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1
Teng, Che-Ming, Ya-Fei Kang, Ya-Ling Chang, Feng-Nien Ko, Shu-Chen Yang, and Feng-Lin Hsu. "ADP-mimicking Platelet Aggregation Caused by Rugosin E, an Ellagitannin Isolated from Rosa rugosa Thunb." Thrombosis and Haemostasis 77, no. 03 (1997): 555–61. http://dx.doi.org/10.1055/s-0038-1656005.
Анотація:
SummaryAmong the nine ellagitannins, rugosin E was the most potent platelet aggregating agent with an EC50 of 1.5 ± 0.1 µM in rabbit platelets and 3.2 ±0.1 µM in human platelets. The aggregations caused by rugosin E and ADP were inhibited by EGTA, PGE1, mepacrine, sodium nitroprusside and neomycin, but not by indomethacin, verapamil, TMB-8, BN52021 and GR32191B. Rugosin E-induced thromboxane formation was suppressed by indomethacin, EGTA, PGE,, verapamil, mepacrine, TMB-8 and neomycin. ADP-scavenging agents, such as CP/CPK and apyrase inhibited concentration-dependently ADP (20 εM)-, but not rugosin E (5 εM)-induced platelet aggregation. In thrombin (0.1 U/ml)-treated and degranulated platelets, rugosin E and ADP still caused 63.5 ± 3.0% and 61.2 ± 3.5% of platelet aggregation, respectively. Selective ADP receptor antagonists, ATP and FSBA inhibited rugosin E- and ADP-induced platelet aggregations in a concentration-dependent manner. Both rugosin E and ADP did not induce platelet aggregation in ADP (1 mM)-desensitized platelets. In contrast to ADP, rugosin E did not decrease cAMP formation in washed rabbit platelets. Both rugosin E and ADP did not cause phosphoinositide breakdown in [3H]myo-inositol-labeled rabbit platelets. In fura-2/AM- load platelets, both rugosin E and ADP induced increase in intracellular calcium concentration and these responses were inhibited by ATP and PGEj. All these data suggest that rugosin E may be an ADP receptor agonist in rabbit platelets.
2
Sugiyama, T., M. Okuma, F. Ushikubi, S. Sensaki, K. Kanaji, and H. Uchino. "A novel platelet aggregating factor found in a patient with defective collagen-induced platelet aggregation and autoimmune thrombocytopenia." Blood 69, no. 6 (June 1, 1987): 1712–20. http://dx.doi.org/10.1182/blood.v69.6.1712.1712.
Анотація:
Abstract We found a novel platelet aggregating factor in a patient with steroid- responsive immune thrombocytopenic purpura that is associated with defective collagen-induced platelet functions. The aggregating factor and platelet functions were analyzed. The patient, a 58-year-old female, had purpura and prolonged bleeding time despite adequate platelet counts (greater than 140,000/microL) after steroid therapy. The patient's platelets responded normally to all agonists except collagen. Platelet adhesion to collagen fibrils was decreased. The patient's plasma induced irreversible aggregation and ATP release in normal platelet-rich plasma (PRP). This platelet aggregating factor was found in F(ab')2 fragments of the patient's IgG, which caused thromboxane B2 synthesis, elevation of cytoplasmic Ca2+ levels, and phosphorylation of 40 kDa protein in normal platelets. Platelet aggregation by the patient's IgG was inhibited by prostacyclin, dibutyryl cAMP, diltiazem, disodium ethylenediaminetetraacetate, and antimycin A plus iodoacetate, but ADP scavengers, cyclo-oxygenase inhibitors, and heparin had little or no effect. The aggregating activity of the patient's IgG absorbed to and eluted from normal platelets. The patient's Fab fragments did not induce platelet aggregation in eight of ten normal PRP but specifically inhibited aggregation induced by collagen and by the patient's IgG. The major component of an immunoprecipitate made with the patient's IgG from radiolabeled membrane proteins of normal platelet extract had a 62 kDa mol wt, while no such precipitate appeared in extracts of the patient's platelets. These results indicated that platelet aggregation by the patient's IgG was induced by the reaction of an antibody with a specific antigen on the normal platelet membrane through stimulus- response coupling. This antigen may be a collagen receptor on the platelet, most likely a polypeptide of 62 kDa under reducing condition. The defect of collagen-induced aggregation of the patient's platelets seemed to be due to alteration of the membrane protein related to this putative collagen receptor.
3
Sugiyama, T., M. Okuma, F. Ushikubi, S. Sensaki, K. Kanaji, and H. Uchino. "A novel platelet aggregating factor found in a patient with defective collagen-induced platelet aggregation and autoimmune thrombocytopenia." Blood 69, no. 6 (June 1, 1987): 1712–20. http://dx.doi.org/10.1182/blood.v69.6.1712.bloodjournal6961712.
Анотація:
We found a novel platelet aggregating factor in a patient with steroid- responsive immune thrombocytopenic purpura that is associated with defective collagen-induced platelet functions. The aggregating factor and platelet functions were analyzed. The patient, a 58-year-old female, had purpura and prolonged bleeding time despite adequate platelet counts (greater than 140,000/microL) after steroid therapy. The patient's platelets responded normally to all agonists except collagen. Platelet adhesion to collagen fibrils was decreased. The patient's plasma induced irreversible aggregation and ATP release in normal platelet-rich plasma (PRP). This platelet aggregating factor was found in F(ab')2 fragments of the patient's IgG, which caused thromboxane B2 synthesis, elevation of cytoplasmic Ca2+ levels, and phosphorylation of 40 kDa protein in normal platelets. Platelet aggregation by the patient's IgG was inhibited by prostacyclin, dibutyryl cAMP, diltiazem, disodium ethylenediaminetetraacetate, and antimycin A plus iodoacetate, but ADP scavengers, cyclo-oxygenase inhibitors, and heparin had little or no effect. The aggregating activity of the patient's IgG absorbed to and eluted from normal platelets. The patient's Fab fragments did not induce platelet aggregation in eight of ten normal PRP but specifically inhibited aggregation induced by collagen and by the patient's IgG. The major component of an immunoprecipitate made with the patient's IgG from radiolabeled membrane proteins of normal platelet extract had a 62 kDa mol wt, while no such precipitate appeared in extracts of the patient's platelets. These results indicated that platelet aggregation by the patient's IgG was induced by the reaction of an antibody with a specific antigen on the normal platelet membrane through stimulus- response coupling. This antigen may be a collagen receptor on the platelet, most likely a polypeptide of 62 kDa under reducing condition. The defect of collagen-induced aggregation of the patient's platelets seemed to be due to alteration of the membrane protein related to this putative collagen receptor.
4
Kelton, JG, JC Moore, and WG Murphy. "Studies investigating platelet aggregation and release initiated by sera from patients with thrombotic thrombocytopenic purpura." Blood 69, no. 3 (March 1, 1987): 924–28. http://dx.doi.org/10.1182/blood.v69.3.924.924.
Анотація:
Abstract Many patients with thrombotic thrombocytopenic purpura (TTP) have a platelet aggregating factor in their serum that may be pathologically linked with the disease process. To help characterize the type of platelet aggregation and platelet release induced by the sera from seven TTP patients, we measured the ability of a variety of inhibitors of platelet function as well as the ability of monoclonal antibodies (MoAbs) against platelet glycoproteins to inhibit TTP sera-induced platelet aggregation and release. These results were compared with the ability of the same inhibitors to block platelet aggregation induced by ristocetin, collagen, ADP, thrombin, and IgG-immune complexes. Monoclonal antibody directed against platelet glycoprotein Ib totally inhibited ristocetin-induced aggregation and release but had no effect on aggregation and release induced by the TTP sera or by any of the other platelet agonists. However, the MoAb against glycoproteins IIb/IIIa inhibited aggregation and release caused by TTP sera as well as by collagen, thrombin, and ADP but had no effect on aggregation and release induced by ristocetin. The aggregating activity could be abolished by heparin but not by the serine protease inhibitor PMSF (1 mmol/L). And although monomeric human IgG and purified Fc fragments of IgG inhibited IgG-immune complex-induced aggregation and release, they had no effect on TTP sera-induced aggregation and release nor on aggregation and release induced by any of the other agonists. Consistent with these in vitro studies showing no effect of IgG were the in vivo observations that intravenous (IV) IgG was without effect when administered to three patients with TTP. This study indicates that although a von Willebrand factor (vWF)-rich preparation of cryoprecipitate enhances the in vitro platelet aggregation and release caused by sera from the seven TTP patients we studied, the pathway of aggregation and release is not via platelet glycoprotein Ib. Also the aggregating factor of TTP sera is not neutralized in vitro or in vivo by IgG.
5
Kelton, JG, JC Moore, and WG Murphy. "Studies investigating platelet aggregation and release initiated by sera from patients with thrombotic thrombocytopenic purpura." Blood 69, no. 3 (March 1, 1987): 924–28. http://dx.doi.org/10.1182/blood.v69.3.924.bloodjournal693924.
