bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct pools of cAMP centre on different isoforms of adenylyl cyclase in pituitary-derived GH3B6 cells
Authors: Wachten Sebastian , Masada Nanako , Ayling Laura-Jo , Ciruela Antonio , Nikolaev Viacheslav O. , Lohse Martin J. , Cooper Dermot M. F.
Published: December 2009

Microdomains have been proposed to explain specificity in the myriad of possible cellular targets of cAMP. Local differences in cAMP levels can be generated by phosphodiesterases, which control the diffusion of cAMP. Here, we address the possibility that adenylyl cyclases, the source of cAMP, can be primary architects of such microdomains. Distinctly regulated adenylyl cyclases often contribute to total cAMP levels in endogenous cellular settings, making it virtually impossible to determine the contribution of a specific isoform. To investigate cAMP dynamics with high precision at the single-isoform level, we developed a targeted version of Epac2-camps, a cAMP sensor, in which the sensor was tagged to a catalytically inactive version of the Ca2+-stimulable adenylyl cyclase 8 (AC8). This sensor, and less stringently targeted versions of Epac2-camps, revealed opposite regulation of cAMP synthesis in response to Ca2+ in GH3B6 pituitary cells. Ca2+ release triggered by thyrotropin-releasing hormone stimulated the minor endogenous AC8 species. cAMP levels were decreased by inhibition of AC5 and AC6, and simultaneous activation of phosphodiesterases, in different compartments of the same cell. These findings demonstrate the existence of distinct adenylyl-cyclase-centered cAMP microdomains in live cells and open the door to their molecular micro-dissection.
Modulation of Wnt signaling by the nuclear localization of cellular FLIP-L
Authors: Katayama Ryohei , Ishioka Toshiyasu , Takada Shinji , Takada Ritsuko , Fujita Naoya , Tsuruo Takashi , Naito Mikihiko
Published: December 2009

Cellular FLIP (cFLIP) inhibits the apoptosis signaling initiated by death receptor ligation. We previously reported that a long form of cFLIP (cFLIP-L) enhances Wnt signaling via inhibition of β-catenin ubiquitylation. In this report, we present evidence that cFLIP-L translocates into the nucleus, which could have a role in modulation of Wnt signaling. cFLIP-L has a functional bipartite nuclear localization signal (NLS) at the C-terminus. Wild-type cFLIP-L (wt-FLIP-L) localizes in both the nucleus and cytoplasm, whereas NLS-mutated cFLIP-L localizes predominantly in the cytoplasm. cFLIP-L also has a nuclear export signal (NES) near the NLS, and leptomycin B, an inhibitor of CRM1-dependent nuclear export, increases the nuclear accumulation of cFLIP-L, suggesting that it shuttles between the nucleus and cytoplasm. Expression of mutant cFLIP-L proteins with a deletion or mutations in the NLS and NES confers resistance to Fas-mediated apoptosis, as does wt-FLIP-L, but they do not enhance Wnt signaling, which suggests an important role of the C-terminus of cFLIP-L in Wnt-signaling modulation. When wt-FLIP-L is expressed in the cytoplasm by conjugation with exogenous NES (NES-FLIP-L), Wnt signaling is not enhanced, whereas the NES-FLIP-L increases cytoplasmic β-catenin as efficiently as wt-FLIP-L. cFLIP-L physically interacts with the reporter plasmid for Wnt signaling, but not with the control plasmid. These results suggest a role for nuclear cFLIP-L in the modulation of Wnt signaling.
Visualizing cellular processes at the molecular level by cryo-electron tomography
Authors: Ben-Harush Kfir , Maimon Tal , Patla Israel , Villa Elizabeth , Medalia Ohad
Published: December 2009

The cellular landscape rapidly changes throughout the biological processes that transpire within a cell. For example, the cytoskeleton is remodeled within fractions of a second. Therefore, reliable structural analysis of the cell requires approaches that allow for instantaneous arrest of functional states of a given process while offering the best possible preservation of the delicate cellular structure. Electron tomography of vitrified but otherwise unaltered cells (cryo-ET) has proven to be the method of choice for three-dimensional (3D) reconstruction of cellular architecture at a resolution of 4-6 nm. Through the use of cryo-ET, the 3D organization of macromolecular complexes and organelles can be studied in their native environment in the cell. In this Commentary, we focus on the application of cryo-ET to study eukaryotic cells – in particular, the cytoskeletal-driven processes that are involved in cell movements, filopodia protrusion and viral entry. Finally, we demonstrate the potential of cryo-ET to determine structures of macromolecular complexes in situ, such as the nuclear pore complex.
Epigenetics and transgenerational transfer: a physiological perspective
Authors: Ho D. H. , Burggren W. W.
Published: December 2009

