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Biomedical subjects

A Hirota

Publications and source records attributed to A Hirota.

At least 37 records · Page 2Linked to original sources
PubMed1997

Optical characterization of a novel GABA response in early embryonic chick brainstem.

To examine the functional expression of embryonic GABA receptors, the inhibitory effects were studied of GABA (GABA responses) on the excitatory postsynaptic potentials evoked by vagal stimulus in seven- to 10-day-old embryonic chick brainstem slice preparations. A multiple-site optical recording technique was used, with a multiple element photodiode array system and a fast voltage-sensitive merocyanine-rhodanine dye (NK2761). First, in the GABA response, three components were pharmacologically identified: component 1, related to GABA(A) receptors; component 2, related to GABA(B) receptors; and component 3 which is insensitive to GABA(A) and GABA(B) antagonists, but is stimulated by both GABA(A) and GABA(B) agonists. Subsequently. the embryogenesis and early development of the three components were investigated, and early developmental maps of regional distribution patterns of the three components were constructed. Components 1 and 3 have already emerged in the seven-day-old embryonic brainstem preparation; component 2 appeared in the eight-day-old preparations. No component related to GABA(C) receptors was observed in the seven- to 10-day-old embryonic stages. From the pharmacological properties of component 3, we suggest that it is related to a new subtype, the GABA(D) receptor.

Animals↗
PubMed1997

Incidence of retinal vein occlusion at the Glaucoma Clinic of Hiroshima University.

We prospectively surveyed the incidence of retinal vein occlusion (RVO) at the glaucoma clinic of Hiroshima University between 1986 and 1991. Among 433 glaucoma patients, 18 (4.2%) subsequently presented with RVO, 9 had central retinal vein occlusion (CRVO) and 9 exhibited branch retinal vein occlusion (BRVO). Seven of 87 (8.1%) patients with primary angle closure glaucoma exhibited RVO, showing the highest incidence among glaucoma types. The incidence of RVO detected by the general outpatient clinic was 0.59% during the same period. The BRVO/CRVO ratio in the glaucoma clinic was 1.0, while it was 4.3 in the general outpatient clinic. Glaucoma is an important risk factor for the development of RVO, especially CRVO.

Adult↗
PubMed1997

Pax-6 is involved in the specification of hindbrain motor neuron subtype.

Pax-6 is a member of the vertebrate Pax gene family, which is structurally related to the Drosophila pair-rule gene, paired. In mammals, Pax-6 is expressed in several discrete domains of the developing CNS and has been implicated in neural development, although its precise role remains elusive. We found a novel Small eye rat strain (rSey2) with phenotypes similar to mouse and rat Small eye. Analyses of the Pax-6 gene revealed one base (C) insertion in an exon encoding the region downstream of the paired box of the Pax-6 gene, resulting in generation of truncated protein due to the frame shift. To explore the roles of Pax-6 in neural development, we searched for abnormalities in the nervous system in rSey2 homozygous embryos. rSey2/rSey2 exhibited abnormal development of motor neurons in the hindbrain. The Islet-1-positive motor neurons were generated just ventral to the Pax-6-expressing domain both in the wild-type and mutant embryos. However, two somatic motor (SM) nerves, the abducent and hypoglossal nerves, were missing in homozygous embryos. By retrograde and anterograde labeling, we found no SM-type axonogenesis (ventrally growing) in the mutant postotic hindbrain, though branchiomotor and visceral motor (BM/VM)-type axons (dorsally growing) were observed within the neural tube. To discover whether the identity of these motor neuron subtypes was changed in the mutant, we examined expression of LIM homeobox genes, Islet-1, Islet-2 and Lim-3. At the postotic levels of the hindbrain, SM neurons expressed all the three LIM genes, whereas BM/VM-type neurons were marked by Islet-1 only. In the Pax-6 mutant hindbrain, Islet-2 expression was specifically missing, which resulted in the loss of the cells harboring the postotic hindbrain SM-type LIM code (Islet-1 + Islet-2 + Lim-3). Furthermore, we found that expression of Wnt-7b, which overlapped with Pax-6 in the ventrolateral domain of the neural tube, was also specifically missing in the mutant hindbrain, while it remained intact in the dorsal non-overlapping domain. These results strongly suggest that Pax-6 is involved in the specification of subtypes of hindbrain motor neurons, presumably through the regulation of Islet-2 and Wnt-7b expression.

Animals↗
PubMed1997

Optical mapping of conduction patterns of normal and tachycardia-like excitations in the rat atrium.

