A comprehensive assessment of the chemical composition, antioxidant, genoprotective and antigenotoxic activities of Lamiaceae species using different experimental models in vitro.

This research was aimed to assess the potential of Glechoma hederacea, Hyssopus officinalis, Lavandula angustifolia, Leonurus cardiaca, Marrubium vulgare and Sideritis scardica (Lamiaceae) methanolic, ethanolic and aqueous extracts against the damaging effects of oxidative stress using different experimental models. The chemical characterization was done spectrophotometrically by quantifying total phenolics, phenolic acids, flavonoids and flavonols in the extracts, as well as by employing HPLC-DAD technique. Moreover, DPPH assay was used to assess the extracts' radical scavenging potential. Genoprotective properties of the extracts were evaluated using plasmid pUC19 Escherichia coli XL1-Blue, whereas their antigenotoxic potential was determined using Salmonella typhimurium TA1535/pSK1002 and normal human lung fibroblasts. All of the extracts showed antioxidant activity in DPPH assay. Furthermore, the results have shown that aqueous extracts provided the best protection for plasmid DNA, while alcoholic extracts most effectively contributed to the preservation of prokaryotic DNA. Additionally, each of the tested samples significantly protected the eukaryotic cells against genomic damages. Finally, despite not showing exceptional results in DPPH assay, S. scardica extracts are regarded as the most favorable in maintaining the integrity of DNA, which might be due to high quantities of phenolics such as quercetin (up to 17.95 mg g-1), naringin (up to 5.07 mg g-1) and luteolin-7-O-glucoside (up to 3.54 mg g-1). Overall, this comprehensive concept highlights the ability of these Lamiaceae species to safeguard the DNA from reactive oxygen species, to curtail the inflicted damage and also improve the efficiency of the DNA repair mechanisms, while emphasizing the importance of polyphenols as their active principles.

High binding affinity of repressor IolR avoids costs of untimely induction of myo-inositol utilization by Salmonella Typhimurium.

Growth of Salmonella enterica serovar Typhimurium strain 14028 with myo-inositol (MI) is characterized by a bistable phenotype that manifests with an extraordinarily long (34 h) and variable lag phase. When cells were pre-grown in minimal medium with MI, however, the lag phase shortened drastically to eight hours, and to six hours in the absence of the regulator IolR. To unravel the molecular mechanism behind this phenomenon, we investigated this repressor in more detail. Flow cytometry analysis of the iolR promoter at a single cell level demonstrated bistability of its transcriptional activation. Electrophoretic mobility shift assays were used to narrow the potential binding region of IolR and identified at least two binding sites in most iol gene promoters. Surface plasmon resonance spectroscopy quantified IolR binding and indicated its putative oligomerization and high binding affinity towards specific iol gene promoters. In competitive assays, the iolR deletion mutant, in which iol gene repression is abolished, showed a severe growth disadvantage of ~15% relative to the parental strain in rich medium. We hypothesize that the strong repression of iol gene transcription is required to maintain a balance between metabolic flexibility and fitness costs, which follow the inopportune induction of an unusual metabolic pathway.

Simplified low-cost production of O-antigen from Salmonella Typhimurium Generalized Modules for Membrane Antigens (GMMA).

The Novartis Vaccines Institute for Global Health is developing vaccines using outer membrane particles, known as Generalized Modules for Membrane Antigens (GMMA). These are blebs of outer membrane and periplasm, shed from the surface of living Gram-negative bacteria following the targeted deletion of proteins involved in maintaining the integrity of the inner and outer membranes. The current study investigates the use of GMMA as starting material for extraction of membrane components, focusing on the O-antigen polysaccharide portion of lipopolysaccharide from Salmonella Typhimurium. We show that the amount of O-antigen extracted from GMMA by acid hydrolysis is comparable to the quantity extracted from whole wild type bacteria, but with less protein and DNA contaminants. Compared to conventional purification, GMMA enabled a reduction in the number of purification steps required to obtain the O-antigen polysaccharide with the same purity. Purification processes from GMMA and bacteria were characterised by similar final yields. Use of GMMA as starting material provides the possibility to simplify the purification process of O-antigen, with a consequent decrease in manufacturing costs of O-antigen-based glyconjugate vaccines against Salmonella strains and potentially other Gram-negative bacteria.

