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Biomedical subjects

F Nakamura

Publications and source records attributed to F Nakamura.

At least 163 records · Page 9Linked to original sources
PubMed1993

Loss of vasoreactivity by laser thermal energy or argon laser irradiation.

Vasoreactivity of laser-treated vessels was investigated in two different experimental conditions. The canine left circumflex coronary artery (LCx) was lased under perfusion with Krebs-bicarbonate buffer by means of a thermal laser (hot-tip probe, HT) at 7 W for 6 seconds and an argon laser beam through a 300 microns optical fiber at 3 W (tip power) for 1 second at 12 spots. A nontreated segment of the LCx served as a control. Two 3-mm long segments were obtained from the treated segment: one to measure the results of potassium (K) induced contraction, and another 3, 4 diaminopyridine (DAP; K channel inhibitor) induced contraction. In 11 instances, coronary angiography of the perfused artery showed less than 50% stenosis after laser treatment. The segments were then mounted isometrically with 1 g tension in Krebs-bicarbonate buffer. Contraction was induced either with 30 mM KCI or 10(-2) M DAP and expressed as developed tension (gram; g). KCI induced vasocontraction of 4.15 +/- 0.93 g in the control, 0.33 +/- 0.71 g in laser irradiated segments (P < 0.0001 vs control), and 0.02 +/- 0.06 g in thermally-treated segments (P < 0.0001 vs control). DAP induced vasocontraction of 5.21 +/- 1.32 g in the control, 0.39 +/- 0.83 g in laser irradiated segments (P < 0.0001 vs control), and 0.07 +/- 0.13 g in thermally treated segments (P < 0.001 vs control). In 4 instances, more than 50% stenosis remained and additional balloon dilatation reduced the stenosis to less than 50%. The lesions also showed reduced vasoreactivity. In vivo thermal angioplasty resulted in reduced vasoreactivity compared to control in 4 anesthetized dogs. Thus, laser and thermal angioplasty reduced vasoreactivity induced by either KCI or 3, 4 DAP. Neither acetylcholine at 10(-6) M nor papaverine at 10(-4) M was able to induce relaxation of treated segments. In conclusion, 1) the lased coronary artery loses its vasoreactivity to either a constrictive or relaxing agent, 2) although stenosis may be produced by laser energy, additional balloon dilatation can reduce residual stenosis, and 3) laser thermal or argon laser angioplasty may prevent severe coronary spasm.

4-Aminopyridine↗
PubMed1993

Reduction of thrombogenicity with argon laser angioplasty. Comparison with balloon angioplasty.

Direct argon or thermal laser angioplasty (LA) was evaluated for thrombogenicity using angioscopy, and compared with balloon angioplasty (BA). In each of 8 dogs, 4 segments (both proximal and distal iliac arteries) were treated by laser-thermal and/or balloon angioplasty. One segment was treated by balloon angioplasty and 3 other segments were treated with either thermal LA with 7 W using a "Hot-Tip" laser probe (2.0 mm), or BA and thermal LA, or a special optical probe which emits a 3 W argon laser beam. Mean percent area stenosis by thrombus was 44 +/- 23 in balloon-dilated, 23 +/- 21 in thermally-treated and balloon-dilated, 3 +/- 3 in thermally-treated, and 1 +/- 4 in directly-lased segments at 30 min. It was 62 +/- 28 in balloon dilated, 31 +/- 29 in thermally-treated and balloon-dilated, 5 +/- 6 in thermally-treated, and 1 +/- 2 in directly-lased segments at 60 min. Balloon-inflated segments had the highest percent area stenosis which was significantly higher than that of either the direct laser or thermally-treated segments (p < 0.0005). Histology showed thermal necrosis in laser-treated sites, and wall tears in BA sites. Thus, LA can provide a less thrombogenic arterial surface than BA.

Angioplasty, Balloon↗
PubMed1993

[Percutaneous coronary angioplasty by ultraviolet and infrared laser].