Epigenetics, the transgenerational transfer of phenotypic characters without modification of gene sequence, is a burgeoning area of study in many disciplines of biology. However, the potential impact of this phenomenon on the physiology of animals is not yet broadly appreciated, in part because the phenomenon of epigenetics is not typically part of the design of physiological investigations. Still enigmatic and somewhat ill defined is the relationship between the overarching concept of epigenetics and interesting transgenerational phenomena (e.g. ‘maternal/parental effects’) that alter the physiological phenotype of subsequent generations. The lingering effect on subsequent generations of an initial environmental disturbance in parent animals can be profound, with genes continuing to be variously silenced or expressed without an associated change in gene sequence for many generations. Known epigenetic mechanisms involved in this phenomenon include chromatin remodeling (DNA methylation and histone modification), RNA-mediated modifications (non-coding RNA and microRNA), as well as other less well studied mechanisms such as self-sustaining loops and structural inheritance. In this review we: (1) discuss how the concepts of epigenetics and maternal effects both overlap with, and are distinct from, each other; (2) analyze examples of existing animal physiological studies based on these concepts; and (3) offer a construct by which to integrate these concepts into the design of future investigations in animal physiology.
On the role of form and kinematics on the hydrodynamics of self-propelled body/caudal fin swimming
Authors: Borazjani I. , Sotiropoulos F.
Published: December 2009

We carry out fluid–structure interaction simulations of self-propelled virtual swimmers to investigate the effects of body shape (form) and kinematics on the hydrodynamics of undulatory swimming. To separate the effects of form and kinematics, we employ four different virtual swimmers: a carangiform swimmer (i.e. a mackerel swimming like mackerel do in nature); an anguilliform swimmer (i.e. a lamprey swimming like lampreys do in nature); a hybrid swimmer with anguilliform kinematics but carangiform body shape (a mackerel swimming like a lamprey); and another hybrid swimmer with carangiform kinematics but anguilliform body shape (a lamprey swimming like a mackerel). By comparing the performance of swimmers with different kinematics but similar body shapes we study the effects of kinematics whereas by comparing swimmers with similar kinematics but different body shapes we study the effects of form. We show that the anguilliform kinematics not only reaches higher velocities but is also more efficient in the viscous (Re∼102) and transitional (Re∼103) regimes. However, in the inertial regime (Re=∞) carangiform kinematics achieves higher velocities and is also more efficient than the anguilliform kinematics. The mackerel body achieves higher swimming speeds in all cases but is more efficient in the inertial regime only whereas the lamprey body is more efficient in the transitional regime. We also show that form and kinematics have little overall effect on the 3-D structure of the wake (i.e. single vs double row vortex streets), which mainly depends on the Strouhal number. Nevertheless, body shape is found to somewhat affect the small-scale features and complexity of the vortex rings shed by the various swimmers.
Individual variation and repeatability in aerobic and anaerobic swimming performance of European sea bass,Dicentrarchus labrax
Authors: Marras S. , Claireaux G. , McKenzie D. J. , Nelson J. A.
Published: December 2009

Studies of inter-individual variation in fish swimming performance may provide insight into how selection has influenced diversity in phenotypic traits. We investigated individual variation and short-term repeatability of individual swimming performance by wild European sea bass in a constant acceleration test (CAT). Fish were challenged with four consecutive CATs with 5 min rest between trials. We measured maximum anaerobic speed at exhaustion (UCAT), gait transition speed from steady aerobic to unsteady anaerobic swimming (Ugt), routine metabolic rate (RMR), post-CAT maximum metabolic rate (MMR), aerobic scope and recovery time from the CATs. Fish achieved significantly higher speeds during the first CAT (UCAT=170 cm s–1), and had much more inter-individual variation in performance (coefficient of variation, CV=18.43%) than in the subsequent three tests (UCAT=134 cm s–1; CV=7.3%), which were very repeatable among individuals. The individual variation in UCAT in the first trial could be accounted for almost exclusively by variation in anaerobic burst-and-coast performance beyond Ugt. The Ugt itself varied substantially between individuals (CV=11.4%), but was significantly repeatable across all four trials. Individual RMR and MMR varied considerably, but the rank order of post-CAT MMR was highly repeatable. Recovery rate from the four CATs was highly variable and correlated positively with the first UCAT (longer recovery for higher speeds) but negatively with RMR and aerobic scope (shorter recovery for higher RMR and aerobic scope). This large variation in individual performance coupled with the strong correlations between some of the studied variables may reflect divergent selection favouring alternative strategies for foraging and avoiding predation.
Variation of the neurofilament medium KSP repeat sub-domain across mammalian species: implications for altering axonal structure
Authors: Barry D. M. , Carpenter C. , Yager C. , Golik B. , Barry K. J. , Shen H. , Mikse O. , Eggert L. S. , Schulz D. J. , Garcia M. L.
Published: December 2009

