A whole-cell and single-channel study of the voltage-dependent outward potassium current in avian hepatocytes.

Voltage-dependent membrane currents were studied in dissociated hepatocytes from chick, using the patch-clamp technique. All cells had voltage-dependent outward K+ currents; in 10% of the cells, a fast, transient, tetrodotoxin-sensitive Na+ current was identified. None of the cells had voltage-dependent inward Ca2+ currents. The K+ current activated at a membrane potential of about -10 mV, had a sigmoidal time course, and did not inactivate in 500 ms. The maximum outward conductance was 6.6 +/- 2.4 nS in 18 cells. The reversal potential, estimated from tail current measurements, shifted by 50 mV per 10-fold increase in the external K+ concentration. The current traces were fitted by n2 kinetics with voltage-dependent time constants. Omitting Ca2+ from the external bath or buffering the internal Ca2+ with EGTA did not alter the outward current, which shows that Ca2+-activated K+ currents were not present. 1-5 mM 4-aminopyridine, 0.5-2 mM BaCl2, and 0.1-1 mM CdCl2 reversibly inhibited the current. The block caused by Ba was voltage dependent. Single-channel currents were recorded in cell-attached and outside-out patches. The mean unitary conductance was 7 pS, and the channels displayed bursting kinetics. Thus, avian hepatocytes have a single type of K+ channel belonging to the delayed rectifier class of K+ channels.

Identification of dopamine receptors across the extant avian family tree and analysis with other clades uncovers a polyploid expansion among vertebrates.

Dopamine is an important central nervous system transmitter that functions through two classes of receptors (D1 and D2) to influence a diverse range of biological processes in vertebrates. With roles in regulating neural activity, behavior, and gene expression, there has been great interest in understanding the function and evolution dopamine and its receptors. In this study, we use a combination of sequence analyses, microsynteny analyses, and phylogenetic relationships to identify and characterize both the D1 (DRD1A, DRD1B, DRD1C, and DRD1E) and D2 (DRD2, DRD3, and DRD4) dopamine receptor gene families in 43 recently sequenced bird genomes representing the major ordinal lineages across the avian family tree. We show that the common ancestor of all birds possessed at least seven D1 and D2 receptors, followed by subsequent independent losses in some lineages of modern birds. Through comparisons with other vertebrate and invertebrate species we show that two of the D1 receptors, DRD1A and DRD1B, and two of the D2 receptors, DRD2 and DRD3, originated from a whole genome duplication event early in the vertebrate lineage, providing the first conclusive evidence of the origin of these highly conserved receptors. Our findings provide insight into the evolutionary development of an important modulatory component of the central nervous system in vertebrates, and will help further unravel the complex evolutionary and functional relationships among dopamine receptors.

Phylogenomic analyses data of the avian phylogenomics project.

BACKGROUND: Determining the evolutionary relationships among the major lineages of extant birds has been one of the biggest challenges in systematic biology. To address this challenge, we assembled or collected the genomes of 48 avian species spanning most orders of birds, including all Neognathae and two of the five Palaeognathae orders. We used these genomes to construct a genome-scale avian phylogenetic tree and perform comparative genomic analyses. FINDINGS: Here we present the datasets associated with the phylogenomic analyses, which include sequence alignment files consisting of nucleotides, amino acids, indels, and transposable elements, as well as tree files containing gene trees and species trees. Inferring an accurate phylogeny required generating: 1) A well annotated data set across species based on genome synteny; 2) Alignments with unaligned or incorrectly overaligned sequences filtered out; and 3) Diverse data sets, including genes and their inferred trees, indels, and transposable elements. Our total evidence nucleotide tree (TENT) data set (consisting of exons, introns, and UCEs) gave what we consider our most reliable species tree when using the concatenation-based ExaML algorithm or when using statistical binning with the coalescence-based MP-EST algorithm (which we refer to as MP-EST*). Other data sets, such as the coding sequence of some exons, revealed other properties of genome evolution, namely convergence. CONCLUSIONS: The Avian Phylogenomics Project is the largest vertebrate phylogenomics project to date that we are aware of. The sequence, alignment, and tree data are expected to accelerate analyses in phylogenomics and other related areas.

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.

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.

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.