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| 2. |
- Hostmann, Arwed, et al.
(författare)
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Biphasic onset of splenic apoptosis following hemorrhagic shock: critical implications for Bax, Bcl-2, and Mcl-1 proteins.
- 2008
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Ingår i: Critical care (London, England). - : Springer Science and Business Media LLC. - 1466-609X .- 1364-8535. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The innate immune response to trauma hemorrhage involves inflammatory mediators, thus promoting cellular dysfunction as well as cell death in diverse tissues. These effects ultimately bear the risk of post-traumatic complications such as organ dysfunction, multiple organ failure, or adult respiratory distress syndrome. In this study, a murine model of resuscitated hemorrhagic shock (HS) was used to determine the apoptosis in spleen as a marker of cellular injury and reduced immune functions.Male C57BL-6 mice were subjected to sham operation or resuscitated HS. At t = 0 hours, t = 24 hours, and t = 72 hours, mice were euthanized and the spleens were removed and evaluated for apoptotic changes via DNA fragmentation, caspase activities, and activation of both extrinsic and intrinsic apoptotic pathways. Spleens from untreated mice were used as control samples.HS was associated with distinct lymphocytopenia as early as t = 0 hours after hemorrhage without regaining baseline levels within the consecutive 72 hours when compared with sham and control groups. A rapid activation of splenic apoptosis in HS mice was observed at t = 0 hours and t = 72 hours after hemorrhage and predominantly confirmed by increased DNA fragmentation, elevated caspase-3/7, caspase-8, and caspase-9 activities, and enhanced expression of intrinsic mitochondrial proteins. Accordingly, mitochondrial pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins were inversely expressed within the 72-hour observation period, thereby supporting significant pro-apoptotic changes. Solely at t = 24 hours, expression of the anti-apoptotic Mcl-1 protein shows a significant increase when compared with sham-operated and control animals. Furthermore, expression of extrinsic death receptors were only slightly increased.Our data suggest that HS induces apoptotic changes in spleen through a biphasic caspase-dependent mechanism and imply a detrimental imbalance of pro- and anti-apoptotic mitochondrial proteins Bax, Bcl-2, and Mcl-1, thereby promoting post-traumatic immunosuppression.
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| 3. |
- Seifi, Nima, 1981, et al.
(författare)
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Downlink performance and capacity of distributed antenna systems based on realistic channel model
- 2008
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Ingår i: WSA 2008. International ITG Workshop on Smart Antennas, Damstdart, Germany. ; , s. 249-253
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Konferensbidrag (refereegranskat)abstract
- Recent academic studies of distributed antenna system (DAS) using a frequency-flat fading channel model show that DAS outperforms standard systems, where the base-station (BS) antenna elements are centralized at one location. In this paper the performance of a DAS under time-varying frequency-selective fading based on a realistic channel model is investigated. Specifically, we show that if we shift the hexagonal cellular layout in the conventional system and use sectorized antennas instead of omnidirectional antennas at each BS, the performance in terms of outage probability and outage capacity will improve by a large extent without a need for additional BS towers. The results show that with the same total transmit power and bandwidth DAS can reduce the inter-cell interference (ICI) in a multicell environment and improve the outage capacity especially near the cell boundary.
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| 4. |
- Seifi, Nima, 1981, et al.
(författare)
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Performance Analysis of Distributed versus Co-located MIMO-OFDM
- 2008
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Ingår i: 1st COST2100 Workshop on MIMO and Cooperative Communications, Trondheim, Norway..
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Konferensbidrag (refereegranskat)abstract
- The predicted capacity gain of a traditional colocatedmultiple-input multiple-output (MIMO) system is oftenseverely limited in realistic propagation scenarios, especially inthe presence of interference. One remedy proposed recently, is toemploy a generalized form of MIMO systems called distributedMIMO. In this paper, we compare the downlink performance ofa wireless orthogonal frequency-division multiplexing (OFDM)-based distributed MIMO system to that of a co-located MIMO system using a realistic channel model. In addition, the presence of co-channel interference is considered.We show that distributed MIMO-OFDM outperforms the traditional co-located MIMO-OFDM in terms of outage capacity and eigenvalue distribution owing to the inherent macro-diversity
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| 5. |
- Tschoeke, Sven K, et al.
(författare)
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Apoptosis of human intervertebral discs after trauma compares to degenerated discs involving both receptor-mediated and mitochondrial-dependent pathways.
- 2008
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Ingår i: Journal of orthopaedic research : official publication of the Orthopaedic Research Society. - : Wiley. - 1554-527X .- 0736-0266. ; 26:7, s. 999-1006
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Tidskriftsartikel (refereegranskat)abstract
- Post-traumatic disc degeneration with consecutive loss of reduction and kyphosis remains a debatable issue within both the operative and nonoperative treatment regimen of thoracolumbar spine fractures. Intervertebral disc (IVD) cell apoptosis has been suggested to play a vital role in promoting the degeneration process. To evaluate and compare apoptosis-regulating signaling mechanisms, IVDs were obtained from patients with thoracolumbar spine fractures (n = 21), patients suffering from symptomatic IVD degeneration (n = 6), and from patients undergoing surgical resection of a primary vertebral tumor (n = 3 used as control samples). All tissues were prospectively analyzed in regards to caspase-3/7, -8, and -9 activity, apoptosis-receptor expression levels, and gene expression of the mitochondria-bound apoptosis-regulating proteins Bax and Bcl-2. Morphologic changes characteristic for apoptotic cell death were confirmed by H&E staining. Statistical significance was designated at p < 0.05 using the Student's t-test. Both traumatic and degenerative IVD demonstrated a significant increase of caspase-3/7 activity with evident apoptosis. Although caspase-3/7 activation was significantly greater in degenerated discs, both showed equally significant activation of the initiator caspases 8 and 9. Traumatic IVD alone demonstrated a significant increase of the Fas receptor (FasR), whereas the TNF receptor I (TNFR I) was equally up-regulated in both morbid IVD groups. Only traumatic IVD showed distinct changes in up-regulated TNF expression, in addition to significantly down-regulated antiapoptotic Bcl-2 protein. Our results suggest that post-traumatic disc changes may be promoted and amplified by both the intrinsic mitochondria-mediated and extrinsic receptor-mediated apoptosis signaling pathways, which could be, in part, one possible explanation for developing subsequent disc degeneration.
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| 6. |
- Wolfgang, Andreas, 1977, et al.
(författare)
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Resource allocation and linear precoding for relay assisted multiuser MIMO systems
- 2008
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Ingår i: WSA 2008. International ITG Workshop on Smart Antennas, Damstdart, Germany. ; , s. 162-168
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the use of infrastructure half-duplex amplify-and-forward (AF) relays in the downlink of a multi-user (MU) multiple-input multiple-output (MIMO) system, which uses linear precoding based on block-diagonalization. Owing to the half-duplex mode of the relay, the communication is divided into two time-slots. During the first time-slot the relay nodes are treated as an additional mobile station (MS), while during the second time-slot the base-station (BS) and the relays form a distributed, virtual antenna array. In contrast to many relay applications, the purpose of the proposed scheme is not to increase diversity, but rather to increase the system throughput at the borders of a communication cell or in areas with a high user density. The performance of the proposed architecture is investigated by examining the sum-capacity of the system as well as the distribution of the capacity over the cell-area.
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