bluuebunny/crossref_metadata_2025_split huggingface dataset:
ANTI-THROMBOTIC EFFECT IN CANINE CORONARY ARTERIES OF A COMBINED TXA2 synthetase/TXA2-prostaglandin ENDOPEROXIDE RECEPTOR INHIBITOR (R 68070)
Authors: Van de Water A , Xhonneux R , De Clerck F 
Published: August 2018

The effects of R 68070 an oxime-alkane carboxylic acid derivative combining specific thromboxane A2 (TXA2) synthetase inhibition with TXA2/prostaglandin endoperoxide receptor blockade in one molecule, on thrombus formation in a coronary artery following electrically-induced endothelial injury and on its myocardial repercussions were examined in dogs. In an open-chest model in anaesthetized dogs, a stainless steel electrode was inserted into the left anterior descending coronary artery (LAD) distally (+ 1 cm) from an electromagnetic flow probe. ECG and heart rate were derived from limb leads. Serum TXB2 levels were measured by RIA on venous spontaneously coagulated blood (1 h, 37°C). Endothelial cell injury in the LAD coronary artery was induced by the application of an anodal current of 300 μA during 30 min; after an additional 60 min observation period, the thrombus wet weight was determined.In comparison with solvent treatment (n = 8), R 68070 (1.25 mg/kg I.V. 10 min before electrical stimulation, n = 7), significantly reduced the thrombus mass (solvent : 43 mg; R 68070 : 18 mg median value, p < 0.05), the incidence of ECG changes indicative for myocardial ischemia (fibrillation : solvent 1/8; R 68070 0/7; arrhythmias : solvent 3/8; R 68070 2/7; ST changes : solvent 7/8; R 68070 1/7, p < 0.05) and the decrease in coronary blood flow after electrical stimulation (solvent : from 13 to 6.5 ml/min; R 68070 : from 13 to 11 ml/min median values, p < 0.05). Serum TXB2 levels were reduced by 92 % at 100 min after the injection of the active compound (median value, n = 7).Heart rate and coronary blood flow measured before the induction of the endothelial injury were not modified by R 68070.The present study thus demostrates that R 68070 exerts a potent anti-thrombotic effect in canine coronary arteries. The relative contributions to this effect of TXA2 synthetase inhibition and of TXA2/prostaglandin endoperoxide receptor blockade exerted by the compound are being investigated.
DETERMINATION OF THE DOMAINS OF FACTOR VIII ESSENTIAL FOR PROCOAGULANT ACTIVITY
Authors: Verbeet M Ph , Evers R F , Leyte A , Lamain H L , Van Ooyen A J J , Van Mourik J A , Pannekoek H 
Published: August 2018

Factor VIII (FVIII) consists of an obvious domain structure that can be represented as A1-A2-B-A3-C1-C2 (Vehar et al., 1984, Nature 312, 337). In order to determine the domains involved in the procoagulant activity of FVIII, we constructed mutant FVIII cDNAs containing deletions in the coding sequence of the full-length molecule. In one of the mutants a large part of the B domain is deleted. In another one we made a deletion in the B domain that extends beyond the thrombine cleavage site. We used pSV-2 derived expression vectors and COS-1 cells in a transient expression system for the full-length and mutant recombinant proteins. Conditioned media (CM) were harvested.In accordance with the described mutants of recombinant FVIII (Toole et al., 1986, PNAS 83, 5939), we demonstrated an increase in activity in the CM for these mutants as compared to the full-length activity. We also found that the specific activity of the mutants is similar to that of plasma FVIII. So, shorter chains lead to an increased amount of procoagulant protein.
RELAXATIONS INDUCED BY LIPOXYGENASE METABOLITES OF ARACHI-DONIC ACID IN SPLENIC ARTERIES OF THE DOG
Authors: Van Diest M J , Verbeuren T J , Herman A G 
Published: August 2018

