Biomedical subjects

T Kumazawa

Publications and source records attributed to T Kumazawa.

At least 181 records · Page 10Linked to original sources

PubMed1993

Is pentobarbital appropriate for basal anesthesia in the working rat heart model?

In the present study we have examined the effects of the general anesthetic agents for the excision of the heart on the hemodynamic function of the ischemic perfused heart. Animals were divided into three groups. In one group rats were anesthetized with sodium pentobarbital intraperitoneally. Animals of the second and third groups were anesthetized with inhalation anesthetics, sevoflurane and isoflurane, respectively. The hearts were then rapidly excised and perfused by a working heart model. After control perfusion, whole-heart ischemia was induced by one-way aortic valve for 15 min followed by reperfusion for 30 min. During preischemic control period, cardiac output (CO) and left ventricular dP/dT maximum (LV dP/dT max) in the isoflurane group were significantly higher than those in the pentobarbital group. During reperfusion, CO and LV dP/dT max in the isoflurane and sevoflurane groups recovered more rapidly than those in the pentobarbital group. Although there were no significant differences in myocardial ATP and glycogen levels among the groups, myocardial lactate in the pentobarbital group was significantly higher than those in the sevoflurane and isoflurane groups. These results suggest that intraperitoneal pentobarbital anesthesia, administered prior to heart excision, may affect the performance of the ischemic perfused heart thereafter. Therefore, we would suggest that isolation of hearts by means of inhalation anesthesia is better than by means of pentobarbital in the working rat heart.

Administration, Inhalation↗

PubMed1993

Eustachian tube function tests and their diagnostic potential in normal and diseased ears.

We have summarized various methods for testing Eustachian tube function since the 1980's. There have been numerous contributions to our knowledge on Eustachian tube and middle ear functions, and the pathophysiology of disorders of the middle ear has been clarified. Understanding of the Eustachian tube function and controlling the Eustachian tube dysfunction are mandatory for adequate clinical management and for improvement of the prognosis.

Adult↗

PubMed1993

Tubotympanoplasty.

Prognostic value of the Eustachian tube function test remains controversial. To prevent ear drum adhesion or the recurrence of cholesteatoma it is important to select cases with severe organic obstruction of the Eustachian tube and to use surgical procedures to restore function. We summarize here the indications and the surgical procedure for organic obstruction of the Eustachian tube, especially in the region of the tympanic orifice. Adequate preoperative evaluation of Eustachian tube function and pertinent surgical procedures will pave the way for a better prognosis for patients subjected to ear surgery.

Adult↗

PubMed1993

Identification of rat brainstem sites with neuronal Fos protein induced by acoustic stimulation with pure tones.

Induction of Fos, a proto-oncogene c-fos protein product, was immunohistochemically examined in the rat brainstem by using pure tone stimuli (0.25 kHz, 4kHz and 8 kHz) at 60 and 80 dB sound pressure levels for 30 min. In comparison with non-stimulated control rats, the brainstem of sound-stimulated rats exhibited distinct Fos-labeled neuronal cell nuclei in i) the ascending auditory nuclei, ii) the brainstem sites which receive afferents from the auditory nuclei, i.e. the pretectum and rostroventrolateral reticular nucleus, iii) the parvocellular part of the ventral lateral geniculate nucleus, lateral reticular nucleus, ventral border region of the spinal trigeminal nucleus, and the medial vestibular and spinal vestibular nuclei, all of which lack established auditory projections, and iv) the brainstem sites where some Fos-labeled neurons were present in controls. Sound stimulation at 80 dB led to widespread Fos-labeling in all these sites. Sound stimulation at 60 dB caused a decrease in number of positive cells in the brainstem sites and yielded a tone-dependent subregional distribution pattern in the dorsal cochlear nucleus and central nucleus of the inferior colliculus.

Animals↗

PubMed1993

A possible masking effect of tinnitus. Evaluation of CNV audiometry.

