The bone and the kidney

Renal tubular diseases may present with osteopenia, osteoporosis or osteomalacia, as a result of significant derangements in body electrolytes. In case of insufficient synthesis of calcitriol, as in renal failure, the more complex picture of renal osteodystrophy may develop. Hypothetically, also disturbed renal production of BMP-7 and Klotho could cause bone disease. However, the acknowledgment that osteocytes are capable of producing FGF23, a phosphaturic hormone at the same time modulating renal synthesis of calcitriol, indicates that it is also bone that can influence renal function. Importantly, a feed-back mechanism exists between FGF23 and calcitriol synthesis, while Klotho, produced by the kidney, determines activity and selectivity of FGF23. Identification of human diseases linked to disturbed production of FGF23 and Klotho underlines the importance of this new bone-kidney axis. Kidney and bone communicate reciprocally to regulate the sophisticated machinery responsible for divalent ions homeostasis and for osseous or extraosseous mineralisation processes.     

Conformational Analysis of a Synthetic Antimicrobial Peptide in Water and Membrane-Mimicking Solvents: A Molecular Dynamics Simulation Study

We have investigated structural and dynamic properties of the synthetic peptide hlF1-11 (GRRRSVQWCA, i.e., the first 11 N-terminal amino acids of the human lactoferrin protein) in water, 250 mM NaCl solution, 50% (V/V) water–trifluoroethanol mixture, and in the membrane mimetic 4:4:1 methanol–chloroform–water mixture. For comparison, we have also performed analogous simulations for the biologically inactive control peptide featuring Ala substitutions in the 2, 3, 6 and 9 positions of the hlF1-11 sequence. Statistical analyses of the trajectories indicate that only in the membrane-mimicking medium hlF1-11 adopts preferentially a conformation suitable to interact effectively with the membrane. In this conformation the peptide cationic region is rather flexible and elongated, while the C-terminal hydrophobic moiety appears as a more rigid hairpin-shaped loop approximately perpendicular to the cationic region. No such conformation is statistically relevant for the control peptide.     

Molecular phylogeny of the New World Dipsadidae (Serpentes: Colubroidea): a reappraisal

We present a phylogenetic analysis of the New World dipsadids based on an expanded data matrix that includes 246 terminal taxa including 196 dipsadids. The species are sampled for eight genes (12S, 16S, cytb, nd2, nd4, bdnf, c‐mos, rag2). The data are explored using two distinct optimality procedures—maximum parsimony and maximum likelihood—and two alignment strategies—dynamic homology and static homology. Two previously unsampled dipsadid genera, Sordellina and Rhachidelus, are now included in the analysis. The definitions of the genera, Erythrolamprus, Clelia, Hypsirhynchus, Philodryas and Phimophis, and the tribes Alsophiini, Echinantherini and Conophiini, are revised. In order to maintain monophyly, the genus Umbrivaga is synonymized with Erythrolamprus, and two new genera are erected to accommodate Phimophis iglesiasi and Clelia rustica, as well as their closely related species. The West Indian genera Schwartzophis, Darlingtonia, Antillophis and Ocyophis are resurrected. © The Willi Hennig Society 2012.     

Harder,better, faster,stronger: Weapon size is more sexually dimorphic than weapon biomechanical components in two freshwater anomuran species

Sexual selection influences the evolution of morphological traits that increase the likelihood of monopolizing scarce resources. When such traits are used during contests, they are termed weapons. Given that resources are typically linked to monopolizing mating partners, theory expects only males to bear weapons. In some species, however, females also bear weapons, although typically smaller than male weapons. Understanding why females bear smaller weapons can thus help us understand the selective pressures behind weapon evolution. However, most of our knowledge comes from studies on weapon size, while the biomechanics of weapons, such as the size of the muscles, efficiency, and shape are seldom studied. Our goal was to test if the theoretical expectations for weapon size sexual dimorphism also occur for weapon biomechanics using two aeglid crab species. Males of both species had larger claws which were also stronger than female claws. Male claws were also more efficient than females' claws (although we used only one species in this analysis). For weapon shape, though, only one species differed in the mean claw shape. Regarding scaling differences, in both species, male claws had higher size scaling than females, while only one species had a higher shape scaling. However, male weapons did not have higher scaling regarding strength and efficiency than females. Thus, males apparently allocate more resources in weapons than females, but once allocated, muscle and efficiency follow a similar developmental pathway in both sexes. Taken together, our results show that sexual dimorphism in weapons involves more than differences in size. Shape differences are especially intriguing because we cannot fully understand its causes. Yet, we highlight that such subtle differences can only be detected by measuring and analysing weapon shape and biomechanical components. Only then we might better understand how weapons are forged.     

4-Thioflavins as active site probes of flavoproteins. Reactions with sulfite

4-Thioflavins react with sulfite under aerobic conditions to yield highly fluorescent products with absorption maxima around 410 nm. These products have been identified as 4-hydroxy-4-sulfonylflavins, and have been shown to arise from a series of reactions following the O2-dependent reoxidation of an intermediate with absorption maxima at 363 and 465 nm. Under anaerobic conditions, the same intermediate is formed, but decays to a 350 nm absorbing species, which is probably the N(5)-sulfite adduct of 4-thioflavin. A plausible mechanism is described for the formation of the derivatives, and several of their chemical and physical properties are described. Distinctly different results between different proteins are obtained when sulfite reacts with enzyme-bound 4-thioflavins. 4-Thio-FAD-D-amino acid oxidase and 4-thio-FMN-lactate oxidase react rapidly to yield the N(5)-sulfite adducts, as occurs with the native enzymes. 4-Thio-FAD-p-hydroxybenzoate hydroxylase reacts slowly in a manner paralleling the reaction with the free 4-thioflavins.     

Purification of the yellow fluorescent protein from Vibrio fischeri and identity of the flavin chromophore

A low molecular weight protein (approximately 25,000 D) exhibiting a yellow fluorescence emission peaking at approximately 540 nm was isolated from Vibrio fischeri (strain Y-1) and purified to apparent homogeneity. FMN is the chromophore, but it exhibits marked red shifts in both the absorption (lambda max = 380, 460 nm) and the fluorescence emission. When added to purified luciferase from the same strain, which itself catalyzes an emission of blue-green light (lambda max approximately 495 nm), this protein induces a bright yellow luminescence (lambda max approximately 540 nm); this corresponds to the emission of the Y-1 strain in vivo. This yellow bioluminescence emission is thus ascribed to the interaction of these two proteins, and to the excitation of the singlet FMN bound to this fluorescent protein.