| 1. |
- Nilsson, E. J. C., et al.
(författare)
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Evaluation of cryoanalysis as a tool for analyzing elemental distribution in live tardigrades using micro-PIXE
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 332, s. 181-186
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Tidskriftsartikel (refereegranskat)abstract
- Although heavy on labor and equipment, thus not often applied, cryoanalysis of frozen hydrated biological specimens can provide information that better reflects the living state of the organism, compared with analysis in the freeze-dried state. In this paper we report a study where the cryoanalysis facility with cryosectioning capabilities at Materials Research Department, iThemba LABS, South Africa was employed to evaluate the usefulness of combining three ion beam analytical methods (mu PIXE, RBS and STIM) to analyze a biological target where a better elemental compositional description is needed - the tardigrade. Imaging as well as quantification results are of interest. In a previous study, the element composition and redistribution of elements in the desiccated and active states of two tardigrade species was investigated. This study included analysis of both whole and sectioned tardigrades, and the aim was to analyze each specimen twice; first frozen hydrated and later freeze-dried. The combination of the three analytical techniques proved useful: elements from C to Rb in the tardigrades could be determined and certain differences in distribution of elements between the frozen hydrated and the freeze-dried states were observed. RBS on frozen hydrated specimens provided knowledge of matrix elements.
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| 2. |
- Nilsson, Charlotta, et al.
(författare)
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Element analysis of the eutardigrades Richtersius coronifer and Milnesium cf. asiaticum using particle induced X-ray emission (PIXE)
- 2013
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Ingår i: Journal of limnology. - : PAGEPress Publications. - 1129-5767 .- 1723-8633. ; 72, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- Semi-terrestrial tardigrades are well-known for their tolerance to a variety of environmental extremes, including desiccation, freezing and radiation. Despite several attempts to reveal the genetic and molecular mechanisms behind the resilience of tardigrades, it is still unknown how these animals are able to maintain the integrity of their cellular components under severe stress. Quantitative or qualitative changes in molecular compounds (e.g., carbohydrates, proteins) are expected, and have been the main line of research towards understanding the tolerance of tardigrades. In radiation tolerant bacteria, a tolerance mechanism based on manganese has been proposed. We evaluate this hypothesis in tardigrades and provide the first data on element composition in desiccated and non-desiccated specimens of two eutardigrade species, Richtersius coronifer and Milnesium cf. asiaticum. A focused 2 MeV proton microbeam was utilised to determine the elemental content, distributions and concentrations, using the ion beam analytical technique particle induced X-ray emission (PIXE). The presence of six elements - phosphorus, sulphur, chlorine, potassium, calcium and iron - were confirmed in all tardigrade specimens, at levels up to a few mg g(-1). However, manganese was found in less than 10% of the analysed specimens, and in low amounts, thus our study provides no evidence for the manganese hypothesis. We also show that the distributions and/or concentrations of some elements differ between the two species as well as between the dehydrated and hydrated state. In particular, very low levels of iron were found in dehydrated M. cf. asiaticum. Our analysis shows that the PIXE technique is a useful tool for investigating questions on the distribution of elements both in dehydrated and hydrated tardigrades.
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| 3. |
- Nilsson, Charlotta, et al.
(författare)
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Tolerance to proton irradiation in the eutardigrade Richtersius coronifer - a nuclear microprobe study
- 2010
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 86:5, s. 420-427
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Tidskriftsartikel (refereegranskat)abstract
- Materials and methods: Dehydrated tardigrades of the species R. coronifer were irradiated with 2.55 MeV (megaelectronvolts) protons at doses ranging from 500 gray (Gy) to 15,000 Gy, to investigate the dose-viability relationship. In addition, a focused proton microbeam was utilised to determine the areal mass distribution, using the ion beam analytical technique STIM (Scanning Transmission Ion Microscopy). Results: The experiment suggests that R. coronifer is unaffected by doses of proton irradiation up to 10,000 Gy, but shows very little viability at higher doses. The STIM analysis revealed that the thickness of the dehydrated tardigrades exceeds 150 mu m, and that a fraction of the protons may not be fully absorbed. Conclusion: Our results are in line with previous studies of exposure to high-LET radiation in tardigrades, indicating that these animals are equally or even more tolerant to high-LET compared to low-LET gamma radiation. The physiological background to this remarkable result is currently unknown, but deserves investigation.
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