bluuebunny/crossref_metadata_2025 huggingface dataset:
Differing Effects Of Ticlopidine And Two Prostaglandin Synthetase Inhibitors On Maximum Rate Of Adp-Induced Aggregation
Authors: Bruno J J , Yang D , Taylor L A
Published: July 2018

Many platelet inhibitors are known which block the secondary (2°) phase of ADP-induced aggregation. These agents normally inhibit platelet cyclooxygenase (CO). Agents which are able to inhibit primary (1°) ADP-induced aggregation usually cause elevation of platelet cAMP. Ticlopidine hydrochloride (T), a drug which does net stimulate platelet adenylate cyclase or inhibit platelet cAMP phosphodiesterase, or platelet CO, inhibits 1° ADP-induced aggregation. Healthy human volunteers were dosed orally from 3-8 days with doses of T from 125 to 500 mg/day. When the maximum rate of ADP-induced aggregation on the day following cessation of dosing was compared with that obtained predosing, statistically significant inhibition of maximum rate was obtained at each dose. Similar studies were done with naproxen (N) a CO inhibitor. Healthy human volunteers were given 125 to 1000 mg/day of N. When the rates of ADP-induced aggregation at 3 and 8 hours postdosing were compared to predose rates, there were no statistically significant differences at any dose. At these times collagen and arachidonic acid-induced aggregation were essentially totally inhibited. An experimental agent, 5-benzoyl-l, 2-dihydro-3H-pyrrolo [l,2-a]-pyrrole- 1.carboxylic acid, with potent platelet CO inhibiting activity, given orally to human volunteers at 2.5 to 200 mg/day showed the same results at 3 and 24 hours post dosing as did N.

We conclude that T is an inhibitor of 1°phase of ADP- induced aggregation, and that agents with CO-inhibiting action alone are incapable of inhibiting 1° phase of ADP- induced aggregation despite occasional reports to the contrary.
Selective Inhibition Of Thromboxane Synthesis By 1-(3-Hydroxy-1-Octenyl)-Imidazole And Its Nicotinic Ester In Human And Rat Platelets
Authors: Bonne C , Martin B , Sincholle D , Regnault F
Published: July 2018

Since Thromboxane A2 (T×A2) is considered to play an important role in platelet aggregation, attempts to develop selective inhibitors of T×A2- synthetase are being made. In this report the activity of 1-(3-hydroxy-1-octenyl)-imidazole, chlorhydrate (CBS612) and of its nicotinic ester, die hiorhydrat e (CBS63b) will be presented.

The inhibitory activity was determined in isolated platelets from human and rat by radiochemical assay and in whole blood by radioimmunoassay of T×B2 and of PGE2 as a criteria of specificity. Human enzyme was more sensitive than the rat one’s (CBS634 : IC50 human = 0.7μM, IC50 rat = 10μM) and the two compounds were more active than imidazole in human platelets (IC50 : imidazole = 50μM, CBS612 = 2μM ; CBS631+ = 0.7μM). Collagen- induced aggregation was inhibited by the drugs at concentrations which suppressed T×B2 formation.

The results of these experiments showed that CBS612 and CBS634 selectively inhibited thromboxane-synthetase since they increased the formation of PGE2. Besides, these compounds did not inhibit PGI2 release from rat aorta ring. The selectivity of the inhibition by the drugs was further shown by the absence of any effect on the first phase of ADP-induced platelet aggregation.

These compounds seemed potentially interesting for the management of thrombotic diseases and for elucidating the role of Thromboxane in physiological and pathological processes.
Adenosine 3‘,5‘-Cyclic Monophosphate (C-AMP) And Inhibitors Of Platelet Aggregation: A Possibility Of A Double C-AMP Pool In Human Platelets
Authors: Zahavi M , Kakkar V V
Published: July 2018

A new method was developed for determining platelet c-AMP in platelet rich plasma (PRP) and washed platelets.

In PRP, using an adenyl cyclase activator Prostaglandin El (PGEl) and phosphodiesterase inhibitors (papaverine, theophylline) and an inhibitor of platelet function, pyridoxal-5-phosphate (PALP) it was found that the phosphodiesterase inhibitors and PALP are more effective than PGEl in inhibiting platelet function at identical c-AMP accumulation. In washed platelets aggregation induced by thrombin was greatly inhibited by papaverine and by PALP with concomitant comparatively small c-AMP accumulation but was in most preparations inhibited by PGEl only to a small extent, although c-AMP accumulation was substantial. This indicated that in platelets there may be two pools of c-AMP, one of them more closely correlated to platelet aggregation.

PALP acts like a phosphodiesterase inhibitor rather than an adenyl-cyclase activator with respect to c-AMP accumulation. However, in contrast to papaverine the small c-AMP accumulations cannot be increased in washed platelets, therefore, it seems that another site in addition to phosphodiesterase inhibition is involved in inhibition of platelet function by PALP. c-AMP accumulation seems to be the main cause for inhibition of platelet function by papaverine, however, at higher concentrations an additional site is also possible. This additional inhibition is more important in inhibition of platelet function by papaverine and PALP in a diabetic patient whose platelets seem to be impaired in ability to accumulate c-AMP.
Storage Pool Disease Associated With Von Willebrand?
Authors: Meschengieser S , Schattner M , Elgue G , Lazzari M A
Published: July 2018

We evaluated a group of 11 patients (10 female, 1 male) complaining of minor bleeding symptoms that showed the pattern of storage pool disease (SPD) and besides, presented a lack of aggregation induced by ristocetin, which corrected with the addition of normal plasma (pool of 15 donors). Only two patients had familiar history of bleeding tendency. Bleeding time (Ivy) was prolonged in 63% of the patients and platelet retention (Pellem II) was decreased in 72% of them.

