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Biomedical subjects

I Moser

Publications and source records attributed to I Moser.

At least 19 recordsLinked to original sources
PubMed2003

Microdevice with integrated dialysis probe and biosensor array for continuous multi-analyte monitoring.

The simultaneous on-line determination of glucose and lactate using a microdevice that consisted of a dialysis sampling system incorporated to the flow-through cell of a microfabricated biosensor array is presented. The fluidic connections between the different device's components were realized by subsequent processing of stacked dry resist layers on a plastic support that provided also the means for electric connections. The performance of the device was evaluated in vitro. The cross-talk effect on the downstream sensor was investigated and found to be negligible. Recoveries of over 95% for both analytes were achieved when flow rates of the perfusion fluid </=0.5 microl/min were used. At this flow rate, the response time of the device was 2.4 min, which is acceptable for on-line analysis. The linear response concentration range extended up to 30 mM for glucose and 15 mM for lactate. Interference from electroactive species such as ascorbic acid, 2-acetamidophenol and uric acid, was minimal (less than 5% increase in biosensors signal for all substances tested). In addition, the device presented long-term run stability both in buffer and serum samples.

Artifacts↗
PubMed2002

BioMEMS device with integrated microdialysis probe and biosensor array.

The fabrication of a microdevice for continuous sampling and on-line monitoring of glucose is described. The device comprised a microdialysis sampling system integrated on the flow through channel of a microfabricated enzyme sensor. The sensor was produced by thin film technology and was assembled to a printed circuit board (PCB) that provided the means for both electrical and fluidic connections. A polyacrilonitrile fibre, with a cut-off of 50 kDa, was used in the fabrication of the sampling probe. The performance of the device was evaluated in-vitro. High sampling efficiency of the microdialysis probe was achieved by appropriate selection of the perfusion fluid flow rate. Response times varying from 1.5 to 3.0 min were determined for flow rates ranging between 1 and 0.2 micro l/min. The linear response range was up to 30 mM glucose and interference from other electroactive substances was almost negligible. The device showed excellent stability under continuous operation for at least 5 days and sensitivity variation less than 3% over a period of 15 days.

Biosensing Techniques↗
PubMed2002

High resolution genotyping of Campylobacter jejuni strains by macrorestriction analysis with XhoI and polymerase chain reaction targeting enterobacterial repetitive intergenic consensus sequences: can we predict the zoonotic potential of strains?

Campylobacter jejuni isolates of human, canine, feline, bovine and poultry origin were investigated for their genomic diversity using O-antigen typing (n = 271), SmaI (n = 158) and XhoI (n = 158) macrorestriction analysis and ERIC-PCR (n = 107). The O-antigens O:1/44, O:2, O:4 complex, O:37. O:40 were identified and 53.7% of the human and 56.1% of the animal strains were typable with the available antisera. Two ERIC-PCR pattern groups were generated representing human and animal strains as well as those exclusively of animal origin. XhoI macrorestriction analysis also distinguished 'human' and 'non-human' strain clusters, but by SmaI restriction mainly serotype-associated clusters were found. In conclusion, genomic differences may occur between 'human' and 'non-human' strains and this may reflect their potential to overcome the barrier from animals to humans.

Animals↗
PubMed2001

Lipopeptide adjuvants: generation of lactate dehydrogenase isoenzyme-specific antibodies for immunochemical diagnosis.

Lactate dehydrogenase catalyzes the final step in glycolysis, the interconversion of pyruvate and lactate. The tetrameric enzyme is composed of one or two subunits (H and/or M) resulting in five isoenzyme forms: LDH-H4, -H3M1, -H2M2, -H1M3, and -M4. The relative distribution of the LDH isoenzymes is tissue dependent and a significant marker for the diagnosis of hepatoma of the liver, myocardial infarction, muscular dystrophy, and a wide variety of other acute and chronic diseases to be detected by alterations of the LDH isoenzyme pattern in serum. Immunochemical approaches to the routine determination of LDH depend on isoenzyme specific antibodies. Since the H- and M-subunits for human LDH are highly homologous, LDH isoenzyme specific antibodies for immunochemical monitoring are hard to generate. Here we present data on the generation and characterization of LDH isoenzyme-specific mono- and polyclonal antibodies in different species in the presence of lipopeptide adjuvants. Western-Blot and ELISA analysis showed that antisera and monoclonal antibodies recognize their homologous antigens with high specificity and are therefore suitable for immunochemical monitoring of the LDH isoenzymes H4 and M4. In addition, they can be used for the determination of LDH isoenzyme specific activity which is an essential prerequisite for online amperometric immunosensor monitoring.

