Ultrastructural changes accompany inhibition of proteoglycan synthesis in chondrocytes by Cyclofenil diphenol

1989 ◽  
Vol 92 (2) ◽  
pp. 271-280 ◽  
Author(s):  
C.A. Lancaster ◽  
P.R. Fryer ◽  
S. Griffiths ◽  
R.M. Mason
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Electron Density ◽  
Lipid Droplets ◽  
Secretory Pathway ◽  
Ultrastructural Changes ◽  
Proteoglycan Synthesis ◽  
Filamentous Material

Cyclofenil diphenol, a weak non-steroidal oestrogen, profoundly inhibits [35S]proteoglycan synthesis in cultures of Swarm chondrosarcoma chondrocytes under conditions in which protein synthesis is only marginally reduced. In the present experiments it was shown that after a 40-min treatment with Cyclofenil diphenol (90 micrograms ml-1) most of the normally abundant Golgi stacks in these cells disappeared and after 60 min they were absent. After 2–3 h treatment the cisternae of the endoplasmic reticulum (ER) were grossly distended and transformed into large ribosome-studded vesicles containing flocculent and filamentous material. These changes were dependent on the concentration of Cyclofenil and were fully reversible within 21 h of withdrawing the drug. The ultrastructural changes differed in some aspects if protein synthesis was blocked with cycloheximide for 15 min or 180 min before and during treatment with Cyclofenil. The Golgi disappeared but the ER cisternae, though distended, formed a continuous network and swollen ribosome-studded vesicles did not develop. However, non-membrane-bounded structures containing lipid droplets and material of low electron density developed in the cytoplasm under these conditions. The ultrastructural changes induced by Cyclofenil differ from those induced by monensin and diethylcarbamazine, suggesting that the drug acts at a different point in the secretory pathway for macromolecules.

scholarly journals Ultrastructural changes in chloroplasts of mesophyll cells of chlorotic and prematurely yellowed leaves of Betula pendula Rothr

2011 ◽  
Vol 72 (4) ◽  
pp. 289-293 ◽  
Author(s):  
Krystyna Przybył ◽  
Krystyna Idzikowska
Keyword(s):  
Electron Density ◽  
Lipid Droplets ◽  
Betula Pendula ◽  
Ultrastructural Changes ◽  
Membrane Systems ◽  
Mesophyll Cells ◽  
Spongy Mesophyll ◽  
Starch Grains ◽  
Interveinal Chlorosis ◽  
The Past

The ultrastructure of chloroplasts was studied in mesophyll cells of the leaves of silver birch (<em>Betula pendula</em>) showing interveinal chlorosis or premature yellowing, in comparison with leaves without symptoms or exhibiting symptoms of natural senescence. The leaves were collected between May 26 to June 7 and additionally in the September 10-12 from the upper part of the crown, from increments of the past four years. No major difference in ultrastructure of chloroplasts was found between spongy and palisade mesophyll cells. The following senescencerelated changes were observed in chloroplasts of prematurely yellowed leaves and showing inteveinal chlorosis: reduced chloroplast size, degeneration of the membrane systems of thylakoids and increased electron density of plastoglobuli. The most electron dark globules (lipid droplets) were found together with starch grains in cells of spongy mesophyll of leaves showing interveinal chlorosis. Abnormal, spherical and rounded chloroplasts with electron-dark inside of thylakoids or the electron-dark stroma between thylakoids were found only in yellowed and chlorotic leaves in spring.

scholarly journals All aboard!: The secretory pathway

2003 ◽  
Vol 25 (3) ◽  
pp. 10-12
Author(s):  
Stephen High ◽  
Samuel G. Crawshaw
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Membrane Protein ◽  
Cell Surface ◽  
Secretory Pathway ◽  
Entry Point ◽  
Eukaryotic Cells ◽  
Secretory Cells ◽  
Intracellular Membrane ◽  
Biosynthetic Activity

The endoplasmic reticulum (ER) is a major subcellular feature of most eukaryotic cells, and in specialized secretory cells, like those of the pancreas, it densely packs most of the cell. It is the de facto entry point into the secretory pathway and one of its key functions is to provide an extensive intracellular membrane network that supports protein synthesis (Figure 1). This biosynthetic activity is highlighted by the large number of ribosomes that are bound tightly to much of its surface, and it is these ribosomes that synthesize the secretory and membrane protein cargoes that are ultimately destined for export from the ER to the cell surface via the Golgi complex1,2.

