bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Red Blood Cells on the ADP-induced Aggregation of Human Platelets in Flow Through Tubes
Authors: Bell David N , Spain Samira , Goldsmith Harry L 
Published: July 2018

SummaryThe effect of red blood cells, rbc, and shear rate on the ADPinduced aggregation of platelets in whole blood, WB, flowing through polyethylene tubing was studied using a previously described technique (1). Effluent WB was collected into 0.5% glutaraldehyde and the red blood cells removed by centrifugation through Percoll. At 23°C the rate of single platelet aggregtion was upt to 9× greater in WB than previously found in platelet-rich plasma (2) at mean tube shear rates Ḡ = 41.9,335, and 1,920 s−1, and at both 0.2 and 1.0 µM ADP. At 0.2 pM ADP, the rate of aggregation was greatest at Ḡ = 41.9 s−1 over the first 1.7 s mean transit time through the flow tube, t, but decreased steadily with time. At Ḡ ≥335 s−1 the rate of aggregation increased between t = 1.7 and 8.6 s; however, aggregate size decreased with increasing shear rate. At 1.0 µM ADP, the initial rate of single platelet aggregation was still highest at Ḡ = 41.9 s1 where large aggregates up to several millimeters in diameter containing rbc formed by t = 43 s. At this ADP concentration, aggregate size was still limited at Ḡ ≥335 s−1 but the rate of single platelet aggregation was markedly greater than at 0.2 pM ADP. By t = 43 s, no single platelets remained and rbc were not incorporated into aggregates. Although aggregate size increased slowly, large aggregates eventually formed. White blood cells were not significantly incorporated into aggregates at any shear rate or ADP concentration. Since the present technique did not induce platelet thromboxane A2 formation or cause cell lysis, these experiments provide evidence for a purely mechanical effect of rbc in augmenting platelet aggregation in WB.
Demonstration of Secondary Lysosomes in Bovine Megakaryocytes and Platelets Using Acid Phosphatase Cytochemistry with Cerium as a Trapping Agent
Authors: Ménard Michèle , Meyers Kenneth M , Prieur David J 
Published: July 2018

SummaryThe ultrastructure of lysosomes from bovine megakaryocytes (MK) and platelets was characterized using acid phosphatase cytochemistry with beta-glycerophosphate as substrate and cerium as a trapping agent. The technique was easily reproducible; cerium-phosphate precipitates were uniform, readily visualized, and there was a virtual absence of nonspecific reaction product. Acid phosphatase was localized in the trans aspect of the Golgi complex and/or granules of less than 50 nm to 650 nm diameters in MK at all stages of maturation. Forty percent of the MK lysosomes contained inclusions of variable shapes, sizes and electron-density and were classified as secondary lysosomes. Twenty-four percent of the platelet sections contained acid phosphatase-positive granules. Fifty-four percent of these were secondary lysosomes. This is the initial report demonstrating
secondary lysosomes in either resting MK or platelets using acid phosphatase cytochemistry. These findings suggest that MK and platelet lysosomes have an intracellular function in resting MK and platelets.
The Decreased Circulating Platelet Mass and Its Relation to Bleeding Time in Chronic Renal Failure
Authors: Michalak E , Walkowiak B , Paradowski M , Cierniewski C S 
Published: July 2018

SummaryThe mean platelet volume, measured optically and by the electrical impedance method, was analysed in the patients with chronic renal failure. All parameters describing the circulating platelet biomass except the platelet volume heterogeneity were decreased in these patients. There is a strong inverse relation between the Ivy bleeding time and the platelet mass in the patient group.Our results indicate that the smaller platelets circulating in the patients with chronic renal failure may contribute to the uremic bleeding diathesis, and disturbed thrombocytopoiesis occurs in chronic renal failure.
Factor VII Hyperactivity in the Elderly
Authors: Kario Kazuomi , Matsuo Takefumi , Nakao Kazukiyo 
Published: July 2018

