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S Zeuzem

Publications and source records attributed to S Zeuzem.

At least 163 records · Page 9Linked to original sources
PubMed1997

CCK, carbachol, and bombesin activate distinct PLC-beta isoenzymes via Gq/11 in rat pancreatic acinar membranes.

Four different isoforms of phospholipase C-beta (PLC-beta 1-4) have been discovered, raising the important question of whether a distinct receptor activates a single PLC-beta isoenzyme or a subset of PLC-beta isoenzymes. The present study was designed to investigate activation of PLC-beta isoenzymes by three different PLC-activating agonists that bind to different receptor entities, i.e., cholecystokinin octapeptide (CCK-8), bombesin, and carbachol in rat pancreatic acinar membranes. PLC activity was measured using exogenous [3H]phosphatidylinositol 4,5-bisphosphate as substrate. Western blot analysis of pancreatic acinar membranes revealed the presence of PLC-beta 1, -beta 3, -gamma 1, and -delta 1, but not of PLC-beta 2, -beta 4, -gamma 2, and -delta 2. Preincubation of the membranes with anti-PLC-beta 1 or -beta 3 antibody reduced agonist-induced activation of PLC. The order of sensitivity toward inhibition by anti-PLC-beta 1 antibody was CCK-8 > bombesin > carbachol. An opposite order of sensitivity was found for inhibition of PLC activity by anti-PLC-beta 3 antibody (carbachol > bombesin > CCK-8). Anti-PLC-beta 2, -beta 4, -gamma 1, -gamma 2, -delta 1, and -delta 2 antibodies had no effect. Preincubation of the membranes with an antibody raised against the COOH terminus of the alpha-subunit of Gq/11 proteins inhibited PLC activity in response to all three different receptor agonists to a similar extent, whereas anti-Gi alpha 1-2 and anti-Gi alpha 3 antibodies had no effect. In conclusion, the data of the present study indicate that CCK-8 and carbachol activate PLC-beta 1 and PLC-beta 3, respectively, whereas bombesin activates both PLC-beta 1 and PLC-beta 3. Activation of PLC-beta by these receptor agonists is mediated by Gq/11.

Animals↗
PubMed1997

Epidermal growth factor activates phospholipase C-gamma 1 via G(i)1-2 proteins in isolated pancreatic acinar membranes.

In the present study, isolated pancreatic acinar membranes were used to investigate the mechanism of epidermal growth factor (EGF)-induced activation of phospholipase C (PLC). The data show that EGF caused a rapid and strong increase in tyrosine phosphorylation of the EGF receptor, with a maximum 5-15 s after the beginning of the incubation followed by a decline. With use of [3H]phosphatidylinositol 4,5-bisphosphate as an exogenous substrate, PLC activity increased fourfold on exposure of the membranes to EGF (85 nM). In contrast, EGF-induced tyrosine phosphorylation of PLC-gamma 1 was rather small, indicating that tyrosine phosphorylation of PLC-gamma 1 is not proportional to changes in PLC activity. EGF-induced activation of PLC was strongly inhibited by pretreatment of the membranes with pertussis toxin, by an antibody raised against a COOH-terminal sequence shared by alpha-subunits of the inhibitory G proteins G(i)1 and G(i)2, and by an anti-PLC-gamma 1 antibody, whereas anti-G(i) alpha 3, anti-Gq/11 alpha, and anti-PLC-beta 1 antibodies had no effect. In contrast, pertussis toxin or the anti-G(i) alpha 1-2 antibody had no effect on EGF-induced tyrosine phosphorylation of PLC-gamma 1. EGF promoted association of G(i) proteins with both the EGF receptor and PLC-gamma 1 with similar kinetics as EGF-receptor autophosphorylation. All EGF-induced responses were abolished by the specific tyrosine kinase inhibitor pp60v-arc (137-157), suggesting that EGF-receptor tyrosine kinase activity is essential for G(i)1-2-mediated activation of PLC-gamma 1. However, there was no evidence of tyrosine phosphorylation of G(i) alpha 1-2. Taken together, these data show that EGF causes activation of PLC-gamma 1 by a mechanism requiring activation of G(i)1-2 and only a small increase in tyrosine phosphorylation of PLC-gamma 1.

Animals↗
PubMed1997

Protein tyrosine phosphorylation in pancreatic acini: differential effects of VIP and CCK.

