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Biomedical subjects

T Iijima

Publications and source records attributed to T Iijima.

At least 343 records · Page 19Linked to original sources
PubMed1988

Cryopreservation of Leucocytozoon caulleryi sporozoites.

Leucocytozoon caulleryi sporozoites that had been stored at -196 degrees C or -80 degrees C for 6 or 12 months in Eagle's minimum essential medium or Medium 199 supplemented with 5% glycerol and 10% chicken serum showed infectivity to chickens. Glycerol at a concentration of 10% and dimethyl sulfoxide at 10% and 5% were found to be ineffective cryoprotective agents for the low temperature preservation of sporozoites. Sporozoites isolated from the intact females of Culicoides arakawae, which had been stored at -80 degrees C for 6 or 12 months without cryoprotective agents, retained their infectivity. No differences were observed in the prepatent period, duration of parasitemia, and presence of serum-soluble antigens between chickens infected with frozen sporozoites and those infected with fresh sporozoites.

Animals↗
PubMed1988

Voltage- and use-dependent block of the inward calcium current by MCI-176, a new non-dihydropyridine calcium antagonist, in canine ventricular muscles and single ventricular cells of the guinea-pig.

Effects of MCI-176, 2-(2,5-dimethoxyphenylmethyl)-3-(2-dimethylaminoethyl)-6-isopro pox y-4(3H)- quinazolinone hydrochloride, on action potentials of canine ventricular muscles and on membrane currents of single ventricular cells of the guinea-pig heart were studied with the microelectrode and the patch-clamp ("whole-cell recording") methods. In canine ventricular trabeculae, MCI-176 (10(-5)-10(-4) M) decreased the plateau potential, the action potential duration at 30%-repolarization and the maximum rate of rise of the action potential; and it also decreased the amplitude and the duration of the slow response action potential in a concentration-dependent manner. Those effects were much more apparent at higher stimulus frequency. Under voltage clamp condition of single ventricular cells of the guinea-pig heart, MCI-176 (3 x 10(-5) M) decreased the inward calcium current (ICa) by 25-30% when the membrane potential was held at the resting membrane potential, and the drug abolished it when the membrane potential was held at -30 mV. MCI-176 added at rest decreased ICa ("initial block") and reduced it further with repetitive depolarizations in a beat-to-beat fashion. MCI-176 facilitated the reduction of ICa by increasing the clamp pulse frequency. These results indicate that MCI-176 decreases ICa of mammalian ventricular muscles in a voltage- and use-dependent manner.

Action Potentials↗
PubMed1987

Pinacidil increases the background potassium current in single ventricular cells.

Pinacidil, a new antihypertensive agent, increased the background (inward rectifier) potassium current and abolished its negative slope, and did not change the time-dependent component of the outward (delayed outward) current in single ventricular cells isolated from the guinea-pig heart. These effects must be responsible for the negative inotropic action of this drug.

Animals↗
PubMed1987

Optical monitoring of excitatory synaptic activity between cultured hippocampal neurons by a multi-site Ca2+ fluorometry.

The fluorescence intensities from cultured hippocampal neurons loaded with a Ca2+-indicator (fura-2), showed spontaneous, periodical oscillations, which were synchronized among the cells. Tetrodotoxin or 2-aminophosphonovalerate, a glutamate-receptor antagonist, blocked the oscillation. The rising phase of the fluorescence was accompanied by a burst of inward currents, as monitored by a patch electrode. It is thus suggested that the fluorescence elevation represents an increase in intracellular Ca2+ concentration accompanied by excitation of neurons which formed synaptic connections between each other. This method for detection of neuronal activity including synaptic excitation escapes from the limitations of the conventional technique employing microelectrodes.

2-Amino-5-phosphonovalerate↗
PubMed1987

Autonomic innervation of the arteriovenous anastomoses in the dog tongue. A histochemical and ultrastructural study.

The innervation of the arteriovenous anastomoses in the dog tongue has been investigated. At the light-microscopic level, the vessels were found to be densely supplied with adrenergic and AChE-positive nerve plexuses and less densely with the quinacrine-binding nerve plexus. At the electron-microscopic level, at least two apparently different types of axon profiles were identified: Small vesicle-containing axons, characterized by many small granular vesicles, variable numbers of small clear vesicles and large granular vesicles. Storage of endogenous amines and uptake of exogenous amines into most small granular vesicles and many large granular vesicles was demonstrated. These axons stained only lightly with reaction products for AChE activity and thus seemed to be adrenergic in nature. Some axons contained numerous large granular vesicles, whose cores occasionally stained with uranyl ions; this suggests a co-localization of ATP or peptides as neurotransmitters. Small granular vesicle-free axons, containing small clear vesicles and large granular vesicles in variable ratio. Most cores of these large granular vesicles were heavily stained with uranyl ions. No storage or uptake of amine into the synaptic vesicles was detected. Some axons appeared to be typically cholinergic, some, typically non-adrenergic, non-cholinergic, and the rest, intermediate between the two. All axons stained heavily with reaction products for AChE activity, suggesting their cholinergic nature.

Acetylcholinesterase↗
PubMed1987

Voltage-dependent K channels in protoplasts of trap-lobe cells of Dionaea muscipula.

