| 1. |
- Borowiec, Jan, et al.
(författare)
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Heparin-coated cardiopulmonary bypass circuits and 25% reduction of heparin dose in coronary artery surgery : a clinical study
- 1992
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Ingår i: Upsala Journal of Medical Sciences. - 0300-9734 .- 2000-1967. ; 97:1, s. 55-66
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Tidskriftsartikel (refereegranskat)abstract
- Cardiopulmonary bypass with systemic heparinization causes trauma to blood cells and coagulation defects. Artificial surfaces could be coated by end-linkage binding of heparin (Carmeda Bioactive Surface, CBAS). Use of such surfaces during cardiopulmonary bypass in animals resulted in less postoperative blood loss and better preservation of blood cells. In this study heparin-coated circuits were employed during coronary artery grafting in 7 patients (Group HC). Concomitantly, the heparin dose was reduced by 25% and an activated clotting time (ACT) of 300 sec was accepted. Additional 7 patients were operated with standard circuits (Group C), requiring ACT above 400 sec with normal doses of heparin. There were no thromboembolic complications in Group HC. The postoperative bleeding was generally low and without significant intergroup differences. Coagulation parameters displayed significantly lower ACT and anti-Factor Xa during bypass in Group HC. A tendency towards less blood cell trauma was observed with heparin-coated circuits. The protamine dose could be reduced by 50%, which significantly reduced the protamine/heparin quotient. This study indicates that routine cardiopulmonary bypass could be performed safely with heparin-coated circuits and reduced intravenous doses of heparin and protamine. It is suggested that the use of heparin-coated circuits may lead to less blood cell trauma.
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| 2. |
- Berg, Roger, et al.
(författare)
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Time-resolved tranillumination imaging
- 1993
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Ingår i: Medical Optical Tomography: Functional Imaging and Monitoring. ; , s. 397-424
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Bokkapitel (refereegranskat)
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| 3. |
- Björklund, Stefan, et al.
(författare)
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An S-phase specific release from a transcriptional block regulates the expression of mouse ribonucleotide reductase R2 subunit
- 1992
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Ingår i: EMBO Journal. - 0261-4189 .- 1460-2075. ; 11:13, s. 4953-4959
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Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductase (RR) activity in mammalian cells is closely linked to DNA synthesis. The RR enzyme is composed of two non-identical subunits, proteins R1 and R2. Both proteins are required for holoenzyme activity, which is regulated by S-phase specific de novo synthesis and breakdown of the R2 subunit. In quiescent cells stimulated to proliferate and in elutriated cell populations enriched in the various cell cycle phases the R2 protein levels are correlated to R2 mRNA levels that are low in G0/G1-phase cells but increase dramatically at the G1/S border. Using an R2 promoter-luciferase reporter gene construct we demonstrate an unexpected early activation of the R2 promoter as cells pass from quiescence to proliferation. However, due to a transcriptional block, this promoter activation only results in very short R2 transcripts until cells enter the S-phase, when full-length R2 transcripts start to appear. The position for the transcriptional block was localized to a nucleotide sequence approximately 87 bp downstream from the first exon/intron boundary by S1 nuclease mapping of R2 transcripts from modified in vitro nuclear run-on experiments. These results identify blocking of transcription as a mechanism to control cell cycle regulated gene expression.
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| 4. |
- Borowiec, Jan, et al.
