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Biomedical subjects

W G Murphy

Publications and source records attributed to W G Murphy.

At least 55 records · Page 3Linked to original sources
PubMed1993

Quality of platelet concentrates irradiated with UVB light: effect of UV dose and dose rate on glycocalicin release and correlation with other markers of the platelet storage lesion.

The amount of membrane-associated glycoprotein Ib in platelet concentrates (PCs) irradiated with a high dose of UVB light has been shown to be significantly reduced after 48 h storage. We recently corroborated this finding when we noted an increase in the supernatant levels of glycocalicin (GC, a major segment of glycoprotein Ib) in UVB-treated PCs during storage. The aim of the present study was to determine whether GC release was related to both the UV dose and the rate of dose delivery. Plateletpheresis concentrates obtained from five donors were pooled and split into five equal parts. Four of these were treated with 7500 and 15,000 mJ/cm2 UVB using two prototype UV sources with differing rates of dose delivery; namely, Baxter (BAT) and British Aerospace (BAC) cabinets, with the latter having the slower rate of delivery. On days 1 and 5 of storage, GC levels in the supernatants of PCs were determined by ELISA. Moreover, the following parameters were also assessed: platelet and WBC count; hypotonic shock response (HSR) and platelet aggregation response to ADP, ADP+collagen, ADP+arachidonic acid and ristocetin; pH; supernatant levels of lactate, glucose, von Willebrand factor (vWf) and beta-thromboglobulin (beta TG). The results revealed an association of GC release with UVB dose using both UV sources, although this was more apparent in the BAC system, in which glycocalicin release at day 5 of storage was as follows (microgram/ml, mean +/- SD): 4.8 +/- 0.3 and 9.5 +/- 3.6 at 7500 and 15,000 mJ/cm2 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1993

Yersinia enterocolitica septicaemia from transfusion of red cell concentrate stored for 16 days.

Two cases of transfusion transmitted Yersinia enterocolitica biotype 3, serotype 09 infection occurred in south east Scotland within four months of each other. In one case, a 79 year old man died the day after receiving a unit of red cell concentrate that had been stored for 29 days after donation. In the second case a 78 year old man died three days after transfusion of a unit of red cell concentrate that had been collected 16 days before transfusion. The donors of both units had no symptoms attributed to gastrointestinal infection. Early outdating of blood for transfusion after three weeks of storage is unlikely to eradicate Y enterocolitica associated fatalities from blood transfusion, and alternative methods should be considered.

Aged↗
PubMed1993

Clinicians' satisfaction with a hospital blood transfusion service: a marketing analysis of a monopoly supplier.

One of the objectives of the NHS reforms is to improve customer focus within the health service. In a study to assess the quality of customer service provided by the Edinburgh and South East Scotland Blood Transfusion Service a 19 item questionnaire survey of the main clinical users of the service was performed to ascertain their satisfaction, measured on a 5 point anchored scale, with important aspects of the service, including medical consultation, diagnostic services, blood and blood components or products and their delivery, and general satisfaction with the service. Of 122 clinicians in medical and surgical disciplines in five hospitals in Edinburgh, 72 (59%) replied. Fourteen (22%) indicated dissatisfaction with any aspect of the medical consultation service, owing to inadequate follow up of clinical contacts and unsatisfactory routing of incoming calls. Diagnostic services were criticised for the presentation, communication, and interpretation of results. The restricted availability of whole blood, the necessity to order platelets and plasma through the duty blood transfusion service doctor, and the use of a group and screen policy, attracted criticism from a small number of clinicians. Ten of 68 respondents expressed dissatisfaction with delivery of blood and components to the wards and theatres. The findings indicate that the clinicians served by this blood transfusion service are largely satisfied with the service. Changes are being implemented to improve reporting of laboratory results and measures taken to improve liaison with clinicians.

Attitude of Health Personnel↗
PubMed1992

Calpain activity in patients with thrombotic thrombocytopenic purpura is associated with platelet microparticles.

