RESUMEN
Phosphine, a widely used fumigant for the protection of stored grain from insect pests, kills organisms indirectly by inducing oxidative stress. High levels of heritable resistance to phosphine in the insect pest of stored grain, Rhyzopertha dominica have been detected in Asia, Australia and South America. In order to understand the evolution of phosphine resistance and to isolate the responsible genes, we have undertaken genetic linkage analysis of fully sensitive (QRD14), moderately resistant (QRD369) and highly resistant (QRD569) strains of R. dominica collected in Australia. We previously determined that two loci, rph1 and rph2, confer high-level resistance on strain QRD569, which was collected in 1997. We have now confirmed that rph1 is responsible for the moderate resistance of strain QRD369, which was collected in 1990, and is shared with a highly resistant strain from the same geographical region, QRD569. In contrast, rph2 by itself confers only very weak resistance, either as a heterozygote or as a homozygote and was not discovered in the field until weak resistance (probably due to rph1) had become ubiquitous. Thus, high-level resistance against phosphine has evolved via stepwise acquisition of resistance alleles, first at rph1 and thereafter at rph2. The semi-dominance of rph2 together with the synergistic interaction between rph1 and rph2 would have led to rapid selection for homozygosity. A lack of visible fitness cost associated with alleles at either locus suggests that the resistance phenotype will persist in the field.
Asunto(s)
Evolución Biológica , Escarabajos/genética , Epistasis Genética , Resistencia a los Insecticidas/genética , Fosfinas/farmacología , Animales , Ligamiento GenéticoRESUMEN
A prospective, triple-blind study was undertaken to determine whether antiheart antibody or a rise in titer to a virus occurred in patients after intrapericardial surgery and, if so, whether either was related to clinical evidence of the postpericardiotomy syndrome. In 257 patients, AHA in high titer appeared in 62 (24%), all of whom had the syndrome. None of the 102 patients with no AHA had the syndrome. In 137 subjects, a rise in titer to one or more viral agents occurred in 21 of 31 (68%) of those with AHA and PPS. This study suggests that an immunologic response and viral illness are related to PPS.