bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of Human Thrombin: Effect on Thrombomodulin Binding
Authors: Thompson E Anne , Salem Hatem H 
Published: June 2018

SummaryThrombomodulin, an endothelial cell protein, binds thrombin with high affinity and alters thrombin from a procoagulant to an anticoagulant molecule. In this study, chemical and/or proteolytic modification of thrombin was carried out to identify the essential components required for its interaction with thrombomodulin.Modification of thrombin at the catalytic site serine and histidine residues, with Diisopropylfluorophosphate and Tosyl-Llysine chloromethyl ketone, resulted in loss of clotting and amidolytic activity. Both Diisopropyl phosphoryl-thrombin and Tosyl-L-chloromethyl ketone-thrombin inhibited native-thrombin: thrombomodulin catalyzed protein C activation with Ki values of 5 nM and 6 nM respectively indicating no loss of affinity for thrombomodulin.Oxidation of tryptophan residues with N-bromosuccinimide or iodination of tyrosine residues of thrombin led to reduced clotting and amidolytic activity as well as a reduced ability to interact with thrombomodulin. Modification of arginine residues with Phenylglyoxal and 2,3,Butanedione led to loss of thrombomodulin binding affinity. Limited proteolysis of thrombin by trypsin yielded the derivative β-thrombin which had also lost its ability to interact with thrombomodulin. Deglycosylation of thrombin did not alter its binding affinity for thrombomodulin.These results indicate that one or more tryptophan, arginine and tyrosine residues are essential for the recognition of thrombin by thrombomodulin whilst the carbohydrate side chain and the active site residues of the thrombin molecule are not involved in thrombomodulin binding.
Mechanism of Rabbit Platelet Agglutination Induced by Acidic Mucopolysaccharide Extracted from Stichopus japonicus Selenka
Authors: Li Jia-Zeng , Lian Eric Chun-Yet 
Published: June 2018

SummaryThe effects of acidic mucopolysaccharide extracted from sea cucumber (Stichopus japonicus Selenka) (SJAMP) on rabbit platelets were studied. Using citrated platelet-rich plasma (PRP), washed platelets, and formaldehyde fixed platelets from 10 New Zealand white rabbits, we investigated the effects of platelet inhibitors and various plasma and its fractions on SJAMP-induced agglutination. It was found that the tracing of platelet agglutination induced by SJAMP showed a single phase without a lag period. The lowest concentration of SJAMP required for the agglutination of rabbit platelets was approximately 2 μg/ml, and the magnitude of agglutination induced by SJAMP was concentration dependent. In 8 out of 10 rabbits, the platelets in PRP were agglutinated by 10 μg/ml of SJAMP. Platelet inhibitors, such as aspirin, indomethacin, apyrase, antimycin, 2-deoxy-D-glucose and EDTA did not inhibit the agglutination induced by SJAMP. Washed rabbit platelets were not agglutinated by SJAMP even though the concentration of SJAMP was raised up to 50 μg/ml. When rabbit plasma, serum, or 50–60% ammonium sulfate saturated plasma fraction was added to the reaction mixture, agglutination of washed platelets by SJAMP was recovered completely. But human plasma or fibrinogen did not have any effect on the reactivity of washed rabbit platelets to SJAMP. From these data we conclude that the SJAMP-induced rabbit platelet agglutination is independent of energy metabolism but requires plasma cofactor(s) other than fibrinogen. The plasma cofactor is present in 50–60% ammonium sulfate saturated plasma fraction.
Standardization of Protein C in Plasma: Establishment of an International Standard
Authors: Hubbard A R 
Published: June 2018

SummaryAn international collaborative study, involving 18 laboratories, was carried out to establish an international standard for protein C in plasma. The proposed standard, which consisted of a freeze-dried ampouled plasma preparation coded 86/622, was assayed against fresh normal plasma and the participants’ local standards. Protein C activity assays were placed in four groups, depending on the method of activation and detection of protein C. The combined potencies (units per ampoule) for the proposed international standard were: thrombin activation/clottirg assays, 0.86; thrombin activation/chromogenic assays, 0.81; snake venom activation/clotting assays, 0.81 and snake venom activation/chromogenic assays, 0.82. Measurement of protein C antigen gave potency estimates of 0.81 and 0.82 units per ampoule for the Laurell electroimmunoassay and ELISA techniques, respectively. The good agreement in potency estimates between the different methods indicates that the overall combined figure (226 assays) for the international standard of 0.82 international units per ampoule should serve for all methods. Accelerated degradation studies have indicated that the standard should be suitably stable when stored at −20° C.The freeze-dried plasma 86/622 has been established by the WHO Expert Committee on Biological Standardization as the 1st International Standard for Protein C in Plasma, with an assigned unitage of 0.82 international units per ampoule.
Uptake and Degradation of Tissue Plasminogen Activator in Rat Liver
Authors: Einarsson Monica , Smedsrød Bård , Pertoft Håkan 
Published: June 2018

