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Biomedical subjects

J R O'Brien

Publications and source records attributed to J R O'Brien.

50 records · Page 3Linked to original sources
PubMed1976

Acute platelet changes after large meals of saturated and unsaturated fats.

Large amounts of saturated fats (S.F.) or unsaturated fats (U.S.F.) were given to healthy volunteers at a single meal. The heparin thrombin clotting-time, which may measure platelet factor 4 released from platelets into the plasma, was shortened after S.F. and prolonged after U.S.F. The antithrombin clotting activity decreased after S.F. and increased after U.S.F. The platelet-count decreased and the platelet volume increased after both S.F. and U.S.F.

Adult↗
PubMed1975

Blood changes in atherosclerosis and long after myocardial infarction and venous thrombosis.

The following clinical groups of volunteers were studied: patients long after recovery from myocardial infarction (MI), others after recovery from deep vein thrombosis (DVT), patients with intermittent claudication, with diabetes, and male and female controls who were well matched. All were subjected to many platelet and clotting tests together with clinical, biochemical and haematological measurements in an attempt to find long term abnormalities in these various diseases. The male MIs differed very significantly from the controls in having much more heparin neutralizing activity (P less than 0.001)and less anti-thrombin (P less than 0.01). Less significantly, some bleeding time tests indicated less bleeding and the patients' platelets were larger. The females with MI had in general the same abnormalities but to a lesser degree. The patients with intermittent claudication, none of whom had a history of MI, had almost the same abnormalities and to the same degree. In deep vein thrombosis the heparin neutralizing activity was also clearly increased; the other tests were generally in the same direction but many were not significant. The diabetics had shorter bleeding times but little else abnormal relative to the controls, suggesting a different pathological process. When all male patients and controls were "scored" according to the degree of atherosclerosis there was a close overall correlation between the degree of atherosclerosis and the increase in the HNA level (r = --0.50, n = 66, P less than 0.001) and the decreased anti-thrombin (r = 0.25, n = 66, P less than 0.05).

Antithrombins↗
PubMed1975

Heparin neutralizing activity test in the diagnosis of acute myocardial infarction.

We have previously shown in patients after recovery from a myocardial infarct (post-MI) that the heparin neutralizing activity (HNA) in the plasma is raised and that this activity may come from platelet factor 4 derived from activated platelets. This report concerns 89 patients admitted with acute chest pain; in 54, with evidence of acute infarction, the level of HNA is much higher than in a post-MI group or controls. Over the ensuing weeks the HNA decreases to the post-MI level. In 34 patients the evidence subsequently collected excluded a diagnosis of infarction; in these there were almost always normal amounts of HNA and little overlap with the results from the patients with infarcts. This easy test is therefore likely to prove clinically useful. Its significance is discussed. The platelet count and platelet volume are both abnormal in patients with acute infarction and also in the chest pain group so these tests do not help to discriminate.

Acute Disease↗
PubMedDate not supplied

Platelet responses to cardiopulmonary bypass. Assessment by a shear stress activation technique.

Platelet responses before and during cardiopulmonary bypass were studied using a shear stress activation technique. Whole blood was passed through a 10 microns micro-porous filter and the percentage of platelets retained was determined. Retention in control subjects (n = 20, age 62 +/- 11 years) was 65.2 +/- 15.1%. Patients with ischaemic heart disease (n = 20, age 61 +/- 9 years) had significantly higher retention at 82.6 +/- 13.2%, p less than 0.001. In valvular heart disease (n = 15, age 57 +/- 14 years) the retention rate was 43.5 +/- 15.4%, lower than both controls and ischaemic heart disease patients (p less than 0.001). In vitro haemodilution had no significant effect on platelet retention. High retention rates were maintained in patients undergoing coronary artery surgery. During valve surgery retention increased before aortic cross-clamp removal (83.5 +/- 13.4%) compared with baseline values (p less than 0.001) and remained high 24 hours postoperatively (79.6 +/- 9.4%). Platelet retention also increased within 20 minutes of thoracotomy without cardiopulmonary bypass (n = 10, age 57 +/- 8 years, 79.3 +/- 11.6% versus 61.6 +/- 10.9% baseline, p less than 0.01) and remained high 24 hours postoperatively. Significant differences in platelet responses, assessed by shear stress activation, were demonstrated between healthy controls and patients with ischaemic and valvular heart disease. Surgery, with or without extracorporeal circulation, caused a significant increase in platelet retention.

Aged↗