Application of an enzyme-linked immunosorbent assay (ELISA) to von Willebrand factor (vWF) and its derivatives

Markers of endothelial activity are related to components of the metabolic syndrome, but not to circulating concentrations of the advanced glycation end-product Nɛ-carboxymethyl-lysine in healthy Swedish men

Endothelial function is considered important in the development of cardiovascular diseases and type 2 diabetes. Circulating advanced glycation end-products (AGEs) and dietary components have been shown to affect endothelial function in type 2 diabetics, but determinants of endothelial function in a non-diabetic population are more poorly investigated. Therefore, we investigated relationships between dietary habits, AGEs and endothelial activation in men with isolated metabolic disturbances. Circulating markers of endothelial activation (soluble forms of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, E-selectin and von Willebrand factor) and plasma N epsilon-carboxymethyl-lysine (CML, the predominant AGE in human plasma) were analyzed in a cross-sectional study of 294 healthy men. Individuals completed a 7-day dietary record, and metabolic and inflammatory parameters were determined. NCEP/ATPIII-criteria were used to define the metabolic syndrome. Endothelial activation was higher in individuals with the metabolic syndrome, and was positively related to certain features of the syndrome (insulin, glucose, inflammation and obesity), but not to others (triacylglycerol and blood pressure). Dietary factors were related to endothelial activation, but CML was not. Multivariate analysis revealed energy and alcohol intake, along with insulin and markers of oxidative stress and inflammation, to be positive predictors of endothelial activation. In this cohort of otherwise healthy men, endothelial activation was increased in individuals with the full metabolic syndrome, but not in those with only some of the components of the metabolic syndrome. Insulin resistance, inflammation, oxidative stress, the dietary intake of energy and alcohol, but not plasma CML, predicted endothelial activation in these men.

Development of a collagen-binding activity assay as a screening test for type II von Willebrand disease in dogs

OBJECTIVE

To develop an assay to measure canine von Willebrand factor (vWF):collagen-binding activity (CBA) to screen for type 2 von Willebrand disease (vWD) in dogs.

SAMPLE POPULATION

293 plasma samples submitted for analysis of canine vWF antigen (vWF:Ag) and 12 control plasma samples from dogs with inherited type 2 or 3 vWD.

PROCEDURE

Bovine collagens were evaluated for suitability as binding substrate for vWF. Assay sensitivity to depletion, proteolytic degradation, or a genetic deficiency of high-molecular-weight vWF were determined. Amounts of vWF:Ag and vWF:CBA were measured. The ratio of vWF:Ag to vWF:CBA was used to discriminate between type 1 and type 2 vWD.

RESULTS

An assay for canine vWF activity was developed by use of mixed collagen (types I and III). When vWF:Ag was used to subtype vWD, 48% of the dogs were classified as clinically normal, 9% as indeterminate, and 43% as type 1 vWD. Inclusion of vWF activity resulted in reclassification of 5% of those identified as type 1 to type 2 vWD. However, vWF:CBA of the reclassified dogs was not persistently abnormal, a finding compatible with acquired type 2 vWD. Some Doberman Pinschers had lower antigen-to-activity ratios than other breeds with type 1 vWD, suggesting that Doberman Pinschers have more functional circulating vWF.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of canine vWF activity should be included among the vWF-specific assays used to confirm type 2 vWD. The prevalence of inherited forms of type 2 vWD in screened dogs is lower than acquired forms that can result secondary to underlying disease.

On the correlation between local fibrinolytic activity in menstrual fluid and total blood loss during menstruation and effects of desmopressin

The primary objective of this study was to investigate the correlation between fibrinolytic activity in menstrual fluid and total menstrual blood loss during menstruation. We also wanted to evaluate the influence of desmopressin nasal inhalation on the local fibrinolytic activity in menstrual fluid. Six women with objectively verified menorrhagia and six women with normal menstrual blood loss were examined. With a slender catheter introduced through the cervical canal, menstrual fluid was collected on the day in the cycle when the most intense bleeding occurred. The fibrinolytic activity in menstrual fluid was measured both as plasmin content using an amidolytic method with chromogenic substrate and with a fibrin plate method. A significant correlation between the amount of menstrual blood loss and fibrinolytic activity was found in menstrual fluid of both groups and with both methods. We could not find an increased fibrinolytic activity in menstrual fluid when the women with menorrhagia were treated with desmopressin nasal inhalation. Knowledge of the local factors influencing monthly blood loss can be valuable when searching for more effective medical treatment of menorrhagia. Apprehension that desmopressin should increase local fibrinolytic activity in menstrual fluid could not be confirmed.

Long-term beneficial effect of islet transplantation on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients

OBJECTIVE

Our aim was to evaluate the long-term effects of transplanted islets on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients.

