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Biomedical subjects

C N Chesterman

Publications and source records attributed to C N Chesterman.

At least 109 records · Page 6Linked to original sources
PubMed1989

Occurrence of platelet-activating factor (PAF) and an endogenous inhibitor of platelet aggregation in diffuse cutaneous mastocytosis.

We have identified PAF in the blister fluid from a patient with bullous mastocytosis, a rare form of mast-cell disease. We have found a novel endogenous inhibitor of platelet aggregation which obscured the presence of the PAF in unprocessed blister fluid and in ethanol or lipid extracts. The PAF was characterized by the demonstration of chromatographic, mass spectral and biological properties identical to those of authentic PAF. Thus this is the first demonstration of PAF in biological fluid from a patient with mastocytosis. High levels of immunoreactive prostaglandin D2 (PGD2) and histamine were also present in the blister fluid. The interaction between PAF and the inhibitor of platelet aggregation in patients with systemic mastocytosis may provide an explanation for some of the manifestations of the disease, in particular the episodic hypotension, cutaneous flushing and pallor.

Blister↗
PubMed1988

Binding specificity of lupus anticoagulants and anticardiolipin antibodies.

Antiphospholipid antibodies have been found to be strongly associated with syndromes characterised by spontaneous arterial and venous thromboses, recurrent miscarriage, immune thrombocytopenia, and occasionally neurological manifestations. These antibodies can be detected using solid phase immunoassays, and by their effect on prolonging phospholipid dependent clotting tests. This latter phenomenon is termed the lupus anticoagulant (LA). The relationship between anticardiolipin antibodies (ACA) and the LA activity of plasma was investigated in 14 patients. Plasma of these patients exhibited both LA activity and high levels of ACA. The patients included 7 with systemic lupus erythematosus, 6 without and 1 chlorpromazine induced lupus anticoagulant. 7 patients had a history of thrombosis and 7 did not, despite high antibody levels. Plasma was incubated in a serial fashion with solid phase cardiolipin and the residual ACA level and LA activity were monitored using a solid phase enzyme linked immunoassay, and the kaolin clotting time (KCT) and activated partial thromboplastin time (APTT) respectively. There was no correlation between baseline ACA levels and parameters of LA activity (dKCT or dAPTT) in contrast to previous reports. However, there was a concurrent reduction in both LA and ACA levels over 24 hours during incubation with cardiolipin in all patients. The rate of reduction of both parameters was highly correlated (r = 0.99. p less than 0.001). The relative reduction of LA activity versus ACA level varied between patients, and may represent different affinities for phospholipid in thromboplastin versus phospholipid in solid phase. Thus, despite the lack of concordance between LA and ACA in many patients, the two activities can be removed concurrently in vitro, suggesting similar binding specificities of the antibodies. The incomplete concordance could be explained by varying affinities for different structural presentations of the lipid antigen.

Adult↗
PubMed1988

Vascular endothelium, haemostasis and thrombosis.

The vascular endothelium consists of a monolayer of cells. Integrity of the endothelium is essential for maintenance of blood fluidity as the subendothelium is composed of structures which rapidly activate platelets and coagulation. Recent research indicates that the endothelium is involved in other processes particularly vasoactivity, immune reactions and inflammatory processes. Much of the information has come from experiments using cells in culture and there has been considerable progress in defining synthesis and release of endothelial products involved. Of particular interest is the evidence for endothelial coagulant activity and exposure of binding sites for coagulation proteins, with the simultaneous suppression of antithrombotic activities, all of which can be brought about by inflammatory mediators. Despite the rapid progress in cell biology, clinical applications have tended to lag behind and there are still few aspects of endothelial cell metabolism and pathophysiology which can be precisely defined in patients with disorders in which the endothelium is without doubt actively involved.

Endothelium, Vascular↗
PubMed1987

Platelets in idiopathic thrombocytopenic purpura are increased in size but are of normal density.

To determine whether platelet size and volume are related to one another or to platelet age, subpopulations of platelets from patients with idiopathic thrombocytopenic purpura (ITP) have been produced on the basis of density using Percoll gradients. The density distribution of platelets from patients with ITP and from patients with other forms of thrombocytopenia (thought to be nonimmune in nature) was the same as in normal controls. However, the platelets in each density subpopulation from ITP patients were increased in size. beta-thromboglobulin (beta TG) content of platelets from each patient group and the normals increased with density and tended to be higher in ITP than in normal controls. beta TG concentration per unit platelet volume and its level in plasma were similar in ITP patients and in normal controls. This suggests that the apparently normal density of ITP platelets was not a result of degranulation of large, dense platelets. Thus platelet size and density are independently determined and the increased size of platelets in immune thrombocytopenia may be the result of abnormalities in their production.

