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Biomedical subjects

J Dawes

Publications and source records attributed to J Dawes.

At least 73 records · Page 4Linked to original sources
PubMed1988

Prostaglandin D2 and histamine release in cold urticaria unaccompanied by evidence of platelet activation.

Six patients with acquired primary cold urticaria and six normal control subjects were challenged with a 5-minute immersion of an arm in cold water, at 10 degrees C, to induce cold urticaria. Venous blood draining the arm was sampled before and at 5 and 20 minutes after challenge. Prostaglandin D2 levels in the serum increased significantly after cold challenge but did not correlate with the severity of the urticaria. Significant elevations in histamine after cold challenge tended to be higher in the patients with a low threshold to cold reaction. Two markers of platelet activation, platelet factor 4 and beta-thromboglobulin, remained at basal levels 5 minutes and 20 minutes after challenge.

Adult↗
PubMed1988

Plasma levels of highly sulphated glycosaminoglycans are raised in patients with chronic myeloid leukaemia.

A study of absolute basophil counts and plasma levels of highly sulphated glycosaminoglycans in 30 peripheral blood samples from 21 patients with different leukaemias was performed. This revealed significantly raised levels of both plasma highly sulphated glycosaminoglycans and basophils in those patients with chronic myeloid leukaemia, as compared to those with other types of leukaemia and 35 normal controls. A strong correlation (r = 0.83) was observed between the levels of highly sulphated glycosaminoglycans and basophil counts in the group as a whole, supporting a direct relationship between the two. The elevated plasma levels of highly sulphated glycosaminoglycans may contribute to the bleeding tendency reported in some patients with chronic myeloid leukaemia.

Adult↗
PubMed1988

Release of highly-sulphated glycosaminoglycans and histamine from human basophils.

A new assay for highly-sulphated glycosaminoglycans (GAGs) has been applied to the study of allergen (Dermatophagoides pteronyssinus)-induced release of GAG from human basophils. Highly-sulphated GAG, which was not heparin, was found only in basophil-containing cellular fractions of whole blood. Its release, like that of histamine, was Ca++-dependent. However, allergen-induced release of GAG from the basophils of atopic individuals exhibited a different time-course and dose-response from that of histamine, and may occur at least in part by a different mechanism.

Adult↗
PubMed1987

Thrombospondin in milk, other breast secretions, and breast tissue.

Colostrum and milk contained high concentrations of thrombospondin, although the concentration relative to total protein content decreased as lactation was established. Thrombospondin occurred in the aqueous phase of milk rather than as a component of the milk fat globule membrane. It could be purified from colostrum using established procedures after removal of lipid from the starting material. The intact protein had a molecular weight of 450 kd, but the product contained small peptides, perhaps as a result of proteolytic activity in the colostrum. Thrombospondin from goat colostrum displayed a different proteolytic fragmentation pattern from thrombospondins isolated from three human sources, but this could be a species- rather than tissue-specific difference. Breast cancer cytosols contained significantly more thrombospondin than cytosols from normal tissue or benign dysplasias. Thrombospondin levels in a variety of breast secretions all fell within the range found in colostrum and milk, as did the fluids from Na+ (group II) breast cysts. K+ (group I) cysts, however, contained fluids with low thrombospondin concentrations, eliminating apocrine cells as the source of thrombospondin in the breast.

Breast↗
PubMed1987

Grey platelet syndrome: studies on platelet alpha-granules, lysosomes and defective response to thrombin.

The platelets of a young man with the grey platelet syndrome were severely depleted of all seven alpha-granule proteins assayed as well as partially deficient in alpha-mannosidase and alpha-fucosidase; four other lysosomal enzymes were present in normal concentrations. Total platelet 5-hydroxytryptamine (5HT) and adenine nucleotides were normal, and 14C-5HT uptake reached normal levels only slightly more slowly than a control. Aggregation and dense body secretion occurred normally in response to ADP, adrenaline, collagen, PAF-acether, sodium arachidonate, A23187, Ionomycin, TPA and U44069, but were very delayed in response to thrombin. The increase in cytosolic free calcium in response to thrombin was very slow and much reduced in amplitude, whether in the presence or absence of extracellular Ca2+. These defects in response to thrombin were not corrected by the separate addition of purified alpha-granule proteins or by a whole releasate from normal platelets. It is suggested that these platelets, in addition to their alpha-granule deficiency, may have a specific defect of thrombin receptor-mediated activation of phospholipase C.

