Cohort profile: the ESC EURObservational Research Programme Non-ST-segment elevation myocardial infraction (NSTEMI) Registry

AIMS

The European Society of Cardiology (ESC) EURObservational Research Programme (EORP) Non-ST-segment elevation myocardial infarction (NSTEMI) Registry aims to identify international patterns in NSTEMI management in clinical practice and outcomes against the 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without ST-segment-elevation.

METHODS AND RESULTS

Consecutively hospitalised adult NSTEMI patients (n = 3620) were enrolled between 11 March 2019 and 6 March 2021, and individual patient data prospectively collected at 287 centres in 59 participating countries during a two-week enrolment period per centre. The registry collected data relating to baseline characteristics, major outcomes (in-hospital death, acute heart failure, cardiogenic shock, bleeding, stroke/transient ischaemic attack, and 30-day mortality) and guideline-recommended NSTEMI care interventions: electrocardiogram pre- or in-hospital, pre-hospitalization receipt of aspirin, echocardiography, coronary angiography, referral to cardiac rehabilitation, smoking cessation advice, dietary advice, and prescription on discharge of aspirin, P2Y12 inhibition, angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB), beta-blocker, and statin.

CONCLUSION

The EORP NSTEMI Registry is an international, prospective registry of care and outcomes of patients treated for NSTEMI, which will provide unique insights into the contemporary management of hospitalised NSTEMI patients, compliance with ESC 2015 NSTEMI Guidelines, and identify potential barriers to optimal management of this common clinical presentation associated with significant morbidity and mortality.

COVID-19 and antiphospholipid antibodies: A position statement and management guidance from AntiPhospholipid Syndrome Alliance for Clinical Trials and InternatiOnal Networking (APS ACTION)

Coronavirus disease 2019 (COVID-19) is associated with a high rate of thrombosis. Prolonged activated partial thromboplastin times (aPTT) and antiphospholipid antibodies (aPL) are reported in COVID-19 patients. The majority of publications have not reported whether patients develop clinically relevant persistent aPL, and the clinical significance of new aPL-positivity in COVID-19 is currently unknown. However, the reports of aPL-positivity in COVID-19 raised the question whether common mechanisms exist in the pathogenesis of COVID-19 and antiphospholipid syndrome (APS). In both conditions, thrombotic microangiopathy resulting in microvascular injury and thrombosis is hypothesized to occur through multiple pathways, including endothelial damage, complement activation, and release of neutrophil extracellular traps (NETosis). APS-ACTION, an international APS research network, created a COVID-19 working group that reviewed common mechanisms, positive aPL tests in COVID-19 patients, and implications of COVID-19 infection for patients with known aPL positivity or APS, with the goals of proposing guidance for clinical management and monitoring of aPL-positive COVID-19 patients. This guidance also serves as a call and focus for clinical and basic scientific research.

Antiphospholipid Antibody Profile Stability Over Time: Prospective Results From the APS ACTION Clinical Database and Repository

OBJECTIVE

The APS ACTION Registry studies long-term outcomes in persistently antiphospholipid antibody (aPL)-positive patients. Our primary objective was to determine whether clinically meaningful aPL profiles at baseline remain stable over time. Our secondary objectives were to determine (1) whether baseline characteristics differ between patients with stable and unstable aPL profiles, and (2) predictors of unstable aPL profiles over time.

METHODS

A clinically meaningful aPL profile was defined as positive lupus anticoagulant (LAC) test and/or anticardiolipin (aCL)/anti-β2 glycoprotein-I (anti-β2-GPI) IgG/M ≥ 40 U. Stable aPL profile was defined as a clinically meaningful aPL profile in at least two-thirds of follow-up measurements. Generalized linear mixed models with logit link were used for primary objective analysis.

