bluuebunny/crossref_metadata_2025 huggingface dataset:
Adenosine Nucleotides and Serotonin Stimulate von Wille-brand Factor Release from Cultured Human Endothelial Cells
Authors: Palmer D S , Aye M T , Ganz P R , Halpenny M , Hashemi S
Published: July 2018

Endothelial cells (ECs) synthesize and release von Willebrand factor (vWf) either constitutively or from Weibel-Palade bodies by a regulated pathway. Although stimulated release of vWf from ECs occurs following exposure to thrombin, histamine, interleukin, tissue necrosis factor and fibrin in vitro, these agents are unlikely to be present in physiologically relevant concentrations during the initial stages of primary hemostasis. Alternatively, agents known to be released from the dense granules of activated platelets at the sites of vascular injury may provide the initial physiological stimuli for vWf release from ECs in vivo. We have examined the effects of the platelet secretagogues ADP, AMP, ATP and serotonin on the release of vWf from ECs and demonstrated enhanced release in all cases. The extent and time at which optimum vWf release was observed depended on the agonist and its concentration. At 3 nM, optimum release occurred after 4 hours with ADP (330 %/ml) or 1 h with AMP (153%/ml) or ATP (450%/ml). At 30 nM, optimum release was seen after 1 hour with ADP (315 %/ml) or AMP (595%/ml) and after 15 min with ATP (938%/ml). With serotonin, optimal release was seen by 30 min at 0.3 μM (1034%/ml) and after 1 h at 1 pM (745%/ml) although the response after 15 min was nearly equivalent (667%/ml). The doses giving 50% of maximal response (ED50) after 1 h were 6.5 nM (ADP), 15.2 nM (AMP) and 2.4 nM (ATP) and 20 nM for ATP or 75 nM for serotonin after 15 or 30 min respectively. ADP also enhanced PGI2 release from ECs in a dose- and time-dependent manner. These observations support a mechanism whereby activated platelets, which interact with and bind to ECs or subendothelium and release adenine nucleotides or serotonin from platelet dense granules, could stimulate the release of vWf from adjacent ECs thereby enhancing EC-platelet interactions and facilitating primary hemostasis.
Construction and Characterization of Thrombin-resistant Variants of Recombinant Human Protein S
Authors: Chang Glenn T G , Aaldering Leonie , Hackeng Tilman M , Reitsma Pieter H , Bertina Rogier M , Bouma Bonno N
Published: July 2018

Protein S is a vitamin K-dependent plasma protein that functions as a cofactor of activated protein C (APC) in the inactivation of coagulation factors Va and Villa.

Protein S, migrates as a doublet on reduced SDS polyacrylamide gel electrophoresis. This heterogeneity in molecular weight has been explained by limited proteolysis of protein S. Human protein S contains at Arg-49, Arg-60 and Arg-70 three potential cleavage sites. Whether cleavage occurs at all three sites is not known. To study the role of these arginine residues in human protein S, we have replaced them by leucine or isoleucine. All seven possible variants were constructed: three variants with single mutations (R49L, R60L, R70I), three variants with double mutations (R49L/R60L, R60L/R70I, R49L/R70I) and one variant with a triple mutation (R49L/R60L/R70I). On reduced SDS polyacrylamide gels the single and double variants migrate as a doublet just like the wild type protein S. The triple variant migrates as a single band at a molecular weight corresponding to the upper band of the doublet. The upper band of the single and double variants but not of the triple variant could be converted into the lower band by thrombin treatment.

All variants showed cofactor activity to APC in a clotting assay. After thrombin treatment, this cofactor activity was abolished for the single (R49L, R60L, R70I) and double variants (R49L/R60L, R60L/R70I, R49L/R70I), while the triple variant (R49L/R60L/R70I) tested at several concentrations, retained its cofactor activity completely, suggesting resistance to thrombin. This shows that thrombin can cleave at all three arginine sites and that cleavage at each of these sites results in the loss of APC cofactor activity. Finally, all variants bind to C4b-binding protein with an affinity similar as the wild type recombinant molecule.
α1-Antitrypsin Pittsburgh (Met358 → Arg) Inhibits the Contact Pathway of Intrinsic Coagulation and Alters the Release of Human Neutrophil Elastase during Simulated Extracorporeal Circulation
Authors: Wachtfogel Yanina T , Bischoff Rainer , Bauer Ross , Hack C Erik , Nuijens Jan H , Kucich Umberto , Niewiarowski Stefan , Edmunds L Henry , Colman Robert W
Published: July 2018

Cardiopulmonary bypass prolongs bleeding time, increases postoperative blood loss, and triggers activation of plasma proteolytic enzyme systems and blood cells referred to as the “whole body inflammatory response”. Contact of blood with synthetic surfaces leads to qualitative and quantitative alterations in platelets, neutrophils, contact and complement systems. Contact and complement pathway proteins both induce neutrophil activation, a j-antitrypsin Pittsburgh (Met358 → Arg), a mutant of α1-antitrypsin, is a potent inhibitor of plasma kalli-krein and thrombin. We investigated whether this recombinant mutant protein inhibited platelet activation, as well as contact and/or complement-induced neutrophil activation during simulated extracorporeal circulation.

