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Biomedical subjects

R Stauber

Publications and source records attributed to R Stauber.

At least 19 recordsLinked to original sources
PubMed2003

Early viral kinetics on treatment with pegylated interferon-alpha-2a in chronic hepatitis C virus genotype 1 infection.

Even with pegylated (PEG) interferons (IFN), therapy of chronic hepatitis C (genotype 1) remains unsatisfactory. The initial viral response to IFN identifies patients infected with IFN resistant viruses not responding to standard IFN/ribavirin therapy. The impact of primary IFN unresponsiveness for PEG-IFN-alpha-2a/ribavirin therapy is unknown. Viral load was measured in 22 chronic hepatitis C (genotype 1) patients before and 24 h after 9 MU IFN-alpha-2a (days 0 and 1), and before and during weekly 180 microg PEG-IFN-alpha-2a (days 7, 8, 11, 14 and 21) administration. Thereafter, ribavirin (800 mg/d) was added for 6 months. Virological responders continued treatment for a further 6 months. Twenty-eight patients treated with standard IFN/ribavirin therapy in a previous study using an analogous protocol served as historic controls. After 6 months 15 (68.2%) patients were (HCV-RNA) negative, eight of whom (36.4%) had a sustained response. The decrease in viral load 24 h after 9 MU IFN-alpha-2a was greater in virological responders (1.05 log [0.25-1.67]) than in nonresponders (NR) (0.34 [0.14-0.65]; P=0.003). In contrast, viral decline was not different between responders and NRs during the first 2 weeks on PEG-IFN-alpha-2a. All patients with an initial decline > 1.4 log became sustained responders. Five of 12 patients with a log change < 0.8 became end of treatment responders, two had a sustained response. Antiviral response to PEG-IFN-alpha-2a is different to that on standard IFN. In spite of a lower initial response PEG-IFN-alpha-2a/ribavirin combination therapy may overcome predicted IFN unresponsiveness.

Adult↗
PubMed2001

SUMO-1 modification required for transformation by adenovirus type 5 early region 1B 55-kDa oncoprotein.

SUMO-1 is a small ubiquitin-related modifier protein that is covalently linked to many cellular and viral protein targets. Modification by SUMO-1 is proposed to play a role in protein targeting and/or stability. We show here that adenovirus type 5 early region 1B 55-kDa (E1B-55kDa) oncoprotein can be covalently modified by SUMO-1 in vivo through a major attachment site comprising a single lysine residue at amino acid position 104. The sequence surrounding this lysine matches the proposed PsiKxE consensus motif required for SUMO-1 conjugation. A single mutation (K104R) that abolishes SUMOylation of E1B-55kDa dramatically reduces the ability of the adenovirus type 5 protein to transform primary baby rat kidney cells in cooperation with E1A and to inhibit p53-mediated transactivation. Overexpression of SUMO-1 in adenovirus type 5 E1A/E1B-55kDa-transformed baby rat kidney cells causes the relocalization of E1B-55kDa from the cytoplasm to the nucleus, where it accumulates with SUMO-1 in dot- or track-like structures. Significantly, when SUMO-1 is ectopically expressed in transformed rat cells no effect on the cytoplasmic localization of the E1B-K104R mutant protein is observed. Our results demonstrate that SUMO-1 modification is required for transformation by adenovirus type 5 E1B-55kDa and provide further evidence for the idea that this posttranslational modification plays a role in protein targeting to specific subcellular sites.

Adenoviridae↗
PubMed2001

Heterogeneous nuclear ribonucleoprotein E1B-AP5 is methylated in its Arg-Gly-Gly (RGG) box and interacts with human arginine methyltransferase HRMT1L1.

