6,208 research outputs found
Measuring Red Blood Cell Aggregation Forces Using Double Optical Tweezers
No full textClassic immunohematology approaches, based on agglutination techniques, have been used in manual and automated immunohematology laboratory routines. Red blood cell (RBC) agglutination depends on intermolecular attractive forces (hydrophobic bonds, Van der Walls, electrostatic forces and hydrogen bonds) and repulsive interactions (zeta potential). The aim of this study was to measure the force involved in RBC aggregation using double optical tweezers, in normal serum, in the presence of erythrocyte antibodies and associated to agglutination potentiator solutions (Dextran, low ionic strength solution [LISS] and enzymes). The optical tweezers consisted of a neodymium:yattrium aluminium garnet (Nd:YAG) laser beam focused through a microscope equipped with a minicam, which registered the trapped cell image in a computer where they could be analyzed using a software. For measuring RBC aggregation, a silica bead attached to RBCs was trapped and the force needed to slide one RBC over the other, as a function of the velocities, was determined. The median of the RBC aggregation force measured in normal serum (control) was 1 × 10-3 (0.1-2.5) poise.cm. The samples analyzed with anti-D showed 2 × 10-3 (1.0-4.0) poise.cm (p < 0.001). RBC diluted in potentiator solutions (Dextran 0.15%, Bromelain and LISS) in the absence of erythrocyte antibodies, did not present agglutination. High adherence was observed when RBCs were treated with papain. Results are in agreement with the imunohematological routine, in which non-specific results are not observed when using LISS, Dextran and Bromelain. Nevertheless, false positive results are frequently observed in manual and automated microplate analyzer using papain enzyme. The methodology proposed is simple and could provide specific information with the possibility of meansuration regarding RBC interaction. © 2013 Informa Healthcare.733262264Acronym; Sponsor: UM; National Science and Technology Development AgencyEylar, E.H., Madoff, M.A., Brody, O.V., Oncley, J.L., The contribution of sialic acid to the surface charge of the erythrocyte (1962) JBiol Chem, 237, pp. 1992-2000Jaime, J.C., Immune-medicated agglutination of cytoskeletonfree RBC microvesicles (2000) Transfusion, 40, pp. 566-570Van Oss, C.J., Absolon, D.R., Zeta potential van der walls forces and hemagglutination (1983) Vox Sang, 44, pp. 183-190Pollack, W., Hager, H.J., Reckel, R., Toren, D.A., Singher, H.O., Astudy of the forces involved in the second stage of hemagglutination (1965) Transfusion, 5, pp. 158-183Storry, J.R., Areview: Modifi cation of the red blood cell membrane and its application in blood group serology (2000) Immunohematology, 16, pp. 101-104Fernandes, H.P., Cesar, C.L., Barjas-Castro, M.L., Electrical properties of the red blood cell membrane and immunohematological investigation (2011) Rev Bras Hematol Hemoter, 33, pp. 297-301Neu, B., Wemby, R., Meiselman, H.J., Effects of Dextran molecular weight on red blood cell aggregation (2008) Biophys J, 95, pp. 3059-3065Silva, D.C., Jovino, C.N., Silva, C.A., Fernandes, H.P., Filho, M.M., Lucena, S.C., Costa, A.M., Fontes, A., Optical tweezers as a new biomedical tool to measure zeta potential of stored red blood cells (2012) PLoS One, 7, pp. e317781-e317786Brandão, M.M., Fontes, A., Barjas-Castro, M.L., Barbosa, L.C., Costa, F.F., Cesar, C.L., Saad, S.T., Optical tweezers for measuring red blood cell elasticity: Application to the study of drug response in sickle cell disease (2003) Eur J Haematol, 70, pp. 207-211Fontes, A., Fernandes, H.P., Thomaz, A.A., Barbosa, L.C., Barjas-Castro, M.L., César, C.L., Measuring electrical and mechanical properties of red blood cells with double optical tweezers (2008) J Biomed Opt, 13, pp. 0140011-0140016Fontes, A., Fernandes, H.P., Thomaz, A.A., Barbosa, L.C., Barja-Castro, M.L., Cesar, C.L., Studying red blood cell agglutination by measuring electrical and mechanical properties with a double optical tweezers (2007) European Conferences on Biomedical Optics, , Munich. Biophotonics 2007 : Opt Life Sci 200766330R.1-10(2011) American Association Of Blood Banks (AABB, , Technical Manual 17th Edition. Bethesda MA USA: AABBHochmuth, R.M., Worthy, P.R., Evans, E.A., Red cell extensional recovery and the determination of membrane viscosity (1979) J Biophys, 26, pp. 101-11