Adjuvants, Immunologic↗
PubMed2001

Genomic heterogeneity and O-antigenic diversity of Campylobacter upsaliensis and Campylobacter helveticus strains isolated from dogs and cats in Germany.

A serotyping scheme based on heat-stable surface antigens was established for 101 Campylobacter upsaliensis and 10 Campylobacter helveticus strains isolated from 261 dogs and 46 cats of different ages originating from two geographically distinct regions in Germany. The prevalence of C. upsaliensis varied between 27.8% in juvenile dogs (<12 months of age) and 55.4% in adult dogs (P < 0.05). Of the cats, 19.6% harbored C. upsaliensis, whereas 21.7% carried C. helveticus. Of the C. upsaliensis isolates from both host species, 93.1% belonged to five different serogroups, two of them being prevalent at rates of 47.5 and 27.7%, with different frequencies in both regions. Six (54.6%) of the C. helveticus isolates also belonged to serotypes found among C. upsaliensis strains, whereas five (45.4%) possessed an O antigen unique for C. helveticus. In contrast, a considerable degree of genomic diversity of the isolates was assessed by macrorestriction analyses with the endonucleases SmaI and XhoI, using pulsed-field gel electrophoresis as well as enterobacterial repetitive intergenic consensus sequence PCR (ERIC PCR). Restriction with SmaI pointed towards the existence of clonal groups associated to some extent with serotypes, while restriction with XhoI disintegrated these groups to smaller noncoherent subgroups. Analysis of ERIC PCR profiles did not exhibit any associations with serotypes. In conclusion these data demonstrate the genomic heterogeneity among C. upsaliensis strains and indicate that the combination of SmaI restriction with serotyping is a useful tool to investigate the expansion of clonal groups of C. upsaliensis.

Animals↗
PubMed1998

Novel system for real-time ex vivo lactate monitoring in human whole blood.

The objective of the study was to evaluate the performance of an amperometric enzyme based lactate sensor and to investigate the possibility of replacing a double lumen catheter based blood withdrawal system with a heparin coated single lumen system. The inner lumen of a double lumen catheter which was placed in a peripheral vein was perfused with heparin solution. The outer lumen was used to collect heparinized blood samples at a defined flow rate. The single lumen system was attached to a heparinized catheter which was also placed in a peripheral vein. The undiluted blood samples were collected at a specified flow rate. A sensor flow chamber incorporating an amperometric thin-film lactate microbiosensor was placed in the sampling line for real-time lactate monitoring. Plasma lactate concentrations were measured during frequently performed hyperlactatemia bicycle ergometer experiments in six healthy volunteers (age 25.8 +/- 2.8 years, BMI 22.7 +/- 1 kg/m2). Additionally, plasma lactate was measured in real-time using the lactate sensors. The first three experiments were performed with a double lumen based catheter system whereas the following three experiments were performed with a heparin coated catheter system. The correlation coefficients of sensor readings and laboratory analyzer results in all six experiments were between 0.93 and 0.99, respectively (P < 0.001). The miniaturized lactate sensors showed a linear range up to 25 mmol/l lactate concentration and 95% response times < 30 s in undiluted serum. During the experiments maximum lactate concentrations of 14 mmol/l were achieved. Improvements of system performance using heparin coated catheter systems could be shown. The overall SD of the sensor readings compared to laboratory results using three double lumen catheter based systems was 0.91 mmol/l whereas the SD using three heparin coated systems was 0.65 mmol/l. In summary, real-time monitoring of lactate in human whole blood is feasible with such a device and can be improved by using heparin coated catheter systems.