The heterogeneous nuclear ribonucleoprotein (hnRNP) family includes predominantly nuclear proteins acting at different stages of mRNA metabolism. A characteristic feature of hnRNPs is to undergo post-translational asymmetric arginine methylation catalysed by different type 1 protein arginine methyltransferases (PRMTs). A novel mammalian hnRNP, E1B-AP5, recently identified by its interaction with adenovirus early protein E1B-55 kDa, has been proposed to have a regulatory role in adenoviral and host-cell mRNA processing/nuclear export [Gabler, Schutt, Groitl, Wolf, Shenk and Dobner (1998) J. Virol. 72, 7960-7971]. Here we report that E1B-AP5 is methylated in vivo in its Arg-Gly-Gly (RGG)-box domain, known to mediate protein-RNA interactions. The activity responsible for E1B-AP5 methylation forms a complex with E1B-AP5 in vivo. The predominant mammalian arginine methyltransferase HRMT1L2 (hPRMT1) did not detectably methylate endogenous E1B-AP5 despite efficiently methylating a recombinant RGG-box domain of E1B-AP5. Using yeast two-hybrid screening we identified HRMT1L1 (PRMT2) as one of the proteins interacting with E1B-AP5. By in situ immunofluorescence we demonstrated that E1B-AP5 co-localizes with the nuclear fraction of HRMT1L1. The Src homology 3 (SH3) domain of HRMT1L1 was essential for its interaction with E1B-AP5 in vivo. We suggest that HRMT1L1 is responsible for specific E1B-AP5 methylation in vivo.

Amino Acid Motifs↗
PubMed2001

Combination of interferon induction therapy and ribavirin in chronic hepatitis C.

The initial clearance of hepatitis C virus (HCV) during interferon-alfa therapy is dose-dependent. Therefore, higher initial interferon doses (induction therapy) may improve treatment results. This concept was tested in a prospective, randomized controlled trial. Previously untreated patients with chronic hepatitis C were randomized to receive 3 different interferon doses during the first 14 weeks of therapy (Group A, n = 130: 10 MU IntronA [AESCA-Schering Plough, Traiskirchen, Austria]/day for 2 weeks, followed by 10 MU/2 days for 12 weeks; Group B, n = 124: 5 MU/day for 14 weeks; Group C, n = 119; 5 MU/2 days for 14 weeks) followed in all by 5 MU/2 days for 24 weeks. Throughout the whole study all patients received 1 to 1.2 g ribavirin/day. On treatment, no differences in viral clearance rates were observed. Sustained response rates were also not different among the groups (A: 48.5%, B and C: 41.3%, intent to treat). When data were analyzed according to genotypes, sustained response was almost twice as high in patients with genotype 1 receiving high-dose interferon induction therapy (A: 44.2%, B: 28.6%, C: 27%, P <.05). In contrast, results were not different in genotype 3a patients (A: 61.3%, B: 75.9%, C: 56.3%; P >.1). These data indicate that high-dose interferon induction therapy may improve the outcome of interferon/ribavirin combination therapy in genotype 1 patients.

Adult↗
PubMed2001

Treatment of patients with chronic hepatitis C not responding to interferon with high-dose interferon alpha with or without ribavirin: final results of a prospective randomized trial. Austrian Hepatitis Study Group.

OBJECTIVE: To investigate the efficacy of high-dose interferon alpha (IFN-alpha) with or without ribavirin in interferon (IFN) non-responders. STUDY DESIGN: 304 chronic hepatitis C patients received 5 MU IFN-alpha2b (IntronA, Schering-Plough, Kenilworth, NJ, USA) three times a week for 3 months. Non-responders were randomized either to continue with IFN (IFN 5 MU/TIW followed by 10 MU/TIW, each for 3 months) alone (group A: n = 76, m: f = 54: 22, age 45.7 +/- 12 years, 16% cirrhosis, alanine aminotransferase [ALT] 66 +/- 35 U/l) or in combination with ribavirin (approximately 14 mg/kg/day) (group B: n = 81, m: f = 57: 24, age 48.2 +/- 12 years, 17% cirrhosis, ALT 71 +/- 40 U/l). At the end of treatment, patients were followed for 6 months. MAIN OUTCOME MEASURES: Virological response at end of treatment and 6 months thereafter. SETTING: University hospitals and tertiary referral centres. RESULTS: At the end of treatment, eight (10.8%) and 25 (31.3%, P= 0.0066) patients were HCV-RNA negative, and 51 and 39 were HCV-RNA positive, in groups A and B, respectively. There were 17 drop-outs in each group. Six months after treatment, only one patient in group A (1.3%) and seven patients (8.6%, P= 0.06) in group B had normal ALT and undetectable serum HCV-RNA. CONCLUSIONS: A combination of high-dose IFN with ribavirin induces a short-lasting complete response in about one-third of IFN-non-responders.