Thrombotic thrombocytopenic purpura (TTP) is characterized by thrombocytopenia and disseminated platelet thrombi throughout the microvasculature. Studies by our group have demonstrated calcium-dependent proteolytic activity (calpain) that is no longer detectable in the serum of patients with acute TTP after their recovery. The purpose of this study was to investigate if the protease activity of TTP was detectable in plasma and, therefore, not an in vitro phenomenon secondary to the formation of serum. Additionally, we looked for evidence of membrane association of the active protease in the patients' samples, which would explain the persistence of its activity in the presence of plasma inhibitors. Acute TTP samples, both serum and plasma, were collected from 10 patients with TTP. Calpain was measured using bioassays for enzyme activity and also by detection of the protein using immunoblotting with an anticalpain monoclonal antibody (MoAb). In all instances, calpain could be detected both functionally and antigenically in the acute TTP sera and plasma. No calpain activity could be detected in any of the controls, although antigenic calpain was detectable in one sample from a patient who had undergone cardiopulmonary bypass surgery. To investigate whether the calpain was associated with microparticles in the plasma, the TTP plasma samples were ultrafiltered and ultracentrifuged. Activity was not lost by passage across a 0.2-micron filter but was detectable only in the pellet following ultracentrifugation. Membrane association of the calpain in the microparticles also was demonstrated using solubilization with Triton X-100. Immunoprecipitation studies demonstrated that the calpain activity could be removed by MoAbs against platelet membrane glycoproteins (IX and IIb/IIa) but not by a MoAb against red blood cell membrane glycophorin. These studies indicate that active calpain is associated with platelet microparticles in plasma from patients with TTP.

Blood Platelets↗
PubMed1992

Glycoproteins Ib and IIb/IIIa in the quality assessment of platelet concentrates during storage.

We have previously shown that levels of soluble glycocalicin (GC) in plasma supernatants derived from units of platelet concentrates (PC) increase progressively during storage. We now report further studies which show that the levels of both microparticle-bound and soluble GC in PC during storage are influenced by exposure of PC samples to EDTA and treatment of PC packs with ultraviolet B (UVB) irradiation. EDTA leads to a significant increase in the release of microvesicle-bound and soluble GC, while UVB irradiation leads to a dose- and rate-dependent increase in GC release. Paradoxically, UVB leads to an unexpected decrease in supernatant levels of von Willebrand factor (vWf) during storage which contrasts with its increase in untreated, stored PC. Moreover, an increase in GC release during storage is associated with a corresponding decrease in platelet size as determined by measurement of mean platelet volume (MPV) in citrated PC. The GC release is significantly correlated with standard platelet functional tests and other new generation tests such as dMPV and supernatant levels of vWf. In addition, preliminary results show the presence of microparticle-bound and soluble glycoprotein (Gp) IIb/IIIa in the supernatant plasma of stored PC. Our results suggest that supernatant levels of GpIb, GpIIb/IIIa, and vWf, together with alteration in MPV, provide essential new informative parameters for quality assessment of PC.

Blood Platelets↗
PubMed1992

Thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura is an uncommon disorder, but it continues to be of considerable interest. The disease mechanisms are unclear and the aetiology is unknown. Perhaps most enigmatic of all, the mode of action of plasma therapy, which successfully induces remission in about two-thirds of cases, is wholly inexplicable. There are currently several areas of debate on the subject of thrombotic thrombocytopenic purpura. This paper addresses these points of contention: the definition of the disease, its distinction from haemolytic uraemic syndrome, the nature of the platelet aggregating factors in the plasma of patients with acute disease, the importance of the abnormalities of von Willebrand's factor observed in the acute and quiescent phases of the disease, the nature of the factor in normal plasma that induces remission, and the possible causes of the observed superiority of plasma exchange combined with plasma infusion, over plasma infusion alone.

Calpain↗
PubMed1991

Monitoring the release of glycocalicin in platelet concentrates by ELISA.

