F. Palitti

Induction of sister-chromatid exchanges by procarcinogens in metabolically competent Chinese hamster epithelial liver cells

An epithelial cell strain has been established from the livers of male Chinese hamsters (CHEL cells). These cells, which proliferate in culture and retain their metabolic enzymatic activities during several subcultures, were used in a sister-chromatid exchange assay to evaluate the effectiveness of polycyclic aromatic hydrocarbons (PAHs), aflatoxin B1 (AFB1) and cyclophosphamide (CP). The results obtained demonstrate that CHEL cells are metabolically competent to activate different classes of procarcinogens into biologically active metabolites. Moreover, they showed a selective capacity to discriminate chemical carcinogens from noncarcinogens. Thus, the CHEL cell system appears to be a promising alternative to the short-term tests that include cell-free rodent liver homogenate to evaluate new promutagens and/or procarcinogens.

Inhibitors of DNA Topoisomerases and Chromosome Aberrations

The molecular mechanisms of formation of chromosomal damages (i.e., structural chromosome aberrations and sister chromatid exchanges) are not completely known. Operationally, chromosome aberrations are believed to be the result of DNA lesions induced by physical and chemical mutagens which, whether “misrepaired” or “misreplicated”, give rise to chromosomal damage (Evans 1968; Kihlman 1971; Bender et al. 1974; Natarajan et al. 1986).

Euploid segregation through multipolar mitosis in mammalian cell cultures

Cultures were made of kidney cells of male Rhesus monkey and a karyological analysis of these cells was carried out at various times after plating using the chromosome banding method of Seabringht (1972), in order to study the segregation phenomena which take place in cell cultures in vitro through multipolar mitoses and to identify segregating cells. — Several segregating cells were found: haploid cells, diploid cells with two X chromosomes and triploid cells which were strictly euploid. Polyploidization-segregation cycles in the cell cultures and their mechanism and chronological sequence were analyzed. — On the basis of these results it was suggested that the genome is organized in haploid sets capable of segregating as units and of producing strictly euploid segregating daughter cells.

Banding patterns of the chromosomes of the Rhesus monkey (Macaca mulatta)

Abstract The Rhesus monkey ( Macaca mulatta ) has 21 pairs of chromosomes, many of which can easily be confused with one another by the traditional staining methods. By using the method of banding with trypsin (Seabright, 1971) we have been able to characterize the various pairs of homologous chromosomes and we have classified them by following the criteria adopted by Rothfels & Siminovich (1958) . The evolutionary meaning of the results are discussed.

Chromosome Studies on Polyploid Cell Strains of Chinese Hamster V: Banding Pattern

SUMMARYThe authors have examined the « banding pattern », revealed by the Seabright method (1972), of chromosomes of an aneuploid-diploid line (C-125) and of certain lines of various degrees of ploidy derived from it. It was found that the line C-125 has preserved a large proportion of normal chromosomes, similar to those of the species, some in a diploid and others in a haploid condition.Analysis of the degree of homology of the chromosomes confirmed that, in the derived polyploid lines, part of the genome is in a triploid condition (Oliveri et al. 1972) even if in some cases only parts of the chromosome are in a triploid condition as a result of deletions. This last type of chromosome rearrangement is the one that has had the greatest importance in the evolution of the karyogram of the induced polyploid lines. The results are discussed in relation to problems of « dosage compensation ».

Effects of actinomycin D and puromycin on colchicine-induced endoreduplication in chinese hamster cells in vitro

Experiments were carried out to study the events through which the process of endoreduplication occurs after treatment with colchicine in Chinese hamster cells cultivated in vitro, and to analyse the differences between the processes leading to normal mitosis and those leading to endoreduplication. Chinese hamster cells (line C-125) were treated with colchicine (10(-4) M) for 1 h, in order to induce endoreduplication. Before and after colchicine treatment the cultures were treated at various intervals with actinomycin D and puromycin. For preparation of mitosis specific RNA synthesis is required, and also synthesis of a specific protein, which is not required for endoreduplication. Moreover this suggests not only that the cells that endoreduplicate do not need new RNA and protein synthesis, but that inhibition of their synthesis apparently favours the processes of endoreduplication.

Chromosome Constitution of in vitro Segregated Haploid and Diploid Cells of the Mouse

The composition in segregated haploid sets of paternal and maternal chromosomes has been studied in order to verify whether their composition is uniparental of mixed, fixed or variable. Primary cultures where prepared using kidneys from hybrids of strains of Mus musculus in which the parental chromosomes are distinguishable; the maternal set consists of 20 teleocentric chromosomes, the paternal set of 9 metacentric chromosomes, derived by Robertsonian fusion and 2 telocentrics. Applying Seabrights banding technique, an analysis of segregated haploid and diploid cells, which have originated spontaneously through polyploidisation-segregation processes was carried out. It was concluded that the haploid sets have a variable composition of paternal and maternal chromosomes.

Chromosome Segregation in Mammalian Cells Cultivated in Vitro: Induction of Diploid Tripolar Mitosis in Chinese Hamster Cells

SUMMARYWe have tried to develop a method of induction of a high frequency of multipolar mitosis in mammalian cells cultivated in vitro to realize the segregating processes necessary to complete parasexual cycles in mammalian and human cells in vitro; and, from another point of view, to deal with the study of the role of multipolar mitosis in inducing the caryological variability in a proliferating cellular population, in relation to the problem of the arise of tumours.Cultures of Chinese Hamster cells (line C-125) were treated with 5-aminouracyl (5-AU) 0,5 mg/ml for 24 hours, then with β-mercaptoethanol (β-ME) 0,1%, benzymydazol (BI) 0,5 mg/ml or pheniluretan (PhU) saturated solution at 25°C tenfold diluited. Tripolar mitosis were obtained by all the treatments, but the higest yield (25–30%) was obtained by the treatment 5AU+PhU.We have, hence studied the capacity of surviving and proliferating of the segregating cells produced by tripolar mitosis; therefore, 2 days after the treatment 5AU + PhU, the cult...

Banding Patterns in the Chromosomes of Macaca Mulatta

Abstract La scimmia Rhesus (Macaca mulatto) ha 21 coppie di cromosomi, molti dei quali sono facilmente confondibili tra loro con i tradizionali metodi di colorazione. Utilizzando il metodo di bandatura dei cromosomi con tripsina (Seabright, 1971), siamo riusciti a caratterizzare le varie coppie di omologhi e le abbiamo classificate seguendo i criteri di Rothfels e Siminovich (1958).