摘要:

Background The study objective was to determine whether Hirulog, a direct thrombin inhibitor, has potential efficacy and safety in the prevention of deep vein thrombosis (DVT) in orthopedic patients.A phase 2 open-label, dose-escalating design was used to study 222 unselected patients undergoing major hip or knee surgery in tertiary-care, university-affiliated hospitals.Methods and Results Subcutaneous Hirulog was initiated postoperatively.Patients were evaluated for bleeding and symptomatic pulmonary embolism, and mandatory bilateral venography was performed before discharge. Dose escalations were made on the basis of observed rates of bleeding and venous thrombosis. There were five dosage regimens used: 0.3 mg/kg every 12 hours, 0.6 mg/kg every 12 hours, 1.0 mg/kg every 12 hours for 3 days followed by 0.6 mg/kg every 12 hours for up to 11 days, 1.0 mg/kg every 12 hours, and 1.0 mg/kg every 8 hours. One hundred seventy-seven patients who had technically adequate bilateral venography or objectively documented pulmonary embolism were included in the primary analysis of efficacy. The highest dosage regimen (1.0 mg/kg every 8 hours) provided the lowest rates of total DVT (17%) and proximal DVT (2%), both of which were significantly lower (P=.010 and P=.023, respectively) than the pooled rates of total (43%) and proximal (20%) DVT seen with the first four regimens. Bleeding rates were low (<5%) with all regimens.Conclusions This study demonstrates that 1.0 mg/kg Hirulog every 8 hours started postoperatively is potentially efficacious and safe for the prevention of DVT after major hip or knee surgery. (Circulation. 1994;90:2385-2389.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Polymorphonuclear leukocytes (PMNs) have been shown to mediate coronary vascular and myocardial tissue injury after coronary artery ischemia and reperfusion.Previous studies using specific monoclonal antibodies directed against P-selectin and L-selectin have demonstrated the involvement of the selectin family of glycoproteins in the early phase of PMN-induced myocardial ischemia-reperfusion injury. We examined the effects of a novel oligosaccharide analog of sialyl Lewisx(SLex), which blocks both P-selectin and E-selectin in an acute canine model of myocardial ischemia and reperfusion.Methods and Results Anesthetized, open-chest dogs were subjected to 1.5 hours of left circumflex coronary artery (LCx) occlusion followed by 4.5 hours of reperfusion and randomly received the SLexanalog CY-1503 (5 mg/kg IV), the nonfucosylated analog of CY-1503, SLN (5 mg/kg IV), or saline 5 minutes before reperfusion. The investigators were blinded to the treatment until all the data analysis was completed. All three groups of dogs exhibited similar and severe reductions in transmural myocardial blood flow in the LCx region as well as pronounced myocardial contractile dysfunction during occlusion, suggesting comparable degrees of myocardial ischemia. After reperfusion, dogs receiving saline (n=6) displayed an enhanced degree of myocardial injury that was evidenced by a dramatic elevation in plasma creatine kinase (CK) activity, PMN accumulation, and myocardial necrosis. Plasma CK activity increased from 1.9+-0.5 IU/micrograms protein at baseline to 73.0+-11.0 IU/micrograms protein (P<.001) at 4.5 hours of reperfusion and myocardial PMN accumulation, as measured by cardiac myeloperoxidase (MPO) activity, and was significantly enhanced (P<.01) within the necrotic zone compared with the nonischemic zone (4.3+-0.6 versus 0.7+-0.1 U/100 mg tissue). After 4.5 hours of reperfusion, 36% of the myocardium within the ischemic zone and 17% of the left ventricle became necrotic in the dogs receiving saline. Treatment with CY-1503 (n=6) significantly (P<.05) blunted plasma CK activity by more than 50% throughout the reperfusion period, reduced necrotic zone PMN accumulation by 63% (P<.05), and reduced myocardial necrosis in the area at risk by 65% (P<.01) and by 72% within the left ventricle (P<.01). In contrast, administration of the nonfucosylated analog of CY-1503, SLN (n=6), failed to exert any detectable cardioprotective effects after myocardial ischemia and reperfusion.Conclusions Our results provide strong evidence that treatment with a unique carbohydrate analog of SLex, CY-1503, significantly reduces the degree of myocardial injury associated with coronary artery ischemia and reperfusion. The profound cardioprotection appears to be related to a reduction in PMN accumulation within the ischemic-reperfused myocardium. Additional studies investigating more-prolonged periods of reperfusion are required to determine whether CY-1503 treatment merely delays the onset or actually reduces the full extent of myocardial necrosis after ischemia and reperfusion. (Circulation. 1994;90:2390-2401.