Paroster peelensis sp. nov.: a new stygobitic water beetle from alluvial gravels in northern New South Wales (Coleoptera: Dytiscidae)

Abstract  A second stygobitic carnivorous water beetle is reported from eastern Australia. Unlike the recently discovered Carabhydrus stephanieae (Watts et al .) from the same general region, the new species is from the inland draining Peel River, part of the Murray-Darling basin. Its morphology and mitochondrial DNA sequences, place it in the Hydroporine genus Paroster Sharp. Phylogenetic analysis shows that the new species is more closely related to the Western Australian species of Paroster than to the geographical less distant Paroster species of the Northern Territory.     

Mass variation in Northern Saw-whet Owls: implications for current sexing criteria

ABSTRACT.   Currently, a protocol using body mass as the primary criterion for assigning sex of Northern Saw-whet Owls ( Aegolius acadicus ) is being used by banders. We assessed mass variation of owls using paired measurements of those recaptured ( N = 372) during fall migration along the lower Delmarva Peninsula (1994–2005) to assess the stability of gender assignments resulting from the protocol in current use. Mass variation ranged from 0 to 26.0 g, with a mean of 6.0 g. There was a positive relationship between body mass and the magnitude of the mass change between measurements. Variation in mass between captures caused a considerable shift in gender designations. Changes were most pronounced for birds classified as male ( N = 43), with 58% remaining either definite or probable male and the remainder changing to either unknown (28%) or female (14%). Female designations ( N = 317) were more stable, with 76% remaining either definite or probable female. Variation in mass and associated changes in gender assignments caused a two-fold shift in perceived sex ratio from 1:13 to 1:6 (M:F). Given that meals cause variation in mass that is large relative to the differences between sexes, we suggest that mass carries an unacceptably high level of uncertainty to be useful in assigning gender. Sex ratios and other demographic parameters generated using the current technique should be used with caution.     

Types of Social Capital and Mental Disorder in Deprived Urban Areas: A Multilevel Study of 40 Disadvantaged London Neighbourhoods

Objectives

To examine the extent to which individual and ecological-level cognitive and structural social capital are associated with common mental disorder (CMD), the role played by physical characteristics of the neighbourhood in moderating this association, and the longitudinal change of the association between ecological level cognitive and structural social capital and CMD.

Design

Cross-sectional and longitudinal study of 40 disadvantaged London neighbourhoods. We used a contextual measure of the physical characteristics of each neighbourhood to examine how the neighbourhood moderates the association between types of social capital and mental disorder. We analysed the association between ecological-level measures of social capital and CMD longitudinally.

Participants

4,214 adults aged 16-97 (44.4% men) were randomly selected from 40 disadvantaged London neighbourhoods.

Main Outcome Measures

General Health Questionnaire (GHQ-12).

Results

Structural rather than cognitive social capital was significantly associated with CMD after controlling for socio-demographic variables. However, the two measures of structural social capital used, social networks and civic participation, were negatively and positively associated with CMD respectively. ‘Social networks’ was negatively associated with CMD at both the individual and ecological levels. This result was maintained when contextual aspects of the physical environment (neighbourhood incivilities) were introduced into the model, suggesting that ‘social networks’ was independent from characteristics of the physical environment. When ecological-level longitudinal analysis was conducted, ‘social networks’ was not statistically significant after controlling for individual-level social capital at follow up.

Conclusions

If we conceptually distinguish between cognitive and structural components as the quality and quantity of social capital respectively, the conclusion of this study is that the quantity rather than quality of social capital is important in relation to CMD at both the individual and ecological levels in disadvantaged urban areas. Thus, policy should support interventions that create and sustain social networks. One of these is explored in this article.

Trial Registration

Controlled-Trials.com ISRCTN68175121 http://www.controlled-trials.com/ISRCTN68175121     

Role of the reticulum in the stability and shape of the isolated human erythrocyte membrane

In order to examine the widely held hypothesis that the reticulum of proteins which covers the cytoplamsic surface of the human erythrocyte membrane controls cell stability and shape, we have assessed some of its properties. The reticulum, freed of the bilayer by extraction with Triton X-100, was found to be mechanically stable at physiological ionic strength but physically unstable at low ionic strength. The reticulum broke down after a characteristic lag period which decreased 500-fold between 0 degrees and 37 degrees C. The release of polypeptide band 4.1 from the reticulum preceded that of spectrin and actin, suggesting that band 4.1 might stabilize the ensemble but is not essential to its integrity. The time-course of breakdown was similar for ghosts, the reticulum inside of ghosts, and the isolated reticulum. However, at very low ionic strength, the reticulum was less stable within the ghost than when free; at higher ionic strength, the reverse was true. Over a wide range of conditions the membrane broke down to vesicles just as the reticulum disintegrated, presumably because the bilayer was mechanically stabilized by this network. The volume of both ghosts and naked reticula varied inversely and reversibly with ionic strength. The volume of the naked reticulum varied far more widely than the ghost, suggesting that its deformation was normally limited by the less extensible bilayer. The contour of the isolated reticulum was discoid and often dimpled or indented, as visualized in the fluorescence microscope after labeling of the ghosts with fluoroscein isothiocyanate. Reticula derived from ghosts which had lost the ability to crenate in isotonic saline were shriveled, even though the bilayer was smooth and expanded. Conversly, ghosts crenated by dinitrophenol yielded smooth, expanded reticula. We conclude that the reticulum is a durable, flexible, and elastic network which assumes and stabilizes the contour of the membrane but is not responsible for its crenation.     

