bluuebunny/crossref_metadata_2025_split huggingface dataset:
CAROTID INTIMAL TRAUMA: A MODEL FOR PLATELET INTERACTIONS WITH DAMAGED ENDOTHELIUM
Authors: Galvin D AJ , Meek A C , German K , Harper R A , McCollum C N 
Published: August 2018

Radiolabelled platelet deposition on prosthetic arterial grafts may be used as a method to evaluate antithrombotic drugs but requires large animals or patients and involves artificial flow surfaces. A rabbit model has been developed to investigate platelet uptake following carotid intimal damage.Both carotid arteries of 10 NZW rabbits were exposed by midline incision and intimal damage inflicted by a 3-minute unilateral artery compression using the jaws from non-toothed dissecting forceps mounted on a G-clamp with compression screw. Twenty-four hours later, autologous platelets were labelled with llllndium by the method of Hawker et al [1], The carotid arteries were excised 40 hours later and radiolabelled platelet uptake counted in a well crystal and expressed as a percentage of the activity in 1ml of blood.Total counts (mean ± sem) in the non-traumatised artery were 2.6±0.35×103 which was similar to background at 2.0±0.07×103. Expressed per gm, radioactivity in the traumatised artery at 4.8±0.38×l05/gm was significantly higher than 2.6±0.43×105 in the undamaged carotid (p<0.01). Platelet uptake on the damaged endothelium, expressed as a percentage of the activity in 1ml of blood, at 55.1±9.8 was also significantly higher than 28.6±6.3 percent on the control artery (p<0.01).This inexpensive model allows the precise measurement of radiolabelled platelet uptake on damaged arterial intima and may therefore be used to evaluate antithrombotic drugs and investigate the role of platelets in arterial repair, intimal hyperplasia and the pathogenesis of atheroma.1. Hawker RJ, Hawker LM, Wilkinson AR. Indium labelled human platelets: Optimal method. Clin Sci 1980; 50: 243-248
ARACHIDONATE METABOLISM IN RAT PLATELETS IN THE PRESENCE OF Ca2+-SUBSTITUTES (Sr2+, BA2+)
Authors: BLACHE D , CIAVATTI M 
Published: August 2018

To further document the involvement of external Ca2+ in the platelet induced-activation process, we have studied the arachidonate (AA) metabolism of intact washed rat platelets in the presence of different concentrations of Ca2+, Sr2+ or Ba2+. The thrombin-induced mobilization of [3H]- or [14C]-AA preincorporated into platelet phospholipids was followed as well as the subsequent formation of labeled cyclooxygenase and lipoxygenase products (CLP). Results indicate that upon thrombin (<0.1 U/ml) stimulation, AA release and CLP formation are reduced by 50 to 90% only by omission of Ca2+ as compared to 1 mM Ca2+ in the suspending medium. In higher Ca2+ concentrations (5 mM), the AA mobilization and CLP formation are inhibited and the data are close to those obtained in the absence of Ca2+. In the presence of Sr2+ or Ba2+, results indicate that these cations can substitute to Ca2+. Similarly to Ca2+, an optimum concentration is found in Sr2+ or Ba2+ (3-5 mM) and higher concentrations inhibit AA release and CLP formation.We have also studied the activity of a semi-purified preparation of phospholipase A2 (PLA2) from rat platelets. This activity was assayed (pH 9) using heat-denaturated (3H)-AA prelabeled phospholipids as substrate. The results show that this PLA2 activity was strongly Ca2+-dependent. We found that unlike Mg2+, Sr2+ and Ba2+ are able to greatly enhance this activity. Relative effiency (Vmax) are in the order Ca2+>Sr2+>Ba2+. Taken together, these findings as well as our previous results (Blache et al, BBA 1987, in press) suggest that external Ca2+ may play a major role in the regulation of rat platelet activity. Our interpretation is in line with the view that Sr2+ or Ba2+ could enter the platelet through a mechanism common to Ca2+ (a kind of Ca2+ channel). Although direct evidence await the results of further studies which are in progress, it can be considered that Sr2+ or Ba2+ might cause platelet induced-activation mimickigci a rise in the cytosolic Ca2+ and subsequent activation of Ca2+-dependent enzymes.
ABNORMAL PLATELET FUNCTION MEASURED IN RELATIVES OF STROKE PATIENTS
Authors: Grotemeyer K-H , Pilawa I , Schlake H P 
Published: August 2018

