Journal articles: 'Urea hosts'

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Shinde, Sudhirkumar, Anil Incel, Mona Mansour, Gustaf D. Olsson, Ian A. Nicholls, Cem Esen, Javier Urraca, and Börje Sellergren. "Urea-Based Imprinted Polymer Hosts with Switchable Anion Preference." Journal of the American Chemical Society 142, no. 26 (May 19, 2020): 11404–16. http://dx.doi.org/10.1021/jacs.0c00707.

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Connor, Alan L., Ting Hu, Cadnel S. F. Detchou, Rui Liu, Surya V. S. R. K. Pulavarti, Thomas Szyperski, Zhonglin Lu, and Bing Gong. "Aromatic oligureas as hosts for anions and cations." Chemical Communications 52, no. 64 (2016): 9905–8. http://dx.doi.org/10.1039/c6cc03681c.

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Intramolecularly H-bonded urea moieties of aromatic oligoureas bind anions in modest affinities. Extending backbone length results in a cation-binding cavity, allowing the resultant oligomer to bind both anions and cations.

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Jia, Chuandong, Qi-Qiang Wang, Rowshan Ara Begum, Victor W. Day, and Kristin Bowman-James. "Chelate effects in sulfate binding by amide/urea-based ligands." Organic & Biomolecular Chemistry 13, no. 25 (2015): 6953–57. http://dx.doi.org/10.1039/c5ob00618j.

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Chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands in water-mixed DMSO-d₆. The urea hosts were highly selective for SO₄²⁻, and displayed enhanced binding and greater tolerance for increasing water content as the number of chelate groups increased.

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Yutronic, Nicolás, Juan Merchán, Guillermo González, and María Teresa Garland. "Protonated bis(quinuclidine) included in layered bis(urea)–bromide and -iodide hosts: new ternary urea inclusion compounds." J. Chem. Soc., Perkin Trans. 2, no. 11 (2002): 1956–59. http://dx.doi.org/10.1039/b201053b.

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Dhall, Manish, and A. K. Madan. "Comparison of cyclodextrins and urea as hosts for inclusion of drugs." Journal of Inclusion Phenomena and Macrocyclic Chemistry 89, no. 3-4 (September 2, 2017): 207–27. http://dx.doi.org/10.1007/s10847-017-0748-y.

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Tanaka, Koichi, Naoki Daikawa, and Shigeru Ohba. "Novel Bisurea Host Compounds." Journal of Chemical Research 2002, no. 11 (November 2002): 579–81. http://dx.doi.org/10.3184/030823402103170853.

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New host molecules, 4,4′-bis(dimethylamino-urea)diphenylmethane (1) and its derivatives (2 and 3), are reported. These hosts are shown to give inclusion complex crystals with a wide variety of organic guest molecules with high selectivity. The crystal structure of 1:2 inclusion complex of 1 with THF has been determined from X-ray crystal structure analysis. The cyclic N–H...O intermolecular hydrogen bonds between host molecules were found to form columns for accommodation of the guest molecules.

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Bell, Thomas W., and Jia Liu. "Hexagonal lattice hosts for urea. A new series of designed heterocyclic receptors." Journal of the American Chemical Society 110, no. 11 (May 1988): 3673–74. http://dx.doi.org/10.1021/ja00219a060.

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Jurczak, Janusz, Michał J. Chmielewski, Paweł Dydio, Dawid Lichosyt, Filip Ulatowski, and Tomasz Zieliński. "Benzopyrrole derivatives as effective anion receptors in highly competitive solvents." Pure and Applied Chemistry 83, no. 8 (June 24, 2011): 1543–54. http://dx.doi.org/10.1351/pac-con-10-11-11.

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Neutral anion receptors working in highly demanding solvents are new materials being sought. Benzopyrroles are more acidic than amides and pyrrole itself, and are promising building blocks in the design of host compounds. A whole series of receptors based upon benzopyrroles were synthesized and evaluated. They include carbazole, dipyrrolonaph-thalene, and 7-aminoindole-based hosts. Most of them demonstrate moderate binding affinities in dimethyl sulfoxide (DMSO) and have good selectivity toward tetrahedral oxyanions. Recently, a group of receptors utilizing 7-aminoindole and urea moieties proved to work in a very competitive solvent—methanol.

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Collins, D., D. C. Winter, A. M. Hogan, L. Schirmer, A. W. Baird, and G. S. Stewart. "Differential protein abundance and function of UT-B urea transporters in human colon." American Journal of Physiology-Gastrointestinal and Liver Physiology 298, no. 3 (March 2010): G345—G351. http://dx.doi.org/10.1152/ajpgi.00405.2009.

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Facilitative UT-B urea transporters enable the passage of urea across cell membranes. Gastrointestinal urea transporters are thought to play a significant role in the urea nitrogen salvaging process that occurs between mammalian hosts and their gut bacteria. This study investigated the expression of UT-B urea transporters in different segments of human colon. Immunoblot analysis showed that human colon expressed a 35-kDa glycosylated UT-B protein in the colonic mucosa. The 35-kDa UT-B transporter was predominantly located in plasma membrane-enriched samples ( P < 0.001; n = 6), and its expression was greater in the ascending colon compared with the descending colon ( P < 0.01; n = 3). At the cellular level, UT-B transporters were located throughout colonocytes situated in the upper portion of the colonic crypts. Bidirectional trans-epithelial urea transport was significantly greater in the ascending colon than the descending colon ( P < 0.05; n = 6). In addition, the facilitative urea transporter inhibitor 1,3,dimethylurea significantly reduced urea transport in the ascending colon ( P < 0.05; n = 6) but had no effect in the descending colon (NS; n = 6). These results illustrate differential protein abundance of functional UT-B protein in different sections of the human colon, strongly correlating to regions that contain the largest populations of intestinal bacteria. This study suggests an important role for UT-B urea transporters in maintaining the symbiotic relationship between humans and their gut bacteria.

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Hollingsworth, Mark D., Kenneth D. M. Harris, William Jones, and John M. Thomas. "ESR and X-ray diffraction studies of diacyl peroxides in urea and aluminosilicate hosts." Journal of Inclusion Phenomena 5, no. 2 (April 1987): 273–77. http://dx.doi.org/10.1007/bf00655664.

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Eytel, Lisa M., Alexander C. Brueckner, Jessica A. Lohrman, Michael M. Haley, Paul H. Y. Cheong, and Darren W. Johnson. "Conformationally flexible arylethynyl bis-urea receptors bind disparate oxoanions with similar, high affinities." Chemical Communications 54, no. 94 (2018): 13208–11. http://dx.doi.org/10.1039/c8cc07301e.

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Despite competing trends and computational predictions to the contrary, three bis-urea receptors bind disparate oxoanions (ClO₄⁻, HSO₄⁻, H₂PO₄⁻) with equal affinities in a non-polar solvent; in a more polar solvent the trend in association constants for one receptor matches that of the pK_b of the guest, as expected for H-bond donating hosts.

