| 1. |
- Dahl, Jonas, et al.
(författare)
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Against the flow: chemical detection of downstream predators in running waters
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1403, s. 1339-1344
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Tidskriftsartikel (refereegranskat)abstract
- In running waters, chemical cues have generally been assumed to always come from upstream locations. Here, we present ¢eld and laboratory evidence that Gammarus pulex can use chemical cues from down- stream predators to adaptively adjust drifting behaviour. In the ¢eld, signi¢cantly fewer Gammarus migrated into stream enclosures where brown trout (Salmo trutta) were present than into control enclo- sures. In a subsequent laboratory experiment, Gammarus actively avoided live trout and trout chemicals placed downstream in an arti¢cial stream, whereas no e¡ects were found in response to control or visual cues.We suggest that the mechanism explaining the ability of Gammarus to detect downstream predators is use of back£ows, which locally transport ¢sh chemicals against the main £ow. Such back£ows are both created by the Gammarus itself and by surrounding substrate heterogeneity. These results profoundly a¡ect the way in which we view the chemical environment of running waters and have important implications for empirical and theoretical work evaluating predator e¡ects in running waters, as they demonstrate that prey immigration rates can depend on downstream predator densities.
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| 2. |
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| 3. |
- Holmström, Anna, et al.
(författare)
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YopK of Yersinia pseudotuberculosis controls translocation of Yop effectors across the eukaryotic cell membrane
- 1997
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 24:1, s. 73-91
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Tidskriftsartikel (refereegranskat)abstract
- Introduction of anti-host factors into eukaryotic cells by extracellular bacteria is a strategy evolved by several Gram-negative pathogens. In these pathogens, the transport of virulence proteins across the bacterial membranes is governed by closely related type III secretion systems. For pathogenic Yersinia, the protein transport across the eukaryotic cell membrane occurs by a polarized mechanism requiring two secreted proteins, YopB and YopD. YopB was recently shown to induce the formation of a pore in the eukaryotic cell membrane, and through this pore, translocation of Yop effectors is believed to occur (Håkansson et al., 1996b). We have previously shown that YopK of Yersinia pseudotuberculosis is required for the development of a systemic infection in mice. Here, we have analysed the role of YopK in the virulence process in more detail. A yopK-mutant strain was found to induce a more rapid YopE-mediated cytotoxic response in HeLa cells as well as in MDCK-1 cells compared to the wild-type strain. We found that this was the result of a cell-contact-dependent increase in translocation of YopE into HeLa cells. In contrast, overexpression of YopK resulted in impaired translocation. In addition, we found that YopK also influenced the YopB-dependent lytic effect on sheep erythrocytes as well as on HeLa cells. A yopK-mutant strain showed a higher lytic activity and the induced pore was larger compared to the corresponding wild-type strain, whereas a strain overexpressing YopK reduced the lytic activity and the apparent pore size was smaller. The secreted YopK protein was found not to be translocated but, similar to YopB, localized to cell-associated bacteria during infection of HeLa cells. Based on these results, we propose a model where YopK controls the translocation of Yop effectors into eukaryotic cells.
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| 4. |
- Pahlm, Ulrika, et al.
(författare)
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Comparison of teaching the basic electrocardiographic concept of frontal plane QRS axis using the classical versus the orderly electrocardiogram limb lead displays
- 1997
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Ingår i: American Heart Journal. - 1097-6744. ; 134:6, s. 1014-1018
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Tidskriftsartikel (refereegranskat)abstract
- This study compares the effectiveness of teaching the calculation of frontal plane QRS axis with the use of the classical versus the orderly electrocardiographic limb lead display. Eighty-three students from two environments were randomized into two groups and were taught to determine frontal plane axis with one of the methods. The accuracy and time to determine the axis were tested on 10 electrocardiograms. In the United States the group using the classical display achieved 4.2 (+/-2.7) correct answers, whereas those using the orderly method achieved 6.8 (+/-3.0) (p = 0.0006). The classical group used 9.2 (+/-2.8) minutes to complete the test, whereas the orderly group needed 7.2 (+/-2.0) minutes (p = 0.015). The results achieved in Sweden were similar. The use of the orderly electrocardiographic limb lead display results in greater diagnostic accuracy in less time than the classical display when determining the frontal plane QRS axis.
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| 5. |
- Pettersson, Jonas, et al.
(författare)
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Modulation of Virulence Factor Expression by Pathogen Target Cell Contact
- 1996
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 273:5279, s. 1231-1233
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Tidskriftsartikel (refereegranskat)abstract
- Upon contact with the eukaryotic cell, Yersinia pseudotuberculosis increased the rate of transcription of virulence genes (yop), as determined by in situ monitoring of light emission from individual bacteria expressing luciferase under the control of the yopE promoter. The microbe-host interaction triggered export of LcrQ, a negative regulator of Yop expression, via the Yop-type III secretion system. The intracellular concentration of LcrQ was thereby lowered, resulting in increased expression of Yops. These results suggest a key role for the type III secretion system of pathogenic bacteria to coordinate secretion with expression of virulence factors after physical contact with the target cell.
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| 6. |
- Pettersson, Jonas, et al.
