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  • 1
    Electronic Resource
    Electronic Resource
    Inoculation and Nitrogen Affect Herbage and Symbiotic Properties of Annual Medicago Species (1998)
    Springer
    Semigroup forum 90 (1998), S. 781-786 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Sinorhizobium inoculants and soil N status should affect the N contribution of annual medics (Medicago spp.) in cropping systems. We determined the effect of N and commercial medic inoculum on nodulation, dry matter, and N yield of annual medics and also determined Sinorhizobium strain occupancy in annual medic nodules. Field experiments were conducted on a sandy, mixed Udorthentic Haploboroll and on a fine-loamy, mixed, mesic Typic Hapludalf. More than 75% of annual medic plants (except M. rugosa Desr.) were nodulated in the absence of commercial inoculum, and nodulation was due in part to a Sinorhizobium strain that frequently nodulates alfalfa (Medicago sativa L.). Among the five strains in the commercial medic inoculum, 102G3 and 102A13 had the greatest nodule occupancy. When no N was applied, inoculation improved the percentage of plants nodulated and nodule mass only in M. rugosa, compared with no inoculation, but inoculation increased herbage yields of spring-seeded M. truncatula Gaertn. Cv. Sephi, M. polymorpha L., and M. rugosa by about 60%, compared with no inoculation. Nitrogen addition reduced the nodule mass of all species when inoculum was applied, and N addition increased only the herbage dry matter yield of spring-seeded M. scutellata (L.) Mill. When inoculum was applied. This suggests that a more effective inoculum could be developed for M. scutellata so that N would not limit herbage growth. Annual medics fixed from 40 to 80 kg N ha-1 if spring-seeded and grown for 60 d, and from 20 to 50 kg N ha-1 if summer-seeded and grown for 43 d.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanism and Kinetics of Transcellular Transport of a New β-Lactam Antibiotic Loracarbef Across an Intestinal Epithelial Membrane Model System (Caco-2) (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1405-1413 
    Details
    ISSN: 1573-904X
    Keywords: transcellular transport ; apical uptake ; basolateral efflux ; oral β-lactam ; carbacephem ; loracarbef ; peptide carrier ; H+ gradient ; cellular pharmacokinetics ; transport model ; Caco-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Various processes involved in the transcellular transport (TT) of loracarbef (LOR) were studied in the Caco-2 cell monolayer, a cell culture model of the small intestinal epithelium. The results provide support for presence of two AP to BL peptide TT pathways in the intestinal epithelial cell monolayer (Caco-2). The H+ gradient-dependent pathway (Km = 0.789 mM, and Jmax = 163 pmol/min per cm2) is relatively “high affinity” and “low capacity” compared to H+ gradient-independent pathway (Km = 8.28 mM, and Jmax = 316 pmol/min per cm2). In addition, TT of LOR in the presence of a H+ gradient was inhibited 77% to 88% (p 〈 0.05) by 10 mM of cephalexin, enalapril, Gly-Pro and Phe-Pro, while TT of LOR in the absence of a H+ gradient was only inhibited 42% to 48% (p 〈 0.05) by 10 mM of Gly-Pro and Phe-Pro. Since AP uptake is H+ gradient-dependent and saturable while the BL efflux is mostly nonsaturable and not driven by a H+ gradient, these two transmembrane transport processes must be different, which could be the result of two different peptide carriers. In vivo, these two transport processes must have worked in concert to produce transcellular flux of loracarbef. To explain the differences between kinetic characteristics of AP uptake and TT transport, a cellular pharmacokinetic (PK) model was developed and the results indicate that the PK model appropriately described the kinetics of LOR TT. The use of this PK model may provide an additional advantage to the use of the cell culture model because kinetic parameters at both sides of the intestinal epithelial membrane may be obtained using the same preparation. Taken together, the Caco-2 model system represents an excellent model system for the study of carrier-mediated processes involved in the TT of peptides and peptide-like drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018935704693
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanisms of Transport of Quinapril in Caco-2 Cell Monolayers: Comparison with Cephalexin (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1120-1125 
    Details
    ISSN: 1573-904X
