Integrative Multi-omics Analysis of Childhood Aggressive Behavior

This study introduces and illustrates the potential of an integrated multi-omics approach in investigating the underlying biology of complex traits such as childhood aggressive behavior. In 645 twins (cases = 42%), we trained single- and integrative multi-omics models to identify biomarkers for subclinical aggression and investigated the connections among these biomarkers. Our data comprised transmitted and two non-transmitted polygenic scores (PGSs) for 15 traits, 78,772 CpGs, and 90 metabolites. The single-omics models selected 31 PGSs, 1614 CpGs, and 90 metabolites, and the multi-omics model comprised 44 PGSs, 746 CpGs, and 90 metabolites. The predictive accuracy for these models in the test (N = 277, cases = 42%) and independent clinical data (N = 142, cases = 45%) ranged from 43 to 57%. We observed strong connections between DNA methylation, amino acids, and parental non-transmitted PGSs for ADHD, Autism Spectrum Disorder, intelligence, smoking initiation, and self-reported health. Aggression-related omics traits link to known and novel risk factors, including inflammation, carcinogens, and smoking.

DNA methylation signatures of aggression and closely related constructs: A meta-analysis of epigenome-wide studies across the lifespan

DNA methylation profiles of aggressive behavior may capture lifetime cumulative effects of genetic, stochastic, and environmental influences associated with aggression. Here, we report the first large meta-analysis of epigenome-wide association studies (EWAS) of aggressive behavior (N = 15,324 participants). In peripheral blood samples of 14,434 participants from 18 cohorts with mean ages ranging from 7 to 68 years, 13 methylation sites were significantly associated with aggression (alpha = 1.2 × 10-7; Bonferroni correction). In cord blood samples of 2425 children from five cohorts with aggression assessed at mean ages ranging from 4 to 7 years, 83% of these sites showed the same direction of association with childhood aggression (r = 0.74, p = 0.006) but no epigenome-wide significant sites were found. Top-sites (48 at a false discovery rate of 5% in the peripheral blood meta-analysis or in a combined meta-analysis of peripheral blood and cord blood) have been associated with chemical exposures, smoking, cognition, metabolic traits, and genetic variation (mQTLs). Three genes whose expression levels were associated with top-sites were previously linked to schizophrenia and general risk tolerance. At six CpGs, DNA methylation variation in blood mirrors variation in the brain. On average 44% (range = 3-82%) of the aggression-methylation association was explained by current and former smoking and BMI. These findings point at loci that are sensitive to chemical exposures with potential implications for neuronal functions. We hope these results to be a starting point for studies leading to applications as peripheral biomarkers and to reveal causal relationships with aggression and related traits.

Urinary Amine and Organic Acid Metabolites Evaluated as Markers for Childhood Aggression: The ACTION Biomarker Study

Biomarkers are of interest as potential diagnostic and predictive instruments in personalized medicine. We present the first urinary metabolomics biomarker study of childhood aggression. We aim to examine the association of urinary metabolites and neurotransmitter ratios involved in key metabolic and neurotransmitter pathways in a large cohort of twins (N = 1,347) and clinic-referred children (N = 183) with an average age of 9.7 years. This study is part of ACTION (Aggression in Children: Unraveling gene-environment interplay to inform Treatment and InterventiON strategies), in which we developed a standardized protocol for large-scale collection of urine samples in children. Our analytical design consisted of three phases: a discovery phase in twins scoring low or high on aggression (N = 783); a replication phase in twin pairs discordant for aggression (N = 378); and a validation phase in clinical cases and matched twin controls (N = 367). In the discovery phase, 6 biomarkers were significantly associated with childhood aggression, of which the association of O-phosphoserine (β = 0.36; SE = 0.09; p = 0.004), and gamma-L-glutamyl-L-alanine (β = 0.32; SE = 0.09; p = 0.01) remained significant after multiple testing. Although non-significant, the directions of effect were congruent between the discovery and replication analyses for six biomarkers and two neurotransmitter ratios and the concentrations of 6 amines differed between low and high aggressive twins. In the validation analyses, the top biomarkers and neurotransmitter ratios, with congruent directions of effect, showed no significant associations with childhood aggression. We find suggestive evidence for associations of childhood aggression with metabolic dysregulation of neurotransmission, oxidative stress, and energy metabolism. Although replication is required, our findings provide starting points to investigate causal and pleiotropic effects of these dysregulations on childhood aggression.

Whole blood assay as a model for in vitro evaluation of inflammasome activation and subsequent caspase-mediated interleukin-1 beta release

Processing of pro-interleukin (IL)-1β and IL-18 is regulated by multiprotein complexes, known as inflammasomes. Inflammasome activation results in generation of bioactive IL-1β and IL-18, which can exert potent pro-inflammatory effects. Our aim was to develop a whole blood-based assay to study the inflammasome in vitro and that also can be used as an assay in clinical studies. We show whole blood is a suitable milieu to study inflammasome activation in primary human monocytes. We demonstrated that unprocessed human blood cells can be stimulated to activate the inflammasome by the addition of adenosine 5'-triphosphate (ATP) within a narrow timeframe following lipopolysaccharide (LPS) priming. Stimulation with LPS resulted in IL-1β release; however, addition of ATP is necessary for "full-blown" inflammasome stimulation resulting in high IL-1β and IL-18 release. Intracellular cytokine staining demonstrated monocytes are the major producers of IL-1β in human whole blood cultures, and this was associated with activation of caspase-1/4/5, as detected by a fluorescently labelled caspase-1/4/5 probe. By applying caspase inhibitors, we show that both the canonical inflammasome pathway (via caspase-1) as well as the non-canonical inflammasome pathway (via caspases-4 and 5) can be studied using this whole blood-based model.

Genome-wide analysis of DNA methylation in buccal cells: a study of monozygotic twins and mQTLs

BACKGROUND

DNA methylation arrays are widely used in epigenome-wide association studies and methylation quantitative trait locus (mQTL) studies. Here, we performed the first genome-wide analysis of monozygotic (MZ) twin correlations and mQTLs on data obtained with the Illumina MethylationEPIC BeadChip (EPIC array) and compared the performance of the EPIC array to the Illumina HumanMethylation450 BeadChip (HM450 array) for buccal-derived DNA.

RESULTS

Good-quality EPIC data were obtained for 102 buccal-derived DNA samples from 49 MZ twin pairs (mean age = 7.5 years, range = 1-10). Differences between MZ twins in the cellular content of buccal swabs were a major driver for differences in their DNA methylation profiles, highlighting the importance to adjust for cellular composition in DNA methylation studies of buccal-derived DNA. After adjusting for cellular composition, the genome-wide mean correlation (r) between MZ twins was 0.21 for the EPIC array, and cis mQTL analysis in 84 twins identified 1,296,323 significant associations (FDR 5%), encompassing 33,749 methylation sites and 616,029 genetic variants. MZ twin correlations were slightly larger (p < 2.2 × 10-16) for novel EPIC probes (N = 383,066, mean r = 0.22) compared to probes that are also present on HM450 (N = 406,822, mean r = 0.20). In line with this observation, a larger percentage of novel EPIC probes was associated with genetic variants (novel EPIC probes with significant mQTL 4.7%, HM450 probes with mQTL 3.9%, p < 2.2 × 10-16). Methylation sites with a large MZ correlation and sites associated with mQTLs were most strongly enriched in epithelial cell DNase I hypersensitive sites (DHSs), enhancers, and histone mark H3K4me3.