Adult↗
PubMed1998

Continuous measurement of subcutaneous lactate concentration during exercise by combining open-flow microperfusion and thin-film lactate sensors.

The present study was carried out to investigate in vivo in healthy humans the method of open-flow microperfusion for monitoring of the subcutaneous (s.c.) lactate concentration during rest and cycle ergometer exercise. Using open-flow microperfusion, a perforated double lumen catheter with an inflow and an outflow connection is inserted into the s.c. adipose tissue and perfused with a sterile, isotonic, ionfree fluid. Due to the low flow rate, the fluid partially equilibrates with the surrounding tissue. The equilibrated perfusate passes a sensor flow chamber where the substance of interest and the rate of recovery (i.e. the ratio of sampled concentration to interstitial concentration) are continuously monitored. Within this study, the method was evaluated in four healthy volunteers during cycle ergometer exercise. The relative increase of the lactate concentration was approximately a third in the s.c. tissue compared to the capillary blood and the peak time was delayed on average by 10 min. The correlation coefficient between blood and s.c. tissue lactate concentration ranged from r = 0.41 to r = 0.90 (n = 29) in the individual experiments. The combination of open-flow microperfusion and lactate and conductivity sensors enables on-line monitoring of the s.c. lactate concentration without in vivo calibration during steady-state and cycle ergometer exercise.

Adipose Tissue↗
PubMed1997

Campylobacter jejuni major outer membrane protein and a 59-kDa protein are involved in binding to fibronectin and INT 407 cell membranes.

Campylobacter jejuni is one of the major causes of human diarrhea throughout the world. Attachment to host cells and extracellular matrix proteins is considered to be an essential primary event in the pathogenesis of enteritis. Outer membrane proteins of three C. jejuni strains, one of which was aflagellate, were investigated for their contribution to the process of adhesion to INT 407 cell membranes and the extracellular matrix protein fibronectin. Using a ligand-binding immunoblotting assay the flagellin, the major outer membrane protein and a 59-kDa protein were detected to be involved in adhesion to both substrates. The MOMP was able to inhibit the attachment of the bacteria to INT 407 cell membranes partly, when the protein was isolated under native conditions. However, it was totally lost when the protein was isolated in the presence of SDS. The 59-kDa protein of one strain was identified by N-terminal sequencing, and regarding the first 14 amino acids it was found to be identical to the 37-kDa CadF protein just recently described as fibronectin-binding protein of C. jejuni. Especially for the aflagellate strain this protein may be of special importance for adhesion of the bacteria to different substrates.

Amino Acid Sequence↗
PubMed1997

Primary structure analysis and adhesion studies on the major outer membrane protein of Campylobacter jejuni.

The major outer membrane protein of Campylobacter jejuni (MOMP, 43 kDa), supposed to be one of the structures responsible for adhesion to INT 407 cells, was isolated from the crude outer membrane preparation by treatment with n-octyl-beta-D-glucopyranoside followed by preparative SDS-polyacrylamide gel electrophoresis. By cleavage of the isolated protein with cyanogen bromide and proteolytic enzymes, peptides were generated, separated by reverse phase high pressure liquid chromatography, and sequenced by automatic Edman degradation. The protein was aligned by identification of overlapping peptides. Treatment of bacteria with proteinase K prior to preparation of the outer membrane yielded a truncated MOMP with an apparent molecular mass of 25 kDa consisting of the C-terminal part of the protein. The isolated MOMP was functionally characterized by significant binding activity towards INT 407 cell membranes when isolated by preparative native gel electrophoresis, however, no binding activity was detected when the protein was isolated in the presence of SDS.

Adhesins, Bacterial↗
PubMed1997

Hydrophobic characterization of thermophilic Campylobacter species and adhesion to INT 407 cell membranes and fibronectin.

