| 1. |
- Vizlin-Hodzic, Dzeneta, et al.
(författare)
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Early onset of inflammation during ontogeny of bipolar disorder: the NLRP2 inflammasome gene distinctly differentiates between patients and healthy controls in the transition between iPS cell and neural stem cell stages
- 2017
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Ingår i: Translational Psychiatry. - : Springer Science and Business Media LLC. - 2158-3188. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Neuro-inflammation and neuronal communication are considered as mis-regulated processes in the aetiology and pathology of bipolar disorder (BD). Which and when specific signal pathways become abnormal during the ontogeny of bipolar disorder patients is unknown. To address this question, we applied induced pluripotent stem cell (iPSC) technology followed by cortical neural differentiation on adipocyte-derived cells from BD type I patients (with psychotic episodes in psychiatric history) and healthy volunteers (controls). RNA sequencing in iPSC and cortical neural stem cell (NSC) lines were used to examine alterations between the transcriptomes from BD I and control samples during transition from the pluripotent stage towards the neural developmental stage. At the iPSC stage, the most highly significant differentially expressed gene (DEG) was the NLRP2 inflammasome (P = 2.66 × 10-10). Also among 42 DEGs at the NSC stage, NLRP2 showed the strongest statistical significance (P = 3.07 × 10-19). In addition, we have also identified several cytoskeleton-associated genes as DEGs from the NSC stage, such as TMP2, TAGLN, and ACTA2; the former two genes are recognised for the first time to be associated with BD. Our results also suggest that iPSC-derived BD-cortical NSCs carry several abnormalities in dopamine and GABA receptor canonical pathways, underlining that our in vitro BD model reflects pathology in the CNS. This would indicate that mis-regulated gene expression of inflammatory, neurotransmitter, and cytoskeletal signalling occurs during early foetal brain development of BD I patients.
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| 2. |
- Wallén-Mackenzie, Åsa, et al.
(författare)
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Restricted cortical and amygdaloid removal of vesicular glutamate transporter 2 in preadolescent mice impacts dopaminergic activity and neuronal circuitry of higher brain function.
- 2009
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401 .- 0270-6474. ; 29:7, s. 2238-51
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge in neuroscience is to resolve the connection between gene functionality, neuronal circuits, and behavior. Most, if not all, neuronal circuits of the adult brain contain a glutamatergic component, the nature of which has been difficult to assess because of the vast cellular abundance of glutamate. In this study, we wanted to determine the role of a restricted subpopulation of glutamatergic neurons within the forebrain, the Vglut2-expressing neurons, in neuronal circuitry of higher brain function. Vglut2 expression was selectively deleted in the cortex, hippocampus, and amygdala of preadolescent mice, which resulted in increased locomotor activity, altered social dominance and risk assessment, decreased sensorimotor gating, and impaired long-term spatial memory. Presynaptic VGLUT2-positive terminals were lost in the cortex, striatum, nucleus accumbens, and hippocampus, and a downstream effect on dopamine binding site availability in the striatum was evident. A connection between the induced late-onset, chronic reduction of glutamatergic neurotransmission and dopamine signaling within the circuitry was further substantiated by a partial attenuation of the deficits in sensorimotor gating by the dopamine-stabilizing antipsychotic drug aripiprazole and an increased sensitivity to amphetamine. Somewhat surprisingly, given the restricted expression of Vglut2 in regions responsible for higher brain function, our analyses show that VGLUT2-mediated neurotransmission is required for certain aspects of cognitive, emotional, and social behavior. The present study provides support for the existence of a neurocircuitry that connects changes in VGLUT2-mediated neurotransmission to alterations in the dopaminergic system with schizophrenia-like behavioral deficits as a major outcome.
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| 3. |
- Bergström, Petra, et al.
(författare)
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Amyloid precursor protein expression and processing are differentially regulated during cortical neuron differentiation
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Amyloid precursor protein (APP) and its cleavage product amyloid beta (A beta) have been thoroughly studied in Alzheimer's disease. However, APP also appears to be important for neuronal development. Differentiation of induced pluripotent stem cells (iPSCs) towards cortical neurons enables in vitro mechanistic studies on human neuronal development. Here, we investigated expression and proteolytic processing of APP during differentiation of human iPSCs towards cortical neurons over a 100-day period. APP expression remained stable during neuronal differentiation, whereas APP processing changed. alpha-Cleaved soluble APP (sAPP alpha) was secreted early during differentiation, from neuronal progenitors, while beta-cleaved soluble APP (sAPP beta) was first secreted after deep-layer neurons had formed. Short A beta peptides, including A beta 1-15/16, peaked during the progenitor stage, while processing shifted towards longer peptides, such as A beta 1-40/42, when post-mitotic neurons appeared. This indicates that APP processing is regulated throughout differentiation of cortical neurons and that amyloidogenic APP processing, as reflected by A beta 1-40/42, is associated with mature neuronal phenotypes.
