Structure of antimicrobial peptides and lipid membranes probed by interface-sensitive X-ray scattering

The conformation and correlations of amphiphilic and antimicrobial peptides and the associated changes of lipid bilayers can be studied in oriented lipid membranes deposited on solid substrates. Here we review recent work on these systems, as studied by modern interface-sensitive X-ray and neutron scattering methods. Density profile, short range order of acyl chains and molecular conformations of peptides and lipids are probed in the fluid state of the bilayer. With an emphasis on technical aspects, we review recent work illustrating the potential of the methods and discuss its potential in the field.     

Estimating Fundamental Host Range: a Host-Specificity Study of a Potential Biocontrol Agent for Prosopis Species (Leguminosae)

One approach to predicting non-target attack by potential biological control agents is to first describe their fundamental host ranges and then to predict how it will be expressed under postrelease field conditions. In this paper, we illustrate how the fundamental host range can be estimated experimentally by excluding possible limiting factors such as time-dependent effects. The example we use is a host-specificity study of a leaf-tying moth (Gelechiidae: Evippe sp. #1) which was being assessed for the biological control of mesquite (Leguminosae: Prosopis spp.) in Australia. Females oviposited all eggs on plants, mostly into cracks and fissures. First instar larvae leaf-mined and subsequent instars leaf-tied. Oviposition was not host-specific in cage trials, although ten times more eggs were laid on Prosopis than on non-targets. The fundamental host range for initiation of larval feeding was restricted to Prosopis and Leucaena leucocephala which both belong to the same tribe, and the fundamental host range for complete larval development was restricted to Prosopis . We predict that if released in Australia Evippe sp. #1 will only attack Prosopis spp., although low levels of 'indiscriminate' oviposition might occur on other taxa, and might result in initiation of feeding on L. leucocephala .     

cDNA cloning of translationally controlled tumor protein/histamine releasing factor (TCTP/HRF) from the intertidal harpacticoid copepod Tigriopus japonicus.

We synthesized a cDNA library from the intertidal copepod Tigriopus japonicus, converted it to phagemids and sequenced expressed sequence tags (ESTs). Of these, Tigriopus translationally controlled tumor protein/histamine releasing factor (TCTP/HRF) was further characterized. The Tigriopus TCTP/HRF gene encoded 172 amino acid residues and showed high similarity to Drosophila but moderate similarity to other annelids (e.g. Brugia, Wuchereria and C. elegans). The Tigriopus TCTP/HRF gene appeared in the same clade as the annelids. Here, we describe the analysis of the Tigriopus TCTP/HRF gene.     

Substrates of Energy Metabolism Attenuate Methamphetamine-Induced Neurotoxicity in Striatum

Abstract: High doses of methamphetamine (METH) produce a long-term depletion in striatal tissue dopamine content. The mechanism mediating this toxicity has been associated with increased concentrations of dopamine and glutamate and altered energy metabolism. In vivo microdialysis was used to assess and alter the metabolic environment of the brain during high doses of METH. METH significantly increased extracellular concentrations of lactate in striatum and prefrontal cortex. This increase was significantly greater in striatum and coincided with the greater vulnerability of this brain region to the toxic effects of METH. To examine the effect of supplementing energy metabolism on METH-induced dopamine content depletions, the striatum was perfused directly with decylubiquinone or nicotinamide to enhance the energetic capacity of the tissue during or after a neurotoxic dosing regimen of METH. When decylubiquinone or nicotinamide was perfused into striatum during the administration of METH, there was no significant effect on METH-induced striatal dopamine efflux, glutamate efflux, or the long-term dopamine depletions measured 7 days later. However, a delayed perfusion with decylubiquinone or nicotinamide for 6 h beginning immediately after the last METH injection attenuated the METH-induced striatal dopamine depletions measured 1 week later. These results support the hypothesis that the compromised metabolic state produced by METH administration predisposes dopamine terminals to the neurotoxic effects of glutamate, dopamine, and/or free radicals.     

