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PubMed1995

Allometry in the uptake of hydrophobic chemicals determined in vivo and in isolated perfused gills.

Uptake rate constants of different classes of hydrophobic organic chemicals have been determined in isolated perfused gills of rainbow trout (Oncorhynchus mykiss) as an alternative for studies in vivo. The uptake rate constants have been compared to those determined in guppy, Poecilia reticulata, in vivo. The organic chemicals which have been used are anthracene, hexabromobenzene, octachloronaphthalene, octachlorodibenzo-p-dioxin, phenol, polychlorinated anisoles, polychlorinated benzenes, polychlorinated biphenyls, and tetrachloroveratrole. Uptake rate constants in guppy are higher than those in rainbow trout gills, and show relatively high variation in both gills and guppy. When uptake rate constants in each study are normalized for that of pentachlorobenzene (pCBz), variation is significantly reduced both in perfused gills and in guppy. All allometric relationship is derived between weight and uptake rate constant. Uptake rate constants determined in one fish can thus be used for prediction of those in other fishes. When a reference chemical, such as pCBz, is included, the gill perfusion experiments can be highly suitable to determine uptake rate constants of organic chemicals, which can be extrapolated to fish of different sizes.

Animals↗
PubMed1985

Allometries of the durations of torpid and euthermic intervals during mammalian hibernation: a test of the theory of metabolic control of the timing of changes in body temperature.

The durations of the intervals of torpor and euthermia during mammalian hibernation were found to be dependent on body mass. These relationships support the concept that the timing of body temperature changes is controlled by some metabolic process. Data were obtained from species spanning nearly three orders of magnitude in size, that were able to hibernate for over six months without food at 5 degrees C. The timing of body temperature changes was determined from the records of copper-constantan thermocouples placed directly underneath each animal. Because all species underwent seasonal changes in their patterns of hibernation, animals were compared in mid-winter when the duration of euthermic intervals was short and relatively constant and when the duration of torpid intervals was at its longest. Large hibernators remained euthermic longer than small hibernators (Fig. 2). This was true among and within species. The duration of euthermic intervals increased with mass at the same rate (mass 0.38) that mass-specific rates of euthermic metabolism decrease, suggesting that hibernators remain at high body temperatures until a fixed amount of metabolism has been completed. These data are consistent with the theory that each interval of euthermia is necessary to restore some metabolic imbalance that developed during the previous bout of torpor. In addition, small species remained torpid for longer intervals than large species (Fig. 3). The absolute differences between different-sized species were large, but, on a proportional basis, they were comparatively slight.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Allometry of mammalian cellular oxygen consumption.

In the 1930s, Max Kleiber and Samuel Brody established that the interspecies correlation between mammalian body mass and metabolic rate (alphaM(0.75)) cannot be explained (solely) by whole body surface area (alphaM(0.66)) to volume ratios. Metabolic considerations must also be taken into account. Decreases in the proportion of visceral organ mass to whole body mass can account for some of the whole body metabolic differences. However, superimposed upon these anatomical differences, the metabolism of tissues and cells has been demonstrated to decrease with increasing body mass. These decreases in oxygen consumption rates (with increasing body mass) in cells and tissues can be explained by a decrease in ATP turnover and mitochondrial density and an increase in mitochondrial functional efficiency (decrease in proton leak). The majority of the proton leak differences reflect differences in mitochondrial inner membrane surface area. Indeed, liver metabolism correlates directly with liver mitochondrial inner membrane surface area. Apart from being a significant contributor (approximately 25%) to basal metabolism, mitochondrial proton leak is a major factor determining the differences in basal metabolism between mammals of different body mass.

Adenosine Triphosphate↗
PubMed1997

Immobilization distorts allometry of rat femur: implications for disuse osteoporosis.

It is inherent to mammalian limb bones that they tend to maintain the same relative proportions of bone mass with changing body mass. This assumption seemed not to comply with experimental data on bone mineral content (BMC) and areal density (BMD) we have previously observed with immobilized rat femora. Using allometric scaling (BMC = aWEIGHTb), we showed in this study that a 3-week period of unilateral immobilization of the left hindlimb of 27 Spraque-Dawley male rats at the age of 13 weeks resulted in disproportionate scaling between femoral BMC and body weight (range: 430-937 g) during subsequent 32 weeks. The allometric exponents (b) were 0.76 (95% confidence interval: 0.64-0.88) for the immobilized left femur and 0.62 (0.51-0.73) for the right intact femur, both of which were in significant contrast to the value of 0.99 (0.90-1.08) observed in 36 free-living control rats (410-910 g). For BMD, the corresponding exponent values were 0.52 (0.44-0.60), 0.44 (0.36-0.52), and 0.67 (0. 61-0.73), the values being significantly different from each other also. We conclude that a short period of immobilization significantly distorts the normal allometric scaling relationships between the body weight and femoral BMC and BMD in growing male rats. The obvious adverse effect on peak bone mass suggests that an immobilization period during growth may condemn the given bone to a lifetime of relative fragility. Therefore, further consideration of this issue is warranted.

Animals↗
PubMed1980

Rethinking allometry.

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Animal Population Groups↗
PubMed1989

Interaction of allometry and development in the mouse Mus musculus: heart rate and hematology.

