Prediction of body volume by a stepwise linear regression technique

Body volume and 35 anthropometric measurements were obtained from 88 active soldiers using standard techniques. These anthropometric measurements were examined for their possible relationships to body volume using stepwise linear regression analysis. Four measurements (Body weight, anterior thigh skinfold thickness, subscapular skinfold thickness and suprailiac skinfold thickness) accounted for 99.7% of the variation in body volume and the introduction of each of these measurements in the equation was significant. The regression equation for predicting body volume from these 4 anthropometric measurements had a multiple correlation coefficient of 0.9987 (P less than 0.001). Body weight alone was correlated with body volume to the extent of 0.9966. An attempt has therefore been made to develop a multiple linear regression equation without incorporation of body weight in the regression analysis. Nine measurements were selected by stepwise linear regression analysis for predicting body volume. These nine measurements accounted for 97.1% of the variation in body volume. These equations have been validated on another small sample of 22 soldiers. The analysis has also revealed that a direct regression of body density from the anthropometric variables gives more accurate results than when estimated body volumes are utilized for calculating body density.     

Taylor's law and body size in exploited marine ecosystems

Taylor's law (TL), which states that variance in population density is related to mean density via a power law, and density‐mass allometry, which states that mean density is related to body mass via a power law, are two of the most widely observed patterns in ecology. Combining these two laws predicts that the variance in density is related to body mass via a power law (variance‐mass allometry). Marine size spectra are known to exhibit density‐mass allometry, but variance‐mass allometry has not been investigated. We show that variance and body mass in unexploited size spectrum models are related by a power law, and that this leads to TL with an exponent slightly <2. These simulated relationships are disrupted less by balanced harvesting, in which fishing effort is spread across a wide range of body sizes, than by size‐at‐entry fishing, in which only fish above a certain size may legally be caught.     

The scale-dependence of population density–body mass allometry: Statistical artefact or biological mechanism?

The relation between population density and body mass has vexed ecologists for nearly 30 years as a consequence of high variability in the observed slope of the relation: No single generalisation of the relation has been accepted as universally representative. Here, we use a simple computational approach to examine how observational scale (the body mass range considered) determines variation in the density–mass pattern. Our model relies on two assumptions: (1) resources are partitioned in an unbiased manner among species with different masses; (2) the number of individuals that can be supported by a given quantity of resources is related to their metabolic rate (which is a function of their mass raised to the power of a scaling coefficient, b). We show that density (1) scales as a function of body mass raised to the power of ?b on average, but (2) the slope of the relation varies considerably at smaller scales of observation (over narrow ranges of body mass) as a consequence of details of species’ ecology associated with resource procurement. Historically, the effect of body mass range on the slope of the density–mass relation has been unfailingly attributed to a statistical effect. Here we show that the effect of body mass range on the slope of the density–mass relation may equally result from a biological mechanism, though we find it impossible to distinguish between the two. We observe that many of the explanations that have been offered to account for the variability in the slope of the relation invoke mechanisms associated with differences in body mass and we therefore suggest that body mass range itself might be the most important explanatory factor. Notably, our results imply that the energetic equivalence rule should not be expected to hold at smaller scales of observation, which suggests that it may not be possible to scale the mass- and temperature-dependence of organism metabolism to predict patterns at higher levels of biological organisation at smaller scales of observation.     

Two‐phase self‐thinning in stream‐living juveniles of lake‐migratory brown trout Salmo trutta L. Compatibility between linear and non‐linear patterns across populations?

