The role of colonization in the dynamics of patchy populations of a cyclic vole species

This is the postprint version of the article. The published article can be located at www.springerlink.comThe crash phase of vole populations with cyclic dynamics regularly leads to vast areas of uninhabited habitats. Yet although the capacity for cyclic voles to re-colonize such empty space is likely to be large and predicted to have become evolved as a distinct life history trait, the processes of colonization and its effect on the spatio-temporal dynamics have been little studied. Here we report from an experiment with root voles (Microtus oeconomus) specifically targeted at quantifying the process of colonization of empty patches from distant source patches and its resultant effect on local vole deme size variation in a patchy landscape. Three experimental factors: habitat quality (1), predation risk (2) and inter-patch distance (3) were employed among 24 habitat patches in a 100x300 m experimental area. The first born cohort in the spring efficiently colonized almost all empty patches irrespective of the degree of patch isolation and predation risk, but dependent on habitat quality. Just after the initial colonization wave the deme sizes in patches of the same quality were underdispersed relative to Poission variance, indicating regulated (density-dependent) settlement. Towards the end of the breeding season local demographic processes acted to smooth out the initial post colonization differences among source and colonization patches, and among patches of initially different quality. However, at this time demographic stochasticity had also given rise to a large (overdispersed) variation in deme sizes that may have contributed to overshadow the effect of other factors. The results of this experiment confirmed our expectation that the space-filling capacity of voles is large. The costs associated with transience appeared to be so low, at least at the spatial scale considered in this experiment, that such costs is not likely to substantially constrain habitat selection and colonization in the increase phase of cyclic patchy populations.2014-09-3

Drømmen om å vinne i lotto : en kvalitativ studie av norske lottomillionærers drøm og erfaringer

Sammendrag Som utgangspunkt for denne oppgaven har jeg gjort fem kvalitative intervjuer av norske lottomillionærer. Målet har vært å finne ut noe om drømmen om – og opplevelsen av å vinne en større pengesum i et lotteri. Jeg har hatt Grounded Theory som metodologisk utgangspunkt, og hvilke temaer jeg skulle ta for meg, har derfor delvis blitt bestemt underveis i prosessen, ut fra hvilken informasjon jeg anså som mest interessant for videre analyse. Oppgaven er delt inn tematisk i tre hoveddeler: ”Drømmen om å vinne i Lotto”, ”Lykken er..?” og ”Norske verdier”. I delen som omhandler lottodrømmen tar jeg for meg det moderne samfunn, og ser lottodrømmen, slik den kommer til uttrykk hos informantene, i lys av dette. Jeg ønsket å se på hvorfor lottodrømmen står så sterkt i Norge og hva den springer ut av. Informantene uttrykte at lottodrømmen dreide seg om materielle goder og opplevelser. Jeg knytter blant annet dette til Giddens teori om selvet som refleksivt prosjekt, samt Frønes og Brusdals forståelse av begrepet selvrealisering. Informantenes drøm påvirkes av et materialistisk samfunn hvor aktørene antas å etterstrebe ”Det Gode Liv”. Likevel viser informantenes forbruk i etterkant av gevinsten at de avstår fra å realisere mange av sine tidligere ønsker. En grunn til dette kan være at det er viktig for informantene å handle i tråd med egen identitet, og å fremstå som autentiske. Ytre omstendigheter som sosiale nettverk kan også tenkes å spille inn. Begrensningene de legger på seg selv er i sin tur med på å hindre virkeligheten i å samsvare med drømmen. At drømmen og virkeligheten er vesensforskjellige må også tas med i betraktningen. Kapitlet som handler om lykke, tar for seg lykkebegrepet i en historisk og samfunnsvitenskapelig sammenheng. Jeg knytter lykkebegrepet til lottodrømmen, fordi lottodrømmen er en drøm om forbedring, og kanskje også et lykkeligere liv. Jeg tar for meg informantenes uttalelser om hva lykke betyr for dem. Det viser seg at det selv innen mitt utvalg er store forskjeller i konnotasjonene til ordet, og dette danner utgangspunktet for en diskusjon om hvorvidt kvantitative lykkeundersøkelser gir et riktig bilde av aggregert lykkenivå i nasjoner og om det er mulig å sammenligne lykke. Flertallet av informantene hevder at de ikke har blitt lykkeligere i etterkant av gevinsten. Dette kan henge sammen med deres oppfattelse av selve lykkebegrepet, fordi de fleste informantene mener at lykke er en øyeblikkspreget tilstand. Om de hevder å ha blitt lykkeligere eller ikke, kan også sees i sammenheng med informantenes tidligere økonomiske situasjon. Ut fra samtalene med informantene ble det tydelig at hvordan de håndterte gevinsten kunne settes i sammenheng med verdigrunnlag. Jeg har derfor viet et kapittel til det jeg kaller for norske verdier. Her tar jeg blant annet for meg Ottar Helleviks inndeling av det han kaller ”de fire norger”; fire norske særkulturer som preges av dimensjonene idealisme/materialisme, samt det moderne/det tradisjonelle. Hvilke verdier vi anser som viktige påvirker vårt handlingsmønster og kan derfor være en viktig forklaringsfaktor for hvorfor vi handler som vi gjør, også i sammenheng med å vinne en lotterigevinst. Informantene uttrykker en del tradisjonelle norske verdier, som preges av en likhetstankegang. Disse verdiene kan være med på å forklare hvorfor informantene ikke, fullt ut, handler i tråd med lottodrømmen