RESEARCH DESIGN AND METHODS

A total of 34 type 1 diabetic kidney-transplanted patients underwent islet transplantation and were divided into two groups: successful islet-kidney transplantation (SI-K; 21 patients, fasting C-peptide serum concentration >0.5 ng/ml for >1 year) and unsuccessful islet-kidney transplantation (UI-K; 13 patients, fasting C-peptide serum concentration <0.5 ng/ml). Patients cumulative survival, cardiovascular death rate, and atherosclerosis progression were compared in the two groups. Skin biopsies, endothelial dependent dilation (EDD), nitric oxide (NO) levels, and atherothrombotic risk factors [von Willebrand factor (vWF) and D-dimer fragment (DDF)] were studied cross-sectionally.

RESULTS

The SI-K group showed a significant better patient survival rate (SI-K 100, 100, and 90% vs. UI-K 84, 74, and 51% at 1, 4, and 7 years, respectively, P = 0.04), lower cardiovascular death rate (SI-K 1/21 vs. UI-K 4/13, chi(2) = 3.9, P = 0.04), and lower intima-media thickness progression than the UI-K group (SI-K group: delta1-3 years -13 +/- 30 micro m vs. UI-K group: delta1-3 years 245 +/- 20 micro m, P = 0.03) with decreased signs of endothelial injuring at skin biopsy. Furthermore, the SI-K group showed a higher EDD than the UI-K group (EDD: SI-K 7.8 +/- 4.5% vs. UI-K 0.5 +/- 2.7%, P = 0.02), higher basal NO (SI-K 42.9 +/- 6.5 vs. UI-K 20.2 +/- 6.8 micro mol/l, P = 0.02), and lower levels of vWF (SI-K 138.6 +/- 15.3 vs. UI-K 180.6 +/- 7.0%, P = 0.02) and DDF (SI-K 0.61 +/- 0.22 vs. UI-K 3.07 +/- 0.68 micro g/ml, P < 0.01). C-peptide-to-creatinine ratio correlated positively with EDD and NO and negatively with vWF and DDF.

CONCLUSIONS

Successful islet transplantation improves survival, cardiovascular, and endothelial function in type 1 diabetic kidney-transplanted patients.

Effects of vaginally administered high estradiol doses on hormonal pharmacokinetics and hemostasis in postmenopausal women

OBJECTIVE

To study the effect of high doses of estradiol released from vaginal rings on the pharmacokinetics of hormones, and the long-term effect on hormones and hemostasis in postmenopausal women.

DESIGN

A pilot, nonrandomized study.

SETTING

Healthy volunteers in an academic research environment.

PATIENTS

Postmenopausal women. Eight women were treated with 17 beta-estradiol from three vaginal rings, releasing 7.5 micro g per ring for a total of 22.5 micro g over 24 hours. The rings were changed every morning for 14 days.

MAIN OUTCOME MEASURE(S)

Hemostatic changes were recorded.

RESULT(S)

Estradiol was rapidly absorbed, and statistically significant increases in the levels were found after 15 minutes; C(max) was obtained after 1 hour and a steady state after 24 hours. No statistically significant changes were found in the levels of coagulation factors V, von Willebrand factor, and activated factor VII; nor were any changes observed for activated protein C resistance, coagulation inhibitors protein C, protein S, or plasminogen activator inhibitor-1. No indication of increased thrombin formation was demonstrated by analyses of prothrombin fragment 1+2, fibrin D-dimer, and soluble fibrin. CONCLUSION(S)No statistically significant changes in hemostasis were observed from the vaginal administration of estradiol using a dose equivalent to transdermal administration with a release rate of 100 micro g per 24 hours.

Desmopressin in the treatment of menorrhagia in women with no common coagulation factor deficiency but with prolonged bleeding time

The objective of this study was to investigate the efficacy and safety of desmopressin (1-desamino-8-D-arginine vasopressin) compared with placebo in the reduction of menstrual blood loss in women with menorrhagia and prolonged bleeding time, but without common coagulation factor deficiencies. We performed a randomized, double-blind, cross-over study using 300 microg desmopressin nasal inhalation or placebo treatment in one of the two first treatment cycles. Desmopressin was given only for the 2 days during which the bleeding had been at a maximum in the previous baseline cycle. A third open cycle involved combined treatment with desmopressin and tranexamic acid during the 2 days for all patients. Menstrual blood loss during the treatment periods was compared with blood loss during placebo-treated periods using objective measurement. A significant reduction of menstrual blood loss was found in the cycles treated with combined desmopressin and tranexamic acid compared with placebo. When analyzing the blood loss during the two treatment days, there was a significant reduction in blood loss for the 2 days with desmopressin alone versus placebo. The treatment was well tolerated and no serious adverse events were recorded. In conclusion, we find that nasal desmopressin is a possible complement for the medical treatment of menorrhagia.

