| 1. |
- Carroll, Christopher, et al.
(författare)
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Hypoxia Generated by Avian Embryo Growth Induces the HIF-α Response and Critical Vascularization
- 2021
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 9, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Cancer research has transformed our view on cellular mechanisms for oxygen sensing. It has been documented that these mechanisms are important for maintaining animal tissues and life in environments where oxygen (O2) concentrations fluctuate. In adult animals, oxygen sensing is governed by the Hypoxia Inducible Factors (HIFs) that are stabilized at low oxygen concentrations (hypoxia). However, the importance of hypoxia itself during development and for the onset of HIF-driven oxygen sensing remains poorly explored. Cellular responses to hypoxia associates with cell immaturity (stemness) and proper tissue and organ development. During mammalian development, the initial uterine environment is hypoxic. The oxygenation status during avian embryogenesis is more complex since O2 continuously equilibrates across the porous eggshell. Here, we investigate HIF dynamics and use microelectrodes to determine O2 concentrations within the egg and the embryo during the first four days of development. To determine the increased O2 consumption rates, we also obtain the O2 transport coefficient (DO2) of eggshell and associated inner and outer shell membranes, both directly (using microelectrodes in ovo for the first time) and indirectly (using water evaporation at 37.5°C for the first time). Our results demonstrate a distinct hypoxic phase (<5% O2) between day 1 and 2, concurring with the onset of HIF-α expression. This phase of hypoxia is demonstrably necessary for proper vascularization and survival. Our indirectly determined DO2 values are about 30% higher than those determined directly. A comparison with previously reported values indicates that this discrepancy may be real, reflecting that water vapor and O2 may be transported through the eggshell at different rates. Based on our obtained DO2 values, we demonstrate that increased O2 consumption of the growing embryo appears to generate the phase of hypoxia, which is also facilitated by the initially small gas cell and low membrane permeability. We infer that the phase of in ovo hypoxia facilitates correct avian development. These results support the view that hypoxic conditions, in which the animal clade evolved, remain functionally important during animal development. The study highlights that insights from the cancer field pertaining to the cellular capacities by which both somatic and cancer cells register and respond to fluctuations in O2 concentrations can broadly inform our exploration of animal development and success.
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| 2. |
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| 3. |
- Andersson, Cecilia, et al.
(författare)
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"Vad förväntas av en?" : Upplevelser av "idealstudenten" och mötet med universitetet
- 2024
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Ingår i: Lifelong Learning and Higher Education: New (and Old) Perspectives : Proceedings from the 2022 Lund University Conference on Teaching and Learning - Proceedings from the 2022 Lund University Conference on Teaching and Learning. - 9789172674844 - 9789172674851 ; , s. 35-53
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Konferensbidrag (refereegranskat)abstract
- Swedish institutions of higher education must promote widening participation. This goal is also expressed in policy documents at Lund University. To accomplish this, teachers at Lund University formed a group to strategically work towards student inclusion. This article reports on an interview study conducted by this group investigating students’ experiences and perceptions of entering education at two different programs. The theory of “the ideal student” was used to analyze the interview material. The result indicates the need for clarity and predictability in course layout and teaching.
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| 4. |
- Arnell, Linn, et al.
(författare)
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Volatility spillovers, structural breaks and uncertainty in technology sector markets
- 2023
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Ingår i: FINANCIAL INNOVATION. - : SPRINGER. - 2199-4730. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- This study uses the dynamic conditional correlation to investigate how technology subsector stocks interact with financial assets in the face of economic and financial uncertainty. Our results suggest that structural breaks have diverse effects on financial asset connectedness and that the level of bond linkage increases when the trend breaks. We see a growing co-movement between the technology sector and major financial assets when uncertainty is considered. Overall, our findings indicate that the connectedness response varies depending on the type of uncertainty shock.
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| 5. |
- Augustsson, Anna, et al.
