Maintenance protein requirements

FIG. 2. The formation of the apical protein complex involves two distinct steps. Bazooka is localized apically in the epithelium from which neuroblasts are derived. In the interphase (G2), delaminating neuroblast formation of the apical complex is initiated. It is thought that Baz acts to allow neuroblasts to retain the apical/basal polarity inherent in the epithelium. Baz recruits Insc to the neuroblast apical stalk during delamination before Pins becomes part of the complex. During this initiation step Baz, Insc and Pins are part of a linear hierarchy. However following delamination and during mitosis, the maintenance of the apical localization of each of these proteins requires all three proteins. 

Dietary protein provides essential amino acids. The quality of a protein is a measure of its ability to provide the essential amino acids required for tissue maintenance. Proteins from animal sources, in general, have a higher quality protein than that derived from plants. However, proteins from different plant sources may be combined in such a way that the result is equivalent in nutritional value to animal protein. 

Net protein ratio (NPR) is used to correct PER values for the amount of protein required for cell maintenance. NPR is often run in conjunction with a PER. The experiment requires that one additional set of animals be added as a treatment group. This group of animals is fed a basal diet with no protein (zero protein or basal diet). Results from RNPR are similar to net protein utilization (NPU) and biological value (BV methods, see Alternate Protocol 4). A 2-week RNPR is thought to be the most appropriate rat test for routine assessment of protein quality. 

PER zero-protein diet formula. For determination of net protein ratio, a test diet that contains no protein is run as one of the test diets. This zero protein diet is used to derive a correction to account for the amount of protein required for cell maintenance. 

Berry KL, Bulow HE, Hall DH, Hobert O. 2003. A C. elegans CLIC-like Protein Required for Intracellular Tube Formation and Maintenance. Science 302 2134-37. 

The remainder of this chapter takes on a more "nutritional" aura, ft concerns the concepts of growth and maintenance- The material may be especially intcresling to those involved in infant nutrition, animal science, and weight reduction by low-energy diets. The material reveals the tecliniques used for determining the protein requirement and the recommended daily allow ancc (RDA) for protein. Clinical issues involving protein nutrition, such as renal disease and gput, arc also Outlined. 

Garza C, Scrimshaw NS, Young VR. Human protein requirements the effect of variations in energy intake within the maintenance range. Am J Chn Nutr. 1976 29(3) 280-7. 

Inoue G, Fujita Y, Niiyama Y. Studies on protein requirements of young men fed egg protein and rice protein with excess and maintenance energy intakes. J Nutr. 1973 103(12) 1673-87. 

The importance of proper nutrition during infancy is illustrated by the infant s nutritional requirement. On a body weight basis, the infant requires far more essential amino acids than the adult. The infant must receive histidine, which is not essential in the adult diet. The 2-month-old premature infant and the 3-month-old term infant may require as much as 8 mg of iron a day. Such an amount is usually not found in the diet, and supplementation is necessary. An adequate protein intake is necessary for the maintenance of health in the infant and growing child, but the exact protein requirement is not known. 

The protein requirements for maintenance adopted by CSIRO (2007) are based on ARC (1980), but they specify separate estimates for EUP and MFP and recognise that MFP varies directly with level of feeding. For B. taurus breeds of cattle, EUP is predicted as follows ... 

As indicated above, most of the protein systems for ruminants (see Chapter 13) used around the world base their estimates of protein requirements for maintenance on endogenous losses of nitrogen but use different factors to translate endogenous losses into dietary requirements. For example, using the UK metabolisable protein... 

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