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  • 1
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    Fgf10+ progenitors give rise to the chick hypothalamus by rostral and caudal growth and differentiation [RESEARCH ARTICLE] (2017)
    The Company of Biologists
    Details
    Publication Date: 2017-09-20
    Description: Travis Fu, Matthew Towers, and Marysia A. Placzek Classical descriptions of the hypothalamus divide it into three rostro-caudal domains but little is known about their embryonic origins. To investigate this, we performed targeted fate-mapping, molecular characterisation and cell cycle analyses in the embryonic chick. Presumptive hypothalamic cells derive from the rostral diencephalic ventral midline, lie above the prechordal mesendoderm and express Fgf10 . Fgf10 + progenitors undergo anisotropic growth: those displaced rostrally differentiate into anterior cells, then those displaced caudally differentiate into mammillary cells. A stable population of Fgf10 + progenitors is retained within the tuberal domain; a subset of these gives rise to the tuberal infundibulum – the precursor of the posterior pituitary. Pharmacological approaches reveal that Shh signalling promotes the growth and differentiation of anterior progenitors, and also orchestrates the development of the infundibulum and Rathke's pouch – the precursor of the anterior pituitary. Together, our studies identify a hypothalamic progenitor population defined by Fgf10 and highlight a role for Shh signalling in the integrated development of the hypothalamus and pituitary.
    Print ISSN: 0950-1991
    Electronic ISSN: 1477-9129
    Topics: Biology
    Published by The Company of Biologists
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  • 2
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    Intrinsic properties of limb bud cells can be differentially reset [RESEARCH ARTICLE] (2017)
    The Company of Biologists
    Details
    Publication Date: 2017-02-01
    Description: Patricia Saiz-Lopez, Kavitha Chinnaiya, Matthew Towers, and Maria A. Ros An intrinsic timing mechanism specifies the positional values of the zeugopod (i.e. radius/ulna) and then autopod (i.e. wrist/digits) segments during limb development. Here, we have addressed whether this timing mechanism ensures that patterning events occur only once by grafting GFP-expressing autopod progenitor cells to the earlier host signalling environment of zeugopod progenitor cells. We show by detecting Hoxa13 expression that early and late autopod progenitors fated for the wrist and phalanges, respectively, both contribute to the entire host autopod, indicating that the autopod positional value is irreversibly determined. We provide evidence that Hoxa13 provides an autopod-specific positional value that correctly allocates cells into the autopod, most likely through the control of cell-surface properties as shown by cell-cell sorting analyses. However, we demonstrate that only the earlier autopod cells can adopt the host proliferation rate to permit normal morphogenesis. Therefore, our findings reveal that the ability of embryonic cells to differentially reset their intrinsic behaviours confers robustness to limb morphogenesis. We speculate that this plasticity could be maintained beyond embryogenesis in limbs with regenerative capacity.
    Keywords: Musculoskeletal system
    Print ISSN: 0950-1991
    Electronic ISSN: 1477-9129
    Topics: Biology
    Published by The Company of Biologists
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  • 3
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    Inhibition of Shh signalling in the chick wing gives insights into digit patterning and evolution [RESEARCH ARTICLE] (2016)
    The Company of Biologists
    Details
    Publication Date: 2016-10-08
    Description: Joseph Pickering and Matthew Towers In an influential model of pattern formation, a gradient of Sonic hedgehog (Shh) signalling in the chick wing bud specifies cells with three antero-posterior positional values, which give rise to three morphologically different digits by a self-organizing mechanism with Turing-like properties. However, as four of the five digits of the mouse limb are morphologically similar in terms of phalangeal pattern, it has been suggested that self-organization alone could be sufficient. Here, we show that inhibition of Shh signalling at a specific stage of chick wing development results in a pattern of four digits, three of which can have the same number of phalanges. These patterning changes are dependent on a posterior extension of the apical ectodermal ridge, and this also allows the additional digit to arise from the Shh-producing cells of the polarizing region – an ability lost in ancestral theropod dinosaurs. Our analyses reveal that, if the specification of antero-posterior positional values is curtailed, self-organization can then produce several digits with the same number of phalanges. We present a model that may give important insights into how the number of digits and phalanges has diverged during the evolution of avian and mammalian limbs.
    Keywords: Musculoskeletal system
    Print ISSN: 0950-1991
    Electronic ISSN: 1477-9129
    Topics: Biology
    Published by The Company of Biologists
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  • 4
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    The role of the RAS pathway in iAMP21-ALL (2016)
    Nature Publishing Group (NPG)
    In: Leukemia
    Details
    Publication Date: 2016-09-08
    Description: The role of the RAS pathway in iAMP21-ALL Leukemia 30, 1824 (September 2016). doi:10.1038/leu.2016.80 Authors: S L Ryan, E Matheson, V Grossmann, P Sinclair, M Bashton, C Schwab, W Towers, M Partington, A Elliott, L Minto, S Richardson, T Rahman, B Keavney, R Skinner, N Bown, T Haferlach, P Vandenberghe, C Haferlach, M Santibanez-Koref, A V Moorman, A Kohlmann, J A E Irving & C J Harrison
    Print ISSN: 0887-6924
    Electronic ISSN: 1476-5551
    Topics: Medicine
    Published by Nature Publishing Group (NPG)
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  • 5
    Electronic Resource
    Electronic Resource
    The temperature characteristics of InGaAsP/InP buried heterostructure lasers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7621-7623 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature characteristics of 1.3 μm InGaAsP/InP buried heterojunction lasers are investigated using a fully self-consistent two dimensional numerical model. Devices operating at 1.3 μm are very temperature sensitive and therefore the model includes for the first time coupled solutions to the thermal as well as the electrical and optical equation sets. Good agreement is found with experimental results, including the temperature dependence of the threshold current and the prediction of a break-point temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354942
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  • 6
    Electronic Resource
    Electronic Resource
    An investigation of the diffusion of silicon in delta-doped gallium arsenide, as determined using high-resolution secondary ion mass spectrometry (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 821-826 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon delta-doped samples of various densities were grown by molecular-beam epitaxy and analyzed using high-resolution secondary ion mass spectrometry. A marked difference was observed between profiles produced from samples doped below a surface density of 1.3×1013 cm−2, where all the silicon was incorporated on gallium sites, and highly doped samples, where autocompensation had occurred. All samples were grown at nominally 580 °C and all the doped planes showed some degree of broadening. A computer model of a two-step diffusion process was developed which produced a set of diffusion coefficients for the lower-doped samples. The diffusion coefficient associated with the post deposition growth for these low-doped samples was approximately 4.2×10−17 cm2 s−1. The more highly doped samples, because of their complicated profiles, were modeled using a graphical technique. This technique revealed the presence of a much larger diffusion coefficient, which is tentatively assigned to silicon diffusing as nearest-neighbor pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349640
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    Paper (German National Licenses)
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