Mutagenic assessment of three synthetic pyridine-diaryl ketone derivatives.

Nowadays, there are increasing numbers of studies about synthetic chemicals according to the supply demands of bioactive chemicals. The current study aims to investigate genotoxic potential of bioactive synthetic pyridine compounds, phenyl-3-pyridinylmethanone (1), p-tolyl-3-pyridinylmethanone (2), and 4-methoxyphenyl-3-pyridinylmethanone (3), using Ames/Salmonella and Escherichia coli WP2 bacterial reversion mutagenicity test systems. The mutant bacterial tester strains sodium azide-sensitive Salmonella typhimurium TA1535, 9-aminoacridine-sensitive S. typhimurium TA1537, and N-methyl-N'-nitro-N-nitrosoguanidine-sensitive E. coli WP2uvrA were used to detect the mutagenic potential of the test compounds. The results indicated that none of the test substances showed significant mutagenic activity on S. typhimurium TA1535, TA1537, and E. coli WP2uvrA bacterial strains up to 1 µg/plate concentrations.

Genotoxicity assessment of magnetic iron oxide nanoparticles with different particle sizes and surface coatings.

Magnetic iron oxide nanoparticles (IONPs) have been widely used for various biomedical applications such as magnetic resonance imaging and drug delivery. However, their potential toxic effects, including genotoxicity, need to be thoroughly understood. In the present study, the genotoxicity of IONPs with different particle sizes (10, 30 nm) and surface coatings (PEG, PEI) were assessed using three standard genotoxicity assays, the Salmonella typhimurium reverse mutation assay (Ames test), the in vitro mammalian chromosome aberration test, and the in vivo micronucleus assay. In the Ames test, SMG-10 (PEG coating, 10 nm) showed a positive mutagenic response in all the five test bacterial strains with and without metabolic activation, whereas SEI-10 (PEI coating, 10 nm) showed no mutagenesis in all tester strains regardless of metabolic activation. SMG-30 (PEG coating, 30 nm) was not mutagenic in the absence of metabolic activation, and became mutagenic in the presence of metabolic activation. In the chromosomal aberration test, no increase in the incidence of chromosomal aberrations was observed for all three IONPs. In the in vivo micronucleus test, there was no evidence of increased micronuclei frequencies for all three IONPs, indicating that they were not clastogenic in vivo. Taken together, our results demonstrated that IONPs with PEG coating exhibited mutagenic activity without chromosomal and clastogenic abnormalities, and smaller IONPs (SMG-10) had stronger mutagenic potential than larger ones (SMG-30); whereas, IONPs with SEI coating (SEI-10) were not genotoxic in all three standard genotoxicity assays. This suggests that the mutagenicity of IONPs depends on their particle size and surface coating.

Assessment of titanium dioxide nanoparticle effects in bacteria: association, uptake, mutagenicity, co-mutagenicity and DNA repair inhibition.

Due to their unique properties, the use of nanoparticles (NPs) is expanding; these same properties may affect their potential risk to humans. However, standard methods for genotoxicity assessment may not be adequate for NPs; altered tests reported here have been developed to address perceived inadequacies. The bacterial reverse mutation assay is an essential part of the battery of tests to determine genotoxicity. The utility of this test for assessing NPs is currently questioned, due to negative results seemingly caused by failure of particle uptake. To probe uptake issues, we examined the physical state in different media, dose and time dependent association, uptake and mutagenicity of titanium dioxide (TiO2) NPs in Salmonella typhimurium and Escherichia coli. The NPs suspended in water were characterized using dynamic light scattering, NP tracking analysis and transmission electron microscopy. NP association with bacteria was assessed by flow cytometry. Association was found to be time and dose dependent, with maximal association by 60 min. Therefore mutagenicity was assessed after a 60 min pre-incubation in a miniaturized assay demonstrating enhanced sensitivity. To assess potential indirect effects on bacterial mutagenicity, the effect of TiO2 NPs on the action of standard mutagens or on DNA repair capability was also investigated. TiO2 NPs did not affect mutant yields in standard strains of S. typhimurium or E. coli, including those detecting oxidative damage, using the modified methods. Nor did TiO2 NPs affect the action of standard mutagens or DNA excision repair capability. Despite particle association with the bacteria, subsequent analysis using electron microscopy and energy dispersive x-ray spectroscopy indicated that the NPs were not internalized. This work demonstrates that additional studies, including flow cytometry, are valuable tools for understanding the action of NPs in biological systems.

