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Biomedical subjects

R van Mastrigt

Publications and source records attributed to R van Mastrigt.

90 records · Page 5Linked to original sources
PubMed1983

Determination of the contractility of children's bladders from isometric contractions.

A new method of determining the contractility of the urinary bladder was applied to children. The method consists in the calculation of the force-velocity relation of the detrusor muscle from isometric contractions. These were measured by urodynamic equipment connected to a remote computer via a telephone line. The resulting force and velocity parameters are satisfactorily reproducible. The velocity parameter is comparable to that given by the stop test, a more direct but in practice more complicated method of assessing contractility. We found that boys' bladders can generate more force and higher contraction velocities than girls', and confirmed that obstructed bladders can generate more force than unobstructed ones. Some differences in the parameters found in enuretic children, and between stable and unstable bladders, are also discussed.

Child↗
PubMed1980

Urodynamic investigation of the wide ureter.

Pressure flow studies constitute a valuable advancement in the investigation of wide ureters without reflux. However, these studies do not in themselves allow the determination of the adequacy of urine transport into the bladder. Radiological examination during perfusion is necessary to assess peristalsis and antiperistalsis, to determine the outflow to the bladder and to judge the geometric changes. Case studies reveal that it is difficult to assess the outflow to the bladder from measurements of renal pelvic pressure and of inflow.

Adult↗
PubMed1979

Contractility of the urinary bladder.

Measurements have been made in vitro of the active mechanical properties of complete pig bladders, electrically stimulated to contract. The results are described with the aid of a model of the bladder wall consisting of a contractile element in series with an elastic element. For the contractile element the active force depends on the velocity of shortening. This relation is well described by a classical Hill equation, provided force is normalized by dividing it by the isometric force at the same bladder volume. The force-extension relation of the series elastic element is non-linear and can be described by an elastic modulus which depends monoexponentially on the extension. In the light of these findings the limitations of existing clinical methods of assessing bladder contractility, and the possibility of developing new methods, are discussed.

Animals↗
PubMed1978

Some influences of the contractile element on the visco-elastic properties of bladder wall strips.

The influence of the inhibition and stimulation of the active element of pig bladder wall on the stress-decrease curves, determined on bladder wall strips, has been investigated. The properties of the strips were investigated by stepwise straining. Stress-decrease curves were analysed in terms of a multi-exponential model. The reduced activity of the active element was found to decrease the spread of the exponents (relaxation constants) of the bladder wall. The smallest of the three relaxation constants did not, however, appear to be influenced by the active element.

Animals↗
PubMed1976

Viscoelastic properties of bladder wall strips at constant elongation.

The experimental and data processing methods used were improved in several respects compared with those described in previous publications. One hundred twenty-two stress decrease curves for bladder wall strips were measured at constant elongation; reproducibility was tested. Consideration of the results led to the addition of two elements (a dashpot and an active element) to our model of the process involved. The influence of the dashpot on the measurements is mathematically analyzed in terms of an increase in rest length during stretch. The model could be successfully fitted to the experimental data and the parameters turned out to be in the physiologic range. Some recent models used to describe muscular stress relaxation were tested and criticized.

Elasticity↗
PubMed1975

Visco-elastic properties of the bladder wall.

Stepwise cystometry is a new method proposed to analyse the visco-elastic properties of the bladder. It is based on a mathematical analysis of the pressure decay after a stepwise filling. By assumption of a mechanical visco-elastic model of bladder tissue and a model of the geometry, the derived parameters are interpreted as elasticity and viscosity moduli. Static cystometry is involved in this new procedure. From analysis by stepwise cystometry it is concluded that static cystometry attained by following a slow-filling procedure is unacceptable in studying elastic behaviour.

Animals↗
PubMedDate not supplied

A computer program for on-line measurement, storage, analysis and retrieval of urodynamic data.

A computer program is presented which allows for direct connection of a minicomputer to a urodynamic set-up. The program stores measured pressure and flow data in a random access disc file with minimal intervention of the urodynamicist, and enables the direct application of a number of methods of analysis to the data. The program is modular, and other analysis methods are easily added. Results of analyses are stored in the same disc file, and both results and measured data can be quickly and easily retrieved. The program is written in FORTRAN; hardware-dependent functions (analog input, graphics display, and random access disc storage) are implemented in subroutines (partly assembler) which can easily be replaced.

Computers↗