| 61. |
- Sanchez, Javier, et al.
(författare)
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Surface-adsorbed fibrinogen and fibrin may activate the contact activation system
- 2008
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Ingår i: Thrombosis Research. - : Elsevier BV. - 0049-3848 .- 1879-2472. ; 122:2, s. 257-263
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: This study was designed to investigate whether fibrinogen, soluble desAA-fibrin, and insoluble desAABB-fibrin are able to induce clotting by triggering the plasma contact activation system when adsorbed to polystyrene. MATERIALS AND METHODS: The above-mentioned substances were individually prepared on polystyrene meshwork squares, and then exposed to a purified FXII solution or non-calcium containing plasma (citrated and dialyzed normal pooled plasma) in polystyrene cuvettes coated with surface-immobilized heparin, to completely block contact activation and the coagulation mechanism that might be induced by the cuvette surfaces. Sodium glass beads were used as the reference material. RESULTS: On exposure to purified FXII solution and plasma, all the tested materials adsorbed and activated FXII to varying degrees. This activation led to the formation of FXIa in the exposed plasma, with the highest activation occurring upon exposure to glass, desAA-fibrin and desAABB-fibrin and the lowest upon exposure to fibrinogen-adsorbed or unmodified polystyrene meshwork squares. Following recalcification, in cuvettes with surface-immobilized heparin, a spectrophotometric assay showed that the surface-exposed plasma aliquots clotted within 5 min after contact with glass, within 10 to 15 min after contact with the two forms of fibrin, and somewhat longer after contact with adsorbed fibrinogen. The longest lag phase, close to 20 min, occurred in plasma exposed to unmodified polystyrene meshwork. Whole blood deposited in surface heparinized cuvettes directly from the cubital vein did not clot during the observation time (2 h). CONCLUSIONS: These results indicate that domains induced by conformational changes in adsorbed fibrinogen and fibrin are capable of activating adsorbed proenzymes and that various forms of fibrin are considerably stronger activators of the contact activation system than are adsorbed fibrinogen or a polystyrene meshwork. The delayed coagulation in plasma exposed to the unmodified polystyrene meshwork can be explained by a two-step process: first, adsorption of fibrinogen, and second, activation of FXII. Under our experimental conditions, the adsorption and activation of FXII on fibrinogen and fibrin seems to be an important mechanism for triggering coagulation.
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| 62. |
- Thorslund, Sara, et al.
(författare)
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A PDMS-based disposable microfluidic sensor for CD4+ lymphotic counting
- 2008
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Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 10:6, s. 851-857
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Tidskriftsartikel (refereegranskat)abstract
- A refined sensor for CD4+ lymphocyte count was developed and evaluated by comparison to flow cytometry. The micropillar structured sensor surface was cast in PDMS polymer and surface modified to gain biocompatibility and CD4-cell capturing properties. The sensor works by pure capillary action and sample filling and rinsing is performed without external equipment. Whole blood samples showed acceptable agreement (79%) with flow cytometry, however when diluting the blood in PBS buffer we discovered that a larger number of cells were drawn into the sensor microchannel compared to the initial sample, explained by enhanced shear-induced cell migration. Using plasma or PBS with glycerol or albumin additives as diluting media greatly influenced this cell behavior, showing the importance of controlling the dilution media when working with devices based on capillary filling. The sensors need to be further tested with blood samples with lower CD4-counts (<500 cells/μl), which are clinically relevant.
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| 63. |
- Thorslund, Sara, et al.
(författare)
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Bioactivated PDMS microchannel evaluated as sensor for human CD4+ cells : The concept of a point-of-care method for HIV monitoring
- 2007
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 123:2, s. 847-855
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Tidskriftsartikel (refereegranskat)abstract
- Up to today, the number of CD4(+) lymphocytes remains the most important biological marker to determine the clinical stage of an HIV-infection. Analysis by flow cytometry, the standard method used today, is unsuitable in many developing countries, because of high costs involved and practical inconveniences. We here present the concept of an inexpensive PDMS-based point-of-care device for CD4(-)count. A simple fluorescence microscope for stained leucocytes counting is the only detection equipment needed. The biosensor surface consists of an initial heparin-based coating that adds hydrophilicity and thromboresistance to the PDMS material. The specific capturing chemistry is based on an avidin/biotin-antibody surface architecture. Pure capillary forces draw whole blood, as well as rinsing buffer, into the biosensor channel, minimizing the need of external equipment. Detection of the captured cells was performed by fluorescence imaging of HOECHST (stains cell nuclei) and CD3-FITC signals. It was shown that the non-specific adsorption of CD4(-) leucocytes was minimal to none. and the detection could therefore be done by only counting the easy identifiable HOECHST+ cells. Characterization of the biosensor coating process was additionally performed with the quartz crystal microbalance-dissipation technique.
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| 64. |
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| 65. |
- Thorslund, Sara, et al.
