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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Living cells respond to their environment by means of an interconnected network of receptors, second messengers, protein kinases and other signalling molecules. This article suggests that the performance of cell signalling pathways taken as a whole has similarities to that of the parallel distributed process networks (PDP networks) used in computer-based pattern recognition. Using the response of hepatocytes to glucagon as an example, a procedure is described by which a PDP network could simulate a cell signalling pathway. This procedure involves the following steps: (a) a bounded set of molecules is defined that carry the signals of interest; (b) each of these molecules is represented by a PDP-type of unit, with input and output functions and connection weights corresponding to specific biochemical parameters; (c) a "learning algorithm" is applied in which small random changes are made in the parameters of the cell signalling units and the new network is then tested by a selection procedure in favour of a specific input-output relationship. The analogy with PDP networks shows how living cells can recognize combinations of environmental influences, how cell responses can be stabilized and made resistant to damage, and how novel cell signalling pathways might appear during evolution.
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PMID:Intracellular signalling as a parallel distributed process. 238 5

Manual and computer analysis of esophageal peristaltic activity induced by swallows of 5ml water were compared in 6 healthy subjects under basal conditions and following i.v. injection of 4 pharmacological agents: edrophonium (E, 0.08mg/kg), atropine (A, 0.6mg), pentagastrin (PG, 0.6mcg/kg), and glucagon (GL, lmcg). Esophageal manometry was performed using a low compliance perfusion system and recorded on paper for standard manual analysis. The signal was concurrently taped on an analog recorder for subsequent digitization and analysis on a PDP-11 computer using a locally developed program. With both methods we determined the wave amplitude, duration, average upward slope (dP/dT), and velocity of wave progression. In addition, the computer allowed calculation of area under each wave and maximum upward slope (Max dP/dT). We found no significant difference between results of the parameters measured using both methods. Wave amplitude was significantly increased by E and significantly decreased by A. Average upward slope was decreased and velocity was significantly increased only by A. Computer-calculated wave area and Max dP/dT were significantly changed by both E and A. PG and GL had no effect on any of the measured parameters of the peristaltic wave. Esophageal peristalsis can be analyzed using a computer-aided method, providing a rapid and objective measurement of classical parameters and access to more in-depth analysis.
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PMID:Computer-Aided analysis of human esophageal peristalsis. I. Technical description and comparison with manual analysis. 669 33