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H Mino

Publications and source records attributed to H Mino.

29 records · Page 2Linked to original sources
PubMed1993

A method of analyzing nonstationary ionic channel current fluctuations in the presence of an additive measurement noise.

A method of estimating the parameters of nonstationary ionic channel current fluctuations (NST-ICF's) in the presence of an additive measurement noise is proposed. The case is considered in which the sample records of NST-ICT's corrupted by the measurement noise are available for estimation, where the experiment can be repeated many times to calculate the statistics of noisy NST-ICF's. The conventional second-order regression model expressed in terms of the mean and variance of noisy NST-ICF's is derived theoretically, assuming that NST-ICF's are binomially distributed. Since the coefficients of the regression model are explicitly related to not only the parameters of NST-ICF's but also the measurement noise component, the parameters of NST-ICF's that are of interest can be estimated without interference from the additive measurement noise by identifying the regression coefficients. Furthermore, the accuracy of the parameter estimates is theoretically evaluated using the error-covariance matrix of the regression coefficients. The validity and effectiveness of the proposed method are demonstrated in a Monte Carlo simulation in which a fundamental kinetic scheme of Na+ channels is treated as a specific example.

Ion Channels↗
PubMed1993

A parametric modeling of ionic channel current fluctuations using third-order statistics and its application to estimation of the kinetic parameters of single ionic channels.

A parametric modeling of stationary ionic-channel current fluctuations (SICF's) using third-order cumulants is presented and its application to estimation of the kinetic parameters of single ionic channels is discussed. We consider the case where third-order cumulants of SICF's are nonzero, and where SICF's are corrupted by an unobservable additive colored Gaussian noise that is independent of SICF's. First, we construct a virtual synthesizer that yields an output whose third-order cumulants are equivalent to those of SICF's on a specific slice. The synthesizer output is expressed by the sum of N5 - 1 first-order differential equation systems, where N8 denotes the number of states of single ionic channels. Next, discretizing the synthesizer output, we derive a discrete autoregressive (AR(N8 - 1)) process driven by the sum of N8 - 1 moving average (MA(N9 - 2)) processes. Then the AR coefficients are explicitly related to the kinetic parameters of single ionic channels, implying that the kinetic parameters can be estimated by identifying the ARMA coefficients using the third-order cumulants. In order to assess the validity of the proposed modeling and the accuracy of parameter estimates, Monte Carlo simulation is carried out in which the closed-open and closed-open-blocked schemes are treated as specific examples.

Ion Channels↗
PubMed1990

Effects of organic Ca antagonist, diltiazem, on neuromuscular transmission.

The effects of the organic "Ca antagonist" diltiazem on the frog neuromuscular junction was investigated. The addition of diltiazem to the bath solution increased the frequency of spontaneous miniature endplate potentials (MEPPs) and quantal content. The amplitude of the endplate current (EPC) recorded from a d-tubocurarine-blocked endplate was significantly decreased by diltiazem (20-200 microM). However, the amplitude of miniature endplate current (MEPC) was relatively unchanged by diltiazem. The same degree of decrease in the decay time constant was observed in both EPC and MEPC. ACh potentials induced by repetitive iontophoresis were depressed gradually by low concentrations of diltiazem (2, 5 microM), suggesting enhanced desensitization. Using a patch-clamp method, the effects of diltiazem on ACh-activated single current in chick cultured myotubes were examined. The addition of diltiazem to the bath solution shortened the mean open time in a dose-dependent manner between 10 and 50 microM. The voltage-dependence of mean open time disappeared in the presence of diltiazem, with little change in the channel conductance. The present experiments suggest that diltiazem acts on the ACh-activated channel as an open channel blocker.

Acetylcholine↗
PubMed1989

A parametric modeling of membrane current fluctuations with its application to the estimation of the kinetic properties of single ionic channels.

A parametric autoregressive moving average (ARMA) signal modeling of membrane current fluctuations observed in biomembranes is described. Kinetic properties of single ionic channels contributing to membrane current fluctuations and the parameters of the corresponding ARMA process are explicitly related. The model was shown to be effectively applied to the estimation of the kinetic parameters of single ionic channels. Estimation of the parameters via ARMA signal identification was examined in detail for the basic closed-open scheme and the three-state sequential blocking scheme. The estimation accuracy of this method was theoretically evaluated. Computer simulation revealed the validity of the proposed modeling and the effectiveness of the parametric method for the estimation of kinetic parameters when the model was applied to the estimation. The proposed modeling may form a theoretical base for the parametric analysis of membrane current fluctuations in a variety of kinetic schemes.

Cell Membrane↗
PubMed1988

An appropriate model for congenital hypothyroidism in the rat induced by neonatal treatment with propylthiouracil and surgical thyroidectomy: studies on learning ability and biochemical parameters.

Hypothyroidism was induced in rats by treatment with propylthiouracil through the mother's milk throughout the suckling period followed by surgical thyroidectomy without use of radioiodine. The growth of these animals was considerably retarded and their light-dark discriminative operant learning ability was also significantly decreased. Replacement therapy with thyroxine to maintain its normal serum concentration was effective for continuing normal growth and development of learning ability. Therefore, these hypothyroid rats are a useful model of congenital hypothyroidism. Biochemical studies showed that the inhibition of cerebral Na,K-ATPase and succinic dehydrogenase activities detected in early postnatal life in these hypothyroid rats was transient and that normal activities of these enzymes were later regained in adult rats. However, the activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase and the brain myelin remained low throughout life unless thyroxine was administered. Though a critical correlation between biochemical parameters and learning ability is still uncertain, these results suggest that the formation of myelin in the neonatal period is at least dependent on thyroid hormone and would play an important role in mental development.

Animals↗