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Biomedical subjects

L von Klitzing

Publications and source records attributed to L von Klitzing.

At least 19 recordsLinked to original sources
PubMed1992

[Do encephalo-electric signals determine the pulse frequency in man?].

One of the most interesting problems in EEG analysis is the question of the genuine generator of these biosignals. Each spontaneous EEG sampled by surface electrodes looks like a summary of stochastically distributed encephalo-electrical events. But analysing these data depending of the time distance of ECG R-waves we found signals which contain the information about the occurrence of the next ECG R-wave. The results make dubious the discussion about the autonomic character of sinus excitation as the heart pacemaker.

Electroencephalography↗
PubMed1990

[ECG-triggered EEG in a static magnetic field].

In static magnetic fields as used in MRT-equipment for clinical diagnosis the "spontaneous" EEG is triggered by each heart activity. The registered signal is characterized by an oscillation of potentials in the frequency range of 8 to 10/s, mostly beginning with the higher frequency. These data sampled are dependent of the magnetic flux vector, but not regularly and independent of the point of lead. These results point to a transition from the isotropic distribution of EEG-currents to an anisotropic state by static magnetic fields.

Electrocardiography↗
PubMed1990

[Is the isotropic load distribution in the cortical space increased by a static magnetic field?].

Obviously, in static magnetic fields the isotropic distribution of cortical electrical charge movements becomes an anisotropic state. By this effect we have the phenomenon that the spontaneous EEG is triggered by external Zeitgeber like electrical stimuli of N. medianus or internally by the ECG. This orientation of charge transports leads to an additional varying magnetic field which induces currents in coils placed at the same positions like EEG-electrodes.

Cerebral Cortex↗
PubMed1989

Static magnetic fields increase the power intensity of EEG of man.

In static magnetic fields the power values of EEG are increased. This influence is different in the two cortical hemispheres and not the same for all EEG-frequencies. The increased control values following on inverted magnetic flux vector point to a - reversible - alteration of brain function induced by a static magnetic field.

Brain↗
PubMed1989

[Effect of a static 0.2 T magnetic field on the EEG power spectrum in periodic median nerve stimulation].

In static magnetic fields as used in n.m.r. equipment for clinical diagnosis we found an increase of the beta-EEG power value at the right hemisphere when stimulating simultaneously the N. medianus of the left hand with a periodicity of 140 ms. By a sequence of 120 ms there was no change of the power in this frequency band. But when stimulating continuously and switching on and off the magnetic field, in the beta- and alpha-frequency bands the power values of the left hemisphere were increased by the influence of the magnetic field, not depending of the field vector. In contrast to these data, in the beta-band the values increased at the right hemisphere, and, additionally are influenced by the field vector. Artifacts in the single frequency bands by the stimulus frequency itself could be excluded. The increase of power value only by a 140 ms-periodicity might be a hint that a "Zeitgeber"-function is activated by this external frequency.

Afferent Pathways↗
PubMed1987

[Static NMR magnetic fields change somatosensory evoked potentials in the human].

In strong static magnetic fields as used by NMR for clinical diagnosis we found oscillations in somatosensory evoked potentials of man when stimulating the Nervus medianus at the wrist joint. These new signals are to register only, when the head of the test person is inside of the magnetic field. A magnetic influence only of the stimulated arm has no effect of the normal SEP-signal.

Electric Stimulation↗
PubMed1986

Do static magnetic fields of NMR influence biological signals?

When measuring auditory evoked potentials on test persons we found that an early signal, measurable between the mastoid and vertex electrodes and possibly caused by capacitive or/and inductive coupling from the electrodynamic headphone, was phase-shifted when the person was exposed to a static 0.35 T field. This shift only slowly (greater than 15 min) returned to zero after termination of the magnetic exposure. Using a circuit stimulating the EEG measurement we now show that this shift is caused by a change in the total capacity of the electrode impedances. Therefore, the magnetically induced shift may be explained by changes in electric capacities of the magnetically exposed biological system.

Evoked Potentials, Auditory↗
PubMed1985

Bactericidal activity and induction of cell volume alterations of cephalosporins in Escherichia coli.

