bluuebunny/crossref_metadata_2025_split huggingface dataset:
Internalization of Recombinant Tissue-Type Plasminogen Activator by Isolated Rat Hepatocytes is via Coated Pits
Authors: Marks Gary J , Hart Timothy K , Rush Glenn F , Hoffstein Sylvia T , Fong Kei-Lai L , Bugelski Peter J 
Published: July 2018

SummaryThe uptake and internalization of tissue-type plasminogen activator (t-PA) by freshly isolated rat hepatocytes was investigated. Electron microscopic examination of the uptake of t-PA-colloidal gold conjugates (t-PA-gold) by isolated rat hepatocytes showed that t-PA-gold was internalized via coated pits. This was inhibited with excess t-PA. Uptake of 125I-t-PA by isolated rat hepatocytes was a rapid, saturable, and specific process. The initial rate of specific uptake was 0.1 fmol/106 cells per min. The specific uptake plateaued at 1.4 fmol/106 cells by 30 min and declined to 0.8 fmol/106 cells at 2 h. Depletion of cellular ATP by 85-90% did not affect the initial rate of specific uptake. However, specific uptake by ATP-depleted hepatocytes at 30 min was reduced by 37%. By 2 h specific uptake by ATP-depleted hepatocytes was only 5% lower than by untreated hepatocytes, suggesting that processing of t-PA and/or its receptor is ATP-dependent. Uptake of 125I-t-PA was temperature dependent. Specific uptake was reduced by ∼20% at 22° C and by 70% at temperatures below 16° C. Finally, inhibition of coated pit formation by K+-depletion with nigericin decreased the uptake of 125I-t-PA. This inhibition was shown to be K+-specific since treatment with nigericin in the presence of K+ did not inhibit coated pit formation or 125I-t-PA uptake. A threshold K+-depletion level for inhibition of coated pit formation was also demonstrated since treatment under conditions that reduced cellular K+ by only 54% had no effect on coated pit formation or 125I-t-PA uptake. These data support our hypothesis that internalization of t-PA by isolated rat hepatocytes is via coated pits and suggest that uptake of t-PA is a receptor-mediated process.
Depletion of Dense Granule Nucleotides during Storage of Human Platelets
Authors: de Korte D , Gouwerok C W N , Fijnheer R , Pietersz R N I , Roos D 
Published: July 2018

SummaryThe energy metabolism of human platelets was studied during storage of platelet concentrates. The platelets were prepared from buffy coats in PVC/DEHP bags and stored for 7 days at room temperature at a concentration of 1.0 × 109/ml with horizontal agitation. The total amount of ATP and ADP decreased with 40% during this storage. This decrease correlated with the disc-tosphere transformation associated with the loss of platelet viability. During storage, the ability to incorporate 3H-adenosine into metabolic ATP and ADP (45 min at 37° C) decreased with 50%. Via measurement of the specific activity of actin-bound ADP and the amount of incorporated radioactivity into total ATP and ADP, we calculated the content of the metabolic and storage pools of ATP and ADP. The results indicate that the decrease in adenine nucleotide levels during storage was mainly caused by a depletion of ATP and ADP from the storage pool, whereas the metabolic pool remained nearly intact. After 7 days, the ATP : ADP ratio of the storage pool had decreased from 1.0 to 0.3, indicating hydrolysis of ATP.Diadenosine-triphosphate and diadenosine-tetraphosphate (present in the storage pool) decreased with only 30%, and the serotonin content remained nearly constant. Therefore, it is unlikely that the storage pool was completely secreted. Probably, the storage pool of nucleotides serves as an internal supply for maintaining the contents of the metabolic pool of ATP and ADP during storage of platelets.
Luminographic Detection of von Willebrand Factor Multimers in Agarose Gels and on Nitrocellulose Membranes
Authors: Budde U , Schneppenheim R , Plendl H , Dent J , Ruggeri Z M , Zimmerman T S 
Published: July 2018

SummaryTwo methods for visualization of vWf multimers were compared with respect to sensitivity and detection of normal vWf and vWd variants IIA, IIB, IIC, IID, HE, and HE Autoradiography and luminography after electrotransfer of vWf multimers onto nitrocellulose showed comparable sensitivity with vWf: Ag detectable after 1:500 dilution of normal plasma. The least sensitive method was luminography in agarose gels with vWf: Ag detectable after 1:300dilution of normal plasma. No difference existed in the banding patterns of plasmas from patients with variant vWd.
Fibrin Affinity and Clearance of t-PA Deletion and Substitution Analogues
Authors: Johannessen M , Diness V , Pingel K , Petersen L C , Rao D , Lioubin P , O’Hara P , Mulvihill E 
Published: July 2018

