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T Meier

Publications and source records attributed to T Meier.

At least 55 records · Page 3Linked to original sources
PubMed1998

Epitope specificity of 30 monoclonal antibodies against cytokeratin antigens: the ISOBM TD5-1 Workshop.

The epitope specificities of 30 monoclonal antibodies (MAbs) against the most common human cytokeratins. i.e., Nos. 8, 18, and 19, in epithelial cells were investigated in the ISOBM TD-5 Workshop. Seven research groups from universities or companies participated independently in the evaluation of the antibody specificities. The complex assembly of cytokeratins in vivo, with obligatory heterologous dimeric combinations of different cytokeratins from each of the two major groups, comprising together more than 20 different individual cytokeratins, made analysis of the antibody reactivity patterns with isolated single cytokeratins necessary. The concordance of the evaluations was striking and independent of the technologies used. As antigens purified individual cytokeratins, chemically degraded purified cytokeratins, recombinant intact and truncated cytokeratins, as well as specific synthesized shorter peptides were used. In order to elucidate the epitope specificity, reactivity patterns in ELISA assays and immunoblots with partial enzymatic degradation of the antigens were performed. Competitive cross-inhibition experiments between antibodies using antigens and antibodies in all possible combinations were performed with radioimmunometric assays, BIAcore, and ELISA technology. All 30 antibodies could convincingly be classified with regard to target cytokeratin. One MAb (192) had to be deleted due to dual specificities in both isotype and epitope specificity against its target. Six antibodies bound selectively to cytokeratin 8, 14 to cytokeratin 18, and 10 to cytokeratin 19, as demonstrated by using native, recombinant, and synthesized antigens. The immunodominant part of the molecule for all three types of cytokeratins was located in the region of amino acid (aa) 270-400. Out of the six MAbs reactive with cytokeratin 8, four MAbs, i.e., 178, 199, 202, and 206, were reactive with a sequence in the interval aa 340-365, and MAb 191 reacted with a closely related epitope. The remaining antibody, 192, presented dual specificities. At least two closely related major immunogenic epitopes could be identified in cytokeratin 8. In cytokeratin 18 four distinct epitopes could be documented, again with the dominating sequence region 270-429 as target for 10 (181, 184, 186, 188, 189, 190, 193, 196, 198, and 200) out of 14 antibodies. Since MAb 193 is known to react with the M3 epitope, aa 322-342 in cytokeratin 18, this entire group is reactive in the region close to the charge shift, in the middle of the rod 2B region, as shown by competitive binding. The remaining four anticytokeratin 18 antibodies (180, 185, 203, and 205) displayed unique, noncompetitive binding to this filament. Cytokeratin 19, reactive with altogether ten antibodies, displayed two major epitopes, all of them also within the large immunodominant region. MAbs 179, 195, 197, and 204 were reactive with the peptides aa 311-335 also known as the KS 19.1 epitope, and MAbs 182, 183, 187, 194, and 201 bound to peptide aa 346-367, known as the BM 19.21 epitope. One antibody, 231, was selectively reactive with aa 356-370 in cytokeratin 19. A complex pattern of binding specificities comprising at least ten different, noncompetitive epitopes, mainly situated in the rod portion, 2A and 2B, situated close to the charge shift in the rod of all three cytokeratins was documented. Out of the 29 classifiable antibodies, altogether 22 were reactive in this very short region, i.e., from aa 311 to 370 in all cytokeratin filaments. The remaining seven antibodies displayed unique binding properties. The implications of the findings are of significance both for immunohistochemistry and for assaying circulating heterodimeric, partially degraded complexes in patients' blood for tumor marker evaluation.

Amino Acid Sequence↗
PubMed1998

Error rates in clinical radiotherapy.

