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Die Nukleinsäure-Amplifikations Testung (NAT) von Blutprodukten wurde Mitte der 90er Jahre von europäischen Plasma verarbeitenden Firmen und großen deutschen Blutspendediensten entwickelt. Primäres Ziel war eine verbesserte Sicherheit von Blutprodukten, indem das so genannte diagnostische Fenster nach einer Virusinfektion bis zum ersten Nachweis von Antikörpern so weit wie möglich geschlossen werden sollte. Bei einer qualitätsgerechten PCR kommen bereits der Probenentnahme, dem Probentransport sowie der Probenlagerung große Bedeutung zu, da vermieden werden muß, daß es durch ungeeignete Antikoagulanzien oder Entnahmetechniken zu einem Sensitivitätsverlust kommt oder daß Kontaminationen falsch positive Ergebnisse hervorrufen. Wird ein Pooling von Proben durchgeführt, ergibt sich ein Verdünnungsfaktor, weshalb darauf zu achten ist, dass gegebenenfalls nachfolgende Anreicherungsschritte für Viren, wie z.B. eine Zentrifugation, implementiert werden. Der Gesamtprozeß von Pooling und Virusanreicherung ist ebenso wie die Probenvorbereitung durch geeignete Maßnahmen zu validieren und durch Qualitätssicherungsmaßnahmen zu flankieren. Die in der Extraktion der viralen Nukleinsäuren verwendeten Reagenzien sollten im Laboralltag möglichst einfach zu handhaben sein, keine Gefährdung des Laborpersonals darstellen und die Virus-Nukleinsäure gleichzeitig mit höchster Effizienz freisetzen und in sehr hoher Reinheit für die anschließende Amplifikation bereitstellen. Qualitätssicherungmaßnahmen sollen hier sowohl die geforderte Effizienz des Prozesses sichern als auch verhindern, daß es in dieser kritischen Phase zu Kontaminationen kommt. Zur Amplifikation stehen verschiedene Methoden zur Verfügung, wobei die PCR, insbesondere bei inhouse-Systemen, die weiteste Verbreitung gefunden hat. Der Prozeß der Amplifikation sollte möglichst im geschlossenen System erfolgen, wie dies z.B. in Real-time PCR-Systemen die Regel ist, ohne daß das Reaktionsgefäß während oder nach dem Amplifikationsprozeß geöffnet werden muß. Dies gewährleistet eine hohe Sicherheit vor Kontaminationen durch freigesetzte Amplifikate. Im Blutspendewesen ist es von höchster Bedeutung, daß negative Ergebnisse tatsächlich negative Blutspenden anzeigen. Interne Kontrollen, die eine korrekte Funktionsweise jeder individuellen PCR signalisieren, sollten deshalb in jeder Reaktion mitgeführt werden. Neben internen Kontrollen sind externe Negativ- und Positiv-Kontrollen mitzuführen, um falsch positive Reaktionen nachzuweisen bzw. auch die vor der PCR liegenden Prozesse wie Virusanreicherung und Extraktion zu überwachen. Alle Prozesse sind nach den von den Behörden festgelegten Kriterien durchgängig zu validieren, und es ist routinemäßig an externen Qualitätskontrollmaßnahmen (Ringversuchen) teilzunehmen.
Im vorliegenden Fall wird von einer Fehldiagnose auf der Grundlage eines falsch-reaktiven Anti-HCV-Tests und eines falsch-reaktiven HCV-Nukleinsäureamplifikationstests (NAT) berichtet, die bei einem 58-jährigen chirurgischen Oberarzt im Rahmen einer arbeitsmedizinischen Vorsorgeuntersuchung im krankenhauseigenen Labor gestellt wurde und zu einem knapp zweimonatigen Berufsverbot führte. Basis dieser Fehldiagnose war ein wiederholt schwach reaktiver HCV-Antikörper-ELISA, der mit einem Nukleinsäureamplifikationstest, der ebenfalls schwach positiv ausfiel, überprüft wurde. Ein Antikörperbestätigungs- bzw. Ergänzungstest (Immunoblot) wurde nicht durchgeführt. Die Fehldiagnose ist jedoch nicht durch einen Testfehler, sondern durch ein Missverständnis entstanden, indem beim Kliniker zwei Laborindizien zu einem Beweis aufsummiert wurden.
Ein Krankenhauslabor und ein Einsendelabor, das mehrere Krankenhäuser versorgt, haben prospektiv 3.907 Blutkulturflaschen für das BACTEC™ 9000–System (BDDiagnostics, Heidelberg, Germany) untersucht. Dabei wurden 1.888 aerobe Flaschen, 1.880 anaerobe Flaschen und 139 pädiatrische Blutkulturflaschen verarbeitet. Es wurden der Zeitpunkt der Beimpfung und der Zeitpunkt des Einlesens der Kulturen in das Gera ̈t dokumentiert. Neben den Medientypen und dem Blutvolumen wurden folgende Daten erhoben: Die Zeit vom Einlesen in das Gerät bis zum positiven Signal (Detektionszeit), die Identifizierung des Erregers bis zur Species, die Antibiotikatherapie und die Wiederfindungsrate verglichen mit der terminalen Subkultur. Die mittlere Transportdauer betrug 21,4 h, die mittlere Detektionszeit 21,5 h. 27 Flaschen waren falsch negativ und sechs Flaschen falsch positiv. Bei sieben der falschnegativen Flaschen hatte die Partnerflasche ein positives Signal gegeben (Staphylococcus aureus, Enterobactercloacae, Enterococcus faecalis, Candida albicans, Burkholderia cepacia, zwei Pseudomonas aeruginosa-Stämme). Davon waren vier Isolate strikte Aerobier, die nichtin der anaeroben Flasche wuchsen, fünf Patienten standen unter Antibiotikatherapie und eine Flasche hatte eine Transportzeit)48 h und ist in dieser Gruppe ebenfalls aufgeführt. 15/27 falsch negative Flaschen hatten eine Transportzeit)48 h, 11 Patienten bekamen in dieser Gruppe eine Antibiotikatherapie. 6/27 falsch negative Flaschen hatten eine Transportzeit-48 h, davon wurden zwei Patienten antibiotisch behandelt. Einmal handelte es sich um C. glabrata, die nicht in der anaeroben Flaschewuchs. Der klinisch relevante Anteil der falsch negativen Blutkulturen (Isolat nicht in der Begleitflasche nachgewiesen), der innerhalb von 48 h in das BACTEC™ 9000-Gerät eingelesen wurde, betrug 0,15%.
