Ultra-high-frequency ultrasound imaging of sural nerve: A comparative study with nerve biopsy in progressive neuropathies.

INTRODUCTION: Nerve ultrasound has been used increasingly in clinical practice as a complementary test for diagnostic assessment of neuropathies, but nerve biopsy remains invaluable in certain cases. The aim of this study was to compare ultra-high-frequency ultrasound (UHF-US) to histologic findings in progressive polyneuropathies. METHODS: Ten patients with severe, progressive neuropathies underwent ultrasound evaluation of the sural nerve before nerve biopsy. Ultrasound data were compared with histologic results in a retrospective manner. RESULTS: Sural nerves were easily identified on UHF-US. Nerve hyperechogenicity correlated with inflammatory infiltrates on biopsy. Nerve fascicles could be identified and measured on ultrasound in the majority of patients. DISCUSSION: Hyperechogenicity on UHF-US may be a marker of nerve inflammation in neuropathies. Furthermore, the UHF-US probe allows for evaluation of sensory nerves in spite of their small size, providing valuable information on their size and on their internal structure.

Pharmacological modulation of Acid-Sensing Ion Channels 1a and 3 by amiloride and 2-guanidine-4-methylquinazoline (GMQ).

Acid-Sensing Ion Channels (ASICs) are cation channels activated by extracellular acidification that emerge as potential pharmacological targets in pain and other neurological disorders. Here, we compare the pharmacological modulation of ASIC1a and ASIC3 channels by amiloride and 2-guanidine-4-methylquinazoline (GMQ), two compounds commonly used for their in vitro and in vivo investigation. We analyzed the effect of amiloride on the pH-dependent activation and inactivation, the relative influence of the extracellular domain and the transmembrane/cytosolic domains on the effect of amiloride and GMQ using chimeras between ASIC1a and ASIC3, and how these compounds potentiate the physiologically relevant ASIC3 sustained window current. We showed that amiloride and GMQ shift the pH-dependent activation and inactivation in the same directions, which depend on the channel, and that their effects rely on the nature of the extracellular domain but can be indirectly modulated in their amplitude by the transmembrane/cytosolic domains. The extracellular domain explains the pharmacological potentiating effect of amiloride and GMQ on the window current in ASIC3, and why these compounds failed to generate a window current in ASIC1a. Amiloride and GMQ have similar and purely additive effects suggesting that they act through a common unique binding site different from acidic pockets. Finally, a simple cycle analysis using GMQ that targets the nonproton ligand-sensor, and two peptide inhibitors of ASIC1a targeting the acidic pockets (PcTx1 and mambalgin-1), shows overlap between the mechanisms by which GMQ and PcTx1 modify inactivation and suggests shared mechanisms of regulation of the pH-dependent inactivation of ASIC1a between these two regions.

Low cost venom extractor based on Arduino(®) board for electrical venom extraction from arthropods and other small animals.

Extracting venom from small species is usually challenging. We describe here an affordable and versatile electrical venom extractor based on the Arduino(®) Mega 2560 Board, which is designed to extract venom from arthropods and other small animals. The device includes fine tuning of stimulation time and voltage. It was used to collect venom without apparent deleterious effects, and characterized for the first time the venom of Zoropsis spinimana, a common spider in French Mediterranean regions.

Mambalgin-1 Pain-relieving Peptide, Stepwise Solid-phase Synthesis, Crystal Structure, and Functional Domain for Acid-sensing Ion Channel 1a Inhibition.

Mambalgins are peptides isolated from mamba venom that specifically inhibit a set of acid-sensing ion channels (ASICs) to relieve pain. We show here the first full stepwise solid phase peptide synthesis of mambalgin-1 and confirm the biological activity of the synthetic toxin both in vitro and in vivo. We also report the determination of its three-dimensional crystal structure showing differences with previously described NMR structures. Finally, the functional domain by which the toxin inhibits ASIC1a channels was identified in its loop II and more precisely in the face containing Phe-27, Leu-32, and Leu-34 residues. Moreover, proximity between Leu-32 in mambalgin-1 and Phe-350 in rASIC1a was proposed from double mutant cycle analysis. These data provide information on the structure and on the pharmacophore for ASIC channel inhibition by mambalgins that could have therapeutic value against pain and probably other neurological disorders.

Binding site and inhibitory mechanism of the mambalgin-2 pain-relieving peptide on acid-sensing ion channel 1a.

Acid-sensing ion channels (ASICs) are neuronal proton-gated cation channels associated with nociception, fear, depression, seizure, and neuronal degeneration, suggesting roles in pain and neurological and psychiatric disorders. We have recently discovered black mamba venom peptides called mambalgin-1 and mambalgin-2, which are new three-finger toxins that specifically inhibit with the same pharmacological profile ASIC channels to exert strong analgesic effects in vivo. We now combined bioinformatics and functional approaches to uncover the molecular mechanism of channel inhibition by the mambalgin-2 pain-relieving peptide. Mambalgin-2 binds mainly in a region of ASIC1a involving the upper part of the thumb domain (residues Asp-349 and Phe-350), the palm domain of an adjacent subunit, and the ß-ball domain (residues Arg-190, Asp-258, and Gln-259). This region overlaps with the acidic pocket (pH sensor) of the channel. The peptide exerts both stimulatory and inhibitory effects on ASIC1a, and we propose a model where mambalgin-2 traps the channel in a closed conformation by precluding the conformational change of the palm and ß-ball domains that follows proton activation. These data help to understand inhibition by mambalgins and provide clues for the development of new optimized blockers of ASIC channels.