Hypercoagulation in surgical postmenopausal women having hormone replacement with overdose estradiol

A benefit of estradiol replacement preventing coronary heart disease (CHD) after menopause has been suggested by clinical investigations. In the department of gynecology at our hospital, we met by chance eight senior women who were hysterectomized due to different benign gynecological disorders. Acting on their own, they took a daily dose of estradiol valerate as high as 8-50 mg for 3 years, in comparison with 1-2 mg used in routine hormonal replacement therapy. We were interested to assess whether the overdose estrogen disturbs the hemostatic function, thus losing the favorable effect on CHD occurrence. Plasma levels of some procoagulants/anticoagulants were assayed in the eight women with replacement therapy and the results were compared with those of seven age-matched senior women and of 14 young healthy women with normal menstrual cycles. Using a new laboratory method recently developed by us, the overall hemostatic potential, shown as a single parameter (Abs-sum), was also determined. Results showed that high-dose estradiol activated coagulation and depressed fibrinolysis, leading to the net effect of elevated overall hemostatic potential. Thus, the overdose estradiol replacement may not be beneficial in preventing CHD after menopause, or it may even increase the risk due to the hypercoagulable state induced therefrom.

Are increased levels of von Willebrand factor in chronic coronary heart disease caused by decrease in von Willebrand factor cleaving protease activity? A study by an immunoassay with antibody against intact bond 842Tyr-843Met of the von Willebrand factor protein

Low levels of von Willebrand factor (VWF) in von Willebrand's disease type 2A (VWD 2A) result from increased cleavage of the bond 842Tyr-843Met in the VWF protein by VWF cleaving protease. On the other hand, decreased levels of this protease result in unusually large VWF in thrombotic thrombcytopenic purpura with thrombotic complications. In the present study, we designed an enzyme-liked immunosorbent assay of VWF cleaving protease activity to be used to assess whether the high levels of VWF in coronary heart disease (CHD) relate to a deficiency of this protease. Plasma samples with added Pefabloc and CaCl(2) were incubated with purified VWF coated on a microtiter plate. The remaining undigested multimers were quantified by an antibody directed against the intact 842Tyr-843Met bond of the VWF protein. Phosphate-buffered saline (PBS), instead of plasma, was used to obtain the initial level of coated undigested VWF. The reduction in absorbance at 492 nm between PBS and the unknown sample was taken as a measure of the protease activity. The assay was applied to plasma samples from 21 senior women with chronic CHD (cases) and 34 age-matched controls, as well as to samples from three patients with VWD 2A. The protease activity was similar in the two women groups (P>.05), although the VWF antigen levels were higher in the cases (P<.01). The VWD 2A patients had similar plasma levels of the protease to that in normal pooled plasma (NPP). In the senior controls, the protease activity correlated with the subject age (r's=-.61, P<.01, n=34). In conclusion, the developed method is specific for evaluating the protease function on VWF cleavage. The moderate increase of VWF antigen in chronic CHD may not depend on the protease activity. The age influence on the protease levels supports earlier findings of higher VWF levels in healthy older subjects. A high sensitivity of the mutated protein of VWF for the protease effect rather than increases in activity or quantity of the enzyme is probably involved in the pathogenesis of VWD 2A.

Circulating immune complexes induced by food proteins implicated in precocious myocardial infarction

BACKGROUND

Circulating immune complexes (CIC) are frequently found in postinfarction patients. The constituents of these CIC are mostly unknown.

AIM

The objective of the current study was to assess whether CIC containing alimentary proteins and antibodies against these proteins are implicated in precocious myocardial infarction (MI).

METHODS

Seventy-six survivors (67 men and 9 women, mean age 39 years) of a first MI before the age of 45 years were enrolled in this study. Two control groups were included. One group consisted of age-matched, randomly selected, population-based healthy individuals, 79 men and 11 women, without features of coronary heart disease. An additional control group was used only for the determination of serum antibodies against some of the alimentary proteins and consisted of 139 healthy blood donors, 95 men and 44 women, with a mean age of 42 years. Sucrose density gradient centrifugation, gel filtration and precipitation by polyethylene glycol were used for the isolation of CIC, and enzyme-linked immunosorbent assay (ELISA) was used to measure the immunoglobulin levels and specific antibodies against alimentary proteins in both sera and isolated CIC. Sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis and Western blotting were used to determine alimentary proteins in the CIC.

RESULTS

Alimentary antigens/antibodies were present in immune complex form in seven out of 14 (50%) postinfarction patients who had persistent high concentrations of CIC, the latter constituting 18% of the entire group. Antibodies of the IgG isotype predominated. A rise in CIC, signs of activation of the classical complement pathway, and a rise in plasma concentrations of von Willebrand factor antigen (vWFAg) were evident within 1 week in four patients subjected to a 2-week elimination diet followed by a single challenge with cow's milk.

CONCLUSION

This study suggests that dietary proteins occasionally give rise to persistent CIC, which may predispose to MI at a young age.

