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Biomedical subjects

Y Harada

Publications and source records attributed to Y Harada.

At least 703 records · Page 39Linked to original sources
PubMed1985

An experimental study on the physical properties of the cupula. Effect of cupular sectioning on the ampullary nerve action potential.

The frog posterior semicircular canal (PSC) was isolated and a part of the ampullary wall was cut to allow removal of the cupula from the crista. The cupula was replaced on the crista and the PSC ampullary action potential was recorded. The cupula was again removed and was sectioned in half, either in the plane vertical to the crista (vertical sectioning), or in the plane parallel to the crista (horizontal sectioning). The sectioned half of the cupula was then replaced on the crista. The action potentials after replacement of the vertical or horizontal segments of the cupula were compared to those achieved when the entire cupula was replaced. After vertical sectioning, the action potentials were significantly reduced; they were 50.3% of the completely replaced cupula when a small stimulus was used and 79.1% when a large stimulus was used. A reduced attachment surface between the cupular base and the crista is possibly responsible for the decreased action potential in the vertically sectioned specimen. After horizontal sectioning, the action potentials were 64.5% for the small stimulus and 108.2% for the large stimulus. These results indicate that elicited responses are related to the height of the cupula and the deflection angle. This further suggests that the movement of the cupula is represented by that of the elastic system.

Action Potentials↗
PubMed1985

Exposure and direct stimulation of the semicircular canal cupula.

The ampullary wall of the posterior semicircular canal was isolated from the frog, cut and the cupula exposed in frog Ringer's solution. The cupula was stimulated by depression with a fine glass micropipette. Three points on the cupula were selected for depression: point A, the lowest point on the midline of the cupula surface on the utricular side; point B, the uppermost on the midline of the same surface; and point C, in the middle of the lateral surface of the cupula. Depression at points A and B was toward the canal, whereas depression at point C was toward the centre of the cupula. The amount of depression was controlled by a micromanipulator. At point A, the minimum depression facilitating the posterior canal action potential was 1 micron; at point B, a greater amount of depression was needed to produce the action potential. Even a large amount of depression at point C resulted in only a small action potential, possibly because the direction of the sensory cell polarity is along the long axis of the canal.

Animals↗
PubMed1985

Physiological localization of the semicircular canal receptors in the crista.

Isolated posterior semicircular canals from the bull frog model were used. The cupula was removed from the crista and the sensory cilia on the crista were depressed toward the canal side by using a glass micropipette. Seven different points were selected for stimulation on the ampullary wall. Ampullary nerve action potentials induced by depression were recorded and were converted into spike-density histograms. Response decremental time constants were measured on these histograms. The longest time constant was measured at the two lateral points of stimulation and progressively shortened toward the central point of stimulation. These results indicate that the origin of the adaptation is possibly sensorineural.

Action Potentials↗
PubMed1985

A new theory for thermal influences on endolymphatic flow.

We applied thermal stimuli to the partly isolated posterior canal of the bullfrog half-head preparation. Warming or cooling stimuli to the canal side changed the activity of the semicircular nerve. Our results suggest that changes in the endolymphatic density might be responsible for convection flow in the semicircular canal as well as calorically induced nystagmus.

Animals↗
PubMed1985

An experimental study on the physiological significance of the mode of cupular movement.

Isolated frog posterior semicircular canals were used. The ampullary nerve action potentials were recorded under three kinds of cupular movement, i.e., swing-door deflection, "cupula fixation-1" and "cupula fixation-2". Cupula fixation-1 was achieved by immobilizing the central top portion of the cupula, while cupula fixation-2 was achieved by immobilizing the entire top of the cupula. Cupula fixation-1 resulted in action potentials which were comparable to those of the swing-door deflection in terms of the maximum spike count and the stimulus-response curve. Cupula fixation-2 resulted in potentials with the maximum spike count comparable to the swing-door deflection; however, the response increase rate was very low. The time courses of the potentials in those cases of cupula fixation-1 and -2 were extremely short (about 2-3s) when compared to that of the swing-door deflection. These findings suggest that the swing-door deflection is physiologically more relevant in giving the optimum increase in response rate, as well as maintaining the time course of the tonic response.

