Home About us Contact
|
Home About us Contact | ||
|
|
||
One Marker (one + marker)
Kinds of One Marker Selected AbstractsRepetition suppression of induced gamma band responses is eliminated by task switchingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2006Thomas Gruber Abstract The formation of cortical object representations requires the activation of cell assemblies, correlated by induced oscillatory bursts of activity >,20 Hz (induced gamma band responses; iGBRs). One marker of the functional dynamics within such cell assemblies is the suppression of iGBRs elicited by repeated stimuli. This effect is commonly interpreted as a signature of ,sharpening' processes within cell-assemblies, which are behaviourally mirrored in repetition priming effects. The present study investigates whether the sharpening of primed objects is an automatic consequence of repeated stimulus processing, or whether it depends on task demands. Participants performed either a ,living/non-living' or a ,bigger/smaller than a shoebox' classification on repeated pictures of everyday objects. We contrasted repetition-related iGBR effects after the same task was used for initial and repeated presentations (no-switch condition) with repetitions after a task-switch occurred (switch condition). Furthermore, we complemented iGBR analysis by examining other brain responses known to be modulated by repetition-related memory processes (evoked gamma oscillations and event-related potentials; ERPs). The results obtained for the ,no-switch' condition replicated previous findings of repetition suppression of iGBRs at 200,300 ms after stimulus onset. Source modelling showed that this effect was distributed over widespread cortical areas. By contrast, after a task-switch no iGBR suppression was found. We concluded that iGBRs reflect the sharpening of a cell assembly only within the same task. After a task switch the complete object representation is reactivated. The ERP (220,380 ms) revealed suppression effects independent of task demands in bilateral posterior areas and might indicate correlates of repetition priming in perceptual structures. [source] ENVIRONMENT-DEPENDENT ADMIXTURE DYNAMICS IN A TIGER SALAMANDER HYBRID ZONEEVOLUTION, Issue 6 2004Benjamin M. Fitzpatrick Abstract After an estimated five million years of independent evolution, the barred tiger salamander (Ambystoma tigrinum mavortium) was introduced by bait dealers into the native range of the California tiger salamander (A. californiense). Hybridization and backcrossing have been occurring in central California for 50,xs60 years, or an estimated 15,30 generations. We studied genetic and ecological factors influencing admixture of these two divergent gene pools by analyzing frequencies of hybrid genotypes in three kinds of breeding habitats: natural vernal pools, ephemeral man-made cattle ponds, and perennial man-made ponds. Perennial ponds tended to have higher frequencies of nonnative alleles than either type of seasonal pond, even in cases where perennial and seasonal ponds are within a few hundred meters. Thus, the hybrid zone has a mosaic structure that depends on pond hydrology or ecology. The presence of some broadly acting constraints on admixture is suggested by linkage disequilibria between physically unlinked molecular markers within ponds. In addition, we found several marker-specific deviations from Hardy-Weinberg equilibrium. One marker showed a consistent deficit of heterozygotes across pond types. Another showed heterozygote deficits only in vernal pools. A third was more likely to have heterozygote excess in ephemeral cattle ponds. These patterns indicate that admixture is influenced by complex genotype-by-environment interactions. [source] IDENTIFICATION AND CLONING OF AMPLIFIED FRAGMENT LENGTH POLYMORPHISM MARKERS LINKED TO THE MATING TYPE LOCUS OF CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)JOURNAL OF PHYCOLOGY, Issue 3 2001Ralf Werner Amplified fragment length polymorphism (AFLP) markers have been widely used to generate molecular maps of plant species, including crops and cereals. We report on a useful protocol to identify AFLPs from Chlamydomonas reinhardtii Dangeard with digoxigenin labeled primers. Although Chlamydomonas has a small genome with a high GC content, we could detect polymorphic bands that led to the identification of several AFLP markers linked to the mating type locus of Chlamydomonas. Three of these markers were isolated from the gel, reamplified, and cloned. The clones were sequenced, and the insertion of the correct fragment was verified in AFLP gels and in Southern blots. One marker showed sequence identity to parts of the fus1 gene, known to be unique in the plus mating type. We also converted some of the AFLP markers into sequence tagged site markers, which allows a fast and convenient screening of progeny of crosses. This procedure will be a useful and fast alternative to the