(författare)
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The V-antigen of Yersinia is surface exposed before target cell contact and involved in virulence protein translocation :
- 1999
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 32:5, s. 961-976
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Tidskriftsartikel (refereegranskat)abstract
- Type III-mediated translocation of Yop effectors is an essential virulence mechanism of pathogenic Yersinia. LcrV is the only protein secreted by the type III secretion system that induces protective immunity. LcrV also plays a significant role in the regulation of Yop expression and secretion. The role of LcrV in the virulence process has, however, remained elusive on account of its pleiotropic effects. Here, we show that anti-LcrV antibodies can block the delivery of Yop effectors into the target cell cytosol. This argues strongly for a critical role of LcrV in the Yop translocation process. Additional evidence supporting this role was obtained by genetic analysis. LcrV was found to be present on the bacterial surface before the establishment of bacteria target cell contact. These findings suggest that LcrV serves an important role in the initiation of the translocation process and provides one possible explanation for the mechanism of LcrV-induced protective immunity.
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| 7. |
- Pettersson, Thomas, 1966, et al.
(författare)
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Modelling of flow pattern and particle removal in an open stormwater detention pond
- 1998
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Ingår i: In: Proc. HydraStorm’98, Adelaide, Australia, 27-30 September 1998. ; , s. 63-68
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Konferensbidrag (refereegranskat)abstract
- In Sweden open stormwater detention ponds are more often used to reduce stormwater pollution through sedimentation. The pollution reduction occurs both during storm events and in between events. Design methods are often simplified and based on detention time only. However, not only the pond volume but also the geometry and thus the flow pattern are of concern when designing open detention ponds. In the city of Göteborg a 6200 m2 open stormwater detention pond was investigated with respect to massflows of pollutants and flow pattern. The observed data has been used to verify a FEM model established for the pond. Both 3-D and 2-D flow simulations have been performed at inflows starting at 20 l/s up to a maximum of 800 l/s. The simulations show that both 2-D and 3-D calculations give reasonable agreement with observed data. The 3-D calculations are however more accurate taking the bottom shape into account. Conclusions drawn from this study is that simulations of pond flow pattern are essential in designing pond geometry, and inlet and outlet locations.
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| 8. |
- Pettersson, Thomas, 1966, et al.
(författare)
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Pollutant removal efficiency in two stormwater ponds in Sweden
- 1999
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Ingår i: In: Proc. 8th International Conference on Urban Storm Drainage, Sydney, Australia, 30 August-3 September 1999. ; 2, s. 866-873
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Konferensbidrag (refereegranskat)abstract
- Open stormwater ponds have been frequently addressed as a method for treatment of stormwater since measurements show a considerable pollutant removal effect. Pollutant removal efficiency in two stormwater ponds in Sweden is studied where field measurements of inflow and outflow pollutant loads for several successive storm events are described. Cumulative effects of inflow and outflow pollutant discharges are studied and for the outflow a strong correlation to constant outflow pollutant discharges appears that indicate an independence of inflow pollutant load for the two ponds. Hereby, it becomes possible to extrapolate the annual loads from the ponds to the receiving waters of studied pollutants. The specific pond area (m2/ha) is 20 times larger in one of the ponds, which affect the pollutant removal efficiencies. A comparison between specific pond area and pollutant removal efficiency gave that the removal efficiency increases up to a certain level of surface/impervious area, 250 m2/ha, and above this level the increase is not as significant as below. Another factor that has an impact on the removal efficiency is the pond geometry.
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| 9. |
- Tilly, Nina, et al.
(författare)
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In vitro determination of toxicity, binding, retention, subcellular distribution and biological efficacy of the boron neutron capture agentDAC-1
- 1996
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 38:1, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- In boron neutron capture therapy (BNCT), 10B is delivered selectively to the tumour cells and the nuclide then forms high-LET radiation (4He2+ and 7Li3+) upon neutron capture. Today much research is focused on development of a variety of boron compounds aimed for BNCT. The compounds must be thoroughly analysed in preclinical tests regarding basic characteristics such as binding and subcellular distribution to enable accurate estimations of dose-modifying factors. DAC-1,2-[2-(3-amino-propyl)-1,2-dicarba-closo-dodecaboran (12)-1-yl-methoxy]- 1,3-propanediol was synthesized at our laboratories and the human colon carcinoma cells LS-174T were used as an in vitro model. The boron compound showed a remarkable intracellular accumulation, 20-100 times higher than the boron content in the culture medium, in cultured cells and was not removed by extensive washes. Approximately half of the boron taken up also remained within the cells for at least 4 days. The DAC-1 compound alone was not toxic at boron concentrations below 2.5 micrograms B/g. The intracellular distribution of the boron compound was investigated by subcellular fractionation experiments and low pH treatments. It is possible that DAC-1 binds to some intracellular molecules or to membranes connected with organelles in the cytoplasm or even to the inside of the outer cell membrane. Another possibility is that the compound, due to the somewhat lipophilic properties, is embedded in the membranes. Thermal neutron irradiations were carried out at the Brookhaven Medical Research Reactor (BMRR). At a survival level of 0.1, DAC-1 + thermal neutrons were about 10.5 times more effective in cell inactivation than the thermal neutrons alone. Monte Carlo calculations gave a mean value of the 10B-dependent specific energy, the dose, of 0.22 Gy. The total physical dose during irradiation of DAC-1-containing cells with a neutron fluence of 0.18 x 10(12) n/cm2 was 0.39 Gy. The dose-modifying factor, at survival level 0.1, when comparing irradiation with thermal neutrons with and without DAC-1 was 3.4, while the dose-modifying factor when comparing neutron irradiations of cells with DAC-1 and irradiation of the cells with 60Co-gamma was 7.3. The results are encouraging and in vivo tests of tissue distributions and tumour uptake should now be carried out.
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| 10. |
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