| 36781. |
- Gylling, Björn, 1978-, et al.
(författare)
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One-carbon metabolite ratios as functional B-vitamin markers and in relation to colorectal cancer risk
- 2019
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Ingår i: International Journal of Cancer. - : John Wiley & Sons. - 0020-7136 .- 1097-0215. ; 144:5, s. 947-956
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Tidskriftsartikel (refereegranskat)abstract
- Background: One-carbon metabolism biomarker are easily measured in plasma, but analyzing them one at a time in relation to disease does not take into account the interdependence of the many factors involved. The relative dynamics of major one-carbon metabolism branches can be assessed by relating the functional B-vitamin marker total homocysteine (tHcy) to transsulfuration (total cysteine) and methylation (creatinine) outputs.Objective: We validated the ratios of tHcy to total cysteine (Hcy:Cys), tHcy to creatinine (Hcy:Cre), and tHcy to cysteine to creatinine (Hcy:Cys:Cre) as functional markers of B-vitamin status. We also calculated the associations of these ratios to colorectal cancer (CRC) risk.Design: The relative contribution of potential confounders to the variance of the ratio-based B-vitamin markers was calculated by linear regression in a nested case-control study of 613 CRC cases and 1211 matched controls. Total B-vitamin status was represented by a summary score comprising Z-standardized plasma concentrations of folate, cobalamin, betaine, pyridoxal 5´-phosphate, and riboflavin. Associations with CRC risk were estimated using conditional logistic regression.Results: The ratio-based B-vitamin markers all outperformed tHcy as markers of total B-vitamin status, in both CRC cases and controls. Associations with CRC risk were similar for the ratio-based B-vitamin markers and total B-vitamin status (approximately 25% lower risk for high versus low B-vitamin status).Conclusions: Ratio-based B-vitamin markers were good predictors of total B-vitamin status, and displayed similar associations with CRC risk. Since tHcy and creatinine are routinely clinically analyzed, Hcy:Cre could be easily implemented in clinical practice to aid interpretation of tHcy results.
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| 36782. |
- Gylling, Björn, et al.
(författare)
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Vitamin B-6 and colorectal cancer risk : a prospective population-based study using 3 distinct plasma markers of vitamin B-6 status
- 2017
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Ingår i: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165 .- 1938-3207. ; 105:4, s. 897-904
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Tidskriftsartikel (refereegranskat)abstract
- Background: Higher plasma concentrations of the vitamin B-6 marker pyridoxal 5#-phosphate (PLP) have been associated with reduced colorectal cancer (CRC) risk. Inflammatory processes, including vitamin B-6 catabolism, could explain such findings. Objective: We investigated 3 biomarkers of vitamin B-6 status in relation to CRC risk. Design: This was a prospective case-control study of 613 CRC cases and 1190 matched controls nested within the Northern Sweden Health and Disease Study (n = 114,679). Participants were followed from 1985 to 2009, and the median follow-up from baseline to CRC diagnosis was 8.2 y. PLP, pyridoxal, pyridoxic acid (PA), 3-hydroxykynurenine, and xanthurenic acids (XAs) were measured in plasma with the use of liquid chromatography-tandem mass spectrometry. We calculated relative and absolute risks of CRC for PLP and the ratios 3-hydroxykynurenine: XA (HK: XA), an inverse marker of functional vitamin B-6 status, and PA:(PLP + pyridoxal) (PAr), a marker of inflammation and oxidative stress and an inverse marker of vitamin B-6 status. Results: Plasma PLP concentrations were associated with a reduced CRC risk for the third compared with the first quartile and for PLP sufficiency compared with deficiency [OR: 0.60 (95% CI: 0.44, 0.81) and OR: 0.55 (95% CI: 0.37, 0.81), respectively]. HK: XA and PAr were both associated with increased CRC risk [OR: 1.48 (95% CI: 1.08, 2.02) and OR: 1.50 (95% CI: 1.10, 2.04), respectively] for the fourth compared with the first quartile. For HK: XA and PAr, the findings were mainly observed in study participants with,10.5 y of follow-up between sampling and diagnosis. Conclusions: Vitamin B-6 deficiency as measured by plasma PLP is associated with a clear increase in CRC risk. Furthermore, our analyses of novel markers of functional vitamin B-6 status and vitamin B-6-associated oxidative stress and inflammation suggest a role in tumor progression rather than initiation.