To determine whether tinnitus has a masking effect similar to that of general external sounds, the hearing threshold shift when the tinnitus was changed by intravenous administration of lidocaine was measured by contingent negative variation (CNV) audiometry. In a preliminary study, the reliability of CNV audiometry was evaluated in 12 patients with tinnitus. The reproducibility of CNV audiometry was confirmed, based on repeated measurements of CNV audiometry at the tinnitus frequency. The threshold difference between CNV audiometry and pure tone audiometry was -0.76 +/- 1.35 dB, and a high statistical correlation between the threshold of CNV audiometry and pure tone audiometry was evident. The CNV threshold shift at tinnitus frequency after lidocaine injection was measured in 89 ears. In the tinnitus-decreased group, the CNV threshold decreased (4-6 dB) in 22% of cases; however, in the tinnitus-unchanged group, the CNV threshold was little changed. These findings suggest that tinnitus may have a masking effect as is the case with external sounds.

Audiometry, Evoked Response↗

PubMed1993

Effects of efferent neurotransmitters on intracellular Ca2+ concentration in vestibular hair cells of the guinea pig.

The effects of putative efferent neurotransmitters on intracellular Ca2+ concentration ([Ca2+]i) in isolated vestibular hair cells (VHCs) of the guinea pig were determined using the Ca2+ sensitive dye Fura-2 and digital imaging microscopy. In the presence of 1 mM acetylcholine (ACh) there was a gradual increase in [Ca2+]i. In the presence of 10 microM ATP there was a rapid rise in [Ca2+]i. Thus, both ACh and ATP seem to be efferent neurotransmitters in VHCs of the guinea pig. When 100 microM Gamma-aminobutyric acid (GABA) was added there was a rapid increase in [Ca2+]i; thus GABA also seems to be an efferent neurotransmitter in VHCs. With the independent addition of 10 microM calcitonin gene-related peptide and 10 microM M- and L-enkephalin there were no significant increase in [Ca2+]i. We presume that these neuropeptides were functioning as efferent neuromodulators rather than as neurotransmitters.

Acetylcholine↗

PubMed1993

Menière's disease and autoimmunity: clinical study and survey.

In order to clarify whether autoimmune mechanisms form part of the etiopathogenesis of Meniere's disease, sera and endolymphatic sac tissues from 30 patients with Meniere's disease were analyzed according to the clinical criteria for autoimmune diseases stated by Mackay & Burnet. Several cases showed hyper gamma-globulinemia, antibody elevation to Type II collagen in the serum and endolymph, positive staining to immunoglobulins and C3 or infiltration of immuno-competent cells in the endolymphatic sac, good response to prednisolone and combination with systemic immune disorders. Other examinations showed a significant elevation of OKT 4/8 ratio and a decrease of OKT8-positive cells, and elevated levels of circulating immune complex and antiviral antibody titers. It is suggested that certain cases of Meniere's disease may have an altered immunological background, which may be attributed to an autoimmune mechanism dependent on humoral and/or cellular responses.

Adult↗

PubMed1993

Surgical anatomy for infralabyrinthine approach to the internal auditory canal.

Surgical anatomy for infralabyrinthine approach to the internal auditory canal was evaluated using human temporal bone in order to understand advantages and disadvantages of this approach. The procedure is extracranial without any damage of labyrinth. Lateral exposure of the internal auditory canal allows for easy separation of the cochlear and vestibular nerves. There are some potential problems of little importance stemming from anatomical variations, such as high jugular bulb, forward positioned sigmoid sinus and poor pneumatization of the infralabyrinthine space. This approach offers access to the eighth cranial nerve with minimal risk and morbidity.

Cochlear Nerve↗

PubMed1993

Regulation of Cl- conductance in delayed shortening and shrinkage of outer hair cells.