Three of the patients showed, apart from the SPD, a clear pattern of VW disease (low factor VIII: C and VIII: Ag). In four patients the levels of factor VIII: C and f, VIII:Ag were normal, but one of them presented a Ristocetin Cofactor (McFarlane) below normal, associated with a prolonged bleeding time and low adhesiveness. Three patients had low levels of VIII: C with normal levels of VIII:Ag. The last patient with border line levels of VIII: C and VIII:Ag, presented a low Ristocetin Cofactor. Thus, 5 of the 11 patients have undoubtful elements of VW. In the others this diagnosis could not be accomplished clearly.

As a conclusion, the presence of a characteristic aggregation pattern of SPD with absence of ristocetin induced aggregation, could suggest a variant of SPD or perhaps an association of both diseases
Megakaryocytic Progenitors (CFU-M) Increase Nonspecifically In Chronic Immune Thrombocytopenia
Authors: Burstein S A , Erb S K , Adamson J W , Harker L A
Published: July 2018

Previous studies from our laboratory have suggested that the numbers of CFU-M do not increase primarily in response to acute thrombocytopenia. To determine the effect and specificity of prolonged thrombocytopenia on CFU-M number, mice were given 4 intravenous injections on alternate days of multiply absorbed rabbit anti-mouse platelet serum (APS), while control animals received a similar regimen of rabbit anti-mouse red cell serum (ARS), normal rabbit serum (NRS), or phosphate-buffered saline (PBS). Two days aftefcthe final injection, the mean platelet count was.0.314 ± 0.129 × 106/ul in animals given APS vs. 1.105 ± 0.048 × 106/ul in animals given other regimens. The numbers of CFU-M, day 7 and day 14 erythroid burst forming cells (BFU-E), and granulocyte-macrophage colony forming cells (CFU-C) were determined in humerus and spleen.

The generalized increase in progenitor cells in marrow in response to APS together with increases in CFU-M in spleen following ARS and NRS indicate that these cells may respond nonspecifically to foreign protein. The data suggest that the elevation in CFU-M numbers with chronic immune thrombocytopenia is at least partially independent of the platelet count.
The Effect Of A Proteinase Inhibitor On Platelet Function In Stored Blood
Authors: Haas S , Wendt P , Blümel G
Published: July 2018

Blood platelets are markedly traumatized by the withdrawal of blood from the donor. Hereby the function of thrombocytes is activated and this platelet stimulation is closely related with the early formation of microaggregates in stored blood. Therefore it is clinically desired to stabilize the platelets but without inhibiting their function irreversibly and causing hemorrhage. Concerning this question an experimental study was carried out.

Blood was drawn from 10 volunteers under blood bank conditions and was stored in presence of 200 KIU aprotinin per ml ACD-blood resp.the same volume of saline at a temperature of +4°C. Immediately after the withdrawal of blood and 1,2,3 and 7 days later blood samples were taken and the following parameters were studied: platelet aggregation induced by ADP, aggregate ratio, PF 4, beta-thromboglobulin and tx B2 in plasma and serum.

In the aprotinin blood the aggregability was slightly diminished and was longer present than in the control group. In addition, the aggregate formation was significantly decreased. The release reaction of platelets was not effected by aprotinin;the increase of PF 4 and beta-thromboglobulin was similar to that of the control group. Also the thromboxane formation was not effected. Thus the protective effect of aprotinin is independent from the prostaglandin metabolism

This study shows that a high dose of aprotinin has a stabilizing effect on platelets in stored blood and that the thrombocyte function is not irreversibly inhibited by this substance. Therefore, aprotinin can be regarded to be effective in the prophylaxis of disseminated platelet aggregation without causing a bleeding risk.
The Influence Of Anticoagulants Upon The Results Of Platelet Function Tests: Aggregation (PA) And Release Reaction(RR)
Authors: Wurzinger J L , Blasberg P
Published: July 2018

Citrate (11 mM) is generally used as anticoagulant when platelet functions are tested. In contrast to heparin anticoagulation, citrate drastically lowers calcium levels creating a milieu, incompatible with life in an organism. However, the effects of heparin on platelet function are still a matter of debate, studies on this subject employing variable protocols of heparin administration and thus probably being responsible for the existing conflict of results. The present study attempts a systematic comparison of spontaneous as well as ADP and adrenaline induced PA and the RR under influence of either heparin or citrate used as anticoagulant. Spontaneous and ADP or adrenaline induced (each 5×10-7 M) PA were tested in a 2-channel rheoaggregometer simultaneously on platelet rich plasma (PRP) samples prepared from blood anticoagulated with 5 U heparin/ml or 11 mM citrate. ADP and adrenaline induced PA were tested 90 and 60 min after blood withdrawal respectively. Spontaneous PA was tested 30, 60, 90, 120 and 180 min after blood withdrawal.

RR was assessed by measuring β-thromboglobulin (β-TG) release from gel filtered platelets, incubated for 30 min with varying doses of heparin (1,5,50 U/ml) or citrate (5,11,22 mM). Strict isothermia of 37°C was kept during all steps of the experimental procedure.

