NUTRIENT-TO-CALORIE RATIOS IN APPLIED NUTRITION.
This paper discusses the desirability of expressing the nutrient require ments of man and animals relative to their associated energy intake, and proposes a format for expressing a dietary standard for humans. Caloric needs are known to vary with size, activity, and productive performance. There is agreement that most of the nutrients quantitatively considered in diet or ration formulation should remain in balance with each other and with energy, for optimal food efficiency. Many nutri tionists believe that it is not possible to state the requirements for individual nutrients without also specifying the amounts of others also to be ingested. In the case of nutrients that must be stored in the body, as during growth, the ratio to energy intake changes progressively to the final adult equilibrium status. In the case of the human, one adult, and 3 juvenile "diet" categories appear to be adequate, within each of which the interbalances between nutrients and that between nutrients and energy are constant. Within these 4 categories, adequate daily nutrition can be accomplished by adjustments in the intake of the diet as a whole. One of the far-reaching concepts in dietetics and animal rationing is the im portance of balance between the nutrients of the diet â€” the realization that relative excesses are no less undesirable than rela tive deficiencies. We have only begun to unravel the picture of nutrient interrela tionships, but it is abundantly clear that the efficiency of food utilization by the animal body may be markedly affected by alterations in the inter-nutrient balance, or between the nutrient and energy pattern, or both. There may be some doubt whether we yet can define the ideal interrelations, but periodically since 1810 tabulations have been made of the quantities of energy and of nutrients that evidence indicated were needed daily by farm animals accord ing to species, weight, age, sex and produc tion performance. One pertinent study was that by Guilbert and Loosli ( 1) in which they computed for farm animals and poultry from the appro priate feeding standards (NAS-NRC series) the recommended daily feed intakes, and total digestible nutrients (TDN); and per unit TDN, the digestible crude protein, calcium, phosphorus, carotene, vitamin A, vitamin D, thiamine, riboflavin, niacin and pantothenic acid for individuals at at tained weights of from 10 to 100% of expected adult size. Although their study was mostly concerned with immature growing animals, and was hampered by excessive variability partly from the fact that the NAS-NRC feeding standard values at that time contained margins of safety of unknown magnitude over the true require ments, they prepared a table of generalized recommended allowances of protein, Ã‡a,P, thiamine and riboflavin in ratio to TDN intake for farm livestock and poultry. They state, 'The feasibility of expressing (in feeding or dietary standards â€”E.W.C.) the relationship of the various nutrients with metabolizable energy rather than with total digestible nutrients should be ex plored." They also comment, "In the pre occupation of seeking new nutritional fac tors, it would appear desirable to pause when they are found to determine their fundamental relations to other nutrients, to body weight, or to caloric intakes, and the quantitative requirements in a sys tematic procedure." Because of incomplete knowledge, the authors of the early tabulations often claimed as requirements, nutrient values later shown to be excessive; and it is sig nificant that, other than inclusion of addi tional nutrients, the chief changes in the chronologically successive "standards," even though by different authors, have been downward revisions of the amounts of nutrients believed to be required rela tive to energy intake. The criteria for such changes have been: increased effi ciency of the ration in producing growth, fattening, milk or egg production, or deReceivedfor publicationAugust8, 1963. J. NUTRITION, 82: '64 353 D ow naded rom http/academ ic.p.com /jn/article-at/82/3/353/4777993 by gest on 19 M arch 2019
EFFECT OF EXERCISE AND DIET ON NITROGENOUS CONSTITUENTS IN SEVERAL TISSUES OF ADULT RATS.
The effects of exercise and dietary protein level on amounts of DNA, RNA and total nitrogen in livers, gastrocnemius muscles and skin samples, and on serum albumin-to-globulin ratios were examined. The purpose was to test the stability of DNA and hence the validity of nitrogen-to-DNA and RNA-to-DNAratios where exercise of various durations was imposed; also to evaluate the hypothesis that exercise might reduce protein reserves by converting labile to stable nitrogen compounds, and that protein in excess of the maintenance requirements might compensate for this conversion. One group of rats was preconditioned by intermittent periods of exercise prior to this test while two other groups underwent no previous exercise. The one- month period of exercise imposed during this test led to reduced serum albumin-to- globulin ratios. Feeding a sub-maintenance protein diet had the same effect, but in combination these treatments did not result in a greater decrease. Preconditioning brought about a marked elevation of plasma globulin level. Preconditioned rats when exercised during this trial had greatly increased amounts of DNA, RNA, and total nitrogen in their gastrocnemius muscles. This increase did not occur in rats exercised daily for 28 days. Liver DNA content was increased in the preconditioned group. Neither exercise nor diet brought about statistically significant changes in skin com position. It was concluded that albumin-to-globulin ratios and DNA ratios could give misleading results in comparisons of exercised and idle rats.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.