Artículos de revistas:

1

Kanvah, Sriram y Gary B. Schuster. "One-electron oxidation of DNA: thymine versus guanine reactivity". Organic & Biomolecular Chemistry 8, n.º 6 (2010): 1340. http://dx.doi.org/10.1039/b922881k.

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2

Farooqui, Huma, Amarjeet Yadav y B. K. Pandey. "Hydroxyl Radical Reactivity with Cytosine and Thymine: A Computational Study". Journal of Physics: Conference Series 1849, n.º 1 (1 de marzo de 2021): 012029. http://dx.doi.org/10.1088/1742-6596/1849/1/012029.

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3

Nomura, A. y A. Okamoto. "Reactivity of Thymine Doublet in Single Strand DNA with Osmium Reagent". Nucleic Acids Symposium Series 52, n.º 1 (1 de septiembre de 2008): 433–34. http://dx.doi.org/10.1093/nass/nrn220.

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4

Wrigstedt, Pauli, Jari Kavakka, Sami Heikkinen, Martin Nieger, Minna Räisänen y Timo Repo. "The Reactivity of Thymine and Thymidine 5,6-Epoxides with Organometallic Reagents – A Route to Thymidine (6-4) Photoproduct Analogues". Journal of Organic Chemistry 81, n.º 9 (22 de abril de 2016): 3848–59. http://dx.doi.org/10.1021/acs.joc.6b00495.

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5

Tan, Rongri, Dongqi Wang, Lin Hu y Feng-Shou Zhang. "Probing the Reactivity of Hydroxyl Radicals toward Isolated Thymine Using Theoretical Calculations". International Journal of Quantum Chemistry 114, n.º 6 (10 de octubre de 2013): 367–74. http://dx.doi.org/10.1002/qua.24567.

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6

Nikolova, Valya y Boris Galabov. "Effects of structural variations on the hydrogen bond pairing between adenine derivatives and thymine". Macedonian Journal of Chemistry and Chemical Engineering 34, n.º 1 (26 de marzo de 2015): 159. http://dx.doi.org/10.20450/mjcce.2015.644.

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Abstract: The hydrogen bonding between substituted adenines and thymine was investigated by density functional theory computations at the B3LYP/6-311+G(2d,2p) level. The effect of 20 different polar substituents at position 8 in adenine was examined in detail. Three different theoretical parameters, reflecting the electrostatics at the atoms involved in hydrogen bonding, were applied. An excellent correlation between electrostatic potentials at the bonding atoms in the monomer adenines and interaction energies was derived (Eqn. 2). It can be employed in designing bioactive adenine derivatives that are able to bind with a finely adjusted strength to thymine bioreceptor sites. NBO and Hirshfeld atomic charges are found to be less successful as reactivity predictors in these interactions.

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7

Jumpathong, Watthanachai, Wan Chan, Koli Taghizadeh, I. Ramesh Babu y Peter C. Dedon. "Metabolic fate of endogenous molecular damage: Urinary glutathione conjugates of DNA-derived base propenals as markers of inflammation". Proceedings of the National Academy of Sciences 112, n.º 35 (17 de agosto de 2015): E4845—E4853. http://dx.doi.org/10.1073/pnas.1503945112.

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Although mechanistically linked to disease, cellular molecules damaged by endogenous processes have not emerged as significant biomarkers of inflammation and disease risk, due in part to poor understanding of their pharmacokinetic fate from tissue to excretion. Here, we use systematic metabolite profiling to define the fate of a common DNA oxidation product, base propenals, to discover such a biomarker. Based on known chemical reactivity and metabolism in liver cell extracts, 15 candidate metabolites were identified for liquid chromatography-coupled tandem mass spectrometry (LC-MS/MS) quantification in urine and bile of rats treated with thymine propenal (Tp). Analysis of urine revealed three metabolites (6% of Tp dose): thymine propenoate and two mercapturate derivatives of glutathione conjugates. Bile contained an additional four metabolites (22% of Tp dose): cysteinylglycine and cysteine derivatives of glutathione adducts. A bis-mercapturate was observed in urine of untreated rats and increased approximately three- to fourfold following CCl4-induced oxidative stress or treatment with the DNA-cleaving antitumor agent, bleomycin. Systematic metabolite profiling thus provides evidence for a metabolized DNA damage product as a candidate biomarker of inflammation and oxidative stress in humans.