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| 36783. |
- Gyuranecz, Miklos, et al.
(författare)
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Phylogeography of Francisella tularensis subsp holarctica, Europe
- 2012
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Ingår i: Emerging Infectious Diseases. - Atlanta : Centers Disease Control. - 1080-6040 .- 1080-6059. ; 18:2, s. 290-293
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Tidskriftsartikel (refereegranskat)abstract
- Francisella tularensis subsp. holarctica isolates from Austria, Germany, Hungary, Italy, and Romania were placed into an existing phylogeographic framework. Isolates from Italy were assigned to phylogenetic group B.FTNF002-00; the other isolates, to group B.13. Most F tularensis subsp. holarctica isolates from Europe belong to these 2 geographically segregated groups.
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| 36784. |
- Gåfvels, Mats, 1955-
(författare)
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Blood flow and metabolism in the corpus luteum of the rat : in vivo and in vitro studies on the ovarian luteal and follicular compartment of the rat
- 1987
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ovary undergoes cyclic changes in follicular growth and luteogenesis due to the action of gonadotropins and steroids. The ovary and especially the corpus luteum has an exteremely high blood flow. There is a gap in our knowledge about the physiological role of the high blood flow of the corpus luteum.The production of lactate, progesterone and cyclic AMP of follicles and corpora lutea incubated in vitro was analyzed and related to the tissue content of ATP to elucidate possible connections between oxygen and substrate levels and energy consumption, steroid output and LH responsiveness in vitro. It was also considered of interest to investigate if the oxygen tensions needed for ATP and progesterone production of the follicle and the corpus luteum differed. A corpus luteum model using adult pseudopregnant rats was developed and characterized according to criteria for identification of corpora lutea as well as levels of plasma steroids and gonadotropins. In vitro progesterone production was compared to plasma progesterone levels. The absolute blood flow of corpora lutea of different ages and the response to injection of hCG, noradrenaline and antidiuretic hormone was investigated with the microsphere technique. Relative blood flow changes of follicles and corpora lutea during follicular growth and luteogenesis in vivo were studied by injecting radiolabelled microspheres to anaesthetized immature rats at different time periods after injection of an ovulatory dose of pregnant mare serum gonadotropin. This approach was chosen to investigate the possible relation between follicular/luteal blood flow, steroid output and morphology in relation to the endogenous gonadotropin surge, ovulation and luteogenesis.Hormonal stimulation by injection of hCG and noradrenaline increased total ovarian blood flow but no evidence was found for a parallelism between luteotropism and blood flow. The increasing effect of hCG on ovarian blood flow was partly due to a shunting of blood from the uterus towards the ovary. The antidiuretic hormone potently decreased ovarian and uterine blood flow by 80-90% while blood flow of some other organs (e.g. kidney and spleen) were hardly affected. The corpus luteum of pseudopregnancy was found to produce 15“ 20 times more progesterone in vitro as compared to the preovulatory follicle. The steroidogenesis and energy production of corpora lutea was found to be more sensitive to decreases in oxygen tension in terms of tissue ATP levels and LH responsiveness of progesterone production while the follicle could compensate by increasing glycolysis. A parallelism between follicular/luteal blood flow and progesterone production in vivo was found. It was shown that the formation, growth and progesterone production of the corpus luteum was accompanied by an increase in blood flow as well as vascularization as seen under the light microscope. The endogenous gonadotropin surge did not change follicular blood flow due to the development of a follicular oedema. We hypothesize that the corpus luteum function in vivo and in vitro is dependent on higher energy levels than the preovulatory follicle and that the transformation of the follicle to a corpus luteum is supported by a high nutritive blood flow possibly to support a high demand for energy-rich substrates.
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| 36785. |
- Gähler, Werner, et al.
(författare)
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Extension structures and compactifications
- 2001
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Ingår i: Proceedings Joint 9th IFSA World Congress and 20th NAFIPS International Conference (Vol. 5). - 0780370783 ; , s. 2940-2945
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Konferensbidrag (refereegranskat)abstract
- Basic results on compactifications are presented applying the notion of extension structure. Eachextension structure has a canonical completion. The related completion constructions can be applied, for instance, for generating completion theorems in algebra, lattice theory and general topology, in particular they lead to a universal completion for Cauchy-spaces in the fuzzy filter case. Sincecompactifications can be identified with special Cauchy-completions, even different types ofcompactifications can be generated. Among others, we present new results on the Richardson compactification in the fuzzy filter case applying new results on fuzzy filters. This type of compactification was treated previously by the authors (1993)
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| 36786. |
- Gähler, Werner, et al.
