The gene-protective effect of sodium humate under conditions of induced oxidative stress

It was shown that sodium humate decreased the level of the dioxidin-induced clastogenic effects in the range of concentrations of 50 to 1000 mg/l; dioxidin, a mutagen with prooxidant properties, was used at the concentration of 20 mg/l. The maximum effect was observed at the concentration of 300 mg/l. No direct dose-response dependence under the effect of sodium humate was found. The feasible antioxidant and desmutagenic mechanisms of a protective effect of sodium humate are discussed.     

Mutagenic and genotoxic effects of Anilofos with micronucleus,chromosome aberrations,sister chromatid exchanges and Ames test

We aimed to evaluate the mutagenic effect of Anilofos, organophosphate pesticide, by using Ames/Salmonella/microsome test. Its cytotoxic and genotoxic effects were also determined by chromosome aberration (CA), sister chromatid exchange (SCE) and micronucleus (MN) test in human peripheral blood lymphocytes. In the Ames test, five different concentrations of Anilofos were examined on TA97, TA98, TA100 and TA102 strains in the absence and presence of S9 fraction. According to the results all concentrations of this pesticide have not shown any mutagenic activity on TA97, TA100 and TA102 strains in the absence and presence of S9 fraction. But, 10, 100 and 1000 µg/plate concentrations of Anilofos were determined to be mutagenic on TA98 strain without S9 fraction. Lymphocytes were treated with various concentrations (25, 50, 100 and 200 µg/ml) of Anilofos for 24 and 48 h. The results of the assays showed that Anilofos did not induce SCE frequency, replication index and MN formation at all concentrations for both treatment periods. Anilofos significantly increased CA frequency at 100 and 200 µg/ml concentrations at 24 h treatment periods and at 50, 100 and 200 µg/ml concentrations in 48 h treatment periods. Additionally, it was determined that this pesticide decreased mitotic index and nuclear division index significantly. It was concluded that Anilofos has genotoxic and cytotoxic effects in human peripheral lymphocytes.     

Comparative study of the effectiveness of selection in diploid and autotetraploid populations]

The mitotic activity and ploidy of cells of three strains of cellus tissue by the addition of the culture medium of 0,01; 0,1 and 1 mg/l of phytohemagglutinin was studied. These strains derived from the leaves of haploid, diploid, and tetraploid plants of Lycopersicon, esculentum. The number of dividing cells under the influence of phytohemagglutinin increased by 1;5 and 4% for haploid, diploid and tetraploid strains respectively. The shift of the peak of the mitotic activity at early stages of subculture under the effect of phytohemagglutinin was noticed. Phytohemagglutinin did not change the frequencies of cells of different ploidy in all the strains analysed. A weak mutagenic activity of phytohemagglutinin in the concentrations used was observed. Cells with single bridges were more frequently observed among the aberrant cells.     

Genetic activity of carbamate herbicides in Escherichia coli and Saccharomyces cerevisiae

DNA-damaging activity and herbicide-induction of gene point mutations, and intragenic mitotic recombination were studied in bacteria and the yeast tester strains. Herbicide (eptam, triallate, tillam, surpass) were not effective in DNA-damaging and mitotic recombination tests. Of the 4 chemicals, only eptam was strongly mutagenic. Dose response curves for eptam differed in bacteria and yeast; maximum mutagenic activity was registered in bacteria at 5 mg/l. Maximum yield of prototrophs was observed after 2 h incubation time. Triallate was moderate, tillam and surpass being weak mutagens for the strains used.     

The nature of DNA damage and its repair after treatment of bacteria with dioxidine

The nature of the lethal effect of antimicrobial drug dioxidin was studied. The treatment of bacterial cells by dioxidin results in an instant repression of DNA synthesis and formation of single strand gaps in DNA molecule. The repair of single strand gaps in polA+ cells involves the DNA polymerase I. The deficit of this enzyme leads to the increased degradation of DNA. The products of the recA, polA1, lexA, recB are relevant for bacterial resistance to dioxidin while the products of uvrA, uvrE and recF genes are not. On the basis of the obtained data dioxidin may be defined as a "gamma-type" agent due to the nature of dioxidin-induced lesions in DNA and their repair.     

