Intracellular signaling pathways regulating net protein balance following diaphragm muscle denervation.

Unilateral denervation (DNV) of rat diaphragm muscle increases protein synthesis at 3 days after DNV (DNV-3D) and degradation at DNV-5D, such that net protein breakdown is evident by DNV-5D. On the basis of existing models of protein balance, we examined DNV-induced changes in Akt, AMP-activated protein kinase (AMPK), and ERK½ activation, which can lead to increased protein synthesis via mammalian target of rapamycin (mTOR)/p70S6 kinase (p70S6K), glycogen synthase kinase-3β (GSK3β), or eukaryotic initiation factor 4E (eIF4E), and increased protein degradation via forkhead box protein O (FoxO). Protein phosphorylation was measured using Western analyses through DNV-5D.

Neuregulin-1 at synapses on phrenic motoneurons.

The neuregulin (NRG) family of trophic factors is present in the central and peripheral nervous systems and participates in the survival, proliferation, and differentiation of many different cell types, including motoneurons. NRG1 was first characterized by its role in the formation of the neuromuscular junction, and recently it was shown to play a crucial role in modulating glutamatergic and cholinergic transmission in the central nervous system of adult rats. However, little is known about NRG1's role in adult motor systems.

Diaphragm motor unit recruitment in rats.

We hypothesized that considerable force reserve exists for the diaphragm muscle (DIAm) to generate transdiaphragmatic pressures (Pdi) necessary to sustain ventilation. In rats, we measured Pdi and DIAm EMG activity during different ventilatory (eupnea and hypoxia (10% O(2))-hypercapnia (5% CO(2))) and non-ventilatory (airway occlusion and sneezing induced by intranasal capsaicin) behaviors. Compared to maximum Pdi (Pdi(max) generated by bilateral phrenic nerve stimulation), the Pdi generated during eupnea (21+/-2%) and hypoxia-hypercapnia (28+/-4%) were significantly less (p<0.

Distribution of major basic protein on human airway following in vitro eosinophil incubation.

Major basic protein (MBP) released from activated eosinophils may influence airway hyperresponsiveness (AHR) by either direct effects on airway myocytes or by an indirect effect. In this study, human bronchi, freshly isolated human eosinophils, or MBP purified from human eosinophil granules were incubated for studying eosinophil infiltration and MBP localization. Eosinophils immediately adhered to intact human airway as well as to cultured human airway myocytes and epithelium.

Impairment of diaphragm muscle force and neuromuscular transmission after normothermic cardiopulmonary bypass: effect of low-dose inhaled CO.

Cardiopulmonary bypass (CPB) is associated with significant postoperative morbidity, but its effects on the neuromuscular system are unclear. Recent studies indicate that even relatively short periods of mechanical ventilation result in significant neuromuscular effects. Carbon monoxide (CO) has gained recent attention as therapy to reduce the deleterious effects of CPB.

Mechanisms underlying hypothermia-induced cardiac contractile dysfunction.

Rewarming patients after profound hypothermia may result in acute heart failure and high mortality (50-80%). However, the underlying pathophysiological mechanisms are largely unknown. We characterized cardiac contractile function in the temperature range of 15-30 degrees C by measuring the intracellular Ca(2+) concentration ([Ca(2+)](i)) and twitch force in intact left ventricular rat papillary muscles.

Correlation of respiratory activity of contralateral diaphragm muscles for evaluation of recovery following hemiparesis.

Respiration is impaired by disruption of the central drive for inspiration to the diaphragm muscle (DIAm). Some function may recover involving nerve regeneration, reinnervation or neuroplasticity. A research animal model involves inducing hemiparesis of the DIAm and monitoring any recovery under different conditions.

Effect of collagen digestion on the passive elastic properties of diaphragm muscle in rat.

Effects of collagen digestion have been defined up to the fibril level. However, the question remains as to whether the alteration of skeletal muscle extracellular matrix (ECM) affects a muscle's passive elastic response. Various elastography methods have been applied as tools for evaluating the mechanical properties and ECM content of skeletal muscle.

Characterization of secophalloidin-induced force loss in cardiac myofibrils.

Secophalloidin (SPH) is known to cause in cardiac myofibrils force without Ca(2+) (half-maximal effect approximately 2 mM) followed by irreversible loss of Ca(2+)-activated force. At maximal Ca(2+) activation, SPH increases force (half-maximal effect < 0.1 mM).

Neuromuscular adaptations to respiratory muscle inactivity.

Cervical spinal cord injury results in significant functional impairment. It is important to understand the neuroplasticity in response to inactivity of respiratory muscles in order to prevent any associated effects that limit functional recovery. Recent studies have examined the mechanisms involved in inactivity-induced neuroplasticity of diaphragm motor units.