Cholecystokinin (CCK) and vasoactive intestinal peptide (VIP) stimulate enzyme secretion from pancreatic acini by binding to heptahelical receptors without intrinsic tyrosine kinase activity. Signal transduction by the CCK receptor involves activation of phospholipase C by Gq proteins and activation of tyrosine kinases, whereas occupation of VIP receptors stimulates adenylyl cyclase through binding to Gs proteins. Here, we use electrophoretic separation of cellular proteins and antiphosphotyrosine immunoblotting to demonstrate a VIP-stimulated rapid and dose-dependent increase in tyrosine phosphorylation of proteins migrating at 130, 115, and 93 kDa in freshly isolated rat pancreatic acini. Phosphorylation of these proteins was increased after direct stimulation of adenylyl cyclase or the adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase with forskolin or dibutyryl cAMP and was inhibited by the tyrosine kinase inhibitors genistein or tyrphostin 23. Compared with VIP, CCK stimulated tyrosine phosphorylation of additional proteins migrating at 60, 66, and 72/78 kDa. Using two-dimensional electrophoretic separation or immunoprecipitation, the 72/78-kDa phosphoprotein was identified as paxillin. We propose that paxillin might be involved in CCK-but not in VIP-induced exocytosis.

Animals↗
PubMed1997

Prevalence of hepatitis C virus antibodies and evaluation of hepatitis C virus genotypes in patients with lichen planus.

BACKGROUND: Several cases of lichen planus (LP) associated with hepatitis C virus (HCV) infection have been described. The reported prevalence rates of anti-HCV in patients with LP show wide geographical variations. An association of HCV-associated disorders with certain HCV geno/subtypes has not been investigated so far. OBJECTIVE: The aim of the present study was to define the prevalence rate of anti-HCV in German patients with LP and to determine the distribution of HCV geno/subtypes. METHODS: All patients with LP of the present study (n = 84) were tested for anti-HCV antibodies by an enzyme-immunoassay (second generation). HCV RNA was detected by reverse-transcription polymerase chain reaction (RT-PCR) and HCV geno/subtyping was performed by the reverse hybridization assay. Serum samples of 87 patients with various cutaneous diseases excluding LP served as control group. RESULTS: Anti-HCV antibodies were detected in 13/84 patients with LP (16%), and 12/13 anti-HCV-positive patients were viraemic as assessed by the presence of HCV RNA. Most patients were infected with subtype HCV-1b (10/12 patients), while the 2 remaining patients were infected with HCV-2b and HCV-3a, respectively. In the control group, anti-HCV antibodies were only observed in 1/87 patients (1.1%), infected with subtype HCV-1b. CONCLUSION: The statistically significant (p < 0.002) high prevalence of HCV RNA in patients with LP is suggestive of an aetiological role of HCV in the pathogenesis of LP. Compared to the geno/subtype distribution of patients with chronic hepatitis C without LP of the same geographical area, no convincing correlation between geno/subtype and the presence of LP was obtained.

Adolescent↗
PubMed1996

Epidermal growth factor regulates adenylate cyclase activity via Gs and Gi1-2 proteins in pancreatic acinar membranes.

In the present study, Western-blot and radioreceptor analyses have revealed the presence of the epidermal growth factor (EGF) receptor in pancreatic acinar membranes. Isolated pancreatic acinar membranes, which allow access of functional antibodies to individual components of the signal transduction cascade, were used to examine EGF-induced regulation of adenylate cyclase activity. Forskolin, vasoactive intestinal peptide (VIP) and to a smaller extent EGF increased cAMP production in pancreatic acinar membranes. Preincubation of the membranes with anti-GS alpha antibody abolished EGF- and VIP-induced cAMP production, but had no effect on forskolin-induced cAMP accumulation. In the presence of either VIP or forskolin, EGF inhibited the VIP- and forskolin-induced cAMP production with an IC50 of 5 nM. Anti-G alpha i1-2 protein antibody, but not anti-G alpha i3 antibody, increased basal cAMP production, indicating that Gi proteins exert an inhibitory influence on basal adenylate cyclase activity. Anti-G alpha i1-2 antibody, but not anti-G alpha i3 antibody, abolished the inhibitory effect of EGF on the forskolin- and VIP-induced cAMP accumulation. A peptide corresponding to the juxtamembrane region in the cytosolic domain of the rat EGF receptor increased cAMP production in pancreatic acinar membranes in an anti-G alpha s antibody-sensitive fashion, whereas the EGF receptor peptide did not mimic the inhibitory effect of the native EGF receptor. The tyrosine kinase inhibitors genistein and pp60v-src (137-157) inhibited both the stimulatory and the inhibitory effects of EGF on cAMP production. Thus the data of the present study show that EGF regulates adenylate cyclase via activation of Gs and Gi proteins by a tyrosine phosphorylation-dependent mechanism in pancreatic acinar membranes. This leads to stimulation of basal and inhibition of forskolin- and VIP-induced adenylate cyclase activity respectively.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Hepatitis C virus sequences encoding truncated core proteins detected in a hepatocellular carcinoma.

