Distinct Contributions of Median Raphe Nucleus to Contextual Fear Conditioning and Fear-Potentiated Startle

Ascending 5-HT projections from the median raphe nucleus (MRN), probably to the hippocampus, are implicated in the acquisition of contextual fear (background stimuli), as assessed by freezing behavior. Foreground cues like light, used as a conditioned stimulus (CS) in classical fear conditioning, also cause freezing through thalamic transmission to the amygdala. As the MRN projects to the hippocampus and amygdala, the role of this raphe nucleus in fear conditioning to explicit cues remains to be explained. Here we analyzed the behavior of rats with MRN electrolytic lesions in a contextual conditioning situation and in a fear-potentiated startle procedure. The animals received MRN electrolytic lesions either before or on the day after two consecutive training sessions in which they were submitted to 10 conditioning trials, each in an experimental chamber (same context) where they. received foot-shocks (0.6 mA, 1 sec) paired to a 4-sec light CS. Seven to ten days later, the animals were submitted to testing sessions for assessing conditioned fear when they were placed for five shocks, and the duration of contextual freezing was recorded. The animals were then submitted to a fear-potentiated startle in response to a 4-sec light-CS, followed by white noise (100 dB, 50 ms). Control rats (sham) tested in the same context showed more freezing than did rats with pre- or post-training MRN lesions. Startle was clearly potentiated in the presence of light CS in the sham-lesioned animals. Whereas pretraining lesions reduced both freezing and fear-potentiated startle, the post-training lesions reduced only freezing to context, without changing the fear-potentiated startle. In a second experiment, neurotoxic lesions of the MRN with local injections of N-methyl-D-aspartate or the activation of 5-HT1A somatodendritic auto-receptors of the MRN by microinjections of the 5-HT1A receptor agonist 8-hydroxy- 2-(di-n-propylamino)tetralin (8-OH-DPAT) before the training sessions also reduced the amount of freezing and the fear-potentiated startle. Freezing is a prominent response of contextual fear conditioning, but does not seem to be crucial for the enhancement of the startle reflex by explicit aversive cues. As fear-potentiated startle may be produced in posttraining lesioned rats that are unable to freeze to fear contextual stimuli, dissociable systems seem to be recruited in each condition. Thus, contextual fear and fear-potentiated startle are conveyed by distinct 5-HT-mediated circuits of the MRN

New minimal weight representations for left-to-right window methods

Abstract. For an integer w ≥ 2, a radix 2 representation is called a width-w nonadjacent form (w-NAF, for short) if each nonzero digit is an odd integer with absolute value less than 2 w−1, and of any w consecutive digits, at most one is nonzero. In elliptic curve cryptography, the w-NAF window method is used to efficiently compute nP where n is an integer and P is an elliptic curve point. We introduce a new family of radix 2 representations which use the same digits as the w-NAF but have the advantage that they result in a window method which uses less memory. This memory savings results from the fact that these new representations can be deduced using a very simple left-to-right algorithm. Further, we show that like the w-NAF, these new representations have a minimal number of nonzero digits. 1 Window Methods An operation fundamental to elliptic curve cryptography is scalar multiplication; that is, computing nP for an integer, n, and an elliptic curve point, P. A number of different algorithms have been proposed to perform this operation efficiently (see Ch. 3 of [4] for a recent survey). A variety of these algorithms, known as window methods, use the approach described in Algorithm 1.1. For example, suppose D = {0, 1, 3, 5, 7}. Using this digit set, Algorithm 1.1 first computes and stores P, 3P, 5P and 7P. After a D-radix 2 representation of n is computed its digits are read from left to right by the “for ” loop and nP is computed using doubling and addition operations (and no subtractions). One way to compute a D-radix 2 representation of n is to slide a 3-digit window from right to left across the {0, 1}-radix 2 representation of n (see Section 4). Using negative digits takes advantage of the fact that subtracting an elliptic curve point can be done just as efficiently as adding it. Suppose now that D

Desafios das novas fronteiras agrícolas de produção de milho e sorgo no Brasil: desafios da região do MATOPIBA.

Compreendendo a região do Bioma Cerrado dos Estados do Maranhão, Piauí, Tocantins e Bahia, tornou-se nos últimos anos a denominada grande fronteira agrícola do Brasil. A topografia plana, os solos profundos e o clima favorável ao cultivo das principais culturas de grãos e fibras possibilitaram o crescimento vertiginoso da região, que até o final da década de 1980 se baseava fortemente na pecuária extensiva

Produção de soja no Estado do Tocantins: percepções inicias sobre o sistema produtivo.

O trabalho foi desenvolvido nos anos de 2011 e 2012, através da sistematização de informações dos principais municípios produtores de soja, segundo dados da CONAB e da Secretaria da Agricultura do Estado do Tocantins (SEAGRO).Editado por Adilson de Oliveira Junior, Regina Maria Villas Bôas de Campos Leite, Cesar de Castro

Cultivo do milho segunda safra e sorgo no Estado do Tocantins: situação atual e demandas de pesquisa.

O cultivo de milho no Estado do Tocantins vem crescendo significativamente. Somente na última safra, o aumento da área cultivada foi superior a 100% quando comparado ao ano anterior. Já o cultivo do sorgo é pouco significativo. Grande parte deste impulso foi decorrente da utilização pelos produtores de cultivares de soja de ciclo precoce, diminuindo os riscos para o milho cultivado na sequência. Mesmo com o aumento da área cultivada, a produtividade de milho ainda é relativamente baixa quando comparada a outras regiões já tradicionais no cultivo do milho segunda safra. Para entender o sistema de cultivo de milho e sorgo adotado e levantar as demandas de pesquisas e transferência de tecnologia no Tocantins, uma equipe de pesquisadores da Embrapa percorreu propriedades em diferentes localidades do Estado, a fim de levantar informações e conhecer as técnicas adotadas pelos produtores. Por meio de questionários foram levantadas informações quanto ao histórico de cultivo de milho e sorgo, os tratos culturais adotados e as demandas a serem atendidas pela Embrapa para impulsionar o cultivo destas culturas. Embora estejam muito bem consolidadas no Bioma Cerrado, quando implementadas no Tocantins, as altas temperaturas, baixa altitude e chuvas irregulares no verão são fatores preponderantes para que os produtores ainda tenham incertezas quanto ao cultivo, pois a janela entre a colheita da soja e a semeadura do milho ou sorgo é menor quando comparada às outras regiões. Além disso, pesquisas básicas envolvendo o cultivo do milho em rotação ainda são escassas e precisam ser intensificadas nesta região

"war to the knife" against thromboinflammation to protect endothelial function of COVID-19 patients

In this viewpoint, we summarize the relevance of thromboinflammation in COVID-19 and discuss potential mechanisms of endothelial injury as a key point for the development of lung and distant organ dysfunction, with a focus on direct viral infection and cytokine-mediated injury. Entanglement between inflammation and coagulation and resistance to heparin provide a rationale to consider other therapeutic approaches in order to preserve endothelial function and limit microthrombosis, especially in severe forms. These strategies include nebulized heparin, N-acetylcysteine, plasma exchange and/or fresh frozen plasma, plasma derivatives to increase the level of endogenous anticoagulants (tissue factor pathway inhibitor, activated protein C, thrombomodulin, antithrombin), dipyridamole, complement blockers, different types of stem cells, and extracellular vesicles. An integrated therapy including these drugs has the potential to improve outcomes in COVID-19