Blood Platelet Disorders↗
PubMed1987

Studies on the effect of heat treatment on the thrombogenicity of factor IX concentrates in dogs.

This study examines the effects of heat treatment for 72 h at 80 degrees C on the potential thrombogenicity of lyophilized human coagulation factor IX concentrates. Since heating generated minor amounts of thrombin, concentrate was prepared with antithrombin III addition prior to heat treatment. Changes in coagulation parameters were followed prior to and after infusion of 100 iu/kg of heated and unheated concentrates to dogs. All batches produced a transient fall in platelet count during infusion and a delayed rise in plasma fibrinopeptide A, accompanied by a minor prolongation of the activated partial thromboplastin time. Such changes were less marked for heated batches. Control infusion of a 'failed' factor IX concentrate showed an additional fall in fibrinogen, rise in fibrin degradation products and a more rapid rise in fibrinopeptide A, while thrombin infusion caused an even more dramatic intravascular coagulation. These studies indicated no increase in the potential thrombogenicity of freeze dried factor IX concentrates as a result of heat treatment.

Albumins↗
PubMed1987

Studies on the procurement of blood coagulation factor VIII in vitro studies on blood components prepared in half-strength citrate anticoagulant.

The effect of replacing a standard citrate anticoagulant with one containing half the amount of citrate on the in vitro properties of components prepared from blood donations was investigated. This resulted in a significant improvement in factor VIII stability such that there was little loss during overnight storage, and this was reflected in the factor VIII yield in cryoprecipitate. The quality of cellular components in red cell units stored up to 35 days or platelet concentrates stored up to 7 days was not adversely affected. Although initial levels were similar to those in standard anticoagulant, the extent of fibrinopeptide A generation and complement C3 breakdown in red cell units stored for 35 days in half-strength citrate was somewhat increased.

Anticoagulants↗
PubMed1987

Assessment of a new centrifugal plasmapheresis machine: the SPC-600.

An approach to the full assessment of new plasmapheresis machines is outlined. This involves testing for changes in donated blood, donors and blood components using fresh donor blood and during full procedures in an animal model prior to performing full procedures in human volunteers. Using this approach, a new centrifugal plasmapheresis machine, the SPC-600, was assessed. No adverse effects associated with the use of the machine were detected in the initial studies. When used for plasmapheresis of volunteers, 500 ml of plasma was obtained in 43 +/- 4 min without adverse effects on donors. The plasma product contained normal levels of plasma proteins, including factor VIII, and 20 +/- 6 X 10(9)/1 platelets. There was no evidence of activation of complement or coagulation systems, and the factor VIII yield in cryoprecipitate prepared from single donations of plasma was equivalent to that observed for standard whole blood donations.

Animals↗
PubMed1987

Circulating basophil counts in atopic individuals.

Absolute numbers of circulating basophils were measured in 55 atopic and 35 non-atopic individuals, using a flow cytometer for automated cell counting. They were significantly elevated in the atopic group (p less than 0.001), but the total leucocyte count was not significantly different between the two groups. Eosinophil counts, which correlated with the number of basophils for both populations, were also significantly raised in the atopic group (p less than 0.001). Individual variation in absolute basophil counts was not detected in sequential samples taken at daily intervals over 5 days, in 5 atopics and 4 non-atopics. In addition, no significant variation was detected in 6 atopics and 5 non-atopics over a period of up to 20 months.

Adolescent↗
PubMed1986

Absorption of heparin, LMW heparin and SP54 after subcutaneous injection, assessed by competitive binding assay.

