bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction Mechanisms of Smectite Illitization Associated with Hydrothermal Alteration from Ponza Island, Italy
Authors: Ylagan Robert F. , Altaner Stephen P. , Pozzuoli Antonio
Published: August 2006

A hydrothermally altered rhyolitic hyaloclastite from Ponza island, Italy, has four alteration zones with unique clay assemblages: (1) a non-pervasive argillic zone characterized by smectite; (2) a propylitic zone with interstratified illite-smectite (I-S) containing 10–85% illite (I); (3) a silicic zone composed of I-S with ≥90% I and pure illite; and (4) a sericitic zone with I-S ranging from 66% I to pure illite. Atomic force microscopy reveals abrupt changes in particle morphology with illitization, including initial changes from anhedral plates to laths and then to euhedral plates and hexagonal plates. I-S particles progressively thicken with illitization and mean particle area (basal plane) remains constant from pure smectite to I-S with 80% I. However, particle area increases from 90 to 100% illite. Computer modeling of I-S structural forms indicates octahedral cation ordering progressively changes fromcis-vacant smectite to interstratifiedcis-andtnuis-vacant I-S, and then totrans-vacant illite. In addition, polytypes progressively change from 1Mdto 1M, and then to 2M, illite. Electron-microprobe and X-ray fluoresence analyses show that I-S chemistry progressively changes during illitization, evolving toward a phengitic composition with ∼0.89 fixed interlayer K+per O10(OH)2. Octahedral Mg2+shows little change with illitization, varying from 0.3 to 0.5 cations per O,10(OH)2. The layer charge of smectite is ~0.38 equivalents per O10(OH)2.

On the basis of abrupt changes in morphology and progressive changes in polytype and chemistry, smectite illitization on Ponza involved a dissolution and recrystallization mechanism with multiple stages of nucléation and crystal growth. In this multi-step model, temperature of alteration provided the major control for the layer composition, polytype, and morphology of I-S crystallites. Other factors that may play a secondary role include: K+availability, water-rock ratio, and permeability. Alternatively, the mechanism of I-S and illite formation at Ponza and other hydrothermal environments may occur by direct precipitation of I-S crystallites from rhyolite glass and may not involve progressive reactions of smectite precursors.
Characterization of Silanol Groups in Protonated Magadiite by 1H and 2H Solid-State Nuclear Magnetic Resonance
Authors: Komori Yoshihiko , Miyoshi Masaki , Hayashi Shigenobu , Sugahara Yoshiyuki , Kuroda Kazuyuki
Published: August 2006

Silanol groups in protonated magadiite (H-magadiite) were characterized by 1H and 2H solid-state nuclear magnetic resonance (NMR). H-magadiite and deuterated (D) magadiite were synthesized by the treatment of Na-rich magadiite with 0.2 N HC1 and 0.2 N DC1, respectively. In the 1H NMR spectrum measured at room temperature, silanol groups of H-magadiite showed two signals at 3.75 and 5.70 ppm, indicating that two types of silanol groups were present. The ratio of silanol groups associated with strong hydrogen bonding (5.70 ppm) to those with weaker hydrogen bonding (3.75 ppm) was 2 to 1. The 2H NMR spectra of deuterated magadiite were measured in the temperature range from 150 to 440 K. In the spectra measured at temperatures below 294 K, silanol groups showed Pake doublet patterns. These patterns were composed of two components corresponding to the two types of silanol groups shown in the 1H NMR analysis. Both silanol groups produced wobbling motions with increasing temperature. Above 294 K, the profile of the Pake doublet pattern was transformed gradually to a near triangular pattern, indicating that the silanol groups underwent other motions also, such as a two-site jump.
Self-Organized Inorganic-Organic Hybrids Induced by Silylating Agents with Phyllosilicate-Like Structure and the Influence of the Adsorption of Cations
Authors: Da Fonseca Maria G. , Barone José S. , Airoldi Claudio
Published: August 2006

Two analogous inorganic-organic hybrids with a phyllosilicate-like structure SILMg1 and SILMg2, containing 3-aminopropyl- and N-propylethylenediaminetrimethoxysilane were synthesized through a sol-gel process. These hybrids adsorbed divalent cations of cobalt, nickel, copper, and zinc from aqueous solution to give the effectiveness of adsorption capacities in the sequence Cu2+ > Zn2+ > Ni2+ > Co2+. SILMg1 has a higher capacity of adsorption than SILMg2. Elemental analysis, X-ray diffractometry, thermal analysis, infrared and nuclear magnetic resonance spectroscopies, and energy dispersive system microscopy characterized all hybrids. The proposed adsorption mechanism involves dissolution of the precursor matrix, formation of a phyllosilicate around the adsorbed ion, and a complexation of the cation by the amino-pendant groups in the interlayer. These new phyllosilicates are more crystalline than the original hybrids. The adsorption of Co2+ increases the interlayer distance to maximum values of 1.81 and 2.24 Å for SILMg1 and SILMg2, respectively. Thermal analysis data showed a decrease of thermal stability with cation adsorption. Si-O-Si groups were detected by infrared spectroscopy in all hybrids and a band at 1384 cm-1 was assigned to the nitrate counter anion, which indicates the participation of this ion in the sphere of coordination of the interlayer complexes. The photomicrographs obtained by scanning electron microscopy showed the organized distribution of the sheet structure for these synthesized phyllosilicates.
Chromate Removal by Dithionite-Reduced Clays: Evidence from Direct X-Ray Adsorption Near Edge Spectroscopy (XANES) of Chromate Reduction at Clay Surfaces
Authors: Taylor Robert W. , Shen Siyuan , Bleam William F. , Tu Shu-I
Published: August 2006