We found that:
1. Adrenaline and ADP induced aggregation were significantly higher in heparinized than in citrated PRP.
2. Spontaneous PA in heparinized PRP too was higher than in citrated PRP during the interval looked upon.
3. Heparin added to gel filtered platelets enhanced, whereas citrate lowered β-TG release as compared to controls.
From our results we conclude that the differences in the behaviour of heparinized and citrated PRP are not only due to an effect of heparin itself, but also to the difference in calcium levels
Thromboxane A2-Stimulated Human Platelet Aggregation Is Potentiated By Epinephrine Acting VIA Alpha Adrenergic Receptors
Authors: Johnson G J , Rao G H R , White J G
Published: July 2018

Epinephrine (E) potentiates arachidonate (A)-induced aggregation of human platelets. A-insensitive dog platelets (AIP), that form thromboxane A2 (T) but do not aggregate when stirred with A alone, aggregate when exposed to E + A. Therefore, we studied the effect of E on T-stimu- lated human platelet aggregation. AIP stirred with A formed T which was confirmed by TLC. 1/100 to 1/200 volume of AIP was removed 30 sec. after A, and transferred to gel- filtered, aspirin-incubated human platelets. Recipient platelet aggregation was proportional to the volume of AIP transferred. The addition of the thromboxane synthetase inhibitor, Azo Analog I, abolished the aggregating activity of AIP. Transfer of an aliquot of AIP that was inadequate to aggregate human gel-filtered, aspirin-incubated platelets resulted in irreversible aggregation in the presence of ≥0.5nM E. E potentiated aggregation when added 3 min. before but not 3 min. after aliquot transfer. T-stimulated aggregation was abolished by the T-antagonist, 13 azapro- stenoic acid (APA), but E added after APA and before T restored aggregation. E potentiation of T-stimulated aggregation was abolished by prior exposure to equimolar yohimbine, dihydroergocryptine and phentolamine, agents that bind to alpha2 adrenergic receptors, but not by prazosin an alpha1 antagonist. Higher concentrations of E reversed the inhibitory effects of the alpha2 adrenergic agents. All of these agents in higher concentrations (1-100μM) also blocked aggregation induced by T alone. Therefore T-induced platelet aggregation is potentiated by E, in concentrations attained in vivo, by a mechanism linked to platelet alpha adrenergic receptors. Platelet alpha2 receptors have a close functional relationship to the postulated T receptor. E may initiate platelet aggregation in vivo when T is formed in quantities inadequate to alone induce aggregation.
Hairy Cell Leukemia: Report Of A Case With A Plasma Mediated Defect In Platelet Function And Platelet Morphology
Authors: Mattson J C , Sanal S
Published: July 2018

A 60-year-old male with hairy cell leukemia developed purpura. Studies performed prior to splenectomy and at a time when purpuric lesions were present demonstrated a severe platelet functional defect characterized by absent primary and secondary wave aggregation with ADP and Ristocetin, absent Collagen aggregation, and diminished Epinephrine aggregation. In addition PF3 was decreased and the bleeding time prolonged. EM demonstrated a mixed population of degranulated, enlarged platelets and normal platelets. Following splenectomy PF3 levels and the bleeding time returned to normal. Repeat aggregation studied performed post-splenectomy showed return of primary wave aggregation but persistent absence of secondary wave aggregation in response to ADP, and virtually absent response to Collagen. Ristocetin aggregation returned to normal, but Epinephrine failed to produce any response. EM performed post-splenectomy demonstrated normal platelets. Tests performed on the patient’s pre-splenectomy plasma indicated the presence of an inhibitor which was capable of inhibiting primary aggregation, nucleotide release and secondary wave aggregation in normal platelets with all agents tested.

This inhibitor had no effect on adhesion in a collagen adhesion assay. Full inhibitory effect was present after incubation of inhibitor plasma and normal platelets for 5 min. but with longer incubation times inhibition of aggregation was less pronounced suggesting either dissociation or destruction of the platelet bound inhibitor. Partial characterization of the inhibitor demonstrated that it was dialyzable, stable at 56 C for 30 min. and at 4 C for 72 hrs., and present in a 50% ammonium sulfate fraction of plasma. These studies suggest that the inhibitor is a globulin which appears to exert its inhibitory effect by nonspecific, easily dissociable binding to the platelet surface.
Effect Of Diet And Clofibrate On Increased Platelet Function In Hyperlipoproteinemia
Authors: Joist J H , Baker R K , Schonfeld G
Published: July 2018

We have previously reported shortened template bleeding times (BT) in patients with type IIb and IV-hyperlipoproteinemia (HLP) and increased platelet coagulant activity (PF3a) in patients with types IIa, IIb and IV-HLP. We now report on a randomized, double-blind crossover study designed to assess the efficacy of lipid lowering diets appropriate for the respective type of HLP and Clofibrate versus placebo in reversing platelet hypersensitivity. 8 patients with IIa, 9 patients with IIb, and 9 patients with IV-HLP completed the study which included (a) baseline study (regular diet), (b) controlled diet (2 months), (c) controlled diet and Clofibrate (6 months), (d) controlled diet and placebo (6 months) (crossover design). In IIa-HLP patients the mean BT remained significantly shortened throughout all study periods whereas PF3a had reversed to normal at the end of the diet period without significant further changes thereafter. In IIb- and IV-HLP patients both shortened BT and increased PF3a observed at baseline normalized at the end of the diet period with a continuous further decline of PF3a thereafter regardless of Clofibrate or placebo. A small but significant decrease in total and LDL-cholesterol in serum was observed during the diet period in IIa-HLP patients and this decrease was not enhanced by Clofibrate. In IV-HLP patients, serum triglycerides had declined by 50% at the end of the diet period and stabilized at 25% of the initial value at the end of the first 6 month treatment period irrespective of Clofibrate or placebo treatment. No significant changes in triglyceride levels were observed in IIa- or IIb-HLP patients throughout the 14 month observation period. The findings indicate that lipid lowering diets may reverse platelet hypersensitivity in HLP patients and that Clofibrate has no effect on platelet function in HLP patients on a controlled lipid lowering diet.
Decrease Of Platelet Aggregation In Rats Under Gastric Ulcer-Causing Stress
Authors: Terano T , Hamazaki T , Hirai A , Tamura Y , Kumagai A
Published: July 2018