Effects of kidney-pancreas transplantation on atherosclerotic risk factors and endothelial function in patients with uremia and type 1 diabetes

Cardiovascular disease and the development of coronary artery disease play a pivotal role in increasing mortality in patients with type 1 diabetes. The aim of our study was to evaluate the effects of pancreas transplantation on atherosclerotic risk factors, endothelial-dependent dilation (EDD), and progression of intima media thickness (IMT) in patients with uremia and type 1 diabetes after kidney-alone (KA) or kidney-pancreas (KP) transplantation. A cross-sectional study comparing two groups of patients with type 1 diabetes was performed. Sixty patients underwent KP transplantation and 30 patients underwent KA transplantation. Age and cardiovascular risk profile were comparable in patients before transplantation. In all patients, atherosclerotic risks factors (lipid profile, fasting and post-methionine load plasma homocysteine, von Willebrand factor levels, D-dimer fragments, and fibrinogen) were assessed and Doppler echographic evaluation of IMT and endothelial function with flow-mediated and nitrate dilation of the brachial artery was performed. Twenty healthy subjects were chosen as controls (C) for EDD. Compared with patients undergoing KA transplantation, patients undergoing KP transplantation showed lower values for HbA1c (KP = 6.2 +/- 0.1% vs. KA = 8.4 +/- 0.5%; P < 0.01), fasting homocysteine (KP = 14.0 +/- 0.7 mcromol/l vs. KA = 19.0 +/- 2.0 micromol/l; P = 0.02), von Willebrand factor levels (KP = 157.9 +/- 8.6% vs. KA = 212.5 +/- 16.2%; P < 0.01), D-dimer fragments (KP = 0.29 +/- 0.02 microg/ml vs. KA = 0.73 +/- 0.11 microg/ml;P < 0.01), fibrinogen (KP = 363.0 +/- 11.1 mg/dl vs. KA = 397.6 +/- 19.4 mg/dl; NS), triglycerides (KP = 122.7 +/- 8.6 mg/dl vs. KA = 187.0 +/- 30.1 mg/dl; P = 0.01), and urinary albumin excretion rate (KP = 13.5 +/- 1.9 mg/24 h vs. KA = 57.3 +/- 26.3 mg/24 h; P < 0.01). Patients undergoing KP transplantation showed a normal EDD (KP = 6.21 +/- 2.42%, KA = 0.65 +/- 2.74%, C = 8.1 +/- 2.1%; P < 0.01), whereas no differences were observed in nitrate-dependent dilation. Moreover, IMT was lower in patients undergoing KP transplantation than in patients undergoing KA transplantation (KP = 0.74 +/- 0.03 mm vs. KA = 0.86 +/- 0.09 mm; P = 0.04). Our study showed that patients with type 1 diabetes have a lower atherosclerotic risk profile after KP transplantation than after KA transplantation. These differences are tightly correlated with metabolic control, fasting homocysteine levels, lower D-dimer fragments, and lower von Willebrand factor levels. Normal endothelial function and reduction of IMT was observed only in patients undergoing KP transplantation.

Haemostatic function in patients undergoing coronary artery bypass grafting: peroperative perturbations and relations to saphenous vein graft closure

Vein graft failure remains a major problem after coronary artery bypass grafting. Occlusion in the first weeks usually is caused by thrombosis, whereas intimal hyperplasia and eventually atherosclerotic changes with superimposed thrombus formation underlie subsequent closure. The present investigation was conducted as a pilot study to examine whether perturbations of haemostatic function predispose to early saphenous vein graft occlusion after coronary artery bypass grafting. Pre- and postoperative determinations (performed on the first, third, and sixth postoperative days) of haemostatic factors and inhibitors were related to the presence of graft occlusion assessed by angiography at 3 months after surgery in 100 men undergoing elective coronary artery bypass grafting for stable angina pectoris. Occlusion of one or more vein grafts within three months of surgery occurred in 23 of the 100 patients examined. The percentage increase in plasma plasminogen activator inhibitor-1 activity on the first postoperative day was significantly higher in patients who subsequently were found to have vein graft occlusion (p<0.05). Otherwise no postoperative haemostatic measurements were found to predict early vein graft closure. A perturbed plasma plasminogen activator inhibitor-1 response to coronary artery bypass grafting tentatively could be added to the vessel-specific factors that remain the main determinants of early vein graft closure.

A laboratory method for determination of overall haemostatic potential in plasma. I. Method design and preliminary results

The aim of this study was to design a simple laboratory method that can screen the overall haemostatic potential in plasma (OHPP) when a hyper- or hypocoagulable state is present. A fibrin time curve was made via spectrophotometric registration of fibrin generation and lysis in plasma, to which exogenous thrombin and tissue type plasminogen activator was added. The area under the curve, calculated by the sum of absorbance (ABS-sum), varied in correlation to the concentrations of platelets or purified pro-/anticoagulants: tissue factor, von Willebrand factor, fibrinogen, antithrombin, plasminogen, or plasminogen activator inhibitor type 1. The ABS-sums also changed in positive relation to the haemostatic function investigated in 16 menopausal women and 14 young healthy nonpregnant women (controls). The findings imply that the ABS-sums not only offer a general information about fibrin generation and lysis in vitro, but also reflect the OHPP (i.e., final combined effects of platelet activity, coagulation, and fibrinolysis in vivo). Preliminary results were satisfactory; the levels of OHPP, expressed as the ABS-sums, were higher in normal pregnant women than in the controls, and even higher in preeclamptic patients than in pregnant women with no complications, which corresponds to the different grades of hypercoagulability in the three groups. Moreover, the level of OHPP was considerably lower in an untreated infant with von Willebrand's disease type 3 and in factor VIII- or factor IX-deficient plasma samples.