SummaryTo investigate the age-related increase in coagulation factor VII (FVII) and its significance in the elderly, we measured FVII coagulation activity (FVIIc), FVII antigen (FVIIag), and D-dimer levels in 150 normal subjects ranging in age from 60 to 98 years. We also measured blood lipid fractions and serum cholinesterase activity (ChE), os an indicator of hepatic protein synthesis. FVIIc (141 ± 36%), FVIIag(136 ± 28%), and D-dimer (0.150 ± 0.372 αd/ml) levels were significantly higher in the elderly than in younger controls (p <0.01). Both FVIIc and FVIIag levels were significantly higher in elderly women than in elderly men (p <0.01). FVIIc levels significantly correlated with FVIIag levels, but not with D-dimer levels. FVIIag was more closely correlated with ChE levels in both sexes (men: r = 0.425, womenr r = 0.365, p <0.001) than with the lipid fractions. When the elderly subjects were divided into atherosclerotic and nonatherosclerotic groups, both FVIIc (p <0.01) and FVIIag (p <0.05) levels were higher in the former group. Moreover, the FVIIc/FVIIag ratio and ChE levels were higher in both the elderly men and women with atherosclerosis. These results suggest that in elderly subjects, especially with atherosclerosis, hepatic FVII synthesis and the activation of FVII zymogen are both accelerated.
Subtle Differences in Active Site Structure between Bovine and Human Thrombins: ESR and Fluorescence Studies
Authors: Nienaber Vicki L , Berliner Lawrence J 
Published: July 2018

SummaryThe primary structures of bovine and human a-thrombins are highly homologous yet their x-ray structures are not yet complete enough to distinguish differences. In order to probe and compare their dynamic conformations in solution, we examined bovine and human α-thombins with a series of active site directed fluorosul-fonylphenyl spin labeled inhibitors and fluorophores which probe a region within 10-15 Å of the catalytic serine residue. Overall, the nitroxide moieties were more immobilized in the bovine vs human derivatives reflecting either more apolar binding regions or steric obstructions to the motion of the nitroxide in bovine thrombin. Most of the labels which distinguish indole (apolar ligand) binding in human thrombin were found to display similar interactions in bovine thrombin, although slight differences in the general topography of this region were suggested. The two active site directed fluorophores, dansyl fluoride and p-nitrophenyl anthranilate showed differences in both λem
max and λex
max of the complexes with bovine and human-a-thrombin, respectively. Several of the effects observed i.e., ligand binding (indole or benzamidine) and the subtle hydrophobic interactions between the nitroxide moiety and the protein active site would be difficult to assess from an x-ray structure determination alone.
Interaction of Plasma Kallikrein with Protein C Inhibitor in Purified Mixtures and in Plasma
Authors: España Francisco , Estelles Amparo , Griffin John H , Aznar Justo 
Published: July 2018

SummaryThe interaction between plasma kallikrein (KK) and protein C inhibitor (PCI) and the influence of KK on the complex formation between activated protein C (APC) and PCI was studied in purified systems as well as in plasma in order to assess the significance of these reactions in the plasma milieu. PCI complexed to KK (KK: PCI) or to APC (APC: PCI) was measured by sandwich ELISA’s using antibodies directed against each protein in the complexes. The formation of KK: PCI complexes assayed by this method paralleled the inhibition of KK amidolytic activity by PCI in purified system. Incubation of normal plasma (NHP) at 4 °C, which can induce prekallikrein activation due to cold activation, resulted in PCI inactivation and appearance of KK: PCI complexes. PCI activity fell to 35% of the NHp and 1.2 μ/ml of KK: PCI complex was formed. However, incubation of NHP at room temperature or of prekallikrein deficient plasma at 4 °C did not result in significant decrease of PCI activity. Thus the PCI inactivation was associated with prekallikrein activation and complexation to PCI following cold activation. Incubation of exogenous purified KK with NHP resulted in PCI inactivation and complexation with KK in a temperaturedependent manner. Addition of 2.8 μ/ml KK to plasma at 4 °C resulted in the inactivation of 55% of plasma PCI and the formation of 0.9 μ/ml KK: PCI which represents 21% of the KK added, whereas at 37 °C PCI was inactivated to 30% and only 0.30 μg/ml KK: PCI complexes were measured. These results indicate that PCI is a major KK inhibitor at 4 °C. At 37 °C, PCI accounted for aborfi 7% of the inhibition of the KK added. In separate experiments, following addition of 2.5 μg/ml APC to NHR more than 1 μg/ml of APC: PCI complex was formed in 3 h. When NHP was prior incubated with KK, PCI activity decreased to 10% of that of the normal plasma. Subsequent addition of APC to the plasma treated with KK resulted in formation of only 35 μg/ml of APC: PCI complex compared to 1,350 μg/ml when plasma was not previously incubated with KK. These results indicate that PCI could play a physiological role in the inhibition of plasma KK, and that, in turn, plasma KK can either complex to or inactivate plasma PCI. Thus, KK could modulate the PCI inhibition of APC in plasma.
Characterization of a Mouse Factor IX cDNA and Developmental Regulation of the Factor IX Gene Expression in Liver
Authors: Yao Shou-Nan , DeSilva Audrey H , Kurachi Sumiko , Samuelson Linda C , Kurachi Kotoku 
Published: July 2018

