Lymphatic vessels in health and disease: Role of the VEGF-C/VEGFR-3 pathway and the transcription factor FOXC2

The circulatory system consists of two vessel types, which act in concert but significantly differ from each other in several structural and functional aspects as well as in mechanisms governing their development. The blood vasculature transports oxygen, nutrients and cells to tissues whereas the lymphatic vessels collect extravasated fluid, macromolecules and cells of the immune system and return them back to the blood circulation. Understanding the molecular mechanisms behind the developmental and functional regulation of the lymphatic system long lagged behind that of the blood vasculature. Identification of several markers specific for the lymphatic endothelium, and the discovery of key factors controlling the development and function of the lymphatic vessels have greatly facilitated research in lymphatic biology over the past few years. Recognition of the crucial importance of lymphatic vessels in certain pathological conditions, most importantly in tumor metastasis, lymphedema and inflammation, has increased interest in this vessel type, for so long overshadowed by its blood vascular cousin. VEGF-C (Vascular Endothelial Growth Factor C) and its receptor VEGFR-3 are essential for the development and maintenance of embryonic lymphatic vasculature. Furthermore, VEGF-C has been shown to be upregulated in many tumors and its expression found to positively correlate with lymphatic metastasis. Mutations in the transcription factor FOXC2 result in lymphedema-distichiasis (LD), which suggests a role for FOXC2 in the regulation of lymphatic development or function. This study was undertaken to obtain more information about the role of the VEGF-C/VEGFR-3 pathway and FOXC2 in regulating lymphatic development, growth, function and survival in physiological as well as in pathological conditions. We found that the silk-like carboxyterminal propeptide is not necessary for the lymphangiogenic activity of VEGF-C, but enhances it, and that the aminoterminal propeptide mediates binding of VEGF-C to the neuropilin-2 coreceptor, which we suggest to be involved in VEGF-C signalling via VEGFR-3. Furthermore, we found that overexpression of VEGF-C increases tumor lymphangiogenesis and intralymphatic tumor growth, both of which could be inhibited by a soluble form of VEGFR-3. These results suggest that blocking VEGFR-3 signalling could be used for prevention of lymphatic tumor metastasis. This might prove to be a safe treatment method for human cancer patients, since inhibition of VEGFR-3 activity had no effect on the normal lymphatic vasculature in adult mice, though it did lead to regression of lymphatic vessels in the postnatal period. Interestingly, in contrast to VEGF-C, which induces lymphangiogenesis already during embryonic development, we found that the related VEGF-D promotes lymphatic vessel growth only after birth. These results suggest, that the lymphatic vasculature undergoes postnatal maturation, which renders it independent of ligand induced VEGFR-3 signalling for survival but responsive to VEGF-D for growth. Finally, we show that FOXC2 is necessary for the later stages of lymphatic development by regulating the morphogenesis of lymphatic valves, as well as interactions of the lymphatic endothelium with vascular mural cells, in which it cooperates with VEGFR-3. Furthermore, our study indicates that the absence of lymphatic valves, abnormal association of lymphatic capillaries with mural cells and an increased amount of basement membrane underlie the pathogenesis of LD. These findings have given new insight into the mechanisms of normal lymphatic development, as well as into the pathogenesis of diseases involving the lymphatic vasculature. They also reveal new therapeutic targets for the prevention and treatment of tumor metastasis and lymphatic vascular failure in certain forms of lymphedema. Several interesting questions were posed that still need to be addressed. Most importantly, the mechanism of VEGF-C promoted tumor metastasis and the molecular nature of the postnatal lymphatic vessel maturation remain to be elucidated.

