RESUMO
Scientists have increasingly recognised that low methodological and analytical rigour combined with publish-or-perish incentives can make the published scientific literature unreliable. As a response to this, large-scale systematic replications of the literature have emerged as a way to assess the problem empirically. The Brazilian Reproducibility Initiative is one such effort, aimed at estimating the reproducibility of Brazilian biomedical research. Its goal is to perform multicentre replications of a quasi-random sample of at least 60 experiments from Brazilian articles published over a 20-year period, using a set of common laboratory methods. In this article, we describe the challenges of managing a multicentre project with collaborating teams across the country, as well as its successes and failures over the first two years. We end with a brief discussion of the Initiative's current status and its possible future contributions after the project is concluded in 2021.
Assuntos
Pesquisa Biomédica/tendências , Projetos de Pesquisa , Brasil , Reprodutibilidade dos TestesRESUMO
Scientists have increasingly recognised that low methodological and analytical rigour combined with publish-or-perish incentives can make the published scientific literature unreliable. As a response to this, large-scale systematic replications of the literature have emerged as a way to assess the problem empirically. The Brazilian Reproducibility Initiative is one such effort, aimed at estimating the reproducibility of Brazilian biomedical research. Its goal is to perform multicentre replications of a quasi-random sample of at least 60 experiments from Brazilian articles published over a 20-year period, using a set of common laboratory methods. In this article, we describe the challenges of managing a multicentre project with collaborating teams across the country, as well as its successes and failures over the first two years. We end with a brief discussion of the Initiative's current status and its possible future contributions after the project is concluded in 2021.
Assuntos
Projetos de Pesquisa , Pesquisa Biomédica/tendências , Brasil , Reprodutibilidade dos TestesRESUMO
Cognitive dysfunction is found in patients with brain tumors and there is a need to determine whether it can be replicated in an experimental model. In the present study, the object recognition (OR) paradigm was used to investigate cognitive performance in nude mice, which represent one of the most important animal models available to study human tumors in vivo. Mice with orthotopic xenografts of the human U87MG glioblastoma cell line were trained at 9, 14, and 18days (D9, D14, and D18, respectively) after implantation of 5×10(5) cells. At D9, the mice showed normal behavior when tested 90min or 24h after training and compared to control nude mice. Animals at D14 were still able to discriminate between familiar and novel objects, but exhibited a lower performance than animals at D9. Total impairment in the OR memory was observed when animals were evaluated on D18. These alterations were detected earlier than any other clinical symptoms, which were observed only 22-24days after tumor implantation. There was a significant correlation between the discrimination index (d2) and time after tumor implantation as well as between d2 and tumor volume. These data indicate that the OR task is a robust test to identify early behavior alterations caused by glioblastoma in nude mice. In addition, these results suggest that OR task can be a reliable tool to test the efficacy of new therapies against these tumors.
Assuntos
Neoplasias Encefálicas/complicações , Glioblastoma/complicações , Transtornos da Memória/etiologia , Reconhecimento Psicológico/fisiologia , Animais , Neoplasias Encefálicas/patologia , Modelos Animais de Doenças , Glioblastoma/patologia , Hipocampo/patologia , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Estatística como Assunto , Fatores de Tempo , Transplante Heterólogo/métodosRESUMO
RATIONALE: D -Serine is an endogenous co-agonist of the N-methyl-D: -aspartate (NMDA) receptor and has been suggested to improve cognitive deficits in schizophrenia. OBJECTIVES: The present study investigates the effects of treatment with D -serine in mice on tasks that require recognition learning and working memory, two cognitive domains that are impaired in schizophrenia. METHODS: We studied the effects of various regimens of systemic administration of D -serine (50 mg/kg/day) on BALB/c mice performing object recognition, T-maze alternation, and open-field exploration tasks. For the object recognition task, we also contrasted the effects of D -serine and D -cycloserine and investigated whether D -serine could reverse alterations induced by subchronic injections of the NMDA antagonist MK-801. D -Serine levels after injections were measured by high-performance liquid chromatography. RESULTS: In the object recognition task, pre-training treatment with D -serine or D -cycloserine significantly enhanced recognition memory 24 h after training. A single administration of D -serine 30 min (but not 6 h) after training produced similar enhancement, suggesting an effect on memory consolidation. Daily treatment with D: -serine enhanced both object recognition and T-maze performance over multiple days and improved short-term memory in MK-801-treated mice. D -Serine treatment did not alter open-field exploration. Behavioral effects were accompanied by increased levels of D -serine in the hippocampus of treated animals. CONCLUSIONS: Our results show that treatment with D -serine can improve performance in tasks related to recognition learning and working memory, suggesting that this agent can be useful for the treatment of disorders involving declines in these cognitive domains.
