Dose-Response Aggregometry in Maternal/Neonatal Platelets

1988 ◽  
Vol 60 (02) ◽  
pp. 314-318 ◽  
Author(s):  
A M A Gader ◽  
H Bahakim ◽  
F A Jabbar ◽  
A L Lambourne ◽  
T H Gaafar ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Dose Response ◽  
Lag Phase ◽  
Phase Slope ◽  
Multiple Doses ◽  
Nonpregnant Adult ◽  
Aggregation Of Platelets

SummaryThe aggregation of platelets collected from maternal/neonatal pairs (n = 240) at the time of childbirth, was studied in response to multiple doses of ADP, collagen, arachidonic acid and ristocetin. Similar responses were obtained from healthy nonpregnant adult controls for comparison. The lag phase, slope of the aggregation curves as well as maximum aggregation (MA%) were recorded and analysed. Neonatal and adult platelets exhibited more enhanced responses to decreasing doses of ADP, arachidonic acid and ristocetin, than maternal platelets. These enhanced responses were exhibited more consistantly in the slopes of the aggregation curves than in MA%. Although neonatal platelets have shown longer lag phase in their responses to collagen, the rate of the aggregation reaction was significantly faster than maternal platelets, with no differences in MA%. These results contradict many previous reports suggesting impaired aggregation responses of neonatal platelets to these agonist. The possible reasons for these contradictions were discussed.

Platelet Aggregation By Membrane Glycoprotein I

1981 ◽  
Author(s):  
K Watanabe ◽  
M Yamamoto ◽  
Y Ando ◽  
H Iri ◽  
K Furihata ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Lag Phase ◽  
Affinity Column ◽  
Membrane Glycoprotein ◽  
Dependent Manner ◽  
Membrane Glycoproteins ◽  
Aggregation Mechanism ◽  
Membrane Components ◽  
Aggregation Of Platelets

It has been recently shown that platelet membrane components, particularly glycoproteins, have a lectin activity, thus mediating an aggregation of platelets. To obtain further evidences for a crucial role of glycoproteins in an aggregation mechanism,we have investigated the possibility that membrane glycoprotein can directly induce an aggregation of platelets. The membrane glycoproteins ( GP I, GP II and GP III ) were isolated from 3-4 mg of human platelet membranes using preparative electrophoresis on 5 % polyacrylamide gels with 0.1% SDS. Platelet aggregation by isolated GP I, GP II or GP III was examined under phase_contrast microscopy after the incubation of these peptides with platelet rich plasma at 37°C for 15 min.. Among glycoproteins tested, only GP I( 20 μg/ml < ) exerted an apparent platelet aggregation. No such aggregation was induced by either GP II or GP III even at concentration of 80 μg/ml. GP I isolated separately using the wheat germ agglutinin affinity column also produced a platelet aggregation. Aggregation curve recorded with an aggregometer showed a long lag phase ( 10 min. < ) followed by an irreversible aggregation. The GP I-induced platelet aggregation occured in a dose dependent manner. This aggregation was completely inhibited by the addition of aggregating inhibitors such as indomethacin ( 25 μM ), PGE1 ( 1 μM ), EDTA ( 0.5 mM ) and TMB-8 ( lmg/ml ). A significant amount of serotonin ( 27% ) and β-thromboglobulin ( 14.6% ) was released from platelets by GP I ( 100 μg/ml ). Treatment of GP I with either trypsin ( 50 μg/ml ) or chymotrypsin ( 40 μg/ml ) reduced the aggregating activity of this glycopeptides. The platelet aggregation by GP I was inhibited in the presense of 30 mM N-acetylneuraminic acid, arginin or L-lysine, but N-acetyl- ated amino sugars and neutral sugars were without effect. This GP I-induced platelet aggregation may be an important findings in elucidating platelet aggregation mechanism.

scholarly journals Bacterial lipopolysaccharides prime macrophages for enhanced release of arachidonic acid metabolites.

1986 ◽  
Vol 164 (1) ◽  
pp. 165-179 ◽  
Author(s):  
A A Aderem ◽  
D S Cohen ◽  
S D Wright ◽  
Z A Cohn
Keyword(s):  
Arachidonic Acid ◽  
Peritoneal Macrophages ◽  
Lag Phase ◽  
Maximal Concentration ◽  
Latex Beads ◽  
Primed State ◽  
Acid Metabolites ◽  
Bacterial Lipopolysaccharides ◽  
Time Required ◽  
Kinetics Of

