Browsing by Subject "CYCLE"

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  • Asvestari, E.; Willamo, T.; Gil, A.; Usoskin, I. G.; Kovaltsov, G. A.; Mikhailov, V. V.; Mayorov, A. (2017)
    Nearly 70 Ground Level Enhancements (GLEs) of cosmic rays have been recorded by the worldwide neutron monitor network since the 1950s depicting a big variety of energy spectra of solar energetic particles (SEP). Here we studied a statistical relation between the event-integrated intensity of GLEs (calculated as count-rate relative excess, averaged over all available polar neutron monitors, and expressed in percent-hours) and the hardness of the solar particle energy spectra. For each event the integral omnidirectional event integrated fluences of particles with energy above 30 MeV (F-30) and above 200 MeV (F-200) were computed using the reconstructed spectra, and the ratio between the two fluences was considered as a simple index of the event's hardness. We also provided a justification of the spectrum estimate in the form of the Band-function, using direct PAMELA data for GLE 71 (17-May-2012). We found that, while there is no clear relation between the intensity and the hardness for weak events, all strong events with the intensity greater 100 % h are characterized by a very hard spectrum. This implies that a hard spectrum can be securely assumed for all extreme GLE events, e.g., those studied using cosmogenic isotope data in the past. (C) 2016 COSPAR. Published by Elsevier Ltd. All rights reserved.
  • Flechard, Chris R.; van Oijen, Marcel; Cameron, David R.; de Vries, Wim; Ibrom, Andreas; Buchmann, Nina; Dise, Nancy B.; Janssens, Ivan A.; Neirynck, Johan; Montagnani, Leonardo; Varlagin, Andrej; Loustau, Denis; Legout, Arnaud; Ziemblinska, Klaudia; Aubinet, Marc; Aurela, Mika; Chojnicki, Bogdan H.; Drewer, Julia; Eugster, Werner; Francez, Andre-Jean; Juszczak, Radoslaw; Kitzler, Barbara; Kutsch, Werner L.; Lohila, Annalea; Longdoz, Bernard; Matteucci, Giorgio; Moreaux, Virginie; Nefte, Albrecht; Olejnik, Janusz; Sanz, Maria J.; Siemens, Jan; Vesala, Timo; Vincke, Caroline; Nemitz, Eiko; Zechmeister-Boltenstern, Sophie; Butterbach-Bahl, Klaus; Skiba, Ute M.; Sutton, Mark A. (2020)
    The effects of atmospheric nitrogen deposition (N-dep) on carbon (C) sequestration in forests have often been assessed by relating differences in productivity to spatial variations of N-dep across a large geographic domain. These correlations generally suffer from covariation of other confounding variables related to climate and other growth-limiting factors, as well as large uncertainties in total (dry + wet) reactive nitrogen (N-r) deposition. We propose a methodology for untangling the effects of N-dep from those of meteorological variables, soil water retention capacity and stand age, using a mechanistic forest growth model in combination with eddy covariance CO2 exchange fluxes from a Europe-wide network of 22 forest flux towers. Total N-r deposition rates were estimated from local measurements as far as possible. The forest data were compared with data from natural or semi-natural, non-woody vegetation sites. The response of forest net ecosystem productivity to nitrogen deposition (dNEP/dN(dep)) was estimated after accounting for the effects on gross primary productivity (GPP) of the co-correlates by means of a meta-modelling standardization procedure, which resulted in a reduction by a factor of about 2 of the uncorrected, apparent dGPP/dN(dep) value. This model-enhanced analysis of the C and N-dep flux observations at the scale of the European network suggests a mean overall dNEP/dN(dep) response of forest lifetime C sequestration to N-dep of the order of 40-50 g C per g N, which is slightly larger but not significantly different from the range of estimates published in the most recent reviews. Importantly, patterns of gross primary and net ecosystem productivity versus N-dep were non-linear, with no further growth responses at high N-dep levels (N-dep > 2.5-3 gNm(-2) yr(-1)) but accompanied by increasingly large ecosystem N losses by leaching and gaseous emissions. The reduced increase in productivity per unit N deposited at high N-dep levels implies that the forecast increased N-r emissions and increased N-dep levels in large areas of Asia may not positively impact the continent's forest CO2 sink. The large level of unexplained variability in observed carbon sequestration efficiency (CSE) across sites further adds to the uncertainty in the dC/dN response.
