Enzyme topology in native, intact endoplasmic reticulum of permeabilized isolated hepatocytes

1985 ◽  
Vol 13 (4) ◽  
pp. 721-722
Author(s):  
DAVID BROWN ◽  
TERENCE HALLINAN
Keyword(s):  
Endoplasmic Reticulum ◽  
Isolated Hepatocytes ◽  
Enzyme Topology

A characterization of heam uptake and intracellular distribution by isolated hepatocytes

1985 ◽  
Vol 5 (7) ◽  
pp. 609-614 ◽  
Author(s):  
A. Lodola
Keyword(s):  
Endoplasmic Reticulum ◽  
Specific Binding ◽  
Isolated Hepatocytes ◽  
Intracellular Distribution ◽  
Distribution Data ◽  
Temperature Dependent ◽  
Rat Hepatocyte ◽  
Isolated Rat ◽  
Endoplasmic Reticulum Fraction

The uptake and intracellular distribution of haem by isolated rat hepatocyte suspensions was studied. An increase in cell haem content occurred after a challenge with 5, 10 or 20 μM haem, supplied as methaemalbumin. The rate of haem uptake was temperature dependent; no non-specific binding occurred. Intracellular haem distribution data are consistent with a rapid association of haem with the endoplasmic reticulum fraction prior to its accumulation in the cytosol and at the mitochondrion.

scholarly journals Rapid Ca2+ influx induced by the action of dibutylhydroquinone and glucagon in the perfused rat liver

1997 ◽  
Vol 323 (2) ◽  
pp. 463-467 ◽  
Author(s):  
Tanya L. APPLEGATE ◽  
Ari KARJALAINEN ◽  
Fyfe L. BYGRAVE
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Transport ◽  
Rat Liver ◽  
Sodium Azide ◽  
Isolated Hepatocytes ◽  
Atp Depletion ◽  
Perfused Rat Liver ◽  
Total Calcium ◽  
Combined Administration ◽  
Prior Administration

Glucagon induces a slight Ca2+ efflux when administered to the perfused rat liver. However, the hormone promotes rapid and significant Ca2+ influx after the prior administration of 2,5-di(t-butyl)-1,4-hydroquinone (BHQ), an agent that promotes Ca2+ release from the endoplasmic reticulum (ER). The concentrations of glucagon that promote Ca2+ influx are similar to those that promote glycogenolysis and gluconeogenesis in isolated hepatocytes. The permeable analogue of cAMP, but not that of cGMP, is able to duplicate the Ca2+-mobilizing effects of glucagon. The influx of Ca2+ into liver is blocked by Ni2+. Administration of sodium azide, an inhibitor of mitochondrial electron transport, also blocks the BHQ plus glucagon-induced Ca2+ influx and this is reversed when azide administration is terminated. The actions of azide are evident within 60 s after administration or withdrawal, and also occur when either oligomycin or fructose is co-administered; this provides evidence for an effect of azide independent of cellular ATP depletion. Measurement of total calcium in mitochondria that were isolated rapidly from perfused livers after the combined administration of glucagon and BHQ confirmed that large quantities of extracellular Ca2+ had entered these organelles. These experiments provide evidence that in the perfused rat liver the artificial emptying of the ER Ca2+ pool allows glucagon to promote rapid and sustained Ca2+ influx that seems to terminate in mitochondria.

Implication of mitochondrial dysfunction and cell death in cold preservation – warm reperfusion-induced hepatocyte injury

2006 ◽  
Vol 84 (5) ◽  
pp. 547-554 ◽  
Author(s):  
Marjolaine Duval ◽  
Catherine Plin ◽  
Aziz Elimadi ◽  
Diane Vallerand ◽  
Jean-Paul Tillement ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Cytochrome C ◽  
Mitochondrial Dysfunction ◽  
Isolated Hepatocytes ◽  
Mitochondrial Pathway ◽  
Liver Graft ◽  
Isolated Cells ◽  
Hepatocyte Injury ◽  
Effector Caspase

Cold ischemia – warm reperfusion (CI/WR) injury of liver transplantation involves hepatocyte cell death, the nature and underlying mechanisms of which remain unclear. Isolated hepatocytes and isolated perfused livers were used to determine the prevalence of necrosis and apoptosis as well as mitochondrial dysfunction. In isolated cells, propidium iodide and Hoechst 33342 staining showed a cold-storage, time-dependent increase in necrosis, whereas apoptosis was minimal even after 48 h of hypothermia. Nonetheless, a progressive loss of mitochondrial membrane potential was observed. Translocation of mitochondrial cytochrome c toward microsomes occurred within 24 h of CI/WR, with cytochrome c reaching the cytosol later. Mitochondria isolated from whole livers subjected to CI/WR also display reduced metabolic parameters and increased susceptibility to swelling. These events are associated with increased activity of major initiator (caspase 9) and effector (caspase 3) caspases. The results demonstrate that CI/WR induces mitochondrial dysfunction in isolated cells and in the whole organ; only in the latter is that sufficient to trigger the classical mitochondrial pathway of apoptosis. Our study also provides evidence for the involvement of endoplasmic reticulum stress in CI/WR hepatocyte injury. Combined protection of mitochondria and endoplasmic reticulum may thus represent an innovative therapeutic avenue to enhance liver graft viability and functional integrity.

