Dynamic activation model for a glutamatergic neurovascular unit

This article considers a dynamic spatially lumped model for brain energy metabolism and proposes to use the results of a Markov chain Monte Carlo (MCMC) based flux balance analysis to estimate the kinetic model parameters. By treating steady state reaction fluxes and transport rates as random variables we are able to propagate the uncertainty in the steady state configurations to the predictions of the dynamic model, whose responses are no longer individual but ensembles of time courses. The kinetic model consists of five compartments and is governed by kinetic mass balance equations with Michaelis-Menten type expressions for reaction rates and transports between the compartments. The neuronal activation is implemented in terms of the effect of neuronal activity on parameters controlling the blood flow and neurotransmitter transport, and a feedback mechanism coupling the glutamate concentration in the synaptic cleft and the ATP hydrolysis, thus accounting for the energetic cost of the membrane potential restoration in the postsynaptic neurons. The changes in capillary volume follow the balloon model developed for BOLD MRI. The model follows the time course of the saturation levels of the blood hemoglobin, which link metabolism and BOLD FMRI signal. Analysis of the model predictions suggest that stoichiometry alone is not enough to determine glucose partitioning between neuron and astrocyte. Lactate exchange between neuron and astrocyte is supported by the model predictions, but the uncertainty on the direction and rate is rather elevated. By and large, the model suggests that astrocyte produces and effluxes lactate, while neuron may switch from using to producing lactate. The level of ATP hydrolysis in astrocyte is substantially higher than strictly required for neurotransmitter cycling, in agreement with the literature.     

Vulnerability of black grouse hens to goshawk predation: result of food supply or predation facilitation?

The plant cycle hypothesis says that poor-quality food affects both herbivorous voles (Microtinae spp.) and grouse (Tetraonidae spp.) in vole decline years, leading to increased foraging effort in female grouse and thus a higher risk of predation by the goshawk Accipiter gentilis. Poor-quality food (mainly the bilberry Vaccinium myrtillus) for these herbivores is induced by seed masting failure in the previous year, when the bilberry is able to allocate resources for chemical defence (the mast depression hypothesis; MDH). The predation facilitation hypothesis (PFH) in turn states that increased searching activity of vole-eating predators during or after the decline year of voles disturbs incubating and brooding grouse females. The behaviours used by grouse to avoid these terrestrial predators make them more vulnerable to predation by goshawks. We tested the main predictions of the MDH and PFH by collecting long-term (21-year) data from black grouse Tetrao tetrix hens and cocks killed by breeding goshawks supplemented with indices of bilberry crop, vole abundance and small carnivores in the vicinity of Oulu, northern Finland. We did not find obvious support for the prediction of the MDH that there is a negative correlation of bilberry crop in year t with vole abundance and with predation index of black grouse hens in year t + 1. We did find obvious support for the prediction of the PFH that there is a positive correlation between predator abundance and predation index of grouse hens, because the stoat Mustela erminea abundance index was positively related to the predation index of black grouse hens. We suggest that changes in vulnerability of grouse hens may mainly be caused by the guild of vole-eating predators, who shift to alternative prey in the decline phase of the vole cycle, and thus chase grouse hens and chicks to the talons of goshawks and other avian predators.     

Microwave assisted synthesis and solid-state characterization of lithocholyl amides of isomeric aminopyridines

Microwave (MW) assisted synthesis and solid state structural characterizations of novel lithocholyl amides of 2-, 3-, and 4-aminopyridine are reported. It is shown that the MW technique is a proper method in the preparation of N-lithocholyl amides of isomeric aminopyridines. It offers many advantages compared to conventional heating. The molecular and crystal structures as well as the polymorphic and hydrated forms of prepared conjugates with their thermodynamic stabilities have been characterized by means of high resolution liquid- and solid-state NMR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Owing to the many biological functions of bile acids and amino substituted nitrogen heterocycles, knowledge of the crystal packing of these novel conjugates may have relevance for potential pharmaceutical applications.     

Sobemovirus RNA linked to VPg over a threonine residue

Positive sense ssRNA virus genomes from several genera have a viral protein genome-linked (VPg) attached over a phosphodiester bond to the 5' end of the genome. The VPgs of Southern bean mosaic virus (SBMV) and Ryegrass mottle virus (RGMoV) were purified from virions and analyzed by mass spectrometry. SBMV VPg was determined to be linked to RNA through a threonine residue at position one, whereas RGMoV VPg was linked to RNA through a serine also at the first position. In addition, we identified the termini of the corresponding VPgs and discovered three and seven phosphorylation sites in SBMV and RGMoV VPgs, respectively. This is the first report on the use of threonine for linking RNA to VPg.     

