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 649 records · Page 36Linked to original sources
PubMed2001

Ethnicity and skeletal Class III morphology: a pubertal growth analysis using thin-plate spline analysis.

A longitudinal retrospective study using thin-plate spline analysis was used to investigate skeletal Class III etiology in Japanese female adolescents. Headfilms of 40 subjects were chosen from the archives of the Orthodontic department at Niigata University Dental Hospital, and were traced at IIIB and IVA Hellman dental ages. Twenty-eight homologous landmarks, representing hard and soft tissue, were digitized. These were used to reproduce a consensus for the profilogram, craniomaxillary complex, mandible, and soft tissue for each age and skeletal group. Generalized least-square analysis revealed a significant shape difference between age-matched groups (P < .001), except for the craniomaxillary complex at stage IVA. T test for size analysis showed unequivocally increased mandibular size in skeletal Class III, which directly increased the craniofacial size collectively (P < .05). A deviant profilogram showed anisotropy displaying as maxillary deficiency, acute cranial base, and obtuse gonial angle in addition to increased facial height at stage IIIB. Maxillary retrusion decreased while the mandible showed excessive incremental growth and a forward position caused by deficient orthocephalization at stage IVA. Craniomaxillary complex total spline and partial warps (PW)3 and 2 showed a maxillary retrusion at stage IIIB opposite an acute cranial base at stage IVA. Mandibular total spline and PW4, 5 showed changes affecting most landmarks and their spatial interrelationship, especially a stretch along the articulare-pogonion axis. In soft tissue analysis, PW8 showed large and local changes which paralleled the underlying hard tissue components. Allometry of the mandible and anisotropy of the cranial base, the maxilla, and the mandible asserted the complexity of craniofacial growth and the difficulty of predicting its outcome.

Adolescent↗
PubMed2003

Population pharmacokinetics of ciprofloxacin in pediatric patients.

The objective of this study was to characterize ciprofloxacin population pharmacokinetics in pediatric patients. A total of 150 pediatric patients (including 28 patients with cystic fibrosis [CF], ages 0.27-16.9 years) received ciprofloxacin by the oral and/or intravenous routes. Population pharmacokinetic analyses were performed with NONMEN software. Exponential error models were used to describe the interindividual variance in pharmacokinetic parameters, and the residual error model included both proportional and additive components. Based on principles of allometry, the patient's body weight was used as a covariate, along with appropriate allometric exponents, in the construction of the base model. Model building was accomplished by a stepwise forward inclusion procedure, and the final model was evaluated by multiple techniques, including bootstrap, leverage analysis, and cross-validation. With body weight included in the model (two compartments with first-order absorption), ciprofloxacin clearance was influenced by age, and the absorption rate constant was altered in CF patients. The final model is summarized as follows: CL(L/h) = 30.3 x (WT/70)0.75 x (1 + 0.045 [AGE-2.5]), VC(L) = 56.7 x (WT/70)1.0, VP(L) = 89.8 x (WT/70)1.0, Q(L/h) = 37.5 x (WT/70)0.75, Ka (1/h) = 1.27 x (1 + [-0.611 x CF]), absorption lag time = 0.35 hours, and bioavailability fraction = 61.1%, where WT and AGE are the patient's body weight (kg) and age (years), respectively, and the variable CF equals 1 for CF patients and 0 for non-CF patients. The interpatient variability in pharmacokinetic parameters (percentage coefficient of variation [%CV]) ranged from 22.5% to 49.8%. The residual variabilities (%CV) for the oral and intravenous data were 40% and 27%, respectively. The shared additive residual variance component was small (SD = 0.04 mg/L). Model evaluation by the different methods indicated that the final model was robust and parameter estimates were precise. A small difference (< 6%) was noted when the patient's age was not used in dose calculation. Therefore, in routine clinical use, for pediatric patients older than 3 months, ciprofloxacin dose may be calculated solely based on body weight.