Die HIV-1-Resistenztestung wird ein immer bedeutenderer Bestandteil des Monitorings der antiretroviralen Therapie und erfolgt in der Regel mittels Genotypisierung. Zur Zeit sind zwei Systeme kommerziell erhältlich und obwohl diese technisch nicht zu den einfach durchführbaren Methoden gehören, haben sie doch einen hohen Grad an Qualität erreicht. Modifikationen der Standardprotokolle sind für bestimmte Fragestellungen durchaus von Vorteil. Obwohl beide Systeme auf Entscheidungsregeln basierende Resistenz-Reports beinhalten, braucht es das zusätzliche Wissen und die Erfahrung des Anwenders, um die detektierten Mutationsmuster in klinisch brauchbare Resultate überführen zu können. Beide der hier detailliert beschriebenen Systeme haben ihre Vor- und Nachteile. Die Entscheidung für das eine oder andere System muss aufgrund der individuellen Bedürfnisse getroffen werden. Microarray-Systemen könnte der Markt der Zukunft gehören.
Die 1990 eingeführten ersten kommerziellen HCV-Antikörper-Screening Tests wurden im Laufe der Jahre bezüglich ihrer Sensitivität und Spezifität erheblich verbessert. Inzwischen sind auch standardisierte Verfahren zum qualitativen und quantitativen HCV-RNA-Nachweis verfügbar, die Dank der Einführung eines internationalen Standards miteinander vergleichbar sind. Aber auch mittels Antigen-ELISA ist es möglich, die im Patientenblut zirkulierende Virusmenge zu quantifizieren. Einer der Hauptübertragungswege – Bluttransfusion und Blutprodukte – der HCV-Infektion wurde durch die Verbesserung der virologischen Diagnostik nahezu eliminiert. Inzwischen sind i. v.-Drogenabhängige die Hauptrisikogruppe für eine HCV-Infektion. Bislang nur zu Forschungszwecken etablierte Methoden zur Messung der zellulären Immunität oder auch die Messung neutralisierender Antikörper könnten zum Beispiel im Rahmen einer Impfstoffentwicklung an Bedeutung gewinnen.
Highly sensitive qualitative and quantitative automatednucleic acid amplification tests (NATs) that are commercially available for the detection of hepatitis B virus (HBV)infection have been developed only in the last few years.The potential indications for HBV NATs are: follow-up ofchronic hepatitis B, therapy and antiviral resistance monitoring, determination of infectivity and transmission risk,detection of occult (HBsAg-negative and HBV DNA-positive) infection and mutant virus which may escape serologic diagnosis, blood donor screening, and resolution ofunusual or discordant serologic constellations. Although NATs are now widely implemented in the routine diagnosis of clinical laboratories, there are several importantissues which need to be further investigated. Standardisation of NATs used for the monitoring of antiviral therapyand follow-up of chronic infection is still lacking, and theclinical significance of HBV DNA levels needs to be clarified. The influence of genetic variability in terms of genotype variation has been poorly investigated so far.Although there are highly sensitive automated NATs forblood donor screening available, their implementation is still subject to discussion and certain countries rejectedHBV DNA testing for blood donation for reasons of poor cost-effectiveness.
Calreticulin is a Ca2+ -binding chaperone that resides in the lumen of the endoplasmic reticulum and is involved in the regulation of intracellular Ca2+ homeostasis and in the folding of newly synthesized glycoproteins. In this study, we have used site-specific mutagenesis to map amino acid residues that are critical in calreticulin function. We have focused on two cysteine residues (Cys(88) and Cys(120)), which form a disulfide bridge in the N-terminal domain of calreticulin, on a tryptophan residue located in the carbohydrate binding site (Trp(302)), and on certain residues located at the tip of the "hairpin-like" P-domain of the protein (Glu(238), Glu(239), Asp(241), Glu(243), and Trp(244)). Calreticulin mutants were expressed in crt(-/-) fibroblasts, and bradykinin-dependent Ca2+ release was measured as a marker of calreticulin function. Bradykinin-dependent Ca2+ release from the endoplasmic reticulum was rescued by wild-type calreticulin and by the Glu(238), Glu(239), Asp(241), and Glu(243) mutants. The Cys(88) and Cys(120) mutants rescued the calreticulin-deficient phenotype only partially ( approximately 40%), and the Trp(244) and Trp(302) mutants did not rescue it at all. We identified four amino acid residues (Glu(239), Asp(241), Glu(243), and Trp(244)) at the hairpin tip of the P-domain that are critical in the formation of a complex between ERp57 and calreticulin. Although the Glu(239), Asp(241), and Glu(243) mutants did not bind ERp57 efficiently, they fully restored bradykinin-dependent Ca2+ release in crt(-/-) cells. This indicates that binding of ERp57 to calreticulin may not be critical for the chaperone function of calreticulin with respect to the bradykinin receptor.
