Normobaric hyperoximia increases hypoxia-induced cerebral injury: DTI study in rats.

Perinatal hypoxia affects normal neurological development and can lead to motor, behavioral and cognitive deficits. A common acute treatment for perinatal hypoxia is oxygen resuscitation (hyperoximia), a controversial treatment. Magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI), was performed in a P7 rat model of perinatal hypoxia to determine the effect of hyperoximia. These studies were performed on two groups of animals: 1) animals which were subjected to ischemia followed by hypoxia (HI), and 2) HI followed by hyperoximic treatment (HHI). Lesion volumes on high resolution MRI and DTI derived measures, fractional anisotropy (FA), mean diffusivity (MD), and axial and radial diffusivities (lambda(l) and lambda(t), respectively) were measured in vivo one day, one week, and three weeks after injury. Most significant differences in the MRI and DTI measures were found at three weeks after injury. Specifically, three weeks after HHI injury resulted in significantly larger hyperintense lesion volumes (95.26 +/- 50.42 mm(3)) compared to HI (22.25 +/- 17.62 mm(3)). The radial diffusivity lambda(t) of the genu of corpus callosum was significantly larger in HHI (681 +/- 330 x 10(-6) mm(2)/sec) than in HI (486 +/- 96 x 10(-6) mm(2)/sec). Over all, most significant differences in all the DTI metrics (FA, MD, lambda(t), lambda(l)) at all time points were found in the corpus callosum. Our results suggest that treatment of perinatal hypoxia with normobaric oxygen does not ameliorate, but exacerbates damage

Early postnatal development of rat brain: In vivo diffusion tensor imaging.

Perinatal hypoxia is a major cause of neurodevelopmental deficits. Neuronal migration patterns are particularly sensitive to perinatal hypoxia/ischemia and are associated with the clinical deficits. The rat model of hypoxia/ischemia at P7 mimics that of perinatal injury in humans. Before assessing the effects of postnatal injury on brain development, it is essential to determine the normal developmental trajectories of various brain structures in individual animals. In vivo longitudinal diffusion tensor imaging (DTI) was performed from postnatal day 0 (P0) to P56 on Wistar rats. The DTI metrics, mean diffusivity (MD), fractional anisotropy (FA), axial (lambdal) and radial (lambdat) diffusivities, were determined for four gray matter and eight white matter structures. The FA of the cortical plate and the body of corpus callosum decreased significantly during the first 3 weeks after birth. The decrease in the cortical plate's FA value was associated mainly with an increase in lambdat. The initial decrease in FA of corpus callosum was associated with a significant decrease in lambdal. The FA of corpus callosum increased during the rest of the observational period, which was mainly associated with a decrease in lambdat. The FA of gray matter structures, hippocampus, caudate putamen, and cortical mantle did not show significant changes between P0 and P56. In contrast, the majority of white matter structures showed significant changes between P0 and P56. These temporal changes in the DTI metrics were related to the neuronal and axonal pruning and myelination that are known to occur in the developing brain

Bioatividade de três espécies vegetais nativas da Floresta Atlântica brasileira frente ao microcrustáceo Artemia salina

Este trabalho teve por objetivo a investigação fitoquímica e propriedades antioxidantes de extratos das folhas de Trigynaea oblongifolia Schltdl (Annonaceae), Ottonia frutescens Trel (Piperaceae), e Bathysa australis (St Hill) Hooz (Rubiaceae), bem como avaliar, in vitro, a letalidade frente ao microcrustáceo Artemia salina Leach. Os extratos foram preparados por maceração em metanol 10% (p/v) por sete dias, à temperatura ambiente. A atividade antioxidante dos extratos foi determinada pela metodologia que utiliza o radical estável DPPH. A toxicidade dos extratos foi avaliada frente ao microcrustáceo A. salina. Os extratos de O. frutescens e B. australis apresentaram as seguintes classes de metabólitos secundários: Alcalóides, Antraquinonas, Cumarinas, Polifenóis (Taninos), Saponinas. Nos extratos de T. oblongifolia, além dos metabólitos citados anteriormente, foi detectada a presença de Flavonóides. A atividade antioxidante, observada em 30 minutos na concentração de 24 µg/mL de extrato, foi de: O. frutescens - 38,3%, T. oblongifolia - 32,3%, e B. australis - 32,1%. A Concentração Letal, CL50, dos extratos em A. salina foi de: O. frutescens - 149,75 ± 1,02 µg/mL, T. oblongifolia - 148,8 ± 1,74 µg/mL, e B. australis - 684 ± 9,04 µg/mL. Neste contexto, destacamos as espécies, nativas da Floresta Atlântica, O. frutescens e T. oblongifolia de grande potencial na bioprospecção de moléculas biologicamente ativas