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 217 records · Page 12Linked to original sources
PubMed1982

Intraspecies allometry: correlation between kidney weight and glomerular filtration rate vs. body weight.

Allometric equations of the form of Y = a*BWb were calculated between body weight (BW) on the one hand and either kidney weight (KW) or glomerular filtration rate (GFR) on the other. By using strain and sex means obtained from 24 different inbred strains of adult mice or F1-hybrids environmental and genetical influences could be separated statistically. Thus, allometric equations reported in this study describe exclusively genetic influence. The parameters for intraspecies allometric equations obtained in these studies were compared to those in the literature presenting interspecies relationships. The double logarithmic regressions of KW vs. BW gave results different from the interspecies equation. The difference between intra- and interspecies results of allometric relationships may be due to the experimental exclusion of environmental influences. The regression parameters for GFR vs. BW obtained for the inbred strains, however, agreed very well with those of the empirical equation for interspecies relationship and also with the theoretically expected value. The dependence of GFR on BW was found to be GFR = 0.036*BW0.74 +/- 0.15, where GFR is measured in ml/min and BW in g. The exponent of 0.74 seems to be a valid biological constant that is genetically determined within and across species lines.

Animals↗
PubMed1984

Allometry of water vapor absorption in two species of tenebrionid beetle larvae.

Water vapor absorption is compared in the two tenebrionid larvae Tenebrio molitor and Onymacris marginipennis. Thresholds for absorption and "absorption capacity," which depend on ion transport by Malpighian tubules, are consistently different over the entire size range of the two species. Because of lower thresholds, uptake rates of Onymacris are over double those of Tenebrio in larvae of the same size at identical ambient water activities. By contrast, passive determinants of uptake, rectal conductance, and morphometry are similarly scaled with size in the two species. A ventilatory mechanism of vapor entry into the rectum is proposed for both species, since the anal canal is too long and narrow for exclusively diffusional entry. Vapor uptake in relation to larval mass was described by a simple diffusion model through rectal tissue, where flux varied directly with surface area and inversely with the distance between the lumen and Malpighian tubules. Failure of rectal conductance to increase proportionally with body mass means that size-specific vapor uptake declines with larval size in both species.

Absorption↗
PubMed1991

Allometry of cooling, supercooling, and freezing in the freeze-tolerant turtle Chrysemys picta.

Although several vertebrates are freeze tolerant, little is known of the relationship between body size and the kinetics of cooling and freezing. We compared these responses for six hatchling and eight adult Chrysemys picta from an Ohio population. All turtles initially recovered from freezing, and all adults, but only two hatchlings (which experienced ice contents of approximately 35%), exhibited long-term survival. Rapid thawing may have compromised hatchling survival. Turtle water content was inversely related to body mass, but we found no significant correlation between the extent of supercooling and body size. Prefreezing and postfreezing cooling rates scaled with body mass to the -0.55 and -0.40 power, respectively, but the latter rate was more than two orders of magnitude slower. Theoretical (assuming 20% bound water) and calorimetric estimates of body ice agreed reasonably well. Ice contents were both body mass and time dependent. The absolute rate of ice formation scaled with body mass to the 0.4 power. Body size strongly influences the freezing response of ectotherms and deserves more attention.

Aging↗
PubMed1995

Allometry of pharmacokinetics and pharmacodynamics of the muscle relaxant metocurine in mammals.

