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Selected AbstractsOscillating trophic control induces community reorganization in a marine ecosystemECOLOGY LETTERS, Issue 12 2007Michael A. Litzow Abstract Understanding how climate regulates trophic control may help to elucidate the causes of transitions between alternate ecosystem states following climate regime shifts. We used a 34-year time series of the abundance of Pacific cod (Gadus macrocephalus) and five prey species to show that the nature of trophic control in a North Pacific ecosystem depends on climate state. Rapid warming in the 1970s caused an oscillation between bottom,up and top,down control. This shift to top,down control apparently contributed to the transition from an initial, prey-rich ecosystem state to the final, prey-poor state. However, top,down control could not be detected in the final state without reference to the initial state and transition period. Complete understanding of trophic control in ecosystems capable of transitions between alternate states may therefore require observations spanning more than one state. [source] Neurodevelopmental outcomes of children with low-grade gliomasDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 3 2008M. Douglas Ris Abstract As a group, children with low-grade gliomas (LGGs) enjoy a high rate of long-term survival and do not require the intensity of neurotoxic treatments used with higher risk pediatric brain tumors. Because they are generally considered to have favorable neurobehavioral outcomes, they have not been studied as thoroughly as higher-grade brain tumors by late-effects researchers. In this article, we review the literature on the neurobehavioral effects associated with low-grade gliomas and conclude that, (1) this is a large, understudied group of survivors of pediatric brain tumors; (2) recent small- and large-scale studies document increased risk in multiple cognitive-behavioral domains after treatment for LGGs compared with healthy peers; (3) such risk is not uniform but varies with tumor location and treatments; and (4) a life span development perspective is essential to a complete understanding of the risks faced by these children. More research on the most efficacious biopsychosocial treatment models for improving the outcomes of survivors of low-grade glioma is recommended, informed by a better understanding of theireducational needs. Investigations of genetic influences on outcome as well as prospective studies of these patients as they age are also recommended. © 2008 Wiley-Liss, Inc. Dev Disabil Res Rev 2008;14:196,202. [source] Predation on mutualists can reduce the strength of trophic cascadesECOLOGY LETTERS, Issue 11 2006Tiffany M. Knight Abstract Ecologists have put forth several mechanisms to predict the strength of predator effects on producers (a trophic cascade). We suggest a novel mechanism , in systems in which mutualists of plants are present and important, predators can have indirect negative effects on producers through their consumption of mutualists. The strength of predator effects on producers will depend on their relative consumption of mutualists and antagonists, and on the relative importance of each to producer population dynamics. In a meta-analysis of experiments that examine the effects of predator reduction on the pollination and reproductive success of plants, we found that the indirect negative effects of predators on plants are quite strong. Most predator removal experiments measure the strength of predator effects on producers through the antagonist pathway; we suggest that a more complete understanding of the role of predators will be achieved by simultaneously considering the effects of predators on plant mutualists. [source] Measuring the emergence of tobacco dependence: the contribution of negative reinforcement modelsADDICTION, Issue 2004Thomas Eissenberg ABSTRACT This review of negative reinforcement models of drug dependence is part of a series that takes the position that a complete understanding of current concepts of dependence will facilitate the development of reliable and valid measures of the emergence of tobacco dependence. Other reviews within the series consider models that emphasize positive reinforcement and social learning/cognitive models. This review summarizes negative reinforcement in general and then presents four current negative reinforcement models that emphasize withdrawal, classical conditioning, self-medication and opponent-processes. For each model, the paper outlines central aspects of dependence, conceptualization of dependence development and influences that the model might have on current and future measures of dependence. Understanding how drug dependence develops will be an important part of future successful tobacco dependence measurement, prevention and treatment strategies. [source] Proteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Daniel Dikovsky Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source] ON THE OPPORTUNITY FOR SEXUAL SELECTION, THE BATEMAN GRADIENT AND THE MAXIMUM INTENSITY OF SEXUAL SELECTIONEVOLUTION, Issue 7 2009Adam G. Jones Bateman's classic paper on fly mating systems inspired quantitative study of sexual selection but also resulted in much debate and confusion. Here, I consider the meaning of Bateman's principles in the context of selection theory. Success in precopulatory sexual selection can be quantified as a "mating differential," which is the covariance between trait values and relative mating success. The mating differential is converted into a selection