NAD(P)H oxidase, the main source of reactive oxygen species in vascular cells, is known to be regulated by redox processes and thiols. However, the nature of thiol-dependent regulation has not been established. Protein disulfide isomerase (PDI) is a dithiol/disulfide oxidoreductase chaperone of the thioredoxin superfamily involved in protein processing and translocation. We postulated that PDI regulates NAD(P)H oxidase activity of rabbit aortic smooth muscle cells (VSMCs). Western blotting confirmed robust PDI expression and shift to membrane fraction after incubation with angiotensin II (AII, 100 nm, 6 h). In VSMC membrane fraction, PDI antagonism with bacitracin, scrambled RNase, or neutralizing antibody led to 26-83% inhibition (p < 0.05) of oxidase activity. AII incubation led to significant increase in oxidase activity, accompanied by a 6-fold increase in PDI refolding isomerase activity. AII-induced NAD(P)H oxidase activation was inhibited by 57-71% with antisense oligonucleotide against PDI (PDIasODN). Dihydroethidium fluorescence showed decreased superoxide generation due to PDIasODN. Confocal microscopy showed co-localization between PDI and the oxidase subunits p22(phox), Nox1, and Nox4. Co-immunoprecipitation assays supported spatial association between PDI and oxidase subunits p22(phox), Nox1, and Nox4 in VSMCs. Moreover, in HEK293 cells transfected with green fluorescent protein constructs for Nox1, Nox2, and Nox4, each of these subunits co-immunoprecipitated with PDI. Akt phosphorylation, a known downstream pathway of AII-driven oxidase activation, was significantly reduced by PDIasODN. These results suggest that PDI closely associates with NAD(P)H oxidase and acts as a novel redox-sensitive regulatory protein of such enzyme complex, potentially affecting subunit traffic/assembling.
Excessive accumulation of the extracellular matrix is a hallmark of many inflammatory and fibrotic diseases, including those of the kidney. This study addresses the question whether NO, in addition to inhibiting the expression of MMP-9, a prominent metalloprotease expressed by mesangial cells, additionally modulates expression of its endogenous inhibitor TIMP-1. We demonstrate that exogenous NO has no modulatory effect on the extracellular TIMP-1 content but strongly amplifies the early increase in cytokine-induced TIMP-1 mRNA and protein levels. We examined whether transforming growth factor beta (TGFbeta), a potent profibrotic cytokine, is involved in the regulation of NO-dependent TIMP-1 expression. Experiments utilizing a pan-specific neutralizing TGFbeta antibody demonstrate that the NO-induced amplification of TIMP-1 is mediated by extracellular TGFbeta. Mechanistically, NO causes a rapid increase in Smad-2 phosphorylation, which is abrogated by the addition of neutralizing TGFbeta antisera. Similarly, the NO-dependent increase in Smad-2 phosphorylation is prevented in the presence of an inhibitor of TGFbeta-RI kinase, indicating that the NO-dependent activation of Smad-2 occurs via the TGFbeta-type I receptor. Furthermore, activation of the Smad signaling cascade by NO is corroborated by the NO-dependent increase in nuclear Smad-4 level and is paralleled by increased DNA binding of Smad-2/3 containing complexes to a TIMP-1-specific Smad-binding element (SBE). Reporter gene assays revealed that NO activates a 0.6-kb TIMP-1 gene promoter fragment as well as a TGFbeta-inducible and SBE-driven control promoter. Chromatin immunoprecipitation analysis also demonstrated DNA binding activity of Smad-3 and Smad-4 proteins to the TIMP-1-specific SBE. Finally, by enzyme-linked immunosorbent assay, we demonstrated that NO causes a rapid increase in TGFbeta(1) levels in cell supernatants. Together, these experiments demonstrate that NO by induction of the Smad signaling pathway modulates TIMP-1 expression.
The tumor necrosis factor family member Fas ligand (FasL) induces apoptosis in Fas receptor-expressing target cells and is an important cytotoxic effector molecule used by CTL- and NK-cells. In these hematopoietic cells, newly synthesized FasL is stored in specialized secretory lysosomes and only delivered to the cell surface upon activation and target cell recognition. FasL contains an 80-amino acid-long cytoplasmic tail, which includes a proline-rich domain as a bona fide Src homology 3 domain-binding site. This proline-rich domain has been implicated in FasL sorting to secretory lysosomes, and it may also be important for reverse signaling via FasL, which has been described to influence T-cell activation. Here we report the identification of the Src homology 3 domain-containing adaptor protein PSTPIP as a FasL-interacting partner, which binds to the proline-rich domain. PSTPIP co-expression leads to an increased intracellular localization of Fas ligand, thereby regulating extracellular availability and cytotoxic activity of the molecule. In addition, we demonstrate recruitment of the tyrosine phosphatase PTP-PEST by PSTPIP into FasL·PSTPIP·PTP-PEST complexes which may contribute to FasL reverse signaling.
Mechanical stress is known to modulate fundamental events such as cell life and death. Mechanical stretch in particular has been identified as a positive regulator of proliferation in skin keratinocytes and other cell systems. In the present study it was investigated whether antiapoptotic signaling is also stimulated by mechanical stretch. It was demonstrated that mechanical stretch rapidly induced the phosphorylation of the proto-oncogene protein kinase B (PKB)/Akt at both phosphorylation sites (serine 473/threonine 308) in different epithelial cells (HaCaT, A-431, and human embryonic kidney-293). Blocking of phosphoinositide 3-OH kinase by selective inhibitors (LY-294002 and wortmannin) abrogated the stretch-induced PKB/Akt phosphorylation. Furthermore mechanical stretch stimulated phosphorylation of epidermal growth factor receptor (EGFR) and the formation of EGFR membrane clusters. Functional blocking of EGFR phosphorylation by either selective inhibitors (AG1478 and PD168393) or dominant-negative expression suppressed stretch-induced PKB/Akt phosphorylation. Finally, the angiotensin II type 1 receptor (AT1-R) was shown to induce positive transactivation of EGFR in response to cell stretch. These findings define a novel signaling pathway of mechanical stretch, namely the activation of PKB/Akt by transactivation of EGFR via angiotensin II type 1 receptor. Evidence is provided that stretch-induced activation of PKB/Akt protects cells against induced apoptosis.
