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Y Cherruault

Publications and source records attributed to Y Cherruault.

35 records · Page 2Linked to original sources
PubMed1987

A study of the effect of decimal and centesimal dilutions of arsenic on the retention and mobilization of arsenic in the rat.

Having developed a pharmacokinetic method for studying the fate of orally administered arsenious anhydride by a radioactive tracer method, the influence of Hahnemannian dilutions of arsenicum album on the elimination and retention of this toxin in the rat was then investigated. The effects of centesimal (cH) and decimal (dH) dilutions were studied. All the dilutions studied were found to be active. The strongest effects were observed after the administration of dilutions corresponding to a concentration of 10(-14) (14dH and 7cH). Overall, the decimal dilutions augmented the elimination of arsenic more than the centesimals. The observed results were submitted to mathematical analysis. A mathematical model, which confirms that Hahnemannian dilutions have biological effects which are a direct function of the degree of dilution, was developed.

Administration, Oral↗
PubMed1986

A three-compartment open model with first order absorption.

Many drugs confer upon the body the characteristics of a three-compartment model. This paper deals with the estimation of pharmacokinetic parameters of a three-compartment open model, with first order absorption from plasma level data. The central compartment (e.g. plasma) is connected to two other peripheral compartments, and (elimination occurs from only the central compartment. The method of solution involves an optimization method which provides a global minimum of delta, the deviation of plasma concentration from the observed values. The distribution volume of the central compartment and the lag time are also identified. The uniqueness of the absorption rate constant is obtained by the minimum energy principle. The model is tested for different sets of data for the drug Guanfacine (Sandoz laboratories), and the results are compared to those obtained by the generalised least square method.

Absorption↗
PubMed1986

Mathematical modelling accounting for discrepancies between blood levels and pharmacodynamic effects of a drug. Application to the numerical optimization of tertatolol.

In this paper we propose a non-linear model for explaining the relation between doses, blood levels and pharmacodynamic effects. Several models are examined and a functional relation (without derivatives or integrals) is retained. From there the medical system is optimized by using optimal control methods. In practice, optimal doses and times are numerically determined for the drug tertatolol.

Adult↗
PubMed1986

Pharmacokinetics of estulic [corrected] in humans.

Estulic [corrected] given orally without food after overnight fast produces a blood concentration curve with a pronounced second peak that does not appear when the drug is taken with food. A two-compartment open model involving two different time lags is used to study the pharmacokinetics of estulic [corrected] in humans after oral administration. The drug accumulates in a tissue or organ that is well perfused in the first pass transfer. The accumulation appears to occur by a competitive process. The second peak apparently is the result of a rapid release of drug and bioreversible drug compounds from the hepatic-biliary system with subsequent reabsorption. This release may occur spontaneously, but appears to be triggered by food intake. We use an optimization method to characterize the pharmacokinetic profiles of drug for this model. This technique which provides the global minimum of the deviation delta, from the given observations, leads to the optimization of a single variable function. The results are compared with those obtained from the generalized least squares method.

Absorption↗
PubMed1986

[Optimization and optimal control of pharmacokinetics].

In the literature there does not exist many efficient methods for solving identification and optimal control problems in pharmacokinetics. We present a global optimization method for finding the optimum of functions involving several real variables. This technique can be applied to many identification problems. Furthermore a method of successive derivations for the resolution of optimal control problems associated to compartmental modelling is developed.

Humans↗
PubMed1985

General treatment of linear mammillary models.

This paper deals with the mathematical analysis of time courses of absorption, distribution and elimination of drug in a body, which is of considerable value in developing dosage schedules to provide optimal therapeutic action and to reduce the unwanted side effects due to accumulation of drug in the body to a minimum. We consider a general n-compartment model, where elimination occurs from the central compartment which, in turn, is connected reversibly with all other compartments. This linear mammillary model can be used to study the kinetics of protein metabolism in organism. We use an optimization method to characterize the pharmacokinetic profiles of drug for a general n-compartment model. Results are compared to those obtained by making use of (a) SAAM program and (b) an asymptotic method.

Biometry↗
PubMed1985

Identification of pharmacokinetic parameters of two compartment open model with first order absorption.

This paper deals with the estimation of pharmacokinetic parameters of a two-compartment open model with first order absorption from plasma level data. The eigen-values of the characteristic matrix of the given system are obtained by transforming them into a single variable and the global minimum of the deviation (for plasma concentrations) from the observed values is obtained through the solution of linear relations involving the eigen-values. The distribution volume and the lag time are also identified. Finally, the uniqueness of the absorption rate constant is obtained by the minimum energy principle. The model is tested for different sets of data for the drug Guanfacine, an antihypertensive drug. The results are compared to those obtained by the SAMM program.