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Gene therapy has been proposed as a possible solution to the problem of restenosis after coronary angioplasty.The current study was undertaken to assess conventional methods of gene transfer and to develop percutaneous techniques for introducing genes directly into the coronary arteries of large mammals. Since the anticipated targets of gene therapy against restenosis include atherosclerotic and previously instrumented arteries, we also evaluated gene transfer in atherosclerotic coronary arteries and in two porcine models of restenosis: one using intracoronary stents and a second using balloon overstretch angioplasty.Methods and Results The conventional method of using perforated balloon catheters to deliver Lipofectin-DNA complexes directly into the coronary arteries of intact animals was applied to 18 porcine coronary arteries including normal arteries, hypercholesterolemic arteries, and those simulating restenosis. The results of this study were consistent with previously published results indicating that only low levels of luciferase gene expression could be obtained by Lipofectin- mediated gene transfer. We therefore undertook a second, parallel study to evaluate percutaneous transluminal in vivo gene transfer using a replication-deficient adenoviral vector. A comparison of the two studies revealed that the mean level of reporter gene expression in the cohort undergoing adenoviral infection was 100-fold higher than in the cohort undergoing Lipofection. Analysis of luciferase activity over time in normal arteries revealed that recombinant gene expression was half- maximal after 1 day, peaked within 1 week, was still half- maximal at 2 weeks, and declined to low levels by 4 weeks. Histochemical analysis of coronary arteries treated with a second adenovirus expressing a nuclear-localized beta -galactosidase gene demonstrated gene transfer to a limited number of cells in the media and adventitia. Immunohistochemical analysis of Ad5-infused arteries using a monoclonal antibody directed against CD44 identified a periadventitial infiltrate composed of leukocytes.Conclusions The recombinant adenoviral vectors proved to be far more effective than Lipofectin at delivering foreign genes directly into the coronary arteries of living mammals.Furthermore, the influences of hypercholesterolemia and arterial injury appeared to have little effect on the levels of gene expression obtained using either method. The results demonstrate that low-level recombinant gene expression, the major obstacle impeding gene therapy for the prevention of restenosis, can potentially be overcome by using adenoviral vectors to mediate coronary gene transfer in vivo. The duration of gene expression provided by these vectors and their effective deployment in atherosclerotic, balloon-overstretched, and stented coronary arteries suggest that recombinant adenovirus may have potential for evaluating gene therapy in the clinically informative porcine models of coronary restenosis. (Circulation. 1994;90:2402-2413.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Efficient methods of introducing genes into myocardial cells must be developed before local somatic cell gene therapy can be implemented against myocardial disease.Although adenoviral (Ad5) vectors have been used to target rodent hearts and plasmid DNA has been directly injected into the myocardium of rats and dogs, the amounts of recombinant protein produced by these procedures have not been reported, and adenoviral vectors have not been used in large mammalian hearts.Methods and Results Replication-deficient recombinant adenoviral vectors carrying either the luciferase or lacZ reporter genes were injected directly into the ventricular myocardium of adult domestic swine for evaluation of reporter gene expression. This procedure did not affect regional myocardial function as assessed by systolic wall thickening using ultrasonic crystals. Luciferase activity was detected 3 days after injection, increased markedly at 7 days, and then declined progressively at 14 and 21 days. Luciferase production was comparable in the right and left ventricular walls and increased with increasing amounts of virus, reaching 61+-21 ng at the highest dose examined (3.6 x 109plaque-forming units). The injection of 200 micrograms of plasmid DNA (pRSVL) produced levels of luciferase comparable to 1.8 x 10895%) of the stained cells were cardiomyocytes and that the percentage of cardiomyocytes infected by the virus could be quite high in microscopic regions adjacent to the needle track (up to 75% in fields of 60 to 70 cells); however, Ad5-infected cells were rarely observed farther than 5 mm from the injection site. Furthermore, the Ad5 vector induced pronounced leukocytic infiltration that was far in excess of that seen after injection of vehicle alone.Conclusions This study demonstrates for the first time that direct intramyocardial injection of replication-deficient adenovirus can program recombinant gene expression in the cardiomyocytes of a large animal species with relevance to human physiology. The efficiency of adenovirus-mediated gene transfer is far superior to that of plasmid DNA injection, and this method appears to be capable of producing more recombinant protein. However, the cell-mediated immune response to the Ad5 vector and the limited distribution of reporter gene expression suggest that less immunogenic recombinant vectors and more homogeneous administration methods will be required before Ad5 vectors can be successfully used for phenotypic modulation. (Circulation. 