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Complex Array (complex + array)
Selected AbstractsEffects of substrate geometry on growth cone behavior and axon branchingDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2006Ginger S. Withers Abstract At the leading edge of a growing axon, the growth cone determines the path the axon takes and also plays a role in the formation of branches, decisions that are regulated by a complex array of chemical signals. Here, we used microfabrication technology to determine whether differences in substrate geometry, independent of changes in substrate chemistry, can modulate growth cone motility and branching, by patterning a polylysine grid of narrow (2 or 5 ,m wide) intersecting lines. The shape of the intersections varied from circular nodes 15 ,m in diameter to simple crossed lines (nodeless intersections). Time-lapse recordings of cultured hippocampal neurons showed that simple variations in substrate geometry changed growth cone shape, and altered the rate of growth and the probability of branching. When crossing onto a node intersection the growth cone paused, often for hours, and microtubules appeared to defasciculate. Once beyond the node, filopodia and lamellipodia persisted at that site, sometimes forming a collateral branch. At nodeless intersections, the growth cone passed through with minimal hesitation, often becoming divided into separate areas of motility that led to the growth of separate branches. When several lines intersected at a common point, growth cones sometimes split into several subdivisions, resulting in the emergence of as many as five branches. Such experiments revealed an intrinsic preference for branches to form at angles less than 90°. These data show that simple changes in the geometry of a chemically homogeneous substrate are detected by the growth cone and can regulate axonal growth and the formation of branches. © 2006 Wiley Periodicals, Inc. J Neurobiol 66: 1183,1194, 2006 [source] PLASTICITY IN REPRODUCTIVE PHENOTYPES REVEALS STATUS-SPECIFIC CORRELATIONS BETWEEN BEHAVIORAL, MORPHOLOGICAL, AND PHYSIOLOGICAL SEXUAL TRAITSEVOLUTION, Issue 5 2008Charlie K. Cornwallis Reproductive success is determined by a complex interplay between multiple sexual traits that promote mate acquisition and, following copulation, provide control over paternity. The intensity of sexual competition that individuals experience often fluctuates, and here we investigate how this influences the expression of reproductive traits and their relationships. We show in the fowl, Gallus gallus, that males of different social status, which experience different intensities of sexual competition, before and after copulation, have different reproductive phenotypes. Dominant males are more vigilant, feed less, and have larger sexual ornaments than subordinate males. Experimentally manipulating social status revealed that these differences were phenotypically plastic, indicating multiple sexual traits were dependent on the social environment. We integrated these data with previous published findings on changes in sperm numbers and velocity to show that relationships between traits were different for males when they were dominant and when they were subordinate. Furthermore, when males switched status a complex array of negative and positive correlations between the degree traits changed was observed. Our results suggest that variation in the intensity of sexual competition generates reversible plasticity in reproductive phenotypes and that relationships between sexual traits may be variable and influence the evolution of reproductive strategies. [source] Artificial Stem Cell Niches,ADVANCED MATERIALS, Issue 32-33 2009Matthias P. Lutolf Abstract Stem cells are characterized by their dual ability to reproduce themselves (self-renew) and specialize (differentiate), yielding a plethora of daughter cells that maintain and regenerate tissues. In contrast to their embryonic counterparts, adult stem cells retain their unique functions only if they are in intimate contact with an instructive microenvironment, termed stem cell niche. In these niches, stem cells integrate a complex array of molecular signals that, in concert with induced cell-intrinsic regulatory networks, control their function and balance their numbers in response to physiologic demands. This progress report provides a perspective on how advanced materials technologies could be used (i) to engineer and systematically analyze specific aspects of functional stem cells niches in a controlled fashion in vitro and (ii) to target stem cell niches in vivo. Such "artificial niches" constitute potent tools for elucidating stem cell regulatory mechanisms with the capacity to directly impact the development of novel therapeutic strategies for tissue regeneration. [source] Quantifying temporal bone morphology of great apes and humans: an approach using geometric morphometricsJOURNAL OF ANATOMY, Issue 6 2002Charles A. Lockwood Abstract The hominid temporal bone offers a complex array of morphology that is linked to several different functional systems. Its frequent preservation in the fossil record gives the temporal bone added significance in the study of human evolution, but its morphology has proven difficult to quantify. In this study we use techniques of 3D geometric morphometrics to quantify differences among humans and great apes and discuss the results in a phylogenetic context. Twenty-three landmarks on the ectocranial surface of the temporal bone provide a high level of anatomical detail. Generalized Procrustes analysis (GPA) is used to register (adjust for position, orientation and scale) landmark data from 405 adults representing Homo, Pan, Gorilla and Pongo. Principal components analysis of residuals from the GPA shows that the major source of variation is between humans and apes. Human characteristics such as a coronally orientated petrous axis, a deep mandibular fossa, a projecting mastoid process, and reduced lateral extension of the tympanic element strongly impact the analysis. In phenetic cluster analyses, gorillas and orangutans group together with respect to chimpanzees, and all apes group together with respect to humans. Thus, the analysis contradicts depictions of African apes as a single morphotype. Gorillas and orangutans lack the extensive preglenoid surface of chimpanzees, and their mastoid processes are less medially inflected. These and other characters shared by gorillas and orangutans are probably primitive for the African hominid clade. [source] Vasomotion dynamics following calcium spiking depend on both cell signalling and limited constriction velocity in rat mesenteric small arteriesJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2008Ed VanBavel Abstract Vascular smooth muscle cell contraction depends on intracellular calcium. However, calcium-contraction coupling involves a complex array of intracellular processes. Quantitating the dynamical relation between calcium perturbations and resulting changes in tone may help identifying these processes. We hypothesized that in small arteries accurate quantitation can be achieved during rhythmic vasomotion, and questioned whether these dynamics depend on intracellular signalling or physical vasoconstriction. We studied calcium-constriction dynamics in cannulated and pressurized rat mesenteric small arteries (,300 ,m in diameter). Combined application of tetra-ethyl ammonium (TEA) and BayK8644 induced rhythmicity, consisting of regular and irregular calcium spiking and superposition of spikes. Calcium spikes induced delayed vasomotion cycles. Their dynamic relation could be fitted by a linear second-order model. The dirac impulse response of this model had an amplitude that was strongly reduced with increasing perfusion pressure between 17 and 98 mmHg, while time to peak and relaxation time were the largest at an intermediate pressure (57 mmHg: respectively 0.9 and 2.3 sec). To address to what extent these dynamics reside in intracellular signalling or vasoconstriction, we applied rhythmic increases in pressure counteracting the vasoconstriction. This revealed that calcium-activation coupling became faster when vasoconstriction was counteracted. During such compensation, a calcium impulse response remained that lasted 0.5 sec to peak activation, followed by a 1.0 sec relaxation time, attributable to signalling dynamics. In conclusion, this study demonstrates the feasibility of quantitating calcium-activation dynamics in vasomoting small arteries. These dynamics relate to both intracellular sig-nalling and actual vasoconstriction. Performing such analyses during pharmacological intervention and in genetic models provides a tool for unravelling calcium-contraction coupling in small arteries. [source] Bone morphogenetic protein-2 modulation of chondrogenic differentiation in vitro involves gap junction-mediated intercellular communicationJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002Wei Zhang Undifferentiated mesenchymal cells in the limb bud integrate a complex array of local and systemic signals during the process of cell condensation and chondrogenic differentiation. To address the relationship between bone morphogenetic protein (BMP) signaling and gap junction-mediated intercellular communication, we examined the effects of BMP-2 and a gap junction blocker 18 alpha glycyrrhetinic acid (18,-GCA) on mesenchymal cell condensation and chondrogenic differentiation in an in vitro chondrogenic model. We find that connexin43 protein expression significantly correlates with early mesenchymal cellular condensation and chondrogenesis in high-density limb bud cell culture. The level of connexin43 mRNA is maximally upregulated 48 h after treatment with recombinant human BMP-2 with corresponding changes in protein expression. Inhibition of gap junction-mediated intercellular communication with 2.5 ,M 18,-GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18,-GCA for only the first 24,48 h after plating does not affect condensation or later chondrogenic differentiation suggesting that gap junction-mediated intercellular communication is not critical for the initial phase of condensation but is important for the onset of differentiation. 