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  • 1
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    [Perspective] Molecular sieves for gas separation (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-07-08
    Description: Separation and purification are critical industrial processes for separating components of chemical mixtures, and these processes account for about half of industrial energy usage (1). Gas mixtures of compounds with very similar physical properties are particularly difficult to separate. On pages 137 and 141 of this issue, Cadiau et al. (2) and Cui et al. (3), respectively, show that microporous materials can be designed to have high adsorption capacity and selectivity for particular hydrocarbons, enabling energy-efficient separation. Author: Jerry Y. S. Lin
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    [Perspective] How to break down crystalline cellulose (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-05-27
    Description: Biomass-degrading microorganisms use lytic polysaccharide monooxygenase (LPMO) enzymes to help digest cellulose, chitin, and starch. By cleaving otherwise inaccessible crystalline cellulose chains, these enzymes provide access to hydrolytic enzymes. LPMOs are of interest to biotechnology because efficient depolymerization of cellulose is a major bottleneck for the production of biologically based chemicals and fuels. On page 1098 of this issue, Kracher et al. (1) compare LPMO-reducing substrates in fungi from different taxonomic groups and lifestyles, based on both biochemical and genomic evidence. The results provide insights into reductive activation of LPMO that are important for developing more efficient industrial enzymes for lignocellulose biorefineries. Author: Angel T. Martínez
    Keywords: Chemistry
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  • 3
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    [Editors' Choice] Engineering open structures using DNA (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-03-25
    Description: Author: Marc S. Lavine
    Keywords: Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    A base dispute (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-08-03
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waldrop, M M -- New York, N.Y. -- Science. 1990 Aug 3;249(4968):472-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2382127" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Information Systems ; Jurisprudence ; Societies, Scientific ; United States
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  • 5
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    Direct measurement of forces between linear polysaccharides xanthan and schizophyllan (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-09-14
    Description: Direct osmotic stress measurements have been made of forces between helices of xanthan, an industrially important charged polysaccharide. Exponentially decaying hydration forces, much like those already measured between lipid bilayer membranes or DNA double helices, dominate the interactions at close separation. Interactions between uncharged schizophyllans also show the same kind of hydration force seen between xanthans. In addition to the practical possibilities for modifying solution and suspension properties through recognition and control of molecular forces, there is now finally the opportunity for theorists to relate macroscopic properties of a polymer solution to the microscopic properties that underlie them.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rau, D C -- Parsegian, V A -- New York, N.Y. -- Science. 1990 Sep 14;249(4974):1278-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institues of Health, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2144663" target="_blank"〉PubMed〈/a〉
    Keywords: Carbohydrate Sequence ; Chemical Phenomena ; Chemistry ; Gels ; *Glycosaminoglycans ; Macromolecular Substances ; Molecular Sequence Data ; Osmosis ; *Polysaccharides, Bacterial ; *Sizofiran ; Solutions ; Viscosity
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Common features of protein unfolding and dissolution of hydrophobic compounds (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-02-02
    Description: Protein unfolding and the dissolution of hydrophobic compounds (including solids, liquids, and gases) in water are characterized by a linear relation between entropy change and heat capacity change. The same slope is found for various classes of compounds, whereas the intercept depends on the particular class. The feature common to these processes is exposure of hydrophobic groups to water. These observations make possible the assignment of the heat capacity change to hydrophobic solvation and lead to the description of protein stability in terms of a hydrophobic and a nonhydrophobic contribution. A general representation of protein stability is given by the heat capacity change and the temperature.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, K P -- Privalov, P L -- Gill, S J -- New York, N.Y. -- Science. 1990 Feb 2;247(4942):559-61.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2300815" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Protein Denaturation ; *Proteins ; Thermodynamics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    Interparticle collisions driven by ultrasound (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-03-02
    Description: Ultrasound has become an important synthetic tool in liquid-solid chemical reactions, but the origins of the observed enhancements remained unknown. The effects of high-intensity ultrasound on solid-liquid slurries were examined. Turbulent flow and shock waves produced by acoustic cavitation were found to drive metal particles together at sufficiently high velocities to induce melting upon collision. A series of transition-metal powders were used to probe the maximum temperatures and speeds reached during such interparticle collisions. Metal particles that were irradiated in hydrocarbon liquids with ultrasound underwent collisions at roughly half the speed of sound and generated localized effective temperatures between 2600 degrees C and 3400 degrees C at the point of impact for particles with an average diameter of approximately 10 microns.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doktycz, S J -- Suslick, K S -- New York, N.Y. -- Science. 1990 Mar 2;247(4946):1067-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Chemical Sciences, University of Illinois, Urbana 61801.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2309118" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Metals ; Microscopy, Electron, Scanning ; Microspheres ; *Ultrasonics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    Changes in mean concentration, phase shifts, and dissipation in a forced oscillatory reaction (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-01-12
    Description: Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference delta G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and delta G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lazar, J G -- Ross, J -- New York, N.Y. -- Science. 1990 Jan 12;247(4939):189-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stanford University, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2294601" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Chemical Phenomena ; Chemistry ; Glucosephosphate Dehydrogenase/*metabolism ; Horseradish Peroxidase/*metabolism ; Kinetics ; NAD/*metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Peroxidases/*metabolism ; Thermodynamics
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  • 9
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    An antibody binding site on cytochrome c defined by hydrogen exchange and two-dimensional NMR (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-08-17
    Description: The interaction of a protein antigen, horse cytochrome c (cyt c), with a monoclonal antibody has been studied by hydrogen-deuterium (H-D) exchange labeling and two-dimensional nuclear magnetic resonance (2D NMR) methods. The H-exchange rate of residues in three discontiguous regions of the cyt c polypeptide backbone was slowed by factors up to 340-fold in the antibody-antigen complex compared with free cyt c. The protected residues, 36 to 38, 59, 60, 64 to 67, 100, and 101, and their hydrogen-bond acceptors, are brought together in the three-dimensional structure to form a contiguous, largely exposed protein surface with an area of about 750 square angstroms. The interaction site determined in this way is consistent with prior epitope mapping studies and includes several residues that were not previously identified. The hydrogen exchange labeling approach can be used to map binding sites on small proteins in antibody-antigen complexes and may be applicable to protein-protein and protein-ligand interactions in general.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3432411/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3432411/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paterson, Y -- Englander, S W -- Roder, H -- GM 31847/GM/NIGMS NIH HHS/ -- GM 35926/GM/NIGMS NIH HHS/ -- R01 GM031847/GM/NIGMS NIH HHS/ -- S07-RR-05415-28/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1990 Aug 17;249(4970):755-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology, University of Pennsylvania, Philadelphia 19104.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1697101" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies, Monoclonal/immunology/metabolism ; Antigen-Antibody Complex ; *Binding Sites, Antibody ; Chemical Phenomena ; Chemistry ; Cytochrome c Group/*immunology ; Deuterium ; Epitopes/immunology ; Hydrogen/*metabolism ; Hydrogen Bonding ; Kinetics ; *Magnetic Resonance Spectroscopy ; Molecular Structure ; Protein Conformation
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  • 10
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    Studies of unusual simple molecules by neutralization-reionization mass spectrometry (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-02-23
    Description: Reactive or unstable molecules are key intermediates in many important reactions, but can be difficult to prepare for experimental studies. Species with missing (:CH-OH) or extra (H3) substituents can often be formed conveniently in the gas phase by neutralizing a beam of a more stable ionic counterpart (CH = O+H, H3+). Reionization of the neutral after approximately 10(-6) seconds tests its stability, whereas its unimolecular chemistry can be probed by preparing it with different amounts of internal energy. The resulting neutral products are reionized and mass analyzed. Isomers are then characterized by ion dissociation and a third mass-analysis step. Many unusual molecules have been characterized with this technique, which can also be used to probe complex unimolecular chemistry, such as that of cyclobutadiene and ethylene oxide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McLafferty, F W -- GM-16609/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 Feb 23;247(4945):925-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cornell University, Baker Laboratory, Ithaca, NY 14853-1301.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2305261" target="_blank"〉PubMed〈/a〉
    Keywords: Butadienes ; Chemical Phenomena ; Chemistry ; Ethylene Oxide ; Free Radicals ; Hydrocarbons ; *Ions ; *Mass Spectrometry ; Methane/analogs & derivatives ; Molecular Structure ; Thermodynamics
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  • 11
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    Inhibition of FKBP rotamase activity by immunosuppressant FK506: twisted amide surrogate (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-05-18
    Description: The immunosuppressive agents cyclosporin A and FK506 inhibit the transcription of early T cell activation genes. The binding proteins for cyclosporin A and FK506, cyclophilin and FKBP, respectively, are peptidyl-prolyl-cis-trans isomerases, or rotamases. One proposed mechanism for rotamase catalysis by cyclophilin involves a tetrahedral adduct of an amide carbonyl and an enzyme-bound nucleophile. The potent FKBP rotamase inhibitor FK506 has a highly electrophilic carbonyl that is adjacent to an acyl-pipicolinyl (homoprolyl) amide bond. Such a functional group would be expected to form a stabilized, enzyme-bound tetrahedral adduct. Spectroscopic and chemical evidence reveals that the drug interacts noncovalently with its receptor, suggesting that the alpha-keto amid of FK506 serves as a surrogate for the twisted amide of a bound peptide substrate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rosen, M K -- Standaert, R F -- Galat, A -- Nakatsuka, M -- Schreiber, S L -- GM-38627/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 May 18;248(4957):863-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Harvard University, Cambridge, MA 02138.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1693013" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Isomerases/*antagonists & inhibitors ; Anti-Bacterial Agents/metabolism/*pharmacology ; Binding Sites ; Carrier Proteins/antagonists & inhibitors/metabolism ; Chemical Phenomena ; Chemistry ; Cloning, Molecular ; Cyclosporins/metabolism/pharmacology ; Escherichia coli/genetics ; Gene Expression ; *Immunosuppressive Agents ; Lymphocyte Activation ; Magnetic Resonance Spectroscopy ; Molecular Structure ; Peptidylprolyl Isomerase ; Recombinant Proteins ; T-Lymphocytes/immunology ; Tacrolimus
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  • 12
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    [This Week in Science] Synthetic twists among lipids (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-04-29
    Description: Author: Jake Yeston
    Keywords: Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 13
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    [This Week in Science] Temporarily caught in a bind (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-03-18
    Description: Author: Marc S. Lavine
    Keywords: Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 14
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    [Perspective] Quantum dynamics in the smallest water droplet (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-03-18
    Description: Water plays a central role in scientific disciplines ranging from geology to astronomy to biology. Yet it is an extraordinarily dif cult liquid to understand because of its complex, ever-changing patterns of hydrogen bonds. Studies of small water clusters have provided important insights into the concerted hydrogen-bond motions that can occur in water. These studies are also crucial for developing an accurate potential function for simulating the properties of liquid water and ice (1). On page 1310 of this issue, Richardson et al. (2) provide evidence for a concerted type of motion in which two hydrogen bonds in a water cluster are broken simultaneously (see the figure). The results have implications for many areas of scientific study, including the chemistry of polar solvents, the conformations of proteins, and the dissolution of ions in minerals. Author: David C. Clary
    Keywords: Chemistry
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  • 15
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    [Editors' Choice] Beyond blank slates in the lab notebook (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-03-18
    Description: Author: Jake Yeston
    Keywords: Chemistry
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  • 16
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    [Perspective] Surprised by selectivity (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-03-04
    Description: Lower olefins, particularly ethylene (C2H4), propylene (C3H6), and butylene (C4H8), are important intermediates in the manufacture of products such as plastics, solvents, paints, and medicines. They are produced worldwide in amounts exceeding 200 million tons per year (see the photo) (1), mostly from crude oil. More recent approaches use methanol or synthesis gas (syngas; a mixture of carbon monoxide and hydrogen) as feedstocks, but capital investments are high and/or selectivities to lower olefins limited. A bifunctional catalyst reported by Jiao et al. on page 1065 of this issue (2) enables the direct conversion of synthesis gas to lower olefins with a surprisingly high selectivity. Author: Krijn P. de Jong
    Keywords: Chemistry
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  • 17
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    Chemists get a taste of life at gathering in San Diego (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-04-01
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Flam, F -- New York, N.Y. -- Science. 1994 Apr 1;264(5155):32-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8140417" target="_blank"〉PubMed〈/a〉
    Keywords: AIDS Vaccines/*chemical synthesis/immunology ; Animals ; Antibodies, Viral/biosynthesis ; Cellobiose ; Chemistry ; HIV Antibodies/biosynthesis ; Herpesvirus 4, Human/*immunology ; Societies, Scientific ; *Vaccines, Synthetic/immunology ; Viral Proteins ; Viral Vaccines/*chemical synthesis/immunology
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  • 18
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    Ligand-accelerated enantioselective methylene C(sp3)-H bond activation (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-09-02
    Description: Effective differentiation of prochiral carbon–hydrogen (C–H) bonds on a single methylene carbon via asymmetric metal insertion remains a challenge. Here, we report the discovery of chiral acetyl-protected aminoethyl quinoline ligands that enable asymmetric palladium insertion into prochiral C–H bonds on a single methylene carbon center. We apply these palladium complexes to catalytic enantioselective functionalization of β-methylene C–H bonds in aliphatic amides. Using bidentate ligands to accelerate C–H activation of otherwise unreactive monodentate substrates is crucial for outcompeting the background reaction driven by substrate-directed cyclopalladation, thereby avoiding erosion of enantioselectivity. The potential of ligand acceleration in C–H activation is also demonstrated by enantioselective β-C–H arylation of simple carboxylic acids without installing directing groups.