Soluble guanylyl cyclase (sGC) is the major cytosolic receptor for nitric oxide (NO) that converts GTP into the second messenger cGMP in a NO-dependent manner. Other factors controlling this key enzyme are intracellular proteins such as Hsp90 and PSD95, which bind to sGC and modulate its activity, stability, and localization. To date little is known about the effects of posttranslational modifications of sGC, although circumstantial evidence suggests that reversible phosphorylation may contribute to sGC regulation. Here we demonstrate that inhibitors of protein-tyrosine phosphatases such as pervanadate and bisperoxo(1,10-phenanthroline)oxovanadate(V) as well as reactive oxygen species such as H2O2 induce specific tyrosine phosphorylation of the β1 but not of the α1 subunit of sGC. Tyrosine phosphorylation of sGCβ1 is also inducible by pervanadate and H2O2 in intact PC12 cells, rat aortic smooth muscle cells, and in rat aortic tissues, indicating that tyrosine phosphorylation of sGC may also occur in vivo. We have mapped the major tyrosine phosphorylation site to position 192 of β1, where it forms part of a highly acidic phospho-acceptor site for Src-like kinases. In the phosphorylated state Tyr(P)-192 exposes a docking site for SH2 domains and efficiently recruits Src and Fyn to sGCβ1, thereby promoting multiple phosphorylation of the enzyme. Our results demonstrate that sGC is subject to tyrosine phosphorylation and interaction with Src-like kinases, revealing an unexpected cross-talk between the NO/cGMP and tyrosine kinase signaling pathways at the level of sGC.
Cathepsin D (CatD) is a lysosomal aspartic proteinase and plays an important role in the degradation of proteins and in apoptotic processes induced by oxidative stress, cytokines, and aging. All of these stimuli are potent inducers of endothelial cell apoptosis. Therefore, we investigated the role of CatD in endothelial cell apoptosis and determined the underlying mechanisms. Incubation with 100-500 microm H2O2 for 12 h induced apoptosis in endothelial cells. To determine a role for CatD, we co-incubated endothelial cells with the CatD inhibitor pepstatin A. Pepstatin A as well as genetic knock down of CatD abolished H2O2-induced apoptosis. In contrast, overexpression of CatD wild type but not a catalytically inactive mutant of CatD (CatDD295N) induced apoptosis under basal conditions. To gain insights into the underlying mechanisms, we investigated the effect of CatD on reactive oxygen species (ROS) formation. Indeed, knocking down CatD expression reduced H2O2-induced ROS formation and apoptosis. The major redox regulator in endothelial cells is thioredoxin-1 (Trx), which plays a crucial role in apoptosis inhibition. Thus, we hypothesized that CatD may alter Trx protein levels and thereby promote formation of ROS and apoptosis. Incubation with 100 microm H2O2 for 6 h decreased Trx protein levels, whereas Trx mRNA was not altered. H2O2-induced Trx degradation was inhibited by pepstatin A and genetic knock down of CatD but not by other protease inhibitors. Incubation of unstimulated cell lysates with recombinant CatD significantly reduced Trx protein levels in vitro, which was completely blocked by pepstatin A pre-incubation. Overexpression of CatD reduced Trx protein in cells. Moreover, H2O2 incubation led to a translocation of Trx to the lysosomes prior to the induction of apoptosis. Taken together, CatD induces apoptosis via degradation of Trx protein, which is an essential anti-apoptotic and reactive oxygen species scavenging protein in endothelial cells.
Human endothelial circulating progenitor cells (CPCs) can differentiate to cardiomyogenic cells during co-culture with neonatal rat cardiomyocytes. Wnt proteins induce myogenic specification and cardiac myogenesis. Here, we elucidated the effect of Wnts on differentiation of CPCs to cardiomyogenic cells. CPCs from peripheral blood mononuclear cells were isolated from healthy volunteers and co-cultured with neonatal rat cardiomyocytes. 6–10 days after co-culture, cardiac differentiation was determined by α-sarcomeric actinin staining of human lymphocyte antigen-positive cells (fluorescence-activated cell-sorting analysis) and mRNA expression of human myosin heavy chain and atrial natriuretic peptide. Supplementation of co-cultures with Wnt11-conditioned medium significantly enhanced the differentiation of CPCs to cardiomyocytes (1.7 ± 0.3-fold), whereas Wnt3A-conditioned medium showed no effect. Cell fusion was not affected by Wnt11-conditioned medium. Because Wnts inhibit glycogen synthase kinase-3β, we further determined whether the glycogen synthase kinase-3β inhibitor LiCl also enhanced cardiac differentiation of CPCs. However, LiCl (10 mm) did not affect CPC differentiation. In contrast, Wnt11-conditioned medium time-dependently activated protein kinase C (PKC). Moreover, the PKC inhibitors bisindolylmaleimide I and III significantly blocked differentiation of CPCs to cardiomyocytes. PKC activation by phorbol 12-myristate 13-acetate significantly increased CPC differentiation to a similar extent as compared with Wnt11-conditioned medium. Our data demonstrate that Wnt11, but not Wnt3A, augments cardiomyogenic differentiation of human CPCs. Wnt11 promotes cardiac differentiation via the non-canonical PKC-dependent signaling pathway.
Alternative NADH dehydrogenases (NADH:ubiquinone oxidoreductases) are single subunit respiratory chain enzymes found in plant and fungal mitochondria and in many bacteria. It is unclear how these peripheral membrane proteins interact with their hydrophobic substrate ubiquinone. Known inhibitors of alternative NADH dehydrogenases bind with rather low affinities. We have identified 1-hydroxy-2-dodecyl-4(1H)quinolone as a high affinity inhibitor of alternative NADH dehydrogenase from Yarrowia lipolytica. Using this compound, we have analyzed the bisubstrate and inhibition kinetics for NADH and decylubiquinone. We found that the kinetics of alternative NADH dehydrogenase follow a ping-pong mechanism. This suggests that NADH and the ubiquinone headgroup interact with the same binding pocket in an alternating fashion.