Blood Platelets↗
PubMed1987

Oral idarubicin as single-agent treatment of acute nonlymphocytic leukemia in poor-risk patients.

Oral idarubicin was given as single-agent treatment of acute nonlymphocytic leukemia in 18 poor-risk patients. They comprised nine previously untreated elderly patients, age range 69-86, and nine relapsed pretreated patients, age range 41-76. Overall, two patients achieved complete remission (including one with preceding refractory anemia with excess of blasts) and seven achieved partial responses. Dose-limiting toxic effects were diarrhea and sepsis. In this limited study, oral idarubicin at a dose of 20-25 mg/m2/day X 3 was a well-tolerated drug with potent antileukemic effects. The oral formulation deserves more widespread evaluation.

Administration, Oral↗
PubMed1986

Small bowel mucosa from celiac patients generates 15-hydroxyeicosatetraenoic acid (15-HETE) after in vitro challenge with gluten.

Celiac disease (gluten-sensitive enteropathy [GSE]) is a disorder characterized by small intestinal mucosal injury caused by dietary exposure to wheat gluten and similar proteins. There is evidence that the mucosal injury is immunologically mediated and there is an inflammatory infiltrate present in the mucosa. It is postulated that release of lipid-derived inflammatory mediators may be involved in the pathogenesis of the mucosal injury. Jejunal mucosal biopsy samples from patients with GSE and from a group of patients who were subsequently shown to have normal jejunal mucosa were incubated with tritiated arachidonate and a peptic/tryptic digest of either gluten or casein. Generation of lipid-derived inflammatory mediators was measured by beta-scintillation counting after separation of metabolites by reverse-phase high performance liquid chromatography with two different buffer systems. The predominant arachidonic acid metabolite generated was 15-hydroxyeicosatetraenoic acid (15-HETE). Mucosa from newly diagnosed GSE patients on a normal diet generated more 15-HETE than either control patients or GSE patients maintained on a gluten-free diet. In addition, gluten acted as a specific stimulus to 15-HETE production by mucosa from the GSE patients on a normal diet. 15-HETE has a number of biologic effects that could contribute to the mucosal changes seen in GSE, and the specific release of 15-HETE by gluten suggests involvement in the pathogenesis of the disorder.

Adolescent↗
PubMed1986

Coronary artery bypass graft failure--an autoimmune phenomenon?

Plasma anticardiolipin antibody (ACA) was measured in 83 patients having coronary artery bypass graft surgery and results were correlated with the incidence of early (1-2 weeks) and late (12 months) graft occlusion, as judged by angiography. There was an association between preoperative ACA level and the incidence of late graft occlusion in relation to both number of patients with an occlusion and number of distal anastomoses occluded. 8 of 15 patients (53.3%) whose maximum ACA level exceeded 4 SD of the mean of controls had a late graft occlusion. When the ACA titre was 2-4, 0-2, or less than 0 SD above the mean of the controls, the occlusion rates were 3 of 13 (23.1%), 3 of 33 (9.1%), and 1 of 15 (6.7%), respectively (p less than 0.03). The incidence of a postoperative rise in ACA level was higher in patients who had had a myocardial infarction in the past than in those with a history of angina only (chi 2 = 4.08, p less than 0.05). This observation supports the notion that one mechanism of ACA production is an immune response to myocardial injury. These results raise the further possibility that the ACA, or related antiphospholipid antibodies, may play a part in progressive coronary vessel disease.

Autoantibodies↗
PubMed1986

Platelet and vessel wall interaction and the genesis of atherosclerosis.

On the basis of in vitro studies, biochemistry and cell biology the interactions between platelets, other circulating blood cells and the vessel wall are complex and wide-ranging. In essence, the effects of platelets adhering to injured luminal surface might include: Aggregation and adherence of further platelets; Activation of coagulation and fibrin formation; Displacement of AT-III from endothelial surface; Recruitment and activation of potentially injurious polymorphonuclear leukocytes and monocytes; Recruitment and proliferation of smooth muscles cells from the vessel media to the intima; Vasoconstriction; Initiation of feedback mechanisms such as PGI2 release to limit the process. These effects are capable of contributing to the initial lesions and the progression of the atherosclerosis. As the lesions become more complex, and particularly as the normal endothelium is lost, there is morphological evidence that there is deposition of thrombus (for discussion see Chapter 4) and 111In-labelled platelet imaging experiments in patients document platelet uptake onto atherosclerotic plaques (Davis et al, 1978).