(författare)
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Managing health risks in urban agriculture: The effect of vegetable washing for reducing exposure to metal contaminants
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 863
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Tidskriftsartikel (refereegranskat)abstract
- A common, yet poorly evaluated, advice to remove contaminants from urban vegetables is to wash the produce before consumption. This study is based on 63 samples of chard, kale, lettuce and parsley that have grown near a heavily trafficked road in the third largest city in Sweden, with one portion of each sample being analysed without first being washed, and the other portion being subjected to common household washing. Concentrations of 71 elements were analysed by ICP-SFMS after a sample digestion that dissolves both the plant tissues and all potentially adhering particles. The results show that the washing effect, or the fraction removed upon washing, varies significantly between elements: from approximately 0 % for K to 68 % for the ∑REEs. Considering traditional metal contaminants, the efficiency decreased from Pb (on average 56 % lost) to Co (56 %) > Cr (55 %) > As (45 %) > Sb (35 %) > Ni (33 %) > Cu (13 %) > Zn (7 %) > Cd (7 %), and Ba (5 %). A clear negative correlation between the washing effect and the different elements' bioconcentration factors shows that the elements' accessibility for plant uptake is a key controlling factor for the degree to which they are removed upon washing. Based on the average washing efficiencies seen in this study, the average daily intake of Pb would increase by 130 % if vegetables are not washed prior to consumption. For the other contaminant metals this increase corresponds to 126 % (Co), 121 % (Cr), 82 % (As), 55 % (Sb), 50 % (Ni), 16 % (Cu), 8 % (Zn), 7 % (Cd) and 5 % (Ba). The advice to wash vegetables is therefore, for many elements, highly motivated for reducing exposure and health risks. For elements which are only slightly reduced when the vegetables are washed, however, advising should rather focus on reducing levels of contamination in the soil itself.
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| 6. |
- Augustsson, Anna, et al.
(författare)
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Trace and major elements in food supplements of different origin : implications for daily intake levels and health risks
- 2021
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Ingår i: Toxicology reports. - : Elsevier. - 2214-7500. ; 8, s. 1067-1080
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Tidskriftsartikel (refereegranskat)abstract
- As the use of food supplements increases, voices are being raised questioning the safety of these products. As a contribution to understanding the trace and major elemental composition of food supplements and their potential health risks, this study presents concentrations of 71 elements in 138 supplements, categorised into synthetic products and three groups of products with natural ingredients. Concentrations were converted into average daily doses (ADDs) and compared to tolerable daily intakes (TDIs). For elements where we found significant ADDs relative to the TDI a comparison was also made to the normal dietary intake. Our main findings are that: 1) Most elements display highly variable concentrations in food supplements; more so than in normal foodstuff; 2) For ten of the analysed elements some products rendered ADDs > 50% of the TDI. Half of the elements were essential (Fe, Mn, Se, Mo, Zn), and as such motivated in food supplements. The other half (As, Pb, Cd, Al, Ni) represent non-essential and highly toxic elements, where the occurrence in food supplements ought to be viewed as contamination. Although none of these toxic metals were declared on any product’s table of content, several products gave high ADDs - in several cases even exceeding the TDIs; 3) The risk of reaching high ADDs for the toxic elements is strongly associated with products that contain marine ingredients (e.g. algae, mussels etc), and to some degree products of terrestrial plant-based origin. The health of consumers would benefit if food regulatory frameworks were updated to better address the risks of food supplements occasionally being contaminated with different toxic metals, for example by setting maximum permissible concentrations for a longer list of elements.
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| 7. |
- Augustsson, Anna, et al.
(författare)
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Urban vegetable contamination - The role of adhering particles and their significance for human exposure
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 900
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Tidskriftsartikel (refereegranskat)abstract
- While urban-grown vegetables could help combat future food insecurity, the elevated levels of toxic metals in urban soils need to be met with measures that minimise transfer to crops. The study firstly examines soil/dust particle inclusion in leafy vegetables and its contribution to vegetable metals (As, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sb, and Zn), using vegetable, soil and dust data from an open-field urban farm in southeastern Sweden. Titanium concentrations were used to assess soil/dust adherence. Results showed that vegetables contained 0.05–1.3 wt% of adhering particles (AP) even after washing. With 0.5 % AP, an adult with an average intake of vegetables could ingest approximately 100mg of particles per day, highlighting leafy vegetables as a major route for soil/dust ingestion. The presence of adhering particles also significantly contributed to the vegetable concentrations of As (9-20%), Co (17-20%), Pb (25-29%), and Cr (33-34%). Secondly, data from an indoor experiment was used to characterise root metal uptake from 20 urban soils from Sweden, Denmark, Spain, the UK, and the Czech Republic. Combining particle adherence and root uptake data, vegetable metal concentrations were calculated for the 20 urban soils to represent hypothetical field scenarios for these. Subsequently, average daily doses were assessed for vegetable consumers (adults and 3-6 year old children), distinguishing between doses from adhering particles and root uptake. Risks were evaluated from hazard quotients (HQs; average daily doses/tolerable intakes). Lead was found to pose the greatest risk, where particle ingestion often resulted in HQs>1 across all assessed scenarios. In summary, since washing was shown to remove only a portion of adhering metal-laden soil/dust particles from leafy vegetation, farmers and urban planners need to consider that measures to limit particle deposition are equally important as cultivating in uncontaminated soil.
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| 8. |
- Baxter, Douglas, et al.
