Exclusive Action Research Articles

Oxazoline functionalized polystyrene as a compatibilizer for dispersion of organoclay in polyphenylene ether blends

AbstractAddition of external additives as compatibilizers is known to improve exfoliation of nanoclay in various polymeric matrices. This study found that oxazoline functionalized polystyrene (OPS) is an effective compatibilizer to improve the dispersion of organoclay (Cloisite 20A) in polyphenylene ether (PPE)‐based blends. The main objective of this study was to understand the mechanism of OPS as a compatibilizer for dispersion of nanoclay in PPE‐based blends and evaluate whether the master‐batch of organoclay in OPS can be used to disperse nanoclay in various PPE‐based blends irrespective of the type of the other polymer component in the blend. Although the addition of OPS to polystyrene (PS) alone resulted in mere intercalation of organoclay, its addition to PPE‐based blends was found to result in mixed clay dispersion of intercalated, exfoliated, and to some extent collapsed phases. Addition of OPS‐organoclay combination in master‐batch mode showed similar results as direct mode addition. At least 15% of OPS was required for effective dispersion of Cloisite 20A in PPE‐high impact polystyrene blend. The possible role of solubility of OPS in the matrix and high melt shear of PPE‐based matrix was investigated to understand the exclusive action of OPS in PPE‐based blends. X‐ray diffraction and transmission electron microscopy techniques were used to study the organoclay dispersion. Further master batches of organoclay in neat OPS and OPS containing PPE‐based blends were evaluated in other PPE‐based commercial blends. Of the various blends studied, blend containing phosphite additive showed better dispersion of organoclay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The reciprocal coordination and mechanics of molecular motors in living cells

Molecular motors in living cells are involved in whole-cell locomotion, contractility, developmental shape changes, and organelle movement and positioning. Whether motors of different directionality are functionally coordinated in cells or operate in a semirandom "tug of war" is unclear. We show here that anterograde and retrograde microtubule-based motors in the flagella of Chlamydomonas are regulated such that only motors of a common directionality are engaged at any single time. A laser trap was used to position microspheres on the plasma membrane of immobilized paralyzed Chlamydomonas flagella. The anterograde and retrograde movements of the microsphere were measured with nanometer resolution as microtubule-based motors engaged the transmembrane protein FMG-1. An average of 10 motors acted to move the microsphere in either direction. Reversal of direction during a transport event was uncommon, and quiescent periods separated every transport event, suggesting the coordinated and exclusive action of only a single motor type. After a jump to 32 degrees C, temperature-sensitive mutants of kinesin-2 (fla10) showed exclusively retrograde transport events, driven by 7 motors on average. These data suggest that molecular motors in living cells can be reciprocally coordinated to engage simultaneously in large numbers and for exclusive transport in a single direction, even when a mixed population of motors is present. This offers a unique model for studying the mechanics, regulation, and directional coordination of molecular motors in a living intracellular environment.

Stochastic Model of Evolutionary and Immunological Multi-Agent Systems: Mutually Exclusive Actions

The mathematical model of the biologically inspired, memetic, agent-based computation systems EMAS and iEMAS conformed to BDI standard is presented. The state of the systems and their dynamics are expressed as stationary Markov chains. Such an approach allows to better understand their complex behavior as well as their limitations.

Conflicts of interest and the evolution of decision sharing

Social animals regularly face consensus decisions whereby they choose, collectively, between mutually exclusive actions. Such decisions often involve conflicts of interest between group members with respect to preferred action. Conflicts could, in principle, be resolved, either by sharing decisions between members ('shared decisions') or by one 'dominant' member making decisions on behalf of the whole group ('unshared decisions'). Both, shared and unshared decisions, have been observed. However, it is unclear as to what favours the evolution of either decision type. Here, after a brief literature review, we present a novel method, involving a combination of self-organizing system and game theory modelling, of investigating the evolution of shared and unshared decisions. We apply the method to decisions on movement direction. We find that both, shared and unshared, decisions can evolve without individuals having a global overview of the group's behaviour or any knowledge about other members' preferences or intentions. Selection favours unshared over shared decisions when conflicts are high relative to grouping benefits, and vice versa. These results differ from those of group decision models relating to activity timings. We attribute this to fundamental differences between collective decisions about modalities that are disjunct (here, space) or continuous (here, time) with respect to costs/benefits.

