The Role of GBPIalpha in Phagocytosis of Platelets by Macrophages.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3958-3958
Author(s):  
Bahram Alamdary Badlou ◽  
Gerit Spierenburg ◽  
Hans Ulricht ◽  
Hans Deckmyn ◽  
W. Martin Smid ◽  
...  
Keyword(s):  
Amino Acids ◽  
Study Design ◽  
Cold Storage ◽  
Human Platelets ◽  
Single Population ◽  
Platelet Storage ◽  
Induced Changes ◽  
Design And Methods

Abstract Platelet storage at 04 C suppresses bacterial multiplication, but induces clusters of glycoprotein (GP) Ibalpha that trigger their phagocytosis by macrophages and reduce their survival after transfusion. We searched for a method that detects cold-induced changes in GPIbalpha involved in phagocytosis. STUDY DESIGN AND METHODS: Human platelets were isolated and stored for up to 48 hrs at 0C. Binding of a PE-labeled antibody directed against amino acids 1–35 on GPIbalpha (AN51-PE) was compared with phagocytosis of platelets by matured monocytic THP-1 cells, analyzed by FACS. RESULTS: Freshly isolated platelets were detected as a single population of AN51-PE positive particles and showed < 5% phagocytosis. Cold storage led to a decrease in AN51-PE binding and an increase in phagocytosis. N-acetylglucosamine (GlcNAc), known to interfere with macrophage recognition of GPIbalpha clusters, restored normal AN51-PE binding to cold-stored platelets and suppressed phagocytosis. CONCLUSIONS: We conclude that binding of an antibody against AA 1–35 on GPIbalpha reflects changes in GPIbalpha that make platelets targets for phagocytosis by macrophages.

Loss of Thrombin-Induced Ca2+ Mobilization in a Subpopulation of Platelets during Storage

1991 ◽  
Vol 66 (03) ◽  
pp. 350-354 ◽  
Author(s):  
Rob Fijnheer ◽  
Christa H E Homburg ◽  
Berend Hooibrink ◽  
Martine N Boomgaard ◽  
Dirk de Korte ◽  
...  
Keyword(s):  
Human Platelets ◽  
Flow Cytometer ◽  
Maximal Concentration ◽  
Gradual Decline ◽  
Platelet Storage ◽  
Functional Defect ◽  
Total Fluorescence ◽  
Induced Changes

SummaryThrombin-induced changes in cytosolic free Ca2+ ([Ca2+]i) were studied in human platelets that had been stored for up to 6 days. Changes in [Ca2+]i were measured with Indo-1-loaded platelets and quantitated with two different methods: (i) measurement of the changes in total fluorescence; (ii) measurement of the [Ca2+]i changes in individual platelets in a flow cytometer, allowing the detection of non-responding platelets. The maximal concentration of [Ca2+]i after stimulation with 0.5 U of thrombin/ml decreased from 544 ± 58 nM (mean ± SEM, n = 6) on day 0, to 276 ± 9 nM on day 3 and to 203 ± 23 nM on day 6. The percentage of platelets responding to 0.5 U of thrombin/ml declined from 90 ± 2% on day 0 to 72 ± 4% on day 3, and to 47 ± 8% on day 6. Nevertheless, also the responding platelets showed a decreased rise in [Ca2+]i.The study shows that during platelet storage a decrease in the rise in [Ca2+]i upon thrombin stimulation occurs. This decrease is partly due to the formation of a subpopulation of platelets that is completely unresponsive and partly due to a decreased responsiveness in the remainder of the platelets; it is not due to a gradual decline in [Ca2+]i rise in all platelets. This phenomenon provides new insight in the functional defect of stored platelets.

