Zebrafish with defective Nodal signaling have a phenotype analogous to the fatal human birth defect anencephaly, which is caused by an open anterior neural tube. Previous work in our laboratory found that anterior open neural tube defects in Nodal signaling mutants were caused by defects in mesendodermal/mesodermal tissue. Defects in these mutants are already apparent at neural plate stage, before the neuroepithelium starts to fold into a tube. Consistent with this, we found that the requirement for Nodal signaling maps to mid-late blastula stages. This timing correlates with the timing of prechordal plate mesendoderm and anterior mesoderm induction, suggesting these tissues act to promote neurulation. To further identify tissues important for neurulation, we took advantage of the variable phenotypes in Nodal signaling-deficient sqt mutant and Lefty1-overexpressing embryos. Statistical analysis indicated a strong, positive correlation between a closed neural tube and presence of several mesendoderm/mesoderm-derived tissues (hatching glands, cephalic paraxial mesoderm, notochord, and head muscles). However, the neural tube was closed in a subset of embryos that lacked any one of these tissues. This suggests that several types of Nodal-induced mesendodermal/mesodermal precursors are competent to promote neurulation.

Tissue regeneration requires not only the replacement of lost cells and tissues, but also the recreation of morphologies and patterns. Skin pigment pattern is a relatively simple system that can allow researchers to uncover the underlying mechanisms of pattern formation. To gain insight into how pigment patterns form, undergraduate students in the senior level course Developmental Biology designed an experiment that assayed pigment patterns in original and regenerated caudal fins of wild-type, striped, and mutant, spotted zebrafish. A majority of the WT fins regenerated with a similar striped pattern. In contrast, the pattern of spots even in the original fins of the mutants varied among individual fish. Similarly, the majority of the spots in the mutants did not regenerate with the same morphology, size, or spacing as the original fins. This was true even when only a small amount of fin was removed, leaving most of the fin to potentially reseed the pattern in the regenerating tissue. This suggests that the mechanism that creates the wild-type, striped pattern persists to recreate the pattern during regeneration. The mechanism that creates the spots in the mutants, however, must include an unknown element that introduces variability.

Current ST-segment elevation myocardial infarction (STEMI) guidelines require persistent electrocardiogram ST-segment elevation, cardiac enzyme changes, and symptoms of myocardial ischemia. Chest pain is the determinant symptom, often measured using an 11-point scale (0-10). Greater severity of chest pain is presumed to be associated with a stronger likelihood of a true positive STEMI diagnosis. This retrospective observational cohort study considered consecutive STEMI patients from May 02, 2009 to December 31, 2018. Analysis of standard STEMI metrics included positive electrocardiogram-to-device and first medical contact-todevice times, presence of comorbidities, false-positive diagnosis, 30-day and 1-year mortality, and 30-day readmission. Chest pain severity was assessed upon admission to the primary percutaneous coronary intervention hospital. We analyzed 1409 STEMI activations (69% male, 66.3 years old ± 13.7 years). Of these, 251 (17.8%) had no obstructive lesion, consistent with false-positive STEMI. Four hundred sixty-six (33.1%) reported chest pain rating of 0 on admission, 378 (26.8%) reported mild pain (1-3), 300 (21.3%) moderate (4-6), and 265 (18.8%) severe (7-10). Patients presenting without chest pain had a significantly higher rate of false-positive STEMI diagnosis. Increasing chest pain severity was associated with decreased time from first medical contact to device, and decreased in-hospital, 30-day and 1-year mortality. Severity of chest pain on admission did not correlate to the likelihood of a truepositive STEMI diagnosis, although it was associated with improved patient prognosis, in the form of improved outcomes, and shorter times to reperfusion.