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Search Results: 1 - 10 of 220857 matches for " Peter D. Currie "
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A Cytochrome P450 Conserved in Insects Is Involved in Cuticle Formation
Tamar Sztal, Henry Chung, Silke Berger, Peter D. Currie, Philip Batterham, Phillip J. Daborn
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036544
Abstract: The sequencing of numerous insect genomes has revealed dynamic changes in the number and identity of cytochrome P450 genes in different insects. In the evolutionary sense, the rapid birth and death of many P450 genes is observed, with only a small number of P450 genes showing orthology between insects with sequenced genomes. It is likely that these conserved P450s function in conserved pathways. In this study, we demonstrate the P450 gene, Cyp301a1, present in all insect genomes sequenced to date, affects the formation of the adult cuticle in Drosophila melanogaster. A Cyp301a1 piggyBac insertion mutant and RNAi of Cyp301a1 both show a similar cuticle malformation phenotype, which can be reduced by 20-hydroxyecdysone, suggesting that Cyp301a1 is an important gene involved in the formation of the adult cuticle and may be involved in ecdysone regulation in this tissue.
Nerve Growth Factor Stimulates Cardiac Regeneration via Cardiomyocyte Proliferation in Experimental Heart Failure
Nicholas T. Lam, Peter D. Currie, Graham J. Lieschke, Nadia A. Rosenthal, David M. Kaye
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0053210
Abstract: Although the adult heart likely retains some regenerative capacity, heart failure (HF) typically remains a progressive disorder. We hypothesise that alterations in the local environment contribute to the failure of regeneration in HF. Previously we showed that nerve growth factor (NGF) is deficient in the failing heart and here we hypothesise that diminished NGF limits the cardiac regenerative response in HF. The capacity of NGF to augment cardiac regeneration was tested in a zebrafish model of HF. Cardiac injury with a HF phenotype was induced in zebrafish larvae at 72 hours post fertilization (hpf) by exposure to aristolochic acid (AA, 2.5 μM, 72–75 hpf). By 168 hpf, AA induced HF and death in 37.5% and 20.8% of larvae respectively (p<0.001). NGF mRNA expression was reduced by 42% (p<0.05). The addition of NGF (50 ng/ml) after exposure to AA reduced the incidence of HF by 50% (p<0.01) and death by 65% (p<0.01). Mechanistically, AA mediated HF was characterised by reduced cardiomyocyte proliferation as reflected by a 6.4 fold decrease in BrdU+ cardiomyocytes (p<0.01) together with features of apoptosis and loss of cardiomyocytes. Following AA exposure, NGF increased the abundance of BrdU+ cardiomyocytes in the heart by 4.8 fold (p<0.05), and this was accompanied by a concomitant significant increase in cardiomyocyte numbers. The proliferative effect of NGF on cardiomyocytes was not associated with an anti-apoptotic effect. Taken together the study suggests that NGF stimulates a regenerative response in the failing zebrafish heart, mediated by stimulation of cardiomyocyte proliferation.
Zebrafish prox1b Mutants Develop a Lymphatic Vasculature, and prox1b Does Not Specifically Mark Lymphatic Endothelial Cells
Shijie Tao, Merlijn Witte, Robert J. Bryson-Richardson, Peter D. Currie, Benjamin M. Hogan, Stefan Schulte-Merker
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028934
Abstract: Background The expression of the Prospero homeodomain transcription factor (Prox1) in a subset of cardinal venous cells specifies the lymphatic lineage in mice. Prox1 is also indispensible for the maintenance of lymphatic cell fate, and is therefore considered a master control gene for lymphangiogenesis in mammals. In zebrafish, there are two prox1 paralogues, the previously described prox1 (also known as prox1a) and the newly identified prox1b. Principal Findings To investigate the role of the prox1b gene in zebrafish lymphangiogenesis, we knocked-down prox1b and found that depletion of prox1b mRNA did not cause lymphatic defects. We also generated two different prox1b mutant alleles, and maternal-zygotic homozygous mutant embryos were viable and did not show any lymphatic defects. Furthermore, the expression of prox1b was not restricted to lymphatic vessels during zebrafish development. Conclusion We conclude that Prox1b activity is not essential for embryonic lymphatic development in zebrafish.
Eta Carinae: Bullet Streams and Colliding Wind Shocks
D. G. Currie
Revista mexicana de astronomía y astrofísica , 2003,
Abstract:
Pattern avoidance with involution
James D. Currie
Computer Science , 2011,
Abstract: We give the avoidance indices (morphic and antimorphic) for all unary patterns with involution.
Infinite ternary square-free words concatenated from permutations of a single word
James D. Currie
Computer Science , 2012,
Abstract: We answer a question of Harju: An infinite square-free ternary word with an $n$-stem factorization exists for any $n\ge 13$. We show that there are uniform ternary morphisms of length $k$ for every $k\ge 23$. This resolves almost completely a problem of the author and Rampersad.