Cell surface hydrophobicity of Campylobacter jejuni, C. coli, C. lari and C. upsaliensis was tested by hydrophobic interaction chromatography on octylsepharose CL-4B. The hydrophobicity was influenced by cultivation mode, presence or absence of intact lipopolysaccharide (LPS) and outer membrane protein structures. Species-specific differences of hydrophobic characteristics were not detected. Bacteria grown in fluid medium exhibited a high degree of hydrophobicity. Agar-grown bacteria showed hydrophobic interaction to a significant lower extent. By oxidation of LPS with sodium meta-periodate the hydrophobicity of agar-grown bacteria was slightly increased. Bacteria pretreated with proteinase K exhibited a marked decrease of hydrophobic interaction, whereas pretreatment with trypsin did not influence the hydrophobic interaction. Live bacteria were allowed to adhere to INT 407 cell membranes. With exception of one aflagellate strain, bacteria grown in fluid medium adhered better to the cellular substrate than agar-grown bacteria. This difference was not found when adhesion to fibronectin was tested. LPS-oxidized bacteria adhered significantly better to both cell membranes and fibronectin, whereas proteinase K treated bacteria exhibited a significant loss of adhesion capacity for both substrates.

Bacterial Adhesion↗
PubMed1997

Novel instrumentation for real-time monitoring using miniaturized flow systems with integrated biosensors.

A prototype miniaturized Total Chemical Analysis System (muTAS) has been developed and applied to on-line monitoring of glucose and lactate in the core blood of anaesthetized dogs. The system consists of a highly efficient microdialysis sampling interface sited in a small-scale extracorporeal shunt circuit ('MiniShunt'), a silicon machined microflow manifold and integrated biosensor array for glucose and lactate detection with associated computer software for analytical process control. During in-vivo testing the device allowed real-time on-screen monitoring of glucose and lactate with system response times of less than 5 min, made possible by the small dead volume of the microflow system. On-line glucose and lactate measurements were made in the basal state as well as during intravenous infusion of glucose or lactate. The prototype muTAS is currently suitable for trend monitoring but refinements are necessary before application of the system for determination of individual lactate values.

Animals↗
PubMed1996

Thin-film microbiosensors for glucose-lactate monitoring.

A miniaturized device for simultaneous measurement of glucose and lactate levels was produced by means of photopatterning of enzyme-containing photosensitive membrane precursors. This device shows no cross-talk and a lifetime for both the glucose and the lactate sensors of more than 2 weeks when continuously operated in undiluted bovine serum. Linear response ranges of up to 40 mM for glucose and 25 mM for L-lactate, in combination with 95% response times of < 30 s, were realized. The devices are mass produced by means of thin-film technology on flexible carriers to give catheter-type multisensing devices for in vivo applications. Ex vivo experiments, performed with human volunteers, where the device was continuously operated in an extracorporeal, undiluted, heparinized blood stream for 6 h, gave a correlation of r > 0.98 with respect to laboratory techniques. Subcutaneous measurements of glucose levels in pigs were close to the corresponding blood levels obtained without in vivo calibration.

Adult↗
PubMed1995

Binding of outer membrane preparations of Campylobacter jejuni to INT 457 cell membranes and extracellular matrix proteins.

Binding of outer membrane (OM) preparations of the thermophilic Campylobacter species C. jejuni to epithelial cell membranes and extracellular matrix proteins were studied in an in vitro model system using enzyme-linked immunosorbent assay. The OM preparations exhibited significant binding to INT 407 intestinal cell membranes. The process of adhesion was modulated by enzymatic, chemical or immunological pretreatment of the bacteria. Following oxidation of the lipopolysaccharide (LPS) with sodium meta-periodate, the OM preparations essentially retained their binding properties. After pretreatment with proteinase K, the OM preparations lost their binding capacity and the apparent molecular mass of the major OM protein shifted from 42 to 24 kDa. Preincubation of C. jejuni bacteria with C. jejuni-specific antiserum reduced adhesion significantly; preincubation with LPS-specific monoclonal antibodies only to a minimal extent. The OM preparations also bound significantly to the extracellular matrix proteins collagen and fibronectin; however, they bound virtually no bovine serum albumin or horse serum.

Antibodies, Bacterial↗
PubMed1995

Miniaturized thin film glutamate and glutamine biosensors.

