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  • Nieminen, Mikko (Helsingin yliopisto, 2014)
    Cancers of the upper digestive tract (oral, pharyngeal, laryngeal, oesophageal and stomach) are among the ten most common cancers worldwide and are associated with high mortality and morbidity. Despite improved treatment strategies, the prognosis of these cancers remains poor. The main aetiological factors for the upper digestive tract cancers are alcohol consumption and smoking. Dietary and genetic factors can also contribute to an increased risk. Alcohol consumption, smoking and poor oral hygiene all lead to exposure of the upper digestive tract mucosa to salivary acetaldehyde. Ethanol is not carcinogenic, but acetaldehyde, its first metabolite, is. The International Agency for Research on Cancer has classified acetaldehyde associated with alcoholic consumption as a group I carcinogen. Cigarette smoke contains acetaldehyde, as does saliva after alcohol intake. Microbially fermented food products can also contain high levels of acetaldehyde. Therefore, salivary acetaldehyde levels are a result of its direct intake as well as systemic, local and microbial ethanol metabolism. The ability of the mucosa and microbes to remove acetaldehyde has been shown to be limited. Chronic Candida mucositis is associated with oro-oesophageal carcinogenesis. Candida yeasts are common colonisers of the upper digestive tract, with an extraordinary ability to form biofilms. Candida albicans is the dominant species in health and disease. The biofilm structure protects fungal cells against hostile actions, and infections are mainly biofilm-related. This is highlighted by high resistance to antifungals by yeast biofilms. Fungal cells can become dispersed from a biofilm, making it a constant source of infection. In immunocompromised patients, this process can lead to fatal systemic infections. The similarity of fungal and human cells makes the development of antifungals difficult, and treatment is often compromised. The primary aim of the research presented in this thesis was to investigate the ability of clinically important Candida yeasts to produce carcinogenic acetaldehyde in planktonic and biofilm modes of growth in vitro. Fermented milk mursik constitutes a major part of the diet in western Kenya, an area with a high local incidence of oesophageal cancer and a low prevalence of common risk factors. The second aim was to identify the microbiota of the starter cultures used for the production of mursik. The ability of these mixed cultures of bacteria and yeast to produce acetaldehyde and ethanol was assessed in a fermentation experiment. Finally, the potential anti-biofilm and anti-inflammatory effect of a Lactobacillus metabolite, 2-hydroxyisocaproic acid (HICA), was explored in vitro and in vivo. HICA has previously shown efficacy against various planktonically grown microbes. The results of the research presented in this thesis demonstrate that C. albicans biofilms can produce mutagenic levels of acetaldehyde when incubated with ethanol and glucose at clinically relevant concentrations. In addition, planktonic C. albicans and non-albicans Candida (NAC) species produce significant levels of acetaldehyde in the presence of ethanol. C. glabrata shows a unique ability among NAC species to produce mutagenic acetaldehyde in the presence of sugars. Interestingly, the production of acetaldehyde by Candida species can be significantly reduced by the sugar alcohol xylitol. Highly mutagenic levels of acetaldehyde and ethanol can be measured during the production of mursik. Candida yeasts are associated with high acetaldehyde and ethanol production during fermentation. C. albicans biofilm formation is significantly reduced in response to HICA treatment in vitro. Interestingly, certain genes belonging to the fermentative pathway and acetaldehyde metabolism are highly up-regulated under stress and during biofilm formation. An attenuated inflammatory response was observed when a C. albicans biofilm was treated with HICA in vivo. Overall, these results underline the significant potential of clinically relevant Candida yeasts to produce carcinogenic acetaldehyde. Colonisation of the upper digestive tract with Candida spp. could expose the mucosa to mutagenic levels of acetaldehyde in the presence of alcohol and dietary sugars. This could play a role in the carcinogenesis associated with Candida infection. In addition, the consumption of fermented food products such as mursik, with a high acetaldehyde and ethanol content, could elevate the risk of cancer. HICA could provide a safe and efficient approach to treat biofilm-related Candida infections and reduce the inflammation and mutagenicity associated with C. albicans biofilms.
