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At least 685 records · Page 38Linked to original sources
PubMed1997

Simulated phase evolution rewinding (SPHERE): a technique for reducing B0 inhomogeneity effects in MR images.

A novel method for reducing field inhomogeneity effects in magnetic resonance images is described in this paper. Observing that image degradation arises from B0 inhomogeneity-induced phase accrual during data acquisition, the present method numerically rewinds the accumulated phase in the k-space data based on an initial estimate of the image and a corresponding field map. The rewinding process generates a corrected k-space data set that is subsequently Fourier transformed to produce the final image. In this paper, a theoretical analysis of the method and applications of the technique to magnetic resonance imaging data are presented. The theoretical analysis of the method indicates that it is a general approach applicable to a variety of sequences. Results obtained by applying the method to experimental data acquired with single-shot echo-planar imaging, segmented echo-planar imaging with centric reordering, and spiral sequences demonstrate that it is robust in reducing image degradation induced by B0 inhomogeneity.

Brain↗
PubMed2005

Proteomic analysis of the proteins expressed by hydrogen peroxide treated cultured human dermal microvascular endothelial cells.

Reactive oxygen species (ROS) have been traditionally regarded as toxic by-products of aerobic metabolism. However, ROS also act as intracellular signaling molecules and can mediate phenotypes in vascular endothelial cells, which may be physiological or pathological in nature. To clarify the molecular mechanisms of ROS signaling, we examined hydrogen peroxide (H(2)O(2))-responsive proteins in cultured human dermal microvascular endothelial cells (HMVEC) using proteomic tools. Protein expression in HMVEC was studied after they had been exposed to low- and high-levels of H(2)O(2) for various times, and intracellular ROS production was examined by flow cytometer and UV spectrophotometer. Proteins obtained from dose- and time-dependent series were separated by two-dimensional gel electrophoresis and tentatively identified by matrix-assisted laser desorption-time of flight mass spectrometry, by matching the tryptic mass maps obtained with entries in the NCBI and Swiss-Prot protein sequence database. At least 163 proteins were changed by H(2)O(2), and 60 proteins were identified. Oxidative stress triggered dramatic change in the expression of proteins in primary microvessel endothelial cells, and their mapping to cellular process provided a view of the ubiquitous cellular changes elicited by H(2)O(2). These results could provide a framework for the understanding of the mechanisms of cellular redox homeostasis and H(2)O(2) metabolism in microendothelium environment in various biological processes as well as pathological conditions.

Amino Acid Sequence↗
PubMed2001

Two-dimensional assembly of pentameric rabbit C-reactive proteins on lipid monolayers.

The problem of pentamer packing on a two-dimensional plane is of concern not only in physics and mathematics but also in biology. The packing styles of pentamers may either be related to or reflect the physiological or biochemical properties of biological macromolecules. C-reactive protein (CRP), one of the classical members of the petraxin family, was recently two-dimensionally (2D) crystallized by us on lipid monolayers by specific adsorption (Wang, H. W., and Sui, S. F., 1999, J. Struct. Biol. 127, 283-286). Another type of the protein's 2D crystal under the same conditions was obtained in the present work. The new 2D crystal was studied using electron microscopy of negatively stained specimens followed by image processing. A projection map at 2.2-nm resolution was obtained. The previous 2D crystal (PI) and the current 2D crystal (PII) show different pentamer-packing styles. Both of them are closely related to the fivefold symmetry of the molecule itself. The coexistence and the spatial contiguity of the two types of pentamer assembly were observed in a visual field. The fivefold symmetrical macromolecule can form a pentiling pattern on a two-dimensional plane, which has never been reported in biological system before. The possible mechanism of the two-dimensional assembly of pentameric CRP on lipid monolayers is discussed.

Adsorption↗
PubMed1993

Propranolol unmasks class III like electrophysiological properties of norepinephrine.