RESULTS

Of 472 patients with clinically meaningful aPL profile at baseline (median follow-up 5.1 yrs), 366/472 (78%) patients had stable aPL profiles over time, 54 (11%) unstable, and 52 (11%) inconclusive. Time did not significantly affect odds of maintaining a clinically meaningful aPL profile at follow-up in univariate (P = 0.906) and multivariable analysis (P = 0.790). Baseline triple aPL positivity decreased (OR 0.25, 95% CI 0.10-0.64, P = 0.004) and isolated LAC test positivity increased (OR 3.3, 95% CI 1.53-7.13, P = 0.002) the odds of an unstable aPL profile over time.

CONCLUSION

Approximately 80% of our international cohort patients with clinically meaningful aPL profiles at baseline remain stable at a median follow-up of 5 years; triple aPL-positivity increase the odds of a stable aPL profile. These results will guide future validation studies of stored blood samples through APS ACTION Core Laboratories.

Acquired von Willebrand Syndrome: Data from an International Registry

The acquired von Willebrand syndrome (AvWS) is a rare bleeding disorder with laboratory findings similar to those of congenital von Willebrand disease (vWD). Despite the numerous cases reported in the literature until 1999 (n = 266), large studies on AvWS are not available. Moreover, diagnosis of AvWS has been difficult and treatment empirical. These considerations prompted us to organize an international registry. A questionnaire, devised to collect specific information on AvWS, was sent to all the members of the International Society on Thrombosis and Haemostasis (ISTH), who were invited to respond if they had diagnosed cases with the AvWS cases. 156 members answered the questionnaire and 54 of them sent information on 211 AvWS cases from 50 centers. Data were compared with those already published in the literature and 25 cases already described or not correctly diagnosed were excluded. The 186 AvWS cases that qualified for the registry were associated with lymphoproliferative (48%) and myeloproliferative disorders (15%), neoplasia (5%), immunological (2%), cardiovascular (21%) and miscellaneous disorders (9%). Ristocetin cofactor activity (vWF:RCo) or collagen binding activity (vWF:CBA) were usually low in AvWS (median values 20 U/dL, range 3-150), while factor VIII coagulant activity was sometimes normal (median 25 U/dL, range 3-191). FVIII/vWF inhibiting activities were present in only a minority of cases (16%). Bleeding episodes in AvWS were mostly of mucocutaneous type (68%) and were managed by DDAVP (32%), FVIII/vWF concentrates (37%), intravenous immunoglobulins (33%), plasmapheresis (19%), corticosteroids (19%) and immunosuppressive or chemotherapic agents (35%). Based upon the data of this international registry, it appears that AvWS is especially frequent in lympho-or myeloproliferative and cardiovascular diseases. Therefore, AvWS should be suspected and searched with the appropriate laboratory tests especially when excessive bleeding occurs in patients with these disorders. On the basis of the information provided by this registry guidelines for diagnosis and management of the AvWS are given.

Antibody-Mediated Disruption of the Annexin-V Antithrombotic Shield: A New Mechanism for Thrombosis in the Antiphospholipid Syndrome

The antiphospholipid (aPL) syndrome is a condition that manifests in patients as vascular thromboembolism or recurrent pregnancy loss together with laboratory evidence for the presence of antibodies against anionic phospholipid-protein complexes. For a recent comprehensive review, the reader is referred to Hughes et al.1 The syndrome was first proposed to be a distinct entity, called anticardiolipin syndrome, in 1985,2 and was later renamed antiphospholipid syndrome.3 The disorder was classified as “primary” in the absence of a concurrent autoimmune condition, such as systemic lupus erythematosus, or “secondary” in the presence of another such autoimmune disorder. Antiphospholipid antibodies are detected by their reactivity to anionic phospholipids (or protein-phospholipid complexes) in solid phase immunoassays, or by their inhibition of phospholipid-dependent coagulation reactions, known as the “lupus anticoagulant” effect. The ever-expanding, yet still insufficiently integrated, knowledge of this enigmatic disorder makes this area an intriguing subject for investigation.

