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.

Cysteinyldopa isomers and dopa in lesions and urine of Japanese patients with malignant melanoma.

Cysteinyldopas and Dopa in the urine and tissues of Japanese melanoma patients were investigated quantitatively by means of high-performance liquid chromatography. Cysteinyldopa isomers were detected in the urine of eumelanic Japanese patients. The amount (X +/- SD%) of each isomer of cysteinyldopa in the urine was 80.26 +/- 4.66% in 5-S-cysteinyldopa, 9.39 +/- 1.64% in 2-S-cysteinyldopa, 7.07 +/- 3.33% in 2, 5-S, S-dicysteinyldopa, and 3.28 +/- 1.43% in 6-S-cysteinyldopa. The amount of cysteinyldopa in melanoma tissues was 26-314 times more than that of Dopa. The amount (X +/- SD%) of cysteinyldopa in the tissues was 80.34 +/- 1.75% in 5-S-cysteinyldopa, 11.06 +/- 1.91% in 2-S-cysteinyldopa, 6.27 +/- 1.43% in 2, 5-S, S-dicysteinyldopa, and 2.34 +/- 0.61% in 6-S-cysteinyldopa. The fact that the percentages of each isomer of cysteinyldopa in the urine and in the tissues were approximately constant suggests that the cysteinyldopas secreted from melanoma cells were excreted into the urine without being metabolized.

Studies on amelanotic melanoma with the fluorescence method (Falck and Hillarp) and biochemical analysis of 5-S-cysteinyldopa in the tissues.

Histochemical findings of primary and metastatic amelanotic melanomas were shown by the formaldehyde-induced fluorescence method (Falck and Hillarp). All or some of the amelanotic melanoma cells were discovered to emit green specific fluorescence. Results of the determination of 5-S-cysteinyldopa and DOPA in amelanotic melanoma tissues indicated that the specific fluorescence emitted by these cells is primarily due to the presence of 5-S-cysteinyldopa. The values of 5-S-cysteinyldopa in these tissues were lower than those in melanotic melanoma, but were approximately the same as those in pigmented nevus. When unpigmented tumors were histopathologically revealed to be malignant, amelanotic melanoma could be definitely diagnosed by the fluorescence method of Falck and Hillarp and the biochemical analysis of 5-S-cysteinyldopa in the tissues.

The effects of piezoelectric poly-L-lactic acid films in promoting ossification in vivo.

Uniaxially drawn poly-L-lactic acid (PLLA) films with piezoelectric properties were inserted onto the periosteum of rabbit tibiae, and the effect of the films in promoting ossification was investigated. We also evaluated the optimum method for PLLA film insertion to promote ossification, by comparing three different types of PLLA films which differed from each other in terms of the direction of their molecular orientation. Furthermore, the course of ossification following the film insertion was observed histologically. Drawn PLLA films promoted ossification to a greater extent than undrawn PLLA film. The effect of drawn PLLA films in promoting ossification was greatest when a shearing stress was applied at 45 degrees to the axis of orientation. The newly formed osteoid was observed at 1 week, and matured over 6 to 8 weeks following insertion. The insertion of piezoelectric PLLA films can promote ossification through their piezoelectric effect, and this seems to be clinically applicable.

Electro-biorheology.

Studies on piezoelectricity in biopolymers are reviewed with some examples. By measuring anisotropy of elastic and piezoelectric constants in fish skin, the direction of preferred orientation of collagen fibers is determined. Temperature and moisture dependence of real and imaginary parts of the piezoelectric constant observed for oriented film of fibrin gel indicates that temperature-time equivalence holds for the piezoelectric relaxation. The piezoelectric constant for oriented film of polyhydroxybutyrate decreases above glass transition temperature, which is related to the elastic and dielectric relaxations. When alpha-helical molecules of poly-gamma-methyl-L-glutamate are electrically oriented in ethylene dichloride solution and shear stress is given by ultrasound, the piezoelectric polarization is observed. When the film of poly-gamma-methyl-glutamate is wrapped around the femur of rat, the formation of new bone is produced.

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.

Piezoelectricity of biopolymers.

The piezoelectricity of semicrystalline biopolymers was first discovered for wood and bone in the 1950's. Piezoelectric properties have since been investigated for a number of biological substances, including polysaccharides, proteins and deoxyribonucleates. The shear piezoelectric constants -d14 = d25 were determined for their oriented structures with a uniaxial symmetry Dinfinity. From studies of synthetic polypeptides and optically active polymers, it was concluded that the origin of piezoelectricity lies in the internal rotation of dipoles such as CONH. Values of d14 = -10 pC/N were determined for highly elongated films of poly-L-lactic acid, optically active and biodegradable. The implantation of this polymer induced the growth of bone, possibly because ionic current caused by piezoelectric polarization stimulated the activity of bone cells. Submicron-thick polyurea films were prepared by evaporating diisocyanate and diamine monomers in vacuum. After poling, the films exhibited pyro- and piezoelectric effects. The tensile piezoelectric constant d31 = 10 pC/N persisting up to 200 degrees C was also observed for aliphatic polyurea films.

Bending piezoelectricity in a microbially produced poly-beta-hydroxybutyrate.

An optically active polymer, poly-beta-hydroxybutyrate (PHB), is produced in cytoplasm of various vacteria. The bending piezoelectric effect was observed in oriented films of PHB. The coefficient between the electrical polarization and the stress gradient was found to be in the order of 10(-18) Cm/N, which was similar to the value reported for bone. Anisotropy in the value of the coefficient was also observed.

Blood modeling using polystyrene microspheres.

The steady flow viscosity at shear rates 0 to 120 sec-1 and dynamic viscoelasticity at frequencies 0.02 to 0.8 Hz were determined for aqueous suspensions of uniform polystyrene microspheres of 1.0 micron diameter. Rheological properties of the microsphere suspensions were Newtonian for particle concentrations up to 32%. By introducing dextran and calcium chloride into the particle suspensions, non-Newtonian behavior was produced similar to that observed for human blood. The cooperative effects of dextran and calcium ions promoted aggregation of particles at a concentration as low as 12%. Thus, a suspension of uniform sized spherical polystyrene particles in aqueous solution of dextran may be made to mimic blood by controlling the surface charge on the polystyrene spheres using addition of calcium ions to the medium.

History and recent progress in piezoelectric polymers.

Electrets of carnauba wax and resin have exhibited good stability of trapped charges for nearly 50 years. Dipolar orientation and trapped charge are two mechanisms contributing to the pyro-, piezo-, and ferroelectricity of polymers. Since the 1950s, shear piezoelectricity was investigated in polymers of biological origin (such as cellulose and collagen) as well as synthetic optically active polymers (such as polyamides and polylactic acids). Since the discovery of piezoelectricity in poled polyvinylidene fluoride (PVDF) in 1969, the pyro-, piezo-, and ferroelectricity were widely investigated in a number of polar polymers, such as copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylcyanide and vinylacetate, and nylons. Recent studies involve submicron films of aromatic and aliphatic polyureas prepared by vapor deposition polymerization in vacuum and the piezoelectricity of polyurethane produced by the coupling of electrostriction and bias electric fields. Gramophone pickups using a piece of bone or tendon were demonstrated in 1959. Microphones using a stretched film of polymethyl glutamate were reported in 1968. Ultrasonic transducers using elongated and poled films of PVDF were demonstrated in 1972. Headphones and tweeters using PVDF were marketed in 1975. Hydrophones and various electromechanical devices utilizing PVDP and its copolymers have been developed during the past 30 years. This paper briefly reviews the history and recent progress in piezoelectric polymers.