Effects of Detergents on in vitro Growth of Diatom Alga Thalassiosira pseudonana

The growth of the diatom alga Thalassiosira pseudonana was studied when exposed to an environment polluted by a detergent. We determined concentrations that inhibit cell division (10 mg/l) instead of algae growth (0.1 and 1 mg/l. It was shown that T. pseudonana can adapt to high detergent concentrations. The stimulation of the growth of Thalassiosira within a range of 0.03–0.08 mg/l concentration has been registered.     

On the genotoxicity of the pesticides Endodan and Kilacar in 6 different test systems

Two pesticides, the fungicide Endodan (ethylene thiuram monosulphide) and the insecticide-acaricide Kilacar (bis(parachlorophenyl)cyclopropyl methanol), produced or used in the neighbouring countries of Bulgaria and Greece were investigated in a coordinated research programme for their genotoxic effects in a variety of test systems. This included the Ames test, Aspergillus nidulans for mitotic segregation, in vitro human lymphocyte cell cultures for SCE and chromosomal aberrations, in vivo bone marrow cells in hamsters and rats and the dominant lethal test in rats. The genotoxicity of Endodan was found to range from negative to slightly positive in different test systems. At concentrations of 7.5 and 12.0 micrograms/plate together with S9 mix it induced base-pair substitutions in the TA100 strain of Salmonella typhimurium at a rather low level. At a dose of 93 mg/kg b.w. it also caused chromosomal aberrations in acutely treated hamster bone marrow cells. A significant increase of SCE was also found in human lymphocyte cultures at a concentration of 20.0 micrograms/ml. Endodan was found to be negative in A. nidulans for somatic segregation, lymphocyte cultures for chromosomal aberrations and mitotic activity and in rats for dominant lethals and chromosomal aberrations. Kilacar was found to be a weak mutagen in the TA97 strain of S. typhimurium at concentrations of 2.5 and 5.0 micrograms/plate together with S9 mix. At concentrations of 1.0, 1.5 and 2 micrograms/ml Kilacar increased the number of mitotic segregants in A. nidulans by 160%, 220% and 156% respectively over the control. In Syrian hamster bone marrow cells after acute administration at concentrations of 0, 40, 80 and 160 mg/kg, the MI was 5.50, 4.30, 3.10 and 1.30 respectively, and an increase in chromosomal aberrations of about 300% over the control was observed with a concentration of 80 mg/kg. In human lymphocytes no significant changes were observed in either MI or SCE. In the dominant lethal test after chronic treatment of male rats at doses of 5.1, 10.2 and 102.0 mg/kg b.w. no significant mutagenic effect was found although a decrease was shown in the percentage of females with implants mated with treated males in the first week.     

Induction of micronuclei in tadpoles of Rana temporaria and Xenopus laevis by the pyrethroid Fastac 10 EC.

The mutagenic properties of the pyrethroid Fastac 10 EC were estimated using the micronucleus test in tadpoles of Rana temporaria and Xenopus laevis. The frequency of erythrocytes with micronuclei was examined in blood smears obtained from animals kept for 14 days in water containing 3 different concentrations of Fastac 10 EC. The study was accompanied by a positive control using the known mutagens cyclophosphamide and N-methyl-N-nitrosourea. The results obtained showed that at high concentrations Fastac 10 EC has a clastogenic activity and/or damages the mitotic spindle, as manifested by a significant increase in the frequency of the micronucleated red blood cells. It was also demonstrated that tadpoles of Rana temporaria are more sensitive to the mutagenic effect of the pyrethroid than are those of Xenopus laevis.     

Mutagenicity in Salmonella typhimurium TA98 and TA100 of nitroso and respective hydroxylamine compounds