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Roy, Kinkini, Chun Wang, Mark D. Smith, Perry J. Pellechia, and Linda S. Shimizu. "Alkali Metal Ions As Probes of Structure and Recognition Properties of Macrocyclic Pyridyl Urea Hosts." Journal of Organic Chemistry 75, no. 16 (August 20, 2010): 5453–60. http://dx.doi.org/10.1021/jo1009596.

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Shaafie, I. A., A. H. Khan, and K. Rambabu. "Biochemical profiles of hydatid cyst fluids of Echinococcus granulosus of human and animal origin in Libya." Journal of Helminthology 73, no. 3 (March 1999): 255–58. http://dx.doi.org/10.1017/s0022149x99000402.

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A comparative study on the biochemical parameters in hydatid cyst fluids of sheep, goats, camels, cattle and human cystic forms of Echinococcus granulosus has been made in Libya. Quantitative variations in the levels of sodium, potassium, calcium, cholesterol, glucose, urea, creatinine and gamma glutamyl transpeptidase (γGT) were found in the cystic fluids of different host origins although these differences were statistically insignificant compared with the hydatid fluids of sheep. However, the concentration of triglycerides and proteins were significantly elevated in the cyst fluids of sheep compared with the other fluids studied. Similarities in the biochemical composition of different hydatid cyst fluids suggest the existence of sheep strains of E. granulosus in human and other domestic animal intermediate hosts in Libya.

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Goldberg, Israel, and Kenneth M. Doxsee. "Binding neutral guests to concave surfaces of molecular hosts. Directional association of water and methylene chloride with hosts containing only cyclic urea binding sites." Journal of Inclusion Phenomena 4, no. 3 (September 1986): 303–22. http://dx.doi.org/10.1007/bf00658005.

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15

Carter, Eric L., and Robert P. Hausinger. "Characterization of the Klebsiella aerogenes Urease Accessory Protein UreD in Fusion with the Maltose Binding Protein." Journal of Bacteriology 192, no. 9 (March 5, 2010): 2294–304. http://dx.doi.org/10.1128/jb.01426-09.

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ABSTRACT Assembly of the Klebsiella aerogenes urease metallocenter requires four accessory proteins, UreD, UreE, UreF, and UreG, to effectively deliver and incorporate two Ni2+ ions into the nascent active site of the urease apoprotein (UreABC). Each accessory protein has been purified and characterized with the exception of UreD due to its insolubility when it is overproduced in recombinant cells. In this study, a translational fusion was made between the maltose binding protein (MBP) and UreD, with the resulting MBP-UreD found to be soluble in Escherichia coli cell extracts and able to complement a ΔureD-urease cluster in this host microorganism. MBP-UreD was purified as a large multimer (>670 kDa) that bound approximately 2.5 Ni2+ ions (Kd of ∼50 μM, where Kd is the dissociation constant) per UreD protomer according to equilibrium dialysis measurements. Zn2+ directly competes with 10-fold higher affinity (∼4 Zn2+ ions per protomer; Kd of 5 μM) for the Ni2+ binding sites. MBP pulldown experiments demonstrated that the UreD domain of MBP-UreD formed in vivo complexes with UreF, UreG, UreF plus UreG, or UreABC when these proteins were overproduced in the same E. coli cells. In addition, a UreABC-(MBP-UreD)-UreFG complex was observed in cells producing all urease components. Comparative in vitro binding experiments with purified proteins demonstrated an approximate 1:1 binding ratio between the UreD domain of MBP-UreD and the UreF domain of the UreEF fusion, only weak or transient interaction between MBP-UreD and UreG, and no binding with UreABC. These studies are the first to describe the properties of purified UreD, and they extend our understanding of its binding partners both in vitro and in the cell.

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Rusa, Cristian C., and Alan E. Tonelli. "Separation of Polymers by Molecular Weight through Inclusion Compound Formation with Urea and α-Cyclodextrin Hosts." Macromolecules 33, no. 5 (March 2000): 1813–18. http://dx.doi.org/10.1021/ma991883l.

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Jokanovic, V., B. Colovic, and N. Jovic. "The luminescent properties of yttrium oxyapatite doped with Eu3+ ions." Science of Sintering 46, no. 1 (2014): 129–34. http://dx.doi.org/10.2298/sos1401129j.

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The structural and luminescent properties of Ca2Y8(SiO4)6O2 (CYS) silicate based oxyapatite doped with Eu3+ ions have been reported in this paper. The sample was synthesized using reflux method assisted by urea subsequent degradation. Very specific, sh?lland rope-like morphologies were observed by SEM. The powder X-ray diffraction study revealed that the Eu3+: CYS system crystallized in a hexagonal lattice structure (space group P63/m) characteristic of oxyapatite. In the host oxyapatite structure, ? partial replacement of Ca2+ ?nd Y3+ ions by luminescent active Eu3+ ions have been done, and its photoluminescent spectra were analyzed. The performed analysis indicate the presence of Eu3+ ions in both, nine-fold coordinated 4f, and seven-fold coordinated 6h sites, showing a slight shift towards the blue area in comparison to a typical spectra of other yttrium-silicate phases as hosts.

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18

Krajaejun, Theerapong, Thidarat Rujirawat, Teerat Kanpanleuk, Pitak Santanirand, Tassanee Lohnoo, Wanta Yingyong, Yothin Kumsang, Pattarana Sae-Chew, Weerayuth Kittichotirat, and Preecha Patumcharoenpol. "Biochemical and genetic analyses of the oomycetePythium insidiosumprovide new insights into clinical identification and urease-based evolution of metabolism-related traits." PeerJ 6 (June 5, 2018): e4821. http://dx.doi.org/10.7717/peerj.4821.

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The oomycete microorganism,Pythium insidiosum, causes the life-threatening infectious condition, pythiosis, in humans and animals worldwide. Affected individuals typically endure surgical removal of the infected organ(s). Detection ofP. insidiosumby the established microbiological, immunological, or molecular methods is not feasible in non-reference laboratories, resulting in delayed diagnosis. Biochemical assays have been used to characterizeP. insidiosum, some of which could aid in the clinical identification of this organism. Although hydrolysis of maltose and sucrose has been proposed as the key biochemical feature useful in discriminatingP. insidiosumfrom other oomycetes and fungi, this technique requires a more rigorous evaluation involving a wider selection ofP. insidiosumstrains. Here, we evaluated 10 routinely available biochemical assays for characterization of 26P. insidiosumstrains, isolated from different hosts and geographic origins. Initial assessment revealed diverse biochemical characteristics across theP. insidiosumstrains tested. Failure to hydrolyze sugars is observed, especially in slow-growing strains. Because hydrolysis of maltose and sucrose varied among different strains, use of the biochemical assays for identification ofP. insidiosumshould be cautioned. The ability ofP. insidiosumto hydrolyze urea is our focus, because this metabolic process relies on the enzyme urease, an important virulence factor of other pathogens. The ability to hydrolyze urea varied amongP. insidiosumstrains and was not associated with growth rates. Genome analyses demonstrated that urease- and urease accessory protein-encoding genes are present in both urea-hydrolyzing and non-urea-hydrolyzing strains ofP. insidiosum. Urease genes are phylogenetically conserved inP. insidiosumand related oomycetes, while the presence of urease accessory protein-encoding genes is markedly diverse in these organisms. In summary, we dissected biochemical characteristics and drew new insights into clinical identification and urease-related evolution ofP. insidiosum.

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Cruz, Alejandra Santana, Jorge Flores, Roberto Guerra, Carlos Felipe, and Enrique Lima. "Organic biocides hosted in layered double hydroxides: enhancing antimicrobial activity." Open Chemistry 16, no. 1 (March 9, 2018): 163–69. http://dx.doi.org/10.1515/chem-2018-0016.

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AbstractSamples of layered double hydroxides containing carbonates as compensating anions were prepared by the urea method. These LDHs were used as hosts of anions coming from pipemidic and nalidixic acid. XRD results confirm that these anions were hosted in the interlayer space of LDHs. Further, from27Al NMR MAS characterization of an interaction between the brucite-like layers and anions was suggested. Then the hybrids LDHs were used as biocide ofSalmonella typhiandEscherichia coli. The release profile of pipemidic and nalidixic anions from hybrid LDHs occurs for periods as long as 3.5 hours. The free-organic acid LDHs were not able to killS.Typhi, neitherE.coli. In contrast, the hybrids LDHs eliminate almost completely bacteria within short times.

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Hay, Benjamin P., Timothy K. Firman, and Bruce A. Moyer. "Structural Design Criteria for Anion Hosts: Strategies for Achieving Anion Shape Recognition through the Complementary Placement of Urea Donor Groups." Journal of the American Chemical Society 127, no. 6 (February 2005): 1810–19. http://dx.doi.org/10.1021/ja043995k.

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Boas, Ulrik, Annika J. Karlsson, B. F. M. de Waal, and E. W. Meijer. "Synthesis and Properties of New Thiourea-Functionalized Poly(propylene imine) Dendrimers and Their Role as Hosts for Urea Functionalized Guests." Journal of Organic Chemistry 66, no. 6 (March 2001): 2136–45. http://dx.doi.org/10.1021/jo001573x.

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Igbinnosa, Imuetinyan, and Patrick A. Thalouarn. "Nitrogen Assimilation Enzyme Activities in Witchweed (Striga) in Hosts Presence and Absence." Weed Science 44, no. 2 (June 1996): 224–32. http://dx.doi.org/10.1017/s0043174500093826.

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N fertilizers suppress witchweed plant growth and development, thus reducing the severity of parasite attack and increasing host yield simultaneously. However, the underlying physiological mode of N action occurring within the parasite cells remains largely unknown. This study aims at screening for the effects of N forms and different growth conditions on some N assimilation enzymes in witchweed seedlings grown aseptically without host plant, and in pots with host plants. Results show that supply of N in NH4+or urea forms resulted in 83 to 92% reduction in nitrate reductase activity (NRc), compared with control. Increasing NO3−concentrations from 0 mM to 100 mM, led to a corresponding increase in NRc in giant witchweed. NRc of giant witchweed seedlings grown under light and dark cycles were about 270 times higher than seedlings grown in continuous darkness. A combination of NH4+and NO3−, resulted in increased giant witchweed NRc, compared with NH4+or NO3−supplied singly. Highest shoot development and NRc was at NH4+and NO3−ratio 1:1, followed by ratios 1:3, 3:1, 0:1, and 1:0, respectively. Addition of N in soils resulted in increased NRc, followed by rapid deterioration and death of giant witchweed plants. NRc, GSc, and GDHc in witchweed, maize, cowpea, and tobacco were affected by diurnal fluctuations with higher enzyme activities occurring during the day than at night. Higher GSc than GDHc suggests that NH4+assimilation occurs mainly through the GS pathway in witchweed plants. NRc and GDHc were two and four times higher in giant witchweed grown in aseptic media without host plant, than that grown in potted soils with host plants. These findings provide insight into the physiological mode of N action and their implications on witchweed control.

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Cejnar, Pavel, Štěpánka Kučková, Jiří Šantrůček, Miroslav Glasa, Petr Komínek, Daniel Mihálik, Lucie Slavíková, et al. "Efficient Confirmation of Plant Viral Proteins and Identification of Specific Viral Strains by nanoLC-ESI-Q-TOF Using Single-Leaf-Tissue Samples." Pathogens 9, no. 11 (November 19, 2020): 966. http://dx.doi.org/10.3390/pathogens9110966.

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Plant viruses are important pathogens that cause significant crop losses. A plant protein extraction protocol that combines crushing the tissue by a pestle in liquid nitrogen with subsequent crushing by a roller-ball crusher in urea solution, followed by RuBisCO depletion, reduction, alkylation, protein digestion, and ZipTip purification allowed us to substantially simplify the sample preparation by removing any other precipitation steps and to detect viral proteins from samples, even with less than 0.2 g of leaf tissue, by a medium resolution nanoLC-ESI-Q-TOF. The presence of capsid proteins or polyproteins of fourteen important viruses from seven different families (Geminiviridae, Luteoviridae, Bromoviridae, Caulimoviridae, Virgaviridae, Potyviridae, and Secoviridae) isolated from ten different economically important plant hosts was confirmed through many identified pathogen-specific peptides from a protein database of host proteins and potential pathogen proteins assembled separately for each host and based on existing online plant virus pathogen databases. The presented extraction protocol, combined with a medium resolution LC-MS/MS, represents a cost-efficient virus protein confirmation method that proved to be effective at identifying virus strains (as demonstrated for PPV, WDV) and distinct disease species of BYDV, as well as putative new viral protein sequences from single-plant-leaf tissue samples. Data are available via ProteomeXchange with identifier PXD022456.

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Radwan, Mahmoud, Sabry Shehata, Yasser Abdelhadi, Ramadan Mohammed, Mohamed Mohamed, and Mohammad Magdy. "Histopathological, Haematological and Biochemical Indices of Clarias gariepinus (Burchell, 1822) Parasitized by Endoparasitic Fauna in Fish Farm of the Northeastern Egypt." Turkish Journal of Fisheries and Aquatic Sciences 21, no. 09 (June 3, 2021): 465–78. http://dx.doi.org/10.4194/1303-2712-v21_9_05.

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Knowledge of the endemic fauna of parasites in fish are of great importance, parasites could synergistically act as stressors to health of their hosts. The objectives of this study were to evaluate prevalence and effect of parasites on hematological, biochemical indices, injury of tissues and length weight relationship of Clarias, gariepinus. Water quality variables were measured and fishes were collected each seasons for examination most common parasites in infected fishes at Abbasa Fish Farm, Egypt. Results indicated that high summer water temperature was strongly associated with parasites infection. The hematological and biochemical analysis showed significant reduction in red blood cells (RBCs) count, hemoglobin (Hb) value, packed cell volume (PCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC), total protein, Albumin, Globulin and A/G ratio, while total white blood cells (WBCs) count, mean corpuscular volume (MCV), aspartate aminotransferase activity (ASAT), alanine aminotransferase activity (ALAT), urea, creatinine, uric acid and glucose were significantly increased in infested catfish. On other hands, histopathological examination of infected fish indicated, organs most affected by infection of parasites. Overall the tendencies observed in data showed the parasites have a strong effect on host fish and drifts observed for all variables showed a strong seasonal decoration.