Multiple-site optical recording of transmembrane voltage activity (MSORTV), using a voltage-sensitive dye and a 12 x 12-element photodiode array, was employed to monitor action potentials in the rat atrium. Atrial preparations including the sinus node area, caval area, and atrial septum were dissected from adult rat hearts and stained with a voltage-sensitive merocyanine-rhodanine dye (NK2761). For suppression of optical artefacts due to contractile movements, a bathing medium containing 2,3-butanedione monoxime (BDM: 10-20 mM) was used. The spread of spontaneous excitation from the pacemaker was assessed optically by timing the initiation of the action potential-related extrinsic absorption changes. The optical signals were recorded from more than 300 contiguous loci in the atrium by sliding the photodiode array over the image of the preparation; in this way, the intra-atrial conduction pattern of spontaneous excitation was mapped. The obtained maps revealed a non-radial spread of excitatory waves originating in the pacemaking area over the atrium. Furthermore, we also mapped the conduction pattern of long-lasting tachycardia-like excitation evoked by a short train of electrical stimulation (5-10 Hz, 1-2s) applied with a bipolar electrode. These maps suggest that excitatory waves are propagated in a circular pathway which often surrounds the ostium of the superior or inferior vena cava. Various patterns for the pathway were also demonstrated optically.

Action Potentials↗
PubMed1997

Response and level of beta-adrenergic, vasoactive intestinal peptide, and PACAP receptors during the circadian cycle.

PURPOSE: To determine whether a nocturnal increase of ciliary process beta-adrenergic receptor responsiveness can explain the observation that timolol decreased the aqueous flow rate and intraocular pressure (IOP) during the night but not during the day in rabbits. METHODS: Rabbits were housed in alternating 12-hour periods of light and dark. In vitro stimulation of tissue cyclic adenosine monophosphate (cAMP) levels by isoproterenol (ISO), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating polypeptide (PACAP), or a soluble derivative of forskolin (sFSK) was measured in ciliary processes harvested at mid-light phase and early and late dark phase. Inhibition of ISO and VIP stimulation of ciliary process cAMP by an alpha 2-adrenergic agonist and maximal binding of [125I]I-pindolol, [125I]I-VIP, and [125I]I-PACAP in ciliary process membranes were measured at the same three times. RESULTS: Although there may have been a nocturnal increase in the sensitivity of ciliary process cAMP levels to stimulation by ISO, this was not observed consistently, VIP, but not PACAP, stimulation increased at night, but there was no change in the response to sFSK. Inhibition by apraclonidine of elevated ciliary process cAMP levels was constant at all three times. Ligand-binding studies showed little change in ciliary process beta-adrenergic, VIP-, or PACAP-receptor levels at the three times. CONCLUSIONS: There is no convincing evidence for a nocturnal increase in beta-adrenergic receptor sensitivity in rabbit ciliary processes that could explain the difference between day and night effects of timolol on aqueous flow and IOP.

Adrenergic alpha-Agonists↗
PubMed1996

Optical studies of the biphasic modulatory effects of glycine on excitatory postsynaptic potentials in the chick brainstem and their embryogenesis.

Multiple-site optical recording of transmembrane potential activity, using a voltage-sensitive dye, was employed to monitor neural activity from the nucleus tractus solitarius of the chick embryo. Optical signals related to glutamate-mediated excitatory postsynaptic potentials were evoked by a brief square current pulse applied with a microsuction electrode to the vagus nerve, and were recorded simultaneously from many sites in the brainstem slice preparation. We have found that glycine has biphasic modulatory effects on the glutamate-mediated excitatory postsynaptic potentials: at lower concentrations, glycine enhances the glutamate-mediated excitatory postsynaptic potential-related optical signal, and at higher concentrations, it reduces the glutamate-mediated excitatory postsynaptic potential-signal. The enhancing effect was insensitive to strychnine, but the reducing effect was blocked by strychnine, suggesting that the former effect was induced by glycine which increased glutamate binding to N-methyl-D-aspartate receptors, and the latter resulted from an increase in chloride conductance through the strychnine-sensitive inhibitory glycine receptors in postsynaptic neurons. The inhibitory effect of glycine was first observed in the brainstem preparations at the seven-day-old embryonic stage, and the enhancing effect was first observed in the nine-day-old preparations. We determined regional distributions of the biphasic effects of glycine in the seven- to nine-day old embryonic preparations. The spatial distribution of the enhancing effect appeared to be concentrated on the ventral side of the nucleus tractus solitarius, and the inhibitory effect was relatively concentrated in the medial portion. Furthermore, we compared the glycine effect with the effect of Mg(2)+ on N-methyl-D-aspartate receptors, and we have found that the Mg(2)+ site is functionally organized prior to the glycine site during embryonic development.

