bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heparin Effects (And Mechanisms) In The α2-Antithrombin Inactivation Of Serine Proteases--Thrombin, Plasmin, And Trypsin
Authors: Smith Gerald F , Sundboom Jacqueline L 
Published: July 2018

It is important to elucidate the effects of heparin on the α2-antithrombin (ATIII) inactivation of serine proteases in order to understand the pharmacological activity of heparin. We have studied the enzyme kinetics of the ATIII inactivation of these proteases, and the effects of heparin on these interactions, using a common amide peptide substrate and protein substrates. We also studied the interactions of heparin with the three proteases.We conclude that the mechanism of the catalytic effect of heparin (observed at 0. 005 unit/ml) toward the thrombin- ATIII reaction is different from the mechanism whereby heparin (only at very high concentration, e.g., 10 unit/ml) can induce an enhanced rate in the plasmin-ATIII reaction. We conclude that the first mechanism involves a heparinthrombin complex, while the mechanism with plasmin involves a heparin-ATIII complex which forms only at high heparin concentrations. This is consistent with known appropriate binding constants. We found that heparin has no effect on the very rapid inactivation of trypsin by ATIII. We further conclude that there is no common mechanism whereby clinically relevant levels of heparin cause general enhanced ATIII-protease reaction rates.We suggest ATIII depletion during heparin therapy might be avoided by using low heparin levels, which would not allow heparin-ATIII complexes to form, yet which would catalyze the thrombin-ATIII reaction. Our finding that ATIII inactivates trypsin at a rate similar to the heparin-catalyzed thrombin-ATIII reaction suggests a physiological role for ATIII in the control of trypsin-like enzymes.
Carrier Detection Of Haemophilia A In Pregnancy By Measurement Of Factor VIIIc/Rag And VIIICAg/RAg Ratios
Authors: Mibashan R S , Peake I R , Newcombe R G , Thumpston J K , Gorer R K , Furlong R A , Rodeck C H 
Published: July 2018

The 1977 WHO Memorandum on carrier detection highlighted the need to test the methods in pregnancy, when plasma modalities of facor VIII are augmented. At KCH blood was taken into citrate from 21 pregnant obligate carriers of severe haemophilia A and 28 pregnant women from unaffected families, matched for age and period of gestation. The women, who were basal after a night’s rest, were tested prior to prenatal diagnosis of haemophilia or other conditions, or to undergoing termination of pregnancy for unrelated causes.One-stage factor VIIIC assays were done immediately; VIIIRAg (Laurell) after -40°C storage within 6 days; and VIIICAg immunoradiometrically in Cardiff on the remainder after varying intervals. Careful standardization was ensured between both laboratories.At 17-22 weeks, VIIIRAg was elevated both in pregnant controls & carriers]; VIIIC & VIIICAg levels were also raised, though less, in the controls (values in units/dl)In pregnant carriers, VIIIC & VIIICAg are both lower than VIIIRAg (p<0.001). Likelihood ratios of carrier probability were plotted by the unequal variances predictive method: VIIIC/RAg discriminated much better between carriers & controls than VIIICAg/RAg, due to the wider spread of VIIICAg in each group, and unlike the findings in a related study of non-pregnant haemophilia A carriers.
Assessment Of Venous Function After Major Gynecological Surgery With Heparin-Dihydroergotamine In The Prophylaxis Of DVT
Authors: Kunz S , Burth O M , Zimmerer E 
Published: July 2018

Dihydroergotamine (DHE) has been shown to have synergistic effects with heparin in the prophylaxis of DVT. To assess the hemodynamic efficacy of DHE in clinical conditions, 72 patients undergoing hysterectomy were randomly allocated to three groups receiving heparin/DHE, heparin or acenocoumarol. Venous function was measured by occlusion plethysmography and doppler ultrasonography. Diagnosis of DVT by 125-I-fibrinogen test.Results: Doppler Ultrasonography: The velocity of venous flow in the left V. femoralis was lower than at the right side in all groups before hysterectomy. After surgery, a significant increase from 11.2 to 15.5 cm/sec in the heparin/DHE group could be demonstrated. Heparin and acenocoumarol patients showed a tendency to lower venous return. The differences were more marked in women with vaginal hysterectomy.Occlusion plethysmography: No differences in venous capacity before and after operation could be found in the heparin and acenocoumarol group. A significant reduction (16%) was measured in heparin/DHE treated patients. The maximal venous outflow also was significantly reduced in this group (18%). This difference also was found in patients with varicose veins.Conclusions: The data confirm that DHE increases the velocity of venous blood flow in the legs by constricting the capacitance vessels. This haemodynamic effect could be demonstrated in clinical conditions.
Extracranial Carotid Artery Disease Assessed By Indium-111 Labelled Platelets In Man
Authors: Goldman M , Simpson D , Hawker R J , Drolc Z , McCollum C N 
Published: July 2018

