Scats and den contents as indicators of the diet of stoats (Mustela erminea) in the Tasman Valley,South Canterbury,New Zealand

Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats.     

HIV-particles in spermatozoa of patients with AIDS and their transfer into the oocyte

By immunocytochemistry and in situ hybridization at the electron microscopy level, and by the PCR technique, we have shown that HIV-1 binds and enters normal sperm; that viral particles, their antigens, and nucleic acid are present in sperm from HIV-1 infected men; and that such sperm can transfer HIV-1 like particles to normal human oocytes. We also present evidence that a galactosylceramide-like compound is present on the sperm membrane and could function as an alternative receptor for HIV.     

Direct immobilization of gangliosides onto gold-carboxymethyldextran sensor surfaces by hydrophobic interaction: applications to antibody characterization

We describe a novel immobilization technique to investigate interactions between immobilized gangliosides (GD3, GM1, and GM2) and their respective antibodies, antibody fragments, or binding partners using an optical biosensor. Immobilization was performed by direct injection onto a carboxymethyldextran sensor chip and did not require derivatization of the sensor surface or the ganglioside. The ganglioside appeared to bind to the sensor surface by hydrophobic interaction, leaving the carbohydrate epitope available for antibody or, in the case of GM1, cholera toxin binding. The carboxyl group of the dextran chains on the sensor surface did not appear to be involved in the immobilization as evidenced by equivalent levels of immobilization following conversion of the carboxyl groups into acyl amino esters, but rather the dextran layer provided a hydrophilic coverage of the sensor chip which was essential to prevent nonspecific binding. This technique gave better reactivity and specificity for anti- ganglioside monoclonal antibodies (anti-GD3: KM871, KM641, R24; and anti-GM2: KM966) than immobilization by hydrophobic interaction onto a gold sensor surface or photoactivated cross-linking onto carboxymethydextran. This rapid immobilization procedure has facilitated detailed kinetic analysis of ganglioside/antibody interactions, with the surface remaining viable for a large number of cycles (>125). Kinetic constants were determined from the biosensor data using linear regression, nonlinear least squares and equilibrium analysis. The values of kd, ka, and KAobtained by nonlinear analysis (KAKM871 = 1.05, KM641 = 1.66, R24 = 0.14, and KM966 = 0.65 x 10(7) M- 1) were essentially independent of concentration and showed good agreement with data obtained by other analytical methods.      

Interaction of slow growth and increased early-life mortality: an hypothesis on the decline of Colorado squawfish in the upstream regions of its historic range

Synopsis The Colorado squawfish, Ptychocheilus lucius, the principal native piscivore of the Colorado River basin, was once widespread and abundant in large rivers and their major tributaries. It occurs today only in the upstream regions of its historic range and is threatened with extinction. Growth rate of the species there is much slower than its potential rate and the rate that might once have been typical in lower-basin rivers. We develop the hypothesis that the interaction of slow growth and increased early-life mortality is an important cause of the decline of Colorado squawfish in the upper basin. We use a growth-rate versus temperature relation for Colorado squawfish to compare temperature regimes of historic and present habitats, and we describe the strong, positive relation between our measure of temperature-regime suitability and first-year growth of Colorado squawfish in upper-basin rivers. The unusually small size of the age-0 fish going into winter might be an important factor affecting recruitment to the adult stock. Simulations showed how the effect of increased early-life mortality can be especially significant on populations of slow-growing fishes. Predation by introduced fishes, as well as other man-induced causes of increased early-life mortality, probably contributed importantly to the decline of Colorado squawfish in the remaining habitat. Management efforts that might help this endangered species to recover include water management to enhance temperatures for growth, and the control of important introduced fishes.     

Communicating oscillatory networks: frequency domain analysis

Background

Endothelial permeability is involved in injury, inflammation, diabetes and cancer. It is partly regulated by the thrombin-, histamine-, and VEGF-mediated myosin-light-chain (MLC) activation pathways. While these pathways have been investigated, questions such as temporal effects and the dynamics of multi-mediator regulation remain to be fully studied. Mathematical modeling of these pathways facilitates such studies. Based on the published ordinary differential equation models of the pathway components, we developed an integrated model of thrombin-, histamine-, and VEGF-mediated MLC activation pathways.

Results

Our model was validated against experimental data for calcium release and thrombin-, histamine-, and VEGF-mediated MLC activation. The simulated effects of PAR-1, Rho GTPase, ROCK, VEGF and VEGFR2 over-expression on MLC activation, and the collective modulation by thrombin and histamine are consistent with experimental findings. Our model was used to predict enhanced MLC activation by CPI-17 over-expression and by synergistic action of thrombin and VEGF at low mediator levels. These may have impact in endothelial permeability and metastasis in cancer patients with blood coagulation.

Conclusion

Our model was validated against a number of experimental findings and the observed synergistic effects of low concentrations of thrombin and histamine in mediating the activation of MLC. It can be used to predict the effects of altered pathway components, collective actions of multiple mediators and the potential impact to various diseases. Similar to the published models of other pathways, our model can potentially be used to identify important disease genes through sensitivity analysis of signalling components.     

Glycosphingolipid expression in pig aorta: identification of possible target antigens for human natural antibodies

Total non-acid glycosphingolipids were isolated from the aortas of more than 80 pigs. The glycolipids were separated by HPLC, analysed by thin- layer chromatography, and tested for reactivity with monoclonal anti- blood group antibodies. The fractions were structurally characterized by NMR spectroscopy and mass spectrometry. Reactivity with both anti- blood group A and H antibodies was seen. The major glycosphingolipid constituents were globotri- and globotetraosylceramides and blood group H pentaglycosylceramides based on type 1 and type 2 core saccharide chains. Globopentaosylceramides, blood group H hexaglycosylceramides based on type 4 chain, and blood group A hexaglycosylceramides based on type 1 core chain were also present. Two structures, that may be important targets for human antibodies initiating hyperacute rejection following pig to human xenotransplantation, were present as minor constituents compared to the blood group components. These were Galalpha1,3neolactotetraosylceramide and a Galalpha1, 3Lexstructure. A Leb/Y hexaglycosylceramide was also present.      

Activation of classical pathway of complement cascade by soluble oligomers of prion

Mice defective for C1q complement factor show enhanced resistance to peripheral prion inoculation, and previous work demonstrated a direct interaction between C1q and conformationally modified PrP. However, the nature and physiological consequences of this interaction remain uncharacterized. PrP amino acids 141-159 has been identified as a potential C1q binding site; we show, by both surface plasmon resonance (SPR) spectroscopy and ELISA, that C1q and its globular region bind to PrP mutagenized in the region of interest with comparable efficiency to that of wild-type protein. To test PrP's ability to activate complement, soluble oligomers of the PrP constructs were made. Only PrP and mutagenized PrP oligomers activate the classical complement cascade while PrP monomer and the C-terminal domain, both in oligomeric and in monomeric form, failed to induce activation. This suggests that a conformational change in PrP, which occurs both when PrP is bound to an SPR sensor chip and when it undergoes oligomerization, is requisite for PrP/C1q interaction and activation of the complement cascade. We propose that C1q may act as a natural sensor for prions, leading to activation of the classical complement cascade, which could result in local inflammation and subsequent recruitment of the immune cells that prions initially infect.     

The molecular evolution of the alcohol dehydrogenase and alcohol dehydrogenase-related genes in the Drosophila melanogaster species subgroup

The DNA sequences of the Adh genes of three members of the Drosophila melanogaster species subgroup have been determined. This completes the Adh sequences of the eight species of this subgroup. Two species, D. yakuba and D. teissieri, possess processed Adh pseudogenes. In all of the species of the subgroup, a gene of unknown function, Adhr, is located about 300 bp 3' to Adh. Although this gene is experiencing a higher rate of synonymous substitution than Adh, it is more constrained at the amino acid level. Phylogenetic relationships between all eight members of the melanogaster subgroup have been analyzed using a variety of methods. All analyses suggested that the D. yakuba and D. teissieri pseudogenes have a single common ancestor, rather than evolving independently in each species, and that D. melanogaster is the sister species to D. simulans, D. sechellia, and D. mauritiana. The evolutionary relationships of the latter three species remain equivocal.