Decreased platelet aggregability may play an important role in gastric ulcer continuation. We attempted to identify an antiaggregatory substance involved in stress induced gastric ulceration in rats. METHODS: 1) Male SD rats (180-220g) were stressed by water immersion, one group for 30 min and another for 120 min. Platelet rich plasma (PRP) and platelet poor plasma (PPP) were obtained from stressed rats and normal rats under ether anesthesia. Platelet aggregation was carried out by addition of 1/10 vol of 50μM ADP and was measured using a Sienco aggregometer. 2) Platelet-plasma mixing experiments. PRP from normal rats and from rats stressed for 30 min was centrifuged and the supernatant was discarded. Packed platelets from normal rats were resuspended in PPP from stressed rats and platelets from stressed rats were resuspended in PPP from normal rats. Also, platelets from each rat were resuspended in PPP of the same rat. Aggregation was then observed. 3) Stability tests of the activity in PPP from stressed rats which depressed platelet aggregation. PPP from normal and stressed rats was stored for 4. hr either in ice or at room temperature. Platelets from a normal rat were then mixed with each PPP. 4) 6 keto PGF1α was measured by RIA. RESULTS: 1) The aggregability of rat platelets was decreased to 1/4-1/5 and to 1/10 of the normal value, after 30 min and 120 min stress, respectively. 2) Normal platelets suspended in PPP from stressed rats did not aggregate. Platelets from stressed rats suspended in normal PPP showed significant aggregability. 3) The antiaggregatory activity of PPP from stressed rats was lost significantly after storage at room temperature for 4 hr, while storage in ice did not greatly affect this activity. DISCUSSION: During water immersion stress which causes stomach ulceration of rats there appear platelet antiaggregatory substance(s) in plasma. Like PGI2, the substance observed in this experiment is more stable at 0°C than at room temperature. However, plasma 6 keto PGF1αconcentrations in stressed rats did not increase enough to explain the decreased platelet aggregation. Identification of this antiaggregatory substance is now under way.
Absence Of Role For Platelet-Derived ADP In Tumor Cell-Induced Platelet Aggregation
Authors: Bastida Eva , Ordinas Antonio , Jamieson G A
Published: July 2018

Interaction with platelets is thought to be a major factor in the metastatic dissemination of human tumors. Previous studies using non-human lines have suggested that aggregation induced by tumor cells is dependent on the release of platelet-derived ADP. We have re-examined this phenomenon in heparinized platelet rich plasma with two human tumor cell lines: Hut 20 derived from a large cell carcinoma of the lung and U87MG derived from a glioblastoma, U87MG caused a single irreversible wave of aggregation simultaneously with the onset of platelet secretion and was inhibited by heparin and hirudin but not by apyrase. In contrast the Hut 20 line gave an initial reversible wave followed by a second irreversible wave which then led to secretion. Aggregation was unaffected by heparin or hirudin but was inhibited by apyrase. Blockage of the cyclooxygenase pathway and platelet secretion by aspirin did not affect the first wave of Hut 20-induced aggregation but gave moderate reductions in the second wave (∼50%) and with U87MG (∼25%). With both cell lines, aggregation was completely blocked by protease inhibitors, and by removal of Ca++ and did not occur with gel-filtered platelets. These results suggest that platelet aggregation by the Hut 20 line is induced by ADP released from the tumor cell themselves while aggregation induced by the U87MG line is dependent on the development of a procoagulant activity of the tumor cell surfac.
Platelet Aggregation Induced By Formaldehyde
Authors: Zeller J A , Eurenius K , Dayhoff R E , Ledley R S , Rotolo L S
Published: July 2018

Formaldehyde causes platelet aggregation (or agglutination) which varies with dosage. Aggregation was studied in ten blood samples drawn from normal volunteers. A small volume of formaldehyde was added to platelet rich plasma in a light transmission aggregcmeter to produce final formaldehyde concentrations between 0.1% and 8%. Measurements were made by three methods: (1) light transmission aggregometry, (2) visual semi-quantitative microscopic analysis, and (3) quantitative image analysis (Computerized Platelet Aggregation Analysis) . Using the visual semi-quantitative microscopic method, the dose response curve (expressed as the percentage of platelets involved in aggregates) increased from 11% at a formaldehyde concentration of 0.1% to 41% at a 0.5% formaldehyde concentration; it then decreased to 11% at a formaldehyde concentration of 8%. This curve may reflect the influence of two different formaldehyde effects: an aggregating effect which increases until about 0.5% concentration, whereafter a fixative effect may predominate. Light transmission aggregometry recordings did not provide a reliable indicator of the presence and degree of aggregation. A comparison of the visual semi-quantitative method and CPAA show similar detection of aggregating effects. In sunmary, formaldehyde has an aggregating effect on normal platelets. The physiologic significance of this effect is unknown; however, because formaldehyde is used to process platelets in studies of platelet aggregation, this effect may be of importance.
Inhibition Of Thromboxane Synthesis And Of Arachidonate- Induced Platelet Behaviour In Platelets From Different Individuals
Authors: Heptinstall S , Bevan J , Cockbill S R , Fox S C , Hanley S P , Luqmani R
Published: July 2018

Several agents inhibit thromboxane synthesis in platelets so might be expected to modulate the arachidonate- induced platelet release reaction and the platelet aggregation that accompanies it. Such agents include the nonsteroidal anti-inflammatory agents (NSAIAs) that inhibit cyclo-oxygenase activity, the selective inhibitor of thromboxane synthetase UK-34787, and dipyridamole. We have assessed their influence on the ability of platelets to convert arachidonate to malondialdehyde (MDA, a marker of thromboxane synthesis) and on the arachidonate-induced release reaction (release of 14C-serotonin from labelled platelets.