A universal fluorescent aptasensor based on AccuBlue dye for the detection of pathogenic bacteria.

We report a universal fluorescent aptasensor based on the AccuBlue dye, which is impermeant to cell membranes, for the detection of pathogenic bacteria. The sensor consists of AccuBlue, an aptamer strand, and its complementary strand (cDNA) that partially hybridizes to the aptamer strand. We have fabricated two models by changing the sequence of the reaction between the elements in the system. One is the "signal on" model in which the aptamer is first bound to the target, followed by the addition of cDNA and AccuBlue, at which time the cDNA hybridizes with the free unreacted aptamer and forms a double-stranded DNA (dsDNA) duplex. Such hybridization causes AccuBlue to insert into the dsDNA and exhibit significantly increased fluorescence intensity because of the specific intercalation of the AccuBlue into dsDNA rather than single-stranded DNA (ssDNA). The other model, "signal off," involves hybridization of the aptamer with cDNA first, resulting in high fluorescence intensity on the addition of AccuBlue. When the target is added, the aptamer binds the target, causing the cDNA to detach from the dsDNA duplex and resulting in low fluorescence as a result of the liberation of AccuBlue. Because this design is based purely on DNA hybridization, and AccuBlue is impermeant to cell membranes, it could potentially be adapted to a wide variety of analytes.

Minor fitness costs in an experimental model of horizontal gene transfer in bacteria.

Genes introduced by horizontal gene transfer (HGT) from other species constitute a significant portion of many bacterial genomes, and the evolutionary dynamics of HGTs are important for understanding the spread of antibiotic resistance and the emergence of new pathogenic strains of bacteria. The fitness effects of the transferred genes largely determine the fixation rates and the amount of neutral diversity of newly acquired genes in bacterial populations. Comparative analysis of bacterial genomes provides insight into what genes are commonly transferred, but direct experimental tests of the fitness constraints on HGT are scarce. Here, we address this paucity of experimental studies by introducing 98 random DNA fragments varying in size from 0.45 to 5 kb from Bacteroides, Proteus, and human intestinal phage into a defined position in the Salmonella chromosome and measuring the effects on fitness. Using highly sensitive competition assays, we found that eight inserts were deleterious with selection coefficients (s) ranging from ≈ -0.007 to -0.02 and 90 did not have significant fitness effects. When inducing transcription from a PBAD promoter located at one end of the insert, 16 transfers were deleterious and 82 were not significantly different from the control. In conclusion, a major fraction of the inserts had minor effects on fitness implying that extra DNA transferred by HGT, even though it does not confer an immediate selective advantage, could be maintained at selection-transfer balance and serve as raw material for the evolution of novel beneficial functions.

Application of Markov State Models to simulate long timescale dynamics of biological macromolecules.

Conformational changes of proteins are an*Author contributed equally with all other contributors. essential part of many biological processes such as: protein folding, ligand binding, signal transduction, allostery, and enzymatic catalysis. Molecular dynamics (MD) simulations can describe the dynamics of molecules at atomic detail, therefore providing a much higher temporal and spatial resolution than most experimental techniques. Although MD simulations have been widely applied to study protein dynamics, the timescales accessible by conventional MD methods are usually limited to timescales that are orders of magnitude shorter than the conformational changes relevant for most biological functions. During the past decades great effort has been devoted to the development of theoretical methods that may enhance the conformational sampling. In recent years, it has been shown that the statistical mechanics framework provided by discrete-state and -time Markov State Models (MSMs) can predict long timescale dynamics from a pool of short MD simulations. In this chapter we provide the readers an account of the basic theory and selected applications of MSMs. We will first introduce the general concepts behind MSMs, and then describe the existing procedures for the construction of MSMs. This will be followed by the discussions of the challenges of constructing and validating MSMs, Finally, we will employ two biologically-relevant systems, the RNA polymerase and the LAO-protein, to illustrate the application of Markov State Models to elucidate the molecular mechanisms of complex conformational changes at biologically relevant timescales.

Mechanisms and fitness costs of resistance to antimicrobial peptides LL-37, CNY100HL and wheat germ histones.