The outward rectification of the K+ current in mesophyll cell protoplasts from trap-lobes of Dionaea muscipula was studied with the patch-clamp technique. The rectification had instantaneous and time-dependent components. Changes in [K+]i strongly affected the conductance voltage relation of the plasma membrane while changes in [K+]o had little effect on the relation. Thus, the outward rectification depends on the membrane voltage and the concentration of intracellular K+. Corresponding single-channel activities were observed both in the intact membrane (cell-attached recording) and in excised patches. The single-channel conductance was about 3.3 pS with symmetrical solutions containing 30 mM K+.

Electric Conductivity↗
PubMed1987

Freeze fracture study of the schizonts and merozoites of Leucocytozoon caulleryi.

The fine structure of the schizonts and merozoites of Leucocytozoon caulleryi was studied by the freeze fracture technique. Young schizonts were spherical, surrounded by a thick fibrous capsule and possessed numerous nuclei. The nucleus was surrounded by the outer and inner nuclear membrane. A number of nuclear pores were evident in the nuclear membranes. Advanced schizonts were characterized by the formation of cytomeres. Each cytomere was surrounded by a membrane. Several nuclei lay along the periphery of the cytomere. The protoplasmic face (P-face) of the membrane of the cytomere contained numerous intramembranous particles (IMP). The exoerythrocytic merozoites were surrounded by a two-layered pellicle consisting of the outer and inner membrane. During freeze fracturing, each of the two membranes could split along its hydrophobic interior to yield a total of four fracture faces. The P-faces of the outer and inner membranes were closely covered with evenly distributed IMP. The external faces (E-face) of these membranes had less IMP than the P-faces. The membrane architecture of the erythrocytic merozoites was similar to that of the exoerythrocytic merozoites. The erythrocytic merozoite was enveloped by an additional membrane probably derived from the plasma membrane of host cell.

Animals↗
PubMed1987

Differential effects of isoproterenol on the canine atrial action potential in the presence of carbachol or nicorandil.

In canine atrial muscles, carbachol and nicorandil hyperpolarized the resting membrane potential and shortened the action potential duration. In the presence of carbachol or nicorandil, isoproterenol further hyperpolarized the resting membrane potential and shortened the action potential duration. Isoproterenol significantly increased the plateau duration in the presence of nicorandil, but further abbreviated it in the presence of carbachol. This increase in the plateau duration by isoproterenol in the presence of nicorandil probably reflects the increase in the slow inward current.

Action Potentials↗
PubMed1987

Changes in membrane potentials and currents of ventricular cells of the guinea pig heart by a new cardiotonic drug, MCI-154.

Effects of MCI-154, a newly synthesized cardiotonic drug with vasodilator property, on the membrane potential and currents of the isolated papillary muscles and the single ventricular cells of the guinea pig were examined. MCI-154 (10(-7)-10(-4) M) increased the developed tension in a dose-dependent manner without significant changes in the action potential configuration of the guinea pig papillary muscle. The slow response action potential obtained by increasing the extracellular K+ concentration to 24 mM was augmented by MCI-154 (10(-6) and 10(-4) M). This effect of MCI-154 was not blocked by atenolol (10(-6) M). In voltage clamp experiments on single ventricular cells, the slow inward current was not affected, but the inward rectifier K+ current was reduced by higher concentration of MCI-154 (10(-4) M). Considering the "run down" phenomenon of the slow inward current, the possibility that MCI-154 might have a slight increasing effect on the slow inward current could not be ruled out. From these results, it can be concluded that the positive inotropic action of MCI-154 can be explained partially by the decrease in the inward rectifier K+ current, and probably by the increase in the Ca2+ sensitivity of the contractile protein system.

Action Potentials↗
PubMed1987

Membrane current changes responsible for the positive inotropic effect of OPC-8212, a new positive inotropic agent, in single ventricular cells of the guinea pig heart.

Effects of OPC-8212, a new positive inotropic drug, and 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, on membrane currents were examined in single ventricular cells of the guinea pig heart. Single ventricular cells were prepared by the collagenase dispersion procedure. Both OPC-8212 (0.1 mM) and IBMX (0.1 mM) augmented the plateau and increased the duration of the action potential without affecting the resting membrane potential. Under voltage clamp condition, OPC-8212 (0.1 mM) increased the inward calcium current and decreased the delayed outward and the inward-rectifying potassium current. IBMX (0.1 mM) increased not only the inward calcium but also the delayed outward current. The isolated inward calcium current obtained by intra- and extracellular perfusion with Cs+, was increased by both drugs. When the inward calcium current was abolished by superfusion with D600 (10 microM) or Co++ (0.9 mM), OPC-8212 (0.1 mM) decreased the delayed outward and the inward-rectifying potassium current. On the other hand, IBMX (0.1 mM) increased the delayed outward current. From these results it can be concluded that OPC-8212 augments the plateau and increases duration of the action potential not only by increasing the inward calcium but also by decreasing both the delayed outward and the inward-rectifying potassium current, and the effects can be a cause of the positive inotropic effect of this drug.

1-Methyl-3-isobutylxanthine↗