The calcineurin signal transduction pathway is essential for successful muscle regeneration in mdx dystrophic mice

Although mdx mice share the same genetic defect and lack dystrophin expression as in Duchenne muscular dystrophy (DMD), their limb muscles have a high regenerative capacity that ensures a more benign phenotype and essentially normal function. The cellular pathways responsible for this enhanced regenerative capacity are unknown. We tested the hypothesis that the calcineurin signal transduction pathway is essential for the successful regeneration following severe degeneration observed in the limb muscles of young mdx mice (2–4 weeks old) and that inhibition of this pathway using cyclosporine A (CsA) would exacerbate the dystrophic pathology. Eighteen-day-old mdx and C57BL/10 mice were treated with CsA for 16 days. CsA administration severely disrupted muscle regeneration in mdx mice, but had minimal effect in C57BL/10 mice. Muscles from CsA-treated mdx mice had fewer centrally nucleated fibers and extensive collagen, connective tissue, and mononuclear cell infiltration than muscles from vehicle-treated littermates. The deleterious effects of CsA on muscle morphology were accompanied by a 30–35% decrease in maximal force producing capacity. Taken together, these observations indicate that the calcineurin signal transduction pathway is a significant determinant of successful skeletal muscle regeneration in young mdx mice. Up-regulating this pathway may have clinical significance for DMD.

Microprocessor-based insulin delivery device with amperometric glucose sensing

This paper details the design of a closed-loop insulin delivery device, consisting of a glucose sensing circuit, and a basic microprocessor-based syringe pump. The glucose sensing circuit contains the required components to interface with CGMS's glucose sensor assembly, while the syringe pump design uses microprocessor to allow flexible control over the pump driver. Instrumentation developed in this paper provides a ready reference to other researchers on the construction of a closed-loop insulin delivery apparatus with amperometric glucose sensor.

Wireless instantaneous neurotransmitter concentration system-based amperometric detection of dopamine, adenosine, and glutamate for intraoperative neurochemical monitoring - laboratory investigation

Object  In a companion study, the authors describe the development of a new instrument named the Wireless Instantaneous Neurotransmitter Concentration System (WINCS), which couples digital telemetry with fast-scan cyclic voltammetry (FSCV) to measure extracellular concentrations of dopamine. In the present study, the authors describe the extended capability of the WINCS to use fixed potential amperometry (FPA) to measure extracellular concentrations of dopamine, as well as glutamate and adenosine. Compared with other electrochemical techniques such as FSCV or high-speed chronoamperometry, FPA offers superior temporal resolution and, in combination with enzyme-linked biosensors, the potential to monitor nonelectroactive analytes in real time.

Methods  The WINCS design incorporated a transimpedance amplifier with associated analog circuitry for FPA; a microprocessor; a Bluetooth transceiver; and a single, battery-powered, multilayer, printed circuit board. The WINCS was tested with 3 distinct recording electrodes: 1) a carbon-fiber microelectrode (CFM) to measure dopamine; 2) a glutamate oxidase enzyme–linked electrode to measure glutamate; and 3) a multiple enzyme–linked electrode (adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase) to measure adenosine. Proof-of-principle analyses included noise assessments and in vitro and in vivo measurements that were compared with similar analyses by using a commercial hardwired electrochemical system (EA161 Picostat, eDAQ; Pty Ltd). In urethane-anesthetized rats, dopamine release was monitored in the striatum following deep brain stimulation (DBS) of ascending dopaminergic fibers in the medial forebrain bundle (MFB). In separate rat experiments, DBS-evoked adenosine release was monitored in the ventrolateral thalamus. To test the WINCS in an operating room setting resembling human neurosurgery, cortical glutamate release in response to motor cortex stimulation (MCS) was monitored using a large-mammal animal model, the pig.

Results   The WINCS, which is designed in compliance with FDA-recognized consensus standards for medical electrical device safety, successfully measured dopamine, glutamate, and adenosine, both in vitro and in vivo. The WINCS detected striatal dopamine release at the implanted CFM during DBS of the MFB. The DBS-evoked adenosine release in the rat thalamus and MCS-evoked glutamate release in the pig cortex were also successfully measured. Overall, in vitro and in vivo testing demonstrated signals comparable to a commercial hardwired electrochemical system for FPA.

Conclusions  By incorporating FPA, the chemical repertoire of WINCS-measurable neurotransmitters is expanded to include glutamate and other nonelectroactive species for which the evolving field of enzyme-linked biosensors exists. Because many neurotransmitters are not electrochemically active, FPA in combination with enzyme-linked microelectrodes represents a powerful intraoperative tool for rapid and selective neurochemical sampling in important anatomical targets during functional neurosurgery.