SEARCH · PubMed Health

Results for “Unique interface”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 145 records · Page 8Linked to original sources

PubMed1992

Shape distributions of protein topography.

A method is presented for measuring protein surface shape. It is an improvement of an earlier method that intersects a sphere with the solvent-excluded volume of a protein molecule. The new method, called a shape distribution, produces a more sophisticated description of the region of the sphere inside the protein than is provided by simply measuring the region's area or solid angle. This method is applied to the prediction of molecular complexes in three systems: the hemoglobin nonallosteric interface, trypsin and trypsin inhibitor, and heme and apomyoglobin. It does not uniquely predict the correct structure, even though the individual structures are taken from the experimentally determined complex structure. However, it does provide a list of several hundred predicted complexes, one of which is correct, and from which the correct complex might be extracted by a subsequent chemical filter.

Algorithms↗

PubMed1998

Basics of flow cytometry.

In summary, a beginner requires fundamental knowledge about flow cytometric instrumentation in order to effectively use this technology. It is important to remember that flow cytometers are very complex instruments that are composed of four closely related systems. The fluidic system transports particles from a suspension through the cytometer for interrogation by an illumination system. The resulting light scattering and fluorescence is collected, filtered, and converted into electrical signals by the optical and electronics system. The data storage and computer control system saves acquired data and is also the user interface for controlling most instrument functions. These four systems provide a very unique and powerful analytical tool for researchers and clinicians. This is because they analyze the properties of individual particles, and thousands of particles can be analyzed in a matter of seconds. Thus, data for a flow cytometric sample are a collection of many measurements instead of a single bulk measurement. Basic knowledge of instrumentation is a tremendous aid to designing experiments that can be successfully analyzed using flow cytometry. For example, it is important to know the emission wavelength of the laser in the instrument that will be used for analysis. This wavelength is critical knowledge for selecting probes. It is also important to understand that a different range of wavelengths is detected for each fluorescent channel. This will aid selection of probes that are compatible with the flow cytometer. Understanding the complication that emission spectra overlap contributes to detection can be used to guide fluorochrome selections for multicolor analysis. All of these experiment design considerations that rely on knowledge of how flow cytometers work are a very practical and effective means of avoiding wasted time, energy, and costly reagents. Data analysis is a paramount issue in flow cytometry. Analysis includes interpreting as well as presenting data that has been stored in list-mode files. Data analysis is very graphically oriented. There are a number of types of graphic representation that are available to visually aid data analysis. Two standard types of displays are used. These data plots are one-parameter histograms and bivariate plots. A user must be familiar with these two fundamental types of display in order to effectively analyze data. Histograms are the most simple modes of data representation. Histograms allow visualization of a single acquired parameter. Mean fluorescence and distributional statistics can be obtained based on markers that the user can graphically set on the plot. Percentages of positively expressing particles relative to a control sample can also obtained in a similar manner. In addition, multiple histograms can be overlayed on one another to depict qualitative and quantitative differences in two or more samples. Two-parameter data plots are somewhat more complicated than histograms; however, they can yield more information. Two-parameter dot plots of FSC vs SSC allow visualization of both light-scattering parameters that are important for identifying populations of interest. Bivariate fluorescent plots allow discrimination of dual-labeled populations that might remain hidden if histograms were used to display fluorescent data. Two-parameter plots that combine one light-scattering parameter and a fluorescent parameter are useful for analyzing control samples to elucidate the origin of nonspecific binding. Data analysis is very graphically oriented. Experience and pattern recognition become important when using two-parameter data plots for qualitative as well as quantitative analysis. The technique of gating or drawing regions on dual parameter light-scatter plots allows one to exclude information and examine the population of interest by disallowing particles that might confound or interfere with analysis. This is one of the fundamental uses for gating. (ABSTRACT TRUNCATED)

Animals↗

PubMed1985

Professional women: are distress and disease inevitable?

The unique sources of stress for professional women are discrimination, stereotyping, the marriage/work interface, and social isolation. The behavioral, physiological, and psychological consequences of mismanaged stress are examined and four preventive stress management moderators specifically for professional women suggested. These moderators that influence the stress-strain relationships are a mentor, locus of control, self-confidence, and self-awareness. Finally, a three-point research agenda is outlined for extending understanding of stress among professional women.

Adult↗

PubMed1990

[Dental sac and its role in periodontal development].