scholarly journals Purification and characterization of autophagosomes from rat hepatocytes

1998 ◽  
Vol 335 (2) ◽  
pp. 217-224 ◽  
Author(s):  
Per Eivind STRØMHAUG ◽  
Trond Olav BERG ◽  
Monica FENGSRUD ◽  
Per O. SEGLEN
Keyword(s):  
Endoplasmic Reticulum ◽  
Density Gradient ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Protein Markers ◽  
Intact Cells ◽  
Cytoskeletal Elements ◽  
Intermediate Density ◽  
Glucose Regulated Protein

To investigate the properties and intracellular origin of autophagosomes, a procedure for the purification and isolation of these organelles from rat liver has been developed. Isolated hepatocytes were incubated with vinblastine to induce autophagosome accumulation; the cells were then homogenized and treated with the cathepsin C substrate glycyl-l-phenylalanine 2-naphthylamide to cause osmotic disruption of the lysosomes. Nuclei were removed by differential centrifugation, and the postnuclear supernatant was fractionated on a discontinuous Nycodenz density gradient. The autophagosomes, recognized by their content of autophagocytosed lactate dehydrogenase (LDH), could be recovered in an intermediate-density fraction, free from cytosol and mitochondria. Finally, the autophagosomes were separated from the endoplasmic reticulum and other membranous elements by centrifugation in a Percoll colloidal density gradient, followed by flotation in iodixanol to remove the Percoll particles. The final autophagosome preparation represented a 24-fold purification of autophagocytosed LDH relative to intact cells, with a 12% recovery. The purified autophagosomes contained sequestered cytoplasm with a normal ultrastructure, including mitochondria, peroxisomes and endoplasmic reticulum in the same proportions as in intact cells. However, immunoblotting indicated a relative absence of cytoskeletal elements (tubulin, actin and cytokeratin), which may evade autophagic sequestration. The autophagosomes showed no enrichment in protein markers typical of lysosomes (acid phosphatase, cathepsin B, lysosomal glycoprotein of 120 kDa), endosomes (early-endosome-associated protein 1, cation-independent mannose 6-phosphate receptor, asialoglycoprotein receptor) or endoplasmic reticulum (esterase, glucose-regulated protein of 78 kDa, protein disulphide isomerase), suggesting that the sequestering membranes are not derived directly from any of these organelles, but rather represent unique organelles (phagophores).

scholarly journals Isolation and subfractionation on ficoll gradients of adult rat hepatocytes. Size, morphology, and biochemical characteristics of cell fractions.

1975 ◽  
Vol 66 (1) ◽  
pp. 1-22 ◽  
Author(s):  
P Drochmans ◽  
J C Wanson ◽  
R Mosselmans
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Gradient Centrifugation ◽  
Parenchymal Cell ◽  
Liver Homogenate ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Isolated Cells ◽  
Adult Rat ◽  
Mean Diameter

The recirculating perfusion of adult rat liver with a Ca-++-free Hanks' solution produces a release of the adhesiveness of cells and a cleaving of the desmosomes. The addition of collagenase and hyaluronidase to the perfusion medium leads to complete dissociation of the liver tissue into a mixture of isolated cells and cell cords in which the hepatocytes remain connected with specific junctional differentiations, namely the gap and tight junctions. Individual cells are released by submitting the suspension of cell trabeculae to a gentle rolling. The gap junctions are ruptured at least in one of the two adjacent cells and remain generally attached to the other cell taking with them a small portion of cytoplasm. This technique of isolation of hepatocytes yields about 60-65% of the parenchymal cells contained in a liver; endothelial cells and other cells of the connective tissue are not recovered. The ultrastructural preservation of the isolated hepatocytes is excellent and the glucose-6-phosphatase activity, confined to the endoplasmic reticulum, appears unaltered in most cells. Protein, DNA and RNA recovery in the preparations of isolated hepatocytes is satisfactory, amounting to 70% of that found in liver homogenate; glycogen, the most labile component examined, is partly lost or degraded during the manipulations. Cell diameters measured by different methods confirm the preservation of the original volume of the in situ hepatocytes and the presence of more than one type of parenchymal cell. By submitting this heterogeneous cell population to an isopycnic density gradient centrifugation, two types of hepatocytes can be distinguished: the light hepatocytes, with a mean diameter of 20.5 mum and a mean density of 1.10, are characterized by an extended smooth-walled endoplasmic reticulum entrapping dispersed alpha-glycogen particles; the heavy hepatocytes, with a mean diameter of 19.0 mum and a mean density of 1.14, present a relatively reduced compartment of smooth endoplasmic reticulum, but large accumulations of glycogen. It is suggested that the cell fraction of low density is enriched in centrolobular cells and the high density fraction in perilobular hepatocytes.