Chromium(VI) in the environment is of particular concern because it is toxic to both plants and animals, even at low concentrations. As a redox-sensitive element, the fate and toxicity of chromium is controlled by soil reduction-oxidation (redox) reactions. In-situ remediation of chromium combines reduction of Cr(VI) to Cr(III) and immobilization of chromium on mineral surfaces. In this study, Fe-rich smectite, montmorillonite, illite, vermiculite, and kaolinite were examined to determine reactivity in sorption-reduction of Cr(VI). The clays were compared to forms that were reduced by sodium dithionite. Clays containing Fe(II) efficiently removed soluble Cr(VI) from solution. Chromium K-edge X-ray absorption near edge structure (XANES) suggested that clays containing Fe(II) reduced Cr(VI) to Cr(III), immobilizing Cr at the clay/water interface. Adsorption of Cr(VI) by the Fe(II)-containing clay was a prerequisite for the coupled sorption-reduction reaction. Sodium dithionite added directly to aqueous suspensions of non-reduced clays reduced Cr(VI) to Cr(III), but did not immobilize Cr on clay surfaces. The capacity of clays to reduce Cr(VI) is correlated with the ferrous iron content of the clays. For dithionite-reduced smectite, the exchangeable cation influenced the sorption reaction, and thus it also influenced the coupled sorption-reduction reaction of Cr(VI). The pH of the aqueous system affected both the amount of Cr(VI) reduced to Cr(III) and the partition of Cr(III) between aqueous and adsorbed species. A plot of pH vs. amount (adsorption envelope) adsorbed for the coupled sorption-reduction reaction of Cr by reduced smectite exhibited a similar pattern to that of typical anion-sorption.
Pedogenic Smectites in Podzols from Central Finland: An Analytical Electron Microscopy Study
Authors: Gillot Florence , Righi Dominique , Elsass Françoise
Published: August 2006

Transmission electron microscopy (TEM) including high-resolution transmission electron microscopy (HRTEM) and analytical electron microscopy (AEM) were used to study the fine clay fraction (<0.1 μm) from the eluvial E horizon of podzols located in central Finland that had developed from till materials. Soils of increasing age (6500-9850 y BP) were selected to represent a chronosequence of soil development. Expandable phyllosilicates (vermiculite, smectites) are formed in the eluvial E horizon of podzols in a short time (6500 y). TEM observations show that dissolution and physical-breakdown processes affect the clay particles. As the age of the soils increases, fragmentation and exfoliation of large precursor minerals lead to thinner clay particles of two to three layers thick. The chemical compositions of individual particles obtained by AEM indicate that expandable phyllosilicates from the E horizon of podzols are heterogeneous, involving a mixture of vermiculite, Mg-bearing smectites, and aluminous beidellite. Results suggest that heterogeneity is related to the nature of their precursors. Vermiculite and Mg-bearing smectites are derived from biotite and chlorite weathering whereas phengitic micas alter to aluminous beidellite. Because the transformation of biotite and chlorite is more rapid than phengitic micas, biotite and chlorite contributes predominantly to smectites in the younger soils, as long as ferromagnesian phyllosilicates are present in the E horizons. If not, a larger proportion of smectites is derived from phengitic micas in the older soils. Direct measurement of d(001 ) values on lattice fringe images from alkylammonium-saturated samples shows that interlayer charge varies from high-charge expandable minerals (0.6–0.75 per half unit cell) in the younger soils to 0.5–0.6 per half unit cell in the oldest soils. Thus, the proportion of the components in the clay assemblage, as well as their chemistry and interlayer charge, change over time with soil evolution.
Use of X-Ray Transmission Diffractometry for the Study of Clay-Particle Orientation at Different Water Contents
Authors: Iñigo A. C. , Tessier D. , Pernes M.
Published: August 2006

Homoionic Ca-saturated clay pastes were prepared and drying curves were obtained by applying suction pressures from 1 kPa to 100 MPa, A transmission device was used to study particle orientation by placing the clay in a cell specially designed to obtain diagrams corresponding to different sample orientations. The 00l and hk0 reflections were compared to determine the best reflections for studying clay-particle orientation. Depending on the clay, 00/ reflections or the 020 reflection and/or hkl bands can be used to analyze orientation. In many cases the 020 reflection is preferred because the intensity of the peak is high and appears to be independent of the H2O content and the degree of stacking order of layers along the [001] direction.

For interstratified clays, the conditions required to obtain 00l reflections depended on several factors, the most important of which is the water content. Also, the intensity relating to particie orientation depends on (1) particle extension (size) in the (001) plane and (2) the crystal structure. Illite crystals of <1000 A gave a poorly oriented clay matrix. In contrast, large aggregates of illite, smectite, and kaolinite particles (>10,000 Å) showed a strongly oriented system. The particles of smectites may be curved and the dry material was poorly oriented owing to weak cohesion forces between the layers in comparison to illite.

The study of the orientation of particles by X-ray diffraction on hydrated samples may be affected by sample mounting techniques. Any change in the content or the way the sample is mounted may modify the microstructure of a material.

