A Computer-Assisted Personalized Approach in an Undergraduate Plant Physiology Class1

We used Computer-Assisted Personalized Approach (CAPA), a networked teaching and learning tool that generates computer individualized homework problem sets, in our large-enrollment introductory plant physiology course. We saw significant improvement in student examination performance with regular homework assignments, with CAPA being an effective and efficient substitute for hand-graded homework. Using CAPA, each student received a printed set of similar but individualized problems of a conceptual (qualitative) and/or quantitative nature with quality graphics. Because each set of problems is unique, students were encouraged to work together to clarify concepts but were required to do their own work for credit. Students could enter answers multiple times without penalty, and they were able to obtain immediate feedback and hints until the due date. These features increased student time on task, allowing higher course standards and student achievement in a diverse student population. CAPA handles routine tasks such as grading, recording, summarizing, and posting grades. In anonymous surveys, students indicated an overwhelming preference for homework in CAPA format, citing several features such as immediate feedback, multiple tries, and on-line accessibility as reasons for their preference. We wrote and used more than 170 problems on 17 topics in introductory plant physiology, cataloging them in a computer library for general access. Representative problems are compared and discussed.

Putting ion channels to work: Mechanoelectrical transduction, adaptation, and amplification by hair cells

As in other excitable cells, the ion channels of sensory receptors produce electrical signals that constitute the cellular response to stimulation. In photoreceptors, olfactory neurons, and some gustatory receptors, these channels essentially report the results of antecedent events in a cascade of chemical reactions. The mechanoelectrical transduction channels of hair cells, by contrast, are coupled directly to the stimulus. As a consequence, the mechanical properties of these channels shape our hearing process from the outset of transduction. Channel gating introduces nonlinearities prominent enough to be measured and even heard. Channels provide a feedback signal that controls the transducer's adaptation to large stimuli. Finally, transduction channels participate in an amplificatory process that sensitizes and sharpens hearing.

The cell wall components peptidoglycan and lipoteichoic acid from Staphylococcus aureus act in synergy to cause shock and multiple organ failure.

Although the incidence of Gram-positive sepsis has risen strongly, it is unclear how Gram-positive organisms (without endotoxin) initiate septic shock. We investigated whether two cell wall components from Staphylococcus aureus, peptidoglycan (PepG) and lipoteichoic acid (LTA), can induce the inflammatory response and multiple organ dysfunction syndrome (MODS) associated with septic shock caused by Gram-positive organisms. In cultured macrophages, LTA (10 micrograms/ml), but not PepG (100 micrograms/ml), induces the release of nitric oxide measured as nitrite. PepG, however, caused a 4-fold increase in the production of nitrite elicited by LTA. Furthermore, PepG antibodies inhibited the release of nitrite elicited by killed S. aureus. Administration of both PepG (10 mg/kg; i.v.) and LTA (3 mg/kg; i.v.) in anesthetized rats resulted in the release of tumor necrosis factor alpha and interferon gamma and MODS, as indicated by a decrease in arterial oxygen pressure (lung) and an increase in plasma concentrations of bilirubin and alanine aminotransferase (liver), creatinine and urea (kidney), lipase (pancreas), and creatine kinase (heart or skeletal muscle). There was also the expression of inducible nitric oxide synthase in these organs, circulatory failure, and 50% mortality. These effects were not observed after administration of PepG or LTA alone. Even a high dose of LTA (10 mg/kg) causes only circulatory failure but no MODS. Thus, our results demonstrate that the two bacterial wall components, PepG and LTA, work together to cause systemic inflammation and multiple systems failure associated with Gram-positive organisms.