Three cases of minor chromosomal aberrations discovered by prenatal chromosome determination

Summary A case of pronounced secondary constriction of a chromosome belonging to pair No. 9, a case of deletion of the short arms of one of the chromosomes in pair No. 13, and a case of partial trisomy of the distal portion of a chromosome in pair No. 14 were discovered by prenatal chromosome determination. Analysis of the parents' karyotypes enabled the clinical importance of the three different chromosomal aberrations to be elucidated.     

Interphase chromosome positioning affects the spectrum of radiation-induced chromosomal aberrations

In interphase, chromosomes occupy defined nuclear volumes known as chromosome territories. To probe the biological consequences of the described nonrandom spatial positioning of chromosome territories in human lymphocytes, we performed an extensive FISH-based analysis of ionizing radiation-induced interchanges involving chromosomes 1, 4, 18 and 19. Since the probability of exchange formation depends strongly on the spatial distance between the damage sites in the genome, a preferential formation of exchanges between proximally positioned chromosomes is expected. Here we show that the spectrum of interchanges deviates significantly from one expected based on random chromosome positioning. Moreover, the observed exchange interactions between specific chromosome pairs as well as the interactions between homologous chromosomes are consistent with the proposed gene density-related radial distribution of chromosome territories. The differences between expected and observed exchange frequencies are more pronounced after exposure to densely ionizing neutrons than after exposure to sparsely ionizing X rays. These experiments demonstrate that the spatial positioning of interphase chromosomes affects the spectrum of chromosome rearrangements.     

Rapid prenatal diagnosis of numerical aberrations of chromosome 21 and 18 by PCR-STR method

In this study we reported the results for the first time of applying Polymerase Chain Reaction-Short Tandem Repeats (PCR-STR) method in the field of detection of aneuploidies for chromosomes 21 and 18 in Croatians. The aims of the study were: (I) validation of the diagnostic informativeness of 6 STR loci (D18S51, D18S858, D18S535, D21S1435, D21S1411, and D21S1414) in sample of 205 unrelated healthy individuals; (II) evaluation of diagnostic power of the PCR-STR method for those 6 microsatellites; (III) establishment protocol for use STRs as routine method for rapid prenatal detection of trisomy 21 and 18. DNA samples were amplified by fluorescence-based PCR reaction, subjected to electrophoresis in automated laser fluorescence DNA sequencer (ALFexpress). Results of our study were: (I) all 6 tested loci are informative (68-85% of heterozygous individuals); (II) comparison between PCR-STR method and conventional cytogenetics did not revealed any false positive or false negative results; (III) in prenatal screening of 105 samples of uncultured amniotic fluid 6 (5.7%) samples with chromosomal abnormalities were identified.     

Numerical chromosomal aberrations of chromosome 1 and 7 in dysplastic cervical smears

Cervical smears with Papanicolaou's staining (PAP) reveal only morphological characteristics of epithelial cells of the cervix uteri. Since chromosomal aberrations are known to play a role in malignant transition, we analyzed cervical smears for numerical changes of the chromosomes 1 and 7 with fluorescence in-situ hybridization to probe for a diagnostic value of these chromosomes in the characterization of cervical dysplasia. Cervical smears were collected from 21 patients with suspect histology of curettage or biopsy specimen, 14 of them having been subsequently graded as cervical intraepithelial neoplasia (CIN) III and 5 as CIN II. Nineteen normal cervical smears (PAP I-II) served as controls. Smears were hybridized with chromosomal enumeration probes for chromosome 1 and 7. Disomic cells (2 copies of chromosome 1 and 7) were decreased in the CIN II (63%) and CIN III group (57%) with respect to the control group (77%). Cells with 3 signals for chromosome 7 were significantly more frequent in the CIN III and the CIN II group than in the control group (6.7, 6.4 and 0.7%, respectively). Only the CIN II group (10%), but not CIN II (6%), showed a significant trisomy for chromosome 1 as compared with the controls (3.8%). A close correlation between the incidence of trisomy 1 or 7 and PAP grading was observed. PAP III-IIID smears with high trisomy 1 counts corresponded to CIN III histology, while all CIN II patients were PAP III-IIID with low incidence of trisomy 1. We conclude that trisomy of chromosome 7 is a feature of cervical dysplasia and seems to be an early event in dysplastic transition. In contrast, trisomy of chromosome 1 is observed only in high grade dysplasia and may be a marker for pre-malignant lesions.     

High frequency of chromosome aberrations induced by DEB with caffeine posttreatment in Vicia faba var. minor

Summary In root tips treated with DEB and caffeine as a posttreatment aberration yield was almost four times higher than after DEB alone. Caffeine applied in simultaneous treatment with DEB was less effective.     

