A medico-genetic study of isolates in Uzbekistan. III. Results of a cytogenetic study]

The cytogenetic examination of the population of the villages of Karakent and Ishan consisted of two directions: the study on the frequency of chromosome aberrations in the culture of lymphocytes and the diagnostics of anomalies and variants of karyotype. The frequency of chromosome aberrations of 40 individuals was studied. It is shown that the frequency of cells with chromosome aberrations of the individuals in different villages does not differ and on the average is 1,4%. The distribution of lymphocyte culture according to the number of aberrations corresponds to that of theoretical Puassonian. Chromatide breaks are the main type of the aberrations. Among 250 karyotypically examined individuals no evident structure reformations were found. In the caryotype of a 7-year old girl trisomia of the 21st autosome was detected. On the basis of differential staining of chromosomes by Hiemse's dye 18 individuals (7,2%) were diagnosed to have insignificant changes in morphology of some chromosomes, considered as variants of caryotype. In the majority of cases these changes were of a family nature. On the medical examination mnay individuals were diagnosed to have different pathological features, though we did not succeed in revealing any correlation between a certain microanomaly of chromosomes and a pathological feature.     

Quantitative characteristics of the frequency of chromosomal aberrations in a group of residents of a large western Siberian industrial region

The results of a 15-year study of chromosome aberration frequency in cultured peripheral blood lymphocytes from subjects living in the Kuzbass industrial region are presented. The database for the analysis of the main parameters of chromosome aberrations contains data on 925 subjects, with the total number of cells examined being 92,900. It has been found that the total frequency of aberrant metaphases in the database is 3.73 +/- 0.1%, whereas this frequency for the sample of subjects from industrial areas of this region (the basic control group) is significantly lower (2.86 +/- 0.26%). It has been demonstrated that the sex and age of the subjects do not affect substantially the frequency of any type of chromosome aberrations. Tobacco smoking is associated with a slight increase in chromosome damage frequency; however, the difference between smokers and nonsmokers is insignificant even among subjects exposed to occupational hazards. The possible causes that have determined the increased basic and background chromosome aberration frequencies in the population of the Kemerovo oblast compared to these parameters for the European part of Russia and the CIS are discussed.     

Chromosome aberrations in a natural population of Tetrix tenuicornis (Sahlb.) (Tetrigidae: Orthoptera).

In the natural population of Tetrix tenuicornis from the Kraków-Czestochowa Upland 26.7% of males showed various aberrations of the morphology and behaviour of chromosomes. The high frequency of chromosome aberrations found in this population indicates their genetic instability.     

Frequencies of chromosomal aberrations in pesticide sprayers working in plastic green houses.

The frequency of chromosome aberrations was studied in peripheral blood lymphocytes of 29 workers occupationally exposed to a mixture of pesticides and in 14 age- and sex-matched healthy controls. There was a significant increase in chromosome aberrations in sprayers when compared to unexposed persons (2.39% compared to 0.54%). No positive correlation between the frequency of chromosome aberrations and the duration of exposure was observed. No significant difference between smokers and non-smokers was found.     

Quantitative Characteristics of Chromosome Aberration Frequency in the Human Population of a Large Western Siberian Industrial Region

The results of a 15-year study of chromosome aberration frequency in cultured peripheral blood lymphocytes from subjects living in the Kuzbass industrial region are presented. The database for the analysis of the main parameters of chromosome aberrations contains data on 925 subjects, with the total number of cells examined being 92 900. It has been found that the total frequency of aberrant metaphases in the database is 3.73 ± 0.1%, whereas this frequency for the sample of subjects from industrial areas of this region (the basic control group) is significantly lower (2.86 ± 0.26%). It has been demonstrated that the sex and age of the subjects do not affect substantially the frequency of any type of chromosome aberrations. Tobacco smoking is associated with a slight increase in chromosome damage frequency; however, the difference between smokers and nonsmokers is insignificant even among subjects exposed to occupational hazards. The possible causes that have determined the increased basic and background chromosome aberration frequencies in the population of the Kemerovo oblast compared to these parameters for the European part of Russia and the CIS are discussed.     

