32 research outputs found
Plio-Pleistocene climatic change had a major impact on the assembly and disassembly processes of Iberian rodent communities
Comprehension of changes in community composition through multiple spatio-temporal scales is a prime challenge in ecology and palaeobiology. However, assembly, structuring and disassembly of biotic metacommunities in deep-time is insufficiently known. To address this, we used the extensively sampled Iberian Plio-Pleistocene fossil record of rodent faunas as our model system to explore how global climatic events may alter metacommunity structure. Through factor analysis, we found five sets of genera, called faunal components, which co-vary in proportional diversity over time. These faunal components had different spatio-temporal distributions throughout the Plio-Pleistocene, resulting in non-random changes in species assemblages, particularly in response to the development of the Pleistocene glaciations. Three successive metacommunities with distinctive taxonomic structures were identified as a consequence of the differential responses of their members to global climatic change: (1) Ruscinian subtropical faunas (5.3–3.4 Ma) dominated by a faunal component that can be considered as a Miocene legacy; (2) transition faunas during the Villafranchian–Biharian (3.4–0.8 Ma) with a mixture of different faunal components; and (3) final dominance of the temperate Toringian faunas (0.8–0.01 Ma) that would lead to the modern Iberian assemblage. The influence of the cooling global temperature drove the reorganisation of these rodent metacommunities. Selective extinction processes due to this large-scale environmental disturbance progressively eliminated the subtropical specialist species from the early Pliocene metacommunity. This disassembly process was accompanied by the organisation of a diversified metacommunity with an increased importance of biome generalist species, and finally followed by the assembly during the middle–late Pleistocene of a new set of species specialised in the novel environments developed as a consequence of the glaciations
Regulation of ProteinKinase D During Differentiation and Proliferation of Primary Mouse Keratinocytes
Diseased skin often exhibits a deregulated program of the keratinocyte maturation necessary for epidermal stratification and function. Protein kinase D (PKD), a serine/threonine kinase, is expressed in proliferating keratinocytes, and PKD activation occurs in response to mitogen stimulation in other cell types. We have proposed that PKD functions as a pro-proliferative and/or anti-differentiative signal in keratinocytes and hypothesized that differentiation inducers will downmodulate PKD to allow differentiation to proceed. Thus, changes in PKD levels, autophosphorylation, and activity were analyzed upon stimulation of differentiation and proliferation in primary mouse keratinocytes. Elevated extracellular calcium and acute 12-O-tetradecanoylphorbol-13-acetate (TPA) treatments induced differentiation and triggered a downmodulation of PKD levels, autophosphorylation at serine 916, and activity. Chronic TPA treatment stimulated proliferation and resulted in a recovery of PKD levels, autophosphorylation, and activity. Immunohistochemical analysis demonstrated PKD localization predominantly in the proliferative basal layer of mouse epidermis. Co-expression studies revealed a pro-proliferative, anti-differentiative effect of PKD on keratinocyte maturation as monitored by increased and decreased promoter activities of keratin 5, a proliferative marker, and involucrin, a differentiative marker, respectively. This work describes the inverse regulation of PKD during keratinocyte differentiation and proliferation and the pro-proliferative/anti-differentiative effects of PKD co-expression on keratinocyte maturation
Regulation of ProteinKinase D During Differentiation and Proliferation of Primary Mouse Keratinocytes
Diseased skin often exhibits a deregulated program of the keratinocyte maturation necessary for epidermal stratification and function. Protein kinase D (PKD), a serine/threonine kinase, is expressed in proliferating keratinocytes, and PKD activation occurs in response to mitogen stimulation in other cell types. We have proposed that PKD functions as a pro-proliferative and/or anti-differentiative signal in keratinocytes and hypothesized that differentiation inducers will downmodulate PKD to allow differentiation to proceed. Thus, changes in PKD levels, autophosphorylation, and activity were analyzed upon stimulation of differentiation and proliferation in primary mouse keratinocytes. Elevated extracellular calcium and acute 12-O-tetradecanoylphorbol-13-acetate (TPA) treatments induced differentiation and triggered a downmodulation of PKD levels, autophosphorylation at serine 916, and activity. Chronic TPA treatment stimulated proliferation and resulted in a recovery of PKD levels, autophosphorylation, and activity. Immunohistochemical analysis demonstrated PKD localization predominantly in the proliferative basal layer of mouse epidermis. Co-expression studies revealed a pro-proliferative, anti-differentiative effect of PKD on keratinocyte maturation as monitored by increased and decreased promoter activities of keratin 5, a proliferative marker, and involucrin, a differentiative marker, respectively. This work describes the inverse regulation of PKD during keratinocyte differentiation and proliferation and the pro-proliferative/anti-differentiative effects of PKD co-expression on keratinocyte maturation
The ENTH domain protein Clint1 is required for epidermal homeostasis in zebrafish
Epidermal hyperproliferation and inflammation are hallmarks of the human
condition psoriasis. Here, we report that a zebrafish line with a mutation in
the cargo adaptor protein Clint1 exhibits psoriasis-like phenotypes including
epithelial hyperproliferation and leukocyte infiltration. Clint1 is an ENTH
domain-containing protein that binds SNARE proteins and functions in vesicle
trafficking; however, its in vivo function in animal models has not been
reported to date. The clint1 mutants exhibit chronic inflammation
characterized by increased Interleukin 1β expression, leukocyte
infiltration, bidirectional trafficking and phagocytosis of cellular debris.
The defects in clint1 mutants can be rescued by expression of
zebrafish clint1 and can be phenocopied with clint1-specific
morpholinos, supporting an essential role for Clint1 in epidermal development.
Interaction studies suggest that Clint1 and Lethal giant larvae 2 function
synergistically to regulate epidermal homeostasis. Accordingly,
clint1 mutants show impaired hemidesmosome formation, loss of
cell-cell contacts and increased motility suggestive of epithelial to
mesenchymal transition. Taken together, our findings describe a novel function
for the ENTH domain protein Clint1 in epidermal development and inflammation
and suggest that its deficiency in zebrafish generates a phenotype that
resembles the human condition psoriasis
If we want to get ahead, we should transcend dualisms and foster paradigm pluralism
In this chapter, I argue for the importance of transcending dualisms and using multi-paradigm perspectives when examining phenomena and issues in mathematics education. I begin by exploring the philosophical bases—ontological, epistemological, axiological, and methodological—underlying three major paradigms in mathematics education research: the modernist (post-)positivist paradigm, the post-modernist interpretive paradigm, and the post-modernist transformative paradigm. Then, I present three modes of thinking that enable researchers to deal with multiple paradigms: dualistic thinking, dialogical thinking, and dialectical thinking. I adopt the dialectical mode of thinking to blend the modernist and post-modernist paradigms with respect to an ontological opposition (mind-world duality) and an epistemological opposition (objectivity-subjectivity duality) prevalent in the literature. A new paradigm begins to emerge from this blend, one which transcends these dualities to better interpret phenomena and issues in mathematics education