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Due to the COVID-19 pandemic, Rice University canceled classes for the week of March 9–13, 2020 and shifted all instruction to online only following spring break. For the second half of the semester, animal physiology was taught exclusively over Zoom. Here we describe how a flipped teaching format that was used before the pandemic eased the transition from face-to-face teaching to online instruction. The preclass preparation resources and the active learning materials that were already in place for flipped teaching were helpful in the transition to solely online teaching. Therefore, the focus during the transition was to reconfigure active learning and examinations from the face-to-face format to the online platform. Instead of small group discussions in the classroom, teams interacted in Zoom Breakout Rooms. Rather than taking exams in-person during scheduled class time, students submitted exams online. Additionally, students prerecorded their project presentations instead of presenting them “live” during the last week of classes. Overall, students felt that the class smoothly transitioned to a remote only format. These and other changes to the instructional methods will be implemented during the Spring 2021 semester when the course is taught fully online.

A remarkable aspect of Dictyostelium development is that cells form evenly sized groups of ∼2 × 10 4 cells. A secreted 450 kDa protein complex called counting factor (CF) regulates the number of cells per group. We find that CF regulates group size by repressing cell–cell adhesion. In both experiments and computer simulations, high levels of CF (and thus low adhesion) result in aggregation streams breaking up into small groups, while no CF (and thus high adhesion) results in no stream breakup and large groups. These results suggest that in Dictyostelium and possibly other systems a secreted factor regulating cell–cell adhesion can regulate the size of a group of cells.

Initial differentiation in Dictyostelium involves both asymmetric cell division and a cell cycle-dependent mechanism. We previously identified a gene, rtoA, which when disrupted randomizes the cell cycle-dependent mechanism without affecting either the underlying cell cycle or asymmetric differentiation. We find that in wild-type cells, RtoA levels vary during the cell cycle. Cytosolic pH, which normally varies with the cell cycle, is randomized in rtoA cells. The middle 60% of the RtoA protein is 10 tandem repeats of an 11 peptide-long serine-rich motif, which we find has a random coil structure. This domain catalyzes the fusion of phospholipid vesicles in vitro. Conversely, rtoA cells have a defect in the fusion of endocytic vesicles. They also have a decreased exocytosis rate, a decreased pH of endocytic/exocytic vesicles, and an increased average cytosolic pH. Our data indicate that the serine-rich domain of RtoA can mediate membrane fusion and that RtoA can increase the rate of vesicle fusion during processing of endoctyic vesicles. We hypothesize that RtoA modulates initial cell type choice by linking vegetative cell physiology to the cell cycle.

Radioisotopes have unstable nuclei that decay in a statistically predictable manner with the release of radiation in the form of particles or electromagnetic waves. In β-decay ‘fast electrons’ called β-particles are released, which have a spectrum of kinetic energies ranging from near zero to a characteristic maximum (Emax). Emax can vary by orders of magnitude among different types of emitters. The low mass of β-particles causes them to lose energy quickly through molecular collisions, producing excitation of valence electrons, ionization of atoms, and in some cases specialized radiation (bremsstrahlung and Ĉerenkov radiation, and Compton scattering). Detection of β-particle emissions is complicated by the wide range of possible energies and the weakness of some emissions so that a single type of detector is inadequate for the analysis of radiation from all β-particle emitters. Detectors are characterized by a sensitive volume in which particles interact with matter to produce a signal, an example of which is the emission of photons. The signal can produce a continuous current or a pulse. In pulse mode, it is desirable to choose a detector such that the pulse is proportional to the energy of the particle, giving the instrument the property of energy discrimination. This property permits spectral analysis and methods of quantitation that are based in part on energy spectra. Liquid scintillation counting (LSC) is the most accurate and widely used method for detecting low-energy β-particles. Usually, the information obtained by LSC must be corrected for signal loss due to absorption of incident particles or emitted photons. This signal loss is called quenching. For quantitation of low-energy β-radiation, quench corrections are usually made using the sample channels ratio (SCR) or an external standard method. All such calculations are subject to error and derived values are subject to the compounding of precision error during mathematical manipulation of the data. Scintillation counting with organic crystal detectors is the method of choice for high-energy β-particle emitters. Gas-filled detectors are of limited value for β-particle detection, although windowless proportional counters are appropriate for detection of low-energy particles, especially in gaseous form. When neither energy discrimination nor precise quantitation is required, Geiger–Muller counters are acceptable for high-energy β-particle detection. They can detect all but the least energetic of low-energy emitters, although Geiger–Muller counters are not practical for the analysis of activity from such emitters because the signal is very weak, and the energies from incident particles are frequently absorbed before reaching the sensitive volume. Silicon-barrier semiconductors support energy discrimination and are of value for some applications. Visual imaging with photographic film is used for localization of β-particle emitter activity, as in labeling of biological tissues or macromolecules.

The morphogenesis of functional myofibrils in chick skeletal and cardiac muscle occurs in greatly different time spans, in about 7 and 2 days, respectively. In chick skeletal myogenic cells, one isoform of the 250 kD actin-binding protein (ABP) filamin is associated with stress fiber-like structures of myoblasts and early myotubes, then disappears for approximately 4 days, whereupon a second filamin isoform reappears at the Z-disc periphery. We sought to determine if cardiac myogenesis involves this sequence of appearance, disappearance, and reappearance of a new filamin isoform in a compressed time scale. It was known that in mature heart, filamin is localized at the Z-disc periphery as in mature (fast) skeletal muscle, and is also associated with intercalated discs. We find that myocardial filamin has an apparent molecular weight similar to that of adult skeletal muscle filamin and lower than that of smooth muscle filamin, and that both skeletal and cardiac muscle contain roughly 200 filamin monomers per sarcomere. Two-dimensional peptide mapping shows that myocardial filamin is very similar to skeletal muscle filamin. Myocardial, slow skeletal, and fast skeletal muscle filamins are all phosphorylated, as previously shown for filamin of non-striated muscle. Using immunofluorescence, we found that filamin could not be detected in the developing heart until the 14-somite stage, when functional myofibrils exist and the heart has been beating for 3 to 4 hours. We conclude that in cardiac and skeletal myogenesis, different sequences of filamin gene expression result in myofibrils with similar filamin distributions and isoforms.

Our modular laboratory teaching program is characterized by two major features. First, each course is taught independently and not linked with a particular lecture course. Second, each course is designed to be completed within one-half semester or less. The modular organization has allowed incorporation of the latest technology, reduction of class sizes, and a greater number of choices to permit students to pursue their own interests. Full-time laboratory teaching personnel work together on the organization of the program as well as design and teach individual courses. The program has distinct and separate instructional goals, namely introduction, reinforcement, and advancement of fundamental scientific capacities. Such focus has facilitated efforts to coordinate laboratory courses within the biological sciences and among other departments in natural sciences and engineering, raising expectations as students progress through a program.