Biomedical subjects

Burkhard Schmidt

Publications and source records attributed to Burkhard Schmidt.

28 records · Page 2Linked to original sources

PubMed2004

Metabolism of the nonylphenol isomer [ring-U-14C]-4-(3',5'-dimethyl-3'-heptyl)-phenol by cell suspension cultures of Agrostemma githago and soybean.

The biotransformation of the nonylphenol isomer [ring-U-14C]-4-(3',5'-dimethyl-3'-heptyl)-phenol (4-353-NP, consisting of two diastereomers) was studied in soybean and Agrostemma githago cell suspension cultures. With the A. githago cells, a batch two-liquid-phase system (medium/n-hexadecane 200:1, v/v) was used, in order to produce higher concentrations and amounts of 4-353-NP metabolites for their identification; 4-353-NP was applied via the n-hexadecane phase. Initial concentrations of [14C]-4-353-NP were 1 mg L(-1) (soybean), and 5 and 10 mg L(-1) (A. githago). After 2 (soybean) and 7 days (A. githago) of incubation, the applied 4-353-NP was transformed almost completely by both plant species to four types of products: glycosides of parent 4-353-NP, glycosides of primary 4-353-NP metabolites, nonextractable residues and unknown, possibly polymeric materials detected in the media. The latter two products emerged especially in soybean cultures. Portions of primary metabolites amounted to 19-22% (soybean) and 21-42% of applied 14C (A. githago). After liberation from their glycosides, the primary 4-353-NP metabolites formed by A. githago were isolated by HPLC and examined by GC-EIMS as trimethylsilyl derivatives. In the chromatograms, eight peaks were detected which due to their mass spectra, could be traced back to 4-353-NP. Seven of the compounds were side-chain monohydroxylated 4-353-NP metabolites, while the remaining was a (side-chain) carboxylic acid derivative. Unequivocal identification of the sites of hydroxylation/oxidation of all transformation products was not possible. The main primary metabolites produced by A. githago were supposed to be four diastereomers of 6'-hydroxy-4-353-NP (about 80% of all products identified). It was concluded that plants contribute to the environmental degradation of the xenoestrogen nonylphenol; the toxicological properties of side-chain hydroxylated nonylphenols remain to be examined.

Agrostemma↗

PubMed2004

Investigation on the chemical structure of nonextractable residues of the fungicide cyprodinil in spring wheat using 13C-C1-phenyl-cyprodinil on 13C-depleted plants-an alternative approach to investigate nonextractable residues.

13C-labelled cyprodinil was applied on 13C-depleted wheat plants with 27-fold field application rate. A control experiment applying same amounts of 14C-cyprodinil showed that main portions of the residues were detected in the cellulose (15% NER), hemicellulose (28.3% NER), and lignin fraction (23.3% NER). 16.7% were detected in water soluble polymers, 6% in both, pectin and protein fraction, and 4% in the starch containing fraction. Free cyprodinil was detectable by TLC in all fractions except lignin. A direct characterization of the residues in vivo by CP-MAS was not successful. Cell wall fractions were further analysed by liquid state NMR to determine the structure of the mobilized highly polymer/polar residues: Within lignin, where most of the residues were located at field application rate, neither intact cyprodinil nor its metabolites could not be detected. The 13C-label introduced was probably incorporated in the polymer as natural lignin monomers and thus are not considered as bound residues according to IUPAC definition.

Carbon Isotopes↗

PubMed2003

Positron emission tomography in non-small-cell lung cancer: prediction of response to chemotherapy by quantitative assessment of glucose use.

