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Structural Organization (structural + organization)
Selected AbstractsSimilarities in the Structural Organization of Major and Minor Ampullate Spider SilkMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2009Periklis Papadopoulos Abstract Minor and major ampullate spider silks are studied under varying mechanical stress by static and time-resolved FT-IR spectroscopy. This enables one to trace the external mechanical excitation on a microscopic level and to determine for the different moieties the time dependence of the molecular order parameters and corresponding band shifts. It is concluded that the hierarchical nanostructure of both types of silk is similar, being composed of highly oriented nanocrystals, which are interconnected by amorphous chains that obey the worm-like chain model and have a Gaussian distribution of pre-strain. By that it is possible to describe the mechanical properties of both silks by two adjustable parameters only, the center and width of the distribution. For major ampullate silk, the observed variability is small in pronounced contrast to the findings for minor ampullate. [source] The Molecular Evolution and Structural Organization of Group I Introns at Position 1389 in Nuclear Small Subunit rDNA of MyxomycetesTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2007ODD-GUNNAR WIKMARK ABSTRACT. The number of nuclear group I introns from myxomycetes is rapidly increasing in GenBank as more rDNA sequences from these organisms are being sequenced. They represent an interesting and complex group of intervening sequences because several introns are mobile (or inferred to be mobile) and many contain large and unusual insertions in peripheral loops. Here we describe related group I introns at position 1389 in the small subunit rDNA of representatives from the myxomycete family Didymiaceae. Phylogenetic analyses support a common origin and mainly vertical inheritance of the intron. All S1389 introns from the Didymiaceae belong to the IC1 subclass of nuclear group I introns. The central catalytic core region of about 100 nt appears divergent in sequence composition even though the introns reside in closely related species. Furthermore, unlike the majority of group I introns from myxomycetes the S1389 introns do not self-splice as naked RNA in vitro under standard conditions, consistent with a dependence on host factors for folding or activity. Finally, the myxomycete S1389 introns are exclusively found within the family Didymiaceae, which suggests that this group I intron was acquired after the split between the families Didymiaceae and Physaraceae. [source] Structural organization of a complex family of palindromic repeats in EnterococciFEMS MICROBIOLOGY LETTERS, Issue 1 2009Eliana De Gregorio Abstract Enterococcus faecalis/faecium repeats (EFARs) are miniature insertion sequences spread in the genome of Enterococcus faecalis and Enterococcus faecium. Unit-length repeats measure 165,170 bp and contain two modules (B and T) capable of folding independently into stem-loop sequences, connected by a short, unstructured module J. The E. faecalis elements feature only one type of B, J and T modules. In contrast, the E. faecium elements result from the assembly of different types of B, J and T modules, and may vary in length because they carry multiple B modules. Most EFARs are located close (0,20 bp) to ORF stop codons, and are thus cotranscribed with upstream flanking genes. In both E. faecalis and E. faecium cells, EFAR transcripts accumulate in a strand-dependent fashion. Data suggest that T modules function as bidirectional transcriptional terminators, which provide a 3,-end to gene transcripts spanning B modules, while blocking antisense transcripts coming in from the opposite direction. [source] Structural organization of the est,31 gene in a Colombian strain of Culex quinquefasciatus differs from that in CubaMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2002D. De Silva Abstract In Culex mosquitoes (Diptera: Culicidae), the most common mechanism for resistance to organophosphorus (OP) insecticides involves amplification of one or more esterases. Two esterase loci are often involved, with different allelic forms co-amplified. Est,31 is co-amplified with est,1 in a Colombian (COL) strain of Culex quinquefasciatus Say. These two alleles co-migrate on acrylamide gels, often leading to misscoring of the phenotype as elevation of a single est, enzyme. By sequencing COL genomic DNA, we determined the est,31 gene length is 1623 nucleotides. The open reading frame of est,31 encodes a 540 amino acid protein, as for est,21 in strain Pel RR from Sri Lanka. The intron/exon boundaries of est,31 are identical to those of est,21, suggesting that they are alleles of the same locus. The COL est,31 gene differs from est,32 in strain MRES from Cuba, although they have equivalent electrophoretic mobility, showing that these two strains contain distinct resistance-associated amplicons. Twenty nucleotide differences were scored between the MRES partial 495 bp sequence and that in the COL strain, with two amino acid changes, demonstrating distinct est, enzymes. Our sequencing data show 95% identity between the three est, genes (each has six introns and seven exons) in OP-resistant Cx. quinquefasciatus. Amplified est,31 and est,1 are at least 10 kb apart in temephos-selected COL and 2.7 kb apart in Pel RR, whereas these non-amplified genes are only 1.7 kb apart in the non-selected parental COL stock, as in Pel SS (susceptible Sri Lankan strain), demonstrating that this region of the genome is susceptible to expansion and contraction. [source] Applying Network Analysis to the Conservation of Habitat Trees in Urban Environments: a Case Study from Brisbane, AustraliaCONSERVATION BIOLOGY, Issue 3 2006MONIKA RHODES conectividad de perchas; fauna que utiliza oquedades; planificación de la conservación; red sin escala; Tadarida australis Abstract:,In Australia more than 300 vertebrates, including 43 insectivorous bat