bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel role for an APC2-Diaphanous complex in regulating actin organization inDrosophila
Authors: Webb Rebecca L. , Zhou Meng-Ning , McCartney Brooke M.
Published: March 2009

The rearrangement of cytoskeletal elements is essential for many cellular processes. The tumor suppressor Adenomatous polyposis coli (APC) affects the function of microtubules and actin, but the mechanisms by which it does so are not well understood. Here we report that Drosophila syncytial embryos null for Apc2 display defects in the formation and extension of pseudocleavage furrows, which are cortical actin structures important for mitotic fidelity in early embryos. Furthermore, we show that the formin Diaphanous (DIA) functions with APC2 in this process. Colocalization of APC2 and DIA peaks during furrow extension, and localization of APC2 to furrows is DIA-dependent. Furthermore, APC2 binds DIA directly through a region of APC2 not previously shown to interact with DIA-related formins. Consistent with these results, reduction of dia enhances actin defects in Apc2 mutant embryos. Thus, an APC2-DIA complex appears crucial for actin furrow extension in the syncytial embryo. Interestingly, EB1, a microtubule +TIP and reported partner of vertebrate APC and DIA1, may not function with APC2 and DIA in furrow extension. Finally, whereas DIA-related formins are activated by Rho family GTPases, our data suggest that the APC2-DIA complex might be independent of RHOGEF2 and RHO1. Furthermore,although microtubules play a role in furrow extension, our analysis suggests that APC2 and DIA function in a novel complex that affects actin directly,rather than through an effect on microtubules.
Steel factor controls primordial germ cell survival and motility from the time of their specification in the allantois, and provides a continuous niche throughout their migration
Authors: Gu Ying , Runyan Chris , Shoemaker Amanda , Surani Azim , Wylie Chris
Published: March 2009

Steel factor is an essential survival and proliferation factor for primordial germ cells (PGCs) during their migration in the early mouse embryo. PGCs arise during gastrulation, and migrate into the posterior endoderm that becomes the hindgut. Previous reports have suggested that PGCs become dependent on Steel factor when they colonize the hindgut. However, in the absence of a good marker for living PGCs, their behavior before hindgut colonization has not been previously studied. We report here the normal behavior of PGCs in live embryos before hindgut colonization, and the roles of Steel factor, using a reporter line in which GFP is driven by the promoter of the Stella gene, whose activation accompanies the initial specification of PGCs. We show first that PGCs are surrounded by Steel factor-expressing cells from their first appearance in the allantois to the time they enter the genital ridges. Second, fewer PGCs are found in the allantois in Steel-null embryos, but this is not due to a failure of PGC specification. Third, the analysis of cultured Steel-null early embryos shows that Steel factor is required for normal PGC motility, both in the allantois and in the hindgut. Germ cells migrate actively in the allantois, and move directionally from the allantois into the proximal epiblast. In the absence of Steel factor, caused by either null mutation or antibody blockade, PGC motility is dramatically decreased, but directionality is maintained, demonstrating a primary role for Steel factor in PGC motility. This was found both before and after colonization of the hindgut. These data,together with previously published data, show that PGCs are Steel factor dependent from their initial specification until they colonize the genital ridges, and suggest the existence of a `spatio-temporal niche' that travels with this important pluripotential cell population in the embryo.
N- and E-cadherins inXenopusare specifically required in the neural and non-neural ectoderm, respectively, for F-actin assembly and morphogenetic movements
Authors: Nandadasa Sumeda , Tao Qinghua , Menon Nikhil R. , Heasman Janet , Wylie Christopher
Published: March 2009

Transmembrane cadherins are calcium-dependent intercellular adhesion molecules. Recently, they have also been shown to be sites of actin assembly during adhesive contact formation. However, the roles of actin assembly on transmembrane cadherins during development are not fully understood. We show here, using the developing ectoderm of the Xenopus embryo as a model,that F-actin assembly is a primary function of both N-cadherin in the neural ectoderm and E-cadherin in the non-neural (epidermal) ectoderm, and that each cadherin is essential for the characteristic morphogenetic movements of these two tissues. However, depletion of N-cadherin and E-cadherin did not cause dissociation in these tissues at the neurula stage, probably owing to the expression of C-cadherin in each tissue. Depletion of each of these cadherins is not rescued by the other, nor by the expression of C-cadherin, which is expressed in both tissues. One possible reason for this is that each cadherin is expressed in a different domain of the cell membrane. These data indicate the combinatorial nature of cadherin function, the fact that N- and E-cadherin play primary roles in F-actin assembly in addition to roles in cell adhesion,and that this function is specific to individual cadherins. They also show how cell adhesion and motility can be combined in morphogenetic tissue movements that generate the form and shape of the embryonic organs.
Function of the extrinsic hindlimb muscles in trotting dogs
Authors: Schilling Nadja , Fischbein Timna , Yang Evelyn P. , Carrier David R.
Published: March 2009

