A polysaccharide isolated from the body wall of the sea cucumber Ludwigothurea grisea has a backbone like that of mammalian chondroitin sulfate: [4-beta-D-GlcA-1-->3-beta-D-GalNAc-1]n but substituted at the 3-position of the beta--glucuronic acid residues with sulfated alpha--fucopyranosyl branches (Vieira, R. P., Mulloy, B., and Mourão, P. A. S. (1991) J. Biol. Chem. 266, 13530-13536). Mild acid hydrolysis removes the sulfated alpha--fucose branches, and cleaved residues have been characterized by 1H NMR spectroscopy; the most abundant species is fucose 4-O-monosulfate, but 2,4- and 3, 4-di-O-sulfated residues are also present. Degradation of the remaining polysaccharide with chondroitin ABC lyase shows that the sulfated alpha-L-fucose residues released by mild acid hydrolysis are concentrated toward the non-reducing end of the polysaccharide chains; enzyme-resistant polysaccharide material includes the reducing terminal and carries acid-resistant -fucose substitution. The sulfated alpha-L-fucose branches confer anticoagulant activity on the polysaccharide. The specific activity of fucosylated chondroitin sulfate in the activated partial thromboplastin time assay is greater than that of a linear homopolymeric alpha-L-fucan with about the same level of sulfation; this activity is lost on defucosylation or desulfation but not on carboxyl-reduction of the polymer. Assays with purified reagents show that the fucosylated chondroitin sulfate can potentiate the thrombin inhibition activity of both antithrombin and heparin cofactor II.

Summary. Recent studies suggest that low-dose oral contraceptives may cause acquired resistance to activated protein C (APC). The aims of this study were to determine whether hormone replacement therapy (HRT) may also induce acquired APC resistance and to study the effects of APC resistance on the risk of recurrent thrombosis. The patients comprised 140 females with at least one previous venous thromboembolism (VTE), who were randomized to receive continuous treatment with 2 mg 17-b-oestradiol and 1 mg norethisterone acetate (n 71) or placebo (n 69). Normalized APC sensitivity ratios (nAPCsr) were calculated by measurement of the effect of APC on thrombin generation in plasma collected at baseline and after 3 months of treatment. Of the 140 women, 121 had plasma samples collected both at baseline and after 3 months.The nAPCsr increased significantly (P , 0´001) on HRT (n 62), both in females not carrying the factor V Leiden mutation [mean change 0´57 (95% CI 0´45±0´70), n 50] and in females heterozygous for the factor V Leiden mutation [mean change 1´10 (0´71±1´49), n 12], but remained unchanged on placebo (n 59). The baseline nAPCsr as well as the increase in nAPCsr associated with HRT use was not higher in the five women who subsequently developed recurrent VTE. Free protein S and free TFPI were both important parameters for the acquired APC resistant phenotype. We conclude that HRT diminishes the efficacy by which APC downregulates in-vitro thrombin formation in a similar fashion to that observed with low-dose oral contraceptives, but the increase in nAPCsr alone is not sufficient to explain the increased risk of VTE associated with use of HRT.

APC resistance can be demonstrated with a thrombin generation-based test in a majority of patients with the LA laboratory phenotype. A history of thrombotic events in patients with LA is associated with a stronger resistance to the anticoagulant effect of APC.

Summary. Spinal cord injured patients are at increased risk of developing deep vein thrombosis (DVT). Whether these patients have increased blood levels of prothrombotic markers remains to be clarified. In general, the risk of developing DVT is highest in the morning hours. In healthy humans, several haemostatic and fibrinolytic parameters exhibit circadian variations, but it is not known whether this also applies to those with spinal cord injury. The aim of the present study was to examine possible circadian variations in prothrombotic markers in tetraplegic patients. We studied six patients with complete tetraplegia and eight control subjects with repetitive blood sampling over a 24 h period. While the control subjects showed marked circadian variations in factor VIII activity, prothrombin fragments 1+2 and D-dimer levels, the tetraplegic patients did not (P < 0AE05). Circadian variation in plasminogen activator inhibitor type-1 was present in both groups, being most marked (P < 0AE05) in tetraplegia. We conclude that the circadian variations of several factors of the haemostatic and fibrinolytic systems are impaired in spinal cord injury. This could possibly reflect a deregulated autonomic nervous system, leading to a dysfunctional link between central and peripheral circadian oscillators.

Summary Inhibition of tissue factor pathway inhibitor type 1 (TFPI) is one of the mechanisms by which lupus anticoagulants (LA) may upregulate tissue factor (TF) activity. We wanted to examine whether purified immunoglobulin G (IgG) from patients with LA may interfere with the ability of TFPI to inhibit ex vivo TF‐induced thrombin generation. The endogenous thrombin potential (ETP) in pooled normal plasma (PNP) supplemented with IgG from either patients with LA or controls was determined in the absence or presence of recombinant TFPI (rTFPI). In the presence of a heparin neutraliser, the ETP was also determined in plasmas from patients with LA and controls before and after heparin injection in order to quantify the anticoagulant effect of heparin‐releasable TFPI in vivo. Compared with IgG from controls (n = 14), IgG from patients with LA (n = 28) induced a wide range of enhancing or inhibitory effects on the ETP in PNP. The response to rTFPI in PNP with IgG from patients with LA correlated inversely with thrombin generation (rs = 0·637, P = 0·0003). Correspondingly, the relative inhibition of ETP in postheparin plasmas was smaller for patients (n = 11) than for controls (n = 9) (32% vs. 68%, P = 0·007). Our findings support the hypothesis that TFPI anticoagulant activity is inhibited in some patients with LA.