Administration, Oral↗
PubMedDate not supplied

Quantitative growth of the eye in the human fetus.

Eye weight growth was studied in 50 human fetuses aged 14 to 39 weeks after conception. The collected date was correlated with fetal maturity parameters (festational age and fetal weight) using the allometric method. Normal eye weight curves were obtained. The results indicate that eye weight growth present negative allometry. These curves may be important for the diagnosis of fetal eye malformations, and may indicate that noninvasive method such as ultrasounds can be used.

Embryonic and Fetal Development↗
PubMedDate not supplied

[Statistical analysis of biological breakdown of nicotinic acid 7-14C in rat liver of various weight].

Statistical methods are considered for eliminating the errors caused by the individual fluctuations of the animals organs weight, different ratio of organs weight to the weight statistical processing the data on the dynamics of labelled nicotinic acid evacuation and determination of the acid half-life in the rat liver. The mean liver weight was estimated by means of Huxley's allometry formula. Dynamics of NA was approximated by using the formula kappa=ate-betat in the computer "MHP-2" and the least squares method.

Analysis of Variance↗
PubMedDate not supplied

[Relative growth of the human cerebellum: a quantitative estimate].

The relative growth of the cerebellum was studied in 300 human foetuses by using of the equation Y = bxk. The cerebellum weight was correlated to the cephalic perimeter and to the fetal weight. The relative growth of the cerebellum presented positive allometry (k = 3.3; k = 1.3 respectively). Masculine foetus presented greater index than feminine foetus.

Cerebellum↗
PubMedDate not supplied

[Prenatal growth of the human skull: quantitative study].

The relative growth of the skull was studied in 300 human foetuses by using of the allometric equation Y = aXb. The skull growth was correlated to the crown-rump length and to the fetal weight. The relative growth of the skull presented positive allometry. Masculine foetus presented greater index than feminine foetus.

Female↗
PubMed2003

A cephalometric comparison of skulls from different time periods--the Bronze Age, the 19th century and the present.

The aim of this study was to evaluate secular trends by means of orthodontic measurements on lateral cephalograms. We use roentgenograms from three populations: 22 Bronze Age skulls from a cemetery near Hainburg/Austria, 140 soldiers who served in the Hapsburg Imperial Army in the late 19th century, and 154 contemporary recruits of the Austrian Federal Army. Using conventional morphometric analysis, no statistically significant differences could be established. But applying geometric morphometrics to the 2D-coordinates of the pentagon composed of the landmarks Sella, Nasion, Articulare, Gonion and Menton, some biologically interpretable differences were detected, the size allometry between the 19th- and 20th-century populations being the only notable one. We conclude that landmarks should be digitized directly (and many more of them) and that conventional methods used in clinical orthodontics are inappropriate for addressing the scientific questions approached here.

Anthropology, Physical↗
PubMed1992

Relationship between the lingual fossa depth, mesiodistal and bucolingual diameter of dental crown in permanent maxillary incisors with the living Slovenians.

On 311 dental stone casts of living children aged from 8 to 12 years, were measured the lingual fossa depth, MD diameter, and the BL diameter of the permanent maxillary incisors. The correlations and the differences of measured variables between left and right incisors, centrals and laterals, male and female incisors as well as the correlations between measured variables themselves were analysed. High left-right symmetry was established, except for directional asymmetry in female centrals. A significant positive correlation in terms of positive allometry between the lingual fossa depth and MD diameter was found. In the light of these results, the significance of the lingual fossa depth as a factor of strength is discussed.

Child↗
PubMed1992

A four-parameter generalization of the Gompertz curve suitable for somatic growth.

