Bio- ja ympäristötieteellinen tiedekunta

 

Nyligen publicerat

  • Tauscher, Petra (Helsingin yliopisto, 2018)
    The variety of species in the animal kingdom notwithstanding, early embryogenesis frequently relies on the same set of molecules. These highly conserved molecules are considered genetic toolkit genes; a set of genes that determines the body plan in various species. For example, the determination of the dorsal-ventral (D/V) axis often relies on bone morphogenetic proteins (BMPs). Studies in various organisms, vertebrates as well as invertebrates, established that the BMP signaling network is crucial for localizing the position of the central nervous system. Given that the same set of molecules is used repeatedly in different species, the question of how animal diversity could evolve arises. In this study, I focused on BMP signaling in the fruit fly Drosophila melanogaster. In Drosophila, BMP signaling takes place at various stages of development. Amongst others, it is crucial for D/V patterning of the early embryo, for growth and patterning of the larval wing imaginal disc, as well as for formation of longitudinal and posterior crossveins (PCV) in the pupal wing. The Drosophila genome contains three BMP-type ligands, Decapentaplegic (Dpp), a BMP2/4 type ligand, and the paralogs Screw (Scw) and Glass bottom boat (Gbb), both of which are BMP5-8-type ligands. Interestingly, Scw is exclusively found in higher Dipterans such as Drosophila, and is expressed only in the early embryo, whereas Gbb is repeatedly used during fly development. Previous studies revealed that Scw can replace Gbb in PCV formation in the pupal wing. On the other hand, Gbb cannot function in the context of early embryogenesis. Based on these facts, Gbb and Scw constitute a highly suitable model to study protein divergence and evolution. Here, I examined how post-translational modifications of BMP-type ligands may affect the signaling outcome, and hence, animal development; the focus was on proteolytic processing and N-glycosylation. BMP-type ligands are produced as inactive pro-proteins and need to be proteolytically processed in order to become mature ligands. Scw has two cleavage sites crucial for fly viability. I showed in a cell–based signaling assay that proteolytic processing of both cleavage sites is needed for rapid, peak-level BMP signaling. Furthermore, there exists one highly conserved N-glycosylation motif in the mature BMP ligand domain. In addition, Scw exhibits a unique N-glycosylation site which is not present in other BMP-type ligands. Cell culture-based signaling assays revealed that both N-glycosylation motifs of Scw ligand are needed for peak level signaling. In addition, lack of N-glycosylation motifs negatively affects the BMP signaling outcome in the early embryo, as well as fly viability. In contrast, fewer N-glycosylations appear to be beneficial in the context of PCV formation. These findings suggest that post-translational modifications of BMP ligands play a role in signal transduction and therefore in animal development. Furthermore, I propose that post-translational modifications can act as flexible modules to allow adaption of conserved molecules to different developmental contexts. Besides, understanding how post-translational modifications affect BMP signaling outcome may improve the chances to develop more signaling-efficient BMPs needed in clinical applications.
  • Mätlik, Kärt (Helsingin yliopisto, 2018)
    The human genome contains approximately 20,000 protein-coding genes and tens of thousands of genes for non-coding RNA. Understanding the function of these genes in a living organism is crucial for learning about key processes in early development, mechanisms of organ function and human behavior. Importantly, many human diseases are caused by abnormal gene expression. Therefore, understanding the causes and pathological processes behind these disorders could provide means for early diagnosis, prevention or treatment. The main aim of this thesis was to develop new strategies for studying gene function and regulation in experimental animals. The techniques described in this work allow increasing gene expression specifically in those cell types, which naturally express the gene. The results presented in this thesis suggest that increasing gene expression in correct physiological context may potentially have widespread applications in basic biological studies and for understanding human disease.
  • Gui, Jinghua (Helsingin yliopisto, 2018)
    In this thesis, I mainly investigate how BMP/Dpp signaling is involved in development of the early pupal wing of Drosophila, and the mechanisms coupling Dpp signaling with morphogenesis.