Ultrastructural changes in the rough endoplasmic reticulum and its contents following Brefeldin A treatment of human chondrocytes in vitro

1991 ◽  
Vol 49 ◽  
pp. 256-257
Author(s):  
H. E. Gruber
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Brefeldin A ◽  
Ultrastructural Level ◽  
Human Chondrocytes ◽  
Ultrastructural Changes ◽  
Ultrastructural Studies

The rough endoplasmic reticulum (rER) is now recognized as a major organelle responsible for ensuring that only structurally correct and properly folded proteins are allowed to enter the cellular secretory pathway. We are especially interested in the behavior of the chondrocyte rER since ultrastructural studies of many skeletal dysplasias have revealed that electron dense material accumulates or is not degraded within the rER of chondrocytes from patients. Remodelling of the rER in chick chondrocytes has also been evaluated at the ultrastructural level and the rER found to play a role in procollagen export from the cell. We have utilized normal human chondrocytes grown in culture to investigate the role of brefeldin A, an antiviral antibiotic, which has been shown to primarily block protein transport from the ER to the Golgi complex.

Microfilaments and Cytoplasmic Streaming: Inhibition of Streaming with Cytochalasin

1973 ◽  
Vol 12 (1) ◽  
pp. 327-343
Author(s):  
M. O. BRADLEY
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Cytoplasmic Streaming ◽  
Cytochalasin B ◽  
Animal Cell ◽  
The Other ◽  
Ultrastructural Changes ◽  
Ultrastructural Studies ◽  
Functional Inhibition ◽  
Cross Bridges

Cytochalasin B reversibly inhibits cytoplasmic streaming in both Nitella and Avena cells. Colchicine, on the other hand, has no effect on streaming in either plant; nor does colchicine prevent the recovery of streaming after cytochalasin is withdrawn. The inhibition of protein synthesis by cycloheximide has no effect on either streaming itself or on the recovery of streaming after cytochalasin withdrawal. All this suggests that microfilaments may provide one component of the structure that generates the streaming force and that microtubules play little, if any,role in the process. Ultrastructural studies of Nitella demonstrate that microfilaments are localized at the boundary of the streaming endoplasm and the stationary ectoplasm. Microfilaments are organized in discrete bundles, with possible cross-bridges between individual filaments in each bundle. These bundles are closely associated with the extensive endoplasmic reticulum. Cytochalasin B does not cause ultrastructural changes in Nitella microfilaments as it does in some animal-cell filaments. Since the molecular mechanism of cytochalasin's action is unknown, there may be no necessary correlation between functional inhibition by the drug and altered microfilament morphology. A model is advanced which proposes that streaming is generated by an interaction between microfilaments and the endoplasmic reticulum.

Ultrastructural Changes Associated with Alcoholic Hyalin in Hepatocytes and Biliary Epithelial Cells

1971 ◽  
Vol 29 ◽  
pp. 572-573
Author(s):  
Odell T. Minick ◽  
Hidejiro Yokoo ◽  
Fawzia Batti
Keyword(s):  
Endoplasmic Reticulum ◽  
Epithelial Cells ◽  
Liver Biopsy ◽  
Alcoholic Hepatitis ◽  
Ultrastructural Changes ◽  
Main Mass ◽  
Biliary Epithelial Cells ◽  
Biopsy Specimens ◽  
Alcoholic Hyalin

To learn more of the nature and origin of alcoholic hyalin (AH), 15 liver biopsy specimens from patients with alcoholic hepatitis were studied in detail.AH was found not only in hepatocytes but also in ductular cells (Figs. 1 and 2), although in the latter location only rarely. The bulk of AH consisted of a randomly oriented network of closely packed filaments measuring about 150 Å in width. Bundles of filaments smaller in diameter (40-90 Å) were observed along the periphery of the main mass (Fig. 1), often surrounding it in a rim-like fashion. Fine filaments were also found close to the nucleus in both hepatocytes and biliary epithelial cells, the latter even though characteristic AH was not present (Figs. 3 and 4). Dispersed among the larger filaments were glycogen, RNA particles and profiles of endoplasmic reticulum. Dilated cisternae of endoplasmic reticulum were often conspicuous around the periphery of the AH mass. A limiting membrane was not observed.

