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I Sugihara

Publications and source records attributed to I Sugihara.

36 records · Page 2Linked to original sources
PubMed1994

Calcium-activated potassium channels in goldfish hair cells.

1. Characteristics of Ca(2+)-activated K+ channels in the basolateral membrane of hair cells isolated from the caudal part of the goldfish saccular macula were studied mainly with the inside-out mode of the patch clamp method. 2. Several types of Ca(2+)-activated K+ channels differing in unitary conductance were identified. The conductances (n = 156) ranged from 130 to 320 pS (when measured in symmetrical 125 mM KCl) and could be roughly separated into four groups, centred on values of 150, 200, 250 and 300 pS. The pharmacological profile, assessed by, for example, tetraethylammonium blockade, and the relatively large conductance indicated that these channels can be classified as large-conductance Ca(2+)-activated K+ channels (BK channels). The relative permeability of these channels to different ion species was in the order K+ (1.0) > Rb+ (0.8) > NH4+ (0.14) > Na+, Cs+ (< 0.05). 3. Curves relating open state probability to [Ca2+]i, for membrane potentials between -50 and +50 mV, were similar to those observed for BK channels of rat muscle. However, the maximum open state probability (100-1000 microM [Ca2+]i and 50 mV membrane potential) was 0.4-0.9, and always less than 1. 4. These channels had a short arithmetic mean open time ranging from 0.08 to 1.2 ms (0.08-0.5 ms in 88% of cases) and an arithmetic mean shut time ranging from 0.24 to 1.2 ms (10 microM [Ca2+]i and 50 mV membrane potential). The shut intervals were more sensitive to changes in [Ca2+]i and membrane potential than were the open intervals. 5. The distribution of individual open and shut intervals was fitted with the sum of exponential functions. Except for the slowest shut component, which only accounted for less than 1% of shut events, all other components had time constants shorter than 1 ms. As a result of these short open and shut intervals, the current trace had a flickery pattern rather than a burst-interburst pattern. 6. There was a rough correlation between unitary conductance and mean open time, i.e. channels with a large unitary conductance had a longer mean open time. 7. The sensitivity to [Ca2+]i of the Ca(2+)-activated K+ channel in goldfish hair cells was one to two orders of magnitude lower than that of BK channels in rat muscle. Channels with a longer mean open time had a higher Ca2+ sensitivity. 8. The stability of the single Ca(2+)-activated K+ channel kinetics was studied by measuring the 'moving' mean duration of open and shut intervals.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Uniform olivocerebellar conduction time underlies Purkinje cell complex spike synchronicity in the rat cerebellum.

1. The issue of isochronicity of olivocerebellar fibre conduction time as a basis for synchronizing complex spike activity in cerebellar Purkinje cells has been addressed by latency measurement, multiple-electrode recording and Phaseolus vulgaris leucoagglutinin (PHA-L) tracing of climbing fibres in the adult rat. 2. The conduction time of the olivocerebellar fibres was measured by recording Purkinje cell complex spike (CS) responses from various areas of the cerebellum. The CSs were evoked by stimulating the olivocerebellar fibres near the inferior olive. In spite of a difference in length, as determined directly by light microscopy, the conduction times of different climbing fibres were quite uniform, 3.98 +/- 0.36 ms (mean +/- S.D., n = 660). 3. Multiple-electrode recording of spontaneous Purkinje cell CS activity was employed to study the spatial extent of CS synchronicity in the cerebellar cortex. Recordings of CS were obtained from Purkinje cells located on the surface and along the walls of lobule crus 2a. The rostrocaudal band-like distribution of simultaneous (within 1 ms) CS activity in Purkinje cells extended down the sides of the cerebellar folia to the deepest areas recorded (1.6-2.6 mm deep). As shown in previous experiments, the distribution of simultaneous CS activity did not extend significantly (500 microns) in the mediolateral axis of the cerebellar cortex. 4. In two animals a detailed determination of the length of the olivocerebellar fibre bundles was performed by staining the fibres with PHA-L injected into the contralateral inferior olive. This measurement included fibre bundles terminating in twenty-six different areas, ranging from the tops of the various folia to the bottoms of the fissures in both the hemisphere and the vermis. There was a 47.5% difference between the length of the longest measured fibre bundle (15.8 mm, terminating in lobule 6b, zone A) and the length of the shortest measured fibre bundle (8.3 mm, terminating in the cortex at the base of the primary fissure, zone D), after correction for tissue shrinkage. To attain an isochronous conduction time the conduction velocities for these two fibre bundles were calculated to be 4.22 m/s and 2.37 m/s, respectively. 5. By interpolating between measured points a simple formula was derived to estimate the average length of olivocerebellar fibres terminating in any given area of the cerebellar cortex, excluding the paraflocculus, the flocculus and the most lateral regions of the hemisphere. 6. We investigated the most likely mechanisms by which conduction velocity variations with length could result in global isochronicity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Glucose metabolism in renal stone patients.