    Keywords: oral β-lactam antibiotic ; cephalexin ; ACE inhibitor ; quinapril ; peptide carrier system ; proton-gradient ; intestinal absorption ; Caco-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine the transport mechanisms of quinapril and cephalexin in Caco-2 cell monolayers, a cell culture model of the human small intestinal epithelium. Methods. Uptake, transepithelial transport and intracellular accumulations of these two drugs were measured using Caco-2 cell monolayers grown onto Millicells™ and magnetically stirred diffusion chambers. Results. Transepithelial transport, apical (AP) uptake and intracellular accumulation of both drugs depended on the maintenance of a transepithelial proton gradient and temperature of the medium. However, quinapril transport and accumulation, which did not display a maximum at approximately pH 6, was more sensitive to proton gradient change, whereas cephalexin transport was more sensitive to concentration change (range 0.5-5 mM). In addition, quinapril (1 mM) transport was decreased significantly (p〈0.05) by 10 mM cephalexin, loracarbef, Gly-Pro and Phe-Pro, but not by enalapril; whereas cephalexin (0.1 mM) transport was decreased significantly (p〈0.05) by all four compounds. Similarly, AP quinapril (1 mM) uptake was also decreased by 10 mM loracarbef, Gly-Pro, cephalexin, and enalapril, but these inhibitory effects (20-50%) were quantitatively less than their inhibitory effects on cephalexin uptake (50-90%). Finally, the AP uptake of quinapril was also significantly (p〈0.05) inhibited by FCCP (10 µg/ml), amiloride (0.5 mM), DEP (0.5 mM), and staurosporine (5 nM). Conclusions. The transport of quinapril in the Caco-2 cells is via a combination of the carrier-mediated proton gradient-dependent peptide transporter and passive diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016247523311
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  • 4
    Electronic Resource
    Electronic Resource
    Dry Matter Accumulation and Dinitrogen Fixation of Annual Medicago Species (1998)
    Springer
    Agronomy journal 90 (1998), S. 103-108 
    Details
    ISSN: 1435-0645
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 2 fixation potential of annual medics (Medicago spp.) in the upper Midwest is important for predicting the net N contribution to cropping systems. Our objectives were to determine the dry matter (DM) accumulation pattern of herbage, roots, and modules of several annual medic species used as summer annuals and to measure the percentage and amount of N derived from N2 fixation by annual medics using isotope dilution and difference methods. Experiments were conducted on a Hubbard loamy sand (Udorthentic Haploboroll) at Becker, MN, and a Tallula silt loam (Typic Hapludoll) at Rosemount, MN. The experimental design at both locations was a randomized complete block with six replicates. Medicago truncatula Gaertn., M. polymorpha L., M. scutellata (L.) Mill., and M. rugosa Desr. were inoculated with commercial rhizobial inoculant and were seeded in late May. Herbage, root, and nodule DM of N2–fixing annual medics continued to increase until about 72 d after planting (DAP). The highest maximum herbage, root, and nodule DM yields were 10 669, 648, and 169 kg ha-1, respectively, from M. polymorpha in 1993. Based on the estimate from the isotope dilution (ID) method, herbage of annual medics at maximum DM accumulation contained 86% N derived from atmosphere (%Ndfa), using ryegrass (Lolium multiflorum Lam.) as a reference crop, or 79% Ndfa, using noninoculated M. rugosa as a reference crop. The amount of Ndfa in annual medic herbage ranged from 100 to 200 kg ha-1 based on estimates using either the ID method or the difference method (D-method), with M. polymorpha producing the highest and M. rugosa producing the lowest amount. Estimates of Ndfa from the ID and D-methods were strongly correlated. We conclude that annual medics have the potential to contribute a significant amount of N to cropping systems when seeded in the spring and harvested or incorporated into the soil 2 to 3 mo. later.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of the Transport Characteristics of D- and L-Methionine in a Human Intestinal Epithelial Model (Caco-2) and in a Perfused Rat Intestinal Model (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1771-1776 
    Details
    ISSN: 1573-904X
    Keywords: D-methionine ; L-methionine ; Caco-2 ; rat ; small intestine ; absorption ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Absorption mechanisms of L- and D-methionine (MET) in an in vitro cultured human intestinal epithelial cell model (Caco-2) and an in situ perfused rat intestinal model were investigated to determine if the kinetic characteristics of absorption are comparable in these two popular absorption models. The results indicate that the transport of L- and D-MET were concentration-dependent in both model systems, and displayed comparable Km values. The Km value for L-MET is 1.34 mM in the Caco-2 model and 3.6 mM in the perfused rat intestinal model, while the Km value for D-MET is 1.79 mM in the Caco-2 model and 2.87 mM in the perfused rat intestinal model. Although the Jmax values were not comparable because of significant methodology differences, the Jmax values for L-MET were always higher than that for D-MET. In addition, transport of L- and D-MET across the Caco-2 cell monolayers were also inhibited by 10 mM Phe and Lys while MeAIB, Pro and Glu were generally ineffective. Similar results were also observed with these inhibitors in the perfused rat intestinal model with the exception that a combination of Pro and Glu stimulated the uptake of L-MET. In conclusion, the transport characteristics of L- and D-MET are comparable in both model systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018923618747
