bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE PLATELET “REBOUND-PHENOMENON” DURING PROLONGED, CONTINUOUS PGI2 INFUSION OCCURS AT THE RECEPTOR LEVEL
Authors: Steurer G , Sinzinger H , Fitscha P 
Published: August 2018

During earlier attempts in optimizing the therapeutic regimen with PGI2 we were able to discover an “ intra- and post-infusion platelet rebound” being characterized by an activated platelet function and a diminished responsiveness of platelets to the action of PGI2 in-vitro.In order to verify this phenomenon at the receptor level we infused continuously 6 patients suffering from peripheral vascular disease (PVD) with PGI2 at a rate of 5 ng/kg/min for 5 days. Anticoagulated venous blood has been drawn at different intervals. Saturation binding experiments on platelet membrane fraction have been performed using [3H]iloprost, a stable PGI2 analoque. Analysis of the binding data according to Scatchard demonstrated a decrease of receptor affinity with an increased number of binding sites.It is concluded, that intrainfusion rebound occurs at the receptor level, whereas the postinfusion rebound does not. This is a further piece of evidence that an intermittent infusion regimen is preferable.
REVERSIBLE REDUCTION OF PLATELET PROSTACYCLIN BINDING SITES AFTER ILOPROST INFUSION IN MAN.
Authors: Modesti P A , Fortini A , Boddi M , Poggesi L , Abbate R , Gensini G F 
Published: August 2018

The reduction of platelet sensitivity to prostacyclin (PGI2), observed in man after the infusion of PGI2 analogues, could suggest the presence of a down regulation mechanism for PGI2 platelet receptors. Robertson (1980) have shown a dcwn-regulaticn of PGE2 binding after PGE2 infusion in rat and Leigfrt (1985) have provided evidence of an homologous desensitizaticn to PGI2 in cultured cells, but direct evidences of PGI2 receptors dcwn-regulaticn in man are lacking.This work was performed to study the behaviour of PGI2 platelet receptors after a PGE2 analogue infusion in man.Eight subjects with peripheral artery disease (stage IV according to Fontaine) treated for 14 consecutive days with six hours iv infusion of Iloprost (Sobering, FRG) at 2 ng/Kg/min were studied. Platelet studies were performed an the 1st, 2nd, 7th and 14th day of therapy, blood sanples being collected immediately before the beginning (between 8.00 and 9.00 a.m.), at the end and 6 and 18 hours (the following morning) after the end of the infusion. PGI2 platelet receptors were investigated by a direct radioligand binding assay. PGI2 inhibitory dose 50 (I.D.50) was evaluated in platelet aggregation induced by ADP 5 ¼M.After six hours of Iloprost infusion a significant reduction of high affinity PGI2 platelet receptor (HAR) nunber was observed (p<0.005) without any change of affinity for the ligand. After 6 hours from the end of the infusion the reduction of the HAR was still statistically significant (p<0.05). The following morning the receptor nunber was restored (n.s.). After one and two weeks from the beginning of the treatment the basal values of PGI2 HAR were not significantly changed from the values recorded on the first day of therapy.PGI2 I.D.50 after the infusion was significantly increased when compared to the basal values (p<0.01). Six hours later the basal sensitivity was restored (n.s.). Eighteen hours later, the following morning PGI2 I.D.50 were still not significantly changed in comparison to the basal values.These data are suggestive for the presence of a reversible down regulation mechanism for the PGI2 receptors.
INHIBITION OF GUINEA-PIG PLATELET FUNCTION IN VIVO AND EX VIVO USING THE THROMBOXANE A2 ANTAGONISTS, AH23848 AND GR32191
Authors: McCabe P J , Stratton L E , Hornby E J , Foster M 
Published: August 2018