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| 4. |
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| 5. |
- Faijerson, Jonas, 1977, et al.
(författare)
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Adult neural stem/progenitor cells reduce NMDA-induced excitotoxicity via the novel neuroprotective peptide pentinin.
- 2009
-
Ingår i: Journal of neurochemistry. - 1471-4159. ; 109:3, s. 858-66
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Tidskriftsartikel (refereegranskat)abstract
- Although the potential of adult neural stem cells to repair damage via cell replacement has been widely reported, the ability of endogenous stem cells to positively modulate damage is less well studied. We investigated whether medium conditioned by adult hippocampal stem/progenitor cells altered the extent of excitotoxic cell death in hippocampal slice cultures. Conditioned medium significantly reduced cell death following 24 h of exposure to 10 microM NMDA. Neuroprotection was greater in the dentate gyrus, a region neighboring the subgranular zone where stem/progenitor cells reside compared with pyramidal cells of the cornis ammonis. Using mass spectrometric analysis of the conditioned medium, we identified a pentameric peptide fragment that corresponded to residues 26-30 of the insulin B chain which we termed 'pentinin'. The peptide is a putative breakdown product of insulin, a constituent of the culture medium, and may be produced by insulin-degrading enzyme, an enzyme expressed by the stem/progenitor cells. In the presence of 100 pM of synthetic pentinin, the number of mature and immature neurons killed by NMDA-induced toxicity was significantly reduced in the dentate gyrus. These data suggest that progenitors in the subgranular zone may convert exogenous insulin into a peptide capable of protecting neighboring neurons from excitotoxic injury.
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| 6. |
- Geremia-Nievinski, F., et al.
(författare)
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SNR-based GNSS reflectometry for coastal sea-level altimetry: results from the first IAG inter-comparison campaign
- 2020
-
Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 94:8
-
Tidskriftsartikel (refereegranskat)abstract
- Ground-based Global Navigation Satellite System Reflectometry (GNSS-R) is quickly maturing toward the objective of becoming a viable alternative for operational coastal sea-level (SL) altimetry in a geocentric reference frame. SL has immense societal implications related to climate change. Of particular interest is the exploitation of existing coastal GNSS sites for reflectometry by means of signal-to-noise ratio (SNR) observables. We report results from the first inter-comparison campaign on SNR-based GNSS-R. The goal was to cross-validate retrieval solutions from independent research groups under comparable conditions. This action was an initiative of the International Association of Geodesy working group 4.3.9 (2015–2019 term). Data collected at the Onsala Space Observatory for a 1-year period (2015–2016) were compared to a co-located tide gauge (TG). SNR data for the GPS L1-C/A signal were processed by four groups, in Sweden, Luxembourg/Brazil, Germany, and the UK. Semidiurnal tidal constituents showed good agreement between TG and all GNSS-R groups. SL variations at diurnal and longer periods were also well captured by all series. Most GNSS-R solutions exhibited spurious tones at integer fractions of one sidereal day, the satellite revisit time of the particular GNSS constellation employed (GPS). Band-pass filtering between 3 h and 30 h confirmed that the dominant tidal components were well captured by most GNSS-R solutions. Higher-frequency SL variations (periods < 3 h) are poorly represented by GNSS-R as a consequence of its low temporal resolution. The solution with the worst agreement neglects a correction associated with the rate of change in sea level and uses narrower satellite elevation ranges per retrieval. Overall, there was excellent agreement, with correlation coefficients exceeding 0.9 and RMSE smaller than 5 cm.
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| 7. |
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| 8. |
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| 9. |
- Hobiger, Thomas, 1978, et al.
