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A Asanuma

Publications and source records attributed to A Asanuma.

34 records · Page 2Linked to original sources
PubMed1989

Regional distribution of metabotropic glutamate response in the rat brain using Xenopus oocytes.

The regional distribution of metabotropic L-glutamate responses was investigated in Xenopus oocytes injected with poly(A)+-RNA from a rat brain which was separated into 3 parts: cerebrum, cerebellum and brainstem. Under voltage-clamp, oscillatory current responses were induced more in cerebellum or brainstem poly (A)+-RNA-injected oocytes, and less in cerebrum poly(A)+-RNA-injected oocytes. These results suggest that the metabotropic glutamate receptor is distributed mostly in cerebellum and brainstem.

Animals↗
PubMed1989

Thrombus formation on the aorta injured by angioplasty and its prevention with dilazep in atherosclerotic rabbits.

To estimate the effect of dilazep in preventing restenosis after a transluminal angioplasty, we have attempted an animal experiment in which the efficacy of drug was tested on an angioplastic injury superimposed on to atherosclerotic lesions. Using a modification of Block's method, atherosclerotic lesions first were made in the rabbit aorta by an initial ablation of the endothelium, followed by successive cholesterol feedings. Then, for our second step, an angioplastic injury was inflicted on the atherosclerotic lesions. The thirty two rabbits used were divided into 3 groups: those given dilazep (100 micrograms/kg i.v.), those given dipyridamole (100 micrograms/kg i.v.) and a control group that was given the same volume of 0.9% saline. The angioplastic area in which thrombi developed was semiquantitatively measured and compared among all three groups. The mean value of the thrombus area in the dilazep group was 60% smaller and the distribution pattern of the thrombus by size was found to be composed of smaller thrombi than those of the control group. Dipyridamole showed the same trend as did dilazep, but less effectively. Our animal model and semiquantitative evaluation method that we employed were found useful from the view point of an easy applicable and inexpensive methodology. Our results point towards the possible clinical use of dilazep in the future, so as to prevent thrombus formation, which seems to cause the restenosis phenomenon that often occurs in patients who have undergone a coronary angioplasty.

Angioplasty, Balloon↗
PubMed1988

Taurine and beta-alanine act on both GABA and glycine receptors in Xenopus oocyte injected with mouse brain messenger RNA.

The responding pathway (process from agonist binding to channel opening) of taurine and beta-alanine was investigated in Xenopus oocytes injected with mouse brain poly(A)+ RNA. Responses to gamma-aminobutyric acid (GABA), glycine, taurine and beta-alanine were induced in oocytes injected with poly(A)+ RNA extracted from 3 regions, cerebrum, cerebellum and brainstem of the mouse brain. From comparison, responses to these 4 inhibitory amino acids in each regional poly(A)+ RNA-injected oocytes were categorized into at least 3 groups: (1) GABA, (2) glycine, and (3) taurine and beta-alanine. No cross-desensitization was observed between GABA response and glycine response, but taurine and beta-alanine responses cross-desensitized both the GABA and glycine responses. Taurine and beta-alanine responses were partially inhibited by the GABA antagonist, bicuculline, and also by the glycine antagonist, strychnine. The results suggest that the taurine or the beta-alanine response in the brain is caused through both the GABA receptor and the glycine receptor.

Alanine↗
PubMed1988

Taurine modulates glycine response in Xenopus oocytes injected with messenger RNA from mouse brain.

The modulatory action of taurine on the glycine response was investigated in Xenopus oocytes injected with messenger RNA from mouse brainstem under voltage-clamped condition. Taurine competitively inhibited the glycine response in a dose-dependent manner. This inhibition was insensitive to bicuculline and intracellularly injected EGTA. The results suggest that taurine could directly modulate glycinergic neurotransmission in the central nervous system.

Animals↗
PubMed1987

The distribution of GABA and glycine response in the mouse brain using Xenopus oocytes.

Injection of mRNA from different regions of the central nervous system (CNS) of the mouse into the Xenopus oocyte caused a difference in the relative glycine to gamma-aminobutyric acid (GABA) response of the oocyte. Glycine caused the response in oocytes injected with brainstem mRNA but hardly in oocytes injected with cerebrum mRNA and in oocytes injected with cerebellum mRNA. In contrast, GABA caused the response in oocytes injected with mRNA from each of the 3 parts of the CNS. These obvious regional differences may reflect the distribution of the receptors to each plausible neurotransmitter in the CNS.

Animals↗
PubMed1986

Induction of taurine responsiveness in Xenopus oocytes by messenger RNA from mouse brain.

A taurine response was induced in the surface membrane of the oocytes of Xenopus laevis by injection of the mRNA from the neonatal mouse brain, and the response was studied electrophysiologically. The permeability of mRNA-injected oocytes to chloride ions was increased by the application of taurine in a dose-dependent manner. The same oocyte also responded to GABA, but bicuculline suppressed only the GABA response. These results suggest a possibility that taurine could be a neurotransmitter of certain neurons as yet unknown in the central nervous system.

Animals↗
PubMed1986

A measurement of galvanic current and electrical potential in extracted human teeth.

When opposing teeth with amalgam and gold restoration are in contact, current flows in the mouth at the instant the dissimilar metals touch. In this study, this condition was simulated by use of resistors and extracted human teeth with amalgam and MOD gold inlay restorations. When both teeth were in contact in a physiological saline solution, we measured current and electrical potential generated in each pulp chamber. Galvanic current generated in the tooth with amalgam was always larger (as much as 18.2 times at the instant of contact) than that in the tooth with gold. Electrical potential generated in the tooth with amalgam was always larger (as much as 9.7 times at the instant of contact) than that in the tooth with gold. It should be emphasized that the larger current generated in the tooth with amalgam was caused mainly by its larger electrical potential. These results correspond well with the clinical phenomenon of galvanic pain, which occurs in the tooth with amalgam rather than in the tooth with gold.