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8

Li, Lei. "Using Organic Synthesis and Chemical Analysis to Understand the Photochemistry of Spore Photoproduct and Other Pyrimidine Dimers". Synlett 29, n.º 01 (30 de noviembre de 2017): 15–33. http://dx.doi.org/10.1055/s-0036-1590981.

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Pyrimidine dimerization is the dominant DNA photoreaction occurring in vitro and in vivo. Three types of dimers, cyclobutane pyrimidine dimers (CPDs), pyrimidine (6-4) pyrimidone photoproducts (6-4PPs), and the spore photoproduct (SP), are formed from the direct dimerization process; it is of significance to understand the photochemistry and photobiology of these dimers. Traditionally, pyrimidine dimerization was studied by using the natural pyrimidine residues thymine and cytosine, which share similar chemical structures and similar reactivity, making it sometimes less straightforward for one to identify the key pyrimidine residue that needs to be excited to trigger the photoreaction. We thus adopted synthetic chemistry to selectively modify the pyrimidine residues or to introduce pyrimidine analogs to the selected positions before UV irradiation is applied. By monitoring the subsequent outcomes from the photoreaction, we were able to gain unique mechanistic insights into the photochemistry of SP as well as of CPDs and 6-4PPs. Moreover, our approaches have resulted in several useful “tools” that can facilitate the understanding of lesion photobiology. Our results summarized in this account illustrate what organic synthesis/chemical analysis may allow us to achieve in future DNA lesion biology studies. 1 Introduction 2 Using the Deuterium Labeling Strategy to Understand SP Formation 3 Using Microcrystals to Reveal the Reaction Intermediates in SP Formation 4 Using a Phosphate Isostere to Understand the SP Structure 5 Synthesis of SP Phosphoramidite and SP Structural Studies 6 Using a Thymine Isostere to Understand CPD Formation 7 Using a Thymine Isostere to Understand 6-4PP Photoreaction 8 Understanding the Chemical Stability of SP 9 Understanding the Chemical Stability of 6-4PP10 Summary and Perspectives for Future Research

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9

Endová, Magdalena, Milena Masojídková, Miloš Buděšínský y Ivan Rosenberg. "3′,5′-O-Phosphonoalkylidene derivatives of 1-(2-deoxy-β-D-threo-pentofuranosyl)thymine: Synthesis and reactivity". Tetrahedron 54, n.º 37 (septiembre de 1998): 11187–208. http://dx.doi.org/10.1016/s0040-4020(98)00654-1.

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10

Ford, George P. y John D. Scribner. "Prediction of nucleoside-carcinogen reactivity. Alkylation of adenine, cytosine, guanine, and thymine and their deoxynucleosides by alkanediazonium ions". Chemical Research in Toxicology 3, n.º 3 (mayo de 1990): 219–30. http://dx.doi.org/10.1021/tx00015a006.

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11

Békési, Angéla, Eszter Holub, Hajnalka Laura Pálinkás y Beáta G. Vértessy. "Detection of Genomic Uracil Patterns". International Journal of Molecular Sciences 22, n.º 8 (9 de abril de 2021): 3902. http://dx.doi.org/10.3390/ijms22083902.