(författare)
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Ground-based GNSS-R solutions by means of software defined radio
- 2016
-
Ingår i: Proceedings of the 2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS 2016). Beijing; China; 10-15 July 2016. - 9781509033324 ; 2016-November, s. Art no 7730472, Pages 5635-5637
-
Konferensbidrag (refereegranskat)abstract
- Usually ground-based GNSS-R installations are either existing geodetic GNSS stations or they are built with dedicated components that enable the deduction and monitoring of physical and geometrical properties of the reflecting area around that particular site. In both cases, hardware components usually enable real-time operation of such instruments. However, as software-defined radio (SDR) technology has advanced in the recent years it is now possible to carry out signal processing in real-time, which makes it an ideal candidate for the realization of a flexible GNSS-R system. It is shown how SDR can help to realize GNSS-R solutions for sea-level monitoring at the Onsala Space Observatory, Sweden. Moreover, such SDR solutions can be mounted on an unmanned aerial vehicle (UAV) in order to collect data from higher altitudes and even provide Delay-Doppler information for extended GNSS-R studies.
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| 10. |
- Hobiger, Thomas, 1978, et al.
(författare)
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Inverse modeling of ground-based GNSS-r - Results and new possibilities
- 2017
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Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS). ; 2017-July, s. 2671-2681
-
Konferensbidrag (refereegranskat)abstract
- Inverse modeling of ground-based GNSS reflections has the potential to improve existing GNSS-R applications and lead to novel concepts for retrieving geophysical parameters around existing or deliberately built GNSS sites. As we will show in this paper, consistent, accurate and precise determination of sea-surface heights can be realized. Moreover, we demonstrate that it is possible to detect sea-ice freeze states at coastal GNSS sites. In addition, it will be shown how the inverse modeling approach can be used for self-calibration of troposphere delays, which would otherwise bias the target parameters and need to be corrected for by external measurements or data-sets.
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| 11. |
- Hobiger, Thomas, 1978, et al.
(författare)
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Software defined radio for ground and airborne GNSS reflectometry
- 2018
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Ingår i: Proceedings of the European Navigation Conference 2018 (ENC 2018) Abstracts and Technical Papers. - 9789188041142 ; , s. 49-50
-
Konferensbidrag (refereegranskat)abstract
- Software defined radio (SDR) appears as a suitable solution for dedicated GNSS reflectometry (GNSS-R) applications. Not only does the flexibility of SDR allow for easy and rapid prototyping, but also do recent technological developments of SDR front-ends support real-time operation of GNSS-R. Our presentation includes a discussion about the technical aspects of SDR for GNSS-R and we show results from a ground-based GNSS-R SDR receiver which was operated continuously over a more than a month at the Onsala Space Observatory. A summary of our current activities in relation to airborne GNSS-R solutions and initial results in the form of Delay-Doppler Maps (DDMs) will conclude the presentation.
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| 12. |
- Izsak, Julia, et al.
(författare)
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TGF-β1 Suppresses Proliferation and Induces Differentiation in Human iPSC Neural in vitro Models
- 2020
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Ingår i: Frontiers in Cell and Developmental Biology. - : Frontiers Media SA. - 2296-634X. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Persistent neural stem cell (NSC) proliferation is, among others, a hallmark of immaturity in human induced pluripotent stem cell (hiPSC)-based neural models. TGF-β1 is known to regulate NSCs in vivo during embryonic development in rodents. Here we examined the role of TGF-β1 as a potential candidate to promote in vitro differentiation of hiPSCs-derived NSCs and maturation of neuronal progenies. We present that TGF-β1 is specifically present in early phases of human fetal brain development. We applied confocal imaging and electrophysiological assessment in hiPSC-NSC and 3D neural in vitro models and demonstrate that TGF-β1 is a signaling protein, which specifically suppresses proliferation, enhances neuronal and glial differentiation, without effecting neuronal maturation. Moreover, we demonstrate that TGF-β1 is equally efficient in enhancing neuronal differentiation of human NSCs as an artificial synthetic small molecule. The presented approach provides a proof-of-concept to replace artificial small molecules with more physiological signaling factors, which paves the way to improve the physiological relevance of human neural developmental in vitro models.
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| 13. |
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| 14. |
- Morud, Julia, 1984, et al.