The bactericidal efficacy of cefuroxime and cephacetril on Escherichia coli cultures was measured by killing curves. Simultaneously bacterial cell volumes were analysed by electronic particle counting using a Coulter Counter Channelanalyser system in order to study the relationship between bactericidal activity and bacterial cell volume alterations. Various concentrations (2-120 mg/l cefuroxime and 16-120 mg/l cephacetril) and different exposure times (over a time period of 12 h) were used. Growth medium was human plasma ultrafiltrate. The bactericidal activity of cefuroxime, as measured by the rate of killing of the E. coli culture, was independent of the concentration and constant in the range 4-120 mg/l. The characteristic cefuroxime-induced change in bacterial cell volume was a marked volume increase up to a maximum of 5-fold after 160-200 min exposure with a low-grade bacteriolysis following. The cefuroxime-induced bacterial volume changes were, in accordance with the bactericidal testing, almost independent of the concentration. In contrast, the killing curves for cephacetril strongly depended on the drug concentration. However, this effect was short-lived and regrowth of the E. coli culture followed. The typical cephacetril-induced volume distribution curves were also highly concentration-dependent. With increasing drug levels bacterial cell volume increased up to 20-fold, and regrowth of a persisting bacterial population occurred at lower antibiotic concentrations. Bacteriolysis started earlier than with cefuroxime. The relationship between loss of viability and cell volume increase was more marked with cefuroxime than with cephacetril.

Autoanalysis↗
PubMed1984

Analysis of cephalosporin-induced changes in the volume distribution of Escherichia coli cultures by an electronic counter-channelanalyser.

The demonstration of morphological alterations of the bacterial cell together with bactericidal kinetics are of value for the description of the antibacterial activity of beta-lactam antibiotics. One of the indicators of antibiotic effect on bacterial morphology is the change in bacterial cell volume. This can be demonstrated graphically and numerically by means of electronic cell counting and volume distribution analysis using the Coulter Counter-Channelanalyser system connected to a computer. After registration of the distribution of the relative volume of the Escherichia coli population, the mean cell volume was calculated. The latter parameter increased more than 6 fold with increasing cefotaxim-exposure times. The onset of the delayed (2 h after cefotaxim administration) bacteriolytic effect was reorganized by the appearance of small cell breakdown particles and quantified by counting. In order to demonstrate the therapeutic process graphically the distribution curves were transformed to a common scale. Since a complete storage of the data per sample is performed normally within one minute, the Coulter Counter-Channelanalyser technique can be carried out simultaneously with the bactericidal kinetic experiment. The data demonstrate the speed and intensity of the morphological cell alterations induced by the beta-lactam antibiotic.

Bacteriological Techniques↗
PubMed1982

The transcutaneous PO2 measurement as an additional evaluation index to the physiological and pathological conditions under delivery.

Transcutaneous PO2 was continuously recorded from 17 newborns sub partu by normal deliveries and four cases with umbilical cord complications. These data were correlated with the corresponding fetal heart rate alterations and the maximum of contraction directly and 30 s thereafter. During the course of delivery three stages are differentiated: first stage of labor, full cervix dilatation, second stage of labor. The statistical evaluation succeeded in the X2-test (P less than 0.01). Deriving from this result the tcPO2 measurement is an additional aiding procedure beside the cardiotocographic control for subpartal supervision.

Female↗
PubMed1982

Solid phase antigen luminescent immunoassays (SPALT) for the determination of insulin, insulin antibodies and gentamicin levels in human serum.

We describe an interesting and novel alternative to conventional immunoassay techniques for the measurement of antigens and antibodies in body fluids. The label used for all assays is a pyruvate kinase-IgG conjugate of the relevant second (species-specific) antibody. All assays follow the same principle in which a solid phase antigen is used to adsorb unreacted first (substance-specific) antibody following a conventional antibody-antigen reaction in a liquid phase. After washing, the solid phase antigen-first antibody is allowed to react with the labelled second antibody. The solid phase is then washed and the pyruvate kinase bound to the solid phase is used to generate ATP which is measured kinetically in a luminometer. Assays are described for insulin, insulin antibodies and gentamicin to demonstrate both the versatility and sensitivity of this type of assay. The insulin assay had a lower detection limit of under 0.25 microU per tube and was comparable with the radioimmunoassay used for routine purposes both in sensitivity and reproducibility. The insulin antibody assay correlated well with the radiometric determination used routinely in the laboratory. The gentamicin assay correlated well with the routine commercial radioimmunoassay and also had comparable coefficients of variation. In all cases, the inter- and intra-assay variation was under 10% in the range of interest.

Animals↗