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The appearance of uracil in the deoxyuridine moiety of DNA is among the most frequently occurring genomic modifications. Three different routes can result in genomic uracil, two of which do not require specific enzymes: spontaneous cytosine deamination due to the inherent chemical reactivity of living cells, and thymine-replacing incorporation upon nucleotide pool imbalances. There is also an enzymatic pathway of cytosine deamination with multiple DNA (cytosine) deaminases involved in this process. In order to describe potential roles of genomic uracil, it is of key importance to utilize efficient uracil-DNA detection methods. In this review, we provide a comprehensive and critical assessment of currently available uracil detection methods with special focus on genome-wide mapping solutions. Recent developments in PCR-based and in situ detection as well as the quantitation of genomic uracil are also discussed.

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12

Zhachkina, Anna y Jeehiun K. Lee. "Uracil and Thymine Reactivity in the Gas Phase: The SN2 Reaction and Implications for Electron Delocalization in Leaving Groups". Journal of the American Chemical Society 131, n.º 51 (30 de diciembre de 2009): 18376–85. http://dx.doi.org/10.1021/ja906814d.

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13

ENDOVA, M., M. MASOJIDKOVA, M. BUDESINSKY y I. ROSENBERG. "ChemInform Abstract: 3′,5′-O-Phosphonoalkylidene Derivatives of 1-(2-Deoxy-β-D-threo-pentofuranosyl)thymine: Synthesis and Reactivity." ChemInform 29, n.º 50 (18 de junio de 2010): no. http://dx.doi.org/10.1002/chin.199850263.

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14

Haddad, Tomas, Joses Nathanael, Jonathan White y Uta Wille. "Oxidative Repair of Pyrimidine Cyclobutane Dimers by Nitrate Radicals (NO3•): A Kinetic and Computational Study". Chemistry 2, n.º 2 (9 de mayo de 2020): 453–69. http://dx.doi.org/10.3390/chemistry2020027.

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Pyrimidine cyclobutane dimers are hazardous DNA lesions formed upon exposure of DNA to UV light, which can be repaired through oxidative electron transfer (ET). Laser flash photolysis and computational studies were performed to explore the role of configuration and constitution at the cyclobutane ring on the oxidative repair process, using the nitrate radical (NO3•) as oxidant. The rate coefficients of 8–280 × 107 M−1 s−1 in acetonitrile revealed a very high reactivity of the cyclobutane dimers of N,N’-dimethylated uracil (DMU), thymine (DMT), and 6-methyluracil (DMU6-Me) towards NO3•, which likely proceeds via ET at N(1) as a major pathway. The overall rate of NO3• consumption was determined by (i) the redox potential, which was lower for the syn- than for the anti-configured dimers, and (ii) the accessibility of the reaction site for NO3•. In the trans dimers, both N(1) atoms could be approached from above and below the molecular plane, whereas in the cis dimers, only the convex side was readily accessible for NO3•. The higher reactivity of the DMT dimers compared with isomeric DMU dimers was due to the electron-donating methyl groups on the cyclobutane ring, which increased their susceptibility to oxidation. On the other hand, the approach of NO3• to the dimers of DMU6-Me was hindered by the methyl substituents adjacent to N(1), making these dimers the least reactive in this series.

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15

Cotton, Richard G. H. y R. Duncan Campbell. "Chemical reactivity of matched cytosine and thymine bases near mismatched and unmatched bases in a heteroduplex between DNA strands with multiple differences". Nucleic Acids Research 17, n.º 11 (1989): 4223–33. http://dx.doi.org/10.1093/nar/17.11.4223.

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16

Lin, Gengjie, Yajun Jian, Karl J. Dria, Eric C. Long y Lei Li. "Reactivity of Damaged Pyrimidines: DNA Cleavage via Hemiaminal Formation at the C4 Positions of the Saturated Thymine of Spore Photoproduct and Dihydrouridine". Journal of the American Chemical Society 136, n.º 37 (4 de septiembre de 2014): 12938–46. http://dx.doi.org/10.1021/ja505407p.

