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Biomedical subjects

R A Hutton

Publications and source records attributed to R A Hutton.

At least 19 recordsLinked to original sources
PubMed1992

Development and evaluation of ELISAs for factor XIIIA and XIIIB subunits in plasma.

Severe, congenital deficiency of factor XIII is extremely rare. However, a moderate reduction in the plasma level of the functional subunit (factor XIIIA) and also to a lesser extent of the carrier subunit (factor XIIIB), and a decrease in the XIIIA:B subunit ratio, have recently been reported in patients with the inflammatory bowel disorder Crohn's disease, particularly during clinical relapse. In order to accurately monitor patients, sensitive, reliable assays for the two subunits of factor XIII are required. We report here the development and validation of ELISAs for these components. The assays are identical except in respect of the specificity of the polyclonal antiserum used as starting material, both of which are commercially available. The antisera are purified by n-octanoic acid precipitation and portions of these purified immunoglobulins are used as coating antibodies. The remaining portions are biotinylated and used with streptavidin and horse-radish peroxidase as tracer antibodies. A normal range (n = 24) was established for factor XIIIA (mean 95 range 60-130 U/dl) and for factor XIIIB (mean 99 range 60-130 U/dl). There were no significant differences between the ELISA and electroimmunodiffusion assays either for factor XIIIA (means +/- 1 standard deviation 95 +/- 15.9 and 89 +/- 22.7 respectively) or for factor XIIIB (99 +/- 18.3 and 106 +/- 23.4 respectively). These assays have been in routine use for six months, during which time two further antisera purifications and biotinylations have been carried out without significant problems of reproducibility or stability.

Adult↗
PubMed1992

Evidence for activation of coagulation in Crohn's disease.

Haemostatic changes in 16 patients with Crohn's disease were studied from active disease into clinical remission and beyond. Elevated concentrations of fibrinopeptide A (FpA) and prothrombin fragments F1 + 2 (F1 + 2) were found at times of both active (FpA median 3.2, range [0.3-40] ng/ml and F1 + 2 median 2.3, range [0.3-18] nm/l) and inactive disease (FpA median 2, range [0.4-40] ng/ml and F1 + 2 median 1.3, range [0.2-20) nm/l]. We also measured the physiological inhibitors of coagulation and fibrinolysis; there was no significant difference in the levels of antithrombin III, protein C or the Exner ratio between active and inactive disease. Free protein S levels were significantly lower in active disease (median 34, range 9-54 U/dl) than in remission (median 40, range 12-65 U/dl). Plasminogen activator inhibitor type 1 (PAI-1) was significantly raised in remission (median 11, range 3-32 ng/ml) when compared to active disease (median 7, range 3-42 ng/ml). The D-dimer correlated significantly with fibrinopeptide A (P < 0.001), suggesting reactive fibrinolysis in some patients. Most (35/52, 67%) samples showed evidence of persistent haemostatic activation (elevated FpA and/or F1 + 2) during phases of apparent clinical remission in Crohn's disease, a factor that is not reflected by clinical activity scores. This study supports the hypothesis that coagulation is activated in the mesenteric vasculature of patients with Crohn's disease.

Adolescent↗
PubMed1991

Coagulopathy and haemorrhage in human victims of Bothrops jararaca envenoming in Brazil.

Thirty-four patients envenomed by Bothrops jararaca in Brazil were studied. Of these, 20 (59%) had incoagulable blood associated with local and/or systemic bleeding and 10 of the 20 were thrombocytopenic. Among 14 patients with coagulable blood, 6 (43%) had bleeding symptoms and 3 (21%) were thrombocytopenic. High levels of von Willebrand factor (vWF), plasminogen activator inhibitor type 1 (PAI-1) and tissue type plasminogen activator (t-PA) antigens were also recorded in some patients with systemic bleeding with or without incoagulable blood. These substances may have been released from endothelial cells. Admission serum venom antigen levels were similar in both groups. The study indicated that systemic haemorrhage may occur in patients with coagulable blood and thrombocytopenia and that coagulopathy is not therefore the primary cause of haemorrhage.