Human breeders for evolving robots

In this article we describe a new approach in evolutionary robotics according to which human breeders are involved in the evolutionary process. While traditionally robots are selected to reproduce automatically according to a fitness formula, which is a quantitative and strictly defined measure, human breeders can operate selection based on qualitative criteria, and rewarding behaviors that can slip between the meshes woven by the fitness formula. In authors’ opinion this may bring advantages to the evolutionary robotics methodology, allowing the production of robots that display more, and more multiform, behaviors. In order to illustrate this approach, the software Breedbot was developed in which human breeders can intervene in evolving robots, complementing the automatic evaluation. After describing the software, some results on sample evolutionary processes are reported showing that the joint use of human and artificial selection on an exploration task generates robots with a higher performance and in a shorter time compared with the exclusive action of each breeding method. Future work will explore this hypothesis further.

Dominance and Affiliation Mediate Despotism in a Social Primate

Group-living animals routinely have to reach a consensus decision and choose between mutually exclusive actions in order to coordinate their activities and benefit from sociality. Theoretical models predict "democratic" rather than "despotic" decisions to be widespread in social vertebrates, because they result in lower "consensus costs"-the costs of an individual foregoing its optimal action to comply with the decision-for the group as a whole. Yet, quantification of consensus costs is entirely lacking, and empirical observations provide strong support for the occurrence of both democratic and despotic decisions in nature. We conducted a foraging experiment on a wild social primate (chacma baboons, Papio ursinus) in order to gain new insights into despotic group decision making. The results show that group foraging decisions were consistently led by the individual who acquired the greatest benefits from those decisions, namely the dominant male. Subordinate group members followed the leader despite considerable consensus costs. Follower behavior was mediated by social ties to the leader, and where these ties were weaker, group fission was more likely to occur. Our findings highlight the importance of leader incentives and social relationships in group decision-making processes and the emergence of despotism.

Testing the spatial phylogenetic structure of local communities: statistical performances of different null models and test statistics on a locally neutral community

Summary Analyzing the phylogenetic structure of natural communities may illuminate the processes governing the assembly and coexistence of species. For instance, an association between species co‐occurrence in local communities and their phylogenetic proximity may reveal the action of habitat filtering, niche conservatism and/or competitive exclusion. Different methods were recently proposed to test such community‐wide phylogenetic patterns, based on the phylogenetic clustering or overdispersion of the species in a local community. This provides a much needed framework for addressing long standing questions in community ecology as well as the recent debate on community neutrality. The testing procedures are based on (i) a metric measuring the association between phylogenetic distance and species co‐occurrence, and (ii) a data set randomization algorithm providing the distribution of the metric under a given ‘null model’. However, the statistical properties of these approaches are not well‐established and their reliability must be tested against simulated data sets. This paper reviews metrics and null models used in previous studies. A ‘locally neutral’ subdivided community model is simulated to produce data sets devoid of phylogenetic structure in the spatial distribution of species. Using these data sets, the consistency of Type I error rates of tests based on 10 metrics combined with nine null models is examined. This study shows that most tests can become liberal (i.e. tests rejecting too often the null hypothesis that only neutral processes structured spatially the local community) when the randomization algorithm breaks down a structure in the original data set unrelated to the null hypothesis to test. Hence, when overall species abundances are distributed non‐randomly across the phylogeny or when local abundances are spatially autocorrelated, better statistical performances were achieved by randomization algorithms preserving these structural features. The most reliable randomization algorithm consists of permuting species with similar abundances among the tips of the phylogenetic tree. One metric, RPD‐DO, also proved to be robust under most simulated conditions using a variety of null models. Synthesis. Given the suboptimal performances of several tests, attention must be paid to the testing procedures used in future studies. Guidelines are provided to help choosing an adequate test.

