Search PubMed⌕ Search

Biomedical subjects

K Martin

Publications and source records attributed to K Martin.

At least 289 records · Page 16Linked to original sources
PubMed1970

The production of adenosine triphosphate in perfused giant axons of Loligo.

1. The light production by squid giant axons perfused with solutions containing extract of firefly tails has been studied to give information about the production of ATP in such axons.2. An initial flash occurs when the perfusion fluid first enters the fibre. There is a secondary production of light, noticeable when the perfusion is halted, providing glutamate or aspartate are present in the perfusion medium.3. There is no secondary light production if glutamate is replaced by sulphate, succinate or alpha-ketoglutarate in the perfusion fluid.4. Ouabain has no effect whereas cyanide and oligomycin both block the secondary light production, the latter irreversibly.5. When the sodium outside the fibre is replaced by lithium or choline the secondary light production is often reduced and occasionally abolished.6. A raised internal sodium does not enhance secondary light production.7. The secondary light production is dependent upon the concentration of AMP in the perfusion solution.8. Fresh axoplasm generates a powerful light on immersion in perfusion fluid whereas dialysed axoplasm, even in the presence of added glutamate, generates no light whatever.9. The evidence, on balance, suggests that, under the conditions of the experiments described, there is no detectable reversal of active transport in perfused nerve fibres but that there is an enzyme system, probably membrane bound, capable of generating ATP from glutamate or aspartate and AMP by oxidative phosphorylation. The enzyme system can be inhibited by the replacement of external sodium.

Adenosine Triphosphate↗
PubMed1969

Effects of quaternary ammonium compounds on choline transport in red cells.

1. Neuromuscular blocking agents have been shown to be powerful inhibitors of choline transport in human erythrocytes. Ganglionic blocking agents were weaker inhibitors.2. The affinity of the choline transport site for alkyltrimethylammonium compounds was considerably higher than its affinity for alkyl-bis-(trimethylammonium) compounds of similar chain length. The affinity increases with increasing length of the alkyl chain in both series.3. Tetramethylammonium (TMA), ethyl- and propyltrimethylammonium appear to enter the cells on the choline carrier while the larger monoquaternary compounds, and the bisquaternary compounds, bind to the carrier but are unable to cross the cell membrane.4. Radioactively labelled carbachol, acetylcholine and decamethonium do not enter the cells on the choline carrier.5. Choline transport in erythrocytes from patients with myasthenia gravis is normal, suggesting that this disorder is not associated with a generalized defect of choline transport.

Acetylcholine↗