Biomedical subjects

Tadashi Kitahara

Publications and source records attributed to Tadashi Kitahara.

25 records · Page 2Linked to original sources

PubMed2003

Up-regulation of cochlear aquaporin-3 mRNA expression after intra-endolymphatic sac application of dexamethasone.

The final aim of the present study is to see if the endolymphatic sac is really available as a drug delivery system to have effect on the inner ear organs. In the present study, we examined effects of a single insertion of dexamethasone into the rat unilateral endolymphatic sac on mRNA expression of the inner ear aquaporin (AQP) family, transmembrane water transporters and putative endolymphatic fluid modulators, by means of real-time quantitative PCR. Only AQP-3 mRNA expression in the ipsilateral cochlea was significantly up-regulated in comparison with controls and the up-regulation was demonstrated both in dose-dependent and time-dependent manners. These findings suggest that the intra-endolymphatic sac steroids could make regulatory effects on the inner ear AQP-3 expression via vestibular aqueduct and modulate the homeostasis of endolymphatic fluids, encouraging the possibility that the endolymphatic sac could be a therapeutic window for the inner ear disease.

Acoustic Stimulation↗

PubMed2003

Magnetic resonance imaging of pleomorphic adenoma arising from the external auditory canal.

Pleomorphic adenoma arising from the external auditory canal is a very rare neoplasm, and there has been no report on magnetic resonance (MR) imaging of pleomorphic adenoma of the external auditory canal. We report here a case of 65-year-old male with this tumour, measuring 12 mm in a diameter. Histopathology was confirmed from the specimen obtained at the surgical excision. MR revealed that the tumour had a well-defined margin showing hypointensity on T1-weighted images and hyperintensity on T2-weighted images relative to the parotid gland. The tumour was well enhanced by contrast material. No invasion to the surrounding tissue was observed. These MR findings were compatible with pleomorphic adenoma of the salivary gland origin. In treating pleomorphic adenoma of the external auditory canal, complete surgical excision is essential for the prevention of recurrence. It can be concluded that MR imaging is helpful for making a differential diagnosis of external auditory canal tumours and selection of adequate treatment.

Adenoma, Pleomorphic↗

PubMed2002

Effects of intratympanic injection of steroids on changes in rat inner ear aquaporin expression.

Although steroid treatment is generally administered for patients with inner ear disorders, including Meniere's disease, the mechanism via which steroids exert their effects remains to be clarified. The aquaporins (AQPs) are a family of small transmembrane water transporters, and it has recently been revealed that they play a role in regulating homeostasis in the inner ear fluids. In order to elucidate the action points of steroids in the inner ear, we firstly identified AQPI, 2, 3, 4, 5 and 6 mRNAs in the rat cochlea and AQP1, 3, 4, 5 and 6 in the rat endolymphatic sac by means of reverse transcription-polymerase chain reaction. Subsequently, we found that intratympanic injections of steroids upregulated AQPI mRNA of the rat cochlea in a dose-dependent manner. These results suggest that steroids may affect water homeostasis in the rat inner ear mainly via AQP1.

Animals↗

PubMed2002

Changes in fos expression in the rat brainstem after bilateral labyrinthectomy.

In order to elucidate the role of the vestibulocerebellar neural circuits during two-stage bilateral labyrinthectomy (BL) we examined Fos-like immunoreactive (-LIR) neurons as a marker of neural activation in the rat brainstem after BL and the projections of these neurons into the vestibulocerebellum using retrograde tracing and immunohistochemical techniques. Simultaneous BL did not show any Fos expression in the medial vestibular nucleus (MVe). However, with an interval of > 6 h between the two stages of BL, Fos-LIR neurons were induced in the ipsilateral (ipsi-) MVe of the side operated on second, partially projecting into the ipsi-vestibulocerebellum. A previous study demonstrated that some of the unilateral labyrinthectomy-induced Fos-LIR neurons in the ipsi-MVe projected into the ipsi-vestibulocerebellum and inhibited the contra-MVe neurons, resulting in the restoration of the right-left balance. Taken together with our present data, it is suggested that some of the labyrinthectomy-induced Fos expression in the ipsi-MVe is representative of a switch-on signal for the vestibulo-cerebello-vestibular inhibitory neural circuits, which remain turned off after symmetrical lesions such as simultaneous BL but are turned on after severe asymmetrical lesions in order to restore the balance.

