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D A Lane

Publications and source records attributed to D A Lane.

At least 181 records · Page 10Linked to original sources
PubMed1984

Anticoagulant activities of heparin oligosaccharides and their neutralization by platelet factor 4.

Oligosaccharides of well-defined molecular size were prepared from heparin by nitrous acid depolymerization, affinity chromatography on immobilized antithrombin III (see footnote on Nomenclature) and gel chromatography on Sephadex G-50. High affinity (for antithrombin III) octa-, deca-, dodeca-, tetradeca-, hexadeca- and octadeca-saccharides were prepared, as well as oligosaccharides of larger size than octadecasaccharide. The inhibition of Factor Xa by antithrombin III was greatly accelerated by all of these oligosaccharides, the specific anti-Factor Xa activity being invariably greater than 1300 units/mumol. The anti-Factor Xa activity of the decasaccharide was not significantly decreased in the presence of platelet factor 4, even at high platelet factor 4/oligosaccharide ratios. Measurable but incomplete neutralization of the anti-Factor Xa activities of the tetradeca- and hexadeca-saccharides was observed, and complete neutralization of octadeca- and larger oligo-saccharides was achieved with excess platelet factor 4. The octa-, deca-, dodeca-, tetradeca- and hexadeca-saccharides had negligible effect on the inhibition of thrombin by antithrombin III, whereas specific anti-thrombin activity was expressed by the octadeca-saccharide and by the larger oligosaccharides. An octadecasaccharide is therefore the smallest heparin fragment (prepared by nitrous acid depolymerization) that can accelerate thrombin inhibition by antithrombin III. The anti-thrombin activities of the octadecasaccharide and larger oligosaccharides were more readily neutralized by platelet factor 4 than were their anti-Factor Xa activities. These findings are compatible with two alternative mechanisms for the action of platelet factor 4, both involving the binding of the protein molecule adjacent to the antithrombin III-binding site. Such binding results in either steric interference with the formation of antithrombin III-proteinase complexes or in displacement of the antithrombin III molecule from the heparin chain.

Anticoagulants↗
PubMed1984

The significance of fibrinogen derivatives in plasma in human renal failure.

The concentrations in plasma of fibrinogen derivatives fibrinopeptide A (FPA), beta 15-42 antigen and fragment E (FgE) antigen have been determined in patients with renal failure and compared to the concentrations of the platelet release products, beta-thromboglobulin (beta TG) and platelet factor 4 (PF4). In 'partial renal failure' (51Cr-EDTA clearance rate 4-60 ml/min) FPA, beta 15-42 antigen, FgE antigen and beta TG levels were significantly raised above a normal laboratory control group. These levels were further raised in a group of patients whose disease required regular maintenance haemodialysis (51Cr-EDTA clearance rate less than 4 ml/min). PF4 levels were not significantly raised in either group. A statistical analysis of all patient results revealed that FPA, beta 15-42 antigen and FgE antigen levels all correlated with beta TG levels but not with PF4 levels. It is known that beta TG is catabolized by the kidney but PF4 is not and that elevated beta TG levels in renal failure are caused by impaired elimination rather than increased production. These results suggest that the plasma levels of these three fibrinogen derivatives are elevated in renal disease at least in part by decreased elimination rather than by increased thrombin and plasmin activities alone.

Adolescent↗
PubMed1984

Objective assessment of heparin requirements for hemodialysis in humans.

The abilities of four heparin regimens to inhibit activation of blood coagulation, fibrinolysis, and the platelet release reaction in humans during renal dialysis have been assessed by visible examination of the extracorporeal circulation and by use of radioimmunoassays to FPA, beta 15-42 antigen, beta gamma G, and PF4. A subcutaneous injection of 5000 IU of heparin administered 1 hour before dialysis in two patients was either unable to sustain dialysis because of excess fibrin formation or allowed elevated plasma FPA and beta gamma G concentrations during dialysis. Injection of 10,000 IU heparin s.c. in five patients could sustain dialysis in only three patients for 5 hours, and allowed progressively increasing concentrations of FPA, beta gamma G, and PF4, as well as fibrin formation, in the extracorporeal circulation. A lower dose of heparin administered intravenously (2500 IU bolus plus 1000 IU/hr) to six patients was also unable to prevent elevations in FPA and beta gamma G 4 hours and 5 hours after the initiation of dialysis. Intravenous administration of heparin at a dose of 5000 IU bolus plus 1500 IU/hr completely suppressed generation of FPA during 5-hour dialysis and was free of visible fibrin formation in the extracorporeal circulation in 13 patients. The concentration of the fibrinolytic system marker beta 15-42 antigen did not change significantly in any of the regimens, and the concentration of PF4 altered in response to infused heparin as well as to inadequate heparinization. We conclude that complete inhibition of activation of coagulation and suppression of the platelet release reaction occurs when high plasma heparin levels (greater than or equal to 0.5 IU/ml) are maintained during dialysis: lower heparin levels may be compatible with dialysis in some patients, but they allow generation of fibrin and the platelet release reaction, which pose a potential risk to the dialysis procedure and to the patient.

