[Show abstract][Hide abstract] ABSTRACT: An autosomal recessive disease of Black Russian Terriers was previously described as a juvenile-onset, laryngeal paralysis and polyneuropathy similar to Charcot Marie Tooth disease in humans. We found that in addition to an axonal neuropathy, affected dogs exhibit microphthalmia, cataracts, and miotic pupils. On histopathology, affected dogs exhibit a spongiform encephalopathy characterized by accumulations of abnormal, membrane-bound vacuoles of various sizes in neuronal cell bodies, axons and adrenal cells. DNA from an individual dog with this polyneuropathy with ocular abnormalities and neuronal vacuolation (POANV) was used to generate a whole genome sequence which contained a homozygous RAB3GAP1:c.743delC mutation that was absent from 73 control canine whole genome sequences. An additional 12 Black Russian Terriers with POANV were RAB3GAP1:c.743delC homozygotes. DNA samples from 249 Black Russian Terriers with no known signs of POANV were either heterozygotes or homozygous for the reference allele. Mutations in human RAB3GAP1 cause Warburg micro syndrome (WARBM), a severe developmental disorder characterized by abnormalities of the eye, genitals and nervous system including a predominantly axonal peripheral neuropathy. RAB3GAP1 encodes the catalytic subunit of a GTPase activator protein and guanine exchange factor for Rab3 and Rab18 respectively. Rab proteins are involved in membrane trafficking in the endoplasmic reticulum, axonal transport, autophagy and synaptic transmission. The neuronal vacuolation and membranous inclusions and vacuoles in axons seen in this canine disorder likely reflect alterations of these processes. Thus, this canine disease could serve as a model for WARBM and provide insight into its pathogenesis and treatment.
Preview · Article · Nov 2015 · Neurobiology of Disease
[Show abstract][Hide abstract] ABSTRACT: Presbyphagia affects approximately 40 % of otherwise healthy people over 60 years of age. Hence, it is a condition of primary aging rather than a consequence of primary disease. This distinction warrants systematic investigations to understand the causal mechanisms of aging versus disease specifically on the structure and function of the swallowing mechanism. Toward this goal, we have been studying healthy aging C57BL/6 mice (also called B6), the most popular laboratory rodent for biomedical research. The goal of this study was to validate this strain as a model of presbyphagia for translational research purposes. We tested two age groups of B6 mice: young (4-7 months; n = 16) and old (18-21 months; n = 11). Mice underwent a freely behaving videofluoroscopic swallow study (VFSS) protocol developed in our lab. VFSS videos (recorded at 30 frames per second) were analyzed frame-by-frame to quantify 15 swallow metrics. Six of the 15 swallow metrics were significantly different between young and old mice. Compared to young mice, old mice had significantly longer pharyngeal and esophageal transit times (p = 0.038 and p = 0.022, respectively), swallowed larger boluses (p = 0.032), and had a significantly higher percentage of ineffective primary esophageal swallows (p = 0.0405). In addition, lick rate was significantly slower for old mice, measured using tongue cycle rate (p = 0.0034) and jaw cycle rate (p = 0.0020). This study provides novel evidence that otherwise healthy aging B6 mice indeed develop age-related changes in swallow function resembling presbyphagia in humans. Specifically, aging B6 mice have a generally slow swallow that spans all stages of swallowing: oral, pharyngeal, and esophageal. The next step is to build upon this foundational work by exploring the responsible mechanisms of presbyphagia in B6 mice.
[Show abstract][Hide abstract] ABSTRACT: This study adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research. Successful outcomes are dependent upon three critical components: test chambers that permit self-feeding while standing unrestrained in a confined space, recipes that mask the aversive taste/odor of commercially-available oral contrast agents, and a step-by-step test protocol that permits quantification of swallow physiology. Elimination of one or more of these components will have a detrimental impact on the study results. Moreover, the energy level capability of the fluoroscopy system will determine which swallow parameters can be investigated. Most research centers have high energy fluoroscopes designed for use with people and larger animals, which results in exceptionally poor image quality when testing mice and other small rodents. Despite this limitation, we have identified seven VFSS parameters that are consistently quantifiable in mice when using a high energy fluoroscope in combination with the new murine VFSS protocol. We recently obtained a low energy fluoroscopy system with exceptionally high imaging resolution and magnification capabilities that was designed for use with mice and other small rodents. Preliminary work using this new system, in combination with the new murine VFSS protocol, has identified 13 swallow parameters that are consistently quantifiable in mice, which is nearly double the number obtained using conventional (i.e., high energy) fluoroscopes. Identification of additional swallow parameters is expected as we optimize the capabilities of this new system. Results thus far demonstrate the utility of using a low energy fluoroscopy system to detect and quantify subtle changes in swallow physiology that may otherwise be overlooked when using high energy fluoroscopes to investigate murine disease models.
