Henrique Amorim

Early Exercise Promotes Positive Hippocampal Plasticity and Improves Spatial Memory in the Adult Life of Rats

There is a great deal of evidence showing the capacity of physical exercise to enhance cognitive function, reduce anxiety and depression, and protect the brain against neurodegenerative disorders. Although the effects of exercise are well documented in the mature brain, the influence of exercise in the developing brain has been poorly explored. Therefore, we investigated the morphological and functional hippocampal changes in adult rats submitted to daily treadmill exercise during the adolescent period. Male Wistar rats aged 21 postnatal days old (P21) were divided into two groups: exercise and control. Animals in the exercise group were submitted to daily exercise on the treadmill between P21 and P60. Running time and speed gradually increased over this period, reaching a maximum of 18 m/min for 60 min. After the aerobic exercise program (P60), histological and behavioral (water maze) analyses were performed. The results show that early‐life exercise increased mossy fibers density and hippocampal expression of brain‐derived neurotrophic factor and its receptor tropomyosin‐related kinase B, improved spatial learning and memory, and enhanced capacity to evoke spatial memories in later stages (when measured at P96). It is important to point out that while physical exercise induces hippocampal plasticity, degenerative effects could appear in undue conditions of physical or psychological stress. In this regard, we also showed that the exercise protocol used here did not induce inflammatory response and degenerating neurons in the hippocampal formation of developing rats. Our findings demonstrate that physical exercise during postnatal development results in positive changes for the hippocampal formation, both in structure and function.

Distinctive hippocampal CA2 subfield of the Amazon rodent Proechimys.

Previous data of our laboratory have shown that the Amazonian rodents Proechimys do not present spontaneous seizures in different models of epilepsy, suggesting endogenous inhibitory mechanisms. Here, we describe a remarkably different Proechimys cytoarchitecture organization of the hippocampal cornu Ammonis 2 (CA2) subfield. We identified a very distinctive Proechimys CA2 sector exhibiting disorganized cell presentation of the pyramidal layer and atypical dispersion of the pyramidal-like cells to the stratum oriens, strongly contrasting to the densely packed CA2 cells in the Wistar rats. Studies showed that CA2 is the only cornu ammonis (CA) subfield resistant to the extensive pyramidal neural loss in mesial temporal lobe epilepsy (MTLE) associated to hippocampal sclerosis. Thus, in order to investigate this region, we used Nissl and Timm staining, stereological approach to count neurons and immunohistochemistry to neuronal nuclei (NeuN), parvalbumin (PV), calbindin (CB) and calretinin (CR). We did not notice statistically significant differences in the total number of neurons of the CA2 region between Proechimys and Wistar. However, Proechimys rodents presented higher CA2 volume than Wistar rats. Furthermore, no significant difference in the optical density of parvalbumin-immunoreactivity was found between subject groups. On the other hand, Proechimys presented significant higher density of calbindin and calretinin-immunoreactivity when compared to Wistar rats. In this context, this unique CA2 subfield seen in Proechimys opens up a new set of possibilities to explore the contribution of CA2 neurons in normal and pathological brain circuits.

Alcohol Abuse Promotes Changes in Non-Synaptic Epileptiform Activity with Concomitant Expression Changes in Cotransporters and Glial Cells

Non-synaptic mechanisms are being considered the common factor of brain damage in status epilepticus and alcohol intoxication. The present work reports the influence of the chronic use of ethanol on epileptic processes sustained by non-synaptic mechanisms. Adult male Wistar rats administered with ethanol (1, 2 e 3 g/kg/d) during 28 days were compared with Control. Non-synaptic epileptiform activities (NEAs) were induced by means of the zero-calcium and high-potassium model using hippocampal slices. The observed involvement of the dentate gyrus (DG) on the neurodegeneration promoted by ethanol motivated the monitoring of the electrophysiological activity in this region. The DG regions were analyzed for the presence of NKCC1, KCC2, GFAP and CD11b immunoreactivity and cell density. The treated groups showed extracellular potential measured at the granular layer with increased DC shift and population spikes (PS), which was remarkable for the group E1. The latencies to the NEAs onset were more prominent also for the treated groups, being correlated with the neuronal loss. In line with these findings were the predispositions of the treated slices for neuronal edema after NEAs induction, suggesting that restrict inter-cell space counteracts the neuronal loss and subsists the hyper-synchronism. The significant increase of the expressions of NKCC1 and CD11b for the treated groups confirms the existence of conditions favorable to the observed edematous necrosis. The data suggest that the ethanol consumption promotes changes on the non-synaptic mechanisms modulating the NEAs. For the lower ethanol dosage the neurophysiological changes were more effective suggesting to be due to the less intense neurodegenertation.