The extrinsic appendicular muscles of mammals have been suggested to impose parasagittal torques on the trunk that require recruitment of the oblique hypaxial muscles for stabilization. To determine if the recruitment of the protractors and retractors of the hindlimb are compatible with this hypothesis, we monitored changes in the recruitment of eleven muscles that span the hip joint to controlled manipulations of locomotor forces in trotting dogs. The results indicate that the primary retractor muscles of the hindlimb produce a small retraction moment at the hip joint early in the support phase during trotting at constant speed on a level surface. Thus, although the forelimb of dogs appears to function as a compliant strut, the hindlimb functions as a lever early in stance phase. Nevertheless, our results indicate that when dogs run at constant speed on a level surface a primary function of both the retractor and protractor muscles of the hindlimb is to produce swing phase of the limb. When the trotting dogs did net work in the fore–aft direction, by running uphill or downhill or by resisting a horizontally directed force, recruitment of the protractor and retractor muscles of the hip joint increased or decreased in the anticipated fashion. These observations are consistent with the hypothesis that recruitment of the oblique hypaxial muscles in trotting dogs function to stabilize the trunk against torques produced by protractor and retractor muscles of the hindlimb.
Impaired tactile learning is related to social role in honeybees
Authors: Scheiner Ricarda , Amdam Gro V.
Published: March 2009

Aging is commonly accompanied by a decline in cognitive functions such as learning and memory. In social insects, aging is tightly linked to social role. The honeybee (Apis mellifera L.) offers the unique opportunity to separate chronological age from social role. In the present paper, we tested whether chronological age, social role and the duration of performing this role affect tactile learning in honeybees. We compared acquisition, retention and discrimination between foragers with short and long foraging durations and age-matched nurse bees. Our data show that chronological age is of minor importance for tactile learning, retention and discrimination whereas social role has a decisive impact. Tactile acquisition is severely impaired in bees that have foraged for more than two weeks but not in nurse bees of the same chronological age. Interestingly, neither discrimination nor retention appear to be impaired by long foraging duration. The complex associations between acquisition, discrimination and retention in bees of different social roles open up rich possibilities for future studies on the neuronal correlates of behavioural performance and underline that the honeybee has great potential as a model system in the biology of aging.
Novel neural correlates of operant conditioning in normal and differentially reared Lymnaea
Authors: Khan Abdullah M. , Spencer Gaynor E.
Published: March 2009

The aerial respiratory behaviour of the mollusc Lymnaea stagnalisis an important homeostatic behaviour that can be operantly conditioned. The central pattern generator underlying this behaviour, as well as motorneurons innervating the respiratory orifice, the pneumostome, have been identified and their activity can be monitored in the semi-intact preparation using electrophysiological recordings. In this study, we used both intact animals and semi-intact preparations to identify novel changes in the respiratory central pattern generator following operant conditioning. In addition, we reared animals in the absence of this respiratory behaviour throughout development, to investigate whether previous experience and activity-dependent plasticity during development are essential to allow neural plasticity in the adult. We found that animals raised normally (allowed to perform aerial respiratory behaviour) exhibited the expected reduction in aerial respiratory behaviour following operant conditioning. Then, using the semi-intact preparation, we identified novel neural changes within the network as a result of the conditioning. These included specific changes at the level of the central pattern generator interneurons, as well as the motor output. In the differentially reared intact animals, there was no behavioural reduction as a result of operant conditioning, although their baseline respiratory behaviour was already significantly reduced as a result of their differential rearing. There were, however, significant differences found in the network parameters in the semi-intact preparation, similar to those observed in normally reared animals. We thus provide evidence for neural plasticity within the network in the absence of significant behavioural changes in differentially reared animals, and show that plasticity was not dependent on previous activity of the network during development.
Movement encoding by a stretch receptor in the soft-bodied caterpillar,Manduca sexta
Authors: Simon Michael A. , Trimmer Barry A.
Published: March 2009

In a wide variety of animals, stretch receptors provide proprioceptive feedback for motion control. However, for animals that lack a stiff skeleton,it is unclear what information is being detected and how this is incorporated into behavior. Because such animals can change their body shape from moment-to-moment, information about body configuration could be particularly important for coordination. This study uses larval stage Lepidoptera(Manduca sexta) to examine how the longitudinal stretch receptor organ (SRO) responds to behaviorally appropriate movements. We characterized the responses of the SRO to changes in strain using magnitudes and velocities matching those seen physiologically. We found that the SRO response characteristics are compatible with the regulation of stance and with the defensive response to noxious stimuli. However, we also found that movements during crawling produce SRO responses that are dominated by the interdependence of phasic, tonic and slowly adaptive components. Ablation of stretch receptors in the proleg-bearing, fourth abdominal segment did not have any observable effect on behaviors, which suggests that the SROs are not essential for coordinating overt movements. We discuss the implications of these findings in the context of specific behaviors, and explore how the SRO response might be utilized during animal behavior.
Local and global navigational coordinate systems in desert ants
Authors: Collett Matthew , Collett Thomas S.
Published: March 2009

While foraging, the desert ant Cataglyphis fortis keeps track of its position with respect to its nest through a process of path integration(PI). Once it finds food, it can then follow a direct home vector to its nest. Furthermore, it remembers the coordinates of a food site, and uses these coordinates to return to the site. Previous studies suggest, however, that it does not associate any coordinates remembered from previous trips with familiar views such that it can produce a home vector when displaced to a familiar site. We ask here whether a desert ant uses any association between PI coordinates and familiar views to ensure consistent PI coordinates as it travels along a habitual route. We describe an experiment in which we manipulated the PI coordinates an ant has when reaching a distinctive point along a habitual route on the way to a feeder. The subsequent home vectors of the manipulated ants, when displaced from the food-site to a test ground, show that also when a route memory is evoked at a significant point on the way to a food site, C. fortis does not reset its PI coordinates to those it normally has at that point. We use this result to argue that local vector memories, which encode the metric properties of a segment of a habitual route,must be encoded in a route-based coordinate system that is separate from the nest-based global coordinates. We propose a model for PI-based guidance that can account for several puzzling observations, and that naturally produces the route-based coordinate system required for learning and following local vectors.
Acoustic scanning of natural scenes by echolocation in the big brown bat, Eptesicus fuscus
Authors: Surlykke Annemarie , Ghose Kaushik , Moss Cynthia F.
Published: March 2009