The present study examined the role of the innermost layer of dental sac tissue in periodontal development. Empty bony crypts were filled with Hydroxylapatite ceramic granules of porous consistency in 5-day-old rats. After 4.5 and 24 weeks the specimens were processed for light and transmission electron microscopy. Only 4 weeks later cement regeneration was seen on ceramic surfaces with bundles of oriented collagen fibers inserting in the cementoid matrix. Ultrastructurally the newly formed cementum-like tissue was in intimate contact to the synthetic hydroxylapatite crystals. A consistent finding was the presence of an interface between cementum and the ceramic surface. The present findings question the unique role of the "investing layer" in periodontal development and the existence of cement-inducting properties of dentin.

Animals↗

PubMedDate not supplied

Liquid chromatographic-atomic absorption spectrophotometric method for determination of methyl mercury in seafood: collaborative study.

A previously developed method that uses a simplified sample preparation procedure and atomic absorption detection of liquid chromatographic eluates for the determination of methyl mercury in seafood has been collaboratively studied. The unique feature of the method involves the use of a specially designed interface for the generation of mercury vapor. Methyl mercury is isolated from the blended sample by chloroform elution from a diatomaceous earth-hydrochloric acid column. The organomercury compound is then extracted into a small volume of 0.01M sodium thiosulfate solution. An aliquot of this solution is injected onto a Zorbax ODS column and eluted with methanol-ammonium acetate solution (3 + 2), pH 5.7, containing 0.01% mercaptoethanol. Mercury is detected by flameless atomic absorption spectrophotometry using the interface. The samples analyzed in the study were unspiked swordfish, unspiked and spiked lobster, and unspiked and spiked tuna. The spiked samples contained methyl mercury both above and below the U.S. Food and Drug Administration guideline level of 1 microgram Hg/g. Reproducibility relative standard deviations ranged from 10.5% at 1 microgram Hg/g to 18.2% at about 0.1 microgram Hg/g. Accuracy, measured by comparison to reference values obtained by the Associate Referee, ranged from 94.4 to 99.6%. The method has been adopted official first action.

Animals↗

PubMed1994

New surface-hardened, low-modulus, corrosion-resistant Ti-13Nb-13Zr alloy for total hip arthroplasty.

To optimize the performance of total hip replacement, scientists and clinicians are seeking new materials and noncemented, press-fit designs that can improve load transfer to the bone and reduce the incidence of loosening and thigh pain. Currently used Co-Cr-Mo alloy has a relatively high elastic modulus (E = 227 GPa), which limits its ability to transfer load to the surrounding bone in the proximal calcar region. Thus to improve load transfer, designs are considered with less cross-sectional area to increase flexibility, but at the expense of fit and fill, and thus stability of the implant within the bone. Should stem loosening occur, the stem stresses may exceed the relatively low fatigue strength of the Co-Cr-Mo alloy and lead to stem breakage. To improve these conditions, lower modulus Ti-6Al-4V alloy (E = 115 GPa) is being used. More recently, a new lower-modulus (E = 79 GPa) Ti-13Nb-13Zr alloy has been developed which does not contain any elemental constituents associated with adverse cell response (i.e., Co, Cr, Mo, Ni, Fe, Al, V), and which possesses comparable or superior strength and toughness to existing Ti-6Al-4V alloy. The carefully selected Nb and Zr constituents improve bone biocompatibility and corrosion resistance compared to that of currently used implant metals. Additionally, a unique diffusion hardening (DH) treatment can be conducted during the age-hardening process of this near-beta alloy to produce a hardened surface with abrasion resistance superior to that of Co-Cr-Mo alloy. This also provides an improvement in the micro-fretting tendencies that may occur within femoral head-neck taper regions and modular interfaces of other implant designs. The present study describes the metallurgy and mechanical properties of this unique low modulus Ti-13Nb-13Zr alloy, and the heat treatments used to obtain the high strength, corrosion resistance, and surface hardening that renders this biocompatible alloy well-suited for press fit hip replacement applications. Because of the relatively lower beta transus (735 degrees C), this alloy is also much easier to net shape forge into more complex stem designs.

Alloys↗

PubMed1995

Materno-fetal immunobiology in normal pregnancy and its possible failure in recurrent spontaneous abortion?

