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Biomedical subjects

K Bartl

Publications and source records attributed to K Bartl.

15 recordsLinked to original sources
PubMed1998

Simple and broadly applicable sample preparation by use of magnetic glass particles.

A key issue in nucleic acid-based assays related to infectious disease testing and genetic testing is the sample preparation. This has to be convenient, efficient and suitable for automation. We describe a new method based on the use of glass magnetic particles. The steps involved are the lysis of bacterial cells and viral particles by chaotropic salts, binding of released nucleic acids to the magnetic glass particles, the removal of inhibitors and the release of purified nucleic acids ready for PCR amplification. The method fulfills most of the requirements for sample preparation such as sensitivity, universality and suitability for automation.

DNA↗
PubMed1996

A simplified calibration method for three-dimensional eye movement recordings using search-coils.

An algorithm is presented which allows the calibration of three-dimensional eye movements in two magnetic fields with two search-coils in one eye, whose relative orientation does not have to be known. Prior to recordings a calibration cube is placed in front of the eye to measure real and apparent crosstalk, produced by imprecisely oriented horizontal or vertical magnetic fields, and to obtain a first approximation of offset voltages. For calibration it suffices if one point is fixated and, in addition, spontaneous eye movements for 30-60 sec are performed. Additional fixation points can be used to improve the calibration. Position quaternions are applied for computing eye movement recordings from man and monkey and to determine Listing's plane.

Algorithms↗
PubMed1996

Contralesionally beating torsional nystagmus in a unilateral rostral midbrain lesion.

The rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and the interstitial nucleus of Cajal (iC) are involved in the generation of vertical and torsional saccades and gaze holding. Midbrain lesions involving either riMLF or iC produce a tonic torsional ocular deviation to the contralesional side. Lesions of the iC are associated with an ipsilesional torsional nystagmus (TN). For the first time, we describe a patient with a unilateral midbrain lesion showing a contralesionally beating torsional nystagmus. This nystagmus was probably caused by a lesion involving the riMLF.

Brain Diseases↗
PubMed1985

Development of a photometric assay for activated partial thromboplastin time and its application to the Cobas Bio centrifugal analyzer.

We describe a two-step procedure for APTT that can be performed on photometric devices. It includes preincubation of diluted plasma with ellagic acid and phospholipids and a starting reagent that contains calcium and a chromogenic peptide substrate for thrombin, Tos-Gly-Pro-Arg-pNA. Reaction time is recorded from addition of the starting reagent until thrombin formation occurs, and a prefixed amount of substrate is cleaved. The pattern of sensitivity to clotting factors and heparin was similar to clotting assays and the substrate used did not interfere with the activity of factor Xa. An application of the method was made for the Cobas(R) Bio centrifugal analyzer. Absorbance readings were sent to an external computer and were transformed into reaction times by a computer program. Although the results are independent on fibrinogen concentrations, from kinetic data of the reaction curve fibrinogen concentrations can be estimated. Correlation studies showed good correspondence to clotting methods (r = 0.92, n = 53) as well as an excellent precision (CV 3% for inter-assays, n = 15) and high throughput of samples (greater than 100/h) in the automated assay.

Apoproteins↗
PubMed1984

A functional photometric assay for plasma fibrinogen.

We have developed a photometric assay for fibrinogen concentration. The sample is mixed with a snake venom enzyme (Batroxobin) and fibrin formation is recorded turbidimetrically at 334 nm. Reaction conditions are such that a linear increase in absorbance is obtained over a concentration range of fibrinogen from 80-700 mg/dl. Higher or lower ranges can be measured by adjusting the sample volume. Calibration is performed with a single standard. Precision and accuracy are comparable with the usual clinical chemical methods. Experiments with plasma samples digested with streptokinase showed that interference of fibrinolytic split products (FSP) is less than using the Clauss method. Large amounts of FSP in the sample, however, delay the increase in absorbance. This phenomenon can be utilized for the additional estimation of the FSP-content of the sample. Results obtained with the present method corresponded well with those obtained using the method of Clauss.

Batroxobin↗
PubMed1984

Automated prothrombin-time test with use of a chromogenic peptide substrate and a centrifugal analyzer.

We modified a test for prothrombin time, to automate its performance by centrifugal analysis. The sample is activated with calcium-thromboplastin in the presence of a thrombin-specific chromogenic peptide substrate, Tos-Gly-Pro-Arg-p-nitroaniline (Chromozym TH). The endpoint of the reaction is set as the time after onset until a defined amount of substrate has been cleaved, as reflected in a fixed change in absorbance. The assay is as sensitive as clotting-type methods are to the clotting factors of the extrinsic pathway--except for fibrinogen, which can be estimated from the maximum absorbance difference. Substrate concentration has little effect on the result, and varying it does not significantly change the sensitivity to factor X, which indicates little interference with the enzymes of the coagulation cascade. The method was applied to the Cobas Bio centrifugal analyzer. An external calculator must be used to convert absorbance readings into reaction times, which can be expressed as percent-of-normal values or as "ratios" by use of reagent-specific factors. CVs were less than 2% within run, less than 6% day to day. Overall correlation with the clotting test (r = 0.95) was good. Using the Cobas Bio, we achieved a throughput rate of 200 samples per hour.