Adolescent↗
PubMed1991

Systemic haemorrhage in rats induced by a haemorrhagic fraction from Bothrops jararaca venom.

The main haemorrhagic fraction of Bothrops jararaca venom, showing in vitro fibrinogenolytic activity and an inhibitory effect on platelets aggregation induced by collagan, was studied in rats. Development of coagulopathy and/or haemorrhage was studied 2 hr after s.c. injection of batroxobin, B. jararaca whole venom and its haemorrhagic fraction. Incoagulable blood, together with low fibrinogen levels, were found only in rats injected with batroxobin and whole venom; thrombocytopenia alone was detected in rats given s.c. injections of haemorrhagin. Intravenous injection of low doses of haemorrhagin (less than 15 micrograms) resulted in significant thrombocytopenia, without any alterations in the blood coagulation mechanism. Severe damage to the vascular endothelium and skeletal muscle following s.c. injection of haemorrhagin together with signs of systemic haemorrhage in the kidneys, lungs and liver occurred. Levels of factor VIII and von Willebrand factor antigen were within the normal range in all animals. Serum levels of both whole venom and haemorrhagin were significantly correlated. This study confirms that B. jararaca haemorrhagin plays a vital role in systemic bleeding.

Animals↗
PubMed1990

Differences between the venoms of two sub-species of Russell's viper: Vipera russelli pulchella and Vipera russelli siamensis.

Ion exchange chromatography was carried out using venoms obtained from two sub-species of Russell's viper; V. russelli siamensis from Burma and V. russelli pulchella from Sri Lanka. Differences were observed in the elution position of venom components having haemolytic and procoagulant activity but not those causing fibrinolysis. Only the V. russelli siamensis venom exhibited any platelet aggregating activity. The Indian (Haffkine) polyspecific and the Burmese (Burma Pharmaceutical Industries) monospecific antivenoms, when used in cross immunoelectrophoresis against the two venoms, revealed differences in the number and/or intensity of the precipitin bands present. An important functional consequence of this was that the Burmese antivenom did not neutralize the haemolytic activity of the V. russelli pulchella venom in vitro and would thus probably not be effective in treating this consequence of envenoming by Russell's viper in Sri Lanka. Differences in the composition and the clinical effects of the two venoms emphasizes the importance of using venom from the local snake for antivenom production if optimal clinical efficacy is to be achieved.

Chromatography, Ion Exchange↗
PubMed1989

Hemostatic evaluation in bleeding disorders from native blood. Clinical experience with the hemostatometer.

Primary hemostasis (PH), i.e., hemostatic platelet plug formation, and the subsequent coagulation were recorded and quantified from the same nonanticoagulated venous blood sample with the use of the Haemostatometer. In addition, platelet thrombus formation induced by interaction of flowing native blood with a collagen fiber under low shear rates (450 s-1) was simultaneously analyzed by this device. The effect of monoclonal antibodies (MoAbs) directed against von Willebrand's factor antigen (vWF:Ag), platelet glycoprotein Ib (GPIb) and the GPIIb/IIIa complex, and fibrinogen were studied. PH was significantly inhibited by MoAbs against vWF:Ag, GPIIb/IIIa, and fibrinogen but was unaffected by antibody against GPIb. Collagen-induced thrombosis was prevented by MoAbs against vWF:Ag and GPIb, slightly inhibited by antifibrinogen, and unaffected by blockage of platelet membrane GPIIb/IIIa. The effect of a single 600-mg dose of aspirin was monitored, and abnormal PH was still detectable five days later. From the 13 hemophiliacs tested, 7 showed significantly prolonged PH. In von Willebrand's disease, a characteristic defect of PH with significant inhibition or absence of collagen-platelet interaction was observed in all the 11 patients. PH was greatly prolonged in both of the two patients with storage pool deficiency. The technique detected improvement of platelet function, i.e., PH in all of six patients with bleeding disorders after replacement therapy or DDAVP infusion. The authors conclude that the Haemostatometer technique is a sensitive test for determining platelet dysfunction and monitoring efficacy of factor-replacement or DDAVP therapy.