The pathophysiologic mechanism of this syndrome has remained obscure, resulting from the apparent multiplicity of antigenic determinants recognized by the antibodies. In addition, a large number of effects1 have been described for the antibodies in vitro and in cell culture systems. These effects, which include the paradoxical lupus anticoagulant (LAC) phenomenon, are a consequence of the numerous roles played by phospholipids in the hemostasis system and in a multitude of biologic processes. The purpose of this review is to introduce the reader to the current state of knowledge of the role of annexin-V in this disorder.

Fibrillin Containing Elastic Microfibrils Support Platelet Adhesion under Dynamic Shear Conditions

The vascular subendothelium contains macromolecular structures called microfibrils. Type VI collagen is one protein found in microfibrils that supports platelet adhesion and aggregation and we have previously evaluated the roles of platelet receptors and vWf involved in these processes under physiological shear conditions. Here we investigate the ability of fibrillin containing elastic microfibrils to support mural thrombus formation. Our results show that elastic microfibril surfaces support platelet adhesion under low shear conditions at a level similar to collagen VI tetramers. However, the degree of aggregation on the elastic microfibril surface is much higher. Both adhesion and aggregation were shown to be mediated by the GPIIb-IIIa platelet receptor. Elastic microfibrils do not support the formation of mural thrombi under high shear conditions. These results suggest roles for both collagen VI and fibrillin containing elastic microfibrils in modulating the platelet response to blood vessel injury.

Human Atheromatous Plaque Extracts Induce Tissue Factor Activity (TFa) in Monocytes and also Express Constitutive TFa

Tissue factor activity (TFa) is a major activator of the coagulation cascade and may play a role in atheroma-induced thrombosis. Mono-cyte-macrophages (MO-MF) generate considerable quantities of TFa when stimulated by a variety of inducers. To test the hypothesis that MO could be induced by atheromatous plaque to generate TFa, plaque extracts obtained from patients with obstructive atheromatous disease were used. These extracts were also assayed for constitutive TFa. The constitutive activity was variable from extract to extract but could be very high, up to 250 U TFa. The TFa induced in MO could be also very high, up to 200 U (i.e. 1/5 of the TFa of full strength rabbit brain thromboplastin). These findings point to a major role for MO-MF TFa in the induction or thrombosis by atheromatous plaque.

ADAMTS13-binding IgG are present in patients with thrombotic thrombocytopenic purpura

Functional assays are commonly used to measure the antibodies of ADAMTS13 found in patients of thrombotic thrombocytopenic purpura (TTP). In this study we used an enzyme-linked immunoassay to analyze the ADAMTS13-binding IgG levels in six groups of individuals: normal, random hospitalized patients, acute TTP,TTP after receiving plasma therapy,TTP in remission, and other types of thrombotic microangiopathy (TMA).The results showed that ADAMTS13-binding IgG levels were elevated in 100% of the acute TTP group, 75% of the TTP group after receiving plasma therapy, and 40% of the remission group. Overall, the ADAMTS13-binding IgG levels correlated with the inhibitory activity levels againstADAMTS13 (r = -0.69,P<0.0001).The assay also detected elevated IgG binding levels in 5% - 15% of the normal, random, and other TMA control groups.Addition of purified ADAMTS13 protein to the plasma samples suppressed the IgG binding in each of the acute TTP patients, but in none of the non-TTP groups. Serial measurement in a patient that had two exacerbations of TTP within the first three weeks revealed that the ADAMTS13 activity levels remained < 0.1 U/ml during this period, and the ADAMTS13-binding IgG remained elevated, suggesting that ADAMTS13 analysis may provide valuable insight to the disease status during the course of therapy. Analysis of ADAMTS13-binding IgG is helpful for the diagnosis and management of TTP.

