Lebanese Plants and Plant-Derived Compounds Against Colon Cancer

Colorectal cancer (CRC) is a major health concern and demands long-term efforts in developing strategies for screening and prevention. CRC has become a preventable disease as a consequence of a better understanding of colorectal carcinogenesis. However, current therapy is unsatisfactory and necessitates the exploration of other approaches for the prevention and treatment of cancer. Plant based products have been recognized as preventive with regard to the development of colon cancer. Therefore, the potential chemopreventive use and mechanism of action of Lebanese natural product were evaluated. Towards this aim the antitumor activity of Onopordum cynarocephalum and Centaurea ainetensis has been studied using in vitro and in vivo models. In vitro, both crude extracts were non cytotoxic to normal intestinal cells and inhibited the proliferation of colon cancer cells in a dose-dependent manner. In vivo, both crude extracts reduced the number of tumors by an average of 65% at weeks 20 (adenomas stage) and 30 (adenocarcinomas stage). The activity of the C. ainetensis extract was attributed to Salograviolide A, a guaianolide-type sesquiterpene lactone, which was isolated and identified through bio-guided fractionation. The mechanism of action of thymoquinone (TQ), the active component of Nigella sativa, was established in colon cancer cells using in vitro models. By the use of N-acetyl cysteine, a radical scavenger, the direct involvement of reactive oxygen species in TQ-induced apoptotic cells was established. The analytical detection of TQ from spiked serum and its protein binding were evaluated. The average recovery of TQ from spiked serum subjected to several extraction procedures was 2.5% proving the inability of conventional methods to analyze TQ from serum. This has been explained by the extensive binding (>98%) of TQ to serum and major serum components such as bovine serum albumin (BSA) and alpha-1-acid glycoprotein (AGP). Using mass spectrometry analysis, TQ was confirmed to bind covalently to the free cysteine in position 34 and 147 of the amino acid sequence of BSA and AGP, respectively. The results of this work put at the disposal for future development new plants with anti-cancer activities and enhance the understanding of the pharmaceutical properties of TQ, a prerequisite for its future clinical development.

Putative neuroprotective compounds in in vitro models of dopaminergic neurodegeneration

Parkinson´s disease (PD) is a debilitating age-related neurological disorder that affects various motor skills and can lead to a loss of cognitive functions. The motor symptoms are the result of the progressive degeneration of dopaminergic neurons within the substantia nigra. The factors that influence the pathogenesis and the progression of the neurodegeneration remain mostly unclear. This study investigated the role of various programmed cell death (PCD) pathways, oxidative stress, and glial cells both in dopaminergic neurodegeneration and in the protective action of various drugs. To this end, we exposed dopaminergic neuroblastoma cells (SH-SY5Y cells) to 6-OHDA, which produces oxidative stress and activates various PCD modalities that result in neuronal degeneration. Additionally, to explore the role of glia, we prepared rat midbrain primary mixed-cell cultures containing both neurons and glial cell types such as microglia and astroglia and then exposed the cultures to either MPP plus or lipopolysaccharide. Our results revealed that 6-OHDA activated several PCD pathways including apoptosis, autophagic stress, lysosomal membrane permeabilization, and perhaps paraptosis in SH-SY5Y cells. Furthermore, we found that minocycline protected SH-SY5Y cells from 6-OHDA by inhibiting both apoptotic and non-apoptotic PCD modalities. We also observed an inconsistent neuroprotective effect of various dietary anti-oxidant compounds against 6-OHDA toxicity in vitro in SH-SY5Y cells. Specifically, quercetin and curcumin exerted neuroprotection only within a narrow concentration range and a limited time frame, whereas resveratrol and epigallocatechin 3-gallate provided no protection whatsoever. Lastly, we found that molecules such as amantadine may delay or even halt the neurodegeneration in primary cell cultures by inhibiting the release of neurotoxic factors from overactivated microglia and by enhancing the pro-survival actions of astroglia. Together these data suggest that the strategy of dampening oxidative species with anti-oxidants is less effective than preventing the production of toxic factors such as oxidative and pro-inflammatory molecules by pathologically activated microglia. This would subsequently prevent the activation of various PCD modalities that cause neuronal degeneration.

