AN OBSERVATION OF ULTRASTRUCTURE OF LUNG TISSUE WITH NEGATIVE STAIN IN CRYO-ULTRAMICROTOMY

Ultra-thin sections of rat lung were cut under extremely low temperatures (-120°C at specimen and -90°C at knife respectively) and were then stained with 1% phosphotungstic acid for 20 sec at 37°C. The lamellar inclusion bodies of type II alveolar cells show concentric lamellations with 70 to 80 Å spacing and the vesicular components also present in inner aspect. The limit membrane of approximately 100Å thickness may be derived from the outer part of the paired endoplasmic reticulum and rarefaction of the inner part may eventually take place to form the lamellated pattern. The dark zone of about 200Å was shown to usually exist between the inner aspect of limit membrane and the lamellation. Lysosomal structure possesses non-cellular dense content which may be derived from autophagic activity of cytomembranes. Identical compounds are frequently encountered in multi-vesicular bodies. In these particular inclusions, rarefaction of the lamellations is not observed but irregular periodicities and undistinct polarities are often observed. The assumption that the lammellated inclusion bodies may have their origin either in lysosomes or multi-vesicular bodies remains a rather remote possibility. The collagen fibrills are disclosed with high constant periodicity, measuring up to 670Å and the elastic fibers are constituted with aggregations of fine flocculant filamentous materials.