Ein einfacher Test für die Bestimmung der Funktion des Von-Willebrand-Faktors: die Kollagenbindungsaktivität

Die Bindung des Von-Willebrand-Faktors (vWF) an immobilisiertes Kollagen ist die Grundlage eines ELISAs, mit dem die Kollagenbindungsaktivität (vWF:CBA), ein funktioneller Parameter des vWF, bestimmt wird. Dieser Test ist so aufgebaut, daß dieselben Probenverdünnungen, Puffer und Instrumente wie bei dem ELISA für das vWF-Antigen (vWF:Ag) benutzt werden können. Damit ist es möglich, Patienten mit einem Morbus von Willebrand-Jürgens (MWJ) in die Typen I und II zu unterteilen. Der ELISA für die vWF : CBA ist sensitiv, schnell und einfach und kann mit standardisierter ELISA-Ausrüstung und minimaler Plasmamenge ausgeführt werden.

Pantoprazole does not affect performance in traffic-related safety tests: a double-blind, randomised, placebo-controlled, crossover study in healthy volunteers

OBJECTIVE AND STUDY PARTICIPANTS: The effects of pantoprazole, a potent inhibitor of gastric acid production, were evaluated in traffic-related performance tests in 18 healthy male and female volunteers, aged 18 to 60 years, in a randomised, placebo-controlled, double-blind, crossover study.

METHODS

Oral pantoprazole (40mg) or a placebo tablet was taken once a day for two periods of 5 days each, with a washout period of 7 to 14 days. Drug tolerability was assessed by vital signs, clinical laboratory parameters and volunteers' own subjective appraisal of their mental condition. The computerised Viennese test system (WTS 90) was used to examine parameters related to traffic safety including visual orientation, concentration span, acoustic reaction time, multiple choice reaction, stress, tolerance, vigilance and motor coordination. The effects were tested one day before and then on the first and fifth days of each medication period.

RESULTS

Results showed that in comparison with placebo, neither single nor multiple doses of pantoprazole led to clinically relevant differences in the performance of standardised, traffic-related safety tests.

CONCLUSION

Pantoprazole did not appear to impede normal everyday activities, including car driving, and thus can be administered without special precautions in this regard.

Radiographic progression in children with polyarticular juvenile rheumatoid arthritis: a pilot study

OBJECTIVE

To assess disease progression on hand/wrist x rays from children with polyarticular juvenile rheumatoid arthritis.

METHODS

Initial and subsequent films of 13 white children (10 girls) were read blind by a paediatric radiologist for the presence of joint space narrowing (JSN), erosions, and relative carpal length (RCL).

RESULTS

One child had subcutaneous nodules; one (of 11) was rheumatoid factor positive; six were ANA positive. Median age at diagnosis was 10.7 years (2.5 to 15.9). Median number of involved joints (swelling, pain, or decreased range of motion) at diagnosis was 16 (6 to 33). Four initial x rays had either erosions or JSN. Subsequent x rays were done at (median) 13.3 (8.3 to 24.9) months after initial x rays. One of 10 subsequent x rays had shortened RCL, and six of 13 were worse than the initial ones. Four of these developed new erosions, one had increased number of erosions, and one developed new JSN.

CONCLUSIONS

About half the children with polyarticular juvenile rheumatoid arthritis will have evidence of radiographic progression within two years after diagnosis. Thus newly diagnosed children are at high risk of substantial joint destruction and potential disability, emphasising the need for prompt treatment.

Efficacy and tolerability of pantoprazole compared with misoprostol for the prevention of NSAID-related gastrointestinal lesions and symptoms in rheumatic patients

AIM

To compare the efficacy and tolerability of pantoprazole 20 mg once daily (o.d.) with misoprostol 200 microg twice daily (b.i.d.), administered for 6 months to rheumatic patients who required long-term therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) and who were at increased risk of developing gastrointestinal lesions.

METHODS

This randomized, double-blind, multicenter, parallel group comparison study was performed with rheumatic patients (n = 515) who were likely to take NSAIDs continuously for at least 6 months. Patients were 55 years or older, at risk to develop gastrointestinal lesions, had less than five erosions/petechiae in the stomach and duodenum, no ulcers, no reflux esophagitis (endoscopy-proven), and gastrointestinal symptoms of at most moderate intensity. A minimum daily dose was defined for NSAIDs (COX-2 inhibitors were not available at the time). Patients were randomized to take either pantoprazole 20 mg o.d. (n = 257) or misoprostol 200 microg b.i.d. (n = 258) for 6 months while continuing NSAID therapy. Endoscopy was performed at baseline, 3, and 6 months.

RESULTS

Pantoprazole was superior to misoprostol (p < 0.001) with regard to 'therapeutic failure' (occurrence of a peptic ulcer, ten or more erosions/petechiae in the stomach/duodenum, reflux esophagitis, severe gastrointestinal symptoms, and/or 'likely' or 'definitely' related adverse event leading to study termination). Estimated remission rates at 3 and 6 months (Kaplan-Meier life-table analysis) were, respectively, 93 and 89% (pantoprazole) and 79 and 70% (misoprostol). Pantoprazole was superior to misoprostol (p = 0.005) with regard to 'endoscopic failure' (occurrence of a peptic ulcer, ten or more erosions/petechiae in the stomach/duodenum, or reflux esophagitis) after 6 months. Estimated remission rates at 3 and 6 months were, respectively, 98 and 95% (pantoprazole) and 95 and 86% (misoprostol). Patients discontinuing the study early due to adverse events 'likely' or 'definitely' related to the study drug accounted for 13/257 (5%) in the pantoprazole and 33/258 (13%) in the misoprostol treatment groups.

