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Cytoskeleton (Hoboken, N.J.) Feb 2010Polarity is a fundamental characteristic of most cell types, and is crucial to early development of the brown alga Silvetia compressa. In eukaryotes the cytoskeleton...
Polarity is a fundamental characteristic of most cell types, and is crucial to early development of the brown alga Silvetia compressa. In eukaryotes the cytoskeleton plays an important role in generating cellular asymmetries. While it is known that F-actin is required for polarization and growth in most tip-growing cells, the roles of microtubules are less clear. We examined the distribution and function of microtubules in S. compressa zygotes as they polarized and initiated tip growth. Microtubules formed asymmetric arrays oriented toward the rhizoid hemisphere early in the polarization process. These arrays were spatially coupled with polar adhesive deposition, a marker of the rhizoid pole. Reorientation of the light vector during polarization led to sequential redistribution of polar axis components, with the microtubules and the polar axis reorienting nearly simultaneously, followed by cell wall loosening and then deposition of new polar adhesive. These findings suggested that microtubules may organize and target endomembrane arrays. We therefore examined the distribution of the endoplasmic reticulum during polarization and found it colocalized with microtubules and became targeted toward the rhizoid pole as microtubule asymmetry was generated. Endoplasmic reticulum association with microtubules remained fully intact following pharmacological disruption of F-actin, whereas microtubule disruption led to aggregation of the endoplasmic reticulum around the nucleus. We propose that brown algae utilize microtubules for organization of the endoplasmic reticulum and migration of exocytotic components to the rhizoid cortex, and present a model for polarity establishment to account for these new findings.
Topics: Cell Polarity; Endoplasmic Reticulum; Microscopy, Confocal; Microtubules; Phaeophyceae
PubMed: 20169534
DOI: 10.1002/cm.20427 -
Cold Spring Harbor Protocols Nov 2013Polarized light microscopy provides unique opportunities for analyzing the molecular order in heterogeneous systems, such as living cells and tissues, without using...
Polarized light microscopy provides unique opportunities for analyzing the molecular order in heterogeneous systems, such as living cells and tissues, without using exogenous dyes or labels. This article briefly discusses the theory of polarized light microscopy and elaborates on its practice using a traditional polarized light microscope and more specialized polarization microscopes such as the LC-PolScope, Oosight, or Abrio. The microscope components specific to analyzing the polarization of light, such as polarizer and compensator, are introduced, and quantitative techniques for measuring the birefringence of the specimen point by point using a traditional polarizing microscope are discussed. The new LC-PolScope greatly improves the analytic power of the technique, providing quantitative birefringence data simultaneously for every image point, thereby revealing molecular order with unprecedented sensitivity and at the highest resolution of the light microscope. Practical aspects discussed include the choice of optics, sample preparation, and combining polarized light with differential interference contrast and fluorescence microscopy. A glossary of polarization optical terms is also included to facilitate the discussion of observations made with a polarized light microscope.
Topics: Microscopy, Fluorescence; Microscopy, Interference; Microscopy, Polarization; Specimen Handling
PubMed: 24184765
DOI: 10.1101/pdb.top078600 -
Chemistry (Weinheim An Der Bergstrasse,... Jun 20201,3-Bis(diphenylene)-2-phenylallyl (BDPA)-based radicals are of interest as polarizing agents for dynamic nuclear polarization (DNP). For this purpose, a BDPA-nitroxide...
1,3-Bis(diphenylene)-2-phenylallyl (BDPA)-based radicals are of interest as polarizing agents for dynamic nuclear polarization (DNP). For this purpose, a BDPA-nitroxide biradical, employing a phosphodiester linkage, was synthesized. Contrary to what is commonly assumed, BDPA-derived radicals were observed to have limited stability. Hence, the effects of various factors on the stability of BDPA radicals were investigated. Solvent polarity was found to play a significant role on degradation; a polar BDPA radical was observed to degrade faster in a non-polar solvent, whereas non-polar radicals were more unstable in polar solvents. The rate of decomposition was found to increase non-linearly with increasing radical concentration; a 2-fold increase in concentration led to a 3-fold increase in the rate of degradation. Collectively, these results indicate that the dimerization is a significant degradation pathway for BDPA radicals and indeed, a dimer of one BDPA radical was detected by mass spectrometry.
PubMed: 32396245
DOI: 10.1002/chem.202001084 -
Scientific Reports Oct 2022Electromagnetic linear-to-circular polarization converters with wide- and multi-band capabilities can simplify antenna systems where circular polarization is required....