Rossijskaja Karelija i karely v imperskoi politike Rossii, 1905-1917

Russian Karelians were one of the small peasant nations of the Russian Empire that began to identify themselves as nations during the late imperial period. At that historical moment Russian Karelia fell between an economically undeveloped empire and the rapidly modernizing borderland of Finland. The economic and cultural lure of Finland drew Karelians into the Finnish camp. This attraction was seen as a challenge to Russia and influenced the straggle between Russia and Finland for the Karelians. This struggle was waged from 1905 to 1917. This work is focused on the beginning stage of the struggle, its various phases, and their results. The confrontation extended into different dimensions (economic, political, ideological, church and cultural politics) and occurred on two levels: central and regional. Countermeasures against local nationalisms developed much earlier both in Russia and in other empires for use were also used in the Russian Karelian case. Economic policies were deployed to try to make relations with Russia more alluring for Karelians and to improve their economic condition. However, these efforts produced only minimal results due to the economic weakness of the empire and a lack of finances. Fear of the economic integration of the Karelians and Finns, which would have stimulated the economy of the Karelia, also hindered these attempts. The further development of the Orthodox Church, the schools and the zemstvos in Karelia yielded fewer results than expected due to the economic underdevelopment of the region and the avoidance of the Finnish language. Policizing measures were the most successfull, as all activities in Russian Karelia by the Finns were entirely halted in practice. However, the aspiration of Russian Karelians to integrate their home districts with Finland remained a latent force that just waited for an opportunity to push to the surface again. Such a chance materialized with the Russian revolution. The Karelian question was also a part of Russian domestic political confrontation. At the and of the 1800s, the Russian nationalist right had grown strong and increasingly gained the favor of the autocracy. The right political forces exploited the Karelian question in its anti-Finnish ideology and in its general resistance to the national emancipation of the minority peoples of Russia. A separate ideology was developed, focusing on the closeness of Karelians to the "great Russian people." Simultaneously, this concept found a place in the ultramonarchist myth of the particularly close connection between the people and tsar that was prominent in the era of Nicholas II. This myth assigned the Karelians a place amongst the "simple people" faithful to the tsar.

Death, Destruction and Commemoration : Tracing ritual activities in Finnish Late Iron Age cemeteries (AD 550-1150)

The thesis is connected with death, memory and ancestor commemoration during the Merovingian Period, the Viking Age and the beginning of the Crusade Period (AD 550-1150) in Finland. During this time, cremation was the dominant burial rite. It was not until the end of the Viking Age that inhumation became more common but both cremations and inhumations are performed even at the same sites throughout the time. Three different burial types 1) cremation cemeteries below level ground, 2) inhumation burials and 3) water burials are discussed in five articles. I consider these burial forms from three different viewpoints; collectivity-individuality, visibility-invisibility and cremation-inhumation. The thesis also discusses the topics of memory, memorialisation and monument re-use, which have been neglected subjects in Finnish archaeology until now. Both cremation cemeteries below level ground and inhumation burials have been re-used during their time of usage, and on most occasions are situated in a landscape that is overlaid by other monuments as well. The main questions of the thesis are: What kinds of ritual behaviour can we detect in the burials during the period (AD 550-1150)? How did people perceive the moraine hills that functioned as burial places? What kind of re-use can be detected in the Iron Age cemeteries? Why have ancient sites and artefacts been re-used? This thesis shows that it is possible to claim that both artefact and site re-use is a much more widespread phenomenon than has previously been thought in Finnish archaeology. It is also a conscious and deliberate behaviour that can be related to an ancestor cult and commemoration of the dead. The funerary rituals during this time period show great variation and complex, both regionally and nationally. Not only have the dead been buried using elaborate rituals, they have also been mourned and commemorated in intricate ways that proves that death was not an end product, but the start of something new.

Kaaoksen kautta tai hitaasti kiiruhtaen : Pedagoginen muutosprosessi luokanopettajan näkökulmasta

