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S Simi

Publications and source records attributed to S Simi.

31 records · Page 2Linked to original sources
PubMed1990

Folate-sensitive fragile sites in Chinese hamster cell lines.

The expression of fragile sites in three different Chinese hamster cell lines was studied. Results showed that folate-sensitive fragile sites were expressed in the pericentromeric regions of chromosomes 1, 3, 4, 6, and 7 and in band 1q22. A comparison of the breakpoints involved in formation of chromosome rearrangements in some established Chinese hamster cell lines was also made. Results showed that while the specific type of rearrangement was random, the breakpoints were not. Three of the chromosomal sites most frequently involved in breaks were regions in which fragile sites were expressed.

Animals↗
PubMed1989

The distribution patterns of sister chromatid exchanges in V79 Chinese hamster cells: relevance to genotoxicity studies.

Sister chromatid exchanges (SCEs) are routinely used in genotoxic studies. The observations that some agents induce SCEs without altering the SCE distribution, while others disrupt such distribution, support the use of SCE distribution as a tool to distinguish between agents which damage DNA and agents which interfere with the replication machinery. In addition to that, it was found that compounds belonging to the latter group, are also able to induce gene amplification. Despite the mechanism by which the two phenomena could be associated is undefined, an aberrant induction of SCEs as a basis of gene amplification it must be taken into account.

Animals↗
PubMed1988

Qualitative analysis of chromosomal evolution in a colcemid-treated Chinese hamster population.

Colcemid is known to inhibit the spindle formation and to induce polyploidy and chromosomal nondisjunction. Using a V79 Chinese hamster cell line, we have shown that colcemid is able to induce the formation of cells that are numerically diploid but whose karyotype, when analyzed with the G-banding technique, differs from that of the untreated ones. Even though these cells have a normal chromosomal constitution, they carry alterations in the chromosomal balance and, consequently, in gene dosage. This could result in an abnormal expression of cellular genes or in the expression of new or preexisting recessive mutations, even in a diploid chromosomal constitution.

Aneuploidy↗
PubMed1988

Gene dosage mutants at adenine phosphoribosyltransferase locus induced by colcemid in Chinese hamster V79-AP4 cells.

Pseudodiploid Chinese hamster V79-AP4 cells, functionally diploid at the adenine phosphoribosyltransferase (aprt) locus, were treated with colcemid, a well-known aneuploidizing agent, under various experimental conditions. Aneuploid and tetraploid cells and variants resistant to 10 micrograms/ml of 2,6-diaminopurine (DAP), which selects for presumptive aprt+/- heterozygotes in the untreated cells, were induced. Many of the induced variants were hypotetraploid with three (rather than four) chromosomes carrying the aprt gene. Dot-blot and Southern analysis of the DNA of these clones confirmed that they had three copies of the aprt gene. Their APRT specific enzymatic activity was 60-80% of that of wild-type V79-AP4. The results of these and other experiments suggest that in these variants resistance to DAP is due to an altered aprt gene dosage and point to a possible genetic effect of colcemid and other aneuploidizing agents in somatic mammalian cells.

2-Aminopurine↗
PubMed1988

A genetic analysis of the adenine phosphoribosyl transferase locus in Chinese hamster V79-AP4 cells: relevance to mutagenesis studies.

The chromosomal location of the autosomal locus aprt has been investigated in the permanent Chinese hamster cell line V79-AP4 by standard somatic cell genetics methodologies. Aprt is functionally dizygous in V79-AP4 and the 2 alleles map on 2 chromosome 3 homologs, in agreement with the chromosome assignment of the gene in Chinese hamster primary cells. Chromosome G-banding and a Southern blot analysis of V79-AP4 DNA, using as a probe the cloned Chinese hamster aprt gene, have not revealed any structural alteration at either of the 2 aprt alleles. One of the chromosomes 3 has, however, a terminal deletion in its long arm and is therefore morphologically marked. These findings could make V79-AP4 an interesting cell system for the study of mutational mechanisms at the aprt locus in Chinese hamster.

2-Aminopurine↗
PubMed1987

Analysis by BrUdR-labelling technique of induced aneuploidy in mammalian cells in culture.

To study the origin of induced aneuploid cells, the BrUdR-labelling technique was applied to V79/AP4 Chinese hamster cells treated with colcemid or benomyl. In this way we were able to recognize the cells which had undergone one cellular division after the treatment since their chromosomes exhibited sister-chromatid differentiation. The results showed that the induced aneuploid cells can have either a few or numerous additional chromosomes depending on the concentrations of the drug. Moreover, it could be established that aneuploid cells with numerous additional chromosomes were obtained mainly when polyploid cells were also present in the treated population. This strongly suggests that the excess of additional chromosomes found in the aneuploid cells induced by the highest concentrations may be derived by disturbances of the whole mitotic apparatus rather than by a multiplicity of errors affecting individual chromosomes.