Comparison of frequencies of radiation-induced stable chromosomal aberrations in somatic and germ tissues of the mouse

Radiation-induced stable chromosome aberrations have been studied in the testes and bone-marrow of the mouse (Mus musculus). 60 days after whole-body irradiation with a dose of 400 rad X-rays, the frequency of visible chromosome aberrations in bone-marrow cells was 19.8%. The frequency of chromosome aberrations in spermatogonia of the same mice, scored as multivalents in spermatocytes, was considerably lower — only 4.7%. The possible mechanisms underlying this marked difference in translocation yield are discussed.     

High Rates of Occurrence of Spontaneous Chromosome Aberrations in DROSOPHILA MELANOGASTER

Spontaneous mutations were accumulated for 40 generations in 140 unrelated second chromosomes with the standard gene arrangement. These were extracted from the same population by using the marked inversion technique, and the following findings were obtained: (1) In 42 out of the 140 chromosome lines, chromosome aberrations were detected by examining the salivary gland chromosomes: 40 paracentric and 15 pericentric inversions, 2 reciprocal translocations between the second and the third chromosomes, and 6 transpositions. (2) In 63 out of the 90 originally lethal-free lines, recessive lethal mutations occurred. (3) There were only 3 lines that acquired chromosome aberrations (inversions) with no lethal effects in the homozygous condition. (4) In a comparison of these results with those of the (CH), (PQ), and (RT) chromosomes in which no chromosome aberrations occurred after accumulating mutations for 22058 chromosome.generations (Yamaguchi and Mukai 1974), it was concluded that some of these 140 chromosomes carried a kind of mutator. (5) The frequency of mutator-carrying chromosome lines was estimated to be 0.66 on the basis of the distribution of the break-points on the chromosome lines and the frequency of lines that acquired neither recessive lethal mutations nor chromosome aberrations. Thus, the average number of breaks per mutator-carrying chromosome was estimated to be about 0.19/generation.On the basis of these estimates, the nature of the mutator factor was discussed.     

Persistence of chromosome rearrangements in peripheral lymphocytes from patients treated with melphalan for ovarian carcinoma

Summary Chromosome aberrations were studied in peripheral lymphocytes from 50 patients treated with melphalan against ovarian carcinoma. The chromosome analyses were carried out 4–132 months (mean 57 months) after the end of melphalan therapy. Most of the patients were studied several times during four years. The mean frequency of cells with chromosome and chromatid aberrations was 5.4% in the patients and 2.3% in an untreated control group. The highest aberration frequency (average 18%) was found in a patient who later developed gastric carcinoma. The dominating types of berrations in the patients were chromosome exchanges occurring as single marker chromosomes or as multiple chromosome rearrangements. These types of aberrations were found in only 0.3% of the control cells as compared to 3.8% of the patient cells. Patients with a high total dose of melphalan (above 420 mg) and a long duration of the therapy (average 22.5 months) had a higher frequency of cells with aberrations (6.3%) than patients with a lower total dose (below 420 mg) and a shorter therapy (12 months) (4.2%). No additive effect of radiation therapy was observed on the aberration frequency.This work was supported by grants from the Swedish Cancer Society (1179), and the Swedish Medical Research Council (3681)     

Allelic variants of polymorphic genes associated with a higher frequency of chromosome aberrations

Genotypic associations were studied for the frequency of chromosome aberrations in human peripheral blood lymphocytes. Cytogenetic analysis (1000 metaphase plate per individual) and genotyping at 19 sites of genes involved in detoxification and DNA repair were performed in a sample of 83 Chernobyl liquidators and a matched control sample of 96 volunteers. In either sample, the frequency of chromosome aberrations was higher in carriers of the minor alleles of the XPD gene (sites 2251T > G and 862G > A) and the positive genotypes of the GSTM1-GSTT1 genes. The highest frequency of chromosome aberrations was observed in carriers of a combined genotype including at least one minor allele of the XPD sites + at least one insertion in the GSTM1-GSTT1 genes. The high-risk genotype, which had a prevalence of 64%, was strongly associated with a higher frequency of chromosome aberrations in both volunteers (OR = 6.9, P = 0.008) and Chernobyl liquidators (OR = 5.6, P = 0.002).     