Adult↗
PubMed1989

The action of Russell's viper venom on fibrin formation and fibrinolysis in vivo.

Envenoming by Russell's viper caused a marked rise in FPA, B beta 15-42 fragment and fibrin derived cross-linked D-dimer fragment indicative of a consumptive coagulopathy with hyperfibrinolysis. There was no increase in tPA or tPA-I levels post envenoming, which suggests that the increase in fibrinolytic activity was not due to venom-induced release of tPA from the vessel walls but may have been attributable to a direct effect of the venom or to a secondary physiological response to fibrin deposition. The effectiveness of the antivenom is demonstrated by its ability to prevent further cleavage of fibrinogen and the return to normal fibrinogen levels by 24 h. A secondary rise in FPA at this time indicates that the initial dose of antivenom may have been too small. The antivenom alone or in combination with the venom causes the release of tPA, tPA-I and vWF by the vessel walls. This may be a consequence of the severe anaphylactic reactions seen in some patients.

Adolescent↗
PubMed1989

Changes in protein C and free protein S during pregnancy and following hysterectomy.

Two longitudinal studies were undertaken to measure the naturally occurring coagulation inhibitors, protein C and protein S, in females who were either pregnant or who were undergoing hysterectomy. Functional and immunological protein C and free protein S were assayed. During pregnancy, protein C levels remained unchanged except for a small increase in protein C antigen at 28-32 weeks gestation. The free protein S fell significantly and progressively during pregnancy, although only in about one-third of patients did the level fall below the normal range. In the hysterectomy study, a significant fall in protein C occurred on days one and three after surgery but had returned to normal by the time of discharge (days 7-10). A small rise in free protein S was observed at time of discharge, but this factor was otherwise unchanged. We conclude that the changes observed may contribute to the hypercoagulable state which is associated with pregnancy or major surgery.

Adult↗
PubMed1989

Binding of apoE-rich high density lipoprotein particles by saturable sites on human blood platelets inhibits agonist-induced platelet aggregation.

High density lipoproteins (HDL, d 1.063-1.21 g/ml) are reported to stimulate, to have no effect on, or to inhibit agonist-induced platelet aggregation. We have hypothesized that these conflicting reports might be explained by opposing effects of individual HDL subclasses on platelet aggregability. Physiologic concentrations of HDL3 had little effect on ADP-induced aggregation of washed platelet suspensions, although higher levels were stimulatory. Normal concentrations of HDL2 (0.2-0.4 mg of protein/ml) inhibited aggregation; further fractionation by heparin-Sepharose chromatography identified the particles rich in apolipoprotein E, termed HDL-E, as the major anti-aggregatory subclass. Washed platelets bound radioiodinated HDL-E to a uniform class of saturable sites; they numbered 4,200 per platelet and the KD was 7.9 x 10(-7) M. Binding of HDL-E by platelets, and its anti-aggregatory action, showed a similar rapidity and both occurred within the physiologic concentration range. Moreover, the two processes were independent of the presence of divalent ions and were impaired by chemical modification of the apolipoprotein constituents of HDL-E. We conclude that occupation of cell-surface receptors by HDL-E particles impairs platelet responsiveness to exogenous agonists and that platelet aggregability in the presence of whole HDL may reflect the relative concentrations of the individual subclasses in the particular sample.

Adenosine Diphosphate↗
PubMed1988

A study of the effect of ethamsylate (Dicynene) on the bleeding time, von Willebrand factor level and fibrinolysis in patients with von Willebrand's disease.