Preincubation of resident peritoneal macrophages with 10-100 ng/ml LPS for 60 min resulted in the cells becoming primed for enhanced (three-to eightfold higher) arachidonic acid (20:4) secretion in response to a variety of triggers. The half-maximal concentration of LPS required for priming was 10 ng/ml irrespective of whether the trigger was particulate (examples: zymosan or immune complexes) or soluble (such as PMA or A23187). Similarly, the time required for half-maximal priming of macrophages was 20 min irrespective of which trigger was used. The primed state persisted for at least 30 h. LPS-priming of macrophages also affected the kinetics of 20:4 metabolite secretion. The lag phase characteristically observed when 20:4 secretion is triggered was reduced in LPS-primed cells. Furthermore, LPS-primed cells secreted 20:4 metabolites when challenged with latex beads, while unprimed cells did not. These data suggest that stimuli such as zymosan, which elicit 20:4 secretion in macrophages, promote two signals, a priming signal and a triggering signal. LPS is capable of establishing the priming signal but not the triggering signal, while latex promotes the triggering signal but is unable to prime the cells for 20:4 release. LPS did not effect the profile of 20:4 metabolites secreted in response to any of the triggers, nor did it effect the profile of products synthesized from exogenously added 20:4, suggesting that it did not regulate the 20:4 cascade at the level of either the cyclooxygenase or lipoxygenase pathways. Macrophages respond to LPS without the intervention of T lymphocytes, since the macrophages from nude mice could be primed for enhanced 20:4 secretion.

Antioxidant Behaviour of Thia Fatty Acids

2002 ◽  
Vol 55 (10) ◽  
pp. 647 ◽  
Author(s):  
C. J. Easton ◽  
A. Ferrante ◽  
T. A. Robertson ◽  
L. Xia
Keyword(s):  
Fatty Acids ◽  
Antioxidant Activity ◽  
Arachidonic Acid ◽  
Oxidation Process ◽  
Free Radical Oxidation ◽  
Lag Phase ◽  
Carboxyl Group ◽  
Radical Oxidation ◽  
Fatty Acid Hydroperoxides ◽  
Thia Fatty Acids

Eight thia fatty acids and other sulfides have been studied as inhibitors of autoxidation of arachidonic acid. The inhibitors extend the lag phase of the oxidation, to varying degrees. A carboxyl group in the vicinity of the sulfur reduces the antioxidant activity, while unsaturated sulfides are more effective than their saturated analogues. The results are consistent with the sulfides acting to reduce fatty acid hydroperoxides, which otherwise accumulate during the early stages of reaction and propagate the free-radical oxidation process.

Specific Desensitization Of Washed Rabbit Platelets By Paf-Acether And Derivatives

1981 ◽  
Author(s):  
C Lalau Keraly ◽  
M Tencé ◽  
F Heymans ◽  
J Benveniste
Keyword(s):  
Arachidonic Acid ◽  
Alkyl Chain ◽  
Synthetic Analog ◽  
Synthetic Compounds ◽  
Glycerol Moiety ◽  
Rabbit Platelets ◽  
Acetyl Group ◽  
Induced Aggregation ◽  
Aggregation Of Platelets ◽  
Very High

PAF-acether-aggregated rabbit platelets did not respond to a second challenge with the same agonist after their spontaneous disaggregation, but still aggregated in the presence of arachidonic acid (AA). When using 1 nM of PAF-acether in the first stimulation, aggregation in response to a second challenge with the same dose was nil. However, when 0.34 nM was used in the first step, aggregation in response to 0.64 nM PAF-acether was 59 96, as compared to control platelets. By contrast, aggregation of platelets pretreated with 1 nM PAF-acether was 72 % in the presence of 2.8 uM AA. Adding fibrinogen (0.34 mg/ml) before the second stimulation did not modify the desensitization pehnom- enon. Supernatants from platelets desensitized with 1 nM PAF- acether exhibited neither aggregating nor inhibitory activity. PAF-acether-induced desensitization could always be overcome, since aspirin-pretreated platelets first stimulated with 10 nM PAF-acether still aggregated with 100 nM of the same agonist, i.e. when using 100 times the amount which induced maximal aggregation. All our experiments were performed in the presence of ADP scavengers and, except for AA-induced aggregation, aspirin. We tested PAF-acether from 4 different cell origins and the semi-synthetic and synthetic compounds. Platelets were cross- desensitized towards PAF-acether from any source. Totally synthetic PAF-acether bearing aC,, alkyl chain at position 1 of the glycerol moiety desensitized platelets as well as the C.g synthetic analog. Lyso-PAF-acether (i.e. a compound lackifig tne acetyl group at the position 2 of the glycerol) (0.5-10.0 nM) and PAF-acether enantiomer (0.5-5.0 nM) neither aggregated nor desensitized platelets to PAF-acether. These results indicate that 1) PAF-acether from any source exhibit at least an identical active molecular site ; 2) the presence and the stereospecific position of the 2-acetyl group are critical for the interaction of PAF-acether with platelets, a result which could indicate the existence of a platelet acceptor (receptor) for PAF-acether. However, these postulated platelet membrane acceptors were never saturated even using very high amounts of the agonist.

