Papers by Author: Duk Young Jung

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Authors: Duk Young Jung, Yu Bong Kang, Toshie Tsuchiya, Sadami Tsutsumi
Abstract: Accurate measurement of the mechanical properties of artificial or cultivated cartilage is a major factor for determining successive regeneration of defective soft tissues. In this study, we developed a novel method that enabled the bulk modulus (k-modulus) to be measured nondestructively using the relationship between volume and pressure of living soft tissues. In order to validate this method we estimated the bulk modulus of soft silicone rubbers using our new method and a conventional method. The results showed a 5 ~ 10% difference between the results obtained with the two methods. Our method was used subsequently to measure the mechanical properties of cultivated cartilage samples (collagen gel type), that had been incubated for four weeks in the presence or absence of human articular chondrocytes (HACs). Our experiments showed that cultivated cartilage tissues grown in the presence of HACs had a higher bulk modulus (120 ± 20 kPa) than samples grown without HACs (90 ± 15 kPa). The results indicated that our novel method offered an effective method for measurement of volume changes in minute living soft tissues, with the measurements having a high degree of accuracy and precision. Furthermore, this method has significant advantages over conventional approaches as it can be used to rapidly and accurately evaluate the strength of soft tissues during cultivation without causing damage to the specimen.
Authors: Yu Bong Kang, T. Oida, Duk Young Jung, A. Fukuma, T. Azuma, J. Okamoto, O. Takizawa, T. Matsuda, Sadami Tsutsumi
Abstract: In order to evaluate the mechanical properties of the human skeletal muscles, the elasticity and viscosity of the human calf muscles were measured with Magnetic Resonance Elastography (MRE). MRE is a novel method to measure the mechanical properties of living soft tissues in vivo quantitatively by observing the strain waves propagated in the object. In this study, the shear modulus and viscosity coefficient were measured with MRE. The shear modulus was 3.7 kPa in relaxed state, and increased with increasing the muscle forces. Interestingly, the viscosity was changed with the vibration frequency applied to the muscles, that was 4.5 Pa·s at 100Hz vibration and 2.4 Pa·s at 200Hz vibration. This shows clearly the visco-elastic property.
Authors: Dong Wook Han, Han Hee Cho, Duk Young Jung, J.J. Lee, Kazuaki Matsumura, Jong Chul Park, Suong Hyu Hyon
Abstract: In this study, such behaviors of vascular smooth muscle cells (VSMCs), as proliferation and migration, with serum stimulation were investigated onto (−)-epigallocatechin-3-O-gallate (EGCG)-blended poly(L-lactide-co-ε-caprolactone, PLCL) copolymers (EGCG-b PLCL). VSMCs were primarily cultured from rat aorta, and EGCG-b PLCL films were fabricated by mixing PLCL with EGCG. The proliferation of VSMCs cultured onto EGCG-b PLCL film was significantly suppressed in spite of serum induction. Moreover, recovery of denuded area by VSMCs receiving conditioned media obtained from EGCG-b films was completely inhibited, whereas VSMCs onto intact films migrated into denuded area in response to serum showing essentially complete recovery. These results suggest that inhibition in the behaviors of serum-stimulated VSMCs may be mediated through the anti-proliferative effects of EGCG released from polymer films, and EGCG-b polymers can be applied for fabricating an EGCG-eluting vascular stent.
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