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Jason Hill

Publications and source records attributed to Jason Hill.

7 recordsLinked to original sources
PubMed2006

Carbon-negative biofuels from low-input high-diversity grassland biomass.

Biofuels derived from low-input high-diversity (LIHD) mixtures of native grassland perennials can provide more usable energy, greater greenhouse gas reductions, and less agrichemical pollution per hectare than can corn grain ethanol or soybean biodiesel. High-diversity grasslands had increasingly higher bioenergy yields that were 238% greater than monoculture yields after a decade. LIHD biofuels are carbon negative because net ecosystem carbon dioxide sequestration (4.4 megagram hectare(-1) year(-1) of carbon dioxide in soil and roots) exceeds fossil carbon dioxide release during biofuel production (0.32 megagram hectare(-1) year(-1)). Moreover, LIHD biofuels can be produced on agriculturally degraded lands and thus need to neither displace food production nor cause loss of biodiversity via habitat destruction.

Agriculture↗
PubMed2006

Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels.

Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We use these criteria to evaluate, through life-cycle accounting, ethanol from corn grain and biodiesel from soybeans. Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more efficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides sufficient environmental advantages to merit subsidy. Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels.

Agriculture↗
PubMed2006

A model of acquired autoresistance to a potent ErbB2 tyrosine kinase inhibitor and a therapeutic strategy to prevent its onset in breast cancer.

The development of acquired resistance to ErbB2 tyrosine kinase inhibitors limits the clinical efficacy of this class of cancer therapeutics. Little is known about the mechanism(s) of acquired resistance to these agents. Here we establish a model of acquired resistance to N-{3-chloro-4-[(3-fluorobenzyl) oxy]phenyl}-6-[5-({[2 (methylsulfonyl)ethyl]amino}methyl)-2-furyl]-4-quinazolinamine (lapatinib), an inhibitor of ErbB2 and ErbB1 tyrosine kinases by chronically exposing lapatinib-sensitive ErbB2-overexpressing breast cancer cells to lapatinib, simulating the clinic where lapatinib is administered on a daily chronic basis. Analysis of baseline gene expression in acquired lapatinib-resistant and parental cells indicates estrogen receptor (ER) signaling involvement in the development of resistance. Using gene interference, we confirm that acquired resistance to lapatinib is mediated by a switch in cell survival dependence and regulation of a key antiapoptotic mediator from ErbB2 alone to codependence upon ER and ErbB2 rather than loss of ErbB2 expression or insensitivity of ErbB2 signaling to lapatinib. Increased ER signaling in response to lapatinib is enhanced by the activation of factors facilitating the transcriptional activity of ER, notably FOXO3a and caveolin-1. Importantly, we confirm that lapatinib induces ER signaling in tumor biopsies from patients with ErbB2-overexpressing breast cancers receiving lapatinib therapy. These findings provided the rationale for preventing the development of acquired resistance by simultaneously inhibiting both ER and ErbB2 signaling pathways. Establishing clinically relevant models of acquired resistance to ErbB2 kinase inhibitors will enhance therapeutic strategies to improve clinical outcomes for patients with ErbB2-overexpressing breast cancers.

Antineoplastic Agents↗
PubMed2005

Genetic diversity and population structure of teosinte.

The teosintes, the closest wild relatives of maize, are important resources for the study of maize genetics and evolution and for plant breeding. We genotyped 237 individual teosinte plants for 93 microsatellites. Phylogenetic relationships among species and subspecific taxa were largely consistent with prior analyses for other types of molecular markers. Plants of all species formed monophyletic clades, although relationships among species were not fully resolved. Phylogenetic analysis indicated that the Mexican annual teosintes divide into two clusters that largely correspond to the previously defined subspecies, Z. mays ssp. parviglumis and ssp. mexicana, although there are a few samples that represent either evolutionary intermediates or hybrids between these two subspecies. The Mexican annual teosintes show genetic substructuring along geographic lines. Hybridization or introgression between some teosintes and maize occurs at a low level and appears most common with Z. mays ssp. mexicana. Phylogeographic and phylogenetic analyses of the Mexican annual teosintes indicated that ssp. parviglumis diversified in the eastern part of its distribution and spread from east to west and that ssp. mexicana diversified in the Central Plateau of Mexico and spread along multiple paths to the north and east. We defined core sets of collections of Z. mays ssp. mexicana and ssp. parviglumis that attempt to capture the maximum number of microsatellite alleles for given sample sizes.

Alleles↗
PubMed2005

Sensitization of DNA damage-induced apoptosis by the proteasome inhibitor PS-341 is p53 dependent and involves target proteins 14-3-3sigma and survivin.

Proteasome inhibition following DNA damage results in the synergistic induction of apoptosis via a nuclear factor-kappaB-independent mechanism. In this study, we identify the role of p53 in mediating apoptosis by the sequence-specific treatment involving the DNA-damaging, topoisomerase I-targeting drug SN-38 followed by the proteasome inhibitor PS-341 (SN-38-->PS-341). The p53-dependent sensitization of DNA damage-induced apoptosis by PS-341 is accompanied by persistent inhibition of proteasome activity and increased cytosolic accumulation of p53, including higher molecular weight forms likely representing ubiquitinated species. In contrast, pretreatment with PS-341 followed by treatment with SN-38 (PS-341-->SN-38), which leads to an antagonistic interaction, results in transient inhibition of proteasome activity and accumulation of significantly lower levels of p53 localized primarily to the nucleus. Whereas cells treated with PS-341-->SN-38 undergo G2 + M cell cycle arrest, cells treated with SN-38-->PS-341 exhibit a decreased G2 + M block with a concomitant increase in the sub-G1 population. Decreased accumulation of cells in the G2 + M phase of the cell cycle in SN-38-->PS-341-treated cells compared with PS-341-->SN-38-treated cells correlates with enhanced apoptosis and reduced expression of two p53-modulated proteins, 14-3-3sigma and survivin, both of which play critical roles in regulating G2 + M progression and apoptosis. The functional role of 14-3-3sigma or survivin in regulating the divergent function of p53 in response to SN-38-->PS-341 and PS-341-->SN-38 treatment in inducing apoptosis versus G2 + M arrest/DNA repair, respectively, was confirmed by targeted down-regulation of these proteins. These results provide insights into the mechanisms by which inhibition of proteasome activity modulates DNA damage-induced apoptosis via a p53-dependent pathway.

14-3-3 Proteins↗
PubMed2003

Array synthesis of novel lipodepsipeptide.

Synthetic array technology was utilized to rapidly synthesize and analyze a diverse set of reductive alkylation analogues of daptomycin. Analysis of the array suggested the use of polar functionality such as sulfonamides or amide or polar spaces such as piperazine would beneficially affect activity.

Alkylation↗