bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organelle transport in melanophores analyzed by white light image correlation spectroscopy
Authors: IMMERSTRAND CHARLOTTE , HEDLUND JOEL , MAGNUSSON KARL–ERIC , SUNDQVIST TOMMY , PETERSON KAJSA HOLMGREN 
Published: March 2007

SummaryIntracellular transport of organelles, vesicles and proteins is crucial in all eukaryotic cells, and is accomplished by motor proteins that move along cytoskeletal filaments. A widely used model of intracellular transport is Xenopus laevis melanophores. These cells help the frog to change color by redistributing melanin‐containing organelles in the cytoplasm. The high contrast of the pigment organelles permits changes in distribution to be observed by ordinary light microscopy; other intracellular transport systems often require fluorescence labeling. Here we have developed white light Image Correlation Spectroscopy (ICS) to monitor aggregation and dispersion of pigment. Hitherto in ICS, images of fluorescent particles from Confocal Laser Scanning Microscopy (CLSM) have been used to calculate autocorrelation functions from which the density can be obtained. In the present study we show that ICS can be modified to enable analysis of light‐microscopy images; it can be used to monitor pigment aggregation and dispersion, and distinguish between different stimuli. This new approach makes ICS applicable not only to fluorescent but also to black‐and‐white images from light or electron microscopy, and is thus very versatile in different studies of movement of particles on the membrane or in the cytoplasm of cells without potentially harmful fluorescence labeling and activation.
Position referencing in optical microscopy thanks to sample holders with out‐of‐focus encoded patterns
Authors: SANDOZ P. , ZEGGARI R. , FROEHLY L. , PRETET J. ‐L. , MOUGIN C. 
Published: March 2007

SummaryThis article introduces smart sample holders for optical microscopy. Their purpose is to allow the absolute determination of the position of the observed zone with respect to the sample holder itself and with a high accuracy. It becomes then straightforward to find a given zone of interest by positioning coarsely the microscope slide to the same position coordinates. Furthermore images recorded during different observation sessions; i.e. for slightly different positions; can be processed numerically in order to superimpose them with a high accuracy. Thus the slight deviations of the microscope slide position and orientation due to the different observations are compensated numerically and a perfect superimposition of the recorded images is performed. Then accurate site‐by‐site image comparisons become possible even for images recorded during different observation sessions and over a long period of time. The subpixel capability of the proposed method is demonstrated and those smart microscope slides constitute a new tool for live cell experiment.In practise, an encoded geometrical pattern used as position reference is inserted in a plane parallel to the surface receiving the tissue section or sample. Then the transition of the focus position from the tissue section to the position reference requires only a vertical adjustment and does not affect the lateral coordinates of observation. The numeric processing of the image of the position reference pattern allows the retrieval of the lateral coordinates that are also used for the tissue section image. Thus each image is recorded with a set of position coordinates that defines accurately the position of the observed area with respect to the sample holder itself.
Differential admixture shapes morphological variation among invasive populations of the lizardAnolis sagrei
Authors: KOLBE JASON J. , LARSON ALLAN , LOSOS JONATHAN B. 
Published: March 2007

AbstractThe biological invasion of the lizardAnolis sagreiprovides an opportunity to study evolutionary mechanisms that produce morphological differentiation among non‐native populations. Because theA. sagreiinvasion represents multiple native‐range source populations, differential admixture as well as random genetic drift and natural selection, could shape morphological evolution during the invasion. Mitochondrial DNA (mtDNA) analyses reveal seven distinct native‐range source populations for 10 introducedA. sagreipopulations from Florida, Louisiana and Texas (USA), and Grand Cayman, with 2–5 native‐range sources contributing to each non‐native population. These introduced populations differ significantly in frequencies of haplotypes from different native‐range sources and in body size, toepad‐lamella number, and body shape. Variation among introduced populations for both lamella number and body shape is explained by differential admixture of various source populations; mean morphological values of introduced populations are correlated with the relative genetic contributions from different native‐range source populations. The number of source populations contributing to an introduced population correlates with body size, which appears independent of the relative contributions of particular source populations. Thus, differential admixture of various native‐range source populations explains morphological differences among introducedA. sagreipopulations. Morphological differentiation among populations is compatible with the hypothesis of selective neutrality, although we are unable to test the hypothesis of interdemic selection among introductions from different native‐range source populations.
Advances in our understanding of mammalian sex‐biased dispersal
Authors: LAWSON HANDLEY L. J. , PERRIN N. 
Published: March 2007

