The Experts below are selected from a list of 1068 Experts worldwide ranked by ideXlab platform
Neil H. Shubin - One of the best experts on this subject based on the ideXlab platform.
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shared developmental mechanisms pattern the vertebrate gill arch and paired fin skeletons
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Andrew J Gillis, Randall D Dahn, Neil H. ShubinAbstract:Here, we describe the molecular patterning of chondrichthyan branchial rays (gill rays) and reveal profound developmental similarities between gill rays and vertebrate appendages. Sonic hedgehog (Shh) and fibroblast growth factor 8 (Fgf8) regulate the outgrowth and patterning of the chondrichthyan gill arch skeleton, in an interdependent manner similar to their roles in gnathostome paired appendages. Additionally, we demonstrate that paired appendages and branchial rays share other conserved developmental features, including Shh-mediated mirror-image duplications of the Endoskeleton after exposure to retinoic acid, and Fgf8 expression by a pseudostratified distal epithelial ridge directing endoskeletal outgrowth. These data suggest that the skeletal patterning role of the retinoic acid/Shh/Fgf8 regulatory circuit has a deep evolutionary origin predating vertebrate paired appendages and may have functioned initially in patterning pharyngeal structures in a deuterostome ancestor of vertebrates.
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the cranial Endoskeleton of tiktaalik roseae
Nature, 2008Co-Authors: Jason P Downs, Neil H. Shubin, Edward B Daeschler, Farish A JenkinsAbstract:Among the morphological changes that occurred during the 'fish-to-tetrapod' transition was a marked reorganization of the cranial Endoskeleton. Details of this transition, including the sequence of character acquisition, have not been evident from the fossil record. Here we describe the braincase, palatoquadrate and branchial skeleton of Tiktaalik roseae, the Late Devonian sarcopterygian fish most closely related to tetrapods. Although retaining a primitive configuration in many respects, the cranial Endoskeleton of T. roseae shares derived features with tetrapods such as a large basal articulation and a flat, horizontally oriented entopterygoid. Other features in T. roseae, like the short, straight hyomandibula, show morphology intermediate between the condition observed in more primitive fish and that observed in tetrapods. The combination of characters in T. roseae helps to resolve the relative timing of modifications in the cranial Endoskeleton. The sequence of modifications suggests changes in head mobility and intracranial kinesis that have ramifications for the origin of vertebrate terrestriality.
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the cranial Endoskeleton of tiktaalik
2008Co-Authors: P Downs, Farish A Jenkins, Edward B Daeschler, Neil H. ShubinAbstract:Amongthemorphologicalchangesthatoccurredduringthe‘fish-to-tetrapod’transitionwasamarkedreorganizationofthecranialEndoskeleton.Details of this transition,including the sequenceof character acquisition,have not been evident fromthe fossil record. Here we describe the braincase, palatoquadrate and branchial skeleton of Tiktaalik roseae, the LateDevonian sarcopterygian fish most closely related to tetrapods. Although retaining a primitive configuration in manyrespects,thecranialEndoskeletonofT.roseaesharesderivedfeatureswithtetrapodssuchasalargebasalarticulationandaflat,horizontallyorientedentopterygoid.OtherfeaturesinT.roseae,liketheshort,straighthyomandibula,showmorphologyintermediate between the condition observed in more primitive fish and that observed in tetrapods. The combination ofcharacters in T. roseae helps to resolve the relative timing of modifications in the cranial Endoskeleton. The sequence ofmodificationssuggestschangesinheadmobilityandintracranialkinesisthathaveramificationsfortheoriginofvertebrateterrestriality.
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Pectoral fin and girdle development in the basal actinopterygians Polyodon spathula and Acipenser transmontanus.