Death in the Bolivian High Plateau : Burials and Tiwanaku Society

My Ph.D. dissertation presents a multi-disciplinary analysis of the mortuary practices of the Tiwanaku culture of the Bolivian high plateau, situated at an altitude of c. 3800 m above sea level. The Tiwanaku State (c. AD 500-1150) was one of the most important pre-Inca civilisations of the South Central Andes. The book begins with a brief introductory chapter. In chapter 2 I discuss methodological and theoretical developments in archaeological mortuary studies from the late 1960s until the turn of the millennium. I am especially interested in the issue how archaeological burial data can be used to draw inferences on the social structure of prehistoric societies. Chapter 3 deals with the early historic sources written in the 16th and 17th centuries, following the Spanish Conquest of the Incas. In particular, I review information on how the Incas manifested status differences between and within social classes and what kinds of burial treatments they applied. In chapter 4 I compare the Inca case with 20th century ethnographic data on the Aymara Indians of the Bolivian high plateau. Even if Christianity has affected virtually every level of Aymara religion, surprisingly many traditional features can still be observed in present day Aymara mortuary ceremonies. The archaeological part of my book begins with chapter 5, which is an introduction into Tiwanaku archaeology. In the next chapter, I present an overview of previously reported Tiwanaku cemeteries and burials. Chapter 7 deals with my own excavations at the Late Tiwanaku/early post-Tiwanaku cemetery site of Tiraska, located on the south-eastern shore of Lake Titicaca. During the 1998, 2002, and 2003 field seasons, a total of 32 burials were investigated at Tiraska. The great majority of these were subterranean stone-lined tombs, each containing the skeletal remains of 1 individual and 1-2 ceramic vessels. Nine burials have been radiocarbon dated, the dates in question indicating that the cemetery was in use from the 10th until the 13th century AD. In chapter 8 I point out that considerable regional and/or ethnic differences can be noted between studied Tiwanaku cemetery sites. Because of the mentioned differences, and a general lack of securely dated burial contexts, I feel that at present we can do no better than to classify most studied Tiwanaku burials into three broad categories: (1) elite and/or priests, (2) "commoners", and (3) sacrificial victims and/or slaves and/or prisoners of war. On the basis of such indicators as monumental architecture and occupational specialisation we would expect to find considerable status-related differences in tomb size, grave goods, etc. among the Tiwanaku. Interestingly, however, such variation is rather modest, and the Tiwanaku seem to have been a lot less interested in expending considerable labour and resources in burial facilities than their pre-Columbian contemporaries of many parts of the Central Andes.

Järjestö jäänmurtajana : Suomen merimiesunioni työmarkkinaosapuolena ja suomalaisten laivatyöntekijöiden turvallisuuden vankentajana 1944-1980

Like an Icebreaker: The Finnish Seamen s Union as collective bargaining maverick and champion of sailors social safety 1944-1980. The Finnish Seamen's Union (FSU), which was established on a national basis in 1920, was one of the first Finnish trade unions to succeed in collective bargaining. In the early 1930s, the gains made in the late 1920s were lost, due to politically based internal rivalries, the Great Depression, and a disastrous strike. Unexpectedly the FSU survived and went on promoting the well-being of its members even during World War II. After the war the FSU was in an exceptionally favorable position to exploit the introduction of coordinated capitalism, which was based on social partnership between unions, employers and government. Torpedoes, mines and confiscations had caused severe losses to the Finnish merchant marine. Both ship-owners and government alike understood the crucial importance of using the remaining national shipping capacity effectively. The FSU could no longer be crushed, and so, in 1945, the union was allowed to turn all ocean-going Finnish ships into closed shops. The FSU also had another source of power. After the sailors of the Finnish icebreaker fleet also joined its ranks, the FSU could, in effect, block Finnish foreign trade in wintertime. From the late 1940s to the 1960s the union started and won numerous icebreaker strikes. Finnish seamen were thus granted special pension rights, reductions on income taxes and import duties, and other social privileges. The FSU could neither be controlled by union federations nor intimidated by employers or governments. The successful union and its tactically clever chairperson, Niilo Välläri, were continuously but erroneously accused of syndicalism. Välläri did not aim for socialism but wanted the Finnish seamen to get all the social benefits that capitalism could possibly offer. Välläri s policy was successfully followed by the FSU until the late 1980s when Finnish ship-owners were allowed to flag their vessels outside the national registry. Since then the FSU has been on the defensive and has yielded to pay cuts. The FSU members have not lost their social benefits, but they are under constant fear of losing their jobs to cheap foreign labor.