The purpose of this study was to describe and get a deep understanding of pedagogical change process. The phases of pedagogical change process and the nature and the role of teacher s pedagogical thinking in it were mapped. The change process as a whole was also modeled. The previous research of teaching change process has had been scarce on an individual teacher level, but on a school level it has been investigated abundantly. The theoretical background of this study consists of theories of teacher s pedagogical thinking and action and how their thinking and action change and develop. Teacher change has been researched from the point of view of both school change and professional development. The basic principle in the theoretical frame is that change in teacher s thinking leads to change in action. Three men teachers and a woman teacher who have put change into practice took part in this study. The data consisted of two parts: teachers essays of their change process and interviews that were based on the essays. The data was analysed by content analysis. The categorizations of both parts of the data were made separately but they were interpreted together. In this way a deep understanding of pedagogical change process could be reached. The results of this study were descriptions of the phases of pedagogical change process and the nature and the role of teacher s pedagogical thinking in it. In addition a model of pedagogical change process was presented. Pedagogical change process started up because of disorder in teacher s pedagogical thinking and action. The disorder leads to an absolute necessity to change the activities. Change activities stabilize throughout intuitive experiments and reflection-on-action. The change in a teacher s thinking is a prerequisite for the start of the process but also, a teacher s thinking develops as a result of the process. Thus, the whole process results in a real, deep level change in instruction and in the teacher s thinking. That is why pedagogical change processes are visible, significant and they have wide and extensive effects. The study gives out information of controlling the change processes. Consequently, the results of this study encourage teachers to confront change and put their new ideas into practice. Keywords change, development, pedagogical thinking, pedagogical action, teaching-studying-learning process

Leisure activities and obesity in adolescence : a follow-up study among twins

The aims of this dissertation were 1) to investigate associations of weight status of adolescents with leisure activities, and computer and cell phone use, and 2) to investigate environmental and genetic influences on body mass index (BMI) during adolescence. Finnish twins born in 1983–1987 responded to postal questionnaires at the ages of 11-12 (5184 participants), 14 (4643 participants), and 17 years (4168 participants). Information was obtained on weight and height, leisure activities including television viewing, video viewing, computer games, listening to music, board games, musical instrument playing, reading, arts, crafts, socializing, clubs, sports, and outdoor activities, as well as computer and cell phone use. Activity patterns were studied using latent class analysis. The relationship between leisure activities and weight status was investigated using logistic and linear regression. Genetic and environmental effects on BMI were studied using twin modeling. Of individual leisure activities, sports were associated with decreased overweight risk among boys in both cross-sectional and longitudinal analyses, but among girls only cross-sectionally. Many sedentary leisure activities, such as video viewing (boys/girls), arts (boys), listening to music (boys), crafts (girls), and board games (girls), had positive associations with being overweight. Computer use was associated with a higher prevalence of overweight in cross-sectional analyses. However, musical instrument playing, commonly considered as a sedentary activity, was associated with a decreased overweight risk among boys. Four patterns of leisure activities were found: ‘Active and sociable’, ‘Active but less sociable’, ‘Passive but sociable’, and ‘Passive and solitary’. The prevalence of overweight was generally highest among the ‘Passive and solitary’ adolescents. Overall, leisure activity patterns did not predict overweight risk later in adolescence. An exception were 14-year-old ‘Passive and solitary’ girls who had the greatest risk of becoming overweight by 17 years of age. Heritability of BMI was high (0.58-0.83). Common environmental factors shared by family-members affected the BMI at 11-12 and 14 years but their effect had disappeared by 17 years of age. Additive genetic factors explained 90-96% of the BMI stability across adolescence. Genetic correlations across adolescence were high, which suggests similar genetic effects on BMI throughout adolescence, while unique environmental effects on BMI appeared to vary. These findings suggest that family-based interventions hold promise for obesity prevention into early and middle adolescence, but that later in adolescence obesity prevention should focus on individuals. A useful target could be adolescents' leisure time, and our findings highlight the importance of versatility in leisure activities.

Essays on Illegal Activities, Institutions and Economic Growth

In public economics, two extremist views on the functions of a government compete: one emphasizes government working for the public interest to provide value for the citizens, while another regards government mainly as a workhorse for private interests. Moreover, as the sole legitimate authority, the government has the right to define the rules and laws as well as to enforce them. With respect to regulation, two extremes arise: from too little regulation to too much of it. If the government does not function or ceases to exist, the state falls into anarchy or chaos (Somalia). If it regulates too much, it will completely suffocate private activities, which might be considered extralegal (the former Soviet Union). In this thesis I scrutinize the government s interventionist policies and evaluate the question of how to best promote economic well-being. The first two essays assume that the government s policies promote illegal activity. The first paper evaluates the interaction between the government and the mafia, and pays attention to the law enforcement of underground production. We show that the revenue-maximizing government will always monitor the shadow economy, as monitoring contributes to the government s revenue. In general, both legal and illegal firms are hurt by the entry of the mafia. It is, however, plausible that legal firms might benefit by the entry of the mafia if it competes with the government. The second paper tackles the issue of the measurement of the size of the shadow economy. To formulate policies it is essential to know what drives illegal economic activity; is it the tax burden, excess regulation, corruption or a weak legal environment? In this paper we propose an additional explanation for tax evasion and shadow production, namely cultural factors as manifested by religion as determinants of tax morality. According to our findings, Catholic and Protestant countries do not differ in their tax morale. The third paper contributes to the literature discussing the role of the government in promoting economic and productivity growth. Our main result is that, given the complex relationship between economic growth and economic freedom, marketization has not necessarily been beneficial in terms of growth. The last paper builds on traditional growth literature and revisits the debate on convergence clubs arising from demographic transition. We provide new evidence against the idea that countries within a club would converge over time. Instead, we propose that since the demographic transition is a dynamic process, one can expect countries to enter the last regime of stable, modern growth in stages.