Platelets are assumed to play a crucical role in stroke. Abnormal reactivity of platelets has been observed in patients suffering from stroke but it seems unclear whether or not this abnormal reactivity represents a basic factor of stroke. If abnormal platelet reactivity is more but a consequence of stroke it should be present before stroke happens.In families with stroke patients stroke is more frequent as usual. In order to obtain more information we determined platelet reactivity in healthy persons with a family history without vascular events and healthy persons with a history showing stroke in the family.Platelet reactivity was measured using a modification ofa platelet test system described by WU and HOAK(1)Platelet-index-value for the 110 healthy persons without history was 0.98 + /- 0.09 and for the 72 healthy relatives of stroke patients 1.18 + /- 0.28 The difference was significant (p<0.01).The results support the hypothesis that increased platelet reactivity may not only be regarded as a consequence of stroke. It may be possible that this increased platelet function may represent a pathogenetic co-factor in ischemic events and in atherosclerosis also.1) Grotemeyer K.-H. et al., DMW (1985) 110, 256
PLATELETS FROM TYPE IIA HYPERCHOLESTEROLEMIC PATIENTS GENERATE MORE INOSITOLPHOSPHATES AFTER THROMBIN STIMULATION IN COMPARISON WITH THOSE OF NORMAL SUBJECTS
Authors: Medini L , Maderna P , Tremoli E , Galli C 
Published: August 2018

Functional and biochemical responses of platelets to stimulating agents have been reported to be amplified in several pathological conditions, including hyperlipidemia. Enhanced aggregation and thromboxane formation are, e.g. frequently observed in the presence of high plasma cholesterol levels (type Ila hypercholesterolemia). Stimulation of phosphoinositides breakdown through specific phosphohydrolases (phospholipase C) resulting in the formation of inositolphosphates (IPs), is one of the early events in platelet activation. A study was thus designed in order to investigate IPs generation in thrombin stimulated platelets from type Ila hypercholesterolemic patients in comparison with a group of normocholesterolemic subjects. Preparation of washed platelets, prelabelling with 2[3H] myo inositol and separation of lipid and water soluble inositides was carried out according to Watson et al (1). Product generation (inositoltrisphosphate, IP3; inositolbisphosphate, IP2; inositol mono phosphate, IP) in relation to the 2[3H) inositol incorporated in phosphoinositides was evaluated at 10 and 90 s after platelet stimulation with 1 U/ml NIH in the presence of 10 mM lithium chloride. The major differences found in platelets from type Ila patients in comparison with those of controls were the following:1) in non stimulated platelets a greater incorporation of myoinositol in phosphoinositides and lower levels of labelled IP2; 2) after stimulation, the levels of all labelled IPs were significantly greater, and those of IP2 were double than in controls. In particular the percent increment of IP2 over basal values in platelets of type Ila patients was more than two fold greater. It is concluded that the enhanced generation of IPs in platelets from type IIa patients, following thrombin stimulation, may contribute to the greater sensitivity to agonists of the aggregatory process in this pathological condition.1) Watson P.S., McConnell R.T. and Lapetina E.G., J. Biol. Chem.21:13199, 1984
DIPYRIDAMOLE INDUCES CHANGES IN THE THROMBOGENIC PROPIERTIES OF ENDOTHELIAL CELL EXTRACELLULAR MATRICES
Authors: Aznar-Salatti J , Escolar G , Almirall L , Ordinas A , Bastida E 
Published: August 2018