18,-GCA can also block the chondrogenic effects of BMP-2 without effects on cell number or connexin43 expression. These observations demonstrate 18,-GCA-sensitive regulation of intercellular communication in limb mesenchymal cells undergoing chondrogenic differentiation and suggest that BMP-2 induced chondrogenic differentiation may be mediated in part through the modulation of connexin43 expression and gap junction-mediated intercellular communication. J. Cell. Physiol. 193: 233,243, 2002. © 2002 Wiley-Liss, Inc. [source] Type II nitric oxide synthase (NOS2) expression correlates with lymph node status in oral squamous cell carcinomaJOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 3 2001Peter A. Brennan Abstract: In tumour biology, nitric oxide (NO) has a complex array of concentration-dependent actions, including both inhibitory and promoting effects. It is thought that the levels of NO found in many human cancers lead to enhanced angiogenesis and tumour dissemination. In the current study, we assessed the immunohistochemical expression of the enzyme type II nitric oxide synthase (NOS2) in 41 cases of oral squamous cell carcinoma and correlated the findings with lymph node status. A significant relationship was found between NOS2 expression and lymph node metastasis (P<0.0002). Furthermore, lymph node metastasis correlated with the degree and intensity of staining seen (P<0.001). No correlation was found between the size of the primary tumour, degree of tumour differentiation or smoking status and NOS2 staining. Western blotting confirmed NOS2 protein expression in select cases. As with many other human tumours, NOS2 is not a ubiquitous finding in oral cancer. Its expression may be of value in assessing lymph node status prior to surgery, and it represents a target for possible therapeutic manipulation. [source] The Cultural Paradigm of the Smaller FirmJOURNAL OF SMALL BUSINESS MANAGEMENT, Issue 4 2004Helen Haugh This paper presents the findings from an ethnographic study of organizational culture and shared values in four smaller firms, the outcome of which was the identification of the cultural values shared between owner,managers (OMs) and employees in each firm. The research employed Schein's conceptualization of culture as a three-layer phenomenon, consisting of surface artifacts, shared values and beliefs, and basic assumptions. The analytical technique of grounded theory was employed to process the large volume of data gathered during the extended research period. The data reveal a complex array of values in each firm, with only one firm exhibiting a homogenous culture where values are shared by all those working in the organization. In the remaining three firms, five values appear to be shared by all employees; however, this is overlaid by a pattern of subcultures differentiated by distinctive shared values. Interfirm analysis among the four firms found that the values of survival, independence, control, pragmatism, and financial prudence were shared by two or more firms. The research collectively defines these shared values as the cultural paradigm of the smaller firm. [source] Hemostatic and hematological abnormalities in gain-of-function fps/fes transgenic mice are associated with the angiogenic phenotypeJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 11 2004W. Sangrar Summary. The Fps/Fes tyrosine kinase has been implicated in the regulation of hematopoiesis and inflammation. Mice expressing an activated variant of Fps/Fes (MFps) encoded by a gain-of-function mutant transgenic fps/fes allele (fpsMF) exhibited hematological phenotypes, which suggested that Fps/Fes can direct hematopoietic lineage output. These mice also displayed marked hypervascularity and multifocal-hemangiomas which implicated this kinase in the regulation of angiogenesis. Here we explored the potential involvement of Fps/Fes in the regulation of hemostasis through effects on blood cells and the vascular endothelium. Hematological parameters of fpsMF mice were characterized by peripheral blood analysis, histology, and transmission electron microscopy. Hemostasis parameters and platelet functions were assessed by flow cytometry and measurements of activated partial thromboplastin time, prothrombin time, thrombin clot time, platelet aggregation, bleeding times and in vitro fibrinolytic assays. Hematological and morphological analyses showed that fpsMF mice displayed mild thrombocytopenia, anemia, red cell abnormalities and numerous hemostatic defects, including hypofibrinogenemia, hyper-fibrinolysis, impaired whole blood aggregation and a mild bleeding diathesis. fpsMF mice displayed a complex array of hemostatic perturbations which are reminiscent of hemostatic disorders such as disseminated intravascular coagulation (DIC) and of hemangioma-associated pathologies such as Kasabach,Merritt phenomenon (KMS). These studies suggest that Fps/Fes influences both angiogenic and hemostatic function through regulatory effects on the endothelium. [source] Levels and chemical speciation of arsenic in polychaetes: a reviewMARINE ECOLOGY, Issue 3-4 2005Daniele Fattorini Abstract Relatively few studies have characterized basal content and variability of arsenic in polychaetes, despite the potential importance of this element as a pollutant of marine environments. Even less have investigated the chemical speciation of arsenic, occurring as inorganic and organic forms, which reflect a different biological