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Biomedical subjects

B Linke

Publications and source records attributed to B Linke.

29 records · Page 2Linked to original sources
PubMed1994

Characterization of clone-specific rearrangement T-cell receptor gamma-chain genes in lymphomas and leukemias by the polymerase chain reaction and DNA sequencing.

The structures of rearranged gamma-chain T-cell antigen receptor (TCR) genes were analyzed in 5 cases of T-cell acute lymphoblastic leukemia (T-ALL), in 15 cases of peripheral T-cell non-Hodgkin's lymphoma (T-NHL), in 1 case with large granular CD8 lymphocytosis, 1 case with CD8 lymphocytosis after autologous bone marrow transplantation for Hodgkin's disease, and in 2 cases with nonneoplastic diseases. Rearranged V-J TCR gamma-gene segments were amplified by the polymerase chain reaction (PCR). Because most of the biopsy tissue or bone marrow samples contained significant amounts of admixed nonmalignant T-cells, direct DNA sequencing of the PCR products yielded mixed sequence data because of coamplification of clonal together with polyclonal TCR gamma V-N-J junctions. Reliable data could only be obtained by cloning the V gamma-J gamma PCR products and sequencing several (4 to 10) randomly chosen clones. In the polyclonal samples, all PCR-derived clones differed in their specific V-N-J junctions, as expected. In the two T-cell lines and in most of the T-cell malignancies, monoclonal PCR products could be identified by the demonstration of clonally restricted V-N-J junctions. In most cases, this information yielded the desired clone-specific sequence and showed a background population of polyclonal TCR gamma cells in each specimen, except for those that were obtained from the T-ALL samples, the cell lines, or the NHL samples with high tumor cell fraction. The results obtained by PCR-directed sequencing were confirmed by temperature-gradient gel electrophoresis (TGGE) that showed distinct DNA bands only with the PCR products containing predominant (ie, monoclonal) TCR gamma V-N-J junctions. By combined sequence and TGGE analysis, it was found that PCR/TGGE is able to distinguish between monoclonal and polyclonal TCR gamma-PCR products. This finding prompted us to complete the analysis of the TCR gamma locus in the samples by PCR/TGGE using primer mixes which covered all possible V gamma and J gamma recombinations. Monoclonality was shown with all mixes by PCR/TGGE in 21 of 24 (87%) of the lymphoproliferations. In summary, the present study shows that the combination of amplifying TCR gamma V-N-J junctions by PCR with the identification of clonal PCR products by TGGE and DNA sequencing is a reliable method for the characterization of clonal TCR gamma sequences.

Base Sequence↗
PubMed1994

[Electron spin resonance measurements on dried fruit. Carbohydrate composition and ESR signal structure of irradiated fruit].

While in a previous work the ESR spectroscopic detection of irradiated dried fruits was reported, in this paper liquid chromatographic determination of the carbohydrate fraction of these fruits is introduced and connected with the ESR results. After irradiation of dried fruits three different types of ESR spectra are observed. In most cases the dried fruits can be attached to these various types by means of their sugar composition. It was also found that the ESR spectra observed for sucrose-rich fruits are very similar to that of pure sucrose. The structure of the ESR spectra can change with storage. Probably, radical rearrangement reactions in the samples are responsible for these changes.

Carbohydrates↗
PubMed1994

Amperometric biosensor for in vivo glucose sensing based on glucose oxidase immobilized in a redox hydrogel.

A potentially implantable glucose sensor, based on glucose oxidase immobilized in a redox hydrogel, is considered. The redox hydrogel consisted of glucose oxidase immobilized in a cross-linkable poly(vinylpyridine) complex of [Os(bis-bipyridine)2Cl]+1/+2 that communicates electrically with the flavin adenine dinucleotide (FADH2) redox centres of the glucose oxidase. The implantable electrode consisted of a Teflon insulated platinum wire (0.25 mm diameter) which was coated at the tip with a cross-linked redox polymer/glucose oxidase film and covered with a thin layer of polycarbonate. In a three-electrode system at +400 mV (Ag/AgCl) the response to increasing glucose concentrations in isotonic phosphate buffer and human plasma was approximately 0.2-0.3 nA/mM, linear in the range between 0 and 15 mM glucose. No oxygen dependence was observed. To determine the in vivo performance, the electrode was implanted into the subcutaneous tissue of a dog. The sensor currents after an oral glucose load paralleled the plasma glucose measurements, with a time lag of 10 min. Three-day implantations in cultured cells showed that the electrode did not affect the growth and differentiation of cell monolayers.

