Comparison of energy efficiency between Wearable Power-Assist Locomotor (WPAL) and two types of knee-ankle-foot orthoses with a medial single hip joint (MSH-KAFO).

OBJECTIVE: To compare the energy efficiency of Wearable Power-Assist Locomotor (WPAL) with conventional knee-ankle-foot orthoses (MSH-KAFO) such as Hip and Ankle Linked Orthosis (HALO) or Primewalk. STUDY DESIGN: Cross over case-series. SETTING: Chubu Rosai Hospital, Aichi, Japan, which is affiliated with the Japan Organization of Occupational Health and Safety. METHODS: Six patients were trained with MSH-KAFO (either HALO or Primewalk) and WPAL. They underwent 6-minute walk tests with each orthosis. Energy efficiency was estimated using physiological cost index (PCI) as well as heart rate (HR) and modified Borg score. Trial energy efficiency with MSH-KAFO was compared with WPAL to assess if differences in PCI became greater between MSH-KAFO and WPAL as time goes on during the 6-minute walk. Spearman correlation coefficient of time (range: 0.5-6.0 minutes) with the difference was calculated. The same statistical procedures were repeated for HR and modified Borg score. RESULTS: Greater energy efficiency, representing a lower gait demand, was observed in trials with WPAL compared with MSH-KAFO (Spearman correlation coefficients for PCI, HR and modified Borg were 0.93, 0.90 and 0.97, respectively, all P < 0.0001). CONCLUSIONS: WPAL is a practical and energy efficient type of robotics that may be used by patients with paraplegia.

Interaction of extracellular loop II of κ-opioid receptor (196-228) with opioid peptide dynorphin in membrane environments as revealed by solid state nuclear magnetic resonance, quartz crystal microbalance and molecular dynamics simulation.

κ-Opioid receptor is a member of the opioid receptor family and selectively interacts with the opioid peptide dynorphin. Extracellular loop II (ECL-II) of the κ-opioid receptor displays an amphiphilic helix in membrane environments and the N-terminal α-helix of dynorphin A(1-17) (hereafter DynA17) is inserted into the membrane with the tilt angle of 21° to the bilayer normal. ECL-II peptides (1-33), corresponding to 196-228 of κ-opioid receptor with [1-(13)C]- or [3-(13)C]-labeled amino acids were incorporated into large [dimyristoylphosphatidyl choline (DMPC)/ dihexanoylphosphatidyl choline (DHPC) = 3, q = 3] and small bicelle (q = 1) systems. (13)C direct detection with dipolar decoupling and magic angle spinning (DD-MAS) nuclear magnetic resonance (NMR) spectra were recorded, and the (13)C chemical shift perturbation clearly indicated that DynA17 interacts with ECL-II at the location of Val10-Ala15. Quartz crystal microbalance measurements were performed to determine the binding constant of ECL-II with DynA17 and indicated that the binding constant between DynA17 and ECL-II embedded in the lipid layer was 72 times larger than that between DynA17 and the lipid. The result of the molecular dynamics simulation clearly indicates that the C-terminus of DynA17 interact with the amino acid residues of the region between Val10-Gln14 of ECL-II. These results suggest that DynA17 interacts with the ECL-II of the κ-opioid receptor through a hydrophobic and short-lived electrostatic interaction with high affinity in the outer surface of the membrane.