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Biomedical subjects

Y Nakaya

Publications and source records attributed to Y Nakaya.

At least 19 recordsLinked to original sources
PubMed1992

Paucity of glutaminase-immunoreactive nonpyramidal neurons in the rat cerebral cortex.

Glutaminase has been considered to be a synthesizing enzyme of transmitter glutamate in pyramidal neurons of the cerebral cortex. In the present study, an attempt was made to examine with a double immunofluorescence method whether or not nonpyramidal neurons of the cerebral cortex are immunoreactive for glutaminase. Glutaminase was stained with mouse anti-glutaminase IgM and FITC-labeled anti-[mouse IgM] antibody. In the same section, parvalbumin (PA), calbindin (CB), choline acetyltransferase (CAT), vasoactive intestinal polypeptide (VIP), corticotropin releasing factor (CRF), cholecystokinin (CCK), somatostatin (SS), or neuropeptide Y (NPY) was visualized as a marker for nonpyramidal neurons with an antibody to each substance, biotinylated secondary antibody and Texas Red-labeled avidin. Virtually no glutaminase immunoreactivity was seen in PA-, CB-, CAT-, VIP-, CRF-, CCK-, SS-, or NPY-immunoreactive neuronal perikarya in the neocortex and mesocortex (cingulate and retrosplenial cortices), although it was detected in a few PA-, CB-, VIP-, CCK-, SS-, or NPY-immunoreactive nonpyramidal neurons in the piriform, entorhinal, and hippocampal cortices. PA- and CB-positive neurons have been reported to constitute the major population of GABAergic neurons in the cerebral cortex. Thus, the present results, together with the previous reports, suggest that most GABAergic, cholinergic and peptidergic nonpyramidal neurons in the neo- and mesocortex do not contain glutaminase.

Animals↗
PubMed1992

Single moving dipole obtained from magnetic field of the heart in patients with left ventricular hypertrophy.

Magnetocardiograms (MCGs) were recorded by means of a second-derivative SQUID (superconducting quantum interference device) magnetometer in 20 normal subjects and 28 patients with left ventricular overload to analyze the activation sequence of the heart and amplitude of estimated current source. In the normal subjects, the dipole was directed to the left and gradually superiorly 40 ms after the beginning of the QRS wave mainly due to the activation of the left ventricle. In the patients with hypertension, the direction and location of the dipoles were similar to those of the normal subjects, but their dipole moments were increased. In the patients with mitral regurgitation, the dipoles of late QRS were directed more inferiorly than in the normal subjects and their amplitude was increased. In the patients with aortic valve disease, the amplitude of the dipoles was increased markedly and their location was deviated more to the left than the dipoles of the normal subjects. We established the criterion for diagnosis of LVO from the dipole moment of 50 ms of 3.13 x 10(-3) A or more. The sensitivity of this criterion is significantly higher in the diagnosis of left ventricular overload than the electrocardiogram (ECG). The present study shows that the moving dipole method is useful to determine the increased electromotive force in patients with left ventricular overload and that sensitivity in diagnosis of left ventricular overload is increased.

Aortic Valve Insufficiency↗
PubMed1992

Changes in plasma free and sulfoconjugated catecholamines before and after acute physical exercise: experimental and clinical studies.

To elucidate whether sulfoconjugated catecholamines in plasma, especially dopamine, serve as a source of free catecholamines, we examined the change in afterload on the deconjugating activity of catecholamines in isolated Langendorff perfused rat hearts. Dopamine-sulfate was administered under ordinary or high-work-load conditions. Free dopamine in the effluent was increased by the high-work-load of the hearts, whereas conjugated dopamine showed an apparent decrease. These results indicate the possibility that deconjugation of sulfoconjugated catecholamines is accelerated by a high-work-load. To obtain further evidence in humans, we also examined the changes in the plasma levels of free and sulfoconjugated catecholamines in healthy volunteers before and after marathon running. Free dopamine increased 1.99-fold from the baseline value after exercise, whereas conjugated dopamine decreased by 12%. Similarly, the plasma levels of free noradrenaline and adrenaline increased after exercise to 2.45- and 1.51-fold their respective baseline values, while conjugated noradrenaline and adrenaline both decreased. These clinical results, as well as those of the experimental studies, suggest that the increase in plasma free catecholamines after exercise is due not only to increased release from the sympathoadrenal system but also to accelerated conversion from sulfoconjugated catecholamines in the plasma.

Adolescent↗
PubMed1992

Magnetocardiography.

Explore the source record for details and available documents.

Electroencephalography↗
PubMed1992

Vasopressin modulates K(+)-channel activities of cultured smooth muscle cells from porcine coronary artery.

The ATP-sensitive K+ channel (KATP channel) and the Ca(2+)-activated K+ channel (KCa channel) were active in cell-attached and excised inside-out patch configurations in cultured smooth muscle cells of the porcine coronary artery. Vasopressin activated the KCa channel (240 pS) when it was applied in the bath in the cell-attached patch mode presumably because of an increase in intracellular Ca2+, but it had no direct effect on the KCa channel. However, vasopressin directly blocked the KATP channel from outside the cell membranes in a concentration-dependent manner in both outside-out and cell-attached patch configurations; the K(+)-channel opener, nicorandil, reversed this effect. The KATP channel (30 pS) was highly active in the intact cell-attached patch configuration when the pipette contained a physiological concentration of Ca2+, suggesting that this channel may control the resting membrane potential. (The block might produce depolarization of the cells and might result in the contraction of smooth muscle cells.) These observations suggest that the KATP channel may play a role, at least in part, in controlling the contraction of smooth muscle cells of the coronary artery and that the control of vascular tone by vasopressin may be related to its ability to block the KATP channel.

Adenosine Triphosphate↗
PubMed1992

Endothelin blocks ATP-sensitive K+ channels and depolarizes smooth muscle cells of porcine coronary artery.

ATP-sensitive K+ channels with a conductance of 30 pS in smooth muscle cells of porcine coronary artery were found to be highly active in the intact cell-attached patch configuration when the pipette contained a physiological concentration of Ca2+ (greater than 10(-4) M). In the inside-out configuration, these channels were activated by extracellular Ca2+ and blocked by cytosolic ATP and glibenclamide. Endothelin applied to the pipette specifically blocked these channels in a concentration-dependent manner in the cell-attached configuration (half-maximal inhibition, 1.3 x 10(-9) M). A K+ channel opener, nicorandil, activated these channels even in the presence of 10(-8) M endothelin. In the whole-cell current-clamp method, the cell membrane was depolarized by endothelin and then repolarized by nicorandil. The membrane depolarization is closely related to contraction of smooth muscle cells. These results suggest that the ATP-sensitive K+ channels are important in controlling the vascular tone of the coronary artery and that endothelin can increase vascular tone by blocking these channels.

Adenosine Triphosphate↗
PubMed1992

[Role of neutrophil and T cell functions in host defense mechanisms of the elderly].

We studied neutrophil functions (phagocytosis, intracellular killing and chemotaxis with or without recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and T cell functions (lymphocyte proliferation and production of GM-CSF in response to phytohemagglutin (PHA)) to clarify host defense mechanisms in the elderly. There was no significant difference in phagocytic activity of neutrophils between the elderly and control young adults. rhGM-CSF enhanced phagocytosis by neutrophils, and a similar degree of enhancement was obtained in both groups. Killing activity of neutrophils evaluated by the new Nitroblue tetrazolium reduction test in the elderly was significantly lower than that in young adults (p < 0.001), however, pretreatment of neutrophils with rhGM-CSF resulted in an increase of killing activity in the elderly, raising their response to a level comparable to that of young adults pretreated with rhGM-CSF. There was no significant difference between the elderly and young adults in chemotaxis of neutrophils. rhGM-CSF alone did not prime chemotaxis, but primed chemotaxis in response to chemoattractant (N-formyl-methionyl-leucyl-phenylalanin) in both individuals. Lymphocyte proliferation and production of GM-CSF in response to PHA in the elderly were significantly lower than those in the young adults (p < 0.001, p < 0.05, respectively). These results indicated that impaired T cell functions may contribute, at least in part, to susceptibility to bacterial infection in the elderly.

Aged↗
PubMed1991

Angiotensin II blocks ATP-sensitive K+ channels in porcine coronary artery smooth muscle cells.

ATP-sensitive K+ channels with small conductance (30 pS in symmetrical K(+)-rich solutions) in porcine coronary artery smooth muscle cells were highly active at physiological concentrations of Ca2+ (greater than 10(-4) M) even in the presence of physiological ATP levels, suggesting that these channels contribute to the generation of the resting membrane potential in vascular smooth muscle cells and their modulation is important in controlling vasomotor tone. Angiotensin II, applied from outside the membrane, blocked these channels in a concentration-dependent manner. This would be expected to cause depolarization and result in vasoconstriction.

Adenosine Triphosphate↗
PubMed1991

Negative U wave during percutaneous transluminal coronary angioplasty.

To clarify the clinical significance of the negative U wave during acute myocardial ischemia, the appearance of the U wave and ST-segment elevation on electrocardiography during percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending artery (LAD group: 11 patients) or right coronary artery (RCA group: 18 patients) was studied. During PTCA, U-wave inversion (newly developed negative U wave, and increased negativity of the pre-existing negative U wave) was observed in 37 (90%) of 41 patients in the LAD group and in 16 (89%) of 18 patients in the RCA group. The incidence of ST-segment elevation was similar to that of U-wave inversion; however, U-wave inversion appeared before detectable ST-segment elevation in 20 patients (49%) in the LAD group and in 4 patients (22%) in the RCA group. Moreover, U-wave inversion was observed frequently in a wider range of leads than ST-segment elevation. These results suggest that the U wave is a more sensitive indicator of myocardial ischemia than ST-segment elevation in some patients, and that a negative U wave may be produced by a different mechanism than that which produces ST-segment deviation, although both are related to myocardial ischemia.

Angioplasty, Balloon, Coronary↗
PubMed1991

[A case of acinar-islet cell tumor of the pancreas body].

Combined carcinoma of the pancreas is very rare. The case of pancreatic tumor featuring both acinar cell and islet cell tumors presented, may be only the fifth case of acinar-islet cell tumor in the world. A 34-year-old-woman visited our hospital complaining of weight loss (8 kg/6 months). A clearly demarcated pancreatic tumor was visualized by ultrasonography, body CT and MRI. Class 3 cells were extracted via ultrasonography guided fine-needle biopsy. Tumor was enucleated on October 5, 1988. Histologic appearance of the tumor by light microscopy was consistent with that of both acinar cell and islet cell tumors. Electron microscopy revealed two distinct populations of zymogen and neuroendocrine granules. The patient is doing well 1 year and 7 months postoperatively with no evidence of liver metastasis or recurrence. This case is significant in terms of the close histogenic relationship between pancreatic exocrine and endocrine components.

Adenoma, Islet Cell↗
PubMed1991

Effects of nitroglycerin on ATP-induced Ca(++)-mobilization, Ca(++)-activated K channels and contraction of cultured smooth muscle cells of porcine coronary artery.

Extracellular application of ATP transiently increases the cytosolic-free Ca++ concentration ([Ca++]i) in cultured smooth muscle cells of porcine coronary artery, and this activates large conductance Ca(++)-activated K (Kca) channels. In the present study effects of nitroglycerin (NG) and 4-aminopyridine (4-AP) on [Ca++]; and contraction were studied. 4-AP blocked Kca channels and enhanced the rise of [Ca++]i with oscillation, which led to contraction of the cells. NG activated the Kca channels of 300 picosiemens and inhibited 4-AP-induced contraction and oscillation of [Ca++]i. These results suggest that the vasorelaxant effect of NG involves hyperpolarization of the cell membrane by activating the Kca channels. NG also cause rapid decrease of [Ca++]i during the Ca(++)-mobilization by ATP in Ca-free solution. Similar effects were observed with cyclic GMP, suggesting that the effects of NG on the Kca channels and [Ca++]i were mediated by cyclic GMP.

4-Aminopyridine↗
PubMed1990

Differentiation between left circumflex and right coronary artery occlusions: studies on ST-segment deviation during percutaneous transluminal coronary angioplasty.

To distinguish between acute occlusion of the right coronary artery (RCA) and the left circumflex artery (LCx) by electrocardiography, we studied ST-segment deviation during balloon inflation in percutaneous transluminal angioplasty. The composite electrocardiographic criteria based on ST-segment deviations increased the diagnostic specificity: that is, the finding of inferior infarction (ST-segment elevation in leads II, III, aVF) without lateral infarction (ST-segment elevation in leads V5,6) was highly suggestive of RCA occlusion (sensitivity and specificity: 35 of 43 cases, 81.4%; and 33 of 36 cases, 91.7%), whereas ST-segment elevation in leads V5,6 (LCx: 23 of 36 cases; 63.9%, RCA: 5 of 43 cases; 11.6%) or isolated ST-segment depression in leads V2-4 (LCx: 9 of 36 cases; 25.0%, RCA: none of 43 cases) was highly suggestive of LCx occlusion. These results indicate that the composite electrocardiographic criteria were useful in predicting the artery involved in acute myocardial infarction, although any single criterion was not sensitive or specific enough to differentiate right from left circumflex coronary artery occlusion.

Angioplasty, Balloon, Coronary↗
PubMed1990

Vector U loop in patients with idiopathic cardiomyopathy.

