The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Noriko Funayama - One of the best experts on this subject based on the ideXlab platform.
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toward understanding the morphogenesis of siliceous Spicules in freshwater sponge differential mrna expression of Spicule type specific silicatein genes in ephydatia fluviatilis
Developmental Dynamics, 2008Co-Authors: Kurato Mohri, Mikiko Nakatsukasa, Kiyokazu Agata, Yoshiki Masuda, Noriko FunayamaAbstract:Siliceous Spicules of sponges are morphologically diverse and provide good models for understanding the morphogenesis of biomineralized products. The silica deposition enzyme silicatein is a component of siliceous Spicules of sponges and is thought to be the key molecule determining the morphology of Spicules. Here, we focused on the silicateins of the freshwater sponge Ephydatia fluviatilis, which has two types of morphologically and functionally different Spicules, called megascleres and gemmoscleres. We isolated six isoforms of silicateins and examined their mRNA expression in the cells producing megascleres and gemmoscleres. The Spicule-type-specific mRNA expression of these isoforms and differential expression during Spicule development suggest that the characteristic morphology of Spicules is due to the specific properties and combinatory functions of silicatein isoforms. Developmental Dynamics 237:3024–3039, 2008. © 2008 Wiley-Liss, Inc.
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Toward understanding the morphogenesis of siliceous Spicules in freshwater sponge: Differential mRNA expression of Spicule‐type‐specific silicatein genes in Ephydatia fluviatilis
Developmental Dynamics, 2008Co-Authors: Kurato Mohri, Mikiko Nakatsukasa, Kiyokazu Agata, Yoshiki Masuda, Noriko FunayamaAbstract:Siliceous Spicules of sponges are morphologically diverse and provide good models for understanding the morphogenesis of biomineralized products. The silica deposition enzyme silicatein is a component of siliceous Spicules of sponges and is thought to be the key molecule determining the morphology of Spicules. Here, we focused on the silicateins of the freshwater sponge Ephydatia fluviatilis, which has two types of morphologically and functionally different Spicules, called megascleres and gemmoscleres. We isolated six isoforms of silicateins and examined their mRNA expression in the cells producing megascleres and gemmoscleres. The Spicule-type-specific mRNA expression of these isoforms and differential expression during Spicule development suggest that the characteristic morphology of Spicules is due to the specific properties and combinatory functions of silicatein isoforms. Developmental Dynamics 237:3024–3039, 2008. © 2008 Wiley-Liss, Inc.
Werner E G Muller - One of the best experts on this subject based on the ideXlab platform.
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flexible minerals self assembled calcite Spicules with extreme bending strength
Science, 2013Co-Authors: Filipe Natalio, Tomas P Corrales, Ingo Lieberwirth, Martin Panthofer, Hansjurgen Butt, Michael Kappl, Werner E G Muller, Dieter Schollmeyer, Wolfgang TremelAbstract:Silicatein-α is responsible for the biomineralization of silicates in sponges. We used silicatein-α to guide the self-assembly of calcite "Spicules" similar to the Spicules of the calcareous sponge Sycon sp. The self-assembled Spicules, 10 to 300 micrometers (μm) in length and 5 to 10 μm in diameter, are composed of aligned calcite nanocrystals. The Spicules are initially amorphous but transform into calcite within months, exhibiting unusual growth along [100]. They scatter x-rays like twinned calcite crystals. Whereas natural Spicules evidence brittle failure, the synthetic Spicules show an elastic response, which greatly enhances bending strength. This remarkable feature is linked to a high protein content. With nano-thermogravimetric analysis, we measured the organic content of a single Spicule to be 10 to 16%. In addition, the Spicules exhibit waveguiding properties even when they are bent.
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evagination of cells controls bio silica formation and maturation during Spicule formation in sponges
PLOS ONE, 2011Co-Authors: Xiaohong Wang, Matthias Wiens, Ute Schlosmacher, Heinz C Schroder, Dario Pisignano, Klaus Peter Jochum, Werner E G MullerAbstract:The enzymatic-silicatein mediated formation of the skeletal elements, the Spicules of siliceous sponges starts intracellularly and is completed extracellularly. With Suberites domuncula we show that the axial growth of the Spicules proceeds in three phases: (I) formation of an axial canal; (II) evagination of a cell process into the axial canal, and (III) assembly of the axial filament composed of silicatein. During these phases the core part of the Spicule is synthesized. Silicatein and its substrate silicate are stored in silicasomes, found both inside and outside of the cellular extension within the axial canal, as well as all around the Spicule. The membranes of the silicasomes are interspersed by pores of ≈2 nm that are likely associated with aquaporin channels which are implicated in the hardening of the initial bio-silica products formed by silicatein. We can summarize the sequence of events that govern Spicule formation as follows: differential genetic readout (of silicatein) → fractal association of the silicateins → evagination of cells by hydro-mechanical forces into the axial canal → and finally processive bio-silica polycondensation around the axial canal. We termed this process, occurring sequentially or in parallel, bio-inorganic self-organization.