Анотація:
Many patients with thrombotic thrombocytopenic purpura (TTP) have a platelet aggregating factor in their serum that may be pathologically linked with the disease process. To help characterize the type of platelet aggregation and platelet release induced by the sera from seven TTP patients, we measured the ability of a variety of inhibitors of platelet function as well as the ability of monoclonal antibodies (MoAbs) against platelet glycoproteins to inhibit TTP sera-induced platelet aggregation and release. These results were compared with the ability of the same inhibitors to block platelet aggregation induced by ristocetin, collagen, ADP, thrombin, and IgG-immune complexes. Monoclonal antibody directed against platelet glycoprotein Ib totally inhibited ristocetin-induced aggregation and release but had no effect on aggregation and release induced by the TTP sera or by any of the other platelet agonists. However, the MoAb against glycoproteins IIb/IIIa inhibited aggregation and release caused by TTP sera as well as by collagen, thrombin, and ADP but had no effect on aggregation and release induced by ristocetin. The aggregating activity could be abolished by heparin but not by the serine protease inhibitor PMSF (1 mmol/L). And although monomeric human IgG and purified Fc fragments of IgG inhibited IgG-immune complex-induced aggregation and release, they had no effect on TTP sera-induced aggregation and release nor on aggregation and release induced by any of the other agonists. Consistent with these in vitro studies showing no effect of IgG were the in vivo observations that intravenous (IV) IgG was without effect when administered to three patients with TTP. This study indicates that although a von Willebrand factor (vWF)-rich preparation of cryoprecipitate enhances the in vitro platelet aggregation and release caused by sera from the seven TTP patients we studied, the pathway of aggregation and release is not via platelet glycoprotein Ib. Also the aggregating factor of TTP sera is not neutralized in vitro or in vivo by IgG.
6
Teng, Che-Ming, and Feng-Nien Ko. "Comparison of the Platelet Aggregation Induced by Three Thrombin-Like Enzymes of Snake Venoms and Thrombin." Thrombosis and Haemostasis 59, no. 02 (1988): 304–9. http://dx.doi.org/10.1055/s-0038-1642776.
Анотація:
SummaryPlatelet aggregation induced by three thrombin-like enzymes of snake venoms was compared with that by thrombin. Acutin was isolated from Agkistrodon acutus venom and thrombocytin and batroxobin were from Bothrops atrox venom. The fibrinogenclotting activities were 700,170 and 7 U/mg for batroxobin, acutin and thrombocytin, respectively. They induced aggregation and ATP release of washed rabbit platelets. The aggregating activity of thrombin was 102, 104 and 105 times more potent than those of thrombocytin, acutin and batroxobin, respectively. Plateletactivating potency of the thrombin-like enzymes was correlated with their effectiveness on the retractility and elasticity of the clots. Platelet aggregation induced by thrombin or thrombocytin could be inhibited by heparin with antithrombin III while that by acutin or batroxobin could not. Indomethacin showed weak inhibition on the aggregation while the ADP-scavenging system, creatine phosphate/creatine phosphokinase, inhibited the aggregation induced by the three thrombin-like enzymes but not that by thrombin. Platelet aggregation induced by the thrombin-like enzymes could not be inhibited by PAF antagonists-BN 52021, kadsurenone or L-652,731. In the presence of EGTA, only thrombin could induce ATP release from platelets. Thrombin-like enzymes and low concentration of thrombin did not form thromboxane B2. Nitroprusside and prostaglandin E1 completely inhibited the aggregation, mepacrine and imipramine showed marked inhibition while verapamil had only weak inhibition. It is concluded that the aggregation induced by the thrombin-like enzymes is different from that of thrombin and mainly due to ADP released from platelets.
7
YAGER, RONALD R. "CHOQUET AGGREGATION USING ORDER INDUCING VARIABLES." International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 12, no. 01 (February 2004): 69–88. http://dx.doi.org/10.1142/s0218488504002667.
Анотація:
We discuss the OWA and Choquet integral aggregation operators and point out the central role the ordering operation plays in these operators. We extend the capabilities of the Choquet integral aggregation by allowing the ordering to be induced by some values other then those being aggregated. This allows us to consider an induced Choquet Choquet integral aggregation operator. We look at the properties of this operator. We then look at its applications. Among the applications considered are aggregations guided by linguistic and other ordinal structures. We look at the use of induced aggregation in nearest neighbor methods. We also consider the Choquet aggregation of complex objects such as matrices and vectors.
8
Cimminiello, C., M. Milani, T. Uberti, G. Arpaia, and G. Bonfardeci. "Effects of Ticlopidine and Indobufen on Platelet Aggregation Induced by A23187 and Adrenaline in the Presence of Different Anticoagulants." Journal of International Medical Research 17, no. 6 (November 1989): 514–20. http://dx.doi.org/10.1177/030006058901700603.
Анотація:
As Ca2+ is known to play a fundamental role in platelet function, the effect of combining two platelet aggregating agents (adrenaline and the ionophore A23187) with different effects on Ca2+ was studied at levels subthreshold for aggregation using platelet-rich plasma from eight atherosclerotic patients. Adrenaline lowered the A23187 threshold required to induce aggregation. The effects of treating patients with the antiplatelet agents, indobufen and ticlopidine, on A23187 and adrenaline induced aggregation of platelets prepared in hirudin or sodium citrate was also evaluated. Aggregation was also studied using platelets resuspended in Ca2+-free and Ca2+-enriched Tyrode solution. Before treatment hirudin treated platelet-rich plasma, which has physiological extraplatelet Ca2+ levels, was more sensitive to A23187 and adrenaline than was citrated platelet-rich plasma, which has suppressed Ca2+ levels. Ticlopidine significantly raised the concentration of A23187 required to induce aggregation in citrated but not hirudin treated platelet-rich plasma. Indobufen did not significantly affect A23187 induced aggregation. Ticlopidine acts by inhibiting the glycoprotein IIb – IIIa complex on the platelet membranes. Low levels of extracellular Ca2+ and ticlopidine may act synergistically to reduce the aggregatory response of stimulated platelets.
9
Tang, B., Z. Zhao, Z. Wang, P. Lu, C. Chan, D. Liu, J. Lam, H. Sung, I. Williams, and Y. Ma. "Aggregation-Induced Emission." Synfacts 2009, no. 12 (November 20, 2009): 1345. http://dx.doi.org/10.1055/s-0029-1218183.
10
Yager, Ronald R. "Induced aggregation operators." Fuzzy Sets and Systems 137, no. 1 (July 2003): 59–69. http://dx.doi.org/10.1016/s0165-0114(02)00432-3.
11
Hong, Yuning, Jacky W. Y. Lam, and Ben Zhong Tang. "Aggregation-induced emission." Chemical Society Reviews 40, no. 11 (2011): 5361. http://dx.doi.org/10.1039/c1cs15113d.
12
Yamamoto, Kazuo, Hisayo Kitagawa, Kenjiro Tanoue, Takashi Tsuruo, Naomasa Yamamoto, and Hiroh Yamazaki. "Role of Heparin in Tumor Cell-Induced Platelet Aggregation." Thrombosis and Haemostasis 56, no. 01 (1986): 090–94. http://dx.doi.org/10.1055/s-0038-1661609.
Анотація:
SummaryB16 mouse melanoma cell lines (B16F1, B16F10 and B16BL6) were able to induce platelet aggregation, and concomitant release of ATP in heparinized platelet-rich plasma (PRP). In citrated PRP, these tumor cells did not induce platelet aggregation. Addition of heparin to citrated PRP enabled these tumor cells to induce aggregation. In heparinized PRP, platelet aggregates induced by B16F10 cells were dissociated by the addition of either 4 mM EDTA, 10 mM CaCl2 or 0.1 μg/ml protamine sulfate. B16F10-induced aggregation in heparinized PRP was inhibited by preincubation with anti-fibronectin antibody, but not with antifibrinogen or anti-von Willebrand factor antibodies. B16F10 cells induced aggregation in washed platelet suspension with the addition of heparinized platelet-poor plasma (PPP). Cryoprecipi-tate from human plasma showed the same effect in the presence of heparin if substituted for PPP. The mixture of purified fibronectin, von Willebrand factor, fibrinogen and heparin were less effective than cryoprecipitate on B16F10-induced aggregation of washed platelets. The results suggest that an interaction between fibronectin and heparin may be important in tumor cell-induced aggregation.
13
Huang, T. F., C. Z. Liu, and S. H. Yang. "Aggretin, a novel platelet-aggregation inducer from snake (Calloselasma rhodostoma) venom, activates phospholipase C by acting as a glycoprotein Ia/IIa agonist." Biochemical Journal 309, no. 3 (August 1, 1995): 1021–27. http://dx.doi.org/10.1042/bj3091021.
Анотація:
A potent platelet aggregation inducer, aggretin, was purified from Malayan-pit-viper (Calloselasma rhodostoma) venom by ionic-exchange chromatography, gel-filtration chromatography and HPLC. It is a heterodimeric protein (29 kDa) devoid of esterase, phospholipase A and thrombin-like activity. Aggretin (> 5 nM) elicited platelet aggregation with a lag period in both human platelet-rich plasma and washed platelet suspension. EDTA (5 mM), prostaglandin E1 (1 microM) and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (‘TMB-8’; 100 microM) abolished its aggregating activity, indicating that exogenous bivalent cations and intracellular Ca2+ mobilization are essential for aggretin-induced platelet aggregation. Neomycin (4 mM) and mepacrine (50 microM) completely inhibited aggretin (33 nM)-induced aggregation; however, creatine phosphate/creatine phosphokinase (5 mM, 5 units/ml) and indomethacin (50 microM) did not significantly affect its aggregating activity. Aggretin caused a significant increase of [3H]InsP formation in [3H]Ins-loaded platelets, intracellular Ca2+ mobilization and thromboxane B2 formation. Neomycin, a phospholipase C inhibitor, completely inhibited both the increase of [3H]InsP and intracellular Ca2+ mobilization of platelets stimulated by aggretin. A monoclonal antibody (6F1) directed against glycoprotein Ia/IIa inhibited platelet shape change and aggregation induced by aggretin. 125I-aggretin bound to platelets with a high affinity (Kd = 4.0 +/- 1.1 nM), and the number of binding sites was estimated to be 2119 +/- 203 per platelet. It is concluded that aggretin may act as a glycoprotein Ia/IIa agonist to elicit platelet aggregation through the activation of endogenous phospholipase C, leading to hydrolysis of phosphoinositides and subsequent intracellular Ca2+ mobilization.