  • Rikula, Ulla Kaisa (Helsingin yliopisto, 2008)
    Canine distemper (CD) is one of the longest-known infectious diseases of dogs and many other carnivores. Control of CD among dogs relies heavily on vaccination, while in fur farms and zoos biosecurity measures in some cases offer the only available means for CD control. Modified live CD virus vaccines have been successfully used to control CD among farmed mink, and since no licensed vaccines for other species kept for fur exist, they have also been used for foxes and raccoon dogs in CD emergency situations. CD vaccines for dogs and mink were studied in experimental settings for their ability to induce virus-neutralising (VN) antibodies in target species. Mink vaccines were also assessed in silver foxes, blue foxes and raccoon dogs. Purpose-bred beagle dogs were vaccinated twice with one of three CD vaccines: Candur® SHP, Canlan®-3 or Dohyvac® DA2P, and the levels of VN antibodies were determined at the time of vaccination and one month after the second vaccination. Fur animals were vaccinated once with Distemink®, Distem®-R-TC or vaccine 3 and the levels of VN antibodies were determined at vaccination and 2-4 times 1-4 months afterwards. Significant differences among vaccine groups were found both in the proportion of animals with measurable levels of VN antibodies and in the mean titres of antibodies. The levels of VN antibodies were also determined from a large field sample (n = 4 627) of vaccinated dogs. In addition to the three CD vaccines in the seroconversion study above, additional two vaccines, Duramune®-4 and Nobivac® DHP, had been used in the field. Each dog with a known vaccination history, date of birth, sex and breed was sampled once. Based on the overall geometric mean titre of the dogs vaccinated with a single vaccine brand, vaccines were divided into high-take (Candur®, Nobivac® and Duramune®) and low-take (Dohyvac® and Canlan®) groups. The vaccine groups differed significantly among dogs less than two years of age both in the proportion of dogs with detectable VN antibodies and in the mean titres. Both the number of vaccinations and age were associated with the titre and vaccine usage. To control for possible confounding factors, the comparison of titres among vaccine usage groups was adjusted by classifying them according to the number of vaccinations (one to four) and the age group (less than one, one to two, or over two years old). The same division into low- and high-take vaccines was observed, irrespective of the number of vaccinations the dogs had received. The observations of this seroprevalence study regarding Candur®, Canlan® and Dohyvac® were consistent with the results of the seroconversion study. CD was reintroduced into Finland in 1990 after 16 years of absence. The disease remained at a low endemic level in 1990-1994, reached epidemic proportions in 1994-1995 and disappeared during 1995. The epidemic also involved vaccinated dogs. Among the virologically-confirmed cases the proportion of Dohyvac®-vaccinated dogs was higher than expected from the market shares on the assumption that all the vaccines had an equal take. As a result of this observation, Dohyvac® was withdrawn from and Nobivac® and Duramune® introduced to the market during 1995. A drastic redistribution of the market shares between the low-take and high-take vaccines took place, and this coincided with the decline and dying out of the outbreak. The observed occurrence pattern of CD from 1990-1996 was largely attributed to the changes in the level of HI, although the possible contribution of other factors, such as developments in the dog demographics, was also recognized. It was concluded that an HI above 75% is needed to keep CD in check, i.e., only sporadic cases of CD, at most, can occur. With the currently used vaccines an HI of 80% corresponds to a vaccine coverage of some 94%. It was concluded that the development of vaccine-induced immunity is a multifactorial process depending on the properties of the vaccine, on the individual variation, age, species and other factors influencing the immunocompetence of the host. On the individual level the prevention of clinical signs is sufficient, but on the population level, halting the circulation of the virus is crucial for the definitive control of CD. The ultimate test and criterion for a vaccine is its contribution to herd immunity.
  • Laurila (os. Heikkilä), Henna (Helsingin yliopisto, 2015)
    Canine idiopathic pulmonary fibrosis (CIPF) is a chronic interstitial lung disease of unknown origin mainly affecting West Highland white terriers (WHWT). No curative treatment exists. Differentiating CIPF from other chronic respiratory diseases is difficult. Therefore, a measurable biomarker would be helpful. CIPF shares clinical features with human idiopathic pulmonary fibrosis (IPF), but the histopathological resemblance of the two diseases has been unclear. We described the clinicopathological and diagnostic imaging findings in dogs with CIPF and compared them with those of healthy WHWTs. The most typical clinical signs were cough and exercise intolerance. Inspiratory Velcro crackles were characteristic and an abdominal breathing pattern was often present. Many dogs were hypoxemic. Bronchointerstitial opacity was the most common radiographic finding. In high resolution computed tomography, ground glass opacity was a consistent feature, whereas honeycombing and traction bronchiectasis were less common. Bronchoalveolar lavage fluid (BALF) total cell count was elevated in CIPF and bronchial changes were common. We investigated the serum and BALF concentrations of two potential fibrosis biomarkers, endothelin-1 (ET-1) and procollagen type III amino terminal propeptide (PIIINP) in dogs with CIPF, chronic bronchitis (CB), eosinophilic bronchopneumopathy (EBP) and healthy dogs. Serum ET-1 was higher in dogs with CIPF than in other groups. BALF ET-1 was measurable only in dogs with CIPF. BALF PIIINP was higher in dogs with CIPF than in dogs with CB or healthy dogs, but not different from dogs with EBP. Serum PIIINP was not useful. We defined the histopathological lesions and their distribution in WHWTs with CIPF and compared them with those of human usual interstitial pneumonia (UIP), which is the histopathological pattern of human IPF, and human nonspecific interstitial pneumonia (NSIP), which is an important differential diagnosis of human IPF. A diffuse mature interstitial fibrosis of varying severity, resembling human NSIP, was seen in the lungs of all CIPF dogs. The majority of CIPF dogs also had multifocal areas of accentuated subpleural and peribronchiolar fibrosis with occasional honeycombing and profound alveolar epithelial changes, reminiscent of human UIP. Interstitial fibroblastic foci, characteristic of UIP, were not seen in WHWTs. In this thesis we provide a detailed description of the clinicopathologic and diagnostic imaging features of CIPF and present quantitative values for arterial blood gases and BALF cytology. Serum ET-1 and BALF PIIINP are elevated in dogs with CIPF and could differentiate CIPF from CB. Histopathologically, CIPF is characterised by two types of interstitial fibrosis and shares features of both human UIP and NSIP.
