The Degradation of Botulinum Neurotoxin Light Chains Using PROTACs.

Botulinum neurotoxins are some of the most potent natural toxins known; they cause flaccid paralysis by inhibiting synaptic vesicle release. Some serotypes, notably serotype A and B, can cause persistent paralysis lasting for several months. Because of their potency and persistence, botulinum neurotoxins are now used to manage several clinical conditions, and there is interest in expanding their clinical applications using engineered toxins with novel substrate specificities.

Peptide-coated nanotube-based biosensor for the detection of disease-specific autoantibodies in human serum.

We demonstrate a label-free peptide-coated carbon nanotube-based immunosensor for the direct assay of human serum. A rheumatoid arthritis (RA)-specific (cyclic citrulline-containing) peptide, was immobilized to functionalized single-walled carbon nanotubes deposited on a quartz crystal microbalance (QCM) sensing crystal. Serum from RA patients was used to probe these nanotube-based sensors, and antibody binding was detected by QCM sensing.

The flutter device and expiratory pressures.

Purpose: Flutter therapy uses a handheld instrument that consists of a pipe-like device with a ball in the central core that oscillates during exhalation, providing oscillating positive expiratory pressure. The purpose of this study was to determine the effect of airflow and the incline of the device at the mouth on expiratory pressure and oscillation frequency.

Methods: A Flutter device was attached to a circuit that consisted of a pneumotachograph and a ventilator.

The ventilatory response to arousal from sleep is not fully explained by differences in CO(2) levels between sleep and wakefulness.

1. Arousal from sleep is associated with transient stimulation of ventilation above normal waking levels that predisposes to subsequent breathing instability and central apnoea. The transient hyperpnoea at arousal is normally explained by differences in arterial partial pressure of CO(2) (P(a,CO2)) between sleep and wakefulness, with a higher P(a,CO2) in sleep leading to stimulation of ventilation at arousal according to the awake ventilatory response to CO(2).

Acute and chronic effects of airway obstruction on canine left ventricular performance.

We used a canine model of chronic obstructive sleep apnea (OSA) to examine the effects of intermittent airway occlusion during sleep on left ventricular (LV) performance. Studies were performed in four dogs. The effects of acute airway occlusion on LV pressure and volume (on a background of chronic OSA) were determined with an impedance catheter and a high fidelity manometer.

Baroreflex control of heart rate in a canine model of obstructive sleep apnea.

We have recently demonstrated the development of systemic hypertension in a canine model of obstructive sleep apnea (OSA), but the underlying physiological mechanisms were not identified. Therefore, the purpose of this study was to examine the effect of OSA on arterial baroreceptor control of heart rate (HR) in this canine model. OSA was produced in three dogs for 1 to 3 mo.

Sleep architecture in a canine model of obstructive sleep apnea.

Obstructive sleep apnea (OSA) causes recurrent sleep disruption that is thought to contribute to excessive daytime sleepiness in patients with this disorder. The purpose of this study was to determine the specific effects of OSA on overall sleep architecture in a canine model of OSA. The advantage of this model is that sleep during long-term OSA can be compared to both normal sleep before OSA and recovery sleep after OSA.

Ventilatory and arousal responses to hypoxia and hypercapnia in a canine model of obstructive sleep apnea.

We have previously described a canine model of obstructive sleep apnea (OSA) in which sleep-wake state is monitored continuously by a computer that produces tracheal occlusion when sleep occurs. Our aim was to assess the effects of long-term application of this model on resting ventilation and on the ventilatory and arousal responses to hypercapnia and hypoxia. Five dogs were maintained on the model for 15.

Effect of obstructive sleep apnea versus sleep fragmentation on responses to airway occlusion.

Although the acute physiologic responses to apnea in patients with obstructive sleep apnea (OSA) have been well documented, the changes in these responses over the course of the disease have not been investigated. The purpose of this study was to use a canine model of OSA to examine the long-term effects of sleep apnea on the acute responses to airway occlusion during sleep. Four dogs were studied during a control period before induction of OSA, during a period of OSA (83-133 d), and following cessation of OSA.

Obstructive sleep apnea as a cause of systemic hypertension. Evidence from a canine model.

Several epidemiological studies have identified obstructive sleep apnea (OSA) as a risk factor for systemic hypertension, but a direct etiologic link between the two disorders has not been established definitively. Furthermore, the specific physiological mechanisms underlying the association between OSA and systemic hypertension have not been identified. The purpose of this study was to systematically examine the effects of OSA on daytime and nighttime blood pressure (BP).

Validation of a telemetry system for long-term measurement of blood pressure.

We have used an implanted telemetry system to continuously monitor blood pressure (BP) in three dogs for durations ranging from 28 to 75 wk after implantation. Measurements of BP obtained by telemetry were compared every 3-12 wk, with measurements of BP recorded with a manometer-tipped catheter that was inserted into a femoral artery. Over a wide range of both physiological and pharmacologically manipulated pressures (40-200 mmHg), the values of BP obtained by the two methods were highly correlated (all r > 0.

Immediate effects of arousal from sleep on cardiac autonomic outflow in the absence of breathing in dogs.

To determine the immediate effects of arousal from non-rapid-eye-movement (non-REM) sleep on cardiac sympathetic and parasympathetic activities, six dogs were studied breathing through an endotracheal tube inserted into a chronic tracheostomy. Mean heart rates (HRs) during non-REM sleep were compared with 1) awake periods immediately after spontaneous arousals (ARs) and 2) later periods of stable relaxed wakefulness (RW). During spontaneous breathing, HR increased after AR (mean = 31.

Respiratory-related heart rate variability persists during central apnea in dogs: mechanisms and implications.

