PET-TAC con 18F-FDG en el diagnóstico de la arteritis de Takayasu y la valoración del tratamiento / PET-CT with 18F-FDG in the diagnosis of Takayasu's arteritis and the assessment of response to therapy

Presentamos un caso clínico de una paciente sin síntomas específicos de vasculitis, con reactantes de fase aguda normales, pero con el diagnóstico anatomopatológico de arteritis de Takayasu que nos fue remitida para realizar un PET-TAC con 18F-FDG. Los hallazgos de la exploración permitieron constatar actividad inflamatoria en las paredes vasculares de la aorta y tras la instauración del tratamiento adecuado, una segunda exploración con 18F-FDG, valoró la respuesta terapéutica correctamente. Se discute las aportaciones de la PET-TAC con 18F-FDG en el manejo de esta entidad patológica (AU)

We present a patient without specific symptoms of vasculitis, with normal acute phase reactants, but with the pathological diagnosis of Takayasu’ arteritis that was referred for a PET-CT with 18F-FDG. Scan findings showed inflammatory activity in the vessel walls of the aorta and after the appropriate treatment, a second scan with 18F-FDG, correctly assessed the therapeutic response. We discuss the contributions of PET-CT with 18F-FDG in the management of this pathological entity (AU)

[PET-CT with ¹8F-FDG in the diagnosis of Takayasu's arteritis and the assessment of response to therapy]. / PET-TAC con ¹8F-FDG en el diagnóstico de la arteritis de Takayasu y la valoración del tratamiento.

We present a patient without specific symptoms of vasculitis, with normal acute phase reactants, but with the pathological diagnosis of Takayasu' arteritis that was referred for a PET-CT with (18)F-FDG. Scan findings showed inflammatory activity in the vessel walls of the aorta and after the appropriate treatment, a second scan with (18)F-FDG, correctly assessed the therapeutic response. We discuss the contributions of PET-CT with (18)F-FDG in the management of this pathological entity.

The red queen in the corn: agricultural weeds as models of rapid adaptive evolution.

Weeds are among the greatest pests of agriculture, causing billions of dollars in crop losses each year. As crop field management practices have changed over the past 12 000 years, weeds have adapted in turn to evade human removal. This evolutionary change can be startlingly rapid, making weeds an appealing system to study evolutionary processes that occur over short periods of time. An understanding of how weeds originate and adapt is needed for successful management; however, relatively little emphasis has been placed on genetically characterizing these systems. Here, we review the current literature on agricultural weed origins and their mechanisms of adaptation. Where possible, we have included examples that have been genetically well characterized. Evidence for three possible, non-mutually exclusive weed origins (from wild species, crop-wild hybrids or directly from crops) is discussed with respect to what is known about the microevolutionary signatures that result from these processes. We also discuss what is known about the genetic basis of adaptive traits in weeds and the range of genetic mechanisms that are responsible. With a better understanding of genetic mechanisms underlying adaptation in weedy species, we can address the more general process of adaptive evolution and what can be expected as we continue to apply selective pressures in agroecosystems around the world.

The Wilhelmine W. Key 2002 Invitational Lecture. Phylogeography, haplotype trees, and invasive plant species.

The distribution of genetic variants in plant populations is strongly affected both by current patterns of microevolutionary forces, such as gene flow and selection, and by the phylogenetic history of populations and species. Understanding the interplay of shared history and current evolutionary events is particularly confounding in plants due to the reticulating nature of gene exchange between diverging lineages. Certain gene sequences provide historically ordered neutral molecular variation that can be converted to gene genealogies which trace the evolutionary relationships among haplotypes (alleles). Gene genealogies can be used to understand the evolution of specific DNA sequences and relate sequence variation to plant phenotype. For example, in a study of the RPS2 gene in Arabidopsis thaliana, resistant phenotypes clustered in one portion of the gene tree. The field of phylogeography examines the distribution of allele genealogies in an explicit geographical context and, when coupled with a nested clade analysis, can provide insight into historical processes such as range expansion, gene flow, and genetic drift. A phylogeographical approach offers insight into practical issues as well. Here we show how haplotype trees can address the origins of invasive plants, one of the greatest global threats to biodiversity. A study of the geographical diversity of haplotypes in invasive Phragmites populations in the United States indicates that invasiveness is due to the colonization and spread of distinct genotypes from Europe ( Saltonstall 2002). Likewise, a phylogeographical analysis of Tamarix populations indicates that hybridization events between formerly isolated species of Eurasia have produced the most common genotype of the second-worst invasive plant species in the United States.

The genetic architecture of disease resistance in plants and the maintenance of recombination by parasites.

Parasites represent strong selection on host populations because they are ubiquitous and can drastically reduce host fitness. It has been hypothesized that parasite selection could explain the widespread occurrence of recombination because it is a coevolving force that favours new genetic combinations in the host. A review of deterministic models for the maintenance of recombination reveals that for recombination to be favoured, multiple genes that interact with each other must be under selection. To evaluate whether parasite selection can explain the maintenance of recombination, we review 85 studies that investigated the genetic architecture of plant disease resistance and discuss whether they conform to the requirements that emerge from theoretical models. General characteristics of disease resistance in plants and problems in evaluating resistance experimentally are also discussed. We found strong evidence that disease resistance in plants is determined by multiple loci. Furthermore, in most cases where loci were tested for interactions, epistasis between loci that affect resistance was found. However, we found weak support for the idea that specific allelic combinations determine resistance to different host genotypes and there was little data on whether epistasis between resistance genes is negative or positive. Thus, the current data indicate that it is possible that parasite selection can favour recombination, but more studies in natural populations that specifically address the nature of the interactions between resistance genes are necessary. The data summarized here suggest that disease resistance is a complex trait and that environmental effects and fitness trade-offs should be considered in future models of the coevolutionary dynamics of host and parasites.

Diversity and molecular evolution of the RPS2 resistance gene in Arabidopsis thaliana.

The RPS2 gene in Arabidopsis thaliana governs resistance to strains of the bacterial pathogen, Pseudomonas syringae pv. tomato, that express the avrRpt2 gene. The two loci are involved in a gene-for-gene interaction. Seventeen accessions of A. thaliana were sequenced to explore the diversity present in the coding region of the RPS2 locus. An unusually high level of nucleotide polymorphisms was found (1.26%), with nearly half of the observed polymorphisms resulting in amino acid changes in the RPS2 protein. Seven haplotypes (alleles) were identified and their evolutionary relationships deduced. Several of the alleles conferring resistance were found to be closely related, whereas susceptibility to disease was conferred by widely divergent alleles. The possibility of selection at the RPS2 locus is discussed.