6-oxo-Prostaglandin F1α and Thromboxane B2 in Uterine Vein Blood - A Possible Role in Menstrual Bleeding

The role of the haemostatic system in relation to menstrual bleeding is poorly understood. Platelet retention to glass beads and plasma concentrations of 6-oxo-PGFα and thromboxane B2 were measured in uterine and peripheral venous blood obtained from 18 women undergoing abdominal hysterectomy. Concentrations of 6-oxo-PGFα were significantly (p<0.01) higher in uterine (1.4 ± 0.3 ng/ml, mean ± SEM) than in peripheral vein blood (0.2 ±0.1 ng/ml) as was the level of thromboxane B2 (0.5 + 0.1 and 0.2 ± 0.1 ng/ml, respectively). Platelet retention in uterine vein blood (11 ± 4%) was significantly lower than in peripheral blood (42 ±4%; p<0.01) and the degree of platelet retention correlated inversely with the plasma concentration of 6-oxo-PGFα (r −0.43; p<0.01). There was a significant rank correlation between time since menstruation and concentrations of 6-oxo-PGFα in uterine (τ + 0.69; p<0.001) and peripheral (τ + 0.56; p<0.05) vein blood. The results indicate that an increased local production of prostacyclin (PGI2) relative to thromboxane A2 at the time of menstruation could contribute to the mechanism of uterine bleeding.

Coagulation and Fibrinolytic Activity in Behçet's Disease

Coagulation and fibrinolytic activities were studied in 18 subjects with Behçet's disease and compared with results from 14 matched control patients suffering from sero-negative arthritis. Significantly higher plasma concentrations (median and range) were found in Behçet's patients for the following variables: fibrinogen 3.7 (1.7-6.9) vs 3.0 (2.0-5.1) g/1, p <0.05; von Willebrand factor antigen, 115 (72-344) vs 74 (60-119)%, p <0.002; plasminogen activator activity (106/ECLT2) 219 (94-329) vs 137 (78-197) units, p <0.002; tissue plasminogen activator inhibitor (t-PA-I) activity, 9.1 (5.5-19.3) vs 5.1 (1.8-12.0) IU/ml, p <0.002; and PAI-1 antigen, 13.9 (4.5-20.9) vs 6.4 (2.4-11.1) ng/ml, p <0.002. Protein C antigen was significantly lower: 97 (70-183) vs 126 (96-220)%, p <0.02. No differences were observed in antithrombin III activity or antigen, factor VIII coagulant activity, fibrinopeptides A and Bβ15-42, plasminogen, α-2-antiplasmin, functional and immunological tissue-plasminogen activator, thrombin-antithrombin complexes and D-dimer. Levels of tissue plasminogen activator inhibitor (activity and antigen) correlated with disease activity while fibrinogen and von Willebrand factor concentrations did not. Seven of the 18 subjects with Behçet's disease had suffered thrombotic events but it was not possible to distinguish these from the 11 patients without thrombosis using the assays performed. The results suggest the abnormal fibrinolytic activity in Behçet's disease is due to increased inhibition of tissue plasminogen activator. No abnormality of coagulation or fibrinolytic activity specific to Behçet's disease was detected.

Coagulation, Fibrinolytic and Platelet Function in Patients on Long-Term Therapy with Aspirin 300 mg or 1200 mg Daily Compared with Placebo

Aspirin has been shown to be beneficial in the prophylaxis of arterial thromboembolic disease. The rationale for its use as an antithrombotic drug lies in its inhibition of thromboxane A2- dependent platelet function. However, the effect of aspirin on coagulation and fibrinolysis during chronic therapy has not been studied. We have measured a range of haemostatic and platelet functions in 49 patients with transient ischaemic attacks randomly allocated to aspirin 300 mg a day, aspirin 1,200 mg a day or placebo. All had been taking their allocated treatment for between 9 months and 4 years prior to investigation. Bleeding time was prolonged, serum thromboxane diminished and platelet aggregation to arachidonic acid but not ADP was abolished by both 300 mg and 1,200 mg aspirin, in a non-dose dependent fashion. Serum salicylate increased with the dose of aspirin ingested. No effect was seen with either dose of aspirin on urinary thromboxane and 6-keto-PGF1α excretion, or on coagulation. Patients taking 1,200 mg aspirin a day had a lower haemoglobin and packed cell volume, lower resting fibrinopeptide A concentration and lower basal plasminogen activator activity than those on placebo. Response to venous occlusion was norrnal in all groups. The results suggest 300 mg and 1,200 mg aspirin have an equivalent platelet inhibitory effect but 1,200 mg aspirin causes greater gastro-intestinal blood loss.

