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Biomedical subjects

T Berg

Publications and source records attributed to T Berg.

At least 91 records · Page 5Linked to original sources
PubMed1999

Interferon-antibodies and the breakthrough phenomenon during ribavirin/interferon-alpha combination therapy and interferon-alpha monotherapy of patients with chronic hepatitis C.

BACKGROUND/AIMS: The significance of interferon antibodies with respect to response to treatment in patients with chronic hepatitis C treated with interferon-alpha (INF-alpha) remains a matter of debate. The influence of ribavirin on IFN-antibody formation in combination therapy with IFN-alpha has not yet been studied. Therefore we evaluated the relationship between IFN-antibodies and response to ribavirin/IFN-alpha combination therapy and IFN-alpha monotherapy. METHODS: We studied 169 patients with chronic hepatitis C who were treated either with IFN alpha 2a (6 MU, thrice weekly) alone or in combination with ribavirin (14 mg/kg per day) for twelve weeks. Thereafter, patients who achieved a virological response (HCV-RNA-negative) were treated with 3 MU IFN-alpha thrice weekly for another 40 weeks. IFN antibodies were analyzed and quantified by a double-antigen sandwich enzyme immunoassay (EIA). In 86 patients two neutralization assays--an antiviral neutralization assay as well as an antiproliferative neutralization assay--were performed in addition. The relationship of the development of IFN-antibodies with the virologically defined response to treatment was analyzed. RESULTS: Ribavirin did neither influence the prevalence nor the level of IFN-antibodies. The frequencies of IFN-antibody formation did not differ in the response groups. However, patients with breakthrough showed significantly higher IFN-antibody titers as compared to responder at end of treatment (median 1,336 BU/ml vs. 148 BU/ml; p = 0.018). Among the breakthrough patients those with IFN-antibodies showed the reappearance of HCV-RNA during therapy significantly earlier (median week 24) than those without IFN-antibodies (median week 32; p = 0.03). CONCLUSION: The addition of ribavirin to IFN-alpha does not influence the formation of IFN-antibodies. The development of high-titer IFN-antibodies during IFN-alpha or ribavirin/IFN-alpha therapy of patients with chronic hepatitis C may account for the early occurrence of breakthrough in some patients, while other mechanisms seem to be responsible for this phenomenon in the majority of the afflicted patients.

Adult↗
PubMed1999

Retinyl esters are hydrolyzed in early endosomes of J774 macrophages.

The aim of the current study was to identify the subcellular compartment(s) responsible for the hydrolysis of chylomicron remnant-retinyl esters, in J774.1 cells. The cells were incubated with medium containing chylomicron remnant [(3)H]retinyl ester. Subcellular fractionation was used to separate early endosomes from late endosomes and lysosomes. About 26% and 80% of the total [(3)H]retinyl esters taken up by the J774 cells were hydrolyzed after 10 min and 60 min of chase, respectively. In the early endosomes, there was a 4-fold increase of radioactivity (nearly all radioactivity associated with retinyl esters) during the first 10 min of chase. The radioactivity in early endosomes was reduced by 43% from 10 min to 60 min and remained stable from 60 to 180 min of chase. From 10 to 60 min the amount of retinol in early endosomes increased from 44% to 82%, indicating an efficient hydrolysis of retinyl esters. Less than 10% and 5% of the total cell-associated radioactivity was found in the late endosomes and lysosomes during the entire chase period. In the chase medium, 84% of the total amount of retinoid released during 180 min was present already after 10 min. The percentage of retinol in the medium increased from 25% to 82% during incubation from 10 to 180 min. These data suggest that retinyl esters are endocytosed together with the chylomicron remnant particle and hydrolyzed in the early endosomes in this cell model.-Hagen, E., A. M. Myhre, T. E. Tjelle, T. Berg, and K. R. Norum. Retinyl esters are hydrolyzed in early endosomes of J774 macrophages.

Animals↗
PubMed1998

In vitro fusion of phagosomes with different endocytic organelles from J774 macrophages.