  • Lume, Maria (Helsingin yliopisto, 2018)
    Neurotrophic factors are small secretory proteins with important functions both in the nervous system and in peripheral tissues. Glial cell line-derived neurotrophic factor (GDNF) is best known for its ability to support the survival of midbrain dopaminergic neurons and enteric neurons. Also, GDNF is essential for the development of kidney and testis. It has been shown that both the absence and excessive amounts of GDNF protein negatively regulate kidney morphogenesis, highlighting the importance of proper spatiotemporal regulation of GDNF. Despite the wealth of knowledge regarding GDNF functions both in and outside the nervous system, relatively little is known about the trafficking mechanisms of GDNF. GDNF is synthesized as a precursor protein, proGDNF. In this thesis, we characterized the cellular localization and secretion of two GDNF splice variants, pre-(α)pro-GDNF and pre-(β)pro-GDNF, that differ in their pro-regions. Both precursor forms were shown to be secreted from cell lines. However, while (α)pro-GDNF co-localized mainly with the Golgi markers, the (β)pro-GDNF was found primarily in the secretogranin-II positive vesicles of the regulated secretory pathway. In accordance, the two splice isoforms responded differently to KCl-induced depolarization that is known to trigger the secretion of neurotrophin family members in neuronal cells. Only (β)pro-GDNF and corresponding mature GDNF were secreted activity-dependently, whereas (α)pro-GDNF and its corresponding mature GDNF were secreted via the constitutive secretory pathway. In addition, we determined which enzymes are responsible for the proteolytic cleavage of proGDNF into mature GDNF. To elucidate, whether secreted proGDNF has any biological activity, the recombinant cleavage-resistant proGDNF mutant protein was expressed in mammalian CHO cells and next purified from the media. Our results demonstrate that proGDNF is biologically active. Furthermore, similarly to mature GDNF, proGDNF can signal via the GDNF receptor α1/RET receptor tyrosine kinase complex and activate downstream MAPK and AKT pathways. Interestingly, proGDNF is not able to activate RET via the GFRα2 receptor. Finally, we identified a novel sorting receptor for GDNF and its receptors. Our results show that SorLA, a member of the vacuolar protein sorting 10-p domain receptor family, can internalize GDNF and GFRα1. While GDNF is subsequently degraded in lysosomes, GFRα1 is recycled back to the cell membrane. In the presence of SorLA and GFRα1, also RET is internalized and directed to early endosomes. By regulating the availability of GDNF and its co-receptors, SorLA can inhibit GDNF-induced neurotrophic activity in SY5Y cells. Moreover, SorLA seems to regulate intracellular localization of GFRα1 in hippocampal neurons. In summary, results of this thesis characterize the cellular regulation of GDNF regarding its secretion, processing, internalization and subsequent degradation. Furthermore, this is the first time that biological functions of the GDNF precursor protein proGDNF are described. Our findings indicate that the trafficking of GDNF is very different from that of other neurotrophic factors, and in contrast to apoptotic proneurotrophins, proGDNF is a trophic protein with increased specificity to GDNF receptor complex GFRα1-RET.
  • Rosa, Elena (Helsingin yliopisto, 2018)
    Variation in biotic and abiotic ecological factors unavoidably shapes the life history of living organisms. The ability to integrate environmental cues and respond adequately can mark the difference between life and death. Phenotypic plasticity consists of a rapid response to variation in environmental variables, and it entails the ability of one genotype to generate multiple phenotypes over an environmental gradient. However, the degree of plasticity a phenotypic trait can display is limited by physiological and ecological constraints, which may impose trade-offs on other traits. Insects are an excellent system to explore phenotypic plasticity, because of their presence at all ecosystem levels making them important bio-indicators, and their occurrence in large numbers with a fast generation time making them optimal study subjects. The aim of this thesis is to uncover the degree of phenotypic plasticity in immunity and life-history traits displayed by a butterfly occurring in the temperate zone, the Finnish Glanville fritillary (Melitaea cinxia), in response to variation in the following ecological factors: food quality, larval density, susceptibility to a pupal parasitoid, food limitation and exposure to cold spells. The ecological factors were tested on different life stages of the butterfly, based on their ecological relevance. Particular importance is given to potential trade-offs among life-history traits, with special attention to the immune response. The immune system entails a complex of