Arg358 α1-antitrypsin did not prevent the 34% drop in platelet count at 5 min of recirculation, did not block the 50% decrease in ADP-induced platelet aggregation at 120 min of recirculation, nor inhibit the release of 6.06 α 1.07 µg/ml (3-thromboglobulin at 120 min of recirculation suggesting that the inhibitor had little effect on platelet activation. However, Arg358 α1 arantitrypsin totally blocked kallikrein-Cl-in-hibitor complex formation but not Cl-Cl-inhibitor complex formation. Most importantly, Arg358 α1-antitrypsin decreased the release of 1.11 α 0.16 µg/ml human neutrophil elastase by 43%. The attenuation of neutrophil activation in the absence of an effect on complement activation via the classical pathway, supports the concept that kallikrein is a major mediator of neutrophil degranulation during cardiopulmonary bypass.
Studies of the Mechanism for Enhanced Cell Surface Factor VIIa/Tissue Factor Activation of Factor X on Fibroblast Monolayers after Their Exposure to N-Ethylmaleimide
Authors: The Le Dzung , Rapaport Samuel I , Vijaya Mohan Rao L
Published: July 2018

Fibroblast monolayers constitutively expressing surface membrane tissue factor (TF) were treated with 0.1 mM N-ethylmaleimide (NEM) for 1 min to inhibit aminophospholipid translocase activity without inducing general cell damage. This resulted in increased anionic phospholipid in the outer leaflet of the cell surface membrane as measured by the binding of 125I-annexin V and by the ability of the monolayers to support the generation of prothrombinase. Specific binding of 125I-rVIIa to TF on NEM-treated monolayers was increased 3- to 4-fold over control monolayers after only brief exposure to 125I-rVIIa, but this difference progressively diminished with longer exposure times. A brief exposure of NEM-treated monolayers to rVIIa led to a maximum 3- to 4-fold enhancement of VIIa/TF catalytic activity towards factor X over control monolayers, but, in contrast to the binding studies, this 3- to 4-fold difference persisted despite increasing time of exposure to rVIIa. Adding prothrombin fragment 1 failed to diminish the enhanced VIIa/TF activation of factor X of NEM-treated monolayers. Moreover, adding annexin V, which was shown to abolish the ability of NEM to enhance factor X binding to the fibroblast monolayers, also failed to diminish the enhanced VIIa/TF activation of factor X. These data provide new evidence for a possible mechanism by which availability of anionic phospholipid in the outer layer of the cell membrane limits formation of functional VIIa/TF complexes on cell surfaces.
The 4G/5G Genetic Polymorphism in the Promoter of the Plasminogen Activator Inhibitor-1 (PAI-1) Gene Is Associated with Differences in Plasma PAI-1 Activity but not with Risk of Myocardial Infarction in the ECTIM Study
Authors: Ye S , Green F R , Scarabin P Y , Nicaud V , Bara L , Dawson S J , Humphries S E , Evans A , Luc G , Cambou J P , Arveiler D , Henney A M , Cambien F
Published: July 2018

We have investigated the interrelationships of plasma PAI-1 activity, the PAI-1 4G/5G polymorphism and risk of myocardial infarction (MI) in the ECTIM study, a case-control study of MI based in Belfast, Lille, Strasbourg and Toulouse. Mean PAI-1 levels in cases were similar across all centres but in controls, levels in the French centres were significantly higher. Only in Belfast were PAI-1 levels higher in cases (11.7AU/ml) than controls (10.5AU/ml). The PAI-1 4G allele frequency was similar in cases and controls (0.55 and 0.54). In all groups, 4G homozygotes had the highest mean plasma PAI-1 level (4G4G vs 5G5G; cases overall: 14.2 vs 12.1 AU/ml; controls overall: 15.0 vs 12.6AU/ml), with the heterozygotes generally intermediate. The data from Belfast are consistent with the literature implicating PAI-1 level as an MI risk factor. In ECTIM, the PAI-1 4G/5G polymorphism is not a genetic risk factor for MI but is associated with PAI-1 activity. Thus homozygosity for the 4G allele may predispose to elevated PAI-1 and impaired fibrinolysis, perhaps requiring interaction with other genetic or environmental factors to influence MI risk.
A Collaborative Study of Proposed European Pharmacopoeia Reference Preparations of Low Molecular Mass Heparin
Authors: Gray E , Heath A B , Mulloy B , Spiese J-M , Barrowcliffe T W
Published: July 2018

A European collaborative study, in which 16 laboratories participated, was carried out to assess the performance of the European Pharmacopoeia (EP) monograph methods for anticoagulant activities (anti-Xa and anti-IIa assays) of low molecular mass (EMM) heparin and to assess the suitability of six candidate materials as the EP working standard for LMM heparin. There was good interlaboratory agreement for both types of assays as indicated by most gcv’s being less than 10%, indicating acceptable performance of the EP assay methods. All the candidate preparations gave dose-response curves parallel to the 1st International Standard for Low Molecular Weight heparin and to each other. All preparations, possibly with the exception of E and F, gave similar performance as measured by interlaboratory agreement and would be suitable as working standards. Based on these data, preparations A, B, C and D have been established by the EP as official EP Biological Reference Preparations and they will be issued as successive batches.
Hemostasis Abnormalities in Patients with Vascular Dementia and Alzheimer’s Disease
Authors: Mari D , Parnetti L , Coppola R , Bottasso B , Reboldi G P , Senin U , Mannucci P M
Published: July 2018

Since it has not been established to what extent abnormalities of hemostasis contribute to the occurrence and development of dementia, selected measurements of coagulation and fibrinolysis were obtained in elderly patients with Alzheimer’s disease (n = 22) or vascular dementia (n = 29), compared with healthy individuals in the same age range (n = 61). Hemostasis abnormalities were more frequent and marked in vascular dementia, being expressed as significant increases of plasminogen activator inhibitor type 1, von Willebrand factor, D-dimer. and activated factor VII. However, some hemostasis measurements (von Willebrand factor, activated factor VII) were abnormally high also in the patients with Alzheimer’s disease, a condition in which vascular damage is not considered to play a major pathogenetic role. It could not be established in this study whether or not these hemostatic abnormalities play a causal role in the pathogenesis of dementia, or whether they are secondary to inflammation and chronic vascular disease. Nevertheless, their presence may contribute to aggravating vascular disease.
A Simplified Procedure for Thromboplastin Calibration -The Usefulness of Lyophilized Plasmas Assessed in a Collaborative Study
Authors: Tripodi A , Chantarangkul V , Manotti C , Poggi M , Braga M , Akkawat B , Bucciarelli P , Mannucci P M
Published: July 2018

