PubMed Health⌕ Search

Biomedical subjects

C Becker

Publications and source records attributed to C Becker.

At least 19 recordsLinked to original sources
PubMed1999

Traumatic neuroma with biliary duct obstruction after orthotopic liver transplantation.

BACKGROUND: Traumatic neuromas may develop after injury to nerve fibers encased in Schwann cells. The incidence of symptomatic neural tumors appears to be low after orthotopic liver transplantation (OLT). Only two cases of biliary stricture caused by infiltrating traumatic neuroma have been described previously. METHODS: We report two new cases of biliary tract obstruction after OLT that failed to respond to percutaneous balloon dilatation and were corrected by a resection of the bile duct stricture followed by biliary reconstruction with a Roux-en-Y jejunal loop. RESULTS: The first patient (17 months after OLT) had a traumatic neuroma appearing as a distinct mass with nerve bundles confirmed histologically; the traumatic neuroma in the second patient (5 months after OLT) was a nerve stump with infiltration of nervous elements in the bile duct. Both patients recovered without complications. CONCLUSIONS: Traumatic neuromas should be considered in the differential diagnosis of late biliary stricture after OLT, in particular when not responding to percutaneous dilatation or stenting.

Anastomosis, Roux-en-Y↗
PubMed1999

Purinergic inhibition of glucose transport in cardiomyocytes.

ATP is known to act as an extracellular signal in many organs. In the heart, extracellular ATP modulates ionic processes and contractile function. This study describes a novel, metabolic effect of exogenous ATP in isolated rat cardiomyocytes. In these quiescent (i.e. noncontracting) cells, micromolar concentrations of ATP depressed the rate of basal, catecholamine-stimulated, or insulin-stimulated glucose transport by up to 60% (IC50 for inhibition of insulin-dependent glucose transport, 4 microM). ATP decreased the amount of glucose transporters (GLUT1 and GLUT4) in the plasma membrane, with a concomitant increase in intracellular microsomal membranes. A similar glucose transport inhibition was produced by P2 purinergic agonists with the following rank of potencies: ATP approximately ATPgammaS approximately 2-methylthio-ATP (P2Y-selective) > ADP > alpha,betameATP (P2X-selective), whereas the P1 purinoceptor agonist adenosine was ineffective. The effect of ATP was suppressed by the poorly subtype-selective P2 antagonist pyridoxal-phosphate-6-azophenyl-2', 4'-disulfonic acid but, surprisingly, not by the nonselective antagonist suramin nor by the P2Y-specific Reactive Blue 2. Glucose transport inhibition by ATP was not affected by a drastic reduction of the extracellular concentrations of calcium (down to 10(-9) M) or sodium (down to 0 mM), and it was not mimicked by a potassium-induced depolarization, indicating that purinoceptors of the P2X family (which are nonselective cation channels whose activation leads to a depolarizing sodium and calcium influx) are not involved. Inhibition was specific for the transmembrane transport of glucose because ATP did not inhibit (i) the rate of glycolysis under conditions where the transport step is no longer rate-limiting nor (ii) the rate of [1-14C]pyruvate decarboxylation. In conclusion, extracellular ATP markedly inhibits glucose transport in rat cardiomyocytes by promoting a redistribution of glucose transporters from the cell surface to an intracellular compartment. This effect of ATP is mediated by P2 purinoceptors, possibly by a yet unknown subtype of the P2Y purinoceptor family.

Adenosine Triphosphate↗
PubMed1999

Direct and indirect T cell priming by dendritic cell vaccines.

The mechanisms by which dendritic cell (DC) vaccines prime host T cells in vivo was analyzed. Mice were immunized with syngeneic bone marrow-derived DC and as surrogate antigen beta-galactosidase (beta-gal) was used. DC either pulsed with peptide, loaded with beta-gal antigen or gene-modified induced beta-gal-specific cytotoxic T lymphocytes (CTL) and moderate rejection of an in vivo challenge with beta-gal expressing tumors. In addition, beta-gal-specific CTL lysed the syngeneic DC that were used as vaccines. Using SCID mice reconstituted with F1 lymphocytes, direct priming by gene-modified DC vaccines was demonstrated by the presence of beta-gal-specific CTL of the haplotype exclusively expressed by DC while indirect priming by host antigen-presenting cells (APC) was shown by the detection of CTL of the haplotype exclusively present on host APC and absent on DC vaccines. Since DC immunization in syngeneic mice was associated with an increase in NK1.1+/Ly49C- cells and detectable lysis of DC in vitro by lymphokine-activated killer cells, DC vaccines appear to interact with host natural killer cells as well as with antigen-specific T cells. These effector cells in turn may lyse DC vaccines thereby leading to the release of antigens that can be taken up by host APC.