Platelet microemboli have been implicated in the aetiology of transient ischaemic attacks and strokes. Current non-invasive diagnostic methods are restricted to assessing blood flow. Arteriography may demonstrate non-occluding atheromatous ulcers but carries a significant morbidity.111-In labelled platelets and gamma camera imaging of diseased carotid vessels have therefore been evaluated.Eight patients proceeding to unilateral carotid endarterectomy received an injection of autologous platelets labelled with 111-In-oxine 48 hours preoperatively. Gamma camera images were taken at 4 and 24 hours. Operative endarterectomy specimens were collected and gamma emissions were measured.The scintigraphic images were independently assessed by two observers. Nine abnormal vessels were identified by platelet accumulation. In 5 cases the observers combined assessment was in complete accord with previous bilateral angiography. Individually each observer identified the symptomatic side in 6 patients. Activity in the endarterectomy specimens measured ex vivo varied from 1.22-84.5 times greater than background activity. The ratio of specimen activity to 5 ml blood samples simultaneously taken varied from 0.017 to 0.360 (mean 0.089).This non-invasive technique allows localisation of platelet activity in the extracranial cerebral circulation. Objective assessment in vivo is hindered by the relatively small amount of activity on the diseased vessels by comparison with circulating blood activity.
Platelet Aggregation Induced In Vivo By Heparin And Heparin Fractions
Authors: Silane M , Lindon J N , Ransil B J , Rosenberg R D , Salzman E W 
Published: July 2018

As we have reported, heparin-induced platelet aggregation in vitro varies among heparin subfractions, being generally less with lower molecular weights and having a reciprocal relationship with antithrombin affinity.We now have studied heparin-induced platelet aggregates in vivo by the technique of Wu and Hoak using arterial blood from unanesthetized rabbits. Porcine mucosal heparin was fractionated by gel filtration into high molecular weight (ave. 15,000 Daltons) or low molecular weight (ave. 6,000 Daltons) preparations. IV administration of commercial porcine mucosal heparin (spec. act. 150 u/mg) or high (spec. act. 183 u/mg) or low (spec. act. 208 u/mg) molecular weight fractions was followed by an increase in the platelet aggregate ratio compared with preinjection control values. The rise in platelet aggregate ratio with heparin was significantly different from the effect of a saline placebo (n=8) but was not significantly different among rabbits receiving the commercial heparin (n=9) or the high (n=8) or low (n=8) molecular weight preparations. Peak rise in circulating aggregate ratio occurred 2 minutes after the injection, and values returned to control levels within 15 to 30 minutes. There was no change in platelet count in blood collected in EDTA, suggesting that the aggregates were not removed from the circulation in vivo.Heparin fractions of low molecular weight were further separated according to antithrombin affinity by an antithrombin binding technique. In 8 rabbits low molecular weight/high antithrombin affinity heparin (spec. act. 480 u/mg) did not cause formation of platelet aggregates. The results were significantly different from those with commercial heparin (p=0.05) or with the other heparin fractions (p=0.06).Clinical use of low molecular weight heparin of high antithrombin affinity may lead to fewer heparin-induced platelet effects and to an improvement in anticoagulant therapy.
Effect Of Prostaglandin E1 On “Inflammatory” Or “Ischemic” Skin Ulcer In The Patients With Peripheral Vascular Disease
Authors: Tohjima T , Uehara N , Sawada K , Tsuda Y , Sakai K , Funayama H , Shiokawa Y 
Published: July 2018