differential by the Bateman gradient, which is the least squares regression of relative reproductive success on relative mating success. Hence, a complete understanding of precopulatory sexual selection requires knowledge of two equally important aspects of mating patterns: the mating differential, which requires a focus on mechanisms generating covariance between trait values and mating success, and the Bateman gradient, which requires knowledge of the genetic mating system. An upper limit on the magnitude of the selection differential on any sexually selected trait is given by the product of the standard deviation in relative mating success and the Bateman gradient. This latter view of the maximum selection differential provides a clearer focus on the important aspects of precopulatory sexual selection than other methods and therefore should be an important part of future studies of sexual selection. [source] SHARED AND UNIQUE FEATURES OF DIVERSIFICATION IN GREATER ANTILLEAN ANOLIS ECOMORPHSEVOLUTION, Issue 2 2006R. Brian Langerhans Abstract Examples of convergent evolution suggest that natural selection can often produce predictable evolutionary outcomes. However, unique histories among species can lead to divergent evolution regardless of their shared selective pressures,and some contend that such historical contingencies produce the dominant features of evolution. A classic example of convergent evolution is the set of Anolis lizard ecomorphs of the Greater Antilles. On each of four islands, anole species partition the structural habitat into at least four categories, exhibiting similar morphologies within each category. We assessed the relative importance of shared selection due to habitat similarity, unique island histories, and unique effects of similar habitats on different islands in the generation of morphological variation in anole ecomorphs. We found that shared features of diversification across habitats were of greatest importance, but island effects on morphology (reflecting either island effects per se or phylogenetic relationships) and unique aspects of habitat diversification on different islands were also important. There were three distinct cases of island-specific habitat diversification, and only one was confounded by phylogenetic relatedness. The other two unique aspects were not related to shared ancestry but might reflect as-yet-unmeasured environmental differences between islands in habitat characteristics. Quantifying the relative importance of shared and unique responses to similar selective regimes provides a more complete understanding of phenotypic diversification, even in this much-studied system [source] DIFFERENTIAL PATTERNS OF INTROGRESSION ACROSS THE X CHROMOSOME IN A HYBRID ZONE BETWEEN TWO SPECIES OF HOUSE MICEEVOLUTION, Issue 9 2004Bret A. Payseur Abstract A complete understanding of the speciation process requires the identification of genomic regions and genes that confer reproductive barriers between species. Empirical and theoretical research has revealed two important patterns in the evolution of reproductive isolation in animals: isolation typically arises as a result of disrupted epistatic interactions between multiple loci and these disruptions map disproportionately to the X chromosome. These patterns suggest that a targeted examination of natural gene flow between closely related species at X-linked markers with known positions would provide insight into the genetic basis of speciation. We take advantage of the existence of genomic data and a well-documented European zone of hybridization between two species of house mice, Mus domesticus and M. musculus, to conduct such a survey. We evaluate patterns of introgression across the hybrid zone for 13 diagnostic X-linked loci with known chromosomal positions using a maximum likelihood model. Interlocus comparisons clearly identify one locus with reduced introgression across the center of the hybrid zone, pinpointing a candidate region for reproductive isolation. Results also reveal one locus with high frequencies of M. domesticus alleles in populations on the M. musculus side of the zone, suggesting the possibility that positive selection may act to drive the spread of alleles from one species on to the genomic background of the other species. Finally, cline width and cline center are strongly positively correlated across the X chromosome, indicating that gene flow of the X chromosome may be asymmetrical. This study highlights the utility of natural populations of hybrids for mapping speciation genes and suggests that the middle of the X chromosome may be important for reproductive isolation between species of house mice. [source] ARE PINNIPEDS FUNCTIONALLY DIFFERENT FROM FISSIPED CARNIVORES?EVOLUTION, Issue 3 2000THE IMPORTANCE OF PHYLOGENETIC COMPARATIVE ANALYSES Abstract., It is widely assumed that adaptations to an aquatic lifestyle are so profound as to produce only obvious differences between pinnipeds and the remaining, largely terrestrial carnivore species ("fissipeds"). Thus, comparative studies of the order Carnivora routinely examine these groups independently. This approach is invalid for two reasons. First, fissipeds are a paraphyletic assemblage, which raises the general issue of when it is appropriate to ignore monophyly as a criterion for inclusion in comparative studies. Second, the claim that most functional characters (beyond a few undoubted characteristic features) are different in pinnipeds and fissipeds has never been quantitatively examined, nor with phylogenetic comparative methods. We test for