PURPOSE: Error rates in clinical oncology are undergoing increasing scrutiny. The purpose of this study was to understand error frequency, error patterns, underlying causal links, consequences, and possible prevention strategies in clinical radiotherapy. PATIENTS AND METHODS: Treatment information, self-reported error documentation, and retrospective analyses of electronic treatment verification transcripts for 1,925 consecutive patients treated with a total of 93,332 individual radiotherapy fields were reviewed and analyzed. RESULTS: A total of 59 separate errors that affected 168 individual treatment fields were detected, which yielded a crude radiation delivery error rate of 0.18%. All 59 errors were judged to be level I (negligible chance of adverse medical outcome) with the most common error category being a minor treatment field block misplacement. A comprehensive quality assurance program and an electronic record-and-verify linear accelerator interlock system seem to have prevented the occurrence of many additional errors. However, nine of the 59 errors were directly related to the use of this system and generally involved the transposition of similar numbers within series of treatment coordinate data-sets. Overall, radiotherapy error rates favorably compare with reported error rates for pharmaceutical administration in large tertiary care hospitals. CONCLUSION: When modern automated error-minimization methods are used along with nonpunitive error reporting systems, clinical radiotherapy seems to be highly safe. Formal error analysis studies may allow the rational design of prevention strategies that are attuned to the frequency, seriousness, and antecedent causes of many classes of potential radiotherapy errors.

Humans↗
PubMed1997

Neural agrin induces ectopic postsynaptic specializations in innervated muscle fibers.

Neural agrin, in the absence of a nerve terminal, can induce the activity-resistant expression of acetylcholine receptor (AChR) subunit genes and the clustering of synapse-specific adult-type AChR channels in nonsynaptic regions of adult skeletal muscle fibers. Here we show that, when expression plasmids for neural agrin are injected into the extrasynaptic region of innervated muscle fibers, the following components of the postsynaptic apparatus are aggregated and colocalized with ectopic agrin-induced AChR clusters: laminin-beta2, MuSK, phosphotyrosine-containing proteins, beta-dystroglycan, utrophin, and rapsyn. These components have been implicated to play a role in the differentiation of neuromuscular junctions. Furthermore, ErbB2 and ErbB3, which are thought to be involved in the regulation of neurally induced AChR subunit gene expression, were colocalized with agrin-induced AChR aggregates at ectopic nerve-free sites. The postsynaptic muscle membrane also contained a high concentration of voltage-gated Na+ channels as well as deep, basal lamina-containing invaginations comparable to the secondary synaptic folds of normal endplates. The ability to induce AChR aggregation in vivo was not observed in experiments with a muscle-specific agrin isoform. Thus, a motor neuron-specific agrin isoform is sufficient to induce a full ectopic postsynaptic apparatus in muscle fibers kept electrically active at their original endplate sites.

Agrin↗
PubMed1997

Induction by agrin of ectopic and functional postsynaptic-like membrane in innervated muscle.

Two factors secreted from the nerve terminal, agrin and neuregulin, have been postulated to induce localization of the acetylcholine receptors (AChRs) to the subsynaptic membrane in skeletal muscle fibers. The principal function ascribed to neuregulin is induction of AChR subunit gene expression and to agrin is the aggregation of AChRs. Here we report that when myoblasts engineered to secrete an agrin fragment were placed into the nerve-free region of denervated rodent muscle, the host muscle fibers expressed AChR epsilon-subunit gene transcripts, characteristic of the neuromuscular synapse in adult muscle. Transcripts were colocalized with agrin deposits and AChR clusters that were resistant to electrical muscle activity. More directly, single innervated muscle fibers injected intracellularly with agrin expression plasmids in their extrasynaptic region developed a functional ectopic postsynaptic membrane with clusters of adult-type AChR channels and acetylcholinesterase and accumulation of myonuclei. The results demonstrate that agrin is the principal neural signal that induces the formation of the subsynaptic apparatus in the muscle fiber and controls locally, either indirectly or directly, the transcription of AChR subunit genes and the aggregation of AChRs.

Agrin↗
PubMed1997

Influence of Mg2+ and temperature on formation of the transcription bubble.

