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Biomedical subjects

S Hotta

Publications and source records attributed to S Hotta.

At least 19 recordsLinked to original sources
PubMed2003

Time-intensity trade of bilaterally bone-conducted sounds in normal hearing subjects.

OBJECTIVE AND METHODS: In an effort to examine the rules by which information of bilaterally applied bone-conducted signals arising from interaural time differences (ITD) and interaural intensity differences (IID) is combined, data were measured for continuous 500 Hz narrow-band noise at 60 dBHL in 30 normal-hearing subjects using a centering method. Time-intensity trading functions were obtained by means of a sound image shifted towards one side by presenting an ITD, and shifted back to a centered sound image by varying the IID in the same ear. ITD values were varied from -600 to +600 microseconds at 200 microseconds steps, where negative values indicate delays to the right ear. RESULTS: Time-intensity trading functions in response to bone-conducted signals showed significantly lower discrimination thresholds across IIDs, when compared to a control group with applied air-conducted signals. These findings can be interpreted as a constructive interference effect related to the intimate mechanism of bilateral bone conduction, where interaural time differences play a major role. CONCLUSION: Time-intensity trade of bilaterally bone-conducted sounds in normal-hearing subjects is the highly sensitive. The high speed of sound through the skull may be the main reason for the high sensitivity of time-intensity trading.

Adult↗
PubMed1999

The effects of tone exposure on the inner ear functions in the guinea pig: impact tone vs. steady state tone.

The damage-risk criterion (DRC) for hearing supposes that sound exposure with equal energy implies equal risk for noise-induced hearing loss (NIHL). We measured cochlear microphonics (CM), compound action potential (CAP), endocochlear potential (EP) and K+ ion concentration in the scala media, to see if the same level of Leq24h (impact tone and steady state tone) induced the same physiological changes in the inner ear function or not. Regarding the equal energy principle (EEP), we also examined if the EEP is appropriate or not at exposure of moderate level tone. We also checked how the time interval between impact tones affects or not the inner ear functions at the same Leq24h tone exposure. Therefore we used exposure at 1 pulse/second or 1 pulse/3 seconds and steady state tone exposure at Leq24h=90, 85 and 80 dB. The results are the following. Both steady state and impact tone exposure causes change of the electrophysiological data. First, CM maximum output voltage after exposure to impact tone of 115 dB (Leq24h=90 dB) was lower than after exposure to a 8 kHz steady state tone of 90 dB. CAP threshold (below 10 microV) obtained after the 115 and 110 dB exposure of impact tone were 5-10 dB higher than that of steady state tone of 90 dB. The negative EP induced by impact tone exposures showed the same tendency as the CM experiments. Having more frequent pulses (1 pulse/second vs. to 1 pulse/3 seconds) showed more inhibition. The K+ concentration time course remained similar to the control when the Leq24h was low (80 dB). Impact tone exposure induced stronger effects to the inner ear at exposure of moderate level tone than that of steady state tone of Leq24h.

Acoustic Stimulation↗
PubMed1998

Experimental study on the effects of gentamicin injection on the guinea-pig: electrophysiological studies.

The inner ear distortion induced by gentamicin (GM), a type of aminoglycoside antibiotic, was examined in guinea-pigs. Previous studies which investigated the function of the eighth cranial nerve and organ of Corti using cochlear microphonics (CM) and compound action potential (CAP) reported ototoxicity following experimental exposure to GM. In this report, the effects of GM on the cochlea and the eighth cranial nerve were investigated systematically by measuring CM, CAP, summating potentials induced by 90 dB (SPL) tone burst, endocochlear potential (EP) and K+ ion concentration of the endolymph. Guinea-pigs were treated with a daily intramuscular injection of GM (60 mg in 1.5 cc) at a dose of 60 mg/kg during different treatment periods. The maximum output voltage of AP was decreased by injection of GM (60 mg/kg x 24). A decrease in the CM maximum output voltage and the elevation of CM pseudothreshold were typically seen after GM injection at a test frequency of 8 kHz and a decrease in CAP was also observed. Changes in EP during 3 min anoxia were observed, in particular a decrease in the absolute value of the negative potential. The endolymph K+ ion concentration remained unchanged. These findings indicate that the diffusion potentials decreased at the same time as reduction of maximum output voltage in CM induced by GM injection.