The contribution of body mass changes to developmental adjustments in heart rate and hematology has been investigated in the mouse Mus musculus. Both resting heart rate (fH) and hematological variables including erythrocyte concentration, hemoglobin concentration, blood oxygen capacity, hematocrit, mean corpuscular hemoglobin and mean corpuscular volume, changed considerably during the increase in body mass from birth (1g) to adulthood (maximum of 50 g). There were two phases of change, one characteristic of preweaned mice (approximately less than 10 g) and the other of postweaned mice (approximately 10-50 g). In preweaned mice resting fH was about 1/2 of the value predicted on the basis of interspecific allometric data from mammals. fH increased steadily until body mass reached 10 g, then began to decrease with further mass increase at the same rate as predicted from interspecific allometric data. Erythrocyte concentration, hematocrit, hemoglobin concentration and blood oxygen capacity were all significantly lower in preweaned mice compared with postweaned mice. It is suggested that the progressive heart rate increase in very young mice may be to increase cardiac output to compensate for the neonatal anemia. After weaning, hematological variables showed little or no further change with increasing body mass. Collectively, these data indicate that during the early phases of postnatal growth, developmental factors other than body mass have the greatest influence on heart rate and hematology, and allometric data derived from interspecific studies on adults have little predictive value in neonates. After weaning, however, body mass is the major influence on these variables, and allometric data derived from interspecific studies on adults are reasonably accurate as predictors. We conclude that interspecific allometric studies must be properly regarded as the study of adult animals of different body sizes, and that untested assumptions about the applicability of these data to intraspecific studies of immature specimens should be made with extreme caution.

Animals↗
PubMed1989

Biochemical correlates of the structural allometry and site-specific properties of mammalian adipose tissue.

1. The maximum activities of the glycolytic enzymes hexokinase (HK) and phosphofructokinase (PFK) were measured in defatted homogenates of adipose tissue from nine homologous depots of 57 wild and captive mammals belonging to 17 species and eight orders and differing in body mass by six orders of magnitude. 2. Site-specific differences in the enzyme activities were similar in all terrestrial species and were not consistently related to adipocyte volume. 3. The specimen-mean maximum activities of HK and PFK did not correlate with body mass, body composition or natural diet. 4. When specimens of different body composition and body mass were compared, glycolytic enzyme activity per adipocyte was directly proportional to adipocyte volume. 5. Site-specific differences in collagen content of adipose tissue did not correspond to those adipocyte volume. When homologous depots of different specimens were compared, the collagen content of adipose tissue was directly proportional to body mass. 6. Adipose tissue of large cetaceans contains more collagen than predicted from the allometric equations fitted to the data from terrestrial mammals. 7. Neither the scaling of the collagen content with body mass nor the site-specific differences in its abundance are consistent with a role as protection or support for adjacent tissues. 8. There are consistent site-specific differences in the extracellular components of adipose tissue as well as in the structure and metabolism of the adipocytes. 9. Adipose tissue differs from most other tissues in that its maximum metabolic capacities do not scale to body mass. 10. Adjustment of the biochemical activity of adipose tissue to changes in body mass and body composition must depend upon neural and endocrine controls, not upon intrinsic differences in its metabolic capabilities.

Adipose Tissue↗
PubMed2004

The allometry and scaling of the size of vertebrate eyes.

We compiled data from the literature and colleagues to examine the relationship between eye axial length and body weight for vertebrates as well as birds, mammals, reptiles, and fishes independently. After fitting the data to logarithmic and semi-logarithmic models, we found that axial length of vertebrate eyes does obey a conventional logarithmic relationship with body weight rather than a semi-logarithmic relationship as suggested by the results of previous studies. The regression slopes and intercepts appear to be characteristic of various animal groups. The axial length of the eye is largest in birds and primates, smaller in other mammals (especially rodents) and reptiles, and widely varying in fishes.

Animals↗
PubMed1998

Host cell allometry and regulation of the symbiosis between pea aphids, Acyrthosiphon pisum, and bacteria, Buchnera.

The symbiotic bacteria Buchnera in aphids are borne in cells, called bacteriocytes, in the insect haemocoel. The number and median volume of bacteriocytes in pre-reproductive adult insects varied significantly among 14 parthenogenetic clones of the pea aphid Acyrthosiphon pisum. After logarithmic transformation of the data, the relationship of both number and median volume of bacteriocytes with aphid weight for the clones could be described by common regression lines with slopes significantly greater than zero. The allometric slope for median bacteriocyte volume was calculated as 1.06, by model I regression and 1.94 by model II regression; and the equivalent values of the allometric slope for total volume of bacteriocytes were 1.51 and 2.50, suggesting that the total volume of bacteriocytes increases disproportionately with aphid body weight. The partial correlation coefficient between the number and median volume of bacteriocytes was +0.07, with body weight held constant. It is proposed that the regulation of number and size of bacteriocytes is not linked and that bacteriocytes may not exhibit compensatory changes in size, in response to alteration in number. Experimental manipulation of the rates of bacteriocyte differentiation and division could therefore perturb the total volume of the symbiosis, on which aphid pests depend for normal growth and reproduction.

Journal Article↗
PubMed1984

Determination of relative size: the "criterion of subtraction" problem in allometry.

By providing a predicted value against which to judge observed values, allometric equations are often used as a "criterion of subtraction" to calculate measurements corrected for the effects of overall size. The observed and predicted values have been used to calculate several different versions of a size-adjusted measurement; two of the more common being (observed/predicted) and (log observed-log predicted). Using data on brain size, tooth size, metabolic rate, and long bone shape, it is found that the manner in which the relative size value is calculated can alter interpretations and statistical results. Some of the assumptions underlying use of a criterion of subtraction calculated from empirical data are reviewed. It is suggested that predicted values determined from a priori theoretical equations often have several advantages over those from empirical equations.

Anatomy↗