Sensorimotor development in neonatal progesterone receptor knockout mice

Early exposure to steroid hormones can permanently and dramatically alter neural development. This is best understood in the organizational effects of hormones during development of brain regions involved in reproductive behaviors or neuroendocrine function. However, recent evidence strongly suggests that steroid hormones play a vital role in shaping brain regions involved in cognitive behavior such as the cerebral cortex. The most abundantly expressed steroid hormone receptor in the developing rodent cortex is the progesterone receptor (PR). In the rat, PR is initially expressed in the developmentally‐critical subplate at E18, and subsequently in laminas V and II/III through the first three postnatal weeks (Quadros et al. [2007] J Comp Neurol 504:42–56; Lopez & Wagner [2009]: J Comp Neurol 512:124–139), coinciding with significant periods of dendritic maturation, the arrival of afferents and synaptogenesis. In the present study, we investigated PR expression in the neonatal mouse somatosensory cortex. Additionally, to investigate the potential role of PR in developing cortex, we examined sensorimotor function in the first two postnatal weeks in PR knockout mice and their wildtype (WT) and heterozygous (HZ) counterparts. While the three genotypes were similar in most regards, PRKO and HZ mice lost the rooting reflex 2–3 days earlier than WT mice. These studies represent the first developmental behavioral assessment of PRKO mice and suggest PR expression may play an important role in the maturation of cortical connectivity and sensorimotor integration. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 74: 16–24, 2014     

Vertical and Horizontal Trust at Work as Predictors of Retirement Intentions: The Finnish Public Sector Study

This prospective cohort study aimed to examine the associations of trust towards the supervisor (vertical trust) and trust towards co-workers (horizontal trust) with retirement intentions. The participants were 14 840 women and men working in the municipal sector in 2000–12 (Finnish Public Sector Study). Trust (vertical trust towards the supervisor and horizontal trust towards co-workers) and retirement intentions were assessed in repeated surveys. Multivariable multinomial logistic regression analyses were conducted to assess the association between baseline trust and retirement intentions at 3.7 years of follow-up. Demographic characteristics, health, psychological distress, health risk behaviors, personality factors, and psychosocial factors were included as covariates. Of the participants, 67.0% trusted their supervisor and 54.9% trusted their co-workers. Employees who trusted their supervisor (odds ratio (OR) 0.60, 95% confidence interval (CI) 0.53–0.67) and employees who trusted their co-workers (odds ratio 0.62, 95% confidence interval 0.55–0.70) at baseline were less likely to have strong retirement intentions at follow-up compared to those who did not trust. These associations largely persisted after adjusting for all covariates and taking into account baseline retirement intentions. In conclusion, trust in the supervisor and co-workers predicted retirement intentions. These observational findings suggest that increasing trust in the workplace may contribute to lengthening working careers and preventing early retirement.     

A life‐stage population model of the European sturgeon (Acipenser sturio L., 1758) in the Elbe River. Part II: assessment of the historic population decline

A post‐hoc analysis on the decline of the European sturgeon (Acipenser sturio) population in the Elbe River was performed for the end of the 19th century. A modeling approach was applied to determine the role of various factors potentially impacting the population. Using an age‐structured population model developed for European sturgeon, the estimates of fishing efficiency in the Elbe were verified. Catches reported from 1850 to 1920 were used as a basis to identify the population size, dynamics of the decline and the impacts contributing to the population decline. According to results of the model, the historic population size of the European sturgeon in the Elbe River exceeded 450 000 individuals. The population revealed a significant response in abundance of adults towards the fishery directed at spawning migrants, even at low fishery effort. Unsustainable fishery was the initial cause of the population decline, while increasing pollution and habitat degradation revealed significant impacts after 1860. The results represent a good example for the fisheries ‘hyperstability’ phenomenon. In the case of the Elbe fishery, an increasing fishery effort was masking the actual population decline while temporarily maintaining the overall yield. The results indicate that, for sturgeons and other species with similar life history patterns, the use of fishery data for the assessment of population dynamics and fishery sustainability has to be applied with due caution, as it might produce false images of the population size and dynamics.     