A child with acquired factor XIII deficiency: case report and literature review

Factor XIII (FXIII) deficiency is a rare bleeding disorder, which can result in life threatening hemorrhage. Rarer still is acquired FXIII deficiency, in which the disorder is due to autoantibodies that inhibit the factor. To describe one of the youngest reported patients with this condition. To discuss the challenges we encountered in monitoring response with the available assays. To review the literature and provide a review of all acquired FXIII cases. We present the case of our patient, a 9-year-old girl with acquired FXIII deficiency. We present a comprehensive review of all acquired FXIII deficiency cases reported globally in English, with focus on clinical presentation, diagnostic assays, treatment and prognosis. There is no current standard for therapy and measuring response to therapy can be complicated by limitations of assays in the presence of inhibitors. Clinicians should be aware of acquired FXIII deficiency as a potentially life threatening bleeding disorder even in young children. The case presented illustrates a young patient with acquired FXIII deficiency with a good clinical response to cryoprecipitate and difficulty in hemostasis monitoring utilizing clinically available assays.

Annexin A2 binds to endosomes following organelle destabilization by particulate wear debris

Endosomal functions are contingent on the integrity of the organelle-limiting membrane, whose disruption induces inflammation and cell death. Here we show that phagocytosis of ultrahigh molecular weight polyethylene particles induces damage to the endosomal-limiting membrane and results in the leakage of cathepsins into the cytosol and NLRP3-inflammasome activation. Annexin A2 recruitment to damaged organelles is shown by two-dimensional DIGE protein profiling, endosomal fractionation, confocal analysis of endogenous and annexin A2-GFP transfected cells, and immunogold labelling. Binding experiments, using fluorescent liposomes, confirms annexin A2 recruitment to endosomes containing phagocytosed polyethylene particles. Finally, an increase in cytosolic cathepsins, NLRP3-inflammasome activation, and IL-1 production is seen in dendritic cells from annexin A2-null mice, following exposure to polyethylene particles. Together, the results indicate a functional role of annexin A2 binding to endosomal membranes following organelle destabilization.

The association between circulating antibodies against domain I of beta2-glycoprotein I and thrombosis: an international multicenter study

BACKGROUND

Diagnosis of the antiphospholipid syndrome (APS) is difficult as a result of limited specificity of existing assays for detecting clinically relevant antiphospholipid antibodies. Anti-beta2-glycoprotein I (beta 2GPI) antibodies play a central role in the disease process of APS.

OBJECTIVES

We have investigated the relation between antiphospholipid antibodies with specificity for domain I of beta 2GPI and thrombosis/pregnancy morbidity in an international multicenter study.

PATIENTS/METHODS

Four hundred and seventy-seven patients derived from nine different centres met the inclusion criterion of having anti-beta 2GPI antibodies in their plasma/serum. Clinical data and results of tests for lupus anticoagulant, anti-cardiolipin antibodies and anti-beta 2GPI antibodies were established at the different centres of inclusion. After being re-tested for the presence of IgG and/or IgM anti-beta 2GPI antibodies, the samples were tested for the presence of IgG-directed against domain I of beta 2GPI and results were correlated with the thrombotic and obstetric history.

RESULTS

Re-testing for the presence of anti-beta 2GPI antibodies resulted in inclusion of 442/477 patients. IgG class anti-domain I antibodies were present in plasma of 243/442 patients (55%). 201/243 (83%) had a history of thrombosis. This resulted in an odds ratio of 3.5 (2.3-5.4, 95% confidence interval) for thrombosis. Anti-domain I IgG antibodies were also significantly correlated with obstetric complications [odds ratio: 2.4 (1.4-4.3, 95% confidence interval)].

CONCLUSION

In this multicenter study, the detection of IgG antibodies that are directed against domain I of beta 2GPI proved to be more strongly associated with thrombosis and obstetric complications than those detected using the standard anti-beta 2GPI antibody assay.

Defective annexin A5 crystallization: a mechanism for pregnancy losses in the antiphospholipid syndrome

We have accumulated a significant body of evidence that support the hypothesis that aPL antibody-mediated disruption of annexin A5 crystallization is a mechanism for RSPL in the APS. Further investigation of the functions of the annexins in placental physiology and disease are likely to be productive areas for future research.