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bio sintering processes in hexactinellid sponges fusion of bio silica in giant basal Spicules from monorhaphis chuni
Journal of Structural Biology, 2009Co-Authors: Werner E G Muller, Alexandra Boreiko, Ute Schlosmacher, Zaklina Burghard, Anatoli Krasko, Heinz C Schroder, Joachim Bill, Xiaohong Wang, Matthias WiensAbstract:Abstract The two sponge classes, Hexactinellida and Demospongiae, comprise a skeleton that is composed of siliceous skeletal elements (Spicules). Spicule growth proceeds by appositional layering of lamellae that consist of silica nanoparticles, which are synthesized via the sponge-specific enzyme silicatein. While in demosponges during maturation the lamellae consolidate to a solid rod, the lamellar organization of hexactinellid Spicules largely persists. However, the innermost lamellae, near the Spicule core, can also fuse to a solid axial cylinder. Similar to the fusion of siliceous nanoparticles and lamella, in several hexactinellid species individual Spicules unify during sintering-like processes. Here, we study the different stages of a process that we termed bio-sintering, within the giant basal Spicule (GBS) of Monorhaphis chuni. During this study, a major GBS protein component (27 kDa) was isolated and analyzed by MALDI-TOF-MS. The sequences were used to isolate and clone the encoding cDNA via degenerate primer PCR. Bioinformatic analyses revealed a significant sequence homology to silicatein. In addition, the native GBS protein was able to mediate bio-silica synthesis in vitro. We conclude that the syntheses of bio-silica in M. chuni, and the subsequent fusion of nanoparticles to lamellae, and finally to Spicules, are enzymatically-driven by a silicatein-like protein. In addition, evidence is now presented that in hexactinellids those fusions involve sintering-like processes.
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crystalline nanorods as possible templates for the synthesis of amorphous biosilica during Spicule formation in demospongiae
ChemBioChem, 2009Co-Authors: Enrico Mugnaioli, Filipe Natalio, Ute Schlosmacher, Werner E G Muller, Xiaohong Wang, Ute KolbAbstract:In tandem: High-resolution TEM shows that during the initial stages of demosponge Spicule formation, a primordial crystalline structure is formed within the axial filament. The recently developed electron diffraction tomography technique (ADT) reveals that the nanorods have a layered structure that matches smectitic phyllosilicates. These intracellular nanorods have been considered as precursors of mature Spicules. High-resolution microscopy shows that, during the initial stages of demosponge Spicule formation, a primordial crystalline structure is formed within the axial filament. The recently developed electron diffraction tomography technique reveals that the nanorods have a layered structure that matches smectitic phyllosilicates. These intracellular nanorods have been considered as precursors of mature Spicules.
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axial growth of hexactinellid Spicules formation of cone like structural units in the giant basal Spicules of the hexactinellid monorhaphis
Journal of Structural Biology, 2008Co-Authors: Xiaohong Wang, Alexandra Boreiko, Hermann Gotz, Jaap A. Kaandorp, Heins Duschner, David Brandt, Ute Schlosmacher, Jinhe Li, Heinz C Schroder, Werner E G MullerAbstract:The glass sponge Monorhaphis chuni (Porifera: Hexactinellida) forms the largest bio-silica structures on Earth; their giant basal Spicules reach sizes of up to 3 m and diameters of 8.5 mm. Previously, it had been shown that the thickness growth proceeds by appositional layering of individual lamellae; however, the mechanism for the longitudinal growth remained unstudied. Now we show, that the surface of the Spicules have towards the tip serrated relief structures that are consistent in size and form with the protrusions on the surface of the Spicules. These protrusions fit into the collagen net that surrounds the Spicules. The widths of the individual lamellae do not show a pronounced size tendency. The apical elongation of the Spicule proceeds by piling up cone-like structural units formed from silica. As a support of the assumption that in the extracellular space silicatein(-like) molecules exist that associate with the external surface of the respective Spicule immunogold electron microscopic analyses were performed. With the primmorph system from Suberites domuncula we show that silicatein(-like) molecules assemble as string- and net-like arrangements around the Spicules. At their tips the silicatein(-like) molecules are initially stacked and at a later stay also organized into net-like structures. Silicatein(-like) molecules have been extracted from the giant basal Spicule of Monorhaphis. Applying the SDS-PAGE technique it could be shown that silicatein molecules associate to dimers and trimers. Higher complexes (filaments) are formed from silicatein(-like) molecules, as can be visualized by electron microscopy (SEM). In the presence of ortho-silicate these filaments become covered with 30-60 nm long small rod-like/cuboid particles of silica. From these data we conclude that the apical elongation of the Spicules of Monorhaphis proceeds by piling up cone-like silica structural units, whose synthesis is mediated by silicatein(-like) molecules. (C) 2008 Elsevier Inc. All rights reserved.
