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  • 1. Abrahamsson, S.
    et al.
    Blom, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Agostinho, A.
    Jans, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jost, A.
    Müller, M.
    Nilsson, Linnea
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bernhem, K.
    Lambert, T. J.
    Heintzmann, R.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Multifocus structured illumination microscopy for fast volumetric super-resolution imaging2017In: Biomedical Optics Express, ISSN 2156-7085, E-ISSN 2156-7085, Vol. 8, no 9, p. 4135-4140, article id #294866Article in journal (Refereed)
    Abstract [en]

    We here report for the first time the synergistic implementation of structured illumination microscopy (SIM) and multifocus microscopy (MFM). This imaging modality is designed to alleviate the problem of insufficient volumetric acquisition speed in superresolution biological imaging. SIM is a wide-field super-resolution technique that allows imaging with visible light beyond the classical diffraction limit. Employing multifocus diffractive optics we obtain simultaneous wide-field 3D imaging capability in the SIM acquisition sequence, improving volumetric acquisition speed by an order of magnitude. Imaging performance is demonstrated on biological specimens.

  • 2. Agostinho, Ana
    et al.
    Manneberg, Otto
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    van Schendel, Robin
    Hernandez-Hernandez, Abrahan
    Kouznetsova, Anna
    Blom, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Höög, Christer
    High density of REC8 constrains sister chromatid axes and prevents illegitimate synaptonemal complex formation2016In: EMBO Reports, ISSN 1469-221X, E-ISSN 1469-3178, Vol. 17, no 6, p. 901-913Article in journal (Refereed)
    Abstract [en]

    During meiosis, cohesin complexes mediate sister chromatid cohesion (SCC), synaptonemal complex (SC) assembly and synapsis. Here, using super-resolution microscopy, we imaged sister chromatid axes in mouse meiocytes that have normal or reduced levels of cohesin complexes, assessing the relationship between localization of cohesin complexes, SCC and SC formation. We show that REC8 foci are separated from each other by a distance smaller than 15% of the total chromosome axis length in wild-type meiocytes. Reduced levels of cohesin complexes result in a local separation of sister chromatid axial elements (LSAEs), as well as illegitimate SC formation at these sites. REC8 but not RAD21 or RAD21L cohesin complexes flank sites of LSAEs, whereas RAD21 and RAD21L appear predominantly along the separated sister-chromatid axes. Based on these observations and a quantitative distribution analysis of REC8 along sister chromatid axes, we propose that the high density of randomly distributed REC8 cohesin complexes promotes SCC and prevents illegitimate SC formation.

  • 3. Aizman, O
    et al.
    Brismar, Hjalmar
    Uhlen, P
    Zettergren, E
    Levey, A I
    Forssberg, H
    Greengard, P
    Aperia, A
    Anatomical and physiological evidence for D-1 and D-2 dopamine receptor colocalization in neostriatal neurons2000In: Nature Neuroscience, ISSN 1097-6256, E-ISSN 1546-1726, Vol. 3, no 3, p. 226-230Article in journal (Refereed)
    Abstract [en]

    Despite the importance of dopamine signaling, it remains unknown if the two major subclasses of dopamine receptors exist on the same or distinct populations of neurons. Here we used confocal microscopy to demonstrate that virtually all striatal neurons, both in vitro and in vivo, contained dopamine receptors of both classes. We also provide functional evidence for such colocalization: in essentially all neurons examined, fenoldopam, an agonist of the D-1 subclass of receptors, inhibited both the Na+/K+ pump and tetrodotoxin (TTX)-sensitive sodium channels, and quinpirole, an agonist of the Dr subclass of receptors, activated TTX-sensitive sodium channels. Thus D-1 and D-2 classes of ligands may functionally interact in virtually all dopamine-responsive neurons within the basal ganglia.

  • 4. Aizman, O.
    et al.
    Uhlen, P.
    Lal, M.
    Brismar, Hjalmar
    Aperia, A.
    Ouabain, a steroid hormone that signals with slow calcium oscillations2001In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 98, no 23, p. 13420-13424Article in journal (Refereed)
    Abstract [en]

    The plant-derived steroid, digoxin, a specific inhibitor of Na,K-ATPase, has been used for centuries in the treatment of heart disease. Recent studies demonstrate the presence of a digoxin analog, ouabain, in mammalian tissue, but its biological role has not been elucidated. Here, we show in renal epithelial cells that ouabain, in doses causing only partial Na,K-ATPase inhibition, acts as a biological inducer of regular, low-frequency intracellular calcium ([Ca2+](i)) oscillations that elicit activation of the transcription factor, NF-KB. Partial inhibition of Na,K-ATPase using low extracellular K+ and depolarization of cells did not have these effects. Incubation of cells in Ca2+-free media, inhibition of voltage-gated calcium channels, inositol triphosphate receptor antagonism, and redistribution of actin to a thick layer adjacent to the plasma membrane abolished [Ca2+](i) oscillations, indicating that they were caused by a concerted action of inositol triphosphate receptors and capacitative calcium entry via plasma membrane channels. Blockade of ouabain-induced [C-a2+](i) oscillations prevented activation of NF-kappaB. The results demonstrate a new mechanism for steroid signaling via plasma membrane receptors and underline a novel role for the steroid hormone, ouabain, as a physiological inducer of [Ca2+](i) oscillations involved in transcriptional regulation in mammalian cells.

  • 5.
    Akpe, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Nyokong, Tebello
    Osadebe, P. O.
    Photophysical and photochemical parameters of octakis (benzylthio) phthalocyaninato zinc, aluminium and tin: Red shift index concept in solvent effect on the ground state absorption of zinc phthalocyanine derivatives2010In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 984, no 1-3, p. 1-14Article in journal (Refereed)
    Abstract [en]

    This paper addresses the synthesis of octa-substituted benzylthio metallophthalocyanines (OBTMPcs) that contain the central metal ions of Zn2+, Al3+ and Sn4+. The ground state absorption of ZnPc(SR)(8) (OBTZnPc) along with the ZnPc derivatives, well documented in literature were used to study a new concept called the red shift index (RsI). The concept is based on the empirical values of RsI of the different complexes in solvent media. Unequivocally, parameters used in this paper show strong correlations that are consistent with the results obtained. For instance, 12,1 of the complexes tend to increase as the refractive index, n(D), and solvent donor, DN, of solvent increases. Photodegradation (photobleaching) quantum yield, phi(d) measurements of these compounds show that they are highly photostable, phi(d) (0.03-0.33 x 10(-5)). The triplet quantum yield, phi(T) (0.40-0.53) and the triplet lifetime, tau(T) (610-810 mu s) are within the typical range for metallophthalocyanines in DMSO. The photosensitisation efficiency. S-Delta, is relatively high for all the molecules (0.74-0.90). (C) 2010 Elsevier B.V. All rights reserved.

  • 6.
    Akpe, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Nyokong, Tebello
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Photophysics and photochemistry of zinc, aluminium and tin octakis (benzylthio) phthalocyanines2008Report (Other academic)
  • 7.
    Akpe, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Ogunsipe, Abimbola
    Madu, Christian
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Red-Shift Index Concept in Solvent Effects of Chromophore-Substituted Metallophthalocyanines: A Look at the Empirical Relationship of the Macroscopic Properties of the Solute-Solvent Interactions2015In: Journal of Solution Chemistry, ISSN 0095-9782, E-ISSN 1572-8927, Vol. 44, no 2, p. 307-326Article in journal (Refereed)
    Abstract [en]

    Solvent effects on the UV/vis spectra of metallopthalocyanines (MPcs) have been interpreted using the red-shift index concept (R (s) I). The concept connects empirically, direct, experimental, easily accessible optical spectral data, which are explained by considering the differential behavior of the solute-solvent interactions at the ground state and excited state using the spectral values of MPcs along with the derived concept, called the associated solvation energy (ASE). R (s) I is formulated from three fundamental parameters, which are: ground state electronic absorption spectrum, polarization red-shift and a scaling factor of MPc (N (dye)) in the respective solvents. The R (s) I is a reflection of the index value of the chromophore substituent of MPc in the solvent; thus, the concept can be used as a solvatochromic parameter to study a wide range of supramolecular and heterocyclic compounds that can be modified at their periphery or 'handles'. Particularly, in this study, the concept has been used to rank MPc candidates by using the statistical mean performance of the solvatochromic parameters, which are red shift index, polarizability efficiency and ASE. We hereby review the solvent effects on the UV/vis spectra of substituted and unsubstituted MPcs.