possible differences between these two groups in relation to 20 morphological, life-history, physiological, and ecological variables. Comparisons employed the method of independent contrasts based on a complete and dated species-level phylogeny of the extant Carnivora. Pinnipeds differ from fissipeds only through evolutionary grade shifts in a limited number of life-history traits: litter weight (vs. gestation length), birth weight, and age of eyes opening (both vs. size). Otherwise, pinnipeds display the same rate of evolution as phylogenetically equivalent fissiped taxa for all variables. Overall functional differences between pinnipeds and fissipeds appear to have been overstated and may be no greater than those among major fissiped groups. Recognition of this fact should lead to a more complete understanding of carnivore biology as a whole through more unified comparative tests. Comparative studies that do not include monophyletic groups for phylogenetically based comparative tests should be reconsidered. [source] New pharmacological strategies against metastatic spreadFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 5 2008G.Y. Perret Abstract Although metastatic spread is the most frequent cause of death in cancer patients, there are very few drugs specifically targeting this process. Bases for a new antimetastatic drug discovery strategy are weak because a great number of unknowns characterize the complete understanding of the metastatic cascade mechanisms. Moreover, the current experimental models are too simplistic and do not account for the complexity of the phenomenon. Some targets have been identified but too few are validated. Among them, the metastasis suppressor genes seem to be the most promising. In spite of this, during recent years, a dozen of molecules, which fulfil the definition of a specific metastatic drug that inhibits the metastases without altering the growth of the primary tumour (which can be eradicated by surgery), have been identified and assessed for the proof of the concept. The continuation of this effort would benefit in terms of efficiency, if the objectives were defined more precisely. It is particularly important to distinguish molecules that prevent spread of the metastatic cells of the early-stage primary tumour from the ones which induce a regression of the established metastases or to inhibit the transition from disseminated occult tumour cells to dormant micrometastasis. This second goal is a priori more relevant in the current clinical setting where the detection of early metastatic spread is very difficult, and therefore would call for greater effort on the part of the scientific community. [source] Karyotypic similarity identified by multiplex-FISH relates four prostate adenocarcinoma cell lines: PC-3, PPC-1, ALVA-31, and ALVA-41GENES, CHROMOSOMES AND CANCER, Issue 4 2001Marileila Varella-Garcia Recently developed molecular cytogenetic techniques for karyotyping are providing new and important insights regarding the chromosomal changes that occur in solid tumors. We used multiplex-FISH to analyze four adenocarcinoma cell lines, PC-3, PPC-1, ALVA-31, and ALVA-41, in which the characterization of a large number of rearranged chromosomes was partially or substantially inconclusive by G-banding. Although the original descriptions of these lines depict them as distinct entities established from different patients, this study demonstrates that these four lines share numerous, highly rearranged chromosomes, strongly supporting the conclusion that they are derived from the same patient material. Our analysis indicates that PPC-1, ALVA-31, and ALVA-41 were derived from PC-3 through mechanisms involving clonal progression represented by sequential changes and clonal diversion represented by differing patterns of changes. Extensive cellular heterogeneity was detected in all four lines, and most rearrangements included segments derived from multiple chromosomes. Each line also showed a set of unique derivative chromosomes. However, a limited number of metaphase cells (approximately 10) was analyzed for each line, and numerous single-cell abnormalities were detected in all of them. Therefore, it is plausible that the number of clonal, shared, and/or unique rearrangements has been underestimated. These cell lines have been utilized as models for understanding the biology of prostate cancer and reportedly differ in their cell physiology. Rather than detracting from their value, a complete understanding of the interrelationships of these lines to one another may provide the opportunity to define the molecular changes that have led to their individual malignant phenotypes. © 2001 Wiley-Liss, Inc. [source] Approaches to identify genes for complex human diseases: Lessons from Mendelian disorders,,HUMAN MUTATION, Issue 4 2003Michael Dean Abstract The focus of most molecular genetics research is the identification of genes involved in human disease. In the 20th century, genetics progressed from the rediscovery of Mendel's Laws to the identification of nearly every Mendelian genetic disease. At this pace, the genetic component of all complex human diseases could be identified by the end of the 21st century, and rational therapies could be developed. However, it is clear that no one approach will identify the genes for all diseases with a genetic component, because multiple mechanisms are involved in altering human phenotypes, including common alleles with small to moderate effects, rare alleles with moderate to large effects, complex gene,gene and gene,environment interactions, genomic