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  • 1
    Electronic Resource
    Electronic Resource
    Uptake and transport of high-density lipoprotein (HDL) and HDL-associated α-tocopherol by an in vitro blood–brain barrier model (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 89 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present study aimed to investigate pathways that contribute to uptake and transcytosis of high-density lipoproteins (HDLs) and HDL-associated α-tocopherol (αTocH) across an in vitro model of the blood–brain barrier (BBB). In primary porcine brain capillary endothelial cells HDL-associated αTocH was taken up in 10-fold excess of HDL holoparticles, indicating efficient selective uptake, a pathway mediated by scavenger receptor class B, type I (SR-BI). SR-BI was present in caveolae of brain capillary endothelial cells and expressed almost exclusively at the apical membrane. Disruption of caveolae with methyl-β-cyclodextrin (CDX) resulted in (mis)sorting of SR-BI to the basolateral membrane. Immunohistochemistry of porcine brain cryosections revealed SR-BI expression on brain capillary endothelial cells and presumably astrocytic endfeet. HDL-associated [14C]αTocH taken up by brain capillary endothelial cells was recovered in sucrose gradient fractions containing the majority of cellular caveolin-1, the major caveolae-associated protein. During mass transfer studies using αTocH-enriched HDL, approximately 50% of cellular αTocH was recovered with the bulk of cellular caveolin-1 and SR-BI. Efflux experiments revealed that a substantial amount of cell-associated [14C]αTocH could be mobilized into the culture medium. In addition, apical-to-basolateral transport of HDL holoparticles and HDL-associated αTocH was saturable. Results from the present study suggest that part of cerebral apolipoprotein A-I and αTocH originates from plasma HDL transcytosed across the BBB and that caveolae-located SR-BI facilitates selective uptake of HDL-associated αTocH at the BBB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02373.x
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  • 2
    Electronic Resource
    Electronic Resource
    Regulated expression of endothelial lipase by porcine brain capillary endothelial cells constituting the blood–brain barrier (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 94 (2005), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Normal neurological function depends on a constant supply of polyunsaturated fatty acids to the brain. A considerable proportion of essential fatty acids originates from lipoprotein-associated lipids that undergo uptake and/or catabolism at the blood–brain barrier (BBB). This study aimed at identifying expression and regulation of endothelial lipase (EL) in brain capillary endothelial cells (BCEC), major constituents of the BBB. Our results revealed that BCEC are capable of EL synthesis and secretion. Overexpression of EL resulted in enhanced hydrolysis of extracellular high-density lipoprotein (HDL)-associated sn-2-labeled [14C]20 : 4 phosphatidylcholine. [14C]20 : 4 was recovered in cellular lipids, indicating re-uptake and intracellular re-esterification. To investigate local regulation of EL in the cerebrovasculature, BCEC were cultured in the presence of peroxisome-proliferator activated receptor (PPAR)- and liver X receptor (LXR)-agonists, known to regulate HDL levels. These experiments revealed that 24(S)OH-cholesterol (a LXR agonist), bezafibrate (a PPARα agonist), or pioglitazone (a PPARγ agonist) resulted in down-regulation of EL mRNA and protein levels. Our findings implicate that EL could generate fatty acids at the BBB for transport to deeper regions of the brain as building blocks for membrane phospholipids. In addition PPAR and LXR agonists appear to contribute to HDL homeostasis at the BBB by regulating EL expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2005.03175.x
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  • 3
    Electronic Resource
    Electronic Resource
    Modulation of microglial superoxide production by α-tocopherol in vitro: attenuation of p67phox translocation by a protein phosphatase-dependent pathway (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 79 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: As in other phagocytic cells, the NADPH-oxidase system in microglia is thought to be primarily responsible for the production of superoxide anion radicals (O2−·), a potentially cytotoxic reactive oxygen species. The assembly of a functional NADPH-oxidase complex at the plasma membrane depends on the phosphorylation and subsequent translocation of several cytosolic subunits. Immunocytochemical and subcellular fractionation experiments performed during the present study revealed that the NADPH-oxidase subunit p67phox translocates from the cytosol to the plasma membrane upon stimulation. Pre-incubation of microglia in α-tocopherol (αTocH) containing medium decreased O2−· production in a time- and