Substitution of the L-proline residue at position 4 of the native peptide with hydroxyproline, valine or D-proline caused a loss of cardioinhibitory activity. Also, replacement of arginine residues at all three positions 2, 7 and 9 with another basic amino acid histidine, reduces cardioinhibitory action of Led-NPF-I. Some modifications selleck of the C-terminal residues, as the Phe(4-NO2)-, Phe(4-NH2)- and Phe(4-NMe2)-analogues, resulted in agonistic peptides with biological activity similar to that of the native peptide. However,

three other C-terminal analogues tested [Tyr(10)]-, [D-Phe(10)]-Led-NPF-I, and Ala-Arg-Gly-Pro-Gln-Leu-Arg-Leu-Arg-Phe-OH were inactive in the heart bioassay, which suggests that this end of the amino acid chain may play an important role in bioactivity and interaction of the native peptide with its receptor on the myocardium. Copyright (C) 2007 European Peptide Society and PP2 John Wiley & Sons, Ltd.”
“Robotic lower limb exoskeletons that can alter joint mechanical power output are novel tools for studying the relationship between the mechanics and energetics of human locomotion. We built pneumatically powered ankle exoskeletons controlled by the user’s own soleus electromyography (i.e. proportional myoelectric control) to determine

whether mechanical assistance at the ankle joint could reduce the metabolic cost of level, steady-speed human walking. We hypothesized that subjects would reduce their net metabolic power in proportion to the average positive mechanical power delivered by the bilateral ankle exoskeletons. Nine healthy individuals completed three 30 min sessions walking at 1.25 m s(-1) while wearing the exoskeletons. Over the three sessions, subjects’ net metabolic energy

expenditure during powered walking progressed from +7% to -10% of that during unpowered walking. With practice, subjects significantly reduced soleus muscle activity ( by similar to 28% root mean square EMG, P < 0.0001) and negative exoskeleton mechanical power (-0.09 W kg(-1) at the beginning of session 1 and -0.03 W kg(-1) at the end of session 3; P = 0.005). Ankle joint kinematics returned to similar patterns to those observed during unpowered walking. At the end of the third session, the powered exoskeletons check details delivered similar to 63% of the average ankle joint positive mechanical power and similar to 22% of the total positive mechanical power generated by all of the joints summed ( ankle, knee and hip) during unpowered walking. Decreases in total joint positive mechanical power due to powered ankle assistance (similar to 22%) were not proportional to reductions in net metabolic power (similar to 10%). The ‘apparent efficiency’ of the ankle joint muscle-tendon system during human walking (similar to 0.61) was much greater than reported values of the ‘muscular efficiency’ of positive mechanical work for human muscle (similar to 0.