Closed-orbit prognosis, correction and manipulation for the PIMMS synchrotron

Closed-orbit control is a basic ingredient for the efficient performance of any circular accelerator. The paper summarises the results of the simulations of the expected orbit distortions before and after correction for the PIMMS (Proton Ion Medical Machine Study) synchrotron. Different situations that lead to a deterioration of the orbit, such as broken position monitors and correctors, misalignment of the magnetic and diagnostic elements with time, have been examined. In particular, the consequences of lowering the injection energy of the space-charge-dominated proton beam have been investigated. The possibility of local orbit correction during extraction by applying closed bumps has been analysed. Finally, on the basis of the demands of both the global orbit correction and the local corrections at top energy, the corrector dipoles specifications have been evaluated

Characteristics of a betatron core for extraction in a proton-ion medical synchrotron

Medical synchrotrons for radiation therapy require a very stable extraction of the beam over a period of about one second. The techniques for applying resonant extraction to achieve this long spill can be classified into two groups, those that move the resonance and those that move the beam. The latter has the great advantage of keeping all lattice functions, and hence the resonance conditions, constant. The present report examines the possibility of using a betatron core to accelerate the waiting ion beam by induction into the resonance. The working principle, the proposed characteristics and the expected performances of this device are discussed. The betatron core is a smooth high-inductance device compared to the small quadrupole lenses that are normally used to move the resonance and is therefore better suited to delivering a very smooth spill. The large stored energy in a betatron core compared to a small quadrupole is also a safety feature since it responds less quickly to transients that could send large beam spikes to the patient

Keeping the Balance Between Proliferation and Differentiation: The Primary Cilium

Primary cilia are post-mitotic cellular organelles that are present in the vast majority of cell types in the human body. An extensive body of data gathered in recent years is demonstrating a crucial role for this organelle in a number of cellular processes that include mechano and chemo-sensation as well as the transduction of signaling cascades critical for the development and maintenance of different tissues and organs. Consequently, cilia are currently viewed as cellular antennae playing a critical role at the interphase between cells and their environment, integrating a range of stimuli to modulate cell fate decisions including cell proliferation, migration and differentiation. Importantly, this regulatory role is not just a consequence of their participation in signal transduction but is also the outcome of both the tight synchronization/regulation of ciliogenesis with the cell cycle and the role of individual ciliary proteins in cilia-dependent and independent processes. Here we review the role of primary cilia in the regulation of cell proliferation and differentiation and illustrate how this knowledge has provided insight to understand the phenotypic consequences of ciliary dysfunction

Neuron's little helper: the role of primary cilia in neurogenesis

The generation of new neurons involves a great variety of cell-extrinsic and cell-intrinsic signals. The primary cilium, long regarded as an "evolutionary vestige," has emerged as an essential signaling hub in many cells, including neural progenitors and differentiating neurons. Most progenitors harbor an apically-localized primary cilium, which is assembled and disassembled following the cell cycle, while the presence, position and length of this organelle appears to be even more variable in differentiating neurons. One of the main extracellular cues acting through the cilium is Sonic Hedgehog, which modulates spatial patterning, the progression of the cell cycle and the timing of neurogenesis. Other extracellular signals appear to bind to cilia-localized receptors and affect processes such as dendritogenesis. All the observed dynamics, as well as the many signaling pathways depending on cilia, indicate this organelle as an important structure involved in neurogenesis.Agencia Nacional de Investigación e InnovaciónPEDECIBAInstitut Pasteur de Montevideo–FOCEM Mercosu

Neuron’s little helper: the role of primary cilia in neurogenesis

The generation of new neurons involves a great variety of cell-extrinsic and cell-intrinsic signals. The primary cilium, long regarded as an “evolutionary vestige,” has emerged as an essential signaling hub in many cells, including neural progenitors and differentiating neurons. Most progenitors harbor an apically-localized primary cilium, which is assembled and disassembled following the cell cycle, while the presence, position and length of this organelle appears to be even more variable in differentiating neurons. One of the main extracellular cues acting through the cilium is Sonic Hedgehog, which modulates spatial patterning, the progression of the cell cycle and the timing of neurogenesis. Other extracellular signals appear to bind to cilia-localized receptors and affect processes such as dendritogenesis. All the observed dynamics, as well as the many signaling pathways depending on cilia, indicate this organelle as an important structure involved in neurogenesis

Insights into in vivo adipocyte differentiation through cell-specific labeling in zebrafish.

White adipose tissue hyperplasia has been shown to be crucial for handling excess energy in healthy ways. Though adipogenesis mechanisms have been underscored in vitro, we lack information on how tissue and systemic factors influence the differentiation of new adipocytes. While this could be studied in zebrafish, adipocyte identification currently relies on neutral lipid labeling, thus precluding access to cells in early stages of differentiation. Here we report the generation and analysis of a zebrafish line with the transgene fabp4a(- 2.7):EGFPcaax. In vivo confocal microscopy of the pancreatic and abdominal visceral depots of transgenic larvae, revealed the presence of labeled mature adipocytes as well as immature cells in earlier stages of differentiation. Through co-labeling for blood vessels, we observed a close interaction of differentiating adipocytes with endothelial cells through cell protrusions. Finally, we implemented hyperspectral imaging and spectral phasor analysis in Nile Red-labeled transgenic larvae and revealed the lipid metabolic transition towards neutral lipid accumulation of differentiating adipocytes. Altogether our work presents the characterization of a novel adipocyte-specific label in zebrafish and uncovers previously unknown aspects of in vivo adipogenesis.Agencia Nacional de Investigación e InnovaciónPrograma de Desarrollo de las Ciencias BásicasFondo de Convergencia Estructural del Mercosu

