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Biomedical subjects

S Miyazaki

Publications and source records attributed to S Miyazaki.

At least 919 records · Page 51Linked to original sources
PubMed1977

Ca and Na spikes in egg cell membrane.

Na, Ca and K channels of the cell membrane are distinguished by different kinetics of their currents, by their different ion selectivities, and by their different sensitivities to different pharmacological agents. These channels are already found in unfertilized egg cells in many animals. Elimination of existing channels and creation of new channels occur during the process of differentiation.

Action Potentials↗
PubMed1976

Lack of cytochalasin E-induced superoxide release by polymorphonuclear leucocytes of patients with chronic granulomatous disease: a new diagnostic test.

Reduction of exogenous cytochrome c was induced by the treatment of human polymorphonuclear leucocytes with cytochalasin E. The reduction was completely inhibited by superoxide, dismutase, indicating that superoxide anions were released from the cells. The leucocytes from two patients with chronic granulomatous disease did not show the release reaction that should have been brought on by the treatment. The cytochalasin-induced reduction of exogenous cytochrome c by polymorphonuclear leucocytes is so specific and sensitive that it seems to be useful for diagnosis of chronic granulomatous disease.

Adult↗
PubMed1976

Interaction of dopamine, methyldopa and reserpine in the sympatho-adrenal system in essential hypertension.

1. The interactions of dopamine, reserpine and methyldopa on blood pressure of normal subjects and of those with essential hypertension were examined. 2. When biosynthesis of noradrenaline from dopamine was blocked by reserpine, dopamine induced a prominent depressor effect in essential hypertension. 3. The long-term treatment with methyldopa induced a marked potentiateion of the pressor action of domapine in hypertension, although no significant pressor response was found in normal subjects. 4. It is suggested that methylnoradrenaline may accumulate in peripheral nerve endings of patients with essential hypertension in comparison with normal subjects, and this accumulated methylnoradrenaline potentiates the pressor response to dopamine in essential hypertension.

Adult↗
PubMed1976

Potassium current and the effect of cesium on this current during anomalous rectification of the egg cell membrane of a starfish.

The kinetics of the membrane current during the anomalous or inward-going rectification of the K current in the egg cell membrane of the starfish Mediaster aequalis were analyzed by voltage clamp. The rectification has instantaneous and time-dependent components. The time-dependent increase in the K conductance for the negative voltage pulse as well as the decrease in the conductance for the positive pulse follows first-order kinetics. The steady-state conductance increases as the membrane potential becomes more negative and reaches the saturation value at about -40 mV more negative than the K equilibrium potential, V(K). The entire K conductance can be expressed by g(K).n; g g(K) represents the component for the time-independent conductance which depends on V-V(K) and [K+]o, and n is a dimensionless number (1 is greater than or equal to n is greater than or equal to 0) and determined by two rate constants which depend only on V-V(K). Cs+ does not carry any significant current through the K channel but blocks the channel at low concentration in the external medium. The blocking effect increases as the membrane potential is made more negative and the potential-dependent blocking by the external Cs+ also has instantaneous and time-dependent components.

Animals↗
PubMed1976

Modification and regeneration of synaptic connections in cultured leech ganglia.

Segmental ganglia of the central nervous system of the leech were maintained in culture medium outside the animal for several weeks in order to study the properties of synapses and regeneration by identified sensory and motor nerve cells. A variety of preparations were used, including single ganglia, chains of ganglia and ganglia connected to the areas of skin and muscle that they normally innervate in the animal. (1) For up to 10 weeks after removal from the animal, resting and action potentials recorded from sensory and motor neurons resembled those seen in normal ganglia. The same individual cell in a cultured ganglion could be recorded from with intracellular electrodes on a second occasion after an interval of a few days. (2) Sensory cells, identified as touch, pressure or nociceptive according to their morphology and electrical properties, continued to respond selectively to stimuli of the appropriate modality applied to their receptive fields in the skin; action potentials in motor cells caused contractions in the appropriate muscles. Culture of ganglia for more than 3 weeks caused the disappearance of synaptic potentials and a loss of transparency in ganglia. (3) Certain chemically mediated synaptic interactions between sensory and motor nerve cells became markedly changed in cultured ganglia. These changes appeared over the first 3 weeks and consisted of abnormally large excitatory and inhibitory synaptic potentials. The changes in synaptic transmission observed in culture were in many respects similar to those occurring in ganglia maintained within an animal after lesions have been made in the nervous system (Jansen et al. 1974). (4) The morphological appearances of sensory cells were compared in cultured and normal ganglia after injection of horseradish peroxidase. In cultured ganglia, the branching pattern appeared normal, but varicosities became more conspicuous. (5) When connectives linking cultured ganglia were crushed or cut, regeneration occurred. By 7 days, impulses propagated through the regenerated fibers and evoked synaptic potentials on cells within the next ganglion. The course taken by regenerating axons was observed in cells injected with horseradish peroxidase. The results again resembled those seen in animals with similar lesions. (6) The cultured ganglia provide preparations in which it is possible to analyze the mechanisms that underlie long-term changes similar to those seen in the leech central nervous system in situ.

