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Biomedical subjects

V M Bresler

Publications and source records attributed to V M Bresler.

At least 37 records · Page 2Linked to original sources
PubMed1978

[Active transport of organic acids in the proximal tubules of a surviving rat kidney normally and under certain actions. I. The effect of temperature, aeration conditions and Na ions].

The transport of a marker organic acid (fluorescein) in the intact proximal tubules was studied with the aid of contact microfluorimetry of the surface of surviving rat kidneys. The kinetics of transport at 20 and 37 degrees obeys to the Michaelis-Menten equation. The increase of oxygen content in the gas phase, from 21 to 100%, results in raising V max by 1.7 times, with an apparent Km being unchanged. With the 100% oxygen content taken as a gas phase, the fluorescein transport rate is maximal at 37--40 degrees, the temperature raising from 20 to 37 degrees results in decreasing Km by 4.5 times and in increasing V max by 45%. Both Na-free medium and the addition of strophantin K inhibit fluorescein uptake at temperature higher than 25 degrees only. At 37 degrees the omission of Na+ from the bath medium inhibits the fluorescein transport via Km augmentation with Vmax being unchanged. Thus, active transport of fluorescein is Na+-dependent in physiological range of temperature and the motive force of the transport is an electrochemical Na+-gradient created by means of Na+, K+-ATPase operation.

Aerobiosis↗
PubMed1977

[Kinetic analysis of mechanisms of Na+-dependent transport of organic acids in the proximal tubules of surviving frog kidney. I. Transport of fluorescein and uranin in a sodium-free environment].

By direct microfluorimetry, the kinetic characteristics of active transport system for organic acid were studied. A removal of sodium from the incubation medium is shown to affect the affinity between a carrier and acids (KS), and the rate of translocation of the transporting complex (which includes a carrier and a substrate) across the plasma membrane. The data obtained are in good accordance with the concept of Na+-dependent transport.

Animals↗
PubMed1977

[Kinetic analysis of mechanisms of Na+-dependent organic acid transport in the proximal tubules of surviving frog kidney. II. Relationship between Na+ concentration in the medium and changes in the parameters of the Michaelis-Menten equation for fluorescein and uranin transport].

The dependence of active transport rates of fluorescein and uranin into proximal tubules was studied, firstly, on the concentration of these substrates in the incubation medium with constant Na-concentration and, secondly, on Na+-concentration in the medium with constant concentrations of fluorescein or uranin, Km, Vmax, and KmNa, VmaxNa values being determined correspondingly. With the decrease of Na+-concentration in the medium the apparent Km values for fluorescein and uranin increase, while Vmax values remain unchanged and ratios Vmax/Km decrease. The 1/Km value for uranin transport is a linear function of Na+-concentration, while it is a quadratic function of Na+-concentration for fluorescein transport. The KmNa value for fluorescein transport is twice as much as that for uranin transport. The obtained data suggest that one Na+-ion is spent from the medium for translocation of one uranin molecule across the basal membrane, whereas two Na+-ions from the medium are necessary for translocation of one fluorescein molecule. It is assumed that fluorescein and uranin transports are carried out by producing a four-fold transporting complex (a carrier+a substratum+2Na+; in the case of fluorescein 2Na+ appear from the medium, whereas in the case of uranin only one Na+ from the medium is used.

Animals↗
PubMed1976

[Active transport of fluorescein in the choroid plexus of the brain and regulation of its rate by cyclic 3',5'-AMP].

With the aid of luminescent microscopy and microfluorimetry in vitro, the transport of labelled fluorescine into the structures of the brain lateral ventricles' chorioid plexus was studied in rabbits. An against-gradient pumping of fluorescine into the cytoplasm of the neuroepithelium cells and into the lumen of adjucent capillaries was shown to occur in the chorioid plexus. Such accumulation of fluorescine proceeds in the active transport way with participation of a carrier. The active transport system is congenial to fluorescine - Km = 4-10(-5) M, which renders even small amounts of this substance to be quickly removed from the milieu. The fluorescine-transporting system fulfills transition of other organic acids as well. The system of organic acids active transport is, apparently, localized in the apical and basal membranes of the neuroepithelial cells surrounding the plexus' filia which makes the concentration of transported acid in the neuroepithelial cells higher than in milieu, and in the capillaries' lumen higher than in the cytoplasm. An enzyme system adenylcyclasa-phosphodiesterase was found in the chorioid plexus' neuroepithelium. The system participates in regulation of velocity of the organic acids transport by means of changing the intracellular concentration 3',5'-AMP.