Clinical, physiological and biochemical studies of PG E1 treatment were done, in a series of 7 collagen disease patients with “inflammatory” skin ulcer and 5 diabetics with ischemic ulcers or apical gangrene of toes. Intravenous infusions of prostaglandin (PG)EL was given continuously in the dose of lng/kg/min for 72 hours. Blood samples were collected from cubital vein, before, during, right after, and at 7 days after PG E1 therapy. Platelet aggregations induced by ADP collagen epinephrine were evaluated by light transmittance. Platelet iPG E(immuno-reactive PG E like material) levels were measured by radioimmunoassay. Essential fatty acid compositions of plasma, platelet, and red cell were analyzed by gas chromatography.Results were as follows: 1. In all of cases, complete or almost complete healing of skin ulcers or abolition of the pain were noted. 2. Skin temperature was elevated during PG E1 treatment. 3. The platelet basal iPG E levels were significantly decreased by PG E1 treatment(p<0.025). 4. The plasma and platelet linoleic acid levels were significantly higher than before the treatment plasma: p<0.05, platelet: p<0.025). 5. In most cases, platelet aggregation was increased during PG E1 treatment than before.Conclusion: Dramatic therapeutic effects of PG E1 were observed on “inflammatory” or “ischemic” skin ulcer in patients with peripheral vascular disease. This effect might be resulted from improvement of PG metabolism abnormality in the platelet etc. Platelet aggregation in vitro may dissociate from the results in vivo.
Production Of Thromboxane B2 By Platelets Is Related To Their Density
Authors: Martin J F , Shaw T , Jakubowski J , Penington D G , Martin T J 
Published: July 2018

Platelets of different densities are probably produced from megakaryocytes of different ploidy. Thromboxane B2 (TxB2) production was studied in density dependent subfractions of the total platelet population.Platelets were isolated by a new technique using velocity sedimentation into a polyvinylpyrrolidone-coated colloidal silica (Percoll) gradient followed by equilibrium centrifugation through a continuous linear Percoll gradient. Fractionation of the second gradient yielded density-dependent platelet subpopulations which were functionally competent and showed minimal leukocyte and plasma protein contamination. By pooling fractions and adding buffer, suspensions containing similar concentrations of platelets representative of low, intermediate and high density subpopulations were prepared, each containing 20–30% of the total population. Aliquots of each suspension were stirred in an aggregometer and thrombin or arachidonic acid (AA) were added to induce aggregation. After three minutes the reaction was arrested by addition of ice cold ethanol and TxB2 measured by radioimmunoassay.When 0.5 mM AA (final concentration) was the aggregating agent, for every 108 platelet the least dense subpopulations produced 10.2 ng TxB2, and the most dense subpopulations 22.4 ng TxB2,(means of four experiments), whilst the intermediate density subpopulations gave intermediate values. However, thrombin at 0.5 or 1.0 units/ml produced similar amounts of TxB2 in all subpopulations. In a second series of experiments, AA-stimulated serotonin secretion in density dependent platelet subpopulations correlated closely with platelet number.These observations imply functional differences between platelet subpopulations.
The Relationship Between The Multimeric Structure Of F VIII-VWF And The Facilitation Of Platelet Adhesion To Human Subendothelium (Von Willebrand Factor Activity VWF-A)
Authors: Sixma Jan J , Sakariassen Kjell S , Bolhuis Piet A 
Published: July 2018

The relation between the VWF-A of F VIII-VWF and its multimeric structure was studied in an annular perfusion chamber according to Baumgartner, with a steady flow system.
51Cr-labelled aspirin treated human platelets and human post mortem renal arteries were employed. F VIII-VWF was purified from cryoprecipitate by agarose gel chromatography and radiolabelled by the lactoperoxydase method. The multimeric distribution was determined by SDS-agarose electrophoresis. Five different commercial high purity concentrates contained multimers between 0.5 and 3.5 x 106 mol wt. None of these concentrates had VWF-A at ristocetin cofactor activities (RIC0F-A) of 1.0 u/ml. A low potency concentrate with mul- timers in the same mol wt range had normal VWF-A. Mild reduction (dithioerythritol-DTE ≤ 2mM) caused a shift in , mol wt range from 3.0 - 20.0 × 106 towards 0.5 - 2.0 × 106 with little decrease in RIC0F-A and VWF-A. Reduction with 10 mM DTE produced multimers of 1.5 and 0.5 × 106 without RICOF-A and VWF-A, but binding normally to the vessel wall. The void volume peak of 125I-VIII-VWF was rechromatographed on Sepharose-2B and arbitrarily divided in fractions A: mol wt 8,0 - 18.0 × 106 ;B: mol wt 4.5 - 11.0 × 106 ; and C: mol wt 2.5 - 6.5 × 106 . Binding of 125I-VIII-VWF to the subendothelium was highest for A, intermediate for B and lowest for C. Correction for mean mol wt showed that almost equal numbers of molecules bound from all three fractions. When the quantity of bound VIII-VWF was thus expressed, all fractions had a similar relative VWF-A.These data indicate that high purity concentrates do not correct the bleeding time at normal RICOF-levels, because they lack VWF-A. Multimers of high mol wt normally carry both RICOF-A and VWF-A, but the high mol wt is no absolute requirement. These data are in agreement with the notion that VWF-A resides on a specific polypeptide chain in the molecule.
Microfibrils (MF) Platelet Interaction: Requirement Of Von Willebrand Factor In Platelet Adhesion To A Placenta Microfibrillar Component (PMC)
Authors: Fauvel F , Legrand Y J , Gutman N , Muh J P , Tobelem G , Souchon H , Karniguian A , Caen J P 
Published: July 2018