A four-parameter generalization of the Gompertz curve is proposed which passes through the origin with respect to total age and is often more suitable for somatic growth than the three-parameter Gompertz curve. Applied to published cross-sectional data on 44 male white rats, the new curve differs from another four-parameter curve proposed earlier by Jolicoeur and Pirlot (1988) in that it does not involve initial growth delays and it avoids an arbitrary assumption concerning the initial curvature, but it nevertheless yields approximately similar descriptions of chronological growth and complex allometry. The new four-parameter version of the Gompertz curve may be useful in cases where other growth curves do not provide a satisfactory fit.

Animals↗
PubMed2005

Conserved ontogeny and allometric scaling of resource acquisition and allocation in the Daphniidae.

Life histories vary widely among taxa, but within phylogenetic groups there may be a fundamental framework around which trait variation is organized, perhaps as a consequence of lineage-specific developmental constraints. In organisms with indeterminate growth, there is an ongoing problem of optimally allocating resources between growth and reproduction, and that allocation decision may manifest itself through allometric scaling. Previous work on freshwater zooplankton has shown that the ontogenetic pattern of resource allocation can be described by simple mathematical functions. An important component of understanding how such functions can explain life-history variation is to discover which parameters in these functions are robust, with respect to both resource availability and evolutionary diversification, and which parameters exhibit interspecific allometry. To shed light on these issues, detailed life table experiments were conducted on eight species in the family Daphniidae (Crustacea) at high and low levels of resources. Using data on growth, reproduction, and instar duration, the ontogeny of resource allocation to growth and reproduction could be described as functions that plateau at or shortly after the onset of maturity. To be sure that the results were not an artifact of phylogenetic structure, the parameters were tested in a phylogenetically controlled fashion. The results suggest a simple set of resource allocation rules for daphniids, whereby all species exhibit a similar form of ontogenetic change in allocation, and reach a plateau where approximately 94% of available resources are allocated to reproduction. The asymptotically maximal rate of net resources incorporated in growth and reproduction was positively related to size at maturity, whereas the rates of approach to plateaus (for both net resource assimilation and proportional allocation to reproduction) were negatively related to body size. Per-offspring investment was positively related to the square root of size at maturity. Using this approach, a wide range of interspecific variation in life-history features can be related to a single underlying trait, the size at first reproductive investment.

Adaptation, Physiological↗
PubMed1992

Ontogenetic body form changes in three ecological morphotypes of anuran tadpoles.

Metamorphic vertebrate species are of particular interest in ecological and evolutionary studies because the decoupling of larval and adult growth patterns potentially allows adaptive diversifications of the separate stages. Larval and adult growth might be much more constrained if allometric patterns were constant throughout ontogeny. To better understand how differential growth patterns might contribute to tadpole diversification, we have analyzed growth allometries in relation to interspecific morphometric differences in Gastrophryne carolinensis, Acris gryllus, and Hyla gratiosa. Growth patterns in all species are significantly allometric and moderately concordant, despite many differences in detail. The species can be completely discriminated in even the smallest post-hatching tadpoles. However, the differences that distinguish the species do not seem to be a function of differential growth patterns at the tadpole stage. Rather, morphological differences ostensibly originate during embryonic development and are well established by the time the tadpoles become free-swimming.

Animals↗
PubMed2005

[Module structure and growth pattern of Stipa baicalansis clone in Songnen Plain of China].

By the method of digging up whole tiller tuft, this paper quantitatively analyzed the module structure and growth pattern of Stipa baicalansis clone under the cultural conditions in the Songnen Plain of Northeast China. The results showed that after two growth seasons of vegetative reproduction, the tuft size of the clone in its growth stopping period at the end of September was 9.4 +/- 3.24 cm, and the total number of the clonal modules was 161.5 +/- 85.2, among which, the individuals of reproductive and vegetative tillers were 14.6 +/- 11.48 and 146.9 +/- 78.70, occupying 9.25% and 90.75% of the total, respectively. The total biomass of the clonal modules was 53.8 +/- 34.22 g, and the biomass of reproductive and vegetative tillers was 25.0 +/- 20.34 g and 28.8 +/- 19.43 g, occupying 43.75% and 56.25% of the total, respectively. With the increase of tuft size, the number of different modules was in a linear isogony growth, while their biomass was in an power allometry growth. There was a significant (P < 0.05) or very significant (P < 0.01) power positive correlation between the biomass of different modules and the number and total biomass of clonal modules. The mean productivity of unit reproductive tiller was about ten times higher than that of unit vegetative tiller, and the phenotype plasticity of the number and biomass of reproductive tiller was larger than that of vegetative tiller.

