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排序方式: 共有158条查询结果,搜索用时 15 毫秒
1.
A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing. 相似文献
2.
For a finite locus model, Markov chain Monte Carlo (MCMC) methods can be used to estimate the conditional mean of genotypic values given phenotypes, which is also known as the best predictor (BP). When computationally feasible, this type of genetic prediction provides an elegant solution to the problem of genetic evaluation under non-additive inheritance, especially for crossbred data. Successful application of MCMC methods for genetic evaluation using finite locus models depends, among other factors, on the number of loci assumed in the model. The effect of the assumed number of loci on evaluations obtained by BP was investigated using data simulated with about 100 loci. For several small pedigrees, genetic evaluations obtained by best linear prediction (BLP) were compared to genetic evaluations obtained by BP. For BLP evaluation, used here as the standard of comparison, only the first and second moments of the joint distribution of the genotypic and phenotypic values must be known. These moments were calculated from the gene frequencies and genotypic effects used in the simulation model. BP evaluation requires the complete distribution to be known. For each model used for BP evaluation, the gene frequencies and genotypic effects, which completely specify the required distribution, were derived such that the genotypic mean, the additive variance, and the dominance variance were the same as in the simulation model. For lowly heritable traits, evaluations obtained by BP under models with up to three loci closely matched the evaluations obtained by BLP for both purebred and crossbred data. For highly heritable traits, models with up to six loci were needed to match the evaluations obtained by BLP. 相似文献
3.
4.
Karen CM Moraes Lívia F Diniz Maria Terezinha Bahia 《Memórias do Instituto Oswaldo Cruz》2015,110(2):181-191
Chagas disease, caused by the intracellular protozoan Trypanosoma
cruzi, is a serious health problem in Latin America. During this
parasitic infection, the heart is one of the major organs affected. The pathogenesis
of tissue remodelling, particularly regarding cardiomyocyte behaviour after parasite
infection and the molecular mechanisms that occur immediately following parasite
entry into host cells are not yet completely understood. When cells are infected with
T. cruzi, they develop an inflammatory response, in which
cyclooxygenase-2 (COX-2) catalyses rate-limiting steps in the arachidonic acid
pathway. However, how the parasite interaction modulates COX-2 activity is poorly
understood. In this study, the H9c2 cell line was used as our model and we
investigated cellular and biochemical aspects during the initial 48 h of parasitic
infection. Oscillatory activity of COX-2 was observed, which correlated with the
control of the pro-inflammatory environment in infected cells. Interestingly,
subcellular trafficking was also verified, correlated with the control of Cox-2 mRNA
or the activated COX-2 protein in cells, which is directly connected with the
assemble of stress granules structures. Our collective findings suggest that in the
very early stage of the T. cruzi-host cell interaction, the parasite
is able to modulate the cellular metabolism in order to survives. 相似文献
5.
Cíntia Júnia Monteiro Suianne Letícia Antunes Mota Lívia de Figueiredo Diniz Maria Terezinha Bahia Karen CM Moraes 《Memórias do Instituto Oswaldo Cruz》2015,110(8):996-1002
Chagas disease, which is caused by the intracellular protozoanTrypanosoma
cruzi, is a serious health problem in Latin America. The heart is one of
the major organs affected by this parasitic infection. The pathogenesis of tissue
remodelling, particularly regarding cardiomyocyte behaviour after parasite infection,
and the molecular mechanisms that occur immediately following parasite entry into
host cells are not yet completely understood. Previous studies have reported that the
establishment of parasitism is connected to the activation of the
phosphatidylinositol-3 kinase (PI3K), which controls important steps in cellular
metabolism by regulating the production of the second messenger
phosphatidylinositol-3,4,5-trisphosphate. Particularly, the tumour suppressor PTEN is
a negative regulator of PI3K signalling. However, mechanistic details of the
modulatory activity of PTEN on Chagas disease have not been elucidated. To address
this question, H9c2 cells were infected with T. cruzi Berenice 62
strain and the expression of a specific set of microRNAs (miRNAs) were investigated.
