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Biomedical subjects

Y Yazawa

Publications and source records attributed to Y Yazawa.

At least 73 records · Page 4Linked to original sources
PubMed1987

Induction of experimental endolymphatic hydrops by immunologic techniques.

Immunologic techniques have been used by many investigators to produce experimental endolymphatic hydrops models. These techniques, however, have achieved little success in producing models simulating the idiopathic endolymphatic hydrops of Meniere's disease, in which no inflammatory changes occur in the perilymphatic spaces. In this study, the antigen horseradish peroxidase (HRP) was injected into the endolymphatic sacs of ninety guinea pigs that had been systematically sensitized to this antigen. Endolymphatic hydrops was induced in sixty-seven of the subjects, sixty-four of which showed no inflammatory changes in the perilymphatic spaces. The endolymphatic sacs of the affected guinea pigs were packed with soft granulation tissue induced by immunologic mechanisms; it is felt that the hydrops was caused by disturbances in endolymph absorption resulting from these tissue formations. Our results suggest that the introduction of antigens into the endolymphatic sac may prove useful in producing endolymphatic hydrops with characteristics similar to those occurring in Meniere's disease.

Animals↗
PubMed1985

Endolymphatic hydrops in guinea pigs after cauterizing the sac with silver nitrate.

There have been several reports of perisaccular fibrosis of the endolymphatic sac in some autopsied cases of Meniere's disease. We attempted to initiate perisaccular fibrosis of the sac in guinea pigs by injecting a small amount of 10% silver nitrate solution that cauterizes the tissue readily to produce scar, ie, fibrosis. Ninety-nine guinea pigs out of 108 (92%) that were treated with silver nitrate showed the endolymphatic hydrops in varied extent, from slight to profound. The extent of hydrops might depend on the extent of destruction of the sac following the cauterization. The lumen of the sac was sometimes occupied with dense fibrous connective tissue with deposition of black-silver particles in it. The silver nitrate injection method is an easy way to produce endolymphatic hydrops in guinea pigs.

Animals↗
PubMed1985

Type II collagen mediated autoimmune middle ear disease: eustachian tube disease, otitis media with effusion and tympanosclerosis.

Intact Eustachian tube and tympanic cavity functions are essential for normal middle ear physiology. Type II collagen is an essential component of ear tissue. Autoimmune response to this type II collagen produces sensorineural hearing loss, vestibular dysfunction, endolymphatic hydrops, otospongiosis-like lesions, Eustachian tube inflammation and Eustachian tube chondritis. In addition, these autoimmune responses occasionally produce otitis media with effusion (not infectious). Tympanosclerosis, which is a frequent sequelae of otitis media with effusions, was also induced by type II collagen immunization together with surgical incision of the tympanic membrane. The exact mechanisms of this type II collagen autoimmune mediated middle ear disease are not clear. However, the animals thus induced have higher antibody titers and cell mediated immune responses to type II collagen. The tympanic membrane showing tympanosclerosis also had C3 and Ig deposits. All the animals with otitis media with effusion induced by type II collagen immunization also had Eustachian tube disease. This could be due to a malfunction of the Eustachian tube. Thus, this model might provide a rational approach for the study of otitis media with effusion associated with vasculitis. Further studies are needed to elucidate the immunologic mechanism involved in the pathogenesis of otitis media with effusion.

Animals↗
PubMed1985

Effect of urea on endolymphatic hydrops in guinea pigs.

The morphological changes of the inner ear were observed after intravenous administration of 2 g/kg of urea to the guinea pigs with endolymphatic hydrops which had previously been produced by injecting 10% silver nitrate solution into the endolymphatic sac. They showed membranous collapse extensively in the saccule, moderately in the lower turns of the cochlea and less in the upper turns and the utricle. Because of these changes, it is reasonable to assume that urea is causing the endolymph to be reabsorbed in the endolymphatic duct. Furthermore, the effect of urea seemed to depend on the pathological condition of the duct which sometimes showed a varying degree of atrophied change after silver nitrate injection.

Animals↗
PubMed1985

Compressed heart and mitral valve prolapse in a case of Duchenne's progressive muscular dystrophy with thorax deformity.

We report on a 15 year old patient with Duchenne's progressive muscular dystrophy who demonstrated a narrowing of the left ventricular inflow and outflow tracts due to compression by a highly deformed thoracic spine. A systolic murmur (4/6) with thrill and a diastolic murmur (2/6) were heard, with these murmurs being louder in the expiratory phase as compared with the inspiratory phase. The second heart sound showed a paradoxical splitting. Echocardiograms revealed a compressed and narrowed left ventricle and a prolapsed mitral valve. The intensities of the heart murmurs changed synchronously with the chamber's narrowing due to respiration. A narrowed left ventricle occurring as a result of the compression by the deformed thoracic spine is thought to be the cause of these cardiac findings.

Adolescent↗
PubMed1984

Mitral valve prolapse related to geometrical changes of the heart in cases of progressive muscular dystrophy.

