Ouabain-induced vacuolar formation in marginal cells in the stria vascularis is dependent on perilymphatic Na(+).

In the stria vascularis (SV), it is known that the Na(+)-K(+)-ATPase is expressed abundantly and its activity in the basolateral membrane of marginal cells is high. Ouabain, an inhibitor of the Na(+)-K(+)-ATPase, causes not only a decline in the endocochlear DC potential but also acute vacuolar formation in marginal cells. We studied the ionic mechanisms underlying the ouabain-induced vacuolar formation in marginal cells using perilymphatic perfusion in guinea pigs. Perilymphatic perfusion with 1 mM ouabain dissolved in the artificial perilymph for 50 min caused many vacuoles of a wide range of sizes in the apical cytoplasm of marginal cells, the bulging of marginal cells into the scala media and strial volume increase. Removal of K(+) from the perilymph reduced the proportion of vacuoles and strial thickening, but the bulging of marginal cells remained. In contrast, the sizes of vacuoles were drastically reduced and extrusion of marginal cells into the scala media could not be observed in the absence of perilymphatic Na(+). Furthermore, the total volume of SV was obviously reduced in comparison with the control. These results indicate that perilymphatic Na(+) and K(+) are responsible for these morphological changes caused by ouabain, and that perilymphatic Na(+) plays an important role in the cellular volume regulation in SV in the presence of ouabain. It is supposed that the transport system of perilymphatic Na(+) and K(+) into marginal cells may contribute to vacuolar formation when ouabain is administered. Regarding Na(+), we hypothesize two possibilities for the perilymphatic Na(+) transporting pathway as follows. Na(+) in the perilymph could enter the endolymph via Reissner's membrane or the basilar membrane; Na(+) in the endolymph would then be taken up by marginal cells via the apical membrane and secreted into the intrastrial space by Na(+)-K(+)-ATPase in the basolateral membrane. Another, less likely, possibility is that Na(+) in the perilymph is transported into basal cells or fibrocytes in the spiral ligament, then into intermediate cells via gap junctions, and finally secreted into the intrastrial space via Na(+)-K(+)-ATPase of intermediate cells. Regarding K(+), it is expected that the K(+) recycling pathway plays a role in ouabain-induced vacuolar formation in marginal cells.

Safe reconstruction of a large cervico-mediastinal tracheal defect with a pectoralis major myocutaneous flap and free costal cartilage grafts.

A large cervico-mediastinal tracheal defect in a 72-year-old man as a result of surgery for thyroid carcinoma with tracheal invasion and mediastinal lymph node metastasis was reconstructed using a pectoralis major myocutaneous flap and free costal cartilage grafts. The tracheal defect (55 mm x 30 mm) was located at the thoracic inlet adjacent to the major mediastinal vessels. Our reconstructive procedure was a two-staged surgery. In the first stage, a pectoralis major myocutaneous flap was transferred to the neck to provide a well-vascularized recipient bed for free costal cartilage grafts and to cover large vessels. Two pieces of free costal cartilage were grafted on the pectoralis major myocutaneous flap, one for the lateral wall reconstruction and the other prefabricated for the anterior wall of the trachea. In the second stage, the re-vascularized cartilage graft for the anterior wall of the trachea with overlying skin was rotated onto the trough of the remaining trachea and the closure of the tracheal defect was completed. We conclude that free cartilage grafts for the reconstruction of a large cervico-mediastinal tracheal defect can be safely used when they are combined with well-vascularized pectoralis major myocutaneous flaps.

Immunohistochemical localization of histamine receptors in rat cochlea.

OBJECTIVE: Histamine may have physiologic functions in the inner ear. The locations of histamine receptors, however, have not yet been identified in the mammalian cochlea. The aim of this study was to investigate the localization of histamine receptor subtypes (H1, H2, and H3 receptors) in rat cochlea. METHODS: Immunohistochemistry was performed with antibodies specific for each of the histamine receptors (H1, H2, and H3). To identify the type I and II spiral ganglion cells in the cochlea, some cryostat sections were double stained with antibodies to both a histamine receptor and neurofilament 200 kD, which predominantly stains type II spiral ganglion cells in the cochlea. RESULTS: All H1, H2, and H3 receptor immunoreactive staining was limited to the spiral ganglion cells of the cochlea. Spiral ganglion cells with positive immunoreactivity to the neurofilament 200 kD antibody were stained only slightly by histamine H1, H2, and H3 receptor antibodies, indicating that histamine receptor immunoreactivity is specific to type I ganglion cells. CONCLUSIONS: These findings indicate that histamine receptors are present in the cochlea and support the hypothesis that histamine plays a physiologic role in the cochlea.

Time course of dehydrating effects of isosorbide on experimentally induced endolymphatic hydrops in guinea pigs.