(författare)
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Progressive modulation of accumbal neurotransmission and anxiety-like behavior following protracted nicotine withdrawal
- 2018
-
Ingår i: Neuropharmacology. - : Elsevier BV. - 0028-3908. ; 128, s. 86-95
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the highly addictive properties of nicotine, a low percentage of users successfully maintain cessation for longer periods of time. This might be linked to neuroadaptations elicited by the drug, and understanding progressive changes in neuronal function might provide critical insight into nicotine addiction. We have previously shown that neurotransmission in the nucleus accumbens (nAc), a key brain region with respect to drug reinforcement and relapse, is suppressed for as long as seven months after a brief period of nicotine treatment. Studies were therefore performed to define the temporal properties of these effects, and to assess behavioral correlates to altered neurotransmission. Ex vivo electrophysiology revealed progressive depression of synaptic efficacy in the nAc of rats previously receiving nicotine. In addition, following three months of nicotine withdrawal, the responses to GABAA receptor modulating drugs were blunted together with downregulation of several GABAA receptor subunits. In correlation to reduced accumbal neurotransmission, a reduced anxiety-like behavior; assessed in the elevated plus-maze and marble burying tests, were identified in animals pre-treated with nicotine. Lastly, to test the causal relationship between suppressed excitability in the nAc and reduced anxiety-like behavior, rats received local administration of diazepam in the nAc while monitoring behavioral effects on the elevated plus-maze. These results show that nicotine produces long-lasting changes in the GABAergic system, which are observed first after extended withdrawal. Our data also suggest that nicotine produces a progressive suppression of accumbal excitability, which could result in behavioral alterations that may have implications for further drug intake. © 2017
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| 15. |
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| 16. |
- Scimemi, Annalisa, et al.
(författare)
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Tonic GABA(A) receptor-mediated currents in human brain.
- 2006
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Ingår i: The European journal of neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 24:4, s. 1157-60
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Tidskriftsartikel (refereegranskat)abstract
- GABA(A) receptors can mediate both phasic (synaptic) and tonic (extrasynaptic) forms of inhibition. It has been proposed that tonic inhibition plays a critical part in controlling neuronal and network excitability. Although tonic GABA(A) receptor-mediated currents have been well characterized in rodents, their existence in human tissue has yet to be demonstrated. Here we show that tonic currents can be recorded from human tissue obtained from patients undergoing temporal lobectomies. Tonic GABA(A) receptor-mediated currents were present in pyramidal cells and interneurons in layer V-VI of temporal neocortex and granule cells in the dentate gyrus. These tonic currents have cell type-specific pharmacologies, opening up the possibility of targeted therapeutics.
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| 17. |
- Strandberg, Joakim, 1991, et al.
(författare)
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Coastal Sea Ice Detection Using Ground-Based GNSS-R
- 2017
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Ingår i: IEEE Geoscience and Remote Sensing Letters. - 1558-0571 .- 1545-598X. ; 14:9, s. 1552-1556
-
Tidskriftsartikel (refereegranskat)abstract
- Determination of sea ice extent is important both for climate modeling and transportation planning. Detection and monitoring of ice are often done by synthetic aperture radar imagery, but mostly without any ground truth. For the latter purpose, robust and continuously operating sensors are required. We demonstrate that signals recorded by ground-based Global Navigation Satellite System (GNSS) receivers can detect coastal ice coverage on nearby water surfaces. Beside a description of the retrieval approach, we discuss why GNSS reflectometry is sensitive to the presence of sea ice. It is shown that during winter seasons with freezing periods, the GNSS-R analysis of data recorded with a coastal GNSS installation clearly shows the occurrence of ice in the bay where this installation is located. Thus, coastal GNSS installations could be promising sources of ground truth for sea ice extent measurements.