(författare)
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Isotope abundance ratio measurements by inductively coupled plasma-sector field mass spectrometry
- 2012
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477 .- 1364-5544. ; 27:8, s. 1355-1381
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Tidskriftsartikel (refereegranskat)abstract
- This tutorial reviews fundamental aspects of isotope abundance ratio measurement by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). After a synopsis of the scope of isotope abundance ratio measurement and a summary introduction to the factors affecting precision and accuracy, attention is turned to noise sources. Detailed theory behind Poisson or counting statistics and plasma flicker noise components is given, since much of the observed imprecision can be attributed to these sources. Using single collector instruments, ion beams from different isotopes are sampled in rapid sequence, and so ratioing of the signals will be subject to fluctuations derived from intensity variations, i.e., flicker noise. It is demonstrated that flicker noise can, under specified circumstances, become the limiting factor for the attainable precision. Furthermore, the practice of partitioning dwell times, ostensibly to optimize precision based on isotopic abundances and assumed Poisson statistics, is shown to be flawed and actually requires accounting for flicker noise. In addition to random uncertainty, various offset factors may contribute to systematic error in measured isotope abundance ratios. Two of these, namely mass scale shift and spectral interferences are ameliorated using ICP-SFMS. The former is eliminated when operating under conditions providing flat-topped peaks, such that the minor drift in mass calibration typical of the technique becomes inconsequential and the intensity remains the same. Isotope abundance ratio measurements are subject to three further important offset factors. First is abundance sensitivity, which quantifies the extent of peak tailing to neighboring masses and can present a considerable source of offset. Second is mass bias, resulting from the fact that all sector field devices exhibit increasing sensitivity with ion mass, and various empirical methods used to correct for this effect are compared and contrasted. Third is detector dead time, which affects mass spectrometers equipped with ion counting systems. Although a well-understood phenomenon, all current methods for determining the dead time on the basis of experimentally measured isotope abundance ratios are likely to yield biased estimates. Finally, the capabilities of ICP-SFMS for the determination of isotope abundance ratios are placed in perspective by making a brief comparison with other techniques.
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| 9. |
- Baxter, Douglas, et al.
(författare)
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Methylmercury measurement in whole blood by isotope-dilution GC-ICPMS with 2 sample preparation methods
- 2007
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:1, s. 111-116
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Tidskriftsartikel (refereegranskat)abstract
- Background: Despite its known toxicity, methylmercury is rarely measured directly in clinical studies; instead, conclusions are based on total mercury measurements. We have developed isotope-dilution-based methods for methylmercury-specific analysis of whole blood by coupled gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS). Methods: We analyzed animal and human blood samples after alkaline digestion or extraction of methylmercury into dichloromethane and back extraction into water. Methylmercury was converted to the volatile ethyl derivative, purged, and trapped on a solid-phase collection medium, and then introduced into the GC-ICPMS system. Results: Limits of quantification were 0.4 and 0.03 mu g/L at a signal-to-noise ratio of 10 with the alkaline digestion and extraction methods, respectively. Extraction met our selected acceptable total error criterion, with an SD of 0.58 mu g/L at the critical maternal blood concentration of 5.8 mu g/L.Results obtained with alkaline digestion indicated the need for improved random analytical uncertainty, which was achieved by increasing the enrichment of the isotope dilution. For 37 blood samples, the mean (SD) proportion of total mercury present as methylmercury was 60 (27)%, range 6%-100%.Conclusions: The combination of extraction and isotope-dilution GC-ICPMS meets the requirements for use as a reference method for measuring methylmercury in whole blood.
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| 10. |
- Baxter, Douglas, et al.
(författare)
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Revised exponential model for mass bias correction using an internal standard for isotope abundance ratio measurements by multi-collector inductively coupled plasma mass spectrometry
- 2006
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 21:4, s. 427-430
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Tidskriftsartikel (refereegranskat)abstract
- An internal standard (IS) can be used to account for moderate, matrix-related shifts in mass bias using multi-collector inductively coupled plasma mass spectrometry through the empirical, linear relationship between measured isotope abundance ratios for different elements in ln-ln space. Unfortunately, erroneous mass bias corrected isotope abundance ratios may be returned by the model, requiring artificial adjustment of the true isotope abundance ratio of the IS. Although inadequate correction for peak tailing has been convincingly used to explain this problem, our analysis of the literature describing the development of the mass bias correction model using an IS reveals the presence of a source of systematic error. The origin of this error is purely mathematical and is eliminated in the revised model presented, in which mass bias corrected isotope abundance ratios are independent of the isotopic composition of the IS. An expression for computing the total combined uncertainty in the corrected ratio, incorporating contributions from the linear model, the isotopic reference material, and measurements of analyte element and IS in the sample, is also derived.
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