  • Charman, D. J.; Beilman, D. W.; Blaauw, M.; Booth, R. K.; Brewer, S.; Chambers, F. M.; Christen, J. A.; Gallego-Sala, A.; Harrison, S. P.; Hughes, P. D. M.; Jackson, S. T.; Korhola, A.; Mauquoy, D.; Mitchell, F. J. G.; Prentice, I. C.; van der Linden, M.; De Vleeschouwer, F.; Yu, Z. C.; Alm, J.; Bauer, I. E.; Corish, Y. M. C.; Garneau, M.; Hohl, V.; Huang, Y.; Karofeld, E.; Le Roux, G.; Loisel, J.; Moschen, R.; Nichols, J. E.; Nieminen, T. M.; MacDonald, G. M.; Phadtare, N. R.; Rausch, N.; Sillasoo, Ue; Swindles, G. T.; Tuittila, E-S.; Ukonmaanaho, L.; Valiranta, M.; van Bellen, S.; van Geel, B.; Vitt, D. H.; Zhao, Y. (2013)
  • Airaksinen, N.; Nurmi-Luthje, I.; Luthje, P. (2016)
    Background and Aims: The coverage of the official statistics is poor in motorcycle and moped accidents. The aim of this study was to analyze the severity of motorcycle and moped crashes, and to define the degree of under-reporting in official statistics. Material and Methods: All first attendances due to an acute motorcyclist or moped driver injury registered in the emergency department between June 2004 and May 2006 were analyzed. The severity of the injuries was classified using the Abbreviated Injury Scale score and the New Injury Severity Score. The hospital injury data were compared to the traffic accident statistics reported by the police and compiled and maintained by Statistics Finland. Results: A total of 49 motorcyclists and 61 moped drivers were involved in crashes, leading to a total of 94 and 109 injuries, respectively. There were slightly more vertebral and midfoot fractures among motorcyclists than among moped drivers (p=0.038 and 0.016, respectively). No significant differences were found between the severity (maximum Abbreviated Injury Scale and median New Injury Severity Scores) of the motorcycle and moped crashes. There was no in-hospital mortality. The degree of agreement (overlap) between the hospital dataset and the official statistics was 32%. The rate of under-reporting was 68%. Conclusions: According to the maximum Abbreviated Injury Scale and New Injury Severity Scores, the injury severity was equal for motorcycle and moped crashes. The degree of agreement between the hospital dataset and the official statistics was 32%.
  • Feldman, Tatiana; Yakovleva, Marina; Viljanen, Martta Leena Maria; Lindström, Magnus; Donner, Kristian; Ostrovsky, M.A. (2020)
    We have studied dark-adaptation at three levels in the eyes of the crustaceanMysis relictaover 2-3 weeks after exposing initially dark-adapted animals to strong white light: regeneration of 11-cisretinal through the retinoid cycle (by HPLC), restoration of native rhodopsin in photoreceptor membranes (by MSP), and recovery of eye photosensitivity (by ERG). We compare two model populations ("Sea", S-p, and "Lake", L-p) inhabiting, respectively, a low light and an extremely dark environment. 11-cisretinal reached 60-70% of the pre-exposure levels after 2 weeks in darkness in both populations. The only significant L-p/S(p)difference in the retinoid cycle was that L(p)had much higher levels of retinol, both basal and light-released. In S-p, rhodopsin restoration and eye photoresponse recovery parallelled 11-cisretinal regeneration. In L-p, however, even after 3 weeks only ca. 25% of the rhabdoms studied had incorporated new rhodopsin, and eye photosensitivity showed only incipient recovery from severe depression. The absorbance spectra of the majority of the L(p)rhabdoms stayed constant around 490-500 nm, consistent with metarhodopsin II dominance. We conclude that sensitivity recovery of S(p)eyes was rate-limited by the regeneration of 11-cisretinal, whilst that of L(p)eyes was limited by inertia in photoreceptor membrane turnover.