The self-thinning rule establishes that, in resource limited populations, increased per-capita requirements by individuals with indeterminate growth may limit density. This invariant rule relating log-log linear declines of cohort density with increased body mass has been well established in sessile organisms. However, few studies have assessed the occurrence of self-thinning in mobile organisms and still fewer have demonstrated its operation in natural situations. In Bisballe Baeck, where brown trout individuals experienced the simultaneous operation of density-dependence on growth and mortality, increased body mass explained 89.0–98.4% of the variations in density. However, relative to the invariant linear line, the decline in density with increased body mass described distinctly nonlinear, two-phase trajectories. An initial phase of variable slopes continued until body mass attained ≈10.2 g, at which the direction of the trajectory switched to a second phase of substantially steeper slopes or severe declines of density per mass unit increment. As inferred by the highly significant relationships between these two sets of slopes and annual recruitment, the two phases were consistent with a major assumption of self-thinning: the rate at which density declined with increased body mass increased with the intensity of intraspecific competition. The results of this study provide prima facie evidence for the occurrence of self-thinning in a mobile species based on observational data. A further comparison among density–body mass relationships described for resident, anadromous and lake-migratory brown trout suggests consistent two-phase self-thinning patterns across populations.     

Consumer–plant interaction strength: importance of body size,density and metabolic biomass

Explaining variability in the strength and sign of trophic interactions between primary consumers and plants is a long‐standing research challenge. Consumer density and body size vary widely in space and time and are predicted to have interactive effects on consumer–plant interactions. In a southern US salt marsh, we used replicate field enclosures to orthogonally manipulate the body size (mass) and density of a dominant consumer (a snail). We investigated impacts (leaf damage and biomass) on monocultures of cordgrass, the foundation species, over three months. Increasing consumer density and body size increased leaf damage additively and, as predicted, multiplicatively reduced plant biomass. Notably, size and density determined the sign of consumer impact on plants: low to medium densities of small consumers enhanced, while high densities of large consumers strongly suppressed, plant biomass. Finally, total consumer metabolic biomass (mass^0.75) within an enclosure parsimoniously explained plant biomass response, supporting theoretical predictions and suggesting that multiplicative effects of density and body size resulted from their effects on total metabolic biomass. The consequences of changes in consumer density and body size resulting from anthropogenic perturbations may therefore be predicted based on metabolic biomass. Synthesis Consumer size, density and biomass can all strongly affect consumer–plant interactions. Though density and body size have been extensively studied as drivers of variation in interaction strength, the role of biomass as the ultimate driver has been less appreciated. We manipulated body size and density of a single consumer species and, based on metabolic theory, integrated these into a single variable: total metabolic biomass. Our results suggest that changes in interaction strength attributed to size or density may in fact be due to changes in metabolic biomass. This metric could thus serve as a useful tool in further understanding species interactions.     

Functional correlates of differences in bone density among terrestrial and aquatic genera in the family Mustelidae (Mammalia)

Summary Increasing body density by increasing bone density has been cited as a means by which semiaquatic mammals are able to control their buoyancy in water. In order to investigate the relationship of bone density to buoyancy and the degree of morphological adaptation to a semiaquatic existence, we examined limb-bone densities in a single mammalian family. Among genera within the Mustelidae, i.e., weasels and their relatives, there is an apparent trend toward increasing limb-bone density associated with a gradation from a terrestrial to an aquatic way of life. However, the association of increasing bone density with increasing adaptation to an aquatic environment is tempered by the realization that increasing body size may also influence bone density in larger, terrestrial mammals. These results are in accordance with previous data on bone density in other mammalian orders and suggest that a new hypothesis which encompasses historical, physiological, and behavioral information would be best suited to explaining differences in this morphological relationship.     

Pseudomonas bacteriophage phi KZ contains an inner body in its capsid

Electron microscopical examination of the new virulent bacteriophage phi KZ, specific for Pseudomonas aeruginosa, has revealed an unusual structure in its capsid. In the center of the phage head is a cylinder of low electron density ("inner body"), surrounded by fibrous material which is packed around the inner body in a spoollike manner. The inner body itself has a springlike appearance. These structures disappear after adsorption of phage particles to bacteria. Various morphological forms, which can be interpreted as intermediate steps in phi KZ DNA condensation, have been seen in ultrathin sections of phi KZ-infected cells.     

