Strategy Use Mediates the Relation between Openness to Experience and Episodic Memory in Younger and Older Adults

Previous research has shown that people with higher levels of Openness to Experience show higher levels of cognitive functioning. However, the mechanisms underlying this personality-cognition relation are not well understood. The goal of the current project was to examine whether strategy use mediates the relation between Openness to experience and retrospective memory, and whether the role of strategy use in the Openness-memory relation was the same in younger and older adults.

METHOD

Two studies were conducted. In each of them, younger and older adults were administered a retrospective memory task (29 younger and 27 older in Study 1, 43 adults of all ages in Study 2). They were asked to report the strategies they used during the task, and to complete an Openness to Experience scale.

RESULTS

Consistent with previous reports, higher scores of Openness to experience and greater use of efficient memory strategies were associated with higher levels of memory performance. In addition, individual differences in memory strategy use mostly mediated the relation between Openness and memory performance. Results did not support a mediation model moderated by age. That is, the role of memory strategy use in the relation between Openness and memory was the same in younger and older adults.

CONCLUSION

Higher levels of Openness are associated with better memory performance, mostly because people with higher levels of Openness use more efficient memory strategies.

Characterization of the PGE receptor subtype mediating inhibition of superoxide production in human neutrophils

1. The aims of this study were to characterize the EP receptor subtype mediating the inhibition of superoxide anion generation by formyl methionyl leucine phenylalanine (FMLP)-stimulated human neutrophils, and to test the hypothesis that adenosine 3':5'-cyclic monophosphate (cyclic AMP) is the second messenger mediating the inhibition of the neutrophil by prostaglandin (PG)E2. 2. PGE2 (0.001-10 microM) inhibited FMLP (100 nM)-induced O2-generation from human peripheral blood neutrophils in a concentration-dependent manner, with an EC50 of 0.15 +/- 0.03 microM, and a maximum effect ranging from 36-84% (mean inhibition of 68.7 +/- 2.5%, n = 32). 3. The EP2-receptor agonists, misoprostol, 11-deoxy PGE1, AH13205 and butaprost, all at 10 microM, inhibited O2- generation, causing 95.5 +/- 2.9%, 56.8 +/- 5.2%, 37.1 +/- 6.6% and 18.9 +/- 4.4% inhibition respectively, the latter two being much less effective than PGE2. Similarly, the EP1-receptor agonist, 17-phenyl PGE2 (10 microM), and the EP3/EP1-receptor agonist, sulprostone (10 microM), also inhibited O2- generation, causing 32.2 +/- 7.0% and 15.3 +/- 3.4% inhibition respectively. 4. The non-selective phosphodiesterase inhibitor, isobutyl methylxanthine (IBMX, 0.25 mM) inhibited the FMLP response by 54.5 +/- 5.0%. In addition, IBMX shifted concentration-effect curves for PGE2, misoprostol, 11-deoxy PGE1, butaprost, and AH 13205 to the left, to give EC50s of 0.04 +/- 0.03 (n = 13), 0.07 +/- 0.03 (n = 4), 0.08 +/- 0.03 (n = 4), 0.33 +/- 0.13 (n = 4) and 0.41 +/- 0.2 microM (n = 3) respectively, allowing equieffective concentration-ratios (EECs, PGE2 = 1) of 11.5, 5.3, 50.7 and 12.7 to be calculated. This agrees well with the relative potencies of these agonists at EP2 receptors.5. By contrast, even in the presence of IBMX (0.25 mM), sulprostone and 17-phenyl PGE2 were only effective at the highest concentration (10 microM), and gave EECs of > 700 and 486 respectively, suggesting that EP1 or EP3 receptors are not involved.6. The selective type IV phosphodiesterase inhibitor, rolipram at 2 and 10 nM did not inhibit the FMLP response, but at the higher concentration of 50 nM, it decreased the FMLP response by 46.6 +/-7.3%.However, rolipram shifted concentration-effect curves for PGE2 to the left to give EC50s of 0.06 +/-0.022,0.015 +/- 0.0, 0.012 +/- 0.006 microM at 2, 10 and 50 nM respectively, compared to the control EC50 of0.27+/- 0.09 microM for PGE2.7. The EP4/TP receptor blocking drug, AH 23848B (10 microM, 10 min) did not inhibit 02- generation by PGE2, but was found to potentiate significantly the effect of PGE2 at the lower concentrations of PGE2 tested (0.001-0.1 microM).8. The adenylate cyclase inhibitor, SQ 22,536 (0.1 mM, 2 min) reduced PGE2-induced inhibition of 02-production, giving an EC50 in the absence of SQ 22,536 of 0.24 +/- 0.1, and 1.9 +/- 1.1 AM in its presence.9. These results suggest that inhibition of superoxide generation by PGE2 is mediated by stimulation ofEP2 receptors and activation of adenylate cyclase, leading to the elevation of intracellular levels of cyclic AMP.

Comparison of the prostaglandin E (EP) receptor of human neutrophils and HL-60 cells differentiated with DMSO

Human promyelocytic leukaemic HL-60 cells can be differentiated with DMSO to become neutrophil-like. In this study, the prostanoid receptors linked to adenylate cyclase have been compared in human neutrophils and in differentiated HL-60 cells. Both cell types appear to express EP2 receptors as recognised by the ability of EP2 agonists and not EP1 or EP3 agonists to increase cell cyclic AMP levels, and the finding that the increase in cyclic AMP induced by PGE2 was not blocked by the EP4 receptor antagonist AH 23,848 (30 microM). Neither cell type appears to express receptors for PGI2, but human neutrophils and not differentiated HL-60 cells express receptors for PGD2. In addition, human neutrophils may contain EP3 receptors linked to a reduction in cyclic AMP levels. The lack of other prostanoid receptors coupled to adenylate cyclase in HL-60 cells suggests that these cells may provide a useful starting point for the cloning of the EP2 receptor.