Models for pattern formation in somitogenesis: a marriage of cellular and molecular biology

Somitogenesis, the process by which a bilaterally symmetric pattern of cell aggregations is laid down in a cranio-caudal sequence in early vertebrate development, provides an excellent model study for the coupling of interactions at the molecular and cellular level. Here, we review some of the key experimental results and theoretical models related to this process. We extend a recent chemical pre-pattern model based on the cell cycle Journal of Theoretical Biology 207 (2000) 305-316, by including cell movement and show that the resultant model exhibits the correct spatio-temporal dynamics of cell aggregation. We also postulate a model to account for the recently observed spatio-temporal dynamics at the molecular level

The Targeting of the atToc159 Preprotein Receptor to the Chloroplast Outer Membrane is Mediated by its GTPase Domain and is Regulated by GTP

The multimeric translocon at the outer envelope membrane of chloroplasts (Toc) initiates the recognition and import of nuclear-encoded preproteins into chloroplasts. Two Toc GTPases, Toc159 and Toc33/34, mediate preprotein recognition and regulate preprotein translocation. Although these two proteins account for the requirement of GTP hydrolysis for import, the functional significance of GTP binding and hydrolysis by either GTPase has not been defined. A recent study indicates that Toc159 is equally distributed between a soluble cytoplasmic form and a membrane-inserted form, raising the possibility that it might cycle between the cytoplasm and chloroplast as a soluble preprotein receptor. In the present study, we examined the mechanism of targeting and insertion of the Arabidopsis thaliana orthologue of Toc159, atToc159, to chloroplasts. Targeting of atToc159 to the outer envelope membrane is strictly dependent only on guanine nucleotides. Although GTP is not required for initial binding, the productive insertion and assembly of atToc159 into the Toc complex requires its intrinsic GTPase activity. Targeting is mediated by direct binding between the GTPase domain of atToc159 and the homologous GTPase domain of atToc33, the Arabidopsis Toc33/34 orthologue. Our findings demonstrate a role for the coordinate action of the Toc GTPases in assembly of the functional Toc complex at the chloroplast outer envelope membrane

A mathematical formulation for the cell-cycle model in somitogenesis: analysis, parameter constraints and numerical solutions

In this work we present an analysis, supported by numerical simulations, of the formulation of the cell-cycle model for somitogenesis proposed in Collier et al.(J. Theor. Biol. 207 (2000), 305–316). The analysis indicates that by introducing appropriate parameter constraints on model parameters the cell-cycle mechanism can indeed give rise to the periodic pattern of somites observed in normal embryos. The analysis also provides a greater understanding of the signalling process controlling somite formation and allows us to understand which parameters influence somite length

Suppression of combustion oscillations with mechanical devices Interim report

Static rocket thrust chamber simulator for cylindrical cold flow-type apparatus desig

Human Neutrophil Elastase Degrades SPLUNC1 and Impairs Airway Epithelial Defense against Bacteria

Background:Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a significant cause of mortality of COPD patients, and pose a huge burden on healthcare. One of the major causes of AECOPD is airway bacterial (e.g. nontypeable Haemophilus influenzae [NTHi]) infection. However, the mechanisms underlying bacterial infections during AECOPD remain poorly understood. As neutrophilic inflammation including increased release of human neutrophil elastase (HNE) is a salient feature of AECOPD, we hypothesized that HNE impairs airway epithelial defense against NTHi by degrading airway epithelial host defense proteins such as short palate, lung, and nasal epithelium clone 1 (SPLUNC1).Methodology/Main Results:Recombinant human SPLUNC1 protein was incubated with HNE to confirm SPLUNC1 degradation by HNE. To determine if HNE-mediated impairment of host defense against NTHi was SPLUNC1-dependent, SPLUNC1 protein was added to HNE-treated primary normal human airway epithelial cells. The in vivo function of SPLUNC1 in NTHi defense was investigated by infecting SPLUNC1 knockout and wild-type mice intranasally with NTHi. We found that: (1) HNE directly increased NTHi load in human airway epithelial cells; (2) HNE degraded human SPLUNC1 protein; (3) Recombinant SPLUNC1 protein reduced NTHi levels in HNE-treated human airway epithelial cells; (4) NTHi levels in lungs of SPLUNC1 knockout mice were increased compared to wild-type mice; and (5) SPLUNC1 was reduced in lungs of COPD patients.Conclusions:Our findings suggest that SPLUNC1 degradation by neutrophil elastase may increase airway susceptibility to bacterial infections. SPLUNC1 therapy likely attenuates bacterial infections during AECOPD. © 2013 Jiang et al

The Final (Oral Ebola) Vaccine Trial on Captive Chimpanzees?

Could new oral vaccine technologies protect endangered wildlife against a rising tide of infectious disease? We used captive chimpanzees to test oral delivery of a rabies virus (RABV) vectored vaccine against Ebola virus (EBOV), a major threat to wild chimpanzees and gorillas. EBOV GP and RABV GP-specific antibody titers increased exponentially during the trial, with rates of increase for six orally vaccinated chimpanzees very similar to four intramuscularly vaccinated controls. Chimpanzee sera also showed robust neutralizing activity against RABV and pseudo-typed EBOV. Vaccination did not induce serious health complications. Blood chemistry, hematologic, and body mass correlates of psychological stress suggested that, although sedation induced acute stress, experimental housing conditions did not induce traumatic levels of chronic stress. Acute behavioral and physiological responses to sedation were strongly correlated with immune responses to vaccination. These results suggest that oral vaccination holds great promise as a tool for the conservation of apes and other endangered tropical wildlife. They also imply that vaccine and drug trials on other captive species need to better account for the effects of stress on immune response

Synthesis of Two Key Fragments of the Complex Polyhalogenated Marine Meroterpenoid Azamerone

A concise route toward two advanced fragments in the context of the total synthesis of the unique natural product azamerone is reported. Key synthetic features include the enantioselective synthesis of an epoxysilane and its Lewis-acid-induced cyclization and the installation of the pyridazine ring via a formylation/condensation sequence. This route provides strategic insights into the chemistry of phthalazinediols, facilitating synthetic approaches toward this class of natural products

Microwave Lens for Polar Molecules

We here report on the implementation of a microwave lens for neutral polar molecules suitable to focus molecules both in low-field-seeking and in high-field-seeking states. By using the TE_11m modes of a 12 cm long cylindrically symmetric microwave resonator, Stark-decelerated ammonia molecules are transversally confined. We investigate the focusing properties of this microwave lens as a function of the molecules' velocity, the detuning of the microwave frequency from the molecular resonance frequency, and the microwave power. Such a microwave lens can be seen as a first important step towards further microwave devices, such as decelerators and traps.Comment: 4 pages, 3 figure

Introducing CatOracle: Corpus-based concatenative improvisation with the Audio Oracle algorithm

CATORACLE responds to the need to join high-level control of audio timbre with the organization of musical form in time. It is inspired by two powerful existing tools: CataRT for corpus-based concatenative synthesis based on the MUBU for MAX library, and PYORACLE for computer improvisation, combining for the first time audio descriptor analysis and learning and generation of musical structures. Harnessing a user-defined list of audio fea- tures, live or prerecorded audio is analyzed to construct an “Audio Oracle” as a basis for improvisation. CatOracle also extends features of classic concatenative synthesis to include live interactive audio mosaicking and score-based transcription using the BACH library for MAX. The project suggests applications not only to live performance of written and improvised electroacoustic music, but also computer-assisted composition and musical analysis