Generation of reactive oxygen species (ROS) is increasingly recognized as an important cellular process involved in numerous physiological and pathophysiological processes. Complex I (NADH:ubiquinone oxidoreductase) is considered as one of the major sources of ROS within mitochondria. Yet, the exact site and mechanism of superoxide production by this large membrane-bound multiprotein complex has remained controversial. Here we show that isolated complex I from Yarrowia lipolytica forms superoxide at a rate of 0.15% of the rate measured for catalytic turnover. Superoxide production is not inhibited by ubiquinone analogous inhibitors. Because mutant complex I lacking a detectable iron-sulfur cluster N2 exhibited the same rate of ROS production, this terminal redox center could be excluded as a source of electrons. From the effect of different ubiquinone derivatives and pH on this side reaction of complex I we concluded that oxygen accepts electrons from FMNH or FMN semiquinone either directly or via more hydrophilic ubiquinone derivatives.
Minimal invazif endoskopik giriflimlerin kalp cerrahisinde kullanımı ancak telemanipülatör sistemlerin kullanıma girmesiyle mümkün olmufltur. Bu çalıflmada total endoskopik revaskülarizasyon için kullanılan robotik destekli telemanipülasyon sistemleri gözden geçirilip, çalıflan ve duran kalpte uygulamalar derlenmifltir. Robotik cerrahi günümüzde halen geliflme aflamasındadır. Maliyetin yüksek oluflu ve sadece seçilmifl bir hasta grubunda uygulanabiliyor olması bu yeni tekni¤in en büyük sınırlayıcı faktörleridir. Ancak teknoloji üzerine çalıflmalar ve özellikle anastomoz tekniklerinin geliflmesiyle koroner revaskülarizasyon için bir alternatif olacaktır. Henüz istenen hedeflere ulaflılmamıflsa da gelecek umut vericidir.
Severe acute respiratory syndrome (SARS) is a new infectious disease caused by a novel coronavirus that leads to deleterious pulmonary pathological features. Due to its high morbidity and mortality and widespread occurrence, SARS has evolved as an important respiratory disease which may be encountered everywhere in the world. The virus was identified as the causative agent of SARS due to the efforts of a WHO-led laboratory network. The potential mutability of the SARS-CoV genome may lead to new SARS outbreaks and several regions of the viral genomes open reading frames have been identified which may contribute to the severe virulence of the virus. With regard to the pathogenesis of SARS, several mechanisms involving both direct effects on target cells and indirect effects via the immune system may exist. Vaccination would offer the most attractive approach to prevent new epidemics of SARS, but the development of vaccines is difficult due to missing data on the role of immune system-virus interactions and the potential mutability of the virus. Even in a situation of no new infections, SARS remains a major health hazard, as new epidemics may arise. Therefore, further experimental and clinical research is required to control the disease.
Keywords: Severe Acute Respiratory Syndrome; SARS; coronavirus; molecular mechanisms; therapy; vaccination
Poster presentation: NO-sensitive guanylyl cyclases (sGCs) are cytosolic receptors for nitric oxide (NO) catalyzing the conversion of GTP to cGMP. sGCs are obligate heterodimers composed of one alpha and beta subunit each. The allosteric mechanism of sGC activation via NO is well understood, however, our knowledge about alternative mechanisms such as protein-protein interactions regulating activity, availability, translocation and expression of sGC is rather limited. In a search by the yeast two-hybrid system using the catalytic domain of the alpha1 subunit as the bait, we have identified two structurally related proteins AGAP1 [1] and MRIP2 as novel sGC interacting proteins. MRIP2 is a multi-domain protein of 75 kDa comprising a single PH and ArfGAP domain each and two ankyrin repeats. Co-immunoprecipitation experiments using COS1 cells overexpressing both proteins demonstrated the interaction of MRIP2 with both subunits of the sGC alpha1beta1. Confocal microscopical analysis showed a prominent plasma membrane staining of MRIP2. This membrane association is mediated through an N-terminal myristoylation site and through binding of its PH domain to phospholipids such as phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2). We hypothesize that MRIP2 may represent an acceptor protein for sGC that mediates recruitment of cytosolic sGC to the plasma membrane or other subcellular compartments.
Poster presentation: NO-sensitive guanylyl cyclases (GC) are the principal receptors for nitric oxide (NO) and convert GTP into the second messenger cGMP. We showed that GC is prone to tyrosine phosphorylation in COS1 cells overexpressing the human holoenzyme. Similar results were obtained in PC12 cells and in rat aortic tissue slices. The major phosphorylation site was mapped to position 192 in the regulatory domain of the beta1 subunit. Tyrosine phosphorylation of GC was reduced in the presence of the inhibitors PP1 and PP2 indicating that Src-like kinases are critically involved in phosphorylation. Moreover, co-immunoprecipitation experiments revealed an interaction between Src and GC. To further analyse the relevance of this posttranslational modification we generated a phospho-specific antibody raised against pTyr192. This antibody clearly distinguishes between phosphorylated and non-phosphorylated GC and may be a powerful tool to analyse the subcellular localisation of the phosphorylated enzyme.