  • 8.
    Akpe, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Vernet, Erik
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Gräslund, Torbjörn
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Characterization studies of aluminum phthalocyanine binding to antibodies from SKBR 3 cell line2008Report (Other academic)
  • 9.
    Akpe, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vernet, Erik
    KTH, School of Biotechnology (BIO), Protein Technology.
    Madu, Christian
    Obirai, Joseph C.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Understanding the Photochemical Pathway of In Vitro Target Delivery of Aluminium Phthalocyanine: A Mechanistic Approach Using Radical Reaction Chemistry2014In: ChemPlusChem, ISSN 2192-6506, Vol. 79, no 5, p. 671-679Article in journal (Refereed)
    Abstract [en]

    A classical dye, aluminium phthalocyanine (AlPc), is used to study the photochemical processes involved in the chromophore-assisted laser inactivation technique. Both cell-free and cell-based systems are investigated by novel methods and radical reaction chemistry. Findings on the photochemical pathways in two models representing cell-free and a cell-based systems are reported. In the cell-free system, the unsubstituted, free, fluorescence-active photosensitiser AlPc recovers its fluorescence signal by means of phosphorescence through a reversible photobleaching process. In the cell-based system, photoactivation of substituted AlPc conjugated to an antibody results in the loss of fluorescence signal at the area examined. Reinjection of the AlPc-conjugated antibodies restores the fluorescence signal.

  • 10. Andersson, R. M.
    et al.
    Aizman, O.
    Aperia, A.
    Brismar, Hjalmar
    KTH, Superseded Departments, Physics.
    Modulation of Na+,K+-ATPase activity is of importance for RVD2004In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 180, no 4, p. 329-334Article in journal (Refereed)
    Abstract [en]

    Aim: This study was performed to examine the role of Na+,K+-ATPase activity for the adaptive response to cell swelling induced by hypoosmoticity, i.e. the regulatory volume decrease (RVD). Methods: The studies were performed on COS-7 cells transfected with rat Na+,K+-ATPase. To study changes in cell volume, cells were loaded with the fluorescent dye calcein and the intensity of the dye, following exposure to a hypoosmotic medium, was recorded with confocal microscopy. Results: Ouabain-mediated inhibition of Na+,K+-ATPase resulted in a dose dependent decrease in the rate of RVD. Total Rb-86(+) uptake as well as ouabain dependent Rb-86(+) uptake, used as an index of Na+,K+-ATPase dependent K+ uptake, was significantly increased during the first 2 min following exposure to hypoosmoticity. Since protein kinase C (PKC) plays an important role in the modulation of RVD, a study was carried out on COS-7 cells expressing rat Na+,K+-ATPase, where Ser23 in the catalytic alpha1 subunit of rat Na+,K+-ATPase had been mutated to Ala (S23A), abolishing a known PKC phosphorylation site. Cells expressing S23A rat Na+,K+-ATPase exhibited a significantly lower rate of RVD and showed no increase in Rb-86(+) uptake during RVD. Conclusion: Taken together, these results suggest that a PKC-mediated transient increase in Na+,K+-ATPase activity plays an important role in RVD.

  • 11. Andersson, R. M.
    et al.
    Carlsson, Kjell
    KTH, Superseded Departments, Physics.
    Liljeborg, A.
    Brismar, Hjalmar
    Characterization of probe binding and comparison of its influence on fluorescence lifetime of two pH-sensitive benzo c xanthene dyes using intensity-modulated multiple-wavelength scanning technique2000In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 283, no 1, p. 104-110Article in journal (Refereed)
    Abstract [en]

    Quantitative pH imaging using the carboxy semi-naphthofluorescein dyes SNAFL-1 and SNAFL-2 can be performed by measurement of intensity ratios or fluorescence lifetimes. However, there is a controversy as to whether the latter method has the practical advantage of a straightforward pH calibration in buffers compared to a cumbersome and time-consuming procedure in cells. In this study we have undertaken a systematic study of the potential factors influencing the fluorescence lifetime of the probes at different pH using confocal microscopy. In vitro results demonstrate that factors such as lipid and protein concentrations have a substantial influence on pH measurements based on fluorescence lifetime. The pH could be overestimated by more than 2 pH units. Studies in permeabilized COS-7 cells demonstrate the same trends as observed in the in vitro studies.

  • 12. Aperia, Anita Chatarina
    et al.
    Akkuratov, Evgeny E
    Fontana, Jacopo Maria
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Na+, K+-ATPase, a new class of plasma membrane receptors2016In: American Journal of Physiology - Cell Physiology, ISSN 0363-6143, E-ISSN 1522-1563, Vol. 310, no 7, p. C491-C495Article in journal (Refereed)
    Abstract [en]

    The Na(+), K(+)-ATPase (NKA) differs from most other ion transporters not only in its capacity to maintain a steep electrochemical gradient across the plasma membrane but also as a receptor for a family of cardiotonic steroids, to which ouabain belongs. Studies from many groups, performed during the last fifteen years, have demonstrated that ouabain, a member of the cardiotonic steroid family, can activate a network of signaling molecules and that NKA will also serve as a signal transducer that can provide a feed back loop between NKA and the mitochondria. This brief review summarizes the current knowledge and controversies with regard to the understanding of NKA signaling.

  • 13.
    Ardabili, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Gantelius, Jesper
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    Kowalewski, Jacob
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Russom, Aman
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Dean flow-coupled inertial focusing for ultra-high-throughput particle filtration2010In: 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2010, MicroTAS 2010: Volume 3, 2010, p. 1586-1588Conference paper (Refereed)
    Abstract [en]

    Particle manipulation represents an important and fundamental step prior to counting, sorting and detecting bio-particles. In this study, we report dean-coupled inertial focusing of particles in flows through a single curve microchannel at extremely high channel Reynold numbers (∼325). We found the lateral particle focusing position, xf to be fixed and largely independent of radius of curvature and whether particles are pre-focused (at equilibrium) entering the curvature or randomly distributed. Finally, using a single inlet, u-shaped, microchannel we demonstrate filtration of 10μm particles from 2 μm particles at throughputs several orders of magnitude higher than previously shown.

  • 14. Azarias, Guillaume
    et al.
    Kruusmagi, Markus
    Connor, Siobhan
    Akkuratov, Evgeny E.
    Liu, Xiao-Li
    Lyons, David
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Broberger, Christian
    Aperia, Anita
    A Specific and Essential Role for Na,K-ATPase alpha 3 in Neurons Co-expressing alpha 1 and alpha 32013In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 288, no 4, p. 2734-2743Article in journal (Refereed)
    Abstract [en]

    Most neurons co-express two catalytic isoforms of Na,K-ATPase, the ubiquitous alpha 1, and the more selectively expressed alpha 3. Although neurological syndromes are associated with alpha 3 mutations, the specific role of this isoform is not completely understood. Here, we used electrophysiological and Na+ imaging techniques to study the role of alpha 3 in central nervous system neurons expressing both isoforms. Under basal conditions, selective inhibition of alpha 3 using a low concentration of the cardiac glycoside, ouabain, resulted in a modest increase in intracellular Na+ concentration ([Na+](i)) accompanied by membrane potential depolarization. When neurons were challenged with a large rapid increase in [Na+](i), similar to what could be expected following suprathreshold neuronal activity, selective inhibition of alpha 3 almost completely abolished the capacity to restore [Na+](i) in soma and dendrite. Recordings of Na, K-ATPase specific current supported the notion that when [Na+](i) is elevated in the neuron, alpha 3 is the predominant isoform responsible for rapid extrusion of Na+. Low concentrations of ouabain were also found to disrupt cortical network oscillations, providing further support for the importance of alpha 3 function in the central nervous system. The alpha isoforms express a well conserved protein kinase A consensus site, which is structurally associated with an Na+ binding site. Following activation of protein kinase A, both the alpha 3-dependent current and restoration of dendritic [Na+](i) were significantly attenuated, indicating that alpha 3 is a target for phosphorylation and may participate in short term regulation of neuronal function.