1994;90:2414-2424.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background The intracellular mechanism of coronary artery spasm is still unknown.The pathway mediated by protein kinase C (PKC) is an important intracellular process of various cellular responses, including vascular smooth muscle contraction. Thus, we examined the role of the PKC-mediated pathway in the pathogenesis of coronary artery spasm in our in vivo swine model.Methods and Results Seven Gottingen miniature pigs underwent coronary balloon injury and x-ray irradiation to induce atherosclerotic lesion. After 6 to 18 months, intracoronary serotonin (3 micrograms/kg) or histamine (3 micrograms/kg) repeatedly induced coronary artery spasm at the atherosclerotic site. At the spastic site, intracoronary administration of phorbol-12,13-dibutyrate (PDBu) (10-9mol/kg), a PKC-activating phorbol ester, also induced coronary artery spasm, which was completely blocked by pretreatment with intracoronary staurosporine (10 micrograms/kg), a PKC inhibitor. Intracoronary administration of an inactive phorbol ester, phorbol-12,13-didecanoate (10-9mol/kg), did not induce coronary vasoconstriction. Coronary artery spasm induced by the autacoids was significantly augmented by pretreatment with intracoronary PDBu and partially inhibited by staurosporine. Intracoronary administration of Bay K 8644 (10 micrograms/kg), a dihydropyridine-sensitive L-type calcium channel agonist, also induced coronary artery spasm at the spastic site, which was significantly inhibited by pretreatment with intracoronary staurosporine or nifedipine (0.1 mg/kg).Conclusions These results suggest (1) the PKC-mediated pathway is importantly involved in the pathogenesis of coronary artery spasm, (2) activation of the PKC-mediated pathway partially accounts for serotonin- and histamine-induced coronary artery spasm, and (3) at the spastic site, calcium influx through dihydropyridine-sensitive L-type calcium channel and/or calcium sensitivity of the contractile proteins may be augmented by the PKC-mediated pathway. (Circulation. 1994;90:2425-2431.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Residual mural thrombus on severely damaged arterial wall is very thrombogenic.We tested the hypothesis that direct thrombin inhibition will block thrombus growth on fresh thrombus better than indirect thrombin inhibition, cyclooxygenase inhibition, or both.Methods and Results A fresh mural thrombus was formed by directly perfusing fresh porcine blood for 5 minutes over severely damaged arterial wall at a high shear rate in a well-characterized ex vivo perfusion system. The average platelet (P) and fibrinogen (F) deposition (D) achieved in 5 minutes were 382+-32 x 106platelets/cm2and 296+-36 x 1012fibrinogen molecules/cm2, respectively. Thrombus growth on the fresh mural thrombus was quantitated by directly perfusing blood from pigs with Indium-111-labeled platelets and Iodine-125-labeled fibrinogen for an additional 5 minutes over the preformed mural thrombus. Treatment included recombinant hirudin (1 mg/kg per hour IV) as a probe for thrombin, aspirin (5 mg/kg IV) as a platelet inhibitor of cyclooxygenase, heparin (moderate, 100 IU/kg per hour IV; high-dose, 250 IU/kg per hour IV) as an indirect thrombin inhibitor, and heparin (100 IU/kg per hour) plus aspirin (5 mg/kg IV). Thrombus growth as measured by labeled PD (x 106/cm2) and FD (x 1012molecules/cm2) was mildly but not significantly reduced by aspirin (1034+-92 and 436+-78, respectively) compared with baseline (1113+-67 and 545+-52, respectively). Inhibition of thrombus growth with heparin was dose dependent. A regression analysis showed an inverse correlation of PD and FD with mean plasma heparin concentrations (r=-.81, P=.0001 and r=-.49, P=.0007, respectively). Recombinant hirudin led to a profound inhibition of thrombus growth (PD, 30+-12; FD, 109+-21), which was significant compared with all groups, even the highest dosage of heparin (250 IU/kg per hour).Conclusions Specific thrombin inhibition markedly inhibits platelet and fibrinogen deposition onto fresh mural thrombus at a high shear rate.Aspirin alone or in combination with heparin has little effect on evolving thrombosis. Heparin dose dependently reduces thrombus growth, but even the highest dosage is less effective than hirudin. Thrombin appears to be the primary activator of platelets by fresh thrombus. (Circulation. 1994;90:2432-2438.