Pharmacological Analysis of Ionotropic Glutamate Receptor Function in Neuronal Circuits of the Zebrafish Olfactory Bulb

Although synaptic functions of ionotropic glutamate receptors in the olfactory bulb have been studied in vitro, their roles in pattern processing in the intact system remain controversial. We therefore examined the functions of ionotropic glutamate receptors during odor processing in the intact olfactory bulb of zebrafish using pharmacological manipulations. Odor responses of mitral cells and interneurons were recorded by electrophysiology and 2-photon Ca2+ imaging. The combined blockade of AMPA/kainate and NMDA receptors abolished odor-evoked excitation of mitral cells. The blockade of AMPA/kainate receptors alone, in contrast, increased the mean response of mitral cells and decreased the mean response of interneurons. The blockade of NMDA receptors caused little or no change in the mean responses of mitral cells and interneurons. However, antagonists of both receptor types had diverse effects on the magnitude and time course of individual mitral cell and interneuron responses and, thus, changed spatio-temporal activity patterns across neuronal populations. Oscillatory synchronization was abolished or reduced by AMPA/kainate and NMDA receptor antagonists, respectively. These results indicate that (1) interneuron responses depend mainly on AMPA/kainate receptor input during an odor response, (2) interactions among mitral cells and interneurons regulate the total olfactory bulb output activity, (3) AMPA/kainate receptors participate in the synchronization of odor-dependent neuronal ensembles, and (4) ionotropic glutamate receptor-containing synaptic circuits shape odor-specific patterns of olfactory bulb output activity. These mechanisms are likely to be important for the processing of odor-encoding activity patterns in the olfactory bulb

Evidence of mother-child transmission of Helicobacter pylori infection Evidência da transmissão mãe-filho da infecção por Helicobacter pylori

BACKGROUND: Low socioeconomical status is a major risk factor for natural acquisition of Helicobacter pylori (H. pylori) infection in developing countries. Its transmission route is unknown but studies suggest person-to-person transmission. AIM: To evaluate seropositivity of anti-H. pylori antibodies in family members of infected symptomatic index patients as compared to family members of symptomatic uninfected index patients. PATIENTS AND METHODS: One hundred and twelve family members of 38 patients who underwent endoscopy to exclude peptic disease were studied. Patients were deemed H. pylori infected or not infected when rapid urease test and histology were both positive or both negative. The family members underwent ELISA serology using the Cobas Core II Kit (Roche) and were classified into three groups: I - 29 family members of 10 H. pylori (+) duodenal ulcer index patients; II - 57 family members of 17 H. pylori (+) index patients without duodenal ulcer; III - 26 family members of 11 H. pylori (-) index patients. RESULTS: Seropositivity of group I and II (infected patients) was higher than the control group, 83% vs 38%, specially in mothers, 81% vs 18%, and in siblings 76% vs 20%. Differences between fathers' seropositivity was not statistically significant in the three groups: 100% vs 86% vs 70%. Seropositivity of all family members (mother, father and siblings) between infected group (I vs II) was similar. CONCLUSION: Prevalence of H. pylori infection was higher in family members of infected patients, but was similar among family members of infected patients with and without duodenal ulcer. H. pylori infection is more frequent in mothers and siblings of infected index children. A common source of infection cannot be excluded, but facts suggest that person-to-person transmission occurs, specially from mother to child.<br>O estrato socioeconômico baixo é o maior fator de risco para a aquisição natural da infecção por Helicobacter pylori em países em desenvolvimento. As vias de transmissão são desconhecidas embora estudos sugerem transmissão pessoa-pessoa. OBJETIVO: Avaliar a soropositividade de anticorpos anti H. pylori em familiares de pacientes sintomáticos infectados comparados a de pacientes não infectados. CASUÍSTICA E MÉTODOS: Foram estudados 112 familiares de 38 pacientes encaminhados para afastar doença péptica. Os pacientes foram submetidos a exame endoscópico, sendo realizadas quatro biopsias gástricas para pesquisa de H. pylori: duas para teste rápido da urease e duas para histologia (HE/Giemsa). Foi considerado infectado por H. pylori quando ambos os exames resultaram positivos. Nos familiares foi realizada sorologia com método ELISA, utilizando-se o Kit Cobas Core II (Roche), sendo considerado resultado positivo a titulação 7U/mL. Os familiares foram divididos em três grupos: grupo I: 29 familiares de 10 pacientes com úlcera duodenal H. pylori+; grupo II: 57 familiares de 17 pacientes sem úlcera duodenal H. pylori+; grupo III: 26 familiares de 11 pacientes H. pylori-. Foi testada a associação entre grupos e positividade através de uma extensão do teste exato de Fisher (método de Montecarlo SPSS), sendo analisada a soropositividade em cada um dos membros da família: pai, mãe, irmãos e o binômio mãe/pai e para a avaliação de múltiplas variáveis utilizou-se ANOVA. RESULTADOS: Os familiares de pacientes H. pylori+ apresentaram maior soropositividade comparado com o grupo controle, 83% vs 38%, sendo maior nas mães 81% vs 18% e irmãos 76% vs 20%. A soropositividade do pai não foi estatiscamente significante, quando comparados os três grupos de pacientes: 100% vs 86% vs 70%. A soropositividade de todos os membros da família, mãe, pai e irmãos nos grupos de úlcera duodenal H. pylori+ e sem úlcera duodenal H. pylori+ foram semelhantes. CONCLUSÃO: Familiares de pacientes infectados apresentam mais infecção por H. pylori. A soropositividade foi semelhante entre os familiares dos pacientes infectados com e sem úlcera duodenal. Infecção por H. pylori é mais freqüente em mães e irmãos de pacientes infectados; ao contrário, nos pais não houve diferença estatisticamente significante nos três grupos. As crianças apresentam mais infecção quando ambos os pais são H. pylori+ e existe uma concordância do resultado da sorologia entre os cônjuges. Não podemos afastar uma fonte comum de infecção, mas os fatos nos sugerem que a transmissão acontece de pessoa a pessoa e especialmente da mãe para filho e entre os irmãos

Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH4

Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (14C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality 14C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal 14C dates from Alaska as a case study, we show that nearly half the 14C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated 14C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated 14C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH4 concentration at the start of the Bølling–Allerød interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH4. Our results demonstrate that subtle methodological changes in the synthesis of basal 14C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle