Borrelia burgdorferi sensu lato detected in skin of Norwegian mountain hares (Lepus timidus) without signs of dissemination

The mountain hare (Lepus timidus) population in southern Norway appears to be in decline. Necropsy and laboratory examinations of 36 hares found dead or diseased during 2007-2009 in Vest- and Aust-Agder counties showed that disease and deaths were attributed to multiple causes, with no specific etiology emerging as a cause for population decline. To investigate whether Borrelia burgdorferi sensu lato (s.l.) infection is associated with mortality in mountain hares, tissues and ticks collected from hares were investigated for infection with the spirochete. Borrelia burgdorferi s.l. DNA was not detected in samples from internal organs, whereas Borrelia afzelii, B. burgdorferi sensu stricto (s.s.), and the not-yet-defined Borrelia sp. SV1 were found in skin samples from hares and in adult and nymphal Ixodes ricinus feeding on hares. Only B. burgdorferi s.s. and Borrelia sp. SV1 were detected in larvae feeding on hares. Our results indicate that disseminated Borrelia infection in hares rarely occurs and, presumably, does not play a central role in the suspected population decline. The results also suggest that the mountain hare to some degree functions as a transmission host for B. burgdorferi s.s. and Borrelia sp. SV1.     

Plastic reproductive allocation as a buffer against environmental stochasticity – linking life history and population dynamics to climate

Empirical work suggest that long‐lived organisms have adopted risk sensitive reproductive strategies where individuals trade the amount of resources spent on reproduction versus survival according to expected future environmental conditions. Earlier studies also suggest that climate affects population dynamics both directly by affecting population vital rates and indirectly through long‐term changes in individual life histories. Using a seasonal and state‐dependent individual‐based model we investigated how environmental variability affects the selection of reproductive strategies and their effect on population dynamics. We found that: (1) dynamic, i.e. plastic, reproductive strategies were optimal in a variable climate. (2) Females in poor and unpredictable climatic regimes allocated fewer available resources in reproduction and more in own somatic growth. This resulted in populations with low population densities, and a high average female age and body mass. (3) Strong negative density dependence on offspring body mass and survival, along with co‐variation between climatic severity and population density, resulted in no clear negative climatic effects on reproductive success and offspring body mass. (4) Time series analyses of population growth rates revealed that populations inhabiting benign environments showed the clearest response to climatic perturbations as high population density prohibited an effective buffering of adverse climatic effects as individuals were not able to gain sufficient body reserves during summer. Regularly occurring harsh winters ‘harvested’ populations, resulting in persistent low densities, and released them from negative density dependent effects, resulting in high rewards for a given resource allocation.     

Detection of nodavirus in seawater from rearing facilities for Atlantic halibut Hippoglossus hippoglossus larvae

We used (1) ultracentrifugation followed by RT-PCR and (2) real-time RT-PCR to detect and quantify nodaviruses in seawater in which Atlantic halibut Hippoglossus hippoglossus larvae/fry had been held at rearing facilities. Evaluated against in vitro propagated viruses, the viral concentration corresponded to 1.6 x 10(4) TCID50 (50% tissue culture infectious dose) ml(-1). Evaluated against in vitro transcribed RNA, the concentration was estimated at 2 x 10(7) virus particles ml(-1) seawater.     

Zebrafish kidney marrow contains ABCG2-dependent side population cells exhibiting hematopoietic stem cell properties

Zebrafish (Danio rerio) has emerged as a powerful genetic model for the study of vertebrate hematopoiesis. However, methods for detection and isolation of hematopoietic stem cells (HSCs) have not yet been reported. In mammals, the combination of Hoechst 33342 staining with flow cytometry can be used for separation of a bone marrow side population (SP), which is highly enriched for HSCs. We applied a similar procedure to hematopoietic kidney marrow cells from adult zebrafish, and identified a segregated cohort of SP cells, which demonstrate a set of features typical of stem cells. SP cells show extremely low scatter characteristics, and are small in size with a minimum of cytoplasm. Treatment of zebrafish kidney marrow cells with reserpine or fumitremorgin C, which inhibit the ABCG2 transporter responsible for Hoechst 33342 efflux, caused a clear reduction in the number of SP cells. Consistent with the quiescent state of HSCs, the SP cells are strongly resistant to the myelosuppressive agent 5-fluorouracil. In addition, SP cells specifically demonstrate higher expression of genes known to be markers of HSCs of mammals. Hence, our results show that the SP phenotype is conserved between mammals and teleosts, and the properties of the zebrafish SP cells indicate a significant enrichment for HSCs. These rapid flow cytometric methods for purification of HSCs from zebrafish may greatly facilitate genetic analysis of stem cells using the advantages of this vertebrate model.     

An integrated population model for a long‐lived ungulate: more efficient data use with Bayesian methods

We develop an integrated population model for Svalbard reindeer Rangifer tarandus platyrhynchus, and demonstrate how this type of model can be used to extract more information from the data and separate different sources of variability in population estimates. Our model combines individual mark–recapture data with population counts and harvesting data within a Bayesian model framework, and accounts for observation error, environmental and demographic stochasticity, and age structure. From this model we obtain annual estimates of age‐specific population size, survival and fecundity. The model provides estimates of age structure at a finer scale than that found in the census data, and enables us to estimate survival for the period before calves are first caught and marked, i.e. before they enter the individual mark–recapture data. The modeling framework provides an improved approach to studying age‐structured populations that are imperfectly censused and where the demography of only a sample of individuals is known. We use data from independent censuses of the same population to evaluate population estimates obtained from the model, and show that it is successful at correcting for different types of observation error. Based on our model results, we suggest that allocating resources to the collection of supplementary mark–recapture data could improve the reliability of population projections more than making regular population censuses as exhaustive as possible. Our work demonstrates how integrated Bayesian population modeling can be used to increase the amount of information extracted from collections of data, identifying and disentangling sources of variation in individual performance and population size. This represents an important step towards increasing the predictive ability of population growth models for long‐lived species experiencing changes in environmental conditions and harvesting regimes.     

The Interaction between Water Currents and Salmon Swimming Behaviour in Sea Cages

Positioning of sea cages at sites with high water current velocities expose the fish to a largely unknown environmental challenge. In this study we observed the swimming behaviour of Atlantic salmon (Salmo salar L.) at a commercial farm with tidal currents altering between low, moderate and high velocities. At high current velocities the salmon switched from the traditional circular polarized group structure, seen at low and moderate current velocities, to a group structure where all fish kept stations at fixed positions swimming against the current. This type of group behaviour has not been described in sea cages previously. The structural changes could be explained by a preferred swimming speed of salmon spatially restricted in a cage in combination with a behavioural plasticity of the fish.     

Ins and outs of ADF/cofilin activity and regulation

The actin-binding proteins of the actin-depolymerisation factor (ADF)/cofilin family were first described more than three decades ago, but research on these proteins still occupies a front role in the actin and cell migration field. Moreover, cofilin activity is implicated in the malignant, invasive properties of cancer cells. The effects of ADF/cofilins on actin dynamics are diverse and their regulation is complex. In stimulated cells, multiple signalling pathways can be initiated resulting in different activation/deactivation switches that control ADF/cofilin activity. The output of this entire regulatory system, in combination with spatial and temporal segregation of the activation mechanisms, underlies the contribution of ADF/cofilins to various cell migration/invasion phenotypes. In this framework, we describe current views on how ADF/cofilins function in migrating and invading cells.     

Valproate affects reproductive endocrine function, testis diameter and some semen variables in non-epileptic adolescent goat bucks

Valproate (VPA) is a major antiepileptic drug with a broad spectrum of antiepileptic activity. There is, however, increasing concern about the possible effects of VPA on reproductive endocrine function. This study investigated the effects of valproate, on the endocrine and reproductive system of adolescent, non-epileptic, goat bucks. Nine goat bucks were orally treated with 62.5mg/kg valproate twice daily from 2 to 10 months of age in order to sustain therapeutic plasma concentrations of between 300 and 600 micromol/l. Seven bucks served as controls. Body weights and testicular diameters were recorded. Blood samples were collected for measurement of luteinising hormone (LH), follicle stimulating hormone (FSH) and testosterone three times weekly until sacrifice at approximately 40 weeks of age. Conventional reproductive endpoints were recorded and flow cytometric (FCM) analyses of spermatogenesis, including the sperm chromatin structure were conducted. Valproate-treated bucks had on average a higher body weight, but a lower testis diameter than controls. No significant differences were found for plasma FSH in comparison to controls. Valproate-treated bucks differed significantly from the control group by showing lower plasma concentrations of LH and testosterone and a later onset of puberty. A significantly higher proportion of sperm from valproate-treated bucks showed abnormal chromatin, demonstrating a harmful effect on DNA from valproate treatment. These results demonstrate that valproate was able to induce reproductive effects in goat bucks related to the hypothalamic-pituitary-axis, as well as to the testes.     

Contrasting effects of summer and winter warming on body mass explain population dynamics in a food‐limited Arctic herbivore

The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain‐on‐snow) can cause ‘icing’, restricting access to forage, resulting in starvation, lower survival and fecundity. As body condition is a ‘barometer’ of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994 to 2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between‐year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long‐term trend (coefficient of variation, CV = 8.8%) and was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to ‘rain‐on‐snow’ events. October body mass (CV = 2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density‐dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important ‘missing’ mechanistic link in the current understanding of the population biology of a keystone species in a rapidly warming Arctic.     

Apolar and polar solvation thermodynamics related to the protein unfolding process.

Thermodynamics related to hydrated water upon protein unfolding is studied over a broad temperature range (5-125 degrees C). The hydration effect arising from the apolar interior is modeled as an increased number of hydrogen bonds between water molecules compared with bulk water. The corresponding contribution from the polar interior is modeled as a two-step process. First, the polar interior breaks hydrogen bonds in bulk water upon unfolding. Second, due to strong bonds between the polar surface and the nearest water molecules, we assume quantization using a simplified two-state picture. The heat capacity change upon hydration is compared with model compound data evaluated previously for 20 different proteins. We obtain good correspondence with the data for both the apolar and the polar interior. We note that the effective coupling constants for both models have small variations among the proteins we have investigated.