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Open Access Publications from the University of California

Scholarly Works (75 results)

  • Article
  • Peer Reviewed
UC Davis Previously Published Works (2017)
The development of castration resistant prostate cancer and anti-androgen resistance remains one of the largest hurdles in the successful treatment of prostate cancer. Therefore, the identification of dysregulated pathways contributing to this resistance and determining ways to target these mechanisms is of utmost importance. In the recent publication in Cancer Research, Fong et al. identify a novel role for cytoplasmic CCN3 in prostate cancer progression and enzalutamide resistance. The authors demonstrate that CCN3 expression inhibits androgen receptor signaling and thereby suppresses enzalutamide-resistant prostate cancer cell proliferation, colony formation, and xenograft tumor growth. The data from this manuscript highlight an intriguing potential therapeutic target for the treatment of CRPC and are a critical step forwards towards treating enzalutamide resistant prostate cancer.
    Cover page: CCN3-EZH2-AR feedback loop: new targets for enzalutamide and castration resistant prostate cancer
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2018)
    To meet sustainable intensification goals in the US Midwest, strategies which maintain or increase yields while minimizing negative impacts on water quality are needed. In this study maize yield response and potential nitrogen (N) leaching losses were simultaneously quantified to test the hypothesis that N rates which produced maximum yields would result in minimum yield-scaled N leaching potential. Field experiments were conducted at two sites in 2015 and 2016 to determine the effect of N rate (0, 79, 179, 269, kg N ha−1) on yield, crop N uptake, potential N leaching losses, and post-harvest soil N concentrations. Results show that a significant yield response (up to 179 kg N ha−1) occurred in all years compared to the control. Nitrogen leaching potential increased at 269 kg N ha−1 compared to the control in 2015 but not 2016. Yield-scaled N leaching potential was not statistically different among treatments in three of four site-years. There was no improvement in crop N uptake or N recovery efficiency for 269 kg N ha−1 compared to 179 kg N ha−1 in three of four site-years, which coincided with a trend of increasing post-harvest soil N concentrations, further escalating the risk of environmental N losses. These results did not support our hypothesis that yield-scaled N leaching potential is minimized at N rates that optimize yields (on a normalized basis yield-scaled N leaching potential increased by 28% compared to the control). However, normalized data indicate that 179 kg N ha−1, the N rate most closely aligned with current recommendations in this region, resulted in 96% of maximum yield while preventing a 25% increase in yield-scaled N leaching potential compared to 269 kg N ha−1, underscoring the potential for achieving high yields while avoiding increased N leaching potential on an environmental efficiency basis.
      • Article
      • Peer Reviewed
      Structure and Dynamics, Volume 5, Issue 2 (2011)

      Discoveries of modern biology are forcing a re-evaluation of even the central pillars of neo-Darwinian evolution. Anthropologists study the processes and results of biological and biocultural evolution, so they must be aware of the scope and nature of these changes in biology. We introduce these changes, comment briefly on how will influence anthropology, and suggest numerous readings to introduce anthropologists to the significance and substance of the new evolutionary synthesis.

      • 1 supplemental file
      Cover page: What Anthropologists Should Know About the New Evolutionary Synthesis
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2012)

      Background

      Consequences of antibiotic overuse are substantial, especially among older adults, who are more susceptible to adverse reactions. Findings about variation in antibiotic prescribing can target policy efforts to focused areas; however, little is known about these patterns among older adults.

      Methods

      Using Medicare Part D data from January 1, 2007, through December 31, 2009 (comprising 1.0-1.1 million patients per year), we examined geographic variation in antibiotic use among older adults in 306 Dartmouth Atlas of Health Care hospital referral regions, 50 states and the District of Columbia, and 4 national regions (South, West, Midwest, and Northeast). In addition, we examined the quarterly change in antibiotic use across the 4 regions. Differences in patient demographics, insurance status, and clinical characteristics were adjusted for across regions.

      Results

      Substantial geographic and quarterly variation in outpatient antibiotic prescribing existed across regions after adjusting for population characteristics. This variation could not be explained by differences in the prevalences of the underlying conditions. For example, the ratios of the 75th percentile to the 25th percentile of adjusted annual antibiotic spending were 1.31 across states and 1.32 across regions. The highest antibiotic use was in the South, where 21.4% of patients per quarter used an antibiotic, whereas the lowest antibiotic use was in the West, where 17.4% of patients per quarter used an antibiotic (P < .01). Regardless of region, the rate of antibiotic use was highest in the first quarter (20.9% in January through March) and was lowest in the third quarter (16.9% in July through September) (P < .01).