Assuntos
Memória de Curto Prazo/efeitos dos fármacos , Reconhecimento Psicológico/efeitos dos fármacos , Serina/farmacologia , Animais , Comportamento Animal/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Ciclosserina/farmacologia , Maleato de Dizocilpina/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Hipocampo/metabolismo , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos BALB C , Receptores de N-Metil-D-Aspartato/agonistas , Receptores de N-Metil-D-Aspartato/metabolismo , Fatores de TempoRESUMO
2,4-Dinitrophenol (DNP) is classically known as a mitochondrial uncoupler and, at high concentrations, is toxic to a variety of cells. However, it has recently been shown that, at subtoxic concentrations, DNP protects neurons against a variety of insults and promotes neuronal differentiation and neuritogenesis. The molecular and cellular mechanisms underlying the beneficial neuroactive properties of DNP are still largely unknown. We have now used DNA microarray analysis to investigate changes in gene expression in rat hippocampal neurons in culture treated with low micromolar concentrations of DNP. Under conditions that did not affect neuronal viability, high-energy phosphate levels or mitochondrial oxygen consumption, DNP induced up-regulation of 275 genes and down-regulation of 231 genes. Significantly, several up-regulated genes were linked to intracellular cAMP signaling, known to be involved in neurite outgrowth, synaptic plasticity, and neuronal survival. Differential expression of specific genes was validated by quantitative RT-PCR using independent samples. Results shed light on molecular mechanisms underlying neuroprotection by DNP and point to possible targets for development of novel therapeutics for neurodegenerative disorders.
Assuntos
2,4-Dinitrofenol/farmacologia , AMP Cíclico/genética , Hipocampo/metabolismo , Fármacos Neuroprotetores/farmacologia , Transdução de Sinais/genética , Regulação para Cima/efeitos dos fármacos , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Técnicas de Cultura de Células , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Regulação para Baixo/efeitos dos fármacos , Perfilação da Expressão Gênica/métodos , Hipocampo/efeitos dos fármacos , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Consumo de Oxigênio/efeitos dos fármacos , Ratos , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
One of the earliest manifestations of Alzheimer's disease (AD) is the characteristic inability of affected individuals to form new memories. Memory impairment appears to significantly predate the death of nerve cells, implying that neuronal dysfunction is responsible for the pathophysiology of early stage AD. Mounting evidence now indicates that soluble oligomers of the amyloid-beta peptide (Abeta) are the main neurotoxins that lead to early neuronal dysfunction and memory deficits in AD. Cyclic AMP (cAMP) is a central component of intracellular signaling pathways that regulate a wide range of biological functions, including memory. Among other actions, cAMP triggers the phosphorylation and activation of the cAMP responsive element binding protein (CREB), a transcription factor that regulates the expression of genes that are important for long-term memory. Here, we discuss recent evidence suggesting that cAMP enhancing compounds may find applications as neurocognitive enhancers in AD and in other neurological disorders, as well as possible roles of cAMP in the regulation of neuronal regeneration. In particular, we review recent results showing that low concentrations of 2,4-dinitrophenol (DNP) upregulate neuronal cAMP and tau levels, promote neurite outgrowth and neuronal differentiation and block the oligomerization and neurotoxicity of Abeta. Possible implications of these findings in the development of novel therapeutic approaches in AD are discussed.