The lipoxygenase metabolites of arachidonic acid, 15 hydroperoxyeicosatetraenoic acid (15HPETE) and its hydroxy derivative (15HETE) evoke contractions in a variety of isolated blood vessels. We recently were able to show that thromboxane A2 (TXA2)-receptor antagonists BM13177 and BM13505 suppress the contractions induced by lipoxygenase metabolites in canine splenic arteries, and that these compounds also inhibit the contractile effects of PGF2α and of the TXA2-mimetic U46619. We also reported that 15HETE and 15HPETE cause relaxations of isolated dog arteries when the tissues are contracted with prostaglandin F2α (PGF2α) or with U46619 and suggested that lipoxygenase metabolites may act as endogenous antagonists towards prostaglandin receptors. The present study was designed to investigate the effects of lipoxygenase metabolites of arachidonic acid in isolated splenic arteries in which the tone is raised by various agonists.Segments of canine splenic arteries with or without endothelium were placed in organ chambers filled with Krebs-Ringer solution at 37°C for isometric tension recording. Responses to 15HPETE were obtained in segments which were contracted with serotonin, K+, PGF2α or noradrenaline (the latter with or without BM13505); concentrations causing comparable levels of contraction were selected. HPETE evoked relaxations in segments with and without endothelium, during the contractions evoked by K+, PGF2α and noradrenaline (with or without BM13505). At higher concentrations, 15HPETE caused relaxations only during contractions induced by PGF2α and noradrenaline with BM13505. Our results suggest that 15HPETE can cause relaxations by two different mechanisms :(1) 15HPETE may act as an antagonist to PGF2α, which causes its contraction via the TXA2-receptor and,(2) in presence of BM13505, it suppresses the contractions to noradrenaline via an endothelium independent mechanism.
CHANGES IN PLATELET SURVIVAL AND SIALIC ACID CONCENTRATION IN PLASMODIUM BERGEI INFECTED RATS
Authors: Essien E M , Inyang A L 
Published: August 2018

Reduced circulating platelet count sometimes to thrombocytopenic levels in man and normally severe thrombocytopenia in animals are well known features of acute Plasmodium falciparum or experimental P. bergei infections in these respective organisms. Suggested mechanism(s), disseminated intravascular coagulation or immune mediated mechanism, thought to be involved in these observations are disputed. Shortened platelet survival has been reported in man.We now present data on platelet survival and total platelet sialic acid concentration in P. bergei-infected Wistar rats. A total of 52 rats were used. For the platelet survival studies each of the 8 suckling test animals was infected by intraperi-toneal route with mouse-passaged P. bergei 4-5 days before inaction of Cr-labelled homologous rat platelets (50 μCi Na51 CrC4/rat) the platelets being obtained from adult Wistarrats. Blood samples were then collected 2 hr after the injection (zero hr sample) and subsequently at 17.0, 42.5 and 66 hr s.Platelet recovery and survival curves were determined on these samples. It was found dat fewer platelets (as % recovery) were obtained from each infected rat sample compared with control, the difference was significant in the 42.5 and 66 hr samples: 7.9 ± 8.1 (test) vs 41.4 ± 15.2% (C) for 42.5 hr and 2.8 ±4.1 (t) vs 26.8 ± 6.2% (C) for the 66 hr samples (p < 0.005 for each). For sialic acid determinations, 40 suckling Wistar rats (30 test, 10 control) were treated as for survival studies.At identical periods, blood was collected, washed platelets obtained, lysed and protein and total sialic acid determined by Lowry (1951) and Aminoff (1961) methods respectively. Total sialic acid of 7.02 ± 4.21 nM/mg protein at 42.5 hrs and 4.8 ± 2.14 at 66 hrs were significantly less than control value of 11.43 nm/mg protein and also showed a negative correlation (r = -0.95) with % parasitaemia.It is concluded that P. bergei infection causes a reduction in total platelet sialic acid with resultant significant shortening of the platelet life span.
INCREASED SECRETION OF A FIBRINOLYTIC INHIBITOR BY HUMAN MONONUCLEAR LEUKOCYTES PARALLELS THE PR0COAGULANT RESPONSE TO SPECIFIC ANTIGEN
Authors: Schwartz B S , Monroe M C 
Published: August 2018

