123 research outputs found
Association between aortic stiffness, carotid vessel wall thickness and stenosis severity in peripheral arterial occlusive disease: a comprehensive MRI study
Site-specific coupling between aortic pulse wave velocity, carotid vessel wall thickness and peripheral stenosis severity in peripheral arterial occlusive disease at 3T MRI
Fácies e sistema deposicional da formação barreiras na região da Barreira do Inferno, Litoral Oriental do Rio Grande do Norte
The Barreiras Formation is composed of sedimentary siliciclastic rocks that crop out at the continental scale along the Brazilian coastline from the State of Rio de Janeiro to the State of Amapá. In the State of Rio Grande do Norte, this formation is well exposed in cliffs along the coastline, best represented by the Barreira do Inferno cliff, which is 1 km long and 20 m high. Facies characterization and interpretation of depositional systems of the Barreiras Formation in this cliff were based on stratigraphic columnar sections and digital photomosaics. The Barreira do Inferno cliff comprises a large area affording continuous exposure of bed geometries, generally tabular in shape with secondary channels filled by mudstones, indicative of a fluvial context. Coarse facies characterize channel environments, whereas fine facies represent flood plains. This interpretation is supported by a lateral decrease in the ration of sandstone/conglomerates versus mudstones along the outcrop. In the central portion of the fluvial belt, sands and conglomerates comprise up to 80% of the deposits. Laterally, in the flood plain, up to 40% of the deposits are mudstones, fine sands, and very fine sands. This system is similar to braided fluvial systems, but the facies association (with pelites) and layer geometries (abandoned channels filled by mudstones) are characteristic of meandering rivers. The model that best explains these deposits is the"coarse-grained meandering river model".Ao longo da costa brasileira são encontrados depósitos sedimentares atribuídos à Formação Barreiras. No Rio Grande do Norte, estes depósitos ocorrem principalmente na linha de costa, tendo como melhor exemplo a Barreira do Inferno, um afloramento com mais de 1 km de extensão e até 20 m de espessura, situado no município de Parnamirim (RN). As associações de fácies descritas foram interpretadas como indicativas da deposição em um contexto fluvial, sendo as de granulação mais grossa relacionadas a depósitos de preenchimento de canais e as de textura mais fina, atribuídas a depósitos de planície de inundação. Estes depósitos mostram lateralmente uma clara diminuição da proporção entre arenitos e conglomerados versus lamitos. Na região que foi interpretada como a porção mais central de um suposto cinturão fluvial, a sucessão apresenta quase 80% de arenitos e conglomerados, ao passo que, lateralmente, a menos de 200 m, chega a ter 40% de rochas de granulação mais fina, o que sugere a proximidade da planície de inundação. Apesar de o sistema fluvial interpretado apresentar algumas características de um sistema entrelaçado, a abundância de fácies pelíticas, bem como a ocorrência freqüente de estratos com geometria de preenchimento de canais, permite estabelecer uma maior aproximação a um sistema fluvial meandrante. Considerando esses aspectos, o modelo"Meandrante de Granulometria Grossa" é o que melhor representa estes depósitos
Identification of novel peptides that stimulate human neutrophils
Neutrophils play a key role in innate immunity, and the identification of new stimuli that stimulate neutrophil activity is a very important issue. In this study, we identified three novel peptides by screening a synthetic hexapeptide combinatorial library. The identified peptides GMMWAI, MMHWAM, and MMHWFM caused an increase in intracellular Ca2+ in a concentration-dependent manner via phospholipase C activity in human neutrophils. The three peptides acted specifically on neutrophils and monocytes and not on other non-leukocytic cells. As a physiological characteristic of the peptides, we observed that the three peptides induced chemotactic migration of neutrophils as well as stimulated superoxide anion production. Studying receptor specificity, we observed that two of the peptides (GMMWAI and MMHWFM) acted on formyl peptide receptor (FPR)1 while the other peptide (MMHWAM) acted on FPR2. Since the three novel peptides were specific agonists for FPR1 or FPR2, they might be useful tools to study FPR1- or FPR2-mediated immune response and signaling
Selective complexation of divalent cations by a cyclic α,β-peptoid hexamer: a spectroscopic and computational study
We describe the qualitative and quantitative analysis of the complexation properties towards cations of a cyclic peptoid hexamer composed of alternating α- and β-peptoid monomers, which bear exclusively chiral (S)-phenylethyl side chains (spe) that have no noticeable chelating properties. The binding of a series of monovalent and divalent cations was assessed by 1H NMR, circular dichroism, fluorescence and molecular modelling. In contrast to previous studies on cations binding by 18-membered α-cyclopeptoid hexamers, the 21-membered cyclopeptoid cP1 did not complex monovalent cations (Na+, K+, Ag+) but showed selectivity for divalent cations (Ca2+, Ba2+, Sr2+ and Mg2+). Hexacoordinated C-3 symmetrical complexes were demonstrated for divalent cations with ionic radii around 1 Å (Ca2+ and Ba2+), while 5-coordination is preferred for divalent cations with larger (Ba2+) or smaller ionic radii (Mg2+)
Variability and directionality of inferior olive neuron dendrites revealed by detailed 3D characterization of an extensive morphological library
The inferior olive (IO) is an evolutionarily conserved brain stem structure and its output activity plays a major role in the
cerebellar computation necessary for controlling the temporal accuracy of motor behavior. The precise timing and synchronization of IO network activity has been attributed to the dendro-dendritic gap junctions mediating electrical coupling
within the IO nucleus. Thus, the dendritic morphology and spatial arrangement of IO neurons governs how synchronized
activity emerges in this nucleus. To date, IO neuron structural properties have been characterized in few studies and with
small numbers of neurons; these investigations have described IO neurons as belonging to two morphologically distinct
types, “curly” and “straight”. In this work we collect a large number of individual IO neuron morphologies visualized using
different labeling techniques and present a thorough examination of their morphological properties and spatial arrangement
within the olivary neuropil. Our results show that the extensive heterogeneity in IO neuron dendritic morphologies occupies
a continuous range between the classically described “curly” and “straight” types, and that this continuum is well represented
by a relatively simple measure of “straightness”. Furthermore, we find that IO neuron dendritic trees are often directionally
oriented. Combined with an examination of cell body density distributions and dendritic orientation of adjacent IO neurons,
our results suggest that the IO network may be organized into groups of densely coupled neurons interspersed with areas of
weaker coupling
Visual masking: past accomplishments, present status, future developments
Visual masking, throughout its history, has been used as an investigative tool in
exploring the temporal dynamics of visual perception, beginning with retinal
processes and ending in cortical processes concerned with the conscious
registration of stimuli. However, visual masking also has been a phenomenon
deemed worthy of study in its own right. Most of the recent uses of visual
masking have focused on the study of central processes, particularly those
involved in feature, object and scene representations, in attentional control
mechanisms, and in phenomenal awareness. In recent years our understanding of
the phenomenon and cortical mechanisms of visual masking also has benefited from
several brain imaging techniques and from a number of sophisticated and
neurophysiologically plausible neural network models. Key issues and problems
are discussed with the aim of guiding future empirical and theoretical
research
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