A case of cystinuria with nephrotic syndrome.
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Adult↗
Biomedical subjects
M Arita
Publications and source records attributed to M Arita.
Nature of "residual fast channel" dependent action potentials and slow conduction in guinea pig ventricular muscle and its modification by isoproterenol.
The nature of "residual fast channel" dependent action potentials and conduction was studied in guinea pig ventricular papillary muscle in which the resting potential was reduced to 58 +/- 1 mV in high K+ (16.7 mM) Tyrode's solution, with or without isoproterenol (0.1 microM). In the absence of isoproterenol, the action potential had a slur on the upstroke and the maximum rate of rise (Vmax) was composed of 2 separable peaks: the early large (32 +/- 7 V/s, Vmax,fast) and the late small (10 +/- 2 V/s, Vmax,slow) ones. The conduction velocity ranged from 30 to 35 cm/s. The Vmax,fast was selectively depressed by l-verapamil (1 microgram/ml), indicating that the impulses were transmitted through incompletely inactivated ("residual") fast channels. Lidocaine (2 micrograms/ml) depressed Vmax,fast with reduction of conduction velocity to about 20 cm/s just before the conduction block. Isoproterenol quadrupled the Vmax,slow but decreased Vmax,fast. As a result, the Vmax,slow overrode the Vmax,fast without change in the conduction velocity. In the absence of isoproterenol, there was no rate-dependent change in the action potential duration and the effective refractory period among the rates of 0.1, 0.5, and 0.9 Hz. Isoproterenol produced rate-dependent shortening in action potential duration with rate-independent shortening of postexcitation refractoriness, thereby resulting in a significant shortening in the effective refractory period at faster rates (0.5 and 0.9 Hz). Results suggest that the "residual fast channel" could produce "slow conduction" and that the ionic channels (fast or slow) responsible for the slow conduction may alternate according to local concentrations of tissue catecholamines.
Action Potentials↗
1,1,3,3-Tetramethylurea and triethanolamine as a new useful matrix for fast atom bombardment mass spectrometry of gangliosides and neutral glycosphingolipids.
Analysis of gangliosides from bovine brain was successfully performed by a newly developed method of fast atom bombardment mass spectrometry (FAB-MS). The use of triethanolamine with a few drops of 1,1,3,3-tetramethylurea as the matrix solution gave intense molecular ions of intact gangliosides tested, namely, GM1 and GD1a, corresponding to (M + Na)+ and (M + 2Na-H)+. Glycerol, that is usually used as a matrix solution for FAB-mass spectrometry, was not suitable for the analysis of gangliosides. Along with the molecular ion species, the ions pertaining to the carbohydrate sequence also appeared on the spectrum. The method was found to be useful for structural analysis using intact molecules of gangliosides and neutral glycosphingolipids.
Animals↗
Negative ion fast atom bombardment mass spectrometry of gangliosides and asialo gangliosides: a useful method for the structural elucidation of gangliosides and related neutral glycosphingolipids.
Structural elucidation, including molecular weight, carbohydrate sequence and molecular species of the ceramide portion, of gangliosides and asialo gangliosides from bovine brain, was successfully performed by negative ion fast atom bombardment mass spectrometry (NEG-FAB-MS). Ceramide monohexoside, ceramide dihexoside, asialo GM2 (GA2) and asialo GM1 (GA1), all of which were prepared from bovine brain gangliosides by treatment with 1 M formic acid and monosialogangliosides, GM3, GM2, and GM1, were analyzed without any derivatization by NEG-FAB-MS. They clearly gave the intensive molecular ion species, (M-H)-, and the fragment ions cleaved at glycosidic linkage sequentially from the non-reducing end with or without the ceramide portion. The spectra were quite simple, easily obtained without expansion of ion intensity, and extremely useful for the structural elucidation of underivatized glycosphingolipids.
Animals↗
GQ1b, a bioactive ganglioside that exhibits novel nerve growth factor (NGF)-like activities in the two neuroblastoma cell lines.
