Hematopoietic stem/progenitor cell commitment to the megakaryocyte lineage

The classical model of hematopoiesis has long held that hematopoietic stem cells (HSCs) sit at the apex of a developmental hierarchy in which HSCs undergo long-term self-renewal while giving rise to cells of all the blood lineages. In this model, self-renewing HSCs progressively lose the capacity for self-renewal as they transit into short-term self-renewing and multipotent progenitor states, with the first major lineage commitment occurring in multipotent progenitors, thus giving rise to progenitors that initiate the myeloid and lymphoid branches of hematopoiesis. Subsequently, within the myeloid lineage, bipotent megakaryocyte-erythrocyte and granulocyte-macrophage progenitors give rise to unipotent progenitors that ultimately give rise to all mature progeny. However, over the past several years, this developmental scheme has been challenged, with the origin of megakaryocyte precursors being one of the most debated subjects. Recent studies have suggested that megakaryocytes can be generated from multiple pathways and that some differentiation pathways do not require transit through a requisite multipotent or bipotent megakaryocyte-erythrocyte progenitor stage. Indeed, some investigators have argued that HSCs contain a subset of cells with biased megakaryocyte potential, with megakaryocytes directly arising from HSCs under steady-state and stress conditions. In this review, we discuss the evidence supporting these nonclassical megakaryocytic differentiation pathways and consider their relative strengths and weaknesses as well as the technical limitations and potential pitfalls in interpreting these studies. Ultimately, such pitfalls will need to be overcome to provide a comprehensive and definitive understanding of megakaryopoiesis.

Is multifunctionality the future of mountain pastoralism? Lessons from the management of semi-natural grasslands in the Pyrenees

Land abandonment is pervasive in mountainous Europe. In the present situation of price-cost squeeze on pastoral households and general shift in the role of farming, the development of farming abandonment risk regions is generally associated with adoption of new multifunctional rural development strategies, such as farm tourism, which in the end entail less time being devoted to farming practices. We explored the effects of such developmental scheme on the preservation of semi-natural grasslands, in particular, and on the sustainability of mountain pastoralism, in general. While the effects on the preservation of semi-natural grasslands of full abandonment have been extensively explored, this is not the case of partial abandonment. Results showed that the adoption of simplified and low-cost management regimes, associated with partial abandonment and the increased adoption of part-time farming, immerses semi-natural grasslands in processes of secondary succession that undermine both their conservation and pastoral functions. This points the need for caution when endorsing multifunctional developmental schemes in farming abandonment risk regions, particularly when those imply less labor being devoted to pastoral practices. In conclusion, we stress that in farming abandonment risk regions it is possible to guarantee both viable pastoralism and diversified rural economy. However, it is necessary to implement developmental strategies that are centered on stimulating synergies between pastoralism and other economic activities, rather than promoting activities that depend on additional farmers’ polyvalence.

A Hafted Halberd Excavated at Trecastell, Powys: from Undercurrent to Uptake – the Emergence and Contextualisation of Halberds in Wales and North-west Europe

Excavations at Trecastell, Powys, south Wales, in 2007 yielded a copper halberd complete with its haft-grip. This has major implications for the mode of hafting halberds, but the discovery has also prompted a reconsideration of insular halberds in their north-west European context. Understanding the relationships between different types of halberd and different regional groups continues to be hampered by the dearth of good dating evidence, but the creation of better classifications for British and Irish weapons and new radiocarbon dates on two examples, one being Trecastell, have allowed a new developmental scheme to be advanced.The emergence of metal-headed halberds is considered more generally. While it is acknowledged that halberd-like implements pre-existed in other materials in some parts of Europe, it is argued that the appearance of metal-headed halberds depended on the transmission of a particular set of metallurgical and related skills. A new model for the vigorous uptake of halberds on a regional basis helps explain the patchiness and anachronism of halberd hotspots.The Trecastell halberd adds to one of the significant concentrations of the weapon type in Britain and prompts a more general review of the earliest metalwork from Wales and the Marches. For the Chalcolithic, halberds are instrumental in identifying a major contrast in depositional behaviour; this contrast dissolves at the beginning of the Early Bronze Age when a ‘new deposition ground’ is established. The former is attributed to the existence of a regional group across much of the region for whom the halberd served as a cultural icon, while the latter may relate to the demise of this enshrined value for the halberd.

Moral Issues in Environmental Crisis: A Feminists Approach

Environmental crisis is one of the biggest problems of the world that involves moral issues. From different perspectives the crisis can be analyzed in order to find out a solution. This paper intends to highlight on feminists ethical theory with the aim of clarifying the standpoints of eco-feminism on the issues of environmental ethics. An attempt has been made to initiate a discussion about the issue of how environmental degradation and exploitation of nature became a feminist issue. The feminists‟ view on the relationship between women and nature has engaged with the debates in environmental ethics and politics, and has, at the same time, developed a counter argument against the domination over women and nature by man- folk as a political activism. The contribution of women in resolving the issues relating to the environmental degradation is worth mentioning. It is observed more clearly in the women ‟s movement over the last few decades. It develops a new field of philosophical inquiry known as „eco - feminism‟. Eco-feminism is a social movement. It is a movement of women to protect natural processes. The feminists‟ discussion on the environmental crisis draws on the idea of a principle of sustainable livelihood as human developmental scheme.

Developmental aspects of morphological disparity dynamics: a simple analytical exploration

We have devised a simple model for assessing the role of development in shaping the evolution of morphological disparity. Disparity of a clade at any given time is expressed in terms of the developmental dynamics that lead to the variety of adult morphotypes observed. We use assumed phenotypic manifestations of developmental processes, as they could be detected from allometric characterizations, to distinguish a few, nonexclusive types of evolutionary changes in ontogeny. On the basis of this formalization, we describe the diversification of hypothetical clades, using the standard curve of adult morphological disparity, the curve of juvenile disparity, and the curve of allometric disparity, the latter quantifying the diversification of clades in allometric space. Contrasts of these curves reflect the underlying developmental scheme that drives temporal changes in disparity. We then vary the parameters of the model to assess the expected signature of each metric under specific conditions: changes in the relative frequencies of the types of evolutionary developmental changes, changes in the transition magnitude attached to each of them, and effects of temporal variation in average adult size on disparity curves and patterns of morphospace occupation. Results emphasize the potential contribution of these proxies for developmental dynamics—juvenile morphological disparity, allometric disparity, and average adult size—in enriching the interpretation of standard disparity curves and the description of clade histories, with possible process-oriented inferences.

The Puzzle of Acupuncture

Acupuncture is based on the theory of channels, which serve as pathways for energy (Qi). On the course of the channels, acupuncture points are described, and by stimulation of these points, therapeutic effects may be achieved. This system is very complex and both channels and acupuncture points are anatomically invisible. Unlike in Western medicine, scientists fail to trace both the origin and the progress of acupuncture theory. Having developed in its full form not later than the 2nd century BC, it never underwent fundamental change. On the other hand, it has become a part of modern Western medicine as an effective therapy and the existence of acupuncture points, specified thousands of years ago, has been demonstrated by modern science. It is hardly probable that acupuncture theory, although dating back to ancient times, could have originated in primitive civilization. The origin of the energy channel theory does not fit into the traditional developmental scheme. The existence of the theory cannot be explained other than by its being a product of a highly developed civilization.