Galactosylation does not prevent the rapid clearance of long-term, 4°C-stored platelets

Blood ◽  
2008 ◽  
Vol 111 (6) ◽  
pp. 3249-3256 ◽  
Author(s):  
Hans H. Wandall ◽  
Karin M. Hoffmeister ◽  
Anne Louise Sørensen ◽  
Viktoria Rumjantseva ◽  
Henrik Clausen ◽  
...  
Keyword(s):  
Cold Storage ◽  
Murine Model ◽  
Phase 1 ◽  
Human Platelets ◽  
C Storage ◽  
Platelet Storage ◽  
Rapid Clearance ◽  
Novel Method ◽  
Apheresis Platelets

AbstractCold storage of platelets for transfusion is desirable to extend platelet storage times and to prevent bacterial growth. However, the rapid clearance of cold-stored platelets prevents their use. A novel method for preventing the rapid clearance of cold-stored platelets has previously been developed in a murine model. Cold storage induces the clustering and recognition of exposed β-N-acetylglucosamine (βGlcNAc) on platelet surfaces. Glycosylation of βGlcNAc residues with uridine 5′-diphosphogalactose (UDP-galactose) results in the normal survival of short-term (2 h) 0°C-stored murine platelets. Based on this finding, we developed a similar glycosylation process by adding UDP-galactose to human apheresis platelets. A phase 1 clinical trial was conducted transfusing radiolabeled autologous apheresis platelets stored for 48 hours at 4°C with or without pretreatment with UDP-galactose. In contrast to the murine study, galactosylation of human platelets did not prevent the accelerated platelet clearance routinely observed after 4°C storage. We next developed a murine model of platelet storage for 48 hours at 4°C and showed that UDP-galactose treatment of murine platelets also did not prevent their rapid clearance, in agreement with the human platelet study. We conclude that different mechanisms of clearance may exist for short- and long-term cold-stored platelets.

scholarly journals Oral and pre-absorptive sensing of amino acids relates to hypothalamic control of food intake in rainbow trout

2020 ◽  
Vol 223 (17) ◽  
pp. jeb221721
Author(s):  
Sara Comesaña ◽  
Marta Conde-Sieira ◽  
Cristina Velasco ◽  
José L. Soengas ◽  
Sofia Morais
Keyword(s):  
Amino Acids ◽  
Rainbow Trout ◽  
Food Intake ◽  
Oral Administration ◽  
Glutamic Acid ◽  
Oral Treatment ◽  
Taste Receptor ◽  
Induced Changes ◽  
First Time

ABSTRACTTo assess the putative role of taste and pre-absorptive sensing of amino acids in food intake control in fish, we carried out an oral administration with l-leucine, l-valine, l-proline or l-glutamic acid in rainbow trout (Oncorhynchus mykiss). Treatment with proline significantly reduced voluntary food intake at 2 h and 3 h after oral administration, while glutamic acid showed a less pronounced satiating effect at 3 h. The mRNA expression of taste receptor subunits tas1r1, tas1r2a, tas1r2b and tas1r3 was measured in the epithelium overlying the bony basihyal of the fish (analogous to the tetrapod tongue) at 10, 20 or 30 min following treatment. No significant changes were observed, except for a tas1r down-regulation by valine at 30 min. Of the downstream taste signalling genes that were analysed in parallel, plcb2 and possibly trpm5 (non-significant trend) were down-regulated 20 min after proline and glutamic acid treatment. The signal originated in the oropharyngeal and/or gastric cavity presumably relays to the brain as changes in genes involved in the regulation of food intake occurred in hypothalamus 10–30 min after oral treatment with amino acids. In particular, proline induced changes consistent with an increased anorexigenic potential in the hypothalamus. We have therefore demonstrated, for the first time in fish, that the peripheral (pre-absorptive) detection of an amino acid (l-proline), presumably by taste-related mechanisms, elicits a satiety signal that in hypothalamus is translated into changes in cellular signalling and neuropeptides regulating food intake, ultimately resulting in decreased food intake.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Collagen-Induced Platelet Aggregation: -Evidence Against the Essential Role of Platelet Adenosine Diphosphate

1979 ◽  
Vol 42 (04) ◽  
pp. 1193-1206 ◽  
Author(s):  
Barbara Nunn
Keyword(s):  
Platelet Aggregation ◽  
Time Course ◽  
Essential Role ◽  
Atp Release ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
High Doses ◽  
Induced Aggregation

