Urinary 11-dehydro-thromboxane B(2) and coagulation activation markers measured within 24 h of human acute ischemic stroke.

The aim of this study was to determine the extent of change in platelet and coagulation markers in the acute phase of ischemic stroke and to assess the utility of marker measurement in stroke subtype classification. Urinary 11-dehydro-thromboxane B(2) (11-dTXB2), a marker of in vivo platelet activation, and markers of coagulation activation, including prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), and fibrinogen, were measured in 25 patients with ischemic stroke within 24 h of onset of symptoms. Marker levels in patients with ischemic stroke were compared with those in 19 age-matched controls who had not taken aspirin for at least 2 weeks before sampling and 25 healthy controls. Median marker levels were significantly increased in stroke over those in age-matched controls for fibrinogen (344 vs. 289 mg/dl; P=0.030), F1+2 (1.40 vs. 0.80 nmol/l; P=0.003), and TAT (6.65 vs. 2.20 microg/l; P<0.0001). Median marker levels for seven patients with cardioembolic stroke and 18 with non-cardioembolic stroke were not significantly different for any marker test. Eight patients taking aspirin at the time of the stroke had significantly lower 11-dTXB2 values than patients not taking aspirin (964 vs. 4,314 pg/mg of creatinine; P=0.007). Stroke patients not taking aspirin had significantly higher 11-dTXB2 concentration than age-matched controls (4,314 vs. 1,788 pg/mg of creatinine; P=0.006). Coagulation and platelet activation markers are increased in the acute phase of stroke regardless of the clinical mechanism. This finding suggests that the markers may not be useful for predicting clinical subtype of ischemic stroke in the acute phase.

Effect of supplementation with dietary seal oil on selected cardiovascular risk factors and hemostatic variables in healthy male subjects.

The average daily consumption of seal oil by the Inuit people is approximately 8-9 g, yet there is very little information on the effect of seal oil consumption on cardiovascular disease risk factors. In this study, 19 healthy, normocholesterolemic subjects consumed 20 g of encapsulated seal oil containing eicosapentaenoic acid (EPA; 20:5n-3), docosahexaenoic acid (DHA; 22:6n-3), and docosapentaenoic acid (DPA; 22:5n-3) or 20 g of vegetable oil (control) per day for 42 days. Levels of selected cardiovascular and thrombotic risk factors as well as fatty acid profiles of serum phospholipid and nonesterified fatty acid (NEFA) were determined. EPA levels in serum phospholipid and NEFA increased by 4.3- and 2.7-fold, respectively, in the seal oil supplemented group. DHA levels rose 1.5- and 2.1-fold, respectively, and DPA levels rose 0.5- and 0.7-fold, respectively. Arachidonic acid (AA) levels dropped by 26% in both serum phospholipid and serum NEFA. There was a significant decrease in the ratio of n-6 to n-3 fatty acids in serum phospholipid from 7.2 to 2.1 and a significant increase in the ratio of EPA/AA in NEFA. Ingestion of seal oil raised the coagulant inhibitor, protein C, values by 7% and decreased plasma fibrinogen by 18%. No alterations in other hemostatic variables, including plasma activity of Factors VII, VIII, IX, and X and antithrombin, or in the concentrations of von Willebrand Factor, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, glucose, Apo A-1, or lipoprotein(a) were observed in either group. Other risk factors for cardiovascular disease, including hematocrit, white blood cell count, plasma viscosity, systolic and diastolic blood pressures, heart rate, and platelet aggregation after stimulation with ADP or collagen did not change. Our results indicate that seal oil supplementation in healthy, normocholesterolemic subjects decreased the n-6/n-3 ratio and increased EPA, DHA, and DPA and the ratio of EPA/AA and DHA/AA in the serum phospholipid and NEFA, while exhibiting a modest beneficial effect on fibrinogen and protein C levels.

Docosahexaenoic acid and docosapentanoic acid incorporation into human platelets after 24 and 72 hours: inhibitory effects on platelet reactivity.

Short-term in vitro platelet membrane lipid enrichment studies and feeding trials of human subjects with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have shown a decreased reactivity in the platelet response to collagen. In this study, exogenous albumin-bound n-3 polyunsaturated fatty acids (PUFAs), namely EPA, DHA and docosapentanoic acid (DPA) were added to platelet suspensions and maintained at 22 degrees C for 24 and 72 hours. Subsequently, the aggregation response to agonist stimulation and the morphological appearance of the platelets were evaluated. A significant enrichment of platelet phospholipids (PL) in n-3 fatty acids occurred upon incubation with n-3 PUFAs in vitro, which was accompanied by a decrease in the aggregation response to collagen and preservation of platelet morphology compared with non-supplemented control platelet preparations. The inhibitory effect of the n-3 PUFAs appeared to be surface mediated in the case of DHA and DPA because the platelet response to agonist returned when the fatty acids were removed by washing. The platelet aggregation response after storage at 22 degrees C was also evaluated in platelet suspensions collected from healthy individuals before and after 42 days of dietary supplementation with seal oil, rich in DPA and DHA. Unlike the in vitro supplementation, in vivo modification and enrichment of platelet PLs by ingestion of seal oil did not appear to improve platelet function during storage relative to the placebo group.