Effects of an ionic and nonionic contrast agent on von Willebrand factor assessed during coronary angiography

This study shows an increase in von Willebrand factor antigen in blood collected from the coronary sinus shortly after coronary angiography with an ionic contrast agent (diatrizoate), but not a nonionic contrast agent (iohexol). These findings suggest that ionic contrast agents may cause more endothelial injury than nonionic contrast agents.

On the value of menorrhagia as a predictor for coagulation disorders

The value of menorrhagia as a predictor for mild bleeding disorders has been very little studied and the results are divergent. In the present study on 30 women with objectively verified menorrhagia, we found a significantly increased prevalence of von Willebrand's disease (20%). By keeping a strict sampling and laboratory routine, and by restricting sampling to cycle days 5-7, we also obtained a very low interindividual variation of von Willebrand factor and coagulation factor VIII. We conclude that menorrhagia is a valuable predictor for coagulation and platelet disorders, and that time of sampling is of importance. This should be considered in the investigation of menorrhagia, and can be a guideline in looking for mild bleeding disorders.

Uremic patients have decreased shear-induced platelet aggregation mediated by decreased availability of glycoprotein IIb-IIIa receptors

Bleeding and platelet dysfunction are prominent features of uremia. Sh ear-induced platelet aggregation (SIPA) involves the interaction of von Willebrand factor (vWF) with platelet membrane glycoproteins (GP) Ib and IIb-IIIa, the same receptor-ligand pair involved in in vivo adhesion and aggregation of platelets in the arterial circulation. We have used a modified rotational cone-plate viscometer to measure SIPA and calcium flux in platelets. Flow cytometric analysis of the surface expression of GP Ib and IIb-IIIa was performed using flourescein isothiocyanate-conjugated monoclonal antibodies CD42b and CD41a, respectively. Uremic patients showed decreased SIPA (controls, 43% +/- 2% [mean +/- SEM]; chronic renal failure patients, 36% +/- 3%; chronic hemodialysis patients, 26% +/- 2%; P < 0.001) along with a decrease in GP IIb-IIIa (controls, chronic renal failure patients, and chronic hemodialysis patients, 840 +/- 25, 649 +/- 42, 661 +/- 38 mean flourescence intensity, respectively; P < 0.0001). Glycoprotein Ib in uremic patients was not significantly different from normal. Chronic hemodialysis patients also demonstrated increased platelet-bound fibrinogen (P < 0.001) and platelet-bound vWF (p < 0.01). Calcium flux and thromboxane B(2) generation during SIPA of uremic platelets was normal. However, uremic plasma showed twice the normal concentration of vWF (P < 0.001) and sodium dodecyl sulfate agarose gel electrophoresis revealed the presence of fibrinogen fragments. Mixing experiments demonstrated an inhibitory effect of uremic plasma on SIPA of normal platelets (decreased from 39% +/- 3% at baseline to 31% +/- 3% after incubation in uremic plasma) along with an activation-independent increase in platelet-bound fibrinogen and platelet-bound vWF. When uremic platelets were incubated in normal plasma, their SIPA increased from 12% +/- 5% at baseline to 18% +/- 4% after incubation in normal plasma; (P = 0.002), although it did not return to normal. These results suggest that the uremic platelet dysfunction results from decreased GP IIb-IIa availability due to receptor occupancy by fibrinogen fragments (and possibly vWF fragments).

Defective platelet aggregation in uremia is transiently worsened by hemodialysis

Bleeding is a prominent feature of uremia and remains a significant cause of morbidity in hemodialysis (HD)-dependent patients. To measure the impact of the HD procedure, we performed a prospective cross-over study in eight patients placed consecutively for 2-week periods each on low-flux biocompatible polymethylmethacrylate, low-flux complement-activating cuprophane, and high-flux biocompatible polysulfone membranes. The primary measure of platelet function studied was shear-induced platelet aggregation (SIPA), which has been shown to be a physiologically relevant marker of platelet function and involves the interaction of von Willebrand factor (vWf) with platelet membrane glycoproteins (GP) Ib and IIb-IIIa. Flow-cytometric analysis of the surface expression of platelet membrane GP Ib and GP IIb-IIIa was performed using fluorescein isothiocyanate (FITC)-conjugated monoclonal antibodies CD42b and CD41a, respectively. Multivariate analysis did not demonstrate a statistically significant effect of the type of dialysis membrane on platelet aggregation, calcium flux, or thromboxane B2 production. There was a marked decrease of SIPA in HD patients (pre-HD, mean +/- SEM, 19% +/- 3%) compared with normal controls (43% +/- 3%, P < 0.001), with a further decrease after the HD procedure (post-HD, 12% +/- 2%, P = 0.015 compared with pre-HD). This intradialytic decrease in SIPA correlated with a decrease in GP Ib (pre-HD, 385 +/- 21 mean fluorescence intensity [MFI]; post-HD, 285 +/- 21 MFI, P = 0.0001). GP IIb-IIIa was also significantly decreased post-HD (pre-HD, 1,022 +/- 70 MFI; post-HD, 881 +/- 64 MFI, P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired von Willebrand's syndrome in association with a lupus-like anticoagulant corrected by intravenous immunoglobulin

