Biochemical stimuli, response

There are a number of assay formats available to test drugs in a functional mode. As discussed in Chapter 2, a main theme throughout the various stimulus-response cascades found in cells is the amplification of receptor stimulus occurring as a function of the distance, in biochemical steps and reactions, away from the initial receptor event. Specifically, the further down the stimulus-... 

Stimulus-response coupling, another term for receptor coupling (see Receptor Coupling). It describes the series of biochemical reactions that link the initial activation of the receptor to the observed cellular (or organ) response. 

Stimulus-response coupling, 30—31 Stimulus-response mechanism biochemical nature of, 23-25 definition of, 9... 

Medical treatments in psychiatry generally do not follow the rule of stimulus-response specificity. Although the particular mechanism of drug action may be identified, the same medication given to two depressed patients, for example, may affect them very differently. Some of these differences may be traced to variations in metabolism from individual to individual (see chapter 3). Or the underlying biochemical abnormality in one depressed patient may be different than the abnormality in another depressed patient, and thus the medications affect different underlying disorders. 

Functional assays give flexibility in terms of what biochemical functional response can be monitored for drug activity. Figure 5.2 shows some of the possibilities. In some cases, the immediate receptor stimulus can be observed, such as the activation of G-proteins by agonist-activated receptor. Specifically, this is in the observation of an increased rate of exchange of GDP to GTP on the G-protein a-subunit. 

Li C, Madsen J, Armes SP, Lewis AL (2006) A new class of biochemically degradable, stimulus-responsive triblock copolymer gelators. Angew Chem Int Ed 45 3510-3513... 

Nomura, H, Ase, K, Sekiguchi, K, Kikkawa, U, Nishizuka, Y, Nakano, Y and Satoh, T (1986) Stereospecificity of diacylglycerol for stimulus-response coupling in platelets. Biochemical Biophysical Research Communications, 140,1143-1151. 

The conjugation of proteins to stimuli responsive polymers are used in the field of protein isolation and separation [29,30]. The ability of some polymers to undergo a reversible change in response to an external physical, chemical, or biochemical stimulus gave them the name smart polymers [31]. Different stimuli have been utilized, such as temperature, light, ionic strength, or electric field for physical factors, or pH and specific ions for chemical triggers or metabolites for biochemical reactions [32, 33]. 

Majerus, P.W., Wilson, D.B., Connolly, T.M., Bross, T.E. and Neufeld, EJ. (1985) Phosphoinositide turnover provides a link in stimulus-response coupling. Trends in Biochemical Sciences, 9,453-456. 

The specific binding of taste-stimulus compounds, and correlations between the biochemical results obtained and the behavioral responses, have also been studied (see Fig. 39). Direct measurement of the binding of... 

The growth rate, however, always returns to the baseline level less than 30 min after the stimulus as shown in Fig. 7. This observation demonstrates that the model is not correct for the growth response as there must be at least two biochemical steps along the light sensory transduction chain which are subject to regulation. One sets the level of sensitivity and the other is responsible for the return of growth rate to the base-line level. Only the first step which sets the level of sensitivity obeys the simple differential equation of Delbriick and Reichardt and only then in cases where a small stimulus was employed. 

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