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Myosin heavy chain composition in rat laryngeal muscle after denervation
P96
Otolaryngology Head and Neck Surgery August 1997
Research Forum - - Monday
mediator of neurotoxicity and an initiator of apoptosis in the CNS, NO may play a role in these processes in the cochlea. Poster 38
Vestibular Deficits in Belgian Waterslager Canaries
(Serinus canarius) SHERRI M. JONES, PhD (presenter), BRENDA M. RYALS,PhD, and STEPHEN H. COLBERT, BS, Columbia, Mo., and Harrisonburg, Va.
Belgian Waterslager canaries (BWC) have been shown to be a useful model for congenital auditory deficits. Studies have demonstrated morphological abnormalities in the cochlear sensory epithelium and associated hearing loss (Gleich et al. 1994, Okanoya and Dooling 1985; 1987). Weisleder et al, (1994) showed that vestibular hair cells of the saccule were abnormal in BWC compared with non-Waterslager canaries; however, no function was reported. The purpose of this study was to measure vestibular function in BWC by using short latency vestibular evoked potentials (VsEPs) to linear acceleration stimuli. Responses were recorded with vertex to mastoid leads by using traditional signal averaging. Response thresholds, latencies, and amplitudes were quantified and compared with non-Waterslager controls. Following measurements, birds were perfused transcardially, the temporal bones were dissected, and cochlear and vestibular organs were processed for scanning electron microscopy. The average number of hair cells in four different 2050 lam: areas of the saccular and utricular macula were determined; stereocilia bundle appearance and orientation were described. Results indicated that vestibular response thresholds were slightly, but significantly, higher for BWC, and response amplitudes were significantly reduced compared with non-Waterslagers. Response peak latenCies were not significantly different. Morphological findings were similar to published results. The stereocilia bundles in the saccule appeared disoriented, and the number of saccular hair cells was reduced for BWC, although not significantly. The utricle and ampullae appeared normal. Overall, results suggest that vestibular function is affected by congenital abnormalities in the vestibular epithelium of BWC and the functional deficits can be detected by VsEPs. (Support: UMC Otolaryngol. Res. Funds [SJ] and NIDCD CD001372 and Amer. Hear. Res. Found. [BR].) Poster 39
Limited Aging Effects in Human Thyroarytenoid Muscle Motor Units NAOYA TAKEDA, MD (presenter), and CHRISTY L. LUDLOW, PhD, Bethesda, Md.
Motor unit action potential durations are reliable for diagnosis of neuromuscular disorders. Increased motor unit durations have been demonstrated in many skeletal muscles in individuals over 60 years of age. To examine the relationship between age and motor unit durations in the thy-
roarytenoid muscle, bipolar needles were used to record from several locations in the right and left muscles in normal volunteers between 20 and 75 years of age. At least 10 firings of the same unit were identified before durations were measured. An average of four units were measured per muscle in 25 subjects. Below the age of 60, motor unit duration did not increase significantly with age. Twenty percent of the units measured in subjects over 60 years of age had longer durations than any of the units measured in subjects below 60 years of age. Aging effects in the thyroarytenoid muscle therefore were no greater than reported for other skeletal muscles. Different criteria for the normal range should be used, however, when diagnosing motor unit abnormalities in patients over 60 years of age. Poster 40
Myosin Heavy Chain Composition in Rat Laryngeal Muscle After Denervation AKIHIRO SHIOTANI, MD (presenter), and PAUL W. FLINT,MD, Baltimore, Md.
The effects of denervation on myosin heavy chain (MHC) expression in specific laryngeal muscles are characterized by using gel electrophoresis. Observed temporal changes in MHC composition will then be used to develop strategies for laryngeal reinnervation and gene therapy. In anesthetized rats the left recurrent and superior laryngeal nerves were divided. Animals were survived for 7, 14, 28, 90, and 180 days. Animals were euthanized, and the thyroarytenoid (TA), vocalis (VOC), posterior cricoarytenoid (PCA), lateral cricoarytenoid (LCA), and cricothyroid (CT) muscles were excised. Each muscle was processed for SDSPAGE, and densitometric measurements were obtained to determine composition of MHC fiber types. The relative MHC composition remains unchanged in the VOC, LCA, and CT. In the PCA the percentage of liB fibers decreases in the denervated condition, and the percentage of IIA/IIX fibers increases. In the TA type IIB remains constant (65%), and there is a moderate decrease in the IlL component. Type IIA/IIX fibers, normally absent in the TA, appear within the first week and remain present in all animals with the relative composition exceeding 20%. This study supports previous work with rat soleus muscle where IIA/IIX expression is favored in conditions with decreased neuromuscular activity. Further study will be undertaken to quantify expression of MHC components and to study factors modulating expression. (Supported by NIDCD grant 5K08 DC0081-03.) Poster 41
The Distribution of Slow Tonic Muscle Fibers in Human Thyroarytenoid Muscles YINGSHI HAM, MD (presenter), JUN WANG, MD, and IRA SANDERS, MD, New York, N.Y.
