Displaying publications 1 - 20 of 28 in total

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  1. Inhibitory effect of compounds from Goniothalamus tapis Miq. and Goniothalamus uvaroides King on platelet-activating factor receptor binding
    Moharam BA, Jantan I, Jalil J, Ahmad F
    Phytother Res, 2012 May;26(5):687-91.
    PMID: 22002630 DOI: 10.1002/ptr.3620
    Phytochemical investigation on the bark of Goniothalamus tapis Miq. and G. uvaroides King has resulted in the isolation of eight styryl-lactones, (-)-cryptomeridiol, liriodenine, 3-methyl-1H-benz[f]indole-4,9-dione, (-)-stigmasterol and dimethyl terephthalate. The structures of the compounds were elucidated by spectroscopic techniques. The compounds were evaluated for their effect on platelet-activating factor (PAF) receptor binding on rabbit platelets using (3) H-PAF as a ligand. Among the compounds tested, (-)-cryptomeridiol, (+)-goniothalamin and (+)-isoaltholactone exhibited a significant and concentration-dependent inhibitory effect on PAF receptor binding, with inhibitory concentration (IC)(50) values of 17.5, 19.7 and 46.5 µm, respectively. The inhibitory effects of the first two compounds were comparable to that obtained from the positive control, cedrol. The results indicated that these compounds were strong PAF receptor binding inhibitors.
    Matched MeSH terms: Blood Platelets/metabolism
  2. Fulltext Inhibitory effects of acetylmelodorinol, chrysin and polycarpol from Mitrella kentii on prostaglandin E₂ and Thromboxane B₂ production and platelet activating factor receptor binding
    Saadawi S, Jalil J, Jasamai M, Jantan I
    Molecules, 2012;17(5):4824-35.
    PMID: 22538486 DOI: 10.3390/molecules17054824
    Acetylmelodorinol, chrysin and polycarpol, together with benzoic acid, benzoquinone and stigmasterol were isolated from the leaves of Mitrella kentii (Bl.) Miq. The compounds were evaluated for their ability to inhibit prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) production in human whole blood using a radioimmunoassay technique. Their inhibitory effect on platelet activating factor (PAF) receptor binding to rabbit platelet was determined using ³H-PAF as a ligand. Among the compounds tested, chrysin showed a strong dose-dependent inhibitory activity on PGE(2) production (IC₅₀ value of 25.5 µM), which might be due to direct inhibition of cyclooxygenase-2 (COX-2) enzymatic activity. Polycarpol, acetylmelodorinol and stigmasterol exhibited significant and concentration-dependent inhibitory effects on TXB₂ production with IC₅₀ values of 15.6, 19.1 and 19.4 µM, respectively, suggesting that they strongly inhibited COX-1 activity. Polycarpol and acetylmelodorinol showed strong dose-dependent inhibitory effects on PAF receptor binding with IC₅₀ values of 24.3 and 24.5 µM, respectively.
    Matched MeSH terms: Blood Platelets/metabolism
  3. Fulltext Platelet-activating factor (PAF) antagonistic activity of a new biflavonoid from Garcinia nervosa var. pubescens King
    Jalil J, Jantan I, Ghani AA, Murad S
    Molecules, 2012 Sep 10;17(9):10893-901.
    PMID: 22964504 DOI: 10.3390/molecules170910893
    The methanol extract of the leaves of Garcinia nervosa var. pubescens King, which showed strong inhibitory effects on platelet-activating factor (PAF) receptor binding, was subjected to bioassay-guided isolation to obtain a new biflavonoid, II-3,I-5, II-5,II-7,I-4',II-4'-hexahydroxy-(I-3,II-8)-flavonylflavanonol together with two known flavonoids, 6-methyl-4'-methoxyflavone and acacetin. The structures of the compounds were elucidated by spectroscopic methods. The compounds were evaluated for their ability to inhibit PAF receptor binding to rabbit platelets using ³H-PAF as a ligand. The biflavonoid and acacetin showed strong inhibition with IC₅₀ values of 28.0 and 20.4 µM, respectively. The results suggest that these compounds could be responsible for the strong PAF antagonistic activity of the plant.
