Experimental study of the antithrombogenic behavior of Dacron vascular grafts coated with hydrophilic acrylic copolymers bearing salicylic acid residues.

The objective of the present work was study of the behavior of active coatings of hydrophilic acrylic polymers bearing salicylic acid residues linked covalently to the macromolecular chains, after their application to woven and knitted Dacron vascular grafts. In vitro tests were carried out under dynamic flow conditions using equipment especially designed to reproduce physiologic conditions, to determine the retention of the coating using a saline solution. Ex vivo tests were carried out in an extracorporeal circuit using the dog as an animal model. The study of the deposition of platelets was followed by labeling of autologous platelets with 111In-oxine, as well as by analysis of the surfaces of the prostheses by scanning electron microscopy. An application of thin coatings of hydrophilic acrylic copolymers improves the antithrombogenicity of the vascular grafts with respect to the uncoated prosthesis. The presence of relatively small amounts of units bearing salicylic acid residues in the copolymer chains (5-20 wt %) gives good results when they are applied to woven and knitten Dacron meshes which have been quantified by analysis of the percentage of radiotracer on the surface of the vascular grafts tested in ex vivo experiments. The salicylic acid residues are released slowly to the medium by hydrolysis of the reversible covalent bonds of this compound to the acrylic macromolecular chains, which provides an additional antiaggregating effect for platelets. The polymeric coating forms a thin active film which improves the antithrombogenic properties of the surface of woven or knitted Dacron vascular grafts in ex vivo experiments.

Application of new coatings for vascular grafts based on polyacrylic systems with antiaggregating activity.

A study has been made of the behaviour of knitted and woven Dacron mesh used in the preparation of vascular grafts when coated with either a layer of poly(2-hydroxyethyl methacrylate) or co-polymers of 2-hydroxyethyl methacrylate with 5, 10 or 20 wt% of an acrylic derivative of salicylic acid, 2-methacryloyloxybenzoic acid. In vitro studies were carried out to quantify the loss of polymer under flow conditions, and ex vivo studies were done in dogs to quantify the deposition of 111In-oxine-labelled platelets. The treated materials showed a lesser deposition of platelet thrombi when compared with the control group.

Prevention of thrombus formation on biomaterials exposed to blood using different antiplatelet drugs: experimental study in dogs.

An ex vivo shunt, established in dogs between both femoral arteries and right atrium, has been used to quantify the platelet deposition on six prosthetic materials used in the construction of cardiovascular prostheses: highly porous knitted Dacron (intervascular HP 800, 1400 mL/cm2/min/120 mm Hg), low-porosity woven Dacron (intervascular LP 200, 200 mL/cm2/min/120 mm Hg), double velour knitted Dacron, Avcothane 51 elastomere, and the mesothelial and epipericardial surfaces of bovine pericardium. In the search for a method to prevent platelet thrombi formation on these materials, we studied four groups of dogs: group 1 (control), group 2 (5 mg/kg body weight (BW)/day acetylsalicylic acid), group 3 (20 mg/kg BW/day acetylsalicylic acid), and group 4 (5 mg/kg BW/day acetylsalicylic acid plus 5 mg/kg BW/day dipyridamole). Platelets were labeled with 111In-oxine. The least thrombogenic material was Avcothane 51 elastomere. The only effective treatment for reduction of platelet deposition on the six materials was 5 mg/kg BW/day of acetylsalicylic acid. The dose used in group 3 only decreased the deposition of platelets on three of the six materials studied. The treatment employed in group 4 did not significantly reduce the deposition of platelets on any of the materials when compared with the control group.

[Thrombosis from prosthetic materials: prevention with different antiaggregatory agents. Low dose aspirin?]. / Trombosis sobre materiales protésicos: prevención con distintos fármacos antiagregantes. Aspirina a dosis bajas?

Using an ex vivo shunt in dogs, platelet deposition on 6 prosthetic materials used in the construction of cardiovascular prostheses [highly porous Knitted Dacron (intervascular HP 800, 1,400 ml/cm2/min/120 mmHg), Woven Dacron of low porosity (intervascular LP 200, 200 ml/cm2/min/120 mmHg), Doble Velour Knitted Dacron, Avcothane 51 elastomere and the mesothelial and epipericardial surfaces of bovine pericardium] was quantified. The study of the prevention of platelet thrombi formation on these materials was carried out in 6 groups of 8 animals: group 1 (control), group 2 (5 mg/kg body weight/day acetylsalicylic acid), group 3 (20 mg/kg body weight/day acetylsalicylic acid), group 4 (15 mg/kg body wt/day triflusal plus 5 mg/kg body wt/day dipyridamole), group 5 (15 mg/kg body wt/day triflusal) and group 6 (5 mg/kg body wt/day acetylsalicylic acid plus 5 mg/kg body wt/day dipyridamole). Platelets were labeled with 111In-oxine. The least thrombogenic material was Avcothane 51 elastomere. The only effective treatment for reduction of platelet deposition on the 6 materials was that used in group 2. The treatment used in group 3 only decreased the deposition of platelets on 3 of the 6 materials. The treatments employed in groups 4, 5 and 6 did not significantly diminish the deposition of platelets on any of the materials when compared with the control group. The platelet count was not modified in the animals in groups 2 and 4 while in the rest it decreased after the test.

[Use of aspirin in the primary prevention of vascular thrombi. A comparative study with other anti-aggregant drugs]. / Utilización de la aspirina en la prevención primaria de trombos vasculares. Estudio comparativo con otros fármacos antiagregantes.

We have induced the formation of arterial (carotid) and venous (femoral) thrombi in dogs by means of an intima lesion produced by continuous current. The platelets were labeled with 111In oxine. Groups of 7 mongrel dogs received treatment for 7 days prior to the trial: group I, control; group II, 5 mg/kg body weight/day acetylsalicylic acid; group III, 20 mg/kg body weight/day acetylsalicylic acid; group IV, 15 mg/kg body weight/day triflusal + 5 mg/kg body weight/day dipyridamole; group V, 15 mg/kg body weight/day triflusal; and group VI, 5 mg/kg body weight/day acetylsalicylic acid + 5 mg/kg body weight/day dipyridamole. The only effective treatment for arterial thrombosis prevention was that employed in group II (p less than 0.05). Venous thrombosis was prevented in groups II (p less than 0.01), III (p less than 0.01) and VI (p less than 0.01).

Lewis phenotypes and secretor character in the "Castilla la Nueva"-region (Spain). ABH and Lewis antigen levels in salivary secretion.

In 1980 blood and saliva samples were taken from Spanish students of the University of Madrid. Red cells were analysed for A1B2BO and Lewis blood groups. Saliva samples were tested to detect the specific group substances ABH, Lea and Leb. A slightly higher frequency of the "le" gene (0.419) was found in our sample as compared to other Spanish samples. The phenotype frequencies of ABH secretors (77.2%) and non-secretors (22.8%) are in the range of other European populations. The levels of A and B antigens of individuals belonging to these blood groups were similar, whereas the average titration of the H substance showed the relation O greater than A2 greater than A1 greater than A1B greater than B. Analysis of variance proved this heterogeneity to be statistically significant. The amount of Lea substance in non-secretors was higher than in secretors. This shows again that the ABH secretor status has some influence on the quantity of this antigen. The average titration of the Leb substance in secretors was higher than that of Lea in individuals belonging to O, A and AB blood groups, but not in those with blood group B.