Adult↗
PubMed2000

Influenza virus-induced NF-kappaB-dependent gene expression is mediated by overexpression of viral proteins and involves oxidative radicals and activation of IkappaB kinase.

Influenza A viruses are capable of inducing the expression of a variety of cytokine and proapoptotic genes in infected cells. The promoter regions of most of these genes harbor binding sites for the transcription factor NF-kappaB which is an important mediator of immune and inflammatory responses. Our present study is based on an observation that influenza A virus infection of cells stimulates transcriptional activation of the HIV-1 long terminal repeat (LTR) which harbors two regulatory NF-kappaB elements, and is aimed at identifying the molecular mechanisms involved in this process. We found that the expression of influenza virus hemagglutinin (HA), matrix protein (M), and nucleoprotein (NP), as single factors is sufficient to transcriptionally activate the HIV-1 LTR. This process is mediated by oxidative radicals because treatment of cells with pyrrolidine dithiocarbamate, a scavenger of such radicals, abolished the transactivating ability. Expression of different influenza proteins induces activation of NF-kappaB-dependent gene expression but not transcriptional activation of an AP-1/Ets-dependent promoter, indicating a selectivity for NF-kappaB transactivation. Furthermore, influenza protein expression induces activation of IkappaB kinase (IKK). Accordingly coexpression of a catalytically inactive mutant of IKK abolishes influenza protein induced activation of NF-kappaB as well as HIV-1 LTR-dependent reporter gene expression, suggesting that IKK is an important intermediate within this signaling process. Taken together, our results show that various influenza virus proteins act as viral transactivators to modulate transcriptional activity of kappaB-element harboring promoters such as the HIV-LTR.

Antioxidants↗
PubMed2000

Scintigraphic long-term follow-up of a patient with metastatic glucagonoma.

Two years after resection of a pancreatic glucagonoma, scintigraphy with 111indium-labeled octreotide revealed hepatic metastases in a 48-yr-old man. Hepatic metastases were also visualized by CT, whereas an additional lesion in the chest was seen only by scintigraphy. A total of 11 follow-up examinations over 46 months proved somatostatin receptor scintigraphy to monitor reliably somatostatin receptor expression, growth and dissemination of glucagonoma metastases, and to indicate therapeutic readjustment if necessary. The survival time of the patient is now >75 months, in comparison with a mean survival time of 59 months reported for metastatic glucagonoma.

Follow-Up Studies↗
PubMed2000

[Epidemiology and transmission of hepatitic C].

Infections with the hepatitis C virus (HCV) are pandemic, and the WHO estimates a world-wide prevalence of 3%. In Middle Europe approximately 1% of the population are infected, mostly with genotype 1 (85% in Austria). Since the discovery of HCV in 1989 and the introduction of the HCV antibody test in 1990, mainly chronic asymptomatic cases were diagnosed. In developed countries, chronic hepatitis C is the most prominent cause for liver cirrhosis, hepatocellular carcinoma, and liver transplantation. In former years, transmission of HCV was predominantly iatrogenic, e.g. by blood transfusions before 1990, blood products such as coagulation factors in hemophiliacs or anti-D-globuline in rhesus incompatibility, parenteral anti-schistosomal treatment in Egypt, contaminated endoscopes or cardiac surgery. Today, sporadic transmission is more prevalent, mostly in drug addicts via needle sharing, and seldom by needle-stick injuries in medical personnel, vertical transmission from mother to baby, tattooing, piercing, or razor sharing. Given the lack of a prophylactic HCV vaccine, preventive measures are very important such as screening of blood products by PCR, use of disposable instruments. or procurement of drug addicts with single-use syringes and needles.

Cross-Cultural Comparison↗
PubMed1999

Interim analysis of a randomized controlled trial of combination of ribavirin and high dose interferon-alpha in interferon nonresponders with chronic hepatitis C.