SummaryThe mechanism of uptake of tissue plasminogen activator (tPA) in rat liver was studied. Radio-iodinated tPA was removed from the circulation after intravenous administration in a biphasic mode. The initial half life, t1/2(α), and the terminal phase, t1/2(β), were determined to be 0.5 min and 7.5 min, resp. Separation of the liver cells by collagenase perfusion and density centrifugation, revealed that the uptake per cell was two to three times higher in the non-parenchymal cells than in the parenchymal cells.Endocytosis of fluorescein isothiocyanate-labelled or 125I-labelled tPA was studied in pure cultures of liver cells in vitro. Liver endothelial cells and parenchymal cells took up and degraded tPA. Endocytosis was more efficient in liver endothelial cells than in parenchymal cells, and was almost absent in Kupffer cells.Competitivb inhibition experiments showing that excess unlabelled tPA could compete with the uptake and degradation of 125I-tPA, suggested that liver endothelial cells and parenchymal cells interact with the activator in a specific manner. Endocytosis of trace amounts of 125I-tPA in cultures of liver endothelial cells and parenchymal cells was inhibited by 50% in the presence of 19 nM unlabelled tPA. Agents that interfere with one or several steps of the endocytic machinery inhibited uptake and degradation of 125I-tPA in both cell types.These findings suggest that 1) liver endothelial cells and parenchymal cells are responsible for the rapid hepatic clearance of intravenously administered tPA; 2) the activator is taken up in these cells by specific endocytosis, and 3) endocytosed tPA is transported to the lysosomes where it is degraded.
Diurnal Variation of the Fibrinolytic System
Authors: Grimaudo V , Hauert J , Bachmahh F , Kruithof E K O 
Published: June 2018

AbstractTo elucidate which component(s) of thei fibrinolytic system is (are) responsible for the diurnal variation of fibrinolytic activity we have studied several parameters of this system in 8 healthy male volunteers during a period of. 24 h. Blood was collected at 8 a. m., 10 a. m., 12 a. m., 4 p.m., 8 p.m. and 8 a. m. next morning. The following tests were performed: euglobulin clot lysis time (ECLT), fibrinolytic activity of euglobulins on fibrin plates in the presence and absence of blocking antibodies to tissue-type plasminogen activator (t-PA) and/or urokinase (u-PA), overall plasminogen activator inhibitor (PAI) activity, antigen levels of t-PA, u-PA and PAI-I and zymography of the euglobulin fraction after SDS-PAGE. From 8-10 a. m. to 4-8 p. m., total fibrinolytic activity increased by 1l3% (p <0.01) or 71%h (p <0.01) when measured by ECIX or by fibrin plate assay, respectively. The immunoquenching experiments showed that this increase was entirely due to t-PA related activity whereas u-PA activity and t-PA/u-PA independent activity remained constant during the day. Average antigen levels of u-PA and t-PA in the afternoon were 6% and 25% lower than those measured in the morning. During this period, overall PAI activity and PAI-1 antigen decreased by 3l% (p <0.01) and 52% (p <0.01) respectively. Electrophoretic-zymographic analysis of_ the euglobulins revealed that throughout the day the majority of t-PA was present in the form of the 110 kDa t-PA/PAI-I complex. The intensity of this cornplex was lowest in the afternoon. Free t-PA was almost undetectable in morning samples, but constituted a significant proportion of total t-PA in the afternoon. The diurnal increase of fibrinolytic activity, therefore, is not due to an augmentation of antigen levels of t-PA and/or u-PA but to a decline of those of PAI-1.
Clinically Mild Thrombasthenia with Normal Platelet Coagulant Activities
Authors: Walsh P. N , Rizza C. R , McLennan R 
Published: June 2018