  • Lilja-Maula, Liisa (Helsingin yliopisto, 2014)
    Canine idiopathic pulmonary fibrosis (CIPF) is an incurable fibrosing lung disease occurring mainly in West Highland White Terriers (WHWTs). The clinical picture of CIPF has many similarities with human idiopathic pulmonary fibrosis (IPF). Signs include dry cough, exercise intolerance, and respiratory difficulties. Prognosis for CIPF and human IPF is poor, and only limited treatment options are available. Histopathological CIPF shares features of both human usual interstitial pneumonia (UIP), the pathological counterpart of human IPF, and other human idiopathic interstitial pneumonia, the non-specific interstitial pneumonia (NSIP). Chronic bronchitis (CB) is the main differential diagnosis for CIPF, but antemortem differentiation can be challenging, as surgical lung biopsies are seldom taken and no clinically useful biomarkers are currently available. The natural history of CIPF has not been previously studied and little is known about the molecular pathophysiology of CIPF. This thesis describes the clinical course, survival, and evaluation of exercise intolerance using the 6-minute walk test in CIPF WHWTs. Bronchoalveolar lavage fluid (BALF) protein expression was studied to find potential biomarkers for CIPF, and aspects of transforming growth factor (TGF)-β related molecular pathways in pathogenesis of CIPF were investigated. In addition, results of TGF-β signaling activity and its known extracellular matrix (ECM) regulatory proteins, latent TGF-β binding protein (LTBP)-1 and fibrillin-2, in CIPF were compared with findings in human IPF/UIP and NSIP. The follow-up study showed that CIPF has a significant negative impact on life expectancy of diseased dogs. The median CIPF-specific survival after onset of clinical signs in WHWTs was 2.7 years, but individual survival varied considerably from only a few months to over 4 years. This variance indicates that CIPF may have either a slow or a rapid disease progression, as also seen in human IPF. In addition, during the disease course acute exacerbations (AEs) occurred. The 6-minute walk distance proved to be an easy and noninvasive parameter to evaluate lung function and level of exercise intolerance in CIPF WHWTs. No significant prognostic factors were identified. The quantitative comparison of BALF proteomes obtained from CIPF WHWTs, CB dogs, and healthy dogs revealed similar changes for CIPF and CB, which suggests a common response to disease processes in these otherwise different lung diseases. Specific biomarkers for CIPF were not identified. The immunohistochemical stainings suggested that increased TGF-β signaling and its ECM regulatory proteins LTBP-1 and fibrillin-2 are part of the molecular pathophysiology of CIPF, as also seen in human IPF/UIP and NSIP. We demonstrated strong expression of activin B, a member of the TGF-β superfamily, in the altered alveolar epithelium of WHWTs with CIPF. Furthermore, activin B was detected in BALF of CIPF WHWTs, most notably in samples from dogs with AE, but not in BALF of healthy WHWTs. This novel finding suggests that activin B is part of the CIPF pathophysiology and might act as a potential marker of alveolar epithelial damage. Our findings add important new knowledge about the natural history and molecular pathophysiology of CIPF in WHWTs and show similarities between CIPF and human IPF. Better understanding of the complex pathogenesis of CIPF and human IPF is crucial for developing novel diagnostic tools and treatment strategies for these yet incurable diseases.
  • Ahonen, Saija (Helsingin yliopisto, 2014)
    The availability of the genome sequence and genomic tools combined with the unique phenotypic diversity and breed structure has increased interest in dog as a large, physiologically relevant animal model for human genetic research. Dogs suffer from hundreds of hereditary conditions of which many resemble closely disorders in humans. Investigation of the genetic background of these conditions is important to understand the disease mechanisms and pathways for therapeutic options, to identify novel candidate genes for corresponding human conditions, and to inform the breeding programs. Remarkable resources have been established in the University of Helsinki for canine genetic research, including one of the largest canine DNA banks. This study has focused on degenerative eye diseases of unknown genetic cause. We combined efforts in basic and clinical veterinary research with a unique network of collaboration with dog breeders and owners to establish clinically relevant study cohorts for two types of retinal degeneration in Papillon and Phaléne, and in Swedish Vallhund, SV breeds and two different types of glaucoma in Dandie Dinmont Terriers, DDT and Norwegian Elkhounds, NE. Genome wide approaches with the latest genomic tools, including SNP arrays and exome sequencing were then utilized to identify causative loci and genes. We report breakthroughs in all projects and highlight shared molecular etiologies in canine and human vision disorders. The cause of the retinal degeneration in Papillons and Phalénes was found in the CNGB1 gene, which is important for the rod cell function and has been linked before to human retinal degenerations. A unique type of multifocal retinal degeneration was described in SV with association to the upregulation of the MERTK gene. MERTK mutations cause also retinal degeneration in humans. DDTs were found to present a primary closed angle glaucoma (PACG) with severe pectinate ligament dysplasia (PLD). The disease was mapped to a region on canine chromosome 8, which is syntenic to human chromosome 14 with multiple glaucoma loci. However, further studies are required to identify the causative mutation. Finally, we found that the primary glaucoma in NEs is caused by a missense mutation in the ADAMTS10 gene. This gene has been associated with a Weill-Marchesani syndrome (WMS) with ocular and non-ocular abnormalities in humans. This study provides new candidate genes, and mechanisms for human eye disorders, and has identified models for potential therapeutic trials. At the same time breeding programs benefit from novel gene tests to eradicate the blinding conditions from the studied breeds.