Kognitiva system i namngivningen av finländska handelsfartyg 1838-1938

This dissertation is an onomastic study of Finland s stock of ship names (nautonomasticon) recorded over the period 1838 1938. The primary material investigated consists of 2 066 examples of ship names from the fleets of coastal towns, distributed over five sample years. The material is supplemented with two bodies of comparative data; one that consists of 2 535 examples of boat names from the archipelago area at the corresponding time, and another that comprises 482 examples of eighteenth century Finnish ship names. This study clarifies the categories of names that appear the frequency of the names, formation, morphology, linguistic origin, functions, and semantic qualities. By comparing the material with boat names from previous centuries, and from other countries, the characteristics of Finnish vessel names are further highlighted. Additional clarification is brought to the chronological, regional, and social variations, and to the emergence of various forms of systematic naming. This dissertation builds on older research from other countries, and uses traditional onomastic methods alongside a more modern methodology. The approach is interdisciplinary, meaning that the names are explored using facts not only from nautical history, but also from a range of other historical disciplines such as economics, culture, art, and literature. In addition, the approach is socio-onomastic, i.e. that the variations in names are studied in a societal context. Using a synchronised perspective, cognitive linguistic theories have provided the tools for this exploration into the metaphorical and the prototypical meaning of the names, and the semantic domains that the names create. The quantitative analysis has revealed the overall picture of Finnish boat names. Personal names, names from mythology, and place names, emerge as significant categories, alongside nonproprial names in Swedish and Finnish. The interdisciplinary perspective has made it possible to explain certain trends in the stock of boat names, for example, the predisposition towards names from classical mythology, the breakthrough of names taken from the national epos Kalevala, names in the Finnish language from around the middle of the nineteenth century, and the continuing rise of place names during the latter part of the period 1838 1938. The socio-onomastic perspective has also identified clear differences between those ship names used in towns, and those ship names used in the archipelago, and it has clarified how naming conventions tend to spread from town centres to peripheral areas. The cognitive linguistic methods have revealed that the greater part of the vessel names can be interpreted as metaphors, in particular personifications, and that many names are related in their content and also form semantic networks and cognitive systems. The results indicate that there is a mental nautonomasticon that consists of a standard set of traditional ship names, but they also reveal the existence of conscious or unconscious cognitive systems (rules and conventions) that guide the naming of boats.

Distribution and adhesion-promoting activity of alpha4 and alpha5 chain laminins in human endothelia and carcinomas

Basement membranes are specialized sheets of extracellular matrix found in contact with epithelia, endothelia, and certain isolated cells. They support tissue architecture and regulate cell behaviour. Laminins are among the main constituents of basement membranes. Due to differences between laminin isoforms, laminins confer structural and functional diversity to basement membranes. The first aim of this study was to gain insights into the potential functions of the then least characterized laminins, alpha4 chain laminins, by evaluating their distribution in human tissues. We thus created a monoclonal antibody specific for laminin alpha4 chain. By immunohistochemistry, alpha4 chain laminins were primarily localized to basement membranes of blood vessel endothelia, skeletal, heart, and smooth muscle cells, nerves, and adipocytes. In addition, alpha4 chain laminins were found in the region of certain epithelial basement membranes in the epidermis, salivary gland, pancreas, esophagus, stomach, intestine, and kidney. Because of the consistent presence of alpha4 chain laminins in endothelial basement membranes of blood vessels, we evaluated the potential roles of endothelial laminins in blood vessels, lymphatic vessels, and carcinomas. Human endothelial cells produced alpha4 and alpha5 chain laminins. In quantitative and morphological adhesion assays, human endothelial cells barely adhered to alpha4 chain-containing laminin-411. The weak interaction of endothelial cells with laminin-411 appeared to be mediated by alpha6beta1 integrin. The alpha5 chain-containing laminin-511 promoted endothelial cell adhesion better than laminin-411, but it did not promote the formation of cell-extracellular matrix adhesion complexes. The adhesion of endothelial cells to laminin-511 appeared to be mediated by Lutheran glycoprotein together with beta1 and alphavbeta3 integrins. The results suggest that these laminins may induce a migratory phenotype in endothelial cells. In lymphatic capillaries, endothelial basement membranes showed immunoreactivity for laminin alpha4, beta1, beta2, and gamma1 chains, type IV and XVIII collagens, and nidogen-1. Considering the assumed inability of alpha4 chain laminins to polymerize and to promote basement membrane assembly, the findings may in part explain the incomplete basement membrane formation in these vessels. Lymphatic capillaries of ovarian carcinomas showed immunoreactivity also for laminin alpha5 chain and its receptor Lutheran glycoprotein, emphasizing a difference between normal and ovarian carcinoma lymphatic capillaries. In renal cell carcinomas, immunoreactivity for laminin alpha4 chain was found in stroma and basement membranes of blood vessels. In most tumours, immunoreactivity for laminin alpha4 chain was also observed in the basement membrane region of tumour cell islets. Renal carcinoma cells produced alpha4 chain laminins. Laminin-411 did not promote adhesion of renal carcinoma cells, but inhibited their adhesion to fibronectin. Renal carcinoma cells migrated more on laminin-411 than on fibronectin. The results suggest that alpha4 chain laminins have a counteradhesive function, and may thus have a role in detachment and invasion of renal carcinoma cells.

