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PubMed2001

Peak VO2 correction for fat-free mass estimated by anthropometry and DEXA.

PURPOSE: Anthropometric (ANTHRO) and dual-energy x-ray absorptiometric (DEXA) estimates of total body and leg fat-free masses (FFM) were obtained in 77 randomly selected sedentary men and women, aged 20-80: intermethod limits of agreement and their clinical significance, as inferred from the differences on peak VO2 corrected for FFMANTHRO and FFMDEXA, were determined. METHODS: Limits of agreement were calculated as mean bias +/- 95% confidence intervals: peak VO2 at maximum cycle ergometry was related to FFMANTHRO and FFMDEXA by using both standard (y x x(-1)) and power function ratios (allometry). RESULTS: Data distribution of the ANTHRO-DEXA differences presented significant heteroscedasticity in both sexes, i.e., differences were proportional to the mean (P < 0.05). After logarithmic transformation, the mean bias +/- 95% limits of agreement were expressed as ratios (ANTHRO x DEXA(-1) x// error ratio): these corresponded to 0.95 x// 1.11 or 0.99 x// 1.15 for total body FFM and 0.90 x// 1.10 or 1.02 x// 1.07 for leg FFM in men and women, respectively. In addition, we found different allometric exponents for FFMANTHRO and FFMDEXA: the intermethod differences, therefore, increased after power function expression (P < 0.05). CONCLUSION: Discrepancies between ANTHRO and DEXA measurements of FFM depend on the magnitude of the estimate: differences are typically within 10 to 15%. Importantly, FFM-corrected peak VO2 values can vary according to the method chosen for body composition assessment, especially when allometry is used for peak VO2 correction. These results demonstrate that ANTHRO-DEXA differences in FFM estimation do have relevant practical consequences for the analysis of maximum aerobic capacity in nontrained humans.

Absorptiometry, Photon↗
PubMedDate not supplied

Interspecies scaling of inhalational anesthetic potency minimum alveolar concentration (MAC): application of a correction factor for the prediction of MAC in humans.

The objective of this study was to predict minimum alveolar concentration (MAC) of inhalational anesthetics in humans from animal data. The MAC of 10 anesthetics was obtained from the literature. At least three animal species (excluding humans) were used in the scaling. Interspecies scaling of MAC was performed in two ways: (1) using the traditional allometric approach, the MAC of each drug was plotted against the body weight of the species on a log-log scale, and MAC in humans was predicted from the resultant equation; and (2) MAC in each species was multiplied by a correction factor obtained by adjusting the lung weight of the species based on per kg body weight. The product of the correction factor and the MAC was then plotted against body weight as described in the traditional approach. Predicted MAC values in humans from animal data using simple allometry produced comparatively more error than the prediction made by incorporating the correction factor into the scaling. The results of this study indicate that MAC may not be predicted in humans from animal data using simple allometry; however, applying a correction factor may significantly improve the prediction of MAC in humans from animal data.

Anesthetics, Inhalation↗
PubMed1989

The pachypleurosaurids (Reptilia: Nothosauria) from the middle triassic of Monte San Giorgio (Switzerland) with the description of a new species.