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Zhao, Rui, José M. Mogollón, Sophie S. Abby, Christa Schleper, Jennifer F. Biddle, Desiree L. Roerdink, Ingunn H. Thorseth, and Steffen L. Jørgensen. "Geochemical transition zone powering microbial growth in subsurface sediments." Proceedings of the National Academy of Sciences 117, no. 51 (December 7, 2020): 32617–26. http://dx.doi.org/10.1073/pnas.2005917117.

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No other environment hosts as many microbial cells as the marine sedimentary biosphere. While the majority of these cells are expected to be alive, they are speculated to be persisting in a state of maintenance without net growth due to extreme starvation. Here, we report evidence for in situ growth of anaerobic ammonium-oxidizing (anammox) bacteria in ∼80,000-y-old subsurface sediments from the Arctic Mid-Ocean Ridge. The growth is confined to the nitrate–ammonium transition zone (NATZ), a widespread geochemical transition zone where most of the upward ammonium flux from deep anoxic sediments is being consumed. In this zone the anammox bacteria abundances, assessed by quantification of marker genes, consistently displayed a four order of magnitude increase relative to adjacent layers in four cores. This subsurface cell increase coincides with a markedly higher power supply driven mainly by intensified anammox reaction rates, thereby providing a quantitative link between microbial proliferation and energy availability. The reconstructed draft genome of the dominant anammox bacterium showed an index of replication (iRep) of 1.32, suggesting that 32% of this population was actively replicating. The genome belongs to aScalinduaspecies which we nameCandidatus Scalindua sediminis, so far exclusively found in marine sediments. It has the capacity to utilize urea and cyanate and a mixotrophic lifestyle. Our results demonstrate that specific microbial groups are not only able to survive unfavorable conditions over geological timescales, but can proliferate in situ when encountering ideal conditions with significant consequences for biogeochemical nitrogen cycling.

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Okunev, A. M. "Pathological changes in dogs with echinococcal infestation in the Tyumen region." Bulletin of NSAU (Novosibirsk State Agrarian University), no. 2 (July 13, 2021): 132–40. http://dx.doi.org/10.31677/2072-6724-2021-59-2-132-140.

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Dogs are the definitive hosts of Echinococcus, so not only do they carry a dangerous infestation for farm animals and humans, but they are also exposed to the substantial toxic effects of helminths themselves. The present work aims to find out the pathological impact of Echinococcus on the intestinal microflora and some blood parameters in the organism of affected dogs under the conditions of the Tyumen region. The authors studied the pathological effect of the sexually mature parasites on the host organism in 8 mongrel dogs. The contents were inoculated on special nutrient media, followed by cell counting as part of the bacteriological analysis of fresh animal faeces. Bacteria were identified by microscopy of isolated cultures, examining morphological features and Gram staining. Blood was taken from dogs from the femoral vein in the morning before feeding for general and biochemical analysis. It was found that the digestive tract of the dogs infected with Echinococcus decreased in bifidoand lactobacilli by a factor of 2 (P<0.001) compared with those of intact individuals. Escherichia increased by 1.6 times, Staphylococcus was augmented by 4.1, and Clostridium increased by 8.3 (P<0.001), leading to intestinal dysbacteriosis, digestive disorders, and secondary toxicosis animals. General blood analysis showed a 30.2% reduction in erythrocytes, 26.7% in platelets and 32.4% in haemoglobin. This reduction is the result of the action of toxins in the body of the patients. In the leukoformula, changes are manifested by a slight increase in the proportion of granulocytes (by 6.6%) due to eosinophils (P<0.01) and a decrease in agranulocytes (by 20.0%). Biochemical blood analyses of dogs with echinococcosis showed a 17.7% reduction in total protein and a 3-fold decrease in cholesterol. A 2-fold increase in creatinine and urea, a 3.2fold increase in bilirubin, a 2.6-fold increase in ALT and AST, and a 2-fold increase in alkaline phosphatase indicate inhibition of liver and kidney function.

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UGOCHUKWU, Iniobong C. I., Chukwunonso K. EZEASOR, Onyinyechukwu A. AGINA, Davinson C. ANYOGU, Ijeoma C. CHUKWUDI, Sunday I. IDOKO, and Emmanuel I. UGOCHUKWU. "Peste des Petits Ruminants: Aetiology, Pathology, Immunology, Disease Status in Africa, Diagnosis, Control, Prevention and Treatment: A Review." Notulae Scientia Biologicae 11, no. 1 (March 21, 2019): 12–20. http://dx.doi.org/10.15835/nsb11110355.

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Peste des petits ruminants (PPR) is a disease of economic and veterinary importance leading to considerable economic losses. PPR affects small domestic and wild ruminants. Sheep and goats are the natural hosts of PPR but cattle, pigs, African buffaloes and camels are also affected by the PPR virus. Clinical signs seen are mainly fever, mucopurulent nasal and ocular discharges, cough, dyspnoea, gastroenteritis leading to severe diarrhoea. The post mortem lesions seen are congested lungs, congestion of gastrointestinal tract, especially the discontinuous streaks of congestion, which is referred to as Zebra stripes or Zebra markings, oedematous and congested retropharyngeal and mesenteric lymph nodes, linear haemorrhages in the intestinal mucosa and splenomegaly. PPR infection is characterized by a rise in packed cell volume (PCV), increase in haemoglobin concentration (HbC), leukopenia with lymphopenia. The serum alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase activities are elevated, blood urea nitrogen and creatinine concentrations are also elevated. The disease is also characterized by disseminated intravascular coagulopathy (DIC) evidenced by prolonged prothrombin time (PT), prolonged activated thromboplastin time (APTT), thrombocytopenia, and hypofibrinogenemia. In PPR infection, serum biomarkers of oxidative stress such as vitamins A, C, E and glutathione activity decreases while serum catalase, superoxide dismutase, glutathione reductase and xanthine oxidase increase. Diagnostic techniques include histopathology, virus isolation, immunocapture enzyme-linked immunosorbent assay (icELISA), Competitive Enzyme Linked Imunnosorbent Assay (cELISA) and Combined Indirect ELISA (CI-ELISA) agar gel immunodiffusion, real-time polymerase chain reaction (RT-PCR), reverse transcription-loop mediated isothermal amplification assay (RT-LAMP), Luciferase immunoprecipitation system (LIPS) and immunohistochemistry. Therefore, this review focused on the aetiology, epidemiology, pathology, immunology, and disease status in Africa, diagnosis, control, prevention, treatment and control of this disease.

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Wiebler, James M., Kevin D. Kohl, Richard E. Lee, and Jon P. Costanzo. "Urea hydrolysis by gut bacteria in a hibernating frog: evidence for urea-nitrogen recycling in Amphibia." Proceedings of the Royal Society B: Biological Sciences 285, no. 1878 (May 2, 2018): 20180241. http://dx.doi.org/10.1098/rspb.2018.0241.