alterations, and noninherited genetic effects. The knowledge gained from the study of Mendelian diseases may be applied to future research that combines linkage-based, association-based, and sequence-based approaches to detect most disease alleles. The technology to complete these studies is at hand and requires that modest improvements be applied on a wide scale. Improved analytical tools, phenotypic characterizations, and functional analyses will enable complete understanding of the genetic basis of complex diseases. Hum Mutat 22:261,274, 2003. Published © 2003 Wiley-Liss, Inc. [source] Approaches to career success: An exploration of surreptitious career-success strategiesHUMAN RESOURCE MANAGEMENT, Issue 1 2006Lloyd C. Harris Theorists have forwarded a vast range of career-success determinants, including sociodemographic, social capital, personality, and other behavioral factors. We suggest that existing studies have overconcentrated on the overt behavioral determinants of career success to the detriment of the covert, clandestine, and concealed. Our analysis of two detailed qualitative case studies involving 112 indepth interviews with executives, managers, supervisors, and front-line staff in a large financial services organization and a medium-sized fashionable restaurant group uncovered five main strategies of surreptitious career success. These strategies are obligation creation and exploitation, personal-status enhancement, information acquisition and control, similarity exploitation, and proactive vertical alignment. Our findings indicate that just over 79% of those interviewed (88 of 112) referred to, at some point in their careers, premeditated strategies to enhance their careers that they concealed from coworkers. Consequently, we argue that surreptitious actions are central to employee career-focused activities and fundamental to a more complete understanding of the complexities of career-oriented employee behavior. © 2006 Wiley Periodicals, Inc. [source] Organic Single-Crystal Schottky Gate TransistorsADVANCED MATERIALS, Issue 36 2009Toshihiko Kaji Schottky contacts and Schottky gate transistors on organic single crystals are successfully fabricated, and enable the complete understanding of the operating mechanism as well as a full description of the energy-band diagram. This represents a considerable step forward in the understanding of organic semiconductors, and offers a viable route for organic-device design. [source] The modern furies: projection and superego subversion in the moral justification of violenceINTERNATIONAL JOURNAL OF APPLIED PSYCHOANALYTIC STUDIES, Issue 1 2007James Poulton Abstract The moral rationalization of violence and prejudice has long been viewed by psychoanalysis as resulting from a subversion of superego functioning. Yet, the specific mechanisms by which such subversions occur have remained obscure. In this paper, the intrapsychic and intersubjective dynamics of rationalizations of violence are explored as they arise in the dyadic interactions of a married couple in psychoanalytic psychotherapy. Those dynamics are then extrapolated to larger group processes (e.g. sects, races, nations, etc.), with the aim of developing a more complete understanding of the cycles of hatred and violence that can occur between them. Copyright © 2006 John Wiley & Sons, Ltd. [source] Vitiligo in an urban academic setting,INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 1 2010Taraneh Paravar MD Background, Vitiligo is a depigmenting disease of unknown etiology. A more complete understanding of vitiligo and associated conditions will provide better insight into the etiology and potential treatment options for this condition. We sought to gather information regarding associated conditions and other epidemiologic data on vitiligo. Methods, A retrospective chart review was performed of 135 patients with vitiligo seen between July 1, 2002 and June 30, 2005 at an academic medical center. Epidemiologic characteristics were recorded. Results, The patient population consisted of 80 women and 55 men with mean age of presentation of 36.8 years and average disease duration of 5.7 years. Vitiligo vulgaris was the predominant type of vitiligo and hypothyroidism was the most common co-morbidity. Anti-thyroid peroxidase and anti-thyroglobulin antibodies were found in 37% and 18% of patients, respectively. The highest proportion of thyroid abnormalities was found in age of onset category 21,30. Anti-nuclear antibodies were found in 33% of patients. Conclusion, The prevalence of anti-nuclear and anti-thyroid peroxidase antibodies was higher in our vitiligo study than that reported elsewhere. In addition, autoimmune thyroid disease may be more common in adult-onset vitiligo. [source] "Do Ourselves Credit and Render a Lasting Service to Mankind": British Moral Prestige, Humanitarian Intervention, and the Barbary PiratesINTERNATIONAL STUDIES QUARTERLY, Issue 1 2003Oded Löwenheim This paper raises the issue of moral credibility in international relations and shows that considerations of preserving moral prestige can become crucial for armed humanitarian intervention. It contrasts realist and constructivist explanations about the causes of humanitarian intervention and demonstrates that traditional accounts do not provide a complete understanding of the phenomenon of intervention. In the case studied here, Britain engaged in a relatively costly humanitarian intervention against the Barbary pirates, slave trade in Christian Europeans due to her willingness to defy moral criticism and exhibit consistency