Browsing by Organization "Helsingfors universitet, bio- och miljövetenskapliga fakulteten, institutionen för bio- och miljövetenskaper"

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  • Puskarjov, Martin (Helsingin yliopisto, 2010)
    The Cl- and HCO3- electrochemical gradients across the plasma membrane dictate the electrical consequences of GABAA receptor (GABAAR) function and thereby play a significant role in neuronal GABA-mediated signalling. In adult pyramidal neurons, responses to GABA are maintained hyperpolarizing mainly by the action of K-Cl cotransporter isoform 2 (KCC2). KCC2 acts as a Cl- extrusion mechanism responsible for setting the intracellular Cl- concentration below the electrochemical equilibrium, a necessary condition for hyperpolarizing inhibition mediated by GABAARs. Recent evidence suggests that plasmalemmal KCC2 has a very high rate of turnover, pointing to a novel role for changes in KCC2 expression in diverse manifestations of neuronal plasticity. Some studies indicate that rapid down-regulation of KCC2 may be a general early response involved in various kinds of neuronal trauma. In this work, whole-cell patch-clamp was used to examine KCC2 function under a pharmacologically induced arrest of protein synthesis in living hippocampal brain slices from rat. The stability of KCC2 function was quantitatively assessed on the basis of the dendritic Cl- extrusion capacity in the presence of protein synthesis inhibitors cycloheximide and emetine. The parameter used for assessing extrusion capacity was a somato-dendritic Cl- gradient, which was imposed by a somatic Cl- load that resulted in a gradient of EGABA (ΔEGABA). The results of this study show that under general protein synthesis inhibitor-induced arrest of translation, KCC2 function persists unperturbed for at least 4 hours and hence that the cessation of mRNA translation cannot rapidly induce downregulation of KCC2-mediated Cl- extrusion. This finding precludes the use of protein synthesis inhibitors for rapid modulation of KCC2 function. Indirectly, the results presented here imply that the levels of KCC2 under pathophysiological conditions are primarily determined by the degradation rate and not by de novo synthesis.
  • Joensuu, Laura (Helsingin yliopisto, 2010)
    Carbon dioxide (CO2) is the most significant greenhouse gas produced by mankind. The oceans play a significant role in the global carbon cycle. Due to its restricted size the Baltic Sea doesn’t play an important role as a global reservoir. However, due to its large annual fluctuations, alternations in salinity in the different basins, and a wide drainage-basin with varying soil, it is an excellent study system. The aim of this research was to examine both the vertical and the horizontal distributions of the components of the inorganic carbon in the Baltic Sea, their interactions and annual fluctuations. In addition, the long-term alterations of the surface water pH were reviewed. The study was performed at the Finnish Meteorological Institute as a part of an international research programme regarding the Baltic Sea (BONUS: Baltic-C). The total alkalinity in the Baltic Sea was found to be determined mainly by salinity. Surface water alkalinity is controlled by mixing of highly saline waters originating in the North Sea and waters of low salinity from the rivers draining into the Baltic Sea. The amount of total alkalinity entering the Baltic Sea through the rivers is dependent on the soilquality in the catchment area. According to the alkalinity-salinity-relation, the Baltic Sea can be divided into four distinguishable basins. The alkalinity is lowest in the Bothnian Bay and grows towards the Kattegat as a function of salinity. Salinity controls alkalinity, which together with biological activity controls the consentration of total inorganic carbon. The distribution of total inorganic carbon is very similar to that of total alkalinity. The results in this study support earlier findings on total inorganic carbon and total alkalinity in the Baltic Sea. As the atmospheric partial pressure of carbon dioxide (pCO2) rises, the partial pressure in the surface waters rises as well. In addition to the concentration of total inorganic carbon, the biological activity has a great impact on the annual fluctuations of pCO2. The primary production forms the basis of the biological uptake of carbon dioxide in the surface waters. The results indicate that the Baltic Sea fluctuates from being a source to being a sink for atmospheric CO2 according to the annual fluctuations in primary production. However, simultaneous measurements on the atmospheric pCO2 are needed to ascertain the assumptions on the direction of CO2 flux between the sea and the atmosphere. The rise of the pCO2 in water leads to descending pH levels, because of a relative shift in the components of total inorganic carbon. The results indicate a slight decreasing trend in pH levels In the Baltic Sea during the 30-year observation period, however more research on the subject is needed. The reliability of pCO2-values calculated from known parameters was estimated by comparing them to the measured values. The study shows that pCO2 results for the Baltic Sea derived from the program developed for the oceans, should be used with caution.