The International Sensitivity Index (ISI) of thromboplastins is determined by calibration using fresh plasmas from 60 patients stabilized on oral anticoagulants and 20 healthy subjects. This procedure is demanding, particularly for those who have no easy access to patients. The alternative use of a smaller number of lyophilized plasmas has already been considered, but one important issue, the number of repeated measurements to be carried out, has never been addressed. Two commercial rabbit thromboplastins, A and B, were calibrated in 3 laboratories against CRM 149R. On each of 10 working days, prothrombin times were measured for a different set of 8 fresh plasmas and for the same set of 8 lyophilized plasmas. The ISI values for both thromboplastins were estimated by orthogonal regression on fresh and lyophilized plasmas. The between- and within-laboratory CV values of the estimated ISI were taken as measures of precision of the calibration. In addition, ISI and CV were calculated daily on cumulative results obtained with lyophilized plasmas from day 1 to day 10. The ISI values for both thromboplastins calculated with lyophilized plasmas were not significantly different from those with fresh plasmas (mean of 3 laboratories: 1.42 vs 1.48 for A and 1.22 vs 1.20 for B). The between-laboratory precision of the calibration with lyophilized plasmas was not considerably different from that with fresh plasmas (CV for 3 labs: 5.2% vs 6.8% for A and 0.9% vs 2.2% for B). The ISI estimated with lyophilized plasmas on results of day 1 were not different from those of days 2 through 10. Good within-laboratory precision of the calibration (CV around 2%) was already achieved on day 3. In conclusion, this study shows that lyophilized plasmas pooled from normals and patients on oral anticoagulants can be used as substitutes for individual fresh plasmas to simplify the existing procedure for thromboplastin calibration.
Characterization of Recombinant Human Coagulation Factor XFriuli
Authors: Kim D J , Girolami A , James H L
Published: July 2018

Naturally occurring plasma factor XFriuli (pFXFr) is marginally activated by both the extrinsic and intrinsic coagulation pathways and has impaired catalytic potential. These studies were initiated to obtain confirmation that this molecule is multi-functionally defective due to the substitution of Ser for Pro at position 343 in the catalytic domain. By the Nelson-Long site-directed mutagenesis procedure a construct of cDNA in pRc/CMV was derived for recombinant factor XFriuli (rFXFr) produced in human embryonic (293) kidney cells. The rFXFr was purified and shown to have a molecular size identical to that of normal plasma factor X (pFX) by gel electrophoretic, and amino-terminal sequencing revealed normal processing cleavages. Using recombinant normal plasma factor X (rFXN) as a reference, the post-translational y-carboxy-glutamic acid (Gla) and (β-hydroxy aspartic acid (β-OH-Asp) content of rFXFr was over 85% and close to 100%, respectively, of expected levels. The specific activities of rFXFr in activation and catalytic assays were the same as those of pFXFr. Molecular modeling suggested the involvement of a new H-bond between the side-chains of Ser-343 and Thr-318 as they occur in anti-parallel (3-pleated sheets near the substrate-binding pocket of pFXFr. These results support the conclusion that the observed mutation in pFXFr is responsible for its dysfunctional activation and catalytic potentials, and that it accounts for the moderate bleeding tendency in the homozygous individuals who possess this variant procoagulant.
Aggregated, Conformationally Changed Fibrinogen Exposes the Stimulating Sites for t-PA-Catalysed Plasminogen Activation
Authors: Haddeland Unni , Sletten Knut , Bennick Anne , Nieuwenhuizen Willem , Brosstad Frank
Published: July 2018

The present paper shows that conformationally changed fibrinogen can expose the sites Aα-(148-160) and γ-(312-324) involved in stimulation of the tissue-type plasminogen activator (t-PA)-catalysed plasminogen activation. The exposure of the stimulating sites was determined by ELISA using mABs directed to these sites, and was shown to coincide with stimulation of t-PA-catalysed plasminogen activation as assessed in an assay using a chromogenic substrate for plasmin. Gel permeation chromatography of fibrinogen conformationally changed by heat (46.5° C for 25 min) demonstrated the presence of both aggregated and monomeric fibrinogen. The aggregated fibrinogen, but not the monomeric fibrinogen, had exposed the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation. Fibrinogen subjected to heat in the presence of 3 mM of the tetrapeptide GPRP neither aggregates nor exposes the rate-enhancing sites. Thus, aggregation and exposure of t-PA-stimulating sites in fibrinogen seem to be related phenomena, and it is tempting to believe that the exposure of stimulating sites is a consequence of the conformational changes that occur during aggregation, or self-association. Fibrin monomers kept in a monomeric state by a final GPRP concentration of 3 mM do not expose the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation, whereas dilution of GPRP to a concentration that is no longer anti-polymerizing, results in exposure of these sites. Consequently, the exposure of t-PA-stimulating sites in fibrin as well is due to the conformational changes that occur during selfassociation.
Factor VII Gene Polymorphisms, Factor VII:C Levels and Features of Insulin Resistance in Non-Insulin-Dependent Diabetes mellitus
Authors: Heywood Daniella M , Mansfield Michael W , Grant Peter J
Published: July 2018

