Elektromagnetsko polje na frekvenciji mobilnih telefona (900 MHz) izaziva stres i modifikacije DNA u gujavici Eisenia fetida

Eisenia fetida earthworms were exposed to electromagnetic field (EMF) at a mobile phone frequency (900 MHz) and at field levels ranging from 10 to 120 V m-1 for a period of two hours (corresponding to specific absorption rates ranging from 0.13 to 9.33 mW kg-1). Potential effects of longer exposure (four hours), field modulation, and a recovery period of 24 h after two hours of exposure were addressed at the field level of 23 V m-1. All exposure treatments induced significant DNA modifications as assessed by a quantitative random amplified polymorphic DNA-PCR. Even after 24 h of recovery following a two hour-exposure, the number of probe hybridisation sites displayed a significant two-fold decrease as compared to untreated control earthworms, implying a loss of hybridisation sites and a persistent genotoxic effect of EMF. Expression of genes involved in the response to general stress (HSP70 encoding the 70 kDa heat shock protein, and MEKK1 involved in signal transduction), oxidative stress (CAT, encoding catalase), and chemical and immune defence (LYS, encoding lysenin, and MYD, encoding a myeloid differentiation factor) were up-regulated after exposure to 10 and modulated 23 V m-1 field levels. Western blots showing an increased quantity of HSP70 and MTCO1 proteins confirmed this stress response. HSP70 and LYS genes were up-regulated after 24 h of recovery following a two hour-exposure, meaning that the effect of EMF exposure lasted for hours.U ovom istraživanju gujavice vrste Eisenia fetida bile su izložene elektromagnetskom polju (EMP) na frekvenciji mobilnih telefona (900 MHz) te poljima jačine 10 do 120 V m-1 u dvosatnom razdoblju (što odgovara specifičnim ratama apsorpcije od 0,13 do 9,33 mW kg-1). Utjecaj dužeg izlaganja (4 sata), modulacije polja te vrijeme oporavka od 24 sata nakon dva sata izlaganja proučavan je pri jačini polja od 23 V m-1. Metoda kvantitativne nasumično umnožene polimorfne DNA (engl. quantitative random amplified polymorphic DNA – qRAPD) otkrila je značajne modifikacije DNA na svim proučavanim tretmanima. Čak i nakon 24-satnog oporavka broj hibridizacijskih mjesta bio je dvostruko manji u odnosu na broj zabilježen u kontrolnim gujavicama, što upozorava na gubitak hibridizacijskih mjesta i na dugoročan utjecaj EMP-a. Ekspresija gena uključenih u odgovor na stres (HSP70: kodira za 70kDa heat shock protein i MEKK1: uključen u provođenje signala), oksidacijski stres (CAT: kodira za katalazu) te kemijsku i imunosnu obranu (LYS: kodira za lysenin i MYD: kodira za faktor mijeloidne diferencijacije) bila je povišena nakon izlaganja polju jačine 10 V m-1 te moduliranome polju jačine 23 V m-1. Western blot analiza potvrdila je odgovor na stres detekcijom povišene količine HSP70 i MTCO1 proteina. HSP70 i LYS geni imali su povišenu ekspresiju i nakon razdoblja oporavka, što upućuje na dugotrajan utjecaj EMP-a

Feeding mice with diets containing mercury-contaminated fish flesh from French Guiana: a model for the mercurial intoxication of the Wayana Amerindians

International audienc

Flucytosine-Fluconazole Cross-Resistance in Purine-Cytosine Permease-Deficient Candida lusitaniae Clinical Isolates: Indirect Evidence of a Fluconazole Uptake Transporter

An unusual interaction between flucytosine and fluconazole was observed when a collection of 60 Candida lusitaniae clinical isolates was screened for cross-resistance. Among eight isolates resistant to flucytosine (MIC ≥ 128 μg/ml) and susceptible to fluconazole (0.5 < MIC < 2 μg/ml), four became flucytosine-fluconazole cross resistant when both antifungals were used simultaneously. Fluconazole resistance occurred only in the presence of high flucytosine concentrations, and the higher the fluconazole concentration used, the greater the flucytosine concentration necessary to trigger the cross-resistance. When the flucytosine- and fluconazole-resistant cells were grown in the presence of fluconazole alone, the cells reversed to fluconazole susceptibility. Genetic analyses of the progeny from crosses between resistant and sensitive isolates showed that resistance to flucytosine was derived from a recessive mutation in a single gene, whereas cross-resistance to fluconazole seemed to vary like a quantitative trait. We further demonstrated that the four clinical isolates were susceptible to 5-fluorouracil and that cytosine deaminase activity was unaffected. Kinetic transport studies with [(14)C]flucytosine showed that flucytosine resistance was due to a defect in the purine-cytosine permease. Our hypothesis was that extracellular flucytosine would subsequently behave as a competitive inhibitor of fluconazole uptake transport. Finally, in vitro selection of spontaneous and induced mutants indicated that such a cross-resistance mechanism could also affect other Candida species, including C. albicans, C. tropicalis, and C. glabrata. This is the first report of a putative fluconazole uptake transporter in Candida species and of a possible resistance mechanism associated with a deficiency in the uptake of this drug

