Yoichiro Sugiyama

Differential Responses to Steroid Hormones in Fibroblasts From the Vocal Fold, Trachea, and Esophagus

There is accumulating evidence that fibroblasts are target cells for steroids such as sex hormones and corticoids. The characteristics of fibroblasts vary among tissues and organs. Our aim in this study is to examine differences in responses to steroid hormones among fibroblasts from different cervicothoracic regions. We compared the actions of steroid hormones on cultured fibroblasts from the vocal folds, which are considered to be the primary target of steroid hormones, and the trachea and esophagus in adult male rats. Expression of steroid hormone receptors (androgen receptor, estrogen receptor α, and glucocorticoid receptor) was identified by immunofluorescence histochemistry. Androgen receptor was much more frequently expressed in fibroblasts from the vocal fold than in those from the trachea and esophagus. Cell proliferation analysis showed that administration of testosterone, estradiol, or corticosterone suppressed growth of all 3 types of fibroblasts. However, mRNA expression for extracellular matrix-associated genes, including procollagen I and III and elastin, and hyaluronic acid synthase I was elevated only by addition of testosterone to fibroblasts from the vocal fold. These results indicate that each steroid hormone exerts region-specific effects on cervicothoracic fibroblasts with different properties through binding to specific receptors.

Activity of respiratory neurons in the rostral medulla during vocalization, swallowing, and coughing in guinea pigs.

To examine the relationship between the neuronal networks underlying respiration and non-respiratory behaviors such as vocalization and airway defensive reflexes, we compared the activity of respiratory neurons in the ventrolateral medulla during breathing with that during non-respiratory behaviors including vocalization, swallowing, and coughing in guinea pigs. During fictive vocalization the activity of augmenting expiratory neurons ceased, whereas the other types of expiratory neurons did not show a consistent tendency of increasing or decreasing activity. All inspiratory neurons discharged in synchrony with the phrenic nerve activity. Most of the phase-spanning neurons were activated throughout the vocal phase. During fictive swallowing, many expiratory and inspiratory neurons were silent, whereas many phase-spanning neurons were activated. During fictive coughing, many expiratory neurons were activated during the expiratory phase of coughing. Most inspiratory neurons discharged in parallel with the phrenic nerve activity during coughing. Many phase-spanning neurons were activated during the expiratory phase of coughing. These findings indicate that the medullary respiratory neurons help shape respiratory muscle nerve activity not only during breathing but also during these non-respiratory behaviors, and thus suggest that at least some of the respiratory neurons are shared among the neuronal circuits underlying the generation of breathing and non-respiratory behaviors.

Nucleus Tractus Solitarius

The nucleus tractus solitarius (NTS) is subdivided into nine subnuclei based on their cellular morphology. The NTS receives afferent input from the vagus, glossopharyngeal, and facial nerves. The NTS neurons mainly project to the medulla oblongata, pons, and thalamus and are involved in the regulation of respiration, heart and blood vessels, taste, and neurohypophysial hormone secretion. A variety of neurotransmitters have been identified in the somata and axons of the NTS neurons. Sensory nerve fibers in the larynx project through the internal branch of the superior laryngeal nerve to the interstitial subnucleus on the central side, and their somata are located in the nodose ganglion. We showed that sensory nerve fibers in the rat inferior laryngeal nerve project to the interstitial subnucleus, using wheat germ agglutinin-horseradish peroxidase (WGA-HRP) as a transganglionic tracer.

Expression of Sex Steroid Hormone Receptors in Vagal Motor Neurons Innervating the Trachea and Esophagus in Mouse

The medullary vagal motor nuclei, the nucleus ambiguus (NA) and dorsal motor nucleus of the vagus (DMV), innervate the respiratory and gastrointestinal tracts. We conducted immunohistochemical analysis of expression of the androgen receptor (AR) and estrogen receptor α (ERα), in relation to innervation of the trachea and esophagus via vagal motor nuclei in mice. AR and ERα were expressed in the rostral NA and in part of the DMV. Tracing experiments using cholera toxin B subunit demonstrated that neurons of vagal motor nuclei that innervate the trachea and esophagus express AR and ERα. There was no difference in expression of sex steroid hormone receptors between trachea- and esophagus-innervating neurons. These results suggest that sex steroid hormones may act on vagal motor nuclei via their receptors, thereby regulating functions of the trachea and esophagus.

Role of the retrotrapezoid nucleus/parafacial respiratory group in coughing and swallowing in guinea pigs

The retrotrapezoid/parafacial respiratory group (RTN/pFRG) located ventral to the facial nucleus plays a key role in regulating breathing, especially enhanced expiratory activity during hypercapnic conditions. To clarify the roles of the RTN/pFRG region in evoking coughing, during which reflexive enhanced expiration is produced, and in swallowing, during which the expiratory activity is consistently halted, we recorded extracellular activity from RTN/pFRG neurons during these fictive behaviors in decerebrate, paralyzed, and artificially ventilated guinea pigs. The activity of the majority of recorded respiratory neurons was changed in synchrony with coughing and swallowing. To further evaluate the contribution of RTN/pFRG neurons to these nonrespiratory behaviors, the motor output patterns during breathing, coughing, and swallowing were compared before and after brain stem transection at the caudal margin of RTN/pFRG region. In addition, the effects of transection at its rostral margin were also investigated to evaluate pontine contribution to these behaviors. During respiration, transection at the rostral margin attenuated the postinspiratory activity of the recurrent laryngeal nerve. Meanwhile, the late expiratory activity of the abdominal nerve was abolished after caudal transection. The caudal transection also decreased the amplitude of the coughing-related abdominal nerve discharge but did not abolish the activity. Swallowing could be elicited even after the caudal end transection. These findings raise the prospect that the RTN/pFRG contributes to expiratory regulation during normal respiration, although this region is not an essential element of the neuronal networks involved in coughing and swallowing.