CONCLUSIONS

We conclude that the contribution of familial factors to individual differences in DNA methylation and the effect of mQTLs are larger for novel EPIC probes, especially those within regulatory elements connected to active regions specific to the investigated tissue.

The Contact-System Dependent Plasminogen Activator from Human Plasma: Identification and Characterization

Apart from tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), a third PA appears to occur in human plasma. Its activity is initiated when appropriate triggers of the contact system are added, and the activation depends on the presence of factor III and prekallikrein in plasma. The activity of this, so-called, contact-system dependent PA accounts for 30% of the PA activity in the dextran sulphate euglobulin fraction of plasma and was shown not to be an intrinsic property of one of the contact-system components, nor could it be inhibited by inhibitory antibodies against t-PA or u-PA. We have succeeded in identifying this third PA in dextran sulphate euglobulin fractions of human plasma. Its smallest unit (SDSPAGE) is an inactive 110 kDa single-chain polypeptide which upon activation of the contact system is converted to a cleaved, disulphide-bridged molecule with PA activity. The native form, presumably, is an oligomer, since the apparent M. on gelchromatography is 600,000. The IEP is 4.8, much lower than that of t-PA and u-PA. Although the active 110 kDa polypeptide cannot be inhibited by anti-u-PA, it yet comprises a 37 kDa piece with some u-PA related antigenic determinants. However, these determinants are in a latent or cryptic form, only detectable after denaturation by SDS. The 110 kDa polypeptide is evidently not a dimer of 55 kDa u-PA or a complex of u-PA with an inhibitor. It is probably a PA derived from a gene quite distinct from that of t-PA or u-PA, but sharing some homology with u-PA. The physiological role of this contact-system dependent PA remains to be established

A Dose-Escalating Study With the Fetal Estrogen Estetrol in Healthy Men

CONTEXT

Luteinizing hormone-releasing hormone (LHRH) agonists have replaced estrogens for endocrine treatment of advanced prostate cancer (PC) because of cardiovascular side effects. The fetal estrogen estetrol (E4) may be safer for PC treatment and is expected to decrease testosterone (T) and prevent estrogen deficiency.

OBJECTIVE

To investigate the safety and T-suppressive effect of E4 in healthy men.

DESIGN

Double-blind, randomized, placebo-controlled, dose-escalating study.

SETTING

The study was conducted at a phase I clinical unit (QPS, Netherlands).

PARTICIPANTS

Healthy male volunteers aged 40 to 70 years.

INTERVENTION(S)

Three treatment cohorts of 15 volunteers with placebo (n = 5) and E4 (n = 10). Estetrol doses tested were 20, 40, and 60 mg/d. Subjects were treated for 4 weeks.

MAIN OUTCOME MEASURES

Subjective side effects, pharmacodynamic effects on hemostatic variables, lipids, glucose, bone parameters, and endocrine parameters related to T metabolism.

RESULTS

Total and free T decreased dose-dependently and significantly. Nipple tenderness occurred in 40% and decrease of libido occurred in 30% of E4-treated men. The unwanted estrogenic effects on hemostasis were small, dose dependent, and in some cases significant. Lipid and bone parameters showed a favorable trend.

CONCLUSION

The effect of E4 on testosterone levels is insufficient for standalone PC treatment. Taking all clinical and pharmacodynamic variables into consideration, a daily dose of 40 mg E4 seems safe for further evaluation of endocrine PC treatment in combination with LHRH analogs.

Identification and Genetic Analysis of a Common Molecular Variant of Histidine-rich Glycoprotein with a Difference of 2KD in Apparent Molecular Weight

Two forms of histidine-rich glycoprotein (HRG) were detected on SDS-PAGE by silver staining and immunoblotting after isolation of the protein from pooled plasma using immuno-affinity chromatography followed by chromatography with heparin-Sepharose. Both forms were single-chain molecules and the apparent molecular weights of form 1 and form 2 were 77 kD and 75 kD respectively. Mendelian inheritance of both HRG forms was observed in four families with 24 informative meioses, strongly suggesting that the two forms are encoded by different alleles. The frequency of form 1 and form 2 in a group of 36 individuals was 0.35 and 0.65 respectively.

The difference between the two molecular variants was studied by direct sequence analysis of amplified exons of the HRG gene from 6 individuals who were homozygous either for form 1 or form 2. Five amino acid polymorphisms in three different exons were observed: Ile/Thr in exon 4; Pro/Ser in exon 5; His/Arg, Arg/Cys and Asn/Ile in exon 7. Analysis of these polymorphisms in 20 volunteers showed that only the Pro/Ser polymorphism at position 186 in exon 5 was coupled to the form of the HRG protein. Ser was found in form 1 and Pro in form 2. The presence of Ser at position 186 introduces a consensus sequence for a N-glycosylation site (Asn-X-Ser/Thr). By removing N-linked sugars with N-glycanase, it could be demonstrated that the difference between the two forms of HRG is caused by an extra carbohydrate group at Asn 184 in form 1.

Estrogens Reduce Plasma Histidine-rich Glycoprotein (HRG) Levels in a Dose-dependent Way

Plasma levels of histidine-rich glycoprotein (HRG) were investigated in three groups of women receiving a different dose of estrogens. First, the effect of low-dose estrogen was studied in a group of 83 postmenopausal women who were treated with 0.625 mg conjugated estrogens (CE). No significant change from baseline levels was found at the end of cycle 3 and cycle 13. Secondly, in 15 mothers and 23 daughters using oral contraceptives (OC) containing 30-50 fig ethinyl estradiol (EE) daily the mean HRG level was 14% and 24% lower than in a group of 144 mothers and 134 daughters not taking oral contraceptives, respectively (p < 0.05). Finally, in 11 excessively tall prepuberal girls who received 300 μg EE daily to reduce their final height the mean plasma HRG levels were decreased by 68% (p < 0.005). The effect of proges- togens administered during low-dose and high-dose estrogen therapy appeared to be minor.

The results from these three studies indicate that estrogens reduce plasma HRG levels in a dose-dependent way.

Thrombolytic Treatment with Tissue-type Plasminogen Activator (t-PA) Containing Liposomes in Rabbits: a Comparison with Free t-PA

In this study, we aimed at improving the therapeutic index of tissue- type Plasminogen Activator (t-PA) as thrombolytic agent in the treatment of myocardial infarction. Liposome-encapsulated t-PA was tested in a rabbit jugular vein thrombosis model: administration of free t-PA (t-PA) as a bolus injection in the ear vein was compared to a similar administration of liposomal t-PA (t-PA-lip), liposomal t-PA in plasminogen-coated liposomes (Plg-t-PA-lip), a mixture of free t-PA and empty liposomes (t-PA+empty lip) and a saline-blank (blank) in terms of thrombolytic activity and side effects.