Adaptation, Physiological↗

PubMed2002

[A rare case of the high jugular bulb associated with only hearing ear].

The jugular bulb may be present in different positions and dimensions within the temporal bone. In general, high jugular bulbs were classified into 2 types: lateral in which the jugular bulb protrudes into the middle ear and up into the tympanic cavity and medial in which the jugular bulb is abnormally placed more superiorly and medial to the cochlea. We report, a unique case of a high jugular bulb which came round from behind of the internal auditory canal and the cochlea protruding into the posterosuperior part of the mesotympanum. It was a very rare pattern of a high jugular bulb which varies in position. The occurrence of adhesive otitis media caused the high jugular bulb to bleed easily in the only hearing ear. There would be risks of making the patient suffer severe bilateral healing impairment due to only one hearing ear and excessive hemorrhage in surgical treatment. With only one hearing ear, we should therefore select transcatheter interventional angiography when the quantity and frequency of bleeding from the jugular bulb increase so.

Cochlea↗

PubMed2002

[Changes in plasma inner ear hormones after endolymphatic sac drainage and steroid-instillation surgery (EDSS)].

We treated 33 cases of intractable Meniere's disease with endolymphatic sac drainage and steroid-instillation surgery (EDSS), attaining good long-term results in vertigo and hearing. To elucidate how EDSS affects the diseased inner ear, we examined changes in plasma inner ear hormones after EDSS. Among inner ear hormones, plasma vasopressin was significantly decreased after EDSS compared to after mastoidectomy. In cases with good long-term results in vertigo and hearing, postoperative plasma vasopressin remained lower over the long term than in cases with poor results. In cases with negative glycerol test results one year after surgery, postoperative plasma vasopressin also remained significantly lower over the long term than in cases with positive results. Previous studies reported that vestibular neurons projected into hypothalamic supraoptic and paraventricular nuclei and that changes in the inner ear pressure were related to plasma vasopressin. Taken together with present findings, this suggests that EDSS may reduce plasma vasopressin through modification of the diseased inner ear environment, resulting in improved inner ear function.

Aldosterone↗

PubMedDate not supplied

Implantation of self-expanding metallic stent for patients with malignant stricture after failure of definitive chemoradiotherapy for T3 or T4 esophageal squamous cell carcinomas.

BACKGROUND/AIMS: Definitive chemoradiotherapy can have curative potential in unresectable patients with malignant stricture due to locally advanced esophageal carcinoma, however, dysphagia is the principal problem in patients who had recurrence or who did not respond to chemoradiotherapy. In this prospective study, we investigated the efficacy and feasibility of metallic stent implantation for patients with dysphagia after chemoradiotherapy failed. METHODOLOGY: Concurrent chemoradiotherapy was performed in 40 patients with severe dysphagia due to esophageal squamous cell carcinomas accompanied by T3 or T4 disease containing M1 lymph node (LYM) disease. A self-expanding metallic stent was inserted for patients with malignant stricture of the thoracic esophagus after failure of chemoradiotherapy using identical protocols. RESULTS: Of 40 patients, 13 (33%) achieved a complete response. However, 12 patients complained of severe dysphagia again after chemoradiotherapy despite a good performance status. Esophageal stricture of these 12 patients was caused by stable disease (n = 4), local progression (n = 5), and compression of metastatic lymph node (n = 3). Metallic stents were successfully inserted for all 12 patients, and dysphagia improved in 10 (83%) of these 12 patients. Life-threatening complication (17%) of sepsis in two patients was found in an early phase after stent insertion, although approximately 200 days had passed in a dysphagia-free state after chemoradiotherapy. CONCLUSIONS: Implantation of self-expanding metallic stent for patients with malignant stricture after failure of chemoradiotherapy is effective, however, serious complication can occur in the early phase.

Aged↗