AbstractSex‐biased dispersal is an almost ubiquitous feature of mammalian life history, but the evolutionary causes behind these patterns still require much clarification. A quarter of a century since the publication of seminal papers describing general patterns of sex‐biased dispersal in both mammals and birds, we review the advances in our theoretical understanding of the evolutionary causes of sex‐biased dispersal, and those in statistical genetics that enable us to test hypotheses and measure dispersal in natural populations. We use mammalian examples to illustrate patterns and proximate causes of sex‐biased dispersal, because by far the most data are available and because they exhibit an enormous diversity in terms of dispersal strategy, mating and social systems. Recent studies using molecular markers have helped to confirm that sex‐biased dispersal is widespread among mammals and varies widely in direction and intensity, but there is a great need to bridge the gap between genetic information, observational data and theory. A review of mammalian data indicates that the relationship between direction of sex‐bias and mating system is not a simple one. The role of social systems emerges as a key factor in determining intensity and direction of dispersal bias, but there is still need for a theoretical framework that can account for the complex interactions between inbreeding avoidance, kin competition and cooperation to explain the impressive diversity of patterns.
Differentiation of sympatric populations of the band‐rumped storm‐petrel in the Galapagos Islands: an examination of genetics, morphology, and vocalizations
Authors: SMITH A. L. , FRIESEN V. L. 
Published: March 2007

AbstractIn each of at least two locations within the Galapagos Islands, breeding band‐rumped storm‐petrels (Oceanodroma castro) form two distinct populations that use the same colony site at separate times of the year for reproduction. Temporal segregation of these populations raises the possibility that they are reproductively isolated and represent cryptic species. We examined variation in mitochondrial DNA, morphology, and vocalizations of storm‐petrel populations nesting 6 months apart on the islet of Plaza Norte in the Galapagos. Seasonal populations displayed low but significant levels of differentiation in the mitochondrial control region, five morphological variables, and one feature of male vocalizations. Breeding populations appear to have been separated for approximately 1700 years. Given the recent divergence date and relatively high effective population sizes (4000–5600 females each), seasonal populations are unlikely to be in genetic equilibrium. As a result, the low divergence estimate probably reflects historical association and not contemporary genetic exchange. These populations are not sufficiently differentiated to be considered cryptic species. However, they are probably in the early stages of divergence. Consequently, we recommend that cool‐ and hot season populations on Plaza Norte be recognized as separate management units.
Sensing the light: photoreceptive systems and signal transduction in cyanobacteria
Authors: Montgomery Beronda L. 
Published: March 2007

SummaryPhotosynthetic prokaryotes have highly developed abilities to detect and react to environmental signals. Light sensing is one of the most important capabilities of organisms that use light for photosynthesis and photomorphogenesis. This review addresses photoreception in cyanobacteria from the perception of light through the physiological responses observed in response to light‐dependent signalling. Recent progress made in our understanding of the structure and function of photosensory receptors and their downstream effector molecules is discussed.
General and specific host responses to bacterial infection in Peyer's patches: a role for stromelysin‐1 (matrix metalloproteinase‐3) during Salmonella enterica infection
Authors: Handley Scott A. , Miller Virginia L. 
Published: March 2007