Effect of pyridoxal-5'-phosphate on aggregation of platelets from stored human concentrates induced by arachidonic acid

1996 ◽  
Vol 24 (1) ◽  
pp. 95S-95S
Author(s):  
Marie-Louise Nolan ◽  
Michael G. Harrington ◽  
Ashur Eljamil
Keyword(s):  
Arachidonic Acid ◽  
Aggregation Of Platelets

In vitro bioassay for human chorionic gonadotrophin

1980 ◽  
Vol 93 (1) ◽  
pp. 114-122 ◽  
Author(s):  
T. Rabe ◽  
U. Hilgenfeldt ◽  
W. E. Merz
Keyword(s):  
Dose Response ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Lag Phase ◽  
In Vitro Tests ◽  
Intracellular Camp ◽  
In Vitro Bioassay ◽  
Assay Sensitivity ◽  
Inter Assay Variation

Abstract. The adenylate cyclase stimulation (ACS) assay is a new in vitro bioassay for human chorionic gonadotrophin (hCG) which is based on the hCG-induced accumulation of cAMP in the incubation medium of decapsulated rat testes. The detection limit for hCG is 0.7 mIU/ml (P < 0.05). A linear dose-response curve on semilogarithmic plots was obtained using 0.18, 0.45, and 1.125 IU hCG/ml. The precision of the ACS assay was satisfactory (λ-value: 0.20 + 0.02, mean ± sd), n = 14). Intra-assay variation: 15% and inter-assay variation: 20%. Medium cAMP was determined by means of a bovine adrenal protein binding assay. Sensitivity: 0.2 pmoles cAMP/ml. Range: 2 to 40 pmoles/ml. Intra-assay variations: 5% and inter-assay variation: 8%. As pre-conditions for the ACS assay, cAMP kinetics and dose-response curves were investigated. In kinetic studies of cAMP production the lag phase between hormone addition and increase of medium cAMP is shortened with higher hCG concentration. The highest concentration of cAMP was measured after an incubation of 3 h. Thereafter the concentration declines exponentially due to a decrease of intracellular cAMP formation and pre-dominating activity of extracellular phosphodiesterase. A prolongation of cAMP half-life from 16.8 min to 218 min was obtained by the addition of theophylline (70 mm). Pre-treatment of rats with 50 IU sc 48 and 24 h prior to in vitro tests caused a complete inhibition of cAMP response to hCG stimulation. Four weeks after this desensitization, the sensitivity of the testes had recovered to 80%.

Platelet Aggregation Induced by a Synthetase-Like Substance and Phospholipase-A.

1975 ◽  
Author(s):  
S. G. Iatridis ◽  
P. G. Iatridis ◽  
S. G. Markidou ◽  
B. H. Ragatz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Adenosine Diphosphate ◽  
Phospholipase A ◽  
Second Phase ◽  
Inhibit Platelet Aggregation ◽  
Phase Type ◽  
Irreversible Aggregation ◽  
Cyclic Endoperoxide ◽  
Aggregation Of Platelets

Platelets contain arachidonic acid-bearing phospholipids and phospholipase-A (Phl-A); it has been suggested that exposure of these substances to each other by stimuli, such as thrombin or adenosine diphosphate (ADP), would result in liberation of arachidonic acid (AA), which is the precursor of cyclic endoperoxide; a factor causing irreversible aggregation of platelets.By using a saline eluate of a polyurethane (SPU, -polyester elastomer of the thermoplastic type-, secured by exposing saline for two minutes to the inner surface of a polyurethane bag) we observed that platelet (human PRP) aggregation (second phase type, irreversible) could be induced by Phl-A plus SPU or AA plus SPU. These mixtures failed to aggregate aspirinized platelets. Aspirin, however, incubated for 10 minutes with SPU, Phl-A or AA did not inhibit platelet aggregation induced by the addition of the missing factor. In control experiments no aggregation was produced by SPU-saline, saline-Phl-A or saline-AA. SPU plus suboptimal concentrations of ADP or epinephrine induced an immediate in onset aggregation. Phl-A added in reversibly, by ADP, aggregated platelets produced a second phase of aggregation.The results show that AA which is the precursor of cyclic endoperoxide could be liberated by Phl-A. The results also provide evidence that at least two enzymes (synthetase-α and synthetase-β; α is inactive whereas β is active and can be blocked by apsirin) are involved in the process of AA activation and biosynthesis of cyclic endoperoxide.Supported by a grant from the U.S. Public Servie HL-15425.

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