Arresting occlusal enamel caries lesions with pit and fissure sealants

The aim of this study was to evaluate the feasibility of pit and fissure sealants and the effectiveness of the two sealant methods applied in every-day practice in public dental health care in Finland. Two sealant methods were evaluated according to their effectiveness in preventing dentin caries and sealant retention. Application time with these sealant methods was compared. The survival rate of sealed first and second molars was followed for nine and 13 year periods, respectively. Caries risk evaluation and observed increased caries risk were the basis for considering sealant application. A questionnaire, sent to all public dental health centers in Finland, monitored the attitudes of the dental profession towards sealant application and explored the current policies used as well as changes noted in the sealant application protocol. DMFT (Decayed, Missing or Filled Teeth) index values collected from the health centers were evaluated. The difference in caries rate between two methods investigated was highly significant. When compared to the glass ionomer sealant method (GIC), the effectiveness of the resin-based method (RB) in preventing dentin caries was 74% and the rate difference 3%. The relative risk for RB-sealed surfaces vs. GIC-sealed surfaces of having detectable dentin caries was 0.3 (95% CI 0.12, 0.57). The retention rate of sealants was higher with RB than GIC (P<0.001). Application of RB sealant material was less time-consuming than application of GIC sealant. Occlusal dentin caries lesions were found in 4% and proximal caries in less than 2% of sealed teeth. The majority of respondents reported application of sealants on a systematic basis along with caries-risk evaluation. Those health centers sealing over suspected or detected enamel caries had lower average DMFT index values (1.0) when compared to DMFT values (1.2) of health centers applying sealants by alternative criteria. It is concluded that the RB sealant method is more effective than the GIC sealant method in preventing dentin caries. Sealant maintenance may increase the costs of a sealant program. Occlusal caries management may be improved if the applied sealant policies are changed towards an interceptive approach i.e. applying the sealants over detected or suspected enamel caries lesions instead of sealing sound teeth in a preventive manner.

VEGFR-3 and Tie pathways in vascular network formation

The blood and lymphatic vascular systems are essential for life, but they may become harnessed for sinister purposes in pathological conditions. For example, tumors learn to grow a network of blood vessels (angiogenesis), securing a source of oxygen and nutrients for sustained growth. On the other hand, damage to the lymph nodes and the collecting lymphatic vessels may lead to lymphedema, a debilitating condition characterized by peripheral edema and susceptibility to infections. Promoting the growth of new lymphatic vessels (lymphangiogenesis) is an attractive approach to treat lymphedema patients. Angiopoietin-1 (Ang1), a ligand for the endothelial receptor tyrosine kinases Tie1 and Tie2. The Ang1/Tie2 pathway has previously been implicated in promoting endothelial stability and integrity of EC monolayers. The studies presented here elucidate a novel function for Ang1 as a lymphangiogenic factor. Ang1 is known to decrease the permeability of blood vessels, and could thus act as a more global antagonist of plasma leakage and tissue edema by promoting growth of lymphatic vessels and thereby facilitating removal of excess fluid and other plasma components from the interstitium. These findings reinforce the idea that Ang1 may have therapeutic value in conditions of tissue edema. VEGFR-3 is present on all endothelia during development, but in the adult its expression becomes restricted to the lymphatic endothelium. VEGF-C and VEGF-D are ligands for VEGFR-3, and potently promote lymphangiogenesis in adult tissues, with direct and remarkably specific effects on the lymphatic endothelium in adult tissues. The data presented here show that VEGF-C and VEGF-D therapy can restore collecting lymphatic vessels in a novel orthotopic model of breast cancer-related lymphedema. Furthermore, the study introduces a novel approach to improve VEGF-C/VEGF-D therapy by using engineered heparin-binding forms of VEGF-C, which induced the rapid formation of organized lymphatic vessels. Importantly, VEGF-C therapy also greatly improved the survival and integration of lymph node transplants. The combination of lymph node transplantation and VEGF-C therapy provides a basis for future therapy of lymphedema. In adults, VEGFR-3 expression is restricted to the lymphatic endothelium and the fenestrated endothelia of certain endocrine organs. These results show that VEGFR-3 is induced at the onset of angiogenesis in the tip cells that lead the formation of new vessel sprouts, providing a tumor-specific vascular target. VEGFR-3 acts downstream of VEGF/VEGFR-2 signals, but, once induced, can sustain angiogenesis when VEGFR-2 signaling is inhibited. The data presented here implicate VEGFR-3 as a novel regulator of sprouting angiogenesis along with its role in regulating lymphatic vessel growth. Targeting VEGFR-3 may provide added efficacy to currently available anti-angiogenic therapeutics, which typically target the VEGF/VEGFR-2 pathway.