Dipyridamole (DIP) is a pirydo-pirymidine drug widely used as an antiplatelet agent.DIP has also been demonstrated to have effects on various cultured cells. We studied platelet reactivity of extracellular matrices (ECMs) produced by untreated (ECM-c) and DIP-treated (ECM-DIP) endothelial cells (ECs).Confluent monolayers of EC were incubated in buffer containing 0 or 10 pM. DIP for 48 h. The ECMs were prepared by removing the EC with 2% EGTA (1 h at 37°C). Platelet deposition onto the ECMs was measured under flow conditions using a flat chamber perfusion model ECM-c and ECM-DIP were exposed for 5 min to whole blood at shear rates of 300 or 1300 sec~1.Then, the perfused ECMs were processed for cross sectional morphometric evaluation using a computer system. The platelet, deposition is expressed as total surface covered with platelets (mean±SEM ) and shown in the table.Platelet aggregate formation on ECM-DIP at 1300 sec-1 was also reduced(by 25%)as measured morphometrically. We conclude that DIP-treatment of EC results in ECM modifications,which in turn decrease ECM-platelet interactions.These data also suggest that pharmacological treatment of the endothelium influences basement membrane reactivity.
THE NEWLY SYNTHESIZED COMPOUND E-5510 IS A HIGHLY POTENT ANTIPLATELET AGENT
Authors: Harada K , Fujimori T , Kogushi M , Kogushi M , Yamatsu I , Ikeda Y 
Published: August 2018

Our newly synthesized compound, 4-cyano-5,5-bis(methoxy-phenyl)-4-pentenoic acid (E-5510) has highly potent antiplatelet activity. In this paper, the effects of E-5510 on platelet functions in vitro and ex vivo in human and in various experimental animals are examined.E-5510 inhibited human platelet aggregation induced by collagen, arachidonate, ADP, PAF and epinephrine (IC50: 1.5, 0.7, 2.0, 1.6 and 1.1 uM, respectively). Thrombin-induced platelet aggregation, which was not inhibited by aspirin and U-53059 (lC50s: 100 uM), was also inhibited by this compound (IC50: 21uM). The IC50 of E-5510 in thrombin-induced ATP secretion fromhuman platelets was only 2 uM. Platelet adhesion to a collagen coated disk, whichwas measured by the method of Buchanan et al (Prost. Leuko. Med., 21, 157, 1986) was inhibited by E-5510 (IC50: 19.3 uM) butnot by aspirin and U-53059. In the PRP ofthe guinea pig, the beagle and the monkey, E-5510 inhibited collagen-induced platelet aggregation in vitro to the same degree as in human PRP(IC50: 1.2, 0.6 and 1.5 uM, respectively). After being administered orally to guinea pigs, E-5510 exhibited extremely potent ex vivo inhibitory effect in collagen-induced platelet aggregation with a very low ED50 of 0.05 mg/kg. In contrast, the ED50’s of ticlopidine, aspirin and U-53059 were 300 , 27.2 and 1.0 mg/kg, respectively. In beagles and monkeys E-5510 also showed ex vivo antiplatelet effects at 0.01 and 0.003 mg/kg, respectively. This effect continued for more than 8 hrs. and disappeared within 24 hrs. The antiplatelet effect in human PRP was highly correlated with that in PRP of experimental animals in which the ex vivo effects were confirmed at a very low dose. Thus, E-5510 will ensure to exert the antiplatelet effect after oral administration to human subjects.In summary, E-5510 is unique among the known antiplatelet agents since it has potent inhibitory effects on thrombin-induced platelet activation and platelet adhesion to collagen. It was also shown that this compound had an ex vivo antiplatelet effect at an extremely low ED50. Our results suggest that E-5510 will be a beneficial agent for antiplatelet therapy in humans.
ANTI-THROMBOTIC EFFECTS OF E-5510 IN EXPERIMENTAL THROMBOSIS MODELS
Authors: Fujimori T , Saeki T , Harada K , Sato M , Ohshima N 
Published: August 2018