Liposomal t-PA (t-PA-lip/Plg-t-PA-lip) showed a significantly better thrombolysis efficiency than equimolar doses of free t-PA (t-PA/ t-PA+ empty lip): about 0.24 mg/kg of liposomal t-PA practically equalled the lysis-activity of a dose of free t-PA of 1.0 mg/kg (t-PAlmg/kg). On the other hand, liposome encapsulation did not affect the systemic activation of alpha2-antiplasmin and plasminogen by t-PA.

We conclude that for this model an improvement in thrombolytic efficacy of t-PA is achieved by liposome encapsulation of t-PA. As t-PA-lip and Plg-t-PA-lip -treatment induced similar results, targeting of liposomal t-PA by coupled glu-Plg remains a topic to be optimized in future studies.

Von Willebrand Factor, Plasminogen Activator Inhibitor-1 and C-Reactive Protein Are Markers of Thrombolytic Efficacy in Acute Myocardial Infarction

Plasma von Willebrand factor, plasminogen activator inhibitor activity and C-reactive protein were assessed as markers of coronary recanalisation in 30 patients with acute myocardial infarction receiving tissue-type plasminogen activator (t-PA). Blood samples were taken before t-PA (time 0), 4-hourly for 24 h and daily up to 72 h. A continuous electrocardiogram was recorded in the first 24 h. Coronary arteriography was performed 90 min and 24 h after the start of t-PA. Patients with a patent infarct artery (n = 17), compared to those with occluded artery (n = 13), showed a fall in von Willebrand factor from 0 to 24 h (p = 0.001), a greater fall in plasminogen activator inhibitor from 24 to 48 h (p = 0.04) and a fall in C-reactive protein from 48 to 72 h (p = 0.002). The accuracy of these indices compared favourably with time to peak plasma MB creatine kinase and ≥ 50% resolution of maximal ST-deviation on the electrocardiogram.

Thus, changes in plasma von Willebrand factor, plasminogen activator inhibitor and C-reactive protein during the first 3 days of myocardial infarction are indicative of thrombolytic efficacy. Their concordant behaviour may reflect a common regulatory mechanism.

Protein C Antigen Levels in Major Abdominal Surgery: Relationships to Deep Vein Thrombosis, Malignancy and Treatment with Stanozolol

Activated protein C is a potent inhibitor of coagulation, and familial protein C deficiency has been associated with recurrent venous thrombosis. We have investigated protein C antigen levels in patients undergoing major elective abdominal surgery, to determine their relationships to postoperative deep vein thrombosis (DVT), malignancy, and preoperative treatment with intramuscular or oral stanozolol. Preoperative and postoperative protein C levels were not significantly different in patients with and without DVT (detected by 125I-fibrinogen leg scans), nor in patients with and without malignancy. In a placebo group (n = 26), a significant fall in protein C was maximal on the first postoperative day and persisted for 7 days. In a group given intramuscular stanozolol, 50 mg on the preoperative day (n = 23) stanozolol shortened the duration of the postoperative fall in protein C, but did not prevent DVT. In a group given oral stanozolol, 10 mg/day for 2 weeks before and 1 week after operation (n = 11), stanozolol significantly increased protein C levels prior to surgery, hence maintaining protein C at pretreatment levels after surgery. The effect of this regimen on the incidence of DVT is under study.

Stanozolol-Induced Changes in Fibrinolysis and Coagulation in Healthy Adults

The effects of orally-administered stanozolol, 5 mg b. d. on fibrinolysis, coagulation and on various haematological and biochemical parameters have been studied in 16 healthy adults, 8 males and 8 females. Statistically significant enhancement of extrinsic (tissue-type) plasminogen activator activity was detected in all subjects studied. This was associated with significant increases in plasma plasminogen and a concomitant reduction in histidine-rich glycoprotein. There were no changes in plasma urokinase activity. Changes in the coagulation system included significant reduction in plasma fibrinogen and elevation of protein C and anti thrombin III. Changes in plasma lipids included significant reduction of HDL cholesterol associated with an increase in LDL triglycerides. No change occurred in total cholesterol. There were no major differences between the sexes, nor were there serious side effects.

The effects of stanozolol on extrinsic (tissue-type) plasminogen activator activity, “free” plasminogen, protein C and antithrombin III, argue strongly in favour of its therapeutic potential.

Fibrinogen Milano II: A Congenital Dysfibrinogenaemia Associated with Juvenile Arterial and Venous Thrombosis

A congenitally abnormal fibrinogen was isolated from blood of a young man with deep-vein thrombosis. Two other affected members of his family had three episodes of severe arterial thrombosis. The fibrinogen showed a delayed clotting by thrombin, but a normal clotting by Arvin®, Reptilase®, and prothrom-bin-staphylocoagulase complex. Analysis of the fibrinopeptides A and B by High Performance Liquid Chromatography did not reveal an abnormal peptide structure. The rate of release of A and B peptides by thrombin was strongly delayed, whereas the rate of release of fibrinopeptide A by Arvin® appeared to be normal. The fibrin polymerization rate was normal. Interactions between the abnormal fibrinogen, platelets and the fibrinolytic system were also normal. Evidence is presented that the defective interaction between fibrinogen Milano II and thrombin is associated with a defective binding of thrombin to the fibrin moiety of the abnormal fibrinogen.

Improved Assay Conditions for Automated Antithrombin III Determinations with the Chromogenic Substrate S-2238

Assays for antithrombin III activity using the chromogenic substrate S-2238 were automated in various modifications on various instruments. Standard curves for the assay showed a deviating “0% point” in several but not all modifications. Addition of polyethylene glycol 6000/8000 (0.40-1.0%) minimizes this deviation. However, the deviation of the 0% point was not completely abolished in every modification of the test. Examination of Lineweaver-Burk plots showed nonlinearity at high concentrations of S-2238 as used in the antithrombin III assays. Addition of Tween-80 (0.01%) restores the Lineweaver-Burk plot and, at the same time, the standard curve in the assays is found to be linear. Therefore, we recommend the use of PEG 6000/8000 as well as Tween-80 in automated assay systems.

Evidence for the Occurrence of a Fast-Acting Inhibitor for Tissue-Type Plasminogen Activator in Human Plasma

Human plasma contains a fast-acting t-PA inhibitor, which is not identical with α2-antiplasmin or α2-macroglobulin. The concentration of this inhibitor in normal plasma is highly variable, much lower than that of known plasma protease inhibitors, and in the range of physiologically occurring plasma concentrations of t- PA (0-2 IU/ml).

The inhibitor binds to concanavalin A-Sepharose, is rather stable when heated, is not precipitated in euglobulin fractions and probably does not originate from platelets. The inhibitor seems to form a 190 Kd complex with t-PA. The relation between this plasma inhibitor and the recently discovered endothelial cell inhibitor is not yet clear.