Enzyme-dependent Variations in the Polysialylation of the Neural Cell Adhesion Molecule (NCAM) in Vivo

Polysialic acid (polySia), an alpha2,8-linked polymer of N-acetylneuraminic acid, represents an essential regulator of neural cell adhesion molecule (NCAM) functions. Two polysialyltransferases, ST8SiaII and ST8SiaIV, account for polySia synthesis, but their individual roles in vivo are still not fully understood. Previous in vitro studies defined differences between the two enzymes in their usage of the two NCAM N-glycosylation sites affected and suggested a synergistic effect. Using mutant mice, lacking either enzyme, we now assessed in vivo the contribution of ST8SiaII and ST8SiaIV to polysialylation of NCAM. PolySia-NCAM was isolated from mouse brains and trypsinized, and polysialylated glycopeptides as well as glycans were analyzed in detail. Our results revealed an identical glycosylation and almost complete polysialylation of N-glycosylation sites 5 and 6 in polySia-NCAM irrespective of the enzyme present. The same sets of glycans were substituted by identical numbers of polySia chains in vivo, the length distribution of which, however, differed with the enzyme setting. Expression of ST8SiaIV alone led to higher amounts of short polySia chains and gradual decrease with length, whereas exclusive action of ST8SiaII evoked a slight reduction in long polySia chains only. These variations were most pronounced at N-glycosylation site 5, whereas the polysialylation pattern at N-glycosylation site 6 did not differ between NCAM from wild-type and ST8SiaII- or ST8SiaIV-deficient mice. Thus, our fine structure analyses suggest a comparable quality of polysialylation by ST8SiaII and ST8SiaIV and a distinct synergistic action of the two enzymes in the synthesis of long polySia chains at N-glycosylation site 5 in vivo.

Democracy in animals: the evolution of shared group decisions

A 'consensus decision' is when the members of a group choose, collectively, between mutually exclusive actions. In humans, consensus decisions are often made democratically or in an 'equally shared' manner, i.e. all group members contribute to the decision. Biologists are only now realizing that shared consensus decisions also occur in social animals (other than eusocial insects). Sharing of decisions is, in principle, more profitable for groups than accepting the 'unshared' decision of a single dominant member. However, this is not true for all individual group members, posing a question as to how shared decision making could evolve. Here, we use a game theory model to show that sharing of decisions can evolve under a wide range of circumstances but especially in the following ones: when groups are heterogeneous in composition; when alternative decision outcomes differ in potential costs and these costs are large; when grouping benefits are marginal; or when groups are close to, or above, optimal size. Since these conditions are common in nature, it is easy to see how mechanisms for shared decision making could have arisen in a wide range of species, including early human ancestors.

Nonalcoholic Fatty Liver Disease: Cytokine-Adipokine Interplay and Regulation of Insulin Resistance

Nonalcoholic fatty liver disease (NAFLD), the major reason for abnormal liver function in the Western world, is associated with obesity and diabetes and is characterized by insulin resistance (IR). IR is regulated by mediators released from cells of the immune system or adipocytes and proinflammatory cytokines such as tumor necrosis factor-α (TNFα). The importance of TNFα in human and animal fatty liver diseases, both caused by genetic manipulation and overnutrition, has been shown convincingly. Furthermore, neutralization of TNFα activity improves IR and fatty liver disease in animals. Adiponectin is a potent TNFα-neutralizing and anti-inflammatory adipokine and in vitro and experimental animal studies have proven the importance of this mediator in counteracting inflammation and IR. Anti-inflammatory effects of adiponectin are exerted both by suppressing TNFα synthesis and by induction of anti-inflammatory cytokines such as interleukin-10 or interleukin-1–receptor antagonist. Therefore, the balance between various mediators, either derived from the immune system or adipose tissue, appears to play an important role in hepatic and systemic insulin action and in the development of fatty liver disease.

