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Biomedical subjects

T Mariani

Publications and source records attributed to T Mariani.

At least 19 recordsLinked to original sources
PubMed1994

Longitudinal patterns similar to G-banding in untreated human chromosomes: evidence from atomic force microscopy.

The structure of human metaphase chromosomes, fixed according to standard procedures for optical microscopy but not treated for banding, was examined by atomic force microscopy (AFM). The images show that chromosomes display a banding pattern very similar to G-banding, detected by the AFM as a variation in the thickness of chromatin. This similarity allows the identification of individual chromosomes.

Chromatin↗
PubMed1994

An atomic force microscope for cytological and histological investigations.

An atomic force microscope (AFM) specifically designed for cytological and histological studies and able to operate on the same scale of the highest optical magnification is described. The AFM is a non-invasive instrument; it operates on samples which do not require any kind of treatment and it can produce information that supplements and completes the information given by traditional microscopical methods. The apparatus has been used to image fixed human chromosomes and to investigate the action of trypsin during the staining for banding. First results showed that banding patterns very similar to G-banding pre-exist to staining and to trypsin treatment in human metaphase chromosomes, and that the trypsin treatment induces a structural collapse in the chromatin. The instrument was also used on thin sections of plant tissue and gave promising results. Experience confirmed that AFM is a suitable tool for this kind of investigation, and proved the importance of developing AFM microscopes specifically designed for routine use in cytology and histology, conceived for non-specialized users.

Chromosome Banding↗
PubMed1993

Analysis of electroporation-induced genetic damages in V79/AP4 Chinese hamster cells.

Electroporation is a recent technique used to introduce exogenous DNA into eukaryotic cells. It is important to establish that the gene of interest is transferred into a functional, non-mutated recipient cell. V79/AP4 Chinese hamster cells were exposed to high-voltage pulsed electric fields and some biological and genetic effects were measured. The results showed that cytotoxicity was related in a dose-dependent manner to the number of applied pulses. Thioguanine-resistant colony-forming cells as well as chromosomal aberrations were also induced whereas ouabain resistants and sister-chromatid exchanges were not or slightly induced. Spontaneous and electroporation-induced clones that were phenotypically TGR/HATS were used to investigate the hprt locus. Molecular screening of the locus showed that the number of deleted exons was significantly higher in induced than in spontaneous TG-resistant clones, suggesting that the genetic damages induced by electroporation concern the loss of regions well over the size of the hprt locus.

Animals↗
PubMed1993

Accumulation of anchorage independent cells showing amplified genes (CAD) during the in vitro propagation of CHEF18 Chinese hamster cells.

Anchorage independence and gene amplification have frequently been associated with a transformed or tumorigenic phenotype in cultured mammalian cells. However, it is unknown whether these two traits occur as related events during transformation, or are independent features of the transformed phenotype. To clarify this point, immortalized, untransformed CHEF18 Chinese hamster cells were propagated in culture until they became transformed and tumorigenic. The frequencies with which CHEF18 cells formed colonies either in soft agar, in medium containing N-phosphonacetyl-L-aspartate or in the two selective media simultaneously, were determined. The results indicate that anchorage independence and CAD gene amplification spontaneously arose during the propagation of the cells and that their concurrent emergence was not the consequence of independent events. However, the kinetics of their appearance suggests that anchorage independence is the early event whereas gene amplification might represent one of the numerous events which can be dynamically selected in anchorage-independent cells.

Animals↗
PubMed1992

Responsiveness of tumorigenic and non-tumorigenic CHEF18 Chinese hamster cells to 1-beta-D-arabinofuranosylcytosine treatment.

In cultured mammalian cells, sister chromatid exchanges are easily induced by agents that perturb the scheduled timing of DNA replication. In this work a blockage of DNA synthesis induced by 1-beta-D-arabinofuranosylcytosine was applied to non-tumorigenic and tumorigenic CHEF18 Chinese hamster cells, and their responsiveness was compared. The data show that both the induction of sister chromatid exchanges and the reduction of the colony-forming ability were less extensive in non-tumorigenic than in tumorigenic CHEF18 cells. The results suggest that a tight control of the scheduled timing of DNA replication is present in non-tumorigenic CHEF18 cells and perhaps this feature avoids the generation of those chromosomal structures that are responsible for the abnormal induction of sister chromatid exchanges and for the elevated cytotoxicity seen in tumorigenic cells.

Animals↗
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

Fragile sites and statistics.

A simple and reliable statistical method is proposed to distinguish real fragile sites from the casual accumulation of aberrations that can occur as a consequence of random distribution. It is based on a study of the expected random distribution, assumed to be equal to a Poisson distribution, with the expected value of events per band as the mean.

Chromosome Fragile Sites↗
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

Multiple congenital anomalies associated with apparently normal maternal intake of vitamin A: a phenocopy of the isotretinoin syndrome?

The teratogenicity of vitamin A has been repeatedly reported in the literature and confirmed on the basis of several cases of adverse pregnancy outcome associated with maternal isotretinoin exposure. We report a case which shows a striking similarity with this syndrome, but the child was born to a mother who took a normal supplementation of vitamin A during pregnancy. The differential diagnosis is discussed.

Abnormalities, Drug-Induced↗
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↗
PubMed1984

Inhibitors of DNA synthesis induce sister chromatid exchanges at the early S phase of the cell cycle.

To investigate the origin of sister chromatid exchanges (SCEs) induced by inhibitors of DNA synthesis, V79/AP4 Chinese hamster cells were treated with aphidicolin, 1-beta-D-arabinofuranosylcytosine, and thymidine. At the end of the treatments we determined both the distribution of the cells in the various phases of the cell cycle and the induction of SCEs. Our data indicate that the cells that were replicating their DNA were arrested at various stages of the S phase. By analyzing the patterns of SCE distribution, we found that the metaphases of the treated cells exhibited either "normal" or enhanced levels of SCEs. Our results suggest that the inhibitors of DNA synthesis induce SCEs in the cells in early S phase probably by activation of potential replicative origins.

Animals↗
PubMed1982

Effect of cocultivation on the levels of spontaneous and induced sister chromatid exchanges in Chinese hamster cells.

The level of sister chromatid exchanges, both spontaneous and induced by UV light or ethylmethanesulphonate (EMS), in Chinese hamster V79/AP4 cell line, is partially reduced upon cocultivation with human cells. Normal and xeroderma pigmentosum (XP) cells are equally effective. On the basis of these observations, cocultivation may represent a good tool for investigating the SCE's formation processes.

Animals↗
PubMed1982

Thioguanine resistance, ouabain resistance and sister chromatid exchanges in V79/AP4 Chinese hamster cells treated with potassium dichromate.

The biological activity of potassium dichromate (K2Cr2O7) was assayed in V79/AP4 Chinese hamster cells by measuring two mutational end points, thioguanine (TG) resistance and ouabain (OUA) resistance, and two non-mutational end points, cytotoxicity and sister chromatid exchanges (SCE). By exposing the cells for 1 h to the chemical, all biological end points examined were affected by the treatment in a dose-dependent manner. Moreover the combined use of the two selective systems indicated that chromium induces base-pair substitutions in mammalian cells in culture.

Animals↗