Osmotic diuretics are therapeutic agents used to reduce endolymphatic hydrops. However, glycerol-induced change in endolymph volume is followed by a rebound phenomenon. In this study, we investigated the rebound phenomenon occurring with isosorbide, an osmotic diuretic used as a therapeutic agent for Ménière's disease in Japan. Forty guinea pigs underwent surgical obliteration of the endolymphatic sac. Thirty received isosorbide orally 1 month after surgery. These animals were sacrificed 3, 6, or 12 h after isosorbide intake. The remaining 10 animals served as controls. Quantitative assessment of changes in the endolymphatic space was performed light-microscopically. Isosorbide reduced cochlear endolymph volume, with a peak reduction 6 h after intake. Thereafter, no prominent rebound phenomenon was noted. Clinically, since isosorbide is orally administered every 8 h, rebound phenomenon need not be considered in the treatment with isosorbide.

Bumetanide-induced enlargement of the intercellular space in the stria vascularis critically depends on Na+ transport.

The intercellular space in the stria vascularis (intrastrial space) is a closed space and isolated from both the endolymph and the perilymph in normal tissue. Loop diuretics such as bumetanide and furosemide cause an acute enlargement of the intrastrial space in association with a decline in the endocochlear potential. It is known that bumetanide inhibits the Na+-K+-2Cl- cotransporter, which is expressed abundantly in the basolateral membrane of marginal cells. We studied ionic mechanisms underlying the bumetanide-induced enlargement of the intrastrial space using perilymphatic perfusion in guinea pigs. Perilymphatic perfusion with artificial perilymph containing 100 microM bumetanide caused marked enlargement of the intrastrial space, as reported previously. Removal of K+ from the perilymph did not affect the bumetanide-induced enlargement, whereas removal of Na+ from the perilymph inhibited it almost completely. Perilymph containing 1 mM amiloride also inhibited the enlargement of the intrastrial space almost completely. These results indicate that perilymphatic Na+, but not K+, and amiloride-sensitive pathways are essential to the bumetanide-induced enlargement of the intrastrial space. Two possible pathways could yield these results. Na+ in the perilymph could enter the endolymph via Reissner's membrane or the basilar membrane; Na+ in the endolymph would then be taken up by marginal cells via the apical membrane and secreted into the intrastrial space by Na+-K+-ATPase in the basolateral membrane of them. Another, less likely possibility is that Na+ in the perilymph is transported into basal cells or fibrocytes in the spiral ligament, then into intermediate cells via gap junctions, and finally secreted into the intrastrial space via Na+-K+-ATPase of intermediate cells.

Electrocochleographic findings in cases of autoimmune disease with sensorineural deafness.

OBJECTIVES: To present electrocochleographic findings in patients with autoimmune disease (AD) with sensorineural deafness (ADSD), and to discuss the etiologies of sensorineural hearing loss (SNHL) in cases of ADSD. METHODS: Study design is a retrospective review of electrocochleographic results of 26 patients with ADSD. To evaluate the electrocochleographic results, average SP/AP ratios were compared between ADSD and normal subjects. In the ADSD group, audiologic pattern, fluctuations in hearing and results of the glycerol test were also reviewed. Electrocochleography (ECoG) was recorded using the extratympanic method, and the SP to AP ratio (SP/AP ratio) was analyzed. RESULTS: The mean of average SP/AP ratios in the ADSD groups (0.46) was significantly higher than that in normal subjects (0.27). Further, 17 of 29 affected ears in patients with ADSD showed fluctuating hearing loss. Eighteen ears showed low tone loss (rising and peak audiologic patterns). Only 5 of 26 ears (19.2%) showed positive results on glycerol test. There was no correlation between glycerol test results and hearing fluctuation or between glycerol test results and the SP/AP ratio on chi(2)-test. There was no tendency between audiologic pattern and glycerol test results or between audiologic pattern and the SP/AP ratio. CONCLUSION: These results suggest the etiologies of SNHL in cases of ADSD remain unclear. However, some cases showed clinical findings similar to endolymphatic hydrops. We should bear in mind that clinical Meniere's syndrome involves ADSD. Further investigation is needed to resolve the etiology of SNHL of ADSD.

Expression of mRNA encoding the H1, H2, and H3 histamine receptors in the rat cochlea.

Histamine may have physiological functions in the inner ear. Histamine receptors, however, have not yet been identified in the mammalian cochlea. We determined, using reverse transcription polymerase chain reaction (RT-PCR), that H1, H2, and H3 histamine receptor mRNA is expressed in the rat cochlea. To investigate the distribution of each receptor, the cochlea was divided into three parts: the lateral portion, the medial portion, and the modiolus. The mRNA for each receptor subtype was detected in the modiolus but not in the lateral and medial portions of the cochlea. This is the first evidence of H1, H2, and H3 histamine receptor mRNA in the rat cochlea. These findings support the suggestion that histamine may play a physiological role in the cochlea.

Staple-assisted laryngectomy for intractable aspiration.