Animals↗
PubMed1994

[Characterization of clonal B-cell populations in gastric MALT lymphomas and chronic gastritis by means of the polymerase chain reaction].

Amplification of the CDR3-region of the immunoglobulin (Ig) heavy chain gene rearrangement by means of the PCR yielded clonal products in the tumor DNA of 12 high or low grade gastric B-cell lymphomas of MALT-type. In four cases, additional clonal bands were found in different areas of tumor free mucosa diagnosed as chronic gastritis associated with Helicobacter pylori (HP). Most of these small clonal populations were found to share identical DNA sequences in their clone specific CDR3-regions with the main lymphoma in each patient; a finding consistent with the multifocal character of the disease. In two cases however, single clonal populations with different CDR3-regions revealed the existence of rare additional clonal B-cell-populations not related to the lymphoma and therefore possibly representing further independent foci.

B-Lymphocytes↗
PubMed1993

[Identification of irradiated pasteurized egg products: a combined method for use in routine control].

Pasteurized egg products (whole egg, egg yolk and egg white) were tested for irradiation treatment in the German food control laboratories in Oldenburg/Niedersachsen and Kassel/Hessen as well as in the food irradiation laboratory of the German federal health office. Gas chromatographic/mass spectrometric measurements on the fat components of egg-products showed clearly whether the product had been irradiated or not. While in unirradiated samples no traces of special hydrocarbons (according to the fatty acid composition of egg) and no traces of the irradiation-specific compound 2-Dodecyl-cyclobutanone were found, irradiated control samples as well as products of two Belgian suppliers contained these substances. Additionally, regarding the rather high time consumption of gas chromatography, electron spin resonance (ESR)-measurements were carried out on the packaging material of egg products. Irradiated packaging material (cellulose) could be easily detected by the appearance of a signal pair in the ESR spectrum (cellulose radical). ESR measurements are very fast and easy to perform so that this method can be used for screening. Microbiological investigations showed remarkably reduced total numbers of microorganisms for some irradiated samples, but the microbiological status is influenced by other factors like storage-time and -temperature, so that microbiological tests can not be used successfully for screening on irradiation treatment.

Animals↗
PubMed1993

The function of a hydrogen peroxide-detecting electroenzymatic glucose electrode is markedly impaired in human sub-cutaneous tissue and plasma.

Electroenzymatic glucose sensors implanted into sub-cutaneous (s.c.) tissue of human subjects and experimental animals exhibit lower sensitivities to glucose than in buffer solutions before implantation. The mechanism of the decrease of sensitivity is not known. Sensors used in this study were fabricated from platinum wires (diameter 0.125 mm) with covalently bound glucose oxidase at the tip of the wire. After coating the tip with polyurethane, wires were placed into 27 gauge steel needles. Sensors were operated potentiostatically at 700 mV against Ag/AgCl pseudo-reference electrodes. These sensors were implanted s.c. in 6 diabetic patients for 7 h. In 4 patients, sensors were responsive to successive increases of plasma glucose levels. Mean sensitivity to glucose in s.c. tissue was 29% of in vitro sensitivity. In 2 patients there was a sudden decrease of sensor currents, unrelated to glucose, shortly after implantation. Sensors were inhibited in human plasma to a similar extent. When sensors were exposed to native plasma and to plasma ultrafiltrate (mol. wt. < 10 kDa) for 10 h, identical decreases of signals were found. Exposure to dialysed plasma (mol. wt. > 12 kDa) caused much less decrease of sensor signals. Losses of sensor sensitivities to glucose in s.c. tissue and in plasma were totally reversible upon re-exposure of sensors to buffer solutions. We conclude that sensor inactivation in plasma and possibly in s.c. tissue is caused by low molecular weight substances not retained by the polyurethane membrane.

