scholarly journals Watching a deep dive: Live imaging provides lessons about tooth invagination

2016 ◽  
Vol 214 (6) ◽  
pp. 645-647 ◽  
Author(s):  
Amnon Sharir ◽  
Ophir D. Klein
Keyword(s):  
Live Imaging ◽  
Cellular Mechanisms ◽  
Deep Dive ◽  
Critical Step ◽  
Organ Morphogenesis ◽  
Cell Biol ◽  
Mouse Incisor

Invagination of epithelium into the surrounding mesenchyme is a critical step that marks the developmental onset of many ectodermal organs. In this issue, Ahtiainen et al. (2016. J. Cell. Biol. http://dx.doi.org/10.1083/jcb.201512074) use the mouse incisor as a model to advance our understanding of the cellular mechanisms underlying ectodermal organ morphogenesis.

scholarly journals Cephalopod Retinal Development Shows Vertebrate-like Mechanisms of Neurogenesis

2021 ◽  
Author(s):  
Francesca Napoli ◽  
Christina M Daly ◽  
Stephanie Neal ◽  
Kyle J McCulloch ◽  
Alexandra Zaloga ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Nervous System ◽  
Progenitor Cells ◽  
Cellular Proliferation ◽  
Imaging Techniques ◽  
Nuclear Migration ◽  
Live Imaging ◽  
Cellular Mechanisms ◽  
High Resolution Data ◽  
Interkinetic Nuclear Migration

Neurogenesis, the regulation of cellular proliferation and differentiation in the developing nervous system, is the process that underlies the diversity of size and cell type found in animal nervous systems. Our understanding of how this process has evolved is limited because of the lack of high resolution data and live-imaging methods across species. The retina is a classic model for the study of neurogenesis in vertebrates and live-imaging of the retina has shown that during development, progenitor cells are organized in a pseudostratified neuroepithelium and nuclei migrate in coordination with the cell cycle along the apicobasal axis of the cell, a process called interkinetic nuclear migration. Eventually cells delaminate and differentiate within the boundaries of the epithelium. This process has been considered unique to vertebrates and thought to be important in maintaining organization during the development of a complex nervous system. Coleoid cephalopods, including squid, cuttlefish and octopus, have the largest nervous system of any invertebrate and convergently-evolved camera-type eyes, making them a compelling comparative system to vertebrates. Here we have pioneered live-imaging techniques to show that the squid, Doryteuthis pealeii, displays cellular mechanisms during cephalopod retinal neurogenesis that are hallmarks of vertebrate processes. We find that retinal progenitor cells in the squid undergo interkinetic nuclear migration until they exit the cell cycle, we identify retinal organization corresponding to progenitor, post-mitotic and differentiated cells, and we find that Notch signaling regulates this process. With cephalopods and vertebrates having diverged 550 million years ago, these results suggest that mechanisms thought to be unique to vertebrates may be common to highly proliferative neurogenic primordia contributing to a large nervous system.

scholarly journals Early epithelial signaling center governs tooth budding morphogenesis

2016 ◽  
Vol 214 (6) ◽  
pp. 753-767 ◽  
Author(s):  
Laura Ahtiainen ◽  
Isa Uski ◽  
Irma Thesleff ◽  
Marja L. Mikkola
Keyword(s):  
Cell Fate ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Cell Fate Specification ◽  
Cellular Mechanisms ◽  
Incisor Tooth ◽  
Fate Specification ◽  
Quiescent Cells ◽  
Signaling Center ◽  
Mouse Incisor