The Vexing Case of Igor Shafarevich, a Russian Political Thinker

The Russian mathematician, academician and former dissident Igor Shafarevich (b. 1923) is commonly mentioned in Western scholarly studies on perestroika and post-perestroika-era Russian politics as one of the most notable anti-Semites and extreme nationalists of the country. This notoriety owes to Shafarevich’s old samizdat article Russophobia, which was published in 1988. The scandal surrounding Russophobia came to a head when the president of The National Academy of Sciences in the United States asked Shafarevich, its honorary member, to resign. Nothing like this had ever happened in the academy’s history. The present dissertation discusses Shafarevich’s political activities, his texts and ideas as well as their reception. Particular attention is given to Russophobia, whose detailed examination proves very clearly that its reputation as an anti-Semitic text is groundless. The reasons for Russophobia’s hasty but fierce condemnation were many, but only one was that when the Soviet system began to tumble, it was commonly assumed that a vigorous rise in anti-Semitism and extreme nationalism in the Soviet Union/Russia would be just a matter of time. Many observers were highly sensitised to detecting its signs and symptoms. The dissertation also shows that most of those to write the first criticisms of Russophobia and to liken Shafarevich to the ideologues of Nazi Germany were the same people he had criticised in Russophobia for their deterministic view of history and irrational manner of connecting things for the purpose of fanning the flames of distrust between Russia’s Jews and Russians. In retrospect, it is fairly evident that Shafarevich actually managed to effectively “neutralise” the message of many of those obsessed with the Jews among his Russian contemporaries and contributed to the fact that anti-Jewish sentiments have been a great deal less popular in post-communist Russia than so many had feared and expected. The thesis also thoroughly discusses Shafarevich’s other texts and activities before Russophobia’s appearance and after it. In the 1970s, Shafarevich was one of the best-known dissidents in the Soviet Union. He worked together with academician Andrei Sakharov in a dissidents’ unofficial human rights committee and co-operated closely with Aleksandr Solzhenitsyn before Solzhenitsyn’s exile. Then, during the chaotic years of perestroika, Shafarevich defended the basic rights of ordinary citizens and warned that the hype concerning democracy could become counterproductive if the most palpable result of the reforms was the disappearance of citizens’ basic security and elementary social justice. One of the conclusions of the thesis is that even if the world around Shafarevich has changed considerably, his views have remained essentially the same since the late 1960s and early 1970s.

Traditional medicinal uses and biological activities of some plant extracts of African Combretum Loefl., Terminalia L. and Pteleopsis Engl. species

