Platelet surface receptor glycoprotein VI-dimer is overexpressed in stroke: The Glycoprotein VI in Stroke (GYPSIE) study results

Objectives

Platelet activation underpins thrombus formation in ischemic stroke. The active, dimeric form of platelet receptor glycoprotein (GP) VI plays key roles by binding platelet ligands collagen and fibrin, leading to platelet activation. We investigated whether patients presenting with stroke expressed more GPVI on their platelet surface and had more active circulating platelets as measured by platelet P-selectin exposure.

Methods

129 ischemic or hemorrhagic stroke patients were recruited within 8h of symptom onset. Whole blood was analyzed for platelet-surface expression of total GPVI, GPVI-dimer, and P-selectin by flow cytometry at admission and day-90 post-stroke. Results were compared against a healthy control population (n = 301).

Results

The platelets of stroke patients expressed significantly higher total GPVI and GPVI-dimer (P<0.0001) as well as demonstrating higher resting P-selectin exposure (P<0.0001), a measure of platelet activity, compared to the control group, suggesting increased circulating platelet activation. GPVI-dimer expression was strongly correlated circulating platelet activation [r² = 0.88, P<0.0001] in stroke patients. Furthermore, higher platelet surface GPVI expression was associated with increased stroke severity at admission. At day-90 post-stroke, GPVI-dimer expression and was further raised compared to the level at admission (P<0.0001) despite anti-thrombotic therapy. All ischemic stroke subtypes and hemorrhagic strokes expressed significantly higher GPVI-dimer compared to controls (P<0.0001).

Conclusions

Stroke patients express more GPVI-dimer on their platelet surface at presentation, lasting at least until day-90 post-stroke. Small molecule GPVI-dimer inhibitors are currently in development and the results of this study validate that GPVI-dimer as an anti-thrombotic target in ischemic stroke.

A comparison of the timing of muscle activity during sitting down compared to standing up

BACKGROUND AND PURPOSE

This study was designed to investigate the temporal pattern of the activation and de-activation of muscles during sitting down to a seated position. The aim was to determine if reproducible patterns existed in the timing of muscle activation and deactivation, in normal subjects, and to compare that produced for sitting down with the pattern produced for standing up.

METHOD

The 10 subjects used for the experiment were a convenience sample consisting of healthy male volunteers aged 19-32 years. The design was that of a descriptive study. Subjects were instructed to stand up and sit back down to a seated position. During this activity kinematic (movement) and electromyographic (EMG) data were collected. A pattern of timing for the activity of different muscles or groups was produced and this was compared with the movement occurring.

RESULTS

The study found a consistent pattern of EMG activity during sitting down from a standing position. This pattern was documented and the pattern was compared with that produced during standing up.

CONCLUSIONS

The results demonstrated that a consistent pattern of muscle activation and de-activation was produced in this group of subjects during sitting down. The pattern of muscle activation and de-activation for sitting down was documented. When comparing the pattern produced during sitting down with that produced during standing up it is apparent that some of the muscles were active during both movement patterns at the same relative point in the pattern.

Upward mobility, status inconsistency, and psychological health

According to much of the theoretical literature, the psychological consequences of intergenerational occupational mobility are associated with poorer psychological health, even when upward mobility is involved. One possible explanation is that mobility results in status inconsistencies that are experienced as stressful. The research reported here reconsiders the notions that mobility is associated with higher levels of stress and that stress results from exposure to status inconsistencies. The results obtained, based on a sample of English men, provide no support for either thesis.