During organogenesis, cell fate specification and patterning are regulated by signaling centers, specialized clusters of morphogen-expressing cells. In many organs, initiation of development is marked by bud formation, but the cellular mechanisms involved are ill defined. Here, we use the mouse incisor tooth as a model to study budding morphogenesis. We show that a group of nonproliferative epithelial cells emerges in the early tooth primordium and identify these cells as a signaling center. Confocal live imaging of tissue explants revealed that although these cells reorganize dynamically, they do not reenter the cell cycle or contribute to the growing tooth bud. Instead, budding is driven by proliferation of the neighboring cells. We demonstrate that the activity of the ectodysplasin/Edar/nuclear factor κB pathway is restricted to the signaling center, and its inactivation leads to fewer quiescent cells and a smaller bud. These data functionally link the signaling center size to organ size and imply that the early signaling center is a prerequisite for budding morphogenesis.

scholarly journals CELL SEGMENTATION WITH RANDOM FERNS AND GRAPH-CUTS

2016 ◽  
Author(s):  
Arnaud Browet ◽  
Christophe De Vleeschouwer ◽  
Laurent Jacques ◽  
Navrita Mathiah ◽  
Bechara Saykali ◽  
...  
Keyword(s):  
Image Segmentation ◽  
Energy Minimization ◽  
Imaging Techniques ◽  
Graph Cuts ◽  
Live Imaging ◽  
Cell Segmentation ◽  
Imaging Data ◽  
Cellular Mechanisms ◽  
Segmentation Framework ◽  
Two Stages

The progress in imaging techniques have allowed the study of various aspect of cellular mechanisms. To isolate individual cells in live imaging data, we introduce an elegant image segmentation framework that effectively extracts cell boundaries, even in the presence of poor edge details. Our approach works in two stages. First, we estimate pixel interior/border/exterior class probabilities using random ferns. Then, we use an energy minimization framework to compute boundaries whose localization is compliant with the pixel class probabilities. We validate our approach on a manually annotated dataset.

scholarly journals Live imaging of Aiptasia larvae, a model system for studying coral bleaching, using a simple microfluidic device

2018 ◽  
Author(s):  
Will Van Treuren ◽  
Kara K. Brower ◽  
Louai Labanieh ◽  
Daniel Hunt ◽  
Sarah Lensch ◽  
...  
Keyword(s):  
Microfluidic Device ◽  
Coral Bleaching ◽  
Model Organism ◽  
Live Imaging ◽  
Environmental Stressors ◽  
Energy Harvest ◽  
Sea Anemones ◽  
Cellular Mechanisms ◽  
Trap Design ◽  
Algal Symbionts

AbstractCoral reefs, and their associated diverse ecosystems, are of enormous ecological importance. In recent years, coral health has been severely impacted by environmental stressors brought on by human activity and climate change, threatening the extinction of several major reef ecosystems. Reef damage is mediated by a process called ‘coral bleaching’ where corals, sea anemones, and other cnidarians lose their photosynthetic algal symbionts (genus Symbiodinium) upon stress induction, resulting in drastically decreased host energy harvest and, ultimately, coral death. The mechanism by which this critical cnidarian-algal symbiosis is lost remains poorly understood. Here, we report ‘Traptasia’, a simple microfluidic device with multiple traps designed to isolate and image individual live larvae of Aiptasia, a sea anemone model organism, and their algal symbionts over extended time courses. Aiptasia larvae are ~100 μm in length, deformable, and highly motile, posing particular challenges for long-term imaging. Using a trap design optimized via fluid flow simulations and polymer bead loading tests, we trapped Aiptasia larvae containing algal symbionts and demonstrated stable imaging for >10 hours. We visualized algal migration within Aiptasia larvae and observed algal expulsion under an environmental stressor. To our knowledge, this device is the first to enable live imaging of cnidarian larvae and their algal symbionts and, in further implementation, could provide important insights into the cellular mechanisms of coral bleaching under different environmental stressors. The device is simple to use, requires minimal external equipment and no specialized training to operate, and can easily be adapted to study a variety of large, motile organisms.

scholarly journals Live imaging of adult zebrafish cardiomyocyte proliferation ex vivo

