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Biomedical subjects

I Moser

Publications and source records attributed to I Moser.

36 records · Page 2Linked to original sources
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↗
PubMed1986

Monoclonal antibodies against the nonhemagglutinating fimbrial antigen 1C (pseudotype 1) of Escherichia coli.

Hybridoma-derived monoclonal antibodies were produced with fimbrial preparations from Escherichia coli 20025 (04:K12:H-) with fimbrial (F) antigens 1C, 13, one related to 12, and one preliminarily termed y and from E. coli 2980 (018ac:K5:H-) with F antigens 1C and 8. Two clones of subclonal hybrid cells were studied which produced monoclonal antibodies (mc-20025-F2b, immunoglobulin G2b [IgG2b]; mc-2980-F2, IgG1) that were reactive with E. coli 20025, 2980, and a number of additional strains which exhibited the F1C antigen. Results of enzyme-linked immunosorbent assay and Western blot analysis indicated that the antibodies had F1C specificity, and competitive enzyme-linked immunosorbent assay with 125I-labeled antibodies showed that they recognized different epitopes on the fimbrial subunit. Neither of the antibodies agglutinated F1C-fimbriated E. coli but bound to the bacteria. There was no binding to E. coli without F1C fimbriae.

Adhesiveness↗
PubMed1980

Salmonellosis in mice: studies on oral immunization with live avirulent vaccines.

The avirulent Salmonella typhimurium galE strain G30, following oral feeding to mice, developed a state of immunity to a secondary oral challenge with virulent Salmonella typhimurium. This immunity was concommitant with the development of intestinal and serum antibodies and delayed-type hyepersensitivity (DTH) to Salmonella antigens. In contrast, repeated oral doses of a hybrid E. coli vaccine, which expresses the O antigens of Salmonella typhimurium, provided a lesser degree of immunity and, although able to stimulate the formation of serum antibodies, it elicited only a low level of intestinal antibodies and no measurable DTH.

Administration, Oral↗
PubMed1973

Light-induced phase shifts of circadian leaf movements of phaseolus: comparison with the effects of potassium and of ethyl alcohol.

Leaves of Phaseolus coccineus were exposed to high concentrations of KCl (0.1-0.3 M) for periods of 4-5 hr, or to ethyl alcohol (5-30%) for periods of 2 hr. The treatment started at various phases of the free-running circadian rhythm in continuous light. Whereas the K(+) pulses induced only advance phase shifts, i.e., shortening of the periods, the alcohol pulses caused stronger advances and also slight delays, i.e., lengthening of the periods. These delays became stronger with lower concentrations of alcohol (1.7%) applied for a longer time. The lengthening effect by alcohol supplied continuously depends on the intensity of light. The rather high intensity of 3500 lux, resulting in very long free-running periods of about 29 hr, inhibits a further strong lengthening by alcohol. The phases reacting with advances to K(+) and to alcohol are about the same phases that respond to light pulses with advances. The advances are reached at earlier phases of the circadian cycle when the concentration of alcohol or the strength of the light pulse is increased. The phases that respond with advances are those which, according to earlier publications, are within the energy-independent part of the cycle. The phases responding with delays belong to the energy-requiring part of the cycle. Consequently, it is suggested that advances are due to accelerated membrane depolarization and delays are due to stabilizing effects on membranes.

Journal Article↗
PubMed1972

Influence of valinomycin on circadian leaf movements of Phaseolus.

Phaseolus coccineus was exposed to valinomycin via the transpiration stream for 5-hr periods. The treatment started at various phases of the free-running circadian rhythm in continuous light; it resulted in phase shifts that varied in a manner dependent on the affected phases. The response curves are similar to those for transient withdrawal of water and for light pulses. The results support the hypothesis that membrane processes are important pacemakers in circadian rhythms.

Anti-Bacterial Agents↗
PubMed1969

Interference of moonlight with the photoperiodic measurement of time by plants, and their adaptive reaction.

Threshold values of photoperiodic time-measurements correspond approximately to moonlight intensities. Experiments with Glycine and Euglena reveal that this is also the threshold value for synchronization of the circadian cycle. Saturation of this reaction is reached with 10 lx in 12:12 hr light-dark cycles. Thus, moonlight might disturb time measurement.In Glycine, Arachis, and Trifolium the intensity of the light coming from the moon to the upper surface of the leaf is reduced by circadian leaf movement to values between 5 and 20 per cent (or even less than 5 per cent) of full-moon light intensity. Such a reduction eliminates the disturbing effects of moonlight. This finding indicates that leaf movements have an adaptive value of the kind that Darwin sought to identify. It also indicates that the behavior of the upper leaf epidermis as a "sense organ for light"(13) has an adaptive value.In the short-day plants Perilla ocymoides and Chenopodium amaranticolor, a specific photoperiodic phenomenon was found that counteracts the disturbing effect of moonlight. Here light intensities similar to those of moonlight, introduced during the night, promote flowering instead of inhibiting it.

Journal Article↗