Thrombolytic properties of a conjugate of liposomal urokinase with a monoclonal antibody specific for cross-linked fibrin in the model of rabbit artery thrombosis

AIM: To observe the targeting thrombolytic effect of a monoclonal antibody specific for cross-linked fibrin connected with liposomal urokinase（UK） in the model of rabbit artery thrombosis.METHODS: Preparation of thrombolytic solutions: with the method of controllable dialysis eradicator in liposomat,empty liposomes,liposomally entrapped urokinase and liposomally entrapped urokinase linked with D-dimer antibody were made.Experiment in vivo: a rabbit thrombosis model of abdominal aorta was induced by ferric chloride.When the blood pressure fall to the lowest,5 different solutions were separately imported (PBS,maximal-level UK,Ab/Lip/UK,Ab/UK-Lip,Ab-UK-Lip) and observed for 40 min continuously.RESULTS: The varieties of 5 groups blood pressures were analyzed with q-test.Significant differences were observed among Ab-UK-Lip group,maximal-level UK group and others (P<0.01).There were marked differences between Ab-UK-Lip group and others in wet weight of thrombuses (P<0.05).However,the quantity of UK in Ab-UK-Lip group was 1/3 of that in maximal-level of UK group.CONCLUSION: The thrombolytic effect on Ab-UK-Lip group is similar to that on maximal-level of UK group,but the dosage of UK is less,and the side-effect is light.This shows,as a homing-device of liposomal urokinase,the D-dimer antibody has targeting effect and the agent of Ab-UK-Lip will be attached importance by-and-by.     

The Sepsis-Coagulant Axis: A Review

Activation of coagulation is a normal component of the acute inflammatory response. Inflammatory cytokines initiate coagulation events locally at sites of inflammation by converting endothelium from an antithrombotic surface to a prothrombotic surface; by stimulating tissue factor production, which activates both the extrinsic and intrinsic coagulation systems; and by stimulating production of platelet-activating factors. The fibrinolytic system is initially activated but is subsequently inhibited. This results in a marked imbalance in coagulation and fibrinolysis resulting in a net procoagulant state. When thrombin generation and platelet activation exceed the body's capacity to inactivate or remove these factors, disseminated intravascular coagulation (DIC) results. DIC directly contributes to multiple organ failure and death associated with sepsis. Presently available treatments (ie, heparin and aspirin) are relatively ineffective in treating DIC; however, newer, more potent drugs may soon be available for clinical use.     

Clinical use of tissue plasminogen activator for systemic thrombolysis in dogs and cats

IntroductionSystemic administration of tissue plasminogen activator (tPA) is seldomly reported in dogs and cats.AnimalsClient-owned animals receiving tPA (2010–2020).Materials and methodsMedical records of dogs and cats receiving tPA for distant known/suspected thrombus were reviewed. Fourteen dog visits (24 injections) and five cat visits (six injections) were included.ResultsCanine known/suspected thrombus included pulmonary thromboembolism (n=6), intracardiac thrombus (n=4), aortic thrombus (n=1), cranial vena cava thrombus (n=2), and femoral and iliac veins thrombus (n=1). Various canine primary diseases were represented, but open-heart surgery was the most common cause. Median time between diagnosis/suspicion of thrombus and tPA injection was 24.5 h (range, 3–150 h). Mean total tPA dose was 1.0±0.78 mg/kg.Clinical improvement occurred in 93% of dogs. Non-fatal complications were reported in 14% of dogs. Dogs’ survival to discharge was 78.6% without identifiable non-survivor characteristics. Feline known/suspected thrombus included unilateral feline aortic thromboembolism (FATE) (n=2), bilateral FATE (n=2), and right renal artery thrombus. Feline primary diseases included cardiomyopathy (n=5). Median time between diagnosis/suspicion of thrombus and tPA injection was 4 h (range, 2–17 h) and median total tPA dose was 1.0 mg/kg (range, 0.6–1.4 mg/kg).Clinical improvement occurred during 40% of the visits. All cats (n=3) with acute kidney injury (AKI) at admission developed worsening AKI and reperfusion injury. Of the remaining two visits, one developed a non-fatal AKI. Cats’ survival to discharge was 40%.ConclusionsSystemic thrombolysis with tPA seems to be effective and safe in dogs. More investigation is needed in cats.     

Hypercoagulability in Dogs with Blastomycosis

Background

Blastomycosis is a potentially fatal fungal disease that most commonly affects humans and dogs. The organism causes systemic inflammation and has a predilection for the lungs. The inflammation might lead to a hypercoagulable state with microemboli in the pulmonary circulation which could contribute to inadequate oxygen exchange in infected dogs.

Hypothesis/Objectives

Dogs with blastomycosis will be hypercoagulable compared with healthy case‐matched controls.

Animals

Client‐owned dogs with a diagnosis of blastomycosis (n = 23) and healthy case‐matched controls (n = 23).

Methods

Prospective case‐controlled study of client‐owned dogs presented to a veterinary teaching hospital with clinical signs compatible with blastomycosis. Complete blood counts, fibrinogen, PT, aPTT, thromboelastometry (TE), thrombin antithrombin complexes (TAT), and thrombin generation were evaluated.