  • 15.
    Barbe, Laurent
    et al.
    KTH, School of Biotechnology (BIO).
    Lundberg, Emma
    KTH, School of Biotechnology (BIO), Proteomics.
    Oksvold, Per
    KTH, School of Biotechnology (BIO), Proteomics.
    Stenius, Anna
    KTH, School of Biotechnology (BIO).
    Lewin, Erland
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Björling, Erik
    KTH, School of Biotechnology (BIO).
    Asplund, Anna
    Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University.
    Pontén, Fredrik
    Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Uhlén, Mathias
    KTH, School of Biotechnology (BIO), Proteomics.
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Proteomics.
    Toward a confocal subcellular atlas of the human proteome2008In: Molecular and cellular proteomics, ISSN 1535-9476, Vol. 7, no 3, p. 499-508Article in journal (Refereed)
    Abstract [en]

    Information on protein localization on the subcellular level is important to map and characterize the proteome and to better understand cellular functions of proteins. Here we report on a pilot study of 466 proteins in three human cell lines aimed to allow large scale confocal microscopy analysis using protein-specific antibodies. Approximately 3000 high resolution images were generated, and more than 80% of the analyzed proteins could be classified in one or multiple subcellular compartment(s). The localizations of the proteins showed, in many cases, good agreement with the Gene Ontology localization prediction model. This is the first large scale antibody-based study to localize proteins into subcellular compartments using antibodies and confocal microscopy. The results suggest that this approach might be a valuable tool in conjunction with predictive models for protein localization.

  • 16.
    Bernhem, Kristoffer
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Blom, H.
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Brismar, Hjalmar
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Quantification of endogenous and exogenous protein expressions of Na,K-ATPase with super-resolution PALM/STORM imaging2018In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, no 4, article id e0195825Article in journal (Refereed)
    Abstract [en]

    Transient transfection of fluorescent fusion proteins is a key enabling technology in fluorescent microscopy to spatio-temporally map cellular protein distributions. Transient transfection of proteins may however bypass normal regulation of expression, leading to overexpression artefacts like misallocations and excess amounts. In this study we investigate the use of STORM and PALM microscopy to quantitatively monitor endogenous and exogenous protein expression. Through incorporation of an N-terminal hemagglutinin epitope to a mMaple3 fused Na,K-ATPase (α1 isoform), we analyze the spatial and quantitative changes of plasma membrane Na,K-ATPase localization during competitive transient expression. Quantification of plasma membrane protein density revealed a time dependent increase of Na,K-ATPase, but no increase in size of protein clusters. Results show that after 41h transfection, the total plasma membrane density of Na,K-ATPase increased by 63% while the endogenous contribution was reduced by 16%. © 2018 Bernhem et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

  • 17.
    Bernhem, Kristoffer
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Blom, Hans
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sweden.
    Quantification of endogenous and exogenous protein expressions of Na,K-ATPase with super-resolution PALM/STORM imagingManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    Transient transfection of fluorescent fusion proteins is a key enabling technology in fluorescent microscopy to spatio-temporally map cellular protein distributions. Transient transfection of proteins may however bypass normal regulation of expression, leading to overexpression artefacts like misallocations and excess amounts. In this study we investigate the ability to quantitatively monitor endogenous and exogenous protein expression competition on the single molecule level. Through incorporation of an N-terminal hemagglutinin (HA) epitope to amMaple3 fused Na,K-ATPase (α1 isoform), using PALM and STORM imaging we investigatethe increase in plasma membrane density at the cost of competitive expression. Quantification of plasma membrane protein density revealed a time dependent increase over time of totalprotein content. Results show that plasma membrane densities increased by more than 60%,comparing 17h and 41h transfection times, whilst endogenous levels were simultaneously reduced by 20 %.

  • 18.
    Bernhem, Kristoffer
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sweden.
    SMLocalizer, a GPU accelerated ImageJ plugin for single molecule localization microscopy2018In: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 34, no 1, p. 137-Article in journal (Refereed)
    Abstract [en]

    SMLocalizer combines the availability of ImageJ with the power of GPU processing for fast and accurate analysis of single molecule localization microscopy data. Analysis of 2D and 3D data in multiple channels is supported.

  • 19.
    Bernhem, Kristoffer
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Krishnan, Kalaiselvan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Bondar, Alexander
    Institute of Chemical Biology and Fundamental Medicine, 630090 Novosibirsk,.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sverige.
    Aperia, Anita
    Karolinska Institutet.
    Scott, Lena
    Karolinska Institutet.
    AT(1)-receptor response to non-saturating Ang-II concentrations is amplified by calcium channel blockers2017In: BMC Cardiovascular Disorders, ISSN 1471-2261, E-ISSN 1471-2261, Vol. 17, no 1, article id 126Article in journal (Refereed)
    Abstract [en]

    Background: Blockers of angiotensin II type 1   receptor (AT 1 R) and the voltage gated calcium channel 1.2 (Ca V 1.2) are commonly used for treatment of hypertension. Yet there is little information about the effect of physiological concentrations of angiotensin II (AngII) on AT 1 R signaling and whether there is a reciprocal regulation of AT 1 R signaling by Ca V 1.2.

    Methods: To elucidate these questions, we have studied the Ca 2+  signaling response to physiological and pharmacological AngII doses in HEK293a cells, vascular smooth muscle cells and cardiomyocytes using a Ca 2+ sensitive dye as the principal sensor. Intra-cellular calcium recordings were performed in presence and absence of Ca V 1.2 blockers.  Semi- quantitative imaging methods were used to assess the plasma membrane expression of AT 1 R and G-protein activation.

    Results: Repeated exposure to pharmacological (100 nM) concentrations of AngII caused, as expected, a down-regulation of the Ca 2+  response. In contrast, repeated exposure to physiological (1 nM) AngII concentration resulted in an enhancement of the Ca 2+  response. The up-regulation of the Ca 2+  response to repeated 1 nM AngII doses and the down- egulation of the Ca 2+  response to repeated 100 nM Angll doses were not accompanied by a parallel change of the AT 1 R plasma membrane expression. The Ca 2+  response to 1 nM of AngII was amplified in the presence of therapeutic concentrations of the Ca V 1.2 blockers, nifedipine and verapamil, in vascular smooth muscle cells, cardiomyocytes and HEK293a cells. Amplification of the AT 1 R response was also observed following inhibition of the calcium permeable transient receptor potential cation channels, suggesting that the activity of AT 1 R is sensitive to calcium influx.

    Conclusions: Our findings have implications for the understanding of hyperactivity of the angiotensin system and for use of Ca 2+  channel blockers as mono-therapy in hypertension. 