    Keywords: Chemistry
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  • 19
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    [Editors' Choice] Sourcing hydrogen directly from wax (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-11-04
    Description: Author: Jake Yeston
    Keywords: Chemistry
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  • 20
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    Phase transition and crystal structure of the 37 degrees C form of cholesterol (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-05-06
    Description: Crystalline cholesterol undergoes a phase transition a few degrees below human body temperature. The high-temperature form has an unusually complex structure with 16 independent molecules. In the transition two molecules change side chain conformation, four reorient about their long axes, and ten remain unchanged. The transition mechanism implies relatively nonspecific intermolecular interactions, qualitatively consistent with the behavior of cholesterol in biomembranes. The transition preserves a remarkably closely obeyed pseudosymmetry present in the structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hsu, L Y -- Nordman, C E -- GM15259/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 May 6;220(4597):604-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836303" target="_blank"〉PubMed〈/a〉
    Keywords: Body Temperature ; Chemical Phenomena ; Chemistry ; *Cholesterol ; Crystallization ; Humans ; Magnetic Resonance Spectroscopy ; Molecular Conformation
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    Cytochrome a3 structure in carbon monoxide-bound cytochrome oxidase (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-07-20
    Description: The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Argade, P V -- Ching, Y C -- Rousseau, D L -- New York, N.Y. -- Science. 1984 Jul 20;225(4659):329-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6330890" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Monoxide/metabolism ; Cattle ; Chemical Phenomena ; Chemistry ; Electron Transport Complex IV/*metabolism ; Myoglobin/metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Spectrum Analysis, Raman
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    Leukotrienes: mediators of immediate hypersensitivity reactions and inflammation (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-05-06
    Description: Arachidonic acid plays a central role in a biological control system where such oxygenated derivatives as prostaglandins, thromboxanes, and leukotrienes are mediators. The leukotrienes are formed by transformation of arachidonic acid into an unstable epoxide intermediate, leukotriene A4, which can be converted enzymatically by hydration to leukotriene B4, and by addition of glutathione to leukotriene C4. This last compound is metabolized to leukotrienes D4 and E4 by successive elimination of a gamma-glutamyl residue and glycine. Slow-reacting substance of anaphylaxis consists of leukotrienes C4, D4, and E4. The cysteinyl-containing leukotrienes are potent bronchoconstrictors, increase vascular permeability in postcapillary venules, and stimulate mucus secretion. Leukotriene B4 causes adhesion and chemotactic movement of leukocytes and stimulates aggregation, enzyme release, and generation of superoxide in neutrophils. Leukotrienes C4, D4, and E4, which are released from the lung tissue of asthmatic subjects exposed to specific allergens, seem to play a pathophysiological role in immediate hypersensitivity reactions. These leukotrienes, as well as leukotriene B4, have pro-inflammatory effects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Samuelsson, B -- New York, N.Y. -- Science. 1983 May 6;220(4597):568-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6301011" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Arachidonic Acids/metabolism/pharmacology/physiology ; Bronchi/drug effects ; Cats ; Chemical Phenomena ; Chemistry ; Cricetinae ; Guinea Pigs ; Haplorhini ; Humans ; Hypersensitivity, Immediate/*physiopathology ; Inflammation/*physiopathology ; Leukocytes/drug effects/metabolism ; Leukotriene B4/pharmacology/*physiology ; Mice ; Microcirculation/drug effects ; Rabbits ; Rats ; SRS-A/*physiology
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    Amphiphilic secondary structure: design of peptide hormones (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-01-20
    Description: Peptide synthesis can be used for elucidating the roles of secondary structures in the specificity of hormones, antigens, and toxins. Intermediate sized peptides with these activities assume amphiphilic secondary structures in the presence of membranes. When models are designed to optimize the amphiphilicity of the secondary structure, stronger interactions can be observed with the synthetic peptides than with the naturally occurring analogs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, E T -- Kezdy, F J -- HL-18577/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1984 Jan 20;223(4633):249-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6322295" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Apolipoprotein A-I ; Apolipoproteins ; Binding Sites ; Calcitonin ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone ; Endorphins ; Glucagon ; Growth Hormone-Releasing Hormone ; *Hormones/pharmacology ; Lipoproteins, HDL ; Melitten ; Models, Structural ; *Peptides/chemical synthesis/metabolism/pharmacology ; Protein Conformation ; Structure-Activity Relationship ; beta-Endorphin
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    Fourier transform mass spectrometry (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-10-19
    Description: Fourier transform mass spectrometry will play an important role in the future because of its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. These features have already found application in gas chromatography-mass spectrometry, multiphoton ionization, laser desorption, and secondary ion mass spectrometry. However, its most notable feature is the ability to store ions. This characteristic, when combined with the others, will allow expeditious study of the interaction of gas-phase ions with both photons (photodissociation) and neutral molecules, and the convenient application of this fundamental information for chemical analysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gross, M L -- Rempel, D L -- 2-8423576/PHS HHS/ -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):261-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6385250" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Fourier Analysis ; Ions ; Lasers ; *Mass Spectrometry/instrumentation/methods
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    Studying enzyme mechanism by 13C nuclear magnetic resonance (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-08-31
    Description: High-resolution carbon-13 nuclear magnetic resonance (NMR) spectra of enzyme-inhibitor and enzyme-substrate complexes provide detailed structural and stereochemical information on the mechanism of enzyme action. The proteases trypsin and papain are shown to form tetrahedrally coordinated complexes and acyl derivatives with a variety of compounds artificially enriched at the site or sites of interest. These results are compared with the structural information derived from x-ray diffraction. Detailed NMR studies have provided a clearer picture of the ionization state of the residues participating in enzyme-catalyzed processes than other more classical techniques. The dynamics of enzymic catalysis can be observed at sub-zero temperatures by a combination of cryoenzymology and carbon-13 NMR spectroscopy. With these powerful techniques, transient, covalently bound intermediates in enzyme-catalyzed reactions can be detected and their structures rigorously assigned.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, N E -- Malthouse, J P -- Scott, A I -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):883-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6433481" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon Isotopes ; Carboxypeptidases/metabolism ; Carboxypeptidases A ; Catalysis ; Chemical Phenomena ; Chemistry ; Coenzymes/*metabolism ; Endopeptidases/metabolism ; Enzymes/*metabolism ; Freezing ; Fructose-Bisphosphate Aldolase/metabolism ; Magnetic Resonance Spectroscopy ; Papain/metabolism ; Pepsin A/metabolism ; Peptide Hydrolases/*metabolism ; Protease Inhibitors ; Pterins/metabolism ; Pyridoxal Phosphate/metabolism ; Serine Endopeptidases
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    What is the risk from chlorofluorocarbons? (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-03-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maugh, T H 2nd -- New York, N.Y. -- Science. 1984 Mar 9;223(4640):1051-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6695193" target="_blank"〉PubMed〈/a〉
    Keywords: *Air Pollutants ; *Atmosphere ; Carbon Tetrachloride ; Chemical Phenomena ; Chemistry ; *Chlorofluorocarbons, Methane ; Free Radicals ; Nitrogen Dioxide ; Nitrous Oxide ; Oxygen ; *Ozone ; Photochemistry ; Risk ; Singlet Oxygen ; Trichloroethanes ; Ultraviolet Rays
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    Pyrolysis mass spectrometry of complex organic materials (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-10-19
    Description: Pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis enables qualitative and quantitative analysis of nonvolatile organic materials containing molecular assemblies of a complexity and size far beyond the capabilities of direct mass spectrometry. The state of the art in pyrolysis mass spectrometry techniques is illustrated through specific applications, including structural determination and quality control of synthetic polymers, quantitative analysis of polymer mixtures, classification and structural characterization of fossil organic matter, and nonsupervised numerical extraction of component patterns from complex biological samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meuzelaar, H L -- Windig, W -- Harper, A M -- Huff, S M -- McClennen, W H -- Richards, J M -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):268-74.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6484572" target="_blank"〉PubMed〈/a〉
    Keywords: Biochemical Phenomena ; Biochemistry ; Chemical Phenomena ; Chemistry ; Coal ; Enterobacteriaceae/analysis/isolation & purification ; Hot Temperature ; Mass Spectrometry/*methods ; Polymers
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    Lariat RNA's as intermediates and products in the splicing of messenger RNA precursors (1984)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1984-08-31
    Description: The splicing of messenger RNA precursors in vitro proceeds through an intermediate that has the 5' end of the intervening sequence joined to a site near the 3' splice site. This lariat structure, which has been characterized for an adenovirus 2 major late transcript, has a branch point, with 2'-5' and 3'-5' phosphodiester bonds emanating from a single adenosine residue. The excised intervening sequence retains the branch site and terminates in a guanosine residue with a 3' hydroxyl group. The phosphate group at the splice junction between the two exons originates from the 3' splice site at the precursor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Padgett, R A -- Konarska, M M -- Grabowski, P J -- Hardy, S F -- Sharp, P A -- P01-CA14051/CA/NCI NIH HHS/ -- P01-CA26717/CA/NCI NIH HHS/ -- R01-GM32467/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):898-903.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6206566" target="_blank"〉PubMed〈/a〉
    Keywords: Adenoviruses, Human/metabolism ; Base Sequence ; Chemical Phenomena ; Chemistry ; Nucleic Acid Conformation ; Nucleic Acid Precursors/analysis/*metabolism ; Oligoribonucleotides/metabolism ; Phosphates/metabolism ; RNA/analysis/*metabolism ; RNA Precursors ; *RNA Splicing ; RNA, Messenger/analysis/*metabolism ; RNA, Viral/analysis/*metabolism
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    beta-Carotene: an unusual type of lipid antioxidant (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-05-11
    Description: The mechanism of lipid peroxidation and the manner in which antioxidants function is reviewed. beta-Carotene is a purported anticancer agent, which is believed by some to have antioxidant action of a radical-trapping type. However, definitive experimental support for such action has been lacking. New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants. Specifically, it exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air. Such low oxygen partial pressures are found in most tissues under physiological conditions. At higher oxygen pressures, beta-carotene loses its antioxidant activity and shows an autocatalytic, prooxidant effect, particularly at relatively high concentrations. Similar oxygen-pressure-dependent behavior may be shown by other compounds containing many conjugated double bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burton, G W -- Ingold, K U -- New York, N.Y. -- Science. 1984 May 11;224(4649):569-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6710156" target="_blank"〉PubMed〈/a〉
    Keywords: Antioxidants/*metabolism ; Carotenoids/*metabolism ; Chemical Phenomena ; Chemistry ; Free Radicals ; Humans ; Linoleic Acids/metabolism ; *Lipid Metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Partial Pressure ; Peroxides/metabolism ; Tetrahydronaphthalenes/metabolism ; beta Carotene
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    Bromine residue at hydrophilic region influences biological activity of aplysiatoxin, a tumor promoter (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-12-16
    Description: Aplysiatoxin and debromoaplysiatoxin, which are isolated from the seaweed, Lyngbya gracilis, differ in their chemical structure only by the presence or absence of a bromine residue in the hydrophilic region. The function and the structure-activity relation of the hydrophilic region are not known. Aplysiatoxin increased malignant transformation, stimulated DNA synthesis, and inhibited the binding of phorbol-12,13-dibutyrate and epidermal growth factor to cell receptors. Debromoaplysiatoxin inhibited the binding of these two substances as strongly as aplysiatoxin but did not increase malignant transformation or stimulate DNA synthesis. These results indicate that a slight change in the chemical structure of the hydrophilic region of aplysiatoxin affects its abilities to increase cell transformation and stimulate DNA synthesis and that the abilities of the tumor promoters to inhibit the binding of phorbol-12,13-dibutyrate and epidermal growth factor are dissociable from their abilities to increase cell transformation and stimulate DNA synthesis under some circumstances.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shimomura, K -- Mullinix, M G -- Kakunaga, T -- Fujiki, H -- Sugimura, T -- New York, N.Y. -- Science. 1983 Dec 16;222(4629):1242-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6316505" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Caenorhabditis elegans Proteins ; Carcinogens/*pharmacology ; Carrier Proteins ; Cell Line ; Cell Transformation, Neoplastic/*drug effects ; Chemical Phenomena ; Chemistry ; DNA/biosynthesis ; Epidermal Growth Factor/metabolism ; Lactones/analysis/*pharmacology ; *Lyngbya Toxins ; Mice ; Phorbol 12,13-Dibutyrate ; Phorbol Esters/metabolism ; *Protein Kinase C ; Receptor, Epidermal Growth Factor ; Receptors, Cell Surface/metabolism ; *Receptors, Drug ; Structure-Activity Relationship