PURPOSE: To prospectively evaluate the use of positron emission tomography with the glucose analog fluorodeoxyglucose (FDG-PET) to predict response to chemotherapy in patients with advanced non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Patients with stage IIIB or IV NSCLC scheduled to undergo platinum-based chemotherapy were eligible for this study. Patients were studied by FDG-PET before and after the first cycle of therapy. Based on previous studies, a reduction of tumor FDG uptake by more than 20% as assessed by standardized uptake values (SUV) was used as a criterion for a metabolic response. Furthermore, changes in tumor SUVs were compared with changes in FDG net-influx constants (Ki) and tumor/muscle ratios (t/m). RESULTS: Fifty-seven patients were included in the study. There was a close correlation between metabolic response and best response to therapy according to Response Evaluation Criteria in Solid Tumors (P <.0001; sensitivity and specificity for prediction of best response, 95% and 74%, respectively). Median time to progression and overall survival were significantly longer for metabolic responders than for metabolic nonresponders (163 v 54 days and 252 days v 151 days, respectively). Similar results were obtained when Ki was used to assess tumor glucose use, whereas changes in t/m showed considerable overlap between responding and nonresponding tumors. CONCLUSION: In NSCLC, reduction of metabolic activity after one cycle of chemotherapy is closely correlated with final outcome of therapy. Using metabolic response as an end point may shorten the duration of phase II studies evaluating new cytotoxic drugs and may decrease the morbidity and costs of therapy in nonresponding patients.

Aged↗

PubMed2003

Biotransformation of [ring-U-14C]4-n-nonylphenol by Agrostemma githago cell culture in a two-liquid-phase system.

The biotransformation of [14C]4-n-nonylphenol (5 mg l(-1); 10 mg l(-1)) by Agrostemma githago cell suspensions was studied using a batch two-liquid-phase system (medium/n-hexadecane 200:1, v/v). The highly lipophilic 4-n-nonylphenol was applied via n-hexadecane phase. After 7 d of incubation, more than 85% of applied 4-n-nonylphenol was absorbed by the cells, and 40% was transformed to 10 side-chain monohydroxylated metabolites (two with additional double bond at side-chain). The primary metabolites were analyzed by GC-EIMS. In the cells, the monohydroxylated products and residual 4-n-nonylphenol were present as glycosides. The method proved to be suitable for the production of primary metabolites of 4-n-nonylphenol on a larger scale for identification purposes and for metabolic profiling of the compound.

Biotransformation↗

PubMed2003

Discordant bone marrow involvement in diffuse large B-cell lymphoma: comparative molecular analysis reveals a heterogeneous group of disorders.

Discordant bone marrow (BM) involvement in patients with a diagnosis of large-cell non-Hodgkin's lymphoma (NHL) is characterized by marrow infiltrates predominantly composed of small lymphoid cell, cytologically compatible with low-grade NHL. Although this phenomenon is well described morphologically, molecular data concerning the relationship of the two lesions are lacking. The aim of the study was to investigate the clonal relationship of discordant lymphoma manifestations by using immunoglobulin heavy chain gene (IgH), as well as bcl-2 rearrangements, as molecular markers. IgH rearrangements were amplified by PCR with consensus primers directed against framework regions 3 or 2 (FR3 and FR2), followed by automated fragment length analysis and sequencing in selected cases. Rearrangements of the bcl-2 gene were identified with primers against the major breakpoint region. Small BM infiltrates were isolated by laser capture microdissection. In addition, immunohistochemistry was performed on paraffin sections using antibodies against CD3, CD10, CD20, bcl-2, bcl-6, p53, and the Ki67 antigen. Paraffin-embedded tissues of 21 cases diagnosed as diffuse large B-cell lymphoma (DLBCL) with discordant BM involvement and no previous history of low-grade B-cell NHL were analyzed. After review of immunohistochemical stains, 5 cases were excluded either as concordant BM infiltrates by large-cell lymphoma with abundant reactive T-cells (2 cases) or as benign, reactive lymphoid infiltrates (3 cases), as confirmed by a polyclonal pattern in the IgH analysis. Of the remaining 16 cases, a common clonal origin was confirmed in 8 cases by the presence of an identical clonal IgH rearrangement or bcl-2 rearrangement. In 4 cases, identification of distinct IgH or bcl-2 rearrangements gave evidence for the presence of two clonally unrelated neoplasms. The remaining 4 cases were not evaluable for technical reasons. Morphological, phenotypical, and molecular findings were compatible with a lymphoma of germinal center origin in the majority of cases. However, in 4 cases, flow cytometric analysis of the BM infiltrates revealed a B-cell chronic lymphocytic leukemia phenotype. Two of these cases were clonally related to the DLBCL and thus represented Richter's transformation. In summary, discordant BM infiltrates in DLBCL represent a heterogeneous group of disorders, encompassing cases with a clonally related, clinically occult small-cell component, as well as cases with two clonally distinct, unrelated B-cell neoplasms presenting synchronously at different locations.

