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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 66 (1982), S. 203-212 
    ISSN: 1432-1424
    Keywords: membrane proteins ; membrane biosynthesis ; membrane potential ; surface potential ; surface charge ; dipole potential ; amino acid sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Although hydrophobic forces probably dominate in determining whether or not a protein will insert into a membrane, recent studies in our laboratory suggest that electrostatic forces may influence the final orientation of the inserted protein. A negatively charged hepatic receptor protein was found to respond totrans-positive membrane potentials as though “electrophoresing” into the bilayer. In the presence of ligand, the protein appeared to cross the membrane and expose binding sites on the opposite side. Similarly, a positively charged portion of the peptide melittin crosses a lipid membrane reversibly in response to atrans-negative potential. These findings, and others by Date and co-workers, have led us to postulate that transmembrane proteins would have hydrophobic transmembrane segments bracketed by positively charged residues on the cytoplasmic side and negatively charged residues on the extra-cytoplasmic side. In the thermodynamic sense, these asymmetrically placed charge clusters would create a compelling preference for correct orientation of the protein, given the inside-negative potential of most or all cells. This prediction is borne out by examination of the few transmembrane proteins (glycophorin, M13 coat protein, H-2Kb, HLA-A2, HLA-B7, and mouse Ig μ heavy chain) for which we have sufficient information on both sequence and orientation. In addition to the usual diffusion and pump potentials measurable with electrodes, the “microscopic” membrane potential reflects surface charge effects. Asymmetries in surface charge arising from either ionic or lipid asymmetries would be expected to enhance the bias for correct protein orientation, at least with respect to plasma membranes. We introduce a generalized form of Stern equation to assess surface charge and binding effects quantitatively. In the kinetic sense, dipole potentials within the membrane would tend to prevent positively charged residues from crossing the membrane to leave the cytoplasm. These considerations are consistent with the observed protein orientations. Finally, the electrostatic and hydrophobic factors noted here are combined in two hypothetical models of translocation, the first involving initial interaction of the presumptive transmembrane segment with the membrane; the second assuming initial interaction of a leader sequence.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Beim Affen ist der Druck im Sinus sagittalis in komplexer Weise abhängig vom zerebralen Blutdurchfluß und intrakraniellen Druck; der Jugularvenendruck gibt ein qualitatives Maß für die zerebrale Durchblutung. Bei einer intrakraniellen Drucksteigerung antwortet der Druck im vorderen Sinus sagittalis auf Änderungen der Durchströmung mit erheblichen Veränderungen, doch gibt es nur wenig Beziehungen zwischen diesen erheblichen Druckschwankungen zu den Druckverhältnissen im Sinus transversus und in der Vena jugularis. Auf Grund dieser Beobachtungen vermuteten wir eine Kompession des Sinus sagittalis als Folge der intrakraniellen Drucksteigerung. Es läßt sich beweisen, daß diese Kompression im Bereich der Hinteraurallinie ihr Maximum hat. Es scheint außerdem bei intrakranieller Drucksteigerung zu einer Verminderung des Durchmessers der zerebralen Gefäße proximal des Sinus zu kommen. Aus der Wechselwirkung zwischen diesen beiden Faktoren resultiert der Druck im Sinus sagittalis. Im Endstadium der zerebralen Dekompension, wenn der intrakranielle und der arterielle Druck gleich sind, nähert sich der Druck im Sinus sagittalis dem diastolischen Blutdruck. Das entspricht einem fast vollständigen Kollaps des Sinus.
    Abstract: Résumé Chez le singe, la pression du sinus sagittal est une fonction complexe du flux sanguin cérébral et de la pression intracrânienne; la pression de la veine jugulaire est la mesure qualitative du flux sanguin cérébral. En présence d'hypertension intracrânienne, la réponse de la pression du sinus sagittal antérieure, aux variations du débit sanguin est grandement exagérée, mais il y a une répercussion minimale de ces grandes fluctuations de pression, au sinus transverse et à la veine jugulaire. Sur la base de ces observations, nous avons postulé la compression du sinus sagittal en réponse à la pression intracrânienne accrue, et l'évidence fait localiser la compression maximum à la region de la ligne «interaurale». La réduction en calibre, des vaisseaux cérébraux proximaux des sinus, apparaît aussi se produire avec l'hypertension intracrânienne et, dans la phase ultime, l'intéraction dynamique de ces deux facteurs est responsable de la pression du sinus sagittal. Dans le stade final de décompensation cérébrale, quand les tensions intracrânienne et artérielle sont égales, la pression du sinus sagittal antérieur se rapproche aussi de la pression diastolique, indiquant un collapsus presque total du sinus.
