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Waramit N.,Iowa State University | Moore K.J.,Iowa State University | Heggenstaller A.H.,Midwest Research Institute
Agronomy Journal | Year: 2011

Information about the interaction of harvesting and N fertilization on composition of warm-season grasses grown as biofuel feedstocks is limited. Our objective was to determine composition of warm-season grasses as influenced by N fertilization rates and harvest dates. A field study was conducted near Ames, IA, during 2006 and 2007. The experimental design was a split-split plot arranged in a randomized complete block with four replications. Big bluestem (Andropogon gerardii Vitman), eastern gamagrass (Tripsacum dactyloides L.), indiangrass (Sorghastrum nutrans L. Nash), and switchgrass (Panicum virgatum L.) were main plots. Three N application rates (0, 65, and 140 kg ha-1) were subplots, and 10 harvest dates were sub-subplots. In both years, delaying harvest increased cellulose, lignin, and C concentrations, but decreased ash and N concentrations, however, the magnitude of these effects varied among species. On average, big bluestem had the highest cellulose (430.5 g kg-1) and C concentration (450.5 g kg-1) while switchgrass had the highest lignin concentration (58.5 g kg-1) among four species. Big bluestem had the lowest ash concentration (47.5 g kg-1) whereas indiangrass had the lowest N concentration (5.5 g kg-1). With increasing rates of N, average N, C, cellulose, and lignin concentrations increased 19 to 29%, 0.6 to 2.2%, 0.7 to 5.7%, and 5.6 to 23.9%, respectively, whereas ash concentration declined 1.8 to 18.4%, varied among species. Our results indicated that in general, warm-season grasses supplied with N fertilizer at 140 kg ha-1 and harvest delayed until fall have the optimal composition for biomass feedstock production. © 2011 by the American Society of Agronomy. Source

Ahlers J.D.,U.S. National Institutes of Health | Belyakov I.M.,Midwest Research Institute
Trends in Immunology | Year: 2010

CD8+ cytotoxic T lymphocyte (CTL) responses are crucial in establishing the control of persistent virus infections. Population studies of HIV-1-infected individuals suggest that CD8+ CTL responses targeting epitopes that take the greatest toll on virus replication are instrumental in immune control. A major question for vaccine design is whether incorporating epitopes responsible for controlling a persistent virus will translate into protection from natural infection or serve solely as a fail-safe mechanism to prevent overt disease in infected individuals. Here, we discuss qualitative parameters of the CD8+ CTL response and mechanisms operative in the control of persistent virus infections and suggest new strategies for design and delivery of HIV vaccines. Source

Mulholland N.,U.S. National Institutes of Health | Mulholland N.,Midwest Research Institute | Xu Y.,Kyoto University | Sugiyama H.,Kyoto University | Zhao K.,U.S. National Institutes of Health
Cell and Bioscience | Year: 2012

Background: Z-DNA is a higher-energy, left-handed form of the double helix. A primary function of Z-DNA formation is to facilitate transcriptional initiation and activation. Sequences favoring Z-DNA formation are frequently located in promoter regions and Z-DNA is stabilized by torsional strain resulting from negative supercoiling, such as that generated by an actively transcribing polymerase or by a nucleosome remodeling event. We previously have shown that activation of the CSF1 gene by a chromatin remodeling event in the promoter results in Z-DNA formation at TG repeats within the promoter.Results: We show that remodeling of a mononucleosome by the human SWI/SNF complex results in Z-DNA formation when the DNA within the mononucleosome contains Z-DNA favoring sequence. Nuclease accessibility patterns of nucleosome core particle consisting of Z-DNA are quite different from counterpart nucleosomes containing classic B-DNA. Z-nucleosomes represent a novel mononucleosome structure.Conclusions: We present evidence that Z-DNA can form on nucleosomes though previous observations indicate the occlusion of nucleosome formation from Z-DNA. © 2012 Mulholland et al; licensee BioMed Central Ltd. Source

Belyakov I.M.,Midwest Research Institute | Ahlers J.D.,National Institute of Allergy and Infectious Diseases
Current Topics in Microbiology and Immunology | Year: 2012

Natural transmission of human immunodeficiency virus type 1 (HIV-1) occurs through gastrointestinal and vaginal mucosa. These mucosal tissues are major reservoirs for initial HIV replication and amplification, and the sites of rapid CD4 + T cell depletion. In both HIV-infected humans and SIV-infected macaques, massive loss of CD4 + CCR5 + memory T cells occurs in the gut and vaginal mucosa within the first 10-14 days of infection. Induction of local HIV-specific immune responses by vaccines may facilitate effective control of HIV or SIV replication at these sites. Vaccines that induce mucosal responses, in particular CD8 + cytotoxic T lymphocytes (CTL), have controlled viral replication at mucosal sites and curtailed systemic dissemination. Thus, there is strong justification for development of next generation vaccines that induce mucosal immune effectors against HIV-1 including CD8 + CTL, CD4 + T helper cells and secretory IgA. In addition, further understanding of local innate mechanisms that impact early viral replication will greatly inform future vaccine development. In this review, we examine the current knowledge concerning mucosal AIDS vaccine development. Moreover, we propose immunization strategies that may be able to elicit an effective immune response that can protect against AIDS as well as other mucosal infections. © 2011 Springer-Verlag Berlin Heidelberg. Source

Ahlers J.D.,National Institute of Allergy and Infectious Diseases | Belyakov I.M.,Midwest Research Institute
Blood | Year: 2010

For acute self-limiting infections a vaccine is successful if it elicits memory at least as good as the natural experience; however, for persistent and chronic infections such as HIV, hepatitis C virus (HCV), human papillomavirus (HPV), and human herpes viruses, this paradigm is not applicable. At best, during persistent virus infection the person must be able to maintain the integrity of the immune system in equilibrium with controlling replicating virus. New vaccine strategies are required that elicit both potent high-avidity CD8+ T-cell effector/memory and central memory responses that can clear the nidus of initial virus-infected cells at mucosal surfaces to prevent mucosal transmission or significantly curtail development of disease. The objective of an HIV-1 T-cell vaccine is to generate functional CD8+ effector memory cells at mucosal portals of virus entry to prevent viral transmission. In addition, long-lived CD8+ and CD4+ central memory cells circulating through secondary lymphoid organs and resident in bone marrow, respectively, are needed to provide a concerted second wave of defense that can contain virus at mucosal surfaces and prevent systemic dissemination. Further understanding of factors which can influence long-lived effector and central memory cell differentiation will significantly contribute to development of effective T-cell vaccines. In this review we will focus on discussing mechanisms involved in T-cell memory and provide promising new approaches toward expanding current vaccine strategies to enhance antiviral memory. Source

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