Clay containing a high water content affects the disorientation of particles, whereas, for the dry samples, pore size, pore volume, and solid continuity are associated with the geometry and crystal structure of the clay matrix.
Detrital Origin of a Sedimentary Fill, Lechuguilla Cave, Guadalupe Mountains, New Mexico
Authors: Foos Annabelle M. , Sasowsky Ira D. , LaRock Edward J. , Kambesis Patricia N.
Published: August 2006

Lechuguilla Cave is a hypogene cave formed by oxidation of ascending hydrogen sulfide from the Delaware Basin. A unique sediment deposit with characteristics suggesting derivation from the land surface, some 285 m above, was investigated. At this location, the observed stratigraphy (oldest to youngest) was: bedrock floor (limestone), cave clouds (secondary calcite), calcite-cemented silstone, finely laminated clay, and calcite rafts. Grain-size analysis indicates that the laminated clay deposits are composed of 59-82% clay-size minerals. The major minerals of the clay were determined by X-ray diffraction analysis and consist of interstratified illite-smectite, kaolinite, illite, goethite, and quartz. Scanning electron microscopy observations show that most of the clay deposit is composed of densely packed irregularshaped clay-size flakes. One sample from the top of the deposit was detrital, containing well-rounded, silt-size particles.

Surface soils are probably the source of the clay minerals. The small amount of sand- and silt-size particles suggests that detrital particles were transported in suspension. The lack of endellite and alunite is evidence that the clays were emplaced after the sulfuric-acid dissolution stage of cave formation. Fossil evidence also suggests a previously existing link to the surface.
Surface Enthalpy of Boehmite
Authors: Majzlan Juraj , Navrotsky Alexandra , Casey William H.
Published: August 2006

The persistence of many seemingly metastable mineral assemblages in sediments and soils is commonly attributed to their sluggish transformation to the stable-phase assemblage. Although undoubtedly kinetics plays a major role, this study shows that thermodynamic factors, particularly surface energy, significantly influence the free energy. Enthalpies of formation of boehmite samples with variable surface area were derived using high-temperature oxide-melt calorimetry. The average surface enthalpy for all faces terminating boehmite particles was calculated at +0.52 ± 0.12 J/m2. This value represents the surface enthalpy for surfaces exposed to vacuum assuming that H2O adsorbed on the surface of boehmite is loosely bound. These results show that the enthalpy of formation of boehmite may vary by ≤8 kJ/mol as a function of particle size. An overview of published values of surface energies of gibbsite, γ-Al2O3, corundum, and the results here indicates that the hydrated phases (boehmite, gibbsite) have lower surface energies than the anhydrous phases (corundum, γ-Al2O3). Lower surface energies allow the hydrated phases to maintain high surface area, i.e., small particle size. Similar surface energies of boehmite and gibbsite suggest kinetic control favoring the crystallization of boehmite or gibbsite from aqueous solution. The enthalpy of formation of bulk boehmite from the elements was calculated at −994.0 ±1.1 kJ/mol. Combining this result with the data in existing thermodynamic databases, we confirm that bulk boehmite is metastable with respect to bulk diaspore at ambient conditions.
Editorial
Authors: Spranger Tade M
Published: August 2006

Mechanisms of alternative dispute resolution become more and more important in the legal world. The decision of the WTO Appellate Body in the so-called “hormone case” highlighted the growing relevance of DR methods in the field of health and consumer protection. The pending case of GM food labelling in the European Community is one major example for the role of ADR in biotechnology law. As biotech is a delicate area of law which makes it extremely hard to analyse, define, and interpret the relevant provisions, it is predestined for the application of ADR.
The Usage of Alternative Dispute Resolution Mechanisms in the Field of Biotechnology
Authors: Hilmer Sarah E
Published: August 2006

The field of biotechnology has lately been, and certainly still is, an area of great development. The movement of high technology in the today's world of the 21st century offers many possiblities, however sometimes towards a great amount of unknown factors.
Indonesia's Regulation on the Biosafety of Genetically Engineered Products
Authors: Spranger Tade Matthias
Published: August 2006

On 19 May 2005, Indonesia set into force Regulation Number 21 on the Biosafety of Genetically Engineered Products (hereinafter: Biosafety Regulation), which implements not only basic requirements of the Convention on Biological Diversity (CBD) and the Biosaftey Protocol, but also several provisions of Law Number 23 of 1997 on Environmental Management. According to art. 2 (1), the purpose of this Regulation is to ensure an adequate level of environmental safety, food safety and or animal feed safety of genetically engineered products (GEP) and its use in the area of agriculture, fishery, forestry, industry, environment and nonpharmaceutical health. In addition, the regulation should improve efficiency and effectiveness of GEP use for the people's welfare based on the principles of health and biological resource management, consumer protection and certainty in operating business. The regulation includes provisions on the type and requirement of GEP, research on and development of GEP, importation of GEP from foreign countries, assessment, release, and distribution and use of GEP, control of GEP, as well as on the institutional framework and cost.
Recent Landmark Changes in Japanese Biotechnology & University Patenting (Part II)
Authors: Tessensohn John A , Yamamoto Shusaku
Published: August 2006

Biotechnology Strategy Council

The finalized 2002 Biotechnology Strategy Guidelines issued by the Biotechnology Strategy Council called for “unified planning, drafting and comprehensive coordination of budgetary allocation policies and their execution, for all budgets biotechrelated science and technology budgets (amongst the Council for Science and Technology Policy, related ministries and agencies)” and to “build up and improve the funding functions of budget-allocating institutions” with competitive research funds and transparent evaluation criteria.