  • Lukkarinen, Vaula (Helsingin yliopisto, 2014)
    Northern white cedar (Thuja occidentalis L.) (NWC) swamps are valuable both commercially and ecologically. Unfortunately, many NWC swamps are degraded and information about them is not abundant. Especially there have been no definitive studies about mosses in northern white cedar swamps and how they react to disturbances. Mosses are sensitive to changes in their environment and thus they could be used to assess ecosystem conditions of NWC swamps. The objective of this study was to determine if mosses could be used to asses conditions in NWC swamps and if there are differences between moss communities in disturbed and undisturbed sites. Seventeen sample plots were taken from 12 disturbed and undisturbed sites around upper Michigan and northern Minnesota in the summer of 2012. All mosses occurring on the plots were identified and several associated environmental parameters were measured. The main environmental conditions affecting moss communities were identified with non-metric multidimensional scaling (NMS). Multiple response permutation procedures (MRPP) were run to ascertain if there were significant differences in community composition between disturbances. Indicator species analysis was then done to identify species that are related to different types of disturbances. A one-way ANOVA was used to check for significant differences between species richness and moss cover of undisturbed and disturbed sites. Over all sixty-two moss species were identified. The results indicate that there was no significant difference in species richness or moss cover between disturbed and undisturbed sites. However, moss community composition was affected by disturbance and strongly divided by a wetness gradient. Dicranum fuscescens was found to indicate undisturbed conditions. Calliergon cordifolium and Climacium dendroides indicated disturbed sites with wet conditions. Brotherella recurvans and Eurhynchium pulchellum indicated swamps with other disturbances.
  • Schultner, Eva (Helsingin yliopisto, 2014)
    In complex societies like ant colonies individuals cooperate in the aim of maximizing offspring production. But cooperation is only flawless from afar. In fact, because adults can differ in their relatedness to brood they often have contrasting inclusive fitness interests, which may lead to outbreaks of social conflict. However, although conflicts in ant colonies typically arise over offspring production, the role of offspring as actors in social conflict has received little attention. The primary aim of this thesis was to investigate the role of larvae in ant societies, with particular emphasis on selfish larval behavior in the form of egg cannibalism. This thesis demonstrates that Formica ant larvae readily engage in egg cannibalism. Egg consumption allows larvae to increase survival and positively affects the expression of key growth-related genes. Levels of cannibalism across species decrease when relatedness between larvae and eggs is high, which suggests that cannibalism is a selfish trait that can underlie social control. Cannibalism appears to be plastic in F. aquilonia, where levels increase when larvae are presented with foreign eggs compared to sibling eggs. In addition, cannibalism intensity is highly dependent on larvae sex and size across eight species. I conclude that ant larvae are far from powerless. Instead, cannibalism may allow larvae to influence important determinants of individual fitness such as caste fate or size. By consuming eggs, larvae may furthermore affect overall colony fitness. For the first time, this thesis identifies larvae as individuals with selfish interests that have the power to act in social conflict, thus adding a new dimension to our understanding of colony dynamics in social insects. In order to understand how relatedness between individuals potentially impacts conflict in ant societies on a larger scale, this thesis furthermore focuses on the genetic network of native wood ant populations. The societies of these ants consist of many interconnected nests with hundreds of reproductive queens, where individuals move freely between nests and cooperate across nest boundaries. The combination of high queen numbers and free mixing of individuals results in extremely low relatedness within these so-called supercolonies. Here, cooperative worker behavior appears maladaptive because it may aid random individuals instead of relatives. I use network analysis to test for spatial and temporal variation in genetic structure, in order to provide a comprehensive picture of genetic substructure in native wood ant populations. I find that relatedness within supercolonies is low but positive when viewed on a population level, which may be due to limited dispersal range of individuals and ecological factors such as nest site limitation and competition against conspecifics. Genetic network analysis thus provides novel evidence that ant supercolonies can exhibit fine-scale genetic substructure, which may explain the maintenance of cooperation in these low-relatedness societies. Overall, these results offer a new perspective on the stability of cooperation in ant societies, and will hopefully contribute to our understanding of the evolutionary forces governing the balance between cooperation and conflict in other complex social systems.
