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PubMedDate not supplied

Correlates of average daily metabolism of field-active zebra-tailed lizards (Callisaurus draconoides).

The extent of variation in reptile field metabolism, and its causal bases, are poorly understood. We studied the energetics of the insectivorous lizard Callisaurus draconoides at a site in the California Desert (Desert Center) and at a site at the southern tip of the Baja Peninsula (Cabo San Lucas; hereafter, Cabo). Reproducing Callisaurus were smaller at Cabo than at Desert Center. The allometry of metabolism with body mass can account for most differences in whole-animal metabolism. There was no significant effect of sex or source population on mass-adjusted metabolic rate in the laboratory (resting metabolism, measured by closed-system respirometry) or in the field (field metabolism, measured with doubly labeled water). The mass-adjusted resting metabolism and field metabolism of gravid females and the field metabolism of juvenile lizards were not significantly different from those of nonreproductive adults. Temperature had a significant effect on resting metabolism (Q10 = 2.7); fed lizards had resting metabolism that was 22% higher than that of fasted lizards; field metabolism was positively correlated with growth rate in juveniles; and field metabolism of adults increased from spring to late summer at Desert Center by 25%, probably because of longer activity period length and slightly higher activity period body temperature. We calculated from water influx and field metabolism that juveniles allocated 18% of their metabolizable energy intake to growth and that most energy deposited into eggs was transferred from energy stores rather than ingested in the weeks prior to laying.

Aging↗
PubMed2005

Interaction between Orobanche crenata and its host legumes: unsuccessful haustorial penetration and necrosis of the developing parasite.

BACKGROUND AND AIMS: Orobanche species represent major constraints to crop production in many parts of the world as they reduce yield and alter root/shoot allometry. Although much is known about the histology and effect of Orobanche spp. on susceptible hosts, less is known about the basis of host resistance to these parasites. In this work, histological aspects related to the resistance of some legumes to Orobanche crenata have been investigated in order to determine which types of resistance responses are involved in the unsuccessful penetration of O. crenata. METHODS: Samples of resistance reactions against O. crenata on different genotypes of resistant legumes were collected. The samples were fixed, sectioned and stained using different procedures. Sections were observed using a transmission light microscope and by epi-fluorescence. KEY RESULTS: Lignification of endodermal and pericycle host cells seems to prevent parasite intrusion into the root vascular cylinder at early infection stages. But in other cases, established tubercles became necrotic and died. Contrary to some previous studies, it was found that darkening at the infection site in these latter cases does not correspond to death of host tissues, but to the secretion of substances that fill the apoplast in the host-parasite interface and in much of the infected host tissues. The secretions block neighbouring host vessels. This may interfere with the nutrient flux between host and parasite, and may lead to necrosis and death of the developing parasite. CONCLUSIONS: The unsuccessful penetration of O. crenata seedlings into legume roots cannot be attributed to cell death in the host. It seems to be associated with lignification of host endodermis and pericycle cells at the penetration site. The accumulation of secretions at the infection site, may lead to the activation of xylem occlusion, another defence mechanism, which may cause further necrosis of established tubercles.

Fabaceae↗
PubMed2006

Above- and below-ground biomass relationships across 1534 forested communities.

BACKGROUND AND AIMS: Prior work has shown that above- and below-ground dry biomass across individual plants scale in a near isometric manner across phyletically and ecologically diverse species. Allometric theory predicts that a similar isometric scaling relationship should hold true across diverse forest-types, regardless of vegetational composition. METHODS: To test this hypothesis, two compendia for forest-level above- and below-ground dry biomass per hectare (M(A) and M(R), respectively) were examined to test the hypothesis that M(A) vs. M(R) scales isometrically and in the same manner as reported for data from individual plants. Model Type II regression protocols were used to compare the numerical values of M(A) vs. M(R) scaling exponents (i.e. slopes of log-log linear relationships) for the combined data sets (n =1534), each of the two data sets, and data sorted into a total of 17 data subsets for community- and biome-types as well as communities dominated by angiosperms or conifers. KEY RESULTS: Among the 20 regressions examined, 15 had scaling exponents that were indistinguishable from that reported for M(A) vs. M(R) across individual plants. The isometric hypothesis could not be strictly rejected on statistical grounds; four of these 15 exponents had broad 95% confidence intervals resulting from small sample sizes. Significant variation was observed in the y-intercepts of the 20 regression curves, because of absolute differences in M(A) or M(R). CONCLUSIONS: The allometries of forest- and individual plant-level M(A) vs. M(R) relationships share strikingly similar scaling exponents, but differ because of considerable variation in y-intercepts. These results support prior allometric theory and provide boundary conditions for the scaling of M(A) and M(R).

