Browsing by Title

Sort by: Order: Results:

Now showing items 722-741 of 24304
  • Kastevaara, Tuulia (2005)
    Dehydraation ja endotoksemian tiedetään huonontavan kudosperfuusiota ja anestesian aikana munuaisten verenkierto heikentyy entisestään. Huonontunut munuaisperfuusio yhdessä anesteettien mahdollisesti toksisten metaboliittien kanssa voi johtaa munuaisvaurioihin, hevosella tavallisimmin akuuttiin tubulusnekroosiin. Munuaisvaurioiden toteamiseksi on useita erilaisia menetelmiä. Tutkimuksen tavoitteena oli löytää menetelmiä, joilla hevosten munuaisvaurioita olisi mahdollista todeta mahdollisimman aikaisessa vaiheessa jo ennen kuin peruuttamattomia vaurioita on tullut. Lisäksi haluttiin selvittää miten eri parametrit korreloivat keskenään. Koeaineistoksi kerättiin virtsa- ja verinäytteitä 12 hevoselta, jotka nukutettiin ähkyleikkausta tai ruunausta varten Yliopistollisessa eläinsairaalassa. Näytteitä otettiin sekä ennen leikkausta että leikkauksen jälkeen. Virtsanäytteistä määritettiin kreatiniini, proteiini, alkalinen fosfataasi (AFOS) ja gammaglutamyylitransferaasi (GGT). Seerumista määritettiin edellisten lisäksi urea, albumiini, sorbitolidehydrogenaasi (SDH) sekä aspartaattiaminotransferaasi (ASAT). Tutkituista virtsan entsyymeistä GGT ja AFOS vapautuvat molemmat proksimaalisen tubuluksen epiteelisoluista. Näiden entsyymien välille ei saatu minkäänlaista korrelaatiota kummassakaan näytteessä. Tutkimuksessamme oli virtsan GGT-aktiivisuus suhteessa virtsan kreatiniinipitoisuuteen kohonnut leikkauksen aikana 11:llä hevosella 12:sta. AFOS-aktiivisuus sen sijaan oli puolella hevosista kohonnut, puolella laskenut. Ilmeisesti AFOS ei vapaudu munuaisvaurioiden yhteydessä virtsaan yhtä herkästi kuin GGT. Tämä tukee sitä kirjallisuuden käsitystä, että GGT on hyvin herkkä munuaisvaurion mittari hevosella.
  • Supponen, Eljas (2012)
    OBJECTIVE: The number of elderly patients with aneurysmal subarachnoid hemorrhage (aSAH) is increasing but their prognosis remains unsatisfactory. Our aim is to determine which patients are most likely to benefit from active treatment. METHODS: Between 1980 and 2008, 289 patients aged ≥70 years were treated for aSAH at the Department of Neurosurgery, Helsinki University Central Hospital (HUCH). We assessed the functional outcome at three months and the mortality at one year after aSAH. RESULTS: Only 30% of actively treated patients had favorable outcome with a one year fatality rate of 36%. Predictive factors of favorable outcome included good initial clinical grade and the absence of intraventricular and intracerebral hemorrhage. Medical complications were associated with unfavorable outcome. CONCLUSION: Elderly aSAH patients have often poor prognosis. Severity of the SAH is the most important determinant of outcome. Active treatment decreases mortality and should be offered to patients with good initial clinical condition.