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    Phenylalanine transfer RNA: molecular dynamics simulation (1984)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1984-03-16
    Description: Yeast phenylalanine transfer RNA was subjected to a 12-picosecond molecular dynamics simulation. The principal features of the x-ray crystallographic analysis are reproduced, and the amplitudes of atomic displacements appear to be determined by the degree of exposure of the atoms. An analysis of the hydrogen bonds shows a correlation between the average length of a bond and the fluctuation in that length and reveals a rocking motion of bases in Watson-Crick guanine X cytosine base pairs. The in-plane motions of the bases are generally of larger amplitude than the out-of-plane motions, and there are correlations in the motions of adjacent bases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey, S C -- Prabhakaran, M -- Mao, B -- McCammon, J A -- New York, N.Y. -- Science. 1984 Mar 16;223(4641):1189-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6560785" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Computers ; Cytosine ; Guanine ; Hydrogen Bonding ; Nucleic Acid Conformation ; *RNA, Fungal ; *RNA, Transfer, Amino Acyl ; Yeasts/analysis
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    Reaction of the antitumor antibiotic CC-1065 with DNA: structure of a DNA adduct with DNA sequence specificity (1984)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1984-11-16
    Description: Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hurley, L H -- Reynolds, V L -- Swenson, D H -- Petzold, G L -- Scahill, T A -- New York, N.Y. -- Science. 1984 Nov 16;226(4676):843-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6494915" target="_blank"〉PubMed〈/a〉
    Keywords: Antibiotics, Antineoplastic/*metabolism ; *Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/*metabolism ; *Indoles ; Leucomycins/*metabolism ; Molecular Conformation ; X-Ray Diffraction
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    Allylamine derivatives: new class of synthetic antifungal agents inhibiting fungal squalene epoxidase (1984)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1984-06-15
    Description: A new class of synthetic antifungal agents, the allylamines , has been developed by modification of naftifine , a topical antimycotic. SF 86-327, the most effective of these compounds so far, is highly active in vitro against a wide range of fungi and exceeds clinical standards in the oral and topical treatment of guinea pig dermatophytoses. SF 86-327 is a powerful specific inhibitor of fungal squalene epoxidase, a key enzyme in sterol biosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petranyi, G -- Ryder, N S -- Stutz, A -- New York, N.Y. -- Science. 1984 Jun 15;224(4654):1239-41.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6547247" target="_blank"〉PubMed〈/a〉
    Keywords: Allylamine/analogs & derivatives/*chemical synthesis/pharmacology ; Amines/*chemical synthesis ; Animals ; Antifungal Agents/*chemical synthesis/pharmacology ; Chemical Phenomena ; Chemistry ; Dermatomycoses/drug therapy ; Fungi/*drug effects/enzymology ; Guinea Pigs ; Naphthalenes/chemical synthesis/pharmacology ; Oxygenases/*antagonists & inhibitors ; Squalene Monooxygenase
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    Disulfide bond engineered into T4 lysozyme: stabilization of the protein toward thermal inactivation (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-11-02
    Description: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perry, L J -- Wetzel, R -- New York, N.Y. -- Science. 1984 Nov 2;226(4674):555-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6387910" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; DNA, Recombinant/metabolism ; Escherichia coli/enzymology ; *Genetic Engineering ; Kinetics ; Muramidase/*genetics/metabolism ; Protein Denaturation
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    DNA-binding proteins (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-09-09
    Description: The structures of three proteins that regulate gene expression have been determined recently and suggest how these proteins may bind to their specific recognition sites on the DNA. One protein (Cro) is a repressor of gene expression, the second (CAP) usually stimulates gene expression, and the third (lambda repressor) can act as either a repressor or an activator. The three proteins contain a substructure consisting of two consecutive alpha helices that is virtually identical in each case. Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event. The modes of repression and activation by Cro and lambda repressor are understood reasonably well, but the mode of action of CAP is still unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Takeda, Y -- Ohlendorf, D H -- Anderson, W F -- Matthews, B W -- GM20066/GM/NIGMS NIH HHS/ -- GM28138/GM/NIGMS NIH HHS/ -- GM30894/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 Sep 9;221(4615):1020-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6308768" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; *DNA Helicases ; DNA-Binding Proteins ; Escherichia coli/genetics ; Gene Expression Regulation ; Models, Chemical ; Protein Conformation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 36
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    A nitrogen pressure of 50 atmospheres does not prevent evolution of hydrogen by nitrogenase (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-06-08
    Description: The effect of a partial pressure of nitrogen of 50 atmospheres (5065 kilopascals ) on the hydrogen evolution reaction of nitrogenase has been investigated. Evolution of hydrogen was not blocked completely by 50 atmospheres of nitrogen in any of four experiments; rather, 27.3 +/- 2.4 percent of the total electron flux through nitrogenase was directed toward production of hydrogen. The ratio of hydrogen evolved to nitrogen fixed was close to 1:1, which implies that hydrogen evolution is obligatory in the fixation of molecular nitrogen by nitrogenase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, F B -- Burris, R H -- AI-00848/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1984 Jun 8;224(4653):1095-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6585956" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen ; *Nitrogen ; Nitrogen Fixation ; *Nitrogenase ; Partial Pressure
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Antiviral agents (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-06-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krenitsky, T A -- Beauchamp, L -- New York, N.Y. -- Science. 1983 Jun 10;220(4602):1106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6857236" target="_blank"〉PubMed〈/a〉
    Keywords: Acyclovir/metabolism ; *Antiviral Agents/metabolism ; Chemical Phenomena ; Chemistry ; Humans ; Vidarabine/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 38
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    Metastable species of hemoglobin: room temperature transients and cryogenically trapped intermediates (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-05-06
    Description: Resonance Raman spectra of photolyzed carbonmonoxyhemoglobin obtained with 10-nanosecond pulses are compared with the spectra of photolyzed carbonmonoxyhemoglobin stabilized at 80 K. In comparing the deoxy with the photodissociated species, the changes in the Raman spectra are the same for these two experimental regimes. These results show that at ambient and cryogenic temperatures the heme pocket in liganded hemoglobin is significantly different from that of deoxyhemoglobin. It is concluded that measurements of the properties of intermediate species from photodissociated hemoglobin stabilized at low temperatures can be used to probe the short-lived metastable forms of hemoglobin present after photodissociation under biologically relevant solution conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ondrias, M R -- Friedman, J M -- Rousseau, D L -- New York, N.Y. -- Science. 1983 May 6;220(4597):615-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836305" target="_blank"〉PubMed〈/a〉
    Keywords: Carboxyhemoglobin ; Chemical Phenomena ; Chemistry ; Freezing ; *Hemoglobins ; Humans ; Ligands ; Spectrum Analysis, Raman ; Temperature
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 39
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    Irreversible ligands with high selectivity toward delta and mu opiate receptors (1983)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1983-04-15
    Description: Alkylating agents that display strong selectivity for opiate receptor types delta or mu were prepared by appropriate modification of the structures of the strong analgesics fentanyl, etonitazene, and endoethenotetrahydrooripavine. The availability of these substances should facilitate studies of the structural basis of receptor specificity and of the physiologic roles of these receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rice, K C -- Jacobson, A E -- Burke, T R Jr -- Bajwa, B S -- Streaty, R A -- Klee, W A -- New York, N.Y. -- Science. 1983 Apr 15;220(4594):314-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6132444" target="_blank"〉PubMed〈/a〉
    Keywords: Alkylation ; Animals ; Benzimidazoles/analogs & derivatives/metabolism ; Brain/physiology ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Enkephalin, Methionine/analogs & derivatives/metabolism ; Fentanyl/analogs & derivatives/metabolism ; *Isothiocyanates ; Ligands ; Rats ; Receptors, Opioid/*metabolism/physiology ; Thebaine/analogs & derivatives/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 40
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    Synthetic competitive antagonists of corticotropin-releasing factor: effect on ACTH secretion in the rat (1984)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1984-05-25
    Description: Polypeptide analogs of the known members of the corticotropin-releasing factor (CRF) family were synthesized and tested in vitro and in vivo for enhanced potency or competitive antagonism. Predictive methods and physicochemical measurements had suggested an internal secondary alpha-helical conformation spanning about 25 residues for at least three members of the CRF family. Maximization of alpha-helix-forming potential by amino acid substitutions from the native known sequences (rat/human and ovine CRF, sauvagine, and carp and sucker urotensin 1) led to the synthesis of an analog that was found to be more than twice as potent as either of the parent peptides in vitro. In contrast, certain amino-terminally shortened fragments, such as alpha-helical CRF or ovine CRF residues 8 to 41, 9 to 41, and 10 to 41, were found to be competitive inhibitors in vitro. Selected antagonists were examined and also found to be active in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rivier, J -- Rivier, C -- Vale, W -- AA03504/AA/NIAAA NIH HHS/ -- AM20917/AM/NIADDK NIH HHS/ -- AM26741/AM/NIADDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1984 May 25;224(4651):889-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6326264" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/secretion ; Animals ; Binding, Competitive ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone/*antagonists & inhibitors ; Rats
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    [Editors' Choice] A clean combination of CO and amines (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-11-25
    Description: Author: Jake Yeston
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    [Perspective] Ammonia activation at a metal (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-11-11
    Description: Although ammonia (NH3) is made on a vast scale for use in fertilizers, its use as a chemical feedstock or as an energy carrier is much more limited. Many reactions that occur easily with its substitution products (amines) are sluggish for NH3, in part because of the difficulty of activating the N-H bond. For fuel cells, NH3 is attractive because it does not generate greenhouse gases, as do methanol and methane (1), and is more easily stored than hydrogen (H2). Amine-containing organic molecules are used in pharmaceutical and materials applications, and accessing these structures directly from ammonia could limit the generation of by-products during their synthesis (2). Bringing NH3 up to speed for these applications will require both the development of catalysts that can activate the strong N–H bond of ammonia and a fundamental understanding of the N–H bond cleavage step. On page 730 of this issue, Bezdek et al. (3) report a molybdenum complex capable of weakening the N–H bond of NH3 and releasing a H atom to generate H2 under mild conditions. Author: Jessica Hoover
    Keywords: Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    Enantioselective cyanation of benzylic C-H bonds via copper-catalyzed radical relay (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-09-02
    Description: Direct methods for stereoselective functionalization of sp 3 -hybridized carbon–hydrogen [C(sp 3 )–H] bonds in complex organic molecules could facilitate much more efficient preparation of therapeutics and agrochemicals. Here, we report a copper-catalyzed radical relay pathway for enantioselective conversion of benzylic C–H bonds into benzylic nitriles. Hydrogen-atom abstraction affords an achiral benzylic radical that undergoes asymmetric C(sp 3 )–CN bond formation upon reaction with a chiral copper catalyst. The reactions proceed efficiently at room temperature with the benzylic substrate as limiting reagent, exhibit broad substrate scope with high enantioselectivity (typically 90 to 99% enantiomeric excess), and afford products that are key precursors to important bioactive molecules. Mechanistic studies provide evidence for diffusible organic radicals and highlight the difference between these reactions and C–H oxidations mediated by enzymes and other catalysts that operate via radical rebound pathways.
