The action of proflavin and actinomycin D in causing chromatid breakage in human cells

Efficacy of a potentized homoeopathic drug (Arsenicum Album-30) in reducing genotoxic effects produced by arsenic trioxide in mice: II. Comparative efficacy of an antibiotic, actinomycin D alone and in combination with either of two microdoses

OBJECTIVE

To determine whether actinomycin-D (AMD), an antibiotic, alters the reported efficacy of a potentized homoeopathic drug, Arsenicum Album, in reducing genotoxic effects produced in arsenic-trioxide-injected mice.

DESIGN

Mice were separately injected with AMD, As2O3, and conjointly with AMD plus As2O3, AMD plus homoeopathic drug, AMD plus As2O3 plus homoepathic drug, and As2O3 plus homoeopathic drug in separate sets.

METHODS

Several standard cytogenetical endpoints were assessed at different fixation intervals by adopting conventional techniques.

RESULTS

Both Ars Alb-30 and Ars Alb-200 showed protective ability against AMD and As2O3 when injected individually, but this ability was reduced considerably in mice injected with AMD and As2O3 together. AMD itself had genotoxic effects, but also apparently reduced genotoxic effects of arsenic to some extent.

CONCLUSION

AMD reduced the protective efficacy of the homoeopathic drug against arsenic. This result suggests a mechanism of action for homoeopathy, as AMD is a known transcription-blocker.

Tests for the genotoxicity of m-AMSA, etoposide, teniposide and ellipticine in Neurospora crassa

The antitumor agents m-AMSA, etoposide, teniposide and ellipticine have been reported to be potent clastogens in mammalian cells but non- or weakly mutagenic in bacteria; these observations have been correlated to the interference of these chemicals with DNA topoisomerase II activity in the former, but not in the latter, organisms. The genotoxicity of these 4 agents was evaluated using ad-3 reverse- and forward-mutation tests in Neurospora crassa. These agents (up to 0.8 mumole/plate) did not cause reversion in conidia of the ad-3A frameshift strains N24 and 12-9-26 using the overlay plate test, as contrasted to the positive control frameshift mutagen ICR-170. Heterokaryon 12 (H-12) of N. crassa permits the recovery of all classes of forward mutation at the ad-3+ region, including multilocus deletions. Using resting conidia of H-12 in a suspension assay, ellipticine was moderately mutagenic but no increase in ad-3 mutants was noted with the other 3 agents at a dose of 100 micrograms/ml. In vegetative cultures of H-12 grown in the presence of these agents, all 4 agents were nonmutagenic at a dose of 100 micrograms/ml. The positive control mutagen ICR-170 was mutagenic in both resting conidia and growing cultures of H-12. A similarity between the topoisomerase II of N. crassa and DNA gyrase of bacteria is suggested.

Free radical formation by antitumor quinones

Quinones are among the most frequently used drugs to treat human cancer. All of the antitumor quinones can undergo reversible enzymatic reduction and oxidation, and form semiquinone and oxygen radicals. For several antitumor quinones enzymatic reduction also leads to formation of alkylating species but whether this involves reduction to the semiquinone or the hydroquinone is not always clear. The antitumor activity of quinones is frequently linked to DNA damage caused by alkylating species or oxygen radicals. Some other effects of the antitumor quinones, such as cardiotoxicity and skin toxicity, may also be related to oxygen radical formation. The evidence for a relationship between radical formation and the biological activity of the antitumor quinones is evaluated.

Mutagenicity and clastogenicity of proflavin in L5178Y/TK +/- -3.7.2.C cells

We evaluated the ability of proflavin to induce specific-locus mutations at the heterozygous thymidine kinase (tk) locus of L5178Y/TK +/- -3.7.2C mouse lymphoma cells, which appears to permit the recovery of mutants due to single-gene and chromosomal mutations. Proflavin was highly mutagenic at the tk locus, producing 724-965 TK mutants/10(6) survivors (background = 56-85/10(6); survival = 29-32%). Most of the mutants were small colonies, which suggested that proflavin may induce chromosomal mutations. The potent clastogenicity of proflavin was confirmed by cytogenetic analysis for chromosomal aberrations. At the highest dose analyzed (1.5 micrograms/ml), proflavin produced 82 aberrations/100 metaphaes (background = 2/100). The large-colony TK mutant frequency produced by proflavin (48-109/10(6) survivors; background = 23/10(6); survival = 57-61%) was similar to published HPRT mutant frequencies produces by proflavin in L5178Y and CHO cells (50-100/10(6) survivors; background = 2-50/10(6); survival = 50-62%). These results lead to the conclusion that proflavin is a potent clastogen and induces a high frequency of small-colony TK mutants; however, it induces a low frequency of HPRT mutants and a low frequency of large-colony TK mutants.

Detectability in vivo of stabilized intercalating agents with the alkaline elution technique. Comparison with in vivo sister chromatid exchange introduction

The purpose of the work reported here was to investigate, with the alkaline elution technique, the capability of in vivo administered actinomycin D, daunomycin and mitomycin C to induce DNA damage, DNA interstrand cross-linking and DNA-protein cross-linking. The ability of these compounds to induce increases in sister chromatid exchange (SCE) in the bone marrow cells of mice was also investigated. Actinomycin D and daunomycin were active in inducing single strands breaks, while mitomycin C was inactive. Mitomycin C showed a clear DNA interstrand cross-linking activity, while this activity was absent in actinomycin D and daunomycin. All three compounds were positive for SCE induction, but mitomycin C was by far the most active compound. Our results seem to suggest that stabilized intercalating agents are often detectable with the alkaline elution technique, after treatment in vivo. However, they cannot be evaluated with the simple alkaline elution technique only. It is convenient to add to the basic method the modification for detecting cross-links. Finally, DNA interstrand cross-linking and sister chromatid exchanges could be correlated.