The thromboxane A2 antagonist, GR32191 (Lumley et al., this meeting) was tested as an inhibitor of platelet aggregation in the guinea-pig and compared with another Tx-antagonist, AH23848 (Brittain et al, 1985). Guinea-pigs were dosed with AH23848 or GR32191 at 0.01-1.0mg/kg. At intervals, blood was taken and PRP was prepared for ex vivo aggregation studies. Collagen concentrations causing half maximal aggregation (IC50) were calculated for test and vehicle-dosed groups. Inhibition was expressed as a concentration ratio (IC50 test/IC50 vehicle). For in vivo studies, 111In-labelled platelets (12μCi, 200μl) were injected into anaesthetised guinea-pigs and 24 hrs later oral doses of AH23848 or GR32191 (0.01-1.0mg/kg) or indomethacin (5mg/kg) were given. After one hour, blood was taken for platelet and radioactivity counting. The carotid artery was exposed under anaesthesia and a current of 2mA was applied for 60 sec. After 90 min, 1cm of the damaged and contralateral carotid vessels were removed for gamma-counting. Inhibition of accumulation of platelets on the injured artery was measured by comparison with the undamaged contralateral artery. Numbers of platelets deposited were calculated from the radioactivity of each section of artery and the radioactivity and platelet count in the blood. Oral doses of AH23848 or GR32191 inhibited ex vivo platelet aggregation induced by collagen. Maximum inhibition occurred one hour after dosing, and was still present at 6 hours for AH23848 (l.Omg/kg) and GR32191 (0.3mg/kg). GR32191 and AH23848 were active in vivo causing inhibition of platelet deposition at doses of 0.01-lmg/kg. The maximum inhibition of deposition was 58% for AH23848 (0.1mg/kg) and 63% for GR32191 (0.1mg/kg), with 50% inhibition at 0.02mg/kg for both. Indomethacin (5mg/kg p.o.) caused maximum inhibition of 58% at 5mg/kg p.o. suggesting that this represents the total thromboxane involvement in platelet deposition. GR32191 and AH23848 are thromboxane A2 antagonists with antithrombotic activity after oral dosing to guinea-pigs.Brittain R.T. et al Circulation, 72, 1208-1218, 1985.
SERENDIPITOUS PROTECTION FROM PLATELET-MEDIATED DISORDERS IN STEROID-TREATED PATIENTS?
Authors: Holloway H , Moriarty A J , Nelson S D , Balnave K 
Published: August 2018

The aim of this study is to investigate the influence of exogenous corticosteroids on platelet aggregation. This is widely recognised to be of significance in the pathogenesis of acute myocardial infarction and other vascular/haematological disorders.Blood was taken from a cohort of patients (N = 10) undergoing treatment with ACTH or corticosteroids for varied systemic illness. Ex vivo measurements of platelet parameters were made with a Coulter Counter Model S Plus III on nonanticoagulated blood directly from the circulation. Subsequently, aliquots of anticoagulated blood in batches of five were processed at intervals over 24 hours. For comparison, a similar study was undertaken in normal volunteers not on any medication. The mean percentage changes ± standard deviations over the 24 hour interval in platelet count (PLT), mean platelet volume (MPV) and plateletcrit or biomass (PCT) in the respective groups were as follows:-PLT: -(3.12 ± 2.68) vs -(14.77 ± 3.96)(p < 0.001);MPV: 28.88±8.92 vs 46.68±12.54 (p <0.01);PCT: 25.18 ± 8.16 vs 23.75 ± 8.97 (NS).The in vitro alteration in PCT over 24 hours in both cohorts is similar and is due to platelet swelling. The change in MPV is partly due to swelling and partly due to aggregation as evidenced by the decrease in PLT. The significantly smaller drop in PLT and smaller rise in MPV in the steroid-treated group clearly demonstrate that platelets from these patients are less aggregable. A possible cause is that the inhibitory effect of steroids on phospholipase may lead to reduced levels of thromboxane A2. Thus patients on steroid therapy or with high endogenous steroid levels may enjoy serendipitous protection from a variety of platelet mediated disorders. The work may also explain in part why such patients are more prone to bleeding diatheses.
CHILDHOOD HEMOLYTIC UREMIC SYNDROME (HUS) : VON WILLEBRAND FACTOR (vWF) AND PLATELET AGGREGATING ACTIVITY (PAA) STUDIES
Authors: SCHLEGEL N , MOAKE J , LOIRAT C , HURTAUD M F , LEVY-TOLEDANO S , MATHIEU H 
Published: August 2018

