bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Hemorheological and Biochemical Studies of a Bovine Fibrinogen
Authors: Copley A. L. , King R. G. , Blombäck B. 
Published: June 2019

Among numerous fibrinogen (Fg) preparations of different mammalian origins (human, bovine, sheep, rabbit, cat) in measurements of viscous resistance -VR- (torque values, τ, dyne, cm) of surface layers (SLs), we found as an exception a bovine Fg, FgSM (Schwarz-Mann, Orangeburg, N.Y. Lot # Y1013), which did not show measurable VR at shear rates (SRs) from 10-3 to 10-1 sec-1 without prior application of high shearing forces (hSF). This led to biochemical characterization, in which FgSM did not exhibit any significant difference in chain structure, as compared with highly purified Fg showing high τ, indicating that a dialysable component in the FgSM was responsible for the inhibition of VR. Our biochemical studies could not detect significant differences between the FgSM and Fg from other sources. A hSF at 1000 sec-1 for 3 min was then applied prior to the rheological tests at low SF from 10-3 to 10-1 sec-1. This procedure always resulted in significant increases in VR of SLs of all Fg preparations, including the FgSM. High shear, which exists at the vessel wall in vivo, is particularly high in the microcirculation and is also augmented in vortex and disturbed flow at sites of branchings, bends and bifurcations in the vascular system. The hSF may contribute to the initiation of thrombus formation due to the proposed progressive adsorption of Fg, layer upon layer, at these sites (Copley, Biorheol. 8, 79, 1971; Microvasc. Res. 8, 192, 1974). A further hypothesis is introduced in which the polymerization sites of the Fg molecule are unfolded by the hSF at the vessel wall, resulting in intravascular polymerization of Fg(Aided in part by Office of Naval Research Contract # N00014-75-C-0222 )
Kinetics of Platelet Adhesion to Artificial Surfaces in Vitro
Authors: Brash J. L. , Feuerstein I. A. 
Published: June 2019

Adhesion of platelets to glass, collagen-coated glass, albumin-coated glass, polystyrene, sulfonated polystyrene and a segmented polyurethane, has been studied in vitro. The apparatus is of the Couette flow type and allows close control of fluid shear and diffusional factors. Suspensions of washed pig platelets constitute the basic platelet medium. This can be modified by adding back red cells and specific plasma proteins in varying concentration and the platelet concentration can be varied without compromising viability. Adhesion is measured by radiolabelling methods.In the absence of red cells, low levels of adhesion were seen on all surfaces with saturation occurring at 4 to 6 platelets/1000 μ2 in 2 to 4 minutes. In the presence of red cells adhesion was much greater. Collagen was the most reactive surface and adhesion data was consistent with a platelet diffusivity 10 to 100 times that predicted by Brownian motion. The diffusivity was dependent on shear rate and hematocrit. All other surfaces showed a 2-fold increase in adhesion compared to the values without red cells. However adhesion was independent of hematocrit above 10% and reached a constant value of about 12 (less for albumin monolayer) in 2 to 10 minutes.
In Vitro Prothrombin Synthesis - The Vitamin K-Dependent Carboxylation of a Prothrombin Precursor
Authors: Suttie John W. , Esmon Charles T. , Grant Gregory A. , Sadowski James A. 
Published: June 2019

Prothrombin is synthesized from a liver microsomal precursor which has now been characterized. The precursor contains functionally active thrombin and can be degraded by thrombin, Xa, or snake venoms to yield products which appear to be identical to those obtained from prothrombin. The molecular weight and amino acid composition of the precursor are similar or identical to prothrombin, but it lacks the calcium-binding sites needed for (Ca++, phospholipid) accelerated activation. In the presence of added vitamin K, an in vitro microsomal preparation incorporates 14

into microsomalbound precursor. It has been demonstrated that this incorporation is at glutamic acid residues in the amino terminal portion of the protein to form γ-carboxygiutamic acid residues. Both 14HC03 incorporation and formation of prothrombin (2-stage activity) in this preparation are dependent on: the presence of precursor in the microsomal preparation; an energy source; O2;