14
Kariyazono, Hiroko, Kazuo Nakamura, Terutoshi Shinkawa, Yukinori Moriyama, Hitoshi Toyohira, Akira Taira, and Katsushi Yamada. "Inhibitory effects of antibiotics on platelet aggregation in vitro." Human & Experimental Toxicology 16, no. 11 (November 1997): 662–66. http://dx.doi.org/10.1177/096032719701601106.
Анотація:
1 We evaluated in vitro inhibitory effects of six types of antibiotic, aztreonam (AZT), cefamandole (CMD), cefmetazole (CMZ), cefotiam (CTM), flomoxef (FMOX) and latamoxef (LMOX), on platelet aggregation, using healthy volunteers' blood. Four types-FMOX, LMOX, CTM and CMD-inhibited, in concentration of 2500 ?g/ml, the secondary aggregation induced by 3.0 ?M adenosine diphosphate (ADP), and also inhibited the aggregation induced by 0.5 ?g/ml collagen. AZT in the same concentration, did not inhibit the aggregation induced by collagen, and it inhibited only ADP induced aggregation. CMZ, in the same concentration, inhibited neither of the two aggregations. 2 The inhibitory effects of the antibiotics on collagen- induced aggregation were dependent on the concen tration of respective antibiotics. When classified by the strength of inhibitory action, LMOX and FMOX were strong, followed by CTM and CMD. The action of AZT and CMZ was weak. In particular, LMOX showed a 32% inhibitory effect at concentration of 50 ?g/ml, a level near the blood concentration obtained with clinical usual dose. 3 No relationship was observed between inhibitory effects of antibiotics on ADP- or collagen-induced aggregation and the presence or absence of carboxyl group and/or N-methyltetrazolethiol group in the chemical structure.
15
Vigil, R. Dennis, Isaac Vermeersch, and Rodney O. Fox. "Destructive aggregation: Aggregation with collision-induced breakage." Journal of Colloid and Interface Science 302, no. 1 (October 2006): 149–58. http://dx.doi.org/10.1016/j.jcis.2006.05.066.
16
Khan, Javed Masood, Ajamaluddin Malik, Fohad Mabood Husain, Mohammed J. Hakeem та Abdullah S. Alhomida. "Sunset Yellow Dye Induces Amorphous Aggregation in β-Lactoglobulin at Acidic pH: A Multi-Techniques Approach". Polymers 14, № 3 (20 січня 2022): 395. http://dx.doi.org/10.3390/polym14030395.
Анотація:
Protein aggregation is of two types: (i) amorphous and (ii) amyloid fibril. Several extrinsic factors (temperature, pH, and small ligands) stimulate protein aggregation in vitro. In this study, we have examined the role of sunset yellow (SY) on the β-lactoglobulin (BLG) aggregation at pH 2.0. We have used spectroscopic (turbidity, Rayleigh light scattering (RLS), far-UV CD) and microscopic (transmission electron microscopy [TEM]) techniques to describe the effects of SY on BLG aggregation. Our results showed that BLG aggregation is dependent on SY concentrations. Very low concentrations (0.0–0.07 mM) of SY were unable to induce aggregation, while SY in the concentrations range of 0.1–5.0 mM induces aggregation in BLG. The kinetics of SY-stimulated aggregation is very fast and monomeric form of BLG directly converted into polymeric aggregates. The kinetics results also showed SY-induced BLG aggregation disappeared in the presence of NaCl. The far-UV CD and TEM results indicated the amorphous nature of SY-induced BLG aggregates. We believe that our results clearly suggest that SY dye effectively stimulates BLG aggregation.
17
Nakamura, K., H. Kariyazono, T. Shinkawal, T. Yamaguchi, T. Yamashita, O. Ayukawal, Y. Moriyama, et al. "Inhibitory effects of H2-receptor antagonists on platelet function in vitro." Human & Experimental Toxicology 18, no. 8 (August 1999): 487–92. http://dx.doi.org/10.1191/096032799678847069.
Анотація:
1 To evaluate in vitro inhibitory effects of four types of histamine H2-receptor antagonist (H2-receptor antagonists), famotidine, roxatidine, cimetidine and ranitidine, on platelet function, we examined aggregating potency and P-selectin levels with agonist-induced aggregation. Ranitidine and cimetidine inhibited, in concentration of 0.35 mM, the secondary aggregation induced by 5 pM adenosine diphosphate (ADP), the aggregation induced by 1,g/mL collagen and 3 gM arachidonic acid. All of H2-receptor antagonists inhibited, in concentration of 1.4 mm, the aggregation induced by ADP, collagen and arachidonic acid. Ranitidine and cimetidine reduced markedly, in same concentration, P-selectin levels after induction of aggregation by 5 gm ADP, 1 ig/xmL collagen and 3 gM arachidonic acid. When classified by the strength of inhibitory action, ranitidine and cimetidine were strong, followed by famotidine and roxatidine. 2 It is considered that inhibitory effects of H.-receptor antagonists on platelet function are weaker than those of acetylsalicylic acid (ASA), since ASA inhibited platelet aggregation in concentration of 100 MM. 3 No relationship was observed between inhibitory effects of H2-receptor antagonists on platelet aggregation induced by above agonists and the presence or absence of imidazole ring in the chemical structure.
18
Higashihara, M., H. Maeda, Y. Shibata, S. Kume, and T. Ohashi. "A monoclonal anti-human platelet antibody: a new platelet aggregating substance." Blood 65, no. 2 (February 1, 1985): 382–91. http://dx.doi.org/10.1182/blood.v65.2.382.382.
Анотація:
Abstract A monoclonal anti-human platelet antibody, TP82, is described, which caused irreversible aggregation of platelets in association with the release of adenosine triphosphate or [14C] serotonin, and which inhibited ristocetin-induced agglutination. Immunofluorescence assay showed that the antibody binds to platelets, megakaryocytes, and common acute lymphoblastic leukemia cells. The antibody (IgG1) immunoprecipitated a polypeptide of 23,000 daltons with an isoelectric point of about 7.0. The aggregation induced by the purified antibody and/or F(ab')2 fragments occurred in platelet-rich plasma and with washed platelets, but not with formalin-fixed washed platelets. TP82- induced aggregation was completely inhibited by disodium ethylendiaminotetraacetate, diltiazem, W-7, PGE1, and several metabolic inhibitors. At a concentration of apyrase or CP/CPK, which inhibited adenosine 5-diphosphate-induced aggregation. TP82-induced aggregation was only partially affected. Thrombin was not required for the antibody- mediated effects, since two thrombin inhibitors failed to block the reaction. The antibody, at least at a high concentration, induced platelet aggregation by a mechanism almost independent of thromboxane A2 formation, since cyclooxygenase inhibitors had little inhibitory effect on aggregation. TP82 monoclonal antibody is a new platelet- aggregating substance that interacts with a low-molecular-weight binding site on the platelet membrane.
19
Higashihara, M., H. Maeda, Y. Shibata, S. Kume, and T. Ohashi. "A monoclonal anti-human platelet antibody: a new platelet aggregating substance." Blood 65, no. 2 (February 1, 1985): 382–91. http://dx.doi.org/10.1182/blood.v65.2.382.bloodjournal652382.
Анотація:
A monoclonal anti-human platelet antibody, TP82, is described, which caused irreversible aggregation of platelets in association with the release of adenosine triphosphate or [14C] serotonin, and which inhibited ristocetin-induced agglutination. Immunofluorescence assay showed that the antibody binds to platelets, megakaryocytes, and common acute lymphoblastic leukemia cells. The antibody (IgG1) immunoprecipitated a polypeptide of 23,000 daltons with an isoelectric point of about 7.0. The aggregation induced by the purified antibody and/or F(ab')2 fragments occurred in platelet-rich plasma and with washed platelets, but not with formalin-fixed washed platelets. TP82- induced aggregation was completely inhibited by disodium ethylendiaminotetraacetate, diltiazem, W-7, PGE1, and several metabolic inhibitors. At a concentration of apyrase or CP/CPK, which inhibited adenosine 5-diphosphate-induced aggregation. TP82-induced aggregation was only partially affected. Thrombin was not required for the antibody- mediated effects, since two thrombin inhibitors failed to block the reaction. The antibody, at least at a high concentration, induced platelet aggregation by a mechanism almost independent of thromboxane A2 formation, since cyclooxygenase inhibitors had little inhibitory effect on aggregation. TP82 monoclonal antibody is a new platelet- aggregating substance that interacts with a low-molecular-weight binding site on the platelet membrane.
20
Knol, E. F., T. W. Kuijpers, F. P. Mul, and D. Roos. "Stimulation of human basophils results in homotypic aggregation. A response independent of degranulation." Journal of Immunology 151, no. 9 (November 1, 1993): 4926–33. http://dx.doi.org/10.4049/jimmunol.151.9.4926.