Modulation of Rapid Plasminogen Activator Inhibitor in Plasma by Stanozolol

Fibrinolytic activity in plasma euglobulin fractions can be increased by oral administration of stanozolol. This increase is not caused by increased synthesis or release of tissue-type plasminogen activator. A decreased level of fast acting t-PA inhibition is very probably the cause of the higher activity. These results suggest that this inhibition has a regulatory role on fibrinolysis in vivo.

Inhibition of Tissue-Type Plasminogen Activator in Plasma of Women Using Oral Contraceptives and in Normal Women During a Menstrual Cycle

Tissue-type plasminogen activator (t-PA) inhibition in plasma was assessed in 15 normal women and in 10 women using oral contraceptives (OC) containing 30 μg ethinyl oestradiol and 150 μg levo-norgestrel. The levels of t-PA inhibition were significantly lower in the OC group with marked fluctuations related to the hormone cycle. Normal women had only minor fluctuations.

Effects of Oral Stanozolol Used in the Prevention of Postoperative Deep Vein Thrombosis on Fibrinolytic Activity

Plasminogen, fibrinogen, antithrombin III, euglobulin lysis time, tissue plasminogen activator (t-PA) and fast-acting t-PA inhibitor were measured in 21 patients receiving either stanozolol (10 mg orally given for 14 days preoperatively) or subcutaneous heparin, during a continuing comparative trial in the prevention of postoperative deep vein thrombosis.

Stanozolol treatment resulted in significant (p <0.01) increases between the 14th and 1st preoperative days in the plasma concentrations of plasminogen (3.4 to 4.9 Cu/ml) and antithrombin III (107% to 132%); t-PA levels did not increase significantly (6.0 to 16.0 mU/ml; p >0.1). There were significant (p <0.02) falls in fast-acting t-PA inhibitor (132% to 75%) and fibrinogen (2.4 to 1.8 g/1).

Surgery reversed the changes in fibrinolytic activity seen preoperatively in the stanozolol-treated patients, and similar changes were seen in the heparin-treated group. In this dosage, stanozolol does not appear to prevent the fibrinolytic shutdown which occurs after elective major surgery.

Behaviour and Quantitation of Extrinsic (Tissue-Type) Plasminogen Activator in Human Blood

Functional assay of extrinsic (tissue-type) plasminogen activator (EPA) in plasma on fibrin plates was evaluated. Using specific quenching antibodies, we demonstrated the method to be specific for EPA under all conditions tested. Contributions of urokinases and intrinsic activators were excluded. The quantity of EPA in blood samples, as compared with purified uterine tissue activator, shows 1 blood activator unit (BAU) to be comparable to 0.93 ng.

The median values for EPA activity for healthy volunteers were: baseline, 1.9 BAU/ml (n = 123); diurnal, 5.5 BAU/ml (n = 12); DDAVP administration, 11.7 BAU/ml (n = 39); exhaustive exercise, 25 BAU/ml (n = 24); venous occlusion (15 min), 35 BAU/ml (n = 61). A large inter-individual variation in EPA activity was found, while individual baseline values tended to be constant for periods of weeks.

In vitro in blood EPA activity shows a disappearance of 50% in about 90 min at 37° C; EPA activity in euglobulin fractions is stable for ≤2 hr at 37° C.

A rapid decrease in EPA activity occurs in vivo, as noted after extracorporal circulation and exercise stimulation (t½ decay, 2-5 min).

Increased Euglobulin Fibrinolytic Potential in Women on Oral Contraceptives Low in Oestrogen – Levels of Extrinsic and Intrinsic Plasminogen Activators, Prekallikrein, Factor XII, and C1-Inactivator

Components of the fibrinolytic system were studied in samples of plasma from 15 normal, young women and from 11 women taking oral contraceptives containing 30 μg ethinyl oestradiol and 150 μg levo-norgestrel. Fibrinolytic activity of euglobulins precipitated at pH 5.9 was higher than normal in the hormone group, with significant fluctuations related to the cycle. Normal women showed only minor fluctuations. The concentration of C1-inactivator was lower in euglobulins of the hormone group. However, the difference in fibrinolytic activity was retained, when C1-inactivator was inactivated with sodium flufenamate. Fluctuations of the extrinsic (tissue-type) plasminogen activator (t-PA) activity parallelled those of the euglobulin activity.

The intrinsic plasminogen activator activity (dextran sulphate precipitated euglobulin) was significantly increased in the hormone group and the cyclic pattern differed from that of the normal group. The increased activity was factor XII-dependent. Plasma prekallikrein did not differ. The factor XII level was increased in the hormone group but this could not explain the increased intrinsic fibrinolytic activity, suggesting an increase in the quantity of an additional factor XII-dependent proactivator.

Decreased Levels of Histidine-Rich Glycoprotein (HRG) and Increased Levels of Free Plasminogen in Women on Oral Contraceptives Low in Estrogen

Determinations by immunologic methods of histidine-rich glycoprotein (HRG) and plasminogen, were made in plasma samples collected during one normal or hormone induced cycle in 15 young, normal women and in 11 women using oral contraceptives with 30 μg ethinyl estradiol and 150 μg levo-norgestrel. The hormone group showed an increase in plasminogen level to about 150% of normal, while the concentration of HRG was decreased to about 75% of normal. This resulted in a considerable relative increase in the concentration of free plasminogen in the hormone group (calculated from the equilibrium: HRG·plasminogen ⇌ HRG + plasminogen, using KD = 1.0 μM), representing a doubling of that in the normal group. Hence, more plasminogen is available for binding to fibrin and activation in the hormone group.

The Suitability of Various Plasmin Preparations for the Functional Assay of α2-Antiplasmin in Plasma

Various plasmin preparations were tested for their suitability for use in the assay of α2-antiplasmin in blood plasma by the immediate plasmin inhibition test.

Activation of plasminogen, viz., 1-Glu-plasminogen and/or 77-Lys-plasminogen, by immobilized urokinase results in plasmin preparations suitable for this α2-antiplasmin test. Plasmins obtained by »spontaneous« activation procedures in glycerol containing solutions, however, appeared not to be suitable. In this second group, the behaviour of the plasmins resembles that of 442-Val-plasmin (miniplasmin), which is known to show a low inactivation rate with α2-antiplasmin due to the absence of lysine-binding sites in the plasmin molecule.

Evidence is presented that, in the nonsuitable plasmins, the lysine-binding sites, although not completely absent, have at least partly lost their functional integrity.

A Simple, Sensitive Spectrophotometric Assay for Extrinsic (Tissue-Type) Plasminogen Activator Applicable to Measurements in Plasma

An indirect spectrophotometric assay for extrinsic plasminogen activator has been devised, which is based on the parabolic assay of Drapier et al. (5). The system contains activator, plasminogen, the synthetic plasmin substrate H-D-Val-Leu-Lys-pNA (S-2251, Kabi) and a mixture of soluble fibrinogen fragments prepared by treatment of fibrinogen with cyanogen bromide. The addition of these fibrinogen fragments considerably enhances the sensitivity and specificity of the method owing to specific stimulation of the plasminogen activation by extrinsic plasminogen activator.

The assay conditions were optimized and the application for extrinsic plasminogen activator measurements in plasma euglobulin fractions is demonstrated.

