956 resultados para quantitative traits analysis


Relevância:

40.00% 40.00%

Publicador:

Resumo:

Although 1–24% of T cells are alloreactive, i.e., respond to MHC molecules encoded by a foreign haplotype, it is generally believed that T cells cannot recognize foreign peptides binding foreign MHC molecules. We show using a quantitative model that, if T cell selection and activation are affinity-driven, then an alloreactivity of 1–24% is incompatible with the textbook notion that self MHC restriction is absolute. If an average of 1% of clones are alloreactive, then according to our model, at most 20-fold more clones should, on average, be activated by antigens presented on self MHC than by antigens presented on foreign MHC. This ratio is at best 5 if alloreactivity is 5%. These results describe average properties of the murine immune system, but not the outcome of individual experiments. Using supercomputer technology, we simulated 100,000 MHC restriction experiments. Although the average restriction ratio was 7.1, restriction was absolute in 10% of the simulated experiments, greater than 100, although not absolute, in 29%, and below 6 in 24%. This extreme variability agrees with experimental estimates. Our analysis suggests that alloreactivity and average self MHC restriction both cannot be high, but that a low average restriction level is compatible with high levels in a significant number of experiments.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Effective transcript profiling in animal systems requires isolation of homogenous tissue or cells followed by faithful mRNA amplification. Linear amplification based on cDNA synthesis and in vitro transcription is reported to maintain representation of mRNA levels, however, quantitative data demonstrating this as well as a description of inherent limitations is lacking. We show that published protocols produce a template-independent product in addition to amplifying real target mRNA thus reducing the specific activity of the final product. We describe a modified amplification protocol that minimizes the generation of template-independent product and can therefore generate the desired microgram quantities of message-derived material from 100 ng of total RNA. Application of a second, nested round of cDNA synthesis and in vitro transcription reduces the required starting material to 2 ng of total RNA. Quantitative analysis of these products on Caenorhabditis elegans Affymetrix GeneChips shows that this amplification does not reduce overall sensitivity and has only minor effects on fidelity.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

We present a general method for rigorously identifying correlations between variations in large-scale molecular profiles and outcomes and apply it to chromosomal comparative genomic hybridization data from a set of 52 breast tumors. We identify two loci where copy number abnormalities are correlated with poor survival outcome (gain at 8q24 and loss at 9q13). We also identify a relationship between abnormalities at two loci and the mutational status of p53. Gain at 8q24 and loss at 5q15-5q21 are linked with mutant p53. The 9q and 5q losses suggest the possibility of gene products involved in breast cancer progression. The analytical techniques are general and also are applicable to the analysis of array-based expression data.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Interpretation of quantitative trait locus (QTL) studies of agronomic traits is limited by lack of knowledge of biochemical pathways leading to trait expression. To more fully elucidate the biological significance of detected QTL, we chose a trait that is the product of a well-characterized pathway, namely the concentration of maysin, a C-glycosyl flavone, in silks of maize, Zea mays L. Maysin is a host-plant resistance factor against the corn earworm, Helicoverpa zea (Boddie). We determined silk maysin concentrations and restriction fragment length polymorphism genotypes at flavonoid pathway loci or linked markers for 285 F2 plants derived from the cross of lines GT114 and GT119. Single-factor analysis of variance indicated that the p1 region on chromosome 1 accounted for 58.0% of the phenotypic variance and showed additive gene action. The p1 locus is a transcription activator for portions of the flavonoid pathway. A second QTL, represented by marker umc 105a near the brown pericarp1 locus on chromosome 9, accounted for 10.8% of the variance. Gene action of this region was dominant for low maysin, but was only expressed in the presence of a functional p1 allele. The model explaining the greatest proportion of phenotypic variance (75.9%) included p1, umc105a, umc166b (chromosome 1), r1 (chromosome 10), and two epistatic interaction terms, p1 x umc105a and p1 x r1. Our results provide evidence that regulatory loci have a central role and that there is a complex interplay among different branches of the flavonoid pathway in the expression of this trait.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Many major weeds rely upon vegetative dispersal by rhizomes and seed dispersal by "shattering" of the mature inflorescence. We report molecular analysis of these traits in a cross between cultivated and wild species of Sorghum that are the probable progenitors of the major weed "johnsongrass." By restriction fragment length polymorphism mapping, variation in the number of rhizomes producing above-ground shoots was associated with three quantitative trait loci (QTLs). Variation in regrowth (ratooning) after overwintering was associated with QTLs accounting for additional rhizomatous growth and with QTLs influencing tillering. Vegetative buds that become rhizomes are similar to those that become tillers--one QTL appears to influence the number of such vegetative buds available, and additional independent genes determine whether individual buds differentiate into tillers or rhizomes. DNA markers described herein facilitate cloning of genes associated with weediness, comparative study of rhizomatousness in other Poaceae, and assessment of gene flow between cultivated and weedy sorghums--a risk that constrains improvement of sorghum through biotechnology. Cloning of "weediness" genes may create opportunities for plant growth regulation, in suppressing propagation of weeds and enhancing productivity of major forage, turf, and "ratoon" crops.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