SummaryA mouse factor IX cDNA was isolated and characterrzed. The cDNA was 1,837 bp in length and contained the coding region as well as short 5’ and 3’ untranslated sequences. Northern blot analysis of liver RNA showed two mRNA species of 3.2 kb (major) and 2.2 kb (minor) for the mouse factor IX. An antisgnse RNA probe prepared from the mouse cDNA was employed to determine the steady state level of factor IX mRNA in mouse liver at various developmental stages. The factor IX mRNA level was very low (2–5% of the adult level) during the gestational period until day –3 (gestational day 17) followed by a rapid increase at day –2 through birth. This phase of rapid increase was followed by a gradual increase before it reached the adult level at around 20 to 24 days. At birth, the factor IX mRNA level was found to be at about 43% of that of the adult. The rnRNA levels in mouse liver agreed well with the plasma factor IX activity levels. These results indicate that reduced factor IX activity in newborns is due to the low levels of factor IX mRNA available for translation.
The Influence of Infusions of 1-Desamino-8-D-Arginine vasopressin (DDAVP) In Vivo on the Anticoaguhht Effect of Recombinant Hirudin (CGP39393) In Vitro
Authors: Ibbotson S H , Grant P J , Kerry R , Findlay V S , Prentice C R M 
Published: July 2018

SummaryHirudin is a specific, potent inhibitor of thrombin that may be a valuable antithrombotic agent. The aim of this study was to investigate the hypothesis that the haemostatic effects of DDAVP counteract the coagulation defect induced by hirudin. The effect of DDAVP was studied in vivo on the anticoagulant action of recombinant hirudin (CGP39393) in vitro. Blood samples were taken at intervals from 10 normal volunteers infused with DDAVP. Factor VIII: C rose from (mean) 0.68 IU/ml before DDAVP to 2.L9 and 2.16 IU/ml after 30 and 60 min infusion, respectively. Samples taken during DDAVP infusion showed a dose related decrease in the hirudin (0.5 and 1.0 αM) induced prolongation of the APTT that occurred at FVIII: C concentrations of up to twice normal. At higher concentrations of hirudin no effect on the APTT occurred. These results demonstrate that DDAVP infusion elevates factor VIII: C levels with an associated significant reduction in the anticoagulant effect of hirudin in vitro.
Modulation of Endothelial Cells Fibrinolytic Activity by Platelets
Authors: Menashi S , He L , Soria C , Soria J , Thomaidis A , Legrand Y 
Published: July 2018

