Extra- and intracellular metabolism of platelet-activating factor by cultured mesangial cells

1989 ◽  
Vol 256 (4) ◽  
pp. F735-F741
Author(s):  
R. Neuwirth ◽  
N. Ardaillou ◽  
D. Schlondorff
Keyword(s):  
Cell Membrane ◽  
Cell Surface ◽  
Phospholipase A2 ◽  
Mesangial Cells ◽  
Platelet Activating Factor ◽  
Outer Cell ◽  
Human Mesangial Cells ◽  
Rapid Inactivation ◽  
Outer Cell Membrane ◽  
Intracellular Metabolism

Metabolism of platelet-activating factor (PAF) was examined in cultured mesangial cells from human and rat glomeruli. Human mesangial cells, similar to those from rat, generated PAF after A23187. Both human and rat mesangial cells rapidly hydrolyzed [3H]PAF to lyso-[3H]PAF, and reacylated it into 1-alkyl-2-acyl glycerophosphocholine. Extra- and intracellular metabolism of PAF was then analyzed separately. The majority of [3H]PAF metabolism occurred extracellularly and generated Lyso-[3H]PAF. Intracellularly generated lyso-PAF was rapidly converted to 1-alkyl-2-acyl glycerophosphocholine. Cells prelabeled with [3H]PAF released some [3H]PAF within minutes and then rapidly converted it to lyso-PAF extracellularly. Under control conditions no acetylhydrolase activity was released from cells into the buffer. Acetylhydrolase activity could, however, be released from cell surface into buffer by limited trypsinization, supporting its location on the outer cell membrane. The acetylhydrolase activity was different from phospholipase A2, since phosphatidylcholine was not a substrate for the enzyme. In summary our results show that both rat and human mesangial cells can generate and metabolize PAF. Acetylhydrolase for PAF is present intracellularly, but also and predominantly on the outer cell surface of cells. This ectoenzymatic acetylhydrolase activity may be important in the rapid inactivation of PAF presented to cells, thus protecting cells from deleterious effects of PAF.

scholarly journals β-catenin activation is not involved in sporadic parathyroid carcinomas and adenomas

2010 ◽  
Vol 17 (1) ◽  
pp. 1-6 ◽  
Author(s):  
F Cetani ◽  
E Pardi ◽  
C Banti ◽  
P Collecchi ◽  
P Viacava ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Signaling Pathway ◽  
Direct Sequencing ◽  
Distant Metastases ◽  
Outer Cell ◽  
Tumor Type ◽  
Nuclear Staining ◽  
Cytoplasmic Staining ◽  
Membrane Staining ◽  
Outer Cell Membrane

Aberrant accumulation of β-catenin has been found in various types of human tumors. The aim of this study was to evaluate whether Wnt/β-catenin signaling is activated in parathyroid carcinomas and adenomas. We studied 154 parathyroid tumors (18 carcinomas (13 with distant metastases), six atypical adenomas, and 130 adenomas). Three normal parathyroid tissues were used as control. Direct sequencing of exon 3 of the CTNNB1 gene showed absence of stabilizing mutations in all the tumors. Immunostaining of β-catenin was performed in all carcinomas and in 66 adenomas (including three atypical). Normal parathyroid showed a homogeneous distinct outer cell membrane staining in the majority of cells and no nuclear staining. A weak cytoplasmic staining was observed in one case. All tumors showed negative nuclear staining. With the exception of one carcinoma, which had a negative membrane staining, all other samples showed a membrane staining which was similar to that of the normal parathyroid. β-Catenin expression was heterogeneous with a range of positive cells between 5 and 80%, independently of tumor type. Our results suggest that the Wnt/β-catenin signaling pathway is not involved in the development of parathyroid carcinomas and adenomas.

scholarly journals Damage of lipopolysaccharides in outer cell membrane and production of ROS-mediated stress within bacteria makes nano zinc oxide a bactericidal agent

2014 ◽  
Vol 5 (7) ◽  
pp. 857-866 ◽  
Author(s):  
Prasun Patra ◽  
Shuvrodeb Roy ◽  
Sampad Sarkar ◽  
Shouvik Mitra ◽  
Saheli Pradhan ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Cell Membrane ◽  
Outer Cell ◽  
Nano Zinc Oxide ◽  
Outer Cell Membrane ◽  
Nano Zinc ◽  
Bactericidal Agent

Vasoconstrictor-evoked prostaglandin synthesis in cultured human mesangial cells

1985 ◽  
Vol 248 (2) ◽  
pp. F240-F246 ◽  
Author(s):  
N. Ardaillou ◽  
J. Hagege ◽  
M. P. Nivez ◽  
R. Ardaillou ◽  
D. Schlondorff
Keyword(s):  
Arginine Vasopressin ◽  
Mesangial Cells ◽  
Platelet Activating Factor ◽  
Feedback Mechanism ◽  
Ang Ii ◽  
Glomerular Mesangial Cells ◽  
Human Mesangial Cells ◽  
Cell Contractility ◽  
Human Glomerular Mesangial Cells ◽  
Cells Cultured

