Biomedical subjects

C Schmitt

Publications and source records attributed to C Schmitt.

At least 127 records · Page 7Linked to original sources

PubMed1999

Dbp5, a DEAD-box protein required for mRNA export, is recruited to the cytoplasmic fibrils of nuclear pore complex via a conserved interaction with CAN/Nup159p.

Dbp5 is a DEAD-box protein essential for mRNA export from the nucleus in yeast. Here we report the isolation of a cDNA encoding human Dbp5 (hDbp5) which is 46% identical to yDbp5p. Like its yeast homologue, hDbp5 is localized within the cytoplasm and at the nuclear rim. By immunoelectron microscopy, the nuclear envelope-bound fraction of Dbp5 has been localized to the cytoplasmic fibrils of the nuclear pore complex (NPC). Consistent with this localization, we show that both the human and yeast proteins directly interact with an N-terminal region of the nucleoporins CAN/Nup159p. In a conditional yeast strain in which Nup159p is degraded when shifted to the nonpermissive temperature, yDbp5p dissociates from the NPC and localizes to the cytoplasm. Thus, Dbp5 is recruited to the NPC via a conserved interaction with CAN/Nup159p. To investigate its function, we generated defective hDbp5 mutants and analysed their effects in RNA export by microinjection in Xenopus oocytes. A mutant protein containing a Glu-->Gln change in the conserved DEAD-box inhibited the nuclear exit of mRNAs. Together, our data indicate that Dbp5 is a conserved RNA-dependent ATPase which is recruited to the cytoplasmic fibrils of the NPC where it participates in the export of mRNAs out of the nucleus.

Adenosine Triphosphatases↗

PubMed1999

Functional and phenotypic analysis of thymic CD34+CD1a- progenitor-derived dendritic cells: predominance of CD1a+ differentiation pathway.

Whether thymic dendritic cells (DC) are phenotypically and functionally distinct from the monocyte lineage DC is an important question. Human thymic progenitors differentiate into T, NK, and DC. The latter induce clonal deletion of autoreactive thymocytes and therefore might be different from their monocyte-derived counterparts. The cytokines needed for the differentiation of DC from thymic progenitors were also questioned, particularly the need for GM-CSF. We show that various cytokine combinations with or without GM-CSF generated DC from CD34+CD1a- but not from CD34+CD1a+ thymocytes. CD34+ thymic cells generated far fewer DC than their counterparts from the cord blood. The requirement for IL-7 was strict whereas GM-CSF was dispensable but nonetheless improved the yield of DC. CD14+ monocytic intermediates were not detected in these cultures unless macrophage-CSF (M-CSF) was added. Cultures in M-CSF generated CD14-CD1a+ DC precursors but also CD14+CD1a- cells. When sorted and recultured in GM-CSF, CD14+ cells down-regulated CD14 and up-regulated CD1a. TNF-alpha accelerated the differentiation of progenitors into DC and augmented MHC class II transport to the membrane, resulting in improved capacity to induce MLR. The trafficking of MHC class II molecules was studied by metabolic labeling and immunoprecipitation. MHC class II molecules were transported to the membrane in association with invariant chain isoforms in CD14+ (monocyte)-derived and in CD1a+ thymic-derived DC but not in monocytes. Thus, thymic progenitors can differentiate into DC along a preferential CD1a+ pathway but have conserved a CD14+ maturation capacity under M-CSF. Finally, CD1a+-derived thymic DC and monocyte-derived DC share very close Ag-processing machinery.

Antigens, CD↗

PubMed1999

Clinical experience with a novel multielectrode basket catheter in right atrial tachycardias.