Biomass↗
PubMed2005

A macroglomerulus in the antennal lobe of leaf-cutting ant workers and its possible functional significance.

Ants have a well-developed olfactory system, and pheromone communication is essential for regulating social life within their colonies. We compared the organization of primary olfactory centers (antennal lobes, ALs) in the brain of two closely related species of leaf-cutting ants (Atta vollenweideri, Atta sexdens). Both species express a striking size polymorphism associated with polyethism. We discovered that the ALs of large workers contain a substantially enlarged glomerulus (macroglomerulus, MG) at the entrance of the antennal nerve. This is the first description of an MG in non-sexual individuals of an insect. The location of the MG is laterally reversed in the two species, and workers of different size express a disproportional allometry of glomerular volumes. While ALs of large workers contain an MG, glomeruli in small workers are all similar in size. We further compared electroantennogram (EAG) responses to two common trail pheromone components of leaf-cutting ants: 4-methylpyrrol-2-carboxylate and 2-ethyl-3,6-dimethylpyrazine. At high concentrations the ratio of the EAG signals to 2-ethyl-3,6-dimethylpyrazine versus 4-methylpyrrol-2-carboxylate was significantly smaller in A. vollenweideri compared with the ratio of EAG signals to the same two components in A. sexdens. The differences in EAG signals and the species specific MG location in large workers provide correlative evidence that the MG may be involved in the detection of the trail pheromone.

Animals↗
PubMed2006

Developmental and functional evidence of nuclear immaturity in prepubertal oocytes.

BACKGROUND: The nuclear compartment has been proposed as responsible for the developmental arrest of prepubertal mouse oocytes while the studies on prepubertal sheep and cow oocyte model suggested the cytoplasm immaturity accounts for this failure. METHODS: The apparent disagreement on the causes of developmental defects between these two species prompted us to study: (i) follicular and oocyte growth allometry in lambs, (ii) oocyte compartment (nucleus versus cytoplasm) responsible for developmental failure by nucleus exchange between lamb and adult sheep oocytes, (iii) nucleolar features of prepubertal oocytes by ultrastructural observation and (iv) in vivo developmental survey of prepubertally derived embryos. RESULTS: The oocyte growth inside the follicle is asynchronous during prepuberty. The nuclear transfer revealed that the lamb nucleus was responsible for developmental failure. Immature fibrillogranular structure of the nucleolus has been revealed in small lamb oocytes and also in a few adult-size lamb oocytes. Studies in vivo revealed a high occurrence of developmental arrest of prepubertal derived fetuses, which we have attributed to the low genome-wide methylation detected in prepubertal oocytes. CONCLUSIONS: Our studies have indicated incomplete nuclear maturation of prepubertal gamete. The implication of this finding suggests caution when the strategy of rescue of prepubertal oocytes for assisted fertilization is considered such as in the case of therapeutic treatment which precludes the maintenance of fertility of sexually immature patients.

Animals↗
PubMed1991

Animal pharmacokinetics and interspecies scaling of FCE 22101, a penem antibiotic.

