From genes to communities : stress tolerance in eelgrass (Zostera marina)

Shallow coastal areas are dynamic habitats that are affected by a variety of abiotic and biotic factors. In addition to the natural environmental stress, estuarine and coastal seagrass ecosystems are exposed to effects of climate change and other anthropogenic impacts. In this thesis the effect of different abiotic (shading stress, salinity and temperature) and biotic stressors (presence of co-occurring species) and different levels and combinations of stressors on the performance and survival of eelgrass (Zostera marina) was assessed. To investigate the importance of scale for stress responses, varying levels of biological organization (genotype, life stage, population and plant community) were studied in field and aquarium experiments. Light limitation, decreased salinity and increased temperature affected eelgrass performance negatively in papers I, II and III, respectively. While co-occurring plant species had no notable effect on eelgrass in paper IV, the presence of eelgrass increased the biomass of Potamogeton perfoliatus. The findings in papers II and III confirmed that more extreme levels of salinity and temperature had stronger impacts on plant performance compared to intermediate levels, but intermediate levels also had more severe effects on plants when they were exposed to several stressors, as illustrated in paper II. Thus, multiple stressors had negative synergetic effects. The results in papers I, II and III indicate that future changes in light climate, salinity and temperature can have serious impacts on eelgrass performance and survival. Stress responses were found to vary among genotypes, life stages and populations in papers I, II and III, respectively, emphasizing the importance of study scale. The results demonstrate that while stress in general affects seagrass productivity negatively, the severity of effects can vary substantially depending on the studied scale or level of biological organization. Eelgrass genotypes can differ in their stress and recovery processes, as observed in paper I. In paper II, eelgrass seedlings were less prone to abiotic stress compared to adult plants, but stress also decreased their survival considerably. This indicates that recruitment and re-colonization through seeds might be threatened in the future. Variation among population responses observed in paper III indicates that long-term local adaptation under differing selection pressures has caused divergence in salinity tolerance between Baltic eelgrass populations. This variability in stress tolerance observed in papers I and III suggests that some eelgrass genotypes and populations have a better capacity to adapt to changes and survive in a changing environment. Multiple stressors and biological level-specific responses demonstrate the uncertainty in predicting eelgrass responses in a changing environment. As eelgrass populations may differ in their stress tolerance both within and across regions, conservation strategies at both local and regional scales are urgently needed in order to ensure the survival of these important ecosystems.

Temporomandibular Disorders and Headache in Adolescents

13-16-vuotiaiden purentaelimistön toimintahäiriöt ja päänsärky Tutkimuksen tarkoituksena oli selvittää purentaelimistön toimintahäiriöihin (TMD) liittyvien oireiden ja kliinisten löydösten esiintyvyyttä ja muutosta kolmen vuoden seurannan aikana päänsärystä kärsivillä nuorilla ja heidän verrokeillaan, TMD-löydösten yhteyttä eri tyyppisiin päänsärkyihin ja päänsärkyyn liittyviin tekijöihin, TMD-löydöksiä ennustavia tekijöitä sekä perhetaustan osuutta TMD-löydösten esiintyvyyteen. Tutkimus perustui kahteen laajaan koululaismateriaaliin Turun seudulla. Ensimmäinen 13-vuotiaiden nuorten ryhmä (n = 311) osallistui myös 16-vuotiaana seuranta-tutkimukseen. Toisen 13-vuotiaiden nuorten ryhmän (n = 154) äidit (n = 154) osallistuivat myös tutkimukseen, jossa selvitettiin tapaus-verrokkiasetelmassa TMD-löydösten ja päänsärkyjen esiintyvyyttä kahdessa sukupolvessa. Nuoret jaettiin päänsärkyryhmiin ja terveisiin kontrolleihin IHS (1988) päänsärky-kriteerien mukaisesti kyselykaavakkeen ja lääkärin suorittaman haastattelun ja kliinisen tutkimuksen antamien tietojen perusteella. Lääkäri määritteli äitien päänsärkydiagnoosin kyselykaavakkeen tietojen perusteella. Kaikki nuoret ja heidän äitinsä haastateltiin ja heille tehtiin kliininen purentafysiologinen tutkimus sokkoutetusti. Tutkimuksen tulokset osoittivat, että tytöillä esiintyi TMD-löydöksiä selvästi enemmän kuin pojilla sekä ennen puberteettia että sen jälkeen. Tutkimuksessa havaittiin selkeä yhteys TMD-löydösten ja molempien päänsärkytyyppien, migreenin ja episodisen tensiotyyppisen päänsäryn, välillä. Kolmen vuoden seurannan aikana TMD-löydöksissä havaittiin runsasta muutosta ja iän myötä vähenemistä, mutta TMD-oireiden kohdalla ei vastaavaa muutosta todettu. TMD-löydösten ja niska-hartiaseudun lihaskipujen välillä havaittiin yhteys 13-vuotiailla nuorilla. Mikään päänsärkyyn liittyvistä tekijöistä 13-vuotiailla ei osoittautunut ennustavaksi taustatekijäksi myöhemmille TMD-löydöksille. TMD-löydösten suhteen ei todettu perheyhteyttä. Päänsäryistä kärsivillä nuorilla on enemmän myös muita kiputiloja, kuten purentaelimistön toimintahäiriöitä ja niska-hartiaseudun kipuja, kuin heidän terveillä verrokeillaan. 1316 vuoden iässä nämä löydökset ovat valtaosaltaan lieviä ja vaihtelevia.

Gut Microbiota and Metabolic Disorders

Obesity and its co-morbidities, such as metabolic syndrome (MetS), non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes, have increased over the last few decades like an epidemic. So far the mechanisms of many metabolic diseases are not known in detail and currently there are not enough effective means to prevent and treat them. Several recent studies have shown that the unbalanced gut microbiota composition (GMC) and activity have an influence on the fat accumulation in the body. Further, it seems that the GMC of obese individuals differs from the lean. The aim of this study was to investigate whether there are differences between the GMC of metabolically impaired overweight/obese (MetS group), metabolically healthy overweight/obese and normal-weight individuals. In addition, the mechanisms by which the gut bacteria as well as their specific structures, such as flagellin (FLG) that stimulates the Toll-like receptor 5 (TLR5) affect metabolism, were investigated both in vivo and in vitro in human adipocytes and hepatocytes. The results of this study show that the abundance of certain gram-positive bacteria belonging to the Clostridial cluster XIV was higher in the MetS group subjects compared to their metabolically healthy overweight/obese and lean counterparts. Metabolically impaired subjects tended to also have a greater abundance of potentionally inflammatory Enterobacteria in their gut and thus seemed to have aberrant GMC. In addition, it was found that subjects with a high hepatic fat content (HHFC group) had less Faecalibacterium prausnitzii in their gut than individuals with low hepatic fat content. Further gene expression analysis revealed that the HHFC group also had increased inflammation cascades in their adipose tissue. Additionally, metabolically impaired individuals displayed an increased expression of FLG-recognizing TLR5 in adipose tissue, and the TLR5 expression levels associated positively both with liver fat content and insulin resistance in humans. These changes in the adipose tissue may further contribute to the impaired metabolism observed, such as insulin resistance and dyslipidemia. In vitro -studies showed that the FLG-induced TLR5 activation in adipocytes enhanced the hepatic fat accumulation by decreasing insulin signaling and mitochondrial functions and increasing triglyceride synthesis due to increased glycerol secretion from adipocytes. In conclusion, the findings of this study suggest that it may be possible that the novel prevention and personalized treatment strategies based on GM modulation will succesfully be developed for obesity and metabolic disorders in the future.