conventional generation of maps for the positional cloning of genes from Chlamydomonas. [source] Isolation and characterization of microsatellite loci for the European tree frog (Hyla arborea)MOLECULAR ECOLOGY RESOURCES, Issue 5 2008L. BERSET-BRäNDLI Abstract We developed 11 new microsatellite markers for the European tree frog (Hyla arborea), and tested patterns of polymorphism in 54 adults (27 males and 27 females) from two ponds close to Lausanne (Western Switzerland). One marker was sex linked and two pairs displayed linkage disequilibrium. Comparisons of allele numbers with heterozygosity values support a stepwise-mutation model at neutral equilibrium, with mutation rates spanning nearly two orders of magnitude. These markers will prove useful for population genetic studies and fine-scale investigations requiring genetic assignment techniques. [source] Development of 25 gene-associated microsatellite markers of Atlantic cod (Gadus morhua L.)MOLECULAR ECOLOGY RESOURCES, Issue 4 2006JØRGEN STENVIK Abstract Microsatellites were identified by screening 2294 GenBank entries available for Atlantic cod (Gadus morhua L.), mainly representing expressed sequence tags and cDNA sequences. Ninety-two novel microsatellite loci (tetra-, tri- and dinucleotides) were characterized on 96 individuals. This strategy yielded 25 gene-associated polymorphic microsatellite markers (11 tri- and 14 dinucleotides) with two to 20 alleles and an average heterozygosity of 0.48 in the population studied (range 0.02,0.89). One marker exhibited significant homozygote excess, and one of the primer pairs amplified two linked markers. The gene identity was determined at nine of the loci, confirming the associated microsatellites as type I markers. [source] Amplified fragment length polymorphism-derived microsatellite sequence linked to the Pch1 and Ep-D1 loci in common wheatPLANT BREEDING, Issue 1 2003J. Z. Groenewald Abstract Amplified fragment length polymorphism (AFLP) markers linked to the Aegilops ventricosa -derived chromosome segment in ,VPM1' on which the eyespot resistance gene, Pch1, and the endopeptidase gene, Ep-D1b, occur were identified. One marker was isolated from the gel, cloned and sequenced. Sequence analysis revealed a microsatellite repeat motif. Sequence-specific primers were designed to amplify a product containing the repeat motif, and the microsatellite marker was tested for cosegregation with the Ep-D1b allele. Distinct alleles were produced by the Pch1 sources, normal wheat and wheat containing the Lr19 translocation. A recombination frequency of 0.02 was calculated between the microsatellite marker and Ep-D1. [source] Localizing the X-linked orange colour phenotype using feline resource familiesANIMAL GENETICS, Issue 1 2005R. A. Grahn Summary Many genes influencing mammalian coat colours are well conserved. While genes responsible for pelage phenotypes in one species provide strong evidence for a candidate gene in a different species, the X-linked orange phenotype of the domestic cat is unique within mammals. The orange locus (O) undergoes X-inactivation, producing females that express both wildtype black (wt) and orange (variant) phenotypes when heterozygous (tortoiseshell). The orange locus has not yet been localized on the X chromosome. Tortoiseshell male cats have been identified but have been shown to be sex chromosome trisomies (XXY). To localize the cat orange locus, 10 feline-derived X-linked microsatellites were analysed in two extended cat pedigrees consisting of 79 and 55 individuals, respectively, segregating for the orange phenotype. Linkage analyses excluded close association of orange in the vicinity of the nine informative X-linked microsatellites. One marker was not polymorphic within either family. Several markers suggested exclusion (Z < ,2.0) at distances of 7.5,33 cM. Exclusion analyses suggested a possible location for orange a 14 cM region near Xcen. Recombination distances of markers in the segregating feline pedigrees were reduced as compared with the feline interspecies backcross family. Thus, the presented pedigrees may be useful as reference families for the domestic cat because more accurate recombination rates for domestic cats can be determined. [source] Ventricular Asynchrony of Time-to-Peak Systolic Velocity in Structurally Normal Heart by Tissue Doppler ImagingECHOCARDIOGRAPHY, Issue 7 2010Hakimeh Sadeghian M.D. Background: Echocardiographic measurements of time-to-peak systolic velocities (Ts) are helpful for assessing the degree of cardiac asynchrony. We assessed the degree of ventricular asynchrony in structurally normal heart according to Ts by tissue Doppler imaging. Methods: We performed conventional echocardiography and tissue velocity imaging for 65 healthy adult volunteers to measure the Ts of 12 left ventricular segments in the mid and basal levels delay of Ts and standard deviation (SD) of Ts in all and basal segments. Six frequently