Animals↗
PubMed1986

Substrate for endothelial prostacyclin production in the presence of platelets exposed to collagen is derived from the platelets rather than the endothelium.

Interactions between vascular endothelial cells and blood platelets have been investigated using a model microcirculation consisting of microcarrier beads colonized with human umbilical vein endothelial cells (HUVECs) and perfused with washed platelet suspensions. To simulate the effects of endothelial desquamation and exposure of subendothelium, fibrillar collagen in suspension was coinjected with the platelets. In this model, neither the passage of platelets alone nor collagen alone stimulated prostacyclin (PGI2) production by the HUVECs. Platelets activated by coinjection with collagen released thromboxane A2 (TXA2), and this was associated with the simultaneous production of PGI2 by the HUVECs. By means of double-isotope experiments with [3H]arachidonic acid (AA) incorporated into platelets and [14C]-AA into HUVECs, it was shown that all the PGI2 generated was derived from platelet AA and/or endoperoxides. This interpretation was strengthened by the finding that PGI2 production was not prevented by treatment of HUVECs with indomethacin followed by perfusion with collagen-stimulated platelets. AA metabolites in double-isotope label experiments were further characterized by reverse-phase chromatography, and it was shown that both cyclooxygenase and lipoxygenase products of the HUVECs were derived from platelet membrane lipid. Thrombin regularly produced transient PGI2 release, but showed rapid tachyphylaxis. Platelet-derived compounds including ADP, ATP, and platelet-activating factor (PAF) did not produce PGI2 release by HUVECs in this system. Thus, the transfer of AA and metabolites from collagen-stimulated platelets is likely to be the mechanism for PGI2 production in the context of minor degrees of endothelial desquamation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1985

Acute postprandial lipaemia does not influence the in vivo activity of human platelets.

Platelet function and serum lipid studies were conducted on nine healthy male subjects before and two hours after three separate meals, two of which were rich in fat: saturated fat (SF) or polyunsaturated fat (PUF), and a third control meal which contained no fat. Platelet activity was assessed by determination of in vivo platelet aggregate formation, and plasma levels of the platelet specific proteins platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG). Serum triglyceride levels increased significantly after both fat containing meals but were unaffected by the fat free meal. Serum cholesterol levels were not affected by any of the three meals. Platelet function tests could not detect any alteration of in vivo platelet activity in terms of platelet aggregate formation or plasma concentrations of PF4 and beta-TG. These results are at variance with previously published studies that used less specific assays of platelet activity and which suggested platelet activation shortly after meals rich in SF.

Adult↗
PubMed1984

In vitro synthesis of low molecular weight proteins in human platelets: absence of labelled release products.

Isolated human blood platelets incubated at 37 degrees C in vitro incorporated labelled amino acids into compounds which included some low molecular weight (less than 80KDa) proteins, as determined by autoradiography after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. Non-dialysable plasma factor(s) inhibited both uptake and incorporation, which although unaffected by Actinomycin D, was inhibited partly by Chloramphenicol and almost completely by Puromycin and Cycloheximide, results which confirm that synthesis is directed by pre-existing mRNAs, some of which is mitochondrial. Assuming that the mRNA coding for proteins which are truly "platelet specific" must be present in megakaryocyte cytoplasm, we investigated the possibility that such RNA may be sufficiently stable for its translation to continue in platelets. Although leakage from platelet alpha-granules and cytoplasm during incubation was negligible and platelets retained their secretory potential we were unable to detect radiolabelled proteins in thrombin-released material after incubation. We conclude that either alpha-granule proteins are not synthesised in platelets or their megakaryocyte progenitors, or that their mRNAs become degraded by the time platelets reach the peripheral circulation. Alternatively, the mechanism which concentrates these proteins in granules does not function in circulating platelets.

Amino Acids↗
PubMed1984

Stimulation of leukocyte phagocytic activity by the platelet release reaction.