CONCLUSION

Pantoprazole 20 mg o.d. is superior to misoprostol 200 microg b.i.d. in the prevention of NSAID-induced gastrointestinal lesions and symptoms in patients on continuous long-term treatment with NSAIDs due to rheumatic diseases and at risk to develop such lesions or symptoms.

Function of von Willebrand factor in children with diarrhea-associated hemolytic-uremic syndrome (D+ HUS)

Reports on von Willebrand factor (vWF) in hemolytic-uremic syndrome (HUS) are not unequivocal. Because of potential pathogenic implications, we examined the ability of vWF to bind to collagen in vitro, which reflects its function. Plasma vWF antigen (vWF:Ag) and collagen-binding activity (vWF:CBA) were measured by enzyme-linked immunosorbent assay in children with (1) diarrhea-associated (D+) HUS (n = 27), (2) chronic renal insufficiency (CRI) (n = 8), (3) gastroenteritis (GE) not associated with HUS (n = 15), (4) immune thrombocytopenia (ITP) (n = 40) and from controls (n = 35). Structural vWF was evaluated by multimer analysis. Children with D+ HUS had vWF:Ag of 2.53 and vWF:CBA of 1.98 U/mL. The corresponding values for patients with ITP were 1.35 and 1.82 U/mL, with CRI 1.55 and 1.55 U/mL, and with GE 1.68 and 2.10 U/mL; all values were higher than in controls (1.04 and 1.16 U/mL). The mean ratio of vWF:CBA to vWF:Ag ratio in controls was 1.13; only children with HUS had a dysfunctional vWF, as indicated by a low ratio of 0.78; the ratio was elevated in children with ITP (1.36) and GE (1.27) and was normal in those with CRI (1.06). No ultralarge molecular multimers of vWF were detected in any group, including HUS. The very high concentration of plasma vWF:Ag in HUS probably reflects endothelial cell damage or irritation. In contrast to all other groups, only children with HUS had a dysfunctional vWF, caused either by a primary (due to enterohemorrhagic Escherichia coli) or secondary (due to consumption of functionally active vWF) process. This abnormality was not obvious as structural anomaly by multimer analysis.

Bleeding and thrombosis in children with acute lymphoblastic leukaemia, treated according to the ALL-BFM-90 protocol

A multi-center retrospective survey was conducted to evaluate the incidence and types of hemostatic complications occurring in children with acute lymphoblastic leukemia (ALL) during treatment according to the ALL-BFM-90 treatment protocol. All of the BFM-treatment centers (n = 77) were approached and a 95% response rate with information on 1100 patients was obtained. Thrombotic or bleeding episodes occurred in 31 patients (2.8%), 19 of whom had thrombosis and 12 bleeding complications, involving the central nervous system (42%), the subclavian vein (29%), the gastro-intestinal tract, skin, lower extremities or pelvis (29%). Recovery was noted in 28 of 31 patients, while 3 died as a result of hemostatic complications. Bleeding or thrombosis occurred in patients receiving prophylactic substitution with plasma or plasma-derived concentrates (n = 16) as well as in those without substitution (n = 13). The majority of hemostatic complications (90%) occurred during the induction therapy of the treatment protocol, in particular during the period which included simultaneous administration of glucocorticoids and E. coli L-asparaginase. The concurrent administration of E. coli L-asparaginase and glucocorticoids may be an additional risk factor for thromboembolic events during therapy according to the ALL-BFM-90 protocol.

Effect of glucocorticoids, E. coli- and Erwinia L-asparaginase on hemostatic proteins in children with acute lymphoblastic leukemia

BACKGROUND

The concentrations of plasma hemostatic proteins were analyzed prospectively in 42 children with acute lymphoblastic leukemia (ALL), treated according to the protocol ALL-BFM-90.

PROCEDURE

Treatment included glucocorticosteroids (GC), E. coli L-asparaginase (Asparaginase, Medac) or Erwinia L-asparaginase (Erwinase, Speywood), vincristine, anthracyclines and intrathecal methotrexate. The analysis of hemostatic proteins was performed during induction and re-induction therapy.

RESULTS

At diagnosis, the plasma concentrations of fibrinogen, antithrombin III (AT), plasminogen and protein C were within normal limits, whereas the von Willebrand factor antigen (vWF:Ag) was elevated. After eight days of mono-therapy with GC the concentration of fibrinogen decreased to 59%, vWF:Ag decreased to 67%, AT increased to 124%, protein C increased to 201% of the initial value (mean all p < or = 0.01), while the concentration of plasminogen remained unchanged. During the re-induction phase, the concentrations of the hemostatic proteins, with exception of vWF:Ag, altered in a similar way in response to GC as observed during the induction phase. Administration of two doses of E. coli L-asparaginase (10,000 U/m2) during the induction therapy led to a significant decrease of AT (123 +/- 24 to 63 +/- 15%/mL), protein C (168 +/- 34 to 87 +/- 19%/mL), plasminogen (94 +/- 21 to 41 +/- 12%/mL) and fibrinogen (148 +/- 59 to 79 +/- 30 mg/dL, p < or = 0.01 for all parameters). In contrast, administration of two doses of Erwinia L-asparaginase (10,000 U/m2) during re-induction therapy did not lead to change in the concentration of AT, protein C or plasminogen, and the decrease in fibrinogen (162 +/- 17 to 121 +/- 24 mg/dL) was less pronounced.