scholarly journals Glucagon and vasopressin interactions on Ca2+ movements in isolated hepatocytes

1986 ◽  
Vol 237 (3) ◽  
pp. 675-683 ◽  
Author(s):  
L Combettes ◽  
B Berthon ◽  
A Binet ◽  
M Claret
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Isolated Rat Liver ◽  
Low Concentration ◽  
Fast Phase ◽  
Rat Liver Cells ◽  
Subsequent Addition ◽  
Isolated Rat

The effects of glucagon and vasopressin, singly or together, on cytosolic free Ca2+ concentration [(Ca2+]i) and on the 45Ca2+ efflux were studied in isolated rat liver cells. In the presence of 1 mM external Ca2+, glucagon and vasopressin added singly induced sustained increases in [Ca2+]i. The rate of the initial fast phase of the [Ca2+]i increase and the magnitude of the final plateau were dependent on the concentrations (50 pm-0.1 microM) of glucagon and vasopressin. Preincubating the cells with a low concentration of glucagon (0.1 nM) for 2 min markedly accelerated the fast phase and elevated the plateau of the [Ca2+]i increase caused by vasopressin. In the absence of external free Ca2+, glucagon and vasopressin transiently increased [Ca2+]i and stimulated the 45Ca2+ efflux from the cells, indicating mobilization of Ca2+ from internal store(s). Preincubating the cells with 0.1 nM-glucagon accelerated the rate of the fast phase of the [Ca2+]i rise caused by the subsequent addition of vasopressin. However, unlike what was observed in the presence of 1 mM-Ca2+, glucagon no longer enhanced the maximal [Ca2+]i response to vasopressin. In the absence of external free Ca2+, higher concentrations (1 nM-0.1 microM) of glucagon, which initiated larger increases in [Ca2+]i, drastically decreased the subsequent Ca2+ response to vasopressin (10 nM). At these concentrations, glucagon also decreased the vasopressin-stimulated 45Ca2+ efflux from the cells. It is suggested that, in the liver, glucagon accelerates the fast phase and elevates the plateau of the vasopressin-mediated [Ca2+]i increase respectively by releasing Ca2+ from the same internal store as that permeabilized by vasopressin, probably the endoplasmic reticulum, and potentiating the influx of extracellular Ca2+ caused by this hormone.

In Vitro Induction of Crystals of MT Protein by Vinblastine-Colcemid in Mouse Spermatids

1974 ◽  
Vol 32 ◽  
pp. 132-133
Author(s):  
John J. Wolosewick ◽  
John H. D. Bryan
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Nuclear Ring ◽  
Rough Er ◽  
Distal Direction ◽  
In Vitro Induction

Early in spermiogenesis the manchette is rapidly assembled in a distal direction from the nuclear-ring-densities. The association of vesicles of smooth endoplasmic reticulum (SER) and the manchette microtubules (MTS) has been reported. In the mouse, osmophilic densities at the distal ends of the manchette are the organizing centers (MTOCS), and are associated with the SER. Rapid MT assembly and the lack of rough ER suggests that there is an existing pool of MT protein. Colcemid potentiates the reaction of vinblastine with tubulin and was used in this investigation to detect this protein.

Ultrastructure of the Parotid Gland of the Nine-Banded Armadillo

1977 ◽  
Vol 35 ◽  
pp. 640-641
Author(s):  
J. R. Ruby
Keyword(s):  
Endoplasmic Reticulum ◽  
Parotid Gland ◽  
Periodic Acid ◽  
Acinar Cells ◽  
Duct System ◽  
Parotid Glands ◽  
Dasypus Novemcinctus ◽  
Anterior Portion ◽  
Periodic Acid Schiff ◽  
Thin Sections

Parotid glands were obtained from five adult (four male and one female) armadillos (Dasypus novemcinctus) which were perfusion-fixed. The glands were located in a position similar to that of most mammals. They extended interiorly to the anterior portion of the submandibular gland.In the light microscope, it was noted that the acini were relatively small and stained strongly positive with the periodic acid-Schiff (PAS) and alcian blue techniques, confirming the earlier results of Shackleford (1). Based on these qualities and other structural criteria, these cells have been classified as seromucous (2). The duct system was well developed. There were numerous intercalated ducts and intralobular striated ducts. The striated duct cells contained large amounts of PAS-positive substance.Thin sections revealed that the acinar cells were pyramidal in shape and contained a basally placed, slightly flattened nucleus (Fig. 1). The rough endoplasmic reticulum was also at the base of the cell.

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