Environmental phenology and geographical gradients in moose body mass

Intraspecific body mass in ungulates has often been shown to increase with latitude. The biological basis for such latitudinal gradients is, however, poorly known. Here we examined whether satellite-derived indices of environmental phenology, based on the normalised difference vegetation index (NDVI), as well as variables derived from meteorological stations, altitude, and population density, can explain latitudinal gradients and regional variation in body mass of Norwegian moose. The best model gave a considerably better fit than latitude alone, and included all explanatory environmental variables. Accordingly, heavy moose were found in areas with short and intense summers that were followed by long, cold winters, at low altitude relative to the tree-limit, and with low population density relative to the available plant biomass. This relationship was stronger for yearlings than for calves, except for the effect of population density. This indicates that differences in the characteristics of the vegetation quality and environmental phenology, as well as winter harshness and population density, are important factors that shape both the latitudinal and other geographical gradients in moose body mass.     

Cholesterol and vitamins: revisited study

The link between low density lipoprotein and coronary heart disease has been widely studied. Oxidized LDL damages the artery wall, and a diet rich in vitamins and low in saturated fat and cholesterol may reduce this risk. Not only hypercholesterolemia but also low levels of high density lipoprotein cholesterol are critical risk factors for atherosclerosis and related diseases. It has been reported that high doses of B complex vitamin may be useful in lowering blood cholesterol and triglyceride levels in the body, however the use of this compound has been limited by an annoying flush and concern for toxicity. Niacin is a B-complex vitamin with anti-atherosclerotic properties and is an effective medication for raising high density lipoprotein. The combination of niacin with other lipid-lowering drugs, such as statins, reduces the dynamic of atherosclerosis disease. In addition, vitamin E is one of the most important lipid soluble anti-oxidants in humans, and reduces atherosclerosis plaque, coronary artery diseases and myocardial infarction. Vitamin E protects the integrity of membranes by inhibiting lipid peroxidation. In this study we revisited the interrelationship between cholesterol, low density lipoproteins and vitamins.     

Insular shifts in body size of rice frogs in the Zhoushan Archipelago, China

1. Differences in body size between mainland and island populations have been reported for reptiles, birds and mammals. Despite widespread recognition of insular shifts in body size in these taxa, there have been no reports of such body size shifts in amphibians. 2. We provide the first evidence of an insular shift in body size for an amphibian species, the rice frog Rana limnocharis. We found significant increases in body size of rice frogs on most sampled islands in the Zhoushan archipelago when compared with neighbouring mainland China. 3. Large body size in rice frogs on islands was significantly related to increased population density, in both breeding and non-breeding seasons. Increases in rice frog density were significantly related to higher resource availability on islands. Increased resource availability on islands has led to higher carrying capacities, which has subsequently facilitated higher densities and individual growth rates, resulting in larger body size in rice frogs. We also suggest that large body size has evolved on islands, as larger individuals are competitively superior under conditions of harsh intraspecific competition at high densities. 4. Increases in body size in rice frogs were not related to several factors that have been implicated previously in insular shifts in body size in other taxa. We found no significant relationships between body size of rice frogs and prey size, number of larger or smaller frog species, island area or distance of islands from the mainland. 5. Our findings contribute to the formation of a broad, repeatable ecological generality for insular shifts in body size across a range of terrestrial vertebrate taxa, and provide support for recent theoretical work concerning the importance of resource availability for insular shifts in body size.     

Apparent inhibition of cholesteryl esters exchange by high density lipoproteins

The kinetics of the exchange of Cholesteryl esters between low density lipoproteins (LDL) and high density lipoproteins (HDL) stimulated by lipoprotein depleted plasma has been studied in vitro. The results indicate that the exchange is inhibited with the increase of HDL present in the assay, although the limiting factor is not the absolute concentration of HDL, since in a simultaneous LDL increase, the exchange augments proportionally to the total cholesteryl esters pool. Implications regarding overall metabolism of body cholesterol are discussed.     