Animals↗
PubMed1999

Methotrexate specifically modulates cytokine production by T cells and macrophages in murine collagen-induced arthritis (CIA): a mechanism for methotrexate-mediated immunosuppression.

Immunosuppressive therapy with methotrexate (MTX) has been established as effective treatment for patients with rheumatoid arthritis. To analyse the therapeutic potential and mechanisms of action of MTX, we determined serum cytokine levels and cytokine production by splenic T cells and macrophages in untreated and MTX-treated mice. Furthermore, we assessed the role of MTX in a murine model of experimental arthritis induced by collagen type II (CIA). MTX reduced spontaneous and IL-15-induced tumour necrosis factor (TNF) production by splenic T cells but not by macrophages from healthy mice in vitro in a dose-dependent manner. In contrast, interferon-gamma (IFN-gamma) production was less strikingly reduced and IL-4 production was virtually unaffected. In addition, treatment of healthy mice with MTX in vivo led to reduced TNF serum levels and diminished TNF production by splenic T cells and macrophages. Intraperitoneal administration of MTX prior to the onset of arthritis completely prevented clinical and pathological signs of CIA. This was associated with a striking reduction of TNF production by spleen cells from MTX-treated mice. The role of TNF in MTX-mediated effects on cytokine production was further underlined by the finding that MTX effects on IFN-gamma production were augmented in TNF-transgenic mice but abrogated in mice in which the TNF-alpha gene had been inactivated by homologous recombination. Thus, MTX specifically modulates spontaneous and IL-15-induced TNF-alpha production in mice and prevents experimental murine CIA. These data suggest that TNF production by T cells is an important target of MTX and may serve as a basis to understand and further analyse MTX-mediated mechanisms of immunosuppression in patients with RA.

Animals↗
PubMed1999

[Assessment of the effective dose for routine protocols in conventional CT, electron beam CT and coronary angiography].

PURPOSE: To compare the effective dose applied by sequential CT (SEQ), spiral CT (SCT), electron beam CT (EBT) and coronary angiography for investigations of the chest, abdomen and the heart. METHODS: The Alderson Phantom was used to compare the effective dose for all modalities. In addition, the effective dose for conventional CT (SEQ and SCT) was estimated with a mathematical phantom. RESULTS: For CT investigation of the chest and abdomen the dose was highest for the EBT (11 mSv and 25 mSv, respectively) and slightly lower for the SEQ (7.8 mSv and 21.5 mSv, respectively), whereas spiral CT required the least dose (5.3 mSv and 8.8 mSv, respectively). For coronary calcium screening (0.8 mSv) and EBT coronary angiography (1.7 mSv) the dose was lower than for coronary catheter angiography (3.3 mSv). For conventional CT the difference between the effective dose derived by the mathematical phantom and by the Alderson phantom was 2% to 20%. CONCLUSIONS: For investigations of the chest and abdomen the effective dose applied by SCT is significantly lower than that with EBT and SEQ. For investigation of the coronary arteries the effective dose applied by EBT is lower than that for coronary catheter angiography.

Body Burden↗
PubMed1998

Does an asparaginyl-specific cysteine endopeptidase trigger phaseolin degradation in cotyledons of kidney bean seedlings?

An asparaginyl-specific cysteine endopeptidase which was named 'legumain-like proteinase' (LLP) and has an apparent molecular mass of 38.1 kDa was isolated from cotyledons of kidney bean (Phaseolus vulgaris L.) seedlings and partially characterized. It is, to our knowledge, the first known proteinase which in vitro extensively degrades native phaseolin, the major storage globulin of this grain legume. Phaseolin that in vitro had been partially degraded by LLP (Pvitro) and phaseolin that was isolated after partial in vivo breakdown 6 days after the start of seed imbibition (Pvivo) showed similar fragment patterns on SDS/polyacrylamide gels. The fragments had identical cleavage sites in Pvitro and Pvivo as determined by partial amino acid sequencing. In both types of partially degraded phaseolin, these cleavage sites have asparagine in the P1 position. Two of the cleavage sites are located in the beta-barrel domain of the C-terminal module and only one cleavage site was found in the beta-barrel domain of the N-terminal module according to the consensus structural model of phaseolin subunits. These results suggest that very likely LLP could in vivo be responsible for the initiation of phaseolin proteolysis. Two different legumain-specific clones named cp6b and p21b were isolated from a cDNA library of germinated bean cotyledons. Cp6b encodes LLP, while p21b encodes a VPE-like enzyme. Southern-blot analysis revealed a single gene copy for Pv-VPE and, presumably, at least two gene copies for LLP in the kidney bean genome. Northern-blot analysis indicated that mRNAs for both clones appear de novo during seed germination. However, the developmental patterns of the transcript levels corresponding to the two clones differed significantly. The temporal pattern of phaseolin degradation and of LLP polypeptide levels agreed well with the suggestion that LLP plays a key role in the mobilization of phaseolin during and after kidney bean germination.

