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Can physiologic research on the effects of weightlessness be conducted using a centrifuge providing an increased G environment? The answer to this question, if affirmative can have extraordinary implications regarding physiologic research in space that now begs the answer to the more general and basic question, what is the 'best environment' to differentiate the biological effects of mass from weight? In considering the best environment, there are several important factors in support of conducting human and animal physiologic 'gravitational' research on centrifuges here on Earth. Increased G research using a centrifuge can be conducted for a small fraction of the cost of research in space. It can be made available to more scientists as the number of centrifuges for this type of research increases. There are far less-detailed and therefore much easier preparation requirements for animal and human studies on a centrifuge compared with space research.

Adult male chickens adapted to 1.75 or 2.5 G from long term centrifugation, were maximally exercised on an animal treadmill at 1 g (Earth's gravity) and compared with the exercise capacities of control chickens raised at 1 g. The increased-G birds had statistically significantly greater exercise capacities than the controls during the first 3 weeks of the study after the initial exercise exposure. Thereafter however for the following two months of the study, there was no difference in either group's exercise capacities. This early increased work capacity was attributed to the increased-G birds improved ability to maximize their muscular strength with neurological adaptation. The increased-G birds lost body mass at a 31% greater rate during exercise than the controls although this difference was not statistically significant. This increased body mass loss was considered to have resulted from increased use of glycogen during exercise.

Hypoxia tolerances in nitrogen dilution chamber of chickens at sea level and high altitudes, discussing role of hematocrit and heart mass

SummaryOrgan and body mass changes in restrained adult, male domestic fowl were compared with tissue from control and fasted animals. Body mass loss rate in the restrained animals was 63.5% (p < .001) greater than in the fasted group, yet the two groups recovered at the same rate. Compared with controls and fasted animals, restrained fowl exhibited an increase in size of heart, lungs, kidneys, liver, and adrenals but a greater loss of spleen, superficial pectoral muscle, small intestine, and pancreas masses. Relative water content of organs generally increased in restrained and decreased in fasted animals. The data suggest that restraint—although accompanied by inanition—affects organ and body mass in the domestic fowl in a different way than does fasting.

Comparison of two kinds of physiological chronic erythrocytic polycythemias in order to differentiate the specific effect of erythrocytic polycythemia from the general effects of high altitude upon the plasma volume. The two kinds were produced hormonally in female chickens, at sea level, or by protracted high-altitude exposures. It appears that the vascular system of the body may account for an increase in red blood cell mass either by reduction in plasma volume, or by no change in plasma volume, resulting in differential changes in total blood volumes.

The responses of domestic fowl to repeated exposures of 4 min to +6Gz (8 times daily, 5 d weekly) are reported. Survivorship curves for the test group of 48 birds divided into three response categories: mode I, highly susceptible, with all individuals dying on the first day; mode II, more tolerant, with mortality occurring within the first 20 d of treatment; and mode III, highly tolerant, with mortality occurring only after 20 d of treatment. Observations of lymphocyte frequency, an index of systemic stress, and postmortem observations indicate that this heterogeniety has a biological basis.

It has been demonstrated both in the Russian and in the American space programs that there is a progressive deconditioning of the circulatory system with exposure to weightlessness. Astronauts and cosmonauts returned to Earth have a significantly reduced orthostatic tolerance which will persist for a few days. We have measured the acceleration tolerance of domestic fowl, acutely exposed to a 6 g+z field, as the time over which a normal heart rate can be maintained. This period of circulatory accommodation ends abruptly with a marked bradycardia, which with continued treatment is terminal. For animals which have been previously chronically accelerated (e.g., physiologically adapted to a 2.5 g field) the acute acceleration tolerance is greatly increased. It appears that the influence of the ambient acceleration field in conditioning the responsiveness of the circulatory system is a general phenomenon.