    Keywords: Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    A highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-09-02
    Description: Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrO x /SrIrO 3 ) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO 3 . This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidic electrolyte. Density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO 3 or anatase IrO 2 motifs. The IrO x /SrIrO 3 catalyst outperforms known IrO x and ruthenium oxide (RuO x ) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte.
    Keywords: Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    [This Week in Science] Cooperation between frustrated partners (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-12-09
    Description: Author: Jake Yeston
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 46
    Electronic Resource
    Electronic Resource
    Three-dimensional imaging and image analysis of hippocampal neurons: Confocal and digitally enhanced wide field microscopy (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 269-278 
    Details
    ISSN: 1059-910X
    Keywords: Three-dimensional light microscopy ; Brain slices ; Neurobiology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The microscopy of biological specimens has traditionally been a two-dimensional imaging method for analyzing what are in reality three-dimensional (3-D) objects. This has been a major limitation of the application of one of science's most widely used tools. Nowhere has this limitation been more acute than in neurobiology, which is dominated by the necessity of understanding both large-and small-scale 3-D anatomy. Fortunately, recent advances in optical instrumentation and computational methods have provided the means for retrieving the third dimension, making full 3-D microscopic imaging possible. Optical designs have concentrated on the confocal imaging mode while computational methods have made 3-D imaging possible with wide field microscopes using deconvolution methods. This work presents a brief review of these methods, especially as applied to neurobiology, and data using both approaches. Specimens several hundred micrometers thick can be sampled allowing essentially intact neurons to be imaged. These neurons Image analysis in 3-D is as important as visualization in 3-D. Automated methods of cell counting and analysis by nuclear detection as well as tracing of individual neurons are presented. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290403
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  • 47
    Electronic Resource
    Electronic Resource
    Confocal imaging of dendritic Ca2+ transients in hippocampal brain slices during simultaneous current- and voltage-clamp recording (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 279-289 
    Details
    ISSN: 1059-910X
    Keywords: Fluorescence microscopy ; Ca channels ; Pyramidal neurons ; CA1 region ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Changes in the intracellular Ca2+ concentration ([Ca2+]i) within CA1 hippocampal pyramidal neurons were imaged using confocal laser scanning microscopy in conjunction with Ca2+ -sensitive fluorescent indicators. The imaging was performed in thick hippocampal brain slices while simultaneously measuring or controlling electrical activity with sharp microelectrodes or whole-cell patch-clamp electrodes. The combination of imaging and electrophysiology was essential for interpreting the changes in [Ca2+]i. We compared the increases in [Ca2+]i produced by either of two methods-direct depolarization of the cell via the somatic electrode or high-frequency stimulations of synaptic inputs. The increases in [Ca2+]i in the soma and proximal dendrites caused by both methods were of comparable magnitude and they always decayed within seconds in healthy cells. However, the spatial patterns of distal Ca2+ increases were different. Separate sets of synaptic inputs to the same cell resulted in different spatial patterns of [Ca2+]i transients. We isolated and observed what appeared to be a voltage-independent component of the synaptically mediated [Ca2+]i transients. This work demonstrates that the combination of neurophysiology and simultaneous confocal microscopy is well suited for visualizing and analyzing [Ca2+]i within neurons throughout the CNS and it raises the possibility of routinely relating subcellular [Ca2+]i changes to structural and functional modifications. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290404
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  • 48
    Electronic Resource
    Electronic Resource
    Synaptic morphology of substance P terminals on catecholamine neurons in the commissural subnucleus of the nucleus tractus solitarii in the rat (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 177-183 
    Details
    ISSN: 1059-910X
    Keywords: Sinus afferent pathway ; SP interneurons ; Double immunocytochemistry ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The ultrastructure of substance P-containing nerve terminals synapsing on catecholamine neurons in the rat commissural subnucleus of the nucleus tractus solitarii (NTScom) was studied using a double immunocytochemical labeling technique. Although there were numerous tyrosine hydroxylase-immunoreactive (TH-I) somata present, substance P immunoreactive (SP-I) cell bodies were only occasionally found in the NTScom. At the light microscopic level, many SP-I terminals were seen closely associated with TH-I dendrites and somata. At the electron microscopic level, SP-I terminals synapsing on TH-I structures were also readily encountered. SP-I terminals contained small, clear, and predominantly spherical vesicles (32 ± 4 nm diameter), as well as large dense-cored vesicles approximately 100 nm in diameter. Postsynaptic TH-I dendritic profiles of various calibers and somata were encountered. These postsynaptic TH-I structures often showed postsynaptic densities. The morphological features of the SP-TH synapses in the present study, that is, the size of synaptic vesicles and the presence of postsynaptic densities, are quite different from those of central carotid sinus afferent synapses reported in our previous study [Chen et al. (1992), J. Neurocytol., 21:137-147]. Therefore, most of the SP terminals of the SP-TH synapses in the NTScom appear not to originate from the carotid sinus afferents. SP-I second-order neurons of the carotid sinus afferent pathway [Chen et al. (1991), J. Auton. Nerv. Syst., 33:97-98] may be one of the possible sources of such terminals. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290216
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  • 49
    Electronic Resource
    Electronic Resource
    Localizing sites of intradendritic electrophysiological recordings by confocal light microscopy (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 310-318 
    Details
    ISSN: 1059-910X
    Keywords: Hippocampus ; Dendrites ; 3-D imaging ; Pyramidal cell ; Neurophysiology ; Confocal microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Studies were undertaken to develop microscopic methods and imaging procedures that would permit identification of sites of intradendritic microelectrode recordings from pyramidal cells in hippocampal slice preparations. Intradendritic recording were obtained with sharp microelectrodes filled with the dye lucifer yellow. Following a recording session a neuron was iontophoretically injected with the dye and imaged by fluorescence videomicroscopy. Images were stored on videotape for later analysis. They provided a record of the location of the microelectrode recording site. After withdrawal of the microelectrode, slices were processed histologically and imaged a second time with a Bio-Rad 600 confocal attachment on an Olympus BH-2 microscope. Confocal images provided detailed anatomical information in three dimensions. In most instances, a clear identification of the recording site was achieved by comparing video images containing the recording electrode and confocal images.Neurophysiological recordings obtained from proximal and distal apical dendrites were markedly different. Proximal dendritic recordings were similar to those obtained from pyramidal cell soma. However, distal dendrites were not electroresponsive when depolarized by intracellular current injection. The techniques described here, or variations that employ patch electrodes, could provide valuable information that should further an understanding of the properties of dendrites in the central nervous system. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/jemt.1070290408
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  • 50
    Electronic Resource
    Electronic Resource
    Construction and analysis of a database representing a neural map (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 329-343 
    Details
    ISSN: 1059-910X
    Keywords: Sensory map ; Neural map ; Mechanosensory afferents ; Database ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We describe the development and analysis of a quantitative database representing the global structural and functional organization of an entire sensory map. The database was derived from measurements of anatomical characteristics of a statistical sample of typical mechanosensory afferents in the cricket cercal sensory system. Anatomical characteristics of the neurons were measured quantitatively in three dimensions using a computer reconstruction system. The reconstructions of all neurons were aligned and scaled to a common standard set of dimensions, according to a highly reproducible set of intrinsic fiducial marks. The database therefore preserves accurate information about spatial relationships between the neurons within the ensemble.Algorithms were implemented to allow the integration of electrophysiological data about the stimulus/response characteristics of the reconstructed neurons into the database. The algorithms essentially map a physiological function onto a “field” representing the continuous distribution of synaptic terminals throughout the neural structure. Subsequent analysis allowed quantitative predictions of several important functional characteristics of the sensory map that emerge from its global organization. First, quantitative and testable predictions were made about ensemble response patterns within the map. The predicted patterns are presented as graphical images, similar to images that might be observed with activity-dependent dyes in the real neural system. Second, the synaptic innervation patterns from the sensory afferent map onto the dendrites of a postsynaptic target interneuron were predicted by calculating the overlap between the interneuron's dendrites with the afferent map. By doing so, several aspects of the stimulus/response properties of the interneuron were accurately predicted. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290502
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  • 51
    Electronic Resource
    Electronic Resource
    Hyaluronate distribution in the regenerating retinal pigment epithelium of the rabbit: A study using confocal laser scanning microscopy (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 344-349 
    Details
    ISSN: 1059-910X
    Keywords: Epithelium ; Eye ; Hyaluronate ; Microscopy ; Rabbit ; Regeneration ; Retina ; Sodium iodate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The distribution of hyaluronate (HA) in regenerating retinal pigment epithelium (RPE) of the rabbit was examined using immunohistochemistry and confocal laser scanning microscopy. The goal was to determine if there is a correlation between differentiation and HA expression, like that seen in developing tissues, where HA accumulates and then disappears as the tissue matures. In normal RPE cells HA is associated mainly with the apical surface. In regenerating RPE (produced by i.v. injection of sodium iodate to damage the epithelium, regeneration arising from spared cells), HA exhibits a patchy distribution among the more immature cells and is especially prominent where they overlap or pile up on each other. Where cells are more mature and form a compact monolayer of cells, HA is expressed mainly on the apical surface, as in normal RPE. The accumulation of HA among the more immature cells in the regenerating epithelial sheet supports the hypothesis that HA influences differentiation by suppressing cell-cell associations until the proper time for their formation. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/jemt.1070290503
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  • 52
    Electronic Resource
    Electronic Resource
    Color figure section (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. C1 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290504
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  • 53
    Electronic Resource
    Electronic Resource
    The radioactivity of X-ray contrast material in PMMA bone cement (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 215-216 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Various x-ray contrast materials, barium sulphate (BaSO4) and zirconium oxide (ZrO2), were tested for their radioactivity by means of a gamma spectrometer. While BaSO4 showed no detectable radiation emission, the ZrO2 materials of various makes showed slight to partially high radioactive emission. From all zirconium oxides, only the pharmaceutic agent OPTIPUR® (MERCK) showed no detectable radioactivity. Taking into account that these x-ray contrast materials remain in the body for decades as components of the bone cement, it would seem prudent to urge cement manufacturers to substitute high purity radiation-free zirconium in place of radioactive zirconium oxide.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/jab.770010303