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17

Cotton, R. G., N. R. Rodrigues y R. D. Campbell. "Reactivity of cytosine and thymine in single-base-pair mismatches with hydroxylamine and osmium tetroxide and its application to the study of mutations." Proceedings of the National Academy of Sciences 85, n.º 12 (1 de junio de 1988): 4397–401. http://dx.doi.org/10.1073/pnas.85.12.4397.

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18

Pohl, Radek, Lubomír Rulíšek y Dominik Rejman. "The stability and reactivity of activated acryloylcarbamates as reagents for the synthesis of N-1 substituted thymine and uracil - an NMR and DFT study". Journal of Physical Organic Chemistry 24, n.º 5 (24 de agosto de 2010): 423–30. http://dx.doi.org/10.1002/poc.1775.

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19

Hoyos-Manchado, Rafael, Sergio Villa-Consuegra, Modesto Berraquero, Juan Jiménez y Víctor A. Tallada. "Mutational Analysis of N-Ethyl-N-Nitrosourea (ENU) in the Fission Yeast Schizosaccharomyces pombe". G3: Genes|Genomes|Genetics 10, n.º 3 (3 de enero de 2020): 917–23. http://dx.doi.org/10.1534/g3.119.400936.

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Forward genetics in model organisms has boosted our knowledge of the genetic bases of development, aging, and human diseases. In this experimental pipeline, it is crucial to start by inducing a large number of random mutations in the genome of the model organism to search for phenotypes of interest. Many chemical mutagens are used to this end because most of them display particular reactivity properties and act differently over DNA. Here we report the use of N-ethyl-N-nitrosourea (ENU) as a mutagen in the fission yeast Schizosaccharomyces pombe. As opposed to many other alkylating agents, ENU only induces an SN1-type reaction with a low s constant (s = 0.26), attacking preferentially O2 and O4 in thymine and O6 deoxyguanosine, leading to base substitutions rather than indels, which are extremely rare in its resulting mutagenic repertoire. Using ENU, we gathered a collection of 13 temperature-sensitive mutants and 80 auxotrophic mutants including two deleterious alleles of the human ortholog ATIC. Defective alleles of this gene cause AICA-ribosiduria, a severe genetic disease. In this screen, we also identified 13 aminoglycoside-resistance inactivating mutations in APH genes. Mutations reported here may be of interest for metabolism related diseases and antibiotic resistance research fields.

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20

Honda, Teruko, Hiroyuki Inagawa, Masakazu Fukushima, Akira Moriyama y Gen-Ichiro Soma. "Development and characterization of a monoclonal antibody with cross-reactivity towards uracil and thymine, and its potential use in screening patients treated with 5-fluorouracil for possible risks". Clinica Chimica Acta 322, n.º 1-2 (agosto de 2002): 59–66. http://dx.doi.org/10.1016/s0009-8981(02)00132-8.

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21

Karunakaran, Indumathi, Abiram Angamuthu y Praveena Gopalan. "Impact of N-(2-aminoethyl) Glycine Unit on Watson-Crick Base Pairs". Zeitschrift für Physikalische Chemie 233, n.º 3 (26 de marzo de 2019): 449–69. http://dx.doi.org/10.1515/zpch-2017-1095.

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Abstract We aim to understand the structure and stability of the backbone tailored Watson-Crick base pairs, Guanine-Cytosine (GC), Adenine-Thymine (AT) and Adenine-Uracil (AU) by incorporating N-(2-aminoethyl) glycine units (linked by amide bonds) at the purine and pyrimidine sites of the nucleobases. Density functional theory (DFT) is employed in which B3LYP/6-311++G∗∗ level of theory has been used to optimize all the structures. The peptide attached base pairs are compared with the natural deoxyribose nucleic acid (DNA)/ribonucleic acid (RNA) base pairs and the calculations are carried out in both the gas and solution phases. The structural propensities of the optimized base pairs are analyzed using base pair geometries, hydrogen bond distances and stabilization energies and, compared with the standard reference data. The structural parameters were found to correlate well with the available data. The addition of peptide chain at the back bone of the DNA/RNA base pairs results only with a minimal distortion and hence does not alter the structural configuration of the base pairs. Also enhanced stability of the base pairs is spotted while adding peptidic chain at the purine site rather than the pyrimidine site of the nucleobases. The stability of the complexes is further interpreted by considering the hydrogen bonded N–H stretching frequencies of the respective base pairs. The discrimination in the interaction energies observed in both gas and solution phases are resulted due to the existence of distinct lowest unoccupied molecular orbitals (LUMO) in the solution phase. The reactivity of the base pairs is also analyzed through the in-depth examinations on the highest occupied molecular orbital (HOMO)-LUMO orbitals.