The macrovascular complications of non-insulin-dependent diabetes mellitus (NIDDM) are related to the features of insulin resistance (IR). High Factor VII :C (FVII:C) levels are associated with increased cardiovascular risk and relate to a base change in the FVII gene detected by Msp I endonuclease, and also to an insertion polymorphism in the promoter region. To examine the association between FVII:C levels, genotype and features of IR, 95 NIDDM patients were studied. Genotype was related to FVII:C levels (M1M1 137%, n = 75; M1M2 and M2M2 114%, n = 20, p <0.005; AA 136%, n = 71; Aa 119%, n = 21, p <0.05), which is consistent with previous studies in healthy populations. FVII: C correlated with cholesterol (r = 0.51, p <0.0005), insulin (r = 0.36, p = 0.002), triglycerides (r = 0.34, p = 0.001), age (r = 0.23, p <0.005) and body mass index (r = 0.23, p <0.05). When analysed by Msp I genotype, the stronger predictor of FVII: C levels, these correlations remained, with no difference in regression slopes. In a multiple regression model, genotype, cholesterol, insulin, and gender remained as independent predictors of FVII:C levels. In conclusion, FVII :C concentrations are elevated in NIDDM in relation to both FVII genotypes and features of IR.
Isolation and Characterization of Canine Factor IX
Authors: Sugahara Yuichi , Catalfamo James , Brooks Marjory , Hitomi Eri , Bajaj S Paul , Kurachi Kotoku
Published: July 2018

Canine plasma factor IX was purified to homogeneity by a combination of barium citrate precipitation and three-step column chromatographies of DEAE sepharose, heparin agarose and a monoclonal antifactor IX antibody-linked agarose. Canine factor IX has an apparent molecular size of 61 kDa, which is slightly smaller than that of human factor IX, as determined by denatured polyacrylamide gel electrophoresis. Its amino acid composition, amino-terminal and carboxyterminal amino acid sequences agreed well with those predicted from the reported cDNA. Unlike purified human factor IX, canine factor IX preparation often showed a discrete smaller molecular species (∼50 kDa) which was generated by a specific proteolytic cleavage between Arg310 and Val311. When purified canine factor IX was utilized as a standard for enzyme linked immunosorbent assay, the concentration of canine factor IX in the pooled normal dog plasma was determined to be 5.3 Μg/ml with 11.2% carbohydrate content (or 4.7 Μg/ml for its polypeptide chain moiety). Concentration of plasma factor IX antigen was measured in six severely affected, unrelated hemophilia B dogs. Four had factor IX antigen of less than 1% of the normal, and two had undetectable levels. The latter two had gross molecular abnormalities in their factor IX genes. Three obligate carrier females had variable but proportionately reduced factor IX antigen and factor IX coagulant activity levels. These results provide a quantitative method for measuring canine factor IX antigen which is a prerequisite for studying hemostasis and development of gene transfer approaches in the canine model of hemophilia B.
Technical and Biological Conditions Influencing the Functional APC Resitance Test
Authors: Freyburger G , Bilhou-Nabera C , Dief S , Javorschi S , Labrouche S , Lerebeller M J , Boisseau M R
Published: July 2018

Poor anticoagulant response to APC is conveniently screened by a commercially available functional test (Coatest® APC Resistance) allowing identification of APC-resistant patients. These patients may then be genotyped with respect to factor V, the Arg - > Gin mutation being the principle cause of APC resistance. However, determination of phenotype generally precedes that of genotype, and the need for an “abnormality threshold” prompted a study of inter-batch variations and the clinical conditions associated with an altered APC response. The response to APC was assessed twice in plasma from 111 patients using two of four successive kit batches. A modest but significant inter-batch variability was observed. At the same time, we also tested 130 patients with retinal venous occlusion (RVO), 28 patients with glaucoma and 24 normal volunteers. The APCaPTT/aPTT ratio was found to be lower in the presence of elevated thrombin-antithrombin complexes (r = 0.167, p <0.02) and low blood viscosity (at high shear rate: r = 0.305, p <0.0001) independently of any alteration in genotype.
Comparison between Recombinant and Rabbit Thromboplastin in the Management of Patients on Oral Anticoagulant Therapy
Authors: Barcellona D , Biondi G , Vannini M L , Marongiu F
Published: July 2018

The aim of this study was to compare recombinant thromboplastin (rTF, ISI = 0.82) with rabbit thromboplastin (RT, ISI = 1.46) in order to evaluate which performed better in our thrombosis centre. To this purpose we randomized 67 patients to be double-blind monitored in two groups for three months either with PT performed with RT or with PT performed with rTF. After this period each patient was shifted to the other group. We considered the following as end points of the study: percentages of PT results within the therapeutic range, number of visits and therapeutic dose adjustments per patient. The “last check in file” method was used to evaluate the laboratory quality of oral anticoagulation for both thromboplastins. The results show that there was no difference in the number of visits per patient between the two groups: 6.9 ± 1.7 in the rTF group versus 7.3 ± 1.9 in the RT group (p = 0.19). The variations of therapeutic dose per patient were not different in the two groups: the dose was changed once (range 0-8) in the rTF group and once (range 0-11) in the RT group (p = 0.15). The percentages of PT results within the therapeutic range were not different between the two groups. The “last check in file” method showed similar percentages in both groups: PT results in the therapeutic range were 67.2% in the RT group and 68.8% in the rTF group. We conclude that the two thromboplastins had a similar effect on the end points of the study in spite of the relatively high ISI of the RT.
Physico-Chemical Properties and the Structure of Dermatan Sulfate Fractions Purified from Plasma after Oral Administration in Healthy Human Volunteers
Authors: Volpi Nicola
Published: July 2018

Dermatan sulfate (DS) was administered by oral route in healthy human volunteers. The structure, physico-chemical properties and biological activity of DS purified from human plasma after oral administration were studied and compared with those of native DS.

DS extracted and purified from pig mucosa has a relative molecular mass (Mr) of about 23,100 and is composed of about 10% nonsulfated disaccharide, 80% monosulfated disaccharides and about 10% disulfat-ed disaccharides, with a sulfate to carboxyl ratio of 1.00 and a heparin cofactor II (HCII) activity of about 160 units/mg. This native polysaccharide is composed of about 94% iduronic acid.