concentration-dependent manner, findings attributed to attenuated p67phox translocation to the plasma membrane. Moreover, αTocH-supplementation of the culture medium resulted in decreased microglial protein kinase C (PKC) activities, an effect that could be partially or completely reversed by the addition of protein phosphatase inhibitors (okadaic acid and calyculin A). The addition of the PKC-inhibitor staurosporine inhibited the microglial respiratory burst in a manner comparable to αTocH. The addition of okadaic acid or calyculin A completely restored O2−· production in αTocH-supplemented cells. The present findings suggest that αTocH inactivates PKC via a PP1 or PP2A-mediated pathway and, as a consequence, blocks the phosphorylation-dependent translocation of p67phox to the plasma membrane. As a result, O2−· production by the microglial NADPH-oxidase system is substantially inhibited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00641.x
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  • 4
    Electronic Resource
    Electronic Resource
    Uptake of Lipoprotein-Associated α-Tocopherol by Primary Porcine Brain Capillary Endothelial Cells (2000)
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: From the severe neurological syndromes resulting fromvitamin E deficiency, it is evident that an adequate supply of the brain withα-tocopherol (αTocH), the biologically most active member of thevitamin E family, is of utmost importance. However, uptake mechanisms ofαTocH in cells constituting the blood-brain barrier are obscure.Therefore, we studied the interaction of low (LDL) and high (HDL) densitylipoproteins (the major carriers of αTocH in the circulation) withmonolayers of primary porcine brain capillary endothelial cells (pBCECs) andcompared the ability of these two lipoprotein classes to transferlipoprotein-associated αTocH to pBCECs. With regard to potential bindingproteins, we could identify the presence of the LDL receptor and a putativeHDL3 binding protein with an apparent molecular mass of 100 kDa. At4°C, pBCECs bound LDL with high affinity (KD = 6nM) and apolipoprotein E-free HDL3 with low affinity (98nM). The binding capacity was 20,000 (LDL) and 200,000(HDL3) lipoprotein particles per cell. αTocH uptake wasapproximately threefold higher from HDL3 than from LDL when[14C]αTocH-labeled lipoprotein preparations were used. Themajority of HDL3-associated αTocH was taken up in alipoprotein particle-independent manner, exceeding HDL3holoparticle uptake 8- to 20-fold. This uptake route is less important forLDL-associated αTocH (αTocH uptake ∼1.5-fold higher thanholoparticle uptake). In line with tracer experiments, mass transfer studieswith unlabeled lipoproteins revealed that αTocH uptake fromHDL3 was almost fivefold more efficient than from LDL. Biodiscrimination studies indicated that uptake efficacy for the eight different stereoisomers of synthetic αTocH is nearly identical. Our findings indicate that HDL could play a major role in supplying the central nervous system with αTocH in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.0741374.x
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  • 5
    Electronic Resource
    Electronic Resource
    Functional Analysis Of Histamine Receptor Subtypes Involved In Endothelium-Mediated Relaxation Of The Human Uterine Artery (2002)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 29 (2002), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. This work was designed to introduce human uterine arteries as a new model for cardiovascular research. Advantages of this model include considerable availability of tissue because of the appearance of uterus myomatosus in post-menopausal women who undergo surgery and the chance to work on dysfunctional and healthy vessels.2. Histamine evoked relaxation of the uterine artery that was prevented by removal of the endothelium or by the presence of NG-nitro-L-arginine.3. Receptor antagonists for histamine H1 (mepyramine) and H2 (ranitidine) receptors increased the EC50 of histamine by 112- and 67-fold, respectively.4. Remarkably, isolated uterine arteries could be stored in incubators for 5 days without any change in contractility to phenylephrine and endothelium-dependent relaxation to acetylcholine and histamine.5. Endothelial cells could be isolated and cultured in high purity, as demonstrated by histochemical staining of factor VIII, low CD45-RO for macrophages and no smooth muscle α-actin. In addition, cultured human uterine artery endothelial cells could be used for single cell Ca2+ measurements.6. In agreement with our findings in the intact vessel, histamine-initiated elevation of the intracellular free Ca2+ concentration was reduced in the presence of mepyramine and ranitidine by 59 and 55%, respectively.7. These data indicate that, in the human uterine artery, H1 and H2 receptors are involved in histamine-induced endothelium-dependent relaxation that is mediated by nitric oxide.8. In addition, this vessel can be stored for possible virus-mediated gene expression for 5 days without any loss of reagibility.9. Finally, endothelial cells can be isolated and cultured from the human uterine artery and maintain their reactivity to histamine in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1681.2002.03704.x