Current understanding of feline diabetes: part 2, treatment

When treating diabetic cats, the primary aim is to control clinical signs without causing clinical hypoglycaemia. Secondary goals are to maximise the chances of attaining diabetic remission and to minimise the risk of complications due to chronic hyperglycaemia. A treatment plan that is convenient for the owner is important for compliance. Underweight or overweight diabetic cats should be fed with the aim of normalising bodyweight. Current evidence suggests that non-obese diabetic cats can be fed ad libitum. The oral hypoglycaemic drug glipizide is well established as a treatment for about a third of diabetic cats, which have residual beta cell function. Preliminary studies on other oral agents such as vanadium salts, metformin, and troglitazone indicate a potential use in some diabetic cats. Insulin treatment remains the treatment of choice for the majority of diabetic cats. Choice of insulin, dose rates and monitoring of treatment are discussed.

Current understanding of feline diabetes: part 1, pathogenesis

Type-1 diabetes, resulting from immune-mediated destruction of beta cells, appears to be rare in cats. Type-2 diabetes, characterised by inadequate insulin secretion and impaired insulin action, is the most common form of diabetes in cats. Other specific forms of diabetes constitute a substantial minority of cases. The most common is pancreatic destruction from pancreatic adenocarcinoma. Less frequent causes are insulin resistance from other endocrinopathies including acromegaly. Diabetes in cats is characterised by variable loss of insulin secretory capacity and insulin resistance. Glucose toxicity, islet amyloid-deposition, and pancreatitis contribute to further loss of beta cells and failure of insulin secretion. A significant number of cats undergo remission of their diabetes, usually 1-3 months after good glycaemic control is instituted. Obesity, old age, and Burmese breed are recognised risk factors for the development of diabetes in cats.

Human atheromatous plaque extracts induce tissue factor activity (TFa) in monocytes and also express constitutive TFa

Tissue factor activity (TFa) is a major activator of the coagulation cascade and may play a role in atheroma-induced thrombosis. Monocyte-macrophages (MO-MF) generate considerable quantities of TFa when stimulated by a variety of inducers. To test the hypothesis that MO could be induced by atheromatous plaque to generate TFa, plaque extracts obtained from patients with obstructive atheromatous disease were used. These extracts were also assayed for constitutive TFa. The constitutive activity was variable from extract to extract but could be very high, up to 250 U TFa. The TFa induced in MO could be also very high, up to 200 U (i.e. 1/5 of the TFa of full strength rabbit brain thromboplastin). These findings point to a major role for MO-MF TFa in the induction or thrombosis by atheromatous plaque.

Functional identification of a vesicular acetylcholine transporter and its expression from a "cholinergic" gene locus

The vesicular acetylcholine transporter (VAChT) has been identified and characterized based on the acquisition of high affinity vesamicol binding and proton-dependent, vesamicol-sensitive acetylcholine accumulation by a fibroblast cell line transfected with a clone from a rat pheochromocytoma cDNA library encoding this protein. The distribution of VAChT mRNA coincides with that reported for choline acetyltransferase (ChAT), the enzyme required for acetylcholine biosynthesis, in the peripheral and central cholinergic nervous systems. A human VAChT cDNA was used to localize the VAChT gene to chromosome 10q11.2, which is also the location of the ChAT gene. The entire sequence of the human VAChT cDNA is contained uninterrupted within the first intron of the ChAT gene locus. Transcription of VAChT and ChAT mRNA from the same or contiguous promoters within a single regulatory locus provides a previously undescribed genetic mechanism for coordinate regulation of two proteins whose expression is required to establish a mammalian neuronal phenotype.