A new agent developed in our laboratory, 4-cyano-5,5-bis(4-methoxyphenyl)-4-pentenoic acid (E-5510), suppressed various human platelet functions in vitro. The compound also showed quite potent ex vivo anti-platelet effects in many experimentalanimals. It is well known that anti-platelet effects are not always parallel to anti-thrombotic effects. Thus, in order to predict the efficacy of E-5510 in thrombotic disorders, the anti-thrombotic effects were examined in 3 different animal models of thrombosis.(1) Anti-thrombotic effect in an extracorporeal shunt model Two hrs after oral administration of the drug to guinea pigs,an extracorporeal shunt between the right carotid artery and the left jugular vein was performed. The thrombus formation on a silk thread inserted in the shunt tube was quantitated by measuring the time from the onset of circulation to the stenosis of blood flow. E-5510 dose-dependently inhibited thrombus formation, the minimum effective dose being 0.03 mg/kg.(2) Effect on microthrombus formation in mesenteric arteriole In order to evaluate the effect on intravascular platelet thrombus formation, thrombosis was induced in vivo in mesenteric arteriole in guinea pigs with filtered light from a mercury lamp and an intravenous fluorescent dye in an intravital microscope system (M. Sato and N. Ohshima, Thromb. Res.,35, 319, 1984). The thrombus formation was quantitated by measuring the time taken for circulating platelets to begin to adhere to vessel wall and the time taken for blood flow to stop completely due to fully developed thrombus. Both the time required for platelet adhesion to vessel wall and for platelet thrombus formation were significantly prolonged after oral administration of E-5510.(3) Effect on pulmonary thromboembolism Acute pulmonary thromboembolism was induced in mice by a bolus intravenous injection of arachidonic acid, and mortality was determined 3 min later. E-5510 dose-dependently reduced pulmonary thromboembolic mortality, and its ED50 was 0.11 mg/kg.
The results described above indicate thatE-5510 may have beneficial effects in clinical treatments of thrombotic disease.
EFFECT OF THE CALCIUM CHANNEL BLOCKER, NIFEDIPINE, ON HAEMOSTASIS, CLOTTING, AND THROMBOLYSIS EX VIVO.
Authors: Rademaker M , Meyrick Thomas R H , Kirby J D , Kovaos I B 
Published: August 2018

Nifedipine, as other calcium channel blockers, has been shown to inhibit platelet aggregation induced by various agonists in vitro. The therapeutic relevance of these findings are, however, questionable, as in vitro inhibition of platelet function occurs at plasma concentrations of nifedipine in excess of 50 uM, while the peak plasma concentration following a single 10 mg oral dose of nifedipine is only 0.2 uM. We have used the Haemostatometer, to assess the effect of nifedipine on haemostasis ex vivo. This instrument allows quantitative assessment of haemostasis by monitoring the pattern of haemostatic plug formation (HPF) in holes punched through polyethylene tubing through which non-anticoagulated blood flows under standard conditions (1,2). The pattern and speed of blood coagulation subsequent to HPF was measured as was the spontaneous thrombolysis time (STT) (taken as the time until expulsion of the haemostatic plug from heparinised blood). All values are for mean + SEM.Blood samples were taken from 10 healthy volunteers before and ninety minutes after a single 10 mg oral dose of nifedipine. Following nifedipine, the initial phase of the haemostatic reaction (HPF) was prolonged from 0.95 ± 0.12 min to 1.57 ± 0.14 min, (p< 0.01); clotting time was also increased from 13.1 ± 1.1 min to 20.7 ± 2.3 min, (p=0.013), and the STT fell from 48.0 ± 9.9 min to 27.5 ± 4.6 min (p=0.014).The increased bleeding time (HPF) provides evidence that a therapeutic dose of nifedipine evokes an anti-platelet effect. The prolongation of the clotting time seen in this study could be explained by,an effect of nifedipine on platelets and hence clotting. The mechanism of the enhanced spontaneous thrombolysis following nifedipine is not known.We suggest that the effect of nifedipine on haemostasis and thrombolysis may contribute to its therapeutic effect.(1) Gorog P and Kovacs I B. Haemostasis 16: 337-345, 1986.(2) Gorog P. Angiology 37: 99-105, 1986.
THE INFLUENCE OF SOME HYPOTENSIVE DRUGS ON THE SEROTONERGIC MECHANISMS IN RATS PLATELETS
Authors: Buczko W , Pietraszek M , Chabielska E , Malinowska B 
Published: August 2018

