An introductory biology research-rich laboratory course shows improvements in students' research skills, confidence, and attitudes.

As part of a wider reform to scaffold quantitative and research skills throughout the biology major, we introduced course-based undergraduate research experiences (CURE) in sections of a large-enrollment introductory biology laboratory course in a mid-level, public, minority-serving institution. This initiative was undertaken as part of the in the National Science Foundation / Council for Undergraduate Research Transformations Project. Student teams performed two or three experiments, depending on semester. They designed, implemented, analyzed, revised and iterated, wrote scientific paper-style reports, and gave oral presentations. We tested the impact of CURE on student proficiency in experimental design and statistical reasoning, and student research confidence and attitudes over two semesters. We found that students in the CURE sections met the reformed learning objectives for experimental design and statistical reasoning. CURE students also showed higher levels of experimental design proficiency, research self-efficacy, and more expert-like scientific mindsets compared to students in a matched cohort with the traditional design. While students in both groups described labs as a positive experience in end-of-semester reflections, the CURE group showed a high level of engagement with the research process. Students in CURE sections identified components of the research process that were difficult, while also reporting enjoying and valuing research. This study demonstrates improved learning, confidence, and attitudes toward research in a challenging CURE laboratory course where students had significant autonomy combined with appropriate support at a diverse public university.

Induction of metamorphosis decreases nitric oxide synthase gene expression in larvae of the marine mollusc Ilyanassa obsoleta (say).

Many marine organisms spend the early part of their lives as larvae suspended in the water column before metamorphosing into benthic reproductive adults. Metamorphosis does not occur until a larva has become competent to respond to appropriate stimuli and after a suitable habitat for the young juvenile has been encountered. The gaseous neurotransmitter nitric oxide is thought to be important in the regulation of metamorphosis by holding the organism in the larval state. We have investigated expression of the neuronal nitric oxide synthase (nNOS) gene in larval and metamorphosing individuals of the marine mud snail Ilyanassa obsoleta. Our results indicate that nNOS is expressed at constant levels throughout larval development. In contrast, expression of nNOS decreases markedly during the first 24 h of metamorphosis. Our observations support previous findings that demonstrate that nitric oxide is present in larvae though competence. The decrease in nNOS gene expression that occurs during metamorphosis corresponds with a previously described reduction in nNOS activity.

Regulation of Xenopus embryonic cell adhesion by the small GTPase, rac.

TGF-beta family signalling pathways are important for germ layer formation and gastrulation in vertebrate embryos and have been studied extensively using embryos of Xenopus laevis. Activin causes changes in cell movements and cell adhesion in Xenopus animal caps and dispersed animal cap cells. Rho family GTPases, including rac, mediate growth factor-induced changes in the actin cytoskeleton, and consequently, in cell adhesion and motility, in a number of different cell types. Ectopic expression of mutant rac isoforms in Xenopus embryos was combined with animal cap adhesion assays and a biochemical assay for rac activity to investigate the role of rac in activin-induced changes in cell adhesion. The results indicate that (1) the perturbation of rac signalling disrupts embryonic cell-cell adhesion, (2) that rac activity is required for activin-induced changes in cell adhesive behavior on fibronectin, and (3) that activin increases endogenous rac activity in animal cap explants.

cDNA cloning, sequence comparison, and developmental expression of Xenopus rac1.

The Rho family of small GTP-binding proteins are important signaling molecules that regulate the dynamics of the actin cytoskeleton and mediate changes in cell morphology and motility. Here, we describe the temporal and spatial patterns of expression of the Rho family member, rac, during the development of the amphibian, Xenopus laevis. We also present the deduced amino acid sequence of Xenopus rac (Xrac). At the amino acid level, Xrac is highly conserved relative to previously characterized rac homologs, and is nearly identical to human rac1. RNase protection assays and Western blot analysis indicate that Xrac mRNA and protein are present from fertilization through tailbud stages of development. Whole-mount in situ hybridizations show that Xrac transcripts are especially abundant in cells of the involuting marginal zone, and later, in the cranial neural crest, the developing central nervous system, and in the somites. The remarkable degree of evolutionary conservation observed in the Xrac primary structure together with its high level of expression in cells and structures critical to morphogenesis suggest a functionally important role for this Rho family member in early vertebrate development.