ABSTRACT
Since technetium-99m (99mTc) was introduced in medical research it has become one of the most employed radionuclides in nuclear medicine. 99mTc is ideal for routine use on the labeling of different radiopharmaceuticals due to its favorable characteristics. However, some biological effects have been described. These effects may be related to internal conversion electron and/or Auger electron emissions from 99mTc decay that present high linear energy transfer and can generate reactive oxygen species (ROS) in the medium. We evaluated in Escherichia coli K12S and Salmonella typhimurium TA102, both proficient in DNA repair, contribution of those decay emissions on the cytotoxicity induced by 99mTc, both either by generating lesions on DNA or by inducing alterations at membrane. We also studied the genotoxic and/or mutagenic potentiality of 99mTc, in Salmonella typhimurium, using the Ames test. The results showed that: i/ 99mTc is cytotoxic to the Escherichia coli K12S strains; ii/ this effect is related to the electrons (Auger and internal conversion) emissions, and iii/ the 99mTc is not mutagenic and/or genotoxic, when measured by Ames test.
Subject(s)
Escherichia coli/radiation effects , Mutagens/toxicity , Technetium/toxicity , Electrons/adverse effects , Escherichia coli/genetics , Escherichia coli/metabolism , Mutagenicity Tests , Radiopharmaceuticals/toxicity , Reactive Oxygen Species/metabolism , Salmonella typhimurium/genetics , Salmonella typhimurium/metabolism , Salmonella typhimurium/radiation effects , Species SpecificityABSTRACT
Three tinctures samples from extracts of the popular medicinal plant Thuya occidentalis were tested in vitro through two short term tests for measuring the activity of genotoxic chemicals. Using the Salmonella/mammalian-microsome (Mutatest) assay and the SOS-chromotest (induction of beta-galactosidase in Escherichia coli), none of the extract was effective in inducing mutagenesis or beta-galactosidase synthesis (as an indicator of general and early sign of DNA damage), even with metabolization.
Subject(s)
Coloring Agents/toxicity , Mutagenicity Tests/methods , Plant Extracts/toxicity , Escherichia coli/drug effects , SOS Response, Genetics , Salmonella typhimurium/drug effectsABSTRACT
Three tinctures samples from extracts of the popular medicinal plant Thuya occidentalis were tested in vitro through two short term tests for measuring the activity of genotoxic chemicals. Using the Salmonella/mammalian-microsome (Mutatest) assay and the SOS-chromotest (induction of beta-galactosidase in Escherichia coli), none of the extract was effective in inducing mutagenesis or beta-galactosidase synthesis (as an indicator of general and early sign of DNA damage), even with metabolization
Subject(s)
Coloring Agents/pharmacology , Escherichia coli/drug effects , Mutagenicity Tests/methods , Plant Extracts/pharmacology , Salmonella typhimurium/drug effects , SOS Response, GeneticsABSTRACT
Technetium-99m (99mTc) has been used in nuclear medicine and in biomedical research to label molecular and cellular structures employed as radiotracers. Here, we have evaluated, on a DNA repair proficient Escherichia coli strain, the 99mTc decay inactivation and the influence of the (i) pre-treatment with metal ion chelators or of the (ii) treatment with a free radical scavenger on the protection of the cells against the lethal effect of the 99mTc. As SnCl2 is frequently used as a reducing agent in the 99mTc-labeling process, we have also studied the capability of SnCl2 to alter the biological effects induced by the 99mTc decay. As we are exposed to either chemical or physical agents in the nature, we have decided to study a possible influence of the ultraviolet solar radiation in the biological phenomena induced by the 99mTc decay. Our data point out (i) a very important role of the Auger and/or conversion electrons in the cytotoxicity induced by the 99mTc decay; (ii) SnCl2, the metal ion chelators and the free radical scavenger protect the cells against the lethal effect of the 99mTc; and (iii) near-UV does not alter the lethal effect of the 99mTc decay.
Subject(s)
Chelating Agents/pharmacology , Escherichia coli/drug effects , Escherichia coli/radiation effects , Free Radical Scavengers/pharmacology , Technetium/toxicity , 2,2'-Dipyridyl/pharmacology , Edetic Acid/pharmacology , Half-Life , Sodium Benzoate/pharmacology , Thiourea/pharmacology , Tin Compounds/pharmacology , Ultraviolet RaysABSTRACT
Stannous chloride (SnCl2) has been widely used in nuclear medicine as a reducing agent of pharmaceutical products radiolabelled with technetium-99m. To verify whether the lethality induced by this salt could be mediated by reactive oxygen species (ROS), Escherichia coli cultures were treated with SnCl2 in the presence of catalase, ROS scavengers or metal-ion chelators. The inactivation effect, as measured by survival determination, was abolished by thiourea, sodium benzoate, dipyridyl or catalase. The results suggest the participation of ROS, generated by a Fenton-like reaction, in the lethal effect induced by SnCl2.
