Haemoglobin switching in humans provides a unique model for investigating the mechanisms underlying expression of a developmentally regulated gene family. Numerous studies have focused on the switch from fetal to adult (that is, gamma----beta) globin, but little is known about the embryonic----fetal (that is, zeta----alpha and epsilon----gamma) switches, as well as the transition from 'primitive' yolk sac to 'definitive' liver erythropoiesis. Here we have studied the embryonic----fetal haemoglobin switches in yolk sac, liver and circulating blood erythroblasts from 25 embryos and 6 fetuses. Globin synthesis was also evaluated in purified 'primitive' and 'definitive' erythroblasts. Primitive erythroblasts synthesize essentially zeta and epsilon chains at 5 weeks and alpha- and epsilon-globin with a minor aliquot of zeta and gamma chains at 6-7 weeks, whereas definitive erythroblasts produce alpha and epsilon + gamma + beta-globin at 6 weeks but only alpha and gamma + beta chains from 8 weeks onward. In both lineages the zeta----alpha and the epsilon----gamma switches are asynchronous, the former preceding the latter. Furthermore, zeta- and beta-globin synthesis is restricted to primitive and definitive erythroblasts respectively. These findings are discussed in terms of a monoclonal model for haemoglobin switching in early human ontogeny.
Introduction The aim of paper is to cluster policies of sustainable mobility in order to define an essential set of specific Transport Performance Indicators (TPI). TPIs are standardized measures suitable for analysis in order to appraise the feasibility of a transport policy or an infrastructural project. Data collection of TPIs is a crucial phase, but data detection and monitoring are not standardized at the city level. Thus, there is no a standard for data collection and storing, this aspect makes much difficult to compare different city contexts. This issue is critical and bounds the analysis of built scenarios. A standardized set of transport performance indicators becomes, hence, essential for monitoring the implemented policies. Methodology and results The paper answers to some of these questions, providing a specific set of sustainable and transport performance indicators to evaluate effects of policy measures. Furthermore, it shows a comparative analysis of different European cities in terms of development, sustainability and infrastructures, by using transport performance indicators. A Normalized Transport Sustainability Index has been built using identified TPIs, in order to measure and hence to compare the whole sustainability of adopted policies in different urban areas. The same NTSI allows to appraise the expected results and thus to tune the policy measures. Conclusion We can affirm that an high value of sustainability is associated, in general, to small-medium cities in term both population and urban area; nevertheless, for large cities, the adoption of policy measures, from a side, to control the urban sprawl, from the other side, to manage the urban transport demand with an adequate public transport development allows to achieve a more sustainable mobility.
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