Urinary Beta-Thromboglobulin Correlates with Impairment of Renal Function in Patients with Diabetic Nephropathy

TBeta-thromboglobulin (βTG) is a platelet-specific protein and since its concentration in plasma rises when platelets are activated, it has been used as an indicator of platelet involvement in vascular disease. Since platelets might be involved in the pathogenesis of diabetic microvascular disease we measured urinary βTG in 20 insulin-dependent diabetics with nephropathy and compared the results with those from 20 normal subjects. Measurement of βTG in urine was undertaken to avoid errors induced by blood sampling and to gain information over a prolonged period using a single assay. Measurements were made of βTG, β2-microglobulin and total protein in urine collected for 24 h and creatinine and β2 microglobulin in plasma. Survival of indium-111-labelled platelets was measured in nine patients. Urinary PTG was significantly (p <0.02) increased in the 20 patients compared with 20 normal volunteers (median value 1.3 vs 0.8 μg/24 h). There was a strong correlation between urinary βTG excretion and plasma creatinine concentration (r = 0.8, p <0.0001) and plasma β2-microglobulin concentration (r = 0.9, p <0.0001). Urinary βTG concentration did not correlate with platelet survival. The results indicate that although urinary βTG is significantly increased in patients with diabetic nephropathy its concentration in urine correlates with indicators of glomerular filtration rather than with a test of platelet activation.

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

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

Intra-Operative Activation of Coagulation - A Stimulus to Thrombosis Mediated by Vasopressin?

Vasopressin infusions in normal volunteers that produce concentrations in plasma comparable to those seen during stress, cause an increase in plasma factor VIII and shortening of the euglobulin clot lysis time (ECLT). We have investigated the relationship between endogenous vasopressin (aVP) release and haemostatic function in 7 patients undergoing major abdominal surgery. Blood samples were taken at nine intervals during the operative procedure. Plasma aVP levels peaked at median values of 51 pg/ml during bowel manipulation and remained elevated on the first post-operative day. Following, and in close temporal relationship with the rise in aVP there were increases in factor VIII coagulant activity, the ristocetin co-factor, von Willebrand antigen, plasminogen activator activity (106/ECLT2) and fibrinopeptide A concentrations with shortening of the activated partial thromboplastin time. The relationship was similar to that seen following infusion of a VP in human volunteers. The results are consistent with the hypothesis that aVP is an important mediator of changes in haemostatic function which accompany stress and might contribute to the thrombotic risk associated with surgical operations.

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

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

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

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

Selective Inhibition of Thromboxane Synthetase with Dazoxiben - Basis of Its Inhibitory Effect on Platelet Adhesion

Platelet adhesion to rabbit aortic subendothelium or collagen-coated glass was quantitated in a rotating probe device by uptake of radio-labelled platelets. Under conditions in which aspirin had no effect, dazoxiben, a selective inhibitor of thromboxane synthetase, reduced platelet adhesion to aortic subendothelium by about 40% but did not affect adhesion to collagen-coated glass. Pre-treatment of aortic segments with 15-HPETE, a selective inhibitor of PGI2-synthetase, abolished the inhibitory effect of dazoxiben on adhesion. Concentrations of 6-oxo-PGFlα in the perfusate were raised in the presence of dazoxiben alone, and following addition of thrombin (10 units/ml) there was a 2-3 fold increase in concentration. Perfusion of damaged aorta with platelets labelled with (14C)-arachidonic acid in the presence of thrombin and dazoxiben resulted in the appearance of (14C)-labelled-6-oxo-PGFiα. Inhibition of thromboxane synthetase limits platelet adhesion probably by promoting vascular synthesis of PGI2 from endoperoxides liberated from adherent platelets, which subsequently promotes detachment of cells from the surface.

The Effects of an Increase in Endogenous Oestrogen on the Haemostatic Mechanism

The effects on the haemostatic mechanism of rises in circulating human oestrogen in a group of women being treated for infertility with pituitary hormones were studied. Despite large but brief rises in oestrogen levels no changes were found.

