Diet selenium improves the antioxidant defense system of juveniles Nile tilapia ( Oreochromis niloticus L) / Selênio na dieta melhora o sistema de defesa antioxidante de juvenis de Tilápia do Nilo (Oreochromis niloticus L)

Abstract From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

Resumo Com o avanço da produção de tilápia nos últimos anos, buscam-se dietas que possibilitem o máximo crescimento, saúde e qualidade do pescado. Neste trabalho foram avaliados parâmetros de crescimento, bioquímicos, sanguíneos e oxidativos de tilápias alimentadas com níveis crescentes de selênio: 0,53, 0,86, 1,04 e 1,22 mg kg-1. Foram utilizados 400 juvenis (peso inicial =36,51 ± 10,88 g), alimentados durante seis semanas. Não ocorreu efeito do selênio no crescimento, nem nos parâmetros bioquímicos e hematológicos dos peixes. Nos parâmetros oxidativos, ocorreu aumento nos níveis de tióis não-proteicos e diminuição de malondialdeído, evidenciando efeitos antioxidantes do selênio. Os níveis de selênio acima de 0.86 mg kg-1 melhoram o sistema antioxidante dos peixes e não compromete os parâmetros bioquímicos, sanguíneos e de crescimento de juvenis de tilápia.

Growth and digestive enzymes of silver catfish fed diets containing fruit residue / Crescimento e enzimas digestivas de jundiás alimentados com dietas contendo resíduos de frutas

In fish farming, the use of alternative ingredients has been studied, so that alternative sources can be used to minimize feed costs. This study evaluated the incorporation of grape, orange, guava, and fig residues in diets for silver catfish and its effects on growth, digestive enzymes and body composition. A total of 180 fish (initial mean weight = 22.93±0.75 g) were reared in a recirculation aquaculture system. There was no difference (P>0.05) in the parameters of growth, dry matter, mineral matter, plasma protein, cholesterol, triglycerides, lipase, and trypsin of fish. Glucose levels were higher in fish fed diets containing fig, orange, and grape residue (P<0.05). Lipase activity was higher in fish fed orange residue, compared to guava (P<0.05). Diets containing guava and fig provided more body protein in silver catfish. The fish fed with diet containing orange residue had a higher content of body lipids. It can be concluded that the tested fruit residues can be used in silver catfish feeding.(AU)

Na piscicultura, o uso de ingredientes alternativos vem sendo estudado, de modo que seja possível utilizar fontes alternativas para minimizar custos com a alimentação. Neste estudo, foi avaliada a incorporação de resíduos de uva, laranja, goiaba e figo em rações para jundiá e seus efeitos no crescimento, em enzimas digestivas e na composição corporal. Foram utilizados 180 peixes (peso médio inicial = 22,93±0,75 g), criados em sistema de recirculação. Não houve diferença (P>0,05) nos parâmetros de crescimento, matéria seca, matéria mineral, proteína plasmática, colesterol, triglicerídeos, lipase e tripsina dos peixes. Os níveis de glicose foram maiores nos peixes alimentados com dietas contendo figo, laranja e uva (P<0,05). A atividade de lipase foi maior nos peixes alimentados com resíduo de laranja, comparado com o de goiaba (P<0,05). As dietas contendo goiaba e figo proporcionaram mais proteína corporal nos jundiás. Os jundiás alimentados com dieta contendo resíduo de laranja apresentaram maior teor de lipídeos corporal. Conclui-se que os resíduos de frutas testados podem ser usados na alimentação do jundiá.(AU)

Diet selenium improves the antioxidant defense system of juveniles Nile tilapia ( Oreochromis niloticus L.).

From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

Diet selenium improves the antioxidant defense system of juveniles Nile tilapia ( Oreochromis niloticus L.)

Abstract From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

Resumo Com o avanço da produção de tilápia nos últimos anos, buscam-se dietas que possibilitem o máximo crescimento, saúde e qualidade do pescado. Neste trabalho foram avaliados parâmetros de crescimento, bioquímicos, sanguíneos e oxidativos de tilápias alimentadas com níveis crescentes de selênio: 0,53, 0,86, 1,04 e 1,22 mg kg-1. Foram utilizados 400 juvenis (peso inicial =36,51 ± 10,88 g), alimentados durante seis semanas. Não ocorreu efeito do selênio no crescimento, nem nos parâmetros bioquímicos e hematológicos dos peixes. Nos parâmetros oxidativos, ocorreu aumento nos níveis de tióis não-proteicos e diminuição de malondialdeído, evidenciando efeitos antioxidantes do selênio. Os níveis de selênio acima de 0.86 mg kg-1 melhoram o sistema antioxidante dos peixes e não compromete os parâmetros bioquímicos, sanguíneos e de crescimento de juvenis de tilápia.

