Multisite silicon probes enable simultaneous recording of spontaneous and evoked activity in multiple isolated C-fibres in rat saphenous nerve.

BACKGROUND: Recordings of electrical activity in nerves have provided valuable insights into normal function and pathological behaviours of the nervous system. Current high-resolution techniques (e.g. teased fibre recordings) typically utilise electrodes with a single recording site, capturing the activity of a single isolated neuron per recording. NEW METHOD: We conducted proof-of-principle C-fibre recordings in the saphenous nerve of urethane-anaesthetised adult Wistar rats using 32-channel multisite silicon electrodes. Data was acquired using the OpenEphys recording system and clustered offline with Kilosort 2.5. RESULTS: In single recordings in 5 rats, 32 units with conduction velocities in the C-fibre range (< 1 m/s) were identified via constant latency responses and classified using activity dependent slowing. In two animals, 6 C-fibres (5 classified as nociceptors) were well isolated after clustering. Their activity could be tracked throughout the recording - including during periods of spontaneous activity. Axonal conduction velocities were calculated from spontaneous activity and/or low frequency electrical stimulation using only the differences in action potential latency as it propagated past multiple probe sites. COMPARISON WITH EXISTING METHODS: Single electrode approaches have a low data yield and generating group data for specific fibre types is challenging as it requires multiple experimental subjects and recording sessions. This is particularly true when the experimental targets are the small, unmyelinated C-fibres carrying nociceptive information. CONCLUSIONS: We demonstrate that multisite recordings can greatly increase experimental yields and enhance fibre identification. The approach is of particular utility when coupled with clustering analysis. Multisite probes and analysis approaches constitute a valuable new toolbox for researchers studying the peripheral nervous system.

Effect of free-radical scavengers and hyperbaric oxygen on random-pattern skin flaps.

OBJECTIVE: To determine whether treatment with the combination of hyperbaric oxygen and free-radical scavengers or inhibitors would result in increased skin-flap survival. DESIGN: An animal model with male Sprague-Dawley rats was used. The flap was a cranial-based dorsal 3 x 12-cm random-pattern skin flap that included the panniculus carnosus. Rats were randomly assigned to one of 10 treatment groups. INTERVENTIONS: The radical scavengers superoxide dismutase, catalase, and alpha-tocopherol acetate and the inhibitor allopurinol were used to combat or scavenge radicals. Oxygen (100%) treatments were for 90 minutes at 2.5 atm absolute daily. MAIN OUTCOME MEASURES: At 7 days, the flaps were examined for survival by fluorescein injection. Lipid peroxidation as a measure of tissue damage was measured by thiobarbituric acid-malondialdehyde analysis. RESULTS: The combination of treatments resulted in significantly increased flap survival compared with untreated controls (P < .05) except in the group treated with allopurinol and hyperbaric oxygen. Lipid peroxidation was inhibited by the superoxide dismutase plus catalase and the alpha-tocopherol treatments but not by treatment with allopurinol. CONCLUSION: Moderate doses of radical scavengers or antioxidants coupled with a conservative hyperoxic exposure regimen can result in the increased survival of random-pattern skin flaps.

Effect of silicon on gastrointestinal absorption of aluminium.

The reported geographical association between Alzheimer's disease and levels of aluminium (Al) in water supplies may reflect the inverse relation between Al and silicon (Si) concentrations in water, and the potential for Si to reduce the bioavailability of the metal. We tested this hypothesis using isotopic 26Al tracer administered orally to five healthy volunteers in the presence and absence of Si. Dissolved Si, at a concentration found in some water supplies (100 mumol/L), reduced the peak plasma 26Al concentration to 15% of the value obtained in the absence of Si. The results indicate that dissolved Si is an important factor in limiting the absorption of dietary Al.

Amygdalin toxicity studies in rats predict chronic cyanide poisoning in humans.

Significant amounts of cyanide are released when amygdalin (Laetrile), a cyanogenic glycoside, is given orally or intravenously to rats. The amount of cyanide liberated following oral administration is dependent in part on the bacterial flora of the gut and can be suppressed by antibiotic pretreatment of the animals. Bacteria from human feces likewise hydrolyze amygdalin with release of cyanide. Humans taking amygdalin orally in the hope of preventing cancer are likely to be exposed to levels of cyanide in excess of that associated with the development of tropical ataxic neuropathy in people of underdeveloped countries where food containing cyanogenic glycosides is a staple part of the diet.

Laetrile toxicity studies in dogs.

Dogs were fed laetrile and fresh, sweet almonds under various conditions. The doses of laetrile were similar to those prescribed for patients with cancer and ranged on a basis of gram to square meter from an equivalent of the oral dose for man to five times this dose. Six of the ten dogs died of cyanide poisoning. One dog recovered, and three dogs, at the time of sacrifice, demonstrated various levels of neurologic impairment, ranging from difficulty in walking to coma. These studies demonstrate that oral laetrile is highly toxic when taken with some common table foods. We predict that there will be an increased incidence of cyanide poisoning in man as laetrile becomes more readily available.