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R Gläser

Publications and source records attributed to R Gläser.

At least 19 recordsLinked to original sources
PubMed2005

The role of mesopores in intracrystalline transport in USY zeolite: PFG NMR diffusion study on various length scales.

PFG NMR has been applied to study intracrystalline diffusion in USY zeolite as well as in the parent ammonium-ion exchanged zeolite Y used to produce the USY by zeolite steaming. The diffusion studies have been performed for a broad range of molecular displacements and with two different types of probe molecules (n-octane and 1,3,5-triisopropylbenzene) having critical molecular diameters smaller and larger than the openings of the zeolite micropores. Our experimental data unambiguously show that, in contrast to what is usually assumed in the literature, the intracrystalline mesopores do not significantly affect intracrystalline diffusion in USY. This result indicates that the intracrystalline mesopores of USY zeolite do not form a connected network, which would allow diffusion through crystals only via mesopores.

Adsorption↗
PubMed2005

Pulsed-field gradient nuclear magnetic resonance study of transport properties of fluid catalytic cracking catalysts.

Pulsed-field gradient nuclear magnetic resonance (PFG NMR) has been applied to study molecular diffusion in industrial fluid catalytic cracking (FCC) catalysts and in USY zeolite for a broad range of molecular displacements and temperatures. The results of this study have been used to elucidate the relevance of molecular transport on various displacements for the rate of molecular exchange between catalyst particles and their surroundings. It turned out that this rate, which may determine the overall rate and selectivity of FCC process, is primarily related to the diffusion mode associated with displacements larger than the size of zeolite crystals located in the particles but smaller than the size of the particles. This conclusion has been confirmed by comparative studies of the catalytic performance of different FCC catalysts.

Catalysis↗
PubMed2001

Interlaboratory evaluation of a new reverse transcriptase polymerase chain reaction-based enzyme-linked immunosorbent assay for the detection of circulating melanoma cells: a multicenter study of the Dermatologic Cooperative Oncology Group.

PURPOSE: Reverse transcription-polymerase chain reaction (RT-PCR)-based detection of tyrosinase mRNA is the most frequently used laboratory method for the detection of circulating tumor cells in melanoma patients. However, previously published results showed considerable variability in the PCR positivity rates. MATERIALS AND METHODS: We designed a collaborative study to assess the sensitivity, specificity, and clinical relevance of a new standardized RT-PCR-based enzyme-linked immunosorbent assay (ELISA) for the detection of circulating melanoma cells. Blood samples of healthy donors mixed with cells of a melanoma cell line were prepared in a blinded fashion, and aliquots were sent to seven participating laboratories experienced in RT-PCR. RESULTS: The results demonstrate a high sensitivity (1 melanoma cell/mL blood) and specificity (no false-negatives and 7.4% [2 of 28] false-positives) of the assay and a satisfactory rate of interlaboratory reproducibility. The analysis of aliquots of blinded samples derived from 60 melanoma patients identified tyrosinase mRNA in 17 of 60 (28.3%): three (20%) of 15 stage I patients, two (13.3%) of 15 stage II patients, five (35.7%) of 14 stage III patients, and seven (43.8%) of 16 stage IV patients. The interlaboratory reproducibility of positive samples, however, was extremely low and indicates the presence of low amounts of target mRNA. CONCLUSION: Reverse transcriptase-PCR ELISA has a high sensitivity and specificity for the detection of tyrosinase mRNA in peripheral blood cells. The low interlaboratory reproducibility for the detection of tumor cells in blood samples of melanoma patients, however, raises the question of relevance of this assay for clinical use.

Adult↗
PubMed2001

Quantification of melanoma-associated molecules in plasma/serum of melanoma patients.

Tumor markers for metastatic melanoma have, so far, been infrequently used. Although there is good evidence from several studies that protein S-100B serum measurement could serve as a valid marker for micro- and/or macrometastasis, the S-100B-LIAmat test has not been established as part of national and international recommendations for the care of melanoma patients. Future studies should focus on early detection of metastatic disease with S-100B compared to routine clinical, laboratory and technical evaluations. Furthermore, preliminary, interesting results on the predictive value of S-100B for the monitoring of metastatic patients during treatment should be verified in multicenter trials. The same considerations are true for melanoma-inhibitory activity (MIA), a new and interesting tool for the detection of metastatic melanoma. However, available data on the clinical use of on the MIA-ELISA are too limited to speculate on an even higher sensitivity and specificity than reported for S-100B. Melanin metabolites are candidates for valid melanoma markers, too. Quantification of 5-S-cysteinyldopa from blood or urine of melanoma patients has not been transferred from the laboratory to daily routine due to several technical problems in the assessment of this particular molecule. Cytokines, adhesion molecules and metalloproteinases are shed from melanoma cells into the serum, but these cells are not the only source of elevated serum levels. Several inflammatory conditions are responsible for high serum concentrations of these molecules. In general, they are not sensitive and specific enough to serve as "melanoma markers."

