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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of heparin and prostacyclin to improve streptokinase-induced recanalization was examined in open-chest dogs subjected to thrombotic occlusion of the left circumflex coronary artery. Vessel injury was produced by electrical stimulation of the intimal surface at the site of a noncircumferential fixed stenosis. Animals were divided into three treatment groups as follows: group 1 received intracoronary streptokinase alone (75,000 units/80 min starting 30 min postocclusion; n = 8); group 2 received streptokinase plus heparin (300 units/kg i.v. at 20 min postocclusion; n = 7); group 3 received streptokinase plus heparin plus prostacyclin (500 ng/kg/min, intracoronary, given intermittently during reperfusion; n = 7). Overall, the groups did not differ with respect to preocclusion coronary blood flow (27 +/- 1 ml/min; +/- SEM), the duration of streptokinase infusion required to achieve reflow (15 +/- 2 min), and the percentage of animals recanalized (85%). They did differ in the average rate of reflow, which was greater in group 2 (16 +/- 2 ml/min) and group 3 (20 +/- 4 ml/min) as compared with group 1 (6 +/- 1 ml/min; p less than 0.05). The intermittent reocclusions which persisted during reperfusion in group 1 and 2 dogs were diminished during the periodic infusions of prostacyclin. Thrombus mass at the site of injury was comparable among groups. In contrast, distal circumflex thrombi, about twice the weight of the proximal mass, were observed in all group 1 dogs and were undetectable in group 2 and 3 animals. Transient improvements in contractile force during reperfusion were observed only with groups 2 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Augmentation of streptokinase-induced thrombolysis by heparin and prostacyclin. 241 Jul 16

Thrombus formation, cell adhesion, mineralization, and the adsorbed protein layer have been investigated on blood contacting surfaces of the Utah-100 total artificial heart (TAH). Retrieval analysis was performed on two calves (at 7 and 97 days) and a sheep (at 21 days). Six locations on each ventricle were systematically evaluated by scanning electron microscopy. Transmission electron microscopy was used to measure the thickness and distribution of proteins (albumin, IgG, and fibrinogen) on the surface. Gross thrombus was detected only on the left atrial cuff in the 97 day calf. SEM demonstrated fairly clear surface morphology, with minimal platelet adhesion and activation, and little thrombus formation. At 97 days, calcium deposits were detected along the diaphragm-housing junction. Protein layer thickness on the diaphragm increased with implant time; dominant proteins detected on the surface were fibrinogen and IgG, rather than albumin. Improvements in design and fabrication techniques have demonstrated decreased intradevice thrombosis with the U-100 TAH. However, systemic thromboembolism still remains a problem, and further improvements in the blood contacting surface of the U-100 TAH are necessary to achieve a thrombus free TAH.
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PMID:Scanning and transmission electron microscopic evaluation of the U-100 total artificial heart blood contacting surface. 268 23

The benefit of autologous endothelial cell seeding in dogs has been widely accepted. This experiment seeks to determine if a similar effect accompanies the use of xenograft (porcine) endothelial cells in dogs. Thirty-two mongrel dogs underwent thoracoabdominal aortic bypass with 25- to 30-cm segments of double velour Dacron 8-mm grafts. Endothelial cell seeding was performed with whole blood suspensions of either autologous endothelial cells (Group I) or heterologous endothelial cells from pigs (Group II). Cell-free culture medium was added to whole blood for preclotting in unseeded control animals (Group III). Ten animals in each group were sacrificed at 30 days and all grafts were patent. Thrombus-free surface areas were Group I = 61.7 (+/- 6.4%, SEM); Group II = 53.2 (+/- 6.8%, SEM); and Group III 42.2 (+/- 8.0%, SEM). There was a significant difference between autologous-seeded and unseeded grafts (P less than 0.04). Endothelialization was confirmed by scanning and transmission electron microscopy in all groups but was better in both seeded groups: Group I-9/10 grafts, Group II-8/10 grafts, and Group III-4/10 grafts. Factor VIII immunofluorescent staining confirmed the presence of endothelium on selected grafts in each group. These results raise questions concerning the proposed mechanism of endothelial seeding since xenograft cells seem to facilitate healing in the canine model. If heterograft cells can be effective, it may not be necessary to harvest cells from the recipient in order to achieve the benefits of seeding.
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PMID:Xenograft seeding of Dacron grafts in dogs. 293 93

