N.C. Peixoto

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.

Behavioral alterations induced by HgCl2 depend on the postnatal period of exposure.

This paper shows the toxicity of mercury (HgCl2 5 mg/kg/day for 5 days, sc) applied at specific stages of development (1–5, 8–12 or 17–21 days old, 1st, 2nd and 3rd phases, respectively) on the performance of rats in three behavioral tasks and on cerebral mercury levels. The mercury exposure at the 1st and 2nd phases affected the performances of rats in the rim escape. Spontaneous alternation behavior was not altered by mercury exposure. In the open field task, habituation was absent when the rats were treated at the 1st phase, and the crossing response number was lower in rats exposed to mercury at the last period. In general, the brain accumulated large quantities of mercury. In short, the first days of postnatal life (1st phase) appeared to be more sensitive to mercury exposure than the other phases studied, since they presented behavioral deficits even at a time period somewhat after 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.

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 HgCl2 (5 mg/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.

Mercury chloride increases hepatic alanine aminotransferase and glucose 6-phosphatase activities in newborn rats in vivo.

This work investigated the in vivo and in vitro effects of HgCl2 and ZnCl2 on metabolic enzymes from tissues of young rats to verify whether the physiological and biochemical alterations induced by mercury and prevented by zinc are related to hepatic and renal glucose metabolism. Wistar rats received (subcutaneous) saline or ZnCl2 (27 mg/kg/day) from 3 to 7 days old and saline or HgCl2 (5.0 mg/kg/day) from 8 to 12 days old. Mercury exposure increased the hepatic alanine aminotransferase (∼6‐fold) and glucose 6‐phosphatase (75%) activity; zinc pre‐exposure prevented totally and partially these mercury alterations respectively. In vitro, HgCl2 inhibited the serum (22%, 10 μM) and liver (54%, 100 μM) alanine aminotransferase, serum (53%) and liver (64%) lactate dehydrogenase (10 μM), and liver (53%) and kidney (41%) glucose 6‐phosphatase (100 μM) from 10‐ to 13‐day‐old rats. The results show that mercury induces distinct alterations in these enzymes when tested in vivo or in vitro as well as when different sources were used. The increase of both hepatic alanine aminotransferase and glucose 6‐phosphatase activity suggests that the mercury‐exposed rats have increased gluconeogenic activity in the liver. Zinc prevents the in vivo effects on metabolic changes induced by mercury.

Copper attenuates early and late biochemical alterations induced by inorganic mercury in young rats

ABSTRACT Mercury (Hg), a divalent metal, produces adverse effects predominantly in the renal and central nervous systems. The aim of this study was to determine the effectiveness of copper (Cu) in prevention of mercuric mercury (Hg2+)-mediated toxic effects as well as the role metallothioneins (MT) play in this protective mechanism in young rats. Wistar rats were treated subcutaneously with saline (Sal) or CuCl2.2H2O (Cu 2.6 mg/kg/day) from 3 to 7 days old and with saline or HgCl2 (Hg 3.7 mg/kg/day) from 8 to 12 days old. The experimental groups were (1) Sal-Sal, (2) Cu-Sal, (3) Sal-Hg, and (4) Cu-Hg. MTs and metal contents were determined at 13 and 33 days of age. Porphobilinogen synthase (PBG-synthase) activity as well as renal and hepatic parameters were measured at 33 days. At 13 day, Hg2+ exposure increased hepatic MT, Hg, zinc (Zn) and iron (Fe) levels, in kidney elevated Cu and Hg and decreased renal Fe concentrations, accompanied by elevated blood Hg levels. At 33 days, Hg2+ exposure inhibited renal PBG-synthase activity, increased serum urea levels and lowered Fe and Mg levels. Copper partially prevented the rise in blood Hg and liver Fe noted at 13 days; and completely blocked urea rise and diminished renal PBG-synthase activity inhibition at 33 days. In 13-day-old rats, Cu exposure redistributed the Hg in the body, decreasing hepatic and blood levels while increasing renal levels, accompanied by elevated renal and hepatic MT levels in Hg2+-exposed animals. These results suggest that hepatic MT might bind to hepatic and blood Hg for transport to the kidney in order to be excreted. Abbreviations: MT: metallothioneins; PBG-synthase: porphobilinogen synthase.

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.

ALTERAÇÕES ALIMENTARES E PONDERAIS DOS USUÁRIOS COM DEPRESSÃO DE UM CAPS DO NOROESTE GAÚCHO

O presente trabalho foi realizado com a finalidade de identificar mudancas de habitos alimentares e de peso corporal relacionados a sindrome depressiva. O estudo foi desenvolvido atraves de entrevistas individuais, compostas por 17 perguntas, com pacientes em tratamento para a depressao frequentadoras de um Centro de Apoio Psicossocial de um municipio no noroeste do RS. Apos a manifestacao da doenca, muitos abandonaram o habito de ingerir alimentos saudaveis, aderiram ao consumo de doces, realizam poucas refeicoes diariamente e relataram alteracao no peso corporal. Grande parte assumiu que frutas e verduras nao fazem parte da sua dieta sistematicamente. Os farmacos mais utilizados sao os ansioliticos/hipnoticos e os antidepressivos ISCS. O ganho de peso pode estar relacionado ao consumo exagerado de alimentos hipercaloricos e a orexia. Ja a perda de peso, a sonolencia consequente ao uso de hipnotico/sedativo, menor tempo em atividade, e ao pequeno numero de refeicoes feitas. A partir deste estudo podemos afirmar que o publico acometido de sindrome depressiva em tratamento neste centro deste municipio, e, na sua imensa maioria, de mulheres. Ha mudancas em relacao a alimentacao e peso nestes pacientes. No entanto, estas alteracoes sao bastante distintas de um individuo para o outro: pode ser a diminuicao do peso, que pode acarretar em subnutricao/desnutricao, ou o aumento do peso, que pode ocasionar sobrepeso/obesidade, causadores de inumeras outras doencas cronicas.

ESTADO NUTRICIONAL E HÁBITOS ALIMENTARES DE ACADÊMICOS DE UMA UNIVERSIDADE DO NORTE DO RIO GRANDE DO SUL

O objetivo da presente pesquisa foi identificar a relacao entre o estado nutricional e habitos alimentares e pratica de atividade fisica de jovens academicos. Tratou-se de um estudo transversal, no qual utilizou-se variaveis antropometricas e questionario sobre habitos alimentares e estilo de vida com os graduandos das mais diversas areas da UFSM/CESNORS, Palmeira das Missoes com faixa etaria de 17 a 24 anos. Os resultados observados no estudo revelam que a amostra tem uma consideravel parcela de individuos com a constituicao corporal inadequada, 26,4% estava com o indice de massa corporal (IMC) acima do preconizado e 30,19% estava com o percentual alto de gordura. Associado a isto, tem habitos alimentares pouco saudaveis, pratica pouca atividade fisica e ingere bebidas alcoolicas com frequencia. Os presentes dados merecem destaque, uma vez que o desenvolvimento de muitas doencas cronicas se da em decorrencia dos maus habitos e acumulo excessivo de gordura. Descritores: Jovens; Estado Nutricional; Habitos Alimentares.