bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Agonists and Antagonists of Platelet Aggregation on von Willebrand Factor-Mediated Platelet Agglutination
Authors: McPherson Jean , Zucker Marjorie B , Mauss Evelyn A , Brownlea Sandra 
Published: July 2018

SummaryRistocetin-induced platelet agglutination (RIPA) in EDTA-treated citrated platelet-rich plasma was reduced to 49 ± 11% by 1.25 ΜM ADP, 41 ± 14% by 1 ΜM A 23187, and 26 ± 7% by 0.1 Μg/ml platelet activating factor (PAF). The effect of 5-110 ΜM epinephrine was not dose-dependent, but varied between donors, with RIPA from 56-100% of the control. The inhibitory effects of these agonists were not altered by prior treatment of platelets with aspirin. Prior addition of 200 ΜM ATP (an ADP receptor antagonist acting at both high and low affinity ADP receptors) prevented the inhibitory action of ADP but not that of A 23187 or PAF, suggesting that the inhibitory actions of the latter are not mediated by released ADP. As 700 ΜM 8-bromoadenosine 5-diphosphate (an ADP receptor antagonist acting mainly at the high affinity receptor) did not prevent ADP-induced inhibition of RIPA, interaction of ADP with the low affinity receptor is presumably responsible for its inhibitory action. As A 23187, but not phorbol myristate acetate (0.1 ΜM) inhibited RIPA, an increase in intracellular calcium ions rather than direct stimulation of protein kinase C appears to mediate agonist-induced inhibition. Cytochalasin B (10.5-21 ΜM), dibucaine (0.5-1 mM), and prostaglandin E1 (25 nM), added before or after the agonist, prevented or reversed ADP-, A23187-, and PAF-induced inhibition of RIPA, suggesting that the state of the platelet cytoskeleton affects inhibition. N-ethylmaleimide (0.25-0.5 mM), an agent that can penetrate cell membranes and block sulphydryl groups, prevented or reversed ADP, A 23187- and PAF-induced inhibition of RIPA, but 0.5 mM dithionitrobisbenzoic acid, a non-penetrating sulphydryl blocker, had no effect. Diamide (0.1-0.5 mM), an agent that can crosslink cytoskeletal proteins by oxidation of sulphydryl groups, reduced RIPA. Thus an increase in intracellular calcium ions with resultant cytoskeletal changes and reorganisation of intracellular sulphydryl groups may mediate the inhibitory action of agonists on RIPA.
Thromboxane Responsiveness of Dog Platelets Is Inherited as an Autosomal Recessive Trait
Authors: Johnson Gerhard J , Leis Linda A , King Richard A 
Published: July 2018

SummaryMost mongrel dogs have platelets that form thromboxane A2 (TXA2) from exogenous arachidonate, but they fail to aggregate or secrete in response to it. In contrast to these TXA2 insensitive (TXA2-) platelets, some dogs have TXA2 sensitive (TXA2+) platelets that aggregate and secrete when stirred with arachidonate. To evaluate the possible genetic basis for this difference, we carried out seven matings of mongrel dogs that yielded 48 viable offspring. Four matings of dogs with TXA2- platelets (presumed genotype TT) including 2 back-crosses, produced 32 pups with TXA2- (TT) platelets and 0 pups with TXA2+ platelets. A cross between a male with TXA2+ platelets (presumed genotype tt) and a female with TXA2+ (tt) platelets yielded 9 offspring with TXA2+ (tt) platelets and 0 with TXA2- platelets. Crossing a male presumed homozygous (TT) for TXA2- platelets with a female with TXA2+ (tt) platelets produced 2 pups with TXA2- (Tt) platelets and 0 pups with TXA2+ (tt) platelets. The same female with TXA2+ platelets crossed with a male presumed to be heterozygous (Tt) for TXA2- platelets yielded 2 pups with TXA2+ (tt) platelets and 3 pups with TXA2- (Tt) platelets. Segregation analysis of these data supports the hypothesis that the ability of dog platelets to aggregate and secrete in response to TXA2 is inherited as an autosomal recessive trait.
Upstream Thrombus Growth Impairs Downstream Thrombogenesis in Non-Anticoagulated Blood: Effect of Procoagulant Artery Subendothelium and Non-Procoagulant Collagen
Authors: Sakariassen Kjell S , Weiss Harvey J , Baumgartner Hans R 
Published: July 2018

