Red Thrombus Research Articles

Decreased plasminogen activator but normal prostacyclin activity in rat veins during development of experimental thrombosis

The course of two vascular activities (plasminogen activator and prostacyclin) was measured on venous specimens taken from rats before and during development of experimental venous thrombosis (induced by venous stasis). Vascular plasminogen activator activity (measured by a histochemical technique) increased immediately after ligature of the inferior vena cava, then progressively declined up till the appearance of a visible red thrombus; it virtually disappeared in concomitance with the formation and growth of the thrombus. Blood fibrinolytic activity closely followed the course of vascular plasminogen activator activity. In contrast, vascular prostacyclin (platelet aggregation inhibitory) activity remained within the normal range throughout the observation period (20 minutes - 48 hours). These results indicate that the course of two potential antithrombotic defence activities may be dissociated during the development of experimental venous thrombosis. The model used may provide some hints as to the relative roles of fibrinolytic and platelet inhibitory activities released from vascular endothelium in response to thrombogenic stimuli.

A simple in vitro screening test for blood compatibility of materials

An in vitro closed-cell kinetic blood-coagulation test was developed and used to evaluate the blood compatibility of materials. The test compares the clotformation rate on a test surface to that of a control material, Silastic. This method avoids anticoagulants, blood flow variations, and the exposure to air and other foreign surfaces. Eight pairs of cells are sequentially evaluated as to the weight of thrombus formed, the amount of unclotted blood, and the reduction in platelet count of the blood exposed to both the test materials and the control. These data are used to calculate a relative index whereby materials can be rated quantitatively as to the rate of clot formation on their surface. The order of decreasing clot formation on one group of materials studied was as follows: biolized (Imai et al., Trans. Amer. Soc. Artif. Int. Organs, 17, 6, 1973) poly (ether urethane), segmented polyurethane, formaldehyde-treated pericardium, Hydron, glutaraldehyde-treated pericardium, biolized natural rubber, Hexsyn, heparinized natural rubber, Silastic, and natural rubber. Urethane and aldehyde-treated natural tissue had a lower percentage of red thrombus formation. These results generally correlate with in vivo observations.

The structure and growth of valve-pocket thrombi in femoral veins.

The structure of 50 small thrombi in femoral valve pockets and the microscopic contents of 35 apparently empty pockets were studied in an attempt to ascertain the nature of the microscopic nidi from which thrombi form and their manner of growth to visible thrombi. Sixteen thrombi had little or no cellular invasion. Most of these recent structures had two main regions, red areas restricted distally in the pocket by the vein wall, and larger white regions comprising most of the thrombus length and often covering the red areas. Red areas are the early sites of cellular adhesion and invasion and the likely sites of origin of most thrombi. They were usually dominated by red cells and fibrin. White zones, which represent propagation growth, are characterized by many foci of platelets with fibrin borders (platelet-fibrin units). Some red areas also contained platelet-fibrin units but they were few and tiny; platelets were not seen in others and one small wholly red thrombus was devoid of platelets. Degenerative changes in platelet-fibrin units were observed, and it is postulated that many become purely fibrin structures. There was no significant evidence of preceding intimal damage in the vein wall. Therefore nidi are laid down on normal endothelium probably on the vein wall near the apex of the pocket. Some pockets, empty of thrombi, contained condensed foci of red cells or tiny fibrin fragments surfaced by endothelial cells and considered to be the remnants of aborted thrombi; a few contained clumps of platelets or leucocytes. It is postulated that any of these may represent the nidi from which thrombi grow. Several thrombi also incorporated large fat droplets, numerous in two. Fat embolic globules derived from fractures are their likely source.

Platelets and thrombogenesis—Current concepts

Anticoagulants, although effective in the treatment of venous thrombotic disease, have not been generally helpful in preventing arterial thrombosis. The reason for this disparity may lie in the type of clot formed in each case. In veins a “red thrombus” is formed, consisting of erythrocytes, leukocytes, fibrin, and platelets randomly distributed, whereas in arteries a “white thrombus” consisting mainly of platelets and fibrin strands is the obstructing lesion 1. The predominance of platelets in this “white” clot has focused attention on their importance in arterial occlusion and has suggested that therapeutic maneuvers directed at platelet function may be more useful than standard anticoagulant therapy. This review presents the recent advances in the study of platelet morphology and function, and concludes by discussing possible therapeutic avenues.

