Relationship between genotoxicity,mutagenicity, and fish community structure in a contaminated stream

Genotoxic responses (chromosomal damage, DNA strandbreakage) of redbreast sunfish (Lepomis auritis)populations exposed to industrial effluent andmutagenicity of the associated sediments weredetermined in order to compare them to changes incommunity structure. Data were collected from areference stream and East Fork Poplar Creek (EFPC), afirst-order stream which originates on the grounds ofthe Department of Energy Y-12 Plant at Oak Ridge, TN. This stream is contaminated with mercury, PCBs, andnumerous other compounds. Previous studies have shownthat sediment contaminant concentrations, as well asphysiological biomarker responses of the local fishpopulations, are highest at the headwaters of EFPC anddecrease with increasing distance from the DOEfacility as contaminant loading decreases. Chromosomal damage was measured by flow cytometry – asreflected by variation in cellular DNA content – andstrand breakage was determined by agarose gelelectrophoresis using blood as the source of DNA. Mutagenicity was determined by theSalmonella/microsome assay using organic solventextracts of sediment surface samples. Community levelresponses included community diversity and percentpollution-tolerant species. Biomarker responses andmutagenicity were found to be highest at theheadwaters of EFPC, and tended to decrease withincreasing distance from the effluent. In general,biomarker responses appeared to be correlated withmutagenicity of the sediment, and both of theserelated to fish community disturbance and level ofstream contamination. Because responses at severallevels of biological organization show similarpatterns of downstream effects, this suggests thatthere may be a causal relationship betweencontamination and biological effects.     

Megazol and its bioisostere 4H-1,2,4-triazole: comparing the trypanocidal,cytotoxic and genotoxic activities and their in vitro and in silico interactions with the Trypanosoma brucei nitroreductase enzyme

Megazol (7) is a 5-nitroimidazole that is highly active against Trypanosoma cruzi and Trypanosoma brucei, as well as drug-resistant forms of trypanosomiasis. Compound 7 is not used clinically due to its mutagenic and genotoxic properties, but has been largely used as a lead compound. Here, we compared the activity of 7 with its 4H-1,2,4-triazole bioisostere (8) in bloodstream forms of T. brucei and T. cruzi and evaluated their activation by T. brucei type I nitroreductase (TbNTR) enzyme. We also analysed the cytotoxic and genotoxic effects of these compounds in whole human blood using Comet and fluorescein diacetate/ethidium bromide assays. Although the only difference between 7 and 8 is the substitution of sulphur (in the thiadiazole in 7) for nitrogen (in the triazole in 8), the results indicated that 8 had poorer antiparasitic activity than 7 and was not genotoxic, whereas 7 presented this effect. The determination of Vmax indicated that although 8 was metabolised more rapidly than 7, it bounds to the TbNTR with better affinity, resulting in equivalent kcat/KM values. Docking assays of 7 and 8 performed within the active site of a homology model of the TbNTR indicating that 8 had greater affinity than 7.     

Biochemical and RAPD Analysis of Hibiscus rosa sinensis Induced by Heavy Metals

The present study was designed to assess the effects of three different metals (cadmium, lead, and zinc) at the same concentrations on Hibiscus rosa sinensis during metal uptake. The effects of different metals at the same concentrations were assessed on biomass, root-shoot length, and biochemical parameters like chlorophyll and antioxidant enzymes like SOD and CAT to establish the tolerance potential and toxic effects on plants in different metals. The accumulation of metals by plants was found to be in the following order: Zn > mixed metals > Cd > Pb, where Zn was accumulated approximately 79.6% in plant tissues. Plants removed from Cd showed more enzyme activities than the other two metals. DNA stability was investigated by a Random Amplified Polymorphic DNA (RAPD) technique, which demonstrated that the samples in Cd and mixed metal showed similar trends, whereas samples in Zn and Pb showed similar band intensity to the control. Results suggested that Cd and/or heavy metal stress influences antioxidant status and also induces DNA changes during remediation. Therefore, these studies could be a useful biomarker assay for better treatment for metals’ remediation from soil by means of phytoremediation.     