  • Mõttus, Matti; Aragão, Luiz; Bäck, Jaana; Clemente, Rocío Hernandez; Maeda, Eduardo Eiji; Markiet, Vincent Robert Leon; Nichol, Caroline; Oliveira, Raimundo Cosme; Restrepo-Coupe, Natalia (2019)
    The spectral properties of plant leaves relate to the state of their photosynthetic apparatus and the surrounding environment. An example is the well known photosynthetic downregulation, active on the time scale from minutes to hours, caused by reversible changes in the xanthophyll cycle pigments. These changes affect leaf spectral absorption and are frequently quantified using the photochemical reflectance index (PRI). This index can be used to remotely monitor the photosynthetic status of vegetation, and allows for a global satellite-based measurement of photosynthesis. Such earth observation satellites in near-polar orbits usually cover the same geographical location at the same local solar time at regular intervals. To facilitate the interpretation of these instantaneous remote PRI measurements and upscale them temporally, we measured the daily course of leaf PRI in two evergreen biomes—a European boreal forest and an Amazon rainforest. The daily course of PRI was different for the two locations: At the Amazonian forest, the PRI of Manilkara elata leaves was correlated with the average photosynthetic photon flux density (PPFD) ( R2=0.59 ) of the 40 minutes preceding the leaf measurement. In the boreal location, the variations in Pinus sylvestris needle PRI were only weakly ( R2=0.27) correlated with mean PPFD of the preceding two hours; for Betula pendula, the correlation was insignificant regardless of the averaging period. The measured daily PRI curves were specific to species and/or environmental conditions. Hence, for a proper interpretation of satellite-measured instantaneous photosynthesis, the scaling of PRI measurements should be supported with information on its correlation with PPFD.
  • Luukkonen, Panu K.; Dufour, Sylvie; Lyu, Kun; Zhang, Xian-Man; Hakkarainen, Antti; Lehtimäki, Tiina E.; Cline, Gary W.; Petersen, Kitt Falk; Shulman, Gerald I.; Yki-Järvinen, Hannele (2020)
    Weight loss by ketogenic diet (KD) has gained popularity in management of nonalcoholic fatty liver disease (NAFLD). KD rapidly reverses NAFLD and insulin resistance despite increasing circulating nonesterified fatty acids (NEFA), the main substrate for synthesis of intrahepatic triglycerides (IHTG). To explore the underlying mechanism, we quantified hepatic mitochondrial fluxes and their regulators in humans by using positional isotopomer NMR tracer analysis. Ten overweight/obese subjects received stable isotope infusions of: [D-7]glucose, [C-13(4)]beta-hydroxybutyrate and [3-C-13]lactate before and after a 6-d KD. IHTG was determined by proton magnetic resonance spectroscopy (H-1-MRS). The KD diet decreased IHTG by 31% in the face of a 3% decrease in body weight and decreased hepatic insulin resistance (-58%) despite an increase in NEFA concentrations (+35%). These changes were attributed to increased net hydrolysis of IHTG and partitioning of the resulting fatty acids toward keto-genesis (+232%) due to reductions in serum insulin concentrations (-53%) and hepatic citrate synthase flux (-38%), respectively. The former was attributed to decreased hepatic insulin resistance and the latter to increased hepatic mitochondrial redox state (+167%) and decreased plasma leptin (-45%) and triiodothyronine (-21%) concentrations. These data demonstrate heretofore unde-scribed adaptations underlying the reversal of NAFLD by KD: That is, markedly altered hepatic mitochondrial fluxes and redox state to promote ketogenesis rather than synthesis of IHTG.
  • Asmala, Eero; Osburn, Christopher L.; Paerl, Ryan W.; Paerl, Hans W. (2021)
    Estuaries regulate transport of dissolved organic carbon (DOC) from land to ocean. Export of terrestrial DOC from coastal watersheds is exacerbated by increasing major rainfall and storm events and human activities, leading to pulses of DOC that are shunted through rivers downstream to estuaries. Despite an upward trend of extreme events, the fate of the pulsed terrestrial DOC in estuaries remains unclear. We analyzed the effects of seven major tropical cyclones (TC) from 1999 to 2017 on the quantity and fate of DOC in the Neuse River Estuary (NC, USA). Significant TC-induced increases in DOC were observed throughout the estuary; the increase lasting from around 50 d at head-of-tide to over 6 months in lower estuary. Our results suggest that pulsed terrestrial DOC associated with TCs temporarily overwhelms the estuarine filter's abiotic and biotic degradation capacity under such high flow events, enhancing the shunt of terrestrial carbon to the coastal ocean.
