Akihiro Katada

Lombard reflex during PAG-induced vocalization in decerebrate cats

The Lombard reflex occurs when a speaker increases his vocal effort while speaking in the presence of ambient noise. The purpose of this study was to clarify whether the Lombard reflex can be evoked during controlled vocalization in an animal model. In decerebrate cats, repetitive electrical stimulation was applied to the midbrain periaqueductal gray (PAG) to evoke vocalization. Pure tone auditory stimulation was delivered through a loudspeaker. The activities of the laryngeal adductor muscle, diaphragm and external oblique abdominal muscle and the voice intensity were measured during PAG stimulation, in the presence and absence of the auditory stimulation. To clarify the effects of the auditory laryngeal reflex on the activity of laryngeal adductor motoneurons, the amplitude of the laryngeal reflex evoked by single shock stimulation of the superior laryngeal nerve was also measured during respiration, in the presence and absence of auditory stimulation. The sound made by the cats due to PAG-induced vocalization was augmented by exposure to auditory stimulation, and the activities of the laryngeal adductor muscle and external oblique abdominal muscle were also augmented. During respiration, auditory stimulation also increased the amplitude of the laryngeal reflex evoked in the laryngeal adductor muscle. These results demonstrate that the essential neuronal mechanisms for evoking the Lombard reflex exist within the brainstem.

Functional role of ventral respiratory group expiratory neurons during vocalization

The activities of expiratory neurons of the caudal ventral respiratory group (cVRG) (n = 31) were recorded extracellularly during vocalization in unanesthetized, decerebrate cats. Vocalization was induced by electrical stimulation (0.2 ms, 20-80 microA, 100 Hz, lasting for 2-5 s) of the periaqueductal gray (PAG). The firing rates of more than two-thirds of the neurons (24/31) increased during periods of vocalization induced by stimulation of the PAG, with an increase in abdominal muscle activities. The axons of most of these neurons (19/24) projected to the contralateral lumbar spinal cord, and one-third of the bulbospinal neurons (6/19) were orthodromically activated by stimulation of the PAG. Even after sectioning of the axons of bulbospinal cVRG neurons by midsagittal lesion between the obex and the C1 spinal cord, stimulation of the PAG still induced adduction of the vocal cords and vocalization. However, activities of abdominal muscles during vocalization were abolished. These results indicate that the efferent signals for vocalization from the PAG may be relayed at the cVRG neurons and converted into adequate activation of these neurons, contributing to the activation of the abdominal muscles for vocalization.

Expression of B7-H3 in hypopharyngeal squamous cell carcinoma as a predictive indicator for tumor metastasis and prognosis

B7-H3 is a member of the B7 family thought to be a co-regulatory factor of antigen-specific T-cell immune response via co-stimulatory and co-inhibitory receptors. We evaluated its potential expression in head and squamous cell carcinoma (SCC) cell lines, and in clinical tissue samples obtained from 37 patients with human hypopharyngeal SCC. All head and neck SCC cell lines tested expressed both the B7-H3 gene and cell surface protein. The staining intensity of immunoreactivity by tumor cells was blindly evaluated by two head and neck surgeons and the results were categorized into 4 grades according to staining intensity. Eighty-seven percent of patients expressed B7-H3. B7-H3 expression was inversely correlated with the number of tumor infiltrating CD8+ T-cells (r=-0.4339, p=0.023). Patients who developed distant metastasis after tumor-free periods showed significantly higher B7-H3 expression scores compared to patients who did not develop distant metastasis during follow-up periods (p=0.048). Distant metastasis control ratio in patients with strong B7-H3 expression was significantly lower compared to that in patients with no to intermediate B7-H3 expression (p=0.040). Cause-specific survival ratio in patients with strong B7-H3 expression was significantly lower compared to that in patients with no to intermediate B7-H3 expression (p=0.028). Moreover, multivariate analysis revealed that strong B7-H3 expression was an independent prognostic factor in tumor-specific death in hypopharyngeal SCC (hazard ratio: 9.803, confidence interval: 0.018-0.539, p=0.0110).

Rehabilitation of bilaterally paralyzed canine larynx with implantable stimulator.

Bilateral stimulation of the posterior cricoarytenoid (PCA) muscles offers a physiologic approach to rehabilitate ventilation to a normal level in case of bilateral laryngeal paralysis. The objective was to evaluate the safety and efficacy of a new generation stimulator in restoring glottal opening, ventilation, and exercise tolerance.

Bilateral Motion Restored to the Paralyzed Canine Larynx with Implantable Stimulator

Bilateral stimulation of posterior cricoarytenoid (PCA) muscles offers a physiologic approach to restore ventilation to a normal level in case of bilateral laryngeal paralysis. The objective of this study was to evaluate the long‐term efficacy and safety of a new generation stimulator in restoring ventilation and exercise tolerance.

Inducible nitric oxide synthase expression in various laryngeal lesions in relation to carcinogenesis, angiogenesis, and patients' prognosis.

