Search PubMed⌕ Search

Biomedical subjects

E Fukada

Publications and source records attributed to E Fukada.

At least 37 records · Page 2Linked to original sources
PubMed1982

Electrical phenomena in biorheology.

Electric polarization is important in various subjects in biorheology. Piezoelectricity, that is, stress-induced polarization and electric field-induced strain, is demonstrated in a variety of biological materials including polysaccharides, proteins and deoxyribonucleic acid. Complex piezoelectric constant depends on measuring frequency, temperature and water content. Piezoelectric relaxation is related to microscopic internal strain. Stress-induced potential in bone is produced by shear piezoelectricity in collagen fibers and/or streaming potential in conaliculae. The growth of bone is regulated to best resist external force. The controlling signal seems to be the electric potential. Application of small d.c. current or piezoelectric polymer film stimulates the formation of bone in femur of animals. Various techniques of electrical stimulation are clinically used for healing bone fracture. Pulsing electromagnetic field enhances the proliferation of cell culture.

Animals↗
PubMed1980

Piezoelectricity in collagen films.

Tissue collagen exhibits several levels of structural organization, and this complicates efforts to determine the origin of its piezoelectricity. We made collagen films-by evaporation and electrodeposition from solution-and examined the relation between collagen's piezoelectricity and its electron microscopic appearance. We found that the electrodeposited films were more organized and exhibited higher piezoelectric coefficients than the evaporated films. Despite this, the evaporated films were piezoelectric, thereby suggesting that the effect originates either at the level of the tropocollagen molecule or, at most, with aggregated structures no larger than 50 A in diameter.

Chemical Phenomena↗
PubMed1977

Effect of temperature on dynamic viscoelasticity during the clotting reaction of fibrin.

The dynamic rigidity and loss moduli for fibrinogen-thrombin solution were determined during clotting in the temperature range between 15 and 45 degrees C. The rigidity of fibrin gel decreased with increasing clotting temperature, owing to the dissociation of cross-links. The rate constant of the dissociation of cross-links increased with increasing temperature. The rate constant of the cross-linking reaction increased and then decreased through a maximum with increasing temperature. It is explained by assuming that denaturation of fibrin occurs at high temperature. The irreversible denaturation becomes appreciable at high ionic strength. The activation energy and the enthalpy change for the cross-linking reaction of fibrin is about 35 and 15 kcal/mol, respectively. The enthalpy change for the reversible denaturation is about 46 kcal/mol.

Animals↗
PubMed1977

Electret induced callus formation in the rat.

Wrapping the mid-femoral shaft of the rat with a Teflon film electret produced a bony callus in 9 out of 10 animals. This model of electret-induced callus formation should lend itself to the histo-biochemical study of electrically induced osteogenesis.

Animals↗
PubMed1976

Piezoelectric and related properties of hydrated collagen.

Two piezoelectric constants (polarization per unit stress, d=d'-id'', and polarization per unit strain, e=e'-ie''), the elastic constant, and dielectric constant are determined for oriented collagen at different hydration levels at 10 Hz from -150 to 50 degrees C. With no hydration (approximately 0% H2O), d' increases slightly with higher temperatures, while e' decreases slightly. Near 11 wt% H2O, both d' and e' increase then decrease around 0 degrees C, and is probably caused by an increase of the dielectric constant and the ionic conductivity in the nonpiezoelectric phase. Hydration greater than 25 wt%, d' and e' decrease above -50 degrees C which is considered to be due to a greater ionic conductivity surrounding the piezoelectric phase.

Collagen↗