PubMed Health⌕ Search

Biomedical subjects

N Vrabchev

Publications and source records attributed to N Vrabchev.

7 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↗
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↗