Chromosome aberrations in lymphocytes of residents living in buildings constructed with radioactively contaminated rebars.

Using the G-banding technique, we examined lymphocytes from 90 individuals (43 males and 47 females, median age 31 years) living in buildings constructed with radioactively contaminated rebars. Forty-five nonexposed control subjects (22 males and 23 females, median age 30 years), matched to the radiation-exposed individuals by sex and age, were selected for comparison. At least 500 metaphases were checked for each individual. All recognizable structural aberrations of chromosomes or chromatids were recorded. After adjusting for age and smoking status, both the percentage of cells with aberrant chromosomes (PCAC) and the number of aberrant chromosomes per 100 cells (NAC) were found to be significantly higher in the radiation-exposed females than in the control females (p < 0.05 for PCAC and NAC). This difference, however, was not observed in the comparison of radiation-exposed and control males. This suggests a possible interaction between sex and radiation exposure in their effects on chromosome aberrations.

A confirmation analysis method for identification of chromosomal fragile sites.

Fragile sites are chromosome bands that do not manifest a presumed breakage pattern. Identification of fragile sites is a way to investigate the mechanism of carcinogenesis because the fragility at a specific chromosome position may be the causation of an associated cancer. A problem in the identification of fragile sites is the high false positive rate arising from simultaneously carrying out a large number of significance tests. To control it, we propose to find a reference study to confirm the identification result of an objective study. We utilize the Bayesian concept for linking two studies. Basically, our method demonstrates a conservative way to take account of the prior information of a binomial parameter. The derived estimate of breakage probability can be interpreted as a resampling weighted sample-pooling method. It is applied to confirm the identification of fragile sites for a data set of neuroblastoma patients.

Chromosomal fragile site expression in lymphocytes from patients with schizophrenia.

Schizophrenia is a common complex mental disorder. The lifetime prevalence of this disease is about 1% across different populations. The etiology is still unknown despite decades of intensive study. This report is aimed at studying the relationship between chromosomal fragile sites and the etiology of schizophrenia. Lymphocytes of 72 schizophrenic patients and 66 healthy controls were cultured in M medium, which is deficient in folic acid, and in medium RPMI 1640 with distamycin A. G-banding was carried out on 100 metaphases of each individual. Fragile sites were characterized as specific chromosomal bands that exhibit nonrandom gaps or breaks. Culture in M medium resulted in significant differences in the total number of chromosomal lesions and the total number of cells with chromosomal lesions between patients and controls (P<0.001), while no difference was noted after exposure to distamycin A. In the case of M medium, 17 bands in both patients and controls were recognized as expressing fragile sites nonrandomly using a statistical method based on the relationship of the binomial and F distributions. Further analysis using Fisher's exact test revealed a significant excess of expression of a rare fragile site at 2q11.2 among patients compared with controls (P<0.05). In the case of distamycin A induction, 13 bands were identified as having nonrandom expression of fragile sites using the same statistical method. A significant excess expression of a fragile site at 9q12 was identified among patients compared with controls by applying Fisher's exact test (P<0.001). Thus, our data suggest that chromosomal bands 2q11.2 and 9q12 are interesting regions that may harbor important genes associated with schizophrenia.

Chromosomal study in lymphocytes from subjects living or working in buildings constructed with radioactively contaminated rebar.

It has recently been found that many buildings in Taiwan were constructed with radioactively contaminated rebar, which raised great concern among the residents as well as governmental officials. In order to investigate the possible cytogenetic damage to the residents of contaminated buildings, a G-banding method was carried out on the lymphocytes of 30 radiation-exposed individuals from four families and one office building, as well as 15 control individuals from laboratory personnel. The estimated cumulative radiation doses for the exposed people range from 19.63 to 280.50 mSv. Altogether, 13 females and 17 males belonging to the radiation-exposed group, and 7 females and 8 males in the control group, were included in this study. With the exception of one sample, at least 500 metaphase spreads were scored and analyzed for each individual. All the recognizable structural aberrations of chromosomes or chromatids were recorded and statistically analyzed. Comparison of either percentage of cells with chromosome aberrations or number of aberrated chromosomes per 100 cells between the radiation-exposed and the control groups manifested insignificant differences (p = 0.1145 and 0.0766, respectively). In addition, the chromosomal regions close to the centromere were found to break more frequently than elsewhere in the genome.

Deletion of integrated hepatitis B virus genome and cellular flanking sequences in hepatocellular carcinoma cells in BALB/c mice.