with her professed moral principles. No material incentives and/or constraints influenced the British decision, and neither was it affected by a sense of felling, with regard to the Christian slaves. Instead, allegations that Britain urged Europe to abolish the black slave trade out of selfish interests, while at the same time turning a blind eye toward the Christian slave trade of the pirates, undermined British moral prestige and became the cause of the Barbary expedition. [source] Mapping the organizational culture research in nursing: a literature reviewJOURNAL OF ADVANCED NURSING, Issue 5 2006Shannon Scott-Findlay PhD RN Aim., This paper reports a critical review of nursing organizational culture research studies with the objectives of: (1) reviewing theoretical and methodological characteristics of the studies and (2) drawing inferences specific to the state of knowledge in this field. Background., Organizational culture is regarded as significant in influencing research use in clinical practice yet it is not understood how culture shapes practitioners' behaviours. Only one review of this empirical literature in nursing has been completed. Method., Using selected computerized databases, published nursing research studies in English that examine organizational culture were accessed. Organizational culture studies were categorized using Hatch's three perspectives on organizational culture: (1) modern, (2) symbolic-interpretive and (3) postmodern. The review was conducted in 2005. Results., Twenty-nine studies were in the final data set. Results pointed to variations in cultural definitions and incorporation of organizational sciences theory. In classifying the studies, modern perspectives dominated (n = 22), symbolic-interpretive approaches were an emerging group (n = 6) and one study was unclassifiable. Our results expand current cultural instrument reviews by pinpointing tools that have been previously overlooked and by identifying ongoing theoretical and methodological challenges for researchers. Conclusion., An exclusive reliance on modernistic approaches in organizational culture research cannot yield a complete understanding of the phenomenon. Rather, the field could benefit from a variety of cultural approaches. In a similar vein, researchers need to be mindful of the terminology and the unit of analysis they use in their research, as these are the two largest research challenges. [source] The intertarsal joint of the ostrich (Struthio camelus): Anatomical examination and function of passive structures in locomotionJOURNAL OF ANATOMY, Issue 6 2009Nina U. Schaller Abstract The ostrich (Struthio camelus) is the largest extant biped. Being flightless, it exhibits advanced cursorial abilities primarily evident in its characteristic speed and endurance. In addition to the active musculoskeletal complex, its powerful pelvic limbs incorporate passive structures wherein ligaments interact with joint surfaces, cartilage and other connective tissue in their course of motion. This arrangement may enable energy conservation by providing joint stabilisation, optimised limb segment orientation and automated positioning of ground contact elements independently of direct muscle control. The intertarsal joint is of particular interest considering its position near the mid-point of the extended limb and its exposure to high load during stance with significant inertial forces during swing phase. Functional-anatomical analysis of the dissected isolated joint describes the interaction of ligaments with intertarsal joint contours through the full motion cycle. Manual manipulation identified a passive engage-disengage mechanism (EDM) that establishes joint extension, provides bi-directional resistance prior to a transition point located at 115° and contributes to rapid intertarsal flexion at toe off and full extension prior to touch down. This effect was subsequently quantified by measurement of intertarsal joint moments in prepared anatomical specimens in a neutral horizontal position and axially-loaded vertical position. Correlation with kinematic analyses of walking and running ostriches confirms the contribution of the EDM in vivo. We hypothesise that the passive EDM operates in tandem with a stringently coupled multi-jointed muscle-tendon system to conserve the metabolic cost of locomotion in the ostrich, suggesting that a complete understanding of terrestrial locomotion across extinct and extant taxa must include functional consideration of the ligamentous system. [source] Participatory research methods in environmental science: local and scientific knowledge of a limnological phenomenon in the Pantanal wetland of BrazilJOURNAL OF APPLIED ECOLOGY, Issue 4 2000D.F. Calheiros Summary 1.,Participatory research methodologies incorporating local knowledge are important to the success of ecological research and the sustainable management of natural systems. However, methods of this type are not commonly employed in the natural sciences. 2.,We adopted a scientifically rigorous ethnographic research methodology to incorporate local knowledge into understanding a natural limnological phenomenon in the Brazilian Pantanal. Known locally as ,dequada', it is associated with fish kills. 3.,Using primarily open-ended questions and semi-structured interviews, 30 older head-of-household men were interviewed, by the same interviewer, in a small community representative of the few local riverside settlements. Their opinions were then contrasted with current scientific knowledge. 