Polyribosome disaggregation

The relative importance of hepatic microsomal lipid peroxidation versus covalent binding of carbon tetrachloride-derived radicals has been the subject of considerable debate. Since cytochrome P-450 loss has been shown to be related to lipid peroxidation and to covalent binding, each in the absence of the other, both of these early consequences of carbon tetrachloride metabolism may contribute to P-450 destruction. Nevertheless, it is still not clear how these initial events are related to subsequent triglyceride accumulation, polyribosomal disaggregation, depression of protein synthesis, cell membrane breakdown and eventual death of the hepatocytes. Carbon tetrachloride... 

Sparsomycin, a sulfur-containing antibiotic, inhibits protein synthesis in mammalian and bacterial cells. Tryptophan administration before or after sparsomycin did not affect the hepatic polyribosomal disaggregation or the decreased protein synthesis due to sparsomycin.188 A possible explanation for the lack of effect by tryptophan may be due to sparsomycin s ability to cause fall-off ribosomes, which are defective as indicated by the decreased formation of polyphenylalanine when assayed in vitro with poly(U).207... 

Sidransky, H., Vemey, E., and Murty, C.. N., Effect of tryptophan on hepatic polyribosomal disaggregation due to hypertonic sodium chloride, Lab. Invest., 34, 291, 1976. 

Sarma, D. S., Reid, I. M., Verney, E., and Sidransky, H., Studies on the nature of attachment of ribosomes to membranes in liver. I. Influence of ethionine, sparsomycin, CC14, and puromycin on membrane-bound polyribosomal disaggregation and on detachment of membrane-bound ribosomes from membranes, Lab. Invest., T7, 39, 1972. 

Compared with some of the other mycotoxins such as aflatoxin, the trichothecenes do not appear to require metabolic activation to exert their biological activity.50 After direct dermal application or oral ingestion, the trichothecene mycotoxins can cause rapid irritation to the skin or intestinal mucosa. In cell-free systems or single cells in culture, these mycotoxins cause a rapid inhibition of protein synthesis and polyribosomal disaggregation.35 47 50 Thus, we can postulate that the trichothecene mycotoxins have molecular capability of direct reaction with cellular components. Despite this direct effect, it is possible to measure the toxicokinetics and the metabolism of the trichothecene mycotoxins. 

The liver and kidneys are subjected to severe damage from tannin ingestion and injection (Price and Butler, 1980 Vohra et al., 1966). At cellular and biochemical levels, injection of tannic acid can cause liver fibrosis and necrosis, polyribosome disaggregation, inhibition of microsomal enzymes, and synthesis of nucleic acid and protein (Badawy et al., 1969 Reddy et al., 1970 Oler et al., 1976). 

Reddy, K.J., Chiga, M., Harris, C.C., and Svoboda, D.J., 1970, Polyribosome disaggregation in rat liver following administration of tannic acid. Cancer Res., 30 58. 

Reid, I. M., Shinozuka, H., and Didransky, H., 1970, Polyribosomal disaggregation induced by puromycin and its reversal with time. Lab. Invest. 23 119. 

Siegel, F.L., Aoki, K. and Colwell, R.E. (1971), Polyribosome disaggregation and cell-free protein synthesis in preparations from cerebral cortex of hyper-phenylalaninaemic rats. J. Neurochem., 18,537. 

Once inside the coil, virulent viruses turn off cellular macromolccular synthesis and disaggregate cellular polyribosomes, thus favoring a shift to viral synthesis. These viruses cause the ultimate destruction of the infected cell. In contrast, moderate viruses may stimulate host DNA, ntRNA, and protein synthesis—a phenomenon which may be of considerable importance in viral carcinogenesis. 

Many reports years ago dealt with the toxic effect of carbon tetrachloride on the liver of experimental animals.182 183 Among the biochemical changes in the liver following the administration of carbon tetrachloride are disaggregation of hepatic polyribosomes and inhibition of hepatic protein synthesis.184-186... 

Aoki, K. and Siegel, F. L., Hyperphenylalaninemia Disaggregation of brain polyribosomes in young rats, Science, 168, 129,1970. 

Sydiskis, R. J., and Roizman, B., 1967, The disaggregation of host polyribosomes in productive and abortive infection with HSV, Virology 32 678. 

Pathogenic vimses, either DNA or RNA, shut olf cellular protein synthesis and disaggregate cellular polyribosomes so that the host cell processes are shifted exclusively to viral synthesis. A general sequence of events can be observed during viral replication ... 

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