SummaryThe hypothesis that platelet ADP is responsible for collagen-induced aggregation has been re-examined. It was found that the concentration of ADP obtaining in human PRP at the onset of aggregation was not sufficient to account for that aggregation. Furthermore, the time-course of collagen-induced release in human PRP was the same as that in sheep PRP where ADP does not cause release. These findings are not consistent with claims that ADP alone perpetuates a collagen-initiated release-aggregation-release sequence. The effects of high doses of collagen, which released 4-5 μM ADP, were not inhibited by 500 pM adenosine, a concentration that greatly reduced the effect of 300 μM ADP. Collagen caused aggregation in ADP-refractory PRP and in platelet suspensions unresponsive to 1 mM ADP. Thus human platelets can aggregate in response to collagen under circumstances in which they cannot respond to ADP. Apyrase inhibited aggregation and ATP release in platelet suspensions but not in human PRP. Evidence is presented that the means currently used to examine the role of ADP in aggregation require investigation.

Correlation Between Noradrenaline Fluxes, Metabolism and Compartmentalisation in Human Platelets

1982 ◽  
Vol 48 (01) ◽  
pp. 062-066 ◽  
Author(s):  
Chantal Legrand ◽  
Véronique Dubernard ◽  
Philippe Meyer
Keyword(s):  
Noradrenaline Release ◽  
Human Platelets ◽  
Release Of Noradrenaline ◽  
Storage Pool ◽  
Platelet Storage ◽  
Efflux Of Noradrenaline ◽  
Preferential Localization

Summary(3H) noradrenaline was taken up by human platelets and partially converted into sulfoconjugated noradrenaline. This uptake was inhibited by drugs which have been previously shown to impair the uptake of 5-HT (ouabain, chlorimipramine) or the storage of 5-HT (tyramine, reserpine) by platelets. In addition, tyramine and reserpine stimulated the formation of sulfoconjugated noradrenaline. The efflux of noradrenaline from platelets was measured in parallel and was found to be directly related to the proportion of non metabolized to metabolized noradrenaline in the cells. Unlike tyramine, which induced a similar release of noradrenaline and 5-HT, reserpine was less effective at inducing noradrenaline release than 5-HT release. This study indicates a preferential localization of noradrenaline in the granular pool of human platelets with the existence of an extragranular sulfoconjugated pool which is increased when the granular storage of noradrenaline is impaired. Studies of noradrenaline fluxes and metabolism may be useful in the understanding of both acquired and inherited platelet storage pool defects.

Role of amino acids and micronutrients on biosynthesis of spiramycins

1981 ◽  
Vol 31 (1) ◽  
pp. 189-193 ◽  
Author(s):  
Mohamed A. Ashy ◽  
Abd El-Galil ◽  
M. Khalil ◽  
Abou-Zeid A. Abou-Zeid
Keyword(s):  
Amino Acids

Exploring power in response inhibition tasks using the bootstrap: The impact of number of participants, number of trials, effect magnitude, and study design

2019 ◽  
Author(s):  
Curtis David Von Gunten ◽  
Bruce D Bartholow
Keyword(s):  
Study Design ◽  
Effect Size ◽  
Statistical Power ◽  
Bootstrap Sampling ◽  
Reliable Measure ◽  
Internal Reliability ◽  
The Impact ◽  
Power Analyses ◽  
Effect Magnitude

A primary psychometric concern with laboratory-based inhibition tasks has been their reliability. However, a reliable measure may not be necessary or sufficient for reliably detecting effects (statistical power). The current study used a bootstrap sampling approach to systematically examine how the number of participants, the number of trials, the magnitude of an effect, and study design (between- vs. within-subject) jointly contribute to power in five commonly used inhibition tasks. The results demonstrate the shortcomings of relying solely on measurement reliability when determining the number of trials to use in an inhibition task: high internal reliability can be accompanied with low power and low reliability can be accompanied with high power. For instance, adding additional trials once sufficient reliability has been reached can result in large gains in power. The dissociation between reliability and power was particularly apparent in between-subject designs where the number of participants contributed greatly to power but little to reliability, and where the number of trials contributed greatly to reliability but only modestly (depending on the task) to power. For between-subject designs, the probability of detecting small-to-medium-sized effects with 150 participants (total) was generally less than 55%. However, effect size was positively associated with number of trials. Thus, researchers have some control over effect size and this needs to be considered when conducting power analyses using analytic methods that take such effect sizes as an argument. Results are discussed in the context of recent claims regarding the role of inhibition tasks in experimental and individual difference designs.

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