Autoantibodies to heparin from patients with antiphospholipid antibody syndrome inhibit formation of antithrombin III-thrombin complexes

The antiphospholipid antibody syndrome (APS) is characteristically associated with thrombosis. Heparan sulfate (HS) is a physiologic endothelial cell surface modulator of normal anticoagulation, containing a specific oligosaccharide sequence that binds antithrombin III with high affinity and also is present in heparin, a related glycosaminoglycan. We hypothesized that a subset of antiphospholipid antibodies with high affinity for heparan sulfate/heparin epitopes may inhibit the function of HS, promoting a procoagulant state. Purified IgG from all seven patients with APS studied were reactive with heparin by enzyme-linked immunosorbent assay, whereas none of five controls had antiheparin reactivity. IgG antiheparin antibodies were purified from two APS patients by affinity chromatography on heparin-Sepharose. Specificity studies showed that low-affinity electrostatic interactions clearly did not account for the observed reactivity with heparin, and that APS IgG antiheparin antibodies were specifically reactive with a disaccharide present in the heparin pentasaccharide that binds antithrombin III. Furthermore, APS IgG antiheparin antibodies inhibited heparin-accelerated formation of antithrombin III-thrombin complexes. We conclude that antiheparan sulfate/heparin antibodies may be a cause of autoimmune vascular thrombosis in the antiphospholipid antibody syndrome.

Protein C and S levels in acute leukemia

Patients with acute leukemia undergoing remission induction chemotherapy occasionally develop venous thrombosis despite severe thrombocytopenia and in the absence of disseminated intravascular coagulation. This observation prompted us to study the levels of the naturally occurring anticoagulant proteins C and S prospectively in patients undergoing remission induction chemotherapy for acute leukemia. Plasma samples from 50 adult patients with acute leukemia (34 AML, 16 ALL) were analyzed for protein C antigen, functional protein C, immunologic total and free protein S as well as levels of C4b binding protein (C4bBP). Plasma levels of immunologic protein C were significantly lower in patients with active acute myelocytic leukemia (mean = 77.9) than in controls (mean = 123.6) or patients in remission (mean = 132). Functional protein C levels were also significantly lower in AML patients with active disease (mean = 58.5) than controls (mean = 95.5) or patients in remission (mean = 98.5). Patients with acute lymphocytic leukemia (ALL) had normal levels of immunologic and functional protein C. Although total protein S levels were normal in all patients studied, levels of free protein S were significantly decreased in patients with active AML (mean = 29.3) compared with patients in remission (mean = 42.0) or controls (mean = 42.4). In contrast, patients with ALL, both with active disease and in remission had normal free protein S levels. This decrease in free protein S seen in active AML was not associated with liver disease, white cell count or an increase in C4bBP. These findings provide a possible explanation for the occasional occurrence of venous thrombosis in patients with acute myelocytic leukemia.

Using neural networks to diagnose cancer

While artificial brains are in the realm of science fiction, artificial neural networks (ANNs) are scientific facts. An artificial neural network is a computational structure modeled somewhat on the neural structure of the brain; both have many highly interconnected processing elements. These biologically inspired processing elements are taught by feeding examples until the results are acceptable. In the past 5 years, neural networks have become successful in providing meaningful second opinions in clinical diagnosis. In our research, a prototype artificial neural network was trained on numeral ultrasound data of 52 actual cases and then correctly identified renal cell carcinoma from renal cysts and other conditions without diagnostic errors. Our nonlinear artificial neural network was trained on software using the standard backpropagation paradigm on a 80386 microcomputer. Our ANN learned from ultrasound data in 52 cases (17 malignant, 30 cysts, and 5 other) at a Memphis hospital. The trained prototype performed without error on 47 cases which were not in the data used for training. This prototype must be validated by extending this study to more cases.

Cerebrospinal fluid analysis and clinical outcome of eight dogs with eosinophilic meningoencephalomyelitis

Eight dogs, 14 weeks to 5.5 years of age, had signs of diffuse or multifocal meningoencephalomyelitis. The total white cell counts of the cerebrospinal fluid (CSF) ranged from 11 to 5,550 cells/microliters; the percentage of eosinophils ranged from 21% to 98%. The total CSF protein content range was 19 to 1,430 mg/dl. On necropsy, two dogs had granulomatous encephalomyelitis due to protozoan infection. The other six dogs, of which three were Golden Retriever dogs, appeared to have an idiopathic eosinophilic meningoencephalitis; four of these dogs recovered. The significance of eosinophils in CSF and the possible emergence of a new encephalitic syndrome of dogs involving a hypersensitivity to an unknown agent is also discussed.

