trixes contain many hydrolytic enzymes that are optimally active at an acidic pH. The intralysosomal environment is maintained at pH 4.5 by membrane-integrated H -ATPase. Lysosomes receive extracellular macromolecules through the endocytic transport system. Intracellular proteins are sequestered into lysosomes via autophagocytosis. A variety of lysosomotropic amines have been employed to analyz...

Endosomal density changes in cell-free systems The mechanism by which dense lysosomes are generated in animal cells has been the subject of intense research and speculation (for reviews, see [ 1-31). Despite much progress in understanding the biosynthesis and trafficking of lysosomal enzymes, the internalization of ligands and solutes and the sorting of receptors and other molecules that are re...

Lysosomes are organelles that support diverse cellular functions such as terminal degradation of macromolecules and nutrient recycling. Additionally, lysosomes can fuse with the plasma membrane, a phenomenon referred to lysosomal exocytosis, release their contents, including hydrolytic enzymes cargo proteins. Recently, neuronal activity has been shown induce exocytosis in dendrites axons. Secre...

Delivery of endocytosed macromolecules to lysosomes occurs by means of direct fusion of late endosomes with lysosomes. This has been formally demonstrated in a cell-free content mixing assay using late endosomes and lysosomes from rat liver. There is evidence from electron microscopy studies that the same process occurs in intact cells. The fusion process results in the formation of hybrid orga...

The interactions between the L. pneumophila phagosome and monocyte lysosomes were investigated by prelabeling the lysosomes with thorium dioxide, an electron-opaque colloidal marker, and by acid phosphatase cytochemistry. Phagosomes containing live L. pneumophila did not fuse with secondary lysosomes at 1 h after entry into monocytes or at 4 or 8 h after entry by which time the ribosome-lined L...

1. The activities of lysosomal enzymes in the cortexes and medullas and the principal subcellular fractions of rat kidney were measured. 2. A method is described for the isolation of rat-kidney lysosomes and a detailed analysis of the enzymic composition of the lysosomes is reported. Enzyme analysis of the other principal subcellular fractions is included for comparison. 3. Studies of the distr...