NADH (NADPH); and vitamin K. Both systems are inhibited by chloro-K, but not significantly by coumarin anticoagulants. However, microsomal preparations obtained from warfarin-treated rats are not as responsive as those obtained from vitamin K-deficient rats. The same microsomal preparations that form prothrombin will also catalyze the conversion of phylloquinone to its 2,3 epoxide. It has been suggested by Willingham and Matschiner (Biochem. J. 140, 435) that this epoxidation is an obligatory process coupled with the action of vitamin K in the conversion of precursor to prothrombin. Requirements for the two systems appear to be very similar, and in vitro conditions which will result in prothrombin production, but not epoxidation, have not yet been demonstrated.(Supported by NIH Grant no. 14881.)
Platelet Membrane Alterations Following Collagen Stimulation
Authors: Webber A. J. , Bennett E. A. , Booth W. 
Published: June 2019

Thrombin stimulates the release from platelets of a lipoprotein membrane complex believed to be platelet factor 3 (Webber and Johnson, Am. J. Path., 60, 19, 1970) and microfilaments of dimensions consistent with thrombosthenin (Webber and Budtz-Olsen, Brit. J. Haemat., 26, 275, 1974).This paper describes an ultrastructural study of stimulation of the lipoprotein membrane complex by collagen. The complex was similar to that produced by thrombin and usually consisted of concentric layers 150-200 Å wide, separated by a similar distance. Cytochalasin B had no effect on the release of the membrane complex.Within 10 seconds of collagen addition to platelet rich plasma scanning electron microscopy showed the adherence of platelets to collagen fibres, pseudopod formation, and surface protrusions consistent with the release of the membrane complex. At 20 seconds, platelets appear fully aggregated with filaments present on the platelet surface.These observations are consistent with the view that, upon collagen stimulation, PF3 becomes available on the platelet surface, accelerates the production of thrombin and, in turn, thrombin acts on the platelet to stimulate the release of contractile microfilaments which contribute to platelet aggregation.
Formation and Destruction of Platelet Aggregates in Viscometric Flow
Authors: Rieger H. , Schmid-Schönbein H. 
Published: June 2019

Even after pseudopodia formation platelets - unlike all other known formed blood elements - remain dispersed in stasis and creeping flow and become aggregated only in the presence of a minimum amount of shearing. The “rheoaggregometer” (Rieger et al., Pflüger’s Archiv, 343, R 33, 1973) allows to measure the minimum shear rates necessary for platelet aggregation (PA), as well as the initial rate and the maximum extent of PA in citrated PRP.PA is quantified photometrically as a function of variable shear rates. The initial rate of PA steadily increases with increasing shear rates up to 460 sec-1. However, the maximal extent of PA (indicating the mechanical integrity of formed aggregates) saturates at about 35 sec-1 and then decreases because of a destruction of formed aggregates and of prevention of further PA. The aggregability of the platelets, as reflected by various degrees of shape changes, is enhanced by a drop of temperature and a rise in pH as well as by the so called aggregating agents (e.g. epinephrine 10-6 up to 10-9 M/l) : consecutively lower shear rates (lower effects of collision) are necessary to induce PA. In citrated PRP stable platelet aggregates are produced only within a defined range of shear rates. Platelet aggregability and aggregate stability are independent variables influenced by different experimental conditions.
Binding of Ca++ to Human Prothrombin
Authors: Benarous R. , Elion J. 
Published: June 2019

The Ca++ binding properties of human prothrombin were studied by equilibrium dialysis using 45 calcium chloride at +4° C with prothrombin concentration of about 1 mg/ml equilibrated in 0.025 M Tris HCl, 0.12 M NaCl buffer pH 7.4. Scatchard plots obtained were similar to those described by Steenflo (1973) for bovine prothrombin, suggesting a positive cooperativity in the binding of Ca++ with a maximum ratio of bound Ca++/free Ca++ of 3 moles of Ca++ bound per mole of protein.The total number of binding sites was found to be at about 7, less than 10 to 12 found for bovine prothrombin. Ca++ binding was dependent on pH variation of the buffer with a maximum value for pH 8.5. Chemical modifications of carboxyl groups of prothrombin according to Hoare and Koshland (1967) abolished the Ca++ binding ability of the molecule confirming the essential role of these residues in this specific property of prothrombin.
Isolation and Properties of the Abnormal Factor X Induced by Vitamin K Antagonist (PIVKA-X)
Authors: Lindhout M. J. , Kop-Klaassen B.H.M. 
Published: June 2019

