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Biomedical subjects

T Morimitsu

Publications and source records attributed to T Morimitsu.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effects of experimental round window membrane laceration on the free amino acid profile of perilymph.

To evaluate biochemical changes of inner ear fluid following perilymphatic fistula (PLF), free amino acid (FAA) profiles of perilymph in experimental PLF were determined using high performance liquid chromatography (HPLC). Thirty-five guinea pigs were anesthetized and prepared as PLF models by perforating the round window membrane (RWM) of the left ear. Right ears served as controls. Samples (2 microliters) were aspirated from scala tympani through a RWM perforation. Animals were divided into two groups according to time of sampling following PLF induction: 2-week group (n = 17) and 4-week group (n = 18). Compound action potential (CAP) evoked by 1, 2, 4 and 8 kHz tone bursts were measured using a round window electrode from the left ear before PLF induction and from both ears before final sampling. RWM perforations were completely closed at the time of the final sampling in 8 of 17 animals from the 2-week group, and 15 of 18 animals from the 4-week group. In comparison with that in control ears, concentrations of FAA throughout all profiles was dramatically elevated in the PLF ears with a healed RWM perforation. Most PLF ears with persistent RWM perforation showed minimal differences between 2-week and 4-week groups. No remarkable CAP threshold changes were found at any frequencies tested following PLF induction in both the 2-week and 4-week groups. The unchanged 8 kHz threshold suggests that FAA concentration increases only at the basal end of the cochlea. FAAs accumulate within the basal end of scala tympani in ears with a healed RWM.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1995

[Postoperative MRI findings after cholesteatoma surgery].

This study was designed to show MRI findings of postoperative middle ear pathologies and to discuss the usefulness of Gadolinium-enhanced MRI in evaluating the postoperative state of cholesteatoma. Thirty-eight ears which underwent intact canal wall tympanoplasty for cholesteatoma were examined. Recurrent cholesteatoma was detected as an iso-intensity area on T1-weighted images with negative enhancement. Notably, residual cholesteatoma were generally depicted as a round iso-intensity area with negative enhancement. Residual cholesteatoma less than 5mm in diameter were, however, not generally detectable with our MRI scanner. Granulation tissue can be separated from cholesteatoma as an area with positive enhancement. Cholesterol granuloma shows a characteristic high signal pattern on both T1 and T2-weighted images. Hypovascular fibrous tissue and fluid collection may be depicted as a pattern similar to that of cholesteatoma. However, the signal is usually more homogeneous than that of cholesteatoma. We conclude that Gadolinium-enhanced MRI is useful for detecting postoperative cholesteatoma and avoiding unnecessary second-look operations after cholesteatoma surgery, by the canal-up procedure.

Adolescent↗
PubMed1995

[Hearing results after anterior tympanotomy in cholesteatoma surgery].

Between 1987 and 1993, 71 ears of attic type cholesteatoma and 20 ears of adhesive type were operated on using the intact canal wall technique combined with anterior tympanotomy. Pre- and postoperative pure tone hearing after the surgery were analyzed, especially to determine whether anterior tympanotomy is harmful to the inner ear. Mean values of 500, 1000 and 2000Hz of air conduction threshold immediately, before and about 1 year after the operation were compared. In attic cholesteatoma, type 1, type 3, and type 4 of ossiculoplasty revealed significant improvement of 8.4dB, 9.3dB, and 8.0dB respectively. In adhesive cholesteatoma, results obtained were 8.4dB, 0.8dB, and -3.0dB. Differences between pre- and postoperative bone conduction threshold at 4000Hz were 1.5dB in type 1, 1.3dB in type 3, and 5.0dB in type 4 in attic cholesteatoma. Those in adhesive cholesteatoma were -2.5dB, -0.2dB, and -10.0dB respectively. From the results obtained, we concluded that (1) our results were satisfactory with regards to hearing ability following all types of ossiculoplasty in attic cholesteatoma and in type 1 in adhesive cholesteatoma, (2) anterior tympanotomy itself is not a harmful procedure to the inner ear in both types of cholesteatoma, (3) an increase in bone threshold in adhesive cholesteatoma is due to the surgical procedure at the stapes and/or the oval window.

Adolescent↗
PubMed1995

Improvement of the surgical technique of anterior tympanoplasty in cholesteatoma.