4.,In concordance with the scientific community, the local community cited decomposition of organic material as the principal cause of fish mortality due to the dequada. Local people therefore can have a well-founded understanding of their environment. 5.,This study demonstrates the importance of incorporating local knowledge to corroborate and, often, to guide the process of scientific inquiry. In this case, local knowledge added to scientific knowledge by providing a more complete understanding of the management and conservation of a natural system. We recommend that ecologists should be ready to acknowledge that local understanding can be greater than that of ,outsiders'. [source] Modelling the efficacy of entomopathogenic nematodes in the regulation of invertebrate pests in glasshouse cropsJOURNAL OF APPLIED ECOLOGY, Issue 2 2000A. Fenton Summary 1. ,Entomopathogenic nematodes belonging to the families Heterorhabditidae and Steinernematidae are lethal obligate parasites of a wide range of invertebrate species. These nematodes exhibit many characteristics that make them ideal candidates as biological control agents of insect pests (rapid host death, high reproductive rates, easily mass-reared in vitro, easy application techniques). 2. ,However, at present, the number of pest species to which these nematodes are applied successfully is small. Clearly, there is a need to develop existing knowledge of the nematode into a more complete understanding of the nematode,pest system as a whole. 3. ,To consider the potential of entomopathogenic nematodes as biological control agents, we adopted a generalized analytical modelling approach and, using realistic parameter estimates, determined the conditions under which these nematodes can regulate a pest population. 4. ,Stability analyses suggested that entomopathogenic nematodes may not be capable of regulating a host population to a stable equilibrium. Long-term persistence of the host and nematode population is unlikely, due to the highly destabilizing effects of the parasite,host relationship. As such, these nematodes may be better suited to short-term control through inundative application techniques rather than long-term regulation. 5. ,This preliminary generalized model highlights areas where further work is needed. This includes estimation of the probability of nematode infection in the field, the effect of host size on the transmission cycle and the influence of spatial heterogeneity on stability. [source] History of science , sporesJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2006Lewis B Perry Memorial Lecture 200 Abstract Bacterial endospores were first studied 130 years ago by Cohn in 1876 and independently by Koch in the same year. Although spore dormancy and resistance have been much studied since then, questions still remain concerning the basic mechanisms and the kinetics of heat inactivation in particular. Likewise, the extreme dormancy and longevity of spores was recognized early on and later greatly extended but still evade complete understanding. Evidence has accumulated for the involvement of specific spore components such as calcium, dipicolinic acid, small acid soluble proteins in the core and peptidoglycan in the cortex. Involvement of physical factors too, such as the relative dehydration of the core, maybe in a high-viscosity state or even in a glassy state, has added to appreciation of the multicomponent nature of dormancy and resistance. Spore-former morphology formed the basis for early classification systems of sporeformers from about 1880 and consolidated in the mid-1900s, well prior to the use of modern genetic procedures. With respect to sporulation, groundbreaking sequence studies in the 1950s provided the basis for later elucidation of the genetic control widely relevant to many cell differentiation mechanisms. With respect to the breaking of dormancy (activation and germination), the elucidation of mechanisms began in the 1940s following the observations of Hills at Porton who identified specific amino acid and riboside ,germinants', and laid the basis for the later genetic analyses, the identification of germinant receptor genes and the elucidation of key germination reactions. The nonexponential nature of germination kinetics has thwarted the development of practical Tyndallization-like processing. So inactivation by heat remains the premier method of spore control, the basis of a huge worldwide industry, and still relying on the basic kinetics of inactivation of Clostridium botulinum spores, and the reasoning regarding safety first evolved by Bigelow et al. in 1920 and Esty and Meyer in 1922. ,Newer' processes such as treatment with ionizing radiation (first proposed in 1905) and high hydrostatic pressure (first proposed in 1899) may be introduced if consumer resistance and some remaining technical barriers could be overcome. [source] Mechanistic insights into oxidosqualene cyclizations through homology modelingJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2003Gasch, Tanja Schulz Abstract 2,3-Oxidosqualene cyclases (OSC) are key enzymes in sterol biosynthesis. They catalyze the stereoselective cyclization and skeletal rearrangement of (3S)-2,3-oxidosqualene to lanosterol in mammals and fungi and to cycloartenol in algae and higher plants. Sequence information and proposed mechanism of 2,3-oxidosqualene cyclases are closely related to those of squalene-hopene cyclases (SHC), which represent functional analogs of OSCs in bacteria. SHCs catalyze the cationic cyclization cascade converting the linear triterpene squalene to fused ring compounds called hopanoids. High stereoselectivity