Antimicrobial peptides (AMPs) represent a potential new class of antimicrobial drugs with potent and broad-spectrum activities. However, knowledge about the mechanisms and rates of resistance development to AMPs and the resulting effects on fitness and cross-resistance is limited. We isolated antimicrobial peptide (AMP) resistant Salmonella typhimurium LT2 mutants by serially passaging several independent bacterial lineages in progressively increasing concentrations of LL-37, CNY100HL and Wheat Germ Histones. Significant AMP resistance developed in 15/18 independent bacterial lineages. Resistance mutations were identified by whole genome sequencing in two-component signal transduction systems (pmrB and phoP) as well as in the LPS core biosynthesis pathway (waaY, also designated rfaY). In most cases, resistance was associated with a reduced fitness, observed as a decreased growth rate, which was dependent on growth conditions and mutation type. Importantly, mutations in waaY decreased bacterial susceptibility to all tested AMPs and the mutant outcompeted the wild type parental strain at AMP concentrations below the MIC for the wild type. Our data suggests that resistance to antimicrobial peptides can develop rapidly through mechanisms that confer cross-resistance to several AMPs. Importantly, AMP-resistant mutants can have a competitive advantage over the wild type strain at AMP concentrations similar to those found near human epithelial cells. These results suggest that resistant mutants could both be selected de novo and maintained by exposure to our own natural repertoire of defence molecules.

The role of RamA on the development of ciprofloxacin resistance in Salmonella enterica serovar Typhimurium.

Active efflux pump is a primary fluoroquinolone resistant mechanism of clinical isolates of Salmonella enterica serovar Typhimurium. RamA is an essential element in producing multidrug resistant (MDR) S. enterica serovar Typhimurium. The aim of the present study was to elucidate the roles of RamA on the development of ciprofloxacin, the first choice for the treatment of salmonellosis, resistance in S. enterica serovar Typhimurium. Spontaneous mutants were selected via several passages of S. enterica serovar Typhimurium CVCC541 susceptible strain (ST) on M-H agar with increasing concentrations of ciprofloxacin (CIP). Accumulation of ciprofloxacin was tested by the modified fluorometric method. The expression levels of MDR efflux pumps were determined by real time RT-PCR. In ST and its spontaneous mutants, the ramA gene was inactivated by insertion of the kan gene and compensated on a recombinant plasmid pGEXΦ(gst-ramA). The mutant prevention concentration (MPC) and mutant frequencies of ciprofloxacin against ST and a spontaneous mutant in the presence, absence and overexpression of RamA were tested. Four spontaneous mutants (SI1-SI4) were obtained. The SI1 (CIP MICs, 0.1 mg/L) without any target site mutation in its quinolone resistant determining regions (QRDRs) and SI3 (CIP MICs, 16 mg/L) harboring the Ser83→Phe mutation in its QRDR of GyrA strains exhibited reduced susceptibility and resistance to multidrugs, respectively. In SI1, RamA was the main factor that controlled the susceptibility to ciprofloxacin by activating MdtK as well as increasing the expression level of acrAB. In SI3, RamA played predominant role in ciprofloxacin resistance via increasing the expression level of acrAB. Likewise, the deficiency of RamA decreased the MPCs and mutant frequencies of ST and SI2 to ciprofloxacin. In conclusion, the expression of RamA promoted the development of ciprofloxacin resistant mutants of S. enterica serovar Typhimurium. The inhibition of RamA could decrease the appearance of the ciprofloxacin resistant mutants.

In vitro mutagenicity assessment of aluminium oxide nanomaterials using the Salmonella/microsome assay.

The aim of the current study was to evaluate the potential mutagenicity of aluminium oxide nanomaterials (NMs) (Al(2)O(3)-30 nm and Al(2)O(3)-40 nm). Characterization of the NMs was done before the initiation of the study. The mutagenicity of the NMs was studied by the Ames test with Salmonella typhimurium TA100, TA1535, TA98, TA97a and TA102 strains, in the presence and absence of the S9 mixture. Based on a preliminary cytotoxicity study conducted on the strains, different concentrations of Al(2)O(3)-30 nm, Al(2)O(3)-40 nm and Al(2)O(3)-bulk were selected. At all the concentrations tested, Al(2)O(3)-30 nm and Al(2)O(3)-40 nm did not significantly increase the number of revertant colonies compared to the Al(2)O(3)-bulk and control with or without S9 mixture. Our findings suggest that Al(2)O(3) NMs were devoid of any size and concentration dependent mutagenicity compared to the Al(2)O(3)-bulk and control.