  • Laakkonen, Johanna (2008)
    The study explores the first appearances of Russian ballet dancers on the stages of northern Europe in 1908 1910, particularly the performances organized by a Finnish impresario, Edvard Fazer, in Helsinki, Stockholm, Copenhagen and Berlin. The company, which consisted of dancers from the Imperial Theatres of St. Petersburg, travelled under the name The Imperial Russian Ballet of St. Petersburg. The Imperial Russian Ballet gave more than seventy performances altogether during its tours of Finland, Sweden, Denmark and central Europe. The synchronic approach of the study covers the various cities as well as genres and thus stretches the rather rigid geographical and genre boundaries of dance historiography. The study also explores the role of the canon in dance history, revealing some of the diversity which underlies the standard canonical interpretation of early twentieth-century Russian ballet by bringing in source material from the archives of northern Europe. Issues like the central position of written documentation, the importance of geographical centres, the emphasis on novelty and reformers and the short and narrow scholarly tradition have affected the formation of the dance history canon in the west, often imposing limits on the historians and narrowing the scope of research. The analysis of the tours concentrates on four themes: virtuosity, character dancing, the idea of the expressive body, and the controversy over ballet and new dance. The debate concerning the old and new within ballet is also touched upon. These issues are discussed in connection with each city, but are stressed differently depending on the local art scene. In Copenhagen, the strong local canon based on August Bournonville s works influenced the Danish criticism of Russian ballet. In Helsinki, Stockholm and Berlin, the lack of a solid local canon made critics and audiences more open to new influences, and ballet was discussed in a much broader cultural context than that provided by the local ballet tradition. The contemporary interest in the more natural, expressive human body, emerging both in theatre and dance, was an international trend that also influenced the way ballet was discussed. Character dancing, now at low ebb, played a central role in the success of the Imperial Russian Ballet, not only because of its exoticism but also because it was considered to echo the kind of performing body represented by new dance forms. By exploring this genre and its dancers, the thesis brings to light artists who are less known in the current dance history canon, but who made considerable careers in their own time.
  • Närhi, Katja (Helsingin yliopisto, 2012)
    Although mammary glands and hair are morphologically and functionally different organs, they share similar early developmental features and arise from ectoderm like other skin appendages. Their development begins by the formation of an epithelial placode and a mesenchymal dermal condensate and crosstalk between these tissue compartments directs the subsequent developmental steps resulting in epithelial morphogenesis and the generation of specific organ shapes. Different types of hair filaments are observed in various anatomical regions and are produced by hair follicles consisting of several epithelial cell layers and a dermal papilla. The mammary gland is constructed of a nipple rising above the skin and the glandular mammary tree producing milk. Both organs continue development postnatally; new hair is produced by repeated hair cycles lasting throughout the lifetime and postpubertal mammary ductal tree is remodelled upon pregnancy and following lactation and involution. Handful of conserved signaling pathways guides both the embryonic and postnatal developmental steps of skin appendages. Hair and mammary gland development are especially known to depend on signals from the -catenin-mediated Wnt pathway. The Wnt pathway is highly complex with multiple ligands, receptors and signaling modulators, and cross-talk with other signaling pathways is apparent. Here, I have examined the role of Wnt signaling in hair and mammary gland patterning and development and its relationship to other signaling molecules within this context. The study has involved three different mouse models in which Wnt signaling is modulated either by continuous activation of -catenin, inactivation of the Wnt and Bmp pathway regulator Sostdc1, or ablation of a Wnt target gene, Fgf20. Continuous Wnt/-catenin signaling in embryonic ectoderm in Catnbex3K14/+ mice caused precocious hair development and, the formation of ectopic and mispatterned hair placodes showing disturbed morphogenesis and hair filament formation. Fgf20-null mice showed a surprisingly early hair phenotype with a loss of expression of several dermal condensate markers but presence of grossly normal morphological patterning of placodes with altered placode marker expression patterns. Loss of Sostdc1 had very mild effects on pelage hair development but interestingly, Sostdc1 appears to play a role in determing correct vibrissal hair and nipple number and the regulation of mammary bud size/form, plausibly through inhibiting Wnt signaling.