Malnutrition in Infancy as a Susceptibility Factor for Temporal Lobe Epilepsy in Adulthood Induced by the Pilocarpine Experimental Model

Malnutrition during the earliest stages of life may result in innumerable brain problems. Moreover, this condition could increase the chances of developing neurological diseases, such as epilepsy. We analyzed the effects of early-life malnutrition on susceptibility to epileptic seizures induced by the pilocarpine model of epilepsy. Wistar rat pups were kept on a starvation regimen from day 1 to day 21 after birth. At day 60, 16 animals (8 = well-nourished; 8 = malnourished) were exposed to the pilocarpine experimental model of epilepsy. Age-matched well-nourished (n = 8) and malnourished (n = 8) rats were used as controls. Animals were video-monitored over 9 weeks. The following behavioral parameters were evaluated: first seizure threshold (acute period of the pilocarpine model); status epilepticus (SE) latency; first spontaneous seizure latency (silent period), and spontaneous seizure frequency during the chronic phase. The cell and mossy fiber sprouting (MFS) density were evaluated in the hippocampal formation. Our results showed that the malnourished animals required a lower pilocarpine dose in order to develop SE (200 mg/kg), lower latency to reach SE, less time for the first spontaneous seizure and higher seizure frequency, when compared to well-nourished pilocarpine rats. Histopathological findings revealed a significant cell density reduction in the CA1 region and intense MFS among the malnourished animals. Our data indicate that early malnutrition greatly influences susceptibility to seizures and behavioral manifestations in adult life. These findings suggest that malnutrition in infancy reduces the threshold for epilepsy and promotes alterations in the brain that persist into adult life.

Brain Electrical Activity After Acute Hippocampal Stimulation in Awake Rats

Objective:  We describe the electrocorticographic findings after hippocampal stimulation in normal awake rats.

Valor-trabalho e trabalho imaterial nas ciências sociais contemporâneas

A teoria do valor foi ate hoje lida com base em tres recortes analiticos amplos. Um recorte anterior a Marx, o de Marx e dos marxistas e o dos neoclassicos. O anterior a Marx tem como elementos centrais a ideia de que o valor e uma categoria central das sociedades de economia mercantil ou de troca, que nas sociedades capitalistas ganharia sua expressao mais avancada no processo de criacao da riqueza. Em Marx, o valor e considerado como a categoria economica mercantil fundamental. No entanto, esse tipo de economia e apreciado como transitorio, isto e, ha uma determinacao historica da economia mercantil que se vincula diretamente a existencia do valor. Ja para os neoclassicos, o valor e uma categoria da atividade economica em geral, sendo, portanto, a atividade economica capitalista uma forma particular dessa atividade economica geral. Sua preocupacao central esta, nesses termos, voltada para o equilibrio geral apoiado na analise marginalista do valor. No entanto, o debate em torno do valor hoje parece ir alem dessas classificacoes. Sua recuperacao se sintetiza na seguinte pergunta: as teses sobre as novas tecnologias da informacao e sobre o trabalho imaterial convergiriam para uma nova forma da teoria do valor-trabalho ou para a superacao dessa teoria? O objetivo central deste artigo e caracterizar introdutoriamente as principais teses do debate na teoria social, que incorporam, atualizam ou negam a teoria do valor-trabalho no processo de analise do trabalho imaterial.

