Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Maps as Topic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed1984

Spatial mapping of the chemical shift in NMR.

In many biological systems, nuclear magnetic resonance chemical-shift studies of 31P, 13C, and 1H can be of great value as a means of studying metabolic processes in vivo. This information is likely to be of great clinical value in the diagnosis of disease and in the study and monitoring of the effect of drug treatment. This paper discusses two new techniques, based on the echo-planar imaging (EPI) method. One is the echo-planar shift mapping (EPSM) technique and the other is a hybrid projection reconstruction-echo-planar (PREP) method. Both methods may be used to obtain complete chemical-shift spectra at each point of a specified grid in a chosen plane through the subject. A major attraction of the EPSM method is the very high speed at which this information is obtained. The major attraction of the PREP hybrid method is its simplicity. Both techniques have the advantage of speed and efficiency over both the point-by-point topical magnetic resonance (TMR) and 3D Fourier transform approaches. The new mapping techniques may also be used to measure magnetic field spatial inhomogeneities, caused by either the presence of magnetic material or simply nonalignment of the magnet.

Magnetic Resonance Spectroscopy↗
PubMed2001

Development of the visual system of the chick. II. Mechanisms of axonal guidance.

The quest to understand axonal guidance mechanisms requires exact and multidisciplinary analyses of axon navigation. This review is the second part of an attempt to synthesise experimental data with theoretical models of the development of the topographic connection of the chick retina with the tectum. The first part included classic ideas from developmental biology and recent achievements on the molecular level in understanding cytodifferentiation and histogenesis [J. Mey, S. Thanos, Development of the visual system of the chick. (I) Cell differentiation and histogenesis, Brain Res. Rev. 32 (2000) 343-379]. The present part deals with the question of how millions of fibres exit from the eye, traverse over several millimetres and spread over the optic tectum to assemble a topographic map, whose precision accounts for the sensory performance of the visual system. The following topics gained special attention in this review. (i) A remarkable conceptual continuity between classic embryology and recent molecular biology has revealed that positional cellular specification precedes and determines the formation of the retinotectal map. (ii) Graded expression of asymmetric genes, transcriptional factors and receptors for signal transduction during early development seem to play a crucial role in determining the spatial identity of neurons within surface areas of retina and optic tectum. (iii) The chemoaffinity hypothesis constitutes the conceptual framework for development of the retinotopic organisation of the primary visual pathway. Studies of repulsive factors in vitro developed the original hypothesis from a theoretical postulate of chemoattraction to an empirically supported concept based on chemorepulsion. (iv) The independent but synchronous development of retina and optic tectum in topo-chronologically corresponding patterns ensures that ingrowing retinal axons encounter receptive target tissue at appropriate locations, and at the time when connections are due to be formed. (v) The growth cones of the retino-fugal axons seem to be guided both by local cues on glial endfeet and within the extracellular matrix. On the molecular level, the ephrins and their receptors have emerged as the most likely candidates for the material substrate of a topographic projection along the anterior-posterior axis of the optic tectum. Yet, since a number of alternative molecules have been proposed for the same function, it remains the challenge for the near future to define the proportional contribution of each one of the individual mechanisms proposed by matching theoretical predictions with the experimental evidence.

Animals↗
PubMed1994

Evaluation of the gene encoding the gamma subunit of rod phosphodiesterase in retinitis pigmentosa.

PURPOSE: To determine whether defects in the gene encoding the gamma subunit of rod cyclic guanosine monophosphate-phosphodiesterase (PDE-g) cause some form of hereditary retinal degeneration or dysfunction. METHODS: A restriction map, an intron/exon map, and a partial sequence of the human genomic locus corresponding to this gene were ascertained. Based on this information, the single-strand conformation polymorphism technique (SSCP) was used to screen the coding region as well as most splice donor and acceptor sites for mutations in a total of 704 unrelated patients with retinitis pigmentosa, Usher's syndrome type I or type II, Leber's congenital amaurosis, the Laurence-Moon-Bardet-Biedl syndrome, or other hereditary retinal disease. RESULTS: Two frequent polymorphisms were found, as well as three rare sequence variations, none of which correlated with any phenotype examined. CONCLUSIONS: In view of these negative results and those of a previously published negative Southern blot analysis of an overlapping set of patients, it is unlikely that mutations in the PDE-g gene are a common cause of any of the forms of retinal degeneration or dysfunction so far examined.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1997

Identifying genetic markers to assess the presence of gene-environment interactions.