  • 20.
    Bernhem, Kristoffer
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Zhang, Liang
    Fontana, Jacopo M.
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Nilsson, Linnea
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Scott, Lena
    Brismar, Hjalmar
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Aperia, Anita
    Mapping the apoptotic process with super resolution microscopy in kidney cells challenged with high glucose2017In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 31Article in journal (Other academic)
  • 21.
    Bernhem, Kristoffer
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zhang, Liang
    Karolinska Institutet.
    Fontana, Jacopo
    KTH, School of Engineering Sciences (SCI), Applied Physics. Karolinska Institutet.
    Scott, Lena
    Karolinska Institutet.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sweden.
    Aperia, Anita
    Karolinska Institutet.
    Super resolution imaging reveals details in hyperglycemic induced apoptosis in kidney cellsManuscript (preprint) (Other academic)
    Abstract [en]

    The role of the Bcl-family proteins in the mitochondrial apoptotic process is well described with biochemical and molecular methods in studies of isolated mitochondria and transfected cell lines. There is however little knowledge about the mechanisms for Bcl protein interaction leading to apoptosis in intact cells. In particular, the time sequence and location for Bcl protein interaction has so far only been described in hypothetical models.Here we have used Stimulated Emission Depletion (STED) microscopy and Single Molecule Localization Microscopy (SMLM) to study the apoptotic process in immune-stained rat renal epithelia cells exposed to 20 mM glucose (HG) and to study its rescue by ouabain. To assess distance between Bcl-2 proteins, we used the nearest-neighbor algorithm. The anti-apoptotic protein Bcl-xLl was predominantly expressed on mitochondria in control cells, and remained so throughout the process, although its abundance decreased. After 2h HG the apoptosis-inducing protein BAD had translocated from the cytoplasm to the mitochondria where it clustered with Bcl-xL. This occurred before an increase in reactive oxygen species and was dependent on activation of the PI3K –AKT pathway. According to current concepts, Bcl-xL interacts with the apoptotic protein Bax on the mitochondria under control conditions to translocate Bax back to the cytosol1. We found that Bax started to accumulate on the mitochondria after 4h HG and, surprisingly, that the interaction between Bcl-xL and Bax became more pronounced during the course of the apoptotic process. After 6h HG Bax also interacted with the non-specific ion transporter VDAC; an interaction described to lead to penetration of the inner mitochondrial membrane and mark the point of no return.

  • 22.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Bernhem, Kristoffer
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sweden.
    Sodium pump organization in dendritic spines2016In: NEUROPHOTONICS, ISSN 2329-423X, Vol. 3, no 4, article id 041803Article in journal (Refereed)
    Abstract [en]

    Advancement in fluorescence imaging with the invention of several super-resolution microscopy modalities (e.g., PALM/STORM and STED) has opened up the possibility of deciphering molecular distributions on the nanoscale. In our quest to better elucidate postsynaptic protein distribution in dendritic spines, we have applied these nanoscopy methods, where generated results could help improve our understanding of neuronal functions. In particular, we have investigated the principal energy transformer in the brain, i.e., the Na+; K+-ATPase (or sodium pump), an essential protein responsible for maintaining resting membrane potential and a major controller of intracellular ion homeostasis. In these investigations, we have focused on estimates of protein amount, giving assessments of how variations may depend on labeling strategies, sample analysis, and choice of nanoscopic imaging method, concluding that all can be critical factors for quantification. We present a comparison of these results and discuss the influences this may have for homeostatic sodium regulation in neurons and energy consumption.

  • 23.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    STED microscopy: increased resolution for medical research?2014In: Journal of Internal Medicine, ISSN 0954-6820, E-ISSN 1365-2796, Vol. 276, no 6, p. 560-578Article, review/survey (Refereed)
    Abstract [en]

    Optical imaging is crucial for addressing fundamental problems in all areas of life science. With the use of confocal and two-photon fluorescence microscopy, complex dynamic structures and functions in a plethora of tissue and cell types have been visualized. However, the resolution of classical' optical imaging methods is poor due to the diffraction limit and does not allow resolution of the cellular microcosmos. On the other hand, the novel stimulated emission depletion (STED) microscopy technique, because of its targeted on/off-switching of fluorescence, is not hampered by a diffraction-limited resolution barrier. STED microscopy can therefore provide much sharper images, permitting nanoscale visualization by sequential imaging of individual-labelled biomolecules, which should allow previous findings to be reinvestigated and provide novel information. The aim of this review is to highlight promising developments in and applications of STED microscopy and their impact on unresolved issues in biomedical science.

  • 24.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Ronnlund, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Scott, Lena
    Spicarova, Zuzana
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Bondar, Alexander
    Aperia, Anita
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Spatial distribution of Na+-K+-ATPase in dendritic spines dissected by nanoscale superresolution STED microscopy2011In: BMC neuroscience (Online), ISSN 1471-2202, E-ISSN 1471-2202, Vol. 12, p. 16-Article in journal (Refereed)
    Abstract [en]

    Background: The Na+,K+-ATPase plays an important role for ion homeostasis in virtually all mammalian cells, including neurons. Despite this, there is as yet little known about the isoform specific distribution in neurons. Results: With help of superresolving stimulated emission depletion microscopy the spatial distribution of Na+,K+-ATPase in dendritic spines of cultured striatum neurons have been dissected. The found compartmentalized distribution provides a strong evidence for the confinement of neuronal Na+,K+-ATPase (alpha 3 isoform) in the postsynaptic region of the spine. Conclusions: A compartmentalized distribution may have implications for the generation of local sodium gradients within the spine and for the structural and functional interaction between the sodium pump and other synaptic proteins. Superresolution microscopy has thus opened up a new perspective to elucidate the nature of the physiological function, regulation and signaling role of Na+,K+-ATPase from its topological distribution in dendritic spines.

  • 25.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Rönnlund, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Scott, L.
    Westin, L.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Aperia, A.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Spatial Distribution of DARPP-32 in Dendritic Spines2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 9, p. e75155-Article in journal (Refereed)
    Abstract [en]

    The phosphoprotein DARPP-32 (dopamine and cyclic adenosine 3́, 5́-monophosphate-regulated phosphoprotein, 32 kDa) is an important component in the molecular regulation of postsynaptic signaling in neostriatum. Despite the importance of this phosphoprotein, there is as yet little known about the nanoscale distribution of DARPP-32. In this study we applied superresolution stimulated emission depletion microscopy (STED) to assess the expression and distribution of DARPP-32 in striatal neurons. Primary culture of striatal neurons were immunofluorescently labeled for DARPP-32 with Alexa-594 and for the dopamine D1 receptor (D1R) with atto-647N. Dual-color STED microscopy revealed discrete localizations of DARPP-32 and D1R in the spine structure, with clustered distributions in both head and neck. Dissected spine structures reveal that the DARPP-32 signal rarely overlapped with the D1R signal. The D1R receptor is positioned in an "aggregated" manner primarily in the spine head and to some extent in the neck, while DARPP-32 forms several neighboring small nanoclusters spanning the whole spine structure. The DARPP-32 clusters have a mean size of 52 +/- 6 nm, which is close to the resolution limit of the microscope and corresponds to the physical size of a few individual phosphoprotein immunocomplexes. Dissection of synaptic proteins using superresolution microscopy gives possibilities to reveal in better detail biologically relevant information, as compared to diffraction-limited microscopy. In this work, the dissected postsynaptic topology of the DARPP-32 phosphoprotein provides strong evidence for a compartmentalized and confined distribution in dendritic spines. The protein topology and the relatively low copy number of phosphoprotein provides a conception of DARPP-32's possibilities to fine-tune the regulation of synaptic signaling, which should have an impact on the performance of the neuronal circuits in which it is expressed.

  • 26.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Rönnlund, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Scott, Lena
    Spicarova, Zuzana
    Rantanen, Ville
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Aperia, Anita
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Nearest neighbor analysis of dopamine D1 receptors and Na plus -K plus -ATPases in dendritic spines dissected by STED microscopy2012In: Microscopy research and technique (Print), ISSN 1059-910X, E-ISSN 1097-0029, Vol. 75, no 2, p. 220-228Article in journal (Refereed)
    Abstract [en]

    Protein localization in dendritic spines is the focus of intense investigations within neuroscience. Applications of super-resolution microscopy to dissect nanoscale protein distributions, as shown in this work with dual-color STED, generate spatial correlation coefficients having quite small values. This means that colocalization analysis to some extent looses part of its correlative impact. In this study we thus introduced nearest neighbor analysis to quantify the spatial relations between two important proteins in neurons, the dopamine D1 receptor and Na+,K+-ATPase. The analysis gave new information on how dense the D1 receptor and Na+,K+-ATPase constituting nanoclusters are located both with respect to the homogenous (self to same) and the heterogeneous (same to other) topology. The STED dissected nanoscale topologies provide evidence for both a joint as well as a separated confinement of the D1 receptor and the Na+,K+-ATPase in the postsynaptic areas of dendritic spines. This confined topology may have implications for generation of local sodium gradients and for structural and functional interactions modulating slow synaptic transmission processes. Microsc. Res. Tech., 2011.