The evolution of larger mammals resulted in a corresponding increase in peripheral nerve length. To ensure optimal nervous system functionality and survival, nerve conduction velocities were likely to have increased to maintain the rate of signal propagation. Increases of conduction velocities may have required alterations in one of the two predominant properties that affect the speed of neuronal transmission: myelination or axonal diameter. A plausible mechanism to explain faster conduction velocities was a concomitant increase in axonal diameter with evolving axonal length. The carboxy terminal tail domain of the neurofilament medium subunit is a determinant of axonal diameter in large caliber myelinated axons. Sequence analysis of mammalian orthologs indicates that the neurofilament medium carboxy terminal tail contains a variable lysine–serine–proline (KSP) repeat sub-domain flanked by two highly conserved sub-domains. The number of KSP repeats within this region of neurofilament medium varies among species. Interestingly, the number of repeats does not change within a species, suggesting that selective pressure conserved the number of repeats within a species. Mapping KSP repeat numbers onto consensus phylogenetic trees reveals independent KSP expansion events across several mammalian clades. Linear regression analyses identified three subsets of mammals, one of which shows a positive correlation in the number of repeats with head–body length. For this subset of mammals, we hypothesize that variations in the number of KSP repeats within neurofilament medium carboxy terminal tail may have contributed to an increase in axonal caliber, increasing nerve conduction velocity as larger mammals evolved.
Prioritizing blood flow: cardiovascular performance in response to the competing demands of locomotion and digestion for the Burmese python,Python molurus
Authors: Secor Stephen M. , White Scott E.
Published: December 2009

Individually, the metabolic demands of digestion or movement can be fully supported by elevations in cardiovascular performance, but when occurring simultaneously, vascular perfusion may have to be prioritized to either the gut or skeletal muscles. Burmese pythons (Python molurus) experience similar increases in metabolic rate during the digestion of a meal as they do while crawling, hence each would have an equal demand for vascular supply when these two actions are combined. To determine, for the Burmese python, whether blood flow is prioritized when snakes are digesting and moving, we examined changes in cardiac performance and blood flow in response to digestion, movement, and the combination of digestion and movement. We used perivascular blood flow probes to measure blood flow through the left carotid artery, dorsal aorta, superior mesenteric artery and hepatic portal vein, and to calculate cardiac output, heart rate and stroke volume. Fasted pythons while crawling experienced a 2.7- and 3.3-fold increase, respectively, in heart rate and cardiac output, and a 66% decrease in superior mesenteric flow. During the digestion of a rodent meal equaling in mass to 24.7% of the snake's body mass, heart rate and cardiac output increased by 3.3- and 4.4-fold, respectively. Digestion also resulted in respective 11.6- and 14.1-fold increases in superior mesenteric and hepatic portal flow. When crawling while digesting, cardiac output and dorsal aorta flow increased by only 21% and 9%, respectively, a modest increase compared with that when they start to crawl on an empty stomach. Crawling did triggered a significant reduction in blood flow to the digesting gut, decreasing superior mesenteric and hepatic portal flow by 81% and 47%, respectively. When faced with the dual demands of digestion and crawling, Burmese pythons prioritize blood flow, apparently diverting visceral supply to the axial muscles.
Slight differences in incubation temperature affect early growth and stress endocrinology of wood duck (Aix sponsa) ducklings
Authors: DuRant S. E. , Hepp G. R. , Moore I. T. , Hopkins B. C. , Hopkins W. A.
Published: December 2009

Early developmental experiences, such as incubation conditions, can have important consequences for post-hatching fitness in birds. Although the effects of incubation temperature on phenotype of avian hatchlings are poorly understood, recent research suggests that subtle changes in incubation conditions can influence hatchling characteristics, including body size and condition. We designed an experiment to explore the effects of incubation temperature on hatching success, survival to 9 days post hatch, growth and the hypothalamo–pituitary–adrenal (HPA) axis in wood ducks (Aix sponsa). Wood duck eggs were collected from nest boxes and experimentally incubated at three temperatures (35.0, 35.9 and 37.0°C), each falling within the range of temperatures of naturally incubated wood duck nests. Survival and growth were monitored in ducklings fed ad libitum for 9 days post hatch. In addition, baseline and stress-induced plasma corticosterone concentrations were measured in 2 and 9 day old ducklings. Hatching success and survival to 9 days was greatest in ducks incubated at the intermediate temperature. Ducklings incubated at 35.9°C and 37.0°C had 43% higher growth rates than ducklings incubated at 35.0°C. In addition, ducklings incubated at 35.0°C had higher baseline (17–50%) and stress-induced (32–84%) corticosterone concentrations than ducklings incubated at 35.9°C and 37.0°C at 2 and 9 days post hatch. We also found a significant negative correlation between body size and plasma corticosterone concentrations (baseline and stress-induced) in 9 day old ducklings. To our knowledge, this is the first study to demonstrate that thermal conditions experienced during embryonic development can influence the HPA axis of young birds. Our results illustrate that subtle changes (<1.0°C) in the incubation environment can have important consequences for physiological traits important to fitness.
Scanning sonar of rolling porpoises during prey capture dives
Authors: Akamatsu T. , Wang D. , Wang K. , Li S. , Dong S.
Published: December 2009

