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- Jonsson, C. E., et al.
(författare)
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Two diatom oxygen isotope records from Naimakka in northern Fennoscandia: implications for Holocene palaeohydrology and atmospheric circulation dynamics
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This study present past changes in lake water oxygen isotope composition (δ18Olakew) calculated from diatom oxygen isotope composition (δ18Odiatom) from two lake sediment records. The two sediment sequences (9500 and 2800 years) are from open-basin lakes, although with different hydrologies, and are located close to a meteorological station in Naimakka, Northern Fennoscandia. The isotope composition of lake waters was analysed to determine the modern regional hydrological setting. Our results show that changes in the isotope composition of precipitation (δ18Op) is the primary forcing mechanism decreasing or increasing the δ18Olakew values in both lakes. Changes in the isotope signals are interpreted as reflecting regional variations in atmospheric circulation and climatic seasonality. δ18Odiatom from Lake Keitjoru, covering the last 9500 years, shows a depletion trend of 1.3‰ from c. 8000 until around 1500 cal yr BP. This decrease is thought to be due to a long term decrease in the influence of a zonal airflow (strong westerlies, relatively high δ18Op) over Fennoscandia in favor of an increasing proportion of colder meridional airflow (weak westerlies, lower δ18Op) from the north. A synchronous shift to lower δ18O values was recorded in Lake Keitjoru and lake Oikojärvi around 700-600 cal yr BP (~AD 1250-1350), a time when European climate deteriorated into the “Little Ice Age”. We argue that a circulation pattern dominated by meridional airflow, with reduced westerlies over Northern Fennoscandia and high amounts of winter precipitation from southeast or north, replaced a zonal atmospheric circulation pattern at this time. The δ18Odiatom minima c. 400 and 50 cal yr BP (~AD 1550 and AD 1900) is likely also a response to shifts in circulation, which is also seen in lower summer temperatures at that time recorded in tree-rings and from pollen data. The fact that the same isotope shifts have been detected in δ18O records from hydrological different lakes lends support to our conclusion that these records reflect variations in atmospheric circulation pattern.
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- Andersson, David C., 1978-, et al.
(författare)
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Design of target-tailored virtual screening experiments
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Discovering molecules with a desired biological function is one of the great challenges in drug research. To discover new lead molecules, in silico virtual screens (VS) are often conducted, in which databases of molecules are screened for potential binders to a specific protein, using molecular docking. The choice of docking software and parameter settings within the software can significantly influence the outcome of a VS. In this study, we have applied chemometric methods such as DoE, principal component analysis (PCA) and partial least-square projections to latent structure (PLS) to simulated VS experiments to find and compare suitable conditions for performing VS against six protein targets selected from the DUD databases. The docking parameters in FRED, and scoring functions in both FRED and GOLD docking software, were varied according to a statistical experimental design and a PLS model was calculated to correlate the experimental setup to the VS outcome. The study revealed that the choice of scoring function has the greatest influence on VS outcome, and that other parameters have varying influence, depending on the protein target. We also found that substantial bias can be introduced by the lack of variation of molecule properties in the databases used in the screening. The results indicate that docking experiments should be tailored to the protein target in order to obtain satisfactory VS results and that our methodology provides a suitable approach for such tailoring.
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- Persson, Marie, et al.
(författare)
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Leukocyte populations in patients undergoing in vitro fertilization: responses to hormone treatment and relation to outcome
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We aimed to prospectively investigate circulating leukocyte populations in infertile women undergoing IVF treatment and to determine whether any differences in cell proportions were associated with the IVF outcome. We also assessed the effect of IVF-based ovarian stimulation on the leukocyte populations. Twenty-five women were included and IVF treatment was successful in six and unsuccessful in 19 women. Blood samples were collected before IVF treatment, at the time of embryo transfer and four weeks after embryo transfer. The numbers and proportions of lymphocytes, T cells, NK cells, monocytes and granulocytes were analysed by flow cytometry, as well as the following lymphocyte subpopulations: CD3+HLA-DR+, CD4+CD45RA+, CD4+CD45R0+, CD8+CD45RA+, CD8+CD45R0+, CD4+CD25+, CD4dimCD25bright regulatory T cells, CD3-CD56bright and CD3-CD56dim NK cells. The proportions and numbers of leukocytes during IVF treatment were not related to the IVF outcome, although pregnant women (four weeks after ET) had a lower proportion of lymphocytes than the non-pregnant women. The absolute counts of lymphocytes, T cells, granulocytes and monocytes, as well as the proportions of granulocytes and T cells, increased at the time of ET, coinciding with high FSH and hCG levels. In conclusion, the proportions and numbers of leukocyte populations were not associated with the IVF outcome, although a larger study should be conducted to confirm this conclusion. Changes in both proportions and numbers of several leukocyte populations were observed during the course of IVF treatment, suggesting a stimulatory effect of the hormonal influence.
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