VEGF-C/VEGFR-3 and PDGF-B/PDGFR-b pathways in embryonic lymphangiogenesis

The circulatory system comprises the blood vascular system and the lymphatic vascular system. These two systems function in parallel. Blood vessels form a closed system that delivers oxygen and nutrients to the tissues and removes waste products from the tissues, while lymphatic vessels are blind-ended tubes that collect extravasated fluid and cells from the tissues and return them back to blood circulation. Development of blood and lymphatic vascular systems occurs in series. Blood vessels are formed via vasculogenesis and angiogenesis whereas lymphatic vessels develop via lymphangiogenesis, after the blood vascular system is already functional. Members of the vascular endothelial growth factor (VEGF) family are regulators of both angiogenesis and lymphangiogenesis, while members of the platelet-derived growth factor (PDGF) family are major mitogens for pericytes and smooth muscle cells and regulate formation of blood vessels. Vascular endothelial growth factor C (VEGF-C) is the major lymphatic growth factor and signaling through its receptor vascular endothelial growth factor receptor 3 (VEGFR-3) is sufficient for lymphangiogenesis in adults. We studied the role of VEGF-C in embryonic lymphangiogenesis and showed that VEGF-C is absolutely required for the formation of lymph sacs from embryonic veins. VEGFR-3 is also required for normal development of the blood vascular system during embryogenesis, as Vegfr3 knockout mice die at mid-gestation due to failure in remodeling of the blood vessels. We showed that sufficient VEGFR-3 signaling in the embryo proper is required for embryonic angiogenesis and in a dosage-sensitive manner for embryonic lymphangiogenesis. Importantly, mice deficient in both VEGFR-3 ligands, Vegfc and Vegfd, developed a normal blood vasculature, suggesting VEGF-C- and VEGF-D- independent functions for VEGFR-3 in the early embryo. Platelet-derived growth factor B (PDGF-B) signals via PDGFR-b and regulates formation of blood vessels by recruiting pericytes and smooth muscle cells around nascent endothelial tubes. We showed that PDGF-B fails to induce lymphangiogenesis when overexpressed in adult mouse skin using adenoviral vectors. However, mouse embryos lacking Pdgfb showed abnormal lymphatic vessels, suggesting that PDGF-B plays a role in lymphatic vessel maturation and separation from blood vessels during embryogenesis. Lymphatic vessels play a key role in immune surveillance, fat absorption and maintenance of fluid homeostasis in the body. However, lymphatic vessels are also involved in various diseases, such as lymphedema and tumor metastasis. These studies elucidate the basic mechanisms of embryonic lymphangiogenesis and add to the knowledge of lymphedema and tumor metastasis treatments by giving novel insights into how lymphatic vessel growth could be induced (in lymphedema) or inhibited (in tumor metastasis).

Vascular growth factors and progenitor cells in cardiac allograft arteriosclerosis