Spatial and temporal scales relevant for conservation of dead-wood associated species: current status and perspectives

Dead wood is a key substrate for forest biodiversity, hosting a rich and often threatened biodiversity of wood-living species. However, the relationship between the occurrence of dead wood and associated species is modified by several environmental factors. Here we review the present state of knowledge on how dead wood on different spatial and temporal scales affects saproxylic biodiversity. We searched for peer-reviewed studies on saproxylic species that compared dead wood distribution on at least two spatial or temporal scales. We scanned close to 300 articles, of which 34 fit our criteria. 20 studies were directed towards the current amount of dead wood at different scale levels and how this relates to the abundance or occurrence of saproxylic species, embracing scales from 10 m to 10 km. 14 studies compared time-lagged effects of dead wood, covering time-lags from 25 years to more than 200 years. The reviewed articles focused mainly on European forest and addressed invertebrates (mostly beetles), alone or in combination with fungi (27 articles), fungi (six articles), or lichens (one article). Although the significance of dead wood for forest biodiversity is firmly established, the reviewed studies show that we still have limited knowledge of the relationship between saproxylic biodiversity and spatial and temporal scales. Based on the reviewed studies, we conclude that there is large variation in response to spatial and temporal dead wood patterns between different taxa and sub-groups. Still, several of the reviewed papers indicate that time-lagged effects deserve more attention, especially on a landscape scale and for specialized or red-listed species. Further work is required before firm management recommendations can be suggested.     

Predator–vole interactions in northern Europe: the role of small mustelids revised

The cyclic population dynamics of vole and predator communities is a key phenomenon in northern ecosystems, and it appears to be influenced by climate change. Reports of collapsing rodent cycles have attributed the changes to warmer winters, which weaken the interaction between voles and their specialist subnivean predators. Using population data collected throughout Finland during 1986–2011, we analyse the spatio-temporal variation in the interactions between populations of voles and specialist, generalist and avian predators, and investigate by simulations the roles of the different predators in the vole cycle. We test the hypothesis that vole population cyclicity is dependent on predator–prey interactions during winter. Our results support the importance of the small mustelids for the vole cycle. However, weakening specialist predation during winters, or an increase in generalist predation, was not associated with the loss of cyclicity. Strengthening of delayed density dependence coincided with strengthening small mustelid influence on the summer population growth rates of voles. In conclusion, a strong impact of small mustelids during summers appears highly influential to vole population dynamics, and deteriorating winter conditions are not a viable explanation for collapsing small mammal population cycles.     

The Orientation and Dynamics of Estradiol and Estradiol Oleate in Lipid Membranes and HDL Disc Models

Estradiol (E₂) and E₂ oleate associate with high-density lipoproteins (HDLs). Their orientation in HDLs is unknown. We studied the orientation of E₂ and E₂ oleate in membranes and reconstituted HDLs, finding that E₂ and E₂ oleate are membrane-associated and highly mobile. Our combination of NMR measurements, molecular dynamics simulation, and analytic theory identifies three major conformations where the long axis of E₂ assumes a parallel, perpendicular, or antiparallel orientation relative to the membrane’s z-direction. The perpendicular orientation is preferred, and furthermore, in this orientation, E₂ strongly favors a particular roll angle, facing the membrane with carbons 6, 7, 15, and 16, whereas carbons 1, 2, 11, and 12 point toward the aqueous phase. In contrast, the long axis of E₂ oleate is almost exclusively oriented at an angle of ∼60° to the z-direction. In such an orientation, the oleoyl chain is firmly inserted into the membrane. Thus, both E₂ and E₂ oleate have a preference for interface localization in the membrane. These orientations were also found in HDL discs, suggesting that only lipid-E₂ interactions determine the localization of the molecule. The structural mapping of E₂ and E₂ oleate may provide a design platform for specific E₂-HDL-targeted pharmacological therapies.     

Furrow Constriction in Animal Cell Cytokinesis

Cytokinesis is the process of physical cleavage at the end of cell division; it proceeds by ingression of an acto-myosin furrow at the equator of the cell. Its failure leads to multinucleated cells and is a possible cause of tumorigenesis. Here, we calculate the full dynamics of furrow ingression and predict cytokinesis completion above a well-defined threshold of equatorial contractility. The cortical acto-myosin is identified as the main source of mechanical dissipation and active forces. Thereupon, we propose a viscous active nonlinear membrane theory of the cortex that explicitly includes actin turnover and where the active RhoA signal leads to an equatorial band of myosin overactivity. The resulting cortex deformation is calculated numerically, and reproduces well the features of cytokinesis such as cell shape and cortical flows toward the equator. Our theory gives a physical explanation of the independence of cytokinesis duration on cell size in embryos. It also predicts a critical role of turnover on the rate and success of furrow constriction. Scaling arguments allow for a simple interpretation of the numerical results and unveil the key mechanism that generates the threshold for cytokinesis completion: cytoplasmic incompressibility results in a competition between the furrow line tension and the cell poles’ surface tension.     

