Bastos VL

References (5)

Title : Cholinesterase activity of muscle tissue from freshwater fishes: characterization and sensitivity analysis to the organophosphate methyl-paraoxon - Lopes_2014_Environ.Toxicol.Chem_33_1331
Author(s) : Lopes RM , Filho MV , de Salles JB , Bastos VL , Bastos JC
Ref : Environ Toxicol Chem , 33 :1331 , 2014
Abstract : The biochemical characterization of cholinesterases (ChE) from different teleost species has been a critical step in ensuring the proper use of ChE activity levels as biomarkers in environmental monitoring programs. In the present study, ChE from Oreochromis niloticus, Piaractus mesopotamicus, Leporinus macrocephalus, and Prochilodus lineatus was biochemically characterized by specific substrates and inhibitors. Moreover, muscle tissue ChE sensitivity to the organophosphate pesticide methyl-paraoxon was evaluated by determining the inhibition kinetic constants for its progressive irreversible inhibition by methyl-paraoxon as well as the 50% inhibitory concentration (IC50) for 30 min for each species. The present results indicate that acetylcholinesterase (AChE) must be present in the muscle from P. mesopotamicus, L. macrocephalus, and P. lineatus and that O. niloticus possesses an atypical cholinesterase or AChE and butyrylcholinesterase (BChE). Furthermore, there is a large difference regarding the sensitivity of these enzymes to methyl-paraoxon. The determined IC50 values for 30 min were 70 nM (O. niloticus), 258 nM (P. lineatus), 319 nM (L. macrocephalus), and 1578 nM (P. mesopotamicus). The results of the present study also indicate that the use of efficient methods for extracting these enzymes, their kinetic characterization, and determination of sensitivity differences between AChE and BChE to organophosphate compounds are essential for the determination of accurate ChE activity levels for environmental monitoring programs.
ESTHER : Lopes_2014_Environ.Toxicol.Chem_33_1331
PubMedSearch : Lopes_2014_Environ.Toxicol.Chem_33_1331
PubMedID: 24648156

Title : Methyl-paraoxon comparative inhibition kinetics for acetylcholinesterases from brain of neotropical fishes - Silva_2004_Toxicol.Lett_153_247
Author(s) : Silva Filho MV , Oliveira MM , Salles JB , Bastos VL , Cassano VP , Bastos JC
Ref : Toxicol Lett , 153 :247 , 2004
Abstract : Acetylcholinesterase (AChE) sensitivity to the organophosphorus (OP) pesticide methyl-paraoxon was measured in fourteen species of Neotropical marine and freshwater fish found in the waters of Brazil. The rate constant for phosphorylation, kp, the dissociation constant, kd, the second order rate constant, ki, and the IC50 value were measured at 28 degrees C in pH 7.5 buffer for AChE extracted from brain. In addition, the substrate affinity constant, km, was measured with acetylthiocholine. The IC50 for 30 min of inhibition ranged from 123 nM (Prochilodus lineatus) to 3340 nM (Percophis brasiliensis), which corresponded to ki values of 187-6.9 mM(-1) min(-1). A 10-fold range in kp values from 0.21 min(-1) (Paralonchurus brasiliensis) to 2.1 min(-1) (Dules auriga) was associated with a 37-fold range in kd values from 4 to 150 microM. These large differences in reactivity with methyl-paraoxon were not reflected in the binding affinity for acetylthiocholine; km values were approximately 0.1-0.3 mM for all species. These results predict that the amino acid sequence involved in AChE sensitivity differs in these fishes, and that consequently some fish species may be resistant to the toxicity of methyl-paraoxon.
ESTHER : Silva_2004_Toxicol.Lett_153_247
PubMedSearch : Silva_2004_Toxicol.Lett_153_247
PubMedID: 15451556

Title : Paraoxonase activity in sera of four neotropical fish -
Author(s) : Bastos VL , Alves MV , Bernardino G , Ceccarelli PS , Bastos JC
Ref : Bulletin of Environmental Contamination & Toxicology , 72 :798 , 2004
PubMedID: 15199996

Title : Different sensitivities to paraoxon of brain and serum cholinesterases from Pacu, an indigenous Brazilian fish -
Author(s) : Bastos VL , Rossini A , Pinto LF , de Lima LM , Ceccarelli PS , Coelho MG , Bastos JC
Ref : Bulletin of Environmental Contamination & Toxicology , 60 :1 , 1998
PubMedID: 9484549

Title : Methyl parathion activation by a partially purified rat brain fraction - De Lima_1996_Toxicol.Lett_87_53
Author(s) : De Lima JS , Bastos Neto JdD , Bastos VL , da Cunha JC , Moraes FF , Ferreira MdF , Moreira JdD , Faria MV
Ref : Toxicology Letters , 87 :53 , 1996
Abstract : Organophosphorus pesticides are one of the most commonly used insecticide classes. They act through a potent inhibition of acetylcholinesterase (AChE). Many of them must undergo transformation into the corresponding oxon analogs to inhibit AChE. This study showed that a brain tissue subfraction transformed methyl parathion (O,O-dimethyl O-p-nitrophenyl phosphorothioate) in vitro. Methyl parathion activation was assayed by solvent extraction of the products followed by HPLC and GC-MS analyses and, indirectly, by the inhibition of AChE present in the incubation mixture. The lack of impairment of AChE after 2 h of incubation of the brain subfraction with methyl parathion and, alternatively, with NADPH, CO, SKF 525-A, piperonyl butoxide or nitrogen indicated that this brain subfraction transformed methyl parathion without the involvement of a mixed-function oxidative pathway. The results from HPLC analysis did not show a peak corresponding to methyl paraoxon (O,O-dimethyl O-p-nitrophenylphosphate), but showed the production of an unidentified peak which eluted nearby standard methyl parathion (retention times of 10.65 and 8.86 min, respectively). GC-MS analysis suggested that the unidentified product could be a methyl parathion isomer.
ESTHER : De Lima_1996_Toxicol.Lett_87_53
PubMedSearch : De Lima_1996_Toxicol.Lett_87_53
PubMedID: 8701445