species, depend on hollows in habitat trees for shelter, with many species using a network of multiple trees as roosts. We used roost-switching data on white-striped freetail bats (Tadarida australis; Microchiroptera: Molossidae) to construct a network representation of day roosts in suburban Brisbane, Australia. Bats were caught from a communal roost tree with a roosting group of several hundred individuals and released with transmitters. Each roost used by the bats represented a node in the network, and the movements of bats between roosts formed the links between nodes. Despite differences in gender and reproductive stages, the bats exhibited the same behavior throughout three radiotelemetry periods and over 500 bat days of radio tracking: each roosted in separate roosts, switched roosts very infrequently, and associated with other bats only at the communal roost. This network resembled a scale-free network in which the distribution of the number of links from each roost followed a power law. Despite being spread over a large geographic area (>200 km2), each roost was connected to others by less than three links. One roost (the hub or communal roost) defined the architecture of the network because it had the most links. That the network showed scale-free properties has profound implications for the management of the habitat trees of this roosting group. Scale-free networks provide high tolerance against stochastic events such as random roost removals but are susceptible to the selective removal of hub nodes. Network analysis is a useful tool for understanding the structural organization of habitat tree usage and allows the informed judgment of the relative importance of individual trees and hence the derivation of appropriate management decisions. Conservation planners and managers should emphasize the differential importance of habitat trees and think of them as being analogous to vital service centers in human societies. Resumen:,En Australia, más de 300 vertebrados, incluyendo 43 especies de murciélagos insectívoros, dependen de oquedades en árboles para refugiarse; muchas de ellas perchan en una red de múltiples árboles. Utilizamos datos de cambio de perchas en Tadarida australis (Microchiroptera: Molossidae) para construir una representación reticular de las perchas diurnas en los suburbios de Brisbane, Australia. Los murciélagos fueron capturados en un árbol con un grupo de varios cientos de individuos y liberados con transmisores. Cada percha utilizada por los murciélagos representó un nodo individual en la red, y los movimientos de murciélagos entre perchas constituyeron los eslabones entre los nodos. A pesar de las diferencias de género y etapas reproductivas, los murciélagos mostraron el mismo comportamiento en tres períodos de radiotelemetría y en más de 500 días de seguimiento de murciélagos: cada uno utilizó perchas separadas, cambiaban de percha poco frecuentemente, y se asociaron con otros murciélagos sólo en las perchas comunales. Esta red fue semejante a una red sin escala en la que la distribución del número de eslabones de cada percha cumplió una ley potencial. A pesar de estar dispersas en un área geográfica extensa (>200 km2), cada percha estaba conectada con otras por menos de tres eslabones. Una percha (el centro o percha comunal) definió la arquitectura de la red porque tenía a la mayoría de los eslabones. El hecho de que la red mostrara propiedades libres de escala tiene implicaciones profundas para la gestión de árboles que funcionan como perchas. Las redes libres de escala proporcionan alta tolerancia a eventos estocásticos como la remoción aleatoria de perchas, pero son susceptibles a la remoción selectiva de nodos centrales. El análisis de redes es una herramienta útil para el entendimiento de la organización estructural del uso de de árboles y permite el juicio informado de la importancia relativa de árboles individuales y por lo tanto la derivación de decisiones administrativas apropiadas Los planificadores y gestores de la conservación deberían enfatizar la importancia diferencial de árboles y considerarlos análogos a los centros de servicio vitales en las sociedades humanas. [source] Microtubule-dependent motility and orientation of the cortical endoplasmic reticulum in elongating characean internodal cellsCYTOSKELETON, Issue 3 2009Ilse Foissner Abstract Motility of the endoplasmic reticulum (ER) is predominantly microtubule- dependent in animal cells but thought to be entirely actomyosin-dependent in plant cells. Using live cell imaging and transmission electron microscopy to examine ER motility and structural organization in giant internodal cells of characean algae, we discovered that at the onset of cell elongation, the cortical ER situated near the plasma membrane formed a tight meshwork of predominantly transverse ER tubules that frequently coaligned with microtubules. Microtubule depolymerization increased mesh size and decreased the dynamics of the cortical ER. In contrast, perturbing the cortical actin array with cytochalasins did not affect the transverse orientation but decreased mesh size and increased ER dynamics. Our data suggest that myosin-dependent ER motility is confined to the ER strands in the streaming endoplasm, while the more sedate cortical ER uses microtubule-based mechanisms for organization and motility during early stages of cell elongation. We show further that the ER has an inherent, NEM-sensitive dynamics which can be altered via interaction with the cytoskeleton and that tubule formation and fusion events are cytoskeleton-independent. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Emilin genes are duplicated and dynamically expressed during zebrafish embryonic developmentDEVELOPMENTAL DYNAMICS, Issue 1 2008Martina Milanetto Abstract Emilins are a family of extracellular matrix proteins with common structural organization and containing a characteristic N-terminal cysteine-rich domain. The prototype of this family, Emilin-1, is found in human and murine organs in association with elastic fibers, and other emilins were recently isolated in mammals. To gain insight into these proteins in lower vertebrates, we investigated the expression of emilins in the fish Danio rerio. Using sequence similarity tools, we identified eight members of this family in zebrafish. Each emilin gene has two paralogs in zebrafish, showing conserved structure with the human ortholog. In situ hybridization revealed that expression of zebrafish emilin genes is regulated in a spatiotemporal manner during embryonic development, with overlapping and site-specific patterns mostly including mesenchymal structures. Expression of certain emilin genes in peculiar areas, such as the central nervous system or the posterior notochord, suggests that they may play a role in key morphogenetic processes. Developmental Dynamics 237:222,232, 2008. © 2007 Wiley-Liss, Inc. [source] Comparative expression analysis of transcription factor genes in the endostyle of invertebrate chordatesDEVELOPMENTAL DYNAMICS, Issue 3 2005Jin Hiruta Abstract The endostyle of invertebrate chordates is a pharyngeal organ that is thought to be homologous with the follicular thyroid of vertebrates. Although thyroid-like features such as iodine-concentrating and peroxidase activities are located in the dorsolateral part of both ascidian and amphioxus endostyles, the structural organization and numbers of functional units are different. To estimate phylogenetic relationships of each functional zone with special reference to the evolution of the thyroid, we have investigated, in ascidian and amphioxus, the expression patterns of thyroid-related transcription factors such as TTF-2/FoxE4 and Pax2/5/8, as well as the forkhead transcription factors FoxQ1 and FoxA. Comparative gene expression analyses depicted an overall similarity between ascidians and amphioxus endostyles, while differences in expression patterns of these genes might be specifically related to the addition or elimination of a pair of glandular zones. Expressions of Ci-FoxE and BbFoxE4 suggest that the ancestral FoxE class might have been recruited for the formation of thyroid-like region in a possible common ancestor of chordates. Furthermore, coexpression of FoxE4, Pax2/5/8, and TPO in the dorsolateral part of both ascidian and amphioxus endostyles suggests that genetic basis of the thyroid function was already in place before the vertebrate lineage. Developmental Dynamics 233:1031,1037, 2005. © 2005 Wiley-Liss, Inc. [source] Diffusion-based magnetic resonance imaging and tractography in epilepsyEPILEPSIA, Issue 2 2008Mahinda Yogarajah Summary Diffusion-based imaging is an advanced MRI technique that is sensitive to the movement of water molecules, providing additional information on the micro-structural arrangement of tissue. Qualitative and quantitative analysis of peri, post and interictal diffusion images can aid the localization of seizure foci. Diffusion tensor tractography is an extension of diffusion-based imaging, and can provide additional information about white matter pathways. Both techniques are able to increase understanding of the effects of epilepsy on the structural organization of the brain, and can be used to optimize presurgical planning of patients with epilepsy. This review focuses on the basis, applications, limitations, and future directions of diffusion imaging in epilepsy. Literature search strategy: We searched Pubmed using the terms "diffusion MRI or diffusion tensor MRI or tractography and epilepsy." [source] Decanuclear Manganese Isobutyrate Clusters Featuring a Novel MnII8MnIII2 CoreEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2009Iurii L. Malaestean Abstract Recrystallization of freshly prepared MnII isobutyrate from PrOH or from EtOH/MeCN mixtures containing pyrazole (pyr) yields neutral mixed-valence decanuclear manganese(II/III) complexes, [Mn10O2(O2CCHMe2)18(HO2CCHMe2)2(PrOH)2] (1) and [Mn10O2(O2CCHMe2)18(pyr)4] (2). The Mn10 metal core of both 1 and 2 consists of eight MnII and two MnIII centers and represents a new motif in the structural organization of polynuclear mixed-valence manganese clusters. Both, 1 and 2 exhibit a net antiferromagnetic exchange coupling resulting in singlet ground states. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Distribution and structure of the initial dental enamel formed in incisors of young wild-type and Tabby miceEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2009Amer Sehic Mouse incisor enamel can be divided into four layers: an inner prism-free layer; an inner enamel with prism decussation; outer enamel with parallel prisms; and a superficial prism-free layer. We wanted to study how this complex structural organization is established in the very first enamel formed in wild-type mice and also in Tabby mice where enamel coverage varies considerably. Unworn incisors from young female wild-type and Tabby mice were ground, etched, and analyzed using scanning electron microscopy. In both wild-type and Tabby mice, establishment of the enamel structural characteristics in the initially formed enamel proceeded as follows, going from the incisal tip in an apical direction: (i) a zone with prism-free enamel, (ii) a zone with occasional prisms most often inclined incisally, and (iii) a zone where prism decussation was gradually established in the inner enamel. The distribution of enamel in Tabby mice exhibited considerable variability. The sequence of initial enamel formation in mouse incisors mimics development from a primitive (prism-free) structure to an evolved structure. It is suggested that genes controlling enamel distribution are not associated with genes controlling enamel structure. The control of ameloblast configuration, life span, organization in transverse rows, and movement is important for establishing the characteristic mature pattern of mouse incisor enamel. [source] Dynamic light scattering study of an amelogenin gel-like matrix in vitroEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006Vassiliki Petta Amelogenin self-assembly is critical for the structural organization