scholarly journals Three-dimensional architecture of murine rod outer segments determined by cryoelectron tomography

2007 ◽  
Vol 177 (5) ◽  
pp. 917-925 ◽  
Author(s):  
Stephan Nickell ◽  
Paul S.-H. Park ◽  
Wolfgang Baumeister ◽  
Krzysztof Palczewski
Keyword(s):  
Plasma Membrane ◽  
Mammalian Species ◽  
Three Dimensional ◽  
Photoreceptor Cells ◽  
Light Signal ◽  
Proper Distance ◽  
Theoretical Approaches ◽  
Internal Structures ◽  
Membrane Components ◽  
Important Structure

The rod outer segment (ROS) of photoreceptor cells houses all components necessary for phototransduction, a set of biochemical reactions that amplify and propagate a light signal. Theoretical approaches to quantify this process require precise information about the physical boundaries of the ROS. Dimensions of internal structures within the ROS of mammalian species have yet to be determined with the precision required for quantitative considerations. Cryoelectron tomography was utilized to obtain reliable three-dimensional morphological information about this important structure from murine retina. Vitrification of samples permitted imaging of the ROS in a minimally perturbed manner and the preservation of substructures. Tomograms revealed the characteristic highly organized arrangement of disc membranes stacked on top of one another with a surrounding plasma membrane. Distances among the various membrane components of the ROS were measured to define the space available for phototransduction to occur. Reconstruction of segments of the ROS from single-axis tilt series images provided a glimpse into the three-dimensional architecture of this highly differentiated neuron. The reconstructions revealed spacers that likely maintain the proper distance between adjacent discs and between discs and the plasma membrane. Spacers were found distributed throughout the discs, including regions that are distant from the rim region of discs.

scholarly journals Three-dimensional organization of nascent rod outer segment disk membranes

2015 ◽  
Vol 112 (48) ◽  
pp. 14870-14875 ◽  
Author(s):  
Stefanie Volland ◽  
Louise C. Hughes ◽  
Christina Kong ◽  
Barry L. Burgess ◽  
Kenneth A. Linberg ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Outer Segment ◽  
3D Visualization ◽  
Mammalian Species ◽  
Three Dimensional ◽  
Initiation Site ◽  
Rod Photoreceptor ◽  
Disk Formation ◽  
3D Data ◽  
Vertebrate Photoreceptor

The vertebrate photoreceptor cell contains an elaborate cilium that includes a stack of phototransductive membrane disks. The disk membranes are continually renewed, but how new disks are formed remains poorly understood. Here we used electron microscope tomography to obtain 3D visualization of the nascent disks of rod photoreceptors in three mammalian species, to gain insight into the process of disk morphogenesis. We observed that nascent disks are invariably continuous with the ciliary plasma membrane, although, owing to partial enclosure, they can appear to be internal in 2D profiles. Tomographic analyses of the basal-most region of the outer segment show changes in shape of the ciliary plasma membrane indicating an invagination, which is likely a first step in disk formation. The invagination flattens to create the proximal surface of an evaginating lamella, as well as membrane protrusions that extend between adjacent lamellae, thereby initiating a disk rim. Immediately distal to this initiation site, lamellae of increasing diameter are evident, indicating growth outward from the cilium. In agreement with a previous model, our data indicate that mature disks are formed once lamellae reach full diameter, and the growth of a rim encloses the space between adjacent surfaces of two lamellae. This study provides 3D data of nascent and mature rod photoreceptor disk membranes at unprecedented z-axis depth and resolution, and provides a basis for addressing fundamental questions, ranging from protein sorting in the photoreceptor cilium to photoreceptor electrophysiology.

Cell culturing in a three-dimensional matrix affects the localization and properties of plasma membrane cholesterol

2009 ◽  
Vol 33 (10) ◽  
pp. 1079-1086 ◽  
Author(s):  
Nadezhda Stefanova ◽  
Galya Staneva ◽  
Diana Petkova ◽  
Teodora Lupanova ◽  
Roumen Pankov ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Three Dimensional ◽  
Membrane Cholesterol ◽  
Dimensional Matrix ◽  
Cell Culturing ◽  
Plasma Membrane Cholesterol

scholarly journals Pseudotypes of Vesicular Stomatitis Virus with CD4 Formed by Clustering of Membrane Microdomains during Budding

2005 ◽  
Vol 79 (11) ◽  
pp. 7077-7086 ◽  
Author(s):  
Erica L. Brown ◽  
Douglas S. Lyles
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Lipid Rafts ◽  
Immunoelectron Microscopy ◽  
Vesicular Stomatitis Virus ◽  
Plasma Membranes ◽  
Membrane Microdomains ◽  
Virus Budding ◽  
Vesicular Stomatitis ◽  
Membrane Components

