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At least 595 records · Page 33Linked to original sources
PubMed1990

Brain growth patterns in four European cyprinid fish species (Cyprinidae, Teleostei): roach (Rutilus rutilus), bream (Abramis brama), common carp (Cyprinus carpio) and sabre carp (Pelecus cultratus).

This study compares brain growth in 4 species of cyprinids, each distinctly different in adult brain morphology: roach have generalized brains; bream are characterized by well-developed visual, octavolateralis and gustatory brain regions; common carp show chemosensory (gustatory)-dominated brains, and sabre carp octavolateralis-dominated brains. The growth patterns of 16 regions relative to total brain volume were investigated by computer-aided quantitative histology to illustrate internal brain allometries. In all species the tectum opticum decreases in relative size during growth, whereas the corpus cerebelli increases. In bream and common carp, primary taste centers steadily increase in relative size during growth. In most if not all fish, the brain attains no definite final morphology. Lifelong, growth-related shifts in relative sizes of primary sensory regions may reflect lifelong shifting sensory capabilities.

Animals↗
PubMed1980

Morphometrical analysis of the aging process in human arteries and aorta.

Ultrastructural and morphometrical studies were conducted on vascular tissue from 205 human Japanese specimens ranging in age from 15 weeks' gestation to 90 years. Comparison of aorta size with overall body length by allometry revealed that the aging aorta has growth and involution stages comparable to other organs, and that progressive increase in aortic diameter was the major involutional change. The cellular and extracellular components of the medial sections of thoracic and abdominal aorta, renal artery, and superior mesenteric artery were quantitated from electron micrographs and compared at different ages. It was found that the renal artery rapidly accumulated extracellular material with increasing age; in the aortic tissue, however, the peak occurrence of extracellular material occurred at pubescence. Ultrastructural studies revealed a general tendency of aging medial smooth muscle cells to transform from a smooth, rounded morphology to become irregularly shaped.

Adolescent↗
PubMed1980

Size and positioning of the teeth and infratemporal fossa relative to taxonomic and dietary variation in primates.

The infratemporal fossa grows allomorphically in primates at a faster rate than general cranial and inferred body size. The coefficient of allometry approximates 1.5 across most primate groups, suggesting direct scaling of the muscsulus temporalis cross-sectional area to body mass. This coefficient is larger than 1.5 in Lorisoidea and Ceboidea. Mediolateral relative growth of the infratemporal passage that accommodates m. temporalis rather than antero-posterior growth absorbs a disproportionate amount of this expansion. Likewise, infratemporal fossa breath is positively allometric to tooth size, especially in insectivorous, frugivorous and folivorous primate samples that are homogeneous with respect tok diet. The seemingly growth-related positive relations between tooth size and distal placement of the zygomatic root that is consistent over the cumulative sample is erased by controlling for diet. Increased relative amounts of m. temporalis per unit of dental occlusal area is indicated in larger-bodied forms; increasing crown height may be a mechanism to adjust for this.

Animals↗
PubMed1982

Scaling of sexual dimorphism in body weight and canine size in primates.

Among primates sexual dimorphism in both body weight and canine size increases exponentially with increasing body size. This suggests that a full explanation of the variance in sexual dimorphism can only be attained if, in addition to sexual selection, parental investment, and various ecological factors, the influence of body size is taken into account. Positive allometry in both body weight dimorphism and canine size dimorphism is demonstrated to be associated with polygyny. In monogamous species the two dimorphisms not only remain constant throughout the size range but actually are minimal or lacking at any given body size.

Animals↗
PubMed1983

Size and diet in the evolution of African ape craniodental form.

Interspecific differences in craniodental morphology among Pan paniscus, Pan troglodytes, and Gorilla gorilla are analyzed. These apes differ in both diet and body size, and thus present an excellent example in which to apply an allometric criterion of subtraction in order to determine morphological differences which might be related to divergent dietary specialization. The use of ontogenetic allometry in particular as a criterion of subtraction is discussed. Bivariate and multivariate results indicate that most of the variation in skull form among the species relates to the extension of a common growth trend to different sizes. Comparative analysis of growth trajectories reveals a number of differences, but none that appear to relate to a reorganization of skull proportions which might correspond to a dietary shift towards increased folivory. The dentition clearly exhibits non-allometric shape changes corresponding to the dietary differences, however. The meaning of these differences between cranial and dental patterns is discussed.