Echolocation allows bats to orient and localize prey in complete darkness. The sonar beam of the big brown bat, Eptesicus fuscus, is directional but broad enough to provide audible echo information from within a 60–90 deg. cone. This suggests that the big brown bat could interrogate a natural scene without fixating each important object separately. We tested this idea by measuring the directional aim and duration of the bat's sonar beam as it performed in a dual task, obstacle avoidance and insect capture. Bats were trained to fly through one of two openings in a fine net to take a tethered insect at variable distances behind the net. The bats sequentially scanned the edges of the net opening and the prey by centering the axis of their sonar beam with an accuracy of ∼5 deg. The bats also shifted the duration of their sonar calls, revealing sequential sampling along the range axis. Changes in duration and directional aim were correlated, showing that the bat first inspected the hole, and then shifted its gaze to the more distant insect,before flying through the net opening. Contrary to expectation based on the sonar beam width, big brown bats encountering a complex environment accurately pointed and shifted their sonar gaze to sequentially inspect closely spaced objects in a manner similar to visual animals using saccades and fixations to scan a scene. The findings presented here from a specialized orientation system, echolocation, offer insights into general principles of active sensing across sensory modalities for the perception of natural scenes.
Nitric oxide increases myocardial efficiency in the hypoxia-tolerant turtle Trachemys scripta
Authors: Misfeldt Mikkel , Fago Angela , Gesser Hans
Published: March 2009

Nitric oxide (NO) may influence cardiac mechanical performance relative to O2 consumption by depressing respiration rate and by affecting the excitation–contraction coupling. Such effects of NO should be particularly important during hypoxia in species such as the hypoxia-tolerant turtle Trachemys scripta. In heart ventricle preparations from this species, the ratio of twitch force to O2 consumption increased by approximately 15% during full oxygenation and by approximately 60% during hypoxia in the presence of added l-arginine [the substrate for nitric oxide synthase (NOS)]. This effect was primarily due to a decrease in O2 consumption and may represent an increase in the twitch force obtained per ATP and/or in the ATP obtained per O2. Lactate production during hypoxia did not differ between preparations treated with either l-arginine or asymmetric dimethylarginine (ADMA), an inhibitor of NOS, suggesting that NO does not elicit a compensatory increase in anaerobic metabolism. ADMA did not reverse the effects of l-arginine on O2 consumption significantly, although pre-treatment with ADMA abolished the effect of l-arginine,consistent with the competitive binding of l-arginine and ADMA to NOS. Histochemical studies using the fluorescent probe 4,5-diaminofluorescein diacetate (DAF-2 DA) revealed NO production in the presence of added l-arginine. In conclusion, NO may augment heart contractility obtained per O2 by deceasing O2 consumption without affecting either lactate production or developed force. This effect was particularly pronounced under O2 deficiency and may therefore contribute towards preserving cardiac function and to the overall excellent hypoxic tolerance of the turtle.
Responses of hatchlingXenopustadpoles to water currents: first function of lateral line receptors without cupulae
Authors: Roberts Alan , Feetham Ben , Pajak Mark , Teare Tom
Published: March 2009

At later stages in larval life and also as adults, Xenopus can respond to water currents detected by their lateral-line sensory system. We have investigated when responses to water currents first appear and whether the first lateral line neuromasts operate in the same way as the adult organs. Just before and after hatching from their egg membranes we show that Xenopus embryos and tadpoles can respond to water currents by swimming into them. Local stimulation in immobilised animals where motor activity was recorded electrically suggested that the receptors detecting water currents were located between the eyes and the gills and were innervated by cranial nerves. In behaving tadpoles, responses to water currents were reduced following skin abrasion caudal to the eyes or treatment with neomycin,which is known to block hair cell function. We therefore used scanning electron microscopy to establish that rows of lateral line neuromasts with hair cells and kinocilia are present just caudal to the eyes at these stages of development. However, careful observations and manipulations of the kinocilia of neuromasts in living tadpoles failed to find any evidence that kinocilia were embedded in a jelly-like cupula. We conclude that, when they first start to function, these early neuromasts detect water movements which directly move their freely exposed hair cell kinocilia projecting out from the skin surface. Possible behavioural roles for the tadpoles responses to water are discussed.
Nervous and humoral control of cardiac performance in the winter flounder(Pleuronectes americanus)
Authors: Mendonça Paula C. , Gamperl A. Kurt
Published: March 2009