Dorsal Motor Nucleus of the Vagus

The general visceral efferent fibers of the glossopharyngeal and vagus nerves originate from the dorsal motor nucleus of the vagus (DMNV), in which the parasympathetic preganglionic neurons are located. We showed that neurons of origin of parasympathetic preganglionic fibers in the superior laryngeal nerve are localized in the rostral DMNV, and some of them in the inferior laryngeal nerve have acetylcholine (Ach) or calcitonin gene-related peptide (CGRP).

Supportive effect of interferential current stimulation on susceptibility of swallowing in guinea pigs

Sensory-motor control of the pharyngeal swallow requires sensory afferent inputs from the pharynx and larynx evoked by introducing bolus into the pharynx. Patients with reduced sensitivity of the pharynx and larynx are likely to have a swallowing impairment, such as pre-swallow aspiration due to delayed swallow triggering. Interferential current stimulation applied to the neck is thought to improve the swallowing function of dysphagic patients, although the mechanism underlying the facilitatory effect of such stimulation remains unknown. In the present study, we examined the changes in the elicitability of swallowing due to the stimulation and the responses of the swallowing-related neurons in the nucleus tractus solitarius and in the area adjacent to the stimulation in decerebrate and paralyzed guinea pigs. The swallowing delay time was shortened by the stimulation, whereas the facilitatory effect of eliciting swallowing was attenuated by kainic acid injection into the nucleus tractus solitarius. Approximately half of the swallowing-related neurons responded to the stimulation. These data suggest that the interferential current stimulation applied to the neck could enhance the sensory afferent pathway of the pharynx and larynx, subserving excitatory inputs to the neurons of the swallowing pattern generator, thereby facilitating the swallowing reflex.

An oral pharyngeal scope for objective oropharyngeal examination: a new device for oropharyngeal study

Abstract Objective: There has been little progress in examination of the oropharynx with a light source such as electric light, a penlight, or a forehead mirror over the past 100 years. It is therefore necessary to develop methods to display and record oropharyngeal observations. Method: Since the aim of this study was to assess the safeness to use from the perspective of physicians, medical staffs, patients, and patients’ families and usefulness of pharyngeal scope, the number of devices was limited, the number of patients was not set based on hypothetical statistical tests. Results: A total of 150 volunteers were enrolled in this study. Among them, 96 underwent examination alone and the remaining 28 underwent treatment procedures. The study was done without any complications in all 150 cases. Most (91.3%) physicians hoped to continue using the new device if available. When comparing the use of the device for observation alone and for treatment procedures, there was no significant difference for evaluation items (pu2009>u2009.05) except convenience factor which received a significantly different (pu2009=u2009.0154) evaluation from physicians for observation alone and for treatment procedures. A positive evaluation was received about examination, recording/display and explanation from the patients and patients’ families. Conclusions: Our new device received positive evaluations by who underwent examination of the oral cavity and pharynx, recording of the results, and treatment procedures.

Clinical Assessment of Elderly Vocal Folds by Laryngoscopy

Laryngoscopy is an effective examination for assessing the morphological features of age-related vocal folds. In addition, disease-associated changes in the vocal folds in elderly people can also be diagnosed. Vocal fold atrophy is commonly identified as vocal fold bowing, which is characterized as a concaved edge of the vocal folds. The other typical disorder caused by atrophic changes in age-related vocal folds is sulcus vocalis. These changes are attributed to the volume reduction and degeneration of the extracellular matrix in the lamina propria in addition to atrophy of the intralaryngeal muscles. Stroboscopy is a useful and reliable method for examining vocal fold vibration. The reduced amplitude, aperiodic, and asymmetric vibration as along with the glottal gap are generally observed in elderly people with vocal fold atrophy. As such, both laryngoscopy and stroboscopy are better techniques not only to diagnose age-related vocal fold disorders, but also to evaluate disease-specific treatment.

Regenerative Effects of Basic Fibroblast Growth Factor on Restoration of Thyroarytenoid Muscle Atrophy Caused by Recurrent Laryngeal Nerve Transection

OBJECTIVESnVocal fold atrophy following unilateral vocal fold paralysis is caused by atrophy of the thyroarytenoid (TA) muscle and remains a challenge. Medialization procedures are popular treatment options; however, hoarseness often remains due to the reduction in mass or tension of the TA muscle. Therefore, in addition to medialization procedures, TA muscle reinnervation is desirable. In vivo studies have shown the potential for basic fibroblast growth factor (bFGF) to affect muscular and nerve regeneration. The present study aimed to examine the regenerative effects of bFGF on restoration of TA muscle atrophy caused by recurrent laryngeal nerve transection.nnnSTUDY DESIGNnProspective animal experiments with controls.nnnMETHODSnTA muscle atrophy was induced by unilateral transection of the recurrent laryngeal nerve. One month after transection, different doses (200u2009ng, 100u2009ng, 10u2009ng) of bFGF in 50u2009µL were repeatedly injected into the TA muscle four times with an interval of 1 week between injections. Saline only was injected in the sham group. Larynges were harvested for histologic and immunohistochemical examination 4 weeks after the final injection.nnnRESULTSnThe cross-sectional TA muscle area was significantly larger in the bFGF-treated groups compared with the sham-treated groups. Immunohistochemistry indicated that bFGF significantly increases the number of neuromuscular junctions and satellite cells in the TA muscle.nnnCONCLUSIONSnThese results suggest that local application of bFGF to the TA muscle may improve TA muscle atrophy caused by recurrent laryngeal nerve paralysis. Furthermore, bFGF may have regenerative effects on both nerves and muscles.