The U loops of vectorcardiograms were recorded in 50 normal subjects, 10 patients with dilated cardiomyopathy (DCM group), and 83 patients with hypertrophic cardiomyopathy (HCM group). The HCM group was divided into three subgroups: those with obstructive hypertrophic cardiomyopathy (HOCM), nonobstructive hypertrophic cardiomyopathy (HNCM), and apical hypertrophy (APH). The spatial characteristics of the U loop were examined qualitatively and quantitatively and were correlated with echocardiographic findings. The magnitude of the U loop was significantly larger in the HCM group, especially in the APH subgroup, than in the normal subjects, but it was not larger in the DCM group. The maximum U vector was significantly displaced anteriorly and to the right in the DCM and HCM groups, especially the APH and HNCM subgroups. In the HNCM and APH subgroups, the magnitude of the U loop correlated significantly with the thickness of the posterior wall of the left ventricle, but not with that of the interventricular septum. These findings suggest that the U loop is related to hypertrophy of the apex and the posterior wall of the left ventricle.

Adult↗
PubMed1990

Signal-averaging electrocardiogram in patients with diabetes mellitus.

In order to detect silent impairment of the heart due to diabetes mellitus, the signal-averaging electrocardiograms (ECG) of 21 healthy subjects and 22 diabetic patients without ventricular tachycardia were compared. The QRS duration in the signal-averaging ECG was longer in diabetic patients than in the normal subjects (87.3 ms vs. 114.5 ms, p less than 0.01). Moreover, late potentials in the terminal portion of the QRS complex were observed in 7 diabetic patients (32%), but in only one normal subject (5%, p less than 0.01). These findings suggested that patients with diabetes mellitus frequently have intraventricular conduction disturbances, presumably due to diabetic microangiopathy.

Adult↗
PubMed1990

[Magnetocardiographic localization of an accessory pathway in patients with WPW syndrome].

The usefulness of magnetocardiography (MCG) in determining the location of an accessory pathway (Kent bundle) was examined by the isomagnetic map at the time of a delta wave, and by gated magnetic resonance imaging (MRI). MCG was performed at 36 points on the anterior chest wall in eight cases with Wolff-Parkinson-White (WPW) syndrome using a SQUID (superconducting quantum interference device) system with the second derivative gradiometer. Based on these records, isomagnetic maps during the QRS and T waves were constructed, and the depth of the accessory pathway from the coil was calculated mathematically. The locations of the accessory pathways were estimated using these data and the MRI findings. The locations of the accessory pathways thus determined were compared with findings obtained by body surface maps. A dipole directed towards the left was deduced, because the maximum was located more superiorly than the minimum in an isomagnetic map 10-40 msec after onset of the delta wave in cases with WPW syndrome, indicating an accessory pathway to be located in the right ventricle. A dipole directed towards the right was deduced, because the maximum was located more superiorly than the minimum in an isomagnetic map 10-40 msec after onset of the delta wave of cases with WPW syndrome indicating an accessory pathway to be located in the left ventricle. Assuming the electric current source is a single dipole, the location of a current dipole might be determined by positions of the maximum and the minimum in the isomagnetic maps. In the present study, the locations as determined by analysis of the isomagnetic map 40 msec after onset of the delta wave and the gated MRI were concordant with the findings obtained by body surface isopotential maps. Furthermore, some cases showed two opposing dipoles on the isomagnetic map at the peak of the T wave in lead II of the standard ECG leads; one directed to the left expressing normal repolarization; the other directed to the right presumably expressing repolarization of the myocardium which was excited by an impulse via the accessory pathway. The location of the current dipole as determined by analysis of the isomagnetic map at the peak of the T wave in lead II was nearly the same as the position of the current dipole as determined by analysis of the isomagnetic map 40 msec after onset of the delta wave.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1990

Effect of magnesium sulfate on ventricular refractoriness and its efficacy for torsade de pointes.

The effect of magnesium sulfate on ventricular refractoriness and its efficacy for torsade de pointes (TdP) were studied in nineteen dogs. After the administration of quinidine sulfate (30 mg/kg), TdP was induced by ventricular pacing in ten of 19 dogs (52.6%), polymorphic ventricular tachycardia in seven (36.8%), ventricular fibrillation in two (10.5%). Quinidine sulfate caused significant increases in QTc interval, ventricular effective refractory period (ERP) and dispersion of ERP(dERP), and decrease in ERP/QT. Magnesium sulfate significantly increased ERP (p less than 0.01), but it did not change QT interval, resulting in significant increasing of ERP/QT (0.41 +/- 0.05 to 0.61 +/- 0.05, p less than 0.01). It decreased dERP but not significantly. Magnesium sulfate prevented the induction of TdP in eight of 10 dogs (80.0%) (30 mg/kg in four and 60 mg/kg in four). In conclusion, magnesium sulfate has value as first aid therapy for drug-induced TdP. If patients have ischemic heart disease or hypertension, we recommend infusion of magnesium for the initial therapy of TdP.

Animals↗