processes and structures that are activated any time insects interact with their environment, and hence its regulation and maintenance are costly. Therefore, extremely plastic immune responses may not be optimal. The study approach involved a combination of laboratory manipulation of the ecological factors tested, collection of observational data of adult life history and mobility in a semi-natural enclosure, and three different immune assays (encapsulation rate, phenoloxidase activity and immune gene expression). Interactions with two components of the natural community were also included: the host plant pathogen powdery mildew (Podosphaera plantaginis), and the generalist pupal parasitoid wasp Pteromalus apum. Key findings include a poorer performance of larvae fed on a diet including powdery mildew, and the upregulation of two immune genes on the same diet. This suggests that larvae feeding on infected host plants may pay a twofold cost of poor nutrient intake and unnecessary immune activation, potentially due to interaction with the plant pathogen. Moreover, larvae reared in high density showed a better performance and a greater ability to kill brood members of a pupal parasitoid wasp, which, however, did not help butterfly survival. This finding indicates that larvae of this species benefit from group living and do not suffer from stressful interactions in absence of food limitation. Further, a trade-off between pupal investment in the encapsulation immune response and adult mobility was detected, indicating potential costs of immunity in regard to expensive activities such as flight. Finally, cold spells during the pupal stage induced an increased melanisation of adult wings. In males, this response also led to a strong immune reaction to a bacterial challenge and markedly reduced lifespan, suggesting a condition-dependent cost of immunity. The findings indicate that the immune system is affected to some extent by most of the factors tested, but the degree of plasticity displayed may be constrained by costs arising from indiscriminate immune activation.
  • Aarnio-Linnanvuori, Essi (Helsingin yliopisto, 2018)
    This doctoral dissertation discusses environmental education integrated into social school subjects and the challenges of teaching a cross-curricular, value-laden topic, with a data-set consisting of school textbooks and teacher interviews. The study concentrates on environmental education in school subjects of Lutheran religion, secular ethics, history, social studies, and geography. This is a qualitative study, where the main analysis methods were abductive content analysis and phenomenological analysis. The findings reveal difficulties in constructing suitable environmental subject-matter for social school subjects, originating from the wicked nature of environmental problems, especially climate change. The analyzed textbooks gave little space for environmental issues, and they included inaccurate information. Both textbook authors and social subject teachers seemed to have difficulties in recognizing the specific environmental content of their own disciplines. However, some interviewees had found such perspectives to environmental issues that draw on their discipline, and were able to use it for promoting critical thinking. Enthusiasm towards the topic and professional agency seemed to promote success in interdisciplinary education. The interviewees presented different perspectives to teaching value-laden issues. Some preferred neutrality, some aimed for plurality in educational discussion, and some preferred educational advocacy. Self-confidence and an identity as a value educator seemed to support pluralist education and educational advocacy. In addition, the findings support the view that that environmental education often concentrates too much on promoting insignificant individual behaviors. Even though the interviewees were well aware of significant environmental behaviours, they viewed their pupils’ range of action possibilities as narrow. Current school practices and traditions do not support environmental action integrated in school work. Based on the results, I suggest that collective responsibility be promoted in environmental education, and practitioners should develop easy options for youth participation. Key words: environmental education, interdisciplinarity, crosscurricular education, environmental responsibility, critical thinking, environmental citizenship
  • Raissadati, Alireza (Helsingin yliopisto, 2018)