Traumatic right coronary artery occlusion incident to retrograde left ventricular catheterization with a stiff catheter ∗

Right coronary arterial occlusion occurred during or after retrograde left ventricular catheterization and angiocardiography in a 55 year old woman with chronic rheumatic heart disease. Ventricular fibrillation developed eight hours later, and she could not be resuscitated. Necropsy showed the occlusion to be due to subintimal hemorrhage at the site of a small atheromatous plaque near the origin of the artery, with dark red thrombus beyond the intimai lesion. The fatal lesion was ascribed to intimai trauma caused by the tip of a Gensini catheter seen to enter the artery during the early stages of the investigation. Eleven other major nonfatal complications were encountered during 97 retrograde catheterizations for left ventricular angiocardiography.

The Modification of Experimental Occlusive Arterial Thrombosis in the Rat by Malayan Pit Viper Venom

SummaryThe effect of Malayan pit viper (Ancistrodon rhodostoma) venom on the fate of experimental arterial thrombosis was studied in rats. A suitable daily dose of venom (500 μg) was used to induce hypofibrinogenaemia in the treated rats for the greater part of each of three consecutive post-operative days.The treated animals showed a statistically significant overall reduction in the incidence of both red thrombus formation and thrombotic arterial occlusion when compared to a control group. This antithrombotic effect of the venom could be observed in the 7-day period following the cessation of the treatment.

Thrombogenesis.

I SHOULD like to develop a concept of the normal hemostatic mechanism and of the pathogenesis of thrombosis consistent with the pathways of coagulation of blood as they are now understood. When possible I shall draw on in vivo experiments to buttress my remarks. The understanding of blood coagulation, however, is still imperfect, and knowledge of it derives primarily from tests performed outside the body.Pathologists recognize 3 types of thrombus, each of which may have a different pathophysiology. The first is the red thrombus, which is composed primarily of red cells and fibrin. Its morphology closely resembles that of . . .

Susceptibility to Thrombosis in Normal Young, Aging, Cortisone-treated, Heparinized and X-irradiated Hamsters as Tested by Topical Application of Thrombin

Abstract 1. Thrombin applied topically to the everted cheek pouch of the hamster produced platelet and not red thrombi in exposed, uninjured blood vessels with circulating blood. Red thrombi were produced in stagnant blood. Thrombus formation occurred in the venules for the most part and seldom in arterioles or capillaries. 2. An in vivo test for platelet thrombus susceptibility, based on the thrombin reaction and the resistance of the hamster to thrombosis, has been described. 3. Thrombus susceptibility, measured by the thrombin test, increased with age and during cortisone treatment, and decreased after heparin injection and following large doses of whole body x-irradiation. 4. The thrombin susceptibility test could be correlated with the platelet count in x-irradiated hamsters, showing a relatively critical minimum concentration of blood platelets (100,000/cu.mm.) required for platelet thrombosis. 5. The relationship of platelet concentration to platelet thrombus formation and predisposition to hemorrhage has been discussed.

PULMONARY EMBOLISM

Any discussion of pulmonary embolism must concern itself primarily with a consideration of the fundamental problem of venous thrombosis. Many years ago Virchow,1Aschoff2and Welch3set forth the fundamentals of the mechanics of red and white thrombus formation, which can still be found in any modern textbook. Innumerable publications on pulmonary embolism and thrombophlebitis have since confirmed the findings of the original investigators. The word thrombophlebitis poorly describes the spontaneous venous thrombosis which occurs postoperatively and in medical patients at rest in bed, because the ending of the word suggests that inflammation is present. Any inflammation in the wall of the vein or in the thrombus is a secondary manifestation and not a primary cause. The type of thrombophlebitis caused by local trauma or infection does not pertain to this discussion. Our concern is with spontaneous intravenous clotting, and this will be referred to in the