  • Tamminen, Tuire; Sahlin, Lena; Masironi-Malm, B.; Dahlbom, Merja; Katila, Terttu; Taponen, Juhani; Vapaavuori, Outi (2019)
    This study aimed to examine the etiology of canine dystocia by measuring the relative expression of oxytocin receptor (OXTR) mRNA and the concentration of serum progesterone, plasma PGF(2 alpha) metabolite (PGFM), and blood ionized calcium (iCa) near term and in dystocia. Altogether 58 bitches were included in this study, 41 of which underwent cesarean section (CS). The four CS groups were based on history: complete uterine inertia (CUI; n = 7), partial uterine inertia (PUI; n = 13), obstructive dystocia (OD; n = 10), and elective cesarean section (ECS; n = 11). An additional group of medically treated dystocia without CS (MD; n = 8) and a control group (C; n = 9) with normal parturition (without CS and medical treatment) were also formed. Blood samples were taken prior to CS or medical treatment. Progesterone concentrations were highest in the ECS and a significant difference (p <0.05) was observed between the ECS and the OD and between the ECS and the combined dystocia (CUI, PUI, OD, MD) groups (COMB). Highest concentrations of PGFM was observed in the C, the difference being significant (p <0.05) between the C and the ECS and between the C and the COMB group. The progesterone:PGFM ratio was significantly (p <0.05) higher in the ECS than in the C and the COMB group. No significant difference (p> 0.05) was observed in iCa concentrations between the groups. Relative OXTR mRNA expression was evaluated with real-time PCR from full-thickness uterine samples taken from the incision site during CS. The expression was highest in the ECS and the difference in expression was significant (p <0.05) between the ECS and the OD and between ECS and the combined dystocia (CUI, PUI, OD) groups (COMB2). The study supports previous reports of decreasing progesterone and increasing PGFM during prepartum luteolysis. Upregulation of OXTR occurs near term. In obstructive dystocia, a prolonged influence of oxytocin and uterine exhaustion may lead to downregulation of OXTR. Complete primary uterine inertia may have a different etiology as no clear decrease in OXTR was observed in CUI as in OD. It remains unclear if parturition ceases because of uterine inertia or if uterine inertia occurs because of ceased parturition and desensitization of receptors. (C) 2019 Elsevier Inc. All rights reserved.
  • Arasu, Uma Thanigai; Deen, Ashik Jawahar; Pasonen-Seppänen, Sanna; Heikkinen, Sami; Lalowski, Maciej; Kärnä, Riikka; Härkönen, Kai; Mäkinen, Petri; Lazaro-Ibañez, Elisa; Siljander, Pia R-M; Oikari, Sanna; Levonen, Anna-Liisa; Rilla, Kirsi (2020)
    Intercellular communication is fundamental to the survival and maintenance of all multicellular systems, whereas dysregulation of communication pathways can drive cancer progression. Extracellular vesicles (EVs) are mediators of cell-to-cell communication that regulate a variety of cellular processes involved in tumor progression. Overexpression of a specific plasma membrane enzyme, hyaluronan synthase 3 (HAS3), is one of the factors that can induce EV shedding. HAS3, and particularly its product hyaluronan (HA), are carried by EVs and are known to be associated with the tumorigenic properties of cancer cells. To elucidate the specific effects of cancerous, HAS3-induced EVs on target cells, normal human keratinocytes and melanoma cells were treated with EVs derived from GFP-HAS3 expressing metastatic melanoma cells. We found that the HA receptor CD44 participated in the regulation of EV binding to target cells. Furthermore, GFP-HAS3-positive EVs induced HA secretion, proliferation and invasion of target cells. Our results suggest that HAS3-EVs contains increased quantities of IHH, which activates the target cell hedgehog signaling cascade and leads to the activation of c-Myc and regulation of claspin expression. This signaling of IHH in HAS3-EVs resulted in increased cell proliferation. Claspin immunostaining correlated with HA content in human cutaneous melanocytic lesions, supporting our in vitro findings and suggesting a reciprocal regulation between claspin expression and HA synthesis. This study shows for the first time that EVs originating from HAS3 overexpressing cells carry mitogenic signals that induce proliferation and epithelial-to-mesenchymal transition in target cells. The study also identifies a novel feedback regulation between the hedgehog signaling pathway and HA metabolism in melanoma, mediated by EVs carrying HA and IHH.