CONCLUSIONS

Our results indicate that GC and E. coli L-asparaginase, in particular, induce hemostatic alterations which have implications on our understanding of thrombotic and hemorrhagic events during the treatment of ALL in children.

Selectivity of von Willebrand factor triplet bands towards heparin binding supports structural model

Human plasma-derived von Willebrand factor (hp-vWF) and recombinant von Willebrand factor (r-vWF) have been fractionated by heparin affinity chromatography followed by multimer analysis using SDS-agarose gel electrophoresis. Because heparin binding sites are contained in each vWF subunit, high molecular weight multimers of r-vWF and hp-vWF, respectively, were eluted with higher salt concentration, in comparison to r-vWF and hp-vWF molecules with a low degree of multimerization. Heparin affinity chromatography did not affect the multimer composition of r-vWF. By contrast, faster migrating satellite bands and slower migrating satellite bands of hp-vWF exhibited reduced and increased heparin affinity, respectively, compared to the intermediate band of the same triplet. Because heparin binding sites are localised in the N-terminal domain of the hp-vWF subunit, this result confirms a structural model of hp-vWF (Fischer et al., Biochem. J. 1998;331:483-488) suggested recently, in which the slower migrating satellite bands have excess of one N-terminal fragment and the faster migrating satellite bands lack one N-terminal fragment, respectively, in comparison with the corresponding intermediate triplet band.

Continuous infusion of FVIII and FIX concentrates: in vitro analysis of clinically relevant parameters

A high purity factor VIII/von Willebrand Factor (FVIII/vWF) concentrate (IMMUNATE [STIM plus]) (n = 6 batches), and a high purity factor IX (FIX) concentrate (IMMUNINE [STIM plus]) (n = 7 batches), were assessed in vitro for their applicability to continuous infusion. Parameters pertinent to continuous infusion were investigated and included stability, sterility and, in the case of FIX, the generation of potentially thrombogenic components. Four stationary or transportable mini infusion pumps, equipped with polyethylene, polypropylene or polyvinylchloride plastic components were used. The concentrates were reconstituted without extra filling volume and perfused at 12.5 mL h-1 and 1 mL h-1; sampling was carried out at the start of the experiment and for up to 48 h. The FVIII procoagulant activity (FVIII:C) was assayed by amidolytic, 1-stage and 2-stage assays; vWF was examined for ristocetin cofactor activity, antigen and multimers. The FIX coagulation activity (FIX:C) was determined by a 1-stage coagulation assay; thrombogenicity potential was assessed in vivo (Wessler stasis model in rabbits) and in vitro (FIXa and nonactivated thromboplastin time). Reconstituted concentrate incubated under the same conditions served as a control. Both concentrates remained sterile throughout the testing period. The perfused and control samples remained stable, retaining over 95% of activity for FVIII:C and over 90% for FIX:C for up to 48 h. Intermittent decrease of FVIII:C or FIX:C was not observed, suggesting no adsorption of FVIII or FIX onto plastic surfaces during either short or long-term exposure. No thrombogenic components were detected in the high purity FIX concentrate. Thus, under the in vitro conditions used, FVIII/vWF and FIX were found to be suitable for administration by continuous infusion.

Elevation of melatonin in chicken retina by 5-hydroxytryptophan: differential light/dark responses

Melatonin is synthesized in the chicken retina under the influence of a circadian clock, which also regulates the expression of tryptophan hydroxylase (TPH) and serotonin N-acetyltransferase (AA-NAT). In order to examine the role of substrate supply in the rhythmic synthesis of melatonin in chicken retina, tryptophan and 5-hydroxytryptophan were administered day and night in light or darkness. When administered systemically at night in darkness, 5-hydroxytryptophan, but not tryptophan, dramatically stimulates melatonin levels in the chick retina in a dose-dependent manner. Intraocular administration of 5-hydroxytryptophan also increases melatonin levels locally, indicating a retinal site of action of the serotonin precursor. The effect of 5-hydroxytryptophan is much greater at night, when TPH and AA-NAT activities are high, than during the day, when the enzyme activities are low. Similarly, unexpected light exposure at night, which inactivates AA-NAT, significantly reduces the ability of 5-hydroxytryptophan to increase retinal melatonin levels. The results suggest that TPH, but not AA-NAT or other enzymes in the melatonin biosynthetic pathway, is saturated with substrate in situ. The rate of melatonin production appears to be a function of the concentration of serotonin, which is regulated by TPH, and by the level of activity of AA-NAT.

von Willebrand factor: measuring its antigen or function? Correlation between the level of antigen, activity, and multimer size using various detection systems

von Willebrand factor (vWF) from normal human plasma was purified and separated into three fractions containing high, medium, and low molecular weight vWF multimers. vWF fractions were tested for (1) vWF-antigen (vWF:Ag); (2) vWF-ristocetin cofactor activity (vWF:RiCof); (3) vWF-collagen binding activity (vWF:CBA); and (4) a monoclonal antibody-binding ELISA (mAB-binding ELISA), based on the vWF binding to immobilized monoclonal antibody directed to the glycoprotein Ib-binding region within the A1 domain of vWF. The three different fractions of vWF showed a correlation between multimer size and vWF:RiCof/vWG:Ag and vWF:CBA/vWF:Ag, respectively. In contrast, results obtained with the mAB-binding ELISA showed identical levels of mAB-binding/vWF:Ag, without regard for the multimer size present in the tested fraction. Our results therefore suggest that in the case of structurally normal vWF the mAB-binding ELISA reflects the concentration of vWF:Ag rather than vWF function. It is feasible that while the mAB-binding ELISA may show reduced levels for abnormal vWF protein, structurally altered within the A1 domain of vWF as in some patients with vWD type 2, this assay does not appear to be suitable for functional analysis of structurally intact vWF.