  • 27. Brismar, Hjalmar
    Observer reliability in the arthroscopic classification of osteoarthritis of the knee - Reply2003In: Journal of Bone and Joint Surgery, ISSN 0301-620X, E-ISSN 2044-5377, Vol. 85B, no 3, p. 464-464Article in journal (Refereed)
  • 28. Brismar, Hjalmar
    et al.
    Agren, M.
    Holtback, U.
    beta-Adrenoceptor agonist sensitizes the dopamine-1 receptor in renal tubular cells2002In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 175, no 4, p. 333-340Article in journal (Refereed)
    Abstract [en]

    The renal effects of dopamine are mainly mediated via the dopamine-1 receptor (D1 receptor). This receptor is recruited from intracellular compartments to the plasma membrane by dopamine and atrial natriuretic peptide (ANP), via adenylyl cyclase activation. We have studied whether isoproterenol, a beta -adrenoceptor (beta -AR) agonist that may interact with dopamine in the regulation of rat renal Na+, K+ -adenosine triphosphatase (ATPase) activity, can recruit D1 receptors to the plasma membrane. The spatial regulation of D1 receptors was examined using confocal microscopy techniques in LLCPK cells and the functional interaction between dopamine and isoproterenol was examined by studying their effects on Na+, K+ -ATPase activity in microdissected single proximal tubular segments from rat. Isoproterenol was found to translocate the D1 receptors from the interior of the cell towards the plasma membrane. The recruitment of dopamine 1 receptors was found to be cyclic adenosine phosphate (cAMP) dependent, while protein kinase C (PKC) activation was not involved. The functional studies on Na+, K+ -ATPase activity showed that the effect of isoproterenol was abolished by a D1-like receptor antagonist (SCH 23390), and mediated via protein kinase A (PKA) and PKC dependent pathways. The results provide an explanation for the interaction between G protein-coupled receptors. The effects of isoproterenol on Na+, K+ -ATPase activity can be explained by a heterologous recruitment of D1 receptors to the plasma membrane.

  • 29.
    Brismar, Hjalmar
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Inst, Astrid Lindgren Childrens Hosp, Dept Woman & Child Hlth, Sweden.
    Aperia, A
    Westin, L
    Moy, J
    Wang, M
    Guillermier, C
    Poczatek, C
    Lechene, C
    Study of protein and RNA in dendritic spines using multi-isotope imaging mass spectrometry (MIMS).2014In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 46, no Suppl 1Article in journal (Refereed)
    Abstract [en]

    The classical view of neuronal protein synthesis is that proteins are made in the cell body and then transported to their functional sites in the dendrites and the dendritic spines. Indirect evidence, however, suggests that protein synthesis can directly occur in the distal dendrites, far from the cell body. We are developing protocols for dual labeling of RNA and proteins using (15)N-uridine and (18)O- or (13)C-leucine pulse chase in cultured neurons to identify and localize both protein synthesis and fate of newly synthesized proteins. Pilot experiments show discrete localization of both RNA and newly synthesized proteins in dendrites, close to dendritic spines. We have for the first time directly imaged and measured the production of proteins at the subcellular level in the neuronal dendrites, close to the functional sites, the dendritic spines. This will open a powerful way to study neural growth and synapse plasticity in health and disease.

  • 30. Brismar, Hjalmar
    et al.
    Holtback, U.
    Aperia, A.
    Mechanisms by which intrarenal dopamine and ANP interact to regulate sodium metabolism2000In: Clinical and experimental hypertension (1993, Print), ISSN 1064-1963, E-ISSN 1525-6006, Vol. 22, no 3, p. 303-307Article in journal (Refereed)
    Abstract [en]

    Maintenance of a normal blood pressure requires a precise and fine-tuned regulation of salt metabolism. This is accomplished by a bidirectional regulation of renal tubular sodium transporters by natriuretic and antinatriuretic hormones. Dopamine, produced in the renal proximal tubular cells, plays an important role in this interactive system. Dopamine inhibits the activity of Na+,K(+)ATPase as well as of many important sodium influx pathways in the nephron. These effects of dopamine are particularly pronounced in situation of sodium loading. There is an abundance of evidence suggesting that the natriuretic effects of ANP are to a large extent mediated via renal dopamine 1 like receptors. The renal tubular dopamine 1 like receptors are, under basal conditions, mainly located intracellularly. ANP and its second messenger, cGMP, cause a rapid translocation of the dopamine 1 like receptors to the plasma membrane. This phenomenon may explain how ANP and dopamine act in concert to regulate sodium metabolism Regulation of sodium metabolism and blood pressure is critically dependent on a normal function of the renal dopamine system. Hence, abnormalities in the interaction between dopamine and ANP may predispose to hypertension.

  • 31. Brismar, Hjalmar
    et al.
    Hua, X.
    Adachi, S.
    Holtback, U.
    The role of endocytosis in renal dopamine D1 receptor signaling2006In: Pflügers Archiv: European Journal of Physiology, ISSN 0031-6768, E-ISSN 1432-2013, Vol. 451, no 6, p. 793-802Article in journal (Refereed)
    Abstract [en]

    Desensitization of G-protein-coupled receptors (GPCR) includes receptor endocytosis. This phenomenon is suggested, at least for some receptors, to be associated with receptor resensitization. Here, we examined the role of receptor endocytosis for two different GPCR, the dopamine-1 (D1) receptor and the beta 1-adrenoceptor (beta(1)-AR) in renal tissue. The functional role of receptor endocytosis was examined on Na+, K+-ATPase activity in microdissected proximal tubules from rat kidney. The spatial regulation of endogenous D1 receptors and beta(1)-AR was examined by confocal microscopy techniques in LLCPK cells. Phenylarsine oxide (PAO) an endocytosis inhibitor, attenuated isoproterenol-induced decrease in Na+, K+-ATPase activity but had no such effect on dopamine-induced decrease in Na+, K+-ATPase activity. We have previously shown that isoproterenol sensitizes the renal dopamine system, by recruiting silent D1 receptors from the interior of the cell towards the plasma membrane. This effect was attenuated by PAO as well as by cytochalasin D while these substances had no effect on dopamine-induced D1 receptor recruitment. The beta(1)-AR was localized to the plasma membrane in control cells. Isoproterenol induced a rapid internalization of the beta(1)-AR; which was prevented by PAO. The results suggest that endocytosis of beta(1)-AR in renal proximal tubular cells is an important step in signal generation, while endocytosis of proximal tubular D1 receptor is not.

  • 32.
    Brismar, Hjalmar
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Scott, Lena
    Malmersjö, Seth
    Kowalewski, Jacob M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Zettergren Markus, Eivor
    Ulfhake, Brun
    Nairn, Angus C.
    Greengard, Paul
    Aperia, Anita
    Kvinnor och barns hälsa, Karolinska Institutet.
    Laterally diffusing dopamine 1 receptors are recruited to dendrtic spines by interaction with allosterically changed NMDA receptors2005In: Neuroscience 2005, 2005Conference paper (Refereed)
  • 33.
    Brismar, Hjalmar
    et al.
    KTH, Superseded Departments, Physics.
    Trepte, O
    Ulfhake, B
    Spectra and fluorescence lifetimes of lissamine rhodamine, tetramethylrhodamine isothiocyanate, texas red, and cyanine 3.18 fluorophores: influences of some environmental factors recorded with a confocal laser scanning microscope.1995In: Journal of Histochemistry and Cytochemistry, ISSN 0022-1554, E-ISSN 1551-5044, Vol. 43, no 7Article in journal (Refereed)
    Abstract [en]

    We report on the spectra and fluorescence lifetimes of four commonly used fluorophores: lissamine rhodamine (LRSC); tetramethyl rhodamine isothiocyanate (TRITC); Texas Red; and cyanine 3.18 (Cy-3). Fluorescence lifetime recordings revealed that these spectrally overlapping fluorophores can be individually detected by their lifetimes, indicating that at least four fluorophores can be individually identified in discrete tissue domains by confocal microscopy. A further advantage of lifetime recordings is that fluorophores that emit light within the same wavelength band can be used and chromatic aberrations are therefore circumvented, thereby improving the spatial accuracy in imaging of multiple fluorophores. Low and high pH, respectively, tended to influence fluorophore emission spectra and fluorescence lifetime. IgG conjugation of the fluorophores tended to shift the spectra towards longer wavelengths and to change the fluorescence lifetimes. The IgG-conjugated form of the fluorophores may, when applied to tissue specimens, change the emission spectrum and lifetime. In addition, different tissue embedding procedures may influence fluorescence lifetime. These observations emphasize the importance of spectral and lifetime characterization of fluorescent probes within the chemical context in which they will be used experimentally. Changes in spectra and fluorescence lifetimes may be a useful tool to gain information about the chemical environment of the fluorophores.