  • Launiainen, Samuli (Helsingin yliopisto, 2011)
    Interaction between forests and the atmosphere occurs by radiative and turbulent transport. The fluxes of energy and mass between surface and the atmosphere directly influence the properties of the lower atmosphere and in longer time scales the global climate. Boreal forest ecosystems are central in the global climate system, and its responses to human activities, because they are significant sources and sinks of greenhouse gases and of aerosol particles. The aim of the present work was to improve our understanding on the existing interplay between biologically active canopy, microenvironment and turbulent flow and quantify. In specific, the aim was to quantify the contribution of different canopy layers to whole forest fluxes. For this purpose, long-term micrometeorological and ecological measurements made in a Scots pine (Pinus sylvestris) forest at SMEAR II research station in Southern Finland were used. The properties of turbulent flow are strongly modified by the interaction between the canopy elements: momentum is efficiently absorbed in the upper layers of the canopy, mean wind speed and turbulence intensities decrease rapidly towards the forest floor and power spectra is modulated by spectral short-cut . In the relative open forest, diabatic stability above the canopy explained much of the changes in velocity statistics within the canopy except in strongly stable stratification. Large eddies, ranging from tens to hundred meters in size, were responsible for the major fraction of turbulent transport between a forest and the atmosphere. Because of this, the eddy-covariance (EC) method proved to be successful for measuring energy and mass exchange inside a forest canopy with exception of strongly stable conditions. Vertical variations of within canopy microclimate, light attenuation in particular, affect strongly the assimilation and transpiration rates. According to model simulations, assimilation rate decreases with height more rapidly than stomatal conductance (gs) and transpiration and, consequently, the vertical source-sink distributions for carbon dioxide (CO2) and water vapor (H2O) diverge. Upscaling from a shoot scale to canopy scale was found to be sensitive to chosen stomatal control description. The upscaled canopy level CO2 fluxes can vary as much as 15 % and H2O fluxes 30 % even if the gs models are calibrated against same leaf-level dataset. A pine forest has distinct overstory and understory layers, which both contribute significantly to canopy scale fluxes. The forest floor vegetation and soil accounted between 18 and 25 % of evapotranspiration and between 10 and 20 % of sensible heat exchange. Forest floor was also an important deposition surface for aerosol particles; between 10 and 35 % of dry deposition of particles within size range 10 30 nm occurred there. Because of the northern latitudes, seasonal cycle of climatic factors strongly influence the surface fluxes. Besides the seasonal constraints, partitioning of available energy to sensible and latent heat depends, through stomatal control, on the physiological state of the vegetation. In spring, available energy is consumed mainly as sensible heat and latent heat flux peaked about two months later, in July August. On the other hand, annual evapotranspiration remains rather stable over range of environmental conditions and thus any increase of accumulated radiation affects primarily the sensible heat exchange. Finally, autumn temperature had strong effect on ecosystem respiration but its influence on photosynthetic CO2 uptake was restricted by low radiation levels. Therefore, the projected autumn warming in the coming decades will presumably reduce the positive effects of earlier spring recovery in terms of carbon uptake potential of boreal forests.
  • Wilkman, Maria (2015)
    The aim of this empirical study is to analyse whether announcements by Moody’s, Standard and Poor’s and Fitch Ratings regarding the credit rating of Ukraine and Russia can explain the movements in the yield spreads on their government bonds during 1st January 2010 – 6th February 2015. The motivation for this research question derives from the results of previous empirical studies, which have found that announcements by the three credit rating agencies regarding the sovereign rating of a country impact the country’s borrowing costs. Particularly negative rating news, concerning either a downgrade or the assignment of a negative outlook to the rating, have been found to impact yield spreads, leading to increased borrowing costs for the country. Against this background, this study analyses whether the many negative announcements from the credit rating agencies regarding the Ukrainian and Russian sovereign ratings can explain the large increases in the countries’ government bond yield spreads since 2010. The methodology used in the empirical study is based on regression analysis, which incorporates an event study through the use of dummy variables. The overall findings indicate that announcements from the rating agencies affect the government borrowing costs of the country concerned, as the results show a statistically significant impact of the announcement events on the country’s bond yield spreads. However, as the impact of the events on the yield spreads is considerably smaller in magnitude than the movements in the spreads, the results indicate that factors other than the rating agency announcements are driving the large increases in the Ukrainian and Russian borrowing costs. The conclusion of the study is therefore that although some of the announcements are found to be statistically significant, the rating events alone cannot explain the movements in the yield spreads on the countries’ government bonds during 1st January 2010 – 6th February 2015. Contrary to previous studies, the results show no clear evidence that negative events affect yield spreads to a greater extent than positive events. There is also no considerable difference in the impact on the yield spreads between announcements by the different agencies. In terms of the magnitude of the impact of rating events on yield spreads, the results of this study are largely in line with previous findings in the literature. The analysis of the relationship between credit rating announcements and government bond yield spreads for Ukraine and Russia since 2010 presented in this paper is divided into five chapters, which approach the research question from different perspectives. Chapter one provides the necessary background for the analysis and offers a theoretical explanation for why announcements by the rating agencies may impact the yield spreads on a country’s government bonds. Chapter two presents an overview of the empirical literature on the topic; three previous papers which use event study analysis to investigate the impact of rating agency announcements on government yield spreads are discussed and evaluated. Against this background, chapter three describes the empirical methodology used in this paper to study the relationship between Ukrainian and Russian credit rating announcements and yield spreads; the data set on which the analysis is based is introduced in chapter four. The results of the analysis are discussed in chapter five, followed by concluding remarks.