Preview · Article · Mar 2015 · Journal of Visualized Experiments
[Show abstract][Hide abstract] ABSTRACT: A/J mice develop progressive hearing loss that begins before 1 month of age and is attributed to cochlear hair cell degeneration. Screening tests indicated that this strain also develops early onset vestibular dysfunction and has otoconial deficits. The purpose of this study was to characterize the vestibular dysfunction and macular structural pathology over the lifespan of A/J mice. Vestibular function was measured using linear vestibular evoked potentials (VsEPs). Macular structural pathology was evaluated using light microscopy, scanning electron microscopy, transmission electron microscopy, confocal microscopy and Western blotting. Individually, vestibular functional deficits in mice ranged from mild to profound. On average, A/J mice had significantly reduced vestibular sensitivity (elevated VsEP response thresholds and smaller amplitudes), whereas VsEP onset latency was prolonged compared to age-matched controls (C57BL/6). A limited age-related vestibular functional loss was also present. Structural analysis identified marked age-independent otoconial abnormalities in concert with some stereociliary bundle defects. Macular epithelia were incompletely covered by otoconial membranes with significantly reduced opacity and often contained abnormally large or giant otoconia as well as normal-appearing otoconia. Elevated expression of key otoconins (i.e., otoconin 90, otolin and keratin sulfate proteoglycan) ruled out the possibility of reduced levels contributing to otoconial dysgenesis. The phenotype of A/J was partially replicated in a consomic mouse strain (C57BL/6J-Chr 17(A/J)/NaJ), thus indicating that Chr 17(A/J) contained a trait locus for a new gene variant responsible to some extent for the A/J vestibular phenotype. Quantitative trait locus analysis identified additional epistatic influences associated with chromosomes 1, 4, 9 and X. Results indicate that the A/J phenotype represents a complex trait, and the A/J mouse strain presents a new model for the study of mechanisms underlying otoconial formation and maintenance.
No preview · Article · Feb 2015 · Mammalian Genome
[Show abstract][Hide abstract] ABSTRACT: Treatment for esophageal dysmotility is currently limited to primarily pharmacologic intervention, which has questionable utility and frequently associated negative side effects. A potential behavioral intervention for esophageal dysmotility is the effortful oropharyngeal swallow. A previous pilot study using water perfusion manometry found an increase in distal esophageal amplitudes during effortful vs non-effortful swallowing. The current study sought to duplicate the previous study with improvements in methodology.
The effects of swallow condition (effortful vs non-effortful), sensor site, and gender on esophageal amplitude, duration, velocity, and bolus clearance were examined for 18 adults (nine males and nine females, mean age = 29.9 years) via combined solid-state manometry and intraluminal impedance.
The effortful swallow condition yielded significantly higher esophageal amplitudes across all sensor locations (P < 0.05). Further, the effortful swallowing decreased the risk of incomplete bolus clearance when compared with non-effortful swallowing (OR: 0.51; 95% CI: 0.30-0.86).
With improved manometric instrumentation, larger participant numbers, and methodology that controlled for potential confounding factors, this study confirms and advances the results of the previous pilot study: Volitional manipulation of the oropharyngeal phase of swallowing using the effortful swallow indeed affects esophageal physiology. Thus, the effortful swallow offers a behavioral manipulation of the esophageal phase of swallowing, and future studies will determine its clinical potential for treating esophageal dysmotility in patient populations.
Full-text · Article · Mar 2012 · Neurogastroenterology and Motility
[Show abstract][Hide abstract] ABSTRACT: We recently established that the SOD1-G93A transgenic mouse is a suitable model for oral-stage dysphagia in amyotrophic lateral
sclerosis (ALS). The purpose of the present study was to determine whether it could serve as a model for pharyngeal-stage
dysphagia as well. Electrophysiological and histological experiments were conducted on end-stage SOD1-G93A transgenic mice
(n=9) and age-matched wild-type (WT) littermates (n=12). Transgenic mice required a twofold higher stimulus frequency (40Hz) applied to the superior laryngeal nerve (SLN)
to evoke swallowing compared with WT controls (20Hz); transgenic females required a significantly higher (P<0.05) stimulus frequency applied to the SLN to evoke swallowing compared with transgenic males. Thus, both sexes demonstrated
electrophysiological evidence of pharyngeal dysphagia but symptoms were more severe for females. Histological evidence of
neurodegeneration (vacuoles) was identified throughout representative motor (nucleus ambiguus) and sensory (nucleus tractus
solitarius) components of the pharyngeal stage of swallowing, suggesting that pharyngeal dysphagia in ALS may be attributed
to both motor and sensory pathologies. Moreover, the results of this investigation suggest that sensory stimulation approaches
may facilitate swallowing function in ALS.