(författare)
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Decreased blood loss after cardiopulmonary bypass using heparin-coated circuit and 50% reduction of heparin dose
- 1992
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Ingår i: Scandinavian journal of thoracic and cardiovascular surgery. - 0036-5580. ; 26:3, s. 177-185
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Tidskriftsartikel (refereegranskat)abstract
- In a randomized, double-blind study of patients undergoing elective coronary artery grafting, the effect of heparin-coated circuit combined with 50% reduction of systemic heparin bolus was investigated. Ten patients comprised group HC (heparin-coated) and ten group C (controls). The mean total doses of heparin were 172 IU/kg in group HC and 416 IU/kg in group C and the respective protamine doses were 0.96 and 3.96 mg/kg (both p < 0.001). Activated clotting times during cardiopulmonary bypass were significantly shorter in group HC, and both intra- and postoperative bleeding was significantly less than in group C (7.7 vs. 11.7 ml/kg, p = 0.036, and 6.9 vs. 9.7 ml/kg, p = 0.004). Hemoglobin loss via the drains was 22.5 g in group HC and 43.7 g in group C (p < 0.005). Hemolysis at the end of bypass was significantly greater in group C. Apart from one perioperative myocardial infarction in group HC the postoperative course was uneventful. Use of a heparin-coated circuit is concluded to permit complication-free reduction of heparin and protamine doses and to decrease both intra- and postoperative bleeding, which may favorably influence the outcome of coronary artery grafting.
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| 5. |
- Borowiec, Jan, et al.
(författare)
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Heparin-coated circuits reduce activation of granulocytes during cardiopulmonary bypass : A clinical study
- 1992
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Ingår i: Journal of Thoracic and Cardiovascular Surgery. - 0022-5223 .- 1097-685X. ; 104:3, s. 642-647
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Tidskriftsartikel (refereegranskat)abstract
- Activated granulocytes release highly active enzymes such as myeloperoxidase and lactoferrin, which can be involved in tissue destruction mediated by oxygen free radicals. Cardiopulmonary bypass has been reported to activate granulocytes. Bypass circuits coated with heparin have been shown to reduce release of granulocyte factors in experimental studies. In the present study, heparin-coated circuits were compared with noncoated circuits. In seven patients undergoing coronary bypass, heparin-coated circuits were used (group HC), and seven served as control patients (group C). In group HC the heparin dose was reduced to 75% (225 IU/kg). Group C had the standard dose of 300 IU/kg. No preoperative differences in myeloperoxidase and lactoferrin were observed between the groups. At the end of bypass in both groups, there was a significant increase of these enzymes (p less than 0.001) followed by a later decrease. In group HC, however, the release of myeloperoxidase was significantly lower than in group C (215 +/- 24 versus 573 +/- 133 micrograms/L, mean +/- standard error of the mean). The release of lactoferrin was significantly lower in group HC than in group C both at the end of cardiopulmonary bypass (659 +/- 79 versus 1448 +/- 121 micrograms/L) and 3 hours after bypass (224 +/- 37 versus 536 +/- 82 micrograms/L). Granulocytes as well as total number of leukocytes continued to increase until 1 hour after bypass (p less than 0.001) and then manifested a slow decrease. It was concluded that the use of heparin-coated circuits reduced the release of granulocyte factors because of lower activation of leukocytes.
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| 6. |
- Brönmark, Christer, et al.
(författare)
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Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes : an alternative mechanism
- 1992
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Ingår i: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 243/244:1, s. 293-301
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Tidskriftsartikel (refereegranskat)abstract
- The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.
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| 7. |
- Graneli, Wilhelm, et al.
(författare)
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Rhizome dynamics and resource storage in Phragmites australis
- 1992
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Ingår i: Wetlands Ecology and Management. - Dordrecht, Netherlands : Springer Netherlands. - 0923-4861 .- 1572-9834. ; 1:4, s. 239-247
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands. Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (< 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m-2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June. Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (> 1000 g m-2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites. The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that "reloading" of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management. Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves. © 1992 SPB Academic Publishing.
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| 8. |
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| 9. |
- Kröll, Stefan, et al.
(författare)
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Influence of excited state Pr3+ on the relaxation of the Pr3+-YAlO3 3H4-1D2 transition
- 1991
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Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 44:1, s. 30-34
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Tidskriftsartikel (refereegranskat)abstract
- Two-pulse photon-echo measurements on the 0.1 at. % Pr3+:YAlO3 H-3(4)-D-1(2) transition suggest that the relaxation time depends on the density of excited states created by the excitation pulses. The dependence of the relaxation time on the intensity of each excitation pulse shows that our results are inconsistent with instantaneous spectral diffusion, a model often invoked in this type of experiment, where excited states created by the second pulse chiefly influence the relaxation time. A homogeneous linewidth contribution, noted in previous work as being of unknown origin, is eliminated at low excitation fluences.