Bart De Pontieu - One of the best experts on this subject based on the ideXlab platform.
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transverse wave induced kelvin helmholtz rolls in Spicules
The Astrophysical Journal, 2018Co-Authors: Patrick Antolin, D Schmit, T M D Pereira, Bart De Pontieu, I De MoortelAbstract:In addition to their jet-like dynamic behavior, Spicules usually exhibit strong transverse speeds, multi-stranded structure, and heating from chromospheric to transition region temperatures. In this work we first analyze Hinode and IRIS observations of Spicules and find different behaviors in terms of their Doppler velocity evolution and collective motion of their sub-structure. Some have a Doppler shift sign change that is rather fixed along the Spicule axis, and lack coherence in the oscillatory motion of strand-like structure, matching rotation models, or long-wavelength torsional Alfven waves. Others exhibit a Doppler shift sign change at maximum displacement and coherent motion of their strands, suggesting a collective magnetohydrodynamic (MHD) wave. By comparing with an idealized 3D MHD simulation combined with radiative transfer modeling, we analyze the role of transverse MHD waves and associated instabilities in Spicule-like features. We find that transverse wave induced Kelvin–Helmholtz (TWIKH) rolls lead to coherence of strand-like structure in imaging and spectral maps, as seen in some observations. The rapid transverse dynamics and the density and temperature gradients at the Spicule boundary lead to ring-shaped Mg ii k and Ca ii H source functions in the transverse cross-section, potentially allowing IRIS to capture the Kelvin–Helmholtz instability dynamics. Twists and currents propagate along the Spicule at Alfvenic speeds, and the temperature variations within TWIKH rolls, produce the sudden appearance/disappearance of strands seen in Doppler velocity and in Ca ii H intensity. However, only a mild intensity increase in higher-temperature lines is obtained, suggesting there is an additional heating mechanism at work in Spicules.
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on the multi threaded nature of solar Spicules
The Astrophysical Journal, 2014Co-Authors: H Skogsrud, Rouppe L Van Der Voort, Bart De PontieuAbstract:A dominant constituent in the dynamic chromosphere is Spicules. Spicules at the limb appear as relatively small and dynamic jets that are observed to stick out everywhere. Many papers emphasize the important role Spicules might play in the energy and mass balance of the chromosphere and corona. However, many aspects of Spicules remain a mystery. In this Letter, we shed more light on the multi-threaded nature of Spicules and their torsional component. We use high spatial, spectral, and temporal resolution observations from the Swedish 1 m Solar Telescope in the Hα spectral line. The data target the limb, and we extract spectra from Spicules far out from the limb to reduce the line-of-sight superposition effect. We discover that many Spicules display very asymmetric spectra with some even showing multiple peaks. To quantify this asymmetry, we use a double-Gaussian fitting procedure and find an average velocity difference between the single-Gaussian components to be between 20 and 30 km s{sup –1} for a sample of 57 Spicules. We observe that Spicules show significant substructure where one Spicule consists of many ''threads''. We interpret the asymmetric spectra as a line-of-sight superposition of threads in one Spicule and therefore have a measure for a perpendicular flowmore » inside Spicules that will be important for future numerical models to reproduce. In addition, we show examples of λ – x slices perpendicular across Spicules and find spectral tilts in individual threads, providing further evidence for the complex dynamical nature of Spicules.« less
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The Effects of Spatio-temporal Resolution on Deduced Spicule Properties
The Astrophysical Journal, 2013Co-Authors: Tiago M. D. Pereira, Bart De Pontieu, Mats CarlssonAbstract:Spicules have been observed on the Sun for more than a century, typically in chromospheric lines such as Hα and Ca II H. Recent work has shown that so-called "type II" Spicules may have a role in providing mass to the corona and the solar wind. In chromospheric filtergrams these Spicules are not seen to fall back down, and they are shorter lived and more dynamic than the Spicules that have been classically reported in ground-based observations. Observations of type II Spicules with Hinode show fundamentally different properties from what was previously measured. In earlier work we showed that these dynamic type II Spicules are the most common type, a view that was not properly identified by early observations. The aim of this work is to investigate the effects of spatio-temporal resolution in the classical Spicule measurements. Making use of Hinode data degraded to match the observing conditions of older ground-based studies, we measure the properties of Spicules with a semi-automated algorithm. These results are then compared to measurements using the original Hinode data. We find that degrading the data has a significant effect on the measured properties of Spicules. Most importantly, the results from the degraded data agree well with older studies (e.g., mean Spicule duration more than 5 minutes, and upward apparent velocities of about 25 km s–1). These results illustrate how the combination of Spicule superposition, low spatial resolution and cadence affect the measured properties of Spicules, and that previous measurements can be misleading.
