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Biomedical subjects

A Miwa

Publications and source records attributed to A Miwa.

At least 163 records · Page 9Linked to original sources
PubMed1988

Color development upon reaction of ferric ion with the toxin JSTX, a glutamate receptor blocker present in the venom gland of the spider Nephila clavata (Joro spider).

A spider toxin, JSTX, derived from Nephila clavata, which blocks glutamate receptor was found to react with Fe3+. Mechanism of the coloration may be chelate formation since the green color completely faded upon the addition of EDTA. The colored JSTX significantly lost its neurophysiological activity. This unique coloration may be useful for not only detecting specific blockers of the glutamate receptor in spider venom but also for characterizing the glutamate receptor.

Animals↗
PubMed1988

Resistance of nerves from certain toxic crabs to paralytic shellfish poison and tetrodotoxin.

The inhibitory effect of paralytic shellfish poison and tetrodotoxin on nerves from toxic and nontoxic crabs was examined. The toxins at concentrations of 10(-3) - 10(-4) M partially or completely inhibited the action potential of nerves isolated from the legs of toxic crab species (Zosimus aeneus, Atergatis floridus and Platypodia granulosa), but had no effect at 10(-6) M, the concentration at which the action potential of nerves from a nontoxic crab (Plagusia dentipes) was inhibited completely. A xanthid crab Daira perlata was intermediate in respect to the resistance to toxins. These results agree with the previous results obtained by i.p. administration of both toxins into those crabs.

Action Potentials↗
PubMed1987

Pertussis toxin blocks presynaptic glutamate receptors--a novel 'glutamateB' receptor in the lobster neuromuscular synapse.

Topical application of L-glutamate to the neuromuscular synapse of the lobster walking leg induced K+-dependent hyperpolarization in the presynaptic membrane. This presynaptic glutamate potential (PGP) was insensitive to Joro spider toxin (JSTX), a spider toxin which specifically blocks the postsynaptic glutamate receptor, but was blocked by pertussis toxin island activating protein (IAP) in a dose-dependent manner. IAP had little effect on the resting conductance channels in pre- and postsynaptic membranes. GTP gamma S, a hydrolysis-resistant analogue of GTP, reduced the PGP supporting the involvement of G-protein in generation of K+ activation. The results suggest that a new type of glutamate receptor exists in the presynaptic membrane in the crustacean neuromuscular synapse.

Animals↗
PubMed1987

Effect of a spider toxin (JSTX) on excitatory postsynaptic current at neuromuscular synapse of spiny lobster.

1. We studied the blocking properties of a spider (Nephila clavata) toxin (JSTX) purified from venom on the spiny lobster neuromuscular junction. 2. When a small amount of JSTX was applied to the neuromuscular junction, the excitatory postsynaptic potential (EPSP) was partially suppressed. The amplitude of EPSPs remained at a steady level for several hours during the washing of the preparation, showing that the action of JSTX is irreversible. 3. We recorded the excitatory postsynaptic current (EPSC) from synaptic site using a macro-patch electrode. The amplitude of EPSC increased linearly with hyperpolarization of the membrane potential in the presence and absence of JSTX. 4. The decay phase time constant of EPSC and spontaneous EPSC was decreased by hyperpolarizing the membrane potential both in the absence and in the presence of JSTX. The relationship between the decay time constant and the membrane potential was not modified by JSTX. 5. It is suggested that JSTX irreversibly blocks EPSC by acting on the site that is apart from the ionic channel of the glutamate receptor molecule.

Animals↗
PubMed1987

Primary hemangiopericytoma of the heart associated with pseudoaneurysm of the pulmonary artery--a case report.

A thirty-three-year-old male with malignant hemangiopericytoma of the right ventricular outflow tract and the pulmonary artery associated with pseudoaneurysm formation at the latter is presented. Contrast computed tomography was helpful in diagnosing the pseudoaneurysm of the pulmonary artery. The positional change of the murmur, with a tumor plop caused by the pedunculated tumor of the right ventricular outflow tract, was detected.

Adult↗
PubMed1986

Presynaptic glutamate receptor--possible involvement of a K+ channel.

Intra-axonal recording was made from the excitatory axon of the lobster walking leg near the nerve terminal and the effects of L-glutamate were studied. Topical application of glutamate to the synapse produced hyperpolarization in the presynaptic membrane with increase in conductance. The glutamate-induced hyperpolarization was reversed to a depolarization at about -100 mV. The reversal potential was not significantly changed by altering the external Cl- but was shifted to more positive values by increasing the external K+. A spider toxin (JSTX), which specifically blocks the postsynaptic glutamate receptor, failed to block the presynaptic glutamate potential. The results suggest that the presynaptic membrane of the lobster neuromuscular synapse has a different type of glutamate receptor from those in the postsynaptic membrane.

Animals↗
PubMed1986

Down's syndrome associated with seminoma.

A case of unilateral seminoma in Down's syndrome is reported. The relation of testicular cancer with Down's syndrome and the necessity of the follow-up biopsy of the contralateral testis are discussed.

Adult↗