| 1. |
- Björnsdottir, Halla, et al.
(författare)
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Phenol-soluble Modulin α Peptide Toxins from aggressive Staphylococcus aureus induce rapid Formation of neutrophil extracellular Traps through a reactive Oxygen species-independent Pathway
- 2017
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophils have the ability to capture and kill microbes extracellularly through the formation of neutrophil extracellular traps (NETs). These are DNA and protein structures that neutrophils release extracellularly and are believed to function as a defense mechanism against microbes. The classic NET formation process, triggered by, e.g., bacteria, fungi, or by direct stimulation of protein kinase C through phorbol myristate acetate, is an active process that takes several hours and relies on the production of reactive oxygen species (ROS) that are further modified by myeloperoxidase (MPO). We show here that NET-like structures can also be formed by neutrophils after interaction with phenol-soluble modulin alpha (PSM alpha) that are cytotoxic membrane-disturbing peptides, secreted from community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). The PSMa-induced NETs contained the typical protein markers and were able to capture microbes. The PSMa-induced NET structures were disintegrated upon prolonged exposure to DNase-positive S. aureus but not on exposure to DNase-negative Candida albicans. Opposed to classic NETosis, PSMa-triggered NET formation occurred very rapidly, independently of ROS or MPO, and was also manifest at 4 degrees C. These data indicate that rapid NETs release may result from cytotoxic membrane disturbance by PSMa peptides, a process that may be of importance for CA-MRSA virulence.
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| 2. |
- Hakansson, P., et al.
(författare)
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Establishment and phenotypic characterization of human U937 cells with inducible P210 BCR/ABL expression reveals upregulation of CEACAM1 (CD66a)
- 2004
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Ingår i: Leukemia. - : Springer Science and Business Media LLC. - 0887-6924 .- 1476-5551. ; 18:3, s. 538-47
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Tidskriftsartikel (refereegranskat)abstract
- Chronic myeloid leukemia (CML) is characterized by the expression of the P210 BCR/ABL fusion protein. The molecular mechanisms behind this oncogene-mediated hematological disease are, however, not fully understood. Here, we describe the establishment and phenotypic characterization of U937 cells in which P210 BCR/ABL can be conditionally expressed using tetracycline. The induction of BCR/ABL in the obtained clones resulted in a rapid phosphorylation of the STAT1, STAT3 and STAT5 molecules, consistent with the findings in other model systems. Phenotypic characterization of the clones revealed that BCR/ABL induces a slight decrease in the proliferation and viability, without a marked effect on cell cycle distribution, the rate of apoptosis or on cellular differentiation, as judged by several cell surface markers and capacity to reduce nitro blue tetrazolium. Interestingly, BCR/ABL was found to upregulate the expression of carcinoembryonic-related antigen (CEA)CAM1 (CD66a), which is a plasma membrane-linked glycoprotein belonging to the CEAs and involved in signal transduction and cellular adhesion. The expression of CEACAM1 was reversible upon imatinib treatment in BCR/ABL-expressing U937 cells as well as in BCR/ABL-positive K562 cells. The established cell lines may prove useful in further modeling and dissection of BCR/ABL-induced leukemogenesis.
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| 3. |
- Holmberg, Jonas, 1976-, et al.
(författare)
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Machining of additively manufactured alloy 718 in as-built and heat-treated condition: surface integrity and cutting tool wear
- 2024
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Nature. - 0268-3768 .- 1433-3015. ; 130:3-4, s. 1823-1842
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing (AM) using powder bed fusion is becoming a mature technology that offers great possibilities and design freedom for manufacturing of near net shape components. However, for many gas turbine and aerospace applications, machining is still required, which motivates further research on the machinability and work piece integrity of additive-manufactured superalloys. In this work, turning tests have been performed on components made with both Powder Bed Fusion for Laser Beam (PBF-LB) and Electron Beam (PBF-EB) in as-built and heat-treated conditions. The two AM processes and the respective heat-treatments have generated different microstructural features that have a great impact on both the tool wear and the work piece surface integrity. The results show that the PBF-EB components have relatively lower geometrical accuracy, a rough surface topography, a coarse microstructure with hard precipitates and low residual stresses after printing. Turning of the PBF-EB material results in high cutting tool wear, which induces moderate tensile surface stresses that are balanced by deep compressive stresses and a superficial deformed surface that is greater for the heat-treated material. In comparison, the PBF-LB components have a higher geometrical accuracy, a relatively smooth topography and a fine microstructure, but with high tensile stresses after printing. Machining of PBF-LB material resulted in higher tool wear for the heat-treated material, increase of 49%, and significantly higher tensile surface stresses followed by shallower compressive stresses below the surface compared to the PBF-EB materials, but with no superficially deformed surface. It is further observed an 87% higher tool wear for PBF-EB in as-built condition and 43% in the heat-treated condition compared to the PBF-LB material. These results show that the selection of cutting tools and cutting settings are critical, which requires the development of suitable machining parameters that are designed for the microstructure of the material.
