Time as a constraint on the distribution of feral goats at high latitudes

We use data on feral goats on the Isle of Rum to explore the hypothesis that time is a major constraint on the latitudinal and altitudinal distribution of this species. Daylength and temperature were the principal factors influencing the main time budget elements (feeding, moving and resting). Because the goats do not feed at night due to low ambient temperatures, they faced particular problems during winter when daylengths were at their shortest. A mean monthly windchill‐adjusted temperature of 5°C appeared to be a critical threshold in terms of the animals’ ability to survive on Rum. We used these data to model the animals’ time budgets at different latitudes and altitudes. We show that winter daylength would be shorter than the required feeding time north of about 60° latitude, with a narrowing altitudinal cone approaching sea level at this latitude. Biogeographic evidence confirms that feral goat populations are not self‐sustaining north of this latitude.     

Milling plant and soil material in plastic tubes over-estimates carbon and under-estimates nitrogen concentrations

Background and aims

Milling of plant and soil material in plastic tubes, such as microcentrifuge tubes, over-estimates carbon (C) and under-estimates nitrogen (N) concentrations due to the introduction of polypropylene into milled samples, as identified using Fourier-transform infra-red spectroscopy.

Methods and results

This study compares C and N concentrations of roots and soil milled in microcentrifuge tubes versus stainless steel containers, demonstrating that a longer milling time, greater milling intensity, smaller sample size and inclusion of abrasive sample material all increase polypropylene contamination from plastic tubes leading to overestimation of C concentrations by up to 8 % (0.08 g?g^?1).

Conclusions

Erroneous estimations of C and N, and other analytes, must be assumed after milling in plastic tubes and milling methods should be adapted to minimise such error.     

Sorting Nexin 1 Loss Results in D5 Dopamine Receptor Dysfunction in Human Renal Proximal Tubule Cells and Hypertension in Mice

The peripheral dopaminergic system plays a crucial role in blood pressure regulation through its actions on renal hemodynamics and epithelial ion transport. The dopamine D5 receptor (D₅R) interacts with sorting nexin 1 (SNX1), a protein involved in receptor retrieval from the trans-Golgi network. In this report, we elucidated the spatial, temporal, and functional significance of this interaction in human renal proximal tubule cells and HEK293 cells stably expressing human D₅R and in mice. Silencing of SNX1 expression via RNAi resulted in the failure of D₅R to internalize and bind GTP, blunting of the agonist-induced increase in cAMP production and decrease in sodium transport, and up-regulation of angiotensin II receptor expression, of which expression was previously shown to be negatively regulated by D₅R. Moreover, siRNA-mediated depletion of renal SNX1 in C57BL/6J and BALB/cJ mice resulted in increased blood pressure and blunted natriuretic response to agonist in salt-loaded BALB/cJ mice. These data demonstrate a crucial role for SNX1 in D₅R trafficking and that SNX1 depletion results in D₅R dysfunction and thus may represent a novel mechanism for the pathogenesis of essential hypertension.     

The floral transition is not the developmental switch that confers competence for the Arabidopsis age-related resistance response to Pseudomonas syringae pv. tomato