(författare)
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Extension structures and compactifications
- 2000
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Konferensbidrag (refereegranskat)abstract
- The notion of extension structure [2] depends on a fixed set functor j: \sf SET --> \sf SET. We therefore also speak on a j-extension structure. This notion contains important structural properties of Cauchy structures and is basically for a general completion theory. Let X be a set. By a j-extension structure on X we mean a triple (S, T, ~ ) consisting of two sets S subset or equal jX and T subset or equal jX ×X and an equivalence relation ~ on S such that, writing M \usebox\ko x instead of (M, x) in T, we have that (1) M \usebox\ko x implies M in S, (2) M \usebox\ko x and M ~ N imply N \usebox\ko x, and (3) from M \usebox\ko x and N \usebox\ko x it follows M ~ N.A j-extension structure (S, T, ~ ) and also the related j-extension space (X, (S, T, ~ )) is said to be separated provided that M \usebox\ko x and M\usebox\ko y imply x = y, and they are said to be complete provided that for each M in S there is an element x of X such thatM \usebox\ko x holds.We have that the category of all separated and complete j-extension spaces is an epireflective subcategory of the category of all separated j-extension spaces. As is shown in [3], the related completion construction can be applied for generating completion theorems in algebra, lattice theory and general topology, in particular they lead to a universal completion for Cauchy-spaces in the fuzzy filter case. Since compactifications can be identified with special Cauchy-completions, even different types of compactifications can be generated.Among others, we present in this paper new results on the Richardson compactification for the fuzzy filter case applying new results on fuzzy filters. Note that this type of compactification was already treated in [1]. For a fixed non-degenerate infinitely distributive complete lattice L, here we mean by a fuzzy filter a mapping M: LX --> L such that M([`0]) = 0 and M([`1]) = 1 for the constant fuzzy sets [`0], [`1] in LX and M(f /\ g) = M(f) /\ M(g) for all fuzzy sets f, g in LX.A fuzzy filter M is said to be bounded in case M(f) <= supf holds for all f in LX. A fuzzy filter M will be called distinguished provided that M(f \/ g) = M(f) \/ M(g) holds for all f, g in LX. Moreover, M will be called balanced provided that a distinguished fuzzy filter finer thanM exists.In the general fuzzy filter case under the zero-condition of L (\alpha > 0, \beta > 0 ===> \alpha /\ \beta > 0) all fuzzy filters are balanced. In this case the Richardson compactification exists.In the case of bounded fuzzy filters there may be fuzzy filters which are not balanced. If in this case we restrict us to balanced fuzzy filters, then the Richardson compactification also exists.[1] P. Eklund, W. Gähler, Completions and compactifications by means of monads, in: Fuzzy Logic, State of Art, Kluwer, Dortrecht/Boston/London 1993, 39-56[2] W. Gähler, Completion theory, in: Mathematisches Forschungsinstitut Oberwolfach, Tagungsbericht 48/1991, 8[3] W. Gähler, Extension structures and completions in topology and algebra, 2000
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| 36787. |
- Gällstedt, Margareta
(författare)
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Working conditions in projects: perceptions of stress and motivation among project team members and project managers
- 2003
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Ingår i: International journal of Project Management. - 0263-7863. ; 21:6, s. 449-455
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of temporary and democratic work forms characterizes work today and organisations to a great extent rely on individuals' performance. Workers' perceptions of working conditions are affected by two important factors: motivation and stress. Projects are motivating due to clear goals, but they are also often time pressured. Incidents like, for example, loss of resources, changing preferences or priorities, or project closure might provoke changes to the set goals, to which individuals have committed. This could obstruct effective goal fulfilment as well as create stress among the people involved. How do project managers and project team members perceive incidents that the typical project encounters? How do they cope with uncertainties the incidents bring about? The finding suggests that incidents cause changes over the project lifecycle, both of goals and of individuals' perceptions of tasks, conditions, and the situation. Different coping strategies are used to reduce uncertainty and stress.
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| 36788. |
- Gälman, Veronika, 1969-, et al.