  • Laurila, Jouni (Helsingin yliopisto, 2002)
  • Leppä, Elli (Helsingin yliopisto, 2011)
    Neurons can be divided into various classes according to their location, morphology, neurochemical identity and electrical properties. They form complex interconnected networks with precise roles for each cell type. GABAergic neurons expressing the calcium-binding protein parvalbumin (Pv) are mainly interneurons, which serve a coordinating function. Pv-cells modulate the activity of principal cells with high temporal precision. Abnormalities of Pv-interneuron activity in cortical areas have been linked to neuropsychiatric illnesses such as schizophrenia. Cerebellar Purkinje cells are known to be central to motor learning. They are the sole output from the layered cerebellar cortex to deep cerebellar nuclei. There are still many open questions about the precise role of Pv-neurons and Purkinje cells, many of which could be answered if one could achieve rapid, reversible cell-type specific modulation of the activity of these neurons and observe the subsequent changes at the whole-animal level. The aim of these studies was to develop a novel method for the modulation of Pv-neurons and Purkinje cells in vivo and to use this method to investigate the significance of inhibition in these neuronal types with a variety of behavioral experiments in addition to tissue autoradiography, electrophysiology and immunohistochemistry. The GABA(A) receptor γ2 subunit was ablated from Pv-neurons and Purkinje cells in four separate mouse lines. Pv-Δγ2 mice had wide-ranging behavioral alterations and increased GABA-insensitive binding indicative of an altered GABA(A) receptor composition, particularly in midbrain areas. PC-Δγ2 mice experienced little or no motor impairment despite the lack of inhibition in Purkinje cells. In Pv-Δγ2-partial rescue mice, a reversal of motor and cognitive deficits was observed in addition to restoration of the wild-type γ2F77 subunit to the reticular nucleus of thalamus and the cerebellar molecular layer. In PC-Δγ2-swap mice, zolpidem sensitivity was restored to Purkinje cells and the administration of systemic zolpidem evoked a transient motor impairment. On the basis of these results, it is concluded that this new method of cell-type specific modulation is a feasible way to modulate the activity of selected neuronal types. The importance of Purkinje cells to motor control supports previous studies, and the crucial involvement of Pv-neurons in a range of behavioral modalities is confirmed.
  • Isokoski, Karoliina (Helsingin yliopisto, 2008)
    Rare-gas chemistry is of growing interest, and the recent advances include the "insertion" of a Xe atom into OH and water in the rare-gas hydrides HXeO and HXeOH. The insertion of Xe atoms into the H-C bonds of hydrocarbons was also demonstrated for HXeCC, HXeCCH and HXeCCXeH, the last of which was the first rare-gas hydride containing two rare-gas atoms. We describe the preparation and characterization of a new rare-gas compound, HXeOXeH. HXeOXeH was prepared in solid xenon by photolysis of a suitable precursor, for example water, and subsequent mobilization of the photoproducts. The experimental identification was carried out by FTIR spectroscopy, isotopic substitution and by use of various precursors. The photolytical and thermal stability of the new rare-gas hydride was also studied. The experimental work was supported by extensive quantum chemical calculations provided by our co-workers. HXeOXeH forms in a cryogenic xenon matrix from neutral O and H atoms in a two-step diffusion-controlled process involving HXeO as an intermediate [reactions (1) and (2)]. This formation mechanism is unique in that a rare-gas hydride is formed from another rare-gas hydride. H + Xe + O → HXeO (1) HXeO + Xe + H → HXeOXeH (2) Similarly to other rare-gas hydrides, HXeOXeH has a strongly IR-active H-Xe stretching vibration, allowing its spectral detection at 1379.3 cm-1. HXeOXeH is a very high-energy metastable species, yet thermally more stable than many other rare-gas hydrides. The calculated bending barrier of 0.57 eV, is not enough to explain the observed stability, and HXeOXeH might be affected by additional stabilization from the solid xenon environment. Chemical bonding between xenon and environmentally abundant species like water is of particular importance due to the “missing-xenon” problem. The relatively high thermal stability of HXeOXeH compared to other oxygen containing rare-gas compounds is relevant in this respect. Our work also raises the possibility of polymeric (–Xe–O)n networks, similarly to the computationally studied (XeCC)n polymers.