Autoanalysis↗
PubMed1983

Turbidimetric kinetic method for serum low density lipoprotein quantitation.

A turbidimetric kinetic fixed-time method for the rapid determination of serum low density lipoprotein (LDL) has been developed. It is based on specifically precipitating this lipoprotein with the use of a combination of heparin, Ca2+, EDTA and lipase. The method has been adapted to the Eppendorf spectrum line photometer and to the ENI Gemsaec centrifugal analyzer. It yielded satisfactory results with regard to linearity and precision. The values agreed closely to those obtained by conventional procedures for LDL-cholesterol and LDL-apolipoprotein B. The predictive value of this new method for the assessment of the individual risk of vascular disease remains to be proven by clinical and epidemiological studies.

Calcium↗
PubMed1980

Determination of the biological activity of heparin by use of a chromogenic substrate.

We describe a new method for determining the biological activity of heparin in plasma with use of thrombin and the substrate Tos-Gly-Pro-Arg-pNA. The procedure is based on the photometric determination of the inactivation of thrombin after incubation with plasma in the presence of endogenous antithrombin III (At III). The method allows the specific determination of heparin concentrations from 0.02 USP to 0.8 USP/ml of plasma in the presence of normal At III levels. It has been carried out manually by use of an Eppendorf spectrum line photometer or automatically by use of a Vitatron Akes analyzer. For evaluation, the results were compared with two standard samples which contained heparin in the low and high therapeutic range, respectively.

Anilides↗
PubMed1979

Improved automated kinetic determination of uric acid in serum by use of uricase/catalase/aldehyde dehydrogenase.

The enzymatic determination of serum uric acid by use of uricase, catalase, and aldehyde dehydrogenase according to Haeckel [J. Clin. Chem. Clin Biochem. 14, 101 (1976)] showed interferences from ethanol-converting enzymes, which are present in some patients' sera. We have identified these enzymes as alcohol dehydrogenase isoenzymes. Among other substances, a mixture of pyrazole and oxalate can be used to eliminate these interferences. This inhibitor system gives good results when used in the automated kinetic uric acid determination, as is shown by a comparison with the manual assay for uric acid according to Kageyama [Clin. Chim. Acta 31, 421 (1971)].

Aldehyde Oxidoreductases↗
PubMed1977

Synthesis of stereospecifically deuterated phenylalamines and determination of their configuration.

1. Starting from trans-cinnamic acid a chiral (-)3-phenyl-[2,3-2H]propionic acid has been synthesized using Clostridium kiuyveri cells as catalyst. 2. The chiral dideuterated acid has been converted by chemical methods to a mixture of (2R) and (2S)-phenyl[2,3-2H]-alanine. 3. By means of 1H nuclear magnetic resonance spectroscopy and the action of D and L-amino acid oxidase the configuration of the phenylalamine has been shown to be (2R, 3S) and (2S, 3S), respectively. The labelled phenylalanine is thus sterically and isotopically homogenous at position 3 but heterogenous at position 2.

Amino Acid Oxidoreductases↗
PubMed1977

Stereospecificity of phenylpyruvate tautomerase. A convenient method for the preparation of chirally labelled phenylpyruvates.

1. By 1H nuclear magnetic resonance spectroscopy it has been shown that phenylpyruvate tautomerase from beef kidney catalyses the stereospecific exchange of one of the enantiotopic 3H-atoms in the side-chain of the substrate with solvent protons, the rate of spontaneous exchange being slow under physiological conditions. 2. Using monodeuterated phenylpyruvate of known absolute configuration it has been shown that the tautomerase removes specifically the 3-pro-R hydrogen atom of the substrate. 3. The circular dichroism spectra of the two enantiomeric 3-phenyl-[3-2H]pyruvates have been determined. 4. Some implications of these findings for the investigation of the metabolism of aromatic amino acids are discussed.

Circular Dichroism↗
PubMedDate not supplied

Total quality in tubing glass manufacturing.

Today's demand for higher quality products can be satisfied through a comprehensive quality assurance system (Total Quality System, "Worldwide Quality Standard") using the latest state of the art measuring technologies. Totally automated state of the art glass vial manufacturing begins once the glass tubes are loaded into the machine and ends with the finished product in the packaging machine, all without human contact. This standard is achieved by measuring dimensions with SPC (statistical process control) and 100% inspection of the products. These systems complement each other and give the machine operator instant data in an overview format. To achieve the visual requirements forma vitrum developed the FVC90 control line. This optical surface inspection device controls online and without contact 100% of the products for cosmetic defects as small as 50 microns. It can detect and eject defects such as dirt, scratches, chips, air-lines, loose glass particles, cracks, etc. The sensitivity of the system can be adjusted and is fixed based on client needs. An important quality assurance technique is the checking of dimensions at the production machine with a Vision System. With this system deviations are instantly recognized and corrections can be made immediately, thus assuring that glass products can be run on the high-speed filling machines for which they are designed. These computer assisted inspection systems are key in producing the highest quality pharmaceutical glassware in the 90's.

Computer-Aided Design↗