Focal cytoplasmic degradation

Liver biopsies taken from 15 workers at a polyvinylchloride producing plant - dependent on the duration of exposure - showed focal hydropic swelling of the hepatocytes, disseminated toxic steatosis, ample hpofuscin deposits, paracrystalline inclusions in enlarged mitochondria, focal cytoplasmic degradation, and occasionally necrotic cells (SCHATTENBERG et al. 1977). 

Among organelles, microbodies have an unusually short half life 1 to 5 days or about /lo of that of mitochondria. The reasons for the rapid turnover of microbodies are not known. The enzymes found in microbodies are synthesized in the endoplasmic reticulum. The mechanism of transfer of the enzymes from endoplasmic reticulum to microbodies has not been discovered. In view of their rapid turnover, microbodies must constantly be eliminated from the cell. Although entrapment in areas of focal cytoplasmic degradation is certainly involved, it appears that other still unknown mechanisms of degradation exist. 

Ultrastructural studies on spleen biopsies of the Gaucher cell have shown the presence of ovoid, irregular cytoplasmic bodies, which correspond to the stria-tion described by the light microscopist (see Fig. 3-35). Degenerate mitochondria were found in close association with these bodies, and it was postulated that the accumulating material was in some way derived from mitochondria. Vesicles of the endoplasmic reticulum were also present in these areas, and the possibility that the lipoid material was incorporated in areas of focal cytoplasmic degradation was not excluded [120]. 

In conclusion, it cannot be excluded that the surrounding of the storage material by membranes results from their segregation in a process akin to focal cytoplasmic degradation (see chapter on necrosis) and is a secondary, rather than a primary, event of the disease [224]. 

After the induction of endoplasmic reticulum membranes and enzymes, enzymes and membranes disappear when the inductive stimulus is withdrawn. The enzyme disappears faster than the membrane, but focal cytoplasmic degradation does not develop, suggesting that the lysosomal hydrolases are not likely to be involved in discrete turnover of the endoplasmic reticulum [80]. 

The autophagic function is performed in autophagic vacuoles consisting of a cytoplasmic area surrounded by a membrane, where mitochondria, fragments of endoplasmic reticulum, etc., are degraded. Considerable experimental data indicate that lysosomal enzymes take part in this focal autolysis. It is not clearly understood how the hydrolases reach the vacuoles, but in some cases fusion may occur between a lysosome and a vacuole containing the cellular component to be digested. 

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