Humoral factors of "spontaneous" mutagenesis in mammals and man

The frequency of chromosome aberrations in bone-marrow cells of mice in tissue incompatibility conflicts, and in the lymphocytes of the peripheral blood of 20 patients suffering from different allergies was studied. It was established that in mice, during allograft rejection, i.e. on the 10th–15th days after grafting of allogeneic skin, the frequency of cells with chromosome aberrations increases significantly up to 12–15% against 4–5% in the control. On the 20th day after grafting, the level of chromosome aberrations falls back to the control level. In allergic patients the frequency of cells with chromosome aberrations was 10.7% (4–22%). In numerous control subjects this value did not exceed 2%. The highest level of aberrations was found during the acute stage of the disease especially in patients in the state of anaphylactic shock. No correlation was found between the frequency of aberrant cells and the action of definite allergens. The problem of the possibility of extending the above described phenomenon to non-immunocompetent cells of mammals, and of the role of immunological stress in spontaneous mutagenesis are discussed.     

Mechanism of adaptive response: Estimation of human lymphocyte adaptive response to radiation using various criteria

Blood lymphocytes of 15 healthy donors have been investigated for their ability to reduce radiosensitivity after low-dose irradiation-radio-induced adaptive response (AR). The frequency of unstable chromosome aberrations was used to evaluate cell radiosensitivity after the irradiation of cells in low adaptive (5 cGy) and high challenge (1 Gy) doses in comparison with the effect of challenge irradiation only. Three indexes have been used, i.e., (A) the frequency of cells with aberrations per total analyzed cell, (B) the number of chromosome aberrations per one cell, (C) and the number of chromosome aberrations per one aberrant cell. It was found that the donors can be divided in the four following groups: 1. AR was not estimated any of the indexes used; 2. AR was estimated with indexes A and B, but not C; 3. AR was shown by indexes B and C; 4. AR was evident with all three indexes. The generally accepted AR repair model only explains the appearance of group-3 and-4 donors, but not group-2. For the purpose of understanding the AR mechanisms and the difference in AR estimations with various criteria, the metaphase distribution by the number of chromosome aberrations has been analyzed for each donor. It was shown that, in group-2 donors, the number of cells without aberrations after adaptive and challenge irradiations was significantly higher than after irradiation with a challenge dose only. Thus, in this group, AR is formed as a result of the changed frequency of cells in the 0 class (population shift). A similar shift is observed in the metaphase distribution in the donors of group 4, but not in group 3. The data obtained show that AR is probably a result of several processes, including the activation of the reparation of premutational genome damages, population shifts evident in the frequency of undamaged cells, and, possibly, the activation of apoptotic cell death. The complex character of AR is reflected to different degrees in each criterion of radiosensitivity.     

Differential sensitivity of peripheral blood lymphocytes of untreated leprosy patients to mitomycin C

The effects of a bifunctional alkylating agent mitomycin C (MMC), an effective inducer of chromosome aberrations and sister-chromatid exchanges (SCEs), have been studied in untreated leprosy patients. This was done to study the mutagen sensitivity of the leprosy patients. The frequency of chromosomal aberrations induced by MMC (conc. 0.01 microgram/ml) was 2.5% in controls, 3.6% in paucibacillary (PB), and 6.8% in multibacillary (MB) patients. The difference in the frequency of MMC-induced chromosome aberrations between the 3 groups studied was highly significant (p less than 0.01). Cultures grown with MMC showed the frequency of SCEs/cell to be 12.70 +/- 1.19 in controls, 19.97 +/- 3.51 in PB, and 29.66 +/- 5.92 in MB patients. The differences in the frequency of MMC-induced SCEs between the 3 groups were found to be highly significant (p less than 0.01). The enhanced frequencies of spontaneous and MMC-induced chromosome aberrations and SCEs observed in PB and MB patients indicate a clear differential mutagen sensitivity between PB and MB patients who are known to have different immunological status and thereby differ in the severity of the disease.     