In the past, this biotechnology funding was jealously controlled by the differing government Ministries and agencies e.g., METI, MEXT, Ministry of Labor, Health and Welfare with their respective broad portfolios, and there were concerns that “eventually the bureaucrats walk off and follow the particular interest of their ministry”, with the result that “the Japanese scientific community does not have very much influence on research funding”. It remains to be seen whether the “unified planning, drafting and comprehensive coordination” will improve the implementation of the 2002 Biotechnology Strategy Guidelines discussed earlier.
Bioprocessing: Engineering Know-How in Greater Demand than Ever
Authors: Hirche Christina , Butcher Charles
Published: August 2006

Introduction

Several studies forecast that the share of biotechnological processes in the total sales volume of chemical products will probably soar to around 15–20 % by 2010. Alone for the chemical industry, the potential value added of biotechnological production has been predicted to reach € 11–22 billion worldwide annually by then. The value added stems not only from new biotechnological products, but also from the effects of improved manufacturing processes. At ACHEMA 2006 in May 2006 in Frankfurt am Main - the world's leading event for the process industries - besides the integral general topic Biotechnological Equipment, which focuses on the equipment sector a special Industrial Biotechnology Exhibition and a Partnering Conference took place, thus paying tribute to the growing significance of industrial biotechnology and supporting international networking.
Industrial Cleaning of Implants: Performance Validation of Cleaning Scheme
Authors: Frauchiger V , Weber B , Maurer T , Ruetti G , Luginbuehl R
Published: August 2006

The quality of medical devices depends strongly on the proper cleaning of the devices in the line of processing. Residue-free implants are not only a benefit for the patient in the long term, but they also help to reduce the number of rejections due to insufficient surface quality. The performance of the new, fully automated aqueous immersion cleaning system revealed a very high cleaning efficiency for metallic implants. An organically based model process adjuvant was used as contaminant. Custom designed metallic bodies made of implant quality material and exhibiting different surface textures served as test coupons. The analysis of the residues was carried out using gas chromatography separation and mass spectrometry analysis. The amount of organic residues found on the test coupons was below the set quantification limit of 0.1 mg—most of the time even below the detection limit of 0.01 mg total organic compounds.
Human Tobacco Smokers in Early Abstinence Have Higher Levels of β2* Nicotinic Acetylcholine Receptors than Nonsmokers
Authors: Staley Julie K. , Krishnan-Sarin Suchitra , Cosgrove Kelly P. , Krantzler Erica , Frohlich Erin , Perry Edward , Dubin Joel A. , Estok Kristina , Brenner Eric , Baldwin Ronald M. , Tamagnan Gilles D. , Seibyl John P. , Jatlow Peter , Picciotto Marina R. , London Edythe D. , O'Malley Stephanie , van Dyck Christopher H.
Published: August 2006

Nicotine, the addictive chemical in tobacco smoke, initiates its actions in brain through nicotinic acetylcholine receptors (nAChRs). In particular, nAChRs containing β2-subunits (β2*-nAChRs) the most prevalent subtype, mediate the reinforcing properties of nicotine. We hypothesized that abnormal numbers of β2*-nAChRs during early abstinence contribute to the perpetuation of addiction to tobacco smoking. Using molecular imaging, specifically single-photon emission computed tomography with the nAChR agonist radiotracer [123I]5-IA-85380 ([123I]5-IA), we imaged β2*-nAChR availability in human smokers. First, using nonhuman primates treated chronically with nicotine, we estimated the time interval necessary for smokers to abstain from smoking so that residual nicotine would not interfere with [123I]5-IA binding to the β2*-nAChR as ∼7 d. Thus, we imaged human smokers at 6.8 ± 1.9 d (mean ± SD) of abstinence. Abstinence was confirmed by daily assessments of urinary cotinine and expired carbon monoxide levels. In smokers, [123I]5-IA uptake was significantly higher throughout the cerebral cortex (26–36%) and in the striatum (27%) than in nonsmokers, suggesting higher β2*-nAChR in recently abstinent smokers. β2*-nAChR availability in recently abstinent smokers correlated with the days since last cigarette and the urge to smoke to relieve withdrawal symptoms but not the severity of nicotine dependence, severity of nicotine withdrawal, or the desire to smoke. Higher brain β2*-nAChR during early abstinence indicates that, when smokers quit smoking, they do so in the face of a significant increase in the receptors normally activated by nicotine. Greater β2*-nAChR availability during early abstinence may impact the ability of smokers to maintain abstinence.
Corticosterone-Sensitive Monoamine Transport in the Rat Dorsomedial Hypothalamus: Potential Role for Organic Cation Transporter 3 in Stress-Induced Modulation of Monoaminergic Neurotransmission
Authors: Gasser Paul J. , Lowry Christopher A. , Orchinik Miles
Published: August 2006