The role of colonization in the dynamics of patchy populations of a cyclic vole species

The crash phase of vole populations with cyclic dynamics regularly leads to vast areas of uninhabited habitats. Yet although the capacity for cyclic voles to re-colonize such empty space is likely to be large and predicted to have become evolved as a distinct life history trait, the processes of colonization and its effect on the spatio-temporal dynamics have been little studied. Here we report from an experiment with root voles (Microtus oeconomus) specifically targeted at quantifying the process of colonization of empty patches from distant source patches and its resultant effect on local vole deme size variation in a patchy landscape. Three experimental factors: habitat quality (1), predation risk (2) and inter-patch distance (3) were employed among 24 habitat patches in a 100x300 m experimental area. The first born cohort in the spring efficiently colonized almost all empty patches irrespective of the degree of patch isolation and predation risk, but dependent on habitat quality. Just after the initial colonization wave the deme sizes in patches of the same quality were underdispersed relative to Poission variance, indicating regulated (density-dependent) settlement. Towards the end of the breeding season local demographic processes acted to smooth out the initial post colonization differences among source and colonization patches, and among patches of initially different quality. However, at this time demographic stochasticity had also given rise to a large (overdispersed) variation in deme sizes that may have contributed to overshadow the effect of other factors. The results of this experiment confirmed our expectation that the space-filling capacity of voles is large. The costs associated with transience appeared to be so low, at least at the spatial scale considered in this experiment, that such costs is not likely to substantially constrain habitat selection and colonization in the increase phase of cyclic patchy populations

Evidence that pericytes regulate aquaporin-4 polarization in mouse cortical astrocytes

Aquaporin-4 (AQP4) water channels are concentrated in astrocytic endfoot membranes at the brain–blood and brain–cerebrospinal fluid interfaces. The mechanisms underpinning the polarized distribution of AQP4 are poorly understood. Here we tested the hypothesis that pericytes regulate AQP4 anchoring to perivascular astrocytic endfoot membranes. AQP4 immunofluorescence of brain sections obtained from novel transgenic double reporter mice expressing enhanced green fluorescent protein (eGFP) in astrocytes and Discoma Red (DsRed) in pericytes revealed strong AQP4 signal in astrocytic processes adjacent to pericytes. Quantitative immunogold analysis of C57BL/6 mice showed that the AQP4 expression was higher in endfoot membranes abutting pericytes than in those facing endothelial cells. Similar findings were made for α-syntrophin, a member of the dystrophin-associated protein complex (DAPC). The enrichment of α-syntrophin in membranes ensheathing pericytes persisted after Aqp4 gene deletion. Our data support the concept that pericytes regulate AQP4 polarization. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited

Home range size and overlap in female root voles: effects of season and density

In small mammals living in highly seasonal environments, observational studies show that female home range size and exclusiveness are smaller in the nonbreeding winter season than in the breeding summer season. This has led to the notion that nonbreeding females are more social and decrease territorial behavior during winter. However, because territoriality decreases with increasing population density, and density normally increases during the breeding season, the effects of density and season on social structure are usually confounded. To find out which of the 2 factors explains space use, we experimentally established 3 high-density and 3 low-density root vole (Microtus oeconomus) populations in late spring and monitored the populations into the nonbreeding winter season. Population sizes were controlled throughout the breeding period to minimize seasonal variation in density. Home range sizes were larger in founder females than in field-born females but did not change with season or density. Area exclusively used by individual females was lower in winter than summer, and founder females decreased exclusiveness as density increased. We argue that this seasonal pattern of space use might be caused by variation in benefits of group living, whereas founder females also responded to density-dependent competition by reducing area exclusively used. Copyright 2008, Oxford University Press.

Acute response in circulating microRNAs following a single bout of short-sprint and heavy strength training in well-trained cyclists

Background: Heavy strength (HS) and short-sprint (SS) are commonly used training methods for competitive road cyclists, with the aim to improve the anaerobic power and short time cycling performance. Knowledge of how such training methods affects biochemical as well as molecular factors, are particularly important for determining individual recovery and long-term adaptations. The primary aim of the current study was to investigate the expression levels of small non-coding RNAs in response to HS and SS training in elite cyclists as potential biomarkers for individual optimal restitution time.Methods: Eleven well trained cyclists performed one session of HS training and one session of SS training on separate days. Blood samples were taken at baseline and 5 min, 1 h and 21 h post training. Along with physiological measurements and biochemical factors (serum creatine kinase, myoglobin, human growth hormone and plasma lactate), real-time quantitative PCR was used to explore whether HS and/or SS training influenced the abundance of 24 circulating miRNAs, in serum, associated with muscle development, angiogenesis, and/or inflammation.Results: Based on complete miRNA profiles from nine cyclists, the miRNAs showing most altered expression after both training sessions included the three striated muscle-specific miRNAs (myomiRs) miR-1-3p, 133a-3p and 133b-3p. While all three miRNAs showed significantly highest expression at 1 h post HS session, the acute effect of the SS session included a significantly higher level of miR-1-3p alone, at 5 min (highest), as well as at 1 h and 21 h post session. Correlation (negative) with biochemical markers was only shown for miR-133a-3p and CK (r = −0.786, p = 0.041) and between miR-133b-3p and [La−] (r = −0.711, p = .032), at 21 h post SS session.Conclusion: Our findings support that unique myomiRs are regulated by HS and SS training. Such knowledge may be important for individually adjusted restitution times