Triplet structure of human von Willebrand factor

Human von Willebrand factor (hp-vWF) is a high-molecular- mass protein found in plasma as a series of multimers. It consists of subunits comprising 2050 amino acids linked by disulphide bonds into multimers of various size ranging in molecular mass up to greater than 10000kDa. Partial proteolysis at position Tyr842-Mer843 of the subunit [Dent et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 6306-6310] by a vWF-specific protease [Furlan et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 7503-7507] results in the generation of an N-terminal and a C-terminal fragment and the appearance of hp-vWF triplet bands. It has been suggested [Furlan et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 7503-7507] that (i) the intermediate triplet band of the primary dimer represents a dimer of two C-terminal fragments, (ii) the slower migrating satellite band of the primary dimer represents an asymmetric structure composed of a mature subunit to which one N-terminal and one C-terminal fragment are linked by disulphide bonds, and (iii) the faster migrating satellite band of the primary dimer contains two N-terminal fragments. Here we used recombinant vWF (r-vWF) for structural analysis of hp-vWF multimers. r-vWF exhibited no proteolytic degradation and all multimers contained mature subunits. High-resolution agarose-gel electrophoresis and two-dimensional electrophoresis demonstrated that (i) r-vWF multimers and hp-vWF intermediate triplet bands exhibited identical molecular mass and electrophoretic mobilities, (ii) the faster and slower migrating satellite bands of hp-vWF differ by less than the molecular mass of one subunit from the corresponding intermediate triplet band, and (iii) the triplet bands of hp-vWF are composed of mature and degraded subunits. The results support a structural model of hp-vWF triplet bands according to which the intermediate triplet bands represent multiple numbers of symmetric and/or asymmetric dimers, the slower migrating satellite bands have one extra N-terminal fragment, and the faster migrating satellite band lacks one N-terminal fragment respectively in comparison with the corresponding intermediate triplet band.

Collagen covalently immobilized onto plastic surfaces simplifies measurement of von Willebrand factor-collagen binding activity

Human collagen type III was immobilized covalently via activated carbohydrate moieties onto hydrazine-treated microtiter plates which could be used to measure von Willebrand factor (vWF) collagen binding activity (vWF:CBA) in an ELISA. Such plates were simple to prepare and remained stable at 4 degrees C and -20 degrees C for at least 2 months. Samples analyzed by this system included (a) normal human vWF fractionated according to the degree of multimerization, (b) normal citrated and EDTA plasma and corresponding serum, and (c) plasma from patients with von Willebrand disease (vWD) types 1 and 2. When related to the concentration of vWF antigen (vWF:Ag), proportionally low levels of vWF:CBA were found for samples lacking the high-molecular-weight multimers, while higher values were obtained for samples containing these multimers. The ratio of vWF:CBA/vWF:Ag sensitively reflected the functional and structural intactness of the vWF molecules for all analyzed samples. Monoclonal antibody directed to the region within the A1 domain of vWF which interacts with the glycoprotein Ib completely inhibited the vWF ristocetin cofactor (vWF:RistCof), while vWF:CBA was not affected. Thus vWF:CBA and vWF:RistCof clearly represent separate, noninterchangeable functional parameters of vWF. In conclusion, our results indicate that the newly described method for the immobilization of collagen onto microtiter plates is suitable for the determination of vWF:CBA. In conjunction with vWF:Ag and the calculated ratio of vWF:CBA/vWF:Ag, this method simplifies the detection and classification of patients with vWD and assists in quality control during the purification of normal vWF.

Von Willebrand disease in childhood

Von Willebrand disease (vWD), a disorder of primary hemostasis, represents the most frequently inherited bleeding diathesis, It is caused by a quantitative reduction or a qualitative abnormality, or both, of von Willebrand factor (vWF), a glycoprotein normally found in plasma, endothelial cells, subendothelial cell space, megakaryocytes and platelets. Patients with vWD represent a heterogeneous group with different phenotypes and with clinical symptoms that vary in severity. Many of the described types and subtypes of vWD are caused by mutations and aberrations of the vWF gene. The aim of this article is to highlight the impact of gene analysis on the current knowledge of the inheritance of vWD as well as on the structure-function relationship of vWF, and to focus on the available diagnostic laboratory tests and treatment options for patients with vWD, especially in childhood.

