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Biomedical subjects

A Noma

Publications and source records attributed to A Noma.

At least 73 records · Page 4Linked to original sources
PubMed1996

Highly sensitive ELISA for soluble Fas in serum: increased soluble Fas in the elderly.

We have developed and characterized a highly sensitive ELISA for soluble Fas (sFas) in the serum. The linearity of calibrator range was 0.06-2.00 micrograms/L and the detection limit was 0.01 microgram/L. The average within- and between-run CVs were 3.9% and 3.8%, respectively. The recovery of added sFas to serum was 93-118%. The effects of possible interferences (tryglyceride, hemoglobin, bilirubin) were negligible. We determined serum sFas in 155 healthy subjects, ages 20-69. The mean value of sFas in men (2.50 +/- 0.63 micrograms/L, n = 78) was significantly higher than that in women (2.01 +/- 0.53 micrograms/L, n = 77) (P < 0.001). Furthermore, there was a significant correlation between serum sFas concentration and age (men, r = 0.397, P < 0.001; women, r = 0.569, P < 0.001). Although the concentrations of sFas tended to increase with aging, it remains to be clarified how Fas-mediated apoptosis relates to aging.

Adult↗
PubMed1995

Non-selective cation current of guinea-pig endocardial endothelial cells.

1. Endocardial endothelial (EE) cells, isolated by the enzymatic treatment of guinea-pig heart, were used for whole-cell voltage clamp experiments. 2. The inward rectifier K+ current was observed in about half of the experiments. The contribution of Ca(2+)-dependent K+ current to the resting membrane conductance was also suggested. 3. After the K+ conductances were suppressed, removal of external Na+ revealed an inward cation current (1.2 pA pF-1, at -45 mV), whose slope conductance was a saturable function of external Na+ concentration. When Na+ was totally replaced by various monovalent cations, the order of the membrane conductances was K+ > Rb+ > Cs+ > Na+ > Li+. 4. This basal non-selective cation current was blocked by either Gd3+ or La3+, and showed slight outward rectification. 5. Addition of 20 mM Ca2+ or Ba2+, but not Mg2+ or Mn2+, to the Na(+)-free solution, induced an inward current, indicating that this current possesses a significant Ca2+ permeability. 6. In approximately 15% of the experiments, ATP and histamine induced another type of non-selective cation current, which showed different ion selectivity (Na+ > K+, Cs+) and rectification (inward). 7. The basal non-selective cation current is responsible for both the low resting potential and the leak Ca2+ influx of EE cells.

Adenosine Triphosphate↗
PubMed1995

Inactivation of the cardiac Na+ channels in guinea-pig ventricular cells through the open state.

1. The inactivation kinetics of the Na+ current were investigated using the improved oil-gap voltage clamp method in single ventricular cells of guinea-pig hearts. 2. Activation of the Na+ current was observed on depolarization more positive than -50 mV from a holding potential of -100 mV, and inactivation was complete during these depolarizations. The time course of current decay was fitted by a double exponential at potentials between -40 and -15 mV, and virtually by a single exponential at more positive potentials. The decay time courses examined either by the double-pulse protocol or the single-pulse protocol were similar. 3. The double-pulse protocol clearly revealed a sigmoidal onset of inactivation on depolarization. The initial delay of inactivation decreased with more positive potentials. The time course of double-pulse inactivation was reconstructed by integrating the Na+ current recorded by a continuous depolarization. 4. These findings are consistent with the hypothesis that the cardiac Na+ channel inactivates exclusively through the open state.

Animals↗
PubMed1995

Hyperpolarization induced by vasoactive substances in intact guinea-pig endocardial endothelial cells.

1. The responses of guinea-pig endocardial endothelial (EE) cells to various vasoactive substances were investigated in either the small tissue preparation or freshly isolated cells using the patch clamp technique. 2. The mean resting potential of the EE cell was -44 mV in the small tissue preparation, and applications of ATP, ADP, AMP, adenosine, histamine and substance P induced transient hyperpolarizations of -22, -21, -9, -10, -23 and -15 mV, respectively. The membrane potential of EE cells failed to respond to acetylcholine, bradykinin, thrombin, atrial natriuretic peptide, vasopressin and serotonin. 3. The whole-cell voltage clamp of dissociated cells revealed a transient increase of K+ conductance underlying the ATP and histamine responses. The agonist-induced current showed no time-dependent change during voltage steps. The response was showed no time-dependent change during voltage steps. The response was prevented by adding 10 mM EGTA to the pipette solution. 4. In the cell-attached single channel recordings, ATP induced transient K+ channel activities having a slope conductance of 34 pS. In inside-out patches, similar K+ channels were activated by applying Ca2+ of more than 0.1 microM. 5. These findings are consistent with the idea that the Ca(2+)-dependent K+ channel is involved in the hyperpolarizing response of EE cells, as described in vascular endothelial cells.

Adenosine↗
PubMed1995

Classification of ion channels in the luminal and abluminal membranes of guinea-pig endocardial endothelial cells.

1. The ion channels on both the luminal and abluminal membranes of endocardial endothelial (EE) cells were separately recorded using the patch clamp technique in the guinea-pig heart. 2. The major population consisted of two types of non-selective cation channels, which showed open probabilities of 0.21 and 0.33 at the resting potential, and conductances of 36 and 11 pS, respectively. 3. The next major class was Cl- channels with an ohmic conductance of 409 pS. The channel was quiescent in the cell-attached mode but was activated by strong depolarization after excising the patch membrane. 4. The channels activated by intracellular Ca2+ were mainly K+ channels showing a 34 pS slope conductance and, less frequently, Ca(2+)-dependent K+ channels having a large conductance (210 pS). The inward rectifier K+ channel (32 pS) was also observed. 5. The non-selective cation channels were recorded on the luminal membrane, but scarcely on the abluminal membrane, suggesting an active transport of K+ and Na+ across the endocardium. 6. The resting membrane conductance of the EE cells may be provided mostly by non-selective cation channels and 34 pS Ca(2+)-dependent K+ channels.

Animals↗
PubMed1995

A sustained inward current activated at the diastolic potential range in rabbit sino-atrial node cells.

1. After blocking both the hyperpolarization-activated current and the membrane K+ conductance, depolarizations from -80 mV to between -70 and -50 mV induced a sustained current in sino-atrial node cells. We have tentatively designated this current Ist. 2. Ist was blocked by both organic and inorganic Ca2+ channel blockers, but was insensitive to tetrodotoxin (30 microM). Isoprenaline increased Ist. 3. The peak of Ist (at about -50 mV) was increased to 149 +/- 13% (n = 8, P < 0.01) by lowering the external Ca2+ concentration ([Ca2+]o) from 1.8 to 0.1 mM, in contrast to the marked depression of the L-type Ca2+ current. In 0.1 mM [Ca2+]o solution, the nicardipine-sensitive current-voltage relation showed the peak amplitude at about -50 mV and a reversal potential of +37.4 +/- 4.4 mV (n = 5). The isoprenaline-sensitive component also showed a reversal potential of about +30 mV. 4. Reducing [Na+]o from 140 to 70 mM in 0.1 mM [Ca2+]o decreased Ist to 53 +/- 5% (n = 7, P < 0.01). Increasing [Ca2+]o or [Mg2+]o decreased the amplitude of Ist. The half-maximum concentration of Mg2+ inhibition was 2.2 mM. 5. At 1.8 mM [Ca2+]o, Ist was inactivated by clamping for 5s at -10 mV, and gradually recovered after repolarization to -80 mV with a half-time of 1.36 +/- 0.4 s (n = 6). 6. The transitional sino-atrial node cell had minimal amplitude of Ist. 7. These characteristics of Ist are qualitatively comparable to those of the monovalent cation conductance of the L-type Ca2+ channel induced by depleting external divalent cations to the micromolar range. We conclude that Ist is generated by a novel subtype of L-type Ca2+ channel.

Action Potentials↗
PubMed1995

Polymorphism and Distribution of Apo(a).

Several apo(a) isoforms, controlled by a series of alleles Lp(a)F, Lp(a)B, Lp(a)S1, Lp(a)S2, Lp(a)S3, Lp(a)S4 and null, were found in 470 healthy Japanese by 4% SDS-PAGE and immunoblotting techniques. There was a strong inverse relationship between the apparent molecular weight of apo(a) isoforms and plasma concentrations of Lp(a). Lp(a) in d < 1.006 fraction increased 2-4h after oral fat load. Lp(a) exhibited a marked avidity for triglyceride-rich lipoprotein (TRL), and we suggest that the TRL-bound Lp(a) is the intact Lp(a) derived from serum. We demonstrated that the lipid-free apo(a) does not contain apo B-100 in serum, and has a molecular mass of ca 200 kDa. The free apo(a) level in normal subjects was 1.75 mg/dl (as Lp(a)) and was no different from the level in CAD patients.

Coronary Disease↗
PubMed1994

Cation-dependent gating of the hyperpolarization-activated cation current in the rabbit sino-atrial node cells.

1. The gating properties of the hyperpolarization-activated cation current (I(f) or Ih) were investigated in single pacemaker cells dissociated from the rabbit sino-atrial node. 2. The whole-cell I(f) was recorded in the presence of different external cations. The inward I(f) was increased when external Na+ was replaced with K+, and was decreased in Li+ or Rb+ solution. In Tris+ and Cs+ solutions, the inward I(f) was negligible. The outward tail current recorded upon depolarization was largest in Li+ solution and smaller in a sequence of Na+, Tris+ and K+ solutions. In Rb+ and Cs+ solutions, only a small tail current was recorded. 3. The outward tail current had a 'shoulder' in Na+ solution, which was much delayed by replacing Na+ with Li+. In K+ solution, the decay of the tail current was much faster, and no obvious shoulder was recorded. The tail current was slowest in Li(+)-rich and 0 mM K+ solution, and was progressively accelerated by adding K+ over the range from 0 to 3 mM. The tail current at 30 mM [K+]o showed only a small shoulder. A common binding site to modulate the I(f) deactivation was suggested for monovalent cations. 4. The shoulder of the I(f) tail became more evident as I(f) was activated to a larger extent either by prolonging the duration or by increasing the amplitude of the preceding hyperpolarization in both Na+ and Li+ solutions. 5. The I(f) was first activated by hyperpolarizing the membrane to -110 mV, and then deactivated by depolarization. The inward tail current at -50 mV showed a single exponential decay. At more positive potentials, the shoulder of the outward tail currents became more evident and the rate of the final decay was increased. 6. The time course of I(f) activation was well fitted with the sum of two exponential functions. Time constants of both components were not affected by the external cation (Na+, K+ or Li+) replacement. Likewise, the quasi-steady state activation was conserved when external Na+ was replaced with Li+. 7. Two closed and three open states were assumed in a sequential state model of the I(f) channel. The cation effects were well simulated by assuming that the deactivation rate was selectively modulated. The flow of I(f) during the spontaneous action potential was calculated. The activation of I(f) started on repolarization to the maximum diastolic potential and reached a maximum in the middle of the diastolic period. Its peak amplitude was 14% of the net inward current during the diastolic period.

Animals↗
PubMed1994

Background conductance attributable to spontaneous opening of muscarinic K+ channels in rabbit sino-atrial node cells.

Single myocytes were dissociated from the rabbit sino-atrial node, and the membrane background conductance produced by spontaneous opening of the muscarinic K+ channels was investigated by recording whole-cell and single channel currents in both normal K+ (5.4 mM) and high-K+ (145 mM) external solutions. Increasing external K+ concentration ([K+]o) from 5.4 to 145 mM induced a large inward shift of the whole-cell current accompanied by considerable current fluctuations at -50 mV. The high-K(+)-induced current was both K+ selective and voltage dependent, which was examined by varying [K+]o. This current was almost completely suppressed by 1-5 mM Ba2+ or 2-10 mM Cs+ and it was partly blocked by 10 microM atropine. In high-K+ (145 mM) solution, 20 nM acetylcholine (ACh) further increased the K+ conductance as well as the current noise. The power density spectrum of the noise was fitted with a sum of two Lorentzian functions. The corner frequencies of both the slow (approximately 5 Hz) and fast (approximately 120 Hz) components were comparable between the noise before and during the ACh application. Internal dialysis with a non-hydrolysable derivative of ATP, 5'-adenylylimido-diphosphate (AMP-PNP) or Mg(2+)-free solution markedly decreased both the amplitude and fluctuations of the high-K(+)-induced current. The relation between the variance of the current fluctuations and the mean current amplitude was linear in every experiment using dialysis of AMP-PNP or Mg(2+)-free internal solution, or using superfusion of ACh. The slopes of these relations gave comparable single channel current amplitudes of -0.7 pA at -50 mV. These results indicate that the spontaneous opening of the muscarinic K+ channels is largely responsible for the high-K(+)-induced current. In the high-K+ solution, the variance-mean relation at -50 mV showed that the muscarinic K+ channel provides an inward current of 3.12 +/- 2.13 pA pF-1 (n = 23), which was about 60% of the total inward background current. In the normal K+ solution, the variance-mean relation at -50 mV indicated that an outward current of 6.0 +/- 2.0 pA (0.33 +/- 0.28 pA pF-1, n = 8) was provided by the K+ channel. The single channel current amplitude was estimated to be 0.06 +/- 0.02 pA (n = 9). Cell-attached recordings in the absence of ACh demonstrated sporadic and brief openings of channels identical to the ACh-induced channels. The power density spectra of the single channel currents exhibited kinetic properties comparable with those of the whole-cell currents.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1994

