The Secret Life of Oilbirds: New Insights into the Movement Ecology of a Unique Avian Frugivore

Background: Steatornis caripensis (the oilbird) is a very unusual bird. It supposedly never sees daylight, roosting in huge aggregations in caves during the day and bringing back fruit to the cave at night. As a consequence a large number of the seeds from the fruit they feed upon germinate in the cave and spoil.

The role of visual landmarks in the avian familiar area map - Commentary

The question of whether homing pigeons use visual landmarks for orientation from distant, familiar sites is an unresolved issue in the field of avian navigation. Where evidence has been found, the question still remains as to whether the landmarks are used independent of the map and compass mechanism for orientation that is so important to birds. Recent research has challenged the extent to which experiments that do not directly manipulate the visual sense can be used as evidence for compass-independent orientation. However, it is proposed that extending a new technique for research on vision in homing to include manipulation of the compasses used by birds might be able to resolve this issue. The effect of the structure of the visual sense of the homing pigeon on its use of visual landmarks is also considered.

The Plasmodium falciparum Malaria M1 Alanyl Aminopeptidase (PfA-M1): Insights of Catalytic Mechanism and Function from MD Simulations

Malaria caused by several species of Plasmodium is major parasitic disease of humans, causing 1-3 million deaths worldwide annually. The widespread resistance of the human parasite to current drug therapies is of major concern making the identification of new drug targets urgent. While the parasite grows and multiplies inside the host erythrocyte it degrades the host cell hemoglobin and utilizes the released amino acids to synthesize its own proteins. The P. falciparum malarial M1 alanyl-aminopeptidase (PfA-M1) is an enzyme involved in the terminal stages of hemoglobin digestion and the generation of an amino acid pool within the parasite. The enzyme has been validated as a potential drug target since inhibitors of the enzyme block parasite growth in vitro and in vivo. In order to gain further understanding of this enzyme, molecular dynamics simulations using data from a recent crystal structure of PfA-M1 were performed. The results elucidate the pentahedral coordination of the catalytic Zn in these metallo-proteases and provide new insights into the roles of this cation and important active site residues in ligand binding and in the hydrolysis of the peptide bond. Based on the data, we propose a two-step catalytic mechanism, in which the conformation of the active site is altered between the Michaelis complex and the transition state. In addition, the simulations identify global changes in the protein in which conformational transitions in the catalytic domain are transmitted at the opening of the N-terminal 8 angstrom-long channel and at the opening of the 30 angstrom-long C-terminal internal chamber that facilitates entry of peptides to the active site and exit of released amino acids. The possible implications of these global changes with regard to enzyme function are discussed.

ISOLATION AND PRIMARY STRUCTURE OF A NOVEL AVIAN PANCREATIC-POLYPEPTIDE FROM 5 SPECIES OF EURASIAN CROW

Chicken pancreatic polypeptide is the prototype of the neuropeptide Y (NPY)/PP superfamily of regulatory peptides. This polypeptide was appended the descriptive term avian, despite the presence of some 8600 extant species of bird. Additional primary structures from other avian species, including turkey, goose and ostrich, would suggest that the primary structure of this polypeptide has been highly-conserved during avian evolution. Avian pancreatic polypeptides structurally-characterised to date have distinctive primary structural features unique to this vertebrate group including an N-terminal glycyl residue and a histidyl residue at position 34. The crow family, Corvidae, is representative of the order Passeriformes, generally regarded as the most evolutionarily recent and diverse avian taxon. Pancreatic polypeptide has been isolated from pancreatic tissues from five representative Eurasian species (the magpie, Pica pica; the jay, Garrulus glandarius; the hooded crow, Corvus corone; the rook, Corvus frugilegus; the jackdaw, Corvus monedula) and subjected to structural analyses. Mass spectroscopy estimated the molecular mass of each peptide as 4166 +/- 2 Da. The entire primary structures of 36 amino acid residue peptides were established in single gas-phase sequencing runs. The primary structures of pancreatic polypeptides from all species investigated were identical: APAQPAYPGDDAPVEDLLR-FYNDLQQYLNVVTRPRY. The peptides were deemed to be amidated due to their full molar cross-reactivity with the amide-requiring PP antiserum employed. The molecular mass (4165.6 Da), calculated from the sequences, was in close agreement with mass spectroscopy estimates. The presence of an N-terminal alanyl residue and a prolyl residue at position 34 differentiates crow PP from counterparts in other avian species. These residues are analogous to those found in most mammalian analogues. These data suggest that the term avian, appended to the chicken peptide, is no longer tenable due to the presence of an Ala1, Pro34 peptide in five species from the largest avian order. These data might also suggest that, in keeping with the known structure/activity requirements of this peptide family, crow PP should interact identically to mammalian analogues on mammalian receptors.

