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Biomedical subjects

U Faust

Publications and source records attributed to U Faust.

At least 37 records · Page 2Linked to original sources
PubMed1988

Measurement of activation energy of gamma-glutamyltransferase as a marker for enzyme heterogeneity.

In order to detect differences between various multiple forms of gamma-glutamyltransferase, the activation energy was measured. In the serum of patients with liver diseases, activation energy was measured. In the serum of patients with liver diseases, activation energy of the serum enzyme is higher than in normal individuals (41.9 +/- 1.2 vs. 38.9 +/- 1.5 kJ/mol, p less than 0.05). Neuraminidase treatment resulted in a reduction of activation energy. Various multiple forms of serum gamma-glutamyltransferase, as prepared by lectin affinity chromatography (concanavalin A, Ricinus communis I and II, wheat germ agglutinin) showed activation energy differences between binding and nonbinding fractions. Similar results were observed in seminal plasma gamma-glutamyltransferase, when patients with accessory gland infection were compared with a reference population. Our results suggest that the activation energy depends upon differences in the carbohydrate part of the enzyme. The low gamma-glutamyltransferase activation energy of tissue extracts increased significantly after butanol extraction and was then comparable with serum activation energy values, which suggests that lipid-binding is a factor in activation energy variation. In most cases, gamma-glutamyltransferase activities measured at a certain temperature can be easily converted to a corresponding activity at another temperature, but in severe liver disease significant errors may be introduced when simple temperature conversion factors are used.

Chromatography, Affinity↗
PubMed1986

[Determination of the acoustical properties of enamel, dentin and alveolar bone].

An ultrasonic method for periodontal diagnosis has been developed by the authors. A fundamental part of this work is the evaluation of the acoustical properties of the hard tissues: enamel, dentine and alveolar bone. Using an adapted measuring device, in combination with a computer-controlled signal acquisition and analysing system, acoustical parameters (velocity, impedance and frequency-dependent attenuation) are determined. The knowledge of these parameters is a prerequisite for a correct interpretation of A-mode and B-mode images, representing parts of the oral/facial aspect of a periodontium.

Acoustics↗
PubMed1985

Indices for the age of the creatine kinase M-chain in the blood.

The apparent activation energy of the CK reaction as well as the Michaelis-Menten constants and the isoelectric point of CK MM can be used as indices for the mean age of the CK M-chain in the blood in vivo and in vitro. Modifications in the CK M-chain take place in vivo in the blood and in vitro in a serum matrix. Gradual increases in the apparent activation energy are also observed both in vivo and in vitro. It is confirmed that the modification in the CK M-chain causes a rise in the apparent activation energy, mu. A gradual increase in apparent activation energy, due to the ageing process of the CK M-chain, was observed after myocardial infarction. A significantly increased value for u was observed at the time that total CK activity already had returned to reference values. In spite of the normal CK value, the apparent activation energy still indicated that there had been myocardial damage. The Michaelis-Menten constants for creatine phosphate and ADP are also influenced significantly by the modification in the M-chain. While the apparent activation energy increases, the Michaelis constants decrease in the order MM3, MM2, MM1. The Michaelis-Menten constants for both ADP and CrP can be used as an index for the mean age of the enzyme in the blood. The Michaelis-Menten constants for CrP and ADP show significant variations with the measuring temperature for virtually all CK MM forms.

Creatine Kinase↗
PubMed1985

The measurement of systolic time intervals. A microprocessor based system for long-term registration of the impedance cardiogram and the systolic time intervals.

The systolic time intervals (STI) are reliable parameters for the characterization of left ventricular heart function. The non-invasive methods for the determination of STI are here introduced and compared. The disadvantage of all these methods is their manual evaluation of time intervals which makes a continuous monitoring of STI impossible. Therefore, a microprocessor based system was developed for the automatic registration of STI, stroke time volume (SV) and heart rate from the impedance cardiogram (ICG) and the electrocardiogram (ECG). In this article the preliminary results are discussed of the long-term monitoring of these parameters with the help of this device.

Cardiography, Impedance↗
PubMed1984

[Digital analysis of ultrasound M images for determining the dynamic behavior of the posterior ocular wall].

A computer-assisted interactive method for M-scan analysis is presented. The digital M-scan, which is taken from the posterior wall of the human eye - in vivo - , is a sequence of digitised, broadband r.f.-time amplitude echograms (center frequency: 15 MHz). The effect of pulsation in the normal posterior wall of the eye and the dynamic changes and tissue movements after stress conditions can be pointed out and estimated quantitatively. A detected set of dynamic features can be used for an exact determination of the layers of the posterior ocular wall. For the indication of the dependence between changes of the thickness of the layers and the heart rate, the finger pulse is digitised and stored synchronously to the echograms. Good correlation will be expected for the movements in the choroid of the eye and the heart rate. The registration of the dynamics is performed in the color-coded M-scan by an adapted image processing software. Results of the M-scan analysis are presented as examples of the normal posterior wall.

Choroid↗
PubMed1982

The catalytic activity and activation energy of creatine kinase isoenzymes.

The catalytic activity and activation energy of an enzyme are obtained by measuring the rate of the enzymic reaction at two different temperatures. With the aid of the Arrhenius equation, these two parameters can be used to calculate a value proportional to the quantity of enzyme. Using this approach to investigate the isoenzymes of creatine kinase, it was shown that the activation energy increased in the order creatine kinase MM, MB, BB. Mixtures of the isoenzymes showed an apparent mean activation energy, which likewise could be determined using the Arrhenius equation. Ageing of the isoenzymes results in an exponential decrease of catalytic activity, accompanied by a continuous increase in activation energy, the calculated quantity of enzyme remaining constant. Inactivation is therefore not an all-or-nothing process; rather a stepwise inactivation of individual molecules must be assumed. The results of these ageing experiments and observations by other authors suggest that a similar inactivation occurs in vivo.

Creatine Kinase↗
PubMed1981

24 hour-monitoring of patients with bladder voiding disturbances.

A system was developed and built for recording and processing urodynamic measurements during a 24 h period. The essential requirement was to obtain these signals without psychological stress. The system was small enough to allow the patient to move freely. Semiconductor pressure transducers were employed for measuring total bladder and rectal pressures and detrusor pressure was obtained by subtraction. Results gained with this method revealed some differences to those obtained with conventional methods.

Adult↗
PubMed1981

Examination of thin tissue layers in the human eye.

A computer-aided interactive method based on A-scan analysis using broadband RF-signals (15 MHz centre frequency) is presented. This method is used for the characterization of tissue layers of the posterior wall of the human eye in vivo. The following topics are discussed: - Automatic signal pre-processing and formation of a patient-specific, representative echogram. - Comparative studies using various methods from the time and frequency domain for the determination of layer thickness. - Analysis of the boundary surfaces by their spectral distribution, taking into account the roughness of the surface in relation to the ultrasonic wavelength. The characterization and differentiation of tissue layers by means of sets of features are explained with examples from intact posterior wall, detached retinas, vitreous membranes and from intraocular tumours. The differentiation of detached retina and other membranes by comparison with adjacent layers is discussed.

Computers↗