ABSTRACT Many plasma membrane components are organized into detergent-resistant membrane microdomains referred to as lipid rafts. However, there is much less information about the organization of membrane components into microdomains outside of lipid rafts. Furthermore, there are few approaches to determine whether different membrane components are colocalized in microdomains as small as lipid rafts. We have previously described a new method of determining the extent of organization of proteins into membrane microdomains by analyzing the distribution of pairwise distances between immunogold particles in immunoelectron micrographs. We used this method to analyze the microdomains involved in the incorporation of the T-cell antigen CD4 into the envelope of vesicular stomatitis virus (VSV). In cells infected with a recombinant virus that expresses CD4 from the viral genome, both CD4 and the VSV envelope glycoprotein (G protein) were found in detergent-soluble (nonraft) membrane fractions. However, analysis of the distribution of CD4 and G protein in plasma membranes by immunoelectron microscopy showed that both were organized into membrane microdomains of similar sizes, approximately 100 to 150 nm. In regions of plasma membrane outside of virus budding sites, CD4 and G protein were present in separate membrane microdomains, as shown by double-label immunoelectron microscopy data. However, virus budding occurred from membrane microdomains that contained both G protein and CD4, and extended to approximately 300 nm, indicating that VSV pseudotype formation with CD4 occurs by clustering of G protein- and CD4-containing microdomains.

scholarly journals Influence of the glycocalyx and plasma membrane composition on amphiphilic gold nanoparticle association with erythrocytes

Nanoscale ◽  
2015 ◽  
Vol 7 (26) ◽  
pp. 11420-11432 ◽  
Author(s):  
Prabhani U. Atukorale ◽  
Yu-Sang Yang ◽  
Ahmet Bekdemir ◽  
Randy P. Carney ◽  
Paulo J. Silva ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Plasma Membrane ◽  
Gold Nanoparticle ◽  
Erythrocyte Membranes ◽  
Membrane Composition ◽  
Membrane Components

Amphiphilic gold nanoparticles spontaneously insert into erythrocyte membranes; we characterize this association as a function of key plasma membrane components.

scholarly journals Understanding Starch Structure: Recent Progress

Agronomy ◽  
2017 ◽  
Vol 7 (3) ◽  
pp. 56 ◽  
Author(s):  
Eric Bertoft
Keyword(s):  
Cluster Model ◽  
Three Dimensional ◽  
Basic Structure ◽  
Dimensional Structure ◽  
Starch Granules ◽  
Growth Rings ◽  
Starch Structure ◽  
Internal Structures ◽  
Size And Morphology ◽  
Amylopectin Structure

Starch is a major food supply for humanity. It is produced in seeds, rhizomes, roots and tubers in the form of semi-crystalline granules with unique properties for each plant. Though the size and morphology of the granules is specific for each plant species, their internal structures have remarkably similar architecture, consisting of growth rings, blocklets, and crystalline and amorphous lamellae. The basic components of starch granules are two polyglucans, namely amylose and amylopectin. The molecular structure of amylose is comparatively simple as it consists of glucose residues connected through α-(1,4)-linkages to long chains with a few α-(1,6)-branches. Amylopectin, which is the major component, has the same basic structure, but it has considerably shorter chains and a lot of α-(1,6)-branches. This results in a very complex, three-dimensional structure, the nature of which remains uncertain. Several models of the amylopectin structure have been suggested through the years, and in this review two models are described, namely the “cluster model” and the “building block backbone model”. The structure of the starch granules is discussed in light of both models.

scholarly journals Activation and assembly of the NADPH oxidase: a structural perspective

2005 ◽  
Vol 386 (3) ◽  
pp. 401-416 ◽  
Author(s):  
Yvonne GROEMPING ◽  
Katrin RITTINGER
Keyword(s):  
Nadph Oxidase ◽  
Protein Interactions ◽  
Structural Information ◽  
Three Dimensional ◽  
Protein Protein Interactions ◽  
Crucial Component ◽  
Enzyme Subunits ◽  
Membrane Components ◽  
Inhibitory Interactions ◽  
Encompassing Model

The NADPH oxidase of professional phagocytes is a crucial component of the innate immune response due to its fundamental role in the production of reactive oxygen species that act as powerful microbicidal agents. The activity of this multi-protein enzyme is dependent on the regulated assembly of the six enzyme subunits at the membrane where oxygen is reduced to superoxide anions. In the resting state, four of the enzyme subunits are maintained in the cytosol, either through auto-inhibitory interactions or through complex formation with accessory proteins that are not part of the active enzyme complex. Multiple inputs are required to disrupt these inhibitory interactions and allow translocation to the membrane and association with the integral membrane components. Protein interaction modules are key regulators of NADPH oxidase assembly, and the protein–protein interactions mediated via these domains have been the target of numerous studies. Many models have been put forward to describe the intricate network of reversible protein interactions that regulate the activity of this enzyme, but an all-encompassing model has so far been elusive. An important step towards an understanding of the molecular basis of NADPH oxidase assembly and activity has been the recent solution of the three-dimensional structures of some of the oxidase components. We will discuss these structures in the present review and attempt to reconcile some of the conflicting models on the basis of the structural information available.

scholarly journals New patterns in high-speed granular flows

2015 ◽  
Vol 769 ◽  
pp. 218-228 ◽  
Author(s):  
Nicolas Brodu ◽  
Renaud Delannay ◽  
Alexandre Valance ◽  
Patrick Richard
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Scaling Law ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Particle Volume ◽  
Rheological Models ◽  
Granular Gas ◽  
Internal Structures