Staple-assisted laryngectomy is a unique method previously reported by Lukyanchenko to prevent wound contamination by using a stapling device for suturing pharyngeal defects in total laryngectomy. We have modified his method and applied it to prevent a postoperative pharyngocutaneous fistula in the treatment of intractable aspiration. In contrast to laryngeal cancer patients, a combined use of an intraluminal light to guide the dissection and laryngofissure to pull the epiglottis can be used to facilitate the use of the stapling device. For most patients with intractable aspiration who have significant malnutrition and drug-resistant bacterial colonization of the pharynx, this method offers certain advantages. This report describes our successful experience with this method in the management of patients with intractable aspiration.

Elevated summating potential in a case of posterior fossa meningioma was normalized by tumor removal.

OBJECTIVE: A change in the summating potential (SP) obtained from a patient with posterior fossa meningioma associated with surgical removal of the tumor was reported and possible mechanisms underlying the change are discussed. METHODS: This paper is a retrospective case review. A tertiary care referral center was the setting for the study. The authors present a 46-year-old female patient with posterior fossa meningioma, which was removed surgically. Pure tone audiometry and electrocochleography (ECoG) were performed before and after surgical removal of the tumor. RESULTS: Pure tone audiogram showed normal hearing levels before surgery, and there were no apparent postoperative changes in hearing levels. ECoG showed a normal compound action potential (AP) level and an elevated SP/AP ratio (0.53) before surgery. After the tumor removal, the SP/AP ratio became 0.16, which was a normal level in our department. CONCLUSIONS: The increased SP/AP ratio was normalized after surgery. Possible mechanisms underlying the increase in SP/AP ratio are an inhibition of the olivocochlear bundle function and endolymphatic hydrops.

Reduction in the endocochlear potential caused by Cs(+) in the perilymph can be explained by the five-compartment model of the stria vascularis.

In an earlier publication (Takeuchi et al., Biophys. J. 79 (2000) 2572-2582), we proposed that K(+) channels in intermediate cells within the stria vascularis may play an essential role in the generation of the endocochlear potential (EP), and we presented an extended version of the five-compartment model of the stria vascularis. In search of further evidence supporting the five-compartment model, we studied the effects of Cs(+) added to the perilymph on guinea pig EP. Cs(+) is known as a competitive K(+) channel blocker. Both the scala tympani and the scala vestibuli of four cochlear turns were perfused at a flow rate of 10 microl/min, and the EP was recorded from the second cochlear turn. Cs(+) at 30 mM caused a biphasic change in the EP; the EP increased transiently from a control level of 89.6 mV to 94.8 mV within 10 min, and then decreased to a steady level of 24.5 mV within the next 40 min. We propose that the initial transient increase in the EP results from Cs(+)-mediated blockade of K(+) conductance in the basolateral membrane of hair cells, and that the subsequent EP decrease is due to effects of Cs(+) on the stria vascularis. We believe that Cs(+) in the perilymph is able to access the stria vascularis by being taken up by fibrocytes in the spiral ligament and then being transported to intermediate cells because it is known that Cs(+) is taken up via Na(+),K(+)-ATPase and that gap junctions connect fibrocytes in the spiral ligament to basal cells and basal cells to intermediate cells. To clarify the effect of intracellular Cs(+) on the electrophysiological properties of intermediate cells, these cells were dissociated from guinea pigs and studied by the whole-cell patch-clamp method. Intracellular Cs(+) depolarized intermediate cells in a dose-dependent manner. In addition, efflux of Cs(+) from the intermediate cell was much less than the efflux of K(+). Thus, Cs(+) may accumulate in the intermediate cell, which depolarizes the cell, which in turn decreases the EP. We conclude that the five-compartment model of the stria vascularis can explain the EP decrease caused by Cs(+) in the perilymph.

Bumetanide-induced enlargement of the intercellular space in the stria vascularis requires an active Na+-K+-ATPase.

OBJECTIVE: Loop diuretics such as bumetanide and furosemide cause an acute enlargement of the intrastrial space of the stria vascularis, with an associated decline in the endocochlear DC potential (EP). The aim of this study was to determine the role played by the Na+-K+-ATPase in the bumetanide-induced enlargement of the intrastrial space, and to examine the importance of the balance between the activities of the Na+-K+-2Cl- cotransporter and the Na+-K+-ATPase to the physiological function of the stria vascularis. MATERIAL AND METHODS: Albino guinea pigs were used in experiments involving perilymphatic perfusion, EP measurement and electron microscopy. The effects of bumetanide on the stria vascularis were examined following inhibition of the Na+-K+-ATPase by ouabain. Ouabain was administered to the perfusate and, when the EP reached 0 mV, both ouabain and bumetanide were administered. RESULTS: Although there was no enlargement of the intrastrial space, vacuoles were apparent in marginal cells. The vacuolar change in marginal cells was similar to that caused by ouabain alone. CONCLUSION: This study indicates that the enlargement of the intrastrial space requires not only the blockade of the Na+-K+-2Cl- cotransporter but also normal activity of the Na+-K+-ATPase, and suggests that the bumetanide-induced enlargement of the intrastrial space resulted from the imbalance between the activities of the Na+-K+-2Cl- cotransporter and the Na+-K+-ATPase.