The calciuric response and the changes of plasma glucose and insulin produced by a 75-gram oral glucose tolerance test were determined in 27 male patients with idiopathic calcium renal stones (6 with dietary hypercalciuria, 5 with nondietary hypercalciuria and 16 with normocalciuria) and 22 healthy male subjects. The subjects were classified as obese (> or = 120% ideal weight) and nonobese. The incidence of an abnormal response to glucose loading was similar in the stone patients and the healthy subjects. In addition, the plasma glucose and insulin levels after oral glucose load did not differ between the stone patients and control subjects and were affected by the individual degree of obesity. Urinary calcium excretion increased significantly after glucose ingestion in both the stone patients and the control subjects. Urinary calcium excretion was greater in the stone patients than in the control subjects due to the presence of patients with nondietary hypercalciuria, and the increment in urinary calcium excretion in the dietary hypercalciuric and normocalciuric stone patients was indistinguishable from that in the control subjects. The degree of obesity did not affect the increment in urinary calcium excretion. These results suggest that overconsumption of refined carbohydrates such as sugar-sweetened soft drinks, soda and cakes may be a risk factor for stone formation, especially in the patients with nondietary hypercalciuria.

Adult↗
PubMed1992

Ibudilast may improve retinal circulation in patients with diabetes mellitus.

Ibudilast selectively vasodilates cerebral vessels without reducing blood pressure. We investigated the effect of the drug on retinal circulation in 8 patients with diabetes mellitus, using the video-densitometric image analysis of fluorescein angiography. We compared the build up time, the time constant of washout rate and the mean circulation time (MCT) before and after oral therapy with ibudilast. After 2 weeks of daily administration (30 mg), MCT was shortened significantly (4.2 +/- 2.8 vs. 3.0 +/- 1.6 s, p = 0.0215). Since retinal circulation in patients with diabetes mellitus was improved by ibudilast, the drug may be useful to treat disorders such as diabetic retinopathy.

Administration, Oral↗
PubMed1992

Effect of moxisylyte hydrochloride (alpha 1-blocker) on the retinal circulation of patients with diabetes mellitus.

Moxisylyte hydrochloride (alpha 1-blocker) selectively vasodilates cerebral vessels without reducing blood pressure. We investigated the effect of the drug on retinal circulation in 15 patients (17 eyes) with diabetes mellitus, using the video-densitometric image analysis of fluorescein angiography. We compared the build-up time (BT), the time constant of washout rate (TC) and the mean circulation time (MCT) before and after oral therapy with moxisylyte. In 16 eyes, BT was shortened significantly and MCT was only slightly shortened 1 h after oral therapy with moxisylyte. After 2 weeks of daily administration, MCT was shortened and TC of the artery was increased significantly in 6 eyes. Since retinal circulation in patients with diabetes mellitus was improved by moxisylyte, the drug may be useful to treat ocular disorders such as diabetic retinopathy.

Administration, Oral↗
PubMed1992

Retinal circulation in primary open-angle glaucoma tested by videodensitometric image analysis.

To investigate the retinal circulation in primary open-angle glaucoma (POAG), we used videodensitometric image analysis of fluorescein angiography to calculate the build-up time, the time constant of the washout rate, and the mean circulation time (MCT) in both the retinal artery and vein. We found the MCT in the POAG group (23 eyes of 20 patients) was significantly longer than in the normal group (3.7 +/- 2.0 sec and 2.8 +/- 1.7 sec, respectively; P less than .05). It correlated significantly with the vertical cup-to-disc ratio (r = .32; P less than .01), the outflow facility (r = -.35, P less than .005), and the glaucomatous visual-field loss. There was no correlation between MCT and intraocular pressure tested at the same time (r = .09, not significant). Therefore, treatment to decrease the intraocular pressure may not be associated directly with improved retinal circulation.

Adult↗
PubMed1991

[Acute and chronic effect of moxisylyte hydrochloride on the retinal circulation in diabetes mellitus].

The effect of moxisylyte hydrochloride, a new type alpha 1-blocking vasodilator, on the retinal circulation was investigated in 14 diabetics, using the video-densitometric image analysis of fluorescein angiography. The build-up time (BT) and the mean circulation time (MCT) were compared before and after oral administration of moxisylyte. The BT one hour after oral administration of 30 mg moxisylyte was significantly shorter than that before therapy (artery; before 5.2 +/- 1.5 vs after 4.6 +/- 1.0 sec; p = 0.0001, vein; before 6.9 +/- 1.3 vs 6.3 +/- 1.1 sec; p = 0.0005). The MCT two weeks after oral administration of 90 mg per day moxisylyte was significantly shortened (before 3.6 +/- 2.3 vs after 2.6 +/- 1.4 sec; p = 0.0180). These results suggested that oral moxisylyte improved the retinal circulation and might support the concept that moxisylyte hydrochloride has clinical usefulness in patients with diabetes mellitus.

Administration, Oral↗
PubMed1990

[Comparison of intraocular penetration level of cefuzonam sodium and cefotiam after intravenous and subconjunctival injection].