Rizatriptan Vs. Rizatriptan Plus Trimebutine for the Acute Treatment of Migraine: A Double-Blind, Randomized, Cross-Over, Placebo-Controlled Study

Gastroparesis frequently happens during migraine attacks, postponing the onset of action of orally administered drugs. Furthermore, triptans seem to work better in the earlier phases of the migraine attacks. Therefore, associating a gastrokinetic drug with a triptan may translate into better efficacy and higher consistency of response. Trimebutine is an opioid derivative with exclusive action on receptors of the Meissner and Auerbach plexus throughout the digestive tube. It has no absorption or central penetration. Herein we contrast the combination of rizatriptan plus trimebutine with rizatriptan alone in the acute treatment of migraine. Forty patients with migraine consecutively seen in our clinic were randomized to treat two consecutive moderate or severe attacks with one tablet of 10 mg rizatriptan plus one capsule of 200 mg trimebutine and two attacks with the same triptan and placebo, in counterbalanced order. We collected information on the severity of the attack, as well as presence of nausea and photophobia at the time of drug intake, and after 1, 2 and 4 h. Recurrence and adverse events were also contrasted. Sixty-four attacks were treated with each drug regimen. At 1 h postdose, 30 (46.8%) of 64 attacks treated with the combination resolved completely, vs. eight (12.5%) of the rizatriptan-treated attacks, a difference of 34% (P < 0.01). At 2 h postdose, 47 (73.4%) attacks treated with the combination vs. 20 (31.2%) of those treated with rizatriptan alone resolved completely, a difference of 42% (95% confidence interval 26, 58, P < 0.001). Regarding nausea and photophobia, the combination was also associated with significantly better response. Recurrence was similar among the two drug regimens, as well as adverse events. The combination rizatriptan and trimebutine is more effective than rizatriptan alone. The combination does not increase adverse events or recurrence of pain.

Opposite to α 2-adrenergic agonists, an imidazoline I 1 selective compound does not influence reflex bradycardia in rabbits

This work aimed to study the respective effects of central α 2-adrenergic receptors (α 2-AR S) and I 1 imidazoline receptors (I 1Rs) in the facilitatory effects of imidazoline-like drugs on the reflex bradycardia (RB). Experiments were performed in anaesthetized rabbits. The reflex bradycardic response was induced by phenylephrine injected i.v. LNP 509, rilmenidine and dexmedetomidine were administered intracisternally (i.c.). LNP509 (1 mg/kg, i.c.), a ligand highly selective for I 1Rs, induced hypotension (54 ± 3 vs. 93 ± 2 mm Hg) and bradycardia (260 ± 13 vs. 322 ± 13 beats/min) ( p < 0.05, n = 5) but did not affect RB. Rilmenidine (1 μg/kg, i.c.), a hybrid ligand which binds to both I 1 and α 2-AR S, also decreased arterial pressure (61 ± 2 vs. 101 ± 2 mm Hg) and heart rate (260 ± 4 vs. 308 ± 8) ( p < 0.01, n = 5); it potentiated the RB (maximum R–R interval: 284 ± 17 vs. 196 ± 6 ms) ( p < 0.05, n = 5). Dexmedetomidine (1 μg/kg, i.c.), a ligand selective for α 2-ARs, reduced blood pressure (53 ± 3 vs. 104 ± 2 mm Hg) and heart rate (246 ± 4 vs. 312 ± 8 beats/min) ( p < 0.05, n = 5) and potentiated the RB (maximum R–R interval: 518 ± 38 vs. 194 ± 4 ms) ( p < 0.05, n = 5). The potentiation of RB was much greater than that observed with rilmenidine and was significantly prevented by L-NNA injected centrally. This study shows that: (i) an exclusive action on I 1Rs which decreases arterial pressure, does not potentiate the RB ii) activation of α 2-ARs potentiates the RB (iii) the R–R prolongation caused by α 2-ARs stimulation is prevented by central NOS inhibition.

