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Central Position (central + position)
Selected AbstractsThree types of cilia including a novel 9+4 axoneme on the notochordal plate of the rabbit embryoDEVELOPMENTAL DYNAMICS, Issue 12 2006Kerstin Feistel Abstract Motile monocilia play a pivotal role in left-right axis determination in mouse and zebrafish embryos. Cilia with 9+0 axonemes localize to the distal indentation of the mouse egg cylinder ("node"), while Kupffer's vesicle cilia in zebrafish show 9+2 arrangements. Here we studied cilia in a prototype mammalian embryo, the rabbit, which develops via a flat blastodisc. Transcription of ciliary marker genes Foxj1, Rfx3, lrd, polaris, and Kif3a initiated in Hensen's node and persisted in the nascent notochord. Cilia emerged on cells leaving Hensen's node anteriorly to form the notochordal plate. Cilia lengthened to about 5 ,m and polarized from an initially central position to the posterior pole of cells. Electron-microscopic analysis revealed 9+0 and 9+2 cilia and a novel 9+4 axoneme intermingled in a salt-and-pepper-like fashion. Our data suggest that despite a highly conserved ciliogenic program, which initiates in the organizer, axonemal structures may vary widely within the vertebrates. Developmental Dynamics 235:3348,3358, 2006. © 2006 Wiley-Liss, Inc. [source] Role of endoscopic ultrasound in superficial esophageal cancerDISEASES OF THE ESOPHAGUS, Issue 2 2009Tan Attila SUMMARY The recent increase in the incidence of superficial esophageal cancer and promising developments in potentially curative endoscopic therapies have placed endoscopic ultrasound in a central position with regard to decision making. This is a review of the literature to determine the role of endoscopic ultrasound and high frequency probe ultrasonography in the assessment of superficial esophageal carcinomas. [source] The notion of ,phonology' in dyslexia research: cognitivism,and beyondDYSLEXIA, Issue 3 2007Per Henning Uppstad Abstract Phonology has been a central concept in the scientific study of dyslexia over the past decades. Despite its central position, however, it is a concept with no precise definition or status. The present article investigates the notion of ,phonology' in the tradition of cognitive psychology. An attempt is made to characterize the basic assumptions of the phonological approach to dyslexia and to evaluate these assumptions on the basis of commonly accepted standards of empirical science. First, the core assumptions of phonological awareness are outlined and discussed. Second, the position of Paula Tallal is presented and discussed in order to shed light on an attempt to stretch the cognitive-psychological notion of ,phonology' towards auditory and perceptual aspects. Both the core assumptions and Tallal's position are rejected as unfortunate, albeit for different reasons. Third, the outcome of this discussion is a search for what is referred to as a ,vulnerable theory' within this field. The present article claims that phonological descriptions must be based on observable linguistic behaviour, so that hypotheses can be falsified by data. Consequently, definitions of ,dyslexia' must be based on symptoms; causal aspects should not be included. In fact, we claim that causal aspects, such as ,phonological deficit', both exclude other causal hypotheses and lead to circular reasoning. If we are to use terms such as ,phonology' and ,phoneme' in dyslexia research, we must have more precise operationalizations of them. Copyright © 2007 John Wiley & Sons, Ltd. [source] Intra- and Intersexual Selection for Multiple Traits in the Peacock (Pavo cristatus)ETHOLOGY, Issue 9 2005Adeline Loyau Animal communication involves a multitude of signals ranging from morphological to behavioural traits. In spite of the diversity of traits used in animal signalling, most studies of sexual selection have focused on single male traits. Moreover, the two forces of sexual selection (male,male competition and female preference) may target different traits and favour the diversification of male signalling. Still, little is known on the combined effects of intra- and intersexual selection on the evolution of multiple signals. The peacock is often cited as one of the best examples of the strength of sexual selection in producing exaggerated traits. Here, we investigated traits under intra- and intersexual selection in a population of free-ranging common peafowl. Peacocks with longer trains and tarsi were more likely to establish a display territory in a central position within the lek and had a higher number of intrusions and agonistic interactions. These traits appeared therefore to be under intrasexual selection. Female selection was assessed as the number of copulations. Mating success was positively correlated with behavioural traits (display activity) and with train ornamentation (number and density of ocelli) suggesting that females use multiple cues during mate selection. Therefore, intra- and intersexual selection seem to operate on different sets of traits. Overall, our results stress the role of multiple receivers on the evolution of multiple signals. [source] Kinetics