Animals↗
PubMed1985

Assessment of left ventricular function before and after Fontan's operation for the correction of tricuspid atresia. Changes in left ventricular function determined by left ventricular volume change.

Functional change in the left ventricle was studied in the light of changes in the left ventricular (LV) volume preload before and after Fontan's operation. Six cases with tricuspid atresia (TA) were studied, and they had either types Ib or IIb. The preoperative LV end-diastolic volume index (LVEDVI) was 123 +/- 44 ml/m2, which corresponds to 166% +/- 45% of normal values. This suggests that in TA the preload of the LV volume is increased because of its peculiar hemodynamic situation. After Fontan's operation, the LVEDV decreased by 24.6% to 119.6 +/- 87.7 ml (P = 0.01), which corresponds to 120% +/- 50.9% of normal values. Presenting a striking contrast to the decrease in LVEDV, the postoperative reduction in LV end-systolic volume (LVESV) was approximately 8%. Preoperative and postoperative values for LVESV were 67.1 +/- 50.8 ml and 62 +/- 45.6 ml, thus, the systolic volume was decreased. Because of the small change in LVESV, the ejection fraction (EF) of the left ventricle significantly decreased from 0.61 +/- 0.1 preoperatively to 0.48 +/- 0.1 postoperatively. The cardiac index (CI) remained in the range of 1.9-2.5 l/min/m2 with a mean of 2.2 +/- 0.2 l/min/m2 at 1 month after operation. But, later, improvement in EF was observed in one case, in which the CI increased from 2.5 to 3.2 l/min/m2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Induction of SOS responses in Escherichia coli by Panfuran-S, 3-di(hydroxymethyl)amino-6-(5-nitro-2-furylethenyl)-1,2,4-triazine.

The inducibility of SOS responses by Panfuran-S, which has been used as an antimicrobial medicine in Japan, was studied in Escherichia coli cells having different DNA-repair capacities for UV lesions. Panfuran-S induced mutations at high frequencies in uvrA and the wild-type strains, and significant killing effects of Panfuran-S were detected in DNA-repair-deficient strains, uvrA and recA. The effective prophage induction was detected in two kinds of lambda-lysogenized cells treated with Panfuran-S. The expression of the umuC+ gene was apparently induced in uvrA and the wild-type strains, but not induced in lexA and recA strains. In particular, high inducibility of the gene expression was detected in uvrA strain as compared with the wild-type strain. From these results, we conclude that Panfuran-S is a DNA-damaging agent and may induce the error-prone SOS responses.

Anti-Bacterial Agents↗
PubMed1985

A study of the nerve endings of the outer hair cells in the organ of Corti--using scanning electron microscopy.

The nerve endings on the outer hair cells of the guinea pig organ of Corti were studied using a scanning electron microscope. The nerve endings in the basal turn were entirely exposed in the space of Nuel, whereas in the upper turns almost all nerve endings were covered by the Deiters' cell bulge. The number and the size of the nerve endings gradually decreased from the basal turn toward the apical turn. The shape of the nerve endings was spindle-shaped in the basal turn, while it was round in the upper turn. Some nerve endings were found to locate close to the outer hair cell surface. No pathological change was observed in the nerve endings 25 hr after completion of series treatments of streptomycin or kanamycin. However, the outer hair cells consistently showed shrinkage, especially in the basal turn.

Animals↗
PubMed1985

Aqueductal stenosis--results of vestibular function tests.