Electromagnetic linear-to-circular polarization converters with wide- and multi-band capabilities can simplify antenna systems where circular polarization is required. Multi-band solutions are attractive in satellite communication systems, which commonly have the additional requirement that the sense of polarization is reversed between adjacent bands. However, the design of these structures using conventional ad hoc methods relies heavily on empirical methods. Here, we employ a data-driven approach integrated with a generative adversarial network to explore the design space of the polarizer meta-atom thoroughly. Dual-band and triple-band reflective polarizers with stable performance over incident angles up to and including 30°, corresponding to typical reflector antenna system requirements, are synthesized using the proposed method. The feasibility and performance of the designed polarizer is validated through measurements of a fabricated prototype.
PubMed: 36220834
DOI: 10.1038/s41598-022-20851-y -
Optics Letters Aug 2022We report a linearly polarized ytterbium-doped fiber (YDF) laser cavity configured by integrating an antiresonant hollow-core fiber-based inline polarizer. The 5-cm-long...
We report a linearly polarized ytterbium-doped fiber (YDF) laser cavity configured by integrating an antiresonant hollow-core fiber-based inline polarizer. The 5-cm-long compact fiber polarizer was fusion spliced to a commercial large-mode-area, polarization-maintaining YDF. Near-diffraction-limited linearly polarized signal output with a polarization extinction ratio of > 21 dB was achieved for up to 25 W of power that was limited only by the available pump power. The performance of the hollow-core fiber polarizer was found to be temperature insensitive, which obviates the need for the precise temperature control required in all-fiber, high-power polarized laser cavities employing crossed fiber Bragg gratings. We used the tapering technique to scale down the geometry of the polarizing fiber and shift its operating wavelength by ∼100 nm, which makes it an attractive candidate for a variety of fiber laser applications.
PubMed: 35913296
DOI: 10.1364/OL.465662 -
FASEB Journal : Official Publication of... Aug 1989Polarized epithelial cells perform many critical physiological functions in multicellular organisms. Recent embryological studies of the conversion of nonpolar... (Review)
Review
Polarized epithelial cells perform many critical physiological functions in multicellular organisms. Recent embryological studies of the conversion of nonpolar mesenchymal cells to epithelium in the developing mouse kidney have provided vital information on the molecular mechanisms that initiate epithelial cell polarization. To become polar, the cells first attach to the basement membrane that is produced by the developing epithelial cells themselves. Of the basement membrane components, laminin has a key role in the development of epithelial cell polarity. Laminin is a multidomain glycoprotein composed of three subunits: A, B1, and B2. One binding site for epithelial cells is found in the carboxyl-terminal part of the A chain of laminin. Antibodies reacting with this part of laminin inhibit polarization of developing epithelial cells in organ cultures of embryonic kidneys. Expression studies also suggest that the A chain of laminin is important for epithelial cell polarization; the A chain appears when the cells begin to polarize, whereas B chains are expressed at an earlier stage of development. The studies of conversion of mesenchyme to epithelium suggest that morphogenesis can be controlled by differential expression of laminin chains.
Topics: Animals; Antigens, Surface; Cadherins; Cell Adhesion; Cell Adhesion Molecules; Cell Differentiation; Cell Line; Epithelial Cells; Epithelium; Kidney; Laminin; Membrane Glycoproteins; Mesoderm; Morphogenesis
PubMed: 2666230
DOI: 10.1096/fasebj.3.10.2666230 -
Magnetic Resonance Imaging Jun 2021We report the design, construction, and initial tests of a hyperpolariser to produce polarised Xe and He gas for medical imaging of the lung. The hyperpolariser uses the...
We report the design, construction, and initial tests of a hyperpolariser to produce polarised Xe and He gas for medical imaging of the lung. The hyperpolariser uses the Spin-Exchange Optical Pumping method to polarise the nuclear spins of the isotopic gas. Batch mode operation was chosen for the design to produce polarised Xe and polarised He. Two-side pumping, electrical heating and a piston to transfer the polarised gas were some of the implemented techniques that are not commonly used in hyperpolariser designs. We have carried out magnetic resonance imaging experiments demonstrating that the He and Xe polarisation reached were sufficient for imaging, in particular for in vivo lung imaging using Xe. Further improvements to the hyperpolariser have also been discussed.
Topics: Heating; Humans; Lung; Magnetic Resonance Imaging; Male; Radiography; Xenon Isotopes
PubMed: 33600894
DOI: 10.1016/j.mri.2021.02.010 -
Plant Communications Jan 2024The phytohormone auxin, and its directional transport through tissues, plays a fundamental role in the development of higher plants. This polar auxin transport...