We analyzed a randomly chosen replicate with the goals of locating the closest markers to the genes involved in the discrete trait and utilizing these as surrogates for the genes in assessing the presence of gene-environment interactions. We screened the markers with an association test prior to using the transmission-disequilibrium test. We performed a segregation analysis, with regressive models and including the selected markers, to understand the underlying genetic mechanism and the role of the environmental factor. We were unsuccessful in locating the relevant markers due to the absence of linkage disequilibrium. Nevertheless, some insights were gained from the methods used.

Chromosome Mapping↗
PubMed1994

Some empirical properties of an all-relative-pairs linkage test.

Olson and Wijsman [Genet Epidemiol 10:87-102, 1993] recently proposed a single test of linkage which combines information from different types of relative pairs in a pedigree. Relative-pair-type-specific regression parameters that relate the squared pair trait difference to the estimated number of marker genes shared identical by descent between the pair are estimated using generalized estimating equation methodology, then combined to give a single linkage test statistic. Questions remain concerning the small sample and robustness properties of this test statistic; these questions are addressed in the present paper using simulation. The test is substantially anti-conservative for samples with fewer than about ten families and are approximately valid for samples larger than about 15 families. In addition, the test appears robust in the presence of trait genotype by environment interaction, trait family-specific errors, a second major trait locus, and trait dominance. Surprisingly, the sibpair test was more powerful than the all-relative-pairs test for dominant traits with high heritability. Finally, adjusting for the presence of a marker known to be linked to one trait locus only marginally improves the power for detecting a second trait locus.

Bias↗
PubMed2000

The reliability of the Aspergillus nidulans physical map.

Here we report an evaluation of the Aspergillus nidulans physical map (a cosmid contig map) emphasizing quantification and description of obvious mapping errors. Classification and appraisal of mapping errors should be helpful to researchers working on particular regions of the map. We estimate between 47 (4.1%) and 63 (5.4%) probe/clone-linking errors. The majority of identified false links (38) permit reciprocal exchanges among linking clones located on disconnected mapping regions. The order of adjacent clones or probes on the affected contigs remains unchanged. In addition we describe an Internet-accessible resource in which genetic and physical maps were integrated through a graphic interface. A simple search engine allows retrieval of cosmids from redundant clone lists and provides links to the minimal clone order. Integration of genetic and physical maps provides an additional level of accountability in which mapping discrepancies are visually located.

Aspergillus nidulans↗
PubMed1994

Present status of the ovine gene map (Ovis aries); comparison with the bovine map (Bos taurus).

The status of the sheep map to the end of June 1993 is presented. Mapping information is available for a total of 107 loci comprising 16 anonymous DNA segments. This is an increase of 66 loci since 1990. No loci have been mapped on 10 of the 26 autosomes. Comparison of the cattle (350 loci) and sheep maps confirms their close evolutionary and genetic relationship and will reduce the effort required for their gene mapping.

Animals↗
PubMed1991

A common disinfectant used in condom processing inhibits endonuclease digestion of sperm DNA.

DNA recovered from a condom found at a crime scene appeared undigestible with restriction enzymes, preventing characterization by Southern blot and polymorphic probe hybridization. Several chemical substances used in the processing and treatment of condoms were tested for inhibitory action of restriction enzymes. In particular dibenzalkonium chloride appeared to promote enzyme inhibition at very low concentrations. The effectiveness of treatments to restore cleavage of sample DNA in the presence of such contaminants is discussed.

Benzalkonium Compounds↗
PubMed2004

Development and implementation of a database system to manage a large-scale mouse ENU-mutagenesis program.

A mouse ENU-mutagenesis program at RIKEN GSC has been initiated to conduct a large-scale, genome-wide, early- and late-onset phenotypic screen of mutant mice. We screened about a hundred mice every week with a comprehensive set of phenotype assays including behavioral tests based on a modified SHIRPA protocol, blood tests (both clinical biochemical testing and hemogram), and measurement of locomotor activity in their home cages. To manage the entire program, we developed a client/server architecture database system and named it MUSDB (Mutagenesis Universal Support DataBase). It manages mouse husbandry, mating protocols, procedures for ENU injection and phenotypic screens, phenotype inheritance tests, preservation of sperm and organs, and other materials generated during the program. We have implemented MUSDB in quite a large-scale system that includes 150 client computers. It has, helped reduce typographical errors and provided simple and efficient operation via its front-end user interface. It significantly contributed to the communication within and between workgroups in the program and in the accumulation of various phenotypic and inheritance data.