Functional behavior of vessels from pigs with von Willebrand disease. Values of platelet deposition are identical to those obtained on normal vessels

Vessels from normal pigs and pigs with severe von Willebrand disease were exposed for up to 30 minutes to both nonanticoagulated and heparinized blood from normal pigs in an ex vivo perfusion system. Shear rates at the vessel surface were varied over a broad physiological range, gamma w = 212 to 3380 sec-1. The deposition of 111In-labeled platelets was determined by radiometric counting. For all shear rates and exposure times investigated, the levels of platelet deposition on de-endothelialized thoracic aorta of normal and von Willebrand disease pigs were not significantly different. Thus, the functional activity of the vessels correlated with the results obtained previously by immunofluorescence. Namely, the von Willebrand factor protein in the thoracic subendothelium of normal pigs is significantly diminished or absent and is comparable to the levels observed in von Willebrand disease pigs.

Uptake of oleate by isolated rat adipocytes is mediated by a 40-kDa plasma membrane fatty acid binding protein closely related to that in liver and gut

A portion of the hepatocellular uptake of nonesterified long-chain fatty acids is mediated by a specific 40-kDa plasma membrane fatty acid binding protein, which has also been isolated from the gut. To investigate whether a similar transport process exists in other tissues with high transmembrane fatty acid fluxes, initial rates (Vo) of [3H]oleate uptake into isolated rat adipocytes were studied as a function of the concentration of unbound [3H]oleate in the medium. Vo reached a maximum as the concentration of unbound oleate was increased (Km = 0.30 +/- 0.03 microM; Vmax = 2470 +/- 90 pmol/min per 5 X 10(4) adipocytes) and was significantly inhibited both by phloretin and by prior incubation of the cells with Pronase. A rabbit antibody to the rat liver plasma membrane fatty acid binding protein inhibited adipocyte fatty acid uptake by up to 63% in dose-dependent fashion. Inhibition was noncompetitive; at an immunoglobulin concentration of 250 micrograms/ml Vmax was reduced from 2480 +/- 160 to 1870 +/- 80 pmol/min per 5 X 10(4) adipocytes, with no change in Km. A basic (pI approximately equal to 9.1) 40-kDa adipocyte plasma membrane fatty acid binding protein, isolated from crude adipocyte plasma membrane fractions, reacted strongly in both agar gel diffusion and electrophoretic blots with the antibody raised against the corresponding hepatic plasma membrane protein. These data indicate that the uptake of oleate by rat adipocytes is mediated by a 40-kDa plasma membrane fatty acid binding protein closely related to that in liver and gut.

Platelet deposition on von Willebrand factor-deficient vessels. Extracorporeal perfusion studies in swine with von Willebrand's disease using native and heparinized blood

Native (nonanticoagulated) and heparinized blood from both normal swine and swine with von Willebrand's disease was exposed to de-endothelialized thoracic aorta from normal pigs under controlled flow conditions. We have shown that these normal de-endothelialized vessel segments do not contain von Willebrand factor (vWF) in the subendothelial surface; thus, the vascular model that we are using here is representative of the conditions in severe von Willebrand's disease. The blood was recirculated for selected periods of time through an extracorporeal circuit (carotid-jugular shunt), containing a tubular perfusion chamber that held the vessel segment. Flow rates and chamber diameters were selected such that the wall shear rates at the vascular segment were 212 to 3380 sec-1. Platelets were labeled with indium 111 and their total deposition determined by a gamma counter; selected areas were also observed by electron microscopy. When native blood was perfused, the deposition of platelets depended on platelet-plasma vWF only at high wall shear rates (1690 sec-1 or greater) typical of the microcirculation, but not at the lower shear rates (212 and 424 sec-1), more characteristic of the larger arteries and veins. In contrast, when heparinized blood was perfused, platelet deposition on the vascular segments depended on the presence of vWF over the entire range of shear conditions studied. These findings demonstrate in an extracorporeal perfusion system that the defect in platelet-vessel wall interaction in swine with von Willebrand's disease is influenced by both the local flow conditions and the level of activation of the coagulation system. In the presence of an intact coagulation system a synergistic interaction between procoagulant moieties and vWF was observed at high shear rates.