Amino Acid Sequence↗
PubMed1998

[Accidental falls and fall-related injuries in the elderly. Diagnosis and intervention].

Falls in the elderly should be seen as treatable symptoms of impending or already present loss of mobility and therefore often loss of independence. The most important European and American epidemiological data are presented, and the diagnostic strategies and appropriate interventions discussed. The latter represent the most effective measures for minimizing functional impairment in the elderly that are currently available. The aim of the present paper is to demonstrate the feasibility of such measures and their value in the prevention of loss of mobility in the elderly.

Accidental Falls↗
PubMed1998

[Splenic vein thrombosis and chronic pancreatitis: therapeutic approach].

10% of chronic pancreatitis (CP) cases are complicated by splenic vein thrombosis (SVT) which is responsible for upper digestive haemorrhages. To improve our approach to treatment we reviewed 30 cases of SVT associated with CP treated in our centre from 1985 to 1995. 14 patients were treated conservatively. Six of them were refused for surgery due to extension of splenic vein thrombosis into the portal vein. Two patients without extrinsic compression of the vein were treated with anticoagulants. 16 patients were treated by surgery with low morbidity and without mortality. The standard treatment in fourteen cases was splenopancreatectomy. The average follow-up of seven years shows that these patients have preserved their body mass index (BMI). The results suggest that early surgical intervention is beneficial in preventing progression of SVT to the portomesenteric vein.

Adult↗
PubMed1998

IL-12 and IL-18 differentially regulate the transcriptional activity of the human IFN-gamma promoter in primary CD4+ T lymphocytes.

We analyzed the molecular mechanisms by which IL-12 and IL-18 induce transcriptional activity of the IFN-gamma promoter in primary human CD4+ T cells. In transfection experiments, we found that IL-18 directly induces IFN-gamma promoter activity, whereas significant activation with IL-12 required costimulation with alphaCD3/CD28. Furthermore, IL-12 caused in vivo protection of a STAT4 (-236) binding site, whereas stimulation with IL-18 or IL-12 plus alphaCD3/CD28 induced occupancy of a downstream AP-1 site. Mutation of this AP-1 site abrogated both IL-12- and IL-18-mediated promoter activation, whereas mutation of the STAT site inhibited IL-12-dependent activation. These data suggest that both AP-1 and STAT4 are required for IL-12-dependent IFN-gamma promoter activity, whereas IL-18 causes direct activation via AP-1. This differential activation of the IFN-gamma promoter gives further insights into molecular pathways governing Th1 T cell development and differentiation.

Base Sequence↗
PubMed1998

A comparison of digital luminescence mammography and conventional film - screen system: preliminary results of clinical evaluation.

The objective of this study was to determine if digital luminescence mammography can be used as a diagnostic tool. We investigated twenty-two patients with mammographically suspicious findings using a conventional film-screen system and a digital phosphor storage plate in order to compare these two techniques. Four radiologists experienced in mammography reviewed each pair of images. Our results indicate that detectability of microcalcifications and solid masses with digital systems is superior to conventional film-screen mammography due to the increased contrast enhancement associated with digital systems. We did, however, find that characterization of morphological details is inferior with the digital system, presumably due to reduced spatial resolution. In addition, we found no statistically significant difference in the differentiation of benign from malignant lesions with both techniques. The accuracy of mammographic diagnosis was investigated in a receiver operating characteristic study and similar values were found with both techniques. Our results indicate that digital mammography will become an acceptable diagnostic tool although improvement, especially in spatial resolution, is desirable.

Aged↗
PubMed1998

Polysialic acid on the neural cell adhesion molecule correlates with expression of polysialyltransferases and promotes neuroblastoma cell growth.