It has been suggested that a vWF High Molecular Weight Multi-mers (HMWM) decrease or a PAA were involved in the pathogenesis of HUS. We have studied 8 children (6 girls,_2 boys; 7 months-8_1/2 years old) with HUS : plasma creatinine /μmol/l; mean(range)/=306 (105-524), hemoglobin (g/100ml)-7(6.3-7.8), schistocytes (%)=8(1-18), platelets (x103/mm3)-57(10-115). The vWF was studied quantitatively (antigen ; vWF RAg assay) and qualitatively (multimeric pattern : immunoblotting and autoradiography). PAA studied by incubating the patient's platelet poor plasma (RPR) with washed normal platelets (aggregometer, % light transmission) and confirmed by Thromboxane B2 (TXB2) assay and [14C] Serotonine release study. The PAA was characterized by studying the in vitro effect of several platelet aggregation inhibitors, Immunoglobulins (Igs) and Fresh Frozen Plasma (FFP) on the platelet aggregation.An increase of vWF RAg (%) was observed in 6 cases : mean:330, and possibly related with renal failure. A vWF HMWM decrease was found in 3 patients : 2/3 with associated infection(E.Coli, Pneumococcus), 1/3 with severe hemolysis. Two of these 3 patients had a favourable renal outcome and 1 a severe course (chronic hemodialysis, Arterial Thrombotic MicroAngiopathy at renal histology).An important PAA was evidenced only in 1 patient : post bone-marrow graft HUS during neuroblastoma(NB),arterial hypertension and chronic renal failure. This PAA was Ca++, TXB2 and cAMP dependent; it was moderately inhibited in vitro by Igs and FFP, but persisted after 5 days of Igs infusion (0.3g/Kg/day). Treatment with aspirin and dipyridamole (10mg/Kg/day each) suppressed the patient platelet auto-aggregation although the PAA persisted (follow up:10months). The PAA did not seem to be related with the NB (absence of GD2 ganglioside, specific marker of NB); it could be related with anti platelet antibodies. The coexistence of the two abnormalities could not be demonstrated in our patients.In conclusion, a vWF HMWM decrease was found in 3 out of 8 children patients with HUS. Its presence was not correlated with the severity of the disease. We could demonstrate the presence of PAA during childhood HUS in only 1 post bone-marrow graft case. The PAA characterization is useful for therapeutic decisions and contributes to a better pathogenetic understanding.
PLATELET DEPOSITION AFTER CAROTID ENDARTERECTOMY DECREASES WITH TIME.
Authors: Meek A C , Jarvis P , Backhouse C M , McCollum CN , Greenhalgh RM 
Published: August 2018

Platelets are deposited on the exposed media following carotid endarterectomy and will continue to accumulate until neointima covers this thrombogenic surface. Radiolabelled platelet uptake was measured to assess the time to intimal repair.Autologous llllndium labelled platelets were infused 2 days and 2 months postoperatively in 10 patients undergoing unilateral carotid endarterectomy. Platelet accumulation was measured daily by gamma camera images counting radioactivity over the operated artery and comparing it to the contralateral side as Carotid Uptake Ratio (CUR).Mean (±sem) counts per gamma camera cell over the operated side at 24 hours were 46.3± 4.3 compared to 38.6± 3.9 on the unoperated side (p<0.001). At 2 months this difference had disappeared with counts of 38.8± 3.2 and 39.1± 3.2 over the operated and reference arteries respectively. Early postoperative CUR at 1.22± 0.04 was significantly higher than 1.01± 0.06 at 2 months which equates to no radiolabelled platelet uptake (p< 0.01). Radioiabellea platelet uptake was visible on 8 of the 10 early scans, but this was seen in only 2 patients at 2 months, both of whom had a persistently high CUR indicating continued platelet accumulation at that time.Early postoperative platelet deposition decreases in the weeks following carotid endarterectomy presumably due to the development of a neointima. Those cases with persistently high platelet accumulation may have luminal thrombus which could lead intimal hyperplasia and restenosis.
PLATELET-ACTIVATING FACTOR (PAF)-INDUCED INTRACELLULAR Ca MOBILIZATION IN HUMAN PLATELETS.
Authors: Matsuno K , Katabami F , Koyama M , Abe K , Sakurada K , Miyazaki T , Ozasa S , Saitoh H , Maekawa I , Matsumiya H 
Published: August 2018