Hormonal Control of Haemostasis During Hypoglycaemia in Diabetes Mellitus

Factor VIII (FVIII) and plasminogen activator activity (PAA) rise during hypoglycaemia, and this might contribute to the vascular complications of diabetes. Similar changes in haemostasis accompany raised plasma levels of vasopressin (aVP) and adrenaline. To investigate the effects of these hormones on haemostasis during hypoglycaemia and the role of plasma insulin concentrations, eight insulin-dependent diabetic patients underwent controlled hypoglycaemia for 20 min and 13 diabetic patients were investigated during hyperinsulinaemia with blood glucose maintained at 8.0 mmol/1. During hypoglycaemia, insulin levels increased to median values of 114 mU/1, aVP rose from 0.5 to 4.4 (p <0.005) pg/ml and adrenaline from 0.4 to 4.4 nmol/l (p <0.005). FVIII coagulant activity (FVIII :C) rose from 0.75 to 1.09 iU/ml (p <0.01) and the ristocetin co-factor (FVIIIR:Co) and von Willebrand factor antigen (vWF:Ag) showed similar responses. PAA increased from 156 to 745 units (p <0.005). During hyperinsulinaemia, insulin rose following infusion from 24 to 52 and 118 mU/l, maintained for an hour at each level. Despite this, plasma aVP, FVIII :C, FVIIIR:Co, vWF:Ag and PAA remained unchanged. This study indicates that the marked changes in FVIII, vWF and PAA concentrations which accompany hypoglycaemia depend on low blood glucose and not raised plasma insulin. The response in probably mediated by increases in adrenaline and aVP, which are part of the physiological response to hypoglycaemia.

Treatment of Hypertension Induces a Fall in Platelet Basal Cytoplasmic Calcium Concentration without Influencing Platelet Aggregation

The relationship between blood pressure and platelet basal cytoplasmic calcium concentration ([Ca2+]i) and platelet sensitivity to aggregating agents in hypertension has been investigated in hypertensive patients and normotensive subjects. Ten severely hypertensive patients whose blood pressures were poorly controlled with metoprolol, were given calcium antagonist (either nifedipine or felodipine) as a second line agent. Venous blood samples were collected at each treatment phase for measurement, in whole blood, of platelet aggregation in response to ADP and collagen, and of basal [Ca2+]i using fura-2. Control of blood pressure by the combination of metroprolol and a calcium antagonist induced a significant decrease in median [Ca2+]i from 116 (76–181) to 73 (60–83) nM, which was similar to the median value of 70 (61–80) nM obtained in 14 normotensive subjects. Overall [Ca2+]i correlated with mean blood pressure (r = 0.51). Treatment of hypertension with calcium antagonist did not change the response of platelets to collagen or ADP. The results confirm that effective treatment of hypertension significantly reduced basal [Ca2+]i in platelets but raise doubts whether elevated basal [Ca2+]i is necessarily the sole mechanism by which the sensitivity of platelets to aggregatory agents is increased in hypertension.

Reduction in Factor VII, Fibrinogen and Plasminogen Activator Inhibitor-1 Activity after Surgical Treatment of Morbid Obesity

The aim of this study was to determine the effects of the surgical treatment of morbid obesity on some aspects of haemostatic and fibrinolytic function. Measurement of haemostatic and fibrinolytic factors was performed before and again 6 and 12 months after operation in 19 patients suffering from morbid obesity. Surgical treatment resulted in a mean decrease in body weight of 50 kg at 6 months and 64 kg at 12 months. Weight loss was accompanied at 12 months by significant reductions in median (interquartile range) concentrations of serum cholesterol from 5.3 (4.5–6.2) mmol/1 to 3.6 (2.9–4.6) mmol/1; factor VII from 113 (92–145)% of normal to 99 (85–107)%; of fibrinogen from 3.5 (3–9.3) g/1 to 2.8 (2.4–3.8) g/1; and of plasminogen activator inhibitor-1 (PAI-1) activity from 21 (11–30) IU/ml to 6.3 (5–10) IU/ml. The decrease in PAI-1 activity probably accounted for a significant reduction in euglobulin clot lysis time. Tissue plasminogen activator activity was undetectable in most patients pre-operatively but increased slightly after 1 year to 110 (100–204) mIU/ml. There were no significant changes in plasma levels of KCCT, factor VIII, von Willebrand factor antigen, alpha-2-antiplasmin, antithrombin III, protein C antigen, beta thromboglobulin, platelet factor 4, fibrinopeptide A or platelet count. These findings provide support for the hypothesis that the surgical treatment of morbid obesity may have a long-term beneficial effect on mortality from cardiovascular and thromboembolic disease.