Africa↗
PubMed1985

Sexual dimorphism in the postcranial skeleton of New World primates.

This study examines sexual dimorphism in 24 dimensions of the postcranial skeleton of four platyrrhine species: Callithrix jacchus, Saguinus nigricollis, Saimiri sciureus, and Cebus albifrons. The two callitrichid species show a relatively small amount of variation in the degree of sexual dimorphism among the different dimensions. Variation is considerably higher in the two cebid species as reflected by a mosaic pattern of sexual dimorphisms with males being significantly larger than females in some dimensions, and females significantly larger than males in others. In dimensions of the pectoral girdle and limb bones, males and females in each of the two cebid species are essentially scaled versions of each other, with males being peramorphic compared to females. This pattern is primarily the result of time hypermorphosis, i.e. an extension of the growth period in time in males. Rate hypermorphosis, i.e. an increase in the rate of growth in time in males, appears to play an additional role, however, in S. sciureus. By contrast, in dimensions of the true pelvis, sex differences in shape are dissociated from those in size. They are interpreted as the result of acceleration, i.e. increase in rate of shape change in females, as an adaptation to obstetrical functions. Interspecific analyses indicate positive allometry of mean degree of postcranial dimorphism with respect to body size. This coincides with previous findings by Leutenegger and Cheverud [1982, 1985] on the scaling of sexual dimorphism in body weight and canine size, and thus supports their model which posits selection on body size as the prime mover for the evolution of sexual dimorphism.

Aging↗
PubMed1986

A volumetric comparison of the vestibular nuclei in primates.

The volumes of each of the four vestibular nuclei, superior, lateral, medial and descending, were measured in 80 brains from 2 species of Scandentia, 18 species of prosimians, and 26 species of anthropoids. Size indices were calculated by comparing species-specific points to the nucleus volume-body weight allometry in prosimians, where the average prosimian was set at 1.00. The indices range from 1.78 in Saimiri to 0.48 in Gorilla, and the distributions by families overlap partially or completely. The observed trend in size indices is independent of changes in the neocortex and the ventral pons; average indices are 1.35 in New World monkeys, 1.20 in Old World monkeys, 0.74 in apes, 0.82 in man. Among prosimians, Galago, Galagoides and Tarsius (leaping locomotion) show significantly higher indices than Nycticebus, Loris and Perodicticus (slow movement without leaping). The lateral vestibular nuclear indices in Pongidae and man are extremely low, about half of those of the average prosimians. Correlation coefficients of size indices between the vestibular nuclei and other motor nuclei, such as the cerebellar nuclei, ventral pons and striatum, are analysed. The ratio of the vestibular nuclear volumes to the total brain volumes and the distribution of percentages of each vestibular nuclear volume to the total complex are also obtained.

Animals↗
PubMed1990

Does a centralized clock for ageing exist?

It is proposed that a centralized clock controlling ageing is located in the pineal gland with the calcification process occurring there providing a highly accurate bio-inorganic timing mechanism and the secreted melatonin carrying a signal to all cells in the organism. An explicit programme of data gathering and experiments suitable for the falsification of the proposal, which is consistent with presently known anatomical and physiological facts, is presented. The underlying motivation comes from evolutionary biology and the invariance, that is the allometry, of life expectancy curves.

Aging↗
PubMed1992

Age-related changes in thyroid structure and function in Sprague-Dawley rats.