Aneuploidy↗
PubMed1985

Mitomycin C-induced mosaicism in C-band regions of human chromosomes 1, 9, 16, and Y.

In order to test the hypothesis that somatic mosaicism involving C-band polymorphism of human chromosomes 1, 9, 16 may arise from mitotic crossing over, peripheral blood lymphocytes from normal males were treated with mitomycin C, which is known to induce somatic crossing over in lower eukaryotes. Evidence is presented which shows that mitomycin C is able to alter the heterochromatic pattern in human lymphocytes.

Cells, Cultured↗
PubMed1982

C-band heterochromatin polymorphism of human chromosomes 1, 9, 16, Y.

Results are presented of a C-band investigation of the chromosomes 1, 9, 16, Y of two unselected populations from Central Italy and of 30 normal families. A high incidence of polymorphism was observed in these populations. Moreover, though the majority of the observed variants were inherited from parents to child in a Mendelian way, 3/30 children presented differences from the parental pattern. The results are discussed together with the data of other reports.

Adult↗
PubMed1982

Polymorphism of human chromosomes 1, 9, 16, Y: variations, segregation and mosaicism.

A study was carried out on C-banded chromosomes 1, 9, 16, Y from an unselected population and from 30 normal families. We found: a) great variability in length and position of the C-bands; b) somatic mosaicism involving C-bands; c) variants in children that were not present in parental patterns. The possible role of crossing-over in generating the last two phenomena is discussed.

Adult↗
PubMedDate not supplied

Superoxide anion production and toxicity in V79 cells of six hydroxy-anthraquinones.

This study investigates the cytotoxic and genotoxic effects of various carboxy AQ, 1,4-dihydroxy 6-carboxy AQ, 1,8-dihydroxy 3-carboxy AQ, 1,4-dihydroxy AQ, 1,5-dihydroxy AQ, 1,8-dihydroxy AQ and 2,6-dihydroxy AQ in V79 Chinese hamster cells. The V79 cells were used since, as they contain flavoproteins but not cytochrome P-450, they can bioactive xenobiotics only through the reductive pathway excluding the oxidative one. In addition, the abilities of AQs to stimulate O2-production using both purified flavoproteins (NADH-dehydrogenase, NADPH-cytochrome P-450 reductase) and V79 subcellular fractions (homogenate and microsomes) were assayed. The NADH and NADPH consumption stimulated by AQs in V79 microsomes was also determined. The results showed that the carboxylic-containing drugs and the 1,4-dihydroxy AQ were weak sister chromatid exchange inducers and the most toxic among the six anthraquinones examined. Dicumarol, a potent inhibitor of DT-diaphorase, reduced, rather than potentiated, both the cytotoxicity and genotoxicity caused by these AQs. Thus, the higher superoxide formation rates stimulated by the carboxylic-containing AQs compared to those of the other quinones with all the in vitro systems used, suggested, except for the 1,4-dihydroxy AQ, a possible relationship between cytotoxicity and O2-production. For the 1,4-dihydroxy AQ toxicity, a specific bioactivation route was hypothesized.

Animals↗
PubMedDate not supplied

Role of cytochrome P-450 isoenzymes in the bioactivation of hydroxy anthraquinones.

The reductive and the P-450-dependent oxidative bioactivation of various anthraquinones (AQs), 1-hydroxy AQ, 1,2-dihydroxy AQ, 1,4-dihydroxy AQ, 1,8-dihydroxy AQ, 1,2,4-trihydroxy AQ, 1,4-dihydroxy 6-carboxy AQ and 1,8-dihydroxy 3-carboxy AQ, were investigated using purified enzymes, subcellular fractions and four Chinese hamster V79 cell lines lacking and expressing cytochrome P-450 oxidative enzymes. The reduction of AQs performed by NADH-dehydrogenase, NADPH-cytochrome P-450 reductase, homogenates and microsomes of V79 cells, indicated that only the carboxy-containing drugs were fairly good superoxide anion stimulators. The P-450 dependent oxidation of AQs, assayed as NADPH consumption with microsomes and reconstituted enzymic systems, demonstrated that the P-450 1A1 and 1A2 were, as expected, the most active catalysts. However, they appeared to catalyze the formation of polyphenols rather than arene oxides or phenoxy radicals. Further support to the lack of generation of reactive intermediates during the oxidative metabolism of AQs came from the genotoxicity studies. In the three V79 cell lines expressing rat cytochrome P-450 1A1, 1A2 and 2B1, AQs did not significantly enhance the sister chromatid exchange induction above that elicited in the parental V79 line. Thus the present results, collectively taken, suggest that the P-450-mediated oxidation pathway plays a minor role in the bioactivation of AQs.

Animals↗