Effects of dietary methylmercury on the zebrafish brain: Histological, mitochondrial, and gene transcription analyses

International audienceThe neurotoxic compound methylmercury (MeHg) is a commonly encountered pollutant in the environment, and constitutes a hazard for wildlife and human health through fish consumption. To study the neurotoxic impact of MeHg on piscivorous fish, we contaminated the model fish species Danio rerio for 25 and 50 days with food containing 13.5 μg/g dry weight (dw) of MeHg (0.6 μg MeHg/fish/day), an environmentally relevant dose leading to brain mercury concentrations of 30 ± 4 μg of Hg g$^-$$^1$ (dw) after 25 days of exposure and 46 ± 7 μg of Hg g$^-$$^1$ (dw) after 50 days. Brain mitochondrial respiration was not modified by exposure to MeHg, contrary to what happens in skeletal muscles. A 6-fold increase in the expression of the sdh gene encoding the succinate dehydrogenase Fe/S protein subunit was detected in the contaminated brain after 50 days of exposure. An up regulation of 3 genes, atp2b3a, atp2b3b, and slc8a2b, encoding for calcium transporters was noticed after 25 days of exposure but the atp2b3a and atp2b3b were repressed and the slc8a2b gene expression returned to its basal level after 50 days, suggesting a perturbation of calcium homeostasis. After 50 days, we detected the up regulation of glial fibrillary acidic protein and glutathione S-transferase genes (gfap and gst), along with a repression of the glutathione peroxidase gene gpx1. These results match well with a MeHg-induced onset of oxidative stress and inflammation. A transmission electron microscopic observation confirmed an impairment of the optical tectum integrity, with a decrease of the nucleal area in contaminated granular cells compared to control cells, and a lower density of cells in the contaminated tissue. A potential functional significance of such changes observed in optical tectum when considering wild fish contaminated in their natural habitat might be an impaired vision and therefore a lowered adaptability to their environment

Impact of dietary gold nanoparticles in zebrafish at very low contamination pressure: the role of size, concentration and exposure time.

The impact of a daily ration of food containing gold nanoparticles (AuNPs) of two sizes (12 and 50 nm) was investigated in the zebrafish Danio rerio at very low doses (from 36-106 ng gold/fish/day). AuNP exposure resulted in various dysfunctions at the sub cellular scale, and AuNP concentration in food, AuNP size and exposure duration modulated the observed adverse effects. Indeed, we showed alteration of genome composition using a RAPD-PCR genotoxicity test as the number of hybridization sites of the RAPD probes was significantly modified after AuNP exposure. Moreover, the expression of genes involved in DNA repair, detoxification processes, apoptosis, mitochondrial metabolism and oxidative stress was also modulated in response to AuNP contamination. Mitochondrial dysfunctions appeared in brain and muscle for both tested doses (40 and 100 ng gold/fish/day), but gold accumulation in fish tissues could only be observed in the case of the highest exposure dose

Molecular Mechanisms of Resistance to 5-Fluorocytosine in Laboratory Mutants of Candida glabrata

International audienceResistance to 5-fluorocytosine (5-FC) has been poorly investigated in the yeast Candida glabrata. This study was conducted on laboratory mutants obtained by exposure of a wild-type isolate to 5-FC. Based on their susceptibility to 5-fluorouracil (5-FU), two of these mutants were selected for further analysis of the molecular mechanisms of 5-FC resistance. One mutant, resistant to both compounds, exhibited a missense mutation in the gene coding the cytosine deaminase and a decrease in the expression level of the gene coding the uridine monophosphate pyrophosphorylase. The other mutant that showed a reduced susceptibility to 5-FC and 5-FU exhibited an overexpression of the genes coding the thymidylate synthase and a cytosine permease, associated with a missense mutation in the last gene. Thus, beside mutations in the FUR1 gene which represent the most common cause of resistance to 5-FC, other mechanisms may also occur in C. glabrata.</p

Impact of dietary cadmium sulphide nanoparticles on Danio rerio zebrafish at very low contamination pressure.

: Abstract To address the impact of cadmium sulphide nanoparticles (CdSNPs) of two different sizes (8 and 50 nm), Danio rerio zebrafish were dietary exposed to very low doses: 100 or 40 ng CdSNPs/day/g body weight for 36 or 60 days, respectively. The results obtained using RAPD-PCR genotoxicity test showed genomic alteration since the number of hybridisation sites of the RAPD probes was significantly modified after CdSNPs exposure. In addition, selected stress response genes were either repressed or upregulated in tissues of CdSNPs-exposed fish. Mitochondrial dysfunction was also caused by the presence of CdSNPs in food. Cadmium accumulation in fish tissues (brain and muscles) could only be observed after 60 days of exposure. CdSNPs toxicity was dependent on their size and concentration