Obesity is a major cause of health-related problems in the developed world and recently studies have demonstrated a link between environmental factors and obesity. 2,2’,4,4’-tetrabromodiphenyl ether (BDE-47) is one toxic chemical used as a flame-retardant in consumer products. BDE-47 contaminants are commonly found in dust, air, and soil and their accumulation in the food chain contributes to significant levels found in humans, particularly children. Recent studies have linked BDE-47 to a range of toxic impacts, including disruption of insulin signaling. The objective of this study is to investigate the in vivo effects of BDE-47 in hepatic metabolism. We hypothesize that the drug will cause increased cell injury, inflammation and accumulation of fat within the liver (hepatic steatosis) and will have significant effects on individuals predisposed to disruption in insulin signaling. In order to disrupt insulin signaling in vivo, we have generated mouse models with liver-specific deletion of Tsc1 and Pten, negative regulators of mTORC1 and Akt respectively. Both of these complexes play critical roles in the cell cycle and insulin metabolism within the liver. Cohorts of Tsc1-/-, Pten-/-, and control mice were exposed to BDE-47 or placebo for six weeks within their first 10-12 weeks of life. During exposure, the mice were tested for insulin sensitivity and glucose tolerance. Liver tissue was also tested for several markers of hepatic insulin signaling post-mortem. Differences in impacts on these genetic mutants could indicate if the BDE-47 targets the Akt or mTOR cascades differently and if those predisposed to aberrations in insulin signaling may be more sensitive to the toxic effects of BDE-47. This study will determine if a significant interaction between the environmental influence of BDE-47 and the genetic deregulation of insulin signaling occurs, which could have deleterious implications for the use of these compounds in consumer products in the future.

Neprilysin (NEP) is a plasma membrane metalloendopeptidase expressed in pancreatic islet β cells. In non-islet tissues, it has been shown to modulate ion flux. Whether NEP modulates potassium and/or calcium flux in β cells that are necessary for glucose-stimulated insulin secretion (GSIS) is unknown. Thus, the purpose of this study was to determine whether NEP acutely regulates GSIS and if so, where NEP acts in the secretion pathway. To do this, islets were isolated from 8-10 week old C57BL/6 mice. Following overnight recovery, islets were pre-incubated for 30 minutes in 2.8 mM glucose and then stimulated for 60 minutes with either 2.8 mM (basal) or 20 mM (stimulated) glucose in the absence or presence of the NEP inhibitor thiorphan (50 uM). To measure the effects of NEP inhibition on GSIS mediated by Ca2+ channel activity independent of K+ATP channel-induced depolarization, in some conditions a Ca2+ channel agonist (BayK-8644, 1 uM) was used in combination with a K+ATP channel opener (diazoxide, 500 uM). The results showed that acute inhibition of NEP significantly reduced 20 mM glucose-stimulated insulin secretion (128.1±16.0 vs. 80.5±11.4 pM/5 islets; n=11, p=0.03) without affecting basal insulin secretion (13.9±3.8 vs. 8.7±2.3 pM/5 islets; n=11, p=0.26). In addition, NEP inhibition did not alter insulin secretion in response to BayK-8644 plus diazoxide (33.0±6.1 vs. 38.2±8.1 pM/5 islets; n=6, p=0.62), suggesting NEP may be acting to modulate GSIS at a step that is proximal to the Ca2+ channel. It can be extrapolated from this data that NEP may play an important role in the insulin-secretion pathway and thus, acutely upregulating NEP may prove effective in treating type 2 diabetes. 

Until recently, little research has been done on C-S bond formation in transition-metal catalyzed transformations compared to other carbon-heteroatom bonds such as C-N, C-O, and C-P. As sulfur-based coupling partners (thiol and disulfide for example) tend to poison transition-metal catalysts, development of C-S bond formation has been slow. However, a recent nickel-catalyzed system shed new light on this difficult transformation. In this context, C-H functionalization is a sustainable and straightforward approach to sulfur-containing heteroaromatic production. C-H activation is a process whereby a carbon-hydrogen bond is cleaved, thereby allowing the exposed carbon atom to form new bonds. Thus, in order to expand the above research of C-S bond formation toward development of short synthesis for fused thiophene systems, focus was placed on a palladium catalyzed cascade-type reaction system. C-H activation reactions can and have been manipulated to work in a cascade-type fashion. By combining cascade-type methodology with the reduced environmental impact of C-H activation, these fused thiophenes can be synthesized cleanly and efficiently. The test substrates in this work are O,O-diethyl S-phenyl phosphorothioate and 4,4,5,5-tetramethyl-2-(thiophen-2-yl)-1,3,2-dioxaborolane. Both substrates were chosen because they contain sulfur, thereby aiding the C-H activation process. By effecting a C-H activation with a palladium catalyst at one of the ortho carbons of the phenyl ring with the boronic ester of the thiophene, the first C-C bond will be formed. In the time immediately after this first transformation, the now-changed palladium complex is able to insert into the S-P bond of the phenyl-based compound. This step sets up the second reaction, whereby the phosphorothioate directing group is cleaved along the S-P bond and the resulting thiol is coupled to a carbon atom to close the ring. This molecule is known as benzo[b]thieno[2,3-d]thiophene.

