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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2013)

The terrestrial biosphere is responsible for removing roughly one quarter of the total anthropogenic emissions of carbon dioxide from the atmosphere.

This process is dominated by the forests. The terrestrial portion of the global carbon cycle is also the most uncertain. Growing forests are a major sink of CO2 while deforestation contributes as a major source of CO2. While the locations of deforestation can be tracked with remote sensing data relatively well, the amount of carbon removed is not well known due to the lack of knowledge on the biomass density of the forests that were disturbed. Spatially explicit distribution of carbon stocks in global forests can greatly reduce this uncertainty by improving estimates of emissions from land use activities. It will also help with green house gas inventory at regional and national scales.

Increasing amounts of remote sensing based forest studies are being conducted, however, there is currently no global spatially explicit map of forest biomass/carbon. This dissertation aims to address that by producing the first global spatially explicit map of live biomass and carbon stock in forests and other living woody vegetation at ~1 km resolution for circa year 2005. A combination of remote sensing data from the Quick Scatterometer (QuikSCAT), Moderate Resolution Imaging Spectroradiometer (MODIS), and Shuttle Radar Topography Mission (SRTM) are used to provide wall-to-wall spatial information. Ground inventory and LiDAR from the Geosciences Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) are used to create a global network of aboveground biomass (AGB) samples. Landcover map based on the GlobCover product from the European Space Agency (ESA) is used as ancillary data. These are combined in a statistical model using Maximum Entropy to create the first global map of AGB and total carbon stock (above + below ground) in living biomass. Uncertainty at the pixel level is also produced alongside the above products. The total global carbon in live woody vegetation is estimated at 337 PgC, with 311.4 PgC being in the forests (92% of total) for circa year 2005, compared with 302.8 PgC in total global live forest biomass as reported in the United Nations Food and Agriculture Organization's 2010 Forest Resources Assessment report (FRA 2010). Shrublands and savannas account for the other 25.6 PgC (8% of total) globally. National carbon stocks are calculated and reported for all the countries using several different thresholds for forest cover.

    Cover page: Global Distribution of Carbon Stock in Live Woody Vegetation
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2020)
    BACKGROUND: Recipients of kidneys from living donors who subsequently develop end-stage renal disease (ESRD) also have higher graft failure, suggesting the 2 donor kidneys share risk factors that could inform recipient outcomes. Given that donor ESRD is rare, an earlier and more common postdonation outcome could serve as a surrogate to individualize counseling and management for recipients. Hypertension is a frequent event before donor ESRD; thus, early postdonation hypertension might indicate higher risk of graft failure. METHODS: We studied Scientific Registry of Transplant Recipients data to quantify the association between early postdonation hypertension and recipient graft failure using propensity score-weighted Cox proportional hazards regression. We also examined the association between postdonation systolic blood pressure and graft failure. RESULTS: Of 37 901 recipients, 2.4% had a donor who developed hypertension within 2 years postdonation. Controlling for donor and recipient characteristics, recipients whose donors developed hypertension had no higher risk for graft failure (adjusted hazard ratio [aHR] 1.03, 95% confidence interval [CI] 0.85-1.25, P = 0.72). This was consistent among subgroups of recipients at higher risk for adverse outcomes due to hyperfiltration: African American recipients (aHR 1.10, 95% CI 0.70-1.73, P = 0.68) and those with ESRD caused by hypertension (aHR 1.10, 95% CI 0.65-1.85, P = 0.73) or diabetes (aHR 0.80, 95% CI 0.56-1.13, P = 0.20). However, graft failure was associated with postdonation systolic blood pressure (per 10 mm Hg, aHR 1.05, 95% CI 1.03-1.08, P < 0.001). CONCLUSIONS: Although postdonation systolic blood pressure is associated with graft failure, the reported diagnosis of hypertension as determined by the requirement for blood pressure treatment early postdonation did not portend a higher risk of recipient graft failure in the same way as eventual postdonation ESRD.
      Cover page: Association Between Living Kidney Donor Postdonation Hypertension and Recipient Graft Failure.
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2020)
      The first sustained increase in live kidney donation in the United States in 15 years was observed from 2017 to 2019. To help sustain this surge, we studied 35 900 donors (70.3% white, 14.5% Hispanic, 9.3% black, 4.4% Asian) to understand the increase in 2017-2019 vs 2014-2016 using Poisson regression. Among biologically related donors aged <35, 35-49, and ≥50 years, the number of donors did not change across race/ethnicity but increased by 38% and 29% for Hispanic and black ≥50. Among unrelated donors <35, 35-49, and ≥50, white donors increased by 18%, 14%, and 27%; Hispanic donors <35 did not change but increased by 22% and 35% for 35-49 and ≥50; black donors <35 declined by 23% and did not change for 35-49 and ≥50; Asian donors did not change. Among kidney paired donors <35, 35-49, and ≥50, white donors increased by 42%, 50%, and 68%; Hispanic donors <35 and 35-49 increased by 36% and 55% and did not change for ≥50; black donors did not change; Asian donors <35 did not change but increased by 107% and 82% for 35-49 and ≥50. The increase in donation was driven predominantly by unrelated and paired white donors. Donation among unrelated black individuals should be promoted.
        Cover page: The first increase in live kidney donation in the United States in 15 years.
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2022)