To clarify the role of gangliosides in the morphological and biochemical differentiation of neuronal cell cultures, the model cell culture system represented by two neuroblastoma cell lines, GOTO and NB-1, which were established from adrenal gland and metastatic neck lymph node, respectively, was examined. We found that the total ganglioside fraction from human brain had two remarkable effects on these cell lines, which are similar to those of nerve growth factor (NGF): (a) an increase in the cell number, and (b) an increase in the neurite number and the total length of neurites. In these cases, the genuine effector in total gangliosides could not be ascribed to a possibly contaminating NGF-like protein, but rather to a particular molecular species of the gangliosides, GQ1b, which could completely replace the effector function not only qualitatively but also quantitatively. Our results provide direct evidence for the participation of gangliosides in such functions.
Cell Line↗
Changes in plasma norepinephrine after intravertebral artery infusion of saralasin in sodium depleted dogs.
This study was designed to investigate the central action of circulating angiotensin II on the regulation of blood pressure in sodium depleted states. The effects of intravertebral arterial infusion of angiotensin II and [Sar-1, Ala-8] angiotensin II (saralasin) on plasma norepinephrine (NE) were studied in alpha-chloralose anesthetized dogs. Intravertebral arterial infusion of angiotensin II (10 ng/kg/min) increased mean arterial pressure (MAP), heart rate (HR) and plasma NE. Plasma NE was decreased by intravertebral arterial infusion of saralasin (0.40 +/- 0.05 to 0.28 +/- 0.04 ng/ml, p less than 0.05) in normal dogs. The administration of furosemide produced significant increases in plasma NE (142.4 +/- 23.7%, p less than 0.01), plasma renin activity (PRA) (158.6 +/- 26.3%, p less than 0.01) and HR (32.3 +/- 6.0 beats/min, p less than 0.01). A slight rise in mean blood pressure (3.9 +/- 1.2 mmHg, p less than 0.05) was observed during the furosemide administration. Saralasin infused into the vertebral artery significantly suppressed the furosemide-induced increases in plasma NE, HR and PRA, and lowered mean arterial blood pressure. Intravenous infusion of the same dose of saralasin produced no changes in arterial blood pressure, HR and plasma NE. These results suggest that the central sympathetic potentiation induced by circulating angiotensin II may contribute to the regulation of blood pressure in sodium and volume depleted states produced by furosemide.
Aldosterone↗
Modification of "depressed fast channel dependent slow conduction" by lidocaine and verapamil in the presence or absence of catecholamines--evidence for alteration of preferential ionic channels for slow conduction.
We studied, with microelectrodes, the effect of lidocaine and 1-verapamil on the upstroke phase of action potentials and conduction velocity in incompletely depolarized ventricular papillary muscle (resting potential, -58 +/- 1 mV) perfused in a high K+ (16.7 mM) Tyrode's solution. The action potential upstroke had a slur and the maximum rate of rise (Vmax) consisted of 2 components: the first large (32 +/- 7 V/sec; Vmax,fast) and the second small (10 +/- 2 V/sec, Vmax,slow). The conduction velocity was slow and ranged about 30-35 cm/sec. Isoproterenol and noradrenaline increased Vmax,slow and decreased Vmax,fast, in a concentration dependent manner (10(-8) - 10(-5)M). These effects were abolished by following application of a beta-blocker, pindolol (1 microgram/ml). Thus, the dominant ionic channel responsible for the slow conduction seemed to alter from the depressed fast channel to the slow channel as the catecholamine concentration was increased. In the absence of isoproterenol, lidocaine (2 micrograms/ml) depressed Vmax with a resultant decrease of conduction velocity to 16.4 +/- 4.2 cm/sec and which was followed by a conduction block, while 1-verapamil was without effect. In the presence of isoproterenol (5 x 10(-7) M), 1-verapamil (1 microgram/ml) depressed the Vmax and decreased the conduction velocity to 16.9 +/- 4.2 cm/sec, just before development of the conduction block, while lidocaine was without effect. These results suggest that the dominant ionic channel responsible for the slow conduction in high K media (16.7 mM), can be readily altered by changes in extracellular catecholamine concentrations and that the slowest possible conduction velocity was approximately the same (about 16 cm/sec) between the depressed fast channel-dependent and the slow channel-dependent conductions. Clinical implications of these findings were discussed.
