Evaluation of Vitamin Requirement Data

Almquist, H. J.

doi:10.3382/ps.0320122

Cited by 20 publications

(7 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: Derivationmentioning

confidence: 99%

“…In practice we find it convenient to adopt a slightly altered terminology when applying this function to nutritional phenomena in higher organisms. Thus, equation 2 may be rewritten: r = (bKj + RmaxIn)/(KI + In) [3] where r = observed response of the organism (i.e., weight gain, plasma concentrations of metabolites, etc.) Rmax = asymptotic or maximum response of the orga- I = nutrient intake n = apparent kinetic order of the response with respect to I as I approaches zero b = calculated ordinate intercept of the nutrientresponse curve K, = nutrition constant Additionally we define Ko.5 as the nutrient intake required for a "halfway" response, i.e., a response equal to (Rmax + By rearranging equation 3 to the slope-intercept form, it is possible to effect a linear transformation of nutrient-response data: r = -K(r -b)/(In) + Rmax [4] Inspection reveals that equation 4 is a more general version of the familiar Eadie-Hofstee equation (10,11).…”

Section: Derivationmentioning

confidence: 99%

“…However, the nutritional responses of animals and humans have been less amenable to satisfactory mathematical analysis. Linear, semi-logarithmic, and quadratic equations have been developed to describe the nutrient-response curves of higher organisms (3)(4)(5). In general, these models have found utility only within narrow ranges of nutrient intake and possess little, if any, theoretical basis.…”

mentioning

confidence: 99%

See 2 more Smart Citations

General model for nutritional responses of higher organisms.

Morgan¹,

Lp²,

Flodin³

1975

Proc. Natl. Acad. Sci. U.S.A.

209

104

View full text Add to dashboard Cite

A general saturation equation is derived which is shown to describe a wide variety of nutrient-response relationships in higher organisms. Iterative multiple linear regression analysis is used to obtain least squares estimates of the constants defining theoretical nutrient-response curves. Curves thus generated accurately predict experimentally observed responses. From this treatment, response parameters are developed which are analogous to Vi.. and Km of enzyme kinetics. It is proposed that this model be applied in evaluating nutritional requirements and in assessing the relative biological efficiency of nutrient sources.It is well established that bacterial growth rates obey saturation kinetics with respect to the concentration of limiting nutrient (1, 2). However, the nutritional responses of animals and humans have been less amenable to satisfactory mathematical analysis. Linear, semi-logarithmic, and quadratic equations have been developed to describe the nutrient-response curves of higher organisms (3-5). In general, these models have found utility only within narrow ranges of nutrient intake and possess little, if any, theoretical basis. In this communication, we report the derivation of a general saturation equation and its application to the nutritional responses of higher organisms. A preliminary report of these findings has recently been published (6, 7). DERIVATIONThe rationale for applying saturation kinetics to gross biological responses derives from the following considerations. Organisms absorb and utilize nutrients via sequences of translocations and transformations, and for any particular metabolic state one step of a sequence would be expected to be ratelimiting for the process as a whole. If the identity of the sequence-controlling reaction does not change with time or nutrient intake, then the overall response of the sequence to graded levels of nutrient will reflect the kinetics of the ratelimiting step. Since many translocations and transformations. of intermediary metabolism obey saturation kinetics individually, we have explored the possibility that data from feeding experiments might be treated mathematically as manifestations of saturable phenomena.Visual inspection of a number of nutrient-response curves from literature sources reveals basic similarities to saturation functions. In general, most nutrient-response curves tend to "plateau out," i.e., to approach an asymptotic or limiting response at high nutrient intake. We have observed that the curvature of nutrient-response functions in approaching this asymptote resembles either hyperbolic saturation curves of the Michaelis-Menten type or sigmoidal saturation curves described by the Hill equation (8, 9). However, direct application of either the Michaelis-Menten or Hill equation to nutrient-response curves is ordinarily precluded by the fact that experimental nutrient-response curves rarely pass through the origin of the coordinate axes as required by these equations. 4327From such considerations, two criteria evolved which...

show abstract

Section: Derivationmentioning

confidence: 99%