The effect of nitrofurans on mitosis, chromosome breakage and sister-chromatid exchanges in human peripheral lymphocytes

Sister-chromatid exchange: second report of the Gene-Tox Program

This paper reviews the ability of a number of chemicals to induce sister-chromatid exchanges (SCEs). The SCE data for animal cells in vivo and in vitro, and human cells in vitro are presented in 6 tables according to their relative effectiveness. A seventh table summarizes what is known about the effects of specific chemicals on SCEs for humans exposed in vivo. The data support the concept that SCEs provide a useful indication of exposure, although the mechanism and biological significance of SCE formation still remain to be elucidated.

A comparative analysis of data on the clastogenicity of 951 chemical substances tested in mammalian cell cultures

A literature review was conducted using original papers published during 1964-1985 on the in vitro clastogenicity of chemical substances. Results of tests on 951 chemical substances were abstracted from over 240 reports to form the database. The evaluation of these data relied on each author's original conclusion on a positive or negative outcome. Of these 951 substances, 447 (47%) were consistently positive either with or without activation; 417 (44%) were negative in the direct test but not tested with metabolic activation systems; 4 were negative but tested only with activation; and 30 (3%) were clearly negative both with and without activation. The remaining 53 substances gave variable results when tested under different experimental protocols or in different cell types, but were positive in at least one test. Although discrepant results were found associated with some cell types, the addition of metabolic activation systems tended to eliminate such variability. No one cell appeared to be superior in response to all clastogens. For screening purposes, the choice of cell may thus depend more on the general usefulness and reliability of a cell type than on a strong response to a particular chemical. However, the use of a suitable metabolic activation system does appear to be of critical importance. The concentration at which clastogenic effects were detected varied extensively for different test substances, ranging from a minimum of 4.3 X 10(-8) to 6.9 X 10(2) mM. Possible mechanisms of action for substances active at only high levels are discussed, but no satisfactory explanation is available at this time. The relevance of tests conducted at concentrations high enough to alter significantly the osmolarity and other culture conditions is considered, and caution urged in the interpretation of test results obtained under physiologically stressful conditions. The clastogenic potential was compared quantitatively using an index of effective concentration (D20) and one which estimates the number of cells with exchange aberrations expected per mg/ml (TR) for data obtained by using a uniform protocol and cultures of Chinese hamster lung (CHL) cells. Both values were distributed over a wide range, demonstrating the variety of genotoxic potential in chemicals. In general, a substance which was active at only high concentrations produced fewer exchange-type aberrations. In vivo activity, as measured by tumourigenic effect and formation of micronuclei in bone marrow, tended to be greater for substances with a D20 below 10(-2) mg/ml and a TR value over 10(3).(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of structural chromosome aberrations and sister chromatid exchanges in human lymphocytes in vitro by aristolochic acid

The medicinal use of Aristolochia clematitis has been known for some time. The main active agent of this medicinal plant is aristolochic acid, a nitrophenanthrenecarbonic acid. Very recently, however, the Federal Health Office withdrew the licence for all drugs containing aristolochic acid, because of the well-founded suspicion that aristolochic acid may be a very potent carcinogen. We investigated the induction of structural chromosome aberrations and sister chromatid exchanges (SCEs) by aristolochic acid in human lymphocytes in vitro. Cells were treated with the agent tested throughout culture time and during the G0 phase of the cell cycle. We tested concentrations over a range of 1 to 20 micrograms/ml. Both treatment conditions resulted in an increased aberration frequency. The induction of gaps and breaks as well as the induction of SCEs showed a dose-dependent increase. The number of SCEs per metaphase was enhanced by a factor of 2 to 3. If conventional cytogenetic methods had been applied in time, one would have recognized the mutagenic risk of aristolochic acid earlier.

Sister chromatid exchange (SCE) and structural chromosome aberration in mutagenicity testing

Data from previous studies published on the induction by mutagens of sister chromatid exchanges (SCEs) and structural chromosome damage were compared qualitatively and quantitatively. Although a good correlation between the incidence of both cytogenetic phenomena has been pointed out in many previous publications, about 30% of the agents for which comparable data were available yielded non-corresponding qualitative results concerning both indicator effects. However, even in groups with good qualitative agreement distinct quantitative differences indicated different molecular mechanisms of the formation of SCEs and breaks. Additional information supporting the importance of these differences for the validity of both indicator systems has been derived from the results obtained using strong clastogens exhibiting a low or no SCE-inducing activity and vice versa, from special observations on chromosomal breakage syndromes, and from studies on the action of known co- and anti-clastogens on SCE-induction by chemical mutagens. As a result, it has been suggested that the SCE-technique should be considered as a valuable additional method for cytogenetic mutagenicity testing, which, however, is not adequate to replace the classical methods of analysis of structural chromosome damage.

Sister-chromatid exchanges: a report of the GENE-TOX program

The effects of a number of chemicals on sister-chromatid exchange (SCE) frequencies in in vivo and in vitro systems are reviewed. Standardized protocols for future SCE testing in important systems, as well as for evaluation of test results, are presented. Data reported thus far suggest that SCE analysis may prove useful, especially at a secondary level, as a test of mutagenic carcinogens. Strengths and limitations of SCE analysis are summarized as a guide for future evaluation and use of this procedure.

Mutagenicity screening of feed additives in the microbial system

18 feed additives were tested for DNA-modifying effects by the repair test named "rec-assay" with Bacillus subtillis H17 (rec+) and M45 (rec-), and for mutagenicity with Escherichia coli WP2 hcr and 5 Salmonella typhimurium tester strains with the use of a top-agar overlay method. Carbadox, furazolidone, panazon and zoalene were positive in both assays. The former 3 were mutagenic for TA100, TA98 and WP2 hcr, while zoalene was mutagenic for all strains. These 4 compounds did not require a metabolic activation for their mutagenic activities. Nicarbazin was weakly mutagenic for TA1538 and TA98 with and without S9 mix. Amprolium and caprylohydroxamic acid also showed very weak mutagenicities only for TA100 with S9 mix and for WP2 hcr with and without S9 mix, resp. The mutagenic activities of carbadox, furazolidone and panazon for TA100 were reduced only by the addition of S9 mix, but not by S9 fraction or blood, whereas that of zoalene was decreased by any of the 3 factors.