RNA was specifically extracted from tumor and peritumor tissue of a hepatitis C virus (HCV)-associated hepatocellular carcinoma after microdissection. RT-PCR products of the HCV 5'-noncoding (NC), core and nonstructural (NS)-5 gene were examined. Nucleotide sequences of the core region derived from the tumor tissue revealed deletions and mutations resulting in truncated proteins. Peritumor and serum HCV sequences were unaffected.

Amino Acid Sequence↗
PubMed1996

Pertussis toxin-sensitive G-proteins inhibit fibroblast growth factor-induced signaling in pancreatic acini.

Signal transduction of fibroblast growth factor (FGF) receptors is known to involve tyrosine phosphorylation of several substrates, including Grb2, phospholipase C-gamma, and phosphatidylinositol 3-kinase, whereas the role of G-proteins in FGF receptor signaling is controversial. In the present study we investigated the role of G-proteins in FGF receptor signaling in rat pancreatic acini. Immunological analysis revealed the presence of FGF receptor and phospholipase C-gamma1 in rat pancreatic acini. Both basic fibroblast growth factor (FGF-2) and guanosine 5'-(gamma-O-thio)triphosphate (GTPgammaS) caused an increase in inositol 1,4,5-trisphosphate (1,4,5-IP3) production and amylase release. Combined stimulation of the acini with GTPgammaS and FGF-2 led to a decrease of these responses as compared to the effect of the single substances. When pancreatic acini were preincubated with FGF-2 (1 nM) or vehicle (water) ADP-ribosylation of the alpha-subunit of Gi-type G-proteins by pertussis toxin was reduced in membranes prepared from FGF-2 pretreated acini as compared to control acini, suggesting functional interaction of FGF receptors with Gi-proteins. Pretreatment of acini with pertussis toxin which inhibits Gi-type G-proteins abolished the inhibitory effect of GTPgammaS on FGF-induced 1,4,5-IP3 production and amylase release, whereas the stimulatory effects of FGF-2 and GTPgammaS on these parameters remained unchanged. In conclusion, these results show communication of FGF receptors and Gi-type G-proteins and that Gi-type G-proteins exert an inhibitory influence on FGF-induced activation of phosphoinositide-specific phospholipase C in pancreatic acinar cells.

Animals↗
PubMed1996

Effect of interferon alfa on the dynamics of hepatitis C virus turnover in vivo.

In about 30% to 40% of patients with chronic hepatitis C, treatment with recombinant interferon alfa (r-IFN alpha) causes a decrease of serum aminotransferases and hepatitis C virus (HCV) RNA. The antiviral mechanism of interferon alfa (IFN alpha) in vivo is unknown. From serial measurements of serum HCV-RNA concentrations following IFN alpha induced perturbation of the balance between virus production and clearance, we obtained kinetic information on the pretreatment steady-state of HCV. In patients with chronic hepatitis C responding to IFN alpha, HCV-RNA declined exponentially with a half life of approximately 2 days. Modeling of the data predicts that in patients with chronic hepatitis C responding to IFN alpha this cytokine predominantly acts as an inhibitor of de novo infection of susceptible cells. HCV is released from infected cells with a mean half life of 2.7 +/- 1.3 days, whereas the clearance rate from serum is faster (mean half life, 0.7 +/- 0.4 days). The minimum virus production and clearance per day in patients with chronic hepatitis C was calculated to be 6.7 x 10(10) virions/d (range, 0.2 to 43.8 x 10(10) virions/d). These values showed no correlation with the HCV genotype, aminotransferase levels, or the histological activity as assessed before the administration of r-IFN alpha. Simultaneous kinetic analysis of serum aminotransferases as surrogate markers of hepatocyte integrity revealed half lifes for the release of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) from hepatocytes of 4.7 +/- 3.8 and 3.0 +/- 3.5 days, respectively. The half life data for HCV in chronically infected patients are remarkably similar to recently published data on human immunodeficiency virus type 1 (HIV-1) suggesting that both RNA viruses replicate continuously and highly productive in vivo. The turnover rates explain the rapid generation of viral diversity and the opportunity for viral escape phenomena from the host immune surveillance.