The focus of this investigation was to examine the potential beneficial effects of the selective thromboxane synthetase inhibitor CGS 13080 (imidazo [1,5-a] pyridine-5-hexanoic acid) on coronary blood flow after streptokinase-induced thrombolysis. Thrombotic occlusion of the circumflex coronary artery was produced by electrolytic (100 microA anodal current) injury to the intimal surface of the circumflex coronary artery at the site of a noncircumferential stenosis in dogs anesthetized with pentobarbital to have open-chest surgery. Intracoronary streptokinase, 6000 IU/kg in 3 ml saline solution, was infused at 0.05 ml/min for 1 hour, beginning 30 minutes after the formation of an occlusive thrombus. The animals were assigned randomly to two groups. In group I (n = 10) the intravenous infusion of vehicle was begun simultaneously with the intracoronary administration of streptokinase and continued for 2 hours after thrombolysis had been achieved. The animals in group II (n = 10) received intravenous CGS 13080 (1 mg/kg/hr) along with intracoronary streptokinase. Infarct size was assessed by a dual perfusion technique with Evans blue and triphenyltetrazolium stains to demarcate the normally perfused myocardium from the area at risk and the infarct zone within the risk region. The two groups did not differ with respect to baseline coronary blood flow, time to the development of coronary artery thrombotic occlusion, or time to achieve thrombolysis. Oscillations in coronary blood flow were more frequent in group I than in group II (group I, 9 +/- 2.2; group II, 4.4 +/- 0.8 oscillation/min X 100, p less than 0.05 [mean +/- SEM)].(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Thromboxane synthetase inhibition with CGS 13080 improves coronary blood flow after streptokinase-induced thrombolysis. 359 2

Thrombi were electrically induced in dogs. The alterations of the vessel wall were studied in samples obtained on the 8th day from control and treated animals. Changes in coagulation parameters were monitored daily. Animals were treated with 600 mg defibrotide (Crinos) daily for a week, starting 24 h after the induction of thrombi. In the control dogs there was thickening of intima with endothelial hyperplasia and smooth muscle proliferation. The treated animals did not show any morphological or ultrastructural alterations (SEM). This observation encourages us to examine the role of fibrinolytic and endothelial supportive therapy for prevention of development of vascular changes.
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PMID:Effect of defibrotide in electrically induced thrombosis in dogs. 375 39

An acute canine ex-vivo femoral A-V shunt technique was used to study thrombus formation and embolization on a number of porous and non-porous polymer surfaces over a one-hour blood contact period. The technique allows for simultaneous exposure of all the surfaces under similar physiological and hematological conditions. This makes comparisons between surfaces more reliable. SEM was used to study changes in the morphology of platelets and thrombi present on the polymer surfaces. Quantitative information was obtained using radiolabeled platelets. In general, platelet deposition, activation, and aggregation was followed by thrombus formation which peaked at about 15-30 minutes of blood contact. Thrombi were composed mainly of platelets with few leukocytes present. Embolization was observed on Silastic (SIL), polyvinylchoride (PVC), polyethylene (PE), and oxidized polyethylene (OX-PE) surfaces between 20 and 60 minutes of blood contact. The mechanism for embolization involved clot retraction under the influence of a shear field. Leukocytes did not appear to be necessary for the initiation of embolization but were present during the embolization phase on OX-PE, possibly due to chemotactic factors. Although extensive thrombus formation was observed on the porous PTFE materials (GORE-TEX and IMPRA), the thrombi formed were flat and did not significantly block the lumen. By 60 minutes of blood contact, only minimal embolization had occurred on the PTFE surfaces. SEM examination of the sequence of thrombus formation and embolization was found to correlate well with trends in platelet deposition measured using radiolabeling techniques.
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PMID:Morphological changes occurring during thrombogenesis and embolization on biomaterials in a canine ex-vivo series shunt. 666 59

A simple venous thrombosis model in rabbits was used for the quantitative evaluation of the thrombolytic effect of human extrinsic (tissue-type) plasminogen activator as compared with urokinase.A thrombus was formed in an isolated segment of the jugular vein from a mixture of (125)I-labeled fibrinogen, whole rabbit blood, and thrombin. In order to immobilize the thrombus during lysis, it was formed around a woolen thread introduced longitudinally in the lumen of the vein. Thrombotic extension of the clot was prevented by subcutaneous injection of heparin. The extent of thrombolysis was measured as the difference between the radioactivity introduced in the clot and that recovered in the vein segment at the end of the experiment. In control animals the extent of thrombolysis was 5.6+/-1.4% (n = 5) after 6 h, 14.5+/-1.7% (n = 10) after 30 h, 16.0+/-1.5% (n = 11) after 78 h, and 48.1+/-2.7% (n = 10) after 174 h (mean+/-SEM). Extrinsic (tissue-type) plasminogen activator, highly purified from the culture fluid of a human melanoma cell line, was administered systemically or locally over a time period of 4 h and the percent thrombolysis measured 2 h after the end of the infusion. One- and two-chain extrinsic plasminogen activator had very similar thrombolytic potency. Systemic infusion resulted in a dose-dependent degree of thrombolysis. The activator-induced thrombolysis, after infusion of 100,000 IU ( congruent with1 mg protein), was approximately 75% for fresh clots, 35% for 1-d-old clots, 30% for 3-d-old clots, and 50% for 7-d-old clots. The thrombolytic activity of urokinase was more than five times lower than that of extrinsic plasminogen activator: Infusion of 500,000 IU resulted in approximately 40% lysis of fresh clots and 25% of 1-3-d-old clots, while 7-d-old clots appeared to have become resistent to urokinase. Local infusion resulted in a 5-10 times higher thrombolytic effect of both extrinsic plasminogen activator and urokinase. Thrombolysis with extrinsic plasminogen activator was not associated with systemic activation of the fibrinolytic system as evidenced by unaltered plasma levels of fibrinogen, plasminogen, and alpha(2)-antiplasmin. Systemic infusion of urokinase resulted in significant thrombolysis only at doses that were associated with disseminated plasminogen activation. Local infusion of urokinase required a 5-10-fold higher dose than extrinsic plasminogen activator to obtain a similar degree of thrombolysis, which also occurred in the absence of systemic activation of the fibrinolytic system. It is concluded that the extent of thrombolysis by extrinsic plasminogen activator is mainly determined by the dose of activator and its delivery in the vicinity of the thrombus and much less by the age of the thrombus or the molecular form of the activator. Extrinsic plasminogen activator appears to be superior to urokinase because of its higher (5-10-fold) specific thrombolytic activity and the absence of systemic activation of the fibrinolytic system, which results in defibrinogenation and a bleeding tendency.
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PMID:Thrombolysis with human extrinsic (tissue-type) plasminogen activator in rabbits with experimental jugular vein thrombosis. Effect of molecular form and dose of activator, age of the thrombus, and route of administration. 668 15