and precision of the skeletal rearrangements has aroused the interest of researchers for nearly half a century, and valuable data on studying mechanistic details in the complex enzyme-catalyzed cyclization cascade has been collected. Today, interest in cyclases is still unbroken, because OSCs became targets for the development of antifungal and hypocholesterolemic drugs. However, due to the large size and membrane-bound nature of OSCs, three-dimensional structural information is still not available, thus preventing a complete understanding of the atomic details of the catalytic mechanism. In this work, we discuss results gained from homology modeling of human OSC based on structural information of SHC from Alicyclobacillus acidocaldarius and propose a structural model of human OSC. The model is in accordance with previously performed experimental studies with mechanism-based suicide inhibitors and mutagenesis experiments with altered activity and product specificity. Structural insight should strongly stimulate structure-based design of antifungal or cholesterol-lowering drugs. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 741,753, 2003 [source] Pulp handling by vertebrate seed dispersers increases palm seed predation by bruchid beetles in the northern AmazonJOURNAL OF ECOLOGY, Issue 6 2002Kirsten M. Silvius Abstract 1The simultaneous use of fruits and seeds by invertebrate seed predators and vertebrate seed dispersers produces complex ecological interactions that reduce the predictability of seed fate. 2Cocosoid palm seeds in the Neotropics are subject to high mortality by bruchid beetle infestation and such attack is the major cause of mortality for seeds of the palm Attalea maripa at our study site in the northern Brazilian Amazon. 3The exocarp and mesocarp of 1400 fruits were manipulated in different ways to simulate handling by vertebrates. No eggs of the bruchid beetle, Pachymerus cardo, were laid on intact control fruits, while the highest numbers of eggs were received by fruits whose exocarp and mesocarp had been partially removed, as if by primates and rodents (mean of 15.9 and 18.9 eggs fruit,1, respectively, during the peak fruiting season). Fruits with intact mesocarp but no exocarp, and fruits with all mesocarp and exocarp removed, received low numbers of eggs (mean of 4.6 and 6.6 eggs per fruit, respectively, during the peak fruiting season). Thus both exocarp and mesocarp deter oviposition, and removal of these fruit structures increases fruit susceptibility to infestation. 4Oviposition rates declined as the fruiting season progressed, but oviposition preferences remained the same. Seed mortality was high for any fruit on which eggs were laid. 5Large rodents and primates, which have been considered among the most effective seed dispersers for large-seeded Neotropical trees such as palms, actually increased the susceptibility of seeds to bruchid beetle attack. Removal of (intact) seeds by other dispersers may be necessary to ensure seed survival. 6These results indicate that the reliability of seed dispersers cannot be gauged without a complete understanding of variables that affect seed viability. [source] Experimental study of the hydraulic operation of an annular centrifugal contactor with various mixing vane geometriesAICHE JOURNAL, Issue 8 2010Kent E. Wardle Abstract The annular centrifugal contactor is a combination mixer/centrifuge that has been developed for solvent extraction processes for recycling used nuclear reactor fuel. The experimental observations presented were part of a simulation-focused research effort aimed at providing a more complete understanding of the fluid flow within these contactors to enable further advancements in design and operation of future units and greater confidence for use of such contactors in a variety of other solvent extraction applications. Laser doppler velocimetry (LDV), particle image velocimetry (PIV), pressure measurements, and high-speed video imaging for a range of flow rates and rotor speeds were performed to characterize the flow of water in the annular mixing region of the contactor using three different mixing vane geometries. It was found that the geometry of the mixing vanes has a significant impact on the annular liquid height and general flow in the contactor mixing zone. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Attitudes of Japanese students toward people with intellectual disabilityJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 5 2002W. Horner-Johnson Abstract Background The purpose of the present study was to gain insight into the structure and organization of the attitudes of Japanese students toward people with intellectual disability (ID). The study also examined how these attitudes are related to individual characteristics, such as experience with people with ID, major field of study and career interests. Methods The participants completed a series of measures developed in the USA: three measures of attitudes toward people with ID, a demographic questionnaire and a social desirability scale. Students completed the measures anonymously. Results The factor structures of all three attitude scales replicated the structures found in the USA. Attitudes toward the community inclusion of people with ID were negatively correlated with an endorsement of eugenics. Students in social work and psychology had more positive attitudes than other students. Participants who expressed an interest in a career working with people with ID had more positive attitudes than students with no interest in such a career. Conclusions