reactivity of the element. In the present paper we integrate existing literature with new data in order to summarize the status quo on arsenic bioaccumulation in polychaetes. We consider species with different trophic habits, phylogenetic relationships, geographic distribution and ecology. Reported data indicate a high variability in arsenic concentration with levels ranging from <1 ,g·g,1 to more than 2500 ,g·g,1 in different species; some additional species analyzed in this work confirm species-specific characteristics which are not easily explained by biological or ecological factors. The profile of arsenic compounds in polychaetes is different to that of most aquatic organisms. Typically this element occurs in non-toxic organic forms, however several polychaete species have been shown to accumulate relatively toxic molecules and subsequently biotransform them by processes such as methylation. Conclusions from the literature review reveal a complex array of arsenic actions in the environment and suggest a biological role of this element in the life history of some polychaete species. [source] Why does elevated CO2 affect time of flowering?NEW PHYTOLOGIST, Issue 2 2009An exploratory study using the photoperiodic flowering mutants of Arabidopsis thaliana Summary ,,Evidence is accumulating that the effect of CO2 on time of flowering involves interactions with photoperiod, but the basis for this interaction is unclear. Here, which components of the photoperiod flowering pathway account for this interaction in Arabidopsis thaliana were examined. ,,Ten mutants deficient in particular loci in the photoperiod pathway, as well as the wild type, were grown under short and long days at either ambient or elevated CO2. Leaf number at flowering and the number of days required for induction of flowering were determined. ,,Elevated CO2 interacted with both the photoreceptors and the subsequent transduction reactions in the photoperiod pathway. The direction and magnitude of the effects varied with photoperiod. Elevated CO2 also affected flowering by increasing rate of leaf production. ,,The net effect of elevated CO2 on time of flowering varies because CO2 has a complex array of effects on different elements of the developmental pathway leading to flower induction that may either hasten or delay flowering depending upon the influence of other environmental factors such as photoperiod. [source] Ion channels and the transduction of light signalsPLANT CELL & ENVIRONMENT, Issue 7 2000E. P. Spalding ABSTRACT Studies of biological light-sensing mechanisms are revealing important roles for ion channels. Photosensory transduction in plants is no exception. In this article, the evidence that ion channels perform such signal-transducing functions in the complex array of mechanisms that bring about plant photomorphogenesis will be reviewed and discussed. The examples selected for discussion range from light-gradient detection in unicellular algae to the photocontrol of stem growth in Arabidopsis. Also included is some discussion of the technical aspects of studies that combine electrophysiology and photobiology. [source] Turbulence decay behind expanded metal screensTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2000Lanre Oshinowo Abstract An experiment study of the turbulent flow behind expanded metal screens has been carried out in a low-turbulence wind tunnel using an X-probe hot-wire anemometer system. The expanded metal screens turn flow due to a complex array of vaned elements. The flow turning was found to vary accordingly with the dimensions of the strands that make up the screen. The turbulence generated by the screens decays at a rate proportional to the downstream distance to the power - 5/7, consistent with studies in the literature of conventional screens types, and was found to scale with the thickness of the screen strands. The mean velocity, pressure drop and turbulence characteristics of expanded metal screens are presented. Une étude expérimentale de l'écoulement turbulent derrière des écrans de metal expansé a été réalisée dans un tunnel de faible turbulence avec un système anémométrique à film chaud couplé à une sonde à rayons X. Les écrans de métal expansé détournent l'écoulement du fait d'un arrangement complexe des éléments déflecteurs. La déviation de l'éecoulement varie en fonction des dimensions des torons qui composent l'écran. La turbulence engendrée par les écrans décro,t à un rythme proportionnel à la distance de l'écoulement descendant à la puissance ,5/7, ce qui concorde avec les études publiées antérieurement pour des écrans de type traditionnel, et on a trouvé qu'elle change d'échelle avec l'épaisseur des torons des écrans. Les propriétés de vitesse, de perte de charge et de turbulence moyennes des écrans de métal expansé sont présentées. [source] The vertical resolution sensitivity of simulated equilibrium temperature and water-vapour profilesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 565 2000Adrian. Abstract Variability of atmospheric water vapour is the most important climate feedback in present climate models. Thus, it is of crucial importance to understand the sensitivity of water vapour to model attributes, such as physical