Dolphins and porpoises have excellent biosonar ability, which they use for navigation, ranging and foraging. However, the role of biosonar in free-ranging small cetaceans has not been fully investigated. The biosonar behaviour and body movements of 15 free-ranging finless porpoises (Neophocaena phocaenoides) were observed using electronic tags attached to the animals. The porpoises often rotated their bodies more than 60 deg., on average, around the body axis in a dive bout. This behaviour occupied 31% of the dive duration during 186 h of effective observation time. Rolling dives were associated with extensive searching effort, and 23% of the rolling dive time was phonated, almost twice the phonation ratio of upright dives. Porpoises used short inter-click interval sonar 4.3 times more frequently during rolling dives than during upright dives. Sudden speed drops, which indicated that an individual turned around, occurred 4.5 times more frequently during rolling dives than during upright dives. Together, these data suggest that the porpoises searched extensively for targets and rolled their bodies to enlarge the search area by changing the narrow beam axis of the biosonar. Once a possible target was detected, porpoises frequently produced short-range sonar sounds. Continuous searching for prey and frequent capture trials appeared to occur during rolling dives of finless porpoises. In contrast, head movements ranging ±2 cm, which can also change the beam axis, were regularly observed during both dives. Head movements might assist in instant assessment of the arbitrary direction by changing the beam axis rather than prey searching and pursuit.
Profiting from Knowledge Management: The Impact of Time and Experience
Authors: Ko Dong-Gil , Dennis Alan R.
Published: December 2009

Although many organizations are implementing knowledge management systems (KMS), there is little empirical evidence about whether KMS use can improve individual performance, and how time and experience influence the value derived from KMS use. Using hierarchical linear modeling (HLM) statistical analysis, we examined the impact of using a codification-based KMS on the sales performance of 2,154 sales representatives in a pharmaceutical firm over a 24-month period. We found that KMS had significant positive impacts on individual performance and that these performance benefits grew over time. Moreover, experience moderated the relationship between KMS use and individual performance. Knowledge workers with more experience were able to more quickly absorb and apply the knowledge from the KMS than were those with less experience, who took longer to benefit from KMS use. However, over time experience played a diminishing role in leveraging performance gains from KMS use, and knowledge workers with less experience eventually derived similar performance benefits as those of their more experienced counterparts.
Research Commentary—Information Transparency in Business-to-Consumer Markets: Concepts, Framework, and Research Agenda
Authors: Granados Nelson , Gupta Alok , Kauffman Robert J.
Published: December 2009

The Internet has brought about significant changes in the availability of market information in many industries. E-commerce technologies provide sellers with opportunities to design electronic mercantile mechanisms that reveal, conceal, bias, and distort market information, depending on their goals and market position (e.g., suppliers versus intermediaries). In particular, in information-intensive industries where electronic markets play an important role, many firms are using advanced technologies to put innovative strategies into play that are based on the provision of differential information to their customers. We examine the role of information transparency in electronic markets. We contend that there is an opportunity to develop research on sellers' strategies regarding information disclosure to customers and competitors. For that purpose, we develop a set of concepts and a framework to guide future research. We then propose an interdisciplinary agenda for research on the emerging and increasingly important topic of transparency strategy, which we define as the set of policies and decisions that a firm makes to disclose, conceal, bias, or distort market information.
Contracting Efficiency and New Firm Survival in Markets Enabled by Information Technology
Authors: Susarla Anjana , Barua Anitesh
Published: December 2009

Application service providers (ASP), who host and maintain information technology (IT) applications across the Internet, emerged as an innovation in the way IT services are delivered to client firms. In spite of many potential benefits of this model, ASPs experienced business failure and high rates of exit. Drawing on agency theory, we argue that the efficiency of contracting arrangements between ASPs and client organizations is an important determinant of ASP survival. We test this prediction using a unique data set combining multiple sources that allows us to track an ASP from the year of founding through the beginning of 2006. Contractual misalignment, or adopting contracts mismatched with the underlying agency costs, significantly lowers the probability of survival of service providers in the ASP marketplace. The impact of misalignment is particularly severe when coupled with adjustment costs that impede the transition to aligned contracts. To account for potential heterogeneity in ASPs' knowledge of contracting, we test for endogenous self-selection of ASPs in the relationship between contractual misalignment and survival. Our results are robust to a variety of model specifications as well as alternate explanations of survival from multiple theoretical domains.
Analyzing Sharing in Peer-to-Peer Networks Under Various Congestion Measures
Authors: Johar Monica , Menon Syam , Mookerjee Vijay
Published: December 2009

Historically, the use of peer-to-peer (P2P) networks has been limited primarily to user-initiated exchanges of (mostly music) files over the Internet. This traditional view of P2P networks is changing, however, and the use of P2P networks has been suggested for delivering general-purpose content over the Web (or corporate intranets), even in real time. We analyze sharing in a P2P community in this new context under three different congestion measures: delay, jitter, and packet loss. Sharing is important to study in the presence of congestion because most existing research on P2P networks views congestion in the network as a relatively insignificant criterion. However, when delivering general-purpose content, congestion and its relationship to sharing is a critical factor that influences end-user performance. This paper looks at P2P networks from this new perspective by explicitly considering the effects of congestion on user incentives for sharing. We also propose a simple incentive mechanism that induces socially optimal sharing.
A Deterministic Smart Market Model for Groundwater
Authors: Raffensperger John F. , Milke Mark W. , Read E. Grant
Published: December 2009

