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PubMed1975

[Method for the immediate measurement of myocardial pressure velocity relationships in situ].

A method for instantaneous measurements and representations of myocardial pressure-velocity relations permitting the analysis of various contractility parameters is described. Basing on a modified two-element model of cardiac muscle the measurement of the relative shortening velocity vce = dp/dt(p) of the contractile elements is carried out by a special analog computer, which calculates the quotient (dp/dt) to the simultaneous left ventricular pressure p. Electronic differentiation of the logarithm of pressure-proportional input voltages is used. The p-v-diagram can be displayed on x-y-oscilloscopes. Over an input voltage range of 20 mV---20V the quotient can be measured within the range of 20 sec-1---250 sec-1. Output voltages can be calibrated automatically. Between (dp/dt)p-1 determined by conventional methods and the dlnp/dt calcuated electronically there exists a correlation gamma = 0.995. An additional electronic circuit which permits the determination of a contractility parameter indicates the point of (dp/dt)max on the p-v-relation display. The application of the method in experimental studies under inotropic changes in the rabbit heart in situ following beta-receptor blockade is demonstrated.

Blood Pressure↗
PubMed1975

[Practical evaluation of methods in pharmacokinetics].

A short discussion of the differences between kinetic processes of zero and first order is followed by an outline of evaluation methods used in pharmacokinetic practice, e.g. "paper and pencil methods" as well as the use of digital and analog computers. The increasing potency of new drugs requires not only more sophisticated methods of analysis and expensive facilities but also more complex models to generate pharmacokinetic information.

Computers↗
PubMed2005

EEG analysis with nonlinear excitable media.

The detection of patterns embedded within a complex, nonstationary, and noisy background activity is a crucial and important task in EEG analysis. The authors present a biologically inspired, analog approach to EEG analysis that is conceptually different from a variety of statistical approaches currently used. A nonlinear, excitable, spatially extended medium that is composed of diffusively coupled model neurons is considered. When EEG recordings are applied as local perturbations to such an excitable neural tissue, the induced transient changes in the dynamics of the perturbed system can be regarded as an instantaneous characterization of transient processes in the brain reflected by the EEG, e.g., in the form of a sequence of correlated dynamical events (patterns). Nonlinear excitable media can be implemented in form of an array of locally coupled integrated analog nonlinear electrical circuits called cellular neural networks, which represent a next evolutionary step in the parallel analog computer architecture. Using cellular neural networks, the authors show that the concept of signal-induced pattern generation allows an almost instantaneous and unsupervised detection of seizure onsets in EEG recordings. In addition, they show that a cellular neural network can be trained in a supervised way to approximate the degree of synchronization in EEG recordings. The resulting pattern-recognition device may be suitable for the prediction of epileptic seizures.

Animals↗
PubMed1969

Which computer?

Explore the source record for details and available documents.

Computers↗
PubMed1978

Pharmacokinetics of papaverine hydrochloride and the biopharmaceutics of its oral dosage forms.

The pharmacokinetics of completely metabolized papaverine hydrochloride were characterized by a linear sum of three exponentials on intravenous administration with respective 1.5, 19 and 107 min apparent half lives. There was a time-dependent partition from plasma water into red blood cells with an apparent half life of 1.5--3 min. The partition coefficient normally ranged between 8 and 15 at therapeutic levels but approached unity at high plasma concentrations to indicate a saturable partition. Apparent compartmental volumes of distribution referenced to total concentrations in the plasma were 4.3--4.8, 11--13 and 20--25 liters. Protein binding was 91--95%. The hepatic clearance of blood was 960 ml/min, corresponding to a hepatic efficiency of 69%, and indicated that the clearance of protein-bound drug was consistent with the observed first pass metabolism of 70% for oral solutions. No dose dependency was observed on intravenous administration or on oral administration of solutions and tablets. Tablets with release lag times of 10--15 min showed relative bioavailabilities of 52%. Two different lots of sustained release capsules showed 68 and 89% relative bioavailabilities. Release lag times among capsules ranged between 0 and 170 min. Loo-Riegelman calculations and analog computer fittings were consistent with a half life of absorption from oral solutions of 19 min and zero order release rates from tablets and sustained release capsules. Chronic studies of tablets q.i.d. and capsules b.i.d. confirmed lack of accumulation. An appropriately designed 300 mg sustained release capsule, b.i.d., for an arbitrary plasma level of 0.200 microgram/ml should have one tenth the release rate of the studied capsules.

Administration, Oral↗
PubMed1984

In vivo-in vitro correlations with sustained-release theophylline preparations.

The in vitro dissolution of four commercially available sustained-release theophylline products was studied. The dissolution of theophylline was evaluated under four conditions: USP-method I or Resotest apparatus, and artificial gastric (pH 3) or artificial intestinal (pH) fluids. The resulting data were evaluated by graphic, first-order transform, dissolution efficiency, non-linear fitting, mean time of dissolution and Weibull analysis methods. The four theophylline preparations and a peroral solution were administered to four male beagle dogs in a cross-over fashion. Parameters were obtained from graphed concentration vs. time data, a one-compartment open model fit, Wagner-Nelson absorption plots, ratios of half values of duration and maximum concentrations, mean times of absorption and analog computer evaluation. Correlations were made between all possible combinations of in vitro and in vivo data by quadrant analysis, Pearson product moment, r, and Spearman rank order correlation methods. A total of 8280 correlation coefficients were calculated. The optimal set of studied conditions for in vivo-in vitro correlations with sustained-release theophylline preparations is the time to reach maximum concentration in the blood (from the fitted data) vs. the time for 15% of the drug to be released into solution from the dosage form (from graphed data) using either the USP I apparatus or the Resotest.

Animals↗
PubMed1982

[The modelling of growth processes].

Hitherto developed presentation of processes of growth will be tested in this paper. For this end a previous explained cybernetical structure is developed to a model of an analog-computer. In this way it is possible to simulate the growth function of the embryofetal curve of the length' increase of man and the curve of the mass' increase of rat. It turns out a very good correspondence between the measured and the simulated curves. There is given an algorithm to simulate every curve of growth of the examined type. Some remarks of the origin of the explained ideas will round this paper.

Animals↗
PubMed1981

Neck muscle resistance to head impact.

The role of neck muscles in the body's response to the "whiplash" type of motion which occurs during frontal impact has been studied. This type of motion was simulated by a sudden backward pull of a subject's head. Head and neck response to low-level acceleration has been researched by recording the externally applied force, the head accelerations in the median sagittal plane, and the electrical activity in the sternomastoid muscle (EMG) as functions of time. The resultant acceleration-time curve and recorded EMG have been analyzed, with numerical values of applied resistance to the external force recorded. An analog computer model was built incorporating resistance developed by two main variable: 1) the elasticity coefficient; 2) the active damping factor. Together these two variables, combined with a resistance function, enable us to measure the resistance of the head/neck response. Using this model, variations in magnitude of these two components were studied under six varying conditions of impact: 1) length of warning time; 2) type of instruction given to the subject; 3) amount of previous experience on the part of the subject in similar situations; 4) anticipation of impact by the subject; 5) magnitude and kind of impact; 6) presence or absence of a preload.

Acceleration↗