SummaryInteraction between endothelial cells (EC) and platelets in culture was shown to regulate the fibrinolytic system of the aortic EC. Untreated porcine EC from aorta exhibited almost no net fibrinolytic activity and zymographic assay have shown a single fibrin lysis band of 105 kDa corresponding to a tPA-PAI complex. Incubation of aortic EC with intact platelets stimulated a cell-associated fibrinolytic activity of the urokinase type as evidenced by a plasminogen-dependent fibrin independent amidolytic activity, and the appearance of a new 48 kDa lysis band on zymography. However, in the culture medium of platelet-treated aortic EC, a new lysis band of. 92 kDa appeared with no associated amidolytic activity suggesting that the 48 kDa plasminogen activator secreted by the aortic EC after treatment with platelets is complexed to the inhibitor PAI1. This modulation of fibrinolytic activity depends on the EC origin sin0e it is not observed with pulmonary artery EC, and represents a new concept in fibrinolysis regulation by cell-cell interaction.
Physical Exercise Induces Enhancement of Urokinase-Type Plasminogen Activator (u-PA) Levels in Plasma
Authors: Dooijewaard G , de Boer A , Turion P N C , Cohen A F , Breimer D D , Kluft C 
Published: July 2018

SummaryThe enhancement of the blood fibrinolytic potential by physical exercise is generally attributed to the release of tissue-type plasminogen activator (t-PA) from the vessel wall. In this study we have investigated the possible contribution of urokinase-type plasminogen activator (u-PA).Six healthy male volunteers (age 21–25 years) were screened for their ability to perform maximal exercise for their age-group for 12 min on a bicycle ergometer. Subsequently, on one occasion they were required to remain supine for 2 h (from 8.30 a. m. onwards) and on another they performed maximal exercise (from 9.00 a.m. onwards). During exercise an increase in u-PA antigen and plasmin-activatable pro-urokinase (proUK) activity, concurrent with t-PA antigen and euglobulin t-PA activity, was observed in all six volunteers, while at rest these parameters remained unaffected. Mean u-PA- and t-PA antigen increased, respectively, from 4.2 ± 1.0 ng/ml and 5.8 ± 2.1 ng/ml before exercise to 9.8 ± 3.0 ng/ml and 18.3 ± 3.8 ng/ml (peak). Mean plasminactivatable proUK activity and t-PA activity increased, respectively, from 2.1 ± 0.4 ng/ml and 0.3 ± 0.2 ng/ml before exercise to 4.3 ± 1.7 ng/ml and 7.2 ± 4.0 ng/ml (peak). The increases were statistically significant throughout (paired t-test, pre vs post, antigen P <0.005 and activity P <0.02). After cessation of exercise u-PA and t-PA declined concurrently to normal values with a 50"/" decay in about 5 min. In conclusion, we found that both u-PA antigen and plasmin-activatable proUK activity are, concurrently with t-PA, enhanced upon exercise and, therefore, we consider that u-PA also contributes to – and co-operates in – the enhancement of the blood fibrinolytic potential and activity under these conditions.
The Acute Effect of Insulin on Tissue Plasminogen Activator and Plasminogen Activator Inhibitor in Man
Authors: Landin Kerstin , Tengborn Lilian , Chmielewska Joanna , Schenck Henning von , Smith Ulf 
Published: July 2018

SummaryThe present study was performed to elucidate the acute effect of insulin on levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor of endothelial cell type (PAI-1). Nine middle-aged, non-obese and non-smoking men were studied during a hyperinsulinemic, euglycemic glucose clamp for 2 h. Plasma insulin level during the clamp averaged 84 ± 12 mU/l and euglycemia was maintained at 4.9 ± 0.6 mmol/l. The t-PA activity gradually increased (75% mean increase after 2h, p <0.001) and the PAI-1 activity decreased (49% mean decrease after 2 h, p <0.001) during the clamp. t-PA activity decreased and PAI-1 activity increased after the insulin infusion was ceased, but they were still 48% higher and 38% lower, respectively, after 60 min. PAI-1 and t-PA activities were not affected by saline infusion for 2h.Thus, acute changes in the insulin levels lead to alterations rapid in the fibrinolytic system even when euglycemia is maintained. These effects may be induced by insulin itself or by the concomitant activation of the sympatho-adrenal system during the euglycemic clamp.
Determination of Human Prothrombin Activation Fragment 1+2 in Plasma with an Antibody against a Synthetic Peptide
Authors: Pelzer Hermann , Schwarz Angela , Stüber Werner 
Published: July 2018

