| 1. |
- Biglarnia, Alireza, et al.
(author)
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The free radical scavenger S-PBN significantly prolongs DSG-mediated graft survival in experimental xenotransplantation
- 2012
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In: Xenotransplantation. - : Wiley. - 0908-665X .- 1399-3089. ; 19:3, s. 166-176
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Journal article (peer-reviewed)abstract
- Background: Nitrones such as 2-sulfo-phenyl-N-tert-butyl nitrone (S-PBN) are known to trap and stabilize free radicals and to reduce inflammation. Recently, S-PBN was shown to reduce infiltration of T lymphocytes and the expression of adhesion molecules on the endothelium in experimental traumatic brain injury. We hypothesized that S-PBN could reduce infiltration of T lymphocytes during cell-mediated xenograft rejection and thereby increase graft survival. The concordant mouse-to-rat heart transplantation model was used to test the hypothesis. In this model, grafts undergo acute humoral xenograft rejection (AHXR) almost invariably on day 3 and succumb to cell-mediated rejection on approximately day 8 if AHXR is inhibited by treatment with 15-deoxyspergualin (DSG). Material and methods: Hearts from Naval Medical Research Institute (NMRI) mice were transplanted to the neck vessels of Lewis rats. Recipients were treated with S-PBN (n = 9), DSG (n = 9), S-PBN and DSG in combination (n = 10) or left untreated (n = 9) for survival studies. S-PBN was given daily intraperitoneally at a dose of 150 mg/kg body weight (BW) on day -1 to 30, and DSG was given daily intraperitoneally at a dose of 10 mg/kg BW on day -1 to 4 and 5 mg/kg BW on day 5 to 21. Nine additional recipients were given S-PBN only on days -1 and 0 in combination with continuous DSG treatment. Grafts were monitored until they stopped beating. Additional recipients were treated with S-PBN (n = 5), DSG (n = 5), S-PBN and DSG in combination (n = 6) or left untreated (n = 5) for morphological, immunohistochemical and flow cytometry analyses on days 2 and 6 after transplantation. Results: S-PBN treatment in combination with DSG resulted in increased median graft survival compared to DSG treatment alone (14 vs. 7 days; P = 0.019). Lower number of T lymphocytes on day 6 (P = 0.019) was observed by ex vivo propagation and flow cytometry when combining S-PBN with DSG, whereas immunohistochemical analyses demonstrated a significant reduction in the number of infiltrated CD4+, but not TCR+, cells. S-PBN treatment alone had no impact on graft survival compared to untreated rats (3 vs. 3 days). No differences were seen in ICAM-1 and VCAM-1 expression or in morphology between the groups. Conclusion: The combination of S-PBN and DSG treatment increases xenograft survival. The main effect of S-PBN appears to be in direct connection with the transplantation. Because of its low toxicity, S-PBN could become useful in combination with other immunosuppressants to reduce cell-mediated xenograft rejection.
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| 2. |
- Carlsson, Fredrik, 1974-
(author)
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Wood Fungi and Forest Fire
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Forest fires have been the major stand-replacing/modifying disturbance in boreal forests. To adapt to fire disturbance, different strategies have evolved. This thesis focuses on wood fungi, and the effect of forest fire on this organism group. In many ways it is a study on adaptation to forest fire, in concurrence with adaptation to dry open habitats. In Paper I we study increased heat resistance in mycelia from species prevalent in fire prone environments. Fungi were cultivated on fresh wood and exposed to different temperatures. Species prevalent in fire affected habitats had a much higher survival rate over all combinations of time and temperature compared to species associated with other environments. Based on this results the competitiveness was tested after temperature stress (paper II), three fire associated species, were tested against three non fire associated species. All fire associated species had a clear advantage after heat treatment, conquering a larger volume of wood than its competitor. In paper III we studied the effect of heat shock on decomposition rate, 18 species was tested. Species were cultivated and monitored for CO2 accumulation for 8 weeks and then heat shocked. All species including non fire associated species seemed to up-regulate decomposition after heat shock, this response was more pronounced in fire associated species. To look at the possible effect of forest fire on population structure (Paper IV), we developed 29 SNP/INDELs for Phlebiopsis. gigantea. We amplified the marker containing fragments in 132 individuals of P. gigantea in 6 populations, 3 which were found in areas affected by forest fire and 3 in unaffected areas. We found no genetic structure in accordance to forest fire. However we detected geographic structure, which stands in contrast to earlier studies. This might be due to the method, using SNP´s and number of individuals in the study. Finally we collected cross-sections of decayed logs to evaluate the number of fungal species domains that are likely to be hit when drilling a saw-dust sample in a log. We used these estimates to simulate how many species that will be found by a certain number of samples. We found that in 99% of the
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| 3. |
- Clausen, Fredrik, 1973-, et al.