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Gut bacteria that produce urease, the enzyme hydrolysing urea, contribute to nitrogen balance in diverse vertebrates, although the presence of this system of urea-nitrogen recycling in Amphibia is as yet unknown. Our studies of the wood frog ( Rana sylvatica ), a terrestrial species that accrues urea in winter, documented robust urease activity by enteric symbionts and hence potential to recoup nitrogen from the urea it produces. Ureolytic capacity in hibernating (non-feeding) frogs, whose guts hosted an approximately 33% smaller bacterial population, exceeded that of active (feeding) frogs, possibly due to an inductive effect of high urea on urease expression and/or remodelling of the microbial community. Furthermore, experimentally augmenting the host's plasma urea increased bacterial urease activity. Bacterial inventories constructed using 16S rRNA sequencing revealed that the assemblages hosted by hibernating and active frogs were equally diverse but markedly differed in community membership and structure. Hibernating frogs hosted a greater relative abundance and richer diversity of genera that possess urease-encoding genes and/or have member taxa that reportedly hydrolyse urea. Bacterial hydrolysis of host-synthesized urea probably permits conservation and repurposing of valuable nitrogen not only in hibernating R. sylvatica but, given urea's universal role in amphibian osmoregulation, also in virtually all Amphibia.

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Li, Qi, Mei Shi, and Thomas C. W. Mak. "Novel inclusion compounds with urea/thiourea/seleno-urea-anion host lattices." Chinese Science Bulletin 46, no. 21 (November 2001): 1761–63. http://dx.doi.org/10.1007/bf02900545.

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Biswakarma, Dipen, Nilanjan Dey, Deepa Bhagat, and Santanu Bhattacharya. "A fluorescent supramolecular host for urea." Materials Today: Proceedings 26 (2020): 11–16. http://dx.doi.org/10.1016/j.matpr.2019.05.352.

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María, Dolores Santa, M. Ángeles Farrán, M. Ángeles García, Elena Pinilla, M. Rosario Torres, José Elguero, and Rosa M. Claramunt. "Synthetic Hosts for Molecular Recognition of Ureas." Journal of Organic Chemistry 76, no. 16 (August 19, 2011): 6780–88. http://dx.doi.org/10.1021/jo201191x.

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Yeo, L., and K. D. M. Harris. "Definitive Structural Characterization of the Conventional Low-Temperature Host Structure in Urea Inclusion Compounds." Acta Crystallographica Section B Structural Science 53, no. 5 (October 1, 1997): 822–30. http://dx.doi.org/10.1107/s0108768197005417.

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Structural properties of the 1,10-dibromodecane/urea and 1,12-dibromododecane/urea inclusion compounds have been determined by single-crystal X-ray diffraction for both the high- and low-temperature phases. In the high-temperature phase both inclusion compounds have the conventional hexagonal urea tunnel structure, with substantial orientational disorder of the guest molecules. In the low-temperature phase the urea tunnel structure distorts to an orthorhombic structure, based on a distorted form of the orthohexaganol cell of the high-temperature structure and with the loss of the C centre. Within this tunnel structure there is evidence that the guest molecules have a narrow distribution of orientations (with respect to rotation about the tunnel axis) and the preferred orientation of the guest molecules correlates well with the observed distortion of the host tunnel. This represents the first accurate and reliable report of the conventional low-temperature structure of urea inclusion compounds. Previous powder X-ray diffraction studies have confirmed that the host structure in the low-temperature phase of 1,10-dibromodecane/urea is the same as that in the low-temperature phase of the alkane/urea inclusion compounds.

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Stewart, Kent D., Michel Miesch, Carolyn B. Knobler, Emily F. Maverick, and Donald J. Cram. "Host-guest complexation. 40. Synthesis and complexation of macrocyclic hosts containing cyclic ureas, anisyls, and steric barriers." Journal of Organic Chemistry 51, no. 23 (November 1986): 4327–37. http://dx.doi.org/10.1021/jo00373a001.

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Garner, Rachel M., John Fulkerson, and Harry L. T. Mobley. "Helicobacter pylori Glutamine Synthetase Lacks Features Associated with Transcriptional and Posttranslational Regulation." Infection and Immunity 66, no. 5 (May 1, 1998): 1839–47. http://dx.doi.org/10.1128/iai.66.5.1839-1847.1998.

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ABSTRACT Helicobacter pylori urease, produced in abundance, is indispensable for the survival of H. pylori in animal hosts. Urea is hydrolyzed by the enzyme, resulting in the liberation of excess ammonia, some of which neutralizes gastric acid. The remaining ammonia is assimilated into protein by glutamine synthetase (EC6.3.1.2 ), which catalyzes the reaction: NH3 + glutamate + ATP→glutamine + ADP + Pi. We hypothesized that glutamine synthetase plays an unusually critical role in nitrogen assimilation by H. pylori. We developed a phenotypic screen to isolate genes that contribute to the synthesis of a catalytically active urease. Escherichia coli SE5000 transformed with plasmid pHP808 containing the entire H. pylori urease gene cluster was cotransformed with a pBluescript plasmid library of the H. pylori ATCC 43504 genome. A weakly urease-positive 9.4-kb clone, pUEF728, was subjected to nucleotide sequencing. Among other genes, the gene for glutamine synthetase was identified. The complete 1,443-bp glnA gene predicts a polypeptide of 481 amino acid residues with a molecular weight of 54,317; this was supported by maxicell analysis of clonedglnA expressed in E. coli. The top 10 homologs were all bacterial glutamine synthetases, including Salmonella typhimurium glnA. The ATP-binding motif GDNGSG (residues 272 to 277) of H. pylori GlnA exactly matched and aligned with the sequence in 8 of the 10 homologs. The adenylation site found in the top 10 homologs (consensus sequence, NLYDLP) is replaced in H. pylori by NLFKLT (residues 405 to 410). Since the Tyr (Y) residue is the target of adenylation and since the H. pyloriglutamine synthetase lacks that residue in four strains examined, we conclude that no adenylation occurs within this motif. Cloned H. pylori glnA complemented a glnA mutation in E. coli, and GlnA enzyme activity could be measured spectrophotometrically. In an attempt to produce a GlnA-deficient mutant of H. pylori, a kanamycin resistance cassette was cloned into the Tth111I site of H. pylori glnA. By using the standard technique of allelic exchange mutagenesis, no verifiable glutamine synthetase double-crossover mutant of strain UMAB41 could be isolated, suggesting that the mutation is lethal. We conclude that glutamine synthetase is critical for nitrogen assimilation in H. pylori and is active under all physiologic conditions.

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Frazzitta, Aubrey E., Haily Vora, Michael S. Price, Jennifer L. Tenor, Marisol Betancourt-Quiroz, Dena L. Toffaletti, Nan Cheng, and John R. Perfect. "Nitrogen Source-Dependent Capsule Induction in Human-Pathogenic Cryptococcus Species." Eukaryotic Cell 12, no. 11 (August 23, 2013): 1439–50. http://dx.doi.org/10.1128/ec.00169-13.

