| 1. |
- Beltran-Pardo, Eliana, et al.
(författare)
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Effects of ionizing radiation on embryos of the tardigrade Milnesium cf. tardigradum at different stages of development
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent one of the most desiccation and radiation tolerant animals on Earth, and several studies havedocumented their tolerance in the adult stage. Studies on tolerance during embryological stages are rare, but differentialeffects of desiccation and freezing on different developmental stages have been reported, as well as dose-dependent effectof gamma irradiation on tardigrade embryos. Here, we report a study evaluating the tolerance of eggs from theeutardigrade Milnesium cf. tardigradum to three doses of gamma radiation (50, 200 and 500 Gy) at the early, middle, andlate stage of development. We found that embryos of the middle and late developmental stages were tolerant to all doses,while eggs in the early developmental stage were tolerant only to a dose of 50 Gy, and showed a declining survival withhigher dose. We also observed a delay in development of irradiated eggs, suggesting that periods of DNA repair might havetaken place after irradiation induced damage. The delay was independent of dose for eggs irradiated in the middle and latestage, possibly indicating a fixed developmental schedule for repair after induced damage. These results show that thetolerance to radiation in tardigrade eggs changes in the course of their development. The mechanisms behind this patternare unknown, but may relate to changes in mitotic activities over the embryogenesis and/or to activation of responsemechanisms to damaged DNA in the course of development.
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| 2. |
- Beltran-Pardo, Eliana, et al.
(författare)
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Tolerance to Gamma Radiation in the Tardigrade Hypsibius dujardini from Embryo to Adult Correlate Inversely with Cellular Proliferation
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades are highly tolerant to desiccation and ionizing radiation but the mechanisms of this tolerance are not well understood. In this paper, we report studies on dose responses of adults and eggs of the tardigrade Hypsibius dujardini exposed to gamma radiation. In adults the LD50/48h for survival was estimated at similar to 4200 Gy, and doses higher than 100 Gy reduced both fertility and hatchability of laid eggs drastically. We also evaluated the effect of radiation (doses 50 Gy, 200 Gy, 500 Gy) on eggs in the early and late embryonic stage of development, and observed a reduced hatchability in the early stage, while no effect was found in the late stage of development. Survival of juveniles from irradiated eggs was highly affected by a 500 Gy dose, both in the early and the late stage. Juveniles hatched from eggs irradiated at 50 Gy and 200 Gy developed into adults and produced offspring, but their fertility was reduced compared to the controls. Finally we measured the effect of low temperature during irradiation at 4000 Gy and 4500 Gy on survival in adult tardigrades, and observed a slight delay in the expressed mortality when tardigrades were irradiated on ice. Since H. dujardini is a freshwater tardigrade with lower tolerance to desiccation compared to limno-terrestrial tardigrades, the high radiation tolerance in adults, similar to limno-terrestrial tardigrades, is unexpected and seems to challenge the idea that desiccation and radiation tolerance rely on the same molecular mechanisms. We suggest that the higher radiation tolerance in adults and late stage embryos of H. dujardini (and in other studied tardigrades) compared to early stage embryos may partly be due to limited mitotic activity, since tardigrades have a low degree of somatic cell division (eutely), and dividing cells are known to be more sensitive to radiation.
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| 3. |
- Bengtsson, Daniel, et al.
(författare)
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Movements, Home-Range Size and Habitat Selection of Mallards during Autumn Migration
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- The mallard (Anas platyrhynchos) is a focal species in game management, epidemiology and ornithology, but comparably little research has focused on the ecology of the migration seasons. We studied habitat use, time-budgets, home-range sizes, habitat selection, and movements based on spatial data collected with GPS devices attached to wild mallards trapped at an autumn stopover site in the Northwest European flyway. Sixteen individuals (13 males, 3 females) were followed for 15-38 days in October to December 2010. Forty-nine percent (SD = 8.4%) of the ducks' total time, and 85% of the day-time (SD = 28.3%), was spent at sheltered reefs and bays on the coast. Two ducks used ponds, rather than coast, as day-roosts instead. Mallards spent most of the night (76% of total time, SD = 15.8%) on wetlands, mainly on alvar steppe, or in various flooded areas (e.g. coastal meadows). Crop fields with maize were also selectively utilized. Movements between roosting and foraging areas mainly took place at dawn and dusk, and the home-ranges observed in our study are among the largest ever documented for mallards (mean = 6,859 ha; SD = 5,872 ha). This study provides insights into relatively unknown aspects of mallard ecology. The fact that autumn-staging migratory mallards have a well-developed diel activity pattern tightly linked to the use of specific habitats has implications for wetland management, hunting and conservation, as well as for the epidemiology of diseases shared between wildlife and domestic animals.