Adult↗

PubMed2002

Identification of vaccinia virus epitope-specific HLA-A*0201-restricted T cells and comparative analysis of smallpox vaccines.

Despite worldwide eradication of naturally occurring variola virus, smallpox remains a potential threat to both civilian and military populations. New, safe smallpox vaccines are being developed, and there is an urgent need for methods to evaluate vaccine efficacy after immunization. Here we report the identification of an immunodominant HLA-A*0201-restricted epitope that is recognized by cytotoxic CD8(+) T cells and conserved among Orthopoxvirus species including variola virus. This finding has permitted analysis and monitoring of epitope-specific T cell responses after immunization and demonstration of the identified T cell specificity in an A*0201-positive human donor. Vaccination of transgenic mice allowed us to compare the immunogenicity of several vaccinia viruses including highly attenuated, replication-deficient modified vaccinia virus Ankara (MVA). MVA vaccines elicited levels of CD8(+) T cell responses that were comparable to those induced by the replication-competent vaccinia virus strains. Finally, we demonstrate that MVA vaccination is fully protective against a lethal respiratory challenge with virulent vaccinia virus strain Western Reserve. Our data provide a basis to rationally estimate immunogenicity of safe, second-generation poxvirus vaccines and suggest that MVA may be a suitable candidate.

Amino Acid Sequence↗

PubMed2002

Biodistribution and kinetics of (131)I-labelled anti-CD20 MAB IDEC-C2B8 (rituximab) in relapsed non-Hodgkin's lymphoma.

The native chimeric human-mouse anti-CD20 antibody IDEC-C2B8 (rituximab) is therapeutically applied in relapsed non-Hodgkin's lymphoma (NHL). The purpose of this study was to evaluate the distribution and pharmacokinetics of iodine-131 labelled rituximab in humans for radioimmunotherapy of relapsed CD20-positive NHL. Thirty-five patients with relapsed NHL were administered 20-40 mg rituximab labelled with 250 MBq (131)I. Biodistribution was determined by the gamma camera whole-body scans, whole-body probe measurements and the analysis of serial blood and urine samples. Dosimetry was performed using the MIRDOSE 3 program. Antibody administration was well tolerated. The whole-body activity showed a mono-exponential decrease with a wide range of effective half-lives, the mean value (88 h) being significantly longer than the half-life of its murine counterpart, tositumomab. This led to appropriately higher dose factors for the whole body and organs. Activity was excreted mainly through the kidneys. Normal organs showed decreasing ratios of organ to whole-body activity over time, whereas the tumour tissue presented different kinetics, with increasing ratios of tumour to whole-body activity as evidence for specific antibody binding. It is concluded that (131)I-labelled rituximab is suitable for pretherapeutic dosimetry. Due to the wide range of whole-body and organ dose factors, individual dosimetry is necessary for radioimmunotherapy with (131)I-labelled rituximab. The therapeutic activities of (131)I-labelled rituximab required to deliver similar doses should be lower than those of its murine counterpart.

Adult↗

PubMed2002

Antihuman epidermal growth factor receptor 2 (HER2) monoclonal antibody trastuzumab enhances cytolytic activity of class I-restricted HER2-specific T lymphocytes against HER2-overexpressing tumor cells.