Effect of Strenuous Exercise on Fibrinogen and Fibrinolysis in Healthy Elderly Men and Women

The elevated incidence of thrombotic disease in elderly people may be associated with an increase in PAI-1 and fibrinogen with ageing. Cross-sectional studies report an inverse relation of PAI-1 and fibrinogen with physical activity, but training studies show inconsistent results. In a controlled intervention study among elderly subjects (aged 60-80 years) we observed a moderate decrease in PAI-1 antigen (4%, -2.1 ± 2.4 ng/ml), a significant increase in t-PA activity (11%, 0.07 ± 0.04 IU/ml) and an unexpected significant increase in fibrinogen (6%, 0.18 ± 0.07 g/1) in subjects following a 6-month intensive training program as compared to controls. Reduction in PAI-1 antigen was significantly associated with a decrease in triglycerides (β = 10.3 ng/ml per 1 mM, p <0.01) and insulin (β = 2.37 ng/ml per 1 mU/1, p = 0.07). Increase in fibrinogen coincided with a rise in C-reactive protein (p <0.001). These data suggest that regular intensive activity may increase fibrinolytic activity in a moderate way, but also may cause chronically elevated plasma levels of acute phase proteins in elderly persons.

Increased Urokinase-Type Plasminogen Activator (u-PA) Levels in Graft Liver Perfusate and Decreased Single Chain u-PA Activation with Higher Levels of Aprotinin

In orthotopic liver transplantation (OLT) the graft liver is perfused with arterial blood prior to the opening of the hepatocaval anastomosis. In the present investigation we focused on the reperfusion of the graft liver in order to study the hepatic influence in the regulation of urokinase-type plasminogen activator (u-PA levels). Two different aprotinin schedules were used in 43 patients. We measured u-PA levels in the perfusate and in the corresponding systemic circulation. u-PA levels were higher in the perfusate as compared to systemic blood samples despite the dilution of the perfusate sample by the preservation fluid. This suggests u-PA secretion by the graft liver. In the presence of lower aprotinin levels signs of single-chain n-PA (scu-PA) activation was in the perfusate more prominent than systemically – a difference which was not seen in the presence of higher aprotinin levels. This seems to be an argument for the effectiveness of higher dosed aprotinin application in preventing scu-PA activation.

Seasonal Variation in Fibrinogen in the Rotterdam Study

As evidence accumulates to implicate fibrinogen as a risk indicator for cardiovascular disease, it is of interest to study its seasonal variation. A population based cross-sectional study was performed among participants of the Rotterdam Study, a cohort of 7,983 men and women, aged 55 years and over. Fibrinogen levels were measured by the prothrombin time derived method in the first 2,325 participants of the study. Fibrinogen levels were considerably higher in winter. The seasonal difference was 0.34 g/1 (95% confidence interval 0.29,0.39) and was more pronounced in subjects aged 75 years and over than in subjects aged 55 to 75 years, 0.43 g/1 (0.34,0.52) and 0.29 g/1 (0.24,0.35), respectively. Additional adjustment for body mass index, systolic and diastolic blood pressure, and total and HDL cholesterol did not materially change the findings. After adjustment for seasons, outdoor temperature was not associated with fibrinogen. Adjustment for outdoor temperature did not change the seasonal variation of fibrinogen, seasonal difference 0.31 g/1 (0.24, 0.37). In conclusion, fibrinogen levels are highest in Winter. The seasonal variation of fibrinogen is more pronounced in the elderly. Outdoor temperature does not seem to play a role in the seasonal variation of fibrinogen. Seasonal variation of fibrinogen may partly explain the increased cardiovascular disease mortality in Winter.

Coagulation Factor VII, Serum-Triglycerides and the R/Q353 Polymorphism: Differences between Older Men and Women

Coagulation factor VII activity (FVIIC) is a risk indicator for cardiovascular disease. It is related to serum-triglycerides and the R/Q353 polymorphism (alleles R and Q) in the gene coding for factor VII is strongly associated with factor VII. The association of serum- triglycerides with factor VII may differ between the genotypes, but the results of earlier studies were inconsistent and did not include older people. We studied FVII, triglycerides and the R/Q353 polymorphism in the Rotterdam Study.

In 1158 older subjects (489 men and 669 women) FVIIC, factor VII: Chr, serum-triglycerides and the R/Q353-genotype were determined.

In women triglycerides were positively associated with FVIIChr and FVIIC (FVIIChr: β = 12.4 % PP/mmol/L, CI: 10.3-14.5; FVII:C: β = 13.1% PP/mmol/L, CI: 10.4-15.8). These associations varied by genotype (FVII:Chr: RR: β = 11.7, CI: 9.6-13.8, RQ/QQ: β = 7.9, CI: 4.6-11.2; FVII:C: RR: β = 12.5, CI: 9.5-15.5, RQ/QQ: β = 6.4, CI: 1.4-11.4).

In men, the associations of FVII:Chr and FVII:C with triglycerides were weaker (FVII:Chr: β = 5.9, CI: 4.1-7.7; FVII:C: β = 8.7, CI: 6.2-11.2). There was no difference between the genotype groups.

These results suggest that only in older women the strength of the association of factor VII with serum-triglycerides varies according to genotype of the R/Q353 polymorphism.

Modulation of Plasma Fibrinogen Levels by Ciprofibrate and Gemfibrozil in Primary Hyperlipidaemia

An elevated plasma fibrinogen level is increasingly accepted as an independent risk indicator of cardiovascular disease. This has enhanced the interest in identifying agents that can normalize elevated plasma fibrinogen levels. One group of agents with this capacity are the fibric acid derivatives, e.g. ciprofibrate and gemfibrozil.

We studied fibrinogen levels after 12 weeks of treatment with ciprofibrate (n = 48) and gemfibrozil (n = 51) in hypercholesterolemic patients. The correlation of the decrease in fibrinogen with lipid lowering and the contribution of the acute phase and genetic polymorphisms to this decrease were also evaluated.

After 12 weeks of treatment, the fibrinogen levels were significantly decreased (p<0.0005) with both drugs, although the decrease in the ciprofibrate group (mean 3.4 g/1 pre-treatment to 2.4 g/1 after 12 weeks) was larger than in the gemfibrozil group (mean 3.4 g/1 to 3.0 g/1.). The lipid lowering effect was comparable for the two drugs but there was no correlation for either ciprofibrate or gemfibrozil between the lipid lowering and the magnitude or the velocity of the fibrinogen lowering effect. An attenuation of the major regulatory mechanism of plasma fibrinogen levels, the acute phase reaction, was invoked as the underlying mechanism. However, pre-treatment C-reactive protein levels were not increased and did not change after treatment. Moreover, no effects of the polymorphisms of the fibrinogen β-gene on the decrease of the plasma fibrinogen levels were observed. This suggests that a new, as yet unknown, mechanism is involved in fibrinogen lowering by fibrates.