Previous studies have suggested that flatfish lack adrenergic cardiac innervation and have a limited humoral adrenergic stress response. However,data on neurohormonal control of flatfish cardiac function is scarce, and has never been directly studied in vivo. Hence, we (1) injected neural and humoral antagonists into flounder (Pleuronectes americanus) in vivo to determine the contribution of autonomic innervation and circulating catecholamines to the control of resting cardiac function; (2)measured pre- and post-stress (90 s chase) catecholamine levels in this species; and (3) constructed in vivo catecholamine dose–response curves for cardiovascular function based on the results of the second experiment. In addition, we quantified the density(Bmax) and ligand-binding affinity(Kd) of flounder ventricular cell-surfaceβ-adrenoreceptors, and established whether they were ofβ 1 or β2 subtype using pharmacological antagonists. The cholinergic contribution to resting flounder heart rate was comparable to other teleosts (cholinergic tonus 26%). Interestingly, however,bretylium increased heart rate, resulting in a negative resting adrenergic tonus (–11.9%), and we were unable to demonstrate that catecholamines supported cardiac function at rest or at circulating concentrations approximating those following an exhaustive chase (adrenaline, 21 nmol l–1; noradrenaline, 14 nmol l–1). Myocardial Bmax was very high in the flounder (252.8 fmol mg–1 protein), and it appears that flounder ventricularβ-adrenoreceptors are predominantly of the β2 subtype[based on the inability of atenolol to displace [3H]CGP from theβ-adrenoreceptors, and the IC50 value for ICI 118551(1.91×10–6 mol l–1)]. However, the extremely low affinity (Kd 1.02 nmol l–1)for these receptors raises the possibility that the flounder heart is also populated by β3-adrenoreceptors.
Conversion of Alcohols to Alkyl Aryl Sulfides by a New Type of Oxidation–Reduction Condensation Using Phenyl Diphenylphosphinite
Authors: Kuroda Kiichi , Maruyama Yuji , Hayashi Yujiro , Mukaiyama Teruaki
Published: March 2009

Preparation of alkyl aryl sulfides from alcohols and arenethiols such as 2-sulfanyl-1,3-benzothiazole (BtzSH) is described by a new type of oxidation–reduction condensation using phenyl diphenylphosphinite (PhOPPh2) and benzoquinone derivatives or azide compounds. This reaction proceeds under mild and neutral conditions and is applicable to the thioetherification of various alcohols in which the chiral secondary and tertiary alcohols are converted into the corresponding chiral sulfides with almost complete inversion of configuration.
Kinetic analysis of apolipoproteins in postprandial hypertriglyceridaemia rabbits
Authors: Hata M , Ito T , Ohwada K
Published: March 2009

The postprandial hypertriglyceridaemia (PHT) rabbit, developed as a new animal model of metabolic syndrome, is characterized by PHT, central obesity and glucose intolerance. For detailed investigation of lipid metabolism characteristics in PHT rabbit, the plasma levels of apolipoproteins A-I, B, C-II, C-III and E were measured. Movements of apolipoproteins B100 and B48 were investigated using sodium dodecyl sulphate–polyacrylamide gel electrophoresis to determine whether postprandially increased triglyceride is exogenous or endogenous. The level of apolipoproteins A-I, B, C-II and E were increased in PHT rabbit after feeding. Apolipoproteins B100 and B48 were detected in the plasma fraction of d < 1.006 g/mL of the PHT rabbit. The postprandial increase in apolipoprotein B in the PHT rabbit reflects a numerical increase in lipoprotein particles in the blood; the increase in apolipoproteins C-II and E suggests some disturbance in lipoprotein catabolism. Apolipoprotein B48 was detected postprandially in PHT rabbits. These results suggest that delayed catabolism of exogenous lipids caused the retention of chylomicron remnants in the blood. Results also suggest that activities of the lipolytic enzyme lipoprotein lipase and hepatic triglyceride lipase were deficient and that the hepatic uptake of exogenous lipoproteins was delayed in the PHT rabbit. Especially, for examining remnant hyperlipoproteinaemia in humans, PHT rabbit is an excellent animal model for hypertriglyceridaemia research.
Contemporary prevalence of infectious agents in laboratory mice and rats
Authors: Pritchett-Corning Kathleen R , Cosentino Janice , Clifford Charles B
Published: March 2009

Periodic health screening of rodents used in research is necessary due to the consequences of unwanted infections. One determinant of the risk of infection for any given agent is its prevalence; other factors being equal, a prevalent agent is more likely than a rare one to be introduced to a research facility and result in infection. As an indicator of contemporary prevalence in laboratory populations of rats and mice, the rate of positive results in the samples received at a major commercial rodent diagnostic laboratory was compiled for this paper. Although samples from laboratory rodent vendors have been excluded, results are tabulated from samples from more than 500,000 mice and 80,000 rats submitted over several years from pharmaceutical, biotechnology, academic, and governmental institutions in North America and Europe, allowing meaningful determination of which agents are common in the research environment versus which agents are rare. In mice, commonly detected infectious agents include mouse norovirus, the parvoviruses, mouse hepatitis virus, rotavirus, Theiler's murine encephalomyelitis virus, Helicobacter spp., Pasteurella pneumotropica, and pinworms. In rats, commonly detected infectious agents include ‘rat respiratory virus’, the parvoviruses, rat theilovirus, Helicobacter spp., P. pneumotropica, and pinworms. A risk-based allocation of health-monitoring resources should concentrate frequency and/or sample size on these high-risk agents, and monitor less frequently for the remaining, lower-risk, infectious agents.
Reported analgesic and anaesthetic administration to rodents undergoing experimental surgical procedures
Authors: Stokes E L , Flecknell P A , Richardson C A
Published: March 2009