Poster presentation NO-sensitive guanylyl cyclases (soluble guanylyl cyclase, sGC) are among the key regulators of intracellular cGMP concentration. The mechanisms underlying NO-mediated activation of sGC are quite well understood, however, little is known about the fine-tuning of sGC activity through alternative mechanisms such as protein phosphorylation. Several reports have demonstrated the reversible phosphorylation of sGC on serine/threonine residues, and it has been speculated, though not experimentally proven, that sGC might also be phosphorylated on tyrosine residues. Using broad-spectrum phosphatase inhibitors we were able to demonstrate tyrosine phosphorylation at Tyr192 of the beta 1 subunit of human sGC in COS1 cells. This residue forms part of a sequence segment (YEDL) representing a preferential binding site for SH2 domains of Src-like kinases. Pull-down assays and co-immunoprecipitation experiments showed that Src can indeed bind via its SH2 domain to pTyr192 of beta 1 indicating that tyrosine phosphorylation of sGC may be followed by recruitment of Src-like kinases to the phosphorylated beta 1 subunit. In support of this hypothesis, immunofluorescence studies showed a colocalization of overexpressed sGC and Src at the plasma membrane of COS1 and Hela cells. Together, our results point to an unexpected crosstalk between tyrosine kinase pathway(s) and the NO/cGMP signalling cascade which may result in translocation of the predominantly cytosolic sGC to the cytosolic face of the plasma membrane.
Neben Brille und Kontaktlinse stehen heute operative Maßnahmen zur Verfügung, um Sehfehler dauerhaft zu korrigieren. Dazu zählen Verfahren, bei denen die Hornhaut moduliert wird, sowie Methoden, bei denen der Sehfehler mit Hilfe eines Kunstimplantats behoben wird. Vor allem Kurzsichtigkeit, Weitsichtigkeit und Astigmatismus (Hornhautverkrümmung) können so effektiv und dauerhaft korrigiert werden. Das vorherrschende Verfahren für niedrige bis mittlere Refraktions(Brechungs)fehler ist die Hornhautkorrektur mit Hilfe eines Argon-Fluorid-Excimer-Lasers. Schon 24 Stunden nach der Operation können die Betroffenen wieder »normal« sehen, das heißt ohne Brille oder Kontaktlinsen. Höhere Refraktionsfehler werden heute vor allem mit implantierbaren Kunstlinsen behandelt. Die größte Herausforderung für die moderne Forschung auf dem Gebiet der Refraktionschirurgie in den nächsten Jahren bis Jahrzehnten wird die sichere Korrektur der Altersweitsichtigkeit bleiben.
»Gönnen Sie Ihrer Haut Zukunft.« Unter diesem Slogan wirbt die Frankfurter Oberbürgermeisterin Petra Roth als Schirmherrin der Deutschen Hautkrebsstiftung (www.hautkrebsstiftung.de) für Maßnahmen zur Prävention von Hauttumoren. Diese Krebsformen nehmen derzeit weltweit in der hellhäutigen Bevölkerung am stärksten zu, wobei aufgrund unserer bereits in frühen Jahren sonnenbelasteten Freizeitgewohnheiten mehr und mehr jüngere Menschen erkranken. Neue Therapieoptionen erlauben es, Krebs sowie Krebsvorstufen früher und effektiver zu behandeln. Dabei spielen insbesondere nichtinvasive Methoden eine immer wichtigere Rolle. Cremen statt schneiden – dies ist nicht immer, aber immer öfter die richtige Lösung.
Kurzfassung Vortrag: Fächerübergreifende Lehre und verpflichtende Fortbildung (CME) für Ärzte erfordern innovative Lernmethoden. Eine Lösung wird teilweise in der Nutzung elektronischer Medien gesehen. Unklar ist jedoch, wie konkret eine Umsetzung in der Aus-, Fort- und Weiterbildung im Fach Allgemeinmedizin bisher erfolgte, welche Chancen und Möglichkeiten es gibt und wie die weitere Entwicklung aussehen kann. Um einen Überblick über die aktuellen E-Learning-Aktivitäten zu erhalten, formierte sich eine universitäts- und bundesländerübergreifende Initiative. In drei Phasen soll die Grundlage für die Entwicklung einer Strategie für die effektive Nutzung elektronischer Lehr- und Lernmedien für das Fach Allgemeinmedizin geschaffen werden: Phase 1 - Nationales Expertentreffen (Juli 2005 in Frankfurt): Diskussion von Erfahrungen, Problemen und Möglichkeiten des Einsatzes elektronischer Medien in der Allgemeinmedizin. Phase 2 - Gründung eines Netzwerks: Zusammenarbeit, Koordination und gegenseitige Unterstützung bei der Entwicklung von E-Learning-Modulen. Phase 3 - Evaluation von E-Learning in der Allgemeinmedizin: systematische qualitative und quantitative Untersuchungen. Im Rahmen eines Workshops sollen die Erfahrungen aus dem Expertentreffen mit Lehrenden und Fortbildenden aus anderen Fachbereichen diskutiert werden. Kooperationen über die Allgemeinmedizin hinaus können weitere Synergien schaffen. Der Workshop dient dem Austausch über Chancen und Limitationen entsprechender Angebote.
Neben dem alltagsbegrifflichen Verständnis der "Unternehmer", das deren Lagerbildung und Interessenhomogenität unterstellt, lassen sich bei genauerem Hinsehen immer schon interne Differenzierungen erkennen, erfassbar v.a. mit der Kategorie der "Kapitalfraktionen". Öffentliche politische Interventionen des "Unternehmerlagers" erscheinen wiederum auf den ersten Blick homogen. Rolf Schmucker zeigt empirisch, dass auch dieser Blick trügt.