The largest and most diverse collection of Pachypleurosauridae (Nothosauria, Reptilia) comes from Monte San Giorgio, Switzerland. Several hundred complete skeletons were collected from four distinct horizons of bituminous limestones and shales of Anisian-Ladinian boundary to early Ladinian age (Middle Triassic). Serpianosaurus mirigiolensis comes from the oldest strata, the Grenzbitumenzone Beds. The three younger strata, all in the Lower Meride Limestone, yield three species of Neusticosaurus. Neusticosaurus pusillus comes from the Cava Inferiore horizon, Neusticosaurus peyeri, new species, from the Cava Superiore horizon, and Neusticosaurus edwardsii, new combination, from the Alla Cascina horizon. Neusticosaurus pusillus is biostratigraphically important because it is one of the rare species reported from both the Germanic and the Alpine Triassic. Neusticosaurus pusillus and N. peyeri are small and very similar in their anatomy. Neusticosaurus species are easiest separated by their number of presacral vertebrae. Ornamentation of the bone surface is distinctive for all four pachypleurosaurids. Soft parts are rarely preserved, except for one partial squamation. The biological age of Neusticosaurus individuals can be determined by skeletochronology (aging by bone annuli). Small species of Neusticosaurus were sexually mature after three to four years and lived for six to nine years. Taphonomic analysis of the small species indicates attritional mortality and suggests weak bottom currents in the Monte San Giorgio basin during early Ladinian times. Morphometric comparison of all four pachypleurosaurids indicates that the changing vertebral numbers between species are largely due to a change in number of segments. All Monte San Giorgio pachypleurosaurids are sexually dimorphic in forelimb development. Sex x has poorly differentiated and relatively short humeri whereas sex y has well differentiated and relatively long humeri. The sexes are of about the same size and represented in roughly equal numbers. Identification of gender was not possible. Good growth series, especially of Neusticosaurus peyeri, from embryo to large adult permitted qualitative and quantitative study of ontogeny. The skull grows with negative allometry; the humerus grows isometrically or with positive allometry, depending on sex and species; the femur grows isometrically. The adult size range in N. peyeri is considerably larger than in modern reptiles. The Monte San Giorgio pachypleurosaurids are a monophyletic group. The phylogeny of this group is congruent with the stratigraphic distribution of its members.

Animals↗
PubMed2001

THOMAS MCMAHON: A Dedication in Memoriam.

Thomas A. McMahon (1943-1999) was a pioneer in the field of biomechanics. He made primary contributions to our understanding of terrestrial locomotion, allometry and scaling, cardiac assist devices, orthopedic biomechanics, and a number of other areas. His work was frequently characterized by the use of simple mathematical models to explain seemingly complex phenomena. He also validated these models through creative experimentation. McMahon was a successful inventor and also published three well-received novels. He was raised in Lexington, Massachussetts, attended Cornell University as an undergraduate, and earned a PhD at MIT. From 1970 until his death, he was a member of the faculty of Harvard University, where he taught biomedical engineering. He is fondly remembered as a warm and gentle colleague and an exemplary mentor to his students.

Journal Article↗
PubMed2004

Theoretical and empirical derivation of cardiovascular allometric relationships in children.

Basic fluid dynamic principles were used to derive a theoretical model of optimum cardiovascular allometry, the relationship between somatic and cardiovascular growth. The validity of the predicted models was then tested against the size of 22 cardiovascular structures measured echocardiographically in 496 normal children aged 1 day to 20 yr, including valves, pulmonary arteries, aorta and aortic branches, pulmonary veins, and left ventricular volume. Body surface area (BSA) was found to be a more important determinant of the size of each of the cardiovascular structures than age, height, or weight alone. The observed vascular and valvar dimensions were in agreement with values predicted from the theoretical models. Vascular and valve diameters related linearly to the square root of BSA, whereas valve and vascular areas related to BSA. The relationship between left ventricular volume and body size fit a complex model predicted by the nonlinear decrease of heart rate with growth. Overall, the relationship between cardiac output and body size is the fundamental driving factor in cardiovascular allometry.

Adolescent↗
PubMed2006

Comparative morphology of the avian cerebellum: I. Degree of foliation.

Despite the conservative circuitry of the cerebellum, there is considerable variation in the shape of the cerebellum among vertebrates. One aspect of cerebellar morphology that is of particular interest is the degree of folding, or foliation, of the cerebellum and its functional significance. Here, we present the first comprehensive analysis of variation in cerebellar foliation in birds with the aim of determining the effects that allometry, phylogeny and development have on species differences in the degree of cerebellar foliation. Using both conventional and phylogenetically based statistics, we assess the effects of these variables on cerebellar foliation among 91 species of birds. Overall, our results indicate that allometry exerts the strongest effect and accounts for more than half of the interspecific variation in cerebellar foliation. In addition, we detected a significant phylogenetic effect. A comparison among orders revealed that several groups, corvids, parrots and seabirds, have significantly more foliated cerebella than other groups, after accounting for allometric effects. Lastly, developmental mode was weakly correlated with relative cerebellar foliation, but incubation period and fledging age were not. From our analyses, we conclude that allometric and phylogenetic effects exert the strongest effects and developmental mode a weak effect on avian cerebellar foliation. The phylogenetic distribution of highly foliated cerebella also suggests that cognitive and/or behavioral differences play a role in the evolution of the cerebellum.