parametrizations and resolution. Here we attempt to determine the minimum vertical resolution necessary for accurate prediction of water vapour. To address this issue, we have run two single-column models to tropical radiative,convective equilibrium states and have examined the sensitivity of the equilibrium profiles to vertical resolution. Both column models produce reasonable equilibrium states of temperature and moisture. Convergence of the profiles was achieved in both models using a uniform vertical resolution of around 25 hPa. Coarser resolution leads to significant errors in both the water vapour and temperature profiles, with a resolution of 100 hPa proving completely inadequate. However, fixing the boundary-layer resolution and altering only the free-tropospheric resolution significantly reduces sensitivity to vertical resolution in one of the column models, in both water and temperature, highlighting the importance of resolving boundary-layer processes. Additional experiments show that the height of the simulated tropopause is sensitive to upper-tropospheric vertical resolution. At resolutions higher than 33 hPa, one of the models developed a high degree of vertical structure in the vapour profile, resulting directly from the complex array of microphysical processes included in the stratiform cloud parametrization, some of which were only resolved at high resolutions. This structure was completely absent at lower resolutions, casting some doubt on the approach of using relatively complicated cloud schemes at low vertical resolutions. [source] Characterization of a novel pectate lyase, Pel10A, from Pseudomonas cellulosaACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2001Simon J. Charnock Biological recycling of plant material is essential for biosphere maintenance. This perpetual task involves a complex array of enzymes, including extracellular polysaccharide hydrolases and lyases. Whilst much is known about the structure and function of the hydrolases, relatively little is known about the structures and mechanisms of the corresponding lyases. To this end, crystals of the catalytic module of a novel family 10 pectate lyase, Pel10A from Pseudomonas cellulosa, were obtained using polyethylene glycol 2000 monomethylether as a precipitant. They belong to space group P21, with unit-cell parameters a = 47.7, b = 106.1, c = 55.4,Å, , = 92.0°, and have two molecules in the asymmetric unit. The crystals diffract beyond 1.5,Å using synchrotron radiation. [source] Cyclopentenone Eicosanoids as Mediators of Neurodegeneration: A Pathogenic Mechanism of Oxidative Stress-Mediated and Cyclooxygenase-Mediated NeurotoxicityBRAIN PATHOLOGY, Issue 2 2005Erik S. Musiek The activation of cyclooxygenase enzymes in the brain has been implicated in the pathogenesis of numerous neurodegenerative conditions. Similarly, oxidative stress is believed to be a major contributor to many forms of neurodegeneration. These 2 distinct processes are united by a common characteristic: the generation of electrophilic cyclopentenone eicosanoids. These cyclopentenone compounds are defined structurally by the presence of an unsaturated carbonyl moiety in their prostane ring, and readily form Michael adducts with cellular thiols, including those found in glutathione and proteins. The cyclopentenone prostaglandins (PGs) PGA2, PGJ2, and 15-deoxy-,12,14 PGJ2, enzymatic products of cyclooxygenase-mediated arachidonic acid metabolism, exert a complex array of potent neurodegenerative, neuroprotective, and anti-inflammatory effects. Cyclopentenone isoprostanes (A2/J2 -IsoPs), products of non-enzymatic, free radical-mediated arachidonate oxidation, are also highly bioactive, and can exert direct neurodegenerative effects. In addition, cyclopentenone products of docosahexaenoic acid oxidation (cyclopentenone neuroprostanes) are also formed abundantly in the brain. For the first time, the formation and biological actions of these various classes of reactive cyclopentenone eicosanoids are reviewed, with emphasis on their potential roles in neurodegeneration. The accumulating evidence suggests that the formation of cyclopentenone eicosanoids in the brain may represent a novel pathogenic mechanism, which contributes to many neurodegenerative conditions. [source] ENDOCRINE REGULATION OF CALCIUM TRANSPORT IN EPITHELIACLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2008Ramesh C Khanal SUMMARY 1Calcium (re)absorption occurs in epithelia, including the intestine, kidney, mammary glands, placenta and gills (in the case of fish). 2Calcium is transported across epithelia by two transport mechanisms, paracellular and transcellular, and the movement is regulated by a complex array of transport processes that are mediated by hormonal, developmental and physiological factors involving the gastrointestinal tract, bone, kidney and the parathyroids. 3Clear understanding of the calcium transport pathways and their endocrine regulation is critical for minimizing various metabolic and health disorders at different physiological stages. Here, we first briefly review the calcium transport mechanisms before discussing in detail the endocrine factors that regulate calcium transport in the epithelia. [source] | ||||||||||||||||