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Biological Organization (biological + organization)
Selected AbstractsChanges in Bone Density During Childhood and Adolescence: An Approach Based on Bone's Biological OrganizationJOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2001Frank Rauch Abstract Bone densitometry has great potential to improve our understanding of bone development. However, densitometric data in children rarely are interpreted in light of the biological processes they reflect. To strengthen the link between bone densitometry and the physiology of bone development, we review the literature on physiological mechanisms and structural changes determining bone mineral density (BMD). BMD (defined as mass of mineral per unit volume) is analyzed in three levels: in bone material (BMDmaterial), in a bone's trabecular and cortical tissue compartments (BMDcompartment), and in the entire bone (BMDtotal). BMDmaterial of the femoral midshaft cortex decreases after birth to a nadir in the first year of life and thereafter increases. In iliac trabecular bone, BMDmaterial also increases from infancy to adulthood, reflecting the decrease in bone turnover. BMDmaterial cannot be determined with current noninvasive techniques because of insufficient spatial resolution. BMDcompartment of the femoral midshaft cortex decreases in the first months after birth followed by a rapid increase during the next 2 years and slower changes thereafter, reflecting changes in both relative bone volume and BMDmaterial. Trabecular BMDcompartment increases in vertebral bodies but not at the distal radius. Quantitative computed tomography (QCT) allows for the determination of both trabecular and cortical BMDcompartment, whereas projectional techniques such as dual-energy X-ray absorptiometry (DXA) can be used only to assess cortical BMDcompartment of long bone diaphyses. BMDtotal of long bones decreases by about 30% in the first months after birth, reflecting a redistribution of bone tissue from the endocortical to the periosteal surface. In children of school age and in adolescents, changes in BMDtotal are site-specific. There is a marked rise in BMDtotal at locations where relative cortical area increases (metacarpal bones, phalanges, and forearm), but little change at the femoral neck and midshaft. BMDtotal can be measured by QCT at any site of the skeleton, regardless of bone shape. DXA allows the estimation of BMDtotal at skeletal sites, which have an approximately circular cross-section. The system presented here may help to interpret densitometric results in growing subjects on a physiological basis. [source] Mixture toxicity and gene inductions: Can we predict the outcome?ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2008Freddy Dardenne Abstract As a consequence of the nature of most real-life exposure scenarios, the last decade of ecotoxicological research has seen increasing interest in the assessment of mixture ecotoxicology. Often, mixtures are considered to follow one of two models, concentration addition (CA) or response addition (RA), both of which have been described in the literature. Nevertheless, mixtures that deviate from either or both models exist; they typically exhibit phenomena like synergism, ratio or concentration dependency, or inhibition. Moreover, both CA and RA have been challenged and evaluated mainly for acute responses at relatively high levels of biological organization (e.g., whole-organism mortality), and applicability to genetic responses has not received much attention. Genetic responses are considered to be the primary reaction in case of toxicant exposure and carry valuable mechanistic information. Effects at the gene-expression level are at the heart of the mode of action by toxicants and mixtures. The ability to predict mixture responses at this primary response level is an important asset in predicting and understanding mixture effects at different levels of biological organization. The present study evaluated the applicability of mixture models to stress gene inductions in Escherichia coli employing model toxicants with known modes of action in binary combinations. The results showed that even if the maximum of the dose,response curve is not known, making a classical ECx (concentration causing x% effect) approach impossible, mixture models can predict responses to the binary mixtures based on the single-toxicant response curves. In most cases, the mode of action of the toxicants does not determine the optimal choice of model (i.e., CA, RA, or a deviation thereof). [source] From organisms to populations: Modeling aquatic toxicity data across two levels of biological organizationENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2006Sandy Raimondo Abstract A critical step in estimating the ecological effects of a toxicant is extrapolating organism-level response data across higher levels of biological organization. In the present study, the organism-to-population link is made for the mysid, Americamysis bahia, exposed to a range of concentrations of six toxicants. Organism-level responses observed were categorized as no effect, delayed reproduction, reduced overall reproduction, or both reduced overall reproduction and survival. Population multiplication rates of each toxicant concentration were obtained from matrix models developed from organism-level endpoints and placed into the four categories of organism-level responses. Rates