Biomedical subjects

Takashi Yoneyama

Publications and source records attributed to Takashi Yoneyama.

3 recordsLinked to original sources

PubMed2004

Pro-oxidative effect of alpha-tocopherol in the oxidation of LDL isolated from co-antioxidant-depleted non-diabetic hemodialysis patients.

The association between the antioxidants in LDL and the oxidizability of LDL assessed by the oxidation lag time during copper ion-catalyzed oxidation was investigated in 69 non-diabetic hemodialysis patients and 23 healthy volunteers. The concentrations of co-antioxidants, including ubiquinol-10, lycopene and beta-carotene, in LDL were significantly lower in the hemodialysis patients than in the healthy volunteers, while there was no difference in the alpha-tocopherol concentration between the groups. The lag time showed a significantly positive correlation with the alpha-tocopherol level (r = 0.62, P < 0.01) in the healthy subjects, but a significantly negative correlation (r = -0.38, P < 0.05) in the hemodialysis patients. Furthermore, in vitro incubation of LDL with alpha-tocopherol prolonged the lag time in the healthy subjects, but shortened it in the hemodialysis patients. These results suggested that the alpha-tocopherol might exert the pro-oxidative effect in co-antioxidant-depleted LDL that was isolated from the hemodialysis patients. Despite such co-antioxidant depletion and the pro-oxidative effect of alpha-tocopherol, the lag time in the hemodialysis patients was not statistically different from that in the healthy volunteers. This might have been because the polyunsaturated fatty acids concentration, another determinant of the lag time, in LDL was less in the hemodialysis patients than in the healthy controls.

Aged↗

PubMed2004

A competitive wavelet network for signal clustering.

This correspondence proposes a novel signal clustering method based on the unsupervised training of a wavelet network. The synaptic weights are parameterized by wavelet basis functions, which are adjusted by a competitive algorithm that makes use of the neighborhood concept proposed by Kohonen. The robustness of the wavelet network with respect to noise is illustrated in a simulated problem, in which dynamic systems are grouped on the basis of their step responses. An example involving clustering of electrocardiographic signals taken from the MIT-BIH database is also presented. In this case, the ability of the proposed network to perform clustering at successive resolution levels is illustrated. The possibility of interpreting the information encoded in the network at the end of training is also discussed.

Letter↗

PubMed2002

Short and long period optimization of drug doses in the treatment of AIDS.

Numerical optimization techniques are useful in solving problems of computing the best inputs for systems described by mathematical models and when the objectives can be stated in a quantitative form. This work concerns the problem of optimizing the drug doses in the treatment of AIDS in terms of achieving a balance between the therapeutic response and the side effects. A mathematical model describing the dynamics of HIV viruses and CD4 cells is used to compute the short term optimal drug doses in the treatments of patients with AIDS by a direct method of optimization using a cost function of Bolza type. The model parameters were fitted to actual published clinical data. In order to simplify the numerical procedures, the control law is expressed as a series and the sub-optimal control is obtained by truncating the higher terms. When the patient reaches a clinically satisfactory state, the LQR - Linear Quadratic Regulator technique is used to determine the long period maintenance doses for the drugs. The doses computed using the LQR technique tend to be smaller than equivalent constant-dose therapy in terms of increase in the counts of CD4+T cells and reduction of the density of free viruses.

Acquired Immunodeficiency Syndrome↗