  • Tallberg, Petra; Räike, Antti; Lukkari, Kaarina; Leivuori, Mirja; Lehtoranta, Jouni; Pitkänen, Heikki (2012)
  • Rödenbeck, Christian; Zaehle, Sönke; Keeling, Ralph; Heimann, Martin (2018)
    The response of the terrestrial net ecosystem exchange (NEE) of CO2 to climate variations and trends may crucially determine the future climate trajectory. Here we directly quantify this response on inter-annual timescales by building a linear regression of inter-annual NEE anomalies against observed air temperature anomalies into an atmospheric inverse calculation based on long-term atmospheric CO2 observations. This allows us to estimate the sensitivity of NEE to inter-annual variations in temperature (seen as a climate proxy) resolved in space and with season. As this sensitivity comprises both direct temperature effects and the effects of other climate variables co-varying with temperature, we interpret it as "inter-annual climate sensitivity". We find distinct seasonal patterns of this sensitivity in the northern extratropics that are consistent with the expected seasonal responses of photosynthesis, respiration, and fire. Within uncertainties, these sensitivity patterns are consistent with independent inferences from eddy covariance data. On large spatial scales, northern extratropical and tropical interannual NEE variations inferred from the NEE-T regression are very similar to the estimates of an atmospheric inversion with explicit inter-annual degrees of freedom. The results of this study offer a way to benchmark ecosystem process models in more detail than existing effective global climate sensitivities. The results can also be used to gap-fill or extrapolate observational records or to separate inter-annual variations from longer-term trends.
  • Elbasani, Endrit; Gramolelli, Silvia; Günther, Thomas; Gabaev, Ildar; Grundhoff, Adam; Ojala, Päivi M. (2020)
    The anaphase-promoting complex, or cyclosome (APC/C), is a large E3 ubiquitin ligase composed of 14 subunits. The activity of APC/C oscillates during the cell cycle to ensure a timely transition through each phase by promoting the degradation of important cell cycle regulators. Of the human herpesviruses, cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) both impair the activity of APC/C during their lytic replication cycle through virus-encoded protein kinases. Here, we addressed whether the oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV) deregulates the activity of APC/C during the lytic replication cycle. To this end, we used the well-characterized iSLK.219 cell model of KSHV infection and established a new infection model of primary lymphatic endothelial cells (LECs) infected with a lytically replicating KSHV BAC16 mutant. In contrast to those of EBV and HCMV, the KSHV lytic cycle occurs while the APC/C is active. Moreover, interfering with the activity of APC/C did not lead to major changes in the production of infectious virus. We further investigated whether rereplication stress induced by the unscheduled activation of the APC/C-CDH1 complex affects the number and integrity of KSHV viral episomes. Deep sequencing of the viral episomes and host chromosomes in iSLK.219 cells revealed that, while distinct regions in the cellular chromosomes were severely affected by rereplication stress, the integrity of the viral episomes remained unaltered. IMPORTANCE DNA viruses have evolved complex strategies to gain control over the cell cycle. Several of them target APC/C, a key cellular machinery that controls the timely progression of the cell cycle, by either blocking or enhancing its activity. Here, we investigated the activity of APC/C during the lytic replication cycle of KSHV and found that, in contrast to that of KSHV's close relatives EBV and HCMV, KSHV lytic replication occurs while the APC/C is active. Perturbing APC/C activity by depleting a core protein or the adaptor proteins of the catalytic domain, and hence interfering with normal cell-cycle progression, did not affect virus replication. This suggests that KSHV has evolved to replicate independently of the activity of APC/C and in various cell cycle conditions.