Organic electronics is a growing area of research that investigates the properties and applications of conjugated polymers and conductive small molecules. Devices made from organic electronic materials can be flexible, inexpensive to process, and have lower weight compared to inorganic devices. Prominent synthetic techniques for conjugated polymers, including the Suzuki reaction, Heck reaction, and Kumada coupling, utilize a palladium or nickel complex as the catalyst. When the reaction completes, organometallic molecules and metal nanoparticles remain stuck in the polymer, decreasing the efficiency of resulting devices by acting as charge trappers or photo quenchers. The potential commercial success of organic electronics is highly dependent on their efficiency, and so the impurities need to be removed. A palladium-catalyzed model Suzuki coupling reaction of bromobenzene and phenylboronic acid was analyzed by 31P-NMR both before and after the post-synthetic addition of thiuram disulfide (TMTD). Pd(PPh₃)₂Br₂ dibromide was present in the solution prior to the post-synthetic disulfide addition, but not after. When TMTD or diphenyl disulfide were added directly to metal catalyst in chloroform, the resulting product precipitated out; the solubility of the product was different from the reactants. The change in solubility indicates that disulfide molecules can behave as metal scavenger for residual palladium or nickel catalyst. In order to restore the performance of organic polymers, scavenger molecules are used post-synthesis. This additional step isolates palladium or nickel atoms and changes their solubility, allowing them to be separated from the polymer. The performance of disulfide-based metal scavengers added to catalyst-metal-contaminated conjugated polymers is discussed.

The work of tutors in the Odegaard Writing & Research Center requires continual adaptation of practices to accommodate and collaborate with writers who range from incoming freshmen to tenured faculty, come from more than 150 different departments and programs, speak more than 80 different home languages, and may visit at any stage of the writing process. Successful interactions require that undergraduate tutors thoughtfully enact writing center scholarship that itself tends to be quite abstract and axiomatic: for example “make better writers, not better papers”. As researchers, we asked: How might communication tools borrowed from other fields help tutors mediate the disconnect between writing center theory/pedagogy and writers’ (sometimes conflicting) expectations? We hypothesized that tutors’ ability to so mediate would be improved by acquisition of concrete active-listening and reflective-responding skills; such skills might enable them to more confidently navigate the endlessly shifting terrain of a tutoring session. To identify needed skills, we reviewed scholarship from legal mediation, nursing, psychology, composition, and social work. To assess the realities of tutor practices -- how practices do and do not align with the pedagogical mission of a writing center -- we surveyed tutors to assess their key concerns, observed tutoring sessions, and created transcripts. Our preliminary findings indicate a considerable gap between writing center theory and practice, despite tutors’ own articulated goals and best intentions. In response, we have undertaken additional research into non-defensive communication strategies and begun to develop and test new training and education materials for fellow tutors. We hope to offer better ways to practically enact ideals of collaborative learning. What we’ve learned through our research to date shows both considerable promise toward this end and value to myriad teaching and learning groups.

Studying human perception from the perspective of a biologist or physician is a recent innovation, whose aims were previously appropriated by the domain of psychology. Yet in recent years, emphasis on perception has grown in fields like psychosomatic medicine, behavioral neuroscience, stress physiology, and complementary/alternative medicine. This new perspective on perception has prevailed with increased rates of psychosomatic disorders that have physiological and cognitive components (Post Traumatic Stress Disorder (PTSD), depression, etc.), and through recent technological advances made available to researchers (EEG, fMRI, etc.) Most specifically, technological innovations have enabled less invasive and more precise studies of neuroanatomy, which enables us to connect precise physiology with corresponding cognitive change. The manner in which a stimulus is perceived, and the resulting trauma, reward, danger or stress, then cognitively processed can have positive or negative physiological outcomes for individuals. However, researchers are just beginning to understand this mechanism and its implications.My research will study activation differences during visual working memory (VWM) tasks in stressed individuals. The ability to hold and process information in the VWM is related to general alertness, and I anticipate finding that stress will impair functionality of the VWM. This can be ascertained using electrophysiology (event-related potentials). These results would help establish the cycles or mechanisms that characterize these disorders and produce their cognitive-processing malfunctions. I hope to increase awareness of the genuine and detrimental progressions of these disorders, while also identifying treatments that effectively ameliorate both symptoms and identifiable lesions (chemical, physical, or otherwise). Understanding these pathways can assist in the recovery from disorders such as PTSD and depression, or potentially shorten a patient’s stay in hospital, where serious infection rates and stress are high, and overall comfort, low.