Serotonin (5HT) is a vasoactive amine that has been reported to be involved in a number of forms of circulatory failure. The 5HT content and metabolism in platelets is changed in hypertension and in peripheral arteriolar diseases. The present study concerns the effect of verapamil (VER), propranolol (PRO) and cap-topril (CAP) - drugs having different hypotensive mechanisms of action, on serotonergic mechanisms in rat blood platelets. In vitro, VER produced noncompetitive inhibition of 14C-5HT uptake (IC50=8.2μM), PRO inhibited the uptake in a competitive fashion (Km =0.9μM), whereas CAP was ineffective. Only PRO released (24%) radioactive 5HT from incubated platelets. Inhibition of amine uptake was also obtained when plateletswere prepared from-irats pretreated with VER (10 mg.kg−1 ), PRO (5 mg.kg−1) or CAP (10 mg.kg−1 ). Moreover, the concentration of endogenous 5HT in blood platelets was reduced after VER and PRO administration. Platelets aggregation induced by ADP was inhibited by VER and CAP. They also diminished the potentiating effect of 5HT on ADP-induced platelet aggregation. It can be concluded that these effects may be a secondary mechanism of action in vivo. Thus “serotonergic component” of studied drugs should be taken under consideration at least in therapy of hypertension.Supported by CPBR, no 11.6
EFFECTS OF FEVERFEW EXTRACT AND PARTHENOLIDE ON PLATELET SECRETION.
Authors: Gronewegen W A , Heptinstall S , Loesche W , Spangenberg P 
Published: August 2018

Feverfew (Tanacetum parthenium) is used for prophylaxis of migraine and it had been suggested that the plant may have antithrombotic potential. We have prepared extracts from the leaves of feverfew and have demonstrated inhibition of 14C-5HT secretion in platelet-rich plasma induced by the phorbol ester PMA, l-oleoyl-2-acetyl-sn-glycerol (OAG), arachidonic acid, the thromboxane analogue U46619, adrenaline, collagen and ADP. The effects of a solution of parthenolide (an∝-methylenebutyro-lactone isolated from feverfew) were determined in parallel. Both feverfew extract (FE) and parthenolide inhibited 14C-5HT release in a concentration-dependent manner and the effectiveness depended on the nature of the aggregating agent used. Both FE and parthenolide were most effective as inhibitors of the secretion induced by PMA and OAG. When we compared the concentrations of FE and parthenolide which gave 50% inhibition of secretion for all the agents tested, a good correlation was found (r= 0.936). Further studies showed that feverfew extract and parthenolide inhiMt release of β-thromboglobulin from platelets as well as 14C-5HT. FE did not cause liberation of LDH. Inhibition of secretion by FE appears to be irreversible since washing platelets after treatment did not restore secretory activity.The structure of parthenolide suggests that it can alkylate sulphydryl (SH) groups. When agents containing SH groups (e.g. cysteine) were added to FE, anti-secretory activity was reduced. We also obtained a considerable decrease in the number of acid-soluble SH groups in platelets treated with feverfew extract or parthenolide at concentrations which inhibit secretion. However there was a less marked decrease in the number of acid-insoluble SH groups. FE itself does not induce formation of disulphide-linked proteins but such proteins were formed when platelets were activated in the presence of FE, probably as a result of decreased glutathione levels.We conclude that parthenolide or parthenolide-like compounds are responsible for the anti-secretory effects of FE, and that alkylation of sulphydryl groups in platelets may be involved.
EFFECTS OF INHIBITORS ON COLLAGEN INDUCED PLATELET AGGREGATION IN SIX DIFFERENT SPECIES.
Authors: Jansen J W C M 
Published: August 2018