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22

Fateev, Ilja V., Konstantin V. Antonov, Irina D. Konstantinova, Tatyana I. Muravyova, Frank Seela, Roman S. Esipov, Anatoly I. Miroshnikov y Igor A. Mikhailopulo. "The chemoenzymatic synthesis of clofarabine and related 2′-deoxyfluoroarabinosyl nucleosides: the electronic and stereochemical factors determining substrate recognition by E. coli nucleoside phosphorylases". Beilstein Journal of Organic Chemistry 10 (22 de julio de 2014): 1657–69. http://dx.doi.org/10.3762/bjoc.10.173.

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Two approaches to the synthesis of 2-chloro-9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)adenine (1, clofarabine) were studied. The first approach consists in the chemical synthesis of 2-deoxy-2-fluoro-α-D-arabinofuranose-1-phosphate (12a, 2FAra-1P) via three step conversion of 1,3,5-tri-O-benzoyl-2-deoxy-2-fluoro-α-D-arabinofuranose (9) into the phosphate 12a without isolation of intermediary products. Condensation of 12a with 2-chloroadenine catalyzed by the recombinant E. coli purine nucleoside phosphorylase (PNP) resulted in the formation of clofarabine in 67% yield. The reaction was also studied with a number of purine bases (2-aminoadenine and hypoxanthine), their analogues (5-aza-7-deazaguanine and 8-aza-7-deazahypoxanthine) and thymine. The results were compared with those of a similar reaction with α-D-arabinofuranose-1-phosphate (13a, Ara-1P). Differences of the reactivity of various substrates were analyzed by ab initio calculations in terms of the electronic structure (natural purines vs analogues) and stereochemical features (2FAra-1P vs Ara-1P) of the studied compounds to determine the substrate recognition by E. coli nucleoside phosphorylases. The second approach starts with the cascade one-pot enzymatic transformation of 2-deoxy-2-fluoro-D-arabinose into the phosphate 12a, followed by its condensation with 2-chloroadenine thereby affording clofarabine in ca. 48% yield in 24 h. The following recombinant E. coli enzymes catalyze the sequential conversion of 2-deoxy-2-fluoro-D-arabinose into the phosphate 12a: ribokinase (2-deoxy-2-fluoro-D-arabinofuranose-5-phosphate), phosphopentomutase (PPN; no 1,6-diphosphates of D-hexoses as co-factors required) (12a), and finally PNP. The substrate activities of D-arabinose, D-ribose and D-xylose in the similar cascade syntheses of the relevant 2-chloroadenine nucleosides were studied and compared with the activities of 2-deoxy-2-fluoro-D-arabinose. As expected, D-ribose exhibited the best substrate activity [90% yield of 2-chloroadenosine (8) in 30 min], D-arabinose reached an equilibrium at a concentration of ca. 1:1 of a starting base and the formed 2-chloro-9-(β-D-arabinofuranosyl)adenine (6) in 45 min, the formation of 2-chloro-9-(β-D-xylofuranosyl)adenine (7) proceeded very slowly attaining ca. 8% yield in 48 h.

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23

Johnston, Priscilla, Yuki Nishikami y Kei Saito. "Synthesis of thyminyl stilbazoles and their photo-reactivity". Photochem. Photobiol. Sci. 13, n.º 9 (2014): 1290–96. http://dx.doi.org/10.1039/c4pp00185k.