within each category were compared with growth rates modeled for control populations. Population multiplication rates were significantly less than control growth rates only for concentrations at which overall reproduction and both reproduction and survival were significantly less than the control values on the organism level. Decomposition analysis of the significant population-level effects identified reduced reproduction as the primary contributor to a reduced population multiplication rate at all sublethal concentrations and most lethal concentrations. Mortality was the primary contributor to reduced population growth rate only when survival was less than 25% of control survival. These results suggest the importance of altered reproduction in population-level risk assessment and emphasizes the need for complete life-cycle test data to make an explicit link between the organism and population levels. [source] A multivariate biomarker-based model predicting population-level responses of Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2003Wim M. De Coen Abstract A multivariate model is proposed relating short-term biomarker measurements in Daphnia magna to chronic effects (21-d exposure) occurring at the population level (time to death, mean brood size, mean total young per female, intrinsic rate of natural increase, net reproductive rate, and growth). The results of the short-term exposure (48h-96 h) to eight model toxicants (cadmium, chromium, mercury, tributyl tin, linear alkylsulfonic acid, sodium pentachlorophenolate, lindane, and 2,4-dichloro-phenoxyacetic acid) on the following biomarkers were used for the multivariate model: digestive enzymes (amylase, cellulase, ,-galactosidase, trypsin, and esterase), enzymes of the intermediary metabolism (glycogen phosphorylase, glucose-6-phosphate de-hydrogenase, pyruvate kinase, lactate dehydrogenase, and isocitrate dehydrogenase), cellular energy allocation (CEA) (protein, carbohydrate, and lipid content and electron transport activity), and DNA damage and antioxidative stress activity. Using partial least squares to latent structures (PLS), a two-component model was obtained with R2 of 0.68 and a Q2 value of 0.60 based on the combined analysis of a limited number of the 48- and 96-h biomarker responses. For the individual population-level responses, the R2 values varied from 0.66 to 0.77 and the Q2 values from 0.52 to 0.69. Energy-related biomarkers (cellular energy allocation, lipid contents, anaerobic metabolic activity,pyruvate kinase, and lactate dehydrogenase), combined with parameters related to oxidative stress (catalase) and DNA damage measured after 48 and 96 h of exposure, were able to predict long-term effects at higher levels of biological organization. [source] Ecological research in the office of research and development at the U.S. Environmental Protection Agency: An overview of new directions,,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000Rick A. Linthurst Abstract In virtually every major environmental act, Congress has required that the U.S. Environmental Protection Agency (U.S. EPA) ensure not only that the air be safe to breathe, the water safe to drink, and the food supply free of contamination, but also that the environment be protected. In response, the U.S. EPA's Office of Research and Development (ORD) has established research to improve ecosystem risk assessment and management, identifying it as one of the highest priority research areas for investment over the next 10 years. The research is intended to provide environmental managers with new tools and flexible guidance that reflect a holistic environmental management perspective of science and that can be applied both to common and unique problems. In keeping with its responsibility to provide the U.S. EPA with science that supports a dynamic changing regulatory agenda, the ORD has set the goal of its Ecological Research Program to "provide the scientific understanding required to measure, model, maintain and/or restore, at multiple scales, the integrity and sustainability of ecosystems now, and in the future." In the context of this program, ecological integrity is defined in relative terms as the maintenance of ecosystem structure and function characteristic of a reference condition deemed appropriate for its use by society, and sustainability is defined as the ability of an ecosystem to maintain relative ecological integrity into the future. Therefore, the research program will emphasize relative risk and consider the impact of multiple stressors, at multiple scales and at multiple levels of biological organization. The program will also shift from chemical to biological and physical stressors to a far greater extent than in the past. The purpose of this paper is to provide an introduction to the U.S. EPA's changing ecological research program. [source] PERSPECTIVE: EVOLUTION AND DETECTION OF GENETIC ROBUSTNESSEVOLUTION, Issue 9 2003J. Arjan G. M. de Visser Abstract Robustness is the invariance of phenotypes in the face of perturbation. The robustness of phenotypes appears at various levels of biological organization, including gene expression, protein folding, metabolic flux, physiological homeostasis, development, and even organismal fitness. The mechanisms underlying robustness are diverse, ranging from thermodynamic stability at the RNA and protein level to behavior at the organismal level. Phenotypes can be robust