We report on new patterns in high-speed flows of granular materials obtained by means of extensive numerical simulations. These patterns emerge from the destabilization of unidirectional flows upon increase of mass holdup and inclination angle, and are characterized by complex internal structures, including secondary flows, heterogeneous particle volume fraction, symmetry breaking and dynamically maintained order. In particular, we evidenced steady and fully developed ‘supported’ flows, which consist of a dense core surrounded by a highly energetic granular gas. Interestingly, despite their overall diversity, these regimes are shown to obey a scaling law for the mass flow rate as a function of the mass holdup. This unique set of three-dimensional flow regimes raises new challenges for extending the scope of current granular rheological models.

scholarly journals Cell-surface attachment of pedestal-forming enteropathogenicE. coliinduces a clustering of raft components and a recruitment of annexin 2

2002 ◽  
Vol 115 (1) ◽  
pp. 91-98
Author(s):  
Nicole Zobiack ◽  
Ursula Rescher ◽  
Sven Laarmann ◽  
Silke Michgehl ◽  
M. Alexander Schmidt ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Surface ◽  
Actin Binding ◽  
Surface Attachment ◽  
Glycosyl Phosphatidylinositol ◽  
Annexin 2 ◽  
Endosomal Membranes ◽  
Membrane Components ◽  
Functional Receptor ◽  
Pedestal Formation

Annexin 2 is a Ca2+-regulated membrane- and F-actin-binding protein implicated in the stabilization or regulation of membrane/cytoskeleton contacts, or both, at the plasma membrane and at early endosomal membranes. To analyze the dynamic nature of such action we investigated whether annexin 2 could be found at sites of localized actin rearrangements occurring at the plasma membrane of HeLa cells infected with noninvading enteropathogenic Escherichia coli (EPEC). We show that adherent EPEC microcolonies, which are known to induce the formation of actin-rich pedestals beneath them, specifically recruit annexin 2 to the sites of their attachment. Mutant EPEC (EPECtir), which lack a functional receptor for intimate attachment (Tir, translocated intimin receptor) and which fail to produce full pedestal formation, are still capable of recruiting annexin 2 to the bacterial contact sites. Accumulation of annexin 2 at sites of EPEC or EPECtir attachment is accompanied by a recruitment of the annexin 2 protein ligand S100A10. EPEC and EPECtir attachment also induces a concentration of cholesterol and glycosyl phosphatidylinositol-anchored proteins at sites of bacterial contact. This indicates that membrane components present in rafts or raft-like microdomains are clustered upon EPEC adherence and that annexin 2 is recruited to the cytoplasmic membrane surface of such clusters, possibly stabilizing raft patches and their linkage to the actin cytoskeleton beneath adhering EPEC.

scholarly journals Synchrotron radiation X-ray tomographic microscopy (SRXTM) of brachiopod shell interiors for taxonomy: Preliminary report

2010 ◽  
pp. 109-117 ◽  
Author(s):  
Neda Motchurova-Dekova ◽  
David Harper
Keyword(s):  
Synchrotron Radiation ◽  
Three Dimensional ◽  
X Rays ◽  
X Ray ◽  
Fine Grained ◽  
Internal Structures ◽  
Efficient Alternative ◽  
Micro Tomography ◽  
Light Beams ◽  
Non Destructive

Synchrotron radiation X-ray tomographic microscopy (SRXTM) is a non-destructive technique for the investigation and visualization of the internal features of solid opaque objects, which allows reconstruction of a complete three-dimensional image of internal structures by recording of the differences in the effects on the passage of waves of energy reacting with those structures. Contrary to X-rays, produced in a conventional X-ray tube, the intense synchrotron light beams are sharply focused like a laser beam. We report encouraging results from the use of SRXTM for purely taxonomic purposes in brachiopods: an attempt to find a non-destructive and more efficient alternative to serial sectioning and several other methods of dissection together with the non-destructive method of X-ray computerised micro-tomography. Two brachiopod samples were investigated using SRXTM. In ?Rhynchonella? flustracea it was possible to visualise the 3D shape of the crura and dental plates. In Terebratulina imbricata it was possible to reveal the form of the brachidium. It is encouraging that we have obtained such promising results using SRXTM with our very first two fortuitous samples, which had respectively fine-grained limestone and marl as infilling sediment, in contrast to the discouraging results communicated to us by some colleagues who have tested specimens with such infillings using X-ray micro-tomography. In future the holotypes, rare museum specimens or delicate Recent material may be preferentially subjected to this mode of analysis.

scholarly journals The Lateral Organization and Mobility of Plasma Membrane Components

Cell ◽  
2019 ◽  
Vol 177 (4) ◽  
pp. 806-819 ◽  
Author(s):  
Ken Jacobson ◽  
Ping Liu ◽  
B. Christoffer Lagerholm
Keyword(s):  
Plasma Membrane ◽  
Membrane Components ◽  
Lateral Organization
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