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| 10. |
- Kröll, Stefan, et al.
(författare)
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Intensity dependent photon echo relaxation in rare earth doped crystals
- 1990
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Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 41:16, s. 11568-11571
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Tidskriftsartikel (refereegranskat)abstract
- Photon-echo-relaxation measurements made on the 3H4-3P0 transition of 0.01 at. % Pr3+:YAG (where YAG represents yttrium aluminum garnet), 3H4-1D2 transition in 0.1 at. % Pr3+:YAlO3, and 7F0-5D0 transition in 0.25 at. % Eu3+:YAlO3 show that the photon-echo relaxation rate increases when the intensities of the excitation pulses are increased. Although a part of the relaxation-rate increase in Pr3+:YAG may be attributed to an instantaneous spectral diffusion (ISD) in which the presence of excited neighboring Pr3+ ions change the local field and the absorption frequency of the rare-earth ions, our data deviate significantly from the ISD-model predictions. An additional intensity-dependent relaxation mechanism is required to explain the results.
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| 11. |
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| 12. |
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| 13. |
- Ström, Erik G, et al.
(författare)
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Propagation Delay Estimation of DS-CDMA Signals in a Fading Environment
- 1994
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Ingår i: IEEE Global Telecommunications Conference, Communication Theory Mini-Conference (1994 IEEE GLOBECOM). ; , s. 85-89
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Konferensbidrag (refereegranskat)abstract
- The problem considered is of estimating propagation delays of the transmitted signals in a direct sequence code division multiple access (DS-CDMA) system operating over fading channels. Special attention is given to the near-far problem. An estimator based on subspace identification techniques is proposed. The Cramer-Rao bound is presented and used as a benchmark when evaluating the performance of the estimator.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Weisner, Stefan E.B. 1954-, et al.
(författare)
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Influence of germination time on juvenile performance of Phragmites australis on temporarily exposed bottoms – implications for the colonization of lake beds
- 1993
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Ingår i: Aquatic Botany. - Amsterdam, Netherlands : Elsevier. - 0304-3770 .- 1879-1522. ; 45:2-3, s. 107-118
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Tidskriftsartikel (refereegranskat)abstract
- Three cohorts of seedlings of Phragmites australis (Cav.) Trin ex Steud., germinated in May, June and July, were allowed to grow in shallow water (depth 5 cm or less) in southern Sweden. In the autumn, size parameters were measured on the plants. In the second year, the water level was raised to 0.8 m and emergence of shoots, plant survival and size parameters were recorded. The mean plant weight by the end of the first year differed markedly between cohorts. Rhizome biomass showed a relationship of 700:70:1 between the May, June and July cohorts. In the second year, rate of emergence above the water surface, and maximum height of plants that did not reach the water surface, was positively related to the size (mass) the plants had achieved after the first year. Only plants that emerged above the water surface survived the second summer, resulting in survival rates for the May, June and July cohorts of 90%, 68% and 0%, respectively. The rhizome weight of the smallest survivors had decreased after the second summer compared with values after the first summer. Hence, they were not capable of ‘reloading’ their rhizomes during the second year. In a temperate climate, the size of juvenile plants after the first year, which is strongly dependent on early germination on exposed bottoms (i.e. bottoms without standing water), determines their water depth tolerance during the second year. The timing and duration of exposure, as well as the subsequent depth of re-flooding, are all of fundamental importance for successful ‘lakeward’ seedling expansion of P. australis.
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| 19. |
- Weisner, Stefan E.B. 1954-, et al.