Platelets from different individuals respond differently to some of these agents. Whereas similar concentrations of each of acetylsalicylic acid, indomethacin, flurbiprofen and tolmetin were required to inhibit MDA production in platelets from different donors, higher concentrations of these NSAIAs were sometimes required to inhibit the arachidonate-induced release reaction in platelets from some donors than were required in platelets from others. UK-34787 inhibited both MDA production and the release reaction in platelets from some donors, but in platelets from others it had little effect on release despite inhibiting MDA generation. Dipyridamole was more effective as an inhibitor of the platelet release reaction in platelets that were responsive to UK-34787 than in platelets that were not.

These different effects of agents on platelets from different individuals might be relevant to their effectiveness in thromboembolic disease. Perhaps participants in clinical trials should be stratified according to the responsiveness of their platelets to the particular drugs under scrutiny.
In Vivo Inhibition Of Thromboxane A2-Synthetase : Protective Effect Against Collagen And Arachidonate Infusion
Authors: Sincholle D , Fontaine C , Martin B , Bonne C , Regnault P
Published: July 2018

Rabbits and rats anaesthetised with thiopental were infused intravenously either with sodium arachidonate or collagen. Blood pressure and pneumogram were recorded and Thromboxane B2 (T×B2) plasma level was measured prior and after infusion. The aggregating agents elicited hypotension, respiratory break down and killed the animals. These events were associated with an increase in plasma T×B2 concentration. Intraperitoneal pretreatment of animals with derivatives of imidazole (1 -(3-hydroxy-1-oct enyl)-imidazole , chlorhydrat e (CBS6l2) and its nicotinic ester (CBS634) delayed toxic effects and death. In the standard conditions used in this study, the lethal dose of arachidonate in the rabbit was 8.4 t 1.0 mg/kg. This dose was increased to 21.6 ± 4.3 and 50.4 ± 8.0 when the animals were pretreated with CBS6l2 at the dose of respectively 12.5 mg/kg and 25 mg/kg. In the same way, the lethal dose of collagen in the rat was 0.5 ± 0.1 mg/kg in controls and 1.2 t 0.1 mg/kg after treatment with thromboxane-synthetase inhibitor (CBS634 = 25 mg/kg). The lethal dose of collagen was correlated to the concentration of T×B2 formed in the blood (controls : 4.4 ± 0.3 ; treated : 1.7 ± 0.2 ng/ml).

Potential interest of these antithrombotic drugs could be strengthened by further pharmacokinetic studies after oral treatment actually in progress.
Synergism Between Platelet Aggregating Agents: Possible Trigger Mechanisms During Hemostatic Plug And/Or Thrombus Formation
Authors: Wong S C , Rock G A
Published: July 2018

number of in-vitro studies have shown that various pair-combinations of aggregating agents such as ADP, epinephrine, collagen, thrombin, arachidonate and ionophore A 23187 can produce synergistic responses to induce platelet aggregation and release reactions. We have also produced synergistic effects by combining much lower doses of 3 or more aggregating agents and found markedly enhanced responses. It appears that the potential for synergistic effects is based both on the combination of the various agents and on the amount of each agent used for stimulation. Epinephrine is the most potent agent among them, although fibrinogen and Ca++ play a very important role. Indomethacin, ASA, PGE 1, and synthetic serine protease inhibitors (carboxylate and sulphonate analog) completely inhibit the platelet aggregation and release response. Of particular interest is the fact that addition of as little as 0.04% of the usual aggregating dose of epinephrine in the presence of 4% of collagen, 2% of thrombin and 10% of the normal plasma level of fibrinogen will initiate a marked response both of platelet aggregation and ATP release. This suggests a possible mechanism whereby acute insults such as stress or exercise, with release of epinephrine, can precipitate a thrombotic event in a patient who has normal or near-normal circulating levels of fibrinogen but who also has exposure of a very limited amount of the vascular endothelium (thereby exposing collagen). Since the effects of the acute insults of epinephrine secretion can be blocked by the presence of indomethacin, ASA, PGE 1 and specific serine protease inhibitors, prostaglandin synthesis must play a major role in this reaction.
Primary Plasma Therapy For Thrombotic Thrombocytopenic Purpura
Authors: Case D C
Published: July 2018