Animals↗
PubMed1996

Neuropeptide Y levels in the aqueous humor of rabbits.

The concentration of neuropeptide Y in the aqueous humor (NPYaq) did not change during the circadian cycle in rabbits. However, NPYaq also did not decrease after superior cervical ganglionectomy or preganglionic section of the cervical sympathetic trunk (decentralization). Nor did NPYaq change after either stimulation, with para-aminoclonidine, or blockade, with rauwolscine, of prejunctional ocular alpha2-adrenergic receptors. Therefore, NPYaq does not reflect NPY release from ocular sympathetic nerves in rabbits.

Adrenergic alpha-Agonists↗
PubMed1996

Ansamycin antibiotics as free radical scavengers isolated from Streptomyces by using the bactericidal action of the hydroxyl radical.

Ansamycin antibiotics (1-4) were isolated from the cultured broth of Streptomyces sp. USF-319 strain as a result of our screening for free radical scavengers. They inhibited the bactericidal effect of the Fenton reagent toward Bacillus subtilis by their radical scavenging activity. Some of them also showed inhibitory activity against lipid peroxidation and lipoxygenases.

Anti-Bacterial Agents↗
PubMed1996

Video-imaging assessment of initial beating patterns of the early embryonic chick heart.

The spatiotemporal pattern and its developmental changes were assessed of the beating of the early embryonic chick tubular heart at the 9- to 17-somite stages of development using a video-imaging method together with the three-dimensional modeling. In the late 9- and early 10-somite stages, contractions were observed only at the right margin of the ventricular wall. As development proceeded to 12-somite or later stages, the propagation of contractile waves from the atrial pacemaking area towards the root of the ventral aortae was observed. The prototype of the peristaltic pattern of contractions was established by the 14-somite stage of development with an increase in the conduction velocity of the contractile wave.

Animals↗
PubMed1995

Evaluation of optimal voltage-sensitive dyes for optical monitoring of embryonic neural activity.

To evaluate the suitability of a variety of fast voltage-sensitive dyes for optical recording of rapid transmembrane potential activity in the embryonic nervous system, we screened over twenty dyes, including several newly synthesized probes, in three different embryonic neural preparations: cervical vagus nerve bundle, nodose ganglion, and brainstem from 7-day old chick embryos. Measurements of voltage-related optical signals were made using a multiple-site optical recording system. Signal size, signal-to-noise ratio, photobleaching, and phototoxicity were examined. Several promising new merocyanine-rhodanine dyes for embryonic nervous systems were found.

Animals↗
PubMed1995

A new simultaneous 1020-site optical recording system for monitoring neural activity using voltage-sensitive dyes.

We have constructed a new 1020-site optical system for simultaneous recording of transmembrane electrical activity, using a 34 x 34-element photodiode array. This new apparatus permits analyses of the spatio-temporal pattern of neural activity, such as action potentials and postsynaptic potentials, in the central nervous system, at higher spatial and temporal resolutions.

Action Potentials↗
PubMed1995

Protein glycation inhibitors from thyme (Thymus vulgaris).

Nonenzymatic glycation of bovine serum albumin (BSA) was inhibited in vitro by some extracts of 34 kinds of spices. The methanol extract of thyme (Thymus vulgaris) had the most potent inhibitory activity among them. Chromatographic purification yielded four flavonoids, quercetin (1), eriodictyol (2), 5,6,4'-trihydroxy-7,8,3'-trimethoxyflavone (3), and cirsilineol (4). These known flavonoids suppressed the levels of advanced glycation end products (AGEs) and fructosamines, shown by the measurement of specific fluorescent groups and the reduction of nitroblue tetrazolium (NBT), respectively. The inhibitory activities were compared with those of other structure-related flavonoids and aminoguanidine.

Flavonoids↗
PubMed1995

USF-19A, a new lipoxygenase inhibitor from Streptomyces sp.

USF-19A, a soybean lipoxygenase (SBL) and human 5-lipoxygenase (5-LO) inhibitor, was isolated from Streptomyces sp. USF-19 strain. Its chemical structure was determined by spectroscopic evidence to be a new member of the antimycin antibiotic family. The IC50 value of USF-19A against 5-LO was 28.0 microM.