Action Potentials↗
PubMed1998

[An autopsy case of intravascular malignant lymphomatosis with hemophagocytic syndrome, mental confusion and liver dysfunction].

A 66-year-old Japanese man was admitted to Hitachi General Hospital because of fatigue, fever, edema, and icterus. A blood examination showed anemia, leukocytosis, and hyperbilirubinemia. Antibiotics did not alleviate the inflammatory symptoms. On the 13th hospital day, the patient demonstrated mental confusion, with progressive anemia and thrombocytopenia. Bone marrow aspiration revealed an increase of macrophages showing erythrophagocytosis. A diagnosis of hemophagocytic syndrome was made, but no viral infection or hematological malignancy could be detected. The patient was treated with gamma-globulin and methylprednisolone for hemophagocytic syndrome, but died of respiratory insufficiency with progressive hyperbilirubinemia and trombocytopenia on the 29th hospital day, A postmortem examination showed proliferation of lymphoma cells within the small blood vessels of the brain, lungs, liver, and many other organs, but the bone marrow was not involved. An immunohistochemical examination resulted in a diagnosis of intravascular malignant lymphomatosis (IML) of B cell origin. No viral infection was detected with in situ hybridization methods. Although IML occasionally accompanies thrombocytopenia, infiltration of lymphoma cells in the bone marrow is rare. Lymphoma associated hemophagocytic syndrome may cause cytopenia in some patients with IML, as indicated in this case.

Aged↗
PubMed1998

Light dose and time dependency of photodynamic cell membrane damage.

We have investigated the light dose and time dependency of photodynamic cell membrane damage using electrophysiological methods. This study controls the level of cell membrane damage by precisely administration of the light dose. The photosensitizer used was 5',5"-bis(aminomethyl)-2,2':5',2"-terthiophene dihydrochloride (BAT). A confocal laser scanning microscope was used to provide rapid light activation (< 1 s) and the subsequent membrane damage was monitored using standard patch clamp techniques. In the presence of 49 microM BAT, light levels less than 0.94 J/cm2 led to a reversible depolarization (approximately 20 mV) and reduction of resistance (approximately 10%) within 3 s of illumination. Higher intensities of illumination (> 1.57 J/cm2) caused a complete and irreversible loss of membrane potential and cell membrane resistance within 8 s illumination. The threshold dose of light required to induce cell death by illumination in the presence of BAT was increased in the presence of the antioxidant Trolox-C.

Animals↗
PubMed1997

An electrophysiological study of the effects of acute methylmercury chloride exposure on the function of the guinea pig cochlea.

The inner ear function of methylmercury chloride (MMC)-exposed guinea-pigs was examined in this study. Previous studies which investigated the function of the eighth cranial nerve and Corti-organ using cochlear microphonics (CM), compound action potential (CAP) and measurement of endocochlear potential (EP) reported ototoxicity following experimental exposure to MMC. In this report, the effect of MMC on the cochlea and the eighth cranial nerve were investigated systematically by measuring CM, action potential (AP), EP and K+ ion concentration of the endolymph. Guinea-pigs were injected with 5 mg/kg MMC (using 0.2% solution) twice a week for 1-3 weeks. The maximum output voltage of AP was decreased by injection of MMC (5 mg/kg x 6). A decrease in the CM maximum output voltage and the elevation of CM pseudothreshold was seen after MMC injection. Changes in EP during 3 min anoxia were observed, especially a decrease in the absolute value of the negative potential. The endolymph K+ ion concentration remained unchanged. These findings indicate that the diffusion potentials decreased and at the same time was reduced the maximum output voltage in CM induced by MMC injection (5 mg/kg x 6) in this experiment.