A structured literature review was carried out to assess recent trends in the administration of analgesics and anaesthetics to laboratory rats and mice undergoing surgical procedures. The ScienceDirect database was used to systematically identify studies published in peer-reviewed journals over two periods (2000–2001 and 2005–2006), 86 studies from each time period were included in the review. The total number of animals that underwent surgery, species used, type of procedure, anaesthetic regimen and analgesic administration were noted for each study. There was an increase in the reported administration of systemic analgesics from 10% in 2000–2001 to 20% in 2005–2006. Buprenorphine was the most commonly reported analgesic in both periods (2000–2001: 78%, 2005–2006: 35%) and reporting the use of non-steroidal anti-inflammatory drugs increased from 11% to 53%. There was also a change in reported anaesthetic practices, notably a decrease in the use of pentobarbital and an increase in the use of isoflurane and ketamine/xylazine. Although reported administration of analgesics has increased and there has been some refinement in the selection of anaesthetic agents used, the findings of this review suggest that there is still significant scope for improvement with respect to the perioperative care of laboratory rodents.
Technical Note—A Multiperiod Model of Inventory Competition
Authors: Nagarajan Mahesh , Rajagopalan S.
Published: March 2009

This paper explores when it is important for firms to consider stockout-based substitution and competitor's inventory levels in making inventory decisions in the context of a duopoly model. To address this question, we consider a model where two newsvendors sell substitutable products in a market with aggregate market demand D. The two firms get a proportion p and (1 − p) of this demand, where p is random. We characterize the equilibrium inventory levels of the two firms in a single-period model and show the striking property that, under certain reasonable conditions on the cost parameters, the two firms ignore their competitor's inventory levels and potential substitution demand, i.e., their inventory decisions are decoupled. Furthermore, we show under slightly more restrictive conditions on the cost parameters that the single-period results can be extended to the case where D is random. Finally, we extend the decoupling property to a multiperiod periodic review scenario and show that the resulting Nash equilibrium can be characterized simply as the solution to a single-product dynamic newsvendor problem that ignores substitution demand.
Dynamic Capacity Management with Substitution
Authors: Shumsky Robert A. , Zhang Fuqiang
Published: March 2009

We examine a multiperiod capacity allocation model with upgrading. There are multiple product types, corresponding to multiple classes of demand, and the firm purchases capacity of each product before the first period. Within each period, after demand arrives, products are allocated to customers. Customers who arrive to find that their product has been depleted can be upgraded by at most one level. We show that the optimal allocation policy is a simple two-step algorithm: First, use any available capacity to satisfy same-class demand, and then upgrade customers until capacity reaches a protection limit, so that in the second step the higher-level capacity is rationed. We show that these results hold both when all capacity is salvaged at the end of the last demand period as well as when capacity can be replenished (in the latter case, an order-up-to policy is optimal for replenishment). Although finding the optimal protection limits is computationally intensive, we describe bounds for the optimal protection limits that take little effort to compute and can be used to effectively solve large problems. Using these heuristics, we examine numerically the relative value of strictly optimal capacity and dynamic rationing, the value of perfect demand information, and the impact of demand and economic parameters on the value of optimal substitution.
Uncertainty, Information Acquisition, and Technology Adoption
Authors: Ulu Canan , Smith James E.
Published: March 2009

Consumers or firms contemplating purchasing a new product or adopting a new technology are often plagued by uncertainty: Will the benefits outweigh the costs? Should we buy now or wait and gather more information? In this paper, we study a dynamic programming model of this technology adoption problem. In each period, the consumer decides whether to adopt the technology, reject it, or wait and gather additional information by observing a signal about the technology's benefit. The technology's actual benefit may be constant or changing stochastically over time. The dynamic programming state variable is a probability distribution that describes the consumer's beliefs about the benefits of the technology. We allow general probability distributions on benefits and general signal processes and assume that the consumer updates her beliefs over time using Bayes' rule. We are interested in structural properties of this model. We show that improving the technology's benefit need not make the consumer better off and that first-order stochastic dominance improvements in the consumer's distribution on benefits need not increase the consumer's value function. Nevertheless, the model possesses a great deal of structure. For example, we obtain monotonic value functions and policies if we order distributions using likelihood-ratio dominance rather than first-order stochastic dominance. We also examine convexity properties and provide many comparative statics results.
Matrix Bidding in Combinatorial Auctions
Authors: Day Robert W. , Raghavan S.
Published: March 2009

In a combinational auction in which bidders can bid on any combination of goods, bid data can be of exponential size. We describe an innovative new combinatorial auction format in which bidders submit “matrix bids.” The advantage of this approach is that it provides bidders a mechanism to compactly express bids on every possible bundle. We describe many different types of preferences that can be modeled using a matrix bid, which is quite flexible, supporting additive, subadditive, and superadditive preferences simultaneously. To utilize the compactness of the matrix bid format in a more general preference environment, we describe a logical language with matrix bids as “atoms” and show that matrix bids compactly express preferences that require an exponential number of atoms in other bidding languages and are as expressive as the most sophisticated languages in the literature. We model the 𝒩𝒫-hard winner-determination problem as a polynomially sized integer program, specifically an assignment problem with side constraints. We show the strength of this formulation with which we rapidly solve winner-determination problems with 72 unique items, indicating that this model may be well suited for practical implementation.
Professional efficacy, exhaustion, and work characteristics among police officers: A longitudinal test of the learning‐related predictions of the demand—control model
Authors: Taris Toon W. , Kompier Michiel A. J. , Geurts Sabine A. E. , Houtman Irene L. D. , Van Den Heuvel Floor F. M.
Published: March 2009