and mechanism of the reaction between maleic anhydride and fatty acid esters and the structure of the productsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2008Florina Stefanoiu Abstract Alkenyl succinic anhydrides (ASA) were obtained by reaction between maleic anhydride and high-oleic sunflower oil (HOSO) esters. A kinetics study of the maleinization of alkyl esters indicated that the maleinization reaction was second order overall and first order with respect to the individual reactants, and the activation energy was 77.2,±,3.3,kJ/mol in the investigated temperature range (185,225,°C). These results showed that the cis configuration and the central position of the double bond in HOSO esters facilitate the maleinization of the latter. On the contrary, the length of the linear ester moiety had no influence on the course of the maleinization reaction. Moreover, new evidence demonstrates that there are two different reaction mechanisms: ene-reaction and addition in allylic position with a 2,:,1 ratio, respectively. This ratio was constant throughout the reaction, thus indicating that these mechanisms are independent. [source] Is there a role of visual cortex in spatial hearing?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2004Ulrike Zimmer Abstract The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, any deviation of the eyes from a central position results in a divergence between the retinal visual and the head-centred auditory coordinates. It has been suggested that this divergence is compensated for by a neural coordinate transformation, using a signal of eye-in-head position. Using functional magnetic resonance imaging, we investigated which cortical areas of the human brain participate in such auditory,visual coordinate transformations. Sounds were produced with different interaural level differences, leading to left, right or central intracranial percepts, while subjects directed their gaze to visual targets presented to the left, to the right or straight ahead. When gaze was to the left or right, we found the primary visual cortex (V1/V2) activated in both hemispheres. The occipital activation did not occur with sound lateralization per se, but was found exclusively in combination with eccentric eye positions. This result suggests a relation of neural processing in the visual cortex and the transformation of auditory spatial coordinates responsible for maintaining the perceptual alignment of audition and vision with changes in gaze direction. [source] Synthesis of Carboxyl-Tethered Symmetric Conjugated Polyenes as Fluorescent Transmembrane Probes of Lipid BilayersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2003Ernesto Quesada Abstract The synthesis of a new series of fluorescent transmembrane probes in which two hydrophilic methyl ester or carboxyl groups are connected by a polymethylene chain, with four, five or six conjugated double bonds in a central position, is reported. The length of the linear structures was designed to match the width of typical lipid bilayers. These bolaamphiphilic compounds result, with overall yields higher than 80%, from an easy PdII -catalyzed double cross-coupling between terminal acetylene esters and conjugated 1,,-dihalopolyenes, followed by selective triple bond partial reduction with activated zinc, and iodine isomerization to the all-(E) isomer. An alternative approach, based on a Stille double cross-coupling between the appropriate all-(E)-,-halopolyenes and (E)-bis(tributylstannyl)ethene, yielded mixtures that could not be resolved by standard chromatographic methods due to the presence of other simultaneous coupling reactions, which are also discussed in detail. Nevertheless, the Stille method can be of utility for the obtention of carbonyl-polyene conjugated analogs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] NMR-Solution Structures of Fluoro-Substituted , -Peptides: A 314 -Helix and a Hairpin Turn.HELVETICA CHIMICA ACTA, Issue 12 2007-Fluoro-Amide Group, The First Case of a 90° OCCF Dihedral Angle in an Abstract To further study the preference of the antiperiplanar (ap) conformation in , -fluoro-amide groups, two , -peptides, 1 and 2, containing a (2-F)- ,3hAla and a (2-F)- ,2hPhe residue, have been synthesized. Their NMR-solution structures in CD3OH were determined and compared with those of non-F-substituted analogs, 3 and 4a. While we have found in a previous investigation (Helv. Chim. Acta2005, 88, 266) that a stereospecifically introduced F-substituent in the central position of a , - heptapeptide is capable of ,breaking' the 314 -helical structure by enforcing the FCCO ap -conformation, we could now demonstrate that the same procedure leads to a structure with the unfavorable ca. 90° FCCO dihedral angle, enforced by the 314 -helical folding in a , - tridecapeptide (cf.1; Fig.,4). This is interpreted as a consequence of cooperative folding in the longer , -peptide. A F-substituent placed in the turn section of a , -peptidic hairpin turn was shown to be in an ap -arrangement with respect to the neighboring CO bond (cf.2; Fig.,7). Analysis of the non-F-substituted , -tetrapeptides (with helix-preventing configurations