One gram of native DS was orally administered to five healthy human volunteers, and 50 ml of blood were collected after 4 h. DS possibly present in plasma after oral administration was extracted and purified. About 130 ± 42 Μg of DS per 50 ml of blood were detected by agarose-gel electrophoresis and DMB assay. This DS shows a broad Mr range. After oral absorption, substantial amounts of species with a Mr of about 7,500 are detected in blood but chains with Mr ranging from 7,500 to 20,000 are also found. Moreover, some very low-Mr species are detected, with a prevalence of disaccharides. After oral absorption, DS is sulfated above all in position 4 of the N-acetyl-galactosamine (60%), with a sulfate to carboxyl ratio of about 0.64, demonstrating that DS is desulfated during or after oral absorption by about 30-40%. A small amount of disulfated disaccharide (in particular 2,4-disulfated, 1.4%) is preserved from catabolic processes, as DS extracted from human plasma is able to inhibit thrombin activity mediated by HCII (about 16 U/mg).
Effect of Lipoprotein(a) and LDL on Plasminogen Binding to Extracellular Matrix and on Matrix-dependent Plasminogen Activation by Tissue Plasminogen Activator
Authors: Pekelharing Hadewijch L M , Kleinveld Henne A , Duif Pieter F C.C.M , Bouma Bonno N , van Rijn Herman J M
Published: July 2018

Lp(a) is an LDL-like lipoprotein plus an additional apolipoprotein apo(a). Based on the structural homology of apo(a) with plasminogen, it is hypothesized that Lp(a) interferes with fibrinolysis. Extracellular matrix (ECM) produced by human umbilical vein endothelial cells was used to study the effect of Lp(a) and LDL on plasminogen binding and activation. Both lipoproteins were isolated from the same plasma in a single step. Plasminogen bound to ECM via its lysine binding sites. Lp(a) as well as LDL were capable of competing with plasminogen binding. The degree of inhibition was dependent on the lipoprotein donor as well as the ECM donor. When Lp(a) and LDL obtained from one donor were compared, Lp(a) was always a much more potent competitor. The effect of both lipoproteins on plasminogen binding was reflected in their effect on plasminogen activation. It is speculated that Lp(a) interacts with ECM via its LDL-like lipoprotein moiety as well as via its apo(a) moiety.
Pentamidine Is a Specific, Non-Peptide, GPIIb/llla Antagonist
Authors: Cox Dermot , Aoki Toshiaki , Seki Jiro , Motoyama Yukio , Yoshida Keizo
Published: July 2018

Pentamidine was previously shown to act on glycoprotein (GP) Ilb/IIIa (Cox et al., Thromb Haemost 1992; 68: 731). In this paper we study the effect of pentamidine on other RGD-dependent receptors. In a cell adhesion assay, pentamidine was 500 times more potent than RGDS at inhibiting platelet adhesion to fibrinogen. While RGDS inhibited platelet adhesion to fibronectin, endothelial cell adhesion to vitronectin or fibronectin, 293 cell adhesion to vitronectin, IMR 32 cell adhesion to fibronectin and C32 cell adhesion to vitronectin; pentamidine failed to inhibit these interactions at doses as high as 1 mM. Resting platelets fixed in the presence of 1 mM RGDS had increased binding of fibrinogen, i.e., RGDS activated GPIMIIa, while pentamidine at 100 ΜM had no effect. Similarly, RGDS induced the binding of an anti-LIBS monoclonal antibody, while pentamidine had no effect. Pentamidine partially, but significantly, inhibited lysosome and a-granule release induced by the thrombin agonist peptide, while RGDS had no effect. Neither pentamidine nor RGDS affected ADP-induced Ca2+ influx. Pentamidine had no effect on ADP-induced intracellular pH changes while RGDS prevented the pH from returning to normal. Thus, pentamidine is a non-peptide GPIIb/IIIa antagonist that is non-activating and is specific for GPIIb/IIIa.
A Prostacyclin-sparing Effect of Indobufen vs. Aspirin
Authors: Caterina R De , Giannessi D , Bernini W , Lazzerini G , Lavezzari M , Stragliotto E , Biagi G , Coccheri S
Published: July 2018

