Alexssandro Geferson Becker

Cadmium toxicity causes oxidative stress and induces response of the antioxidant system in cucumber seedlings

In this study, the effects of cadmium (Cd) on lipid peroxidation, electrolyte leakage, protein oxidation, ascorbate peroxidase (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) and superoxide dismutase (SOD; E.C. 1.15.1.1) activities, and ascorbic acid, non-protein thiol groups and total soluble protein contents in cucumber seedlings (Cucumis sativus L.) were investigated. Seedlings were grown in vitro in an agar-solidified substrate containing four Cd levels as CdCl2 (0, 100, 400, and 1000 µmol L-1) for 10 d. The lowest Cd level decreased the malondialdehyde concentration. Electrolyte leakage increased only at 1000 µmol Cd L-1, whereas protein oxidation and total soluble protein content were enhanced at 400 and 1000 µmol Cd L-1. Activity of APX was inhibited while the activities of CAT and SOD were increased at all Cd concentrations. Ascorbic acid was enhanced at 400 and 1000 µmol Cd L-1 whereas non-protein thiol groups were increased at all Cd supplies. The results evidence the importance of the enzymatic and non-enzymatic antioxidant system in response to cadmium toxicity in cucumber seedlings.

Aluminum-induced oxidative stress in cucumber.

Aluminum (Al) is one of the most abundant elements of the planet and exposure to this metal can cause oxidative stress and lead to various signs of toxicity in plants. Plants are essential organisms for the environment as well as food for humans and animals. The toxic effect of aluminum is the major cause of decreased crop productivity. Thus, the objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT - E.C. 1.11.1.6), superoxide dismutase (SOD - E.C.1.15.1.1) and ascorbate peroxidase (APX - E.C. 1.11.1.11), and on lipid peroxidation, electrolyte leakage percentage (ELP) and chlorophyll and protein oxidation levels in Cucumis sativus L. (cv. Aodai). Seedlings were grown at different concentrations of aluminum ranging from 1 to 2000 microM for 10 days. The increase in ELP and H(2)O(2) production observed in the seedlings may be related to the decreased efficiency of the antioxidant system at higher aluminum concentrations. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation, protein oxidation and a decrease in the growth of Cucumis seedlings. Aluminum toxicity triggered alterations in the antioxidant and physiological status of growing cucumber seedlings.

Pesticide contamination of water alters the metabolism of juvenile silver catfish, Rhamdia quelen

We investigated how pesticide contamination of water affects the metabolism of the silver catfish, Rhamdia quelen, by studying fish maintained at two sites with low and high anthropic activity (Lino Creek, southern Brazil). Several pesticides were found at both stream sites. After 30 days plasma glucose levels were higher in fish exposed to water in the low anthropic activity site than those exposed to water in the high anthropic activity site. Plasma K+ levels, however, were lower after exposure to low anthropic water than after exposure to high anthropic water. Moreover, values of hepatic glycogen, muscle lactate and protein were higher, but glycogen and protein of the kidney were lower in fish exposed to water at the high anthropic activity site. Our results show that these fish can be used as pesticide toxicity indicators in streams near agricultural fields.

Lipid stability during the frozen storage of fillets from silver catfish exposed in vivo to the essential oil of Lippia alba (Mill.) NE Brown.

BACKGROUND Lippia alba is effective in sedating and reducing stress to fish during transportation. Because some in vitro studies have demonstrated the antioxidant activity of L. alba, we hypothesized that its use in vivo could result in antioxidant effects post mortem. Therefore, in this study we evaluated whether the essential oil of L. alba (EO) used as sedative for fish transport would increase the lipid stability of fillets from silver catfish during frozen storage. RESULTS The exposure to the EO in vivo did not affect conjugated diene values. However, EO (30 and 40 µL L(-1)) delayed the peak formation of peroxides (from the third to the sixth month of storage) and thiobarbituric reactive substances (from the ninth to the twelfth month of storage) when compared to control fillets. After exposure to 40 µL L(-1) EO the free fatty acid content was higher than for control at the start of fillet storage, with no differences among groups thereafter. CONCLUSION The essential oil of L. alba used as sedative in the water to transport silver catfish can delay lipid oxidation of fillets during frozen storage. Thus L. alba may be a promising source of natural active compounds for use in aquaculture and the food industry.

