Research areas include animal physiology, cell biology, marine biology, mathematical modeling of biological systems, molecular biology, and plant ecology.
Animal Physiology: Vascular Responses to Stress - Dr. Jeff Jasperse
Research in my laboratory examines the regulation of blood flow to skeletal muscle. Blood flow is controlled primarily by changing the diameter of arteries and arterioles perfusing skeletal muscle. Arteries and arterioles sense chemical stimuli such as metabolites or hormones and physical stimuli such as shear stress or pressure and respond by constricting (to decrease flow) or dilating (to increase flow). Arteries and arterioles are comprised of different cell types (e.g. smooth muscle cells, endothelial cells) that communicate with each other to coordinate changes in diameter and we study signaling mechanisms that include nitric oxide, prostacyclin, various potassium channels, etc. These mechanisms can vary with location in the vascular tree, muscle fiber type, and fitness level. We investigate mechanisms that regulate arterial diameter under resting conditions, how these mechanisms contribute to the rapid and substantial elevations in blood flow observed during a bout of exercise, and how they adapt to the stress of repeated bouts of exercise (exercise training). We primarily use an in vitro isolated artery/arteriole model to examine the role of signaling mechanisms in dilation and constriction, but also occasionally use the human forearm model to examine in vivo vascular function. We are also developing Western blotting techniques to quantify levels of specific signaling proteins (e.g. integrins) in endothelial and smooth muscle cells of arteries/arterioles of different sizes and from various regions.
Cell Biology: Apoptosis and Cellular Stress Response - Dr. Jay Brewster
Research in my laboratory focuses on the initiation of stress-responsive and apoptotic programs in eukaryotic cells. The mechanisms through which cells adapt and respond to external and internal stresses are diverse and fascinating. Severe stress can activate a cellular suicide program known as apoptosis (programmed cell death). Entrance of a cell into apoptosis initiates a cascade of proteolytic events, culminating in the destruction of cellular macromolecules, membranes, and organelles by cytosolic and nuclear enzymes. Using mouse cells in tissue culture, we are currently characterizing the activation of cell death that results from abnormalities in the endoplasmic reticulum (ER). The loss of glycosylation activity during protein synthesis in the ER results in a dramatic apoptotic phenotype. Also of interest to our research group are the downstream targets of stress-activated signal transduction cascades (the genes being activated in response to cellular stress). We employ the budding yeast, Saccharomyces cerevisiae, as a model system for stress-activated signal transduction. We have recently cloned and are currently characterizing a set of genes that are activated by the HOG (high osmolarity glycerol response) signal transduction cascade following osmotic stress.
Marine Biology: Physiology and Ecology of the California Grunion in an Ecosystem under Stress - Dr. Karen Martin
Beaches play critical roles in many plant and animal life cycles, and support unique biodiversity. Traditionally managed as recreational areas to protect human health and safety, urban sandy beaches are also important natural coastal ecosystems. Compared to other coastal ecosystems, sandy beaches have been relatively understudied. Our group focuses on an endemic beach spawning fish, the California Grunion, with research on development, behavior, ecology, genetics, histology, and physiology. We are also working collaboratively to develop new methods for identifying and monitoring indicator species to assess the status of sandy beach ecosystems in southern California.
Mathematical Modeling of Biological Systems: Models of Newt-Crayfish Interactions in the Southern California Streams - Dr. Timothy Lucas, Dr. Courtney Davis
Ecologists at Pepperdine University have spent over twenty years studying newt and crayfish populations in local Malibu streams. They have observed the decline of local newt populations and explored the impact of drought and invasive crayfish on the newt populations. With this rich data set, we mathematically explore how rainfall and crayfish predation alter newt reproduction and survivorship. We utilize a variety of mathematical approaches to describe these population dynamics and species interactions, including differential equations, discrete-time models, and agent-based approaches. These mathematical models will be used to predict the long-term effects of California's extreme drought on the local river ecosystem and to mathematically explore how intervention methods such as crayfish trapping affect newt populations long term.
Molecular Biology: Biochemical Adaptations to UV-B Stress in Hylid Frogs - Dr. Thomas L. Vandergon
DNA may be damaged through a variety of agents including exogenous chemicals and radiation. Mechanisms to repair DNA damage are wide-spread and of major interest. We study a DNA repair enzyme known as photolyase, a light-dependent photoreactivating enzyme that is highly conserved in basic structure from bacteria to mammals. The enzyme utilizes blue light energy to repair damage known as pyrimidine dimers caused by low level UV radiation. We examine tissue-specific and developmental expression of the photolyase gene in organisms that experience differing levels of UV radiation. Possible projects include measuring levels of photolyase mRNA or protein in specific tissues during development, comparing expression of photolyase relative to UV radiation exposure, or cloning and sequencing photolyase genes.
Plant Ecology: Environmental Stress Physiology of Plants Native to the Santa Monica Mountains - Dr. Stephen D. Davis
Pepperdine's Malibu campus is nestled in the foothills of the Santa Monica Mountains, providing easy access to a natural laboratory of native plant communities. Most research projects will focus on physiological adaptation to wildfire, summer drought, and winter freezing. Some possible projects are: 1) the adaptive mechanisms of chaparral species to survive periodic wildfires--seed germination, seedling survival, and resprout success, 2) mechanisms of fern drought tolerance--stomatal regulation, osmotic adjustment, and resistance of xylem to cavitation, and 3) the interactive effects of freezing and water stress on xylem dysfunction and lethal temperatures for cells and tissues in chaparral and coastal sage scrub.