Development ◽  
2021 ◽  
Author(s):  
Hessel Honkoop ◽  
Phong D. Nguyen ◽  
Veronique E.M. van der Velden ◽  
Katharina F. Sonnen ◽  
Jeroen Bakkers
Keyword(s):  
Culture System ◽  
Ex Vivo ◽  
Live Imaging ◽  
Slice Culture ◽  
Heart Regeneration ◽  
Dependent Manner ◽  
Cardiomyocyte Proliferation ◽  
Adult Zebrafish ◽  
Cellular Mechanisms ◽  
Zebrafish Heart

Zebrafish are excellent at regenerating their heart by reinitiating proliferation in pre-existing cardiomyocytes. Studying how zebrafish achieve this holds great potential in developing new strategies to boost mammalian heart regeneration. Nevertheless, the lack of appropriate live imaging tools for the adult zebrafish heart has limited detailed studies into the dynamics underlying cardiomyocyte proliferation. Here, we address this by developing a system in which cardiac slices of the injured zebrafish heart are cultured ex vivo for several days while retaining key regenerative characteristics including cardiomyocyte proliferation. In addition, we show that the cardiac slice culture system is compatible with live timelapse imaging and allows manipulation of regenerating cardiomyocytes with drugs that normally would have toxic effects that prevent its use. Finally, we use the cardiac slices to demonstrate that adult cardiomyocytes with fully assembled sarcomeres can partially disassemble their sarcomeres in a calpain and proteasome dependent manner to progress through nuclear division and cytokinesis. In conclusion, we have developed a cardiac slice culture system, which allows imaging of native cardiomyocyte dynamics in real time to discover cellular mechanisms during heart regeneration.

scholarly journals SHOT-R: A next generation algorithm for particle kinematics analysis

2021 ◽  
Author(s):  
Eloina Corradi ◽  
Walter Boscheri ◽  
Marie-Laure Baudet
Keyword(s):  
Numerical Method ◽  
Live Imaging ◽  
Single Particle Tracking ◽  
Kinematics Analysis ◽  
Cellular Mechanisms ◽  
Accurate Analysis ◽  
Imaging Experiment ◽  
Bona Fide ◽  
First Time ◽  
Polynomial Reconstruction

Analysis of live-imaging experiments is crucial to decipher a plethora of cellular mechanisms within physiological and pathological contexts. Kymograph, i.e. graphical representations of particle spatial position over time, and single particle tracking (SPT) are the currently available tools to extract information on particle transport and velocity. However, the spatiotemporal approximation applied in particle trajectory reconstruction with those methods intrinsically prevents an accurate analysis of particle kinematics and of instantaneous behaviours. Here, we present SHOT-R, a novel numerical method based on polynomial reconstruction of 4D (3D+time) particle trajectories. SHOT-R, contrary to other tools, computes bona fide instantaneous and directional velocity, and acceleration. Thanks to its high order continuous reconstruction it allows, for the first time, kinematics analysis of co-trafficked particles. Overall, SHOT-R is a novel, versatile, and physically reliable numerical method that achieves all-encompassing particle kinematics studies at unprecedented accuracy on any live-imaging experiment where the spatiotemporal coordinates can be retrieved.

scholarly journals A unique form of collective epithelial migration is crucial for tissue fusion in the secondary palate and can overcome loss of epithelial apoptosis

2021 ◽  
Author(s):  
Teng Teng ◽  
Camilla Teng ◽  
Vesa Kaartinen ◽  
Jeffrey O. Bush
Keyword(s):  
Live Imaging ◽  
Tissue Fusion ◽  
Unique Form ◽  
Cellular Mechanisms ◽  
Epithelial Migration ◽  
Actomyosin Contractility ◽  
Secondary Palate ◽  
Epithelial Marker ◽  
Peristaltic Movement ◽  
Cell Extrusion

