Reversible aggregation is a form of erythrocyte behavior. The presence of αand β -adrenergic receptors on erythrocyte membranes suggests that aggregation can be influenced by agonists of these receptors. Human erythrocyte aggregation (EA) was studied in the presence of αand β -agonists of adrenergic receptors (in the concentration range from 10 -6 to 10 -8 M). The α 2 -agonist clonidine stimulated EA most strongly (by 163%, P < 0.01). The cell reaction decreased from the α -agonist clonidine to the β -agonist metaproterenol. The phosphodiesterase inhibitor papaverine and the penetrating cAMP analogue dibutyryl cAMP (dB-cAMP) increased the intracellular cAMP and decreased EA by 46-50% ( P < 0.05). Clonidine-induced stimulation of EA sharply decreased upon erythrocyte incubation in the presence of clonidine + dB-cAMP and became even lower than in the control. Thus, α -agonists of adrenergic receptors markedly stimulated EA. The adenylate cyclase-cAMP system is likely involved as an intracellular signaling pathway.
On the basis of reanalysis data and hydrodynamic modeling the spatial-temporal features of Wallace-Gutzler circulation indices, calculated at daily intervals, are studied. The circulation index extremes are interpreted as "weather regimes" with the alteration closely related to the low frequency variability of the atmospere. The outliers and extreme values are studied using nonparametric statistics and exploratory techniques. On the basis of the experiments performed assessments of the potential predictability of the outlier and extreme value characteristics for the summer and winter seasons are given.
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