of apatite crystals during enamel mineralization. The aim of the present study was to investigate the influence of temperature and protein concentration on the aggregation of amelogenin nanospheres at high protein concentrations (> 4.4 mg ml,1) in order to obtain an insight into the mechanism of amelogenin self-assembly to form higher-order structures. Amelogenins were extracted from enamel scrapings of unerupted mandibular pig molars. The dynamics of protein solutions were measured using dynamic light scattering (DLS) as a function of temperature and at acidic pH. At pH 4,5.5, three kinds of particles were observed, ranging in size from 3 to 80 nm. At pH 6, heating the solution above ,,30°C resulted in a drastic change in the solution transparency, from clear to opaque. Low pH showed no aggregation effect, whilst solutions at a slightly acidic pH exhibited diffusion dynamics associated with the onset of aggregation. In addition, at the same temperature range, the hydrodynamic radii of the aggregates increased drastically, by almost one order of magnitude. These observations support the view that hydrophobic interactions are the primary driving force for the pH- and temperature-sensitive self-assembly of amelogenin particles in a ,gel-like' matrix. The trend of self-assembly in a ,gel-like matrix' is similar to that in solution. [source] Abundance of intrinsic disorder in SV-IV, a multifunctional androgen-dependent protein secreted from rat seminal vesicleFEBS JOURNAL, Issue 4 2008Silvia Vilasi The potent immunomodulatory, anti-inflammatory and procoagulant properties of protein no. 4 secreted from the rat seminal vesicle epithelium (SV-IV) have previously been found to be modulated by a supramolecular monomer,trimer equilibrium. More structural details that integrate experimental data into a predictive framework have recently been reported. Unfortunately, homology modelling and fold-recognition strategies were not successful in creating a theoretical model of the structural organization of SV-IV. It was inferred that the global structure of SV-IV is not similar to that of any protein of known three-dimensional structure. Reversing the classical approach to the sequence,structure,function paradigm, in this paper we report novel information obtained by comparing the physicochemical parameters of SV-IV with two datasets composed of intrinsically unfolded and ideally globular proteins. In addition, we analyse the SV-IV sequence by several publicly available disorder-oriented predictors. Overall, disorder predictions and a re-examination of existing experimental data strongly suggest that SV-IV needs large plasticity to efficiently interact with the different targets that characterize its multifaceted biological function, and should therefore be better classified as an intrinsically disordered protein. [source] The resident endoplasmic reticulum protein, BAP31, associates with ,-actin and myosin B heavy chainFEBS JOURNAL, Issue 2 2003Analysis by capillary liquid chromatography microelectrospray tandem MS BAP31 is a 28-kDa integral membrane protein of the endoplasmic reticulum whose cytosolic domain contains two caspase recognition sites that are preferentially cleaved by initiator caspases, such as caspase-8. Recently, we reported that the caspase-resistant BAP31 inhibited Fas-mediated apoptotic membrane fragmentation and the release of cytochrome c from mitochondria in KB epithelial cells (Nguyen M., Breckenridge G., Ducret A & Shore G. (2000) Mol. Cell. Biol.20, 6731,6740). We describe here the characterization by capillary liquid chromatography microelectrospray tandem MS of a BAP31 immunocomplex isolated from a HepG2 cell lysate in the absence of a death signal. We show that BAP31 specifically associates with nonmuscle myosin heavy chain B and nonmuscle ,-actin, two components of the cytoskeleton actomyosin complex. Collectively, these data confirm that BAP31, in addition to its potential role as a chaperone, may play a fundamental role in the structural organization of the cytoplasm. Here we also show that Fas stimulation of apoptosis releases BAP31 associations with these motor proteins, a step that may contribute to extranuclear events, such as membrane remodelling, during the execution phase of apoptosis. [source] Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroidesFEBS JOURNAL, Issue 7 2002Francesco Francia The core complex of Rhodobacter sphaeroides is formed by the association of the light-harvesting antenna 1 (LH1) and the reaction center (RC). The PufX protein is essential for photosynthetic growth; it is located within the core in a 1 : 1 stoichiometry with the RC. PufX is required for a fast ubiquinol exchange between the QB site of the RC and the Qo site of the cytochrome bc1 complex. In vivo the LH1,PufX,RC complex is assembled in a dimeric form, where PufX is involved as a structural organizer. We have modified the PufX protein at the N and the C-terminus with progressive deletions. The nine mutants obtained have been characterized for their ability for photosynthetic growth, the insertion of PufX in the core LH1,RC complex, the stability of the dimers and the kinetics of flash-induced reduction of cytochrome b561 of the cytochrome bc1 complex. Deletion of 18 residues at the N-terminus destabilizes the dimer in vitro without preventing photosynthetic growth. The dimer (or a stable dimer) does not seem to be a necessary requisite for the photosynthetic phenotype. Partial C-terminal deletions impede the insertion of PufX, while the complete absence of the C-terminus leads to the insertion of a PufX protein composed of only its first 53 residues and does not affect the photosynthetic growth of the bacterium. Overall, the results point to a complex role of the N and C domains in the structural organization of the core complex; the N-terminus is suggested to be responsible mainly for dimerization, while the C-terminus is thought to be involved mainly in PufX assembly. [source] COST action 921: food matrices: structural organization from nano- to macro scale