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| 18. |
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| 19. |
- Strandberg, Joakim, 1978
(författare)
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Developmental plasticity of the glutamate synapse: Roles of low frequency stimulation, hebbian induction and the NMDA receptor
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The glutamate synapse is by far the most common synapse in the brain and acts via postsynaptic AMPA, NMDA and mGlu receptors. During brain development there is a continuous production of these synapses where those partaking in activity resulting in neuronal activity are subsequently selected to establish an appropriate functional pattern of synaptic connectivity while those that do not are elimimated. Activity dependent synaptic plasticities, such as Hebbian induced long-term potentiation (LTP) and low frequency (1 Hz) induced long-term depression (LTD) have been considered to be of critical importance for this selection. However, in the neonatal brain the glutamate synapse displays a seemingly distinct plasticity in that even very low frequency stimulation (0.05-0.2 Hz) results in depression of the AMPA receptor mediated signaling and hence to possible synaptic elimination. The aim of this thesis was to investigate the relationship and interaction between this very low frequency induced plasticity and the more conventional forms of synaptic plasticity, such as mGlu receptor dependent LTD and NMDA receptor dependent LTP and LTD, using the neonatal rat hippocampal CA3-CA1 synapse as a model synapse. This thesis shows that very low frequency induced depression is related to NMDA receptor dependent LTD. While elicited even during NMDA receptor blockade, this plasticity is facilitated and stabilized by NMDA receptor activity and largely occludes NMDA receptor dependent LTD. Surprisingly, considering their role in conventionally induced LTD, mGlu receptors were not found to participate in either the very low frequency induced depression or in low frequency induced long-lasting depression. A preceding LTP-inducing Hebbian stimulation was found to only partially stabilize against the very low frequency induced depression, and possibly also only in a temporary manner. In conclusion; during brain development glutamate activated AMPA receptors are very easily lost upon activation rendering these synapses AMPA silent, and Hebbian activity will only temporarily rescue them from AMPA silence. Thus, synapses in the developing brain will maintain their AMPA signaling only by more or less continuous participation in cooperative neuronal activity, synaptic activity outside this context leading to AMPA silencing and possible elimination.
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| 20. |
- Strandberg, Joakim, 1991, et al.
(författare)
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Improving GNSS-R sea level determination through inverse modeling of SNR data
- 2016
-
Ingår i: Radio Science. - 0048-6604 .- 1944-799X. ; 51:8, s. 1286-1296
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new method for retrieving sea surface heights from Global Navigation Satellite Systems reflectometry (GNSS-R) data by inverse modeling of SNR observations from a single geodetic receiver. The method relies on a B-spline representation of the temporal sea level variations in order to account for its continuity. The corresponding B-spline coefficients are determined through a nonlinear least squares fit to the SNR data, and a consistent choice of model parameters enables the combination of multiple GNSS in a single inversion process. This leads to a clear increase in precision of the sea level retrievals which can be attributed to a better spatial and temporal sampling of the reflecting surface. Tests with data from two different coastal GNSS sites and comparison with colocated tide gauges show a significant increase in precision when compared to previously used methods, reaching standard deviations of 1.4 cm at Onsala, Sweden, and 3.1 cm at Spring Bay, Tasmania.
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| 21. |
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| 22. |
- Strandberg, Joakim, 1991, et al.
(författare)
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Inverse modelling of GNSS multipath for sea level measurements - initial results
- 2016
-
Ingår i: Proceedings of the International Geoscience and Remote Sensing Symposium (IGARSS) Volume 2016-November, 1 November 2016, Article number 7729479, Pages 1867-1869 36th IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2016; Beijing; China; 10 - 15 July 2016. - 9781509033324 ; 2016-November, s. 1867-1869
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Konferensbidrag (refereegranskat)abstract
- We present a new method to retrieve sea level from GNSS SNRdata that relies upon inverse modelling of the detrended SNR. This method can simultaneously use data from both GPS and GLONASS, and both L1 and L2 frequencies, to improve thesolution with respect to prior studies. Results from the GNSS-R installation at Onsala Space Observatory are presented and the retrieved sea level heights are compared with a co-located pressure mareograph. The method is found to give an RMS error of 1.8 cm. The results are also compared against previous implementations of GNSS tide gauges and found to have lower RMS than both the earlier SNR algorithm and also the dual receiver, phase delay method.
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| 23. |
- Strandberg, Joakim, 1978, et al.
(författare)
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Ketogenic diet does not disturb neurogenesis in the dentate gyrus in rats
- 2008
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Ingår i: Neuroreport. - 0959-4965. ; 19:12, s. 1235-1237
-
Tidskriftsartikel (refereegranskat)abstract
- The ketogenic diet, a high-fat diet, is a therapeutic alternative in the treatment of refractory epilepsy, especially in children. However, there are concerns that a high-fat diet may influence the normal development of the central nervous system and cognition. In this study we investigated the influence of ketogenic diet on adult neurogenesis in the dentate gyrus. Rats were provided with either a high-fat diet (80% fat) or a standard rat diet (5% fat) ad libitum for 4 weeks. In both female and male rats, the amounts of bromodeoxyuridine immunoreactive cells in the dentate gyrus were the same in the different groups. Our results suggest that the ketogenic diet does not disturb the neurogenesis in the rat dentate gyrus.
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| 24. |
- Strandberg, Joakim, 1978, et al.
