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

QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

Proliferative events experimentally induced by transient cold shock in the brain of adult terrestrial heterothermic vertebrates: Preliminary analysis of PCNA expression in Triturus carnifex

Experimental procedures used to investigate the persistence, location and abundance of scattered ("matrix cells") and/or clustered ("matrix areas") stem cells in the brain, responsible for proliferation in adult terrestrial heterothermic vertebrates have included an induced transient drop in body temperature in specimens subsequently deprived of encephalic areas. In a set of coordinated investigations focused on the influence of an exposure to a drastic thermally environment on these activities, we gave priority to Triturus carnifex, since there is a much larger amount of detailed, unequivocal experimental evidence available for this species than for other vertebrates of the same evolutionary level. In the present study, cold-shocked newts were examined after a stay at external temperature (the most suitable one based on previous experience) to allow the maximal expression of cerebral proliferation. In a qualitative evaluation, the brain of experimental specimens compared with that of normal individuals seemed not to show, contrary to expectations, more pronounced cell proliferation as assessed by Proliferating Cell Nuclear Antigen immunolabelling of neural-like cells in the S phase of cell cycle. This discrepancy with previous reports from other authors may depend on having used cold stress alone, while other traumatic stimuli (operatory shock, encephalic injury) administered by the previous authors might have induced a greater number of cells to move from a stand-by condition to proliferation, allowing for reparative and/or regenerative phenomena. © 2013 Firenze University Press

PCNA-negativity in the telencephalon of adul female songbirds (Serinus serinus): absence of signs of normal proliferation

In a recent study, we demonstrated the persistence of normal proliferation in the telencephalon of adult male songbirds (Serinus serinus), as shown by the expression of Proliferating Cell Nuclear Antigen (PCNA), a test that uses monoclonal antibodies to reveal cells in the S phase. Near the start of the breeding season, this proliferation was observed in circumscribed areas of the ventricular ependymal epithelium (zona germinativa dorsalis and zona germinativa ventralis) and in small masses of cells that were grouped or separated ("hot spots"). Therefore, we decided to extend this research to normal adult females of the species, using the same marker and the same time period as in the previous study. This time, however, we did not observe PCNA-positivity, and thus any sign of natural proliferation, in the telencephalic areas that showed it in the male songbirds. The immunocytochemical patterns recorded in females and males of Serinus serinus agree with the information reported in the literature, namely that in adult homeothermic Vertebrates the presence of spontaneous cerebral neurogenesis is limited to male songbirds

Signs of normal proliferation in the telencephalon od adult male songbirds (Serinus serinus), as shown by PCNA-positivity

The immunocytochemical expression of Proliferating Cell Nuclear Antigen (PCNA) (a cycline that coadjuvates DNA polymerase delta) becomes appreciable in the cell cycle when DNA synthesis occurs; hence cells in the S phase can be revealed by means of monoclonal antibodies. Therefore, PCNA can be considered a marker of proliferation, and numerous literature reports have demonstrated the reliability of the PCNA test. Since normal neurogenic events can still occur in the brain tissue of adult homeothermic vertebrates (especially songbirds), we evaluated if the persistence of spontaneous proliferation could be revealed in adult male songbirds (Serinus serinus) using the PCNA marker, the same test we used previously to study the persistence of natural proliferation in the encephalon of adult heterothermic vertebrates. The patterns of PCNA positivity showed normal proliferation in the telencephalon of the adult male Serinus serinus. This activity was shown by cells interposed among the epithelial cells lining the lateral side of each ventricular cavity, both in correspondence to the apical tracts and declivities of the ependyma and arranged, here and there, either in groups or slightly separated. As in our previous studies on PCNA expression and persistence of spontaneous encephalic proliferation in adult poikilothermal vertebrates (in the telencephalon of Podarcis, Triturus and Rana, and in the telencephalon, mesencephalon and cerebellum of Carassius), the results of the present research largely agree with the findings of previous Authors, usually obtained with different methods. This agreement confirms the reliability of the PCNA test used for this type of investigation