of the two central ,2/,3 -amino acid residues) provides unusually tight hairpin structural clusters (cf.3 and 4a; Figs.,8 and 9). The skeleton of the , -tetrapeptide H-(R),3hVal-(R),2hVal-(R),3hAla-(S),3hPhe-OH (4a) is proposed as a novel, very simple backbone structure for mimicking , -peptidic hairpin turns. [source] Adjusting magnetic moments of Sc13 and Y13 clusters by doping different X atom (X = Na, Mg, Al, Si, P)INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 8 2010Fu-Yang Tian Abstract We have investigated the structural and magnetic properties of the doped XM12 and charged M13 (X = Na, Mg, Al, Si, P; M = Sc, Y) clusters using the density-functional theory with spin-polarized generalized gradient approximation. It was found that doped atoms can induce significant change of the magnetic moments of Sc13 and Y13 clusters. The total magnetic moments of the NaM12, MgM12, AlM12, SiM12, and PM12 clusters are regular 5, 6 (12), 7, 8, and 9 ,b, respectively (but 19 ,b for Sc13 and Y13, 12 ,b for Y, 18 ,b for Sc, Sc, and Y). The doped atom substituting the surface atom of the plausible icosahedral configuration is viewed as the ground-state structure of the XM12 (X = Na, P; M = Sc, Y) and MgSc12 clusters. While for XM12 (X = Al, Si; M = Sc, Y) and MgY12 clusters, the doped atom occupying the central position of the icosahedral configuration is viewed as the ground-state structure. The doping and the charging both enhance the stability of the Sc13 and Y13 clusters. These findings should have an important impact on the design of the adjustable magnetic moments systems. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Hybrid ,/,3 -peptides with proteinogenic side chains. monosubstituted analogues of the chemotactic tripeptide For-Met-Leu-Phe-OMeJOURNAL OF PEPTIDE SCIENCE, Issue 8 2004Cesare Giordano Abstract The ,/,3 -mixed tripeptides R-CO-,3 -HMet-Leu-Phe-OMe (1a,b), R-CO-Met-,3 -HLeu-Phe-OMe (2a,b) and R-CO-Met-Leu-,3 -HPhe-OMe (3a,b) (a, R = tert -butyloxy-; b, R = H,), analogues of the potent chemoattractant For-Met-Leu-Phe-OMe, have been synthesized by classical solution methods and fully characterized. The activities of the new analogues as chemoattractants, superoxide anion producers and lysozyme releasers have been determined on human neutrophils. Whereas all of the three N -formyl derivatives are significantly less active than the parent tripeptide as chemoattractants, compound 1b has been found to be highly active as a superoxide anion producer and 3b as a lysozyme releaser. The results show that the replacement of the native Leu residue at the central position is, in each of the examined cases, the least favourable modification. The three N -Boc derivatives are, as expected, devoid of activity as agonists, but they are all good inhibitors of chemotaxis. Information on the solution conformation has been obtained by examining the involvement of the NH groups in intramolecular H-bonds using 1H NMR. The conformation of the N -Boc analogue 1a has also been determined in the crystal state by x-ray diffraction analysis. The molecule is extended at the ,3 -HMet residue (,1 = ,87°;,1 = 172°;,1 = 126° ) and no intramolecular H-bond is present. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Divergences in American psychiatry during the Depression: Somatic psychiatry, community mental hygiene, and social reconstruction,JOURNAL OF THE HISTORY OF THE BEHAVIORAL SCIENCES, Issue 4 2001Hans Pols Ph.D. postdoctoral fellow The differences between somatic psychiatrists and mental hygienists, already apparent earlier, became much more pronounced during the Depression years, partly as a consequence of their different perspectives on this social crisis. Somatic psychiatrists, emboldened by the apparent success of new medical treatment methods, reasserted the central position of the mental hospital within psychiatry, attempted to improve the discipline's position within medicine, and promoted basic research. Mental hygienists, following the ideal of prevention, proposed far-reaching programs of community mental hygiene to alleviate widespread mental distress. A small group of mental hygienists embraced socialism and advocated measures of radical social reconstruction. © 2001 John Wiley & Sons, Inc. [source] Exodus as Travelling Theory: Excavating the Promised Land in the African American ImaginationLITERATURE COMPASS (ELECTRONIC), Issue 3 2007Anna Hartnell This essay won the 2006 Literature Compass Graduate Essay Prize, American Section. Exodus, this article suggests, is one of the defining texts through which Americans have imaginatively re-mapped the nation's relationship to the spectre of ,Egyptian' oppression. This article proposes to consider the evolution of the Exodus text from its pivotal place in an often imperialist presidential rhetoric to its central position in African American elaborations of resistance. I suggest that the story of Exodus issuing from the lips of W. E. B. Du Bois, Martin Luther King or Toni Morrison crucially unsettles the ,innocent' position assumed by America's political establishment in relation to the enigmatic question of ,freedom'. This article reviews the interruptive