A recent discovery in reproductive endocrinology, the kisspeptin system has been found to play a pivotal role in the regulation of the brain-pituitary-gonadal axis. Kisspeptin signaling in the brain is vital to the onset of puberty, control and regulation of sex steroid production, and regulation of fertility and reproductive function in mammals. However, the importance of the kisspeptin system in other vertebrates, such as fish, is not as clear. The goal of the current study was to clone the kisspeptin genes (kiss1, kiss2, and the receptor kiss1ra) for the first time in the marine teleost Anoplopoma fimbria (sablefish), and explore their potential roles in gonadal development. Previously, expression of the kiss2 gene was demonstrated in the gonads of sablefish. Partial kiss mRNA sequences were obtained by PCR and rapid amplification of cDNA ends (RACE) cloning techniques. Semi-quantitative PCR assays developed for each gene allowed us to measure kiss1, kiss2 and kiss1ra mRNA levels in a variety of adult tissues. We found the highest abundance of these mRNAs in the gonads, brain, and pituitary. In particular, kiss2 mRNA was abundant in the ovary and appeared to be the most highly expressed of the kiss genes. We are currently analyzing the expression of the kiss genes in gonads of fish undergoing sexual differentiation. Preliminary data suggest that there is sexually dimorphic expression of all three genes early in life. The ultimate goal of this project is to determine if gonadal kiss gene expression plays an important role in sexual differentiation and/or gametogenesis in fish.

Currently there are three major classes of known viruses: exclusively RNA viruses, which do not require a DNA intermediate in their replication and propagation; DNA viruses, which use DNA dependent processes to perform their genome replication; so-called retroviruses, which go through both an RNA and a DNA phase with the help of a reverse transcriptase enzyme. Until very recently there was no evidence that there was genetic exchange between these distinct virus classes. However, a single stranded DNA (ssDNA) virus genome, recently found using metagenomics in Boiling Springs Lake in Lassen Volcanic National Park, USA (BSL) contains elements homologous to both ssRNA and ssDNA viruses. The genome of this RNA-DNA hybrid virus (BSL-RDHV) contains a gene similar to that of ssDNA circoviruses that infect animals and a capsid protein (CP) gene similar to that of the ssRNA tombusviruses that infect plants. It is currently unclear how the RNA virus capsid gene integrated into the DNA virus genome and what, if any, evolutionary impacts are associated with this recombination. My current work focuses on the characterization of the BSL-RDHV CP using recombinantly expressed protein. The CP gene will be amplified from the BSL viral metagenome using Polymerase Chain Reaction and expressed in bacterial cells. The long term goal is to determine the structure of this protein using X-ray crystallography and use the protein for in vitro assembly reactions. Successful completion of this work will be an important step towards understanding virus evolution and possibly the emergence of novel virus disease.

A century of fire suppression has led to higher tree densities, higher basal area, and increased abundance of shade-tolerant Abies concolor and Calocedrus decurrens in the lower montane forests of Yosemite National Park. Although fire was reintroduced to these systems over forty years ago, the effects of fire on forest structure and radial tree growth are still not well understood. This study compares live tree and snag basal area and density, seedling establishment, and radial growth patterns at four 0.1 ha plots in A. concolor-dominated stands of similar climatic water balance. Two sites had burned at different levels of low-severity fire in 2005, and two sites had not burned since the onset of fire suppression. On average, unburned plots had three times the tree density and 2.6 times more trees with DBH between 2.5 cm and 30.0 cm than burned plots. Burned plots had a mean seedling density 3.8 times greater than unburned plots. Low-severity fire also appeared to affect radial growth patterns as both burned plots showed decreased growth relative to the control plots for two years immediately post-fire. However, only burned plot 1, which burned at a higher severity than burned plot 2, showed increased growth relative to control plots 3 to 5 years post-fire. This study has implications pertaining to frequent fire forests of the West.