Many features contributing to the success of pregnancy in humans have been identified over the last 20 years. Trophoblast cells (which form the interface of fetal tissue with the mother) have specialized immunological features which may confer unique transplantation protection for the fetus throughout pregnancy. Both syncytiotrophoblast and cytotrophoblast cells do not express classical class I [human leucocyte antigen (HLA)-A or -B] or II (HLA-DP, -DQ or -DR) major histocompatibility complex (MHC) alloantigens, and the regulation of these cell surface glycoproteins appears to be at the transcriptional level. In contrast, extravillous cytotrophoblast cells express the non-classical class I MHC molecule HLA-G. One form of HLA-G (HLA-G1) is potentially capable of presenting a variety of peptide antigens to T cells. Alternatively, HLA-G may act as a cell surface class I MHC molecule, protecting cytotrophoblast from maternal MHC non-restricted natural killer (NK) cell attack; the expression of HLA-G by otherwise HLA-null cell transfectants has been shown to decrease their sensitivity to NK cell-mediated cytolysis. All fetal trophoblast populations throughout gestation express high levels of cell surface complement regulatory proteins, providing protection from complement-mediated damage at the materno-fetal interface. Analyses of trials with allogeneic leucocytes for the treatment of recurrent spontaneous abortion show little evidence of an improved success rate in immunized patients.

Abortion, Habitual↗

PubMed1997

Care of the terminally ill cachectic cancer patient: interface between nursing and psychological anthropology.

The wasted appearance of the terminally ill cachectic cancer patient is a major source of concern for both patients and families. To date, this experience has mainly been understood from a biomedical perspective. However, considering this experience occurs within unique social, historical and cultural contexts, a more holistic approach to capturing this experience is warranted. This paper will argue that the interface between psychological anthropology and nursing provides an alternative approach from which the experience of 'wasting away' might be examined. Special attention to the use of explanatory models of illness and illness narratives in capturing this interface will be explored.

Anthropology, Cultural↗

PubMed1993

Cross-sectional AEM preparation technique for ceramic-coated WC-Co cutting tools.

The preparation of cross-sectional specimens for AEM studies of materials such as ceramic coated tungsten carbide presents some unique problems. Pieces joined by the use of epoxides often separate at the interface between the WC and ceramic coating during the initial mechanical grinding and subsequent thinning process as a result of the vibration and physical strain placed on the sample. These problems have been overcome through the use of a preparation process which essentially encapsulates the sample within the confines of an epoxy filled quartz tube. This preparation process has allowed for facile AEM cross-sectional analysis of TiN/TiCN coatings on WC-Co substrates, and has revealed two distinct grain morphologies within the TiCN coating.

Ceramics↗

PubMed1997

Use of mutator cells as a means for increasing production levels of a recombinant antibody directed against Hepatitis B.

A mutation strategy which utilises phage display technology and the Escherichia coli mutator strains, mutD5-FIT and XL1-RED, was applied to a Hepatitis B (HepB) specific single-chain Fv (scFv) to incorporate random mutations throughout the gene. Messenger RNA from a hybridoma producing antibodies against HepB was isolated, reverse transcribed and used as template for the production of scFv. Following production of the scFv protein using an E. coli expression vector (pGC), the scFv gene was recloned into a phage display vector (pHFA). This gene construct was introduced into E. coli mutator cells and the transformed cells were used as an inoculum for liquid cultures. After five cycles of growth at 37 degrees C, each followed by dilution and re-inoculation of fresh media, recombinant phage were recovered. Nucleotide sequence analysis of the scFv gene in phage selected on HBsAg-coated magnetic beads identified amino acid substitutions which produced an increase of greater than 10-fold in apparent production levels. Competitive ELISA studies showed that the selected scFv mutants appeared to have similar affinity to HBsAg as the parent scFv. The apparent increase in production was not the result of improved surface characteristics of regions uniquely exposed in scFvs, as the sites did not correlate with the variable/constant interface of the scFv variable region normally masked in Fabs or IgGs.

Amino Acid Sequence↗

PubMed1996

Raman spectroscopy of the Ff gene V protein and complexes with poly(dA): nonspecific DNA recognition and binding.