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  • 54
    Electronic Resource
    Electronic Resource
    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994) 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050101
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    Metallic wear debris in metal-backed patellar failure (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 9-16 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Eight patients with failure of metal-backed patellar components were studied for evidence of intraarticular and systemic metal deposition. Seven of the eight patients had failure of a titanium-based patellar component that then articulated with a cobaltchromium femoral component. One patient had articulation of a cobalt-chromium patellar component against a cobalt-chromium femoral component. All components failed by the same pattern of failure. Wearing of the ultra high molecular weight polyethylene was followed by displacement of the polyethylene and then metal-to-metal contact of the components.Methods for analysis of the debris included light and electron microscopy of synovial tissue and electron dispersive x-ray analysis (EDAX) of tissue. Graphite furnace atomic absorption spectroscopy (GFAAS) was done on synovial fluid and synovial tissue as well as urine and blood specimens taken at various times from implantation to patellar revision.Massive deposition of metallic debris within the knee joint was documented both histologically and by GFAAS. Titanium levels reached as high as 2776 ppm (mg/L) in the synovial fluid and as high as 917 mg/g of synovial tissue. Elevation of all the pertinent metals was seen in the tissue and body fluids. Titanium and aluminum levels were the highest. Titanium levels in the serum generally were highest near the time of implant failure. Other metal elevations were variable and could not be related to the time of failure. Synovial fluid levels of all metals and serum levels of titanium are reflective of intraarticular generation of metallic debris.This study demonstrates that in situations of failure of a device, massive intraarticular debris generation occurs and systemic transport will occur. To date no systemic consequences can be attributed to the deposition of debris and follow-up urine and blood specimens suggest that debridement and revision of the failed device results in lowering of the ion levels. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050103
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    Characterization of polyesterurethane degradation products (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 1-7 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Microthane foam, a poly(ester)urethane, used as a covering of some breast implants (Meme or Replicon by Surgitek) degrades readily in phosphate buffer pH 7.4 producing multiple unknown products in addition to 2,4 and 2,6 toluenediamine (TDA). The cumulative weight loss of the foam in buffer was 1.5% at 1 week and 2% at 2 weeks. Multiple peak molecular weights from 105 to 665 000 were found in the aqueous foam extracts following 2 weeks of incubation at 37°C using size exclusion chromatography (SEC). TDA was measured in the foam buffer extracts by high pressure liquid chromatography (HPLC) and confirmed by gas chromatography/mass spectroscopy (GC/MS). The total cumulative levels of 2,4 TDA and 2,6 TDA measured were 3 ± 0.65 μg/g of foam and 1.13 ± 0.19 μg/g of foam following 36 days of incubation at 37 °C. Higher amounts, 8.96 μg/g of 2,4 TDA and 3.3 μg/g of 2,6 TDA, were obtained at 50 °C. The cumulative release of TDA in aqueous extracts was found to correlate linearly with time suggesting a slow but continuous production of TDA under neutral conditions. However, less than 0.2 μg/g of TDA was detected as residual TDA in the methylene chloride extracts following up to 60 days at 37 °C. PU foam extracted with methylene chloride under similar conditions showed higher foam weight loss, 4.4 and 5% at 1 and 2 weeks, respectively. The results presented in this study provide further evidence that Microthane undergoes hydrolysis under neutral conditions in aqueous solutions producing TDA and other unknown low molecular weight components and oligomers. © 1994 John Wiley & Sons, Inc.
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    Chemical and mechanical degradation of UHMWPE: Report of the development of an in vitro test (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 17-21 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ultra high molecular weight polyethylene (UHMWPE), used in total joint replacement implants, undergoes oxidative degradation due to gamma radiation sterilization and to exposure to oxidizing agents in the body environment. UHMWPE components also experience large stresses both on and near the articulating surface. It is hypothesized that there is a causal relationship between chemical degradation and mechanical loading of UHMWPE joint components. This report describes the development of an in vitro test to examine the combined effects of chemical environment and cyclic loading history on the chemical, physical, and mechanical properties of UHMWPE. The test apparatus consists of modular load trains, in which strings of UHMWPE test specimens can be subjected to cyclic tensile and compression load ranges, while being exposed to either control or degrading environments. Following cyclic loading for specified time intervals, the specimens can be statically loaded to determine the effect of cyclic loading and environment on the monotonic tensile and compressive stress-strain behavior of UHMWPE. To determine the appropriate control and degrading environments, gamma radiation sterilized UHMWPE specimens were maintained (unloaded) for up to 6 months in aqueous environments of distilled water and three concentrations of hydrogen peroxide (0.01, 0.1, and 1.0%) in distilled water at 37°C. Specimens were evaluated with depth from the surface for changes in density. Infrared spectroscopy (IR) analysis was conducted on selected surface sections. No significant changes in density or surface IR spectra occurred for specimens in distilled water as compared with the UHMWPE in the initial radiation sterilized condition. Specimens exposed to hydrogen peroxide solutions demonstrated changes in density and IR spectra consistent with oxidative degradation and comparable to the changes previously observed on retrieved UHMWPE components. Based on these results, distilled water was selected for the control environment. A 0.5% hydrogen peroxide solution was selected for the test environment, to produce moderate changes at a rate compatible with the maximum 12-month time period of the experiment. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050104
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    A method for transmission electron microscopy investigation of the osteoblast/hydroxyapatite interface (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 39-45 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Neonatal rat calvaria osteoblasts were cultured on hydroxyapatite (as received or relatively-rough surface and mechanically polished to a 0.3-m̈m finish) and on glass (reference material) in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, 50 μg/mL ascorbic acid, and 10 mM β-glycerophosphate under standard, sterile, cell-culture conditions for 1, 3, 7, 14 and 21 days. At the end of the prescribed time periods, the cells were fixed and embedded in resin before removing the material substrates by exposure to acid solutions. Transmission electron microscopic examination of stained, ultrathin sections of the biological structures revealed osteoblast monolayers at 1 day of culture but multilayered cell structures at later time periods (14 and 21 days). The osteoblasts exhibited continuous contact and intimate apposition on polished hydroxyapatite and on glass; in contrast, osteoblasts on as received or rough hydroxyapatite made contact with discrete high points, spanned low regions of the material surface, and did not conform to all substrate contours. An electron dense layer (composed of mucopolysaccharides and proteins) was observed on all substrates tested after 7 days of culture. Collagen fibrils were seen interspersed among the osteoblasts as early as 3 days of culture; at later culture times, (i.e., 21 days) mineralized loci were observed in the extracellular matrix. © 1994 John Wiley & Sons, Inc.
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    Behaviour of endothelial cells cultured in the presence of polymers impregnated with adsorbable proteins (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 47-50 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study is the in vitro evaluation of the functional modifications of human endothelial cells in the presence of Dacron® impregnated with resorbable proteins. For this purpose, human endothelial cells isolated from the umbilical vein have been put in contact for 48 h with knitted Dacron® impregnated with collagen or gelatin and with nonimpregnated knitted Dacron® and double velour Dacron®. As control, endothelial cells cultured in the absence of material were used. After the contact time, cell counts were performed. In addition, the concentrations of two proteins synthesized by endothelium, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1), were evaluated on the supernatants. In the cultures in contact with Dacron® impregnated with collagen or gelatin and in those in contact with knitted Dacron®, we have observed a smaller cell growth than that observed in cultures without materials. The synthesis of t-PA showed some significant variations between the control cultures and those in contact with the materials. PAI-1 production was significantly reduced in the cultures in contact with gelatin impregnated Dacron® and with knitted Dacron®. Double velour Dacron® caused no significant variation in any of the examined parameters. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050107
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    A new technique for quantitation of metal particulates and metal reaction products in tissues near implants (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 191-193 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue specimens retrieved from four regions adjacent to hip implants during revision surgery were subjected to a novel treatment to make possible the quantitative separation of residual metal particulates and metal reaction products (metal ions and metal-protein complexes). The tissues were exposed to sodium hypochlorite solution that degraded and solubilized them, liberating metal reaction products and leaving behind metal wear particles, which were separated by centrifugation. Atomic absorption spectrophotometry was used to analyze the concentrations of the separated metal ions and wear particles. Co ion concentrations were 0.05 to 0.9 mM, Cr ion concentrations were 0.04 to 2.1 mM, and Ti ion concentrations were 0.30 to 0.60 mM. The weight of Co metal particles was 0.1 to 4.9 mg/100 mg tissue, of Cr metal particles 0.07 to 2.2 mg/100 mg tissue, and of Ti particles 0.09 to 5.2 mg/100 mg tissue; one black tissue sample contained 3333 mg Ti/100 mg tissue. No correlation was found between the concentrations of these two entities in the samples examined, probably due to the complex and varied processes creating them. The procedures discussed here will result in data that can help elucidate the separate contributions of metal reaction products and metal particulates to implant loosening. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/jab.770050303
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    Fatigue behavior of a titanium femoral hip prosthesis with proximal sleeve-stem modularity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 195-201 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Modular hip prostheses are increasing in variety and utilization. Component stability, high endurance limit, and minimal particulate debris generation are critical for long-term clinical success. The purpose of this study was to characterize the fatigue response and evaluate the in vitro potential for component motion and wear of the S-ROMTM, a Ti-6Al-4V hip prosthesis with a modular design based on a Morse taper connection. A fatigue jig was desiged to simulate fixation of the device at the sleeve-bone interface only with distal support mainly against the lateral endosteal cortex. Two series of tests were performed in air at room temperature: one with direct vertical loading (to produce high bending moments in the coronal plane) and one with a compound loading angle directed at 15° out-of-plane (to include torsional physiological loads). Applied loads using a servohydraulic test machine ranged from 5 × BW (body weight) to 9 × BW (1 × BW = 73 kg, ≈ 160 lb) at 10 Hz on an Instron apparatus. No mechanical failures were observed on the 11-mm size stems below 6 × BW for in-plane vertical loading, and at or below 7 × BW for out-of-plane loading. Using displacement monitoring with a sensitivity of 35 μm, no measurable slippage or relative motion was detected between the stem and sleeve when they were properly assembled. Examination of the contact areas with scanning electron microscopy revealed random surface modification (an indication of fretting or burnishing) with occasional evidence of transfer of material between stem and sleeve. At loads under 7 × BW there was no visual evidence of loose wear debris in the presence of gross stability. Overall, the extent of surface change or wear was relatively small in all components tested at physiological load levels. © 1994 John Wiley & Sons, Inc.
