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Biomedical subjects

S C King

Publications and source records attributed to S C King.

48 records · Page 3Linked to original sources
PubMed1983

Pharmacological characterization of the acetylcholine transport system in purified Torpedo electric organ synaptic vesicles.

A wide variety of pharmacologically active compounds was surveyed for effects on active transport of [3H]acetylcholine by synaptic vesicles isolated from the electric organ of Torpedo californica. In over 80 compounds tested, inhibitors of a wide range of potencies were found. The most potent inhibitor was 2-(4-phenylpiperidino)cyclohexanol (AH5183), which half-inhibited transport at 40 nM. This compound had been predicted by Marshall [Br. J. Pharmacol. 38:503-516 (1970)] to block acetylcholine storage by vesicles in vivo. The synaptic vesicle active transport system is shown to be pharmacologically distinct from other cholinergic systems. The site of action of AH5183 and other potent inhibitors is not certain, but the possibility of trivial action on the vesicle ATPase or a vesicle proton gradient was eliminated. The results constitute new evidence supporting vesicle exocytosis as the source of evoked acetylcholine release by nerve terminals. AH5183 appears to be the prototype for a new family of anticholinergics. The possibility that some drugs that exhibit secondary anticholinergic effects act in part by antagonizing acetylcholine storage is discussed.

Acetylcholine↗
PubMed1983

Inhibition of [3H]acetylcholine active transport by tetraphenylborate and other anions.

The effects of tetraphenylborate and other anions on the active uptake of [3H]acetylcholine by synaptic vesicles isolated from Torpedo californica electric organ were studied. Tetraphenylborate completely inhibits active uptake with a half-inhibitory concentration of 0.3 microM. Dipicrylaminate also half-inhibits at 0.3 microM, phenyldicarbaundecaborane at 14 microM, fluoride at 2 mM, thiocyanate at 3 mM, and azide at 16 mM. Tetraphenylborate had no effect on the vesicle ATPase activity or the transmembrane electric potential at low concentrations where it inhibits [3H]acetylcholine active transport. The mechanism for tetraphenylborate inhibition is uncertain, but it might be similar to that of its action as a mitochondrial uncoupler. Solubility products for the acetylcholine, choline, and potassium salts of the tetraphenylborate and dipicrylaminate anions also were measured. The inhibition results confirm the hypothesis of Marshall and Parsons [Br. J. Pharmacol. 54:333-338 (1975)] that tetraphenylborate acts on intact neuromuscular preparations to inhibit transmitter storage, and constitute new pharmacological evidence that evoked release of acetylcholine is mediated by synaptic vesicles.

Acetylcholine↗
PubMed1982

Proton gradient linkage to active uptake of [3H]acetylcholine by Torpedo electric organ synaptic vesicles.

It has been confirmed that cholinergic synaptic vesicles isolated from the electric organ of Torpedo californica exhibit adenosine 5'-triphosphate (ATP) dependent active uptake of [3H]acetylcholine. Active uptake can be completely inhibited by low concentrations of the mitochondrial uncouplers carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone, nigericin, gramicidin, valinomycin, and A 23187. Under similar conditions uncouplers stimulate the vesicle adenosinetriphosphatase (ATPase) by from 40 to 80%. ATP-supported uptake of [3H]acetylcholine increases greatly as the external pH is increased from 6.6 to 7.6 and remains approximately constant from pH 7.8 to pH 8.6. The uptake also becomes more selective for [3H]acetylcholine compared to [14C]choline as the pH is increased from 6.6 to 7.6, achieving 12-fold selectively, in a manner similar to the increase in the amount of [3H]acetylcholine taken up. Bicarbonate stimulates both the amount and selectivity of [3H]acetylcholine uptake over the lower pH range, but it has no effect over the higher pH range. Exogenous ammonium ion completely inhibits active [3H]acetylcholine uptake, with lower concentrations of ammonium ion required at higher pH values in a manner consistent with ammonia being the active species. Adenosine 5'-diphosphate and a nonhydrolyzable ATP analogue do not support active [3H]acetylcholine uptake. It is concluded that an ATPase pumps protons into the cholinergic synaptic vesicle to produce an internally acidic and positively charged proton gradient that is linked to [3H]acetylcholine uptake.

Acetylcholine↗
PubMed1980

An instrument for checking the radioactivity in shielded syringes.

A description is given of an instrument that can be used for checking, to within ten percent, the radioactivity in shielded syringes. The unit is simple in design and construction and easy to use. The lead shield of the syringe does not have to be removed, since only radiation emitted along the direction of the barrel is detected. A range of syringe sizes can be accommodated and, whilst the instrument is calibrated for 99Tcm with activities in the range 1-10 mCi, both higher and lower activities and other radionuclides can be used. Each measurement takes only a few seconds and the activity of radiopharmaceuticals can be routinely checked immediately before injection.

Radiometry↗
PubMed1978

Respiratory function of blood of the avians.

Individual blood samples were collected from wing veins of eight adult pigeons, two adult chickens and four adult geese and were analyzed for oxygen dissociation curves by hemo-scan, an instrument measuring PO2 and O2 saturation simultaneously. The findings agree with the common belief that avian blood in general has a low affinity for oxygen. Blood pH, PCO2, concentration of 2,3-DPG, lactic acid, pyruvic acid, red blood cell, hemoglobin and hematocrit were also determined, the related parameters have been calculated. Normal values of those variables were reported and the possible effects of some of those parameters on oxygen affinity are postulated.

Animals↗
PubMedDate not supplied

Autoradiographic localization of binding sites for galanin and VIP in small intestine.

The distribution of the binding sites for [125I]galanin and [125I]iodotyrosyl VIP in sections of small intestine from rat, rabbit, guinea pig and man was investigated using in vitro receptor autoradiography. The specific binding sites for [125I]galanin were most concentrated in the myenteric plexus and longitudinal muscle layers. The distribution of [125I]VIP binding was similar, with the highest level of binding in the myenteric plexus. Some VIP binding was also seen in the mucosa. The abundance of binding sites for both peptides in the myenteric plexus suggests that this is the anatomical site of the functional antagonism between these endogenous peptides in the mammalian intestine.

Animals↗