UNLABELLED: This trial investigated the efficacy of a combination of high-dose interferon-alpha (IFN-alpha) with ribavirin in IFN nonresponders. STUDY PROTOCOL: 304 patients with chronic hepatitis C were treated with 5 MU IFN-alpha2b (IntronA(R), Schering-Plough) per TIW for 3 months. Nonresponders (defined by HCV-RNA positivity in serum after the 3 months of therapy) were randomized either to continue with IFN (5 MU IFN per TIW followed by 10 MU per TIW for each 3 months) alone (group A) or in combination with ribavirin (1-1.2 g per day) (group B). ALT was measured in monthly intervals, HCV-RNA in 3 monthly intervals. Pretreatment characteristics of the randomized patients were as follows: group A, n = 76; m/f, 54/22; 16% cirrhosis, age, 45. 7 +/- 12 years; ALT (U per litre), 66 +/- 35; group B, n = 81; m/f, 57/24; 17% cirrhosis, age, 48.2 +/- 12; ALT, 71 +/- 40. After 9 months of treatment, nine (11.6%) and 27 (32.5%, P = 0.0066) patients were HCV-RNA negative and 51 and 39 were HCV-RNA positive, in groups A and B, respectively. There were 17 drop-outs in group A and 15 in group B. Six months after treatment only two patients in group A (2.5%) and five (6%, P = 0.06) in group B had normal ALT and no detectable HCV-RNA in serum. In addition to the well-known side-effects of IFN the mean haemoglobin concentration dropped by 2 g per litre in group B. These data indicate that a combination of high-dose IFN with ribavirin is effective in inducing a short-lasting complete response in one-third of IFN nonresponders. Prolonged treatment with IFN/ribavirin may be necessary to obtain a sustained response.

Adult↗
PubMed1999

Transcription-dependent nuclear-cytoplasmic trafficking is required for the function of the von Hippel-Lindau tumor suppressor protein.

Mutation of the von Hippel-Lindau tumor suppressor gene (vhl) causes the von Hippel-Lindau cancer syndrome as well as sporadic renal clear cell carcinoma. To pursue our study of the intracellular localization of VHL protein in relation to its function, we fused VHL to the green fluorescent protein (GFP) to produce the VHL-GFP fusion protein. Like VHL, VHL-GFP binds to elongins B and C and Cullin-2 and regulates target gene product levels, including levels of vascular endothelial growth factor and glucose transporter 1. VHL-GFP localizes predominantly to the cytoplasm, with some detectable nuclear signal. Inhibition of transcription by actinomycin D or 5,6-dichlorobenzimidazole riboside (DRB) causes VHL to be redistributed to the nucleus. A cellular fusion assay was used to demonstrate that inhibition of transcription induces a decrease in the nuclear export rate of VHL. The dependence of transcription for trafficking is lost with a deletion of exon 2, a region with a mutation causing a splice defect in the VHL gene in sporadic renal clear cell carcinoma. Addition of a strong nuclear export signal (NES) derived from the Rev protein results in complete nuclear exclusion and abrogates the redistribution of VHL-GFP-NES into the nucleus upon inhibition of transcription. Leptomycin B, which inhibits NES-mediated nuclear export, reverts the distribution of VHL-GFP-NES to that of VHL-GFP and restores sensitivity to actinomycin D and DRB. Uncoupling of VHL-GFP trafficking to transcription either by an exon 2 deletion or fusion to NES abolishes VHL function. We suggest that VHL function requires not only nuclear or cytoplasmic localization, but also exon 2-mediated transcription-dependent trafficking between these two cellular compartments.

Animals↗
PubMed1998

The human poly(A)-binding protein 1 shuttles between the nucleus and the cytoplasm.

We have studied the intracellular localization of poly(A)-binding protein 1 (PABP1) by indirect immunofluorescence as well as by tagging with the green fluorescent protein (GFP) in living cells. We show that PABP1 is able to enter the nucleus. Accumulation of PABP1 in the nuclei was observed upon transcription inhibition, suggesting that active transcription is required for PABP1 export. The nuclear import of PABP1 is an energy-dependent process since PABP1 fails to enter the nucleus upon ATP depletion and at low temperature. Transfection of PABP1 or PABP1-GFP resulted in heterogeneity of intracellular distribution of the protein. In the low expressing cells, PABP1 was localized in the cytoplasm, whereas in the high expressors, we observed accumulation of the protein in the nucleus. Nuclear PABP1 observed either after overexpression or after transcription inhibition was found in speckles and colocalized with splicing factor SC35. The ability of PABP1 to shuttle between nucleus and cytoplasm was also shown by heterokaryon formation upon cell fusion. Deletion mutagenesis showed that the minimal part of PABP1 retaining the ability to shuttle consists of the first two RNA-binding domains. This mutant interacted with poly(A) RNA with high affinity and accumulated in the nucleus. Deletion mutants exhibiting reduced RNA binding affinity did not accumulate in the nucleus. PABP1 has been proposed to participate at various steps of mRNA utilization. Our results suggest involvement of PABP1 in nuclear events associated with the formation and transport of mRNP to the cytoplasm and identify a new trafficking pattern for RNA-binding proteins.

