Active manual control of object views facilitates visual recognition.
(49/2878)
Active exploration of large-scale environments leads to better learning of spatial layout than does passive observation [1] [2] [3]. But active exploration might also help us to remember the appearance of individual objects in a scene. In fact, when we encounter new objects, we often manipulate them so that they can be seen from a variety of perspectives. We present here the first evidence that active control of the visual input in this way facilitates later recognition of objects. Observers who actively rotated novel, three-dimensional objects on a computer screen later showed more efficient visual recognition than observers who passively viewed the exact same sequence of images of these virtual objects. During active exploration, the observers focused mainly on the 'side' or 'front' views of the objects (see also [4] [5] [6]). The results demonstrate that how an object is represented for later recognition is influenced by whether or not one controls the presentation of visual input during learning. (+info)
Development of the human dispermic embryo.
(50/2878)
In a recent CD-ROM, we portrayed the microstructure of the pre-implantation human embryo (Sathananthan et al., 1999), which was a multimedia production with computer colour-enhanced electron micrographs of mainly monospermic embryos. This disk portrays light and electron micrographs of over 250 tripronuclear (3PN), dispermic, human embryos during pre-implantation development, viewed in thick and thin Araldite sections, as well as appearances of whole embryos flat embedded in Araldite blocks visualized with the light microscope. The 100 figures were computerized (IBM TIFF format), edited and labelled using Adobe Photoshop 5. Some of the figures were coloured on computer. The early development of 3PN embryos overtly resembles that of normal embryos but there are important differences in their microstructure which are portrayed in this presentation. This is a multicentric study involving researchers from four IVF centres. (+info)
Computer-assisted animation of atrial tachyarrhythmias recorded with a 64-electrode basket catheter.
(51/2878)
OBJECTIVES: The aim of this study was to assess the value of a new mapping technique based on computer-assisted animation of multielectrode basket catheter (BC) recordings in patients with atrial arrhythmias. BACKGROUND: The three-dimensional activation patterns of cardiac arrhythmias are not completely understood owing to limitations of conventional mapping techniques. METHODS: The study included 32 patients with atrial tachycardia (AT) and 38 patients with atrial flutter (AFL). A software program was developed to analyze the activation patterns based on 56 bipolar electrograms recorded with a 64-electrode BC deployed in the right atrium (RA). RESULTS: The total time needed for the animation of activation patterns of atrial arrhythmias was 5 +/- 0.8 min. In 22 patients with right AT, the animated maps revealed that arrhythmia was unifocal in 15 patients, multifocal in 2 patients, polymorphic in 4 patients and reentrant in 1 patient. In 10 patients with left AT, breakthroughs on the right side of the septum (2 in 8 patients and 1 in 2 patients) and a left-to-right activation of the RA were demonstrated. In patients with typical AF, the reentrant excitation was a broad activation front with preferential propagation around the tricuspid annulus. In patients with atypical AFL, the reentry circuit involved one of the venae cavae and a line of block located in the posterior wall. CONCLUSIONS: The computer-assisted animation of multiple electrograms recorded with a BC is a valuable mapping tool that delineates the three-dimensional activation patterns of various atrial arrhythmias. The technique is appropriate for complex, short-lived or unstable arrhythmias. (+info)
ProtoMap: automatic classification of protein sequences and hierarchy of protein families.
(52/2878)
The ProtoMap site offers an exhaustive classification of all proteins in the SWISS-PROT database, into groups of related proteins. The classification is based on analysis of all pairwise similarities among protein sequences. The analysis makes essential use of transitivity to identify homologies among proteins. Within each group of the classification, every two members are either directly or transitively related. However, transitivity is applied restrictively in order to prevent unrelated proteins from clustering together. The classification is done at different levels of confidence, and yields a hierarchical organization of all proteins. The resulting classification splits the protein space into well-defined groups of proteins, which are closely correlated with natural biological families and superfamilies. Many clusters contain protein sequences that are not classified by other databases. The hierarchical organization suggested by our analysis may help in detecting finer subfamilies in families of known proteins. In addition it brings forth interesting relationships between protein families, upon which local maps for the neighborhood of protein families can be sketched. The ProtoMap web server can be accessed at http://www.protomap.cs.huji.ac.il (+info)
ProDom and ProDom-CG: tools for protein domain analysis and whole genome comparisons.
