Impact of urban fragmentation on the genetic structure of the eastern red-backed salamander

Urban development is a major cause of habitat loss and fragmentation. Few studies, however, have dealt with fragmentation in an urban landscape. In this paper, we examine the genetic structure of isolated populations of the eastern red-backed salamander (Plethodon cinereus) in a metropolitan area. We sampled four populations located on a mountain in the heart of Montréal (Québec, Canada), which presents a mosaic of forested patches isolated by roads, graveyards and buildings. We assessed the genetic structure of these populations using microsatellite loci and compared it to the genetic structure of four populations located in a continuous habitat in southern Québec. Our results indicate that allelic richness and heterozygosity are lower in the urban populations. Exact differentiation tests and pairwise F _ST also show that the populations found in the fragmented habitat are genetically differentiated, whereas populations located in the continuous habitat are genetically homogeneous. These results raise conservation concerns for these populations as well as for rare or threatened species inhabiting urban landscapes.     

Seleno-independent glutathione peroxidases. More than simple antioxidant scavengers

Glutathione peroxidases (GPXs, EC 1.11.1.9) were first discovered in mammals as key enzymes involved in scavenging of activated oxygen species (AOS). Their efficient antioxidant activity depends on the presence of the rare amino-acid residue selenocysteine (SeCys) at the catalytic site. Nonselenium GPX-like proteins (NS-GPXs) with a Cys residue instead of SeCys have also been found in most organisms. As SeCys is important for GPX activity, the function of the NS-GPX can be questioned. Here, we highlight the evolutionary link between NS-GPX and seleno-GPX, particularly the evolution of the SeCys incorporation system. We then discuss what is known about the enzymatic activity and physiological functions of NS-GPX. Biochemical studies have shown that NS-GPXs are not true GPXs; notably they reduce AOS using reducing substrates other than glutathione, such as thioredoxin. We provide evidence that, in addition to their inefficient scavenging action, NS-GPXs act as AOS sensors in various signal-transduction pathways.     

The 'pair of sugar tongs' site on the non-catalytic domain C of barley alpha-amylase participates in substrate binding and activity

Some starch-degrading enzymes accommodate carbohydrates at sites situated at a certain distance from the active site. In the crystal structure of barley alpha-amylase 1, oligosaccharide is thus bound to the 'sugar tongs' site. This site on the non-catalytic domain C in the C-terminal part of the molecule contains a key residue, Tyr380, which has numerous contacts with the oligosaccharide. The mutant enzymes Y380A and Y380M failed to bind to beta-cyclodextrin-Sepharose, a starch-mimic resin used for alpha-amylase affinity purification. The K(d) for beta-cyclodextrin binding to Y380A and Y380M was 1.4 mm compared to 0.20-0.25 mm for the wild-type, S378P and S378T enzymes. The substitution in the S378P enzyme mimics Pro376 in the barley alpha-amylase 2 isozyme, which in spite of its conserved Tyr378 did not bind oligosaccharide at the 'sugar tongs' in the structure. Crystal structures of both wild-type and S378P enzymes, but not the Y380A enzyme, showed binding of the pseudotetrasaccharide acarbose at the 'sugar tongs' site. The 'sugar tongs' site also contributed importantly to the adsorption to starch granules, as Kd = 0.47 mg.mL(-1) for the wild-type enzyme increased to 5.9 mg.mL(-1) for Y380A, which moreover catalyzed the release of soluble oligosaccharides from starch granules with only 10% of the wild-type activity. beta-cyclodextrin both inhibited binding to and suppressed activity on starch granules for wild-type and S378P enzymes, but did not affect these properties of Y380A, reflecting the functional role of Tyr380. In addition, the Y380A enzyme hydrolyzed amylose with reduced multiple attack, emphasizing that the 'sugar tongs' participates in multivalent binding of polysaccharide substrates.     

Comparing methods for estimating the abundance of Western Capercaillie Tetrao urogallus males in Pyrenean leks: singing counts versus genetic analysis of non-invasive samples

ABSTRACT

Population estimates of male Western Capercaillies Tetrao urogallus were carried out during the mating season using two methods: counts of singing males and non-invasive genetic analysis. Estimates of male numbers were 50% lower using the singing counts compared to the estimates obtained through genetic analysis, and underestimates were greatest when the number of Capercaillies was lowest.     

Phosphorylation of NHERF1 S279 and S301 differentially regulates breast cancer cell phenotype and metastatic organotropism

Metastatic cancer cells are highly plastic for the expression of different tumor phenotype hallmarks and organotropism. This plasticity is highly regulated but the dynamics of the signaling processes orchestrating the shift from one cell phenotype and metastatic organ pattern to another are still largely unknown. The scaffolding protein NHERF1 has been shown to regulate the expression of different neoplastic phenotypes through its PDZ domains, which forms the mechanistic basis for metastatic organotropism. This reprogramming activity was postulated to be dependent on its differential phosphorylation patterns. Here, we show that NHERF1 phosphorylation on S279/S301 dictates several tumor phenotypes such as in vivo invasion, NHE1-mediated matrix digestion, growth and vasculogenic mimicry. Remarkably, injecting mice with cells having differential NHERF1 expression and phosphorylation drove a shift from the predominantly lung colonization (WT NHERF1) to predominately bone colonization (double S279A/S301A mutant), indicating that NHERF1 phosphorylation also acts as a signaling switch in metastatic organotropism.     

Possible complication regarding phosphorus removal with a continuous flow biofilm system: diffusion limitation

Diffusion limitation of phosphate possibly constitutes a serious problem regarding the use of a biofilm reactor for enhanced biological phosphorus removal. A lab-scale reactor for simultaneous removal of phosphorus and nitrate was operated in a continuous alternating mode of operation. For a steady-state operation with excess amounts of carbon source (acetate) during the anaerobic phase, the same amount of phosphate was released during the anaerobic phase as was taken up during the anoxic phase. The measured phosphorus content of the biomass that detached during backwash after an anoxic phase was low, 2.4 +/- 0.4% (equal to 24 +/- 4 mg P/g TS). A simplified computer model indicated the reason to be phosphate diffusion limitation and the model revealed a delicate balance between the obtainable phosphorus contents of the biomass and operating parameters, such as backwash interval, biofilm thickness after backwash, and phase lengths. The aspect of diffusion is considered of crucial importance when evaluating the performance of a biofilter for phosphate removal.     

Src homology 2 domain-containing inositol 5-phosphatase 1 mediates cell cycle arrest by FcgammaRIIB

We previously found that low affinity receptors for the Fc portion of IgG, FcgammaRIIB, which are widely expressed by hematopoietic cells, can negatively regulate receptor tyrosine kinase-dependent cell proliferation. We investigated here the mechanisms of this inhibition. We used as experimental models wild-type mast cells, which constitutively express the stem cell factor receptor Kit and FcgammaRIIB, FcgammaRIIB-deficient mast cells reconstituted with wild-type or mutated FcgammaRIIB, and Src homology 2 domain-containing inositol polyphosphate 5-phosphatase 1 (SHIP1)-deficient mast cells. We found that, upon coaggregation with Kit, FcgammaRIIB are tyrosyl-phosphorylated, recruit SHIP1, but not SHIP2, SH2 domain-containing protein tyrosine phosphatase-1 or -2, abrogate Akt phosphorylation, shorten the duration of the activation of mitogen-activated protein kinases of the Ras and Rac pathways, abrogate cyclin induction, prevent cells from entering the cell cycle, and block thymidine incorporation. FcgammaRIIB-mediated inhibition of Kit-dependent cell proliferation was reduced in SHIP1-deficient mast cells, whereas inhibition of IgE-induced responses was abrogated. Cell proliferation was, however, inhibited by coaggregating Kit with FcgammaRIIB whose intracytoplasmic domain was replaced with the catalytic domain of SHIP1. These results demonstrate that FcgammaRIIB use SHIP1 to inhibit pathways shared by receptor tyrosine kinases and immunoreceptors to trigger cell proliferation and cell activation, respectively, but that, in the absence of SHIP1, FcgammaRIIB can use other effectors that specifically inhibit cell proliferation.     

The effect of passive vertebral rotation on pressure in the nucleus pulposus

To study the immediate effects of axial rotation on the intervertebral disc, six pig cadaver lumbar functional spinal units were exposed to rotations of up to 2 degrees, while disc height and intradiscal pressure were measured. The results showed that rotary movements are capable of causing an immediate increase in disc height and drop in nucleus pressure. However, the long-term effects were opposite in direction.     

Atypical forms of incontinentia pigmenti in male individuals result from mutations of a cytosine tract in exon 10 of NEMO (IKK-gamma)

Familial incontinentia pigmenti (IP [MIM 308310]), or Bloch-Sulzberger syndrome, is an X-linked dominant and male-lethal disorder. We recently demonstrated that mutations in NEMO (IKK-gamma), which encodes a critical component of the NF-kappaB signaling pathway, were responsible for IP. Virtually all mutations eliminate the production of NEMO, causing the typical skewing of X inactivation in female individuals and lethality in male individuals, possibly through enhanced sensitivity to apoptosis. Most mutations also give rise to classic signs of IP, but, in this report, we describe two mutations in families with atypical phenotypes. Remarkably, each family included a male individual with unusual signs, including postnatal survival and either immune dysfunction or hematopoietic disturbance. We found two duplication mutations in these families, at a cytosine tract in exon 10 of NEMO, both of which remove the zinc (Zn) finger at the C-terminus of the protein. Two deletion mutations were also identified in the same tract in additional families. However, only the duplication mutations allowed male individuals to survive, and affected female individuals with duplication mutations demonstrated random or slight skewing of X inactivation. Similarly, NF-kappaB activation was diminished in the presence of duplication mutations and was completely absent in cells with deletion mutations. These results strongly indicate that male individuals can also suffer from IP caused by NEMO mutations, and we therefore urge a reevaluation of the diagnostic criteria.     

MHC class I recognition by NK receptors in the Ly49 family is strongly influenced by the beta 2-microglobulin subunit

NK cell recognition of targets is strongly affected by MHC class I specific receptors. The recently published structure of the inhibitory receptor Ly49A in complex with H-2Dd revealed two distinct sites of interaction in the crystal. One of these involves the alpha1, alpha2, alpha3, and beta2-microglobulin (beta2m) domains of the MHC class I complex. The data from the structure, together with discrepancies in earlier studies using MHC class I tetramers, prompted us to study the role of the beta2m subunit in MHC class I-Ly49 interactions. Here we provide, to our knowledge, the first direct evidence that residues in the beta2m subunit affect binding of MHC class I molecules to Ly49 receptors. A change from murine beta2m to human beta2m in three different MHC class I molecules, H-2Db, H-2Kb, and H-2Dd, resulted in a loss of binding to the receptors Ly49A and Ly49C. Analysis of the amino acids involved in the binding of Ly49A to H-2Dd in the published crystal structure, and differing between the mouse and the human beta2m, suggests the cluster formed by residues Lys3, Thr4, Thr28, and Gln29, as a potentially important domain for the Ly49A-H-2Dd interaction. Another possibility is that the change of beta2m indirectly affects the conformation of distal parts of the MHC class I molecule, including the alpha1 and alpha2 domains of the heavy chain.