PubMed Health⌕ Search

Biomedical subjects

Y J Legrand

Publications and source records attributed to Y J Legrand.

36 records · Page 2Linked to original sources
PubMed1984

Differentiation of the elastase-type protease of platelets from other elastases.

Elastase activities were determined near neutral pH on several specific substrates using platelet-derived preparations mixed with decreasing amounts of leukocytes. Activities were extrapolated to zero leukocyte content enabling the estimation of intrinsic platelet elastase activity. In contrast to human leukocyte elastase, metal chelating agents inhibited partly the elastase activity of the platelet extract and soybean trypsin inhibitor did not modify its activity. Serine active site titrants (phenylmethane sulfonyl fluoride) as well as acetyl-di-L-alanyl-L-propyl-L-valine chloromethylketone completely abolished the activity of platelet lysates. The platelet protease was purified from Triton X-100 platelet lysates. No cross-reactivity could be demonstrated by immunoelectrophoresis with either porcine pancreatic elastase or human leukocyte elastase using monospecific antisera. Applying gel electrophoresis, most of the elastase activity of the platelet protease migrated towards the anode, whereas the pancreatic and leukocyte elastases migrated towards the cathode. The anionic character of the platelet enzyme might explain its capacity to degrade better elastin treated with cationic detergents in contradistinction to other elastases which act better on anionic detergent-treated elastins.

Animals↗
PubMed1983

Effect of a collagen derived octapeptide on different steps of the platelet/collagen interaction.

The interaction of platelets with collagen involves short aminoacid sequences which recur along the fibres. Platelet aggregation by collagen and serotonin release is inhibited by a synthetic octapeptide LYS-PRO-GLY-GLU- PRO-GLY-PRO-LYS- derived from type III collagen. In contrast, this octapeptide inhibits only weakly the retention of platelets labelled with 111Indium to collagen, suggesting that it has a limited effect on platelet adhesion. Preincubation of the octapeptide with platelets inhibits the rise of cAMP level caused by activating adenylate cyclase by various concentrations of PGI2. The octapeptide at 5 mM reverses the inhibition by PGI2 of the adhesion of platelets to collagen. These results suggest that the octapeptide affects the intrinsic activity (manifested as platelet aggregation and secretion) more than the recognition of collagen by its receptor (manifested by adhesion).

Adenylyl Cyclases↗
PubMed1983

[Collagen nonapeptide, a trap for platelets].

Biochemical methods involving chemical and enzymatic cleavage of type III collagen (characteristic of arterial subendothelium) have led to the identification of a nonapeptide common to different overlapping collagen fragments capable of interacting with platelets. This nonapeptide has been synthesized; it specifically inhibits platelet aggregation and secretion of endogenous platelet serotonin by type III collagen from which it originates. Its effect on platelet adhesion is moderate. In view of its specificity in the platelet-collagen interaction, its use as a mean of preventing thrombosis can be envisaged.

Blood Platelets↗
PubMed1983

Interaction of blood platelets with a microfibrillar extract from adult bovine aorta: requirement for von Willebrand factor.

Adult bovine aortic tissue was treated with 6 M guanidinium chloride in the presence of proteinase inhibitors to obtain an extract that was essentially devoid of collagenous components and appeared homogeneous by electron microscopy. When this extract was dispersed by sonication it was found to be a very potent inducer of human platelet aggregation. This interaction required the presence of von Willebrand factor and of its receptor (glycoprotein Ib) on platelet membrane. This was demonstrated by the fact that the aggregation of normal blood platelets resuspended in plasmas deficient in von Willebrand factor was significantly diminished as compared to aggregation in control plasma. Moreover, this aggregation was inhibited by a monoclonal antibody, IgG AN51, to platelet glycoprotein Ib. These studies provide direct biochemical evidence for the existence of a thrombogenic constituent of the vessel wall that is noncollagenous and von Willebrand factor-dependent.

Amino Acids↗
PubMed1983

The molecular interaction between platelet and vascular wall.

Two different subendothelial macromolecules have been identified as being thrombogenic: collagen and the microfibrils associated with elastin. The interaction between platelets and collagen involves the binding of platelet membrane receptors by numerous sites repeatedly staggered along a collagen fiber: this explains why the preservation of ordered structures (quaternary and tertiary structures) is so important in the reactivity of collagen towards platelets. In the case of Type III collagen, a nonapeptide has been identified as possibly being part of these repetitive sites. The microfibrils have not yet been characterized, although the biochemical data presently available show that they are acidic glycoproteins resistant to collagenase. Microfibrils extracted from human placenta or bovine aorta induce the aggregation of platelets in a reaction which involves platelet glycoprotein Ib and FVIII/vWF. A general model proposed for explaining platelet adhesion to subendothelium suggests that two different mechanisms should be envisaged depending on the thrombogenic macromolecules (collagen, microfibrils) involved.