(författare)
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Modulation of low-frequency-induced synaptic depression in the developing CA3-CA1 hippocampal synapses by NMDA and metabotropic glutamate receptor activation.
- 2009
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 101:5, s. 2252-62
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Tidskriftsartikel (refereegranskat)abstract
- Brief test-pulse stimulation (0.2-0.05 Hz) of naïve (previously nonstimulated) developing hippocampal CA3-CA1 synapses leads to a substantial synaptic depression, explained by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) silencing. Using field recordings in hippocampal slices from P8 to P12 rats, we examined this depression of naïve synapses using more prolonged test-pulse stimulation as well as low-frequency (1 Hz) stimulation (LFS). We found that 900 stimuli produced depression during stimulation to approximately 40% of the naïve level independent of whether test-pulse stimulation or LFS was used. This result was also observed during combined blockade of N-methyl-d-aspartate/metabotropic glutamate receptors (NMDAR/mGluRs) although the depression was smaller (to approximately 55% of naïve level). Using separate blockade of either NMDARs or mGluRs, we found that this impairment of the depression resulted from the NMDAR, and not from the mGluR, blockade. In fact, during NMDAR blockade alone, depression was smaller even than that observed during combined blockade. We also found that mGluR blockade alone facilitated the LFS-induced depression. In conclusion, test-pulse stimulation produced as much depression as LFS when applied to naïve synapses even when allowing for NMDAR and mGluR activation. Our results seem in line with the notion that NMDARs and mGluRs may exert a bidirectional control on AMPA receptor recruitment to synapses.
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| 25. |
- Strandberg, Joakim, 1991, et al.
(författare)
-
Real-time sea-level monitoring using Kalman filtering of GNSS-R data
- 2019
-
Ingår i: GPS Solutions. - : Springer Science and Business Media LLC. - 1080-5370 .- 1521-1886. ; 23:3
-
Tidskriftsartikel (refereegranskat)abstract
- Current GNSS-R (GNSS reflectometry) techniques for sea surface measurements require data collection over longer periods, limiting their usability for real-time applications. In this work, we present a new, alternative GNSS-R approach based on the unscented Kalman filter and the so-called inverse modeling approach. The new method makes use of a mathematical description that relates SNR (signal-to-noise ratio) variations to multipath effects and uses a B-spline formalism to obtain time series of reflector height. The presented algorithm can provide results in real time with a precision that is significantly better than spectral inversion methods and almost comparable to results from inverse modeling in post-processing mode. To verify the performance, the method has been tested at station GTGU at the Onsala Space Observatory, Sweden, and at the station SPBY in Spring Bay, Australia. The RMS (root mean square) error with respect to nearby tide gauge data was found to be 2.0 cm at GTGU and 4.8 cm at SPBY when evaluating the output corresponding to real-time analysis. The method can also be applied in post-processing, resulting in RMS errors of 1.5 cm and 3.3 cm for GTGU and SPBY, respectively. Finally, based on SNR data from GTGU, it is also shown that the Kalman filter approach is able to detect the presence of sea ice with a higher temporal resolution than the previous methods and traditional remote sensing techniques which monitor ice in coastal regions.
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| 26. |
- Strandberg, Joakim, 1978, et al.
(författare)
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The endogenous peptide antisecretory factor promotes tonic GABAergic signaling in CA1 stratum radiatum interneurons
- 2014
-
Ingår i: Frontiers in Cellular Neuroscience. - : Frontiers Media SA. - 1662-5102. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Tonic GABAergic inhibition regulates neuronal excitability and has been implicated to be involved in both neurological and psychiatric diseases. We have previously shown that the endogenous peptide antisecretory factor (AF) decreases phasic GABAergic inhibition onto pyramidal CA1 neurons. In the present study, using whole-cell patch-clamp recordings, we investigated the mechanisms behind this disinhibition of CA1 pyramidal neurons by AF We found that application of AF to acute rat hippocampal slices resulted in a reduction of the frequency, but not of the amplitude, of spontaneous inhibitory postsynaptic currents (sIPSCs) in CA1 pyramidal neurons. Miniature inhibitory postsynaptic currents (mIPSCs), recorded in the presence of tetrodotoxin (TTX), were however not affected by AF, neither in CA1 pyramidal cells, nor in stratum radiatum interneurons. Instead, AF caused an increase of the tonic GABA(A) current in stratum radiaturn intemeurons, leaving the tonic GABAergic transmission in CA1 pyramidal cells unaffected. These results show that the endogenous peptide AF enhances tonic, but not phasic, GABAergic signaling in CA1 stratum radiatum interneurons, without affecting tonic GABAergic signaling in CA1 pyramidal neurons. We suggest that this increased tonic GABAergic signaling in GABAergic interneurons could be a mechanism for the AF mediated disinhibition of pyramidal neurons.
