Biology Honors Theses

HIV-1 PR P51 Mutant Complex Formation with Inhibitors

Shaquita T. Greene et al. — Thu, 10 Jan 2013 06:05:10 PST

Human Immunodeficiency Virus (HIV) has become a global pandemic with at least 25 million deaths and no cure. One of the most important targets to inhibit this virus is HIV-1 protease (PR), which is required to cleave the viral proteins needed for maturation of the virus after it invades and replicates in the host cell. There are nine protease inhibitors that are used in AIDS treatment. The virus loses susceptibility to these inhibitors by drug resistance due to mutations. The goal of the project is to examine the highly drug resistant HIV PR P51 in its complex with inhibitors. In this experiment we expressed and purified HIV PR P51 protein. We performed protein crystallization with inhibitors Tipranavir, Amprenavir, Darunavir, and Saquinavir to obtain the structure of the protease and the inhibitors in their complexes. Future analysis of the crystal structures will help with the development of successful therapeutic inhibitors.

Glial Cell Activity within the Ventrolateral Periaqueductal Gray of Male and Female Rats

Jean-Marc A. Sauzier et al. — Thu, 31 May 2012 10:14:27 PDT

Morphine is one of the most commonly prescribed medications for the relief of prolonged pain. Both basic science and clinical studies indicate that females require 2-3 times more morphine than males to achieve the same analgesic effect. To date, the mechanisms underlying sex differences in opiate responsiveness are unknown. Recent studies suggest that glial cells are potent modulators of morphine-based analgesia, and in particular, decrease the analgesic effect of opiates. Therefore, we tested the hypothesis that the sexually dimorphic effects of morphine were due to sex differences in glial cell activity. Our studies focused on the midbrain periaqueductal gray (PAG) as this region of the brain is critical for the analgesic effects of morphine. Adult male and female Sprague Dawley rats (250g- 400g) were procured from Charles River Laboratories, and were allowed 7 days to acclimate to the new facility. On the day of the experiment, animals received a subcutaneous injection of morphine (5mg/kg) or were handled in a similar manner. Thirty or 60 minutes after injections or handling, animals were perfused with a 4% paraformaldehyde and 2.5% acrolein tissue fixative solution. Brains were removed and stored in 20% sucrose until ready for sectioning. Brains were sectioned at 25mm using a freezing microtome, and immunohistochemical localization of markers for astrocyte glial cell activity was performed. Antibodies to glial fibrillary acidic protein (GFAP) were used to label activated astrocytes. If our hypothesis is correct, then females will have significantly greater density of the astrocyte cell activity marker GFAP as compared with males. Sex differences in PAG glial cell activity may provide the biological bases for the sexually dimorphic effect of morphine. This research may lead to better treatment for females experiencing prolonged chronic or neuropathic pain.

Role of Chemotaxis Genes in Wheat Root Colonization by Azospirillum brasilense

Mariam Wasim — Mon, 08 Feb 2010 15:26:32 PST

Previous studies have shown that chemotaxis plays an important role in the colonization of the wheat roots surfaces by Azospirillum brasilense and a chemotaxis operon shown to control motility and chemotaxis in A. brasilense has been isolated. This study looked at the effects of mutations in individual genes coding for chemotaxis proteins from this operon on the ability of the cells to colonize the surface of sterile wheat roots. Using both quantitative and qualitative assays, the study shows differences in the colonization ability of the mutants relative to the wild type: the cheB, cheR, cheBR, and cheOp mutants were significantly impaired in wheat root colonization. Interestingly, the cheA mutant was not affected in its ability to colonize the wheat root surface relative to the wild type. Future studies will look for the factors that compensate for cheA impairment in the rhizosphere.

Fat-Pad Specific Effects of Lipectomy on Appetitive and Consummatory Ingestive Behaviors in Siberian Hamsters (Phodopus sungorus)

Kelly Deshon Johnson — Mon, 08 Feb 2010 15:26:31 PST

The aim of this experiment was to test whether LIPX-induced decreases in body fat affect appetitive (foraging effort and food hoarding) or consummatory (food intake) ingestive behaviors and whether the effects of LIPX on these behaviors is in turn affected by changes in energy expenditure produced by varying the amount of work required to obtain food. This was accomplished by housing male Siberian hamsters (Phodopus sungorus) in a foraging/hoarding apparatus where food pellets (75 mg) could be earned by completing various wheel running requirements. Requiring a foraging effort (10 revolutions/pellet) abolished the normal compensation of WAT mass by the non-excised WAT pads that typically follows IWATx or EWATx. After foraging, food hoarding was increased more than food intake when hamsters were required to forage for food (10 revolutions/pellet). The magnitude of the LIPX-induced lipid deficit (IWATx > EWATx) did not correspond to a proportional change in either appetitive or consummatory ingestive behaviors.