Early Stages Of Selection Research Articles

Failing to Ignore: Paradoxical Neural Effects of Perceptual Load on Early Attentional Selection in Normal Aging

We examined visual selective attention under perceptual load--simultaneous presentation of task-relevant and -irrelevant information--in healthy young and older adult human participants to determine whether age differences are observable at early stages of selection in the visual cortices. Participants viewed 50/50 superimposed face/place images and judged whether the faces were male or female, rendering places perceptible but task-irrelevant. Each stimulus was repeated, allowing us to index dynamic stimulus-driven competition from places. Consistent with intact early selection in young adults, we observed no adaptation to unattended places in parahippocampal place area (PPA) and significant adaptation to attended faces in fusiform face area (FFA). Older adults, however, exhibited both PPA adaptation to places and weak FFA adaptation to faces. We also probed participants' associative recognition for face-place pairs post-task. Older adults with better place recognition memory scores were found to exhibit both the largest magnitudes of PPA adaptation and the smallest magnitudes of FFA adaptation on the attention task. In a control study, we removed the competing perceptual information to decrease perceptual load. These data revealed that the initial age-related impairments in selective attention were not due to a general decline in visual cortical selectivity; both young and older adults exhibited robust FFA adaptation and neither group exhibited PPA adaptation to repeated faces. Accordingly, distracting information does not merely interfere with attended input in older adults, but is co-encoded along with the contents of attended input, to the extent that this information can subsequently be recovered from recognition memory.

On the issue of peptide recognition in T cell development.

CD4-CD8 double positive (DP) thymocytes undergo a differentiation process in the thymus where they are selected based on their ability to recognize peptide antigens presented on self major histocompatibility complex (MHC) molecules. The first stage of this process is positive selection, a quality-control mechanism which ensures that the T cell receptors (TCR) presented on developing thymocytes can transmit signals via peptides presented on either MHC class I (MHC1) or MHC class II (MHC2) molecules. Work over the past decade has revealed that the peptides that drive positive selection of both CD4 and CD8 lineage cells deliver only weak TCR signals. In line with these observations, specialized protein degradation machineries have been discovered in the thymic cortex that presumably generate specialized low-affinity peptide repertoires for presentation on MHC1 and MHC2 molecules. TCR signals transduced through these weak-affinity ligands in the early stages of positive selection alter the kinetics of expression of CD4 and CD8 molecules and play a crucial role in commitment of thymocytes to either the CD4 or CD8 lineages. In this work, we review the experiments that explore the peptide repertoires that are presented to developing thymocytes during positive selection, the observed signaling patterns that lead to CD4 versus CD8 lineage commitment, and speculate about how specialized organization of the signaling machinery in DP thymocytes may allow for efficient transduction of weak signals during the course of positive selection.

Developing Probabilistic Well Construction Estimates Using Regression Analysis

This paper proposes regression analysis as an appropriate method to develop probabilistic estimates for well construction cost and schedule estimates. These estimates are of sufficient quality for use in portfolio management decisions, lease sales, property valuations, project feasibility studies, and in the early stages of concept selection. The paper provides a brief theoretical overview of the method and discusses potential problems encountered in its implementation. A demonstration is provided using recent deepwater drilling data from the Gulf of Mexico.

Stochastic Analysis of CAN-Based Real-Time Automotive Systems

Many automotive applications, including most of those developed for active safety and chassis systems, must comply with hard real-time deadlines, and are also sensitive to the average latency of the end-to-end computations from sensors to actuators. A characterization of the timing behavior of functions is used to estimate the quality of an architecture configuration in the early stages of architecture selection. In this paper, we extend previous work on stochastic analysis of response times for software tasks to controller area network messages, then compose them with sampling delays to compute probability distributions of end-to-end latencies. We present the results of the analysis on a realistic complex distributed automotive system. The distributions predicted by our method are very close to the probability of latency values measured on a simulated system. However, the faster computation time of the stochastic analysis is much better suited to the architecture exploration process, allowing a much larger number of configurations to be analyzed and evaluated.