Анотація:
Abstract For a better insight into the mechanisms determining the recruitment of human basophilic granulocytes from the circulation to sites of allergic reactions, we studied the homotypic aggregation of these cells. The aggregation was studied with > 95% pure basophil suspensions obtained from peripheral blood in a double-color flow cytometric analysis. Homotypic aggregation was induced by treatment of the basophils with anti-IgE, house dust mite allergen, the chemoattractant FMLP, PMA, or IL-3. The aggregation by anti-IgE was, in part, mediated by interactions with Fc gamma R-II as indicated by 43 +/- 15% inhibition after pretreatment with CD32 antibodies. The aggregation was mediated by beta 2-integrins, as was shown by inhibition of the response by CD18 antibodies. The aggregation induced by anti-IgE, allergen, and PMA displayed comparable kinetics (t1/2 max, 3 to 4 min), in contrast to the degranulation of basophils. FMLP induced the most rapid response (t1/2max, 1.6 min). Inhibition of protein kinase C by staurosporine resulted in a strong (> 90%) inhibition of the PMA-induced aggregation, whereas the FMLP-induced aggregation was more than doubled (from 11.7 +/- 1.9 to 24.4 +/- 1.9%). Staurosporine did not affect the extent of the anti-IgE-induced aggregation, but it induced a retardation of congruent to 10 min. In most experiments, no clear correlation was found between degranulation and aggregation of human basophils. Most strikingly, IL-3 did not induce degranulation but did induce aggregation. Thus, the homotypic aggregation response of human basophils is induced by intracellular signals not necessarily leading to degranulation. This might be important in the physiologic appearance of basophils at sites of allergic late-phase responses or inflammation.
21
Chia, Jean-San, Ya-Lin Lin, Huei-Ting Lien, and Jen-Yang Chen. "Platelet Aggregation Induced by Serotype Polysaccharides from Streptococcus mutans." Infection and Immunity 72, no. 5 (May 2004): 2605–17. http://dx.doi.org/10.1128/iai.72.5.2605-2617.2004.
Анотація:
ABSTRACT Platelet aggregation plays an important role in the pathogenesis of infective endocarditis induced by viridans streptococci or staphylococci. Aggregation induced in vitro involves direct binding of bacteria to platelets through multiple surface components. Using platelet aggregometry, we demonstrated in this study that two Streptococcus mutans laboratory strains, GS-5 and Xc, and two clinical isolates could aggregate platelets in an irreversible manner in rabbit platelet-rich plasma preparations. The aggregation was partially inhibited by prostaglandin I2 (PGI2) in a dose-dependent manner. Whole bacteria and heated bacterial cell wall extracts were able to induce aggregation. Cell wall polysaccharides extracted from the wild-type Xc strain, containing serotype-specific polysaccharides which are composed of rhamnose-glucose polymers (RGPs), could induce platelet aggregation in the presence of plasma. Aggregation induced by the serotype-specific RGP-deficient mutant Xc24R was reduced by 50% compared to the wild-type strain Xc. In addition, cell wall polysaccharides extracted from Xc24R failed to induce platelet aggregation. The Xc strain, but not the Xc24R mutant, could induce platelet aggregation when preincubated with plasma. Both Xc and Xc24R failed to induce platelets to aggregate in plasma depleted of immunoglobulin G (IgG), but aggregation was restored by replenishment of anti-serotype c IgG. Analysis by flow cytometry showed that S. mutans RGPs could bind directly to rabbit and human platelets. Furthermore, cell wall polysaccharides extracted from the Xc, but not the Xc24R, strain could induce pseudopod formation of both rabbit and human platelets in the absence of plasma. Distinct from the aggregation of rabbit platelets, bacterium-triggered aggregation of human platelets required a prolonged lag phase and could be blocked completely by PGI2. RGPs also trigger aggregation of human platelets in a donor-dependent manner, either as a transient and reversible or a complete and irreversible response. These results indicated that serotype-specific RGPs, a soluble product of S. mutans, could directly bind to and activate platelets from both rabbit and human. In the presence of plasma containing IgG specific to RGPs, RGPs could trigger aggregation of both human and rabbit platelets, but the degree of aggregation in human platelets depends on the donors.
22
Natella, F., M. Nardini, F. Belelli, P. Pignatelli, S. Di Santo, A. Ghiselli, F. Violi, and C. Scaccini. "Effect of coffee drinking on platelets: inhibition of aggregation and phenols incorporation." British Journal of Nutrition 100, no. 6 (December 2008): 1276–82. http://dx.doi.org/10.1017/s0007114508981459.
Анотація:
Epidemiological studies indicate a J-shaped relationship linking coffee consumption and cardiovascular risk, suggesting that moderate coffee consumption can be beneficial. Platelet aggregation is of critical importance in thrombotic events, and platelets play a major role in the aetiology of several CVD. The aim of this study was to evaluate the effect of coffee drinking on platelet aggregationex vivo, using caffeine as control. A crossover study was performed on ten healthy subjects. In two different sessions, subjects drank 200 ml coffee, containing 180 mg caffeine, or a capsule of caffeine (180 mg) with 200 ml water. Platelets were separated from plasma at baseline and 30 and 60 min after coffee drinking. Platelet aggregation was induced with three different agonists: collagen, arachidonic acid and ADP. Coffee drinking inhibited collagen (P < 0·05 from baseline at time 30 min) and arachidonic acid (P < 0·05 from baseline at time 60 min) induced platelet aggregation. Caffeine intake did not affect platelet aggregation induced by the three agonists. Coffee consumption induced a significant increase of platelet phenolic acids (likely present as glucuronate and sulphate derivatives), caffeic acid, the principal phenolic acid in coffee, raising from 0·3 (sem0·1) to 2·4 (sem0·6) ng/mg (P < 0·01). Caffeine was not detectable in platelets. Coffee drinking decreases platelet aggregation, and induces a significant increase in phenolic acid platelet concentration. The antiplatelet effect of coffee is independent from caffeine and could be a result of the interaction of coffee phenolic acids with the intracellular signalling network leading to platelet aggregation.
23
Packham, M. A., A. A. Livne, D. H. Ruben, and M. L. Rand. "Activation of phospholipase C and protein kinase C has little involvement in ADP-induced primary aggregation of human platelets: effects of diacylglycerols, the diacylglycerols, the diacylglycerol kinase inhibitor R59022, staurosporine and okadaic acid." Biochemical Journal 290, no. 3 (March 15, 1993): 849–56. http://dx.doi.org/10.1042/bj2900849.
Анотація:
The primary phase of ADP-induced aggregation of human platelets does not involve appreciable formation of thromboxane A2 or release of granule contents; lack of formation of inositol trisphosphate has also been noted. Because these responses of platelets to ADP differ so markedly from their responses to other aggregating agents, the roles in ADP-induced aggregation of diacylglycerol, protein kinase C, increases in cytosolic [Ca2+], phosphorylation of pleckstrin (47 kDa) and phosphatases 1 and 2a were investigated. Washed human platelets, prelabelled with [14C]5-hydroxytryptamine and suspended in Tyrode solution (2 mM Ca2+, 1 mM Mg2+), were used for comparisons between the aggregation induced by 2-4 microM ADP, in the presence of fibrinogen, and that induced by 0.05 units/ml thrombin. The diacylglycerol kinase inhibitor 6-(2-[(4-fluorophenyl)phenyl-methylene]-1-piperidinylethyl)-7-meth yl-5H-thiazolo[3,2-a]-pyrimidin-5-one (R59022; 25 microM) had no, or only a slight, enhancing effect on ADP-induced aggregation, but potentiated thrombin-induced responses to a much greater extent. 1,2-Dihexanoyl-sn-glycerol or 1-oleoyl-2-acetyl-sn-glycerol (25 microM) added with or 30-90 s before ADP greatly potentiated aggregation without formation of thromboxane; staurosporine, an inhibitor of protein kinase C, reduced this potentiation. Staurosporine (25 nM) did not inhibit ADP-induced aggregation, although it strongly inhibited thrombin-induced aggregation and release of [14C]5-hydroxytryptamine. All these observations indicate little or no dependence of primary ADP-induced aggregation on the formation of diacylglycerol or on the activation of protein kinase C. At 2-4 microM, ADP did not significantly increase the phosphorylation of pleckstrin (studied with platelets prelabelled with [32P]orthophosphate), but 1,2-dihexanoyl-sn-glycerol- induced phosphorylation of pleckstrin was increased by ADP. Surprisingly, the diacylglycerols strongly inhibited the ADP-induced rise in cytosolic [Ca2+] concurrently with potentiation of ADP-induced aggregation; thus the extent of primary aggregation is independent of the level to which cytosolic [Ca2+] rises. Incubation of platelets with 1,2-dihexanoyl-sn-glycerol or 1-oleoyl-2-acetyl-sn-glycerol for several minutes reversed their potentiating effects on aggregation, and inhibition was observed. Incubation of platelets with okadaic acid, an inhibitor of phosphatases 1 and 2a, inhibited ADP- and thrombin-induced aggregation; although the reason for this effect is unknown, it is unlikely to involve inhibition of phospholipase C, since formation of diacylglycerol appears to have little involvement in the primary phase of ADP-induced aggregation.
24
Barzaghi, Giovanna, Chiara Cerletti, and Giovanni de Gaetano. "Phospholipase C from Clostridium Perfringens Induces Human Platelet Aggregation in Plasma." Thrombosis and Haemostasis 59, no. 02 (1988): 236–39. http://dx.doi.org/10.1055/s-0038-1642761.