The effects of nickel oxide nanoparticles on structural changes,heme degradation,aggregation of hemoglobin and expression of apoptotic genes in lymphocytes

Abstract

Nickel oxide nanoparticles (NiO NPs) have received great interests in medical and biotechnological applications. However, their adverse impacts against biological systems have not been well-explored. Herein, the influence of NiO NPs on structural changes, heme degradation and aggregation of hemoglobin (Hb) was evaluated by UV-visible (Vis) spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), and molecular modeling investigations. Also, the morphological changes and expression of Bax/Bcl-2 mRNA in human lymphocyte cell exposed to NiO NPs were assayed by DAPI staining and quantitative real-time PCR (qPCR), respectively. The UV-Vis study depicted that NiO NPs resulted in the displacement of aromatic residues and heme groups and production of the pro-aggregatory species. Intrinsic and Thioflavin T (ThT) fluorescence studies revealed that NiO NPs resulted in heme degradation and amorphous aggregation of Hb, respectively, which the latter result was also confirmed by TEM study. Moreover, far UV-CD study depicted that NiO NPs lead to substantial secondary structural changes of Hb. Furthermore, near UV-CD displayed that NiO NPs cause quaternary conformational changes of Hb as well as heme displacement. Molecular modelling study also approved that NiO NPs resulted in structural alterations of Hb and heme deformation. Moreover, morphological and genotoxicity assays revealed that the DNA fragmentation and expression ratio of Bax/Bcl-2 mRNA increased in lymphocyte cells treated with NiO NPs for 24?hr. In conclusion, this study indicates that NiO NPs may affect the biological media and their applications should be limited.

Communicated by Ramaswamy H. Sarma     

U-Shaped Dose-Response Relationships for Mutation and Cancer

A biologically based mutation model that can be parameterized to reflect U-shaped behavior at low doses of genotoxic substances is derived. The U-shaped behavior results from an efficient, adaptive DNA repair process, by which some endogenous DNA damage that would not be repaired in the absence of the genotoxic substance is repaired when low levels of the substance are present. Hence, the model embodies a type of hormesis. The dose response is U shaped even though the genotoxic mechanism is additive to an existing background mutation process. The risk-assessment implications regarding possible hormetic effects, instead of the generally expected low-dose-linear effects, for agents that are both genotoxic and additive to background are discussed.     

Sericin from Bombyx mori cocoons. Part I: Extraction and physicochemical-biological characterization for biopharmaceutical applications

In the present research effort, production of crude sericin extracts from Bombyx mori silk cocoons was attempted using two different approaches. Sericin was extracted from cocoons by high-temperature autoclaving followed either by lyophilization or freezing-thawing precipitation, to obtain a crude sericin powder. The physico-chemical and biological characteristics of the crude sericin extracts were evaluated in detail, via FTIR, XRD, XRF, XRT, UV–vis scanning, TGA and DSC, protein quantification, antimicrobial activity, free radical scavenging activity, cytotoxic activity, potential for inducing chromosomal aberrations via Allium cepa assays, and genotoxicity via Comet™ analyses. The molecular weight distribution of the crude sericin extracts was also investigated, via sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and the results duly compared to standard sericin. The results gathered clearly suggest that the crude sericin extracts had both obvious radical scavenging effects with the 2.2-diphenyl-1-picryl-hydrazil (DPPH) assay, and antibacterial activity, further suggesting that this protein might be a valuable addition for either food and biopharmaceutical applications.     

Evaluation of insecticidal and genotoxic effects of imidacloprid and acetochlor in Drosophila melanogaster

Two pesticides, the insecticide imidacloprid and the herbicide acetochlor, were evaluated for their insecticidal and genotoxic effects in Drosophila melanogaster . Their insecticidal effects were assessed by calculating LC₅₀ values after acute or chronic exposure of larvae and adults to different concentrations of the test compounds. After acute exposure, the LC₅₀ of imidacloprid was 7.59 × 10⁻⁵ M for larvae and 1.43 × 10⁻⁴ M for adults, and after chronic exposure, it was 2.67 × 10⁻⁵ M and 6.09 × 10⁻⁵ M for larvae and adults, respectively. On the contrary, the herbicide acetochlor showed no acute or chronic insecticidal effect against either larvae or adults, even at very high concentrations (8 × 10⁻³ M). For the evaluation of genotoxic properties of the two pesticides, the Somatic Mutation and Recombination Test in D. melanogaster was used. Our results suggest that neither imidacloprid nor acetochlor exhibits mutagenic or recombinogenic activity at applicable concentrations.     