BACKGROUND: The complexity of atrial tachycardias (ATs) makes the electroanatomic characterization of the arrhythmogenic substrate difficult with conventional mapping techniques. The aim of our study was to evaluate possible advantages of a novel multielectrode basket catheter (MBC) in patients with AT. METHODS AND RESULTS: In 31 patients with AT, an MBC composed of 64 electrodes was deployed in the right atrium (RA). The possibility of deployment, spatial relations between MBC and RA, MBC recording and pacing capabilities, mapping performance, and MBC-guided ablation were assessed. MBC deployment was possible in all 31 patients. The MBC was left in the RA for 175+/-44 minutes. Stable bipolar electrograms were recorded in 88+/-4% of electrodes. Pacing from bipoles was possible in 64+/-5% of electrode pairs. The earliest activity intervals, in relation to P-wave onset, measured from the MBC and standard roving catheters were 41+/-9 and 46+/-6 ms, respectively (P=0.21). Radiofrequency ablation was successful in 15 (94%) of 16 patients in whom it was attempted, including 2 patients with polymorphic right atrial tachycardia (RAT), 2 with RAT-atrial flutter combination, 1 with macroreentrant AT, and 1 with focal origin of atrial fibrillation. CONCLUSIONS: These data demonstrate that MBC can be used safely in patients with right atrial arrhythmias. The simultaneous multielectrode mapping aids in the rapid identification of sites of origin of the AT and facilitates radiofrequency ablation procedures. The technique is especially effective for complex atrial arrhythmias.

Adult↗

PubMed1999

TAP binds to the constitutive transport element (CTE) through a novel RNA-binding motif that is sufficient to promote CTE-dependent RNA export from the nucleus.

The constitutive transport element (CTE) of the simian type D retroviruses overcomes nuclear retention and allows nuclear export of unspliced viral RNAs by recruiting TAP, a host factor which is thought to be required for export of cellular mRNAs. In this report, we show that the first 372 amino acid residues of TAP, comprising a stretch of leucine-rich repeats, are both necessary and sufficient for binding to the CTE RNA and promoting its export to the cytoplasm. Moreover, like the full-length protein, this domain migrates to the cytoplasm upon nuclear co-injection with the CTE RNA. Together, these results indicate that the CTE-binding domain includes the signals for nuclear export. We also describe a derivative of TAP that bears a triple amino acid substitution within the CTE-binding domain and substantially reduces the export of mRNAs from the nucleus. This provides further evidence for a role for TAP in this process. Thus, the CTE-binding domain of TAP defines a novel RNA-binding motif which has dual functions, both recognizing the CTE RNA and interacting with other components of the nuclear transport machinery.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Chronic urticaria is not significantly associated with hepatitis C or hepatitis G infection: a case-control study.

OBJECTIVE: To study the prevalence of hepatitis C virus (HCV) and hepatitis G virus (HGV) infection in patients with chronic urticaria. DESIGN: Prospective case-control study and literature review. SETTING: Dermatology department of an academic medical center in Strasbourg, France. PATIENTS: One hundred ten consecutive patients with typical urticaria lasting longer than 2 months were seen between March 1, 1997, and August 31, 1998. None had a history of viral hepatitis. Age- and sex-matched patients (n = 110) seen in the same department and during the same period were included for controls. None of the controls had a history of urticaria, pruritic dermatosis, or hepatitis. MAIN OUTCOME MEASURES: The detection of HCV antibodies through a third-generation enzyme-linked immunosorbent assay. To detect early HCV infection without plasmatic antibodies, genomic amplification of HCV RNA was carried out in all patients using 2 different methods. Hepatitis G virus RNA was detected only by genomic amplification. All measures were planned before data collection. RESULTS: Antibodies to HCV were found in 1 patient with urticaria and in 1 of the control group (0.9% of each group). None had circulating HCV RNA, and liver function test results were within the reference range. Genomic amplification without HCV antibodies was not observed. Two patients with urticaria and 2 of the control group (1.8% of each group) had circulating HGV RNA, but they had neither coinfection with HCV nor changes in their liver function test results. CONCLUSIONS: Systematic HCV screening in patients with chronic urticaria is not cost-effective, at least in Europe, because hepatitis C rates were similar to those of the general population. We could not confirm the hypothesis that urticaria occurs in an early phase of HCV infection-ie, before evidence of HCV can be detected by serologic testing. Hepatitis C virus is unlikely to be the cause of urticaria in the infected patient detected in this study because of the absence of HCV RNA and changes on liver function tests. Hepatitis G virus is also unlikely to be a cause of urticaria, as the rate of HGV positivity in this study was even lower than that in the general French population.

Adult↗

PubMed1999

High prevalence of GB virus C/hepatitis G virus RNA in patients infected with human immunodeficiency virus.

