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At least 649 records · Page 36Linked to original sources

PubMed2002

Experience in the application of Java Technologies in telemedicine.

Java language has been demonstrated to be an effective tool in supporting medical image viewing in Russia. This evaluation was completed by obtaining a maximum of 20 images, depending on the client's computer workstation from one patient using a commercially available computer tomography (CT) scanner. The images were compared against standard CT images that were viewed at the site of capture. There was no appreciable difference. The client side is a lightweight component that provides an intuitive interface for end users. Each image is loaded in its own thread and the user can begin work after the first image has been loaded. This feature is especially useful on slow connection speed, 9.6 Kbps for example. The server side, which is implemented by the Java Servlet Engine works more effective than common gateway interface (CGI) programs do. Advantages of the Java Technology place this program on the next level of application development. This paper presents a unique application of Java in telemedicine.

Journal Article↗

PubMed2006

Unified analysis and mathematical representation of film-thickness behavior of film-substrate systems.

The ellipsometric function p of a film-substrate system is studied as the film thickness d is kept constant and the angle of incidence phi is changed. The generated constant-thickness contours (CTCs) are characterized by an introduced mathematical behavior indicator that represents a group of CTCs. The behavior of each group is developed and studied in the four planes phi-d, X, Z, and p, where X is the film-thickness exponential function and Z is a previously introduced intermediate plane. In the phi-d plane the film-thickness domain is identified and divided into a sequence of disconnected thickness subdomains (DTSs), depending on only N0 and N1, and their number depending on the range in which N0/N1 lies. The behavior of the CTCs in the successive planes X, Z, and p is then studied in each DTS, and the CTC's space is divided into disconnected subfamilies according to the behavior indicator. Equivalence classes that reduce the infinite number of subfamilies into a finite number are then introduced. The transformation from each plane to the next is studied with the origin of the Z plane mapped onto the point at infinity of the p plane, forming a singularity. A multiple-film-thickness inequality is derived to determine the unique solution of the film thickness. The type of reflection being internal or external at both ambient-film and film-substrate interfaces affects the analysis and is also considered. To conclude we introduce the design of polarization-preserving devices and a novel oscillating single-element ellipsometer to fully characterize zero film-substrate systems as examples of applying the knowledge developed here.

Journal Article↗

PubMed2006

TSAO derivatives, inhibitors of HIV-1 reverse transcriptase dimerization: recent progress.

There is an urgent need for the development of new and safer drugs for the treatment of HIV (human immunodeficiency virus) infection, active against the currently resistant viral strains or directed to novel targets in the viral replicative cycle that may be useful for multiple drug combination. TSAO derivatives are a peculiar group of highly functionalized nucleosides that belong to the so-called nonnucleoside RT inhibitors (NNRTIs). HIV-1 reverse transcriptase (RT) is a key enzyme that plays an essential and multifunctional role in the life cycle of the virus and thus represents a key target for antiviral chemotherapeutic intervention. The dimeric form of the enzyme is absolutely required for all enzymatic activities. Thus, the process of dimerization and subsequent maturation into the p66/p51 heterodimer is essential for a fully functional RT and constitutes a target for therapeutic intervention, however to date such agents have not been developed. TSAO molecules are a peculiar group of non-nucleoside RT inhibitors that exert a unique selectivity for HIV-1 through a specific interaction with the p51 subunit of HIV-1 RT. They interact at the p66/p51 heterodimer interface of the enzyme. They were the first small non peptidic molecules shown to interfere with the dimerization process of the enzyme. This review covers the recent work within this family of compounds aimed at enhancing their interaction with the dimer interface of HIV-1 RT.

Binding Sites↗

PubMedDate not supplied

Microencapsulation with carrageenan-locust bean gum mixture in a multiphase emulsification technique for sustained drug release.