Delayed biochemical changes induced by mercury intoxication are prevented by zinc pre-exposure.

This work evaluated the delayed effects of mercury and the effectiveness of zinc in preventing such effects. Pups were pre-treated with 1 daily dose of ZnCl(2) (27 mg/kg/day, by subcutaneous injections) from 3rd to 7th postnatal day and received 1 daily dose of 5 mg/kg of HgCl(2), for 5 subsequent days (8-12 days old). Animals were euthanized 21 days after the end of Hg-exposure. Porphobilinogen-synthase activity as well as zinc and mercury contents was determined in the liver and kidneys. Alanine aminotransferase, aspartate aminotransferase and lactic dehydrogenase activities as well as urea, creatinine and glucose levels were analyzed in plasma or serum. Some animals were considered more sensitive to mercury, since they did not recover the body weight gain and presented an increase of renal and hepatic mercury content, urea and creatinine levels; a decrease in renal porphobilinogen-synthase and alanine aminotransferase activities, as well as a decrease in the liver and an increase in kidney weights. Some animals were considered less sensitive to mercury because they recovered the body weight and presented no biochemical alterations in spite of mercury in the tissues. Zinc prevents partially or totally the alterations caused by mercury even those that persisted for a long time after the end of exposure. These findings suggest that there is difference among the animals regarding the sensitivity to mercury.

ZnCl2 exposure protects against behavioral and acetylcholinesterase changes induced by HgCl2.

This study examined the effects of inorganic mercury exposure on behavioral and biochemical parameters and investigated the possible preventive effects of zinc on the alterations induced by mercury. Pups were exposed from 3rd to 7th postnatal day to ZnCl2 (27 mg/kg/day, s.c.) and subsequently to HgCl2 (5 doses of 5 mg/kg/day, s.c.). Each litter contained two rats for each treatment. The rats were submitted to behavioral task and litters were killed at 13 or 33 days old for acetylcholinesterase activity assays and for the determination of metal levels. Based on the results obtained from 13-day-old rats, they were divided in two groups of litters that were defined at the end of the experimental period (33 days) as less sensitive rats to mercury and more sensitive rats to mercury in accordance with the recovery of body weight until day 33. The mercury exposure caused accumulation of this metal in cerebrum and cerebellum in all mercury treated rats, and inhibited the cerebellum acetylcholinesterase activity from 13-day-old rats. Besides, the mercury-animals of the most sensitive litters to mercury presented impairment in motor function and muscular strength verified in the beaker test, as well as a reduction of the locomotor and exploratory activities in the open field task. Zinc partially prevented all the alterations induced by mercury exposure and reduced the mercury level accumulated in cerebrum and cerebellum. This study confirms the preventive effect of zinc on behavioral alterations induced by mercury in young rats and demonstrates that the mercury behavioral effects are present even for a long time after the end of the exposure.

Changes in levels of essential elements in suckling rats exposed to zinc and mercury.

The effect of mercury and its interaction with zinc on the content of essential metals in tissues from neonate rats was investigated. Three-day-old Wistar rats were treated with saline or 27 mg kg(-1)d(-1) ZnCl2 (s.c.) for five consecutive days. From the 8th to the 12th day of life, the rats received one daily dose of saline or 5.0 mg kg(-1) HgCl2 (s.c). Twenty-four hours after the last injection liver, kidneys and blood were collected for metal quantification. The HgCl(2) exposure induced alterations on metal levels, such as increase of Fe, Hg and Zn in liver, decrease of Fe and Mg and increase of Cu and Hg contents in kidneys. The Hg exposure also increased Hg levels in the blood. The treatment with ZnCl2, administered previously to HgCl2, partially prevented the increase of Fe in the liver, and not only prevented the decrease of renal Mg but also increased it to levels higher than those found in control group. The Zn-Hg rats also presented higher renal Cu levels, and showed partially lower blood and hepatic Hg levels and higher renal Hg levels. The pre-administration of Zn caused no severe alterations in levels of essential metals (Cu, Fe, Mg and Mn). In short, Zn appears to be an alternative treatment of Hg poisoning in young animals in comparison to chelating drugs since these have low metal selectivity.