Анотація:
SummaryWe studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37° C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAG) of PLC was 3-4 U/ml.We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoper- oxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.
25
Lian, EC, and FA Siddiqui. "Investigation of the role of von Willebrand factor in thrombotic thrombocytopenic purpura." Blood 66, no. 5 (November 1, 1985): 1219–21. http://dx.doi.org/10.1182/blood.v66.5.1219.1219.
Анотація:
Abstract Von Willebrand factor (vWF) has been implicated to function as a cofactor in platelet aggregation induced by thrombotic thrombocytopenic purpura (TTP) plasma. To investigate further this role of vWF, we have used rabbit monospecific anti-FVIII/vWF antibodies and a monoclonal antibody to platelet glycoprotein Ib (GP Ib) that blocks the ristocetin- induced platelet aggregation. The monoclonal anti-platelet GP Ib antibody inhibited the platelet aggregation induced by ristocetin in the presence of normal plasma, but not that by any of the five TTP plasma samples. The TTP plasma samples from five patients were incubated with the monospecific antibodies to FVIII/vWF. In all of the samples, the FVIII/vWF:Ag was drastically reduced; however, there was almost no effect on the platelet-aggregating activity. Therefore, it is concluded that vWF is unlikely to play a major role in platelet aggregation induced by majority of TTP plasmas and that the site of platelet GP Ib, to which vWF binds in the presence of ristocetin, is not involved in TTP plasma-induced aggregation.
26
Lian, EC, and FA Siddiqui. "Investigation of the role of von Willebrand factor in thrombotic thrombocytopenic purpura." Blood 66, no. 5 (November 1, 1985): 1219–21. http://dx.doi.org/10.1182/blood.v66.5.1219.bloodjournal6651219.
Анотація:
Von Willebrand factor (vWF) has been implicated to function as a cofactor in platelet aggregation induced by thrombotic thrombocytopenic purpura (TTP) plasma. To investigate further this role of vWF, we have used rabbit monospecific anti-FVIII/vWF antibodies and a monoclonal antibody to platelet glycoprotein Ib (GP Ib) that blocks the ristocetin- induced platelet aggregation. The monoclonal anti-platelet GP Ib antibody inhibited the platelet aggregation induced by ristocetin in the presence of normal plasma, but not that by any of the five TTP plasma samples. The TTP plasma samples from five patients were incubated with the monospecific antibodies to FVIII/vWF. In all of the samples, the FVIII/vWF:Ag was drastically reduced; however, there was almost no effect on the platelet-aggregating activity. Therefore, it is concluded that vWF is unlikely to play a major role in platelet aggregation induced by majority of TTP plasmas and that the site of platelet GP Ib, to which vWF binds in the presence of ristocetin, is not involved in TTP plasma-induced aggregation.
27
Barr, Stephen C., John W. Ludders, Andrea L. Looney, Robin D. Gleed, and Hollis N. Erb. "Platelet aggregation in dogs after sedation with acepromazine and atropine and during subsequent general anesthesia and surgery." American Journal of Veterinary Research 53, no. 11 (November 1, 1992): 2067–70. http://dx.doi.org/10.2460/ajvr.1992.53.11.2067.
Анотація:
Summary Platelet aggregation and adenosine triphosphate (atp) release were measured by use of the impedance method in blood samples obtained from 25 adult female Beagles before and after sedation with acepromazine (0.13 mg/kg of body weight) and atropine (0.05 mg/kg), and during general anesthesia. General anesthesia was induced by iv administration of thiamylal (average dosage, 2.1 mg/kg; range, 1.2 to 4.2 mg/kg) and was maintained with halothane in oxygen. Samples of jugular venous blood were obtained from each dog, using citrate as anticoagulant. Platelet count was done on each sample. Platelet aggregation and atp released from the aggregating platelets were measured within 2.5 hours of sample collection, using a whole-blood aggregometer. Adenosine diphosphate (adp) or collagen was used as aggregating agent. For each aggregating agent, platelet aggregation and atp release were measured over 6 minutes. After sedation with acepromazine and atropine, significant (P < 0.01) reduction was observed in platelet count (from median values of 341,000 cells/μl to 283,000 cells/μl) and in the ability of platelets to aggregate in response to adp (from 14.0 to 7.0 Ω). During the same period, maximal release of atp in response to collagen also was reduced (from 5.56 μmol to 4.57 μmol; P < 0.01); however, this difference ceased to be significant when atp release was normalized for platelet count. During general anesthesia and surgery (200 minutes after sedation), platelet count and aggregation responses to adp and collagen had returned to presedation values. None of the dogs in this study appeared to have hemostasis problems during surgery. In conclusion, sedation with acepromazine and atropine induces measurable inhibition of adp-induced platelet aggregation that resolves during subsequent general anesthesia and surgery. Transient inhibition of platelet aggregation is not manifested by a change in gross hemostasis during surgery.
28
Chiang, T. M., A. Jin, and A. H. Kang. "Platelet-collagen interaction. Inhibition by a monoclonal antibody raised against collagen receptor." Journal of Immunology 139, no. 3 (August 1, 1987): 887–92. http://dx.doi.org/10.4049/jimmunol.139.3.887.
Анотація:
Abstract Monoclonal antibodies to the purified platelet type I collagen receptor were produced to study platelet receptor function. The antibody specifically reacted with the platelet receptor in immunoblot experiments. The IgG purified from the monoclonal antibodies and isolated Fab' fragments inhibited the binding of radiolabeled alpha 1(I) chain to washed platelets competitively. Soluble and fibrillar type I collagen-induced platelet aggregations were inhibited by purified IgG suggesting that soluble and fibrillar collagens shared a common receptor. The adhesion of platelets to an artificial collagen matrix was also inhibited by the monoclonal antibody. However, adenosine diphosphate-induced platelet aggregation was not inhibited by the same amount of IgG that inhibited collagen-induced platelet aggregation. The results suggest that collagen-induced platelet aggregation is mediated through the interaction of collagen with the platelet receptor.
29
Nie, Han, Kun Hu, Yuanjing Cai, Qian Peng, Zujin Zhao, Rongrong Hu, Junwu Chen, Shi-Jian Su, Anjun Qin, and Ben Zhong Tang. "Tetraphenylfuran: aggregation-induced emission or aggregation-caused quenching?" Materials Chemistry Frontiers 1, no. 6 (2017): 1125–29. http://dx.doi.org/10.1039/c6qm00343e.
Анотація:
Tetraphenylfuran, structurally similar to AIE-active siloles, exhibits the traditional aggregation-caused quenching, which is co-caused by the restriction of intramolecular rotation and the conjugation effect.
30
Abdelouahed, Mustapha, Mohamed Hatmi, Gérard Helft, Sharareh Emadi, Ismaïl Elalamy, and Meyer Michel Samama. "Comparative Effects of Recombinant Staphylokinase and Streptokinase on Platelet Aggregation." Thrombosis and Haemostasis 77, no. 05 (1997): 0815–17. http://dx.doi.org/10.1055/s-0038-1656058.
Анотація:
SummaryRecombinant staphylokinase (RSTA) has been shown to offer promise as a thrombolytic agent. In contrast to streptokinase (SK), few studies have been devoted to possible effects of RSTA on platelets. We have compared the capacity of RSTA and SK to trigger platelet aggregation and to modify ADP (2.5 µM) response in platelet-rich plasma (PRP) of 25 healthy subjects. Thus, exposure of PRP to SK (40 to 50 µg/ml) induced platelet aggregation in 6 out of 25 subjects. However, under the same conditions, RSTA failed to induce platelet aggregation in all cases (25 out of 25 subjects). In contrast to RSTA, SK (0.4 to 50 µg/ml) greatly reduced ADP-induced platelet aggregation in 12 out of 25 subjects. Preincubation of plasma with SK is associated with a decrease in the fibrinogen concentration. Furthermore, there was a good correlation between SK-induced fibrinogenolysis and SK- induced platelet aggregation defect (r2 = 0.9; p = 0.001). No fibrino genolysis was observed when different amounts of RSTA (0.4 to 50 µg/ml) were incubated in plasma for one min. However, there was a marked decrease in fibrinogen level (about 50%) when the plasma was incubated for five min with a very high concentration of RSTA. SK markedly enhanced the platelet response to ADP in 13 out of 25 subjects. In PRP of 6 out of 25 subjects, SK induces platelet aggregation and potentiates platelet response to ADP, however in PRP of 7 out of 25 subjects, SK caused only the increase of platelet response to ADP. The monoclonal antibody anti-FcγRIIal, IV-3 (2 [µ/ml), abolished SK-induced platelet aggregation and SK-enhanced ADP-induced platelet aggregation. In all cases (25 out of 25 subjects), RSTA failed to potentiate platelet response to ADP.These findings confirm that RSTA has a lesser fibrinogenolytic ability than SK and suggest its negligeable effect on platelet function.
31
Zhang, Zechen, Jared R. Arkfeld, and William A. Ducker. "Proximity-induced surfactant aggregation." Colloid and Interface Science Communications 50 (September 2022): 100657. http://dx.doi.org/10.1016/j.colcom.2022.100657.
32
ZELLER, J. A., RUTH E. DAYHOFF, K. EURENIUS, W. RUSSELL, and R. S. LEDLEY. "Aldehyde-induced platelet aggregation." Clinical & Laboratory Haematology 6, no. 2 (June 28, 2008): 145–55. http://dx.doi.org/10.1111/j.1365-2257.1984.tb00537.x.