Alterations in blood platelet morphology during aggregate formation in the Asian elephant (Elephas maximus).

The ultrastructure of Asian elephant (Elephas maximus) platelets before and after activation with the agonist platelet activating factor (PAF) was studied. The unactivated platelet has a distinct ultrastructural appearance: the cytoplasm contains large randomly distributed granules but lacks the internal cristae that typify the open canalicular system in many types of mammalian platelets. Following PAF stimulation, large platelet aggregates form, but many platelets remain discrete, with little evidence of pseudopod formation or fusion of membranes. Two types of platelets are visible within the aggregates: those that are morphologically intact and those with gaplike features on the outer membrane and that have become degranulated, appearing as empty swollen sacs. The lack of platelet membrane fusion within the aggregates may permit the reversal of aggregation that is a characteristic response of elephant platelets to PAF.

Alterations in bovine platelet function and acute phase proteins induced by Pasteurella haemolytica A1.

Platelet function was assessed by aggregometry in 10 Holstein calves before and after exposure to Pasteurella haemolytica (biotype A, serotype 1) by intrabronchial challenge. At 24 h after exposure the platelets had become more reactive to stimulation with known platelet agonists such as adenosine diphosphate (ADP) and platelet-activating factor (PAF) and the platelet aggregates that formed were more resistant to disaggregation. The activation of platelets was an early response in the challenged calves as platelet function had returned to pretreatment levels 72 h after exposure to the bacteria while the acute phase reactant proteins, haptoglobin and fibrinogen, were approaching their peak values and alpha 2-macroglobulin levels had also risen significantly (P < 0.05) at this time. The plasma levels of these proteins were still elevated and albumin levels were depressed 6 d post-treatment. At post-mortem all calves exhibited pneumonic tissue damage. When P. haemolytica leukotoxin was added directly to bovine platelet suspensions both spontaneous aggregation and an increase in the aggregation response to ADP and PAF stimulation were observed. The morphological appearance of the platelet aggregates exhibited the typical pattern for bovine platelets with 2 distinct zones of cells being visible within each aggregate. One zone contained platelets in which the cytoplasmic granules were still evident and the other zone contained irregularly shaped platelets devoid of granular content. In the latter zone, discrete gaps, or pores, were evident in the plasma membrane of numerous platelets. This pore formation is characteristic of leukotoxin action and is not observed in ADP or PAF induced aggregates.

An inherited platelet function defect in a Simmental crossbred herd.

An inherited bleeding disorder, resembling Simmental hereditary thrombopathy (SHT), has been identified in a Simmental crossbred herd. In an affected bull calf, initially evaluated because of excessive bleeding from a vaccination site, the platelet aggregation response to the agonist, adenosine-diphosphate (ADP) was essentially absent and the aggregation response to platelet activating factor (PAF16) was reduced by at least 70%. The initial laboratory assessment of platelet function in the dam and sire yielded results which were within normal limits. The sire was not available for further testing. The dam, also a daughter of this sire, was subsequently shown to have a partially reduced aggregation response to ADP. Of 18 other offspring of the sire evaluated, 6 were also identified as having a partially impaired aggregation response. The maximum aggregation response to ADP and PAF16 in these 6 calves was approximately 50% of the level exhibited by unaffected animals. In contrast, the coagulation profiles were normal for all animals except for a heifer calf which also exhibited a partially impaired aggregation response. The plasma level of the coagulation protein, factor XI, was reduced in this heifer calf which suffered a fatal hemorrhage following dehorning. This report appears to be the 1st to have identified animals putatively heterozygous for SHT on the basis of the in vitro platelet aggregation response to ADP.

Modulation of bovine platelet function by C-reactive protein.

The addition of C-reactive protein (CRP) to bovine platelets suspended in homologous plasma consistently produced a reversible aggregation response following stimulation with either platelet activating factor or adenosine diphosphate while untreated control samples exhibited irreversible aggregation. This deaggregation response was independent of the amount of CRP incorporated into the platelet aggregates but did appear to be mediated through a component either present in bovine plasma or loosely bound to the exterior platelet membrane. The aggregation response of bovine platelets, separated from plasma by gel-filtration, was not affected by the addition of CRP to the platelet suspensions. It is proposed that one of the physiological actions of bovine CRP is to modulate platelet function.