      Conclusions

      Areas with high rates of antibiotic use may benefit from targeted programs to reduce unnecessary prescription. Quality improvement programs can set attainable targets using the low-prescribing areas as a reference, particularly targeting older adults.
        Cover page: Geographic Variation in Outpatient Antibiotic Prescribing Among Older Adults
        • Thesis
        • Peer Reviewed
        UC Davis Electronic Theses and Dissertations (2024)

        Effective cover crop termination by roller crimping remains a challenge in organic no-till vegetable systems. In addition, slow decomposition of surface residues can delay planting and lead to competition for soil resources. Application of microbial inoculants to promote residue decomposition could potentially address these constraints. Two field studies were conducted in Davis, California to evaluate the effect of microbial tea treatments on the rate of cover crop surface residue decomposition, labile carbon and inorganic N pools, and sweet potato yield under different environmental conditions. To assess fall termination of a summer cover crop, four treatments were applied to sorghum sudangrass following roller crimping: thermophilic compost tea, vermicompost tea, a commercially available microbial inoculant (EM-1), and a roller crimped control. To assess spring termination of a winter cover crop, four treatments were applied to a multispecies cover crop mix (bell beans, peas, vetch, wheat) following roller crimping: vermicompost tea, EM-1, a roller crimped control, and a tilled treatment. Litter bags were used to measure residue decomposition and soil samples were obtained from 0-10 cm to determine inorganic N and POXC concentrations. In contrast to our hypothesis, we found no effect of the microbial tea treatments on the rate of residue decomposition in either study. Decomposition following roller crimping was much greater in the spring than the fall (41.6 vs 16.4%), likely due to the presence of legumes in the winter cover crop mix and higher soil surface moisture due to increased rainfall throughout the litter bag retrieval period in the spring. The microbial tea treatments had no effect on soil ammonium-N, nitrate-N, or POXC concentrations. However, soil ammonium-N and nitrate-N concentrations significantly increased by 39 and 51% in the tilled vs. roller crimped treatments, respectively (ammonium-N: 1.2 mg N kg-1 and 0.73 mg N kg-1; nitrate-N: 5.5 mg N kg-1 and 2.7 mg N kg-1). Meanwhile, POXC increased significantly over time in the fall termination study, but decreased over time in the spring termination study. There were no significant differences in sweet potato yield between the roller crimped treatments and the tilled treatment, indicating the presence of surface residues combined with the difference in soil N levels had no effect on sweet potato yield.

          • Thesis
          • Peer Reviewed
          UC Davis Electronic Theses and Dissertations (2024)

          Rice lands are important agroecosystems for providing food for over half the world's population while also mimicking wetland environments which support wildlife habitat and are known for carbon sequestration. At the same time, rice lands are facing a number of challenges related to climate change, increased herbicide resistance, labor shortages, and market shift. In response, diversification of rice systems of historically rice dominated landscapes is becoming more common. Crop rotations are being proposed as a practice for California’s rice sector to mitigate challenges related to herbicide resistance and water scarcity in the Sacramento Valley region. However, while crop rotations have been shown to support aerobic cropping systems with regards to weed control, soil health, and yields, switching between a flooded environment to an upland environment can be complex, and may compromise certain soil health related properties related to storing carbon and nitrogen. Furthermore, profitability of crop rotations with rice remains uncertain. Limited data exists on the benefits and tradeoffs of crop rotations with rice systems and their overall feasibility in the Sacramento Valley region. With the help of multiple collaborators, I assess the implications of crop rotations with rice systems by evaluating growers’ perceptions and experiences on barriers to adoption, compare long term profitability of crop rotations with rice compared to continuous rice, and evaluate differences in soil health and agronomic factors between these systems.

          In chapter one, I use semi structured interviews to gather a breadth of information from growers regarding the types of rotations that exist in California with rice, the benefits, and barriers to adoption growers’ experiences with rotations, and the requirements for rotations to be successful. Crop rotations ranged in complexity and incorporated many upland crops such as tomato, sunflower, beans, safflower, vine seed, cool season forages, and more. I learned that multiple factors limit growers’ ability to rotate including environmental limitations, lack of available contracts and markets for other crops, financial barriers, and limited experience and knowledge of other viable crops. Growers who rotated agreed that weed control and reduced reliance on herbicides were benefits of rotation, as well as soil health and economic benefits. In chapter two, I investigate the economics of crop rotations with rice systems by evaluating long-term profitability of crop rotations, one with tomato and sunflower, and one with safflower and beans, over a 15-year time frame, and show how rotational benefits and water scarcity events impact these outcomes. I used a Monte Carlo to randomly select variable costs based on data collected from growers and published work to account for economic uncertainty. I found that there is a high likelihood that crop rotations can be as or more profitable than continuous rice, under the assumptions of rotations providing increased rice yields and reduced herbicide inputs or under scenarios where fallowing becomes more common with continuous rice systems. However, there could be a substantial investment period for farmers depending on number of factors. In chapter three, I sample soil from 46 farmers’ fields to assess differences in soil health and agronomic indicators between rotated and continuous rice fields, under both organic and conventional management. Furthermore, I evaluate tradeoffs between systems using a multifunctionality lens to assess system performance and effects on broader ecosystem service categories. This study found that crop rotations had reduced organic carbon and nitrogen pools, as well as less weed abundance and increased yields and minor elements. Organic rotated systems showed less soil health differences and had no significant changes with weed abundance. Conventional rotated fields had higher agronomic efficiencies with lower environmental and regulating services, compared to continuous rice systems.

