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- Axelsson, Rikard, 1970-
(författare)
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Cyanobacterial Hydrogen Metabolism : Transcriptional Regulation of the Hydrogenases in Filamentous Strains
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cyanobacteria are a heterogeneous group of phototrophic microorganisms. Many cyanobacteria have the capacity to fix atmospheric nitrogen. During the process of nitrogen fixation, molecular hydrogen is produced. Three enzymes are directly involved in hydrogen metabolism in cyanobacteria. A nitrogenase, evolving hydrogen during nitrogen-fixation, an uptake hydrogenase, recycling the hydrogen produced by nitrogenase, and a bidirectional hydrogenase that has the capacity to both take up and produce hydrogen. The main objective in this thesis was to examine the transcriptional regulation of both the uptake and the bidirectional hydrogenase in filamentous cyanobacteria.The transcriptional regulation of the uptake hydrogenase was demonstrated to be influenced by external conditions in Nostoc muscorum and Nostoc punctiforme. Nickel, molecular hydrogen, and anaerobic conditions all induced the relative amount of uptake hydrogenase transcript. In addition, a transcript could be detected in nitrogen-fixing, but not in non-nitrogen fixing conditions.The transcriptional regulation of the bidirectional hydrogenase in N. muscorum and Anabaena PCC 7120 was also examined. The relative amount of transcript from the bidirectional hydrogenase in both strains was demonstrated to increase during anaerobic conditions. Moreover, experiments using N. muscorum demonstrated that addition of nickel also increase the amount of transcript. However, no change in the relative amount of transcript from the bidirectional hydrogenase could be observed by additional hydrogen or during a shift from non-nitrogen fixing to nitrogen fixing conditions.The genes responsible for maturation of the hydrogenase were identified, cloned and sequenced in N. punctiforme. The transcription of the genes was examined and all genes were located on a single transcript. Like the uptake hydrogenase, a transcript could be detected under nitrogen-fixing but not under non-nitrogen fixing conditions. Initial studies, using microarrays, were used to analyse and compare the transcription of a large set of Anabaena PCC 7120 genes under non-nitrogen and nitrogen-fixing conditions. Both up- and down-regulated genes could be identified.This thesis advances the knowledge about the transcriptional regulation of the hydrogenases in filamentous cyanobacteria and can be used as a platform for further experiments aiming at a modified hydrogen metabolism.
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| 2. |
- Bergman, Eva, 1959-
(författare)
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Symphysis Fundus Measurements for Detection of Intrauterine Growth Retardation
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A case-control study was performed to evaluate the Swedish population-based symphysis fundus (SF) reference curves. The study included 242 small for gestational age (SGA) neonates (169 term and 73 preterm infants) as cases and 296 non-SGA infants as controls. Two Swedish SF curves were evaluated. In term pregnancies they showed a sensitivity of 32 % and 51 % and a specificity of 90 % and 83 %, respectively, at a cut-off level of < - 2 SD from the mean according to the SF reference curve. The sensitivity for SGA was higher in preterm pregnancies (49 % and 58 %, respectively) and the first alarm below – 2 SD was noted before 32 weeks in 37 % and 43 % of the preterm pregnancies, respectively. (Study I) A study of self-administered SF measurements was designed to achieve more regular and frequent SF measurements. Thirty-three women with singleton, ultrasound dated pregnancies performed SF measurements on average 14 weeks from gestational week 20 to 25 until delivery. Self-administered SF measurements were higher and had higher variance than midwives’ measurements. Four consecutive SF measurements on each occasion can compensate for higher variance. Reliable self-administered SF measurements can be obtained. (Study II) Self-administered SF measurements from 191 women were used to construct absolute and relative SF growth references. The influence of fetal sex, maternal obesity and parity was assessed in regression models. The lnSF growth was statistically influenced by maternal obesity, and a borderline significance was recorded for fetal sex and parity. Statistical analysis and graphical displays show no evidence that the relative lnSF growth should be dependent on these variables. (Study III) To improve detection of infants with intrauterine growth restriction (IUGR) rather than SGA a new statistical model (the SR method) was used. The SR method was evaluated with SF measurements from 1122 pregnant women. The sensitivity for neonatal morbidity and SGA was low, between 6 and 36 % for SGA (< -2SD). Neonates classified as SGA (< -2SD and < 10th percentile) had increased morbidity compared with the total study group. Neonates suspected to be SGA before delivery by the population-based SF measurement method had lower morbidity than those not suspected. The SR method was found not to improve detection of fetuses with increased morbidity or SGA neonates in this study. Better screening methods to detect IUGR and SGA prior to delivery are needed. (Study IV)
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| 3. |
- Hildebrand, Eric
(författare)
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Prenatal diagnosis of structural malformations and chromosome anomalies : Detection, influence of Body Mass Index and ways to improve screening