        Aims

        Cabotegravir delivered as a long-acting intramuscular injection has shown superior efficacy to oral tenofovir-emtricitabine as pre-exposure prophylaxis (PrEP) for HIV. Cabotegravir pharmacokinetics (PK), like those of other long-acting depot preparations, exhibit variability between individuals and between injection occasions. The aim of this study is to describe the population pharmacokinetics of long-acting cabotegravir (CAB-LA).

        Methods

        Using available PK measurements from 133 participants in the HIV Prevention Trials Network (HPTN) 077 trial, we analysed CAB-LA PK data using nonlinear mixed-effects modelling to develop a population PK model.

        Results

        A two-compartment model with first order absorption best described the CAB-LA PK. The analysis identified between-occasion variability (BOV, i.e., differences in PK within one individual from one injection to the next) as a significant covariate affecting the absorption rate, with an estimated contribution of BOV to PK variability on the absorption rate (ka ) of 38.5%. Sex and body weight were identified as significant covariates influencing the absorption rate and apparent clearance of CAB-LA after intramuscular injection at various doses and frequencies. Male participants had 67% higher ka than female participants. Serially adding to the model body weight on clearance, sex on ka , and BOV on ka led to a decrease in the objective function value (OFV) of 24.4, 36 and 321.4, respectively.

        Conclusion

        The public availability of this model will facilitate and enable a wide variety of future clinically relevant simulations to inform the optimal use of CAB-LA.
          Cover page: A population pharmacokinetic model based on HPTN 077 of long‐acting injectable cabotegravir for HIV PrEP
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2020)
          Simple (Bosniak I) renal cysts are considered acceptable in living kidney donor selection in terms of cancer risk. However, they tend to increase in number and size over time and might compromise renal function in donors. To clarify their implications for long-term renal function, we characterized the prevalence of renal cysts in 454 individuals who donated at our center from 2000 to 2007. We estimated the association between the presence of cysts in the kidney remaining after nephrectomy (ie, retained cysts) and postdonation eGFR trajectory using mixed-effects linear regression. Donors with retained cysts (N = 86) were older (P < .001) and had slightly lower predonation eGFR (median 94 vs 98 mL/min/1.73 m2 , P < .01) than those without cysts. Over a median 7.8 years, donors with retained cysts had lower baseline eGFR (-8.7 -5.6 -2.3  mL/min/1.73 m2 , P < .01) but similar yearly change in eGFR (-0.4 0.02 0.4  mL/min/1.73 m2 , P = .2) compared to those without retained cysts. Adjusting for predonation characteristics, there was no difference in baseline eGFR (P = .6) or yearly change in eGFR (P > .9). There continued to be no evidence of an association when we considered retained cyst(s) ≥10 mm or multiple retained cysts (all P > .05). These findings reaffirm current practices of accepting candidates with simple renal cysts for donor nephrectomy.
            Cover page: Long-term renal function in living kidney donors with simple renal cysts: A retrospective cohort study.
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2021)
            Osteoarthritis (OA) impacts hundreds of millions of people worldwide, with those affected incurring significant physical and financial burdens. Injuries such as focal defects to the articular surface are a major contributing risk factor for the development of OA. Current cartilage repair strategies are moderately effective at reducing pain but often replace damaged tissue with biomechanically inferior fibrocartilage. Here we describe the development, transcriptomic ontogenetic characterization and quality assessment at the single cell level, as well as the scaled manufacturing of an allogeneic human pluripotent stem cell-derived articular chondrocyte formulation that exhibits long-term functional repair of porcine articular cartilage. These results define a new potential clinical paradigm for articular cartilage repair and mitigation of the associated risk of OA.
              Cover page: Long-term repair of porcine articular cartilage using cryopreservable, clinically compatible human embryonic stem cell-derived chondrocytes
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