We have previously reported the establishment of well-differentiated BALB/c mouse liver (ML) cell lines. Transfection of these cell lines with hepatitis B virus (HBV) DNA led to the expression of HBV-specific antigens and integration of HBV sequences in the cellular genome. Two cloned HBV-transfected ML cell lines, ML-2(HBV) and ML-3(HBV), expressed viral antigens and were highly tumorigenic in nude mice. However, the tumorigenicity of the two cell lines was significantly reduced in BALB/c mice. Southern blot analyses showed that the integrated HBV sequences were retained in tumors growing in nude mice but deleted in tumors growing in BALB/c mice. Furthermore, the deletion of HBV DNA was accompanied by deletion of chromosomal sequences flanking the HBV integration sites. In ML-2(HBV) cells, a significant reduction in chromosomal number was also observed. These results suggest that the immune response of BALB/c mice selected against hepatocellular carcinoma (HCC) cells expressing viral antigens and led to the proliferation of cells with deleted HBV sequences and concomitant chromosome aberrations. By using this mechanism, HCC cells escape the immune surveillance and gain the advantage of cell growth.

Cytogenetic Study of Mentally Retarded Children in Taipei.

560 blood samples collected from mentally retarded children in Taipei were karyotypically analyzed for the incidence of fragile X and other chromosome abnormalities. The fragile site at Xq27.3 was observed in 18 patients (3.21%), 11 males and 7 females, out of the 560 blood cultures using M medium. Down syndrome (6.25%), 24 males and 11 females, was the other major category of abnormality. Other abnormalities, including inversion, translocation, deletion, duplication, ring as well as an extra marker chromosome were observed. The overall incidence of chromosomal abnormalities in these children was 14.82%. Copyright 1994 S. Karger AG, Basel

Karyotypic analysis of seven established human esophageal carcinoma cell lines.

Fifty metaphases from each of seven esophageal carcinoma cell lines (TE-1, TE-4, TE-5, TE-6, TE-9, HCE-6, and HCE-8) were karyotypically analyzed for both numerical and structural chromosomal abnormalities. The modes of numerical variation found in the TE cell lines were as follows: 1) a wide range of variation in chromosome numbers (45-100)/cell with a modal number of 52 (TE-1); and 2) a narrow range of variation at the hypertetraploidy level (TE-4), hypotriploidy level (TE-5 and TE-6) and hypertriploidy level (TE-9). The distribution of chromosomal number/cell in cell lines HCE-6 and HCE-8 was extremely diverse. It was difficult to find a modal number in the range of 94-117 in the HCE-6 line or in the range of 45-52 in the HCE-8 line. The structural changes were extensive in all of these cell lines. Chromosomes most frequently involved in the structural changes were 1, 2, 3, 6, 7 and 9. Most of these abnormalities resulted from simple deletion, duplication, insertion, inversion or translocation. A few of them were complicated rearrangements. No breakpoint was shared by all of the cell lines.

A method for testing the nonrandomness of chromosomal breakpoints.

Testing the nonrandomness of breakage at a chromosome band is an essential step fo identifying a fragile site. In this paper, we propose a method derived by using the relationship between the binomial and F distributions for testing nonrandomness. The method is simple in calculation. It was applied to the detection of fragile sites for Chinese patients with colorectal carcinoma.

Chromosomal screening of mentally retarded school children in Taipei.

The major concern of the national population policy in Taiwan in recent years has been to lower the incidence of hereditary diseases and mental retardation in the general population. It has been estimated that there are around 10,000 mentally retarded school children in Taiwan. If effective chromosomal screening can be extended to these children, some of the family members who are carriers of balanced chromosomal rearrangements may benefit from follow-up studies and genetic counseling. The present report is the result of a pilot study conducted from 1988 to 1991 to explore the possibility of chromosomal screening of mentally retarded school children in Taipei. A total of 871 blood samples were collected from 1,147 children registered in 46 schools or residing in homes for the retarded. Chromosomal analysis was successfully accomplished on 674 out of 871 blood samples. The following chromosomal abnormalities were observed: 28 Down's syndrome, four Klinefelter syndrome, one XYY, one triple X, 11 translocations, seven inversions, four mosaics, three duplications, one deletion and one with an extra marker chromosome. After follow-up cytogenetic analyses of 13 families with probands with structural chromosomal anomalies, three of these families were shown to have one or two carriers of balanced translocated chromosomes. It seems that the present screening system would not be practical or cost-effective if it were applied island-wide in the future.

Chromosomal analysis of sixteen human rhabdomyosarcomas.