and impact on flavour release and perceptionFLAVOUR AND FRAGRANCE JOURNAL, Issue 1 2006Béatrice Conde-Petit No abstract is available for this article. [source] A New Poly(thienylenevinylene) Derivative with High Mobility and Oxidative Stability for Organic Thin-Film Transistors and Solar CellsADVANCED MATERIALS, Issue 27 2009Bogyu Lim A novel thiophene-thienylenevinylene copolymer is synthesized and evaluated for use in organic field-effect transistors and organic solar cells. PETV12T shows good solution processability and high structural organization after annealing. Organic thin-film transistors based on the polymer exhibit high mobility and a high resistance to oxidation. In addition, PETV12T shows potential as an electron donor in bulk heterojunction solar cells. [source] Stratum corneum keratin structure, function and formation , a comprehensive reviewINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2006L. Norlén Synopsis A comprehensive review on stratum corneum keratin organization, largely based on the recently published cubic rod-packing and membrane templating model [J. Invest. Dermatol., 123, 2004, 715], is presented. Keratin is the major non-aqueous component (wt/wt) of stratum corneum. As 90,100% of the stratum corneum water is thought to be located intracellularly one may presume that keratin also is a major factor (together with filaggrin-derived free amino acids) determining stratum corneum hydration level and water holding capacity. This water holding capacity depends in turn on the structural organization of the corneocyte keratin intermediate filament network. The cubic rod-packing model for the structure and function of the stratum corneum cell matrix postulates that corneocyte keratin filaments are arranged according to a cubic-like rod-packing symmetry. It is in accordance with the cryo-electron density pattern of the native corneocyte keratin matrix and could account for the swelling behaviour and the mechanical properties of mammalian stratum corneum. The membrane templating model for keratin dynamics and for the formation of the stratum corneum cell matrix postulates the presence in viable epidermal cellular space of a highly dynamic small lattice parameter (<30 nm) membrane structure with cubic-like symmetry, to which keratin is associated. It further proposes that membrane templating, rather than spontaneous self-assembly, is responsible for keratin intermediate filament formation and dynamics. It is in accordance with the cryo-electron density patterns of the native keratinocyte cytoplasmic space and could account for the characteristic features of the keratin network formation process, the dynamic properties of keratin intermediate filaments, the close lipid association of keratin, the insolubility in non-denaturating buffers and pronounced polymorphism of keratin assembled in vitro, and the measured reduction in cell-volume and hydration level between stratum granulosum and stratum corneum. Résumé, La kératine est le composant majeur anhydre de la couche cornée. Etant donné que l'on considère que 90 à 100% de l'eau de la couche cornée est localisée à l'intérieur des cellules, on peut penser que la kératine joue également un rôle important (en association avec les acides aminés libres dérivés de la filagrine) dans le niveau d'hydratation de la couche cornée et sa capacité de rétention de l'eau. Cette capacité de rétention de l'eau dépend elle-même de l'organization structurelle du réseau de filaments intermédiaires de la kératine des cornéocytes. Le modèle de cylindre en réseau cubique appliquéà la structure et aux fonctions de la matrice des cellules de la couche cornée stipule que les filaments de la kératine des cornéocytes sont disposés symétriquement, les paquets de fibrilles formant une structure cubique. Ceci est conforme au modèle de densité cryo-électronique de la matrice kératinique des cornéocytes natifs et pourrait expliquer le comportement de gonflement et les propriétés mécaniques de la couche cornée des mammifères. Le modèle d'assemblage membranaire appliquéà la dynamique de la kératine et à la formation de la matrice cellulaire du stratum cornéum postule la présence dans l'espace cellulaire viable de l'épiderme d'une structure membranaire hautement dynamique présentant un petit paramètre de maille (<30 nm) et une organization en forme de cube, à laquelle la kératine est associée. D'autre part, ce modèle suggère qu'un assemblage membranaire plutôt qu'un auto-assemblage spontané puisse être à l'origine de la formation des filaments intermédiaires de kératine et de leur dynamique. Ceci concorde avec les modèles de densité cryo-électronique du cytoplasme des kératinocytes natifs et pourrait expliquer les caractéristiques du processus de formation du réseau kératinique, les propriétés dynamiques des filaments intermédiaires de kératine, l'association de la kératine avec les lipides, l'insolubilité dans les tampons non dénaturants, le polymorphisme caractéristique de la kératine assemblée in vitro, ainsi que la diminution mesurée du volume cellulaire et du niveau d'hydratation entre le stratum granulosum et le stratum corneum. [source] Protein Import Into MitochondriaIUBMB LIFE, Issue 3-5 2001Stefan A. Paschen Abstract Most mitochondrial proteins are encoded by the nuclear genome and thus have to be imported into mitochondria from the cytosol. Protein translocation across and into the mitochondrial membranes is a multistep process facilitated by the coordinated action of at least four specialized translocation systems in the outer and inner membranes of mitochondria. The outer membrane contains one general translocase, the TOM complex, whereas three distinct translocases are located in the inner membrane, which facilitates translocation of different classes of preproteins. The TIM23 complex mediates import of matrix-targeted preproteins with N -terminal presequences, whereas hydrophobic preproteins with internal targeting signals are inserted into the inner membrane via the TIM22 complex. The OXA translocase mediates the insertion