Five aromatic nitroso compounds were prepared and their mutagenicity in Salmonella typhimurium strains TA98 and TA100 compared with that of the corresponding hydroxylamines and the previously studied nitroarenes. A remarkable correspondence of the dose-response curves was observed between the nitroso and the respective hydroxylamine compounds. This effect could be observed in TA98 and TA100. It was only marginally dependent on the metabolical activation by rat liver S9-mix. Even the presence of a bulky alkyl substituent either near to the functional group, or far away from it, previously shown to considerably influence the mutagenic properties of nitroarenes, does not remarkably affect the properties of the nitroso and hydroxylamine species. The similarity between the latter two is likely to be due to a fast reduction of the nitrosoarenes to the hydroxylamine species under the test conditions. It seems that enzymes are not responsible for that reduction step, because sterical crowding near the functional group does not influence that behaviour.The test results of the aromatic hydroxylamines bearing a bulky substituent show that there are at least two ways to influence the mutagenicity of an aromatic nitro compound by such a group. A substituent near the functional group (ortho-position) disturbs the enzymatic reduction of the nitro group, because 3-tert-butyl-4-hydroxylaminobiphenyl and its corresponding nitroso compound are highly mutagenic, whereas 3-tert-butyl-4-nitrobiphenyl was previously shown to be inactive even after addition of S9-mix. In contrast, 4'-tert-butyl-4-hydroxylaminobiphenyl with the tert-butyl group "far away" from the hydroxylamino functionality clearly shows decreased mutagenic activity suggesting a different influence of a substituent in that position. In addition, the substance shows only little cell toxicity even at higher concentrations. Both effects could be due to a reduced effective dose of the hydroxylamine in the cells compared to the non-alkylated compound, caused by a faster degradation of the hydroxylamine or a hindered interaction between that substance and the cells.     

Mutagenic and cytotoxic effectiveness of diisopropyl xanthogen polysulphide in human lymphocyte cultures

The mutagenic and cytotoxic effectiveness of the new rubber vulcanisation accelerator diisopropyl xanthogen polysulphide (Robac AS 100) was tested in human lymphocyte cultures of four healthy probands. The concentrations of Robac AS 100 were 0.57, 5.7 and 57.0 microg/ml. Higher concentrations showed too high cytotoxicity to be evaluable.Without external activation, incubation time with Robac AS 100 was 21 h. In the presence of rat liver microsomes from aroclor-induced rats (2mg microsomal protein/ml), incubation of the test compound was 2h.Mutagenicity testing was performed by analysis of micronuclei (MN), structural chromosome aberrations (CAs) and sister chromatid exchanges (SCEs). The MN-rate was determined using the cytochalasin B (cyt B) block method. For evaluation of cytotoxicity, mitotic index (MI) and nuclear division index (NDI) were determined. The validity of the test methods was ascertained by positive controls: mitomycin C (MMC) and bleomycin (BLM) were used in experiments without exogenous activation and cyclophosphamide (CP) in experiments with exogenous activation.The presence of rat liver microsomes increased the mutagenic effect of Robac AS 100 in the SCE- and MN-test. But only the highest Robac AS 100-concentration (57.0 microg/ml) showed significantly increased mutagenic activity in all tests. However, cytotoxicity at this concentration was already substantial. Therefore, we consider the evidence for mutagenicity of Robac AS 100 as limited.     

Genetic activity of sim-triazine herbicides on Saccharomyces cerevisiae yeast strains

Triazine chloro derivatives: atrazine, simazine manifest no mutagenic and recombinogenic properties in yeasts; triazine methylthio derivatives: prometryne, semeron (desmetryne) generate both genetic events with low concentrations of 0.5 and 5 mg/l. It is found that prometryne is more able to generate point mutations, while semeron--to generate mitotic recombinations. In this case frequency of experimental prototrophs is twice higher than the control level.     

Herbicidal Effects on Water Uptake of Seeds of Selected Weed Species

Seeds of yellow foxtail, johnsongrass, pigweed and quackgrass were investigated to determine the effects of certain herbicides on water uptake by these species. Seeds of johnsongrass showed slight increase in water uptake over the 20-h period when treated with 1, 5, 10, and 500 mg/1 of 2,4-D. Tordon caused a most pronounced increase in water uptake at 0.1 and 1 mg/l as compared with the controls. Johnsongrass gave indications of either increases or decreases in water uptake when treated with herbicides during the 20-h period, but showed no effects during the 10-h period. Dormant seeds of yellow foxtail indicated an enhancement in water uptake at all 2,4-D concentrations during the 20 h period. The effects which the different herbicides had upon the uptake of water in yellow foxtail seeds seemed to be directly proportional to increase in imbibition time. In all cases, more water was imbibed after 20 h over that observed at 10 h. During the 10-h imbibition period, pigweed seeds treated with 2,4-D was noted to have a slight stimulating effect on water uptake at all concentrations employed except 5 mg/l, which indicated a depressing effect. It was also observed that 2,4-D caused a significant stimulating effect on water uptake of pigweed seeds over the 20-h period as compared with the controls. A stimulation in the total quantity of water imbibed after 20 h was noted at dacthal concentrations below 100 mg/l whereas at the 500 mg/l, a slight depression in water imbibition was observed. At dalapon concentrations of 1 to 100 mg/l, a marked stimulation in total water imbibed by quackgrass seeds was shown during the 10-h period.     

