Paolo Perticone

MECHANISMS OF FIXATION AND ACCUMULATION OF CENTRIC FUSIONS IN NATURAL POPULATIONS OF MUS MUSCULUS L. I. KARYOLOGICAL ANALYSIS OF A HYBRID ZONE BETWEEN TWO POPULATIONS IN THE CENTRAL APENNINES

Chromosomal mutations causing partial sterility of the heterozygote are decisive in speciation processes in animals of limited vagility (e.g., Orthoptera and small mammals). In this regard the stasipatric speciation model (production of a heterozygous mutant, fixation in a small colony and subsequent spread of the homozygous mutant population) was proposed (see White, 1968, 1973, 1975, 1977), as opposed to the hypothesis of allopatric speciation (e.g., Key, 1974). Rodents offer several suitable characteristics for this type of study: 1) A variety of chromosomal rearrangements are involved: pericentric inversions, as in Spalax (Soldatovic and Savic, 1967; Wahrman et al., 1969; Lay and Nadler, 1972), Thomomys (Patton and Dingman, 1970), Perognathus (Patton, 1969), Peromyscus (Hsu and Arrighi, 1968) and, above all, centric fusions-and to a lesser extent, fissions-in Spalax (Wahrman et al., 1969; Lay and Nadler, 1972), Thomomys (Thaeler, 1968a; Nevo et al., 1974), Perognathus (Patton, 1969), Gerbillus (Wahrman and Gourevitz, 1973), Acomys (Wahrman and Goitein, 1972), Geomys (Selander et al., 1974) and Leggada (Matthey, 1970). 2) Different steps in the speciation process are evident: among different species of the same genus, among sibling species, among incipient species and among interbreeding populations. In Thomomys (Thaeler, 1968a, 1968b; Patton and Dingman, 1970;

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.

Effect of l-ethionine on spontaneous and MMC-induced SCEs in G0 and G1 human lymphocytes under liquid-holding recovery conditions

L-Ethionine is an ethyl analogue of the amino acid, methionine, well known as a carcinogen but not as a mutagen. Its activity is clearly related to its capacity to hypomethylate DNA and RNA. At a final concentration of 5 mM, L-ethionine completely inhibits DNA synthesis in PHA-stimulated human lymphocytes, probably acting on a methylation reaction critical for the initiation of the S phase. This block can be reversed. Utilizing this capacity of L-ethionine to block cell proliferation, we have studied the influence of G0 and G1 repair of premutational damage (PMD) (equivalent to liquid-holding recovery in bacteria) on spontaneous and MMC-induced SCEs in human lymphocytes. Our results clearly show that L-ethionine in our experimental conditions significantly increases the frequencies of spontaneous and MMC-induced SCEs. In view of the hypomethylating activity of the analogue, we hypothesize that this action at the replication fork level may increase the error-prone ligation of unrepaired lesions, thus influencing the frequency of occurrence of SCEs.

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.

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).