The discovery that the epsilon 4 allele of the apolipoprotein E (apoE) gene is a putative risk factor for Alzheimer disease (AD) in the general population has highlighted the role of genetic influences in this extremely common and disabling illness. It has long been recognized that another genetic abnormality, trisomy 21 (Down syndrome), is associated with early and severe development of AD neuropathological lesions. It remains a challenge, however, to understand how these facts relate to the pathological changes in the brains of AD patients. We used computerized image analysis to examine the size distribution of one of the characteristic neuropathological lesions in AD, deposits of A beta peptide in senile plaques (SPs). Surprisingly, we find that a log-normal distribution fits the SP size distribution quite well, motivating a porous model of SP morphogenesis. We then analyzed SP size distribution curves in genotypically defined subgroups of AD patients. The data demonstrate that both apoE epsilon 4/AD and trisomy 21/AD lead to increased amyloid deposition, but by apparently different mechanisms. The size distribution curve is shifted toward larger plaques in trisomy 21/AD, probably reflecting increased A beta production. In apoE epsilon 4/AD, the size distribution is unchanged but the number of SP is increased compared to apoE epsilon 3, suggesting increased probability of SP initiation. These results demonstrate that subgroups of AD patients defined on the basis of molecular characteristics have quantitatively different neuropathological phenotypes.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

A growing number of authors have been suggesting the necessary incorporation of children in the analysis of gender violence and, specifically, in the analysis of intimate partner violence against women (IPV). Such incorporation would be relevant not only for reducing children's invisibility and vulnerability, but also for achieving a better understanding of the characteristics and dynamics of IPV. Based on these considerations, we present in this paper the results of a secondary analysis applied to the data obtained in the last Spanish Survey on Violence Against Women. The available information allows us to analyze: 1) the presence of children exposed to IPV, 2) the relationship between this presence and the probability of reporting the violence, and 3) women's perception about the parental role of the aggressors.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

A wide variety of different socially motivated organisations perform exceptional feats in alleviating societal ills using creativity and entrepreneurial spirit in their quest to scale their social impact. Their focus is seldom limited to one specific region – instead they strive to benefit the largest possible number of people, thereby often transcending national borders. After all, societal issues usually don’t stop at a countries’ borders – why then should good ideas and impactful concepts aimed at solving these issues? For many socially motivated organisations, the goal of disseminating their social impact remains a solemn wish due to lacking experience and know-how of how to plan and conduct systematic scaling.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Assessment of protein dynamics in living cells is crucial for understanding their biological properties and functions. The SNAP-tag, a self labeling suicide enzyme, presents a tool with unique features that can be adopted for determining protein dynamics in living cells. Here we present detailed protocols for the use of SNAP in fluorescent pulse-chase and quench-chase-pulse experiments. These time-slicing methods provide powerful tools to assay and quantify the fate and turnover rate of proteins of different ages. We cover advantages and pitfalls of SNAP-tagging in fixed- and live-cell studies and evaluate the recently developed fast-acting SNAPf variant. In addition, to facilitate the analysis of protein turnover datasets, we present an automated algorithm for spot recognition and quantification.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Ecological and taxonomic study of the mollusk-rich fauna of the Golfe d'Arguin, North Mauritania, investigates the various environmental influences affecting this tropical shelf. The upwelling of nutrient-rich waters leads to a highly productive environment under tropical conditions. The resulting mixed carbonate-siliciclastic sediment contains a large portion of calcareous components produced by heterotrophic organisms-e.g., mollusks, foraminifers, worms, barnacles-that are reworked on the open shelf. On the basis of mollusk assemblages, six taphocoenoses are defined, all being characterized by a mixed fauna of tropical (e.g., Tellina densestriata), subtropical (e.g., Macoma cumana) and temperate (e.g., Spisula subtruncata) species. Differences between the assemblages are related to the medium-grain size ranging from mud to gravel-that results from local hydrodynamic conditions and water depth. Among carbonate grains, Donax burnupi shells are very abundant in the swell-exposed, northern part of the Golfe d'Arguin and reflect the tropical to subtropical, high-energy, and high-nutrient waters. Mollusk assemblages are demonstrated to be a sensitive tool for deciphering complex environmental conditions in sedimentary archives.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

"A revised edition" (mimeographed) was published in 1939.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Mode of access: Internet.