Heads of seven different types of unused and used intravenous catheters as well as tips of the corresponding needles for venipuncture, artificially cut and ruptured surfaces were either directly mounted on stubs or previously fixed in 1% phosphate buffered glutaraldehyde (pH 7.4), dehydrated with acidified 2, 2-dimethoxy-propane, dried in a critical point drying apparatus using CO2, mounted with silver-paint and sputter coated with 20 nm gold. In addition tensile tests of unused catheters were carried out. According to the tensile tests and to the SEM findings neither spontaneous breakage nor manufacturing defects may be reason of catheter embolism. Manufacturing defects at the tips of needles for venipuncture, as well as rough surfaces of the introducers or catheter walls may cause endothelial lesions. Settling of formed elements of the blood apparently is related to ruggedness of the catheter wall or to manufacturing defects. Thrombi, grown on he outer surface of the catheters are very rare. In Cavafix catheters thrombus formation is mostly related to the roughness of radio-opaque parts of the catheter wall. Outgrowth of the thrombus via the top to the outer surface could be demonstrated frequently
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PMID:Surface morphology and tensile force at breaking point or different kinds of intravenous catheters before and after usage. 733 May 73

Annexin V is a human phospholipid binding protein (M(r) 36,000) that binds with high affinity to activated platelets in vitro. We studied the biodistribution and thrombus binding of annexin V in rabbit and swine models of fully occlusive arterial thrombi formed 1-2 h prior to injection of annexin V. Iodinated annexin V was cleared from blood in a rapid early phase (t1/2 = 6.4 min, 76% of radioactivity) and a slower late phase (t1/2 = 71 min, 24% of radioactivity). Organ uptake was highest in the kidney and spleen and lowest in heart and skeletal muscle. Thrombus/blood uptake ratios were (mean +/- SEM): 6.39 +/- 1.80 for rabbit iliac artery, 6.97 +/- 1.45 for swine carotid artery, and 7.68 +/- 1.70 for swine femoral artery (all p values < 0.01 versus control artery); a control protein, ovalbumin, showed an uptake ratio of 0.59 +/- 0.08 in swine femoral artery thrombi. These results indicate that annexin V is useful as an agent for selective targeting of platelet-containing thrombi.
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PMID:Evaluation of annexin V as a platelet-directed thrombus targeting agent. 799 50

A small ventricular assist device intended for long-term implantation has been developed by a cooperative effort between the Baylor College of Medicine and the NASA/Johnson Space Center. To date, in vitro tests have been performed to address hemolysis and pump performance issues. In this Phase 1 study, we assessed the durability and atraumatic features aiming for 2 day implantation. Eight pumps were implanted in 2 calves as paracorporeal left ventricular assist devices. The pump running times ranged from 18 to 203 h (78.1 +/- 23.7; mean +/- SEM). All the pump implantations were terminated because of thrombus formation. Plasma-free hemoglobin levels were below 13.7 mg/dl, except for 1 case complicated by inflow cannula obstruction. The pump speed was maintained between 10,100 and 11,400 rpm. Pump outputs were from 3.6 to 5.2 L/min. The electrical power required by the system ranged between 9 and 12 W. Clinically there was no detectable organ dysfunction noted, and postmortem evaluation demonstrated no pump related adverse effects in either calf except for small kidney infarctions. Thrombus deposition was observed mainly at the hub portions and the flow straightener.
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PMID:Ex vivo phase 1 evaluation of the DeBakey/NASA axial flow ventricular assist device. 864 29


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