The transcription bubble formed in the binding complex of T7A1 promoter upon Escherichia coli RNA polymerase was analyzed by chemical probes, namely by single-strand specific reagents, to map the unpaired bases in the bubble, and by FeEDTA, to analyze the accessibility of the DNA backbone. The latter probe could also be used as a local hydroxyl radical probe placed close to the Mg2+-binding site in the active center. The data show that the transcription bubble consists of two parts, an Mg2+-dependent part and an Mg2+-independent part, both having individual transition temperatures. The data further suggest that formation of a transcription active open complex is preceded by a transition state complex having enhanced affinity for those Mg2+ ions presumably participating in the formation of the catalytic site. Our data also suggests that the three catalytically active Mg2+ ions in RNA polymerase are functionally not equivalent. One/two of the three Mg2+ ions are responsible for the polymerization, the other two/one for enlargement of the transcription bubble.

Amino Acid Sequence↗
PubMed1997

Comparison of topical anaesthesia methods for venous cannulation in adults.

A prospective, randomized clinical trial was performed in order to assess the efficacy and side-effects of commonly used topical anaesthesia methods in adults receiving peripheral venous cannulation. The study was double-blinded to the degree that the methodologies allowed. One hundred and fifty healthy adults undergoing elective surgery were allocated at random to five groups: EMLA cream, ethyl chloride spray, intracutaneous infiltration with 2% lidocaine, placebo cream and no treatment. Venipuncture was performed with a 18G cannula on the dorsal side of the hand. Puncture pain and pain caused by the topical treatment itself were measured using a visual analogue scale (VAS, range: 0-100 mm). Haemodynamic response, difficulties in performing the puncture and side-effects were recorded. All analgesic techniques were well tolerated. Haemodynamic response and degree of puncture difficulty showed no differences among the groups. Puncture pain (median mrnVAS) following infiltration (1.0) and EMLA (10.0) was significantly lower than no treatment (30.0) or placebo (30.0). The benefit of local infiltration was altered by injection pain (11.5). Spray did not significantly lower puncture pain (26.5) and, in addition, was associated with discomfort (10.5). In adults, EMLA cream significantly reduces puncture pain and represents an acceptable alternate method for topical anaesthesia in venous cannulation. Local lidocaine infiltration is impaired by applicational pain, whereas spraying the puncture site with ethyl chloride has no analgesic benefit.

Clinical Trial↗
PubMed1997

[Keratoconjunctivitis sicca in patients with lipoprotein (a) elevation].

BACKGROUND: Elevated Lp(a) levels are known as risk factor for premature coronary artery disease and apoplexy. To our knowledge ophthalmologic alterations have not been described in combination with elevated Lp(a) levels. We examined whether patients with LP (a) elevation had an increased incidence of keratoconjunctivitis sicca. PATIENTS AND METHODS: 27 patients, 16 women and 11 men were examined. The Lp(a) value was in all patients definitively pathological. The following examinations were performed: history, slitlamp examination, Schirmer-test, impressioncytology, fluorescein staining of the cornea, applanation tonometry and examination of the ocular fundus. RESULTS: The results show a pathologic Schirmer-test in 70.3% of the eyes, in 81.5% a pathologic impressioncytology, and in 48.1% a pathologic fluorescein staining. The Schirmer-test is not sufficiently sensitive and specific in diagnosing the dry eye, whereas impression cytology is highly sensitive and specific. CONCLUSIONS: We could show, that in more than 80% of the examined patients at least one sign of keratoconjunctivitis sicca was found; however we did not find a correlation between the height of the Lp(a) level and the degree of pathologic impression cytology. Further examinations are needed to investigate the causal connection between keratoconjunctivitis sicca and Lp(a) elevation.

Adolescent↗
PubMed1996

AChR phosphorylation and aggregation induced by an agrin fragment that lacks the binding domain for alpha-dystroglycan.