Role of neurotrophins in recovery of phrenic motor function following spinal cord injury.

Many individuals who sustain a cervical spinal cord injury are unable to maintain adequate ventilation due to diaphragm muscle paralysis. These patients become dependent on mechanical ventilators and this situation is associated with ongoing problems with pulmonary clearance, infections, and lung injury leading to significant morbidity and reduced life expectancy. Therefore, functional recovery of rhythmic phrenic activity and the ability to generate expulsive forces would dramatically affect the quality of life of patients with cervical spinal cord injury.

Retrograde labeling of phrenic motoneurons by intrapleural injection.

Studies of motoneuron plasticity during development or in response to injury or disease rely on the ability to correctly identify motoneurons innervating specific muscle groups. Commonly, injections of retrograde tracer molecules into a target muscle or into a transected nerve are used to label specific motoneuron pools. However, intramuscular injection does not consistently label all motoneurons in the target pool; and either injection site may involve additional surgical procedures and muscle or nerve perturbations.

The effect of denervation on protein synthesis and degradation in adult rat diaphragm muscle.

Previous studies showed that unilateral denervation (DNV) of the rat diaphragm muscle (DIAm) results in loss of myosin heavy chain protein by 1 day after DNV. We hypothesize that DNV decreases net protein balance as a result of activation of the ubiquitin-proteasome pathway. In DIAm strips, protein synthesis was measured by incorporation of 3H-Tyr, and protein degradation was measured by Tyr release at 1, 3, 5, 7, and 14 days after DNV.

Wireless Instantaneous Neurotransmitter Concentration System-based amperometric detection of dopamine, adenosine, and glutamate for intraoperative neurochemical monitoring.

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.

Effect of proinflammatory cytokines on regulation of sarcoplasmic reticulum Ca2+ reuptake in human airway smooth muscle.

Airway inflammation leads to increased intracellular Ca(2+) ([Ca(2+)](i)) levels in airway smooth muscle (ASM) cells. Sarcoplasmic reticulum Ca(2+) release and reuptake are key components of ASM [Ca(2+)](i) regulation. Ca(2+) reuptake occurs via sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA) and is regulated by the inhibitory protein phospholamban (PLB) in many cell types.

Characterization of primary cilia in human airway smooth muscle cells.

Background: Considerable evidence indicates a key role for primary cilia of mammalian cells in mechanochemical sensing. Dysfunctions of primary cilia have been linked to the pathogenesis of several human diseases. However, cilia-related research has been limited to a few cell and tissue types; to our knowledge, no literature exists on primary cilia in airway smooth muscle (ASM).

Changes in cardiovascular beta-adrenoceptor responses during hypothermia.

The purpose of this study was to determine cardiovascular beta-adrenergic responses during hypothermia. In the present study, we used isoproterenol (Iso), a nonselective, potent beta-adrenoceptor agonist, well known for its positive chronotropic and inotropic pharmacologic actions at normothermia. Rats were instrumented to measure mean arterial pressure (MAP) and left ventricular (LV) pressure-volume changes using a Millar pressure-volume conductance catheter.

Trophic factor expression in phrenic motor neurons.

The function of a motor neuron and the muscle fibers it innervates (i.e., a motor unit) determines neuromotor output.

Key aspects of phrenic motoneuron and diaphragm muscle development during the perinatal period.

At the time of birth, respiratory muscles must be activated to sustain ventilation. The perinatal development of respiratory motor units (comprising an individual motoneuron and the muscle fibers it innervates) shows remarkable features that enable mammals to transition from in utero conditions to the air environment in which the remainder of their life will occur. In addition, significant postnatal maturation is necessary to provide for the range of motor behaviors necessary during breathing, swallowing, and speech.

Regulation of sarcoplasmic reticulum Ca2+ reuptake in porcine airway smooth muscle.

Regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) in airway smooth muscle (ASM) during agonist stimulation involves sarcoplasmic reticulum (SR) Ca(2+) release and reuptake. The sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) is key to replenishment of SR Ca(2+) stores. We examined regulation of SERCA in porcine ASM: our hypothesis was that the regulatory protein phospholamban (PLN) and the calmodulin (CaM)-CaM kinase (CaMKII) pathway (both of which are known to regulate SERCA in cardiac muscle) play a role.

Developmental effects on myonuclear domain size of rat diaphragm fibers.

During early postnatal development in rat diaphragm muscle (Diam), significant fiber growth and transitions in myosin heavy chain (MHC) isoform expression occur. Similar to other skeletal muscles, Diam fibers are multinucleated, and each myonucleus regulates the gene products within a finite volume: the myonuclear domain (MND). We hypothesized that postnatal changes in fiber cross-sectional area (CSA) are associated with increased number of myonuclei so that the MND size is maintained.