Identification of a candidate missense mutation in a family with von Willebrand disease type IIC

A screening project to identify candidate molecular defects causing von Willebrand disease type IIC (VWD IIC) in a German family was carried out using polymerase chain reaction (PCR) amplification of all 52 exons of the von Willebrand factor (VWF) gene, subsequent electrophoresis of single and double stranded DNA and direct sequencing of PCR products with aberrant electrophoretic patterns. Only one candidate mutation, G550R, caused by a G-->A transition, was detected in exon 14 of the pro-VWF gene sequence. This mutation was not found on 200 chromosomes of normal individuals. The propositus was homozygous for the mutation and for an extended intragenic haplotype, composed of eight polymorphic markers. Further family members were heterozygous for the mutation and were phenotypically normal or only mildly affected, in accordance with the recessive pattern of inheritance for VWD type IIC. The mutation could influence one of the presumed active centers for the suspected multimerizing enzymatic activity of pro-VWF localized in the D1 and D2 domain, which corresponds to exon 5 and exon 14 of the VWF gene.

von Willebrand factor-collagen binding activity is increased in newborns and infants

von Willebrand factor (vWF) antigen (vWF:Ag) and vWF-collagen binding activity (vWF:CBA) were measured in plasma by parallel quantitative ELISAs in normal newborns and infants (n = 71). The medians for vWF:Ag (IU/ml) and vWF:CBA (U/ml), respectively, were 1.46 and 1.91 for 2-7 day-old (n = 43), 1.22 and 1.40 for 2-4 week-old (n = 14), 1.22 and 1.15 for 2-6-month-old (n = 14) infants and 0.98 and 1.08 (n = 36) in normal adults. Elevated levels of vWF:Ag, but particularly vWF:CBA were seen for up to 4 weeks of life reaching adult levels between 2 and 6 months of life. The elevated levels of the vWF parameters indicate that caution should be exercised when interpreting laboratory data and diagnosing von Willebrand disease in newborns and young infants and warrant the use of age-specific reference ranges. The efficient haemostasis observed during early neonatal life may in part be due to the increased ability of vWF to interact with collagen.

Selective suppression of cytochrome P-450 gene expression by interleukins 1 and 6 in rat liver

Inflammatory stimuli suppress constitutive hepatic expression of the CYP2C11 and CYP2C12 genes in male and female rat livers, respectively. We have shown previously that injection of interleukin-1 (IL1), but not interleukin-6 (IL6), to female rats also suppresses CYP2C12. In the present study, we examined the effects of these cytokines on CYP2C12 expression in rat hepatocyte cultures, and their in vivo effects on expression of multiple cytochrome P-450 (P450) gene products in male rat livers. IL1 suppressed the expression of CYP2C12 mRNA and protein in hepatocytes cultured on Matrigel in the presence of growth hormone. No consistent effect of IL6 was observed. Maximal suppression of CYP2C12 mRNA after 24 h of IL1 treatment reached 12 and 32% of control levels in two separate experiments. The approximate ED50 for IL1 was 5 ng/ml. CYP2C12 protein was suppressed to 28% of control levels as early as 12 h after IL1 treatment. Injection of IL1, low doses of dexamethasone, or both, in male rats produced decreases in total P450, and in CYP3A2 and CYP2C11 mRNA and protein expression similar to effects previously seen for CYP2C12 expression in females. CYP2E1 mRNA and protein was significantly suppressed only by the combination of IL1 and dexamethasone. IL6 treatment of male rats down-regulated the CYP2C11 and CYP2E1 mRNAs at a dose of 4.5 micrograms/kg, which was lower than that required to induce haptoglobin mRNA, a prototype acute phase gene product. CYP2C11 protein content of the microsomes was also decreased by IL6 treatment, with a slower time-course than for suppression of its mRNA. No significant effects of IL6 treatment were seen on CYP3A2 mRNA or CYP3A2/1 proteins. These results demonstrate that IL1 and IL6 treatments in vivo differentially affect subsets of P450 gene products in rat liver.

Parallel determination of von Willebrand factor--Ristocetin and Botrocetin cofactors

The quantitative determinations of von Willebrand Factor (vWF)-Ristocetin cofactor (vWF:RCof) and the Botrocetin cofactor (vWF:BCof) are important parameters for the diagnosis of von Willebrand's disease. These cofactors are usually determined in a platelet aggregometer using separate platelet reagents and assay protocols. We describe a method for the preparation of platelets made from outdated platelet concentrates and fixed with paraformaldehyde which agglutinate to ristocetin and to botrocetin. The platelet agglutination assay protocol has been simplified such that the same aggregometer instrument, platelet reagent, buffers and the reaction volumes can be used for parallel determination of vWF:RCof and vWF:BCof.

Melatonin synthesis and circadian tryptophan hydroxylase activity in chicken retina following destruction of serotonin immunoreactive amacrine and bipolar cells by kainic acid

The neurotoxic excitatory amino acid analog, kainic acid, was used to destroy serotonin-immunoreactive inner retinal neurons, bipolar cells and amacrine cells, in retinas of chickens. Tryptophan hydroxylase activity and melatonin content were examined in the kainic acid-lesioned retinas. Tryptophan hydroxylase activity was present in kainic acid-lesioned retinas and displayed a circadian rhythm. Nocturnal levels of activity in lesioned and control retinas were similar. Melatonin synthesis occurred in kainic acid-lesioned retinas in a diurnal cycle as in normal retinas. Dark-phase melatonin content of kainic acid-lesioned retinas exceeded that of controls. We conclude that most, if not all, circadian tryptophan hydroxylase activity and melatonin synthesis occurs in cells other than the cells that contain most of the serotonin in retina, serotonin-immunoreactive bipolar and amacrine cells.