SummaryThe present investigation describes a novel approach to prepare a specific antibody against prothrombin activation fragment 1+2 (F 1+2). The antibody discriminates between native prothrombin and F 1+2 in plasma. A synthetic peptide from the negatively charged region of F 1+2, which becomes the carboxyterminal sequence after cleavage of prothrombin by factor Xa, was used for immunization of rabbits. Obtained antiserum was immunopurified and an enzyme-linked immunosorbent assay (ELISA) was constructed for determination of F 1+2. The test system follows the sandwich principle and uses two different antibodies directed against F 1+2 and prothrombin, respectively. The ELISA was calibrated with purified F 1+2 added to F 1+2-poor plasma. The lower limit of sensitivity of the assay was 0.02 nmol/1. Coefficients of variation of 6.9 to 10.4% (intraassay) and 6.7 to 11% (interassay) were found for F 1+2 concentrations between 0.08 and 4.9 nmol/1. A reference range from 0.32 to 1.2 nmol/l was calculated from 95 healthy donors (mean value ± SD: 0.67 ± 0.19 nmol/l). In patients with deep vein thrombosis (n = 7) confirmed by phlebography and in patients with pulmonary embolism (n = 8) confirmed by lung scan, F 1+2levels were found up to 1.5 to 9.5 nmol/l. In plasma samples of patients under oral anticoagulant therapy in the stable state F 1+2 concentrations were found to be in the range of 0.08 to 0.5 nmol/l. The results indicate that the antibody is specific and highly sensitive for quantification of F 1+2 in plasma. It can be supposed that the ELISA we have developed is a valuable tool for detection of both hypercoagulable as well as hypocoagulable states.
Thrombolytic and Pharmacokinetic Properties of Human Tissue-Type Plasminogen Activator Variants, Obtained by Deletion and/or Duplication of Structural/Functional Domains, in a Hamster Pulmonary Embolism Model
Authors: Collen D , Lijnen H R , Vanlinthout I , Kieckens L , Nelles L , Stassen J M 
Published: July 2018

SummaryA pulmonary embolism model in hamsters was used for the quantitative evaluation of the thrombolytic and pharmacokinetic properties of variants of tissue-type plasminogen activator (t-PA). A 25 μi 125I-fibrin labeled human plasma clot was made in vitro and injected into the jugular vein of heparinized hamsters. The extent of thrombolysis within 90 min was determined as the difference between the radioactivity injected in the jugular vein and that recovered in the heart and lungs.Recombinant t-PA (home-made rt-PA or Activase®) infused intravenously over 60 min caused dose-dependent progressive thrombolysis. The results of thrombolytic potency (clot lysis in percent versus dose administered in mg/kg) and of specific thrombolytic activity (clot lysis in percent versus steady state plasma level in μg/ml) were fitted with an exponentially transformed sigmoidal function y = 100 c/(1+e−a(ex−eb)) and the maximal percent lysis (c), the dose or plasma level at which maximal rate of lysis is achieved (b) and the maximal rate of lysis (z = ¼ ac .eb) were determined. With rt-PA, these parameters were c = 72 ± 6% (mean ± SEM), b = 0.19 ± 0.08 mg/kg, z = 68 ± 25% lysis per mg/kg, with corresponding values of 87 ± 5%, 0.07 ± 0.03 mg/kg and 150 ± 38% lysis per mg/kg for Activase® (p = NS). Deletion of the finger and growth factor domains in rt-PA ( rt-PA-ΔFE) was not associated with marked alteration of the thrombolytic potency (c = 90 ± 30%, b = 0.34 ± 0.35 mg/kg, and z = 54 ± 14% per mg/kg), but was associated with a significant reduction of the specific thrombolytic activity. Substitution of the kringle 1 domain by a second copy of the kringle 2 domain in rt-PA and in rt-PA-ΔFE did not significantly alter the thrombolytic potency as characterized by a simultaneous decrease of the b value and an increase of the z value (b = 0.07 ± 0.03 mg/kg and z = 210 ± 70% per mg/kg for rt-PA-ΔK1∇K2 and b = 0.13 ± 0.02 mg/kg and z = 210 ± 29% per mg/kg for rt-PA-ΔFEK1∇K2). Deletion of either the finger or the growth factor domain in rt-PA-ΔK1∇K2 also did not significantly alter the thrombolytic potency (b = 0.08 ± 0.008 mg/kg and z = 320 ± 33% per mg/kg for rt-PA-ΔEK1∇K2 and b = 0.05 ± 0.01 mg/kg and z = 270 ± 48% per mg/kg for rt-PA-ΔFK1∇K2). Likewise, none of the variants had a higher specific thrombolytic activity than wild-type rt-PA. Plasma clearance rates were reduced 10- to 20-fold for the rt-PA mutants lacking the FE domains, and 3- to 5-fold for rt-PA-ΔK1∇K2.
PAI-1 Synthesis in the Human Hepatoma Cell Line Hep G2 Is Increased by Cytokines - Evidence that the Liver Contributes to Acute Phase Behaviour of PAI-1
Authors: de Boer J P , Abbink J J , Brouwer M C , Meijer C , Roem D , Voorn G P , Lambers J W J , van Mourik J A , Hack C E 
Published: July 2018

