Biomedical subjects

I Taniguchi

Publications and source records attributed to I Taniguchi.

At least 37 records · Page 2Linked to original sources

PubMed1999

Insulin resistance and angiotensin converting enzyme polymorphism in Japanese hypertensive subjects.

Renin-angiotensin system activity has been shown to affect insulin sensitivity. However, the relationship between I/D polymorphism and insulin resistance is controversial. Therefore, we examined the relationship between the ACE genotype and insulin sensitivity in 51 Japanese hypertensive patients using the glucose clamp technique. The ACE genotype distribution in the hypertensive subjects was: 7 subjects with DD, 20 subjects with ID, and 24 subjects with II. Insulin sensitivity in terms of the glucose disposal rate was not significantly different among the three ACE genotypes, although there was a tendency for insulin sensitivity to decrease in the order of II, ID and DD, DD being the lowest. These findings are contrary to previous reports that insulin sensitivity was increased in normotensive subjects with the DD genotype who were Caucasian or African-American. There might be a difference due to race and whether the subjects are hypertensive or obese. We concluded that insulin sensitivity was not different among the ACE genotypes in the Japanese hypertensive subjects, supporting a previous report on the Chinese population. To date, insulin sensitivity has not been found to differ with ACE genotypes in the oriental population.

Adult↗

PubMed1999

Evaluation of new 4 French catheters by comparison to 6 French coronary artery images.

The use of 4 Fr catheters for diagnostic coronary arteriography improves patient comfort and could potentially reduce costs by decreasing arterial complications and encouraging outpatient examination. We examined the performance of recently developed 4 Fr catheters (100 cm long, 0.042 inch internal diameter) through in vitro flow rate patterns and in vivo image quality. Flow patterns (flow rate calculated from pressure with the Hagen Poiseuille relation) were obtained by hand (10 ml volume; maximal effort, one-handed full injection) and power injection (10 ml volume; 5 ml/sec) in the 4 Fr catheters were compared to 5 Fr (0.047 inch) and 6 Fr (0.057 inch) catheters. In 20 patients, coronary arteriograms were obtained from 4 Fr hand injection (4 HI), 4 Fr power injection (4 PI), 6 Fr hand injection (6 HI ), and 6 Fr power injection (6 PI) were compared after being scored into 5 grades. Coronary diameter was assessed at two sites for all injections in the same group of patients. In power injections, peak flow rates were consistently 5.5 ml/sec in all catheters. Hand injections were much more variable; peak flow rate ranges for 5 different physicians were 3.5-6.0 ml/sec. in 6 Fr, 1.8-3.0 ml/sec. in 5 Fr and 1.4-2.0 ml/sec in 4 Fr catheters. Mean image scores of left arteriograms were significantly higher for 4 PI versus 4 HI and for 6 Fr images compared to 4 PI (p < 0.001). In right arteriograms, 4 HI scored significantly lower than other methods (4 PI, 6 HI and 6 PI; p < 0.001). In 4 HI left coronary arteriograms, the frequency of grade > 2 was 96% and > 3 was 82%. Power injection improved 4 Fr imaging to 99% greater than grade 2 and 93% greater than grade 3. There were no differences in the frequency of images above grade 3 in right coronary arteriograms. Measured coronary artery diameters at 40 normal and 17 stenotic sites by QCA analysis (Acom, Siemens AZ, Erlangen, Germany) did not influence the study data. We concluded that coronary arteriograms by hand injection with 4 Fr catheters were inferior compared to 6 Fr images. Power injection and/or larger catheters may be necessary to ensure the highest quality images are obtained.

Blood Flow Velocity↗

PubMed1998

Anisotropic neural interaction in the primary auditory cortex of guinea pigs with sound stimulation.