  • Aivelo, Tuomas (Helsingin yliopisto, 2009)
    Patogeenit ja loiset ovat merkittävä evolutiivinen tekijä, koska ne ovat yleisiä. Näiltä suojautuminen on evolutiivisesti merkittävä tekijä ja tärkeä trade-off: Immuunipuolustuksen ylläpito on kallista, mutta toisaalta edistää selviytyvyyttä. Selkärangattomilla ei ole yhtä hienostunutta immuunipuolustusta kuin selkärankaisilla, mutta on esitetty arvailuja, että Erityisesti yhteiskuntahyönteisillä voisi odottaa olevan sosiaalisia menetelmiä immuunipuolustuksen käynnistämisessä. Vanhemmat työläiset voisivat ”rokottaa” vastakuoriutuneita työläisiä ja näin tehostaa näiden immuunipuolustusta. Tavoitteeni oli selvittää onko näin tarkastelemalla antimikrobiaalisien peptidien määrää muurahaisten hemolymfassa kuoriutumisen jälkeen. Tutkin bakteerimaljauskokeiden avulla antimikrobiaalisten peptidien määrää loviniskamuurahaisten (Formica exsecta) vastakuoriutuneiden työläisten hemolymfassa. Pilottikokeissa selvitin sopivan bakteerilajin ja –annoksen varsinaisiin kokeisiin ja pidin luonnosta tuotuja muurahaisia karanteenissa, jotta saisin selville aleneeko immuunivaste pienemmässä patogeenipaineessa. Varsinaisissa kokeissa käytin viittä eri käsittelyä. Tartutin muurahaisia antamalla suun kautta (1) kuollutta bakteeria tai (2) elävää bakteeria. Annoin muurahaisten kasvaa (3) vanhojen työläisten kanssa tai (4) kuolleelle bakteerille altistettujen muurahaisten kanssa. (5) Kontrollina toimi käsittely, jossa muurahaisille ei tehty mitään. Antimikrobiaalisten peptidien määrän selvittämisen lisäksi tarkkailin työläisten kuolleisuutta eri käsittelyissä. Pilottikokeiden tulokset eivät antaneet bakteeriannostuksen tai –valinnan suhteen vahvoja tuloksia. Tarkastelin määrän ja bakteerin vaikutusta varianssianalyysillä ja lineaarisella regressiolla, mutta selkeitä riippuvuuksia ja merkitsevyyksiä ei löytynyt. Päädyin käyttämään Micrococcus luteus –bakteeria ja tarttuttamaan muurahaiset juottamalla niille bakteerilientä. Karanteenikokeessa ei tapahtunut merkittävää immuunivasteen sammumista Varsinaisten kokeiden aineiston analysoin tilastollisesti varianssianalyysillä. Immuunivasteen käynnistymiseen vaikutti tilastollisesti merkitsevästi vain aika: Kahden päivän näytteissä ei ollut lähes lainkaan antimikrobiaalisia peptidejä, kun taas viikon ja kahden näytteistä hieman yli puolessa oli peptidejä. Käsittelyillä tai pesillä ei ollut tilastollisesti merkitseviä eroja immuunivasteen käynnistymisessä. Kuolleisuus oli suurinta käsittelyissä, joissa työläisiä tartutettiin kuolleella ja elävällä bakteereilla ja pienintä käsittelyissä, joissa työläisiä kasvatettiin yhdessä kuolleella bakteerilla tartutettujen ja tartuttamattomien vanhojen työläisten kanssa. Kontrollikäsittely erosi näistä molemmista merkittävästi ja kuolleisuus oli näiden kahden ryhmän välissä. Tutkimukseni puoltaa näkemystä, että vastakuoriutuneilla muurahaisilla ei ole vielä toimivaa immuunipuolustusta, mutta se käynnistyy ympäristöstä riippumatta muutaman päivän kuluessa. Omassa tutkimuksessani vanhemmat työläiset eivät auttaneet immuunivasteen käynnistymisessä, eikä ympäristön patogeenipaine nopeuttanut tai tehostanut immuunivasteen syntymistä. Täydellinen muodonmuutos on fysiologisesti rankka prosessi, jonka aikana muurahainen on hyvin suojattu kotelon sisällä – työläinen ei siis välttämättä tarvitse puolustusta vaan voi panostaa muihin kustannuksiin.
  • Hardwick, Bess (Helsingin yliopisto, 2008)
    A parabiologist is an assistant in biological research without formal academic training. In this study, I use volunteer parabiologists to conduct a national survey of oak cynipid gall wasps, tribe Cynipini (Hymenoptera: Cynipidae). My objectives were to produce an updated list of Finnish oak cynipid species, to map the distribution of these species, and to examine factors that could have an effect on local species richness and on the regional distribution and local abundance of individual species. I also wanted to examine whether the two generations of a species tend to occur on the same or on different individual trees. Empirical data on local gall wasp assemblages were collected by over a hundred volunteers from all over Finland, mostly people with a general interest in nature. Since most gall wasps occur as two discrete generations, volunteers sampled oak trees twice during the summer of 2007, with the spring round encompassing 218 trees and the autumn one 180. From each tree, five half-metre branches were examined, followed by a ten-minute scan of the rest of the branches. The recovered samples were then sent to me for identification. Based on tree-specific information supplied by the volunteers, I used generalised linear models to examine the effects of the number of neighbouring oaks, of oak circumference and of sampling location on the species richness of gall wasps, on the local incidence of species and on their local abundance. The survey produced data on 16 oak cynipid species, two of which were new to Finland. These new records bring the total number of species recorded in Finland up to 21. The centre of oak cynipid species richness was in the southwest, but some species were found as far north as Ostrobothnia. Within some species, different generations occurred on different individual trees. For this reason, I separated the generations in the distribution maps and statistical analyses. Against a backdrop of large-scale clines in species richness, local species richness was affected by the number of neighbouring oaks and by tree circumference. Large oaks that are surrounded by many other oaks support the most species-rich communities of oak cynipids, and the local incidence of certain species and of generations within species exhibit similar patterns. To conclude, oak cynipids are suitable targets for sampling by parabiologists, and this survey has improved our knowledge of the Finnish oak cynipid fauna. Oak cynipids have successfully spread beyond the host plant’s narrow natural distribution and colonised the planted trees in the north. Since large oaks close to other oaks exhibit the most diverse gall wasp communities, the natural old oak forests in the southwest of Finland are particularly important to these species.