Thrombin Activity by Intrinsic Activation of Plasma In-Vitro Accelerates with Increasing Age of the Donor

Thrombotic diseases increase in incidence with advancing years and this might be partly due to an increased propensity for fibrin formation in older individuals. Accordingly we decided to investigate whether the time taken to generate 50% thrombin activity in vitro varied with the age of the plasma donor. Coagulation was initiated in defibrinated, diluted plasma by contact activation and thrombin activity measured using the chromogenic substrate, S2238. The rate of thrombin generation was assessed by measuring the time taken to reach 50% maximal activity (T50/s). There was a highly significant negative correlation between T50 and age, T50 declining from 93 s at 19 years to 71 s at 65 years (r = −0.637, p <0.0001). A strong negative correlation was demonstrated between T50 and FVII level (r = -0.415, p = 0.0007) and FVIII: C level (r = -0.465, p = 0.0001). Although FVII concentration correlated with age (r = 0.307, p = 0.014) no relationship was seen between age and FVIII :C. These data suggest that coagulation rates in plasma accelerate with age.

The Influence of Infusions of 1-Desamino-8-D-Arginine Vasopressin (DDAVP) In Vivo on Thrombin Generation In Vitro

To investigate the effect of increasing FVIII:C in-vivo on coagulation ex-vivo, DDAVP was infused over 15 min in 10 volunteers and in-vitro thrombin generation measured. FVIII:C rose from 0.42 and 0.43 IU/ml before DDAVP to 1.38, 1.73 and 1.78 IU/ml at 15, 30 and 60 min respectively (p <0.001).

A computer-assisted thrombin generation test was performed in defibrinated plasma using chromogenic substrate, S2238. Time to reach 50% maximal thrombin activity (T50/s) and lag phase of thrombin generation (lag/s) were measured. Lag shortened from 75 and 60 s before to 45 s during and after infusion (p <0.001). T50 shortened from 78.5 and 76.0 to 62.5, 60.0 and 58.5 s at times 15 (p <0.01), 30 (p <0.001) and 60 (p <0.001) min. FVIII:C correlated inversely with lag and T50 (r = –0.847, p <0.001, r = –0.826, p <0.001, n = 10) respectively.

These findings show that acute elevations of FVIII:C in-vivo accelerate in-vitro thrombin production. This work suggests that elevated FVIII:C levels in-vivo may be important in thrombo-occlusive disease.

Anti-Hypertensive Drugs Non-Specifically Reduce “Spontaneous” Activation of Blood Platelets

Abnormal activation of blood platelets may be a contributory factor in the accelerated vascular disease which occurs in hypertension. We investigated the effects of lowering blood pressure in 12 patients with mild hypertension on several aspects of platelet function, initially in a placebo-controlled, double-blind, crossover study with nisoldipine, and subsequently in the same patients comparing nisoldipine with the patients’ usual anti-hypertensive therapy. Values were compared with those from an age, sex-matched control population. Seven hypertensive patients with renal failure were also studied. Administration of nisoldipine reduced ex vivo “spontaneous” aggregation of blood platelets significantly, and a similar significant effect was seen when blood pressure was lowered by the patients usual anti-hypertensive therapy. “Spontaneous” aggregation occurring in the control population was similar to that in the treated hypertensives. Blood platelet count, and aggregation in response to ADP and adrenalin were unaffected by treatment. Median plasma beta thromboglobulin levels were significantly higher in the untreated hypertensive patients (43 ng ml-1) than in the controls (30 ng ml-1), and there was a trend to reduced values for beta thromboglobulin on treatment of the hypertension. These results indicate that blood platelet activity is enhanced in hypertension and that function returns towards normal when blood pressure is lowered by treatment.

Effect of Physiological Concentrations of Vasopressin on Components of the Fibrinolytic System