The influence of material released by activated human platelets on the phagocytic activity of human neutrophils and monocytes has been investigated under conditions where there was a low background level of exposure of the leukocytes to platelet release products (PRPr). Incubation with PRPr prepared from 400 X 10(9)/l platelets resulted in an approximate 3-fold increase in the proportion of leukocytes which ingested particles. Stimulation was produced by dilutions of PRPr down to 1:4 to indicate that phagocytic activity was affected by material released by concentrations of platelets within the physiological range. This response appeared to reflect stimulation of the overall phagocytic capability of the leukocytes as equivalent ingestion was observed with particles which possessed or lacked the capacity to bind complement to their surface. Enhancement of phagocytic activity was evidently secondary to induction of a change in leukocyte behaviour which was sustained in the absence of continued exposure to preparations of PRPr. These observations extend the range of human biological processes known to be responsive to PRPr, and have implications for the assessment of leukocyte phagocytic activity in vitro as this particular property could be modified by contact with PRPr during the isolation of leukocytes from peripheral blood.

Adult↗
PubMed1983

Comparison of platelet-derived growth factor prepared from release products of fresh platelets and from outdated platelet concentrates.

Platelet-derived growth factor was isolated from the release products of washed, human platelets and from freeze-thawed outdated platelet concentrates. On the basis of sodium dodecyl sulphate polyacrylamide gel electrophoresis and amino acid sequence determination we conclude that platelet derived growth factor released from platelets by the agonist thrombin (EC 3.4.4.13) is structurally similar to that isolated from lysed platelets and from platelet concentrates stored for more than 72 hr at room temperature.

Amino Acid Sequence↗
PubMed1983

Phosphorylation sites for ribosomal S6 protein kinases in mouse 3T3 fibroblasts stimulated with platelet-derived growth factor.

Platelet release products and purified platelet-derived growth factor stimulated the phosphorylation of ribosomal protein S6 in cultured mouse Balb/c 3T3 fibroblasts. The post-nuclear fraction of the stimulated cells was enriched in S6 kinase activity specific for sites resembling those phosphorylated within intact cells in response to PDGF as determined by tryptic peptide mapping. 3T3-S6 sites closely resembled those phosphorylated in S6 of rat hepatocytes stimulated with insulin and included sites for both cAMP-dependent and independent kinases.

Animals↗
PubMed1983

Platelets, coagulation and fibrinolysis in patients with diabetic retinopathy.

Twenty control subjects, 12 insulin treated and 10 non-insulin treated diabetics were studied. All diabetics had retinopathy documented by fluorescein angiography and fluorophotometry. Factor VIIIR:Ag and plasma fibrinogen concentrations were elevated in both diabetic groups, but more so in the insulin treated patients. Within this latter group the plasma fibrinogen was also correlated with the degree of retinopathy. Platelets separated on linear isosmolar Percoll gradients showed an increase in intraplatelet beta TG content and concentration and a slight increase in volume of the lightest platelets in the insulin treated diabetics. Plasma platelet factor 4 and antithrombin III concentrations were normal and plasma beta TG levels were elevated only in those patients with renal insufficiency. Platelet aggregometry was performed in 18 diabetic subjects and found to be normal. It is concluded that abnormalities of coagulation and platelets in diabetes are determined by metabolic factors rather than the severity of microvascular disease per se.

Adult↗
PubMed1983

Regulation of prostaglandin production and ectoenzyme activities in cultured aortic endothelial cells.

Prostaglandin production, angiotensin-converting enzyme, and 5'-nucleotidase were measured in porcine aortic endothelial cells in situ (with a multi-well template on an opened aorta), in primary culture and in subcultures. Changes during culture were monitored and the effects of culture conditions were investigated by growing cells on a biological matrix or on plastic, by adding different sera to the growth medium, and by harvesting cells enzymically or mechanically. Prostacyclin production by endothelium in primary culture is highest immediately after cell isolation and subsequently declines; this pattern is repeated each time the cells are subcultured. The level at which production stabilises is approximately 200 pg X 10(6) cells-1 X h-1. Detaching cells by physical means stimulates production much more than enzymic dispersion; the type of serum or the presence of a biological matrix does not alter prostaglandin production. The relative amount of prostaglandin E produced increases with time, from approximately 20% of the prostacyclin production shortly after isolation to greater than 100% in subcultured cells. None of the culture conditions that we tested altered this trend. Angiotensin-converting enzyme activity decreases during primary culture, but activity can be sustained by including homologous serum (from whole blood or from platelet-free plasma) in the culture medium. The method of harvesting cells, or the presence of a matrix, did not affect enzyme activity. 5'-Nucleotidase also declines during culture, with a progressive decrease in both Km and Vmax from template to primary culture to subcultures. None of the variations in culture conditions prevented this change. Ecto-adenosine-deaminase activity, not detectable in cultured cells, can be measured in the template. Part of this activity was released by the vascular wall and could be due to plasma diffusing from the interstitial space.

5'-Nucleotidase↗