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Biomedical subjects

L Muszbek

Publications and source records attributed to L Muszbek.

At least 91 records · Page 5Linked to original sources
PubMed1981

Effect of prostaglandin I2 on platelet adhesion.

The adherence of platelets to collagen fibrils was not affected by prostaglandin I2 (PGI2) applied in a wide concentration range (0.1-100 ng/ml). The retention of platelets on glass beads which includes adhesion as well as subsequent clumping of platelets was, however, greatly reduced at PGI2 concentrations higher than 0.5 ng/ml. The results suggest that PGI2 even at high concentration does not interfere with the primary process of platelet adhesion, i.e., with the formation of a monocellular platelet layer on collagen fibrils and artificial surfaces, but it inhibits clumping of further platelets to this layer and prevents subsequent platelet thrombus formation.

Collagen↗
PubMed1980

Inhibition of platelet factor 3 availability by prostacyclin.

Preincubation of human platelet rich plasma with PGI2 in a concentration preventing collagen induced platelet aggregation abolished also platelet factor 3 availability brought about by collagen. Following PGI2 pretreatment no second wave aggregation could be elicited by ristocetin. However, primary aggregation as well as platelet factor 3 activity were only partially inhibited in this case and the inhibitory action of PGI2 was not increased by raising its concentration. Similarly, marked but not complete inhibition of platelet factor 3 availability was obtained when kaolin was used as activating agent.

Blood Coagulation Factors↗
PubMed1979

Fragmentation of actin by thrombin-like snake venom proteases.

The effect of thrombin-like snake venom proteases (Ancrod of Agkistrodon rhodostoma and Batroxobins of Bothrops moojeni and Bothrops marajoensis) on skeletal muscle actin was studied and compared to the thrombic cleavage of this protein. Only EDTA-pretreated G- and F-actin were split by thrombin and Ancrod, while Batroxobins hydrolyzed native G-actin, too. The time course of digestion was followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. A split product of 37 500 daltons appeared first which was cleaved further resulting in three lower molecular weight fragments. The sodium dodecyl sulfate gel pattern of thrombic fragmentation was well distinguishable from those caused by Ancrod and Batroxobins. The first split products of Batroxobin digestion--a smaller peptide and the 37 500 dalton fragment--were isolated and by estimating their N-, and C-terminal end groups and amino acid compositions the peptide bond hydrolyzed first was located in the primary structure of actin. It was established that while thrombin split off two actino-peptides (at Arg(28)-Ala(29) and Arg(39)-His(40) from the N-terminal end of the molecule only Arg(39)-His(40) was cleaved by Batroxobins.

Actins↗
PubMed1979

Biochemical mechanism of platelet activation. Involvement of contractile proteins.

The present state of knowledge of the biochemical mechanism of platelet activation (adhesion, shape change, microspike formation, aggregation, release reaction, clot retraction) is presented under involvement of contractile proteins. The working hypothesis on the contractile mechanism of platelet activation is explained.

Actomyosin↗
PubMed1977

Platelet activating factor, the trigger of haemostatic alterations in rat anaphylaxis.

Platelet-activating factor (PAF) generated by an IgE-mediated reaction in the peritoneal cabity of rats was partially purified by adsorption to diatomaceous earth. It aggregated rat platelets and, as a consequence, activated Hageman factor in in vitro, as well as in vivo, conditions. The haemostatic alterations induced by PAF showed similarity to those observed in the early phase of rat anaphylaxis.

Anaphylaxis↗
PubMed1976

Cleavage of thrombosthenin A by thrombin. Evidence for the existence of two types of bovine platelet actin.