An ERP Examination of the Different Effects of Sleep Deprivation on Exogenously Cued and Endogenously Cued Attention

Behavior and neuroimaging studies have shown selective attention to be negatively impacted by sleep deprivation. Two unresolved questions are (1) whether sleep deprivation impairs attention modulation of early visual processing or of a later stage of cognition and (2) how sleep deprivation affects exogenously versus endogenously driven selective attention. To investigate the time course and different effects of sleep deprivation on exogenously and endogenously cued selective attention. Participants performed modified Attention Network Tests (ANTs) using exogenously and endogenously cued targets to index brain networks underlying selective attention. Target-locked event-related potentials (ERPs) were recorded as participants performed the Attention Network Tests on 2 days separated by 24 hours of total sleeplessness. Fourteen US Military Academy cadets and 12 US Army soldiers from the Ironhorse Brigade, Ft. Hood, Texas. For both Attention Network Tests, sleep deprivation led to slowed response times, decreased accuracy rates, a diminished positive P3 (450- to 550-ms) ERP component, and an enhanced P2 (312- to 434-ms) ERP component. In contrast, the parietal N1 (157- to 227-ms) ERP response was reduced with sleep deprivation for endogenously, but not exogenously, cued targets. These sleep deprivation-related effects occurred in the context of typical behavior and ERP patterns expected in a cued spatial-attention task. These findings suggest that as little as 24 hours of sleep deprivation affects both early and late stages of attention selection but affects endogenously driven selective attention to a greater degree than it does exogenously driven selective attention.

Adaptation strategy, germplasm type and adaptive traits for field pea improvement in Italy based on variety responses across climatically contrasting environments

A pea breeding strategy is required to cope with the large climatic variation featuring south-European environments. Thirty-seven recent cultivars bred by 21 European or Australian institutions were grown in two climatically contrasting Italian sites (Lodi, subcontinental; Foggia, Mediterranean), two cropping years per site and two sowing times per year, to define various elements of this strategy. The study assessed: (i) the impact of genotype × environment (GE) interaction due to spatial and temporal factors on the consistency of top-yielding cultivars; (ii) the similarity between environments for GE effects and its implications on adaptation strategies; (iii) the extent of genotypic and GE interaction effects, and the relationship with adaptive responses, for various morphophysiological traits; (iv) the adaptation pattern and the combination of adaptive traits featuring three germplasm types, i.e. European spring and winter types, and germplasm selected in Mediterranean environments; (v) the predicted efficiency of direct and indirect selection procedures for grain yield. The geoclimatic area had a major impact on crop yield (5.15 t/ha in Lodi vs. 2.52 t/ha in Foggia) but tended to affect GE interaction less than time or year of autumn sowing, suggesting to breed for wide adaptation. Top-yielding cultivars as modeled by additive main effects and multiplicative interaction were environment-specific. On average, spring and winter materials outyielded the Mediterranean germplasm but the spring type, characterized by wide entry variation, included most widely- and specifically-adapted top-yielding cultivars. Cold-tolerant spring-type germplasm is preferable to breed for wide adaptation as it may combine high yield potential with adaptation to winter cold and terminal drought and heat stress. Lodging susceptibility, harvest index, onset and duration of flowering, and canopy height at maturity assessed in individual environments showed moderate to fairly high broad-sense heritability on a plot basis ( h 2 > 0.20) and tended to correlation with yield over test environments ( r ≥ 0.20). An indirect selection index including harvest index and canopy height exhibited about 20% greater predicted efficiency than direct selection for yield when using one selection environment and could be preferred for early selection stages. Direct yield selection in late selection stages should ideally be performed across 2 years in two environments that contrast for geoclimatic area and time of autumn sowing.

Relative performance of the sugarcane families in early selection stages

Family selection is widely used in early stages of selection in sugarcane breeding programs. Families are evaluated in the first one or two stages of selection and individual clones are selected from within superior families. These selected clones are evaluated for their performance in two or three selection stages before commercial release of superior clones. This study was undertaken to assess the relative performance of five sugarcane families for predicting potential parental combinations and also to identify rare and elite recombinants that can be exploited in future. Results from this study highlighted that two families viz., Co 7704 x Co 8209 and Co 85002 x Co 86011 contributed a greater proportion of elite clones combining acceptable levels of cane yield and sugar yield. The top ten clones selected based on sugar yield from the stage II evaluation holds greater promise in the subsequent regional selection programs. Overall, the findings suggest that selection of the best families based on their mean performance and further selection of individual clones based on their sugar yield in early stages would improve the efficiency of selection and increase heritability in the genetic populations being tested.