Results

Cases had a leukocytosis compared with controls [mean (SD) 16.6 (7.6) × 10³/μL versus 8.2 (1.8) × 10³/μL, P < .001], hyperfibrinogenemia [median 784 mg/dL, range 329–1,443 versus median 178 mg/dL, range 82–257, P < .001], and increased TAT concentrations [mean (SD) 9.0 (5.7) μg/L versus 2.0 (2.8) μg/L, P < .001]. As compared to controls, cases were also hypercoagulable as evaluated by thromboelastometry and had increased in vitro thrombin generation on calibrated automated thrombography.

Conclusions and Clinical Importance

Hypercoagulability occurs in dogs with systemic blastomycosis. Additional studies are needed to explore a possible contribution of thrombogenicity to the clinical manifestations of systemic blastomycosis.     

Comparative aspects of blood coagulation

Blood coagulation is a basic physiological defense mechanism that occurs in all vertebrates to prevent blood loss following vascular injury. In all species the basic mechanism of clot formation is similar; when endothelium is damaged a complex sequence of enzymatic reactions occurs that is localized to the site of trauma and involves both activated cells and plasma proteins. The reaction sequence is initiated by the expression of tissue factor on the surface of activated cells and results in the generation of thrombin, the most important enzyme in blood clot formation. Thrombin converts soluble fibrinogen, via soluble fibrin monomers, into the insoluble fibrin that forms the matrix of a blood clot as well as exerting positive-feedback regulation that effectively promotes additional thrombin generation that facilitates the rapid development of a thrombus. Both spontaneous and trauma-induced haemorrhagic episodes can develop in all mammals with inherited or acquired abnormalities in one or more of the coagulant proteins. Experimental studies with plasma from a wide range of species have led to the conclusion that there are extensive differences in the rates of thrombin generation and fibrin formation among species. However, current evidence suggests that at least some of these quantitative differences are likely due to the use of non-species specific laboratory reagents. Although the individual proteins involved in the procoagulant pathways exhibit similar functions in all animals, differences in amino acid sequence cause incomplete homology and varying degrees of immunological cross-reactivity for the same protein across species.     

Effects of clopidogrel and aspirin on platelet aggregation, thromboxane production, and serotonin secretion in horses

Background: Critically ill horses are susceptible to thrombotic disease, which might be related to increased platelet reactivity and activation. Objectives: To compare the effect of oral clopidogrel and aspirin (ASA) on equine platelet function. Animals: Six healthy adult horses. Methods: Horses received clopidogrel (2 mg/kg PO q24h) or ASA (5 mg/kg PO q24h) for 5 days in a prospective randomized cross‐over design. Platelet aggregation responses to adenosine diphosphate (ADP) and collagen via optical aggregometry, and platelet secretion of serotonin (5HT) and production of thromboxane B₂ (TXB₂) by ELISA were evaluated. In horses receiving clopidogrel, high‐performance liquid chromatography analysis for clopidogrel and its carboxylic‐acid metabolite SR 26334 was performed. Results: SR 26334 was identified in all clopidogrel‐treated horses, although the parent compound was not detected. Clopidogrel resulted in decreases in ADP‐induced platelet aggregation persisting for 120 hours after the final dose. ADP‐induced platelet aggregation decreased from a baseline of 70.2 ± 14.7% to a minimum of 15.9 ± 7.7% 24 hours after the final dose (P < .001). Collagen‐induced aggregation decreased from a baseline of 93 ± 9.5% to a minimum of 70.8 ± 16.9% 48 hours after the final dose (P < .001). ASA did not decrease platelet aggregation with either agonist. ASA decreased serum TXB₂ from a baseline value of 1310 ± 1045 to 128 ± 64 pg/mL within 24 hours (P < .01). Conclusions and Clinical Importance: Clopidogrel effectively decreases ADP‐induced platelet aggregation in horses, and could have therapeutic applications for equine diseases associated with platelet activation.     

Role of CXCR4 in changes of protein C system in ulcerative colitis mice

AIM: To explore the role of chemokine receptor CXCR4 in the pathogenesis of protein C system (PCS) in ulcerative colitis (UC).METHODS: In vivo, the mice were divided into control group and UC group. The macroscopic score, microscopic score and ulcer index were assessed. The mRNA levels and activity of myeloperoxidase (MPO), cyclooxygenase-2 (COX-2), stromal cell-derived factor-1α (SDF-1α) and monocyte chemotactic protein 1 (MCP-1) both in colonic tissue and plasma were determined. The expression and location of CXCR4, β-arrestin, p-JNK, endothelial cell protein C receptor (EPCR) and thrombomodulin (TM) were detected. The activity of protein C (PC) and protein S (PS) was measured in each group. In vitro, mouse colonic microvascular endothelial cells were isolated, cultured and identified. Both CXCR4-overexpressing and CXCR4-silencing colonic mucosa microvascular endothelial cells were constructed. The effects of SDF-1α on the protein levels of EPCR, TM, β-arrestin and p-JNK, and on the activity of PC, PS and activated protein C (APC) were observed.RESULTS: Compared with control group, UC mice showed increased gross score, histopathological score and ulcer index (P<0.05). The mRNA levels and activity of MPO, COX-2, SDF-1α and MCP-1 in colon and plasma were increased (P<0.01). The protein levels of CXCR4, β-arrestin and p-JNK were up-regulated, EPCR expression was down-regulated in colon, and the activity of PC and PS in plasma was decreased (P<0.05 or P<0.01). CXCR4 overexpression further aggravated SDF-1α-induced PCS inhibition in colonic mucosa microvascular endothelial cells, and further up-regulated the protein levels of β-arrestin and p-JNK (P<0.05).CONCLUSION: PCS is inhibited in UC. CXCR4 is involved in the regulation of PCS inhibition by mediating chemokines and acting on colonic mucosa microvascular endothelial cells through β-arrestin-JNK pathway.     