Recently, the existence of slow tonic muscle fibers (STF) was reported in the human thyroarytenoid muscle (TA). The
Otolaryngology Head and Neck Surgery August 1997
Research Forum - - Monday
mediator of neurotoxicity and an initiator of apoptosis in the CNS, NO may play a role in these processes in the cochlea. Poster 38
Vestibular Deficits in Belgian Waterslager Canaries
(Serinus canarius) SHERRI M. JONES, PhD (presenter), BRENDA M. RYALS,PhD, and STEPHEN H. COLBERT, BS, Columbia, Mo., and Harrisonburg, Va.
Belgian Waterslager canaries (BWC) have been shown to be a useful model for congenital auditory deficits. Studies have demonstrated morphological abnormalities in the cochlear sensory epithelium and associated hearing loss (Gleich et al. 1994, Okanoya and Dooling 1985; 1987). Weisleder et al, (1994) showed that vestibular hair cells of the saccule were abnormal in BWC compared with non-Waterslager canaries; however, no function was reported. The purpose of this study was to measure vestibular function in BWC by using short latency vestibular evoked potentials (VsEPs) to linear acceleration stimuli. Responses were recorded with vertex to mastoid leads by using traditional signal averaging. Response thresholds, latencies, and amplitudes were quantified and compared with non-Waterslager controls. Following measurements, birds were perfused transcardially, the temporal bones were dissected, and cochlear and vestibular organs were processed for scanning electron microscopy. The average number of hair cells in four different 2050 lam: areas of the saccular and utricular macula were determined; stereocilia bundle appearance and orientation were described. Results indicated that vestibular response thresholds were slightly, but significantly, higher for BWC, and response amplitudes were significantly reduced compared with non-Waterslagers. Response peak latenCies were not significantly different. Morphological findings were similar to published results. The stereocilia bundles in the saccule appeared disoriented, and the number of saccular hair cells was reduced for BWC, although not significantly. The utricle and ampullae appeared normal. Overall, results suggest that vestibular function is affected by congenital abnormalities in the vestibular epithelium of BWC and the functional deficits can be detected by VsEPs. (Support: UMC Otolaryngol. Res. Funds [SJ] and NIDCD CD001372 and Amer. Hear. Res. Found. [BR].) Poster 39
Limited Aging Effects in Human Thyroarytenoid Muscle Motor Units NAOYA TAKEDA, MD (presenter), and CHRISTY L. LUDLOW, PhD, Bethesda, Md.
Motor unit action potential durations are reliable for diagnosis of neuromuscular disorders. Increased motor unit durations have been demonstrated in many skeletal muscles in individuals over 60 years of age. To examine the relationship between age and motor unit durations in the thy-
roarytenoid muscle, bipolar needles were used to record from several locations in the right and left muscles in normal volunteers between 20 and 75 years of age. At least 10 firings of the same unit were identified before durations were measured. An average of four units were measured per muscle in 25 subjects. Below the age of 60, motor unit duration did not increase significantly with age. Twenty percent of the units measured in subjects over 60 years of age had longer durations than any of the units measured in subjects below 60 years of age. Aging effects in the thyroarytenoid muscle therefore were no greater than reported for other skeletal muscles. Different criteria for the normal range should be used, however, when diagnosing motor unit abnormalities in patients over 60 years of age. Poster 40
Myosin Heavy Chain Composition in Rat Laryngeal Muscle After Denervation AKIHIRO SHIOTANI, MD (presenter), and PAUL W. FLINT,MD, Baltimore, Md.
The effects of denervation on myosin heavy chain (MHC) expression in specific laryngeal muscles are characterized by using gel electrophoresis. Observed temporal changes in MHC composition will then be used to develop strategies for laryngeal reinnervation and gene therapy. In anesthetized rats the left recurrent and superior laryngeal nerves were divided. Animals were survived for 7, 14, 28, 90, and 180 days. Animals were euthanized, and the thyroarytenoid (TA), vocalis (VOC), posterior cricoarytenoid (PCA), lateral cricoarytenoid (LCA), and cricothyroid (CT) muscles were excised. Each muscle was processed for SDSPAGE, and densitometric measurements were obtained to determine composition of MHC fiber types. The relative MHC composition remains unchanged in the VOC, LCA, and CT. In the PCA the percentage of liB fibers decreases in the denervated condition, and the percentage of IIA/IIX fibers increases. In the TA type IIB remains constant (65%), and there is a moderate decrease in the IlL component. Type IIA/IIX fibers, normally absent in the TA, appear within the first week and remain present in all animals with the relative composition exceeding 20%. This study supports previous work with rat soleus muscle where IIA/IIX expression is favored in conditions with decreased neuromuscular activity. Further study will be undertaken to quantify expression of MHC components and to study factors modulating expression. (Supported by NIDCD grant 5K08 DC0081-03.) Poster 41
The Distribution of Slow Tonic Muscle Fibers in Human Thyroarytenoid Muscles YINGSHI HAM, MD (presenter), JUN WANG, MD, and IRA SANDERS, MD, New York, N.Y.
Recently, the existence of slow tonic muscle fibers (STF) was reported in the human thyroarytenoid muscle (TA). The