Effects of Single Metals and their Mixtures on Selected Enzymes of Carcinus Maenas

In this work, the acute effects of copper, chromium and mixtures of both metals on females of the marine crab Carcinus maenas were investigated. The parameters indicative of toxicity were mortality and the activity of the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and glutathione-S-tranferases (GST). LC50 values determined at 96 hr were 51.8 mg L^-1 for copper, 49.8 mg L^-1 for chromium and 15 mg L^-1 Cu + 43.6 mg L^-1 Cr for the mixture of both metals. Copper, chromium and the mixtures of both metals significantly inhibit haemolymph AChE, ovarian LDH and hepatopancreas GST after an in vivo exposure of 96 hr to concentrations lower than NOEC values for mortality. Furthermore, the mixtures tested showed a more pronounced effect than individual agents.     

An application of digital imagery analysis to understand the effect of N application on light interception,radiation use efficiency,and grain yield of maize under various agro-environments in Northern Mozambique

Light-based analysis is a fundamental approach to quantify the effects of factors determining crop growth in a given environment. The objectives of this study are to confirm the applicability of a digital imagery technique to extract green leaf areas for estimating light interception (LI) of maize canopy and to understand the effect of fertilizer application on the LI and radiation use efficiency (RUE) of maize under various agro-environments in Northern Mozambique. A locally recommended variety, Matuba, was grown in a single season with three different N application rates (0, 30, and 80 kgN ha^?1) at one hot/dry low-elevation site, two hot/humid mid-elevation sites, and one cool/humid high-elevation site. Repeated measurements with quantum sensors revealed that the digital imagery is applicable to estimate the LI of maize except for leaf-senescing period close to maturity. The N application demonstrated profitable yield increases with agronomic nitrogen use efficiencies (kg grain yield per kg N input) of 20.6–35.3 kg kg^?1 except for the low-elevation site with severe drought stress. In the mid-elevation sites, the yield increases were mostly explained by the improvement of RUE while the effect on LI was small because the vegetative growth was naturally vigorous under high temperatures irrespective of N inputs. At the high-elevation site, the N application improved its stagnant initial canopy development and increased both RUE and LI. The simple and inexpensive imagery technique should be useful to identify physiological basis of maize responses to fertilizer application and its interaction with regional environment even under poorly equipped regions in the tropics.     

Effects of dimethoate and beta-naphthoflavone on selected biomarkers of Poecilia reticulata

The main objective of the present study was to investigate if a battery of enzymatic biomarkers was suitable for use as effect criteria in acute toxicity tests with Poecilia reticulata. To attain this objective, the in vivo effects of dimethoate and beta-naphthoflavone on acetylcholinesterase (AChE), cytochrome P4501A-dependent monooxygenase activity of 7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GST), lactate dehydrogenase (LDH) and Na⁺-K⁺-ATPase activities of P. reticulata were studied. After 96 h of exposure to sublethal concentrations (0.063 mg l⁻¹ to 1 mg l⁻¹) of the pesticide, an inhibition of the enzymes AChE and GST, as well as an induction of LDH was observed. The compound beta-naphthoflavone significantly induced both EROD and GST. The remaining enzymes analysed were not significantly altered by the exposure to beta-naphthoflavone (0.82 mg l⁻¹ to 1.7 mg l⁻¹). These results suggest that in vivo toxicity tests based on the biomarkers used in this study are sensitive and present advantages to conventional acute tests based on mortality, since they were able to detect sublethal effects in a short-period of time (96 h) indicating target and/or detoxification mechanisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biological Parameters Towards Polycyclic Aromatic Hydrocarbons Pollution: A Study with Dicentrarchus labrax L. Exposed to the Model Compound Benzo(a)pyrene