  • 34.
    Brismar, Hjalmar
    et al.
    KTH, Superseded Departments, Physics.
    Ulfhake, B
    Fluorescence lifetime measurements in confocal microscopy of neurons labeled with multiple fluorophores.1997In: Nature Biotechnology, ISSN 1087-0156, E-ISSN 1546-1696, Vol. 15, no 4Article in journal (Refereed)
    Abstract [en]

    In order to resolve multiple fluorophores by their lifetimes in discrete tissue domains, the labeling intensity must be sufficiently strong and the intensity-difference between the labels must not be too large, the rate of fading should be similar for all fluorophores, and the lifetimes of the fluorophores should be sufficiently discrete. We could readily distinguish Cyanine-3.18 (Cy-3), Lissamine Rhodamine (LRSC), and Texas Red when they were not colocalized in tissue profiles. Colocalization of Cy-3 and LRSC, as well as Cy3 and Texas Red, could also be distinguished, while the combination of LRSC and Texas Red was more difficult. We have used fluorescence lifetime recordings in confocal microscopy to detect different neuropeptides in neurons. We demonstrate that somatostatin and galanin are colocalized in axon profiles of the spinal cord dorsal horn.

  • 35. Brundin, L.
    et al.
    Brismar, Hjalmar
    Danilov, A. I.
    Olsson, T.
    Johansson, C. B.
    Neural stem cells: A potential source for remyelination in neuroinflammatory disease2003In: Brain Pathology, ISSN 1015-6305, E-ISSN 1750-3639, Vol. 13, no 3, p. 322-328Article in journal (Refereed)
    Abstract [en]

    In multiple sclerosis, the central nervous system is lesioned through invasion of plaque-forming inflammatory cells, primarily contributing to immune attack of myelin and oligodendrocytes. In this report we address the possible activation and differentiation of central nervous system stem cells following such immunological insults in a well-characterized rat model of multiple sclerosis characterised by spinal cord pathology. Dye-labeled central nervous system stem cells, residing within the ependymal layer of the central canal responded to the multiple sclerosis-like conditions by proliferation, while some of the migrating stem cell-derived cells expressed markers typical for oligodendrocytes (04) and astrocytes (glial fibrillary acidic protein, GFAP) in the demyelinated area. Our results indicate that regenerative stem cell activation following immunoactivity is different from that after trauma, exemplified by the slower time course of stem cell proliferation and migration of progeny, in addition to the ability of the stem cell-derived cells to express oligodendrocyte markers. Finally,, deleterious effects of macrophages on the stem cell population were evident and may contribute to the, depletion of the stem cell population in neuroinflammatory disorders.

  • 36. Burlaka, Ievgeniia
    et al.
    Liu, Xiao Li
    Rebetz, Johan
    Arvidsson, Ida
    Yang, Liping
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Karpman, Diana
    Aperia, Anita
    Ouabain Protects against Shiga Toxin-Triggered Apoptosis by Reversing the Imbalance between Bax and Bcl-xL2013In: Journal of the American Society of Nephrology, ISSN 1046-6673, E-ISSN 1533-3450, Vol. 24, no 9, p. 1413-1423Article in journal (Refereed)
    Abstract [en]

    Hemolytic uremic syndrome, a life-threatening disease often accompanied by acute renal failure, usually occurs after gastrointestinal infection with Shiga toxin 2 (Stx2)-producing Escherichia coli. Stx2 binds to the glycosphingolipid globotriaosylceramide receptor, expressed by renal epithelial cells, and triggers apoptosis by activating the apoptotic factor Bax. Signaling via the ouabain/Na,K-ATPase/IP3R/NF-B pathway increases expression of Bcl-xL, an inhibitor of Bax, suggesting that ouabain might protect renal cells from Stx2-triggered apoptosis. Here, exposing rat proximal tubular cells to Stx2 in vitro resulted in massive apoptosis, upregulation of the apoptotic factor Bax, increased cleaved caspase-3, and downregulation of the survival factor Bcl-xL; co-incubation with ouabain prevented all of these effects. Ouabain activated the NF-B antiapoptotic subunit p65, and the inhibition of p65 DNA binding abolished the antiapoptotic effect of ouabain in Stx2-exposed tubular cells. Furthermore, in vivo, administration of ouabain reversed the imbalance between Bax and Bcl-xL in Stx2-treated mice. Taken together, these results suggest that ouabain can protect the kidney from the apoptotic effects of Stx2.

  • 37. Burlaka, Ievgeniia
    et al.
    Nilsson, Linnea M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Scott, Lena
    Holtback, Ulla
    Eklöf, Ann-Christine
    Fogo, Agnes B.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sweden.
    Aperia, Anita
    Prevention of apoptosis averts glomerular tubular disconnection and podocyte loss in proteinuric kidney disease2016In: Kidney International, ISSN 0085-2538, E-ISSN 1523-1755, Vol. 90, no 1, p. 135-148Article in journal (Refereed)
    Abstract [en]

    There is a great need for treatment that arrests progression of chronic kidney disease. Increased albumin in urine leads to apoptosis and fibrosis of podocytes and tubular cells and is a major cause of functional deterioration. There have been many attempts to target fibrosis, but because of the lack of appropriate agents, few have targeted apoptosis. Our group has described an ouabain-activated Na,K-ATPase/IP3R signalosome, which protects from apoptosis. Here we show that albumin uptake in primary rat renal epithelial cells is accompanied by a time-and dose-dependent mitochondrial accumulation of the apoptotic factor Bax, down-regulation of the antiapoptotic factor Bcl-xL and mitochondrial membrane depolarization. Ouabain opposes these effects and protects from apoptosis in albumin-exposed proximal tubule cells and podocytes. The efficacy of ouabain as an antiapoptotic and kidney-protective therapeutic tool was then tested in rats with passive Heymann nephritis, a model of proteinuric chronic kidney disease. Chronic ouabain treatment preserved renal function, protected from renal cortical apoptosis, up-regulated Bax, down-regulated Bcl-xL, and rescued from glomerular tubular disconnection and podocyte loss. Thus we have identified a novel clinically feasible therapeutic tool, which has the potential to protect from apoptosis and rescue from loss of functional tissue in chronic proteinuric kidney disease.

  • 38. Carannante, Valentina
    et al.
    Olofsson, Karl
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Van Oojen, Hanna
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Edwards, Steven
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lundqvist, Andreas
    Wiklund, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Önfelt, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Novel platform for studying infiltration, migration and cytotoxicity of human Natural Killer cells in solid tumors2017In: Scandinavian Journal of Immunology, ISSN 0300-9475, E-ISSN 1365-3083, Vol. 86, no 4, p. 315-315Article in journal (Other academic)
  • 39. Carlen, M.
    et al.
    Cassidy, R. M.
    Brismar, Hjalmar
    Smith, G. A.
    Enquist, L. W.
    Frisen, J.
    Functional integration of adult-born neurons2002In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 12, no 7, p. 606-608Article in journal (Refereed)
    Abstract [en]

    Over the past decade, it has become clear that neural stem cells in the adult mammalian brain continuously generate new neurons, predominantly in the hippocampus and olfactory bulb [1]. However, the central issue of whether these new neurons participate in functional synaptic circuitry has yet to be resolved. Here, we use virus-based transsynaptic neuronal tracing and c-Fos mapping of odor-induced neuronal activity to demonstrate that neurons generated in the adult functionally integrate into the synaptic circuitry of the brain.