    Matched MeSH terms: Blood Platelets/metabolism
  4. Isorhapontigenin, a resveratrol analogue selectively inhibits ADP-stimulated platelet activation
    Ravishankar D, Albadawi DAI, Chaggar V, Patra PH, Williams HF, Salamah M, et al.
    Eur J Pharmacol, 2019 Nov 05;862:172627.
    PMID: 31461638 DOI: 10.1016/j.ejphar.2019.172627
    Isorhapontigenin is a polyphenolic compound found in Chinese herbs and grapes. It is a methoxylated analogue of a stilbenoid, resveratrol, which is well-known for its various beneficial effects including anti-platelet activity. Isorhapontigenin possesses greater oral bioavailability than resveratrol and has also been identified to possess anti-cancer and anti-inflammatory properties. However, its effects on platelet function have not been reported previously. In this study, we report the effects of isorhapontigenin on the modulation of platelet function. Isorhapontigenin was found to selectively inhibit ADP-induced platelet aggregation with an IC50 of 1.85 μM although it displayed marginal inhibition on platelet aggregation induced by other platelet agonists at 100 μM. However, resveratrol exhibited weaker inhibition on ADP-induced platelet aggregation (IC50 > 100 μM) but inhibited collagen induced platelet aggregation at 50 μM and 100 μM. Isorhapontigenin also inhibited integrin αIIbβ3 mediated inside-out and outside-in signalling and dense granule secretion in ADP-induced platelet activation but interestingly, no effect was observed on α-granule secretion. Isorhapontigenin did not exert any cytotoxicity on platelets at the concentrations of up to 100 μM. Furthermore, it did not affect haemostasis in mice at the IC50 concentration (1.85 μM). In addition, the mechanistic studies demonstrated that isorhapontigenin increased cAMP levels and VASP phosphorylation at Ser157 and decreased Akt phosphorylation. This suggests that isorhapontigenin may interfere with cAMP and PI3K signalling pathways that are associated with the P2Y12 receptor. Molecular docking studies emphasised that isorhapontigenin has greater binding affinity to P2Y12 receptor than resveratrol. Our results demonstrate that isorhapontigenin has selective inhibitory effects on ADP-stimulated platelet activation possibly via P2Y12 receptor.
    Matched MeSH terms: Blood Platelets/metabolism
  5. Anticoagulation Therapy in Patients with Chronic Kidney Disease
    Saheb Sharif-Askari F, Syed Sulaiman SA, Saheb Sharif-Askari N
    Adv Exp Med Biol, 2017;906:101-114.
    PMID: 27628006
    Patients with chronic kidney disease (CKD) are at increased risk for both thrombotic events and bleeding. The early stages of CKD are mainly associated with prothrombotic tendency, whereas in its more advanced stages, beside the prothrombotic state, platelets can become dysfunctional due to uremic-related toxin exposure leading to an increased bleeding tendency. Patients with CKD usually require anticoagulation therapy for treatment or prevention of thromboembolic diseases. However, this benefit could easily be offset by the risk of anticoagulant-induced bleeding. Treatment of patients with CKD should be based on evidence from randomized clinical trials, but usually CKD patients are excluded from these trials. In the past, unfractionated heparins were the anticoagulant of choice for patients with CKD because of its independence of kidney elimination. However, currently low-molecular-weight heparins have largely replaced the use of unfractionated heparins owing to fewer incidences of heparin-induced thrombocytopenia and bleeding. We undertook this review in order to explain the practical considerations for the management of anticoagulation in these high risk population.
