PubMed Health⌕ Search

Biomedical subjects

M Hirabayashi

Publications and source records attributed to M Hirabayashi.

At least 91 records · Page 5Linked to original sources
PubMed1985

Auditory brainstem response (ABR) to tone pips in hearing-impaired children.

The correspondence between ABR thresholds to tone pips and behavioral thresholds at 500, 1000 and 2000 Hz was studied in 13 normal and 55 hearing-impaired children, including 42 sensori-neural losses and 13 conductive losses. The children's ages ranged from 1 year 3 months to 8 years. Tone pips were provided with 2-cycle rise-fall times and 2-cycle plateaus. The correlations between the two measures were highly significant at 3 frequencies both in sensori-neural losses and conductive losses. In the subjects with sensori-neural losses, the ABR thresholds tended to be lower than the behavioral thresholds. Mean threshold differences between the ABR and behavioral audiometry at each frequency in sensori-neural losses were 1.6, 0.26 and 5.8 dB, respectively. On the other hand, in the subjects with conductive losses, the ABR thresholds were higher than the behavioral ones by 9.6, 7.8 and 7.5 dB at respective frequencies. Therefore, the hearing acuity in young children with sensori-neural losses can be predicted with accuracy from the ABR thresholds to tone-pips at 500, 1000 and 2000 Hz.

Audiometry↗
PubMed1985

[Development of reverse tolerance to the ambulation-increasing effect of ephedrine after repeated administration in mice].

Effects of repeated administration of ephedrine (EPH) 40 and 80 mg/kg sc, and 20, 40, and 80 mg/kg ip on ambulatory activity in adult male mice of the dd strain were investigated. The drug was administered 5 times at intervals of 1 and 7 days. The ambulatory activity of each mouse was measured by a tilting-type round activity cage of 25 cm in diameter for 150-210 min after the drug administration. Repeated administration of EPH 80 mg/kg ip produced a marked augmentation in the sensitivity of the mouse, i.e. reverse tolerance, to the ambulation-increasing effect of the drug regardless of the administration intervals. However, repeated administration of 80 mg/kg sc and 40 mg/kg ip at intervals of 7 days caused a slight reverse tolerance, while 40 mg/kg sc at intervals of 7 days as well as 20 and 40 mg/kg ip at intervals of 1 day did not produce reverse tolerance. In contrast, a poorer development of reverse tolerance to the ambulation-increasing effect of EPH was observed when a mouse was confined in a glass jar of 5 cm in diameter to impede ambulation for 150-180 min after each administration. Mice showing reverse tolerance to EPH demonstrated an increased sensitivity to methamphetamine as compared with the saline-pretreated control mice. The present results suggest that the characteristics of reverse tolerance to ambulation-increasing effect of EPH are almost identical with those after methamphetamine and methylphenidate.

Animals↗
PubMed1984

An electron-microscopic study of the endothelium in mammalian bronchial microvasculature.

The endothelial ultrastructure and permeability in sequential segments of the bronchial microvasculature of the rat, guinea pig, and hamster, were examined electron-microscopically before and after perfusion with horseradish peroxidase (HRP) or tannic acid. Transendothelial channels are common in the bronchial venules of all three species. Fenestrated capillaries are present just beneath the bronchial epithelium. The endothelial fenestrae, transendothelial channels, and leaky endothelial junctions in venules are permeable to tracers such as HRP and tannic acid, indicating that the microvasculature of the bronchial circulation may be more permeable than that of the pulmonary circulation.

Animals↗
PubMed1983

Frequency composition of auditory middle responses.

Power spectral analysis and digital filtration were performed on the auditory middle responses (AMR) to click stimuli in six subjects with normal hearing. The spectral analysis revealed that the main power of the AMR was located at frequencies between 30 and 50 Hz with a peak at 40 Hz. A small elevation of power observed in the spectrum between 90 and 180 Hz was considered to be due to the ABR and the earliest part of the AMR. Typical AMR components, namely Na, Pa, Nb and Pb, were constantly recognised with digital high-pass (HP) filtration at 30 Hz. With increasing cut-off frequencies up to 50 Hz, the peak latencies of Na and Pa remained unchanged, while their magnitudes markedly decreased. On the other hand, Pb completely disappeared with 40 Hz filtration, forming two distinct positive peaks at about 55 and 80 ms after the stimulus onset. In some cases, three small positive peaks were seen following Pa with HP filtration at 50 Hz. With 60 Hz HP filtration, main components of the AMR substantially disappeared.

