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| 5. |
- Dahlmann, J, et al.
(författare)
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Different methods for toxin analysis in the cyanobacterium Nodularia spumigena (Cyanophyceae)
- 2001
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Ingår i: Toxicon. - 0041-0101. ; 39:8, s. 1183-1190
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The brackish water cyanobacterium Nodularia spumigena produce the hepatotoxic cyclic pentapeptide nodularin. Intoxications for both human as well as animal may arise when water reservoirs are contaminated with potentially toxic Nodularia species. Here, results of three independent methods for the determination of nodularin in different strains of N. spumigena are presented. The results obtained with a protein phosphatase assay and a HPLC/UV/MS method are compared with the results obtained with a bioluminescence assay, which is successfully introduced here for nodularin determination. Statistical evaluation of the three applied methods revealed a good comparability towards the detected toxin content. The methods were evaluated taking into consideration the parameters: handling, efficiency, sensitivity and selectivity. The detection limit in the protein phosphatase assay is highest (0.05 ng nodularin) and lowest (250 ng nodularin) in the bioluminescence assay— it was determined with 5 ng (MS) and 25 ng (UV) for the HPLC/UV/MS methods. The different selectivities and sensitivities are critically discussed and an analytical pathway for the determination of the biotoxin nodularin from Nodularia samples is proposed.
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| 10. |
- Gisselson, L Å, et al.
(författare)
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Dinophysis blooms in the deep euphotic zone of the Baltic Sea: do they grow in the dark?
- 2002
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Ingår i: Harmful Algae. - 1878-1470. ; 1:4, s. 401-418
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Tidskriftsartikel (refereegranskat)abstract
- In situ growth rates of the toxin-producing dinoflagellate Dinophysis norvegica collected in the central Baltic Sea were estimated during the summers of 1998 and 1999. Flow cytometric measurements of the DNA cell cycle of D. norvegica yielded specific growth rates (μ) ranging between 0.1 and 0.4 per day, with the highest growth rates in stratified populations situated at 15–20 m depth. Carbon uptake rates, measured using 14C incubations followed by single-cell isolation, at irradiances corresponding to depths of maximum cell abundance were sufficient to sustain growth rates of 0.1–0.2 per day. The reason for D. norvegica accumulation in the thermocline, commonly at 15–20 m depth, is thus enigmatic. Comparison of depth distributions of cells with nutrient profiles suggests that one reason could be to sequester nutrients. Measurements of single-cell nutrient status of D. norvegica, using nuclear microanalysis, revealed severe deficiency of both nitrogen and phosphorus as compared to the Redfield ratio. It is also possible that suitable prey or substrate for mixotrophic feeding is accumulating in the thermocline. The fraction of cells containing digestive vacuoles ranged from 2 to 22% in the studied populations. Infection by the parasitic dinoflagellate Amoebophrya sp. was observed in D. norvegica in all samples analysed. The frequency of infected cells ranged from 1 to 3% of the population as diel averages, ranging from 0.2 to 6% between individual samples. No temporal trends in infection frequency were detected. Estimated loss rates based on observed infection frequencies were 0.5–2% of the D. norvegica population daily, suggesting that these parasites were not a major loss factor for D. norvegica during the periods of study.
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| 12. |
- Graneli, Annette, 1973, et al.
(författare)
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Long-distance lateral diffusion of human Rad51 on double-stranded DNA
- 2006
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Ingår i: Proc Natl Acad Sci U S A. ; 103:5, s. 1221-6
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Tidskriftsartikel (refereegranskat)abstract
- Rad51 is the primary eukaryotic recombinase responsible for initiating DNA strand exchange during homologous recombination. Although the subject of intense study for over a decade, many molecular details of the reactions promoted by Rad51 and related recombinases remain unknown. Using total internal reflection fluorescence microscopy, we directly visualized the behavior of individual Rad51 complexes on double-stranded DNA (dsDNA) molecules suspended in an extended configuration above a lipid bilayer. Here we show that complexes of Rad51 can bind to and slide freely along the helical axis of dsDNA. Sliding is bidirectional, does not require ATP hydrolysis, and displays properties consistent with a 1D random walk driven solely by thermal diffusion. The proteins move freely on the DNA for long periods of time; however, sliding terminates and the proteins become immobile upon encountering the free end of a linear dsDNA molecule. This study provides previously uncharacterized insights into the behaviors of human Rad51, which may apply to other members of the RecA-like family of recombinases.
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| 13. |
- Graneli, Annette, 1973, et al.