  • 40.
    Carlsson, Kjell
    et al.
    KTH, Superseded Departments, Physics.
    Liljeborg, A.
    Andersson, R. M.
    Brismar, Hjalmar
    Confocal pH imaging of microscopic specimens using fluorescence lifetimes and phase fluorometry: influence of parameter choice on system performance2000In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 199, p. 106-114Article in journal (Refereed)
    Abstract [en]

    We investigate the performance of confocal pH imaging when using phase fluorometry and fluorophores with pH-dependent lifetimes. In these experiments, the specimen is illuminated by a laser beam, whose intensity is sinusoidally modulated. The lifetime-dependent phase shift in the fluorescent signal is detected by a lock-in amplifier, and converted into a pH value through a calibration procedure. A theoretical investigation is made of how the different system parameters will influence the results concerning sensitivity and noise. Experiments carried out with the fluorophore SNAFL-2 support these theoretical predictions. It is found that, under realistic experimental conditions, we can expect a pH change of 0.1 units to be easily detected in an 8-bit digital image. However, the pixel-to-pixel root mean square noise is often of the order of one pH unit. This comparatively high level of noise has its origin in photon quantum noise. pH measurements on living cells show a systematic deviation from expected values. This discrepancy appears to be the result of fluorophore interaction with various cell constituents, and is the subject of further investigation.

  • 41.
    Carrick, Christopher
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Aidun, Cyrus
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Native and functionalized micrometre-sized cellulose capsules prepared by microfluidic flow focusing2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 37, p. 19061-19067Article in journal (Refereed)
    Abstract [en]

    Cellulose capsules with average outer and inner radii of approximately 44 mu m and 29 mm respectively were prepared from cellulose dissolved in a mixture of lithium chloride and dimethylacetamide using a microfluidic flow focusing device (MFFD). The MFFD had three inlets where octane oil in a cellulose solution in silicone oil was used to produce a double emulsion containing a cellulose capsule. This technique enables the formation of capsules with a narrow size distribution which can be beneficial for drug delivery or controlled release capsules. In this respect, cellulose is a highly interesting material since it is known to cause no autoimmune reactions when used in contact with human tissue. Furthermore, by controlling the chemical properties of the cellulose, it is possible to trigger a swelling of the capsules and consequentially the release of an encapsulated substance, e. g. a model drug, when the capsule becomes exposed to an external stimulus. To demonstrate this, capsules were functionalized by carboxymethylation to be pH- responsive and to expand approximately 10% when subjected to a change in pH from 3 to 10. The diffusion constant of a model drug, a 4 kDa fluorescently labelled dextran, through the native capsule wall was estimated to be 6.5 X 10(-14) m(2) s(-1) by fitting fluorescence intensity data to Fick's second law.

  • 42. Chen, Yun
    et al.
    Molnar, Mátyás
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Li, Li
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Friberg, Peter
    Gan, Li-Ming
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Fu, Ying
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Characterization of VCAM-1-Binding Peptide-Functionalized Quantum Dots for Molecular Imaging of Inflamed Endothelium2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 12, p. e83805-Article in journal (Refereed)
    Abstract [en]

    Inflammation-induced activation of endothelium constitutes one of the earliest changes during atherogenesis. New imaging techniques that allow detecting activated endothelial cells can improve the identification of persons at high cardiovascular risk in early stages. Quantum dots (QDs) have attractive optical properties such as bright fluorescence and high photostability, and have been increasingly studied and developed for bio-imaging and bio-targeting applications. We report here the development of vascular cell adhesion molecule-1 binding peptide (VCAM-1 binding peptide) functionalized QDs (VQDs) from amino QDs. It was found that the QD fluorescence signal in tumor necrosis factor alpha (TNF-alpha) treated endothelial cells in vitro was significantly higher when these cells were labeled with VQDs than amino QDs. The VQD labeling of TNF-alpha-treated endothelial cells was VCAM-1 specific since pre-incubation with recombinant VCAM-1 blocked cells' uptake of VQDs. Our ex vivo and in vivo experiments showed that in the inflamed endothelium, QD fluorescence signal from VQDs was also much stronger than that of amino QDs. Moreover, we observed that the QD fluorescence peak was significantly blue-shifted after VQDs interacted with aortic endothelial cells in vivo and in vitro. A similar blue-shift was observed after VQDs were incubated with recombinant VCAM-1 in tube. We anticipate that the specific interaction between VQDs and VCAM-1 and the blue-shift of the QD fluorescence peak can be very useful for VCAM-1 detection in vivo.

  • 43. Clausson, Carl-Magnus
    et al.
    Arngarden, Linda
    Ishaq, Omer
    Klaesson, Axel
    Kuhnemund, Malte
    Grannas, Karin
    Koos, Bjorn
    Qian, Xiaoyan
    Ranefall, Petter
    Krzywkowski, Tomasz
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Nilsson, Mats
    Wahlby, Carolina
    Soderberg, Ola
    Compaction of rolling circle amplification products increases signal integrity and signal-to-noise ratio2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 12317Article in journal (Refereed)
    Abstract [en]

    Rolling circle amplification (RCA) for generation of distinct fluorescent signals in situ relies upon the self-collapsing properties of single-stranded DNA in commonly used RCA-based methods. By introducing a cross-hybridizing DNA oligonucleotide during rolling circle amplification, we demonstrate that the fluorophore-labeled RCA products (RCPs) become smaller. The reduced size of RCPs increases the local concentration of fluorophores and as a result, the signal intensity increases together with the signal-to-noise ratio. Furthermore, we have found that RCPs sometimes tend to disintegrate and may be recorded as several RCPs, a trait that is prevented with our cross-hybridizing DNA oligonucleotide. These effects generated by compaction of RCPs improve accuracy of visual as well as automated in situ analysis for RCA based methods, such as proximity ligation assays (PLA) and padlock probes.

  • 44.
    Errando-Herranz, Carlos
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Vastesson, Alexander
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Zelenina, Marina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Pardon, Gaspard
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Bergström, Gunnar
    Wijngaart, Wouter van der
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Haraldsson, Tommy
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Biocompatibility of OSTE polymers studied by cell growth experiments2013In: Proceedings of the 17th Int. Conf. on Miniaturized Systems for Chemistry  and Life Sciences (microTAS), Freiburg, Germany, 2013Conference paper (Refereed)
    Abstract [en]

    The recently introduced OSTE polymer technology has shown very useful features for microfluidics for lab-on-a-chip applications. However, no data has yet been published on cell viability on OSTE. In this work, we study the biocompatibility of three OSTE formulations by cell growth experiments. Moreover, we investigate the effect of varying thiol excess on cell viability on OSTE surfaces. The results show poor cell viability on one OSTE formulation, and viability comparable with polystyrene on a second formulation with thiol excess below 60%. In the third formulation, we observe cell proliferation. These results are promising for cell-based assays in OSTE microfluidic devices.

  • 45.
    Fontana, Jacopo
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Fritz, Nicolas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Aperia, Anita
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Apoptosis caused by excessive mitochondrial albumin uptake in renal cells is initiated by increased mitochondrial calcium concentration2015In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 29Article in journal (Other academic)
  • 46. Fontana, Jacopo M.
    et al.
    Burlaka, Ievgeniia
    Khodus, Georgiy
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Aperia, Anita
    Calcium oscillations triggered by cardiotonic steroids2013In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 280, no 21, p. 5450-5455Article, review/survey (Refereed)
    Abstract [en]

    Na+, K+-ATPase (NKA) is well known for its function as an ion pump. Studies during the last decade have revealed an additional role for NKA as a signal transducer. In this brief review, we describe how cardiotonic steroids, which are highly specific NKA ligands, trigger slow Ca2+ oscillations by promoting the interaction between NKA and the inositol trisphosphate receptor, and how this Ca2+ signal activates the NF-B subunit p65 and increases the expression of the antiapoptotic factor Bcl-xL. The potential tissue-protective effects of this signal are discussed.