Bovin platelet actin prepared by Spudich's method (Spudich, J. A. (1972) Cold Spring Harbor Symp. Quant. Biol. 27, 585-594) separated into two peaks on a Sephadex G-200 column. The actin of both peaks had a mol. wt. of 42 000 on sodium dodecyl sulfate-polyacrylamide gel and activated myosin ATPase, although in a quantitatively different manner. Actin eluted in the first peak (probably an oligomeric form) was not polymerized in 2 mM MgCl2 and 0.05 M KCl, while that of the second peak went through normal G-F transformation. If CaATP was present in the incubation mixture neither actin was attacked by thrombin. However, if EDTA was added, thrombin split G-actins and the pattern of cleavage was the same as that found for muscle actin in our earlier studies, i.e. the final split products were two actinopeptides and two larger fragments of 26 500 and 11 000 daltons. It is suggested that the possible attraction of membrane-associated platelet actin for thrombin may have an importance in thrombin-induced platelet aggregation.

Actins↗
PubMed1976

Platelets in rat anaphylaxis.

The number of circulating platelets dropped abruptly in the early phase of severe anaphylactic shock (AS) of the rat and could be inhibited by Persantin but not by heparin pretreatment. The results strongly suggest that an aggregating agent, perhaps "platelet aggregating factor", formed or released during anaphylaxis is responsible for the decrease of platelet number. The organ distribution of 51Cr labelled platelets showed that in AS the aggregated platelets were removed from the circulation mostly by the spleen and part of them were trapped in the lung and the small intestine. The remaining platelets retained their functional integrity. The loss of circulating platelets is manifested by the prolongation of rat tail bleeding time and is one of the factors participating in the haemostatic disturbances during anaphylaxis.

Anaphylaxis↗
PubMed1976

Activation and consumption of Hageman factor in the anaphylactic shock of the rat.

In the early stages of anaphylactic shock of rats pretreated with Bordetella pertussis vaccine, a prompt and parallel activation of the factor XIIa-dependent intrinsic coagulation, kinin generation, and fibrinolytic acticity was observed. The coagulation studies, the similarity of anaphylactic results with those produced by a single injection of ellagic acid, and the effective inhibition of the anaphylactic and the ellagic acid-induced activation of these pathways by lysozyme all suggest that factor XII itself becomes activated in rat anaphylaxis. As the reaction proceeded, considerable anticoagulant activities emerged, but the bradykinin and the plasminogen activator levels even further increased. During the first 10 min of anaphylactic shock, factor XII was partly consumed and this was prevented by epsilon-aminocaproic acid infusion. The results show that in pathological conditions such as anaphylaxis there is an intimate in vivo interaction among the three factor XIIa-dependent pathways.

Aminocaproates↗
PubMed1975

Evidence of fibrinogen degradation in rat anaphylaxis.

In active anaphylactic shock of rats pretreated with Bordetella pertussis vaccine, both plasma thrombin clotting time and the amount of antigenically active fibrinogen degradation products in the serum were increased. The formation of clottable fibrinogen fragments was shown by SDS polyacrylamide gel electrophoresis of thrombin-induced clots. When plasma of rats pretreated with 125I rat fibrinogen and then subjected to anaphylaxis was submitted to SDS polyacrylamide gel electrophoresis, fibrinogen-split products were also detected. Fibrinogen degradation results from the proteolytic effect of an activated fibrinolytic enzyme.

Anaphylaxis↗
PubMed1974

Cleavage of actin by thrombin.

Under certain conditions actin can be split by thrombin. Actin prepared in the presence of excess Ca(++) was found to be resistant to thrombin. However, if actin was purified without added Ca(++), both G- and F- actin underwent thrombic digestion, although a considerable proportion of actin molecules remained intact. Similar results were obtained with actin (in 50% sucrose) devoid of nucleotide and divalent cations but retaining its native characteristic. The removal of tightly bound Ca(++) from actin by EDTA accelerated the thrombic splitting and made the complete fragmentation of G-actin possible. Thrombin first cleaves actin into two pieces and subsequently one of them, fragment K (molecular weight 37,000 on sodium dodecyl sulfate-polyacrylamide gel), splits further, resulting in fragments L (molecular weight 27,000) and M (molecular weight about 10,000).

Actins↗