In plasma membranes of intact cells an enzymatic pump actively transports sodium ions inward and potassium ions outward. In preparations of broken membranes it appears as an adenosine triphosphatase dependent on magnesium, sodium, and potassium ions together. In this adenosine triphosphatase a phosphorylated intermediate is formed from adenosine triphosphate in the presence of sodium ions and is hydrolyzed with the addition of potassium ions. The normal intermediate was not split by adenosine diphosphate. However, selective poisoning by N-ethylmaleimide or partial inhibition by a low magnesium ion concentration yielded an intermediate split by adenosine diphosphate and insensitive to potassium ions. Pulse experiments on the native enzyme supported further a hypothesis of a sequence of phosphorylated forms, the first being made reversibly from adenosine triphosphate in the presence of sodium ion and the second being made irreversiblyfrom the first and hydrolyzed in the presence of potassium ion. The cardioactive steriod inhibitor, ouabain, appeared to combine preferentially with the second form. Phosphorylation was at the same active site according to electrophoretic patterns of proteolytic phosphorylated fragments of both reactive forms, It is concluded that there is a conformational change in the active center for phosphorylation during the normal reaction sequence. This change may be linked to one required theoretically for active translocation of ions across the cell membrane.The basic idea in this paper is a change in the shape of the sodium and potassium pump during its reaction cycle. This change is not necessarily that assumed for translocation (1), but rather a change in the conformation of an active center. The evidence is indirect. It is assumed that the reactivity of a phosphoryl group attached covalently to an active site in an active center depends on the conformation of the active center surrounding the site. Thus a change in reactivity implies a change in conformation. It should be enough to show that this group at a single active site changes its reactivity in the course of the normal reaction sequence. The phosphoryl group is attached to sodiumpotassium-dependent adenosine triphosphatase, an aspect of the pump.
(ACEP) organized a multidisciplinary effort to create a clinical practice guideline specific to unscheduled, time-sensitive procedural sedation, which differs in important ways from scheduled, elective procedural sedation. The purpose of this guideline is to serve as a resource for practitioners who perform unscheduled procedural sedation regardless of location or patient age. This document outlines the underlying background and rationale, and issues relating to staffing, practice, and quality improvement. [
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