Electroencephalography↗
PubMed1983

Auditory middle responses in young children.

In order to ascertain if any substantial difference exists in the auditory middle responses (AMR) between adults and young children, a digital high-pass (HP) filtering technique was applied to the responses in 26 young children aged 1-7 years and nine adults with normal hearing. Two significant differences were found between the HP-filtered responses in children and those in adults. Pa in the responses from adults was consistently recognized with HP filtering up to 50 Hz, while Pa in young children was effectively detected only with 20 Hz HP filtering. It was mostly eliminated when the HP filter was set at 30 or 40 Hz. Pb was identified in most of the adult responses, particularly with HP filtering at 30 Hz. On the other hand, it was not visually distinguished in the responses from young children with any HP filter setting.

Adult↗
PubMed1983

[Development and characteristics of reverse tolerance to repeatedly administered morphine in mice manifested by enhanced motor activities].

Characteristics of changes in ambulatory activity after repeated administration of morphine, 5, 10 or 20 mg/kg s.c., were investigated in male mice of dd strain. The drug was administered 10 times at intervals of 1, 3-4 or 7 days, and the ambulatory activity of each mouse was measured by a tilting-type round activity cage with a 25 cm diameter for 180 min after each administration. Morphine, 5-20 mg/kg induced a dose-dependent increase in the ambulatory activity, and this effect attained to a peak at 60-90 min and persisted for 120-180 min after the administration. An augmentation of sensitivity (a reverse tolerance) to the ambulation-increasing effect of morphine was induced by the repeated administration of 10 and 20 mg/kg morphine, regardless of the intervals. The reverse tolerance achieved the maximum on the 5-6th administration day, and almost the same level of sensitivity was maintained until the 10th administration day. There was no significant difference in the activity counts at the peak time among the groups of mice varying the administration intervals. However, the persistence of increased ambulatory activity tended to be longer in the group of mice given morphine at intervals of 7 days than in the group given it at intervals of 1 day. The reverse tolerance, once produced, attenuated 2 months after the cessation of the repeated administration. However, the ambulatory activity counts did not return to those on the 1st administration day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

[Characteristics of reverse tolerance to ambulation-increasing effect of methylphenidate after repeated administration in mice].

Effects of repeated administration of methylphenidate (MPD) 2, 4, 8 and 16 mg/kg, sc on ambulatory activity in adult male mice of old strain were studied. The ambulatory activity of each mouse was measured by a tilting-type activity cage for 90-150 min after the drug administration. The repeated administration of MPD 2 and 4 mg/kg at intervals of 3-4 days, and 4 mg/kg at intervals of 7 days produced an augmentation in the sensitivity of the mice, i.e., a reverse tolerance, to the ambulation-increasing effect of the drug. However, the repeated administration of MPD 4 mg/kg at intervals of 1 day, and 8 and 16 mg/kg at intervals of 3-4 days did not produce the reverse tolerance to it. The mice repeatedly given 16 mg/kg at intervals of 3-4 days exhibited an augmentation in stereotyped behaviors. The reverse tolerance, once produced, was well maintained 45 days after cessation of the repeated administration. Only a little reverse tolerance to MPD was produced in the mice repeatedly given the drug in their home cage, in which the mice were group-housed, and the extent was significantly less than that observed in the mice given the drug in the activity cage. In addition, the mice showing the reverse tolerance to MPD demonstrated an increase in sensitivity to methamphetamine as compared with the saline-given control mice. The present results suggest that the characteristics of reverse tolerance to the ambulation-increasing effect of MPD is almost identical with that after methamphetamine.

Amphetamine↗
PubMed1981

Enhancing effect of methamphetamine on ambulatory activity produced by repeated administration in mice.

