Water as an Essential Resource: Orb Web Spiders Cannot Balance Their Water Budget by Prey Alone

Water is essential for all living organisms because it acts as a major solvent and reaction medium. Terrestrial animals may lose water through evaporation and excretion and consequently have evolved strategies to balance their water budget by either minimising losses or by gaining water. The major pathway to gain water is via food intake, although many animals additionally drink free water. Spiders acquire substantial amounts of water by ingesting enzymatically liquefied prey. However, this may not account for the water needs of some species. We tested whether drinking is essential for orb web spiders of the genus Argiope by experimentally manipulating the diet (flies or crickets) and water supply (no water or a daily shower) to females and then measuring their subsequent drinking behaviour. Individuals of Argiope trifasciata, which are typically found in dry habitats, increased their body mass when fed crickets but not when fed flies. However, spiders deprived of water subsequently ingested significantly more water than spiders that received water every day, regardless of their feeding regime. This pattern was replicated in Argiope aetherea, which is found in the tropics and perhaps less likely to be water deprived in natural populations. Our results reveal that drinking allows these spiders to realise their water balance independent from the nutritional status. We suggest that the spiders may need to drink fresh water to process ingested nutrients.     

NAD kinase regulates the size of the NADPH pool and insulin secretion in pancreatic β-cells

NADPH is an important component of the antioxidant defense system and a proposed mediator in glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells. An increase in the NADPH/NADP(+) ratio has been reported to occur within minutes following the rise in glucose concentration in β-cells. However, 30 min following the increase in glucose, the total NADPH pool also increases through a mechanism not yet characterized. NAD kinase (NADK) catalyzes the de novo formation of NADP(+) by phosphorylation of NAD(+). NAD kinases have been shown to be essential for redox regulation, oxidative stress defense, and survival in bacteria and yeast. However, studies on NADK in eukaryotic cells are scarce, and the function of this enzyme has not been described in β-cells. We employed INS-1 832/13 cells, an insulin-secreting rat β-cell line, and isolated rodent islets to investigate the role of NADK in β-cell metabolic pathways. Adenoviral-mediated overexpression of NADK resulted in a two- to threefold increase in the total NADPH pool and NADPH/NADP(+) ratio, suggesting that NADP(+) formed by the NADK-catalyzed reaction is rapidly reduced to NADPH via cytosolic reductases. This increase in the NADPH pool was accompanied by an increase in GSIS in NADK-overexpressing cells. Furthermore, NADK overexpression protected β-cells against oxidative damage by the redox cycling agent menadione and reversed menadione-mediated inhibition of GSIS. Knockdown of NADK via shRNA exerted the opposite effect on all these parameters. These data suggest that NADK kinase regulates intracellular redox and affects insulin secretion and oxidative defense in the β-cell.     

The mitochondria-targeted antioxidant MitoQ decreases features of the metabolic syndrome in ATM+/-/ApoE-/- mice

A number of recent studies suggest that mitochondrial oxidative damage may be associated with atherosclerosis and the metabolic syndrome. However, much of the evidence linking mitochondrial oxidative damage and excess reactive oxygen species (ROS) with these pathologies is circumstantial. Consequently the importance of mitochondrial ROS in the etiology of these disorders is unclear. Furthermore, the potential of decreasing mitochondrial ROS as a therapy for these indications is not known. We assessed the impact of decreasing mitochondrial oxidative damage and ROS with the mitochondria-targeted antioxidant MitoQ in models of atherosclerosis and the metabolic syndrome (fat-fed ApoE(-/-) mice and ATM(+/-)/ApoE(-/-) mice, which are also haploinsufficient for the protein kinase, ataxia telangiectasia mutated (ATM). MitoQ administered orally for 14weeks prevented the increased adiposity, hypercholesterolemia, and hypertriglyceridemia associated with the metabolic syndrome. MitoQ also corrected hyperglycemia and hepatic steatosis, induced changes in multiple metabolically relevant lipid species, and decreased DNA oxidative damage (8-oxo-G) in multiple organs. Although MitoQ did not affect overall atherosclerotic plaque area in fat-fed ATM(+/+)/ApoE(-/-) and ATM(+/-)/ApoE(-/-) mice, MitoQ reduced the macrophage content and cell proliferation within plaques and 8-oxo-G. MitoQ also significantly reduced mtDNA oxidative damage in the liver. Our data suggest that MitoQ inhibits the development of multiple features of the metabolic syndrome in these mice by affecting redox signaling pathways that depend on mitochondrial ROS such as hydrogen peroxide. These findings strengthen the growing view that elevated mitochondrial ROS contributes to the etiology of the metabolic syndrome and suggest a potential therapeutic role for mitochondria-targeted antioxidants.     

Paternity assignment and demographic closure in the New Zealand southern right whale

The identification and characterization of reproductively isolated subpopulations or 'stocks' are essential for effective conservation and management decisions. This can be difficult in vagile marine species like marine mammals. We used paternity assignment and 'gametic recapture' to examine the reproductive autonomy of southern right whales (Eubalaena australis) on their New Zealand (NZ) calving grounds. We derived DNA profiles for 34 mother-calf pairs from skin biopsy samples, using sex-specific markers, 13 microsatellite loci and mtDNA haplotypes. We constructed DNA profiles for 314 adult males, representing 30% of the census male abundance of the NZ stock, previously estimated from genotypic mark-recapture modelling to be 1085 (95% CL 855, 1416). Under the hypothesis of demographic closure and the assumption of equal reproductive success among males, we predict: (i) the proportion of paternities assigned will reflect the proportion of the male population sampled and (ii) the gametic mark-recapture (GMR) estimate of male abundance will be equivalent to the census male estimate for the NZ stock. Consistent with these predictions, we found that the proportion of assigned paternities equalled the proportion of the census male population size sampled. Using the sample of males as the initial capture, and paternity assignment as the recapture, the GMR estimate of male abundance was 1001 (95% CL 542, 1469), similar to the male census estimate. These findings suggest that right whales returning to the NZ calving ground are reproductively autonomous on a generational timescale, as well as isolated by maternal fidelity on an evolutionary timescale, from others in the Indo-Pacific region.     

Discovery of a new family of amphibians from northeast India with ancient links to Africa

The limbless, primarily soil-dwelling and tropical caecilian amphibians (Gymnophiona) comprise the least known order of tetrapods. On the basis of unprecedented extensive fieldwork, we report the discovery of a previously overlooked, ancient lineage and radiation of caecilians from threatened habitats in the underexplored states of northeast India. Molecular phylogenetic analyses of mitogenomic and nuclear DNA sequences, and comparative cranial anatomy indicate an unexpected sister-group relationship with the exclusively African family Herpelidae. Relaxed molecular clock analyses indicate that these lineages diverged in the Early Cretaceous, about 140 Ma. The discovery adds a major branch to the amphibian tree of life and sheds light on both the evolution and biogeography of caecilians and the biotic history of northeast India-an area generally interpreted as a gateway between biodiversity hotspots rather than a distinct biogeographic unit with its own ancient endemics. Because of its distinctive morphology, inferred age and phylogenetic relationships, we recognize the newly discovered caecilian radiation as a new family of modern amphibians.     

The Ph1 locus suppresses Cdk2-type activity during premeiosis and meiosis in wheat

Despite possessing multiple sets of related (homoeologous) chromosomes, hexaploid wheat (Triticum aestivum) restricts pairing to just true homologs at meiosis. Deletion of a single major locus, Pairing homoeologous1 (Ph1), allows pairing of homoeologs. How can the same chromosomes be processed as homologs instead of being treated as nonhomologs? Ph1 was recently defined to a cluster of defective cyclin-dependent kinase (Cdk)-like genes showing some similarity to mammalian Cdk2. We reasoned that the cluster might suppress Cdk2-type activity and therefore affect replication and histone H1 phosphorylation. Our study does indeed reveal such effects, suggesting that Cdk2-type phosphorylation has a major role in determining chromosome specificity during meiosis.     

Identification of the fibroblast growth factor (FGF)-interacting domain in a secreted FGF-binding protein by phage display

Fibroblast growth factor-binding proteins (FGF-BP) are secreted carrier proteins that release fibroblast growth factors (FGFs) from the extracellular matrix storage and thus enhance FGF activity. Here we have mapped the interaction domain between human FGF-BP1 and FGF-2. For this, we generated T7 phage display libraries of N-terminally and C-terminally truncated FGF-BP1 fragments that were then panned against immobilized FGF-2. From this panning, a C-terminal fragment of FGF-BP1 (amino acids 193-234) was identified as the minimum binding domain for FGF. As a recombinant protein, this C-terminal fragment binds to FGF-2 and enhances FGF-2-induced signaling in NIH-3T3 fibroblasts and GM7373 endothelial cells, as well as mitogenesis and chemotaxis of NIH-3T3 cells. The FGF interaction domain in FGF-BP1 is distinct from the heparin-binding domain (amino acids 110-143), and homology modeling supports the notion of a distinct domain in the C terminus that is conserved across different species. This domain also contains conserved positioning of cysteine residues with the Cys-214/Cys-222 positions in the human protein predicted to participate in disulfide bridge formation. Phage display of a C214A mutation of FGF-BP1 reduced binding to FGF-2, indicating the functional significance of this disulfide bond. We concluded that the FGF interaction domain is contained in the C terminus of FGF-BP1.     

Crystallohydrodynamics of protein assemblies: Combining sedimentation, viscometry, and x-ray scattering

Crystallohydrodynamics describes the domain orientation in solution of antibodies and other multidomain protein assemblies where the crystal structures may be known for the domains but not the intact structure. The approach removes the necessity for an ad hoc assumed value for protein hydration. Previous studies have involved only the sedimentation coefficient leading to considerable degeneracy or multiplicity of possible models for the conformation of a given protein assembly, all agreeing with the experimental data. This degeneracy can be considerably reduced by using additional solution parameters. Conformation charts are generated for the three universal (i.e., size-independent) shape parameters P (obtained from the sedimentation coefficient or translational diffusion coefficient), nu (from the intrinsic viscosity), and G (from the radius of gyration), and calculated for a wide range of plausible orientations of the domains (represented as bead-shell ellipsoidal models derived from their crystal structures) and after allowance for any linker or hinge regions. Matches are then sought with the set of functions P, nu, and G calculated from experimental data (allowing for experimental error). The number of solutions can be further reduced by the employment of the D max parameter (maximum particle dimension) from x-ray scattering data. Using this approach we are able to reduce the degeneracy of possible solution models for IgG3 to a possible representative structure in which the Fab domains are directed away from the plane of the Fc domain, a structure in accord with the recognition that IgG3 is the most efficient complement activator among human IgG subclasses.     

Moderate overexpression of AIB1 triggers pre-neoplastic changes in mammary epithelium

Here we report a new model of pre-clinical breast cancer which has been generated by overexpressing the steroid receptor coactivator AIB1 at moderate levels in breast epithelium. Transgenic female mice display mammary hyperplasia at the onset of puberty, consistent with enhanced proliferation of primary mammary epithelial cultures and augmented levels of cyclin D1 and E-cadherin. Studies of BrdU incorporation revealed that AIB1 localizes to the nucleus during or after S phase, implicating a new role for AIB1 in cell-cycle progression subsequent to G1. Our findings suggest that moderate overexpression of AIB1 may represent one of the pre-neoplastic changes in breast tissue.