Realtà, realismo, straniamento : Auerbach e il romanzo cavalleresco fino a Cervantes
No full textAuerbach’s research, besides exploring the three main fields the author explicitly names (i.e. the succession of different and differently grounded forms of realism in literary fiction, the alternate splitting and melting of styles, the link between literary work and a Christian vision of the world), in various chapters of Mimesis, and particularly in chs. 2, 6, 12, 14 and 20, is also focused, albeit only implicitly, on the developments of a further distinctive feature in Western literature, which is the emergence of subjectivity in the representation of reality. Focusing mainly on the chapter on courtly romance (ch. 6) and on the Quijote (ch. 14), this essay will examine Auerbach’s interpreting work on texts that adopt, in different ways, a ‘subjective point of view’; this kind of interpretation is, in part, unexpectedly similar to the approach of other critics and theorists of literature contemporary to Auerbach, like Bachtin, Américo Castro and Viktor Šklovskij
Studying Red Blood Cell Agglutination By Measuring Membrane Viscosity With Optical Tweezers
No full textThe red blood cell (RBC) viscoelastic membrane contains proteins and glycoproteins embedded in a fluid lipid bilayer that are responsible for cell agglutination. Manipulating RBCs rouleaux with a double optical tweezers, we observed that the cells slide easily one over the others but are strongly connected by their edges. An explanation for this behavior could be the fact that when the cells slide one over the others, proteins are dragged through the membrane. It confers to the movement a viscous characteristic that is dependent of the velocity between the RBCs and justifies why is so easy to slide them apart. Therefore, in a first step of this work, by measuring the force as a function of the relative velocity between two cells, we confirmed this assumption and used this viscous characteristic of the RBC rouleaux to determine the apparent membrane viscosity of the cell. As this behavior is related to the proteins interactions, we can use the apparent membrane viscosity to obtain a better understanding about cell agglutination. Methods related to cell agglutination induced by antigen-antibody interactions are the basis of most of tests used in transfusion centers. Then, in a second step of this work, we measured the apparent membrane viscosity using antibodies. We observed that this methodology is sensitive to different kinds of bindings between RBCs. Better comprehension of the forces and bindings between RBCs could improve the sensibility and specificity of the hemagglutination reactions and also guides the development of new potentiator substances.6644Fontes, A., Fernandes, H.P., Barjas-Castro, M.L., Thomaz, A.A., Pozzo, L., Barbosa, L.C., Cesar, C.L., Red blood cell membrane viscoelasticity, agglutination and zeta potential measurements with double optical tweezers (2006) Proceedings of SPIE, 6088, pp. 296-305Eylar, E.H., Madoff, M.A., Brody, O.V., Oncley, J.L., The contribution of sialic acid to the surface charge of the erythrocyte (1962) J. Biol. Chem, 237, pp. 1992-2000Pollack, W., Reckel, R.P., A reappraisal of the forces involved in Hemagglutination (1977) Int Archs Allergy Appl. Immun, 54, pp. 29-42Fontes, A., Giorgio, S., de Castro Jr., A.B., Neto, V.M., Pozzo, L.Y., Marques, G.P., Barbosa, L.C., Cesar, C.L., Determination of femto Newton forces and fluid viscosity using optical tweezers: Application to Leishmania amazonensis (2005) Proceedings of SPIE, 5699, pp. 419-425Saffman, P.G., Delbruck, M., Brownian motion in biological membranes (1975) Proc. Nat. Acad. Sci. USA, 72, pp. 3111-3113Dimova, R., Danov, K., Pouligny, B., Ivanov, I.B., Drag of a solid particle trapped in a thin film or at an interface: Influence of surface viscosity and elasticity (2000) J. Colloid and Interface Science, 226, pp. 35-4
