1,720,985 research outputs found
Delayed toxicity of three fluoroquinolones and their mixtures after neonatal or embryonic exposure, in Daphnia magna
Full text linkFluoroquinolones (FQs) are antibacterial drugs, used both in human and veterinary medicine, that are currently considered as emerging micropollutants. This study investigated the delayed toxic effects of enrofloxacin (ENR), flumequine (FLU), levofloxacin (LEV) and their binary mixtures in D. magna. For this purpose, a 10-day follow-up in pure medium was added to the standard D. magna immobilization test. During this follow-up, phenotypic alterations were evidenced, which were related to scarce or zeroed egg production and early mortality. Consequently, the EC50 s recalculated at the end of the follow-up were always remarkably lower than those obtained after the 48 h immobilization test: ENR 3.13 vs. 16.72 mg L−1; FLU 7.18 vs. 25.35 mg L−1; LEV 15.11 vs. > 40 mg L−1. To analyse the possible interactions within the binary mixtures, the method of nonlinear additive isoboles was applied. The three compounds showed invariably to follow the principle of concentration addition. Furthermore, as previous experiments showed toxicity of FLU and ENR after embryonic exposure of D. magna at a concentration of 2 mg L−1, an additional two embryonic tests were conducted with identical design: one with 2 mg L−1 LEV and the other with a ternary mixture containing 0.66 mg L−1 of each of the three FQs. The embryos were exposed for three days in vitro to the drug solutions and were then reconducted to pure medium for 21 days observation. Both the tests ended-up with only non-significant effects on growth and reproduction, confirming the lower toxicity of LEV, when compared to ENR and FLU, and the absence of any evident synergistic interaction among the three FQs. Overall, these studies have shown two relevant features related to the toxicity of the three FQs: (1) they give rise to delayed toxic effects in D. magna that are undetectable by the standard immobilization test; (2) their interaction in mixtures follow the principle of Concentration Addition. Both these indications concern the Environmental Risk Assessment of FQs and may be of interest to regulatory authorities
On the Inapproximability of Finding Minimum Monitoring Edge-Geodetic Sets (short paper)
Full text linkGiven an undirected connected graph G = (V(G), E(G)) on n vertices, the minimum Monitoring Edge-Geodetic Set (MEG-set) problem asks to find a subset M subset of V(G) of minimum cardinality such that, for every edge e in E(G), there exist x, y in M for which all shortest paths between x and y in G traverse e. We show that, for any constant c < 1/2, no polynomial-time (c log n)-approximation algorithm for the minimum MEG-set problem exists, unless P = NP
Levels of p,p '-DDE in liver of predatory birds from Calabria, Italy
No full textIn the present study, the levels of OCs in the liver of predatory birds were evaluated. Liver samples were collected from 80 birds (9 different species) found dead or dying in the territory of Calabria region of Southern Italy from 1993 to 1997. Collected data were compared to data already available regarding the OCs contamination in predatory birds from Italy and other European countries
Toxicity of individual and binary mixtures of perfluoroalkyl compounds in freshwater algae <i>Raphidocelis subcapitata</i>
No full textIntroduction: Per- and polyfluoroalkyl substances (PFAS) are environmental pollutants of increasing scientific
interest. Widely used for several commercial and industrial applications, they are potentially harmful to the
environment and biota. Following the ban of legacy PFAS such as perfluorooctanoic sulfonic acid (PFOS),
several next-generation substitutes have been developed and introduced in the industry (1). Our study
investigated the effects of one PFAS monitored by EFSA and two next-generation substitute compounds, either
individually or in binary mixtures, in the unicellular algae model of ecotoxicology Raphidocelis subcapitata.
Materials and Methods: Algal toxicity tests for perfluorononanoic acid (PFNA), PFOS, perfluorobutanesulfonic
acid (PFBS) and perfluorobutanoic acid (PFBA) were executed using the US-EPA 96h Acute Toxicity Test (2),
with minor modifications. Each compound was dissolved in Bold’s Basal Medium (1.0 g/L) and serial dilutions
were made using a dilution factor of 2.0. Binary mixtures were set up according to the individually obtained
concentration inhibiting the algal growth by 50% (EC 50 ), with the highest concentration represented by the sum of
each EC 50 and using a dilution factor of 2.0.
Results: Data obtained (four replicates) allowed us to determine the EC 50 for each tested PFAS and the type of
interaction (additive effect, synergism or antagonism) in PFAS binary mixtures. PFBA was the most toxic PFAS
(EC50 30.3 mg/L), followed by PFOS (47.3 mg/L), PFNA (90.5 mg/L) and PFBS (105.8 mg/L). The EC 50 of binary
mixtures were 57.0 mg/L (PFOS-PFBS), 44.5 mg/L (PFOS-PFBA), 116.6 mg/L (PFNA-PFBA), 221.5 mg/L
(PFNA-PFBS) and 121.4 mg/L (PFBA-PFBS).
Discussion: Overall, PFAS toxicity (e.g., trend to bioaccumulation) is directly proportional to the carboxyl chain
length; moreover, it increases with the presence of the sulfonate functional group at the end of the carboxyl
chain (3). Our study highlights the highest toxicity of PFBA (a short-chain perfluoroalkyl substitute) on the
freshwater algae R. subcapitata. Among the binary mixtures, PFOS-PFBS and PFOS-PFBA combinations were
proved additive. However, antagonism was observed in the PFNA-PFBA, the PFNA-PFBS, and the PFBA-BFBS
mixtures. We hypothesize this might be due to competition for the same molecular targets. Further studies are
needed to shed a light on molecular mechanisms involved in PFAS uptake and toxicity in this ecotoxicology
model species
In vitro comparison of aldicarb oxidation in various food-producing animal species
No full textAldicarb (ALD) metabolism was studied in vitro using hepatic microsomes from chickens, rabbits, sheep and pigs. The microsomal activities of mono-ooxygenase enzymes (flavin-containing and cytochrome P-450-dependent mixed function oxygenases) were compared by measuring the quantity of the 2 oxidized metabolites, ALD sulfoxide and ALD sulfone, produced during 60 min of incubation. Pig microsomes produced the greatest quantity of ALD sulfoxide and the lowest quantity of ALD sulfone; the latter being produced in greater quantities in sheep than in chickens and rabbits. Aldicarb and its metabolites were degraded fastest in rabbits, probably by hydrolytic reactions. These in vitro results, which are consistent both with the levels of cytochrome P450 found in hepatic microsomes and previous in vivo data on ALD kinetics in pigs, rabbits and chickens, indicate that preliminary in vitro studies can limit the necessary use of animals for drug metabolism experiments.[...
The oxidative metabolism of aldicarb in pigs: in vivo - in vitro comparison
No full textAldicarb was administered (1 mg/kg b.w.) to four female pigs and the kinetics of its major oxidized metabolites (sulfoxide and sulfone) was followed for 6 hours. The in vitro transformations of the carbamate pesticide into these two still active metabolites were also investigated in hepatocytes and in microsomes from pig livers. In all cases, aldicarb was quickly oxidized to the sulfoxide (major metabolite) and only a minor quantity of sulfone was produced. The in vivo toxic symptomatology was related to the peak serum concentration of sulfoxide, suggesting that this metabolite is principally responsible for the aldicarb toxicity. Selective in vitro inhibition of flavin-containing and cytochrome P-450 monooxygenases confirmed that the former enzymes catalyze mainly sulfoxide production whereas the latter that of sulfone.[...
- …