(författare)
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Influence of Macrophytes on Nitrate Removal in Wetlands
- 1994
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Ingår i: Ambio. - Dordrecht : Springer Netherlands. - 0044-7447 .- 1654-7209. ; 23:6, s. 363-366
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Tidskriftsartikel (refereegranskat)abstract
- Efficient nitrate removal from wetlands depends on denitrification. Macrophytes support denitrification by supplying organic carbon. Organic carbon available to denitrifying bacteria is released from plant litter and from living macrophytes. Macrophytes offer attachment surfaces for epiphytes, also producing organic matter, and for denitrifying bacteria. Emergent macrophytes are generally more productive than submerged macrophytes, but submerged macrophytes have more epiphytes and offer a larger attachment area in the water column for denitrifying bacteria. Emergent and submerged vegetation differ in their seasonal patterns of release of organic carbon. We conclude that a mixture of emergent and submerged macrophytes may be beneficial for nitrogen removal in wetlands with a surface-flow of nitrate-rich water. The influence of vegetation on wetland hydraulics must also be considered. A wetland design with deeper parts favoring submerged macrophytes alternating, along the water flow, with shallower parts covered by emergent macrophytes, may promote denitrification processes and distribution of water flow.
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| 20. |
- Weisner, Stefan E.B. 1954-, et al.
(författare)
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Influence of submergence on growth of seedlings of Scirpus lacustris and Phragmites australis
- 1993
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Ingår i: Freshwater Biology. - Chichester, United Kingdom : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 29:3, s. 371-375
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Tidskriftsartikel (refereegranskat)abstract
- 1. Seeds of Scirpus lacustris and Phragmites australis were germinated in early June, and twenty-four seedlings of each species were subsequently exposed to submerged conditions (eight seedlings at each of the water depths 0.2, 0.4 and 0.8 m), in outdoor 500-l tanks in southern Sweden. Weight and shoot length of the plants were measured in September. 2. The Phragmites seedlings did not show any significant growth when submerged. The Scirpus seedlings, however, developed submerged leaves and exhibited considerable submerged growth. One Scirpus plant, in shallow water (0.2 m), had developed an aerial shoot by September. Shoot length of the remaining (submerged) Scirpus plants was positively related to plant weight within water depth treatments, and was higher, in relation to plant weight, in deeper water. Mean weight in September of the submerged Scirpus plants decreased with increased water depth. 3. In south Swedish lakes with a lowered water table, Scirpus often occupies large areas on the lakeward side of the reed belt, which is generally dominated by Phragmites. The differences between the two species, in performance of submerged seedlings, suggest that this zonation may be created through successful submerged seedling establishment of Scirpus on the lakeward side of Phragmites.
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| 21. |
- Weisner, Stefan E.B. 1954-
(författare)
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Long-term competitive displacement of Typha latifolia by Typha angustifolia in a eutrophic lake
- 1993
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Ingår i: Oecologia. - Heidelberg, Germany : Springer Berlin/Heidelberg. - 0029-8549 .- 1432-1939. ; 94:3, s. 451-456
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Tidskriftsartikel (refereegranskat)abstract
- This study follows the outcome of long-term competition between a broad-leaved and a narrow-leaved Typha species, T. latifolia and T. angustifolia respectively, in a eutrophic lake. The lake was bordered by a zone of T. latifolia, at one location interrupted by a T. angustifolia stand. Distributional changes of the T. angustifolia stand and the adjacent zone of T. latifolia were measured on aerial photographs (less-than-or-equal-to 13 years) and along ground-level transects (6 years). A second stand of T. angustifolia was established with transplanted ramets within a formerly homogeneous zone of T. latifolia, and displacement between the two species was measured along ground-level transects after 6 years. Differences between the species in shoot performance were investigated to help explain the relative competitive abilities of the two Typha species. T. angustifolia expanded at the expense of T. latifolia at all water depths where both species occurred, except in very shallow water. Expansion rates suggest that T. angustifolia was not affected by the presence of T. latifolia in water depths exceeding 0.25 m. The Typha species were significantly negatively associated according to rank correlations of shoot densities, and changes of shoot densities, along the transects. These results suggest that T. angustifolia is competitively superior to T. latifolia, contradicting earlier studies. The higher competitive ability of T. angustifolia is consistent with its having taller shoots and a higher standing crop in early summer. Further, shoot height distributions indicated a closer integration of shoot emergence during spring in T. angustifolia than in T. latifolia. A high leaf area/shoot weight ratio suggest that T. latifolia may instead be relatively fast-growing, achieving competitive superiority over narrower-leaved Typha species during a transient period after simultaneous seedling establishment.