Journal of Morphology, 2004Co-Authors: Marcus C Davis, Neil H. Shubin, Allan ForceAbstract:The pectoral fins of Acipenseriformes pos- sess Endoskeletons with elements homologous to both the fin radials of teleosts and the limb bones of tetrapods. Here we present a study of pectoral fin development in the North American paddlefish, Polyodon spathula, and the white sturgeon, Acipenser transmontanus, which reveals that aspects of both teleost and tetrapod endoskeletal patterning mechanisms are present in Acipenseriformes. Those elements considered homologous to teleost radials, the propterygium and the mesopterygial radials, form via subdivision of an initially chondrogenic plate of mesenchy- mal cells called the endoskeletal disc. In Acipenseri- formes, elements homologous to the sarcopterygian metapterygium develop separately from the endoskeletal disc as an outgrowth of the endoskeletal shoulder girdle that extends into the posterior margin of the finbud. As in tetrapods, the elongating metapterygium and the metapterygial radials form in a proximal to distal order as discrete condensations from initially nonchondrogenic mesenchyme. Patterns of variation seen in the Acipens- eriform fin also correlate with putative homology: all vari- ants from the "normal" fin bauplan involved the metapterygium and the metapterygial radials alone. The primary factor distinguishing Polyodon and Acipenser fin development from each other is the composition of the endoskeletal extracellular matrix. Proteoglycans (visual- ized with Alcian Blue) and Type II collagen (visualized by immunohistochemistry) are secreted in different places within the mesenchymal anlage of the fin elements and girdle and at different developmental times. Acipenseri- form pectoral fins differ from the fins of teleosts in the relative contribution of the Endoskeleton and dermal rays. The fins of Polyodon and Acipenser possess elaborate en- doskeletons overlapped along their distal margins by der- mal lepidotrichia. In contrast, teleost fins generally pos- sess relatively small endoskeletal radials that articulate with the dermal fin skeleton terminally, with little or no proximodistal overlap. J. Morphol. 262:608 - 628, 2004. © 2004 Wiley-Liss, Inc.
Patrick T Spicer - One of the best experts on this subject based on the ideXlab platform.
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microfluidic production of Endoskeleton droplets with controlled size and shape
Powder Technology, 2018Co-Authors: Marco Caggioni, Daniela Traini, Paul M Young, Patrick T SpicerAbstract:Abstract Oil-in-water emulsion droplets, containing an elastic Endoskeleton that holds the droplets in various non-spherical shapes, are formed by crystallizing a portion of the oil phase into a network of wax crystals. Such structures have recently been found to provide enhanced active ingredient delivery and shape-changing responsiveness, but robust methods of producing such droplets are needed that enable control of droplet size and shape. A continuous microfluidic flow is used here to produce Endoskeleton droplets whose size is controlled by fluid flow rate and whose shape is varied between spheres, ellipsoids, and rods by control of exit temperature. A wide range of anisotropic shapes is produced using a single flow channel geometry by allowing the Endoskeleton droplet to relax its deformation by varying degrees in response to fluid interfacial tension. Flexible production of shaped Endoskeleton droplets will expand their application in enhanced delivery, deposition testing, and additive manufacturing processes.
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temperature induced collapse and arrested collapse of anisotropic Endoskeleton droplets
Langmuir, 2015Co-Authors: Marco Caggioni, Alexandra V Bayles, Jessica Lenis, Eric M Furst, Patrick T SpicerAbstract:Micron-scale rod-shaped droplets with a range of aspect ratios are produced using extrusion of oil containing a soft wax crystal network to permit shape customization. A physical model of the droplet shape stability is developed based on balancing interfacial stresses with the internal crystal network yield stress. The model predicts the mechanical properties required for particular droplet size stability, in a given physicochemical environment, and is tested by microscopic observations of droplets over a range of relevant applied temperatures. The time-dependent response to temperature of individual rods is monitored and used to identify the collapse temperature based on structural yielding. Precise temperature control allows variation of the droplet Endoskeleton yield stress and direct determination of the droplet stability as a function of size, by observing the onset of collapse by interfacial compression, and enables validation of the model predictions. Mapping the regions of droplet stability and in...