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    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994) 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050201
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    FEM analysis of stress and deformation in the vicinities of arterial graft anastomosisThis work was performed at the Department of Biomedical Control, Research Institute of Applied Electricity, Hokkaido University, Sapporo, Japan. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 79-87 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Effects of compliance mismatch at end-to-end artery/graft anastomoses on the distributions of wall stresses and compliance were studied using the finite element method. The canine common carotid artery (CCA), and expanded polytetrafluoro-ethylene (EPTFE) thin-walled graft, and a newly developed polyurethane graft (HS-2) were used as the models for the host artery, stiff graft, and compliant graft, respectively. Mechanical properties of CCA and HS-2 were determined from a pressure-diameter test, those of EPTFE graft were obtained by tensile test. Nonlinear elasticity of CCA and HS-2 was incorporated by iterating a linear FEM analysis: elastic moduli of the vessel walls were changed every 5 mmHg. The results showed that, in the case of the artery/EPTFE anastomosis in which the diameters of the artery and the graft were matched at 0 mmHg, regions of high tensile and shear stresses appeared in the graft near the anastomosis at the intraluminal pressure of 100 mmHg. The stress concentrations were remarkable, even if the diameters were matched at 100 mmHg and the pressure was varied within a physiological range (60-140 mmHg). Moreover, a hypercompliant zone appeared in the arterial wall near the anastomosis in this case. On the other hand, neither high stress concentrations nor hypercompliant zone appeared near the artery/HS-2 anastomosis. Because the mechanical complications at the compliance-mismatched anastomosis might finally result in graft failure and occlusion, it is important to match the compliance of graft to that of natural arteries, particularly to improve the patency of small-calibered arterial grafts. © 1994 John Wiley & Sons, Inc.
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    Technical note. Symmetry of biomechanical properties in canine femora (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 99-101 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770050112
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    Physical properties of hyaluronic acid and hydroxypropylmethylcellulose in solution: Evaluation of coating ability (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 89-98 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hyaluronic acid (HA) and hydroxypropylmethylcellulose (HPMC) in buffered saline are “viscoelastics” used in ophthalmic surgery to prevent mechanical damage to delicate eye structures and to form a protective coating over corneal endothelium.HA is a high molecular weight polysaccharide that exhibits decreasing viscosity at increased shear rates. HPMC is a cellulose derivative that exhibits low surface tension. This study examines the physical properties of HA and HPMC solutions and attempts to correlate these properties with the ability of those macromolecules to coat and protect ocular structures.Results presented in this article suggest mixtures of HA and HPMC exhibit low surface tension and ease of aspiration characteristics that are desired in viscoelastic materials. For this reason a blend of these two macromoleculars offers handling advantages over each of these individual macromolecules. © 1994 John Wiley & Sons, Inc.
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    Effects of metallic debris on adult bovine articular chondrocyte metabolism in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 109-115 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to examine the effects of particles, derived from metals commonly used in joint prostheses, on chondrocyte proliferation, metabolism, and morphology in vitro. Chondrocyte viability was influenced by the type and concentration of metal particle added. Cobalt was toxic to chondrocytes at all particle concentrations (0.83-0.000083%, v/v), whereas the chromium, titanium and titanium-aluminum particles only effected chondrocyte viability at high concentrations. The metabolic response of chondrocytes to particulate debris as assessed by caseinase, collagenase, and hexosaminidase activities were variable at low concentrations but were always reduced at high concentrations (0.83% v/v). Prostaglandin E2 levels in the medium showed a steady increase when particle load increased, except in the medium of chondrocytes exposed to titanium-aluminum. Scanning electron microscopy of chondrocytes exposed to titanium showed ruffled cell borders and frequent membrane blebbings. This was in contrast to chondrocytes exposed to cobalt, where the crenated appearance indicated cell death, and titanium-aluminum, where the cells appeared quiescent. These findings show that metal particles alter chondrocyte viability and metabolism and suggest that particulate debris may influence the integrity and stability of articular cartilage following hemiarthroplasty. © 1994 John Wiley & Sons, Inc.
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    Patterns of intercellular connectivity in the mammalian cumulus-oocyte complex (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 125-133 
    Details
    ISSN: 1059-910X
    Keywords: Follicle cell ; Cumulus-oocyte-complex ; Transzonal processes ; Tubulin ; Actin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Electron and fluorescence microscopic techniques have been used in a complementary fashion to study the patterns of follicle cell-oocyte interactions within cumulus-oocyte-complexes of various mammals. The principal findings are: (1) two distinct types of transzonal processes exist that are distinguishable on the basis of cytoskeletal composition; (2) in some of the species examined (pig, goat, primate), corkscrew-shaped processes rich in tubulin, traverse the zona pellucida and are invaginated into the oocyte cortex; (3) actin-rich processes either ramify as a network at the outer surface of the zona pellucida or penetrate the zona and make contact with the oolemma in a species specific manner. These results are discussed with respect both to the need to employ complementary optical methods in assessing connectivity patterns within COC and to the possible role that extracellular matrix-cell interactions play in the homeostatic control of oocyte growth and maturation. © 1994 Wiley-Liss, Inc.
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    Interactions between brain mitochondria and cytoskeleton: Evidence for specialized outer membrane domains involved in the association of cytoskeleton-associated proteins to mitochondria in situ and in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 233-261 
    Details
    ISSN: 1059-910X
    Keywords: Brain mitochondria ; Microtubules ; Neurofilaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The surface distribution of several proteins (porin, hexokinase, and two proteins associated with microtubules or actin filaments) on the outer membrane of brain mitochondria was analyzed by immunogold labelling of purified mitochondria in vitro. The results suggest the existence of specialized domains for the distribution of porin in the outer mitochondrial membrane. Similarities between the distribution of porin and the distribution of microtubule-associated proteins bound in vitro to mitochondria suggested that mitochondria and microtubules interact by binding microtubule-associated proteins to porin-containing domains of the outer membrane. This hypothesis was supported by biochemical studies on outer mitochondrial proteins involved in in vitro binding of cytoskeleton elements. In vitro interactions between mitochondria and microtubules or neurofilaments were analyzed by electron microscopy. These studies revealed cross-bridging between the outer membrane of mitochondria and the two cytoskeleton elements. Cross-bridging was influenced by ATP hydrolysis and by several proteins associated with the surface of mitochondria or with microtubules. In addition, unidentified proteins which were recognized by antibodies to all intermediate filaments subunits were associated either with the mitochondrial surface or with microtubules. This data suggest the participation of additional cytoplasmic proteins in the interactions between cytoskeleton elements and mitochondria. © 1994 Wiley-Liss, Inc.
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    Molecular and cellular mechanisms of mitochondrial nuclear division and mitochondriokinesis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 220-232 
    Details
    ISSN: 1059-910X
    Keywords: Mitochondrial DNA ; Mitochondrial nuclear division ; Mitochondriokinesis ; Physarum polycephalum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Our present understanding of mitochondrial division can be summarized as follows:Mitochondria contain a specific genome, synthesize their own DNA, and multiply semi-autonomously. Strands of mitochondrial DNA (mt-DNA) in the in vivo organelles of all eukaryotes are organized to form mitochondrial nuclei (nucleoids) (mt-nuclei) with specific proteins including a histone-like protein and transcription factors at the central region of the mitochondrion. We can easily observe the mt-nucleus in vivo mitochondria in various organisms such as fungi, algae, plants, and animals by using high-resolution epifluorescence microscopy. Therefore, the process of mitochondrial division can be clearly separated into two main events: division of the mt-nuclei and mitochondriokinesis analogous to cytokinesis.Mitochondria undergo binary division which is accompained by the division of the mt-nucleus. A remarkable characteristic of mitochondrial multiplication during the mitochondrial life cycle is that mitochondria can multiply the mt-chromosome by endoduplication until 50-100 copies are present. Mitochondria can then divide without mitochondrial DNA synthesis to eventually contain 1-5 copies of the mt-chromosome. This characteristic phenomenon can be observed during cell differentiation, such as during the formation of plasmodia and sclerotia of Physarum polycephalum and during embryogenesis and the formation of meristematic tissues in plants.The mitochondrial chromosome has a mitochondrial “kinetochore (centromere)” which is A-T rich and contains specific sequences such as topoisomerase binding sites, tandem repeats, and inverted repeats. A bridge of proteins may exist between the kinetochore DNA and membrane systems. Mitochondrial chromosomes can divide according to the growth of a membrane system between the kinetochores.Mitochondriokinesis progresses steadily along with mitochondrial nuclear division. As the membrane at the equatorial region of a mitochondrion contracts, the neck of the cleavage furrow narrows, and eventually the daughter mitochondria are separated. An actin-like protein may power mitochondriokinesis by separating the daughter mitochondria. In general, mitochondriokinesis occurs by contraction rather than by partition of the inner membrane. © 1994 Wiley-Liss, Inc.
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    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994) 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070270401
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    Scanning tunneling microscopy I and scanning tunneling microscopy II, edited by R. Wiesendanger and H.-J. Güuntherodt. Springer Series in Surface Science #20 and #28, Springer Verlag, New York, 1992, 246 pp, $59.00 and 308 pp, $69.00 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 268-268 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070270307
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    Electron microscopy of the F1F0 ATP synthase: From structure to function (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 294-306 
    Details
    ISSN: 1059-910X
    Keywords: Cryo-electron microscopy ; Image analysis ; ATPase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The 1F0 ATP synthase is the large multisubunit complex which uses the proton gradient of energetically active membranes to synthesize ATP. While biochemical and genetic approaches have characterized the composition of the enzyme and elucidated many details of its mechanism and assembly, electron microscopy has been the tool of primary importance in determining the arrangement of the many subunits which comprise the F1F0. The highly cooperative catalytic mechanism is tightly coupled to transmembrane proton translocation in a separate and rather distant sector of the complex. An understanding of this intricate process and its control requires an appreciation of subunit interactions, starting with their locations relative to one another. Electron microscopy has provided most of the available structural information on the F1F0, and recent applications of cryo-electron microscopy have captured different functionally relevant configurations which may finally address longstanding questions about subunit rearrangement during the catalytic cycle. © 1994 Wiley-Liss, Inc.
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    Variations in mitochondrial ultrastructure and dynamics observed by high resolution scanning electron microscopy (HRSEM) (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 269-277 
    Details
    ISSN: 1059-910X
    Keywords: Cristae ; 3D structure ; Hepatocytes ; Fibroblasts ; Adrenal cortex ; Brown fat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Rat adrenal cortex was processed for high resolution scanning electron microscopy (HRSEM) to confirm tubular cristae, reported by transmission electron microscopy to be present in cortex mitochondria. Mitochondria in several other tissue and cell types were also observed and their ultrastructure confirmed by using three-dimensional, stereo, high resolution scanning electron microscopy. The mitochondria in rat and human hepatocytes as well as human skin fibroblasts mitochondria proved to be long, up to 46 micrometers and branching, as compared to those in liver which were spherical in shape. Cold adapted brown fat cells were packed with mitochondria, these containing plate or shelf-like cristae. Branched, rat striated muscle mitochondria were observed to curve around contractile protein filament bundles. The muscle mitochondrial cristae were found to be both tubular and plate-like, within the same mitochondrion. The ratio of tubular cristae to plate-like cristae varied considerably between muscle mitochondria. In order to use ultrastructural changes in mitochondria for differential diagnosis, and because 3D reconstruction of mitochondria based on transmission electron microscopy serial sections is severely limited in resolution, it is imperative to first develop a correct understanding of tissue specific, normal mitochondrial ultrastructure based on three-dimensional, HRSEM methods. © 1994 Wiley-Liss, Inc.
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    The internal compartmentation of rat-liver mitochondria: Tomographic study using the high-voltage transmission electron microscope (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 278-283 
    Details
    ISSN: 1059-910X
    Keywords: Matrix ; Membrane ; SEM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The three-dimensional organization of the internal compartments of conventionally fixed and embedded rat-liver mitochondria has been determined by tomographic reconstruction from tilt-series images collected on the Albany high-voltage electron microscope. The results indicate that the inner membranes of these organelles are predominantly tubular in the orthodox (expanded matrix) conformation, as previously suggested by scanning electron microscopy. In the condensed (contracted matrix) conformation, the intracristal space opens up into large irregularly shaped compartments which are connected to each other and to the external (intermembrane) space by tubes with approximately the same diameter (20 nm) as those observed in the orthodox state. These results raise several questions, in particular about the nature of the structural transitions that occur in the cristae during matrix expansion and contraction, and about the influence of inner-membrane shape on the diffusion of ions and metabolites between the intracristal and intermembrane compartments. © 1994 Wiley-Liss, Inc.