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  • 6
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    Inoculation and Nitrogen Affect Herbage and Symbiotic Properties of Annual Medicago Species (1998)
    Wiley
    Details
    Publication Date: 1998-11-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 7
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    Dry Matter Accumulation and Dinitrogen Fixation of Annual Medicago Species (1998)
    Wiley
    Details
    Publication Date: 1998-01-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 8
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    Effect of cerium on microstructures and mechanical properties of AZ61 wrought magnesium alloy (2004)
    Springer
    Details
    Publication Date: 2004-12-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 9
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    Structural basis for DNA recognition by STAT6 (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-11-01
    Description: STAT6 participates in classical IL-4/IL-13 signaling and stimulator of interferon genes-mediated antiviral innate immune responses. Aberrations in STAT6-mediated signaling are linked to development of asthma and diseases of the immune system. In addition, STAT6 remains constitutively active in multiple types of cancer. Therefore, targeting STAT6 is an attractive proposition for treating related diseases. Although a lot is known about the role of STAT6 in transcriptional regulation, molecular details on how STAT6 recognizes and binds specific segments of DNA to exert its function are not clearly understood. Here, we report the crystal structures of a homodimer of phosphorylated STAT6 core fragment (STAT6CF) alone and bound with the N3 and N4 DNA binding site. Analysis of the structures reveals that STAT6 undergoes a dramatic conformational change on DNA binding, which was further validated by performing molecular dynamics simulation studies and small angle X-ray scattering analysis. Our data show that a larger angle at the intersection where the two protomers of STAT meet and the presence of a unique residue, H415, in the DNA-binding domain play important roles in discrimination of the N4 site DNA from the N3 site by STAT6. H415N mutation of STAT6CF decreased affinity of the protein for the N4 site DNA, but increased its affinity for N3 site DNA, both in vitro and in vivo. Results of our structure–function studies on STAT6 shed light on mechanism of DNA recognition by STATs in general and explain the reasons underlying STAT6’s preference for N4 site DNA over N3.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Materials, Vol. 11, Pages 1538: Fretting Wear Behavior and Photoelectron Spectroscopy (XPS) Analysis of a Ti/TiN Multilayer Film Deposited on Depleted Uranium (2018)
    MDPI Publishing
    In: Materials
    Details
    Publication Date: 2018-08-28
    Description: Materials, Vol. 11, Pages 1538: Fretting Wear Behavior and Photoelectron Spectroscopy (XPS) Analysis of a Ti/TiN Multilayer Film Deposited on Depleted Uranium Materials doi: 10.3390/ma11091538 Authors: Shengfa Zhu Yanping Wu Zhengyang Li Liping Fang Anyi Yin Jiawei Yan Fan Jiang Xiandong Meng Piheng Chen Zhenbing Cai Depleted uranium has been widely applied in nuclear energy fields. However, its poor corrosion and wear resistance restrict its applications. A titanium/titanium nitride (Ti/TiN) multilayer film was deposited on a uranium surface to improve its fretting wear resistance. Fretting wear tests were carried out using a pin-on-disc configuration. The fretting behaviors of uranium and the Ti/TiN film were investigated under different normal loads. With the normal load increasing, the mode of fretting wear gradually transformed from slip region (SR) to mixed fretting region (MFR) and then to partial slip region (PSR). It is illustrated that the normal load had an obvious effect on the fretting wear behavior. The friction coefficients of both uranium and Ti/TiN multilayer film decreased with the increase of the normal load. In SR, the main wear mechanisms were delamination and abrasion for uncoated uranium, and delamination and oxidation for uranium coated with the Ti/TiN multilayer film. Photoelectron spectroscopy (XPS) analysis also showed that the Ti/TiN coating was oxidized and formed TiO2 during fretting wear. The wear depth of naked uranium was much greater than that of coated uranium, which demonstrated that the Ti/TiN multilayer film could effectively improve the wear properties of uranium.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by MDPI Publishing
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