Study on Cause of Death in Rat Neonates with Congenital Osteochondrodysplasia (ocd/ocd) I. Morphological Abnormalities in Lung and Respiratory Tract

Abstract The rat with congenital osteochondrodysplasia with systemic subcutaneous edema (ocd/ocd) dies shortly after parturition. The cause of death has not been fully understood in the similar lethal disorders in other species. The present study describes the morphological abnormalities in the respiratory tract in relation to the cause of death in ocd/ocd. Mid saggital section of the respiratory tract of the ocd/ocd neonate revealed that the air flow from nose to lung is disturbed by occlusion of the pharynx and larynx area with the cleft palate and relatively large tongue. Smaller thoracic volume was also noted in the ocd/ocd neonate. Of intra-thoracic organs, only the lung showed significantly smaller weight in the ocd/ocd neonate than that of phenotypically normal (+/quest;). Histology of the fetal and neonatal lung showed atelectasis and many small alveolar cavities with abundant lung surfactants in the ocd/ocd. Disarrangement of the cells composing the alveolar wall was also revealed in the ocd/ocd. Electron microscopy of the fetal lung demonstrates the lamella bodies in the alveolar cavities and the pneumocyte type II cells in both genotypes. Insufficiency of the surfactant was excluded for the cause of death in the ocd/ocd.