either against heritable perturbations (e.g., mutations) or nonheritable perturbations (e.g., the weather). Here we primarily focus on the first kind of robustness,genetic robustness,and survey three growing avenues of research: (1) measuring genetic robustness in nature and in the laboratory; (2) understanding the evolution of genetic robustness; and (3) exploring the implications of genetic robustness for future evolution. [source] Computational physiology and the physiome projectEXPERIMENTAL PHYSIOLOGY, Issue 1 2004Edmund J. Crampin Bioengineering analyses of physiological systems use the computational solution of physical conservation laws on anatomically detailed geometric models to understand the physiological function of intact organs in terms of the properties and behaviour of the cells and tissues within the organ. By linking behaviour in a quantitative, mathematically defined sense across multiple scales of biological organization , from proteins to cells, tissues, organs and organ systems , these methods have the potential to link patient-specific knowledge at the two ends of these spatial scales. A genetic profile linked to cardiac ion channel mutations, for example, can be interpreted in relation to body surface ECG measurements via a mathematical model of the heart and torso, which includes the spatial distribution of cardiac ion channels throughout the myocardium and the individual kinetics for each of the approximately 50 types of ion channel, exchanger or pump known to be present in the heart. Similarly, linking molecular defects such as mutations of chloride ion channels in lung epithelial cells to the integrated function of the intact lung requires models that include the detailed anatomy of the lungs, the physics of air flow, blood flow and gas exchange, together with the large deformation mechanics of breathing. Organizing this large body of knowledge into a coherent framework for modelling requires the development of ontologies, markup languages for encoding models, and web-accessible distributed databases. In this article we review the state of the field at all the relevant levels, and the tools that are being developed to tackle such complexity. Integrative physiology is central to the interpretation of genomic and proteomic data, and is becoming a highly quantitative, computer-intensive discipline. [source] In situ-based effects measures: Determining the ecological relevance of measured responsesINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 2 2007Donald J Baird Abstract The aim of this review is to examine how the choice of test species and study design employed in the use of in situ approaches in ecological risk assessment can maximize the ecological relevance of data. We provide a framework to define and assess ecological relevance that permits study designs to remain focused on the ecological question being addressed. This framework makes explicit the linkages between effects at lower levels of biological organization and higher-order ecological effects at the population, community, and ecosystem levels. The usefulness of this framework is illustrated by reference to specific examples from aquatic ecotoxicology. The use of models as both interpretive and predictive tools is discussed, with suggestions of appropriate methods for different protection goals. [source] The problem of similarity: analysis of repeated patterns of microsculpture on gastropod larval shellsINVERTEBRATE BIOLOGY, Issue 3 2004Carole S. Hickman Abstract. The problem of similarity is one of explaining the causes of striking resemblances between patterns and architectural themes that recur in organisms at various scales of biological organization. Classical explanations that have considered only the alternatives of homology and analogy overlook similarities of form that are primarily a consequence of fabrication, conveying little information about evolutionary relationships or functional role. When viewed at successively higher magnifications and when mapped onto a phylogeny, patterns of delicate cancellate microsculpture and granular microprotuberances on the surfaces of larval shells of marine gastropods fail to meet the predictions of exclusively historical or exclusively functional explanations, but are shown to be rich in fabricational information. Similar patterns suggest that early biomineralization of the initial organic shell is under weaker biological control than the processes that modulate assembly of the multi-layered, hierarchically-organized composite materials of the adult shell. Some patterns suggest remote biomineralization, without direct influence of living tissue. Scanning electron microscopy of larval shell features reveals previously undetected variation on basic themes that may have implications for the traditional disciplines of systematics, functional morphology, and fabricational morphology. The integration of the approaches of the traditional divisions of biology is required for full explanation of similarity and to generate a unified set of principles for the analysis of form in living and fossil organisms. [source] From molecules to ecosystems through dynamic energy budget modelsJOURNAL OF ANIMAL ECOLOGY, Issue 6 2000R. M. Nisbet Summary 1. Dynamic energy budget (DEB) models describe how individuals acquire and utilize energy, and can serve as a link between different levels of biological organization. 