018167:tubular myelin