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Now showing items 949-968 of 27945
  • Kanerva, Kristiina (Helsingin yliopisto, 2010)
    Polyamines are organic polycations that participate in various physiological functions, including cell proliferation, differentiation and apoptosis. Cellular polyamines originate from endogenous biosynthesis and exogenous sources. Their subcellular pool is under strict control, achieved by regulating their uptake and metabolism. Polyamine-induced proteins called antizymes (AZ) act as key regulators of intracellular polyamine concentration. They regulate both the transport of polyamines and the activity and degradation of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis. AZs themselves are negatively regulated by antizyme inhibitor (AZIN). AZIN functions as a positive regulator of cellular polyamine homeostasis, which by binding to AZs reactivates ODC and induces the uptake of polyamines. In various pathological conditions, including cancer, polyamine levels are misregulated. Polyamine homeostasis has therefore become an attractive target for therapeutic interventions and it is thus crucial to characterize the molecular basis underlying the homeostatic regulation. A novel human AZIN-resembling protein was previously identified in our group. The purpose of this study was to elucidate the function and distribution of this protein, termed as an antizyme inhibitor 2 (AZIN2). According to my results, AZIN2 functions as a novel regulator of polyamine homeostasis. It shows no enzymatic activity, but instead it binds AZs and negates their activity, which subsequently leads to reactivation of ODC and inhibition of its degradation. Expression of AZIN2 is restricted to terminally differentiated cells, such as mast cells (MC) and neurosecretory cells. In these actively secreting cell types, AZIN2 localizes to subcellular vesicles or granules where its function is important for the vesicle-mediated secretion. In MCs, AZIN2 localizes to the serotonin-containing subset of MC granules, and its expression is coupled to MC activation. The functional role of polyamines as potential mediators of MC activity was also investigated, and it was observed that the secretion of serotonin is selectively dependent on activation of ODC. In neurosecretory cells, AZIN2-positive vesicles localize mainly to the trans-Golgi network (TGN). Depletion of AZIN2 or cellular polyamines causes selective fragmentation of the TGN and retards secretion of proteins. Since addition of exogenous polyamines reverses these effects, the data indicate that AZIN2 and its downstream effectors, polyamines, are functionally implicated in the regulation of secretory vesicle transport. My studies therefore reveal a novel function for polyamines as modulators of both constitutive and regulated secretion. Based on the results, I propose that the role of AZIN2 is to act as a local in situ activator of polyamine biosynthesis.
  • Korpinen, Kasperi Nikolai (2005)
    Opinnäytetyössä on analysoitu pankkiryhmien yrityksille ja elinkeinonharjoittajille toimialoittain myöntämien lainojen korkoja. Korkoja on mallinnettu kovarianssianalyysin avulla. Estimointimenetelminä on käytetty pienimmän neliösumman ja painotetun pienimmän neliösumman menetelmiä. Korkoaineistolle estimoiduista paneeliaineistomalleista on johdettu aggregoimalla makromallit ja verrattu näitä suoraan aggregaattitasolla estimoituihin tavanomaisiin makromalleihin. Heterogeenisista paneeliaineistomalleista saadaan johdettua makromallit, joiden kertoimien keskivirheet ovat pienimmät. Kun painoina käytettiin uusien lainojen määrien neliöjuurimuunnoksia, painotetun pienimmän neliösumman menetelmällä päästiin paneeliaineistomalleissa parempiin aggregaattitason sovitteisiin. Muutokset eri pankkiryhmien eri toimialoille myöntämien uusien lainojen määrissä vaikuttavat aggregaattikorkoon. Tavanomaiset makromallit eivät sisällä informaatiota näissä markkinaosuuksissa tapahtuvista muutoksista. Selittävinä tekijöinä käytettiin konkurssialttiutta, keskuspankin ohjauskorkoa, kuluttajabarometriä, toimi-aloittaisia liikevaihto- ja arvonlisätietoja, Herfindahl-indeksiä, uusien lainojen osuuksia toimialan lainoista yhteensä sekä kokonaistuotannon kuukausikuvaajaa. Toimialakohtaiset muuttujat osoittautuivat epästabiileiksi ja aiheuttivat multikollineaarisuusongelmia. Merkitsevimmiksi ja vakaimmiksi selittäviksi tekijöiksi osoittautuivat ohjauskorko, uusien lainojen osuus toimialan uusista lainoista, kuluttajabarometri ja vuosivakiot. Tutkimuksessa todetaan, että korot vaihtelevat pankkiryhmittäin ja toimialoittain. Korkojen erot ovat vähentyneet koko tarkasteluperiodin aikana vuoden 1997 alusta vuoden 2002 loppuun. Lainamarkkinoiden keskittyneisyys on laskenut kaikilla toimialoilla paitsi maa- ja kalataloustoimialoilla. Samoin korkojen poikkeamat keskuspankin ohjauskorosta ovat pienentyneet. Korkojen ja ohjauskoron välisten erojen pieneneminen on tapahtunut eri vauhtia.
  • Lietsala, Leena (Helsingfors universitet, 2010)
  • Salokannel, Juhani (1971)
  • Pelkonen, L. ((191)
  • Otava, T. K. (Tunt)
  • Toivola, Impi Siviä (1935)
  • Halila, Aimo Oskari ((193)
  • Julkunen, Asta-Maija (1985)
  • Grönqvist, Inkeri (1961)
  • Raunio, Jussi (Helsingin yliopisto, 2015)
    Automatic measurement of temporally varying soil moisture content could result in benefits both in agriculture and other applications. Mainly due to the ease of automation only electrical methods are suitable for measuring the variability of temporal moisture content. Capacitance technology is one of the most suitable methods for this kind of purpose. When determining soil moisture content by dielectricity means one will face two main properties: soil permittivity and soil electrical conductivity. Moisture measurement is based mainly on the changes of soil permittivity. Instead, changes in the soil electrical conductivity typically hamper the accuracy of moisture measurements. The measurement accuracy can be improved, however, by increasing the measurement frequency. The aim of this study was to determine the impact of sensor’s physical geometry and measuring frequency to the reliability of measurement. Combination of two measurement frequencies and an additional measurement of soil resistance were also determined for improving the accuracy. This study was carried out as part of the SAFETOOL project which aims were to monitor and to develop measurement tools for measuring and monitoring the status of the environment in field conditions. The sampling volume of capacitive sensors was examined in both field and laboratory conditions. To stabilize the weather moisture measurements were done only in laboratory conditions. The study was divided into two parts: pre-study and main-study. During the main-study five different capacitive geometries and the measurement of soil resistance were examined. Capacitance was measured using three frequencies: 5,5, 70 and 95 MHz. A commercial EC-5 capacitance sensor (Decagon Devices, Pullman, WA, USA) was used as control. Measurements were carried out in containers of volume about 3 litres filled with fine sand. Moisture measurements were conducted with volumetric water contents of 5 %, 15 %, 25 % and 35 % while the electrical conductivity varied between 2 and 24. Changes in the physical geometry did not result in remarkable differences of accuracy. The measurement volumes were also similar within the variable geometries. The impact of changes in the electrical conductivity, or salinity, however, was significant. Measuring the resistance of the soil lead typically to better results. However, this could be due to relatively high soil electrical conductivity. While working within the framework of normal field conditions and the right calibration one might expect to get reliable moisture measurements with a capacitance moisture sensor.