Neural interaction in the primary auditory cortex of guinea pigs anesthetized with sodium pentobarbital was studied using a single line multi-electrode (4 x 1) aligned across and along the isofrequency band. Under the spontaneous condition, the neural interaction was isotropic; the amplitude of cross-correlogram peaks decreased as the electrode separation increased both across and along the isofrequency band. Under tone stimulation, the neural interaction was anisotropic; the amplitude of peaks was decreased rapidly beyond 400 microm across the isofrequency band, while it decreased little up to 700 microm along the isofrequency band. This anisotropic interaction was dependent on the stimulus intensity.

Acoustic Stimulation↗

PubMed1998

Delayed recovery of auditory cortical evoked potentials is correlated with cortical neuronal death after transient cerebral ischemia in awake gerbils.

Early detection of irreversible neuronal change after transient cerebral ischemia is important so that adequate treatment can be initiated within the therapeutic window. We have examined the correlation between changes in middle-latency auditory evoked potentials (MAEPs) and histological changes in the auditory cortex of awake Mongolian gerbils subjected to 4 min or 12 min of transient cerebral ischemia. Post-ischemic MAEPs were characterized by the appearance of a markedly large negative and positive component at approximately 17-22 ms latency in both groups. Delay in the appearance of the high amplitude (maximal amplitude at 45 min after recirculation in the 12-min ischemia group) precedes the slowly developing death of neurons in the auditory cortex that results from transient cerebral ischemia.

Animals↗

PubMed1998

Optical recording of responses to frequency-modulated sounds in the auditory cortex.

Using an optical recording method with a voltage-sensitive dye, we recorded activities in the primary auditory cortex (AI) of anesthetized guinea pigs in response to frequency-modulated (FM) sounds and sounds with stepwise changes in frequency (SF). Responses to the FM sound showed a spatiotemporal pattern in which a localized active spot traversed the isofrequency bands in the AI, and they differed from the band-like responses to the SF sound. These results indicate that time-varying sounds are represented as spatiotemporal activation of tonotopic organization in the AI by spectral cues with interactions between frequency bands.

Acoustic Stimulation↗

PubMed1998

Electrophysiological characteristics of classes of neuron in the HVc of the zebra finch.

Whole cell recordings were made from zebra finch HVc neurons in slice preparations. Four distinct classes of neuron were found on the basis of their electrophysiological properties. The morphological characteristics of some of these neurons were also examined by intracellular injection of Lucifer yellow. Type I neurons (21 of 65 cells) had longer time-to-peak of an afterhyperpolarization following an action potential than the other classes. They exhibited both fast and time-dependent inward rectification and an initial high-frequency firing followed by a slower constant firing. Type I neurons had large somata and thick dendrites with many spines. The axons of some of the neurons in this class projected in the direction of area X of the parolfactory lobe. Type II neurons (30 of 65 cells) had a more negative resting membrane potential than the other classes. They exhibited fast inward rectification. Type II neurons could be divided into two subclasses by the absence (IIa; 22 cells) and the presence (IIb; 8 cells) of a low-threshold transient depolarization. Type IIa neurons had relatively small somata and thin, spiny dendrites. The axons of some of the neurons in this class projected in the direction of the robust nucleus of the archistriatum (RA). Type IIb neurons had relatively large somata and thick dendrites with many spines. Type III neurons (6 of 65 cells) had a shorter action-potential duration than the other classes. They exhibited prominent time-dependent inward rectification and a regular tonic firing with little or no accommodation. Type III neurons had beaded, aspiny dendrites. Type IV neurons (8 of 65 cells) had a longer action-potential duration, a much larger input resistance, and longer membrane time constant than the other classes. Type IV neurons had small somata and thin, short, sparsely spiny dendrites. The axons of some of the neurons in this class projected in the direction of the RA. These classes of neuron may play distinct roles in song production and representation in the HVc.

Action Potentials↗

PubMed1998

Angiographic evaluation of culprit lesions in acute coronary syndrome: relation to the original site on previous coronary angiography.

