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  • 2000-2004  (2)
  • 2002
  • 2000  (2)
  • Amiloride cAMP ENaC Epithelial sodium channel Protein kinase A  (1)
  • Endokarditis  (1)
  • 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: Amiloride cAMP ENaC Epithelial sodium channel Protein kinase A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The rate of Na+ (re)absorption across tight epithelia such as in distal kidney nephron and colon is to a large extent controlled at the level of the epithelial Na+ channel (ENaC). In kidney, antidiuretic hormone (ADH, vasopressin) stimulates the expression/activity of this channel by a cAMP/protein-kinase-A- (PKA-) mediated pathway. However, a clear upregulation of ENaC function by cAMP could not be reproduced with cloned channel subunits in the Xenopus oocyte expression system, suggesting the hypothesis that an additional factor is missing. In contrast, we show here that membrane-permeant cAMP can activate ENaC expressed in Xenopus oocytes (3.8-fold) upon replacement of the rat α-subunit by a new α-subunit cloned from guinea-pig colon (gpα). This α-subunit is 76% identical with its rat orthologue originating from ADH-insensitive rat colon. The biophysical fingerprints of the hybrid ENaC formed by this guinea-pig α-subunit together with rat β- and γ-subunits are indistinguishable from those of rat ENaC (rENaC). Injection of the PKA inhibitor PKI-(6–22)-amide into the oocyte had no effect on the basal activity of rat ENaC but inhibited the activity of gpα-containing hybrid ENaC and greatly decreased its stimulation by cAMP. This suggests that, unlike for rat ENaC, tonic PKA activity is required for basal function of gpα-containing ENaC and that PKA mediates its cAMP-induced activation. This regulatory behaviour is not common to all ENaCs containing an α-subunit cloned from an ADH-responsive tissue since xENaC, which was cloned from the ADH-sensitive Xenopus laevis A6 epithelia, is, when expressed in oocytes, resistant to cAMP, similar to rat ENaC. This study demonstrates that the PKA sensitivity of ENaC can depend on the nature of the ENaC α-subunit and raises the possibility that cAMP can stimulate ENaCs by different mechanisms.
    Type of Medium: Electronic Resource
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