Quantitative Retention‐Activity Relationship Studies by Liposome Electrokinetic Chromatography to Predict Skin Permeability

AbstractLiposome electrokinetic chromatography (LEKC) provides a simple and facile approach for drug membrane interactions using liposome as a pseudostationary phase. This study evaluated the potential of LEKC for high‐throughput skin permeability profiled as an in vitro technique. A quantitative retention‐activity relationship (QRAR) model for the estimation of skin permeability was proposed. For the 16 structurally diverse chemicals, lg k correlated well with permeability values (R2=0.886). The predictive ability of the model was evaluated by cross‐validation. The result was compared to traditional quantitative structure‐activity relationship, QSAR, models using some molecular descriptors and physicochemical parameters. Interestingly, a single LEKC retention parameter was capable of describing the skin permeability, while three variables in QSAR were needed to achieve a similar correlation (R2=0.704). The QRAR models developed in this paper may be a useful method to screening new chemicals and in the early stage of development and selection of chemicals.

MicroRNA Regulation of Cell Lineages in Mouse and Human Embryonic Stem Cells

Cell fate decisions of pluripotent embryonic stem (ES) cells are dictated by activation and repression of lineage-specific genes. Numerous signaling and transcriptional networks progressively narrow and specify the potential of ES cells. Whether specific microRNAs help refine and limit gene expression and, thereby, could be used to manipulate ES cell differentiation has largely been unexplored. Here, we show that two serum response factor (SRF)-dependent muscle-specific microRNAs, miR-1 and miR-133, promote mesoderm formation from ES cells but have opposing functions during further differentiation into cardiac muscle progenitors. Furthermore, miR-1 and miR-133 were potent repressors of nonmuscle gene expression and cell fate during mouse and human ES cell differentiation. miR-1's effects were in part mediated by translational repression of the Notch ligand Delta-like 1 (Dll-1). Our findings indicate that muscle-specific miRNAs reinforce the silencing of nonmuscle genes during cell lineage commitment and suggest that miRNAs may have general utility in regulating cell-fate decisions from pluripotent ES cells.

A cassava clonal evaluation trial based on a new cassava breeding scheme

Cassava (Manihot esculenta) breeding at the earlier stages so far has been mainly based on a mass phenotypic recurrent selection, as little data is taken. This has resulted in a long breeding cycle and lack of organised information on the breeding values of parental lines used in the breeding programmes. The International Institute of Tropical Agriculture (CIAT) recently initiated a scheme to try and correct this, by introduction of replication and blocking in the clonal evaluation trial (CET) and collection of data on all genotypes at early stages of breeding. The aim of the study was to evaluate a CET using the new breeding scheme. Replicating and blocking of clones improved the accuracy of the data obtained. High broad-sense heritability values, comparable to those at advanced selection stages, were obtained, as environmental effects were minimised. The highest was for harvest index (HI) (0.80), followed by cassava frogskin disease (CFSD) (0.79), dry matter content (DMC) (0.75) fresh and dry root yields (DRY) (0.73), root weight (RtWt) (0.61), number of commercial roots (0.60) and roots per plant (RtPlt) (0.43). DMC, HI and RtWt were identified as important variables in selection and determination of economic yield at early stages of selection.