Investigation of thyroid glands from 500 male and 500 female Sprague-Dawley rats, at time points of 8, 17, 30, 56, and 108 weeks of toxicity studies conducted at the Huntingdon Research Centre between 1981 and 1984, revealed age-related structural and functional changes that have previously not been well documented. The number of ultimobranchial cysts decreased with age, while area(s) of C-cell hyperplasia appeared with age. Beginning at 56 weeks, some of the thyroid follicles were hyperdistended with colloid, had irregular lumens, and were lined by flattened epithelium. These follicles had clumped, granular, and stratified colloid. Follicular tumors were found in 8% of the males and 6% of the females at 108 weeks. There was an increase in absolute thyroid weights (males from 21.8 +/- 4.0 g to 46.5 +/- 19.05 g, females from 17.2 +/- 4.53 g to 41.7 +/- 26.92 g) and body weights (males from 382.0 +/- 70.6 g to 806.0 +/- 120.7 g, females from 220.0 +/- 21.0 g to 495.0 +/- 127.3 g) with age in both sexes, but the relative thyroid weights were not significantly affected. Negative allometry was observed. With an increase in the age of the rats, there was a decrease in the height of the follicular epithelium and an increase in the internal follicular diameter and the total number of follicles. No prediction for sex could be detected. Serum T3 and T4 concentrations were constant until 56 weeks of age, but at 108 weeks, the values were markedly reduced (in males, serum T3 concentration decreased from 91.60 +/- 13.970 ng/100 ml to 32.90 +/- 10.878 ng/100 ml, and in females, from 90.80 +/- 11.338 ng/100 ml to 48.10 +/- 8.875 ng/100 ml; in males, serum T4 concentration decreased from 5.94 +/- 0.679 microgram/100 ml to 3.04 +/- 0.604 microgram/100 ml, and in females, from 4.59 +/- 0.717 microgram/100 ml to 2.77 +/- 0.786 microgram/100 ml). The data suggest that the thyroid function of Sprague-Dawley rats reduces as the rats age.

Aging↗
PubMed1981

Compensatory renal growth in the mouse. I. Allometric approach to the effect of age.

Allometry, defined as the relationship between the growth rates of organs to the weight of the whole body (38), was used to study the effect of age on the degree of compensatory renal growth (CRG) in the mouse. The normal growth of the kidneys relative to body weight (BW) was determined in animals between 5 to 50 days of age. In one group, nephrectomy and sham operations were performed at 5, 15, and 35 days of age. The remaining ("renoprival") kidney was removed 15 days postnephrectomy. In a second group, nephrectomy was performed on 5-day-old animals, the renoprival kidney being removed after 30 or 45 days. Regression equations were calculated by least-squares after logarithmic transformation and different groups were compared by analysis of covariance. The regression equation for the control kidney was kidney weight (KW) = 0.0093 BW0.86 (r = 0.96). The regression for renoprival kidneys in females was KW = 0.0142 BW0.83 (R = 0.96) after 15 days and, in comparison, was not significantly different from 30 to 45 days. The interval between control and renoprival regressions was equivalent to a difference of congruent to 43% KW. In male mice, the regression for renoprival kidneys after 15 days was KW = 0.0103 BM0.96 (r = 0.98) and was not significantly different from 30 to 45 days. This study suggests that in young mice the time required for complete CRG may be a maximum of 15 days and that the amount of CRG does not depend on the age at operation. After CRG, a new equilibrium is reached which is thereafter maintained up to a minimum of 50 days of age.

Adaptation, Physiological↗
PubMed1981

Compensatory renal growth in the mouse. II. The effect of growth hormone deficiency.