Efficient management of water requires balancing environmental needs, externality considerations, and economic efficiency. Toward that end, this paper presents a deterministic linear program that could be used to operate a smart spot market for groundwater. The market design uses the existing hydrological programs MODFLOW and GWM along with standard linear programming methods. In principle, a market could be set up anywhere that a MODFLOW model is available. The market design has parallels to markets in the electricity and gas sectors, which we discuss. We present a case study with notional bids for Marlborough, New Zealand. Our approach would reduce transaction costs for a water market, reduce users' risk, and increase the reliability of environmental flows. We discuss a number of cautions and limitations to the model and recommend further work on introducing a stochastic framework to the model.
Clopidogrel Hypersensitivity: A Novel Multi-Day Outpatient Oral Desensitization Regimen
Authors: Fajt Merritt , Petrov Andrej
Published: December 2009

BACKGROUND

Clopidogrel hypersensitivity has posed a problem for the acute treatment and long-term care of a particular patient population with coronary artery disease and stent placement. Patients with clopidogrel hypersensitivity have had an increased risk of hypersensitivity reactions, including anaphylaxis, if they ingest clopidogrel without undergoing an oral desensitization procedure. The previously published desensitization protocols have either been performed in the intensive care unit, requiring significant cost and healthcare utilization, or have required a full-day outpatient commitment on behalf of the patient.

OBJECTIVE

To determine whether a multi-day outpatient oral clopidogrel desensitization protocol is effective and safe for patients with clopidogrel hypersensitivity.

METHODS

gWe retrospectively assessed the efficacy of a 10-dose outpatient multiday clopidogrel desensitization protocol performed in a university allergy-immunology center from April 2006 to October 2008 in patients with clopidogrel hypersensitivity. Patients were desensitized over 2–3 half-day clinical visits and were able to go home between desensitization sessions. A preliminary cost analysis was performed using the average of actual costs for the outpatient clopidogrel desensitization procedure and was compared with the average cost for an inpatient oral desensitization completed at our institution.

RESULTS

Eight patients with coronary artery disease, cardiac stent placement, and clopidogrel hypersensitivity underwent an outpatient multi-day oral clopidogrel desensitization procedure. All patients were successfully desensitized with the multi-day protocol without complications. No patient had recurrence of allergic reaction 3 months after the procedure. A preliminary cost analysis demonstrated a lower cost for the outpatient compared to the inpatient oral clopidogrel desensitization protocol.

CONCLUSIONS

This outpatient 10-dose multi-day clopidogrel desensitization protocol is a safe and effective novel approach for the treatment of clopidogrel hypersensitivity in patients with coronary artery disease and cardiac stent placement. In addition to safety and efficacy, this protocol offers the patient the convenience of avoiding hospital admission or full-day time commitments.
Introduction: What works in investigative psychology?
Authors: Granhag Pär Anders , Vrij Aldert
Published: December 2009

This is an introduction to the special issue entitled ‘What works in investigative psychology?’, guest edited by Pär Anders Granhag and Aldert Vrij. This special issue focuses on eight research themes and aims to discuss how psychological research can help solve concrete problems that occur in investigative contexts.
A Conflict Revisited
Authors: Simmons John S.
Published: December 2009

The demand that public school students, especially at the high school level, write under time pressure has been the subject of debate for at least the last seventy-five years. As state after state has added a timed writing component to its testing apparatus in recent years, the debate has intensified. Those teachers who are alumni of the National Writing Project (NWP) continue to voice their belief that students internalize the Writing Process, an approach largely free from rigid time constraints. Proponents of featuring timed writing activity, however, continue to support the belief that such instructional demands will assist young people in coping with a variety of challenges in the real, i.e., adult world. The writer of this essay has attempted to present both sides of the argument.
Unknowing Susan Sontag's Regarding : Recutting with Georges Bataille
Authors: Kaplan Louis
Published: December 2009

This essay reviews and challenges Susan Sontag's use and abuse of Georges Bataille in her last book, Regarding the Pain of Others . Sontag takes up Bataille's understanding of and fascination with a group of Chinese torture (or lingchi ) photographs from the beginning of the twentieth century. Her somber reading glosses over Bataille's "anguished gaiety" in the face of these images and his post-Nietzschean tendency to laugh in the face of the impossible. Sontag overlooks Bataille's atheological and iconoclastic approach to these images steeped in transgression and non-knowledge in an attempt to frame his thinking as somehow full of religious meaning and allied to the Christian transmutation of suffering into sacrifice. Bound to a restricted (or Hegeilian) economy that remains servile to knowledge, Sontag's encounter with these images misses the opportunity to acknowledge the sovereign (and comic) operation as "absolute rending" inscribed in an excessive economy without reserve. Unlike Sontag in Regarding , Bataille looks to these deathly images in terms of an ethics of the impossible and risks bringing together non-knowledge, laughter, and tears. The essay concludes with a look at the limits of Sontag's analysis of Jeff Wall's Dead Troops Talk to underscore the profound practical joke that non-knowledge plays on those who would seek to turn death into a pedagogical exercise. The essay also suggests the relevance of Jean-Luc Nancy's thinking about such images (and photography in general) beyond the logic of representation and in terms of exposure (or of being posed in exteriority).
The Person in Between Moods and Affects
Authors: Rosfort René , Stanghellini Giovanni
Published: December 2009