The presence of fibrin is a characteristic finding of Immune mediated tissue lesions. It is known that peripheral blood mononuclear cells (PBM) express tissue factor in response to recognition of a specific protein antigen. We have found PBM secrete a plasminogen activator (PA) Inhibitor (I) in parallel to expression of tissue factor upon exposure to a sensitizing antigen. Increased PA-I can be detected by Inhibition of urokinase (UK) in an 125I-fibrin plate assay, Inhibition of 125I-plasminogen cleavage, and formation of complexes between 125I-urokinase and UK-I. PA-I secretion is dose dependent, and antigen specific, i.e. a nonsensitizing antigen does not Induce a PA-I response.The PA-I is secreted by monocytes, however the recognition of antigen is a T-cell function. Inhibition of PBM protein or RNA synthesis abrogates the PA-I response. The PA-I appears to be the type 2 Inhibitor, in that 1) it is a much more efficient Inhibitor of UK than of tissue type PA, 2) it is labile in acid and detergent, and 3) it is neutralized by IgG to human placental PA-I, but not by antiserum to PA-I of endothelial cells. It is concluded that PBM respond to a foreign stimulus by elaborating molecules that lead to both the deposition and persistence of ftbrln.
PLASMINOGEN ACTIVATOR INHIBITOR ACTIVITY AND ANTIGEN (PAI 1), RELATIONSHIP TO FIBRINOLYTIC RESPONSE AFTER VENOUS OCCLUSION IN 48 PATIENTS WITH DEEP VEIN THROMBOSIS
Authors: Nguyen G , Horellou M H , Conard J , Van Dreden P , Kruithof E K O , Samana M 
Published: August 2018

Fibrinolytic parameters were studied before and after a 10 minute venous occlusion (VO) in 48 patients with confirmed deep vein thrombosis (DVT), at least 3 months after the last thrombotic episode. Congenital antithrombin III or protein C deficiencies were ruled out in these patients. The following tests were performed : euglobulin clot lysis time (ECLT), diluted whole blood lysis times (DWBLT), tissue plasminogen activator (t-PA) antigen (Biopool kit) and activity (fibrin plates), PAI activity (Verheijen et al.) and PAI i antigen (RIA, Kruithof et al.).Patients were divided in 2 groups : group 1 (27 patients) with normal fibrinolytic response (ECLT and DWBLT less than 90 min. after VO), group 2 (21 patients) with defective fibrinolytic response at least twice with a few weeks time interval. In group 1, the mean t-PA antigen release after VO was 32.0 ± 27.2 ng/ml (post-occlusion value minus preocclusion value) and was associated with low or normal levels of basal PAI activity (7.1 ±3.1 IU/ml), and PAI 1 antigen (15.1 ±4.1 ng/ml, n = 7). These results could explain the good response to VO, and a PAI activity suppression after stasis (PAI activity undetectable in 20 out of 27 patients).In contrast, in group 2, a low t-PA Ag increase after VO:10.5 ± 8.2 ng/ml as compared to group 1 (p <0.001) was associated with high levels of basal PAI activity : 22.4 ± 15.4 IU/ml (p <0.001), and PAI 1 Ag : 43.6 ± 24.9 ng/ml (n = 11, p <0.001). This association may account for the impaired fibrinolytic response aftep V0, and for persistant high PAI activity levels after stasis (17.6 ± 22.5 IU/ml). Before V0, PAI 1 Ag levels were in good correlation with PAI activity (r = 0.66, p <0.01), and , were significantly higher in group 2 as compared to group 1 (only 3 patients belonging to group 2 had normal PAI levels).Since elevated PAI 1 antigen and PAI activity levels were associated with an abnormal fibrinolytic response to venous stasis, VO test could be restricted to patients with normal PAI levels, in order to detect hypofibrinolysis related to insufficient t-PA release.
ROLE OF MEMBRANE DEPOLARIZATION IN PLATELET ACTIVATION INDUCED BY THROMBIN
Authors: Yamaguchi A , Azuma H , Sekizaki S , Tanoue K , Yamazaki H 
Published: August 2018