KeywordsAmyotrophic lateral sclerosis-ALS-Dysphagia-Superoxide dismutase-SOD1-G93A-Mouse Superior laryngeal nerve-Electrical stimulation-Deglutition-Deglutition disorders
[Show abstract][Hide abstract] ABSTRACT: There is an increasing interest in using mouse models for electrodiagnostic research. Studying transgenic mice with various pathologies adds to our knowledge of the natural history of a disease. It is imperative, however, to compare disease models with the appropriate control.
For these animals to be used in electrodiagnostic research, reference values must be set. If reference values are not available, the validity of data are highly questionable. We propose a method of obtaining mixed nerve action potentials and collect reference values from the sural nerve of mice.
The results were a mean peak latency of 1.74 msecs on the right and 1.89 msecs on the left. The mean amplitude was 17.0 microV on the left and 21.6 microV on the right.
In future studies, these reference values can be useful tools in analysis of murine subjects.
No preview · Article · Apr 2009 · American journal of physical medicine & rehabilitation / Association of Academic Physiatrists
[Show abstract][Hide abstract] ABSTRACT: Relatively little is known about the underlying neuropathology of dysphagia in amyotrophic lateral sclerosis (ALS); thus, effective treatments remain elusive. Tremendous progress toward understanding and treating dysphagia in ALS may be possible through the use of an animal model of dysphagia in ALS research; however, no such animal model currently exists. The most logical candidate to consider is the SOD1-G93A transgenic mouse, the most widely investigated animal model of ALS. To investigate whether this animal model develops dysphagia, oral behaviors (lick and mastication rates) of SOD1-G93A transgenic mice (n = 30) were evaluated at three time points based on hind limb motor function: asymptomatic (60 days), disease onset (approximately 110 days), and disease end-stage (approximately 140 days). Age-matched nontransgenic littermates (n = 30) served as controls. At each time point, lick and mastication rates were significantly lower (p < 0.05) for transgenic mice compared with controls. Histologic analysis of the brainstem showed marked neurodegeneration (vacuolation) of the trigeminal and hypoglossal nuclei, two key motor components involved in mastication and licking behaviors. These results demonstrate a clinicopathologic correlation of oral dysfunction in SOD1-G93A transgenic mice, thereby establishing the SOD1-G93A transgenic mouse as a bona fide animal model of oral dysphagia in ALS.
[Show abstract][Hide abstract] ABSTRACT: The effect of an effortful swallow on the healthy adult esophagus was investigated using concurrent oral and esophageal manometry (water perfusion system) on ten normal adults (5 males and 5 females, 20-35 years old) while swallowing 5-ml boluses of water. The effects of gender, swallow condition (effortful versus noneffortful swallows), and sensor site within the oral cavity, esophageal body, and lower esophageal sphincter (LES) were examined relative to amplitude, duration, and velocity of esophageal body contractions, LES residual pressure, and LES relaxation duration. The results of this study provide novel evidence that an effortful oropharyngeal swallow has an effect on the esophageal phase of swallowing. Specifically, effortful swallowing resulted in significantly increased peristaltic amplitudes within the distal smooth muscle region of the esophagus, without affecting the more proximal regions containing striated muscle fibers. The findings pertaining to the LES are inconclusive and require further exploration using methods that permit more reliable measurements of LES function. The results of this study hold tremendous clinical potential for esophageal disorders that result in abnormally low peristaltic pressures in the distal esophageal body, such as achalasia, scleroderma, and ineffective esophageal motility. However, additional studies are necessary to both replicate and extend the present findings, preferably using a solid-state manometric system in conjunction with bolus flow testing on both normal and disordered populations, to fully characterize the effects of an effortful swallow on the esophagus.
[Show abstract][Hide abstract] ABSTRACT: Recent observations demonstrated that translation of mRNAs may occur in axonal processes at sites that are long distances away from the neuronal perikaria. While axonal protein synthesis has been documented in several studies, the mechanism of its regulation remains unclear. The aim of this study was to investigate whether RNA interference (RNAi) may be one of the pathways that control local protein synthesis in axons. Here we show that sciatic nerve contains Argonaute2 nuclease, fragile X mental retardation protein, p100 nuclease, and Gemin3 helicase-components of the RNA-induced silencing complex (RISC). Application of short-interfering RNAs against neuronal beta-tubulin to the sciatic nerve initiated RISC formation, causing a decrease in levels of neuronal beta-tubulin III mRNA and corresponding protein, as well as a significant reduction in retrograde labeling of lumbar motor neurons. Our observations indicate that RNAi is functional in peripheral mammalian axons and is independent from the neuronal cell body or Schwann cells. We introduce a concept of local regulation of axonal translation via RNAi.
Full-text · Article · Apr 2007 · The FASEB Journal