Binding Sites↗
PubMed1982

A comparison of the inhibitory effects of prostacyclin and carbacyclin on platelet adhesion to collagen.

The effect of carbacyclin, a chemically stable analogue of prostacyclin (PGI2), on the adhesion of platelets to collagen has been examined. The compound was compared to PGI2 which is unstable and rapidly hydrolysed to the inactive derivative, 6-oxo-PGF 1 alpha. The adhesion of 111Indium-labelled human platelets to collagen in the absence of platelet aggregation and secretion was measured. The cAMP level in the platelets was also monitored. Both PGI2 and carbacyclin inhibited platelet-collagen adhesion and caused a rise in the platelet cAMP level. Carbacyclin was approximately 15-fold less effective than PGI2, however, its effect was longer lasting, remaining constant for at least 30 minutes.

Blood Platelets↗
PubMed1982

Prostaglandins: specific inhibition of platelet adhesion to collagen and relationship with cAMP level.

The effect of 3 prostaglandins (PG's) (I2, D2 and E1) on the adhesion of platelets to purified type III collagen has been investigated. A quantitative method for a specific evaluation of the adhesion has been applied and has revealed an inhibition of adhesion by low concentrations (10(-10)M) of PGs added before collagen; the effect varied as a function of the dose of PGs (maximum at 10(-6)M) which also induced an increase in the level of platelet cAMP. The inhibition of adhesion and the elevation of platelet cAMP followed the same time course and were either of short duration (rapid decrease in the induced effects after 15 and 45 seconds in the case of PGE1) or longer lasting (maximum effect maintained for 5 minutes in the case of PGI2 and D2). These effects were potentiated by a phosphodiesterase inhibitor such as theophylline (10(-3)M). The addition of PGs after collagen resulted in a reduction of the enhancement of cAMP, associated with a decrease in the inhibition of adhesion. Moreover, the addition of exogenous cAMP (dibutyryl N6-02' cAMP) induced a comparable inhibition. A correlation between the adhesion of platelets to collagen and the level of either endogenous or exogenous cAMP has been established. The PGs also inhibited the platelet release reaction from the alpha granules (beta TG) and the dense bodies. (5-HT and ADP). A greater inhibition of release than of adhesion was observed for the same doses of PGs added.

Alprostadil↗
PubMed1982

Histochemical and ultrastructural characterization of subendothelial glycoprotein microfibrils interacting with platelets.

The interaction of human blood platelets with collagenase-treated rabbit subendothelium was studied by histochemical ultrastructural methods and by morphometric semi-quantitative analysis. Aortas were deendothelialized and incubated: 1) with a highly purified bacterial collagenase whose specificity was controlled; and 2) with the same collagenase followed by chymotrypsin. For histochemical studies, tannic acid, ruthenium red, and peroxidase-labeled Ricinus communis and concanavalin A were used. Electron microscopy showed that after digestion of fibrillar collagen by collagenase, adherent and aggregated platelets were observed on Ricinus communis-, concanavalin A-, and ruthenium red-positive glycoprotein microfibrils. After successive incubation with collagenase and chymotrypsin, the microfibrils disappeared. No platelets were observed on the remnant amorphous elastin. Morphometric analysis confirmed the interaction of platelets with collagenase-treated subendothelium. In addition, glycoproteins were extracted from collagenase-treated rabbit aortas using 5 M guanidine. Using an in vitro quantitative test, significant platelet adhesion to these glycoproteins was observed. Our results show an interaction between platelets and noncollagenic glycoprotein microfibrils.

Animals↗
PubMed1979

Specific and quantitative method for estimation of platelet adhesion to fibrillar collagen.

A quantitative method (Sepharose test) was devised to measure the adhesion of blood platelets to fibrillar collagen. [14C]5HT-labeled platelets were isolated from plasma, resuspended in EDTA buffer, and incubated with buffer (control) or with fibrillar collagen for 150 sec at 33 degrees C. The mixtures were then filtered through Sepharose 2B columns. In controls the platelets were rapidly eluted, and this was confirmed after 51Cr labeling. [C]5HT was recovered in two stages: 60% with the platelets and 40% retarded, as free 5HT. After incubation with fibrillar collagen (50 micrograms), platelets were retained with the fibrils on the top of the column, and only free [14C]5HT (released from the platelets) was eluted. The percentage of adhesion depended on the number of platelets, the amount of collagen, its degree of polymerization, and the time of incubation at 33 degrees C. [14C]5HT release was markedly diminished when both incubation and filtration were performed at low temperature. ASA, used either in vitro or in vivo in rabbits, did not change the percentage of adhesion but significantly diminished the total amount of [14C]5HT eluted. This method offers a quantitative and reproducible system for the differentiation of adhesion and release, independent of platelet aggregation.

Animals↗