Electron Staining Characteristics of the Inclusion Bodies of Type II Alveolar Epithelial Cells
The inclusion bodies of Type II epithelial cells of the mammalian lung are oval and limited by a unit membrane. They contain highly osmiophilic material. With the standard method of fixation this material is irregularly separated by a number of electron-lucent spaces (Figure 1). Because of this appearance, the inclusion bodies are often referred to as “lamellar inclusions”. Measurable periodic lamellae, however, have never been observed in the inclusions which are located intracellularly.During the course of the studies to localize acid mucopolysaccharides in the distal air way of the rabbit and rat, it is found that the alveolar surface of the cell membranes of both Type I and II cells and the inclusion bodies within Type II cells satin heavily with colloidal iron at pH 2.0 following the osmication of the tissue with phosphate-buffered solution at pH 7.4 (Figure 2). In addition, the inclusion bodies for the first time show regular periodic lamellae. Each line is granular and measures about 60 Å in width (Figure 3).