SummaryThe acute phase behaviour of the fast inhibitor of tissue-type plasminogen activator (PAI-1) in vivo has been attributed to increased synthesis by endothelial cells. However, most other acute phase proteins in vivo are synthesized in the liver, which process is regulated by cytokines and can be studied in the hepatoma derived cell line HepG2.In this study, we investigated whether the synthesis of PAI-1 by HepG2 cells is regulated by the cytokines recombinant IL-1, rlL-6 and rTNF. Recombinant IL-1 and rTNF each increased PAI-1 synthesis by Hep G2 cells two to three fold, whereas rIL-6 hardly had an effect. Mixtures of rIL-1, rIL-6 and rTNF increased PAI-1 synthesis up to eleven fold. The effects observed were not due to non-specific effects on Hep G2 cell metabolism, since synthesis of alpha-2-antiplasmin was not effected by any of those cytokines, whereas fibrinogen synthesis was increased three to four fold by rIL-6, but was unaffected by rIL-1. Thus, our results demonstrate that synthesis of PAI-1 by Hep G2 cells is regulated by cytokines and implicate that the acute phase behaviour of PAI-1 in vivo at least in part may be due to an increased synthesis by the liver.
Evaluation of the Buccal Bleeding Time and Platelet Glass Bead Retention as Assays of Hemostasis in the Dog: The Effects of Acetylsalicylic Acid, Warfarin and von Willebrand Factor Deficiency
Authors: Brassard Jacqueline A , Meyers Kenneth M 
Published: July 2018

SummaryThe study evaluated two hemostatic assays in the dog, a modified version of the buccal mucosal bleeding time (BMBT) and the platelet glass bead retention (PR), to describe the aspects of hemostasis measured by these assays. Von Willebrand factor (vWf)-deficient Doberman pinscher dogs were used in evaluating the effects of altered platelet adhesion. Normal dogs were treated with either acetylsalicylic acid (ASA) or warfarin to evaluate the effects of altered platelet aggregation and coagulation. There was significant prolongation of the BMBT and reduction of the PR in vWf-deficient dogs as compared to normal dogs. In ASA treated dogs the BMBT was slightly prolonged; the PR was significantly reduced. The change in ASA-induced BMBT did not correlate with the sensitivity of the dog platelets to arachidonic acid. In warfarin treated dogs there was no change in the BMBT; however, the PR was significantly reduced. The BMBT is a test of hemostasis that is sensitive to platelet adhesion and aggregation deficits. The PR is useful in detecting general abnormalities in hemostasis including platelet adhesion defects due to reduced vWf.