RESUMEN
The molecular basis of adaptation is a major focus of evolutionary biology, yet the dynamic process of adaptation has been explored only piecemeal. Experimental evolution of two bacteriophage lines under strong selection led to over a dozen nucleotide changes genomewide in each replicate. At least 96 percent of the amino acid substitutions appeared to be adaptive, and half the changes in one line also occurred in the other. However, the order of these changes differed between replicates, and parallel substitutions did not reflect the changes with the largest beneficial effects or indicate a common trajectory of adaptation.
Asunto(s)
Adaptación Fisiológica , Bacteriófago phi X 174/genética , Bacteriófago phi X 174/fisiología , Evolución Molecular , Genoma Viral , Salmonella typhimurium/virología , Sustitución de Aminoácidos , Genotipo , Mutación , Selección Genética , Eliminación de Secuencia , Temperatura , Ensayo de Placa Viral , Proteínas Virales/química , Proteínas Virales/genética , Replicación ViralRESUMEN
Right and left gastrocnemius-plantaris muscle preparations in 20 dogs anesthetized with pentobarbital sodium were used to investigate the effect of hyperoxia on tension maintenance. Muscles were stimulated via the sciatic nerve for 20 min at 60 200-ms tetanic contractions/min (10 impulses/contraction). Direct muscle stimulation after the experimental period resulted in no significant change in tension. In control experiments the tension developed by the right or left muscles over the 20 min was not different. The tension developed by muscles perfused with hyperoxic blood decreased 14% after 20 min, whereas tension in the normoxic muscles decreased 35%. Blood flow in the hyperoxic muscles was significantly higher at 20 min (P less than 0.05). Pump perfusion of one of a pair of normoxic muscles resulted in a tension decrease of 13% in the pump-perfused muscles, whereas tension in the control muscles decreased 34%. Tension maintenance was flow dependent. The effect of hyperoxia could be mediated through the involvement of oxygen in the long-term control of muscle blood flow.