We investigated the effects of body size on the pharmacokinetics and pharmacodynamics of the renally cleared muscle relaxant metocurine. We hypothesized that pharmacokinetics of the drug would change allometrically in proportion to physiological time [infinity Mb0.25, where Mb is body mass] and that pharmacodynamics would be independent of size because of the highly conserved structure of the acetylcholine receptor. Metocurine effects during general anesthesia were examined in 17 rats, 8 cats, 6 dogs, 5 pigs, 7 sheep, and 12 horses. Allometric analysis demonstrated size dependence for pharmacokinetics, which were affected by physiological time (Mb0.25). Pharmacodynamics were size independent, except for the value for effect compartment concentration associated with 50% twitch paralysis (IC50). Data from individual species had a bimodal distribution that was significant: pigs and sheep were more sensitive than other large species, and their IC50 appeared size independent. IC50 was size dependent in more active species (horse, dog, cat, rat). Although the mechanism is unknown, we speculate that this trend might relate to receptor density within the end plate. Thus pharmacokinetics changed in proportion to physiological time, and pharmacodynamics were in part size independent.

Anesthesia, General↗
PubMed1996

Allometry of mitochondrial proton leak: influence of membrane surface area and fatty acid composition.

We investigated why liver mitochondria from small mammals are leakier to protons than those from larger mammals. Sixty-nine percent (+/-23%) of the proton leak differences appeared to relate to membrane area (less inner membrane surface area in larger animals); any residual differences must reflect differences in membrane properties. There were differences in phospholipid fatty acid composition; unsaturation index, monounsaturates, palmitate (16:0), stearate (18:0), docosahexaenoate [22:6(n-3)], and the 22:6(n-3)/22:5(n-3) ratio all correlated with body mass. Proton flux per square centimeter did not correlate significantly with body mass or, in general, with phospholipid fatty acid composition, suggesting little role for fatty acid composition in determining proton leak in mammals of different body mass. However, unsaturation index and n-3 polyunsaturated fatty acid content correlated significantly with proton leak per milligram phospholipid when literature data from reptiles and rats in different thyroid states were included, giving some support to suggestions of a general role for phospholipid fatty acid composition in determining mitochondrial proton leak.

Animals↗
PubMed2004

Interspecific allometry of the brain and brain regions in parrots (psittaciformes): comparisons with other birds and primates.

Despite significant progress in understanding the evolution of the mammalian brain, relatively little is known of the patterns of evolutionary change in the avian brain. In particular, statements regarding which avian taxa have relatively larger brains and brain regions are based on small sample sizes and statistical analyses are generally lacking. We tested whether psittaciforms (parrots, cockatoos and lorikeets) have larger brains and forebrains than other birds using both conventional and phylogenetically based methods. In addition, we compared the psittaciforms to primates to determine if cognitive similarities between the two groups were reflected by similarities in brain and telencephalic volumes. Overall, psittaciforms have relatively larger brains and telencephala than most other non-passerine orders. No significant difference in relative brain or telencephalic volume was detected between psittaciforms and passerines. Comparisons of other brain region sizes between psittaciforms and other birds, however, exhibited conflicting results depending upon whether body mass or a brain volume remainder (total brain volume - brain region volume) was used as a scaling variable. When compared to primates, psittaciforms possessed similar relative brain and telencephalic volumes. The only exception to this was that in some analyses psittaciforms had significantly larger telencephala than primates of similar brain volume. The results therefore provide empirical evidence for previous claims that psittaciforms possess relatively large brains and telencephala. Despite the variability in the results, it is clear that psittaciforms tend to possess large brains and telencephala relative to non-passerines and are similar to primates in this regard. Although it could be suggested that this reflects the advanced cognitive abilities of psittaciforms, similar studies performed in corvids and other avian taxa will be required before this claim can be made with any certainty.

Animals↗
PubMed2005

Brain allometry in bumblebee and honey bee workers.

Within a particular animal taxon, larger bodied species generally have larger brains. Increased brain size usually correlates with increased behavioral repertoires and often with superior cognitive abilities. Bumblebees are eusocial insects that show pronounced size polymorphism among workers, whereas in honey bees size variation is much less pronounced. Recent studies suggest that within a given colony, large bumblebee workers are more efficient foragers and are better learners than their smaller sisters. Here we examine the allometric relationship between brain and body size of worker bumblebees and honey bees. We find that larger bees have larger brains and that most brain components show a similar size increase as the overall brain. One particular brain structure, the central body, is relatively smaller in large bumblebees compared to small bees. The same is true for the mushroom body lobes, whereas the mushroom body calyces, which receive sensory input, are not reduced in larger bumblebees or honey bees. Honey bees have relatively smaller brains, as well as smaller mushroom bodies, than bumblebee workers. We discuss why brain or mushroom body size does not necessarily correlate with the degree of a species' social organization.