STUDIES IN EXPERIMENTAL EXTRACORPOREAL THROMBOSIS

In experimental obstructive jaundice in rabbits, thrombosis is definitely delayed in the extracorporeal loop. White thrombi are laid down at the normal rate in many instances; in others there is a delay in deposition of platelets, while in still others cauliflower-like masses of platelets are rapidly deposited and tend to slow or even stop the blood stream before much fibrin is apparent. Fibrin deposits and formation of the red thrombus usually appear late in the experiment and often only at the ends of the collodion tubes. In vigorous animals, the thrombi rarely tend to obstruct and usually cease growing when they have made up the difference between the lumen of the glass tube and of the collodion tube. On the other hand, if the animal's general condition is poor and its circulation depressed, red thrombus forms more rapidly and tends to encroach progressively on the lumen until obstruction takes place. Even in such cases circulation through the loop persists for periods much longer than in the normal animal. Judging from the gross appearance of the thrombus the quantity and quality of fibrin seem deficient. Single injections of bile salts yield pictures similar to those seen in experimental obstructive jaundice. White thrombi are deposited but obstruction of the lumen is delayed because of inadequate formation of fibrin. The continuous intravenous injection of bile salts resulted in a progressive increase of the clotting time and in the level of bile acids of the blood. The state of the extracorporeal loop was likewise similar in many respects to that seen in obstructive jaundice. There was, however, a definite decrease in the size and numbers of white thrombi deposited on the collodion membrane. From the evidence presented it is obvious that the processes of blood coagulation and of thrombosis in the extracorporeal loop are definitely delayed in experimental obstructive jaundice and in animals that have received intravenous injections of bile salts. No attempt is made to explain the changes found in jaundice on the basis of the increased levels of bile acids in the blood although these experiments would indicate that such a possibility has not been ruled out.

STUDIES IN EXPERIMENTAL EXTRACORPOREAL THROMBOSIS

1. Distilled water dialyzes through the collodion tube and causes hemolysis. Clotting of the hemolyzed blood in the collodion tube occurs later. 2. Bile salts accelerate the appearance and development of white thrombi in the heparinized animal. The masses of white thrombi are very loose, soft, fragile and easily broken into clumps of platelets. They are poor in fibrin or the fibrin is abnormal, since they have less retractility than those obtained from the use of physiologic sodium chloride solution or calcium chloride or serum. Despite the increase in number and size of white thrombi, normal clotting does not occur. 3. When the collodion tube is surrounded by 1 or 2 per cent d-glucose solution, tiny and numerous white thrombi appear as radiating figures. The masses of white thrombi are rather loose and fragile. The clotting time of the heparinized blood does not appear to be shortened. 4. When a 1 to 2 per cent solution of calcium chloride is used as the dialyzing fluid outside the collodion tube, or when it is injected into the circulation, the formation of white thrombi is accelerated. They grow very rapidly. In spite of the action of heparin, the white thrombi formed are not so fragile as when bile salts are placed outside of the collodion tube. Fibrin seems to form easily. Obstruction of venous cannula takes place speedily and if the clots in the cannula are not removed, the white thrombi in the collodion tube remain small and become red by sedimentation of red cells. 5. Intravenous use of 10 per cent solution of magnesium sulfate without heparin retards the coagulation of circulating blood and permits the blood to flow through the extracorporeal loop from three to four times as long as normal. The formation of white thrombi, as well as red, is retarded. Magnesium sulfate (1 per cent) in physiologic sodium chloride solution placed outside the collodion tube markedly retards the formation of white and red thrombi in the heparinized animal. Magnesium sulfate (10 per cent), 50 mg. for each kilo of body weight each hour, administered intravascularly in the heparinized animal definitely prevents the first stages of thrombosis, and consequently prevents clotting. 6. It is possible by the combined use of adequate amounts of magnesium sulfate and of heparin intravenously to prevent all stages of thrombus formation for from 1 to 3 hours.

AN EXPERIMENTAL STUDY OF THE LATE GLOMERULAR LESIONS CAUSED BY CROTALUS VENOM

The acute exudative glomerular lesion of the rabbit's kidney caused by crotalus venom does not lead to a subacute or chronic glomerulonephritis. The hemorrhagic lesion of the glomerular tuft may show a process of repair characterized by the ingrowth, into the hemorrhagic masses, of endothelial cells from the uninjured part of the tuft. This process is, however, more analogous to the organization of a red thrombus than it is to any form of glomerular lesion known in man, and can hardly serve as an experimental demonstration of the mode of development of a subacute or chronic glomerular nephritis. On the other hand, crotalus venom causes a persistent albuminuria and extensive tubular degeneration and cast formation, with death, preceded by great emaciation, after five to six weeks.