The experiment was designed to demonstrate the effects of exercise and confinement on the calcium metabolism of rats. A subsidiary purpose was to determine if any such effects are mediated by a humoral agent. Twenty-four male Sprague Dawley rats were divided into three groups. One group was exercised in motorized activity cages for one hour per day five days per week; one group was confined in small individual metabolism cages for 26 days and in body holders for 12 days; one group was housed in individual metabolism cages and served as controls. Half of the rats of each of the above three groups received 2 ml whole blood from rats similarly treated (exercised, confined or control), on each of the last five days of the experiment. Thus the exercised rats received blood from confined rats, the confined rats received blood from exercised rats and the control rats received blood from control rats. A calcium balance study was carried out for the last 26 days of the 38 day experiment and a calcium-45 balance study was carried out for the last six hours of the experiment. Thus the following specific parameters of calcium metabolism were measured: calcium balance, per cent calcium utilization, food intake, faecal calcium, urinary calcium, total carcass calcium, femur calcium, calcium-45 absorption and femur calcium-45. The entire experiment was performed twice and the data analyzed using a randomized complete block design analysis of variance. The exercise or confinement did not significantly alter the calcium metabolism of the male Sprague Dawley rat under the conditions of this study. Two possible conclusions were discussed. Either this experiment casts some doubt on the current concepts regarding immobilization and osteoporosis, or that the humane conditions adopted in this study did not successfully immobilize the rats. The present experiment also suggests that regular vigorous exercise may not affect the calcium metabolism of the rat to a greater extent than normal activity or mild exercise. No conclusions could be drawn about the role of the blood in regulating or controlling the effects of exercise or confinement on calcium metabolism. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Supplementation with graded levels of threonine to an all barley-lysine diet (0.75% total lysine) improved the daily gain, feed efficiency and carcass quality of growing-finishing pigs. An addition of 0.10% threonine produced the optimum growth response in the experimental animals. No additional improvement was obtained with higher levels of threonine or threonine plus methionine supplementation of the diet. The 0.10% level of threonine supplementation gave performance criteria which were comparable to those obtained with the barley-soybean control diet, except the former diet resulted in significantly higher backfat measurements. Threonine added at levels of 0.15% resulted in higher nitrogen retention than the other barley-lysine-threonine diets. Nitrogen retention on this diet did not differ significantly from the control diet. Barley-amino acid diets resulted in better protein ultilization than barley-soybean control diets. Feeding trials and metabolism trials indicated that methionine was not limiting in barley and that threonine was the second limiting amino acid. Growth trials with weanling rats confirmed the results obtained in the pig nutritional experiments. Rat experiments indicated that no additional beneficial effects were obtained when lysine levels were increased from 0.75% to 0.90% even when supplemented with additional threonine. Results indicated that supplementation with lysine to a total level of 0.75% and threonine at a level of 0.10% resulted in a highly balanced amino acid ratio for rats, and gave growth rates which approached those obtained on the control diet. Supplementation of the barley-lysine diet with 0.20% threonine and all other essential amino acids resulted in growth rates and nitrogen retentions which resembled the results obtained with the control diet. The replacement of the essential amino acid mixture with glycine on an equal nitrogen basis did not result in adequate nitrogen retention or growth rates. / Land and Food Systems, Faculty of / Graduate

Early studies of the permeability of the animal cell membrane were difficult to compare, because of the variety of cell types involved. In the late nineteenth century, workers chose to use erythrocytes due to their advantages over using a variety of cell types. With erythrocytes a comparison could be developed between strictly homologous cells of many different species. Erythrocytes are easily obtainable and mature cells are separate from all other cells of the body as well as from each other. Of even greater importance is the fact that the mature erythrocyte’s major function is the uptake of the greatest possible amount of gases and solutes in the shortest possible time and elimination of these materials without loss or change. The erythrocyte eliminates the complications arising from metabolism of the penetrant being studied. This is attributed to the fact that the erythrocyte is metabolically almost inactive. TO illustrate this point, the human erythrocyte has a rate of glucose utilization of 0.019 ug/hr/million cells while the human leucocyte’s glucose utilization rate is 7.24 ug/hr/million cells or nearly 380 times as great (Guest et al., 1953). The importance of a nearly inactive cell is the lack of complications due to interpretation of data as a function of metabolic processes rather than membrane transport.

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