SummaryThe results of assaying platelet coagulant activities in a patient with clinically mild thrombasthenia are compared with those previously reported in 4 patients with clinically severe and 2 patients with moderately severe thrombasthenia. Contact product forming activity and platelet factor 3 activity were normal in the present patient, and decreased in the more severely affected patients. Intrinsic factor-Xa forming activity was normal or supranormal in all patients. Collagen-induced coagulant activity was present in mildly and moderately affected patients and absent in severely affected patients. The present patient would appear to possess both alternative mechanisms by which platelets can initiate intrinsic clotting, compared to the moderately affected patients who lack one and the severely affected patients who lack both pathways. Although the present patient’s platelets failed to aggregate in response to ADP they responded normally to ADP in the assay for contact product forming activity.
Studies on the Activation of Human Factor XIII
Authors: Sheltawy Marion J. , Miloszewski Krzysztof , Losowsky Monty S. 
Published: June 2018

SummaryStudies on antithrombin levels of heat-treated plasma showed that thrombin is rapidly removed during the first five minutes of incubation and thereafter removed more slowly until a plateau is reached at 25 minutes when about 20% of the thrombin remained regardless of the initial amount.The calcium requirements of thrombin activation were studied by using thrombin in insoluble form bound to Sepharose - 4B. Calcium ions were not essential for activation of factor XIII in plasma or purified factor XIII. With purified factor XIII calcium ions decreased activation, whereas with plasma factor XIII calcium ions increased activation.Activation of plasma factor XIII can be accomplished by Reptilase or trypsin as well as thrombin, when activity is measured by the ability to stabilise fibrin. When measured by the dansyl cadaverine method, only Reptilase and thrombin activate factor XIII. Arvin did not activate factor XIII and formed an unstable clot.
The Effects of Brinolase (Fibrinolytic Enzyme from Aspergillus Oryzae) on Platelet Aggregation of Dog and Man
Authors: Roschlau W. H. E , Gage R 
Published: June 2018

SummaryInhibition of blood platelet aggregation by brinolase (fibrinolytic enzyme from Aspergillus oryzae) has been demonstrated with human platelets in vitro and with dog platelets in vivo and in vitro, using both ADP and collagen as aggregating stimuli. It is suggested that the optimal inhibitory effects of brinolase occur indirectly through the generation of plasma fibrinogen degradation products, without compromising platelet viability, rather than by direct proteolysis of platelet structures.
Evaluation of the Fibrin Plate Method for Estimating Plasminogen Activators
Authors: Marsh N. A , Arocha-Pinango C. L 
Published: June 2018

SummaryA study was carried out in order to evaluate the Astrup and Mullertz fibrin plate method for estimating plasminogen activators.Choice of a suitable fibrinogen substrate was found to be the most important factor in setting up a workable assay. Many preparations contained a large proportion of non-clottable protein and plates made from these fibrinogens were usually unreliable. In addition, plasminogen content varied appreciably between preparations so that sensitivity of the method required careful calibration with each new batch of fibrinogen.The effect of additives in the fibrin plate was considered and it was found that calcium chloride alone was sufficient to ensure a stabilised plate which could be stored at 4° C for some time. The addition of tranexamic acid (AMCHA) was found to be a slightly more convenient way of estimating direct proteolytic activity, compared with the traditional heated plate. However neither method distinguished completely between proteolysis and plasminogen activation.In order to improve the precision of the method, the use of an analysis of variance technique has been studied. This technique provides information on the dose-response curves of test and unknown substances, and in addition produces an approximately threefold increase in precision over single plate tests.
The Treatment of Patients Having Spontaneously Occurring Antibodies to Antihaemophilic Factor (Factor VIII)
Authors: Rizza C.R , Edgcumbe J.O.P , Pitney W.R , Child J.A 
Published: June 2018

SummaryThe appearance of antibodies to factor VIII in the blood of previously normal people is a very rare occurrence but when it does happen the haemorrhagic condition which results can be very serious and difficult to treat.From experience of three cases described here it is recommended that treatment be witheld unless there is serious haemorrhage in which case steroids, large doses of cryoprecipitate or other human AHG should be given. In the case of life endangering haemorrhages it is justified to use the much more potent animal AHG preparations along with an immuno-suppressive drug.
Oral Contraceptives and Platelet Function
Authors: Mettler L , Selchow Meseck B. 
Published: June 2018