The objective of the present study was to investigate the short-term effects of benzo(a)pyrene (BaP) on juvenile sea bass (Dicentrarchus labrax L.) using a multiparameter approach. At the end of the 96?h of exposure to a range of BaP concentrations (2?C256???g?l^?1) in laboratorial conditions, a suite of biomarkers involved in biotransformation pathways, oxidative stress and damage, neurotransmission and energetic metabolism were analysed. Levels of BaP metabolites in bile and BaP-type compounds in tissues were also included as biomarkers of exposure, and the post-exposure swimming velocity was used as a toxicity endpoint at a higher level of biological organisation. In addition, a time-series experiment on the levels of bile BaP metabolites was also performed. Increased levels of BaP metabolites in bile and BaP-type compounds in liver and brain of exposed fish were found, indicating BaP uptake, metabolisation and distribution by different tissues. BaP induced oxidative stress and damage, but no significant effects on the post-exposure swimming velocity, neurotransmission and energetic pathways were found. An increase in the levels of BaP metabolites in bile over time was also observed, reaching a threshold similar at all the concentrations tested. Overall, this integrative multiparameter study reflecting different biological responses of D. labrax was suitable to assess the effects caused by the short-term exposure to BaP and may be useful in the marine environmental risk assessment of polycyclic aromatic hydrocarbons pollution. The observed toxic effects also highlight the relevance of short-term exposure to relatively high concentrations of chemicals, as can occur in the case of punctual heavy chemical releases, such as oil spills in the marine environment.     

Can the Activities of Acetylcholinesterase and Glutathione S-Transferases of Crangon crangon (L.) be Used as Biomarkers of Fuel Oil Exposure?

This work aimed to determine the sensitivity of acetylcholinesterase (AChE) and glutathione S-transferases (GST) activities of Crangon crangon (L.) to the water-accommodated fraction (WAF) of the fuel oil spilled by the oil tanker Prestige, in order to assess their usefulness as markers for this kind of pollution. Laboratory exposure of shrimps to WAF of weathered Prestige fuel oil showed no significant interference with AChE activity. Significant induction of GST activity was observed, potentially as a result of high concentrations of polycyclic aromatic hydrocarbons. However, these results were only obtained with the higher WAF concentrations tested. It was concluded that AChE and GST activities of C. crangon were not useful biomarkers for short-term exposure to the WAF of fuel oil spilled by the tanker Prestige and carried to the beaches of Galicia (NW Spain).     

Alterations of reproductive parameters in the crab Carcinus maenas after exposure to metals

The objective of this study was to investigate the effects of acute exposure to copper, chromium and mixtures of these metals on reproductive parameters of female Carcinus maenas. The parameters studied were ovarian esterase, acid and alkaline phosphatase activity, ovarian protein content, gonadosomatic index (GSI) and hepatosomatic index (HSI). Metals induced significant decreases on ovarian alkaline phosphatase activity, esterase activity and protein content. Ovarian acid phosphatase activity significantly increased in crabs exposed to chromium, while only a slightly increase was found in females exposed to copper and to mixtures of these metals. Furthermore, a dose-dependent reduction of both GSI and HSI were observed in crabs exposed to metals. These observations suggest that copper and chromium may interfere with the ovarian cycle in Carcinus maenas and, therefore, with the reproduction of this species. In general, the mixture had more pronounced effects than individual metals. This subject requires further investigation because in polluted estuaries, crabs may be simultaneously exposed to several metals.     

Effect of dichlorvos on cholinesterase activity of the European sea bass (Dicentrarchus labrax)

In this study, the acute toxicity of the organophosphorous pesticide (OP) dichlorvos and both in vitro and in vivo effects of dichlorvos on cholinesterase (ChE) activity of the European sea bass (Dicentrarchus labrax) were investigated. The characterisation of ChE and the “normal” range of activity in brain and muscle of non-exposed fish were determined in a first phase of the study. Acetylthiocholine was the substrate preferred of both brain and muscle ChE. Eserine sulphate and BW284C51 significantly inhibited the brain and muscle enzyme activity at low concentrations (μM range). Iso-OMPA had a significant effect in muscle, but not in brain tissue. These results suggest that acetylcholinesterase (AChE) is the predominant ChE form in brain tissue. In contrast, both acetylcholinesterase and butyrylcholinesterase seem to exist in muscle. Using acetylthiocholine as substrate, the “normal” range of fingerling head and muscle ChE were 58.05±2.11 and 118.03±8.67 U/mg protein, respectively. Corresponding values for juveniles were 43.32±4.42 and 19.44±2.44 U/mg protein for brain and muscle, respectively. Dichlorvos significantly inhibited the activity of ChE in the selected tissues, both in vitro and in vivo conditions. Differences in ChE sensitivity were found in relation to the age of the fish and the tissue analysed. The present study also showed that fingerlings of the European sea bass are relatively resistant to in vivo acute (96 h) dichlorvos exposure to concentrations between 0.125 and 1 mg/L, being able to tolerate high percentages of head ChE inhibition (37% and 76%) without lethal effects.