SummaryIn the present experiments we have investigated the influence of wall shear rate and axial position on platelet and fibrin deposition which results when flowing human non-anticoagulated blood is exposed to either non-procoagulant fibrillar collagen (human type III) or procoagulant subendothelium (rabbit aorta). Platelet adhesion, thrombus volume and fibrin deposition were morphometrically evaluated at axial positions of 1 and 13 mm following perfusions for 5 min at shear rates of 100, 650 and 2,600 s-1.An axially-dependent decrease of platelet adhesion (34-57%, p <0.01-0.05) and thrombus volume (57-80%, p <0.05) was observed on collagen at all shear rates. On subendothelium, an axially-dependent decrease was observed for platelet adhesion only at 100 s-1 (29% ; p <0.01) and for thrombus volume at shear rates of 650 s-1 and above (49-58%, p <0.01). Deposition of fibrin on subendothelium was axially decreased (16-42%, p <0.05) at all shear rates, while no significant axial differences were seen on collagen. However, substantially more fibrin was deposited on the subendothelium (p <0.05), and the upstream platelet adhesion and thrombus volume were lower than on collagen (p <0.05) at 100 s-1 and 650 s-1. The axially-dependent phenomena on the two surfaces are consistent with the concept of rapid-growing upstream thrombi which deplete the blood layer streaming adjacent to the surface of platelets, leading to decreased platelet deposition farther downstream. The observations suggest that deposition of fibrin is enhanced by subendothelial tissue factor, and that upstream depletion of clotting factors may lower the downstream deposition of fibrin, analogous to the depletion of platelets.
Low Molecular Weight Heparin versus Warfarin in the Prevention of Recurrences after Deep Vein Thrombosis
Authors: Pini M , Aiello S , Manotti C , Pattacini C , Quintavalla R , Poli T , Tagliaferri A , Dettoi A G 
Published: July 2018

SummaryTo evaluate the role of low-molecular weight heparin (LMWH) as an alternative to oral anticoagulants in the prevention of recurrent venous thromboembolism, we compared in a randomized trial conventional warfarin treatment with a three-month course of enoxaparin 4000 anti-Xa units once a day subcutaneously. 187 patients with symptomatic deep-vein thrombosis (DVT), diagnosed by strain-gauge plethysmography plus D-dimer latex assay and confirmed by venography in most cases, were treated with full-dose subcutaneous heparin for ten days and then randomized to secondary prophylaxis. During the 3-month treatment period, 6 of the 93 patients who received LMWH (6%) and 4 of the 94 patients on warfarin (4%) had symptomatic recurrence of venous thromboembolism confirmed by objective testing (p = 0.5; 95% confidence interval [Cl] for the difference, -3% to 7%). Four patients in the LMWH group had bleeding complications as compared with 12 in the warfarin group (p = 0.04; 95% Cl for the difference, 4% to 14%). In the 9-month follow-up period, during which 34 patients on warfarin prolonged treatment for other 3 months and 14 up to one year, 10 patients in the enoxaparin group and 4 patients in the warfarin group suffered a documented recurrence of venous thromboembolism. Of these 14 late recurrences, just one occurred in patients with postoperative DVT. After one year there were 16 recurrences (17%) in the LMWH group and 8 (9%) in the warfarin group (p = 0.07; 95% Cl for the difference, 1% to 16%).These results confirm the potential of LMWH as an alternative to oral anticoagulants in this setting, and suggest to evaluate in a prospective study a slightly higher dose of enoxaparin in patients with postoperative DVT.
On the Immunogenicity of Recombinant Staphylokinase in Patients and in Animal Models
Authors: Vandaerscheren Steven M F , Marie Stassen Jean , Collen Désiré 
Published: July 2018

