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N Vrabchev

Publications and source records attributed to N Vrabchev.

11 recordsLinked to original sources
PubMed1990

[A compartment analysis of the significance of extracellular fluid volume for body fluid dynamics].

The curve of a reduction in plasma concentration of the indicator substance creatinine for a period of 120 to 240 min was investigated after single intravenous administration of creatinine in a dose of 150 mg/kg on dogs. A model for two compartment distribution of the indicator substance was used as the first compartment was intravasal, but the second--interstitial space of body fluids. The following parameters were estimated: renal clearance, volume of distribution, glomerular filtration, intercompartment clearance and velocity constants of transport between the two compartments. An increase of the volume of extracellular fluid (ECF) was induced by intravenous infusion of 2% of sodium chloride solution in the amount of 30 ml/kg. A reduction in the volume of ECF was caused by peritoneal dialysis with isotonic solution of glucose in the amount of 5% of the body mass. After an increase of the volume of ECF there was an increase in the volume of distribution, elevation of glomerular filtration and a reduction in the velocity constant of transport from the intravasal to interstitial fluid. There was a reduction in the volume of distribution, limitation of glomerular filtration and increment of velocity constant of the transport. The established changes in the velocity constants of the transport showed changes in the dynamics of body fluids, which could be due to vasoconstriction or vasodilation as a mechanism of myogenic autoregulation during changes in the volume of ECF.

Animals↗
PubMed1986

Studying the stability of clear vision using microcomputer "Pravets-82".

The method of Ferree and Rand assesses the efficiency of the eye and is very sensitive to fatigue in the visual system. A modification of the method is developed using microcomputer "Pravetz-82". The proposed algorithm is realised in Extended Basic. The features of the modified method include: display of the stimulus on the monitor of the microcomputer, option for interactive change of the parameters of the stimulus from test to test, storage of the data on a diskette, measuring of the time intervals by a programme clock, statistical evaluation of the results with graphic display. The modification makes the method more versatile, precise, and easy to perform.

Computers↗
PubMed1985

Dynamics of renal excretory function after furosemide or ethacrynic acid administration to unanaesthetized dogs after mannitol infusion or chronic renal denervation.

To unanesthetized dogs with exteriorized ureter allowing separate collection of urine from both kidneys, furosemide 0.2 mg/kg b.w. or ethacrynic acid 0.22 mg/kg b.w. was given intravenously. The volume of collected urine and the excretion of sodium, chloride, potassium and calcium were studied. The dynamics of diuretic administration was programmed. After unilateral renal denervation furosemide or ethacrynic acid was given and the response of the denervated (left) and intact (right) kidneys was compared. Prior to renal denervation the same dogs were infused with a 15% mannitol solution in a quantity and at a rate causing an increase of diuresis approximately equal to that after renal denervation. The effect of furosemide given with and without mannitol infusion was compared. Description of the dynamics of renal excretory function used by us allowed to demonstrate the modulating role of renal nerves in the regulation of water, chloride and sodium excretion after the administration of diuretics. The principal part of the compensatory reabsorption of chloride after renal denervation occurred in the ascending limb of Henle's loop. Comparison of calcium excretion after renal denervation and administration of furosemide with that after mannitol and furosemide allows to assume that after renal denervation calcium load from the proximal to the distal tubules does not increase.

Animals↗
PubMed1984

Method and programme for automated analysis of the dynamics of renal excretory function.

The present study is an effort to investigate the dynamics of renal excretory function on the basis of an experimental estimation of the total excretion for given intervals of time. The usage of an improved and universalized variant of the mathematical model of Leary W.P. et al. for description of the cumulative curve of the excretory process makes possible the study of the excretory process after treatment with diuretics different in the strength and duration of their effect. It also allows to compare the results obtained after the administration of diuretics under different conditions. A computer programme has been elaborated with the purpose of implementing the suggested model into practice and of determining the numerical characteristics used to describe the dynamics of the excretory process.

Animals↗
PubMed1984

Evaluation and comparison of the renal excretory function after different diuretics through criteria based on a mathematical model of the excretory function.

The subject of the present study is to compare various diuretic effects through a number of criteria included in a programme developed by us on the basis of an improved model of the method of W.P. Leary and A.J. Reyes for description of the dynamics of the renal excretory function. The effects compared were: of diuretics different in potency and duration of action; of different doses of one and the same diuretic; of different diuretics and placebo--0.9% solution of sodium chloride. The rate of excretion prior to the diuretic administration is graphically represented which enables the estimation of presence or absence of diuretic effect of the pharmacological substance applied. This also makes possible the evaluation of the specific effect of the diuretics with regard to different electrolytes which improves the approach when the diuretics are to be combined and helps their optimum dosage and distribution within time.

Animals↗
PubMed1981

Automated analysis of circadian rhythms when data are collected at intervals.

The subject of consideration is circadian rhythmicity studied on the grounds of data collected at intervals. Such are the cases of food and water intake, urine and electrolytes excretion and so on. The problem for determining the parameters of the circadian rhythmicity and their statistic estimation by dispersion analysis is discussed in details. The proposed method allows to calculate the parameters of the circadian rhythmicity for both the individual members and the whole group (mesor, amplitude, phase) and also the parameters of the population through the partial dispersion. A programme for a computer is developed on the grounds of the adduced mathematical apparatus.

Animals↗
PubMed1981

Simultaneous study of the circadian rhythms of food intake, water intake and renal excretion and analysis of their interrelations in rats.

The circadian rhythms of food intake, water intake and urine and electrolyte excretion were studied simultaneously at 4-hour intervals in male Wistar rats. The animals were housed individually in metabolism cages at constant conditions: temperature 22 +/- 2 degrees C, humidity 60 +/- 10%, light regime at 12 hours light and 12 hours dark. The results were processed using a method for automated analysis of circadian rhythms, which permitted the interpretation of the rhythms both for experimental group and for the population. It was established that the circadian rhythms under consideration had the following time sequence: food intake, water intake, potassium, sodium, chlorides excretion. It was demonstrated that the sinusoidal approximation of the data for food and water intakes was not quite appropriate, since the experimental data showed two maxima during the dark period.

Animals↗
PubMed1978

Method and programme for compartment analysis of exogenously introduced indicator substance.

The concept of the compartment structure of body fluids gives possibilities for finding the values of physiological characteristics such as volume of distribution, transport rate, kidney and intercompartment clearance. Their determination is made indirectly and it is based on the solution of a system of differential equations describing the behaviour of an open two-compartment system when an indicator substance is introduced. The determination of the coefficients of the equations involves a number of difficulties leading to inaccurate results due to the use of graphic-analytical methods. It is proposed to avoid this shortcoming by applying multiple approximation of the function describing the change in time of the concentration of the indicator substance in the intravasal space by a sum of two exponents, which corresponds to the system of differential equations. The approximation is performed by the least squares method, the precision criterion being the mean quadratic error of the approximation. An algorithm for which a computer programme is elaborated is proposed.

Biological Transport↗