An Amino Acid Polymorphism in Histidine-rich Glycoprotein (HRG) Explains 59% of the Variance in Plasma HRG Levels

A pedigree-based maximum likelihood method developed by Lange et al. (12) was used to study the contribution of a newly defined di-allelic polymorphism in histidine-rich glycoprotein (HRG) to the plasma levels of HRG. In four families (n = 99) and 20 volunteers we found a heritability of 70%, an age effect of 3% and an effect of individual environmental factors of 27%. These results are remarkably similar to the results found in a previous parent-twin study in which a heritability of 69% and an effect of random environment of 31% was found. The overall genetic influence in the present study can be subdivided into an effect of 59% by the HRG phenotype and 11% by residual genetic factors. The influence of the HRG phenotype of 59% can entirely be explained by adding up the effect of the two alleles that make up the phenotype. These results indicate a codominant inheritance pattern of HRG levels in which the genetic influence can almost completely be ascribed to the additive effect of the di-allelic HRG locus whereas only a small part is due to other loci.

Fibrin Binding of Plasminogen Coated Liposomes In Vitro

In this study, the fibrin binding properties of liposomes containing a number of plasminogen (Pig) molecules on the outside were compared to those of free (non-liposomal) Pig in an in vitro model system. Fibrin monolayer coated 96-wells plates were used, containing fibrin monomer at a density of around 3.4 to 3.9 × 10-4 nmol/cm2. These densities are similar to liposomal Plg-densities, thus allowing multivalent interactions to occur.

In the panel of experimental conditions that was chosen, binding of free Pig and liposomes with Pig showed three main differences in characteristics. Firstly, in the fibrin binding of Plg-liposomes not all Pig may be involved, but on the average 40% of the total amount of liposomal Pig. This was shown by lysing the liposomes after binding to the fibrin and estimation of truly bound Pig. With Plg-densities on the liposomes below the fibrin binding sites density, the maximal number of bound Pig molecules remains below the amount of available fibrin binding sites. Secondly, a higher binding rate by at least one order of magnitude was observed for liposomes with Pig compared to free Pig. Thirdly, liposomes with Pig exhibit a fibrin binding affinity which increases with Plg-density, because of the multivalent character of interaction. Liposomal Pig can successfully compete for fibrin binding sites with a 100 fold higher concentration of free Pig.

These in vitro findings indicate that in view of avid and rapid fibrin binding, liposomes with attached plasminogen may be suitable for in vivo targeting to fibrin based thrombi.

Factor XII-Dependent Fibrinolysis: A Double Function of Plasma Kallikrein and the Occurrence of a Previously Undescribed Factor XII- and Kallikrein-Dependent Plasminogen Proactivator

Fibrinolytic studies in euglobulin fractions of Fletcher trait plasma (deficient in prekallikrein) revealed reduced activities as compared to normal plasma. A quantitative assay for total plasminogen activator plus proactivator in plasma showed that the amount in Fletcher trait patients is about half of normal (normal = ± 100 blood activator units [BAU]/ ml). Plasma kallikrein partially purified in a high and low molecular weight form exerted plasminogen activator activity amounting to 10–15 BAU/ml plasma. So, the absence of kallikrein in the deficient plasma can not fully account for the reduction in activator activity. Additions of kallikrein preparations or normal plasma fractions resulted in additional activator activity in Fletcher trait plasma which was assessed at 30–40 BAU/ml. This activity was assumed to originate from a previously undescribed plasminogen proactivator whose activation is kallikrein- and factor XH-dependent.

Fractionation experiments demonstrated the presence of two major activities and a minor activity caused by kallikrein in normal plasma.

It is concluded that plasma kallikrein has two functions in the generation of factor XII- dependent fibrinolytic activity: one as a direct plasminogen activator and another as a factor in the activation of a major factor XH-dependent plasminogen proactivator.

Protection of Single-chain Urokinase-type Plasminogen Activator (scu-PA) in Aprotinin Treated Cardiac Surgical Patients Undergoing Cardiopulmonary Bypass

Intraoperative high-dose aprotinin administration has been shown to reduce the intra-and postoperative blood loss in cardiac surgery. The haemostatic effect has been attributed to platelet preserving properties and to inhibition of contact activation reducing thrombotic and fibrinolytic activity during and after cardiopulmonary bypass (CPB).

Here we report on the effects of aprotinin on urokinase-type plasminogen activator, especially on the protection of the zymogen singlechain urokinase-type plasminogen activator (scu-PA). scu-PA occurs cell associated as well as free in the circulation (concentration 50 pM, half-life 5 min), and is potentially activated by kallikrein and plasmin, both potent targets for aprotinin. The generated active two-chain u-PA (tcu-PA) is a powerful activator of fibrinolysis.

Sixteen male patients undergoing myocardial revascularization were randomly assigned to aprotinin treatment (A) or control group (C).

Plasma concentration of total u-PA antigen and of the specific forms scu-PA(zymogen) and tcu-PA(active enzyme) were measured at different stages intraoperatively and two hours postoperatively. After an initial drop due to haemodilution at the onset of CPB, the concentrations of circulating u-PA forms restored intraoperatively in A, but remained subnormal in C until the end of the observation period. The concentration of total u-PA antigen of shed mediastinal blood was both in A and C two-fold higher than in the circulation, but the antigen was preserved as the zymogen scu-PA in A and largely converted to an inactive, non activatable form in C. Intra- and postoperative blood losses were less than half the amount in A as compared to C.

It is concluded that without aprotinin administration activation of circulatory scu-PA occurs, accompanied by stimulation of fibrinolysis and bleeding, finally resulting in elimination of tcu-PA complexed with endogenous inhibitors. Furthermore, cellular release of scu-PA occurs at or near the bleeding sites, as evidenced by the two-fold higher u-PA antigen concentration in the shed mediastinal blood. The released scu-PA is also activated and subsequently converted to an inactive form unless aprotinin is administered. High-dose aprotinin application during CPB effectively protects circulating and released scu-PA from activation and attenuates bleeding consequences.

Studies on the Fibrinolytic System in Human Plasma: Quantitative Determination of Plasminogen Activators and Proactivators

Effects due to plasma plasminogen activators and proactivators are usually studied in assay systems where inhibitors influence the activity and where the degree of activation of proactivators is unknown. Quantitative information on activator and proactivator levels in plasma is therefore not available

Studies on the precipitating and activating properties of dextran sulphate in euglobulin fractionation presented in this paper resulted in the preparation of a fraction in which there was optimal recovery and optimal activation of a number of plasminogen activators and proactivators from human plasma. The quantitative assay of these activators on plasminogen-rich fibrin plates required the addition of flufenamate to eliminate inhibitors. The response on the fibrin plates (lysed zones) could be coverted to arbitrary blood activator units (BAU). Consequently, a new activator assay which enables one to quantitatively determine the plasma level of plasminogen activators and proactivators together is introduced.