    Heart transplantation is often the last resort for end-stage heart disease. Despite increasing success in this medical field, transplant recipients remain at significant risk for both early and late allograft failure. The cascade of events leading to heart transplant rejection are initiated by donor brain death, progress throughout ex vivo preservation of the organ, are exacerbated during reperfusion, and culminate in cardiac allograft vasculopathy (CAV). The aim of this thesis was to evaluate the efficiency of adeno-associated virus (AAV) as a vector for gene therapy of the heart transplant, elaborate on the role of vascular endothelial growth factor B (VEGF-B) in heart transplant ischemia-reperfusion injury (TX-IRI) and hypoxia-inducible factor (HIF) in the inflammatory properties of allograft-infiltrating myeloid-derived cells. The long-term kinetics and safety of AAV serotypes 2, 8, and 9 were evaluated by perfusing the coronary tree of rat heart transplants with each serotype and comparing the reporter gene expression at set time-points and inflammatory response at the end-point of the study. We studied the role of VEGF-B in ischemia-reperfusion injury of cardiac allografts by transgene- and AAV-mediated overexpression of VEGF-B in rat cardiac allografts. The significance of HIF as an immunoregulatory switch in myeloid-derived cells was determined by using transgenic mice with myeloid cell-targeted activation or knock-out (KO) of HIF-1α and -2α as heart transplant recipients. We found that AAV2 was most effective in transducing heart transplants after intracoronary injection, whereas AAV9 was most effective when injected systemically into the transplant donor. Adeno-associated virus serotype 9 caused a mild inflammatory response in cardiac allografts, whereas AAV2 and 8 did not. Chronic, but not short-term, VEGF-B overexpression in rat cardiac transplants resulted in cardiomyocyte hypertrophy and higher energy demands, with subsequent higher susceptibility towards TX-IRI. HIF-1α and -2α activation in recipient myeloid cells established an immunoregulatory phenotype that significantly suppressed both TX-IRI and acute rejection and prolonged allograft survival. Our results highlight the importance of the route of administration on heart transplant AAV gene therapy and suggest AAV2 as the preferred vector for intracoronary perfusion and AAV9 for systemic delivery in experimental rat heart transplant models. Vascular endothelial growth factor B may regulate heart energy demand and thus might play an important role in transplant ischemic tolerance. Hypoxia-inducible factor-1α and -2α act as important switches for the immunoregulatory phenotype of myeloid cells, and may offer a viable therapeutic target to alleviate allograft rejection.
  • Svensson, Jonas (Helsingin yliopisto, 2017)
    Snow and ice are essential components of the Earth system, modulating the energy budget by reflecting sunlight back into the atmosphere, and through its importance in the hydrological cycle by being a reservoir for fresh water. Light-absorbing impurities (LAI), such as black carbon (BC) and mineral dust (MD), have a unique role in influencing the reflectance of the cryosphere. Deposition of the anthropogenic and natural LAI constituents onto these bright surfaces initiates powerful albedo feedbacks that will accelerate melt. This is important globally, but especially for regions such as the Arctic and the Himalaya. In this thesis, observations from both ambient and laboratory experiments are presented. The overarching research goal has been to better understand the climatic effect of LAI on snow. More specifically, an emphasis has been placed on exploring the process-level interactions between LAI and snow, which will enable better comprehension of LAI affecting the cryosphere. Key findings in this thesis involves the investigations on the horizontal variability of BC concentrations in the surface snow that indicate a larger variability on the order of meter scale at a pristine Arctic site compared to a polluted site nearby a major urban area. In outdoor experiments, where LAI were used to artificially dope natural snow surfaces, the snow albedo was observed to decrease following LAI deposition. The albedo decrease was on the same order as in situ measurements of LAI and albedo conducted elsewhere. As snow melted during the experiment, the snow density was observed to decrease with increasing LAI concentration, while this effect was not observed in non-melting snow. The water retention capacity in melting snow is likely to be decreased by the presence of LAI. Measurements examining the absorption of BC indicate that BC particles in the snow have less absorbing potential compared to BC particles generated in the laboratory. The LAI content of snow pit investigations from two glaciers in the Sunderdhunga valley, northern India, an area not previously examined for LAI, presented high BC and MD content, affecting the radiative balance of the glacier snow. At different points, MD may be greater than BC in absorbing light at the snow surface. A continued monitoring of LAI in the cryosphere, both on the detailed scale explored here, as well as on the larger modelling perspective is needed in order to understand the overall response of the cryosphere to climate change.
