Evander de Jesus Oliveira Batista

Role of serotonin in zebrafish (Danio rerio) anxiety: relationship with serotonin levels and effect of buspirone, WAY 100635, SB 224289, fluoxetine and para-chlorophenylalanine (pCPA) in two behavioral models.

Serotonin (5-HT) is a neurotransmitter that is involved in many behavioral functions, including the organization of defense, and its putative pathological correlate, anxiety and stress disorders. Recently, behavioral tests for anxiety have been proposed in zebrafish. Exposure to the novel tank test or to the light/dark test increased extracellular fluid 5-HT content in the brain; anxiety-like behavior correlated positively with 5-HT content in the novel tank test, while the correlation was negative in the light/dark test. Acute treatment with a low dose of fluoxetine was anxiolytic in the geotaxis test and anxiogenic in the scototaxis test, while treatment with a higher dose produced a hyperlocomotor effect in both tasks. Buspirone and WAY 100635 were anxiolytic in both tests, while SB 224289 was anxiolytic in the geotaxis and slightly anxiogenic in the scototaxis test. Serotonin depletion with pCPA was anxiogenic in the geotaxis and anxiolytic in scototaxis. These results underline the differential sensitivity of these tasks to assess serotonergic agents; alternatively, serotonin might regulate zebrafish behavior differently in the novel tank test and in the light/dark test.

Possible role of serotoninergic system in the neurobehavioral impairment induced by acute methylmercury exposure in zebrafish (Danio rerio)

Adult zebrafish were treated acutely with methylmercury (1.0 or 5.0 μg g(-1), i.p.) and, 24h after treatment, were tested in two behavioral models of anxiety, the novel tank and the light/dark preference tests. At the smaller dose, methylmercury produced a marked anxiogenic profile in both tests, while the greater dose produced hyperlocomotion in the novel tank test. These effects were accompanied by a decrease in extracellular levels of serotonin, and an increase in extracellular levels of tryptamine-4,5-dione, a partially oxidized metabolite of serotonin. A marked increase in the formation of malondialdehyde, a marker of oxidative stress, accompanied these parameters. It is suggested that methylmercury-induced oxidative stress produced mitochondrial dysfunction and originated tryptamine-4,5-dione, which could have further inhibited tryptophan hydroxylase. These results underscore the importance of assessing acute, low-level neurobehavioral effects of methylmercury.

A comparison of the light/dark and novel tank tests in zebrafish

The recent introduction of tasks to assess the behavior of zebrafish in novel and/or aversive environments has spurred great interest, prompting attempts to determine which constructs are modeled by these tasks (e.g., fear, anxiety, or some other construct). A review of the pharmacological and behavioral experiments indicates that not all behavioral testing models are equivalent. A more precise understanding of the parameters that influence task performance affords a wider selection of experimental procedures for investigating a particular construct, and also provides tools for differentiating the various constructs that may ultimately be of interest. In this review we will more closely examine two behavioral assays commonly used to measure the construct of ‘anxiety’ in adult zebrafish, with the conclusion that they do not both appear to be measuring a single underlying state.

Occurrence of strongyloidiasis among patients with HTLV-1/2 seen at the outpatient clinic of the Núcleo de Medicina Tropical, Belém, State of Pará, Brazil

INTRODUCTION This study investigated the occurrence of Strongyloides stercoralis infestation and coinfection with HTLV-1/2 in Belém, Brazil. METHODS S. stercoralis was investigated in stool samples obtained from individuals infected with HTLV-1/2 and their uninfected relatives. RESULTS The frequency of S. stercoralis was 9% (9/100), including six patients infected with HTLV-1 (14.3%), two patients infected with HTLV-2 (11.1%), and one uninfected relative. Two cases of hyperinfestation by S. stercoralis were characterized as HTLV-1. CONCLUSIONS These results support the need for the routine investigation of S. stercoralis in patients with HTLV-1, in an attempt to prevent the development of severe forms of strongyloidiasis.