O trabalho imaterial em discussão: teoria e política

Nas ultimas duas decadas, o trabalhoimaterial foi objeto de muitas analises nas CienciasSociais. Grosso modo, as consideracoes sobre o temaforam influenciadas por duas grandes transforma-coes nas sociedades contemporâneas. De um lado,o fim da bipolaridade politico-economica entre Es-tados Unidos e Uniao Sovietica e, de outro, as trans-formacoes, tais como a robotica, a microeletronica eas novas formas de gestao empresarial da mais re-cente reestruturacao produtiva caracterizaram ospilares empiricos de redimensionamento das ana-lises sobre a producao e o trabalho.A diminuicao de postos de trabalho nasindustrias de paises de economia avancada e, aomesmo tempo, o aumento das ocupacoes profissi-onais que passam a exigir maior intervencao inte-lectual pareciam indicar a tendencia de eliminacaodo trabalho imediato e a predominância de traba-lhos mediatos, isto e, atividades predominantemen-te intelectualizadas ou imateriais.Em fins da decada de 1970, um conjuntode teses procurou explicar como a nova constitui-cao da producao nao mais poderia ser analisadapelo marxismo, ja que a sociabilidade nao era maisdeterminada pelo trabalho. Nos anos 1980, essaperspectiva se radicaliza com a expansao do setorde servicos e do trabalho imaterial e o corpo teori-co da analise marxiana e questionado.O trabalho imaterial foi, a partir de entao,um objeto de estudos recorrente no debate sociolo-gico, politico e economico contemporâneo, na me-dida em que trazia consigo novas formas de explo-racao e de luta politica ainda nao mapeadas e naoproblematizadas teoricamente. Nesse contexto, pelomenos duas grandes perspectivas analiticas, commuitas nuancas internas, se digladiaram. De umlado, vislumbrou-se o esgotamento do capitalismocomo uma sociedade organizada em torno do traba-lho e da industria e, por consequencia, das utopiasrevolucionarias. De outro, houve uma retomada deMarx para qualificar as transformacoes produtivase gerenciais como expressao de uma nova fase doprocesso de valorizacao e acumul acao capitalista.

Retraction Statement. Paper by Michael W. Miller and Huaiyu Hu [Developmental Neuroscience 2009;31:50–57]

E-Mail karger@karger.ch www.karger.com On August 6, 2010, the Editor-in-Chief of Developmental Neuroscience , Steven W. Levison, was contacted by the legal counsel for SUNY Upstate Medical University and informed that an investigative committee at SUNY Upstate had determined that Dr. Michael Miller was guilty of multiple counts of research misconduct, and they requested that Developmental Neuroscience retract the 2009 article authored by Drs. Miller and Huaiyu Hu. The committee did not find Dr. Hu at fault for any scientific misconduct. After independently reviewing the reports of the investigative committee and the rebuttals provided by Dr. Miller, the Editor-in-Chief and the publisher concurred that there were errors in reporting sample sizes and in mathematical calculations. However, at that time it was our view that an erratum was more appropriate than a retraction of the article. Despite the flaws in the analyses of the data, it was our determination that those flaws could be corrected in a published erratum to produce a final product that would be more useful to the scientific community than a complete retraction of the work. On December 10, 2010, we requested that Dr. Miller provide a corrected figure with an explanation of the mistakes that had been previously published. However, that erratum was never published as we were provided with additional information and testimonies that convinced us that the collected data may also be unreliable. Accordingly, on October 18, 2011, we requested that a letter of retraction be provided that was co-authored and co-signed by both authors. It was our view that for an action as severe as an article retraction, both authors needed to sign the retraction letter. However, Drs. Miller and Hu were unable to agree upon a letter that could be jointly signed. Therefore, at the request of the President of SUNY Upstate, with this statement we formally retract the article by Drs. Miller and Hu, Developmental Neuroscience 2009;31:50–57. We have sent correspondence to both authors, to the President of SUNY Upstate and to Dr. Steven Goodman, Vice President for Research at SUNY Upstate, to inform them in advance that this action is being taken by the journal.