The significance of geometrical changes of the heart for the development of mitral valve prolapse (MVP) was studied by echocardiograms and chest x-ray films in 58 cases of progressive muscular dystrophy (PMD). The incidence of MVP was significantly higher (p less than 0.001) in cases where the thoracic spine was straight or lordotic compared with cases of kyphotic thoracic spine. The flattening of the thorax associated with deformation of the thoracic spine was correlated with the left atrial dimension and left ventricular dimension (r = 0.62, r = 0.37, respectively; p less than 0.001), and MVP developed predominantly in cases with flattened thorax and small left atrial or left ventricular dimensions. The left atrial and left ventricular dimensions were significantly smaller in cases with MVP compared to cases without MVP (p less than 0.001, p less than 0.005, respectively). When both the left atrial and the left ventricular dimension shortened to certain levels, MVP was observed in almost all cases. From these results, it was suggested that the portion from the left atrium to the left ventricle was pressed by the forward bending of the thoracic spine, and the subsequent geometrical changes of the mitral ring and the left ventricle could produce redundancy of the chorda tendinea of the mitral valve, resulting in the occurrence of MVP.

Adolescent↗
PubMed1984

Different response of left ventricular dimensions to nitroglycerin in patients with artificial pacemaker. A possible significance of reflex tachycardia for the reduction of LV cavity after nitroglycerin.

The effects of nitroglycerin (NTG) on cardiac function can be evaluated by echocardiography. In this paper, we discuss the effects of NTG on cardiac function in two groups of subjects, one with artificial pacemakers implanted with a fixed heart rate, and the other examined as the control group. Left ventricular dimension was obtained in the standard manner using the electronic sector scanning system of Toshiba SSH-11A. Left ventricular end-diastolic and end-systolic dimensions (Dd and Ds) were obtained in each case and the ejection fraction was calculated. After the sublingual administration of NTG (0.6 mg), the blood pressure decreased in both groups. The ventricular rate was fixed in the pacemaker group but increased significantly in the control group. Dd and Ds were found to decrease only in the control group. The ejection fraction showed an increase in the majority of the control group but remained unchanged in the pacemaker group. Heart rate change therefore may play a role in dimensional change and pumping function of heart after NTG.

Adolescent↗
PubMed1984

The causative mechanisms of mitral valve prolapse in progressive muscular dystrophy in reference to thorax and thoracic spine deformities and left ventricular dysfunction.

The causative mechanisms of mitral valve prolapse (MVP) were evaluated in 58 patients with progressive muscular dystrophy (PMD). Two possible causes, 1) left ventricular (LV) dysfunction and 2) thoracic spine and thorax deformities were assessed. Patients were classified into three groups by echocardiographic findings. Group 1: 31 patients without MVP, group 2: 11 patients with MVP confirmed only by M-mode echocardiogram, group 3: 16 patients with MVP confirmed by both two-dimensional and M-mode echocardiograms. LV functions evaluated by systolic time intervals and fractional shortening showed no significant differences among the three groups. Scoliosis of the thoracic spine was not related to the incidence of MVP. Lordotic or straight spines were found in 32.3%, 100%, 93.8% of cases in group 1, group 2 and group 3, respectively, and the incidences of MVP in cases with kyphosis, straight spine and lordosis were 4.8%, 66.7% and 77.8%, respectively. The shape of the thorax as evaluated by the ratio of anteroposterior internal diameter to transverse diameter was more flattened in groups 2 and 3 than in group 1. From these results, we concluded that LV dysfunction was not related to the incidence of MVP and that the lordotic or straight spine and the flattened thorax were supposed to be the major factors in the occurrence of MVP in PMD.

Adolescent↗
PubMed1984

Rebound phenomenon in glycerol test.

The glycerol effect for endolymphatic hydrops is well known for an improvement in pure tone threshold three hours after glycerol administration. However, long-term effects of glycerol, i.e., longer than three hours after administration, are unknown. In this study, audiometric tests were administered during 10 hours following glycerol administration in order to determine the long-term effects of glycerol in cases of Meniere's disease, sudden deafness, and normal subjects. The following results were obtained; 1) The long-term effects of glycerol in the pure tone threshold were observed only in cases of Meniere's disease and were classified into the following four types: "descending type", "descending and ascending type", "ascending type" and "unchanged type". 2) The long-term effects, including rebound phenomenon, on hearing ability did not appear in cases of sudden deafness and normal subjects. 3) About 50% of patients with Meniere's disease showed rebound phenomenon on hearing ability and it was considered to be specific for Meniere's disease.

Audiometry↗
PubMed1983

Type II collagen-induced autoimmune endolymphatic hydrops in guinea pig.

Endolymphatic hydrops was induced in guinea pigs by immunizing them with native bovine type II collagen. Histopathologic changes consisted of moderate extension of the Reissner's membrane, spiral ganglion degeneration, atrophied organ of Corti, and mild atrophy of the surface epithelium in the endolymphatic duct. These findings suggest that an immune response directed against type II collagen--a type of collagen found in the membranous labyrinth, subepithelial layer of the endolymphatic duct, spiral ligament, and enchondral layer of the otic capsule--may induce endolymphatic hydrops.

Animals↗