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    A morphological view on mitochondrial protein targeting (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 284-293 
    Details
    ISSN: 1059-910X
    Keywords: Mitochondrion ; Contact sites ; Protein translocation ; Ribosomes ; Import intermediates ; Receptor proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Mitochondrial protein targeting includes both intramitochondrial sorting of proteins encoded by the organellar genome and import and subsequent sorting of nuclear encoded precursor proteins. Only a few proteins are encoded by the mitochondrial genome and synthesized in the organellar matrix. These include predominantly inner membrane proteins that are perhaps co-translationally inserted into this membrane. Biochemical data suggest that insertion into the inner membrane may be confined to the inner boundary membrane. Ultrastructurally, however, a preferential association of ribosomes with either inner boundary or cristae membranes has not been established.The majority of the mitochondrial proteins are nuclear encoded and synthesized as precursors in the cytosol. Electron microscopic studies revealed that import of precursor proteins is generally confined to sites where both mitochondrial envelope membranes are closely apposed. In line with these observations, biochemical studies indicated that precursor proteins destined for the inner membrane or matrix have to interact with the energized inner membrane to allow complete passage of the precursor through the outer membrane. As a consequence, the mitochondrial envelope membranes have to be in close proximity at protein import sites.In isolated mitochondria distinct sites (designated as contact sites) exist where both envelope membranes are closely apposed and presumably stably associated. In situ, however, mitochondrial boundary membranes are in close proximity over large areas that cover almost the entire mitochondrial periphery. Consequently, the relative area of the mitochondrial surface, where both boundary membranes are in sufficient proximity for allowing protein translocation, is generally larger in situ compared to that in isolated organelles.Immunocytochemical localization studies showed a rather random distribution of components of the mitochondrial protein translocation machinery over the entire mitochondrial surface and not confined to contact sites.Based on these ultrastructral data and recent biochemical findings we propose that mitochondrial protein import sites are dynamic in nature and include relatively labile regions of close association of the boundary membranes. In vitro, however, mitochondrial protein import may preferentially take place at or near the presumably stable contact sites. © 1994 Wiley-Liss, Inc.
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    Proceedings of the fifth meeting of the great lakes electron microscopy affiliates, held in Indianapolis, IN, October 21-23, 1993 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 350-354 
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    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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    URL: http://dx.doi.org/10.1002/jemt.1070270409
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    Electron diffraction techniques, Vol. II, edited by J. M. Cowley. Oxford University Press and The International Union of Crystallography, Oxford, UK, 1993, 423 pp, $70,00 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 79-79 
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    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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    URL: http://dx.doi.org/10.1002/jemt.1070280113
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    Quantitative X-ray microanalysis of P, Ca, and S in the mucus secretory granules of the cryofixed frog palate epithelium (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 141-148 
    Details
    ISSN: 1059-910X
    Keywords: X-ray microanalysis ; Respiratory epithelium ; Secretory cells ; Cryofixation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In respiratory epithelium, the mucus is densely packed inside the secretory granules (SG) of secretory cells (SC) before being released by exocytosis in the airway lumen. We have previously shown that the frog palate is a representative model of respiratory epithelium and that rapid cryofixation is a very effective technique in preserving the integrity of the mucus SG. The concentration of phosphorus (P), sulphur (S), and calcium (Ca) were analysed inside the SG of the SC of frog palate after quick freezing, cryosubstitution, and embedding in Lowicryl resin at low temperature. The experiments were carried out using X-ray microanalysis conducted with energy dispersive spectrometry (EDS) at 100 kV. The quantitation was carried out using the continuum method with reference to Agar standards. The cryofixation permitted us to distinguish two types of SG depending on whether they were electron dense (serous cells) or electron-lucent (mucous cells). A significant (P 〈 0.001) difference in the S concentration was observed between the individual serous (239 ± 79 mmol.kg-1) and the mucous SG (161 ± 48 mmol.kg-1). No significant difference could be identified in the Ca concentration between the two SG phenotypes. In the serous SG, the P content was high (41 ± 17 mmol.kg-1) compared with the mucous SG where it was not measurable. The comparison of the three element concentrations in each type of secretory cells showed that significant differences in concentration of S and Ca concentration could be observed from one SC cell to another. A significant correlation (r = 0.76, P 〈 0.01) was observed between the S concentration and the topographical position of the SG inside the SC, the more proximal to the lumen, the higher the S concentration, suggesting that the maturation of the SG involves an increase in the protein content possibly due to a maturation process before the mucus exocytosis. Therefore, these results suggest that the elemental composition of granules varies according to the phenotype of the secretory cells and that changes in the S content from one SG to another or even inside the same cell may reflect a differential state in the functional activity of the secretory cells. © 1994 Wiley-Liss, Inc.
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    Preface (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 359-359 
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    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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    URL: http://dx.doi.org/10.1002/jemt.1070270502
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    An introduction to biomimetics: A structural viewpoint (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 360-375 
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    ISSN: 1059-910X
    Keywords: Biological composites ; Structural biocomposites ; Microarchitecture ; Materials design ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Biomimetics is a newly emerging interdisciplinary field in materials science and engineering and biology in which lesson learned from biology form the basis for novel technological materials. It involves investigation of both structures and physical functions of biological composites of engineering interest with the goal of designing and synthesizing new and improved materials. This paper discusses microarchitectural aspects of some structural biocomposites, presents microstructural criteria for future materials design and processing, and identifies areas of future research. © 1994 Wiley-Liss, Inc.
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    Biomineralization: New directions in crystal science (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 376-388 
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    ISSN: 1059-910X
    Keywords: Biomineralization ; Crystal nucleation ; Crystal growth ; Crystal engineering ; Biomimetic chemistry ; Molecular recognition ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Effective protocols for controlling crystal structure, size, and morphology attract considerable interest given the requirement for particles of modal size and shape in many areas of materials fabrication and the importance of crystallochemical selectivity in determining the exploitable properties of inorganic solids. For this reason biomineralization merits particular attention since many biominerals are deposited in a highly controlled manner to produce crystals which are uniformly sized and crystallographically unique. Studies of biominerals have revealed that while a complex array of strategies have evolved for regulating their formation, one feature is common to the biological paradigm; interactions between organized biopolymeric assemblies and the nascent inorganic solids play a pivotal role in controlling the crystallization process. In order to gain a better understanding of the molecular interactions which take place at organic-inorganic interface and address the fundamental chemical problems of biomineralization, a crystal chemical approach has been adopted. Organized organic assemblies (phospholipid vesicles, Langmuir monolayers, polypetide templates) of precise molecular design (head group identity, packing conformation, peptide sequence, etc.) were assayed for their effectiveness in controlling the nucleation and growth of inorganic solids. This work has established that through systematic changes in the nature of the organic matrix the size, crystallographic orientation, and growth of the mineral phase can be controlled. Critical to this process was the translation of specific molecular information at the organic-inorganic interface: epitaxial alignment, stereochemical complementarity, and electrostatic interactions were an essential feature of this recognition event. © 1994 Wiley-Liss, Inc.
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    High voltage immunoelectron microscopy of complement receptor type 3-mediated capping and internalization of group a streptococcal cell walls by Human Neutrophils (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 263-276 
    Details
    ISSN: 1059-910X
    Keywords: Phagocytosis ; Mac 1 ; Arthritis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The mechanism of human neutrophil clearance of peptidoglycan group A-specific polysaccharide polymers derived from streptococcal cell walls (PG-APS) was investigated by high voltage immunoelectron microscopy (HVEM) in order to determine how neutrophils process this highly inflammatory bacterial debris. Neutrophil monolayers were incubated from 5-30 min with serum-opsonized PG-APS. Cells were lightly fixed with 0.5% glutaraldehyde, and the PG-APS was localized on the neutrophil surface by immunogold using antibodies to N-acetyl-glucosamine and 15 nm colloidal gold coupled to goat anti-rabbit IgG. Neutrophils were viewed unsectioned by stereo HVEM. Patches of PG-APS were distributed randomly on the plasmalemma of well-spread neutrophils within 5 min. In polarized cells, PG-APS was densely localized on the uropod and retraction fibers. Within 15 min, PG-APS was predominantly concentrated into a large aggregate, measuring approximately 1 μm in diameter, near the cell margin or nucleus. The aggregate of PG-APS was engulfed in the vicinity of the indentation of the nucleus (hof). Intact microfilaments were required for aggregation and internalization of PG-APS. Binding of PG-APS was dependent upon complement fixation. Furthermore, PG-APS elicited an increase in density of complement receptor type 3 (CR3, C3bi receptor) on the neutrophil surface as determined by morphometry of immunogold labeled anti-CR3. When cells were stained for both PG-APS and CR3, co-localization was observed, and stereomicroscopy revealed clusters of CR3 in areas associated with phagocytosis. These data suggest that neutrophils use an efficient mechanism for removal of bacterial debris. Unlike whole streptococci which are phagocytosed at multiple sites, these bacterial cell walls are first collected into a large aggregate, or cap, which is then internalized at one site. © 1994 Wiley-Liss, Inc.
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    Combined use of immunocytochemical techniques and ligand-gold complexes for investigation of platelet membrane responses to surface activation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 308-326 
    Details
    ISSN: 1059-910X
    Keywords: Glycoproteins ; Spread cells ; GPIIb-IIIa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Exposure of blood platelets to foreign surfaces results in dramatic changes in physical appearance and conversion from a non-sticky to an adhesive state. Membrane glycoproteins and cytoskeletal assembly play a pivotal role in these interactions. Cytochemical techniques commonly applied for demonstration of macromolecules in tissues have been used for the localization of target glycoproteins on spread cells. The present review examines different experimental strategies and immunocytochemical techniques that can be combined to better understand the organization of platelet receptors during surface activation. Glycoprotein IIb-IIIa (GPIIb-IIIa) was localized by immunocytochemical techniques on fixed, surface-activated platelets. The distribution of functional fibrinogen receptors expressed on GPIIb-IIIa was revealed by incubation of fixed platelets with fibrinogen-gold conjugates (Fgn/Au). The movement of receptor complexes was investigated in additional experiments in which surface-activated platelets were interacted with Fgn/Au and then fixed at different periods. The overall impression of these observations suggests that fibrinogen receptors on surface-activated platelets do not redistribute spontaneously and that particulates (gold particles), rather than fibrinogen, may trigger the movement. These results are presented in detail and their significance discussed in the light of current theory. Applications and limitations of such techniques are also discussed. © 1994 Wiley-Liss, Inc.
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    Scanning and transmission electron microscopy of clonal peripheral blood lymphocytes in low grade non-Hodgkin's B-cell lymphomas with predominant splenomegaly (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 345-355 
    Details
    ISSN: 1059-910X
    Keywords: Lymphoma ; Splenomegaly ; SEM ; TEM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Peripheral blood mononuclear cells (PBLs) from 14 patients with low grade non-Hodgkin's B-cell lymphomas with predominant splenomegaly were studied by means of scanning (SEM) and transmission electron microscopy (TEM). All patients had peripheral blood and bone marrow involvement, the absence of lymphoadenopathy, and, except in one case, immunophenotypic features of a malignant proliferation of mature spleen B-cells arising from outside the germinal center, but not consistent with CLL or HCL. Several distinctive cytological features were observed in PBLs of the different subgroups. The SEM surface features of PBLs in patients with intermediate differentiation lymphocytic lymphoma (IDL) (five cases), lymphoplasmacytoid immunocytoma (LP-IC) (two cases), and mixed small and large cells malignant lymphoma (one case) were characterized by the presence of numerous well-developed microvilli. Some distinctive TEM ultrastructural features were also seen in the different cases. In the two cases of splenic lymphoma with villous lymphocytes (SLVL), SEM revealed large and elongated surface microvilli generally arising from two or three poles of the cells. This surface morphology, confirmed by TEM analysis, may be pathognomonic of this disease. Four additional cases, tentatively classified as small lymphocytic lymphoma on the basis of immunophenotypic data, were extremely heterogeneous at both SEM and TEM analysis. The ultrastructural features revealed by SEM and TEM may be useful for the more precise characterization of this heterogenous group of diseases, which is generally difficult to define even when immunophenotypic and molecular approaches are used. © 1994 Wiley-Liss, Inc.