PAF-induced intracellular Ca2+ mobilization and platelet aggregation were investigated in human platelets. Cytosolic free Ca2+ concentration ([Ca2+]cyt) was measured by using fluorescent 45Ca2+ probe quin2 and fura-2, and photoprotein aequorin. Ca2+ uptake was measured after stimulation by PAF. Platelet aggregation was studied by recording the change in light transmission with platelet rich plasma (PRP) or washed platelet suspension (WPS).These three Ca2+ -indicators could determine the elevation of [Ca2+ ]cyt that was stimulated by PAF in the presence of extra- cellular Ca2+ (quin2 method: 98.2nM to 289.7nM; fura-2 method: 102.OnM to 351.4nM; aequorin method: 4.1μM to 8.2μM). In the absence of extracellular Ca2+ , however, little elevation of [Ca2+ ]cyt was detected after stimulation by PAF. PAF could evoke the transient Ca2+ uptake.New PAF specific antagonist, ONO-6240 inhibited PAF-induced platelet aggregation at a concentration from lμM dose-dependently, whereas it didn’t inhibit collagen- and thrombin-induced platelet aggregation at a concentration of lOOyM. ONO-6240 inhibited PAF- induced increase in [Ca2+ ]cyt in a dose-dependent manner as deter mined by these Ca2+ -indicators, as well as platelet aggregation.These results suggest the increase in [Ca2+ ]cyt is responsible for platelet aggregation induced by PAF, and the increased Ca2+ is derived from external Ca2+ influx chiefly.
IS IT POSSIBLE TO IDENTIFY HUMAN PLATELETS IN VITRO AS BEING DESENSITIZED TO PLATELET ACTIVATING FACTOR (PAF-ACETHER,PAF) IN VIVO?
Authors: Perger Cs , von Felten A 
Published: August 2018

PAF is suggested to be of pathophysiological importance in a variety of diseases. Since platelets exhibit a reduced sensitivity to PAF after a contact with this agent, this behavior may be used as indicator of PAF released into the circulation. In extrinsic asthma, platelets show a diminished reaction to PAF after exposition of the patients to the antigen compared to their own platelets before exposition (Beer and von Felten, Adv. Inflamm. Res. 10:323,1986). We were therefore looking for a test system indicating directly whether platelets had been in contact with PAF.Preparation of PAF-desensitized platelets: Citrated PRP was placed in a cuvette of an aggregometer, and PAF was added in 10 portions at intervals of 10 sec (37oc, constant stirring) to a final concentration of 10 to 100 nM, depending on the individual sensitivity of each platelet preparation. Therby, only a minimal, completely reversible aggregation was registered without any release of serotonin (ST) or 3-thromboglobulin (BTG). Control platelets were pretreated with buffer instead of PAF. Both platelets preparations were kept at 37°C for 45 min. Whereas control platelets showed a secondary aggregation to PAF (5x conc. used for desensitization), PAF-pretreated piatelets were only reversibly aggregated.Sensitivity of PAF-desensitized and control platelets to other platelet agonists: No difference in aggregation, ST-or BTG-relea-se was observed after stimulation with several concentrations of ADP, collagen and arachidonate (p>0.05,n= 41).Binding of 3H-PAF to platelets: PAF-desensitized and control platelets were separated from plasma by filtration through sepharose CL-2B (Pharmacia) in hepes-buffered Tyrode’s solution. After incubation with 3H-PAF, platelets were washed on Whatman 934-AH filters (vacuum filtration). On desensitized and control platelets, we found 175±48 (mean±sd) and 231±70 3H-PAF molecules / platelet respectively after incubation with 5 nM ^h-PAF, 399±36 and 504±66 ^H-PAF molecules / platelet after incubation with 20 nM. In spite of a statistically significant reduction of PAF-binding after desensitization (p<0.01),the variability of PAF-binding between platelets of different individuals is too high to allow a discrimination of normal from PAF-desensitized platelets.
THE PROFILE OF IN VIVO PLATELET ACTIVATION IN NOCTURNAL ASTHMA
Authors: Morrison J EJ , Latif A B , Mason C , Bramley P , Criag T R 
Published: August 2018