In Africa various species of Combretum, Terminalia and Pteleopsis are used in traditional medicine. Despite of this, some species of these genera have still not been studied for their biological effects to validate their traditional uses. The aim of this work has been to document the ethnomedicinal uses of several species of Combretum and Terminalia in Mbeya region, south-western Tanzania, and to use this information for finding species with good antimicrobial and cytotoxic potential. During a five weeks expedition to Tanzania in spring 1999 sixteen different species of Combretum and Terminalia, as well as Pteleopsis myrtifolia were collected from various locations in the districts of Mbeya, Iringa and Dar-es-Salaam. Traditional healers in seven different villages in the Mbeya region were interviewed in Swahili and Nyakyusa on the medicinal uses of Combretum and Terminalia species shown to them. A questionnaire was used during the interviews. The results of the interviews correlated well between different villages, the same species being used in similar ways in different villages. Of the ten species shown to the healers six were frequently used for treatment of skin diseases, bacterial infections, diarrhea, oedema and wounds. The dried plants were most commonly prepared into hot water decoctions or mixed into maize porridge, Ugali. Infusions made from dried or fresh plant material were also common. Wounds and topical infections were treated with ointments made from the dried plant material mixed with sheep fat. Twenty-one extracts of six species of Combretum and four of Terminalia, collected from Tanzania, were screened for their antibacterial effects against two gram-negative and five gram-positive bacteria, as well as the yeast, Candida albicans, using an agar diffusion method. Most of the screened plants showed substantial antimicrobial activity. A methanolic root extract of T. sambesiaca showed the most potent antibacterial effects of all the plant species screened, and gave a MIC value of 0.9 mg/ml against Enterobacter aerogenes. Also root extracts of T. sericea and T. kaiserana gave excellent antimicrobial effects, and notably a hot water extract of T. sericea was as potent as extracts of this species made from EtOH and MeOH. Thus, the traditional way of preparing T. sericea into hot water decoctions seems to extract antimicrobial compounds. Thirty-five extracts of five species of Terminalia, ten of Combretum and Pteleopsis myrtifolia were screened for their antifungal effects against five species of yeast (Candida spp.) and Cryptococcus neoformans. The species differed from each other to their antifungal effects, some being very effective whereas others showed no antifungal effects. The most effective extracts showed antifungal effects comparable to the standard antibiotics itraconazol and amphotericin B. Species of Terminalia gave in general stronger antifungal effects than those of Combretum. The best effects were obtained with methanolic root extracts of T. sambesiaca, T. sericea and T. kaiserana, and this investigation indicates that decoctions of these species might be used for treatment of HIV-related fungal infections. Twenty-seven crude extracts of eight species of Combretum, five of Terminalia and Pteleopsis myrtifolia were evaluated for their cytotoxic effects against human cancer cell lines (HeLa, cervical carcinoma; MCF 7, breast carcinoma, T 24 bladder carcinoma) and one endothelial cell line (BBCE, bovine brain capillary endothelial cells). The most outstanding effects were obtained with a leaf extract of Combretum fragrans, which nearly totally inhibited the proliferation of T 24 and HeLa cells at a concentration of 25 ug/ml and inhibited 60 % of the growth of the HeLa cells at a concentration of 4.3 ug/ml. The species of Terminalia were less cytotoxically potent than the Combretum species, although T. sericea and T. sambesiaca gave good cytotoxic effects (< 30 % proliferation). In summary this study indicates that some of the species of Terminalia, Combretum and Pteleopsis, used in Tanzanian traditional medicine, are powerful inhibitors of both microbial and cancer cell growth. In depth studies would be needed to find the active compounds behind these biological activities.

Synthesis of neoglycoconjugates and oligosaccharides with potential anti-Helicobacter pylori activity

The significance of carbohydrate-protein interactions in many biological phenomena is now widely acknowledged and carbohydrate based pharmaceuticals are under intensive development. The interactions between monomeric carbohydrate ligands and their receptors are usually of low affinity. To overcome this limitation natural carbohydrate ligands are often organized as multivalent structures. Therefore, artificial carbohydrate pharmaceuticals should be constructed on the same concept, as multivalent carbohydrates or glycoclusters. Infections of specific host tissues by bacteria, viruses, and fungi are among the unfavorable disease processes for which suitably designed carbohydrate inhibitors represent worthy targets. The bacterium Helicobacter pylori colonizes more than half of all people worldwide, causing gastritis, gastric ulcer, and conferring a greater risk of stomach cancer. The present medication therapy for H. pylori includes the use of antibiotics, which is associated with increasing incidence of bacterial resistance to traditional antibiotics. Therefore, the need for an alternative treatment method is urgent. In this study, four novel synthesis procedures of multivalent glycoconjugates were created. Three different scaffolds representing linear (chondroitin oligomer), cyclic (γ-cyclodextrin), and globular (dendrimer) molecules were used. Multivalent conjugates were produced using the human milk type oligosaccharides LNDFH I (Lewis-b hexasaccharide), LNnT (Galβ1-4GlcNAcβ1-3Galβ1-4Glc), and GlcNAcβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glc all representing analogues of the tissue binding epitopes for H. pylori. The first synthetic method included the reductive amination of scaffold molecules modified to express primary amine groups, and in the case of dendrimer direct amination to scaffold molecule presenting 64 primary amine groups. The second method described a direct procedure for amidation of glycosylamine modified oligosaccharides to scaffold molecules presenting carboxyl groups. The final two methods that were created both included an oxime-linkage on linkers of different length. All the new synthetic procedures synthesized had the advantage of using unmodified reducing sugars as starting material making it easy to synthesize glycoconjugates of different specificity. In addition, the binding activity of an array of neoglycolipids to H. pylori was studied. Consequently, two new neolacto-based structures, Glcβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-Cer and GlcAβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-Cer, with binding activity toward H. pylori were discovered. Interestingly, N-methyl and N-ethyl amide modification of the GlcAβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-Cer glucuronic acid residue resulted in more effective H. pylori binding epitopes than the parent molecule.