Action Potentials↗
Contributions of central sympathetic neural activity to furosemide-induced increases in plasma renin activity and noradrenaline.
To evaluate the role of the central nervous system on the furosemide-induced increases in plasma noradrenaline (PNA), renin activity (PRA), and aldosterone concentration (PAC), central vasoactive sympathetic structures were inhibited by intravertebral artery infusion of colnidine. Intravertebral artery infusion of clonidine (0.06 microgram/Kg/min) significantly reduced basal PNA, heart rate, and arterial pressure, while both PRA and PAC were increased. Intravenous infusion of the same dose of clonidine caused no significant changes in PNA, PRA, and PAC. Intravertebral artery infusion of clonidine (0.02 or 0.1 microgram/Kg/min) significantly suppressed the furosemide-induced increases in PNA and heart rate, and induced a drop in arterial pressure. Although the furosemide-induced increase in PRA was suppressed by intravertebral artery infusion of clonidine, the furosemide-induced increase in PAC was not affected. These results suggest that the furosemide-induced increase in PNA may be mediated by the central sympathetic nervous system and that some of the furosemide-induced increase in PRA may be mediated by central sympathetic neural activation.
Aldosterone↗
Electrocardiogram and His bundle electrogram of Japanese monkeys (Macaca fuscata).
Electrocardiogram (ECG) was taken from Macaca fuscata in the supine position under secobarbital anesthesia. The ECGs were recorded in the leads of standard (I, II, III), augmented unipolar limb (aVR, aVL, aVF) and unipolar chest (V4R, V1, V2, V3, V4, V5, V6,). The ECG was similar to that of humans as well as the monkeys of other species in their general patterns and the voltage of each wave (P, Q, R, S, T), though the heart rate was considerably different. The direction of T wave was consistent with that of human ECG. The PR, QRS and QT intervals and the duration of P wave were in good agreement with those of monkeys of other species, and amounted to about 50% of those of human ECG. His bundle electrogram (HBE) was recorded with a tripolar electrode catheter inserted into the right ventricle via the femoral vein, and PA, AH, HV and PV intervals were measured. All of the values were also approximately 50% and PV intervals were measured. All of the values were also approximately 50% of those reported in human HBE. Such short time intervals observed in Macaca fuscata may be due to a smaller heart size of the monkey as compared to the human's. The measurements of ECG and HBE reported in the present study may be used as a normal reference in ECG and HBE of Macaca fuscata under anesthesia. The study suggests that the Macaca fuscata is useful as an animal model to investigate the repolarization process of human ECG.
Animals↗
Na, K-ATPase activity, ATP and Pi concentrations in various regions of monkey heart and their relation to post-overdrive hyperpolarization.
The relationship among Na, K-ATPase activity, ATP and inorganic phosphate (Pi) concentrations in functionally different regions of cardiac and skeletal muscles were studied in the Japanese monkey (Macaca fuscata). The activity of Na, K-ATPase was determined by the method of FIske and SubbaRow, and the concentrations of ATP and Pi, by isotachophoresis. The ATP concentrations in several regions of cardiac and skeletal muscles correlated positively with the Na, K-ATPase activities and Pi concentrations, whereas there was no significant correlation between the Na, K-ATPase activities and the Pi concentrations. Therefore, the ATP concentrations in functionally different regions of the tissues seemed to be a feasible measure of Pi concentrations and the Na, K-ATPase activities. The Na, K-ATPase activity was significantly higher in the epicardium than in the endocardium of the ventricle. The post-overdrive hyperpolarization was compared in these two tissues, using microelectrode methods. The hyperpolarization which followed overdrive stimulation (3.3-3.8 Hz) in the epicardium exceeded that in the endocardium, and was attributed to the difference in Na, K-ATPase activity. Our findings suggest that tissues with a higher Na, K-ATPase activity may have a more potent Na, K-pump activity, in association with higher tissue concentrations of ATP and Pi.