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interfacial stability and shape change of anisotropic Endoskeleton droplets
Soft Matter, 2014Co-Authors: Marco Caggioni, Alexandra V Bayles, Jessica Lenis, Eric M Furst, Patrick T SpicerAbstract:The delivery of suspended active ingredients to a surface is a central function of numerous commercial cosmetic, drug, and agricultural formulations. Many products use liquid droplets as a delivery vehicle but, because interfacial tension keeps droplets spherical, these materials cannot exploit the benefits of anisotropic shape and shape change offered by solid colloids. In this work, individual droplet manipulation is used to produce viscoelastic droplets that can stably retain non-spherical shapes by balancing the Laplace pressure of the liquid–liquid interface with the elasticity of an internal crystalline network. A stability criterion is developed for idealized spherocylindrical droplets and shown to agree with experimental data for varying droplet size and rheology. Shape change can be induced in the anisotropic droplets by upsetting the balance of droplet interfacial tension and internal rheology. Using dilution to increase the interfacial tension shows that external stimuli can trigger collapse and shape change in these droplets. The droplets wrap around substrates during collapse, improving contact and adhesion. The model is used to develop design criteria for production of droplets with tunable response.
Marco Caggioni - One of the best experts on this subject based on the ideXlab platform.
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microfluidic production of Endoskeleton droplets with controlled size and shape
Powder Technology, 2018Co-Authors: Marco Caggioni, Daniela Traini, Paul M Young, Patrick T SpicerAbstract:Abstract Oil-in-water emulsion droplets, containing an elastic Endoskeleton that holds the droplets in various non-spherical shapes, are formed by crystallizing a portion of the oil phase into a network of wax crystals. Such structures have recently been found to provide enhanced active ingredient delivery and shape-changing responsiveness, but robust methods of producing such droplets are needed that enable control of droplet size and shape. A continuous microfluidic flow is used here to produce Endoskeleton droplets whose size is controlled by fluid flow rate and whose shape is varied between spheres, ellipsoids, and rods by control of exit temperature. A wide range of anisotropic shapes is produced using a single flow channel geometry by allowing the Endoskeleton droplet to relax its deformation by varying degrees in response to fluid interfacial tension. Flexible production of shaped Endoskeleton droplets will expand their application in enhanced delivery, deposition testing, and additive manufacturing processes.
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temperature induced collapse and arrested collapse of anisotropic Endoskeleton droplets
Langmuir, 2015Co-Authors: Marco Caggioni, Alexandra V Bayles, Jessica Lenis, Eric M Furst, Patrick T SpicerAbstract:Micron-scale rod-shaped droplets with a range of aspect ratios are produced using extrusion of oil containing a soft wax crystal network to permit shape customization. A physical model of the droplet shape stability is developed based on balancing interfacial stresses with the internal crystal network yield stress. The model predicts the mechanical properties required for particular droplet size stability, in a given physicochemical environment, and is tested by microscopic observations of droplets over a range of relevant applied temperatures. The time-dependent response to temperature of individual rods is monitored and used to identify the collapse temperature based on structural yielding. Precise temperature control allows variation of the droplet Endoskeleton yield stress and direct determination of the droplet stability as a function of size, by observing the onset of collapse by interfacial compression, and enables validation of the model predictions. Mapping the regions of droplet stability and in...