The present study addressed the relationships among professional efficacy, emotional exhaustion, and job characteristics (job demands and job control) in the context of a two‐wave panel study among 828 Dutch police officers. Based on the demand–control model, we expected that high demands/high control would be positively related to professional efficacy, and that high demands/low control would be related to high levels of exhaustion. Moreover, we hypothesized that high levels of exhaustion would lead to lower levels of professional efficacy and that high levels of efficacy would lead to low levels of exhaustion. Structural equation modelling largely supported these predictions. High demands were longitudinally related to high levels of efficacy and high levels of exhaustion; high control was longitudinally related to high levels of efficacy. Further, efficacy and exhaustion were indeed mutually related. Finally, high levels of exhaustion were longitudinally related to high levels of demands. We conclude that there are complex, yet theoretically, and practically interpretable relations among efficacy, strain and work characteristics.
It's not my fault, it's theirs: Explanatory style of bullying targets with unipolar depression and its susceptibility to short‐term therapeutical modification
Authors: Bechtoldt Myriam N. , Schmitt Kathrin D.
Published: March 2009

Depression is one of the most frequent psychic impairments prevalent among bullying targets. It is typically characterized by an internal, global, and stable explanatory style. However, whether bullying targets with depression would apply this style to explain their social conflicts at work was unclear. Therefore, individuals who had been bullied and developed depression were compared to individuals with depression who had not been bullied. Both groups differed significantly regarding their explanatory style, as individuals with bullying experience made more external attributions to explain social conflicts they had experienced both at work and in their private lives. This preference did not change over the course of a 6‐week in‐patient psychotherapy programme.
Tumor Cell Targeting Using Folate-Conjugated Fluorescent Quantum Dots and Receptor-Mediated Endocytosis
Authors: Song Er-Qun , Zhang Zhi-Ling , Luo Qing-Ying , Lu Wen , Shi Yun-Bo , Pang Dai-Wen
Published: March 2009

Background: Luminescent nanobioprobes with cell-targeting specificity are likely to find important applications in bioanalysis, biomedicine, and clinical diagnosis. Quantum dots (QDs) are unique and promising materials for such a purpose because of their fluorescence and large surface area for attaching cell-targeting molecules.

Methods: We produced water-dispersible QDs by coating hydrophobic QDs with small amphiphilic polyethylene glycol (PEG) molecules via hydrophobic interactions. We covalently coupled folate (FA) onto the water-dispersible PEG-coated QDs (PEG-QDs) to produce FA-coupled PEG-QDs (FA-PEG-QDs).

Results: These FA-PEG-QD nanoparticles functioned as fluorescent nanobioprobes that specifically recognized folate receptors (FRs) overexpressed in human nasopharyngeal cells (KB cells) but not in an FR-deficient lung carcinoma cell line (A549 cells). Using confocal fluorescence microscopy, we demonstrated uptake of FA-PEG-QDs by KB cells but no uptake of folate-free PEG-QDs. The specificity of this receptor-mediated internalization was confirmed by comparing the uptake by KB vs A549 cells.

Conclusions: Our results suggest that such cell-targeting fluorescent nanobioprobes are potentially very powerful tools for recognizing target cells and delivering and tracking drugs and other therapeutic materials.
Day 5 Morning Serum Cortisol Predicts Hypothalamic-Pituitary-Adrenal Function after Transsphenoidal Surgery for Pituitary Tumors
Authors: Jayasena Channa N , Gadhvi Kunal A , Gohel Bhavini , Martin Niamh M , Mendoza Nigel , Meeran Karim , Dhillo Waljit S
Published: March 2009

Background: Adrenal insufficiency is a complication of transsphenoidal surgery (TSS) for pituitary adenoma, and correct identification of patients requiring glucocorticoid replacement is important. Controversy exists over which early postoperative 9 AM cortisol concentration reliably predicts hypothalamic-pituitary-adrenal (HPA) axis reserve, as defined by the insulin tolerance test (ITT).

Methods: Data were reviewed for 36 patients undergoing TSS followed by day 5 postoperative 9 AM cortisol measurement and ITT 6 weeks postsurgery. All patients received postoperative glucocorticoid replacement, which was discontinued if the 9 AM serum cortisol was >300 nmol/L.

Results: Of 23 patients who failed the ITT (peak cortisol <500 nmol/L), 20 also had a day 5, 9 AM serum cortisol <300 nmol/L. Nine of 13 patients who passed the ITT had a day 5, 9 AM cortisol >300 nmol/L. The cutoff cortisol concentration of 300 nmol/L had 86.9% (66.4%–97.2%) diagnostic sensitivity, 69.2% (38.6%–90.9%) diagnostic specificity, and 83.3% (61.8%–94.5%) positive predictive value (PPV) for detecting secondary adrenal insufficiency. Increasing the cutoff to 392 nmol/L resulted in 100% (85.2%–100%) sensitivity, 46.1% (19.2%–74.9%) specificity, and 76.6% (57.3%–89.4%) PPV. Decreasing the cutoff to 111 nmol/L resulted in 100% (75.3%–100%) specificity and 100% (67.9%–100%) PPV, although sensitivity was 47.8% (26.8%–69.4%).