Active beta-catenin signaling is an inhibitory pathway for human immunodeficiency virus replication in peripheral blood mononuclear cells

The Wnt/β-catenin pathway is involved in cell functions governing development and disease. In modeling postentry restriction of human immunodeficiency virus (HIV) replication in astrocytes, we reported that part of this natural resistance to productive replication of HIV in astrocytes involved expression of proteins of the Wnt/β-catenin signaling pathway. We determined here whether induction of β-catenin signaling in peripheral blood mononuclear cells (PBMCs) can modulate HIV replication. Given that lithium is an inducer of β-catenin signaling, we used it as a tool to determine the impact of β-catenin signaling on HIV replication in PBMCs. We demonstrated that lithium inhibited the replication of T-tropic and primary isolates of HIV by >90% and did so in noncytotoxic/noncytostatic concentrations and in a β-catenin-dependent manner. Specifically, inhibiting β-catenin signaling by transfection of dominant-negative mutant constructs to either T-cell factor 4, the downstream effector of Wnt signaling, or β-catenin, the central mediator of this pathway, abrogated the ability of lithium to inhibit HIV replication. Moreover, when Wnt/β-catenin signaling was inhibited, the level of HIV replication was enhanced by fourfold. To confirm the in vivo relevance of the β-catenin pathway in repressing HIV replication, we evaluated HIV-positive antiretroviral therapy-naive patients who were on lithium therapy. These patients demonstrated a reduction in viral load, which increased as the dose of lithium was reduced. Collectively, these data indicate that β-catenin signaling is an intrinsic molecular pathway restricting HIV replication in PBMCs.     

Slow variable dominance and phase resetting in phantom bursting

Bursting oscillations are common in neurons and endocrine cells. One type of bursting model with two slow variables has been called ‘phantom bursting’ since the burst period is a blend of the time constants of the slow variables. A phantom bursting model can produce bursting with a wide range of periods: fast (short period), medium, and slow (long period). We describe a measure, which we call the ‘dominance factor’, of the relative contributions of the two slow variables to the bursting produced by a simple phantom bursting model. Using this tool, we demonstrate how the control of different phases of the burst can be shifted from one slow variable to another by changing a model parameter. We then show that the dominance curves obtained as a parameter is varied can be useful in making predictions about the resetting properties of the model cells. Finally, we demonstrate two mechanisms by which phase-independent resetting of a burst can be achieved, as has been shown to occur in the electrical activity of pancreatic islets.     

Lipid-Induced Modulation of the Protein Packing in Two-Dimensional Crystals of Bacteriorhodopsin

The mechanism by which bacteriorhodopsin (BR), the light-driven proton pump from the purple membrane (PM) of Halobacterium halobium, arranges in a 2D hexagonal array has been studied by reconstitution of BR in complexes of two types of bilayer made either with PM-derived lipids or with PM lipids and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The unit cell dimensions of the 2D protein crystals, determined by correlation averaging analysis of freeze-fracture electron micrographs, were compared with the lattice constant of the PM. In complexes made with delipidated BR and with the polar lipids extracted from H. halobium cells (HHPL), BR trimers are arranged in a hexagonal lattice with the same lattice constant of 5.9 ± 0.2 nm as found in the PM. In BR-containing complexes made with PM-derived lipids and DMPC at several protein:lipid mole ratios, BR trimers are also arranged in a hexagonal lattice, but with a unit cell dimension of 9.2 ± 0.2 nm, which is about one-third larger compared to that measured in PM (Michel et al. , 1980). In a subclass of this type of complexes, orthogonal BR arrays were observed with a lattice constant of 5.9 × 9.9 ± 0.2 nm. It appears that insertion of DMPC into the BP/PM-derived lipid complexes increases the center-to-center distances in both array types by a discrete amount.     

Antigen endocytosis and presentation mediated by human membrane IgG1 in the absence of the Ig(alpha)/Ig(beta) dimer.

Membrane immunoglobulin (mIg) M and D heavy chains possess minimal (KVK) cytoplasmic tails and associate with the Ig alpha/Ig beta (CD79) dimer to achieve surface expression and antigen presentation function. In contrast, the cytoplasmic tail of mIgG is extended by 25 residues (gamma ct). We have tested the possibility that mIgG can perform antigen capture and presentation functions independently of the Ig(alpha)/beta dimer. We show that CD4/(gamma)ct chimeras are efficiently endocytosed partially dependent on a tyrosine residue in (gamma)ct. In addition, human mIgG was expressed on the surface of Ig(alpha)/Ig(beta)-negative non-lymphoid cells and mediated antigen capture and endocytosis. Antigen-specific human mIgG targeted antigen to MIIC-type vesicles in the Ig(alpha)/beta negative melanoma Mel JuSo and augmented antigen presentation 1000-fold, identical to the augmentation seen in Ig(alpha)/beta-positive B-cells expressing the same transfected mIgG. Thus, unlike mIgM, mIgG has autonomous antigen capture and presentation capacity, which may have evolved to reduce or eliminate the BCR's dependence on additional accessory molecules.