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    Nitric oxide modulates sympathetic neurotransmission at the prejunctional level (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 161-168 
    Details
    ISSN: 1059-910X
    Keywords: Heart ; Catecholamine fluorescence ; NADPH diaphorase ; NO synthase ; Nitric oxide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In spite of accumulating evidence for a modulation of sympathetic neurotransmission by endogenously produced nitric oxide (NO), it remains unclear in which parts of the vascular system and at what level this interaction takes place. The aim of the present study was to investigate the distribution of endothelial and neuronal NO synthase (NOS) along the vascular tree of the heart at the light and electron microscopic level using NADPH-diaphorase (NADPH-d) staining as a marker for NOS. In addition, the functional effects of exogenous NO on coronary vascular resistance and cardiac adrenergic nerves was studied using the isolated perfused rat heart as a model. The intraaxonal catecholamine content of adrenergic nerve fibers was visualised and morphometrically assessed by applying glyoxylic acid-induced histofluorescence. The expression of endothelial NOS in the heart was found to depend on the diameter of the blood vessel. Arteries 〉100 μm always showed intense staining, whereas staining in smaller arteries and veins was considerably weaker. Smooth-muscle free vessels were essentially devoid of NADPH-d activity. In atrial and ventricular myocardium, neuronal NOS localised in autonomic nerve fibers along the entire vascular tree. Ultrastructurally, NADPH-d staining revealed adjacent localisation of NOS-positive and -negative axons, suggesting an interaxonal modulation of adjacent autonomic nerve fibers by NO. In isolated perfused rat hearts, the intracoronary application of 10-8 M NO produced a marked decrease of coronary perfusion pressure, which was accompanied by a distinct increase in intraaxonal catecholamine levels of intramural adrenergic nerve fibers. These results suggest that the entire vascular system from arteries to veins is under the influence of NO and implies that two independently operating NO-driven processes are involved in the modulation of blood vessel tone: the well-known pathway of endothelium-derived NO acting directly on smooth muscle, and a second indirect pathway that inhibits noradrenaline release from perivascular nerve endings by endothelially or neuronally produced NO. The uneven distribution of endothelial NOS furthermore suggests that the latter mechanism predominates when the size of the blood vessel decreases. © 1994 Wiley-Liss, Inc.
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    Morphological observations of small granule-containing (Chromaffin) cells in the celiac ganglion of the guinea pig, with emphasis on cell contacts (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 169-176 
    Details
    ISSN: 1059-910X
    Keywords: Celiac ganglion ; Chromaffin cells ; Autonomic nervous system ; Ultrastructure ; Guinea pig ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Utilizing electron microscopic observation, several contacts between small, granule-containing cells (SGC) and postganglionic neurons (PGN) in the celiac ganglion of the guinea pig have been observed. A SGC in very close association with a PGN was seen to receive a distinct synaptic contact that contained many vesicles with dense cores. This contact was morphologically unlike cholinergic synapses previously reported on chromaffin cells. Because the SGC and PGN were clearly separated by a thin rim of satellite cell cytoplasm mutual to both cells, it is not known how or if the SGC would possibly exert a synaptic or paracrine effect on the PGN. Also, intraganglion SGC existed as large well-vascularized islands within the celiac ganglion. These intraganlion clusters sometimes contained more than 50 cells and perhaps could be considered to function as localized neuroendocrine components within the ganglion by secreting granule products into the nearby blood vessels for local or distant effects, although this certainly is not known. This work reports a unique synaptic ending upon a single-occurring SGC, which, in turn, closely approximates a ganglion neuron in a soma-somatic relationship. In addition, a very close association (but no actual contact) was observed between granule-containing processes, presumably emanating from the intraganglion clusters, and PGN. Whatever the function of ganglionic SGC may be, the exact relationship between SGC and PGN presumably would be of great interest and potential importance. © 1994 Wiley-Liss, Inc.
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    A poly-HEMA based aqueous humor draining device (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 321-327 
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    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An aqueous humor draining device, with size comparable to that of the Krupin tube, was constructed by using poly-HEMA material. Deposits were found on the surface of poly-HEMA when contacted in vitro with the aqueous humor of the rabbit's eye. A fibrous structure, probably composed of proteins and other macromolecules, developed on poly-HEMA surface in 15 days after the draining device was implanted into the rabbit's eye. The draining device was still in function 250 days after its implantation. SEM analysis of the retrieved poly-HEMA draining device indicated that the poly-HEMA tube opening was not blocked by any substance. These results suggest that poly-HEMA could be used as a biomaterial for construction of the aqueous humor draining device to relieve the intraocular pressure of glaucoma patients. Its long-term application awaits further investigation.
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    The editor's corner: New (and improved?) vs. tried and true - A biomedical dilemma (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 329-329 
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    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    FDA - Medical device news corner: The export dilemma facing the U.S. medical device industry (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 333-333 
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    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    URL: http://dx.doi.org/10.1002/jab.770010411
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    Applied biomaterials standards report (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 331-332 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterialsrelated standards produced by both private groups and government agencies, and standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This inviation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat-since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in September 1990.
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    Patent news (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 335-338 
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    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The patent literature can be a morass of confusion. It is complicated by legalese, often uncommunicative titles, and difficult, as well as cryptic, categorization. To keep current with the broad arena of patents on biomaterials and medical devices is much more difficult than keeping current with the scientific literature of the international journals.It is the goal of my column to provide readers with techiques and tools to better utilize this rich source of scientific information. Also, I intend to provide focused surveys of recent patents in specific areas relating to biomaterials and medical devices. Finally, I will try to include discussion of what constitutes patentable material and educate those of us who are new to patent literature and new to the requirements of applying for patents for our discoveries.I appeal to the readership to submit request for specific areas to be addressed in this column. The interaction will enrich us all.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770010412
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    A nondenaturing solid phase pharmaceutical carrier comprised of surface-modified nanocrystalline materials (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 289-294 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Numerous carrier systems have been developed for the controlled delivery of biologically active molecules such as drugs and diagnostic agents. The biophysical interactions between the biologically active molecules and their carriers, however, may denature the former and lead to reduced biological activity. In this study, a model nondenaturing carrier comprised of a nanocrystalline (10-7 m) tin oxide core and a surface-charge-reducing organic bonding layer (GF292) was synthesized. A subsequently bound protein (human transferrin) showed significant retained conformation by immunoelectron microscopy. In the synthesis of targeted drug systems and vaccines, nanocrystalline cores treated with appropriate surface-modifying agents may be suitable carriers.
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    URL: http://dx.doi.org/10.1002/jab.770010404
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    Parametric analysis of interfacial stress concentrations in porous coated implants (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 3-12 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Porous coated Ti-6Al-4V has a high-cycle fatigue strength that is approximately one-third the strength of the uncoated material. Stress concentrations at the interface between the porous coating and the substrate contribute to this fatigue strength reduction. Modification of the interfacial geometry may reduce the severity of the stress concentrations. The interface between the porous coating and substrate was modeled using two-dimensional finite element analysis. This analysis identified geometric parameters that affect the value of the stress concentration factor, Kt. The effect of five geometric parameters onKt was determined: contact area between porous coating and substrate (CA), sinterneck radius (r), porous coating particle radius (R), interparticle distance (d), and interparticle sintering. Increased contact areas, decreased sinterneck radii, and decreased interparticle distances increased Kt, while porous coating particle size had a small effect on Kt. Sintering between neighboring porous coating particles increased Kt at the outermost sinternecks, but decreased Kt at inner sinternecks. The results can help predict how varying these coating parameters can reduce stress concentrations in a porous coated material.
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    URL: http://dx.doi.org/10.1002/jab.770010103
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    Ventricular assist device (VAD) pathology analyses: Guidelines for clinical studies (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 49-56 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/jab.770010108
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    Influence of needle holder jaw configuration on the biomechanics of curved surgical needle bendingThis research was supported by a generous gift from the Texaco Philanthropic Foundation, White Plains, New York. (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 39-47 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770010107
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    The editor's corner: A question of ethics (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 91-92 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770010111
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    Workshop on characterization of calcium phosphate materials (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 79-90 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Calcium phosphate materials are being extensively investigated for orthopaedic and dental applications. Bone grafts and bone substitutes are being developed using many forms of these materials. Numerous medical devices are being coated with them. Because of the many forms that calcium phosphate materials take, characterization of the material under investigation is essential. Aworkshop sponsored by the Society For Biomaterials on characterization of calcium phosphate materials was held on June 14 and 15, 1989. Sessions discussing the historical development, in vitro characterization, in vitro coating characterization, in vivo coating characterization, the FDA perspective, and the manufacturers perspective were held. A summary of the workshop with references is presented.
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    URL: http://dx.doi.org/10.1002/jab.770010110
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    FDA - Medical device news corner: Tips on conducting investigational clinical studies under IDE regulations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 95-97 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770010113
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    Applied biomaterials standards report (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 93-94 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterialsrelated standards produced by both private groups and government agencies, and standardsrelated activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards informations but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to all members of any and all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat - since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in November 1989.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770010112
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    Mechanical properties of biodegradable polymers and composites proposed for internal fixation of bone (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 1 (1990), S. 57-78 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mechanical properties of biodegradable polymers and composites proposed for use in internal fixation (in place of stainless steel) are crucial to the performance of devices made from them for support of healing bone. To assess the reported range of properties and degradation rates. we searched and reviewed papers and abstracts published in English from 1980 through 1988. Mechanical property data were found for poly(lactic acid), poly (glycolic acid), poly(∊-caprolactone), polydioxanone, poly(ortho ester), poly(ethylene oxide), and/or their copolymers. Reports of composites based on several of these materials, reinforced with nondegradable and degradable fibers, were also found. The largest group of studies involved poly(lactic acid). Mechanical test methods varied widely, and studies of the degradation of mechanical properties were performed under a variety of conditions, mostly in vitro rather than in vivo.Compared to annealed stainless steel, unreinforced biodegradable polymers were initially up to 36% as strong in tension and 54% in bending, but only about 3% as stiff in either test mode. With fiber reinforcement, reported highest initial strengths exceeded that of stainless steel. Stiffness reached 62% of stainless steel wiht nondegradable carbon fibers, 15% with degradable inorganic fibers, but only 5% with degradable polymeric fibers.The slowest-degrading unreinforced biodegradable polymers were poly(L-lactic acid) and poly(ortho ester). Biodegradable composites with carbon or inorganic fibers generally lost strength rapidly, with a slower loss of stiffness, suggesting the difficulty of fiber-matrix coupling in these system. The strength of composites reinforced wiht (lower modulus) degradable polymeric fibers decreased more slowly.Low implant stiffness might be expected to allow too much bone motion for satisfactory healing. However, unreinforced or degradable polymeric fiber reinforced materials have been used successfully clinically. The key has been careful selection of applications, plus use of designs and fixation methods distinctly different from those appropriate for stainless steel devices.
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    URL: http://dx.doi.org/10.1002/jab.770010109
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