Allometry was used to study the effect of growth hormones (GH) deficiency on compensatory renal growth (CRG) in a dwarf mouse strain (Little). Nucleic acid and protein estimations were used to assess changes in cellular hyperplasia and hypertrophy. Nephrectomy was performed at 5, 15, or 35 days of age with removal of the renoprival kidney 15 days later. Controls underwent sham nephrectomies at 35 days of age. The allometric growth of the normal kidney in the homozygote dwarf (lit/lit) between 8 and 50 days of age was closely related to that of the normal heterozygote (lit/+). A regression line for the renoprival kidneys in lit/lit animals was parallel to that of the control right kidney (P less than 0.001). The interval between the regression lines was equivalent to a constant difference of approximately 40% between renoprival and control right kidneys and was similar to that found in the normal heterozygote (43%). Increases in DNA, RNA, and protein in control animals during CRG indicate that cell division and hypertrophy were occurring in similar proportions. In the GH-deficient mouse, the total amount of DNA in renoprival kidneys was 0.451 mg compared with 0.439 mg in controls (NS). This suggests that cell replication was suppressed. The protein:DNA ratio increased from 20.91 to 24.27 (P less than 0.001) and the RNA:DNA ratio increased from 0.732 to 0.912 (P less than 0.001), suggesting that cell size was markedly increased. These findings suggest that reduced amounts of GH may produce a dissociation between hyperplasia an hypertrophy, with CRG occurring predominantly by cellular hypertrophy.

Adaptation, Physiological↗
PubMed2001

Pharmacokinetics and interspecies scaling of a novel VEGF receptor inhibitor, SU5416.

The pharmacokinetics and allometric relationships of SU5416, a novel small anti-angiogenesis agent, were studied. The pharmacokinetics of SU5416 were examined in mice, rats, dogs, and cancer patients. The in-vitro intrinsic clearance (CLint) was estimated from the in-vitro metabolism study in mouse, rat, dog, monkey and human liver microsomes. The parameters of interest were correlated across species as a function of bodyweight using an allometric approach. The steady-state volume of distribution (Vd(ss)), plasma clearance (CLs), and CLint of SU5416 were well correlated across species. The exponent of the allometric relationship (b) of the corresponding parameters was 0.92, 0.80 and 0.66, respectively. The elimination half-life (t1/2) was consistent across species and independent of bodyweight. The prediction of CLs, Vd(ss), CLint, and t1/2 in humans using the data from mouse, rat, and dog, and monkey (for CLint) was reasonably good (within 4-fold of the observed values). However, an improved prediction (within 2-fold of the observed values) of the corresponding parameters in humans was obtained when extrapolation from only the rodent data was performed, suggesting that the rodent data are sufficient for the scale-up of SU5416 pharmacokinetic parameters in humans. Using allometry, it was possible to achieve reasonable predictions of the pharmacokinetic parameters of SU5416 in cancer patients with various solid tumours.

Angiogenesis Inhibitors↗
PubMed1999

Interspecies pharmacokinetic comparisons and allometric scaling of napsagatran, a low molecular weight thrombin inhibitor.

The objective of this work was to assess the pharmacokinetics of napsagatran, a low molecular weight thrombin inhibitor, after intravenous administration in a variety of laboratory animals, and prospectively to help design the first pharmacokinetic studies in man. Napsagatran is actively excreted into the bile and urine of various species and pronounced species-differences in its pharmacokinetics are observed. It is, therefore, an interesting compound to use in tests of the limitations of presently available inter-species scaling methods. The present data suggest that allometric exponent values which are consistent with the values expected for physiological processes and small organic molecules are not necessarily associated with successful predictions in man when active transport processes are involved in the disposition of the compounds. For example, compared with the values observed in man, the clearance (CL), non-renal clearance (CL(nr)) and the volume of distribution at steady state (Vd(ss)) were over-predicted by 3-, 7- and 2-fold, respectively, by use of allometry. Of the species tested, the cynomolgus monkey seemed to be the most useful for predicting kinetics in man when the approach based on concentration-time transformations was used. Thus, for half-life (t(1/2)), CL and Vd(ss), the observed mean values of 1.7 h, 459 mL min(-1) and 24 L kg(-1) in man were very close to the values predicted from the cynomolgus monkey (1.7 h, 652 mL min(-1) and 22 L kg(-1), respectively). The results show that there are large inter-species differences for kidney and liver excretion of napsagatran. This is probably because of the involvement of active transport processes, which compromised the kinetic extrapolation from animal to man, although a more thorough investigation of the transporters involved in the disposition of napsagatran is necessary to enable better understanding of the species differences observed.