High physiological concentrations of plasma vasopressin (aVP) when achieved by infusion cause an increase in plasma factor VIII coagulant activity and shortening of the euglobulin clot lysis time (ECLT). To investigate the effects of aVP on components of the fibrinolytic pathway and on thrombin generation, t healthy volunteers were infused with saline for 30 min followed by aVP for L hour and blood samples taken every 30 min for measurement of aVR ECtf tissue-type plasminogen activator (t-PA), t-PA inhibition (tPA-I), plasminogen activator inhibitor L (PAI-1 Ag), activated partial thromboplastin time (APTT), fibrinopeptide A (FPA), fibrinopeptide B 15-42 (FPBß 15-42) and crosslinked fibrin breakdown products (XL-FDP). Plasma aVP rose to a median of 75 pg/ml after 90 min and fell to 13.8 pdml 30 min later. The APTT fell from 43.5 to 35 sec (p <0.01) but there was no change in plasma FPA or in XL-FDP. Plasminogen activator activity (106/ECLT2) increased from 25 to 736 units (p <0.01) and t-PA from 200 to 1012 mlU/ml (p <0.01). tPA-I fell from 8.0 to 2.7 IU/ml at 90 min (p <0.05) but PAI-1 Ag remained unchanged. Plasma FPBß 15-42 was 2.4 and 1.2 pmol/ml before infusion with aVP and showed a small rise to 3.5 pmol/ml after 60 min (p <0.05). The results show the effects of aVP on fibrinolysis are mediated by an increase in t-PA. In the absence of thrombin generation the rise in t-PA was not accompanied by changes in XL-FDP.

A Prospective Study of Haemostatic Tests at 28 Weeks Gestation as Predictors of Pre-Eclampsia and Growth Retardation

A panel of haemostatic tests was perfomed on 400 primiparous women at 28 weeks to test whether one or more could predict the development of pregnancy complications. Fifteen women subsequently developed pre-eclampsia with significant proteinuria and 13 delivered growth retarded infants. There were no significant differences between mothers in the pre-eclampsia group and 22 randomly selected controls. A stepwise logistic discriminant analysis of the data did not produce a significant model. In the growth retarded group only beta thromboglobulin levels were significantly lower than in the controls (p <0.05), although in the logistic discriminant analysis the inclusion of both beta thromboglobulin and fibrin degradation products led to a borderline significant improvement in fit of the model. We conclude that the haemostatic variables studied are not significantly changed at 28 weeks nor clinically useful predictors of either pre-eclampsia or fetal growth retardation.

Poor Compliance Is a Major Factor in Unstable Outpatient Control of Anticoagulant Therapy

Control of oral anticoagulant therapy in outpatients is often unsatisfactory. The contribution of poor compliance with prescribed warfarin to unstable anticoagulant control was investigated prospectively using low-dose phenobarbitone as an indicator of compliance in 30 out-patients, 15 with stable and 15 with unstable control. Following entry to the study, there was no significant change in anticoagulation (p = 0.36) in the group with stable control. In the group who previously had unstable control, there was a significant change in INR (p = 0.0045) and anticoagulant control greatly improved. It appears that the considerable fluctuation in INR seen in many of the latter patients before the study was due to poor compliance and that entering them into the study modified their behaviour. Two patients in this group who continued to have unstable anticoagulant control were shown to be poorly compliant using the phenobarbitone indicator. The results suggest that, in outpatients, poor compliance is the major cause of unstable anticoagulation with warfarin.

Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory

We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%-35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first-order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point.

Polarization selective electro-optic polymer waveguide devices by direct electron beam writing

A novel technique for the fabrication of polarization selective electro-optic polymer waveguide devices with direct electron beam writing was described. Birefringence induced by the electric field poling in the electro-optic polymer film was erased in the electron beam exposed regions. The formed waveguides had stronger confinement for the light polarized along the poling direction. High fabrication resolution on the 100 nm scale or smaller could be achieved. Fabrication of polymer polarizer and polarization selective microring resonators with this technique was reported. The highest polarization extinction ratio was measured to be 21.4 dB.

Direct electron beam writing of electro-optic polymer microring resonators

Electro-optic polymer waveguides in electron beam sensitive polymethyl methacrylate (PMMA) polymer matrix doped with organic nonlinear chromophores could be directly patterned by electron beam exposure with high resolution and smoothness. The polymer in the exposed regions was removed with standard electron beam resist developer and without damaging the chromophore containing polymer waveguides. Feature sizes on the order of 100 nm could be clearly resolved. High quality microring resonators made of YL124/PMMA electro-optic polymer were successfully fabricated with this technique. The measured resonance extinction ratios were more than 16 dB and quality factors were in the range of 10(3) approximately 10(4).

A home-based exercise programme improves ankle range of motion in long-term venous ulcer patients

BACKGROUND AND OBJECTIVES

Decreased ankle mobility is associated with delayed healing of venous ulcers. The aim of this study was to assess the efficacy of a 24-week home-based exercise programme in increasing ankle range of motion and increasing the strength and endurance of the calf muscle. The secondary aim was to see whether subjects with venous ulcers were able to maintain a consistent exercise programme.