    Matched MeSH terms: Blood Platelets/metabolism
  6. Pharmacometabolomics analysis of plasma to phenotype clopidogrel high on treatment platelets reactivity in coronary artery disease patients
    Amin AM, Sheau Chin L, Teh CH, Mostafa H, Mohamed Noor DA, Abdul Kader MASK, et al.
    Eur J Pharm Sci, 2018 May 30;117:351-361.
    PMID: 29526765 DOI: 10.1016/j.ejps.2018.03.011
    Dual antiplatelet therapy (DAPT) of clopidogrel and aspirin is crucial for coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI). However, some patients may endure clopidogrel high on treatment platelets reactivity (HTPR) which may cause thromboembolic events. Clopidogrel HTPR is multifactorial with some genetic and non-genetic factors contributing to it. We aimed to use nuclear magnetic resonance (1H NMR) pharmacometabolomics analysis of plasma to investigate this multifactorial and identify metabolic phenotypes and pathways associated with clopidogrel HTPR. Blood samples were collected from 71 CAD patients planned for interventional angiographic procedure (IAP) before the administration of clopidogrel 600 mg loading dose (LD) and 6 h after the LD. Platelets function testing was done 6 h post-LD using VerifyNow® P2Y12 assay. Pre-dose and post-dose plasma samples were analysed using 1H NMR. Multivariate statistical analysis was used to indicate the discriminating metabolites. Two metabotypes, each with 34 metabolites (pre-dose and post-dose) were associated with clopidogrel HTPR. Pathway analysis of these metabotypes revealed that aminoacyl-tRNA biosynthesis, nitrogen metabolism and glycine-serine-threonine metabolism are the most perturbed metabolic pathways associated with clopidogrel HTPR. Furthermore, the identified biomarkers indicated that clopidogrel HTPR is multifactorial where the metabolic phenotypes of insulin resistance, type two diabetes mellitus, obesity, gut-microbiota and heart failure are associated with it. Pharmacometabolomics analysis of plasma revealed new insights on the implicated metabolic pathways and the predisposing factors of clopidogrel HTPR.
    Matched MeSH terms: Blood Platelets/metabolism
  7. Platelet-activating factor (PAF) receptor binding activity of the roots of Enicosanthellum pulchrum
    Nordin N, Jalil J, Jantan I, Murad S
    Pharm Biol, 2012 Mar;50(3):284-90.
    PMID: 22103812 DOI: 10.3109/13880209.2011.602416
    Enicosanthellum pulchrum (King) Heusden (Annonaceae) is a coniferous tree that is confined to mountain forests. The chemical constituents of this species have been studied previously; however, its biological activity has never been investigated before and is reported here for the first time.
    Matched MeSH terms: Blood Platelets/metabolism*
  8. Human platelet lysate permits scale-up of dental pulp stromal cells for clinical applications
    Govindasamy V, Ronald VS, Abdullah AN, Ganesan Nathan KR, Aziz ZA, Abdullah M, et al.
    Cytotherapy, 2011 Nov;13(10):1221-33.
    PMID: 21929379 DOI: 10.3109/14653249.2011.602337
    BACKGROUND AIMS. Dental pulp stromal cells (DPSC) are considered to be a promising source of stem cells in the field of regenerative therapy. However, the usage of DPSC in transplantation requires large-scale expansion to cater for the need for clinical quantity without compromising current good manufacturing practice (cGMP). Existing protocols for cell culturing make use of fetal bovine serum (FBS) as a nutritional supplement. Unfortunately, FBS is an undesirable additive to cells because it carries the risk of transmitting viral and prion diseases. Therefore, the present study was undertaken to examine the efficacy of human platelet lysate (HPL) as a substitute for FBS in a large-scale set-up. METHODS. We expanded the DPSC in Dulbecco's modified Eagle's medium-knock-out (DMEM-KO) with either 10% FBS or 10% HPL, and studied the characteristics of DPSC at pre- (T25 culture flask) and post- (5-STACK chamber) large-scale expansion in terms of their identity, quality, functionality, molecular signatures and cytogenetic stability. RESULTS. In both pre- and post-large-scale expansion, DPSC expanded in HPL showed extensive proliferation of cells (c. 2-fold) compared with FBS; the purity, immune phenotype, colony-forming unit potential and differentiation were comparable. Furthermore, to understand the gene expression profiling, the transcriptomes and cytogenetics of DPSC expanded under HPL and FBS were compared, revealing similar expression profiles. CONCLUSIONS. We present a highly economized expansion of DPSC in HPL, yielding double the amount of cells while retaining their basic characteristics during a shorter time period under cGMP conditions, making it suitable for therapeutic applications.