Analysis of Variance↗
PubMed1997

The length of the vertebral column of primates: an allometric study.

The length of the vertebral column of 425 primates (151 prosimians, 76 platyrrhines and 198 catarrhines) was related to body mass from bibliographic sources. Regressions were calculated for the whole sample and separately for the three taxonomic groups quoted above. In parallel, the lengths of the cervical, thoracic and lumbar regions were calculated in a sample of 105 primates (30 prosimians, 19 platyrrhines and 56 catarrhines) and partial correlations established. In all cases except one, the correlation coefficients were significant. Of these, 12 correlations (out of 16) scaled with negative allometry (< 0.33), 4 with positive allometry (> 0.33), and in 6 cases the exponents were not significantly different from the criterion for isometry (0.33). The lumbar region showed the highest variability, mainly in platyrrhines and catarrhines. Results from catarrhines are globally the closest to the expectations of elastic similarity. No obvious direct relationship was found between the length of the vertebral column and the number of vertebrae.

Analysis of Variance↗
PubMed2004

On the scaling of mammalian long bones.

Although there is much data available on mammalian long-bone allometry, a theory explaining these data is still lacking. We show that bending and axial compression are the relevant loading modes and elucidate why the elastic similarity model failed to explain the experimental data. Our analysis provides scaling relations connecting bone diameter and length to the axial and transverse components of the force, in good agreement with experimental data. The model also accounts for other important features of long-bone allometry.

Animals↗
PubMed2005

Multi-level regulation and metabolic scaling.

Metabolic control analysis has revealed that flux through pathways is the consequence of system properties, i.e. shared control by multiple steps, as well as the kinetic effects of various pathways and processes over each other. This implies that the allometric scaling of flux rates must be understood in terms of properties that pertain to the regulation of flux rates. In contrast, proponents of models considering the scaling of branching or fractal-like systems suggest that supply rates determine metabolic rates. Therefore, the allometric scaling of supply alone provides a sufficient explanation for the allometric scaling of metabolism. Examination of empirical data from the literature of comparative physiology reveals that basal metabolic rates (BMR) are driven by rates of energy expenditure within internal organs and that the allometric scaling of BMR can be understood in terms of the scaling of the masses and metabolic rates of internal organs. Organ metabolic rates represent the sum of tissue metabolic rates while, within tissues, cellular metabolic rates are the outcome of shared regulation by multiple processes. Maximal metabolic rates (MMR, measured as maximum rates of O2 consumption, VO2max) during exercise also scale allometrically, are also subject to control by multiple processes, but are due mainly to O2 consumption by locomotory muscles. Thus, analyses of the scaling of MMR must consider the scaling of both muscle mass and muscle energy expenditure. Consistent with the principle of symmorphosis, allometry in capacities for supply (the outcome of physical design constraints) is observed to be roughly matched by allometry in capacities for demand (i.e. for energy expenditure). However, physiological rates most often fall far below maximum capacities and are subject to multi-step regulation. Thus, mechanistic explanations for the scaling of BMR and MMR must consider the manner in which capacities are matched and how rates are regulated at multiple levels of biological organization.

Animals↗
PubMed2005

Biomechanical consequences of scaling.

