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  • 1
    Electronic Resource
    Electronic Resource
    Estimation of Fructose by Cyanohydrin Reaction (1953)
    s.l. : American Chemical Society
    Analytical chemistry 25 (1953), S. 511-512 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60075a038
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  • 2
    Electronic Resource
    Electronic Resource
    Cerebral and pial microvessels: differential expression of γ-glutamyl transpeptidase and alkaline phosphatase (1999)
    Springer
    Anatomy and embryology 199 (1999), S. 29-34 
    Details
    ISSN: 1432-0568
    Keywords: Key words γ-Glutamyl transpeptidase ; Alkaline phosphatase ; Blood-brain barrier ; Pial microvessels ; Astrocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Pial microvessels have several important blood-brain barrier (BBB) characteristics in common with cerebral microvessels, despite lacking their astrocytic ensheathment. We have therefore determined whether they have the same distribution of two enzymes, γ-glutamyl transpeptidase (GGTP) and alkaline phosphatase, both of which are known to be astrocyte-dependent. GGTP was absent from all rat pial microvessels but strongly present in brain cortical capillaries. Alkaline phosphatase was heterogeneously expressed in pial microvessels, including capillaries, but strongly positive in brain cortical capillaries. Diffusible, inductive factors produced by astrocytes could account for these differences in enzyme distribution between the two vessel types. Furthermore, differences in expression between the two markers may reflect their differing sensitivities to the astrocytic factors. Caution is urged in the common usage of the pial microvessel as a model system in BBB studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050206
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of blood-brain barrier and blood-nerve barrier endothelial cell markers (1999)
    Springer
    Anatomy and embryology 199 (1999), S. 509-517 
    Details
    ISSN: 1432-0568
    Keywords: Key words Blood-brain barrier ; Blood-nerve barrier ; Endothelial cell ; Membrane markers ; Inductive mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A number of major properties of endothelial cells (EC) at the blood-brain barrier (BBB) have been shown to be astrocyte-dependent. Whether analogous properties at the blood-nerve barrier (BNB) are induced and maintained by Schwann cells has not been investigated. As a preliminary investigation we have undertaken a comparative study of six EC membrane markers at the BBB and BNB and perineurium. Employing immunoblotting and immunocytochemistry the relative distribution between rat brain cortex and sciatic nerve was determined for the glucose transporter (GLUT-1), the transferin receptor (OX-26), the endothelial barrier antigen (EBA) and the OX-47 antigen. Using enzyme cytochemistry the same comparison was made for γ-glutamyl transpeptidase (GGTP) and alkaline phosphatase. By immunocytochemistry GLUT-1 was uniformly strongly represented in brain EC, nerve EC and perineurium. OX-26 was strongly positive in brain EC but present only in trace quantities in nerve EC and perineurium. EBA similarly showed strong positivity in brain EC and trace amounts in nerve EC but was absent from perineurium. OX-47 was present moderately in brain EC and perineurium but absent from nerve EC. Quantitative immunoblotting of brain and sciatic nerve homogenates showed statistically significant differences in the level of expression of EBA and OX-26 between the two tissues. Enzyme cytochemistry showed that GGTP was strongly positive in brain EC but absent from nerve EC and perineurium. Alkaline phosphatase stained strongly in brain and nerve EC and was absent from perineurium. In summary the six membrane markers were heterogeneously represented in nerve compared with brain. This pattern of distribution in the nerve cannot simply be accounted for by the absence of astrocytes and their inductive influences. Any inductive influences of Schwann cells require investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050248
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of emitter metallization on thermal properties of small AlGaAs heterojunction bipolar transistors (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4195-4197 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have extended an experimental technique to measure thermal resistance by pulsed current–voltage measurements to small bipolar transistors with thermal time constants of several hundred nanoseconds. Results for a 3×3 μm2 AlGaAs/GaAs heterojunction bipolar transistor are compared with detailed finite element method simulations, and show good agreement when heat flow into the emitter metallization is accounted for. Simulation results indicate that emitter metallization plays a significant role in reducing temperature nonuniformity across the emitter. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352672
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  • 5
    Electronic Resource
    Electronic Resource
    Blood-nerve barrier: Distribution of anionic sites on the endothelial plasma membrane and basal lamina of dorsal root ganglia (1991)
    Springer
    Journal of neurocytology 20 (1991), S. 759-768 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous investigations of the blood-nerve barrier have correlated the greater permeability of ganglionic endoneurial vessels, compared to those of nerve trunks, with the presence of fenestrations and open intercellular junctions. Recent studies have demonstrated reduced endothelial cell surface charge in blood vessels showing greater permeability. To determine the distribution of anionic sites on the plasma membranes and basal laminae of endothelial cells in dorsal root ganglia, cationic colloidal gold and cationic ferritin were used. Electron microscopy revealed the existence of endothelial microdomains with differing labelling densities. Labelling indicated that caveolar and fenestral diaphragms and basal laminae are highly anionic at physiological pH, luminal plasma membranes and endothelial processes are moderately charged and abluminal plasma membranes are weakly anionic. Tracers did not occur in caveolae or cytoplasmic vesicles.In vitro tracer experiments at pH values of 7.3, 5.0, 3.5 and 2.0 indicated that the anionic charge on the various endothelial domains was contributed by chemical groups with differing pKa values. In summary, the labelling of ganglionic and sciatic nerve vessels was similar except for the heavy labelling of diaphragms in a minority of endoneurial vessels in ganglia. This difference is likely to account in part for the greater permeability of ganglionic endoneurial vessels. The results are discussed with regard to the blood-nerve and -brain barriers and vascular permeability in other tissues and a comparison made between the ultrastructure and anionic microdomains of epi-, peri- and endoneurial vessels of dorsal root ganglia and sciatic nerves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01187849