The pharmacokinetics of FCE 22101 were studied in rats, rabbits, Cynomolgus monkeys and dogs after intravenous administration. Pertinent pharmacokinetic parameters were determined according to a two-compartment model and correlated among species as an exponential function of body weight, thereby allowing an estimation of pharmacokinetic parameters corresponding to a 70 kg man. Allometric equations, including data on humans reported in the literature, were also established and used to study similarities and differences in the disposition of FCE 22101 among species. The pharmacokinetic profile of FCE 22101 was consistent with the principles of allometry in all animal species studied (and in man) with the exception of the Cynomolgus monkey, in which clearance of FCE 22101 was slower than expected.

Animals↗
PubMed1988

Arterial drug infusion: pharmacokinetic problems and pitfalls.

The pharmacokinetic theory of intra-arterial drug administration has been clearly articulated. It provides a useful guide to the development and interpretation of preclinical studies and clinical trials. Despite the clarity and usefulness of the theory, there are misunderstandings of its implications and technical problems associated with its implementation. Few studies have been properly designed to validate the theory experimentally. Independence of steady-state pharmacokinetic advantage on intraregion blood flow differences predicted for a nonextracted drug is counterintuitive. Extrapolation from laboratory animals to humans raises some important questions of allometry, particularly for the brain, which does not follow the scaling rules applicable to other organs. Finally, drug streaming from the site of infusion has been observed in vitro and in vivo. The extent of the resulting clinical problem has not been adequately characterized, but it may be severe under some circumstances.

Animals↗
PubMed2006

Stay wet or else: three ways in which plants can adjust hydraulically to their environment.

The literature on whole-plant acclimation to drought is reviewed and it is proposed that leaf-level homeostasis in water status is attained during ontogeny largely thanks to whole-plant changes in physical resistance to liquid water flow caused by morphological and anatomical adjustments. It is shown that, in response to water deficits, plant resistance changes at different levels (tissue, organ, individual), levels that are correlated with the time scale of the response. It was found that such adjustments apparently tend to increase resistance to flow in the short term and to reduce it in the long term. A critical view of those findings is provided based on the principle that drought-induced changes cannot be analysed separately from the allometric changes that take place through ontogeny, as for example proposed by the widely cited hydraulic limitation hypothesis. A graphic synthetic model is presented according to which developmental responses to water deficits operate largely through reductions in whole-plant water transport capacity, combined with more or less strong reductions in leaf area (different "hydraulic allometries"), depending on the intrinsic tolerance of leaf tissues to partial desiccation. The model is used to show that, as the result of such adjustments, the water transport capacity per unit leaf area can decrease, remain constant, or increase, and it is argued that the expected leaf-level response would be different in each case, respectively involving a decreased, constant, or increased potential for transpiration. The article ends with a plea to collect the evidence needed to evaluate the occurrence of these three different response types across taxa and their association with different environments, including the reanalysis of existing data.

Acclimatization↗
PubMed1997

Finite element analysis of the cranial base in subjects with Class III malocclusion.

The association between cranial base morphology and Class III malocclusion is poorly understood. This study analyses local shape- and size differences in cranial base configurations of Class I and Class III subjects, employing finite element (FEM) analysis. Seventy-three prepubertal European-American children with Class III malocclusion were compared to their counterparts with a normal, Class I molar occlusion. Lateral cephalographs were traced, checked and subdivided into age- and sex-matched groups. Thirteen points on the cranial base were identified and digitized, providing a geometrical cranial base representation. Average cranial geometries were scaled to an equivalent size and a FEM analysis, capable of depicting and quantifying local shape- and size-change, employed to highlight regionalized, morphological differences. While the anterior cranial base was more homogeneous for shape-change, significant, localized anisotropy in the posterior regions of the cranial base and around sella turcica was evident. For size-change, areas of negative allometry were located posteriorly, but dilations in the mid- and anterior cranial base also were apparent. It is concluded that morphological alterations within the petro-occipital complex accompanied by changes in the sphenoidal and ethmoidal regions induce deviation from a normal cranial base configuration to one associated with deficient orthocephalization and an appearance of Class III malocclusion.

Age Factors↗
PubMed1999

Evaluation of the parameters needed to describe the overall growth, the chemical growth, and the growth of feathers and breast muscles of broilers.

