Platelet Thromboxane Receptors: Biology and Function

1999 ◽  
pp. 38-79
Author(s):  
Gerhard J. Johnson
Keyword(s):  
Thromboxane Receptors ◽  
And Function ◽  
Platelet Thromboxane

Platelet Thromboxane A2Receptor Number and Function in Normal and Hypertensive Pregnancy

1993 ◽  
Vol 30 (2-3) ◽  
pp. 160-166 ◽  
Author(s):  
GIAN CARLO DI RENZO ◽  
GIULIANA COATA ◽  
SERENA DE FRANCESCHI ◽  
ELISABETTA CHIARADIA ◽  
ATTILA KETT ◽  
...  
Keyword(s):  
Hypertensive Pregnancy ◽  
And Function ◽  
Platelet Thromboxane

The effect of pregnancy on the response to the TxA2/PGH2 analogue U-46619 in rabbits

1993 ◽  
Vol 265 (4) ◽  
pp. R772-R780 ◽  
Author(s):  
G. Losonczy ◽  
I. Mucha ◽  
J. DiPirro ◽  
J. Sweeney ◽  
G. Brown ◽  
...  
Keyword(s):  
Body Weight ◽  
Arterial Pressure ◽  
Intravenous Injection ◽  
Superior Vena ◽  
Vena Cava ◽  
Thromboxane Receptors ◽  
Induced Aggregation ◽  
Aggregation Of Platelets ◽  
Platelet Thromboxane

We compared the hemodynamic actions of U-46619, a stable thromboxane A2 (TxA2) prostaglandin H2 (PGH2) analogue, in nonpregnant (NP) rabbits with those observed in late pregnant (P) rabbits. An intravenous injection of U-46619 (10 micrograms) to each of eight NP chronically instrumented rabbits (mean body weight 3.4 kg) induced an immediate (1 min) and reversible fall of cardiac output (CO, 66%) and mean arterial pressure (MAP, 41%, both P < 0.01). P rabbits (n = 6, mean body weight 3.8 kg), however, responded with an elevation of MAP (5%, P < 0.02) upon intravenous injection of the drug (10 micrograms), while CO remained unchanged. The fall of CO in NP rabbits was associated with the temporary disappearance of a fraction of circulating platelets between the superior vena cava and the aortic arch. The number of platelets at 30 and 60 s after U-46619 was reduced (P < 0.05) by 14 and 20% respectively in the aortic blood, whereas caval platelet counts were unchanged until 90 s (-6%, P < 0.05). In contrast, intraaortic administration of this drug (10 micrograms) to NP rabbits resulted in neither thrombocytopenia nor hypotension. U-46619 (10-30 micrograms i.v.) caused no decrease in platelet count in the aorta of P rabbits. In vitro, U-46619-induced aggregation of platelets harvested from P rabbits was also blunted (P < 0.001). This could not be attributed to reduced affinity or number of platelet thromboxane receptors. The data indicate that U-46619 induces a fall of arterial pressure simultaneous with intravascular platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Characterization of prostaglandin and thromboxane receptors expressed on a megakaryoblastic leukemia cell line, MEG-01s

Blood ◽  
1991 ◽  
Vol 78 (9) ◽  
pp. 2328-2336 ◽  
Author(s):  
T Watanabe ◽  
Y Yatomi ◽  
S Sunaga ◽  
I Miki ◽  
A Ishii ◽  
...  
Keyword(s):  
Cell Line ◽  
Binding Sites ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Camp Production ◽  
Megakaryoblastic Leukemia ◽  
Ic50 Values ◽  
Thromboxane Receptors ◽  
And Function