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interfacial stability and shape change of anisotropic Endoskeleton droplets
Soft Matter, 2014Co-Authors: Marco Caggioni, Alexandra V Bayles, Jessica Lenis, Eric M Furst, Patrick T SpicerAbstract:The delivery of suspended active ingredients to a surface is a central function of numerous commercial cosmetic, drug, and agricultural formulations. Many products use liquid droplets as a delivery vehicle but, because interfacial tension keeps droplets spherical, these materials cannot exploit the benefits of anisotropic shape and shape change offered by solid colloids. In this work, individual droplet manipulation is used to produce viscoelastic droplets that can stably retain non-spherical shapes by balancing the Laplace pressure of the liquid–liquid interface with the elasticity of an internal crystalline network. A stability criterion is developed for idealized spherocylindrical droplets and shown to agree with experimental data for varying droplet size and rheology. Shape change can be induced in the anisotropic droplets by upsetting the balance of droplet interfacial tension and internal rheology. Using dilution to increase the interfacial tension shows that external stimuli can trigger collapse and shape change in these droplets. The droplets wrap around substrates during collapse, improving contact and adhesion. The model is used to develop design criteria for production of droplets with tunable response.
Matt Friedman - One of the best experts on this subject based on the ideXlab platform.
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endoskeletal structure in cheirolepis osteichthyes actinopterygii an early ray finned fish
Palaeontology, 2015Co-Authors: Sam Giles, Zerina Johanson, Michael I. Coates, Russell J Garwood, Martin D Brazeau, Robert Atwood, Matt FriedmanAbstract:As the sister lineage of all other actinopterygians, the Middle to Late Devonian (Eifelian-Frasnian) Cheirolepis occupies a pivotal position in vertebrate phylogeny. Although the dermal skeleton of this taxon has been exhaustively described, very little of its Endoskeleton is known, leaving questions of neurocranial and fin evolution in early ray-finned fishes unresolved. The model for early actinopterygian anatomy has instead been based largely on the Late Devonian (Frasnian) Mimipiscis, preserved in stunning detail from the Gogo Formation of Australia. Here, we present re-examinations of existing museum specimens through the use of high-resolution laboratory- and synchrotron-based computed tomography scanning, revealing new details of the neuro-cranium, hyomandibula and pectoral fin Endoskeleton for the Eifelian Cheirolepis trailli. These new data highlight traits considered uncharacteristic of early actinopterygians, including an uninvested dorsal aorta and imperforate propterygium, and corroborate the early divergence of Cheirolepis within actinopterygian phylogeny. These traits represent conspicuous differences between the endoskeletal structure of Cheirolepis and Mimipiscis. Additionally, we describe new aspects of the parasphenoid, vomer and scales, most notably that the scales display peg-and-socket articulation and a distinct neck. Collectively, these new data help clarify primitive conditions within ray-finned fishes, which in turn have important implications for understanding features likely present in the last common ancestor of living osteichthyans.
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early evolution of the lungfish pectoral fin Endoskeleton evidence from the middle devonian givetian pentlandia macroptera
Frontiers in Earth Science, 2014Co-Authors: Emma Jude, Zerina Johanson, A T Kearsley, Matt FriedmanAbstract:As the closest living relatives of tetrapods, lungfishes are frequently used as extant models for exploring the fin-to-limb transition. These studies have generally given little consideration to fossil taxa. This is because although lungfish fins are relatively common in the fossil record, the internal structure of these fins is virtually unknown. Information on pectoral-fin Endoskeletons in fossil representatives of Dipnomorpha (the lungfish total group) is limited to poorly preserved remains in the lungfish Dipterus and Conchopoma and more complete material in the porolepiform Glyptolepis. Here we describe a well-preserved pectoral-fin Endoskeleton in the Middle Devonian (Givetian) lungfish Pentlandia macroptera from the John O’Groats fish bed, Caithness, northeastern Scotland. The skeleton is in association with a cleithrum and clavicle, and consists of a series of at least eight mesomeres. Extensive series of preaxial and postaxial radials are present. Some of the radials are jointed, but none branch. No mesomere articulates with multiple radials on either its pre- or post-axial face. The first two mesomeres, corresponding to the humerus and ulna, bear well-developed axial processes. Uniquely among dipnomorphs, a distinct ossification centre corresponding to the radius is present in Pentlandia. A review of anatomy and development of the pectoral-fin Endoskeleton in the living Neoceratodus is presented based on cleared and stained material representing different size stages. These developmental data, in conjunction with new details of primitive lungfish conditions based on Pentlandia, highlight many of the derived features of the pectoral-fin skeleton of Neoceratodus, and clarify patterns of appendage evolution within the dipnomorphs more generally.
