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Elements Underlying (element + underlying)
Selected AbstractsKnowledge Networks in an Uncompetitive Region: SME Innovation and GrowthGROWTH AND CHANGE, Issue 2 2009ROBERT HUGGINS ABSTRACT Knowledge networks are now recognised as a crucial element underlying the economic success and competitiveness of geographic locations, in particular regions. The aim of this paper is to assess the types of knowledge networks utilised and formed by knowledge-based small- and medium-sized enterprises (SMEs) in the relatively uncompetitive regional setting of Yorkshire and Humberside in the UK. It explores the relationship between knowledge networking activity and the levels of innovation and growth achieved by these SMEs. It is found that SMEs tend to utilise and value more knowledge networks with actors outside the region. However, more innovative SMEs possess a balance of inside and outside the region knowledge networks. Knowledge networking activity is sometimes negatively associated with growth, suggesting that networks with certain actors, such as public sector support agencies, may be formed by SMEs when they are facing competitive pressures. In terms of policy implications, the paper recommends a shift from the cluster policies implemented by many regional authorities to a regional innovation systems approach, focusing equally on the regional and more global dimensions of knowledge networks. It is concluded that regional public policy makers need to renew their efforts to support SMEs in creating and sustaining their knowledge networks. [source] A novel role for polyamines in adult neurogenesis in rodent brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004Jordane Malaterre Abstract Although neurogenesis in the adult is known to be regulated by various internal cues such as hormones, growth factors and cell-adherence molecules, downstream elements underlying their action at the cellular level still remain unclear. We previously showed in an insect model that polyamines (putrescine, spermidine and spermine) play specific roles in adult brain neurogenesis. Here, we demonstrate their involvement in the regulation of secondary neurogenesis in the rodent brain. Using neurosphere assays, we show that putrescine addition stimulates neural progenitor proliferation. Furthermore, in vivo depletion of putrescine by specific and irreversible inhibition of ornithine decarboxylase, the first key enzyme of the polyamine synthesis pathway, induces a consistent decrease in neural progenitor cell proliferation in the two neurogenic areas, the dentate gyrus and the subventricular zone. The present study reveals common mechanisms underlying birth of new neurons in vertebrate and invertebrate species. [source] Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolutionBIOLOGICAL REVIEWS, Issue 3 2003BRIAN K. HALL ABSTRACT Homology is at the foundation of comparative studies in biology at all levels from genes to phenotypes. Homology similarity because of common descent and ancestry, homoplasy is similarity arrived at via independent evolution However, given that there is but one tree of life, all organisms, and therefore all features of organisms, share degree of relationship and similarity one to another. That sharing may be similarity or even identity of structure the sharing of a most recent common ancestor,as in the homology of the arms of humans and apes,or it reflect some (often small) degree of similarity, such as that between the wings of insects and the wings of groups whose shared ancestor lies deep within the evolutionary history of the Metazoa. It may reflect sharing entire developmental pathways, partial sharing, or divergent pathways. This review compares features classified homologous with the classes of features normally grouped as homoplastic, the latter being convergence, parallelism, reversals, rudiments, vestiges, and atavisms. On the one hand, developmental mechanisms may be conserved, when a complete structure does not form (rudiments, vestiges), or when a structure appears only in some individuals (atavisms). On the other hand, different developmental mechanisms can produce similar (homologous) features Joint examination of nearness of relationship and degree of shared development reveals a continuum within expanded category of homology, extending from homology , reversals , rudiments , vestiges , atavisms , parallelism, with convergence as the only class of homoplasy, an idea that turns out to be surprisingly old. realignment provides a glimmer of a way to bridge phylogenetic and developmental approaches to homology homoplasy, a bridge that should provide a key pillar for evolutionary developmental biology (evo-devo). It will and in a practical sense cannot, alter how homoplastic features are identified in phylogenetic analyses. But rudiments, reversals, vestiges, atavisms and parallelism as closer to homology than to homoplasy should guide toward searching for the common elements underlying the formation of the phenotype (what some have called deep homology of genetic and/or cellular mechanisms), rather than discussing features in terms of shared independent evolution. [source] Epineurial compartments and their role in intraneural ganglion cyst propagation: An experimental studyCLINICAL ANATOMY, Issue 7 2007Robert J. Spinner Abstract New patterns of intraneural ganglion cyst formation are emerging that have not previously been explained in current pathoanatomic terms. We believe there are three important elements underlying the appearance of these cysts: (a) an articular branch of the nerve that connects to a nearby synovial joint; (b) ejected synovial fluid following the path of least resistance along tissue planes; and (c) the additional effects of pressure and pressure fluxes. The dynamic nature of cyst formation has become clearly apparent to us in our clinical, operative and pathologic practice, but the precise mechanism underlying the process has not been critically studied. To test our hypothesis that a fibular (peroneal) or tibial intraneural cyst derived from the superior tibiofibular joint could ascend proximally into the sciatic nerve, expand within it and descend into terminal branches of this major nerve, we designed a series of simple, qualitative laboratory experiments in two cadavers (four specimens, six experiments). Injecting dye into the outer or "epifascicular" epineurium of the fibular and the tibial nerves we observed its ascent, cross over and descent patterns in three of three specimens as well as its cross over after an outer epineurial sciatic injection. In contrast, injecting dye into the inner or "interfascicular" epineurium led to its ascent within the tibial nerve and its division within the sciatic nerve in one specimen and lack of cross over in a sciatic nerve injection. Histologic cross-sections of the nerves at varying levels demonstrated a tract of disruption within the outer epineurium of the nerve injected and the nerve(s) into which the dye, after cross over, descended. Those specimens injected in the inner epineurium demonstrated dye within this tract but without disruption of or dye intrusion into the outer epineurium. In no case did the dye pass through the perineurial layers. Coupled with our observations in previous detailed studies, these anatomic findings provide proof of concept that sciatic cross over occurs due to the filling of its common epineurial sheath; furthermore, these findings, support the unifying articular theory, even in cases wherein patterns of intraneural ganglion cyst formation are unusual. Additional work is needed to be done to correlate these anatomic findings with magnetic resonance imaging and surgical pathology. Clin. Anat. 20:826,833, 2007. © 2007 Wiley-Liss, Inc. [source] | ||||||||||