RESUMEN
The viscoelastic properties of the human arm were measured by means of short force perturbations during fast reaching movements in two orthogonal directions. A linear spring model with time delay described the neuromuscular system of the human arm. The obtained viscoelastic parameters ensured movement stability in spite of the time delay of 50 ms. The stiffness and viscosity ellipses appeared to be predominantly orthogonal to the movement direction, which reduced the effect of force perturbation in the direction orthogonal to the reaching movement. Thus, it can be argued that the viscoelastic properties of the neuromuscular system of the human arm are adjusted to the direction of movement according to a "path preserving" strategy, which minimizes the deviation of the movement path from a straight line, when exposed to an unexpected external force.
Asunto(s)
Adaptación Fisiológica/fisiología , Brazo/fisiología , Movimiento/fisiología , Desempeño Psicomotor/fisiología , Adulto , Brazo/inervación , Fenómenos Biomecánicos , Electromiografía , Retroalimentación , Humanos , Modelos Lineales , Masculino , Persona de Mediana Edad , Modelos Biológicos , Músculo Esquelético/fisiología , Dinámicas no Lineales , Tiempo de Reacción , Reflejo de Estiramiento/fisiología , Factores de TiempoRESUMEN
Interaction of two groups of bioregulators, which oppositely affect activity of adenylate cyclase and phosphoinositide cellular signaling systems, with the Langmuir monolayer films made of natural lecithin was studied. Most significant influence on the structural and energy characteristics of lipid monolayers was revealed for the group of bioregulators, which inhibit polyphosphoinositide signaling system or/and activate adenylate cyclase signaling system. It is shown, that using the cluster analysis the bioregulators can be divided into two groups according to general orientation of their action on the considered systems of transduction of a signal.
Asunto(s)
Adenilil Ciclasas , Membrana Celular/metabolismo , Membranas Artificiales , Modelos Biológicos , Fosfatidilinositoles , Transducción de Señal , Inhibidores de Adenilato Ciclasa , Adenilil Ciclasas/química , Membrana Celular/efectos de los fármacos , Análisis por Conglomerados , Metabolismo Energético/efectos de los fármacos , Humanos , Metabolismo de los Lípidos/efectos de los fármacos , Preparaciones Farmacéuticas/administración & dosificación , Fosfatidilcolinas/química , Fosfatidilinositoles/antagonistas & inhibidores , Fosfatidilinositoles/química , Transducción de Señal/efectos de los fármacosRESUMEN
3D dipole tracing with 1 ms step of visual evoked potentials recorded from 40 electrodes was performed under exposition of crosses in 5 healthy human subjects. The data on dipole displacement were compared with prediction of the simulation study on distortion of dipole localization by the signal filtration in the low-frequency band. These predictions were experimentally confirmed: the effect depends on the degree of filtration (0.1 or 0.5 Hz) and on the latency of EP waves. Localization and strength of P1 dipoles were not changed under filtration, while for later components--N2 and especially P3--they changed significantly. For the improvement of these distortions time constant of the amplification tract must be some times longer than the time of the dipole activity.
Asunto(s)
Encéfalo/fisiología , Potenciales Evocados Visuales/fisiología , Electroencefalografía , Electrooculografía , Filtración , Humanos , Neurofisiología , Percepción Visual/fisiologíaRESUMEN
We are proposing a human arm model that consists of three rigid segments with seven degrees of freedom. The shoulder joint was modeled as a ball-and-socket joint and the elbow and wrist joints were modelled as skew-oblique joints. Optimal parameters for this model were calculated on the base of in vivo recordings with a spatial tracking system. The criterion of optimality was defined as the minimum of the mean-square deviation between the experimentally obtained sensor positions and orientations and their positions and orientations calculated by solving the direct kinematics problem. The minimal value of the direct kinematics error was found to be 0.5-0.6cm for sensor positions and 5-7 degrees for sensor orientations. We are proposing that these values serve as the assessment for the accuracy of the arm model.
Asunto(s)
Brazo/fisiología , Modelos Biológicos , Adulto , Brazo/anatomía & histología , Fenómenos Biomecánicos , Diagnóstico por Imagen/instrumentación , Diagnóstico por Imagen/métodos , Diagnóstico por Imagen/normas , Fenómenos Electromagnéticos/instrumentación , Fenómenos Electromagnéticos/normas , Femenino , Humanos , Articulaciones/fisiología , Masculino , Persona de Mediana Edad , Movimiento , RotaciónRESUMEN
The paper deals with the methodological features of investigations of the interaction of cells and foreign material surfaces by scanning electron microscopy. The proposed technique for obtaining electron microscopic images results in their easy binarization and further treatment using computer software. The specificity of obtaining electron microphotographs permits detailed quantitative image analysis. This approach enables one to study both quantity of objects and their individual morphologies, as well as to define distributions of objects by their diameter, area, etc. Human platelet adhesion to glass and metal is considered as an example.
Asunto(s)
Adhesión Celular , Procesamiento de Imagen Asistido por Computador , Microscopía Electrónica de Rastreo , Adhesividad Plaquetaria , Aluminio , Vidrio , Humanos , Fotomicrografía , Programas Informáticos , Factores de TiempoRESUMEN
Effects of chlorpromazine, haloperidol (neuroleptics and calmodulin antagonists), and verapamil on rat platelet aggregation induced by thrombin, on calcium current in snail neurones and on both tonic tension of high potassium contracture and phasic contraction of isolated guinea-pig ureter preparations were studied. Moreover, droperidol, sulpiride and prazosine effects were studied for models of phasic contractility and platelet aggregation. Sulpiride and prazosine were ineffective, verapamil was ineffective on platelet aggregation, while droperidol was the most potent inhibitor of platelet aggregation. These results, the similarity revealed in the blockage of neuronal calcium current by neuroleptics and verapamil, and the potent inhibitory action of haloperidol and chlorpromazine on contractility and aggregation suggest that both phenothiazine and butyrophenone neuroleptics possess some properties of calcium antagonists and may also have intracellular sites of action other than calmodulin.
Asunto(s)
Antipsicóticos/farmacología , Canales de Calcio/fisiología , Clorpromazina/farmacología , Haloperidol/farmacología , Contracción Isométrica/efectos de los fármacos , Músculo Liso/fisiología , Neuronas/fisiología , Inhibidores de Agregación Plaquetaria/farmacología , Agregación Plaquetaria/efectos de los fármacos , Animales , Butirofenonas/farmacología , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio/efectos de los fármacos , Calmodulina/antagonistas & inhibidores , Droperidol/farmacología , Estimulación Eléctrica , Cobayas , Técnicas In Vitro , Masculino , Músculo Liso/efectos de los fármacos , Neuronas/efectos de los fármacos , Fenotiazinas/farmacología , Prazosina/farmacología , Ratas , Ratas Wistar , Caracoles , Sulpirida/farmacología , Trombina/farmacología , Uréter , Verapamilo/farmacologíaRESUMEN
The effects of specific agonists and antagonists of adrenoceptors and inhibitors of cAMP phosphodiesterase on electrostimulated phasic contractions in the ureter of guinea pig were studied. It has been shown that there mainly excitatory alpha 1-adrenoceptors in this object, the density of beta-adrenoceptors is slight and functional alpha 2-adrenoceptors are probably absent. Some aspects of adrenergic regulation of the contractile function of guinea pig ureter are discussed.