Efficacy of eugenol and the methanolic extract of Condalia buxifolia during the transport of the silver catfish Rhamdia quelen

This study evaluated extracts of Condalia buxifolia as anesthetics for the silver catfish Rhamdia quelen. The effectiveness of eugenol and of the methanolic extract (ME) of C. buxifolia during the transport of this species was also assessed. Fish of two different weights (1.50±0.02 g and 165.70±22.50 g) were transferred to aquaria containing water with the C. buxifolia ME or with fractions obtained from the ME, such as the n-hexane, dichloromethane, ethyl acetate, n-butane and aqueous fractions, at concentrations from 0-300 °L L-1. The C. buxifolia ME in the 0.5-120 °L L-1range caused only light sedation, and the fractions did not have an effect on the fish. In the second experiment, another group of fish was transported for 12 h in 15 plastic bags. The fish were divided into five groups: control, 1 or 2.5 °L L-1 eugenol and 25 or 50 °L L-1C. buxifolia ME. The non-ionized ammonia levels were lower at the end of transport in the groups with the compounds than in that with water alone. Moreover, both compounds decreased the Na+, Cl-, and K+ net effluxes; therefore, their addition to the water during transport is advisable because they reduce fish mortality and ion loss.

Photosynthetic pigments content, δ-aminolevulinic acid dehydratase and acid phosphatase activities and mineral nutrients concentration in cadmium-exposed Cucumis sativus L.

In this study, the effects of cadmium chloride (CdCl2) on plant growth, histology of roots, photosynthetic pigments content, δ-aminolevulinic acid dehydratase (ALA-D; E.C. 4.2.1.24) and acid phosphatase activities (AP; E.C. 3.1.3.2), soluble phosphorus (Pi) measurement and mineral nutrients content in cucumber seedlings (Cucumis sativus L.) were investigated. Cucumber seedlings were grown in vitro in an agar-solidified substrate containing four CdCl2 treatments (0, 100, 400, and 1000 μM) for ten days. Cd was readily absorbed by seedlings and its content was greater in the roots than in the shoot. Cd reduced shoot and root length, and fresh and dry biomass of seedlings. Inhibition of root cell elongation in Cd-treated seedlings was observed by the increase of the mean radial size of cells belonging to three zones of the root tip. The highest level of Cd reduced in a similar manner chlorophyll a, chlorophyll b and total chlorophyll contents. Increasing concentrations of Cd resulted in a linear decrease in carotenoids levels of cotyledons. Interestingly, the ALA-D activity in cotyledons was inhibited only at the highest level of Cd. Root and shoot AP activities were, respectively, activated and inhibited at all CdCl2 concentrations. Root Pi concentration was increased in all Cd treatments and it was not altered in the shoot tissues. Moreover, in general, the nutrient contents were increased in the root and decreased in the shoot. Therefore, we suggest that Cd affects negatively growth, photosynthetic pigments, ALA-D and AP activities and partition of mineral nutrients in cucumber seedlings.

Biochemistry, cytogenetics and bioaccumulation in silver catfish (Rhamdia quelen) exposed to different thorium concentrations.