Comparative mutagenicity of 4 DNA-intercalating agents in L5178Y mouse lymphoma cells

The mutagenicity of 4 known intercalating agents acridine orange (AO), quinacrine mustard (QM), proflavin (PF) and ethidium bromide (EB) has been investigated in L5178Y mouse lymphoma cells. Methyl methanesulfonate (MMS) was used as a positive control in these studies. AO, QM and PF induced mutation in the excess thymidine- and thioguanine-selective systems. These 3 compounds were negative in the ouabain- and cytosine-arabinoside-selective systems while EB was positive only in the cytosine arabinoside system. It would appear that the EB-induced mutagenesis is different from that of AO, QM and PF though all are intercalating agents. Since the molecular origin of cytosine arabinoside mutants is unknown, further interpretation of the EB results is not possible.

Mutations in rDNA. 2. Effects of Actinomycin D on chromatid aberration induction in nucleolus organizer regions

A reconstructed karyotype of barley with all chromosomes interdistinguishable was treated with hydroxyurea (HU) and Actinomycin D (Act D). The distribution pattern of chromatid aberrations after treatment with HU alone is characterized by a marked preferential involvement in chromatid translocations of segments 36 (NOR of satellite chromosome 6) and 43 (NOR of satellite chromosome 7). Act D applied at the low concentration of 0.05 μg/ml (4.10(-8) M) before HU treatment, or combined with HU, was found to cause an apparent decrease of HU-induced aberration frequencies in NORs. The exchanges in both segments proved to be approximately a half lower after Act D application when compared to the respective controls (treatment with HU alone). A recovery period of 5 h between the prolonged pretreatment with Act D (15 h) and the HU treatment eliminated the effect of the drug. The possible dependence of mutation induction upon the transcriptional activity of rDNA in NORs after Act D application is discussed.

A simple reproducible method for prometaphase chromosome analysis

A method is described for the analysis of chromosomes in prophase and early metaphase. It involves culturing the lymphocytes in medium RPMI-1640, supplemented with 10% autologous plasma instead of fetal bovine serum. Living cells are treated with actinomycin D and colcemid for 1 h prior to harvest and harvested early at 65 h of incubation, using a hypotonic solution formulated by Ohnuki (1968). The method has been tested on several hundred clinical samples on a routine basis. On average, 30% of the dividing cells were in prometaphase.

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

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.

Genetic effects of acridine compounds

Acridines and a very large number of acridine derivatives are used in enormous quantities both in medicine and industry. The mutagenic action of these compounds has been demonstrated in a wide variety of organisms and is known to occur both in the dark as well as in the presence of light (photodynamic action). At the molecular level, acridines have been shown to cause frameshift mutations of both the addition and deletion types, a characteristic which has been of tremendous help in elucidating the nature of the genetic code. These and various other biological effects of acridines, such as inhibition of DNA repair, curing of plasmids and cell-growth inhibition, are examined in this review.

Further studies on the histological cytological and cytogenetic effects of nogalamycin in mammals

The histological, cytological and cytogenetic effects of nogalamycin were studied in rats, mice and cultured human leukocytes. Four standard test systems were used in the cytological studies: (1)analysis of spermatogonial cells, (2)cytological evaluation of bone marrow metaphase plates, (3)micronucleus test in polychromatic erythrocytes, and (4)determination of chromosomal aberrations in cultured human leukocytes. The results of the studies indicated that the types and frequenices of cytological errors induced by the drug were not significantly different from the concurrent control. The reduced incidence of fertile matings from 22 to 35 days after treatment is attributed to the cytostatic effect of nogalamycin (NM) on spermatogonia and spermatocytes. Subsidence of NM-induced inhibition of spermatogonium differentiation and spermatocyte maturation occurred 37 days post-treatment. Accordingly, fertile matings, which had reached a zero level by 23rd day, occurred 35 days after treatment, and reached the control level between 47 and 49 days post-treatment.

Interaction of daunomycin with meiotic chromosomes in Vicia faba

Daunomycin interferes with the meiotic cycle and structural integrity of chromosmes if administered to microsporocytes of Vicia faba during the meiotic prophase substages prior to diplotene. The principal cytological consequences of daunomycin treatment are as follows: induced achromatic lesions, chromosome fragmentation, terminal and interstitial deletions, loose or non-pairing regions, multivalent associations, reduced chromosome condensation, chromosome stickiness, dicentric and side-arm bridges and chromatid loops. A correlation between inhibition of DNA or RNA and the cytological manifestation of structural anomalies or unfolding of meiotic events is discussed.

Labeling and other effects of actinomycin D on human chromosomes

(3)H-actinomycin D, a guanine-binding agent, labels fixed human chromosomes nonrandomly. Actinomycin D added in G2 inhibits secondary constrictions and breaks chromosomes. There is some tendency for label to be concentrated at the ends of chromosomes and near the centromere. Labeling with (3)H-thymidine in the late stage of DNA synthesis shows a different pattern and in general lacks the telomeric concentrations. The sites of actinomycin D-induced breaks do not show good correspondence with the sites of actinomycin D label.