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  • 2000-2004  (2)
  • Capacitance measurements Endogenous ion channels Maitotoxin Nonselective cation channel Stretch-activated cation channel Xenopus laevis oocyte  (1)
  • Cerebritis  (1)
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  • 2000-2004  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 40 (2000), S. 1017-1029 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Hirnabszess ; Zerebritis ; Metastatische Herdenzephalitis ; Endokarditis ; MRT ; Gd-DTPA ; Keywords Brain abscess ; Cerebritis ; Metastatic focal encephalitis ; Endocarditis ; MRI ; Gd-DTPA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract The hematogenous spread of bacteria, fungi and protozoa may also reach the brain vessels, which happens mostly through septic emboli. From such an embolus a metastatic focal encephalitis and later a septic-embolic brain abscess may arise. The most frequently underlying infections that may cause septic emboli are bacterial endocarditis as well as bacterial infections of artificial heart valve prostheses. Congenital heart malformations with a right-to-left shunt also play here a certain role. Basically, however, all septic conditions and bacteriemias may cause septic-embolic brain abscesses. They occur frequently as multiple lesions. MRI is superior to CT in depicting the different stages of evolution from focal encephalitis, through the hardly encapsulated early abscess, to the formation of a membrane and later a dense fibrous capsule. The medical treatment of a brain abscess requires properly performed CT or MRI follow-up examinations in order to realize early enough a possible growing of such a lesion.
    Notes: Zusammenfassung Die hämatogene Ausbreitung von Bakterien, Pilzen oder Protozoen bis in die Hirngefäße erfolgt meist durch eine septische Embolie. Es entstehen eine metastatische Herdenzephalitis und im weiteren Verlauf daraus ein septisch-embolischer Hirnabszess. Die häufigste Grunderkrankung die zu septischen Embolien führt ist die bakterielle Endokarditis sowie die bakterielle Infektion von Herzklappenprothesen. Eine besondere Bedeutung kommt hier den angeborenen kardialen Fehlbildungen mit Rechts-Links-Shunt zu. Grundsätzlich können jedoch alle Bakteriämien zu septisch-embolischen Hirnabszessen führen. Septisch-embolische Hirnabszesse treten aufgrund ihres Entstehungsmechanismus häufig multipel auf. Die CT und besser noch die MRT erlauben die Darstellung aller Entwicklungsstadien von der Herdenzephalitis über den kaum abgegrenzten Abszess, die Membranbildung bis zur Entstehung einer dicken, die eitergefüllte Höhle allseits umgebenden Abszesskapsel. Die medikamentöse Therapie von Hirnabszessen erfordert Verlaufsuntersuchungen, um einer eventuellen Größenzunahme der Läsion(en) frühzeitig durch Umstellung der antibiotischen Medikation oder durch operative Abszessentfernung zu begegnen.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Capacitance measurements Endogenous ion channels Maitotoxin Nonselective cation channel Stretch-activated cation channel Xenopus laevis oocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The activation of cation channels in oocytes of Xenopus laevis by the marine poison maitotoxin (MTX) was monitored as membrane current (I m), conductance (G m) and membrane surface area determined by continuous measurements of membrane capacitance (C m). When MTX (25 pM) was added to the bathing solution there was an abrupt, large increase in inward membrane currents. Current/voltage relationships (I/V curves) were linear and suggested activation of voltage-independent nonselective cation channels (NSCC). MTX-induced Ca2+-sensitive currents were mainly carried by Na+ and were suppressed by low (0 mM) or high (40 mM) external Ca2+ concentrations and removal of Na+. Gadolinium (Gd3+, 10–500 µM) also had inhibitory effects, demonstrating the possible involvement of stretch-activated cation channels (SACC). In a high concentration (500 µM), amiloride substantially reduced the MTX-activated current while lower amiloride concentrations (50–100 µM) stimulated the current further. Continuous measurements of C m revealed that MTX induced exocytotic delivery and functional insertion of new channel proteins into the plasma membrane, indicated by a Ca2+-dependent increase in membrane surface area by around 28%. From these data we conclude that MTX activates NSCC that require relatively high concentrations of amiloride to be blocked. Furthermore, MTX possibly stimulates activation of Gd3+- and Ca2+-sensitive mechanosensitive cation channels. Stimulation of these channels is achieved by exocytotic delivery and functional insertion of new channels into the plasma membrane in a pathway that depends on the presence of extracellular Ca2+.
    Type of Medium: Electronic Resource
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