2. We describe the formulation and testing of DEB models, and show how the dynamics of individual organisms link to molecular processes, to population dynamics, and (more tenuously) to ecosystem dynamics. 3. DEB models offer mechanistic explanations of body-size scaling relationships. 4. DEB models constitute powerful tools for applications in toxicology and biotechnology. 5. Challenging questions arise when linking DEB models with evolutionary theory. [source] Species concepts and species reality: salvaging a Linnaean rankJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2003M. S. Y. Lee Abstract The validity of the species category (rank) as a distinct level of biological organization has been questioned. Phenetic, cohesion and monophyletic species concepts do not delimit species-level taxa that are qualitatively distinct from lower or higher taxa: all organisms throughout the tree of life exhibit varying degrees of similarity, cohesion, and monophyly. In contrast, interbreeding concepts delimit species-level taxa characterized by a phenomenon (regular gene flow) not found in higher taxa, making the species category a distinct level of biological organization. Only interbreeding concepts delimit species-level taxa that are all comparable according to a biologically meaningful criterion and qualitatively distinct from entities assigned to other taxonomic categories. Consistent application of interbreeding concepts can result in counterintuitive taxonomies , e.g. many wide polytypic species in plants and narrow cryptic species in animals. However, far from being problematic, such differences are biologically illuminating , reflecting differing barriers to gene flow in different clades. Empirical problems with interbreeding concepts exist, but many of these also apply to other species concepts, whereas others are not as severe as some have argued. A monistic view of species using interbreeding concepts will encounter strong historical inertia, but can save the species category from redundancy with other categories, and thus justify continued recognition of the species category. [source] Pelvic growth: Ontogeny of size and shape sexual dimorphism in rat pelvesJOURNAL OF MORPHOLOGY, Issue 1 2007S. Berdnikovs Abstract The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization. J. Morphol., 2006. © 2006 Wiley-Liss, Inc. [source] Shrubs as ecosystem engineers in a coastal dune: influences on plant populations, communities and ecosystemsJOURNAL OF VEGETATION SCIENCE, Issue 5 2010J. Hall Cushman Abstract Question: How do two shrubs with contrasting life-history characteristics influence abundance of dominant plant taxa, species richness and aboveground biomass of grasses and forbs, litter accumulation, nitrogen pools and mineralization rates? How are these shrubs , and thus their effects on populations, communities and ecosystems , distributed spatially across the landscape? Location: Coastal hind-dune system, Bodega Head, northern California. Methods: In each of 4 years, we compared vegetation, leaf litter and soil nitrogen under canopies of two native shrubs ,Ericameria ericoides and the nitrogen-fixing Lupinus chamissonis, with those in adjacent open dunes. Results: At the population level, density and cover of the native forb Claytonia perfoliata and the exotic grass Bromus diandrus were higher under shrubs than in shrub-free areas, whereas they were lower under shrubs for the exotic grass Vulpia bromoides. In contrast, cover of three native moss species was highest under Ericameria and equally low under Lupinus and shrub-free areas. At community level, species richness and aboveground biomass of herbaceous dicots was lower beneath shrubs, whereas no pattern emerged for grasses. At ecosystem level, areas beneath shrubs accumulated more leaf litter and had larger pools of soil ammonium and nitrate. Rates of nitrate mineralization were higher under Lupinus, followed by Ericameria and then open dune. At landscape level, the two shrubs , and their distinctive vegetation and soils , frequently had uniform spatial distributions, and the distance separating neighbouring shrubs increased as their combined sizes increased. Conclusions: Collectively, these data suggest that both shrubs serve as ecosystem engineers in this coastal dune, having influences at multiple levels of biological organization. Our data also suggest that intraspecific competition influenced the spatial distributions of these shrubs and thus altered the distribution of their effects throughout the landscape. [source] Evolutionary consequences of autopolyploidyNEW PHYTOLOGIST, Issue 1 2010Christian Parisod Summary Autopolyploidy is more common in plants than traditionally assumed, but has received little attention compared with allopolyploidy. Hence, the advantages and disadvantages of genome doubling per se compared with genome doubling coupled with hybridizations in allopolyploids remain unclear. Autopolyploids are characterized by genomic redundancy and polysomic inheritance, increasing effective population size. To shed light on the evolutionary consequences of autopolyploidy, we review a broad range of studies focusing on both synthetic and natural autopolyploids encompassing levels of biological organization from genes to evolutionary lineages. The limited evidence currently available suggests that autopolyploids neither experience strong genome restructuring nor wide reorganization of gene expression during the first generations