Adenosine Triphosphate↗
Effects of SG-75 (nicorandil) on electrical activity of canine cardiac Purkinje fibers: possible increase in potassium conductance.
The effects of various concentrations (1-1000 microM) of SG-75 nitrate or nicorandil) were investigated in action potentials of canine Purkinje fibers with microelectrodes. In normal fibers stimulated at the standard cycle length of 1500 msec, the drug (1-100 microM) produced dose-dependent shortening in action potential duration without changes in the resting potential, the maximum rate of rise of phase 0 and the slope of phase 4 depolarization. The drug-induced percentage of shortening in the action potential duration was more pronounced at lower rates of stimulation and lower external K+ concentrations, but the shortening was unchanged in lower external Na+ concentrations. Depolarizations produced by Ba++ (0.04 mM) and low K+ (less than or equal to 1.35 mM) solution were partially reversed by the drug, whereas there were no effects on the high K+ (5.4-24.7 mM)-induced depolarizations. Stretch-induced depolarization was also partially recovered in the presence of the drug. SG-75 shortened the duration of the slow response produced by isoproterenol (1 microM) in the presence of 24.7 mM K+, with little change in the maximum rate of rise. We concluded that SG-75 increases membrane K+ conductance in cardiac Purkinje fibers probably by modifying ix1 and iK1 channels without changing the slow inward currents and that the effects are not mediated by muscarinic receptors. The computed action potentials indicated that this view was reasonable.
Action Potentials↗
[Cardiovascular diseases and clinical laboratory examination. (2). Electrical and mechanical disturbances in the ischemic myocardium-- modification by catecholamines and electrolytes].
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Action Potentials↗
Enantioselective synthesis of new analogues of neplanocin A.
An efficient synthesis of analogues of (-)-aristeromycin (1) and (-)-neplanocin A (2) has been developed in an enantioselective and stereocontrolled manner by chemicoenzymatic strategy. The symmetric unsaturated dimethyl ester (3) was quantitatively hydrolyzed with pig liver esterase to yield a half ester (4). Decarboxylative ozonolysis followed by chemical transformation afforded versatile chiral intermediates, cyclopentylamine (7) and cyclopentenylamine (9), which were converted to carbocyclic analogues of 5-aminoimidazole-4-carboxamide riboside (16), (18), uridine (21), cytidine (23), and guanosine (25). The cytidine analogue (23) was found most active against KB cells in culture.
Adenosine↗
[Myasthenia gravis developed after extirpation of thymoma].
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Adult↗
Magnesium restores high K-induced inactivation of the fast Na channel in guinea pig ventricular muscle.
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Action Potentials↗
Further evaluation of the Biken test (modified Elek test) for detection of enterotoxigenic Escherichia coli producing heat-labile enterotoxin and application of the test to sampling of heat-stable enterotoxin.
A total of 2,229 strains of Escherichia coli isolated from subjects with traveller's diarrhea were tested for heat-labile enterotoxin production by the Biken test (Honda et al., J. Clin. Microbiol. 13:1--5, 1981). Results of the Biken test showed a 99.0% coincidence with those obtained by Chinese hamster ovary cell assay. The use of antiserum against E. coli heat-labile enterotoxin gave sharper and clearer results than did the use of antiserum against cholera enterotoxin. Samples for heat-stable enterotoxin assay were obtained from the agar plates used for the Biken test, and the heat-stable enterotoxin activities of these samples were compared with those of samples obtained from standard liquid cultures. Results for samples of 2,229 strains from the Biken agar plates and from liquid cultures were almost identical.
Bacteriological Techniques↗
Detection of intracardiac thrombi in a case of cardiomyopathy by two dimensional echocardiography.
A case of cardiomyopathy with systemic emboli is reported. Two dimensional and M-mode echocardiography showed abnormal intracavitary echoes. After further systemic emboli, echocardiograms showed the complete disappearance of the abnormal echoes found previously in the apex, which suggested that the emboli resulted from detachment of the left ventricular mural thrombi.
Child↗