SEXUAL CONFLICT AND SEXUAL SELECTION: MEASURING ANTAGONISTIC COEVOLUTION

Abstract Arnqvist (2004) raises some concerns with several of the points made by Pizzari and Snook (2003) on the study of sexually antagonistic coevolution (SAC) generated by sexual conflict, arguing that: (1) sexual conflict cannot be expressed in terms of average male and female fitness; (2) our criticism of current experimental approaches, particularly interpopulation crosses, is unjustified; and (3) the alternative experimental approach we proposed is problematic. Here we discuss and respond to these criticisms by: (1) clarifying that we can distinguish between SAC and mutualistic sexual coevolution by measuring changes in the average fitness of the reproducing subsamples of males and females of a population across generations, (2) maintaining that testing SAC using interpopulation crosses is undermined by the lack of a priori knowledge of what traits mediate SAC across isolated populations, and (3) reinforcing the advantages of our experimental approach to distinguish between sexually mutualistic and antagonistic selection.     

The stimulatory effects of diethylstilbestrol and diethylstilbestrol diphosphate on the reticuloendothelial cells of the rat spleen.

The effects of the estrogenic compounds, diethylstilbestrol (DS) and diethylstilbestrol dophosphate (DSP) on morphologically demonstrable characteristics of reticuloendothelial (RE) cells were studied in rat spleen. These included metalophilia, acid phosphatase, nonspecific esterase and phagocytosis. Routine histological and histochemical techniques were used to determine the distribution of metalophilic cells, hydrolytic enzymes, the presence of intracytoplasmic PAS-positive material, hemosiderin sequestration, and the ability to phagocytose injected carbon particles and bacterial organisms. Changes in these parameters associated with increased RE function were observed in several regions of spleens of DS or DSP-treated animals. The marginal metalophils at the periphery of the nodule, normally not phagocytic in animals of the age studied, became phagocytic and demonstrated increased metalophilic and enzymatic activity. The red pulp was characterized by increased densities of cells in pulp cords demonstrating metalophilia, hydrolytic enzyme activity, PAS positivity and hemosiderin. Phagocytosed material was limited to cells in the pulp cord. The reactions of the sinus-lining cells were not affected by this treatment. Results indicated that the marginal metalophils have the capacity to become fully functional RE cells under the influence of these drugs.     

Effects of intravenous infusion of prostacyclin (PGI2) in man

Prostacyclin infused intravenously in human volunteers induces ex vivo inhibition of platelet aggregation, tachycardia and hypotension. The inhibition of platelet aggregation is obtained with slightly lower doses than those which exhibit cardiovascular effects.The cardiovascular effects disappeared within a few minutes after discontinuing the infusion of prostacyclin but the platelet effects were longer lasting.Prostacyclin did not have any effect on platelet count, platelet factor 3, accelerated partial thromboplastin time, prothrombin time, euglobulin clot lysis time, fibrinogen degradation products, blood glucose concentration or urine sodium potassium ratio.     

Ambulance ride: fixed or floating stretcher?

The alternatives of a purpose-bult ambulance and a specially designed stretcher suspension system were considered and the features of the latter assessed by subjective and objective tests. The results showed a significant improvement in the quality of the ride offered to the patient.     

Sexual selection and interacting phenotypes in experimental evolution: a study of Drosophila pseudoobscura mating behavior

Sexual selection requires social interactions, particularly between the sexes. When trait expression is influenced by social interactions, such traits are called interacting phenotypes and only recently have the evolutionary consequences of interacting phenotypes been considered. Here we investigated how variation in relative fitness, or the opportunity for sexual selection, affected the evolutionary trajectories of interacting phenotypes. We used experimentally evolved populations of the naturally promiscuous Drosophila pseudoobscura , in which the numbers of potential interactions between the sexes, and therefore relative fitness, were manipulated by altering natural levels of female promiscuity. We considered two different mating interactions between the sexes: mating speed and copulation duration. We investigated the evolutionary trajectories of means and (co)variances ( P ) and also the influence of genetic drift on the evolutionary response of these interactions. Our sexual selection treatments did not affect the means of either mating speed or copulation duration, but they did affect P . We found that the means of both traits differed among replicates within each selection treatment whereas the P s did not. Changes as a consequence of genetic drift were excluded. Our results show that although variable potential strengths of sexual interactions influence the evolution of interacting phenotypes, the influence may be nonlinear.     

Derivation and fluidity of acutely induced dysfunctional CD8+ T cells

Dysfunctional CD8(+) T (T(CD8(+))) cells lacking cytokine production have been identified in many viral infections, but their genesis is not well understood. Established results indicate that such cells could be either high avidity that enter a refractory state due to overstimulation or low avidity that are only partially stimulated. Using an acute, resolving infection model that results in rapid production of dysfunctional cells, we show that this IL2 unresponsive phenotype emerges from the low end of the avidity spectrum and is characterized by broad TCR usage and a reduced proliferation rate. Furthermore, the dysfunctional population is extremely fluid, being sustained by high Ag dose but virtually eliminated following low dose boosting. Together, these results suggest that persistence of dysfunctional cells generated in this manner depends upon continual exposure to high Ag levels and that such cells may ultimately predominate if functional cells become exhausted.