Journal of Biomechanical Science and Engineering
Online ISSN : 1880-9863
ISSN-L : 1880-9863
Volume 7, Issue 3
Displaying 1-4 of 4 articles from this issue
  • Noriko TOMITA, Yoshiyuki KAMIO, Makoto OHTA
    2012 Volume 7 Issue 3 Pages 292-304
    Published: 2012
    Released on J-STAGE: June 15, 2012
    Staphylococcal γ-hemolysin (Hlg) is a two-component cytolysin, which consists of LukF (Hlg1) and Hlg2. Our previous study has suggested that LukF and Hlg2 are alternatively arranged on the human erythrocyte membrane and form a ring-shaped heterooligomeric transmembrane pore with a functional diameter of approximately 2 nm. Quantitative image analyses using high-resolution transmission electron microscopy have revealed that LukF and Hlg2 tend to be arranged in several mismatch patterns. Several previous studies have reported that the LukF component has a binding pocket for phosphatidylcholine. In the present study, membranedamaging activities by Hlg were investigated by using carboxyfluoresceine (CF)-loading liposomes consisting of mammalian erythrocyte phospholipids or one kind of phospholipid. Our results revealed that Hlg shows membrane-damaging activities on horse, rabbit and human erythrocyte total phospholipid liposomes. Such activity was closely related to the ratio of phosphatidylcholine. Hlg showed membrane-damaging activity against phosphatidylcholine liposome by formation of ring-shaped pore complex and cluster. Besides, it was revealed that Hlg could target cardiolipin, which is not included in the mammalian erythrocyte membrane, but exists in the bacterial cytoplasmic membrane and in the inner mitochondrial membrane of mammal cell. The results suggest that Hlg has the potential to recognize several phospholipids in both erythrocyte and non-erythrocyte membranes and induce cytolysis not only of mammalian cells but also of bacterial cells by the formation of pores and clusters. These novel findings will contribute to the elucidation of mutual actions between cytotoxicity protein and phospholipids, and eventually lead to the development of a treatment for staphylococcal infection.
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  • Yo KOBAYASHI, Takahiro SATO, Takeharu HOSHI, Masakatsu G. FUJIE
    2012 Volume 7 Issue 3 Pages 305-317
    Published: 2012
    Released on J-STAGE: June 15, 2012
    Needle insertion treatments require accurate placement of a needle tip into the target cancer. However, it is difficult to insert the needle into a lesion because of tumor displacement during organ deformation. Therefore, path planning using a needle insertion simulation to analyze deformation of an organ is important for accurate needle insertion. A frictional model for needle insertion simulation is presented in this report. In particular, we focus on a model of frictional force based on the relative velocity between a needle and liver tissue ranging from hyper to slow velocity. In vitro experiments using porcine liver were performed at several relative velocities to measure the velocity dependence of the frictional force. Sixty trials of frictional force data were used to obtain average data at each relative velocity. The model of frictional force was then developed using the averages of the experimental results. This model was defined according to relative velocity, including hyper-slow velocity. Our modeling and experimental results show that the frictional force between the tissue and the needle increased during low relative velocity (under 1.5mm/s) and became constant (over 1.5mm/s).
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  • Shigeo M. TANAKA
    2012 Volume 7 Issue 3 Pages 318-327
    Published: 2012
    Released on J-STAGE: July 03, 2012
    In bone cells, intracellular Ca2+ (iCa2+) functions as a second messenger in the mechanotransduction pathway. Its responses to mechanical stimulation can be observed microscopically on a rigid flat surface with a Ca2+ fluorescent indicator, generally, under fluid flow. However, bone cells are physiologically exposed to dynamic loading accompanied by bone matrix deformation. In this situation, microscopic methods of observing iCa2+ responses cannot be used because of the loss of focus or movement of cells out of the observation area. The purpose of this study was to develop a compact optical device for the observation of iCa2+ responses of osteoblasts to dynamic loadings accompanied by substrate deformation. This system comprised four light emitting diodes (LEDs) and a photodetector (PD) placed underneath a culture chamber, specifically designed for tissue-level iCa2+ observations. This device was used to study the frequency dependence of iCa2+ responses of osteoblasts to dynamic loading. MC3T3-E1 osteoblasts were cultured three-dimensionally in a collagen sponge scaffold with the fluorescent Ca2+ indicator Fluo-4 AM and mechanically stimulated by a 0.2% deformation of the sponge at 0.2, 2, or 20 Hz for 150 s. Our device succeeded in detecting temporal changes in the intensity of emitted fluorescent light, showing a frequency-dependent increase in fluorescence intensity. This device may contribute to further understanding of the mechanosensing and mechanotransduction mechanisms in bone under near-physiological conditions.
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  • Takeshi ANDO, Kazuya KAWAMURA, Junko FUJITANI, Tomokazu KOIKE, Yukiko ...
    2012 Volume 7 Issue 3 Pages 328-334
    Published: 2012
    Released on J-STAGE: August 01, 2012
    Improvement of thoracic mobility is important for patients with diseases such as chronic obstructive pulmonary disease (COPD). Chest expansion training is often conducted to increase the thoracic excursion. However, it is difficult for the patients to keep the motivation for rehabilitation, because the chest excursion is only measured. In this paper, we analyze the effect of real-time biofeedback on thoracic excursion. In 30 healthy subjects, thoracic excursion was increased by 6 mm (17%) when using the biofeedback system. Our results confirmed that we have developed an effective system for rehabilitation of respiratory function.
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