Involvement of regulatory volume decrease in the migration of nasopharyngeal carcinoma cells

The transwell chamber migration assay and CCD digital camera imaging techniques were used to investigate the relationship between regulatory volume decrease (RVD) and cell migration in nasopharyngeal carcinoma cells (CNE-2Z cells). Both migrated and non-migrated CNE-2Z cells, when swollen by 47% hypotonic solution, exhibited RVD which was inhibited by extracellular application of chloride channel blockers adenosine 5‘-triphosphate (ATP), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen. However, RVD rate in migrated CNE-2Z cells was bigger than that of non-migrated cells and the sensitivity of migrated cells to NPPB and tamoxifen was higher than that of nonmigrated cells. ATP, NPPB and tamoxifen also inhibited migration of CNE-2Z cells. The inhibition of migration was positively correlated to the blockage of RVD, with a correlation coefficient (r) = 0.99, suggesting a functional relationship between RVD and cell migration. We conclude that RVD is involved in cell migration and RVD may play an important role in migratory process in CNE-2Z cells.     

The conserved ubiquitin-like protein Hub1 plays a critical role in splicing in human cells

Different from canonical ubiquitin-like proteins, Hub1 does not form covalent conjugates with substrates but binds proteins noncovalently. In Socchoromyces cerevisioe, Hub1 associates with spUceosomes and mediates alternative splicing of SRCI, without affecting pre-mRNA splicing generaity. Human Hub1 is highty similar to its yeast homotog, but its cellular function remains largely unexplored. Here, we show that human Hub1 binds to the spliceosomal protein Snu66 as in yeast; however, unlike its 5. cerevisioe homolos, human Hub1 is essential for viability. Prolonged in vivo depletion of human Hub1 leads to various cellular defects, including splicing speckle abnormalities, partial nuclear retention of mRNAs, mitotic catastrophe, and consequently cell death by apoptosis. Early consequences of Hub1 depletion are severe splicing defects, however, only for specific splice sites leading to exon skipping and intron retention. Thus, the ubiquitin-iike protein Hub1 is not a canonlcal spliceosomal factor needed generally for splicing, but rather a modulator of spliceosome performance and facilitator of alternative splicing.     

Metabolic Stability of Hippocampal Slice Preparations During Prolonged Incubation

Abstract: Hippocampal slices were prepared under three conditions: (1) in medium containing glucose and oxygen at 4°C; (2) as in (1), but at 37°C; (3) in medium devoid of glucose and oxygen at 37°C. The rates of recovery to roughly steady-state levels and through 8 h of incubation were monitored for energy metabolite levels and related parameters. In vitro stable values are compared with in situ hippocampal levels. Regardless of the conditions under which slices were prepared, metabolite levels required up to 3 h to stabilize, and these levels were maintained or improved through 8 h of incubation. Further, the maximal concentrations of metabolites were independent of the conditions of slice preparation. Total adenylates and total creatine levels reached 55% of those in vivo. Lactate decreased from the decapitation-induced high levels, but stabilized at concentrations about twice those in rapidly frozen brain. Cyclic AMP and cyclic GMP exhibited peak levels at 30 min of incubation, and cyclic GMP remained elevated for 3 h. Although all three methods of slice preparation resulted in similar metabolite profiles on incubation, the initial decreases in high energy phosphates were delayed by chilling. Most striking, the slices prepared in the absence of glucose and oxygen exhibited much smaller orthodromic evoked potentials in the dentate gyrus. The presence of glucose and oxygen during preparation of the slices appears to be critical to the electrophysiological response of the tissue.     

Animal movements in fire‐prone landscapes

Movement is a trait of fundamental importance in ecosystems subject to frequent disturbances, such as fire‐prone ecosystems. Despite this, the role of movement in facilitating responses to fire has received little attention. Herein, we consider how animal movement interacts with fire history to shape species distributions. We consider how fire affects movement between habitat patches of differing fire histories that occur across a range of spatial and temporal scales, from daily foraging bouts to infrequent dispersal events, and annual migrations. We review animal movements in response to the immediate and abrupt impacts of fire, and the longer‐term successional changes that fires set in train. We discuss how the novel threats of altered fire regimes, landscape fragmentation, and invasive species result in suboptimal movements that drive populations downwards. We then outline the types of data needed to study animal movements in relation to fire and novel threats, to hasten the integration of movement ecology and fire ecology. We conclude by outlining a research agenda for the integration of movement ecology and fire ecology by identifying key research questions that emerge from our synthesis of animal movements in fire‐prone ecosystems.