Age-related resistance (ARR) is a plant defense response characterized by enhanced resistance to certain pathogens in mature plants relative to young plants. In Arabidopsis thaliana the transition to flowering is associated with ARR competence, suggesting that this developmental event is the switch that initiates ARR competence in mature plants (Rusterucci et al. in Physiol Mol Plant Pathol 66:222–231, 2005). The association of ARR and the floral transition was examined using flowering-time mutants and photoperiod-induced flowering to separate flowering from other developmental events that occur as plants age. Under short-day conditions, late-flowering plant lines ld-1 (luminidependens-1), soc1-2 (suppressor of overexpression of co 1-2), and FRI ⁺ (FRIGIDA) displayed ARR before the transition to flowering occurred. Early-flowering svp-31, svp-32 (short vegetative phase), and Ws-2 were ARR-defective, whereas early-flowering tfl1-14 (terminal flower 1-14) displayed ARR at the same time as Col-0. While svp-31, svp-32 and Ws-2 produced few rosette leaves, tfl1-14 produced a rosette leaf number similar to Col-0, suggesting that the development of a minimum number of rosette leaves is necessary to initiate ARR competence under short-day conditions. Photoperiod-induced transient expression of FT (FLOWERING LOCUS T) caused precocious flowering in short-day-grown Col-0 but this was not associated with ARR competence. Under long-day conditions co-9 (constans-9) mutants did not flower but displayed an ARR response at the same time as Col-0. This study suggests that SVP is required for the ARR response and that the floral transition is not the developmental event that regulates ARR competence.     

Thermodynamic and kinetic characterization of hydroxyethylamine β-secretase-1 inhibitors

Alzheimer’s disease (AD) is a devastating neurodegenerative disease affecting millions of people. β-Secretase-1 (BACE-1), an enzyme involved in the processing of the amyloid precursor protein (APP) to form Aβ, is a well validated target for AD. Herein, the authors characterize 10 randomly selected hydroxyethylamine (HEA) BACE-1 inhibitors in terms of their association and dissociation rate constants and thermodynamics of binding using surface plasmon resonance (SPR). Rate constants of association (k_a) measured at 25 °C ranged from a low of 2.42 × 10⁴ M⁻¹ s⁻¹ to the highest value of 8.3 × 10⁵ M⁻¹ s⁻¹. Rate constants of dissociation (k_d) ranged from 1.09 × 10⁻⁴ s⁻¹ (corresponding to a residence time of close to three hours), to the fastest of 0.028 s⁻¹. Three compounds were selected for further thermodynamic analysis where it was shown that equilibrium binding was enthalpy driven while unfavorable entropy of binding was observed. Structural analysis revealed that upon ligand binding, the BACE-1flap folds down over the bound ligand causing an induced fit. The maximal difference between alpha carbon positions in the open and closed conformations of the flap was over 5 Å. Thus the negative entropy of binding determined using SPR analysis was consistent with an induced fit observed by structural analysis.     

Hormonal changes and energy substrate availability during the hibernation cycle of Syrian hamsters

Animals have to adapt to seasonal variations in food resources and temperature. Hibernation is one of the most efficient means used by animals to cope with harsh winter conditions, wherein survival is achieved through a significant decrease in energy expenditure. The hibernation period is constituted by a succession of torpor bouts (hypometabolism and decrease in body temperature) and periodic arousals (eumetabolism and euthermia). Some species feed during these periodic arousals, and thus show different metabolic adaptations to fat-storing species that fast throughout the hibernation period. Our study aims to define these metabolic adaptations, including hormone (insulin, glucagon, leptin, adiponectin, GLP-1, GiP) and metabolite (glucose, free fatty acids, triglycerides, urea) profiles together with body composition adjustments. Syrian hamsters were exposed to varied photoperiod and temperature conditions mimicking different phases of the hibernation cycle: a long photoperiod at 20 °C (LP20 group), a short photoperiod at 20 °C (SP20 group), and a short photoperiod at 8 °C (SP8). SP8 animals were sampled either at the beginning of a torpor bout (Torpor group) or at the beginning of a periodic arousal (Arousal group). We show that fat store mobilization in hamsters during torpor bouts is associated with decreased circulating levels of glucagon, insulin, leptin, and an increase in adiponectin. Refeeding during periodic arousals results in a decreased free fatty acid plasma concentration and an increase in glycemia and plasma incretin concentrations. Reduced incretin and increased adiponectin levels are therefore in accordance with the changes in nutrient availability and feeding behavior observed during the hibernation cycle of Syrian hamsters.     