Mauritia flexuosa L. protects against deficits in memory acquisition and oxidative stress in rat hippocampus induced by methylmercury exposure.

Objective: Methylmercury (MeHg) is the most toxic form of mercury that can affect humans through the food chain by bioaccumulation. Human organism is capable of triggering visual and cognitive disorders, neurodegeneration, as well as increased production of reactive species of O2 and depletion of natural anti-oxidant agents. In this context, Mauritia flexuosa L., a fruit rich in compounds with anti-oxidant properties, emerged as an important strategy to prevent the MeHg damages. So, this work has aimed to elucidate the protective effect of Mauritia flexuosa L. on the damage caused by the exposure of rats to MeHg. Methods: In order to evaluate the effect of MeHg on rat aversive memory acquisition and panic-like behavior, we have used elevated T-maze apparatus and after behavioral test, the hippocampus was removed to perfom lipid peroxidation. Results: Our results demonstrated that the exposure to MeHg caused deficits in inhibitory avoidance acquisition (aversive conditioning) and in the learning process, and increased levels of lipid peroxidation in hippocampus tissue. However, the pretreatment with feed enriched with Mauritia flexuosa L. showed a protective effect against cognitive deficits caused by MeHg and also prevented the occurrence of cytoplasmic membrane damage induced by lipid peroxidation in the hippocampal region. Discussion: Therefore, this study suggests that Mauritia flexuosa L. represents an important strategy to prevent neurocytotoxics and behavioral effects of MeHg.

Determination of glutamate uptake by high performance liquid chromatography (HPLC) in preparations of retinal tissue

The present study describes a simple and efficient method utilizing high performance liquid chromatography (HPLC) coupled to fluorescence detection for the determination of kinetic parameters of glutamate uptake in nervous tissue. Retinal tissue obtained from 7-day-old chicks was incubated with known concentrations of glutamate (50-2000 μM) for 10 min, and the levels of the o-phtaldehyde (OPA)-derivatized neurotransmitter in the incubation medium were measured. By assessing the difference between initial and final concentrations of glutamate in the medium, a saturable uptake mechanism was characterized (K(m)=8.2 and V(max)=9.8 nmol/mg protein/min). This measure was largely sodium- and temperature-dependent, strongly supporting that the mechanism for concentration decrements is indeed uptake by high-affinity transporters. Added to this, our results also demonstrated that zinc chloride (an inhibitor of glutamate/aspartate transporters) evoked a concentration-dependent decrease in glutamate uptake, demonstrating the specificity of our methodology. Overall, the present work characterizes an alternative methodology to evaluate glutamate uptake in nervous tissue using HPLC. This approach could be an important tool for studies associated to the characterization of minute alterations in glutamate transport related with central nervous system injury.

Diet enriched with the Amazon fruit açaí (Euterpe oleracea) prevents electrophysiological deficits and oxidative stress induced by methyl-mercury in the rat retina

Background: The protective effect of a diet supplemented by the Amazonian fruit Euterpe oleracea (EO) against methylmercury (MeHg) toxicity in rat retina was studied using electroretinography (ERG) and biochemical evaluation of oxidative stress. Method: Wistar rats were submitted to conventional diet or EO-enriched diet for 28 days. After that, each group received saline solution or 5 mg/kg/day of MeHg for 7 days. Full-field single flash, flash and flicker ERGs were evaluated in the following groups: control, EO, MeHg, and EO+MeHg. The amplitudes of the a-wave, b-wave, photopic negative response from rod and/or cone were measured by ERGs as well as the amplitudes and phases of the fundamental component of the sine-wave flicker ERG. Lipid peroxidation was determined by thiobarbituric acid reactive species. Results: All ERG components had decreased amplitudes in the MeHg group when compared with controls. EO-enriched food had no effect on the non-intoxicated animals. The intoxicated animals and those that received the supplemented diet presented significant amplitude reductions of the cone b-wave and of the fundamental flicker component when compared with non-intoxicated control. The protective effect of the diet on scotopic conditions was only observed for bright flashes eliciting a mixed rod and cone response. There was a significant increase of lipid peroxidation in the retina from animals exposed to MeHg and EO-supplemented diet was able to prevent MeHg-induced oxidative stress in retinal tissue. Conclusion: These findings open up perspectives for the use of diets supplemented with EO as a protective strategy against visual damage induced by MeHg.