Glucocorticoid hormones act within the brain to alter physiological and behavioral responses to stress-related stimuli. Previous studies indicated that acute stressors can increase serotonin [5-hydroxytryptamine (5-HT)] concentrations in the dorsomedial hypothalamus (DMH), a midline hypothalamic structure involved in the integration of physiological and behavioral responses to stress. The current study tests the hypothesis that rapid, stress-induced accumulation of 5-HT is attributable to the inhibition of 5-HT transport via organic cation transporters (OCTs). OCTs are a family of high-capacity, bidirectional, multispecific transporters of organic cations (including 5-HT, dopamine, and norepinephrine) only recently described in brain. In peripheral tissues, organic cation transport via some OCTs is inhibited by corticosterone. We examined the expression and function of OCTs in the periventricular medial hypothalamus of male Sprague Dawley rats using reverse-transcriptase (RT)-PCR, immunohistochemistry, andin vitrotransport assays. RT-PCR revealed expression of OCT3 mRNA, but not OCT1 or OCT2 mRNA, in the medial hypothalamus. OCT3-like immunoreactivity was observed in ependymal and glial-like cells in the DMH. Acutely prepared minces of rat medial hypothalamic tissue accumulated the OCT substrates [3H]-histamine and [3H]-N-methyl-4-phenylpyridinium ([3H]-MPP+). Consistent with the pharmacological profile of OCT3, corticosterone, 5-HT, estradiol, and the OCT inhibitor decynium22 dose-dependently inhibited histamine accumulation. Corticosterone and decynium22 also inhibited efflux of [3H]-MPP+from hypothalamic minces. These data support the hypothesis that corticosterone-induced inhibition of OCT3 mediates stress-induced accumulation of 5-HT in the DMH and suggest that corticosterone may acutely modulate physiological and behavioral responses to stressors by altering serotonergic neurotransmission in this brain region.
Right–Left Asymmetries in the Whisking Behavior of Rats Anticipate Head Movements
Authors: Towal R. Blythe , Hartmann Mitra J.
Published: August 2006

Rats use rhythmic movements of their vibrissae (whiskers) to tactually explore their environment. This “whisking” behavior has generally been reported to be strictly synchronous and symmetric about the snout, and it is thought to be controlled by a brainstem central pattern generator. Because the vibrissae can move independently of the head, however, maintaining a stable perception of the world would seem to require that rats adjust the bilateral symmetry of whisker movements in response to head movements. The present study used high-speed videography to reveal dramatic bilateral asymmetries and asynchronies in free-air whisking during head rotations. Kinematic analysis suggested that these asymmetric movements did not serve to maintain any fixed temporal relationship between right and left arrays, but rather to redirect the whiskers to a different region of space. More specifically, spatial asymmetry was found to be strongly correlated with rotational head velocity, ensuring a “look-ahead” distance of almost exactly one whisk. In contrast, bilateral asynchrony and velocity asymmetry were only weakly dependent on head velocity. Bilateral phase difference was found to be independent of the whisking frequency, suggesting the presence of two distinct left and right central pattern generators, connected as coupled oscillators. We suggest that the spatial asymmetries are analogous to the saccade that occurs during the initial portion of a combined head–eye gaze shift, and we begin to develop the rat vibrissal system as a new model for studying vestibular and proprioceptive contributions to the acquisition of sensory data.
A Pheromone Receptor Mediates 11-cis-Vaccenyl Acetate-Induced Responses inDrosophila
Authors: Ha Tal Soo , Smith Dean P.
Published: August 2006

Insect pheromones elicit stereotypic behaviors that are critical for survival and reproduction. Defining the relevant molecular mechanisms mediating pheromone signaling is an important step to manipulate pheromone-induced behaviors in pathogenic or agriculturally important pests. The only volatile pheromone identified inDrosophilais 11-cis-vaccenyl acetate (VA), a male-specific lipid that mediates aggregation behavior. VA activates a few dozen olfactory neurons located in T1 sensilla on the antenna of both male and female flies. Here, we identify a neuronal receptor required for VA sensitivity. We identified two mutants lacking functional T1 sensilla and show that the expression of the VA receptor is dramatically reduced or eliminated. Importantly, we show misexpression of this receptor in non-T1 neurons, normally insensitive to VA, confers pheromone sensitivity at physiologic concentrations. Sensitivity of T1 neurons to VA requires LUSH, an extracellular odorant-binding protein (OBP76a) present in the sensillum lymph bathing trichoid olfactory neuron dendrites. Here, we show LUSH are also required in non-T1 neurons misexpressing the receptor to respond to VA. These data provide new insight into the molecular components and neuronal basis of volatile pheromone perception.
Sparse Odor Coding in Awake Behaving Mice
Authors: Rinberg Dmitry , Koulakov Alex , Gelperin Alan
Published: August 2006

Responses of mitral cells represent the results of the first stage of odor processing in the olfactory bulb. Most of our knowledge about mitral cell activity has been obtained from recordings in anesthetized animals. We compared odor-elicited changes in firing rate of mitral cells in awake behaving mice and in anesthetized mice. We show that odor-elicited changes in mitral cell firing rate were larger and more frequently observed in the anesthetized than in the awake condition. Only 27% of mitral cells that showed a response to odors in the anesthetized state were also odor responsive in the awake state. The amplitude of their response in the awake state was smaller, and some of the responses changed sign compared with their responses in the anesthetized state. The odor representation in the olfactory bulb is therefore sparser in awake behaving mice than in anesthetized preparations. A qualitative explanation of the mechanism responsible for this phenomenon is proposed.
Masking by Inaudible Sounds and the Linearity of Temporal Summation
Authors: Plack Christopher J. , Oxenham Andrew J. , Drga Vit
Published: August 2006