Nine patients with clinically moderate or severe Type I von Willebrand's disease were treated for 2 weeks with ethamsylate (2 g/day in four equal doses) and with a matched placebo in a randomised double-blind trial. Template bleeding time, von Willebrand factor activity (ristocetin co-factor) and antigen, euglobulin lysis time and type I tissue plasminogen activator inhibitor were determined before and at the end of each treatment period. None of these parameters showed any significant change attributable to ethamsylate. Thus, despite the fact that five patients thought subjectively that their bleeding symptoms improved during ethamsylate treatment compared to only one while on placebo, we obtained no evidence that the drug was of benefit to patients with von Willebrand's disease.

Adolescent↗
PubMed1988

Platelet aggregation and thromboxane A2 release in primary biliary cirrhosis and effect of D-penicillamine treatment.

Platelet function was assessed in 28 patients with primary biliary cirrhosis (PBC), of whom 10 were receiving D-penicillamine. Patients not on D-penicillamine treatment had platelet aggregation similar to that in the healthy control group; the group treated with D-penicillamine showed significantly enhanced platelet aggregation in response to threshold doses of adrenaline and collagen but not ADP. Median thromboxane B2 production was also higher in D-penicillamine treated patients than in controls or untreated patients; this difference did not reach statistical significance. The addition of D-penicillamine in vitro to platelet rich plasma from normal subjects was shown to enhance adrenaline- and collagen-induced platelet aggregation. Abnormalities of platelet function in PBC patients did not correlate with serum cholesterol concentration or with liver function tests but were related to the stage of disease. The present study emphasises the need to consider the aetiology, disease stage and type of treatment when assessing platelet function and prostanoid release in liver disease.

Aged↗
PubMed1988

Haemostatic disturbances in patients bitten by Russell's viper (Vipera russelli siamensis) in Burma.

Patients who are severely envenomed by Russell's viper develop DIC which is frequently associated with spontaneous bleeding and incoagulable blood. These haemostatic disturbances may be responsible for death or organ/tissue damage both through haemorrhage and microvascular occlusion by fibrin thrombi. The most striking laboratory features of the coagulopathy developing after Russell's viper bite in the 42 patients studied were depletion of fibrinogen (mean 0.09 g/l, range 0-0.6), factor V (6.5 u/dl, range 0-17), factor X (35 u/dl, range 1-85), factor XIIIa (57 u/dl, range 15-82), plasminogen (61 u/dl, range 10-92), antiplasmin (36 u/dl, range 14-62). Protein C (49 u/dl, range 15-100) and platelets (104 x 10(9)/l, range 25-197). Intense fibrinolytic activity was detected in all cases with marked elevation of FDPs (1614 micrograms/ml, range 350-3000), a large proportion of which were cross-linked (1058 micrograms/ml, range 38-3000). The monospecific Burmese antivenom appeared to be very effective in neutralizing the venom procoagulants and in restoring blood coagulability. Moreover, the unexpectedly normal level of AT III provides a theoretical basis for the use of heparin to enhance the inactivation of those serine proteases present before antivenom administration.

Adolescent↗
PubMed1988

The effect of cooling on in vitro vascular prostacyclin and platelet thromboxane A2 synthesis: relevance to cold-induced pathology.

The effect of cooling (at 27 degrees C) on the synthesis of prostacyclin (PGI2) by rat aortic rings, thromboxane A2 (TXA2) synthesis by human platelets and phosphodiesterase activity in human platelets was investigated. Cooling induced a significant reduction in both PGI2 synthesis by rat aortic rings and TXA2 synthesis by human platelets, but the inhibition of the former was proportionately greater. Platelet phosphodiesterase activity decreased, with a subsequent increase in intraplatelet c-AMP content. Diminished PGI2 synthesis/release associated with the previously described diminution in the sensitivity of platelets to PGI2 after cooling probably contributes to the hyperaggregability of platelets at lower temperatures. This occurs in spite of the potential antiaggregatory effect of diminished TXA2 synthesis by platelets and the increase in intraplatelet c-AMP. These observations are relevant to the pathogenesis of hyperaggregability of platelets in Raynaud's syndrome.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

Paralysis, rhabdomyolysis and haemolysis caused by bites of Russell's viper (Vipera russelli pulchella) in Sri Lanka: failure of Indian (Haffkine) antivenom.

