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Biomedical subjects

J G Schindler

Publications and source records attributed to J G Schindler.

At least 19 recordsLinked to original sources
PubMed1996

[O2 sensitive L-lactate biosensors with enzyme membranes based on L-lactate-2-monooxygenase and L-lactate-oxidase with electroanalytic comparison].

O2-sensitive biosensors using oxidase membranes have acquired considerable electro-analytical importance. Since some of these O2-converting enzymes also produce H2O2, the use of additive reagents for the O2-free breakdown of the H2O2 in the second reaction has repeatedly been reported. In contrast to L-lactate oxidase, L-lactate-2-monooxygenase converts its substrate without producing H2O2. Employing reference sera, tests with L-lactate showed that bioelectrochemical membrane electrodes with H2O2-producing enzymes of high purity, require no additive reagents to ensure reliable analysis. Continuous measurements with citrated blood using the principle of intermediate carrier analysis are demonstrated.

Biosensing Techniques↗
PubMed1994

[Long-functioning beta-D-glucose and L-lactate biosensors for continuous flow-through measurements for "fouling"-resistant and selectivity-optimized serum- and hemoanalysis].

Bioelectrochemical membrane-electrodes for O2-sensitive enzymatic flow-through analysis of beta-D-glucose and L-lactate are described. The enzyme-membranes of the biosensors consist of glucose-oxidase or lactate-oxidase molecules cross-linked with glutardialdehyde between two dialysis membranes. The accuracy of the biosensors is demonstrated by electroanalysis of diluted control serum and compared with redox-mediator-free H2O2 detection and photometric methods. Continuous haemoanalysis of uncoagulated blood was carried out, using an intermediate carrier stream with additive systems. Tangential streaming to the miniaturized dialysis chamber with a circular channel minimizes blockage of the pores of the dialysis membrane by erythrocytes, leukocytes or protein. An oxygenator pump for the exchange of gases between the buffered solution of the intermediate carrier and the surrounding atmosphere guarantees a constant oxygen partial pressure within the carrier stream. The pulsations produced by the oxygenator pump are dampened by a miniature pressure balance chamber with an unsignificant dead space volume for protecting the enzyme membrane of the sensor. Glutardialdehyde inhibits growth of microorganisms and any resulting oxygen consumption, so that even in protein-containing measuring solutions enzyme electrodes can be used without interference from microbial contamination. The bioelectrochemical measuring system can therefore also be employed for the electroanalysis of fermentation solutions. For continuous flow-through measurements, it is necessary to change the glucose-oxidase membranes after 100-150 days, and the lactate-oxidase membranes after 3-6 weeks.

Biosensing Techniques↗
PubMed1994

[Urea sensor for the continuous ammonium-selective enzymatic process control of the artificial kidney].

Presented is a flow-through method for continuous ammonium-selective enzymatic monitoring of the artificial kidney by means of a bioelectrochemical urea electrode. The urea is converted in an enzyme membrane by covalently bound urease and the ammonium ions are detected by a Nonactin-PVC-membrane. In addition to detailed data from the oxygen-independent solid-state contact sensor, curves are obtained on-line from the patient during the haemodialysis session. The advantages of the method are described in detail. Furthermore, the urea sensor can be used for measurements in heparinized blood.

Anti-Bacterial Agents↗
PubMed1991

[Ion-selective electro-analyser with tubular solid contact flow-through sensors for continuous bioelectrochemically controlled hemodialysis of K+, Na+, Ca2+, Cl- and pH].

An ion-selective electroanalyzer for bio-electrochemically controlled hemodialysis will be described. The bedside analysers are solid-contact flow-through electrodes based on tubular carrier-PVC-membranes for potassium, sodium, calcium and chloride. This multi-measurement system with series-connected biosensors in modular construction is provided with a chemosensor for pH measurements. Besides the technical aspects of the apparatus, the quantitative electrode characteristics and the fundamental basis for the application of ion activities in clinical analytic measurement will be described.