THE CORRECTED PRIMARY STRUCTURE OF CHICKEN (AVIAN) PANCREATIC-POLYPEPTIDE

Chicken (avian) pancreatic polypeptide was the first member of the pancreatic polypeptide (PP)/neuropeptide Y (NPY) superfamily to be discovered and structurally-characterised. In this 36 amino acid residue, C-terminally amidated peptide, residues 22 and 23 were identified as Asp and Asn, respectively. However, sequencing of chicken PP using modem automated gas-phase sequencing technology has revealed that the original primary structure is incorrect in that residue 22 is Asn and that residue 23 is Asp. After digestion of chicken PP with endoproteinase Asp-N, fragments of chicken PP corresponding in molecular mass to residues 16-22 and 23-36, were unequivocally identified. The corrected primary structure of chicken PP is therefore: Gly-Pro-Ser-Gln-Pro-Thr-Tyr-Pro-Gly-Asp-Asp-Ala-Pro-Val-Glu-Asp-Leu-Ile-Arg-Phe-Tyr-Asn-Asp-Leu-Gln-Gln-Tyr-Leu-Asn-Val-Val-Thr-Arg-His-Arg-Tyr-NH2.

Diphenylamine increases cloacin DF13 sensitivity in avian septicemic strains of Escherichia coli

Thirteen avian septicemic isolates of Escherichia coli were examined for the presence of the aerobactin iron transport system. All of the strains possessed a functional aerobactin system and hybridization experiments showed that the aerobactin genes were located on ColV-type plasmids in all cases. The expression of the aerobactin receptor IutA was also studied by determining the bacterial susceptibility to the bacteriocin cloacin DF13. Twelve of the 13 isolates were cloacin-resistant but became sensitive to this bacteriocin upon treatment with diphenylamine which caused a reduction in the amount of O-side chain lipopolysaccharide.

Nitrofurazone accumulates in avian eyes - a replacement for semicarbazide as a marker of abuse

Intact nitrofurazone is present in whole eyes of chickens fed varying levels of this banned antibiotic and may therefore be used as an alternative to the controversial marker residue, semicarbazide, to monitor for abuse of this drug in primary production.

Aminopeptidases of malaria parasites:new targets for chemotherapy

Novel targets for new drug development are urgently required to combat malaria, a disease that puts half of the world's population at risk. One group of enzymes identified within the genome of the most lethal of the causative agents of malaria, Plasmodium falciparum, that may have the potential to become new targets for antimalarial drug development are the aminopeptidases. These enzymes catalyse the cleavage of the N-terminal amino acids from proteins and peptides. P. falciparum appears to encode for at least nine aminopeptidases, two neutral aminopeptidases, one aspartyl aminopeptidase, one aminopeptidase P, one prolyl aminopeptidase and four methionine aminopeptidases. Recent advances in our understanding of these genes and their protein products are outlined in this review, including their potential for antimalarial drug development.

The M17 leucine aminopeptidase of the malaria parasite Plasmodium falciparum:importance of active site metal ions in the binding of substrates and inhibitors

The M17 leucine aminopeptidase of the intraerythrocytic stages of the malaria parasite Plasmodium falciparum (PfLAP) plays a role in releasing amino acids from host hemoglobin that are used for parasite protein synthesis, growth, and development. This enzyme represents a target at which new antimalarials could be designed since metalloaminopeptidase inhibitors prevent the growth of the parasites in vitro and in vivo. A study on the metal ion binding characteristics of recombinant P. falciparum M17 leucine aminopeptidase (rPfLAP) shows that the active site of this exopeptidase contains two metal-binding sites, a readily exchangeable site (site 1) and a tight binding site (site 2). The enzyme retains activity when the metal ion is removed from site 1, while removal of metal ions from both sites results in an inactive apoenzyme that cannot be reactivated by the addition of divalent metal cations. The metal ion at site 1 is readily exchangeable with several divalent metal ions and displays a preference in the order of preference Zn(2+) > Mn(2+) > Co(2+) > Mg(2+). While it is likely that native PfLAP contains a Zn(2+) in site 2, the metal ion located in site 1 may be dependent on the type and concentration of metal ions in the cytosolic compartment of the parasite. Importantly, the type of metal ion present at site 1 influences not only the catalytic efficiency of the enzyme for peptide substrates but also the mode of binding by bestatin, a metal-chelating inhibitor of M17 aminopeptidases with antimalarial activity.

Detection of avian influenza virus by fluorescent DNA barcode-based immunoassay with sensitivity comparable to PCR

In this paper, a coupling of fluorophore-DNA barcode and bead-based immunoassay for detecting avian influenza virus (AIV) with PCR-like sensitivity is reported. The assay is based on the use of sandwich immunoassay and fluorophore-tagged oligonucleotides as representative barcodes. The detection involves the sandwiching of the target AIV between magnetic immunoprobes and barcode-carrying immunoprobes. Because each barcode-carrying immunoprobe is functionalized with a multitude of fluorophore-DNA barcode strands, many DNA barcodes are released for each positive binding event resulting in amplification of the signal. Using an inactivated H16N3 AIV as a model, a linear response over five orders of magnitude was obtained, and the sensitivity of the detection was comparable to conventional RT-PCR. Moreover, the entire detection required less than 2 hr. The results indicate that the method has great potential as an alternative for surveillance of epidemic outbreaks caused by AIV, other viruses and microorganisms.

Detection of Avian Influenza Virus with PCR-Like Sensitivity by Fluorescent DNA Barcode-Based Immunoassay

In this paper, we report a coupling of fluorophore-DNA barcode and bead-based
immunoassay for the detection of Avian Influenza Virus (AIV), a potential pandemic threat for human health and enormous economic losses. The detection strategy is based on the use of sandwich immunoassay and fluorophore-tagged oligonucleotides as representatively fluorescent barcodes. Despite its simplicity the assay has sensitivity comparable to RT-PCR amplification, and possesses a great potential as a rapid and sensitive on-chip detection format.

Ornithokinin (avian bradykinin) from the skin of the Chinese bamboo odorous frog, Odorrana versabilis

One of the most widespread and abundant families of pharmacologically active peptides in amphibian defensive skin secretions is the bradykinins and related peptides. Despite retaining certain primary structural attributes that assign them to this peptide family, bradykinins and related peptides are unique among amphibian skin peptides in that they exhibit a wide range of primary structural variations, post-translational modifications and/or N-terminal or C-terminal extensions. Initially it was believed that their high degree of primary structural heterogeneity was reflective of random gene mutations within species, but latterly, there is an increasing body of evidence that the spectrum of structural modifications found within this peptide family is reflective of the vertebrate predator spectrum of individual species. Here we report the discovery of ornithokinin (avian bradykinin – Thr6, Leu8-bradykinin) in the skin secretion of the Chinese bamboo odorous frog, Odorrana versabilis. Molecular cloning of its biosynthetic precursor-encoding cDNA from a skin secretion-derived cDNA library revealed a deduced open-reading frame of 86 amino acid residues, encoding a single copy of ornithokinin towards its C-terminus. The domain architecture of this ornithokinin precursor protein was consistent with that of a typical amphibian skin peptide and quite different to that of the ornithokininogen from chicken plasma. Ornithokinin was reported to induce hypotension in the chicken and to contract the chicken oviduct but to have no obvious effect on the rat uterus. However, in this study, synthetic ornithokinin was found to contract the rat ileum (EC50 = 539 nM) and to increase contraction frequency in the rat uterus (EC50 = 1.87 μM).