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Biomedical subjects

A W Cuthbert

Publications and source records attributed to A W Cuthbert.

At least 145 records · Page 8Linked to original sources
PubMed1973

Adrenoceptors and adenyl cyclase in gills.

The content of cyclic 3',5'-adenosine monophosphate (cAMP) in the gills of the mullet (Mugil capito) has been measured. The basal level was found to be 2.9+/-0.3 pmol/mg wet weight. When fish were first anaesthetized with MS222 (tricaine) and the gills perfused to remove blood, the concentration of cAMP was raised to 14.3+/-1.9 pmol/mg wet weight.Adrenaline caused a significant increase in cAMP content, an effect that was blocked by propranalol, a beta-adrenoceptor antagonist. In the presence of the alpha-adrenoceptor block- ing agent phentolamine, adrenaline still caused an increase in nucleotide content.The results are discussed in relation to adrenaline and the adenyl cyclase system.

Adenylyl Cyclases↗
PubMed1973

The number of muscarinic receptors in chick amnion muscle.

1. [(3)H]-Propyl benzilylcholine mustard ([(3)H]-PrBCM) an irreversible specific antagonist of muscarinic acetylcholine receptors, has been used to label the muscarinic receptors in the aneuronal muscle of isolated 11 day amniotic membranes of chick embryos.2. This muscle was found to have about 9 fmol/mg dry weight of receptor material. This is only 1-2% of the amount found in intestinal muscle.3. Pharmacological studies with isolated amniotic membranes using PrBCM show that labelling is to functional receptors and that the receptor reserve is small.4. The significance of the difference in receptor reserve in innervated and aneuronal plain muscle is discussed.

Acetylcholine↗
PubMed1973

An upper limit to the number of sodium channels in frog skin epithelium.

1. Binding of [(14)C]amiloride to the mucosal surface of frog skin epithelium has been measured in the presence and absence of an excess of unlabelled amiloride. Simultaneous records were obtained of the sodium transport through the skin as indicated by the short circuit current.2. The number of binding sites with affinities for amiloride of 5 x 10(7) l./mole was around 400/mum(2).3. The relation between the binding sites and sodium channels is discussed.4. Making certain assumptions it is concluded that when frog skin epithelium is bathed in Ringer solution each sodium channel can handle 8000 sodium ions/sec.

Abdomen↗
PubMed1972

The effects of calcium and magnesium on sodium fluxes through gills of Carassius auratus, L.

1. Removal of calcium from Carassius either with chelating agents or by adaptation to deionized water increased sodium influx through the gills twofold.2. Treatment of fish with chelating agents increased sodium outflux, whereas adaptation to deionized water reduced sodium outflux. The effects on outflux do not appear to result from calcium removal.3. Addition of calcium (2-20 mM) reversed the effects on influx of chelating agents and of adaptation to deionized water.4. Magnesium (2-10 mM) was without significant effect on sodium influx, but increased the outflow in fish adapted to deionized water.

Adaptation, Physiological↗
PubMed1972

The effects of calcium on branchial sodium fluxes in the sea-water adapted eel, Anguilla anguilla, L.

1. The sodium influx through the gills of eels placed in calcium-free sea water for 15 hr was double that of controls. The effect was reversed in 1 hr by addition of calcium.2. The total sodium outflux through the gills of fish placed in calcium-free sea water for 15 hr was double that of controls. The effect was only partially reversed in 15 hr by addition of calcium.3. The passive outflux component of the total outflux was increased fourfold when calcium was removed and was restored to normal in 15 hr by addition of calcium. The active (exchange) outflux component of the total outflux was halved by calcium removal and increased above normal following calcium addition.4. The inability of calcium to restore the total outflux to normal within 15 hr in calcium-depleted fish, together with the raised plasma sodium concentration at this time, suggests that the raised outflux is caused by homoeostatic mechanisms, rather than permeability changes in the gill epithelium.

Adaptation, Physiological↗