Shunkichi Baba

Expression of caspase-activated deoxyribonuclease (CAD) and caspase 3 (CPP32) in the cochlea of cisplatin (CDDP)-treated guinea pigs

Cisplatin, an anti-cancer drug, is known to induce apoptosis. During apoptosis, double-stranded DNA is broken into single-stranded DNA by the action of caspases and caspase activated deoxyribonuclease (CAD). We immunohistochemically examined the cochlea of guinea pigs for signs of the apoptosis after the administration of cisplatin. Cisplatin (10 mg/kg b.w.) was intraperitoneally injected to guinea pigs and 3 days later, the animals were sacrificed by intracardiac perfusion of 4% paraformaldehyde. The temporal bones were then removed and immunohistochemically stained for CAD and caspase 3, using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling method. CAD was observed in the stria vascularis and the spiral ligament. Caspase 3 was also detected in the stria vascularis, the spiral ligament and the supporting cells of the organ of Corti. These findings suggest that apoptosis is involved in the cochlear damage observed in cancer patients treated with cisplatin.

Cochlin-Tomoprotein: A Novel Perilymph-Specific Protein and a Potential Marker for the Diagnosis of Perilymphatic Fistula

Background: Perilymphatic fistula (PLF) is an abnormal connection between the inner and middle ear. A procedure for obtaining definite proof of a PLF remains elusive, and methods of diagnosis remain controversial. To date, there is no clinically relevant biochemical marker for perilymph leakage. Using proteomic analysis of inner ear proteins, we have previously found unique properties of cochlin, encoded by the COCH gene. We detected 3 cochlin isoforms (p63s, p44s and p40s) in the inner ear tissue and a short 16-kDa isoform of cochlin-tomoprotein (CTP) in the perilymph. Since cochlin was found to be highly specific to the inner ear, we speculated that CTP might also be specific to the perilymph. The aim of this study was to determine whether CTP, a novel perilymph-specific protein, could be used as a marker for the diagnosis of PLF. Methods: By Western blotting, we investigated the specificity of CTP expression in a range of body fluids that included perilymph, serum, saliva and cerebrospinal fluid. To elucidate the detection limit of CTP, serially diluted recombinant human (rh)CTP as well as human perilymph was tested. Results: CTP was selectively expressed in all 20 perilymph samples tested, but not in 77 samples of the other body fluids. The detection limit of rhCTP was 0.27 ng or 0.022 μl of perilymph per well on Western blot analysis. Conclusion: The results strongly suggest that CTP can be a specific marker of perilymph leakage. Moreover, CTP has the potential to be a biochemical marker that allows a definitive diagnosis of the etiology of PLF-related hearing loss and vestibular disorders.

Carboplatin Induces Less Apoptosis in the Cochlea of Guinea Pigs than Cisplatin

Background: Cisplatin (CDDP) is known to cause inner ear damage while carboplatin (CBDCA) induces less ototoxicity than CDDP. We examined apoptotic changes in the cochlea of guinea pigs after injection of CDDP or CBDCA using immunohistochemical and electrophysiological techniques. Methods: Three days after the injection of each solution, the cochleas were immunohistochemically examined for the presence of fragments of single-stranded DNA (ssDNA). The auditory brain stem response was recorded before and three days after the injection. Results: We detected fragments of ssDNA in the stria vascularis and the spiral ligament of the CDDP-treated cochlea. In this group, the threshold of the auditory brainstem response was significantly elevated, however, in the CBDCA group, no apparent change of the threshold was detected. In the CBDCA group, fragments of ssDNA were detected in the stria vascularis and the spiral ligament. The number of cells that stained positive for ssDNA, was less than that in the CDDP group. Conclusions: Our findings indicate that CBDCA induces less apoptosis than CDDP and that this phenomenon contributes to the ototoxicity of CDDP.