SummaryPlatelet function was studied in women receiving two oral oestrogen-progestagen compounds (Neogynon and Noracyclin-22). Platelet count, adhesiveness, spreading, aggregation (PAT) and thromboelastography (TEG) were studied twice monthly for six months in 186 cycles. Platelet counts in rotated plasma were decreased in both groups. A significant increase in non-spread platelets was found in the Neogynon group only. PAT-degrees were significantly increased in both groups. Platelet adhesiveness and thromboelastographic measurements were not affected. Increased platelet aggregation during oral contraceptive therapy is regarded as a predisposing factor to thrombosis.
The Effect of Neuraminidase on Platelet Aggregation Induced by ADP, Norepinephrine, Collagen or Serotonin
Authors: Davis James W. , Yue Kenneth T. N. , Phillips Phyllis E. 
Published: June 2018

SummaryIncubation of human platelet-rich plasma (PRP) with neuraminidase enhanced platelet aggregation induced by adenosine diphosphate (ADP), norepinephrine, collagen or serotonin. Both first and second phases of ADP- and norepinephrine -induced aggregation were enhanced. In two plasmas a second phase of ADP-induced aggregation occurred after incubation with neuraminidase, but not in the control preparations. In one plasma a second phase of serotonin-induced platelet aggregation occurred after incubation with neuraminidase. The incubation of PRP with exogenous N-acetylneuraminic acid (a product of the action of neuraminidase) had no effect on platelet aggregation. A possible explanation of the observed enhancement of platelet aggregation by neuraminidase is that the enzyme may have released sialic acid from platelet membranes and thereby reduced their net negative surface charge.
Factor VIII International Units and Reference Materials
Authors: Bangham Derek R , Brozović Milica 
Published: June 2018

SummaryThe establishment of the International Standard for factor VIII has introduced a common yardstick, the international unit, which all countries can apply. This standard is a concentrate of intermediate purity, shown to be very stable on long term storage. As with all international standards it is available in limited quantities and is primarily used for the calibration of national standards used to monitor patients and in the control of therapeutic preparations.Since 1969 in Great Britain such a national standard has been made from freeze-dried pooled plasma. This has been available in larger quantities and has been introduced into routine use in coagulation laboratories. As factor VIII in freeze-dried plasma has limited stability even when stored at —20° C, successive new batches are prepared every two years or so. The availability of a common working standard with factor VIII content specified in international units makes it possible to define diagnostic and therapeutic criteria with more precision than hitherto. This system can be applied in other countries and to other clotting factors for which an international yardstick is needed.
The Corrective Effect of Factor VIII-coated Red Blood Cells in Haemophilic Plasma with Antibodies to Factor VIII
Authors: Uszyński Leszek 
Published: June 2018

SummaryFactor VIII-coated red blood cells had an evident corrective effect on plasma of haemophiliacs with inhibitors. This effect was especially significant when tanned coated red cells were used. The direct coating of washed red blood cells by factor VIII concentrates is also feasible. The results were better with fraction C-I (AHG concentrate containing dextran) than with fibrinogen-free concentrate. It seems that dextran enhances the attachment of factor VIII to human erythrocytes. In the direct coating-procedure the time of incubation was important, but temperature and pH were not critical. The results obtained indicate that factor VIII attached to red blood cells is more resistant to inhibitors than factor VIII in solution.The possibility of using factor VIII-coated red cells for the management of patients with antibodies to factor VIII is discussed.
The Effect of Major Surgical Procedures on Plasma and Platelet Levels of Factor XIII
Authors: Letheby Beth A , Davis Richard B , Larsen Arden E 
Published: June 2018

SummaryFactor XIII (FSF or fibrinoligase), an enzyme required for normal blood coagulation, can be measured by its catalysis of the incorporation of a fluorescent amine, monodansylcadaverine (N-(5-aminopentyl)-5-dimethylamino-l-naphthalene-sulfon-amide) into casein. The amine incorporation test was applied to fourteen patients who had major operations. Levels of factor XIII were measured before surgery and at intervals of two, four, and six days after operation. Plasma factor XIII showed a significant, linear decrease for each day after surgery. Patients having orthopedic surgery showed less pronounced changes than the remaining patients. Factor XIII also decreased after operation in patients with neoplastic disease, but the change was not different from that after general surgical procedures done in the absence of neoplasia. Platelet factor XIII levels were increased on the second day after operation, diminished on day four, and increased above pre-operative levels on the sixth day after surgery. Possible explanations of the observations are presented.
A Direct Enzymatic Assay for the Esterolytic Activity of Activated Hageman Factor
Authors: Ulevitch Richard J , Letchford David , Cochrane C. G 
Published: June 2018

