Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Allometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1989

Intraspecific allometry of basal metabolic rate: relations with body size, temperature, composition, and circadian phase in the kestrel, Falco tinnunculus.

The relationship between body size and basal metabolic rate (BMR) in homeotherms has been treated in the literature primarily by comparison between species of mammals or birds. This paper focuses on the intraindividual changes in BMR when body mass (W) varies with different maintenance regimens. BMR varied in individual kestrels in proportion to W1.67, which is considerably steeper than the mass exponents for homomorphic change (0.667; Heusner, 1984) for interspecific comparison among all birds (0.677) or raptors (0.678), for interindividual comparison of kestrels on ad libitum maintenance regimens (0.786), and for mass proportionality (1.00). The circadian range of telemetered core temperature also varied more strongly with intraindividual than with interspecific (Aschoff, 1981a) variation in mass. This was due to reduced nocturnal core temperature at low-maintenance regimens, which was, however, insufficient to account for the excessive reduction in BMR. kidney lean mass at Carcass analysis of eight birds sacrificed revealed a disproportionate reduction in heart and kidney lean mass at low-maintenance regimens. We surmise that variation in BMR primarily reflects variation in these metabolically highly active tissues. This may account for positive correlations found between heart, kidney, and BMR residuals relative to interspecific allometric prediction, and between alpha and rho residuals, as expected on the basis of the constant excess of BMR during alpha above BMR during rho (Aschoff & Pohl, 1970a).

Animals↗
PubMed1989

The role of time and size in ontogenetic allometry: II. An empirical study of human growth.

The changes in shape that occur as a consequence of size changes during the third trimester (22 to 36 weeks post conception) of human growth are examined for muscular, tendinous and skeletal measurements of the lower limb. Gestational age and weight were highly correlated, but not linear. Several models appear to have equivalent fits to these data. The skeletal measurements were linear with body weight, but did not follow the predictions of any biomechanical model. Femur length grows more quickly than body weight, as does femur diameter. The ratio of length to diameter is nearly one, suggesting that the relative shape of the femur does not change with weight. The weights of the two muscles examined were nonlinear as functions of age or weight; Gompertz models with different coefficients fits these data best. The lengths of the two tendons were linear with age, but tendon weights were best described by nonlinear Gompertz models. One difficulty of the Gompertz models stems from the lack of an upper asymptote in these data. The data fit the lower half of the curve, however the model predicts an asymptote beyond the range of data available. The relative patterns of growth, i.e. muscles growing faster than tendons, suggest hypotheses that need to be tested with a larger data set. These include growth of muscles relative to bones or tendons in other regions, e.g., the upper limb or the cranium, and an extension of the data in time.

Anthropometry↗
PubMed1988

Postnatal brain growth and allometry in the rabbit Oryctolagus cuniculus.

A new four-parameter version of Pütter's growth curve (Pütter, 1920) recently developed by Jolicoeur and Pirlot (1988) is applied to cross-sectional data on brain and body weight in 66 male rabbits (Oryctolagus cuniculus) ranging up to one year in postnatal age. Apart from the olfactory bulb, in which there appears to be no initial delay, the estimated initial delays range from 21.7 days (after fertilization) for the cerebellum to 29.9 days for the cerebrum, which suggests that the weight of most regions of the brain, as well as body weight, start increasing rapidly only toward the end of pregnancy (30 days on the average). These initial delays may be related to the fact that rabbits are born very small, naked, blind, and helpless. Expressed on log-log scales, bivariate allometric trajectories have very diverse shapes, including approximate straight lines, curves possessing a single upward or downward convexity, and even sigmoid or inverted sigmoid curves. It seem doubtful whether, if age were unknown, a reasonably simple mathematical function could possess enough flexibility to describe all of these kinds of relationships satisfactorily.

Aging↗
PubMed1978

Encephalization in vertebrates. A new mode of calculation for allometry coefficients and isoponderal indices.

The conventional allometric power function, with its slope near 2/3, works well for interspecific scaling of brain vs. body weight in all groups of vertebrates. It fails, however, in extrapolation to vertebrates of the largest size within their groups: these have smaller brains than the equation would predict. We propose a correction, the hyperbolic tangent, to linearize the data over all sizes, and we discuss evolutionary reasons for the relatively small brain size of the largest vertebrates.

Anatomy, Comparative↗
PubMed1993

Multiphasic allometry.

A multiphasic linear model is presented that describes the allometric relation between body components and permits a smooth transition from one linear segment to the next. Three applications of a diphasic linear model to allometric growth problems were used to illustrate the model. The data sets were selected because a breakpoint exists in the allometric relation. Relations between growth of the alimentary tract and of empty body weight in rabbits, growth of length and of body weight in larval-carp and growth of protein and of fat in pullets were described by a diphasic allometric model. For rabbits and larval-carp, relations were described significantly better by a diphasic instead of a monophasic (simple) allometric model. For situations where response is expected to consist of more than one linear segment, the multiphasic model is recommended.

Animals↗