  • Valve, Heikki (2012)
    Tässä tutkielmassa tarkastellaan Cantorin joukkoa ja sen soveltamista muutamiin matemaattisiin tarkoituksiin. Cantorin joukon määrittelyssä otetaan huomioon sen monet topologiset ominaisuudet. Tarkoituksena on muotoilla Cantorin joukkoon liittyvät matemaattiset erikoisuudet mahdollisimman ymmärrettävällä tavalla matematiikkaa vain vähän opiskelleelle. Cantorin joukko on hämmentänyt matemaatikkoja sen ensimmäisestä esiintymisestä lähtien. Joukko muodostetaan vaiheittain poistamalla yksikkövälistä [0, 1] avoimia kolmanneksia. Prosessin ensimmäisessä vaiheessa välistä [0, 1] poistetaan väli (1/3, 2/3). Seuraavassa vaiheessa kahdesta välistä [0, 1/3] ja [2/3, 1] poistetaan jälleen niiden keskimmäiset kolmannekset eli välit (1/9, 2/9) ja (7/9, 8/9). Kun tätä prosessia jatketaan loputtamasti, välistä [0, 1] lopulta jäljelle jäävät pisteet muodostavat Cantorin joukon. Cantorin joukkoon kuuluvat ainakin kaikkien poistettujen välien päätepisteet. Yhtenä joukon erikoisuutena on kuitenkin se, että siihen kuuluu vielä ylinumeroituvasti ääretön määrä pisteitä, jotka eivät ole poistettujen välien päätepisteitä. Tämän seurauksena myös Cantorin joukko on siis ylinumeroituvasti ääretön. Topologiset ominaisuudet ovat Cantorin joukolla myös erikoisia. Voidaan osoittaa, että joukolla ei ole sisäpisteitä eli pisteitä, joilla olisi jokin Cantorin joukkoon kuuluva ympäristö. Lisäksi voidaan osoittaa, että jokainen Cantorin joukon piste on kasautumispiste eli piste, jonka jokaisessa ympäristössä on jokin toinen Cantorin joukon piste. Pirunporrasfunktionakin tunnetun Cantorin funktion lähtö- ja maalijoukko on yksikköväli [0, 1] eli gamma : [0, 1] -> [0, 1]. Funktion määrittely aloitetaan kuitenkin usein Cantorin joukon avulla. Nimen pirunporrasfunktio on saanut portaikkoa muistuttavasta kuvaajastaan. Vaikka gamma muistuttaa portaikkoa ja ensisilmäyksellä vaikuttaa katkonaiselta, niin se on kuitenkin jatkuva ja jopa tasaisesti jatkuva. Viimeisenä asiana tässä tutkielmassa esitetään lyhyesti Cantorin joukkoon liittyvä Lebesguen käyrä. Lebesguen käyrää sanotaan avaruuden täyttäväksi käyräksi, koska se kulkee jokaisen maalijoukkonsa, tässä tapauksessa yksikköneliön [0; 1] x [0; 1], pisteen kautta.
  • Tschamurov, Viveka (2013)
    A model is been built where two countries compete for a multinational enterprise’s (MNE’s) foreign direct investment (FDI) provided that its arrival will increase the host country’s social welfare. Both potential host countries have unionised labour markets where monopoly labour unions determine the level of the wage setting to be either decentralised, intermediate level, or centralised. The governments may influence the unions’ decision by setting a lump-sum tax on them. Both countries have two sectors, a non-sheltered and sheltered sector. The MNE will enter in the non-sheltered sector and is assumed to be more productive than the incumbent firms there. Product market competition between the MNE and domestic incumbent firms is ruled out to isolate the effect of product market competition from the effect of pure wage compression. The game evolves in five stages: (1) the governments set taxes, (2) the monopoly unions choose the level of the wage setting, (3) the MNE chooses its investment location, (4) the monopoly unions set wages, and (5) the firms set output. The purpose of the model is to learn whether the degree of centralisation of wage setting can be used as a strategic choice to attract foreign direct investment. The main results of the paper are the following. It was found that the MNE’s (incumbent unions’) most preferred choice is always centralised (decentralised) wage setting. It was shown that the governments’ most preferred choice is either decentralised or centralised wage setting – depending on the relative sizes of the two sectors. If the social welfare in country 1 is the highest under decentralised wage setting, then the optimal policy of government 1 is to set zero income taxes. If the social welfare in country 2 is the highest under centralised wage setting, then the optimal policy of government 2 is to set positive taxes slightly over that required to make the domestic incumbent labour unions prefer centralised wage setting. Given this, the MNE will always invest in country 2. The exact expressions for the stage-contingent lump-sum taxes were derived. To my best knowledge, this is a novel contribution that cannot be found elsewhere.
  • D'Ulivo, Lucia (Helsingin yliopisto, 2010)
    This doctoral thesis describes the development of a miniaturized capillary electrochromatography (CEC) technique suitable for the study of interactions between various nanodomains of biological importance. The particular focus of the study was low-density lipoprotein (LDL) particles and their interaction with components of the extracellular matrix (ECM). LDL transports cholesterol to the tissues through the blood circulation, but when the LDL level becomes too high the particles begin to permeate and accumulate in the arteries. Through binding sites on apolipoprotein B-100 (apoB-100), LDL interacts with components of the ECM, such as proteoglycans (PGs) and collagen, in what is considered the key mechanism in the retention of lipoproteins and onset of atherosclerosis. Hydrolytic enzymes and oxidizing agents in the ECM may later successively degrade the LDL surface. Metabolic diseases such as diabetes may provoke damage of the ECM structure through the non-enzymatic reaction of glucose with collagen. In this work, fused silica capillaries of 50 micrometer i.d. were successfully coated with LDL and collagen, and steroids and apoB-100 peptide fragments were introduced as model compounds for interaction studies. The LDL coating was modified with copper sulphate or hydrolytic enzymes, and the interactions of steroids with the native and oxidized lipoproteins were studied. Lipids were also removed from the LDL particle coating leaving behind an apoB-100 surface for further studies. The development of collagen and collagen decorin coatings was helpful in the elucidation of the interactions of apoB-100 peptide fragments with the primary ECM component, collagen. Furthermore, the collagen I coating provided a good platform for glycation studies and for clarification of LDL interactions with native and modified collagen. All methods developed are inexpensive, requiring just small amounts of biomaterial. Moreover, the experimental conditions in CEC are easily modified, and the analyses can be carried out in a reasonable time frame. Other techniques were employed to support and complement the CEC studies. Scanning electron microscopy and atomic force microscopy provided crucial visual information about the native and modified coatings. Asymmetrical flow field-flow fractionation enabled size measurements of the modified lipoproteins. Finally, the CEC results were exploited to develop new sensor chips for a continuous flow quartz crystal microbalance technique, which provided complementary information about LDL ECM interactions. This thesis demonstrates the potential of CEC as a valuable and flexible technique for surface interaction studies. Further, CEC can serve as a novel microreactor for the in situ modification of LDL and collagen coatings. The coatings developed in this study provide useful platforms for a diversity of future investigations on biological nanodomains.