The precise pathophysiology of nocturnal asthma still remains to be elucidated. Activated platelets have the ability to release potent broncho- and vaso-constrictors and therefore, have been implicated in asthma. However, there is no information on the status of in vivo platelet activation in patients with nocturnal asthmaIn a randomised controlled study five healthy volunteers and five asthmatics were investigated during a period of 24h after acclimatisation for one day. Both peak flow rate (PFR) and blood samples were obtained at 4 hourly intervals. Plasma levels of platelet factor 4 (PF4) and beta- thromboglobulin(BTG) were measured by radioimmunoassay and adrenaline (A), noradrenaline (NA) and dopamine (DOP) by radioenzymatic analysis.PFR (1/min) for the 24h period was significantly lower in asthmatics (401±15SEM, P<0.001) than in controls (598+4SEM) with an apparent circadian rhythm peak (442±73, P<0.05 Wilcoxon's test) at 4.00pm only in asthmatics. Although there was no significant differences in either PF4 and BTG (ng/ml) or A, NA and DOP (nmol/1) between asthmatics and controls an apparent circadian rhythm in all of these parameters was demonstrated in both groups. Peak values (mean+SEM) for PF4 (8.9±1.5) and BTG (44.4±3.8) occurred at 8.00am whereas the highest values for the catecholamines (A: 0.36±0.08, NA: 1.75±0.23, DOP: 0.78±0.16) were observed at 4.00pm indicating a lag of 8h between the peaks for catecholamines and the platelet specific proteinsThese initial data demonstrate a clear difference in PFR between asthmatics and controls which is apparently not associated with changes in either PF4 or BTG but which may concur with circadian changes in plasma levels of catecholamines at least in asthmatic patients. Thus, in vivo platelet activation is probably not a contributing factor in nocturnal asthma. Finally, the phase lag between peak plasma levels of platelet proteins and catecholamines requires further investigation
DIFFERENTIAL NEUTRALIZATION OF UNFRACTIONATED HEPARIN (UH) AND LOW MOLECULAR WEIGHT HEPARINS (LMWHS) BY HUMAN PLATELET FACTOR FOUR (PF-4)
Authors: Racanelli A , Fareed J 
Published: August 2018

Platelet factor 4 neutralization profiles of four newly developed LMWHs, PK 10169 (Pharmuka, Gennevilliers, France)
CY 216 (Choay, Paris, France), KABI 2165 (KabiVitrum, Stockholm, Sweden), OP 2123 (Opocrin, Corlo Italy) and an unfractionated porcine mucosal heparin were studied utilizing amidolytic (anti-factor Xa, anti-factor Ila) and clot based (APTT, Heptest ) assays. The neutralization studies were carried out in normal human pooled plasma in two experimental protocolsIn one set of experiments, PF-4 (10μg/ml) was added to varying amounts of UH or LMWH (10-2.5 μg/ml). In the second set of experiments, the concentration of heparins was fixed at 5 μg/ml and varying amounts of PF-4(10-2.5 μg/ml) were added. The relative neutralization profiles of these heparins were assay dependant. The anticoagulant effects of UH and LMWHs as measured by APTT were equally neutralizable. Similarly the anti-factor Ila actions of both UH and LMWH were effectively neutralized, whereas the anti-factor Xa activity of the LMWHs was less neutralizable than the UH. Different levels of residual anti-Xa activity of the LMWHs were seen whereas the UH was effectively neutralized. Interestingly, although the anti Xa activity of the UH and Kabi 2165 as measured by amidolytic and clot based methods were similiar and more potent than the other LMWHs, however there were differences between their PF-4 neutralization profile. At a gravimetric ratio of 2:1 , the anti Xa activity of the UH was completely neutralized whereas the Kabi 2165 was least neutralized of all of the LMWHs. The slope of the PF-4 titration curves in the anti-factor Xa assays for all of the LMWHs were similar and varied significantly from the UH. PF-4 neutralization of UH and LMWHs was not dependant on the molecular weight or pharmacopoeial potency (USP or antifactor Xa). These results show that UH and LMWHs exhibit a dissociation between the anti-factor Xa and anti-factor Ila neutralization which may contribute to their sustained antithrombotic effects.
THE INTERACTION OF BLOOD ELEMENTS WITH ENDOCARDIAL ENDOTHELIUM DAMAGED BY LACTIC ACID
Authors: Carter G , Gavin B J 
Published: August 2018