Platelet membrane glycoprotein Ib (GPIb) is one of many GPs on the platelet membrane which contribute to the functional and morphological properties of platelets. A principal function of GPIb is its attachment to von Willebrand Factor (vWF) on injured blood vessels which leads to the adhesion of platelets to these vessels. The binding site to vWF resides on glycocalicin (GC), which is a major segment of GPIb. Glycoprotein Ib is particularly susceptible to centrifugation and storage of platelets. The assessment of GPIb status on platelets, therefore, comprises one of many traditional methods for monitoring the quality of platelets during storage. We have recently developed a novel ELISA to monitor GC levels in the supernatant of platelet concentrates (PCs) during storage. Using this ELISA we observed a progressive rise of GC in PC supernatants during storage. A recent study of citrated PCs with or without EDTA produced similar results, and showed a substantial increase of GC levels in EDTA-treated PCs. The GC ELISA could therefore be used as a novel method to monitor PCs during storage under various conditions.

Blood Platelets↗
PubMed1991

A clinical trial of red-cell concentrate prepared from blood collected in half-strength citrate anticoagulant.

Earlier studies have indicated that plasma from blood donations drawn into half-strength citrate anticoagulant (0.5 CPD-A2) may give improved yields of factor VIII:C after fractionation. It has also been shown previously that cellular components from blood donations drawn into 0.5 CPD-A2 have satisfactory in-vitro and in-vivo properties. The present study examines the clinical use of red cell concentrate (RCC) from 0.5 CPD-A2 blood donations. Forty-nine patients who were undergoing elective orthopaedic surgery and who required blood transfusion received 0.5 CPD-A2 RCC. A transfused control group of 107 patients received standard CPD-A1 RCC for their transfusion requirements. Patients in the two transfused groups had similar haemoglobin responses to transfusion. All patients experienced a moderate pyrexia following the operation. Both study groups showed similar responses to serum lactate dehydrogenase levels in the 2 weeks following surgery, and in postoperative peripheral blood platelet counts. Serious postoperative complications arose in both groups. In the 0.5 CPD-A2 group two patients had pulmonary emboli (one fatal) and one patient had a non-fatal myocardial infarction. Three patients had pulmonary emboli in the CPD-A1 transfused group. These incidences of major adverse events were within the expected range of these complications in patients who were undergoing major joint replacement surgery and did not differ significantly between the study groups. This study indicates that red cell concentrate prepared in half-strength citrate anticoagulant is comparable to that prepared in CPD-A1 for patients undergoing orthopaedic surgery.

Adenine↗
PubMed1990

A new competitive binding enzyme-linked immunosorbent assay for glycocalicin in plasma and platelet concentrate supernatants.

A new competitive binding enzyme-linked immunosorbent assay (CB ELISA) for glycocalicin (GC) was developed using GC coated wells and a monoclonal antibody (MAb) to glycoprotein Ib (AN51). The principal stages of the CB ELISA consisted of coating the plate with GC extract overnight, blocking with 3% BSA, incubating the wells with test or standard sample dilution and AN51, and a final incubation with horseradish peroxidase-conjugated goat anti-mouse IgG. Serial dilutions of purified GC, starting in 2% BSA, yielded standard curves which were linear between 10 and 0.4 micrograms/ml. Parallel curves were obtained for platelet concentrate supernatants and for citrated plasma. We used the ELISA to measure GC levels in platelet concentrates during storage. The results indicated that soluble GC increased progressively during storage from 3.3 to 6.7 micrograms/ml, while GC levels in platelet-poor plasma remained at 1.9-2.2 micrograms/ml. These results show that the new CB ELISA is a simple and short assay for the direct measurement of GC in plasma solutions, and may be of use in clinical studies.

Binding, Competitive↗
PubMed1990

Calpain proteolysis of von Willebrand factor enhances its binding to platelet membrane glycoprotein IIb/IIIa: an explanation for platelet aggregation in thrombotic thrombocytopenic purpura.