Animals↗
PubMed1999

Genetic analysis of leaf form mutants from the Arabidopsis Information Service collection.

Although a vast inventory of morphological mutants of Arabidopsis thaliana is available, only some have been used for genetic studies of leaf development. Such is the case with the Arabidopsis Information Service (AIS) Form Mutants collection, assembled by A. R. Kranz and currently stored at the Nottingham Arabidopsis Stock Centre, which includes a large number of mutant lines, most of which have been little studied. With the aim of contributing to the genetic dissection of leaf ontogeny, we have subjected 57 mutant lines isolated by others to genetic analysis; 47 of which were from the AIS collection. These are characterized by vegetative leaves of abnormal shape or size, and were chosen as candidates for mutations in genes required for leaf morphogenesis. The mutant phenotypes studied were shown to be inherited as single recessive Mendelian traits and were classified into 10 phenotypic classes. These mutant strains were found to fall into 37 complementation groups, 7 of which corresponded to known genes. Results of the phenotypic analysis and data on the genetic interactions of these mutants are presented, and their possible developmental defects discussed.

Arabidopsis↗
PubMed2002

TAIR: a resource for integrated Arabidopsis data.

The Arabidopsis Information Resource (TAIR; http://arabidopsis.org) provides an integrated view of genomic data for Arabidopsis thaliana. The information is obtained from a battery of sources, including the Arabidopsis user community, the literature, and the major genome centers. Currently TAIR provides information about genes, markers, polymorphisms, maps, sequences, clones, DNA and seed stocks, gene families and proteins. In addition, users can find Arabidopsis publications and information about Arabidopsis researchers. Our emphasis is now on incorporating functional annotations of genes and gene products, genome-wide expression, and biochemical pathway data. Among the tools developed at TAIR, the most notable is the Sequence Viewer, which displays gene annotation, clones, transcripts, markers and polymorphisms on the Arabidopsis genome, and allows zooming in to the nucleotide level. A tool recently released is AraCyc, which is designed for visualization of biochemical pathways. We are also developing tools to extract information from the literature in a systematic way, and building controlled vocabularies to describe biological concepts in collaboration with other database groups. A significant new feature is the integration of the ABRC database functions and stock ordering system, which allows users to place orders for seed and DNA stocks directly from the TAIR site.

Arabidopsis↗
PubMed1995

Identification of five Rhodobacter capsulatus genes encoding the equivalent of ND subunits of the mitochondrial NADH-ubiquinone oxidoreductase.

We previously reported the sequencing of two genes (ndhA and ndhI) encoding two of the subunits of the type-I NADH-ubiquinone oxidoreductase from Rhodobacter capsulatus (Rc). The present paper deals with the cloning and characterization of a chromosomal fragment clustering five new Rc genes which encode subunits of this enzyme. This gene cluster is located immediately downstream from ndhA and ndhI, and also contains two unidentified open reading frames (urf2, urf3). The five genes, nuoJ, nuoK, nuoL, nuoM and nuoN, encode proteins related, respectively, to mitochondrial (mt) subunits ND6, ND4L, ND5, ND4 and ND2. The overall organization of the nuo genes identified in Rc shows similarity to that of the Paracoccus denitrificans (Pd) nqo gene cluster.

Amino Acid Sequence↗
PubMed2006

Biological parametric mapping: A statistical toolbox for multimodality brain image analysis.

In recent years, multiple brain MR imaging modalities have emerged; however, analysis methodologies have mainly remained modality-specific. In addition, when comparing across imaging modalities, most researchers have been forced to rely on simple region-of-interest type analyses, which do not allow the voxel-by-voxel comparisons necessary to answer more sophisticated neuroscience questions. To overcome these limitations, we developed a toolbox for multimodal image analysis called biological parametric mapping (BPM), based on a voxel-wise use of the general linear model. The BPM toolbox incorporates information obtained from other modalities as regressors in a voxel-wise analysis, thereby permitting investigation of more sophisticated hypotheses. The BPM toolbox has been developed in Matlab with a user-friendly interface for performing analyses, including voxel-wise multimodal correlation, ANCOVA, and multiple regression. It has a high degree of integration with the SPM (statistical parametric mapping) software relying on it for visualization and statistical inference. Furthermore, statistical inference for a correlation field, rather than a widely used T-field, has been implemented in the correlation analysis for more accurate results. An example with in vivo data is presented, demonstrating the potential of the BPM methodology as a tool for multimodal image analysis.

Brain↗