Action Potentials↗
PubMed1997

Dengue hemorrhagic fever in Jakarta, Indonesia in 1988: isolation of dengue virus from patient whole blood using cell cultures.

During an outbreak of dengue hemorrhagic fever (DHF) in Jakarta, Indonesia in 1988, we attempted to isolate dengue virus using mosquito cells and a medium containing heparin. Whole blood, immediately after being drawn from patients, was inoculated into Aedes albopictus cell cultures temporarily maintained in the heparin-containing medium. The overall virus isolation rate was 25% (17 of 69) samples collected within three days after admission of the patients to hospital. No virus was obtained thereafter. The successful virus isolation was apparently not related to titers of anti-dengue virus hemagglutination-inhibiting antibodies present in patients' sera. The viruses were recovered from cases of each of the four World Health Organization grades of DHF without significant differences. The technique is simple and easily performed at bedside.

Aedes↗
PubMed1996

A comparative study on the effect of pure-tone exposure of the guinea pig cochlea.

Electrophysiological methods were applied to 160 healthy adult male guinea pigs in order to investigate the effects of pure-tone exposure for 24 h on the inner ear. A reduction in cochlear microphonics (CM), action potential (AP) and endocochlear potential was observed following exposure to 110 dB at 100 Hz, 100 dB at 200 and 600 Hz and 95 dB at 2 kHz. The observed K+ endolymphatic concentration during 40 min anoxia remained unchanged. In contrast K+ decreased in control animals and following exposure to pure tones varying from 110 dB at 60 Hz to 85 dB at 2 kHz. These findings indicate that high frequency tones have a greater effect on inner ear functions than those of lower frequency, decreasing the maximum output voltage of CM and AP but not changing K+ endolymphatic concentration.

Acoustic Stimulation↗
PubMed1996

Combined effects of acute lead acetate exposure and tone exposure of the guinea pig cochlea.

Lead acetate exposure to humans can induce various disorders of the cranial nerves. Although vertigo and sensorineural deafness have been reported in lead workers, the dose effects of lead acetate on the cochlea and eighth cranial nerve are not well documented. We investigated the effects of lead acetate on the male albino Hartley guinea pig cochlea by measuring cochlear microphonics (CM), whole nerve action potential (AP), endocochlear potential (EP) and K+ ion concentration of the endolymph. Animals were given lead acetate by intraperitoneal injection as 20 mg/week for 4 consecutive weeks. A total dose < 80 mg did not induce electrophysiological changes in the cochlea. However, the AP output voltage (N1) decreased if the 80 mg lead acetate treatment was followed by an 80 dB tone exposure at 6 kHz during 24 h. A change was observed in CM and EP but not K+ ion concentration in the scala media.

Action Potentials↗
PubMed1995

Immediate changes in subcellular structures of transplanted tumors following photodynamic and laser hyperthermic therapy.

BACKGROUND AND OBJECTIVE: To further understand the precise process of the tumor cell degeneration after photodynamic therapy (PDT), laser hyperthermic therapy (LH), and combined treatments using an Nd:YAG laser. It is important to examine initial morphological alteration of tumor cells after these treatments. STUDY DESIGN/MATERIALS AND METHODS: In this study, nude mice bearing HeLa cell tumors were treated with PDT, LH, and combined treatments of the two. Tumor tissues obtained immediately after these treatments were analyzed using electron microscopy and morphometry. RESULTS: In the combined treatments, which produced more severe effects on tumor cells, morphological features of apoptosis such as cytoplasmic condensation, blebs, and apoptotic bodies appeared in the cells, although the typical alteration in the nuclear chromatin was not seen. CONCLUSION: Cytoplasmic alterations may proceed more rapidly than nuclear alterations in the cellular degeneration induced by the single or combined treatments of PDT and LH.