SummaryStreptokinase and staphylokinase, the presently available thrombolytic agents of bacterial origin, are immunogenic in man; their use may cause allergic reactions and/or refractoriness to renewed administration. Infusion of 2 to 10 mg of recombinant staphylokinase (STAR) in 20 patients with acute myocardial infarction or peripheral arterial occlusion induced IgG-related neutralizing activity in plasma with a lag phase of 10 to 12 days, from a baseline of 0.2 ± 0.06 |ig STAR neutralized per ml plasma (mean ± SEM) to a maximum of 30 ± 6.2 µml after 3 to 9 weeks, which persisted at a level of 14 ± 5.8 µml after 18 months (n = 4).In 4 baboons with a 125I-fibrin labeled clot in an extracorporeal arteriovenous loop, i. v. administration of 63 fig/kg STAR over 1 h, repeated at weekly intervals, induced a progressive increase of STAR-neutralizing activity (from 0.05 ± 0.1 µml at baseline to 4.8 ± 1.5 µml at week 6), which was paralleled by a reduction of in vivo clot lysis (from 60 ± 7% to 8 ± 3%). After temporary discontinuation of STAR-administration, neutralizing activity reverted to baseline within 7 weeks, whereafter the sensitivity of in vivo clot lysis to STAR was restored. In rabbits, i. v. administration of 250 µkg STAR over 1 h, repeated at weekly intervals, also induced a progressive increase of STAR-neutralizing activity (from 0.5 ± 0.2 µml at baseline to 6.4 ± 1.1 [ig/ml at week 6), which was paralleled by a reduction of in vivo clot lysis (from 68 ± 3% to 31 ± 7%). Thus a single STAR-administra-tion elicits an immune response in patients with persistence of neutralizing antibodies for over 18 months. Although antibody induction in baboons and rabbits required repeated administrations and was more transient than in man, these animal models appear to be suitable for the evaluation of the thrombolytic and immunogenic properties of staphylokinase variants.
The Calcium Modulator Nifedipine Exerts Its Antiaggregatory Property via a Nitric Oxide Mediated Process
Authors: Berkels R , Klaus W , Boiler M , Rösen R 
Published: July 2018

SummaryThe in vitro effect of nifedipine, a calcium channel blocker of the dihydropyridine (DHP) type, on platelet aggregation was reinvestigated considering especially the capability of platelets to form endogenous nitric oxide (NO). We studied the dose-dependent antiaggregatory property of nifedipine in porcine platelet rich plasma. Aggregation was stimulated by collagen (7.5 ¼g/ml). Nifedipine inhibited collagen-induced platelet aggregation with an IC50 of 380 nmol/1. The antiaggregatory effect of nifedipine could be significantly diminished by N-nitro-L-arginine (NNA) in a concentration dependent manner, whereas oxy haemoglobin (4 ¼M), a NO scavenger, totally abolished the effect of nifedipine. L-Arginine, the precursor of NO, dose-dependently inhibited the collagen-induced platelet aggregation but did not potentiate the effects of nifedipine. Therefore, we propose that in platelet rich plasma the nifedipine induced inhibition of platelet aggregation is mediated by NO, a potent endogenous inhibitor of aggregation. We could confirm this hypothesis by measuring NO directly with a specific electrode.
The Half-Life of Plasmic Degradation Products of Human Fibrinogen in Rabbits
Authors: Ardaillou N , Dray L , Budzynski A. Z , Marder V. J , Larrieu M. J 
Published: July 2018