A 96-well plate fluorescence assay for assessment of cellular permeability and active efflux in Salmonella enterica serovar Typhimurium and Escherichia coli.

OBJECTIVES: Multiply antibiotic-resistant (MAR) mutants of Escherichia coli and Salmonella enterica are characterized by reduced susceptibility to several unrelated antibiotics, biocides and other xenobiotics. Porin loss and/or active efflux have been identified as a key mechanisms of MAR. A single rapid test was developed for MAR. METHODS: The intracellular accumulation of the fluorescent probe Hoechst (H) 33342 (bisbenzimide) by MAR mutants and those with defined disruptions in efflux pump and porin genes was determined in 96-well plate format. RESULTS: The accumulation of H33342 was significantly (P < 0.0001) reduced in MAR mutants of S. enterica serovar Typhimurium (n = 4) and E. coli (n = 3) by 41 +/- 8% and 17.3 +/- 7.2%, respectively, compared with their parental strains, which was reversed by the transmembrane proton gradient-collapsing agent carbonyl cyanide-m-chlorophenyl hydrazone (CCCP) and the efflux pump inhibitor phenylalanine-arginine-beta-naphthylamide (PA beta N). The accumulation of H33342 was significantly reduced in mutants of Salmonella Typhimurium with defined disruptions in genes encoding the porins OmpC, OmpF, OmpX and OmpW, but increased in those with disruptions in efflux pump components TolC, AcrB and AcrF. Reduced accumulation of H33342 in three other MAR mutants of Salmonella Typhimurium correlated with the expression of porin and efflux pump proteins. CONCLUSIONS: The intracellular accumulation of H33342 provided a sensitive and specific test for MAR that is cheap and relatively rapid. Differential sensitivity to CCCP and PA beta N provided a further means to phenotypically identify MAR mutants and the role of active efflux in each strain.

The fitness cost of streptomycin resistance depends on rpsL mutation, carbon source and RpoS (sigmaS).

Mutations that cause antibiotic resistance often produce associated fitness costs. These costs have a detrimental effect on the fate of resistant organisms in natural populations and could be exploited in designing drugs, therapeutic regimes, and intervention strategies. The streptomycin resistance (StrR) mutations K42N and P90S in ribosomal protein S12 impair growth on rich medium. Surprisingly, in media with poorer carbon sources, the same StrR mutants grow faster than wild type. This improvement reflects a failure of these StrR mutants to induce the stress-inducible sigma factor RpoS (sigmaS), a key regulator of many stationary-phase and stress-inducible genes. On poorer carbon sources, wild-type cells induce sigmaS, which retards growth. By not inducing sigmaS, StrR mutants escape this self-imposed inhibition. Consistent with this interpretation, the StrR mutant loses its advantage over wild type when both strains lack an RpoS (sigmaS) gene. Failure to induce sigmaS produced the following side effects: (1) impaired induction of several stress-inducible genes, (2) reduced tolerance to thermal stress, and (3) reduced translational fidelity. These results suggest that RpoS may contribute to long-term cell survival, while actually limiting short-term growth rate under restrictive growth conditions. Accordingly, the StrR mutant avoids short-term growth limitation but is sensitized to other stresses. These results highlight the importance of measuring fitness costs under multiple experimental conditions not only to acquire a more relevant estimate of fitness, but also to reveal novel physiological weaknesses exploitable for drug development.

Stably integrated luxCDABE for assessment of Salmonella invasion kinetics.