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  • 6
    Electronic Resource
    Electronic Resource
    Grazing by large river zooplankton: a key to summer potamoplankton decline? The case of the Meuse and Moselle rivers in 1994 and 1995 (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 199-216 
    Details
    ISSN: 1573-5117
    Keywords: potamoplankton ; plankton interactions ; in situ grazing ; European rivers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To explain summer declines in phytoplankton biomass in large rivers, we compared the effect of zooplankton grazing on the planktonic algae of two large European rivers, the Meuse and the Moselle. In situ grazing was measured during two years (1994 and 1995), using the Haney method. Total zooplankton community filtration rates recorded in the river Meuse ranged between 1 and 32% of the water volume filtered per day. A drastic algal decline was observed early July both years and may be explained by high densities of a rotifer-dominated zooplankton community (500–700 ind. l-1) with more than 75% of Brachionus calyciflorus. During the summer period in 1994, when grazing was over 20%, edible algal biomass was controlled by a diversified rotifer community (up to 2500 ind. l-1), while a non-edible algal assemblage developed. In contrast, phytoplankton biomass remained comparatively low in the Moselle throughout the low-flow period, as did zooplankton numbers during most of this time (fewer than 200 ind. l-1 during the summer period). The proportion of crustaceans in this zooplankton was rather higher than in the Meuse, and they dominated at times, in biomass as well as in numbers. Nevertheless, measured in situ grazing rates (1–15%) could not explain the low summer algal biomass, even if low filtration rates may at times represent a significant carbon loss for phytoplankton, when and where net algal production was low. As a conclusion, the role of phytoplankton – zooplankton interactions in controlling algal biomass in large rivers is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017071909997
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  • 7
    Electronic Resource
    Electronic Resource
    Expression of HLA class I molecules in human first trimester and term placenta trophoblast (1996)
    Springer
    Cell & tissue research 286 (1996), S. 439-447 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Placenta ; Trophoblast ; Monoclonal antibodies ; HLA class I ; HLA ; G ; HLA ; C ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Expression of HLA class I molecules in trophoblast cells from various locations in normal human first trimester and term placenta was investigated by immunohistochemistry with a panel of monoclonal antibodies against the heavy chains or complete HLA class I molecules complexed with β2-microglobulin. These reagents were also employed to distinguish between the products of different HLA class I loci. In addition to previously characterized reagents, a novel monoclonal antibody against HLA-A molecules (TÜ155) was used. Various choriocarcinoma and transfected cell lines served as controls for the specificities of the monoclonal antibodies. Cells in close contact with maternal cells, such as invading trophoblast cells and cells of the basal plate, expressed β2-m micro globulin in association with HLA-G and HLA-C heavy chains. These class I heavy chains may also have been present as isolated molecules, although not in each of the cells. In contrast, cells of the chorion laeve exclusively expressed HLA-G, and not HLA-A, -B, or -C antigens. Our data support the often discussed immune protective function and the regulatory function of the HLA-G molecule, during invasion. In addition, by using monoclonal antibodies HCA2 (anti-HLA-A and -G), HC10 (anti-HLA-B and -C), TÜ149 (anti-HLA-B, -C, and some -A alleles), SFR8-B6 (anti-HLA-Bw6 and some -C), LA45 (some HLA-A and -B), TÜ48 (anti-HLA-Bw4 and some -A), and TÜ155 (anti-HLA-A), we show the presence of HLA-C molecules in all extravillous trophoblast cells of the cell columns and in the basal plate; the trophoblast cells of the chorion laeve lack this antigen. The function of this molecule is not clear, although a protective function against natural killer cell activity in the endometrium is postulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050713
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  • 8
    Electronic Resource
    Electronic Resource
    Erratum: Expression of HLA class I molecules in human first trimester and term placenta trophoblast (1997)
    Springer
    Cell & tissue research 287 (1997), S. 625-625 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050786
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