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1. The substrate kinetic properties of cerebral hexokinases (mitochondrial and cytoplasmic) were studied at limiting concentrations of both glucose and MgATP(2-). Primary plots of the enzymic activity gave no evidence of a Ping Pong mechanism in three types of mitochondrial preparation tested (intact and osmotically disrupted mitochondria, and the purified mitochondrial enzyme), nor in the purified cytoplasmic preparation. 2. Secondary plots of intercepts from the primary plots (1/v versus 1/s) versus reciprocal of second substrate of the mitochondrial activity gave kinetic constants which differed from those obtained directly from the plots of 1/v versus 1/s or of s/v versus s, although the ratios of the derived constants were consistent. The kinetic constants obtained with the cytoplasmic enzyme from primary and secondary plots were consistent. 3. Deoxyglucose, as alternative substrate, inhibited cytoplasmic hexokinase by competition with glucose, but did not compete when MgATP(2-) was the substrate varied. The K(i) for deoxyglucose when glucose concentrations were varied was 0.25mm. 4. A range of ATP analogues was tested as potential substrates and inhibitors of hexokinase activity. GTP, ITP, CTP, UTP and betagamma-methylene-ATP did not act as substrates, nor did they cause significant inhibition. Deoxy-ATP proved to be almost as effective a substrate as ATP. AMP inhibited but did not act as substrate. 5. N-Acetyl-glucosamine inhibited all preparations competitively when glucose was varied and non-competitively when MgATP(2-) was varied. AMP inhibition was competitive when MgATP(2-) was the substrate varied and non-competitive when glucose was varied. 6. The results are interpreted as providing evidence for a random reaction mechanism in all preparations of brain hexokinase, cytoplasmic and mitochondrial. The kinetic properties and reaction mechanism do not change on extraction and purification of the particulate enzyme. 7. The results are discussed in terms of the participation of hexokinase in regulation of cerebral glycolysis.

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While the data do not allow for the testing of causal relationships, the data do suggest that providing adequate staffing, perceived fair pay, sufficient work resources (e.g., towels, gowns), management support and adequate training may result in less direct-care worker burnout on the job.

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Hands-on exercises promote active learning where student experience reinforces material presented in lectures or reading assignments [1]. Drawing the student into a meaningful context where student decisions have clear consequences strengthens the learning experience and thus improves the potential for internalization of knowledge. The CyberCIEGE video game was designed to confront students with computer security decision points within an environment that encourages experimentation, failure and reflection. The game includes over twenty scenarios that address a range of computer and network security concepts.

This paper describes a computer simulation game being developed to teach computer security principles. The player of the game constructs computer networks and makes choices affecting the ability of these networks and the game’s virtual users to protect valuable assets from attack by both vandals and well-motivated professionals. The game introduces the player to the need for well formed information security policies, allowing the player to deploy a variety of means to enforce security policies, including authentication, audit and access controls. The game will depict a number of vulnerabilities ranging from trivial passwords to trap doors planted by highly skilled, well-funded adversaries.