It has already been demonstrated that ischaemic metabolites, which could diffuse frcm a myocardial infarct in vivo, can cause substantial damage to the endocardial endotheliun and this could predispose to mural thrombosis.To investigate the role of ischaemic metabolites in the pathogenesis of mural thrombosis, lactic acid (pH6.4) was passed through a two-way concentric catheter ligated into the left ventricle of isolated beating rat hearts that were perfused with oxygenated Krebs-Henseleit buffer (KHB) through an aortic cannula. After periods of 1, 2, and 4 hours, the lactic acid was followed for 10 minutes by 10 mis of whole blood from hepa-rinized donor rats. Ventricles were then flushed with KHB, fixed in 2.5% glutaraldehyde and post-fixed in 1% osmium tetrox-ide in cacodylate buffer.Scanning and transmission electron microscopy showed that platelets adhered to exposed basal lamina, microfibrils and collagen but not to intact or damaged endothelial cells. However densely aggregated thrombi only farmed on regions of exposed connective tissue and never on basal lamina. Fibrin, leukocytes and red blood cells were associated with these platelet thrombi. Thus lactic acid and other ischaemic metabolites which could possibly diffuse in vivo from an infarct can contribute to endocardial damage which predisposes to mural thrombosis.
THROMBOGENICITY OF THE VESSEL WALL AFTER SINGLE AND REPEATED INJURY
Authors: Pasche B , Swedenborg J , Ljungqvist A 
Published: August 2018

Departments of Experimental Surgery and Pathology, Karolinska HospitalStockholm, Sweden Injury to the endothelial lining of the vessel wall gives rise to increased thrombogenicity but fibrin formation is only seen after repeated injuryThe purpose of the present study was to simultaneously study the appearance of thrombin enzymatic activity and morphological changes on the injured vascular surface after primary and repeated injury. Endothelial injury was caused by balloon catheter in rabbits. The animals were sacrificed and the aorta was excised, inverted and mounted on a plastic rod. Thrombin enzymatic activity was measured on the surface by exposing it to either a chromo-genic substrate (thrombin$) or fibrinogen (thrombinp). In the latter case generation of fibrinopeptide (FPA) was measured. Standard light microscopic procedures were also performed After injury no endothelial cells were seen. Thickening of the internal elastic lamina and accumulation of granulocytes and platelets was also noted. Thrombin^ and thrombinp was detected on the surface. One week after injury the vessel wall had healed but the endothelial . cells were metachromatic and had numerable mitoses. No thrombin activity exceeding the control was seen. After repeated injury thrombins and thrombinp were again demonstrated but the fraction constituting thrombinp was larger than after primary injury. Microscopy at this time showed severe changes including vacuolisationThe capacity of the surface to inhibit thrombin in vitro was also studied and it was found that this capacity was lower after repeated injury particularly in the case of thrombinpIt is concluded that injury of the endothelium gives rise to appearance of thrombin enzymatic activity. After repeated injury proportionally more thrombinp is found, which may explain why fibrinogen is more easily demonstrated on the surface after repeated injury