Biological Transport↗
PubMed1997

The inducibly expressed GTPase localizes to the endoplasmic reticulum, independently of GTP binding.

The inducibly expressed GTPase (IGTP) is representative of a newly identified group of interferon gamma-inducible GTPases, whose functions are currently unknown. We have begun to address the cellular function of IGTP by examining its subcellular distribution and its guanine nucleotide binding status. Using immunofluorescence, electron microscopy, and subcellular fractionation, IGTP was localized predominantly to the endoplasmic reticulum of both RAW 264. 7 macrophages and C127 fibroblasts. In the immunostaining experiments, staining of discrete cytoplasmic structures on the periphery of the endoplasmic reticulum was also evident. Using polyethyleneimine-cellulose thin layer chromatography, the guanine nucleotides that complexed to immunoprecipitated IGTP, in both control and interferon gamma-stimulated cells, were 90-95% GTP and 5-10% GDP, suggesting that the protein was in an active state. A mutant IGTP protein was created that had no detectable complexed GTP, and in both subcellular fractionation and IGTP-green fluorescent protein fusion studies, this mutant also localized to the endoplasmic reticulum. These results suggested that the GTP binding status of IGTP is independent of its capacity to localize to the endoplasmic reticulum. Given these results, we propose that IGTP is representative of a new family of endoplasmic reticulum GTPases that may be involved in protein processing or trafficking.

Amino Acid Sequence↗
PubMed1996

Dose increase augments response rate to interferon-alpha in chronic hepatitis C.

Approximately 50% of patients with chronic hepatitis C respond to treatment with interferon-alpha. The aim of this randomized controlled trial was to evaluate whether an increase in dose of interferon-alpha augments response rate. One hundred thirty-eight patients with newly diagnosed chronic hepatitis C received a three-month course of 3 MU IFN-alpha2b administered every two days. All patients were anti-HCV and HCV-RNA (PCR) positive. Prior to treatment, a liver biopsy was performed. Complete response was defined by normal serum ALT concentrations and disappearance of HCV-RNA. After three months, 60 nonresponders were randomized (stratified according to histology) either to continue 3 MU interferon-alpha2b every two days for another six months (group A, total dose: 410 MU) or to receive increasing doses of interferon-alpha2b (6 MU every two days for three months, followed by 10 MU every two days for three months) (group B, total dose: 870 MU). Serum ALT concentrations were measured monthly and HCV-RNA at three-month intervals. Liver biopsy was repeated six months after end of treatment. Pretreatment characteristics of the randomized patients were: group A: N = 30; male/female: 20/10; age: 54 +/- 10 years; CPH 9, CAH 8, cirrhosis 13; mean ALT 108 +/- 98 units/liter; group B: N = 30; male/female: 21/9; age: 57 +/- 15 years; CPH 10, CAH 9, cirrhosis 11; mean ALT 90 +/- 40 units/liter. At the end of treatment six patients in group B but none in group A became responders [P = 0.011 (Fisher's exact test), intent-to-treat analysis]. All six responders were noncirrhotics. High-dose interferon was not tolerated by six patients in group B. Noncompliance resulted in five dropouts in group A and one in group B. During the six-month follow-up, four of the six responders relapsed. A patient in group A with increased serum ALT concentration but negative HCV-RNA at the end of treatment became a full responder after six months. Of nonresponders to 3 MU interferon alpha2b every two days for three months, 20% responded to higher interferon doses, but none to continued standard dose. Prolonged treatment with interferon may be necessary to obtain a sustained response. However, treatment with higher-dose interferon was not tolerated in 20% of the patients.