Summary Salmonella enterica serovar Typhimurium (S. typhimurium) and Yersinia enterocolitica are enteric pathogens capable of colonizing and inducing inflammatory responses in Peyer's patches (PPs) and mesenteric lymph nodes (MLNs). Although the tissue colonization pattern is similar between these two pathogens, their pathogenic lifestyles are quite different. For example, while S. typhimurium is primarily an intracellular pathogen, Y. enterocolitica survives primarily extracellularly. We determined and compared the transcriptional changes occurring in response to S. typhimurium and Y. enterocolitica colonization of PP using Affymetrix GeneChip technology. Both pathogens elicited a general inflammatory response indicated by the upregulation of cytokines and chemokines. However, specific differences were also observed, most notably in the transcriptional regulation of gamma interferon (IFN‐γ) and IFN‐γ‐regulated genes in response to S. typhimurium but not Y. enterocolitica. Of particular note, a group of genes encoding matrix metalloproteinases (MMPs) had increased transcript numbers in the PPs following infection with both pathogens. The experiments described here compare oral S. typhimurium or Y. enterocolitica infection in stromelysin‐1 (MMP‐3)‐deficient mice (mmp‐3–/–) with mice possessing functional MMP‐3 (mmp‐3+/+). There was little difference in the survival of MMP‐3‐deficient mice infected with Y. enterocolitica when compared with littermate controls. Surprisingly though, mmp‐3–/– mice were markedly more resistant to S. typhimurium infection than the control mice. S. typhimurium was able to colonize mmp‐3–/– mice, albeit in a delayed fashion, to equivalent levels as mmp‐3+/+ mice. Nevertheless, significantly lower levels of inflammatory cytokines were detected in tissues and serum in the mmp‐3–/– mice in comparison with mmp‐3+/+ mice. We hypothesize that MMP‐3 is involved in initiating an early and lethal cytokine response to S. typhimurium colonization.
Regulation of polar flagellum genes is mediated by quorum sensing and FlhDC in Burkholderia glumae
Authors: Kim Jinwoo , Kang Yongsung , Choi Okhee , Jeong Yeonhwa , Jeong Jae‐Eun , Lim Jae Yun , Kim Minkyun , Moon Jae Sun , Suga Hiroaki , Hwang Ingyu 
Published: March 2007

SummaryThe bacterium Burkholderia glumae causes rice grain rot by producing toxoflavin, whose expression is regulated by quorum sensing (QS). We report a major deviation from the current paradigm for the regulation of bacterial polar flagellum genes. The N‐octanoyl homoserine lactone (C8‐HSL)‐deficient mutant of B. glumae is aflagellate and has lost the ability to swim and swarm at 37°C. Mutagenesis of the bacterium with the mini‐Tn5rescue identified an IclR‐type transcriptional regulator, called QsmR, which is important for flagellum formation. TofR, which is a cognate C8‐HSL receptor, activated qsmR expression by binding directly to the qsmR promoter region. From the flagellum gene cluster, we identified flhDC homologues that are directly activated by QsmR. FlhDC in turn activates the expression of genes involved in flagellum biosynthesis, motor functions and chemotaxis in B. glumae. Non‐motile qsmR, fliA and flhDC mutants produced toxoflavin, but lost pathogenicity for rice. The unexpected discovery of FlhDC in a polarly flagellate bacterium suggests that exceptions to the typical regulatory mechanisms of flagellum genes exist in Gram‐negative bacteria. The finding that functional flagella play critical roles in the pathogenicity of B. glumae suggests that either QS or flagellum formation constitutes a good target for the control of rice grain rot.
Selection for functional diversity drives accumulation of point mutations in Dr adhesins of Escherichia coli
Authors: Korotkova Natalia , Chattopadhyay Sujay , Tabata Tami A. , Beskhlebnaya Viktoria , Vigdorovich Vladimir , Kaiser Brett K. , Strong Roland K. , Dykhuizen Daniel E. , Sokurenko Evgeni V. , Moseley Steve L. 
Published: March 2007

SummaryImmune escape is considered to be the driving force behind structural variability of major antigens on the surface of bacterial pathogens, such as fimbriae. In the Dr family of Escherichia coli adhesins, structural and adhesive functions are carried out by the same subunit. Dr adhesins have been shown to bind decay‐accelerating factor (DAF), collagen IV, and carcinoembryonic antigen‐related cell adhesion molecules (CEACAMs). We show that genes encoding Dr adhesins from 100 E. coli strains form eight structural groups with a high level of amino acid sequence diversity between them. However, genes comprising each group differ from each other by only a small number of point mutations. Out of 66 polymorphisms identified within the groups, only three were synonymous mutations, indicating strong positive selection for amino acid replacements. Functional analysis of intragroup variants comprising the Dr haemagglutinin (DraE) group revealed that the point mutations result in distinctly different binding phenotypes, with a tendency of increased affinity to DAF, decreased sensitivity of DAF binding to inhibition by chloramphenicol, and loss of binding capability to collagen, CEACAM3 and CEACAM6. Thus, variability by point mutation of major antigenic proteins on the bacterial surface can be a signature of selection for functional modification.
Engulfment during sporulation in Bacillus subtilis is governed by a multi‐protein complex containing tandemly acting autolysins
Authors: Chastanet Arnaud , Losick Richard 
Published: March 2007