Animals↗
PubMed2004

Respiration rate of hepatocytes varies with body mass in birds.

Hepatocytes were isolated from eight species of birds ranging from 13 g zebra finches to 35 kg emus. This represents a 2800-fold range of body mass (Mb). Liver mass (g) was allometrically related to species body mass by the equation: liver mass=19.6 x Mb(0.91). There was a significant allometric decline in hepatocyte respiration rate (HRR; nmol O2 mg(-1) dry mass min(-1)) with species body mass (kg) described by the relationship: HRR=5.27 x Mb(-0.10). The proportions of hepatocyte oxygen consumption devoted to (i) mitochondrial ATP production, (ii) mitochondrial proton leak and (iii) non-mitochondrial processes were estimated by using excess amounts of appropriate inhibitors. It was found that although hepatocyte respiration rate varied with body mass in birds, these processes constitute a relatively constant proportion of hepatocyte metabolic rate irrespective of the size of the bird species. The respective percentages were 54%, 21% and 25%. The portion of hepatocyte respiration devoted to ATP production for use by the sodium pump was estimated and found to be a relatively constant 24% of hepatocyte respiration and 45% of mitochondrial ATP production in different-sized bird species. These results are discussed in the context of competing theories to explain the metabolism-body size allometry, and are found to support the 'allometric cascade' model.

Adenosine Triphosphate↗
PubMed2004

Ontogenetic patterns of limb loading, in vivo bone strains and growth in the goat radius.

As tetrapods increase in size and weight through ontogeny, the limb skeleton must grow to accommodate the increases in body weight and the resulting locomotor forces placed upon the limbs. No study to date, however, has examined how morphological changes in the limb skeleton during growth reflect ontogenetic patterns of limb loading and the resulting stresses and strains produced in the limbs. The goal of this study was to relate forelimb loads to in vivo bone strains in the radius of the domestic goat (Capra hircus) across a range of gaits and speeds through ontogeny while observing how the growth patterns of the bone relate to the mechanics of the limb. In vivo bone strains in the radius were recorded from two groups of juvenile goats (4 kg, 6 weeks and 9 kg, 15 weeks) and compared with previously reported strain data for the radius of adult goats. Ontogenetic strain patterns were examined in relation to peak forelimb ground reaction forces, ontogenetic scaling patterns of cross-sectional geometry and bone curvature, and percentage mineral ash content. Peak principal longitudinal tensile strains on the cranial surface and compressive strains on the caudal surface of the radius increased during ontogeny but maintained a uniform distribution, resulting in the radius being loaded primarily in bending through ontogeny. The increase in strain occurred despite uniform loading (relative to body weight) of the forelimb through ontogeny. Instead, the increase in bone strain resulted from strong negative growth allometry of the cross-sectional area (proportional to M(0.53)) and medio-lateral and cranio-caudal second moments of area (I(ML) proportional to M(1.03), I(CC) proportional to M(0.84)) of the radius and only a small increase (+2.8%) in mineral ash content. Even though bone strains increased with growth and age, strains in the younger goats were small enough to suggest that they maintain safety factors at least comparable with adults when moving at similar absolute speeds. Increased variability of loading in juvenile animals may also favor the more robust dimensions of the radius, and possibly other limb bones, early in growth.

Analysis of Variance↗
PubMed2005

A functional morphological approach to the scaling of the feeding system in the African catfish, Clarias gariepinus.