Raman spectra of crystals and solutions of the single-stranded DNA binding protein of bacteriophage Ff (gene V protein, gVp) and of solution complexes of gVp with single-stranded poly-(deoxyadenylic acid) [poly(dA)] reveal the following: (i) The gVp secondary and tertiary structures are similar in solution and in the crystal and are dominated by beta-sheet domains, in agreement with NMR and X-ray findings. (ii) Subunit conformation and side chain environments of gVp are virtually unchanged over a wide range of salt concentration (0 < [NaCl] < 100 mM); however, the solution conformation of poly(dA) exhibits sensitivity to added salt. The perturbed Raman markers indicate subtle changes in helix backbone geometry with accompanying small differences in base stacking as the concentration of NaCl is changed. (iii) In complexes with poly(dA), neither the conformation of gVp nor its side chain environments are altered significantly in comparison to the free protein. This is the case at both high salt (nucleotide-to-subunit binding stoichiometry n = 4) and low salt (n = 3). (iv) The Raman signature of poly(dA) undergoes small perturbations upon gVp binding, indicative of small changes in base stacking and phosphodiester backbone conformation. The present results show that the different stoichiometric binding modes of gVp to poly(dA) are accomplished without significant changes in gVp subunit structure and with only modest changes in the single-stranded poly(dA) ligand. This contrasts sharply with sequence-specific double-stranded DNA binding proteins, such as the phage lambda and D108 repressors, which undergo substantial structural changes upon DNA binding, and which also alter more dramatically the Raman fingerprints of their DNA target sites. Thus, nonspecific and specific nucleic acid recognition modes are distinguishable by Raman spectroscopy. The Raman signature of gVp also allows examination of hydrogen bonding interactions of unique side chains within the hydrophobic core (cysteine 33) and at the binding interface (tyrosine 41). These are discussed in relation to the recently published gVp crystal structure.

Amino Acid Sequence↗

PubMed1994

HLA-G polymorphisms in African Americans.

HLA-G is a class I MHC gene most notable for its restricted tissue distribution. The unique expression of this gene in extravillous cytotrophoblast at the maternal-fetal interface suggests that HLA-G plays a critical role in human pregnancy. Previous studies have reported that HLA-G has a limited repertoire of rare alleles, unlike the classical class I alleles, which are among the most polymorphic human genes. To determine the full extent of sequence variation in this gene, we examined the nucleotide variation in the first six exons of this gene in 45 healthy African American persons. By using sensitive techniques that detect > 95% of nucleotide substitutions, we detected two sequence variations in the alpha-1 domain (exon 2) and 24 sequence variations in the alpha-2 domain (exon 3) that result in amino acid substitutions. These data indicate that HLA-G is potentially capable of presenting a wide variety of peptides and of eliciting an allogeneic response, similar to the classical class I HLA genes.

Adult↗

PubMed1996

Microbial lipases: production and applications.

Lipases occupy a prominent place among biocatalysts and have a wide spectrum of biotechnological applications. Lipases are unique as they hydrolyse fats into fatty acids and glycerol at the water-lipid interface and can reverse the reaction in non-aqueous media. The stability of these enzymes in organic solvents have pushed them into the frontier areas of organic synthesis leading to the designing of novel drugs, surfactants, bioactive compounds and oleochemicals. In addition, lipase-catalysed trans-esterification and inter-esterification reactions have been exploited in the fat industry. Looking into the wide scenario of lipase applications, commercialization of lipase production is a prime area of interest for microbiologists, process engineers and biochemists. Research carried out in this field has revealed that microbes, especially fungi and bacteria, are the tools of choice for commercial production. Recently, the structure determination of a few microbial lipases has widened our knowledge about the unique mechanism of catalysis of this enzyme.

Animals↗

PubMed1990

Magnetic resonance imaging simulator: a teaching tool for radiology.

The increasing use of magnetic resonance imaging (MRI) as a clinical modality has put an enormous burden on medical institutions to cost effectively teach MRI scanning techniques to technologists and physicians. Since MRI scanner time is a scarce resource, it would be ideal if the teaching could be effectively performed off-line. In order to meet this goal, the radiology Department at the University of Pennsylvania has designed and developed a Magnetic Resonance Imaging Simulator. The simulator in its current implementation mimics the General Electric Signa (General Electric Magnetic Resonance Imaging System, Milwaukee, WI) scanner's user interface for image acquisition. The design is general enough to be applied to other MRI scanners. One unique feature of the simulator is its incorporation of an image-synthesis module that permits the user to derive images for any arbitrary combination of pulsing parameters for spin-echo, gradient-echo, and inversion recovery pulse sequences. These images are computed in 5 seconds. The development platform chosen is a standard Apple Macintosh II (Apple Computer, Inc, Cupertino, CA) computer with no specialized hardware peripherals. The user interface is implemented in HyperCard (Apple Computer Inc, Cupertino, CA). All other software development including synthesis and display functions are implemented under the Macintosh Programmer's Workshop 'C' environment. The scan parameters, demographics, and images are tracked using an Oracle (Oracle Corp, Redwood Shores, CA) data base. Images are currently stored on magnetic disk but could be stored on optical media with minimal effort.