Absorption↗
PubMed1983

[Biologic systems and optimal control].

A lot of biological systems can be modeled by mathematical relations. Furthermore, existence of regulations and optimizations lead to optimal control systems. In this paper we want to describe with simple examples some difficulties and advantages of such systemic approaches.

Hormones↗
PubMed1982

[Control of recruitment of muscle motor units by optimization of energy expenditure].

In order to vary the force it is exerting a muscle calls upon a variable number of motor elements (spatial mobilisation) and modulates the contraction frequency of each of the fibers (temporal mobilisation). We have studied the frequency distribution as a function of the strength developed and of the elongation of the muscle, as well as the number of fibers recruited. Based on a double approach, experimental and mathematical, we propose a function controlling this two-fold muscular mobilisation: the optimisation of the energy expenditure. In other words, to develop a particular force, the number of fibers called upon and the contraction frequencies of each of them are such that the quantity of energy required by the muscle is a minimum. The study is limited to voluntary isometric muscular contraction. Using optimization techniques, numerical results corresponding to the model's simulation has been obtained by using a digital computer.

Energy Metabolism↗
PubMed1981

[Hemodynamic control by optimization of the cardiac pump].

Transport of energy appears as the ultimate finality of the force convection cardiovascular system. Blood pressure cardiac output and vascular resistances are the three major components of the circulatory system. Among them, blood pressure is regarded as the regulated parameter whose control value is the best adapted parameter, to each kind of activity, neurogenic mechanisms. The authors, considering the physiological variations of blood pressure during increasing energetic loads imposed on the organism, propose a new control function: optimization of cardiac mechanical power necessary to assure convection of the energy needed by the organism. Blood pressure is no more regarded as a constant. Simultaneous changes in cardiac output and blood pressure are both significant, adjusted to realize energetic minimisation of the cardiac pump. This cardiovascular regulation is described by a system of equations whose resolution leads to results in good accordance with physiological data.

Adaptation, Physiological↗
PubMed1979

[Model of the function of the nephron].

After a short review of the functional anatomy of the kidney, we express the usual hypotheses about the phenomena of reabsorption and filtration in the loop of Henle and the collecting duct. Starting from these hypotheses and the laws of biophysics, we formulate the equations of the model. This model accounts for the great increase in concentration of electrolyte and urea in the loop of Henle, the collecting duct and the interstitium, as we "go down" from the outer medullary area towards the inner areas, the active transportation of sodium in the loop of Henle being limited to the thick ascending limb.

Absorption↗
PubMed1978

[Pulmonary gas exchange model: influence of the heterogeneity of distribution on the ventilation-perfusion and diffusion-perfusion ratios of oxygen transfer].

The purpose of this pulmonary gas exchange model is to study the effect produced by an inhomogeneous distribution of the ventilation-perfusion (V A/Q) and diffusion-perfusion (D/Q) ratios on the oxygen transfer. We calculate partial pressures of oxygen and carbon dioxide in venous blood, in capillary blood and alveolar gas of each element as the unique solution of a non-linear system, the parameters of which are the local values of ventilation, perfusion and diffusion. We show that an inhomogeneous distribution of any ratio leads to a decrease of the mixed arterial concentration of oxygen and that the greater the inhomogeneity, the greater the decrease. We show by numerical stimulation that if two inhomogeneities (V A/Q) and (D/Q) are associated, the oxygen arterial concentration decrease is rather less important if the diffusion-ventilation ratio has a distribution almost homogeneous, i.e. if the V A/Q and D/Q inhomogeneities are almost identical.

Carbon Dioxide↗
PubMed1978

Computer analog simulation of a model for the regulation of ago-antagonistic couples.

A system of quadratic differential equations is proposed within the framework of 'non-linear mechanics', but also outside this framework in respect of certain features, and it is used with a view to formalising a feedback control system. The model helps to simulate states of balance or imbalance within an ago-antagonistic couple and to suggest methods for correcting the imbalances, which do not require modification of the parameter space. Its possibilities of synchronic or diachronic functioning are emphasised. The model may apparently be used for the construction of similar models which include several ago-antagonistic couples. Finally, the aims of such a model, which could be considered as an 'action' model, are defined; its place would be assigned midway between a black-box system and 'knowledge' models.

Computers↗
PubMedDate not supplied

New deterministic methods for global optimization and applications to biomedicine.

We propose two methods for solving numerically minimization problems involving non-linear functions of n variables. The first method is based on an approximation of a n variables function by a separated variables function. The second uses a reducing transformation (ALIENOR) allowing to approach a n variables function by a function of one variable. Applications to biomedical problems and specially to identification of models are given.

Mathematical Computing↗