Metallothionein, zinc, and mercury levels in tissues of young rats exposed to zinc and subsequently to mercury.

Several studies have described mercury toxicity and the role of metallothioneins (MT) in the detoxification and regulation of metal homeostasis. However, little data exist on this topic during the specific post-natal developmental phase in young mammals. This developmental phase is particularly important since young animals are more sensitive to toxicants than adults. The objective of this work was to investigate whether MT participates in the mechanism of protection conferred by zinc pre-treatment on the toxic effects induced by mercury in neonate rats. Pups were exposed to ZnCl(2) (5 doses of 27 mg/kg/day, s.c.) and subsequently to HgCl(2) (5 doses of 5 mg/kg/day, s.c.); metal (Zn and Hg) and MT contents were analyzed in the liver, kidney, and blood. MT was induced in the liver and kidney of pups of both Zn-sal and Zn-Hg groups, although the greatest increase was in neonates exposed to Zn only. A direct relationship exists between MT and metals for both hepatic and renal tissues, which indicates that the increase in metal levels occurs in parallel to the increase in MT content. Although the heat-treated cytosolic fraction is rich in MT and metals, higher Zn and Hg contents were detected in the insoluble fraction of all tissues. These results suggest that MT is, at least in part, responsible for preventing Hg accumulation in the liver and blood and decreasing renal toxicity.

Effects of HgCl2 on porphobilinogen-synthase (E.C. 4.2.1.24) activity and on mercury levels in rats exposed during different precocious periods of postnatal life.

Porphobilinogen-synthase (PBG-synthase) is an enzyme extensively used as a bioindicator of metals and other oxidizing agents. The objective of this study was to verify the effects of HgCl(2) (5mg/kg/day, s.c.), a metal that mainly affects the nervous and renal systems, on kidney, liver and brain from rats exposed during one of the phases considered critical for development. Mercury decreased PBG-synthase activity from liver, kidney and brain and altered corporal, renal and cerebral weights. The kidney was the most sensitive tissue. It accumulated a large amount of metal and PBG-synthase activity was decreased up to 50%. The second period seemed to be the most sensitive, because in this phase the rats presented alterations in body, brain and kidney weights, and there was also an expressive inhibition in hepatic and renal PBG-synthase activities. In general, large quantities of metal accumulated in the tissues are in agreement with the inhibition verified in these tissues.

Effectiveness of ZnCl2 in protecting against nephrotoxicity induced by HgCl2 in newborn rats.

This work investigated the preventive effects of ZnCl(2) on renal and hepatic alterations induced by HgCl(2) in young rats. Wistar rats of 3 days old were treated (s.c.) on consecutive days with saline or ZnCl(2) 27 mg/kg/day from the 3rd to the 7th and with saline or HgCl(2) 5.0mg/kg/day from the 8th to the 12th day of life. Pups were sacrificed 24h after the last dose and samples were collected. The creatinine and urea dosages, used as renal parameters, presented increases of 35% and 500%, respectively. The alanine aminotransferase and lactic dehydrogenase activities, used as hepatic parameters, presented a decrease (40%) and no alteration, respectively, by mercury exposure. The glycemia was diminished and the hepatic glycogen was not modified by mercury. All the mercury effects were prevented by zinc. These results suggest that mercury intoxication of young rats alters the renal function but does not modify the hepatic parameters, and previous exposure to zinc is able to avoid the renal damage.

Perspectives of digestive pest control with proteinase inhibitors that mainly affect the trypsin-like activity of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae).