Aged↗
PubMed1983

Binding of platelet factor 4 to heparin oligosaccharides.

Heparin fractions of differing Mr (7800-18 800) prepared from commercial heparin by gel filtration and affinity chromatography on immobilized anti-thrombin III had specific activities when determined by anti-Factor Xa and anti-thrombin assays that ranged from 228 to 448 units/mg. The anti-Factor Xa activity of these fractions could be readily and totally neutralized by increasing concentrations of platelet factor 4 (PF4). That these fractions bound to immobilized PF4 was indicated by the complete binding under near physiological conditions of 3H-labelled unfractionated commercial heparin. An anti-thrombin III-binding oligosaccharide preparation (containing predominantly eight to ten saccharide units), prepared by degradation of heparin with HNO2 had high (800 units/mg) anti-Factor Xa, but negligible anti-thrombin, specific activity. The anti-Factor Xa activity of this material could not be readily neutralized by PF4, and the 3H-labelled oligosaccharides did not completely bind to immobilized PF4. A heterogeneous anti-thrombin III-binding preparation containing upwards of 16 saccharides had anti-thrombin specific activity of just less than one-half the anti-Factor Xa specific activity. This material was completely bound to immobilized PF4 and was eluted with similar concentrations of NaCl to those that were required to elute unfractionated heparins from these columns. Furthermore, increasing concentrations of PF4 neutralized the anti-Factor Xa activity of this material in a manner similar to that of unfractionated heparin. It is concluded that heparin oligosaccharides require saccharide units in addition to the anti-thrombin III-binding sequence in order to fully interact with PF4.

Antithrombins↗
PubMed1983

Fibrinogen Manchester: identification of an abnormal fibrinopeptide A with a C-terminal arginine leads to histidine substitution.

Purified samples of fibrinogen Manchester, a congenital dysfibrinogenaemia with impaired fibrinopeptide A (FPA) release, were digested with thrombin. Amino acid sequencing of the fibrin showed that FPA had been completely released. High performance liquid chromatographic (HPLC) analysis of the clot supernatant showed the presence of a new peptide eluting ahead of the normal FPA. The amino acid composition and sequence of the new peptide established its identity as a variant of FPA containing histidine in position 16 instead of the usual arginine. The chromatograms from both siblings with the defect demonstrated that they were heterozygous for this clotting defect.

Amino Acid Sequence↗
PubMed1983

Delayed release of an abnormal fibrinopeptide A from fibrinogen Manchester: effect of the A alpha 16 Arg leads to His substitution upon fibrin monomer polymerization and the immunological crossreactivity of the peptide.

Fibrinogen Manchester is an abnormal fibrinogen with an impaired release of fibrinopeptide A (FPA) and a polymerization abnormality. In the accompanying article we have identified the amino acid substitution in fibrinogen Manchester as A alpha 16 Arg leads to His. When fibrinogen Manchester was digested with low thrombin concentrations approximately 40-50% of the total FPA content was release at a rate similar to FPA release from normal fibrinogen. The fibrin so formed exhibited an impaired polymerization of monomers. Digestion of fibrinogen Manchester with high concentrations of thrombin for prolonged times released the remaining FPA which had an abnormal retention time when studied by high performance liquid chromatography (HPLC). This fibrinopeptide has been shown previously to contain the A alpha 16 Arg leads to His substitution. fibrin resulting from this exhaustive digestion had normal polymerization of monomers. The normal and substituted FPAs were isolated by HPLC and compared in a double antibody competitive-binding assay for normal FPA. The immunological cross-reactivity of the abnormal peptide was reduced, so that approximately 5 times more abnormal peptide was required on a molar basis to displace labelled normal FPA. Normal intact fibrinogen was 10-fold less reactive (on a half molar basis) than free normal FPA and the crossreactivity of fibrinogen Manchester was measurably less than that of normal fibrinogen. It is concluded that immunological measurement alone of FPA released from abnormal fibrinogens may not give a complete description of the kinetics of peptide release if the amino acid substitution lies within the FPA sequence. The combination of radioimmunoassay and HPLC, however, provides a powerful analytical approach that should be useful in classifying and characterizing abnormal fibrinogens.