  • Lehtimäki, Jenni (Helsingin yliopisto, 2017)
    Biodiversity on earth is threatened and already drastically decreased due to anthropogenic actions. The ravenous utilization of natural resources has reached the point of payback in the forms of climate change, diseased crops, and disturbed water cycles. Obviously, these changes influence wellbeing of mankind. Besides these measurable problems, an invisible world, which covers all surfaces on earth, is altering. Loss of diversity in macroscopic organisms is repeated at the level of micro-organisms, many of which may have disappeared before ever described. The human body is a lively ecosystem hosting millions of microbial organisms, which together form the microbiota. These bacterial, viral, fungal, and other microscopic residents are faced with our immune system, challenging their survival. However, the relationship between the host and the residents is often not hostile, but in most cases reciprocal. Actually, the human immune system has partly shared the responsibility of immune-regulation with commensals. This evolved dependency between human and microbial residents highlights that several health problems may arise if this ancient collaboration is disturbed. Indeed, numerous inflammatory diseases coincide with disturbed host microbiota. These diseases, such as allergies, asthma, inflammatory bowel disease, and cancers, have increased rapidly since recent modernization of human habitats and lifestyle. Still, in traditional farming and hunter-gatherer communities allergies are almost absent. The biodiversity hypothesis, which is the concept tested in this thesis, suggest that change in the invisible world can seriously increase morbidity in human populations. This hypothesis states that the destruction of natural environments has altered our contact with microbial world, which can disturb our immune function, potentially leading to the development of inflammatory diseases. In this thesis, the emphasis is on the effect of exposure to environmental microbes, via the living environment and lifestyle, on health; central factors suggested by the biodiversity hypothesis. The key results from four separate projects, which are based on new datasets, are following. (I) Skin microbiota differs between rural and urban newborns and children. In teenagers this difference disappears, probably due to lifestyle-related changes. (II) Children who attend to nature-oriented outdoor-daycares have considerably more diverse skin microbiota than children in other daycares. However, their life differs in many ways from that of other children, indicating also the importance of lifestyle. (III) In the canine model, the prevalence of allergies is clearly lower in rural environments, also when the effect of dog-breed is controlled. Finally, (IV) the exposure to environmental microbes in residential environment, and through lifestyle, are concurrently related to the skin microbiota and allergies in the canine model. This thesis suggests the importance of living environment and lifestyle, which jointly influence the individual’s contact with environmental microbes, for health. Therefore, the human living environments, and the residing biodiversity in those, can either promote or disrupt human health. Currently, accumulating evidence projects that exposure to green environments, farms, children and animals, basically to all factors that increase microbial exposure directly or indirectly, are beneficial for human health. My thesis adds to this by showing interrelations between microbial exposure, microbiota and allergies. Therefore, people, especially children, and their fellow-animals, should increase their contact with diverse environments and lifeforms in order to support both microbial and immunological balance in their bodies. Finally, natural environments provide yet again one more invaluable ecosystem service, which should be recognized and protected.
  • Salomaa, Anna (Unigrafia, 2017)
    Scientific knowledge shows compelling evidence of intensifying global environmental problems such as biodiversity loss and climate change. Unfortunately, this knowledge has not been directly translated into actions that would have reversed these worrying trends. The effectiveness of conservation, i.e. its ability to produce a desired result, is the outcome of interaction between knowledge and policy process. Efforts have recently been made to use existing scientific knowledge to combine current policy instruments and to develop new innovative approaches to conservation. In this PhD thesis I empirically study the perspectives of various actors and their roles in topical Finnish conservation efforts: green infrastructure, voluntary forest conservation and conflicting peatland policy. I examine how different knowledge types and policy instruments contribute to conservation effectiveness. The study utilizes an expert survey, focus groups, combining multiple methods using the case study approach, and integrating social and ecological data. The results illustrate how actors may interpret differently complex concepts, such as ecosystem services and ecological connectivity; the use of these concepts may even be politically coloured. Ambiguity concerning the definition of green infrastructure may create obstacles for practical implementation. In the peatland conservation policy case, where actors’ interests differed, implemented policy instruments did not match existing knowledge. The role of other knowledge types along with ecological knowledge may be more important when designing voluntary rather than compulsory instruments, because participation to voluntary actions needs to be attractive. The collaboration of actors is an integral part of increasing conservation efforts in the voluntary conservation. Interaction and valuation of various knowledge types may have a complicating effect on conservation practices, but different knowledge types can be integrated for more effective results. The study shows that policies should be designed in a way that allows the practical application of knowledge. The study elucidates what kind of challenges and opportunities for increasing effectiveness are faced in different phases of a policy process. I argue that the use of scientific evidence must be combined with the usage of other knowledge types and involvement of various actors. In addition, potential interest differences of actors should be considered when planning participation. In this way a combination of policy instruments can be developed, which simultaneously increases evidence uptake, acceptance and effectiveness leading to a more sustainable future.