Alanine Transaminase↗
PubMed1996

Phylogenetic analysis of hepatitis C virus isolates and their correlation to viremia, liver function tests, and histology.

Nucleotide sequence analysis of hepatitis C virus (HCV) strains showed substantial variability leading to a classification into several genotypes and subtypes. The data correlating HCV genotypes and subtypes with hepatitis C viremia levels, demographic characteristics of patients (age, mode of transmission, duration of infection), and severity of liver disease are conflicting. The interpretation of several studies is further complicated because the molecular methods used lacked specificity for genotyping/subtyping and underestimated viremia levels, especially in patients infected with HCV genotypes 2 and 3. In the present study we investigated 97 consecutive patients with chronic hepatitis C using molecular "gold standard" methods. HCV subtyping was performed by sequence and phylogenetic analysis of the nonstructural (NS)-5 region and serum HCV-RNA concentration was assessed by a validated genotype-independent quantitative reverse-transcription-polymerase chain reaction assay using an internal RNA standard. Patients infected with subtypes HCV-1b, HCV-2a-c, and HCV-4 were older than patients infected with HCV-1a and HCV-3a. Serum HCV-RNA levels ranged from 1.5 x 10(4) to 1.0 x 10(8) copies/mL with no significant differences between median serum HCV-RNA concentrations in patients infected with different genotypes/subtypes. Although patients infected with HCV-1b were older, no biochemical or histological evidence was obtained that this subtype is associated with more severe liver disease. Furthermore, the present study showed a lack of correlation between the serum HCV-RNA concentration, biochemical parameters, and liver histology. The median serum HCV-RNA levels in patients with chronic persistent hepatitis, chronic active hepatitis, and liver cirrhosis were 5.0 x 10(6) copies/mL, 2.5 x 10(6) copies/mL, and 5.0 x 10(6) copies/mL, respectively. These differences were not significant. In conclusion, using optimized and validated molecular techniques, the present cross-sectional study showed no correlation between HCV genotypes/subtypes, viremia, liver function test results, and histology.

Adult↗
PubMed1996

Clinical evaluation of a single reaction, diagnostic polymerase chain reaction assay for the detection of hepatitis C virus RNA.

BACKGROUND/AIMS: In the past few years the detection of HCV-RNA by polymerase chain reaction has become a well-established diagnostic tool for patients with chronic hepatitis C. However, the lack of reproducible results between laboratories and the relatively high proportion of false-positive results, has indicated the need for a standardized and reliable polymerase chain reaction assay. In the present study we have analyzed the performance of a commercial, HCV-RNA polymerase chain reaction assay based on a single, combined reverse transcription and amplification reaction and on the use of Uracil-N-glycosilase to prevent carry-over contamination (Amplicor HCV, Roche Molecular Systems). METHODS: In this assay the amplification products are detected in microwell plates using biotinylated primer and the HRP avidin colorimetric system. Serum samples collected from 446 patients, including 181 with chronic active hepatitis C, 50 with autoimmune chronic hepatitis, 117 in hemodialysis, 30 asymptomatic carriers of anti-HCV and 68 with indeterminate serology (RIBA indeterminate results), as well as from 121 controls were tested with the commercial, single-step assay and with nested polymerase chain reaction. Both techniques use primers located within the 5' non-coding region of the HCV genome. RESULTS: In all cases a good concordance was observed between the commercial, single-step assay and nested polymerase chain reaction which, for patients with chronic active hepatitis, showed a sensitivity and specificity of 100% and 99.3% for the former and of 98.8% and 100% for the latter, when compared to clinical diagnosis taken as the gold standard. Most of the 11 discordant samples were seen in the group of RIBA-indeterminate cases and in patients with chronic active hepatitis C. Further analysis of these cases, based on repeat testing and clinical data showed that 64% and 36% of the discrepancies were due, respectively, to nested polymerase chain reaction and Amplicor inconsistent reactions. In hemodialyzed patients, patients with autoimmune hepatitis and asymptomatic carriers of anti-HCV, both assays produced results which were consistent with the clinical diagnosis. In the former group, polymerase chain reaction was able to identify the presence of active viral replication in some antibody negative samples. CONCLUSIONS: Taken together, these results indicate that the commercial, single-step polymerase chain reaction assay has the same clinical sensitivity and specificity as nested polymerase chain reaction and that, because of its simplified procedures and fast turn-around time, it may be a valuable test for routine diagnostic applications.