The objective of this study was to evaluate the effect of thorium (Th) bioaccumulation on the metabolism of silver catfish (Rhamdia quelen) through biochemical parameters of the muscle (glycogen, glucose, lactate, protein, and ammonia). In addition, lipidic peroxidation levels (TBARS), catalase (CAT) and glutathione-S-transferase (GST) in the gills and in hepatic and muscular tissues were also analyzed. Cytogenetic parameters were studied through the evaluation of nuclear abnormalities in red blood cells. Silver catfish juveniles were exposed to different waterborne Th levels (in microg L(-1)): 0 (control), 25.3+/-3.2, 69.2+/-2.73, 209.5+/-17.6, and 608.7+/-61.1 for 15 days. The organs that accumulated the highest Th levels were the gills and skin. The increase of waterborne Th concentration corresponded to a progressive increase of Th levels in the gills, liver, skin and kidneys, with the highest accumulation in the gills and skin. Metabolic intermediates in the muscle were altered by Th exposure, but no clear relationship was found. CAT and GST activities in the hepatic and muscular tissues of this species suggest that the enzymatic activities can be stimulated at the lowest Th levels and inhibited at the higher levels (mainly in 608.7 microg L(-1)). The results of the cytogenetic assay contribute to this hypothesis because the higher toxicity in blood samples was found in juveniles exposed to 69.2 and 209.5 microg L(-1) Th.

Oxidative stress parameters in silver catfish (Rhamdia quelen) juveniles infected with Ichthyophthirius multifiliis and maintained at different levels of water pH

The aim of this study was to determine oxidative stress parameters in the liver, gill and muscle of silver catfish juveniles infected with Ichthyophthirius multifiliis and maintained at pH 5.0 or 7.0 for three days. Juveniles were infected by adding one I. multifiliis-infected juvenile and water containing theronts to tanks. After the appearance of white spots on the skin, infected juveniles exposed to pH 5.0 and 7.0 showed significantly higher thiobarbituric acid reactive substances (TBARS) levels in the liver and gills compared to uninfected juveniles. Liver of infected juveniles exposed to pH 7.0 showed higher catalase (CAT) and lower glutathione-S-transferase (GST) activities, but those maintained at pH 5.0 showed significantly higher GST activity than uninfected juveniles. The gills of infected juveniles showed significantly higher CAT (day two) and GST activity at both pH 5.0 and 7.0 compared to uninfected juveniles. Muscle of infected juveniles showed significantly lower CAT and GST activity and TBARS levels (at day three) when maintained at both pH 5.0 and 7.0 compared to uninfected juveniles. In conclusion, I. multifiliis infection induces liver and gill damage via lipid peroxidation products in silver catfish, but higher antioxidant enzyme activity could indicate a greater degree of protection against this parasite.

Waterborne ammonia and silver catfish, Rhamdia quelen: survival and growth

The aim of the present study was to determine the effects of waterborne un-ionized ammonia (NH3) on the survival and growth of silver catfish (Rhamdia quelen). Juveniles were exposed to 0.10, 0.22, and 0.42mg L-1 NH3 at pH 8.2 for 45 days. After 15 days, a significant mortality rate (33%) was observed in the fish exposed to 0.42mg L-1 NH3. After 20 days, 23% and 43% mortality (both significant) was observed in fish exposed to 0.22 and 0.42mg L-1 NH3, respectively. A significant negative relationship between survival, length, daily weight gain, standard growth rate, and biomass of juveniles of silver catfish per tank with waterborne NH3 levels was found at the end of the experiment. The resulting survival and waterborne NH3 relationship indicated that, to avoid any mortality of silver catfish, the maximum level of chronic NH3 exposure at pH 8.2 would be 0.01mg L-1.

Low water hardness and pH affect growth and survival of silver catfish juveniles

The objective of this study was to investigate the effects of exposure to low water hardness (0, 25 and 50mg CaCO3L-1) into the 6.0-8.0 pH range to silver catfish juveniles (Rhamdia quelen) survival and growth after 32 days. Juveniles kept at zero water hardness presented higher mortality at pH 7.0 and 8.0 than those submitted to other treatments. Weight of juveniles exposed to pH 6.0 and zero water hardness was significantly higher than those kept at the same water hardness and other pH. Survival and growth of juveniles exposed to 25 and 50mg CaCO3 L-1 was not affected in the 6.0-8.0 pH range. Therefore, the best water hardness for silver catfish juveniles growth is 25-50mg CaCO3 L-1 and at low water hardness (next zero) pH must be reduced.