The purpose of this study is to propose a quantitative method of image analysis of the behavior of captured animals with video surveillance systems with a variable acquisition rate. A total of 11 male C57BL/6J mice (aged 6-119 weeks) were used for the experiments. The behavior of the animals in the house cage was recorded for two hours. Matlab was used for image analysis. The projected form of the animal was quantified in the binary image, and the center of gravity was measured to determine the position of the animal in the cage. In each animal position, an area of the animal form and the residence time of the center of gravity in each pixel were calculated. The amount of animal motion between two consecutive frames was also measured. To test the compression of the recorded movie, the image was resampled from 30 to 3 frames per second. If the acquisition rate was set at 3 frames per second, the animal’s travel distance and resting time was underestimated on average of 27±8% and 54±13%, respectively, relative to the captured image at 30 frames per second. In contrast, the maximum residence time was not influenced by the acquisition rate. Furthermore, referring to xy coordinate of the center of gravity of the animal, it was possible to compare the regional difference in the animal form. We observed a significantly larger area of the animal’s form in the surrounding areas relative to the center of the cage. The results were consistent with the short length of stay in the surrounding areas relative to the center of the cage, which indicate that the animal moved more actively near the wall of the cage. Finally, 24-hours monitoring of animal behavior with the infrared camera system at a rate of acquisition of 3 frames per second showed a successful characterization of the animal behavior patterns corresponding to the measurements of animal movements. In conclusion, the present method of image analysis based on the maximum residence time of the animal’s center of gravity allows for regional comparisons of animal behavior and for reliable quantification independent of the acquisition rate of the monitoring systems.

In our previous study, we developed heart valve-like tissue (Biovalve), which was fabricated by employing the technique of in-body tissue architecture (iBTA). We fabricated Biovalve so that it can closely mimic the functionalities of the native mitral valve, papillary muscles, and chordae tendineae. However, owing to its complex structure, Biovalve has not yet been implemented. Hence, the objective of this study is to develop a novel artificial atrioventricular valve by incorporating a sheet of autologous tissue (Biosheet) through iBTA. Since a period of approximately two months is required for obtaining Biosheet, it is unsuited for developing the aforementioned artificial valve. Hence, we fabricated an experimental model by employing a polyurethane sheet, which has comparable mechanical properties as Biosheet. To validate the experimental model, the valve functions of the actual model and experimental model were compared by using Biosheet and the polyurethane sheet, respectively. Furthermore, to determine the optimal shape of the valve cusps, the amount of sheet overhanging from the stent, sheet suture angle, and sheet thickness were varied as experimental parameters. A model of the valve cusps with mechanical anisotropy was fabricated by sandwiching Ni-Ti alloy wires between two polyurethane sheets and thermally welding them. Subsequently, an isotropic model and the fabricated anisotropic model were compared. The experiment was conducted by incorporating our fabricated in-vitro simulator under the physiological conditions of a healthy adult human. The valve function was evaluated on the basis of the ISO 5840-1 and ISO 5840-2 international standards for artificial valves. The obtained results indicate that the valve functions of the actual model and experimental model are nearly identical, which confirms the validity of the experimental model. Furthermore, in the case of the anisotropic model, it is found that when the sheet thickness is 200µm, sheet overhang is 3mm, and suture angle is 0 deg. , the pressure drop reduces by approximately 25%and the regurgitant fraction decreases by approximately 90%, as compared to the isotropic model of the same shape. These results suggest that anisotropic valve cusps can improve both valve opening and closing functionalities.