We are reporting on a 47-year-old man who presented with a prolongation of the activated partial thromboplastin time (APTT) prior to orthopedic surgery. An evaluation suggested an inhibitor when his plasma prolonged a normal control APTT upon 50:50 solution of patients with normal plasma. The platelet-neutralizing procedure (PNP), anticardiolipin antibody, and antinuclear antibody (ANA) were positive. Further studies revealed decreased von Willebrand factor ristocetin cofactor (vWF:RCoF), von Willebrand factor antigen (vWF:Ag), an inhibitor to vWF, and absent high-molecular-weight vWF multimeters. Assays of FVIII:C, FIX, and FXI were nonparallel to the standard curve. Intravenous immunoglobulin (IVIG) corrected the APTT, multimeric pattern, and FVIII:C by the 7th day postinfusion. This case demonstrates the efficacy of IVIG for acquired von Willebrand's syndrome (vWS) and also represents a unique combination of a lupus-like anticoagulant and acquired vWS in a patient without the full serological requirement for systemic lupus erythematosus (SLE). Whether patients with acquired vWS and lupus inhibitors are more or less susceptible to either a thrombotic complication or hemorrhage is not established. Prospective studies for the incidence of lupus inhibitor/antiphospholipid syndromes and vWF deficiencies are needed to assess this question.

Release of von Willebrand factor by cardiopulmonary bypass, but not by cardioplegia in open heart surgery

von Willebrand Factor (vWF) is released from endothelial cells. Increased vWF in the coronary circulation during cardiac surgery could be a potential indicator of coronary endothelial injury or stimulation, and thus a possible tool to evaluate regimens of myocardial protection. Release of vWF was investigated in 12 patients undergoing coronary artery bypass surgery with cardiopulmonary bypass (CPB). Concomitant samples of arterial and coronary sinus blood for measurement of vWF (antigen method) were drawn before start of CPB and 1, 4, 10 and 30 min after release of the aortic cross clamp. Additional arterial samples were drawn pre-, per-, and postoperatively. Preoperative arterial vWF was 1.58 +/- 0.59 IU/ml (mean +/- SD), and increased during CPB (highest level 2.37 +/- 0.76 IU/ml, p < 0.0026). No difference between arterial and coronary sinus vWF levels was found. Arterial vWF increased further the first postoperative day (3.96 +/- 0.92 IU/ml, p < 0.0026). In conclusion, systemic vWF is increased during CPB, and may be a possible marker of endothelial injury/activation to evaluate deleterious effects of different equipment for CPB. Reperfusion of the ischaemic, cardioplegic heart did not release vWF in the coronary circulation.

Genetic and blood coagulation characterization of "Swedish" families with von Willebrand's disease types I and III: new aspects of heredity

Twenty-five patients with von Willebrand's disease (vWD) type III were analysed with regard to blood coagulation variables and possible deletions. Nine of the probands and their families were further investigated with DNA linkage analyses. Different patterns of heredity can be suggested in our families with vWD type III, on the basis of blood coagulation analyses. The findings suggest homozygosity in five families and the possibility of compound heterozygosity or a new mutation in the proband in three families. The linkage analyses confirm the results of the coagulation analyses. The segregation of the von Willebrand factor (vWF) gene can be followed in the families, and carrier diagnosis can be made in several of the probands' relatives. The possibility of large deletions in the vWF gene of the probands and their parents was investigated with probes representing the whole vWF cDNA. No deletions were found.

Twenty-four-hour heparin-free veno-right ventricular ECMO: an experimental study

Platelets and coagulation factors were studied during 24-hour heparin-free veno-right ventricular extracorporeal membrane oxygenation (ECMO) in 6 healthy pigs. An endpoint attached and covalently bonded heparin-coated ECMO system was used in these experiments. The veno-right ventricular ECMO supplied the total lung function of the animals, and after 24 hours, all the animals were successfully weaned from ECMO. Lung function and central hemodynamics were not affected by the procedure. Because all the animals showed a significant reduction in plasma volume, the concentration of measured coagulation variables was corrected both for plasma volume changes and for hemodilution. The platelet count and the plasma-free hemoglobin level were not significantly altered by ECMO. Similarly, the prothrombin complex, antithrombin, thrombin-antithrombin complex, factor XII, and the urinary excretion of 2,3-dinor-thromboxane B2 were not significantly altered. Fibrinogen and fibrin monomer increased significantly, whereas von Willebrand factor was significantly decreased after ECMO. In summary, 24-hour heparin-free veno-right ventricular total extracorporeal lung assistance does not affect the platelets and the coagulation system significantly in healthy juvenile pigs.