Kurzfassung eines Vortrags gehalten auf der GMA-Tagung vom 04.11.-06.11.2005 in Münster. Aufgrund wenig überzeugender Leistungen seiner Studierenden im vorklinischen Studienabschnitt hat der Fachbereich Medizin der Goethe-Universität zum Wintersemester 2001/02 eine völlig neue Studienordnung eingeführt, deren wesentliche Ziele das erfolgreiche Erlernen natur-, geistes- und sozialwissenschaftlicher Komponenten der normalen Biologie des Menschen mit optimaler Vorbereitung auf den klinischen Studienabschnitt binnen zweier Studienjahre und die Kompatibilität mit der ÄAppO und der ZÄAppO (jeweils alte und neue Version bzw. Vorentwurf) sind. Grundprinzipien des Curriculums sind: 1. Logisch aufeinander abgestimmte Themenblöcke, 2. Integration von makroskopischer und mikroskopischer Anatomie, 3. Interdisziplinärität der Themenblöcke, 4. Immanente Wiederholung von Lehrinhalten durch enge Verzahnung von Plenar- und Kleingruppenveranstaltungen, 5. Aufteilung der Studienanfänger in gemischte Gruppen nach den Kriterien Geschlecht, Herkunft und Studienfach, 6. Erlernen des Umgangs mit Patienten schon vom ersten Semester an durch "Anatomie am Lebenden"-Kurse und durch den Kurs Einführung in die klinische Medizin. Wichtigste Ergebnisse: Steigerung der Referenzgruppe beim Physikum von ca. 25% auf >60%, relativ guter Prüfungserfolg, hervorragende Sozialisation durch die frühe randomisierte Zuordnung in Kleingruppen und der sehr glatte Übergang in den klinischen Abschnitt des Medizin- bzw. Zahnmedizinstudiums.
Multiple choice (MC)-Klausuren sind im deutschen Medizinstudium trotz weitgehend fehlender Daten zur Validität dieser Prüfungsform zur Regelprüfung geworden. Darüber hinaus ist unklar, in welchem Ausmaß die Studierenden - auch solche mit guten Prüfungsergebnissen - den geprüften Lernstoff tatsächlich beherrschen. Am Fachbereich Medizin der Johann-Wolfgang-Goethe-Universität Frankfurt wurde am Ende des SS 2003 im Fach Mikrobiologie für die Studierenden des 2. klinischen Semesters eine MC-basierte Abschlussprüfung geschrieben. Die Studierenden des 1. klinischen Semesters hatten - bedingt durch Umstellungen des Curriculums - eine identische Ausbildung. Diese wurde durch eine inhaltlich weitgehend identische, im Format aber andere Klausur abgeschlossen, in der sowohl offene Fragen enthalten waren als auch Fragen, bei denen die Studierenden jede Aussage einzeln auf Korrektheit bewerten mussten. Der Vergleich der Ergebnisse für inhaltlich gleiche Fragen zeigt, dass die Studierenden im MC-Format eine hohe Quote richtiger Antworten erzielen, diese jedoch durch ein geändertes Fragenformat stark reduziert wird. So erreichten nur 20 - 30% der Studierenden ein vollständig richtiges Ergebnis, wenn jede Aussage einzeln bewertet werden musste, während die inhaltlich gleiche Frage im MC-Format 80 - 90% richtige Ergebnisse erzielte. In freien Fragen konnten nur 30 - 40% der Studierenden die richtige Antwort aktiv niederschreiben, während 90 -99% der Studierenden die richtige Lösung passiv erkannten. Wir interpretieren diese Ergebnisse dahin, dass der Entscheidungszwang in MC-basierten Fragen einen starken Einfluss auf die Quote richtiger Antworten hat, und die Prüfungsergebnisse damit wesentlich durch das Format beeinflusst werden, das Wissen dagegen nicht beherrscht wird. Die Ergebnisse dieser Studie legen nahe, Sorgfalt bei der Auswahl des Prüfungsverfahrens walten zu lassen und der Steuerung des studentischen Lernverhaltens durch das Prüfungsformat wesentlich mehr Aufmerksamkeit zu widmen als bisher.
The illusion of apparent motion can be induced when visual stimuli are successively presented at different locations. It has been shown in previous studies that motion-sensitive regions in extrastriate cortex are relevant for the processing of apparent motion, but it is unclear whether primary visual cortex (V1) is also involved in the representation of the illusory motion path. We investigated, in human subjects, apparent-motion-related activity in patches of V1 representing locations along the path of illusory stimulus motion using functional magnetic resonance imaging. Here we show that apparent motion caused a blood-oxygenation-level-dependent response along the V1 representations of the apparent-motion path, including regions that were not directly activated by the apparent-motion-inducing stimuli. This response was unaltered when participants had to perform an attention-demanding task that diverted their attention away from the stimulus. With a bistable motion quartet, we confirmed that the activity was related to the conscious perception of movement. Our data suggest that V1 is part of the network that represents the illusory path of apparent motion. The activation in V1 can be explained either by lateral interactions within V1 or by feedback mechanisms from higher visual areas, especially the motion-sensitive human MT/V5 complex.
Kongressbericht: Auf der Tagung der Deutschen Gesellschaft für Allgemeinmedizin und Familienmedizin e.V. (DEGAM) 2004 entstand die Idee, E-Learning-Aktivitäten in der Allgemeinmedizin sichtbar zu machen und zu bündeln. Ein Kongress sollte die allgemeinmedizinischen Vertreter aus Lehre und Forschung sowie Industrievertreter zusammenbringen, um das Spektrum der Möglichkeiten und laufende Projekte kennen zu lernen. Mit motivierten Referenten, über 60 aktiven Teilnehmern und einem positiven Feedback, kann der Kongress in Frankfurt am 8. und 9. Juli 2005 als erster dieser Art in Deutschland als erfolgreich bezeichnet werden.
