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R A Markosian

Publications and source records attributed to R A Markosian.

At least 19 recordsLinked to original sources
PubMed1989

[A new highly sensitive method of analysis of thrombocyte aggregation].

The new method for studies of the platelet aggregation kinetics is based on the creation of a platelet stream through the optic canal and on an analysis of fluctuations in the intensity of the luminous flux that has passed through the sample. The relative dispersion of fluctuations in the intensity of the light passed through the sample is suggested as a parameter for the estimation of the platelet aggregation and for analysis of their aggregation kinetics. The method permits recording the platelet aggregation in citrate plasma, enriched for platelets, after exposure to the inductor in very low concentrations (0.05-0.15 microM ADP). Scanning electron microscopy has shown that aggregates are indeed formed in such cases, and they can be recorded from the increase of the relative dispersion in the fluctuations in the passed light intensity but cannot be recorded by Born's optic method.

Adenosine Diphosphate↗
PubMed1989

[New methodical approach to the study of platelet aggregation in vitro].

A new approach to the investigation of the kinetics of platelet aggregation is described. The method is based on the analysis of light transmission fluctuations produced on the changes in the number of platelets in optical channel. The relative dispersion of the fluctuations of transmitted light intensity was used as a parameter to estimate the degree of platelet aggregation. Application of this method for the analysis of platelet aggregation permits to get new information about this process.

Adenosine Diphosphate↗
PubMed1987

[Morphofunctional characteristics of the bipolar forms of thrombocytes].

The formation and circulation of bipolar platelet forms in the vasculature have been first studied. All the transitional stages of platelet metamorphosis from disk-shaped to bipolar forms have been traced. The basic functions in bipolar platelets (adhesion and aggregation) were inhibited. Such cells were shown to appear in various pathologic conditions (pheochromocytoma, intravascular coagulation syndrome). Prazosin, alpha-blocker, was capable of inducing reverse metamorphosis accompanied by the recovery of platelet functional properties.

Adrenal Gland Neoplasms↗
PubMed1986

[Effect of alternating pressure on thrombin-stimulated thrombocytes].

The effect of alternating pressure on circulating platelet function was studied with particular reference to changes in platelet shape, aggregation and release reaction, MDA synthesis and intracellular calcium redistribution. Pressure effects were dependent on the magnitude of pressure impulses, platelet suspension storage time and the interval between the exposure to pressure and the challenge of platelets.

Adenosine Triphosphate↗
PubMed1985

[pH changes in the matrix of serotonin organelles of stimulated thrombocytes].

The changes of pH gradient on serotonin organelle membranes can be observed using the fluorescent marker acridine orange. This gradient decreases with thrombin activation of the blood plates. The fall of delta pH can be induced by ammonium salts which also influence the ADP-induced cellular aggregation. NH4 ions added simultaneously with low doses of ADP potentiate cellular aggregation, and added after ADP-induced interaction of cells lead to another wave of intercellular contacts inhibited by mepacrin. Fluorescent acridin aminoderivatives can be used both for kinetic observations of delta pH on the serotonin organelle membranes of native platelets and for studying the interaction of the systems responsible for maintaining this gradient with the systems of prostaglandin and adenine nucleotide metabolism.

Adenosine Diphosphate↗
PubMed1985

[Characteristics of the activation of rabbit platelets induced by 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (platelet activation factor)].

A study was made of the action of alkyl acetylglycerophosphocholine, a semi-synthetic platelet activation factor. The compound was shown to have both marked aggregation activity and to interact with serotonin granules (5-HT-organelles) of the cells, inducing the release of the fluorescent marker acridine orange. Some features of the platelet aggregation factor interaction with platelet rich plasma suggest that the latter contains enzymes inducing degradation of the factor.

Animals↗
PubMed1983

[Antiaggregating action on thrombocytes of a new anti-arrhythmia agent of the phenothiazine series--diethylamine ethmozine analog].

A new antiarrhythmic drug of phenothiazine series diethylamine ethmozine analogue inhibited the rabbit's platelet aggregation induced by ADP, serotonin and thrombin. The degree of inhibition depended on the drug concentration and time of its incubation with platelets as well as on the inducer concentration. The transition from ADP-induced (5 microM) aggregation to reversible one was observed under the influence of relatively small doses of the drug. A gradual restoration of the platelet aggregating capacity occurred after washing platelets off the drug. The nonadditive character of the studied agent effects and that of theophylline on the platelets makes it possible to suppose that cAMP participates in the mechanism of the drug action on the platelets. The described antiaggregating effect of the drug on the platelets should be taken into account when it is used as an antiarrhythmic agent.

Adenosine Diphosphate↗
PubMed1982

[Changes in thrombocyte functional properties after hyperbaric exposure].