(author)
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Acute Inflammatory Biomarker Responses to Diffuse Traumatic Brain Injury in the Rat Monitored by a Novel Microdialysis Technique
- 2019
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In: Journal of Neurotrauma. - : Mary Ann Liebert Inc. - 0897-7151 .- 1557-9042. ; 36:2, s. 201-211
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Journal article (peer-reviewed)abstract
- Neuroinflammation is a major contributor to the progressive brain injury process induced by traumatic brain injury (TBI), and may play an important role in the pathophysiology of axonal injury. The immediate neuroinflammatory cascade cannot be characterized in the human setting. Therefore, we used the midline fluid percussion injury model of diffuse TBI in rats and a novel microdialysis (MD) method providing stable diffusion-driven biomarker sampling. Immediately post-injury, bilateral amphiphilic tri-block polymer coated MD probes (100 kDa cut off membrane) were inserted and perfused with Dextran 500 kDa-supplemented artificial cerebrospinal fluid (CSF) to optimize protein capture. Six hourly samples were analyzed for 27 inflammatory biomarkers (9 chemokines, 13 cytokines, and 5 growth factors) using a commercial multiplex biomarker kit. TBI (n = 6) resulted in a significant increase compared with sham-injured controls (n = 6) for five chemokines (eotaxin/CCL11, fractalkine/CX3CL1, LIX/CXCL5, monocyte chemoattractant protein [MCP]1α/CCL2, macrophage inflammatory protein [MIP]1α /CCL3), 10 cytokines (interleukin [IL]-1α, IL-1β, IL-4, IL-6, IL-10, IL-13, IL-17α, IL-18, interferon [IFN]-γ, tumor necrosis factor [TNF]-α), and four growth factors (epidermal growth factor [EGF], granulocyte-macrophage colony-stimulating factor [GM-CSF], leptin, vascular endothelial growth factor [VEGF]). Therefore, diffuse TBI was associated with an increased level of 18 of the 27 inflammatory biomarkers at one through six time points, during the observation period whereas the remaining 9 biomarkers were unaltered. The study shows that diffuse TBI induces an acute increase in a number of inflammatory biomarkers. The novel MD technique provides stable MD sampling suitable for further studies on the early neuroinflammatory cascade in TBI.
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| 4. |
- Clausen, Fredrik
(author)
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Animal models of traumatic brain injury
- 2016
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In: Experimental Neurosurgery in Animal Models. - New York : Springer-Verlag New York. - 9781493937288 - 9781493937301 ; , s. 1-12
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Book chapter (peer-reviewed)abstract
- Animal models of traumatic brain injury (TBI) have been the core of the research on the molecular, cellular, and functional effects of the disease. To be able to simulate the heterogeneous aspects of TBI several models have been designed. This chapter aims to describe the three most commonly used experimental models of TBI in rodents.
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| 5. |
- Clausen, Fredrik, et al.
(author)
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Cerebral glucose metabolism after traumatic brain injury in the rat studied by C-13-glucose and microdialysis
- 2011
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In: Acta Neurochirurgica. - : Springer Science and Business Media LLC. - 0001-6268 .- 0942-0940. ; 153:3, s. 653-658
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Journal article (peer-reviewed)abstract
- Following traumatic brain injury (TBI), a disturbed cerebral glucose metabolism contributes to secondary brain damage. To study local cerebral glucose metabolism after TBI, we delivered C-13-labeled glucose into brain tissue by microdialysis (MD). MD probes were inserted bilaterally into the parietal cortex of rat brain, one probe in the shear stress zone of the injury and the other at the corresponding contralateral coordinates. A moderately severe controlled cortical contusion was used to model TBI. Dialysate concentrations of glucose, pyruvate, lactate, and glycerol were measured, and following derivatization, C-13 enrichments of the compounds were determined by gas chromatography-mass spectrometry. We found that C-13-labeled glucose was rapidly converted into C-13-lactate and C-13-glycerol. In the hours following TBI, concentrations and C-13 enrichments of lactate and glycerol increased. The findings confirm the occurrence of anaerobic local glucose metabolism early after TBI. Only a small fraction of the glycerol was newly synthesized, suggesting that the hypothesis that most of the released glycerol after TBI comes from degradation of membrane phospholipids still holds. We conclude that the combination of microdialysis and stable isotope technique is a useful tool for investigating local glucose metabolism following brain injury.