  • Owusu, Henry (2000)
    That the financial system is an important source of instability and the propagation mechanism for cyclical fluctuations has come to the fore in the face of the Asian financial crisis. Many economist have argued that, the unregulated operation of the financial markets can lead to excessive fluctuations even in the absense of shocks impinging on the rest of the economy. The study analyses the effects of financial market integration in developing market economies. The basic model is a dynamic open-economy model with two inputs; tradable and non-tradable inputs being used in production and a credit-constraint as to the amount of credit firms' can borrow. We first show that economies at an intermediate level of financial development are more vulnerable to instability than either advanced or least developed economies. In these economies, temporary shocks may have large and long lasting effects. However, there is a limit to which such economies may cycle. This suggests that countries going through financial restructuring may become unstable in the short run. In addition, combining capital market imperfections and unequal access to investment opportunities for individuals can lead to permanent fluctuations in income and investment. Thus governments should aim at reducing inequality of access to credit which may be necessary for macroeconomic stability. Aside the above, other factors such as increases in interest rates, increased uncertainty,and assest market effects on balance sheets may impinge on the stability of small economies. These calls for countercyclical policies targeted at specific problems to be implemented in order to put the economy on a sound footing, for example, during recessions.
  • Eriksson, Einar (1994)
    Capnocytophaga cynodegmi löytyi 9:stä eläimestä (26%) ja C.canimorsus 5:sta (14%) 35 kissan otoksestamme. Rapid-paneelit olivat nopeat ja helppokäyttöiset. Testisarjojen antamat tulokset on esitetty taulukoissa 2A - 4B. C. cynodegmikantojen "mikrokoodeja" ei löytynyt valmistajan käsikirjasta. C. canimorsus antoi satunnaisesti saman mikrokoodin kuin Gardenella vaginalis, mutta bakteerit ovat helposti erotettavissa toisistaan, koska G. vaginalis on aina katalaasinegatiivinen. Sakkaroositestinsä ansiosta Rapid NH kykeni erottamaan C. cynodegmin ja C. canimorsuksen toisistaan, mihin Rapid NF+ ei kunnolla pystynyt. Rapid NF+ erotti kuitenkin eläinperäiset Capnocytophagat muista testitietokantaan kuuluvista bakteereista. Mikäli valmistaja lisäisi kyseiset mikrokoodit luetteloihinsa, eläinperäisten Capnocytophagojen identifioiminen olisi nykyistä huomattavasti nopeampaa (4 h verrattuna 5-7 päivään). Bakteeri pystyttäisiin löytämään useammin kuin ennen, sillä usein verilevyt hävitetään 3 vrk:n inkubaation jälkeen, vaikka Capnocytophagat kasvavat silmin näkyviksi pesäkkeiksi CO2-atmosfäärissäkin vasta n. 5 vrk:ssa. Harvinaisia bakteereita ei laboratorioissa monesti osata lainkaan epäillä. Mikäli DF-2-bakteerien nimi tulisi "automaattisesti" kaupallisen testisarjan tiedostosta, niiden tunnistus osuisi oikeaan nykyistä selvästi useammin.
  • Liljeroos, Lassi (Helsingin yliopisto, 2013)
    Paramyxoviridae constitute a family of pleomorphic, enveloped viruses including several human pathogens. Understanding of the structure and assembly of paramyxoviruses has been hindered by the lack of whole-virion three-dimensional structures. In this work, measles and human respiratory syncytial viruses were studied with three-dimensional electron microscopy and biochemical analysis of recombinant proteins. The analysis revealed significant differences in the structure and assembly of the two viruses. The differences were most notable in the way the matrix protein, the main factor driving budding from host cell, was organized inside the virions. In measles virions, the matrix was found to cover the genome-containing ribonucleocapsid, whereas in human respiratory syncytial virus the matrix was lining the inner surface of the membrane vesicle. These differences have implications on models of how each ribonucleoprotein complex assembles and how the viruses bud from the host cell. The early control of measles ribonucleoprotein assembly was subsequently investigated to further reveal the details of the precise manner in which the intricate molecular ballet of viral assembly is orchestrated inside the host cell. The results presented in this thesis expand the understanding of enveloped virus structure and assembly, which is important in rational approaches to fight the pathogenic members in the group.