33
O'Brien, J. R. "Shear-induced platelet aggregation." Lancet 335, no. 8691 (March 1990): 711–13. http://dx.doi.org/10.1016/0140-6736(90)90815-m.
34
Liu, Hao, Jingjing Guo, Zujin Zhao, and Ben Zhong Tang. "Aggregation‐Induced Delayed Fluorescence." ChemPhotoChem 3, no. 10 (June 27, 2019): 993–99. http://dx.doi.org/10.1002/cptc.201900118.
35
CALZADA, Catherine, Evelyne VERICEL, and Michel LAGARDE. "Low concentrations of lipid hydroperoxides prime human platelet aggregation specifically via cyclo-oxygenase activation." Biochemical Journal 325, no. 2 (July 15, 1997): 495–500. http://dx.doi.org/10.1042/bj3250495.
Анотація:
There is mounting evidence that lipid peroxides contribute to pathophysiological processes and can modulate cellular functions. The aim of the present study was to investigate the effects of lipid hydroperoxides on platelet aggregation and arachidonic acid (AA) metabolism. Human platelets, isolated from plasma, were incubated with subthreshold (i.e. non-aggregating) concentrations of AA in the absence or presence of hydroperoxyeicosatetraenoic acids (HPETEs). Although HPETEs alone had no effect on platelet function, HPETEs induced the aggregation of platelets co-incubated with non-aggregating concentrations of AA, HPETEs being more potent than non-eicosanoid peroxides. The priming effect of HPETEs on platelet aggregation was associated with an increased formation of cyclo-oxygenase metabolites, in particular thromboxane A2, and was abolished by aspirin, suggesting an activation of cyclo-oxygenase by HPETEs. It was not receptor-mediated because the 12-HPETE-induced enhancement of AA metabolism was sustained in the presence of SQ29,548 or RGDS, which blocked the aggregation. These results indicate that physiologically relevant concentrations of HPETEs potentiate platelet aggregation, which appears to be mediated via a stimulation of cyclo-oxygenase activity.
36
Surapinit, Serm, and Nuttakorn Baisaeng. "Macrostachyols A-D, oligostilbenes from Gnetum macrostachyum inhibited in vitro human platelet aggregation." Journal of Herbmed Pharmacology 10, no. 3 (July 2, 2021): 339–43. http://dx.doi.org/10.34172/jhp.2021.39.
Анотація:
Introduction: Gnetum macrostachyum is a known Thai medicinal plant as a source of bioactive oligostilbenes, which possess platelet inhibitory activities. The study aimed to evaluate the in vitro human platelet aggregation inhibitory activities of macrostachyols A-D (compounds 1-4) isolated from the roots of G. macrostachyum. Methods: The in vitro human platelet aggregation assay was assayed with a 96-well microtiter plate format. The well-known aggregating agents were used to investigate the possible mechanism of inhibition, including adenosine diphosphate (ADP), arachidonic acid (AA), thromboxane A2 analog (U-46619), collagen, thrombin, and thrombin receptor-activating peptide-6 (TRAP-6). Results: Compound 1 was more potent than ibuprofen (positive control) on the adenosine diphosphate- induced platelet aggregation assay (P < 0.05). Compound 3 was more potent than 1, 2, and 4 (P < 0.05), but all active oligostilbenes were less potent than the positive control (P < 0.05) on the arachidonic acid-induced platelet aggregation assay. The oligostilbenes 1, 2, 3, and 4 also displayed the inhibitory effects on the U-46619-induced platelet aggregation. The tetrameric stilbenes 1 was the only compound that exhibited inhibitory effects on thrombin-induced platelet aggregation without TRAP-6 mediated platelet aggregation. Conclusion: The findings revealed the inhibitory effects of oligostilbenes on human platelet aggregation through a target-specific experimental design. It suggests that oligostilbenes from this plant might be applied as antiplatelet aggregation agents in platelet hyperreactivity- related diseases.
37
Yan, Yan, and Julián F. Hillyer. "The immune and circulatory systems are functionally integrated across insect evolution." Science Advances 6, no. 48 (November 2020): eabb3164. http://dx.doi.org/10.1126/sciadv.abb3164.
Анотація:
The immune and circulatory systems of mammals are functionally integrated, as exemplified by the immune function of the spleen and lymph nodes. Similar functional integration exists in the malaria mosquito, Anopheles gambiae, as exemplified by the infection-induced aggregation of hemocytes around the heart valves. Whether this is specific to mosquitoes or a general characteristic of insects remained unknown. We analyzed 68 species from 51 families representing 16 orders and found that infection induces the aggregation of hemocytes and pathogens on the heart of insects from all major branches of the class Insecta. An expanded analysis in the holometabolous mosquito, Aedes aegypti, and the hemimetabolous bed bug, Cimex lectularius, showed that infection induces the aggregation of phagocytic hemocytes on the hearts of distantly related insects, with aggregations mirroring the patterns of hemolymph flow. Therefore, the functional integration of the immune and circulatory systems is conserved across the insect tree of life.
38
Whitin, J. C., and H. J. Cohen. "Dissociation between aggregation and superoxide production in human granulocytes." Journal of Immunology 134, no. 2 (February 1, 1985): 1206–11. http://dx.doi.org/10.4049/jimmunol.134.2.1206.
Анотація:
Abstract Aggregation and the activation of the granulocyte (PMN) superoxide (O2-) generating system occur when certain stimuli are added to resting cells. It had previously been postulated that PMN aggregation is essential for maximal O2- production. This study was undertaken to test the hypothesis that PMN aggregation is required for full expression of PMN O2- production. We examined aggregation and O2- production induced by four stimuli; concanavalin A (Con A), phorbol myristate acetate (PMA), N-formylmethionyl-leucyl-phenylalanine (FMLP), and ionophore A23187. Cytochalasin B enhanced aggregation by all four stimuli but only enhanced the rate of O2- production by Con A; 2-deoxyglucose inhibited aggregation by all stimuli. Dissociation of PMN aggregation and O2- production was achieved by using NEM, TPCK, and divalent cations. NEM and TPCK prevent Con A-induced O2- production but have no effect on Con A-induced aggregation. PMA-stimulated PMN generate O2- in the presence or absence of Ca++ and Mg++. In contrast, PMA stimulated maximum PMN aggregation only in the presence of both Ca++ and Mg++. Thus PMN can generate O2- without aggregating, and PMN can aggregate without producing O2-. PMN from patients with chronic granulomatous disease do not generate O2- or undergo membrane potential depolarization in response to PMA. These PMN aggregated when stimulated with PMA, providing evidence that depolarization is not required for PMN aggregation. We conclude that aggregation and the activation of the O2- generating system, though temporally related, are not necessarily causally related.
39
Zhang, Yun-Xiang, Ting-Ting Yang, Liu Xia, Wei-Fen Zhang, Jia-Fu Wang, and Ya-Ping Wu. "Inhibitory Effect of Propolis on Platelet Aggregation In Vitro." Journal of Healthcare Engineering 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/3050895.
Анотація:
Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was aimed to investigate the effects of different extracts of propolis and components of flavonoids on platelet aggregation. Platelet-rich plasma was prepared and incubated in vitro with different concentrations of the tested extracts and components of flavonoids. Platelets aggregation was induced by different agonists including adenosine diphosphate (ADP, 10 μM), thrombin receptor activator peptide (TRAP, 50 μM), and collagen (5 μg/mL). At 25 mg/L to 300 mg/mL, the water extract propolis (WEP) inhibited three agonists-induced platelet aggregations in a dose-dependent manner. The flavonoids isolated from the propolis also showed markedly inhibited platelet aggregation induced by collagen, ADP, and TRAP, respectively. The components including caffeic acid phenethyl ester (CAPE), galangin, apigenin, quercetin, kaempferol, ferulic acid, rutin, chrysin, pinostrobin, and pinocembrin and their abilities of inhibiting platelet aggregation were studied. It was concluded that propolis had an antiplatelet action in which flavonoids were mainly implicated.
40
Haserück, Nadine, Wolfgang Erl, Dharmendra Pandey, Gabor Tigyi, Philippe Ohlmann, Catherine Ravanat, Christian Gachet, and Wolfgang Siess. "The plaque lipid lysophosphatidic acid stimulates platelet activation and platelet-monocyte aggregate formation in whole blood: involvement of P2Y1 and P2Y12 receptors." Blood 103, no. 7 (April 1, 2004): 2585–92. http://dx.doi.org/10.1182/blood-2003-04-1127.
Анотація:
Abstract Despite the fact that lysophosphatidic acid (LPA) has been identified as a main platelet-activating lipid of mildly oxidized low-density lipoprotein (LDL) and human atherosclerotic lesions, it remains unknown whether it is capable of activating platelets in blood. We found that LPA at concentrations slightly above plasma levels induces platelet shape change, aggregation, and platelet-monocyte aggregate formation in blood. 1-alkyl-LPA (16:0 fatty acid) was almost 20-fold more potent than 1-acyl-LPA (16:0). LPA directly induced platelet shape change in blood and platelet-rich plasma obtained from all blood donors. However, LPA-stimulated platelet aggregation in blood was donor dependent. It could be completely blocked by apyrase and antagonists of the platelet adenosine diphosphate (ADP) receptors P2Y1 and P2Y12. These substances also inhibited LPA-induced aggregation of platelet-rich plasma and aggregation and serotonin secretion of washed platelets. These results indicate a central role for ADP-mediated P2Y1 and P2Y12 receptor activation in supporting LPA-induced platelet aggregation. Platelet aggregation and platelet-monocyte aggregate formation stimulated by LPA was insensitive to inhibition by aspirin. We conclude that LPA at concentrations approaching those found in vivo can induce platelet shape change, aggregation, and platelet-monocyte aggregate formation in whole blood and suggest that antagonists of platelet P2Y1 and P2Y12 receptors might be useful preventing LPA-elicited thrombus formation in patients with cardiovascular diseases.