(författare)
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A comparison of sediment varves (1950–2003 AD) in two adjacent lakes in northern Sweden
- 2006
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Ingår i: Journal of Paleolimnology. - Dordrecht : Kluwer. - 0921-2728 .- 1573-0417. ; 35, s. 837-853
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Tidskriftsartikel (refereegranskat)abstract
- Koltjärnen and Nylandssjön are two closely situated lakes (<2 km apart) in northern Sweden. During the past century, distinct varved sediments have formed in these lakes. Nylandssjön has two varved, deep basins. Since lake and catchment characteristics superficially appear very similar for the two lakes and they are exposed to the same climate, one would expect the sediment varves to be similar. This investigation compares the varves in the two deep basins of Nylandssjön, and in the two lakes. The comparison of basins of Nylandssjön shows that varve thickness, water content and annual accumulation rates of organic matter and nitrogen are correlated for the period (1970–2003). The grey-scale curves are only clearly similar in about 50% of the varves. In the between-lake comparison varve thickness, water content and annual accumulation rates of organic matter and nitrogen are correlated for the period (1950–1996). However, the annual accumulation rates of dry mass, minerogenic matter and biogenic silica differ between the lakes, as well as within-varve successions in grey-scale. A general explanation to the differences is that the prerequisites for varve formation are not totally similar because of differences in catchment size, catchment- to-lake material fluxes, lake productivity and land-use influence. This study illustrates the complex relationships that exist between a lake, its catchment, in-lake productivity and formation of sediment varves. As a consequence, we must not apply a too simplistic view of the potential of varves as past climatic indicators, especially if the lakes are affected by land-use.
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| 36789. |
- Gälman, Veronika, et al.
(författare)
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Carbon and nitrogen loss rates during aging of lake sediment : Changes over 27 years studied in varved lake sediment
- 2008
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Ingår i: Limnology and Oceanography. - Waco, Tex. : American Society of Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 53:3, s. 1076-1082
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Tidskriftsartikel (refereegranskat)abstract
- We used a collection of ten freeze cores of annually laminated (varved) lake sediment from Nylandssjön in northern Sweden collected from 1979 to 2007 to follow the long-term loss of carbon (C) and nitrogen (N) due to processes that occur in the lake bottom as sediment ages. We compared specific years in the different cores. For example, the loss of C from the surface varve of the 1979 core (sediment deposited during 1978) was followed in the cores from 1980, 1985, 1989, and so on until 2006. The C concentration of the sediment decreased by 20% and N decreased by 30% within the first five years after deposition, and after 27 yr in the sediment, there was a 23% loss of C and 35% loss of N. Because the relative loss of C with time was smaller than loss of N, the C:N ratio increased with increasing age of the sediment; the surface varves start with a ratio of ~10, which then increases to ~12.
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| 36790. |
- Gälman, Veronika, et al.
(författare)
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Decadal diagenetic effects on d13C and d15N studied in varved lake sediment
- 2009
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Ingår i: Limnology and Oceanography. - : Association for the Sciences of Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 54:3, s. 917-924
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Tidskriftsartikel (refereegranskat)abstract
- To assess the long-term (27 yr) effects of sediment aging on stable carbon and nitrogen isotope values (δ13C and δ15N), we used a collection of eight freeze cores of annually laminated (varved) lake sediment collected from 1979 to 2007 in Nylandssjon (northern Sweden). Previous research has shown that 20–23% of carbon and 35% of nitrogen is lost in 27 yr. Material from specific years was compared in the cores, e.g., δ13C and δ15N of the surface varve of the 1979 core was followed in cores retrieved in 1980, 1989, 1993, 2002, 2004, and 2006. δ13C increased by 0.4–1.5% during the first 5 yr. After this initial increase, only minor fluctuations were recorded. There is a good correlation between the magnitude in δ13C changes and the initial carbon and nitrogen concentrations, indicating that the initial sediment composition is important for the 13C fractionation. δ15N gradually decreased by 0.3–0.7% over the entire 27-yr period. The lack of correlation with the initial sediment composition and the gradual decrease in δ15N indicates a microbial control on δ15N change. The diagenetic changes in the stable isotope values that occur in Nylandssjon are small, but of the same magnitude as the down-core variation in the varves deposited 1950–2006. Diagenetic effects should be considered when δ13C and δ15N are used to study organic matter sources or paleoproductivity, especially when dealing with recent trends or small changes. Based on our findings, diagenetic effects for δ13C are observed during the first 5–10 yr, whereas no delimitation can be recommended for δ15N.
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