Technical improvements in anterior tympanotomy with a transmastoid approach in cholesteatoma surgery are reported. Mastoidectomy must be extended to the root of the zygoma and the space anterior to the malleus head must be opened. For this purpose, the visual axis must coincide with the external meatal axis. In this head position, complete removal of the anterior attic bony plate becomes possible only through the transmastoid approach, without touching the ossicular chain. In the case of the pyramidal type bony plate with a normal ossicular chain, the incudo-malleal joint is temporary subluxated, as this is more convenient for access and removal of pathology than incudostapedial joint subluxation. Our clinical results on postoperative hearing showed no damage to the inner ear by the improved technique.

Cholesteatoma, Middle Ear↗
PubMed1994

Anionic sites in blood capillaries of the mouse cochlear duct.

The blood-cochlear barrier, which consists of the molecular size and ionic charge barriers, is known to play an important role in production and absorption of inner ear fluids. In this study, we employed poly-L-lysine colloidal gold conjugates (PL-CG) in combination with Lowicryl K4M resin to demonstrate anionic sites in blood capillaries of the cochlear duct. Male ICR mice weighing 30-40 g with a positive Preyer's reflex were used. The basement membranes of blood capillaries of the stria vascularis and the spiral ligament were successfully labeled with PL-CG pH 2.5. The luminal surface of capillaries in the stria vascularis and the spiral ligament intensely reacted with PL-CG pH 2.5. However, PL-CG pH 1.0 stained only the basement membrane of the spiral ligament. Predigestion with several glycosidases nearly eliminated PL-CG labeling. Anionic charge located on the luminal surface of the endothelial cell was mainly caused by the presence of sialic acid. On the contrary, anionic charge of the basement membrane was caused in a substantial degree by chondroitin and heparan sulfate-rich glycosaminoglycans. We obtained histochemical evidence that blood capillaries of the stria vascularis differ from those of the spiral ligament.

Animals↗
PubMed1994

Effects of arterial occlusion on endocochlear DC potential and cochlear blood flow in guinea pigs.

The present study was undertaken to investigate the role of collateral arteries in cochlear circulation by examining the effect of occlusion of branches of the basilar artery on endocochlear DC potential (EP) and cochlear blood flow (CBF). EP and CBF were measured at the basal turn of the cochlea during microclamp occlusion of the basilar artery, its branches and the posterior inferior cerebellar artery (PICA). CBF was measured with a laser Doppler flowmeter. Systemic blood pressure (SBP) increased at occlusion of the basilar artery, but was not influenced by any occlusion of its branches. Changes of EP and CBF at occlusion of the basilar artery were classified into two types: recovery type and non-recovery type. Thirty-five guinea pigs were classified into three groups according to the number of branches of the basilar artery: Group A with one branch in 10 animals (29%), Group B with two branches in 20 animals (57%), and group C with three branches in 5 animals (14%). From the results obtained at successive occlusions of branches of the basilar artery and PICA, it is clear that the anterior inferior cerebellar artery (AICA) supplies blood to the cochlea more or less in all animals, although the reduction of the blood volume by its occlusion is not enough to decrease EP in some animals. When vascular dysfunction occurs in AICA of such animals, other branches of the basilar artery and/or PICA will play an important role to maintain cochlear circulation.

Animals↗
PubMed1994

Magnetic resonance imaging in patients with sudden deafness.

Although many theories on the etiology of sudden deafness have been proposed, the main pathological focus remains uncertain. In this study, MR examinations were performed on patients with unilateral sudden deafness to study the relationship between MRI findings and response to treatments, i.e. amidotrizoate, steroid, or both. In 7 out of 30 cases, the cochlea and/or the vestibule showed higher signal intensity on proton density and T2-weighted images on the diseased side (MRI positive cases). These findings suggest changes in the chemical composition of the perilymph and/or the endolymph, since proton density and T2-weighted images reflect water content. It appears that MRI positive sudden deafness is more difficult to cure even with the use of amidotrizoate or steroid than MRI negative sudden deafness. Amidotrizoate seems to be more effective in MRI negative sudden deafness. MRI would help us to further classify the etiology of sudden deafness.

Adolescent↗
PubMed1994

Effects of contrast media on the stria vascularis.

The effects of contrast media on the stria vascularis were electron microscopically studied in mice after intravenous injection of amidotrizoate, iopamidol or ioxaglic acid at 10 or 20 ml/kg body weight. In furosemide-load groups, contrast media were injected via the tail vein at 10 ml/kg with preadministration of furosemide at 20 mg/kg body weight. In both groups, the stria vascularis was prepared for study 10 min after the injection of contrast media. No morphological changes could be found after administration of 10 ml/kg injection of any of the three contrast media. However, administration of 20 ml/kg of amidotrizoate caused a high degree of intercellular dilatation between marginal and intermediate cells. Iopamidol caused a slight degree of dilatation, and ioxaglic acid caused no change. In the furosemide-load groups, amidotrizoate induced severer effects than iopamidol while ioxaglic acid induced no effect. From these results it was concluded that contrast media affect the stria vascularis parallel with osmolality, although some ionic effect of amidotrizoate should be considered when it is used in combination with furosemide.