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ABSTRACTCryptococcus neoformansandC. gattiicause meningoencephalitis and are an increasing human health threat. These pathogenicCryptococcusspecies are neurotropic and persist in the cerebrospinal fluid (CSF) of the mammalian host during infection. In order to survive in the host, pathogenic fungi must procure nutrients, such as carbon and nitrogen, from the CSF. To enhance our understanding of nutrient acquisition during central nervous system infection byCryptococcusspecies, we examined the utilization of nitrogen sources available in CSF. We screened for the growth and capsule production of 817 global environmental and clinical isolates on various sources of nitrogen. Both environmental and clinical strains grew robustly on uric acid, Casamino Acids, creatinine, and asparagine as sole nitrogen sources. Urea induced the greatest magnitude of capsule induction. This induction was greater inCryptococcus gattiithan inC. neoformans. We confirmed the ability of nonpreferred nitrogen sources to increase capsule production in pathogenic species ofCryptococcus. Since urea is metabolized to ammonia and CO2(a known signal for capsule induction), we examined urea metabolism mutants for their transcriptional response to urea regarding capsule production. The transcriptional profile ofC. neoformansunder urea-supplemented conditions revealed both similar and unique responses to other capsule-inducing conditions, including both intra- and extracellular urea utilization. As one of the most abundant nitrogen sources in the CSF, the ability ofCryptococcusto import urea and induce capsule production may substantially aid this yeast's survival and propagation in the host.

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Lee, Rachael, Michael Probert, and Jonathon Steed. "The changeable nature of urea inclusion compounds." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1706. http://dx.doi.org/10.1107/s205327331408293x.

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Urea inclusion compounds (UICs), the β-phase of urea, have been known only since 1949 and have revealed various structural and behavioural characteristics of interest, largely influenced by the type of guest molecule present in the crystal. These structures have a hexagonally symmetrical honeycomb structure of a hydrogen-bonded urea network encapsulating the guest molecules, a defining motif of these clathrates. The simplest of this class contains an alkane guest (C7-C20), creating an incommensurate relationship between host and guest and a significantly disordered crystal structure with respect to the guest. As a result, diffuse scattering is typical in the diffraction patterns of UICs. As the guest molecules are altered, so too is the behaviour of the host network. With certain dihaloalkanes for example, the guest may coil into an atypical conformation in order to present a commensurate relationship with the host. This increase in guest order creates a distortion of the host network away from hexagonal symmetry, creating an internal stress which causes domain switching within the system. A number of different effects such as this can be seen on changing the guest molecule, ferroelasticity being an example for certain diketone guests. In this work we are exploring examples of UICs which, due to unusual interaction between the host and guest, display atypical structural features, symmetry or behaviour. These crystal structures are under investigation at a range of temperatures and pressures, by both X-ray and neutron diffraction techniques in order to fully understand the nature and bonding of UICs.

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Weber, Thomas, Hans Boysen, and Friedrich Frey. "Longitudinal positional ordering of n-alkane molecules in urea inclusion compounds." Acta Crystallographica Section B Structural Science 56, no. 1 (February 1, 2000): 132–41. http://dx.doi.org/10.1107/s0108768199010617.

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The profiles of diffuse layers, which are present in diffraction patterns of urea inclusion compounds, are interpreted quantitatively by a longitudinal positional paracrystalline order of the alkane guest molecules within the channels of the urea-host framework structure, in agreement with the expected behaviour of a one-dimensional system. With decreasing temperature there is a gradual transition into long-range order behaviour. This ordering process remains unaffected by structural changes related to lateral correlations within and between both host and guest substructures, including a structural phase transformation. The differing behaviour of a mixed system (pentadecane/hexadecane) with average period almost commensurate with the urea host lattice is explained by the superposition of main and satellite layers. The distribution of both molecules within each tunnel is random.

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Ghosh, Kumaresh, Suman Adhikari, and Roland Fröhlich. "A pyridine-based macrocyclic host for urea and acetone." Tetrahedron Letters 49, no. 34 (August 2008): 5063–66. http://dx.doi.org/10.1016/j.tetlet.2008.06.030.

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Bryant, Judi A., Siew Peng Ho, Carolyn B. Knobler, and Donald J. Cram. "Host-guest complexation. 54. Spherands containing cyclic urea units." Journal of the American Chemical Society 112, no. 15 (July 1990): 5837–43. http://dx.doi.org/10.1021/ja00171a025.

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40

Hall, Andrew J., Panagiotis Manesiotis, Marco Emgenbroich, Milena Quaglia, Ersilia De Lorenzi, and Börje Sellergren. "Urea Host Monomers for Stoichiometric Molecular Imprinting of Oxyanions§." Journal of Organic Chemistry 70, no. 5 (March 2005): 1732–36. http://dx.doi.org/10.1021/jo048470p.

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Merchán, Juan, Nicolás Yutronic, María T. Garland, and Ricardo Baggio. "Protonated Bis(quinuclidine) Included in a Novel “Bichannel” (Urea)–Chloride Host: a Very Large Urea Channel." Supramolecular Chemistry 16, no. 2 (March 1, 2004): 147–52. http://dx.doi.org/10.1080/10610270310001614223.

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42

Xue, Feng, and Thomas C. W. Mak. "Channel- and layer-type anionic host structures in inclusion compounds of urea, tetraalkylammonium terephthalate/trimesate and water." Acta Crystallographica Section B Structural Science 56, no. 1 (February 1, 2000): 142–54. http://dx.doi.org/10.1107/s0108768199011283.

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New crystalline adducts of tetraalkylammonium terephthalate/trimesate with urea and water molecules result from hydrogen-bond directed assembly of complementary acceptors and donors, and the anionic host lattices are described using the graph-set notation to identify distinct hydrogen-bonding motifs and patterns. Tetra-n-butylammonium terephthalate–urea–water (1/6/2), C46H104N14O12 (1), triclinic, space group P1¯, a = 8.390 (2), b = 9.894 (2), c = 18.908 (3) Å, α = 105.06 (2), β = 94.91 (1), γ = 93.82 (2)°, Z = 1, is composed of hydrogen-bonded terephthalate–urea layers, which are intersected by urea layers to generate a three-dimensional network containing large channels for accommodation of the cations. Tetraethylammonium terephthalate–urea–water (1/1/5), C25H58N4O10 (2), triclinic, P1¯, a = 9.432 (1), b = 12.601 (1), c = 14.804 (1) Å, α = 79.98 (1), β = 79.20 (1), γ = 84.18 (1)°, Z = 2, has cations sandwiched between hydrogen-bonded anionic layers. Tetraethylammonium trimesate–urea–water (1/2/7.5), C35H86N7O15.5 (3), triclinic, P1¯, a = 13.250 (1), b = 14.034 (1), c = 15.260 (1) Å, α = 72.46 (1), β = 78.32 (1), γ = 66.95 (1)°, Z = 2, manifests a layer-type structure analogous to that of (2). Tetra-n-propylammonium hydrogen trimesate–urea–water (1/2/5), C35H78N6O13 (4), orthorhombic, Pna21, a = 16.467 (3), b = 33.109 (6), c = 8.344 (1) Å, Z = 4, features hydrogen trimesate helices in a three-dimensional host architecture containing nanoscale channels each filled by a double column of cations.