Isolated perfused spontaneously beating rabbit hearts were treated with increasing concentrations of norepinephrine (0.01, 0.1, 0.5 mumol/l) either alone or in presence of propranolol (0.1 mumol/l). For analysis of the epicardial activation and repolarization process and epicardial mapping (256 unipolar leads) was performed. For each electrode the activation and repolarization time was determined. From these data the "breakthrough-points" (BTP) of epicardial activation were determined. At each electrode an activation vector (VEC) was calculated giving direction and velocity of the local excitation wave. The beat similarity of various heart beats (under NE) compared to control was evaluated by determination of the percentage of identical BTP and of similar VEC (deviation < or = 5 degrees). Moreover at each electrode the local activation recovery interval (ARI) and its standard deviation (of 256 leads, dispersion, DISP) were determined. Norepinephrine alone (0.01, 0.1, 0.5 mumol/l) led to an increase in left ventricular pressure, heart rate and DISP with concomitant frequency dependent reduction in ARI, and to changes in the epicardial activation pattern (reduction in BTP, VEC). We found that in the presence of propranolol (0.1 mumol/l) norepinephrine prolonged ARI and reduced ARI-dispersion. This effect was not due to changes in heart rate. The disturbing effects on the activation pattern were diminished. These effects could be prevented by pretreatment with 1 mumol/l prazosin. From these results we conclude, that norepinephrine prolongs the relative action potential duration via stimulation of alpha 1-adrenoceptor and enhances cellular coupling.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1981

mus(3)312D1, A mutagen sensitive mutant with profound effects on female meiosis in Drosophila melanogaster.

The third chromosome, mutagen sensitive mutant mus(3)312D1 impairs the meiotic process in females by increasing the frequency of first division nondisjunction and decreasing the frequency of meiotic crossing over. These genetic properties connote 312 to be defective in DNA replication and/or repair intimately associated with the crossing over exchange process. The mutant maps to the left arm of chromosome III between ru and h, and represents a new genetic site for a meiotic mutant.

Animals↗
PubMed1994

Biochemical mapping of neurofibrillary degeneration in a case of progressive supranuclear palsy: evidence for general cortical involvement.

A biochemical study was performed to quantify and map the neurodegenerating process in cortical and subcortical brain areas from a case of progressive supranuclear palsy (PSP). Our approach was based on a Western blot analysis of pathological Tau proteins, which are the basic components of neurofibrillary lesions. We found that: (i) the abnormal Tau proteins can be detected in all cortical areas, sometimes in larger amounts than in some subcortical areas; (ii) these abnormal Tau proteins consist of a doublet called Tau 64 and 69, except for in the entorhinal cortex where we detected, as for Alzheimer brains, the triplet of Tau proteins called Tau 55, 64 and 69; (iii) the amounts of abnormal Tau proteins were higher in some neocortical regions, especially in the frontal lobe, than in the hippocampal formation. Our results show that the neocortical pathology in PSP, as revealed by the presence of pathological proteins, is more extended than thought so far. Our biochemical approach appears to be more sensitive than the immunohistochemical one and can clearly differentiates between two types of neurofibrillary pathology, the Alzheimer type with a triplet of abnormal Tau proteins (Tau 55, 64 and 69) and the PSP type with a characteristic doublet (Tau 64 and 69).

Aged↗
PubMed1988

The application of molecular biology to the prenatal diagnosis of renal disease.

The rapid development of new techniques in molecular biology is leading to identification of the genes responsible for a wide variety of diseases. Several renal conditions are caused by gene defects and are amenable to this approach. The process of gene mapping is discussed and the current position regarding prenatal diagnosis and carrier testing for genetic renal disease is reviewed.

DNA↗
PubMed1998

Genetic linkage of progressive pseudorheumatoid dysplasia to a 3-cM interval of chromosome 6q22.

Progressive pseudorheumatoid dysplasia (PPD), MIM 208230, is an autosomal-recessive disorder, clinically characterized by spondyloepiphyseal dysplasia and progressive arthropathy. Linkage analysis of three families of different geographic and ethnic origin, including 11 affected individuals, showed strong evidence for localization of a gene for progressive pseudorheumatoid dysplasia to chromosome 6q with a maximum two-point lod score for D6S1647 of 8.34 at theta=0. Analysis of regions of homozygosity placed the gene in a 3-cM interval between D6S 1594 and D6S432. No significant shared haplotype was found for markers of the linked interval in the three families analyzed. Five genes encoding collagen and one encoding a specific procollagen-processing enzyme that map near this interval represent good candidates for the PPD gene.

Arthritis, Rheumatoid↗
PubMed2003

Implementing a MIRC query interface for a database driven teaching file.