Our cellular model demonstrated that miRNA-190b is correlated to the decrease of
cellular viability rates by negatively modulating PTEN protein expression in
T. cruzi-infected cells. 相似文献
6.
Background
Designing maximally selective ligands that act on individual targets is the dominant paradigm in drug discovery. Poor selectivity can underlie toxicity and side effects in the clinic, and for this reason compound selectivity is increasingly monitored from very early on in the drug discovery process. To make sense of large amounts of profiling data, and to determine when a compound is sufficiently selective, there is a need for a proper quantitative measure of selectivity. 相似文献7.
Sebastian A Baldauf Harald Kullmann Stefanie H Schroth Timo Thünken Theo CM Bakker 《BMC evolutionary biology》2009,9(1):129-9
Background
Assortative mating patterns for mate quality traits like body size are often observed in nature. However, the underlying mechanisms that cause assortative mating patterns are less well known. Sexual selection is one important explanation for assortment, suggesting that i) one (usually the female) or both sexes could show preferences for mates of similar size or ii) mutual mate choice could resolve sexual conflict over quality traits into assortment. We tested these hypotheses experimentally in the socially monogamous cichlid fish Pelvicachromis taeniatus, in which mate choice is mutual. 相似文献8.
Liviu R Totir Rohan L Fernando Jack CM Dekkers Soledad A Fernández Bernt Guldbrandtsen 《遗传、选种与进化》2003,35(7):585-604
An increased availability of genotypes at marker loci has prompted the development of models that include the effect of individual genes. Selection based on these models is known as marker-assisted selection (MAS). MAS is known to be efficient especially for traits that have low heritability and non-additive gene action. BLUP methodology under non-additive gene action is not feasible for large inbred or crossbred pedigrees. It is easy to incorporate non-additive gene action in a finite locus model. Under such a model, the unobservable genotypic values can be predicted using the conditional mean of the genotypic values given the data. To compute this conditional mean, conditional genotype probabilities must be computed. In this study these probabilities were computed using iterative peeling, and three Markov chain Monte Carlo (MCMC) methods – scalar Gibbs, blocking Gibbs, and a sampler that combines the Elston Stewart algorithm with iterative peeling (ESIP). The performance of these four methods was assessed using simulated data. For pedigrees with loops, iterative peeling fails to provide accurate genotype probability estimates for some pedigree members. Also, computing time is exponentially related to the number of loci in the model. For MCMC methods, a linear relationship can be maintained by sampling genotypes one locus at a time. Out of the three MCMC methods considered, ESIP, performed the best while scalar Gibbs performed the worst. 相似文献
9.
CM van der Loos 《Biotechnic & histochemistry》2013,88(3):141-154
Three fixation issues related to immunostaining are discussed here: 1) Generally, a tissue block is fixed, then embedded and sectioned (pre-fixation). The type of fixative applied, crosslinking or coagulating, has an impact on selecting an epitope retrieval method. Individual antigens have a fixation–retrieval characteristic. 2) A long fixation time, especially with crosslinking fixatives, may compromise the result of immunostaining. This negative effect varies among different antigens and can be partially restored by applying a more sensitive/efficient detection system such as tyramide amplification. 3) Sections cut from a fresh frozen tissue block usually are acetone fixed (post-fixation). This was accepted as the “gold standard” for a long time. Post-fixation, however, may have serious consequences for preservation of small peptides leaking from the cut open cells, whereas this is not the case with pre-fixed intact cells. Consequently, the concept of an acetone post-fixed cryostat tissue section as “gold standard” no longer exists and a more appropriate use of the terms immunohistochemistry and immunocytochemistry therefore seems justified. For many antibodies, it is not known whether a formalin fixed, paraffin embedded tissue specimen is appropriate. Suggestions are made for creating a positive control cell block for testing such antibodies. 相似文献
10.
Abstract Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata. 相似文献