Abstract:
In this paper, we consider the nature of two aspects of human emotional experience—moods and affects—in their relation to the concept of the person. We argue for the importance of the concept of the person in an approach to human emotional experience. This paper differentiates between the concepts of minimal self, extended self, and person. Furthermore, it offers a phenomenological proposal to understand the feeling dimension of moods and affects as critical for the differentiation of human emotional experience, and hence an understanding of that experience. By way of conclusion, we opt for a narrative approach to the question of the normative dimension of emotional experience to clarify the intricate relationship between mood and personhood.
Auditory Cortical Activity after Intracortical Microstimulation and Its Role for Sensory Processing and Learning
Authors: Deliano Matthias , Scheich Henning , Ohl Frank W.
Published: December 2009

Several studies have shown that animals can learn to make specific use of intracortical microstimulation (ICMS) of sensory cortex within behavioral tasks. Here, we investigate how the focal, artificial activation by ICMS leads to a meaningful, behaviorally interpretable signal. In natural learning, this involves large-scale activity patterns in widespread brain-networks. We therefore trained gerbils to discriminate closely neighboring ICMS sites within primary auditory cortex producing evoked responses largely overlapping in space. In parallel, during training, we recorded electrocorticograms (ECoGs) at high spatial resolution. Applying a multivariate classification procedure, we identified late spatial patterns that emerged with discrimination learning from the ongoing poststimulus ECoG. These patterns contained information about the preceding conditioned stimulus, and were associated with a subsequent correct behavioral response by the animal. Thereby, relevant pattern information was mainly carried by neuron populations outside the range of the lateral spatial spread of ICMS-evoked cortical activation (∼1.2 mm). This demonstrates that the stimulated cortical area not only encoded information about the stimulation sites by its focal, stimulus-driven activation, but also provided meaningful signals in its ongoing activity related to the interpretation of ICMS learned by the animal. This involved the stimulated area as a whole, and apparently required large-scale integration in the brain. However, ICMS locally interfered with the ongoing cortical dynamics by suppressing pattern formation near the stimulation sites. The interaction between ICMS and ongoing cortical activity has several implications for the design of ICMS protocols and cortical neuroprostheses, since the meaningful interpretation of ICMS depends on this interaction.
Serotonin Affects Association of Aversive Outcomes to Past Actions
Authors: Tanaka Saori C. , Shishida Kazuhiro , Schweighofer Nicolas , Okamoto Yasumasa , Yamawaki Shigeto , Doya Kenji
Published: December 2009

Impairment in the serotonergic system has been linked to action choices that are less advantageous in a long run. Such impulsive choices can be caused by a deficit in linking a given reward or punishment with past actions. Here, we tested the effect of manipulation of the serotonergic system by tryptophan depletion and loading on learning the association of current rewards and punishments with past actions. We observed slower associative learning when actions were followed by a delayed punishment in the low serotonergic condition. Furthermore, a model-based analysis revealed a positive correlation between the length of the memory trace for aversive choices and subjects' blood tryptophan concentration. Our results suggest that the serotonergic system regulates the time scale of retrospective association of punishments to past actions.
Preparation to Inhibit a Response Complements Response Inhibition during Performance of a Stop-Signal Task
Authors: Chikazoe Junichi , Jimura Koji , Hirose Satoshi , Yamashita Ken-ichiro , Miyashita Yasushi , Konishi Seiki
Published: December 2009

Inhibition of inappropriate responses is an essential executive function needed for adaptation to changing environments. In stop-signal tasks, which are often used to investigate response inhibition, subjects make “go” responses while they prepare to stop at a suddenly given “stop” signal. However, the preparatory processes ongoing before response inhibition have rarely been investigated, and it remains unclear how the preparation contributes to response inhibition. In the present study, a stop-signal task was designed so that the extent of the preparation could be estimated using behavioral and neuroimaging measures. Specifically, in addition to the conventional go trials where preparation to stop was required (“uncertain-go” trials), another type of go trial was introduced where a stop-signal was never given and such preparation was unnecessary (“certain-go” trials). An index reflecting the “preparation cost” was then calculated by subtracting the reaction times in the certain-go trials from those in the uncertain-go trials. It was revealed that the stop signal reaction time, a common index used to evaluate the efficiency of response inhibition, decreased as the preparation cost increased, indicating greater preparation supports more efficient inhibition. In addition, imaging data showed that response inhibition recruited frontoparietal regions (the contrast “stop vs uncertain-go”) and that preparation recruited most of the inhibition-related frontoparietal regions (the contrast “uncertain-go vs certain-go”). It was also revealed that the inhibition-related activity declined as the preparation cost increased. These behavioral and imaging results suggest preparation makes a complementary contribution to response inhibition during performance of a stop-signal task.
The Small GTPase Rac1 Regulates Auditory Hair Cell Morphogenesis
Authors: Grimsley-Myers Cynthia M. , Sipe Conor W. , Géléoc Gwenaëlle S. G. , Lu Xiaowei
Published: December 2009