SummaryHuman fibrinogen and purified plasmic degradation fragments X (stages 1 and 2), D and E were labelled with 125-1 using the lactoperoxidase method. The chromatographic, elec-trophoretic and immunologic properties of the labelled proteins were found to be similar to those of non-labelled fragments. All the degradation products diffused rapidly (T½ 0.27–0.75 hours) from the intravascular space of rabbits, as compared with fibrinogen (4.26 hours). In addition, the metabolic half-life was found to be 49.3 hours for fibrinogen, as compared with only 5.1, 6.1, 2.3 and 1.4 for fragments X (stage 1), X (stage 2), D and E, respectively. The metabolic half-life roughly reflects the molecular size of the degradation products.
Alterations in the Effects of Warfarin in Dogs by Halofenate
Authors: Weintraub Michael , Griner Paul F 
Published: July 2018

SummaryThe interaction between warfarin and the new lipid lowering agent halofenate (MK 185) [2 - acetamidoethyl (p-chlorophenyl) (m-trifluoromethylphenoxy) acetate] was studied in dogs in both short- and long-term experiments. Our data suggest that halofenate potentiates the anticoagulant effect of warfarin by increasing the degradation of prothrombin (factor II) (Kdeg on placebo = 211 ± 32 × 10−4 × Hr−1 mean ± SEM; on halofenate = 268 ± 39 × 10−4 × Hr−1 mean ± SEM; P < 0.01). However, a concomitant increase in factor II synthesis of 34% results in resistance to warfarin’s effect if halofenate is administered prior to warfarin. The mean prothrombin time of 4 dogs on 2 mg of warfarin following halofenate pretreatment for 8 weeks was 74.8% ± 17.3 (SE) of the anticoagulated control dog. On 2 mg of warfarin alone, it was 133.7% ± 42.0 (P < 0.001). Cessation of halofenate from combined therapy results in a delayed augmentation of warfarin effect. These data suggest that the nature of the interaction between warfarin and drugs such as halofenate which alter the kinetics of prothrombin may depend on the sequence of administration.
Absence of Blocking Antibody in Non-Inhibitor Haemophilic Plasma
Authors: Pool Judith , Kaelin A. C 
Published: July 2018

SummaryThis study examined the hypothesis that non-inhibitor haemophilic plasma contains antibodies which are specific for sites other than the active procoagulant site on factor VIII, and that some of them might be sufficiently close to the active site that pre-incubation of such plasma with factor VIII would block the subsequent binding of inhibitor antibody. Among the 26 non-inhibitor plasmas examined, none was found to contain such blocking antibody. This result does not eliminate the possibility that antibody is present in such non-inhibitor plasmas which is neither specific for the active enzyme site of factor VIII nor capable of blocking the binding of antibody which does have that specificity.
Rapid Isolation Of Native Urokinase From Normal Human Urine
Authors: Huber K , Kirchheimer J , Binder B R 
Published: July 2018

Urokinase (UK) has been isolated to complete homogeneity starting mainly from commercially available prepurified preparations. When native human urine was the starting material, high amounts of urine were necessary because of low yields due to time consuming and complicated procedures. Furthermore, without addition of inhibitors a shift to lower molecular weight (Mr) forms could not be avoided. In order to develop a rapid isolation procedure yielding final UK preparations of complete homogeneity and as unaltered as possible, we avoided concentration procedures at the beginning of the preparation as well as antibody columns because of high activity losses and binding of non active UK antigen, respectively, and employed two affinity chromatography steps.Two liters of native human urine were dialysed and adsorbed to gelatine-Sepharose; UK was completely bound and could be eluted with 0.1M Tris-HCl buffer, 0.7M CaCl2, pH 7.4. Active material was pooled, dialysed, and adsorbed to agmatine-Sepharose. Again, activities applied were totally bound and could be eluted with 0.1M phosphate buffer, 0.4M KC1, pH=7.4. Active material was freeze dried and gel filtrated on Sephadex G-150 in 0.1M Tris-HCl buffer, 1M NaCl, pH=8.0. During the whole isolation procedure Tween-80 (0.1%) was used in the buffer systems. Gelatine (0.02%) was present during dialysis. The procedure resulted in a UK preparation with a Mr=56.000 (SDS-PAGE) of complete homogeneity, and with a yield of l0-20% calculated from the starting material. Specific activity was about 16 pmoles of active enzyme per μg of protein (3H-DFP incorporation). The final product cleaved Glu-plasminogen to plasmin with an apparent KM≃lμM and a kcat≃0.5 s-1.The method described is a simple and efficient procedure resulting in a product with a specific activity comparable to those described for completely purified preparations and in a Mr form identic to that predominantly present in native urine.
Isolation And Characterization Of A Plasminogen Activator (PA) From Human Myocardial Tissue
Authors: Binder B R , Reissert G , Beckmann R 
Published: July 2018

