Transformation of inorganic mercury (Hg) to methyl mercury (MeHg) is a biotic process that is proposed to be conducted primarily by sulphate reducing bacteria (SRB). The formation of MeHg is of great interest because it is the mercury species that biomagnifies to the greatest extent in the aquatic food webs; about 90 % of all Hg in fish is MeHg. Our understanding of factors involved in the production of MeHg is very important for making a reliable risk assessment. The purposes of this study were to investigate the different factors that control the solubility of Hg and the production of MeHg in a contaminated lake sediment. The lake Ala-Lombolo, Kiruna municipality, is well-known to be contaminated by mercury from different sources. Sediment cores were sampled at three different locations (N, SW and SE) in the lake and divided in three different layers; 0-5, 5-10 and 10-15 cm.

The limit for mercury in fish, set by health authorities, is exceeded in about half of the lakes in Sweden. Methyl mercury (MeHg) is the most toxic form of mercury and accumulates in fish. Therefore transformation of inorganic mercury (Hg) to methylmercury (MeHg) is an important process that we need to understand in order to possibly counteract the negative effects of mercury in the environment. The seasonal dynamics of mercury biogeochemistry is likely of great importance for the accumulation of MeHg in the aquatic food web. In thesis the chemical speciation and transformations of Hg and MeHg in bottom waters and sediments is followed in Ängessjön, a small lake located on the east coast in the middle of Sweden. The lake is not directly affected by any industrial pollution and concentrations of Hg in the sediment reflect the atmospheric deposition in this area, as well as processes taking place along the hydrological pathways from soil to lake. Samples from sediment, bottom- and streamwater were collected in average every second month during the period Feb.

Mammary tumors are the most frequent type of tumors in bitches in Sweden. Many studies have been published concerning mammary tumors, but there is still much to be learned about this disease. One has, since some time ago, had the knowledge that addition to or removal of methyl groups to genes can inhibit or activate gene-expression. Methylation and deMethylation is a normal phenomenon in the body and it is essential for the development and survival of the individual. The risk of developing a tumor disease is increased if the global Methylationstatus is changed; if oncogenes demethylates (activates) or if tumor suppressor genes methylates (inactivates). In the human medicine one has seen that there are differences in Methylationstatus between different tumors. In this study tumor and normal tissue from ten dogs were examined with regard to Methylationstatus.

The aim of this master thesis was to examine a possible connection between chromatin functions and the DNA damage repair system, with the imprinted IGF2/H19 locus as a bait. Interactions can occur within and between chromosomes and it has been shown that H19 ICR on both alleles can communicate with alleles on other chromosomes. The Methylation-sensitive insulator protein CTCF is bound on the maternal H19 ICR and acts as an insulator by blocking the IGF2 promoter to access its enhancers. This is possible by formation of loop structures by CTCF that enables intra and inter-chromosomal interactions. CTCF is poly(ADP-ribosyl)ated by PARP-1 when it is bound to H19 ICR.

This study was conducted at the University of Bath, UK, from September to December 2014 as part of an ongoing research project aimed at elucidating how the Grb10 gene might act as a mediator of long-term health effects (such as predisposition to obesity, diabetes, coronary heart disease and hypertension) caused by environmental factors during development. This phenomenon is known as developmental programming. The purpose of this thesis was not primarily to answer any of the broader questions posed by this research project at large since this would require much more data than is reasonable to acquire over the course of a few months, but rather to evaluate the methods used in this project and reveal whether they are working the way they are presumed to. In the research project, which employs mice with the Grb10 gene knocked out as well as wild-type control mice, a dietary restriction model is utilized during gestation, which is supposed to generate offspring with lower birth weight and subsequent detrimental health effects in adulthood. This is supposed to be achieved by restricting the protein content of the pregnant mothers? diet to 9 % (as opposed to the control diet of 20 %) throughout gestation.

High levels of Hg in fish in Swedish lakes have been a problem along time in Sweden. The major concern is production and accumulation of the most toxic form of mercury; methyl mercury (MeHg). Consequently, in about half of our 83 000 lakes fish contain concentrations above the recommended limit for human consumption of 0,5 mg mercury per kg fresh weight (most of it in the form of MeHg). Consumption of fish containing too high levels of MeHg may cause problems for both humans and animals. Three major sources of MeHg in surface waters are: 1) runoff from terrestrial areas, 2) deposition from the atmosphere, and 3) internal production of MeHg in lakes and streams. The aim of this study was to investigate the effect of clear-cutting on the concentration of Hg and MeHg into draining streams.