Functionality and DNA-damage properties of blood cells in lactating cows exposed to glyphosate contaminated feed at different feed energy levels

ABSTRACT

Glyphosate (GL) inhibits the aromatic amino acid biosynthesis in plants and is worldwide the most used non-selective herbicide. Less is known about in vivo effects of GL contaminated feedstuffs on the health of dairy cows. The aim of this study was to examine the effects of GL residues in feed at different concentrate feed proportions (CFP) on haematology, immunological and redox parameters and on DNA-damage of blood cells in lactating dairy cows. During a 16-trial, 61 German Holstein cows (207 ± 49 d in milk; mean ± SD) were fed the same ration in week 0. Afterwards, they were assigned to either a group receiving a GL contaminated or a group receiving an uncontaminated total mixed ration (CON). Each group was subdivided into a “low concentrate” group (LC) and a “high concentrate” group (HC) with an energy content of 6.63 MJ NEL and 7.18 MJ NEL/kg dry matter, respectively. The diets were offered for ad libitum consumption. Blood samples were taken at weeks 0, 4, 8, 12 and 16. All blood samples were analysed for white and red blood cell counts. T-cell subpopulations, oxidative burst capability of leukocytes, apoptosis rate, phagocytic activity, activities of superoxide dismutase and glutathione peroxidase, the total non-enzymatic antioxidative capacity, viability and stimulation capacity of peripheral blood mononuclear cells and micronucleus- and comet assay on bovine leukocytes were measured only in week 16. The average individual GL intake of groups CON, GL_LC and GL_HC was 1.2 µg, 112.6 µg and 132.8 µg per kg body weight and day, respectively. GL contamination did not affect any of the tested parameters whereas CFP and time-influenced leukocytes, granulocytes, red blood cells, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin and CD4⁺ T-cells in an interactive manner characterised by a time-dependent increase in HC groups. It can be concluded that GL and GL in combination with different CFP showed no influence on any of the tested endpoints, whereas CFP and time influenced most parameters in an interactive manner.     

Antibacterial,Cytotoxic and Genotoxic Assessment of New Sulfonamide Derivatives

In the last few years, the interest in sulfonamides has expanded owing to their broad spectrum of biological activities. Their flexible structure turns them into amazing candidates to replace old drugs or develop modern multi-target agents. In this study, a series of new sulfonamides ( sul1-5 ) was evaluated, in vitro, for the antibacterial, cytotoxic and genotoxic effects. The antibacterial activity was investigated against 12 clinical and 4 reference strains. Cytotoxic activity was carried out by the brine shrimp bioassay and the genotoxicity was assessed in the Ames test. An interesting antibacterial activity was showed especially against Gram negative strains. The inhibition zones varied between 15 and 30 mm, and the Minimum Inhibitory Concentrations (MIC's) values between 0.5 and 256 μg/ml. No antibacterial activity was shown with S. aureus isolates. Only Sul1 and Sul4 were active against P. aeruginosa. Compounds Sul1 and Sul2 showed a significant cytotoxicity with LC₅₀ equal to 18.29 and 18 μg/ml respectively, and a genotoxic effect against TA100 and TA1535 Salmonella strains. Only compounds Sul3 , Sul4 and Sul5 with an interesting antibacterial activity, no cytotoxicity and no genotoxic effects, could be exploited against resistant pathogens as new drugs.     

Synaptonemal complex damage as a measure of genotoxicity at meiosis

Synaptonemal complex aberrations can provide a sensitive measure of chemical-specific alterations to meiotic chromosomes. Mitomycin C, cyclophosphamide, amsacrine, ellipticine, colchicine, vinblastine sulfate, and cis-platin exposures in mice have been shown to cause various patterns of synaptonemal complex structural damage and synaptic irregularity. These effects are suggestive of abnormal homologue pairing/synapsis/recombination effects which, theoretically, could be implicated in mechanisms leading to aneuploidy and other potentially heritable chromosomal disorders.