It has been shown that collagenase resistant arterial microfibrils (MF) are able to interact with platelets and therefore represents, besides collagen, a second thrombogenic structure in the vessel wall. In vitro observation using a PMC purified from the villosities of human placenta by a mechanical non denaturing procedure confirm this interaction between platelets and MF. PMC was homogenous under electron microscope (feltwork of MF with a mean diameter of 120 – 130 A) and was glycoproteic in nature. PMC were able to induce an aggregation of human platelets only if the platelets were in plasma. The role of Von Willebrand factor (F VIII/WF) as a cofactor of the aggregation of platelets by MF has been postulated from the fact that twice washed platelets from normal subject resuspended in PPP obtained from a severe Von Willebrand deficient patient were not aggregated by the PMC. Furthermore, aggregation was restored after resuspension of the same platelets in the PPP of the same patient 30 and 120 minutes after perfusion of cryoprecipitate (40 units F VIII/RA per kg).F VIII/WF mediates platelet adhesion after binding to subendothelium of human artery. Our observation strongly supports the idea that MF are the subendothelial components to which F VIII/WF binds, thus promoting an adhesion of platelets.
Following Mild Carotid Endothelial Injury, Platelet-Arterial Wall Interaction Is Impaired In Pigs With Von Willebrand'S Disease
Authors: Fuster V , Dewanjee M K , Kaye M P , Fass D N , White J G , Bowie E J W 
Published: July 2018

Platelet-arterial wall interaction appears to be important in the genesis of atherosclerosis. Pigs with homozygous von Willebrand’s disease (vWd) appear resistant to atherosclerosis. We investigated whether there is impairment in platelet-arterial wall interaction in porcine vWd. Superficial endothelial injury was produced in a 4 cm segment of carotid artery by drying for 3 minutes in a stream of air which entered one end (100 ml/min) and exited through a small hole in the other end. This procedure was performed in 9 normal and 6 vWd pigs 24 hours after the I.V. infusion of III-Indium-labeled platelets. Carotid blood flow was re-established and the pigs were sacrificed 24 hours later and the carotids fixed in glutaraldehyde.The ratio of radioactivity (cpm/g) of injured/noninjured carotid arteries was markedly decreased in the vWd pigs. In addition, transmission and scanning electron microscopy confirmed superficial endothelial damage in all injured segments, but only significant platelet deposition in the normal pig injured segments.After a mild endothelial injury, this “in vivo” evidence of impaired platelet-arterial wall interaction in vWd may be related to the resistance to atherosclerosis in these animals.
Purification And Characterization Of Calmodulin From Bovine Platelet
Authors: Kambayashi J , Sakon M , Kōsaki G , Sobue K , Kakiuchi S 
Published: July 2018