The monoclonal antibody trastuzumab (Herceptin) directed against the human epidermal growth factor receptor 2 (HER2) results in tumor regressions when administered to patients with HER2-overexpressing breast cancer. One of the underlying mechanisms of this antibody-induced tumor regression is based on the internalization and degradation of HER2 by tumor cells on interaction with trastuzumab, subsequently inhibiting signal transduction pathways. As antibody-induced degradation of HER2 is likely to be accompanied with increased numbers of HER2 peptides presented with MHC, we asked whether trastuzumab-treated tumor cells were more susceptible to CTL-mediated lysis. Here we show that the cytolytic activity of human, HER2-specific CD8(+) CTLs is augmented by anti-HER2 antibody trastuzumab. HER2-reactive CTL clones lyse class I-matched, HER2-overexpressing tumor cells more efficiently after treatment with trastuzumab. The potentially synergistic activity of HER2-specific antibody and CTL encourages the development of an HER2-targeted immunotherapy using a combination of inhibitory antibodies and CTLs for patients with HER2-overexpressing tumors.

Antibodies, Monoclonal↗

PubMed2002

Reversible MHC multimer staining for functional isolation of T-cell populations and effective adoptive transfer.

Recently developed major histocompatibility complex (MHC) multimer technologies allow visualization and isolation of antigen-specific T cells. However, functional analysis and in vivo transfer of MHC multimer-stained cells is hampered by the persistence of T-cell receptor (TCR) MHC interactions and subsequently induced signaling events. As MHC monomers do not stably bind to TCRs, we postulated that targeted disassembly of multimers into MHC monomers would result in dissociation of surface-bound TCR ligands. We generated a new type of MHC multimers, which can be monomerized in the presence of a competitor, resulting in rapid loss of the staining reagent. Following dissociation, the T cells are phenotypically and functionally indistinguishable from untreated cells. This 'reversible' T-cell staining procedure, which maintains the specificity and sensitivity of MHC multimer staining while preserving the functional status of T lymphocytes, may be of broad benefit for ex vivo investigation of T-cell functions and clinical applications.

Adoptive Transfer↗

PubMedDate not supplied

Metabolism of 4-n-nonylphenol by non-modified and CYP1A1- and CYP1A2-transgenic cell cultures of tobacco.

The metabolism of 14C-4-n-nonylphenol (l4C-4-n-NP), as a model for the xenoestrogen nonylphenol, was investigated in three types of tobacco cell suspension cultures: one genetically non-modified culture (NT) and two cultures constitutively expressing human cytochrome P450 CYP1A1 or CYP1A2. With 1 mg l(-1) of 14C-4-n-NP and 24 h of incubation, the xenobiotic was transformed almost completely to glycosides. After glycosidic cleavage, 14C-4-n-NP and several primary metabolites of 4C-4-n-NP were liberated. Portions of the primary metabolites were 29.3% (NT culture), 34.3% (CYP1A1 culture), and 50.7% of applied 14C (CYP1A2 culture). Thus, the endogenous capacity of the tobacco cells to form primary metabolites of 4-n-NP was noticeably higher than that of CYP1A1 or CYP1A2. The results however clearly suggest that 4-n-NP is - even though a poor - substrate of CYP1A1 and CYP1A2. In order to examine metabolic profiles of 4-n-NP in the NT, CYP1A1 and CYP1A2 cultures, the suspensions were exposed to 10 mg 1(-1) of 14C-4-n-NP using a two-liquid-phase system with carrier n-hexadecane and 192 h of incubation. Results obtained resembled those of the low concentration study. The oxidative metabolic profiles determined after hydrolytic cleavage using GC-EIMS were similar in the NT, CYP1A1 and CYP1A2 cultures. Main metabolites were side-chain mono-hydroxylated derivatives of 4-n-NP with 6'-, 7'- and 8'-OH-4-n-NP as prominent metabolites. In addition, olefinic side-chain hydroxy, ring methoxylated, keto and ring hydroxylated derivatives were observed. The lack of differences in metabolic profiles among the CYP1A1, CYP1A2 and NT cultures was referred to the low enzymatic activity of CYP1A1 and CYP1A2 as compared to the higher endogenous oxidative capacity of tobacco, as well as to similar metabolic profiles of 4-n-NP produced by CYP1A1 and CYP1A2 and tobacco itself.

Carbon Radioisotopes↗