scholarly journals Cisternal Organization of the Endoplasmic Reticulum during Mitosis

2009 ◽  
Vol 20 (15) ◽  
pp. 3471-3480 ◽  
Author(s):  
Lei Lu ◽  
Mark S. Ladinsky ◽  
Tom Kirchhausen
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Mammalian Cells ◽  
Three Dimensional ◽  
Freeze Substitution ◽  
High Resolution Electron Microscopy ◽  
Animal Cells ◽  
Resolution Electron ◽  
Major Transformation ◽  
Membrane Bound

The endoplasmic reticulum (ER) of animal cells is a single, dynamic, and continuous membrane network of interconnected cisternae and tubules spread out throughout the cytosol in direct contact with the nuclear envelope. During mitosis, the nuclear envelope undergoes a major rearrangement, as it rapidly partitions its membrane-bound contents into the ER. It is therefore of great interest to determine whether any major transformation in the architecture of the ER also occurs during cell division. We present structural evidence, from rapid, live-cell, three-dimensional imaging with confirmation from high-resolution electron microscopy tomography of samples preserved by high-pressure freezing and freeze substitution, unambiguously showing that from prometaphase to telophase of mammalian cells, most of the ER is organized as extended cisternae, with a very small fraction remaining organized as tubules. In contrast, during interphase, the ER displays the familiar reticular network of convolved cisternae linked to tubules.

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

scholarly journals The Endoplasmic Reticulum and the Golgi Structures in Maize Root Cells

1959 ◽  
Vol 5 (3) ◽  
pp. 501-506 ◽  
Author(s):  
W. Gordon Whaley ◽  
Hilton H. Mollenhauer ◽  
Joyce E. Kephart
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Electron Microscope ◽  
Nuclear Envelope ◽  
Epoxy Resin ◽  
Maize Root ◽  
Root Tips ◽  
Animal Cells ◽  
Root Cells ◽  
Vesicular Structure

Maize root tips were fixed in potassium permanganate, embedded in epoxy resin, sectioned to show silver interference color, and studied with the electron microscope. All the cells were seen to contain an endoplasmic reticulum and apparently independent Golgi structures. The endoplasmic reticulum is demonstrated as a membrane-bounded, vesicular structure comparable in many aspects to that of several types of animal cells. With the treatment used here the membranes appear smooth surfaced. The endoplasmic reticulum is continuous with the nuclear envelope and, by contact at least, with structures passing through the cell wall. The nuclear envelope is characterized by discontinuities, as previously reported for animal cells. The reticula of adjacent cells seem to be in contact at or through the plasmodesmata. Because of these contacts the endoplasmic reticulum of a given cell appears to be part of an intercellular system. The Golgi structures appear as stacks of platelet-vesicles which apparently may, under certain conditions, produce small vesicles around their edges. Their form changes markedly with development of the cell.

Role of an endoplasmic reticulum Ca2+-independent phospholipase A2 in oxidant-induced renal cell death

2002 ◽  
Vol 283 (3) ◽  
pp. F492-F498 ◽  
Author(s):  
Brian S. Cummings ◽  
Jane McHowat ◽  
Rick G. Schnellmann
Keyword(s):  
Lipid Peroxidation ◽  
Endoplasmic Reticulum ◽  
Subcellular Localization ◽  
Mammalian Cells ◽  
Cumene Hydroperoxide ◽  
Physiological Role ◽  
Antimycin A ◽  
Bacterial Cells ◽  
Tert Butylhydroperoxide ◽  
Membrane Bound

Phospholipase A2(PLA2) hydrolyzes the sn-2 ester bond in phospholipids, releasing a fatty acid and a lysophospholipid. Recently, a novel 85-kDa membrane-bound-Ca2+-independent PLA2 (iPLA2) was identified in insect and bacterial cells transfected with candidate PLA2 sequences. However, few data exist demonstrating a membrane-bound-iPLA2 in mammalian cells, its subcellular localization, or its physiological role. Herein, we demonstrate the expression of an 85-kDa endoplasmic reticulum (ER)-Ca2+-iPLA2 (ER-iPLA2) in rabbit renal proximal tubule cells (RPTC) that is plasmalogen selective and is inhibited by the specific Ca2+-iPLA2inhibitor bromoenol lactone (BEL). RPTC exposed to tert-butylhydroperoxide for 24 h exhibited 20% oncosis compared with 2% in controls. Inhibition of ER-iPLA2 with BEL before tert-butylhydroperoxide exposure resulted in 50% oncosis. To determine whether this effect was common to oxidants, we tested the ability of BEL to potentiate oncosis induced by cumene hydroperoxide, menadione, duraquinone, cisplatin, and the nonoxidant antimycin A. All oxidants tested produced oncosis after 24 h, and prior inhibition of ER-iPLA2 potentiated oncosis at least twofold. In contrast, inhibition of ER-iPLA2 did not alter antimycin A-induced oncosis. Lipid peroxidation increased from 1.4- to 5.2-fold in RPTC treated with BEL before oxidant exposure, whereas no change was seen in antimycin A-treated RPTC. These results are the first to demonstrate the expression and subcellular localization of an ER-iPLA2. These results also suggest that ER-iPLA2 functions to protect against oxidant-induced lipid peroxidation and oncosis.

scholarly journals Reshaping of the endoplasmic reticulum limits the rate for nuclear envelope formation

2008 ◽  
Vol 182 (5) ◽  
pp. 911-924 ◽  
Author(s):  
Daniel J. Anderson ◽  
Martin W. Hetzer
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Mammalian Cells ◽  
Time Lapse ◽  
Principal Mechanism ◽  
Nuclear Assembly ◽  
Nuclear Envelope Formation ◽  
Rate Limiting