Adenylyl Cyclases↗
PubMed1976

[Changes in the chromatin structure of hepatocyte nuclei of rats trained to hypoxia].

Structure of chromatin in the nuclei of the isolated surviving hepatocytes and in the isolated nuclei of hepatocytes were studied by fluorochroming with acridine orange and by microfluorimetry of fluorescenc connected with the stain chromatin at 530 and 590 nm in intact rats and in the animals trained to hypoxia in a pressure chamber for 60 days. The nuclei of hepatocytes of intact rats were distributed by fluorescence at 530 nm into three classes with the intensity ratio of 1:2:4; as to the nuclei of hepatocytes of the rats trained to hypoxia - they formed a single class corresponding to the second class of control. In intact rats the ratio of the fluorescence intensity at 590 nm to such at 530 nm (alpha coefficient) formed normal distribution; in trained rats - a bimodal distribution with a shift of the maximum in the direction of reduction and increase of alpha in comparison with control. It is supposed that in hypoxia there is a repression of one and depression of other genes in the chromatine of the nuclei of the liver.

Acridines↗
PubMed1976

[The peroxidase activity of rat cerebral hemisphere neurons during hypoxia training].

Peroxidase activity (PA) was studied in the rat's brain cortex during a 2 months training to hypoxia according to the Barbashova method. PA was investigated histochemically by an ammonium--molibdate--benzidine method on blocks of surviving brain tissue, thereafter they were studied by the contact microscopy. PA was also determined biochemically in water-salt extracts of the brain tissue. A progressive increase of PA in the course of training was shown by both the techniques. The increase of activity is accounted for by the growing quantity of neurons developing the reaction as well as by the growing intensity of reaction in each neuron. The nature of PA of neurons and its adaptive significance in hypoxic conditions is discussed.

Adaptation, Physiological↗
PubMed1975

Structure and active transport in the plasma membrane of the tubules of frog kidney.

The active transport of organic anions through the plasma membrane of the proximal tubules of frog kidney was studied. For this purpose a marker anion, fluorescein, was used, its flow into the tubules registered by the increase of fluorescense. The kinetics of transport was measured as function of time, concentration of substrate, concentration of a competing acid (p-aminohippuric acid) and temperature. The process is inhibited by strophantin, a specific poison for (Na++K+)-dependent ATPase. These data show that fluorescein transport is effected with the participation of a charged carrier, probably by the downfield mechanism postulated by Mitchell. To confirm this mechanism, a passive flow of K+ was created inwards across the membrane of the proximal tubules by means of valinomycin. It led to the discharge of the membrane and to the inhibition of fluorescein transport. Anions are transported downfield across the membrane, probably in a state of complexes with two Na+ ions. A magnetic field of 10000-28000 oersted inhibits the fluorescein transport strongly. This can be regarded as a proof of the liquid-crystalline structure of biological membranes and demonstrates the importance of this structure for active transport.

Aminohippuric Acids↗
PubMed1975

[The state of the vascular net and the hematoencephalic barrier in the cerebral cortex of rats during hypoxic training].

With the aid of vital contact microscopy of the brain cortex, a sharp increase up to 613.2% in the total length of capillaries for a space unit by the 60 th day of training was shown to occur in the pia and the cortex in the course the training for hypoxia. Also the excessive blood volume, enlargement and lengthening of the small arteries and veins as well as increase in the capillaries diameter by 25-30%, were noted. In the course of the training, the blood flow speed increases considerably in cortical vessels. Study of the cortical blood-brain barrier by means of supravital microfluorimetry showed that, in the course of the training, the acid stainer (fluorescin) permeability through the barrier does not decrease. The readjustment of the cortical vascular net during the training does not affect the blood-brain permeability.

Animals↗