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| 4. |
- Bolstad, Ingeborg, et al.
(författare)
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Aversive event anticipation affects connectivity between the ventral striatum and the orbitofrontal cortex in an fMRI avoidance task
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 8:6
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Tidskriftsartikel (refereegranskat)abstract
- Ability to anticipate aversive events is important for avoiding dangerous or unpleasant situations. The motivation to avoid an event is influenced by the incentive salience of an event-predicting cue. In an avoidance fMRI task we used tone intensities to manipulate salience in order to study the involvement of the orbitofrontal cortex in processing of incentive salience. In the task, cues predicting either aversive or neutral avoidable tones were presented. Ventral striatum, amygdala and anterior insula activations were significantly stronger during presentation of cues for aversive than neutral tones. A psychophysiological interaction analysis showed stronger connectivity between the ventral striatum and the orbitofrontal cortex during aversive than neutral conditions. The present study shows an interaction between the ventral striatum, a structure previously linked to negative incentive salience, and the orbitofrontal cortex supporting a role for this region in processing salience. In addition, this study replicates previous findings suggesting that the task is robust.
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| 5. |
- Czernekova, Michaela, et al.
(författare)
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A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress
- 2018
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent an invertebrate phylum with no circulatory or respiratory system.Their body cavity is filled with free storage cells of the coelomocyte-type, which are responsible for important physiological functions. We report a study comparing the ultrastructure of storage cells in anhydrobiotic and hydrated specimens of the eutardigrade Richtersius coronifer. We also analysed the effect of temperature stress on storage cell structure. Firstly, we verified two types of ultrastructurally different storage cells, which differ in cellular organelle complexity, amount and content of reserve material and connection to oogenetic stage. Type I cells were found to differ ultrastructurally depending on the oogenetic stage of the animal. The main function of these cells is energy storage. Storage cells of Type I were also observed in the single male that was found among the analysed specimens. The second cell type, Type II, found only in females, represents young undifferentiated cells, possibly stem cells. The two types of cells also differ with respect to the presence of nucleolar vacuoles,which are related to oogenetic stages and to changes in nucleolic activity during oogenesis. Secondly, this study revealed that storage cells are not ultrastructurally affected by six months of desiccation or by heating following this desiccation period. However, heating of the desiccated animals (tuns) tended to reduce animal survival, indicating that longterm desiccation makes these animals more vulnerable to heat stress. We confirmed the degradative pathways during the rehydration process after desiccation and heat stress. Our study is the first to document two ultrastructurally different types of storage cells in tardigrades and reveals new perspectives for further studies of tardigrade storage cells.
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| 6. |
- Czernekova, Michaela, et al.
(författare)
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Experimentally induced repeated anhydrobiosis in the Eutardigrade Richtersius coronifer
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent one of the main animal groups with anhydrobiotic capacity at any stage of their life cycle. The ability of tardigrades to survive repeated cycles of anhydrobiosis has rarely been studied but is of interest to understand the factors constraining anhydrobiotic survival. The main objective of this study was to investigate the patterns of survival of the eutardigrade Richtersius coronifer under repeated cycles of desiccation, and the potential effect of repeated desiccation on size, shape and number of storage cells. We also analyzed potential change in body size, gut content and frequency of mitotic storage cells. Specimens were kept under non-cultured conditions and desiccated under controlled relative humidity. After each desiccation cycle 10 specimens were selected for analysis of morphometric characteristics and mitosis. The study demonstrates that tardigrades may survive up to 6 repeated desiccations, with declining survival rates with increased numberof desiccations. We found a significantly higher proportion of animals that were unable to contract properly into a tun stage during the desiccation process at the 5th and 6th desiccations. Also total number of storage cells declined at the 5th and 6th desiccations, while no effect on storage cell size was observed. The frequency of mitotic storage cells tended to decline with higher number of desiccation cycles. Our study shows that the number of consecutive cycles of anhydrobiosis that R. coronifer may undergo is limited, with increased inability for tun formation and energetic constraints as possible causal factors.