Animals↗
PubMed1993

Histochemical demonstration of mucin in lymphatic vessels of human middle ear cholesteatoma.

We investigated the possible existence of mucin in lymphatic vessels in cholesteatoma perimatrix using the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method. Histochemical staining distinguished two types of lymphatic vessels, one of which contained PA-TCH-SP reacting substance showing a loose mesh-like appearance. Connective tissue was edematous around this vessel and was infiltrated by abundant round cells. The second type of lymphatic vessel did not contain PA-TCH-SP reacting substance and few round cells were seen infiltrating tissue around this vessel. Gland-like structures of mucous epithelium in the perimatrix were heavily stained by the PA-TCH-SP method. Secretory granules of the mucous epithelium and its luminal content had a loose mesh-like appearance. Since contents of the gland-like structures may leak through the chinks of epithelial cells into subepidermal connective tissues, the resultant inflow of mucin into the lymphatic vessels may then cause inflammation of the cholesteatoma perimatrix.

Cell Nucleus↗
PubMed1993

[A case of superficial siderosis of the central nervous system with total deafness].

Superficial siderosis of the central nervous system (SSCN) in a disease characterized by chronic deposition of hemosiderin in the leptomeninges, subpial tissue, spinal cord, and cranial nerves. Previously the diagnosis of SSCN could only be made at autopsy or during a neurosurgical procedure. Now, however, a diagnosis of SSCN can be made non-invasively by magnetic resonance imaging (MRI). We present the case of a 50-year-old male with SSCN accompanied by bilateral sensorineural hearing loss which gradually progressed to total deafness over a seven year period. This patient also had associated bilateral caloric weakness with episodes of severe recurrent headaches over the two preceding years. The deafness and gait disturbance, which were his chief complaints, were followed by other neurological manifestations including pyramidal tract signs, anosmia, and ageusia. High-field MRI on T-2 weighted images of the CNS showed diffuse marginal hypointensity of the cerebrum, brain stem, and cerebellum. Atrophy of the cerebellum and brain stem was also apparent. Low signal intensity along the proximal segment of the acoustic nerve and the facial nerve was noted from the cistern to the internal auditory canal. Neither bilateral transtympanic promontory nor round window electrical stimulation elicited any sound sensation. In this case it was thought that the acoustic nerve alone or both the acoustic nerve and the cochlea were affected by this disease. Consequently, cochlear implantation was not indicated. The source of bleeding into the subarachnoid space could not be detected despite thorough examination. This diagnosis will be made only by physicians who are aware of this rare entity and have knowledge of the characteristic clinical pathology.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1992

Venous drainage through the internal auditory meatus of the guinea pig cochlea.

The angioarchitecture of the guinea pig cochlea has been investigated closely using light microscopy and resin injections. However, detailed information concerning the vasculature of the modiolus is still unavailable, and even the existence of venous drainage through the internal auditory meatus is not agreed upon. In the present investigation, vascular casts of guinea pig temporal bones were studied using scanning electron microscopy. A vessel, formed by the confluence of the vascular network on the modiolar wall and having a spiral course into the internal auditory meatus was found in the modiolus of the basal turn. The vessel had a venous pattern on its cast surface and, after existing from the internal auditory meatus, drained finally into the dural sinus. These scanning electron microscopic findings were confirmable by serial sections of the dural veins in the internal auditory meatus and the modiolus. The vessel found may correspond to the so-called internal auditory vein, but it would be more appropriate to call it "the vein of the internal auditory meatus," since it appears to be an independent route of venous drainage from the modiolus.

Animals↗
PubMed1992

Histopathology of eighth cranial nerve of mass stranded dolphins at Goto Islands, Japan.

We examined four dolphins (Grampus griseus) of 582 mass-stranded. Almost no contents were found in the alimentary canal. Nasitrema gondo and Crassicauda grampicola were found in the tympanic cavity. Severe degeneration of the eighth cranial nerve was observed microscopically in all animals and an egg of Nasitrema was found in a tissue crevice of the nerve. We propose that the nerves were damaged directly by Nasitrema.