of preproteins from the matrix space into the inner membrane. This review focuses on the structural organization and function of the import machinery of the model organisms of Saccharomyces cerevisiae and Neurospora crassa . In addition, the molecular basis of a new human mitochondrial disorder is discussed, the Mohr-Tranebjaerg syndrome. This is the first known disease, which is caused by an impaired mitochondrial protein import machinery leading to progressive neurodegeneration. [source] Anticipating bipedalism: trabecular organization in the newborn iliumJOURNAL OF ANATOMY, Issue 6 2009Craig A. Cunningham Abstract Trabecular bone structural organization is considered to be predominantly influenced by localized temporal forces which act to maintain and remodel the trabecular architecture into a biomechanically optimal configuration. In the adult pelvis, the most significant remodelling forces are believed to be those generated during bipedal locomotion. However, during the fetal and neonatal period the pelvic complex is non-weight bearing and, as such, structural organization of iliac trabecular bone cannot reflect direct stance-related forces. In this study, micro-computed tomography scans from 28 neonatal ilia were analysed, using a whole bone approach, to investigate the trabecular characteristics present within specific volumes of interest relevant to density gradients highlighted in a previous radiographic study. Analysis of the structural indices bone volume fraction, trabecular thickness, trabecular spacing and trabecular number was carried out to quantitatively investigate structural composition. Quantification of the neonatal trabecular structure reinforced radiographic observations by highlighting regions of significant architectural form which grossly parallel architectural differences in the adult pattern but which have previously been attributed to stance-related forces. It is suggested that the seemingly organized rudimentary scaffold observed in the neonatal ilium may be attributable to other non-weight bearing anatomical interactions or even to a predetermined genetic blueprint. It must also be postulated that whilst the observed patterning may be indicative of a predetermined inherent template, early non-weight bearing and late stance-related locomotive influences may subsequently be superimposed upon this scaffolding and perhaps reinforced and likely remodelled at a later age. Ultimately, the analysis of this fundamental primary pattern has core implications for understanding the earliest changes in pelvic trabecular architecture and provides a baseline insight into future ontogenetic development and bipedal capabilities. [source] Anthropometry of fetal vasculature in the chorionic plateJOURNAL OF ANATOMY, Issue 6 2007Z. Gordon Abstract Normal fetal development is dependent on adequate placental blood perfusion. The functional role of the placenta takes place mainly in the capillary system; however, ultrasound imaging of fetal blood flow is commonly performed on the umbilical artery, or on its first branches over the chorionic plate. The objective of this study was to evaluate the structural organization of the feto-placental vasculature of the chorionic plate. Casting of the placental vasculature was performed on 15 full-term placentas using a dental polymer mixed with colored ink. Observations of the cast models revealed that the branching architecture of the chorionic vessel is a combination of dichotomous and monopodial patterns, where the first two to three generations are always of a dichotomous nature. Analysis of the daughter-to-mother diameter ratios in the chorionic vessels provided a maximum in the range of 0.6,0.8 for the dichotomous branches, whereas in monopodial branches it was in the range of 0.1,0.3. Similar to previous studies, this study reveals that the vasculature architecture is mostly monopodial for the marginal cord insertion and mostly dichotomous for the central insertion. The more marginal the umbilical cord insertion is on the chorionic plate, the more monopodial branching patterns are created to compensate the dichotomous pattern deficiency to perfuse peripheral placental territories. [source] Transcriptional analysis of the gdhA gene in Streptococcus thermophilusJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2009C. Lazzi Abstract Aims:, To study the transcriptional analysis of glutamate dehydrogenase gene, involved in the amino acid conversion to aroma compound in Streptococcus thermophilus. Methods and Results:, Analysis of the gdhA gene nucleotide sequence of S. thermophilus CNRZ1066 revealed that the coding region is 1353 nucleotides long. The deduced amino acids sequence exhibits the putative GDH active site and some conserved domains characteristic of family I of hexameric GDHs. Phylogenetic analysis revealed that the gdh gene of S. thermophilus clustered with the orthologues of other streptococci such as Streptococcus mutans, Streptococcus agalactiae and Streptococcus infantarius. Studying the structural organization of the gdhA locus the amino acid similarity of GDHs was higher than 87%, but the locus organization was not conserved. A dominant transcript of approximately 1·4 kbp was revealed by Northern blot hybridization, suggesting that gdhA mRNA is monocystronic. Primer extension showed that transcription start point of gdhA was localized 43 bp upstream of the potential start codon (ATG). Conclusions:, The gdhA represents a monocistronic operon highly conserved in phylogenetic-related bacteria. Significance and Impact of the Study:, A deeper knowledge of gdh transcriptional mechanisms could lead to develop S. thermophilus industrial starter cultures with optimized aromatic properties. [source] The structural organization in aqueous solutions of ionic liquidsAICHE JOURNAL, Issue 1 2009Xiao Zhu Abstract The 1H NMR combined with the local composition (LC) model has been employed to investigate the structural organization of two aqueous solutions of ionic liquids (ILs), namely 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) and n-butylammonium nitrate (N4NO3). The correlation of chemical shifts using the LC model shows that the self-association of IL plays the leading role, and water prefers to interact with IL rather than self-association in IL-rich region. Instead the network of water molecules is established in water-rich region, because the self-association of water predominates. Furthermore, the difference between the local and the bulk composition presents the turnover at x(IL) (mole fraction of IL) close to 0.6 for EmimBF4/water, which is in accordance with the change of excess function. Accordingly, it could be presumed that the excess properties for N4NO3/water system should behave turnover at x(IL) , 0.55 since the local and the bulk exhibit maximal difference at this composition. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Human liver autofluorescence: An intrinsic tissue parameter discriminating normal and diseased conditions,,LASERS IN SURGERY AND MEDICINE, Issue 5 2010Anna C. Croce PhD Abstract Background and Objective Autofluorescence (AF) emission is an intrinsic parameter that can provide real-time information on morpho-functional properties of biological tissue, being strictly related with their biochemical composition and structural organization. The diagnostic potentials of AF-based techniques have been investigated on normal, fibrotic, and steatotic liver tissues, in reference to histological features as evidenced by specific histochemical stainings. Materials and Methods AF emission under excitation at 366,nm has been examined on cryostatic tissue sections obtained from biopsies collected during surgical operation, by means of fluorescence imaging and microspectrofluorometric techniques. Results NAD(P)H, collagen, and vitamin A were found to be the endogenous fluorophores characterizing normal, fibrotic, and steatotic liver tissue AF, respectively. The differences of their photo-physical properties, in terms of emission amplitude, spectral shape, and response to irradiation, give rise to modifications of overall AF signal collected from tissues that allow the liver conditions to be distinguished. Conclusion The study provides a valid premise for a development of AF-based optical biopsy techniques for a real-time discrimination of liver anatomo-pathological patterns. Lasers Surg. Med. 42:371-378, 2010. © 2010 Wiley-Liss, Inc. [source] In vivo diffusion tensor imaging of the human optic nerve: Pilot study in normal controlsMAGNETIC RESONANCE IN MEDICINE, Issue 2 2006C.A.M. Wheeler-Kingshott Abstract Diffusion tensor imaging (DTI) of the optic nerve (ON) was acquired in normal controls using zonally oblique multislice (ZOOM) DTI, which excites a small field of view (FOV) using a fast sequence with a shortened EPI echo train. This combines the benefit of low sensitivity to motion (due to the single-shot acquisition used), with the additional advantage of reduced sensitivity to magnetic field susceptibility artifacts. Reducing the bright signal from the fat and cerebrospinal fluid (CSF) surrounding the nerve are key requirements for the success of the presented method. Measurements of mean diffusivity (MD) and fractional anisotropy (FA) indices were made in a coronal section of the middle portion of the optic nerve (ON) in the right (rON) and left (lON) ONs. The average values across 10 healthy volunteers were FArON = 0.64 ± 0.09 and FAlON = 0.57 ± 0.10, and MDrON = (1173 ± 227) × 10,6 mm2 s,1 and MDlON = (1266 ± 170) × 10,6 mm2 s,1. Measurements of the principal eigenvalue of the DT and its orthogonal component were also in agreement with those expected from a highly directional structural organization. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Peripheral synaptic contacts at mechanoreceptors in arachnids and crustaceans: Morphological and immunocytochemical characteristicsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2002Ruth Fabian-Fine Abstract Two types of sensory organs in crustaceans and arachnids, the various mechanoreceptors of spiders and the crustacean muscle receptor organs (MRO), receive extensive efferent synaptic innervation in the periphery. Although the two sensory systems are quite different,the MRO is a muscle stretch receptor while most spider mechanoreceptors are cuticular sensilla,this innervation exhibits marked similarities. Detailed ultrastructural investigations of the synaptic contacts along the mechanosensitive neurons of a spider slit sense organ reveal four important features, all having remarkable resemblances to the synaptic innervation at the MRO: (1) The mechanosensory neurons are accompanied by several fine fibers of central origin, which are presynaptic upon the mechanoreceptors. Efferent control of sensory function has only recently been confirmed electrophysiologically for the peripheral innervation of spider slit sensilla. (2) Different microcircuit configuration types, identified on the basis of the structural organization of their synapses. (3) Synaptic contacts, not only upon the sensory neurons but also between the efferent fibers themselves. (4) Two identified neurotransmitter candidates, GABA and glutamate. Physiological evidence for GABAergic and glutamatergic transmission is incomplete at spider sensilla. Given that the sensory neurons are quite different in their location and origin, these parallels are most likely convergent. Although their significance is only partially understood, mostly from work on the MRO, the close similarities seem to reflect functional constraints on the organization of efferent pathways in the brain and in the periphery. Microsc. Res. Tech. 58:283,298, 2002. © 2002 Wiley-Liss, Inc. [source] MicroCommentary: Subcellular localization of Escherichia coli osmosensory transporter ProP: focus on cardiolipin membrane domainsMOLECULAR MICROBIOLOGY, Issue 6 2007Eugenia Mileykovskaya Summary The role for specific lipids in the spatial distribution of the membrane proteins and formation of the lipid-protein membrane domains is an emerging theme in the studies of the