Biomarkers, Tumor↗
PubMed1999

Predictive value of serum S100B for monitoring patients with metastatic melanoma during chemotherapy and/or immunotherapy.

In the immunohistology of malignant melanoma the use of polyclonal antibodies against protein S100 is well established. Recently, it was shown that S100B, a subunit of the S100 protein family, is detectable in the serum of melanoma patients and correlates with the stage of the disease in patients with metastatic melanoma. In the present study, the first evaluation of a large number of treatment observations (n = 77) in 64 different patients during chemotherapy and/or immunotherapy for advanced metastatic melanoma (stage IV) is presented. All patients received treatment according to standardized protocols comprising 8 weeks of treatment followed by routine staging procedures to evaluate therapeutic outcome. In 13 patients with tumour enlargement after first-line therapy, a second-line treatment was subsequently given. S100B immunoradiometric assay (IRMA) tests were performed before, during and after treatment at scheduled time points. In the interim analysis at 4 weeks 29 of 37 (78%) patients with tumour progression during treatment showed a raised S100B level. In the final analysis at 8 weeks, 31 of these 37 patients (84%) demonstrated rising S100B values (P < 0.001). Patients who responded to treatment (stable or regressing metastatic disease) showed constant or declining S100B levels in 38 of 40 patients (95%) at the interim analysis, at 8 weeks this was further increased to 39 of 40 patients (98%; P < 0.001). Thus, the use of S100B for monitoring treatment is adequate in the majority of cases. Our observations are of great interest for therapeutic trials of adjuvant and palliative therapies as the rise of S100B levels might indicate that re-staging and/or changes in therapy strategies should be chosen.

Adult↗
PubMed1999

Prognostic significance of serum S100B detection compared with routine blood parameters in advanced metastatic melanoma patients.

Recent reports on the use of a quantitative measurement of S100B protein for the detection of metastatic melanoma have yielded promising results. In this study we evaluated 489 serum samples from 64 patients suffering from advanced melanoma (UICC/AJCC stage IV) to compare the sensitivity of a S100B immunoradiometric assay (IRMA) with that of conventional blood parameters as well as other known clinical prognostic factors. In a univariate statistical analysis, gender, bone metastasis, and lactate dehydrogenase and S100B levels in serum samples were found to be significant prognostic markers (P<0.05). The S100B level represented the only relevant independent prognostic marker that was sustained in a multivariate analysis (P = 0.016). Furthermore, we were able to demonstrate that S100B is of relevance irrespective of the specific sites of metastatic involvement. The other laboratory parameters could not match the sensitivity rate of S100B. Overall survival rate was strongly associated with serum S100B values. The results of our study suggest that S100B might be a useful tool as a melanoma marker and an independent prognostic factor in advanced metastatic melanoma. S100B serum detection is likely to be of great interest for the pretreatment stratification and/or monitoring of patients enrolled in clinical studies.

Blood Platelets↗
PubMed1999

S100B protein detection in serum is a significant prognostic factor in metastatic melanoma.

The serum detection of S100B, a new melanoma marker, has shown clinical significance in early studies. The aim of our study of 1, 339 serum samples from 412 different melanoma patients and 107 control patients was to prove the prognostic value of serum S100B levels in melanoma patients at different stages of disease and at follow-up (median: 30 months). Using a cutoff level of 0.2 microgram/l S100B, 5 of 286 patients (1.7%) with primary tumors (stage I/II), 14/73 (19.2%) patients with locoregional metastasis (stage III) and 57/84 (67.9%) patients with advanced disease (stage IV) were S100B positive (statistically significant differences for stage I/II vs. III, I/II vs. IV, and III vs. IV, p < 0.001). The estimated overall survival time was significantly longer (p < 0.001) for patients with S100B values below 0.2 microgram/l compared to patients with elevated S100B levels (>/=0.2 microgram/l), which was independent of the stage of disease (I-IV). Regarding prognosis, we were furthermore able to distinguish different subgroups among stage III and IV patients using S100B serum levels (p < 0.01). Patients with different cutaneous non-melanoma diseases served as S100B-negative controls. S100B serum evaluations using the Sangtec(R)100 IRMA are highly specific and sensitive for the detection of metastatic melanoma. S100B has been shown to be a relevant prognostic factor for survival in a study with a large sample size of melanoma patients including close follow-up evaluations.