The abnormal factor X induced by vitamin K antagonist could be isolated from the plasma obtained from a cow under short term treatment with Marcoumar®. A 3,500 fold purification was achieved at a 10% yield. A single band was seen on polyacrylamide gel electrophoresis. The protein was immunologically identical to normal factor X.After incubation with an activator of factor X from Russell’s Viper Venom (RVV), PIVKA-X shows esterase and proteolytic activity. Although PIVKA-XRVv has no activity in a one-stage factor Xa assay, it seems that the active site is intact, as it could be titrated with p-nitrophenyl-p-guanidinobenzoate (p-NPGB).In the absence of phospholipids and Ca++-ions both factor Xa and PIVKA-XRVv activate prothrombin at the same low rate. Identical prothrombin subunits are obtained in both cases.
Subunit Structure of Human Factor VIII
Authors: Mourik J. A. van , LaBruyère W. T. , Mochtar I. A. 
Published: June 2019

Several investigations have shown that factor VIII is a high molecular weight aggregate and that both non-covalent and disulphide bonds contribute to the stabilization of the macromolecular factor VIII aggregate. As shown previously (1) disruption of non-covalent bonds can be accomplished at relatively low ionic strength and neutral pH and results via a series of homologous oligomers (having constant charge/mass ratios) in 2 immunologically non-related subunits. Thus, the generally accepted concept that factor VIII is constructed of identical subunits seems incorrect. For several reasons we assume that the observed fragmentation at low ionic strength is not due to proteolytic breakdown. However, this view is not favoured by the observation that tryptic and plasmic digestion of factor VIII (in aggregated form) results in gel electrophoresis patterns comparable with those obtained of factor VIII after low ionic strength dissociation. Further, evidence will be presented that the assumption that reduction of factor VIII under denaturating conditions results in a single polypeptide chain is also no longer tenable. As far as the reduction of aggregated factor VIII is concerned our observations agree with data from the literature, that is, reduction of factor VIII results in 1 major subunit with an apparent molecular weight of approximately 270.000. However, when factor VIII is first dissociated at low ionic strength followed by reduction, smaller fragments appear in the electrophoresis pattern. Thus, it seems most likely that the apparent single chain subunit is in fact, constructed of smaller non-covalently linked fragments.(1) J. A. van Mourik et al. Thrombosis Research, 4, 155, 1974.
Relationship between Factor VIII and von Willebrand’s Factor in Plasma and Serum
Authors: Koutts J. , Gude N. , Firkin B. 
Published: June 2019

A monospecific precipitating antibody with no factor VIII procoagulant neutralisation activity, but which inhibited normal ristocetin induced platelet aggregation was produced. The antibody was insolubilised on Sepharose beads. On mixing with normal plasma, factor VIII procoagulant activity (VIII C), von Willebrand factor (vWf) and factor VIII antigen (VIII Ag) were removed in equal proportions. The VIII C lost from plasma was detectable on the Sepharose beads. This activity was removed after treatment of these beads with high molarity solution. Subsequent addition of plasma resulted in a high transfer of VIII C from the plasma to the Sepharose beads without accompanying vWf and VIII Ag. Similar experiments, initially mixing with normal serum showed equivalent binding of vWf and VIII Ag. No independent attachment of VIII C to these beads was demonstrated when they were treated with high molarity solutions and normal plasma then added.It is suggested that VIII C and vWf exist in plasma as separate but attached molecules in a dynamic equilibrium. In serum, vWf has lost its ability to attach VIII C.
The Plasminogen Activator Content of the Arterial Wall in Different Arteries
Authors: Donner L. , Šafránková D. 
Published: June 2019

Six hundred and sixty specimens of thoracic, abdominal aortas, cerebral, carotid, vertebral, pulmonary, coronary, kidney and mesenteric arteries from 110 fresh cadavers were examined for their plasminogen activator content by means of the histochemical method of Todd. The plasminogen activator in pulmonary arteries, kidney and splenic arteries obtained during surgery was estimated. Differences between the fibrinolytic activities, generally found in the adventitia, are given.Intact arterial endothelium, in contrast to the venous endothelium, is only slightly or not at all active. Endothelium of thoracic aortas detached by scraping and repeatedly washed was tested on fibrin plates with streptokinase. Under these conditions arterial endothelium showed fibrinolytic activity suggesting that endothelium contains proactivator. The fibrinolytic activity of arteries adventitia with atheromatous plaques examined by the histochemical method was higher than in normal arteries.
Evaluation of Five Methods for the Determination of Heparin
Authors: Teien A. , Lie M. 
Published: June 2019