METHODS

Eleven patients with long-standing venous ulcers were encouraged to undertake a thrice-weekly 5-10 min ankle exercise programme using elastic resistance bands and stretching in a 24-week single-arm pilot study. Ankle range of motion was measured monthly using a bi-plane ankle goniometer. Pain scores and participation levels were also recorded.

RESULTS

There were significant improvements in ankle range of motion achieved at 12 and 24 weeks. Median pain scores (scale of 1-10) were reduced from 5.2 at baseline to 2.0 at weeks 12 and 24.

CONCLUSION

These results show that a simple, home-based exercise programme is effective in achieving gains in ankle range of motion and may help to reduce pain. Good participation levels show that it is not only effective, but also feasible. A larger randomized controlled study is needed to show whether there is a positive effect on ulcer healing.

von Willebrand factor: evidence for variable clearance in vivo according to Y/C1584 phenotype and ABO blood group

BACKGROUND

The plasma von Willebrand factor (VWF) level (VWF:Ag) is known to correlate with the VWF Y/C1584 variation and with ABO blood group. The ratio of the VWF propeptide (VWFpp) to VWF:Ag and the ratio of coagulation factor VIII (FVIII:C) to VWF:Ag have previously been used as indicators of VWF clearance and/or secretion.

OBJECTIVES AND METHODS

To investigate the mechanism underlying the relationship between VWF phenotype and VWF:Ag, the VWFpp/VWF:Ag ratio and FVIII:C/VWF:Ag ratio were determined for plasmas of phenotype Y/C1584, Y/Y1584, blood group O and blood group A (n = 50 for each set). The blood group O plasmas comprised two sets of 25 with low and high mean VWF levels (Low-O and High-O), respectively; similarly for group A (Low-A and High-A).

RESULTS AND CONCLUSIONS

The VWFpp/VWF:Ag ratio was greater than 1 (unity) for Y/C1584 plasmas and significantly higher than for Y/Y1584 plasmas; however, the FVIII:C/VWF:Ag ratio was near unity for both and was not significantly different. These results are consistent with increased clearance for Y/C1584 VWF. Similarly, the VWFpp/VWF:Ag ratio and FVIII:C/VWF:Ag ratio in combination were consistent with increased VWF clearance in blood group O compared with blood group A, and in Low-O and Low-A, respectively, compared with High-O and High-A. The data indicate that in vivo C1584 and blood group O are associated with increased VWF clearance, and that clearance contributes to differing VWF level within a given blood group.

Spontaneous generation of self-organized solitary wave structures at earth's magnetopause

Spontaneous formation of solitary wave structures has been observed in Earth's magnetopause, and is shown to be caused by the breakup of a zonal flow by the action of drift wave turbulence. Here we show matched observations and modeling of coherent, large-scale solitary electrostatic structures, generated during the interaction of short-scale drift wave turbulence and zonal flows at the Earth's magnetopause. The observations were made by the Cluster spacecraft and the numerical modeling was performed using the wave-kinetic approach to drift wave-zonal flow interactions. Good agreement between observations and simulations has been found, thus explaining the emergence of the observed solitary structures as well as confirming earlier theoretical predictions of their existence.

Theory-guided design and synthesis of multichromophore dendrimers: an analysis of the electro-optic effect

Extensive experimental and theoretical study suggests that interchromophore electrostatic interactions are among the most severe impediments to the induction and stability of large electro-optic coefficients in electric-field-poled organic materials. In this report, multichromophore-containing dendritic materials have been investigated as a means to minimize unwanted attenuation of nonlinear optical (electro-optic) activity at high chromophore loading. The dendritic molecular architectures employed were designed to provide optimized molecular scaffolding for electric-field-induced molecular reorientation. Design parameters were based upon past experimental results in conjunction with statistical and quantum mechanical modeling. The electro-optic behavior of these materials was evaluated through experimental and theoretical analysis. Experimental data collected from the dendrimer structures depict a reasonably linear relationship between chromophore number density (N) and electro-optic activity (r(33)) demonstrating a deviation from the dipolar frustration that typically limits r(33) in conventional chromophore/polymer composite materials. The observed linear dependence holds at higher chromophore densities than those that have been found to be practical in systems of organic NLO chromophores dispersed in polymer hosts. Theoretical analysis of these results using Monte Carlo modeling reproduces the experimentally observed trends confirming linear dependence of electro-optic activity on N in the dendrimer materials. These results provide new insight into the ordering behavior of EO dendrimers and demonstrate that the frequently observed asymptotic dependence of electro-optic activity on chromophore number density may be overcome through rational design.