Culprit lesions in acute coronary syndrome [acute myocardial infarction (AMI) and unstable angina pectoris (UAP)] were examined angiographically in 222 patients who had previously undergone coronary angiography (CAG). The observation period lasted 5 years after primary CAG in medically treated patients (group M, 127 cases) and after final follow-up CAG in patients treated by percutaneous transluminal coronary angioplasty (PTCA) (group B, 95 cases). There were 33 AMIs, including 5 deaths (22/127, 17.3%, in group M vs 11/95, 11.6%, in group B; p<0.01) and 189 UAPs (105/127, 82.7%, in group M vs 84/95, 88.4%, in group B; NS). High-grade stenoses (>75%) were found in 76 (59.8%) patients in group M, of which 41 lesions (54%) resulted in acute coronary syndromes (ACSs). In group M, ACSs resulted from insignificant stenosis (< or =50%) in 67 (53%) patients and from significant stenosis (>50%) in 60 (47%) patients. In group B, ACSs resulted from insignificant stenosis in 78 (82%) patients and from significant stenosis in 17 (18%) patients. Out of 95 PTCA sites, high-grade restenosis occurred in 3 lesions and ACSs (2 AMI, 14 UAP) in 16 (16.8%). We conclude that ACSs are more likely to develop from insignificant lesions than from significant lesions. High-grade stenoses are prone to become occlusive lesions and PTCA reduces this potential risk. Most target sites of PTCA that escaped restenosis were stable in the long term.

Aged↗

PubMed1998

Delayed recovery of cortical auditory evoked potentials and blood flow precede cortical neuronal death after transient cerebral ischemia in gerbils.

Cortical neurons develop into neuronal death four days after transient cerebral ischemia. The aim of this study is to detect early post-ischemic changes in the cortex that will develop into cortical neuronal death later. The detection is important for starting adequate treatment within the therapeutic window. We have examined changes in middle-latency auditory evoked potentials (MAEPs) and cortical blood flow (CBF) in relation to the histological changes in the auditory cortex of Mongolian gerbils subjected to transient cerebral ischemia. At 2 min after bilateral carotid occlusion, the amplitude of MAEPs and CBF were reduced to 22.2 to 23.4% and 24.3 to 27.4% of the pre-ischemic level, respectively. In the 4-min ischemia group, the amplitude of each parameter recovered rapidly to the pre-ischemic level. In the 12-min ischemia group, the recovery of MAEPs and CBF was delayed by, from 20 to 30 min, and about 10 min, respectively. Also, scattered eosinophilic neurons were observed in the auditory cortex, and a mild but significant decrease in the number of surviving neurons was also detectable. The recovery of MAEPs in both groups was characterized by the appearance of a transient high amplitude (2.67 +/- 0.6 microV) low frequency (62.2 +/- 3.4Hz) wave. The present findings show that cortical neuronal death in the auditory cortex, which results from transient cerebral ischemia in the gerbil, is predictable by detecting the delay in the recovery of MAEPs amplitude and CBF during the very early post-ischemic phase. Clinical data is mandatory for the application of the presented method in clinical cases to save many patients with acute cerebrovascular diseases in the future.

Animals↗

PubMed1997

Optical imaging of dynamic horizontal spread of excitation in rat auditory cortex slices.

Optical recordings using a voltage-sensitive dye (RH482) were conducted in brain slice preparations to investigate spatiotemporal patterns of excitation in the rat auditory cortex. Electrical stimulation of the border between the white matter and layer VI evoked vertical as well as horizontal spreading responses. While velocities of vertical and horizontal propagation of excitation were similar to those reported in non-disinhibited preparations, the horizontal propagation was widespread and strong especially in layers II/III in auditory cortex slices. This horizontal spread was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) but not by D-2-amino-5-phosphonopentanoic acid (D-AP5). These results suggest that the horizontal responses, especially in layers II/III, are prominent and are mediated primarily by non-N-methyl-D-aspartic acid (NMDA) receptors in the auditory cortex.

2-Amino-5-phosphonovalerate↗

PubMed1997

Pulse-spray thrombolysis in acutely obstructed coronary artery in critical situations.