SummaryTo investigate structure-function relationships in tissue-type plasminogen activator (t-PA) we deleted the following domains in the heavy chain: a) The epidermal growth factor domain (t-PA del. G), b) the finger domain, and the epidermal growth factor domain (t-PA del. FG), and c) the finger, the epidermal growth factor and Kr-ingle 1 (1-PA del, FGK1). To study specificly the function of the growth factor domain we made two substitutions of d) 8 amino acids (consensus sequence) in the growth factor domain (t-PA G-CS) and c) the whole domain with factor IX growth factui doniuin (t-PA G-IX). Finally, f) an analogue with substitution in the finger domain (fibronectin consensus sequence) was constructed (t-PA F-CS).A reduced fibrin binding of all the analogues was found. The fibrin stimulated activity of all analogues was also reduced and correlated to the fibrin binding. In contrast, the activity of the analogues in the clot lysis assay and the plate assay were only slightly reduced as compared to authentic t-PA. This suggested that at high fibrin concentrations the decreased fibrin affinity was less ciitical for obtaining a high fibrinolytic activity.All analogues had a prolonged half-life in vivo as compared to authentic t-PA. The assumption of clearance mechanism involving mainly the growth factor region (or Kringlc 1) was not challenged by the observation of a prolonged half-life for the substitution analogue t-PA F-CS.Our results indicate that a high affinity for fibrin and rapid elimination in vivo of t-PA require a nearly intact conformation of the N-terminal part of the molecule.
Fibrinolytic Activity in Chinese Patients with Diabetes or Hyperlipidemia in Comparison with Healthy Controls
Authors: Ho Chao Hung , Jap Tjin Shing 
Published: July 2018

SummaryPlasma tissue-type plasminogen activator (tPA), plasminogen activator inhibitor (PAI) and euglobulin lysis time (ELT) were determined before and after the venous occlusion test (VOT) in 3 groups of patients with mean age about 60 years: 29 diabetic patients (D group), 8 hyperlipidemic patients (H group) and 19 healthy controls (C group). In the D and H groups, the mean of morning tPA was significantly higher than that of the C grogp, but the means of PAI were not significantly different among the 3 groups. ELI was significantly shortened and tPA was markedly increased after the VOT in all 3 groups whereas PAI had not significantly changed. In conclusion, high tPA activity and good fibrinolytic response without significant change of PAI .activity were found in the diabetic and hyperlipidemic patients, and no definite impairment of the fibrinolytic activity could be found in the Chinese patients with diabetes and hyperlipidemia. This might be one of the reasons why the Chinese has low incidence of thromboembolic diseases.
Binding of Platelet Agglutinating Protein p 37 from the Plasma of a Patient with Thrombotic Thrombocytopenic Purpura to Human Platelets
Authors: Lian Eric C-Y , Siddiqui Farooq A 
Published: July 2018

SummaryWe have previously reported the purification of a 37 kDa platelet agglutinating protein (PAP p37) from the plasma of a patient with thrombotic thrombocytopenic purpura (TTP) that was shown to be present in a subset of TTP patients. To gain further insight into the interaction between PAP p37 and platelets, we have studied the properties of PAP p37 binding to platelets. Washed human platelets from two normal donors and two TTP patients after recovery were used for the experiments. The PAP p 37 binding to platelets was specific, concentration dependent and saturable. Scatchard analysis demonstrated about 20,564–27,090 PAP p37 binding sites per platelet. Stimulation of platelets with thrombin or ADP did not have any significant effect on its binding.Thiol- and serine-specific protease inhibitors did not inhibit PAP p37 binding to the platelets. Sugars such as glucose, fructose, mannose, and sialic acid, at 40 mM, inhibited its binding to platelets by 44%, 73%, 79%, and 91% respectively, but galactose and amino sugars did not have any significant effect. At 250 μg/ml, Concanavalin-A inhibited 42% of binding, but other lectins, such as phytohemagglutinin-P, potato lectin and helix pomatia lectin (snail), did not. Pre-incubation of 125I-PAP p37 with the adult human IgG, decreased its binding to the platelets. The monoclonal antibodies to GP Ib (6D1) and GP IIb-IIIa complex (10E5) did not inhibit the binding of 125I-PAP p37 to platelets. Fibrinogen and von Willebrand factor did not affect the binding either. These results suggest that PAP p37 binds to platelets on the sites other than GP lb or GP IIb-IIIa complex.
Protein C, Protein S and c4b-Binding Protein in Severe lnfection and Septic Shock
Authors: Hesselvik J F , Malm J , Dahlbäck B , Blombäck M 
Published: July 2018