Heparin was added in vitro to plasma and the heparin content assayed by five clotting methods. The accuracy was lower in pathological than in normal plasma. At a heparin concentration of 0.5 U/ml plasma the coefficient of variation in eleven pathological plasmas was: Polybrene titration 3 per cent, method of Denson and Bonnar 15 per cent, method of Yin et al. 20 per cent, calcium thrombin time 40 per cent. With the APTT method the results ranged from 0.05 U/ml to above 0.6 U/ml (no clotting in five pathological plasmas).At a heparin concentration of 0.05 U/ml plasma, only the calcium thrombin time and the factor Xa methods were sensitive, but the coefficient of variation ranged from 61 to 78 per cent. The influence of the concentration of fibrinogen, antithrombin III and α1-acid glucoprotein was studied. It is concluded that of the methods tested, only polybrene titration gives accurate results in pathological plasmas. This method is, however, laborious and insensitive to heparin concentrations below 0.1 U/ml.
Experimental Arterial Thrombosis
Authors: Bourgain R. H. 
Published: June 2019

A method for inducing white platelet thrombi in a mesenteric artery of the rat has been standardized. After application of a platinum electrode to the vessel wall a DC current of 200 μA is passed for 60 seconds while the polarity is inversed every five seconds.After passage of the current topical application of ADP or ATP for three minutes results in the formation of white platelet thrombi.Mieroprojection of the arterial segment performed on a series of LDR’s (Light Depending Resistances) allows registration of potential variations due to white thrombus formation.The magnitude of these potentials is linearly related to the thrombus mass.Computerization of these data is possible after A-D conversion of the signals and appropriate programmation.
Subfractions of Fibrinogen Isolated from Human Plasma by Affinity Chromatography
Authors: Hörmann H. , Stemberger A. , Jilg W. 
Published: June 2019

Fibrinogen was isolated from human plasma by affinity chromatography using thrombin activated immobilized fibrinogen. Elution with 1.0 M KBr yielded a preparation of 90–95% clottability. It contained, in addition to fibrinogen, polymers and proteins of lower molecular weight. Most of the associated proteins were removed by adsorption of fibrinogen on DEAE-Cellulose followed by stepwise elution. Under these conditions fibrinogen was also separated into several fractions including high solubility fibrinogen, high molecular weight derivatives and a fibrinogen fraction which was associated with another protein. High solubility fibrinogen was investigated in more detail. Its plasmic digestion showed a lag phase which was not recognized, if normal fibrinogen was degraded. This indicates a relatively stable conformation of high solubility fibrinogen.(Supported by Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 51.)
Prophylaxis of Thromboembolism by Depotheparin in Orthopedic Patients
Authors: Hey D. , Schöndorj T. H. 
Published: June 2019

198 patients (mean 59 yrs.) with major hip joint operations were randomized in two groups. Two schedules of depotheparin were administered for thromboembolic prophylaxis: a low dose of heparin (LDH) 3 × 500 LE/10 kg. b.w. started the preoperative day, and a high dose of heparin (HHD) 3 × 1 250 IE/10 kg b.w. beginning the evening of the first postoperative day. 27 control patients received no anticoagulants unless thrombosis occured.Undue wound bleeding was observed in 10% in all three groups. The mean values of blood (ml) from the drains as well as the postoperative hemoglobin decrease did not show significant differences between the three groups. Wound healing was not retarded in any of the heparin groups, all patients had in the mean the same duration of hospitalization. Significant alterations of clotting factor XIII were not found.The lowest incident of pulmonary embolism and of phlebothrombosis diagnosed by the Doppler ultrasound technic was in the HDH-group. Similar results reflected the 125-lod-Fibrinogen test which was conducted additionally in 40 patients; deep vein thrombosis of the lower limbs was also significantly reduced in the HDH-group. The prophylaxis by LDH proved to be better than in the untreated controls but was not as effective as the HDH.The immunological determinations of antithrombin III were of no diagnostic value.
Activation and Consumption of Factor VII as Reflected by Thrombotest During Fibrinolytic Therapy with Streptokinase
Authors: Arnesen H. , Venneröd A. M. , Laake K. , Godal H. C. 
Published: June 2019