Gallinaceous birds, presenting a wide range of body size, were adapted physiologically to hyperdynamic environments, provided by chronic centrifugation. Chemical composition was measured directly on prepared carcasses, which were anatomically comparable, and more amenable to analysis than the intact body. Body mass and body fat decreased arithmetically with increasing field strength and also with increasing body mass. Water content of lean tissue increased in hyperdynamic environments, but irrespectively of body size.

Increased chronic acceleration physiological effects on chickens, comparing hematological observations with exercise capacity, survival and sexual development

Chronic acceleration effects on erythrocyte number, plasma volume, globulin fractions, erythrocyte size and plasma A/G ratio in chickens

THE ability to evaluate an animal with respect to its physiological status is of great value to the environmental physiologist. When environmental alterations exceed the ability of an animal to change homeostatically (accommodate) it becomes physiologically “stressed.” This stressed condition results in, or is induced by an elevated corticosteroid blood level which is manifest in an altered leucocytic hematology. The lymphocytic and heterophilic response in the chicken to injections of ACTH and/or cortisone have been amply demonstrated previously (Huble, 1955; Newcomer, 1957; Wolford and Ringer, 1962; and Shapiro and Schechtman, 1949), as well as in our laboratory. Newcomer (1957) states, “The magnitude and constancy of the acidophilia obtained following ACTH injection suggests its possible use as a qualitative criterion of ACTH and/or acute stress in the bird.” The lymphocytic and heterophilic responses in the chicken to various stressors such as anoxia, restraint, environmental temperatures, starvation, handling, and centrifugation have also . . .

HISTOLOGICAL examination of birds’ lungs indicates a considerable variation in air and blood volumes (Olander et al., 1967). However, in order to obtain quantitative estimates of these changes, methods are needed which can be applied to the entire organ. Such information is of importance in evaluating respiratory function in conditions where the lung becomes anatomically altered. Previous measurements of lung blood volumes in birds (Altman and Dittmer, 1961; McFarland, 1964) have not been made so as to prevent postmortem changes in blood volume in the organ. Other estimates of air volumes in the avian lung (King and Payne, 1958, 1962; Zeuthen, 1942) have been made by filling the respiratory tract with some foreign substance, the difficulties of which have been recognized. Consequently, new methods have been devised to measure air volumes (by buoyancy) and blood volumes (by isotope dilution) and these as well as data on normal chickens are reported . . .

THE use of human radio-iodinated (I131) serum albumin in birds as a method for determining whole body blood volumes has been reported previously by others (Kotula and Helbacka, 1966; Portman et al., 1952). It has also been used in our laboratory as a method to determine blood volumes in chickens. Human radio-iodinated serum albumin (I131) has been recommended for the determination of plasma volume (directly) and blood volume (indirectly) in humans. Since it is not foreign to the human body, the loss rate is slow; i.e., limited to the rate of metabolization by the body (Abbott, 1966). Its use in other species however probably results in an altered loss rate (Portman et al., 1952). The use of human radio-iodinated serum albumin and its physiological characteristics to determine whole body blood volumes in chickens were investigated and reported herein. METHODS Single Comb White Leghorn adult female chickens were used in this . . .

THE resistance of neonatal mammals to hypoxia is well known (Britton and Kline, 1945; Chiodi, 1963; Van Liere and Stickney, 1963; Fazekas et al., 1941). This tolerance decreases in all mammals until within a few days or weeks they are as susceptible as adults. The hypoxic tolerance of the newly hatched chick, however, has never been determined. Several investigations, however, have found that newly hatched chicks are not completely homeothermic until they are several days old (Romanoff, 1941; Randall, 1943; King, 1956; Lamoreux and Hutt, 1939; Deaton and Reece, 1968; Klieber and Winchester, 1933; Klieber, 1938). Since it is well known that poikiliothermic animals are very tolerant to hypoxia (Hock, 1964), it would be anticipated that newly hatched chicks would be very tolerant to reduction in environmental oxygen. METHODS Single Comb White Leghorn chicks, 0 to 31 days of age were exposed in groups of 10 to acute hypoxia in…