von Willebrand factor antigen in plasma and urine in patients with type I (insulin-dependent) diabetes mellitus with and without nephropathy

von Willebrand factor (vWF) antigens were quantitatively and qualitatively analyzed in plasma and urine in 41 patients with type I (insulin-dependent) diabetes. The patients were divided into three groups according to their albumin excretion: group N (n = 24) without any excretion (less than 20 micrograms/min), group M (n = 8) with microalbuminuria (20-200 micrograms/min), and group P (n = 9) with persistent albuminuria (greater than 200 micrograms/min). Healthy subjects served as controls (n = 28). The plasma concentration of vWF was higher (p less than 0.05) in the patients with diabetes mellitus than in the controls. Differences between the groups of patients were not statistically significant. The typical multimeric structure described for vWF in normal plasma was observed in all patients. In urine, significantly higher excretion of vWF fragments was observed in the three diabetic study groups as compared with the controls. In group P the patients' urinary vWF/creatinine levels tended to be higher than in groups N and M. Qualitative analysis of urinary vWF fragments demonstrated a similar distribution pattern of fragments, with three distinctive peaks, in the patients of groups N and M and in the controls. The distribution pattern of vWF fragments in group P, however, differed clearly from that in the controls and showed a great variation within the group. The urinary fragments tended to be of a higher molecular weight and several less distinct fragments with the whole spectrum of molecular weight were observed. Because in these patients with proteinuria no qualitative changes appeared in plasma, it is suggested that abnormal degradation of vWF occurred in the kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)

A sensitive immunoassay for von Willebrand factor

We have developed an ELISA specific for canine von Willebrand factor antigen (vWF:Ag) that also strongly reacts with the VWF:Ag of humans and many other vertebrates. This assay was designed to avoid the use of immunoreagents of human origin, however, commercially available antibodies to human vWF:Ag may also be used. von Willebrand factor (vWF) was quantitated using a modified double-sandwich ELISA with polyclonal antibodies specific for canine vWF:Ag. The assay was as sensitive for measuring canine vWF:Ag as previously published immuno-radiometric assays and the most sensitive ELISA for human vWF:Ag. Employing commercially available antibodies to human vWF:Ag in the same double-sandwich configuration, the lower limit of detection for human vWF:Ag was 4.8 x 10(-6) units/ml, lower by a factor of ten than previously reported ELISAs. In addition, a wide range of vWF:Ag levels can be determined with just a single plasma dilution. The assay readily distinguishes type III von Willebrand disease from other types of von Willebrand disease having very low levels of vWF. This vWF ELISA can be used to evaluate large numbers of plasma samples simultaneously and is therefore well-suited for large-scale screening programs.

Determination of urinary Tamm-Horsfall protein by ELISA using a maleimide method for enzyme-antibody conjugation

A method for enzyme-antibody conjugation using a new maleimide derivative as coupling reagent has been developed. Since a monomeric conjugate of horseradish peroxidase and Fab' antibody could be readily prepared with high efficiency and reproducibility, the enzyme activity and antigen-binding activity were well preserved and nonspecific staining was greatly reduced. The conjugate is suitable for use in both ELISA procedures and immunohistochemistry. Using both methods we examined the pathophysiological significance of Tamm-Horsfall protein (THP) and the present study describes the ELISA method to quantify urinary THP using the new method with rabbit anti-THP antibody. A low concentration (0.04 M) of urea added to the urine samples increased the linearity of the standard curve and the sensitivity of the assay, permitting the detection of as little as 20 ng/ml THP. Freezing and thawing the urine resulted in variable or lower values of THP concentration. THP concentrations in urine as determined by ELISA were stable for at least one month after -70 degrees C storage, but not after -30 degrees C storage. There was no correlation between THP concentrations in 24 h urine samples and the morning urine of the same patient. These results suggest that it is essential to use fresh or -70 degrees C stored 24 h urine samples with added urea (0.04 M) for the determination of THP concentrations in urine by the present enzyme-antibody conjugation method. The THP concentration in normal 24 h urine of young children was found to be less than 51.8 mg/g Cr.

Structural characterization of urinary von Willebrand factor by using monoclonal antibodies

The presence of von Willebrand factor (vWF) related antigens has been previously described in urine. By gel filtration, three immunoreactive peaks have been demonstrated having Mr about 350 kDa, 60 kDa and 20 kDa. In this report, a structural characterization of the urinary fragments of vWF was studied by using monoclonal antibodies having known specificities towards the plasma sub-unit. The biggest urinary fragments contain the C-terminal portion and the central portion of the sub-unit. The other two urinary fragments come from the central part of the sub-unit. Antibodies to the N-terminus of the sub-unit do not react with any of the urinary fragments. These results led to a picture for degradation of vWF that is complex and may involve sequential degradation by several proteases. Patients with different types of vWD show qualitatively the same vWF degraded material in their urines, suggesting that whatever the mechanisms for degradation of vWF they are intact in these patients. Quantitatively, it seems that in patients receiving factor VIII-vWF concentrates there is an increased tendency to vWF excretion, which may be due to the presence of denatured material in the concentrates infused to these patients.