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| 6. |
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| 7. |
- Clausen, Fredrik, et al.
(author)
-
Combination of growth factor treatment and scaffold deposition following traumatic brain injury has only a temporary effect on regeneration
- 2014
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In: Brain Research. - : Elsevier BV. - 0006-8993 .- 1872-6240. ; 1588, s. 37-48
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Journal article (peer-reviewed)abstract
- The recovery after traumatic brain injury (TBI) is hampered by the poor regenerative capacity of the brain. Today there is no treatment available that effectively restores lost brain tissue, but much research is focused on the stimulation of endogenous neural stem cells to viably and functionally repopulate the injured parenchyma. It is crucial that the therapies have a proven long-term effect on both regeneration and functional recovery to be clinically interesting. Here we have studied the induction of stem cell activation in rats at three weeks and six weeks after inducing TBI using controlled cortical impact model at a severe setting. We combined intracerebroventricular growth factor and scaffold treatment in order to accomplish an optimal effect on the stem cell regeneration. Immediately after TBI epidermal growth factor infusion with osmotic minipumps was started and continued for seven days. The pumps were removed and an extracellular matrix scaffold containing vascular endothelial growth factor was deposited into the cortical cavity. Three weeks after injury there was a positive effect of the treatment with a significant increase in neuronal and astrocytic regeneration. However, after six weeks there was no difference in the number of newly generated neurons and astrocytes in treated or untreated rats. Evaluation of tissue loss and spatial learning in the Morris water maze corroborated that the treatment had no effect at the later time point. Our results highlight the importance of long-term studies to ensure that a promising effect on tissue regeneration and functional outcome is not only temporary.
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| 8. |
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| 9. |
- Clausen, Fredrik, 1973-
(author)
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Delayed Cell Death after Traumatic Brain Injury : Role of Reactive Oxygen Species
- 2004
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Doctoral thesis (other academic/artistic)abstract
- Traumatic brain injury (TBI) is a leading cause of death and disability TBI survivors often suffer from severe disturbances of cognition, memory and emotions. Improving the treatment is of great importance, but as of yet no specific neuroprotective treatment has been found. After TBI there are changes in ion homeostasis and protein regulation, causing generation of reactive oxygen species (ROS). Overproduction of ROS can lead to damage cellmembranes, proteins and DNA and secondary cell death. In the present thesis experimental TBI in rats were used to study the effects of the ROS scavengers α-phenyl-N-tert-butyl-nitrone (PBN) and 2-sulfophenyl-N-tert-butyl-nitrone (S-PBN) on morphology, function, intracellular signalling and apoptosis. Posttreatment with PBN and S-PBN resulted in attenuation of tissue loss after TBI and S-PBN improved cognitive function evaluated in the Morris water maze (MWM). Pretreatment with PBN protected hippocampal morphology, which correlated to better MWM-performance after TBI.To detect ROS-generation in vivo, a method using 4-hydroxybenzoic acid (4-HBA) microdialysis in the injured cortex was refined. 4-HBA reacts with ROS to form 3,4-DHBA, which can be quantified using HPLC, revealing that ROS-formation was increased for 90 minutes after TBI. It was possible to attenuate the formation significantly with PBN and S-PBN treatment. The activation of extracellular signal-regulated kinase (ERK) is generally considered beneficial for cell survival. However, persistent ERK activation was found in the injured cortex after TBI, coinciding with apoptosis-like cell death 24 h after injury. Pretreatment with the MEK-inhibitor U0126 and S-PBN significantly decreased ERK activation and reduced apoptosis-like cell death. Posttreatment with U0126 or S-PBN showed robust protection of cortical tissue.To conclude: ROS-mediated mechanisms play an important role in secondary cell death following TBI. The observed effects of ROS in intracellular signalling may be important for defining new targets for neuroprotective intervention.
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| 10. |
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