(författare)
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Organized arrays of individual DNA molecules tethered to supported lipid bilayers
- 2006
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Ingår i: Langmuir. ; 22:1, s. 292-9
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Tidskriftsartikel (refereegranskat)abstract
- An unappreciated aspect of many single-molecule techniques is the need for an inert surface to which individual molecules can be anchored without compromising their biological integrity. Here, we present new methods for tethering large DNA molecules to the surface of a microfluidic sample chamber that has been rendered inert by the deposition of a supported lipid bilayer. These methods take advantage of the "bio-friendly" environment provided by zwitterionic lipids, but still allow the DNA molecules to be anchored at fixed positions on the surface. We also demonstrate a new method for constructing parallel arrays of individual DNA molecules assembled at defined positions on a bilayer-coated, fused silica surface. By using total internal reflection fluorescence microscopy to visualize the arrays, it is possible to simultaneously monitor hundreds of aligned DNA molecules within a single field-of-view. These molecular arrays will significantly increase the throughput capacity of single-molecule, fluorescence-based detection methods by allowing parallel processing of multiple individual reaction trajectories.
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| 14. |
- Granéli, C., et al.
(författare)
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Urinary tract anomalies and urinary tract dysfunction in children with Hirschsprung disease—Is follow-up indicated?
- 2019
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Ingår i: Journal of Pediatric Surgery. - : Elsevier BV. - 0022-3468. ; 54:10, s. 2012-2016
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Tidskriftsartikel (refereegranskat)abstract
- Background/Purpose: Urinary tract function in children with Hirschsprung disease (HD) is rarely considered. Aim: to evaluate the prevalence of urinary tract anomalies and dysfunction in children with HD compared to controls. Methods: This was an observational cross sectional case–control study. Children with HD who underwent transanal endorectal pull-through technique (TERPT) from 2005 to 2017 were invited to participate. Ultrasound of the urinary tract was performed postoperatively. Children > 4 years were asked to answer a urinary tract function questionnaire. Controls were age-matched healthy children. Ethical approval was obtained. Results: Seventy two children with HD and TERPT were included. Ultrasound was performed in 58 children (83%) post-TERPT. Ten anomalies were diagnosed in six children (10%). Structural anomalies included abnormal kidney size (7%), renal agenesis (2%), prominent calyces (2%) and renal pelvis anomaly (25). Probable acquired anomalies included hydronephrosis (2%), hydroureter (2%) and parenchymal damage (2%). One child had a prior nephrectomy owing to a Wilms’ tumor. All 37 children > 4 years (27 boys and 10 girls), median aged 8 years (range 4–12), answered the questionnaire as did 284 healthy controls (144 boys and 140 girls). Boys with HD reported a higher frequency of enuresis: 65% versus 9% (p = 0.001) and urinary tract infections: 18% versus 3% (p = 0.012). Girls with HD reported enuresis more frequently (60%) than healthy girls (7%) (p = 0.001). Children with HD with constipation reported enuresis more frequently (p = 0.038). Conclusions: Urinary tract anomalies and dysfunction deserve attention in the follow-up of children with HD. We suggest screening for urinary tract anomalies and urinary tract symptoms in follow-up of children with HD. Type of study: Treatment study. Level: III.
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| 15. |
- Granéli, E., et al.
(författare)
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Allelopathy in marine ecosystems
- 2003
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Ingår i: Allelopathy: a physiological process with ecological implications. - : Kluwer Academic Publishers.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 19. |
- 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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| 20. |
- Kozlowsky-Suzuki, Betina, et al.
(författare)
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Food selectivity and grazing impact on toxic Dinophysis spp. by copepods feeding on natural plankton assemblages
- 2006
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Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 5:1, s. 57-68
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Tidskriftsartikel (refereegranskat)abstract
- Food selectivity and grazing impact by Acartia bifilosa, Temora longicornis and Centropages typicus on Dinophysis spp. plankton assemblages were experimentally investigated in the Baltic Sea. Toxin analyses were carried out on phyto- and zooplankton-dominated size fractions from field-collected samples to assess if toxins produced by Dinophysis spp. would end up in the zooplankton. All copepod species fed,actively on toxic Dinophysis spp. (Dinophysis acuta and Dinophysis norvegica). Despite the non-selective feeding behaviour by T longicornis and C. typicus, selectivity coefficients on D. acuta progressively decreased as food availability increased. Similar response was not observed for A. bifilosa, which displayed an even less selective behaviour. A. bifilosa had no significant negative effect on the net growth of D. norvegica at the lowest food concentration offered, whereas T longicornis and C typicus had significant negative effects on the net growth of D. acuta at low concentrations, similar to those observed in situ. Both species could potentially contribute as a substantial loss factor for Dinophysis spp. provided they are abundant at the onset of the blooms. The estimated grazing impact by the copepod populations was only considerable when C typicus abundance was high and D. acuta population in sharp decline. Our results suggest that when high abundance of grazers and poor growth condition of prey populations prevail, grazing impact by copepods can contribute considerably to prevent Dinophysis spp. populations to grow or to cause the populations to decline. Okadaic acid was detected in the zooplankton size fraction at one occasion, but the concentration was far lower than the one expected from the ingested toxins. Thus, even if copepods may act as vectors of DSP-toxins to higher trophic levels, the amount of these toxins transported in the food web by copepods seems limited. (C) 2005 Elsevier B.V. All rights reserved.
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| 22. |
- McNamee, Sara E., et al.
