Squirrel monkeys (N = 4) were trained with food reinforcement to press one of two levers after administration of IV cocaine (0.3 or 1.0 mg/kg) or the other lever after saline. After training, IV ...cocaine (0.03-3.0 mg/kg) produced dose-related increases in the percentage of responses on the cocaine lever (ED50 = 0.15 mg/kg). Cocaine delivered IM also produced dose-related increases in cocaine-appropriate responding (ED50 = 0.32 mg/kg), but was approximately half as potent as IV cocaine. Similar relative potency relations were obtained for decreases in response rates produced by cocaine. Prior to some sessions subjects were placed in a Plexiglas chamber and exposed for 60 s to cocaine vapor created with an ultrasonic nebulizer. Exposure to vapor from cocaine solutions (1.0-30.0 mg/ml) produced concentration-dependent increases in cocaine-appropriate responding and decreases in response rates. Exposure to vapor from a 30 mg/ml concentration produced virtually exclusive cocaine-appropriate responding. Concentration-effect curves for inhaled cocaine were similar to dose-effect curves obtained when cocaine was administered by the other routes. The time course of the minimally effective concentration of inhaled cocaine was compared to that of the minimally effective doses of systemically administered cocaine. Inhaled cocaine had a duration of action longer than IV cocaine. The results indicate that inhaled cocaine vapor has effects qualitatively similar to those of IV cocaine, and may have a duration of action longer than that of an IV cocaine dose producing a similar degree of drug-appropriate responding.
Porphobilinogen synthase (PBGS) catalyzes the condensation of two identical substrate molecules, 5‐aminolevulinic acid (ALA), in an asymmetric manner to form porphobilinogen. E. coli PBGS is an ...homooctameric enzyme. The number of active sites is not clear, but each subunit binds one ZnII ion and one MgII ion. Diffraction‐quality crystals of native E. coli PBGS have been obtained, and unit‐cell dimensions (a 130.8, c 144.0 Å) are reported. These crystals diffract to about 3.0 Å resolution.
In the development of complex military electronic equipment, It is necessary to consider the effects of many interacting operational and design factors. For both the over-all weapon system, and for ...the electronic subsystems with which we are concerned, optimum trade-offs for such interdependent parameters as reliability, weight, accuracy, maintainability, cost, mission time, and target vulnerability must be determined. Considered individually, these parameters do not adequately describe the operational worth of equipment incorporating multiple redundancies and operating modes. Operational worth is the probability that a system will achieve success in performing its required functions, and is obviously a prime consideration in the planning and selection of systems for military applilcation. The inadequacy in describing operational worth in terms of its individual parameters was encountered in the synthesis of an optimum redundant configuration for the B-58 bombing-navigation system. To resolve this difficulty, operational worth models describing the interaction between parameters were developed and utilized by Sperry Gyroscope Company. These techniques enabled Sperry to design this bombing-navigation system to have a high operational worth and an inherent mission reliability in excess of 95 per cent. In this paper, the model for ``system worth,'' the interaction between reliability and information quality, is discussed.
