Gender-related differences in thrombogenic factors predicting recurrent cardiac events in patients after acute myocardial infarction. The THROMBO Investigators

Thrombosis contributes to recurrent coronary events in patients after acute myocardial infarction (AMI), but prognostic significance of thrombogenic factors by gender is unknown. This study aimed to determine gender-related differences in the prognostic significance of thrombogenic factors for predicting cardiac events (nonfatal reinfarction or cardiac death) in postinfarction patients. Blood levels of the following factors were measured 2 months after AMI in 791 men and 254 women: fibrinogen, von Willebrand factor, factor VII and VIIa, plasminogen activator inhibitor, D-dimer, cholesterol, apolipoprotein A-1, apolipoprotein B, lipoprotein(a), triglycerides, and high-density lipoprotein cholesterol. After adjustment for clinical covariates, levels of apolipoprotein A, high-density lipoprotein cholesterol, fibrinogen, and factor VIIa were significantly higher in postinfarction women than men. During a mean 26-month follow-up, there were 67 cardiac events (8.5%) in men and 14 (5.5%) in women (p = 0.11). In the multivariate Cox model, elevated levels of factor VIIa were a significant predictor of cardiac events in women (p = 0.022) but not in men (p = 0.80), with significant gender-related effect (hazard ratio 2.80 vs 0.92, respectively; p <0.05). D-dimer had prognostic value in men (p = 0. 006) but not in women (p = 0.36), although the difference between hazard ratios for men and women was not significant (2.35 vs 1.58, respectively; p = 0.49). In conclusion, elevated levels of factor VIIa are associated with an increased risk of recurrent cardiac events in postinfarction women, but not in men. D-dimer is more predictive for cardiac events in postinfarction men than women. These observations indicate possible gender-related differences in the pathophysiologic mechanisms of recurrent cardiac events.

Platelet factor V New York: a defect in factor V distinct from that in factor V Quebec resulting in impaired prothrombinase generation

Studies were performed on a patient with a longstanding bleeding disorder whose major defects were impaired platelet prothrombinase activity in the absence of added factor Va, and a platelet factor V value that was either decreased or at the lower limit of normal when assayed on multiple occasions. In contrast, plasma factor V values were consistently normal. Unlike Scott Syndrome, in which platelet prothrombinase activity is decreased in both the presence and absence of added factor V, her platelets appeared to utilize added factor Va normally in supporting the generation of prothrombinase activity. These findings suggest an intrinsic defect in platelet factor V as the basis of her platelet prothrombinase defect. This defect appears to be different than that described in the Quebec platelet disorder (factor V Quebec). Immunoblot analyses of washed platelet lysates demonstrated a pattern of variably sized factor V molecules that was entirely similar to that observed in normal platelets, and both the heavy and light chains of her factor V after thrombin cleavage were of the same size as that observed in normal platelets. In addition, her platelet multimerin was normal and immunoblot analysis excluded the type of generalized granular protein defect and pathological proteolysis that has been suggested to explain the factor V defect in the Quebec platelet disorder. The findings in this patient thus suggest a new type of platelet factor V defect as the basis for the impaired capacity of her activated platelets to support prothrombinase generation. The findings further support an important role for platelet factor V in hemostasis.

The storage defects in grey platelet syndrome and alphadelta-storage pool deficiency affect alpha-granule factor V and multimerin storage without altering their proteolytic processing

Among proteins stored in alpha-granules, multimerin and factor V share unusual features: they bind to each other, are proteolysed to unique forms and are stored eccentrically in alpha-granules. These unique features of their processing led us to study these proteins in alpha delta storage pool deficiency (alphadelta-SPD) and grey platelet syndrome (GPS, alpha-SPD), two conditions known to impair alpha-granule protein storage. Platelet factor V and multimerin were severely reduced in GPS, whereas they ranged from reduced to normal in alphadelta-SPD. The platelet levels of factor V and multimerin in these disorders indicated multimerin deficiency was not predictive of platelet factor V deficiency, although it reduced the amount of multimerin associated with platelet factor V. In GPS only, the defect in storing proteins was associated with increased multimerin and multimerin-factor V complexes in plasma. Like normal platelets, GPS and alphadelta-SPD platelets contained factor V mainly in granules. Platelet factor V and multimerin were proteolysed to normal platelet forms in GPS and alphadelta-SPD platelets, indicating that these conditions preserve some aspects of normal alpha-granule protein processing. Although we found factor V can be stored in platelets deficient in multimerin, our data indicate that multimerin storage influences the point at which multimerin binds factor V.