Tetanic electrical field stimulation induces slow and delayed shortening of isolated outer hair cells (OHCs) from guinea pigs concomitant with a decrease in cell volume and intracellular Cl- concentration ([Cl-]i). These responses are dependent on the entry of Ca2+ and the activation of both Ca(2+)-activated K+ channels and furosemide-sensitive Cl- channels. In this study, the regulatory mechanisms of the Cl- channels of OHCs were investigated. Tetanic stimulation induced shrinkage and a decrease in [Cl-]i, the latter being unrelated to the activity of the Na+/K+/2Cl- cotransporter. These responses were inhibited by tetraethylammonium, and the inhibition was overcome by an increase in the K+ conductance by valinomycin, though valinomycin alone did not affect the resting cell volume and [Cl-]i. The deprivation of extracellular Ca2+ inhibited the stimulation-induced changes in volume and [Cl-]i even in the presence of valinomycin. These results suggest that electrical stimulation-induced delayed shortening and shrinkage of OHCs are induced by Cl- efflux, which is electrically coupled to K+ efflux and independently activated following an increase in intracellular Ca2+ concentration.

Animals↗

PubMed1993

Thermal influence on intracellular calcium concentration in vestibular hair cells isolated from the guinea pig. A preliminary report.

Caloric responses to intracellular calcium homeostasis of vestibular hair cells isolated from the guinea pig were examined. An increase in intracellular free calcium ion concentration ([Ca2+]i) in the isolated cells was observed by direct heat stimulation. The cells, dissociated enzymatically or mechanically, were stimulated by perfusion of solution, in the temperature range of 2.2-5.2 degrees C. The [Ca2+]i was analysed using a digital imaging microscope and the Ca2+ sensitive dye, Fura-2. There was an increase in [Ca2+]i in both Types I and II vestibular hair cells with this heat stimulation. The direct thermal influence on vestibular sensory cells is discussed in relation to mechanisms involved in caloric nystagmus.

Animals↗

PubMed1993

Effects of acetazolamide on acid-base balance in the endolymphatic sac of the guinea pig.

The effects of acetazolamide, a carbonic anhydrase inhibitor, on acid-base parameters in the endolymphatic sac of the guinea pig were investigated using ion-selective microelectrodes. Bicarbonate concentration was reduced and pH shifted to being acidic immediately after administration of acetazolamide. Chloride concentration in the endolymphatic sac increased after carbonic anhydrase inhibition. These findings provide evidence of an active function of carbonic anhydrase in the endolymphatic sac and suggest that carbonic anhydrase activity is involved in the formation of endolymphatic sac fluid.

Acetazolamide↗

PubMed1993

MR imaging of vascular compression in hemifacial spasm.

Hemifacial spasm is related to vascular compression of the root entry zone of the facial nerve at the brainstem by elongated tortuous vessels of the vertebrobasilar arterial system. In this study, we performed MR imaging in 16 patients with hemifacial spasm and investigated the vascular structures in bilateral-cerebellopontine angles and the relationship of each vessel to the root entry zone of the facial nerve. MR examination was performed with a 0.5 tesla MRI system, and MR angiography (3D time-of-flight) was obtained. Of 15 patients in whom both the nerve and vessels were clearly visible and could be observed to contact each other at the root entry zone, in 11 the tortuous artery could be identified by name. In only 1 patient was the contact between the nerve and vessel indeterminate, due to nonvisualization of the vessel around the facial nerve at its root entry zone. These findings suggest that MRI is a useful screening method in the preoperative assessment of hemifacial spasm.

Adult↗

PubMed1993

Enhanced MRI in patients with Ramsay-Hunt's syndrome.

Enhanced MRI was performed in 14 patients with Ramsay-Hunt's syndrome to investigate the pathogenesis of this syndrome. All MRI studies were performed on a 0.5T superconductivity MRI system using a head coil with Gd-DTPA. Enhancement was observed in the areas of the distal internal auditory canal and labyrinthine segment in many patients, and was especially prominent in patients suffering from vertigo, tinnitus, and hearing loss. In some patients it involved not only the facial nerve of the internal auditory canal but also the cochlear nerve and vestibular nerves. Since histological changes of the facial nerve in patients with Ramsay-Hunt's syndrome are assumed to occur in the distal internal auditory canal and labyrinthine segment, which is more proximal than the geniculate ganglion, and the possibility is suggested that inflammation may spread to the vestibular and cochlear nerve via the internal auditory canal.