Morphogenesis of sensory hair cells, in particular their mechanotransduction organelle, the stereociliary bundle, requires highly organized remodeling of the actin cytoskeleton. The roles of Rho family small GTPases during this process remain unknown. Here we show that deletion ofRac1in the otic epithelium resulted in severe defects in cochlear epithelial morphogenesis. The mutant cochlea was severely shortened with a reduced number of auditory hair cells and cellular organization of the auditory sensory epithelium was abnormal.Rac1mutant hair cells also displayed defects in planar cell polarity and morphogenesis of the stereociliary bundle, including bundle fragmentation or deformation, and mispositioning or absence of the kinocilium. We further demonstrate that a Rac–PAK (p21-activated kinase) signaling pathway mediates kinocilium–stereocilia interactions and is required for cohesion of the stereociliary bundle. Together, these results reveal a critical function of Rac1 in morphogenesis of the auditory sensory epithelium and stereociliary bundle.
An Intrinsic Neuronal Oscillator Underlies Dopaminergic Neuron Bursting
Authors: Deister Christopher A. , Teagarden Mark A. , Wilson Charles J. , Paladini Carlos A.
Published: December 2009

Dopaminergic neurons of the ventral midbrain fire high-frequency bursts when animals are presented with unexpected rewards, or stimuli that predict reward. To identify the afferents that can initiate bursting and establish therapeutic strategies for diseases affected by altered bursting, a mechanistic understanding of bursting is essential. Our results show that bursting is initiated by a specific interaction between the voltage sensitivity of NMDA receptors and voltage-gated ion channels that results in the activation of an intrinsic, action potential-independent, high-frequency membrane potential oscillation. We further show that the NMDA receptor is uniquely suited for this because of the rapid kinetics and voltage dependence imparted to it by Mg2+ion block and unblock. This mechanism explains the discrete nature of bursting in dopaminergic cells and demonstrates how synaptic signals may be reshaped by local intrinsic properties of a neuron before influencing action potential generation.
Direct Interaction of GABABReceptors with M2Muscarinic Receptors Enhances Muscarinic Signaling
Authors: Boyer Stephanie B. , Clancy Sinead M. , Terunuma Miho , Revilla-Sanchez Raquel , Thomas Steven M. , Moss Stephen J. , Slesinger Paul A.
Published: December 2009

Downregulation of G-protein-coupled receptors (GPCRs) provides an important mechanism for reducing neurotransmitter signaling during sustained stimulation. Chronic stimulation of M2muscarinic receptors (M2Rs) causes internalization of M2R and G-protein-activated inwardly rectifying potassium (GIRK) channels in neuronal PC12 cells, resulting in loss of function. Here, we show that coexpression of GABABR2 receptors (GBR2s) rescues both surface expression and function of M2R, including M2R-induced activation of GIRKs and inhibition of cAMP production. GBR2 showed significant association with M2R at the plasma membrane but not other GPCRs (M1R, μ-opioid receptor), as detected by fluorescence resonance energy transfer measured with total internal reflection fluorescence microscopy. Unique regions of the proximal C-terminal domains of GBR2 and M2R mediate specific binding between M2R and GBR2. In the brain, GBR2, but not GBR1, biochemically coprecipitates with M2R and overlaps with M2R expression in cortical neurons. This novel heteromeric association between M2R and GBR2 provides a possible mechanism for altering muscarinic signaling in the brain and represents a previously unrecognized role for GBR2.
Selection and Maintenance of Spatial Information by Frontal Eye Field Neurons
Authors: Armstrong Katherine M. , Chang Mindy H. , Moore Tirin
Published: December 2009

Voluntary attention is often allocated according to internally maintained goals. Recent evidence indicates that the frontal eye field (FEF) participates in the deployment of spatial attention, even in the absence of saccadic eye movements. In addition, many FEF neurons maintain persistent representations of impending saccades. However, the role of persistent activity in the general maintenance of spatial information, and its relationship to spatial attention, has not been explored. We recorded the responses of single FEF neurons in monkeys trained to remember cued locations in order to detect changes in targets embedded among distracters in a task that did not involve saccades. We found that FEF neurons persistently encoded the cued location throughout the trial during the delay period, when no visual stimuli were present, and during visual discrimination. Furthermore, FEF activity reliably predicted whether monkeys would detect the target change. Population analyses revealed that FEF neurons with persistent activity were more effective at selecting the target from among distracters than neurons lacking persistent activity. These results demonstrate that FEF neurons maintain spatial information in the absence of saccade preparation and suggest that this maintenance contributes to the selection of relevant visual stimuli.
Bandgap Engineering of Silicon Quantum Dot Nanostructures for High Efficient Silicon Solar Cell: The Tandem Approach
Authors: Rezgui B. , Sibai A. , Nychyporuk T. , Marty O. , Lemiti M. , Brémond Georges
Published: December 2009