41
Perrault, Christelle, Nadine Ajzenberg, Paulette Legendre, Ghassem Rastegar-Lari, Dominique Meyer, Jose A. Lopez, and Dominique Baruch. "Modulation by Heparin of the Interaction of the A1 Domain of von Willebrand Factor With Glycoprotein Ib." Blood 94, no. 12 (December 15, 1999): 4186–94. http://dx.doi.org/10.1182/blood.v94.12.4186.
Анотація:
Abstract The conformation of the A1 domain of von Willebrand factor (vWF) is a critical determinant of its interaction with the glycoprotein (GP) Ib/V/IX complex. To better define the regulatory mechanisms of vWF A1 domain binding to the GPIb/V/IX complex, we studied vWF-dependent aggregation properties of a cell line overexpressing the GPIb, GPIbβ, and GPIX subunits (CHO-GPIbβ/IX cells). We found that CHO-GPIbβ/IX cell aggregation required the presence of both soluble vWF and ristocetin. Ristocetin-induced CHO-GPIbβ/IX cell aggregation was completely inhibited by the recombinant VCL fragment of vWF that contains the A1 domain. Surprisingly, the substitution of heparin for ristocetin resulted in the formation of CHO-GPIbβ/IX cell aggregates. Using monoclonal antibodies blocking vWF interaction with GPIb/V/IX or mocarhagin, a venom metalloproteinase that removes the amino-terminal fragment of GPIb extending from aa 1 to 282, we demonstrated that both ristocetin- and heparin-induced aggregations involved an interaction between the A1 domain of vWF and the GPIb subunit of the GPIb/V/IX complex. The involvement of heparin in cell aggregation was also demonstrated after treatment of heparin with heparinase that abolished CHO-GPIbβ/IX cell aggregation. These results indicated that heparin was able to induce vWF-dependent CHO-GPIbβ/IX cell aggregation. In conclusion, we demonstrated that heparin is capable of positively modulating the vWF interaction with the GPIb/V/IX complex.
42
Perrault, Christelle, Nadine Ajzenberg, Paulette Legendre, Ghassem Rastegar-Lari, Dominique Meyer, Jose A. Lopez, and Dominique Baruch. "Modulation by Heparin of the Interaction of the A1 Domain of von Willebrand Factor With Glycoprotein Ib." Blood 94, no. 12 (December 15, 1999): 4186–94. http://dx.doi.org/10.1182/blood.v94.12.4186.424k24_4186_4194.
Анотація:
The conformation of the A1 domain of von Willebrand factor (vWF) is a critical determinant of its interaction with the glycoprotein (GP) Ib/V/IX complex. To better define the regulatory mechanisms of vWF A1 domain binding to the GPIb/V/IX complex, we studied vWF-dependent aggregation properties of a cell line overexpressing the GPIb, GPIbβ, and GPIX subunits (CHO-GPIbβ/IX cells). We found that CHO-GPIbβ/IX cell aggregation required the presence of both soluble vWF and ristocetin. Ristocetin-induced CHO-GPIbβ/IX cell aggregation was completely inhibited by the recombinant VCL fragment of vWF that contains the A1 domain. Surprisingly, the substitution of heparin for ristocetin resulted in the formation of CHO-GPIbβ/IX cell aggregates. Using monoclonal antibodies blocking vWF interaction with GPIb/V/IX or mocarhagin, a venom metalloproteinase that removes the amino-terminal fragment of GPIb extending from aa 1 to 282, we demonstrated that both ristocetin- and heparin-induced aggregations involved an interaction between the A1 domain of vWF and the GPIb subunit of the GPIb/V/IX complex. The involvement of heparin in cell aggregation was also demonstrated after treatment of heparin with heparinase that abolished CHO-GPIbβ/IX cell aggregation. These results indicated that heparin was able to induce vWF-dependent CHO-GPIbβ/IX cell aggregation. In conclusion, we demonstrated that heparin is capable of positively modulating the vWF interaction with the GPIb/V/IX complex.
43
Hornberger, Zachary, Bruce Cox, and Raymond R. Hill. "Analysis of the effects of spatiotemporal demand data aggregation methods on distance and volume errors." Journal of Defense Analytics and Logistics 5, no. 1 (May 10, 2021): 29–45. http://dx.doi.org/10.1108/jdal-03-2020-0003.
Анотація:
Purpose Large/stochastic spatiotemporal demand data sets can prove intractable for location optimization problems, motivating the need for aggregation. However, demand aggregation induces errors. Significant theoretical research has been performed related to the modifiable areal unit problem and the zone definition problem. Minimal research has been accomplished related to the specific issues inherent to spatiotemporal demand data, such as search and rescue (SAR) data. This study provides a quantitative comparison of various aggregation methodologies and their relation to distance and volume based aggregation errors. Design/methodology/approach This paper introduces and applies a framework for comparing both deterministic and stochastic aggregation methods using distance- and volume-based aggregation error metrics. This paper additionally applies weighted versions of these metrics to account for the reality that demand events are nonhomogeneous. These metrics are applied to a large, highly variable, spatiotemporal demand data set of SAR events in the Pacific Ocean. Comparisons using these metrics are conducted between six quadrat aggregations of varying scales and two zonal distribution models using hierarchical clustering. Findings As quadrat fidelity increases the distance-based aggregation error decreases, while the two deliberate zonal approaches further reduce this error while using fewer zones. However, the higher fidelity aggregations detrimentally affect volume error. Additionally, by splitting the SAR data set into training and test sets this paper shows the stochastic zonal distribution aggregation method is effective at simulating actual future demands. Originality/value This study indicates no singular best aggregation method exists, by quantifying trade-offs in aggregation-induced errors practitioners can utilize the method that minimizes errors most relevant to their study. Study also quantifies the ability of a stochastic zonal distribution method to effectively simulate future demand data.
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Bhat, Waseem Feeroze, Azaj Ahmed, Shabeena Abbass, Mohammad Afsar, Bilqees Bano, and Akbar Masood. "Deciphering the Nature of Caffeic Acid to Inhibit the HSA Aggregation Induced by Glyoxal." Protein & Peptide Letters 27, no. 8 (September 24, 2020): 725–35. http://dx.doi.org/10.2174/0929866527666200129105141.
Анотація:
Background: Under certain circumstances, the path for protein folding deviates and attains an alternative path forming misfolded states, which are the key precursors for protein aggregation. Protein aggregation is associated with variety of diseases and leads to the cytotoxicity. These protein aggregate related diseases have been untreated so far. However, extensive attempts have been applied to develop anti-aggregating agents as possible approaches to overcome protein aggregation. Different types of substances have been reported to halt or decrease the formation of ordered protein aggregates both in vitro and in vivo, such as polyphenols and metal ions. Objective: In the present study the in vitro aggregation of human serum albumin (HSA) by using a reactive dicarbonyl glyoxal has been investigated, simultaneously an attempt has been done to inhibit the glyoxal (GO) induced aggregation of (HSA) by caffeic acid (CA). Methods: Different methods have been employed to investigate the process, fluorescence spectroscopy, circular dichroism, cango red binding assay, thioflavin T dye binding, turbidimetric analysis, docking study and transmission electron microscopy. Results: Results have shown that elevated concentration of GO forms aggregates of HSA, and the activity of CA suggested the possibility of inhibiting the HSA aggregation at higher concentrations, and this compound was found to have an anti-aggregation property. Conclusion: The present study explained that micro molar concentrations of CA inhibits the aggregation of HSA and showed pronounced anti-aggregation effect at increasing concentrations in the presence of GO which is elevated in diabetic and hyperglycaemia conditions.
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Kuckleburg, Christopher J., Shaadi F. Elswaifi, Thomas J. Inzana, and Charles J. Czuprynski. "Expression of Phosphorylcholine by Histophilus somni Induces BovinePlatelet Aggregation." Infection and Immunity 75, no. 2 (November 21, 2006): 1045–49. http://dx.doi.org/10.1128/iai.01177-06.
Анотація:
ABSTRACT Histophilus somni-induced platelet aggregation was inhibited by antagonists of the platelet-activating factor (PAF) receptor but not inhibitors of PAF synthesis. In addition, H. somni cells expressing phosphorylcholine (ChoP) induced aggregation, while ChoP− H. somni cells did not. This suggests that H. somni ChoP may induce platelet aggregation via interactions with the PAF receptor.
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Lova, Paolo, Francesca Campus, Alessandra Bertoni, Fabiola Sinigaglia, Cesare Balduini, and Mauro Torti. "Mechanisms for Thrombopoietin-Induced Potentiation of Platelet Aggregation." Blood 104, no. 11 (November 16, 2004): 3535. http://dx.doi.org/10.1182/blood.v104.11.3535.3535.