Background: Depression is a disorder with high prevalence in primary health care and a significant burden of illness. The delivery of health care for depression, as well as other chronic illnesses, has been criticized for several reasons and new strategies to address the needs of these illnesses have been advocated. Case management is a patient-centered approach which has shown efficacy in the treatment of depression in highly organized Health Maintenance Organization (HMO) settings and which might also be effective in other, less structured settings. Methods/Design: PRoMPT (PRimary care Monitoring for depressive Patients Trial) is a cluster randomised controlled trial with General Practice (GP) as the unit of randomisation. The aim of the study is to evaluate a GP applied case-management for patients with major depressive disorder. 70 GPs were randomised either to intervention group or to control group with the control group delivering usual care. Each GP will include 10 patients suffering from major depressive disorder according to the DSM-IV criteria. The intervention group will receive treatment based on standardized guidelines and monthly telephone monitoring from a trained practice nurse. The nurse investigates the patient's status concerning the MDD criteria, his adherence to GPs prescriptions, possible side effects of medication, and treatment goal attainment. The control group receives usual care – including recommended guidelines. Main outcome measure is the cumulative score of the section depressive disorders (PHQ-9) from the German version of the Prime MD Patient Health Questionnaire (PHQ-D). Secondary outcome measures are the Beck-Depression-Inventory, self-reported adherence (adapted from Moriskey) and the SF-36. In addition, data are collected about patients' satisfaction (EUROPEP-tool), medication, health care utilization, comorbidity, suicide attempts and days out of work. The study comprises three assessment times: baseline (T0) , follow-up after 6 months (T1) and follow-up after 12 months (T2). Discussion: Depression is now recognized as a disorder with a high prevalence in primary care but with insufficient treatment response. Case management seems to be a promising intervention which has the potential to bridge the gap of the usually time-limited and fragmented provision of care. Case management has been proven to be effective in several studies but its application in the private general medical practice setting remains unclear.
Background: Diabetes model projects in different regions of Germany including interventions such as quality circles, patient education and documentation of medical findings have shown improvements of HbA1c levels, blood pressure and occurrence of hypoglycaemia in before-after studies (without control group). In 2002 the German Ministry of Health defined legal regulations for the introduction of nationwide disease management programs (DMP) to improve the quality of care in chronically ill patients. In April 2003 the first DMP for patients with type 2 diabetes was accredited. The evaluation of the DMP is essential and has been made obligatory in Germany by the Fifth Book of Social Code. The aim of the study is to assess the effectiveness of DMP by example of type 2 diabetes in the primary care setting of two German federal states (Rheinland-Pfalz and Sachsen-Anhalt). Methods/Design: The study is three-armed: a prospective cluster-randomized comparison of two interventions (DMP 1 and DMP 2) against routine care without DMP as control group. In the DMP group 1 the patients are treated according to the current situation within the German-Diabetes-DMP. The DMP group 2 represents diabetic care within ideally implemented DMP providing additional interventions (e.g. quality circles, outreach visits). According to a sample size calculation a sample size of 200 GPs (each GP including 20 patients) will be required for the comparison of DMP 1 and DMP 2 considering possible drop-outs. For the comparison with routine care 4000 patients identified by diabetic tracer medication and age (> 50 years) will be analyzed. Discussion: This study will evaluate the effectiveness of the German Diabetes-DMP compared to a Diabetes-DMP providing additional interventions and routine care in the primary care setting of two different German federal states.
Background: Osteoarthritis (OA) has a high prevalence in primary care. Conservative, guideline orientated approaches aiming at improving pain treatment and increasing physical activity, have been proven to be effective in several contexts outside the primary care setting, as for instance the Arthritis Self management Programs (ASMPs). But it remains unclear if these comprehensive evidence based approaches can improve patients' quality of life if they are provided in a primary care setting. Methods/Design: PraxArt is a cluster randomised controlled trial with GPs as the unit of randomisation. The aim of the study is to evaluate the impact of a comprehensive evidence based medical education of GPs on individual care and patients' quality of life. 75 GPs were randomised either to intervention group I or II or to a control group. Each GP will include 15 patients suffering from osteoarthritis according to the criteria of ACR. In intervention group I GPs will receive medical education and patient education leaflets including a physical exercise program. In intervention group II the same is provided, but in addition a practice nurse will be trained to monitor via monthly telephone calls adherence to GPs prescriptions and advices and ask about increasing pain and possible side effects of medication. In the control group no intervention will be applied at all. Main outcome measurement for patients' QoL is the GERMAN-AIMS2-SF questionnaire. In addition data about patients' satisfaction (using a modified EUROPEP-tool), medication, health care utilization, comorbidity, physical activity and depression (using PHQ-9) will be retrieved. Measurements (pre data collection) will take place in months I-III, starting in June 2005. Post data collection will be performed after 6 months. Discussion: Despite the high prevalence and increasing incidence, comprehensive and evidence based treatment approaches for OA in a primary care setting are neither established nor evaluated in Germany. If the evaluation of the presented approach reveals a clear benefit it is planned to provide this GP-centred interventions on a much larger scale.
Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is performed mainly in patients with high-risk or advanced hematologic malignancies and congenital or acquired aplastic anemias. In the context of the significant risk of graft failure after allo-HSCT from alternative donors and the risk of relapse in recipients transplanted for malignancy, the precise monitoring of posttransplant hematopoietic chimerism is of utmost interest. Useful molecular methods for chimerism quantification after allogeneic transplantation, aimed at distinguishing precisely between donor's and recipient's cells, are PCR-based analyses of polymorphic DNA markers. Such analyses can be performed regardless of donor's and recipient's sex. Additionally, in patients after sex-mismatched allo-HSCT, fluorescent in situ hybridization (FISH) can be applied. Methods: We compared different techniques for analysis of posttransplant chimerism, namely FISH and PCR-based molecular methods with automated detection of fluorescent products in an ALFExpress DNA Sequencer (Pharmacia) or ABI 310 Genetic Analyzer (PE). We used Spearman correlation test. Results: We have found high correlation between results obtained from the PCR/ALF Express and PCR/ABI 310 Genetic Analyzer. Lower, but still positive correlations were found between results of FISH technique and results obtained using automated DNA sizing technology. Conclusions: All the methods applied enable a rapid and accurate detection of post-HSCT chimerism.