  • 47. Foo, K. S.
    et al.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Broberger, C.
    DISTRIBUTION AND NEUROPEPTIDE COEXISTENCE OF NUCLEOBINDIN-2 mRNA/NESFATIN-LIKE IMMUNOREACTIVITY IN THE RAT CNS2008In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 156, no 3, p. 563-579Article in journal (Refereed)
    Abstract [en]

    The protein fragment nesfatin-1 was recently implicated in the control of food intake. Central administration of this fragment results in anorexia and reduced body weight gain, whereas antisense or immunological nesfatin-1 antagonism causes increased food intake and overweight. Nesfatin-1 is derived from the precursor nucleobindin-2 (NUCB2). To identify the neurocircuitry underpinning the catabolic effects of NUCB2/nesfatin-1, we have used in situ hybridization and immunohistochemistry to map the distribution of this protein and its mRNA in the rat CNS and performed double-labeling experiments to localize its expression to functionally defined neuronal populations. These experiments confirm previous observations but also present several novel NUCB2 cell populations. Both NUCB2 mRNA and nesfatin-like immunoreactivity was most concentrated in the hypothalamus, in the supraoptic, paraventricular, periventricular and arcuate nuclei and the lateral hypothalamic area/perifornical region. Additionally, outside of the hypothalamus, labeling was observed in the thalamic parafascicular nucleus, the Edinger-Westphal nucleus, locus coeruleus, ventral raphe system, nucleus of solitary tract and in the preganglionic sympathetic intermediolateral cell column of the spinal cord, and the pituitary anterior and intermediate lobes. In neurons, immunoreactivity was almost exclusively confined to perikarya and primary dendrites with virtually no labeling of axonal terminals. Double-labeling immunohistochemistry revealed colocalization of nesfatin with vasopressin and oxytocin in magnocellular neuroendocrine neurons, thyrotropin-releasing hormone, corticotropin-releasing hormone, somatostatin, neurotensin, and growth-hormone-releasing hormone in parvocellular neuroendocrine neurons, pro-opiomelanocortin (but not neuropeptide Y) in the arcuate nucleus and melanin-concentrating hormone (but not hypocretin) in the lateral hypothalamus. Furthermore, nesfatin was extensively colocalized with cocaine- and amphetamine-regulated transcript in almost all NUCB2-expressing brain regions. These data reveal a wider distribution of NUCB2/nesfatin-1 than previously known, suggesting that the metabolic actions of this protein may involve not only feeding behavior but also endocrine and autonomic effects on energy expenditure. In addition, the subcellular distribution of nesfatin-like immunoreactivity indicates that this protein may not be processed like a conventional secreted neuromodulator.

  • 48.
    Friedman, Mikaela
    et al.
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Lindström, Sara
    KTH, School of Biotechnology (BIO), Nano Biotechnology.
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Nano Biotechnology.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Ståhl, Stefan
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Engineering and characterization of a bispecific HER2 × EGFR-binding affibody molecule2009In: Biotechnology and applied biochemistry, ISSN 0885-4513, E-ISSN 1470-8744, Vol. 54, p. 121-131Article in journal (Refereed)
    Abstract [en]

    HER2 (human epidermal-growth-factor receptor-2; ErbB2) and EGFR (epidermal-growth-factor receptor) are overexpressed in various forms of cancer, and the co-expression of both HER2 and EGFR has been reported in a number of studies. The simultaneous targeting of HER2 and EGFR has been discussed as a strategy with which to potentially increase efficiency and selectivity in molecular imaging and therapy of certain cancers. In an effort to generate a molecule capable of bispecifically targeting HER2 and EGFR, a gene fragment encoding a bivalent HER2-binding affibody molecule was genetically fused in-frame with a bivalent EGFR-binding affibody molecule via a (G(4)S)(3) [(Gly(4)-Ser)(3)]-encoding gene fragment. The encoded 30 kDa affibody construct (Z(HER2))(2)-(G(4)S)(3)-(Z(EGFR))(2), with potential for bs (bispecific) binding to HER2 and EGFR, was expressed in Escherichia coli and characterized in terms of its binding capabilities. The retained ability to bind HER2 and EGFR separately was demonstrated using both biosensor technology and flow-cytometric analysis, the latter using HER2- and EGFR-overexpressing cells. Furthermore, simultaneous binding to HER2 and EGFR was demonstrated in: (i) a sandwich format employing real-time biospecific interaction analysis where the bs affibody molecule bound immobilized EGFR and soluble HER2; (ii) immunofluorescence microscopy, where the bs affibody molecule bound EGFR-overexpressing cells and soluble HER2; and (iii) a cell-cell interaction analysis where the bs affibody molecule bound HER2-overexpressing SKBR-3 cells and EGFR-overexpressing A-431 cells. This is, to our knowledge, the first reported bs affinity protein with potential ability for the simultaneous targeting of HER2 and EGFR. The potential future use of this and similar constructs, capable of bs targeting of receptors to increase the efficacy and selectivity in imaging and therapy, is discussed.

  • 49.
    Friedman, Mikaela
    et al.
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Nordberg, Erika
    Uppsala Univ, Dept Oncol Radiol & Clin Immunol, Rudbeck Lab.
    Höidén-Guthenberg, Ingmarie
    Affibody AB, Bromma.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Adams, Gregory P.
    Fox Chase Canc Ctr, Dept Med Oncol, Philadelphia.
    Nilsson, Fredrik Y.
    Uppsala Univ, Dept Oncol Radiol & Clin Immunol, Rudbeck Lab.
    Carlsson, Jörgen
    Uppsala Univ, Dept Oncol Radiol & Clin Immunol, Rudbeck Lab.
    Ståhl, Stefan
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Phage display selection of Affibody molecules with specific binding to the extracellular domain of the epidermal growth factor receptor2007In: Protein Engineering Design & Selection, ISSN 1741-0126, E-ISSN 1741-0134, Vol. 20, no 4, p. 189-199Article in journal (Refereed)
    Abstract [en]

    Affibody molecules specific for the epidermal growth factor receptor (EGFR) have been selected by Phage display technology from a combinatorial protein library based on the 58-residue, protein A-derived Z domain. EGFR is overexpressed in various malignancies and is frequently associated with poor patient prognosis, and the information provided by targeting this receptor could facilitate both patient diagnostics and treatment. Three selected Affibody variants were shown to selectively bind to the extracellular domain of EGFR (EGFR-ECD). Kinetic biosensor analysis revealed that the three monomeric Affibody molecules bound with similar affinity, ranging from 130 to 185 nM. Head-to-tail dimers of the Affibody molecules were compared for their binding to recombinant EGFR-ECD in biosensor analysis and in human epithelial cancer A431 cells. Although the dimeric Affibody variants were found to bind in a range of 2550 nM affinities in biosensor analysis, they were found to be low nanomolar binders in the cellular assays. Competition assays using radiolabeled Affibody dimers confirmed specific EGFR-binding and demonstrated that the three Affibody molecules competed for the same epitope. Immunofluorescence microscopy demonstrated that the selected Affibody dimers were initially binding to EGFR at the cell surface of A431, and confocal microscopy analysis showed that the Affibody dimers could thereafter be internalized. The potential use of the described Affibody molecules as targeting agents; for radionuclide based imaging applications in various carcinomas ils discussed.

  • 50. Frisk, T.
    et al.
    Guldevall, Karolin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Vanherbergen, B.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Önfelt, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Live-cell imaging of natural killer cell mediated tumor rejection in arrays of microwells2010In: 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2010, MicroTAS 2010: Volume 2, 2010, p. 950-952Conference paper (Refereed)
    Abstract [en]

    Due to the inherent heterogeneity of immune cell populations a comprehensive view of immune functions can only be achieved by collecting data from many individual cells. We here demonstrate a novel multi-well microchip platform for cell analysis, which we use to study the interaction between natural killer (NK) cells and their target cells.

1234 1 - 50 of 176
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