Mutagenicity of potentially carcinogenic mycotoxins produced byFusarium moniliforme

The mutagenic behaviour of two potentially carcinogenic mycotoxins produced byFusarium moniliforme was investigated in theSalmonella mutagenicity test using tester strains TA97a, TA98, TA100, and TA102. The mutagenic response obtained with fusarin C (1, 5, and 10μg/plate) against tester strains TA98 and TA100 in the presence of microsomal activation confirmed previous observations on the mutagenic behaviour of this mutagen while that obtained against TA97a is reported for the first time. No dose-response relationship could be detected for the concentration levels (0.2, 0.5, 1, 5, 10 mg/plate) tested for FB₁, FB₂, and FB₃ against any of the tester strains used in either the plate incorporation and / or the pre-incubation tests. A cytotoxic effect was obtained at concentration levels of 5 and 10mg/plate in the absence of the microsomal activation mixture. From the studies it became evident thatF moniliforme produces two compounds, a mutagenic compound, fusarin C which has been shown to lack carcinogenic activity in rats and the non-mutagenic fumonisin B mycotoxins of which FB₁ is known to be responsible for the hepatocarcinogenicity of the fungus in rats.     

Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg Cd/l. In addition, a proportionality between delay in development and weight reduction was found in Cd-treated adults. Survival of adult females was decreased at concentrations higher than 10 mg Cd/l, while males were only affected at 30 mg Cd/l or higher doses. Reproduction was the most affected parameter. Oviposition rate, fecundity and fertility of females exposed to 10 mg Cd/l were significantly lower than controls (73%, 58% and 55% relative to controls, respectively). Hatchability of the eggs laid by treated females was also reduced. These results show that development and reproduction of O. fasciatus are seriously impaired at sublethal Cd concentrations.     

Mutagenic and cytotoxic activities of benfuracarb insecticide

Benfuracarb is a carbamate insecticide used to control insect pests in vegetables and it has anti-acetylcholinesterase activity lower than other carbamates. Cytotoxic effects of benfuracarb were evaluated by using root growth inhibition (EC₅₀), mitotic index (MI), and mitotic phase determinations on the root meristem cells of Allium cepa and mutagenic effects were determined in Salmonella typhymurium Ames test by TA98 and TA100 strains with and without metabolic activation. In Allium test, 1 % DMSO was used as negative control group and 10 ppm MMS was used as positive control group. 75 ppm concentration of benfuracarb was found as EC₅₀. In MI and mitotic phases determination study, 37.5, 75 and 150 ppm doses of benfuracarb were used. Dose-dependent cytotoxic activity was found by root growth inhibition and MI studies. It was identified that mitotic inhibition activity of benfuracarb was higher than 10 ppm MMS. In Ames test, mutagenic activity was not observed and over 200 µg/plate of benfuracarb was determined as cytotoxic to S. typhymurium strains. Benfuracarb can be called as “mitotic inhibitor” but not called as mutagen.     

Inhibition and promotion by abscisic acid of growth in Spirodela

Summary The effect of different concentrations of abscisic acid on the growth of Spirodela oligorrhiza has been studied. Abscisic acid effectively permanently arrests growth at concentrations down to 10^-1 mg/l (one part per 10 million). Normal growth tends to be resumed at concentrations of 10^-2 and 10^-3 mg/l between 9 and 12 days after treatment. A concentration of 10^-8 mg/l, however, results in a significant increase in dry weight at both 9 and 12 days after introduction to the culture medium. It is suggested that the resumption of growth 12 days after treatment at those concentrations which inhibit growth up to 9 days, is due to a possible progressive inactivation of abscisic acid resulting in a lowering of its concentration to a level that is promotive. Sterile plants must be used since abscisic acid has shown no effect whatsoever in controlling growth of Saprolegnia, a water-mould of the Phycomycetes to which Spirodela apparently is the host.The authors gratefully acknowledge R. J. Reynolds Tobacco Company, North Carolina, U.S.A., for donating the abscisic acid.This research was supported by a grant to the senior author from the Council for Industrial and Scientific Research, Pretoria, S.A.     