Electrocochleographic Analysis of the Suppression of Tinnitus by Electrical Promontory Stimulation

To investigate the origin, and evaluate the mechanism by which tinnitus is suppressed we performed electrical promontory stimulation (EPS) in 56 patients with tinnitus, and measured the compound action potential (CAP) using electrocochleography before and after EPS. In the group of patients in whom tinnitus was suppressed, the CAP amplitudes increased significantly, whereas the latencies showed no remarkable change. In the group of patients in whom tinnitus was not suppressed, both the CAP amplitudes and latencies exhibited no significant change. These data indicate that the effect on the cochlear nerve plays an important role in the suppression of tinnitus by EPS. The CAP reflects the number of the auditory nerve fibers which discharge synchronously. It is speculated that an increase of the CAP amplitudes is caused by synchronizing discharges of the auditory nerve fibers, and that the mechanism by which EPS suppresses tinnitus may be related to synchronizing these discharges.

Evaluation of the brain-stem function by the auditory brain-stem response and the caloric vestibular reaction in comatose patient

ZusammenfassungBei 100 Patienten, die im tiefen Koma lagen, wurden die akustisch evozierten Hirnstammpotentiale abgeleitet und die kalorische Vestibularisprüfung durchgeführt. Dabei zeigte sich, daß ein totales oder teilweises Verschwinden der akustischen Hirnstammpotentiale bei komatösen Patienten einen Hinweis für eine schlechte Prognose darstellt. Im Gegensatz dazu läßt das Fehlen einer Reaktion bei der kalorischen Vestibularisprüfung diesen Schluß nicht zu.SummaryThe auditory brain-stem response (ABR) and the caloric vestibular reaction (CVR) were investigated in 100 patients in deep coma to evaluate the brain-stem function of these patients precisely and to predict their prognosis accurately. In the first ABR examination, 54 patients showed normal and 46 abnormal ABRs. Among the latter, five showed partial wave disappearance and 21 exhibited no ABRs. Twenty-six of the 30 patients who recovered (87%) showed normal ABRs and 21 of the 57 who died (37%) also exhibited normal latency at that time. On the other hand, all the patients who showed wave disappearance (the absence of or only wave I response) died. Forty of 86 patients who underwent the CVR test showed some reaction. However, 46 patients showed no CVRs even in the first examination. Twenty-two of 26 patients who recovered exhibited some eye movements, while the remaining four showed no reaction at that time. From these results the following statements can be made. If total or partial (wave I) disappearance of the ABR in comatose patients is observed, one can predict a poor prognosis or death. If no reaction is observed in the CVR, however, one cannot always expect a poor prognosis.

Cochlin-tomoprotein (CTP) detection test identifies traumatic perilymphatic fistula due to penetrating middle ear injury.

Abstract Conclusions: The cochlin-tomoprotein (CTP) detection test can be used to make a definite, objective diagnosis of traumatic perilymphatic fistula (PLF), and therefore offers valuable information on patient selection for surgical treatment. Objectives: Penetrating middle ear injury can cause traumatic PLF, which is a surgically treatable otologic emergency. Recently, we have reported on CTP, a novel perilymph-specific protein. The purpose of this study was to determine if the CTP detection test is useful for the diagnosis of traumatic PLF. Methods: This was a prospective study of CTP detection in penetrating middle ear injury cases with tympanic membrane perforation and hearing loss. Results: A total of seven individuals were included in this study. CTP was detected in three of four cases with posterosuperior quadrant perforation of the tympanic membrane. In one of these three cases, even though the high resolution CT scan was not suggestive of PLF and the perilymph leakage could not be visualized intraoperatively, the CTP detection test was able to detect PLF. In two cases, the preoperative positive test results enabled us to make a diagnosis of PLF and a decision for surgical treatment. CTP was not detected in the cases with anterior or inferior tympanic membrane perforation.

Congenital malformations of the middle ear with an intact external ear: a review of 38 cases.