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Weber, Th, H. Boysen, F. Frey, and R. B. Neder. "Modulated Structure of the Composite Crystal Urea/n-Heptadecane." Acta Crystallographica Section B Structural Science 53, no. 3 (June 1, 1997): 544–52. http://dx.doi.org/10.1107/s0108768196014966.

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The structure of the composite crystal urea/heptadecane was determined by single-crystal X-ray diffraction. The lattice constants of the hexagonal substructures are a = 8.218 (2), b = 8.218 (3), c h = 11.017 (3) Å for the urea (host) structure and c g = 23.713 (1) Å for the heptadecane (guest) structure, respectively. The (3+ 1)-dimensional space group is P6122(00\rho)011. Refinements on 786 reflections converged to wR = 0.0232 for 608 main host reflections, wR = 0.1506 for 10 main guest reflections, wR = 0.0328 for 49 common main reflections and wR = 0.753 for 119 pure satellite reflections. A comparison of the refinement of only the urea substructure and a refinement of the whole composite crystal, including the guest subsystem and the mutual modulations of both subsystems, shows that the main reflections, previously assigned to the urea host exclusively, are affected by a nonnegligible contribution of the heptadecane satellite scattering. The modulation of the guest structure has a maximum when the CH2 groups of the heptadecane molecule are facing the channel walls at heights corresponding to troughs in this wall. Thus, the modulation of the guest structure can be interpreted by an adaptation of the guest molecules to the host structure. The modulation of the host structure was found to be very weak, as the satellite scattering of the host structure is low. \psi-scans of the 00 l reflections revealed that the observed violation of the 61 screw axis extinction rule of the host structure and guest structure modulation can be explained by considerable umweganregung.

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Li, Q., and T. C. W. Mak. "Hydrogen-Bonded Urea–Anion Host Lattices. 6. New Inclusion Compounds of Urea with Tetra-n-propylammonium Halides." Acta Crystallographica Section B Structural Science 54, no. 2 (April 1, 1998): 180–92. http://dx.doi.org/10.1107/s0108768196014498.

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New inclusion complexes tetra-n-propylammonium fluoride–urea–water (2/7/3), 2(n-C3H7)4N+F−.7(NH2)2CO.3H2O (1), tetra-n-propylammonium chloride–urea (1/2), (n-C3H7)4N+Cl−.2(NH2)2CO (2), tetra-n-propylammonium chloride–urea (1/3), (n-C3H7)4N+Cl−.3(NH2)2CO (3), tetra-n-propylammonium bromide–urea–water (1/3/1), (n-C3H7)4N+Br−.3(NH2)2CO.H2O (4), and tetra-n-propylammonium iodide–urea–water (1/3/1), (n-C3H7)4N+I−.3(NH2)2CO.H2O (5), have been prepared and characterized by X-ray crystallography. Crystal data, Mo Kα radiation: (1), space group P21/c, Z = 4, a = 8.560 (2), b = 16.301 (3), c = 37.004 (7) Å, β = 92.31 (3)°, R F = 0.075 for 3945 observed data; (2), space group P21/n, Z = 4, a = 9.839 (2), b = 15.160 (3), c = 14.583 (3) Å, β = 108.82 (3)°, R F = 0.058 for 1770 observed data; (3), space group P21/c, Z = 4, a = 9.866 (2), b = 16.274 (3), c = 15.277 (3) Å, β = 103.36 (3)°, R F = 0.060 for 2272 observed data; (4), space group P1¯, Z = 2, a = 8.857 (2), b = 10.639 (2), c = 15.115 (3) Å, α = 88.01 (3), β = 75.02 (3), γ = 66.72 (3)°, R F = 0.064 for 2694 observed data; (5), space group P1¯, Z = 2, a = 9.045 (2), b = 10.781 (2), c = 15.169 (3) Å, α = 87.98 (3), β = 76.00 (3), γ = 65.73 (3)°, R F = 0.052 for 4973 observed data. In the crystal structure of (1) an alternate crisscross arrangement of urea ribbons, which are cross-bridged by other urea molecules, water molecules and fluoride ions, generates a three-dimensional host lattice containing an open-channel system running parallel to the b axis, with the (n-C3H7)4N+ cations accommodated in a zigzag column within each channel. In the crystal structure of (2) the cations are sandwiched between puckered layers resulting from parallel urea ribbons that are cross-bridged by chloride anions. In (3) the (n-C3H7)4N+ cations are accommodated in a channel-type host lattice built of planar arrays of twisted ribbons constructed from three independent urea molecules, which are cross-linked by bridging chloride ions. Complexes (4) and (5) are isomorphous with the same channel host framework built of parallel corrugated urea layers that are interlinked by cyclic (H2O.X −)2 tetramers.

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Mamani-Huanca, Maricruz, Sandra Marcia Muxel, Stephanie Maia Acuña, Lucile Maria Floeter-Winter, Coral Barbas, and Ángeles López-Gonzálvez. "Metabolomic Reprogramming of C57BL/6-Macrophages during Early Infection with L. amazonensis." International Journal of Molecular Sciences 22, no. 13 (June 26, 2021): 6883. http://dx.doi.org/10.3390/ijms22136883.

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Leishmania survival inside macrophages depends on factors that lead to the immune response evasion during the infection. In this context, the metabolic scenario of the host cell–parasite relationship can be crucial to understanding how this parasite can survive inside host cells due to the host’s metabolic pathways reprogramming. In this work, we aimed to analyze metabolic networks of bone marrow-derived macrophages from C57BL/6 mice infected with Leishmania amazonensis wild type (La-WT) or arginase knocked out (La-arg−), using the untargeted Capillary Electrophoresis-Mass Spectrometry (CE-MS) approach to assess metabolomic profile. Macrophages showed specific changes in metabolite abundance upon Leishmania infection, as well as in the absence of parasite-arginase. The absence of L. amazonensis-arginase promoted the regulation of both host and parasite urea cycle, glycine and serine metabolism, ammonia recycling, metabolism of arginine, proline, aspartate, glutamate, spermidine, spermine, methylhistidine, and glutathione metabolism. The increased L-arginine, L-citrulline, L-glutamine, oxidized glutathione, S-adenosylmethionine, N-acetylspermidine, trypanothione disulfide, and trypanothione levels were observed in La-WT-infected C57BL/6-macrophage compared to uninfected. The absence of parasite arginase increased L-arginine, argininic acid, and citrulline levels and reduced ornithine, putrescine, S-adenosylmethionine, glutamic acid, proline, N-glutamyl-alanine, glutamyl-arginine, trypanothione disulfide, and trypanothione when compared to La-WT infected macrophage. Moreover, the absence of parasite arginase leads to an increase in NO production levels and a higher infectivity rate at 4 h of infection. The data presented here show a host-dependent regulation of metabolomic profiles of C57BL/6 macrophages compared to the previously observed BALB/c macrophages infected with L. amazonensis, an important fact due to the dual and contrasting macrophage phenotypes of those mice. In addition, the Leishmania-arginase showed interference with the urea cycle, glycine, and glutathione metabolism during host–pathogen interactions.

