Vuorokaudenaikaan sidottu vaihtelu kesy- ja villisikojen melatoniinirytmeissä

Summary: Circadian melatonin rhythms of the European wild boar and domestic gilts

Maantieteen rytmit

Kirjallisuusarvostelu

NADPH-Dependent Thioredoxin System In Regulation of Chloroplast Functions

Photosynthesis, the process in which carbon dioxide is converted into sugars using the energy of sunlight, is vital for heterotrophic life on Earth. In plants, photosynthesis takes place in specific organelles called chloroplasts. During chloroplast biogenesis, light is a prerequisite for the development of functional photosynthetic structures. In addition to photosynthesis, a number of other metabolic processes such as nitrogen assimilation, the biosynthesis of fatty acids, amino acids, vitamins, and hormones are localized to plant chloroplasts. The biosynthetic pathways in chloroplasts are tightly regulated, and especially the reduction/oxidation (redox) signals play important roles in controlling many developmental and metabolic processes in chloroplasts. Thioredoxins are universal regulatory proteins that mediate redox signals in chloroplasts. They are able to modify the structure and function of their target proteins by reduction of disulfide bonds. Oxidized thioredoxins are restored via the action of thioredoxin reductases. Two thioredoxin reductase systems exist in plant chloroplasts, the NADPHdependent thioredoxin reductase C (NTRC) and ferredoxin-thioredoxin reductase (FTR). The ferredoxin-thioredoxin system that is linked to photosynthetic light reactions is involved in light-activation of chloroplast proteins. NADPH can be produced via both the photosynthetic electron transfer reactions in light, and in darkness via the pentose phosphate pathway. These different pathways of NADPH production enable the regulation of diverse metabolic pathways in chloroplasts by the NADPH-dependent thioredoxin system. In this thesis, the role of NADPH-dependent thioredoxin system in the redox-control of chloroplast development and metabolism was studied by characterization of Arabidopsis thaliana T-DNA insertion lines of NTRC gene (ntrc) and by identification of chloroplast proteins regulated by NTRC. The ntrc plants showed the strongest visible phenotypes when grown under short 8-h photoperiod. This indicates that i) chloroplast NADPH-dependent thioredoxin system is non-redundant to ferredoxinthioredoxin system and that ii) NTRC particularly controls the chloroplast processes that are easily imbalanced in daily light/dark rhythms with short day and long night. I identified four processes and the redox-regulated proteins therein that are potentially regulated by NTRC; i) chloroplast development, ii) starch biosynthesis, iii) aromatic amino acid biosynthesis and iv) detoxification of H₂O₂. Such regulation can be achieved directly by modulating the redox state of intramolecular or intermolecular disulfide bridges of enzymes, or by protecting enzymes from oxidation in conjunction with 2-cysteine peroxiredoxins. This thesis work also demonstrated that the enzymatic antioxidant systems in chloroplasts, ascorbate peroxidases, superoxide dismutase and NTRC-dependent 2-cysteine peroxiredoxins are tightly linked up to prevent the detrimental accumulation of reactive oxygen species in plants.

”Du sköna sång, vårt bästa arv” - kanonisering av en sångskatt ur ett hermeneutiskt perspektiv

Songs have the power to get through to people. When lyrics are combined with a tune, the result is an entity where the first few notes of a melody can evoke emotions of recognition and belonging. A song treasury consists of such songs that are part of a canonized song tradition. The process where certain songs become part of an established song treasury is long, and many other aspects than the tune itself influence the forming of a song treasury. By examining the characteristics of a song tradition, the history of an ethnic group can be illuminated. In this study, music, pedagogy, and the sociocultural context are merged into a whole where a common song tradition, the song treasury, is in focus. The main aim of this study is to deepen the understanding of a song treasury, its development and contents. This understanding is accomplished by analyzing the musical and lyrical characteristics of 60 songs, which have been sung in schools, homes, and communities, thereby becoming popular among the Swedish-speaking Finns during the 20th century. The songs have been chosen by combining three song lists, of which two lists are closely related to school curricula. The third song list is a result of a survey on favourite songs, according to the situation around year 2000. The songs are examined in their notated versions, a number of song books and text books (n = 29) forming the empirical material. In this study, a hermeneutical approach is applied, content analysis being the method. The analysis is based on three perspectives: the sociocultural perspective, the music-pedagogical perspective, and the musico-analytical perspective. Within each perspective, two aspects are studied. This results in a hexagonal model which forms the structure of the study as a whole. The first two perspectives form the background; a historical context where nation, education, home country, and homestead are regarded as highly important. A common song repertoire is considered to be an effective means of building collective identity within ethnic groups, the common language and the cultural heritage being used as rhetorical arguments. During the early 1900s, choir festivals become an educational platform where conceptions of a common belonging are developed and strengthened through religious, patriotic, and poetical expressions. National school curricula in singing and music have similar characteristics, cultural heritage and values education being in focus. The song lyrics often describe nature and emotions, and they also appear to be personal and situated in a given time and place. Patriotic expressions and songs about music are also fairly common. The songs generally express positive attitudes, which are intensified by major tonality, rich and varied melodies with stable rhythms, and a strong tonal base. The analyzed details of the studied aspects are merged into a thick description, which results in an interpretation pattern with three dimensions: a song treasury can be considered an expression of collective identity, cultural heritage, and values education.

Diel patterns and tissue-specificity of environmental responses in fish

Humans are profoundly changing aquatic environments through climate change and the release of nutrients and chemicals. To understand the effects of these changes on natural populations, knowledge on individuals’ environmental responses is needed. At the molecular level, the environmental responses are partly mediated by chances in messenger RNA and protein levels. In this thesis I study messenger RNA and protein responses to an assortment of environmental stressors in fish. As daily (diel) rhythms are known to be ubiquitous in different tissues, I particularly focus on diel patterns in the responses. The studied species are the three-spined stickleback (Gasterosteus aculeatus L.) and the Arctic char (Salvelinus alpinus L.), both of which have circumpolar distribution in the Northern hemisphere. In the first two studies, three-spined sticklebacks were exposed to both the non-steroidal anti-inflammatory drug diclofenac and low-oxygen conditions (hypoxia), and their responses measured at separate time points in the liver and gills. The results show how the seemingly unrelated environmental stressors, hypoxia and anti-inflammatory drugs, can have harmful combined effects that differ from the effects of each stressor alone. Moreover, both stressors disturbed natural diel patterns in gene expression. In the third study, I studied the responses of three-spined sticklebacks to two test chemicals: one used in hormonal medicine (17α-ethinyl-oestradiol) and one used as a plasticizer and solvent chemical (di-n-butyl phthalate). The results suggest that the phthalate can affect genes related to spermatogenesis in fish testes, while estrogen-mimicking compounds can lead to numerous disturbances in the endocrine system. In the final study, the temperature-dependence of diel rhythms in messenger RNA levels were evaluated in the liver tissue of the Arctic char, a cold-adapted salmonid. The results show that cold acclimation repressed diel rhythms in gene expression compared to warm-acclimated fish, in which the expression of hundreds of genes was rhythmic, suggesting the circadian clock of the Arctic fish species can be sensitive to temperature. Overall, the results of the thesis indicate that fishes’ responses to abiotic factors interact with their diel rhythms, and more studies on the consequences of these interactions are needed to comprehensively understand human impacts on ecosystems.