Adult↗
PubMed1998

Hyperpigmentation due to topical calcipotriol and photochemotherapy in two psoriatic patients.

The vitamin D3 analogue calcipotriol (calcipotriene) is an effective topical treatment for psoriasis. In combination with other antipsoriatic agents, such as ultraviolet radiation, calcipotriol is reported to improve the overall efficacy of the treatment. Here we describe two patients treated with a combination treatment of calcipotriol and bath psoralens and ultraviolet A who developed hyperpigmentation at the lesional sites where calcipotriol ointment was applied.

Adult↗
PubMed1997

Detection of circulating melanoma cells by specific amplification of tyrosinase complementary DNA is not a reliable tumor marker in melanoma patients: a clinical two-center study.

PURPOSE: Recently, the reverse-transcription polymerase chain reaction (RT-PCR) of tyrosinase messenger RNA (mRNA) was reported to be a useful tool for the detection of circulating tumor cells in the peripheral blood of melanoma patients. Our aim was to evaluate critically the diagnostic value of this marker by investigating a significant number of patients in different stages of the disease in a two-center study. PATIENTS AND METHODS: Different techniques of blood collection, RNA isolation, and RT-PCR were compared, and the detectability of tyrosinase mRNA was tested using nine different melanoma cell lines. The sensitivity of the method was confirmed by blood spiking experiments and the specificity by restriction enzyme analysis. Subsequently, a total of 153 blood samples from 137 individuals (30 healthy subjects, five basal cell carcinoma, and 102 melanoma patients) were investigated. RESULTS: The detection level of melanoma cells differed between the cell lines tested. However, we could reproducibly detect single melanoma cells by spiking whole blood samples from healthy volunteers. One of 43 patients with primary melanoma (2.3%), zero of 15 patients with regional metastasis (0%), and 12 of 44 patients with advanced disease (27.3%) were found to be RT-PCR positive. All blood samples obtained from controls and patients with basal cell carcinoma were tyrosinose mRNA negative. CONCLUSION: Our data support the recent doubts that the detection of circulating tumor cells in melanoma patients using the tyrosinase mRNA RT-PCR is not sensitive enough to be used either as a melanoma progression marker in early stages of the disease or to monitor therapy in advanced stages of the disease.

Biomarkers, Tumor↗
PubMed1993

HLA DNA preorgan retrieval donor typing in renal transplantation.

For the first time, a DNA technique was used in clinical practice for pre-organ donor retrieval typing in renal transplantation. The method is based on the polymerase chain reaction with nested sequence-specific pairs (nested PCR-SSP) for all serological HLA-DR specificities of DR1-DR18. A panel of reference-typed individuals (n = 101) was investigated in a blind quality control study and the results revealed a sensitivity of 99.5% and a specificity of 100%. Semi-automation of PCR-SSP provided rapid, accurate and reliable typing results demonstrating that this DNA test is most suitable for replacing the error-prone HLA-DR serological technique. Twenty-seven consecutive cadaveric organ donors have been successfully typed so far. The results were available within less than 3 h after blood sampling and in all cases prior to the retrieval of organs. In conclusion, the introduction of this accurate DNA typing in HLA matching programs may significantly improve the graft survival rate in renal transplantation.

Blood Grouping and Crossmatching↗
PubMed1992

Rapid HLA-DRB1 genotyping by nested PCR amplification.

State of the art genotyping of HLA class II alleles with group-specific DNA amplification by the polymerase chain reaction (PCR) (1) and subsequent probing with sequence-specific oligonucleotides (2-4) is not suitable for typing cadaveric organ donors since the typing procedure takes far more than one working day. We designed specific oligonucleotide primer sets for nested PCR amplification which allowed typing for all serological HLA-DR specificities (DR1-DRw18) solely by the detection of amplified DNA in the reaction mixtures after agarose gel electrophoresis. Exon 2 of the DRB genes and a DRw52-group-specific part of DRB1 exon 2 was amplified directly from cell lysates without prior DNA extraction. The amplified DNA was subjected to a second round of amplification, which employed a set of 18 nested allele- or group-specific primer pairs. All alleles which have at least a single mismatched base at the terminal 3'-nucleotide of one primer were completely refractory to amplification. This assay is easy to perform and takes less than one working day to complete. Thus, this method may prove to be suitable for DNA typing of organ donors for prospective HLA-DR matching in renal transplantation.

Alleles↗