    Notes: Summary In the monkey, sagittal sinus pressure is a complex function of cerebral blood flow and intracranial pressure; jugular vein pressure is a qualitative measure of cerebral blood flow. In the presence of intracranial hypertension, the response of anterior sagittal sinus pressure to blood flow changes is greatly exaggerated, but there is minimal communication of these large fluctuations in pressure to the transverse sinus and jugular vein. On the basis of these observations, we postulated compression of the sagittal sinus in response to increased intracranial pressure, and evidence is presented to localize maximum compression to the region of the interaural line. Reduction in diameter of cerebral vessels proximal to the sinus also appears to occur with intracranial hypertension, and ultimately, the dynamic interaction of these two factors is responsible for sagittal sinus pressure. In the end stage of cerebral decompensation, when intracranial and arterial tensions are equal, anterior sagittal sinus pressure also approaches the diastolic pressure, indicating nearly total collapse of the sinus.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die intrakraniellen Gefäße von Affen wurden untersucht, bei denen eine Hirnschwellung und eine intrakranielle Drucksteigerung durch allmählich zunehmendes Aufblasen eines extraduralen Ballons hervorgerufen worden war. Die Schädel wurden im Augenblick der Tötung in flüssigem Stickstoff gefroren und in der Folge in Serie geschnitten. Der auffallendste Befund seitens des vaskulären Systems war ein Kollaps des Sinus sagittalis und eine erhebliche Konstriktion des Sinus rectus bei den Versuchstieren, bei denen es zu einer vollständigen zerebralen Dekompensation gekommen war. In einem Fall war die A. pericallosa kollabiert, wahrscheinlich bedingt durch die Ausdehnung des Gehirns mit Verlegung der Balkencisterne. Die Lumina vieler kleiner Arterien und Venen in den Furchen und an der Oberfläche des Kortex waren ebenfalls verlegt, während andere kleine Gefäße nicht beeinträchtigt waren. Die Bedeutung des Kollapses der zerebralen Gefäße im Zusammenhang mit der Ischämie, die durch Hirnschwellung und intrakranielle Drucksteigerung entsteht, wird diskutiert.
    Abstract: Resumé Nous avons examiné des vaisseaux intra-crâniens de singes chez lesquels l'oedème cérébral et l'hypertension intrac ânienne étaient chez lesquels l'oedème cérébral et l'hypertension intrac ânienne étaient profus par l'expansion progressive d'un ballon extra-dural. Les crânes furent congelés dans de l'azote liquide au moment de la mort et, par la suite, mis en coupes suivant des plans stéréotaxiques. Les altérations vasculaires les plus remarquables furent le collapsus du sinus sagittal, et une grave sténose du sinus droit dans ces préparations avec décompensation cérébrale complète. Dans l'une de ces préparations, l'artère péricalleuse était collabée, probablement à cause de l'expansion de l'oedème cérébral et de l'oblitération de la citerne supracalleuse. La lumière de beaucoup d'artérioles et veinules «in sulci» et sur la surface corticale étaient aussi oblitérés, alors que d'autres petits vaisseaux étaient inaltérés. La contribution du collapsus vasculaire cérébral à l'ischémie produite par l'oedème cérébral et l'hypertension intracrânienne est discutée.
    Notes: Summary Intracranial vessels have been examined in monkeys in which brain swelling and intracranial hypertension were produced by gradual expansion of an extradural balloon. The heads were frozen in liquid nitrogen at the time of sacrifice and subsequently sectioned in stereotaxic coronal planes. The most conspicuous vascular alterations were collapse of the sagittal sinus and severe constriction of the straight sinus in those preparations with complete cerebral decompensation. In one preparation, the pericallosal artery was collapsed, probably due to expansion of the brain and obliteration of the supracallosal cistern. The lumens of many small arteries and veins in sulci and on the cortical surface were also obliterated whereas other small vessels were unaffected. The contribution of cerebrovascular collapse to the ischemia produced by brain swelling and intracranial hypertension is discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 157 (1988), S. 271-277 
    ISSN: 0006-291X
    Keywords: [abr] BSF-2; B-cell stimulatory factor-2 ; [abr] CRP; C-reactive protein ; [abr] IFN B2; Interferon B2 ; [abr] IL-1; interleukin-1 ; [abr] IL-6; interleukin-6 ; [abr] SAA; serum amyloid A ; [abr] SDS; sodium dodecyl sulfate
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 157 (1988), S. 271-277 
    ISSN: 0006-291X
    Keywords: [abr] BSF-2; B-cell stimulatory factor-2 ; [abr] CRP; C-reactive protein ; [abr] IFN B2; Interferon B2 ; [abr] IL-1; interleukin-1 ; [abr] IL-6; interleukin-6 ; [abr] SAA; serum amyloid A ; [abr] SDS; sodium dodecyl sulfate
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 7 (1962), S. 276-280 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Bioorganic & Medicinal Chemistry Letters 3 (1993), S. 2177-2182 
    ISSN: 0960-894X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Physiology-Paris 88 (1994), S. 383 
    ISSN: 0928-4257
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Physics, Section A 508 (1990), S. 371-376 
    ISSN: 0375-9474
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Physics B (Proceedings Supplements) 21 (1991), S. 207-219 
    ISSN: 0920-5632
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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