To prevent nosocomial transmission of new coronavirus variants and strains (COVID-19), containers that can be used for PCR testing outside hospitals is under development. In this study, to investigate the risk of COVID-19 infection while in a container for PCR testing, we performed computational fluid dynamics simulations of the airflow in the container and the aerosol dispersion emitted from the subject. The 3D model of the container, consisting of a doctor’s room, a PCR examination room, and a waiting room, was configured based on a container installed at the Higashi Chiba Medical Center. Models of the subject and examiner were configured based on measurements of shape and posture obtained using a 3D scanner. Simulations were performed by varying the average particle size of the aerosol (1µm, 10µm, 80µm) and the orientation of a seated subject (four equally spaced orientations). Aerosol contamination in the container was evaluated by counting the aerosols suspended in the air and deposited in the room. From the results, contamination outside the PCR test room may be prevented by installing an exhaust port in the testing room and using an air conditioning system to control airflow. The ratio of aerosols suspended and deposited in the PCR room to the total number of emissions varied from 16% to 46% (1µm) and from 22% to 69% (10µm) for small-sized particles and depended on the orientation of the subject. This ratio was found to be lowest when the airflow from the subject to the exhaust port was not blocked by the examiner. For large-sized particles (80µm), the ratio was approximately 94% regardless of the orientation of the subject, indicating that most of the aerosols had deposited either on the subject or the floor.

During the course of evolution, the vertebrate heart has undergone many changes and adaptations. Transition from aquatic to terrestrial environments required the ability to circulate blood against the force of gravity;therefore, it is likely that the structure and function of the ventricles changed during this transition. In the present study, we focused on pressure resistance in amphibians which were the first vertebrates to migrate to land. We investigated the pressure resistance and histology of the ventricles of three Anuran species (frogs and toads) from different habitats:the African clawed frog (aquatic), dark-spotted frog (semiaquatic), and Japanese common toad (terrestrial). To analyze the pressure resistance of the ventricles, intraventricular pressure was recorded during continuous injection of cardioplegic solution into the ventricles. The results showed that maximum stiffness, the pressure at which the solution leaked from the ventricle, and the maximum ventricular pressure were the highest in the Japanese common toad among the three species, demonstrating that the ventricles of the Japanese common toad were the stiffest and had the highest pressure resistance. To determine the factors responsible for the differences in pressure resistance, we measured the thickness of ventricle walls and the amount of collagen fibers in ventricle walls. The wall of the ventricles of the Japanese common toad and dark-spotted frog were thicker than that of the African clawed frog. The isolated cardiomyocyte size was similar for all the species, suggesting that the ventricular wall of the Japanese common toad and dark-spotted frog became thicker not by hypertrophying cardiomyocytes, but by increasing the number of cardiomyocytes. The collagen fibers in the ventricular wall of the Japanese common toad were richer compared to those of the African clawed frog and dark-spotted frog. Taken together, these results suggest that the pressure resistance in Anura increased through the increase in collagen. Vertebrate ventricles may have become resistant to higher pressure as an adaptive process to terrestrial life that facilitates blood circulation against the force of gravity.

In recent years, the regenerative treatment of osteoarthritis (OA) by transplantation of autologous cultured cartilage has been developed, but biomechanical diagnostic evaluation of cartilage has not yet been performed in the follow-up after transplantation as well as typical OA diagnostic treatment. In this study, we constructed an Optical Coherence Doppler Velocigraphy (OCDV) system based on low coherence interferometer (OCT) and a compression tester as loading device, which can provide micro-tomographic visualization of tissue deformation and joint fluid flow inside cartilage tissue. The constructed system was applied to not only the normal sample of porcine knee cartilage but also the simulated degenerative one by collagenase enzyme treatment for 2 hours. As experimental results, during compression period, the both cartilage samples in the middle layer were observed to move toward surface, generating the compressive strain further in superficial layer. Doppler velocity of the degenerated cartilage was detected to be about 50µm/sec in the middle layer, which was twice as high as that of normal cartilage. Just after stress relaxation, Doppler velocity decreased immediately to be less than 5µm/sec in the normal cartilage, whereas are keeping about 10µm/sec in the degenerated one. These are considered to be due to the decrease in biomechanical properties, i. e. visco-elasticity, of degenerated cartilage. In conclusions, the proposed method can discriminate quantitatively between normal and OA cartilage from the spatiotemporal change of the detected Doppler velocity, in the virtue of revealing microscopic tissue deformation and joint fluid flow with high spatio-temporal resolution, therefore OCDV has an effective potential as a real-time diagnostic imaging system.