Dispersal of the estuarine gastropod Pyrazus ebeninus is only weakly influenced by pneumatophore density

Studies on rocky intertidal gastropods indicate habitat complexity and body size to be major determinants of dispersal patterns. Considerations of effects of habitat complexity and body size on soft sediment gastropods are, however, less common. In neither habitat has the interaction between habitat complexity and body size been considered despite the increasing recognition in the general ecological literature that complexity effects are body-size-dependent. We tested independent and interacting effects of habitat complexity and body size on movement of the mud-whelk, Pyrazus ebeninus, by marking large (61-85 mm) and small (31-55 mm) snails in sites with low and high densities of pneumatophores and determining the distance and direction of their dispersal over periods of 1 week, 2 weeks and 1 month. Contrary to our expectation, we found no effect of pneumatophore density on the distance of snail migration over each of the temporal scales; net distance travelled by snails was determined only by body size and idiosynchratic, site-specific factors. The direction of snail movement was, by contrast, influenced on some temporal scales by both pneumatophore density and snail size. Over 1 week, site effects dominated patterns of movement and neither size of snail nor density of pneumatophore produced statistically significant effects. As the temporal scale increased, effects of size and pneumatophore density became increasingly apparent. Over the 1-month period, large snails at all sites and small snails at sites with high pneumatophore density migrated down the shore, while small snails at sites with low pneumatophore displayed non-directional movement. Thus, overall this study provides only weak support for effects of pneumatophore density on snail movement. In combination with other studies, our results suggest that, in comparison to on rocky shores where habitat complexity has strong effects on the distribution, abundance and behaviour of gastropods in soft-sediment systems habitat complexity is a less important structuring agent.     

A tale of two polar bear populations: ice habitat, harvest, and body condition

One of the primary mechanisms by which sea ice loss is expected to affect polar bears is via reduced body condition and growth resulting from reduced access to prey. To date, negative effects of sea ice loss have been documented for two of 19 recognized populations. Effects of sea ice loss on other polar bear populations that differ in harvest rate, population density, and/or feeding ecology have been assumed, but empirical support, especially quantitative data on population size, demography, and/or body condition spanning two or more decades, have been lacking. We examined trends in body condition metrics of captured bears and relationships with summertime ice concentration between 1977 and 2010 for the Baffin Bay (BB) and Davis Strait (DS) polar bear populations. Polar bears in these regions occupy areas with annual sea ice that has decreased markedly starting in the 1990s. Despite differences in harvest rate, population density, sea ice concentration, and prey base, polar bears in both populations exhibited positive relationships between body condition and summertime sea ice cover during the recent period of sea ice decline. Furthermore, females and cubs exhibited relationships with sea ice that were not apparent during the earlier period (1977–1990s) when sea ice loss did not occur. We suggest that declining body condition in BB may be a result of recent declines in sea ice habitat. In DS, high population density and/or sea ice loss, may be responsible for the declines in body condition.     

Plumage Bacterial Assemblages in a Breeding Wild Passerine: Relationships with Ecological Factors and Body Condition

Microorganisms have been shown to play an important role in shaping the life histories of animals, and it has recently been suggested that feather-degrading bacteria influence the trade-off between parental effort and self-preening behavior in birds. We studied a wild breeding population of great tits (Parus major) to explore habitat-, seasonal-, and sex-related variation in feather-degrading and free-living bacteria inhabiting the birds' yellow ventral feathers and to investigate associations with body condition. The density and species richness of bacterial assemblages was studied using flow cytometry and ribosomal intergenic spacer analysis. The density of studied bacteria declined between the nest-building period and the first brood. The number of bacterial phylotypes per bird was higher in coniferous habitat, while bacterial densities were higher in deciduous habitat. Free-living bacterial density was positively correlated with female mass; conversely, there was a negative correlation between attached bacterial density and female mass during the period of peak reproductive effort. Bacterial species richness was sex dependent, with more diverse bacterial assemblages present on males than females. Thus, this study revealed that bacterial assemblages on the feathers of breeding birds are affected both by life history and ecological factors and are related to body condition.     