This paper describes the authors' experience with integrating an existing database-driven teaching file with the RSNA (Radiological Society of North America) Medical Imaging Resource Center (MIRC). MIRC is the product of an RSNA-sponsored initiative to enable medical institutions to share their electronic medical content (images, text, and multimedia) by creating a distributed repository accessible from the Internet. An existing database-driven teaching file, developed by the authors and used extensively by the University of California San Francisco (UCSF) Department of Radiology since 1998, was retrofitted to include an interface for handling broadcast queries initiated by a MIRC query service. These queries take place through the exchange of XML documents via HTTP. After all the storage services have responded, the results are collated by the query service and presented to the user. The teaching file and MIRC interface were developed using the 4th Dimension Relational Database Management System (RDBMS). The integration process primarily involved mapping the "MIRCdocument" schema to the teaching file's schema, translating the actual MIRC query into the internal query language of the database and extending the access control mechanisms of the teaching file to allow public access. A working implementation of the interface required only 3 days of development time, with refinements taking place over several months. Interface development was greatly aided by MIRC's use of well-established Internet standards. This project has demonstrated the feasibility of implementing a MIRC interface on an existing teaching file server.

Computer-Assisted Instruction↗
PubMed1993

Dif, a dorsal-related gene that mediates an immune response in Drosophila.

There are striking parallels between the regulation of gene expression along the dorsoventral (DV) axis of Drosophila embryos and lymphoid-restricted expression in the mammalian immune system. Both depend on regulatory factors containing rel domains (dorsal and NF-kappa B) that are controlled at the level of nuclear transport. A novel Rel-containing gene in Drosophila, Dif (dorsal-related immunity factor), provides a potential link between these seemingly disparate processes. Although Dif maps close to dorsal, it does not appear to participate in DV patterning, but instead mediates an immune response in Drosophila larvae. Dif is normally localized in the cytoplasm of the larval fat body, but quickly accumulates in the nucleus upon bacterial infection or injury. Evidence is presented that once in the nucleus, Dif binds to kappa B-like sequence motifs present in promoter regions of immunity genes. These results suggest that mammalian and insect immunity share a common evolutionary origin.

Adipose Tissue↗
PubMed1989

Propositional knowledge and mere responding.

This commentary examines views recently offered by Furedy and Riley (1987) on the nature of classical conditioning. Their analysis identifies propositional learning as a component of conditioning separate from response acquisition. They reserve to this component the label cognitive on the epistemological grounds of falsifiability. We suggest that this analysis does not do justice to the concept of cognition in human conditioning. In particular it limits the scope of propositional knowledge to a formal role in the conditioning paradigm and ignores the recent development of propositional models in cognitive science. In seeking to integrate their propositional account with animal conditioning theory they usefully map their two processes on to the conditioned response/instrumental response distinction proposed by Gormezano and Kehoe (1975). However, their propositional contingency interpretation of the Rescorla and Wagner (1972) theory ignores the essentially associative mechanism used in the model to account for interevent relations.

Animals↗
PubMed1989

Nucleotide sequence of a regulatory region controlling alginate synthesis in Pseudomonas aeruginosa: characterization of the algR2 gene.

Alginate (Alg), an exopolysaccharide with strong gelling properties, is produced by Pseudomonas aeruginosa primarily during its infection of the cystic fibrosis (CF) lung. The alg genes are normally not expressed in other environments. The promoter for a critical Alg biosynthetic gene, algD, encoding GDP-mannose dehydrogenase, is activated only under conditions reminiscent of the CF lung (i.e., under high osmolarity), and at least two regulatory genes, algR1 and algR2, have been implicated in this activation process. The physical mapping of a 4.4-kb region harboring algR2 has been accomplished and the complete nucleotide sequence of this fragment, including that of algR2, is presented. The cloning and complementation experiments also demonstrate the presence, on this fragment, of regulatory gene(s) different from algR1 and algR2. The expression of the algR2 gene allows a high level of activation of the algD promoter in Escherichia coli, in the presence of algR1 in a high osmotic environment, suggesting that the AlgR2 and AlgR1 proteins act cooperatively to activate the algD promoter. Hyperexpression of the algR2 gene from the tac promoter also allows the conversion of nonmucoid cells of strain 8822, a spontaneous revertant of the mucoid CF isolate strain 8821, back to mucoidy, but not that of the clinical isolate, strain PAO1.

