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Comparative tensile and relaxation experiments on fresh and glutaraldehyde-treated porcine aortic valve tissue
Abstracts
of the third meeting
of the European
Society of Biomechanics
803
D. SOFT TISSUE BIOMECHANICS
BIOMECHANICAL
ANALYSIS OF THE DEFORMATION LABOUR
OF THE LOWER UTERUS DURING
.I. M. EGAN, J. D. RICHARDSON(Medical Engineering University of Southampton, U.K.)
Department,
A model of the deformation of the soft tissues of the lower uterus during the first stage of labour is proposed. It is suggested that this tissue behaves as a visco elastic liquid allowing an alignment of the fibrous microstructure to take place without inducing residual stresses as the cervix is effaced. This results in an anisotropic and nonhomogeneous lower uterus which is subsequently dilated by the uterine contractions, A model has been developed from the membrane analysis of the tissue deformation which stimulates experimental dilatation data. The prediction by the model of the pressure between the foetal head and the cervix is in agreement with experimental data and shows that this pressure can reach three to four times the intra-uterine pressure.
SERIES ELASTIC PROPERTIES
OF STRIPS OF SMOOTH BLADDER
MUSCLE FROM PIG URINARY
R. VANMASTRIGTand E. A. TAUECCHIO (Department of Urology, The Netherlands)
Erasmus
University,
Rotterdam,
The series elasticity of strips of smooth muscle from pig urinary bladder was investigated by means of a series of computerized quick-release and quick-stretch measurements, with and without stimulation of the muscle and at different shortenings and force levels. The results cannot be interpreted in terms of a discrete passive series elastic element. On the assumptions that: (I) the series elasticity resides in the cross bridges; (2) the cross bridges cannot push but only pull : (3) the lengths of the cross bridges during isometric contraction are distributed uniformly within a given range ; the results can consistently be described in terms of a sliding filament model with cross bridges having an exponential elastic characteristic.
COMPARATIVE TENSILE AND RELAXATION EXPERIMENTS ON FRESH AND GLUTARALDEHYDE-TREATED PORCINE AORTIC VALVE TISSUE E. ROCISSEAL. A. SAUREN, M. VAN H~UT and A. VAN STEENHOVEN(Eindhoven Technology, The Netherlands)
University
of
Comparative tensile and relaxation experiments have been performed with strips taken from porcine aortic valve tissue in fresh condition and after treatment with glutaraldehyde. The usual treatment, where the whole valve was preserved under a hydrostatic pressure, was simulated by treating the strips under a corresponding preload. The hydrostatic pressures of 94 and 1OOm Hg were simulated. Also leaflet strips from a Hancock bioprosthesis were measured. Due to the treatment the stress-strain relation shifted to the stress-axis for the strips treated at 100 mm Hg and in the opposite direction for the strips treated at 0 and 4 mm Hg. For all strips the total relaxation decreased after treatment, this effect being most pronounced (60”;) for the strips treated at 1OOmm Hg. The measurements on the Hancock strips confirmed the findings with the 100 mm Hg-treated tissue.
THE EFFECT OF MECHANICAL STRESS ON PROTEIN AND DNA SYNTHESIS AND ON MEMBRANE TRANSPORT IN RAT SKIN N. CHEUG, P. DELPORT, M. J. HOOGMARTENS,J. C. MULIER and W. DE LOEKER (Departments of Biochemistry and Orthopaedics, University of Leuven, Belgium) Mechanical stimulation results in tissue growth stimulation. This implies an effect on metabolism which has been examined in rat skin during mechanical stretching. The rat skin is incubated for 2 hr in 100 ml KrebsRinger bicarbonate buffer containing 10 &i [2-“V] glycine, or 2OpCi [6-3H] thymidine to follow the incorporation into proteins and nucleic acids: or JOpCi of O![J-14C] ammo isobutyric acid to evaluate membrane transport. Mechanical stretching with weight from 5 to 1OOg applied during incubation results in a stimulation ofprotein and DNA synthesis and in an increase in amino acid transport. Weights from 1OOg to 5OOg reduce the stimulatory effects to control values. It is assumed that mechanical strain possibly initiates piezoelectricity which may effect tissue growth and repair.
of the third meeting
of the European
Society of Biomechanics
803
D. SOFT TISSUE BIOMECHANICS
BIOMECHANICAL
ANALYSIS OF THE DEFORMATION LABOUR
OF THE LOWER UTERUS DURING
.I. M. EGAN, J. D. RICHARDSON(Medical Engineering University of Southampton, U.K.)