Conclusions: The inducible nitric oxide synthase (iNOS) expression leading to vascular endothelial growth factor (VEGF) overexpression may be useful as a factor for predicting recurrence after initial treatment and prognosis in laryngeal squamous cell carcinoma (SCC). Objective: We analyzed expression of iNOS, p53, and VEGF in various laryngeal lesions. Materials and methods: The study samples consisted of 63 SCC, 20 dysplasia, 7 polyp, and 5 normal epithelium of the larynx. The expression of iNOS, p53, and VEGF was identified by immunohistological methods. Results: No positive immunostaining for iNOS, p53, and VEGF was observed in normal epithelium and polyps. In contrast, with the progression from mild/moderate dysplasia to severe dysplasia to carcinoma, their expression levels increased. In dysplasia, there was a significant positive correlation among expression of iNOS, p53, and VEGF. In SCC, iNOS expression correlated with VEGF overexpression and microvessel density, but not with p53 overexpression. In SCC, the expression of iNOS and VEGF significantly increased in patients who developed local recurrence and/or metastases after initial treatments. Kaplan–Meier analysis showed that disease-free survival was significantly shorter in patients with iNOS or VEGF expression. Multivariate analysis showed expression of iNOS and VEGF as independent indicators for poor disease-free survival.

Evaluation of a Deep Brain Stimulation Electrode for Laryngeal Pacing

Objectives: The purpose of the present study was to evaluate the suitability of a deep brain stimulation electrode for laryngeal pacing. Of interest was whether the smaller and more closely spaced channels could provide sufficient channel redundancy, controlled current distribution, and discrete activation of the posterior cricoarytenoid (PCA) muscle. Methods: A study was conducted in dogs under differing states of PCA muscle innervation representing complete denervation to complete synkinetic reinnervation. In 3 animals, stimulated glottal opening was assessed in the innervated state and after chemical denervation by pancuronium bromide. In 3 additional dogs, the left side of the larynx was surgically denervated and compared to the innervated, right side to study an anatomic model of clinical paralysis. Results: The thresholds were lower and the maximum level of abduction was greater for the innervated state. The stimulated glottal opening equaled that of a spontaneously breathing animal. Abductory responses were obtained across all channels in the array, demonstrating its anatomic and physiological compatibility for this application. In the denervated state, responses were only 20% of that of the innervated state with a pulse duration of 0.5 ms. The response could be enhanced to 40% and 60% by increasing the pulse duration to 1 and 2 ms. Conclusions: A deep brain stimulation electrode could effectively reanimate the PCA muscle to a normal level in a case of synkinetic reinnervation and to as much as 60% of the normal level in a case of complete denervation.

Stimulation of denervated muscle promotes selective reinnervation, prevents synkinesis, and restores function

Previously, electrical stimulation of denervated canine laryngeal muscle was shown to promote reinnervation by native over foreign motoneurons. The goal of this study was to assess the effect of different stimulus paradigms on reinnervation quality and functional recovery.

Electrical stimulation prevents apoptosis in denervated skeletal muscle

The purpose of this study was to investigate the hypothesis that electrical stimulation regulates the levels of gene expression related to apoptosis in denervated muscle and prevents muscle atrophy after denervation.Nineteen rats were used in this study. To denervate soleus muscle, sciatic nerve was resected under aseptic condition. Electrical stimulation with 4 mA rectangular pulses of 0.5 ms duration at 2 Hz lasting for 1 hour was delivered to lower limb including the soleus muscle using two surface electrodes. After the stimulation periods of 4 weeks, the levels of gene expression related to apoptosis were evaluated. Electrical stimulation increased valosin-containing protein (VCP) expression and decreased cleaved caspase-12 expression in denervated muscles. These results indicated that electrical stimulation to denervated muscle suppresses ER-specific apoptosis by enhancing VCP expression. We proposed that electrical stimulation would be a potential treatment for preventing atrophy of denervated skeletal muscles.

Laryngeal plexiform schwannoma as first symptom in a patient with neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder characterized by bilateral vestibular schwannomas. The initial symptoms of NF2 are usually hearing loss and tinnitus caused by vestibular schwannomas. Although other intracranial, spinal, or skin tumors also occur in NF2, laryngeal lesions are very rare. We report a rare case of NF2 with laryngeal plexiform schwannoma as first symptom. A 38-year-old man presented with a smooth-surfaced submucosal supraglottic mass. Two round masses in the left chest wall and left supraclavicular fossa were noted incidentally during investigation of the laryngeal mass. Magnetic resonance imaging (MRI) findings for these masses were identical to those of the laryngeal mass. No typical symptoms related to NF2 were identified. Histologically, the laryngeal tumor represented plexiform schwannoma. We thus considered that the two round masses in the left chest wall and left supraclavicular fossa might also represent plexiform schwannomas. NF2 was suspected, as a high incidence of multiple plexiform schwannomas has been suggested for patients with NF2. MRI of brain lesions demonstrated bilateral vestibular schwannomas and multiple meningiomas. Finally, NF2 with laryngeal plexiform schwannoma was diagnosed. Recognizing that multiple plexiform schwannomas could be associated with NF2 is important.