Two different contributions could be distinguished: an activity originating from extrinsic activator and one originating from intrinsic proactivators. The former could be assayed separately by means of its resistance to inhibition by Cl-inactivator. Considering the relative concentrations of extrinsic and intrinsic activators, an impression of the pattern of activator content in plasma was gained. In morning plasma with baseline levels of fibrinolysis, the amount of extrinsic activator was negligible as compared to the level of potentially active intrinsic activators. Consequently, the new assay nearly exclusively determines the level of intrinsic activators in morning plasma. A pilot study gave a fairly stable level of 100 ± 15 BAU/ml (n = 50). When fibrinolysis was stimulated by venous occlusion (15 min), the amount of extrinsic activator was greatly increased, reaching a total activator level of 249 ± 27 BAU/ml (n = 7).

On the Role of C1-Inhibitor as Inhibitor of Tissue-type Plasminogen Activator in Human Plasma

An enzyme immuno assay was developed to measure complexes of tissue-type plasminogen activator (t-PA) with C1-inhibitor in order to study the role of C1-inhibitor as an inhibitor of t-PA in plasma. In vitro experiments with melanoma and recombinant t-PA learned that purified C1-inhibitor reacts with both single chain t-PA and two chain t-PA. The rate constants ranged from 3.0 to 5.2 M-1s-1 In plasma, melanoma and recombinant two chain t-PA were hardly inhibited by C1-inhibitor, in contrast to melanoma and recombinant single chain t-PA which were inhibited to the same extent by endogenous C1-inhibitor as they were by purified C1-inhibitor. In vivo, t-PA/C1-inhibitor complex could be measured in plasma in a few cases in healthy volunteers (0.62 ± 0.43 ng/ml t-PA equivalents), after exercise (0.84 ± 0.25 ng/ml t-PA equivalents) and after a desmopressin infusion (0.26 ± 0.04 ng/ml t-PA equivalents). However, t-PA/C1-inhibitor complex was found in plasma in all cases after venous occlusion (1.7 ± 0.5 ng/ml t-PA equivalents), in peritoneal fluid from patients suffering from peritoneal inflammatory disease (2.2 ± 1.3 ng/ml t-PA equivalents) and in plasma from healthy volunteers during a t-PA infusion (27.7 ± 18.5 ng/ml t-PA equivalents at peak level). In the last case, about 8 % of the infused dose of recombinant t-PA (alteplase) was inhibited by C1-inhibitor at peak level. The half-life (t1/2α) of t-PA antigen in plasma was found not to be altered when t-PA was inhibited by C1-inhibitor (4.0 min and 4.2 min, respectively). Thus, in vivo, t-PA/C1-inhibitor complex is mostly present when t-PA escapes rapid liver clearance and accumulates in one place (e.g. during venous occlusion or in peritoneal fluid) or when it circulates in high concentrations (e.g. during t-PA infusion).

Effect of Isotretinoin on Endogenous Tissue-Type Plasminogen Activator (t-PA) and Plasminogen Activator Inhibitor 1 (PAI-1) in Humans

The effect of isotretinoin on fibrinolysis was investigated in 10 healthy, male volunteers in a randomized, double-blind, crossover-designed study. Isotretinoin (40 mg) was administered in the morning and in the evening for 5 days. t-PA, u-PA and PAI-1 antigen and activity in plasma were measured every morning at 9 a.m. on days 1 to 4 and every 3 hours over 24 hours on day 5. Isotretinoin treatment had no significant stimulatory effect on endogenous t-PA antigen and activity in morning plasma samples nor on their circadian variation. Also, u-PA antigen levels did not change after isotretinoin treatment. Mean PAI-1 antigen and PAI activity in 9 a.m. plasma samples were non-significantly higher during isotretinoin than during placebo treatment. After treatment with isotretinoin a significant rise of fasting triglyceride plasma levels was observed as compared to placebo. The study shows that isotretinoin has no clinically significant effect on endogenous fibrinolysis.

Hereditary Increase of Plasma Histidine-Rich Glycoprotein Associated with Abnormal Heparin Binding (HRG Eindhoven)

Plasma histidine-rich glycoprotein (HRG) was found to be persistently increased in a patient with a history of recurrent arterial thromboembolic events. The mean concentration was 270% of normal pooled plasma. Increased HRG was found in eight of the 17 relatives studied, but none of them has experienced thrombo-embolism yet. Apparently, increased HRG was hereditary with autosomal dominant inheritance. A significant correlation was found between the increased plasma concentration of the protein and the age of the subjects (P<0.02), whereas no such relation is present in a normal population.

The plasma HRG of the proposita and 9 of her family members displayed abnormal binding to heparin, as assessed in a crossed affinity immuno-electrophoresis system: the usual increase in mobility after binding to heparin was absent. The binding of this variant HRG to plasminogen was normal. This case represents the first abnormal HRG variant reported and it is proposed to designate it: HRG Eindhoven.

Treatment of Hereditary Protein C Deficiency with Stanozolol

Five type I protein C deficient male patients received 5 mg stanozolol b.i.d. during 4 weeks. After four weeks of treatment plasma protein C activity increased from 0.42 to 0.74 U/ml and protein C antigen from 0.49 to 0.75 U/ml. This approximately 1.6 fold increase in plasma protein C was accompanied by an increase in factor II antigen (1.5 fold), factor V activity (1.6 fold), factor X antigen (1.1 fold), antithrombin III antigen (1.3 fold) and heparin cofactor II antigen (1.5 fold), while the concentration of factor VII, factor VIII, and factor IX activity, and of protein S antigen remained unchanged. Prothrombin fragment F1+2, measured in two patients, increased 1.3 fold. In addition to its effect on procoagulant and anticoagulant factors stanozolol had profibrinolytic effects, reflected in an increase in tPA activity and in the concentration of plasminogen. These data indicate that in type I protein C deficient patients stanozolol increases the concentrations of both procoagulant and anticoagulant factors and favours fibrinolysis. The efficacy of stanozolol in preventing thrombotic disease in type I protein C deficient patients, however, remains to be established. During the four weeks of stanozolol treatment no thrombotic manifestations were observed in the protein C deficient patients.

Multicentre Evaluation of Commercial Kit Methods: Plasminogen Activator Inhibitor Activity

In order to study the analytical performance of different commercial kits for determination of plasminogen activator inhibitor (PAI) activity we distributed eight selected split samples to 11 European laboratories experienced with haemostasis testing. Three different laboratories were involved in the production of data from each of the commercial kits tested. A considerable variation of PAI activity results reported from the laboratories testing the same commercial kits was observed. The range of reported results could in individual samples exceed the median value indicating an interlaboratory variation of more than 100%.

When we harmonized the results reported from different kits in different laboratories by means of an international standard from National Institute for Biological Standards and Control (NIBSC) we still observed that the results produced by some kits deviated systematically from results produced by other kits. Also, the harmonized results were used to estimate the overall coefficient of variation (CV) of PAI activity determined in various laboratories by different kits. We observed an inverse correlation between the PAI activity level and the CV with a CV of about 10Q% for low PAI activity levels and a CV of about 16% for high PAI activity levels. The high imprecision of the kits in the low concentration range of PAI activity indicates that unspecific factors in plasma may interfere with determination of active PAI. This was confirmed by the evaluation of the results from one of the plasma samples, which was PAI-1 depleted. The laboratories involved in the testing reported for this sample a mean value of 6.1 IU/ml.

