Negative feedback regulation ensures the one receptor-one olfactory neuron rule in mouse

In the mouse olfactory system, each olfactory sensory neuron (OSN) expresses only one odorant receptor (OR) gene in a monoallelic and mutually exclusive manner. Such expression forms the genetic basis for OR-instructed axonal projection of OSNs to the olfactory bulb of the brain during development. Here, we identify an upstream cis-acting DNA region that activates the OR gene cluster in mouse and allows the expression of only one OR gene within the cluster. Deletion of the coding region of the expressed OR gene or a naturally occurring frame-shift mutation allows a second OR gene to be expressed. We propose that stochastic activation of only one OR gene within the cluster and negative feedback regulation by that OR gene product are necessary to ensure the one receptor-one neuron rule.     

Protein synthesis and neurotrophin-dependent structural plasticity of single dendritic spines

Long-term potentiation (LTP) at glutamatergic synapses is considered to underlie learning and memory and is associated with the enlargement of dendritic spines. Because the consolidation of memory and LTP require protein synthesis, it is important to clarify how protein synthesis affects spine enlargement. In rat brain slices, the repetitive pairing of postsynaptic spikes and two-photon uncaging of glutamate at single spines (a spike-timing protocol) produced both immediate and gradual phases of spine enlargement in CA1 pyramidal neurons. The gradual enlargement was strongly dependent on protein synthesis and brain-derived neurotrophic factor (BDNF) action, often associated with spine twitching, and was induced specifically at the spines that were immediately enlarged by the synaptic stimulation. Thus, this spike-timing protocol is an efficient trigger for BDNF secretion and induces protein synthesis-dependent long-term enlargement at the level of single spines.     

The rotational spectrum and structure of the HOOO radical

The adduct of the hydroxyl radical with oxygen has been studied theoretically, in connection with atmospheric reactions, but its stability and structure remained an open question. Pure rotational spectra of the HOOO and DOOO radicals have now been observed in a supersonic jet by using a Fourier-transform microwave spectrometer with a pulsed discharge nozzle. The molecular constants extracted from 12 rotational transitions with fine and hyperfine splittings support a trans planar molecular structure, in contrast to the cis planar structure predicted by most ab initio calculations. The bond linking the HO and O2 moieties is fairly long (1.688 angstroms) and comparable to the F-O bond in the isoelectronic FOO radical.     

Characterization of fast skeletal myosin from white croaker in comparison with that from walleye pollack

ABSTRACT:   Enzymatic and structural properties of white croaker fast skeletal muscle myosin were determined and compared with those of walleye pollack counterpart. Ca²⁺-ATPase activity of white croaker myosin was decreased to approximately 70% of the original activity during 1 day of storage at 0°C and pH 7.0 in 0.5 M KCl and 0.1 mM dithiothreitol, whereas that of walleye pollack was decreased to approximately 20% under the same condition. The activation energy ( E _a) for inactivation of white croaker myosin calculated by the Arrhenius plot for inactivation rate constant (K_D) was 1.2-fold higher than that of walleye pollack. While Ca²⁺-ATPase showed a similar KCl-dependency for the two species, the maximal activity was observed at pH 6.2 and 6.3 for white croaker and walleye pollack, respectively. Actin-activated myosin Mg²⁺-ATPase activity of white croaker was approximately half that of walleye pollack at 0.05 M KCl and pH 7.0, although the two myosins showed a similar affinity to F-actin with K _m of 1.7 and 1.4, respectively. Limited proteolysis with α-chymotrypsin cleaved heat-denatured white croaker myosin mainly at heavy meromyosin/light meromyosin (HMM/LMM) junction, whereas walleye pollack myosin was cleaved at several sites in LMM as well as at the HMM/LMM junction.     

Light acclimation potential and carry-over effects vary among three evergreen tree species with contrasting patterns of leaf emergence and maturation

We compared light acclimation potential among three evergreen broadleaved species with contrasting patterns of shoot elongation, leaf emergence and leaf maturation. Understory saplings were transferred to a high-light environment before bud break, grown for 13 months, and then transferred back to the understory to observe subsequent carry-over effects. Acclimation potential was highest and sapling mortality was lowest for Cinnamomum japonicum Sieb. ex Nakai. Indeterminate growth and successive leaf emergence allowed this species to acclimate to both high and low light by adjusting leaf production as well as leaf properties. Sapling mortality occurred after both transfers for Camellia japonica L., which also has indeterminate growth and successive leaf emergence. In this species, carry-over effects were observed at the individual level, but leaf-level acclimation potential was high. Acclimation potential was lowest and sapling mortality occurred soon after the transfer to high light for Quercus glauca Thunb. ex Murray. Determinate growth and flush-type leaf emergence resulted in significant carry-over effects in this species. Indeterminate growth and successive leaf emergence increase whole-plant acclimation potential by extending the period of growth and architectural development during the growing season. Similarly, we inferred that delayed leaf maturation, observed in many evergreen species, increases the acclimation potential of current-year leaves by extending the period of leaf development. In evergreen species, the acclimation potential of preexisting leaves determines the role that leaf turnover plays in whole-plant light acclimation, resulting in diverse strategies for light acclimation among species, as observed in this study.     

Effect of different droplet size on the knockdown efficacy of directly sprayed insecticides

BACKGROUND: Although insecticidal aerosols have been widely accepted for household use, the discharged amount should be maintained at minimum levels because they contain volatile organic compounds. Hence, it would be valuable to develop a technique whereby insecticide droplets adhere efficiently to an insect's body. The present study was undertaken in order to clarify how differences in the mode of adhesion to the insect body influence the knockdown effect. RESULTS: When the discharged volume of droplets with different diameters was the same, the adhesion volume of larger droplets was twice that of smaller droplets, resulting in a higher insect knockdown. In contrast, when the adhesion volume of the two droplet types was the same, a greater number of smaller droplets than larger droplets adhered, and the smaller droplets caused higher insect knockdown. The knockdown effect of both droplet types was lowered when the mesothoracic spiracles of cockroaches were blocked; however, the effect of larger droplets was lowered to a lesser degree. CONCLUSION: The results suggest that, the probability of adhesion to the more susceptible regions of an insect's body, i.e., areas surrounding the mesothoracic spiracles, was improved when a greater number of smaller droplets were adhered, resulting in higher knockdown. Copyright © 2011 Society of Chemical Industry     

An H5N1 highly pathogenic avian influenza virus that invaded Japan through waterfowl migration

In 2010, an H5N1 highly pathogenic avian influenza virus (HPAIV) was isolated from feces of apparently healthy ducks migrating southward in Hokkaido, the northernmost prefecture of Japan. The H5N1 HPAIVs were subsequently detected in domestic and wild birds at multiple sites corresponding to the flyway of the waterfowl having stopovers in the Japanese archipelago. The Hokkaido isolate was genetically nearly identical to H5N1 HPAIVs isolated from swans in the spring of 2009 and 2010 in Mongolia, but less pathogenic in experimentally infected ducks than the 2009 Mongolian isolate. These findings suggest that H5N1 HPAIVs with relatively mild pathogenicity might be selected and harbored in the waterfowl population during the 2009-2010 migration seasons. Our data provide "early warning" signals for preparedness against the unprecedented situation in which the waterfowl reservoirs serve as perpetual sources and disseminators of HPAIVs.