Phospholipid Transfer Protein Is Expressed in Cerebrovascular Endothelial Cells and Involved in High Density Lipoprotein Biogenesis and Remodeling at the Blood-Brain Barrier

Phospholipid transfer protein (PLTP) is a key protein involved in biogenesis and remodeling of plasma HDL. Several neuroprotective properties have been ascribed to HDL. We reported earlier that liver X receptor (LXR) activation promotes cellular cholesterol efflux and formation of HDL-like particles in an established in vitro model of the blood-brain barrier (BBB) consisting of primary porcine brain capillary endothelial cells (pBCEC). Here, we report PLTP synthesis, regulation, and its key role in HDL metabolism at the BBB. We demonstrate that PLTP is highly expressed and secreted by pBCEC. In a polarized in vitro model mimicking the BBB, pBCEC secreted phospholipid-transfer active PLTP preferentially to the basolateral (“brain parenchymal”) compartment. PLTP expression levels and phospholipid transfer activity were enhanced (up to 2.5-fold) by LXR activation using 24(S)-hydroxycholesterol (a cerebral cholesterol metabolite) or TO901317 (a synthetic LXR agonist). TO901317 administration elevated PLTP activity in BCEC from C57/BL6 mice. Preincubation of HDL₃ with human plasma-derived active PLTP resulted in the formation of smaller and larger HDL particles and enhanced the capacity of the generated HDL particles to remove cholesterol from pBCEC by up to 3-fold. Pre-β-HDL, detected by two-dimensional crossed immunoelectrophoresis, was generated from HDL₃ in pBCEC-derived supernatants, and their generation was markedly enhanced (1.9-fold) upon LXR activation. Furthermore, RNA interference-mediated PLTP silencing (up to 75%) reduced both apoA-I-dependent (67%) and HDL₃-dependent (30%) cholesterol efflux from pBCEC. Based on these findings, we propose that PLTP is actively involved in lipid transfer, cholesterol efflux, HDL genesis, and remodeling at the BBB.     

Varying impacts of cervid, hare and vole browsing on growth and survival of boreal tree seedlings

The negative impacts of mammalian herbivores on plants have been studied quite extensively, but typically with only a single herbivore species at a time. We conducted a novel comparison of the browsing effects of voles, hares and cervids upon the growth and survival of boreal tree seedlings. This was done by excluding varying assemblages of these key mammalian herbivores from silver birch, Scots pine and Norway spruce seedlings for 3 years. We hypothesised that the pooled impacts of the herbivores would be greater than that of any individual group, while the cervids would be the group with the strongest impact. Growth of birch seedlings advanced when cervids were excluded whereas growth of seedlings accessible to cervids was hindered. Survival of all seedlings was lowest when they were accessible to voles and voles plus hares, whereas cervids seemed not to influence seedling survival. Our results show that the impact of herbivores upon woody plants can be potent in the boreal forests, but the mechanism and strength of this link depends on the tree and herbivore species in question. Risk of abated stand regeneration appears highest for the deciduous birch, though there is need for seedling protection also in coniferous stands. The clear cervid-mediated growth limitation of birch also indicates potential for a trophic cascade effect by mammalian top predators, currently returning to boreal ecosystems.     

Sampling the rarest: threatened beetles in boreal forest biodiversity inventories

Presence or absence of threatened species in samples is information that is widely used in designing and implementing conservation actions. We explored the effectiveness of beetle (Coleoptera) inventories and contribution of different sampling methods in revealing occurrences of threatened and near threatened species in boreal forests. The number of species caught using traps in a particular area proved to be a useful indicator of the representativeness of data, the relationship between total number of species and the number of threatened and near threatened species being almost exponential. Samples containing less than 200 trapped species (or 2000 individuals) are almost useless in surveying threatened and near threatened species. The probability of finding such species increases considerably when the number of trapped species exceeds 400. Window traps attached directly on the trunks of dead trees proved to be the most efficient sampling method in trapping threatened beetles, whereas many other standard methods gave relatively poor results. We suggest that the best alternative in surveying threatened species in boreal forests is a combination of intensive direct searching and trunk window traps. Finding threatened beetles with rigorous probability requires very large sample sizes, even if the most effective sampling methods are used. For example, ranking 10 boreal forest areas to be protected according to the occurrence of threatened species with some reliability may require trapping of over 100000 beetle individuals. Collecting and identifying these large samples routinely in conservation actions is not feasible, which means that shortcuts (indicators etc.) are necessary. However, a lot of good-quality inventories with appropriate sampling efforts are needed before these shortcuts can be identified and elaborated. Such inventories are also crucial for the improvement of the classification of threatened species and full assessment on how past forest management has eventually affected the biota.