Ultrastructural Changes of Smoooth Endoplasmic Reticulum in the Retinal Pigment Epithelium by Choline Chloride

1972 ◽  
Vol 30 ◽  
pp. 58-59
Author(s):  
Kazushige Hirosawa ◽  
Eichi Yamada
Keyword(s):  
Endoplasmic Reticulum ◽  
Epithelial Cell ◽  
Smooth Endoplasmic Reticulum ◽  
Pigment Epithelium ◽  
Choline Chloride ◽  
Retinal Pigment ◽  
Ultrastructural Changes ◽  
Lower Vertebrate ◽  
Visual Cells ◽  
Pigment Epithelial

The pigment epithelium is located between the choriocapillary and the visual cells. The pigment epithelial cell is characterized by a large amount of the smooth endoplasmic reticulum (SER) in its cytoplasm. In addition, the pigment epithelial cell of some lower vertebrate has myeloid body as a specialized form of the SER. Generally, SER is supposed to work in the lipid metabolism. However, the functions of abundant SER and myeloid body in the pigment epithelial cell are still in question. This paper reports an attempt, to depict the functions of these organelles in the frog retina by administering one of phospholipid precursors.

Spatial localization of unknown proteins in the endoplasmic reticulum predicts functions

2007 ◽  
Vol 30 (4) ◽  
pp. 84
Author(s):  
Michael D. Jain ◽  
Hisao Nagaya ◽  
Annalyn Gilchrist ◽  
Miroslaw Cygler ◽  
John J.M. Bergeron
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Folding ◽  
Protein Synthesis ◽  
Protein Function ◽  
Protein Translocation ◽  
Spatial Localization ◽  
Predict Protein Function ◽  
Insight Into ◽  
Soluble Fractions ◽  
Er Membrane

Protein synthesis, folding and degradation functions are spatially segregated in the endoplasmic reticulum (ER) with respect to the membrane and the ribosome (rough and smooth ER). Interrogation of a proteomics resource characterizing rough and smooth ER membranes subfractionated into cytosolic, membrane, and soluble fractions gives a spatial map of known proteins involved in ER function. The spatial localization of 224 identified unknown proteins in the ER is predicted to give insight into their function. Here we provide evidence that the proteomics resource accurately predicts the function of new proteins involved in protein synthesis (nudilin), protein translocation across the ER membrane (nicalin), co-translational protein folding (stexin), and distal protein folding in the lumen of the ER (erlin-1, TMX2). Proteomics provides the spatial localization of proteins and can be used to accurately predict protein function.

scholarly journals Cell wall and organelle modifications during nitrogen starvation in Nannochloropsis oceanica F&M-M24

2021 ◽  
Author(s):  
Roncaglia Bianca ◽  
Papini Alessio ◽  
Chini Zittelli Graziella ◽  
Rodolfi Liliana ◽  
Mario R. Tredici
Keyword(s):  
Cell Wall ◽  
Wall Thickness ◽  
Lipid Droplets ◽  
Nitrogen Starvation ◽  
Photosynthetic Apparatus ◽  
Ultrastructural Changes ◽  
Total Biomass ◽  
Nannochloropsis Oceanica ◽  
Final Phase ◽  
Cell Functions

AbstractNannochloropsis oceanica F&M-M24 is able to increase its lipid content during nitrogen starvation to more than 50% of the total biomass. We investigated the ultrastructural changes and the variation in the content of main cell biomolecules that accompany the final phase of lipid accumulation. Nitrogen starvation induced a first phase of thylakoid disruption followed by chloroplast macroautophagy and formation of lipid droplets. During this phase, the total amount of proteins decreased by one-third, while carbohydrates decreased by 12–13%, suggesting that lipid droplets were formed by remodelling of chloroplast membranes and synthesis of fatty acids from carbohydrates and amino acids. The change in mitochondrial ultrastructure suggests also that these organelles were involved in the process. The cell wall increased its thickness and changed its structure during starvation, indicating that a disruption process could be partially affected by the increase in wall thickness for biomolecules recovery from starved cells. The wall thickness in strain F&M-M24 was much lower than that observed in other strains of N. oceanica, showing a possible advantage of this strain for the purpose of biomolecules extraction. The modifications following starvation were interpreted as a response to reduction of availability of a key nutrient (nitrogen). The result is a prolonged survival in quiescence until an improvement of the environmental conditions (nutrient availability) allows the rebuilding of the photosynthetic apparatus and the full recovery of cell functions.

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