We have previously observed calpain activity (calcium-dependent cysteine protease) in sera from patients with acute thrombotic thrombocytopenic purpura (TTP). The calpain activity was not present following recovery and was not detected in other thrombocytopenic disorders. We postulated that this enzyme could participate in the pathogenesis of TTP. Because other investigators have demonstrated abnormalities of von Willebrand factor (vWF) in patients with TTP, we proposed that calpain might interact with vWF in TTP. To challenge this hypothesis, we measured the binding of untreated and calpain-treated vWF to normal and ADP or calpain activated platelets. Untreated vWF bound in a specific and saturable fashion to activated platelets, but only at low (30 microM) calcium concentrations. Von Willebrand factor did not bind to activated platelets at physiological (2 mM) calcium concentrations. Calpain proteolysis of vWF changed the binding characteristics of the vWF so that it had greatly increased binding to both ADP and calpain activated platelets. The calpain-proteolyzed vWF bound to activated platelets at both low and physiological calcium concentrations, and was capable of causing platelet aggregation. The calpain-proteolyzed vWF bound to the activated platelets via glycoproteins IIb/IIIa as demonstrated by inhibition studies using monoclonal antibodies against glycoproteins IIb/IIIa and Ib. It also had a high binding affinity and was capable of inhibiting the binding of radiolabelled fibrinogen to the activated platelets at physiological calcium concentrations. Calpain also proteolyzed fibrinogen, but the calpain altered fibrinogen had normal platelet reactivity. These studies provide further insight into the pathogenesis of the platelet aggregation of thrombotic thrombocytopenic purpura. Calpain proteolyses vWF and can produce the characteristic loss of large multimers seen on sodium dodecyl sulphate (SDS)-agarose gel electrophoresis. The altered vWF is highly reactive with activated platelets and binds to platelet glycoproteins IIb/IIIa and participates in formation of the platelet aggregates that characterize this disease.

Binding, Competitive↗
PubMed1990

Effects of a brief theory-based intervention on the practice of testicular self-examination by high school males.

This preliminary study evaluated a brief intervention, based on the theory of planned behavior, designed to encourage high school students to practice testicular self-examination (TSE). Ninety-nine male ninth and 10th grade students were exposed to a message challenging beliefs about outcomes of performing TSE as suggested by the theory of planned behavior, a message providing information about TSE and testicular cancer, or a control message, after which they completed a questionnaire operationalizing components of the theoretical model. Four weeks later, students reported their practice of TSE. As predicted, students exposed to the theory-based message reported a stronger intention to perform TSE and, at follow-up, were more likely to report having performed the exam than study participants exposed to other messages. Data provide partial support for the utility of the theory of planned behavior as a framework for constructing health-promoting messages. Future research recommendations are offered.

Adolescent↗
PubMed1990

The platelet aggregating factor(s) of thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura is characterized by disseminated platelet aggregates throughout the microcirculation and a large body of clinical, experimental and pathological evidence implicates in vivo platelet aggregation as being pivotal in the disease. For this reason considerable energy has been spent by many investigators to identify a platelet aggregating factor. The understated reason for these studies is that the characterization of such a factor could lead to the subsequent identification of a medication or a plasma factor that could neutralize the aggregating factor. Although a platelet aggregating factor has been suspected to play a causal role in TTP for almost 50 years, only in recent years have investigators systematically attempted to identify such a factor. One group has identified a 37 kD protein in the plasma of TTP patients which can initiate platelet aggregation through a unique pathway of aggregation and this factor can be inhibited by normal IgG. The other group of workers (ourselves) have provided evidence that the platelet aggregating factor of TTP is calpain. Thus, the very nature of the aggregating factor, and by implication its inhibitors, is very different for the two groups, and it may take other investigators to resolve whether there are multiple platelet aggregating factors of TTP. Nonetheless, it is apparent that recent research has dramatically improved our understanding of this uncommon but important disorder and it is possible that such investigations will lead to more successful treatments of this condition.

Blood Coagulation Factors↗
PubMed1989

A prospective comparison of four techniques for measuring platelet-associated IgG.