Biomass↗
PubMed2006

Inbreeding depression, increased phenotypic variance, and a trade-off between gonads and appendages in selfed progeny of the aphid Prociphilus oriens.

Trade-offs are potentially common among two or more traits whose development is dependent on the same resources. To detect genetic trade-offs, the techniques of quantitative genetics, pedigree analyses, and selection experiments have been used. This study demonstrates genetically based trade-offs between gonads and appendages in hatched larvae of the aphid Prociphilus oriens by focusing on enlarged variance among the families of selfed progeny. The selfed and outbred families were compared in respect to the size of morphological traits, gonad volume, and hatch dates as well as egg volume. Selfing not only increased the among-family variance component in all larval traits examined, but it also increased the mean size of all the morphological traits significantly. In contrast, gonad volume, a fitness component, was reduced with selfing. Calculation of the allometry (log-transformed regression) of larval traits to egg volume indicated that in the outbred group, morphological traits grew slowly relative to egg volume with slopes below 0.25, whereas gonads exhibited isometric growth. With selfing, most morphological traits had significantly steeper slopes, whereas the slope for gonads was greatly decreased. When the effect of egg volume was statistically removed from the means of selfed families, significant negative correlation was detected between the adjusted means of gonad volume and those of tibia length. This result suggests genetic trade-offs between gonad volume and tibia length. Thus, the evidence implies that at the loci governing the development of appendages, the dominant alleles function to canalize the development of tibiae into an optimal size, irrespective of egg volume. It is hypothesized that increased homozygosity of the deleterious recessive alleles reduced gonad volume through increasing the resource allocation to tibiae. The hypothesis of the gonad-appendage trade-off could be applied to explain the phenotypic evolution in some aphid species.

Animals↗
PubMed2006

Life-history and ecological correlates of geographic variation in egg and clutch mass among passerine species.

Broad geographic patterns in egg and clutch mass are poorly described, and potential causes of variation remain largely unexamined. We describe interspecific variation in avian egg and clutch mass within and among diverse geographic regions and explore hypotheses related to allometry, clutch size, nest predation, adult mortality, and parental care as correlates and possible explanations of variation. We studied 74 species of Passeriformes at four latitudes on three continents: the north temperate United States, tropical Venezuela, subtropical Argentina, and south temperate South Africa. Egg and clutch mass increased with adult body mass in all locations, but differed among locations for the same body mass, demonstrating that egg and clutch mass have evolved to some extent independent of body mass among regions. A major portion of egg mass variation was explained by an inverse relationship with clutch size within and among regions, as predicted by life-history theory. However, clutch size did not explain all geographic differences in egg mass; eggs were smallest in South Africa despite small clutch sizes. These small eggs might be explained by high nest predation rates in South Africa; life-history theory predicts reduced reproductive effort under high risk of offspring mortality. This prediction was supported for clutch mass, which was inversely related to nest predation but not for egg mass. Nevertheless, clutch mass variation was not fully explained by nest predation, possibly reflecting interacting effects of adult mortality. Tests of the possible effects of nest predation on egg mass were compromised by limited power and by counterposing direct and indirect effects. Finally, components of parental investment, defined as effort per offspring, might be expected to positively coevolve. Indeed, egg mass, but not clutch mass, was greater in species that shared incubation by males and females compared with species in which only females incubate eggs. However, egg and clutch mass were not related to effort of parental care as measured by incubation attentiveness. Ecological and life-history correlates of egg and clutch mass variation found here follow from theory, but possible evolutionary causes deserve further study.

