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  • Electronic Resource  (49)
  • 1985-1989  (43)
  • 1930-1934  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 53 (1989), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We have correlated myelin membrane structure with biochemical composition in the CNS and PNS of a phylogenetic series of animals, including elasmobranchs, teleosts, amphibians, and mammals. X-ray diffraction patterns were recorded from freshly dissected, unfixed tissue and used to determine the thicknesses of the lipid bilayer and the widths of the spaces between membranes at their cytoplasmic and extracellular appositions. The lipid and protein compositions of myelinated tissue from selected animals were determined by TLC and sodium dodecyl sulfate-polyacrylamide gel elec-trophoresis/immunoblotting, respectively. We found that(l) there were considerable differences in lipid (particularly gly-colipid) composition, but no apparent phylogenetic trends; (2) the lipid composition did not seem to affect either the bilayer thickness, which was relatively constant, or the membrane separation; (3) the CNS of elasmobranch and teleost and the PNS of all four classes contained polypeptides that were recognized by antibodies against myelin Po glycoprotein; (4) antibodies against proteolipid protein (PLP) were recognized only by amphibian and mammalian CNS; (5) wide extracellular spaces (ranging from 36 to 48 Å) always correlated with the presence of Po-immunoreactive protein; (6) the narrowest extracellular spaces (∼31 Å) were observed only in PLP-containing myelin; (7) the cytoplasmic space in PLP-containing myelin (∼31 Å) averaged ∼5Å less than that in Po-containing myelin; (8) even narrower cytoplasmic spaces (∼24Å) were measured when both Po and 11–13-kilodalton basic protein were detected; (9) proteins immu-noreactive to antibodies against myelin P2 basic protein were present in elasmobranch and teleost CNS and/or PNS, and in mammalian PNS, but not in amphibian tissues; and (10) among mammalian PNS myelins, the major difference in structure was a variation in membrane separation at the cytoplasmic apposition. These findings demonstrate which features of myelin structure have remained constant and which have become specifically altered as myelin composition changed during evolutionary development.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Isolated myelin has been used for determinations of membrane surface charge density and topographical mapping of components in the membrane. To determine how similar such myelin is to myelin of intact tissue, we have used x-ray diffraction to compare their intermembrane interactions. The interactions were monitored by measuring the myelin period in samples treated with distilled water, buffered saline at pH 4–9 and ionic strength 0.06–0.18, and saline containing HgCl2 or triethyl tin sulfate. Myelin was isolated from whole brains and sciatic nerves of mice by conventional methods involving sucrose gradient centrifugation and osmotic shock. Consistent with previous findings, electron microscopy showed that the multilamellar morphology, staining, and repeat periods of isolated myelin were essentially like those of intact myelin; however, the membrane stacks were less extensive than those in whole tissue. X-ray diffraction revealed that isolated CNS myelin was like intact myelin in showing reversible compaction in acidic media and in distilled water. However, unlike the myelin in whole tissue, isolated CNS myelin did not swell in hypotonic or alkaline media, or in the presence of HgCl2-saline or triethyl tin. The altered membrane interactions could result from an increase in adhesiveness of the apposed membrane surfaces. Reorganization of proteolipid protein and/or a reduction of surface charge could account for the change in surface properties of isolated CNS myelin. Isolated PNS myelin, like the membranes in whole tissue, showed both compaction and swelling; however, the membrane pairs were disordered in the swollen structure. This irregular membrane swelling could result from charge variation in the extracellular surfaces.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We have correlated membrane structure and interactions in shiverer sciatic nerve myelin with its biochemical composition. Analysis of x-ray diffraction data from shiverer myelin swollen in water substantiates our previous localization of an electron density deficit in the cytoplasmic half of the membrane. The density loss correlates with the absence of the major myelin basic proteins and indicates that in normal myelin, the basic protein is localized to the cytoplasmic apposition. As in normal peripheral myelin, hypotonic swelling in the shiverer membrane arrays occurs in the extracellular space between membranes; the cytoplasmic surfaces remain closely apposed notwithstanding the absence of basic protein from this region. Surprisingly, we found that the interaction at the extracellular apposition of shiverer membranes is altered. The extracellular space swells to a greater extent than normal when nerves are incubated in distilled water, treated at a reduced ionic strength of 0.06 in the range of pH 4–9, or treated at constant pH (4 or 7) in the range of ionic strengths 0.02–0.20. To examine the biochemical basis of this difference in swelling, we compared the lipid composition of shiverer and normal myelin. We find that sulfatides, hydroxycerebroside, and phosphatidylcholine are 20–30% higher than normal; non-hydroxycerebroside and sphingomyelin are 15–20% lower than normal; and ethanolamine phosphatides, phosphatidylserine, and cholesterol show little or no change. A higher concentration of negatively charged sulfatides at the extracellular surface likely contributes to an increased electrostatic repulsion and greater swelling in shiverer. The cytoplasmic surfaces of the apposed membranes of normal and shiverer myelins did not swell apart appreciably in the pH and ionic strength ranges expected to produce electrostatic repulsion. This stability, then, clearly does not depend on basic protein. We propose that P0 glycoprotein molecules form the stable link between apposed cytoplasmic membrane surfaces in peripheral myelin.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5915-5920 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin polarization analysis of electrons from ferromagnets has proven to be a valuable tool for the study of near-surface magnetism. High-resolution imaging of domains and domain walls in the scanning electron microscope is demonstrated. Analysis of the temperature dependence of Stoner excitations in Ni may be carried out in a "complete'' inelastic electron scattering experiment with a polarized electron source. Examples for probing the electronic structure of epitaxially grown thin films of Co on Cu(100) by spin-polarized photoemission are given. Two recent applications of ion beam probes are discussed: (i) the analysis of ion-excited spin-polarized secondary electrons and its use for "magnetic sputter depth profiling,'' and (ii) the capture of polarized electrons in ion-surface scattering resulting in the emission of circularly polarized light.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2640-2642 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and performance of a simple sputter ion gun is given. It uses a commercial Bayard–Alpert ionization gauge. A two-stage extraction and acceleration system provides a variable beam profile as well as high currents at low energies (〉1 μA above 200 eV). At a distance of 4 cm from the end of the gun a current density of more than 150 μA/cm2 was obtained at 1.2 keV. A narrow energy distribution may also be obtained (≤1.6 eV FWHM at 1.2 keV).
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 8 (1988), S. 0 
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Currently, vadose zone monitoring is required under the Resource Conservation and Recovery Act (RCRA) only at land treatment facilities. Contaminant leak detection through ground water monitoring is very important, but it is considered to be after the fact. Remedial action costs can be reduced considerably by monitoring the vadose zone for compounds that exhibit high rates of movement. Volatile organic compounds (VOCs) exhibit this property and are present at many municipal landfills, recycling facilities, and treatment storage and disposal facilities (TSDFs). Through the authors’personal experience, it has been noted that gaseous phase transport of VOCs through the vadose zone is at least an order of magnitude greater than advective transport of VOCs in ground water. Therefore, VOCs in soil gas are an effective early warning leak detection parameter. Downward movement of leachate can be intercepted by porous cup lysimeters. Attenuation in the vadose zone slows the apparent movement of contaminants; however, it is only a matter of time before leachate reaches the water table. The authors believe that soil-gas and pore-water monitoring should and eventually will be required at all RCRA sites. If vadose zone monitoring becomes an additional requirement under RCRA, both the facility owner and the taxpayer will benefit. During the interim, facility owners can benefit by employing vadose zone monitoring techniques coupled with either qualitative or quantitative chemical analyses.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 466 (1986), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 466 (1986), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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