Prevalence of GBV-C/HGV was determined in a cohort of HIV-infected patients, via a reverse transcription-polymerase chain reaction detection of RNA in serum, amplifying the NS5 region of GBV-C/HGV genome. GBV-C/HGV RNA was detected in 143 (37.7%) of 379 patients, with similar results in the different HIV risk groups: 25/56 (44.6%) in intravenous drug users, 66/161 (41%) in homo- and bisexual men, 35/108 (32.4%) in heterosexual patients, 6/20 (30%) in transfusion recipients (P=0.41). There was no difference according to the presence or absence of hepatitis C virus infection. In univariate analysis, GBV-C/HGV genome prevalence was lower in patients over 50 years old (18.2%), compared to other age groups (20-29 years: 34.2%; 30-39 years: 44.3%; 40-49 years: 36.7%, P=0.03), as well as in patients with normal CD4 cell count (29.2% vs. 45.4% between 200-500/mm3, and 35.3% below 200 CD4/mm3, P=0.012) and individuals with a chronic hepatitis B. However, in the multivariate analysis, the only prognostic factor of GBV-C/HGV RNA positivity was the presence of a chronic hepatitis B, compared to the absence of any HBV marker, or a previous exposition to HBV (presence of anti-HBc and/or anti-HBs, absence of HBsAg), or the presence of anti-HBs alone.

Adult↗

PubMed1999

[Psycho-neurogenic factors as a cause of life-threatening arrhythmias].

Tachyarrhytmias often occur during increased emotional arousal or mental excitation. The implantable cardioverter defibrillator (ICD) allows the exact documentation of arrhythmic episodes and their time of onset. Therefore, the type of arrhythmia can be differentiated as well as the circumstances surrounding the event. These features allow the assessment of possible psychic arrhythmogenic factors in the natural environment. We analyzed the ICD-protocols of three male patients (in ages between 60 and 68), whose devices had successfully terminated a ventricular tachycardia and compared the onset of the episodes with the patients' detailed descriptions of the corresponding life situations. The analysis of the circumstances at the time of arrhythmia-onset revealed a relationship between the occurrence of life-threatening arrhythmias in natural environment and emotional stress. The stressors could be defined as situations of increased vulnerability leading to sympathetic excitation. The induction of tachyarrhythmia was promoted in case 1 by acute psychic distress (public speaking), by the increasing panic-attack-like vicious circle of the cognitive anticipation of an unfavorable outcome (case 2), and an adverse anger reaction superimposed on persistent feelings of help- and hopelessness (case 3). These findings are in line with several experimental and epidemiological studies providing evidence for a relationship between psychic arousal and the induction of tachyarrhythmias. The knowledge of emotional and mental factors that function as a trigger for arrhythmias may lead to new therapeutic approaches in the prevention of sudden cardiac death.

Aged↗

PubMed1999

Analysis of expression kinetics and activity of a new B-domain truncated and full-length FVIII protein in three different cell lines.

Transient expression of full-length wild-type (wt) and a new B-domain truncated (deltaB) FVIII has been investigated in three eukaryotic cell lines (HEK-293, COS, CHO). When expressed in CHO cells, both FVIII proteins reached the same peak antigen levels, whereas in HEK-293 and COS cells those of FVIII/deltaB were up to sixfold those of FVIII/wt. Investigation of specific activity of the recombinant FVIII proteins using a chromogenic and a one-stage assay in addition to the FVIII-antigen ELISA revealed large variations: In HEK-293 cells specific activity of FVIII/deltaB measured with both assays was higher than that of FVIII/wt. In COS cells specific activity of both FVIII proteins was higher measured in the one-stage assay than in the chromogenic assay. In CHO cells both FVIII proteins had similar specific activity in each assay. In summary, expression kinetics and specific activity of conditioned medium vary depending on cell type used.

Animals↗

PubMed1999

Follow-up of hepatitis C virus RNA in peripheral blood mononuclear cells during interferon therapy.