(53/2878)
ProDom contains all protein domain families automatically generated from the SWISS-PROT and TrEMBL sequence databases (http://www. toulouse.inra.fr/prodom.html ). ProDom-CG results from a similar domain analysis as applied to completed genomes (http://www.toulouse. inra.fr/prodomCG.html ). Recent improvements to the ProDom database and its server include: scaling up to include sequences from TrEMBL, addition of Pfam-A entries to the set of expert validated families, assignment of stable accession numbers, consistency indicators for domain families, domain arrangements of sub-families and links to Pfam-A. (+info)
Keio Mutation Database (KMDB) for human disease gene mutations.
(54/2878)
A database of mutations in human disease-causing genes has been constructed and named as Keio Mutation Database (KMDB). This KMDB utilizes a database software called MutationView which was designed to compile various mutation data and to provide graphical presentation of data analysis. Currently, the KMDB accommodates mutation data of 38 different genes for 35 different diseases which are involved in eye, heart, ear and brain. These KMDBs are accessible through http://mutview.dmb.med.keio.ac.jp with advanced internet browsers. (+info)
Immunochemical evidence that cholesteryl ester transfer protein and bactericidal/permeability-increasing protein share a similar tertiary structure.
(55/2878)
Cholesteryl ester transfer protein (CETP) plays an important role in plasma lipoprotein metabolism through its ability to transfer cholesteryl ester, triglyceride, and phospholipid between lipoproteins. CETP is a member of a gene family that also includes bactericidal/permeability-increasing protein (BPI). The crystal structure of BPI shows it to be composed of two domains that share a similar structural fold that includes an apolar ligand-binding pocket. As structurally important residues are conserved between BPI and CETP, it is thought that CETP and BPI may have a similar overall conformation. We have previously proposed a model of CETP structure based on the binding characteristics of anti-CETP monoclonal antibodies (mAbs). We now present a refined epitope map of CETP that has been adapted to a structural model of CETP that uses the atomic coordinates of BPI. Four epitopes composed of CETP residues 215-219, 219-223, 223-227, and 444-450, respectively, are predicted to be situated on the external surface of the central beta-sheet and a fifth epitope (residues 225-258) on an extended linker that connects the two domains of the molecule. Three other epitopes, residues 317-331, 360-366, and 393-410, would form part of the putative carboxy-terminal beta-barrel. The ability of the corresponding mAbs to compete for binding to CETP is consistent with the proximity of the respective epitopes in the model. These results thus provide experimental evidence that is consistent with CETP and BPI having similar surface topologies. (+info)
Crystal structure of the ARF-GAP domain and ankyrin repeats of PYK2-associated protein beta.
(56/2878)
ADP ribosylation factors (ARFs), which are members of the Ras superfamily of GTP-binding proteins, are critical components of vesicular trafficking pathways in eukaryotes. Like Ras, ARFs are active in their GTP-bound form, and their duration of activity is controlled by GTPase-activating proteins (GAPs), which assist ARFs in hydrolyzing GTP to GDP. PAPbeta, a protein that binds to and is phosphorylated by the non-receptor tyrosine kinase PYK2, contains several modular signaling domains including a pleckstrin homology domain, an SH3 domain, ankyrin repeats and an ARF-GAP domain. Sequences of ARF-GAP domains show no recognizable similarity to those of other GAPs, and contain a characteristic Cys-X(2)-Cys-X(16-17)-Cys-X(2)-Cys motif. The crystal structure of the PAPbeta ARF-GAP domain and the C-terminal ankyrin repeats has been determined at 2.1 A resolution. The ARF-GAP domain comprises a central three-stranded beta-sheet flanked by five alpha-helices, with a Zn(2+) ion coordinated by the four cysteines of the cysteine-rich motif. Four ankyrin repeats are also present, the first two of which form an extensive interface with the ARF-GAP domain. An invariant arginine and several nearby hydrophobic residues are solvent exposed and are predicted to be the site of interaction with ARFs. Site-directed mutagenesis of these residues confirms their importance in ARF-GAP activity. (+info)