    Matched MeSH terms: Blood Platelets/metabolism*
  9. Fulltext Effects of chalcone derivatives on players of the immune system
    Lee JS, Bukhari SN, Fauzi NM
    Drug Des Devel Ther, 2015;9:4761-78.
    PMID: 26316713 DOI: 10.2147/DDDT.S86242
    The immune system is the defense mechanism in living organisms that protects against the invasion of foreign materials, microorganisms, and pathogens. It involves multiple organs and tissues in human body, such as lymph nodes, spleen, and mucosa-associated lymphoid tissues. However, the execution of immune activities depends on a number of specific cell types, such as B cells, T cells, macrophages, and granulocytes, which provide various immune responses against pathogens. In addition to normal physiological functions, abnormal proliferation, migration, and differentiation of these cells (in response to various chemical stimuli produced by invading pathogens) have been associated with several pathological disorders. The unwanted conditions related to these cells have made them prominent targets in the development of new therapeutic interventions against various pathological implications, such as atherosclerosis and autoimmune diseases. Chalcone derivatives exhibit a broad spectrum of pharmacological activities, such as immunomodulation, as well as anti-inflammatory, anticancer, antiviral, and antimicrobial properties. Many studies have been conducted to determine their inhibitory or stimulatory activities in immune cells, and the findings are of significance to provide a new direction for subsequent research. This review highlights the effects of chalcone derivatives in different types of immune cells.
    Matched MeSH terms: Blood Platelets/metabolism
  10. Fulltext The endogenous antimicrobial cathelicidin LL37 induces platelet activation and augments thrombus formation
    Salamah MF, Ravishankar D, Kodji X, Moraes LA, Williams HF, Vallance TM, et al.
    Blood Adv, 2018 11 13;2(21):2973-2985.
    PMID: 30413433 DOI: 10.1182/bloodadvances.2018021758
    Platelet-associated complications including thrombosis, thrombocytopenia, and hemorrhage are commonly observed during various inflammatory diseases such as sepsis, inflammatory bowel disease, and psoriasis. Despite the reported evidence on numerous mechanisms/molecules that may contribute to the dysfunction of platelets, the primary mechanisms that underpin platelet-associated complications during inflammatory diseases are not fully established. Here, we report the discovery of formyl peptide receptor 2, FPR2/ALX, in platelets and its primary role in the development of platelet-associated complications via ligation with its ligand, LL37. LL37 acts as a powerful endogenous antimicrobial peptide, but it also regulates innate immune responses. We demonstrate the impact of LL37 in the modulation of platelet reactivity, hemostasis, and thrombosis. LL37 activates a range of platelet functions, enhances thrombus formation, and shortens the tail bleeding time in mice. By utilizing a pharmacological inhibitor and Fpr2/3 (an ortholog of human FPR2/ALX)-deficient mice, the functional dependence of LL37 on FPR2/ALX was determined. Because the level of LL37 is increased in numerous inflammatory diseases, these results point toward a critical role for LL37 and FPR2/ALX in the development of platelet-related complications in such diseases. Hence, a better understanding of the clinical relevance of LL37 and FPR2/ALX in diverse pathophysiological settings will pave the way for the development of improved therapeutic strategies for a range of thromboinflammatory diseases.