          Together this dissertation understands the role crop rotations can play for California rice sector, as well as the expected challenges and tradeoffs. Overall, this research confirms multiple benefits for crop rotations with rice systems and concludes that rotations should be considered as a tool for farmers to adapt to if challenges continue to persist. However, rotations are unlikely to become a common practice due to low feasibility. Outcomes of this research can be used for developing extension programing, supporting farmers decision making, and supporting policy goals.

          • 1 supplemental PDF
          Cover page: Sustainability Implications of Crop Rotations in California Rice Systems: Evaluating Agronomic, Economic, and Environmental Benefits and Tradeoffs
          • Article
          • Peer Reviewed
          UC Davis Previously Published Works (2017)
          To prevent nutrient limitations to crop growth, nitrogen is often applied in agricultural systems in the form of organic inputs (e.g., crop residues, manure, compost, etc.) or inorganic fertilizer. Inorganic nitrogen fertilizer has large environmental and economic costs, particularly for low-input smallholder farming systems. The concept of combining organic, inorganic, and biological nutrient sources through Integrated Nutrient Management (INM) is increasingly promoted as a means of improving nutrient use efficiency by matching soil nutrient availability with crop demand. While the majority of previous research on INM has focused on soil quality and yield, potential climate change impacts have rarely been assessed. In particular, it remains unclear whether INM increases or decreases soil nitrous oxide (N2O) emissions compared to organic nitrogen inputs, which may represent an overlooked environmental tradeoff. The objectives of this review were to (i) summarize the mechanisms influencingN2O emissions in response to organic and inorganic nitrogen (N) fertilizer sources, (ii) synthesize findings from the limited number of field experiments that have directly compared N2O emissions for organic N inputs vs. INM treatments, (iii) develop a hypothesis for conditions under which INM reduces N2O emissions and (iv) identify key knowledge gaps to address in future research. In general, INM treatments having low carbon to nitrogen ratio C:N (<8) tended to reduce emissions compared to organic amendments alone, while INM treatments with higher C:N resulted in no change or increased N2O emissions.
            • Article
            • Peer Reviewed
            Cliodynamics, Volume 9, Issue 2 (2018)
            The Extended Evolutionary Synthesis (EES) is beginning to fulfill the whole promise of Darwinian insight through its extension of evolutionary understanding from the biological domain to include cultural information evolution. This constitutes the origins of an evolutionary study of culture change free of the social-darwinism and ecologically-deterministic baggage that characterized earlier such approaches.
              Cover page: The Extended Evolutionary Synthesis Facilitates Evolutionary Models of Culture ChangeCreative Commons 'BY' version 4.0 license
              • Article
              • Peer Reviewed
              UC San Francisco Previously Published Works (2014)
              Patients harboring brain arteriovenous malformation (bAVM) are at life-threatening risk of rupture and intracranial hemorrhage (ICH). The pathogenesis of bAVM has not been completely understood. Current treatment options are invasive, and ≈ 20 % of patients are not offered interventional therapy because of excessive treatment risk. There are no specific medical therapies to treat bAVMs. The lack of validated animal models has been an obstacle for testing hypotheses of bAVM pathogenesis and testing new therapies. In this review, we summarize bAVM model development and bAVM pathogenesis and potential therapeutic targets that have been identified during model development.
                Cover page: Brain Arteriovenous Malformation Modeling, Pathogenesis, and Novel Therapeutic Targets
                • Article
                • Peer Reviewed
                UC Davis Previously Published Works (2020)
                To address the global challenge of increasing the efficiency of food production in an era of climate change, integrated research frameworks based on multiple performance criteria are required to promote synergies while minimizing tradeoffs. In this study, we investigated spatial and temporal trends in yield gaps, resource use efficiencies for nitrogen and water, and yield stability at the county-level in the U.S. Corn Belt, the world's largest maize production region. Our results provide an integrated assessment of regions with higher vs. lower relative performance across indicators, while also revealing high spatial variability in relationships between yield gaps and nitrogen and water use efficiencies. Despite overall positive trends in maize production, there was evidence of increasing disparity over time, with more improvements occurring in highly productive areas. This study provides a holistic framework for balancing efforts to increase crop production, resource use efficiencies, and yield stability at the regional scale.
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