Indobufen ((±)-2-[p-(l-oxo-2-insoindolinyl)-phenyI]-butyric acid, indo) is a drug inhibiting platelet function by a reversible block of the arachidonic acid metabolism at the level of cyclooxygenase. Since tolerability profile of such drugs is mostly linked to extra-platelet cyclooxygenase inhibition, we prospectively evaluated the extent of platelet and extra-platelet cyclooxygenase inhibition by in vivo administration of indo in comparison with ASA. We assessed the effects of the two drugs on the ex vivo generation of TXB2 and 6-keto-PGFlΑ in whole blood, as indices of the production of TXA2 and PGI2 (prostacyclin), respectively, either after spontaneous clotting at 37° C for 1 h (Study 1) or after the addition of 2 Μg/ml collagen (Study 2). Generation of 6-keto-PGFlΑ in whole blood is a mixed index of platelet and extra-platelet cyclooxygenase activity, deriving from both platelet and white blood cell arachidonic acid metabolization. Fifteen patients with ischemic heart disease and baseline serum TXB2 levels > 300 ng/ml were allocated to receiving one single administration of either indobufen 200 mg (n = 6) or aspirin 500 mg (n = 9). Whole blood prostanoid generation was assessed at 0,1,2,4,6, 8,12 and 24 h after drug administration (Study 1). Ten healthy male volunteers were allocated to a double-blind, randomized crossover comparison of indo 200 mg b.i.d. vs. ASA 300 mg/d for 7 days (Study 2). Prostanoid generation and whole blood platelet aggregation were performed before and at the end of each study period (Day 0 and Day 7). At each time-point after single dose administration (Study 1), indobufen caused less % inhibition of whole blood 6-keto-PGFlΑ than of TXB2. At 2 h, TXB2 was reduced to a similar extent after ASA (98 ± 4%) and indo (97 ± 6%) (p = N.S.), while inhibition of 6-keto-PGFla was clearly different (> 98% after ASA, 81 ± 2.5% after indo, p < 0.01). After one week of ASA or indo (Study 2) the maximum extent of whole blood platelet aggregation was similarly inhibited (from 17.2 ± 1.4 ohms to 3.6 ± 1.3 ohms with ASA; from 18.3 ± 1.0 ohms to 1.6 ± 0.7 ohms with indo (p ASA vs. indo = N. S.). Despite equal inhibition of whole blood TX production after collagen (from 49.0 ± 4.3 ng/ml to 1.1 ± 0.6 ng/ml with ASA, from 49.8 ± 1.3 ng/ml to 1.4 ± 0.6 ng/ml with indo), again, however, 6-keto-PGFlΑ production was less affected by indo than by ASA (from 409 ± 30 pg/ml to 37 ± 13 pg/ml with ASA, inhibition = 91%; from 396 ± 35 to 318 ± 40 with indo, inhibition = 20%). These differential effects of indo and ASA might lead to a better platelet selectivity, tolerability and benefit/risk profile of indo vs. ASA, which are worthy of further assessment.
Comparative Effects of Staphylokinase and Alteplase in Rabbit Bleeding Time Models
Authors: Vanderschueren Steven , Collen Désiré
Published: July 2018

Background: The pathogenesis of bleeding associated with thrombolytic therapy remains largely unknown, although spontaneous bleeding appears to correlate with bleeding time prolongation. Here, the comparative effects on cuticle bleeding times (CBT) and ear puncture bleeding times (EBT) of recombinant staphylokinase (Sak) and alteplase (recombinant tissue-type plasminogen activator, rt-PA) at equivalent doses, alone and in combination with aspirin and heparin, were studied in rabbits.

Methods and Results: Groups of 4 to 9 rabbits were allocated to one of the 8 following intravenous infusions: saline; aspirin 15 mg/kg and heparin - 100 IU/kg bolus and 10 IU/kg infusion over one hour; 1.5 mg/kg rt-PA; 1.5 mg/kg rt-PA plus aspirin and heparin; 4.5 mg/kg rt-PA; 0.5 mg/kg Sak; 0.5 mg/kg Sak plus aspirin and heparin and 1.5 mg/kg Sak. Bleeding times were determined 30 and 15 min before and 5,15,30 and 60 min after the administration over one min of saline, rt-PA or Sak, by simultaneously severing a nail cuticle (CBT) and by puncturing the ear (EBT). Bleeding times were unaffected by saline and by both doses of Sak in monotherapy. Heparin-aspirin and low dose rt-PA significantly lengthened EBT but not CBT. Both CBT and EBT were significantly prolonged (to a mean of >4 times pretreatment at 5 min) after high-dose rt-PA and after the combined administration of heparin and aspirin with either Sak or rt-PA. rt-PA provoked significantly longer bleeding than Sak in the CBT (p = 0.001; mean estimated difference = 23 min), but not in the EBT. rt-PA but not Sak degraded plasma fibrinogen dose-dependently. CBT correlated inversely with fibrinogen (r = −0.66, p = 0.001) but EBT did not.

Conclusions: At equivalent doses Sak displays a significantly higher fibrin specificity and prolongs bleeding time less than rt-PA, particularly in the nail cuticle bleeding time model in which larger vessels are injured that require fibrinogen for hemostasis.
Antithrombin-mediated Inhibition of Factor Vlla-Tissue Factor Complex by the Synthetic Pentasaccharide Representing the Heparin Binding Site to Antithrombin
Authors: Claude Lormeau Jean , Pascal Herault Jean , Marc Herbert Jean
Published: July 2018

We examined the effect of the synthetic pentasaccharide representing the minimal binding site of heparin to antithrombin on the antithrombin-mediated inactivation of factor Vila bound to tissue factor. This effect was compared to the effect of unfractionated heparin. Using purified recombinant human coagulation factors and either a clotting or an amidolytic assay for the determination of the residual activity of factor Vila, we showed that the pentasaccharide was an efficient antithrombin-dependent inhibitor of the coagulant activity of tissue factor-factor Vila complex. In our experimental conditions, assuming a mean MW of 14,000 for heparin, the molar pseudo-first order rate constants for ATIII-mediated FVIIa inhibition by ATIII-binding heparin and by the synthetic pentasaccharide were found to be similar with respective values of 104,000 ± 10,500 min-1 and 112,000 ± 12,000 min-1 (mean ± s.e.m., n = 3)
T Lymphocyte Proliferative Responses Induced by Recombinant Factor VIII in Hemophilia A Patients with Inhibitors
Authors: Singer Sylvia T , Addiego Joseph E , Reason Donald C , Lucas Alexander H
Published: July 2018