SummaryThe conversion of a growing cell into an endospore in Bacillus subtilis involves a phagocytic‐like process in which the developing spore (the forespore) is wholly engulfed by the adjacent mother cell. A prerequisite for engulfment is the removal of peptidoglycan from the septum that separates the forespore from the mother cell, a process that depends on the autolysin SpoIID and two proteins of unknown function, SpoIIM and SpoIIP. Here we present evidence that SpoIIP is also an autolysin, that it acts in tandem with SpoIID, and that all three proteins are in a complex with each other. We further show that the members of the complex exhibit a hierarchical relationship in which SpoIIM is responsible for localization to the septal membrane, SpoIIP localizes to the septal membrane by interacting with SpoIIM, and SpoIID, in turn, localizes by interacting with SpoIIP. Finally, we show that localization of SpoIIM depends on a fourth protein SpoIIB, raising the possibility that the complex contains an additional component and creating an overall hierarchy of the form: SpoIIB→SpoIIM→SpoIIP→SpoIID.
Evaporative enrichment and time lags between δ18O of leaf water and organic pools in a pine stand
Authors: BARNARD ROMAIN L. , SALMON YANN , KODAMA NAOMI , SÖRGEL KARIN , HOLST JUTTA , RENNENBERG HEINZ , GESSLER ARTHUR , BUCHMANN NINA 
Published: March 2007

ABSTRACTUnderstanding ecosystem water fluxes has gained increasing attention, as climate scenarios predict a drier environment for many parts of the world. Evaporative enrichment of 18O (Δ18O) of leaf water and subsequent enrichment of plant organic matter can be used to characterize environmental and physiological factors that control evaporation, based on a recently established mechanistic model. In a Pinus sylvestris forest, we measured the dynamics of oxygen isotopic composition (δ18O) every 6 h for 4 d in atmospheric water vapour, xylem sap, leaf water and water‐soluble organic matter in current (N) and previous year (N‐1) needles, phloem sap, together with leaf gas exchange for pooled N and N‐1 needles, and relevant micrometeorological variables. Leaf water δ18O showed strong diel periodicity, while δ18O in atmospheric water vapour and in xylem sap showed little variation. The Δ18O was consistently lower for N than for N‐1 needles, possibly related to phenological stage. Modelled leaf water Δ18O showed good agreement with measured values when applying a non‐steady state evaporative enrichment model including a Péclet effect. We determined the time lags between δ18O signals from leaf water to water‐soluble foliar organic matter and to phloem sap at different locations down the trunk, which clearly demonstrated the relevance of considering these time‐lag effects for carbon transport, source‐sink and carbon flux partitioning studies.
Phototropic bending of non‐elongating and radially growing woody stems results from asymmetrical xylem formation
Authors: MATSUZAKI JUN , MASUMORI MASAYA , TANGE TAKESHI 
Published: March 2007