Heart transplantation is the only therapeutic modality for many end-stage heart diseases but poor long-term survival remains a challenging problem. This is mainly due to the development of cardiac allograft arteriosclerosis (TxCAD) that is an accelerated form of coronary artery disease. Both traditional cardiovascular and transplantation-related risk factors for TxCAD have been identified but options for therapy are limited. TxCAD involves dysfunction of cardiac allograft vascular cells. Activated endothelial cells (EC) regulate allograft inflammation and secrete smooth muscle cell (SMC) growth factors. In turn, SMC and their progenitors invade the intima of the injured vessels and occlude the affected coronary arteries. Different vascular growth factors have to be delicately regulated in normal vascular development. In the present study, experimental heterotopic transplantation models were used to study the role of angiogenic and pro-inflammatory vascular endothelial growth factor (VEGF), EC growth factor angiopoietin (Ang), and SMC mitogen platelet-derived growth factor (PDGF) in the development of TxCAD. Pharmacological and gene transfer approaches were used to target these growth factors and to assess their therapeutic potential. This study shows that alloimmune response in heart transplants upregulates VEGF expression, and induces allograft angiogenesis that involves donor-derived primitive EC. Intracoronary adenoviral VEGF gene transfer increased macrophage infiltration, intimal angiogenesis and TxCAD. VEGF inhibition with PTK787 decreased allograft inflammation and TxCAD, and simultaneous PDGF inhibition with imatinib further decreased TxCAD. Specific inhibition of two VEGF-receptors (VEGFR) decreased allograft inflammation and TxCAD, and VEGFR-2 inhibition normalized the density of primitive and mature capillaries in the allografts. Adenovirus-mediated transient Ang1 expression in the allograft had anti-inflammatory and anti-arteriosclerotic effects. Adeno-associated virus (AAV)-mediated prolonged Ang1 or Ang2 expression had similar anti-inflammatory effects. However, AAV-Ang1 activated allograft SMC whereas AAV-Ang2 had no effects on SMC activation and decreased the development of TxCAD. These studies indicate an interplay of inflammation, angiogenesis and arteriosclerosis in cardiac allografts, and show that vascular growth factors are important regulators in the process. Also, VEGF inhibition, PDGF inhibition and angiopoietin therapy with clinically-relevant pharmacological agents or novel gene therapy approaches may counteract vascular dysfunction in cardiac allografts, and have beneficial effects on the survival of heart transplant patients in the future.

Essays on the Bioeconomics of the Northern Baltic Fisheries

World marine fisheries suffer from economic and biological overfishing: too many vessels are harvesting too few fish stocks. Fisheries economics has explained the causes of overfishing and provided a theoretical background for management systems capable of solving the problem. Yet only a few examples of fisheries managed by the principles of the bioeconomic theory exist. With the aim of bridging the gap between the actual fish stock assessment models used to provide management advice and economic optimisation models, the thesis explores economically sound harvesting from national and international perspectives. Using data calibrated for the Baltic salmon and herring stocks, optimal harvesting policies are outlined using numerical methods. First, the thesis focuses on the socially optimal harvest of a single salmon stock by commercial and recreational fisheries. The results obtained using dynamic programming show that the optimal fishery configuration would be to close down three out of the five studied fisheries. The result is robust to stock size fluctuations. Compared to a base case situation, the optimal fleet structure would yield a slight decrease in the commercial catch, but a recreational catch that is nearly seven times higher. As a result, the expected economic net benefits from the fishery would increase nearly 60%, and the expected number of juvenile salmon (smolt) would increase by 30%. Second, the thesis explores the management of multiple salmon stocks in an international framework. Non-cooperative and cooperative game theory are used to demonstrate different "what if" scenarios. The results of the four player game suggest that, despite the commonly agreed fishing quota, the behaviour of the countries has been closer to non-cooperation than cooperation. Cooperation would more than double the net benefits from the fishery compared to a past fisheries policy. Side payments, however, are a prerequisite for a cooperative solution. Third, the thesis applies coalitional games in the partition function form to study whether the cooperative solution would be stable despite the potential presence of positive externalities. The results show that the cooperation of two out of four studied countries can be stable. Compared to a past fisheries policy, a stable coalition structure would provide substantial economic benefits. Nevertheless, the status of the salmon stocks would not improve significantly. Fourth, the thesis studies the prerequisites for and potential consequences of the implementation of an individual transferable quota (ITQ) system in the Finnish herring fishery. Simulation results suggest that ITQs would result in a decrease in the number of fishing vessels, but enables positive profits to overlap with a higher stock size. The empirical findings of the thesis affirm that the profitability of the studied fisheries could be improved. The evidence, however, indicates that incentives for free riding exist, and thus the most preferable outcome both in economic and biological terms is elusive.

