Criteria for Physiological Stress Produced by Increased Chronic Acceleration ∗

Abstract

The physiological phenomenon of stress as described by Selye as part of a General adaptation syndrome is well known (1). This syndrome has been incriminated as significantly affecting the physiology and biochemistry of animals in a general yet consistent way regardless of the Initial stimulus.

In 1953 Sir Bryan Matthews found that rats could adapt to living on a centrifuge for several months at an accelerative intensity of 6G (2). 1 This finding enabled the use of the centrifuge and increased chronic acceleration adaptation to investigate the effects of weight as opposed to mass upon the physiology and anatomy of laboratory animals. Since that time several laboratories have been conducting this type of research (3-6).

Recently increased chronic acceleration has been recognized as a stressor eliciting a General adaptation syndrome the pathology of which is known as “chronic acceleration sickness” (7) indicating, that certain data obtained from acceleration studies should be evaluated relative to the physiological status of the animal.

Accordingly, criteria for physiological status relative to stress were developed by comparing hematological observations with exercise capacity, survival, and sexual development in chickens exposed to increased chronic acceleration. Another criterion, the response of lymphocytes—relative and absolute lymphopenia—in the chicken to various stressors and to injections of cortical and corticotropic hormones, is well documented (8-13).

Methods. A “selected” strain of adult male single comb white leghorn (SCWL) chicken developed for its resistance to “chronic acceleration sickness” was the experimental animal used in this study (7, 14). All of the birds were maintained using standard poultry husbandry practices. The use of the chicken as a laboratory animal in this type of study has been previously reviewed (14).

The birds were exposed continuously for several months, except for approximately 10 min each day necessary for animal care, to increased accelerations up to 3G in a 20-foot diameter centrifuge which has been partially described in the literature (15, 16).