Though membrane depolarization is an imoportant step in signal transduction in living cells, it is immpossible to use microelectrode for analyses of the phenomenon in platelets due to the size limitation. Cetiedil, oc-cyclohexyl�3�thiophenacetic acid 2-(hexahydro-1H-azep in-1-yl) ester, is the drug which inhibits erythrocyte sickling by promoting net salt and water gain. It increases flux of both Na and K, and net Na gain exceeds net K loss. We used cetiedil as a tool to modify intracellular Na and K contents which are closely related to membrane potential.Normal human platelets contained 23.5±3.7 nEq of Na and 82.7±5.6 nEq of K per 108 platelets measured by atomic absorption spectrophotometer (n=6, meantSE). When 0.5 µ/ml of thrombin was added, Na content increased to 200 % and K content decreased to 80% of the resting value after 15 sec. 22 Na spaces of platelets (0.3L±0.07 µl/l0° platelets in the resting stage, n=4) increased to 0.53±0.12 at 2 min after thrombin. After 5 min incubation with 50 µM cetiedil, Na contents increased and K contents decreased slightly. Under the cetiedil treatment, the increase in Na and decrease in K contents induced by thrombin were inhibited significantly. The increase in 22 Na spaces induced by thrombin was also inhibited. Thrombin-induced membrane depolarization measured by membrane potential probe dye, diS, also was inhibited by cetiedil. In the presence of 50 yM cetiedil, magnitude of depolarization was 27.6±1.0 mV (n=30). The depolarization was not affected by Na transport inhibitors, such as procaine and tetrodotoxine, but inhibited by low Na content in the suspension medium. Cetiedil also inhibited platelet aggregation and TXA2 synthesis by thrombin. However, the treatment did not induce any changes in platelet volume, their morphology under elecrton microscope, Ca content and LDH leakage. There is a concept that a small degree of depolarization can inhibit the stimulus-response coupling of various kinds of cells. A similar mechanism might be present in platelet membrane. A role of membrane depolarization in platelet activation is suggested
ROLE OF GUANINE NUCLEOTIDES IN Ca2+ - DEPENDENT LYSOSOMAL SECRETION FROM ELECTROPERMEABILISED PLATELETS
Authors: Athayde C M , Scrutton M C 
Published: August 2018

Previous studies have shown that the maximal extent of Ca2+ dependent secretion of β-N-acetylglucosaminidase (B-N-AcGlc) from electropermeabilised human platelets can be enhanced by addition of thrombin or of 1-oleyl-2-acetylglycerol or 12-0-tetradecanoyl phorbol-13-acetate without a significant alteration in the EC^q for Ca2+. (Knight et al. Europ. J. Biochem.,143337 (1984)). We have found a similar Ca2+ dependent increase in the maximal extent of β-N-AcGlc and β-galactosidase secretion on addition of metabolically stable analogues of GTP (GTPγS and GppNHp) in the absence of thrombin or of GTP added in the presence of a nonsaturating concentration of thrombin. The EC50 values for GTP and GppNHp do not differ significantly for β-N-AcGlc and 3H-5HT secretion, but GTPγS is significantly more effective for 3H-5HT secretion.The time course of β-N-AcGlc secretion induced by GTPγS shows a significant delay as compared with that induced by thrombin + Ca2+. No significant differences could be detected between the properties of β-N-AcGlc or β-galactosidase secretion in this system. The results are consistent with involvement of a GTP binding protein (Np) in receptor-phospholipase C coupling mediating lysosomal secretion, but provide no indication that an additional protein of this type (Ne) is involved as has been proposed for lysosomal secretion from neutrophils. We have thus far failed to find evidence for heterogeneity in lysosomal secretion in this system (supported by SERC and Ciba-Geigy).
REFRACTORINESS OF PLATELETS AFTER REVERSIBLE STIMULATION BY ADP, PAF AND AA
Authors: Voss R , Ohanes H D , Ditter H , Matthias F R 
Published: August 2018