Calmodulin, which was originally reported as a Ca2+ dependent activator of phosphodiesterase, mediates a number of actions of Ca2+ as a second messenger for stimulus linked cellular responces in eukaryotic cells. In blood platelets, the availability of Ca2+is a prerequisite for steps of platelet reaction leading to the formation of hemostatic plug. The presence of this protein in platelets has been reported. In the present study, calmodulin was purified from bovine platelets and was extensively characterized.The identification of the protein was based on the activity to activate the brain calmodulin deficient phosphodiesterase. Calmodulin was purified 600 fold from bovine platelet pellet by a 3-step purification method consisted of trichloroacetic acid treatment, DEAE-cellulose column chromatography and phenothiazine affinity chromatography. The recovery rate was more than 70% and the purified protein was homogenous on polyacrylamide gel electrophoresis. The mobility of the purified material upon polyacrylamide gel electrophoresis was identical with that of brain calmodulin in the presence of either Ca2+or EGTA. In the quantitative analysis of the phosphodiesterase activation, the behaviour of the purified protein was also identical with brain calmodulin.From these strict characterization, it may be concluded that the purified protein is indistinguishable from brain calmodulin. The amount of the protein in bovine platelet was estimated to be 63 micrograms per wet gram, which is about one sixth of the amount in brain tissue.
Arachidonic Acid-Induced Platelet Aggregation Independent Of Cyclooxygenase And Lipoxygenase
Authors: Maclouf J , Levy-Toledano S , de la Baume H , Hardisty R M , Caen J P 
Published: July 2018

It is generally admitted that arachidonic acid (20:4 W6) can stimulate platelet aggregation after transformation into prostaglandin G2 and H2 further converted in thromboxane A2. This action is prevented by cyclooxygenase inhibitors. Washed platelets were isolated on metrizamide gradient and resuspended in a Ca2+ free buffer. Their stimulation by C20:4W6 was followed by (14C)-serotonin (5HT) release, thromboxane (TX) synthesis and a change of light transmission, not dependent on aggregation, accompanied by a slight lysis (14%). The addition of external Ca2+ suppressed lysis and allowed the formation of aggregates. Under these conditions, ccyclooxygenase inhibitors like acetyl salicylic acid, indomethacin or flurbiprofen totally suppressed TX synthesis without preventing platelet aggregation or (14C)- 5HT release. Other C 20 polyunsaturated fatty acids could not substitute for C20 : 4W6-induced aggregation and Ca2+ was found to be the most effective divalent cation for protection of the cell against lysis as well as in allowing the platelet to aggregate in the absence of TX formation. The use of the lipoxygenase inhibitor BW 755C did not prevent C20: 4W6 - induced aggregation of aspirin-treated platelets, suggesting that the phenomenon was independent of this pathway also. The total suppression of oxidative metabolism with these inhibitors was verified by the analysis of eicosanoids using glass capillary column gas chromatography.It is suggested that under these conditions, C20 : 4 W6-induced platelet aggregation might be due to an ionophoric action of C20 : 4W6 in the absence of oxidation.
Lack Of Inhibition Of Thromboxane Production Despite Inhibition Of Platelet Function By 1,3-Bis(2 Chloroethyl)-1-Nitrosourea (BCNU)
Authors: McKenna R , Ahmad T , Prancan A , Simon D , Frischer H 
Published: July 2018

We have previously shown that BCNU inhibits human platelet glutathione reductase (GSSG-R) prior to inhibiting platelet function; since thromboxane production is important in platelet function, we evaluated the effect of BCNU induced inhibition of GSSG-R on platelet thromboxane production.Control platelet GSSG-R activity was 0.091 ]jmoles NAD(P)H oxidized min-1lmg-1 protein at 37°C (±0.015 S.D.; n=9); inhibition was detectable at 10-7M% BCNU (70% of control) with a >90% inhibition at and above 10-5M BCNU. Platelet aggregation in response to 1.5×10-3M Arachidonic acid (AA), 10 μM epinephrine, 6 μg/ml equine collagen and 3 μM ADP were inhibited at 10-5M BCNU and abolished at 10-4 BCNU.BCNU (10-3M) did not affect the increase in oxygen consumption induced by AA. Using the rabbit aorta superfusion bioassay for thromboxane A2 (TXA2), threshold concentrations of AA in 10-5 and 10-4 BCNU platelets resulted in an increased measure of aortic tension 13.5 ± 9.4 mm S.D. (n=6) and 23.2 ± 9.5 mm respectively, compared with control values of 4.5 ± 2.4. Acetylsalicylic acid (5 × l0-4M) inhibited the contraction: 1.7 ± 1.1 (n=5). The conversion of 14C AA to thromboxane B2 (TXB2) and PGE2, as measured by radio TLC, was not decreased in BCNU treated platelets. There is a significant increase in TXB2 (p<0.05;n=4) and in the ratio of TXB2:PGE2 in platelets treated with 10-4M BCNU and 10-3M imidazole when compared to platelets treated with imidazole alone.In conclusion BCNU induced inhibition of platelet GSSG-R and platelet function occurs despite preservation of thromboxane production