Laser angioplasty can now be performed on the coronary arteries as sources of pulsed laser and steerable multifibre catheters have become available. The aim of this study was to analyse the immediate results, the outcome and secondary effects of coronary angioplasty with excimer and holmium YAG laser. The homium-YAG laser was used in 40 patients (Group I) and the excimer laser in 46 patients (Group II). The immediate success rates were 55% in Group I and 71.7% in Group II. The highest success rates were obtained in lesions of saphenous vein grafts. The primary success rate was remarkably high in calcific lesions and complete occlusions. It was less impressive in long than in short stenoses in Group I. Treatment by laser coronary angioplasty alone was successful in 21.7% of patients in Group II and 5.0% of patients in Group I (p < 0.05). The failures were related to difficulty in reading the lesion, in passing the stenosis or in obtaining a reduction of its severity. The failures were more common in Group I (45%) than in Group II (28.3%). In this preliminary series there were no deaths, myocardial infarcts or emergency coronary bypass procedures. The following complications were observed: acute occlusions in 17.1% of patients in Group I and 7.5% of patients in Group II; spasm (10-13%); coronary dissection was commoner in Group II (28.3%) than in Group I (7.5%, p < 0.04). Angiographic and clinical follow-up at 6 months showed a restenosis rate of 46% in Group I and 43% in Group II.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Carotid endarterectomy under cervical epidural anesthesia].

General anesthesia for carotid endarterectomy (CEA) imposes the need for various monitorings of cerebral function during occlusion of the carotid artery. However, there is no ideal method for detecting all the signs of cerebrovascular insufficiency under general anesthesia. We suggest that the patient's neurological state is the best monitor of cerebral function. Therefore, our patients underwent cervical epidural anesthesia (EDA) enabling them to remain conscious while experiencing analgesia of the operated areas throughout the course of the operation. Five patients with cervical internal carotid artery stenosis were operated on under EDA with lidocaine. In all patients, EDA was effective in maintaining an analgesic state in the areas being operated on. It was able to do this either alone, or in combination with a light sedation. Under EDA, although there was no complete suppression of the patient's respiration, blood pressure was elevated beyond 200mmHg in three patients and depressed to 70mmHg in one patient transiently during the operation. But control of abnormal blood pressure was achieved easily by injections of calcium antagonist or ephedrine. When consciousness of two patients deteriorated during the clamping of the internal carotid artery, it completely recovered to its preoperative level after the insertion of an internal shunt. The patient's level of neurological condition became a good guide for predicting the need for an internal shunt during the periods of occlusion of the internal carotid artery. In conclusion, we suggest that EDA which is a safe and useful anesthesia should be employed in many patients who undergo CEA.

Aged↗
PubMed1992

Inhibition of actin-activated myosin Mg(2+)-ATPase in smooth muscle by ruthenium red.

Ruthenium red was found to inhibit actin-activated myosin Mg(2+)-ATPase in smooth muscle and to bind to myosin heavy chain, but not to F-actin. The inhibition by Ruthenium red of actin-activated Mg(2+)-ATPase was of the competitive type with respect to actin (Ki 4.4 microM) and of the non-competitive type with respect to ATP (Ki 6.6 microM). However, Ruthenium red scarcely dissociated the acto-heavy meromyosin complex during the ATPase reaction. These results suggest that Ruthenium red interacts directly with the binding site for F-actin on the myosin heavy chain. This site is considered to be necessary not for maintaining the binding affinity of myosin for F-actin, but for activation of the Mg(2+)-ATPase.

Actins↗
PubMed1992

Glutamate-induced inhibition of paired pulse facilitation of monosynaptic excitatory post-synaptic potentials in frog spinal motoneurons.