Further studies on the presence of functional tissue factor activity on the subendothelium of normal human and rabbit arteries

Although tissue factor (TF) activity has been observed on the subendothelial surface of rabbit aorta and human umbilical cord, immunofluorescent and in situ hybridization methods have failed repeatedly to demonstrate TF in the intima of human blood vessels. In the present study, TF activity on everted, de-endothelialized arteries was studied by two methods. One utilized a flow system and measured fibrin deposition and fibrinopeptide A formation. The other utilized a newly developed rotating probe system and measured the conversion of factor X to factor Xa in the presence of factor VIIa and Ca+2. The study attempted to control, or assess, the possibility that functional TF could have been exposed on the vessel surface by the procedures used to prepare the arterial segments. By both methods, TF activity was detected on the subendothelium of rabbit aortae and human umbilical arteries, and was unaffected by the length of storage or by inclusion of actinomycin D in the storage buffer. TF activity was also observed in the subendothelium of adult human ileo-colic, internal mammary, and renal arteries, studied by the rotating probe method. The latter may underestimate TF activity, as some of the factor Xa formed appears to bind to the subendothelial surface. TF activity (Xa formation) was detected on the luminal surface (subendothelium) of non-everted arteries, but increased activity was observed after eversion of the vessel. The source of the subendothelial TF, and its presence in normal subendothelium in vivo, requires further study. In addition, if any of the TF activity observed in this study was derived from injured endothelial or myointimal cells during preparation of the everted vessel segments, the techniques described could serve as a useful model for studying TF-induced thrombosis and factor Xa formation on injured blood vessels, and for evaluating the anti-thrombotic properties of TF-inhibitors.

Specific correction of impaired acid hydrolase secretion in storage pool-deficient platelets by adenosine diphosphate

Storage pool-deficient (SPD) platelets, which have decreased amounts of dense-granule and/or alpha-granule constituents, contain normal amounts of lysosomal acid hydrolases, but in some cases exhibit impaired secretion of these enzymes. We examined this impaired secretion response in SPD patients with varying extents of granule deficiencies, and determined the effects of added dense-granule constituents. Acid hydrolase secretion was impaired in patients with severe dense-granule deficiencies, but not in patients with lesser dense-granule deficiencies, including those with alpha-granule deficiencies as well. When dense-granule constituents (ADP, ATP, serotonin, Ca+2, pyrophosphate) were added to gel-filtered platelets, ADP, but none of the other constituents, completely corrected the impairment of thrombin and A23187-induced secretion in SPD platelets. The concentration of ADP required to normalize thrombin-induced secretion varied markedly, from 0.01 to 10 microM, among the individual patients. Fixation of platelets with formaldehyde before centrifugation did not prevent the enhancement of secretion by ADP. Excess ATP, which acts as a specific antagonist of ADP-mediated responses, completely blocked this enhancement of secretion in SPD platelets by ADP, and partially inhibited acid hydrolase secretion induced by low, but not high, concentrations of thrombin in normal platelets as well. Treatment of normal platelets with acetylsalicylic acid in vivo, but not in vitro, produced an impairment of acid hydrolase secretion similar in extent to that in SPD platelets, but which could not be completely corrected by added ADP. One possible explanation of these results is that the impairment of acid hydrolase secretion may be secondary to the dense-granule deficiency in SPD platelets, and that secreted ADP may potentiate the lysosomal secretion response in normal platelets as well.

A Study of the Cation-and pH-Dependent Stability of Factors V and VIII in Plasma*

The in vitro lability of factors V and VIII in plasma has been studied. In agreement with previous reports, an increase in anticoagulant concentration renders both factors more labile (cation-deficient decay), as does an increase in the pH above 7.3 (alkaline-decay). Calcium appears to be the plasma cation which protects factors V and VIII against in vitro loss of activity. The protection obtained by the addition of other divalent cations depended on the type of plasma used. When resin-EDTA plasma was made cation free by dialysis at 4° C and then incubated at 37° C, the rapid loss of factors V and VIII activity could be prevented by prior addition of strontium, manganese and magnesium. In oxalate plasma, nickel, manganese, cadmium and strontium were effective.

The alkaline decay of both factors V and VIII is irreversible. Partial reversibility of the cation-deficient decay was demonstrated for factor V, but not for factor VIII. The temperature coefficient for both the cation-deficient and alkaline decay is 2-3, suggesting an enzymatic rather than a physical reaction.

There was no evidence to implicate thrombin, plasmin or trypsin since inhibitors of these enzymes failed to modify either type of decay.

Optimal ordering policies for continuous review perishable inventory models

This paper extends the notions of perishable inventory models to the realm of continuous review inventory systems. The traditional perishable inventory costs of ordering, holding, shortage or penalty, disposal and revenue are incorporated into the continuous review framework. The type of policy that is optimal with respect to long run average expected cost is presented for both the backlogging and lost-sales models. In addition, for the lost-sales model the cost function is presented and analyzed.