Perilous Crossings

ABSTRACT The author argues for an understanding of subjective gender whereby under dichotomous gender conventions people espouse multiple, complex, chaotic, and mutually exclusive feelings, ideas, and actions. Like sexuality, gender is a fluid, ambiguous and contextual aspect of identity. She critiques theory that puts forth a stage related, linear, content-based construction of gender and describes how attachment theory and intersubjectivity can contribute to newer gender theory. Case material is provided to illustrate the intersubjective nature of gender in the analytic process.

Symplectic evolution of Wigner functions in Markovian open systems

The Wigner function is known to evolve classically under the exclusive action of a quadratic Hamiltonian. If the system also interacts with the environment through Lindblad operators that are complex linear functions of position and momentum, then the general evolution is the convolution of a non-Hamiltonian classical propagation of the Wigner function with a phase space Gaussian that broadens in time. We analyze the consequences of this in the three generic cases of elliptic, hyperbolic, and parabolic Hamiltonians. The Wigner function always becomes positive in a definite time, which does not depend on the initial pure state. We observe the influence of classical dynamics and dissipation upon this threshold. We also derive an exact formula for the evolving linear entropy as the average of a narrowing Gaussian taken over a probability distribution that depends only on the initial state. This leads to a long time asymptotic formula for the growth of linear entropy. We finally discuss the possibility of recovering the initial state.

I(1) imidazoline receptors involved in cardiovascular regulation: where are we and where are we going?

Clonidine-like drugs (hybrid drugs) reduce blood pressure by acting centrally at both alpha(2)-adrenergic receptors (alpha(2)AR) and I(1) receptors (I(1)R). Some attempts at cloning I(1)R have failed, probably because of the lack of selectivity of the ligands. Recently, compounds acting exclusively at I(1)R were synthesized: LNP 911, LNP509, and S23515. For example, LNP911 has a K(d) value of 1.7 nmol/L at I(1)R. LNP509 and S23515 reduce blood pressure when injected centrally in anesthetized animals, whereas S23757 behaves as an antagonist of hypotensive imidazolines. LNP509 reduces blood pressure even in genetically engineered mice lacking functional alpha(2)AR. An exclusive action at central I(1)R is therefore sufficient to modify blood pressure. With the help of drugs selective for I(1)R and alpha-methylnoradrenaline, selective for alpha(2)AR, we showed that imidazoline and alpha(2)-adrenergic mechanisms interact synergistically in controlling the blood pressure. Such a synergism may explain the very powerful hypotensive effects of hybrid drugs. The new ligands selective for I(1)R will be very helpful to investigate the molecular features and the signaling system of I(1)R.

Relative contributions of eyelid and eye-retraction motor systems to reflex and classically conditioned blink responses in the rabbit.

Early compensatory mechanisms between eyelid and eye-retraction motor systems following selective nerve and/or muscle lesions were studied in behaving rabbits. Reflex and conditioned eyelid responses were recorded in 1). controls and following 2). facial nerve section, 3). retractor bulbi muscle removal, and 4). facial nerve section and retractor bulbi muscle removal. Animals were classically conditioned with a delay paradigm by using a tone (350 ms, 600 Hz, 90 dB) as conditioned stimulus, followed 250 ms later by an air puff (100 ms, 3 kg/cm(2)) as unconditioned stimulus. Conditioned eyelid responses generated in the absence of the facial motor system (i.e., by the almost sole action of the retractor bulbi motor system) presented a wavy profile, due to the succession of eye-retraction movements. Learned eyelid responses generated in the absence of the eye-retraction motor system (i.e., by the almost exclusive action of the facial motor system) were similar to those of controls, but were reduced in amplitude and peak velocity. Finally, the isolated action of the extraocular recti muscle produced very small eyelid movements during both reflex and learned eyelid responses. Although each of these motor systems could act independently of the others, the motor result of their joint action did not coincide with the simple addition of their separate actions. Both facial and eye-retraction motor systems appear to be necessary for normal eyelid closure during blinking in rabbits. Central reorganization to compensate for loss of either of these systems may explain why the response of each system in isolation cannot be added linearly to obtain normal blink response magnitudes and profiles.