  • Astuti, Davide Nicola (Helsingin yliopisto, 2014)
    The provision of wireless access to voice and data services experienced an impressive growth of importance during the last 20 years. Most of the Internet applications employ the TCP/IP protocol suite to deliver their services. TCP has been developed to operate in a terrestrial network environment. However, with the rapid rise in wireless communication in recent years, it has become important to adapt TCP to heterogeneous environments that include both wireline networks and Wireless Wide-Area Networks (W-WANs), such as satellite and terrestrial wireless networks, in order to optimize performance. The specific link characteristics of wireless and satellite links, in particular high latencies and frequent frame losses due to bit-corruption, affect performance of transport protocols. TCP suffers because of low bandwidth, long connection set-up times, high latency and error rate, inefficient use of air link capacity. Most of next generation satellite systems utilizes Bandwidth-on-Demand (BoD) mechanisms to efficiently share radio resources among a large number of users. BoD mechanisms often causes additional link delay, which has a detrimental effect on TCP performance. In this thesis, we propose a new TCP/IP-friendly link level protocol, namely Satellite Link Aware Communication Protocol (SLACP) which incorporates a novel error-recovery mechanism aimed at drastically reduce the residual Packet Error Rate (PER) as seen by higher layers without producing significant extra delay. The protocol has been validated with experimental evaluations conducted in a Digital Video Broadcasting-Return Channel System (DVB-RCS) satellite environment, where the BoD technique Demand Assignment Multiple Access (DAMA) is employed to regulate the access to the satellite channel. Cross-layer interactions between link layer and transport layer as well as the impact of BoD mechanisms on TCP dynamics are investigated. Furthermore, experiments using a selected set of state-of-the-art TCP enhancements in conjunction with our TCP/IP-friendly link-level protocol have been carried out. The proposed mechanisms and improvements of the link and transport layer would be relevant for many wireless WAN systems.
  • Hopkins, Tapani (2012)
    Quantitative food webs have been used since the 1990s to describe the ecology of ecosystems. Such webs describe not only ‘who eats whom’ but also how many individuals get eaten, giving a detailed picture of the connections in an ecosystem. This detail allows far-reaching ecological conclusions to be drawn, for all manner of questions ranging from the influence of abiotic and biotic factors on population dynamics to the effect of latitude on ecosystem structure. Currently the webs’ greatest limitations are their incompleteness and lack of geographic coverage: most published webs focus on a tiny fragment of the total food web, and there are few webs from higher latitudes. In this thesis I address these limitations, by extending a parasitoid-lepidopteran web which is being collected in the High Arctic. I add data on bird and spider predation of the web’s Lepidoptera, and on the lepidopterans’ herbivory of their food plants. Specifically, I ask what the relative strengths of predation and parasitism are in this community, and what effect herbivory has on the plants’ seed production. I measured predation rates using both live caterpillars and modelling clay dummies as bait. The former, caterpillars of Sympistis nigrita tethered to threads, gave an estimate of both spider and bird predation. The latter showed bird predation only, but gave a larger sample size than tethered caterpillars. For the herbivory rates, I measured the seed production of avens flowers (Dryas octopetala x integrifolia, one of the main lepidopteran food plants) when damaged by feeding caterpillars. I found that predation is an important cause of mortality for S. nigrita, comparable to the high rates of parasitism already observed. During the larval period, some 38% of S. nigrita caterpillars are killed by spiders, 8% by parasitoids and 8% by birds. The caterpillars ate highly variable amounts of avens flowers, with 14.4% of flowers damaged by feeding in a set of 743 flowers, and 8.3% in another set of 672 flowers. The damaged flowers produced fewer and smaller seeds than did undamaged ones, causing overall avens seed production to drop by 7%. Overall, my findings show spider predation to be a relevant addition to the current parasitoid-lepidopteran food web. Bird predation, however, is relatively light – both when compared to spider predation and also to earlier predation rates reported from warmer latitudes. It is nevertheless comparable to the (naively twice as strong) parasitism since almost half the parasites die when their host is predated. When comparing food webs in order to address large scale ecological questions, such as the effect of latitude on food web structure, broader webs may be required instead of the mere parasitoid-host webs produced to date.