A 25-year old male was admitted for an episode of right sided headache and subsequent generalized seizure. On admission his temperature was 37.6°. He had generalized petechiae and conjunctival hemorrhages. Organomegaly and lymphadenopathy were absent. There was mild left sided weakness. The Hgb. was 6.9 g/dl., reticulocyte count 10%, WBC 11,500/mm3, and platelet count 10,000/mm3. There were numerous schistocytes on the peripheral smear; bone marrow revealed panhyperplasia. Coagulation studies were normal. The BUN was 30, and the creatinine 1.7 mg/dl. Plasma was positive for Hgb. CT scan was negative for gross intracranial bleeding. The diagnosis of T.T.P. was made. On admission, the patient received 10 units of platelets and 2 units of packed red blood cells. He did not require further red cell or platelet transfusions during the rest of his hospital course. He was then started on infusions of fresh-frozen plasma. He then received one unit every 3 hours for 6 days, one unit every 6 hours for 2 days, then one unit every 12 hours for 2 days and finally 1 unit daily for 5 days. The response was immediate. After the infusions were started, the hematologic parameters steadily improved. The patient’s hematuria rapidly improved. Further CNS symptoms did not appear. The patient’s Hgb. was 12 g/dl, and reticulocyte count was 2.5% by the 9th day. His platelet count was normal by the 4th day. The patient was discharged on the 15th day. Infusions of plasma were discontinued at the time of discharge. The patient required plasma therapy 4 weeks later for recurrent thrombocytopenia (50,000/mm3). The patient has remained normal for 9 months since therapy and further plasma has not been required. Primary plasma therapy for T.T.P. as sole treatment should be further studied.
Normal Prostacyclin-Like Activity In A Patient With Thrombotic Thrombocytopenic Purpura
Authors: Pini M , Manotti C , Quintavalla R , Dettori A G
Published: July 2018

Deficiency of prostacyclin (PGI2) has been related to the pathogenesis of thrombotic thrombocytopenic purpura (TTP), and reduced PGI2 activity is thought to be secondary to a lack of plasma factor(s) which normally stimulates PGI2 production. We measured PGI2 production by means of the method of Moncada et al (Lancet 1:18, 1977), as platelet aggregation inhibitory activity released by venous specimen removed surgically in a 52 year-old woman with TTP in the acute phase of the disease. The patient was subsequently cured by plasma exchange.

Platelet aggregation inhibitory activity released from venous tissues of the patient was normally detectable and comparable to that of a healthy control. Moreover, patient plasma was able to induce release of prostacyclin-like activity from exhausted veins (both from patient and normal control) as well as normal plasma. Hence release of PGI2 like activity from venous tissues and ability of plasma to stimulate prostacyclin synthesis in normal vascular tissues were not impaired in our patient with TTP in the acute phase of the disease.

Our findings demonstrate that PGl2 deficiency is not implicated in the pathogenesis of all cases of TTP.
Thrombasthenia: A Heterogenous Disorder
Authors: Zonneveld G , van Leeuwen N , Sturk A , ten Cate J W
Published: July 2018

We investigated the relation of the expression of platelet specific allo-antigens of Zw-, Ko- and Bak system and the glycoprotein (GP) and protein composition of platelets and isolated platelet membranes from a group (7) of Glanzmann Thrombasthenia (GT) patients. Using the platelet immunofluorescence test and the platelet agglutination test platelets of 6 GT patients were typed Zw Zwb negative, Koa and Kob positive and Bak (a) negative. These findings suggested a linkage between a regulator gene concerned in the synthesis of GP IIb and IIIa and the gene responsible for Bak (a) negativity. Quantitative polyacrylamide gelelectrophoresis revealed that platelets from one GT patient had the strongest periodic acid Schiff’s reagent (PAS) staining of GP IIIa (although just outside the normal range) and in addition showed a weak positive reaction with anti-Zwa serum, indicative of Zw3 antigenic marker to be associated with GP IIIa. The remaining 6 patients had a marked reduction in PAS staining of GP IIb and IIIa (mean value 80%) and protein staining of these GPs. GP profiles of thrombasthenic platelets also showed alterations in the GP I (one GT patient had two major PAS staining bands in this region) and GP IIIb region (broad diffuse PAS staining band). Total GP, GP IIIa and IIIb content, number and content of GP I and protein composition varied per patient and strongly suggested that thrombasthenia is a heterogenous disorder.
Virus Induced Thrombocytopenia: The Role Of Viral Hemolysin And Neuraminidase
Authors: Chernesky M , Bromke A
Published: July 2018

Newcastle disease virus (NDV) which aggregates washed suspensions of human or rabbit platelets in vitro was compared to non-aggregating viruses such as influenza A and chikungunya virus (CV) in their capacities to induce thrombocytopenia in rabbits previously infused with 5lCr- labelled platelets. NDV and influenzavirus induced a dramatic drop in platelet and radioactive counts. Five minutes after the injection of NDV, platelet counts fell to 78% of preinjection levels and only 40% of the radioactivity was recoverable. Platelet numbers returned to normal by 30 min. but label never responded past 55% of preinjection. Influenza virus demonstrated a similar pattern of platelet and radioactive counts but the responses were approximately 65% of those induced by NDV. Magnitude of thrombocytopenia was dependent upon the strength of virus injected. CV did not induce a significant drop in platelet counts. Plotting radioactive counts against a constant number of platelets in the circulation suggested that during thrombocytopenia the radioactive label may have been removed from the platelets which could be cleared from the circulation. Return to preinjection numbers may have been due to subsequent removal of platelet- free radioactivity or a movement of platelets from sequestration or storage pools. A second series of rabbits were injected with 51Cr-labelled platelets previously reacted in vitro with virus or purified neuraminidase. Approximately 80% of the platelets pretreated with NDV or influenzavirus were cleared from the circulation within 10 minutes. Only 3.6% of radioactivity was present in the rabbit circulation 10 min. after the injection of platelets which had had 8.65 nanograms of NANA/ml cleaved from their surface by neuraminidase. A mechanism for virus-induced thrombocytopenia may involve platelet aggregation and/or enzymatic platelet membrane modification, which may result in immunological clearance in the animal.
Effect Of Prednisone On Platelet Function In Patients With Bleeding Disorders
Authors: McKenna R , Bachmann F , Pichairut O , Whittaker B
Published: July 2018

There is considerable controversy regarding the effect of Prednisone on the hemostatic mechanism of normal people versus patients with bleeding diatheses. We administered Prednisone 15 mg TID to patients with a positive history of a bleeding disorder, and evaluated the bleeding time and other in-vitrc tests of platelet function prior to and between the 5th and 7th day after Prednisone.

