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Biomedical subjects

R Suzuki

Publications and source records attributed to R Suzuki.

At least 757 records · Page 42Linked to original sources
PubMed1979

Studies on human finger tapping neural networks by phase transition curves.

The human finger tapping was studied psychologically by the phase transition curves. We assumed that some oscillatory neural network controls the tapping. One of our future works on the human finger tapping is to devise a method to change the magnitude of perturbation continuously in phase resetting experiments of a constant tapping interval with a same kind of task. If this is achieved, we can obtain a phase transition surface (i.e. the new phase as a function of the old phase and the magnitude of perturbation). From the shape of a phase transition surface, the intrinsic properties of the oscillatory network which controls the tapping can be studied (Kawato et al., 1978).

Conditioning, Psychological↗
PubMed1979

The application of the Gierer-Meinhardt equations to the development of the retinotectal projection.

Model calculations are presented for the several properties of the development of the retinotectal projection in amphibians and fishes, using the Gierer-Meinhardt equations. One of these properties is the maintenance of topographic mapping between the retina and the tectum during their development despite the fact that the two tissues grow in morphologically different ways. Another is the existence of a "critical period", at which the coordinates of the retina with respect to the tectum are irrevocably determined. It is assumed that the connections between the retinal and the tectal cells are made on the correspondence of positional markers which are given as a form of the distribution of a specific activator, the dynamics of which is described by the Gierer-Meinhardt equations. The monotonic distributions of the activator and the existence of the critical period are shown by a computer simulation of the proliferating retina. Several changes of the retinotectal projection after surgical operations on the retina or the tectum are also explained.

Amphibians↗
PubMed1979

Synergism and antagonism of neurons caused by an electrical synapse.

To investigate the role of electrical junction, a model system consisting of two electrically coupled neurons was studied. It was revealed that the model system generates both the in-phase pattern and the anti-phase pattern stably. Physiological condierations revealed the following. The in-phase discharge pattern (synergism) is a unique output of a electrically coupled pacemaker neurons. However, both the in-phase (synergism) and the anti-phase (antagonism) discharge patterns are possible for electrically coupled bursting neurons. We may expect other discharge patterns, such as a random discharge pattern (chaos), than the inphase and the anti-phase pattern in electrically coupled neurons. Random firing patterns in the inferior olive may be attributed to electrical synapses. Until now, we have assumed that excitation periods of two neurons were almost the same. When two periods are greatly different, various phenomena are expected. Determination of the stability of the anti-phase solution by the analytical methods, when diffusion constants are very small, is one of our future problems.

Action Potentials↗
PubMed1978

Determination of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (virazole) in blood and urine by chemical ionization-mass fragmentography.

A combined gas chromatographic-mass spectrometric technique is described for the quantification of virazole in serum and urine. Proteins are removed by molecular filtration, lipids by extraction with dichloromethane and interfering endogenous constituents by acidic and basic ion-exchange resins. Virazole is quantified by monitoring the protonated molecular ions of the fully silylated derivatives of virazole (m/e 533) and the arabinose analog (internal standard) obtained by methane chemical ionization. The detection limit is 150 pg (0.6.10(-12) mole) of virazole injected. In serum 10 ng/ml (4.10(-8) mole) can be detected, 25 ng/ml quantified. In urine 0.5 microgram/ml can be quantified without preconcentration. Virazole was detected in serum for at least 96 h at the 70-ng/ml level.

Gas Chromatography-Mass Spectrometry↗
PubMed1978

Biological oscillators can be stopped--topological study of a phase response care.

Many biological oscillators are stable against noise and perturbation (e.g. circadian rhythms, biochemical oscillators, pacemaker neurons, bursting neurons and neural networks with periodic outputs). The experiment of phase shifts resulting from discrete perturbation of stable biological rhythms was developed by Perkel and coworkers (Perkel et al., 1964). By these methods, they could get important insights into the entrainment behaviors of biological rhythms. Phase response curves, which are measured in these experiments, can be classified into two types. The one is the curve with one mapping degree (Type 1), and the other is that with zero mapping degree (Type 0) (Winfree, 1970). We define the phase response curve mathematically, and explain the difference between these two types by the homotopy theory. Moreover, we prove that, if a Type 0 curve is obtained at a certain magnitude of perturbation, there exists at least one lower magnitude for which the phase response curve cannot be measured. Some applications of these theoretical results are presented.

Acclimatization↗
PubMed1978

Mass fragmentographic determination of pyrazinamide and its metabolites in serum and urine.

A combined gas chromatographic-mass spectrometric technique is described for the simultaneous determination of pyrazinamide and its two main metabolites, pyrazinoic acid and 5-hydroxypyrazinoic acid. Serum (200 microliter) is deproteinized and evaporated to dryness; urine (20 microliter) is evaporated. The crude residues are silylated and selected ions are monitored in the chemical-ionization mode with isobutane as both chromatographic carrier and reagent gas. The sensitivity is 10 ng/ml for pyrazinamide and pyrazinoic acid and 20 ng/ml for the 5-hydroxy metabolite in a single analysis. Nicotinic acid and nicotinamide are internal standards. Both unchanged drug and metabolites were identified and quantified in the serum and urine of human subjects.

Gas Chromatography-Mass Spectrometry↗