Circadian rhythm of tryptophan hydroxylase activity in chicken retina

1. Retinal tryptophan hydroxylase activity in chickens (1-4 weeks old and embryos) was estimated by determination of levels of 5-hydroxytryptophan (5HTP) in retinas at defined intervals after inhibition of aromatic L-amino acid decarboxylase with m-hydroxybenzylhydrazine (NSD1015). 2. The relationship of tryptophan hydroxylase activity to photoperiod was explored. In chickens maintained on a 12-hr light: 12-hr dark cycle, a diurnal cycle in tryptophan hydroxylase activity was observed. Activity during middark phase was 4.4 times that seen in midlight phase. Cyclic changes in tryptophan hydroxylase activity persisted in constant darkness with a period of approximately 1 day, indicating regulation of the enzyme by a circadian oscillator. The phase of the tryptophan hydroxylase rhythm was found to be determined by the phase of the light/dark cycle. The relationship of the tryptophan hydroxylase rhythm to the light/dark cycle mirrors previously described rhythms of melatonin synthesis and serotonin N-acetyltransferase (NAT) activity in the retina. 3. Light exposure for 1 hr during dark phase suppressed NAT activity by 82%, while tryptophan hydroxylase activity was suppressed by only 30%. 4. Based on the differential responses of retinal NAT activity and tryptophan hydroxylase activity to acute light exposure during dark phase, it was predicted that exposure to light during dark phase would divert serotonin in the retina from melatonin biosynthesis to oxidation by MAO. In support of this, levels of 5-hydroxyindole acetic acid (5HIAA) in retina were found to be elevated approximately two-fold in chickens exposed to 30 min of light during dark phase. In pargyline-treated chickens, 2 hr of light exposure during dark phase was found to increase retinal serotonin levels by 64% over pargyline-treated controls. 5. Cyclic changes in tryptophan hydroxylase activity and NAT activity persisted for 2-3 days in constant light. Tryptophan hydroxylase activity at mid-night gradually decreased on successive days in constant light; on the first day of constant light, tryptophan hydroxylase activity at mid-night was 70% of activity seen during middark phase of the normal light/dark cycle and decreased further on subsequent days. In contrast, on each of 3 days of constant light, NAT activity at mid-night was approximately 15% of normal middark phase activity. 6. Cycloheximide completely inhibited the nocturnal increase in tryptophan hydroxylase activity when given immediately before light offset. The nocturnal increase in NAT activity was inhibited in a similar fashion. 7. Like the development of the NAT rhythm, cyclic changes of tryptophan hydroxylase activity in the retinas of chickens began on or immediately before the day of hatching. hatching.(ABSTRACT TRUNCATED AT 400 WORDS)

Arylalkylamine (serotonin) N-acetyltransferase assay using high-performance liquid chromatography with fluorescence or electrochemical detection of N-acetyltryptamine

A sensitive, rapid, and economical method has been developed for determination of serotonin N-acetyltransferase activity from a variety of enzyme sources. The assay is based upon separation and detection of N-acetyltryptamine formed from tryptamine and acetyl coenzyme A, by means of high-performance liquid chromatography with either electrochemical or fluorometric detection. The limit of sensitivity with both detection methods is less than 20 pmol of N-acetyltryptamine formed per sample. A method for synthesis of N-acetyltryptamine, used as an external standard in the assay, is described.

Changes in the cofactor binding domain of bovine striatal tyrosine hydroxylase at physiological pH upon cAMP-dependent phosphorylation mapped with tetrahydrobiopterin analogues

The structure of the cofactor binding domain of tyrosine hydroxylase (TH) was examined at physiological pH by determining kinetic parameters of (R)-tetrahydrobiopterin [(R)-BH4] and a series of tetrahydropterin (PH4) derivatives (6-R1-6-R2-PH4: R1 = H and R2 = methyl, hydroxymethyl, ethyl, methoxymethyl, phenyl, and cyclohexyl; R1 = methyl and R2 = methyl, ethyl, propyl, phenyl, and benzyl). A minimally purified TH preparation that was not specifically phosphorylated (designated as "unphosphorylated") was compared with enzyme phosphorylated with cAMP-dependent protein kinase. The Km for tyrosine with most tetrahydropterin analogues ranged between 20 and 60 microM with little decrease upon phosphorylation. Two exceptions were an unusually low Km of 7 microM with 6-ethyl-PH4 and a high Km of 120 microM with 6-phenyl-6-methyl-PH4, both with phosphorylated TH. Tyrosine substrate inhibition was elicited only with (R)-BH4 and 6-hydroxymethyl-PH4. With unphosphorylated TH (with the exception of 6-benzyl-6-methyl-PH4, Km = 4 mM) an inverse correlation between cofactor Km and side-chain hydrophobicity was observed ranging from a high with (R)-BH4 (5 mM) to a low with 6-cyclohexyl-PH4 (0.3 mM). An 8-fold span of Vmax was seen overall. Phosphorylation caused a 0.6-4-fold increase in Vmax and a 35-2000-fold decrease in Km for cofactor, ranging from a high of 60 microM with 6-methyl-PH4 to a low of 0.6 microM with 6-cyclohexyl-PH4. A correlation of the size of the hydrocarbon component of the side chain with affinity is strongly evident with phosphorylated TH, but in contrast to unphosphorylated enzyme, the hydroxyl groups in hydroxymethyl-PH4 (20 microM) and (R)-BH4 (3 microM) decrease Km in comparison to that of 6-methyl-PH4. Although 6,6-disubstituted analogues were found with affinities near that of (R)-BH4 (e.g., 6-propyl-6-methyl-PH4, 4 microM), they were frequently more loosely associated with phosphorylated TH than their monosubstituted counterparts (6-phenyl-PH4, 0.8 microM; cf. 6-phenyl-6-methyl-PH4, 8 microM). A model of the cofactor side-chain binding domain is proposed in which a limited region of nonpolar protein residue(s) capable of van der Waals contact with the hydrocarbon backbone of the (R)-BH4 dihydroxypropyl group is opposite to a recognition site for hydroxyl(s). Although interaction with either the hydrophilic or hydrophobic regions of unphosphorylated tyrosine hydroxylase is possible, phosphorylation by cAMP-dependent protein kinase appears to optimize the simultaneous operation of both forces.