(författare)
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Functionality and stability of heparin immobilized onto poly(dimethylsiloxane)
- 2005
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Ingår i: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 45:2, s. 76-81
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Tidskriftsartikel (refereegranskat)abstract
- Poly(dimethylsiloxane) (PDMS) has become an attractive material when working in the field of microfluidics, mainly because of the rapid prototyping process it involves. The increased surface volume ratio in microchannels makes the interaction between sample and material surface highly important, evident when handling complex biological samples such as plasma or blood. This study demonstrates a new grade of non-covalent heparin surface that adds efficient anticoagulant property to the PDMS material. The surface modification is a simple and fast one-step process performed at neutral pH, optimal when working with closed microsystems. The heparin formed a uniform and functional coating on hydrophobic PDMS with comparatively high level of antithrombin-binding capacity. In addition, long-term studies revelaed that the immobilized heparin was more or less stable in the microchannels over a time of three weeks. Recalcified plasma in contact with native PDMS showed complete coagulation after 1 h, while no fibrin formation was detected in plasma incubated on heparin-coated PDMS within the same time. In conclusion, we see the heparin coating developed and evaluated in this study as a tool that greatly facilitates the use of PDMS in microfluidics dealing with plasma or blood samples.
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| 66. |
- Trulson, Agneta, et al.
(författare)
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The functional heterogeneity of eosinophil cationic protein is determined by a gene polymorphism and post-translational modifications
- 2007
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Ingår i: Clinical and Experimental Allergy. - : Wiley. - 0954-7894 .- 1365-2222. ; 37:2, s. 208-218
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Tidskriftsartikel (refereegranskat)abstract
- Background The eosinophil is a cytotoxic cell and takes part in parasite killing and tissue-destructive processes by secretion of proteins such as eosinophil cationic protein (ECP). A polymorphism was demonstrated in the ECP gene, giving rise to a substitution of arginine at position 97 with threonine. This polymorphism is related to disease development. Objective To investigate the functional and molecular heterogeneity of native ECP and the functional consequences of the replacement of arginine with a threonine. Methods ECP was purified from healthy blood donors by gel filtration, ion-exchange chromatography and reversed-phase chromatography. Recombinant ECPs i.e. rECP 97arg and rECP 97thr were produced by the pFASTBAC baculovirus expression system. The cytotoxic activity was determined against an erythroleukaemia or a small cell lung cancer cell line. Results Native ECP was purified to apparent homogeneity and showed a considerable molecular heterogeneity and a corresponding functional heterogeneity with respect to cytotoxic activity. After reduction, the native cytotoxic ECP showed three bands on sodium dodecylsulphate polyacrylamide gel electrophoresis: one major band at 18-20 kDa and two minor bands at about 10 and 5 kDa, respectively. The 5 kDa contained two masses differing with 56.2 Da, which corresponds to the difference in molecular masses of arginine and threonine. rECP 97arg was cytotoxic in contrast to rECP97thr. Deglycosylation with N-glycosidase F did not affect the cytotoxic activity of native ECP to any measurable extent nor the activity of rECP 97arg, whereas rECP 97thr achieved cytotoxic activity. The RNase activities of the recombinant and native ECPs were similar. Conclusion We conclude that ECP is present in several molecular forms with varying biological activities. Some of this functional heterogeneity is based on the genetic polymorphism of the ECP gene and some on post-translational modifications. In subjects carrying the ECP 97thr variant, the cytotoxic activity may be disguised by N-linked glycosylation of the active site.
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| 67. |
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| 68. |
- Vik, Anders, et al.
(författare)
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Antimicrobial and cytotoxic activity of agelasine and agelasimine analogs
- 2007
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Ingår i: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896 .- 1464-3391. ; 15:12, s. 4016-4037
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Tidskriftsartikel (refereegranskat)abstract
- Agelasine and agelasimine derivatives with substantially less complicated terpenoid side chains compared to the naturally occurring compounds have been synthesized and their ability to inhibit growth of microorganisms and cancer cells has been studied. Compounds with excellent activity against cancer cell lines (MIC ca. 1 μM for the most potent compounds), including a drug resistant renal cell line, have been identified. Most compounds studied also exhibited broad spectrum antimicrobial activity including activity against Mycobacterium tuberculosis.
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| 69. |
- Villani, Mattias, et al.
(författare)
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The multivariate split normal distribution and asymmetric principal components analysis
- 2006
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Ingår i: Communications in Statistics: Theory and Methods.
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Tidskriftsartikel (refereegranskat)abstract
- The multivariate split normal distribution extends the usual multivariate normal distribution by a set of parameters which allows for skewness in the form of contraction/dilation along a subset of the principal axes. This paper derives some properties for this distribution, including its moment generating function, multivariate skewness and kurtosis. Maximum likelihood estimation is discussed and a complete Bayesian analysis of the multivariate split normal model is developed.Keywords: Bayesian inference, Elicitation, Estimation, Maximum likelihood, Multivariate analysis, Skewness.
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| 70. |
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