Innexins in the lobster stomatogastric nervous system: cloning, phylogenetic analysis, developmental changes and expression within adult identified dye and electrically coupled neurons

Gap junctions play a key role in the operation of neuronal networks by enabling direct electrical and metabolic communication between neurons. Suitable models to investigate their role in network operation and plasticity are invertebrate motor networks, which are built of comparatively few identified neurons, and can be examined throughout development; an excellent example is the lobster stomatogastric nervous system. In invertebrates, gap junctions are formed by proteins that belong to the innexin family. Here, we report the first molecular characterization of two crustacean innexins: the lobster Homarus gammarus innexin 1 (Hg-inx1) and 2 (Hg-inx2). Phylogenetic analysis reveals that innexin gene duplication occurred within the arthropod clade before the separation of insect and crustacean lineages. Using in situ hybridization, we find that each innexin is expressed within the adult and developing lobster stomatogastric nervous system and undergoes a marked down-regulation throughout development within the stomatogastric ganglion (STG). The number of innexin expressing neurons is significantly higher in the embryo than in the adult. By combining in situ hybridization, dye and electrical coupling experiments on identified neurons, we demonstrate that adult neurons that express at least one innexin are dye and electrically coupled with at least one other STG neuron. Finally, two STG neurons display no detectable amount of either innexin mRNAs but may express weak electrical coupling with other STG neurons, suggesting the existence of other forms of innexins. Altogether, we provide evidence that innexins are expressed within small neuronal networks built of dye and electrically coupled neurons and may be developmentally regulated.

A method for cold storage and transport of viable embryonic kidney rudiments

Organ culture of mouse embryonic kidneys is a powerful system for studying normal renal development and for researching the developmental effects of experimental perturbations (drugs, antibodies, interfering RNA, and so on). In standard protocols, embryonic kidneys are isolated by delicate micro-dissection and placed in organ culture as soon as possible after the death of the donor mouse, before there is time to genotype them or to transport them elsewhere. This report demonstrates that fully viable embryonic kidneys can be isolated and cultured from crudely dissected caudal portions of embryos that have been stored on ice or at 4 degrees C for several days. This very simple technique can save considerable resources in laboratories that culture kidneys of transgenic mice: (i) cold storage allows embryos to be genotyped before their kidneys are cultured, and (ii) cold transport allows kidney research laboratories to study kidneys of transgenic mice raised elsewhere without the need for expensive importing of the mouse line itself. It will therefore substantially augment the ability of kidney research labs to perform pilot experiments on large numbers of different transgenic animals and to collaborate in new ways.

Designing follow-up intervals

When an examination is needed to determine if an event has occurred there will be a loss of efficiency in using the resulting interval-censored data instead of the exact event times. In designing follow-up intervals this loss for longer intervals needs to be weighed against extra visits required by shorter intervals. We obtain results to quantify this for the estimation of the median and mean survival and for covariates in parametric regression models with equally spaced examination times. Asymptotic information loss for the log-normal and Weibull distributions are similar when comparisons are made between corresponding members of the two families. For distributions with coefficients of variation of 50 per cent or more, a choice of interval from 0.25 to 0.7 times the median is recommended.

Real-time scanning tunnelling microscopy imaging of protein motion at electrode surfaces

A mutant (K27C) of the blue copper protein azurin [Eur. J. Biochem. 194 (1990) 109; J. Mol. Biol. 221 (1991) 765] for orientated immobilisation on gold surfaces was analysed by scanning tunnelling microscopy (STM) both in a resting state and following the application of a short potential pulse between the tip and sample.

Structural determinants of heparan sulphate modulation of GDNF signalling

Glial cell line-derived neurotrophic factor (GDNF) has many functions including regulation of kidney morphogenesis and of neuron growth and survival in the enteric, sensory and central nervous systems. Reports of GDNF being used against Parkinson's disease in human patients have sparked intense clinical interest in GDNF signalling. We recently showed that GDNF signalling requires cell surface heparan sulphate glycosaminoglycans (Barnett et al., 2002, J. Cell Sci. 115, 4495-4503). Here we use exogenous modified heparins to determine those structural features required to inhibit GDNF signalling in ex vivo assays. 2-O-sulphate groups were found to impart high activity but were not absolute requirements for the inhibition of GDNF signalling. These findings may explain the similarities between the phenotypes of transgenic mice lacking GDNF and those lacking heparan sulphate 2-sulphotransferase, the enzyme responsible for achieving 2-O-sulphation of uronic acids in vivo.

