Knowledge-based simulation of DNA metabolism: prediction of enzyme action.

We have developed a knowledge-based simulation of DNA metabolism that accurately predicts the actions of enzymes on DNA under a large number of environmental conditions. Previous simulations of enzyme systems rely predominantly on mathematical models. We use a frame-based representation to model enzymes, substrates and conditions. Interactions between these objects are expressed using production rules and an underlying truth maintenance system. The system performs rapid inference and can explain its reasoning. A graphical interface provides access to all elements of the simulation, including object representations and explanation graphs. Predicting enzyme action is the first step in the development of a large knowledge base to envision the metabolic pathways of DNA replication and repair.

Absence of a tachycardic response to shock in penetrating intraperitoneal injury.

The belief that tachycardia is an early and reliable indicator of shock has recently been challenged. We examined 144 battlefield casualties with penetrating intraperitoneal injury to determine whether patients in shock presented with pulse rates that were significantly more rapid than those in patients not in shock. No differences in mean pulse rates were found when using objective operational definitions of shock. In contrast, the only pulse rate difference was noted when shock was defined on the basis of the surgeon's subjective clinical impression and this was attributed to selection bias. The absence of a tachycardic response in battlefield casualties with penetrating abdominal wounds cannot be taken as an indication that serious injury and significant intraperitoneal bleeding have not occurred. Caution should be exercised when using this parameter as a guide for therapeutic interventions, and further study is indicated to determine whether a similar pattern is seen in civilian practice.

Interactive videodisc to teach combat trauma life support.

Training military physicians in trauma management is a dilemma in peacetime, since there are few opportunities to gain clinical experience within the military care system. This program provides experience in clinical decision making through case simulation. Five cases, of increasing difficulty, are presented in a single videodisc side. The program is implemented on a system based on the IBM PC, and is written in the C programming language. The program emphasizes clinical realism by providing many clinical options at each decision point, and by audiovisually depicting combat clinical care in very realistic ways. The user interface is flexible and, though complex, is easy to use; it is supported by a narrated, on-line tutorial.