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| 7. |
- Elmberg, Johan, et al.
(författare)
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Climate change-induced shifts in survival and size of the worlds' northernmost oviparous snake : A 68-year study
- 2024
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 19:3
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Tidskriftsartikel (refereegranskat)abstract
- Because of their dependence on ambient temperature ectothermic animals can serve as sentinels of conservation problems related to global warming. Reptiles in temperate areas are especially well suited to study such effects, as their annual and daily activity patterns directly depend on ambient temperature. This study is based on annual data spanning 68 years from a fringe population of Grass Snakes (Natrix natrix), which is the world's northernmost oviparous (egg-laying) reptile, and known to be constrained by temperature for reproduction, morphology, and behavior. Mark-recapture analyses showed that survival probability was generally higher in males than in females, and that it increased with body length. Body condition (scaled mass index) and body length increased over time, indicative of a longer annual activity period. Monthly survival was generally higher during winter (i.e., hibernation) than over the summer season. Summer survival increased over time, whilst winter survival decreased, especially duringrecent decades. Winter survival was lower when annual maximum snow depth was less than 15 cm, implying a negative effect of milder winters with less insulating snow cover. Our study demonstrates long-term shifts in body length, body condition and seasonal survival associated with a warming climate. Although the seasonal changes in survival ran in opposite directions and though changes were small in absolute terms, the trends did not cancel out, but total annual survival decreased. We conclude that effects of a warming climate can be diverse and pose a threat for thermophilic species in temperate regions, and that future studies should consider survival change by season, preferably in a long-term approach.
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| 8. |
- Fismen, Anne-Siri, et al.
(författare)
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Trends in food habits and their relation to socioeconomic status among Nordic adolescents 2001/2002-2009/2010
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Background In the Nordic countries, substantial policy and intervention efforts have been made to increase adolescents' consumption of fruit and vegetables and to reduce their intake of sweets and soft drinks. Some initiatives have been formulated in a Nordic collaboration and implemented at national level. In recent years, social inequalities in food habits have been attracted particular governmental interest and several initiatives addressing the socioeconomic gradient in food habits have been highlighted. However, few internationally published studies have evaluated how trends in adolescents' food habits develop in the context of Nordic nutrition policy, or have compared differences between the Nordic countries. Methods The study was based on Danish, Finnish, Norwegian and Swedish cross-sectional data from the international Health Behaviour in School-Aged Children (HBSC) study, collected via three nationally representative and comparable questionnaire surveys in 2001/2002, 2005/2006 and 2009/2010. Food habits were identified by students' consumption of fruit, vegetables, sweets and sugar sweetened soft drink. Socioeconomic status (SES) was measured with the Family Affluence Scale (FAS). Multilevel logistic regression was used to analyze the data. Results Trends in fruit consumption developed differently across countries, characterized by an increase in Denmark and Norway and more stable trends in Sweden and Finland. Vegetable consumption increased particularly in Denmark and to a lesser extent in Norway, whereas Sweden and Finland displayed stable trends. Decreased trends were observed for sweet and soft drink consumption and were similar in Norway, Sweden and Finland. Sweet consumption decreased across all survey years, whereas soft drink consumption decreased between 2001/2002–2005/2006 and was stable thereafter. Denmark displayed an increase between 2001/2002–2005/2006 followed by a similar decrease between 2005/2006–2009/2010 for both sweet and soft drink consumption. Socioeconomic inequalities in fruit and vegetable consumption were observed in all countries, with no cross-country differences, and no changes over time. Small but not significant cross-country variation was identified for SES inequalities in sweet consumption. Reduced SES inequalities were observed in Sweden between 2005/2006 and 2009/2010. SES was not associated with soft drink consumption in this study population, with the exception of Denmark for the survey year 2009/2010. Conclusion Different trends resulted in increased country differences in food habits during the time of observations. In survey year 2009/2010, Danish students reported a higher intake of fruit and vegetable consumption than their counterparts in the other Nordic countries. Finnish students reported the lowest frequency of sweets and soft drink consumption. Despite the positive dietary trends documented in the present study, the majority of Nordic adolescents are far from meeting national dietary recommendations. Our findings underline the need for more comprehensive initiatives targeting young people's food habits as well as a more deliberate and focused action to close gaps in social inequalities that affect food choices.