To function over a lifetime of use, materials and structures must be designed to have sufficient factors of safety to avoid failure. Vertebrates are generally built from materials having similar properties. Safety factors are most commonly calculated based on the ratio of a structure's failure stress to its peak operating stress. However, yield stress is a more likely limit, and work of fracture relative to energy absorption is likely the most relevant measure of a structure's safety factor, particularly under impact loading conditions characteristic of locomotion. Yet, it is also the most difficult to obtain. For repeated loading, fatigue damage and eventual failure may be critical to the design of biological structures and will result in lower safety factors. Although area:volume scaling predicts that stresses will increase with size, interspecific comparisons of mammals and birds show that skeletal allometry is modest, with most groups scaling (l proportional, variant d0.89) closer to geometric similarity (isometry: l proportional, variant d1.0) than to elastic similarity (l proportional, variant d0.67) or stress similarity (l proportional, variant d0.5). To maintain similar peak bone and muscle stresses, terrestrial mammals change posture when running, with larger mammals becoming more erect. More erect limbs increases their limb muscle mechanical advantage (EMA) or ratio of ground impulse to muscle impulse (r/R= integral G/integral Fm). The increase in limb EMA with body weight (proportional, variant W0.25) allows larger mammals to match changes in bone and muscle area (proportional, variant W0.72-0.80) to changes in muscle force generating requirements (proportional, variantW0.75), keeping bone and muscle stresses fairly constant across a size range 0.04-300 kg. Above this size, extremely large mammals exhibit more pronounced skeletal allometry and reduced locomotor ability. Patterns of ontogenetic scaling during skeletal growth need not follow broader interspecific scaling patterns. Instead, negative allometric growth (becoming more slender) is often observed and may relate to maturation of the skeleton's properties or the need for younger animals to move at faster speeds compared with adults. In contrast to bone and muscle stress patterns, selection for uniform safety factors in tendons does not appear to occur. In addition to providing elastic energy savings, tendons transmit force for control of motion of more distal limb segments. Their role in elastic savings requires that some tendons operate at high stresses (and strains), which compromises their safety factor. Other 'low stress' tendons have larger safety factors, indicating that their primary design is for stiffness to reduce the amount of stretch that their muscles must overcome when contracting to control movement.

Animals↗
PubMed1996

Pectoral fin locomotion in the striped surfperch. II. Scaling swimming kinematics and performance at a gait transition

In this study, we report the first allometric equations relating gait parameters and swimming speed to body size for fish employing pectoral fin locomotion. Comparisons of locomotor kinematics and performance among striped surfperch (Teleostei: Embiotocidae) are made at the pectoral&shy;caudal gait transition speed (Up-c). Up-c is considered to elicit physiologically equivalent levels of exercise in animals varying over 100-fold in body mass (Mb) by virtue of dynamically similar pectoral fin movements (constant duty factor, length-specific stride length and fin-beat amplitude) and size-independent propulsive efficiency. At Up-c, pectoral fin-beat frequency scales in proportion to Mb-0.12&plusmn;0.03, a size-dependence consistent with that observed for stride frequency in fishes swimming by axial undulatory propulsion and in many running tetrapods. It is proposed that the similarity in the scaling of frequency in these vertebrate groups reflects an underlying similarity in the allometry of the maximal velocity of muscle shortening. Absolute Up-c (m s-1) generally increases with body size, but the fastest speeds are not exhibited by the largest animals. A pattern of declining performance in fish 23 cm in standard length and longer may be related to their disproportionately small fin areas and aspect ratios. The pronounced negative allometry of Up-c expressed as standard body lengths per second indicates that a given length-specific speed does not induce comparable levels of activity in large and small fish. Thus, normalization of swimming speed to body length may not be a sufficient correction for kinematic comparisons across size.