possibilities of African American re-tellings of the Exodus narrative in the context of Edward Said's notion of ,travelling theory'. In his examination of theories devolved from their point of origin, Said poses a crucial distinction between theories that lose their critical power via domestication to the status quo and those which ,flame out' from this path by reaffirming and even furthering their radical potential. I argue here that it is these destablizing currents that largely animate the African American counter-cultural tradition that excavates the promised land in order to tell of a fundamentally ,unhomely' exodus. Where mainstream invocations of Exodus present America's rendition as an epochal overcoming of Hegel's seemingly inexorable master/slave dialectic, the appropriation of this story by America's internal ,others' is a standing reminder that America is not , contra Hegel's memorable suggestion , the destination of ,History's' end. [source] Food, Not Nutrients, Is the Fundamental Unit in NutritionNUTRITION REVIEWS, Issue 10 2007David R. Jacobs Jr. The identification of nutrients and the study of their bioactivity were significant developments in the evolution of contemporary nutrition science. This review argues for shifting the focus towards food in order to better understand the nutrition-health interface. It begins by introducing the concept of food synergy (a perspective that more information can be obtained by looking at foods than at single food components) to denote the action of the food matrix (the composite of naturally occurring food components) on human biological systems. A proposal is then made for the means by which food-focused research might build the knowledge base for etiologic discovery and appropriate dietary advice. The diet-heart disease dilemma is put forward as an example of where a nutrient-based approach has limitations, and a summary of studies targeting food composition strengthens the case for a food-based approach. Finally, the argument is made that evidence from interventions points back to the central position of food in the relationship between nutrition and health, a position that begs for more whole food-based research. [source] Kondo effect in oscillating moleculesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009Jernej Mravlje Abstract We consider electronic transport through break-junctions bridged by a single molecule in the Kondo regime. We describe the system by a two-channel Anderson model. We take the tunneling matrix elements to depend on the position of the molecule. It is shown, that if the modulation of the tunneling by displacement is large, the potential confining the molecule to the central position between the leads is softened and the position of the molecule is increasingly susceptible to external perturbations that break the inversion symmetry. In this regime, the molecule is attracted to one of the leads and as a consequence the conductance is small. We argue on semi-classical grounds why the softening occurs and corroborate our findings by numerical examples obtained by Wilson's numerical renormalization group and Schönhammer,Gunnarsson's variational method (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The use of the past and the present in the clinical setting Pasts and presentsTHE INTERNATIONAL JOURNAL OF PSYCHOANALYSIS, Issue 6 2006JANINE PUGET The author provides a brief summary of Latin American literature concerning temporality. She shows that a common theme throughout all these papers is that the analytical relationship is considered to be bipersonal and symmetrical, thus demonstrating a concern for establishing the basis by which social subjectivity can be reconsidered. This literature displaces the idea of linear time from its central position and introduces other measures of time. The analytical relationship takes place not only in the past but also in a newly created present. This is the ongoing present, of what is happening now, instantaneous and without a prior history attached to it. This leads the author to suggest that there is a present to one's history and a history to one's present. She then analyses the consequences of this proposition by examining some clinical material where she attempts to pinpoint those instances in which the analyst may have reacted defensively, tending to position himself in the analysand's past instead of being able to take action in the present. Clinical material from the IJP is used. [source] Kepler, Galileo, the telescope and its consequencesASTRONOMISCHE NACHRICHTEN, Issue 6 2009J. Hamel Abstract In the beginning Copernicus' system of the world did not have empirical confirmation. In this situation, Kepler's research, as well as the astronomical observations with the telescope, invented in 1608, played a decisive role. Under the assumption of the central position of the Sun, Kepler discovered the elliptical orbital motion of the planets as a base of the computation of noticeably improved ephemerides. The first telescopic observations , Jupiter's moons, phases of Venus, sunspots, surface features of the moon, gave important arguments for Copernicus' system. Galilei