Experimentally induced chromosome aberrations in plants. I. The production of chromosome aberrations by cyanide and other heavy metal complexing agents

The finding of Lilly and Thoday that potassium cyanide produces structural chromosome changes in root tips of Vicia faba was confirmed. Like mustards, diepoxides, and maleic hydrazide, potassium cyanide seems to act on cells at early interphase. A tendency of cyanide breaks to be concentrated in heterochromatic segments of the chromosomes was evident. The production of chromosome aberrations by cyanide proved to be practically unaffected by the temperature during treatment. In agreement with Lilly and Thoday, the effect of potassium cyanide was found to be dependent on oxygen tension during treatment. The effect of potassium cyanide increases with increasing oxygen concentration up to 100 per cent oxygen. In the absence of oxygen, potassium cyanide was not completely inactive, but produced a low, though significant frequency of aberrations. Pretreatments with 2.4-dinitrophenol did not influence the effect of potassium cyanide. When bean roots were treated with potassium cyanide before a treatment with 8-ethoxycaffeine, or at the same time as they were treated with 8-ethoxycaffeine, the effect of 8-ethoxycaffeine was almost completely suppressed. The effects of a number of other heavy metal complexing agents were also tested. Sodium fluoride, potassium thiocyanate, carbon monoxide, o-phenanthroline, 2.2-bipyridine, and sodium azide were without radiomimetic effect under the conditions employed, and so was a mixture of sodium azide and sodium fluoride. A low, but quite significant, radiomimetic effect was obtained after treatments with sodium diethyldithiocarbamate, cupferron, and 8-hydroxyquinoline. Under anaerobic conditions, the effects of cyanide and cupferron were both quantitatively and qualitatively indistinguishable. Unlike the effect of cyanide, the effect of cupferron was not enhanced by the presence of oxygen. The effects of the same heavy metal complexing agents were tested on the activities of the enzymes catalase and peroxidase. The activities of both of these enzymes were found to be totally inhibited only by potassium cyanide. In the other cases, little correlation was found between ability to inhibit the activities of these enzymes and ability to produce chromosome aberrations. In a number of experiments, hydrogen peroxide was found to be without radiomimetic effect, whether alone or in combination with potassium cyanide. t-Butyl hydroperoxide proved to be active. The effect of t-butyl hydroperoxide was substantially increased by pretreatments with 2.4.-dinitrophenol. The results are discussed, and it is concluded that the observations made do not support the hypothesis that hydrogen peroxide is involved in the production of chromosome aberrations by potassium cyanide. The possibility that organic peroxides are involved cannot be excluded on the bases of the experimental results. As an alternative hypothesis, it is suggested that iron or other heavy metals are present in the chromosomes and that cyanide and other heavy metal complexing agents produce chromosome aberrations by reacting with these metals.     

Inducibility of chromosomal aberrations by metal compounds in cultured mammalian cells.

Metal compounds were tested for their ability to induce chromosomal aberrations in cultured mammalian cells. Chromosomal aberrations were induced by the application of some Cr, Mn and Ni compounds. Among 6-valent Cr compounds, K2Cr2O7 and CrO3 induced high levels of aberrations, at rates which were similar for Cr-equivalent doses. The perchromate compounds were more efficient in producing chromosomal aberrations than was a chromate compound, K2CrO4. A 3-valent Cr compound, Cr2(SO4)3, was less toxic and failed to induce a demonstrable increase in chromosomal aberrations. KMnO4 induced aberrations, but at a low rate. As to Ni compounds, NiCl2 and (CH3COO)2Ni induced few aberrations. Administration of K2Ni(CN)4 induced only gaps. NiS induced a low but definite increase in chromosomal aberrations. The rate of these aberrations increased with an increase in treatment time from 24 to 48 h, indicating a time-dependent increase in the hereditable toxicity of metal compounds. CdCl2 and HgCl2 were somewhat toxic, but failed to induce chromosomal aberrations in the present study.     

Detection of chromosomal aberrations by a whole-genome microsatellite screen

Chromosomal aberrations are a common cause of multiple anomaly syndromes that include developmental and growth retardation. Current microscopic techniques are useful for the detection of such aberrations but have a limit of resolution that is above the threshold for phenotypic effect. We hypothesized that a genomewide microsatellite screen could detect chromosomal aberrations that were not detected by standard cytogenetic techniques in a portion of these individuals. To test this hypothesis, we performed a genomewide microsatellite screen of patients, by use of a currently available genetic-marker panel that was originally designed for meiotic mapping of Mendelian traits. We genotyped approximately 400 markers on 17 pairs of parents and their children who had normal karyotypes. By using this approach, we detected and confirmed two cases of segmental aneusomy among 11 children with multiple congenital anomalies. These data demonstrate that a genomewide microsatellite scan can be used to detect chromosomal aberrations that are not detected by microscopic techniques.     

Maternal and fetal chromosomal aberrations in mice following prenatal exposure to subembryotoxic doses of lead nitrate

Maternal exposure to low levels of lead nitrate (12.5, 25, 50 mg/kg body weight), administered on the 9th day of gestation, did not cause embryonic resorption and fetal lethality, but induced chromosomal deletions and other forms of aberrations in fetal liver and maternal bone marrow cells.     