Brain-Electrical Correlates of Negative Priming

Over the past three decades research using event-related brain potentials (ERPs) has lead to important advances in the study of human attention (for a review, see Luck, Woodman, & Vogel, 2000). The list of well-known examples includes, among many other things, the operating of attention at early stages of selection (Hillyard, Hink, Schwent, & Picton, 1973), the factors eliciting early selective attention (Luck & Hillyard, 1999), the functional analysis of attentional networks (Posner & Petersen, 1990), and the controlled and automatic aspects of auditory match and mismatch (Naatanen, 1992). This special issue follows the tradition of using ERPs as a means to develop further the insight into attentional mechanisms. If one object is selectively attended, distracting objects must be ignored. It has been known for quite some time that ignoring a distracting object leaves processing traces that can be measured in participants’ behavior at some point later in time. Specifically, reactions to recently ignored objects are slower and typically also more errorprone than reactions to novel objects (Dalrymple-Alford & Budayr, 1966), which is why “negative priming” has evolved as the term representing the behavioral consequences of ignoring. These behavioral consequences of ignoring are extremely robust. They can be observed with stimuli as diverse as simple geometric shapes (Yee, 1991), line drawings of objects (Tipper, 1985), photographs of faces (Buchner, Steffens, & Berry, 2000), written letters (Neumann & DeSchepper, 1991), written words (Rothermund, Wentura, & De Houwer, 2005), spoken words (Banks, Roberts, & Ciranni, 1995), animal sounds (Mayr & Buchner, in press), instrument sounds (Buchner & Mayr, 2004) and even across the visual and auditory modalities (Buchner, Zabal, & Mayr, 2003; Driver & Baylis, 1993). In fact, research on the behavioral consequences of ignoring an object has become so numerous and so diverse that the customarily cited reviews (most often Fox, 1995; May, Kane, & Hasher, 1995; Neill, Valdes, & Terry, 1995; Tipper, 2001) have ceased being adequate for characterizing the field. Despite the abundance of experimental evidence pertaining to the behavioral consequences of ignoring, hardly anything seems to have been published about the concurrent brain-electrical correlates of ignoring. In fact, this empirical gap in our understanding of the negative priming phenomenon began to be closed only recently (Kathmann, Bogdahn, & Endrass, 2006; Mayr, Niedeggen, Buchner, & Pietrowsky, 2003). The apparent gap has also stimulated the current special issue on brain-electrical correlates of negative priming, the more so as one may hope that this research may help deciding which theory best explains the negative priming phenomenon by enabling us to look beyond mere reaction times and error rates using a high temporal resolution research tool. Needless to say, the experimental work collected here is just about as diverse as the rest of the negative priming literature. The contribution by Ruge and Naumann is based on a spatial negative priming task. In this task, participants report the location of a target object while ignoring a distractor object. The typical slowdown in reactions and increase in error rates are observed when the target object appears at the location at which a distractor was presented on the preceding trial, that is, when the previous distractor location (the prime distractor location) becomes the subsequent target location (the probe distractor location). When compared to a control condition with no overlap of prime and probe locations, this condition was characterized by a lower-amplitude N1 and an enhanced-amplitude N2pc, both contralateral to the visual half-field of the target location, and a posteriorly distributed enhanced-amplitude N2 without lateralization. Ruge and Naumann interpret their findings as evidence in favor of a variant of a distractor inhibition account of negative priming. According to the distractor inhibition account (Houghton & Tipper, 1994; Neill, 1977; Tipper, 1985), negative priming reflects the operation of an attentional selection mechanism that prevents access of ignored objects to overt responses by suppressing competing distractor input. This mechanism enables more efficient responding to the current target, but causes a delay in responding when the previously ignored (and, hence, inhibited) distractor becomes the new target. Neill and colleagues (Neill & Valdes, 1992; Neill, Valdes, Terry, & Gorfein, 1992) later argued that a © 2006 Federation of European Psychophysiology Societies

Role of female parent in the inheritance of brix in early selection stages of sugarcane

Breeding for high levels of sugar yield requires basic information on the mode of inheritance of brix in seedling population derived from parental clones differing in sucrose content. The research aimed to examine the role of female parent in the inheritance of brix in early stages of sucrose accumulation. One thousand eight hundred and ninety seedlings derived from thirty biparental crosses involving 20 Indian commercial hybrids and five Foreign hybrids were studied. Brix measurement on the parent clones and seedlings were taken during October (8 months), December (10 months) and February (12 months). The heritability of brix estimated from the regression of offspring on the midparent was 0.63 in the month of October, 0.60 in December and 0.52 in February with a highly significant regression mean squares. Selection for high brix is therefore effective in early stages of Sugarcane. A large proportion of the seedling population recorded high brix value when clones such as CoC 671, Co 85002 and Co 86002 were used as the female parent. Among the foreign hybrids, Puerto Rico clones viz., PR 1068 and PR 1095 gave more number of high quality progenies when used as female. The results of the present study indicated the potential to generate high quality progenies when high sucrose parent clones were used as female instead of male.