Pig heart is one of the major sources for isolation of PAs. However, no attempt has been made to isolate PA from human heart. It was the aim of the study to isolate a PA from human myocardial tissue and to compare it with the vascular plasminogen activator (VPA) derived from cadaver vessel eluates.Human heart was obtained from cadavers and myocardial tissue was prepared, homogenized, and after extraction with a neutral buffer, a pH=4.2 extract was obtained containing about 60-70% of PA activity originally present in the homogenate. The latter extract was made 2 M with (NH4)2SO4 at pH=7.0 precipitating all of the activator activity. PA activity could be purified to apparent homogeneity by reverse ammonium sulfate gradient solubilization followed by hydrophobic interaction chromatography on octly- Sepharose, affinity chromatography on arginin-Sepharose and gel filtration on Sephadex G-150. The material obtained showed a single band in SDS polyacrylamide gel electrophoresis corresponding to Mr=70.000 and the region of the gel where PA activities could be eluted.Kinetic analysis of the purified activator with synthetic paranitroanilide substrates revealed a KM of 0.8 mM,4 mM, and 0.4 mM for H-D-Ile-Pro-Arg-paranitroanilide, H-D-Val- Gly-Arg-paranitroanilide, and H-D-Phe-Aze-Arg-paranitro- anilide, respectively, which were almost identic to those obtained with the VPA using the same subtrates. Plasminogen activation with the myocardial PA showed in a purified system a strong dependence on the presence of fibrin as it could be observed with VPA.From the similar isolation characteristics, the molecular weight, the amidolytic activities, and the fibrin effect on plasmin formation it can be concluded that the PA isolated from human myocardial tissue is similar or identic to the VPA.
The Carboxylation Of Bovine Vitamin K-Dependent Proteins By Bovine Carboxylase
Authors: Vermeer C , Soute B A M , Hemker H C , de Metz M 
Published: July 2018

Bovine vitamin K-dependent carboxylase was prepared, both from normal cows and from warfarin-treated ones. The two carboxylating enzyme systems were similar except for the fact that carboxylase from warfarin-treated cows contained a 100-fold higher amount of endogenous substrate. About 65% of this substrate consisted of one-chain factor X-precursor (s) and 25% of prothrombin-precursor(s). Solubilized carboxylase could be purified more than 100-fold by immuno- specific adsorption onto immobilized antifactor X antibodies. The purified enzyme contained 40% (w/w) phospholipid (mainly phosphatidylcholine), which was absolutely required for the carboxylating activity.Carboxylase from non-anticoagulated cows was used for studying exogenous substrates. Bovine descarboxyprothrombin, descarboxyfragment-1 and the pentapeptide Phe-Leu-Glu- Glu-Leu were carboxylated with a low efficiency (Km, between 0.4 and 11 mM). On the other hand a peptide, identical to the amino acid residues 13-29 in descarboxyprothrombin, had a Km of 0.001 mM. It seems probable therefore that the latter peptide contains all information required for a good substrate.
The Extravascular Coagulation System: The Production Of Prothrombin, Factors V, X, IX, VII And Tissue Factor In Macrophages
Authors: Østerud B , Lindahl U , Bøgwald J , Seljelid R 
Published: July 2018

