Prosthetic avian vocal organ controlled by a freely behaving bird based on a low dimensional model of the biomechanical periphery

Because of the parallels found with human language production and acquisition, birdsong is an ideal animal model to study general mechanisms underlying complex, learned motor behavior. The rich and diverse vocalizations of songbirds emerge as a result of the interaction between a pattern generator in the brain and a highly nontrivial nonlinear periphery. Much of the complexity of this vocal behavior has been understood by studying the physics of the avian vocal organ, particularly the syrinx. A mathematical model describing the complex periphery as a nonlinear dynamical system leads to the conclusion that nontrivial behavior emerges even when the organ is commanded by simple motor instructions: smooth paths in a low dimensional parameter space. An analysis of the model provides insight into which parameters are responsible for generating a rich variety of diverse vocalizations, and what the physiological meaning of these parameters is. By recording the physiological motor instructions elicited by a spontaneously singing muted bird and computing the model on a Digital Signal Processor in real-time, we produce realistic synthetic vocalizations that replace the bird's own auditory feedback. In this way, we build a bio-prosthetic avian vocal organ driven by a freely behaving bird via its physiologically coded motor commands. Since it is based on a low-dimensional nonlinear mathematical model of the peripheral effector, the emulation of the motor behavior requires light computation, in such a way that our bio-prosthetic device can be implemented on a portable platform.     

The crystal structure of <Emphasis Type="Italic">Escherichia coli</Emphasis> TdcF,a member of the highly conserved YjgF/YER057c/UK114 family

Background  

The YjgF/YER057c/UK114 family of proteins is widespread in nature, but has as yet no clearly defined biological role. Members of the family exist as homotrimers and are characterised by intersubunit clefts that are delineated by well-conserved residues; these sites are likely to be of functional significance, yet catalytic activity has never been detected for any member of this family. The gene encoding the TdcF protein of E. coli, a YjgF/YER057c/UK114 family member, resides in an operon that strongly suggests a role in the metabolism of 2-ketobutyrate for this protein.     

PKA and Epac cooperate to augment bradykinin-induced interleukin-8 release from human airway smooth muscle cells

Background

Platelet-derived growth factor A (PDGF-A) signals solely through PDGF-Rα, and is required for fibroblast proliferation and transdifferentiation (fibroblast to myofibroblast conversion) during alveolar development, because pdgfa-null mice lack both myofibroblasts and alveoli. However, these PDGF-A-mediated mechanisms remain incompletely defined. At postnatal days 4 and 12 (P4 and P12), using mouse lung fibroblasts, we examined (a) how PDGF-Rα correlates with ki67 (proliferation marker) or alpha-smooth muscle actin (αSMA, myofibroblast marker) expression, and (b) whether PDGF-A directly affects αSMA or modifies stimulation by transforming growth factor beta (TGFβ).

Methods

Using flow cytometry we examined PDGF-Rα, αSMA and Ki67 in mice which express green fluorescent protein (GFP) as a marker for PDGF-Rα expression. Using real-time RT-PCR we quantified αSMA mRNA in cultured Mlg neonatal mouse lung fibroblasts after treatment with PDGF-A, and/or TGFβ.

Results

The intensity of GFP-fluorescence enabled us to distinguish three groups of fibroblasts which exhibited absent, lower, or higher levels of PDGF-Rα. At P4, more of the higher than lower PDGF-Rα + fibroblasts contained Ki67 (Ki67+), and Ki67+ fibroblasts predominated in the αSMA + but not the αSMA- population. By P12, Ki67+ fibroblasts comprised a minority in both the PDGF-Rα + and αSMA+ populations. At P4, most Ki67+ fibroblasts were PDGF-Rα + and αSMA- whereas at P12, most Ki67+ fibroblasts were PDGF-Rα- and αSMA-. More of the PDGF-Rα + than - fibroblasts contained αSMA at both P4 and P12. In the lung, proximate αSMA was more abundant around nuclei in cells expressing high than low levels of PDGF-Rα at both P4 and P12. Nuclear SMAD 2/3 declined from P4 to P12 in PDGF-Rα-, but not in PDGF-Rα + cells. In Mlg fibroblasts, αSMA mRNA increased after exposure to TGFβ, but declined after treatment with PDGF-A.

Conclusion

During both septal eruption (P4) and elongation (P12), alveolar PDGF-Rα may enhance the propensity of fibroblasts to transdifferentiate rather than directly stimulate αSMA, which preferentially localizes to non-proliferating fibroblasts. In accordance, PDGF-Rα more dominantly influences fibroblast proliferation at P4 than at P12. In the lung, TGFβ may overshadow the antagonistic effects of PDGF-A/PDGF-Rα signaling, enhancing αSMA-abundance in PDGF-Rα-expressing fibroblasts.     

Effect of abrupt weaning at housing on leukocyte distribution,functional activity of neutrophils,and acute phase protein response of beef calves

Background  

Sixteen, spring-born, single suckled, castrated male calves of Limousin × Holstein-Friesian and Simmental × Holstein-Friesian dams respectively, were used to investigate the effect of weaning on total leukocyte and differential counts, neutrophil functional activity, lymphocyte immunophenotypes, and acute phase protein response. Calves grazed with their dams until the end of the grazing season when they were housed in a slatted floor shed. On the day of housing, calves were assigned to a treatment, (i) abruptly weaned (W: n = 8) or (ii) non-weaned (controls) (C: n = 8). Weaned calves were housed in pens without their dams, whereas non-weaned (control) calves were housed with their dams. Blood was collected on day -7, 0 (housing), 2, 7, and 14 to determine total leukocyte and differential counts and concentration of fibrinogen and haptoglobin. Lymphocyte immunophenotypes were characterised using selected surface antigens (CD4⁺, CD8⁺, WC1⁺ (γδ T cells), MHC Class II⁺ lymphocytes), and the functional activities of neutrophils (surface expression of L-selectin (CD62L), phagocytic and oxidative burst activity) were investigated using flow cytometry.     

Actin filaments elongate from their membrane-associated ends

In limulus sperm an actin filament bundle 55 mum in length extends from the acrosomal vacuole membrane through a canal in the nucleus and then coils in a regular fashion around the base of the nucleus. The bundle expands systematically from 15 filaments near the acrosomal vacuole to 85 filaments at the basal end. Thin sections of sperm fixed during stages in spermatid maturation reveal that the filament bundle begins to assemble on dense material attached to the acrosomal vacuole membrane. In micrographs fo these early stages in maturation, short bundles are seen extending posteriorly from the dense material. The significance is that these short, developing bundles have about 85 filaments, suggesting that the 85-filament end of the bundle is assembled first. By using filament bundles isolated and incubated in vitro with G actin from muscle, we can determine the end “preferred” for addition of actin monomers during polymerization. The end that would be associated with the acrosomal vacuole membrane, a membrane destined to be continuous with the plasma membrane, is preferred about 10 times over the other, thicker end. Decoration of the newly polymerized portions of the filament bundle with subfragment 1 of myosin reveals that the arrowheads point away from the acrosomal vacuole membrane, as is true of other actin filament bundles attached to membranes. From these observations we conclude that the bundle is nucleated from the dense material associated with the acrosomal vacuole and that monomers are added to the membrane-associated end. As monomers are added at the dense material, the thick first-made end of the filament bundle is pushed down through the nucleus where, upon reaching the base of the nucleus, it coils up. Tapering is brought about by the capping of the peripheral filaments in the bundle.     

Conservation of alternative splicing and genomic organization of the myosin alkali light-chain (Mlc1) gene among Drosophila species

The Mlc1 gene of Drosophila melanogaster encodes two MLC1 isoforms via developmentally regulated alternative pre-mRNA splicing. In larval muscle and tubular and abdominal muscles of adults, all of the six exons are included in the spliced mRNA, whereas, in the fibrillar indirect flight muscle of adult, exon 5 is excluded from the mRNA. We show that this tissue-specific pattern of alternative splicing of the Mlc1 pre-mRNA is conserved in D. simulans, D. pseudoobscura, and D. virilis. Isolation and sequencing of the Mlc1 genes from these three other Drosophila species have revealed that the overall organization of the genes is identical and that the genes have maintained a very high level of sequence identity within the coding region. Pairwise amino acid identities are 94%-99%, and there are no charge changes among the proteins. Total nucleotide divergence within the coding region of the four genes supports the accepted genealogy of these species, but the data indicate a significantly higher rate of amino acid replacement in the branch leading to D. pseudoobscura. A comparison of nucleotide substitutions in the coding portions of exon 5 and exon 6, which encode the alternative carboxyl termini of the two MLC1 isoforms, suggests that exon 5 is subject to greater evolutionary constraints than is exon 6. In addition to the coding sequences, there is significant sequence conservation within the 5' and 3' noncoding DNA and two of the introns, including one that flanks exon 5. These regions are candidates for cis- regulatory elements. Our results suggest that evolutionary constraints are acting on both the coding and noncoding sequences of the Mlc1 gene to maintain proper expression and function of the two MLC1 polypeptides.      

Molecular phylogenetic evidence that the phylum Haplosporidia has an alveolate ancestry

The phylogenetic position of the phylum Haplosporidia among other protists was investigated with the complete 16S-like rRNA gene sequences from two species in the phylum: Haplosporidium nelsoni, a parasite of oysters, and Minchinia teredinis, a parasite of shipworms. Because the lack of obvious morphological homologies with other protists hampered decisions regarding taxonomic composition for sequence alignment and phylogenetic analysis, the complete sequences for these two haplosporidians were directed as search queries to the blast/ncbi.nlm.nih.gov electronic mail server. The results of this heuristic similarity search provided a basis for constructing a preliminary higher-taxonomic-level analysis comparing the haplosporidians with species from the slime molds, fungi, algae, amoebae, ciliates, dinoflagellates, and apicomplexans. Maximum parsimony yielded equivocal results, whereas transversionally weighted parsimony suggested an affinity with the alveolates (i.e., the ciliates, dinoflagellates, and apicomplexans). Multiple alignment of the two haplosporidian sequences against 17 taxa in a secondary analysis focusing on the alveolates and subsequent parsimony analysis placed the phylum Haplosporidia as a monophyletic group within the Alveolata and as a taxon of equal rank with the other three alveolate phyla. The precise placement within the Alveolata was sensitive to weighting.