Integrated thin film biosensors were developed for the simultaneous measurement of L-glutamine and L-glutamate in a mu-flow cell. Due to a novel glutaminase with an activity optimum in the neutral pH range, direct monitoring of glutamine in a mammalian cell culture medium could be performed. The glutamine bienzyme sensor was prepared by co-immobilization of glutaminase with glutamate oxidase within a photopatterned poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel membrane. The sensor response was linear in the concentration range of 50 mumol to 10 mmol glutamine/l. Additionally, a glutamate biosensor was integrated on the sensor chip for difference measurement of possible glutamate interferences. The sensor-chip could be used for at least 300 measurements without any alteration in the performance of its sensors. A new sensor-chip with an integrated flow cell provided the possibility of simultaneous measurement of four different parameters at a cell volume of 1 microliter. In order to complete the microsystem, and in order to obtain a "lab on chip", a battery operated surface mounted device (SMD) potentiostat was developed.

Biosensing Techniques↗
PubMed1992

In vitro binding of Campylobacter jejuni/coli outer membrane preparations to INT 407 cell membranes.

Outer membrane fractions (OMs) of nine Campylobacter (C.) jejuni and two C. coli strains belonging to different serovars, from human and various animal origins, were extracted by treatment with sodium N-lauryl sarcosinate. Using n-octyl-beta-D-glucopyranoside a 42-kDa protein and a flagella-enriched fraction were obtained. The capacity of the crude bacterial OM preparations, the purified 42-kDa protein and the flagella to bind to membranes of the human embryonic intestinal cell line INT 407 was tested by an enzyme-linked immunosorbent assay. The crude OM and the 42-kDa-enriched fraction were found to bind very well to the cell membranes, whereas the flagella preparation showed only a weak binding. Using monoclonal antibodies (mAbs) with HS 2-lipopolysaccharide (LPS) specificity, binding of crude HS 2 strain OM preparations to cell membranes was detected in a significant range, whereas with flagellin-specific mAbs binding of OMs and flagella to cell membranes was only detected to a very low extent. Binding of OMs to cell membranes was inhibited by preincubation of OMs with serovar-specific mouse hyperimmune serum, whereas on preincubation with mAbs directed against LPS or flagella binding was practically not inhibited. OMs extracted after pretreatment of the bacteria with proteinase K showed an altered SDS-PAGE pattern especially for the 42-kDa protein subunit and and their capacity to bind to cell membranes was significantly reduced. The binding was also reduced by preincubation of the OMs with L-fucose or D-mannose.

Animals↗
PubMed1989

In vitro binding of Campylobacter jejuni surface proteins to murine small intestinal cell membranes.

Surface proteins of nine Campylobacter jejuni strains belonging to three different serovia were extracted with lysozyme/ethylenediamine-tetraacetic acid. The preparations bound to isolated murine small intestinal cells and to a membrane fraction (MF) of isolated brush borders obtained by detergent treatment with Triton X-100 and Nonidet P40. Binding was demonstrated by an enzyme-linked immunosorbent assay procedure. Using lipopolysaccharide (LPS)- and flagella-specific antisera the contribution of flagella and LPS, present in the protein preparations, to the total binding to MF was investigated. Only up to approximately 10% of the total binding of each strain was found to be mediated by LPS, 10%-33% of binding was flagella dependent. The preparations of four strains (serovar HS2) bound in a trypsin-sensitive manner (45%-85% reduction), while the others (serovaria HS1 and HS13) were hardly influenced by trypsin treatment. Binding to MF was not impaired by preincubation of the bacterial surface protein preparations with several sugars and lectins.

Animals↗
PubMed1988

Degradation of bacterial cell walls by immobilized lysozyme.

Lysozyme was immobilized by two different methods in two different ways in order to obtain a preparation with an activity as high as possible toward a macromolecular substrate. The enzyme was bound as a Schiff base to a silicate carrier by using oxidized dextrans of different lengths as spacer and also was bound to controlled pore aminoglass via pyridino-4-aldehyde and BrCN. The latter preparations had activities up to 2.5% of the free lysozyme.

Buffers↗