used markers of dyssynchrony were measured and were also compared between men and women. Data are presented as median (25th and 75th percentile). Results: Septal-lateral and anteroseptal-posterior delays were 50 (20, 90) and 20 (0, 55) ms. The delay between the longest and the shortest Ts in basal and all segments were 100 (80, 120) and 110 (83, 128) ms, respectively. SD of Ts was 39 (24, 52) ms for basal and 41 (28, 51) ms for all segments. Overall, 76.9% of cases had at least one marker of dyssynchrony. Frequencies of dyssynchrony markers were almost significantly higher in women compared to men. The most frequently observed dyssynchrony marker was SD of Ts of all segments (70.8%) and the lowest was anteroseptal-posterior delay (21.5%). Conclusions: Normal population almost had dyssynchrony by previously described markers and many of these markers were more frequent in women. Conducting more studies on normal population by other tissue Doppler modalities may give better description of cardiac synchronicity. (Echocardiography 2010;27:823-830) [source] A preliminary linkage map of the hard tick, Ixodes scapularisINSECT MOLECULAR BIOLOGY, Issue 2 2003A. J. Ullmann Abstract A linkage map of the Ixodes scapularis genome was constructed, based upon segregation amongst 127 loci. These included 84 random amplified polymorphic DNA (RAPD) markers, 32 Sequence- Tagged RAPD (STAR) markers, 5 cDNAs, and 5 microsatellites in 232 F1 intercross progeny from a single, field-collected P1 female. A preliminary linkage map of 616 cM was generated across 14 linkage groups with one marker every 10.8 cM. Assuming a genome size of , 109 bp, the relationship of physical to genetic distance was found to be , 300 kb/cM in the I. scapularis genome. [source] Real-time RT-PCR detection of CK19, CK7 and MUC1 mRNA for diagnosis of lymph node micrometastases in non small cell lung carcinomaINTERNATIONAL JOURNAL OF CANCER, Issue 5 2005Pierre Saintigny Abstract Metastatic lymph nodes (LNs) are the major prognostic factor in resected non small cell lung carcinoma (NSCLC). However, almost 50% of pN0 patients relapse, suggesting metastatic cells undetected by current staging procedures. A combination of markers [cytokeratins 19 and 7 (CK19, CK7) and mucin type 1 (MUC1) mRNAs] was therefore evaluated by real-time RT-PCR in order to detect occult cancer cells. Forty-three NSCLC tumor samples, 4 micrometastatic, 6 metastatic and 84 histologically negative mediastinal LNs from 19 patients with NSCLC were evaluated as well as blood mononuclear cells from 29 healthy volunteers and 17 benign LNs. When tested on cell lines, RT-PCR was particularly efficient for evaluation of CK19, CK7 and MUC1 mRNA expression. All tumor samples were positive for at least 1 marker and 74% of samples were positive for all 3 markers. CK7 and CK19 mRNA were not detected in benign LN and blood cells from healthy donors in contrast with MUC1 mRNA. Only CK7 and CK19 mRNA were therefore used for evaluation of mediastinal LNs: the 6 histologically metastatic and the 4 micrometastatic LNs were positive for at least one marker. Among the 84 histologically negative LNs, 6 (7%) were positive for at least one marker, potentially changing the stage of 2 out of 19 patients. In conclusion, in our feasibility study, parallel molecular detection of CK19 and CK7 mRNA can be considered a specific diagnostic tool for the assessment of microscopic lymphatic spread. Its prognostic impact remains to be evaluated in a prospective study. © 2005 Wiley-Liss, Inc. [source] HPLC flavonoid profiles as markers for the botanical origin of European unifloral honeysJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2001Francisco A Tomás-Barberán Abstract The HPLC phenolic profiles of 52 selected unifloral honey samples produced in Europe were analysed to detect possible markers for the floral origin of the different honeys. Lime-tree (five markers), chestnut (five markers), rapeseed (one marker), eucalyptus (six markers) and heather (three markers) honeys had specific markers with characteristic UV spectra. In addition, the flavanone hesperetin was confirmed as a marker for citrus honey, as well as kaempferol for rosemary honey and quercetin for sunflower honey. Abscisic acid, which had been reported to be a possible marker for heather honey, was also detected in rapeseed, lime-tree and acacia honeys. Ellagic acid in heather honey and the hydroxycinnamates caffeic, p -coumaric and ferulic acids in chestnut, sunflower, lavender and acacia honeys were also detected. The characteristic propolis-derived flavonoids pinocembrin, pinobanksin and chrysin were present in most samples in variable amounts. © 2001 Society of Chemical Industry [source] Detection, isolation and characterization of Shiga toxin-producing Escherichia coli in retail-minced beef using PCR-based techniques, immunoassays and colony hybridizationLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2007F. Auvray