An experiment was carried out to collect data suitable for testing methods used to describe the potential growth and body composition curves of broilers. Males and females of two commercial broiler strain-crosses were grown to 16 wk of age with birds taken at 0, 2, 4, 6, 8, 12, and 16 wk of age for chemical analysis and for the measurement of feather weight and breast meat (Pectoralis major and Pectoralis minor) weight at these ages. The data were used to test the Gompertz growth equation and the assumption of chemical allometry, as well as to estimate the values of the growth parameters for the different genotypes. Feeding and environmental conditions were intended to be such that potential growth and body composition could be attained. The weights of the chemical components for each of the four genotypes were described in terms of the mature weight of these components, their rates of maturing, and the time taken to reach the maximum rate of growth of each component. Allometric relationships between the weights of the chemical components and that of body protein were estimated. The ratio of ash to protein was essentially constant. Water matured more slowly, and lipid faster, than protein. For males, and for females up to 8 wk, the models were satisfactory. For females after this age, lipid growth was faster than expected from the earlier period, probably in preparation for egg production. There were small, but important, differences in the values of some parameters between the strain-crosses. For each of the four genotypes the changes in weight of feathers and breast meat with time were described in terms of the Gompertz growth function, which described the data very well. The parameters of the function for each component and genotype-mature weight, rate of maturing, and the time taken to reach the maximum rate of growth B were evaluated. For the feathers, the value of the rate parameter was higher than that estimated for the body as a whole. For the two breast muscles, and for their total weight, the value of the rate parameter was similar to that for the body as a whole. There was a simple allometric relationship between the weights of the breast muscles and that of the whole body. As a consequence, the development of the yield of breast meat for a given genotype could be described by the values of the two parameters: mature yield and the allometric exponent. A description of each genotype of interest is seen as an essential first step in using a simulation model either to predict requirements, or to predict the effects of different feeding programs, and environmental conditions, on the performance of broilers.

Animal Husbandry↗
PubMed1997

Evidence for red:far red signaling and photomorphogenic growth response in Douglas-fir (Pseudotsuga menziesii) seedlings.

In a greenhouse experiment, potted coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown in miniature "Nelder" (Nelder 1962) plots where growing space varied from 265 to 2555 cm(2) per plant. After thirty weeks, mean plant height, crown biomass and branch number increased significantly (P = 0.0141) with decreasing growing space (increasing plant density). Differences in height growth became apparent about six weeks after sowing. Furthermore, horizontally reflected radiation measured within the Nelder plots showed a decrease in red:far-red ratio (R:FR) from 1.2 at the lowest density to 0.71 at the highest. Plant height was strongly inversely correlated with estimated phytochrome photoequilibrium values (r(2) = 0.893). Field measurements made in a three-year-old variable density plantation also showed a decrease in R:FR with increasing planting density from 300 to 3,000 trees ha(-1). These results support the hypothesis that young Douglas-fir seedlings are able to detect, through the phytochrome system, the presence of nearby seedlings owing to the depletion of R relative to FR in the spectra reflected by the foliage of the adjacent plants. They then adjust their growth allometry in a way that reduces the possibility of being over topped by these future competitors.

Journal Article↗
PubMed1999

Above- and belowground biomass and primary productivity of a Larix gmelinii stand near Tura, central Siberia.

We assessed above- and belowground biomass and net primary production (NPP) of a mature Larix gmelinii (Rupr.) Rupr. forest (240-280 years old) established on permafrost soils in central Siberia. Specifically, we investigated annual carbon budgets in roots in relation to root system development and availability of soil resources. Total stand biomass estimated by allometry was about 39 Mg per ha. Root biomass (17 Mg per ha) comprised about 43% of total biomass. Coarse root (>/= 5 mm in diameter) biomass was about twice that of fine roots (< 5 mm). The aboveground biomass/root biomass ratio (T/R) of the larch stand was about unity, which is much less than that of other boreal and subalpine conifer forests. The proportion of fine roots in total root biomass (35%) was relatively high compared with other cold-climate evergreen conifer forests. Total NPP, defined as the sum of annual biomass increment of woody parts and needle biomass, was estimated to be 1.8 Mg per ha per year. Allocation of total NPP to needle production was 56%. The proportion of total NPP in belowground production (27%) was less than for evergreen taiga forests. However, belowground NPP was probably under-estimated because root mortality was excluded. We conclude that L. gmelinii trees invested annual carbon gains largely into needle production or roots, or both, at the expense of growth of aboveground woody parts. This carbon allocation pattern, which resulted in the construction of exploitative root networks, appeared to be a positive growth response to the nutrient-poor permafrost soil of central Siberia.