    Matched MeSH terms: Blood Platelets/metabolism
  11. Effect of menopause on platelet activation markers determined by flow cytometry
    Roshan TM, Normah J, Rehman A, Naing L
    Am J Hematol, 2005 Dec;80(4):257-61.
    PMID: 16315264
    Pre-menopausal women have a lower risk of cardiovascular disease compared to post-menopausal women. Cardiovascular disease is more age dependent in women than in men. The association of platelet activation and cardiovascular thrombotic events is well established. Standardized techniques were used to evaluate platelet activation markers by flow cytometry, using 3-color analysis (CD 61PerCP, CD 62P, and PAC-1) in 49 post-menopausal (mean +/- SD age, 56.16 +/- 33.51 years) and 42 pre-menopausal (age, 39.38 +/- 7.07 years) women. Results of our study showed a significant increase in CD 62P in post-menopausal women as compared to the pre-menopausal group (2.66 +/- 4.26% vs. 0.52 +/- 2.71%, P < 0.001). Similarly, PAC-1 was significantly increased in post-menopausal women (21.54 +/- 2.48% vs. 3.70 +/- 2.31%, P < 0.001). Furthermore, there was a significant association of CD 62P with serum estradiol in both groups. PAC-1 was significantly associated with age in both groups. The results suggest the role of platelets in the increased incidence of thrombotic events and disease in post-menopausal women.
    Matched MeSH terms: Blood Platelets/metabolism*
  12. Risk factors and clinical outcome of profound thrombocytopenia in adult patients with DENV infections
    Dhanoa A, Rajasekaram G, Hassan SS, Ramadas A, Azreen Adnan NA, Lau CF, et al.
    Platelets, 2017 Nov;28(7):724-727.
    PMID: 28287000 DOI: 10.1080/09537104.2017.1293802
    Severe thrombocytopenia is common in dengue virus (DENV) infections. However, studies focusing on the role of profound thrombocytopenia (PT) (nadir platelet counts ≤ 20 000/mm3) in DENV infections are scarce. This study aims to identify the associated features and outcome of DENV patients with PT. It involves 237 adult hospitalized patients who were DENV PCR positive. The presence of comorbidity (AOR = 4.625; 95% CI = 1.113-19.230), higher admission hematocrit (AOR = 1.213; 95% CI = 1.067-1.379), lower admission albumin (AOR = 0.870; 95% CI = 0.766-0.988) and lower admission platelets (AOR = 0.980; 95% CI = 0.969-0.991) was associated with platelets ≤ 20 000/mm3 in multivariate logistic regression. PT was not affected by DENV serotypes, coinfections and secondary DENV infections. Patients with PT had significantly higher risk of experiencing warning signs (AOR = 3.709, 95% CI = 1.089-12.634) and longer hospital stay (AOR = 1.943, 95% CI = 1.010-3.774). However, severe dengue disease, hemorrhagic manifestations and need for intensive care were not significantly associated with PT.
    Matched MeSH terms: Blood Platelets/metabolism
  13. Fulltext Neonatal alloimmune thrombocytopaenia associated with maternal HLA antibodies
    Wendel K, Akkök ÇA, Kutzsche S
    BMJ Case Rep, 2017 Jul 05;2017.
    PMID: 28679510 DOI: 10.1136/bcr-2016-218269
    Neonatal alloimmune thrombocytopaenia (NAIT) generally results from platelet opsonisation by maternal antibodies against fetal platelet antigens inherited from the infant's father. Newborn monochorionic twins presented with petechial haemorrhages at 10 hours of life, along with severe thrombocytopaenia. Despite the initial treatment with platelet transfusions and intravenous immunoglobulin, they both had persistent thrombocytopaenia during their first 45 days of life. Class I human leucocyte antigen (HLA) antibodies with broad specificity against several HLA-B antigens were detected in the maternal serum. Weak antibodies against HLA-B57 and HLA-B58 in sera from both twins supported NAIT as the most likely diagnosis. Platelet transfusion requirements of the twins lasted for 7 weeks. Transfusion of HLA-matched platelet concentrates was more efficacious to manage thrombocytopaenia compared with platelet concentrates from random donors. Platelet genotyping and determination of HLA antibody specificity are needed to select compatible platelet units to expedite safe recovery from thrombocytopaenia in NAIT.