Mononuclear cells can be infected in vitro by hepatitis C virus and the viral RNA can be detected in mononuclear cells of chronically infected patients. It was suggested that the virus could persist in the mononuclear cells of some patients treated by interferon. The aim of this study was to follow the presence of viral RNA in the plasma and peripheral blood mononuclear cells of 16 chronically infected patients treated by alpha 2b interferon for 1 year. The RNA was detected by reverse transcription followed by nested PCR and quantified using the branched DNA method at regular intervals for at least one year. Before PCR, the mononuclear cells were treated by RNase and trypsin in order to eliminate the viral particles that could be stuck at the cell surface. Six patients were non responders and had persistent plasmatic viral RNA during the treatment. Two patients were good responders and had persistently negative PCR in both plasma and mononuclear cells. Eight patients had initial negativation of plasmatic hepatitis C virus RNA but showed a relapse characterized by positive plasmatic PCR. Positive PCR in mononuclear cells despite negativity of plasmatic PCR was noted 18 times in 8 patients. Persistently positive PCR in mononuclear cells in absence of detectable viraemia was followed by a virological relapse in 5 of these patients. This study confirms that hepatitis C virus RNA can be detected in mononuclear cells despite negative plasmatic PCR in patients treated by interferon. Moreover, the persistence of viral RNA in peripheral mononuclear cells could be a predictive factor of treatment failure. Our data also suggest that detection of viral RNA in mononuclear cells is probably not only due to passive virus adsorption from plasma.

Adult↗

PubMed1999

Recent advances in cardiac mapping techniques.

Recently several new mapping modalities have been introduced into clinical electrophysiologic laboratories, including basket catheter mapping, electromagnetic mapping, and noncontact mapping. In addition, intracardiac echocardiography is being used increasingly to visualize important intracardiac structures for catheter ablation. Basket catheter mapping and noncontact mapping are simultaneous mapping devices, whereas electromagnetic mapping is a sequential mapping tool. The new basket-shaped catheters provide up to 64 electrodes mounted on a variable number of splines that encircle the cardiac contour. Animation programs help in identifying the earliest activation and analyzing the activation sequence. Electromagnetic mapping uses low density magnetic fields to navigate the catheter position and to allow nonfluoroscopic mapping and ablation. Sequential recording of intracardiac potentials produces a real-time, color-coded, three-dimensional activation map. Noncontact mapping does not require direct contact with the endocardium and permits the reconstruction of more than 3000 simultaneous computed electrograms via mathematical algorithms. Three-dimensional isopotential maps are generated to visualize the impulse propagation and guide catheter ablation.

Algorithms↗

PubMed1999

Primary cultured human thymic epithelial cells express both membrane-bound and soluble HLA-G translated products.

This report demonstrates that both membrane-bound and soluble HLA-G isoforms are present in primary cultured human thymic epithelial cells (TEC). HLA-G transcriptional isoforms have been detected by RT-PCR, using different sets of HLA-G specific primers. A flow cytometry analysis, using two anti-HLA-G mAbs, namely 87G and BFL.1, revealed the presence of HLA-G translated products at the cell surface of a subpopulation of TEC. Finally, it was shown that HLA-G soluble forms were secreted in TEC culture supernatant, using a sandwich ELISA with BFL.1 and W6/32 mAbs. These results confirm and extent those previously described showing that HLA-G expressing cells were detectable by immunohistochemistry in thymic medullary epithelial cells.

Cell Membrane↗

PubMed1999

Effects of corticosteroids on HCV infection.

The risk factors for clinical recurrent hepatitis C in liver transplant recipients are not clearly defined. It has been suggested that the corticosteroids included in the treatments of patients undergoing allograft rejection might induce acute hepatitis by increasing HCV replication. In this study we investigated the effects of corticosteroid boluses on HCV viremia in liver allograft recipients treated for acute rejection. Since we had previously developed a model of HCV replication in peripheral blood mononuclear cells (PBMC) in vitro, we also studied the effects of corticosteroids on HCV replication in vitro. A transient peak of HCV viremia was observed in patients treated with corticosteroid boluses for an acute allograft rejection. In the cell cultures, corticosteroids induced an increase of the total amount of viral RNA detectable. Our results demonstrate that corticosteroids induce an increase of hepatitis C virus replication in vivo and in vitro.

Adrenal Cortex Hormones↗

PubMed1999

Computer-assisted animation of atrial tachyarrhythmias recorded with a 64-electrode basket catheter.