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| 27. |
- Strandberg, Joakim, 1991, et al.
(författare)
-
Towards Real-Time GNSS Reflectometry Using Kalman Filtering
- 2018
-
Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS). ; , s. 2043-2046
-
Konferensbidrag (refereegranskat)abstract
- GNSS-R has emerged as an attractive way of using a signal of opportunity that is collected by GNSS stations all around the world to measure a wide variety of properties of the surroundings of the stations. Current state-of-the-art algorithms based on the inversion of SNR values rely on off-line processing, causing a significant delay before results are available. We present a new approach for ground-based GNSS-R that uses Kalman filtering with a realistic physical model that allows close to real-time inversion of SNR oscillations into sea-surface height with high precision. From the analysis of test measurements from the GTGU GNSS installation at the Onsala Space Observatory, Sweden, we conclude that the new method provides better estimates than single-arc retrievals from spectral analysis and that the final precision is close to that of post-processing inversion algorithms.
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| 28. |
- Wasling, Pontus, 1970, et al.
(författare)
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AMPA receptor activation causes silencing of AMPA receptor-mediated synaptic transmission in the developing hippocampus
- 2012
-
Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 7:4
-
Tidskriftsartikel (refereegranskat)abstract
- Agonist-induced internalization of transmembrane receptors is a widespread biological phenomenon that also may serve as a mechanism for synaptic plasticity. Here we show that the agonist AMPA causes a depression of AMPA receptor (AMPAR) signaling at glutamate synapses in the CA1 region of the hippocampus in slices from developing, but not from mature, rats. This developmentally restricted agonist-induced synaptic depression is expressed as a total loss of AMPAR signaling, without affecting NMDA receptor (NMDAR) signaling, in a large proportion of the developing synapses, thus creating AMPAR silent synapses. The AMPA-induced AMPAR silencing is induced independently of activation of mGluRs and NMDARs, and it mimics and occludes stimulus-induced depression, suggesting that this latter form of synaptic plasticity is expressed as agonist-induced removal of AMPARs. Induction of long-term potentiation (LTP) rendered the developing synapses resistant to the AMPA-induced depression, indicating that LTP contributes to the maturation-related increased stability of these synapses. Our study shows that agonist binding to AMPARs is a sufficient triggering stimulus for the creation of AMPAR silent synapses at developing glutamate synapses.
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| 29. |
- Wintzell, Lisa, 1992, et al.
(författare)
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Upregulation of the Endogenous Peptide Antisecretory Factor Enhances Hippocampal Long-term Potentiation and Promotes Learning in Wistar Rats.
- 2022
-
Ingår i: Neuroscience. - : Elsevier BV. - 0306-4522. ; 490, s. 120-130
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Tidskriftsartikel (refereegranskat)abstract
- Antisecretory Factor (AF) is an endogenous peptide known for its powerful antisecretory and anti-inflammatory properties. We have previously shown that AF also acts as a neuromodulator of GABAergic synaptic transmission in rat hippocampus in a way that results in disinhibition of CA1 pyramidal neurons. Disinhibition is expected to facilitate the induction of long-term potentiation (LTP), and LTP is known to play a crucial role in learning and memory acquisition. In the present study we investigated the effect of AF on LTP in CA3-CA1 synapses in rat hippocampus. In addition, endogenous AF plasma activity was upregulated by feeding the rats with specially processed cereals (SPC) and spatial learning and memory was studied in the Morris Water Maze (MWM). We found that LTP was significantly enhanced in the presence of AF, both when added exogenously in vitro as well as when upregulated endogenously by SPC-feeding. In the presence of the GABAA-receptor antagonist picrotoxin (PTX) there was however no significant enhancement of LTP. Moreover, rats fed with SPC demonstrated enhanced spatial learning and short-term memory, compared with control animals. These results show that the disinhibition of GABAergic transmission in the hippocampus by the endogenous peptide AF enhances LTP as well as spatial learning and memory.
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