Unbuffered osmium staining of cell organelles: alterations induced by cell injury

We have studied the localization of osmium reduction products to investigate the functional state of organelles as well as organelle interrelationships during cell injury. In normal hepatocytes osmium deposits of variable intensity are seen in nuclear envelope, endoplasmic reticulum. Golgi cisternae and vesicles and lysosomes. Buffering of osmium with s- collidine (pH 7.4) prevents the deposition of osmium. Reversible (30 min) and irreversible (60 min) ischemia without reflow causes no change in the pattern of osmium deposition. Irreversible ischemia followed by reflow causes decreased staining of endoplasmic reticulum (ER) and redistribution of the osmium deposits through the cytoplasm. Reversibly injured pancreatic acinar cells in cultured explants manifest a similar loss of osmium staining in the endoplasmic reticulum cisternae. The administration of antimicrotubule drugs induces an accentuation of osmium staining in localized cisternal elements of hepatocytes. These heavily stained cisternae appear to give rise to the bounding membranes of drug-induced autophagic vacuoles. Cytoplasmic organelles sequestered inside the autophagic vacuoles acquire intense staining when they begin to undergo degradation. In homogenized liver tissue all the subcellular organelles show osmium deposits. The deposits are preferentially localized along the organelle membranes. In particular the dense deposits in the ER lumen are not seen in the subcellular fractions. Phospholipase A2 (3 units/mg protein) enhances the deposition of osmium in the lumen of microsomal vesicles, whereas the presence of detergent has no such effect. Addition of EDTA to the homogenizing medium enhances the ultrastructural preservation of the subcellular fractions but has little effect on the deposition of osmium. OsO4 deposition occurs at acid pH and the intensity and pattern of the stain can be modified in vivo and in vitro. Osmium tetroxide deposition is induced at sites of membrane transformation (autophagic vacuoles) and degradation (lysosomes). Calcium influx and phospholipase activation (ischemia, tissue homogenization, phospholipase addition) enhance osmium deposition and/or influence the localization of the staining pattern.

The localization of thiamine pyrophosphatase activity in Meckel's cartilage cells during endochondral ossification

The cytochemical distribution of thiamine pyrophosphatase (TPPase) activity in Meckel's cartilage cells of the mouse embryo has been studied during the endochondral ossification. All the cartilage cells contain reaction product within the Golgi apparatus. In immature chondrocytes, at the reserve cell zone, TPPase activity is restricted to several inner cisternae of independent Golgi apparatus. In mature cells at the proliferative cell zone, several Golgi complexes form a Golgi network connecting with each other by the TPPase positive tubular stalks. Golgi cisternae, condensing vacuoles and vesicles also contain reaction product. In the hypertrophic chondrocytes located in the calcifying zone, their disorganized Golgi apparatus still retain reaction product. Some chondrocytes, even those located within calcified or opened lacunae, exhibit intact structures and normal cytochemical enzyme distribution. These data indicate the possibility that some chondrocytes may survive and contribute the formation of mandible.