  • EFSA Panel Dietetic Prod Nut (2018)
    Following an application from Lonza Ltd., submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No1924/2006 via the Competent Authority of Germany, the EFSA Panelon Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to L-carnitine and normal lipid metabolism. The food that is proposed as the subject of the health claim is L-carnitine. The Panelconsiders that L-carnitine is sufficiently characterised. The claimed effect proposed by the applicant is normal lipid metabolism'. The target population proposed by the applicant is the general population. The Panelconsiders that contribution to normal lipid metabolism is a beneficial physiological effect. The applicant proposes that the claim submitted with this application is based on the essentiality of a nutrient. The Panelconsiders that the evidence provided does not establish that dietary L-carnitine is required to maintain normal lipid metabolism in the target population, for which the claim is intended. The Panelconcludes that a cause and effect relationship has not been established between the consumption of L-carnitine and contribution to normal lipid metabolism in the target population. (c) 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.
  • Myllys, M.; Partamies, N.; Juusola, L. (2015)
    To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level. We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57-61 degrees in 1996 and at the latitudes 64-67 degrees in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64-67 degrees, the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57-61 degrees, the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.
  • Erkkilä, Kukka-Maaria; Ojala, Anne; Bastviken, David; Biermann, Tobias; Heiskanen, Jouni J.; Lindroth, Anders; Peltola, Olli; Rantakari, Miitta; Vesala, Timo; Mammarella, Ivan (2018)
    Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2) and methane (CH4) to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, k CC (introduced by Cole and Caraco, 1998), for calculating diffusive flux with the boundary layer method (BLM). We compared CH4 and CO2 fluxes from BLM with k CC and two other gas transfer velocities (k TE and k HE), which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC) and floating chamber (FC) fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajarvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model k TE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajarvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference between CO2 fluxes from shallower and deeper areas. We highlight that while all flux measurement methods have their pros and cons, it is important to carefully think about the chosen method and measurement interval, as well as their effects on the resulting flux.
  • Allmeroth, Kira; Kim, Christine S.; Annibal, Andrea; Pouikli, Andromachi; Koester, Janis; Derisbourg, Maxime J.; Chacon-Martinez, Carlos Andres; Latza, Christian; Antebi, Adam; Tessarz, Peter; Wickström, Sara A.; Denzel, Martin S. (2021)
    Stem cell differentiation is accompanied by increased mRNA translation. The rate of protein biosynthesis is influenced by the polyamines putrescine, spermidine and spermine, which are essential for cell growth and stem cell maintenance. However, the role of polyamines as endogenous effectors of stem cell fate and whether they act through translational control remains obscure. Here, we investigate the function of polyamines in stem cell fate decisions using hair follicle stem cell (HFSC) organoids. Compared to progenitor cells, HFSCs showed lower translation rates, correlating with reduced polyamine levels. Surprisingly, overall polyamine depletion decreased translation but did not affect cell fate. In contrast, specific depletion of natural polyamines mediated by spermidine/spermine N1-acetyltransferase (SSAT; also known as SAT1) activation did not reduce translation but enhanced stemness. These results suggest a translation-independent role of polyamines in cell fate regulation. Indeed, we identified N1-acetylspermidine as a determinant of cell fate that acted through increasing self-renewal, and observed elevated N1-acetylspermidine levels upon depilation-mediated HFSC proliferation and differentiation in vivo. Overall, this study delineates the diverse routes of polyamine metabolism-mediated regulation of stem cell fate decisions. This article has an associated First Person interview with the first author of the paper.