The aim of this study was to determine the mechanism(s) responsible for the persistence of respiratory sinus arrhythmia (RSA) during central apnea. In five awake dogs, heart rate (HR) was recorded during constant mechanical ventilation (MV) and during central apneas produced by cessation of MV. For each of 10 control ventilator cycles before MV was stopped, instantaneous HR was plotted against the time from the onset of lung inflation; the fundamental and first harmonic of a sine wave (at the ventilator frequency) was then fitted to the HR data.

Canine model of obstructive sleep apnea: model description and preliminary application.

This report describes a canine model of obstructive sleep apnea (OSA) developed in our laboratory and the results of its preliminary short-term application. Healthy adult dogs were prepared with a tracheostomy and with implanted electroencephalographic and nuchal electromyographic recording electrodes. A silent occlusion valve was attached to the outer end of the endotracheal tube.

Tonic respiratory drive in the absence of rhythm generation in the conscious dog.

This study was designed to determine whether a chemoreceptor-mediated tonic respiratory drive exists below the apneic threshold. Expiratory (triangularis sterni) and inspiratory (diaphragm and parasternal intercostal) electromyographic activities were recorded in three awake relaxed dogs breathing through an endotracheal tube inserted into a permanent tracheostomy. The cervical vagus nerves were cold blocked to avoid the complicating effects of vagal inputs on respiratory activity.

Effects of sleep on the tonic drive to respiratory muscle and the threshold for rhythm generation in the dog.

1. The present study was designed to determine the effect of sleep on the tonic output to respiratory muscle and on the level of chemical respiratory stimulation required to produce rhythmic respiratory output. 2.

Effect of aging on metabolic respiratory control in sleeping dogs.

We examined the effects of aging on the metabolic respiratory control system by measuring changes with time in steady-state minute volume of ventilation (VI), alveolar carbon dioxide pressure (PACO2), and ventilatory and arousal responses to hypercapnia and hypoxia during slow-wave sleep (SWS). Studies were performed longitudinally in six healthy dogs over a span of 3 to 7 yr, corresponding biologically to 12 to 24 human yr. In each of the dogs aging was associated with a decrease in steady state VI during SWS, from 6.

Effect of inspiratory muscle unloading on arousal responses to CO2 and hypoxia in sleeping dogs.

Chemical respiratory stimuli can induce arousal from sleep, but the specific mechanisms involved have not been established. Therefore, we tested the hypothesis that mechanoreceptor stimuli arising in the ventilatory apparatus have a role in the arousal responses to progressive hypercapnia and hypoxia by comparing arousal responses during spontaneous ventilation with those obtained when the inspiratory muscles were unloaded by mechanical ventilatory assistance. Studies were performed in three trained dogs in which the adequacy of inspiratory muscle unloading was verified by diaphragmatic electromyographic (EMG) recordings.

Abdominal muscle activation by respiratory stimuli in conscious dogs.

The responses of the diaphragm, external oblique, and transversus abdominis muscles to hyperoxic hypercapnia and isocapnic hypoxia were studied in four awake dogs to test the hypothesis that central and peripheral chemoreceptor inputs result in different patterns of respiratory muscle activation. The dogs were trained to lie quietly in place, and electromyographic (EMG) discharges of the diaphragm (EMGdi), external oblique (EMGeo), and transversus abdominis (EMGta) were recorded from chronically implanted electrodes. Both hypercapnia and hypoxia recruited EMGeo and EMGta activity, but at comparable levels of minute volume of ventilation the EMG activity of the abdominal muscles was greater during hypercapnia than during hypoxia.

Interaction of chemical and mechanical respiratory stimuli in the arousal response to hypoxia in sleeping dogs.

The role of respiratory mechanoreceptor stimuli in the arousal response to hypoxia was studied in three trained dogs. The dogs breathed through a cuffed endotracheal tube inserted through a chronic tracheostomy, and resistive loads of 8 to 49 cm H2O/L/s were added to the expiratory circuit. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and isocapnic progressive hypoxia was induced by a rebreathing technique.

Respiratory muscle activation by chemical stimuli in awake and sleeping dogs.

The present findings in awake and sleeping dogs confirm the early observations in anesthetized cats (Bainton et al., 1978; Sears et al., 1982), and more recent studies in awake and sleeping humans (Takasaki et al.

Replication-defective vectors of reticuloendotheliosis virus transduce exogenous genes into somatic stem cells of the unincubated chicken embryo.

Replication-defective vectors derived from reticuloendotheliosis virus were used to transduce exogenous genes into early somatic stem cells of the chicken embryo. One of these vectors transduced and expressed the chicken growth hormone coding sequence. The helper cell line, C3, was used to generate stocks of vector containing about 10(4) transducing units per ml.

Germline transmission of exogenous genes in the chicken.

Difficulties associated with in vitro manipulation and culture of the early chicken embryo have restricted generation of transgenic chickens to approaches that use replication-competent retroviruses. The need to produce transgenic chickens in the absence of replicating virus prompted development of a new method of gene transfer into the chicken. Microinjection of the replication-defective reticuloendotheliosis virus (REV) vector ME111 beneath unincubated chicken embryo blastoderms results in infection of germline stem cells.

Effect of acute diaphragm paralysis on ventilation in awake and sleeping dogs.

The mechanisms responsible for hypoventilation during rapid-eye-movement (REM) sleep in patients with diaphragmatic weakness are not clear. Therefore, we studied the effects of unilateral (UDP) and bilateral (BDP) diaphragmatic paralysis on ventilation during wakefulness (W), slow-wave sleep (SWS), and REM sleep. Studies were performed in 3 trained dogs in which small silicone cuffs had been implanted surgically around the phrenic nerves.