  • Hintsala, Emilia (2010)
    TAUSTA: Syöpään liittyvää angiogeneesiä eli verisuonten uudismuodostusta on tutkittu hyvin paljon mm. mahdollisena syöpähoitojen kohteena. Kiinteissä kasvaimissa ja leukemioissa on havaittu esimerkiksi angiogeneesiä säätelevien molekyylien tuotannon ja syöpäkudoksen ympäristön hiussuonitiheyden lisääntymistä. Tämän tutkimuksen tarkoituksena oli selvittää kahden angiogeneesiä säätelevän molekyylin, VEGF:n ja Angiopoietiini-2:n, pitoisuuksia lapsisyöpäpotilailla. METODIT: Määritimme VEGF- ja Angiopoietiini-2-pitoisuudet 49 kiinteäkasvainpotilaan plasmanäytteistä ja 35 leukemiapotilaan plasma- ja luuydinnäytteistä diagnoosivaiheessa ja hoidon aloittamisen jälkeen. TULOKSET: Kiinteäkasvainryhmässä mitattiin korkeampia VEGF-pitoisuuksia kuin leukemiaryhmässä ja pitoisuudet laskivat hoidon aloittamisen seurauksena. Leukemiaryhmässä mitattiin kiinteitä kasvaimia korkeampia Angiopoietiini-2-pitoisuuksia ja pitoisuudet laskivat hoidon aikana. Leukemiapotilailla hoidon aloittamisen jälkeen todettu korkea luuytimen VEGF-pitoisuus liittyi matalampaan elossaolo-osuuteen. VEGF- ja Angiopoietiini-2-pitoisuudet korreloivat plasma- ja luuydinnäytteiden välillä. Diagnoosivaiheessa lymfoomapotilailla oli korkeampia ja aivokasvainpotilailla matalampia Angiopoietiini-2-pitoisuuksia kuin muilla kiinteäkasvainpotilailla ja AML-potilailla korkeampia VEGF-pitoisuuksia kuin ALL-potilailla. PÄÄTELMÄT: Tutkimus antaa uutta tietoa lapsisyöpäpotilaiden angiogeneettisistä tekijöistä. VEGF- ja Angiopoietiini-2-pitoisuuksissa havaittiin eroja eri syöpätyyppien välillä ja muutoksia hoidon aloittamisen seurauksena. VEGF-pitoisuudella oli myös ennusteellista merkitystä.
  • Kärkkäinen, Johannes (2015)
    Vähäinen liikunta ja runsaasti energiaa sisältävä ravitsemus ovat aikaansaaneet räjähdysmäisen ylipainon ja lihavuuden yleistymisen. Ylipainoon ja lihavuuteen liittyvät sairaudet, kuten tyypin 2 diabetes mellitus, rasvamaksa, verenpainetauti, sepelvaltimotauti, hyperkolesterolemia, aivoinfarkti ja metabolinen oireyhtymä, ovat merkittäviä sairastavuuden ja ennenaikaisen kuolleisuuden aiheuttajia. Lihavuus ja insuliiniresistenssi ovat tyypin 2 diabetes mellituksen keskeisimmät riskitekijät. Patologinen reniini-angiotensiini-aldosteroni –järjestelmän (RAAS) aktivaatio on keskeisessä roolissa endoteelin toimintahäiriön ja insuliiniresistenssin kehityksessä useissa elimissä. Laajoissa kliinisissä lääketutkimuksissa on tullut esiin ACE-estäjien ja angiotensiini 2:den (AT2) tyypin 1 reseptoria salpaavien lääkeaineiden insuliiniherkkyyttä parantava ja uusia diabetestapauksia vähentävä vaikutus. AT2:den ja insuliinin aineenvaihdunta on monilta osin toisiinsa kietoutunutta ja RAAS-järjestelmällä on keskeinen rooli verenpaineen säätelyn lisäksi myös insuliinin klassisissa kohdekudoksissa. Selvittääksemme AT2:den roolia insuliiniresistenssin synnyssä ihmisen luurankolihaksessa tutkimme glukoosin kuljetusta 14 terveen koehenkilön vastus lateralis -lihaksesta avolihasbiopsiatekniikalla otetuissa lihasnäytteissä. Tutkimuksemme perusteella AT2:lla on ihmisen luurankolihassoluissa insuliinivälitteistä glukoosin soluun kuljetusta vähentävä vaikutus ex vivo. AT2 vähensi glukoosin kuljetusta 20 % insuliinin läsnä ollessa, mutta insuliinin puuttuessa AT2:lla ei ollut tilastollisesti merkittävää vaikutusta glukoosin kuljetukseen. RAAS-järjestelmä ja AT2 ovat siten mielenkiintoinen kohde pyrittäessä lisäämään lihaksen insuliiniherkkyyttä.
