(1983). Ionizing Radiation: Sources and Biological Effects. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine: Vol. 43, No. 5, pp. 585-586.

Ionizing Radiation: Sources and Biological Effects

Cyclophosphamide (CP) is used to treat a wide range of neoplastic diseases as well as some non-malignant ones such as rheumatoid arthritis It is also used as an immunosuppressive agent prior to organ transplantation CP is, however, a known carcinogen in humans and produces secondary tumors There is little absorption either orally or intravenously and 10% of the drug is excreted unchanged CP is activated by hepatic mixed function oxidases and metabolites are delivered to neoplastic cells via the bloodstream Phosphoramide mustard is thought to be the major anti-neoplastic metabolite of CP while acrolein, which is highly toxic and is produced in equimolar amounts, is thought to be responsible for most of the toxic side effects DNA adducts have been formed after CP treatment in a variety of in vitro systems as well as in rats and mice using 3H-labeled CP 32P-postlabeling techniques have also been used in mice However, monitoring of adducts in humans has not yet been carried out CP has also been shown to induce unscheduled DNA synthesis in a human cell line CP has produced mutations in base-pair substituting strains of Salmonella tryphimurium in the presence of metabolic activation, but it has been shown to be negative in the E coli chromotest It has also been shown to be positive in Saccharomyces cerevisiae in D7 strain for many endpoints but negative in D62M for aneuploidy/malsegregation It has produced positive responses in Drosophila melanogaster for various endpoints and in Anopheles stephensi In somatic cells, CP has been shown to produce gene mutations, chromosome aberrations, micronuclei and sister chromatid exchanges in a variety of cultured cells in the presence of metabolic activation as well as sister chromatid exchanges without metabolic activation It has also produced chromosome damage and micronuclei in rats, mice and Chinese hamsters, and gene mutations in the mouse spot test and in the transgenic lacZ construct of Muta Mouse Increases in chromosome damage and gene mutations have been found in the peripheral blood lymphocytes of nurses, pharmacists and female workers occupationally exposured to CP during its production or distribution Chromosome aberrations, sister chromatid exchanges and gene mutations have been observed in somatic cells of patients treated therapeutically with CP In general, there is a maximum dose and an optimum time for the detection of genetic effects because the toxicity associated with high doses of CP will affect cell division In germ cells, CP has been shown to induce genetic damage in mice, rats and hamsters although the vast majority of such studies have used male mice(ABSTRACT TRUNCATED AT 400 WORDS)

Cyclophosphamide: Review of its mutagenicity for an assessment of potential germ cell risks

This report presents an assessment made by the U.S. Environmental Protection Agency Gene-Tox Program's Work Group on mammalian cytogenetics of the clastogenic effects of chemicals in in vivo and in vitro mammalian cell assays. This assessment is based on information provided by the Environmental Mutagen Information Center, Oak Ridge National Laboratory, with the proviso that the experimental protocol used in these papers was adjudged to be acceptable by standards outlined by the Work Group. Some data were accepted as "qualitative only" because the protocol used was fairly close to that proposed as suitable. Using these criteria, 177 papers were selected for review. 6 assays were reviewed: bone marrow (32 papers, 31 chemicals), spermatogonial (10 papers, 10 chemicals), spermatocyte (25 papers, 25 chemicals), oocyte or early embryo (18 papers, 19 chemicals), in vitro cell culture (30 papers, 66 chemicals), and leukocyte (66 papers, 53 chemicals). Each assay was considered separately, and comparisons were then made between them for their similarities or differences in producing a positive or negative clastogenic effect of a particular chemical or chemical class. A large proportion of the available cytogenetic data was not suitable for inclusion in the final data base because of poor experimental design or unsatisfactory reporting of the information. It was not possible to recommend any one assay for determining potential clastogenicity because each had its own particular advantages and limitations and provided unique information. For demonstrating in vivo effects, the bone-marrow assay is probably the simplest and most economical. If only in vitro exposures were considered, leukocytes or cultured mammalian cell lines would be suitable. However, there are advantages to using leukocytes because they are a synchronous population, at least through their cell division, and because of the ready availability of human cells. In general, there was good agreement between clastogenicity and carcinogenicity.

Mammalian in vivo and in vitro cytogenetic assays: a report of the U.S. EPA's gene-tox program.

Gene amplification in cultured cells.

Cytogenetic preparations from oocytes remaining unfertilised after in vitro fertilisation revealed single chromatids (as opposed to whole chromosomes) in 4 out of 38 meiosis II metaphases. In one oocyte, a single chromatid was present in addition to the normal 23,X complement, and in three oocytes, two identical but separate chromatids replaced one whole chromosome within the complement. The data indicate that the chromatids have arisen as a result of premature division of the centromeres at meiosis I (“predivision”). None of the oocytes were hyperhaploid with an extra whole chromosome. These findings are at variance with the general belief that trisomy in man is largely a consequence of nondisjunction of whole bivalents at meiosis I and they suggest that predivision resulting in separate chromatids may be a significant mechanism for human trisomy.

Predivision in human oocytes at meiosis I: a mechanism for trisomy formation in man

Just before ovulation we treated 10–12-week-old female mice of the strains C3H and (101×C3H)F1 with 2.3.5.-triethyleneimonobenzoquinone-1.4 (T), cyclophosphamide (C) and methotrexat (M). The chromosome analysis took place shortly after ovulation at the time of metaphase II. The method described in detail seems to be appropriate to examine the induction of genetic defects during oogenesis by chemical agents.

Induced chromosome aberrations in unfertilized oocytes of mice.

10–12-week-old female mice of the C3H strain and (101xC3H)F1 hybrids were treated with 2,3,5-triethyleneiminobenzoquinone-1,4 (T) shortly before induced ovulation. Then the animals were mated with untreated males of the same type. The embryos from these matings were flushed out of the oviduct usually during the 2-cell-stage and subjected to chromosome analysis. We found significant differences between both experimental series and matching controls, especially with the frequency of aneuploidy. Thus, we could demonstrate that chromosome aberrations can be chemically induced in the pre-ovulatory phase of oogenesis.

Induced chromosome aberrations in early embryogenesis of mice

We investigated the cytogenetic effects of X-rays on unfertilized mouse oocytes. NMRI females received an irradiation with 0, 22.2, 66.6, 200, and 600 R during the preovulatory phase 3 hrs after HCG (human chorionic gonadotrophin). This is a stage during oogenesis in which the oocytes pass from late dictyotene to diakinesis. Chromosome analysis was performed after ovulation at metaphase II.

Chromosome anomalies in mouse oocytes after irradiation

10-to 12-week-old (101xC3H)F1 female mice were treated with 0.25 mg/kg triazoquinone (T) during the preovulatory phase of oogenesis. Immediately after administration they were mated with untreated males of the same strain and age. 68 hrs after detection of a vaginal plug checked for hourly, the fallopian tubes of the control and experimental females were flushed out. The cleavage stages were cytologically prepared and chromosome analysis was performed during the early morula stage.

I. Hansmann

Papers

Induced chromosome aberrations in unfertilized oocytes of mice.

Induced chromosome aberrations in early embryogenesis of mice

Chromosome anomalies in mouse oocytes after irradiation

Chromosome aberrations in preimplantation stages of mice after treatment with triazoquinone.

Letter: Comments in response to: Seasonal Variation in the Birth of Children with Aneuploid Chromosome Abnormalities.