Eleven patients were admitted into this study over a one year period. All patients had a history of excessive bruising, epistaxis, bleeding after dental extractions, and gastrointestinal or other bleeding in various combinations. Two out of the eleven had template bleeding times of greater than 15 minutes both before and after the Prednisone. These two patients were subsequently proven to have von Willebrand’s disease by the washed platelet ristocetin assay. In the remaining 9 patients, the pre-Prednisone bleeding time was 9.3 ±3.7 minutes (x ± 1 S.D.) whereas the post-Prednisone bleeding time was 5.8 ±3.6 minutes (x ±1 S.D.). These results were significant(td=3.83;df:7;p=0.007).

Platelet aggregation in response to exogenous ADP (1 μM, 3 μM) Sigma bovine tendon collagen (1.8 mg/ml F) and epinephrine (5.5 × 104M), platelet retention in a glass bead column or platelet factor 3 availability did not improve or worsen after Prednisone therapy. The mean platelet count of 328,000±94,000 (x ±1 S.D.) was significantly (p=0.05) higher than the mean pre-Prednisone platelet count of 268,000±77,000 (x ±1 S.D.).

In conclusion, we have shown that large doses of Prednisone appear to shorten the bleeding time in patients with significant defects in the primary hemostatic mechanism. However the bleeding time improvement is not evident in patients with von Willebrand’s disease.
Hemodynamic Effects And Changes Of Blood Flow Distribution By Dextran 70, Dihydroergotamin (DHE) And Their Combination
Authors: Lindblad B , Bergqviat D
Published: July 2018

Dextran 70 and DHE are both effective in reducing the risk for postoperative thromboembolic complications. As they at least in part have different mechanisms of action it is important to analyse if their combination potentiates the prophylactic effect. Therefore it is necessary to study the effect on hemodynamics and tissue blood flow, a problem which is delt with in this report.

MATERIAL AND METHODS: In 18 dogs the following parameters were followed: cardiac output, heart rate, arterial blood pressure, central venous pressure, pulmonary artery pressure, left atrium pressure and volume blood flow in the femoral vein. Blood flow distribution was determined by the radioactive microsphere technique.

RESULTS: Dextran 70 gave an increase of cardiac output and femoral vein flow. Other hemodynamic parameters were mainly unaffected. Total peripheral resistance decreased. DHE increased arterial blood pressure, central venous pressure and pulmonary arterial pressure. Cardiac output and femoral vein flow were unchanged.

Tissue blood flow increased in general slightly after infusion of dextran 70. No significant change in blood flow distribution was seen. DHE reduced pancreatic and thyroid blood flow and increased tissue blood flow to the central nervous system. The blood flow to other organs including the heart was unaffected. The combination of dextran 70 and DHE influenced hemodynamic parameters and flow distribution in an additative way.

CONCLUSIONS: From this experimental study it is concluded that it is possible to combine dextran and DHE without inducing a circulatory overload. DHE increased tissue blood flow to the central nervous system.
Alterations Of Platelet Morphology In Human Ischemic Heart Disease And In An Acute Thrombosis Rabbit Model
Authors: Frojmovic M M , Milton J G , Yung W , Burgess J , Rose C , Buchanan M , Hirsh J
Published: July 2018

Methods are needed for screening patients at risk for thrombo-embolic diseases. We present an assessment of the relative usefulness of platelet shape distribution and mean volume measurements for probing abnormalities in ischemic heart disease (IHD). Platelet morphology in whole blood (WB) from the antecubital vein and/or abdominal aorta, and citrated platelet-rich plasma (PRP), which have been fixed by 4 volumes 0.8% glutaraldehyde-Tyrodes, pH 7.4, is compared for 17 healthy and 13 IHD donors: (I) 6 post-myocardial infarction (2-16 days), 1 acute coronary insufficiency (7 days) and (II) 6 angiographically characterized coronary artery disease. Platelets were examined under phase contrast microscopy classified as discocytes (D), disco-echi- nocytes (DE) and sphero-echinocytes (SE). WB of IHD donors has fewer D than WB from healthy donors (27(5-57)%* vs 71 (65-80%); *mean (range)) and more SE (24(6-65)% vs 1(0-8)%). Although platelet morphology in PRP from healthy donors Was similar to that of WB, PRP from TED donors contained fewer SE (3(0-11)%) and D (52(20-87)%) than WB. Platelet mean volumes, measured by microscopy, were increased by <7% for IHD donors. Rabbits with induced acute thrombosis (indwelling catheter model) studied at 2 hrs, 24 hrs, 1 day and 5 days showed no alterations in platelet morphology distribution evaluated in fixed whole blood, from either normal (4) or sham-operated (4) rabbits. The distributions in morphologies were essentially identical to those seen for normal human donors. These results indicate that changes in platelet morphology in IHD (i) are best measured in whole blood, (ii) probably do not reflect acute thrombo-embolic events and, (iii) are much larger than the changes in platelet mean volume, suggesting that morphology is the more sensitive probe for abnormalities in IHD.
Nonocclusive Coronary Thrombosis In Acute Myocardial Infarction
Authors: Frink R J
Published: July 2018

TIn depth histologic study was performed on 23 patients who died during the acute phase or within the first three months following acute myocardial infarction. Six died suddenly and unexpectedly out of the hospital, five of these with the acute myocardial infarction unrecognized.