Subject(s)
DNA Damage/drug effects , Escherichia coli/drug effects , Reactive Oxygen Species/metabolism , Tin Compounds/toxicity , 2,2'-Dipyridyl/pharmacology , Benzoates/pharmacology , Benzoic Acid , Catalase/pharmacology , Chelating Agents/pharmacology , Culture Media , DNA Damage/genetics , DNA Repair/drug effects , DNA Repair/genetics , Escherichia coli/genetics , Escherichia coli/metabolism , Free Radical Scavengers/pharmacology , Indicators and Reagents/pharmacology , Thiourea/pharmacologyABSTRACT
Stannous chloride (SnCl2) is a reducing agent largely employed in industry and in medical procedures. To evaluate its potential genotoxicity, several Escherichia coli strains were treated with SnCl2 and their survival rates determined. Results showed that the double mutant on specific genes for the repair of deoxyribonucleic acid damage was the most sensitive strain. Simultaneous near-UV illumination inhibited the lethal effect of SnCl2 in the wild type strain. Although the nature of the induced lesions are not known these results indicate the potential genotoxicity of SnCl2.
Subject(s)
Escherichia coli/drug effects , Tin Compounds/pharmacology , Ultraviolet Rays , DNA Repair/genetics , Escherichia coli/radiation effects , Radiation ToleranceABSTRACT
Reductone (HOCH2-CO-CHO), a keto-aldehyde formed, in alkaline pH, by thermal degradation of reducing sugars, blocks cellular respiration and macromolecular biosynthesis, inactivates far-UV (254 nm)-irradiated wild-type E. coli cells, and causes DNA strand breaks. So it may be supposed to be an inducer of SOS functions. Indeed, when Salmonella tester strains TA98, TA100 and TA102 were treated with reductone solutions, without metabolization, a mutagenic effect was detected for all of them. Besides, reductone induced lysogenic E. coli cells and cell filamentation, as measured by the Inductest and the SOS Chromotest. So reductone must be considered a genotoxic drug.
Subject(s)
Escherichia coli Proteins , Malonates/toxicity , Malondialdehyde/toxicity , Mutagens , Bacterial Proteins/genetics , Escherichia coli/drug effects , Glucose , Hot Temperature , Lysogeny/drug effects , Malondialdehyde/analogs & derivatives , SOS Response, Genetics/drug effects , Salmonella typhimurium/drug effectsABSTRACT
The development of short term tests for measuring the mutagenic activity of genotoxic chemicals has been helpful in increasing security. Natural products from the flora are largely used in popular medicine. Using the Salmonella/mammalian-microsome assay, we investigated the genetic toxicity of two plant species popularly used in malaria treatment, Pothomorphe umbellata and Pothomorphe peltata. The data show the absence of genetic toxicity for both plant species.
Subject(s)
Plant Extracts/toxicity , Plants, Medicinal , Salmonella typhimurium/genetics , Animals , Malaria/drug therapy , Mice , Mutagenicity Tests/methods , Plant Extracts/therapeutic useABSTRACT
The development of short term tests for measuring the mutagenic activity of genotoxic chemicals has been helpful in increasing security. Natural products from the flora are largely used in popular medicine. Using the Salmonella/mammalian-microsome assay, we investigated the genetic toxicity of two plant species popularly used in malaria treatment, Pothomorphe umbrellata and Pothomorphe peltata. The data show the absence of genetic toxicity for both plant species
Subject(s)
Plant Extracts/toxicity , Plants, Medicinal , Salmonella typhimurium/genetics , Malaria/drug therapy , Mutagenicity Tests , Plant Extracts/therapeutic useABSTRACT
Curvas de sobrevivencia a radiacao ultravioleta de culturas de diversas cepas de E. coli K 12, proficientes ou nao em sistemas de reparacao, foram obtidas apos carenciamento em glicose e em fatores indispensaveis a multiplicacao bacteriana. Estas curvas foram matematicamente ajustadas a modelo previamente descrito, o que permitiu estabelecer parametro para expressar o aumento de fotorresistencia induzida pelo carenciamento (SIRE). Os resultados obtidos reforcam a hipotese de estar o SIRE relacionado com o mecanismo de reparacao por excisao