ABSTRACTActive phototropic bending of non‐elongating and radially growing portion of stems (woody stems) has not been previously documented, whereas negative gravitropic bending is well known. We found phototropic bending in woody stems and searched for the underlying mechanism. We inclined 1‐year‐old Quercus crispula Blume seedlings and unilaterally illuminated them from a horizontal direction perpendicular to (‘normal’ illumination) or parallel to (‘parallel’ illumination) the inclination azimuth. With normal illumination, active phototropic bending and xylem formation could be evaluated separately from the negative gravitropic response and vertical deflection resulting from the weight of the seedlings. One‐year‐old stems with normal illumination bent significantly, with asymmetrical xylem formation towards the illuminated upper surface and side of the stem, whereas those with parallel illumination showed non‐significant lateral bending, with asymmetrical xylem formation only on the upper side. A mechanical model was built on the assumption that a bending moment resulted from the asymmetrical xylem formation during phototropic bending of the woody stems. The model fitted the relationship between the observed spatial distributions of the xylem and the observed lateral bending, and thus supported the hypothesis that phototropic bending of woody stems results from asymmetrical xylem formation, as such occurs during gravitropism.
Renal function with delayed or immediate cyclosporine microemulsion in combination with enteric‐coated mycophenolate sodium and steroids: results of follow up to 30 months post‐transplant
Authors: Mourad Georges , Karras Alexandre , Kamar Nassim , Garrigue Valérie , Legendre Christophe , Lefrançois Nicole , Charpentier Bernard , Bourbigot Bernard , Pouteil‐Noble Claire , Bayle François , Lebranchu Yvon , Mariat Christophe , Meur Yann Le , Kessler Michèle , Moulin Bruno , Ducloux Didier , Delahousse Michel , Lang Philippe , Merville Pierre , Chaouche‐Teyara Kamel , Rostaing Lionel ,   for The French Myriade FR01 Study Group
Published: March 2007

Abstract:  Background:  In the multicenter, open‐label Myriade study, renal transplant patients were randomized to early cyclosporine microemulsion (CsA‐ME, day 0) or delayed CsA‐ME (day 6) with enteric‐coated mycophenolate sodium (EC‐MPS), steroids and interleukin‐2 receptor induction. One‐yr results have been published previously. We now report the results of an extension study in which patients were followed up for a period of three yr post‐transplant.Methods:  All patients completing the one‐yr core study on‐treatment were eligible to enter the extension study.Results:  Of the 203 patients, 153 completed the core trial on‐treatment; 144 (94%) entered the extension study with a minimum follow‐up of one yr (73 early CsA‐ME, 71 delayed CsA‐ME). In 75% of patients receiving EC‐MPS during the extension, the recommended dose was administered (1440 mg/d). Median creatinine clearance remained constant (57 mL/min) at 12, 24 and 30 months post‐transplant and was similar in the early and delayed CsA‐ME groups as well as in subpopulations with or without delayed graft function. One patient in the early CsA‐ME group died. No grafts were lost. The incidence of BPAR from time of transplant to the end of the extension study was 17% (24/139). Seven patients (5%) discontinued the extension study prematurely because of adverse events.Conclusion:  These results suggest that a regimen of CsA‐ME, EC‐MPS and steroids results in excellent survival rates with stable renal function over a mean follow‐up of 30 months. Immediate introduction of CsA‐ME has no deleterious effect on long‐term renal function, even among patients with delayed graft function.
KIR genes polymorphism in Argentinean Caucasoid and Amerindian populations
Authors: Flores A. C. , Marcos C. Y. , Paladino N. , Capucchio M. , Theiler G. , Arruvito L. , Pardo R. , Habegger A. , Williams F. , Middleton D. , Fainboim L. 
Published: March 2007

AbstractIn natural killer cells, killer immunoglobulin‐like receptors (KIRs) loci code for either inhibitory or activating receptors, and according to the number of genes present in each individual, it is possible to identify a high rate of polymorphism in the populations. We performed KIR typing by polymerase chain reaction–sequence‐specific oligonucleotide probing in 402 Argentinean Caucasoid and in two Amerindian populations (101 Wichis and 54 Chiriguanos) from the North of Argentina. KIR2DL4, KIR3DL2, KIR3DL3 and KIR3DP1 were always present, whereas the frequencies of KIR2DL1, KIR2DL3, KIR2DS4, KIR3DL1 and KIR2DP1 ranged between 84% and 96%. The frequencies of KIR2DS2, KIR2DL2, KIR2DL5, KIR2DS5, KIR2DS1 and KIR3DS1 ranged between 41% and 62%. The KIR2DS3 with a frequency of 29% in Argentinean Caucasoid population was present at a very low frequency in Amerindian populations. Haplotype segregation studies performed in 10 Wichi families showed the presence of only three haplotypes: A, B5 and B1. The Amerindian populations showed several similarities to Asian but not to Caucasoid populations with regard to the frequency of KIR2DS3, full‐length KIR2DS4 gene and KIR2DL4 alleles.