SummaryWe measured concentrations of the natural anticoagulant protein C; its cofactor, protein S; and the carrier protein C4bbinding protein (C4BP), in 24 patients with severe infection and 13 with septic shock. Decreased antithrombin III levels were found in 16 of 24 infection patients and all shock patients; high thrombin-antithrombin (TAT) complexes were present in 16 of 24 infection and 12 of 13 shock patients. Protein C concentrations were significantly reduced compared to healthy blood donors, to 60 ± 14% (infection) and 47 ± 20% (septic shock) (mean ± 1 SD). Total protein S levels were not reduced (119 ± 36.7 and 88 ± 20.0%, normal value 96±15%). Free protein S was also normal (27 ± 9.4 and 30 ± 8.7%, normal value 29 ± 9%). The percentage free of total protein S was normal in shock patients (35 ± 8.5%), but significantly reduced in patients without shock (23 ± 5.3%). C4BP was significantly higher than normal in the latter group (135 ± 43%), but not in the shock group (118 ± 40%), possibly due to increased consumption. Thus, no deficiency of total or free protein S was found in these patients, who had evidence of activated coagulation but no clinical DIC.
Factors Affecting the lnteraction of Tissue Factor/Factor Vll with Factor X in a Heterogeneous Tubular Reactor
Authors: Gemmell Cynthia H , Turitto Vincet T , Nemerson Yale 
Published: July 2018

SummaryA novel reactor recently described for studying phospholipiddependent blood coagulation reactions under flow conditions similar to those occurring in the vasculature has been further charactenzed. The reactor is a capitlary whose inner wall is coated with a stable phospholipid bilayer (or two bilayers) containing tissue factor, a transmembrane protein that is required for the enzymatic activation of factor X by factor VIIa. Perfusion of the capillary at wall shear rates ranging from 25 s−1 to 1,200 s−1 with purified bovine factors X and VIIa led to steady state factor Xa levels at the outlet. Assay were performed using a chromogenic substrate, SpectrozymeTMFXa, or by using a radiometric technique. In the absence of Ca2+ or factor VIIa there was no product formation. No difference was noted in the levels of factor Xa achieved when non-activated factor VII was perfused. Once steady state was achieved further factor Xa production continued in the absence of factor VIIa implying a very strong association of factor VIIa with the tissue factor in the phospholipid membrane. In agreement with static vesicle-type studies the reactor was sensitive to wall tissue factor concentration, temperature and the presence of phosphatidylserine in the bilayer.
An Analysis of the Activators of Single-Chain Urokinase-Type Plasminogen Activator (scu-PA) in the Dextran Sulphate Euglobulin Fraction of Normal Plasma and of Plasmas Deficient in Factor XII and Prekallikrein
Authors: Binnema D J , Dooijewaard G , Turion P N C 
Published: July 2018

SummaryAn analysis was made of the various possible activators of single-chain urokinase-type plasminogen activator (scu-PA) in the dextran sulphate euglobulin fraction (DEF) of human plasma. scu-PA activators were detected in an assay system in which the substrate scu-PA, in physiological concentration (50 pM), was immuno-immobilized. After activation of the immobilized scu-PA for a certain period of time the activity of the generated amount of immuno-immobilized two-chain u-PA was determined with plasminogen and the chromogenic substrate S-2251. The scu-PA activator activity (scuPA-AA) in the DEF of plasmas deficient in factor XII or prekallikrein was about half of that in the DEF of normal plasma. Separation of scuPA-AA in the DEF by gel chromatography showed to major peaks, one eluting with an apparent Mr of 500,000 and the other around Mr 100,000. The former peak, which coincided with the activity peak of the kallikrein-kininogen complex, was absent in the DEF of plasma depleted of prekallikrein and therefore was identified as kalli-krein. The latter peak was still present in the depleted plasma and most likely represents plasmin, because its scuPA-AA coincided with the activity peak of plasmin and could be fully inhibited by antibodies raised against human plasminogen. It is concluded that plasmin and the contact-activation factor kallikrein each contribute for about 50% to the scuPA-AA in the DEF. Compared on a molar basis, however, plasmin was found to be almost 1,000 times more effective than kallikrein, and we conclude, therefore, that in vivo plasmin is the primary activator of scu-PA and the role of the contact system is of secondary importance.
A Synthetic Analog of Fibrinogen α27–50 Is an Inhibitor of Thrombin
Authors: Binnie Cameron G , Lord Susan T 
Published: July 2018