Correlation between plasma levels of growth factors and von Willebrand factor

Intimal proliferation of smooth muscle cells is an important characteristic of developing atherosclerotic lesions and late occlusion of venous bypass grafts. Platelet-derived growth factor, released from aggregating platelets at sites of endothelial injury, has been suggested as a main factor responsible for intimal hyperplasia. The von Willebrand factor is a platelet binding protein secreted by endothelial cells and increased plasma levels of this factor has been identified as a marker of endothelial injury. In the present study we have analysed plasma levels of von Willebrand factor and growth factors in healthy controls, young post-infarction patients and patients with recent coronary bypass surgery. The results demonstrate a significant correlation between plasma growth factor activity and the level of von Willebrand factor (R = 0.52, p less than 0.01) and support the notion of a coupling between endothelial injury and release of platelets mitogens.

The combined use of monoclonal antibody-based enzyme-linked immunosorbent assays (ELISA) for factor VIII antigen (VIII:Ag) and von Willebrand factor antigen (vWF:Ag) for the detection of carriers of haemophilia A

Enzyme-linked immunosorbent assays (ELISA) for factor VIII antigen (VIII:Ag) and von Willebrand factor antigen (vWF:Ag) have been developed, each employing monoclonal antibodies. In the majority of severe haemophilic plasmas tested, VIII:Ag was undetectable by ELISA and also by immunoradiometric assay (IRMA) using haemophilic VIII:C antibodies. In haemophilic plasmas with mild/moderate deficiency of coagulant factor VIII (VIII:C), there was no significant difference between the two immunoassays although there was a general trend for ELISA VIII:Ag results to be higher. Assay of von Willebrand's disease (vWd) plasmas with the ELISA for vWF:Ag demonstrated reduced levels of this antigen in type I vWd, normal levels in type IIA, and a severe reduction of vWF:Ag in type III vWd. The discrimination of obligate carriers of haemophilia from normal was determined using ratios of factor VIII/vWF. Factor VIII antigen/von Willebrand factor antigen measured by IRMA and Laurell immunoelectrophoresis respectively, gave a superior discriminant to that of VIII:C/vWF:Ag (Laurell), but optimal discrimination was obtained with the combination of ELISAs for VIII:Ag and vWF:Ag.

Interstitial-tissue localization of high-molecular-weight kininogen in guinea-pig skin

A rabbit antibody against the light-chain of guinea-pig high-molecular-weight (HMW) kininogen, which was specific to HWM kininogen and did not recognize low-molecular-weight kininogen, was prepared. This antibody demonstrated the presence of HMW kininogen antigen at the interstitial-tissue space in the guinea-pig skin by means of immunohistochemistry. The interstitial-tissue HMW kininogen antigen was extracted from the skin. This antigen molecule in the skin extract behaved identically as HWM kininogen of plasma in slab-polyacrylamide gel electrophoresis under the presence of sodium dodecyl sulfate followed by immunoblotting. Therefore, it was concluded that HMW kininogen was present in the interstitial-tissue fluid in the skin. The amount of HMW kininogen in the skin extract was quantified by a sandwich enzyme-linked immunosorbent assay with the anti-light-chain antibody and a goat anti-guinea-pig HMW kininogen antibody. On the assumption that the interstitial-tissue volume is 50 ml/100 g wet skin tissue, the average concentration of HMW kininogen in the interstitial-tissue fluid of the skin was calculated to be 23% of the plasma concentration. On the other hand, the proportion of intravascular HMW kininogen (derived from blood remaining in the vessels of the harvested skin) in relation to the total HMW kininogen in the skin extract was quantified by measuring the radio-labelled HMW kininogen which had been injected intravenously as a tracer of the intravascular HMW kininogen. About 5% of the total HMW kininogen in the skin extract was calculated to be derived from the intravascular blood volume of the skin, indicating that the majority of the HMW kininogen in the skin extract was derived from the extravascular-tissue space.

von Willebrand factor antigen in urine

Human urine was analyzed using a sensitive enzyme linked immunosorbent assay (ELISA) for von Willebrand factor (VWF) antigen. Urine of healthy persons contained VWF immunoreactivity. In the urine of a patient with severe von Willebrand disease, the VWF antigen was not detectable before but after intravenous infusion of von Willebrand factor-Factor VIII (VWF-FVIII) concentrate. The VWF antigen in normal urine was analyzed by gel permeation high performance liquid chromatography (HPLC). Three immunoreactive components of Mr 350 KDa, 60 KDa, and 20 KDa, respectively, were observed. Chromatography on concanavalin A-Sepharose revealed heterogeneity of the major 60 KDa component since only part of the material had affinity for the matrix. The 350 KDa material displayed affinity for Con A-Sepharose but not the 20 KDa. Gel electrophoresis combined with immunoblotting of normal urine gave similar results to those obtained by HPLC analysis. Immunoreactive components with apparent molecular weights similar to the largest urinary antigens were also observed in normal plasma but they were, nevertheless, not identical to the urinary antigens.