Benzamides↗
PubMed1995

Responses to glossopharyngeal stimulus in the early embryonic chick brainstem: spatiotemporal patterns in three dimensions from repeated multiple-site optical recording of electrical activity.

In an effort to assess the spatial patterning of glossopharyngeal responses in the early embryonic chick brainstem, we used a multiple-site optical recording system with a 12 x 12 element photodiode array and a voltage-sensitive merocyanine-rhodanine dye (NK2761) to monitor neural transmembrane voltage activities. Seven and 8 d old embryonic chick brainstems were sliced into 1400-1600 microns thick sections with the glossopharyngeal and vagal nerves attached, and then stained with the dye. Neural voltage-related optical signals were evoked by a positive brief (depolarizing) square current pulse applied to the glossopharyngeal nerve with a microsuction electrode, and then recorded simultaneously from many loci in the objective two-dimensional image plane of a compound microscope. In addition to the multiple-site optical recording technique, we tried to introduce an optical sectioning method by changing the focal plane of the microscope to obtain three-dimensional information. Thus, we have been able to assess semiquantitatively the three-dimensional profiles of two glossopharyngeal response areas corresponding to the nucleus of the glossopharyngeal nerve (nucleus nervi glossopharyngei) and the nucleus of the tractus solitarius. Furthermore, glutaminergic excitatory postsynaptic potentials were determined within the response area corresponding to the nucleus of the tractus solitarius. In addition, we also compared the glossopharyngeal and vagal response areas and found that the cores of the related nuclei are separated in three dimensions.

2-Amino-5-phosphonovalerate↗
PubMed1994

Exercise intensity determines the magnitude of IOP decrease after running.

The effects of the intensity, duration and quantity (intensity x duration) of exercise on the reduction of intraocular pressure (IOP) in healthy and physically fit individuals were studied. Five minutes after 15 minutes of exercise at 70%, 55% and 40% of maximum exercise load (%HRmax) the IOP decreased 4.3 +/- 0.7 mmHg, 2.2 +/- 0.7 mmHg and 0.6 +/- 0.5 mmHg, respectively. The magnitude of IOP reduction increased with exercise load. Running for 7.5 minutes at 70%HRmax decreased IOP comparable to 15 minutes of running at the same exercise load (4.4 +/- 0.6 mmHg). Twenty-five minutes of running at 40%HRmax is almost the same quantity of exercise as 15 minutes of running at 70%HRmax. However, the former did not result in IOP reductions to equal the latter (2.3 +/- 0.5 vs 4.4 +/- 0.6 mmHg). The amount of IOP reduction after short-term exercise seems to depend on the intensity of exercise, not on the duration of exercise or the quantity of exercise.

Adult↗
PubMed1994

Optical mapping of early embryonic expressions of Mg(2+)-/APV-sensitive components of vagal glutaminergic EPSPs in the chick brainstem.

Multiple-site optical recording of transmembrane voltage activity, using a voltage-sensitive dye (NK2761) and a 12 x 12 element photodiode array, was employed to monitor neural responses in the slice preparations that were dissected from 6-9-d-old embryonic brainstems. Transmembrane voltage-related optical responses evoked by a brief square current pulse applied with a microsuction electrode to the vagus nerve were recorded simultaneously from many sites in the preparation. In preparations from 6-d-old embryos, only action potential-related spike-like optical signals were often detected in the normal bathing solution containing 0.5 mM Mg2+. However, in several loci of some preparations, excitatory postsynaptic potential-related slow signals were elicited in a Mg(2+)-free bathing medium, and these elicited slow signals were blocked by DL-2-amino-5-phosphonovaleric acid (2-APV). These results show a possible embryonic expression of NMDA receptor-mediated excitatory postsynaptic potentials. The slow signals were usually detected from tested preparations from 7-9-d-old embryos in normal bathing solution. The later phase of the slow signals was enhanced in a Mg(2+)-free bathing medium, and the enhanced component was also sensitive to 2-APV and insensitive to 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). There were regional differences in the degree of the enhancement of the slow signals in the Mg(2+)-free bathing medium, and of the 2-APV-induced reduction of the slow signals. We have constructed early developmental maps of the spatial patterns of the slow signals related to Mg(2+)- and 2-APV-sensitive postsynaptic potentials. These maps reflect the spatial distribution of functional expression of the NMDA receptors during early development of the chick brainstem. The present findings are new data that have not been reported previously, and they have been obtained for the first time using the multiple-site optical recording technique with a voltage-sensitive dye.

2-Amino-5-phosphonovalerate↗