Animals↗
PubMed1994

GnRH cell size and number in a teleost fish with two male reproductive morphs: sexual maturation, final sexual status and body size allometry.

Gonadotropin releasing hormone-like immunoreactive (GnRH-ir) cells in both the ganglion of the terminal nerve (TN) and the preoptic area (POA) have been implicated in the development and maintenance of reproductive behavior and physiology in teleost fishes. One marine species, the plainfin midshipman, Porichthys notatus, exhibits two sexually mature male morphs (types I and II) which differ with respect to size at sexual maturation, gonad/body weight index, reproductive tactic and vocal motor traits. Type II males become reproductively active at a smaller body size than either females or type I males. Immunocytochemical techniques and quantitative analyses were used here to determine the size and number of GnRH-ir cells in the TN and POA amongst field collected juveniles, sexually mature females, and type I and II males. Mean GnRH-ir cell size and number in the TN did not vary across the entire range of specimens. However, mean GnRH-ir cell size and number in the POA were 50-100% greater in sexually mature adults compared to juveniles. Analyses of covariance indicated that increases in cell number, but not cell size, could be explained solely on the basis of changes in body size. However, regression analyses showed that body size had a significant influence on increasing cell number only in the juvenile-type I male transition and the juvenile-female transition, not in the juvenile-type II male transition. The latter suggests that type II males, unlike the other adult morphs, have 'escaped' from a body size constraint imposed on increasing GnRH-ir cell number in the POA. There were also significant differences among the adult morphs in the size of GnRH-ir POA cells that could not be explained on the basis of differences in body size but, rather, appear to reflect differences in the temporal onset of sexual maturation. Together, the data suggest that the timing of changes in POA phenotype may provide a proximate mechanism permitting the development of alternative male reproductive morphs.

Animals↗
PubMed1992

Call patterns and basilar papilla tuning in cricket frogs. II. Intrapopulation variation and allometry.

We determined the influence of body size on the male advertisement call's dominant frequency and basilar papilla's (BP) tuning in male and female cricket frogs (Acris crepitans) in two Texas populations (Wimberley and Stengel Ranch). In both populations, call and tuning characters correlated negatively with body size; females were larger than males and their BPs were tuned to a lower frequency. Analysis of covariance showed that neither the sex difference in tuning nor the population differences in calls or tuning were due to the difference in body size alone, but instead represented differences in the allometric relationships of each character with body size. The analysis implied that differences between sexes or populations were due more to shifts in the Y-intercept rather than the slope of the relationship with body size. This suggests a developmental model in which sexes or populations possess resonant structures in the ear or larynx with similar growth rates but different starting points or initial growth phases, resulting in different frequency characteristics as adults. The examination of the relationship between female BP tuning and male call dominant frequency predicts potentially different patterns of sexual selection in the two populations, with the Wimberley population males subject to much greater directional selection for low frequency calls.

Animals↗
PubMed1986

Allometry of major CNS divisions: towards a reevaluation of somatic brain-body scaling.

For each of four rodent species, average weights for the brainstem, cerebellum, and forebrain were determined and average cross-sectional area of the cervical spinal cord (SCA) was calculated. Linear regression analyses against log body weight were performed on these data (log translated), along with data (except SCA) from the literature for insectivores and primates. Results indicate that the different CNS divisions scale by different powers of body weight in different mammals and that the rodent SCA varies by less than the 2/3 power of body weight. Based on the results, we conclude that there are at least two general brain scaling factors, somatic and nonsomatic, that necessitate a more complex general allometric equation; the exponent for somatic brain scaling is approximately 0.52, and body surface area is not a primary determinant of brain size.