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Although it has been demonstrated in short-term preparations that ischemia with early reperfusion results in coronary vascular injury manifested by abnormal endothelium-dependent relaxation and increased permeability to plasma proteins, it has not been clear whether these abnormalities are permanent or reversible.Methods and Results In a canine model, regional coronary ischemia was accomplished by 1 hour of left anterior descending coronary artery ligation, and follow-up studies were performed after reperfusion for 1 hour, 48 hours, 2 weeks, or 9 weeks. Vasorelaxation was measured in vitro with preconstricted epicardial coronary artery rings subjected to increasing concentrations of the endothelium-dependent vasodilator ADP and the endothelium-independent vasodilator nitroprusside. At 1 and 48 hours of reperfusion, relaxation of rings from the ischemic reperfused artery to ADP was blunted, but relaxation to nitroprusside was normal. At 2 weeks there was a nonsignificant trend toward a blunted response to ADP in the ischemic/reperfused rings, and at 9 weeks a completely normal response to ADP was observed. Coronary microvascular permeability was assessed by measurement of protein leak index (PLI), by using a double-isotope technique with autologous radiolabeled transferrin and erythrocytes. At 1 and 48 hours of reperfusion there were substantial increases in PLI in the previously ischemic regions, indicative of increased extravascular transferrin. There was a small increase in PLI at 2 weeks but a completely normal measurement at 9 weeks. Electron microscopy of ischemic/reperfused vessels demonstrated endothelial cell swelling and other abnormalities in epicardial arteries and the microcirculation at 48 hours of reperfusion but normal endothelium at 2 weeks of reperfusion.Conclusions After 1 hour of regional coronary ischemia, coronary endothelial injury occurs early in reperfusion with abnormalities in epicardial coronary artery endothelium-dependent relaxation, coronary microvascular permeability, and both epicardial coronary artery and microvascular histology. This pattern of injury persists for at least 48 hours, but there is partial functional and complete histological recovery within 2 weeks and complete functional recovery within 9 weeks. (Circulation. 1994;90:2439-2447.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Thrombolytic agents used clinically rely on the activation of plasminogen to plasmin.Plasmin possesses multiple actions including increasing thrombin activity and activation of platelets. Thus, after successful thrombolytic therapy, arterial hyperactivity and reocclusion may be the result of a predominant plasmin-induced thrombogenic action at the site of the residual thrombus. Fibrolase, a direct-acting fibrinolytic enzyme from southern copperhead snake venom, induces rapid clot lysis in vitro. Fibrolase does not rely on plasminogen activation or any other bloodborne components for activity and is not inhibited by any of the rapidly acting serine proteinase inhibitors in blood.Methods and Results We investigated the efficacy of fibrolase to lyse an occlusive thrombus formed in the carotid artery of the anesthetized dog.Electrolytic injury was initiated in both the right and left carotid arteries. Thirty minutes after both arteries were occluded, each vessel was infused with either fibrolase (4 mg/kg over 5 minutes) or physiological saline (over 5 minutes). In two separate groups of dogs, anisoylated plasminogen streptokinase activator complex (APSAC) (0.1 U/kg) was infused into the occluded vessel. In the artery infused with fibrolase, five of five dogs exhibited patency within 6+-1 minutes of the infusion (P<.05 versus vehicle-treated artery; Fisher's exact test). In the contralateral carotid artery that received vehicle, the occlusion was maintained throughout the experimental protocol. APSAC alone lysed the thrombus in each vessel within 17+-3 minutes. Five minutes after the end of fibrolase administration and in one of the groups administered APSAC, a glycoprotein (GP)IIb/IIIa antibody, 7E3 (0.8 mg/kg IV), was administered to prevent reocclusion of the patent artery. After 7E3 administration, the vessel treated with fibrolase remained patent in four of five dogs, and six of six APSAC-treated vessels were patent for the remainder of the observation period (2 hours).Conclusions These studies demonstrate that local administration of fibrolase lyses a carotid arterial thrombus rapidly without excessive hemorrhage or hemodynamic compromise.The enzyme in combination with antiplatelet therapy (7E3) offers a unique mechanism for clot dissolution and may prove useful as a clinically efficacious alternative to presently used thrombolytic agents or may act in a synergistic manner with plasminogen activators. (Circulation. 1994;90:2448-2456.