Non-selective and cyclo-oxygenase-2-specific non-steroidal anti-inflammatory drugs impair the hyperaemic response of skin to brief axillary artery occlusion

BACKGROUND

Cyclo-oxygenase-2 (COX-2)-specific inhibitors are marketed as safer analgesics than non-selective non-steroidal anti-inflammatory drugs. However, there has been conflicting evidence concerning endothelial function and cardiovascular risk after COX-2 inhibitor use. We investigated forearm skin vascular reactivity to brief axillary artery occlusion in healthy volunteers after a single dose of the non-steroidal anti-inflammatory drugs ibuprofen (non-selective) and rofecoxib (COX-2 specific).

METHODS

Ten healthy male volunteers were studied. Forearm skin blood flow was measured using laser Doppler flowmetry. Two non-invasive probes were placed on the volar surface of the forearm. The magnitude of hyperaemic response to brief (20 s) and prolonged (5 min) occlusion of the axillary artery was measured before and 2-3 h after administration of ibuprofen 800 mg or rofecoxib 25 mg. The transient hyperaemic response ratio (THRR), defined as the net peak hyperaemic flow-flux divided by the net baseline flow-flux, was calculated. Each volunteer received both drugs in random order at least 1 week apart.

RESULTS

Ibuprofen and rofecoxib increased net baseline blood flow (median (range): ibuprofen, from 23.3 (12.1-40.8) to 31.5 (17.4-77.3); rofecoxib, from 22.0 (14.6-41.0) to 29.9 (19.5-112.0); P<0.01). The net hyperaemic peak flow-flux after brief and prolonged occlusion was unchanged after both drugs. THRR was reduced by both drugs (ibuprofen, from 2.92 (2.38-3.86) to 2.09 (1.45-3.54); rofecoxib, from 3.36 (2.06-5.16) to 2.67 (1.15 -3.84); P<0.01).

CONCLUSIONS

Both COX-2 and non-selective non-steroidal anti-inflammatory drugs, when given to healthy volunteers as single therapeutic doses, decrease skin microvascular tone but do not impair maximal vasodilatory ability.

Effects of bilobalide on cerebral amino acid neurotransmission

Bilobalide is one of many active constituents found in EGb 761 (definition see editorial), which is extracted from Ginkgo biloba leaves. Whilst there is good, sound evidence that bilobalide exhibits neuroprotective actions in a variety of model systems, there is currently no consensus on its mechanism of action. This present communication summarises the results we have obtained with this compound on excitatory amino acid neurotransmission in the central nervous system using both neurochemical and electrophysiological techniques. Bilobalide was shown to reduce glutamate and aspartate release elicited by both high potassium-containing artificial cerebrospinal fluid (aCSF) or veratridine from mouse cortical slices. In addition, bilobalide had a very potent effect (IC (50) 2.7 microM) on glutamate release elicited by hypoxia/hypoglycaemia-induced release from rat cortical slices. Electrophysiologically, bilobalide also decreased the frequency of gamma-aminobutyric acid (GABA) uptake inhibitor-induced depolarisations in mouse cortical slices, an effect probably mediated by a decrease in glutamate release. No definitive conclusions can be reached concerning the mechanism of action of bilobalide, but an ability to decrease excitotoxic amino acid release, particularly glutamate, would suggest that this is a probable mechanism to account for its neuroprotective properties.

Effects of bilobalide on amino acid release and electrophysiology of cortical slices

This study investigated the effects of bilobalide, a constituent of Ginkgo biloba, on potassium and veratridine-induced release of glutamate and aspartate from mouse cortical slices. We also studied its effects on spontaneous and N-methyl-D-aspartate (NMDA)-induced depolarizations elicited in magnesium-free artificial cerebrospinal fluid (aCSF) as well as its effect on NO-711 (a gamma-aminobutyric acid (GABA) uptake inhibitor)-induced depolarizations. Bilobalide, 100 microM significantly reduced both glutamate and aspartate release elicited by potassium or veratridine. Bilobalide (5-100 microM) also significantly reduced the frequency of NO-711 induced depolarizations, however, it had no effect on spontaneous or on NMDA-induced depolarizations at 5-200 microM. These results suggest that the neuroactive properties of bilobalide may be mediated by a reduction in excitatory amino acid neurotransmitter release.