The phytohormone auxin, and its directional transport through tissues, plays a fundamental role in the development of higher plants. This polar auxin transport predominantly relies on PIN-FORMED (PIN) auxin exporters. Hence, PIN polarization is crucial for development, but its evolution during the rise of morphological complexity in land plants remains unclear. Here, we performed a cross-species investigation by observing the trafficking and localization of endogenous and exogenous PINs in two bryophytes, Physcomitrium patens and Marchantia polymorpha, and in the flowering plant Arabidopsis thaliana. We confirmed that the GFP fusion did not compromise the auxin export function of all examined PINs by using a radioactive auxin export assay and by observing the phenotypic changes in transgenic bryophytes. Endogenous PINs polarize to filamentous apices, while exogenous Arabidopsis PINs distribute symmetrically on the membrane in both bryophytes. In the Arabidopsis root epidermis, bryophytic PINs have no defined polarity. Pharmacological interference revealed a strong cytoskeletal dependence of bryophytic but not Arabidopsis PIN polarization. The divergence of PIN polarization and trafficking is also observed within the bryophyte clade and between tissues of individual species. These results collectively reveal the divergence of PIN trafficking and polarity mechanisms throughout land plant evolution and the co-evolution of PIN sequence-based and cell-based polarity mechanisms.
Topics: Arabidopsis; Arabidopsis Proteins; Indoleacetic Acids; Plant Roots; Membrane Transport Proteins
PubMed: 37528584
DOI: 10.1016/j.xplc.2023.100669 -
Developmental Cell Oct 2003The anterior-posterior axis of Drosophila becomes polarized early in oogenesis, when the oocyte moves to the posterior of the germline cyst because it preferentially... (Comparative Study)
Comparative Study
The anterior-posterior axis of Drosophila becomes polarized early in oogenesis, when the oocyte moves to the posterior of the germline cyst because it preferentially adheres to posterior follicle cells. The source of this asymmetry is unclear, however, since anterior and posterior follicle cells are equivalent until midoogenesis, when Gurken signaling from the oocyte induces posterior fate. Here, we show that asymmetry arises because each cyst polarizes the next cyst through a series of posterior to anterior inductions. Delta signaling from the older cyst induces the anterior polar follicle cells, the anterior polar cells signal through the JAK/STAT pathway to induce the formation of the stalk between adjacent cysts, and the stalk polarizes the younger anterior cyst by inducing the shape change and preferential adhesion that position the oocyte at the posterior. The anterior-posterior axis is therefore established by a relay mechanism, which propagates polarity from one cyst to the next.
Topics: Animals; Body Patterning; Cell Differentiation; Cell Movement; Cysts; Drosophila; Drosophila Proteins; Embryonic Induction; Female; Germ-Line Mutation; Immunohistochemistry; In Situ Hybridization; Insect Proteins; Intracellular Signaling Peptides and Proteins; Membrane Proteins; Models, Biological; Oocytes; Oogenesis; Ovarian Follicle; Receptors, Notch; Signal Transduction
PubMed: 14536057
DOI: 10.1016/s1534-5807(03)00272-7 -
ELife Nov 2018Despite continual renewal and damages, a multicellular organism is able to maintain its complex morphology. How is this stability compatible with the complexity and...
Despite continual renewal and damages, a multicellular organism is able to maintain its complex morphology. How is this stability compatible with the complexity and diversity of living forms? Looking for answers at protein level may be limiting as diverging protein sequences can result in similar morphologies. Inspired by the progressive role of apical-basal and planar cell polarity in development, we propose that stability, complexity, and diversity are emergent properties in populations of proliferating polarized cells. We support our hypothesis by a theoretical approach, developed to effectively capture both types of polar cell adhesions. When applied to specific cases of development - gastrulation and the origins of folds and tubes - our theoretical tool suggests experimentally testable predictions pointing to the strength of polar adhesion, restricted directions of cell polarities, and the rate of cell proliferation to be major determinants of morphological diversity and stability.
Topics: Animals; Biomechanical Phenomena; Cell Adhesion; Cell Polarity; Cell Proliferation; Collagen; Computer Simulation; Drug Combinations; Eukaryotic Cells; Gastrulation; Laminin; Machine Learning; Models, Biological; Organoids; Proteoglycans; Sea Urchins
PubMed: 30477635
DOI: 10.7554/eLife.38407