Chromosomal analysis of 16 rhabdomyosarcomas was done from four primary tumors and from 12 tumors after nude mouse passage. Seven tumors were alveolar; four of these had t(2;13)(q37;q14) and in two tumors it was the only structural abnormality. The other three alveolar tumors were near tetraploid with marker chromosomes and double minutes. In the nine embryonal tumors studied, one had a normal karyotype, and eight were abnormal. Although the eight tumors had no common structural abnormality, trisomy 2 was present in all.

Cytogenetic and chemical detection of human exposure to polyhalogenated aromatic hydrocarbons.

Peripheral lymphocytes from Taiwanese women (n = 35) exposed to polychlorinated aromatic hydrocarbons and from matched controls (n = 24) were assessed for the levels of sister chromatid exchanges (SCEs) after a 72-hour incubation of whole blood in the presence or absence of alpha-naphthoflavone (ANF) and for chromosome aberrations after 48 hours of incubation. Serum levels of polychlorinated biphenyl (PCB) congeners were measured for all individuals, and serum levels of several polychlorinated dibenzofurans (PCDFs) were measured for 12 exposed individuals by gas chromatography-mass spectometry. Blood concentrations of total PCBs in the exposed population averaged approximately 15 ppb, whereas mean PCDF values were 14 ppt. Major PCB congeners detected were 2,2' 4,4', 5,5'-hexa CB and 2,2'3,4,4',5-hexa CB. PCDFs detected were primarily 1,2,3,4,7,8,-hexachlorodibenzofuran (10.8 ppt) and 2,3,4,7,8-pentachlorodibenzofuran (2.7 ppt). Average SCE frequencies were 7.61 for controls and 7.30 for exposed individuals when assays were conducted in the absence of ANF, whereas respective values were 8.85 and 10.75 in the presence of ANF. Differences in the level of ANF-induced SCEs between the two populations were highly significant (P less than .001). Moreover, the ANF-induced SCEs were highly correlated with the serum concentrations of total PCBs and of several PCB congeners (P less than .001). Increases in ANF-induced SCEs appeared to be linear up to a PCB concentration of approximately 30 ppb. Chromosome aberration frequencies were similar in control and exposed populations. These studies demonstrate that in vivo exposure to PCBs and PCDFs result in an enhanced sensitivity of lymphocytes to the SCE-causing actions of ANF.

Karyotypic characterization of an established human hepatoma cell line HA22T/VGH.

The karyotype of an established human hepatoma cell line HA22T/VGH was characterized by G-banding. A majority of the 200 cells counted had around 70 chromosomes at passage 24, and 60 at passage 338. Of the 50 cells karyotyped from each of passage 24 and passages 338-339, chromosomes #13 and #18 were absent. The presence of the Y chromosome was reduced dramatically from a mean value of 1.12/cell at passage 24 to 0.12/cell at passages 338-339. In general, most of the chromosomes--particularly chromosomes #5, #7, #9, #15, and #21--tended to be less represented in the course of propagation in vitro. The presence of multiple copies of a normal chromosome in a single cell was quite common for chromosomes #5 and #7 at both early and late passages. Numerous structural rearrangements of the chromosomes were observed.

Differential effects of pre- and posttreatment of sodium arsenite on the genotoxicity of methyl methanesulfonate in Chinese hamster ovary cells.

Pretreatment of sodium arsenite reduces hypoxanthine-guanine phosphoribosyltransferase mutagenicity and overcomes the inhibition of mitosis and cell proliferation but has no apparent effect on the cytotoxicity and clastogenicity in methyl methanesulfonate (MMS)-treated Chinese hamster ovary cells. Posttreatment of sodium arsenite drastically increases the cytotoxicity, clastogenicity, hypoxanthine-guanine phosphoribosyltransferase mutagenicity, and inhibition of mitosis and cell proliferation induced by MMS. Sodium arsenite either pre- or posttreatment has no apparent effect on the MMS-induced sister chromatid exchanges. The present results indicate that pretreatment of sodium arsenite not only does no harm but may even benefit the MMS-treated cells. On the contrary, posttreatment of sodium arsenite is cogenotoxic.

Chromosome analysis on a cell line (CE48T/VGH) derived from a human esophageal carcinoma.

The cell line CE48T/VGH was established from an epidermoid carcinoma of the middle third of the esophagus of a 58-year-old male patient. Cytogenetic analysis at passages 90-99 showed that the line was hypotetraploid, with a mean chromosome number of 73. None of the 50 karyotyped cells had a normal chromosome #1 or Y. Cells with multiple copies of some of the autosomes were observed frequently. Structural rearrangements were numerous, especially of chromosomes #1, #9, #14, X, and Y.