Parameters Affecting the Extraction of Polycyclic Aromatic Hydrocarbons with Pressurised Hot Water

Pressurised hot water extraction (PHWE) exploits the unique temperature-dependent solvent properties of water minimising the use of harmful organic solvents. Water is environmentally friendly, cheap and easily available extraction medium. The effects of temperature, pressure and extraction time in PHWE have often been studied, but here the emphasis was on other parameters important for the extraction, most notably the dimensions of the extraction vessel and the stability and solubility of the analytes to be extracted. Non-linear data analysis and self-organising maps were employed in the data analysis to obtain correlations between the parameters studied, recoveries and relative errors. First, pressurised hot water extraction (PHWE) was combined on-line with liquid chromatography-gas chromatography (LC-GC), and the system was applied to the extraction and analysis of polycyclic aromatic hydrocarbons (PAHs) in sediment. The method is of superior sensitivity compared with the traditional methods, and only a small 10 mg sample was required for analysis. The commercial extraction vessels were replaced by laboratory-made stainless steel vessels because of some problems that arose. The performance of the laboratory-made vessels was comparable to that of the commercial ones. In an investigation of the effect of thermal desorption in PHWE, it was found that at lower temperatures (200ºC and 250ºC) the effect of thermal desorption is smaller than the effect of the solvating property of hot water. At 300ºC, however, thermal desorption is the main mechanism. The effect of the geometry of the extraction vessel on recoveries was studied with five specially constructed extraction vessels. In addition to the extraction vessel geometry, the sediment packing style and the direction of water flow through the vessel were investigated. The geometry of the vessel was found to have only minor effect on the recoveries, and the same was true of the sediment packing style and the direction of water flow through the vessel. These are good results because these parameters do not have to be carefully optimised before the start of extractions. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) were compared as trapping techniques for PHWE. LLE was more robust than SPE and it provided better recoveries and repeatabilities than did SPE. Problems related to blocking of the Tenax trap and unrepeatable trapping of the analytes were encountered in SPE. Thus, although LLE is more labour intensive, it can be recommended over SPE. The stabilities of the PAHs in aqueous solutions were measured using a batch-type reaction vessel. Degradation was observed at 300ºC even with the shortest heating time. Ketones and quinones and other oxidation products were observed. Although the conditions of the stability studies differed considerably from the extraction conditions in PHWE, the results indicate that the risk of analyte degradation must be taken into account in PHWE. The aqueous solubilities of acenaphthene, anthracene and pyrene were measured, first below and then above the melting point of the analytes. Measurements below the melting point were made to check that the equipment was working, and the results were compared with those obtained earlier. Good agreement was found between the measured and literature values. A new saturation cell was constructed for the solubility measurements above the melting point of the analytes because the flow-through saturation cell could not be used above the melting point. An exponential relationship was found between the solubilities measured for pyrene and anthracene and temperature.

Strategic Information Acquisition: Applications to Herding and Auctions

The information that the economic agents have and regard relevant to their decision making is often assumed to be exogenous in economics. It is assumed that the agents either poses or can observe the payoff relevant information without having to exert any effort to acquire it. In this thesis we relax the assumption of ex-ante fixed information structure and study what happens to the equilibrium behavior when the agents must also decide what information to acquire and when to acquire it. This thesis addresses this question in the two essays on herding and two essays on auction theory. In the first two essays, that are joint work with Klaus Kultti, we study herding models where it is costly to acquire information on the actions that the preceding agents have taken. In our model the agents have to decide both the action that they take and additionally the information that they want to acquire by observing their predecessors. We characterize the equilibrium behavior when the decision to observe preceding agents' actions is endogenous and show how the equilibrium outcome may differ from the standard model, where all preceding agents actions are assumed to be observable. In the latter part of this thesis we study two dynamic auctions: the English and the Dutch auction. We consider a situation where bidder(s) are uninformed about their valuations for the object that is put up for sale and they may acquire this information for a small cost at any point during the auction. We study the case of independent private valuations. In the third essay of the thesis we characterize the equilibrium behavior in an English auction when there are informed and uninformed bidders. We show that the informed bidder may jump bid and signal to the uninformed that he has a high valuation, thus deterring the uninformed from acquiring information and staying in the auction. The uninformed optimally acquires information once the price has passed a particular threshold and the informed has not signalled that his valuation is high. In addition, we provide an example of an information structure where the informed bidder initially waits and then makes multiple jumps. In the fourth essay of this thesis we study the Dutch auction. We consider two cases where all bidders are all initially uninformed. In the first case the information acquisition cost is the same across all bidders and in the second also the cost of information acquisition is independently distributed and private information to the bidders. We characterize a mixed strategy equilibrium in the first and a pure strategy equilibrium in the second case. In addition we provide a conjecture of an equilibrium in an asymmetric situation where there is one informed and one uninformed bidder. We compare the revenues that the first price auction and the Dutch auction generate and we find that under some circumstances the Dutch auction outperforms the first price sealed bid auction. The usual first price sealed bid auction and the Dutch auction are strategically equivalent. However, this equivalence breaks down in case information is acquired during the auction.