We describe novel biochemical and electron microscopy assays to investigate in vitro fusion of latex bead phagosomes with three different endocytic organelle fractions from J774 macrophages. After formation, early phagosomes fuse avidly with early and late endosomes and for a longer period of time with lysosomes, but they subsequently become fusion-incompetent. The fusion of early, but not late, phagosomes with all three endocytic fractions could be significantly stimulated by Rab5. In contrast to other cell types investigated, this Rab is uniquely enriched on both early and late endosomes in J774 macrophages. Moreover, exogenous Rab5 stimulates homotypic fusion between both sets of organelles. This was shown by a quantitative electron microscopy fusion assay that can directly assay fusion between any combination of morphologically defined organelles. By the same approach, we discovered an unexpected Rab5-stimulatable fusion between early and late endosomes in J774, but not in BHK cells. Thus, in J774 cells both Rab5 and the endocytic pathway seem to have evolved additional functions not yet seen in nonphagocytic cells.

Animals↗
PubMed1998

Isolation and characterization of rat liver amphisomes. Evidence for fusion of autophagosomes with both early and late endosomes.

Amphisomes, the autophagic vacuoles (AVs) formed upon fusion between autophagosomes and endosomes, have so far only been characterized in indirect, functional terms. To enable a physical distinction between autophagosomes and amphisomes, the latter were selectively density-shifted in sucrose gradients following fusion with AOM-gold-loaded endosomes (endosomes made dense by asialoorosomucoid-conjugated gold particles, endocytosed by isolated rat hepatocytes prior to subcellular fractionation). Whereas amphisomes, by this criterion, accounted for only a minor fraction of the AVs in control hepatocytes, treatment of the cells with leupeptin (an inhibitor of lysosomal protein degradation) caused an accumulation of amphisomes to about one-half of the AV population. A quantitative electron microscopic study confirmed that leupeptin induced a severalfold increase in the number of hepatocytic amphisomes (recognized by their gold particle contents; otherwise, their ultrastructure was quite similar to autophagosomes). Leupeptin caused, furthermore, a selective retention of endocytosed AOM-gold in the amphisomes at the expense of the lysosomes, consistent with an inhibition of amphisome-lysosome fusion. The electron micrographs suggested that autophagosomes could undergo multiple independent fusions, with multivesicular (late) endosomes to form amphisomes and with small lysosomes to form large autolysosomes. A biochemical comparison between autophagosomes and amphisomes, purified by a novel procedure, showed that the amphisomes were enriched in early endosome markers (the asialoglycoprotein receptor and the early endosome-associated protein 1) as well as in a late endosome marker (the cation-independent mannose 6-phosphate receptor). Amphisomes would thus seem to be capable of receiving inputs both from early and late endosomes.

Ammonia↗
PubMed1998

Endocytosed ricin and asialoorosomucoid follow different intracellular pathways in hepatocytes.

Earlier studies have suggested that fluid phase endocytosis in rat hepatocytes takes place via a clathrin-independent mechanism [1,2]. This observation suggests that a relatively large amount of plasma membrane outside coated pits may be involved in hepatic endocytosis. Ricin, which binds to galactose residues on glycoproteins and glycolipids, has, in this report, been used as a general marker for the plasma membrane of hepatocytes. The endocytosis of ricin was compared with that of asialoorosomucoid (AOM) which is taken up exclusively via clathrin-coated pits. Hypertonic medium has been shown to inhibit uptake via coated pits more effectively than clathrin-independent uptake [3-5]. It was found, in this study, that the addition of 100 mM sucrose to the incubation medium inhibited the uptake of 125I-tyramine-cellobiose-asialoorosomucoid (125I-TC-AOM) more extensively than that of 125I-tyramine-cellobiose-ricin (125I-TC-ricin), compatible with the notion that the two probes are internalised via different mechanisms. Subcellular fractionation experiments indicated that 125I-TC-ricin entered a denser endocytic organelle than that receiving 125I-TC-AOM. To determine whether the separation of the two probes was due to a different transport kinetics (i.e. that 125I-TC-ricin is transported more rapidly to a later, denser compartment than 125I-TC-AOM) the cells were incubated at 18 degreesC to allow a slower internalisation/transport of the labelled probes. The results obtained showed, again, that the early endosomes containing 125I-TC-ricin were significantly denser than those containing 125I-TC-AOM. We also employed the horseradish peroxidase (HRP)-diaminobenzidine (DAB) density shift technique of Courtoy et al. [6] to determine whether 125I-TC-ricin and 125I-TC-AOM were in separate endosomes early after their uptake. The results showed that early endosomes containing 125I-TC-AOM were density shifted whereas those containing 125I-TC-ricin were unaffected by the density shift procedure. The use of probes labelled with 125I-TC allowed us to identify compartments involved in the degradation of 125I-TC-AOM and 125I-TC-ricin, by measuring acid soluble radioactivities in the gradient fractions. It was found that 125I-TC-ricin was degraded mainly in endosomes, whereas 125I-TC-AOM, as expected, was degraded mainly in lysosomes.