To evaluate actions of glutamate on excitatory synaptic transmission in the central nervous system, we examined glutamate-induced changes in the paired pulse facilitation of monosynaptic excitatory post-synaptic potentials evoked by stimulation of the lateral column fibers (LC-EPSPs) on lumbar motoneurons in the frog spinal cord. Glutamate (1 mM) depolarized motoneurons both in the presence and absence of Mg2+. In most cells perfused with Mg(2+)-free or high Ca(2+)-Mg2+ solutions, the glutamate potential was accompanied by a reduction in peak amplitude of EPSPs, although the degree of change varied with the cells. Glutamate enhanced the EPSP amplitude in a few cells with Mg(2+)-free and high Ca(2+)-Mg2+ solutions, and in most cells with high Mg2+ medium. In 3/5 cells tested, the paired pulse facilitation of EPSPs was reduced by glutamate when the EPSP amplitude either increased or decreased. NMDA (50 microM), kainate (50-100 microM), quisqualate (5-50 microM) and L-2-amino-4-phosphonobutyrate (L-AP4, 1 mM) also decreased the facilitation in about half of the cells tested. The glutamate-induced decrease in the facilitation was observed in both the presence and absence of Mg2+ and was not affected by the concomitant application of glutamate and antagonists for non-NMDA or NMDA receptors, such as 6-cyano-7-nitro-quinoxalinediones (CNQX, 60 microM) or 2-amino-5-phosphonovalerate (APV, 250 microM). Glutamate reduced the facilitation of excitatory post-synaptic currents (EPSCs) recorded at a constant membrane potential under voltage clamp, when the EPSC amplitude either increased or decreased and when the input conductance either increased or decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1992

Ruthenium red inhibits the binding of calcium to calmodulin required for enzyme activation.

The Ca(2+)-calmodulin (CaM)-dependent activation of myosin light chain kinase is inhibited by ruthenium red competitively with respect to Ca2+, with a Ki value of 8.6 microM. The binding of Ca2+ to CaM is inhibited by micromolar concentrations of ruthenium red. In the absence of Ca2+, CaM has two binding sites for ruthenium red with the dissociation constants of 0.36 and 8.7 microM, respectively. Ca2+ antagonizes the binding of ruthenium red to the low-affinity site on CaM. Binding of ruthenium red to the high-affinity site is not affected by Ca2+. The low- and high-affinity sites for ruthenium red are shown to be located in the NH2-terminal half and the COOH-terminal half of CaM, respectively. Lower concentrations of ruthenium red are needed for enzyme inactivation than for the dissociation of enzyme-CaM-Sepharose complex, suggesting these events have different Ca2+ requirements. Moreover, ruthenium red inhibits Ca(2+)-induced contraction of depolarized vascular smooth muscle in a competitive manner with respect to Ca2+. These results suggest that ruthenium red may be a new type of CaM antagonist that inhibits the binding of Ca2+ to CaM and thereby inhibits Ca(2+)-CaM-dependent enzymes and smooth muscle contraction competitively with respect to Ca2+.

Animals↗
PubMed1992

Salvage of infarcted myocardium by angiogenic action of basic fibroblast growth factor.

Coronary collateral vessels reduce damage to ischemic myocardium after coronary obstruction. Factors that stimulate collateral formation are expected to have ameliorating effects on myocardial infarction. In a canine experimental myocardial infarct model, intracoronary injection of basic fibroblast growth factor (bFGF) improved cardiac systolic function and reduced infarct size. Treatment with bFGF increased the number of arterioles and capillaries in the infarct. Thus, the angiogenic action of bFGF might lead to a reduction in infarct size. The application of bFGF might bring about a therapeutic modality for the salvage of infarcted myocardium.

Animals↗
PubMed1992

Isolation and structural characterization of a new crosslinking amino acid, cyclopentenosine, from the acid hydrolysate of elastin.