Animals↗
PubMed1992

Clinical application of a newly developed surveying system for designing and fabricating removable partial dentures.

In this paper, some problems in commercially available surveying systems were discussed, and a clinical technique for designing and fabricating clasps by using an improved 'Digital Surveyor' and a computer system were presented. This system has the advantages as follows: (1) morphological factors on abutment teeth could be measured and evaluated using the improved 'Digital Surveyor' and its accessories set, (2) clasps providing with proper mechanical properties according to various conditions in the mouth could be designed and fabricated precisely and easily. It became clear that conventional surveying methods involved empirical rules should be re-examined and replaced by the more rational surveying method like this system.

Computer-Aided Design↗
PubMed1992

Three dimensional shape measurement system for residual ridges.

It is very important for design and construction of complete dentures to evaluate the condition of residual ridges of edentulous patients objectively and precisely. The authors have been developing a shape measurement system for residual ridges. In this study, the outline of the system is described and the accuracy of the system is evaluated. The system consists of a high precision laser displacement meter, a working table and its controller, and a personal computer. The working table, on which a plaster model is placed, can move until the end of the moving range at a speed of 0.7 mm/sec. The height of the plaster model was measured intermittently with a frequency of 7 points/sec. To determine the accuracy of this system, experimental plaster models, which simulated the simplified shape of residual ridge, were measured and analyzed. The measurement error was 2.5%, which seemed to be highly accurate. The accuracy of the measurement decreased with the darkness of the color of the plaster model.

Alveolar Bone Loss↗
PubMed1991

Myringoplasty in children.

Our 11 years of experience of myringoplasty in 87 children aged 3 to 14 years were retrospectively studied. The children were followed up over a period of 3 years. Children in the 3-to-12-year-old age group had a success rate of 57.7%. Graft-take rate was 100% in children operated on at the age of 13 and 14 years. Revision surgery was needed in 33 ears, and ultimate success was achieved in 88.9%. Within the same period, 38 ears were conservatively treated and 20 perforations of them were spontaneously closed. The state of the opposite ear and the perforation size were not a decisive factor in the results of myringoplasty. Children between 7 and 10 years old with small mastoid pneumatization had a statistically lower graft-take rate. We concluded that myringoplasty is warranted for children 13 years of age and older or children aged 7 to 12 years with large mastoid pneumatization.

Adolescent↗
PubMed1990

Long term effects of intense sound on endocochlear DC potential.

Changes in endocochlear DC potential (EP) after single and repeated intense sound exposure and negative EP induced by anoxia were observed in guinea pigs with passage of time. The intense sound used was a pure tone of 2 kHz at 145 dB SPL for 4 h. The single exposure group was divided into 8 groups of 1, 2, 5, 10, 20, 30, 45, and 60 days after sound exposure. The EP level dropped remarkably in the 1 and 2 day groups and recovered almost completely in the remaining groups. In the 60 day group, EP was significantly higher than that of the control group. The double exposure group consisted of 1, 2, 5, 10, 20, and 30 day groups after the second exposure at an interval of 30 to 40 days. EP in the 1, 2, 5, and 10 day groups was significantly lower than the control level and in the 20 and 30 day groups was almost the same as that of the controls. In all groups after single and double sound exposure, disappearance of negative EP during anoxia was observed. The EP decrease after sound exposure was apparently caused by a mechanical but reversible lesion at the stria vascularis. The disappearance of negative EP after sound exposure was thought to be induced by an irreversible lesion of Corti's organ.

Animals↗
PubMed1990

Long-term effects of intense sound on hair cells of Corti's organ and endocochlear DC potential.

Cochleograms of guinea pig ears were made 30-40 days after exposure to intense pure tones of 300 Hz, 500 Hz, 2 kHz, or 4 kHz at 130-150 dB SPL for 4-24 h. At 4 kHz, hair cells in the basal turn disappeared totally, in the second turn moderately, and were relatively undamaged in the third and apical turns. At 500 Hz, hair cells in the second and third turns were almost completely injured and at 300 Hz moderately damaged in the third and apical turns although the basal turn remained undamaged. At 2 kHz for 9 h, hair cells were almost completely injured in all turns. Negative endocochlear DC potential (negative EP) induced by furosemide was observed in the basal turn but not in the third turn of animals exposed to 300 Hz. Contrarily, negative EP was observed in the third turn but not in the basal turn of animals exposed to 4 kHz. We conclude that the hair cells of Corti's organ play an essential role in the production of negative EP.

Acoustic Stimulation↗