Monitoring Activity Of Living Cells Marked With Colloidal Semiconductor Quantum Dots
No full textFluorescent semiconductor nanocrystals in quantum confinement regime (quantum dots) present several well known features which make them very useful tools for biological labeling purposes. Low photo-bleaching rates, high chemical stability, active surface allowing conjugation to living cells, explains the success of this labeling procedure over the commonly used fluorescent dyes. In this paper we report the results obtained with high fluorescent core-shell CdTe-CdS (diameter = 3-7 nm) colloidal nanocrystals synthesized in aqueous medium and conjugated to glucose molecules, incubated with living yeast cells, in order to investigate their glucose up-take activity.6088Menezes, F.D., Brasil Jr., A.G., Moreira, W.L., Barbosa, L.C., Ferreira, R.C., Cerar, C.L., Farias, P.M.A., Santos, B.S., (2005) Microelectronics Journal, 36, pp. 989-991Alivisatos, A., (1996) J. Phys. Chem., 100, p. 13226Castro, V., Farias, P.M.A., Santos, B.S., Menezes, F.D., Ferreira, R., Fontes, A., Lima, P.R.M., Cesar, C.L., (2004) Blood, 104 (11), pp. 741aBrus, L.E., (1991) Appl. Phys. A, 53, p. 465Weller, H., (1993) Adv. Mater., 5 (2), p. 88Brus, L.E., Harkless, J.A.W., Stillinger, F.H., (1996) J. Am. Chem. Soc., 118, p. 4834Schaller, R.D., Klimov, V.I., (2004) Phys. Rev. Lett., 92, p. 186601Gao, M., Sun, J., Dulkeith, E., Gaponik, N., Lemmer, U., Feldmann, J., (2002) Langmuir, 18, p. 4098Pileni, M.P., (2000) Catal. Today, 58, p. 151Moreira, W.L., Fontes, A., Neves, A.A.R., Thomas, A.A., Barbosa, L.C., De Menezes, F.D., Farias, P.M.A., Cesar, C.L., (2005) Proc. Spie: Genet. Eng. Opt. Probes Biomed. Appl. III, 5704, p. 36Farias, P.M.A., Santos, B.S., Menezes, F.D., Cesar, C.L., Fontes, A., Barjas-Castro, M.L., Castro, V., Ferreira, R.C., (2005) Journal of Biomedical Optics, 10 (4), pp. 44023-44026Farias, P.M.A., Santos, B.S., Menezes, F.D., Cesar, C.L., Fontes, A., Barjas-Castro, M.L., Castro, V., Ferreira, R.C., (2005) Journal of Microscopy, 219 (3), pp. 103-108Borchert, H., Talapin, D.V., Gaponik, N., McGinley, C., Adam, S., Lobo, A., Möller, T., Weller, H., (2003) J. Phys. Chem. B, 107, p. 9662Rockenberger, J., Trögr, L., Rogach, A.L., Tischer, M., Grundmann, M., Eychmüller, A., Weller, H., (1998) J. Chem. Phys, 108, p. 780
Mechanical Properties Of Stored Red Blood Cells Using Optical Tweezers
No full textWe have developed a method for measuring the red blood cell (RBC) membrane overall elasticity μ by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.593016Ashkin, A., Dziedzic, J.M., Optical trapping and manipulation of viruses and bacteria (1987) Science, 235, pp. 1517-1520Barjas-Castro, M.L., Brandão, M.M., Fontes, A., Costa, F.F., Cesar, C.L., Saad, S.T.O., Elastic properties of irradiated red blood cell units measured by optical tweezer (2002) Transfusion, 42, pp. 1196-1199Brandão, M.M., Fontes, A., Barjas-Castro, M.L., Barbosa, L.C., Costa, F.F., Cesar, C.L., Saad, S.T.O., Optical tweezers for measuring red blood cell elasticity: Application to the study of drug response in sickle cell disease (2003) European Journal of Haematology, 70, pp. 207-211Williamson, L.M., Warwick, R.M., Transfusion-associated graft-versus-host disease and its prevention (1995) Blood Rev., 9, pp. 251-261Button, L.N., Dewolf, W.C., Newburger, P.E., The effecr of irradiation on blood components (1981) Transfusion, 21, pp. 419-426Platt, O.S., The sickle syndrome (1995) Blood: Principles and Practice of Hematology, , R. I