The data are presented of the investigation of the effect of single pressure impulses on the shape and aggregation ability of platelets. The pressure impulses have been shown to lead to the activation of platelets which is not unequivocally associated with cell spherulation. It is suggested that the activating of the pressure impulses in vivo may maintain platelets in the state of activation which only slightly differs from the level of activation necessary for adhesion to an impaired site of the vascular wall.

Adenosine Diphosphate↗
PubMed1982

[Simultaneous recording of 4 thrombocyte functional parameters].

A method is offered for simultaneous measurement of four functional parameters of platelets: aggregation, cell shaped, adenine nucleotide release and redistribution of intracellular Ca2+. Variation in intracellular Ca2+ distribution in the course of processes induced by thrombin in platelets is described.

Adenine Nucleotides↗
PubMed1981

[Certain mechanisms of the effect of EDTA on thrombocyte aggregation].

Effect of EDTA on the ADP-induced platelet aggregation and intraplatelet regulatory mechanisms were examined. EDTA (and EGTA) was shown to inhibit platelet aggregation and to potentiate the similar effect of theophylline and dibutyryl cAMP. Inhibition of platelet aggregation was seen during incubation of EDTA in conjunction with dibutyryl cAMP at concentrations that did not change the platelet aggregation profile provided the agents cited were incubated alone. Verapamil and tetracain potentiated the inhibitory effect on aggregation of EDTA, dibutyryl cAMP and EDTA plus dibutyryl cAMP.

Blood Platelets↗
PubMed1981

[pH gradient in the membranes of serotonin-containing granules of thrombocytes: principles for studying them using fluorescent amino-derivatives of acridine].

A new method has been devised for determination of gradient pH and buffering capacity in 5-HT-containing granules of platelets. It is based on the ability of 5-HT granules to accumulate acridine derivatives so that the ratio of the label concentrations outside and inside is equal to the proton concentration ratio. Simultaneous recording of the fluorescence intensity and light transmission of the platelet-rich plasma has been made use of in comparing the kinetics of the intragranular pH collapse and platelet aggregation.

Acridine Orange↗
PubMed1981

[Determination of the probability of thrombocyte aggregation for evaluation of their functional state].

Basing on an analysis of the initial area of the aggregatogram a method has been suggested for determining the probability of platelet aggregation on collision. Calculation was performed in terms of a kinetic equation of coagulation according to the Smolukhovsky's approximation method and in terms of own experimental data. Good agreement of a theoretical depiction with experimental facts indicates the efficacy of the approach suggested to the appraisal of the probability of platelet aggregation, enabling the comparison of the results obtained with different plasma specimens. In contradistinction to a routine analysis of the aggregatograms (determination of the aggregation amplitude, and the time from the onset of the maximum aggregation), the probability of aggregation is determined only from platelet function.

Adenosine Diphosphate↗
PubMed1981

[Blood platelet functional state and exposure to an aggregation inducer].

Proceeding from experimental and literature data the authors evaluated the effect of hemodynamic factors on the process of induced changes in blood platelet function. A scheme of the process was developed, which puts together the data on the effect of local hemodynamics on the platelet functional properties. A hypothesis has been suggested on possible adhesion of native platelets to the surface of injured vessel wall without preceding activation.

Adenosine Diphosphate↗
PubMed1981

[Intracellular calcium redistribution in the thrombocytes during aggregation and release reaction].

With the aid of an original installation there was simultaneously measured aggregation, reaction of release of adenine nucleotides, and redistribution of calcium (by fluorescence of calcium-sensitive probe of chlortetracyclin) in one sample of the suspension of washed platelets of rabbit. For the first time there was found an increase in the intensity of fluorescence in the presence of ADP-induced aggregation which continued long after the platelets desaggregation. The obtained results suggest that this increase indicating the redistribution of calcium ions in cells, is associated with the refractory state of the platelets.

Adenosine Diphosphate↗
PubMed1980

[Electron-acceptor (acid) properties of the contents of blood platelet intracellular granules and their significance for the reactions of these cells].

The fluorescent marker method and measurements of aggregation were utilized to study the significance of the acidic intragranular space in blood platelets. Acridine orange is liberated from 5-HT granules after alkalinization by the ammonia ion which inhibits the induction of platelet aggregation by ADP and causes the platelet disaggregation. At low doses, ammonia ion enhances ADP-induced aggregation. The transformation kinetics of 5-HT granules was investigated in the course of clot formation with a new instrument that simultaneously monitors the light transmittance (aggregation, clot formation) and fluorescence intensity (accumulation and liberation of fluorescent marker). These experiments provide the evidence that processes of fibrin filament sedimentation and fibrin-blood platelet interaction were followed by a liberation of fluorescent marker from 5-HT granules.

Animals↗