A novel polyfunctional crosslinking amino acid, which was developed slower than lysinonorleucine and faster than desmosine on thin layer chromatography, was isolated from the hydrolysate of bovine aorta elastin. Its proposed structure was verified by ultraviolet spectroscopy, fast atom bombardment mass spectroscopy, and nuclear magnetic resonance spectroscopy. The data indicated it to be a trifunctional amino acid with a cyclopentene structure. The mass spectral analysis indicated a parent compound with a mass of 381 (C18H27N3O6). The proposed structure is one derived from the condensation of three allysine residues. Based on the names of other crosslinking amino acids found in elastin, the trivial name of cyclopentenosine is given to this compound.

Amino Acids↗
PubMed1992

Amygdala kindling does not alter the N-methyl-D-aspartate receptor-channel complex which modulates dopamine release in the rat striatum and amygdala.

Kindling is suggested to be critically associated with enhancement of N-methyl-D-aspartate (NMDA) type excitatory amino acid synaptic transmission. The present study examined effects of kindling on NMDA-induced dopamine (DA) efflux from slices of the rat striatum and amygdala. When assayed 5-7 days after the last evoked seizure, no difference was observed between kindled and non-kindled striatum in the ability of NMDA to induce DA release, or in the effect of MK-801 or 7-chlorokynurenic acid to inhibit the amino acid-induced transmitter release. The present study revealed that NMDA receptors are also involved in the modulation of DA release in the amygdala. However, no difference was observed between kindled and non-kindled amygdala in the ability of NMDA to induce DA release. These results suggest that amygdala kindling does not alter activity of the NMDA receptor-channel complex modulating DA release in the striatum and amygdala.

Amygdala↗
PubMed1992

Aneurysmal formation after successful pulsed laser coronary angioplasty.

We report two cases of coronary artery aneurysmal formation as long term consequences of Ho:YAG and excimer laser coronary angioplasty. This case report suggests that pulsed laser angioplasty may result in severe vessel wall damage that may lead ultimately to aneurysmal formation.

Angina, Unstable↗
PubMed1992

Cardiac free wall rupture in acute myocardial infarction: ameliorative effect of coronary reperfusion.

To investigate the pathophysiology of cardiac free wall rupture (cardiac rupture) following acute myocardial infarction (AMI), and to clarify whether reperfusion therapy prevents cardiac rupture, 1,329 cases of AMI (conventional therapy group: 807 cases and reperfusion therapy group: 533 cases) were studied retrospectively. The overall incidence of cardiac rupture was 2.3% (2.7% in the conventional therapy group vs. 1.7% in the reperfusion therapy group). Patients with cardiac rupture were divided into two subgroups according to the time interval from the onset of AMI to cardiac rupture (early rupture less than or equal to 72 h and late rupture greater than or equal to 4 days). The indices of initial evolution of AMI was a significant risk of early cardiac rupture. The reperfusion therapy group showed significantly lower incidence of late rupture (0.4 vs. 1.5% in conventional therapy group; p less than 0.05). The incidence of cardiac rupture in the unsuccessful reperfusion therapy group was higher than that of the successful group (5.9% of 118 cases vs. 0.5% of 404 cases; p less than 0.05). It is concluded that the etiology of cardiac rupture following AMI cannot be explained by any single factor. Early rupture depends on the initial evolution of AMI, and early reperfusion and collateral flow prevent the late onset cardiac rupture.

Angioplasty, Balloon, Coronary↗
PubMed1992

Percutaneous angioscopic evaluation of luminal changes induced by excimer laser angioplasty.

Angioscopy has been shown to provide more detailed information on lesion morphology before and after interventional procedures than angiography. Therefore to evaluate the effects of laser angioplasty, angioscopy was performed in five patients with peripheral or coronary vascular disease who underwent excimer laser angioplasty. The excimer laser was operated at 308 nm, 135 nsec, 25 Hz, and 40 to 60 mjoules/mm2 and was coupled into multifiber wire-guided catheters of 1.4 to 2.0 mm diameter for coronary lesions and into catheters of 2.2 mm diameter for peripheral lesions. There were three coronary (one left anterior descending, one circumflex, one right coronary artery) and two peripheral (one common iliac artery, one superficial femoral artery) lesions. Angioscopy was successfully performed before and after laser ablation without any complications in all five lesions. The characteristics of angioscopic findings after excimer laser angioplasty consisted of flaps, fractures of plaques, and abundant tissue remnants. There was no apparent thermal injury. Recanalized channels were small and irregular. These results indicate that (1) angioscopy is effective and safe for evaluation of lesion morphology after laser angioplasty; (2) laser ablation does not result in thermal injury; and (3) irregular channels after recanalization and abundant tissue remnants may explain the suboptimal results after laser angioplasty.

