The contractility of tissue-engineered muscle on the application of electrical signals is required for the development of bio-actuators and for muscle tissue regeneration. Investigations have already reported on the contraction of myotubes differentiated from myoblasts and the construction of tissue-engineered skeletal muscle using electrical pulses. However, the relationship between myotube contraction and electrical pulses has not been quantitatively evaluated. We quantitatively investigated the effect of electrical pulse frequency on the excitability of myotubes and developed bio-actuators made of tissue-engineered skeletal muscle. C2C12 cells were seeded on a collagen-coated dish and in collagen gel and were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum and antibiotics. When the cells reached confluence or after 2 days in culture, the medium was shifted to DMEM containing 7% horse serum to allow them to differentiate to C2C12 myotubes. We electrically stimulated the myotubes and tissue-engineered skeletal muscle, and contractions were observed under a microscope. The myotubes contracted synchronously with electrical pulses between 0.5 and 5 Hz and unfused tetanus was generated at 10 Hz. The contractile performance of tissue-engineered skeletal muscle made of collagen gel and C2C12 was similar to that of the myotubes. Both the rheobase and chronaxie of the myotubes were lowest when the electric field was applied parallel to the myotube axis, and the values were 8.33 +/- 2.78 mA and 1.19 +/- 0.38 ms, respectively. The motion of C2C12 myotube contraction depended on the pulse frequency and showed anisotropy in the electric field. These results suggest that a tissue-engineered bio-actuator may be controlled using electrical signals.
The hydrodynamic effect of periodically fluctuating shear rate on erythrocyte destruction was quantitatively studied in vitro in comparison with constant shear rates. Uniform shear rates (<1,000 s-'; constant or sinusoidally fluctuating with time) were applied to hepannized canine blood contained in the concavo-convex type of Couette flow testing machine for (1.8-9.0) x lo3 s at 24°C. The results show that the erythrocyte destruction (evaluated with hemolysis ratio; plasma hemoglobin count per whole blood hemoglobin count) decreases when the exposure time of larger (>500 s-') shear rates is interspersed with smaller (<300 s-l) shear rates.
A multifunctional main chain liquid crystal elastomer (MCLCE) with large mechanical and optical effects in applied electric fields is investigated, when MCLCE is swollen in a low molecular weight liquid crystal, 4-n-pentyl-4-cyanobiphenyl, a nematic solvent. The size change by the field effects is linearly proportional to the transmittancy change. This suggests the possibility of broad application as a field-induced-optical actuator device.
A case of early gastric cancer arising from Ménétrier's disease in the stomach is described. The patient was a 53-year-old man, who suffered from epigastralgia. Radiological and endoscopic examination demonstrated giant mucosal folds along the greater curvature of the stomach. On the distal margin, signet-ring cell carcinoma was demonstrated by biopsy. The coexistence of Ménétrier's disease and early gastric cancer has rarely been reported. Cases reported in the literature were reviewed and the increased malignant potential of Ménétrier's disease was discussed.
The hydrodynamic effect on clot growth at foreign surfaces was investigated quantitatively in vitro. Shear rates from 2 to 1,000 s-1 were applied to a blood sample contained in a cone and plate viscometer. Four different artificial materials were used for cone and plate combination, namely, stainless steel, polytetrafluoroethylene, polycarbonate, and polymethylmethacrylate. Evaluation of clot growth was derived from the clotting ratio (the volumetric fraction of clot in the whole blood), which was experimentally determined from the rate of increase of frictional torque between the rotating cone and the stationary plate. The results show that the clotting ratio decreases markedly as the shear rate increases to 400 s-1, regardless of material used. This study demonstrates that at a shear rate of greater than 400 s-1, clot growth at foreign surfaces is considerably inhibited.
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