Microbial activities in boreal soils: Biodegradation of organic contaminants at low temperature and ammonia oxidation

This thesis deals with the response of biodegradation of selected anthropogenic organic contaminants and natural autochthonous organic matter to low temperature in boreal surface soils. Furthermore, the thesis describes activity, diversity and population size of autotrophic ammonia-oxidizing bacteria (AOB) in a boreal soil used for landfarming of oil-refinery wastes, and presents a new approach, in which the particular AOB were enriched and cultivated in situ from the landfarming soil onto cation exchange membranes. This thesis demonstrates that rhizosphere fraction of natural forest humus soil and agricultural clay loam soil from Helsinki Metropolitan area were capable of degrading of low to moderate concentrations (0.2 50 µg cm-3) of PCP, phenanthrene and 2,4,5-TCP at temperatures realistic to boreal climate (-2.5 to +15 °C). At the low temperatures, the biodegradation of PCP, phenanthrene and 2,4,5-TCP was more effective (Q10-values from 1.6 to 7.6) in the rhizosphere fraction of the forest soil than in the agricultural soil. Q10-values of endogenous soil respiration (carbon dioxide evolution) and selected hydrolytic enzyme activities (acetate-esterase, butyrate-esterase and β-glucosidase) in acid coniferous forest soil were 1.6 to 2.8 at temperatures from -3 to +30 °C. The results indicated that the temperature dependence of decomposition of natural autochthonous soil organic matter in the studied coniferous forest was only moderate. The numbers of AOB in the landfarming (sandy clay loam) soil were determined with quantitative polymerase chain reaction (real-time PCR) and with Most Probable Number (MPN) methods, and potential ammonium oxidation activity was measured with the chlorate inhibition technique. The results indicated presence of large and active AOB populations in the heavily oil-contaminated and urea-fertilised landfarming soil. Assessment of the populations of AOB with denaturing gradient gel electrophoresis (DGGE) profiling and sequence analysis of PCR-amplified 16S rRNA genes showed that Nitrosospira-like AOB in clusters 2 and 3 were predominant in the oily landfarming soil. This observation was supported by fluorescence in situ hybridization (FISH) analysis of the AOB grown on the soil-incubated cation-exchange membranes. The results of this thesis expand the suggested importance of Nitrosospira-like AOB in terrestrial environments to include chronically oil-contaminated soils.

Expression, Enzymatic Activities and Subcellular Localization of Hepatitis E Virus and Semliki Forest Virus Replicase Proteins

Viruses are submicroscopic, infectious agents that are obligate intracellular parasites. They adopt various types of strategies for their parasitic replication and proliferation in infected cells. The nucleic acid genome of a virus contains information that redirects molecular machinery of the cell to the replication and production of new virions. Viruses that replicate in the cytoplasm and are unable to use the nuclear transcription machinery of the host cell have developed their own transcription and capping systems. This thesis describes replication strategies of two distantly related viruses, hepatitis E virus (HEV) and Semliki Forest virus (SFV), which belong to the alphavirus-like superfamily of positive-strand RNA viruses. We have demonstrated that HEV and SFV share a unique cap formation pathway specific for alphavirus-like superfamily. The capping enzyme first acts as a methyltransferase, catalyzing the transfer of a methyl group from S-adenosylmethionine to GTP to yield m7GTP. It then transfers the methylated guanosine to the end of viral mRNA. Both reactions are virus-specific and differ from those described for the host cell. Therefore, these capping reactions offer attractive targets for the development of antiviral drugs. Additionally, it has been shown that replication of SFV and HEV takes place in association with cellular membranes. The origin of these membranes and the intracellular localization of the components of the replication complex were studied by modern microscopy techniques. It was demonstrated that SFV replicates in cytoplasmic membranes that are derived from endosomes and lysosomes. According to our studies, site for HEV replication seems to be the intermediate compartment which mediates the traffic between endoplasmic reticulum and the Golgi complex. As a result of this work, a unique mechanism of cap formation for hepatitis E virus replicase has been characterized. It represents a novel target for the development of specific inhibitors against viral replication.