Many natural sounds, including speech and animal vocalizations, involve rapid sequences that vary in spectrum and amplitude. Each sound within a sequence has the potential to affect the audibility of subsequent sounds in a process known as forward masking. Little is known about the neural mechanisms underlying forward masking, particularly in more realistic situations in which multiple sounds follow each other in rapid succession. A parsimonious hypothesis is that the effects of consecutive sounds combine linearly, so that the total masking effect is a simple sum of the contributions from the individual maskers. The experiment reported here tests a counterintuitive prediction of this linear-summation hypothesis, namely that a sound that itself is inaudible should, under certain circumstances, affect the audibility of subsequent sounds. The results show that, when two forward maskers are combined, the second of the two maskers can continue to produce substantial masking, even when it is completely masked by the first masker. Thus, inaudible sounds can affect the perception of subsequent sounds. A model incorporating instantaneous compression (reflecting the nonlinear response of the basilar membrane in the cochlea), followed by linear summation of the effects of the maskers, provides a good account of the data. Despite the presence of multiple sources of nonlinearity in the auditory system, masking effects by sequential sounds combine in a manner that is well captured by a time-invariant linear system.
Endogenous Cannabinoid Signaling through the CB1Receptor Is Essential for Cerebellum-Dependent Discrete Motor Learning
Authors: Kishimoto Yasushi , Kano Masanobu
Published: August 2006

Cannabinoids exert their psychomotor actions through the CB1cannabinoid receptor in the brain. Genetic deletion of CB1in mice causes various symptoms, including changes in locomotor activity, increased ring catalepsy, supraspinal hypoalgesia, and impaired memory extinction. Although the cerebellar cortex contains the highest level of CB1, severe cerebellum-related functional deficits have not been reported in CB1knock-out mice. To clarify the roles of CB1in cerebellar function, we subjected CB1knock-out mice to a delay version of classical eyeblink conditioning. This paradigm is a test for cerebellum-dependent discrete motor learning, in which conditioned stimulus (CS) (352 ms tone) and unconditioned stimulus (US) (100 ms periorbital electrical shock) are coterminated. We found that delay eyeblink conditioning performance was severely impaired in CB1knock-out mice. In contrast, they exhibited normal performance in a trace version of eyeblink conditioning with 500 ms stimulus-free interval intervened between the CS offset and the US onset. This paradigm is a test for hippocampus-dependent associative learning. Sensitivity of CB1knock-out mice to CS or US was normal, suggesting that impaired delay eyeblink conditioning is attributable to defects in association of responses to CS and US. We also found that intraperitoneal injection of the CB1antagonist SR141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole carboxamide] to wild-type mice caused severe impairment in acquisition but not extinction of delay eyeblink conditioning. SR141716A treatment had no effect on trace eyeblink conditioning with a 500 or 750 ms trace interval. These results indicate that endogenous cannabinoid signaling through CB1is essential for cerebellum-dependent discrete motor learning, especially for its acquisition.
Rule Learning and Reward Contingency Are Associated with Dissociable Patterns of Dopamine Activation in the Rat Prefrontal Cortex, Nucleus Accumbens, and Dorsal Striatum
Authors: Stefani Mark R. , Moghaddam Bita
Published: August 2006

The midbrain dopamine system has been ascribed roles in reward expectancy, error detection, prediction, and memory. However, these theories typically do not differentiate between dopamine response and action in different forebrain terminal fields. We measured dopamine release in the prefrontal cortex (PFC), nucleus accumbens (NAc), and dorsal striatum (DS) of rats exposed to the same maze apparatus under three behavioral conditions: a set-shift task in which reward depended on discrimination learning and extradimensional set-shifting, a yoked condition in which reward was intermittent and not under the control of the subject, and a “reward-retrieval” variant in which reward was certain on every trial. We found dissociable patterns of dopamine release associated with learning, uncertainty, and reward. Dopamine increased in all three regions when reward was contingent on rule learning and shifting or was uncertain. These increases were sustained after behavior. There was a significant correlation between the magnitude of increase in PFC dopamine and the rapidity with which rats shifted between discrimination rules. In the yoke condition, in which the receipt of reward was always uncertain, the opposite relationship between dopamine levels and likelihood of reward was observed. Predictable, noncontingent reward was associated with increased dopamine levels in the NAc and DS. In contrast, PFC dopamine did not increase significantly above baseline levels. Thus, the dopaminergic projections to the PFC and nucleus accumbens were selectively, yet differentially, activated in situations of uncertainty and cognitive demand, whereas the dopaminergic projection to the DS responded independently of task differences in learning and reward.
Trace Conditioning and the Hippocampus: The Importance of Contiguity
Authors: Bangasser Debra A. , Waxler David E. , Santollo Jessica , Shors Tracey J.
Published: August 2006

Trace conditioning, a form of classical conditioning in which the presentation of the conditioned stimulus (CS) and the unconditioned stimulus (US) is separated in time by an interstimulus interval, requires an intact hippocampus. In contrast, classical conditioning procedures in which the CS and US are not separated by an interstimulus interval (i.e., delay conditioning procedures) typically do not (Solomon et al., 1986). However, why trace conditioning is dependent on the hippocampus is unknown. Several theories suggest that it is specifically the discontiguity between the CS and US in trace conditioning that critically engages the hippocampus. However, there are other explanations that do not depend on discontiguity. To determine whether the lack of contiguity renders trace conditioning hippocampal dependent, we designed a “contiguous trace conditioning” (CTC) paradigm in which CS–US contiguity is restored by re-presenting the CS simultaneously with the US. Although rats with excitotoxic lesions of the hippocampus could not learn a standard trace fear-conditioning paradigm, lesioned rats trained on CTC showed significant conditioning, at levels similar to those with sham surgeries. Importantly, lesioned rats trained solely with simultaneous CS–US presentations did not demonstrate conditioning. Together, these data suggest that rats with hippocampal lesions can form a memory of a trace CS–US association when contiguity is restored. Therefore, the dependence of traditional trace paradigms on the hippocampus can be attributed to the absence of temporal contiguity.
Diversity of Gain Modulation by Noise in Neocortical Neurons: Regulation by the Slow Afterhyperpolarization Conductance
Authors: Higgs Matthew H. , Slee Sean J. , Spain William J.
Published: August 2006