Isolation and properties of a capillary injury-related protease from lung lymph

Lung microvascular injury induced in sheep by intravenous infusion of Escherichia coli endotoxin, oleic acid, or air emboli caused the appearance in lung lymph of high levels of a protease with trypsin-like activity. The enzyme was isolated as an apparently homogeneous protein from pooled samples of active lung lymph, after an almost 9000-fold purification by affinity chromatography on columns of Reactive Blue 2-agarose, aprotinin-agarose, and p-aminobenzamidine-agarose, and chromatography on a column of Sephadex G-100. A molecular weight of about 70,000 to 75,000 was determined from mobility in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The pH optimum was between 7.3 and 7.6. The isolated enzyme was quite labile, rapidly losing activity at both 37 and 25 degrees C. Addition of albumin to enzyme solutions protected against inactivation. Inhibition by diisopropylfluorophosphate and phenylmethanesulfonyl fluoride indicated that the enzyme belongs to the class of serine proteases. The enzyme cleaved peptide bonds on the carboxyl side of arginine residues and showed a relatively high affinity toward peptides containing several basic amino acid residues. Bonds involving the carboxyl group of lysine were cleaved at a much slower rate. The enzyme showed no plasminogen activator activity and its substrate specificity was quite different from that of several proteases of the clotting cascade. Its appearance in lymph was not influenced by lymph clotting and the isolated enzyme was not capable of correcting the clotting defect of plasmas deficient in factors XII, XI, IX, VII, and X.

Indium-111 platelet kinetics in normal human subjects: tropolone versus oxine methods

The effect of labeling media on the kinetics of[111In]platelets was evaluated by performing a paired crossover study in eight normal human subjects using tropolone and oxine methods. Platelets were labeled in autologous plasma with [111In]tropolone (In-tr) and in ACD-saline with [111In]oxine (In-ox) and reinjected. Starting at 1 hr, ten blood samples were obtained over an 8-day period. The in vivo platelet recovery was higher at 1 hr and throughout the 8 days of study with In-tr and the gamma camera images showed less uptake in liver and spleen than with In-ox. When platelet life-span (PLS) was estimated using all ten samples, only linear regression showed that the platelet life-span was longer with In-tr (10.7 +/- 1.5) than with In-ox (9.5 +/- 0.8). When the PLS was estimated excluding the 1-hr sample point, the life-span of platelets was significantly longer with In-tr than with In-ox based on three out of four models of curve fitting. These results demonstrate that platelets labeled with In-tr in plasma are preserved better in circulation and have equal or longer life-span than platelets labeled with In-ox in ACD-saline.

The use of technetium-99m sulfur colloid as a marker for experimental venous thrombosis: concise communication

The binding of technetium-99m sulfur colloid to in vivo thrombi was studied in a rat model of deep vein thrombosis. After thrombosis was induced by mechanical traumatization of a right femoral vein segment, technetium-99m sulfur colloid was injected into the peripheral veins of different experimental groups at intervals of 30 min and 1-7 days. Ratios of mean activity in traumatized right femoral vein segment to activity in control segments of left femoral vein (R/L ratios) ranged form 2.97-11.0 for all in situ venous thrombi studied. There was no relation between clot size and R/L ratios. The significant uptake ratios observed by us for venous thrombi up to 1 wk in age suggest that in vivo thrombus detection may be feasible by imaging with a gamma camera after technetium-99m sulfur colloid injection in a peripheral vein.