Acid-Base Equilibrium↗
PubMed1991

[Electrochemical measuring system for the registration of transmucosal gastrointestinal potential differences].

An electrochemical measuring system for the recording of transmucosal gastrointestinal potential differences based on silver electrodes with double-junctions and continuous-flow saline bridges is described. Under bioelectrochemical control, a probe can passed from the esophagus via the stomach into the duodenum can be accurately assigned to each of these three segments of the intestine. Measurements are demonstrated and applications discussed.

Animals↗
PubMed1982

Transient response of the calcium homeostatic system of the conscious pig to bolus calcium injections.

Calcium injection in the pig elicits a fast transient response which reinstates the calcium concentration to within normal limits between 30 and 40 min after injection. Although the fate of the calcium that disappeared is not known, the present experiments eliminate the kidneys and the bone remodeling cells as the main short-term regulators. The fast response is independent of parathyroid hormone but is greatly dependent of calcitonin. Further experiments are being performed to discover the nature and site of the regulating mechanisms.

Animals↗
PubMed1981

[Flow-optimized multianalytical system for haemoanalysis with ion-selective disc and coated glass electrodes (author's transl)].

Using theoretical models based on the low resistance coefficients of variously shaped bodies subjected to a streaming fluid, a flow-optimized multianalytical system was developed for ion-selective disc electrodes and for Na+-, K+- and Ca2+-selective coated glass electrodes. Due to the streamlined configuration of the carrier PVC membrane region, the flow is uncongested and free of dead spaces. This allows a rapid and precise measurement in serum, plasma or heparinized blood. The system was subjected to a durability test.

Blood Chemical Analysis↗
PubMed1981

[Continuous measurement of cations in the blood-stream of patients (author's transl)].

An electrochemical flow-through system in the blood-stream of patients is described, which allows continuous measuring of Na+-, K+- and Ca++-concentrations. The ion-selective electrodes show excellent selectivity constants. Activity potentials of greater than 97% of the theoretical measurement characteristics of the electrodes (Nernst-factor) could be achieved. This electrochemical measuring device makes it possible to measure continuously the electrolyte activities in the blood. Results of direct patient measurements are demonstrated.

Calcium↗
PubMed1980

Continuous and discontinuous ionography of the pancreatic juice and the parotid saliva using carrier-membrane disc-electrodes.

The methodology for continuous ionography (monitoring of electrolytic composition) of the pancreatic secretion using a multianalyser is described. The system employs special electrodes which make use of sensing elements constructed of carrier-membrane discs. The procedure has been applied successfully in investigations on animals and is presently being tested in the clinical diagnostic laboratory. The apparatus can also be used for discontinuous measurements, in which case it has the advantage of needing only extremely small quantities of fluid which can be analyzed successively for the different ions, as the electrodes are connected in series.

Calcium↗
PubMed1979

[The influence of menstruation cycle on human parotid saliva composition (author's transl)].

The influence of different sexual hormone levels during menstrual cycle on the composition of human parotid saliva was investigated. During mid-cycle there were significantly enhanced concentrations of ionized calcium, total calcium, inorganic phosphate and sodium in parotid saliva. The changes in chloride concentrations were parallel to that of sodium and the excretion of postassium was inverse to that of sodium. The maximal out-put of total protein and alpha-amylase was found during midcycle and menstruation.

Fasting↗
PubMed1978

[Investigations in the streaming blood of the alert animal and man. III. Postprandial and therapeutically induced changes of electrolyte concentration and hematocrit in man during hemodialysis (author's transl)].

Arterial haematocrit and blood electrolyte concentrations are measured continuously by conductometry in three hemodialysis patients. Haematocrit elevation during meals, particularly when rich in carbohydrates, indicate fluid losses into the gut. Simultaneous biphasic responses in electrolyte concentration indicate osmotic and diffusional shifts of water and electrolytes. Similarly, blood volume and electrolyte concentration changes can be followed during and after intravenous infusion of colloid and crystalloid solutions. The quantitative aspects of such measurements are discussed.

Adult↗