It has been observed that platelets which have been, stimulated by thrombin, ADP or platelet-activating factor (PAF) show an inhibited response to a subsequent stimulation by the same agonist. We performed a crossover stimulation of human platelets (PRP) with the four agonists ADP, PAF, arachidonic acid(AA) and collagen (COL); after a first stimulation with a dose giving a reversible aggregation (0,1-0,4×10-6M ADP, 0,1-0,5×10-8 M PAF) or a shape change (0,05-0, 1mM AA., 0,4 ug/ml COL) the platelets were again stimulated after 5 min with the same or a higher dose, usuallyresulting in an irK8
reversible aggregation (1,0-3,0×10-6 M ADP, 1,0-5,0×10-8 M PAF, 0,3-0,5mM AA, 1,0 ug/ml COL).ADP-, PAF- and AA-stimulation were inhibited by a prestimulation with the same agonist (ADP/ADP 60% inhibition, PAF/PAF 100% inhibition, AA/AA 10% inhibition) ; ADP and PAF did not or only slightly inhibit each other. Prestimulation with AA changed a reversible ADP- or PAF-induced aggregation into an irreversible one, and a reversible AA-stimulation was increased to irreversible by ADP-prestimulation. COL-aggregation was not influenced by any prestimulation nor did a COL-presti-mulation influence the second stimulation by any of the four agonists.The refractoriness of platelets for ADP and PAF after prestimulation with the same agonist may be explained by receptor internalization; in the case of ADP the effect lasted for at least one hour. The enhancement of ADP- and PAF-aggregation by an AA-prestimulation can be explained by other investigations which have shown that the arachidonic acid pathway acts as a positive feedback mechanism in platelets.
CONTAMINATING LEUKOCYTES INFLUENCE THE STORAGE CONDITIONS OF PLATELET CONCENTRATES
Authors: Pietersz R N I , de Korte D , Roos D , Reesink H W 
Published: August 2018

Leukocyte poor platelet concentrates (PC), containing less than 10 leukocytes, prepared from buffycoats can be stored in normal PVC bags for 7 days at 22°C without deterioration of the pH. We assumed that a low number of leukocytes present in the PC, is a critical factor to maintain the pH. To test this hypothesis increasing amounts of leukocytes were added to four groups of three PC with comparable plasma volumes (mean 58.6 ± 0.8 (SD) ml) and platelet concentrations (1.01 ± 0.04×109 /ml). Group I had a leukocyte concentration of 0.14±0.048×106 /ml, group II 1.96±0.09×106 /ml, group III 5.53±0.98×106 /ml, and group IV 13.0±0.93×106 /ml. The PC were stored in normal PVC bags for 7 days at 22°C. Measurements in vitro were performed at day 0, 2, 5 and 7.The initial mean pH value was 7.12±0.02 (SD) for all PC and dropped to 6.89, 6.85, 6.77 and 6.61 for group I to IV respectively, at day 7. A significant correlation (Spearman rank test) between low pH values and high leukocytes was found. The same significant positive correlation was observed between high leukocyte concentrations and high glucose consumption and high lactate production and LDH release during storage.These results show that the amount of leukocytes in PC has a significant contribution to the detrimental effect on pH during platelet storage. It is therefore important to prepare PC with a leukocyte count lower than 10 . Moreover the risk of alloimmunisation against HLA antigens will be diminished.
ACTIVATION OF PROTEIN KINASE C INHIBITS THROMBIN AND FLUORIDE STIMULATED EICOSANOID PRODUCTION IN HUMAN PLATELETS
Authors: Poll C T , Kyrle P A , Westwick J 
Published: August 2018