Conclusions: A day 5 post-TSS 9 AM serum cortisol <111 nmol/L reliably detects secondary adrenal insufficiency, and concentrations >392 nmol/L support intact HPA function. Because concentrations of 111–392 nmol/L are poorly predictive of HPA function, glucocorticoid replacement should continue in such cases until definitive testing is performed using an ITT.
Design and Evaluation of Two Laboratory Tests for the Nets of a Flexible Anchored Slope Stabilization System
Authors: Castro-Fresno Daniel , López Q. Luis , Blanco-Fernandez Elena , Zamora-Barraza David
Published: March 2009

This paper evaluates two new tests to characterize cable nets used in slope stabilization; a concentrated load test (CLT) and a distributed load test (DLT). These tests enable engineers to obtain the stress versus displacement graph and the maximum resistance. Both test devices and test methodology have been designed by the Construction Technology Research Group (GITECO) at the University of Cantabria. These two tests have enabled the certification of two different manufacturers of cable nets, Geobrugg and Malla Talud Cantabria (MTC). The results showed that these tests provide representative results of the net resistance. To verify the effectiveness of these new tests, they have been performed with various cable nets, from which homogeneous, logical results have been obtained, which are representative of the real working conditions. When performing the distributed load test, the force was applied to a pyramid of fine gravel sacks that enabled the forces to be distributed throughout the net. With this configuration, the net was deformed, acquiring an elliptical form in the lower free area. In the concentrated load test, the force was applied through a metallic plate of 600 mm diameter that deformed the net locally. The result always showed homogeneous behavior of the different samples tested. This allowed the test to be repeated in the same conditions several times. With the results of both tests an analysis was carried out relating the net grid, the load applied, and the displacement obtained. This enabled the generation of regression functions that provided information about the resistance value and the net displacement according to the chosen grid.
Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni-18Cr-6Fe Alloys
Authors: Ezuber Hosni M.
Published: March 2009

The breakdown potentials of mill-annealed Ni-18Cr-6Fe alloys were measured in wide range of chloride concentrations (0.001–1 M NaCl) and various concentrations of thiosulfate ranging from 0–0.25 M (Na2S2O3) at 80°C using the potentiodynamic technique. These potentials were compared with heat treated alloys for one or five hours at 900°C (and quenched). This work aimed to study the effect of sensitization on the pitting characteristics of this alloy in chloride-thiosulfate solutions. The anodic polarization curves revealed that sensitized alloys became more susceptible to chloride and thiosulfate pitting attack, or both. Addition of thiosulfate was potentially detrimental to chloride pitting resistance and the aggressiveness of thiosulfate species was found dependent on the ratio of chloride to thiosulfate concentration as the overall ionic strength is varied. A thiosulfate to chloride ratio of 1:40 (S2O2–3 / Cl–=0.025) was found be the most aggressive, regardless of ionic strength or heat treatment duration.
Der Bogen des Lebens
Authors: Bahr Hans-Dieter
Published: March 2009

Es geht hier nicht um die Selbigkeit des Umschlages von Lebendigem (zon) in Totes (tetnekos) und umgekehrt, von welcher Heraklit auch spricht, sondern um die zum Schwingen gebrachte Gespanntheit sterblichen Lebens. Das Wort ,Bogen' ruft  der Tat dieses Wortes nach  mit dem Leben dessen Tod zur Anwesenheit, und es wäre nicht Leben, wenn es nicht sterblich wäre. Der Bogen nennt sterbliches Leben, eine Sterblichkeit, die zum Verstehen ihrer selbst nur über den Unterschied zu dem gelangt, was nicht sterblich ist. Aber nun geht es nicht mehr um einen Gegensatz zwischen Sterblichem und Göttlichem, vielmehr wendet sich, im Schritt über die Sterblichkeit hinaus, das Leben zu dieser zurück. Mythisch allerdings wurde die Sterblichkeit zumal von der Unsterblichkeit im Sinne des Unvergänglichen her betrachtet und dadurch oft ihrem Wesen nach mehr verschattet als beleuchtet.
Leben und Erkenntnis. Über eine Entwicklung im Werk von Georges Canguilhem
Authors: Schmidgen Henning
Published: March 2009

1952 veröffentlicht der Philosoph und Wissenschaftshistoriker Georges Canguilhem die Aufsatzsammlung La connaissance de la vie. 1968 erscheint in seinen Etudes d′histoire et de philosophie des sciences ein Abschnitt mit dem Titel La nouvelle connaissance de la vie. Er enthält nur einen einzigen Beitrag, den grundlegenden Aufsatz Le concept et la vie. Die vorliegende Studie nimmt das Attribut nouvelle zum Anlaß, die auf Abstammungslinien von Begriffen ausgerichtete Wissenschaftsgeschichte von Canguilhem auf ihre Entwicklung in den Jahren zwischen 1950 und 1965 zu befragen. Es wird die These formuliert, dass Canguilhem in den sechziger Jahren, angesichts neuerer Entwicklungen in den Lebenswissenschaften (u.a. die Entdeckung der DNA-Struktur) und trotz einer durchgehend von Nietzsche inspirierten Sichtweise des Verhältnisses von Leben und Erkenntnis, eine Revision früherer Positionen vorgenommen hat: Während er das Erkenntnisproblem in den fünfziger Jahren vor allem auf eine Individualität des Verhaltens und Erlebens innerhalb einer bestimmten Umwelt bezieht und erkennen gleichsetzt mit analysieren, vermessen und berechnen, verbindet er es in späteren Jahren mit einer Kollektivität der Vererbung, der Transmission, Transkription und Expression von genetischer Information. Folgerichtig wird erkennen nunmehr definiert als sich informieren, sich üben im Entziffern und Dekodieren.
Die Kürze des Lebens und der Wunsch nach Ruhe
Authors: Bilstein Johannes
Published: March 2009