Department,
A model of the deformation of the soft tissues of the lower uterus during the first stage of labour is proposed. It is suggested that this tissue behaves as a visco elastic liquid allowing an alignment of the fibrous microstructure to take place without inducing residual stresses as the cervix is effaced. This results in an anisotropic and nonhomogeneous lower uterus which is subsequently dilated by the uterine contractions, A model has been developed from the membrane analysis of the tissue deformation which stimulates experimental dilatation data. The prediction by the model of the pressure between the foetal head and the cervix is in agreement with experimental data and shows that this pressure can reach three to four times the intra-uterine pressure.
SERIES ELASTIC PROPERTIES
OF STRIPS OF SMOOTH BLADDER
MUSCLE FROM PIG URINARY
R. VANMASTRIGTand E. A. TAUECCHIO (Department of Urology, The Netherlands)
Erasmus
University,
Rotterdam,
The series elasticity of strips of smooth muscle from pig urinary bladder was investigated by means of a series of computerized quick-release and quick-stretch measurements, with and without stimulation of the muscle and at different shortenings and force levels. The results cannot be interpreted in terms of a discrete passive series elastic element. On the assumptions that: (I) the series elasticity resides in the cross bridges; (2) the cross bridges cannot push but only pull : (3) the lengths of the cross bridges during isometric contraction are distributed uniformly within a given range ; the results can consistently be described in terms of a sliding filament model with cross bridges having an exponential elastic characteristic.
COMPARATIVE TENSILE AND RELAXATION EXPERIMENTS ON FRESH AND GLUTARALDEHYDE-TREATED PORCINE AORTIC VALVE TISSUE E. ROCISSEAL. A. SAUREN, M. VAN H~UT and A. VAN STEENHOVEN(Eindhoven Technology, The Netherlands)
University
of
Comparative tensile and relaxation experiments have been performed with strips taken from porcine aortic valve tissue in fresh condition and after treatment with glutaraldehyde. The usual treatment, where the whole valve was preserved under a hydrostatic pressure, was simulated by treating the strips under a corresponding preload. The hydrostatic pressures of 94 and 1OOm Hg were simulated. Also leaflet strips from a Hancock bioprosthesis were measured. Due to the treatment the stress-strain relation shifted to the stress-axis for the strips treated at 100 mm Hg and in the opposite direction for the strips treated at 0 and 4 mm Hg. For all strips the total relaxation decreased after treatment, this effect being most pronounced (60”;) for the strips treated at 1OOmm Hg. The measurements on the Hancock strips confirmed the findings with the 100 mm Hg-treated tissue.
THE EFFECT OF MECHANICAL STRESS ON PROTEIN AND DNA SYNTHESIS AND ON MEMBRANE TRANSPORT IN RAT SKIN N. CHEUG, P. DELPORT, M. J. HOOGMARTENS,J. C. MULIER and W. DE LOEKER (Departments of Biochemistry and Orthopaedics, University of Leuven, Belgium) Mechanical stimulation results in tissue growth stimulation. This implies an effect on metabolism which has been examined in rat skin during mechanical stretching. The rat skin is incubated for 2 hr in 100 ml KrebsRinger bicarbonate buffer containing 10 &i [2-“V] glycine, or 2OpCi [6-3H] thymidine to follow the incorporation into proteins and nucleic acids: or JOpCi of O![J-14C] ammo isobutyric acid to evaluate membrane transport. Mechanical stretching with weight from 5 to 1OOg applied during incubation results in a stimulation ofprotein and DNA synthesis and in an increase in amino acid transport. Weights from 1OOg to 5OOg reduce the stimulatory effects to control values. It is assumed that mechanical strain possibly initiates piezoelectricity which may effect tissue growth and repair.