Salmonella Typhimurium is a common cause of gastroenteritis in humans and also localizes to neoplastic tumors in animals. Invasion of specific eukaryotic cells is a key mechanism of Salmonella interactions with host tissues. Early stages of gastrointestinal cell invasion are mediated by a Salmonella type III secretion system, powered by the adenosine triphosphatase invC. The aim of this work was to characterize the invC dependence of invasion kinetics into disparate eukaryotic cells traditionally used as models of gut epithelium or neoplasms. Thus, a nondestructive real-time assay was developed to report eukaryotic cell invasion kinetics using lux+ Salmonella that contain chromosomally integrated luxCDABE genes. Bioluminescence-based invasion assays using lux+ Salmonella exhibited inoculum dose-response correlation, distinguished invasion-competent from invasion-incompetent Salmonella, and discriminated relative Salmonella invasiveness in accordance with environmental conditions that induce invasion gene expression. In standard gentamicin protection assays, bioluminescence from lux+ Salmonella correlated with recovery of colony-forming units of internalized bacteria and could be visualized by bioluminescence microscopy. Furthermore, this assay distinguished invasion-competent from invasion-incompetent bacteria independent of gentamicin treatment in real time. Bioluminescence reported Salmonella invasion of disparate eukaryotic cell lines, including neoplastic melanoma, colon adenocarcinoma, and glioma cell lines used in animal models of malignancy. In each case, Salmonella invasion of eukaryotic cells was invC dependent.

Photoelectrocatalytic oxidation of remazol turquoise blue and toxicological assessment of its oxidation products.

The ability of photoelectrocatalytic oxidation to degrade the commercially important copper-phtalocyanine dye, remazol turquoise blue 15 (RTB) was investigated. The best experimental condition was optimized, evaluating the performance of Ti/TiO2 thin-film electrodes prepared by sol-gel method in the decolourization of 32 mg L(-1) RTB dye in 0.5 mol L(-1) Na2SO4 pH 8 and applied potential of +1.5 V versus SCE under UV irradiation. Spectrophotometric measurements, high performance liquid chromatography, dissolved organic carbon (TOC) evaluation and stripping analysis of yielding solution obtained after 3 h of photoelectrolysis leads to 100% of absorbance removal from wavelength of 250-800 nm, 79.6% of TOC reduction and the releasing of up to 54.6% dye-bound copper (0.85 mg L(-1)) into the solution. Both, original and oxidized dye solution did not presented mutagenic activity with the strains TA98 and TA100 of Salmonella in the presence and absence of S9 mix at the tested doses. Nevertheless, the yielding photoelectrocatalytic oxidized solution showed an increase in the acute toxicity for Vibrio fischeri bacteria, explained by copper liberation during treatment.

Assessment of DNA damage by extracts and fractions of Strychnos pseudoquina, a Brazilian medicinal plant with antiulcerogenic activity.

Strychnos pseudoquina St. Hil. is a native plant of the Brazilian Savannah, used in popular medicine to treat a number of conditions. Since it contains large quantities of alkaloids with proven antiulcer activity, we tested the genotoxic potential of crude extracts and fractions containing alkaloids and flavonoids from the leaves of this plant, on Salmonella typhimurium and performed the micronucleus test on peripheral blood cells of mice treated in vivo. The results showed that the methanol extract of the leaves of S. pseudoquina is mutagenic to the TA98 (-S9) and TA100 (+S9, -S9) strains of Salmonella. The dichloromethane extract was not mutagenic to any of the tested strains. Fractions enriched with alkaloids or flavonoids were not mutagenic. In vivo tests were done on the crude methanol extract in albino Swiss mice, which were treated, by gavage, with three different doses of the extract. The highest dose tested (1800 mg/kgb.w.) induced micronuclei after acute treatment, confirming the mutagenic potential of the methanol extract of the leaves of S. pseudoquina. In high doses, constituents of S. pseudoquina compounds act on DNA, causing breaks and giving rise to micronuclei in the blood cells of treated animals.

An assessment of the genotoxicity of 2-hydroxy-1,4-naphthoquinone, the natural dye ingredient of Henna.

