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Biomedical subjects

M D Rayner

Publications and source records attributed to M D Rayner.

33 records · Page 2Linked to original sources
PubMed1981

Gating currents in th intact crayfish giant axon.

Both single-sweep and signal-averaged asymmetry current are measured from intact crayfish axons after ionic currents are blocked with tetrodotoxin and 4-aminopyridine. The ON asymmetry charge saturates at about 0 mV and no ON charge movement is detectable at voltages negative to -140 mV. The areas of ON and OFF asymmetry charge are equal for short depolarizations but the ratio QOFF/QON decreases for longer depolarizing pulses. Sodium and asymmetry current magnitudes can be changed in parallel by lowering the hold potential or by imposing conditioning prepulses. Our results are consistent with the concept that asymmetry current in generated by movement of trapped charge in association with Na channel gating.

Animals↗
PubMed1976

The gating currents of sodium channels: pore-population-size effects.

Sodium-channel behavior has been modeled in order to determine the answer to the following question: How large must a population of "on-off" sodium pores be before the inherently random behavior of the individual channels becomes smoothed to yield the expected gating current-conductance relationships which would be predicted from an infinite pore array? Results of this analysis show that for the "opening" situation, an excellent fit was obtained whenever more than about 10 pores were considered. Significant discrepancies were observed in the "closing" situation, however, for pore arrays of 50 or less. Marked hysteresis is apparent in the behavior of small port populations.

Membranes↗
PubMed1976

Mitotic changes in neuroblastoma transplanted into denervated host tissue.

Tumors were transplanted to denervated and innervated hind limbs of A/J mice and grown for 5 days in all groups. The host tissues were denervated by femoral and sciatic nerve section 4 days prior to tumor implantation. Dnervation of host tissues resulted in a significant reduction in tumor mitotic rate as assessed by mitotic counts in the histological sections. Neurotrophic factors may thus be an additional feature of the host-tumor environment.

Animals↗
PubMed1975

Palytoxin: effects on contractility and 45Ca2+ uptake in isolated ventricle strips.

Palytoxin (PTX) inhibited phasic tension production and initiated tonic contracture in isolated paced ventricle strips at concentrations greater than 10(-10) M. PTX-induced contracture was associated with increased 45Ca2+ uptake. PTX-induced additional 45Ca2+ uptake was completely blocked by 2 mM La3+. All observed PTX effects were enhanced by elevation of [Ca2+] o from 1.9 to 6 mM and this threefold increase in [Ca2+] o resulted in a threefold increase in isotope-determined Ca2+ uptake in presence of 10(-8) M PTX. It is concluded that the observed effects of PTX could be mediated by an increase in calcium permeability of myocardial cells.

Acrylamides↗
PubMed1968

Ciguatoxin: more than an anticholinesterase.

Anticholinesterase action of ciguatoxin has been reported. A study of the pharmacology of the action of the toxin on the respiratory system suggests that additional properties may be involved in the respiratory failure-the usual cause of death in ciguatera poisoning.

Acetylcholine↗