title: Different expression of surfactant protein B mature peptide and proprotein at 21 weeks' gestation in human fetal pulmonary epithelial cells.
abstract: OBJECTIVE
  The aim of this study is to evaluate the maturation of pulmonary epithelial cells in human fetal lungs at 21 weeks' gestation.
  
  
  METHODS
  Eight fetuses at 21 weeks' gestation were evaluated. The maturation of pulmonary epithelial cells was assessed by immunohistochemical examination for surfactant proteins and by electron microscopy.
  
  
  RESULTS
  Surfactant protein B mature peptide was detected slightly in the epithelial lining of the bronchioles, but was totally absent in the terminal airways. Surfactant protein B proprotein was clearly detected in the epithelial lining of both bronchioles and terminal airways. Transmission electron microscopy of terminal airway cells showed abundant glycogen granules and few intracellular organelles.
  
  
  CONCLUSIONS
  The production of mature surfactant protein B in terminal airways is scarce at 21 weeks' gestation, which is associated with the immature mechanism of proprotein processing in the cytoplasm.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan. kazuiked@sc.itc.keio.ac.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mori
authors.forename: Kazushige
authors.initials: K
authors.lastname: Ikeda
authors.forename: Mamoru
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D004847:Epithelial Cells / Q000648:ultrastructure; D005260:Female; D005865:Gestational Age; D006801:Humans; D008168:Lung / Q000196:embryology*; D008854:Microscopy, Electron; D011247:Pregnancy; D011498:Protein Precursors / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism*; D037701:Pulmonary Surfactant-Associated Protein B / Q000378:metabolism*
chemical_list: D011498:Protein Precursors; D011510:Proteolipids; D037701:Pulmonary Surfactant-Associated Protein B; C105511:surfactant protein B propeptide