A multiphase emulsification technique was modified in this process of micro-encapsulating gentamicin sulphate, thus avoiding the necessity for a surfactant in preparing the secondary emulsion for a W/O/W emulsion. Various proportions of iota-carrageenan (i-C) and locus bean gum (LBG) were investigated for the W/O/W emulsion after forming the primary W/O emulsion with sorbitan trioleate, Span 85. Upon removal of the oil phase (chloroform) from the W/O/W emulsion by heating (60-65 degrees C), microcapsules or 'W/W' particles containing drug dissolved in sodium hyaluronate were spontaneously formed. These were dispersed in a solution of a mixture of 5-10 per cent w/v polyvinyl alcohol, PVA (average MW 50,000-106,000; 98 per cent hydrolysed) and 3 per cent v/v polyethylene glycol 200 (PEG 200), and dried to form the hydrogel film casts. Our in vitro experiments in isotonic phosphate buffer solution (pH 7.4) at 37 degrees C, showed that the release of gentamicin sulphate was dependent on concentration of LBG, and concentration or molecular weight of PVA. With the exception of PVA hydrogel matrix preparations containing 20 per cent w/v LBG, all other formulations showed a significant initial 'burst' release of drug within 6 h. The drug-containing microcapsules in the PVA hydrogel film with 20 per cent w/v LBG, exhibited an almost zero-order release of drug up to 140 h. It is postulated that an effective barrier or high-density membrane enveloping the microcapsules was formed between i-C and LBG because of their unique molecular configurations. This phenomenon, together with the possible adsorption of i-C molecules at the transient oil and outer aqueous phase interface, presumably eliminated the need for a permanent oil phase and/or an O/W surfactant normally required for preparing W/O/W emulsions.

Biocompatible Materials↗

PubMed1992

Comparison between B-scan ultrasound and MRI in the detection of diabetic vitreous hemorrhage.

The efficacy of proton magnetic resonance imaging (MRI) was evaluated and compared with that of B-scan ultrasound in the detection and differentiation of diabetic vitreous hemorrhage. Although conventional spin-echo MRI could not locate vitreous hemorrhages, gradient-recalled-echo (GRE) MRI readily did so. The aberrant signals appeared to originate from the interfacing between hemorrhages and the vitreous, and possibly also from the paramagnetic effect of the ferrous ion. The information provided by boundary/susceptibility detection, unique to the GRE sequence, is useful in delineating the extent of vitreous hemorrhage and hemolysis. However, for the diagnosis and follow up of diabetic vitreous hemorrhages, MRI appears no more informative than B-scan ultrasonography.

Aged↗

PubMed1992

Antecedents and outcomes of work-family conflict: testing a model of the work-family interface.

A comprehensive model of the work-family interface was developed and tested. The proposed model extended prior research by explicitly distinguishing between work interfering with family and family interfering with work. This distinction allowed testing of hypotheses concerning the unique antecedents and outcomes of both forms of work-family conflict and a reciprocal relationship between them. The influence of gender, race, and job type on the generalizability of the model was also examined. Data were obtained through household interviews with a random sample of 631 individuals. The model was tested with structural equation modeling techniques. Results were strongly supportive. In addition, although the model was invariant across gender and race, there were differences across blue- and white-collar workers. Implications for future research on the work-family interface are discussed.

Adaptation, Psychological↗

PubMed2001

Dynamic features of the subunit interface of Cu,Zn superoxide dismutase as probed by tryptophan phosphorescence.

As part of the more general inquiry on the molecular basis of specific recognition between macromolecules, the subunit-subunit interface structure of dimeric superoxide dismutase from Photobacterium leiognathi has been probed selectively by the phosphorescence emission of Trp-73, located at the subunit contact region. Copper at the catalytic site was found to quench completely the delayed emission and therefore all studies were conducted with the copper-free or Cd(2+)-substituted protein. The spectrum at 140 K is diagnostic for an indole ring located in a hydrophobic environment whereas a degree of spectral broadening indicates that the local structure is not unique. Environmental heterogeneity is confirmed by the nonuniform phosphorescence decay in buffer, at 274 K, with lifetime components of 44 and 20 ms of practically equal amplitude. Information on the flexibility of the interface region was gathered from both the intrinsic lifetime and the accessibility of acrylamide to the site of the chromophore. The magnitude of the intrinsic lifetime, its temperature dependence, and the accessibility to solutes like acrylamide describe a tight dimeric structure in which hydrophobic interactions seem to play an important role. In particular the acrylamide bimolecular rate constant is 1.4 x 10(4) M(-1) s(-1) and indicates highly hindered diffusion of the solute through the interface region. Cd(2+) complexation to the apoprotein caused no detectable changes in protein conformation although the metal was able to influence the flexibility of the Trp-73 environment, indicating the occurrence of a long-range communication between the intersubunit surface and the active site, which is more than 16 A away.

Copper↗

PubMed1999

The laboratory-clinical interface: point-of-care testing.

