The Regenerative Capacity of the Zebrafish Caudal Fin Is Not Affected by Repeated Amputations

Background: The zebrafish has the capacity to regenerate many tissues and organs. The caudal fin is one of the most convenient tissues to approach experimentally due to its accessibility, simple structure and fast regeneration. In this work we investigate how the regenerative capacity is affected by recurrent fin amputations and by experimental manipulations that block regeneration. Methodology/Principal Findings: We show that consecutive repeated amputations of zebrafish caudal fin do not reduce its regeneration capacity and do not compromise any of the successive regeneration steps: wound healing, blastema formation and regenerative outgrowth. Interfering with Wnt/ß-catenin signalling using heat-shock-mediated overexpression of Dickkopf1 completely blocks fin regeneration. Notably, if these fins were re-amputated at the non-inhibitory temperature, the regenerated caudal fin reached the original length, even after several rounds of consecutive Wnt/ß-catenin signalling inhibition and re-amputation. Conclusions/Significance: We show that the caudal fin has an almost unlimited capacity to regenerate. Even after inhibition of regeneration caused by the loss of Wnt/ß-catenin signalling, a new amputation resets the regeneration capacity within the caudal fin, suggesting that blastema formation does not depend on a pool of stem/progenitor cells that require Wnt/ßcateni

Notch signaling coordinates cellular proliferation with differentiation during zebrafish fin regeneration

Zebrafish can completely regenerate amputated fins via formation of a blastema, a proliferative mass of undifferentiated precursor cells. During regenerative growth, blastema proliferation must be tightly coordinated with cellular differentiation, but little is known about how this is achieved. Here, we show that Notch signaling is essential for maintenance of blastema cells in a proliferative undifferentiated state. We found that the Notch pathway is activated in response to fin amputation in the highly proliferative region of the blastema. Chemical interference with Notch signaling resulted in a complete block of regeneration. Notch signaling was not required for the earliest known cellular processes during blastema formation, i.e. dedifferentiation and migration of osteoblasts, but specifically interfered with proliferation of blastema cells. Interestingly, overactivation of the pathway via misexpression of the intracellular domain of the Notch receptor (NICD) likewise inhibited regenerative outgrowth. In NICD-overexpressing fins, overall blastemal cell proliferation was not enhanced, but expanded into proximal regions where cellular differentiation normally occurs. Similarly, blastemal and epidermal gene expression territories invaded proximal regions upon sustained Notch activation. Concomitantly, NICD overexpression suppressed differentiation of osteoblasts and caused an expansion of the undifferentiated blastema. Together, these data suggest that Notch signaling activity maintains blastemal cells in a proliferative state and thus coordinates proliferation with differentiation during regenerative growth

Prospective zones for unconventional hydrocarbon resources in Cambrian, Ordovician, Silurian and Carboniferous rocks of Poland : integration of the research results

The paper presents the characteristics of prospective zones identified for the first time within the lower Palaeozoic shale formations occurring in the Baltic-Podlasie-Lublin Basin and within the Carboniferous shale, sandstone, and mixed shale-sandstone complexes (the so-called hybrid complexes) in the basin of south-western Poland. The lateral and vertical ranges of these zones are determined based on specific criteria using the results of various research methods and analyses, i.e.: stratigraphic, sedimentological, mineralogical, petrological and geochemical of organic matter, petrographic and petrophysical, including interpretation of well logs. Archived geological materials and those coming from the boreholes drilled recently in the concession areas were also used. Four prospective zones have been distinguished in the lower Palaeozoic of the so-called shale belt: SP1, SP2, SP3 and SP4. The most prospective area for the occurrence of unconventional hydrocarbon deposits in shale formations is the Baltic region – the Łeba Elevation, where there are all four perspective zones, only partially covering the range of potentially prospective formations. In each of these zones, both liquid and gas hydrocarbons can be expected in this area. Due to the low percentage of organic matter, the lowest hydrocarbon generation potential is attributed to the Lublin region. However, the low values of this parameter are compensated by other parameters, i.e. the considerable thickness and lateral extent of zone SP4 corresponding partly to the Pelplin Formation. In the Carboniferous rocks of south-western Poland, seven prospective zones have been distinguished in four borehole sections. Four of them are “tight” zones in compact sandstones, while the other three zones represent a hybrid type in complexes with mixed lithology. No prospective zones have been defined in complexes with homogeneous shale lithologies. Determination of lateral extents of the identified zones has not been possible due to the scarcity of data on the geological structure and stratigraphy of the Carboniferous succession in the study are