Dental Amalgam↗
PubMed1983

Frequency and amplitude representations in anterior primary auditory cortex of the mustached bat.

The orientation sound emitted by the Panamanian mustached bat, Pteronotus parnellii rubiginosus, consists of four harmonics. The third harmonic is 6-12 dB weaker than the predominant second harmonic and consists of a long constant-frequency component (CF3) at about 92 kHz and a short frequency-modulated component (FM3) sweeping from about 92 to 74 kHz. Our primary aim is to examine how CF3 and FM3 are represented in a region of the primary auditory cortex anterior to the Doppler-shifted constant-frequency (DSCF) area. Extracellular recordings of neuronal responses from the unanesthetized animal were obtained during free-field stimulation of the ears with pure tones. FM sounds, and signals simulating their orientation sounds and echoes. Response properties of neurons and tonotopic and amplitopic representations were examined in the primary and the anteroventral nonprimary auditory cortex. In the anterior primary auditory cortex, neurons responded strongly to single pure tones but showed no facilitative responses to paired stimuli. Neurons with best frequencies from 110 to 90 kHz were tonotopically organized rostrocaudally, with higher frequencies located more rostrally. Neurons tuned to 92-94 kHz were overpresented, whereas neurons tuned to sound between 64 and 91 kHz were rarely found. Consequently a striking discontinuity in frequency representation from 91 to 64 kHz was found across the anterior DSCF border. Most neurons exhibited monotonic impulse-count functions and responded maximally to sound pressure level (SPL). There were also neurons that responded best to weak sounds but unlike the DSCF area, amplitopic representation was not found. Thus, the DSCF area is quite unique not only in its extensive representation of frequencies in the second harmonic CF component but also in its amplitopic representation. The anteroventral nonprimary auditory cortex consisted of neurons broadly tuned to pure tones between 88 and 99 kHz. Neither tonotopic nor amplitopic representation was observed. Caudal to this area and near the anteroventral border of the DSCF area, a small cluster of FM-FM neurons sensitive to particular echo delays was identified. The responses of these neurons fluctuated significantly during repetitive stimulation.

Animals↗
PubMed1980

Potentials of outer hair cells and their membrane properties in cationic environments.

The intracellular potentials of outer hair cells were identified by means of Alcian Blue dye marking in the guinea pig cochlea. The d.c. resting potentials were less negative than in the supporting cells. Mean maximal amplitude of the a.c. component in intracellular responses to middle tone stimulation was about 3.8 mV. The phase of the a.c. component was opposite to that of the subtectorial space. The a.c. component decreased as the potential gradient across the sensory hair surface was reduced. Calcium ions and the other divalent cations introduced into the scala media reduced cochlear microphonics roughly in proportion to their concentration. Calcium reduction produced by chelation in the scala media induced the reduction of the microphonics. The intracellular potentials of outer hair cells are unstable and different from those of inner hair cells. Calcium levels may be important in controlling the receptive function of the sensory hair surface, which is exposed to endolymph with a high potassium concentration.

Animals↗
PubMed1978

The chemical receptive mechanism in the lateral-line organ.

Stimulating effects of various mono- and divalent cations on the lateral-line organ were theoretically analysed by use of the site binding chemical adsorption model with the principle of "hard and soft acids and bases." A linear relation between the softness parameter and the logarithmic value of the intrinsic association constant was obtained for the cations of Na, K, Tl, Ag, Ca, Mg, and Cd. The order of effectiveness of these cations agreed with that of the intrinsic association constant. Using these values for various cations, the critical concentration of divalent cations necessary to supress the effect of monovalent cations was calculated and compared with the experimental values. The calculated concentration of the hard divalent cations (Ca2+, Mg2+), which suppressed the effect of the hard monovalent cations (K+, Na+), agreed with the experimental concentration. The same relations were obtained between the suppressive effect of a soft divalent and a soft monovalent cation. The chemical adsorption of Ag+ on the lateral-line organ of Xenopus laevis was investigated by using a transmission electron microscope equipped with an X-ray microprobe analyser in order to get further confirmation of this model. Silver applied to the lateral-line organ was found around a kinocilium but not in the hair cells of the lateral-line organ. Thus chemical adsorption of the cation on the surface of the receptor membrane was directly proved.

Animals↗
PubMed1977

Electrical potentials of the subtectorial space in the guinea pig cochlea.

Precipitation of cobalt ions and iontophoretic marking by Alcian Blue were utilized in examination of physiological properties of the subtectorial space in the guinea pig cochlea. Cobalt ions injected into the scala media were sulfurated and observed as a black precipitation in cross sections. Precipitation was seen on the upper and the lower surface of the tectorial membrane, and on the reticular membrane. Alcian Blue was the most suitable dye for marking in the organ of Corti. Recording sites of potentials in the subtectorial space were identified by Alcian Blue marking. The potentials were similar to those measured in the scala media. These facts verify that the subtectorial space communicates with the scala media through the outermost margin of the tectorial membrane. Thus the sensory hairs of hair cells are bathed in the endolymph of high potassium concentration, and the condition for optimum sensitivity of their receptor function is maintained.

Alcian Blue↗