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Folding Pattern (folding + pattern)
Selected AbstractsFolding of the tectal cortex by local remodeling of neural differentiationDEVELOPMENTAL DYNAMICS, Issue 3 2004Tatsuo Mima Abstract The folding pattern of the brain cortex is a precisely regulated process, but the mechanism involved during development remains unclear. A proposed theory predicts that the initiation of cortical folding depends, at least partly, on nonuniform distribution of neuronal differentiation and neurite growth. We tested this theory experimentally, by remodeling the normal pattern of neuronal cell differentiation within the embryonic optic tectum. Multiple foci of activated fibroblast growth factor signaling were created in the tectal cortex to locally change the neural differentiation and axonal growth patterns. At these foci, tectal cells remained undifferentiated and their radial and tangential migration was suppressed. These local changes in the neuronal cell differentiation resulted in a conversion of the tectal cortex from smoothly extended into precociously folded. The results provide in vivo experimental evidence that microscopic changes in the neuronal cell differentiation pattern can induce or remodel the folding pattern of the brain cortex. Developmental Dynamics 229:475,479, 2004. © 2004 Wiley-Liss, Inc. [source] Development of the dentition: four-dimensional visualization and open questions concerning the morphogenesis of tooth form and occlusionORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2003RJ Radlanski Structured Abstract Author, Radlanski RJ Objectives , The formation of the dental primordial should be visualized with special reference to characteristic differences for each single primordium. Until today, it has not been clear how traffic of the ameloblasts is controlled, how the folding pattern of the occlusal relief is generated or how the enamel production is terminated at the enamel surface. Design , Using computer-aided reconstructions from histological serial sections, the dental primordial were visualized and, using fractured enamel specimens, the traces of each single ameloblast were followed by means of scanning electron microscopy. In this way, the developmental movements of the inner enamel epithelium can be reconstructed. Results , Gathering morphological knowledge, three-dimensional polygon sets of shape data were input into a computer workstation and animated by means of the software Soft Image (Microsoft). Conclusions , The development of the human primary and permanent dentition was animated to simulate growth. [source] Characterization of an unusual folding pattern in a catalytically active guanine quadruplex structureBIOPOLYMERS, Issue 6 2006Pinaki R. Majhi Abstract In the presence of certain metal ions, DNA and RNA can form guanine quadruplex structures, which have been proposed to play a functional role in a variety of biological processes. An 18-nucleotide DNA oligomer, PS2.M, d(GTG3TAG3CG3T2G2), was previously reported to bind hemin and the resulting complex exhibited peroxidase activity. It was proposed that PS2.M folds unimolecularly into an antiparallel quadruplex with unusual, single-base loops and terminal guanines positioned in adjacent quartets. Here we describe structural and stability properties of PS2.M alone in different buffers and metal ions, using gel electrophoresis, circular dichroism (CD), ultraviolet (UV)-visible spectroscopies, and one-dimensional 1H nuclear magnetic resonance (NMR). Native gel behavior of PS2.M in the presence of either Na+ or Pb2+ suggests the formation of unimolecular structures but, in the presence of K+, both unimolecular and multistranded structures are observed. In the presence of Pb2+ ions, PS2.M forms a unimolecular quadruplex containing three guanine quartets. CD titrations reveal that binding of Pb2+ ions to PS2.M is stoichiometric, and a single lead cation suffices to fully fold PS2.M. The PS2.M,Na+ system also forms a similar unimolecular quadruplex. In the presence of K+, the PS2.M,K+ system forms mixed species. With increasing time and PS2.M concentration, the contribution of unimolecular species decreases while that of multimolecular species increases, and this behavior is independent of buffer media. These results suggest that the catalytically active form, studied in the presence of K+, may be a parallel, multistranded quadruplex rather than an antiparallel, unimolecular quadruplex. © 2006 Wiley Periodicals, Inc. Biopolymers 82:558,569, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Simplified intersubject averaging on the cortical surface using SUMAHUMAN BRAIN MAPPING, Issue 1 2006Brenna D. Argall Abstract Task and group comparisons in functional magnetic resonance imaging (fMRI) studies are often accomplished through the creation of intersubject average activation maps. Compared with traditional volume-based intersubject averages, averages made using computational models of the cortical surface have the potential to increase statistical power because they reduce intersubject variability in cortical folding patterns. We describe a two-step method for creating intersubject surface averages. In the first step cortical surface models are created for each subject and the locations of the anterior and posterior commissures (AC and PC) are aligned. In the second step each surface is standardized to contain the same number of nodes with identical indexing. An anatomical average from 28 subjects created using the AC,PC technique showed greater sulcal and gyral definition than the corresponding volume-based average. When applied to an fMRI dataset, the AC,PC method produced greater maximum, median, and mean t -statistics in the average activation map than did the volume average and gave a better approximation to the theoretical-ideal average calculated from individual subjects. The AC,PC method produced average activation maps equivalent to those produced with surface-averaging methods that use high-dimensional morphing. In comparison with morphing methods, the AC,PC technique does not require selection of a template brain and does not introduce deformations of sulcal and gyral patterns, allowing for group analysis within the original folded topology of each individual subject. The tools for performing AC,PC surface averaging are implemented and freely available in the SUMA software package. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] | ||||||||||