Hadlin, S. E. Lux, T. P. Stossel, J. B. Lippincott, PhiladelphiaBallas, S.K., Dover, G.J., Charache, S., Effect of hydroxyurea on the rheological properties of sickle erythrocytes in vivo (1989) Am. J. Hematol, 32, pp. 104-111Groner, W., Mohandas, N., Bessis, M., New optical technique for measuring erythrocyte deformability with the ektacytometer (1980) Clin. Chem., 26, pp. 1435-1442De Franceschi, L., Bachir, D., Galacteros, F., Tchernia, G., Cynober, T., Alper, S., Platt, O., Brugnara, C., Oral magnesium supplements reduce erythrocyte dehydration in patients with sickle cell disease (1997) J Clin Invest, 100, pp. 1847-1852Hochmuth, R.M., Worthy, P.R., Evans, E.A., Red cell extensional recovery and the determination of membrane viscosity (1979) Biophys. J., 26, pp. 101-114Evans, E.A., La Celle, P.L., Intrinsic material properties of the erythrocyte membrane indicated by mechanical analysis of deformation (1975) Blood, 45, pp. 29-43Itoh, T., Chien, S., Usami, S., Effects of hemoglobin concentration on deformability of individual sickle cells after deoxygenation (1995) Blood, 85, pp. 2245-2253Evans, E.A., Mohandas, N., Membrane-associated sickle hemoglobin: A major determinant of sickle erythrocyte rigidity (1987) Blood, 70, pp. 1443-1449Dong, C., Chadwick, R.S., Schechter, A.N., Influence of sickle hemoglobin polymerization and membrane properties on deformability of sickle erythrocytes in the microcirculation (1992) Biophys. J., 63, pp. 774-783Suzuki, Y., Tateishi, N., Cicha, I., Decreased deformability of the X-ray irradiated red blood cells stored in manitol-adenine-phosphate medium (2000) Clin. Hemorheol. Micro-cire., 22, pp. 131-14
Realtà, realismo, straniamento: Auerbach e il romanzo cavalleresco fino a Cervantes
No full textAuerbach’s research, besides exploring the three main fields the author explicitly names (i.e. the succession of different and differently grounded forms of realism in literary fiction, the alternate splitting and melting of styles, the link between literary work and a Christian vision of the world), in various chapters of Mimesis, and particularly in chs. 2, 6, 12, 14 and 20, is also focused, albeit only implicitly, on the developments of a further distinctive feature in Western literature, which is the emergence of subjectivity in the representation of reality. Focusing mainly on the chapter on courtly romance (ch. 6) and on the Quijote (ch. 14), this essay will examine Auerbach’s interpreting work on texts that adopt, in different ways, a ‘subjective point of view’; this kind of interpretation is, in part, unexpectedly similar to the approach of other critics and theorists of literature contemporary to Auerbach, like Bachtin, Américo Castro and Viktor Šklovskij
Shedding light on the black hole: The roll-out of broadband access networks by private operators
No full textSeveral market studies have indicated that the roll-out of broadband has significant economic and social relevance. The investments in broadband infrastructures needed to realise these economic and social benefits are, however, high-risk. This is firstly caused by the fact that the roll-out of access networks is extremely costly and requires high initial investments. Moreover, the multidisciplinary environment and involvement of many actors with diverging objectives and interests cause high complexity. Moreover, the market for broadband is changing fast and continuously. Although broadband has been on the academic research agenda for quite some time, this has as yet not resulted in a structured insight into the decision-making process around the upgrading of broadband networks, seen from the perspective of private operators and taking into account the vast complexity of the surroundings in which this decision-making process takes place in. The objective of this research was to provide a unifying theory combining technical, economic, market-related and regulatory factors with regard to an evolutionary, flexible approach of network upgrading from a decision-maker perspective. The result of this research is a robust, explanatory, parsimonious model for the impact and outcomes of broadband roll-out. This model provides a certain degree of stability in this multidisciplinary, unpredictable and highly dynamic research field.Technology, Policy and Managemen