OBJECTIVES: The aim of this study was to assess the value of a new mapping technique based on computer-assisted animation of multielectrode basket catheter (BC) recordings in patients with atrial arrhythmias. BACKGROUND: The three-dimensional activation patterns of cardiac arrhythmias are not completely understood owing to limitations of conventional mapping techniques. METHODS: The study included 32 patients with atrial tachycardia (AT) and 38 patients with atrial flutter (AFL). A software program was developed to analyze the activation patterns based on 56 bipolar electrograms recorded with a 64-electrode BC deployed in the right atrium (RA). RESULTS: The total time needed for the animation of activation patterns of atrial arrhythmias was 5 +/- 0.8 min. In 22 patients with right AT, the animated maps revealed that arrhythmia was unifocal in 15 patients, multifocal in 2 patients, polymorphic in 4 patients and reentrant in 1 patient. In 10 patients with left AT, breakthroughs on the right side of the septum (2 in 8 patients and 1 in 2 patients) and a left-to-right activation of the RA were demonstrated. In patients with typical AF, the reentrant excitation was a broad activation front with preferential propagation around the tricuspid annulus. In patients with atypical AFL, the reentry circuit involved one of the venae cavae and a line of block located in the posterior wall. CONCLUSIONS: The computer-assisted animation of multiple electrograms recorded with a BC is a valuable mapping tool that delineates the three-dimensional activation patterns of various atrial arrhythmias. The technique is appropriate for complex, short-lived or unstable arrhythmias.

Adult↗

PubMed1999

Noninvasive localization of accessory pathways in patients with Wolff-Parkinson-White syndrome with the use of myocardial Doppler imaging.

This study sought to examine the diagnostic accuracy of noninvasive prediction of accessory pathway localization in patients with manifest Wolff-Parkinson-White syndrome with the use of myocardial Doppler imaging as a new noninvasive mapping procedure. Myocardial Doppler imaging measures myocardial velocities and therefore can determine the site of earliest ventricular activation in patients with accessory bypass tracts. Twenty-five patients with manifest preexcitation were studied with the use of pulsed wave and M-mode myocardial Doppler imaging for the evaluation of the shortest electromechanical time interval in 9 basal myocardial segments. The new diagnostic test was compared with 3 electrocardiographic algorithms. An invasive mapping procedure served as reference standard. Abnormally short electromechanical time intervals were found in preexcited segments (27 +/- 12 ms vs 64 +/- 27 ms). Myocardial Doppler imaging correctly localized 84% of the accessory pathways and electrocardiographic algorithms only 48% to 60% of cases. Noninvasive prediction of accessory pathway localization by myocardial Doppler imaging is accurate and proved to be superior to prediction based on electrocardiographic algorithms.

Adult↗

PubMed1999

Irinotecan in second-line treatment of metastatic colorectal cancer: improved survival and cost-effect compared with infusional 5-FU.

In a recent multicentre, randomised, controlled, open-label study (Rougier and colleagues, Lancet 1998, 352, 1407-1412), irinotecan significantly increased survival without any deterioration in quality of life compared with best-estimated infusional 5-fluorouracil (5-FU) therapy in the setting of second-line treatment for metastatic colorectal cancer. The aim of the cost-effectiveness analysis reported here was to compare the economic implications, from a U.K. perspective, of replacing 5-FU therapy [either as a single agent (Lokich regimen, B2) or in combination with folinic acid (de Gramont regimen, B1, or AIO regimen, B3)] with irinotecan as second-line therapy for metastatic colorectal cancer. Resource utilisation data collected prospectively during the study, supplemented by both a questionnaire to investigators and local expert clinical opinion, were used as a basis for estimating cumulative drug dosage, chemotherapy administration and treatment of complications. Drug acquisition costs were derived from the British National Formulary (March 1998), and unit costs for clinical consultation and services were derived from relevant 1996/1997 cost databases. Although cumulative drug acquisition costs per patient were higher with irinotecan than with infusional 5-FU therapy, these were at least partially offset by lower cumulative costs per patient associated with administration of therapy and treatment of complications in the irinotecan arm than in the 5-FU arm. Based on the incremental costs per life year gained (LYG), irinotecan was considered to be cost-effective by commonly accepted criteria compared with either the B1 or B2 regimens. Irinotecan was cost-saving compared with the B3 regimen (that is significant survival gain and a reduction in costs). Thus, not only is there strong evidence for the use of irinotecan as standard second-line therapy in metastatic colorectal cancer,but the results of this prospective economic evaluation have shown that irinotecan also represents good value for money in this clinical setting.