  • Asvestari, E.; Heinemann, S. G.; Temmer, M.; Pomoell, J.; Kilpua, E.; Magdalenic, J.; Poedts, S. (2019)
    The adopted Wang-Sheeley-Arge (WSA) model embedded in EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is compared to EUV observations. According to the standard paradigm, coronal holes are sources of open flux; thus, we use remote sensing EUV observations and CATCH (Collection of Analysis Tools for Coronal Holes) to extract CH areas and compare them to the open flux areas modeled by EUHFORIA. From the adopted WSA model we employ only the Potential Field Source Surface (PFSS) model for the inner corona and the Schatten Current Sheet (SCS) model for the outer (PFSS+SCS). The height, R-ss, of the outer boundary of the PFSS, known as the source surface, and the height, R-i, of the inner boundary of the SCS are important parameters affecting the modeled CH areas. We investigate the impact the two model parameters can have in the modeled results. We vary R-ss within the interval [1.4, 3.2]R-circle dot with a step of 0.1R(circle dot), and R-i within the interval [1.3, 2.8]R-circle dot with the same step, and the condition that R-i
  • Gustafsson, Erik; Hagens, Mathilde; Sun, Xiaole; Reed, Daniel C.; Humborg, Christoph; Slomp, Caroline P.; Gustafsson, Bo G. (2019)
    Enhanced release of alkalinity from the seafloor, principally driven by anaerobic degradation of organic matter under low-oxygen conditions and associated secondary redox reactions, can increase the carbon dioxide (CO2) buffering capacity of seawater and therefore oceanic CO2 uptake. The Baltic Sea has undergone severe changes in oxygenation state and total alkalinity (TA) over the past decades. The link between these concurrent changes has not yet been investigated in detail. A recent system-wide TA budget constructed for the past 50 years using BALTSEM, a coupled physical-biogeochemical model for the whole Baltic Sea area revealed an unknown TA source. Here we use BALTSEM in combination with observational data and one-dimensional reactive-transport modeling of sedimentary processes in the Faro Deep, a deep Baltic Sea basin, to test whether sulfate (SO42-) reduction coupled to iron (Fe) sulfide burial can explain the missing TA source in the Baltic Proper. We calculated that this burial can account for up to 26% of the missing source in this basin, with the remaining TA possibly originating from unknown river inputs or submarine groundwater discharge. We also show that temporal variability in the input of Fe to the sediments since the 1970s drives changes in sulfur (S) burial in the Faro Deep, suggesting that Fe availability is the ultimate limiting factor for TA generation under anoxic conditions. The implementation of projected climate change and two nutrient load scenarios for the 21st century in BALTSEM shows that reducing nutrient loads will improve deep water oxygen conditions, but at the expense of lower surface water TA concentrations, CO2 buffering capacities and faster acidification. When these changes additionally lead to a decrease in Fe inputs to the sediment of the deep basins, anaerobic TA generation will be reduced even further, thus exacerbating acidification. This work highlights that Fe dynamics plays a key role in the release of TA from sediments where Fe sulfide formation is limited by Fe availability, as exemplified by the Baltic Sea. Moreover, it demonstrates that burial of Fe sulfides should be included in TA budgets of low-oxygen basins.
  • Makela, Jarmo; Minunno, Francesco; Aalto, Tuula; Makela, Annikki; Markkanen, Tiina; Peltoniemi, Mikko (2020)
    Forest ecosystems are already responding to changing environmental conditions that are driven by increased atmospheric CO2 concentrations. These developments affect how societies can utilise and benefit from the woodland areas in the future, be it for example climate change mitigation as carbon sinks, lumber for wood industry, or preserved for nature tourism and recreational activities. We assess the effect and the relative magnitude of different uncertainty sources in ecosystem model simulations from the year 1980 to 2100 for two Finnish boreal forest sites. The models used in this study are the land ecosystem model JSBACH and the forest growth model PREBAS. The considered uncertainty sources for both models are model parameters and four prescribed climates with two RCP (representative concentration pathway) scenarios. Usually, model parameter uncertainty is not included in these types of uncertainty studies. PREBAS simulations also include two forest management scenarios. We assess the effect of these sources of variation at four different points in time on several ecosystem indicators, e.g. gross primary production (GPP), ecosystem respiration, soil moisture, recurrence of drought, length of the vegetation active period (VAP), length of the snow melting period and the stand volume. The uncertainty induced by the climate models remains roughly the same throughout the simulations and is overtaken by the RCP scenario impact halfway through the experiment. The management actions are the most dominant uncertainty factors for Hyytiala and as important as RCP scenarios at the end of the simulations, but they contribute only half as much for Sodankyla. The parameter uncertainty is the least influential of the examined uncertainty sources, but it is also the most elusive to estimate due to non-linear and adverse effects on the simulated ecosystem indicators. Our analysis underlines the importance of carefully considering the implementation of forest use when simulating future ecosystem conditions, as human impact is evident and even increasing in boreal forested regions.