Unfractionated heparin, pentosan polysulphate (SP54) and the low molecular weight heparins CY216 and CY222 were injected subcutaneously at a minimum of weekly intervals into 5 healthy volunteers. The dose was 75 mg in all cases. Concentrations of administered glycosaminoglycan in serial plasma samples and voidings of urine were measured using a competitive binding assay, and biological activity was assessed in plasma using APTT and anti-Xa clotting assays. There was wide individual variation in the absorption of unfractionated heparin as indicated both by the maximal plasma concentrations reached 2-3 h after injection and by the area under the concentration vs. time curve. The efficiency of absorption increased and the individual variation decreased with decreasing molecular weight of the administered glycosaminoglycan. Urinary excretion correlated with plasma concentration, and recovery in the urine also increased with decreasing molecular weight. Similar patterns of uptake and clearance were indicated by the APTT and competitive binding assays, but anti-Xa clotting activity could be detected in the plasma after clearance of the administered glycosaminoglycan.

Absorption↗
PubMed1986

Anticoagulant activities of pentosan polysulphate (Hémoclar) due to release of hepatic triglyceride lipase (HTGL).

Subcutaneous injections of 50 mg pentosan polysulphate (Hémoclar) were given to normal volunteers and the effects on anti-Factor Xa activity, thrombin generation and lipase release measured. Concentrations of pentosan polysulphate were measured by a competitive binding assay and the mean peak level found to be 1.6 micrograms/ml. Anti-Xa clotting activity rose to 0.034 iu/ml and thrombin generation induced by lipid peroxides was inhibited by approximately 50%. Neither of these effects could be accounted for by the direct action of pentosan polysulphate at the concentrations measured. Pentosan polysulphate was very effective in releasing lipase, approximately 70-80% of the total enzyme activity being due to hepatic triglyceride lipase (HTGL). In vitro addition of purified HTGL to plasma markedly enhanced anti-Xa clotting activity, and caused a 70% inhibition of lipid peroxide induced thrombin generation. Anti-Xa activity of post-injection plasma was increased rather than neutralised by addition of polybrene, and this effect could be mimicked by addition of polybrene to plasma containing pentosan polysulphate and purified HTGL. It is concluded that, when given in low doses subcutaneously, pentosan polysulphate acts as an indirect anticoagulant, its major effects being due to release of HTGL.

Adult↗
PubMed1986

Structural and immunological comparison of human thrombospondins isolated from platelets and from culture supernatants of endothelial cells and fibroblasts. Evidence for a thrombospondin polymorphism.

Thrombospondin is a 450-kDa glycoprotein secreted by a variety of cells including endothelial cells, fibroblasts and platelets. The aim of this study was to compare the structural and immunological properties of human endothelial, fibroblast and platelet thrombospondins. All three thrombospondins were purified, digested with thermolysin, and the subsequent thermolysin-generated fragments isolated on a Superose 12 gel-permeation column using non-denaturating conditions. Each isolated proteolytic fragment of thrombospondins was then detected using either a radioimmunoassay with a polyclonal antibody or an enzyme-linked immunosorbent assay with three monoclonal antibodies (P10, MA-I, MA-II) directed against different epitopes of whole platelet thrombospondin. The fragmentation pattern of human endothelial thrombospondin consists of six major thermolysin-generated fragments (135-110, 98-82, 54-47, 25-20, 18-15 and 10 kDa) having molecular masses very similar to those observed with human fibroblast thrombospondin (115-100, 92-80, 54-49, 27-21, 17-13 and 12-10 kDa). Treatment of platelet thrombospondin with thermolysin only generated four proteolytic fragments having molecular masses of 110, 50, 25 and 12/10 kDa respectively. All these proteolytic fragments of endothelial, fibroblast and platelet thrombospondins were recognized by a polyclonal antibody. Monoclonal antibodies MA-I and P10 essentially recognized two proteolytic fragments (135-110, 98-82 kDa) of endothelial and fibroblast (115-100, 92-80 kDa) thrombospondins, and the 110-kDa fragment of platelet thrombospondin. Monoclonal antibody MA-II recognized three proteolytic fragments (54-47, 25-20, 18-15 kDa) of endothelial and fibroblast (54-49, 27-21, 17-13 kDa) thrombospondins, and two fragments (50, 25 kDa) of platelet thrombospondin, different from those detected by P10 an MA-I. The results clearly demonstrate that, under non-denaturating conditions, endothelial and fibroblast thrombospondins are structurally different from platelet thrombospondin since two fragments of endothelial thrombospondin (98-82, 18-15 kDa), equivalent to those of fibroblast thrombospondin (92-80, 17-13 kDa), are not released from platelet thrombospondin after thermolysin treatment. These three forms of thrombospondin are, however, immunologically indistinguishable. To investigate further the structural differences observed between platelet and the two other forms of thrombospondin, their degree of polymerization was compared. Prior to thermolysin treatment, the three forms of thrombospondin were separated into several oligomers ranging from 450 kDa to 3300 kDa when injected onto a Superose 6 gel-permeation column.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Tandem purification of mouse IgM monoclonal antibodies produced in vitro using anion-exchange and gel fast protein liquid chromatography.