2-Hydroxy-1,4-naphthoquinone (HNQ; Lawsone; CAS 83-72-7) is the principal natural dye ingredient contained in the leaves of Henna (Lawsonia inermis). Published genotoxicity studies on HNQ suggested it was a weak bacterial mutagen for Salmonella typhimurium strain TA98 or was more clearly mutagenic for strain TA 2637, both in the presence of metabolic activation. HNQ was unable to induce sex-linked recessive lethal mutations in Drosophila melanogaster. However, a small increase in micronucleus frequency was reported in the bone marrow of mice at a single mid-range dose level, 24h after intraperitoneal injection. In view of the wide use of Henna hair dyes it was deemed necessary to conduct a thorough investigation, under Good Laboratory Practice conditions, of the genotoxicity of HNQ. HNQ was non-mutagenic in bacterial (Ames test) or mammalian (V79 hprt) assays. It was borderline positive in a mouse lymphoma tk mutation assay and a chromosome aberration test (CHO cells), results that may reflect a similar clastogenic mechanism. Negative in vivo genotoxicity results were noted in the rat hepatocyte in vivo/in vitro UDS test, in peripheral lymphocytes (chromosome aberrations) of rats receiving repeated oral doses of HNQ at the MTD for 28 days, and in mouse and hamster bone marrow chromosome aberration tests. However small, but statistically significant increases in the incidence of bone marrow micronuclei were observed in two out of five tests at 72 h after dosing, but not at 24 or 48 h. There was evidence of haematotoxicity at 72 h, which may have been enhanced by the vehicle (DMSO) used in the positive tests. As erythropoiesis and administration of haematotoxic agents are known to induce small increases in the frequency of bone marrow micronuclei, typically at delayed sampling times, the data suggest that the positive 72 h response produced by HNQ is consistent with stimulation of haematopoiesis subsequent to haematological toxicity of HNQ, and not due to a DNA-reactive mechanism. Overall, the weight of evidence suggests that Henna and HNQ pose no genotoxic risk to the consumer.

Assessment of the genotoxic potential of ISIS 2302: a phosphorothioate oligodeoxynucleotide.

ISIS 2302, a phosphorothioate oligodeoxynucleotide with antisense activity against human ICAM-1 mRNA, was evaluated in a battery of tests to assess genotoxic potential. There was no evidence of genotoxicity in three in vitro studies performed: (i) a bacterial reverse mutation test; (ii) a chromosomal aberration test in Chinese hamster ovary cells; (iii) a mammalian cell gene mutation assay in L5187Y cells. Additionally, there was no in vivo evidence of genetic toxicity in a bone marrow micronucleus study in male and female mice. For all tests, top concentrations or doses assessed met harmonized regulatory guidelines. The cellular uptake of ISIS 2302 into target cells was confirmed using capillary gel electrophoresis and immunohistochemistry. Intracellular uptake into CHO cells, L5187Y cells, Salmonella typhimurium TA98 and bone marrow was concentration- and time-dependent. Consistent with what is known about the physical and chemical properties of phosphorothioate oligodeoxynucleotides, there was no evidence of genotoxicity in any of the assessed end-points. Furthermore, the absence of genotoxicity could not be ascribed to test system insensitivity or to an absence of exposure of the test system to ISIS 2302.

A comparative assessment of Boise, Idaho, ambient air fine particle samples using the plate and microsuspension Salmonella mutagenicity assays.

The primary objective of this study is to characterize the genotoxic potential of the ambient air aerosols collected within an air shed impacted primarily by wood smoke and automotive emissions. The study also examines the relative merits of a microsuspension assay and the standard plate assay for monitoring the presence of airborne particle-bound mutagens. Wintertime ambient air particulate samples collected from Boise, Idaho, USA, were shown to contain extractable organic matter that is mutagenic in the Salmonella typhimurium microsuspension and plate-incorporation assays. Differences in the results from the primary sites, auxiliary sites and the background site demonstrate that the particle-bound mutagens are not evenly distributed within the air shed and are more associated with the location of sampling than with the time of sampling or the type of bioassay used to evaluate the samples. This study also demonstrates that the bioassay protocol used in such studies should depend upon the characteristics of the air shed's mutagens and the purpose of the study. For example, the microsuspension assay gave somewhat more variable results between samples but was approximately threefold more sensitive than the plate assay. When strain TA98 was used in the microsuspension assay, the mutagenic response was greater without an exogenous activation system. The reverse was true for the plate assay in which the use of an exogenous activation system increased the mutagenicity response. TA100 in the microsuspension assay provided results comparable to those with TA98. This is important because TA100 can also be used to bioassay semivolatile and volatile organics associated with ambient air mutagenicity. This, in turn, allows a comparison of the mutagenicity of organics collected by differing methods due to their volatility. Future studies should be directed toward correlation of mutagenicity results with other analytical results in order to further develop methods for better characterization of the genotoxicity of ambient air.