Abstract Aims:, To provide information on detection of Shiga toxin-producing Escherichia coli (STEC) in retail-minced beef using an approach combining (i) PCR-based techniques and automated immunoassay for stx screening and detection of the five major serogroups associated with human infection, and (ii) immunomagnetic separation (IMS) and colony hybridization assays for bacterial strain isolation. Methods and Results:, Twenty-seven out of 164 minced beef samples were stx -positive by PCR-ELISA, nine of which were also positive by real-time PCR for at least one marker of the five main serogroups tested (O26, O103, O111, O145 and O157). Two E. coli O103 stx -negative strains were isolated from two out of 10 IMS and nine STEC strains that did not belong to the five main serogroups were isolated by colony hybridization. Conclusions:, PCR techniques are applicable for rapid screening of samples containing both an stx gene and an O-group marker of the five main pathogenic STEC serogroups. Isolation of STEC strains belonging to the main non-O157 serogroups remains difficult. Significance and Impact of the Study:, This study presents an evaluation of a multi-faceted approach for the detection of the most frequently reported human pathogenic STEC serogroups. The advantages and limits of this strategy are presented. [source] Fine-scale genetic structure and gene dispersal inferences in 10 Neotropical tree speciesMOLECULAR ECOLOGY, Issue 2 2006OLIVIER J. HARDY Abstract The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift,dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies. [source] A genomewide linkage study of age at onset in schizophrenia,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 5 2001Alastair G. Cardno Abstract There is strong evidence for a genetic contribution to age at onset of schizophrenia, which probably involves both susceptibility loci for schizophrenia and modifying loci acting independent of disease risk. We sought evidence of linkage to loci that influence age at onset of schizophrenia in a sample of 94 affected sibling pairs with DSM-IV schizophrenia or schizoaffective disorder, and age at first psychiatric contact of 45 years or less. Individuals were genotyped for 229 microsatellite markers spaced at approximately 20 cM intervals throughout the genome. Loci contributing to age at onset were sought by a quantitative maximum-likelihood multipoint linkage analysis using MAPMAKER/SIBS. A nonparametric multipoint analysis was also performed. The genomewide significance of linkage results was assessed by simulation studies. There were six maximum-likelihood LOD score peaks of 1.5 or greater, the highest being on chromosome 17q (LOD,=,2.54; genomewide P,=,0.27). This fulfils Lander and Kruglyak's [1995: Nat Genet 11:241,247] criteria for suggestive linkage in that it would be expected to occur once or less (0.3 times) per genome scan. However, this finding should be treated with caution because the LOD score appeared to be almost solely accounted for by the pattern of ibd sharing at one marker (D17S787), with virtually no evidence of linkage over flanking markers. None of the linkage results achieved genomewide statistical significance, but the LOD score peak on chromosome 13q (LOD,=,1.68) coincided with the region showing maximum evidence for linkage in the study by Blouin et al. [1998: Nat Genet 20:70,73] of categorical schizophrenia. © 2001 Wiley-Liss, Inc. [source] Control of ,-catenin/Tcf-directed transcription in medulloblastomaACTA PAEDIATRICA, Issue 2004C Raffel The ,-catenin, glycogen synthase kinase 3, (GSK-3,), and adenomatous polyposis coli (APC) gene products interact to form a network that influences the rate of cell proliferation. Medulloblastoma occurs as part of Turcot's syndrome and patients with Turcot's syndrome, who develop medulloblastomas, have been shown to harbor germline APC mutations. While APC mutations have been investigated and not identified in sporadic medulloblastomas, the status of the ,-catenin and GSK-3, genes has not been evaluated in this tumor. This study shows that 3 of 67 medulloblastomas harbor ,-catenin mutations, each of which converts a GSK-3, phosphorylation site from serine to cysteine. The ,-catenin mutation seen in the tumors was not present in matched constitutional DNA in the 2 cases where matched normal DNA was available. A loss of heterozygosity (LOH) analysis of 32 medulloblastomas with paired normal DNA samples was performed with 4 microsatellite markers flanking the GSK-3, locus; LOH with at least one marker was identified in 7 tumors. Sequencing of the remaining GSK-3, allele in these cases failed to identify any mutations. Taken together, these data suggest that activating mutations in the ,-catenin gene may be involved in the development of a subset of medulloblastomas. The GSK-3, gene does not appear to be a target for inactivation in this tumor. [source] | |||||||||||||