Journal Article↗
PubMed1998

Flight of the vampire: ontogenetic gait-transition in vampyroteuthis infernalis (Cephalopoda: vampyromorpha)

Vampyroteuthis infernalis is a cosmopolitan cephalopod that lives in the oxygen minimum layer between 600 and 800 m depth. Morphometric and physiological studies have indicated that V. infernalis has little capacity for jet propulsion and has the lowest metabolic rate ever measured for a cephalopod. Because fin swimming is inherently more efficient than jet propulsion, some of the reduction in energy usage relative to other cephalopods may result from the use of fins as the primary means of propulsion. V. infernalis undergoes a rapid metamorphosis which consists of changes in the position, size and shape of the fins. This suggests that there are changes in the selective factors affecting locomotion through ontogeny. The present study describes these changes in relation to models for underwater 'flight'. Citrate synthase (CS) and octopine dehydrogenase (ODH) activities, indicative of aerobic and anaerobic metabolism, respectively, were measured in fin, mantle and arm tissue across a range of body size of four orders of magnitude. The low enzymatic activities in both posterior and anterior fin tissue and the relatively high activity in mantle muscle prior to metamorphosis indicate that jet propulsion using mantle contraction is the primary means of propulsion in juvenile V. infernalis. The increase in CS activity with size after metamorphosis suggests an increased use of the fins for lift-based propulsion. Fin swimming appears to be the primary means of propulsion at all adult sizes. The negative allometry of CS activity in mantle and arm muscle is consistent with the scaling of oxygen consumption previously measured for V. infernalis and with the scaling of aerobic metabolism observed in most animals. The unusual positive allometry of fin muscle CS activity suggests that the use of fins is either relatively more important or more costly in larger animals. Positive scaling of ODH activity in all tissues suggests that fin propulsion, jet propulsion and medusoid 'bell-swimming' are all important for burst escape responses. Enzyme activities in Cirrothauma murrayi are consistent with fin-swimming observed from submersibles, while those in Opisthoteuthis californiana suggest a strong reliance on medusoid swimming using the arms. The transition from jet propulsion to paired-fin 'flight' with increasing body size in Vampyroteuthis infernalis appears functionally to be an ontogenetic 'gait-transition'.

Journal Article↗
PubMed2001

Interspecies scaling: is a priori knowledge of cytochrome p450 isozymes involved in drug metabolism helpful in prediction of clearance in humans from animal data?

The objective of this study was to evaluate whether a priori knowledge of cytochrome P450 isozymes involved in drug metabolism coupled with Mahmood' and Balian's 'rule of exponents' can be helpful for the prediction of clearance in humans using animal data. The clearance of 27 randomly selected drugs metabolized by different isozymes were scaled up from the animal data (at least three animal species) obtained from the literature. Three methods were utilized to generate allometric equations to scale up the clearance values: (i) clearance vs body weight (simple allometry); (ii) product of the clearance and maximum life-span potential (MLP) vs body weight; and (iii) the product of clearance and brain weight vs body weight. The choice of one of the methods was based on the 'rule of exponents' as described by Mahmood and Balian. The results of this study indicate that the knowledge of a particular isozyme does not provide a guide for the failure or success of allometry for the prediction of clearance. There is no trend which indicates that the chances of accurate prediction of clearance for a given drug are comparatively higher or lower when they are metabolized by a particular isozyme.

Administration, Oral↗
PubMed1995

Multivariate analysis of limb long bone growth during the human prenatal period.

Prenatal development of the human limb bones (humerus, ulna, radius, femur, tibia, fibula) was studied. Cross-sectional data, consisting of 21 anthropometric measures of these bones were collected from 122 Japanese fetuses between the gestational ages of 18 and 40 weeks. Principal component analysis was applied to the data to provide multivariate assessments of morphological patterning among the variables. Three orthogonal components that accounted for 94.2% of the overall sample variation were extracted. The first component accounted for 88.2% of the variation and represented an axis of overall body size that was dependent on gestational age. The second and third components both reflected a trend in shape involving the cartilaginous parts of the humerus and femur. The findings indicated that different growth factors existed between the ossified and cartilaginous parts of fetal long bones. Multivariate allometric coefficients were extracted from the first principal component. The variables that were related to the construction of the articulate showed positive allometry, and the central widths of the diaphysis showed negative allometry compared with total size. In prenatal skeleton, certain shape changes are functionally linked to and required by changes in body size. A comparison among the coefficients of long bone length revealed that lower limb bones grew faster than upper limb bones during the period under study here. Allometric coefficients were equivalent among bones within a limb, whereas homologous bones in the upper and lower limb grew at different rates.