Application Of Colloidal Semiconductor Quantum Dots As Fluorescent Labels For Diagnosis Of Brain Glial Cancer
No full textIn this work we present the preparation, characterization and conjugation of colloidal core shell CdS-Cd(OH)2 quantum dots to health and cancer glial rats living cells in culture media. The particles were obtained via colloidal synthesis in aqueous medium, with final pH=7.3-7.4. Laser Scan Confocal Microscopy (LSCM) and Fluorescence Microscopy were used to evaluate fluorescence intensities and patterns of health and cancer (glioblastoma) glial cells labeled with the quantum dots in different time intervals. Health and cancer glial cells clearly differ in their fluorescence intensities and patterns. These different fluorescence intensities and patterns may be associated to differences concerning cellular membrane and metabolic features of health and cancer cells. The results obtained indicate the potential of the methodology for fast and precise cancer diagnostics.6096Borchert, H., Talapin, D.V., McGinley, C., (2003) J. Chem. Phys., 271, pp. 1800-1807Alivisatos, A.P., (1996) Science, 271, pp. 933-937Nowak, C., Döllefeld, H., Eychmüller, A., (2001) J. Chem. Phys., 114, pp. 489-494Eychmuller, A., (1996) J. Phys Chem. B., 59, pp. 13226-13239Bruchez Jr., M.P., Moronne, M., Gin, P., Weiss, S., Alivisatos, A.P., (1998) Science, 281, pp. 2013-2016Chan, W.C.W., Nie, S., (1998) Science, 281, pp. 2016-2018Ballou, B., Lagerholm, B.C., Ernst, L.A., Bruchez, M.P., Waggoner, A.S., (2004) Bioconjug. Chem., 15, pp. 79-86Gao, X., Nie, S., (2003) Trends Biotech., 21 (9), pp. 371-373Äkerman, M.E., Chan, W.C.W., Laakkonen, P., Bhatia, S.N., Ruoslahti, E., (2002) Appl. Biol. Sci., 99 (20), pp. 12617-12621Chan, W.C.W., Maxwell, D.J., Gao, X., Bailey, R.E., Han, M., Nie, S., (2002) Curr. Op. Bioteh., 13 (1), pp. 40-46Mattheakis, L.C., Dias, J.M., Choi, Y., Gong, J., Bruchez, M.P., Liu, J., Wang, E., (2004) Anal Biochem., 327, pp. 200-208Trentin, A.G., Alvarez-Silva, M., Moura-Neto, V., (2001) Am J Physiol Endocrinol Metab., 281, pp. E1088-E1094Sousa, V.O., Romão, L., Moura-Neto, V., Gomes, F.C.A., (2004) Eur. J. Neurosci., 19, pp. 1721-1734Petrov, D.V., Santos, B.S., Pereira, G.A.L., Donegá, C.M., (2002) J. Phys. Chem. B., 106 (21), pp. 5325-5334Farias, P.M.A., Santos, B.S., Menezes, F.D., Ferreira, R.C., Barjas-Castro, M.L., Castro, V., Lima, P.R.M., Cesar, C.L., (2005) J. Microscopy, 219 (3), pp. 103-108. , 2005Farias, P.M.A., Santos, B.S., Menezes, F.D., Ferreira, R.C., Barjas-Castro, M.L., Castro, V., Lima, P.R.M., Cesar, C.L., (2005) J. Biom. Opt., 10 (4), pp. 440231-44023
The Frequency Of The New Platelet Antigen Cab In The Brazilian Population
No full text[No abstract available]1003343343Metcalfe, P., Watkins, N.A., Ouwehand, W.H., Nomenclature of human platelet antigens (2003) Vox Sang, 85, pp. 240-245Bertrand, G., Jallu, V., Saillant, D., The new plateloantigen Cab a: a single point mutation Gln 716 His on the alpha 2 integrin (2009) Transfusion, 49, pp. 2076-2083Castro, V., Origa, A.F., Annichino-Bizzacchi, J.M., Frequencies of platelet-specific alloantigen systems 1-5 in three distinct ethnic groups in Brazil (1999) Eur J Immunogenet, 26, pp. 355-360Castro, V., Kroll, H., Origa, A.F., A prospective study on the prevalence and risk factors for neonatal thrombocytopenia and plateloimmunization among 9332 unselected Brazilian newborns (2007) Transfusion, 47, pp. 59-66Davoren, A., Curtis, B.R., Aster, R.H., Human platelet antigen-specific alloantibodies implicated in 1162 cases of neonatal alloimmune thrombocytopenia (2004) Transfusion, 44, pp. 1220-122
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