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Jin, Di, Shengguo Zhao, Nan Zheng, Yves Beckers, and Jiaqi Wang. "Urea Metabolism and Regulation by Rumen Bacterial Urease in Ruminants – A Review." Annals of Animal Science 18, no. 2 (May 1, 2018): 303–18. http://dx.doi.org/10.1515/aoas-2017-0028.

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AbstractUrea is used as non-protein nitrogen in the rations of ruminants as an economical replacement for feed proteins. Urea transferred from the blood to the rumen is also an important source of nitrogen for rumen microbial growth. It is rapidly hydrolyzed by rumen bacterial urease to ammonia (NH3) and the NH3is utilized for the synthesis of microbial proteins required to satisfy the protein requirements of ruminants. Urea has commonly become an accepted ingredient in the diets of ruminants. In recent decades, urea utilization in ruminants has been investigated by using traditional research methods. Recently, molecular biotechnologies have also been applied to analyze urea-degrading bacteria or urea nitrogen metabolism in ruminants. Combining traditional and molecular approaches, we can retrieve better information and understanding related to the mechanisms of urea metabolism in ruminants. This review focuses on urea utilization in ruminants and its regulation by rumen bacterial urease in the host. The accumulated research provides foundations for proposing further new strategies to improve the efficiency of urea utilization in ruminants.

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Navarathna, Dhammika H. M. L. P., Aditi Das, Joachim Morschhäuser, Kenneth W. Nickerson, and David D. Roberts. "Dur3 is the major urea transporter in Candida albicans and is co-regulated with the urea amidolyase Dur1,2." Microbiology 157, no. 1 (January 1, 2011): 270–79. http://dx.doi.org/10.1099/mic.0.045005-0.

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Hemiascomycetes, including the pathogen Candida albicans, acquire nitrogen from urea using the urea amidolyase Dur1,2, whereas all other higher fungi use primarily the nickel-containing urease. Urea metabolism via Dur1,2 is important for resistance to innate host immunity in C. albicans infections. To further characterize urea metabolism in C. albicans we examined the function of seven putative urea transporters. Gene disruption established that Dur3, encoded by orf 19.781, is the predominant transporter. [14C]Urea uptake was energy-dependent and decreased approximately sevenfold in a dur3Δ mutant. DUR1,2 and DUR3 expression was strongly induced by urea, whereas the other putative transporter genes were induced less than twofold. Immediate induction of DUR3 by urea was independent of its metabolism via Dur1,2, but further slow induction of DUR3 required the Dur1,2 pathway. We investigated the role of the GATA transcription factors Gat1 and Gln3 in DUR1,2 and DUR3 expression. Urea induction of DUR1,2 was reduced in a gat1Δ mutant, strongly reduced in a gln3Δ mutant, and abolished in a gat1Δ gln3Δ double mutant. In contrast, DUR3 induction by urea was preserved in both single mutants but reduced in the double mutant, suggesting that additional signalling mechanisms regulate DUR3 expression. These results establish Dur3 as the major urea transporter in C. albicans and provide additional insights into the control of urea utilization by this pathogen.

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Li, Qi, Wai Hing Yip, and Thomas C. W. Mak. "Hydrogen-bonded urea-anion host lattices. Part 2. Crystal structures of inclusion compounds of urea with tetraalkylammonium bicarbonates." Journal of Inclusion Phenomena and Molecular Recognition in Chemistry 23, no. 3 (1995): 233–44. http://dx.doi.org/10.1007/bf00709581.

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Couzi, Michel, François Guillaume, and Kenneth D. M. Harris. "A phenomenological model for structural phase transitions in incommensurate alkane/urea inclusion compounds." Royal Society Open Science 5, no. 6 (June 2018): 180058. http://dx.doi.org/10.1098/rsos.180058.

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n -Alkane/urea inclusion compounds are crystalline materials in which n -alkane ‘guest’ molecules are located within parallel one-dimensional ‘host’ tunnels formed by a helical hydrogen-bonded arrangement of urea molecules. The periodic repeat distance of the guest molecules along the host tunnels is incommensurate with the periodic repeat distance of the host substructure. The structural properties of the high-temperature phase of these materials (phase I), which exist at ambient temperature, are described by a (3 + 1)-dimensional superspace. Recent publications have suggested that, in the prototypical incommensurate composite systems, n -nonadecane/urea and n -hexadecane/urea, two low-temperature phases II and ‘III’ exist and that one or both of these phases are described by a (3 + 2)-dimensional superspace. We present a phenomenological model based on symmetry considerations and developed in the frame of a pseudo-spin–phonon coupling mechanism, which accounts for the mechanisms responsible for the I ↔ II ↔ ‘III’ phase sequence. With reference to published experimental data, we demonstrate that, in all phases of these incommensurate materials, the structural properties are described by (3 + 1)-dimensional superspace groups. Around the temperature of the II ↔ ‘III’ transition, the macroscopic properties of the material are not actually associated with a phase transition, but instead represent a ‘crossover’ between two regimes involving different couplings between relevant order parameters.

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Mustafa, Siti Fatimah Zaharah, Hasmerya Maarof, Mohammed Abu Naser, Hassan H. Abdallah, Ahmad Irfan, and Rashid Ahmed. "Behavioral pattern exploration of single guest, hexadecane-1,16-diol and hexadecane in urea inclusion compounds via molecular dynamics simulation." Journal of Theoretical and Computational Chemistry 15, no. 06 (September 2016): 1650047. http://dx.doi.org/10.1142/s0219633616500474.

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The urea inclusion compounds, a unique polar organic crystalline complex, are considered as a potential candidate for a molecular separator of long chain alkane molecule. A well-defined structure of the crystalline channel systems constructed from hydrogen bonding arrangement of the urea molecules, can be used to understand the fundamental aspects of the processes involving ions or molecules transportation. To do so, in our work, molecular dynamics approach is implemented to understand the behavioral pattern of the hexadecane-1,16-diol and hexadecane guests’ related to translational and rotational orientation along the urea tunnel. Our obtained results reveal that high interaction of hexadecane-1,16-diol with urea host molecules offers a restricted environment inside urea tunnel, resulting in slowing down the guest movement. Hexadecane guest system, on the contrary, exhibits lower interaction whereby the translational and rotational movement is faster. Moreover, as the distance increases (along [Formula: see text]-axis) in the urea tunnel, both guest systems favor a clockwise rotational orientation. Preference of the respected orientation indicates the influence of chiral urea tunnel on achiral guests that is clathrate inside the tunnel structure.

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Journal articles on the topic 'Urea hosts'

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