Cranial vena caval syndrome secondary to transvenous pacemaker implantation in two dogs

Superior vena caval syndrome is a rare, but reported complication of transvenous pacemaker implantation in humans. This syndrome can occur secondary to fibrotic and/or thrombotic obstruction of venous blood flow into the right atrium. The therapeutic approach depends on the suspicion of the presence of an active thrombus and may include antithrombotics, angioplasty and/or surgical venoplasty. We describe two dogs that developed severe pleural effusion secondary to stricture formation in the cranial vena cava 4 years after dual chamber transvenous pacemaker implantation. The stenosis was most likely due to fibrosis secondary to the transvenous pacemaker leads. Balloon angioplasty of the lesion resulted in resolution of the pleural effusion in both patients. Balloon angioplasty appears to be a viable therapeutic approach in dogs with cranial vena caval syndrome caused by focal stenotic lesions.     

Disseminated intravascular coagulation in cats

The purpose of this study was to describe the clinical characteristics of cats with disseminated intravascular coagulation (DIC), including associated diseases and hemostatic abnormalities, and to identify risk factors for death and treatments that potentially altered outcome. Medical records for cats with DIC from 1990-2004 were evaluated retrospectively. Inclusion criteria were the presence of an underlying disorder associated with DIC and either postmortem examination findings of intravascular fibrin deposition or thrombosis, or both of 2 or more organs or coagulation profiles that meet 3 of 5 criteria: prolonged prothrombin time (PT), activated partial thromboplastin time (aPTT), presence of fibrin degradation products (FDP), low plasma fibrinogen (FIB) concentration, and thrombocytopenia (<160,000 platelets/microL). Signalment, historical data, clinical findings, clinicopathologic data, underlying disorders, management, and outcome were recorded. Forty-six cats fulfilled the criteria for DIC. Cats ranged in age from 7 weeks to 17 years (median, 9 years). Hemorrhage was noted in 7 of 46 cats (15%). Three of 46 cats (7%) survived, whereas 43 of 46 (93%) died or were euthanized. The most common underlying disorders were lymphoma, other forms of neoplasia, pancreatitis, and sepsis. There was no association detected between outcome and signalment; underlying disease; hemorrhage; abnormalities in aPTT, FIB, FDPs, platelet count; transfusion of blood products; and heparin therapy. However, the median PT of nonsurvivors was more prolonged than in survivors (P < .005). DIC in cats can result from a variety of neoplastic, infectious, and inflammatory disorders, and is associated with a high case fatality rate.     

Results of diagnostic investigations and long-term outcome of 33 dogs with brain infarction (2000-2004)

Medical records of 33 dogs presented for acute onset, nonprogressive, intracranial dysfunction that had a magnetic resonance imaging diagnosis of brain infarction were reviewed. Postmortem confirmation of brain infarction was available in 10 dogs. All dogs were evaluated by CBC, serum biochemistry, thyroid and adrenal testing, urinalysis, thoracic and abdominal imaging, and cerebrospinal fluid analysis. Results of coagulation profile and arterial blood pressure were available in 32/33 and 28/33 dogs, respectively. On the basis of the imaging findings, infarcts were classified depending on their type (territorial or lacunar) and location within the brain (telencephalic, 10/33; thalamic/midbrain, 8/33; cerebellar, 15/33). No marked associations among location or type of infarct and patient age and sex, occurrence of systemic hypertension, and the presence or absence of a concurrent medical condition were identified. Small breed dogs (< or =15 kg) were significantly more likely to have territorial cerebellar infarcts, whereas large breed dogs (>15 kg) were significantly more likely to have lacunar thalamic or midbrain infarcts. A concurrent medical condition was detected in 18/33 dogs with brain infarcts, with chronic kidney disease (8/33) and hyperadrenocorticism (6/ 33) being most commonly encountered. Of 33 dogs, 10 were euthanized because of the severity and lack of improvement of their neurologic status or the severity of their concurrent medical condition. No association was identified between type or location of infarct and patient outcome. Dogs with concurrent medical conditions had significantly shorter survival times than those with no identifiable medical condition and were significantly more likely to suffer from recurrent neurologic signs because of subsequent infarcts.