Transglutaminase activity and subcellular distribution have been examined in both normal and tumour tissue. Subcellular fractionation of rat liver demonstrated a bimodial distribution for transglutaminase between the particulate (approximately 40%) and cytosol (approximately 60%) fractions. Isolation of enriched plasma membrane fractions indicated the presence of membrane associated transglutaminase activity which co-distributed with that of 5'-nucleotidase and Na+/K+-ATPase. Induction of hepatocellular carcinomas in rats by treatment with either diethylnitrosamine or 6-p-dimethylaminophenylazobenzothiazole resulted in a reduction in transglutaminase activity which was accompanied by redistribution of the enzyme to the particulate fraction of the cell. The tumour bearing liver appeared to represent an intermediate stage between the hepatocellular carcinoma and control liver when assayed for content and distribution of transglutaminase activity. The transglutaminase activity of four transplantable rat sarcomas (P7, P8, MC3 and CC5) was found to be greatly reduced when compared with the normal tissues of rat liver, lung and spleen. A further reduction in this activity occurred in the primary growths of the sarcomas P7 and P8 following detection of metastases. Our data suggest that such changes in the distribution and content of transglutaminase may be a feature of tumour tissue and may be of value in both monitoring and investigating the carcinogenic process.
The chromosomes of Platynereis dumerilii (Audouin & Milne-Edwards) are described here for the first time. A modal chromosome number of 2n=28 was recorded, based on counts conducted on metaphase spreads prepared from 24-h-old larvae. The karyotype comprises seven pairs, each of relatively large median (arm ratio, p/q=l.00–0.59) and submedian (arm ratio, 0.59–0.33) chromosomes. Attempts were also made to band the chromosomes using C-banding and silver staining methods. C-band-positive regions were localized on four chromosome pairs (three median, one submedian). A further two chromosome pairs (both median) were observed to have terminal nucleolar organizer regions (NORs). To our knowledge, this is the first time that these banding methods have been successfully applied to any polychaete species. These results are discussed in relation to the karyotypic variation within the class Polychaeta, and the family Nereidae in particular. A stable karyotype consisting of a moderate number of large and morphologically well-differentiated chromosomes, coupled with the ease of culture under laboratory conditions and short generation time, suggests that P. dumerilii is a potentially suitable model for evaluating marine contaminants for genotoxic activity.
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