Greater inhibition of platelet procoagulant activity by antibody-derived glycoprotein IIb--IIIa inhibitors than by peptide and peptidomimetic inhibitors

Antibody-derived GPIIb-IIIa antagonists, such as the c7E3 Fab fragment abciximab, have been shown to inhibit platelet procoagulant activity as well as platelet aggregation. Whether low-molecular-weight peptide-derived and peptidomimetic antagonists also inhibit platelet procoagulant activity in a similar manner has not been fully investigated. We compared the effects of the antibody-derived antagonists c7E3 Fab and m10E5 IgG, the peptide-derived antagonists eptifibatide, MK-852 and RGDS, and the peptidomimetic RO44--9883 on platelet procoagulant activity and on the stimulated cytosolic calcium increases that promote procoagulant activity. Procoagulant activity was measured as prothrombinase activity in gel-filtered platelets, activated by collagen plus thrombin or collagen alone, with and without stirring. The stimulated increases in cytosolic calcium were measured in parallel samples of platelets loaded with fura-2AM. Both c7E3 and m10E5 inhibited prothrombinase activity by 40--50% under all conditions of activation tested and inhibited cytosolic calcium increases to a similar extent in stirred, but not unstirred, platelets. The low-molecular-weight antagonists caused significantly less inhibition of prothrombinase activity in collagen plus thrombin-stimulated platelets, and produced no inhibition but rather a slight enhancement of activity in platelets stimulated by collagen alone. These antagonists also had little or no effect on the cytosolic calcium increases in stirred platelets. These differential effects of antibody-derived versus non-antibody GPIIb-IIIa antagonists on procoagulant activity may be a factor contributing to the differing anti-thrombotic effects of these antagonists seen in clinical trials.

Preclinical characterization of 2-[3-[3-[(5-ethyl-4'-fluoro-2-hydroxy[1,1'-biphenyl]-4-yl)oxy]propoxy]-2-propylphenoxy]benzoic acid metabolism: in vitro species comparison and in vivo disposition in rats

Assessment of the pharmacokinetics of [14C]2-[3-[3-[(5-ethyl-4'-fluoro-2-hydroxy[1,1'-biphenyl]-4-yl)oxy]propoxy]-2-propylphenoxy-]benzoic acid ([14C]LY293111), an experimental anti-cancer agent, suggested long-lived circulating metabolites in rats. In vivo metabolites of LY293111 were examined in plasma, bile, urine, and feces of Fischer 344 (F344) rats after oral administration of [14C]LY293111. Metabolites were profiled by high-performance liquid chromatography-radiochromatography, and identified by liquid chromatography (LC)/mass spectrometry and LC/NMR. The major in vivo metabolites of LY293111 identified in rats were phenolic (ether), acyl, and bisglucuronides of LY293111. Measurement of radioactivity in rat plasma confirmed that a fraction of LY293111-derived material was irreversibly bound to plasma protein and that this bound fraction increased over time. This was consistent with the observed disparity in half-lives between LY293111 and total radioactivity in rats and monkeys, and is likely due to covalent modification of proteins by the acyl glucuronide. In vitro metabolism of [14C]LY293111 in liver slices from CD-1 mice, F344 rats, rhesus and cynomolgus monkeys, and humans indicates that glucuronidation was the primary metabolic pathway in all species. The acyl glucuronide was the most prevalent radioactive peak (16% of total 14C) produced by F344 rat slices, whereas the ether glucuronide was the major metabolite in all other species (26-36% of total 14C). Several minor hydroxylated metabolites were detected in F344 rat slice extracts but were not observed in other species. The data presented suggest that covalent modification of proteins by LY293111 acyl glucuronide is possible in multiple species, although the relative reactivity of this metabolite appears to be low compared with those known to cause adverse drug reactions.

Concentration-dependent dissociation of factor VIII in 1 M NaCl

Plasma, cryoprecipitate, Hemofil, and human factor VIII concentrate were dissolved in 1.0 M NaCl and chromatographed on Bio-Gel A-5m. With high concentrations of factor VIII the activity eluted as a symmetrical peak in the void volume; with a low factor VIII concentration the procoagulant activity was retarded. Dilution curves were performed for several human factor VIII concentrates. When the concentration of factor VIII was decreased, elution patterns showed a gradual transition from a peak in the void volume to a peak with a Ve/Vo of 1.7. Cryoprecipitate exhibited a similar behavior in 1.0 M NaCl, but the percent dissociation was greater than expected at high concentrations of factor VIII. When gel filtration was performed with 0.25 M CaCl2, significant dissociation occurred at all concentrations of factor VIII tested. The behavior of factor VIII in 1.0 M NaCl closely fit a theoretically derived curve for the dissociation of a protein from its binder. We conclude that the dissociation of factor VIII in 1 M NaCl is dependent on the concentration and purification of the procoagulant protein.