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Malibu Campus
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Research areas include animal physiology, cell biology, developmental biology, molecular biology, population genetics, and plant ecology.
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. For more information click here.
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My research is focused on attempting to identify natural products and characterize their biological properties. Natural products are chemical compounds that are produced by a living organism in order to augment its interactions with its environment. These compounds may be used for a vast array of purposes by an organism, such as reducing competition from neighboring life forms or communicating with dissimilar organisms to gain access to new resources. Due in large part to the naturally occurring biological functions of these compounds, natural products have traditionally been exceedingly valuable as a source of new drugs. Many of the great discoveries in medicine in the past few decades have come from natural products, including antibiotics such as penicillin G and cancer treatments such as paclitaxel (also known as Taxol(r)). For more information click here
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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. For more information click here.
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Members of the Notch family of transmembrane receptors are believed to play a central role in development by regulating cell-fate decisions in both invertebrates and vertebrates. Notch signaling is thought to influence the cell's ability to respond to instructive signals by keeping cells in an undetermined, undifferentiated state. Although Notch signaling has been shown to inhibit the differentiation of a number of different cell types, the molecular mechanisms involved in Notch signaling are not well characterized. In order to study the molecular mechanisms of Notch-mediated inhibition of cellular differentiation we have developed a cell assay system utilizing a mouse myoblast (muscle) cell line. Expression of normal and mutant forms of Notch in these muscle cells affects the ability of these cells to differentiate. Possible projects may include: 1) construction and characterization of mutant forms of Notch, 2) identification and analysis of molecules that lie in the Notch signaling pathway, and 3) examination of genes induced by Notch signaling. For more information click here.
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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. For more information click here.
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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 the physiological adaptation of chaparral and coastal sage scrub to wildfire, summer drought, and winter freezing. Some possible projects are: 1) the adaptive mechanisms of shrub species to survive periodic wildfires--seed germination, seedling survival, and resprout success, 2) mechanisms of 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. For more information click here.
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The Santa Monica Mountains depict a Mediterranean-type ecosystem, characterized by plants and animals adapted to periods of aridity and seasonal rainfall. Our research program utilizes both nucleotide sequence data and nuclear microsatellites to investigate the impact of recent anthropological processes on the structure and genetic variation within and between populations of animals and plants found in the Santa Monica Mountains and the Channel Islands. We are specifically interested in the characterization of historical and recent events responsible for current patterns of genetic variation in both mainland and island communities. Examples of the types of projects are: 1) Genetic Studies of Chaparral - We have developed a panel of genetic markers (nuclear DNA microsatellites) that are useful for studies designed to examine the fine-scale structure of populations, especially those influenced by more recent perturbations and demographic bottlenecks. 2) Plant Defense Mechanisms and the Impact of Herbivory on Chaparral Communities - Plant/herbivore interactions can impact the composition of plant communities. As a result, most species of plants have evolved defense mechanisms to counter predation by herbivores. Projects might investigate the vulnerable seedling stage of recruitment and to determine differential responses and quantify potential changes in plant community structure. 3) Population Subdivision and Breeding Biology of Stream Amphibians - The California Newt, Taricha torosa torosa, represents a species of special concern that utilizes streams in the Santa Monica Mountains for breeding, and they show strong site fidelity for particular pools and streams. This site fidelity may play an important role in the population structure and gene flow of Taricha torosa between streams. Possible future projects would investigate the degree to which population density and sex ratio influence the breeding biology of Taricha. For more information click here.
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Paul M. Martin ('60) was appointed president of American Baptist Seminary of the West, the first African American president in the 138-year history of the school.