We investigated the intraocular penetration of a new Cephem type antibiotic: Cefuzonam sodium (CZON) following intravenous and subconjunctival injection. CZON was administered to 28 eyes in 26 patients by 1 g intravenous injection (IV) and to 11 eyes in 10 patients by 20 mg/0.2 ml subconjunctival injection (SCI). The penetration level of CZON by the IV method was from less than 0.0025-3.35 micrograms/ml into aqueous humor, from less than 0.0025-0.315 microgram/mg into iris tissue and 2.7-157.5 micrograms/ml into serum. The penetration level of CZON by the SCI method was from less than 0.0025-12.8 micrograms/ml into aqueous humor, from less than 0.0025-0.0426 microgram/mg into iris tissue and 1.03-18.5 micrograms/ml into serum. The penetration level of CZON into aqueous humor by SCI was higher than by IV administration. In comparison with the penetration level of CZON and Cefotiam (CTM), both aqueous humor and serum levels of CTM were higher than those of CZON. These results suggested that therapeutic levels in aqueous humor effective against gram-positive and gram-negative pathogens were achieved with the 1 g IV and 20 mg SCI of CZON. However levels effective against Staphylococcus epidermidis were only erratically attained.

Adult↗
PubMed1989

Morphological and functional aspects of two different types of hair cells in the goldfish sacculus.

1. With the use of whole-cell mode of the patch-clamp method, we examined the electrical responses of hair cells enzymatically isolated from the goldfish sacculus. 2. Hair cells from the rostral saccule had a short cell body and were ovoidal or eggplantlike in shape, whereas hair cells from the caudal saccule had a variable shape. Many had a longer cell body and were cylindrical or gourd-like in shape, but some short hair cells were also present in the caudal saccule. 3. The short hair cells had a resting potential of about -75 mV. In current-clamp experiments, these hair cells elicited damped oscillatory-potential changes of a relatively small amplitude in response to a depolarizing current. A current in the opposite direction produced a slow hyperpolarization, much larger in amplitude. 4. Resonant frequency of the short, or the oscillatory, type of hair cells ranged from 40 to 200 Hz or higher. However, resonance was generally of a poor quality as compared with that noted for hair cells in the turtle cochlea or frog sacculus. 5. The long hair cells had a resting potential of -90 to -100 mV. In current-clamp experiments, these hair cells elicited an all-or-none spike approximately 50 mV in amplitude in response to a depolarizing current. The spike was usually followed by a plateau, which was maintained for the duration of the depolarizing pulse. In some hair cells, damped slow oscillatory waves were evoked at a rate of 5-15 Hz. On the other hand, a hyperpolarizing current produced potential changes much smaller in amplitude. 6. Voltage-clamp experiments showed that Ca2+-activated K+ channel and A-current, especially its high-threshold subclass, were involved in the generation of outward rectification in the oscillatory-type hair cells. On the other hand, Na+, in addition to Ca2+, was involved in the generation of spike in the spike-type hair cells. Spike potentials were elicited even in the presence of tetrodotoxin (TTX), but the rate of rise was slower as compared with the intact spikes. 7. The spike-type hair cells had an inwardly rectifying K+ channel similar to that noted in the tunicate egg and chick vestibular hair cell. However, the oscillatory-type hair cells had an inwardly rectifying channel similar to the hyperpolarization-activated current, Ih, of the rod inner segment, or sinoatrial nodal cell, or lacked the inwardly rectifying channel. Differences in the resting membrane potential between the oscillatory- and spike-type hair cells are probably related to differences in the inwardly rectifying channels. 8. Effects of sound stimulation were simulated by injecting a half-wave rectified sinusoidal current of various frequencies.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1989

[Measurement of retinal circulation in uveitis of Behçet's and Harada's disease].

In order to investigate retinal circulation in patients with Behçet's disease and Harada's disease, we divided 27 patients into three groups; Behçet's group (8 patients), Harada's group (8 patients) and the control group (11 normal subjects). By means of video-densitometric image analysis of fluorescein angiography, we measured the buildup time (BT), time constant of washout rate (TC) and mean circulation time (MCT) for both the retinal artery and vein. The results were as follows: 1) The BT in Behçet group was slightly prolonged compared to that in the control group, while the BT in Harada's disease was shorter than that in the control group. 2) The TC in both the Behçet's and Harada's groups was significantly prolonged compared to that in the control group. 3) The MCT in both Behçet's and Harada's groups was not significantly different from that in the control group. These results suggest that Behçet's disease cases may have normally and compensatory retinal circulation, whatever vasculitis occurs on retinal vessels. On the other hand, choroiditis in Harada's disease has no influence on retinal circulation.

Adult↗
PubMed1986

Quickly flickering inwardly rectifying K channels in goldfish hair cell membrane.

The kinetics of the quickly flickering inwardly rectifying K channel were studied with the cell-attached patch clamp method in goldfish hair cells. The activity of the channel was very unique in repeating continuously open and closed events at an ultrafast rate. Moreover, open-close events of the channel showed a marked dependence on membrane potential; a shift toward hyperpolarized levels brought about an elongation of closed events resulting in a decrease in the open state probability, although no marked change was produced in open event duration itself. The unitary conductance of the channel was 109 pS as 123 mM KCl solution was used.

Animals↗