In conclusion, the currently available kits for determination of PAI activity are not accurate for measurement of PAI-1 in plasma, and the kits give imprecise results particularly at low activity levels.

Multicenter Evaluation of Commercially Available Methods for the Immunological Determination of Plasminogen Activator Inhibitor-1 (PAI-1)

In order to evaluate the comparability of data obtained with various available kits for the immunological determination of PAI-1 antigen in plasma and in order to investigate the underlying cause of observed differences, e. g. problems of specificity or of proper calibration of the provided standard, a multicenter study was organised in the framework of the Subcommittee of Fibrinolysis of the Scientific and Standardization Committee.

Eight different plasma samples were distributed among 16 laboratories: a pooled normal plasma, NIBSC 87/512, PAI-1 antigen depleted plasma, PAI-1 depleted plasma supplemented with 59 ng/ml active PAI-1 and four different individual plasma samples. A considerable variation in absolute values is observed between the various kits, e.g. in pooled normal plasma a value is found ranging between 7.4 and 28 ng/ml. Harmonization of all data relative to the PAI-l-depleted plasma supplemented with an exact amount of active PAI-1 (59 ng/ml), followed by a statistical analysis using a two way analysis of variance, revealed that 6 out of 7 kits yielded values that were not significantly different with coefficients of variation around 30%. Correlations between the values obtained with these kits yielded slopes between 0.75 and 1.44 with correlation coefficients between 0.973 and 0.999. Values obtained with one kit appeared to be significantly different (even after harmonization) from the other kits (p <0.001 to p <0.05). Comparison of PAI-1 antigen with the PAI activity values in the analysed samples suggests that one kit may deal with a problem of a difference in reactivity between active and latent PAI-1.

In conclusion 6 different kits yield results that, only after harmonization, are comparable and do correlate very well. Thus proper calibration of the provided standards may solve the majority of the problems observed with PAI-1 antigen kits. Differential specificity towards different conformational forms of PAI-1, as a consequence of the use of different monoclonal antibodies, is a minor, but a potential problem, that needs to be considered when comparing data obtained with various methods.

A Parent-Twin Study of Plasma Levels of Histidine-Rich Glycoprotein (HRG)

Histidine-rich glycoprotein (HRG) is a non-enzymatic glycoprotein that acts as a modulator of several plasma proteins involved in coagulation and fibrinolysis. The contributions of genetic and environmental influences to inter-individual variation in plasma levels of HRG were studied in 160 Dutch families consisting of adolescent twin pairs and their parents. Results showed that 69% of the variance in plasma HRG concentrations could be accounted for by genetic factors. Heritability was the same in males and females and in parents and their offspring. There was no association between HRG levels of husband and wife and no evidence was found for the influence of shared family environment on the resemblance between relatives.

Pharmacokinetics of Saruplase, a Recombinant Unglycosylated Human Single-Chain Urokinase-Type Plasminogen Activator and Its Effects on Fibrinolytic and Haemostatic Parameters in Healthy Male Subjects

Pharmacokinetics of two doses of the recombinant single-chain urokinase-type plasminogen activator (r-scu-PA) saruplase (40 and 20 mg) and its effect on fibrinolytic and haemostatic parameters were studied in six healthy male subjects using a randomized, double-blind, placebo-controlled, cross-over study. Special precautions were taken to prevent artefactual in vitro effects on fibrinolytic activity.

The clearance of saruplase ranged from 310 to 862 ml/min and the apparent volume of distribution of the central compartment was about 8 1. Both doses of saruplase caused α2-antiplasmin consumption, indicating some systemic fibrinolytic activation. However, the 20 mg dose caused no detectable fibrinogen breakdown and only a small increase in total fibrin/fibrinogen degradation products (TDP) (from 0.16 μg/ml [range 0.14 to 0.19] to 0.78 μg/ml [range 0.56 to 1.26]), while the 40 mg dose produce a fibrinogen breakdown to an average value of 44% (range 19 to 60%) and TDP increased from 0.12 μg/ml (range 0.11–0.12) to 2.29 μg/ml (range 0.45 to 5.55). The breakdown of fibrinogen was related to the quantity of saruplase converted to active two-chain u-PA (tcu-PA) in vivo (6 to 22% conversion). There were no important effects of saruplase on overall blood coagulation (activated partial thromboplastin time) and platelet function (collagen induced platelet aggregation, urinary [2,3-dinor]-thromboxane B2 excretion and plasminogen activator inhibitor 1 [PAI-1] release from platelets).

Saruplase is cleared rapidly from the plasma and a variable amount is converted to tcu-PA. This two-chain form of u-PA probably causes the dose-dependent systemic fibrinolytic activation.

Influence of Heparin and a Low Molecular Weight Heparinoid on Specific Endogenous and Exogenous Fibrinolytic Factors during Rest and Exercise

The effects of heparin (5,000 IU i.v.) and the low molecular weight heparinoid Org 10172 (Orgaran®) (3,250 anti-Xa units i. v.) on components of the fibrinolytic system were studied in two double-blind, randomised, placebo-controlled, cross-over trials using healthy subjects. In study A (n = 6) the effects were studied during rest and standardized exercise and in study B (n = 6) during a low dose infusion of recombinant tissue-type plasminogen activator (rt-PA; 80 µg over 16 min). At rest, heparin and Org 10172 did not influence the plasma concentrations of endogenous t-PA antigen, and activity, urokinase-type PA (u-PA) antigen, plasmin activatable pro-urokinase (scu-PA), active urokinase (tcu-PA) and plasminogen activator inhibitor-1 (PAI-1) antigen. Recombinant t-PA antigen and activity during rt-PA infusion were also not affected. During exercise, neither heparin nor Org 10172 influenced the area under the curve (AUC) of t-PA and u-PA antigen and t-PA activity when compared with placebo. Unexpectedly, after heparin the AUC of t-PA activity was 49% larger (range +19 to +245%) than after Org 10172 (p <0.05). The last difference was considered spurious. scu-PA, tcu-PA and PAI-1 antigen levels at 2 min after termination of exercise were unaffected by both compounds (p >0.05). Sulphated polysaccharides do not increase fibrinolytic activity of the plasma by changing the concentrations of the components of the fibrinolytic system.

Hereditary Cerebral Hemorrhage with Amyloidosis -Dutch Type: A Study of Fibrinolysis

In view of reported associations between increased bleeding tendency and systemically decreased α2-antiplasmin in patients with systemic amyloid deposition we studied α2-antiplasmin, fibrinogen, C-reactive protein and blood levels of locally produced endothelial hemostasis factors in the acute and quiescent phase in 16 patients with hereditary cerebral hemorrhage with amyloidosis - Dutch type (HCHWA-D).

None of the factors measured in the quiescent phase of the disease was abnormal. In the acute phase, shortly after a stroke, only factor VIII: Ag was evidently elevated. We concluded that systemic abnormalities in the part of the fibrinolysis system studied are not likely to be responsible for multifocal and recurrent cerebral hemorrhages in HCHWA-D. The role of an elevated factor VIII: Ag level in the acute phase is unclear.