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Fiber Morphology (fiber + morphology)
Selected AbstractsCortical radial glial cells in human fetuses: Depth-correlated transformation into astrocytesDEVELOPMENTAL NEUROBIOLOGY, Issue 3 2003Leonardo C. deAzevedo Abstract In the human brain, the transformation of radial glial cells (RGC) into astrocytes has been studied only rarely. In this work, we were interested in studying the morphologic aspects underlying this transformation during the fetal/perinatal period, particularly emphasizing the region-specific glial fiber anatomy in the medial cortex. We have used carbocyanine dyes (DiI/DiA) to identify the RGC transitional forms and glial fiber morphology. Immunocytochemical markers such as vimentin and glial fibrillary acidic protein (GFAP) were also employed to label the radial cells of glial lineage and to reveal the early pattern of astrocyte distribution. Neuronal markers such as neuronal-specific nuclear protein (NeuN) and microtubule-associated protein (MAP-2) were employed to discern whether or not these radial cells could, in fact, be neurons or neuronal precursors. The main findings concern the beginning of RGC transformation showing loss of the ventricular fixation in most cases, followed by transitional figures and the appearance of mature astrocytes. In addition, diverse fiber morphology related to depth within the cortical mantle was clearly demonstrated. We concluded that during the fetal/perinatal period the cerebral cortex is undergoing the final stages of radial neuronal migration, followed by involution of RGC ventricular processes and transformation into astrocytes. None of the transitional or other radial glia were positive for neuronal markers. Furthermore, the differential morphology of RGC fibers according to depth suggests that factors may act locally in the subplate and could have a role in the process of cortical RGC transformation and astrocyte localization. The early pattern of astrocyte distribution is bilaminar, sparing the cortical plate. Few astrocytes (GFAP+) in the upper band could be found with radial processes at anytime. This suggests that astrocytes in the marginal zone could be derived from different precursors than those that differentiate from RGCs during this period. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 288,298, 2003 [source] Microwave-Assisted Hydrothermal Synthesis of Structurally and Morphologically Controlled Sodium Niobates by Using Niobic Acid as a PrecursorEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2008Amauri J. Paula Abstract There are many advantages to using a microwave as a source of heat in hydrothermal reactions. Because it is a quick and homogeneous way to crystallize ceramic powders, it was used in this work for the production of antiferroelectric sodium niobate (NaNbO3) in a cubic-like form and its intermediary phase, disodium diniobate hydrate (Na2Nb2O6.H2O), with a fiber morphology. The syntheses were carried out by treating niobic acid (Nb2O5·nH2O) with NaOH. By changing the reaction time and the concentration of the reactants, particles with different structures and different morphologies could be obtained. The structural evolution of the products of this reaction was elucidated on the basis of the arrangement of the NbO6 octahedral units. Conclusive results were obtained with morphological and structural characterizations through XRD, TEM, MEV, and NMR and Raman spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synergetic behavior of low Tg polybutadiene polymers and polysiloxanes as components for glass fiber sizing in composite materialsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Katherine M. Danner Abstract The effect of low Tg polybutadiene (PBD) rubbery polymer as a part of polysiloxane/PBD E-glass fibers sizing on mechanical properties of a corresponding epoxy composite material has been evaluated by the punch shear test technique. The results show that the use of hydroxyl terminated PBD led to significant increase in interface shear strength, energy absorption, as well as dynamic modulus and Tg in a corresponding composite material. The sizing composition and fiber morphology were characterized by FTIR spectroscopy and AFM microscopy, respectively. Possible rational for such sizing composition/material property relationship is discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Melt spun thermoresponsive shape memory fibers based on polyurethanes: Effect of drawing and heat-setting on fiber morphology and propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Jasmeet Kaursoin Abstract Thermoresponsive shape memory (SMP) fibers were prepared by melt spinning from a polyester polyol-based polyurethane shape memory polymer (SMP) and were subjected to different postspinning operations to modify their structure. The effect of drawing and heat-setting operations on the shape memory behavior, mechanical properties, and structure of the fibers was studied. In contrast to the as-spun fibers, which were found to show low stress built up on straining to temporary shape and incomplete recovery to the permanent shape, the drawn and heat-set fibers showed significantly higher stresses and complete recovery. The fibers drawn at a DR of 3.0 and heat-set at 100°C gave stress values that were about 10 times higher than the as-spun fibers at the same strain and showed complete recovery on repeated cycling. This improvement was likely due to the transformation brought about in the morphology of the permanent shape of the SMP fibers from randomly oriented weakly linked regions of hard and soft segments to the well-segregated, oriented and strongly H-bonded regions of hard-segments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2172,2182, 2007 [source] Development of Electrospun Three-arm Star Poly(, -caprolactone) Meshes for Tissue Engineering ApplicationsMACROMOLECULAR BIOSCIENCE, Issue 8 2010Dario Puppi Abstract We have developed three-dimensional electrospun microfibrous meshes of a novel star branched three-arm poly(, -caprolactone) (*PCL) as potential scaffolds for tissue engineering applications. The processing conditions required to obtain uniform fibers were optimized by studying their influence on fiber morphology and size. Polymer molecular weight and solution feed rate influenced both the mesh microstructure and the tensile properties of the developed mats. Electrospun samples were also tested for their mechanical properties in wet conditions, showing higher yield strength and strain in comparison to that observed in dry conditions. Cell culture experiments employing MC3T3-E1 osteoblast like cells showed good cell viability adhesion and collagen production on the *PCL scaffolds. [source] A simple protocol for paraffin-embedded myelin sheath staining with osmium tetroxide for light microscope observationMICROSCOPY RESEARCH AND TECHNIQUE, Issue 7 2008Federica Di Scipio Abstract Experimental investigation of peripheral nerve fiber regeneration is attracting more and more attention among both basic and clinical researchers. Assessment of myelinated nerve fiber morphology is a pillar of peripheral nerve regeneration research. The gold standard for light microscopic imaging of myelinated nerve fibers is toluidine blue staining of resin-embedded semithin sections. However, many researchers are unaware that the dark staining of myelin sheaths typically produced by this procedure is due to osmium tetroxide postfixation and not due to toluidine blue. In this article, we describe a simple pre-embedding protocol for staining myelin sheaths in paraffin-embedded nerve specimens using osmium tetroxide. The method involves immersing the specimen in 2% osmium tetroxide for 2 h after paraformaldeyde fixation, followed by routine dehydration and paraffin embedding. Sections can then be observed directly under the microscope or counterstained using routine histological methods. Particularly good results were obtained with Masson's trichrome counterstain, which permits the imaging of connective structures in nerves that are not detectable in toluidine blue-stained resin sections. Finally, we describe a simple protocol for osmium etching of sections, which makes further immunohistochemical analysis possible on the same specimens. Taken together, our results suggest that the protocol described in this article is a valid alternative to the conventional resin embedding-based protocol: it is much cheaper, can be adopted by any histological laboratory, and allows immunohistochemical analysis to be conducted. Microsc. Res. Tech., 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||