Animals↗
PubMed1991

[Component analysis of craniologic characters of silver foxes (Vulpes fulvus Desm.) and their changes arising under domestication].

The data on cranial measurements performed in silver foxes indicate that there are differences in sizes measured between the farm foxes--bred population and the population selected for domestication. A method of principal components was used to analyse the cranial measurements and their changes under domestication. The first component covers about 50% of cranial diversity, which is interpreted as variation in the total skull size. This component clearly separates the two sexes, but not different populations. The second component presumably reflects the growth rate allometry between the skull length and width. The third and fourth components are measurements of skull width; the fifth one reflects the sizes of brain skull. None of these components clearly separate the foxes from farm--bred and domesticated populations. However, some differences in distribution are observed.

Animals↗
PubMed1991

The brain sizes of living elasmobranchii as their organization level indicator. I. General analysis.

The relationship between brain and body masses of 64 species and subspecies of modern sharks and skates was investigated. It was established that the level of their encephalization in terms of the polygons of encephalization and the allometry coefficient (alpha), shows quite obviously the general organization level of one or another taxon of sharks and skates. Alpha = 0.56 for the class of cartilaginous fishes, and for the superorder of sharks and skates alpha = 0.54 and 0.61, accordingly. For several orders alpha constitutes: sharks--common for relict Hexanchiformes and Heterodontiformes 0.44, Squaliformes 0.43 and Carcharhiniformes 0.52 and skates--Rajiformes 0.44 and Dasyatiformes 0.52. All values are similar to those of other vertebrates and the theoretically calculated value of alpha (0.67). It was established the "place" of present-day Elasmobranchii and all cartilaginous fishes in the evolutionary row of Gnathostomata and Craniata on the developing and relative sizes of CNS, and the corrected alpha value for this particular vertebrate class was specified which was found to be sensationally high also in the works of foreign and native authors (Bauchot et al., 1976; Northcutt, 1978; Ebbesson, 1980; Kreps, 1980).

Animals↗
PubMed1991

Cardiac growth in staged human embryos--stages from 15 to 23, post-somitic period.

The cardiac growth was studied in 27 human embryos staged in post-somitic period (stages from 15 to 23, Carnegie Institution of Washington). The cardiac volume was determined by morphometric methods (point-counting planimetry on serial sections) and examined relative to gestational age, to crown-rump length and to the embryo body weight. The data were transformed into logarithms and bivariate relations were analyzed according to allometric equations of the form log y = k (log x) + log b. The data were fitted according to 3 techniques: least squares, major axis and reduced major axis. The allometric regressions slopes (k) indicate positive allometry of the cardiac volume relative to the embryonic age and isometry relative to body weight. The present work will be useful when image techniques, as ultrasonography, turn it possible to evaluate quantitatively the embryonic heart.

Cross-Sectional Studies↗
PubMed1991

Scaling placental oxygen diffusion to birthweight: studies on placentae from low- and high-altitude pregnancies.

Stereological analysis of tissue sections has been used to estimate partial and total conductances of the human placental oxygen diffusion pathway. Analyses were undertaken for neonates and term placentae from populations living at low (400 m) and high (3600 m) altitude in Bolivia. Relationships between conductances and birthweight (and between trophoblast volume and birthweight) were explored by linear regression analysis and allometry. At both altitudes, the three partial conductances on the maternal side of the oxygen pathway scaled to birthweight in a similar fashion. This similarity did not extend to conductances on the fetal side. Beyond a limiting weight of roughly 3 kg, the highland fetus was disadvantaged in terms of its placental oxygen diffusive conductances and trophoblast volume. The findings support the notion that the structural adaptations seen at high altitude are more successful on the maternal rather than the fetal side of the placenta.

Adaptation, Physiological↗