Neuroblastomas and cell lines derived from these tumors bear the oncodevelopmental antigen polysialic acid (PSA) bound to the neural cell adhesion molecule. Polysialyation of neural cell adhesion molecule can be achieved by two different polysialyltransferases, ST8SiaII and ST8SiaIV. This study was undertaken to investigate the pattern of polysialyltransferases expressed in the human neuroblastoma cell line SH-SY5Y. Reverse transcription-PCR showed simultaneous expression of the two enzymes, and in situ hybridization demonstrated that the polysialyltransferase mRNA expression parallels immunoreactivity with the PSA-specific monoclonal antibody 735. After retinoic acid-induced differentiation, only the PSA-positive, neuron-like cell type gave clear signals for ST8SiaII and ST8SiaIV in in situ hybridization, whereas both signals were drastically reduced in the weakly PSA-positive substrate adherent phenotype. Like the SH-SY5Y cells, a primary, PSA-positive neuroblastoma specimen revealed expression of the two polysialyltransferases. To investigate the role of PSA for cell growth and differentiation, SH-SY5Y cells were treated with the PSA-specific endo-N-acetylneuraminidase E. Although loss of PSA was accompanied with a marked reduction of cell growth, it did not interfere with retinoic acid-induced differentiation. Together, our results suggest that PSA surface expression is regulated on the level of polysialyltransferase transcription. Moreover, the similarity to the primary neuroblastoma tissue makes SH-SY5Y cells a suitable model system to examine further the role of polysialylation in tumor cell growth and the orchestration of PSA synthesis in neuroblastoma.

Cell Differentiation↗
PubMed1998

Determination and analysis of antigenic epitopes of prostate specific antigen (PSA) and human glandular kallikrein 2 (hK2) using synthetic peptides and computer modeling.

Prostate specific antigen (PSA) and human glandular kallikrein 2 (hK2), produced essentially by the prostate gland, are 237-amino acid monomeric proteins, with 79% identity in primary structure. Twenty-five anti-PSA monoclonal antibodies (Mabs) were studied for binding to a large array of synthetic linear peptides selected from computer models of PSA and hK2, as well as to biotinylated peptides covering the entire PSA sequence. Sixteen of the Mabs were bound to linear peptides forming four independent binding regions (I-IV). Binding region I was localized to amino acid residues 1-13 (identical sequence for PSA and hK2), II (a and b) was localized to residues 53-64, III (a and b) was localized to residues 80-91 (= kallikrein loop), and IV was localized to residues 151-164. Mabs binding to regions I and IIa were reactive with free PSA, PSA-ACT complex, and with hK2; Mabs binding to regions IIb, IIIa, and IV were reactive with free PSA and PSA-ACT complex, but unreactive with hK2; Mabs binding to region IIIb detected free PSA only. All Mabs tested (n = 7) specific for free PSA reacted with kallikrein loop (binding region IIIb). The presence of Mabs interacting with binding region I did not inhibit the catalytic activity of PSA, whereas Mabs interacting with other binding regions inhibited the catalysis. Theoretical model structures of PSA, hK2, and the PSA-ACT complex were combined with the presented data to suggest an overall orientation of PSA with regard to ACT.

Amino Acid Sequence↗
PubMed1998

[Virtual and three-dimensional bronchoscopy with spiral and electron beam computed tomography].

PURPOSE: To compare spiral computed tomography (CT) and electron-beam CT (EBT) for 3D and virtual CT-bronchoscopy. MATERIALS AND METHODS: 17 patients with various disorders of the tracheobronchial system were examined using fiberoptic bronchoscopy, spiral CT and EBT. 3D images were reconstructed from CT data sets using automated segmentation based on volume-growing methods. Surface-rendered, volume-rendered, and hybrid reconstructions were visualized in real time using a data helmet. RESULTS: All data sets could be processed to high-quality three-dimensional (3D) and virtual reconstructions. The reduction of motion artifacts due to shorter scan times made EBT data sets better suited for automated segmentation and less susceptible to motion artifacts. 3D and virtual reconstructions did not increase the diagnostic sensitivity of CT compared to axial reconstructions alone. CONCLUSIONS: Shorter scan times of CT imaging yield higher-quality 3D and virtual reconstructions. Modern reconstruction techniques are valuable visualization tools for select indications and are the prerequisite for future developments in computer-aided medicine.

Bronchial Neoplasms↗