Chromosome breakage

Mitomycin C was found to have broad activity against a range of tumors and has been used clinically since the early 1960s [14, 15]. It causes many specific cellular effects, including inhibition of DNA synthesis, recombination, chromosome breakage, sister chromatid exchange, induction of DNA repair, and induction of... 

This indicates that endosulfan is capable of inducing chromosome breakage and loss. Endosulfan also induced cytotoxic activity (significant increase in the number of crossover colonies) in the yeast strain S. cerevisiae T2 (deficient in repair system), but not in S. cerevisiae T1 (L Vova 1984). 

Mice exposed to 2,000 ppm of trichloroethylene, 4 hours/day for a 5-day period, had a significant increase in abnormal sperm morphology of 1% 28 days after the exposure (Land et al. 1981). No effect was seen at 200 ppm. A 6% increase in abnormal sperm was observed 4 weeks, but not 4 days or 10 weeks, after mice were exposed to 100 ppm trichloroethylene 7 hours per day for 5 days (Beliles et al. 1980). Based on the time after exposure at which sperm were affected, the study authors indicated that trichloroethylene damages sperm precursor cells but that spermatogonia were either unaffected or were capable of recovery. Reproductive performance was not tested in these studies. Another mouse study tested the effects of a 5-day exposure (6 hours/day) on spermatid micronuclei frequency no effects were observed at exposure levels of up to 500 ppm, the highest concentration tested (Allen et al. 1994). These results were interpreted as evidence that trichloroethylene did not cause meiotic chromosome breakage or loss. No treatment-related reproductive effects were seen in female rats exposed to 1,800 ppm trichloroethylene for 2 weeks (6 hours/day, 7 days/week) before mating (Dorfmueller et al. 1979). 

The mouse micronucleus test (which detects chromosome breakage or chromosome loss from mitotic abnormalities in bone marrow erythrocytes) (MacGregor et al. 1979). 

Ziemsen, B., J. Angerer, and G. Lehnert. 1987. Sister chromatid exchange and chromosomal breakage in pentachlorophenol (PCP) exposed workers. Ini. Arch. Occup. Environ. Health 59 413 417. 

Binding of Hg2 + to DNA may cause degeneration and chromosomal breakage of spermatogenic cells [235]. Moreover, mercuric chloride gives a direct inhibition of sequence synthesis in murine spermatogonia cells and possibly an inhibition of essential spermatogenic enzymes [236]. 

Pioneer work in this field has been carried out by J. S. Mitchell.1 The idea is to select a radiosensitizing compound which blocks entry of cells into mitosis and also provides chromosome breakage. The compound itself must also be of low toxicity. 

Chen H, Eastmond DA. 1995a. Synergistic increase in chromosomal breakage within the euchromatin induced by an interaction of the benzene metabolites phenol and hydroquinone in mice. Carcinogenesis 16 1963-1969. 

The micronucleus assay may be used not only for the detection of acute but also chronic genetic damage. In mice, chromosomal breakage in bone marrow erythroblasts produces an accumulation of micronuclei in normochromatic erythrocytes in peripheral blood and there is little, if any, selective removal of micronucleated cells from circulation. This is not the case with rats, which limits their usefulness in long-term studies using peripheral blood. 

Examining the chromosomes of some of our volunteers before and after LSD exposure turned up no significant changes. Nevertheless, reports both of chromosome breakage and non-breakage continued until an almost equal number of negative and positive findings had accumulated in about 40 scientific articles. 

Fetner, R. H. Chromosome breakage in Vida jaba by ozone. Nature 181 504-505, 1958. 

Fetner, R. H. Ozone-induced chromosome breakage in human cell cultures. Nature 194 793-794, 1%2. 

Sharma AK, Battacharya NK. 1956. Chromosome breakage through paradichlorobenzene treatment. Cytologia 21 353-360. 

Armstrong MJ, Galloway SM, Ashby J 2,4,6-Trichlorophenol (TCP) induces chromosome breakage and aneuploidy in vitro. Mutat Res 303(3) 101-108, 1993... 

Ochs K, Sobol RW, Wilson SH, Kaina B (1999) Cells deficient in DNA polymerase beta are hypersensitive to alkylating agent-induced apoptosis and chromosomal breakage. Cancer Res 59 1544-1551... 

Clastogens Agents which cause chromosome breakage. 

C. Blount et al., Folate Deficiency Causes Uracil Misincorporation into Human DNA and Chromosome Breakage Implications for Cancer and Neuronal Damage, Proc. Natl. Acud. Sci. USA94 (1997) 3290-95. 

Vitamins and minerals, whose main dietary sources are other than fruits and vegetables, are also likely to play a significant role in the prevention and repair of DNA damage, and thus are important to the maintenance of long-term health. Vitamin B12 is found in animal products, and deficiencies of B12 cause a functional folate deficiency, accumulation of the amino acid homocysteine (a risk factor for heart disease),46 and chromosome breaks. B12 supplementation above the RDA was necessary to minimize chromosome breakage.47 Strict vegetarians are at increased risk for developing vitamin B12 deficiency. 

Inhibition of repair can be a major part of the process of chromosome breakage, for example, the chemical hydroxylamine will inhibit the repair of radiation-induced strand breaks. 

Chromosome breakage may therefore be linked to other mechanisms of mutagenesis in some fundamental manner. The correction of errors involves breakage of the DNA molecule for both the "cut and patch" type of repair and for sister-strand exchange (Fig. 6.46). 

Some chemicals are progressor agents such as benzene, asbestos, and arsenic salts, for instance, and these could also be complete carcinogens. These may induce chromosomal breakage (clastogenesis) or progression could be spontaneous. 

It induced sister chromatid exchanges, chromosome breakage and chromosome loss... 

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