In Sri Lanka, Russell's viper, Vipera russelli pulchella, kills more people than any other species of snake. At Anuradhapura in the dry central zone of the island we studied 23 patients with systemic envenoming after proven bites. Seventy-three per cent had swelling at the bite site. Neurotoxicity was the commonest sign of systemic envenoming: 82 per cent had external ophthalmoplegia and 77 per cent had ptosis. Incoagulable blood was found in 59 per cent but only 36 per cent had spontaneous bleeding. Other signs included generalized muscle tenderness (32 per cent), black urine (27 per cent) and persistent oliguria (9 per cent). Laboratory studies showed evidence of a severe clotting disorder: fibrinogen was often depleted as were factors V and X. Fibrin degradation products, including cross-linked moieties, were grossly elevated, clear evidence for enhanced fibrinolysis. Intravascular haemolysis, unrelated to G6PD deficiency, was often present. Myoglobin was detected in the plasma of all 19 patients tested (range 100- greater than 8000 ng/ml) and in the urine in 14 of 18 patients (110- greater than 16,000 ng/ml). Venom antigen (16.5-702 ng/ml) was detected by specific ELISA in the serum of all patients. Its concentration fell with the administration of 50-200 ml of Haffkine polyspecific antivenom raised against Indian venoms. Complete permanent clearance of venom antigen from the circulation was seen in only one of 21 patients who were followed until discharge. Blood coagulability was restored between one and 25 h (mean 8.8) after the first dose of antivenom in the 12 surviving patients whose clotting defect could be followed; no dramatic reversal of neuromyotoxic signs was seen. Haffkine antivenom thus has limited efficacy against systemic poisoning by Russell's viper in Sri Lanka.

Adolescent↗
PubMed1987

In vitro studies of Russell's viper venom on blood coagulation and fibrinolysis.

The effect of Russell's viper venom (RVV) on clot formation and lysis and the effect thereon of specific antivenom for Russell's viper venom, were studied in vitro. RVV had fibrinogenolytic activity, but only at a concentration greatly in excess of that likely to be achieved in vivo after Russell's viper bite. Similarly, RVV did not directly activate the fibrinolytic system in vitro, even at very high concentrations (10,000 micrograms/ml). Furthermore, 40 ml of antivenom (ASV) was found to be sufficient to neutralise the average amount of venom (60 mg) injected by a snake, but insufficient to neutralise amounts in excess of 75 mg.

Animals↗
PubMed1987

Chromogenic substrates in haemostasis.

Advances in knowledge of the structure-function relationships of the proteins involved in haemostatic pathways, have made it possible to synthesize small peptides which mimic the active site of many of the serine proteases concerned. Attachment to the cleavage site of such synthetic peptides, of a detector molecule such as para-nitroaniline which, when released, produces a coloured compound has enabled many of the enzyme reactions of haemostasis, and most of the co-factors and naturally-occurring inhibitors, to be individually and sensitively quantitated. Chromogenic substrate assays are very specific and overcome the criticism levelled at many conventional assays that, being based on the speed of formation or the rate of destruction of a fibrin clot, they frequently involve enzymatic reactions in addition to that being examined. Moreover, chromogenic substrate assays are generally simple and quick to perform and are readily automated. They are thus economical of manpower and, more importantly from the point of view of patient care, they permit the rapidly-changing status of those with acute derangements of haemostasis to be monitored more frequently and comprehensively than is possible using some conventional assays. Chromogenic substrate assays have some limitations, however. Since they mimic only a small portion of the natural substrate, they may not be sensitive to structural defects elsewhere in the molecule, and may thus not totally reflect biological activity. Though technically simple to perform, the defined incubation times and temperatures must be rigidly adhered to if reliable results are to be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromogenic Compounds↗