POC testing provides an opportunity for clinicians and laboratorians to work together to consider how best to serve the patients within an individual institution. Each health system has unique characteristics relative to patient population, as well as a unique laboratory structure. If physicians, nurses, laboratorians, and pathologists work collaboratively, the best interests of patients will be served. In some institutions that cater to specific patient groups, POC testing may offer clear and distinct advantages. In other institutions with sophisticated transport systems and established rapid response capabilities, the quality resulting from central laboratory testing may outweigh any advantages of bedside testing. Clearly, attention to regulatory issues, QC issues, the importance of proper documentation, proficiency testing, performance enhancement, and cost-effectiveness is requisite. As the technology for diagnostic testing advances through more microcomputerization, microchemistry, and enhanced test menus, the concept of POC testing will need perpetual revisiting. We hope that the information provided here will aid clinicians, laboratorians, and administrators in their quest to best serve their patients.

Costs and Cost Analysis↗

PubMed2005

X-ray emission spectroscopy with a laser-heated diamond anvil cell: a new experimental probe of the spin state of iron in the Earth's interior.

Synchrotron-based X-ray emission spectroscopy (XES) is well suited to probing the local electronic structure of 3d transition metals such as Fe and Mn in their host phases. The laser-heated diamond anvil cell technique is uniquely capable of generating ultra-high static pressures and temperatures in excess of 100 GPa and 3000 K. Here X-ray emission spectroscopy and X-ray diffraction have been interfaced with the laser-heated diamond cell for studying the electronic spin states of iron in magnesiowüstite-(Mg0.75,Fe0.25)O and its crystal structure under lower-mantle conditions. X-ray emission spectra of the ferrous iron in a single crystal of magnesiowüstite-(Mg0.75,Fe0.25)O indicate that a high-spin to low-spin transition of ferrous iron occurs at 54 to 67 GPa and 300 K and the ferrous iron remains in the high-spin state up to 47 GPa and 1300 K. This pilot study points to the unique capability of the synchrotron-based XES and X-ray diffraction techniques for addressing the issue of electronic spin transition or crossover in 3d transition metals and compounds under extreme high-P-T conditions.

Journal Article↗

PubMed2005

MICheck: a web tool for fast checking of syntactic annotations of bacterial genomes.

The annotation of newly sequenced bacterial genomes begins with running several automatic analysis methods, with major emphasis on the identification of protein-coding genes. DNA sequences are heterogeneous in local nucleotide composition and this leads sometimes to sequences being annotated as authentic genes when they are not protein-coding genes or are true but uncharacterized protein-coding genes. This first annotation step is generally followed by an expert manual annotation of the predicted genes. The genomic data (sequence and annotations) organized in an appropriate databank file format is subsequently submitted to an entry point of the International Nucleotide Sequence Database. These procedures are inevitably subject to mistakes, and this can lead to unintentional syntactic annotation errors being stored in public databanks. Here, we present a new web program, MICheck (MIcrobial genome Checker), that enables rapid verification of sets of annotated genes and frameshifts in previously published bacterial genomes. The web interface allows one easily to investigate the MICheck results, i.e. inaccurate or missed gene annotations: a graphical representation is drawn, in which the genomic context of a unique coding DNA sequence annotation or a predicted frameshift is given, using information on the coding potential (curves) and annotation of the neighbouring genes. We illustrate some capabilities of the MICheck site through the analysis of 20 bacterial genomes, 9 of which were selected for their 'Reviewed' status in the National Center for Biotechnology Information (NCBI) Reference Sequence Project (RefSeq). In the context of the numerous re-annotation projects for microbial genomes, this tool can be seen as a preliminary step before the functional re-annotation step to check quickly for missing or wrongly annotated genes. The MICheck website is accessible at the following address: http://www.genoscope.cns.fr/agc/tools/micheck.

Computer Graphics↗

PubMedDate not supplied

IVE (Image Visualization Environment): a software platform for all three-dimensional microscopy applications.

IVE (Image Visualization Environment) is a software platform designed from the outset to handle all aspects of modern computerized multidimensional microscopy. This platform provides users with an execution environment in which 5D data (XYZ, wavelength, and time) can be easily manipulated for the purpose of data collection, processing, display, and analysis. During the entire process, powerful data display functions are readily available for extracting complicated three-dimensional information through data visualization. By employing both the shared memory and multitasking features of the UNIX operation system, individual functions can be implemented as separate programs, and multiple programs can access the same data pool simultaneously. This enables users to combine the functionalities of different programs to facilitate each unique data analysis task. Furthermore, by defining an appropriate program execution model, commonly shared functional components such as data display, data I/O and user interface, etc. can be implemented using simple IVE library calls. This dramatically reduces the program development time and ensures consistency throughout the entire software system. As a result, users can quickly master the microscopy software system and new functions can be easily integrated, as different functional requirements arise for different research projects.