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24

Farr, A., A. Nelson y S. Hosier. "Characterization of an antigenic determinant preferentially expressed by type I epithelial cells in the murine thymus." Journal of Histochemistry & Cytochemistry 40, n.º 5 (mayo de 1992): 651–64. http://dx.doi.org/10.1177/40.5.1374092.

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A hamster monoclonal antibody (MAb), designated 8.1.1, was raised against murine thymic stromal cell lines and was found to react with cell surface molecules expressed by a morphologically distinct population of epithelial cells of the murine thymus comprising the subcapsular environment, cells investing vascular structures throughout the thymus, and some of the cellular elements in the medulla. The epithelial nature of the labeled cells was confirmed with immunoelectron microscopy. Reactivity with MAb 8.1.1 was associated with thymic epithelial cells in contact with basal laminae. Ontological studies of thymic tissue demonstrated that the epitope recognized by this MAb was expressed before Day 14 of gestation, although the restricted subcapsular and medullar expression of 8.1.1 was not apparent until sometime after birth. MAb 8.1.1 also reacted with a number of extra-thymic tissues, including lamina propria of gut, glomeruli and tubules in the kidney, mesothelia covering a number of organs, and the dermis and epidermis of skin. Within the epidermis, reactivity of MAb 8.1.1 was largely restricted to basal epithelial cells. Immunochemical analysis of 8.1.1 reactivity with detergent-soluble extracts of thymic stromal cell lines and thymus tissue indicated that detergent-soluble extracts of thymic stromal cell lines and thymus tissue indicated that the epitope recognized by this MAb was associated with a glycoprotein bearing terminal N-acetylglucosamine residues and possessing an Mr of approximately 36-38 KD under reducing or non-reducing conditions.

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25

Sun, Huabing, Marisa L. Taverna Porro y Marc M. Greenberg. "Independent Generation and Reactivity of Thymidine Radical Cations". Journal of Organic Chemistry 82, n.º 20 (10 de octubre de 2017): 11072–83. http://dx.doi.org/10.1021/acs.joc.7b02017.

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26

Farr, A., A. Nelson, J. Truex y S. Hosier. "Epithelial heterogeneity in the murine thymus: a cell surface glycoprotein expressed by subcapsular and medullary epithelium." Journal of Histochemistry & Cytochemistry 39, n.º 5 (mayo de 1991): 645–53. http://dx.doi.org/10.1177/39.5.2016514.

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A monoclonal antibody (MAb), G8.8, was raised against glycoconjugates isolated from a cloned line of murine medullary thymic epithelial cells. Flow cytometric analysis of the reactivity of this MAb with cultured thymic epithelium demonstrated that the ligand was expressed on the cell surface. Immunohistochemical examination of normal murine thymus revealed labeling of cells in the subcapsular and medullary areas. Immunoelectron microscopy revealed surface labeling restricted to cells possessing ultrastructural features of epithelium (desmosomes, tonofilaments, and cytoplasmic cysts). During thymic ontogeny, G8.8+ cells predominated in fetal development at the earliest time point examined (Day 14 of gestation). There was an expansion of the cortical epithelial component so that by Day 18 cortical and medullary compartments could be clearly distinguished. Immunoprecipitation of radioiodinated thymic stroma with MAb G8.8 detected a molecule with an apparent Mr of approximately 38 KD under non-reducing conditions. When reduced, the apparent Mr was slightly increased (42 KD). This MAb also exhibited reactivity with gut and epidermal epithelium and some tubular epithelium in the kidney, but did not react with epithelial parenchymal cells of the liver.

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27

Meylan, Françoise, Magda De Smedt, Georges Leclercq, Jean Plum, Olivier Leupin, Samuel Marguerat y Bernard Conrad. "Negative thymocyte selection to HERV-K18 superantigens in humans". Blood 105, n.º 11 (1 de junio de 2005): 4377–82. http://dx.doi.org/10.1182/blood-2004-07-2596.