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Prenatal diagnosis of structural malformations and chromosome anomalies is possible in the presence of an effective screening with ultrasound during pregnancy. The continuous evolution of the ultrasound equipment facilitates the examination. However there are challenges in terms of the increasing prevalence of obesity among the pregnant women and the need of training of the personnel performing the scans. In the Southeast region of Sweden all pregnant women are offered screening with ultrasound during pregnancy. From 2009 almost all women in the region are offered two examinations, one in week 11-14 assessment of gestational age and combined screening for aneuploidy. Congenital heart disease (CHD) is the most common congenital defect. About one third of the CHD cases will have a duct-dependent anomaly that is potentially life-threatening if not detected before birth.Aims: To assess the sensitivity for detecting structural malformations and chromosome anomalies by a routine ultrasound either in gestational week 11-14 or 18-20. To estimate the influence of a high Body Mass Index (BMI) in detecting fetal structural anomalies by ultrasound. To evaluate the possibility for introducing a more accurate fetal cardiac ultrasound screening based on five different transverse views and color Doppler. To determine if the risk-estimate for trisomy 21 from the screening procedure varies over BMI strata and if obesity is associated with an increased risk of Down syndrome in the offspring.Material and methods: Outcome measures from 21189 consecutive ultrasound examinations in the first and second trimester were analyzed and compared. The fetal anomaly diagnoses were also grouped in four BMI-groups. Then, a two-day course in examining of the fetal heart was given, analyzed and followed up. To evaluate the effect of BMI on the combined screening, 10224 patients were divided in six BMI categories. Outcomes were evaluated over BMI strata. The possibility of an association between maternal obesity and Down syndrome was analyzed in a nationwide cohort of 1568604 women giving birth in Sweden.Results: At the first trimester scan 13% of all anomalies were detected vs 29% in the second trimester. For aneuploidy the corresponding results were 71% vs 42%, and for lethal anomalies 88% vs 92%. If divided into BMI-groups 26% of the malformations were detected in the group of normal weight women compared to 19% among the obese. For malformations with long-term handicap the corresponding figures were 46% vs 27%. After the course in examination of the fetal heart uncertainty was lower and the familiarity with the new technique was enhanced. The ability to perform the new method remained at follow up. In the combined screening, the observed and expected number with a risk of Downs syndrome >1/300 were similar in each BMI-group. Obese women had an increased risk of giving birth to an infant with Downs syndrome compared with normal weight women.Conclusions: There was an advantage to the scan in the second trimester discovering malformations overall and an advantage to the early scan concerning aneuploidy. Lethal malformations were detected at a high level in both groups. The detection rate seemed lower for the obese women. In the screening for Down syndrome, the risk-estimate is unaffected by BMI. Detection of heart malformations needs improvement. By implementing new image modalities and providing hands-on training uncertainty in examining the fetal heart can be reduced.
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| 4. |
- Hobbins, Jennifer
(författare)
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Samhälle, individ och ansvar : En studie om synen på arbetslöshet
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the thesis is to highlight and to problematize conceptions of unemployment in Swedish society. The questions guiding my work have been: Which conceptions of unemployment emerge in society? How are these dealt with by the unemployed? Work on the thesis has been guided by a social constructionist approach. The empirical findings are constituted by four publications which, in various ways, are linked to overarching aim of the thesis. These publications consist of an analysis of the legal regulation surrounding the unemployed, a study of the activities of civil society organisations working with unemployed and two publications based on interviews with long-term unemployed young adults.The thesis provides increased knowledge of conceptions of unemployment in Swedish society. It shows that there is a widespread societal discourse concerning the individual being responsible for her/his unemployment, and that this conception has historically been well-grounded in Swedish labour market and social policy, as well as in people’s understandings. Among representatives of civil society organisations and unemployed individuals, there is also both a questioning of and a resistance to this understanding, indicating a possible change in the discourse. The thesis further shows that the individualisation of responsibility greatly affects individuals’ approaches in social contexts, as well as in their contacts with government agencies, but also when it comes to relationships with politics and political involvement. These insights are significant, for example during both policy formulation and efforts for the unemployed, bearing in mind that consideration needs to be paid to individual prerequisites in order for the individual’s strengths and abilities to be utilized. This is particulary important when it comes to those in an exposed position.
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