Uncertainty in estimating land use and management impacts on soil organic carbon storage for US agricultural lands between 1982 and 1997

Uncertainty was quantified for an inventory estimating change in soil organic carbon (SOC) storage resulting from modifications in land use and management across US agricultural lands between 1982 and 1997. This inventory was conducted using a modified version of a carbon (C) accounting method developed by the Intergovernmental Panel on Climate Change (IPCC). Probability density functions (PDFs) were derived for each input to the IPCC model, including reference SOC stocks, land use/management activity data, and management factors. Change in C storage was estimated using a Monte‐Carlo approach with 50 000 iterations, by randomly selecting values from the PDFs after accounting for dependencies in the model inputs. Over the inventory period, mineral soils had a net gain of 10.8 Tg C yr^?1, with a 95% confidence interval ranging from 6.5 to 15.3 Tg C yr^?1. Most of this gain was due to setting‐aside lands in the Conservation Reserve Program. In contrast, managed organic soils lost 9.4 Tg C yr^?1, with a 95% confidence interval ranging from 6.4 to 13.3 Tg C yr^?1. Combining these gains and losses in SOC, US agricultural soils accrued 1.3 Tg C yr^?1 due to land use and management change, with a 95% confidence interval ranging from a loss of 4.4 Tg C yr^?1 to a gain of 6.9 Tg C yr^?1. Most of the uncertainty was attributed to management factors for tillage, land use change between cultivated and uncultivated conditions, and C loss rates from managed organic soils. Based on the uncertainty, we are not able to conclude with 95% confidence that change in US agricultural land use and management between 1982 and 1997 created a net C sink for atmospheric CO₂.     

Comparison of cyclopropene, 1-methylcyclopropene, and 3,3-dimethylcyclopropene as ethylene antagonists in plants

A comparison has been made of cyclopropene (CP), 1-methylcyclopropene (1-MCP), and 3,3-dimethyl-cyclopropene (3,3-DMCP) in their ability to protect plants against ethylene. In bananas, both CP and 1-MCP are effective around 0.5 nL L^–1, and 3,3-DMCP was effective at 1 L L^–1. Bananas treated with CP and 1-MCP again become sensitive to ethylene at 12 days and those treated with 3,3-DMCP at 7 days. Mature green tomatoes are protected by 5–7 nL L^–1 of 1-MPC for 8 days at 25°C and tomatoes treated with 3,3-DMCP at 5–10 L L^–1 are protected for 5 days. Carnation flowers are protected with CP or 1-MCP after exposure to 0.5 nL L^–1 for 24 hours and by 1 L L^–1 of 3,3-DMCP. The display life of Campanula flowers is increased from 3.3 to 5.4 days by 10 L L^–1 of 3,3-DMCP and to 9 days by 20 nL L^–1 of 1-MCP. Ethylene inhibition of pea seedlings is reduced by treatment with 1-MCP at 10 L L^–1 of ethylene but as ethylene is increased to 3000 L L^–1 growth inhibition increases. 3,3-DMCP treatment causes very little reduction of the ethylene effect even at very low concentrations.     

Subcellular Localization of a UDP-Glucose:Aldehyde Cyanohydrin beta-Glucosyl Transferase in Epidermal Plastids of Sorghum Leaf Blades

Epidermal and mesophyll protoplasts, prepared from leaf blades of 6-day-old light-grown Sorghum bicolor seedlings were separated by differential sedimentation and assayed for a number of enzymes. The epidermal protoplasts contained higher levels of NADPH-cytochrome c reductase (EC 1.6.2.4), triose phosphate isomerase (EC 5.3.1.1), phosphoenolpyruvate carboxylase (EC 4.1.1.31), and a UDP-glucose:cyanohydrin β-glucosyl transferase (EC 2.4.1.85), but lower levels of NADP⁺ triosephosphate dehydrogenase (EC 1.2.1.13) than did mesophyll protoplasts. When protoplast preparations were lysed and applied to linear sucrose density gradients, triosephosphate isomerase was found to be present in epidermal plastids. A significant fraction (41%) of the glucosyl transferase activity was also associated with the epidermal plastids.     

Binding of the 2F5 monoclonal antibody to native and fusion-intermediate forms of human immunodeficiency virus type 1 gp41: implications for fusion-inducing conformational changes

We investigated how the broadly neutralizing monoclonal antibody 2F5 affects the human immunodeficiency virus type 1 envelope glycoprotein as it undergoes receptor-induced conformational changes and show that 2F5 binds both native and fusion-intermediate conformations, suggesting inhibition of a late step in virus entry. We also demonstrate conformational changes in the C heptad of gp41.     

Redox control of changes in protein sulfhydryl levels during human sperm capacitation

Capacitation, the series of transformations that spermatozoa undergo to become fertile, is regulated by reactive oxygen species (ROS) and associated with an increase in the sulfhydryl content of Triton-soluble proteins. Our aims were to determine the fate of sulfhydryl groups in Triton-soluble proteins from capacitating human spermatozoa using two-dimensional (2D) gel electrophoresis, to evaluate the role of ROS in the changes observed, and to correlate the time course of the changes with that of the sperm generation of O(2)(*)(-). Triton-soluble proteins of control and capacitating human spermatozoa were labeled with 3-(N-maleimidylpropionyl) biocytin, separated by 2D gel electrophoresis, and probed with horseradish peroxidase-conjugated streptavidin. The sulfhydryl content of 10 out of the 14 proteins studied (pI: 4-7) was modified by the induction of capacitation, and the increases (by 200-400%, five proteins) and decreases (by 45-95%, five proteins) were prevented by superoxide dismutase and/or catalase. The alterations in protein sulfhydryl content occurred within 5-15 min but were reversed within 30-120 min. Three capacitation inducers triggered similar modifications. Therefore, human sperm capacitation is associated with rapid and reversible changes in protein sulfhydryl groups that appear to be redox regulated. The number of proteins affected, the types, and the kinetics of changes emphasize the complexity of sperm capacitation.