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Abstract An experimental system to explore central tolerance in humans is unavailable. However, the human endogenous retrovirus K-18 (HERV-K18) region on chromosome 1 provides an excellent model: HERV-K18 encodes a superantigen (SAg) stimulating Vβ7CD4 T cells that is implicated in type 1 diabetes and Epstein-Barr virus persistence. In this study, we have addressed thymic HERV-K18 SAg expression, the capacity of SAg to induce negative selection, and the consequences of this for peripheral tolerance compared with SAg reactivity. We demonstrate that thymic HERV-K18 SAg expression is constitutive and is restricted in time and space such that it can induce negative selection. We developed an in vitro assay capable of detecting negative human thymocyte selection by bacterial SAgs presented on extrathymic antigen-presenting cells (APCs). Using this assay, the HERV-K18 SAg is necessary and sufficient for negative selection of immature or semimature Vβ7CD4 thymocytes. Decreases of SAg reactive Vβ7CD4 T cells generated in the thymus predict low or absent SAg reactivity. Therefore, these results indicate that negative thymic selection to HERV-K18 SAgs constitutes a first checkpoint controlling peripheral tolerance compared with SAg reactivity. This study now offers a framework to dissect negative selection and its interplay with viral persistence and autoimmunity in humans.

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28

Kariv, I., R. R. Hardy y K. Hayakawa. "Selective enrichment of major histocompatibility complex class II-specific autoreactive T cells in the thymic Thy0 subset." Journal of Experimental Medicine 177, n.º 5 (1 de mayo de 1993): 1429–37. http://dx.doi.org/10.1084/jem.177.5.1429.

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We show here a unique enrichment of autoreactive T cells in the CD4+ mouse thymic subset, Thy0. A single- and 10-cell AMLR (autologous mixed leukocyte reaction) assay demonstrates that more than 30% (one cell per well) and almost all (10 cells per well) Thy0 cultures from normal mice exhibit reactivity specific to autologous cells, resulting in induction of interleukin 3 secretion. In contrast, no other mature thymic or splenic CD4+ T cell subsets showed such a high frequency. The majority of this AMLR reactivity in the Thy0 subset is accounted for by reactivity with self-major histocompatibility complex class II. Furthermore, antigenic selection in generating Thy0 subset is suggested by studies with T cell hybrids from a T cell receptor (TCR) V beta transgenic mouse line, 2B4 beta EH. TCR V-gene analysis of T cell hybrids revealed that those from Thy0, half of which responded to self-class II, consisted predominantly of cells that expressed endogenous TCR V beta s alone (without the transgene), unlike hybrids generated from peripheral naive T cells. Thus, we suggest that the presence of Thy0 results from selective stimulation of cells expressing TCR with sufficient affinity for autoantigens in the thymic CD4+ T cell repertoire.

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29

Salkova, E., M. Flajshans y C. Steinbach. "Immunohistochemical mapping of thymic microenvironment in sterlet (Acipenser ruthenus)". Veterinární Medicína 65, No. 7 (10 de julio de 2020): 301–8. http://dx.doi.org/10.17221/181/2019-vetmed.

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In this study, we describe the immunohistochemical characterisation of the thymus, the main lymphoid organ, in sturgeon. The wide range cytokeratin, vimentin, S-100 protein, LCA (CD45) and CD3 were selected as the immunohistochemical markers to map the thymus in juvenile sterlet (Acipenser ruthenus). The epithelial cells and Hassall’s corpuscles were labelled with a wide range cytokeratin. The fibroblasts and connective tissue within the thin fibrous capsule on the thymic surface expressed vimentin positivity. The stromal reticular cells were S-100 protein positive. The Leukocyte Common Antigen LCA (CD45) was negative on the thymic lymphocytes. The CD3 was negative on the thymic lymphocytes with cross-reactivity on the non-targeted structures. In conclusion, the commercially available antibodies against the wide range cytokeratin, vimentin and S-100 protein can be used to differentiate components of the sturgeon thymus, while the LCA (CD45) and CD3 application failed. We suggest that further studies are needed to generate fish specific antibodies.

