Engineering topics

Simmons, J. B., II

Publications and source records attributed to Simmons, J. B., II.

4 records

NASA NTRS1982

Effect of simulated weightlessness on energy metabolism in the rat

Results of measurements of food uptake and body weight changes occurring in rats suspended from a harness so that the antigravity muscles were not used for locomotion are presented. The rats were tested in pairs, with both in a harness but only one suspended off its hind legs; this section lasted 7 days. A second phase of the experiment involved feeding the nonsuspended rat the same amount of food the experimental rat had consumed the previous day. All rats experienced decreased in body weight and food intake in the first stage, while in the second stage the suspended rat lost more weight. The total oxygen uptake, CO2 output, and rate of C-14O2 production were depressed in the suspended rats, then returned to normal levels once the rats were back on the ground. It is concluded that the gross metabolic processes are unaffected by simulated weightlessness.

Jordan, J. P.↗

NASA NTRS1980

Simulated weightlessness - Effects on bioenergetic balance

As a prelude to a flight experiment, an attempt was made to separate energy requirements associated with gravity from all other metabolic needs. The biological effects of weightlessness were simulated by suspending animals in a harness so that antigravity muscles were not supporting the body. Twelve pairs of rats were allowed to adapt to wearing a harness for 5 d. Experimental animals were then suspended in harness for 7 d followed by recovery for 7 d. Control animals were harnessed but never suspended. Oxygen consumption, carbon dioxide production and rate of (C-14)O2 expiration from radio-labeled glucose were monitored on selected days. Food intake and body mass were recorded daily. Metabolic rate decreased in experimental animals during 7 d of suspension and returned to normal during recovery. Although some of the metabolic changes may have related to variation in food intake, simulated weightlessness appears to directly affect bioenergetic balance.

Jordan, J. P.↗

NASA NTRS1973

An environmental chamber system for prolonged metabolic studies on small animals

Measurement of metabolic adaptation to marginally stressful environments requires both precise regulation of a variety of atmospheric factors for extended periods of time and the capacity to employ sensitive parameters in an undisturbed subject. This paper describes a metabolic chamber system which can simultaneously maintain groups of small animals in two completely separate closed environments having different pressures, temperatures and gas compositions for an indefinite period. Oxygen consumption, carbon dioxide production, food and water consumption and animal activity cycles can be continuously monitored and quantified 24 h per day while the animals are in an unrestrained state. Each chamber can be serviced and the animals handled, injected and sacrificed without subjecting them to barometric stress. Several unique electrical and mechanical components allow semi-automated data collection on a continuous basis for indefinite periods of time.

Jordan, J. P.↗

NASA NTRS1973

Nonthermal metabolic response of rats to He-O2, N2-O2, and Ar-O2 at 1 atm.

Experiments were performed to describe qualitatively and quantitatively the nonthermal metabolic response of rats to normoxic mixtures of helium, nitrogen, or argon at 1 atm ambient pressure. Hypoxic mixtures were similarly tested to determine any differences in hypoxic response as a function of the diluent gas. Rats exposed to argon for 5 days had a reduced metabolic rate relative to nitrogen, as evidenced by oxygen and food consumption, CO2 production, and the catabolism of radiosubstrates. While some parameters indicated that helium increased metabolic rate, oxygen consumption did not significantly differ from that in nitrogen. The physiologic and metabolic response to an imposed hypoxia varied among the different environments. Certain indices suggested that the hypoxic effects were less severe in helium and more pronounced in argon than in nitrogen. The mechanisms by which the diluent gases produced the observed changes could not be identified, but some possibilities are discussed.

Schatte, C. L.↗