Neuronal firing is known to depend on the variance of synaptic input as well as the mean input current. Several studies suggest that input variance, or “noise,” has a divisive effect, reducing the slope or gain of the firing frequency–current (f–I) relationship. We measured the effects of current noise onf–Irelationships in pyramidal neurons and fast-spiking (FS) interneurons in slices of rat sensorimotor cortex. In most pyramidal neurons, noise had a multiplicative effect on the steady-statef–Irelationship, increasing gain. In contrast, noise reduced gain in FS interneurons. Gain enhancement in pyramidal neurons increased with stimulus duration and was correlated with the amplitude of the slow afterhyperpolarization (sAHP), a major mechanism of spike-frequency adaptation. The 5-HT2receptor agonist α-methyl-5-HT reduced the sAHP and eliminated gain increases, whereas augmenting the sAHP conductance by spike-triggered dynamic-current clamp enhanced the gain increase. These results indicate that the effects of noise differ fundamentally between classes of neocortical neurons, depending on specific biophysical properties including the sAHP conductance. Thus, noise from background synaptic input may enhance network excitability by increasing gain in pyramidal neurons with large sAHPs and reducing gain in inhibitory FS interneurons.
Isoform Specificity of PKC Translocation in LivingAplysiaSensory Neurons and a Role for Ca2+-Dependent PKC APL I in the Induction of Intermediate-Term Facilitation
Authors: Zhao Yali , Leal Karina , Abi-Farah Carole , Martin Kelsey C. , Sossin Wayne S. , Klein Marc
Published: August 2006

Protein kinase Cs (PKCs) are important effectors of synaptic plasticity. InAplysia, there are two major phorbol ester-activated PKCs, Ca2+-activated PKC Apl I and Ca2+-independent PKC Apl II. Functional Apl II, but not Apl I, in sensory neurons is required for a form of short-term facilitation induced at sensorimotor synapses by the facilitatory transmitter serotonin (5-HT). Because PKCs are activated by translocating from the cytoplasm to the membrane, we used fluorescently tagged PKCs to determine the isoform and cell-type specificity of translocation in livingAplysianeurons. In Sf9 cells, low levels of diacylglycerol translocate Apl II, but not Apl I, which requires calcium for translocation at low concentrations of diacylglycerol. Accordingly, application of 5-HT toAplysiasensory neurons in the absence of neuronal firing translocates Apl II, but not Apl I, consistent with the role of Apl II in short-term facilitation. This translocation is observed in sensory neurons, but not in motor neurons. Apl I translocates only if 5-HT is coupled to firing in the sensory neuron; firing alone is ineffective. Because combined 5-HT and firing are required for the induction of one type of intermediate-term facilitation at these synapses, we asked whether this form of synaptic plasticity involves activation of Apl I. We report here that dominant-negative Apl I, but not Apl II, blocks intermediate-term facilitation. Thus, different isoforms of PKC translocate under different conditions to mediate distinct types of synaptic plasticity: Ca2+-independent Apl II is involved in short-term facilitation, and Ca2+-dependent Apl I contributes to intermediate-term facilitation.
GABAB(1)Receptor Isoforms Differentially Mediate the Acquisition and Extinction of Aversive Taste Memories
Authors: Jacobson Laura H. , Kelly Peter H. , Bettler Bernhard , Kaupmann Klemens , Cryan John F.
Published: August 2006

Conditioned taste aversion (CTA) is a form of aversive memory in which an association is made between a consumed substance and a subsequent malaise. CTA is a critical mechanism for the successful survival, and hence evolution, of most animal species. The role of excitatory neurotransmitters in the neurochemical mechanisms of CTA is well recognized; however, less is known about the involvement of inhibitory receptor systems. In particular, the potential functions of metabotropic GABABreceptors in CTA have not yet been fully explored. GABABreceptors are metabotropic GABA receptors that are comprised of two subunits, GABAB(1)and GABAB(2), which form heterodimers. TheGabbr1gene is transcribed into two predominant isoforms, GABAB(1a)and GABAB(1b), which differ in sequence primarily by the inclusion of a pair of sushi domains (also known as short consensus repeats) in the GABAB(1a)N terminus. The behavioral function of mammalian GABAB(1)receptor isoforms is currently unknown. Here, using a point mutation strategy in mice, we demonstrate that these two GABAB(1)receptor isoforms are differentially involved in critical components of CTA. In contrast to GABAB(1b)−/−and wild-type mice, GABAB(1a)−/−mice failed to acquire CTA. In contrast, GABAB(1b)−/−mice robustly acquired CTA but failed to show any extinction of this aversion. The data demonstrate that GABABreceptors are involved in both the acquisition and extinction of CTA; however, receptors containing the GABAB(1a)or the GABAB(1b)isoform differentially contribute to the mechanisms used to learn and remember the salience of aversive stimuli.
Phenotypes ofDrosophilaBrain Neurons in Primary Culture Reveal a Role for Fascin in Neurite Shape and Trajectory
Authors: Kraft Robert , Escobar Mindy M. , Narro Martha L. , Kurtis Jackie L. , Efrat Alon , Barnard Kobus , Restifo Linda L.
Published: August 2006