SummaryA direct enzymatic assay for activated Hageman factor (HFa) has been developed utilizing N-α-acetylgiycine lysine methyl ester (AGLME). This assay allowed the measurement of the esterolytic activity of purified Hageman factor (HF) which had been activated by enzymatic (trypsin) and non-enzymatic (kaolin) mechanisms. No esterolytic activity was detected in preparations of purified HF prior to activation.Studies with purified HF activated on kaolin demonstrated the following: (1) Simple saturation kinetics (Km = 9 mM, Turnover number = 2.5 min–1) at AGLME concentrations less than 0.04 M and substrate inhibition at AGLME concentrations greater than 0.04 M. (2) The substrate AGLME behaved as a competitive inhibitor of the activation of prekallikrein (PK) by HFa with an inhibition constant (Ki) of about 10 mM. (3) Both the esterolytic (AGLME hydrolysis) and the proteolytic activities (PK activation) were inhibited by diisopropylfluorosphosphate (DFP) with an approximate Ki of 5 × 10–4 M.
Isolation and Characterization of Plasminogen Activator from Pig Leucocytes
Authors: Kopitar M , Stegnar M , Accetto B , Lebez D 
Published: June 2018

SummaryPlasminogen activator was isolated from disrupted pig leucocytes by the aid of DEAE chromatography, gel filtration on Sephadex G-100 and final purification on CM cellulose, or by preparative gel electrophoresis.Isolated plasminogen activator corresponds No. 3 band of the starting sample of leucocyte cells (that is composed from 10 gel electrophoretic bands).pH optimum was found to be in pH range 8.0–8.5 and the highest pH stability is between pH range 5.0–8.0.Inhibition studies of isolated plasminogen activator were performed with EACA, AMCHA, PAMBA and Trasylol, using Anson and Astrup method. By Astrup method 100% inhibition was found with EACA and Trasylol and 30% with AMCHA. PAMBA gave 60% inhibition already at concentration 10–3 M/ml. Molecular weight of plasminogen activator was determined by gel filtration on Sephadex G-100. The value obtained from 4 different samples was found to be 28000–30500.
The Relationship between Platelet Aggregation and Time Interval after Venepuncture
Authors: Warlow Charles , Corina Anne , Ogston D , Douglas A. S 
Published: June 2018

SummaryThe relationship between the rate of platelet aggregation and the time interval after venepuncture has been studied. Considerable changes in the rates of aggregation and disaggregation of platelets in citrated plasma take place between 30 and 120 minutes after venepuncture. There is a reduction in the rates of irreversible ADP-induced aggregation, the first and second phase of the double wave of ADP-induced aggregation, disaggregation after reversible ADP-induced aggregation, collagen-induced aggregation and the second phase of the double wave of adrenaline-induced aggregation. In contrast, the rate of the first wave of adrenaline-induced aggregation increases with time after venepuncture. 5-HT induced aggregation appears to be unaffected. These effects were not due to changes in the pH of the plasma. It is suggested that any attempt to quantify platelet aggregation during the comparison of groups of individuals, or in the study of the effect of anti-platelet drugs in single individuals must take into account the time interval between venepuncture and the measurement of platelet aggregation.
Studies on the Shape Change in Rabbit Platelets Induced by Adenosine Diphosphate or Several Metabolic Inhibitors
Authors: Kobayashi Norio , Maekawa Tadashi 
Published: June 2018

Summary1. The shape change of platelet was induced in vitro by an addition of ADP, NEM, KCN or distilled water. The change induced by ADP occurred very rapidly.2. Among these reagents, only ADP induced the platelet aggregation.3. When ADP was added before the completion of the shape change by NEM, the shape change by ADP took place, while both ADP and NEM were added simultaneously, the pattern of the shape change was similar to that of ADP alone.4. The shape change of platelet by ADP was inhibited by the previous addition of adenosine, which did not affect the shape change induced by NEM.5. Correlation of the shape change of platelets to their aggregation was discussed.