Pulse-spray thrombolysis (PST) was performed to treat large coronary thrombus in 3 patients in critical situations. The originally developed pump system and a custom infusion catheter (SciMed/Boston Scientific, Maple Grove, MN) were used in combination. Case 1, a 48-yr-old male with extensive anterior myocardial infarction, failed to be recanalized by systemic thrombolysis. He underwent emergent coronary angiography, which revealed proximal occlusion of a large left anterior descending artery (LAD). TIMI 3 flow was achieved after 20 min with 200,000 units of urokinese by PST, followed by balloon angioplasty. In case 2, a 57-yr-old male, subacute stent thrombosis occurred 4 days after two and a half Palmatz-Schatz stents were implanted in mid-LAD. TIMI 3 flow was recovered at 20 min with 240,000 units of urokinese and an additional 72,000 units of rt-PA, followed by redilatation with a quarter-size larger balloon than that used in stent deployment. In case 3, a 70-yr-old male, during ultrasound study for unstable angina, a massive thrombotic complication occurred which occluded the left main trunk. PST was immediately performed under cardiac resuscitation, and the patient recovered from shock after 15 min. TIMI 3 flow was restored after 25 min. Two Palmatz-Schatz stents were implanted after thrombus completely disappeared. There were no complications, including distal embolization, intimal dissection, or bleeding. There was also no recurrence of the ischemic event. PST may be considered a potential treatment modality for coronary artery disease where large thrombus plays a major role.

Aged↗

PubMed1997

Time course of tissue elasticity and fluidity in vasogenic brain edema.

We examined chronological changes in regional tissue elasticity (stiffness) and fluidity (1/viscosity) of the white matter during the development and resolution of vasogenic brain edema. Cryogenic injury was created in the cortex of cat brain, and the brain was prepared for measurement of regional tissue elasticity and fluidity. The results were then compared with the histology and tissue water content. Vasogenic edema developed in the white matter under the lesioned cortex (4-24 h) and was resolved by day 10. Regional tissue elasticity decreased significantly during the initial 24 h (45.3 +/- 32.5% of the control (mean +/- S.D.), and then increased to 158.6 +/- 32.3% of the control level at day 10. Regional tissue fluidity increased to 376.7 +/- 240.4% of the control level during the initial 24 h decreased to 77.7 +/- 17.9% of the control level at day 10. Histological examination of the white matter revealed widening of the inter-fiber space at 4-24 h after lesioning and astrocytosis at day 10. Thus vasogenic edema causes an increase of tissue fluidity with a decrease of tissue elasticity. Reactive astrocytosis after the resolution of edema causes an increase of tissue elasticity with mild decrease in tissue fluidity.

Animals↗

PubMed1997

Real-time imaging of neural activity during binaural interaction in the guinea pig auditory cortex.

Spatio-temporal patterns of binaural interaction in the guinea pig auditory cortex (AC) were observed using optical recording with a 12 x 12 photodiode array and a voltage-sensitive dye. The amplitudes of the sound-induced light signals from the cortex were transformed into sequential two-dimensional images every 0.58 ms. Binaural sound stimuli evoked an excitatory response followed by a strong inhibition, and contralateral stimuli evoked a strong excitatory response followed by a weak inhibition. Ipsilateral sound stimuli evoked a weak response. Binaural stimulation induced two types of ipsilateral inhibition: a fast binaural inhibition which was detected only after the contralateral and ipsilateral responses were subtracted from the binaural responses, and which appeared 12-25 ms after the onset of stimulation, and a slow binaural inhibitory effect which was clearly observed in the binaural responses themselves, appearing 70-95 ms after the onset of stimulation. The fast binaural inhibition was observed in the same area as the contralateral excitatory response. The inhibited area became stronger and more widespread with increasing intensity of ipsilateral stimulation. We did not observe the specialized organization of binaural neurons as electrophysiologically found in the cat AC, in which binaural neurons of the same binaural response type are clustered together and alternate with clusters of other response types.

Acoustic Stimulation↗

PubMed1997

Optical study of spatiotemporal inhibition evoked by two-tone sequences in the guinea pig auditory cortex.