SummaryBinding of the synthetic peptide AAKDSDWPEASDEDWNYKAPSGAR, a fibrinogen α27–50 analog, to thrombin was studied by inhibition assays and affinity chromatography. Peptide α27–50 corresponds to a segment of human fibrinogen downstream from the thrombin cleavage site, with cysteine residues at positions 28, 36, 45 and 49 replaced by alanine. The peptide inhibited clotting of fibrinogen with an inhibition constant of 190–400 μM. Cleavage of fibrinopeptides A and B was inhibited by the peptide and the peptide was competitive with fibrinogen for thrombin. Inhibition of the small substrate tosyl-Gly-Pro-Arg-p-nitroaniline was not observed indicating that the peptide did not block the active site of the enzyme. Peptide α27–50 that was covalently linked to Sepharose bound active siteinhibited thrombin at low ionic strength and was eluted at higher salt concentration. The peptide was not cleaved on overnight exposure to thrombin as determined by reverse phase HPLC. In summary, the peptide bound to, but was not a substrate for thrombin. These results suggest that this region of fibrinogen contributes to binding of thrombin.
Failure of Computerized Impedance Plethysmography in the Diagnostic Management of Patients with Clinically Suspected Deep-Vein Thrombosis
Authors: Prandoni P , Lensing A W A , Büller H R , Carta M , Vigo M , Cogo A , Cuppini S , ten Cate J W 
Published: July 2018

SummaryBefore a new diagnostic modality can be introduced in clinical medicine, the validity of both a normal and abnormal test result have to be assessed prospectively in an appropriate patient group. We have evaluated the clinical validity of. a new computerized impedance plethysmography (CIP) in the diagnostic management of 381 consecutive patients with clinically suspected venous thrombosis. In patients with serially normal CIP results, the diagnosis of venous thrombosis was refuted and, consequently, they were not treated with anticoagulant therapy and all were followed up for a period of 6 months to estimate the occurrence of symptomatic venous thromboembolism.The study was prematurely terminated by the safety monitoring committee because of an unacceptably high incidence of confirmed venous thromboembolism (10 patients, 3.2%; 95% confidence interval: 1.6% to 6%), including 4 episodes of fatal pulmonary embolism. In a subsequent explanatory study using ultrasonography in 29 other symptomatic patients who had at least 2 repeated normal CIP test results, the failure of CIP to detect proximal vein thrombosis was confirmed in 4 patients (14%). The reasons for this failure are probably related to the use of a modified device to measure impedance in the CIP apparatus, resulting in a lower ability to separate patients without venous thrombosis from those with the disease.We concluded that CIP is insensitive for the detection of proximal vein thrombosis and, therefore, not clinically useful in the diagnostic management of patients with suspected venous thrombosis.
Bleeding/Bruising Symptomatology in Children with and without Bleeding Disorders
Authors: Nosek-Cenkowska B , Cheang M S , Pizzi N J , Israels E D , Gerrard J M 
Published: July 2018

SummaryA questionnaire, designed to assess bleeding/bruising tendencies, was administered to 251 otherwise healthy children undergoing a tonsillectomy and/or adenoidectomy. 23 children with excessive bleeding during or after the operation, with a long bleeding time or who reported taking aspirin recently were excluded, to give a population of 228 non-bleeders. For comparative purposes, 31 patients with bleeding disorders (von Wille-brand’s disease and/or platelet function defects) were studied. A considerable proportion of “non-bleeding” children reported easy bruising (24%), had bruises at least once a week (36%) and suffered from nosebleeds (39%). The respective frequencies (67%, 68% and 69%) for children with bleeding disorders were significantly higher. Occurrence of bruises usually on more than one part of the body, frequent large bruises or hematomas were rare in “non-bleeders” (4.9%, 3.5% and 2.7% respectively), but more common in “bleeders” (38.5%, 29.6% and 21.7% respectively).
The Role of Blood and Platelets in Atherosclerosis and the Complications of Atherosclerosis
Authors: Mustard J. F , Packham M. A 
Published: July 2018