Agrin induces both phosphorylation and aggregation of nicotinic acetylcholine receptors (AChRs) when added to myotubes in culture, apparently by binding to a specific receptor on the myotube surface. One such agrin receptor is alpha-dystroglycan, although binding to alpha-dystroglycan appears not to mediate AChR aggregation. To determine whether agrin-induced AChR phosphorylation is mediated by alpha-dystroglycan or by a different agrin receptor, fragments of recombinant agrin that differ in affinity for alpha-dystroglycan were examined for their ability to induce AChR phosphorylation and aggregation in mouse C2 myotubes. The carboxy-terminal 95 kDa agrin fragment agrin-c95(A0B0), which binds to alpha-dystroglycan with high affinity, failed to induce AChR phosphorylation and aggregation. In contrast, agrin-c95(A4B8) which binds less strongly to alpha-dystroglycan, induced both phosphorylation and aggregation, as did a small 21 kDa fragment of agrin, agrin-c21(B8), that completely lacks the binding domain for alpha-dystroglycan. We conclude that agrin-induced AChR phosphorylation and aggregation are triggered by an agrin receptor that is distinct from alpha-dystroglycan.

Agrin↗
PubMed1996

Effect of tetrahydroaminoacridine on sleep in healthy subjects.

The present study investigated the impact of the cholinesterase inhibitor tetrahydroaminoacridine (THA; tacrine) on sleep in healthy subjects. According to the reciprocal interaction model of non-rapid eye movement (NREM) and REM sleep regulation, which postulates a primary role in cholinergic neurotransmission for the initiation and maintenance of REM sleep, it was expected that THA would lead to an earlier onset of REM sleep. In 12 healthy subjects aged from 21 to 50 years two different doses (20 mg, 40 mg) were administered 1 hour prior to bed time and compared to placebo. Only the higher dose of THA significantly shortened REM latency. No other significant effects on sleep architecture were observed, although administration of 40 mg tacrine was associated with a decrease in sleep efficiency and a prolongation of sleep latency. Blood plasma levels of tacrine and its metabolite 1-hydroxytacrine measured prior to sleep and during the first 90 min of sleep were significantly correlated with the onset of REM sleep in relation to the timing of drug administration (only for the 20 mg dose). The reversible cholinesterase inhibitor THA exerts effects on REM latency comparable to those observed with other cholinomimetic agents.

Adult↗
PubMed1996

[Hepatic veno-occlusive disease--simulating acute abdomen in chemotherapy of Wilms' tumors].

Two of fifteen patients treated in the last 5 years in our hospital for malignant renal tumors developed a venoocclusive disease (VOD). Both had stage II Wilms' tumors with favorable histology. The VOD occurred in the pre- and postoperative period, respectively, some days after application of vincristine and dactinomycin. The boys were aged 2 years and 3 months and 2 years and 9 months, respectively, with body weights of 13 kg and 19 kg, respectively. The treatment of VOD required intensive care procedures. The tumours were removed by nephrectomy and the patients have now remained in remission for 3 years and 1 year and 4 months, respectively. Jaundice, enlargement of the liver, ascites and fever were the symptoms in both patients. Initially, the VOD presented like appendicitis.

Abdomen, Acute↗
PubMed1995

Degradation of 2-(3-aminopropylamino)-ethanethiol (WR-1065) by Cu-dependent amine oxidases and influence on glutathione status of Chinese hamster ovary cells.

The radioprotective drug 2-(3-aminopropylamino)ethanethiol (WR-1065) can be degraded when incubated in cell culture medium in vitro. The degradation reaction consumes oxygen and results from the action of Cu-dependent amine oxidases present in the serum content of the medium. Analysis of the degradation products of WR-1065 demonstrates the formation of cysteamine, acrolein and H2O2. WR-2721, the inactive prodrug of WR-1065, is not a substrate for these enzymes. Extracellular degradation of WR-1065 by Cu-dependent amine oxidases leads to an intracellular depletion of glutathione (GSH) in Chinese hamster ovary (CHO) cells and to reduction of clonogenic cell survival. Addition of aminoguanidine, an inhibitor of Cu-dependent amine oxidases, protects CHO cells from the toxic effects of WR-1065 and under these conditions an increase of intracellular GSH levels occurs. These data demonstrate that WR-1065 can be degraded to toxic compounds by the presence of Cu-dependent amine oxidases which might have further implications for the clinical use of WR-2721.

Acrolein↗