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Biting insect and tick allergens
Published in Richard F. Lockey, Dennis K. Ledford, Allergens and Allergen Immunotherapy, 2020
Donald R. Hoffman, Jennifer E. Fergeson
There are over 18,000 species of Simulium, blackflies, identified worldwide. This species is also referred to as the bloodsucking blackfly due to the large amount of bleeding that can occur at the site of the bite. Studies on the saliva of blackflies are limited. Anticoagulation factors against thrombin in blackfly saliva may account for this abnormality in hemostasis [30,31]. Cupp et al. isolated and cloned a major protein of molecular weight 15.35 kDa with strong vasodilator activity manifested by rapid and persistent induction of erythema [31]. The enzyme apyrase is found in blackfly salivary gland secretions. Wirtz demonstrated easily measurable amounts of histamine, putrescine, spermine, N-monoacetyl-spermine and spermidine, as well as the presence of proteins with esterase activity in salivary gland secretion [32]. Almost all reactions to blackfly bites are not IgE mediated, and the dermatologic reactions are classified into six forms by Farkas [33]. These include edematous, erythematous-edematous, erysipeloid, inflammatory-indurative, hemorrhagic (plaques, nodules, or vesicles), and allergic.
The Diseases – Malaria, Filariasis and Dengue
Published in Jacques Derek Charlwood, The Ecology of Malaria Vectors, 2019
Once the incubation period is over and the mosquito has sporozoites in the salivary glands (and so is infectious rather than just being infected), then the situation is reversed and the more probing and feeding that the mosquito undertakes the greater the amount of transmission. A number of factors affect this. A simple mechanical blockage of the hypopharynx may reduce the mosquito’s ability to salivate so it may make several attempts to feed on more than a single host. The enzyme apyrase, involved in feeding efficiency, is also reduced in sporozoite-infected females which may also result in increased probing. The mosquitoes may also take smaller (and so more frequent) blood meals. All of these factors may enhance transmission.
Platelet Function in Hemostasis
Published in Genesio Murano, Rodger L. Bick, Basic Concepts of Hemostasis and Thrombosis, 2019
Thrombin activation of platelets is complete and irreversible. ADP is likely required at some step because adenosine block of the release reaction or apyrase removal of ADP both inhibit thrombin-induced platelet aggregation.74,81-82 That thrombin produces fibrin on the platelet surface to account for platelet aggregation is doubtful in view of these observations.83,84 In addition, snake venoms and staphylococcal coagulase will clot fibrinogen without platelet aggregation.85,86 These clots will not retract, indicating lack of platelet function at that physiologic level.
Apyrase decreases phage induction and Shiga toxin release from E. coli O157:H7 and has a protective effect during infection
Published in Gut Microbes, 2022
Ida Arvidsson, Ashmita Tontanahal, Karl Johansson, Ann-Charlotte Kristoffersson, Sára Kellnerová, Michael Berger, Ulrich Dobrindt, Diana Karpman
The ectonucleoside apyrase/CD39 hydrolyses ATP to ADP and ADP to AMP.20 In this study, the aim was to investigate whether administration of apyrase, which would eliminate extracellular ATP, could have a beneficial effect during E. coli O157:H7 infection using bacterial cultures and an established mouse model.21 The effect of apyrase on induction of the bacteriophage, as reflected by RecA levels, stx2 gene levels and toxin release from E. coli O157:H7, were demonstrated in vitro. Infected mice treated with apyrase, or left untreated, were assessed for clinical signs of disease, weight loss, goblet cell depletion, intestinal apoptosis as well as the release of fecal ATP and Stx2. Additionally, the effect of apyrase on collagen-induced platelet aggregation in human plasma, in the presence of Stx2 and E. coli O157 lipopolysaccharide (O157 LPS), was investigated.
Sorting and magnetic-based isolation of reticulated platelets from peripheral blood
Published in Platelets, 2021
Isabell Bernlochner, Melissa Klug, Ditya Larasati, Moritz Von Scheidt, Donato Santovito, Michael Hristov, Christian Weber, Karl-Ludwig Laugwitz, Dario Bongiovanni
CRITICAL: Set acceleration and deceleration to the lowest level. (3)The sample is now separated into red blood cells (RBC), buffy coat and plasma. Take only the plasma phase. Depending on the donor, take ~1–2 mL of plasma per vial and collect it in a fresh 15 mL tube. Be careful to not aspirate the buffy coat.(4)Add apyrase to prevent ADP-mediated platelet activation (0.6 U ADPase/mL) to the plasma. For example, add 6 µL of the aliquot solution to 1 mL of plasma. Additionally, add 1 µM prostaglandin E1 (e.g. 10 µL from the PGE1 aliquot to 1 mL of plasma). Carefully tip against the tube to mix.(5)Incubate the sample in a 37°C water bath for 30 min.(6)Further platelet aggregation can be prevented by adding 5 mM EDTA (e.g. 10 µL stock/mL plasma) and reducing the pH adding 1 mM citric acid (e.g. 10 µL of stock/mL plasma). Gently roll the tube without inversion to mix, do not pipet up and down. CRITICAL: EDTA irreversibly denaturates many proteins including the integrin complex GPIIb/IIIa. Consider avoiding the usage of EDTA if downstream proteomic investigation is planned.(7)Immediately centrifuge the sample at 800 × g for 15 min at room temperature without brake.
T cell inhibitory mechanisms in a model of aggressive Non-Hodgkin's Lymphoma
Published in OncoImmunology, 2018
Tamara Hilmenyuk, Carla A. Ruckstuhl, Michael Hayoz, Christian Berchtold, Jean-Marc Nuoffer, Shyam Solanki, Hector C. Keun, Paul A. Beavis, Carsten Riether, Adrian F. Ochsenbein
Experiments with apyrase that leads to the degradation of ATP to ADP and AMP, with CD39−/− T cells that prevent the degradation of ATP and with A2A−/− T cells indicated that ATP itself and its degradation products reduce T cell proliferation. Moreover, T cells isolated from Eµ-myc x CD39−/−+L mice proliferated more efficiently ex vivo than T cells isolated from control lymphoma-bearing mice. These data indicate that although CD39 deficiency results in substantially higher concentrations of ATP, the lack of its degradation products leads to an improved T cell response in lymphoma bearing CD39−/− x Eµ-myc mice. However, although T cell function was partially improved, there was no significant survival difference between CD39-competent or -deficient lymphoma mice. Of note, absence of CD39 resulted in substantially higher concentrations of ATP that by itself mediates T cell suppression.