Journal Article↗
PubMed2004

Modeling topographic effects on net ecosystem productivity of boreal black spruce forests.

Current regional estimates of net primary productivity (NPP) of boreal black spruce overlook the large variation in NPP caused by small-scale topographic effects on soil water, temperature and nutrient availability. Topographic effects on black spruce NPP could likely be modeled by simulating the lateral and vertical movement of water, and its effects on soil nutrient transformation and uptake, through three-dimensional watersheds defined by aspects and slopes of their topographic positions. To examine this likelihood, the ecosystem model 'ecosys' was run for 120 years on a transect that included upper- and lower-slope positions and a basin in which a basal water table was set 0.5 m below the soil surface. For the run, we used soil properties and weather conditions recorded at the 115-year-old BOREAS Southern Old Black Spruce site. Short-term model performance was tested by comparing diurnal and annual carbon (C) transfers simulated under 1994 weather conditions during the 115th year of the model run with those measured at this site during 1994 by eddy covariance, surface chambers and allometry. After 115 years, annual spruce NPP simulated at the upper-slope positions was twice that at the basin (350 versus 170 g C m-2), whereas accumulated wood C was almost three times as large (6.8 versus 2.4 kg C m-2). In the model, increases in NPP and wood growth in upper-slope positions were caused by lower soil water contents, higher soil temperatures, and more rapid O2 uptake that accelerated heterotrophic respiration and hence nutrient mineralization and uptake. Modeled differences in wood growth with topographic position were quantitatively consistent with measurements of boreal black spruce at several research sites differing in water table depth. Modeled differences also agreed with differences in wood growth rates derived from allometric measurements at boreal black spruce sites differing in productivity indices as a result of differences in subsurface hydrology. The magnitude of these differences clearly indicates the importance of accounting for subsurface hydrology in regional estimates of boreal forest productivity.

Cell Respiration↗
PubMed2005

Analysis of biomass accumulation and stem size distributions over long periods in managed stands of Pinus sylvestris in Finland using the 3-PG model.

We tested the performance of a process-based model (PBM) in relation to long-term mensuration data from two sites in Finland where the stands were up to 90 years old and had been thinned at approximately 5-year intervals over the last 50 years. The PBM used was based on the 3-PG (Physiological Principles to Predict Growth) model developed by Landsberg and Waring (1997), with modifications in the biomass allocation routine, for which we used data and calculations by Vanninen (2003) to estimate the allocation coefficients and turnover rates. Site fertility was estimated in terms of known site-type characteristics. The model was evaluated in terms of stand development and its ability to simulate responses to thinning; stem numbers after thinning were specified at the dates when the thinning took place. Stand development in terms of basal area, volume and mean diameter at breast height, closely followed the measured characteristics of all stands. Foliage mass predictions were close to estimates obtained by an empirical method. The analysis shows that, under normal thinning regimes, a range of different thinning intensities can be adequately described using a simple multiplicative model relating the proportion of volume and foliage mass removed to the corresponding proportion of stem numbers. This model, together with stem allometry data, described the "growth" in mean diameter after thinning, which simply reflected the removal of the smaller trees. These results indicate that, with a single set of parameter values, 3-PG can provide good descriptions of the growth patterns of trees-in this case Pinus sylvestris L.-over long periods, including growth after repeated thinning. One of the outputs from the 3-PG model is mean stem diameter (B): we show that it is feasible to estimate stem size distributions, which changed considerably over the life of these stands, from B using the Weibull function. This shows that, given information about the Weibull parameters for particular species and cultural systems, it should be possible to use stem numbers and the B obtained from the 3-PG model to produce information about stem size distributions from simulated data.