Cytogenetic effects of ribavirin on mouse bone marrow

The micronucleus test and mitotic chromosome analysis were used to study the in vivo mutagenic activity of ribavirin on bone marrow cells of Swiss albino mice. To determine the incidence of micronuclei, mice were injected i.p. twice, at an interval of 24 h. with the drug at doses of 20, 100 and 200 mg/kg. Animals were killed 6 h after the second dose and bone marrow was examined for the presence of micronuclei in developing erythrocytes. Ribavirin significantly (P less than 0.05) induced micronuclei in polychromatic erythrocytes at all doses. A study was conducted to investigate the cytogenetic effect of the drug on mitotic chromosomes. Ribavirin at 200 mg/kg/day was administered to mice for 3 and 5 days. Repeated treatment with the high dose of ribavirin produced a highly significant (P less than 0.02) increase in abnormal metaphase spreads. The results indicate that ribavirin is mutagenic to bone marrow cells of mice as evaluated by the micronucleus test and by chromosome analysis.     

Influence of somatostatin and epidermal growth factor (EGF) on the proliferation of thyroid follicular cells in organ culture

The aim of the present study has been to examine the effects of various concentrations of somatostatin (SS), epidermal growth factor (EGF), as well as of interactions among SS, EGF and thyrotropin (TSH) in their influence upon the mitotic activity of thyroid follicular cells (TFC) in organ culture. The stathmokinetic method was employed. It was shown that: (1) SS, at the concentration of 10(-7) M, suppressed the mitogenic effect of TSH, as well as of TSH and EGF employed together, on TFC; (2) EGF, at the concentration of 10 and 100 ng/ml, increased the mean mitotic activity rate of TFC; (3) TSH and EGF revealed an additive action on TFC proliferation. The obtained results evidently suggest an antiproliferative effect of SS and mitogenic action of EGF on TFC in organ culture.     

Aluminum induces chromosome aberrations in wheat root meristem cells]

The yield and pattern of chromosome structure aberrations in wheat seedlings treated with aluminum nitrate and aluminum sulfate at various concentrations have been determined by the anaphase method. Aluminum has a genotoxic effect causing genome, chromatid, and chromosome aberrations in apical root meristem cells. The relationship between the total yield of structural mutations and the aluminum concentration follows a bell-shaped curve. The mutagenic activity of aluminum nitrate peaks at 10(-3) mg/ml, which is twice as high as the permissible concentration limit (PCL) of aluminum in potable water. The maximum of the mutagenic activity of aluminum sulfate is observed at 5 x 10(-4) mg/ml, i.e., one PCL. Tap water boiled for 2 h in an aluminum vessel has virtually no genotoxic effect on wheat cells.     

Effect of heavy metals on samples and model population of rotifers <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> muller at different salinity

Effect of Cu²⁺ and Cr⁶⁺ on samples and on model populations of rotifers Brachionus plicatilis Muller in chronic conditions at different salinity was investigated. The LC₅₀ (48 h) at salinities 10, 20, and 30‰ were 53.9, 0.25, and 0.1 mg Cr/l, respectively. The concentrations of 0.3 mg Cu/l and more led to the death of 100% of rotifers in 48 h in salinities 10 and 20‰, but at 30‰ the concentration 0.1 mg Cu/l was lethal. LC₅₀ (48 h) at salinities 10, 20, and 30‰ were 7.06, 0.07, and 0.01 mg Cu/l, respectively. The toxicity of Cr and Cu for samples became higher with increasing salinity. For the model populations, the salinity influenced toxicity only at high concentrations of Cr (20 mg/l). The effect of Cr was higher on samples than on model populations.