Attitude measures developed in the USA can be used in Japan, and can provide useful information as well as an opportunity for cross-cultural comparisons. For a more complete understanding of the attitudes of Japanese people toward people with ID, these attitudes should also be studied using measures based in Japanese culture which have specifically developed to measure attitudes in Japan. [source] Transforming growth factor-,1 induced alteration of skeletal morphogenesis in vivoJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2004Cristin M. Ferguson Abstract Transforming growth factor beta (TGF-,) is expressed in the growth plate and is an important regulator of chondrocyte maturation. Loss of function results in premature chondrocyte maturation both in vitro and in vivo. While TGF-, inhibits chondrocyte maturation in cell cultures, the effect of increased TGF-, has not been well characterized in an in vivo development model. Addition of Affi-gel agarose beads loaded with TGF-,1 (10 ng/,l) to developing stage 24,25 chick limb buds resulted in limb shortening and altered morphology. In situ hybridization studies showed down regulation of Indian hedgehog (ihh), bone morphogenetic protein 6 (bmp6), and collagen type X (colX) expression, markers of chondrocyte maturation, in TGF-,1 treated limbs. TGF-,1 also decreased chondrocyte proliferation in the developing anlage. The findings confirm a critical role for TGF-, during skeletal development. A more complete understanding of the role of TGF-, and its down-stream signals will lead to improved understanding and treatment of cartilage diseases. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Determination of outer layer and bulk dehydration kinetics of trehalose dihydrate using atomic force microscopy, gravimetric vapour sorption and near infrared spectroscopyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Matthew D. Jones Abstract Knowledge of the kinetics of solid state reactions is important when considering the stability of many medicines. Potentially, such reactions could follow different kinetics on the surface of particles when compared with their interior, yet solid state processes are routinely followed using only bulk characterisation techniques. Atomic force microscopy (AFM) has previously been shown to be a suitable technique for the investigation of surface processes, but has not been combined with bulk techniques in order to analyse surface and bulk kinetics separately. This report therefore describes the investigation of the outer layer and bulk kinetics of the dehydration of trehalose dihydrate at ambient temperature and low humidity, using AFM, dynamic vapour sorption (DVS) and near infrared spectroscopy (NIR). The use of AFM enabled the dehydration kinetics of the outer layers to be determined both directly and from bulk data. There were no significant differences between the outer layer dehydration kinetics determined using these methods. AFM also enabled the bulk-only kinetics to be analysed from the DVS and NIR data. These results suggest that the combination of AFM and bulk characterisation techniques should enable a more complete understanding of the kinetics of certain solid state reactions to be achieved. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4404,4415, 2008 [source] Theoretical evidence on O,N type smiles rearrangement mechanism: a computational study on the intramolecular cyclization of N -methyl-2-(2-chloropyridin-3-yloxy)-acetamide anionJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2008Hui Sun Abstract Smiles rearrangement (SR) falls under a broad category of organic synthesis for many important compounds. A complete understanding toward SR process appeals to the assistance of theoretical research. Herein, by performing quantum chemistry calculations, we give a theoretical evidence for the mechanism of a representative O,N type SR, the intramolecular cyclization of N -methyl-2-(2-chloropyridin-3-yloxy)acetamide anion. It is found that the SR to the ipso -position involves a two-step mechanism and is energetically more favorable than the direct nucleophilic attack by N atom on the ortho -position. The present result rationalizes well the experimentally observed ipso -SR product and provides a consistent picture of the O,N SR process. Copyright © 2008 John Wiley & Sons, Ltd. [source] Review article: a critical view on impaired accommodation as therapeutic target for functional dyspepsiaALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 11 2006B. D. J. VAN DEN ELZEN Summary Several important pathophysiological mechanisms have been identified in functional dyspepsia, however a complete understanding of these mechanisms and beneficial therapeutic strategies are still lacking. Based on the currently available literature we aimed at providing a critical view on one of these pathophysiological mechanisms, impaired accommodation. Although impaired gastric accommodation is identified as a major pathophysiological mechanism, the clinical evidence supporting its role as an important therapeutic target is currently still lacking. Treatment with fundic relaxant drugs has shown conflicting results and has been rather disappointing in general. These negative findings could be explained by the fact that impaired fundic accommodation is part of a more complex disorder involving other regions of the proximal gut or by the increasing insight that central mechanisms may play an important role. Future studies of impaired accommodation should take these considerations into account. [source] | ||||||||||||||||||||||||||||