Susceptibility of Perennial Small Grains to Soilborne wheat mosaic virus and Wheat spindle streak mosaic virus

Perennial small grains offer the potential for sustainable production of forage and grain on marginal and erodable lands. The authors' results suggest that perennial small grains are at risk for infection by Soilborne wheat mosaic virus (SBWMV) and Wheat spindle streak mosaic virus (WSSMV) and that resistant cultivars may be needed for management of these diseases. Ideally, breeders should screen perennial small grain lines for resistance to soilborne viruses in the early stages of selection. Accepted for publication 27 October 2005. Published 30 November 2005.

Cassava breeding: opportunities and challenges

Although cassava is a major food crop, its scientific breeding began only recently compared with other crops. Significant progress has been achieved, particularly in Asia where cassava is used mainly for industrial processes and no major biotic constraints affect its productivity. Cassava breeding faces several limitations that need to be addressed. The heterozygous nature of the crop and parental lines used to generate new segregating progenies makes it difficult to identify parents with good breeding values. Breeding so far has been mainly based on a mass phenotypic recurrent selection. There is very little knowledge on the inheritance of traits of agronomic relevance. Several approaches have been taken to overcome the constraints in the current methodologies for the genetic improvement of cassava. Evaluations at early stages of selection allow for estimates of general combining ability effect or breeding values of parental lines. Inbreeding by sequential self-pollination facilitates the identification of useful recessive traits, either already present in the Manihot gene pool or induced by mutagenesis.

Inheritance of glucose content in tubers of diploid potato families

During two consecutive years 17 unselected families of diploid potatoes in comparison to their parents and standard cultivars were assessed for glucose content in tubers. Glucose content was evaluated using Potato Test Strips in tubers stored at 10 C, 4 C, and 4 C followed by reconditioning at 18 C. Distribution of glucose content in families indicated that the trait is inherited in a polygenic way. Transgressive individuals in families in comparison to respective parents were found in all treatments applied. Maternal effect on glucose content in tubers was found in one out of three tested families after cold storage (4 C) and the same families after reconditioning. Analysis of variance showed significant influence of year on the trait. Significance of GCA and SCA showed that both additive effects and genetic interactions are involved in determining of glucose content in tubers in all applied treatments. It was found that glucotests can be recommended for evaluation of chipping ability in early stages of selection.

Comparison of alamar blue and MTT assays for high through-put screening

The performance of alamar blue and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) cell viability assays in a high through-put format were compared. A total of 117 drugs chosen for their wide range of therapeutic areas were screened at 10 μM using both assays in human hepatoma cell line HepG2. Except for terfenadine and astemizole, which performed consistently in both assays, the alamar blue assay was slightly more sensitive than the MTT assay for most compounds. The MTT assay was less sensitive detecting an effect for daunorubicin and trifluoperazine. Seven drugs, astemizole, daunorubicin, ellipticine, fluphenazine, terfenadine, thioridazine and trifluoperazine, had percent viability results of 55% or less in the alamar blue assay at the single point screen. These were re-tested in both assays for reconfirmation of cytotoxicity and determination of the EC 50 values. Except for daunorubicin, the EC 50 values were comparable in both assays. Based on these results and the Z ′-factor assessment of assay quality, both assays provided useful information to identify in vitro cytotoxic drugs at early stages of drug candidate selection. However, careful interpretation of data is warranted due to the possibility of false positive or negative results caused by inducers and/or inhibitors of metabolic enzymes that are responsible for transformation of cell toxicity end points, as we demonstrated using dicumarol.

Complementary approaches to preliminary foreign market opportunity assessment: country clustering and country ranking

Companies seeking to expand abroad are faced with the complex task of screening and evaluating foreign markets. How can managers define, characterize, and express foreign market opportunity? What makes a good market, an attractive industry environment? National markets differ in terms of market attractiveness, due to variations in the economic and commercial environment, growth rates, political stability, consumption capacity, receptiveness to foreign products, and other factors. This research proposes and illustrates the use of two complementary approaches to preliminary foreign market assessment and selection: country clustering and country ranking. These two methods, in combination, can be extremely useful to managerial decision makers in the early stages of foreign market selection.

