Infrared neurostimulation in ex-vivo rat sciatic nerve using 1470 nm wavelength.

OBJECTIVE: To design and implement a setup for ex-vivo optical stimulation for exploring the effect of several key parameters (optical power and pulse duration), activation features (threshold, spatial selectivity) and recovery characteristics (repeated stimuli) in peripheral nerves. APPROACH: A nerve chamber allowing ex-vivo electrical and optical stimulation was designed and built. A 1470 nm light source was chosen to stimulate the nerve. A photodiode module was implemented for synchronization of the electrical and optical channels. MAIN RESULTS: Compound Neural Action Potentials (CNAPs) were successfully generated with infrared light pulses of 200-2000 µs duration and power in the range of 3-10 W. These parameters determine a radiant exposure for stimulation in the range 1.59-4.78 J/cm2. Recruitment curves were obtained by increasing durations at a constant power level. Neural activation threshold is reached at a mean radiant exposure of 3.16 ± 0.68 J/cm2 and mean pulse energy of 3.79 ± 0.72 mJ. Repetition rates of 2-10 Hz have been explored. In 8 out of 10 sciatic nerves, repeated light stimuli induced a sensitisation effect in that the CNAP amplitude progressively grows, representing an increasing number of recruited fibres. In 2 out of 10 sciatic nerves, CNAPs were composed of a succession of peaks corresponding to different conduction velocities. SIGNIFICANCE: The reported sensitisation effect could shed light on the mechanism underlying Infrared NeuroStimulation (INS). Our results suggest that, in sharp contrast with electrical stimuli, optical pulses could recruit slow fibres early on. This more physiological order of recruitment opens the perspective for specific neuromodulation of fibre population who remained poorly accessible until now. Short high-power light pulses at wavelengths below 1.5 µm offer interesting perspectives for neurostimulation

Analysing vagus nerve spontaneous activity using finite element modelling

Objective. Finite element modelling has been widely used to understand the effect of stimulation on the nerve fibres. Yet the literature on analysis of spontaneous nerve activity is much scarcer. In this study, we introduce a method based on a finite element model, to analyse spontaneous nerve activity with a typical bipolar electrode recording setup, enabling the identification of spontaneously active fibres. We applied our method to the vagus nerve, which plays a key role in refractory epilepsy. Approach. We developed a 3D model including dynamic action potential propagation, based on the vagus nerve geometry. The impact of key recording parameters – inter-electrode distance and temperature – and uncontrolled parameters – fibre size and position in the nerve – on the ability to discriminate active fibres were quantified. A specific algorithm was implemented to detect and classify action potentials from recordings and tested on six rats in vivo vagus nerve recordings. Main results. Fibre diameters can be discriminated if they are below 3 µm and 7 µm, respectively for inter-electrode distances of 2 mm and 4 mm. The impact of the position of the fibre inside the nerve on fibre diameter discrimination, is limited. The range of active fibres identified by modelling in the vagus nerve of rats is in agreement with ranges found at histology. Significance. The nerve fibre diameter, directly proportional to the action potential propagation velocity, is related to a specific physiological function. Estimating the source fibre diameter is thus essential to interpret neural recordings. Among many possible applications, the present method was developed in the context of a project to improve vagus nerve stimulation therapy for epilepsy

Design of a sacro-lumbar anterior root stimulator implant for exercise and urological functions.

info:eu-repo/semantics/publishe

Sacro-lumbar anterior root stimulator implant for exercising.

info:eu-repo/semantics/publishe

Functionning of sacro-lumbar anterior root stimulator implant.

info:eu-repo/semantics/publishe

Redistribution of Epidermal Growth-factor Immunoreactivity in Renal Tissue After Nephrotoxin-induced Tubular Injury

Tubular necrosis elicits a process of renal tissue repair characterized by an increase of cell turnover in tubular epithelium. The present study was undertaken to examine the distribution of epidermal growth factor (EGF) and/or of its larger precursor proEGF in the kidney undergoing tubular regeneration. Sprague-Dawley rats were exposed to various drugs (aminoglycosides or platinum-based anticancer agents) known to induce tubular necrosis. The proliferative response resulting from renal tissue damage was measured by the incorporation of [H-3]thymidine into DNA of renal cells. EGF immunoreactivity was evidenced by immunocytochemical staining, using anti-EGF antibody and immunogold-silver staining. Concomitantly with the increase of cell proliferation resulting from tubular injury, a redistribution of EGF immunoreactivity was observed in renal tissue (from the inner stripe of outer medulla towards renal cortex). Amazingly, EGF was detected in proximal tubules of nephrotoxin-treated rats whereas, in the kidneys of control animals, it was almost exclusively found in distal tubules and collecting ducts. Insofar as the administration of exogenous EGF has recently been shown to enhance renal tubular regeneration after ischaemic injury [Humes et al: J Clin Invest 1989; 84:1757-1761], our observations lend further support to the concept that EGF might be involved in renal tissue repair

Distribution of Epidermal Growth-factor in the Kidneys of Rats Exposed To Amikacin

The distribution of epidermal growth factor (EGF) was examined by immunocytochemistry in the kidneys of rats exposed to amikacin, an aminoglycoside antibiotic causing tubular necrosis at high dose. Five-animal groups were treated for 4 or 10 days with amikacin at daily doses of 15, 40, 80 or 200 mg/kg. The drug was delivered i.p. twice a day. One hour before termination, each rat received an i.p. injection of [H-3] thymidine to evaluate DNA synthesis in renal tissue. After sacrifice, the kidneys were processed for morphological (semithin and paraffin sections) and biochemical analysis (measurement of DNA synthesis by [H-3] thymidine incorporation in vivo). Amikacin induced in proximal tubules a dose-related lysosomal phospholipidosis, which was assessed by the morphometric evaluation of altered lysosomes ("myeloid bodies") on semithin section. However, frank evidence of acute tubular necrosis was only observed in rats receiving amikacin at a daily dose of 200 mg/kg. Concomitantly with the development of tubular necrosis, there was a rise in the rate of cell turnover, reflected by an increase of DNA synthesis in renal tissue. This sign of tubular regeneration was accompanied by a redistribution of EGF immunoreactivity, as revealed by immunocytochemical staining. Within renal cortex of control rats, EGF immunoreactivity predominantly appeared in distal tubules and collecting ducts (97% of examined tubular sections). In contrast, in treated animals where the renal cortex displayed evidence of tubular necrosis/regeneration, EGF immunoreactivity was frequently associated with proximal tubules (more than 30% of examined tubular sections, as compared to 3% in controls). This change in the topography of EGF immunoreactivity suggests that the growth factor might be involved in the process of tissue repair consecutive to drug-induced tubular necrosis

QoS and Routing Performance Evaluation for IEEE 802.15.6 Body Sensor Networks Using Accurate Physical Layer

This chapter addresses the development of a specific framework for the accurate computation of the network topology (i.e., routing) suitable for medical applications. First, a comprehensive and detailed analytical framework for BAN performance evaluation is developed, obtaining closed-form expressions for the link probabilities of outage in the context of multi-user communications. This framework encompasses the effect of the environment, the topology, and the traffic intensity