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ubiquitous torsional motions in type ii Spicules
The Astrophysical Journal, 2012Co-Authors: Bart De Pontieu, Robert J. Rutten, V H Hansteen, Rouppe L Van Der Voort, M Carlsson, Hiroko WatanabeAbstract:Spicules are long, thin, highly dynamic features that jut out ubiquitously from the solar limb. They dominate the interface between the chromosphere and corona and may provide significant mass and energy to the corona. We use high-quality observations with the Swedish 1 m Solar Telescope to establish that so-called type II Spicules are characterized by the simultaneous action of three different types of motion: (1) field-aligned flows of order 50-100 km s–1, (2) swaying motions of order 15-20 km s–1, and (3) torsional motions of order 25-30 km s–1. The first two modes have been studied in detail before, but not the torsional motions. Our analysis of many near-limb and off-limb spectra and narrowband images using multiple spectral lines yields strong evidence that most, if not all, type II Spicules undergo large torsional modulation and that these motions, like Spicule swaying, represent Alfvenic waves propagating outward at several hundred km s–1. The combined action of the different motions explains the similar morphology of Spicule bushes in the outer red and blue wings of chromospheric lines, and needs to be taken into account when interpreting Doppler motions to derive estimates for field-aligned flows in Spicules and determining the Alfvenic wave energy in the solar atmosphere. Our results also suggest that large torsional motion is an ingredient in the production of type II Spicules and that Spicules play an important role in the transport of helicity through the solar atmosphere.
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propagating waves along Spicules
The Astrophysical Journal, 2011Co-Authors: Takenori J Okamoto, Bart De PontieuAbstract:Alfvenic waves are thought to play an important role in coronal heating and acceleration of solar wind. Here we investigate the statistical properties of Alfvenic waves along Spicules (jets that protrude into the corona) in a polar coronal hole using high-cadence observations of the Solar Optical Telescope on board Hinode. We developed a technique for the automated detection of Spicules and high-frequency waves. We detected 89 Spicules and found (1) a mix of upward propagating, downward propagating, as well as standing waves (occurrence rates of 59%, 21%, and 20%, respectively); (2) the phase speed gradually increases with height; (3) upward waves dominant at lower altitudes, standing waves at higher altitudes; (4) standing waves dominant in the early and late phases of each Spicule, while upward waves were dominant in the middle phase; (5) in some Spicules, we find waves propagating upward (from the bottom) and downward (from the top) to form a standing wave in the middle of the Spicule; and (6) the medians of the amplitude, period, and velocity amplitude were 55 km, 45 s, and 7.4 km s–1, respectively. We speculate that upward propagating waves are produced near the solar surface (below the Spicule) and downward propagating waves are caused by reflection of (initially) upward propagating waves off the transition region at the Spicule top. The mix of upward and downward propagating waves implies that exploiting these waves to perform seismology of the spicular environment requires careful analysis and may be problematic.
Lia Addadi - One of the best experts on this subject based on the ideXlab platform.
