Naoki Hata

Distinct and Essential Roles of Transcription Factors IRF-3 and IRF-7 in Response to Viruses for IFN-α/β Gene Induction

Induction of the interferon (IFN)-alpha/beta gene transcription in virus-infected cells is an event central to innate immunity. Mice lacking the transcription factor IRF-3 are more vulnerable to virus infection. In embryonic fibroblasts, virus-induced IFN-alpha/beta gene expression levels are reduced and the spectrum of the IFN-alpha mRNA subspecies altered. Furthermore, cells additionally defective in IRF-7 expression totally fail to induce these genes in response to infections by any of the virus types tested. In these cells, a normal profile of IFN-alpha/beta mRNA induction can be achieved by coexpressing both IRF-3 and IRF-7. These results demonstrate the essential and distinct roles of thetwo factors, which together ensure the transcriptional efficiency and diversity of IFN-alpha/beta genes for the antiviral response.

Positive feedback regulation of type I IFN genes by the IFN‐inducible transcription factor IRF‐7

The interferon regulatory factor (IRF) family of transcription factors regulate the interferon (IFN) system, among which IRF‐3 is involved in the virus‐induced IFN‐β gene expression. Here we show that another member IRF‐7 is critical for the IFN‐α gene induction. Unlike the IRF‐3 gene, the IRF‐7 gene is induced by IFNs through activation of the ISGF3 transcription factor, and IRF‐7 undergoes virus‐induced nuclear translocation. In cells lacking p48, an essential component of IFN stimulated gene factor 3 (ISGF3), ectopic expression of IRF‐7 but not IRF‐3 can rescue the deficiency to induce IFN‐α genes. These results indicate that IRF‐7 is a key factor in the positive feedback regulation of IFN‐α/β production.

Involvement of the IRF family transcription factor IRF-3 in virus-induced activation of the IFN-β gene

The virus‐induced activation of interferon α/β (IFN‐α/β) gene transcription is essential for host defense. The IFN‐β promoter is controlled primarily by the virus‐inducible enhancer elements, the IRF‐Es. Here we show that IRF‐3, an IRF family transcription factor, translocates to the nucleus from the cytoplasm upon virus infection in NIH/3T3 cells. The nuclear IRF‐3 is phosphorylated, interacts with the co‐activators CBP/p300, and binds specifically to the IFN‐β IRF‐E. Furthermore, overexpression of IRF‐3 causes a marked increase in virus‐induced IFN‐β mRNA expression. Thus, IRF‐3 is a candidate transcription factor mediating the activation of the IFN‐β gene.

Integrated Motion Control of a Wheelchair in the Longitudinal, Lateral, and Pitch Directions

The motion of a wheelchair is different from any other vehicle. It needs control in three dimensions: the longitudinal, the lateral, and the pitch direction. This paper takes this point into consideration and provides a 3-D control of a wheelchair. We focus on the control of a push-rim power-assist wheelchair. The main objective of this paper is to provide a wheelchair rider with 3-D assistance that guarantees power and safety. To this end, three kinds of assist controls are proposed: the disturbance attenuation controls are designed for the longitudinal and lateral directions while the tip-over prevention control is designed for the pitch direction. These controls for three directions can be integrated by appropriately taking advantage of system configuration. We demonstrate that all these controls can work independently for each purpose and we show experimental results.

Integrated motion control of a wheelchair in the longitudinal, lateral and pitch directions

The motion of a wheelchair is different from any other vehicles. It needs controlling in the three dimensions: the longitudinal direction, the lateral direction, and the pitch direction. This paper provides this three-dimensional control of a wheelchair taking users manipulation into considerations. A power-assisted wheelchair is the main target of this paper. Three controls for all directions are combined to provide excellent assistance to a user. To this end, for the longitudinal and lateral directions, disturbance attenuation control is designed. For the pitch direction, tip-over protection control is designed. Lastly, we demonstrate all these controls can work independently for each purpose

Proposal of human-friendly motion control: control design for power assistance tools and its application to wheelchair

In this paper, we expand the human-friendly control concept, which has been restricted only to the robot controls into general assistive controls. For a demonstration of this generalized human-friendly control, we adopt a power-assisted wheelchair and apply a novel control to it. We investigate some requirements for this generalized human-friendly control and suggest solutions to it. Our solution approach consists of two parts: one is on the observation problem; the other is on the control problem. We pick up two problems, which happen in power-assisted wheelchair control by gravity. The first is the tendency of falling backward that is related to the observation problem, and the other is the difficulty in propulsion on a hill that is related to the control problem. We propose solutions to each problem, generalize them, and try to establish the human-friendly control.

Control developments for wheelchairs in slope environments

We have developed an observer and controllers for wheelchairs in slope environments in this paper. We select two problems that frequently happen in power-assisted wheelchair caused by gravity. The first problem lies in overturning of wheelchairs and the second problem occurs when the difficulty happens in propulsion of wheelchairs on a hill. The former is related to the observation problem, and the latter is related to the control problem. We would like to propose solutions to the both problems. The observer, which we would like to propose here can estimate three main physical values; (1) the speed of the wheelchair, (2) the leaning angle of the wheelchair body from the ground, and (3) external disturbances. The observer can sensor-fuse the informations from three sensors, which it uses the Kalman filter theory. In order to prevent the problem of the wheelchairs overturning, assistive power by the motor attached to the wheelchair should be decreased according to the state of the wheelchair concerning the leaning angle and its angular velocity. By this, it can realized by using the proposed observer and varying assistance-ratio controller.

A Novel Design and Realization of Robot Arm Based on the Principle of Bi-articular Muscles

Recently there are many trials to introduce animal characteristics into robots. Conventional robot arm has only actuators similar to mono-articular muscles. Though animals arm has not only mono-articular muscles but also bi-articular muscles. Existence of bi-articular muscles can give robots remarkable ability to realize various motions without feedback control, which may provide skillfulness and safety like animals. In this paper, we consider some properties of robot arm based on the principle of bi-articular muscles. We suggest a driving mechanism using equilibrium position originated muscular elasticity. This mechanism realize trajectory tracking as feedforward control in simulations. Finally we described our attempt to make a robot arm based on the principle of bi-articular muscles.

Backward tumbling control for power-assisted wheelchair based on phase plane analysis

We propose a novel control strategy of backward tumbling for power-assisted wheelchair operated by moving the push rims. The power-assistance units of wheelchair amplify the torque applied to the push rims. Excessive amplified torque sometimes causes dangerous backward tumbling. This paper analyzes backward tumbling as the interaction between the position of center-of-mass on man-wheelchair system and its angular velocity on the phase-plane. However, center-of-mass(COM) of man-wheelchair system cannot be directly measured. Therefore, the proposed control method prevents dangerous backward tumbling by decreasing assistance-ratio based on both COM observer to estimate the position of the COM considering some uncertainties; and phase plane analysis using the estimated. We show the effectiveness of the proposed control method in some experiments.

Prevention of overturn of power assisted wheelchair using novel stability condition

Last 10 years we have been experiencing a constant evolution in the field of power assisted wheelchairs, which allows more flexibility of use for disabled people. However, motor output is quite big, and without proper control, power assisted wheelchair are much easier to fall backward than traditional ones. Therefore, in this work, to prevent the overturn, three kinds of stability conditions, including the novel one based on Lagrange equation have been proposed. They are compared by using experimental data and the best one is adopted. Its validity, as well as practicality, is authenticated by experiments on both horizontal plane and slope.