Spatiotemporal response patterns in the anterior and dorsocaudal fields of the guinea pig auditory cortex after two-tone sequences were studied in anesthetized animals (Nembutal 30 mg kg-1) using an optical recording method (voltage-sensitive dye RH795, 12 x 12 photodiode array). Each first (masker) and second (probe) tone was 30 ms long with a 10-ms rise-fall time. Masker-probe pair combinations of the same or different frequencies with probe delays of 30-150 ms were presented to the ear contralateral to the recording side. With same-frequency pairs, responses to the probe were inhibited completely after probe delays of less than 50 ms and the inhibition lasted for more than 150 ms, and the inhibition magnitudes in different isofrequency bands of the anterior field were essentially the same. With different-frequency (octave-separated) pairs, responses to the probe were not inhibited completely even after probe delays as short as 30 ms, and the inhibition lasted only for 110-130 ms. Inhibition magnitudes were different from location to location.

Acoustic Stimulation↗

PubMed1997

The columnar and layer-specific response properties of neurons in the primary auditory cortex of Mongolian gerbils.

The columnar and layer-specific response properties of neurons in the primary auditory cortex (AI) of Mongolian gerbils were studied using single-unit recordings of responses to tone-burst stimuli presented to the ear contralateral to the recording side. During near-radial microelectrode penetrations of the AI in 100-microm steps, the best frequency (BF), best threshold (BT), best amplitude (BA), latency, tuning curve and Q10dB were recorded. Neurons encountered during single penetrations showed similar BFs, indicating a columnar frequency organization, but their latencies and Q10dBs differed. The BAs and BTs recorded within single penetrations often showed a similar value in the middle cortical layers. The latencies and Q10dBs of these neurons exhibited a tendency toward a layer-specific distribution. The latencies of neurons located in layers I-V were longer than those located in layer VI. The Q10dBs of neurons located in layers III and IV were higher than those located in layers I and VI. These results are almost consistent with those of previous studies on frequency representation, and indicated the existence of an integrative mechanism of frequency processing in the AI. This is the first study in which a layer-specific, partially columnar organization for stimulus amplitude is described.

Acoustic Stimulation↗

PubMed1997

Inhibitory effects of insulin on intracellular calcium and aggregatory response of platelets are impaired in hypertensive subjects with insulin resistance.

To determine the effects of insulin on intracellular calcium and platelet aggregatory responses in hypertensive subjects with insulin resistance, we measured insulin sensitivity in terms of glucose disposal rate (GDR) by the hyperinsulinemic euglycemic clamp technique (GC) in 14 non-diabetic untreated hypertensive subjects, and determined basal ([Ca2+]i) and thrombin-stimulated (T-[Ca2+]i) platelet-free calcium concentrations and thrombin-stimulated platelet aggregatory response (AG) before (PRE[Ca2+]i, T-PRE[Ca2+]i, and PRE AG, respectively) and during (POST[Ca2+]i, T-POST[Ca2+]i, and POST AG, respectively) GC. As a control for GC, vehicle (normal saline) was infused on another day. No significant difference was observed between PRE[Ca2+]i and POST[Ca2+]i, T-PRE[Ca2+]i and T-POST[Ca2+]i, or PRE AG and POST AG, GDR inversely correlated with delta[Ca2+]i (POST [Ca2+]i-PRE[Ca2+]i, r = -0.75, p < 0.02), delta T-[Ca2+]i, (T-POST[Ca2+]i-T-PRE[Ca2+]i, r = -0.63, p < 0.02) and delta AG (POST AG-PRE AG, r = -0.67, p < 0.01). No significant changes were observed in these variables during vehicle infusion. [Ca2+]i, T-[Ca2+]i, and AG decreased during GC as compared with baseline in hypertensive subjects with normal insulin sensitivity, but were unchanged in those with insulin resistance, suggesting that the vasodilatory and anti-platelet aggregatory effects of insulin are impaired in patients with insulin-resistant hypertension.

Adult↗

PubMed1997

Optical imaging of neural activity in auditory cortex induced by intracochlear electrical stimulation.

