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Biomedical subjects

S Odman

Publications and source records attributed to S Odman.

12 recordsLinked to original sources
PubMed1992

Mechanical pulse wave propagation in gel, normal and oedematous tissues.

The velocity, attenuation and frequency content of the mechanical pulse wave propagation in gels of various water contents, in normal tissues from various sites and in oedematous tissues from different patients were investigated. The properties of the propagated pulse wave depend on the water content of the gel and the viscoelastic properties of the tissues. From the dependence of the pulse wave propagation velocity on elasticity, viscosity and density, information may be obtained concerning the effects of oedema on the mechanical properties of tissue.

Biomechanical Phenomena↗
PubMed1992

Measurements of light transmission through single melanophores.

A photometrical method has been developed that allows assessment of subcellular pigment migration in melanophores of the fish cockoo wrasse (Labrus ossifagus L.) The pigment migration was studied with local light spot transmission measurements. Depending on where the light beam is placed on the melanophores it is possible to study events within an area of approximately 75 microns 2. Measuring pigment translocation in different parts of a melanophore gives new possibilities to study how cell membrane receptor-mediated signals are spread within a single cell, which will increase our understanding of how receptor activating drugs exert their cellular effect. The technique can be used in pharmacological and biophysical studies and in biosensors, pharmaceutical screens, environmental detectors, etc. The method clearly has the ability to study local and small changes in light transmission due to displacement of melanophore pigment granules. Since one melanophore on the tip of an optical fibre would be enough to obtain a measurable effect, the presented technique provides the basis for future development of biosensors small enough for in vivo applications, e.g., to monitor the catecholamine levels of circulating blood.

Animals↗
PubMed1991

Impression technique for the assessment of oedema. Technical improvement and methodological evaluation of a new technique.

A new instrument for the assessment of oedema based on the impression method is described. The measurement parameters are defined and the errors corresponding to the electrical and mechanical stability of the instrument are measured. The overall accuracy is calculated theoretically for the translocated volume. The accuracy and reproducibility are evaluated on plastic foam. The clinical procedure to measure oedema with this instrument is described. We show that the accuracy of the translocated volume parameter is very dependent on the overall stability of the instrument and that this instrument has an overall relative error of less than 7.3 per cent for a representative measurement. Experimental measurements on plastic foam show that the measurement parameters could be reproduced with standard deviations of less than 6 per cent and that the standard deviations for translocated volume are within the calculated overall relative error. Measurements on four patients with chronic oedema in an extremity show significantly different results on locations where pitting could be recognised compared to the contralateral nonoedematous extremity.

Aged↗
PubMed1990

Effects of sodium nitrite on ultraviolet light-induced relaxation and ultraviolet light-dependent activation of guanylate cyclase in bovine mesenteric arteries.

It was demonstrated that precontracted strips from different bovine mesenteric arteries showed variation in sensitivity to ultraviolet radiation (366 nm). Some strips relaxed when they were exposed to ultraviolet light, others showed no sensitivity at all and, finally, some showed contraction. However, all arteries relaxed when they were irradiated with UV-light in the presence of 10 microM NaNO2. Ultraviolet radiation (366 nm) increased the activity of guanylate cyclase in crude homogenate from bovine mesenteric arteries by about 20-fold in the presence of NaNO2, while UV-light in the absence of sodium nitrite had no effect on the guanylate cyclase activation. These results support the notion that nitrite may be essential for vascular smooth muscle relaxation by UV-light, possibly through the release of nitric oxide.

Animals↗
PubMed1990

Fish scales as biosensors for catecholamines.

Certain fish scales contain specialized cells (chromatophores) with pigment granulas, which can be dispersed or aggregated in the cells. The degree of aggregation is determined by a transmitter substance, noradrenaline, released by the sympathetic nerve endings in the skin. Isolated scales from, for example, cuckoo wrasse (Labrus ossifagus) retain a large sensitivity to externally applied noradrenaline (or more generally catecholamines) for several weeks. The degree of aggregation in isolated scales can be measured objectively by simple photometric techniques. We demonstrate in this paper how fish scales can be used to monitor catecholamine levels in human blood plasma. A discussion of other potential biosensor applications of this intact biological receptor-effector system is also given.

Animals↗
PubMed1989

Changes in skin potentials induced by skin compression.

Changes in skin potentials are known to occur upon stretching and compressing the skin. In this work the relationship between compressional force and changes was studied for forces up to 13.7 N. For a given force, a flatter compressing surface gave lower potential changes than a more curved surface. When temperature increased both changes in potential and current decreased.

Adult↗
PubMed1989

Fluid translocation measurement. A method to study pneumatic compression treatment of postmastectomy lymphoedema.

Tissue fluid translocation under the action of deformation was measured to study the pneumatic compression treatment of postmastectomy lymphoedema of the arm. Analysis of the results provides statistically significant parameters for characterization of the oedema. Mobility of the fluid in pitting oedematous tissue was significantly greater than that of normal tissue and decreased after pneumatic compression treatment. Oedematous fluid at the distal sites of the arm showed a greater mobility than that of the proximal sites. Improvement in the oedema due to pneumatic compression treatment was found to be greater at the distal sites than at the proximal sites. In addition, oedema recurred between the treatments and repeated treatments produced the best results. Measurement of fluid translocation is useful in selecting and evaluating the effectiveness of lymphoedema treatment, as well as in determining the viscoelastic properties of the oedematous tissues.

Adult↗
PubMed1979

ECG electrodes. A study of electrical and mechanical long-term properties.

The long-term properties of commercially available ECG-electrodes were studied by investigating the parameters: polarization potential, electrical impedance, adhesion, and skin reactions during a period of 7 days. As expected, the most stable polarization potentials were obtained for Ag/AgCl electrodes. Certain simple disposable electrodes showed large polarization potential variations. The most stable electrode impedance was obtained for disposable electrodes with stable adhesion and equipped with an electrode cup or similar. Unchanged adhesion and mechanical properties during the test period were shown by the disposable electrodes with a large self-adhesive collar.

Adhesiveness↗