Alcohol Oxidoreductases↗
PubMed1988

Localization of the gene encoding human factor V to chromosome 1q21-25.

The gene encoding human coagulation Factor V (FV), one of the cofactors in the blood clotting process, has been mapped to chromosome 1 by both Southern hybridization to DNA from human-hamster somatic cell hybrids and in situ hybridization. The whole plasmid pUC3A containing a 1.5-kb cDNA sequence for FV was 32P-labeled for Southern analysis and 3H-labeled for in situ hybridization to metaphase chromosomes. The results localized the FV gene to the region of 1q21-25.

Animals↗
PubMed1992

Assignment of two human alpha-1,3-galactosyltransferase gene sequences (GGTA1 and GGTA1P) to chromosomes 9q33-q34 and 12q14-q15.

alpha-1,3-Galactosyltransferase is a terminal glycosyltransferase that is widely expressed in a variety of mammalian species, with the notable exception of man, apes, and Old World monkeys. Although transcripts for this enzyme are not detectable in humans, homologous sequences have been identified in human genomic DNA. These sequences correspond to a processed pseudogene that maps to chromosome 12 and the inactivated remnant of the once functional source gene that maps to chromosome 9. We have now established that the former sequence (GGTA1P) is localized to 12q14-q15 and the latter sequence (GGTA1) is localized to 9q33-q34 [corrected].

Chromosome Banding↗
PubMed2005

Neurobiology of decision making: a selective review from a neurocognitive and clinical perspective.

We present a temporal map of key processes that occur during decision making, which consists of three stages: 1) formation of preferences among options, 2) selection and execution of an action, and 3) experience or evaluation of an outcome. This framework can be used to integrate findings of traditional choice psychology, neuropsychology, brain lesion studies, and functional neuroimaging. Decision making is distributed across various brain centers, which are differentially active across these stages of decision making. This approach can be used to follow developmental trajectories of the different stages of decision making and to identify unique deficits associated with distinct psychiatric disorders.

Animals↗
PubMed2006

A neuronal identity code for the odorant receptor-specific and activity-dependent axon sorting.

In the mouse, olfactory sensory neurons (OSNs) expressing the same odorant receptor (OR) converge their axons to a specific set of glomeruli in the olfactory bulb. To study how OR-instructed axonal fasciculation is controlled, we searched for genes whose expression profiles are correlated with the expressed ORs. Using the transgenic mouse in which the majority of OSNs express a particular OR, we identified such genes coding for the homophilic adhesive molecules Kirrel2/Kirrel3 and repulsive molecules ephrin-A5/EphA5. In the CNGA2 knockout mouse, where the odor-evoked cation influx is disrupted, Kirrel2 and EphA5 were downregulated, while Kirrel3 and ephrin-A5 were upregulated, indicating that these genes are transcribed in an activity-dependent manner. Mosaic analysis demonstrated that gain of function of these genes generates duplicated glomeruli. We propose that a specific set of adhesive/repulsive molecules, whose expression levels are determined by OR molecules, regulate the axonal fasciculation of OSNs during the process of glomerular map formation.

Animals↗
PubMed2005

3-D quantification and visualization of vascular structures from confocal microscopic images using skeletonization and voxel-coding.

This paper presents an image processing approach for information extraction from three-dimensional (3-D) images of vasculature. It extracts quantitative information such as skeleton, length, diameter, and vessel-to-tissue ratio for different vessels as well as their branches. Furthermore, it generates 3-D visualization of vessels based on desired anatomical characteristics such as vessel diameter or 3-D connectivity. Steps of the proposed approach are: (1) pre-processing, (2) distance mappings, (3) branch labeling, (4) quantification, and (5) visualization. We have tested and evaluated the proposed algorithms using simulated images of multi-branch vessels and real confocal microscopic images of the vessels in rat brains. Experimental results illustrate performance of the methods and usefulness of the results for medical image analysis applications.

Animals↗
PubMed2005

From protein networks to biological systems.

A system-level understanding of any biological process requires a map of the relationships among the various molecules involved. Technologies to detect and predict protein interactions have begun to produce very large maps of protein interactions, some including most of an organism's proteins. These maps can be used to study how proteins work together to form molecular machines and regulatory pathways. They also provide a framework for constructing predictive models of how information and energy flow through biological networks. In many respects, protein interaction maps are an entrée into systems biology.

Animals↗