  • Uhlenius, Nina (Helsingin yliopisto, 2002)
  • Holopainen, Inka (Helsingin yliopisto, 2012)
    The study is on the human dimension of animal-based tourism. There is a growing interest in nature and wildlife tourism but also a dire need for more research, especially of tourist experiences and expectations. Animal-based tourism is a little studied subject and a rarely used term. Animal-based tourism, unlike wildlife tourism, includes the use of domesticated animals and also other types of encounters than watching. Wildlife, nature and adventure tourism literature is used for defining animal-based tourism. Experiencing is another substantial sector of tourism business nowadays, alongside nature and wildlife tourism. Instead of services and products, the tourists are seeking experiences. Experience is a complex and diverse concept that is comprised of many different elements. The main object of the study is to understand the phenomenon of animal-based tourism, to interpret the experiences animal-based tourism creates and the elements in the animal encounters that contribute to creating them. The study draws from humanistic geography and uses the hermeneutic understanding of the world in the interpretation of tourists' experiences. Travel magazine Matkalehti's destination descriptions and travel stories are used as data. The research includes altogether 419 different articles in 111 magazines over 16 years of time. The articles are studied with content analysis, by looking for the typical characteristics of animal-based tourism (presented in the background chapter) and finding the various experiences and the elements that cause them (defined in the theoretical framework). The study is deductive, leaning strongly on the experience theories and frameworks presented in animal-based tourism literature. It was found that the animal-based tourism presented in the magazines was quite substantial and it reflected the definitions presented in the tourism literature. However, some variations were found: riding as an encounter had a far greater role than was expected. In Finland, alongside fishing, it was almost as important as watching animals. Abroad, watching was clearly the most popular encounter type. The destinations of animal-based tourism in the magazines varied greatly and they reflected the destinations typically of importance for Finns. However, clear focus points were seen. For example safaris (on land) typically took place in Sub-Saharan Africa, and whales and dolphins were watched in Iceland, Norway, Canary islands and the Azores, etc. Animals were encountered in many different settings but between captive- and wild-settings there was not a big difference, both occurred equally often. Captive-settings were usually located near cities or available areas for attracting bigger user groups, when wild-settings demanded more effort from the tourists. Species of animals reflected the findings in similar studies, and it was noticed that specific types of animals were preferred over others. Watching animals in captive-settings and in shows did not seem to evoke as many or as strong experiences as meeting them in the wild. Rare and endangered species as well as exotic and strange ones were preferred over others almost in every case. Some species were found to be icons for certain areas and were always mentioned with the same destinations. With certain species like dolphins, close interaction was sought after, and domesticated animals were found interesting only if there was a chance for touching and feeding them. Especially in fishing, riding and diving the settings and the beauty of the surroundings were important, but also the intensity of the activity. Education and conservation, which are a part of animal-based tourism according to literature, were not mentioned as often as was expected. The naturalness of the settings, the well-being of animals and the engaging nature of the encounters were the most crucial elements for creating experiences in animal-based tourism. Experiences of animal-based tourism were multiple as were the elements creating them.
