Sodium

About: Sodium is a research topic. Over the lifetime, 68944 publications have been published within this topic receiving 1208422 citations. The topic is also known as: element 11 & natrium.

Radiochemical micro assays for the determination of choline acetyltransferase and acetylcholinesterase activities.

Abstract: 1. The methods for the assay of choline acetyltransferase were based on the reaction between labelled acetyl-CoA and unlabelled choline to give labelled acetylcholine. 2. Both synthetic acetyl-CoA and acetyl-CoA formed from sodium [1-(14)C]acetate or sodium [(3)H]acetate by incubation with CoA, ATP, Mg(2+) and extract from acetone-dried pigeon liver were used. 3. [1-(14)C]Acetylcholine was isolated by extraction with ketonic sodium tetraphenylboron. 4. [(3)H]Acetylcholine was precipitated with sodium tetraphenylboron to remove a ketone-soluble contaminant in sodium [(3)H]acetate and then extracted with ketonic sodium tetraphenylboron. 5. The values of choline acetyltransferase activity obtained in the presence of sodium cyanide or EDTA and synthetic acetyl-CoA were similar to those obtained with acetyl-CoA synthesized in situ. 6. The assay of acetylcholinesterase was based on the formation of labelled acetate from labelled acetylcholine. The labelled acetylcholine could be quantitatively removed from the acetate by extraction with ketonic sodium tetraphenylboron. 7. The methods were tested with samples from central and peripheral nervous tissues and purified enzymes. 8. The blank values for choline acetyltransferase and acetylcholinesterase corresponded to the activities in 20ng. and 5ng. of brain tissue respectively.

Electrical conductivity in ionic complexes of poly(ethylene oxide)

Abstract: The temperature dependence of d.c. conductivity of poly(ethylene oxide) complexes with sodium iodide and the thiocyanates of sodium, potassium and ammonium has been investigated. In each case a transition to a lower activation energy at higher temperatures was observed. For the sodium complexes this transition occurs at ca 55°C which is well below the crystalline melting points at 200°C. For the potassium and ammonium complexes however, the transitions coincide with the melting points at ca 100 and 70°C respectively. It is proposed that at the transitions, thermal disintegration of complexes in the amorphous regions occurs. The complexes involve coordination of the cations to the ether oxygen atoms in the polymer backbone.

Tetrodotoxin Blockage of Sodium Conductance Increase in Lobster Giant Axons

Abstract: Previous studies suggested that tetrodotoxin, a poison from the puffer fish, blocks conduction of nerve and muscle through its rather selective inhibition of the sodium-carrying mechanism. In order to verify this hypothesis, observations have been made of sodium and potassium currents in the lobster giant axons treated with tetrodotoxin by means of the sucrose-gap voltage-clamp technique. Tetrodotoxin at concentrations of 1 x 10-7 to 5 x 10-9 gm/ml blocked the action potential but had no effect on the resting potential. Partial or complete recovery might have occurred on washing with normal medium. The increase in sodium conductance normally occurring upon depolarization was very effectively suppressed when the action potential was blocked after tetrodotoxin, while the delayed increase in potassium conductance underwent no change. It is concluded that tetrodotoxin, at very low concentrations, blocks the action potential production through its selective inhibition of the sodium-carrying mechanism while keeping the potassium-carrying mechanism intact.

Croonian Lecture: The Antidiuretic Hormone and the Factors which Determine Its Release

Abstract: When water is given under specified conditions to the living dog, there is a lag of 15 min. between the peak of the animal's water load and the maximum rate of water excretion by the kidney. The diuresis is inhibited by emotional stress, the inhibition being of post-pituitary origin and itself suppressed by an immediately preceding injection of adrenaline or tyramine. Reasons are given for the view that this action of adrenaline is independent of any accompanying increase in arterial pressure or cerebral blood flow. The intracarotid injection (short period, 5 to 20 sec.) of 'hypertonic' solutions of sodium chloride (but not of urea) causes a similar inhibition, the response being diminished by some 90% after removal of the posterior lobe. The response to sodium chloride is shown to be osmotically determined, and the term 'osmoreceptors' has therefore been introduced as descriptive of the autonomic receptive elements with which the neurohypophysis is functionally linked. The receptors are somewhere in the vascular bed of the internal carotid artery. The results of long-period (10 and 40 min.) intracarotid infusions and of the short-period injections, show that the osmoreceptors are freely permeable to urea, less freely permeable to dextrose and relatively impermeable to sodium chloride and sucrose. The local increase in osmotic pressure required in the 40 min. infusions (unilateral) to reduce the urine flow during water diuresis to about 10% of its maximum, is some 2% only; and assay of such response shows it to have a post-pituitary extract equivalence of $1\mu \text{U/sec.}$ $(0.5\times 10^{-9}$ $\text{g./sec.}$ in terms of the standard powder). These facts give an intelligible interpretation to the time-lag between the peak of the water load and the peak of diuresis. Water diuresis, therefore, is fitly and accurately described as a condition of physiological diabetes insipidus, the antidiuretic secretion of the neurohypophysis being a hormone in the sense that its liberation is continually governed by the concentration of sodium chloride, and of other osmotically active substances, in the arterial plasma.