MEG-01s, an established human megakaryoblastic leukemia cell line, exhibited specific high-affinity binding sites for [3H]iloprost, a stable prostaglandin (PG) I2 analogue, for [3H]SQ-29548, a stable thromboxane (TX) A2 antagonist and, for [3H]PGE2/PGE1, but not for [3H]PGD2. In the MEG-01s cells, iloprost/PGI2, or PGE1 stimulated cAMP production with ED50 values practically identical to the IC50 values for the [3H] iloprost binding. STA2 and U46619, TXA2/PGH2 agonists, PGE2/PGE1, iloprost/PGI2, and thrombin elevated the intracellular concentrations of Ca2+ ([Ca2+]i), as determined by Fura-2 fluorescence signals. Elevation of [Ca2+]i by PGE2/PGE1 and iloprost, but not that by TX-agonists or thrombin, was totally dependent on the presence of extracellular Ca2+. This effect by PGE2/PGE1 was partially inhibited by prior treatment of the cells with islet-activating protein (IAP), while that by TX-agonists or by PGI2/iloprost was not affected. We tentatively conclude from these results that: (1) MEG-01s cells express (a) PGI2/PGE1 receptor(s) coupled to adenylate cyclase and Ca2+ influx, a TXA2/PGH2 receptor coupled to the phosphatidylinositol-turnover-Ca2+ system, and the PGE2/PGE1 receptor coupled to Ca2+ influx; (2) the receptors for TXA2/PGH2 and iloprost and those for PGE2/PGE1 and thrombin are coupled to IAP-insensitive and IAP-sensitive GTP-binding proteins, respectively, and function in a different manner to elevate [Ca2+]i. Thus, the MEG-01s cell line is a pertinent model for studying eicosanoid receptor-mediated signal transduction in platelet/megakaryocyte systems.

scholarly journals Characterization of prostaglandin and thromboxane receptors expressed on a megakaryoblastic leukemia cell line, MEG-01s

Blood ◽  
1991 ◽  
Vol 78 (9) ◽  
pp. 2328-2336 ◽  
Author(s):  
T Watanabe ◽  
Y Yatomi ◽  
S Sunaga ◽  
I Miki ◽  
A Ishii ◽  
...  
Keyword(s):  
Cell Line ◽  
Binding Sites ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Camp Production ◽  
Megakaryoblastic Leukemia ◽  
Ic50 Values ◽  
Thromboxane Receptors ◽  
And Function

Abstract MEG-01s, an established human megakaryoblastic leukemia cell line, exhibited specific high-affinity binding sites for [3H]iloprost, a stable prostaglandin (PG) I2 analogue, for [3H]SQ-29548, a stable thromboxane (TX) A2 antagonist and, for [3H]PGE2/PGE1, but not for [3H]PGD2. In the MEG-01s cells, iloprost/PGI2, or PGE1 stimulated cAMP production with ED50 values practically identical to the IC50 values for the [3H] iloprost binding. STA2 and U46619, TXA2/PGH2 agonists, PGE2/PGE1, iloprost/PGI2, and thrombin elevated the intracellular concentrations of Ca2+ ([Ca2+]i), as determined by Fura-2 fluorescence signals. Elevation of [Ca2+]i by PGE2/PGE1 and iloprost, but not that by TX-agonists or thrombin, was totally dependent on the presence of extracellular Ca2+. This effect by PGE2/PGE1 was partially inhibited by prior treatment of the cells with islet-activating protein (IAP), while that by TX-agonists or by PGI2/iloprost was not affected. We tentatively conclude from these results that: (1) MEG-01s cells express (a) PGI2/PGE1 receptor(s) coupled to adenylate cyclase and Ca2+ influx, a TXA2/PGH2 receptor coupled to the phosphatidylinositol-turnover-Ca2+ system, and the PGE2/PGE1 receptor coupled to Ca2+ influx; (2) the receptors for TXA2/PGH2 and iloprost and those for PGE2/PGE1 and thrombin are coupled to IAP-insensitive and IAP-sensitive GTP-binding proteins, respectively, and function in a different manner to elevate [Ca2+]i. Thus, the MEG-01s cell line is a pertinent model for studying eicosanoid receptor-mediated signal transduction in platelet/megakaryocyte systems.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

The Effect of Oxidized Cholesterol on the Aorta of Rabbits- Scanning Electron Microscopic Observations