  • von Schantz-Fant, Carina (Helsingin yliopisto, 2009)
    Neuronal ceroid lipofuscinoses (NCLs) are a family of inherited pediatric neurodegenerative disorders, leading to retinal degeneration, death of selective neuronal populations and accumulation of autofluorscent ceroid-lipopigments. The clinical manifestations are generally similar in all forms. The Finnish variant late infantile neuronal ceroid lipofuscinosis (vLINCLFin) is a form of NCL, especially enriched in the Finnish population. The aim of this thesis was to analyse the brain pathology of vLINCLFin utilising the novel Cln5-/- mouse model. Gene expression profiling of the brains of already symptomatic Cln5-/- mice revealed that inflammation, neurodegeneration and defects in myelinization are the major characteristics of the later stages of the disease. Histological characterization of the brain pathology confirmed that the thalamocortical system is affected in Cln5-/- mice, similarly to the other NCL mouse models. However, whereas the brain pathology in all other analyzed NCL mice initiate in the thalamus and spread only months later to the cortex, we observed that the sequence of events is uniquely reversed in Cln5-/- mice; beginning in the cortex and spreading to the thalamus only months later. We could also show that even though neurodegeneration is inititated in the cortex, reactive gliosis and loss of myelin are evident in specific nuclei of the thalamus already in the 1 month old brain. To obtain a deeper insight into the disturbed metabolic pathways, we performed gene expression profiling of presymptomatic mouse brains. We validated these findings with immunohistological analyses, and could show that cytoskeleton and myelin were affected in Cln5-/- mice. Comparison of gene expression profiling results of Cln5-/- and Cln1-/- mice, further highlighted that these two NCL models share a common defective pathway, leading to disturbances in the neuronal growth cone and cytoskeleton. Encouraged by the evidence of this defected pathway, we analyzed the molecular interactions of NCL-proteins and observed that Cln5 and Cln1/Ppt1 proteins interact with each other. Furthermore, we demonstrated that Cln5 and Cln1/Ppt1 share an interaction partner, the F1-ATP synthase, potentially linking both vLINCLFIN and INCL diseases to disturbed lipid metabolism. In addition, Cln5 was shown to interact with other NCL proteins; Cln2, Cln3, Cln6 and Cln8, implicating a central role for Cln5 in the NCL pathophysiology. This study is the first to describe the brain pathology and gene expression changes in the Cln5-/- mouse. Together the findings presented in this thesis represent novel information of the disease processes and the molecular mechanisms behind vLINCLFin and have highlighted that vLINCLFin forms a very important model to analyze the pathophysiology of NCL diseases.
  • Herva, Tuomas (Helsingin yliopisto, 2015)
    Animal welfare (AW) is an issue of growing concern in Finland as well as in other developed countries. A public debate has focused on the potential AW problems resulting from current production systems. Possibilities to find mutual benefit for animals, farmers, industry and society have received less attention. According to the reviewed literature the inconsistency of determination and perception of AW appeared to be a major barrier to enhance AW. Farmers should be confident that their measures to promote AW satisfy public opinion and are ecomically sustainable. The main objective of the study was a thorough understanding of relationships between AW and beef production economics to find barriers and opportunities for enhanced AW. A version of the Animal Needs Index (ANI/TGI 35L), modified for Finnish beef production, called A-index was used for AW assessments. The A-Index was modified and evaluated based on Test Theory. On-field associations between A-index and production parameters were determined on 180 farms and over 12 000 bulls using statistical multilevel models. Economic evaluation of AW was based on comparison between cold and warm housing using the confirmed association between AW and production results. AW was associated with good production results. A-Index and the best subset of items used as welfare score (WFS) were covering different aspects of AW. The association between the used measures and production results, reflecting AW in certain degree, can be considered as a proof of the criterion validity of A-Index and WFS. Cold housing with enhanced welfare and bedding based on own straw at a reasonable price was economically favourable. Profitability of cold housing was sensitive to fluctuation in bedding price. Developing a reasonably priced market for bedding material would be a major way to enhance AW. Rubber covered slats were found to be a profitable way to enhance AW in warm housing. A reform of the subsidy system was suggested to be needed to fulfil the aims of the subsidy regime to support AW.