Hepacivirus↗
PubMed1996

Phylogenetic analysis of hepatitis C virus isolates from hemodialysis patients.

A high prevalence of hepatitis C virus (HCV) infection has been reported in hemodialysis patients. Main risk factors for transmission are previous blood transfusions and possibly nosocomial infections within the dialytic environment. In the present study 224 hemodialysis patients from the same department were tested for the presence of anti-HCV antibodies and HCV-RNA. The presence of anti-HCV in hemodialysis patients was correlated with a history of more than 10 blood transfusions (P = 0.001) and with a duration of hemodialysis treatment for more than 10 years (P = 0.001). The issue of possible patient-to-patient infection was addressed by sequence analysis of all HCV-RNA positive hemodialysis patients (N = 14) together with a control panel of HCV isolates from 56 unrelated non-hemodialysis patients with hepatitis C from the same geographical area. Subsequent phylogenetic analysis of nucleotide sequences obtained from the 5'-noncoding region and the nonstructural NS-5 region of the HCV genome revealed that only two hemodialysis patients were infected by a highly related HCV isolate. The remaining HCV-RNA positive hemodialysis patients including those without previous blood transfusions were all infected by phylogenetically-distant HCV isolates, providing evidence against a nosocomial transmission route. The data of the present study show that molecular epidemiological techniques are important to investigate the issue of nosocomial infection. In our hemodialysis unit patient-to-patient infection appears uncommon and draws attention towards other possible (such as, blood products such as human serum albumin, immunoglobulins) or even yet unrecognized transmission routes.

Adult↗
PubMed1996

p53 autoantibodies in patients with pancreatitis and pancreatic carcinoma.

In human pancreatic carcinoma (PCa) mutations in the p53 tumor suppressor gene are present in up to 50% of cases. Conformational change and cellular accumulation, together with subsequent release of mutant and normal p53 protein from transformed cells, may initiate a B-cell response with generation of circulating autoantibodies to p53 protein (anti-p53). In the present study we analyzed the sera of 85 consecutive patients with acute pancreatitis (N = 19), chronic pancreatitis (N = 33), and PCa (N = 33) to evaluate the specificity of autoantibodies to p53 protein as a serological marker for PCa. Detection of anti-p53 was performed using an enzyme-linked immunosorbent assay system with immobilized recombinant wild-type p53 protein. Autoantibodies to p53 were detectable in 1 of 19 patients with acute (5.3%) and in 4 of 33 patients with chronic pancreatitis (12.1%). All anti-p53-positive patients with acute or chronic pancreatitis were carefully examined and no underlying malignant disease was found. During follow-up (range, 281-647 days; mean, 472 days) none of these patients showed any evidence for subsequent development of PCa or any other malignant disease. In patients with PCa, anti-p53 was detected in 6 of 33 cases, resulting in a sensitivity of 18.2% with a specificity of 90.4%. In contrast to anti-p53, detection of serum carbohydrate antigen (CA 19-9) resulted in a sensitivity and specificity of 69.7 and 71.2% (CA 19-9, > 37 U/ml) and 51.5 and 96.2% (CA 19.9, > 100 U/ml) for the detection of PCa, respectively. Taken together, the sensitivity of anti-p53 formation was low in patients with PCa (18.2%). Furthermore, the detection of anti-p53 was not specific for malignancy, indicating that severe inflammatory processes may also induce anti-p53 formation.

Acute Disease↗
PubMed1996

Comparison of two quantitative hepatitis C virus reverse transcriptase PCR assays.