Animals↗
PubMed1991

Growth allometry of the myocardium in human embryos (from stages 15 to 23).

The relative growth of the myocardium was studied in 27 staged human embryos (Carnegie stages). The volume of the myocardium was determined for each embryo according to Cavalieri's principle (by using point-counting planimetry to determine the area of the profiles of the myocardium). The volume of the myocardium (variable Y) was correlated to embryonic crown-rump length (variable X in millimeters) and age (in days). The bivariate allometric equation was used as Y = aXb. The scatterplot was discontinuous, presenting two trends during the postsomitic period. The first part was composed of embryos staged from stages 15 to 20, and the second part by embryos staged from stages 21 to 23. The breakpoint between these different trends was found at the level of stage 20 (embryo of 22 mm in crown-rump length and age nearly of 52 days). From stages 15 to 20, the growth rate of the myocardium was allometrically negative. On the other hand, from stages 21 to 23 this growth rate was moderately allometrically positive. These differences in growth of the myocardium were analyzed and, at least partially, might be due to the functional circulatory increase in the peripheral vascular bed in correlation to the cardiac hemodynamic demand required at the end of the embryonic period proper.

Fetal Heart↗
PubMed1979

Locomotion, limb proportions, and skeletal allometry in lemurs and lorises.

The allometric patterns of postcranial scaling in lemurs (Lemuridae and Indriidae) and lorises (Lorisinae) are established and discussed in relation to locomotor and postural adaptations. The scaling trends of each limb and its components vary significantly among these three prosimian groups, but all are functionally explicable in reference to habitual locomotor behavior and details of substrate utilization.

Animals↗
PubMed1987

Structural allometry of the femur and tibia in Hominoidea and Macaca.

Allometric scaling relationships between body weight, bone length, and cross-sectional dimensions of the lower limb bones which measure structural strength and rigidity (area, second moments of area) are investigated in Homo, Gorilla, Pan, Pongo, and Macaca. Cross-sectional dimensions are slightly positively allometric and highly correlated with body weight; within-bone proportional differences are largely a result of differences in relative bone length to body weight. Orangutans show the greatest deviation from general scaling relationships between lower limb bone structural strength and weight, probably due to habitual upper limb suspension. Formulas for the prediction of weight from cross-sectional dimensions are presented.

Adult↗
PubMed1994

Adaptation, allometry, and hypertension.

Essential hypertension is a "disease of civilization" but has a clear genetic component. From an evolutionary perspective, persistence in the human genome of elements capable of raising blood pressure presupposes their adaptive significance. Recently, two hypotheses that explicitly appeal to selectionist arguments, the "slavery" and "thrifty gene" theories, have been forwarded. We find neither completely successful, and we advance an alternative explanation of the adaptive importance of genes responsible for hypertension. We propose that blood pressure rises during childhood and adolescence to subserve homeostatic needs of the organism. Specifically, we contend that blood pressure is a flexible element in the repertoire of renal homeostatic mechanisms serving to match renal function to growth. The effect of modern diet and lifestyle on human growth stimulates earlier and more vigorous development, straining biologically necessary relationships between renal and general somatic growth and requiring compensation via homeostatic mechanisms preserved during evolution. Prime among such mechanisms is blood pressure, which rises as a compensation to maintain renal function in the face of greater growth. Since virtually all members of acculturated societies share in the modern lifestyle, the demands imposed by accelerated growth and development result in a populational shift to higher blood pressures, with a consequent increase in the prevalence of hypertension. We propose that hypertension is the product of maladaptation of highly genetically conserved mechanisms subserving important biological homeostatic needs. Elucidation of the mechanisms underlying hypertension will require approaches that examine the developmental processes linking growth to blood pressure.

Adaptation, Physiological↗