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the transient phase of amorphous calcium carbonate in sea urchin larval Spicules the involvement of proteins and magnesium ions in its formation and stabilization
Advanced Functional Materials, 2003Co-Authors: P C Hamilton, Fred H Wilt, Steve Weiner, Lia AddadiAbstract:Amorphous calcium carbonate (ACC) is a precursor phase of calcite in the formation of the sea urchin larval Spicule. The goal of this research is to study the formation and stabilization mode of this transient phase. We first characterized the mineralogy of the Spicules from the sea urchin Strongylocentrotus purpuratus. We then examined the role of the macromolecules extracted from the Spicules at different growth stages in the formation of transient ACC in vitro.The biogenic amorphous transient phase is shown to be both structurally and compositionally different from the known stable ACC phases. It does not contain bound water, and is thus the first dehydrated ACC phase to be detected. The macromolecules that were extracted at early stages of Spicule growth, when the amorphous content of the biogenic mineral is high, induced the formation of transient ACC in vitro in the presence of magnesium ions. In contrast, the macromolecules extracted at a later stage, when the Spicules are completely crystalline, induced the formation of single crystals of low magnesian calcite. We therefore deduce that the macromolecules from the sea urchin larval Spicules together with magnesium ions, mediate the transient formation of ACC as a precursor to calcite. These observations may well provide novel ideas for improved materials synthesis.
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cellular control over Spicule formation in sea urchin embryos a structural approach
Journal of Structural Biology, 1999Co-Authors: Elia Beniash, Lia Addadi, Stephen WeinerAbstract:Abstract The Spicules of the sea urchin embryo form in intracellular membrane-delineated compartments. Each Spicule is composed of a single crystal of calcite and amorphous calcium carbonate. The latter transforms with time into calcite by overgrowth of the preexisting crystal. Relationships between the membrane surrounding the spiculogenic compartment and the Spicule mineral phase were studied in the transmission electron microscope (TEM) using freeze-fracture. In all the replicas observed the Spicules were tightly surrounded by the membrane. Furthermore, a variety of structures that are related to the material exchange process across the membrane were observed. The spiculogenic cells were separated from other cell types of the embryo, frozen, and freeze-dried on the TEM grids. The contents of electron-dense granules in the spiculogenic cells were shown by electron diffraction to be composed of amorphous calcium carbonate. These observations are consistent with the notion that the amorphous calcium carbonate-containing granules contain the precursor mineral phase for Spicule formation and that the membrane surrounding the forming Spicule is involved both in transport of material and in controlling Spicule mineralization.
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amorphous calcium carbonate transforms into calcite during sea urchin larval Spicule growth
Proceedings of The Royal Society B: Biological Sciences, 1997Co-Authors: Elia Beniash, Lia Addadi, Joanna Aizenberg, Stephen WeinerAbstract:Sea urchin larvae form an endoskeleton composed of a pair of Spicules. For more than a century it has been stated that each Spicule comprises a single crystal of the CaCO3 mineral, calcite. We show...
Stephen Weiner - One of the best experts on this subject based on the ideXlab platform.
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cellular control over Spicule formation in sea urchin embryos a structural approach
Journal of Structural Biology, 1999Co-Authors: Elia Beniash, Lia Addadi, Stephen WeinerAbstract:Abstract The Spicules of the sea urchin embryo form in intracellular membrane-delineated compartments. Each Spicule is composed of a single crystal of calcite and amorphous calcium carbonate. The latter transforms with time into calcite by overgrowth of the preexisting crystal. Relationships between the membrane surrounding the spiculogenic compartment and the Spicule mineral phase were studied in the transmission electron microscope (TEM) using freeze-fracture. In all the replicas observed the Spicules were tightly surrounded by the membrane. Furthermore, a variety of structures that are related to the material exchange process across the membrane were observed. The spiculogenic cells were separated from other cell types of the embryo, frozen, and freeze-dried on the TEM grids. The contents of electron-dense granules in the spiculogenic cells were shown by electron diffraction to be composed of amorphous calcium carbonate. These observations are consistent with the notion that the amorphous calcium carbonate-containing granules contain the precursor mineral phase for Spicule formation and that the membrane surrounding the forming Spicule is involved both in transport of material and in controlling Spicule mineralization.
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amorphous calcium carbonate transforms into calcite during sea urchin larval Spicule growth
Proceedings of The Royal Society B: Biological Sciences, 1997Co-Authors: Elia Beniash, Lia Addadi, Joanna Aizenberg, Stephen WeinerAbstract:Sea urchin larvae form an endoskeleton composed of a pair of Spicules. For more than a century it has been stated that each Spicule comprises a single crystal of the CaCO3 mineral, calcite. We show...