1982 ◽  
Vol 40 ◽  
pp. 340-341
Author(s):  
S. K. Pena ◽  
C. B. Taylor ◽  
J. Hill ◽  
J. Safarik
Keyword(s):  
Cholesterol Biosynthesis ◽  
Cholesterol Content ◽  
Arterial Injury ◽  
Electron Microscopic ◽  
Aortic Smooth Muscle ◽  
Oxidized Cholesterol ◽  
Initial Event ◽  
Membrane Structure And Function ◽  
Scanning Electron Microscopic ◽  
And Function

Introduction: Oxidized cholesterol derivatives have been demonstrated in various cell cultures to be very potent inhibitors of 3-hvdroxy-3- methylglutaryl Coenzyme A reductase which is a principle regulator of cholesterol biosynthesis in the cell. The cholesterol content in the cells exposed to oxidized cholesterol was found to be markedly decreased. In aortic smooth muscle cells, the potency of this effect was closely related to the cytotoxicity of each derivative. Furthermore, due to the similarity of their molecular structure to that of cholesterol, these oxidized cholesterol derivatives might insert themselves into the cell membrane, alter membrane structure and function and eventually cause cell death. Arterial injury has been shown to be the initial event of atherosclerosis.

Ultrastructure of developing visual cortical synapses in the cat superior colliculus

1991 ◽  
Vol 49 ◽  
pp. 156-157
Author(s):  
Caroline A. Miller ◽  
Laura L. Bruce
Keyword(s):  
Superior Colliculus ◽  
Phosphate Buffer ◽  
Receptive Fields ◽  
Visual Cortical Area ◽  
Cortical Synapses ◽  
Visual Cortical ◽  
And Function ◽  
Phosphate Buffered Saline ◽  
The Brain ◽  
Cat Superior Colliculus

The first visual cortical axons arrive in the cat superior colliculus by the time of birth. Adultlike receptive fields develop slowly over several weeks following birth. The developing cortical axons go through a sequence of changes before acquiring their adultlike morphology and function. To determine how these axons interact with neurons in the colliculus, cortico-collicular axons were labeled with biocytin (an anterograde neuronal tracer) and studied with electron microscopy.Deeply anesthetized animals received 200-500 nl injections of biocytin (Sigma; 5% in phosphate buffer) in the lateral suprasylvian visual cortical area. After a 24 hr survival time, the animals were deeply anesthetized and perfused with 0.9% phosphate buffered saline followed by fixation with a solution of 1.25% glutaraldehyde and 1.0% paraformaldehyde in 0.1M phosphate buffer. The brain was sectioned transversely on a vibratome at 50 μm. The tissue was processed immediately to visualize the biocytin.

Structural modifications of intercellular junctions.

1978 ◽  
Vol 36 (2) ◽  
pp. 330-331
Author(s):  
J. Metz ◽  
M. Merlo ◽  
W. G. Forssmann
Keyword(s):  
Gap Junctions ◽  
Intercellular Junctions ◽  
Cell Isolation ◽  
Extrahepatic Cholestasis ◽  
Structural Modifications ◽  
Pancreatic Duct Ligation ◽  
Pancreatic Cells ◽  
Duct Ligation ◽  
Thin Sectioning ◽  
And Function

Structure and function of intercellular junctions were studied under the electronmicroscope using conventional thin sectioning and freeze-etch replicas. Alterations of tight and gap junctions were analyzed 1. of exocrine pancreatic cells under cell isolation conditions and pancreatic duct ligation and 2. of hepatocytes during extrahepatic cholestasis.During the different steps of cell isolation of exocrine pancreatic cells, gradual changes of tight and gap junctions were observed. Tight junctions, which formed belt-like structures around the apex of control acinar cells in situ, subsequently diminished, became interrupted and were concentrated into macular areas (Fig. 1). Aggregations of membrane associated particles, which looked similar to gap junctions, were intermixed within tight junctional areas (Fig. 1). These structures continously disappeared in the last stages of the isolation procedure. The intercellular junctions were finally separated without destroying the integrity of the cell membrane, which was confirmed with porcion yellow, lanthanum chloride and horse radish peroxidase.

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