    Matched MeSH terms: Blood Platelets/metabolism*
  14. Fulltext Lyophilised Platelet-Rich Fibrin: Physical and Biological Characterisation
    Ngah NA, Dias GJ, Tong DC, Mohd Noor SNF, Ratnayake J, Cooper PR, et al.
    Molecules, 2021 Nov 25;26(23).
    PMID: 34885714 DOI: 10.3390/molecules26237131
    BACKGROUND: Platelet-rich fibrin (PRF) has gained popularity in craniofacial surgery, as it provides an excellent reservoir of autologous growth factors (GFs) that are essential for bone regeneration. However, the low elastic modulus, short-term clinical application, poor storage potential and limitations in emergency therapy use restrict its more widespread clinical application. This study fabricates lyophilised PRF (Ly-PRF), evaluates its physical and biological properties, and explores its application for craniofacial tissue engineering purposes.

    MATERIAL AND METHODS: A lyophilisation method was applied, and the outcome was evaluated and compared with traditionally prepared PRF. We investigated how lyophilisation affected PRF's physical characteristics and biological properties by determining: (1) the physical and morphological architecture of Ly-PRF using SEM, and (2) the kinetic release of PDGF-AB using ELISA.

    RESULTS: Ly-PRF exhibited a dense and homogeneous interconnected 3D fibrin network. Moreover, clusters of morphologically consistent cells of platelets and leukocytes were apparent within Ly-PRF, along with evidence of PDGF-AB release in accordance with previously reports.

    CONCLUSIONS: The protocol established in this study for Ly-PRF preparation demonstrated versatility, and provides a biomaterial with growth factor release for potential use as a craniofacial bioscaffold.

    Matched MeSH terms: Blood Platelets/metabolism
  15. In vitro inhibitory effect of rubraxanthone isolated from Garcinia parvifolia on platelet-activating factor receptor binding
    Jantan I, Pisar MM, Idris MS, Taher M, Ali RM
    Planta Med, 2002 Dec;68(12):1133-4.
    PMID: 12494345
    Rubraxanthone and isocowanol isolated from Garcinia parvifolia Miq. were investigated for their inhibitory effects on platelet-activating factor (PAF) binding to rabbit platelets using 3H-PAF as a ligand. Rubraxanthone showed a strong inhibition with IC 50 value of 18.2 microM. The IC 50 values of macluraxanthone, 6-deoxyjacareubin, 2-(3-methylbut-2-enyl)-1,3,5-trihydroxyxanthone, 2-(3-methylbut-2-enyl)-1,3,5,6-tetrahydroxyxanthone and 1,3,5-trihydroxy-6,6'-dimethylpyrano(2',3':6,7)-4-(1,1-dimethylprop-2-enyl)-xanthone were also determined for comparison. In the course of our study on structure-activity relationship of xanthones, the results revealed that a geranyl group substituted at C-8 was beneficial to the binding while a hydroxylated prenyl group at C-4 resulted in a significant loss in binding to the PAF receptor.
    Matched MeSH terms: Blood Platelets/metabolism
  16. Fulltext Platelets kill circulating parasites of all major Plasmodium species in human malaria
    Kho S, Barber BE, Johar E, Andries B, Poespoprodjo JR, Kenangalem E, et al.
    Blood, 2018 Sep 20;132(12):1332-1344.