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| 22. |
- Weisner, Stefan E.B. 1954-
(författare)
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Within-lake patterns in depth penetration of emergent vegetation
- 1991
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Ingår i: Freshwater Biology. - Chichester, United Kingdom : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 26:1, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- 1. Within-lake relations of wave exposure (WE), and substratum softness (cone penetration depth; CPD) and organic content (loss on ignition; LOI), to water depth penetration of the emergent vegetation (DPE) was investigated in seven eutrophic lakes in southern Sweden, ranging in area from 1 to 46 km2. 2. There was a positive relationship between WE and DPE within lakes. This relationship, however, only occurred for sites with relatively soft substrata, for which CPD and LOI were negatively related to both WE and DPE. 3. Analysis of aerial photographs revealed that expansion of the emergent vegetation towards open water, or recession from open water, was not related to wave exposure or water depth, except in one lake where expansion mainly occurred at high exposures. 4. For relatively static vegetation on soft substrata, regressions with CPD0.5 explained 62-88% of the within-lake variation of DPE. These regressions did not differ among lakes. Expanding and recessing vegetation were significantly dislocated towards shallower and deeper water, respectively, than predicted from the regression models for static vegetation. 5. Phragmites australis dominated at the lakeward edge of the emergent vegetation, followed in frequency by Typha angustifolia. More broad-leaved species were generally restricted to shallow water and very soft substrata. 6. The results suggest that changes in the distribution of emergent vegetation in moderately wave exposed eutrophic lakes can be predicted largely from substratum character and water depth.
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| 23. |
- Willers, Stefan, et al.
(författare)
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Passive smoking and childhood asthma. Urinary cotinine levels in children with asthma and in referents
- 1991
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Ingår i: Allergy. - 1398-9995. ; 46:5, s. 330-334
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Tidskriftsartikel (refereegranskat)abstract
- Passive exposure to tobacco smoke was assessed in children with asthma (age 3-15) and in referents. There was statistically significantly (P less than 0.0005) higher excretion of the nicotine metabolite, cotinine, in the urine of 49 children with asthma (geometric mean 10 ng/ml) compared with 77 referents (4.8 ng/ml). Maternal smoking was statistically significantly more prevalent among the asthmatics than among the referents (relative risk = RR = 2.6, 95% C1 = 1.2-5.3). In conclusion, the exposure to environmental tobacco smoke in asthmatic children was higher than among healthy children, indicating that passive smoking may be a predisposing and/or aggravating factor for childhood asthma.
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| 24. |
- Xu, E. Y, et al.
(författare)
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Nanosecond image processing using stimulated photon echoes
- 1990
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Ingår i: Optics Letters. - 0146-9592. ; 15:10, s. 562-564
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Tidskriftsartikel (refereegranskat)abstract
- Processing of two-dimensional images on a nanosecond time scale is demonstrated using the stimulated photon echoes in a rare-earth-doped crystal (0.1 at. \% Pr3$+$:LaF3). Two spatially encoded laser pulses (pictures) resonant with the 3P0-3H4 transition of Pr3$+$ were stored by focusing the image pulses sequentially into the Pr3$+$:LaF3 crystal. The stored information is retrieved and processed by a third read pulse, generating the echo that is the spatial convolution or correlation of the input images. Application of this scheme to high-speed pattern recognition is discussed.
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