Papers by Juan C. Sanchez-Hernandez
Polar Biology, 1998
Accumulation of Hg, Cd and Pb by moss was studied in a coastal ice-free area (Edmonson Point, nor... more Accumulation of Hg, Cd and Pb by moss was studied in a coastal ice-free area (Edmonson Point, northern Victoria Land) in relation to the water and nutrient availability and substratum characteristics. Although metal concentrations in surface soils were among the lowest ever reported from remote areas, those of Hg and Cd in mosses were higher, being in the same range as those usually reported in regional surveys in the northern hemisphere. By contrast, Antarctic mosses showed very low Pb concentrations, and no impact from local human activities was detected. Marine aerosols, seabird guano and volcanic emissions appeared to be the more probable sources of Cd and Hg. Besides atmospheric deposition, the main pathway of metals to mosses was probably through evapo-transpiration at their surface which determines an upward migration of ions and their bioaccumulation.
Applied Herpetology, 2005
We compared some hematological parameters and values of plasma cholinesterase activity in adult B... more We compared some hematological parameters and values of plasma cholinesterase activity in adult Bufo arenarum from a control site and agricultural sites. The mean values of the plasma cholinesterase activity did not vary among toads collected in pristine forest and agricultural sites. The blood parameters (hematocrit, hemoglobin concentration, white blood cells, and heterophils) from agricultural sites differed from the control site. The results suggest a high pesticide impact from intensive cropping in mid-eastern Santa Fe Province of Argentina.
Chemosphere, Jan 25, 2015
Effects of pesticides on non-target organisms have been studied in several taxa at different leve... more Effects of pesticides on non-target organisms have been studied in several taxa at different levels of biological organization, from enzymatic to behavioral responses. Although the physiological responses may be associated with higher energy costs, little is known about metabolic costs of pesticide detoxification in birds. To fill this gap, we exposed orally (diet) 15-d old Coturnix coturnix japonica individuals to sublethal doses of chlorpyrifos (10 and 20 mg active ingredient/kg dry food) for four weeks. Carboxylesterase (CbE), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities were periodically measured in multiple tissues along with measurements of resting (RMR) and maximum metabolic rates (Msum). Furthermore, glucuronic acid in bird excreta was also assessed at the end of the trial. While CbE and BChE activities were inhibited by chlorpyrifos in all tissues during the third and fourth weeks following pesticide treatment, AChE activity was unaffected. At thi...
Toxicological & Environmental Chemistry, 2008
We determined the normal levels of butyrylcholinesterase (BChE), carboxylesterase (CbE), and glut... more We determined the normal levels of butyrylcholinesterase (BChE), carboxylesterase (CbE), and glutathione S-transferases (GST) activities in three South American toad species in order to establish reference values for field pesticide monitoring purposes. Interspecies variations in B-esterase and GST activities were examined according to body mass. In addition, comparative inhibition of BChE and CbE activities using malaoxon, and chemical reactivation of malaoxon-inhibited BChE activity using pyridine-2-aldoxime methochloride (2-PAM) were investigated. Bufo fernandezae had average activity values for BChE: 17.31 mmol min À1 ml À1 ; CbE: 621.49 nmol min À1 ml À1 and GST: 1.94 mmol min À1 ml À1 while B. arenarum enzymatic average activities were BChE: 9.51 mmol min À1 ml À1 ; CbE: 270.07 nmol min À1 ml À1 , and GST: 1.59 mmol min À1 ml À1 ; finally Bufo schneideri had enzymatic mean values of BChE: 2.08 mmol min À1 ml À1 ; CbE: 301.95 nmol min À1 ml À1 , and GST: 1.60 mmol min À1 ml À1 . Moreover, we found an allometric relationship between plasma BChE and CbE activities and body size for the three toad species. We suggest that B. fernandezae would be the species with a higher tolerance capacity to organophosphorous insecticides compared to the other toad species, while B. schneideri may be the most vulnerable toad species to field pesticide exposure, although some other factors (e.g., brain AChE sensitivity or pesticide metabolism by phosphotriesterases) should be also taken into account. The malaoxoninhibited BChE activity of the three toad species was reactivated in the presence of 2-PAM, and it is recommended as a specific and sensitive methodology in the assessment of field exposure to OP insecticides together to compare BChE activity levels between OP-exposed and nonexposed individuals.
Journal of Hazardous Materials, 2011
Exposure to mercury is often assessed by the measurement of molecular and biochemical antioxidant... more Exposure to mercury is often assessed by the measurement of molecular and biochemical antioxidant defences against an excessive production of reactive oxygen species. Here we examined some selected biomarkers of oxidative stress in the earthworm Lumbricus terrestris short-(2 d) and long-term (44 d) exposed to Hg-contaminated soils (up to 1287 mg/kg dry wt). This level of Hg exposure did not cause earthworm mortality, however it yielded organisms to a situation of oxidative stress which was evidenced by the time-dependent responses of biomarkers. The reduced to oxidized glutathione ratio was a sensitive and early biomarker of Hg exposure, although the glutathione reductase activity back returned their normal physiological concentrations. Metallothioneins and total glutathione seemed to have a significant role in reducing Hg-induced oxidative stress when exposure to Hg prolonged up to 44 d. We combined biomarker responses into an integrate biomarker index which positively correlated with the Hg concentrations measured in the postmitochondrial fraction of the earthworm muscle, and with the available Hg fraction in soil. Current results suggest that glutathione redox cycle can be a complementary tool in the exposure and effect assessment of Hg-polluted soils.
International Geology Review, 2005
Page 1. International Geology Review, Vol. 47, 2005, p. 11201130. Copyright © 2005 by VH Winston... more Page 1. International Geology Review, Vol. 47, 2005, p. 11201130. Copyright © 2005 by VH Winston & Son, Inc. All rights reserved. 0020-6814/05/836/1120-11 $25.00 1120 Pre-industrial Metal Anomalies in Ice Cores: A Simplified ...
Environmental Science and Pollution Research, 2012
Ecotoxicology and Environmental Safety, 2008
To test the hypothesis that eutrophication ponds modulate some aspects of the health responses an... more To test the hypothesis that eutrophication ponds modulate some aspects of the health responses and survival of anuran tadpoles, we conducted field experiments using Scinax nasicus as sentinel organism to evaluate the quality of two ponds filled with agricultural runoff in a dominant agricultural landscape of Mid-Western Entre Rı´os Province (Argentina). The survival, growth and development rates, erythrocytes nuclei aberrations, parasite infection, and brain cholinesterase activity were monitored after seven days of exposure. Water samples from the ponds were also analyzed for physico-chemical variables and levels of pesticide residues. Residues of organochlorine pesticides and nutrients were higher in the agricultural ponds with respect to those from the control pond. We suggest that the interactions among washed-off nutrients and pesticides from agriculture and environmental factors account for deleterious effects on S. nasicus survival, growth and development rate, thereby compromising their health status. These effects can lead, in turn, to an increase in tadpole vulnerability to opportunistic parasites, erythrocytes nuclei aberrations or hemolysis. r
Applied Herpetology, 2005
We compared some hematological parameters and values of plasma cholinesterase activity in adult B... more We compared some hematological parameters and values of plasma cholinesterase activity in adult Bufo arenarum from a control site and agricultural sites. The mean values of the plasma cholinesterase activity did not vary among toads collected in pristine forest and agricultural sites. The blood parameters (hematocrit, hemoglobin concentration, white blood cells, and heterophils) from agricultural sites differed from the control site. The results suggest a high pesticide impact from intensive cropping in mid-eastern Santa Fe Province of Argentina.
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Papers by Juan C. Sanchez-Hernandez