Blood Coagulation Disorders↗
PubMed1983

Activation of coagulation and fibrinolytic systems following stroke.

When the human blood coagulation and fibrinolytic systems are activated thrombin cleaves fibrinopeptide A (FPA) and plasmin cleaves b beta1 leads to 42 from fibrin(ogen). Elevated plasma concentrations of FPA and B beta 1 leads to 42 are evidence for enhanced thrombin and plasma activities in plasma. We have determined the plasma concentrations of FPA and B beta 1 leads to 42 in patients who have had thrombotic stroke. Patients who were studied immediately following stroke were found to have greatly elevated plasma FPA and B beta 1 leads to 42 levels, but these decreased to the concentrations found in an apparently healthy age-matched control group 1 month after the infarct. In contrast, the plasma concentrations of the platelet release product beta-thromboglobulin (beta TG) were slightly, but significantly, elevated immediately following the stroke and these did not alter with time after the infarct. It is concluded that following thrombotic stroke increased thrombin and plasmin activities are to be found in plasma. These increased protease activities are probably not directly associated with an increased in vivo platelet release reaction and may be useful in deciding which patients are at risk of reinfarction or stroke progression.

Aged↗
PubMed1982

In vivo platelet release in myeloproliferative disorders.

The in vivo platelet release reaction in 22 patients with myeloproliferative disorders has been studied by measuring plasma concentrations of the platelet release product beta-thromboglobulin (beta TG). Mean beta TG and mean beta TG: whole blood platelet count ratio were significantly raised in the patient group taken as a whole compared to an age matched control group. No significant increases were observed in the plasma concentrations of thrombin and plasmin sensitive fibrinogen fragments fibrinopeptide A (FpA) and B beta 1-42. The patients were divided into those who had normal, increased or decreased responses to in vitro ADP-induced platelet aggregation. Mean beta TG and the mean beta TG: whole blood platelet count ratio were higher in the increased and decreased responders to ADP than in the normal aggregation group, but the differences in means were not statistically significant. Aspirin given to six patients at a dose sufficient to eliminate the secondary phase of ADP-induced platelet aggregation reduced mean beta TG and the mean beta TG: whole blood platelet count ratio but did not alter mean FpA and B beta 1-42. It is concluded that the enhanced platelet release reaction seen in myeloproliferative disorders is independent of plasma protease activity that arises when coagulation and fibrinolytic systems are activated.

Aged↗
PubMed1982

Proteolysis of fibrinogen in healthy volunteers following major and minor vivo plasminogen activation.

Changes in immunoreactive fibrinopeptide A, fragment B beta 1-42 and fragment E were followed after major and minor in vivo plasminogen activation, after infusion of streptokinase and acylated streptokinase-plasminogen complex respectively, in healthy male volunteers. Major activation resulted in a dramatic rise in all three peptides, fragment E persisting in the circulation longest. Fragment B beta 1-42 was also markedly increased after minor systemic plasminogen activation despite apparently adequate levels of immediate antiplasmin.

Anistreplase↗
PubMed1982

Plasma concentrations of fibrinopeptide A, fibrinogen fragment B beta 1-42 and beta-thromboglobulin following total hip replacement.