In this study we sought to determine whether factor VUI-reactive T lymphocytes were present in hemophilia A patients with inhibitor antibodies. Peripheral blood mononuclear cells (MNC) were obtained from 12 severe hemophilia A patients having high titer inhibitors, 4 severe hemophilia A patients without inhibitors and 5 normal male subjects. B cell-depleted MNC were cultured in serum-free medium in the absence or presence of 2 µg of recombinant human factor VIII (rFVIII) per ml, and cellular proliferation was assessed after 5 days of culture by measuring 3H-thymidine incorporation. rFVIII induced marked cellular proliferation in cultures of 4 of 12 inhibitor-positive hemophilia patients: fold increase over background (stimulation index, SI) of 7.8 to 23.3. The remaining 8 inhibitor-positive patients, the 4 hemophilia patients without inhibitors and the 5 normal subjects, all had lower proliferative responses to rFVIII, SI range = 1.6 to 6.0. As a group, the inhibitor-positive subjects had significantly higher proliferative responses to rFVIII than did the inhibitor-negative and normal subjects (p < 0.05 by t-test). Cell fractionation experiments showed that T lymphocytes were the rFVIII-responsive cell type, and that monocytes were required for T cell proliferation. Thus, rFVIII-reactive T lymphocytes are present in the peripheral circulation of some inhibitor-positive hemophilia A patients. These T cells may recognize FVIII in an antigen-specific manner and play a central role in the regulation of inhibitor antibody production
Cysteinyl Leukotriene D4 Induced Vascular Smooth Muscle Cell Proliferation: A Possible Role in Myointimal Hyperplasia
Authors: Porreca Ettore , Di Febbo Concetta , Sciullo Anna Di , Angelucci Domenico , Nasuti Mimmo , Vitullo Paola , Reale Marcella , Conti Pio , Cuccurullo Franco , Poggi Andreina
Published: July 2018

Cysteinyl leukotrienes (i.e. LTC4, LTD4), produced by activated leukocytes or by transcellular metabolism may act at different levels on vascular smooth muscle cells (VSMC) during inflammatory processes or atherosclerosis. We studied the effect of LTC4, LTD4, and LTE4 on the in vitro proliferation of rat VSMC, measured by [3H]-thymidine incorporation and cell count. LTD4 had a stronger stimulatory effect on [3H]-thymidine incorporation than LTC4, whereas LTE4 was inactive. The effect of LTD4 on [3H]-thymidine incorporation was dose-dependent, with the maximal activity at 10−6 M. The stimulatory activity of LTD4 was inhibited in a dose-dependent manner by MK-571, a specific LTD4 receptor antagonist. In addition, MK-571 (1 mg/kg/day) given for at least 1 day after injury in a model of balloon catheter injury of rat carotid artery, provided effective inhibition of myointimal VSMC proliferation, with a 58% reduction of 5-bromo-2’-deoxyuridine (BrdU) uptake in the neointima and 69% reduction of neointimal thickening. Our data support the importance of inflammatory mechanisms in the pathogenesis of atherosclerosis and suggest a possible role for cysteinyl leukotrienes, specifically LTD4, in the control of VSMC proliferation.
Deep Venous Thrombosis and Lupus Anticoagulant
Authors: Simioni Paolo , Prandoni Paolo , Zanon Ezio , Saracino Maria A , Scudeller Alberta , Villalta Sabina , Scarano Luigi , Girolami Bruno , Benedetti Lino , Girolami Antonio
Published: July 2018

Background. A definite evidence in favour of an association of deep-vein thrombosis (DVT) with lupus anticoagulant (LA) in patients free from systemic lupus erythematosus is still lacking.

Methods. In a case-control study, LA was determined in 176 consecutive outpatients who underwent phlebography because of the first episode of clinically suspected DVT of lower limbs. The association between DVT and LA was described using odds ratios (OR).

Results. Contrast venography confirmed the clinical suspicion in 59 patients (33.5%). LA was detected in 5 of the 59 patients with DVT (8.5%), and in none of the 117 subjects with normal venogram (P = 0.007). The OR for having an acute DVT in patients with LA was 10.7 (95% CI: 1.2-94.2).

Conclusions. LA is significantly associated with DVT in symptomatic patients. Further studies are needed to establish the clinical implications of this association.
Surface Coverage of Vascular Grafts with Cultured Human Endothelial Cells from Subcutaneous Fat Tissue Obtained with a Biopsy Needle
Authors: Koyama Masayuki , Satoh Kei , Yoshida Hidemi , Suzuki Sohei , Koie Hisaaki , Takamatsu Shigeru
Published: July 2018

Surface coverage with autogeneous endothelial cells is effective in reducing thrombogenicity of an artificial vascular graft, but procedure for obtaining the cells is invasive for patients. The purpose of this study was to establish cultures of human endothelial cells separated from a small piece of subcutaneous fat tissue. A piece of tissue weighing about 10 mg was obtained from subcutaneous fat using a biopsy needle, and treated with collagenase and dispase. Microvascular endothelial cells were selected and other types of cells contaminating the cultures were eliminated by scraping with a needle under a microscope. The yield of the cells was 8362 ± 4264/10 mg of subcutaneous fat (n = 7). The cultures reached confluence in about 2 weeks. The cells were positive for von Willebrand factor, P-selectin, and uptake of acetylated low density lipoprotein. The cells produced 15.9 ± 3.3 ng/mg cell protein/h of 6-ketoprostaglandin F1α (n = 5) when stimulated with thrombin. Thrombin also stimulated the production of platelet-activating factor: 7653 ± 4297 dpm/106 cells (n = 5). Endothelin-1 accumulation in the medium of unstimulated endothelial cells was 0.54 ± 0.16 ng/mg cell protein/10 h (n = 8). As a preliminary experiment for graft seeding, the cells were also cultured on pieces of a gelatin-coated Dacron graft, and scanning electron microscopy revealed the surface coverage of the graft. We herein described about successful culture of human microvascular endothelial cells from subcutaneous fat tissue obtained using a biopsy needle. The cultured cells may be applicable to a seeded vascular graft.
A Monoclonal Antibody To VIII:C Produced By A Mouse Hybridoma
Authors: Muller H P , van Tilburg N H , Bertina R M , Derks J , Klein-Breteler E
Published: July 2018

Spleen cells of a Balb-c mouse immunized with VIII:C (isolated by affinity chromatography) were fused with mouse myeloma cells (MOPC-21 derivative). After the fusion 12/32 wells produced an inhibitor to VIII:C. After subclonation (3 x) a stable hybridoma line was obtained. The antibody in the supernatant was detected with a modified VIII: Cinhibitor technique. The supernatant of in vitro cell cultures of the hybridoma cells contained anti-VIII:C titers (Bethesda) of about 0.3-1.0 units/ml. Injection of the hybridoma cells in pristane pretreated Balb-c mice results in anti-VIII:C titers of 5,000-10,000 units/ml ascites.