Gene amplification in the oocytes of dytiscid water beetles

A conspicuous mass of extrachromosomal DNA (Giardina's body) is found in oogonia and oocytes of Dytiscid water beetles. Since in older oocytes this DNA is associated with numerous nucleoli, it seemed probable that the ovary might contain extra copies of the genes for ribosomal RNA (rRNA). This hypothesis has been confirmed by centrifugation and molecular hybridization studies. —In Dytiscus marginalis and Colymbetes fuscus a high density satellite DNA is found in somatic cells and in sperm. Hybridization experiments show that all of the rDNA, i.e., those sequences complementary to rRNA, are located in this satellite, although quantitatively they make up only a small fraction of the satellite. In both species the DNA isolated from ovariole tips is enriched with respect to the satellite. A parallel enrichment of the rDNA has been shown in ovariole tips of Colymbetes, but for technical reasons has not been examined in Dytiscus. —The following model is proposed. In somatic cells and sperm the rDNA is part of an extensive region of high density DNA in one or more chromosomes. In oogonia and oocytes the entire high density region is replicated extrachromosomally and appears cytologically as Giardina's body.     

Population cycles caused by selection by density dependent competitive interactions

Several animal species have cyclic population dynamics with phase-related cycles in life history traits such as body mass, reproductive rate, and pre-reproductive period. Although many mechanisms have been proposed there is no agreement on the cause of these cycles, and no population equation that deduces both the abundance and the life history cycles from basic ecological constraints has been formulated. Here I deduce a population dynamic equation from the selection pressure of density dependent competitive interactions in order to explain the cyclic dynamics in abundance and life history traits. The model can explain cycles by evolutionary changes in the genotype or by plastic responses in the phenotype. It treats the population dynamic growth rate as an initial condition, and its density independent fundament is Fisher’s (1930, The Genetical Theory of Natural Selection, Oxford: Clarendon) fundamental theorem of natural selection that predicts a hyper-geometrical increase in abundance. The predicted periods coincide with the cyclic dynamics of Lepidoptera, and the Calder hypothesis, which suggests that the period of population cycles is proportional to the 1/4 power of body mass, follows from first principles of the proposed density dependent ecology.     

Axial mesenchyme structure in the anlage of the human vertebral column. Light microscopy study of a human embryo of 9 mm CRL (Carnegie stage 16)

The anlage of the cervical vertebral column of a human embryo has been investigated (9 mm CRL, Carnegie stage 16). The nuclear density in the axial mesenchyme increases rhythmically from cranial to caudal. This phenomenon superimposes a metameric pattern on the blastema. Furthermore, cell formations are shaped by the orientation of the mesenchymal cells. The name 'formationes quasi distensae' is proposed for this system. The anlage of the atlas shows a distinct mesenchymal anlage of a vertebral body. The conclusion is drawn that the dens axis is predominantly formed out of the anlage of the atlas body. The opinion that man does not show an anlage of the atlas body can no longer be sustained.     

Principal components analysis of regional bone density in black and white women: relationship to body size and composition.

Black and white women in the United States differ with respect to bone mass and the risk of developing osteoporosis. It has been suggested that greater body size among U.S. blacks may contribute to greater bone density in this group. It is not known whether the fat or lean component contributes more to this relationship. Bone density was measured at seven sites in 161 normal black and white women using single and dual photon absorptiometry. The first principal component accounted for 73% of the variance in the sample and constitutes an index of skeletal mass. The second principal component added another 10% and contrasts the axial and appendicular sites. Both the regional bone densities and the first principal component showed significantly greater bone densities for blacks; adjustment for body size reduced bone mass differences by approximately 50%. Body composition analysis done on a subset of these women indicated that the fat component of body mass may be the more important factor in its effect on bone mass.     

Method of determining the colloidal status of the vitreous body

A new method for the quantitative estimation of the vitreous body colloidal state has been suggested. For realization of the method a fragment of the vitreous body and an equal volume of water are dried out, and the drying time is registered. The higher is the ratio between the drying time of the vitreous body fragment and water, the higher is the density of the vitreous body gel. The drying out of the vitreous body fragment and water on the analytical balance cups permits the registration of the drying out process in the time course. Thus some additional parameters are obtained that characterize the object studied more completely. The method can be used in experimental and clinical investigations of the vitreous body and other biological liquids.     

The analysis of interaction of lipoproteins and steroid hormones

Using the methods of gel-filtration and fluorescence quenching, it has been demonstrated that plasma lipoproteins bind steroid hormones and can therefore play a role in their active transport in the body. High density lipoproteins demonstrate the highest affinity for steroids.