    PMID: 30026183 DOI: 10.1182/blood-2018-05-849307
    Platelets are understood to assist host innate immune responses against infection, although direct evidence of this function in any human disease, including malaria, is unknown. Here we characterized platelet-erythrocyte interactions by microscopy and flow cytometry in patients with malaria naturally infected with Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, or Plasmodium knowlesi Blood samples from 376 participants were collected from malaria-endemic areas of Papua, Indonesia, and Sabah, Malaysia. Platelets were observed binding directly with and killing intraerythrocytic parasites of each of the Plasmodium species studied, particularly mature stages, and was greatest in P vivax patients. Platelets preferentially bound to the infected more than to the uninfected erythrocytes in the bloodstream. Analysis of intraerythrocytic parasites indicated the frequent occurrence of platelet-associated parasite killing, characterized by the intraerythrocytic accumulation of platelet factor-4 and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling of parasite nuclei (PF4+TUNEL+ parasites). These PF4+TUNEL+ parasites were not associated with measures of systemic platelet activation. Importantly, patient platelet counts, infected erythrocyte-platelet complexes, and platelet-associated parasite killing correlated inversely with patient parasite loads. These relationships, taken together with the frequency of platelet-associated parasite killing observed among the different patients and Plasmodium species, suggest that platelets may control the growth of between 5% and 60% of circulating parasites. Platelet-erythrocyte complexes made up a major proportion of the total platelet pool in patients with malaria and may therefore contribute considerably to malarial thrombocytopenia. Parasite killing was demonstrated to be platelet factor-4-mediated in P knowlesi culture. Collectively, our results indicate that platelets directly contribute to innate control of Plasmodium infection in human malaria.
    Matched MeSH terms: Blood Platelets/metabolism
  17. Fulltext Anti-inflammatory and antiplatelet activities of plasma are conserved across twelve mammalian species
    Ahmed S, Gul S, Idris F, Hussain A, Zia-Ul-Haq M, Jaafar HZ, et al.
    Molecules, 2014;19(8):11385-94.
    PMID: 25090125 DOI: 10.3390/molecules190811385
    Human plasma inhibits arachidonic acid metabolism and platelet aggregation. This helps human form a haemostatic control system that prevents the progress of certain aggregatory or inflammatory reactions. Whether this property of plasma is unique to human or extends to other species is not well known. It is speculated that this protective ability of plasma remains evolutionarily conserved in different mammals. In order to confirm this, the effect of plasma from 12 different mammalian species was investigated for its inhibitory potential against arachidonic acid metabolism and platelet aggregation. Metabolism of arachidonic acid by cyclooxygenase and lipoxygenase pathways was studies using radio-immuno assay and thin layer chromatography while platelet aggregation in the plasma of various mammals was monitored following turbedmetric method in a dual channel aggregometer. Results indicate that inhibition of AA metabolism and platelet aggregation is a common feature of plasma obtained from different mammalian species, although there exists large interspecies variation. This shows that besides human, other mammals also possess general protective mechanisms against various aggregatory and inflammatory conditions and this anti-inflammatory property of the plasma is evolutionarily conserved in mammalian species. The most likely candidates responsible for these properties of plasma include haptoglobin, albumin and lipoproteins.
    Matched MeSH terms: Blood Platelets/metabolism
  18. In vitro capacity of different grades of chitosan derivatives to induce platelet adhesion and aggregation
    Periayah MH, Halim AS, Hussein AR, Saad AZ, Rashid AH, Noorsal K
    Int J Biol Macromol, 2013 Jan;52:244-9.