The present study describes the main characteristics of the proteolytic activities of the velvetbean caterpillar, Anticarsia gemmatalis Hübner, and their sensitivity to proteinase inhibitors and activators. Midguts of last instar larvae reared on an artificial diet were homogenized in 0.15 M NaCl and centrifuged at 14,000 g for 10 min at 4 degrees C and the supernatants were used in enzymatic assays at 30 degrees C, pH 10.0. Basal total proteolytic activity (azocasein hydrolysis) was 1.14 +/- 0.15 absorbance variation min(-1) mg protein(-1), at 420 nm; basal trypsin-like activity (N-benzoyl-L-arginine-p-nitroanilide, BApNA, hydrolysis) was 0.217 +/- 0.02 mmol p-nitroaniline min(-1) mg protein(-1). The maximum proteolytic activities were observed at pH 10.5 using azocasein and at pH 10.0 using BApNA, this pH being identical to the midgut pH of 10.0. The maximum trypsin-like activity occurred at 50 degrees C, a temperature that reduces enzyme stability to 80 and 60% of the original, when pre-incubated for 5 and 30 min, respectively. Phenylmethylsulfonyl fluoride inhibited the proteolytic activities with an IC50 of 0.39 mM for azocasein hydrolysis and of 1.35 mM for BApNA hydrolysis. Benzamidine inhibited the hydrolysis with an IC50 of 0.69 and 0.076 mM for azocasein and BApNA, respectively. The absence of cysteine-proteinases is indicated by the fact that 2-mercaptoethanol and L-cysteine did not increase the rate of azocasein hydrolysis. These results demonstrate the presence of serine-proteinases and the predominance of trypsin-like activity in the midgut of Lepidoptera insects, now also detected in A. gemmatalis, and suggest this enzyme as a major target for pest control based on disruption of protein metabolism using proteinase inhibitors.

Perspectives of digestive pest control with proteinase inhibitors that mainly affect the trypsin-like activity of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)

The present study describes the main characteristics of the proteolytic activities of the velvetbean caterpillar, Anticarsia gemmatalis Hübner, and their sensitivity to proteinase inhibitors and activators. Midguts of last instar larvae reared on an artificial diet were homogenized in 0.15 M NaCl and centrifuged at 14,000 g for 10 min at 4°C and the supernatants were used in enzymatic assays at 30°C, pH 10.0. Basal total proteolytic activity (azocasein hydrolysis) was 1.14 ± 0.15 absorbance variation min-1 mg protein-1, at 420 nm; basal trypsin-like activity (N-benzoyl-L-arginine-p-nitroanilide, BApNA, hydrolysis) was 0.217 ± 0.02 mmol p-nitroaniline min-1 mg protein-1. The maximum proteolytic activities were observed at pH 10.5 using azocasein and at pH 10.0 using BApNA, this pH being identical to the midgut pH of 10.0. The maximum trypsin-like activity occurred at 50°C, a temperature that reduces enzyme stability to 80 and 60 percent of the original, when pre-incubated for 5 and 30 min, respectively. Phenylmethylsulfonyl fluoride inhibited the proteolytic activities with an IC50 of 0.39 mM for azocasein hydrolysis and of 1.35 mM for BApNA hydrolysis. Benzamidine inhibited the hydrolysis with an IC50 of 0.69 and 0.076 mM for azocasein and BApNA, respectively. The absence of cysteine-proteinases is indicated by the fact that 2-mercaptoethanol and L-cysteine did not increase the rate of azocasein hydrolysis. These results demonstrate the presence of serine-proteinases and the predominance of trypsin-like activity in the midgut of Lepidoptera insects, now also detected in A. gemmatalis, and suggest this enzyme as a major target for pest control based on disruption of protein metabolism using proteinase inhibitors.

Sensitivity of delta-ALA-D (E.C. 4.2.1.24) of rats to metals in vitro depends on the stage of postnatal growth and tissue.

Heavy metals, like cadmium, lead, and mercury, are potential toxic substances. The exposure to these metals can cause renal disturbances and neurological alterations. Young rats are more sensitive to harmful agents than adult animals. Delta-ALA-D enzyme acts as a biomarker of these exposures, since it has high affinity for divalent metals. The purpose of this search was to investigate the sensitivity of delta-ALA-D from suckling rats to cadmium, lead or mercury in vitro. IC(50) for delta-ALA-D activity of brain, kidneys, and liver from rats with ages between 1 and 6, 8 and 13 or 17 and 21 days was determined using metals concentrations that range from 0 to 200 microM for CdCl(2), 0 to 600 microM for HgCl(2) and from 0 to 50 microM for lead acetate. The results demonstrated that the cerebral delta-ALA-D activity is more sensitive to lead acetate than to cadmium and mercury. Delta-ALA-D from hepatic tissue is the most resistant to presence of mercury chloride in assay medium. Lead and cadmium are more toxic to renal enzyme than mercury. To sum up, the sensitivity of delta-ALA-D enzyme of young rats to heavy metals studied depends on the phase of development and tissue.