Lexicographically least words in the orbit closure of the Rudin-Shapiro word
James D. Currie
Computer Science , 2009,
Abstract: We give an effective characterization of the lexicographically least word in the orbit closure of the Rudin-Shapiro word w having a specified prefix. In particular, the lexicographically least word in the orbit closure of the Rudin-Shapiro word is 0w. This answers a question Allouche et al.
Morphogenesis and Cell Fate Determination within the Adaxial Cell Equivalence Group of the Zebrafish Myotome
Mai E. Nguyen-Chi,Robert Bryson-Richardson,Carmen Sonntag,Thomas E. Hall,Abigail Gibson,Tamar Sztal,Wendy Chua,Thomas F. Schilling,Peter D. Currie
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1003014
Abstract: One of the central questions of developmental biology is how cells of equivalent potential—an equivalence group—come to adopt specific cellular fates. In this study we have used a combination of live imaging, single cell lineage analyses, and perturbation of specific signaling pathways to dissect the specification of the adaxial cells of the zebrafish embryo. We show that the adaxial cells are myogenic precursors that form a cell fate equivalence group of approximately 20 cells that consequently give rise to two distinct sub-types of muscle fibers: the superficial slow muscle fibers (SSFs) and muscle pioneer cells (MPs), distinguished by specific gene expression and cell behaviors. Using a combination of live imaging, retrospective and indicative fate mapping, and genetic studies, we show that MP and SSF precursors segregate at the beginning of segmentation and that they arise from distinct regions along the anterior-posterior (AP) and dorsal-ventral (DV) axes of the adaxial cell compartment. FGF signaling restricts MP cell fate in the anterior-most adaxial cells in each somite, while BMP signaling restricts this fate to the middle of the DV axis. Thus our results reveal that the synergistic actions of HH, FGF, and BMP signaling independently create a three-dimensional (3D) signaling milieu that coordinates cell fate within the adaxial cell equivalence group.
Development and Evolution of the Muscles of the Pelvic Fin
Nicholas J. Cole,Thomas E. Hall,Emily K. Don,Silke Berger,Catherine A. Boisvert,Christine Neyt,Rolf Ericsson,Jean Joss,David B. Gurevich,Peter D. Currie
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001168
Abstract: Locomotor strategies in terrestrial tetrapods have evolved from the utilisation of sinusoidal contractions of axial musculature, evident in ancestral fish species, to the reliance on powerful and complex limb muscles to provide propulsive force. Within tetrapods, a hindlimb-dominant locomotor strategy predominates, and its evolution is considered critical for the evident success of the tetrapod transition onto land. Here, we determine the developmental mechanisms of pelvic fin muscle formation in living fish species at critical points within the vertebrate phylogeny and reveal a stepwise modification from a primitive to a more derived mode of pelvic fin muscle formation. A distinct process generates pelvic fin muscle in bony fishes that incorporates both primitive and derived characteristics of vertebrate appendicular muscle formation. We propose that the adoption of the fully derived mode of hindlimb muscle formation from this bimodal character state is an evolutionary innovation that was critical to the success of the tetrapod transition.
FishNet: an online database of zebrafish anatomy
Robert J Bryson-Richardson, Silke Berger, Thomas F Schilling, Thomas E Hall, Nicholas J Cole, Abigail J Gibson, James Sharpe, Peter D Currie
BMC Biology , 2007, DOI: 10.1186/1741-7007-5-34
Abstract: To overcome this deficit we have utilized the technique of optical projection tomography to produce three-dimensional (3D) models of larval fish. In order to view and display these models we have created FishNet http://www.fishnet.org.au webcite, an interactive reference of zebrafish anatomy spanning the range of zebrafish development from 24 h until adulthood.FishNet contains more than 36 000 images of larval zebrafish, with more than 1 500 of these being annotated. The 3D models can be manipulated on screen or virtually sectioned. This resource represents the first complete embryo to adult atlas for any species in 3D.Zebrafish possess a number of attributes that have facilitated their uptake as a developmental model system. Zebrafish uniquely combine embryological manipulability, optical clarity of the early embryo and larvae (allowing simple visualization of cell biological events directly in vivo) and the ability to apply invertebrate-style forward genetics to questions of vertebrate development. More recently, research has extended into later aspects of zebrafish development and adulthood, examining aspects of organogenesis and tissue maintenance. Many of the same strengths that made zebrafish a superior model for the study of development also complement those of existing mammalian disease models. Thus a huge variety of human conditions are now being modeled in zebrafish, ranging from drug and alcohol addiction to cancer [1-8].The usefulness of any model organism is limited by the available accurate anatomical information for that system. At present, there is a lack of a detailed anatomical reference for zebrafish. While the earliest stages of zebrafish development have been intensively studied over the last two decades, and an embryological staging series described [9], comparatively little is known about the development of larval, juvenile and adult anatomy. Whilst the vascular anatomy of the embryonic fish [10], the anatomy of the embryonic and adult brain [
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