  • Le Tortorec, Anniina (Helsingin yliopisto, 2017)
    Phytoplankton constitute the basis of food webs and are responsible for almost all photosynthesis in the open sea. Occasionally, given suitable conditions, one phytoplankton species can increase in abundance and form a mass occurrence known as a bloom. Harmful Algal Blooms (HABs), in turn, can have adverse effects on the ecosystem, for example causing oxygen depletion, clogging of fish gills, or toxicity. HABs are common in shallow and stratified coastal waters and the number, frequency and coverage of areas affected by HABs are increasing globally mainly due to eutrophication, changes in nutrient ratios and global climate change. One of the main phytoplankton groups forming HABs are dinoflagellates. Among dinoflagellates the genus Alexandrium is particularly notorious with many species in this genus producing a variety of potent neurotoxins. Dinoflagellates are the only known photosynthetic organisms that can produce bioluminescence and the majority of bioluminescence in marine surface waters is produced by dinoflagellates. Bioluminescence in dinoflagellates is considered a defensive mechanism against grazing and many harmful dinoflagellate taxa produce bioluminescence. The dinoflagellate Alexandrium ostenfeldii forms dense bioluminescent blooms in shallow and sheltered areas of the Baltic Sea during the late summer. These blooms pose a potential threat to humans and ecosystems in the region due to observed production of toxins. The distribution and abundance of A. ostenfeldii is poorly known in the coastal waters of the Baltic Sea. The aim of this thesis was to study the variability of A. ostenfeldii bioluminescence production to evaluate whether bioluminescence can be used as an early warning signal of harmful dinoflagellate blooms in the Baltic Sea. More precisely, the aim was to study the expression of A. ostenfeldii bioluminescence to learn how much genetic, phenotypic and environmentally induced variability there is in bioluminescence production in the species. Studies conducted on luciferase genes and bioluminescence emission showed that bioluminescence is a prominent feature in Baltic A. ostenfeldii. Measurements on individual cell cultures and natural populations revealed large daily and seasonal variation in bioluminescence emission relating to the circadian rhythm in bioluminescence expression and seasonal changes in A. ostenfeldii abundance. Large intraspecific variation in bioluminescence production was observed in response to changes in temperature and salinity. A. ostenfeldii abundance, toxin concentrations and bioluminescence intensity were positively correlated in our field data. All tested A. ostenfeldii strains produced both bioluminescence and toxins and it can be assumed that concurrent production of both is a predominant property in Baltic A. ostenfeldii. The obtained results show that it is possible to relate bioluminescence to A. ostenfeldii bloom succession using automated measurements. However, the highly-localized distribution of blooms may require advance knowledge of potential bloom locations to be able to target the monitoring efforts. Species distribution modelling showed promise to address this problem by identifying potentially suitable habitats for A. ostenfeldii.
  • Piirainen, Mikko (Helsingin yliopisto, 2017)
    The subfamily Salicornioideae (Amaranthaceae) consists of 11 genera and c. 100 species of obligatory halophytes with a reduced morphology mainly in coastal and inland salt marshes from tropical mangroves to the subarctic. The plants are succulent, often with articulated stems and highly reduced leaves and flowers. This, together with their phenotypic plasticity, has caused much confusion in the morphology-based taxonomy. The study starts with the morphology, taxonomy and nomenclature of the genus Salicornia in northern Europe, extends to cover the whole Eurasian continent and use of molecular data and finally proceeds to a comprehensive DNA-based phylogeny and phylogeography of the subfamily. The new taxonomy of the annual Eurasian Salicornia presented aims to reflect a plausible phylogeny, using monophyly as the main criterion. Several taxa with a limited geographical distribution are neither supported in the molecular analysis nor morphologically separable and are thus placed in synonymy. On the other hand, unresolved clades, cryptic speciation and the fact that all involved taxa were not available in the molecular analysis offer a challenge for future studies. The monophyly of Salicornioideae is confirmed by the phylogenetic analysis. Five clades are found: 1) Kalidium, 2) Halopeplis, 3) Halocnemum/Halostachys and 4) Allenrolfea/Heterostachys. 5) The remainder of the subfamily forms the fifth clade, in which Eurasian Arthrocnemum macrostachyum, Microcnemum, the North American Arthrocnemum subterminale and Tecticornia form an unresolved polytomy. Sarcocornia and Salicornia form a monophyletic clade in which the American and Eurasian species of Sarcocornia and Salicornia respectively form well-supported clades. The Southern and Eastern African and Australian Sarcocornia are moderately supported. Salicornioideae probably originated in Eurasia during the late Eocene to early Oligocene. The divergence of the early main clades took place in the middle Oligocene. Long-distance dispersal has taken place several times to the Americas, South Africa and Australia. An updated generic classification of Salicornioideae is proposed with two main novelties: 1) the two species of Arthrocnemum are separated and described as two different genera, Arthrocaulon and Arthroceras, 2) Sarcocornia is treated as congeneric with Salicornia. In addition, all Australian plants are treated under Tecticornia as proposed earlier by Australian researchers. For Salicornia a new infrageneric classification is proposed to accommodate the four phylogenetically and geographically well-supported lineages within the genus.