Nonrandom distribution of chromosomal aberrations induced by three chemicals

The G-band locations of 3244 breakpoints induced by cis-platinum (II) diamminedichloride (PDD), 1460 breakpoints induced by cytosine arabinoside (ara-C), and 1257 breakpoints induced by triethylenemelamine (TEM) in human lymphocyte chromosomes were identified. The breakpoints induced by each of these chemicals demonstrated a significantly nonrandom distribution within the human karyotype. The overall pattern of the interarm distribution was dependent upon the chemical used, but certain chromosomes arms exhibited similar responses to all 3 chemicals. Comparison of the frequencies of breakpoints within individual G-bands indicated that (1) certain bands were susceptible to damage induced by all 3 chemicals; (2) certain bands were resistant to damage by all 3 chemicals; (3) certain bands demonstrated variable susceptibility to induced damage dependent upon the chemical agent; and (4) other bands demonstrated near expected frequencies of damage (by length) to all 3 agents.     

Induction of chromosomal aberrations by camptothecin in root-tip cells of Vicia faba.

When root-tip cells of Vicia faba were exposed during early and middle interphase to camptothecin (Cpt), the aberrations obtained were exclusively of the chromatid type and tended to be localized in late replicating heterochromatic regions of the chromosomes. In these respects the clastogenic effect of Cpt resembles that of agents that act by an S-phase-dependent mechanism. In contrast to typical S-phase-dependent agents, Cpt produced lesions capable of giving rise to aberrations only in S-phase cells that were synthesizing DNA at the time of treatment. The dependence on ongoing DNA synthesis was suggested in autoradiographic experiments and by the fact that the clastogenic effect of Cpt was strongly suppressed by hydroxyurea, an inhibitor of DNA synthesis. After Cpt treatments, there were many more cells with 3-12 aberrations and far fewer cells with 0, 1 or 2 aberrations than expected on the basis of a Poisson distribution. Cpt further differed from typical S-phase-dependent agents by being capable of inducing lesions in the G2 phase that give rise to chromosomal aberrations in the first mitosis after treatment. This effect was obtained at Cpt concentrations around 10 microM, whereas only 0.03 microM Cpt was required to produce chromatid aberrations in the S phase. Results of G2-phase experiments with Cpt and 5-fluorodeoxyuridine, an inhibitor of DNA synthesis, suggest that DNA synthesis is required for the clastogenic effect of Cpt not only during the S phase, but also during the G2 phase, although the DNA syntheses involved are both quantitatively and qualitatively different.     

Possible mechanisms of the occurrence of chromosome aberrations. II. The formation of aberrations induced by UV irradiation

The report is concerned with one of possible mechanisms of emergence of chromosome aberrations after UV-irradiation of mammalian cells. The process is initiated by DNA cross-links following thymine dimerization, and is completed during mitosis. A model to account for formation of chromosome aberrations has been offered. It is compatible with the modern concept of a scaffolding model for metaphase chromosome structure in which the scaffold organizes DNA into loops along its length. The model predicts the importance of a process of mitotic chromosome isolation during aberration formation (in addition to the processes of DNA replication, reparation and chromosome association). Another feature of the model is an attempt to describe formation of aberrations under conditions of true DNA reparation.     

Hyperthermic potentiation of chromosome aberrations by anticancer antibiotics

In view of the success of hyperthermia as a modality in cancer treatment, we have studied its effect on chromosomes in combination with anticancer antibiotics. Three classes of chemicals, one with a non-delayed type of effect (adriamycin), one with a delayed type of effect (mitomycin C), and one with a truely radio-mimetic effect (bleomycin) were selected for study on human lymphocytes and Chinese hamster K-1 cells. Propane sultone was also included because its effect on plants is suppressed by hyperthermia. The data show increased because its effect on plants is suppressed by hyperthermia. The data show increased potential of these chemicals to induce chromosome aberrations when applied at temperatures higher than 37 degrees C, irrespective of the phase of cell cycle. The potentiation may be due to true synergism (bleomycin) of facilitation of entry of larger quantities of the drug (adriamycin). No potentiating effect was observed on the induction of sister chromatid exchanges (SCEs).     

Induction of chromosomal aberrations in Chinese hamster ovary cells by triethyllead acetate.

Organolead compounds enter the environment primarily through the combustion of leaded gasoline and industrial discharge. Lead and lead-containing compounds have been shown to induce a broad spectrum of toxic effects, including hematopoietic, renal, neurologic, and carcinogenic effects. In this study, the mutagenic activity of triethyllead acetate (Et3PbAc) was determined by measuring the induction of chromosomal aberrations in Chinese hamster ovary cells. The results indicate that Et3PbAc is very cytotoxic and a potent clastogen. In preliminary cytotoxicity studies used to determine appropriate test concentrations for chromosomal aberration analysis, the LC50 of Et3PbAc was approximately 10 microM in the absence of metabolic activation, and 80 microM in the presence of metabolic activation. The maximal response was greater with metabolic activation than without. However, a much higher dose was required to elicit a significant response in the presence of metabolic activation than in its absence.