Daniel S. Mitchell

Effects of Combustion Gases on Escape Performance of the Baboon and the Rat

In postcrash aircraft fires, only a few minutes are often available for egress. To assess the potential of selected combustion gases (CO, acrolein and HCl) to impair human escape, a signalled avoidance task was developed for use with the juvenile African Savannah baboon. After a 5-minute exposure, the animal was required to select and depress the correct lever to open an escape door and then to exit into the adjacent compartment of a shuttlebox. With CO, the EC50 for escape failure was 6850 ppm. Acrolein (12 to 2780 ppm) neither prevented escape nor affected escape times, despite irritant effects at all concentrations. Similar results were obtained with HCI (190 to 17,200 ppm) in that, despite severe irritant effects, all animals successfully performed the escape task. With a comparable shuttlebox and escape paradigm for rats, the EC50 of CO was 6780 ppm. Five-minute exposures to HCI (11,800 to 76,730 ppm) did not prevent escape but severe post-exposure respiratory effects and lethality occurred at 15,000 ppm and higher. In both species, escape time was not affected by HCI but a concentration-related increase in intertrial responses was evident. The data suggest that laboratory test methods for measurement of incapacitation of rodents may be useful in evaluating potential effects of atmospheres containing CO or irritant gases on human escape capability.

Flavor preferences, food intake, and weight gain in baboons (Papio sp.).

To evaluate the influence of flavor on ad lib consumption and on associated changes in body weight, female baboons, 7-15 years of age, served in two experiments with seven monkey chows which were identical except for flavor: lemon, orange, apple, sugar, fruit punch, chocolate, and unflavored. In the first experiment, two groups of animals (n=7 and 4) received five of the seven flavors, presented in daily pair-wise combinations. Analysis of quantities consumed demonstrated marked and consistent flavor preferences in individual baboons. Although specific preference varied between animals, total amounts consumed of the various flavors differed significantly, with rank ordering clearly evident. Overall food intake and body weights increased significantly over baseline values obtained with a standard, unflavored chow. In the second experiment, three baboons received chow of a preferred flavor for nine weeks. Amounts consumed and body weights increased significantly over baseline. These results indicate that flavored chows may be useful for producing a nonhuman primate behavioral model of obesity and for inducing animals to eat otherwise unpalatable diets.

Salt taste preference in baboons

Dietary salt (NaCl) has been implicated in the etiology of hypertension and atherosclerosis, although its role remains controversial. The human preference for salted foods is well-known and many investigators believe the taste for salt is acquired. An experiment we conducted suggests that the baboon does not have an acquired taste for salt. A sample of 36 baboons from a population of 70 baboons of known sire, sex, and dietary history was used; each had been raised since birth on a diet of fixed salt content in a study of dietary salt and blood pressure. Given this unique group of animals, we decided to test whether baboons raised on one dietary salt level (low, medium, or high) would prefer a different level. After baseline consumption was measured for 9 days, we offered each animal equal amounts of all 3 diets simultaneously in a counterbalanced randomized sequence for 9 days, controlling for tray position preference and color preference. We measured consumption of each diet by weighing the amount of food remaining. Our statistical analyses indicated an overwhelming preference for the lowest dietary salt level, regardless of which diet the animal had been fed since birth (p less than 0.0001).

Operant conditioning permits voluntary, noninvasive measurement of blood pressure in conscious, unrestrained baboons (Papio cynocephalus)

This report describes a computerized apparatus and procedure for completely automated noninvasive measurement of systolic, diastolic, and mean arterial blood pressure in conscious, unrestrained nonhuman primates. We used a specially constructed, cage-mounted oscillometric blood pressure instrument and operant reward conditioning methods to train adult baboons(Papio cynocephalus) to submit voluntarily to frequent self-initiated determinations of their blood pressures in the absence of a human operator/observer. Details concerning the operant training procedure and illustrative blood pressure data are presented. The accuracy of the method was evaluated by comparing the noninvasive blood pressure readings with simultaneously taken direct measurements obtained by means of chronically indwelling arterial catheters.

AN APPARATUS AND PROCEDURE FOR OPERANT CONDITIONING OF ELEVATED BLOOD PRESSURE IN UNRESTRAINED BABOONS

Publisher Summary Attempts to produce animal behavioral models of experimental hypertension have utilized various conditioning procedures to induce and maintain elevated blood pressure in numerous species including dogs, cats, and nonhuman primates. These procedures have included Pavlovian pairings of exteroceptive stimuli with unavoidable electric shocks, concurrent autonomic conditioning procedures in which elevations in blood pressure occur in conjunction with the performance of various food reward or shock avoidance tasks, and operant conditioning methods involving explicit contingent relationships between blood pressure level and the delivery of reinforcers. This chapter describes a further modification wherein electric shocks were combined with unavoidable blasts of compressed air. It presents the results that demonstrate that food rewards, compressed air blasting, and electric shocks can be combined to facilitate operant conditioning of autonomically mediated responses. These results also illustrate how operant conditioning procedures, in conjunction with suitable instrumentation designs and physiological monitoring techniques, can be applied to produce behavioral models of altered cardiovascular function in nonhuman primates. This behavioral model may be useful for the study of hypertension, atherosclerosis, and related cardiovascular diseases. An important advantage of this technique over earlier operant approaches is that it completely eliminates chairing. The highest conditioned elevations in blood pressure and heart rate occurred when the combination of contingencies controlling the delivery of rewards and punishments varied unpredictably from one session to the next.

Behavioral incapacitation of rats during full-scale combustion of natural-fiber and synthetic polymeric furnishings

Thirty Long-Evans rats served in each of six experiments to determine the time-course of behavioral incapacitation during exposure to full-scale combustion of household furnishings. Three experiments involved furniture constructed of natural-fiber materials, and three experiments involved furniture dominated by synthetic polymers. Groups of rats, previously trained to stable levels of performance on three tasks (rotorod, operant shock-avoidance, and a jump/escape test), were exposed to combustion products at three locations in a full-scale burn facility. Animals were removed from the exposure environment when they reached each of three operationally defined stages of behavioral incapacitation. Measures of time-to-incapacitation revealed that a given degree of behavioral dysfunction occurred 3 to 5 times sooner during exposure to the combustion of polymeric as compared to natural-fiber furnishings. Temperature, hydrocarbons, carbon dioxide, and oxides of nitrogen were the most frequent statistically significant correlates of time to behavioral incapacitation in polymeric fires; carbon monoxide, carbon dioxide, and total hydrocarbon concentration were the most frequent statistically significant correlates of behavioral dysfunction in natural-fiber fires. Animals that survived the first 24-hour interval after exposure showed no evidence of lasting behavioral incapacitation.