RESEARCH

Sabrina Brougher, Ph. D.
It has been well-established across many species that stress negatively affects endocrine and behavioral components of reproduction. Of particular concern are the domestic fowl, which are routinely exposed to environmental and social stressors, including heat stress, negative social interactions, and poor air quality (high dust and ammonia levels). We are investigating how stressful housing conditions adversely impact reproduction at the hypothalamic and/or pituitary tiers of the hypothalamic-pituitary-gonadal (HPG) axis. Students in the lab will examine endocrine, neuroendocrine, and behavioral endpoints related to stress and reproduction in domestic fowl. Sexual behavior will be recorded using The Observer for Windows (Noldus, Inc.), while neural and peripheral endocrine patterns will initially be evaluated by ELISA and by IHC. Our primary findings will direct the design of future studies, which will involve molecular-based analyses (e.g. Western immunoblotting, real-time RT-PCR, in-situ hybridization) of neuroendocrine response to CORT,  for example, GnRH receptor availability in the anterior pituitary, and subsequent mRNA expression of LH and FSH.

Leonard Davis, Ph. D.
The use of mollusks as models for learning has a very long history, notably with the marine slug Aplysia californica. My lab is utilizing Dr. Harrington’s model of slime trail following in a predatory snail as a model to investigate the role of different signal transduction systems in controlling learning and memory. Evidence from Dr. Harrington’s lab shows that Euglandina rapidly learn to follownovel trails associated with eating prey and exposure to potential mates. My lab will test the targeted mutation technique of RNA interference to knock out specific genes that are candidates for involvement in snails learning to follow new trails. Current work is focused on cloning candidate genes from Euglandina by homology screening. The first genes targeted are nitric oxide synthase and the serotonin-gated ion channel. Nitric oxide has been implicated in controlling olfactory processing and learning in other slug and snail model systems, and will likely be involved in slime trail following as well. A serotonin receptor with a pharmacology suggestive of the 5-HT3 receptor (serotonin-gated ion channel) has also been shown to be involved in olfactory processing in snail model systems. Homology cloning by PCR has resulted in promising bands for each gene. Once the sequences of these genes are verified, small interfering RNAs generated from these sequences will be injected into snails and the effect on trail following and RNA levels will be assessed.

Harbinder Dhillon, Ph. D.
The courtship ritual of fruit-flies follows an interesting sequence of behaviors: (1) a male orients on and follows a prospective mate, (2) taps her on the abdomen, (3) sings a courtship song using wing vibrations, (4) licks the female genitalia, and (5) attempts mounting. This sequence may be repeated several times.  A female’s usual response to courtship is to run away, and the male follows.  If the female is eventually stimulated enough to become receptive, she slows down and allows copulation.  The behaviors of courtship and receptivity are mediated in part by chemosensory cues emanating from the opposite sex in the form of cuticular hydrocarbon pheromones.  Hydrocarbons on the female cuticle stimulate males to court and those on the male help induce the female to slow down and allow copulation. In addition to chemosensory cues, courtship entails visual and acoustic cues, as well as somatosensory agility of both sexes.

Drosophila olfactory sensory neurons are located in the antenna and maxillary palps of the adult fly, and the gustatory receptors are distributed all over the body surface including proboscis, legs, wings and genitalia. These receptors are G-protein linked 7-transmembrane proteins receptor families share little sequence homology with each other outside the seventh trans-membrane domain. In addition to chemoreceptors, a large family comprising 51 odorant binding proteins (OBPs) or pheromone binding proteins (PBPs) have been predicted from the Drosophila genome. Typically, OBPs are soluble proteins with six conserved cystein residues, and are secreted into sensillar perilymph bathing the olfactory neurons. It has been hypothesized that OBPs facilitate the transport of lipophylic pheromones and odorants to the odor receptors located in the sensory neuronal membranes.  Research in our lab focuses on the role of OBPs in olfaction in general, and mating behavior in particular.

Melissa A. Harrington, Ph.D.
Euglandina rosea, the rosy wolfsnail, is a carnivorous snail native to the southeast. It preys on other snails and slugs and it tracks down its prey by following the slime trails that they leave. In the laboratory, Euglandina follow >90% of slime trails encountered. Following heterospecific trails (those left by other species) ends in predation, while following trails of their own species leads to mating. Detection of chemosensory stimuli from slime trails results in two readily apparent behavioral outputs in Euglandina. First, a change in direction of motion in order to follow the trail, and second, once the animal leaving the trail is encountered, a choice between an aggressive versus an agonistic interaction (predation versus mating). These reliable and easily detected behavioral changes are the result of a precise discrimination between very similar chemosensory cues and provide an excellent model system for studying the mechanism of sensory discrimination and its effect on behavior. In addition, Euglandina snails may also be a good model for studying the acquisition of long-term memories, as our experiments suggest that slime trail tracking is a learned behavior in which snails learn that particular slime constituents are associated with prey species, and so follow trails containing those chemicals.
We are searching for the neural correlates of slime trail detection and discrimination.  By using multi-electrode recording with the MED64 a 64 electrode planar micro-array  we hope to identify the neural systems involved in trail following, and characterize the neural signals representing slime trail stimuli. By studying the physiological basis of slime trail tracking, we hope to identify a neural circuit that guides the behavior of the snails as they identify and follow trails of chemicals associated with prey snails or potential mates.

Stan Ivey, Ph. D.  
About 25% of cancers that develop multidrug resistance during chemotherapy overexpress P-glycoprotein (Pgp).  Pgp is an energy driven, ATP efflux plasma membrane pump that removes toxins and foreign molecules from normal and cancerous cells; it removes anti-cancer drugs from targeted cancer cells during multidrug resistance very well!  Our lab is studying the molecular structure of overexpressed human Pgp, including its complement of sugar groups (glycosylation) and their role in the targeting and function of Pgp at the plasma membrane.  Using specific lectins, we have identified key sugars that may be involved in this important membrane protein’s role in removing anti-cancer drugs during chemotherapy treatments.  If researchers can learn how Pgp functions through examining its structure, then we can shut down the pump in aggressive, multidrug resistant tumors, making chemotherapy much more effective in destroying tumors.

Robert MacBride, Ph. D./Veronica Ernst  
Apoptosis of skeletal muscle cells is an initiating step in a variety of muscular dystrophies, and may be related to age-related muscle loss. The overall goal of my laboratory is to investigate the effects of apoptosis on skeletal muscle and the factors aiding the recovery of these cells from the initial stages of cell death. Since skeletal muscle cells are multinucleate, they should be able to recover from the loss of one or two nuclei and maintain homeostasis, rather than progressing to full-blown apoptosis and loss of the entire fiber. My lab uses primary cultures of embryonic chicken breast muscle cells to study myodomain activity involved in the selective shedding of apoptotic myonuclei. Apoptosis is induced with UV irradiation, and monitored with TUNEL labeling. The loss of myonuclie is monitored  with acridine orange /ehtidium bromide staining. Calcium dynamics of apoptotic and partially apoptotic muscle cells are monitored with fura imaging to indicate the extent of injury and recovery from apoptotic events.