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular characterization of anionic sites on the luminal front of endoneurial capillaries in sciatic nerve (1994)
    Springer
    Journal of neurocytology 23 (1994), S. 29-37 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distribution of anionic microdomains has been described in cerebral vessels and more recently in capillaries of peripheral nerve. Evidence is accumulating that these sites play a role in the barrier function of vascular endothelia in the PNS and CNS. The chemical nature of anionic sites has been at least partly determined for cerebral vessels but not in peripheral nerve. This study reports our preliminary investigations to determine the nature of endothelial anionic sites in sciatic nerve. The effects of digestion of ultra-thin sections of nerve with a battery of proteolytic and glycolytic enzymes (papain, trypsin, proteinase K, hyaluronidase, heparinase, heparitinase and neuraminidase) on the distribution of anionic sites was determined using the label, cationic colloidal gold. Papain, a proteolytic enzyme of broad specificity, succeeded in removing the majority of cationic colloidal gold-binding sites on the luminal surface of vascular endothelia. In contrast trypsin and proteinase K were less effective, reflecting their narrower specificity. Hyaluronidase, heparinase and heparitinase did not significantly affect cationic colloidal gold-labelling. However, a considerable reduction in cationic colloidal gold-binding occurred following neuraminidase digestion. These results suggest that, as in cerebral vessels, sialic acid-containing glycoproteins are largely responsible for the negatively charged domains on the luminal membrane of endothelial cells in peripheral nerve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189814
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  • 7
    Electronic Resource
    Electronic Resource
    Corneal glycoconjugates: an ultrastructural lectin--gold study (1998)
    Springer
    Journal of molecular histology 30 (1998), S. 51-60 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The oligosaccharide chains of cell surface and extracellular matrix glycoconjugates are essential for the biological properties of these molecules. We have, therefore, investigated carbohydrate residues in the rat cornea using biotinylated lectin--gold probes. Fixed corneas were removed and embedded in Lowicryl HM20 or LR White. Ultrathin sections were incubated in one of the lectins: Triticum vulgare (WGA), Canavalia ensiformis (Con A), Griffonia simplicifolia (GS-1), Limax flavus (LFA) and Allomyrina dichotoma (Allo A), followed by streptavidin--gold, or the sections were incubated in cationic colloidal gold. Semi-quantification of gold labelling was determined for corneal endothelium, Descemet's membrane, stroma and epithelium from electron micrographs. WGA and Con A binding sites were expressed either moderately or strongly through out the cornea, suggesting a preponderance of alpha-mannose and N-acetylglucosamine residues. A particular concentration of these sugars was found in Descemet's membrane. In contrast, GS-1 (specific for alpha-galactose) and Allo A (specific for beta-galactose) labelled all regions weakly. Sialic acid residues, as defined by LFA labelling and the expression of neuraminidase-sensitive cationic colloidal gold binding sites, were sparsely distributed throughout the stroma, Descemet's membrane and endothelium. In contrast, sialoglycoconjugates were found in significant concentrations in the epithelium. Electron microscopy proved useful in providing new information on the cellular and subcellular localization of these lectin binding sites. © Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003218630093
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular characteristics of pial microvessels of the rat optic nerve. Can pial microvessels be used as a model for the blood-brain barrier? (1997)
    Springer
    Cell & tissue research 288 (1997), S. 259-265 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Pial microvessels ; Optic nerve ; Blood-brain barrier ; Anionic sites ; Lectin-gold ; Cationic colloidal gold ; Enzyme digestion ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Pial microvessels have commonly been used in studies of the blood-brain barrier because of their relative accessibility. To determine the validity of using the pial microvessel as a model system for the blood-brain barrier, we have extended the comparison of pial and cerebral microvessels at the molecular level by a partial characterization of the glycocalyx of pial endothelial cells, in view of the functional importance of anionic sites within the glycocalyx. Rat optic nerves were fixed by vascular perfusion. Anionic sites on the endothelium were labelled with cationic colloidal gold by means of post- and pre-embedding techniques. The effects of digestion of ultrathin sections on subsequent gold labelling was quantified following their treatment with a battery of enzymes. Biotinylated lectins, viz. wheat germ agglutinin and concanavalin A with streptavidin gold, were employed to identify specific saccharide residues. The results demonstrate that the luminal glycocalyx of pial microvessels is rich in sialic-acid-containing glycoproteins. Neuraminidase, which is specific for N-acetylneuraminic (sialic) acid, and papain (a protease with a wide specificity) significantly reduce cationic colloidal gold binding to the luminal endothelial cell plasma membrane. Wheat germ agglutinin (with an affinity for sialic acid) binds more to the luminal than abluminal plasma membrane, whereas concanavalin A, which binds mannose, binds more to the abluminal surface. Similar results have been obtained for cerebral cortical endothelial cells. With respect to these molecular characteristics, therefore, the pial and cortical microvessels appear to be the same. However, since the two vessel types differ in other respects, caution is urged regarding the use of pial microvessels to investigate the blood-brain barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050811
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