Analysis of the produced immunoglobulin demonstrated the presence of one band after isoelectric focussing, which contained heavy chains both of IgG1 and IgG2B subclass. Because of the unusual kinetics of the monoclonal antibody with VIII:C extensive characterisation of the nature of its VIII: C neutralising properties was necessary.

The monoclonal antibody does not bind 125I-fibrinogen or isolated VIIIR:AG, it reacts with isolated VIII:C and can be used in a two-site immunoradiometric assay for VIIICAG. The epitope against which the antibody is directed is not present on ‘serum-VIIICAG’.
Abnormal Prothrombin Consumption (Pc) In Bernard Soulier-Syndrome (BSS)
Authors: Pizzuto J , Reyna M P , González-Angulo A , Morales M R , Dorantes S
Published: July 2018

The abnormal PC in BSS is a defect that has not been extensively studied to date. For this reason 4 patients with BSS who had normal platelet aggregation tests (except with bovine fibrinogen and with Ristocetin), but abnormal bleeding times and PC on different occasions, during which they showed variable thrombocytopenia, were studied. The PC was normal in only one case and in only one occasion, which was coincidental with a circulating platelet count that also approximated normal.

The abnormal PC in the 4 cases was corrected when platelet substitute, or washed platelets from normal subjects or from patients with BSS were added. These same platelets also corrected the abnormal PC in cases of ITP or aplastic anemia, and shortened the recalcification time of platelet-poor plasmas from normal subjects and patients with specific plasma deficiencies (Factors V, VIII and XI).

The above suggests that the abnormal PC in some cases of BSS may be due to the thrombocytopenia rather than to a defect in the procoagulant activity of the platelets in this syndrome.
A Functional Basis For The Platelet Storage Pool Deficiency In Chediak-Higashi Cattle
Authors: Meyers K M , Fukami M , Holmsen H
Published: July 2018

Platelets from cattle with the morphologic homolog of the Chediak-Higashi (CH) syndrome are essentially devoid of secretable nucleotides and serotonin. There are reduced but still substantial amounts of secretable calcium and magnesium. The storage pool deficiency may be, in part, due to a functional granule defect. Platelets from CH cattle take up serotonin and protect it from degradation for several hours. If these platelets are treated with thrombin, serotonin and bivalent cations are released by mechanisms similar to that of secretion, suggesting a granule location for the released serotonin and cations. This suggestion is verified by subcellular fractionation studies where platelets are first incubated with 14C-serotonin then lysed using a French press. Organelles were then separated on a sucrose gradient by centrifugation. Serotonin in normal bovine platelets is associated with the dense granule or pellet while in CH platelets serotonin is primarily found in a region of the sucrose density zone that in normal platelets contain alpha granules. These findings suggested that some granules in CH platelets are able to acquire the bivalent cation and amine but not the nucleotide component of the bivalent cation-nucleotide-amine storage complex that is thought to occur in normal dense granules.

Ultrastructural identification of the serotonin-containing CH granule is not known. There are 2 identifiable granule populations in CH platelets, alpha granules and fibrous matrix granules. Based on serial sectioning freeze fracture and morphometric studies, there are less than 4 of these granules/platelet. Mepacrine studies also demonstrate 2 granule populations. One population has an incidence of 2 per granule and characteristics of normal dense granules. Since the number of fibrous matrix granules and mepacrine granules is similar, a common basis for these granules which has at least some dense granule characteristics, i.e., mepacrine storage, is suggested.
Megakaryocyte Sizes
Authors: Levine R F
Published: July 2018

The size range of megakaryocytes (megas) is widely given as 30-100 μm; however, extensive direct data are lacking. Large numbers of guinea pig (gp) and human megas have been examined at 1000X by phase contrast microscopy with an eyepiece micrometer. In a suspension of gp bone marrow cells megas had an average diameter of 26.0±10.2 (SD) ym with a range of 10-51 (N=1037). Nonmegas had a mean diameter of 8.5±1.9 with a range of 3-17 μm (N=1120). A threshold value of 13 μm was found to separate these two populations with no more than 2% overlap. Electronic size analysis confirmed the above range and distribution of gp mega sizes and the existence of a threshold at 13 μm. To evaluate the sizes of human megas in three marrow aspirates megas were measured on clinical smears and in cell suspensions from the same specimens. The megas in suspension (N=247-289) were 24.0±8.9 μm (range 10-58) and the nonmegas were 9.3±2.0 μm. The smeared cells had two-dimensional diameters of 31.7 ± 10.1 (range 8-82) and 10.8±3.2, respectively. On the clinical smears the threashold shifted from 13.0 to 18.4 μm (approx, two neutrophil diameters) and separated 93% of the megas from 98% of the nonmegas. Relative DNA content was determined by microdensitometry on fuel gen-stained cells. Megas of different ploidy levels had different size distributions (32N>16N>8N>4N) but 4N megas had the same size range as 4N nonmegas. Within each ploidy class size was related to maturation stage, judged by nuclear configuration. The data indicated that maturation and ploidy state are not completely independent variables. In summary, mega sizes in suspension were mostly 10-50 μm for gp and human samples. On clinical smears some flattening had apparently occurred, but most megas were 10-65 μm. The smaller megas, often missed in past studies, were still larger than most of the nonmegas; the size differences between megas and the other cells are probably related to the higher ploidy levels of the megas. The size variation among the megas is related to both cell maturation and ploidy state.