Alanine Transaminase↗
PubMed1996

Exercise increases plasma concentrations of (R)- and (S)-propranolol.

OBJECTIVE: We recently reported a highly stereoselective increase in plasma concentrations of (S)-atenolol during exercise which is most likely due to a release of the drug from adrenergic cells. The objective of the present study was to investigate the influence of physical exercise on plasma concentrations of the (R)- and (S)-enantiomers of propranolol. METHODS: Blood samples were taken immediately before and at the end of exercise in 12 patients receiving chronic treatment with racemic (R, S)-propranolol. Plasma concentrations of (R)- and (S)-propranolol were determined by HPLC. RESULTS: In contrast to atenolol, mean plasma concentrations of (S)-propranolol were significantly higher (+20%) than those of (R)-propranolol at rest. During exercise there was an increase in plasma concentrations of both (R)-propranolol (+129%) and (S)-propranolol (+109%). CONCLUSION: Based on information from in vitro studies we conclude that the increase in plasma concentrations of (S)-propranolol during exercise is caused by a release of the drug from adrenergic nerves, whereas the reason for the increase in (R)-propranolol remains to be determined. This release of the beta-adrenoceptor blocking (S)-enantiomer directly at the synaptic gaps might be one reason for the poor correlation between plasma concentration and effect of beta-adrenoceptor antagonists repeatedly described in the literature.

Adrenergic beta-Antagonists↗
PubMed1995

Analysis of trafficking of Rev and transdominant Rev proteins in living cells using green fluorescent protein fusions: transdominant Rev blocks the export of Rev from the nucleus to the cytoplasm.

Expression of gag/pol and env genes of human immunodeficiency virus requires the viral Rev protein. Mutant Rev proteins, displaying a transdominant phenotype (TDRev), were shown to inhibit Rev function. To investigate the underlying mechanism of this inhibition, the green fluorescent protein (GFP) of Aequorea victoria was fused to Rev and TDRev, which allowed the study of their trafficking and interactions in living human cells. Both Rev-GFP and TDRev-GFP were shown to retain appropriate nucleolar localization and function. Upon actinomycin D treatment, Rev-GFP was transported to the cytoplasm within 1.5 hr, while TDRev, although partially dissociated from the nucleolus, was retained in the nucleus. Coexpression of Rev-GFP and TDRev in the same cell demonstrated that TDRev inhibited the transport of Rev-GFP from the nucleus to the cytoplasm. This inhibition was specific for Rev, since the export of the functionally analogous Rex protein of the human T-cell leukemia virus type I was not inhibited by TDRev. These results indicate that Rev and TDRev form heteromultimers in the nucleolus and that this interaction prevents Rev's export from the nucleus to the cytoplasm. In addition to providing a model for the function of TDRev, these results also demonstrate the successful application of protein fusions to GFP to study localization and trafficking of proteins in living mammalian cells.

Base Sequence↗
PubMed1995

Quantitative perfusion parameters of focal nodular hyperplasia and normal liver parenchyma as determined by electron beam tomography.

Eight patients with known focal nodular hyperplasia (FNH) were studied by electron beam tomography (EBT) in a multisection flow mode at defined time intervals after intravenous contrast agent injection. Various regions of interest (ROIs) were defined in the areas of FNH, normal liver parenchyma, aorta and portal vein. In each ROI density changes were measured and plotted against time. In those time-density curves (TDCs) the slope, the time of maximal enhancement and the absolute density value of peak enhancement were determined. Arterial tissue perfusion was calculated for normal liver parenchyma and FNH. In all eight patients significant differences in peak density (123.88 +/- 18.92 HU vs 102.5 +/- 15.49 HU, p = 0.012), in the rate of arterial contrast enhancement (252.63 +/- 28.05 HU min-1 vs 38.88 +/- 4.19 HU min-1, p = 0.012) and in the arterial tissue perfusion (1.36 +/- 0.19 ml min-1 cm-3 vs 0.21 +/- 0.03 ml min-1 cm-3, p = 0.012) between FNH and normal liver parenchyma were found. Perfusion values of normal liver parenchyma correspond to those determined by inert gas clearance. Further studies will determine the practicability of this quantitative method in the evaluation of global and other focal liver diseases.

Adolescent↗