We previously demonstrated that Amblyomma americanum tick serine protease inhibitor 6 (AamS6) was secreted into the host during tick feeding and that both its mRNA and protein were ubiquitously and highly expressed during the first 3 days of tick feeding. This study demonstrates that AamS6 is a cross-class inhibitor of both serine- and papain-like cysteine proteases that has apparent antihaemostatic functions. Consistent with the typical inhibitory serpin characteristics, enzyme kinetics analyses revealed that Pichia pastoris-expressed recombinant (r) AamS6 reduced initial velocities of substrate hydrolysis (V0) and/or maximum enzyme velocity (Vmax) of trypsin, chymotrypsin, elastase, chymase, and papain in a dose–response manner. We speculate that rAamS6 inhibited plasmin in a temporary fashion in that while rAamS6 reduced V0 of plasmin by up to ~53%, it had no effect on Vmax. Our data also suggest that rAmS6 has minimal or no apparent effect on V0 or Vmax of thrombin, factor Xa, and kallikrein. We speculate that AamS6 is apparently involved in facilitating blood meal feeding in that various amounts of rAamS6 reduced platelet aggregation by up to ~47% and delayed plasma clotting time in the recalcification time assay by up to ~210 s. AamS6 is most likely not involved with the tick’s evasion of the host’s complement defense mechanism, in that rAamS6 did not interfere with the complement activation pathway. Findings in this study are discussed in the context of expanding our understanding of tick proteins that control bloodmeal feeding and hence tick-borne disease transmission by ticks.

The primary objective of the present experiment was to examine the influence of recent practice in a random and blocked format for future motor learning. First, individuals practiced three unique discrete sequence production tasks in either a blocked or random schedule. One day later, all individuals practiced a new motor sequence not previously practiced. On day three, mean total time for the test performance of the original three motor sequences was lower for individuals that practiced in a random format. This emerged as a significant reduction in mean total time from the completion of practice and the test trials implicating offline consolidation as a key contributor to the random practice performance advantage. A novel finding from the present work was that the acquisition of the novel discrete sequence production task practiced on Day 2 was better for individuals that had prior random rather than blocked practice experience. This benefit was robust appearing early during acquisition as significantly lower mean total time. This benefit from random practice experience remained during the delayed test trials administered on Day 3 for the novel motor sequence.

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