Subtle cellular phenotypes in the CNS may evade detection by routine histopathology. Here, we demonstrate the value of primary culture for revealing genetically determined neuronal phenotypes at high resolution. Gamma neurons ofDrosophila melanogastermushroom bodies (MBs) are remodeled during metamorphosis under the control of the steroid hormone 20-hydroxyecdysone (20E).In vitro, wild-type γ neurons retain characteristic morphogenetic features, notably a single axon-like dominant primary process and an arbor of short dendrite-like processes, as determined with microtubule-polarity markers. We found three distinct genetically determined phenotypes of cultured neurons from grossly normal brains, suggesting that subtlein vivoattributes are unmasked and amplifiedin vitro. First, the neurite outgrowth response to 20E is sexually dimorphic, being much greater in female than in male γ neurons. Second, the γ neuron-specific “naked runt” phenotype results from transgenic insertion of an MB-specific promoter. Third, the recessive, pan-neuronal “filagree” phenotype maps tosinged, which encodes the actin-bundling protein fascin. Fascin deficiency does not impair the 20E response, but neurites fail to maintain their normal, nearly straight trajectory, instead forming curls and hooks. This is accompanied by abnormally distributed filamentous actin. This is the first demonstration of fascin function in neuronal morphogenesis. Our findings, along with the regulation of humanFascin1(OMIM 602689) by CREB (cAMP response element-binding protein) binding protein, suggestFSCN1as a candidate gene for developmental brain disorders. We developed an automated method of computing neurite curvature and classifying neurons based on curvature phenotype. This will facilitate detection of genetic and pharmacological modifiers of neuronal defects resulting from fascin deficiency.
The Circadian Clock Modulates Core Steps in Long-Term Memory Formation inAplysia
Authors: Lyons Lisa C. , Collado Maria Sol , Khabour Omar , Green Charity L. , Eskin Arnold
Published: August 2006

The circadian clock modulates the induction of long-term sensitization (LTS) inAplysiasuch that long-term memory formation is significantly suppressed when animals are trained at night. We investigated whether the circadian clock modulated core molecular processes necessary for memory formationin vivoby analyzing circadian regulation of basal and LTS-induced levels of phosphorylated mitogen-activated protein kinase (P-MAPK) andAplysiaCCAAT/enhancer binding protein (ApC/EBP). No basal circadian regulation occurred for P-MAPK or total MAPK in pleural ganglia. In contrast, the circadian clock regulated basal levels ofApC/EBP protein with peak levels at night, antiphase to the rhythm in LTS. Importantly, LTS training during the (subjective) day produced greater increases in P-MAPK andApC/EBP than training at night. Thus, circadian modulation of LTS occurs, at least in part, by suppressing changes in key proteins at night. Rescue of long-term memory formation at night required both facilitation of MAPK and transcription in conjunction with LTS training, confirming that the circadian clock at night actively suppresses MAPK activation and transcription involved in memory formation.

The circadian clock appears to modulate LTS at multiple levels. 5-HT levels are increased more when animals receive LTS training during the (subjective) day compared with the night, suggesting circadian modulation of 5-HT release. Circadian modulation also occurred downstream of 5-HT release because animals treated with 5-HT to induce LTS exhibited significantly greater LTS when treated during the (subjective) day compared with the night. Together, our studies suggest that the circadian clock modulates LTS at multiple steps and locations during the formation of long-term memory.
Complete Dissociation of Motor Neuron Death from Motor Dysfunction by Bax Deletion in a Mouse Model of ALS
Authors: Gould Thomas W. , Buss Robert R. , Vinsant Sharon , Prevette David , Sun Woong , Knudson C. Michael , Milligan Carol E. , Oppenheim Ronald W.
Published: August 2006

The death of cranial and spinal motoneurons (MNs) is believed to be an essential component of the pathogenesis of amyotrophic lateral sclerosis (ALS). We tested this hypothesis by crossing Bax-deficient mice with mice expressing mutant superoxide dismutase 1 (SOD1), a transgenic model of familial ALS. Although Bax deletion failed to prevent neuromuscular denervation and mitochondrial vacuolization, MNs were completely rescued from mutant SOD1-mediated death. However, Bax deficiency extended lifespan and delayed the onset of motor dysfunction of SOD1 mutants, suggesting that Bax acts via a mechanism distinct from cell death activation. Consistent with this idea, Bax elimination delayed the onset of neuromuscular denervation, which began long before the activation of cell death proteins in SOD1 mutants. Additionally, we show that denervation preceded accumulation of mutant SOD1 within MNs and astrogliosis in the spinal cord, which are also both delayed in Bax-deficient SOD1 mutants. Interestingly, MNs exhibited mitochondrial abnormalities at the innervated neuromuscular junction at the onset of neuromuscular denervation. Additionally, both MN presynaptic terminals and terminal Schwann cells expressed high levels of mutant SOD1 before MNs withdrew their axons. Together, these data support the idea that clinical symptoms in the SOD1 G93A model of ALS result specifically from damage to the distal motor axon and not from activation of the death pathway, and cast doubt on the utility of anti-apoptotic therapies to combat ALS. Furthermore, they suggest a novel, cell death-independent role for Bax in facilitating mutant SOD1-mediated motor denervation.