Little is known about the representation of electrically evoked activity in the auditory cortex. We observed evoked activity in guinea pig auditory cortex evoked by acoustical and electrical stimulation to the cochlea by optical imaging with the aid of a voltage-sensitive dye. Light signals from the cortex were recorded with a 12 x 12 array of photodiodes, and transferred to the spatio-temporal images by every 0.57 ms. The activity by pure tones was shown spatio-temporally through tonotopical organization in the cortex according to the sound frequencies. The tonotopic responses were dynamically changed. When the cochlea was stimulated with single electrical pulses, focal activities were observed in the cortex as spatio-temporal patterns. Activated cortical regions were not sharply localized, but varied with stimulating positions of the cochlea. The curves of response magnitude versus stimulus intensity showed the narrow dynamic range, and that of latency was almost constant. These results were significantly different from those for normal sound stimulation.

Acoustic Stimulation↗

PubMed1997

Optical recording of azimuth representation in guinea pig auditory cortex.

The frequency dependency of directional sensitivity of the auditory cortex of barbiturate-anesthetized guinea pigs in response to tone bursts was studied by an optical equipment and a voltage sensitive dye (RH795). Tone bursts at 4, 8 and 14 kHz were presented from loudspeakers placed at the azimuths from contralateral 90 degrees to ipsilateral 90 degrees in 30 degrees steps on a front-horizontal semi-circular board (100 cm in radius). The maximum responses were observed at around contralateral 30 degrees (best azimuth). The onset and peak latencies were the shortest at the best azimuth. The best azimuth was the same for all these frequencies, but the azimuth selectivity became broader for the lower frequencies. These results indicate that the azimuth selectivity observed in the guinea pig auditory cortex is mainly associated with pinna characteristics.

Animals↗

PubMed1997

Diagnostic Brachial Coronary Arteriography Using a Power-Assisted Injector and 4 French Catheters with New Shapes.

BACKGROUND: Right brachial access in diagnostic coronary arteriography (CAG) has demonstrated advantages over femoral approaches, including earlier ambulation and more predictable hemostasis, particularly when small diameter catheters were used. Poor results from some earlier reports of brachial CAG have been due partially to the need to use large diameter catheters for positional control. Technical advances in catheters and contrast injection may increase the utility of brachial access CAG. PURPOSE AND STUDY DESIGN: We evaluated three 4 French (Fr) catheters with new shapes and with a large internal to external diameter ratio that were designed to overcome previous limitations to brachial CAG. Contrast agent was delivered with a novel power injector (CAG-20) intended for arteriography using small catheters. Routine right brachial access CAG and left ventriculography (LVG) were evaluated in 2663 (69%) of 3880 consecutive patients admitted for examination from 1991 to 1995. The study population included 128 patients (5%) with left main trunk disease, 819 (21%) with old myocardial infarctions and 1747 (66%) with more than one vessel disease. For this trial, 1217 patients with valvular disease, ischemia associated with aortic or peripheral vascular disease, congenital cardiac disease and post-surgical and emergency catheterization were excluded because femoral access or a larger catheter (> 4 Fr) were required in those cases. RESULTS: A total of 2573 (97%) diagnostic quality CAG (> grade 3/5) were obtained solely with 4 Fr catheters placed via the right brachial artery. Of the other 66 examinations, 50 were completed through the brachial route but with alternate size or shape catheters and 16 cases required the femoral JudkinÕs technique. Useful LVG (> grade 2/4) were obtained from 2604 patients (98%). Overall, 2536 (95%) of cases provided clinically valuable images for both CAG and LVG from brachial access. We experienced one semi-emergency bypass operation and one emergency stent implantation caused by coronary dissection. There were no deaths, acute myocardial infarctions, loss of pulse or nerve injuries. CONCLUSION: Power-injector assisted, brachial 4 Fr CAG and LVG proved to be safe and cost-effective. Brachial access has the potential to become a routine method for out-patient cardiac opacification.

Journal Article↗