One approach to the development of antithrombotics is inhibition of platelet aggregation. The pharmacological approach often used is to test compounds on collagen induced platelet aggregation measured in platelet rich plasma. Therefore we have compared inhibitors with different mechanism of action on aggregation of platelets from six different species commonly used in pharmacological studies. Aggregation was induced with submaximal amounts of collagen (Hormone Chemie).Inhibitors of the cyclooxygenase system, aspirin and indomethacin, were very potent in inhibiting aggregation of platelets from humans guinea pig and dog (IC50 20-60 and 1-3 ¼M resp.). Aggregation of pig and rat platelets was poorly inhibited by both of these compounds (IC5: 700-900 ¼M), whereas platelets from mice showed intermediate sensitivety (IC50 ca.100 ¼M).The combined lipoxygenase/cyclooxygenase inhibitor BW755C, was extremely active on platelets of guinea pig (IC50 1 ¼M) and was poorly active in mice platelets (IC50 300 ¼M). In the other species the inhibitory activity ranged from 20-80 ¼M.The phosphodiesterase inhibitors, papaverine and BL3459 inhibited aggregation in all species (IC50 50-100 and 1-5 ¼M resp.). Dipyridamole inhibited aggregation also in all species but with lower activity (IC50 > 100 ¼M).Conclusion: remarkable species differences are present with respect to inhibition of collagen induced platelet aggregation by the various compounds e.g. rat and porcine platelet aggregation was hardly inhibited by cyclooxygenase inhibitors. The effects of the compounds on human platelets are comparable to the effects on canine plateletes.
INHIBITION OF THE THROMBOPENIC EFFECT OF ELLAGIC ACID BY PCR 4099, AN ANTIAGGRGATING AGENT, IN RATS.
Authors: DAMAS J , GREGG V , REMACLE-VOLON G 
Published: August 2018

In the rat, intravenous injection of large doses (30 mg/Kg) of ellagic acid (EA) induced a decrease in the plasma level of fibrinogen and in the blood platelet content and an increase of the activated partial thromboplastin time. EA induced the accumulation of Crs1-labelled platelets into the lung and the liver accompanied by a 64% fall in Cr51 blood radioactivity.The long-lasting thrombocytopenia induced by EA was inhibited by heparin (4 mg/Kg), defibrase (20 U/Kg), and clocoumarol (4 mg/Kg). It was not inhibited by aspirin (90 mg/Kg), indomethacin (8 mg/Kg) and ketoprofen (4-10 mg/Kg). The thrombocytopenia would depend on an intravascular coagulation.Using this model of platelet stimulation, we studied the protective effect of PCR 4099. This drug was first given as a single dose, orally four hours before the injection of EA. It reduced the thrombocytopenia for 10 mg/Kg and suppressed it for 40 mg/Kg. The thrombocytopenia was also inhibited by 3 day oral administration of PCR 4099 4 mg/Kg. PCR 4099 is thus a potent inhibitor of this kind of platelet stimulation.
MICROEMBOLISATION DURING SURGICAL SHOCK: EFFECT OF PROSTAGLANDIN E1
Authors: Poskitt K R , Irwin J T C , Backhouse C M , McCollum C N 
Published: August 2018

Embolisation of microaggregates following major surgery may be a cause of pulmonary arterio-venous shunt and postoperative respiratory failure (1). Prostaglandin E1 may prevent intravascular aggregation and we studied this possibility in a pig model of surgical shock.Following autologous platelet labelling with Indium, 16 pigs (20-30kg) were randomised to receive a perioperative infusion of PGE1 (100ng/kg/min) or placebo. Arterial and Swann Ganz catheters were inserted under anaesthesia prior to surgery consisting of midline laparotomy, exteriorisation of small bowel 1.5 hours of aortic clamping and 1 hour of hypotension. On induction, during shock and at 3 days in survivors platelet and leucocyte count, blood radioactivity, venous aggregates (SFP), lung platelet uptake (LPU), pulmonary vascular resistance (PVR) and alveolar-arterial p02 difference (A-ad02) were measured.All results mean ± sem *p <0.05 Mann Whitney U-testDuring surgical shock, the formation of venous aggregates, the fall in circulating radiolabelled platelets and their accumulation in lungs were reduced by PGE1 (p< 0.05). BP, CVP and PWP were all lower on PGE1 and at 3 days the improvement in A-ad02 in PGE1 pigs failed to reach significance.PGE1 reduced platelet aggregate formation and their subsequent pulmonary microembolisation despite worsening shock due to vasodilation.1. McCollum CN, Campbell IT. The value of measuring intravascular platelet aggregation in the prediction of postoperative pulmonary dysfunction. Br J Surg 1979: 66; 703-707