Phase-contrast imaging of living tissue is one of the most important techniques for investigating biological structures. We have developed phase-contrast optical microscopy by integrating dynamic hollow-cone illumination and active image processing to visualize the phase and amplitude structures of biological tissues. A figure-of-8-shaped median spatial frequency enhancement filter, which had an optical transfer function with sign correction and was split into two areas, was applied to extract separate phase and amplitude spectra of biological tissues. All spatial frequencies were covered by superimposing the figure-of-8-shaped optical transfer functions at different azimuth angles. Imaging revealed clear phase and absorptive liver structures, such as those of lymphocytes and cell nuclei. We also evaluated the imaging features of the microscope using transparent microspheres, and examined the possibility of applying it to the observation of thick biological tissue by reducing nonlinear imaging components.
This study investigated the effect of haptic and position sensory input through contact with cloth on physiological tremor (PT) during postural maintenance. Eleven healthy, right-handed females in the sitting position were asked to raise their left upper limbs forward while extending their hands and fingers for 30 s under two different conditions. One condition was to normally hold this posture. The other was to maintain the posture while the forearm was in light contact with a piece of cloth. During posture maintenance, the PT signal of the forearm was measured using an acceleration sensor and analyzed by power spectrum analysis. The amplitude of PT decreased significantly during contact with the cloth. This decrease was primarily influenced by frequency components < 4.9 Hz. Furthermore, changes in amplitude of PT correlated with changes in frequency components < 4.9 Hz (r = 0.85, p < 0.01). These findings suggest that the haptic sensory input through light contact with cloth provides information about the relative movement of the limb. This contact allows posture to be maintained easily because of the influence of the stretch reflex mechanism (frequency components < 4.9 Hz).
Ultraviolet (UV) radiation exerts adverse effects on genome stability, alters the normal state of life, and causes many diseases by inducing DNA damage. Although mechanical stimulation, such as stretching and compressing, to cells has beneficial effects in the prevention and treatment of diseases, whether it influences the nuclear morphology and/or intranuclear functions associated with DNA damage remains unknown. In this study, we investigated the effects of mechanical stimulation by cyclic stretching on nuclear morphology and resistance to UV radiation of DNA in epithelial-like cells derived from Xenopus laevis (XTC-YF). Cells adhering to silicone membranes were subjected to 10% cyclic uniaxial stretch at a frequency of 0.5 Hz for 12 h. We observed that the intracellular actin cytoskeleton and nucleus became elongated and aligned with the direction ofzero normal strain (∼62° with respect to the stretch direction) following the cyclic stretch exposure. The fluorescent intensity ofintranuclear DNA, which represents the DNA density, increased significantly. The intercellular tension, assessed by the retraction of cells upon detachment from the silicone membrane, also increased following the cyclic stretch exposure. Furthermore, UV radiation-induced DNA damage, estimated by the fluorescent intensity ofphospho-histone γ-H2AX, was significantly inhibited following the cyclic stretch exposure. These results indicate that cyclic stretch-induced morphological changes ofthe nucleus possibly improve the UV radiation resistance in XTC-YF cells, and this improvement may be caused by intracellular force-induced chromatin condensation. To our knowledge, this study is the first to demonstrate the inhibition of UV radiation-induced DNA damage by mechanical stimulation.