Chromosomes↗

PubMed2026

Structural insights into histone mimicry by the small hepatitis delta antigen.

Hepatitis delta virus (HDV) is a satellite RNA virus that requires hepatitis B virus (HBV) for propagation but replicates its genome independently in the nucleus. The small form of the hepatitis delta antigen (S-HDAg) is essential for replication and is regulated by post-translational modifications. Acetylation at lysine 72 (K72ac) enables S-HDAg to interact with the bromodomain (BRD) of the host chromatin remodeler bromodomain adjacent to zinc finger domain protein 2B (BAZ2B) to promote viral replication. However, the structural basis for this interaction has remained elusive. Here, we provide structural and biophysical insights into this interaction through quantitative binding assays and X-ray crystallography. Isothermal titration calorimetry revealed that BRDs of BAZ2B and its close homolog BAZ2A bind to the viral peptide weakly, with BAZ2A-BRD exhibiting a modestly higher affinity. The crystal structure of BAZ2A-BRD in complex with the S-HDAg-K72ac peptide demonstrates an inverted binding orientation relative to canonical histone ligands, rationalizing the weak interaction. Mutagenesis studies confirmed the critical binding interface both in vitro and in cells. These findings elucidate the molecular mechanism by which HDV co-opts host BAZ2 bromodomains via a unique, weak-affinity interaction, providing a structural framework for understanding viral replication.

Hepatitis delta Antigens↗

PubMed2001

Order and disorder in mitochondrial aldehyde dehydrogenase.

One of the most notable and currently unexplained features of the mitochondrial form of aldehyde dehydrogenase is its property of half-of-the-sites reactivity. An appropriate description of this phenomenon can be to consider this as the extreme example of negative cooperativity. This implies, therefore, that a pathway of communication must exist between active sites in order to convey the structural consequences of ligand binding. Data from four different structures of human ALDH2 collected during the past 2 years may shed some light on one possible pathway for the propagation of structural information. We recently published a 2.6 A structure of a binary complex between ALDH2 and NAD(+) in which the predominant conformation of the cofactor differed between different subunits in the structure. We now have three unpublished structures, a wild-type apo-enzyme structure at 2.25 A resolution, a wild-type structure complexed with NADH at 2.45 A resolution, and a site-directed mutant of ALDH2 where Arg475 is mutated to Gln, as an apo-enzyme to 2.75 A resolution. A detailed comparison of their structures reveals that a disorder-to-order transition occurs upon coenzyme binding in the area immediately surrounding the adenosine-binding site (residues 224-233 and 246-262). These residues correspond to the two helices that surround the adenine ring of the cofactor. Since the helix comprised of residues 246-262 contacts its dimer related helix across the subunit interface, this could induce as of yet unidentified subtle changes in structure that impair productive binding of the cofactor in the second subunit. The unique characteristics and three-dimensional structure of the R475Q variant of ALDH2 supports a role in subunit communication for these residues. This mutated enzyme displays positive cooperativity for cofactor binding. The structure of the apo-enzyme shows that the average thermal parameters for the residues involved in adenosine binding are drastically elevated as is a stretch of amino acids surrounding the site of mutation (residues 471-480). We hypothesize that cofactor binding displays a Hill coefficient of approximately 2 because binding of coenzyme to one subunit in a dimer orders the residues responsible for cofactor binding in the second, thus promoting binding. The difference between these alterations being positively versus negatively cooperative is likely related to the magnitude of the structural changes. Further work is in progress to confirm this hypothesis as it may shed light on the dominant effects of the E487K allelic variant, since Glu487 interacts with Arg475.

Aldehyde Dehydrogenase↗

PubMed2001

Probing the structure and stability of a hybrid protein: the human-E. coli thioredoxin chimera.