Plasma concentrations of thrombin sensitive peptide fibrinopeptide A (FpA), plasmin sensitive fibrinogen fragment B beta 1-42 and the platelet release product beta-thromboglobulin (beta TG) have been measured in 36 patients before and after total hip replacement. Statistically significant elevations of all three activation products were observed in the days following operation. There were small differences in plasma concentrations of FpA, B beta 1-42 and beta TG in patients who did (n = 13) and did not (n = 23) develop post operative deep vein thrombosis, as assessed by ascending venography on post operative day 10, but these differences were not statistically significant. It is concluded that coagulation and fibrinolytic systems and also blood platelets are activated following total hip replacement operations. However, the formation of post operative deep vein thrombosis can not be effectively monitored by measurement of the activation products.

Adult↗
PubMed1980

The heparin-accelerated neutralisation of bovine alpha and beta thrombins by antithrombin III.

The heparin-accelerated neutralisation of bovine alpha and beta thrombins has been examined using a peptide substrate H-D-phenylalanyl-pipecolyl-arginine-paranitroanilide-HCl to measure thrombin amidase activity. Alpha and beta thrombins were both neutralised by antithrombin III and this neutralisation was further accelerated by the presence of small amounts of heparin. Low and high molecular weight heparin and heparins fractionated by their affinity for antithrombin III were all able to accelerate the neutralisation of alpha and beta thrombin. This work is therefore unable to confirm reports that alpha and beta thrombins have different heparin sensitivities.

Animals↗
PubMed1980

The anti-heparin properties of human low-density lipoprotein.

High-density (HDL), low-density (LDL) and very low-density lipoproteins (VLDL) have been purified from normal human plasma by a combination of ultracentrifugation in high-density salt and agarose gel filtration. The ability of these lipoproteins to inhibit different molecular weight heparin fractions has been compared, using incubation mixtures comprised of antithrombin III and factor Xa. Residual factor Xa activity was measured using the chromogenic peptide substrate Bz-Ile-Glu-Gly-Arg-pNA. LDL inhibited the high molecular weight (but not low molecular weight) heparin accelerated neutralisation of factor Xa by antithrombin III. VLDL showed a similar, though much reduced anti-heparin activity, while the addition of HDL to the factor Xa incubation mixture produced no measurable anti-heparin activity. These observations suggest that certain plasma lipoproteins may selectively modulate the inhibitory action of heparin against factor Xa.

Amidohydrolases↗
PubMed1980

On site determination of Sulfotep air levels in a fumigating greenhouse.

Sulfotep air levels in a greenhouse were monitored continuously in real time, for 4-40 hours after fumigation, using a trace atmospheric gas analyzer system. Sulfotep air levels were below the threshold limit value of 15 ppb following overnight ventilation but, when ventilation was stopped to conserve heat, the Sulfotep air levels exceeded the threshold limit value. This study also showed that worker activity in the greenhouse significantly increased Sulfotep air levels. It is recommended, therefore, that ventilation of a greenhouse following Sulfotep fumigation should continue during the entire day and workers exposed to such conditions should wear appropriate protective equipment.

Air Pollutants↗
PubMed1980

Dysfibrinogenaemia characterized by abnormal fibrin monomer polymerization and normal fibrinopeptide A release.

Routine testing on plasma from a patient due to undergo a coronary artery bypass graft operation revealed a prolonged thrombin clotting time associated with a normal plasma fibrinogen level when this was determined by a method not dependent upon the rate of fibrin formation. Fibrinogen purified from the patient's plasma by precipitation with beta-alanine also gave a prolonged thrombin time and this confirmed the presence of a dysfibrinogenaemia. Increasing calcium chloride concentration, addition of protamine sulphate and decreasing ionic strength all produced a partial correction of the clotting defect. Addition of normal plasma to patient's plasma failed to correct the prolonged thrombin clotting time and a pH dependence of the defect was also observed. Kinetic studies of fibrinopeptide release, using a specific radioimmunoassay, demonstrated no delay in the release of patient fibrinopeptide A. The functional defect was localized as an abnormality in the polymerization of fibrin monomers by studying fibrin monomers prepared and isolated from plasma and from purified fibrinogen solution. An electrophoretic examination of the patient's fibrinogen using both agarose and polyacrylamide gels failed to demonstrate any alteration in mobility or any structural defect associated with the polypeptide chains A alpha, B beta and gamma. All seven of the living siblings of the propositus and also his daughter showed no abnormality in any clotting assay. However, because the propositus did not suffer from liver disease it has been assumed that the abnormality is genetic in origin.

Adult↗