A simple, integrative assay to quantify nutritional quality of browses for herbivores

Many regard the concentrations of nitrogen (N), tannins and plant cell wall constituents (fibre) as key indicators of food quality and habitat suitability for browsing herbivores; yet there is no method for measuring their combined effects. We have developed a simple in vitro assay for measuring the effects of tannins and fibre on N availability in browse. We determined the effects of tannins by measuring the polyethylene glycol (PEG)-binding capacity (PEG-BC) of Eucalyptus leaf samples, followed by a two-stage in vitro digestion with pepsin and cellulase to determine the digestibility of dry matter and N. There was a significant relationship between concentrations of digestible N and the PEG-BC of the leaves. Furthermore, adding PEG significantly improved the digestibility of N. Our results concur with in vivo observations from several mammalian species. This suggests that our method is effective for measuring the nutritional quality of browse and the benefits of adding PEG, providing some index of the detrimental effects of tannins. We further simplified the assay by removing the PEG step, allowing us to quickly analyse samples in bulk. Nevertheless, this simplified method is still not practical for analysing the many samples necessary to compare the nutritional values of different tracts of forest. We used near-infrared reflectance spectroscopy to produce calibration equations and predicted total and digestible N in 322 trees at eleven sites. Both within and between sites, we found a wide variation in concentrations of digestible N but a much lower variation in total N, with either no relationship or poor relationships between the two measures. This confirms the variability in the nutritional quality of eucalypt forests, which may explain the distribution and abundance of mammalian herbivores. Thus, our assay provides a useful tool for understanding how food resources influence herbivore populations at different scales. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Six new recombinant inbred populations for the study of quantitative traits in Arabidopsis thaliana

Quantitative approaches are now widely used to study the genetic architecture of complex traits. However, most studies have been conducted in single mapping populations, which sample only a fraction of the natural allelic variation available within a gene pool and can identify only a subset of the loci controlling the traits. To enable the progress towards an understanding of the global genetic architecture of a broad range of complex traits, we have developed and characterised six new Arabidopsis thaliana recombinant inbred populations. To evaluate the utility of these populations for integrating analyses from multiple populations, we identified quantitative trait loci (QTL) controlling flowering time in vernalized plants growing in 16 h days. We used the physical positions of markers to align the linkage maps of our populations with those of six existing populations. We identified seven QTL in genomic locations coinciding with those identified in previous studies and in addition a further eight QTL were identified. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

The Intercostal NMJ Assay: a new alternative to the conventional LD50 assay for the determination of the therapeutic potency of botulinum toxin preparations

Therapeutic botulinum neurotoxin type A preparations have found an increasing number of clinical uses for a large variety of neuromuscular disorders and dermatological conditions. The accurate determination of potency in the clinical application of botulinum toxins is critical to ensuring clinical efficacy and safety, and is currently achieved by using a lethal dose (LD50) assay in mice. Ethical concerns and operational constraints associated with this assay have prompted the development of alternative assay systems that could potentially lead to its replacement. As one such alternative, we describe the development and evaluation of a novel ex vivo assay (the Intercostal Neuromuscular Junction [NMJ] Assay), which uses substantially fewer animals and addresses ethical concerns associated with the LD50 assay. The assay records the decay of force from electrically-stimulated muscle tissue sections in response to the toxin, and thus combines the important mechanisms of receptor binding, translocation, and the enzymatic action of the toxin molecule. Toxin application leads to a time-related and dose-related reduction in contractile force. A regression model describing the relationship between the applied dose and force decay was determined statistically, and was successfully tested as able to correctly predict the potency of an unknown sample. The tissue sections used were found to be highly reproducible, as determined through the innervation pattern and the localisation of NMJs in situ. Furthermore, the efficacy of the assay protocol to successfully deliver the test sample to the cellular target sites, was critically assessed by using molecular tracer molecules.     

Composition and function of haemolymphatic tissues in the European common shrew

Background

Studies of wild animals responding to their native parasites are essential if we are to understand how the immune system functions in the natural environment. While immune defence may bring increased survival, this may come at a resource cost to other physiological traits, including reproduction. Here, we tested the hypothesis that wild common shrews (Sorex araneus), which produce large numbers of offspring during the one breeding season of their short life span, forgo investment in immunity and immune system maintenance, as increased longevity is unlikely to bring further opportunities for mating. In particular, we predicted that adult shrews, with shorter expected lifespans, would not respond as effectively as young animals to infection.

Methodology/Principal Findings

We examined haemolymphatic tissues from wild-caught common shrews using light and transmission electron microscopy, applied in conjunction with immunohistology. We compared composition and function of these tissues in shrews of different ages, and the extent and type of inflammatory reactions observed in response to natural parasitic infections. All ages seemed able to mount systemic, specific immune responses, but adult shrews showed some signs of lymphatic tissue exhaustion: lymphatic follicles in adults (n = 21) were both smaller than those in sub-adults (n = 18; Wald = 11.1, p<0.05) and exhibited greater levels of depletion (Wald = 13.3, p<0.05).