A tandem chromatographic procedure was used to isolate rapidly mouse IgM monoclonal antibodies produced by cultivation of hybridomas in vitro. Hybridoma culture supernatants containing mouse IgM monoclonal antibodies were first chromatographed on an anion-exchange Mono Q column connected to a fast protein liquid chromatography system. This anion-exchange step offers the advantage of obtaining IgM antibodies in a concentrated form. The IgM-rich fractions from the Mono Q column were then injected on a gel filtration Superose 6 column equilibrated with a low-ionic strength buffer and eluted with a high-ionic strength buffer. Assessment of the purity of isolated IgM monoclonal antibodies was performed by sodium dodecyl sulphate polyacrylamide gel electrophoresis together with a Coomassie Brillant Blue R 250 staining technique. Assessment of the immunoreactivity of isolated IgM monoclonal antibodies was performed by an enzyme linked immunosorbent assay using a solid phase adsorbed antigen against which IgM monoclonal antibodies were directed. The chromatographic procedures described allows the rapid isolation of mouse IgM monoclonal antibodies produced in vitro at a high degree of purity and in an immunoreactive state.

Animals↗
PubMed1986

Structural and immunological differences between human platelet and endothelial thrombospondins.

The structural and immunological properties of human thrombospondins isolated from platelets and from endothelial cells were compared. Both thrombospondins were digested with either trypsin or thermolysin, in the presence or absence of calcium, then injected onto a Superose 12 gel filtration column. The isolated thermolysin-generated fragments of thrombospondins were identified by radioimmunoassays using either different monoclonal antibodies or a polyclonal antibody directed against platelet thrombospondin. The results show that platelet and endothelial thrombospondins are both partially protected from trypsin digestion in the presence of calcium but have different trypsin and thermolysin fragmentation patterns. The thermolysin-generated fragments from platelet and endothelial thrombospondins are recognized differently by a monoclonal antibody whereas all of them are identified by a polyclonal antibody.

Antibodies, Monoclonal↗
PubMed1986

Relationship between biological activity and concentration of a low-molecular-weight heparin (PK 10169) and unfractionated heparin after intravenous and subcutaneous administration.

The pharmacokinetics of unfractionated heparin and the low-molecular-weight (LMW) heparin PK 10169 after intravenous and subcutaneous injection were compared by crossover study in 8 healthy volunteers. The heparin concentrations in plasma were measured by a competitive binding assay, and anti-IIa and anti-Xa activities were also assayed. Unfractionated heparin was cleared after intravenous administration with a half-life of 35 min irrespective of assay method. However, the concentration of PK 10169 declined with the longer half-life of 60 min, and its anti-IIa and anti-Xa activities had half-lives of 40 and 275 min, respectively. Some of this anti-Xa activity may be mediated by a compound released by PK 10169 rather than by the LMW heparin itself. The bioavailability of PK 10169 was 3-fold greater than that of unfractionated heparin, due to more effective absorption after subcutaneous administration.

Adult↗