Effect of delayed blood processing on the yield of factor VIII in cryoprecipitate and factor VIII concentrate

Current standards for the preparation of factor VIII (FVIII) concentrates from human plasma recommend separation of plasma from red cells (RBCs) within 6 hours of blood donation, thereby reducing the volume of plasma from donated whole blood available for processing to FVIII concentrate. The decay of FVIII clotting activity (FVIII:C) in whole blood and plasma stored at 22 and 4 degrees C and the recovery of FVIII:C in cryoprecipitate and FVIII concentrate prepared from plasma separated from whole blood stored overnight at 4 degrees C were investigated. In whole blood stored at 22 degrees C and plasma stored at either 4 or 22 degrees C, 90 percent of the original FVIII:C was present at 6 hours, 80 percent at 12 hours, and 65 to 70 percent at 18 hours. At these times lower levels of FVIII:C were recovered from whole blood stored at 4 degrees C, that is, 84, 68, and 56 percent, respectively. In cryoprecipitates prepared from plasma separated from RBCs after 18 hours' storage at 4 degrees C (18-hour plasma), 43 percent of FVIII:C activity was recovered, as compared with 61 percent recovered from standard plasma separated within 6 hours of donation (6-hour plasma), p less than 0.05. With large-scale preparation of FVIII concentrates, however, the yield of FVIII:C was similar whether 18- or 6-hour plasma was used. Thus FVIII concentrates--but not cryoprecipitates--can be prepared from plasma separated from whole blood stored at 4 degrees C for up to 18 hours without undue loss of potency.

Effect of virucidal heat treatment on proteins in human factor VIII concentrates

Intermediate-purity and fibrinogen-poor factor VIII concentrates were heated in the lyophilized state at 60 degrees C for up to 72 hours to inactivate blood-borne viruses. The effect of heat treatment on factor VIII, von Willebrand factor (vWf), and other proteins present in the concentrates (albumin, fibrinogen, fibronectin, IgG, and IgM) was evaluated. Heat-induced protein aggregation, particularly of fibrinogen and fibronectin, occurred within 48 hours in the intermediate-purity concentrates and correlated well with decreased solubility of these products. Heated fibrinogen-poor concentrates were readily soluble and did not show protein aggregation even after 72 hours at 60 degrees C. Neither concentrate developed detectable neoantigens when tested against antisera to whole human plasma and to heated and unheated concentrates. Aggregation of the vWf molecule, detected by altered mobility in crossed immunoelectrophoresis and multimeric analysis in SDS agarose gels, occurred in heated intermediate-purity concentrates but not in fibrinogen-poor concentrates. Thus, higher-purity factor VIII concentrates withstand heat treatment better than concentrates that contain greater levels of contaminating proteins, particularly fibrinogen.

General practice consultations: is there any point in being positive?

A group of 200 patients who presented in general practice with symptoms but no abnormal physical signs and in whom no definite diagnosis was made were randomly selected for one of four consultations: a consultation conducted in a "positive manner," with and without treatment, and a consultation conducted in a "non-positive manner," called a negative consultation, with and without treatment. Two weeks after consultation there was a significant difference in patient satisfaction between the positive and negative groups but not between the treated and untreated groups. Similarly, 64% of those receiving a positive consultation got better, compared with 39% of those who received a negative consultation (p = 0.001) and 53% of those treated got better compared with 50% of those not treated (p = 0.5).

Analysis of platelet von Willebrand factor antigen

Platelet lysates were obtained from suspensions of normal washed platelets by freeze-thawing or Triton X-100 lysis. The resultant platelet lysates contained 0.34 +/- 0.15 U/10(9) platelets (n = 8) of von Willebrand factor antigen (vWf:Ag) as determined by radioelectroimmunoassay using a monospecific antibody to vWf:Ag. The vWf:Ag level was higher in platelet lysates prepared from freshly drawn blood than from outdated platelet packs. Platelet lysates from patients with severe von Willebrand's disease type I (n = 2) did not contain detectable vWf:Ag. When normal platelet lysates were analyzed by radiocrossed immunoelectrophoresis in agarose using a monospecific polyclonal antibody to plasma vWf:Ag, two immunochemically identical precipitin peaks were seen. One of the platelet vWf:Ag peaks corresponded in its electrophoretic mobility to plasma vWf:Ag, while the other peak, i.e. platelet vWf:Ag-peak II, migrated to a more anodal position. The presence of the platelet vWf:Ag-peak II suggests structural differences between plasma and platelet vWf:Ag and illustrates previously unrecognized heterogeneity of platelet vWf:Ag.

Use of heat-treated clotting-factor concentrates in patients with haemophilia and a high exposure to HTLV-III

In a group of 126 Australian patients with haemophilia, who were receiving lyophilized clotting-factor concentrates prepared from locally collected plasma, a high prevalence of antibody to human T-cell lymphotropic virus III (HTLV-III) was demonstrated in those with severe disease. Patients with moderate or mild disease had a much lower prevalence of HTLV-III antibody. After heat treatment of lyophilized factor VIII and factor IX concentrates (60 degrees C for 72 hours) to inactivate the virus, the losses of activity of an intermediate-purity and of a fibrinogen-poor factor VIII concentrate, and of the coagulant activity of a factor IX concentrate, were within acceptable limits. The solubility of the intermediate-purity factor VIII concentrate was markedly decreased; the fibrinogen-poor factor VIII concentrate and the factor IX concentrate were readily soluble. In-vivo recovery and survival of heated concentrates were equivalent to those of the unheated products, and they were effective in the treatment of spontaneous and traumatic haemorrhages.