Conclusions/Significance

Contrary to our expectations, shrews respond effectively to their natural parasites, and show little indication of immunosenescence as adults. The pancreas of Aselli, a unique lymphoid organ, may aid in providing efficient immune responses through the storage of large numbers of plasma cells. This may allow older animals to react effectively to previously encountered parasites, but infection by novel agents, and eventual depletion of plasma cell reserves, could both still be factors in the near-synchronous mortality of adult shrews observed shortly after breeding.     

Being there: cellular targeting of voltage-gated sodium channels in the heart

Voltage-gated sodium (Na_v) channels in cardiomyocytes are localized in specialized membrane domains that optimize their functions in propagating action potentials across cell junctions and in stimulating voltage-gated calcium channels located in T tubules. Mutation of the ankyrin-binding site of Na_v1.5, the principal Na_v channel in the heart, was previously known to cause cardiac arrhythmia and the retention of Na_v1.5 in an intracellular compartment in cardiomyocytes. Conclusive evidence is now provided that direct interaction between Na_v1.5 and ankyrin-G is necessary for the expression of Na_v1.5 at the cardiomyocyte cell surface.     

The use of modelling and simulation approach in reconstructing past landscapes from fossil pollen data: a review and results from the POLLANDCAL network

Information on past land cover in terms of absolute areas of different landscape units (forest, open land, pasture land, cultivated land, etc.) at local to regional scales is needed to test hypotheses and answer questions related to climate change (e.g. feedbacks effects of land-cover change), archaeological research, and nature conservancy (e.g. management strategy). The palaeoecological technique best suited to achieve quantitative reconstruction of past vegetation is pollen analysis. A simulation approach developed by Sugita (the computer model POLLSCAPE) which uses models based on the theory of pollen analysis is presented together with examples of application. POLLSCAPE has been adopted as the central tool for POLLANDCAL (POLlen/LANdscape CALibration), an international research network focusing on this topic. The theory behind models of the pollen–vegetation relationship and POLLSCAPE is reviewed. The two model outputs which receive greatest attention in this paper are the relevant source area of pollen (RSAP) and pollen loading in mires and lakes. Six examples of application of POLLSCAPE are presented, each of which explores a possible use of the POLLANDCAL tools and a means of validating or evaluating the models with empirical data. The landscape and vegetation factors influencing the size of the RSAP, the importance of pollen productivity estimates (PPEs) for the model outputs, the detection of small and rare patches of plant taxa in pollen records, and quantitative reconstructions of past vegetation and landscapes are discussed on the basis of these examples. The simulation approach is seen to be useful both for exploring different vegetation/landscape scenarios and for refuting hypotheses.     

Sex differences in control of blood pressure: role of oxidative stress in hypertension in females

In general, blood pressure is higher in normotensive men than in age-matched women, and the prevalence of hypertension in men is also higher until after menopause, when the prevalence of hypertension increases for women. It is likely then that the mechanisms by which blood pressure increases in men and women with aging may be different. Although clinical trials to reduce blood pressure with antioxidants have typically not been successful in human cohorts, studies in male rats suggest that oxidative stress plays an important role in mediating hypertension. The exact mechanisms by which oxidative stress increases blood pressure have not been completely elucidated. There may be several reasons for the discrepancies between clinical and animal studies. In this review, the data obtained in selected clinical and animal studies are discussed, and the hypothesis is put forward that oxidative stress may not be as important in mediating hypertension in females as has been shown previously in male rats. Furthermore, it is likely that differences in genetics, age, length of time with hypertension, endothelial dysfunction, and sex are all factored in to modulate the responses to antioxidants in humans. As such, future clinical trials should be designed and powered to evaluate the effects of oxidative stress on blood pressure separately in men and women.     

α4β2-Nicotinic Receptor Binding with 5-IA in Alzheimer’s Disease: Methods of Scan Analysis

Five patients with Alzheimer’s disease and five healthy volunteers were examined by SPECT with the nicotinic receptor ligand ¹²³I-5-IA-85380. Patients were scanned before and after 6 weeks of treatment with donepezil. Quantification by regions of interest was reliable and the optimal normalisation procedure used cerebellar ratios. We found relative reductions in 5-IA binding capacity in patients in thalamus, frontal and central regions of interest of approximately one standard deviation unit (Cohen’s d = 1). Reductions in binding after treatment with the acetylcholinesterase inhibitor donepezil of the same magnitude occurred in the brain stem. The study was clearly too small to confirm group differences, but it suggests that 5-IA can be used to examine both group differences and treatment effects in patients with Alzheimer’s disease. Special issue article in honor of George Fink.