Adult↗
PubMed1992

[Electron spin resonance spectroscopy as probes for spices. Detection of treatment with ionizing radiation].

Detection of irradiated spices by electron spin resonance (ESR) measurements was not successful in the past because a central line of unknown origin was detected in the ESR-spectra of both irradiated and unirradiated samples. Identification of irradiated samples by measuring the increase of intensity of this signal after irradiation is limited because the signal intensity decreases over a period of some weeks of storage and reaches the range of unirradiated samples. By changing the measurement conditions (low microwave power) we could detect two additional lines on both sides of the main signal. This line pair appears only in the spectra of irradiated spices. A similar line pair was found in the spectra of irradiated nutshells and possibly derives from cellulose radicals in the sample. For some spices, especially paprika, the identification of irradiated samples by detecting these additional lines was possible even after relatively long periods of storage.

Condiments↗
PubMed1992

[Status of the development of electron spin resonance measurement for the detection of irradiated food].

Electron spin resonance spectroscopy can be used for the detection of irradiation of various groups of foodstuffs. The results of ESR-measurements on irradiated meat and fish and fresh fruit, as well as dried fruit, spices and nuts as performed by the food irradiation laboratory of the German Federal Health Office are summarized in this report. For the detection of irradiated meat and fish, we examined the bones. Using the results from 10 different animal bones, we were able to develop an official method according to the German law section 35 LMBG. A similar routine method for fish will be established in 1992 (at the moment, an intercomparison with German food control laboratories is in progress). Irradiated dried fruit can be identified easily, because unirradiated samples give no ESR-spectra, while irradiated fruit show a partially resolved spectrum, which is caused by radiation induced sugar radicals. Interestingly, the structure of the resulting spectra is not identical for all irradiated species of fruit. We found three different types of ESR-spectra for irradiated dried fruit. Irradiated nutshells show an ESR-spectrum which reveals two additional lines (from cellulose-radicals) beside the main signal, while unirradiated samples show only the main signal. An official method for identifying irradiated nuts will be proposed in 1992. Irradiation specific ESR-signals of the cellulose radical were not only found for nutshells but also for fresh fruit and some spices, while most of the irradiated spices and herbs could not be identified by ESR-measurements.

Animals↗
PubMed1991

Characterization of a hexammineruthenium-stimulated external NADH oxidase from rat liver mitochondria.

The existence of an external hexammineruthenium-stimulated NADH oxidase in rat liver mitochondria is postulated. This enzyme is localized on the outer surface of the inner mitochondrial membrane, is specific for NADH and requires oxygen. The apparent affinity of the enzyme for NADH amounts to about 4 microM. Furthermore, the enzyme is characterized by an alkaline pH optimum and a linear Arrhenius plot (14 kJ/mol). The electron transfer from NADH to oxygen is not linked with the respiratory chain but is connected with the formation of superoxide radicals.

Animals↗
PubMedDate not supplied

Identification of an external NADH oxidase in rat kidney cortex mitochondria.

Intact rat kidney cortex mitochondria oxidize external NADH and NADPH. Basal NADH oxidation of mitochondria, but not basal NADPH oxidation, is stimulated by hexammine-ruthenium (HR). 10.7 mumol/l HR induce 50% of the maximal NADH-oxidizing activity and amounted to 169 nmol NADH/min/mg of mitochondrial protein. The HR-stimulated NADH oxidation involves a stoichiometric 1:1 oxygen consumption. The electron transfer from NADH to oxygen does not occur via the respiratory chain complex I, but is connected with a superoxide anion radical formation. Experiments with intact mitochondria, submitochondrial particles and inner mitochondrial membranes show that rat kidney cortex mitochondria possess a NADH oxidase localized on the outer surface of the inner mitochondrial membrane.

Animals↗