  • Kinaret, Pia (Helsingin yliopisto, 2017)
    Nanotechnology and engineered nanomaterials (ENM) are providing outstanding innovations in several fields of science and technology, spanning from medicine to aeronautics. However, some ENM are known to be harmful to humans and the environment, thus, their toxic potential need to be thoroughly tested. The production of ENM is drastically increasing, making traditional toxicity testing impractical and in some cases impossible. The classical hazard assessment involves extensive animal exposures, which are not applicable to vast growing number of novel nanomaterials. Their unique properties and behaviour in biological entities are differing from their bulk sized counterparts, making predictions of the effects difficult. Thus, new efficient and rapid methods need to be developed for nanomaterial toxicity testing and hazard assessment. The main ENM exposure route to humans is through airways. Studying the effects of nanoparticles and their toxic potential on the airways is hence necessary for creating a comprehensive understanding of the ENM-induced phenotypic, cellular and molecular changes. Inhalation exposure to murine models is considered as the state of the art method for studying the pulmonary responses. This expensive and laborious method is not practical for testing all nanomaterials with all the relevant doses. In another airway exposure method, the oropharyngeal aspiration, the ENM are introduced to the airways of test animals as a liquid dispersion under anesthesia. The aspiration method is debated, since the anesthesia and the dispersion might cause additional effects and responses. In the first part of this thesis, these two different airway exposure methods were compared, aiming at understanding whether the easier and faster oropharyngeal aspiration method could substitute the time-consuming and expensive whole-body inhalation method. The conjecture was indeed valid, as both methods showed similar outcomes at cellular and molecular level in response to rigid multi-walled carbon nanotubes after four-day exposure. Since the ongoing effort in reducing laboratory animal testing in hazard assessment as well as for faster and simpler testing, methods for replacing animals are being examined also by in vitro exposures. Cell exposures are even more argued, since they do not resemble the comprehensive responses of an animal and even less of the human organism, where different cell types are interacting and communicating in very intricated manner. Novel computational methods are being developed to mine the large exposure datasets for finding relevant features, that would explain and predict the human responses to ENM from in vitro and in vivo exposures. In the second part of the thesis, the possibility to interpret the complicated pulmonary responses by examining the transcriptional patterns of human macrophages and mouse lungs when exposed to carbon nanomaterials (CNM) were investigated. Gene co-expression networks revealed specific molecular patterns related to distinct properties of the CNM, namely aspect ratio, length, diameter and surface area, but which were common between in vitro and in vivo. These results aid the establishment of systems toxicology approaches in ENM hazard assessment and the shift from the classical, animal-based hazard assessment towards predictive models, ultimately supporting the development of new “safe-by-design” nanomaterials (safe design, safe production, and safe use).