Animals↗
PubMed1998

Pretransplant virological markers hepatitis C virus genotype and viremia level are not helpful in predicting individual outcome after orthotopic liver transplantation.

BACKGROUND: Recurrence of hepatitis C viremia after orthotopic liver transplantation (OLT) is nearly universal, leading to variable outcome from no to severe recurrent disease. In the present study, the prognostic relevance of hepatitis C virus (HCV) genotypes and viremia for the development and severity of graft hepatitis was investigated. METHODS: A total of 79 patients with chronic hepatitis C who could be followed for 1 to 78 months (mean: 30 months) after OLT were included in this study. HCV RNA concentrations were measured before OLT, 1 month after OLT, as well as in the long-term follow-up after OLT in 54 of the 79 patients. RESULTS: Graft hepatitis could be documented in 40 of the 79 patients (51%), and 7 of them (9%) progressed to liver cirrhosis. More severe forms of graft hepatitis predominated in patients with subtype 1b infection, and all seven patients with progression to liver cirrhosis had subtype 1b (P=NS). Neither the pretransplant nor the posttransplant HCV RNA levels were significantly associated with the occurrence of graft hepatitis. However, there was a trend of more severe recurrent disease in subtype 1b-infected patients with high level viremia in the early course after OLT. CONCLUSIONS: Pretransplant HCV virological markers are not helpful to predict the outcome after OLT. However, it should be further investigated whether estimation of HCV genotype and viremia levels very early after OLT, i.e., within the first weeks, may be a better approach to recognize high-risk patients.

Adult↗
PubMed1998

Lysosomal enzyme trafficking between phagosomes, endosomes, and lysosomes in J774 macrophages. Enrichment of cathepsin H in early endosomes.

In this study we take advantage of recently developed methods using J774 macrophages to prepare enriched fractions of early endosomes, late endosomes, dense lysosomes, as well as phagosomes of different ages enclosing 1-micron latex beads to investigate the steady state distribution and trafficking of lysosomal enzyme activity between these organelles. At steady state these cells appear to possess four different cellular structures, in addition to phagolysosomes, where acid hydrolases were concentrated. The first site of hydrolase concentration was the early endosomes, which contained the bulk of the cellular cathepsin H. This enzyme was acquired by phagosomes significantly faster than the other hydrolases tested. The second distinct site of lysosomal enzyme concentration was the late endosomes which contain the bulk of cathepsin S. The third and fourth large pools of hydrolases were found in two functionally distinct types of dense lysosomes, only one of which was found to be secreted in the presence of chloroquine or bafilomycin. Among this secreted pool was soluble furin, generally considered only as a membrane-bound trans-Golgi network resident protein. Thus, the organelles usually referred to as "lysosomes" in fact encompass a growing family of highly dynamic but functionally distinct endocytic organelles.

Animals↗
PubMed1998

Hepatitis B virus with antigenically altered hepatitis B surface antigen is selected by high-dose hepatitis B immune globulin after liver transplantation.