    PMID: 23063426 DOI: 10.1016/j.ijbiomac.2012.10.001
    Chitosan-derived hemostatic agents with various formulations may have distinct potential in hemostasis. This study assessed the ability of different grades and forms of chitosan derivatives as hemostatic agents to enhance platelet adhesion and aggregation in vitro. The chitosan derivatives utilized were 2% NO-CMC, 7% NO-CMC (with 0.45 mL collagen), 8% NO-CMC, O-C 52, 5% O-CMC-47, NO-CMC-35, and O-C 53. Samples of chitosan derivatives weighing 5mg were incubated at 37°C with 50 μL of phosphate buffer saline (PBS) (pH 7.4) for 60 min. The morphological features of the platelets upon adherence to the chitosan were viewed using scanning electron microscope (SEM), and the platelet count was analyzed with an Automated Hematology Analyzer. For platelet aggregation, we added an adenosine diphosphate (ADP) agonist to induce the chitosan-adhered platelets. O-C 52 bound with platelets exhibited platelet aggregates and clumps on the surface of the membrane layer with approximately 70-80% coverage. A statistically significant correlation (p<0.01) for the platelet count was identified between the baseline value and the values at 10 min and 20 min. The results indicate that O-C 53 and O-C 52 were able to promote clotting have the potential to induce the release of platelets engaged in the process of hemostasis.
    Matched MeSH terms: Blood Platelets/metabolism*
  19. Platelets of habitual smokers have reduced susceptibility to aggregating agent
    Foo LC, Roshidah I, Aimy MB
    Thromb. Haemost., 1991 Mar 4;65(3):317-9.
    PMID: 2048056 DOI: 10.1055/s-0038-1648142
    Platelet aggregation to collagen, and productions of 6-keto-prostaglandin-F1-alpha and thromboxane B2 during aggregation were measured after an overnight fast, involving both food and cigarettes, in 19 clinically healthy habitual smokers (10 or more cigarettes/day) and 23 non-smokers receiving the same diet. The subjects (all males; ages = 21-30 years) were residents of a school hostel. Mean platelet aggregation was significantly lower in smokers than non-smokers (23.2 ohms vs 31.5 ohms, p less than 0.005). Non-smokers had significantly higher mean concentration of 6-keto-prostaglandin-F1-alpha than smokers (109.8 pmol/l vs 92.3 pmol/l, p less than 0.05). The level of thromboxane B2 did not differ significantly between the two groups. These observations suggest that the role of smoking as a risk factor for ischaemic heart disease is unlikely to be related to a direct enhancement of aggregation. On the contrary, the observations seem to suggest that habitual smoking may directly reduce platelet aggregability.
    Matched MeSH terms: Blood Platelets/metabolism
  20. Fulltext Effect of ultrapure lipopolysaccharides derived from diverse bacterial species on the modulation of platelet activation
    Vallance TM, Ravishankar D, Albadawi DAI, Layfield H, Sheard J, Vaiyapuri R, et al.
    Sci Rep, 2019 12 03;9(1):18258.
    PMID: 31796818 DOI: 10.1038/s41598-019-54617-w
    Platelets are small circulating blood cells that play essential roles in the maintenance of haemostasis via blood clotting. However, they also play critical roles in the regulation of innate immune responses. Inflammatory receptors, specifically Toll-like receptor (TLR)-4, have been reported to modify platelet reactivity. A plethora of studies have reported controversial functions of TLR4 in the modulation of platelet function using various chemotypes and preparations of its ligand, lipopolysaccharide (LPS). The method of preparation of LPS may explain these discrepancies however this is not fully understood. Hence, to determine the impact of LPS on platelet activation, we used ultrapure preparations of LPS from Escherichia coli (LPSEC), Salmonella minnesota (LPSSM), and Rhodobacter sphaeroides (LPSRS) and examined their actions under diverse experimental conditions in human platelets. LPSEC did not affect platelet activation markers such as inside-out signalling to integrin αIIbβ3 or P-selectin exposure upon agonist-induced activation in platelet-rich plasma or whole blood whereas LPSSM and LPSRS inhibited platelet activation under specific conditions at supraphysiological concentrations. Overall, our data demonstrate that platelet activation is not largely influenced by any of the ultrapure LPS chemotypes used in this study on their own except under certain conditions.
    Matched MeSH terms: Blood Platelets/metabolism
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