The structure and stability of a hybrid protein composed of N-terminal human and C-terminal E. coli thioredoxin domains were investigated by NMR, fluorescence, and circular dichroism spectroscopy. We demonstrate that the chimeric protein is correctly folded and exhibits the common thioredoxin architecture. However, the stability of the hybrid protein toward thermal and chemical denaturation is clearly reduced when compared with both parent proteins. Altogether, our data indicate that the interface between the two folding units of thioredoxin is tolerant toward changes in exact interdigitation of side chains, allowing for the formation of the unique overall thioredoxin fold. Further, the gene encoding the human-E. coli chimera was tested in vivo whether it supports the assembly of filamentous phages. No complementation of a thioredoxin-deficient E. coli mutant for the replication of the phages M13 or fd was observed, suggesting that parts of the overall protein structure in the N-terminal domain are crucial for this activity.

Amino Acid Sequence↗

PubMed1995

Structure and dynamics of lipid monolayers: implications for enzyme catalysed lipolysis.

We have investigated the role of the substrate on the interfacial activation of lipases by an interdisciplinary study of the structure and dynamics of 1,2-sn dipalmitoylglycerol monolayers at distinct surface pressures. The diglyceride Langmuir film undergoes two phase transitions occurring at 38.3 and 39.8 A2 per molecule. The first transition is unique for diglyceride molecules and is driven by a reorganization of the headgroups causing a change in the hydrophobicity of the oil-water interface. X-ray diffraction studies of different mesophases shows that in the two highest pressure phases, the alkyl chains pack in an hexagonal structure relaxing to a distorted-hexagonal lattice in the lowest pressure phase with the alkyl chains tilted by approximately 14 degrees in a direction close to a nearest neighbour direction.

Computer Simulation↗

PubMed2005

Structure of a bacterial BLUF photoreceptor: insights into blue light-mediated signal transduction.

Light is an essential environmental factor, and many species have evolved the capability to respond to it. Blue light is perceived through three flavin-containing photoreceptor families: cryptochromes, light-oxygen-voltage, and BLUF (sensor of blue light using flavin adenine dinucleotide, FAD) domain proteins. BLUF domains are present in various proteins from Bacteria and lower Eukarya. They are fully modular and can relay signals to structurally and functionally diverse output units, most of which are implicated in nucleotide metabolism. We present the high resolution crystal structure of the dark resting state of BlrB, a short BLUF domain-containing protein from Rhodobacter sphaeroides. The structure reveals a previously uncharacterized FAD-binding fold. Along with other lines of evidence, it suggests mechanistic aspects for the photocycle that is characterized by a red-shifted absorbance of the flavin. The isoalloxazine ring of FAD binds in a cleft between two helices, whereas the adenine ring points into the solvent. We propose that the adenine ring serves as a hook mediating the interaction with its effector/output domain. The structure suggests a unique photochemical signaling switch in which the absorption of light induces a structural change in the rim surrounding the hook, thereby changing the protein interface between BLUF and the output domain.

Bacterial Proteins↗

PubMed2004

Characteristics of waves guided by a grounded "left-handed" material slab of finite extent.

The properties of waves guided by a plane-parallel finite slab of material having an ideal, homogeneous, and causal permittivity epsilon (f) , and permeability mu (f) , are investigated analytically and numerically through simulations done via a finite difference time domain (FDTD) code. Lorentzian functional forms are chosen for epsilon (f) and mu (f) . Wave guidance is examined for frequency ranges where the material in the slab is in the left-handed material (LHM) regime, i.e., the real parts of epsilon (f) and mu (f) are negative. It is shown that for reasonably thin slabs, and unlike ordinary materials, there is a unique power recirculation or feedback mechanism wherein the fields in the vicinity of the slab exchange power across the free-space/LHM slab interface. Within the LHM slab, the power travels backwards towards the source. This results in significant but bounded energy accumulation near the edge of the slab closest to the source. The energy exchange across the slab interface is necessary in order to sustain the resulting backward wave in the slab. Slabs thicker than a wavelength are also analyzed, leading to a reversal of the power loop description. The agreement between analytical and numerical results is excellent. They confirm the guided wave physics of a LHM slab.

Journal Article↗

PubMed2005

Depth profile of uncompensated spins in an exchange bias system.

We have used the unique spatial sensitivity of polarized neutron and soft x-ray beams in reflection geometry to measure the depth dependence of magnetization across the interface between a ferromagnet and an antiferromagnet. The net uncompensated magnetization near the interface responds to applied field, while uncompensated spins in the antiferromagnet bulk are pinned, thus providing a means to establish exchange bias.

Journal Article↗