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Chronic treatment with high doses of angiotensin-converting enzyme (ACE) inhibitors prolongs survival after myocardial infarction. Since the plasma renin-angiotensin system (RAS) is not consistently activated in the chronic phase after myocardial infarction, the beneficial effects of ACE inhibition have been attributed, in part, to inhibition of an activated tissue RAS. However, a relation between tissue ACE inhibition and long-term efficacy (ie, concerning left ventricular (LV) hypertrophy and survival) has not been established. The present study was designed to evaluate the impact of low-dose ACE inhibition (predominant inhibition of plasma ACE) and high-dose ACE inhibition (associated with substantial tissue ACE inhibition) on reversal of LV hypertrophy and 1-year mortality after myocardial infarction in the rat.Methods and Results Infarcted rats were randomized to placebo, low-dose lisinopril, or high-dose lisinopril (each, n=80) and compared with sham-operated animals (n=40). In a separate group of animals, tissue ACE activity was determined after 6 weeks of therapy, demonstrating that both regimens were effective with regard to both plasma and pulmonary ACE inhibition; however, only high-dose lisinopril inhibited renal ACE. Neither dose affected LV ACE activity and ACE mRNA levels as determined by competitive polymerase chain reaction, whereas LV ANF mRNA levels were significantly reduced by high-dose lisinopril. High-dose lisinopril reduced arterial blood pressure and normalized right ventricular and LV weight and resulted in a substantial reduction of 1-year mortality, whereas the low dose did not (1 year mortality: placebo, 56.3%; low dose, 53.3%; high dose, 22.9%, P<.0001 versus low dose and versus placebo).Conclusions Hemodynamically effective ACE inhibition is required for reduction of LV hypertrophy and long-term mortality after myocardial infarction in the rat. Sustained inhibition of renal ACE during long-term therapy may contribute to the beneficial effect of high-dose lisinopril. Low-dose lisinopril, although exerting sustained inhibition of the plasma ACE, does not improve survival after myocardial infarction. (Circulation. 1994;90:2457-2467.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Smooth muscle proliferation and extracellular matrix formation in the subintimal region of blood vessels that have been subjected to intimal injury are responsible for restenosis following balloon angioplasty of the coronary arteries and for accelerated atherosclerosis in a variety of other pathophysiological states.The immediate early-response gene c-myc is overexpressed in proliferating vascular smooth muscle cells in vitro, and c-myc antisense oligomers have been shown to reduce c-myc expression and to inhibit proliferation of vascular smooth muscle cells in culture. Mithramycin is a commercially available G-C-specific DNA binding drug that selectively inhibits transcription of genes, such as c-myc, that have G-C-rich promoter sequences. This study tested the hypothesis that mithramycin inhibits transcription of the c-myc proto-oncogene and prevents myointimal proliferation after balloon injury of the rat carotid artery in vivo.Methods and Results Ten-week-old male Sprague-Dawley rats received mithramycin (150 micrograms/kg IP) or distilled H2O 1 hour before and 1 hour after balloon injury of the right common carotid artery. After 2 weeks, the rats were killed by overdose of pentobarbital, and the injured right and uninjured control left arteries were pressure-fixed and subjected to morphological analysis for evaluation of the degree of myointimal thickening. Separate groups of rats were killed at 2 and 6 hours after vascular injury, and total RNA from injured and control vessels of mithramycin-and vehicle-treated rats was subjected to Northern analysis for assessment of steady-state c-myc mRNA levels. The areas of neointima and the ratios of neointimal to medial area were significantly less in mithramycin-treated than in control rats (0.6+-0.1 versus 1.2+-0.1 mm2, P<.01 and 95+-16% versus 190+-14%, P<.01). Lumen size was significantly greater in mithramycin-treated than in control rats (1.5+-0.1 versus 0.8+-0.1 mm2, P<.01). Steady-state c-myc mRNA levels were increased 10-fold and 2-fold (compared with undamaged carotid arteries) at 2 and 6 hours after balloon injury, respectively; mithramycin treatment reduced c-myc mRNA levels at 2 and 6 hours by 66% and 53%, respectively.Conclusions These results support the hypothesis that systemic administration of mithramycin immediately (1 hour before and after intervention effectively inhibits transcription of the c-myc proto-oncogene and prevents myointimal proliferation after balloon injury of the rat carotid artery in vivo. Because mithramycin has been shown to be well tolerated by humans and to effectively inhibit transcription of c-myc in proliferating human cells, this agent may be useful in the prevention of coronary restenosis. (Circulation. 1994;90:2468-2473.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID