Methodology for in situ gas sampling, transport and laboratory analysis of gases from stranded cetaceans

Gas-bubble lesions were described in cetaceans stranded in spatio-temporal concordance with naval exercises using high-powered sonars. A behaviourally induced decompression sickness-like disease was proposed as a plausible causal mechanism, although these findings remain scientifically controversial. Investigations into the constituents of the gas bubbles in suspected gas embolism cases are highly desirable. We have found that vacuum tubes, insulin syringes and an aspirometer are reliable tools for in situ gas sampling, storage and transportation without appreciable loss of gas and without compromising the accuracy of the analysis. Gas analysis is conducted by gas chromatography in the laboratory. This methodology was successfully applied to a mass stranding of sperm whales, to a beaked whale stranded in spatial and temporal association with military exercises and to a cetacean chronic gas embolism case. Results from the freshest animals confirmed that bubbles were relatively free of gases associated with putrefaction and consisted predominantly of nitrogen

The ordinary city trap

The paper is a critique of a critique, it explains why the most salient and influential critiques of the neo-Marxist world city and global city concepts, made by those arguing to further postcolonialize urban studies through such suppositions that all cities are ‘ordinary’, are misguided. First, it is explained how the charges of economism and ethnocentrism against the world city and global city concepts are ignoratio elenchi: they do not even begin to address or critique their neo-Marxist argument that, across the difference and diversity of the world’s cities, a few major cities have the necessary economic specialization and therefore extraordinary function of commanding and controlling neoliberal globalization. Second, the error made by advocates of ordinary cities of supposing that world-systems analysis and the world city concept are forms of developmentalism is understood as the source for a wider postcolonial mistake of conflating the neo-Marxist world city and global city literatures with the very neoliberal practices toward urban development that they have long attempted to disclose and counter. Finally, the charges against the world city and global city concepts as paradigmatic, peripheralizing, and normative are also rebutted, not only to highlight how those critiques are consequentialist and dependent on the respective charges of economism, ethnocentrism, and developmentalism having veracity, but to demonstrate how an acceptance of the ordinary cities argument for an idiographic, provincial, nominalist, and comparative approach to urban studies, as an alternative to the two neo-Marxist concepts, is only to fall into the trap of making the mistake of confusing evidence of absence for absence of evidence

Olfactory perireceptor and receptor events in moths: a kinetic model revised

Modelling reveals that within about 3 ms after entering the sensillum lymph, 17% of total pheromone is enzymatically degraded while 83% is bound to the pheromone-binding protein (PBP) and thereby largely protected from enzymatic degradation. The latter proceeds within minutes, 20,000-fold more slowly than with the free pheromone. In vivo the complex pheromone–PBP interacts with the receptor molecule. At weak stimulation the half-life of the active complex is 0.8 s due to the postulated pheromone deactivation. Most likely this process is enzymatically catalysed; it changes the PBP into a scavenger form, possibly by interference with the C-terminus. The indirectly determined PBP concentration (3.8 mM) is close to direct measurements. The calculated density of receptor molecules within the plasma membrane of the receptor neuron reaches up to 6,000 units per μm2. This is compared with the estimated densities of the sensory-neuron membrane protein and of ion channels. The EC50 of the model pheromone–PBP complex interacting with the receptor molecules is 6.8 μM, as compared with the EC50 = 1.5 μM of bombykol recently determined using heterologous expression. A possible mechanism widening the range of stimulus intensities covered by the dose–response curve of the receptor-potential is proposed

Reaction rates and transport in neutron stars

Understanding signals from neutron stars requires knowledge about the transport inside the star. We review the transport properties and the underlying reaction rates of dense hadronic and quark matter in the crust and the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes, references updated, overview graphic added in the introduction, improvements in Sec IV.A.

Tracing Carbon Sources through Aquatic and Terrestrial Food Webs Using Amino Acid Stable Isotope Fingerprinting

Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring delta C-13 patterns among amino acids (delta C-13(AA)) could distinguish between multiple aquatic and terrestrial primary production sources. We found that delta C-13(AA) patterns in contrast to bulk delta C-13 values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their delta C-13(AA) patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk delta C-13 values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer delta C-13 patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs

Computational Model of the Insect Pheromone Transduction Cascade

A biophysical model of receptor potential generation in the male moth olfactory receptor neuron is presented. It takes into account all pre-effector processes—the translocation of pheromone molecules from air to sensillum lymph, their deactivation and interaction with the receptors, and the G-protein and effector enzyme activation—and focuses on the main post-effector processes. These processes involve the production and degradation of second messengers (IP3 and DAG), the opening and closing of a series of ionic channels (IP3-gated Ca2+ channel, DAG-gated cationic channel, Ca2+-gated Cl− channel, and Ca2+- and voltage-gated K+ channel), and Ca2+ extrusion mechanisms. The whole network is regulated by modulators (protein kinase C and Ca2+-calmodulin) that exert feedback inhibition on the effector and channels. The evolution in time of these linked chemical species and currents and the resulting membrane potentials in response to single pulse stimulation of various intensities were simulated. The unknown parameter values were fitted by comparison to the amplitude and temporal characteristics (rising and falling times) of the experimentally measured receptor potential at various pheromone doses. The model obtained captures the main features of the dose–response curves: the wide dynamic range of six decades with the same amplitudes as the experimental data, the short rising time, and the long falling time. It also reproduces the second messenger kinetics. It suggests that the two main types of depolarizing ionic channels play different roles at low and high pheromone concentrations; the DAG-gated cationic channel plays the major role for depolarization at low concentrations, and the Ca2+-gated Cl− channel plays the major role for depolarization at middle and high concentrations. Several testable predictions are proposed, and future developments are discussed

A doublecortin containing microtubule-associated protein is implicated in mechanotransduction in Drosophila sensory cilia

Mechanoreceptors are sensory cells that transduce mechanical stimuli into electrical signals and mediate the perception of sound, touch and acceleration. Ciliated mechanoreceptors possess an elaborate microtubule cytoskeleton that facilitates the coupling of external forces to the transduction apparatus. In a screen for genes preferentially expressed in Drosophila campaniform mechanoreceptors, we identified DCX-EMAP, a unique member of the EMAP family (echinoderm–microtubule-associated proteins) that contains two doublecortin domains. DCX-EMAP localizes to the tubular body in campaniform receptors and to the ciliary dilation in chordotonal mechanoreceptors in Johnston's organ, the fly's auditory organ. Adult flies carrying a piggyBac insertion in the DCX-EMAP gene are uncoordinated and deaf and display loss of mechanosensory transduction and amplification. Electron microscopy of mutant sensilla reveals loss of electron-dense materials within the microtubule cytoskeleton in the tubular body and ciliary dilation. Our results establish a catalogue of candidate genes for Drosophila mechanosensation and show that one candidate, DCX-EMAP, is likely to be required for mechanosensory transduction and amplification

A neural signature of the unique hues

Since at least the 17th century there has been the idea that there are four simple and perceptually pure “unique” hues: red, yellow, green, and blue, and that all other hues are perceived as mixtures of these four hues. However, sustained scientific investigation has not yet provided solid evidence for a neural representation that separates the unique hues from other colors. We measured event-related potentials elicited from unique hues and the ‘intermediate’ hues in between them. We find a neural signature of the unique hues 230 ms after stimulus onset at a post-perceptual stage of visual processing. Specifically, the posterior P2 component over the parieto-occipital lobe peaked significantly earlier for the unique than for the intermediate hues (Z = -2.9, p = .004). Having identified a neural marker for unique hues, fundamental questions about the contribution of neural hardwiring, language and environment to the unique hues can now be addressed

Olfactory receptors on the maxillary palps of small ermine moth larvae: evolutionary history of benzaldehyde sensitivity

In lepidopterous larvae the maxillary palps contain a large portion of the sensory equipment of the insect. Yet, knowledge about the sensitivity of these cells is limited. In this paper a morphological, behavioral, and electrophysiological investigation of the maxillary palps of Yponomeuta cagnagellus (Lepidoptera: Yponomeutidae) is presented. In addition to thermoreceptors, CO2 receptors, and gustatory receptors, evidence is reported for the existence of two groups of receptor cells sensitive to plant volatiles. Cells that are mainly sensitive to (E)-2-hexenal and hexanal or to (Z)-3-hexen-1-ol and 1-hexanol were found. Interestingly, a high sensitivity for benzaldehyde was also found. This compound is not known to be present in Euonymus europaeus, the host plant of the monophagous Yponomeuta cagnagellus, but it is a prominent compound in Rosaceae, the presumed hosts of the ancestors of Y. cagnagellus. To elucidate the evolutionary history of this sensitivity, and its possible role in host shifts, feeding responses of three Yponomeuta species to benzaldehyde were investigated. The results confirm the hypothesis that the sensitivity to benzaldehyde evolved during the ancestral shift from Celastraceae to Rosaceae and can be considered an evolutionary relict, retained in the recently backshifted Celastraceae-specialist Y. cagnagellus