Effects of size are pervasive and affect nearly all aspects of the biology of animals and plants. Theoretical scaling models have been developed to predict the effects of size on the functioning of musculo-skeletal systems. Although numerous experimental studies have investigated the effects of size on the movements of skeletal elements during locomotion and feeding in vertebrates, relatively little is known about the scaling of the muscles and bones responsible for the actual movements. Here, we examine the scaling of external morphology, skeletal elements of the feeding system, and a number of cranial muscles to understand how this may affect the movements observed during suction feeding in the African catfish, Clarias gariepinus. The results show that neither the head nor the cranial elements themselves scale according to geometric similarity models. Relative to head size, distinct changes in the mass and configuration of the feeding structures takes place. Unexpectedly, different cranial muscles show different scaling patterns that ultimately all lead to a positive allometry of muscle cross-sectional area relative to fish head size. This suggests that (1) the scaling of the cranial elements cannot be predicted a priori based on the scaling of external head dimensions and (2) the scaling of the feeding system is optimised towards high force output in the larger animals. An analysis of the consequences of the observed changes in morphology with size on performance traits, including bite force and jaw closing velocity, suggests a tight link between the scaling of the feeding system and the natural diet of these fish. Whereas for smaller size classes the system is tuned towards high bite forces, for animals with cranial lengths greater than 65 mm the scaling of the feeding system appears to be dictated by the hydrodynamic constraints on suction feeding.

Africa↗
PubMed1991

Activities of key metabolic enzymes in the heater organs of scombroid fishes.

Maximal in vitro activities of key metabolic enzymes were measured in brain and eye heaters of five species of scombroid fishes. Istiophorid billfishes (blue marlin, striped marlin and Mediterranean spearfish), xiphiid billfishes (Pacific and Mediterranean stocks) and a scombrid fish (butterfly mackerel) were included in the analysis. Our main objectives were (1) to assess the maximum possible substrate flux in heater tissue, and (2) to determine what metabolic substrates could fuel heat production. Heater tissue of all scombroids examined showed extremely high oxidative capacity. Activities of citrate synthase, a commonly measured index of oxidative metabolism, included the highest value ever reported for vertebrate tissue. In most billfishes, citrate synthase activities were similar to or higher than those found for mammalian cardiac and avian flight muscle. Marker enzymes for aerobic carbohydrate metabolism (hexokinase) and fatty acid metabolism (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) also displayed extraordinarily high activities. Activities of carnitine palmitoyltransferase measured in heater organs were among the highest reported for vertebrates. These results indicate that heat production could be fueled aerobically by either lipid or carbohydrate metabolism. Inter- and intraspecifically, heater organs of fishes from the colder Mediterranean waters had a higher aerobic capacity and, hence, a greater heat-generating potential, than fishes from the warmer waters of the Pacific. This difference may be attributed to different thermal environments or it may result from allometry, since fishes caught in the Mediterranean were considerably smaller than those caught in the Pacific.

Animals↗
PubMed1998

Theoretical and empirical scaling patterns and topological homology in bone trabeculae.

Trabecular or cancellous bone is a major element in the structural design of the vertebrate skeleton, but has received little attention from the perspective of the biology of scale. In this study, we investigated scaling patterns in the discrete bony elements of cancellous bone. First, we constructed two theoretical models, representative of the two extremes of realistic patterns of trabecular size changes associated with body size changes. In one, constant trabecular size (CTS), increases in cancellous bone volume with size arise through the addition of new elements of constant size. In the other model, constant trabecular geometry (CTG), the size of trabeculae increases isometrically. These models produce fundamentally different patterns of surface area and volume scaling. We then compared the models with empirical observations of scaling of trabecular dimensions in mammals ranging in mass from 4 to 40x10(6)g. Trabecular size showed little dependence on body size, approaching one of our theoretical models (CTS). This result suggests that some elements of trabecular architecture may be driven by the requirements of maintaining adequate surface area for calcium homeostasis. Additionally, we found two key consequences of this strongly negative allometry. First, the connectivity among trabecular elements is qualitatively different for small versus large animals; trabeculae connect primarily to cortical bone in very small animals and primarily to other trabeculae in larger animals. Second, small animals have very few trabeculae and, as a consequence, we were able to identify particular elements with a consistent position across individuals and, for some elements, across species. Finally, in order to infer the possible influence of gross differences in mechanical loading on trabecular size, we sampled trabecular dimensions extensively within Chiroptera and compared their trabecular dimensions with those of non-volant mammals. We found no systematic differences in trabecular size or scaling patterns related to locomotor mode.

Animals↗