Thrombotest is sensitive to the procoagulant effect of plasmin in vitro (Godal & Theodor 1965), and an initial transient increase in Thrombotest values has been observed in patients on treatment with streptokinase (Blix & Arnesen 1969) and urokinase (Godal & Arnesen 1971). Recently, plasmin has been shown to activate and later destroy factor VII in a purified system (Laake & Österud 1974).In the present study, Thrombotest and coagulation factor analyses were performed during the initial phase of therapy with streptokinase. A marked initial increase in Thrombotest values was found. Simultaneously, a corresponding activation of factor VII was obtained, whereas the factors II, IX and X remained unchanged. Subsequently, a fall in the factor VII activity and a corresponding fall in Thrombotest values were observed.It is concluded that activation and consumption of factor VII are responsible for the changes in Thrombotest values observed during fibrinolytic therapy.
Epidemiology of Thrombosis in Nigerians. Study of Platelet and Fibrinolytic Parameters
Authors: Dupuy E. , Flemming A.F. , Caen J. P. 
Published: June 2019

The infrequency of atherosclerosis and arterial disease and the relative thrombocytopenia reported in Nigerians led us to investigate platelet number and function and fibrinolytic activity in Nigerian non-elite (blood donors) Nigerian elite (hospital senior staff) and Europeans living in Zaria.The relative thrombocytopenia in Nigerians was confirmed, and counts were between 100–180 × 109/1 in 26 out of 35 subjects. Platelet aggregation using adrenaline and collagen were in the same range in all groups. An early disaggregation with ADP was found in one third of all Nigerians. Platelet aggregation with ristocetin in the Nigerian elite was less than 50 per cent of European values in 10/16 subjects; platelets of 12/17 non-elite subjects did not aggregate at all.The bleeding time (Ivy) and factor VIII coagulant activity did not differ in the three groups. Fibrinolytic activity was higher in Nigerians than Europeans.Many factors could be involved in these differences, including splenomegaly, parasitic infections, increases in immunoglobulins, greater physical activity and the healthier endothelium in Nigerians.
A Rare Case of Bilateral Vertebral Artery Dissection Associated with Essential Thrombocythemia
Authors: Raza Hafiz Khuram , Jing Jia , Chen Hao , Zhu Jienan , Zhang Zuohui , Chansysouphanthong Thitsavanh , Cui Guiyun , Hua Fang , Ye Xinchun , Shi Hongjuan , Jiang Haiyang 
Published: June 2019

AbstractA young patient presented to our hospital with ischemic stroke. She underwent a routine blood test, head computed tomography (CT), brain magnetic resonance imaging, a bone marrow biopsy, and CT angiography. Her diagnosis was a bilateral vertebral artery dissection associated with essential thrombocythemia (ET). She was treated with antiplatelet therapy and a stent implantation. The association of bilateral vertebral artery dissection with ET is rare. An early diagnosis and timely management is key to the best outcome.
Photoelastic Analysis of Two Different Cementless Femoral Stems for Total Hip Arthroplasty in a Canine Model
Authors: Kawamoto Fernando Y. K. , Minto Bruno W. , Diogo Lucia M. I. , de Faria Luis G. , Shimano Antonio C. , Macedo Ana P. , Camassa José A. A. , Dias Luis G. G. G. 
Published: June 2019

Objectives The aim of this article was to analyse and compare internal stress generated at different points of a femoral photoelastic model after insertion and axial load application using two different cementless femoral stems for total hip arthroplasty in dogs: a collared stem combined with limited textured surface and absence of grooves and a collarless stem with fully textured surface and grooves.
Methods Ten femoral photoelastic models, divided into two groups, were created using two different designs of cementless femoral stems. The models were submitted to axial loading on the femoral head in a universal test machine. The internal stress (kPa) around the femoral stems was evaluated at seven predetermined points using a transmission polariscope.
Results The internal stress at the femoral calcar was larger in the models with collared stem combined with limited textured surface and absence of grooves (p < 0.05). No differences were identified between the groups in the other points (p > 0.05), corresponding to the tip of the stems and proximal lateral region of the femur.
Conclusions The collar of femoral stem combined with the absence of grooves and more limited textured surface increase the axial load transmission to the femoral calcar, and in vivo, it may act to reduce complications, such as subsidence and stress shielding. However, other biomechanical tests and clinical evaluations must be performed to determine other important aspects for the implantation of these prostheses.