In patients with middle ear malformations, one can expect an improvement in hearing following ear surgery. Thus, it is crucial for the ear surgeon to have an increased awareness of this disease. For a better understanding of this condition, 38 patients who underwent ear surgery were studied. All patients had congenital ossicular malformations but with an intact external ear. On the basis of our intra-operative observations, 15 cases were assigned to group A (single malformation) and 23 cases to group B (multiple malformations). The pre-operative air-conduction threshold in group B patients was higher than that in group A. Pre-operatively in group A 2 out of 20 ears had mild, 17 had moderate and 1 had severe hearing loss (HL). In group B, out of 25 ears, 3 had mild, 13 had moderate and 9 had severe HL. Post-operatively in group A, 2 had normal hearing, 16 had mild, 2 had moderate and none had severe HL. In group B, postoperatively 1 had normal hearing, 18 had mild, 4 moderate and 2 severe HL. Therefore, in patients with multiple middle ear malformations, the surgeon should know that the prospect of an improvement in the hearing threshold is rather low even after surgical reconstruction.

A study of cases with partial disappearance of the waves in the auditory brain stem response.

ZusammenfassungBericht über 20 Fälle, bei denen nur ein Teil der akustischen Hirnstammpotentiale registriert werden konnte. Bei 18 Ohren war nur das Potential I abzuleiten. Die Potentiale I und II, I–III und I–IV waren bei 4, 8 und 5 Ohren zu registrieren. Bei den untersuchten Fällen handelte es sich um Brückengliome (8), Akustikustumoren (4), West-Syndrom (2), Leukodystrophie (2), Fazialisneurinom (1), Epidermoidtumor (1), Brückenblutung (1) sowie um eine Erkrankung unbekannter Genese. Da bei 14 der 20 Patienten ein Tumor nachzuweisen war, sollte immer dann, wenn die akustischen Hirnstammpotentiale nicht vollständig registriert werden können, an einen raumfordernden Prozeß gedacht werden.SummaryTwenty cases which showed partial loss of ABR waves were reported. Only wave I was recorded in 18 ears tested. Wave I and II; I–III; and I–IV responses were observed in four, eight, and five ears tested, respectively. Cases included pontine glioma (8), acoustic tumor (4), West syndrome (2), leukodystrophy (2), facial neurinoma (1), epidermoid tumor (1), pontine bleeding (1), and unknown cause (1). Fourteen of 20 were tumor cases. This fact indicates that if the ABR shows partial loss of waves, the examiner should first suspect the space-occupying lesions of the brain stem.

CTP (Cochlin-tomoprotein) detection in the profuse fluid leakage (gusher) from cochleostomy

Abstract Conclusions: By testing 125 samples, we confirmed that Cochlin-tomoprotein (CTP) is present in the perilymph, not in cerebrospinal fluid (CSF). Perilymph and CSF exist in two distinct compartments, even in the case of a malformed inner ear with a bony defect in the lamina cribrosa, as described here. Cochleostomy might have suddenly decreased the perilymph pressure, allowing the influx of CSF into the inner ear resulting in profuse fluid leakage, first perilymph then CSF. Objectives: The first purpose of this study was to further confirm the specificity of the perilymph-specific protein CTP that we reported recently. Secondly, we assessed the nature of the fluid leakage from the cochleostomy using the CTP detection test. Methods: A standardized CTP detection test was performed on 65 perilymph and 60 CSF samples. Samples of profuse fluid leakage collected from cochleostomy during cochlear implantation surgery of one patient with branchio-oto-renal (BOR) syndrome were also tested by the CTP detection test. Results: CTP was detected in 60 of 65 perilymph samples but not in any of the CSF samples. The leaked fluid was shown to contain CTP, i.e. perilymph, at the outset, and then the CTP detection signals gradually disappeared as time elapsed.

Relationship between Auditory Brainstem Response Waveform and Head Size

The relationship between the head size and the latency and amplitude of the auditory brainstem response (ABR) was investigated in 60 normal-hearing adults (30 males and 30 females). We found a strong positive correlation between the latency of ABR waves and the head size and a strong negative correlation surfaced between the ABR amplitude and head size. These results indicate that the head size is one of the most important factors influencing the waveform of the ABR.