Ultrastructural characteristics of inclusion bodies of type II cells in late embryonic mouse lung

Abstract

As we reported earlier, type II alveolar epithelial cells make their appearance in the early embryonic mouse lung around day 14.2, and show distinctive ultrastructural features. The present study focuses on the ultrastructural characteristics of the inclusion bodies by investigating embryos aged 17-19 days (birth on day 19), using transmission electron microscopy. Late embryonic type II cells appear also as low-columnar or cuboid cells having large, approximately round nuclei and cytoplasm displaying typical features of a differentiated cell. The inclusion bodies show a widespread distribution and are extremely variable in appearance. Schematically we discern five main types, namely cytoplasmic, granular/flocculent, multivesicular, dense, and (multi)lamellar, which occur with intermediate and composite forms. All these inclusion bodies frequently contain glycogen particles, and show a structural relation to profiles of endoplasmic reticulum which are wrapped around them. Other distinctive properties are the osmiophily of multivesicular inclusion bodies, and the presence of vesicles in many dense inclusion bodies. The possible interrelationship, and the differences in various aspects of electron density, suggest that the five main types of inclusion bodies may represent different stages in the formation of mature multilamellar bodies.

Surfactant lipid synthesis and lamellar body formation in glycogen-laden type II cells

“…2, D and E). Incidental examples of LBs within the glycogen-rich zones have often been reported without major discussion (14,16,30,34,38,47). Clearly, the glycogen stores do not represent a barrier to LBs or at least some types of lipid-rich structures.…”

Arrested pulmonary alveolar cytodifferentiation and defective surfactant synthesis in mice missing the gene for parathyroid hormone‐related protein

“…The sequence of distinctive ultrastructural features in embryonic mouse lungs that appear from the onset of the pseudoglandular stage (∼E14.5) to birth (Ten Have‐Opbroek et al, 1988, 1990; Hepworth et al, 1989) facilitated developmental stage comparisons among the genotypes. Electron photomicrographs of the E18.5 normal lungs showed numerous mature‐appearing type II cells (Fig.…”

“…The interstitial thickness is defined as the average thickness of the interstitium across the whole septum. Distal airway epithelial cytodifferentiation (type II cell maturation) was scored by using the criteria developed for fetal mice by Ten Have‐Opbroek et al (1988, 1990), i.e., low‐columnar to cuboidal cell shape, glycogen fields, apical microvilli, lamellar bodies, and cytoplasmic staining for surfactant‐associated proteins. The number and proportion of type II cells in the airway epithelium were determined from low‐magnification EM of randomly selected sections obtained in different levels from >3 genotype‐identical lungs.…”

The influence of PM2.5 on lung injury and cytokines in mice

“…In addition, the morphological changes in type II alveolar epithelial cells and macrophages from the lungs were also observed by electron microscopy. The morphological features of type II alveolar epithelial cells include large nuclei and multiple vacuoles, and mitochondria and rough endoplasmic reticulum in the cytoplasm (31). The surfaces of macrophages were covered with multiple irregular folds, microvilli and pseudopods; the cytoplasm contained a large number of lysosomes, phagosomes and vesicles; and there were many microfilaments and microtubules near the cell membrane (32).…”