Objective-To relate weakness

Objectives of this case-control study were (1) to examine membrane conformational changes and dynamics in platelets of patients with stroke prior to and following short-term aspirin administration and (2) to investigate changes in platelet membrane fluidity which may be associated with the ageing process. The study population consisted of 10 patients with ischaemic stroke (age range 61–92, mean 76 years; 6 females and 4 males) 9 age- and sex-matched controls (age range 64–88, mean 73 years; 5 females and 4 males), and 8 healthy young controls (age range 22–39, mean 32 years; 4 females and 4 males). The patients were recruited from the medical and geriatric wards, whereas both young and old controls were recruited from hospital staff and the local community. Aspirin, at a dose of 150 mg/day, was administered to all three groups for 7 days. The order parameter S, which is an index of membrane fluidity and conformation, was measured by the techniques of spin labelling and electron spin resonance spectroscopy on platelets from venous blood samples from patients prior to (within 48 h of admission) and following 7 days of aspirin therapy and from venous blood samples from both young and old controls before and after 7 days of oral aspirin therapy. There was an age-relateted decrease in platelet membrane fluidity. There was no significant difference in the value of ‘S’ between patients with ischaemic stroke and old controls. Treatment with aspirin led to a significant decrease in membrane fluidity in both patients and old controls, but had no apparent effect on the platelet membrane fluidity of younger controls. We conclude that the ageing process is associated with a decrease in platelet membrane fluidity and that aspirin therapy leads to a further significant fall in membrane fluidity in both patients with stroke disease and old controls. No apparent effect on the platelet membrane fluidity of younger controls was observed.

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