Effect of repeated administration of methamphetamine (MAM) on ambulatory activity was studied under various experimental conditions. Nine groups of mice received 10 doses of 1, 2 or 4 mg/kg MAM on a daily, 3-4 day or weekly schedule. Increases in activity were enhanced progressively in proportion to the number of MAM doses, but the extent varied with the dose and interval of repetition. One mg/kg caused slight enhancement under all conditions. In the case of 2 mg/kg, marked enhancement was observed until the 7th-8th administration in 3-7 day schedules, but poorer enhancement was elicited by daily administration. Four mg/kg of daily repetition caused no enhancement, because of marked stereotyped behavior which competed with ambulation. However, the enhancement was observed in the 3-7 day schedule when stereotyped behavior was not prominent. The enhancement was well maintained after a 2 months drug-free period. When a mouse was confined in a jar of small diameter to impede ambulation after MAM, the enhancement was blocked. These results suggest a possibility that learning of drug effect in association with environmental factors may play an important role in the enhancing effect.

Animals↗
PubMed1980

Single crystal alumina for dental implants and bone screws.

When ground to a suitable form, flexural strength of single crystal alumina (Al2O3) decreases to as low as one third the strength of the intact crystal. This flexural strength decrease is, however, recovered by chemical etching at a high temperature to eliminate surface defects caused by grinding. By using this strength recovery treatment, various types of single crystal implants with fine structure were able to be designed. Four kinds of single crystal bone screws and single crystal dental implants of screw and anchor type were designed. Flexural strength and impact strength of the implants were measured.

Aluminum↗
PubMed1979

[Individual differences in the accelerating effect of methamphetamine, d-amphetamine and morphine on ambulatory activity in mice (author's transl)].

Several problems concerning the ambulatory activity were discussed from the viewpoint of drug assay using about 700 adult male mice of ddG strain. Each response pattern for 180 approximately 400 min obtained from the temporal changes of ambulatory activity after administration of methamphetamine (1 approximately 16 mg/kg s.c.), d-amphetamine (1.25 approximately 5 mg/kg s.c.) or morphine (5 approximately 20 mg/kg s.c.) was recorded and used for the data analysis. All the above mentioned drugs markedly accelerated the activity when the doses were optimal. However, the individual response to the drugs sometimes reached a 40- approximately 70-fold difference, even though both animal and measurement conditions were fixed as constant way as possible. The time when the experiments took place did not explain the individual differences, nor did the season or body weight of the animal. However, there was the possibility of colony differences. Animals with relatively high activity prior to drug administration tended to respond more forcibly after administration of the drugs. It was found from the statistical investigation that constant observation of over 1 hr using at least 15 animals was required in order to determine a standard effect of the drug. Furthermore, the accelerating effect of methamphetamine and d-amphetamine on the activity was observed to be dose-dependent when below 4 and 5 mg/kg was given, respectively. On the contrary, the effect decreased dose-dependently when higher doses were given as stereotyped behavior such as head-swaying, continuous sniffing and circular movements in opposition to the horizontal movements also developed dose-dependently. As the qualitatively different behavior could be simultaneously measured, the individual differences were more apparent.

Amphetamines↗
PubMed1978

[Simple and easy method for measurement of ambulatory activity in mice (author's transl)].

A hand-made apparatus which is easily manipulative, cheap, durable and clean was used to measure ambulatory activity of a mouse. The apparatus was assembled with the same type of two plastic round basins commercially available (25 cm in diameter) put one upon another. A pivot was fixed at the center of the outsurface of the inner basin (A), and its open end was inserted into the open socket fixed at the center on the bottom of the outer basin (B). Three microswitches equipped on the brim of (B) at equal intervals were activated and the counts were recorded according to the tiltings of (A) through the movements of the mouse. In order to examine accuracy of the measurement, effects of d-amphetamine (1.25 approximately 5.0 mg/kg), methamphetamine (1.0 approximately 4.0 mg/kg), cocaine (10 approximately 40 mg/kg) and morphine (5.0 approximately 20.0 mg/kg) on the ambulatory activity were investigated. Marked accelerating effects were observed dose dependently after the administrations of all the drugs. Furthermore, the patterns of the activity showed characteristic properties of each drug. This method is especially useful to measure the acute effect of drugs on the ambulatory activity in mice, and many units can be set up at the same time.

Amphetamines↗