Frequency of chromosome aberrations induced by mutagens of various functions in cells of the first division at various times of fixation

The dynamics of chromosome aberrations in human lymphocyte culture cells of the 1-st division after exposure in the G0 phase for 1h to functionally different alkylating mutagens - ethyleneimine derivatives (bifunctional phosphamide, threefunctional thiophosphamide, tetrafunctional dipine and pentafunctional photrin) was analysed. The frequency of chromosome aberrations was constant after exposure to "dicentric" mutagens (dipine, photrin) at all times of fixation, while under the action of "monocentric" mutagens (phosphamide, thiophosphamide) this declined significantly with increasing the duration of cultivation. The portion of aberrations of the chromatid remains unaltered in time, in case of both "dicentric" and "monocentric" mutagens, reaching 75% for "monocentric" and 50% for "dicentric" of the total number of chromosome aberrations.     

Chromosome analysis of human sperm

Summary A modified technique has been developed for the visualization of the chromosomes in human sperm. The cytogenetic analysis of 129 G-banded human sperm metaphases of 6 normal donors showed an incidence of structural and numerical chromosome abnormalities of 7.8%. Two out of 129 spermatozoa were aneuploid (1.6%). The frequency of sperms with chromatid-type aberrations was 2.3% (3/129). Chromosome-type aberrations were found in 5 out of 129 (3.9%) spermatozoa. X to Y ratio did not differ significantly from the expected one-to-one ratio. Twenty-six sperm complements from a patient 18–20 months after testes exposure to 30 Gy were examined. A significant increase of numerical and structural chromosome abnormalities was not observed. Chromatidtype aberrations were found in two sperm complements (7.7%) and chromosome-type aberrations in one sperm complement (3.9%). The cytogenetic analysis of 15 human sperms from a cancer patient 26 months after chemotherapy showed an increased frequency of aberrant sperm complements (33.4%). One chromatid-type (6.7%), three chromosometype aberrations (20.0%) and one (6.7%) hyperploid sperm complement could be observed. The sample size is still too small to answer the question whether chemical mutagens may increase the frequency of chromosomal abnormalities in human sperm.     

Chromosomal analysis in mouse eggs fertilized in vitro with sperm exposed to ultraviolet light (UV) and methyl and ethyl methanesulfonate (MMS and EMS)

Chromosome aberrations were analyzed at the first-cleavage metaphase of mouse eggs fertilized in vitro with sperm exposed to ultraviolet light (UV) as well as to methyl and ethyl methanesulfonate (MMS and EMS). The frequencies of chromosome aberrations markedly increased with dose of UV as well as with concentration of MMS and EMS. In the UV-irradiation group, the frequency of chromosome-type aberrations was much higher than that of chromatid-type aberrations. About 90% of chromosome aberrations observed in the eggs following MMS and EMS treatment to sperm were chromosome type in which the frequency of chromosome fragments was the highest. The effects of UV on the induction of chromosome aberrations were clearly potentiated by post-treatment incubation of fertilized eggs in the presence of Ara-C or caffeine, but the effects of MMS and EMS were not pronounced by post-treatment of Ara-C or caffeine. The results indicate a possibility that UV damage induced in mouse sperm DNA is reparable in the eggs during the period between the entry of sperm into the egg cytoplasm and the first-cleavage metaphase.     

Rubber solvent: a clastogenic agent that fails to induce sister-chromatid exchanges.

Rubber solvent was tested for its ability to induce chromosome aberrations and sister-chromatid exchanges in human whole blood cultures. Following exposure to relatively low rubber solvent concentrations (0.0125% and greater) significant increases in the frequencies of chromatid gaps and breaks were observed. At higher rubber-solvent concentrations (0.05% and greater) there were also significant increases in the frequency of chromosome breaks. In contrast to the increase in chromosome aberrations following rubber-solvent exposure, rubber-solvent concentrations up to the toxic level failed to produce increases in the sister-chromatid exchange frequency.     