supramolecular organization of the bacterial cell. A combination of the lipid and protein visualization techniques with manipulation of the cell lipid composition provides a useful tool for these studies. This MicroCommentary reviews the first experimental example demonstrating an involvement of the phospholipid cardiolipin in recruitment of a membrane protein (specifically H+ -osmoprotectant symporter ProP) to the Escherichia coli cell poles. The properties of cardiolipin domains employed in creating a specific environment for structural organization and function of membrane protein complexes are also discussed. [source] Tomographic reconstruction of treponemal cytoplasmic filaments reveals novel bridging and anchoring componentsMOLECULAR MICROBIOLOGY, Issue 3 2004Jacques Izard Summary An understanding of the involvement of bacterial cytoplasmic filaments in cell division requires the elucidation of the structural organization of those filamentous structures. Treponemal cytoplasmic filaments are composed of one protein, CfpA, and have been demonstrated to be involved in cell division. In this study, we used electron tomography to show that the filaments are part of a complex with a novel molecular organization that includes at least two distinct features decorating the filaments. One set of components appears to anchor the filaments to the cytoplasmic membrane. The other set of components appears to bridge the cytoplasmic filaments on the cytoplasmic side, and to be involved in the interfilament spacing within the cell. The filaments occupy between 3 and 18% of the inner surface of the cytoplasmic membrane. These results reveal a novel filamentous molecular organization of independent filaments linked by bridges and continuously anchored to the membrane. [source] Oligopeptide permease is required for expression of the Bacillus thuringiensis plcR regulon and for virulenceMOLECULAR MICROBIOLOGY, Issue 4 2001Myriam Gominet PlcR is a pleiotropic regulator of virulence factors in the insect pathogen Bacillus thuringiensis and in the opportunistic human pathogen Bacillus cereus. It activates the transcription of at least 15 genes encoding extracellular proteins, including phospholipases C, proteases and enterotoxins. Expression of the plcR gene is autoregulated and activated at the onset of stationary phase. Here, we used mini-Tn10 transposition to generate a library of B. thuringiensis mutants, with the goal of characterizing genes involved in the expression of the plcR gene. Three mutant strains were identified carrying distinct mini-Tn10 insertions. The mutations impaired plcR expression and caused a deficient haemolytic phenotype, similar to the phenotype of a B. thuringiensis strain in which the plcR gene had been disrupted. The insertion sites of the three mini-Tn10 transposons mapped in a five-gene operon encoding polypeptides homologous to the components of the oligopeptide permease (Opp) system of Bacillus subtilis, and with a similar structural organization. By analogy, the five B. thuringiensis genes were designated oppA, B, C, D and F. In vitro disruption of the B. thuringiensis oppB gene reproduced the effect of the mini-Tn10 insertions (i.e. the loss of haemolytic activity) and reduced the virulence of the strain against insects. These phenotypes are similar to those of a ,plcR mutant. Opp is required for the import of small peptides into the cell. Therefore, plcR expression might be activated at the onset of stationary phase by the uptake of a signalling peptide acting as a quorum-sensing effector. The opp mutations impaired the sporulation efficiency of B. thuringiensis when the cells were cultured in LB medium. Thus, Opp is on the pathway that ultimately regulates Spo0A phosphorylation, as is the case in B. subtilis. However, analysis of plcR expression in ,oppB, ,spo0A and ,oppB,spo0A mutants indicates that Opp is required for plcR expression via a Spo0A-independent mechanism. [source] Gene for porcine pregnancy-associated glycoprotein 2 (poPAG2): Its structural organization and analysis of its promoter,MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2001Bozena Szafranska Abstract The pregnancy-associated glycoproteins (PAG) are abundant secretory products of the placental trophectoderm of ungulate species. They are structurally related to pepsin, having the capability to bind peptides. However, many cannot function as enzymes due to amino acid substitutions in and around the catalytic site. Here, we demonstrate that pigs, like cattle and sheep, but unlike equids, have multiple PAG genes. One of the transcribed porcine PAG (poPAG) genes, the one for poPAG2, was cloned. It had a nine-exon organization similar to that of other mammalian aspartic proteinase genes with an atypical TATA sequence. A total of 1.2 kbp upstream from exon 1 was sequenced. This region shared identity (>,65%) with the promoter regions of the bovine (bo) PAG1, boPAG2 and equine (eq) PAG genes, but not with other aspartyl proteinase genes, including that of pepsinogen A. Nor were there clear similarities to the promoters of other genes with trophoblast-specific expression. Of the different poPAG2 promoter constructs tested in transfection experiments in two human (JAr and JEG3) and one rat (Rcho) choriocarcinoma cell lines, only the shortest (,149 bp) was required to provide full expression of a luciferase reporter. Although this short promoter was not active in Cos-1 and L-929 cells, it was active in CHO cells, a transformed non-trophoblast hamster ovarian cell line. Co-transfection of Ets2 elevated the activity of this short promoter approximately six-fold in JAr cells, but, disruption of the two putative Ets sites did not alter the ability of Ets2 to transactivate the promoter. In the non-trophoblast cell lines, Ets2 failed to elicit any response. Ets2 responsiveness may be a common feature of most or all trophoblast-expressed genes, although in the case of poPAG2, the effect may be indirect. Mol. Reprod. Dev. 60: 137,146, 2001. © 2001 Wiley-Liss, Inc. [source] | |||||||||||||||||||