Photoreceptor progenitor dynamics in the zebrafish embryo retina and its modulation by primary cilia and N-cadherin

Photoreceptor cells of the vertebrate neural retina originate in the neuroepithelium, and like other neurons, must undergo cell body translocation and polarity transitions to acquire their final functional morphology, which includes features of neuronal and epithelial cells. We analyzed this process in detail in zebrafish embryos using in vivo confocal microscopy and electron microscopy. Photoreceptor progenitors were labeled by the transgenic expression of enhanced green fluorescent protein under the regulation of the photoreceptor-specific promoter crx, and structures of interest were disrupted using morpholino oligomers to knock-down specific genes. Photoreceptor progenitors detached from the basal retina at pre-mitotic stages, rapidly retracting a short basal process as the cell body translocated apically. They remained at an apical position indefinitely to form the outer nuclear layer (ONL), initially extending and retracting highly dynamic neurite-like processes, tangential to the apical surface. Many photoreceptor progenitors presented a short apical primary cilium. The number and length of these cilia was gradually reduced until nearly disappearing around 60 hpf. Their disruption by knocking-down ift88 and elipsa caused a notorious defect on basal process retraction. To assess the role of cell adhesion in the organization of photoreceptor progenitors, we knocked-down cdh2/N-cadherin and observed the cell behavior by time-lapse microscopy. The ectopic photoreceptor progenitors initially migrated in an apparent random manner, profusely extending cell processes, until they encountered other cells to establish cell rosettes in which they stayed, acquiring photoreceptor-like polarity. Altogether, our observations indicate a complex regulation of photoreceptor progenitor dynamics to form the retinal ONL, previous to the post-mitotic maturation stages.ANII: FCE_1_2014_1_498

Characterization of primary cilia during the differentiation of retinal ganglion cells in the zebrafish

BACKGROUND: Retinal ganglion cell (RGC) differentiation in vivo is a highly stereotyped process, likely resulting from the interaction of cell type-specific transcription factors and tissue-derived signaling factors. The primary cilium, as a signaling hub in the cell, may have a role during this process but its presence and localization during RGC generation, and its contribution to the process of cell differentiation, have not been previously assessed in vivo. METHODS: In this work we analyzed the distribution of primary cilia in vivo using laser scanning confocal microscopy, as well as their main ultrastructural features by transmission electron microscopy, in the early stages of retinal histogenesis in the zebrafish, around the time of RGC generation and initial differentiation. In addition, we knocked-down ift88 and elipsa, two genes with an essential role in cilia generation and maintenance, a treatment that caused a general reduction in organelle size. The effect on retinal development and RGC differentiation was assessed by confocal microscopy of transgenic or immunolabeled embryos. RESULTS: Our results show that retinal neuroepithelial cells have an apically-localized primary cilium usually protruding from the apical membrane. We also found a small proportion of sub-apical cilia, before and during the neurogenic period. This organelle was also present in an apical position in neuroblasts during apical process retraction and dendritogenesis, although between these stages cilia appeared highly dynamic regarding both presence and position. Disruption of cilia caused a decrease in the proliferation of retinal progenitors and a reduction of neural retina volume. In addition, retinal histogenesis was globally delayed albeit RGC layer formation was preferentially reduced with respect to the amacrine and photoreceptor cell layers. CONCLUSIONS: These results indicate that primary cilia exhibit a highly dynamic behavior during early retinal differentiation, and that they are required for the proliferation and survival of retinal progenitors, as well as for neuronal generation, particularly of RGCs.Agencia Nacional de Investigación e InnovaciónPEDECIBAInstitut Pasteur de Montevide

Characterization of primary cilia during the differentiation of retinal ganglion cells in the zebrafish

Background: Retinal ganglion cell (RGC) differentiation in vivo is a highly stereotyped process, likely resulting from the interaction of cell type-specific transcription factors and tissue-derived signaling factors. The primary cilium, as a signaling hub in the cell, may have a role during this process but its presence and localization during RGC generation, and its contribution to the process of cell differentiation, have not been previously assessed in vivo. Methods: In this work we analyzed the distribution of primary cilia in vivo using laser scanning confocal microscopy, as well as their main ultrastructural features by transmission electron microscopy, in the early stages of retinal histogenesis in the zebrafish, around the time of RGC generation and initial differentiation. In addition, we knocked-down ift88 and elipsa, two genes with an essential role in cilia generation and maintenance, a treatment that caused a general reduction in organelle size. The effect on retinal development and RGC differentiation was assessed by confocal microscopy of transgenic or immunolabeled embryos. Results: Our results show that retinal neuroepithelial cells have an apically-localized primary cilium usually protruding from the apical membrane. We also found a small proportion of sub-apical cilia, before and during the neurogenic period. This organelle was also present in an apical position in neuroblasts during apical process retraction and dendritogenesis, although between these stages cilia appeared highly dynamic regarding both presence and position. Disruption of cilia caused a decrease in the proliferation of retinal progenitors and a reduction of neural retina volume. In addition, retinal histogenesis was globally delayed albeit RGC layer formation was preferentially reduced with respect to the amacrine and photoreceptor cell layers. Conclusions: These results indicate that primary cilia exhibit a highly dynamic behavior during early retinal differentiation, and that they are required for the proliferation and survival of retinal progenitors, as well as for neuronal generation, particularly of RGCs