Der Beitrag setzt sich mit den traditionellen Topoi von der Kürze des Lebens und mit den in der gegenwärtigen Bildungspolitik erkennbaren Tendenzen und Parolen zur Beschleunigung und Effektivierung des Lebens auseinander. Dabei werden diesen einer ungebrochenen Fortschritts-Orientierung folgenden Tendenzen Argumentationsmuster der biographischen Vollendung entgegengesetzt.
Auch eine Poetik des Hörbuchs  Goethes Empfehlung des Vorlesens
Authors: Meyer-Kalkus Reinhart
Published: March 2009

Es ist die ironische Pointe im Leben eines Theaterdirektors, dass er nach über 20-jähriger Tätigkeit zur Einsicht gelangt, die wichtigsten Dramatiker der Weltliteratur wie Shakespeare und Calderón seien auf der Bühne eigentlich nicht spielbar, am besten würden sie vorgelesen. Goethe war dieser Theaterdirektor. Das Vorlesen dramatischer Teste erschien ihm nicht nur als Hilfsmittel der Proben oder als Ersatz für Theater-Aufführungen, sondern als eine eigene Kunstform, die geeignet ist, die Einbildungskraft des Zuhörers auf besondere Weise anzusprechen.
Lob der Wunderlichkeit. Lebensweisen und Life Sciences
Authors: Schulze Holger
Published: March 2009

Was ist Wunderlichkeit? Ausgehend von neurotischen Übersprungshandlungen oder Ticks zeigt sich wunderliches Verhalten als Riss in ansonsten perfekten Persone. Die statuarische Körper-Maske bricht auf (vgl. Michel Serres) und weist auf ein dynamischeres Konzept von Leben und Körper hin als das gegenwärtig vorherrschend medial dargestellte (vgl. Georges Canguilhem). Sind Freaks of Nature dann nicht der Normalfall? - Was, wenn Wunderlichkeit wiederum strategisch eingesetzt wird?
Kinetic and Mechanistic Investigations on Oxidation of L-tryptophan by Diperiodatocuprate(III) in Aqueous Alkaline Medium
Authors: Shetti Nagaraj P. , Nandibewoor Sharanappa T.
Published: March 2009

The oxidation of L-tryptophan (L-TRP) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.20 mol dm-3was studied spectrophotometrically at 298 K. The reaction between DPC and L-tryptophan in alkaline medium exhibits 1:4 stoichiometry (L-tryptophan: DPC). The reaction is of first order in [DPC] and has less than unit order in [L-TRP] and negative fractional order in [periodate] and [alkali]. Intervention of free radicals was observed in the reaction. The oxidation reaction in alkaline medium has been shown to proceed via a DPC- L-tryptophan complex, which decomposes slowly in a rate determining step followed by other fast steps to give the products. The main products were identified by spot test, IR,1H NMR,13CNMR and LC-MS spectral studies. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed and thermodynamic quantities were also determined.
Contraceptive potential of porcine and feline zona pellucida A, B and C subunits in domestic cats
Authors: Eade Joyce A , Roberston Ian D , James Cassandra M
Published: March 2009

Feral cat populations are a major problem in many urban regions throughout the world, threatening biodiversity. Immunocontraception is considered as an alternative and a more humane means to control overpopulation of pest animals than current methods including trapping, poisoning and shooting. In this study, we evaluate porcine zona pellucida (ZP) polypeptide (55 kDa) and feline ZP A, B and C subunits expressed by plasmid vectors as candidate vaccines against fertility in the female domestic cat. Cats were injected subcutaneously with three doses of the ZP vaccines. Vaccinated cats were compared with naïve cats for ZP-antibody response, ovarian histology and fertility after mating. Vaccination with native porcine ZP 55 kDa polypeptide induced anti-porcine ZP antibodies detected by ELISA. However, these antibodies did not cross-react with feline ZP as assessed by immunohistochemistry and no effect on fertilityin vivowas observed after mating. However, vaccination of cats with feline ZPA or feline ZPB+C DNA vectors elicited circulating antibodies specific for feline ZP as assessed by ELISA, with reactivity to native feline ZP in ovarian folliclesin situ. Vaccination with feline ZPA and ZPB+C DNA did not elicit changes in ovarian histology. Although sample sizes were small, conception rates in mated females were 25 and 20% in the ZPA and ZPB+C vaccinated groups respectively, compared with 83% in the control group. We conclude that feline ZPA and ZPB+C subunits are potential candidate antigens for immunocontraceptive vaccines in the domestic cat.