VEGFR-2 and VEGFR-3 Specific Signaling in Lymphangiogenesis and Angiogenesis

The circulatory system consists of the blood and lymphatic vessels. While blood vessels transport oxygen, cells, and nutrients to tissues, the lymphatic vessels collect fluid, cells, and plasma proteins from tissues to return back to the blood circulation. Angiogenesis, the growth of new blood vessels from pre-existing ones, is an important process involved in several physiological conditions such as inflammation, wound healing, and embryonic development. Furthermore, angiogenesis is found in many pathological conditions such as atherosclerosis and the growth and differentiation of solid tumors. Many tumor types spread via lymphatic vessels to form lymph node metastasis. The elucidation of the molecular players coordinating development of the vascular system has provided an array of tools for further insight of the circulatory system. The discovery of the Vascular Endothelial Growth Factor (VEGF) family members and their tyrosine kinase receptors (VEGFRs) has facilitated the understanding of the vasculature in different physiological and pathological situations. The VEGFRs are expressed on endothelial cells and mediate the growth and maintenance of both the blood and lymphatic vasculatures. This study was undertaken to address the role of VEGFR-2 specific signaling in maturation of blood vessels during neoangiogenesis and in lymphangiogenesis. We also wanted to differentiate between VEGFR-2 and VEGFR-3 specific signaling in lymphangiogenesis. We found that specific VEGFR-2 stimulation alone by gene therapeutic methods is not sufficient for production of mature blood vessels. However, VEGFR-2 stimulation in combination with expression of platelet-derived growth factor D (PDGF-D), a recently identified member of the PDGF growth factor family, was capable of stabilizing these newly formed vessels. Signaling through VEGFR-3 is crucial during developmental lymphangiogenesis, but we showed that the lymphatic vasculature becomes independent of VEGFR-3 signaling after the postnatal period. We also found that VEGFR-2 specific stimulation cannot rescue the loss of lymphatic vessels when VEGFR-3 signaling is blocked and that VEGFR-2 specific signals promote lymphatic vessel enlargement, but are not involved in vessel sprouting to generate new lymphatic vessels in vivo, in contrast to the VEGFR-2 dependent sprouting observed in blood vessels. In addition, we compared the inhibitory effects of a small molecular tyrosine kinase inhibitor of VEGFR-2 vs. VEGFR-3 specific signaling in vitro and in vivo. Our results showed that the tyrosine kinase inhibitor could equally affect physiological and pathological processes dependent on VEGFR-2 and VEGFR-3 driven angiogenesis or lymphangiogenesis. These results provide new insights into the VEGFR specific pathways required for pre- and postnatal angiogenesis as well as lymphangiogenesis, which could provide important targets and therapies for treatment of diseases characterized by abnormal angiogenesis or lymphangiogenesis.

Role of HMGB1 in cells of the circulation

The matrix of blood is a liquid plasma that transports molecules and blood cells within vessels lined by endothelial cells. High-mobility group B1 (HMGB1) is a protein expressed in blood cells. Under normal circumstances, HMGB1 is virtually absent from plasma, but during inflammation or trauma its level in plasma is increased. In resting and quiescent cells, HMGB1 is usually localized in the intracellular compartment, with the exception of motile cells that express HMGB1 on their outer surface to mediate cell migration. During cell transformation or immune cell activation HMGB1 can be actively secreted outside of the cell. Further, when a cell is damaged, HMGB1 can passively leak into extracellular environment. Extracellular HMGB1 can then participate in regulation of the immune response and under some conditions it can mediate lethality in systemic inflammatory response. The aim of this study was to evaluate the expression and functions of HMGB1 in cells of the vascular system and to investigate the prognostic value of circulating HMGB1 in severe sepsis and septic shock. HMGB1 was detected in platelets, leukocytes, and endothelial cells. HMGB1 was released from platelets and leukocytes, and it was found to mediate their adhesive and migratory functions. During severe infections the plasma levels of HMGB1 were elevated; however, no direct correlation with lethality was found. Further, the analysis of proinflammatory mechanisms suggested that HMGB1 forms complexes with other molecules to activate the immune system. In conclusion, HMGB1 is expressed in the cells of the vascular system, and it participates in inflammatory mechanisms by activating platelets and leukocytes and by mediating monocyte migration.