Aged↗

PubMed1993

Active opening function of the human eustachian tube: comparison between sonotubometry and pressure equilibration test.

Sonotubometry and pressure equilibration test are representative test methods to evaluate the active opening capacity of the Eustachian tube. We applied these tests to 72 ears with otitis media with effusion and 21 ears with chronic otitis media. In 73 ears, both tests showed identical results (11 ears with good active function and 62 ears with poor function). Twenty ears showed good active opening by sonotubometry despite inability to relieve applied negative pressure by swallowing. This inconsistency is believed to result from a too short duration of the tubal opening, by which sound is transmitted through the Eustachian tube, without pressure change in the middle ear cavity. We propose that sonotubometry is a suitable method of detecting impairment of the tubal active opening function, but that a good result by sonotubometry does not always indicate a satisfactory pressure equilibration capacity of the Eustachian tube.

Adult↗

PubMed1993

Otitis media with effusion and eustachian tube dysfunction in adults and children.

Eustachian tube (ET) function was studied in 162 ears with otitis media with effusion (OME) and chronic otitis media (COM), using tubo-tympanoaerodynamic graphy, patency and pressure equilibration test in the inflation-deflation test. Severe impairment of active opening function was found in both OME children and adults compared with that of COM patients. This impairment in active opening was thought to result from functional obstruction of the ET in 71.8% of OME children and 51.8% of OME adults. However, 45.6% of OME adults had an organic obstruction while such was present only in 28.2% of OME children. We deduce from this study that impaired active opening function of the ET in both OME children and adults is the result of functional obstruction rather than organic obstruction, but organic obstruction is considered to be related to the pathogenesis of OME in adults.

Adolescent↗

PubMed1993

Animal model of otitis media with effusion.

A rat model of otitis media with effusion (OME) was developed by intratympanic injection of E. coli endotoxin and section of the third branch of the trigeminal nerve (V3). The period of fluid retention induced by the endotoxin was prolonged for 5 days or longer, in cases when tubal function was impaired by cutting of V3. Three Eustachian tube function tests (patency test of inflation-deflation tests, forced response test and negative pressure test) were carried out before and after the endotoxin inoculation and V3 sectioning. At 4 days after these procedures, passive opening pressure (Po), closing pressure (Pc) and tubal resistance (R2) were significantly lowered. The negative pressure test showed impaired capacity of active opening. This model of Eustachian tube dysfunction is considered to reveal functional obstruction, a condition similar to that of clinical cases of OME. The study shows that both inflammation in the middle ear and tubal dysfunction, such as functional obstruction, are factors in the development and prolongation of OME.

Animals↗

PubMed1993

Culture of middle ear epithelium: a review.

We discuss several techniques of culturing middle ear epithelium from several species, which was formerly difficult but is now possible because of recent advances in culture methods. The three main methods of initiating a culture are organ culture, primary explant culture, and cell culture. Although each method has both advantages and disadvantages, investigators can choose the method most suitable to their purpose. A few researchers, including ourselves, have succeeded in obtaining serial culture of middle ear epithelium. Using 3T3 feeder layer technique or conditioned medium enabled us to develop a fibroblast-free cultured middle ear epithelium. The availability of cultured middle ear epithelium provides a potential tool in future middle ear research.

Animals↗

PubMed1993

Regional blood flow volume in the eustachian tube.

Measurements of regional blood flow around the pharyngeal orifice of the Eustachian tube were carried out after topical administration of various inflammatory mediators in 14 mongrel dogs by the hydrogen clearance method. Histamine and platelet-activating factor (PAF) resulted in a significant alteration of blood flow volume. Histamine was found to induce a dose-response related increase, whereas blood flow volume tended to decrease in each concentration range in the series of PAF administration. There was no significant difference in blood flow between topical application of leukotriene C4 and leukotriene D4. It is likely that in upper respiratory tract inflammation, such as in otitis media and in nasal allergy, activated histamine and PAF affect the microcirculation of the tubal orifice. These results suggest that disturbance of the microcirculatory system in the Eustachian tube mucosa could be involved in the pathogenesis of chronic otitis media with effusion.

Animals↗