| 1. |
- Fagerlund, Michael
(författare)
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Progenitor cells in the brainstem and filum terminale
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neurogenesis prevails in the adult mammalian CNS. New neurons are constitutively formed invivo in the subventricular zone (SVZ) of the lateral ventricle wall and in the subgranular zone of the dentate gyrus. However, other regions along the entire neuroaxis have been found to harbor cells with the ability to form neurospheres, self-renew and differentiate into neurons, oligodendrocytes and astrocytes. Adult rodents were subjected to axotomies of the hypoglossal nerve (n.XII) followed by assessment of the endogenous neural progenitor cell (NPC) response and the fate of grafted adult eGFP SVZ NPCs in the brainstem. Sox2 expressing endogenous NPCs were abundant in the ependymal region of the central canal and 4th ventricle and activated after n.XII avulsion injury, which induced massive loss of motor neurons, but not after transection where the cell loss was minimal. Activation included NPC proliferation and subsequent migration to the hypoglossal nucleus (nucl.XII) where they expressed astrocytic markers. However, neurogenesis failed and no neuroprotective effect on motor neurons was observed. Therefore, a transplantation model was developed; SVZ NPCs were harvested from inbred eGFP transgenic animals and cells grafted to the nucl.XII of their wt siblings after n.XII injuries. The SVZ NPCs from transgenic animals where characterized in-vitro prior to grafting, and found to have same NPC characteristics as cells from wt animals. Upon transplantation after avulsion injury NPCs survived, differentiated into neurons, oligodendrocytes and astrocytes and integrated with the host circuitry. Grafted NPCs expressed VEGF and GPx1 that after avulsion exerted a neuroprotective effect on motor neurons. Moreover, we suggest that GPx1 expression contributed to the survival of transplanted cells in the nucl.XII post avulsion. This was in contrast to the results on grafting after transection since NPCs did not survive to the same extent and only differentiated into cells with astrocytic phenotype. Also, some of the cells continued to express Sox2. The cells did not integrate and no neuroprotective effects were found. Differences in activation after the two types of axotomies were correlated to levels of motor neuron death in the nucl.XII, and hence differences in the microenvironment with regards also to levels of free radicals and inflammatory compounds. The beneficial effects after grafting post avulsion initiated the development of an autologous transplantation model where the distribution of NPCs in the filum terminale was investigated. Sox2 and Mushasi-1 expressing cells in the human filum terminale were found, i.e. cells expressing NPC markers. The cells were abundant and when isolated and propagated in-vitro they formed neurospheres, proliferated and differentiated into neurons and glia. Clonal expansion indicated a relatively strong self-renewal capacity. The cells responded to the addition of PDGF-BB with an increase in neuronal cell numbers. In summary, the findings suggest a repair strategy based on transplantation of adult NPCs in neural repair after severe motor nerve injuries. The filum terminale is a potential source of NPCs in future autologous cell therapies, even in human.
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| 2. |
- Fagerlund, Michael, et al.
(författare)
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Proliferation, migration and differentiation of ependymal region neural progenitor cells in the brainstem after hypoglossal nerve avulsion
- 2011
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Ingår i: Restorative Neurology and Neuroscience. - 1878-3627. ; 29:1, s. 47-59
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Cells in the ependymal region in the adult central nervous system (CNS) have been found to possess neural progenitor cell (NPC) like features including capacity for generating new neurons and glia in response to injury and inflammatory disease. Whether these cells are activated after a peripheral nerve injury has not previously been extensively evaluated. Methods: We investigate the possible activation and effect of NPCs in the ependymal region in the immediate vicinity to the hypoglossal nucleus in the brainstem using two models of injuries, hypoglossal nerve transection and nerve avulsion after which the proliferation, migration and differentiation of ependymal regional NPCs were evaluated. Results: We showed that: (i) immunoreactivity for Sox2 was detected in cells in the ependymal region of the brainstem and that BrdU/Sox2-positive cells were observed after avulsion, but not after transection injury; (ii) avulsion induces re-expression of nestin in the ependymal layer as well as induced NPC migration from the ependymal layer; (iii) the chemokine SDF-1 alpha (a marker for migrating cells) was upregulated ipsilateral to the nerve injury; (iiii) the NPCs migrating differentiated only into GFAP-positive astrocytes in the hypoglossal nucleus. Conclusion: These results suggest that nerve avulsion injury induces in parallel with the retrograde "axon reaction" activation of endogenous NPCs in the ependymal region and further suggest that these cells could be involved in repair and neuroregeneration after injury within the brainstem.
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| 3. |
- Fridh, Katja, et al.
(författare)
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Effect of water storage time on frost resistance of concrete
- 1999
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Ingår i: Durability of Building Materials and Components 8 : Proceedings. - 0660177374 ; 1: Service life and durability of materials and components, s. 212-221
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In high performance concrete (HPC) with low water-cement ratio, cement reaction will cause substantial drying expressed in terms of relative humidity (RH) of the pore water. This phenomenon is called self-desiccation. The RH-values as low as 85% have been measured in dense concretes that have been stored for more than 18 months in water. This means that there is almost no freezable water in the concrete until very low temperatures are reached. It also means that freeze-thaw tests made with young concrete might give results on the unsafe side. In this report some results from a bigger study of the effect of longterm water storage on the frost resistance of HPC are presented. The results show that previously self-desiccated concrete absorbs water when it is stored for a long time in water. Dilation tests during freezing indicate that concrete that was frost resistant when tested during the first months might become non-frost resistant after a long period of water storage. This must be considered in the design of freeze-thaw test methods.