AbstractTissue fusion is an oft-employed process in morphogenesis which often requires the removal of the epithelia intervening multiple distinct primordia to form one continuous structure. In the mammalian secondary palate, a midline epithelial seam (MES) forms between two palatal shelves and must be removed to allow mesenchymal confluence. Abundant apoptosis and cell extrusion in this epithelial seam support their importance in its removal. However, by genetically disrupting the intrinsic apoptotic regulators BAX and BAK within the MES, we find a complete loss of cell death and cell extrusion, but successful removal of the MES, indicating that developmental compensation enables fusion. Novel static and live imaging approaches reveal that the MES is removed through a unique form of collective epithelial cell migration in which epithelial trails and islands stream through the mesenchyme to reach the oral and nasal epithelial surfaces. These epithelial trails and islands begin to express periderm markers while retaining expression of the basal epithelial marker ΔNp63, suggesting their migration to the oral and nasal surface is concomitant with their differentiation to an epithelial intermediate. Live imaging reveals anisotropic actomyosin contractility within epithelial trails that drives their peristaltic movement, and genetic loss of non-muscle myosin IIA-mediated actomyosin contractility results in dispersion of epithelial collectives and dramatic failure of normal MES migration. These findings demonstrate redundancy between cellular mechanisms of morphogenesis and reveal a crucial role for a unique form of collective epithelial migration during tissue fusion.

Freeze-Fracture Replication in the Ultrastructure of Blue-Green Algae

1967 ◽  
Vol 25 ◽  
pp. 74-75
Author(s):  
L. V. Leak
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Green Algae ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Electron Microscopic ◽  
Photosynthetic Membranes ◽  
Blue Green Algae ◽  
Cell Biol ◽  
Cellular Components

Electron microscopic observations of freeze-fracture replicas of Anabaena cells obtained by the procedures described by Bullivant and Ames (J. Cell Biol., 1966) indicate that the frozen cells are fractured in many different planes. This fracturing or cleaving along various planes allows one to gain a three dimensional relation of the cellular components as a result of such a manipulation. When replicas that are obtained by the freeze-fracture method are observed in the electron microscope, cross fractures of the cell wall and membranes that comprise the photosynthetic lamellae are apparent as demonstrated in Figures 1 & 2.A large portion of the Anabaena cell is composed of undulating layers of cytoplasm that are bounded by unit membranes that comprise the photosynthetic membranes. The adjoining layers of cytoplasm are closely apposed to each other to form the photosynthetic lamellae. Occassionally the adjacent layers of cytoplasm are separated by an interspace that may vary in widths of up to several 100 mu to form intralamellar vesicles.

Vascular adaptations to hypoxia: molecular and cellular mechanisms regulating vascular tone

2007 ◽  
Vol 43 ◽  
pp. 105-120 ◽  
Author(s):  
Michael L. Paffett ◽  
Benjimen R. Walker
Keyword(s):  
Vascular Tone ◽  
Cellular Proliferation ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Hypoxia Inducible Factor ◽  
Systemic Circulation ◽  
Cellular Mechanisms ◽  
Hypoxia Inducible Factor 1 ◽  
Pulmonary Vasoconstriction ◽  
Adaptive Mechanisms ◽  
Adaptive Processes

Several molecular and cellular adaptive mechanisms to hypoxia exist within the vasculature. Many of these processes involve oxygen sensing which is transduced into mediators of vasoconstriction in the pulmonary circulation and vasodilation in the systemic circulation. A variety of oxygen-responsive pathways, such as HIF (hypoxia-inducible factor)-1 and HOs (haem oxygenases), contribute to the overall adaptive process during hypoxia and are currently an area of intense research. Generation of ROS (reactive oxygen species) may also differentially regulate vascular tone in these circulations. Potential candidates underlying the divergent responses between the systemic and pulmonary circulations may include Nox (NADPH oxidase)-derived ROS and mitochondrial-derived ROS. In addition to alterations in ROS production governing vascular tone in the hypoxic setting, other vascular adaptations are likely to be involved. HPV (hypoxic pulmonary vasoconstriction) and CH (chronic hypoxia)-induced alterations in cellular proliferation, ionic conductances and changes in the contractile apparatus sensitivity to calcium, all occur as adaptive processes within the vasculature.

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