We describe a prospective study comparing four different assays for PAIgG. Platelets from patients with a variety of thrombocytopenic disorders were collected into ACD, washed, and the PAIgG then measured using three assays for surface PAIgG. These included: (a) a direct binding assay using 125I-monoclonal anti-IgG (MoAb); (b) a direct binding assay using 125I-staphylococcal protein A (SPA); and (c) a two-stage assay. PAIgG also was measured using an assay for 'total' PAIgG following platelet lysis. The mean +/- SD number of molecules of IgG per platelet on washed platelets from 29 healthy, non-thrombocytopenic controls was: 86 +/- 80 (125I-MoAb); 94 +/- 96 (125I-SPA); 3520 +/- 1890 (two-stage surface assay); and 10,850 +/- 3720 (total PAIgG). A total of 62 different patients with idiopathic thrombocytopenic purpura or thrombocytopenia complicating systematic lupus erythematosus, and 73 different patients with 'non-immune' thrombocytopenia, were tested using each of the four assays. These 'non-immune' thrombocytopenic patients included patients with carcinoma, septicaemia, pre-eclampsia, chronic leukaemia, thrombotic thrombocytopenic purpura, haemolytic uraemic syndrome, acute leukaemia and myelodysplasia. All four assays gave similar results for both the immune and non-immune thrombocytopenic patients. The sensitivity of the assays for the most severely thrombocytopenic patients with immune thrombocytopenia was: MoAb 60%; SPA 88%; two-stage 82%; and 'total' PAIgG 88%. The specificity of the four assays in the non-immune thrombocytopenic patients was 57% 'total' PAIgG; 63% two-stage surface; 25% SPA; 38% MoAb.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1989

Deceptively low morbidity from failure to practice safe blood transfusion: an analysis of serious blood transfusion errors.

Within a 24-month period, 5 patients in a large teaching hospital were mistakenly transfused with blood that had been crossmatched for different patients. Each of the incidents was due to failure by ward staff to adhere to established safely procedures. Three incidents were entirely due to failure to make the standard checks comparing the identity details on the blood pack label with the patient identification details. The fourth incident was due to a combination of inadequate checking and incomplete patient identification procedure. The fifth incident was due to a series of errors that consisted of inadequate checking, plus putting the wrong patient's blood into the sample tube, plus misspelling of the patient's name on both sample tube and request form. There was no serious morbidity. All of these incidents took place when an unusual coincidence or contributing error lead to unmasked inadequate checking of blood unit against patient's identity by ward staff. The incidence of inadequate checking technique may be much higher than the incidence of erroneous transfusion events. It may be difficult to test the ability of an 'improved' transfusion procedure to prevent disasters from erroneous unit-to-patient matching, since assessment will need to include actual 'worst case' situations, which should be rare.

Adolescent↗
PubMed1988

Methyldopa-induced autoantibodies against red blood cells.

Methyldopa therapy results in the formation of red cell autoantibodies in 10-20% of patients taking the drug for longer than 4 months. These red cell antibodies are true autoantibodies, that is they are directed against an autoantigen on the red blood cell membrane and not against the drug or against a drug-altered antigen. The target membrane antigen is usually within the Rhesus system, although often the antibody specificity cannot be defined. Red cell antibody is usually detectable in the patient's sera as well as on the red cells. The autoantibody is usually a warm reacting IgG antibody. Most patients who develop these autoantibodies do not go on to develop hemolytic anemia in spite of high titres of antibodies on their red cells. In addition, these patients do not tend to develop hemolysis if methyldopa therapy is continued. Rarely patients develop hemolytic anemia which can be severe. Differences in antibody characteristics, including subclass restriction, complement-binding ability, or titre do not explain why some patients with autoantibody hemolyze while most do not. One group of investigators found that hemolyzing patients had IgM on their red cells while those who did not had IgG only. But while this observation could explain why some patients (IgM-sensitized red cells) hemolyze, it does not explain why most patients with IgG-sensitized red cells do not hemolyze. Why the autoantibody forms is not known but some investigators have proposed that the drug may directly affect B or T cells with resulting impairment of immune tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia, Hemolytic, Autoimmune↗