Prevalent role of TCR alpha-chain in the selection of the preimmune repertoire specific for a human tumor-associated self-antigen.

The specificity of recognition of pMHC complexes by T lymphocytes is determined by the V regions of the TCR alpha- and beta-chains. Recent experimental evidence has suggested that Ag-specific TCR repertoires may exhibit a more V alpha- than V beta-restricted usage. Whether V alpha usage is narrowed during immune responses to Ag or if, on the contrary, restricted V alpha usage is already defined at the early stages of TCR repertoire selection, however, has remained unexplored. Here, we analyzed V and CDR3 TCR regions of single circulating naive T cells specifically detected ex vivo and isolated with HLA-A2/melan-A peptide multimers. Similarly to what was previously observed for melan-A-specific Ag-experienced T cells, we found a relatively wide V beta usage, but a preferential V alpha 2.1 usage. Restricted V alpha 2.1 usage was also found among single CD8(+) A2/melan-A multimer(+) thymocytes, indicating that V alpha-restricted selection takes place in the thymus. V alpha 2.1 usage, however, was independent from functional avidity of Ag recognition. Thus, interaction of the pMHC complex with selected V alpha-chains contributes to set the broad Ag specificity, as underlined by preferential binding of A2/melan-A multimers to V alpha 2.1-bearing TCRs, whereas functional outcomes result from the sum of these with other interactions between pMHC complex and TCR.

Assessing the identity of grapevine plants from vineyards from Crete and Samos by microsatellite profiling

<p style="text-align: justify;">Four nuclear microsatellite markers were used for testing 45 plants visually selected from 18 locations in controlled origin wine areas of Crete and Samos, and representing 7 cultivars. Discrepancies between the obtained profile and a profile from a plant of reference of a given cultivar, were found for 26 plants. This suggested that microsatellite profiling at a small number of loci was an efficient procedure in order to detect and remove inappropriate material at an early stage of selection. In a second case, three plants were sampled from a vineyard, located in the controlled origin wine area of Dafnes in Crete, for testing their identity in comparison to cultivars of reference at 15 nuclear microsatellite loci. Only one matched its identity profile of reference. One of them was found to be a continental cultivar, named Fegi and not usually grown in Crete. This showed the resolution of microsatellite profiling for problems where misnaming at an early stage in nursery or trade could have important consequences for growers in controlled origin wine areas.</p>

Resistance to multiple novel antifolates is mediated via defective drug transport resulting from clustered mutations in the reduced folate carrier gene in human leukaemia cell lines.

We have studied the molecular basis of resistance of multiple human leukaemia CCRF-CEM sublines to the novel antifolates ZD9331, GW1843, AG2034, PT523 and edatrexate, which use the reduced folate carrier (RFC) as their main cellular uptake route and that target different folate-dependent enzymes. Antifolate-resistant sublines established by stepwise and single-step selections displayed up to 2135-fold resistance to the selection drug, and up to 2323-fold cross-resistance to various hydrophilic antifolates. In contrast, these sublines were up to 17- and 20-fold hypersensitive to the lipophilic antifolates AG377 and trimetrexate, respectively. The total reduced folate pool of these antifolate-resistant sublines shrunk by 87-96%, resulting in up to 42-fold increased folic acid growth requirement. These sublines lost 92-97% of parental [(3)H]methotrexate influx rates. Genomic PCR single-strand conformational polymorphism analysis and sequencing revealed that most of these drug-resistant sublines harboured RFC mutations that surprisingly clustered in two confined regions in exons 2 and 3. The majority of these mutations resulted in frame-shift and/or premature translation termination and lack of RFC protein expression. The remaining mutations involved single amino acid substitutions predominantly residing in the first transmembrane domain (TMD1). Some RFC-inactivating mutations emerged during the early stages of antifolate selection and were stably retained during further drug selection. Furthermore, some sublines displayed a markedly decreased or abolished RFC mRNA and/or protein expression. This constitutes the first demonstration of clustering of multiple human RFC mutations in TMD1, thereby suggesting that it plays a functional role in folate/antifolate binding and/or translocation. This is the first molecular characterization of human RFC-associated modalities of resistance to various novel antifolates in multiple leukaemia sublines.