Studies of Euglena gracilis in aging cultures II. Ultrastructure

Open Access
Publisher Website
Google Scholar
Abstract
The manifestations of age-related changes in cellular systems often are not readily identificable, although at the ultrastructural level there are sites in certain organelles that may be indicative of such changes, e.g., the lysosome system, microbodies, mitochondria, plasma membrane, other membrane systems and cytoplasmic vacuoles. In this study, cytochemistry and electron microscopy reveal a number of age-related changes in the unicellular euglenoid alga, Euglena gracilis “Z”. The use of modified Gomori technique shows change in latency in acid phosphatase with age in the lysosome system, formation of secondary lysosomes, coalescence with other vacuoles which results in alteration of size and matrix composition. The microbodies increase in size and peroxidative activity, particularly at the subpellicular regions as revealed by DAB/H2O2 tests. Modification of temperature and pH conditions of DAB medium produces a decrease in presumptive cytochrome oxidase activity in the mitochondria. With increasing time, lysis and subsequent fragmentation of the mitochondrial reticulum occurs. Ruthenium red labelling suggests a decrease in acid mucopolysaccharides at the outer surface of the plasma membrane. Other observable subcellular changes include the appearance of myelin figures, accumulation of lipofuscin-like pigments and lipid bodies, increase in vacuolisation and autolysis of certain organelles. All of the above are part of the biological process of focal cytoplasmic degradation (FCD), which involves the general deterioration of the lipoprotein complex structure of the cell.