Putative involvement of the nitrergic system on the consolidation, but not initiation, of behavioral sensitization after conspecific alarm substance in zebrafish.

Stressful manipulations can sensitize the behavior of an organism, increasing anxiety-like behavior after a delay; this long-term stress sensitization can represent the pathophysiological basis of trauma- and stress-related disorders (TRSDs), of which the most prevalent is post-traumatic stress disorder (PTSD). A role for the glutamate-nitric oxide pathway in this sensitization is implied by behavioral, neurophysiological and genomic data on different species. Here, we report on the long-term sensitization of anxiety-like behavior in zebrafish and the possible participation of nitric oxide in this process. Zebrafish exposed to a conspecific alarm substance (AS) show increased anxiety-like behavior at least 24h after stimulus delivery. Blocking nitric oxide synthesis with l-NAME (5mg/kg) 30min, but not 90min, after AS exposure blocks the sensitization of scototaxis and risk assessment, while treatment 90min after exposure blocks the sensitization of thigmotaxis and erratic swimming; l-NAME was not effective when administered 30min before AS exposure. These data suggest a participation of nitric oxide in the consolidation, but not in the initiation, of behavioral sensitization after predator threat.

Interaction between 5-HT1B receptors and nitric oxide in zebrafish responses to novelty

Nitric oxide (NO) and serotonin (5-HT) interact at the molecular and systems levels to control behavioral variables, including agression, fear, and reactions to novelty. In zebrafish, the 5-HT1B receptor has been implicated in anxiety and reactions to novelty, while the 5-HT1A receptor is associated with anxiety-like behavior; this role of the 5-HT1A receptor is mediated by NO. This work investigated whether NO also participates in the mediation of novelty responses by the 5-HT1B receptor. The 5-HT1B receptor inverse agonist SB 224,289 decreased bottom-dwelling and erratic swimming in zebrafish; the effects on bottom-dwelling, but not on erratic swimming, were blocked by pre-treatment with the nitric oxide synthase inhibitor L-NAME. These effects underline a novel mechanism by which 5-HT controls zebrafish reactivity to novel environments, with implications for the study of neotic reactions, exploratory behavior, and anxiety-like states.

Human Bertielliasis in Amazonia: Case Report and Challenging Diagnosis

In May, 2009, a 4-year-old girl from thetown of Oriximina´, Para´ state, Brazil,experienced 15 days of nocturnal abdom-inal pain, weight loss, abdominal disten-sion, and the presence of ‘‘white worms’’in the stool, but no diarrhea. At the localhospital, even though a conclusive diag-nosis was not available, albendazole wasprescribed for 5 days. Following thistreatment, worms were still found in thepatient’s faeces, so the child was taken tothe Tropical Medicine Nucleus of theFederal University of Para´ (UFPA), wherecestode infection was confirmed. Thisdiagnosis was followed by a single oraldose of praziquantel (10 mg/kg).During treatment, a further seven smallfragments and one large portion of theworm’s strobilus were expelled by thepatient. The largest fragments were fixedin 10% formalin and others stored insaline solution, which were sent to the CellBiology and Helmintology Laboratory atthe UFPA for taxonomic analysis.The smaller fragments were still movingwhen they arrived at the laboratory(Figure 1A), and were exuding a whitesubstance, which was analyzed under amiscroscope. A large number of sphericaleggs—0.042–0.047