Stevens, C. Edward, and Ian D. Hume. Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients. Physiol. Rev. 78: 393–427, 1998. — The vertebrate ga...

Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients

The importance of size as a determinant of metabolic rate (MR) was first suggested by Sarrus and Rameaux over 160 years ago. Max Rubner's finding of a proportionality between MR and body surface area in dogs (in 1883) was consistent with Sarrus and Rameaux's formulation and suggested a proportionality between MR and body mass (Mb) raised to the power of 2/3. However, interspecific analyses compiled during the first half of the 20th century concluded that mammalian basal MR (BMR, ml O2 h(-1)) was proportional to Mb3/4, a viewpoint that persisted for seven decades, even leading to its common application to non-mammalian groups. Beginning in 1997, the field was re-invigorated by three new theoretical explanations for 3/4-power BMR scaling. However, the debate over which theory accurately explains 3/4-power scaling may be premature, because some authors maintain that there is insufficient evidence to adopt an exponent of 3/4 over 2/3. If progress toward understanding the non-isometric scaling of BMR is ever to be made, it is first essential to know what the relationship actually is. We re-examine previous investigations of BMR scaling by standardising units and recalculating regression statistics. The proportion of large herbivores in a data set is positively correlated both with the scaling exponent (b, where BMR=aMb b) and the coefficient of variation (CV: the standard deviation of ln-ln residuals) of the relationship. Inclusion of large herbivores therefore both inflates b and increases variation around the calculated trendline. This is related to the long fast duration required to achieve the postabsorptive conditions required for determination of BMR, and because peak post-feeding resting MR (RMRpp) scales with an exponent of 0.75+/-0.03 (95% CI). Large herbivores are therefore less likely to be postabsorptive when MR is measured, and are likely to have a relatively high MR if not postabsorptive. The 3/4 power scaling of RMRpp is part of a wider trend where, with the notable exception of cold-induced maximum MR (b=0.65+/-0.05), b is positively correlated with the elevation of the relationship (higher MR values scale more steeply). Thus exercise-induced maximum MR (b=0.87+/-0.05) scales more steeply than RMRpp, field MR (b=0.73+/-0.04), thermoneutral resting MR (RMRt, b=0.712+/-0.013) and BMR. The implication of this observation is that contamination of BMR data with non-basal measurements is likely to increase the BMR scaling exponent even if the contamination is randomly distributed with respect to Mb. Artificially elevated scaling exponents can therefore be accounted for by the inclusion of measurements that fail to satisfy the requirements for basal metabolism, which are strictly defined (adult, non-reproductive, postabsorptive animals resting in a thermoneutral environment during the inactive circadian phase). Similarly, a positive correlation between Mb and body temperature (Tb) and between Tb and mass-independent BMR contributes to elevation of b. While not strictly a defined condition for the measurement of BMR, the normalisation of BMR measurements to a common Tb (36.2 degrees C) to achieve standard metabolic rate (SMR) further reduces the CV of the relationship. Clearly the value of the exponent depends on the conditions under which the data are selected. The exponent for true BMR is 0.686 (+/-0.014), Tb normalised SMR is 0.675 (+/-0.013) and RMRt is 0.712 (+/-0.013).

https://digital.library.adelaide.edu.au/dspace/bitstream/2440/16422/1/hdl_16422.pdf

Allometric scaling of mammalian metabolism.

Food is vital for life. It provides nutrients for growth, maintenance, and reproduction, and is the source of energy that drives the chemical reactions occurring in every cell.1,2 However, most food, as it is initially procured, is not in a form suitable for use; it must first be broken down so that it can be transported through cell membranes.1 The breaking down of food molecules via a system of both mechanical and chemical processes so that they are of use to the body is called digestion.2,3 © 1998 Wiley-Liss, Inc.

Primate Digestion: Interactions Among Anatomy, Physiology, and Feeding Ecology

While common marmosets are increasingly used as alternative primate models in biomedical research, their life history, specialized behavior and unique physiology are not well known. This paper describes important marmoset attributes that are particularly relevant for biomedical research, including reproduction, neurobiology, immunology, endocrine signaling, obesity and aging, in addition to fetal and postnatal development. While common marmosets exhibit characteristic anthropoid primate traits, they clearly differ from Old World primates and humans in a variety of functions, including reproduction, endocrine signaling and immunology. These differences, however, permit the use of common marmosets in unconventional research strategies targeted on human pathology.

Aspects of common marmoset basic biology and life history important for biomedical research.

Introduction To sustain animal populations, an adequate supply of consumable resources is essential. Effects of insufficient resources are well documented in primate populations in the form of reduced rates of fecundity, growth, and survival (Altmann et al . 1977; Hamilton 1985; Gould et al . 1999). Weight loss (Goldizen et al . 1988) and mortality peak during periods of low food availability on an annual (Milton 1980) or interannual basis (Foster 1982; Wright et al . 1999). Food availability relative to consumer requirements has been estimated as seasonally deficient in some (Smythe et al . 1982; Terborgh 1986; Janson & Emmons 1990) but not all (Coehlo et al . 1976) cases. Identifying food-limiting periods generally involves comparisons between estimates of food supply and animal requirements, which in turn require estimates of population density, biomass, energy intake, and metabolic rate. Field techniques measuring doubly labeled water (Nagy & Milton 1979; Williams et al . 1997) and products of fat metabolism in urine samples (Knott 1998) (see also Chapter 12) are highly informative in determining whether consumers are operating at a negative energy balance. The great majority of studies, however, rely on phenological monitoring to suggest periods of food scarcity for vertebrate consumers. Phenological monitoring has revealed spatial and temporal variation in the availability of ripe fruits and young leaves in practically all forests studied (see reviews by van Schaik et al . [1993], [Fenner 1998], [Jordano [2000], and van Schaik & Pfannes [Chapter 2 of this book]).

G.A. Crook

Papers

The digestive strategy of the common marmoset, Callithrix jacchus