Brood size manipulations in a spatially and temporally varying environment: male Tengmalm’s owls pass increased reproductive costs to offspring

A key tool used to assess reproductive trade-offs in birds is brood size manipulation (BSM) experiments. Most BSM studies have examined the influence on short-term measures of reproductive output. Seldom evaluated are the effects on long-term fitness proxies under temporally or spatially varying environments. Unpredictable environments may affect reproductive trade-offs by altering the value of the brood or hampering optimization of reproductive effort. We reduced or enlarged broods of 140 male Tengmalm’s owls Aegolius funereus by one chick during their first lifetime reproductive event. Males differed in age and bred in environments that varied in quality spatially (habitat structure) and temporally (abundance of main food). We measured the short-term (nestling number and condition) and long-term fitness proxies (survival, lifetime fledgling and recruits produced) until all experimental males disappeared from the population. BSMs did not affect fledgling number or condition, but in enlarged broods, offspring condition was lower in territories with a high proportion of agricultural fields. Importantly, no obvious impacts on long-term fitness proxies emerged; lifetime fledgling and recruit production of males did not differ between the BSM treatments. Thus, the primary caregiver (i.e. Tengmalm’s owl males) passed increased reproductive costs to their offspring, which is in agreement with other studies investigating intergenerational reproductive trade-offs in species of intermediate lifespan. Reluctance to accept increased current reproductive costs in these systems highlights the potential for sexual conflict in bi-parental care systems in which one of the pair is the primary caregiver.     

Effect of temperature and precipitation on the annual diameter growth of Scots pine on drained peatlands and adjacent mineral soil sites in Finland

The climate conditions of the current and previous growing seasons have been shown to influence growth of coniferous trees in mineral soils sites. These dependencies may be different in peatlands where growth is generally more dependent on variations in soil water conditions. In the Nordic and Baltic countries, millions of hectares of peatlands and wetlands have been drained in order to enhance forest production. These drainage networks do not guarantee stable soil water conditions for the whole stand rotation. It is thus likely that precipitation in particular may have a different influence on annual growth in peatland to that in mineral soil sites. We studied the effect of precipitation and temperature on the inter-annual diameter growth of Scots pine (Pinus sylvestris L.) in Finland in drained peatland forests. The diameter growth data were limited to periods when growth response to drainage had levelled out. For comparison, growth data were also collected from adjacent mineral soil trees. The climate variables were monthly mean temperature and precipitation in a given location estimated from observations at the nearest weather stations by means of spatial smoothing. We used mixed linear models in describing the annual diameter growth of individual trees as a function of tree size and stand properties and expressed the residual variation as a function of climate parameters. The peatland and mineral soil growth variations showed different dependence on climate parameters. Peatland trees within 5 m of a ditch showed different climate responses compared to those located further away. Precipitation in July was negatively correlated with the diameter growth of peatland trees but there was no correlation with temperature. Growth of trees in mineral soils was positively correlated with March and April mean temperatures and May and June mean precipitation. The residual growth indices showed largely similar patterns in peatlands and mineral soil sites.     

Factors Affecting the Duration of Nestling Period and Fledging Order in Tengmalm’s Owl (Aegolius funereus): Effect of Wing Length and Hatching Sequence

In altricial birds, the nestling period is an important part of the breeding phase because the juveniles may spend quite a long time in the nest, with associated high energy costs for the parents. The length of the nestling period can be variable and its duration may be influenced by both biotic and abiotic factors; however, studies of this have mostly been undertaken on passerine birds. We studied individual duration of nestling period of 98 Tengmalm’s owl chicks (Aegolius funereus) at 27 nests during five breeding seasons using a camera and chip system and radio-telemetry. We found the nestlings stayed in the nest box for 27 – 38 days from hatching (mean ± SD, 32.4 ± 2.2 days). The individual duration of nestling period was negatively related to wing length, but no formally significant effect was found for body weight, sex, prey availability and/or weather conditions. The fledging sequence of individual nestlings was primarily related to hatching order; no relationship with wing length and/or other factors was found in this case. We suggest the length of wing is the most important measure of body condition and individual quality in Tengmalm’s owl young determining the duration of the nestling period. Other differences from passerines (e.g., the lack of effect of weather or prey availability on nestling period) are considered likely to be due to different life-history traits, in particular different food habits and nesting sites and greater risk of nest predation among passerines.     

Evaluating the influence of diet-related variables on breeding performance and home range behaviour of a top predator

Diet composition is linked to reproductive performance directly or indirectly by other life-history traits, including home range behaviour. The relationships between prey abundance, diet and individual fitness have often been explored. However, these relationships are complex and difficult to disentangle, especially in vertebrate top predators. Here, we present the results of a long-term study using multi-model inference procedures to elucidate the influence of diet-related variables on breeding parameters and home range behaviour of a top predator, the eagle owl Bubo bubo. Superpredation, diet diversity, rat biomass and rabbit mean weight were the most important variables when analysing reproductive parameters, suggesting that less diverse diets with greater rabbit biomass percentage may benefit reproductive performance, whereas rat biomass percentage is apparently associated with greater variation of breeding success. Earlier laying dates seem to be associated with the consumption, on average, of smaller rabbits. On the other hand, edge density was the most relevant factor determining the variation in home range behaviour, with individual characteristics, such as age and sex, also being important. Although the relative importance of the diet-related variables was generally low, mean weight of alternative prey, diet diversity and rabbit biomass also helped to explain home range parameters. In an optimal foraging context, centred on the abundance of the main prey species, our results suggest that when rabbits are less available eagle owls may increase home range size in order to obtain alternative prey, increasing at the same time their dietary diversity, which may also require higher movement speed.