following genome doubling, but that these processes may become more important in the longer term. Biogeographic and ecological surveys point to an association between the formation of autopolyploid lineages and environmental change. We thus hypothesize that polysomic inheritance may provide a short-term evolutionary advantage for autopolyploids compared to diploid relatives when environmental change enforces range shifts. In addition, autopolyploids should possess increased genome flexibility, allowing them to adapt and persist across heterogeneous landscapes in the long run. [source] Fallback foods, eclectic omnivores, and the packaging problemAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Stuart A. Altmann Abstract For omnivorous primates, as for other selective omnivores, the array of potential foods in their home ranges present a twofold problem: not all nutrients are present in any food in the requisite amounts or proportions and not all toxins and other costs are absent. Costs and benefits are inextricably linked. This so-called packaging problem is particularly acute during periods, often seasonal, when the benefit-to-cost ratios of available foods are especially low and animals must subsist on fallback foods. Thus, fallback foods represent the packaging problem in extreme form. The use of fallback foods by omnivorous primates is part of a suite of interconnected adaptations to the packaging problem, the commingling of costs and benefits in accessing food and other vital resources. These adaptations occur at every level of biological organization. This article surveys 16 types of potential adaptations of omnivorous primates to fallback foods and the packaging problem. Behavioral adaptations, in addition to finding and feeding on fallback foods, include minimizing costs and requirements, exploiting food outbreaks, living in social groups and learning from others, and shifting the home range. Adaptive anatomical and physiological traits include unspecialized guts and dentition, binocular color vision, agile bodies and limbs, Meissner's corpuscles in finger tips, enlargement of the neocortex, internal storage of foods and nutrients, and ability internally to synthesize compounds not readily available in the habitat. Finally, during periods requiring prolonged use of fallback foods, life history components may undergo changes, including reduction of parental investment, extended interbirth intervals, seasonal breeding or, in the extreme, aborted fetuses. Am J Phys Anthropol 140:615,629, 2009. © 2009 Wiley-Liss, Inc. [source] Towards an integrated environmental assessment for wetland and catchment managementTHE GEOGRAPHICAL JOURNAL, Issue 2 2003R Kerry Turner This paper develops a decision support system for evaluation of wetland ecosystem management strategy and examines its, so far partial, application in a case study of an important complex coastal wetland known as the Norfolk and Suffolk Broads, in the east of England, UK. Most managed ecosystems are complex and often poorly understood hierarchically organized systems. Capturing the range of relevant impacts on natural and human systems under different management options will be a formidable challenge. Biodiversity has a hierarchical structure which ranges from the ecosystem and landscape level, through the community level and down to the population and genetic level. There is a need to develop methodologies for the practicable detection of ecosystem change, as well as the evaluation of different ecological functions. What is also required is a set of indicators (environmental, social and economic) which facilitate the detection of change in ecosystems suffering stress and shock and highlight possible drivers of the change process. A hierarchical classification of ecological indicators of sustainability would need to take into account existing interactions between different organization levels, from species to ecosystems. Effects of environmental stress are expressed in different ways at different levels of biological organization and effects at one level can be expected to impact other levels, often in unpredictable ways. The management strategy, evaluation methodologies and indicators adopted should also assess on sustainability grounds whether any given management option is supporting, or reducing, the diversity of functions which are providing stakeholders with the welfare benefits they require. [source] Everything depends on everything elseCLINICAL MICROBIOLOGY AND INFECTION, Issue 2009J. Davies Abstract In physics the concept of entanglement is well established and it has become increasingly apparent that all levels of biological organization (communities, organisms, cells, metabolism) consist of mosaics of interactive networks. There is a universe of bioactive microbial chemicals that have so far only been considered for their therapeutic applications; for example, the environmental roles of antibiotics have been little investigated. At sub-inhibitory concentrations, so-called antibiotics have been shown to modulate bacterial functions in subtle ways; they behave more like signals than toxins. It is proposed that networks of microbial cell signalling are primarily based on the interactions of low molecular weight compounds with macromolecular receptors; studies of the nature of these signals will reveal important information on the functions of microbial communities. [source] | ||||||||||||||||