During mitosis in metazoans, segregated chromosomes become enclosed by the nuclear envelope (NE), a double membrane that is continuous with the endoplasmic reticulum (ER). Recent in vitro data suggest that NE formation occurs by chromatin-mediated reorganization of the tubular ER; however, the basic principles of such a membrane-reshaping process remain uncharacterized. Here, we present a quantitative analysis of nuclear membrane assembly in mammalian cells using time-lapse microscopy. From the initial recruitment of ER tubules to chromatin, the formation of a membrane-enclosed, transport-competent nucleus occurs within ∼12 min. Overexpression of the ER tubule-forming proteins reticulon 3, reticulon 4, and DP1 inhibits NE formation and nuclear expansion, whereas their knockdown accelerates nuclear assembly. This suggests that the transition from membrane tubules to sheets is rate-limiting for nuclear assembly. Our results provide evidence that ER-shaping proteins are directly involved in the reconstruction of the nuclear compartment and that morphological restructuring of the ER is the principal mechanism of NE formation in vivo.

Atomic Scale Aluminum and Strain Distribution in a Gan/AlxGa1−XN Heterostructure

1997 ◽  
Vol 482 ◽  
Author(s):  
Christian Kisielowski ◽  
Olaf Schmidt ◽  
Jinwei Yang
Keyword(s):  
Three Dimensional ◽  
Chemical Vapor ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Organic Chemical ◽  
Well Test ◽  
Lattice Constants ◽  
Resolution Electron ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

AbstractA GaN/AlxGalxN multi-quantum well test structure with Al concentrations 0 ≤ xAl ≤ 1 was utilized to investigate the growth of AlxGal–xN barrier layers deposited by metal organic chemical vapor deposition (MOCVD). A transition from a two dimensional (2D) to a three dimensional (3D) growth mode was observed in AlxGa1–xN barriers with XAl ≥ 0.75. It is argued that the transition occurs because of growth at temperatures that are low compared with the materials melting points Tmelt. The resulting rough AlxGa1–xN surfaces can be planarized by overgrowth with GaN. Quantitative high resolution electron microscopy (HREM) was applied to measure composition and strain profiles across the GaN/AlxGa1−xN stacks at an atomic level. The measurements reveal a substantial variation of lattice constants at the AlxGa1−xN/GaN interfaces that is attributed to an Al accumulation.

scholarly journals p180 Is Involved in the Interaction between the Endoplasmic Reticulum and Microtubules through a Novel Microtubule-binding and Bundling Domain

2007 ◽  
Vol 18 (10) ◽  
pp. 3741-3751 ◽  
Author(s):  
Kiyoko Ogawa-Goto ◽  
Keiko Tanaka ◽  
Tomonori Ueno ◽  
Keisuke Tanaka ◽  
Takeshi Kurata ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Cultured Cells ◽  
Specific Interaction ◽  
Endoplasmic Reticulum Membrane ◽  
Dependent Manner ◽  
Small Interfering Rnas ◽  
Animal Cells ◽  
Microtubule Binding

p180 was originally reported as a ribosome-binding protein on the rough endoplasmic reticulum membrane, although its precise role in animal cells has not yet been elucidated. Here, we characterized a new function of human p180 as a microtubule-binding and -modulating protein. Overexpression of p180 in mammalian cells induced an elongated morphology and enhanced acetylated microtubules. Consistently, electron microscopic analysis clearly revealed microtubule bundles in p180-overexpressing cells. Targeted depletion of endogenous p180 by small interfering RNAs led to aberrant patterns of microtubules and endoplasmic reticulum in mammalian cells, suggesting a specific interaction between p180 and microtubules. In vitro sedimentation assays using recombinant polypeptides revealed that p180 bound to microtubules directly and possessed a novel microtubule-binding domain (designated MTB-1). MTB-1 consists of a predicted coiled-coil region and repeat domain, and strongly promoted bundle formation both in vitro and in vivo when expressed alone. Overexpression of p180 induced acetylated microtubules in cultured cells in an MTB-1-dependent manner. Thus, our data suggest that p180 mediates interactions between the endoplasmic reticulum and microtubules mainly through the novel microtubule-binding and -bundling domain MTB-1.

scholarly journals Properties of membrane-bound bilirubin UDP-glucuronyltransferase in rough and smooth endoplasmic reticulum and in the nuclear envelope from rat liver

1989 ◽  
Vol 259 (3) ◽  
pp. 659-663 ◽  
Author(s):  
F Vanstapel ◽  
L Hammaker ◽  
K Pua ◽  
N Blanckaert
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Membrane System ◽  
Permeability Barrier ◽  
Membrane Bound ◽  
Marker Studies ◽  
High Degree ◽  
Regulatory Properties

We examined regulatory properties of bilirubin UDP-glucuronyltransferase in sealed RER (rough endoplasmic reticulum)- and SER (smooth endoplasmic reticulum)-enriched microsomes (microsomal fractions), as well as in nuclear envelope from rat liver. Purity of membrane fractions was verified by electron microscopy and marker studies. Intactness of RER and SER vesicles was ascertained by a high degree of latency of the lumenal marker mannose-6-phosphatase. No major differences in the stimulation of UDP-glucuronyltransferase by detergent or by the presumed physiological activator, UDPGlcNAc, were observed between total microsomes and RER- or SER-enriched microsomes. Isolated nuclear envelopes were present as a partially disrupted membrane system, with approx. 50% loss of mannose-6-phosphatase latency. The nuclear transferase had lost its latency to a similar extent, and the enzyme failed to respond to UDPGlcNAc. Our results underscore the necessity to include data on the integrity of the membrane permeability barrier when reporting regulatory properties of UDP-glucuronyltransferase in different membrane preparations.

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