The synthesis of coagulation factors and tissue factor (T.F.) has been investigated in macrophage cultures. The macrophages were obtained from mice by peritoneal washing. Serum free medium collected after 24 h macrophage culturing contained 4-12% of prothrombin, Factors VII, IX and X. These factors were not produced when either cycloheximide or warfarin were added to the growth medium. Factor V, secreted from the macrophages, was detected by the use of a clotting assay and a coupled amidolytic assay. Warfarin had no effect whereas cycloheximide blocked the synthesis of Factor V.T.F. activity in lysed macrophages was determined by incubation of the test sample with purified F.VII, F.X and CaCl2. The production of the T.F. was dependent on lymphocytes. Lymphocytes themselves did not synthesize T.F., but they were required for the production of T.F. in macrophages as the use of anti-theta antibody + complement blocked the generation of T.F.. Endotoxin added to the cultures enhanced the synthesis of T.F. 10-40 fold (i.e. expressed in F.Xa generated in the T.F. assay: macrophages alone 0.5%, macrophages + endotoxin 18.0%, lymphocytes alone + endotoxin < 0.1%).Macrophages secreted variable amounts of activated F.X due to the tissue factor production. However, endotoxin stimulated macrophages with high concentration of T.F. secreted less F.Xa probably caused by the synthesis of an inhibitor to F.Xa.This study demonstrates that there exists a complete extravascular coagulation system that can be triggered by the synthesis of T.F..
Obesity Is Not A Risk Factor In Thrombophlebitis
Authors: Kerstein M D , O’Connell R C , McSwain N E 
Published: July 2018

It is alleged that obesity is a risk factor in the occurrence of thrombophlebitis. It is the purpose of this investigation to study that inter-relationship.One hundred consecutive patients (21 male, 79 female) with an average age of 34 years were the subjects for this study. All patients were candidates for surgical intervention (gastric bypass procedure) because of obesity with minimum of 100 lbs over predicted weight. The mean weight was 279.2 lbs with a range of 191 - 500 lbs. The mean body mass index was 48 (weight kg/ (height cm)2). The incidence of deep vein thrombophlebitis by history was 3/100. The history of documented thromboembolism was zero.The incidence of post-operative clinical deep vein thrombophlebitis was zero. The incidence of postoperative thromboembolism was 3/100 (3.0%). None of these patients had a history of deep vein thrombophlebitis. The diagnosis of thromboembolism was confirmed by ventilation-perfusion scan. The mortality rate secondary to thromboembolism was 1/100 (1.0%).Obesity is not a risk factor in the occurrence of postoperative deep vein thrombophlebitis and thromboembolism. The various prophylactic medications and therapies for this group of patients may be an inappropriate risk, an undue cost and un-necessary discomfort.
Structure And Function Of The Human Platelet Von Willebrand Factor Receptor
Authors: Clemetson K J , Naim H Y , Lüscher E F 
Published: July 2018

The interactions between platelets and subendothelium involving von Willebrand factor play an important role in haemostasis and thrombosis. The identity of the von Willebrand factor receptor with human platelet membrane glycoprotein Ib has now been fairly conclusively established but the precise nature of the binding site and the changes induced by binding have yet to be demonstrated.Asialoglycoprotein Ib and asialoglycocalicin have been isolated from neuraminidase treated platelets by affinity-chromatography on peanut agglutinin and compared by tryptic peptide mapping. The results clearly show that glycocalicin is closely related to the α-chain of glycoprotein Ib and is probably a proteolytic fragment of it. Unreduced and reduced glycocalicin showed minor differences in their tryptic peptide maps indicating that glycocalicin and by extension the α-chain of glycoprotein Ib probably contain at least one intramolecular disulphide bond.Treatment of platelets with reducing agents such as dithiothreitol results in loss of response to bovine von Willebrand factor. Similar treatment of surface-labelled platelets did not release any glycoprotein subunits into the supernatant, implying that disulphide bridge-linked subunits are tightly associated with the membrane or with other subunits. Hydrophobic chromatography of reduced, purified glycoprotein Ib indicates that both α and β subunits are hydrophobic and thus probably integral membrane glycoproteins. Intact disulphide bridges seem to be a prerequisite for von Willebrand factor receptor activity.