"Escape" variants of hepatitis B virus (HBV) can cause infection despite previous immunization. These viruses show alterations of the immunogenic major hydrophilic loop of the HBV small surface protein (s-protein). We studied whether HBV "escape" variants were selected in patients with graft infection after liver transplantation for HBV-related diseases who received passive immunoprophylaxis with high-dose polyclonal hepatitis B hyperimmune globulin (HBIG). For that, pre- and posttransplantation sera of 34 patients were analyzed for the occurence of HBV S-gene variants. In addition, binding of in vitro-translated variant s-proteins to HBIG was studied. Variants with exchanges of amino acid (aa) 144 (s144) in HBV genotype A and 145 in genotype D (s145) were found to emerge, persist, and predominate during HBIG, and thus fulfilled criteria of "escape" variants selected. In addition to already-known variants sG145R/K/E, we could demonstrate that newly described variants sX144G and sG145A were antigenically altered and showed impaired recognition by polyclonal HBIG in vitro. Diminished recognition of variant s-proteins correlated with the failure of HBIG to prevent infection of the liver graft with antigenically altered variant HBV Patients infected with "escape" variants s144 or s145 showed a worse clinical outcome compared with the other patients on high-dose, long-term HBIG prophylaxis (44% vs. 23% graft failure caused by HBV infection). Our results suggest that antigenically altered HBV variants s144 and s145 can be selected by HBIG and can influence clinical outcome after liver transplantation.

Adult↗
PubMed1998

Searching for the optimal management of hepatitis C patients after liver transplantation.

The optimal immunosuppressive regimen in patients transplanted for hepatitis C (HCV) is still under discussion. High immunosuppression may promote viral replication and recurrent graft hepatitis. But acute and chronic rejection frequently seen in conjunction with HCV recurrence may require some rescue therapy. One hundred and thirty-seven patients transplanted for HCV cirrhosis, who were HCV-RNA positive prior to transplantation, were analyzed. Seventy-nine patients received CSA-based immunosuppression and 58 patients FK506-based immunosuppression. One-month patient survival was 100% in both groups. Three month and 1-year survival rates and the cumulative 1-5-year patient survival was similar in CsA-treated [67/79 (84.8%)] and FK506-treated patients [50/58 (86.2%)]. Retransplantations for HCV recurrence were performed in 5.1% of CsA-treated patients and 6.9% of FK506-treated patients; it was successful in 50% and 75% of patients, respectively. Conversion from CsA to FK506 and vice versa was high with 25 out of 79 patients (31.6%) converting in the CsA group and 8 out of 58 patients (13.8%) converting in the FK506 group. Conversion to FK506 was performed due to acute and chronic rejection and to CsA because of toxicity and HCV recurrence. In both groups, 25% of converted patients died. Five patients of the CsA group and 9 of the FK506 group received OKT3; more than one-third of each group died. Five patients in the CsA group and 6 in the FK506 group received mycophenolate mofetil (MMF) for HCV recurrence or acute and chronic rejection in conjunction with HCV recurrence. All patients of this critical group are alive with good graft function. In conclusion, survival rates of HCV patients were similar to those seen for other indications. Conversion from CsA to FK506 and vice versa was high and reflects a critical group concerning patient survival. OKT3 treatment should be avoided. A promising therapeutic option for critical patients experiencing acute or chronic rejection in conjunction with HCV recurrence may be treatment with MMF.

Hepatitis C↗
PubMed1998

Effects of periodontal support and fixed splinting on load transfer by removable partial dentures.

STATEMENT OF PROBLEM: Periodontally compromised abutment teeth complicate the design of bilateral distal extension removable partial dentures. PURPOSE: This study investigated the stress induced in the remaining oral structures by a bilateral distal extension I-bar-retained RPD with periodontally involved abutments in a photoelastic simulation model. MATERIAL AND METHODS: Composite photoelastic models were used as a simulation model in determining the stress generating characteristics of I-bar RPDs with varying degrees of periodontal involvement of the distal abutments. Effects of fixed splinting were considered. RESULTS AND CONCLUSIONS: Under the same load conditions, the highest stresses developed in the model with the largest osseous defect. Increasing the number of splinted teeth did not provide a proportional decrease in maximum stress levels. The more severe the osseous defect, the greater assistance was provided by splinting to periodontally sound teeth. This simulation study suggests that routine cross-arch splinting may not be appropriate.

Acrylic Resins↗