A tandem approach is proposed using Silicon nanostructures to increase the efficiency of so-called third generation photovoltaic solar cells.Si quantum dot nanostructures (or silicon nanocrystals)are synthesized by depositing silicon-rich nitride (SRN) layers using plasma-enhanced chemical vapour deposition (PECVD). We have shown the intrinsic formation of silicon nanocrystals (nc-Si) in non-stoechiometric amorphous hydrogenated silicon nitride (a-SiNx:H) layers using pure silane (SiH4) and ammonia (NH3) as reactants. The NH3 would provide more hydrogen in the silicon nitride film leading to an improvement of the crystallinity of Si quantum dots (QD) by favouring the disorder-to-order transition. Furthermore, hydrogen dissociated from the NH3 would passivate the surface of a Si QD more effectively.Transmission Electron Microscopy (TEM) was employed to explore the microstructure of the as-deposited Si-in-SiNx composite films. The chemical bonds of these films were examined by using Fourier Transform Infrared (FTIR) spectroscopy in the wavenumber range from 400 to 4000 cm-1 with a resolution of 4 cm-1.
The photoluminescence (PL) property of silicon nanocrystals in silicon-rich nitride (SRN) layers are also investigated. The peak position of PL could be controlled by adjusting the flow rates of ammonia and silane . Two types of luminescent mechanisms, such as radiative defects in the film and the quantum confinement effect (QCE) in silicon nanocrystals, have been proposed to explain the origin of light emission from these structures. These two mechanisms are inherently coexisting in our samples and the photoluminescence spectrum depends on the contribution of each other.
The optical absorption properties of the deposited films are obtained and analyzed from light transmittance measurements. Spectroscopique ellipsometry have been performed in order to analyse the refractive index and the extension coefficient. All these measurements were carried out at room temperature. These techniques have given good correlation in the extraction of the absorption coefficient induced by the Si nanocrystal in the visible /UV energy range. Measurements of photocurrent have shown a great increase of the induced currrent in the visible/UV energy range for an optimum of deposition conditions. These results will be discussed in order to reach a better knowledge of the physical properties of this third generation photovoltaic all silicon included material for the tandem solar cell application approach.
Pressure Sensing with PVDF Gated AlGaN/GaN High Electron Mobility Transistor
Authors: Hung Sheng-Chun , Chu Byung Hwan , Chang Chih-Yang , Lo Chien Fong , Chen Ke Hung , Pearton S. J. , Dabiran Amir , Chow P. P. , Chi G. C. , Ren F.
Published: December 2009

AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized Polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an inkjet plotter. Next, the PDVF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10 kV and 70 °C. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change of surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. Our results indicate that HEMTs have potential for use as pressure sensors.
High Sensitivity of Hydrogen Sensing Through N-polar GaN Schottky Diodes
Authors: Wang Yu-Lin , Chu B.H. , Chang Chih-Yang , Chen Ke Hung , Zhang Yu , Sun Qian , Han Jung , Pearton S.J. , Ren F
Published: December 2009

N-polar and Ga-polar GaN grown on c-plane sapphire by a metal-organic chemical vapor deposition (MOCVD) system were used to fabricate platinum deposited Schottky contacts for hydrogen sensing at room temperature. Wurtzite GaN is a polar material. Along the c-axis, there are N-face (N-polar) or Ga-face (Ga-polar) orientations on the GaN surface. The Ohmic contacts were formed by lift-off of e-beam deposited Ti (200 Å)/Al (1000 Å)/Ni (400 Å)/Au (1200 Å). The contacts were annealed at 850°C for 45 s under a flowing N2 ambient. Isolation was achieved with 2000 Å plasma enhanced chemical vapor deposited SiNx formed at 300°C. A 100 Å of Pt was deposited by e-beam evaporation to form Schottky contacts. After exposure to hydrogen, Ga-polar GaN Schottky showed 10% of current change, while the N-polar GaN Schottky contacts became fully Ohmic. The N-polar GaN Schottky diodes showed stronger and faster response to 4% hydrogen than that of Ga-polar GaN Schottky diodes. The abrupt current increase from N-polar GaN Schottky exposure to hydrogen was attributed to the high reactivity of the N-face surface termination. The surface termination dominates the sensitivity and response time of the hydrogen sensors made of GaN Schottky diodes. Current-voltage characteristics and the real-time detection of the sensor for hydrogen were investigated. These results demonstrate that the surface termination is crucial in the performance of hydrogen sensors made of GaN Schottky diodes.
Band Gap States in AlGaN/GaN Hetero-Interface Studied by Deep-Level Optical Spectroscopy
Authors: Nakano Yoshitaka , Nakamura Keiji , Irokawa Yoshihiro , Takeguchi Masaki
Published: December 2009

Planar Pt/AlGaN/GaN Schottky barrier diodes (SBDs) have been characterized by capacitance-voltage and capacitance deep-level optical spectroscopy measurements, compared to reference Pt/GaN:Si SBDs. Two specific deep levels are found to be located at ∼1.70 and ∼2.08 eV below the conduction band, which are clearly different from deep-level defects (Ec - 1.40, Ec - 2.64, and Ec - 2.90 eV) observed in the Pt/GaN:Si SBDs. From the diode bias dependence of the steady-state photocapacitance, these levels are believed to stem from a two-dimensional electron gas (2DEG) region at the AlGaN/GaN hetero-interface. In particular, the 1.70 eV level is likely to act as an efficient generation-recombination center of 2DEG carriers.