Adult↗
PubMed1992

Effect of phencyclidine on spontaneous and N-methyl-D-aspartate (NMDA)-induced efflux of dopamine from superfused slices of rat striatum.

Phencyclidine (PCP) acts as an indirect dopamine (DA) agonist by inhibiting the neuronal reuptake of DA, while it also works as a N-methyl-D-aspartate (NMDA) antagonist. Aiming to investigate characteristics of these two properties of PCP in the same experimental system, the effects of PCP on spontaneous and NMDA-induced efflux of DA from superfused slices of the striatum of the rat were examined. Dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) in the samples of superfusate were extracted by alumina extraction and measured by high-performance liquid chromatography with electrochemical detection (HPLC-EC). Phencyclidine at concentrations greater than 1 microM, produced a concentration-dependent increase of the spontaneous efflux of DA. The efflux of DOPAC was also concentration-dependently increased by PCP. However, PCP inhibited the efflux of DA induced by NMDA, even at a small concentration (0.1 microM), which did not alter the spontaneous efflux of the transmitter. The mode of the inhibition by PCP was shown to be noncompetitive, with an estimated IC50 value of 280 nM. These results suggest that PCP, at small concentrations, reduces the synaptic levels of DA by blocking the facilitating effect of endogenous glutamate on the release of DA and, at slightly greater concentrations, the drug also works as an indirect DA agonist, to increase the levels of the transmitter in the synaptic clefts. The clinical significance of the dual effects of PCP is discussed in relation with the unique schizophrenomimetic property of PCP.

Animals↗
PubMed1992

A new superbright LED stimulator: photodiode-feedback design for linearizing and stabilizing emitted light.

A new, reliable LED photic generator is described for analog stimulus presentation in vision research. A "superbright" red-emitting diode is controlled via optical feedback using a PIN-photodiode. A Maxwellian-view stimulator developed this way has been proven capable of covering intensities of retinal illuminance of over 26,000 td with a linear dynamic range of 3.7 log units. The device also has outstanding properties in linearity (distortion less than 0.12% at 100 Hz), frequency characteristics (d.c. to 2 kHz full-modulation bandwidth), stability (0.0002% fluctuation), and noise (S/N ratio greater than 76 dB).

Electronics↗
PubMed1992

Tissue ablation with excimer laser and multiple fiber catheters: effects of optical fiber density and fluence.

This study was performed to assess the ablational properties of 1.4-, 1.7-, and 2.0-mm wire-guided multiple fiber catheters coupled to a XeCl excimer laser. Samples of postmortem human aorta were irradiated in blood at fluences of 40, 50, and 60 mJ/mm 2. Our results indicate that: 1) an increase in the active irradiation coverage results in an increase in the ablation efficiency; 2) the ablation efficiency is not fluence related using the 1.4- or 1.7-mm multiple fiber catheter but efficiency is fluence dependent using the 2.0-mm multiple fiber catheter; 3) the depth of tissue ablated with a multiple fiber catheter depends primarily upon the proportion of the active irradiation coverage at the catheter tip; 4) the 2.0-mm multiple fiber catheter induces craters surrounded by a larger zone of tissue damage than that observed with the 1.4- or 1.7-mm multiple fiber catheter; and 5) the 2.0-mm multiple fiber catheter should be used cautiously for laser angioplasty because of its high penetration and its risk of arterial wall damage.

Angioplasty, Laser↗