SummaryThere appear to be at least three ways in which the blood, and particularly the platelets, may contribute to the development of atherosclerosis and its complications :1. In the mechanism causing endothelial injury and the response of the smooth muscle cells to vessel injury.2. Through the formation of persistent mural thrombi which are organized into intimai thickenings.3. Through the formation of thrombi in association with advanced atherosclerosis that may be either (a) mural thrombi which fragment and shower the distal circulation with platelet emboli or (b) occlusive thrombi.
Changes of Coagulation and Fat-Metabolism Following Pulmonary Microembolism after Trauma and Hemorrhage
Authors: Saggau W. W , Ulmer H. E , Bleyl U 
Published: July 2018

SummaryIn 16 of 24 anesthetized mongrel dogs a standardized bone trauma was performed to both hind legs by open osteotomy. During the following 6 hours the most important hemodynamic parameters, total platelet count (GTZ) and its separate fractions (NKF, KF) were continously monitored.Five hours after the trauma 50% of the total blood volume (taken to be 80 ml/kg body weight) was withdrawn from two of the four groups of animals.The trauma caused no direct effect on the pulmonary hemodynamics.In the following hours there was a slight decrease of cardiac output (HZV) in the traumatised animals. Besides a moderate increase in mean pulmonary pressure (MPP), pulmonary vascular resistance (PVP) increased by 72% of the pretraumatic values. The application of intravascular catheters diminished the total platelet count markedly in the injured, as in the uninjured animals. The increase in PVR was caused less by a mechanical obstruction of the pulmonary capillary bed than by vasoactive substances released by the platelets. The following hemorrhage led to a more marked hemodynamic reaction in the injured animals. All these animals died before the end of the calculated hemorrhage. All animals without trauma survived. Irreversible aggregation of platelets developed in the pulmonary capillary bed caused by the marked pulmonary hypocirculation.Histological examination showed a marked disseminated pulmonary microthrom-bosis in all animals with trauma and hemorrhage.The initial phase of experimental pulmonary microembolism caused by trauma was characterized by pulmonary hypocirculation and an activated coagulation with simultaneously diminished total platelet count.
Plasminogen-Plasmin System IX. Specific Binding of Tranexamic Acid to Plasmin
Authors: Iwamoto Masahiro 
Published: July 2018

SummaryInteractions between tranexamic acid and protein were studied in respect of the antifibrinolytic actions of tranexamic acid. Tranexamic acid did neither show any interaction with fibrinogen or fibrin, nor was incorporated into cross-linked fibrin structure by the action of factor XIII. On the other hand, tranexamic acid bound to human plasmin with a dissociation constant of 3.5 × 10−5 M, which was very close to the inhibition constant (3.6 × 10−5 M) for this compound in inhibiting plasmin-induced fibrinolysis. The binding site of tranexamic acid on plasmin was not the catalytic site of plasmin, because TLCK-blocked plasmin also showed a similar affinity to tranexamic acid (the dissociation constant, 2.9–4.8 × 10−5 M).In the binding studies with the highly purified plasminogen and TLCK-plasmin preparations which were obtained by affinity chromatography on lysine-substituted Sepharose, the molar binding ratio was shown to be 1.5–1.6 moles tranexamic acid per one mole protein.On the basis of these and other findings, a model for the inhibitory mechanism of tranexamic acid is presented.
The Effect of Brinase on Fibrinogen in Vivo
Authors: Nyman D 
Published: July 2018

SummaryBrinase infusions in man cause, without excessive lowering of the inhibitor capacity, a slowing of the fibrin polymerization. This is combined with a degradation of the A α chain into two major fragments. Both fragments carry crosslinking sites. Brinase infusion also causes positive ethanol gelation. Evidence for the formation of γ dimers was found.
Clinical Correlations
Authors: Moore Sean 
Published: July 2018

SummaryThere are two aspects which are clinically relevant in the relationships among thrombosis and arteriosclerosis. First, the relationship of thrombosis to atherogenesis. Thrombosis is closely related to endothelial injury and there is recent evidence that repeated or continuous endothelial damage leads to the development of all the lesions seen in human atherosclerosis. This occurs in the absence of dietary lipid supplement. The relative importance of the parts played by injury and thrombosis in this process need further delineation. Secondly, established arteriosclerotic disease is associated with thrombosis. This thrombosis is usually mural, seldom occlusive. Embolism by platelet aggregates which has been well described in the retinal and cerebral circulations may affect other vascular territories such as the heart and the kidney. Such a mechanism may explain some cases of otherwise unexplained sudden cardiac death and some cases of hypertension. We need better clinical tools to detect the occurrence of thrombo-embolism and to monitor it’s progress. Measures to modify thrombosis and embolism may be as useful or more useful than those we currently employ in the clinical management of atherosclerotic disease.