  • Jonsson, Martina (Helsingin yliopisto, 2017)
    The red mold Fusarium, is a fungal pathogen, infecting mainly small-grain cereals in the temperate regions of the world. In Scandinavia, F. avenaceum, F. culmorum, F. poae, and F. sporotrichioides infections are most common, but in recent years F. graminearum and F. langsethiae infections have increased, as well. Most Fusarium species are capable of producing a variety of mycotoxins, possibly providing an edge over competing strains at the site of infection. Mycotoxins can evoke a broad range of toxic effects in humans and animals, including neurotoxicity, immunotoxicity, reproductive-, and developmental toxicity and carcinogenicity. The most toxic fusariatoxins include the tricothecenes, fumonisins and zearalenone. However, less studied mycotoxins, as enniatins (Enns) and moniliformin (MON) are frequently found in grain products, hence, causing a risk of a daily, low-level exposure of human and livestock, the significance of which is still unclear. The aim of this study was to provide further insights into the toxicity of Enns and MON, and into the mechanism of action of EnnB, monitored at gene expression level. Furthermore, the acute oral toxicity and repeated, low-dose, oral toxicity of MON in Sprague-Dawley rats was assessed, adapting OECD Guidelines 423 and 407. We report clear toxic outcomes of EnnB in vitro, as it affected cellular energy metabolism by reducing ATP levels in cell cultures and cell proliferation, already at low concentrations (below 10 μM) in the cell lines Balb 3T3 and HepG2. EnnB exposure slightly increased the proportion of early apoptotic cells, as well. Gene expression studies revealed alteration of energy metabolism, due to effects on gene expression of genes associated with mitochondrial organization and function and assembly of complex I of the electron transport chain. Moniliformin (MON) did not induce significant toxicity in vitro. However, high doses of MON (50 mg/kg b.w.) caused acute toxicity in rats, seen as cardiovascular changes and respiratory distress, resulting in death. According to the OECD Globally Harmonized System, the toxicity of MON could be classified into category 2, and a LD50 cut of value of 25 mg/kg b.w. was determined. Long term, low dose exposure affected mainly the innate immunity, by reducing the phagocytic activity of rat neutrophils in all tested groups. Hence, a LOAEL of 3 mg/kg b.w. for MON was suggested. The rats of the lowest dose groups (3-6 mg/kg b.w.) remained clinically healthy. Two rats of five in the highest dose group (15 mg/kg b.w.) showed similar signs as in the acute oral toxicity test and died. Excretion kinetics revealed that MON is rapidly excreted in urine, in less than 6 h, but only 1-2% was found in feces. This indicates that the urinary excretion is the main route for elimination.
  • Gateva, Gergana (Helsingin yliopisto, 2017)
    The ability of cells to migrate, adhere, and contract is an essential feature, governing basically every process in the human body. These include fundamental functions such as development, muscle contraction, immune responses, wound healing, and a plethora of diseases including cancer metastasis, vascular diseases, and cardiomyopathies. Contractile actomyosin bundles are the central cellular structures, which enable the cell to perform all these processes, and thus it is crucial to understand how such structures are assembled in cells. Assembly of actomyosin bundles both in non-muscle and in muscle cells is regulated by a multitude of proteins, acting synchronously in a fascinating complexity. Many aspects of this process have remained mysterious, because of the sheer number of the involved actin-binding proteins, the intricate signalling pathways, and the complexity of the underlying interactions. This thesis aimed at understanding of some of the fundamental processes behind the assembly of contractile structures in non-muscle cells (human osteosarcoma cells U2OS), and in heart muscle cells (primary rat cardiomyocytes). Previous studies revealed that contractile actomyosin bundles in U2OS cells, called ventral stress fibers, are generated from a network of precursors, named dorsal stress fibers and transverse arcs. This work revealed that the tropomyosin family proteins (Tpm) play central role in stress fiber assembly. Our studies on U2OS cells indicate that four functionally distinct tropomyosins orchestrate stress fiber assembly. Tpms 1.6/1.7, Tpm 2.1, and Tpms 3.1/ 3.2 stabilize specific stress fiber regions. In contrast, Tpm 4.2 regulates the recruitment of myosin II to diaphanous (Dia) 2 formin-nucleated actin filament population in stress fiber precursors. Our in vitro experiments revealed that these tropomyosin isoforms possess an intrinsic ability to segregate to different actin filaments and bind F-actin with distinct dynamics. Our results revealed that these tropomyosins determine some of the biochemical properties of actin filaments, such as their ability to associate with non-muscle myosin II and actin depolymerizing factor (ADF)/cofilin. Additionally, our studies demonstrated that the interaction between palladin and vasodilator-stimulated phosphoprotein (VASP) promotes dorsal stress fiber assembly. In contrast, the tension generated by transverse arcs inhibits this process. Tension also controls the length of ventral stress fibers and inhibits ADF/cofilin-mediated stress fiber disassembly. Furthermore, our studies in primary rat cardiomyocytes revealed that ADF/cofilins are also crucial for the length regulation and proper function of muscle sarcomeres. Collectively these studies reveal important biochemical and mechanobiological principles that regulate the assembly of contractile actin bundles in non-muscle and in muscle cells.