Biomass↗
PubMed1986

Allometric determination of the distance from the central venous pressure port to wedge position of balloon-tip catheters in pediatric patients.

Position of the CVP port on a flow-directed balloon-tip pulmonary arterial catheter affects the accuracy of both thermodilution cardiac output determinations and CVP measurements. Systemic allometry (the study of the growth of a part in relation to the total organism) has been used to determine an easily measured independent variable that would predict this position. Sixty-one pediatric patients (aged 0 to 165 months) were studied either at autopsy or at the time of cardiac catheterization. The distance from the central venous port to the wedge position was best predicted by nonlinear manipulation of age.

Adolescent↗
PubMed1989

Serial allometric factor extrapolation: compartmental and physiological pharmacokinetic approaches.

Interspecies dose-response equivalence is most frequently estimated as the product of a reference species dose and a single scaling ratio based on a physiological parameter such as body weight, body surface area, maximum lifespan potential, DNA repair rate, etc. This approach may suffice for certain narrowly defined applications but is likely to be inadequate or inappropriate for many others. A biologically plausible rationale for these inadequacies and for their resolution can be demonstrated using a structured approach to dose scaling, termed serial allometric factor extrapolation (SAFE). The SAFE procedure is unique in that variations in chemical-specific toxic interaction mechanisms can be incorporated into the scaling process. The compartmental and physiological pharmacokinetic (PPK) bases for the procedure are demonstrated using published data on acute intravenous toxicity of chemotherapeutic agents in animals and humans. The interrelationships of SAFE equations, PPK, and regression allometry of dose response are discussed.

Animals↗
PubMed2002

Intraindividual allometric development of aerobic power in 8- to 16-year-old boys.

PURPOSE: The aims of this study are two-fold: first, to analyze intraindividual allometric development of aerobic power of 73 boys followed at annual intervals from 8 to 16 yr, and second, to relate scaled aerobic power with level of habitual physical activity and biological maturity status. METHODS: Peak VO2 (treadmill), height, and body mass were measured. Biological maturity was based on age at peak height velocity (PHV) and level of physical activity was based on five assessments between 11 and 15 yr and at 17 yr. Interindividual and intraindividual allometric coefficients were calculated. Multilevel modeling was applied to verify if maturity status and activity explain a significant proportion of peak VO2 after controlling for other explanatory characteristics. RESULTS: At most age levels, interindividual allometry coefficients for body mass exceed k = 0.750. Intraindividual coefficients of peak VO2 by body mass vary widely and range from k' = 0.555 to k' = 1.178. Late maturing boys have smaller k' coefficients than early maturing boys. CONCLUSION: Peak VO2 is largely explained by body mass, but activity level and its interaction with maturity status contribute independently to peak VO2 even after adjusting for body mass.

Adolescent↗
PubMedDate not supplied

Interspecies scaling of maximum tolerated dose of anticancer drugs: relevance to starting dose for phase I clinical trials.

This analysis was carried out to compare the predictive performance of two different approaches of allometry for the prediction of maximum tolerated dose (MTD) in humans from animal data. The two approaches used to predict MTD in humans in this analysis were (1) the use of a fixed exponent of 0.75 and the LD(10) in mice and (2) the use of the LD(10) or MTD data from at least three animal species (interspecies scaling). Twenty-five anticancer drugs were taken from the literature and used in this analysis. The results of the study indicate that MTD can be predicted more accurately using interspecies scaling than using a fixed exponent of 0.75. Incorporation of a correction factor known as mean life-span potential can also be used for the improved prediction of MTD for some drugs. One third of the predicted MTD from interspecies scaling can be used as a starting dose in humans. This approach will save time and avoid many unnecessary steps in attaining MTD in humans.

Animals↗