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| 4. |
- Jensdottir, Margret, et al.
(författare)
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Learning Curve Analysis and Adverse Events After Implementation of Neurosurgical Laser Ablation Treatment: A Population-Based Single-Institution Consecutive Series.
- 2023
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Ingår i: Neurosurgery clinics of North America. - : Elsevier BV. - 1558-1349 .- 1042-3680. ; 34:2, s. 259-267
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Tidskriftsartikel (refereegranskat)abstract
- We conducted a retrospective review of the first 30 patients treated with stereotactic laser ablation (SLA) at our institution since the introduction of the technique in September 2019. We aimed to analyze our initial results and potential learning curve by investigating precision and lesion coverage and assessing the frequency and nature of adverse events according to the Landriel-Ibanez classification for neurosurgical complications.Indications were de novo gliomas (23%), recurrent gliomas (57%), and epileptogenic foci (20%). There was a trend toward improvement of lesion coverage and target deviation, and a statistically significant improvement in entry point deviation, over time. Four patients (13.3%) experienced a new neurological deficit, where three patients had transient and one patient had permanent deficits, respectively. Our results show a learning curve on precision measures over the first 30 cases. Based on our results the technique can safely be implemented at centers with experience in stereotaxy.
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| 5. |
- Kaijser, Magnus, et al.
(författare)
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Two years of neurosurgical intraoperative MRI in Sweden : evaluation of use and costs
- 2024
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Ingår i: Acta Neurochirurgica. - : Springer. - 0001-6268 .- 0942-0940. ; 166:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The current shortage of radiology staff in healthcare provides a challenge for departments all over the world. This leads to more evaluation of how the radiology resources are used and a demand to use them in the most efficient way. Intraoperative MRI is one of many recent advancements in radiological practice. If radiology staff is performing intraoperative MRI at the operation ward, they may be impeded from performing other examinations at the radiology department, creating costs in terms of exams not being performed. Since this is a kind of cost whose importance is likely to increase, we have studied the practice of intraoperative MRI in Sweden.METHODS: The study includes data from the first four hospitals in Sweden that installed MRI scanners adjacent to the operating theaters. In addition, we included data from Karolinska University Hospital in Solna where intraoperative MRI is carried out at the radiology department.RESULTS: Scanners that were moved into the operation theater and doing no or few other scans were used 11-12% of the days. Stationary scanners adjacent to the operation room were used 35-41% of the days. For scanners situated at the radiology department doing intraoperative scans interspersed among all other scans, the proportion was 92%.CONCLUSION: Our study suggests that performing exams at the radiology department rather than at several locations throughout the hospital may be an efficient approach to tackle the simultaneous trends of increasing demands for imaging and increasing staff shortages at radiology departments.
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| 6. |
- Niemi, Auli, et al.
(författare)
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Heletz experimental site overview, characterization and data analysis for CO2 injection and geological storage
- 2016
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 48, s. 3-23
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides an overview of the site characterization work at the Heletz site, in preparation to scientifically motivated CO2 injection experiments. The outcomes are geological and hydrogeological models with associated medium properties and baseline conditions. The work has consisted on first re-analyzing the existing data base from similar to 40 wells from the previous oil exploration studies, based on which a 3-dimensional structural model was constructed along with first estimates of the properties. The CO2 injection site is located on the saline edges of the Heletz depleted oil field. Two new deep (> 1600 m) wells were drilled within the injection site and from these wells a detailed characterization program was carried out, including coring, core analyses, fluid sampling, geophysical logging, seismic survey, in situ hydraulic testing and measurement of the baseline pressure and temperature. The results are presented and discussed in terms of characteristics of the reservoir and cap-rock, the mineralogy, water composition and other baseline conditions, porosity, permeability, capillary pressure and relative permeability. Special emphasis is given to petrophysical properties of the reservoir and the seal, such as comparing the estimates determined by different methods, looking at their geostatistical distributions as well as changes in them when exposed to CO2.
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| 7. |
- Niemi, Auli, et al.
(författare)
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Small-Scale CO2 Injection into a Deep Geological Formation at Heletz, Israel
- 2012
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 23, s. 504-511
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the experimental plans and designs as well as examples of predictive modeling of a pilot-scale CO2 injection experiment at the Heletz site (Israel). The overall objective of the experiment is to find optimal ways to characterize CO2 -relevant in-situ medium properties, including field-scale residual and dissolution trapping, to explore ways of characterizing heterogeneity through joint analysis of different types of data, and to detect leakage. The experiment will involve two wells, an injection well and a monitoring well. Prior to the actual CO2 injection, hydraulic, thermal and tracer tests will be carried out for standard site characterization. The actual CO2 injection experiments will include (i) a single well injection-withdrawal experiment, with the main objective to estimate in-situ residual trapping and (ii) a two-well injection-withdrawal test with injection of CO2 in a dipole mode (injection of CO2 in one well with simultaneous withdrawal of water in the monitoring well), with the objective to understand the CO2 transport in heterogeneous geology as well as the associated dissolution and residual trapping. Tracers will be introduced in both experiments to further aid in detecting the development of the phase composition during CO2 transport. Geophysical monitoring will also be implemented. By means of modeling, different experimental sequences and injection/withdrawal patterns have been analyzed, as have parameter uncertainties. The objectives have been to (i) evaluate key aspects of the experimental design, (ii) to identify key parameters affecting the fate of the CO2 and (iii) to evaluate the relationships between measurable quantities and parameters of interest.
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