An analysis of structural aberrations in human sperm chromosomes

We have analyzed structural aberrations in 5,000 sperm chromosome complements obtained from 20 men over a 5-yr period by fusion of human sperm with hamster eggs. Detailed data are presented on 366 abnormal cells with 379 analyzable breakpoints. The frequency of cells with structural aberrations ranged from 1.9% to 14.5% among donors; this interindividual variability was statistically significant (p less than 0.0001). In contrast, repeat samples from individual men showed no significant variation over time. The number of sperm chromosome sets processed per hamster egg had no effect on the frequency with which structural aberrations occurred, nor were sperm chromosome abnormalities altered by varying capacitation or culture conditions. The spectrum of structural aberrations observed in human sperm chromosomes and a chi-square analysis of breakpoints based on DNA content are presented. Although human sperm chromosome abnormalities were visualized with a cross-species system, we believe that they represent an inherent, biologically significant phenomenon.     

Analysis of the Chromosome Aberrations Induced by X-Rays in Somatic Cells of DROSOPHILA MELANOGASTER

A technique has been perfected for enabling good microscope preparations to be obtained from the larval ganglia of Drosophila melanogaster. This system was then tested with X-rays and an extensive series of data was obtained on the chromosome aberrations induced in the various stages of the cell cycle.-The analysis of the results obtained offers the following points of interest: (1) There exists a difference in radio-sensitivity between the two sexes. The females constantly display a greater frequency of both chromosome and chromatid aberrations. They also display a greater frequency of spontaneous aberrations. (2) In both sexes the overall chromosome damage is greater in cells irradiated in stages G(2) and G(1). These two peaks of greater radiosensitivity are produced by a high frequency of terminal deletions and chromatid exchanges and by a high frequency of dicentrics, respectively. (3) The aberrations are not distributed at random among the various chromosomes. On the average, the Y chromosome is found to be more resistant and the breaks are preferentially localized in the pericentromeric heterochromatin of the X chromosome and of the autosomes. (4) Somatic pairing influences the frequency and type of the chromosome aberrations induced. In this system, such an arrangement of the chromosomes results in a high frequency of exchanges and dicentrics between homologous chromosomes and a low frequency of scorable translocations. Moreover, somatic pairing, probably by preventing the formation of looped regions in the interphase chromosomes, results in the almost total absence of intrachanges at both chromosome and chromatid level.     

Spectrum of chromosomal aberrations in peripheral lymphocytes of hospital workers occupationally exposed to low doses of ionizing radiation

Chromosome aberrations frequency was estimated in peripheral lymphocytes from hospital workers occupationally exposed to low levels of ionizing radiation and controls. Chromosome aberrations yield was analyzed by considering the effects of dose equivalent of ionizing radiation over time, and of confounding factors, such as age, gender and smoking status. Frequencies of aberrant cells and chromosome breaks were higher in exposed workers than in controls (P = 0.007, and P = 0.001, respectively). Seven dicentric aberrations were detected in the exposed group and only three in controls, but the mean frequencies were not significantly different. The dose equivalent to whole body of ionizing radiation (Hwb) did appear to influence the spectrum of chromosomal aberrations when the exposed workers were subdivided by a cut off at 50 mSv. The frequencies of chromosome breaks in both subgroups of workers were significantly higher than in controls (< or =50 mSv, P = 0.041; >50 mSv, P = 0.018). On the other hand, the frequency of chromatid breaks observed in workers with Hwb >50 mSv was significantly higher than in controls (P = 0.015) or workers with Hwb < or =50 mSv (P = 0.046). Regarding the influence of confounding factors on genetic damage, smoking status and female gender seem to influence the increase in chromosome aberration frequencies in the study population. Overall, these results suggested that chromosome breaks might provide a good marker for assessing genetic damage in populations exposed to low levels of ionizing radiation.     

Long-Term Monitoring of Cytogenetic Aberrations in Adolescents of a Large Industrial Town

Long-term cytogenetic monitoring was carried out in adolescents of the town of Kemerovo. In total, aberrant metaphase frequency increased from 1.53% in 1992 to 4.40% in 1996 in Kemerovo adolescents, being significantly higher than a control frequency from 1993 to 1996. In all samples, chromosome aberrations mostly included acentric fragments, while exchanges were rare. The highest number of aberrations per aberrant metaphase was 2 in Kemerovo adolescents and 1 in the control sample. The observed increase in total number of chromosome aberrations suggests that the mutagenic effect of chemical environmental pollutants on Kemerovo adolescents increased over the five years.