Adult↗

PubMed1999

Highly sensitive and species-specific assay for quantification of human transgene expression levels.

During the past few years great efforts have been made to construct and to test human factor VIII (hFVIII) and IX (hFIX) vectors suitable for haemophilia gene therapy in vivo. However, little is known about the molecular mechanisms of persistence and shut-off of transgene expression in the target organs after gene transfer using recombinant adenoviral vectors. To evaluate low transgene mRNA levels in different tissues, especially at long times after the gene transfer, the common northern blot method is often not sensitive enough. For this reason we developed a new, highly sensitive and species-specific method for hFIX mRNA quantification and employed it in mice treated with an adenoviral vector (Ad5CMVFIX) expressing human FIX. In addition to its very high sensitivity (lowest detection level=1 fg RNA), the method was shown to be strictly species-specific, since hFIX mRNA signals were never detected in untreated mice. In a long-term study of 18 vector-treated mice we compared the human FIX:Ag levels in the mouse plasma, the human FIX mRNA levels and human FIX vector DNA concentrations in the mouse liver. We found that a slow but continuous decrease of hFIX:Ag levels in mouse plasma was associated with a corresponding decrease of hFIX mRNA levels in the liver. However, the Ad5CMVFIX vector DNA levels did not decrease to a comparable degree, suggesting that the decrease of human FIX:Ag levels in mouse plasma is, to a significant extent, also caused by CMV promotor shut-off and only to a minor degree by loss of vector DNA.

Adenoviridae↗

PubMed1999

HLA-G in the human thymus: a subpopulation of medullary epithelial but not CD83(+) dendritic cells expresses HLA-G as a membrane-bound and soluble protein.

The human MHC class Ib gene HLA-G is transcribed and translated in different placental cell subpopulations during pregnancy. In addition to this restricted tissue distribution, HLA-G proteins were also recently detected in the thymus of HLA-G transgenic mice, as well as in some human thymic epithelial cells (TEC). There was a need to further define the phenotype of the HLA-G-expressing cells in the human thymus as well as the type of translated forms that they produce. Using several HLA-G-specific mAb and immunohistochemistry performed on cryosections of human thymi at different ages, we found that the HLA-G-expressing cells are present on medullary cells exhibiting the epithelial morphological type 6. Co-localization experiments performed by double or triple immunofluorescence staining demonstrate that these HLA-G-expressing cells express various cytokeratins, epithelial cell markers but not the CD83 dendritic cell marker. We further show by ELISA measurements that a subset of primary cultured human TEC also expresses soluble HLA-G. Therefore, HLA-G protein tissue distribution is not restricted solely to placental cells. A subpopulation of medullary TEC also expresses HLA-G both at their cell surface and in secreted form, raising the question of the functional significance of such MHC class Ib molecules. Whether thymic soluble and/or membrane-bound HLA-G contribute to inhibit NK cells or to a negative selection of autoreactive T cells which could be harmful in case of pregnancy and/or to a positive selection of viral peptides/HLA-G-restricted CD8(+) T cells remains to be demonstrated.

Adolescent↗

PubMed1999

Medical care consumption in a phase III trial comparing irinotecan with infusional 5-fluorouracil (5-FU) in patients with metastatic colorectal cancer after 5-FU failure.

We evaluated economic implications of treatment with irinotecan, following a RCT which demonstrated significantly increased survival at 1 year with irinotecan (45%) compared to infusional 5-fluorouracil (5-FU) (32%) in patients with metastatic colorectal cancer. Medical care consumption data were collected prospectively alongside the trial, with 256 patients followed for a median of 10 months. Follow-up was prolonged beyond treatment failure and medical care consumption was not protocol driven, enabling a realistic evaluation of economic implications. Medical care consumption associated with chemotherapy administration was lower with irinotecan as compared with infusional 5-FU. The cumulative number of days in hospital due to treatment toxicity and cancer complications, which is the key cost driver, was 14.4 (95% CI: 10.7-18.1) with irinotecan versus 17.5 (95% CI: 11.7-23.3) with infusional 5-FU. Thus, the survival benefit with second-line irinotecan compared to infusional 5-FU in patients with advanced colorectal cancer was achieved without increasing medical care consumption.

Ambulatory Care↗