was one of the first who used the telescope for astronomical research (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Traditional therapies: glucocorticoids, azathioprine, methotrexate, hydroxyureaCLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 7 2002G. Belgi Summary The ,old favourites' used for treatment of inflammatory diseases, and hence, the original immunomodulators, include the glucocorticoids, azathioprine, methotrexate and hydroxyurea. Glucocorticoids are still one of the most effective anti-inflammatory agents because they work on several different intracellular processes and hence, block many components that contribute to inflammatory and immune responses. They bind to intracellular glucocorticoid receptors which transport them into the nucleus. Here the receptor/steroid complex may bind to many genes that interact with transcription factors including NF,B and AP-1, to inhibit their activation, thereby preventing activation of many genes encoding immune effector and pro-inflammatory cytokines. Also, protein kinases involved in intracellular signalling, are directly activated resulting in phosphorylation of various targets of which Annexin (AXA)-1 is critical in inhibiting biosynthesis of both purines and DNA. This results in reduced proliferation of B and T lymphocytes, reduced immune effector mechanisms and reduced recruitment of mononuclear cells including monocytes into sites of immune inflammation. Methotrexate also blocks DNA synthesis and hence cellular proliferation but also induces release of adenosine. This inhibits chemotaxis of polymorph neutrophils and release of critical cytokines such as TNF-, and Interleukins 6 and 8. Hydroxyurea also inhibits DNA synthesis with inhibitory effects on proliferation of lymphocytes and possibly kerationcytes. Even though many new agents with much greater selectivity are coming through into clinical use, this group of old agents still have an absolutely central position in the therapeutic armamentarium. Their value lies in the fact that they are not ,clean' drugs with narrow effects but they inhibit a wide range of mechanisms involved in immune and inflammatory processes. [source] Anti-Predator Strategies and Grouping Patterns in White-Tailed Deer and Mule DeerETHOLOGY, Issue 4 2001Susan Lingle White-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) are closely related species of similar size that differ in their anti-predator behavior. White-tails flee from coyotes (Canis latrans), whereas mule deer typically stand their ground and attack this predator. I used observations of coyotes hunting deer to identify: (i) changes in group structure made in response to coyotes; and (ii) the relationship between group structure and the risk of predation for each species. In response to coyotes, groups of mule deer merged with other groups and individuals bunched together. Predation attempts were more likely to escalate when groups split and individuals failed to bunch. Coyotes typically attacked mule deer that were in outlying positions, and these deer had to move to central positions to end attacks. Due to the high frequency of attacks on small groups as well as to the level of dilution of risk, individuals in small mule deer groups were at high risk of being attacked compared with those in larger groups. In contrast to mule deer, white-tails made no consistent changes in group size or formation, and coyotes attacked individuals in central as well as in outlying positions. Variation in aspects of group cohesion was not related to the vulnerability of white-tails, and there was no obvious difference in the risk of attack facing individuals in groups of different size. These results suggest that coyote predation selects for relatively large, cohesive groups in mule deer, apparently because this type of group improves their ability to deter coyotes. Coyote predation does not have similar effects on groups formed by white-tails, which use flight rather than deterrence to avoid predation. The benefits of responding cohesively, occupying certain positions within groups, and forming groups of a certain size can vary widely depending on the anti-predator strategies used by an animal. [source] Conformational Study of Short Peptoid Models for Future Applications as Potent Antimicrobial CompoundsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2007Fateh Singh Nandel Abstract Development of peptides as clinically useful drugs is limited by their poor metabolic stability and low bioavailability. Recent progresses in chemical synthesis and design have led to several strategies for producing potent mimetics. This study aims to analyze sequence/structure requirements and composition for antimicrobial peptoid designs, as use of peptoids is one of the most representative approaches to meet the goal of biomimicry. Analysis of the designs showed that for maximum activity and minimum hemolysis, the plane of the aromatic residues should be at an angle between 0 and 90,° with respect to membranes, cationic residues need not be at the terminal position, and central positions should be uniform in NIle, NLys, and NPhe residues. [source] | ||||||||||||||||||||||