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Biomedical subjects

Ichiro Tsuda

Publications and source records attributed to Ichiro Tsuda.

8 recordsLinked to original sources
PubMed2006

Clinical study of therapeutic angiogenesis by autologous peripheral blood stem cell (PBSC) transplantation in 92 patients with critically ischemic limbs.

Patients with critically ischemic limbs due to maintenance hemodialysis and diabetes are increasing in number markedly in Japan. The difficulty of treating critically ischemic limbs is well recognized. Despite active medication and surgical therapy, many critically ischemic limbs are amputated. Ninety-two patients with critically ischemic limbs were treated by transplantation of autologous peripheral blood stem cells (PBSCs). The stem cells were mobilized into the peripheral blood by administration of granulocyte colony stimulating factor (G-CSF). The mobilized mononuclear cells were separated by an apheresis technique using a centrifuge. The separated mononuclear cells contained approximately 4.0 x 10(7) CD34-positive cells. The collected cell suspension was divided into aliquots of 0.5-1.0 ml and transplanted into the muscle of ischemic limbs at 50-70 transplantation points. At 1.5 months after PBSC transplantation, a strong immunostaining of CD34-positive cells and factor VIII, as well as capillary formation, was observed in the muscles into which stems cells had been transplanted. In each patient tested, the serum vascular endothelial growth factor (VEGF) level increased after stem cell transplantation; the mean VEGF level increased by 176%. Of 11 diabetic patients (DM) who were not receiving hemodialysis (HD), there were no amputees regardless of their Fontaine classification. Of 19 patients in the HD(+)DM(-) category, there were no amputations in Fontaine stage I, II, and III patients, whereas three limbs and one toe were amputated in Fontaine stage IV patients. Of 13 patients in the HD(-)DM(+) category, none of the Fontaine stage I, II, or III patients underwent amputation, but six Fontaine stage IV patients underwent amputation. Of 49 patients in the HD(+)DM(+) category, 38 (78%) were classified as Fontaine stage IV, 71% (27/38) of whom had a toe or a limb amputated. In nine patients over 80 years of age, one toe and one limb were amputated. Nondiabetic, nondialyzed patients with ischemic limbs are strongly indicated for stem cell transplantation regardless of Fontaine classification. Therapeutic angiogenesis is effective for critically ischemic limbs resulting from hemodialysis and diabetes until Fontaine stage III, but is of limited effectiveness for stage IV cases.

Adult↗
PubMed2004

Prologue--The pioneering work of the late professor Gen Matsumoto.

The late Professor Gen Matsumoto not only accomplished pioneering work of neuroscience such as nerve excitation as a dissipative structure in far-from-equilibrium systems but also inspired many students and young researchers by his sincere and attractive personality.

Brain↗
PubMed2004

Chaotic itinerancy as a mechanism of irregular changes between synchronization and desynchronization in a neural network.

We investigate the dynamic character of a network of electrotonically coupled cells consisting of class I point neurons, in terms of a finite dimensional dynamical system. We classify a subclass of class I point neurons, called class I* point neurons. Based on this classification, we use a reduced Hindmarsh-Rose (H-R) model, which consists of two dynamical variables, to construct a network model consisting of electrotonically coupled H-R neurons. Although biologically simple, the system is sufficient to extract the essence of the complex dynamics, which the system may yield under certain physiological conditions. The network model produces a transitory behavior as well as a periodic motion and spatio-temporal chaos. The transitory dynamics that the network model exhibits is shown numerically to be chaotic itinerancy. The transitions appear between various metachronal waves and all-synchronization states. The network model shows that this transitory dynamics can be viewed as a chaotic switch between synchronized and desynchronized states. Despite the use of spatially discrete point neurons as basic elements of the network, the overall dynamics exhibits scale-free activity including various scales of spatio-temporal patterns.

Action Potentials↗
PubMed2004

Functional relevance of 'excitatory' gaba actions in cortical interneurons: a dynamical systems approach.

The non-classical, but frequently reported behavior of GABA(A) receptor-mediated excitation in mature CNS has long been regarded as a puzzle. We theorize that the function of cortical GABAergic interneurons, which might constitute a subsystem of brain's GABA interneurons, is their ability of switching from inhibitory action to excitatory action depending on the level of spatio-temporal activity in progress. From the perspective of a dynamical systems approach, such "excitatory" GABAergic responses may serve to temporarily invoke attractor-like memories when extensively activated by, for example, top-down signals as category information or attention, while an ongoing background state of GABA changes its action to inhibition, returning the dynamical nature of the memory structure back to attractor ruins.

Action Potentials↗
PubMed2003

Chaotic itinerancy generated by coupling of Milnor attractors.

We report the existence of chaotic itinerancy in a coupled Milnor attractor system. The attractor ruins consist of tori or local chaos generated from the original Milnor attractors. The chaotic behavior exhibited by a single orbit can be considered a "nonstationary" state, due to the extremely slow convergence of the Lyapunov exponents, but the behavior averaged over randomly chosen initial conditions is consistent with the limit theorem. We present as a possibly new indication of chaotic itinerancy the presence of slow decay of large fluctuations of the largest Lyapunov exponent.

Journal Article↗
PubMed2003

Chaotic itinerancy.

Chaotic itinerancy is universal dynamics in high-dimensional dynamical systems, showing itinerant motion among varieties of low-dimensional ordered states through high-dimensional chaos. Discovery, basic features, characterization, examples, and significance of chaotic itinerancy are surveyed.

Journal Article↗
PubMed1998

Singular-continuous nowhere-differentiable attractors in neural systems.

We present a neural model for a singular-continuous nowhere-differentiable (SCND) attractors. This model shows various characteristics originated in attractor's nowhere-differentiability, in spite of a differentiable dynamical system. SCND attractors are still unfamiliar in the neural network studies and have not yet been observed in both artificial and biological neural systems. With numerical calculations of various kinds of statistical quantities in artificial neural network, dynamical characters of SCND attractors are strongly suggested to be observed also in neural systems experiments. We also present possible information processings with these attractors.

Journal Article↗