We examined the influence of angiotensin II (ANG II), arginine vasopressin (AVP), and platelet activating factor (PAF) on prostaglandin (PG) synthesis and cell contractility in human glomerular mesangial cells in culture. Addition of sodium butyrate to the culture medium for 40 h significantly increased synthesis of both 6-keto-PGF1 alpha and PGE2 in the presence of exogenous arachidonic acid and of PGE2 under basal conditions. To optimize conditions in all further experiments, cells cultured with butyrate were studied. Under basal conditions, cultured mesangial cells produced predominantly 6-keto-PGF1 alpha and much less PGE2. Addition of either ANG II, AVP, or PAF all resulted in a rapid (within minutes) two- to threefold stimulation of 6-keto-PGF1 alpha and PGE2. Threshold stimulations were obtained at 10 pM for ANG II, 1 nM for AVP, and 10-100 pM for PAF. Preincubation of the cells with [Sar1,Ala8]ANG II, an antagonist of ANG II, inhibited ANG II-enhanced PG production, and preincubation with 1-desamino-8-D-arginine vasopressin, an antidiuretic analogue, blunted AVP-enhanced PG production. Under phase-contrast microscopy, PAF, ANG II, and, to a lesser degree, AVP caused decrease in cell surface area of mesangial cells cultured without butyrate at concentrations similar to those stimulating PG synthesis. Only PAF contracted cells cultured with butyrate, indicating attenuation of the vasoactive effects of ANG II and AVP when synthesis of PG was increased. However, a lower dose of PAF was only active when PG synthesis was inhibited, suggesting the same feedback mechanism for the three agonists.

The Electrical Potential Difference Across the Epithelium of Isolated Gills of the Crayfish Austropotamobius Pallipes (Lereboullet)

1965 ◽  
Vol 42 (3) ◽  
pp. 463-474
Author(s):  
P. C. CROGHAN ◽  
R. A. CURRA ◽  
A. P. M. LOCKWOOD
Keyword(s):  
Epithelial Cells ◽  
Cell Membrane ◽  
Body Fluid ◽  
External Medium ◽  
Electrical Potential ◽  
Ringer Solution ◽  
Outer Cell ◽  
Electrical Potential Difference ◽  
Austropotamobius Pallipes ◽  
Outer Cell Membrane

1. A technique is described for recording the electrical potential differences across the epitheium (epithelial potential) of isolated podobranch gills of Austropotamobius pallipes continuously perfused with Ringer solution in various external media. 2. In a medium of 0.01 Ringer, in which the animals had previously been kept, the mean epithelial potential ± standard deviation was -60 ± 12 mV. (Sign defines potential of body fluid with respect to external medium.) Chloride, sodium and potassium must be actively transported into the body fluid against an electrochemical gradient. Calcium and magnesium ions appear to be approximately in equilibrium. 3. The steady-state membrane potentials were recorded in various external concentrations of Ringer solution. The potential is about zero with Ringer solution outside and rises to a maximum with 0.01 Ringer outside. 4. Changes of the electrical potential were recorded when the concentration of a single electrogenic ion was changed in the external medium (0.01 Ringer), and were used to define an apparent transport number of the ion in the outer cell membrane. 5. There was no correlation between the transport numbers and the epithelial potential. 6. There was a continuous gradation of gill types from a predominantly cationpermeable type towards a more chloride permeable type. There is a correlation between the type of gill and the position in the gill series. 7. The properties of the epithelial cells of Austropotamobius gill are significantly different from those of the epithelial cells of frog skin. It is suggested that in Austropotamobius a chloride pump is situated in the outer cell membrane.

The feeding site and probable feeding mechanism of the parasitic nematode Capillaria hepatica (Bancroft, 1893)

1974 ◽  
Vol 52 (10) ◽  
pp. 1215-1220 ◽  
Author(s):  
K. A. Wright
Keyword(s):  
Cell Membrane ◽  
Light And Electron Microscopy ◽  
Circulatory System ◽  
Outer Cell ◽  
Feeding Site ◽  
Capillaria Hepatica ◽  
Parenchymal Liver ◽  
Outer Cell Membrane ◽  
Tissue Fluids ◽  
Nucleolar Components

Examination by light and electron microscopy of the tissue surrounding the anterior end of the trichuroid nematode Capillaria hepatica in the liver of its mouse host indicates that the nematode is enclosed by multinucleate cytoplasmic masses originating from parenchymal liver cells. These cytoplasmic masses have desmosomal contacts with adjacent cells. Nuclei often have an irregularly expanded nuclear envelope, greatly increased amounts of heterochromatin or increases in interchromatinic and perichromatinic granules, and segregated nucleolar components. Mitochondria are swollen and endoplasmic reticulum is swollen or vesiculated to varying degrees. The outer cell membrane of the cytoplasmic masses is thrown into extensive irregular folds, but on the surface next to the nematode, no cell membrane can be found. As the nematode's intestinal contents include remnants of cellular materials, it seems likely that the nematode feeds upon the cytoplasm surrounding its anterior region. Unsuccessful attempts to demonstrate the uptake of trypan blue, colloidal gold, or ferritin injected into the host's circulatory system further suggest that this nematode feeds from the induced host reaction rather than from blood or tissue fluids.

Extracellular release of protease III (ptr) by Escherichia coli K12

1991 ◽  
Vol 37 (9) ◽  
pp. 718-721 ◽  
Author(s):  
María R. Díaz-Torres ◽  
Christine C. Dykstra ◽  
Félix Claverie-Martín ◽  
Sidney R. Kushner
Keyword(s):  
Escherichia Coli ◽  
Cell Membrane ◽  
Growth Medium ◽  
Signal Sequence ◽  
Secretion System ◽  
Outer Cell ◽  
Cell Fractionation ◽  
Extracellular Release ◽  
Outer Cell Membrane ◽  
Key Words Protein Secretion

Escherichia coli strains carrying the protease III structural gene (ptr) on a plasmid secreted the protein into the growth medium. Plasmid-encoded β-lactamase and chloramphenicol acetyl transferase, which served as periplasmic and cytoplasmic markers during cell fractionation, were not released into the growth medium. There appeared to be some strain dependence on the proficiency of the secretion system. Protease III was not detectably processed upon export through the outer cell membrane. Key words: protein secretion, protease III, Escherichia coli, signal sequence, growth medium.

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