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| 4. |
- Karlsson, Urban, 1967-
(författare)
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GABA-, glycine- and glutamate-induced currents in rat medial preoptic neurons : functional interactions and modulation by capsaicin
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The medial preoptic nucleus (MPN) of the hypothalamus plays a major role in many functions involved in maintaining bodily homeostasis, such as thermoregulation and osmoregulation, as well as in the control of complex behaviours, e.g. sexual behaviour. A fundamental basis for the control and execution of these functions is the synaptic communication between neurons of the MPN. However, the functional properties of the synapses involved are largely unknown. The present thesis is a study of ligand-gated ion channels involved in the pre- and post-synaptic aspects of neuronal communication in the MPN of rat. The aim was to clarify synaptic properties in the MPN, to identify the major channel types involved and to obtain a better understanding of their functional properties. By fast application of agonists to isolated neurons, it was first demonstrated that all neurons responded to glutamate with currents mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and a majority of neurons also with currents mediated by N-Methyl-D-aspartate (NMDA) receptors. All neurons also responded to γ-aminobutyric acid (GABA) and glycine with currents mediated by GABAA receptors and glycine receptors, respectively. These findings show that fast-acting excitatory and inhibitory amino-acid transmitters are most likely important for communication between hypothalamic neurons. Application of agonists to isolated neurons revealed cross-talk, detected as an apparent cross-desensitization, between the responses to GABA and those to glycine. Parallel analysis of current and conductance, using gramicidin-perforated patches to avoid perturbing intracellular chloride concentration, showed that the cross-talk was not dependent on a direct interaction between the receptors as previously suggested, but was a consequence of the change in the intracellular chloride concentration during receptor activation. Strengthened by a computer model, the analysis also showed that the current decay in the presence of GABA or glycine was mainly due to a change in the chloride driving force and that receptor desensitization played a minor role only. The role of thermo-sensitive transient receptor potential TRPV1 channels in the regulation of glutamate- and GABA-mediated transmission was studied in the slice preparation, where much of the synaptic connections between neurons are preserved. It was shown that application of the TRPV1 agonist capsaicin increased the frequency of excitatory AMPA receptor- mediated as well as inhibitory GABAA receptor-mediated postsynaptic currents. This effect was partly presynaptic and demonstrates that TRP channels play a role in regulating synaptic transmission in the MPN. The results imply that such mechanisms may possibly contribute to the thermoregulation by MPN neurons.
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| 5. |
- Klawonn, Anna, 1985-, et al.
(författare)
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Motivational valence is determined by striatal melanocortin 4 receptors
- 2018
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Ingår i: Journal of Clinical Investigation. - : AMER SOC CLINICAL INVESTIGATION INC. - 0021-9738 .- 1558-8238. ; 128:7, s. 3160-3170
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Tidskriftsartikel (refereegranskat)abstract
- It is critical for survival to assign positive or negative valence to salient stimuli in a correct manner. Accordingly, harmful stimuli and internal states characterized by perturbed homeostasis are accompanied by discomfort, unease, and aversion. Aversive signaling causes extensive suffering during chronic diseases, including inflammatory conditions, cancer, and depression. Here, we investigated the role of melanocortin 4 receptors (MC4Rs) in aversive processing using genetically modified mice and a behavioral test in which mice avoid an environment that they have learned to associate with aversive stimuli. In normal mice, robust aversions were induced by systemic inflammation, nausea, pain, and. opioid receptorinduced dysphoria. In sharp contrast, mice lacking MC4Rs displayed preference or indifference toward the aversive stimuli. The unusual flip from aversion to reward in mice lacking MC4Rs was dopamine dependent and associated with a change from decreased to increased activity of the dopamine system. The responses to aversive stimuli were normalized when MC4Rs were reexpressed on dopamine D1 receptor-expressing cells or in the striatum of mice otherwise lacking MC4Rs. Furthermore, activation of arcuate nucleus proopiomelanocortin neurons projecting to the ventral striatum increased the activity of striatal neurons in an MC4R-dependent manner and elicited aversion. Our findings demonstrate that melanocortin signaling through striatal MC4Rs is critical for assigning negative motivational valence to harmful stimuli.
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| 6. |
- Larsson, Johan, 1990-, et al.
(författare)
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Combining endocannabinoids with retigabine for enhanced M-channel effect and improved KV7 subtype selectivity
- 2020
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Ingår i: The Journal of General Physiology. - : ROCKEFELLER UNIV PRESS. - 0022-1295 .- 1540-7748. ; 152:8
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Tidskriftsartikel (refereegranskat)abstract
- Retigabine is unique among anticonvulsant drugs by targeting the neuronal M-channel, which is composed of KV7.2/KV7.3 and contributes to the negative neuronal resting membrane potential. Unfortunately, retigabine causes adverse effects, which limits its clinical use. Adverse effects may be reduced by developing M-channel activators with improved KV7 subtype selectivity. The aim of this study was to evaluate the prospect of endocannabinoids as M-channel activators, either in isolation or combined with retigabine. Human KV7 channels were expressed in Xenopus laevis oocytes. The effect of extracellular application of compounds with different properties was studied using two-electrode voltage clamp electrophysiology. Site-directed mutagenesis was used to construct channels with mutated residues to aid in the mechanistic understanding of these effects. We find that arachidonoyl-L-serine (ARA-S), a weak endocannabinoid, potently activates the human M-channel expressed in Xenopus oocytes. Importantly, we show that ARA-S activates the M-channel via a different mechanism and displays a different KV7 subtype selectivity compared with retigabine. We demonstrate that coapplication of ARA-S and retigabine at low concentrations retains the effect on the M-channel while limiting effects on other KV7 subtypes. Our findings suggest that improved KV7 subtype selectivity of M-channel activators can be achieved through strategically combining compounds with different subtype selectivity.
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