Fast migrating protein, immunochemically related to human factor VIII, studied by crossed immunoelectrophoresis in agarose

A fast migrating protein (FMP) was detected by agarose radio-crossed immunoelectrophoresis, in addition to factor VIII antigen (VIII:RAg), using antiserum to human factor VIII (FVIII). FMP had partial immunochemical identity with FVIII, migrated as an alpha-protein, and was distinct from alpha-2 macroglobulin, fibronectin or IgM. FMP was precipitated by concanavalin A and was separable from the bulk of VIII:RAg by ammonium sulphate fractionation. A significant amount of FMP was seen in normal serum (n = 12), plasma from patients with: (a) disseminated intravascular coagulation (n = 12) and (b) severe haemophilia A (n = 6). Trace amounts of FMP were observed in plasma from normal donors (n = 12), but neither VIII:ARg nor FMP was detectable in the plasma or serum from patients with severe von Willebrand's disease (n = 3). Freshly prepared cryoprecipitate contained trace amounts of FMP, similar to normal plasma, but increased levels were observed in antihaemophilic factor concentrates prepared for patient use. Significant levels of FMP were also seen in cryoprecipitate after storage at 4 degrees C for 7 d and this generation of FMP was diminished by the addition of protease inhibitors. The presence of significant levels of FMP in situations where proteolytic enzymes may be activated and inhibition of its generation by protease inhibitors, suggest that this protein is produced by proteolytic action of enzyme(s) on the FVIII molecule.

Variant von Willebrand's disease type B--revisited

Results of investigations of the factor VIII (FVIII) of a patient with an unusual variant form of von Willebrand's disease (vWD) are presented. A two-peak crossed-immunoelectrophoresis (CIE) pattern was seen when fresh plasma was electrophoresed, but the CIE pattern became normal by incubating the plasma at 37 degree C for more than 72 hr. The two peaks on CIE were separated by cryoprecipitation: the slow-moving peak precipitating and the fast-moving forms of FVIII remaining in the cryosupernate. An additional protein band was seen on multimeric analysis of FVIII. The platelet-rich plasma (PRP) from this patient did not respond to ristocetin, but agglutinated normally in response to botrocetin. Multimeric and CIE analysis of the FVIII post agglutination and 125I-FVIII binding studies to normal formalin-fixed platelets indicated that this patient's FVIII interacted normally with botrocetin but failed to interact with ristocetin. These data strongly suggest that the sites on the FVIII molecule or the multimeric forms involved for ristocetin and botrocetin are different and that the ristocetin reaction is more closely aligned to the physiologic function of FVIII.

Simplified immunoradiometric assay for factor VIII coagulant antigen

A simplified, non-competitive, solid phase immunoradiometric assay has been developed for the quantitation of factor VIII coagulant antigen (VIII:CAg)--the antigenic counterpart of FVIII coagulant activity (VIII:C). Both homologous and heterologous antibodies to human factor VIII (FVIII) were used in this assay. Initially, FVIII in a test sample was attached to immobilized, human IgG obtained from a polytransfused haemophilia A patient with a high titre antibody to VIII:C. The bound FVIII was then detected using rabbit 125I-IgG specific for human FVIII. The concentration of VIII:CAg correlated well with VIII:C levels in the plasma from normal donors (r = 0.84, n - 15). Homozygote von Willebrand's disease patients had undetectable levels of VIII:CAg in their plasma. Patients with severe haemophilia A (VIII:C less than 0.01 u/ml) could be divided into groups on the basis of the VIII:CAg levels, i.e. those having undetectable VIII:CAg and other with measurable VIII:CAg. VIII:CAg detected in normal serum was less than 0.002 u/ml. In this assay the use of human antibody to FVIII is considerably decreased compared to other methods for VIII:CAg, and the time-consuming steps to immunopurify human anti-FVIII antibody are eliminated.

Abnormal factor VIII in chronic renal failure

Factor VIII procoagulant activity (VIII-C), related antigen (VIII-AG), and von Willebrand factor (VIII-vWf) were measured in 38 patients with chronic renal failure (CRF), in 19 patients with normal renal function from a general medical ward, and in 17 normal subjects. Wide variation in the levels of factor VIII (FVIII) functions were found in the group of CRF patients. There was no correlation between the levels of the three individual activities of FVIII in renal disease. The levels of the three functions were elevated in the patient controls and no significant differences were found between the two groups of patients, although both groups were significantly different from the normal subjects. Increased electrophoretic mobility (EM) was detected in 22 of the 38 patients with CRF (58%) compared to seven of the 19 patients controls (37%). These studies suggest caution in interpretation of changes in FVIII status in patients with other clinical disorders, such as liver disease.

The consultation and the therapeutic illusion

At 45 general-practice surgery sessions 200 patients in whom no definite diagnosis could be made were randomly selected for one of two procedures. Either they were given a symptomatic diagnosis and medications, or they were told that they had no evidence of disease and therefore they required no treatment. No difference in outcome was found between these two methods as judged by the return or not of the patient within one month and his statement that he did or did not get better.