(författare)
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Distribution, occurrence and biotoxin composition of the main shellfish toxin producing microalgae within European waters : A comparison of methods of analysis
- 2016
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 55, s. 112-120
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Tidskriftsartikel (refereegranskat)abstract
- Harmful algal blooms (HABs) are a natural global phenomena emerging in severity and extent. Incidents have many economic, ecological and human health impacts. Monitoring and providing early warning of toxic HABs are critical for protecting public health. Current monitoring programmes include measuring the number of toxic phytoplankton cells in the water and biotoxin levels in shellfish tissue. As these efforts are demanding and labour intensive, methods which improve the efficiency are essential. This study compares the utilisation of a multitoxin surface plasmon resonance (multitoxin SPR) biosensor with enzyme-linked immunosorbent assay (ELISA) and analytical methods such as high performance liquid chromatography with fluorescence detection (HPLC-FLD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for toxic HAB monitoring efforts in Europe. Seawater samples (n = 256) from European waters, collected 2009-2011, were analysed for biotoxins: saxitoxin and analogues, okadaic acid and dinophysistoxins 1/2 (VDU /DTX2) and domoic acid responsible for paralytic shellfish poisoning (PSP), diarrheic shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP), respectively. Biotoxins were detected mainly in samples from Spain and Ireland. France and Norway appeared to have the lowest number of toxic samples. Both the multitoxin SPR biosensor and the RNA microarray were more sensitive at detecting toxic HABs than standard light microscopy phytoplankton monitoring. Correlations between each of the detection methods were performed with the overall agreement, based on statistical 2 x 2 comparison tables, between each testing platform ranging between 32% and 74% for all three toxin families illustrating that one individual testing method may not be an ideal solution. An efficient early warning monitoring system for the detection of toxic HABs could therefore be achieved by combining both the multitoxin SPR biosensor and RNA microarray. (C) 2016 Elsevier B.V. All rights reserved.
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| 23. |
- Panosso, R, et al.
(författare)
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Effect of grazing by a neotropical copepod, Notodiaptomus, on a natural cyanobacterial assemblage and on toxic and non-toxic cyanobacterial strains
- 2003
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 25:9, s. 1169-1175
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Tidskriftsartikel (refereegranskat)abstract
- The neotropical, freshwater copepod Notodiaptomus iheringi decreased the growth of small colonies in cyanobacteria-dominated plankton, indicating that they can be efficiently ingested and that they may represent an important food source for this copepod in reservoirs dominated by cyanobacteria. Cultured, colonial, toxic Microcystis aeruginosa was not affected, indicating that toxicity may cause a decrease in its ingestion by N. iheringi.
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| 24. |
- Rasmus, K. E., et al.
(författare)
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Optical studies in the Southern Ocean
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2583-2597
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Tidskriftsartikel (refereegranskat)abstract
- During the Austral summer of 1997-1998, measurements of absorption, attenuation, downwelling and upwelling irradiance were made in the Southern Ocean along a S-N transect at 6degreesE. Measurements were made to quantify the penetration of ultraviolet B radiation (UVBR) in the water column and daily doses of UVBR at different water depths, to study the attenuation of photosynthetically active radiation (PAR), and to judge if in the investigated areas of the Southern Ocean phytoplankton are light limited. The results show that the UVBR affects a substantial portion of the upper mixed layer. The diffuse attenuation coefficients (K-PAR) for PAR were found to vary between 0.03 and 0.09 m(-1). Using the values for KPAR and the definition of the Sverdrup critical depth, the studied Southern Ocean plankton systems were found not to be light limited. (C) 2004 Elsevier Ltd. All rights reserved.
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| 25. |
- Sakshaug, E, et al.
(författare)
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Chemical composition and alkaline phosphatase activity of nutrient-saturated and P-deficient cells of four marine dinoflagellates
- 1984
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 77, s. 241-254
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Tidskriftsartikel (refereegranskat)abstract
- Four marine dinoflagellates, Amphidinium carterae Hulburt, Ceratium tripos (O.F. Müll.) Nitzsch, Prorocentrum minimum (Pav.) J. Schiller, and Scrippsiella trochoidea (Stein) Loeblich III were grown as dilution cultures at 18°C, S = 29%. and 30 μE·m−2·s−1 at L:D = 14:10 h. In nutrient-saturated cultures, the growth rates (doubl·day−1) ranged from 0.38 for Scrippsiella to 0.80 for Prorocentrum, and carbon content (pg·cell−1) from 83 for Amphidinium to 6900 for Ceratium. The atomic N/C ratio was 0.13–0.15, but for Ceratium it was 0.088, because of its thick, cellulose theca. The atomic N/P ratio ranged from 12–13 for Ceratium and Scrippsiella to 15–17 for Prorocentrum and Amphidinium. Under P-deficient conditions (growth rate 39–70% of the maximum), cellular P decreased considerably, but so did N, so that the N/P ratio was only slightly affected. There was a concomitant increase in carbon content per cell of 1.2- to 1.7-fold. Alkaline phosphatase activity was virtually nil in nutrient-saturated cells, but was readily demonstrable in all species when P-deficient.
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