Marcos Paulo Alves De Sousa - One of the best experts on this subject based on the ideXlab platform.
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deep evolutionary origin of limb and fin regeneration
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Sylvain Darnet, Aline C Dragalzew, Danielson B Amaral, Andrew W Thompson, Amanda N Cass, Jamily Lorena, Josane F Sousa, Carinne M Costa, Eder Soares Pires, Marcos Paulo Alves De SousaAbstract:Salamanders and lungfishes are the only sarcopterygians (lobe-finned vertebrates) capable of paired appendage regeneration, regardless of the amputation level. Among actinopterygians (ray-finned fishes), regeneration after amputation at the fin Endoskeleton has only been demonstrated in polypterid fishes (Cladistia). Whether this ability evolved independently in sarcopterygians and actinopterygians or has a common origin remains unknown. Here we combine fin regeneration assays and comparative RNA-sequencing (RNA-seq) analysis of Polypterus and axolotl blastemas to provide support for a common origin of paired appendage regeneration in Osteichthyes (bony vertebrates). We show that, in addition to polypterids, regeneration after fin Endoskeleton amputation occurs in extant representatives of 2 other nonteleost actinopterygians: the American paddlefish (Chondrostei) and the spotted gar (Holostei). Furthermore, we assessed regeneration in 4 teleost species and show that, with the exception of the blue gourami (Anabantidae), 3 species were capable of regenerating fins after Endoskeleton amputation: the white convict and the oscar (Cichlidae), and the goldfish (Cyprinidae). Our comparative RNA-seq analysis of regenerating blastemas of axolotl and Polypterus reveals the activation of common genetic pathways and expression profiles, consistent with a shared genetic program of appendage regeneration. Comparison of RNA-seq data from early Polypterus blastema to single-cell RNA-seq data from axolotl limb bud and limb regeneration stages shows that Polypterus and axolotl share a regeneration-specific genetic program. Collectively, our findings support a deep evolutionary origin of paired appendage regeneration in Osteichthyes and provide an evolutionary framework for studies on the genetic basis of appendage regeneration.
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deep evolutionary origin of limb and fin regeneration
bioRxiv, 2018Co-Authors: Sylvain Darnet, Aline C Dragalzew, Danielson B Amaral, Andrew W Thompson, Amanda N Cass, Jamily Lorena, Josane F Sousa, Carinne M Costa, Marcos Paulo Alves De Sousa, Nadia B FrobischAbstract:Salamanders and lungfishes are the only sarcopterygians (lobe-finned vertebrates) capable of complete limb and paired fin regeneration, respectively. Among actinopterygians (ray-finned fishes), regeneration after amputation at the fin Endoskeleton has only been demonstrated in Polypterid fishes (Cladistia). Whether complete appendage regeneration in sarcopterygians and actinopterygians evolved independently or has a common origin remains unknown. Here we combine fin regeneration assays and comparative RNA-seq analysis to provide support for a common origin of a paired appendage regeneration in osteichthyes (bony vertebrates). We show that, in addition to Polypterids, regeneration after fin Endoskeleton amputation occurs in extant representatives of all major actinopterygian clades: the American paddlefish, (Chondrostei), the spotted gar (Holostei), as well as in two cichlid species, the white convict and the oscar (Teleostei). Our comparative RNA-seq analysis of regenerating blastemas of axolotl and Polypterus reveals the activation of common genetic pathways and expression profiles, consistent with a pan-osteichthyes genetic program of appendage regeneration. Collectively, our findings support a deep evolutionary origin of paired appendage regeneration in osteichthyes and provide an evolutionary framework for studies on the genetic basis of appendage regeneration.