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Biomedical subjects

L Lacko

Publications and source records attributed to L Lacko.

At least 19 recordsLinked to original sources
PubMed1985

Interaction of some beta-receptor blockers with the transport system of glucose in human erythrocytes.

The influence of 15 of the most frequently used beta-receptor blockers on the glucose transport in human erythrocytes was investigated. It was found out that 10 compounds have no effect on the glucose transport and that their lipophilicities are very low. The inhibition constants and the inhibition kinetics of the glucose uptake of the other 5 beta-receptor blockers were estimated. No correlation exists between their affinities to the glucose transport sites and the partition coefficients.

Adrenergic beta-Antagonists↗
PubMed1984

An interspecies approach to the investigation of the red cell membrane glucose transporter.

Glucose transport differs in red cells of various species. The following sequence of transport velocities was found: man greater than newborn pig greater than rat, dog greater than cattle greater than pig. No correlation was found between the amount of protein in band 3 and glucose transport activity. By contrast, a very clear peak in the band 4.5 region was found for newborn pigs, whereas adult pigs did not exhibit a corresponding peak in the electrophoresis. Thus further evidence is provided by our investigations in favour of band 4.5 region for glucose transport activity in red cells.

Animals↗
PubMed1984

The affinities of benzodiazepines to the transport protein of glucose in human erythrocytes.

By kinetic analysis we estimated that all the 16 benzodiazepines investigated are inhibitors of the glucose uptake in human erythrocytes; their affinities, however, differ remarkably. The individual KI values ranged over 2 orders, the partition coefficients in a mixture of octanol/water over 3 orders of magnitude. Thus, the lipophilities of the benzodiazepines differ considerably; they don't agree with the trend of the KI values with exception of structurally very similar preparations. The thermodynamic parameters delta F degree, delta H degree and delta S degree for the association of the benzodiazepines to the transport protein were mostly of negative sign. From the results we discussed the importance of the chemical groupings for the inhibitory effect of the benzodiazepines on the glucose uptake as well as the mode of interaction between the benzodiazepines and the transport protein. Some parallels between the affinities of the benzodiazepines to the transport protein, to the serum albumin and to the receptors of the central nervous system were considered.

Benzodiazepines↗
PubMed1982

The competitive inhibition of glucose transport in human erythrocytes by compounds of different structures.

By kinetic analysis we found that the transport protein for glucose in human erythrocyte membranes has different binding sites for competitive inhibitors. They all change the transport protein with the effect that it loses its affinity to glucose. Some of the competitive inhibitors alter the conformation of the transport protein, so that other ones cannot be bound. There are inhibitors, however, which do not affect the affinity of other competitive inhibitors. A schematic model of our assumption about the mechanism of the competitive inhibition of glucose transport is presented.

Binding, Competitive↗
PubMed1980

[Antioxidant stabilization of the antifoaming agents used in the fermentation process].

Oils used as antifoaming agents in fermentation are subjected to oxidation to form various products, such as aldehydes, carboxylic acids, peroxides, etc. The negative effect of such products on biosynthesis of chlortetracycline by strains VUA 84 and Iz 22/VUPL of Str. aureofaciens was recorded. The level of the oil oxidation was characterized by the contents of peroxides and epihydrinaldehydes. The Kreiss qualitative test was modified for quantitative estimation of epihydrinalydehydes. The oil antifoaming agents characterized by the routine parameters used in determination of oil quality, such as acid number, saponification number and iodine number. In the control experiments lard and soybeen oil were oxidized by air at a temperature of 100 degrees C without an antioxidant (2,6-ditetrabutyl-4-methylphenol). The oil antifoaming agents such as soybeen oil and lard were tested in biosynthesis of chlortetracycline carried out in flasks and pilot plant 750 1 apparatus. Antioxidant 4K, an alkylphenol antioxidant, in a 2% concentration proved to be effective for prevention of oxidation and nontoxic for the culture.

Antifoaming Agents↗
PubMed1980

Interaction of chlorpromazine with the transport system of glucose in human erythrocytes.

The characteristics of inhibition of the glucose uptake in human erythrocytes by chlorpromazine (CPZ) was investigated. It was found that CPZ is a strong inhibitor. The inhibition kinetics indicates that also two molecules of CPZ can bind to the transport system and so from two different CPZ-complexes. The dissociation constants of both the CPZ-complexes and the pH- and temperature-dependence of the inhibition were estimated.

Biological Transport↗
PubMed1979

The effect of homologous local anesthetics of the 4-alkoxy- and 4-alkylamino-benzoic acid-diethylamino-esthylester- hydrochloride series on the glucose transport in human erythrocytes.

The homologous compounds of the 4-alkoxy- and 4-alkylamino-series inhibit the exchange transport of glucose in human erythrocytes; they show a competitive inhibition with one or two inhibitor molecules which become bound to a singular site of the transport system for glucose. The importance of length of hydrocarbon chain of the localanesthetics for the mode of their action is discussed.

4-Aminobenzoic Acid↗
PubMed1979

Interaction of DL-, D- and L-propranolol with the transport system of glucose in human erythrocytes.

The effect of D-, L- and DL-propranolol on the glucose uptake in human erythrocytes was studied. It was observed that all three compounds competitively inhibit the glucose transport and have identical inhibition constants. The pH dependence of the inhibition constant indicates that uncharged propranolol is a more potent inhibitor than the charged one. The thermodynamic parameters of the interaction of propranolol with the glucose transport system were determined and discussed.

Blood Glucose↗
PubMed1977

The pH and temperature dependence of the interaction of steroid hormones with the transport system of glucose in human erythrocytes.

The thermodynamic parameters deltaH degrees, deltaF degrees, deltaS degrees and the pH dependence of the interaction between steroids and the glucose carrier in human erythrocytes have been studied. The results indicate that, according to the structure of the steroids, hydrophilic as well as hydrophobic bonds can be involved in the association. For the binding of the C-21-steroids to the carrier the polarity rule has been observed to be valid. On the basis of the thermodynamic parameters it has been found that in the association process of the steroids with the carrier, simultaneous randomization of ordered water molecules is important.

Androstanes↗
PubMed1975

Interaction of steroids with the transport system of glucose in human erythrocytes.

Steroids inhibit the exchange transport of glucose in human erythrocytes. The extent of inhibition is roughly correlated to the affinity of the steroids to the membrane lipids. All C-21-steroids tested show a competitive inhibition while the C-19-steriods show different types of inhibition. 5Beta-androstane-3,17-dione acts as a competitive inhibitor. The inhibition by testosterone is of mixed type, while with androst-4-ene-3,17-dione and 5alpha-androstane-3,17-dione a non-competitive inhibition is observed. In this case two inhibitor molecules can be bound per transport molecule. The "non-competitive" inhibitors compete also to some extent with the glucose binding. This effect, however, is at high inhibitor concentrations masked by the more powerful non-competitive inhibition. Competitive and non-competitive inhibitors compete with each other. The structural requirements for the different types of inhibition are discussed.

17-Ketosteroids↗