Voltage- and time-dependent block of I(f) by Sr2+ in rabbit sino-atrial node cells.

The hyperpolarization-activated cation current (I(f)) was recorded in single myocytes dissociated from the rabbit sino-atrial node and the Sr(2+)-mediated block of I(f) examined. In the presence of 0.1-10 mM Sr2+, the activation phase of I(f) was followed by a slower decay during hyperpolarization. In the steady state I/V diagram, the Sr2+ block progressed with increasing hyperpolarization. Ba2+ also blocked I(f), but no time dependency could be observed. The blocking effect of Ca2+ was weak, and Mg2+ had little effect on I(f). The relationship between extracellular Sr2+ concentration [Sr2+]o and the block was described by a Hill coefficient of 1. The half-saturating [Sr2+]o were 2.0, 1.6, 1.1 and 0.65 mM at -90, -100, -110 and -120 mV, respectively. The rapid application of Sr2+ during the full activation of I(f) using the jet-stream method induced an exponential decline of I(f). The reciprocal time constants were linearly correlated to [Sr2+]o, suggesting 1:1 binding stoichiometry. The fractional electrical distance for the binding site was approximately 0.5 from the external side of the channel. Based on the multiple closed and open states for the I(f) channel, a mathematical model for the Sr2+ block was constructed in which the time course of I(f) in the presence of Sr2+ was described by the sum of three exponential functions. Fitting the model to the original traces revealed blocking and unblocking rates similar to those obtained from the jet-stream method. At -110 mV, the blocking rate was 410 M-1 s-1 while the unblocking rate was 0.16 s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Lp(a): an acute-phase reactant?

The present study was designed to confirm the transient increases of plasma Lp(a) levels as an acute-phase reactant and to clarify the significance of these increases with the use of patients with acute myocardial infarction and patients subjected to surgical operations. Although interleukin 6, C-reactive protein and alpha 1 antitrypsin reached the maximal levels 1-2 days, 3 days and 4-5 days, respectively, after the episodes, the peak time of Lp(a) levels was delayed some extent in both patient groups. Studying the transient increases of Lp(a) levels as a function of apo(a) isoforms analyzed by density-gradient ultracentrifugation and SDS-PAGE, the higher-density Lp(a) particles preferentially containing high-molecular-weight apo(a) isoforms increased more than the lower-density Lp(a) particles containing low-molecular-weight apo(a) after the episodes. The immunohistochemical findings suggest that Lp(a) may play an important role as an acute-phase reactant in the repair of tissue injury, especially in the process of angiogenesis.

Acute-Phase Reaction↗
PubMed1994

Fully mechanized latex immunoassay for serum lipoprotein(a).

We have developed a fully automated system to quantify lipoprotein(a) (Lp(a)) in human serum, based on the latex-enhanced turbidimetric immunoassay by application of the Immuno Chemistry Analyzer 501X. This assay was carried out with undiluted serum and was able to detect at Lp(a) levels higher than 4.0 mg/l. When judged to be out of range of the calibration (> 600 mg/l), the sample was automatically re-tested after automatic 10-fold dilution. Within-run C.V.s ranged from 1.9 to 2.1% and between-run C.V.s from 2.7 to 3.9%. Results by the present method were in good agreement with those by the in-house ELISA (r = 0.978) and the commercial ELISA (r = 0.990). The distribution of Lp(a) levels in sera from 508 healthy donors was highly skewed; the mean and median were 158 mg/l and 105 mg/l, respectively.

Adolescent↗