Animals↗
PubMed1976

Experimental models for prevention of graft-versus-host reaction in bone marrow transfusion. I. Selective suppression and augmentation of splenomegaly and cytotoxicity.

Induction and suppression of splenomegaly and cytotoxicity against C57BL/L cells were studied in (AKR X C57BL/6) F1 hybrid adult mice after the transfer of AKR lymphoid and bone marrow cells. 1) Splenomegaly and cytotoxicity were dissociated in the developmental stages of the graft-versus-host reaction. When lymphoid and bone marrow cells of normal AKR mice were injected into F1 recipients, splenomegaly was prominent on days 5 and 7, but cytotoxicity of spleen cells was not detected. Splenomegaly became less prominent but the cytotoxicity became detectable on day 14 after the injection. 2) Cytotoxic activity of spleen cells of F1 recipients was suppressed by the treatment of AKR donors with C57BL/6 lymphoid cells in Freund's complete adjuvant. Splenomegaly, however, was substantially enhanced by such a treatment of the donors. On the other hand, induction of the cytotoxic activity was facilitated by the treatment of donors with C57BL/6 skin grafts. 3) F1 hybrid mice could be protected from the graft-versus-host reaction by the injection of AKR anti-C57BL/6 serum or pretreatment of AKR donors with sonicated cellular antigens of C57BL/6.

Animals↗
PubMed1976

Action potentials in the rat chromaffin cell and effects of acetylcholine.

1. Electrophysiological properties of the rat chromaffin cell were studied using intracellular recording techniques. 2. The resting potential in the chromaffin cell was -49 +/- 6 mV (mean +/- S.D., n = 14) in standard saline containing 10 mM-Ca whereas that in Na-free saline was -63 +/- 9 mV (n = 17). At rest, the membrane has a substantial Na permeability. 3. Action potentials were evoked by passing current through the recording electrode. In standard saline the major fraction of the action potential disappeared either upon omission of external Na ions from standard saline or addition of 1 muM tetrodotoxin (TTX). We conclude that action potentials in the chromaffin cell are due mainly to an increase in the permeability of the membrane to Na ions. 4. Small but significant regenerative action potentials were observed in Na-free saline, and when Ca in Na-free saline was replaced by Ba, prolonged action potentials occurred. We conclude that action potentials in the chromaffin cell also have a Ca component. 5. Iontophoretic application of acetylcholine (ACh) produced a transient membrane depolarization in standard saline. 6. Spontaneous action potentials were recorded extracellularly by microsuction electrodes. They occurred at a rate of 0-05-0-1/sec in almost all cells. 7. When the perfusion fluid contained 3 x 10(-7) M to 10(-4) M ACh the spike frequency increased up to about 2/sec. This stimulatory effect of ACh was blocked by 10(-7) M atropine but not by 10(-3) M hexamethonium nor by 10(-5) M-d-tubocurarine. 8. The importance of Ca entry during action potentials for catecholamine secretion is discussed

Acetylcholine↗
PubMed1976

Comparison of progenitor toxins of nonproteolytic with those of proteolytic Clostridium botulinum Type B.

A nonproteolytic strain of Clostridium botulinum type B produces two toxins of different molecular weight (16S and 12S) that are indistinguishable from the corresponding toxins of a proteolytic strain in molecular weight and construction but differ in potential toxicity, activation ratio, and hemagglutinability. Successful hybridization between the toxic and nontoxic components (both7S) of 12S toxins of biologically heterologous type B strains confirmed the physico-chemical similarity between the toxic as well as the nontoxic components.

Botulinum Toxins↗