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| 9. |
- Gunnarsson, Gunnar, et al.
(författare)
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Disease Dynamics and Bird Migration – Linking Mallards Anas platyrhynchos and subtype diversity of Influenza A Virus in Time and Space
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 7:4, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The mallard Anas platyrhynchos is a reservoir species for influenza A virus in the northern hemisphere, with particularly high prevalence rates prior to as well as during its prolonged autumn migration. It has been proposed that the virus is brought from the breeding grounds and transmitted to conspecifics during subsequent staging during migration, and so a better understanding of the natal origin of staging ducks is vital to deciphering the dynamics of viral movement pathways. Ottenby is an important stopover site in southeast Sweden almost halfway downstream in the major Northwest European flyway, and is used by millions of waterfowl each year. Here, mallards were captured and sampled for influenza A virus infection, and positive samples were subtyped in order to study possible links to the natal area, which were determined by a novel approach combining banding recovery data and isotopic measurements (d2 H) of feathers grown on breeding grounds. Geographic assignments showed that the core natal areas of studied mallards were in Estonia, southern and central Finland, and northwestern Russia. This study demonstrates a clear temporal succession of latitudes of natal origin during the course of autumn migration. We also demonstrate a corresponding and concomitant shift in virus subtypes. Acknowledging that these two different patterns were based in part upon different data, a likely interpretation worth further testing is that the early arriving birds with more proximate origins have different influenza A subtypes than the more distantly originating late autumn birds. If true, this knowledge would allow novel insight into the origins and transmission of the influenza A virus among migratory hosts previously unavailable through conventional approaches.
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| 10. |
- Hellström, Amanda, et al.
(författare)
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A classical test theory evaluation of the Sleep Condition Indicator accounting for the ordinal nature of item response data
- 2019
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 14:3, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Background Insomnia symptoms are common among young adults and affect about 5% to 26% of 19 to 34-year-olds. In addition, insomnia is associated with poor mental health and may affect daily performance. In research, as well as in clinical practice, sleep questionnaires are used to screen for and diagnose insomnia. However, most questionnaires are not developed according to current DSM-5 diagnostic criteria. An exception is the recently developed Sleep Condition Indicator (SCI), an eight-item scale screening for insomnia. Aim The aim of this study was to perform a Classical Test Theory (CTT) based psychometric evaluation of the SCI in a sample of Swedish university students, by taking the ordinal nature of item level data into account. Methods The SCI was translated into Swedish and distributed online to undergraduate students at three Swedish universities, within programs of health, psychology, science or economy. Of 3673 invited students, 634 (mean age 26.9 years; SD = 7.4) completed the questionnaire that, in addition to the SCI, comprised other scales on sleep, stress, lifestyle and students' study environment. Data were analyzed according to CTT investigating data completeness, item homogeneity and unidimensionality. Results Polychoric based explorative factor analysis suggested unidimensionality of the SCI, and internal consistency was good (Cronbach's alpha, 0.91; ordinal alpha, 0.94). SCI scores correlated with the Insomnia Severity Index (-0.88) as well as with sleep quality (-0.85) and perceived stress (-0.50), supporting external construct validity. Conclusions These observations support the integrity of the of the SCI. The SCI demonstrates sound CTT-based psychometric properties, supporting its use as an insomnia screening tool.
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