scholarly journals ULTRASTRUCTURAL STUDY OF MEMBRANE-BOUND ENZYMES IN THYMOCYTES

1974 ◽  
Vol 22 (12) ◽  
pp. 1128-1134 ◽  
Author(s):  
ARIANE MONNERON ◽  
JEAN-CLAUDE BENICHOU ◽  
INSTITUT PASTEUR ◽  
YVETTE FLORENTIN ◽  
ELIANE GUERRY
Keyword(s):  
Plasma Membrane ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Uridine Diphosphate ◽  
Lead Phosphate ◽  
Isolated Nuclei ◽  
Whole Cells ◽  
Diphosphate Glucose ◽  
Membrane Bound ◽  
Membrane Bound Enzymes ◽  
Phosphate Deposits

Calf thymocytes in suspension, as well as isolated calf thymocyte nuclei, were incubated in the presence of several phosphorylated substrates. 5'-Nucleotidase was easily detected on the plasma membrane of thymocytes (external side), but could be demonstrated on isolated nuclei only to a small extent. No other substrates were detectably hydrolyzed by isolated nuclei except adenosine triphosphate and 3'-thymidine monophosphate. The surface of whole cells was found to be much more reactive. A 3'-nucleotidase activity was shown to occur on the plasma membrane of a number of thymocytes and produced large lead phosphate deposits, some of them protruding into the cytoplasm. Enzymic activities splitting β-nicotinamide adenine dinucleotide phosphate and uridine diphosphate glucose were also readily detectable on the surface of cells. Since the pattern of the lead phosphate deposits and the number of reactive cells varied with the added substrate, and since cells were compared with their isolated nuclei, the positive reactions were considered to indicate the presence (on the exposed membranes) of the corresponding enzymes on the exposed membranes.

Studies of the endoplasmic reticulum and plasma membrane-bound ribosomes in erythropoietic cells

1978 ◽  
Vol 31 (1) ◽  
pp. 165-178
Author(s):  
J.A. Grasso ◽  
A.L. Sullivan ◽  
S.C. Chan
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Exact Role ◽  
Whole Cells ◽  
Cytoplasmic Face ◽  
Close Proximity ◽  
Haem Biosynthesis ◽  
Hypotonic Buffer ◽  
Membrane Bound ◽  
Hypotonic Lysis

Erythropoietic cells of 5 species, including man, contain endoplasmic reticulum present as individual cisternae or tubules scattered throughout the cytoplasm of all stages except mature RBCs. The endoplasmic reticulum is mainly agranular but occurs frequently as a variant of granular ER which is characterized by an asymmetrical and irregular distribution of ribosomes along one cytoplasmic face. In most cells, the endoplasmic reticulum occurs in close proximity to mitochondria or the plasma membrane, suggesting that the organelle may be involved in functions related to these structures, e.g. haem biosynthesis. Endoplasmic reticulum is more abundant in early than in late erythroid cells. Its exact role in RBC development is unclear. Since endoplasmic reticulum could account for ‘plasma membrane-bound ribosomes’ reported in lysed reticulocytes, studies were performed which ruled out this possibility and which suggested that such ribosomes were an artifact of the lysing conditions. Hypotonic lysis in less than 20 vol. of magnesium-containing buffers yielded ghosts variably contaminated by ribosomes and other structures. Lysis of reticulocytes in 20–30 vol. of magnesium-free buffer or homogenization of whole cells or crude membrane fractions in hypotonic buffer removed virtually all contaminating ribosomes from the purified membrane fraction.

Effects of ethanol administration on rat liver plasma membrane-bound enzymes

1985 ◽  
Vol 34 (15) ◽  
pp. 2685-2689 ◽  
Author(s):  
Jorge L. Gonzalez-Calvin ◽  
John B. Saunders ◽  
Ian R. Crossley ◽  
Christopher J. Dickenson ◽  
Heather M. Smith ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Ethanol Administration ◽  
Liver Plasma Membrane ◽  
Membrane Bound ◽  
Membrane Bound Enzymes

Traffic to the endocytic compartment of plants

1989 ◽  
Vol 47 ◽  
pp. 754-755
Author(s):  
L. R. Griffing ◽  
R. D. Record ◽  
H. H. Mollenhauer
Keyword(s):  
Plasma Membrane ◽  
Golgi Complex ◽  
Fluid Phase ◽  
Multivesicular Body ◽  
Endocytic Pathway ◽  
Cationized Ferritin ◽  
Plant Protoplasts ◽  
Whole Cells ◽  
Membrane Bound ◽  
And Function

The endocytic pathway of plants has been identified and partially characterized using nonspecific membrane-bound and fluid phase probes . The function of endocytosis in plants is, however, unknown. We shall describe how ultrastructural histochemistry, immunocytochemical analyses and fluorescence imaging have been used to explore the physiology and function of the endocytic pathway in plant protoplasts and whole cells.Cationized ferritin (CF) can be used as a marker of plasma membrane uptake in plant protoplasts. Several different organelles become labeled upon exposure of protoplasts to CF: clathrin-coated vesicles (CV), the partially coated reticulum (PCR), the Golgi complex (GC), the multivesicular body (MVB), and the vacuole (V). These organelles also participate in the pathways of secretion and delivery of protein to the lysosome (vacuole). What are the sites of overlap/divergence among the secretory, endocytic and lysosomal pathways in these cells?

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