Анотація:
Abstract Thrombopoietin (TPO) is the major cytokine regulating megakaryocytes proliferation and thrombopoiesis. Binding of TPO to the c-Mpl receptor expressed on human platelets promotes tyrosine phosphorylation of a number of proteins and potentiates platelet aggregation induced by low concentrations of a variety of agonists including ADP. Nevertheless, TPO alone is not able to induce any platelet functional response, such as shape change, granule secretion, or aggregation. It is now clear that platelet aggregation induced by many different agonists results from the concomitant activation of both Gi-and Gq-dependent signaling pathways. In particular, activation of a Gi-dependent pathway is essential, albeit not sufficient, to elicit complete platelet aggregation. Recently, it has been proposed that the small GTPase Rap1B is an important element in the Gi-dependent pathway for platelet aggregation. ADP activates Gq and Gi-dependent pathways by binding to the P2Y1 and the P2Y12 receptors, respectively. In this study we investigated the contribution of TPO in platelet activation induced by ADP. We found that TPO could restore ADP-induced platelet aggregation when the Gq-coupled receptor was blocked, but failed to restore ADP-induced aggregation in absence of Gi stimulation. Similarly, TPO was unable to restore U46619-induced platelet aggregation, when the Gi-coupled P2Y12 receptor for ADP was blocked, but caused irreversible platelet aggregation when added in combination with epinephrine, which binds to a Gi-coupled receptor. TPO did not cause any detectable calcium movements or pleckstrin phosphorylation in human platelets. Moreover, TPO failed to restore ADP-induced cytosolic calcium incresases and pleckstrin phosphorylation when the Gq-coupled P2Y1 receptor was blocked, although aggregation was completely restored. Moreover, we found that TPO induced activation of Rap1B in platelets, and could completely restore ADP-induced Rap1B activation, which was partially reduced upon blockade of the P2Y1 receptor. Finally, ADP-induced binding of both fibrinogen and PAC-1 monoclonal antibody to integrin αIIbβ3 was prevented by the blockade of the Gq-coupled P2Y1 receptor, but completely restored by the simultaneous addition of TPO. These findings indicate that TPO can complement Gi-, but not Gq-dependent pathways for integrin αIIbβ3 activation and platelet aggregation, through a new mechanism that does not involve activation of phospholipase C, but may involve the small GTPase Rap1B.
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Cantón, R., J. Manzanares, E. Alvarez, and F. Zaragozá. "In Vitro and In Vivo Antiaggregant Effects of Magnesium Halogenates." Thrombosis and Haemostasis 58, no. 04 (1987): 957–59. http://dx.doi.org/10.1055/s-0038-1646034.
Анотація:
SummaryThe in vitro antiplatelet aggregating activity of magnesium and magnesium associated with soluble citroflavomJids (hesperidin and eriodictin, 1:1) is well-established.The degree of inhibition of in vitro platelet aggregation activity produced by different concentrations of magnesium halogenates was determined. ADP (4 μM) was used to induce aggregation following Cardinal and Flowers’ (1) technique.Antithtombotic activity was studied in vivo. The differencein duration. of ADP-induced respiratory dysfunction was compared between animals fed 25 mg/kg magnesium halogenates for 10 days before testing and controls.An increase in circulating platelets was observed in rats treated with magnesium halogenates.
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Wallén, N. Håkan, Claes Held, Nina Rehnqvist, and Paul Hjemdahl. "Impact of Treatment with Acetylsalicylic Acid on the Proaggregatory Effects of Adrenaline in vitro in Patients with Stable Angina Pectoris: Influence of the Anticoagulant." Clinical Science 85, no. 5 (November 1, 1993): 577–83. http://dx.doi.org/10.1042/cs0850577.
Анотація:
1. The impact of oral acetylsalicylic acid treatment on the enhancing effect of adrenaline on platelet aggregation in vitro was investigated in patients with stable angina pectoris. In addition, the influence of different anticoagulants (i.e. hirudin and citrate) on platelet aggregation in vitro was compared. 2. Eighty-four patients with stable angina pectoris were studied. Sixteen patients were on acetylsalicylic acid treatment (150-250 mg daily), whereas 68 patients were free from acetylsalicylic acid. Platelet-rich-plasma was prepared from citrate- or hirudin-antkoagulated blood. The EC50 (i.e. the concentration of agonist required to produce half-maximal aggregation) for the ADP-induced extent of aggregation was determined. Thereafter the enhancing effect of adrenaline (10 and 50 nmol/l) on ADP-induced aggregation (at EC50) was investigated. 3. In the patients with angina, acetylsalicylic acid caused the expected effects on ADP-induced platelet responses. Adrenaline significantly enhanced both the extent of aggregation and the initial rate of aggregation (primary aggregation), irrespective of the anticoagulant used. In acetylsalicylic acid-treated patients (citrated platelet-rich plasma) the extent of aggregation was partly inhibited, but no significant effect on the rate of aggregation could be observed. 4. A comparative substudy of the anticoagulants in healthy subjects (n = 8) showed that both the aggregating effect of ADP per se and the enhancing effect of adrenaline on ADP-induced aggregation (at EC50) were less influenced by acetylsalicylic acid when evaluated in hirudinized platelet-rich plasma (i.e. with physiological levels of extracellular calcium) as compared with citrated platelet-rich plasma. 5. It is concluded that acetylsalicylic acid treatment slightly attenuates the proaggregatory effect of high physiological concentrations of adrenaline in vitro. The impact of acetylsalicylic acid in vitro is, however, strongly dependent on the anticoagulant used, and is significantly weaker when evaluated in a medium with normal extracellular calcium levels (i.e. hirudin) than in a medium with low levels of extracellular calcium (citrate). Thus, acetylsalicylic acid may be a weak antagonist of catecholamine-induced platelet activation in vivo.
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Lanza, F., A. Beretz, A. Stierle, D. Hanau, M. Kubina, and J. P. Cazenave. "Epinephrine potentiates human platelet activation but is not an aggregating agent." American Journal of Physiology-Heart and Circulatory Physiology 255, no. 6 (December 1, 1988): H1276—H1288. http://dx.doi.org/10.1152/ajpheart.1988.255.6.h1276.
Анотація:
Epinephrine can in certain in vitro conditions induce the aggregation of human platelets and could play an important role in vivo in the appearance of thrombotic disorders when catecholamine levels are increased. This study examines some functional and biochemical responses to epinephrine. Epinephrine induces the aggregation and serotonin secretion of human platelets in citrated plasma. This is not due to a direct effect of citrate itself, such as the lowering of plasma free Ca2+ but more likely to the generation of traces of thrombin during blood collection, as suggested by abrogation of these platelet responses when hirudin was added before citrate. When washed human platelets suspended in Tyrode buffer containing 2 mM Ca2+, 0.35% albumin and apyrase, and 0.1-100 microM epinephrine were used, no shape change, aggregation, or secretion of serotonin was observed, nor was the platelet ultrastructure modified. Epinephrine does not modify platelet membrane fluidity, as studied with the lipophilic fluorescent probe trimethylammonium-diphenylhexatriene. It has no direct effect on fibrinogen binding to intact platelets, intracellular Ca2+ levels measured by quin2, or protein phosphorylation. Epinephrine potentiates the action of all types of aggregating agents on aggregation, secretion, intracellular Ca2+ levels, membrane fluidity, fibrinogen binding, or protein phosphorylation. These effects are mediated by alpha 2-adrenergic agonists and inhibited by alpha 2-adrenergic antagonists. This study shows that epinephrine alone does not induce modifications of morphology, metabolism, or function of intact and functional washed human platelets and that it cannot be considered per se as an aggregating agent. However, epinephrine interacts with alpha 2-adrenergic receptors on human platelets and potentiates biochemical and aggregatory responses induced by other platelet agonists.
50
Lorenz, HM, AS Lagoo, and KJ Hardy. "The cell and molecular basis of leukocyte common antigen (CD45)- triggered, lymphocyte function-associated antigen-1-/intercellular adhesion molecule-1-dependent, leukocyte adhesion." Blood 83, no. 7 (April 1, 1994): 1862–70. http://dx.doi.org/10.1182/blood.v83.7.1862.1862.
Анотація:
Abstract We recently reported that cross-linking the leukocyte common antigen (CD45) can rapidly induce aggregation of human peripheral blood mononuclear cells via lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) interactions. Herein, we have examined both T-cell--monocyte cellular interactions and the molecular signaling that are involved in this phenomenon. Experiments using highly purified T lymphocytes showed that CD45-induced aggregation requires the presence of both T cells and monocytes. Cross- linking CD45 only on T lymphocytes, but not on monocytes, initiated cellular clustering after reconstituting to the respective untreated cell type. By several criteria, CD45-induced clustering of T cells to autologous monocytes was shown to be Fc-receptor--independent. When comparing intracellular signaling in leukocyte aggregation induced by CD45 cross-linking versus phorbol myristate-12–13-acetate (PMA) treatment, the former was found to be fivefold to 10-fold more sensitive to H-8, a reagent that effectively blocks cAMP- and cGMP- dependent protein kinases. On the other hand, reagents that increase intracellular cAMP levels (eg, dbcAMP, forskolin, and IBMX), protein kinase C (PKC) inhibitors (eg, staurosporine), and tyrosine kinase inhibitors (eg, herbimycin A and genistein) all readily inhibited PMA- induced, but not CD45 monoclonal antibody-induced, aggregation. We conclude that cross-linking the leukocyte common antigen on T cells induces LFA-1--/ICAM-1--dependent T-cell--monocyte aggregation through a unique signaling pathway independent of PKC, which involves instead cAMP-/cGMP-dependent protein kinases.