Bone and Bones↗
PubMed1990

Allometric growth of the adrenal gland in Brazilian fetuses.

The growth of the adrenal gland was studied in 60 brazilian fetuses (12-37 weeks post-conception). The right adrenal gland was quantitatively evaluated; its weight, length and thickness were correlated to the fetal body weight, to the Crown-Pump length and to the gestational age by the allometric method (LogY = kLogX + LogB). The width was the only linear measure with positive allometry, and was the one which presented the greatest relative growth, while the thickness had the smallest one. The adrenal weight presented positive allometry relating to the Crown-Rump length (k = 2.32) and to the gestational age (k = 2.40). The importance of these knowledges in the precocious ultrasonographic diagnosis of congenital adrenal pathologies is discussed.

Adrenal Glands↗
PubMed1976

[Comparison of the intraspecific growth of the endocranial organs (hypophyseal lobes, pineal gland, SFO) in the white Wistar rat. Rattus norvegicus (Berkenhout), with their interspecific growth in the rodents].

The intraspecific growth of various endocranian organs (hypophysis, pineal gland and SFO) in the Rat compared to a group of Rodents shows that their allometry coefficient/somatic weight is : close to isometry for the anterior and intermediate lobes of the hypophysis which is suitable for endocrine glands; lower and close to that found for the relation brain weight/somatic weight for the nervous lobe in the Rat and in Rodents; and extremely low (0,33) for the SFO in the Rat, which is comparable to that found in Rodents (0,44). The allometry coefficient found for the pineal gland is not comparable to that found in Rodents (1,25). Many facts (important intra and interspecific variations, existence of species or individuals deprived of pineal gland) seem to indicate that this gland is not related to an essential somatic function.

Animals↗
PubMed2001

Structural homology and developmental transformations associated with ovary diversification in Lithophragma (Saxifragaceae).

Lithophragma, comprising only ten species, encompasses a remarkable diversity of ovary positions, reported to range from inferior to superior. The structural homology of the gynoecium and developmental transformations associated with ovary diversification are investigated for Lithophragma. Scanning electron and light microscopy indicate that all species of Lithophragma have epigynous flowers. Lithophragma campanulatum, L. glabrum, and L. heterophyllum have ovaries that externally appear nearly superior, but are actually shallowly inferior or "pseudosuperior." The inferior ovaries of Lithophragma species can be conceptually divided into superior and inferior regions that meet at the point of perianth and androecial insertion. Static and ontogenetic allometry reveal that across the species of Lithophragma the lengths of these two ovary regions are coordinated. Ovary regions in mature flowers display an approximately linear relationship that can be expressed through the allometric equation SL = -0.5314 IL + 2.0348 (where SL and IL are the lengths of the superior and inferior regions of the ovary, respectively; r = 0.7683, df = 35, P = 2.45 × 10). Mapping ontogenetic allometries onto a recent phylogeny for Lithophragma shows that ovary position evolution is bidirectional and has shifted toward greater superiority in some species and greater inferiority in others.

Journal Article↗
PubMed1992

Spleen's relative growth in human fetuses.

The growth of the spleen weight was studied by bivariate allometry. It was correlated to fetal parameters of development as gestational age (in weeks), crown-rump length (mm) and weight (gm). Thirty human fetuses ranging from 16 to 36 weeks were studied. These were analysed in second and third trimesters separately and together. The growth of the spleen weight presents statistically significant positive allometry relative to age, C-R length and fetal weight. In second trimester the allometric coefficient, analysing spleen's weight and fetus' weight, calculated by reduced major axis method (RMA) was 1.21. In the third one the RMA was 1.73. Considering fetuses together the RMA = 1.65. This study presents growth curves of the spleen weight useful in medical branches such as anatomy, forensic medicine, medical imagery, fetophatology, obstetrics and pediatrics.

Embryonic and Fetal Development↗