A quantitative hepatitis C virus reverse transcriptase PCR (HCV RT-PCR) assay established in our laboratory was compared with the Roche Amplicor HCV Monitor test kit for agreement of test results and intra-assay variability. Both assays rely on reverse transcription and amplification of extracted RNA from patients' sera together with an internal RNA standard derived from the 5'-noncoding region of HCV. A panel of clinical serum samples (n = 33) was quantitatively analyzed in parallel by both test systems. The methods demonstrated substantial agreement between 1 x 10(3) and 5 x 10(5) HCV RNA molecules per ml of serum. However, with sera containing more than 5 x 10(5) copies per ml, according to our in-house assay, the results diverged on average in a nonacceptable range of 2 orders of magnitude. Our in-house HCV RT-PCR assay measured up to 5 x 10(7) HCV-RNA molecules per ml in some serum samples. However, the Roche Amplicor HCV Monitor test kit did not detect more than 2 x 10(6) molecules in any of the serum samples tested. After dilution of serum samples prior to testing, an approximately 0.5 order of magnitude more HCV RNA molecules was detected by the Roche HCV test kit in sera containing high copy numbers (> 5 x 10(5) RNA copies according to the in-house assay). The in-house PCR and the Roche Amplicor HCV Monitor test kit revealed coefficients of variation of 6.2 and 7.5%, respectively.

Base Sequence↗
PubMed1996

Immunoreactive elastase I: clinical evaluation of a new noninvasive test of pancreatic function.

We have evaluated the diagnostic value of the fecal elastase test in comparison with the secretin-pancreozymin test in the diagnosis of exocrine pancreatic insufficiency. Pancreatic elastase was measured immunologically. Immunoreactive elastase activity in spot stools from controls ranged from 136 to 4440 microgram/g; 95% of all values were within 175 to 1500 microgram/g. The elastase assay CVs ranged from 3.3% to 6.3% (intraassay) and from 4.1% to 10.2% (interassay). The output of elastase correlated well with those of amylase, lipase, and trypsin, yielding respective correlation coefficients of 0.83, 0.82, and 0.84 in controls and 0.86, 0.91, and 0.91 in patients with impaired pancreatic function. In contrast to fecal chymotrypsin, the test results were unaffected by pancreatic enzyme replacement therapy. These results indicate that fecal immunoreactive elastase may be recommended as a new, noninvasive tubeless test of pancreatic function.

Adolescent↗
PubMed1996

Quantification of fecal carbohydrates by near-infrared reflectance analysis.

Established methods for quantitative analysis of fecal carbohydrates (CHO) are time consuming, require unpopular sample handling, and are therefore rarely performed. The aim of this study was to evaluate the efficiency, validity, and practicability of near-infrared reflectance analysis (NIRA), compared with standard methods for measurement of fecal CHO. Excretion of fecal CHO was cross- validated spectrophotometrically with the anthrone method. Fecal CHO concentrations ranged form 2.7 to 24.5 g/kg wet weight. Methods comparison showed linear regression over the entire range of diagnostic relevance with a correlation coefficient of 0.869 (S(y/x) +/- 0.31). Repeated measurements from the same stool collections obviated the need for homogenization. These results indicate that NIRA may be a new, reliable, and accurate test in the diagnosis of CHO malabsorption.

Adolescent↗
PubMed1996

Risk factors for the transmission of hepatitis C.

BACKGROUND: Due to the availability of testing for antibodies to the hepatitis C virus (anti-HCV) and with the use of the polymerase chain reaction (RT-PCR) to detect HCV-RNA, more sensitive and specific measures can be applied to assess routes of HCV transmission. The aim of the present study was to investigate possible risk factors for transmission of HCV. METHODS: 160 consecutive patients with chronic hepatitis C (mean age 47.1 +/- 14.1 yr) attending a hepatology out-patient clinic were interviewed to identify transmission risk factors. Genotyping of HCV isolates was performed by direct sequencing of RT-PCR products in the 5'-noncoding and the NS-5 region. RESULTS: The risk factors of HCV infection were as follows: transfusion of blood or blood products 34.4%, intravenous drug abuse 20.6%, heterosexual contact 3.8%, occupational risk 1.9% and tattoo 0.6%. In 62/160 (38.7%) the route of transmission remained unknown. In one HCV-infected couple we analyzed the nucleotide sequences of the NS-5 region of the respective HCV isolates and found almost complete sequence homology (> 97%). The majority of patients with post-transfusional or unknown mode of transmission were infected with genotype HCV-1a and -1b, while in 6/10 patients with previous i.v. drug abuse, genotype HCV-3a was present. We found no evidence that the mode of disease acquisition influences the course of liver disease. CONCLUSION: The majority of patients with chronic hepatitis C have a classical parenteral transmission risk factor. In our study, no source of HCV acquisition was identified in 38.7% of patients. It may well be that the major factors in these "sporadic" HCV infections are variations on the known risk factors. However, since the proportion of these cases is rather high, further attention should be on alternative and as yet unclear transmission routes.

Adolescent↗