Video-Based Education Improves Sampling (Grossing) Confidence in Pathology Trainees.

CONTEXT.­: Pathology resident education has a steep learning curve. Specimen sampling (grossing) is a procedural task, and procedural fields add video materials to their curricula to familiarize trainees with procedure(s), reduce errors, and improve patient care. Our team applied this strategy to develop original in-house sampling videos for our program. OBJECTIVES.­: To evaluate the effect of in-house sampling videos on resident sampling confidence. DESIGN.­: Sampling videos covering all major organ systems (AMOS) were created for our postgraduate year 1 (PGY1) trainees. Videos were hosted on a Northwestern cloud server for on-demand access. Trainees completed 3 surveys (0, 6, 12 months) evaluating sampling confidence comparing those who used in-house videos as an educational supplement with those who did not use the videos. RESULTS.­: Sampling confidence significantly improved at 6 and 12 months (P < .001) across AMOS and PGY levels. When compared with those who did not use in-house sampling videos, trainees who supplemented their education with in-house sampling videos had significantly higher confidence ratings across AMOS and PGY levels at the start of the study (P < .001) and at 6 months (P = .004). Sampling confidence significantly improved for PGY1 trainees at 6 and 12 months (P < .001); for PGY2 and PGY3 trainees, confidence significantly improved at 6 months (P < .001). When evaluated by organ-specific analyses, sampling and teaching confidence improved across all organ systems and, except for the gastrointestinal system, reached significance at 12 months for all PGY levels. CONCLUSIONS.­: Sampling videos, when used as a supplement to the existing curriculum, significantly improved trainee confidence.

Cytology-histology correlation of myoepithelial tumors harboring EWSR1-POU5F1 fusions: A report of two cases.

Myoepithelial tumors (MET) constitute a group of neoplasms with a variety of morphologic, immunophenotypic, and molecular features. Approximately half of MET of soft tissue harbor EWSR1 gene rearrangements with a subset showing EWSR1-POU5F1 fusions and demonstrating distinctive tendency towards aggressive behavior in children. Histologically, EWSR1-POU5F1-positive MET typically show clear-cell morphology with malignant features including marked pleomorphism and atypical mitotic figures. The cytomorphology of these tumors has not been well characterized. Reported here are the cytomorphologic features of two cases of EWSR1-POUF1-positive MET with histology correlation.

Experimental coevolution: rapid local adaptation by parasites depends on host mating system.

Host-parasite interactions can drive rapid, reciprocal genetic changes (coevolution), provided both hosts and parasites have high heritabilities for resistance/infectivity. Similarly, the host's mating system should also affect the rate of coevolutionary change in host-parasite interactions. Using experimental coevolution, we determined the effect of obligate outcrossing verses partial self-fertilization (mixed mating) on the rate of evolutionary change in a nematode host (Caenorhabditis elegans) and its bacterial parasite (Serratia marcescens). Bacterial populations were derived from a common ancestor. We measured the effects of host mating system on host adaptation to the parasite. We then determined the extent of parasite adaptation to their local host populations. Obligately outcrossing hosts exhibited more rapid adaptation to parasites than did mixed mating hosts. In addition, most of the parasites became adapted to infecting their local hosts, but parasites from obligately outcrossing hosts showed a greater level of local adaptation. These results suggest that host populations evolved along separate trajectories and that outcrossing host populations diverged further than partially selfing populations. Finally, parasites tracking outcrossing host populations diverged further than parasites tracking the partially selfing host populations. These results show that the evolutionary trajectories of both hosts and parasites can be shaped by the host's mating system.

Temporal dynamics of outcrossing and host mortality rates in host-pathogen experimental coevolution.

Cross-fertilization is predicted to facilitate the short-term response and the long-term persistence of host populations engaged in antagonistic coevolutionary interactions. Consistent with this idea, our previous work has shown that coevolving bacterial pathogens (Serratia marcescens) can drive obligately selfing hosts (Caenorhabditis elegans) to extinction, whereas the obligately outcrossing and partially outcrossing populations persisted. We focused the present study on the partially outcrossing (mixed mating) and obligately outcrossing hosts, and analyzed the changes in the host resistance/avoidance (and pathogen infectivity) over time. We found that host mortality rates increased in the mixed mating populations over the first 10 generations of coevolution when outcrossing rates were initially low. However, mortality rates decreased after elevated outcrossing rates evolved during the experiment. In contrast, host mortality rates decreased in the obligately outcrossing populations during the first 10 generations of coevolution, and remained low throughout the experiment. Therefore, predominant selfing reduced the ability of the hosts to respond to coevolving pathogens compared to outcrossing hosts. Thus, we found that host-pathogen coevolution can generate rapid evolutionary change, and that host mating system can influence the outcome of coevolution at a fine temporal scale.

Running with the Red Queen: host-parasite coevolution selects for biparental sex.

Most organisms reproduce through outcrossing, even though it comes with substantial costs. The Red Queen hypothesis proposes that selection from coevolving pathogens facilitates the persistence of outcrossing despite these costs. We used experimental coevolution to test the Red Queen hypothesis and found that coevolution with a bacterial pathogen (Serratia marcescens) resulted in significantly more outcrossing in mixed mating experimental populations of the nematode Caenorhabditis elegans. Furthermore, we found that coevolution with the pathogen rapidly drove obligately selfing populations to extinction, whereas outcrossing populations persisted through reciprocal coevolution. Thus, consistent with the Red Queen hypothesis, coevolving pathogens can select for biparental sex.