The remainder were hospital deaths, five within the first 48 hours, 8 between 2-14 days, and 4 between 14 and 94 days. Five cases showed subendocardial infarction (SI). Four of these occuring out of hospital. The remaining 18 cases were transmural infarctions (TI). Sixteen of 17 hospital deaths exhibited TI.

Special emphasis was given to a histologic search for coronary artery thrombosis, particularly nonocclusive thrombosis (NT), and fibrin fragments in the microcirculation. An acute coronary thrombus (ACT) was found in 22 of 23 (96%) cases. The ACT was totally occlusive in 12 of 23 (52%), and NT in 17 of 23 (74%). TI was associated with an acute occlusive thrombus (OT) in 11 of 18 (61%) , and with NT in 12 (67%). All five cases with SI had a NT. Seven (30%) exhibited both an OT and NT located in different coronary arteries. Six of these had TI.

Fibrin fragments were located in the microcirculation of the myocardium in 15 of 23 (65%). These were associated with the fresh OT in 8 of 15 (53%) and with a NT in 12 of 15 (80%).

Conclude:
1. NT is more common than OT in deaths associated with acute myocardial ’infarction
2. Fibrin fragments are present in the majority of patients with ACT, particularly NT.
3. SI was consistently asscoiated with NT.
4. OT and NT are frequently present in different arteries in the same heart.
5. NT are common in patients with TI.
Digital Capillary Pressure In Diabetics With Retinopathy
Authors: Tooke J E
Published: July 2018

Patients with diabetes mellitus have an impaired capacity to di late their digital circulation. This impairment may contribute to the pathogenesis of digital ischaemia. In this study the capacity to di late digita l capillary circulation was assessed in diabetics with established microvascular disease (retinopathy) and compared with that found in diabetics who were clinically free of complications. Ten non-insulin-dependent diabetics (NIDDS) with severe retinopathy and 10 newly diagnosed NIDDS were studied in a constant temperature room maintained at 24°C following 30 minutes acclimatization. Nailfold capillary pressure (CP) was determined using a modified Landis microinjection technique. Mean ar ter ial limb CP was significantly (p<0.05) lower at 38.0 cm H2O in the patients with retinopathy compared to 47.2 cm H2 0 in the uncomplicated diabetics. Mean transcapilla ry pressure gradient in the patients with retinopathy was 6 cm H2O compared to 17 cm H2O in the uncomplicated group. There was no signif icant difference in the mean blood glucose level of the 2 groups at the time of pressure measurement. In the patients with retinopathy a r ter ial limb CP showed a negative correlation with blood glucose level (r = -0.6, p<0.05), but no correlation with duration of diabetes (r = +0.26, N.S.). These results support the contention that diabetic digital capillary perfusion is dependent on the level of blood glucose.

The lower mean capillary perfusion pressure observed in the patients with retinopathy despite a similar blood glucose level to the uncomplicated patients suggests that the diabetic who develops retinopathy has a propensity for digital ischaemia that is independent of diabetic control.
Platelet Function Parameters In Diabetic Patients
Authors: Woods A I , Meschengieser S S , Sutton N M , Lazzari M A
Published: July 2018

Abnormalities in platelet function tests have already been described in diabetic patients reflecting platelet hyperreactivity. An attempt to determine which of the tests seemed to be more affected in the diabetic population was done in a group of 34 diabetic patients (20 men and 14 women, age range 15-76). The tests performed included assay of Ristocetin Cofactor (McFarlane et al.) circulating
platelet aggregates (CPA) (Wu-Hoak) and platelet
aggregation induced by ADP in low concentration
(0.6 x 10-6M) and Bovine Factor VIII (0.001 U/ml). In matched controls only 3.5% had a positive aggregation induced by Bovine F VIII and with ADP (0.6 x 10-6M% ) the extent of maximum aggregation was 30%.

In 15 of the 34 patients (44%) aggregation induced by ADP in high dilution was greater than 50% and this was the test more frequently affected. The level of Ristocetin Cofactor was increased (>160%) in 12 of 34 patients (35%) and aggregation induced by BF VIII was positive also in 12 patients (35%). The detection of CPA was positive in 9 patients (26%). Two patients had spontaneous platelet aggregation and in them all the other tests performed were also positive. Three patients had 3 of the tests altered, and 11 patients only had 2 affected tests.

The assay more affected was the ADP induced aggregation followed by the Ristocetin Cofactor levels and BF VIII induced aggregation. The test less affected was the CPA. A correlation with clinical data will be mentioned.
Interest Of The Study Of Prekallikrein And Fibrinolysis In Diabetic Patients
Authors: Adjizian J C , Janody D , Droulle C , Jeunehomme G , Leutenegger M , Potron G
Published: July 2018

For the comprehension of macro and microangiopathy diabetes physiopathology, it appeared to us interesting to study the contact factors and plasmatic fibrinolysis. The study covered 144 patients with all types of diabetes. Measurement of prekallikrein, plasminogen and fast α2 antiplasmin were carried out on chromogen substrates (S 2302 and 2251 - Kabi) using an automatic apparatus (Kern 0 Mat 2 Coultronics).

At the same time, we studied the glycemia response, A1C hemoglobin and Willebrand factor.

A dynamic and evolutive study was made on patients with an artificial pancreas. Results showed variations due to age, diabetes equilibration and in particular low rates of prekallikrein with a decrease of the fibrinolytic system in diabetic patients with macroangiopathy.