Touqui et al (1986) have suggested that phosphorylation by protein kinase C of a 1ipomodulin-1 ike polypeptide extracted from platelets renders it inactive as an inhibitor of phospholipase A2. We have examined this suggestion by measuring thromboxane (Tx) B2 generation and cytosolic free calcium concentration ([Ca++]i) in stimulated, washed human platelets loaded with or without quin-2. Addition of thrombin (0.077, 0.23, 0.77, 2.3 and 7.7 nM) to control platelets produces a dose-related elevation of [Ca++]i (10±5, 50±7, 260±30, 550±25 and 1500±100 nM respectively) and generation of TxB2 (0, 9±4, 45±6, 194±10 and 375±30 pmoles/108 platelets respectively). Preincubation of platelets for 1 min with 1-oleoyl-2-acetyl-rac-glycerol (OAG, 22-198 μM), phorbol myristate acetate (PMA, 1.616 nM) or EGTA (2 mM) produces a marked inhibition of high and low dose thrombin (7.7 nM and 0.77 nM) or NaF (18 mM) induced elevation of [Ca++]i and TxB2 generation. Pretreatment of platelets with the protein kinase C inhibitor, H-7 (60 uM), prevented the inhibition of TxB2 formation induced by PMA (4.816 nM) or OAG (66-198 μM) in either thrombin (0.77 nM) or NaF (18 mM) stimulated platelets. When arachidonic acid (AA, 10 μM) is used as the stimulus, the Δ[Ca++]i is 190±15 nM and TxB2 generation is 35.9±2 pmoles/108 platelets. While pretreatment with 4.8 nM PMA obliterates the AA-induced Δ[Ca++]i and partially reduces (p< 0.05) the TxB2 generation to 27.8+3 pmoles/108 platelets. PMA and OAG pretreatment also inhibits TxB2 generation in thrombin-stimulated, non-quin-2-1oaded platelets. Thus, at least with intact, agonist- and NaF-stimulated platelets, activation of protein kinase C inhibits eicosanoid production.We thank the British Heart Foundation and Ciba-Geigy USA for financial support.
HUMAN MEIZOTHROMBIN 1, ITS ISOLATION AND PROPERTIES
Authors: Latallo Zbigniew S , Jackson Craig M 
Published: August 2018

Meizothrombin (MT) and meizothrombin des Fragment 1 (MT1) are intermediates in the conversion of prothrombin to α-thrombin (αTH). Due to their transient character, properties of these enzymes are difficult to establish. Isolation of MT1 was achieved by affinity chromatography on D-Phe-Pro-Arginal (FPRal)immobilized on Affi-Gel 10 as originally employed for thrombin purification (Patel et al. Biochim.Biophys. Acta 748,321 (1983)). Human prethrombin 1 was activated with the purified activator from Echis carinatus venom in the presence of Ca++;, benzamidine and FPRal gel at pH 7.8. After exhaustive washing the MT1 was eluted with 0.1 M hydroxylamine in 0.15 M Na acetate buffer, pH 5.5. Under these conditions the MT1 is stable and can bestored at -70°C. Upon changing the pH of the preparation to 8.0, complete conversion into aTH occurred atroom temperature within 48 hours. Homogeneity of both preparations wasdemonstrated by PAGE. The Km and ke, values for MT1 measured on Tos-Gly-Pro-Arg pNA(0.1 M NaCl, 0.01 M TRIS, 0.01 M HEPES, 0.1% PEG, pH 7.8, 25°C) were 15.7 /iM and 126 s-1. The kinetic con stants for the aTH resulting from autocatalytic degradation of MT1 were indistinguishable from those previously established forαTH obtained by Xa activation i.e. 4.77 /μM and 126 s-1. Clotting activity of MT1 was found to be only one fifth as high as that of the resulting μTH(746 u/mg vs. 3900 u/mg as tested using the NIH standard) .Inhibitionof MTl by antithrombin III was alsomuch less rapid than αTH andmost importantly, it was not affected by high affinity heparin( Mr20,300). Under conditions of the experiment (0.3 M NaCl, 0.0rl M TRIS, 0.01 M HEPES, 2.5 mM EDTA, 0.1% PEG, pH 7.8, 25°C; [ATIII] 100 nM, [E] 10 nM), the pseudo first order rate constants in the absence of heparin were 4.04 × 10-3V1 (MTl) and 1.13 × 10-3V1 (αTH), giving apparent second order rate constants of 4.04 × 103 and 1.13 × 10-4M-1s-1. In the presence of 4.5 nM of heparin the observed first order rate constant for MTl remained unchanged whereas it increased to 6.241 × 10-3s-1 (5.5 fold) for αTH. This apparent lack of an effect of heparin may be of significance in vivo.Supported by a Matching Grant from the American National Red Cross and by the Southeastern Michigan Blood Service.