Decision analysis as a tool to support an analytical pattern-of-reasoning.

Decision analysis is offered as a tool to aid nurses' decision-making in complex and troublesome situations where there are mutually exclusive actions and time is available for deliberation. Decision analysis can be formal or informal. Formal decision analysis provides a structure for representing the decision situation and a mathematical procedure for prescribing the alternative action that is most consistent with what is known and what one values. Informal decision analysis uses the concepts and sometimes the structure of decision analysis, but usually does not include the mathematical calculations. In the present paper, the authors illustrate how formal and informal decision analysis might be used by nurses to: (i) enhance their own decision-making; (ii) assist patients or family caregivers with decision-making and; (iii) promote informed health care policy development. Finally, the advantages and limitations of decision analysis are discussed.

Targeting thalamic nuclei is not sufficient for the full anti-absence action of ethosuximide in a rat model of absence epilepsy

Absence epilepsy is characterised by recurrent periods of physical and mental inactivity coupled to bilateral, synchronous spike and wave discharges (SWDs) on the electroencephalogram. The mechanism of action of ethosuximide (ETX), a drug specific for absence seizures, is believed to involve a reduction in the low threshold T-type Ca 2+ current in thalamocortical and nucleus reticularis thalami (NRT) neurones, although other electrophysiological data have questioned this. Here, we employed a genetic rat model of absence seizures to investigate the effects of directly administering ETX to the thalamus. SWDs were immediately and substantially reduced (∼90%) by systemic administration of ETX (177–709 μmol/kg), or by bilateral microinfusion into the thalamus of the GABA B antagonist, CGP 36742 (5–27 nmol per side). However, infusion of ETX (1–200 nmol per side) into the ventrobasal complex or the NRT resulted in a reduction of SWDs that was delayed (30–60 min) and less marked (∼50%). Administration of ETX (0.2 mM to 1 M) to a greater volume of thalamus by reverse microdialysis also produced significant but delayed reduction of SWDs at concentrations >1 mM. Only at 5 mM were seizures significantly reduced (∼70%) within 30 min of administration. These results suggest that targeting of the thalamus alone may be insufficient for an immediate and full anti-absence action for ETX. Concomitant or exclusive actions in the cortex remain a possibility.

Exclusive Action of Transmembrane TNF in Adipose Tissue Leads to Reduced Adipose Mass and Local But Not Systemic Insulin Resistance

Exclusive Action of Transmembrane TNF in Adipose Tissue Leads to Reduced Adipose Mass and Local But Not Systemic Insulin Resistance

Exclusive action of transmembrane TNF alpha in adipose tissue leads to reduced adipose mass and local but not systemic insulin resistance.

Aberrant TNF alpha expression in adipocytes is a molecular mechanism by which insulin action is modulated in adipose tissue. While this might be a compensatory response to limit adipose expansion, neither the mechanisms underlying this local effect nor its systemic biological consequences have been studied. It is also not clear whether TNF alpha-induced insulin resistance in adipocyte alone is responsible for systemic insulin resistance in the absence of obesity. In a transgenic mouse model deficient in endogenous TNF alpha, we demonstrate that specific expression of the transmembrane TNF alpha (mTNF alpha) in adipocytes leads to decreased whole body adipose mass, and local, but not systemic insulin resistance. These data demonstrate that exclusive action of TNF alpha in adipose tissue strongly inhibits insulin action at this site and leads to reduced adiposity in mice. However, this isolated adipocyte insulin resistance in the context of reduced fat mass and/or the absence of obesity is insufficient to alter systemic glucose homeostasis.