Animals↗
PubMed1994

The effect of 6 kHz tone exposure on inner ear function of the guinea pig: relation to changes in cochlear microphonics, action potential, endocochlear potential and chemical potentials of K(+)-ions and Na(+)-ions, using a double-barrel glass electrode.

Using 97 male albino guinea pigs and applying electrophysiological methods, the effects of a 6 kHz tone were investigated at a moderate sound pressure level to the inner ear during a 24-h exposure time. Following exposure to the 6 kHz tone at 90 dB, cochleas showed decreased maximum output voltage of cochlear microphonics (CM) and action potential (AP). In the endolymph, K+ ion and Na+ ion concentrations remained unchanged during 40 min anoxia and 90 dB tone exposure. At 80 dB sound exposure decreases in maximum output voltage of CM and AP and decreases in the absolute value of EP could not be detected. Endolymph K(+)-ion Na(+)-ion concentrations were also unchanged. These findings indicate that diffusion potentials are induced at the same time as decreases of maximum output voltage in CM induced by exposure to sound at 90 dB.

Action Potentials↗
PubMed1994

Molecular comparison of dengue type 1 Mochizuki strain virus and other selected viruses concerning nucleotide and amino acid sequences of genomic RNA: a consideration of viral epidemiology and variation.

Dengue-1 (D1) Mochizuki strain was examined for its nucleotide and amino acid sequences of genomic RNA and the data obtained were compared with those of other selected virus strains reported previously. Genomic regions corresponding to C, preM and M proteins were the major subjects of study. Parts of E protein were additionally examined. Among the D1 viruses investigated, the Mochizuki virus which was isolated in 1943 in Japan was shown to be close to Philippine 836-1 strain isolated in 1984 and Nauru Island strain isolated in 1974 at the respective places, in contrast with Thai AHF 82-80 strain isolated in 1980 and Caribbean CV1636/77 strain isolated in 1977. At the same time, a difference was noted between the Mochizuki and Philippine/Nauru strains at the cleavage site of preM/M junction: Mochizuki possessed RRGKR/S sequence whereas the Philippine/Nauru had RRDKR/S. The glycosylation site in preM and hydrophobic regions at the carboxyl termini of M and E were well conserved. Significances of the data are discussed in connection with viral epidemiology and variation.

Amino Acid Sequence↗
PubMed1994

Proton beam therapy for patients with esophageal carcinoma.

Fifteen patients with esophageal carcinoma (superficial, six cases; advanced, nine cases) were treated with 250 MeV proton beam irradiation with or without external x-ray irradiation (12 MV linear accelerator) from October, 1985, to May, 1991. Eleven patients were initially treated with x-ray at doses of 16.2-50.4 (mean 42.5) Gy, followed by proton beam at doses of 30.0-52.9 (mean 37.6) Gy. The other four patients were treated with proton beams alone at total doses of 75.0-88.5 (mean 81.4) Gy. The mean total dose for the 15 patients was 80.4 Gy. As a result, the primary tumor lesions of all 15 patients disappeared and complete responses were obtained. Approximately four to five months later, nine of the 15 patients developed esophageal ulcer formations at the circumferences of their primary lesions. The ulcerations were healed, however, by conservative management. There was no evidence of local recurrence throughout the observations on six cases of superficial carcinoma. Among nine advanced carcinoma patients, three relapsed into esophageal carcinoma. Recurrences were observed eight, 16 and 44 months, respectively, after the treatment. Ten of the 15 patients died, but eight died of other diseases. Three of four cases at autopsy did not show any cancer cells in irradiated primary lesions. Four of the 15 patients lived for over five years. The results suggest that a high dose of irradiation delivered by a well-defined proton field could result in improved local control and long-term survival in esophageal carcinoma without undue risk of injury to primary and adjacent organs.

Aged↗