Computer Simulation↗

PubMed1989

Ordered disruption of subunit interfaces during the stepwise reversible dissociation of Escherichia coli phosphofructokinase with KSCN.

The reversible inactivation and dissociation of the allosteric phosphofructokinase from Escherichia coli has been studied in relatively mild conditions, i.e., in the presence of the chaotropic agent KSCN. At moderate KSCN concentration, the loss of enzymatic activity involves two separated phases: first, a rapid dissociation of part of the tetramer into dimers, second, a slower displacement of the dimer-tetramer equilibrium upon further dissociation of the dimer into monomers. These two reactions can no longer be distinguished above 0.3 M KSCN since complete inactivation occurs in a single reaction. Different changes are observed for the fluorescence and the activity of the enzyme in KSCN: the fluorescence is not affected by the dissociation into dimers which is responsible for inactivation. The decrease in fluorescence reflects the change in environment of the unique tryptophan residue, Trp 311, during the dimer to monomer dissociation. This residue belongs to the interface containing the regulatory site, and its native fluorescence indicates that this interface is still present in the dimer. The substrate fructose 6-phosphate protects phosphofructokinase from inactivation by binding to the tetramer and prevents its dissociation into dimers. The presence of phosphoenolpyruvate prevents the slow dissociation of the dimer into monomers, which shows the ability of the dimer to bind the inhibitor. Two successive processes can be observed during reassociation of the protein upon KSCN dilution. First, a fast reaction (k1 = 2 x 10(5) M-1.s-1) is accompanied by a fluorescence increase and results in the formation of the dimeric species.(ABSTRACT TRUNCATED AT 250 WORDS)

Allosteric Regulation↗

PubMed1983

Submersion culture of the intact fetal lung.

Intact whole lungs from 14 d rat fetuses were explanted to organ culture and maintained fully submerged in medium or positioned at the gas-fluid interface. Striking differences were observed in the morphological development of submersion cultured and interface cultured explants after 7 d in vitro. Submersion cultured lung developed as an expanded hollow organ, whereas the tissue of interface cultures was glandular in appearance and attenuated against the culture substrate. This difference in the development of the cultured lung may be attributed to the influence of surface tension forces at the gas-fluid interface versus the fluid immersed environment. In submersion culture the fetal lung followed a unique pattern of morphogenetic development. Under these culture conditions the lung expanded in three dimensions and retained its discrete lobar structure. The primitive bronchial epithelial tree of the fetal lung at explantation exhibited substantial histoarchitectural changes in vitro. Progressive branching of the epithelium into the surrounding lung mesenchyme gave rise to a pulmonary parenchyma bearing characteristics of the presumptive alveolar region of the late gestation fetal lung. The epithelium consisted predominantly of large, glycogen rich cuboidal cells interspersed with numerous structurally differentiated type II cells, containing lamellar bodies. The pulmonary parenchyma of the submersion cultured explant occupied a narrow margin of the lung wall, surrounding a large central lumen. This unique form of the cultured lung made it possible to examine the pulmonary epithelium by scanning electron microscopy. Data from the present study suggest that submersion culture of the intact fetal lung may provide a useful model system for study of the maturation of epithelial cell surface features during pulmonary development.

Animals↗

PubMed1997

HLA-G polymorphisms: neutral evolution or novel function?

HLA-G is a non-classical class Ib gene with many unusual features. Because of its unique expression pattern, which is primarily limited to fetal cells at the maternal fetal interface, this gene has gained the attention of many investigators. In this paper we review some of the novel features of HLA-G, with particular reference to polymorphic variants in the gene, and discuss the implications of these features for the potential function and evolutionary history of HLA-G.

Alleles↗

PubMed1995

Molecular basis for interaction of the protein tyrosine kinase ZAP-70 with the T-cell receptor.

The crystal structure of the tandem SH2 domains of human ZAP-70 in complex with a peptide derived from the zeta-subunit of the T-cell receptor reveals an unanticipated interaction between the two domains. A coiled coil of alpha-helices connects the two SH2 domains, producing an interface that constitutes one of the two critical phosphotyrosine binding sites. These and other unique features provide the molecular basis for highly selective association of ZAP-70 with the T-cell receptor.

Amino Acid Sequence↗