Getting to the guts of the matter: The status and potential of ‘omics’ research of parasitic protists of the human gastrointestinal system

Parasitic protists are a major cause of diarrhoeal illnesses in humans globally. Collectively, enteric pathogens exceed all other forms of infectious disease, in terms of their estimated global prevalence and socioeconomic impact. They have a disproportionately high impact on children in impoverished communities, leading to acute (diarrhoea, vomiting, dehydration and death) and chronic disease (malabsorption, malnutrition, physical and cognitive stunting and predisposition to chronic, non-communicable disease) consequences. However, historically, investment in research and disease control measures has been disproportionately poor, leading to their current classification as neglected pathogens. A sound understanding of their biology is essential in underpinning detection, treatment and control efforts. One major tool in rapidly improving our knowledge of these parasites is the use of biological systems, including ‘omic’ technologies. In recent years, these tools have shown significant success when applied to enteric protists. This review summarises much of this knowledge and highlights the significant remaining knowledge gaps. A major focus of the present review was to provide a perspective on a way forward to address these gaps using advanced biotechnologies.     

Sensitivity of continental United States atmospheric budgets of oxidized and reduced nitrogen to dry deposition parametrizations

Reactive nitrogen (N_r) is removed by surface fluxes (air–surface exchange) and wet deposition. The chemistry and physics of the atmosphere result in a complicated system in which competing chemical sources and sinks exist and impact that removal. Therefore, uncertainties are best examined with complete regional chemical transport models that simulate these feedbacks. We analysed several uncertainties in regional air quality model resistance analogue representations of air–surface exchange for unidirectional and bi-directional fluxes and their effect on the continental N_r budget. Model sensitivity tests of key parameters in dry deposition formulations showed that uncertainty estimates of continental total nitrogen deposition are surprisingly small, 5 per cent or less, owing to feedbacks in the chemistry and rebalancing among removal pathways. The largest uncertainties (5%) occur with the change from a unidirectional to a bi-directional NH₃ formulation followed by uncertainties in bi-directional compensation points (1–4%) and unidirectional aerodynamic resistance (2%). Uncertainties have a greater effect at the local scale. Between unidirectional and bi-directional formulations, single grid cell changes can be up to 50 per cent, whereas 84 per cent of the cells have changes less than 30 per cent. For uncertainties within either formulation, single grid cell change can be up to 20 per cent, but for 90 per cent of the cells changes are less than 10 per cent.     

On the concept and elucidation of endogenous retroviruses

Endogenous retrovirus (ERV) genomes integrated into the chromosomal DNA of the host were first detected in chickens and mice as Mendelian determinants of Gag and Env proteins and of the release of infectious virus particles. The presence of ERV was confirmed by DNA hybridization. With complete host genomes available for analysis, we can now see the great extent of viral invasion into the genomes of numerous vertebrate species, including humans. ERVs are found at many loci in host DNA and also in the genomes of large DNA viruses, such as herpesviruses and poxviruses. The evolution of xenotropism and cross-species infection is discussed in the light of the dynamic relationship between exogenous and endogenous retroviruses.     

The life history of Turnerella pennyi (Harv.) Schmitz

The life-history and phenology of T. pennyi, regarded as the only species of Turnerella in the north Atlantic Ocean, are described on the basis of culture, cytology and field investigations.

In Newfoundland and Labrador, heteromorphic phases occur: tetraspores from an encrusting tetrasporophyte resembling Cruoria arctica/rosea give rise to a similar perennial sterile phase from which the foliose T. pennyi phase arises directly. These foliose plants are dioecious gametophytes. The male gametophyte, reported for the first time, bears spreading spermatangial sori over most of its surface. Old cystocarpic plants may exhibit in situ germination of carpospores. Chromosome counts show that n = 18–20; 2n = 36–40.

The indications are that the life-history of the species is similar in other parts of its range, although the longevity of the foliose stage may vary with geographical location and depth. Regeneration of old loose-lying plants readily occurs.