A case of aqueductal stenosis is reported. The patient was a 14-year-old Japanese girl who was suffering from bilateral tinnitus and unsteadiness of gait. A series of neuro-otological tests revealed prolonged acoustically evoked brain stem response (ABR) latency, disturbed standing reflex, inhibited optokinetic nystagmus (OKN) and ataxic eye tracking test (ETT). Marked distension of the lateral and third ventricles was noticed on CT examination of the brain. A positive contrast ventriculogram using iotalamic acid showed occlusion of the cerebral (Sylvian) aqueduct. All of these results are suggestive of benign, non-neoplastic aqueductal stenosis with associated hydrocephalus. The patient underwent ventriculo-peritoneal shunt and, following the surgery, the results of neuro-otological, including radiological, re-examination indicated a remarkable recovery.

Adolescent↗
PubMed1985

In vitro IgE-secreting cells in man. I. Mitogen-independent and -dependent subpopulations.

In vitro IgE secretion by atopic and normal peripheral-blood lymphocytes was examined in culture with pokeweed mitogen or Staphylococcus aureus strain Cowan-I (StaCw) or without mitogen. IgE secreted in culture supernatants was measured with double antibody radioimmunoassay. Enumeration of IgE-secreting cells was made by a protein-A plaque assay. IgE was detected in increasing quantities in supernatants of cultured lymphocytes without mitogen up to the 12th day. IgE-plaque-forming cells were formed by the lymphocytes in large numbers on days 4-7 in cultures with mitogen. These results suggest that not only mitogen-independent but also mitogen-dependent subpopulations may exist in the IgE-secreting cells.

Antibody-Producing Cells↗
PubMed1985

Differential effects of carbon dioxide and pH on central chemoreceptors in the rat in vitro.

The brain stem, cervical cord and attached phrenic nerve were excised from neonatal rats and superfused in vitro. Respiratory activity was recorded from the phrenic nerve following transection of all the cranial nerves and dorsal roots. The frequency of spontaneous periodic activity recorded from the phrenic nerve was 6-14/min during superfusion with a saline solution equilibrated with 5% CO2 in O2 at 25 degrees C (pH 7.3). The magnitude of respiration was estimated from the peak value of phrenic activity integrated for each 0.1 s period. When the pH of the superfusion fluid was altered by changing the HCO3-concentration at constant PCO2, respiratory activity increased in low pH and decreased in high pH. These changes were maintained as long as a given pH was held. Respiratory changes observed under these conditions were characterized by alterations in both respiratory frequency and magnitude. When the CO2 level of the superfusion fluid was altered, maintaining constant pH by modified HCO3-concentrations, respiratory activity increased at high PCO2 and decreased at low PCO2. These changes were transient and lasted only for a few minutes after exposure to a new level of PCO2. Respiratory changes observed under these conditions were characterized by alterations in magnitude but not in frequency. At constant PCO2 an increase in the HCO3-concentration occasionally enhanced the magnitude of respiration before respiratory activity was depressed by the increased pH. This suggests that HCO3- may act independently as a stimulus to the central chemoreceptor. It is concluded that the mammalian central chemoreceptor for respiratory control is responsive independently to H+ and CO2 and that H+ and CO2 exert differential effects on the respiratory centre in terms of frequency and magnitude. It is suggested that frequency modulation and magnitude (tidal volume) modulation for respiratory control are triggered at different regions in the respiratory centre and/or rely on different mechanisms.

Animals↗
PubMed1985

An experimental study on the frog semicircular canal--functions of cupula and vestibular ganglion.

An isolated frog posterior semicircular canal was stimulated either by mechanical or thermal endolymphatic flow. Ampullofugal stimulation induced action potentials from the posterior ampullary nerve. These potentials adapted in six to eight seconds. While mechanical endolymphatic flow was induced, the cupula maintained its shift position without swinging back to the neutral point. This indicates that adaptation is mainly of sensorineural origin. When the canal was stimulated by a piece of frozen Ringer's solution, an increase in spike discharge was observed. The responses from the vestibular nerve trunk were compared to those from the posterior ampullary nerve. The time course of the response was shorter and the maximum spike count was smaller in the recordings from the vestibular nerve trunk.

Action Potentials↗