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30

Loziiński, T. y K. L. Wierzchowski. "Mg2+ ions do not induce expansion of the melted DNA region in the open complex formed by Escherichia coli RNA polymerase at a cognate synthetic Pa promoter. A quantitative KMnO4 footprinting study." Acta Biochimica Polonica 48, n.º 2 (30 de junio de 2001): 495–510. http://dx.doi.org/10.18388/abp.2001_3933.

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Footprinting studies of prokaryotic open transcription complexes (RPO), based on oxidation of pyrimidine residues by KMnO4 and/or OsO4 at a single oxidant dose, have suggested that the extent of DNA melting in the transcription bubble region increases in the presence of Mg . In this work, quantitative KMnO4 footprinting in function of the oxidant dose of RPO, using Escherichia coli RNA polymerase (E(sigma)70) at a fully functional synthetic promoter Pa having -35 and -10 consensus hexamers, has been used to determine individual rate constants of oxidation of T residues in this region at 37degrees C in the absence of Mg2+ and in the presence of 10 mM MgCl2, and to evaluate therefrom the effect of Mg2+ on the extent of DNA melting. Population distributions of end-labeled DNA fragments corresponding to oxidized Ts were quantified and analyzed according to the single-hit kinetic model. Pseudo-first order reactivity rate constants, ki, thus obtained demonstrated that Mg2+ ions bound to RPO merely enhanced the reactivity of all 11 oxidizable thymines between the +3 and -11 promoter sites by a position-dependent factor: 3-4 for those located close to the transcription start point +1 in either DNA strand, and about 1.6 for those located more distantly therefrom. On the basis of these observations, we conclude that Mg2+ ions bound to RPO at Pa do not influence the length of the melted DNA region and propose that the higher reactivity of thymines results mainly from lower local repulsive electrostatic barriers to MnO4 diffusion around carboxylate binding sites in the catalytic center of RPO and promoter DNA phosphates.

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31

Longato, Bruno, Giuseppe Pilloni, Gian Maria Bonora y Benedetto Corain. "Reactivity of novel cis-platinum(II) complexes with thymidine derivatives". Journal of the Chemical Society, Chemical Communications, n.º 19 (1986): 1478. http://dx.doi.org/10.1039/c39860001478.

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32

Chen, Shih-Heng, Angela Pearson, Donald M. Coen y Shun-Hua Chen. "Failure of Thymidine Kinase-Negative Herpes Simplex Virus To Reactivate from Latency following Efficient Establishment". Journal of Virology 78, n.º 1 (1 de enero de 2004): 520–23. http://dx.doi.org/10.1128/jvi.78.1.520-523.2004.

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ABSTRACT Thymidine kinase-negative mutants of herpes simplex virus did not reactivate from latency in mouse trigeminal ganglia, even when their latent viral loads were comparable to those that permitted reactivation by wild-type virus. Thus, reduced establishment of latency does not suffice to account for the failure to reactivate.

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33

Roux, Etienne, Florence Dumont-Girard, Michel Starobinski, Claire-Anne Siegrist, Claudine Helg, Bernard Chapuis y Eddy Roosnek. "Recovery of immune reactivity after T-cell–depleted bone marrow transplantation depends on thymic activity". Blood 96, n.º 6 (15 de septiembre de 2000): 2299–303. http://dx.doi.org/10.1182/blood.v96.6.2299.

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Abstract To evaluate the importance of the thymus for the reconstitution of immunity in recipients of a T-cell–depleted bone marrow, we measured the appearance of CD4+CD45RA+RO−naive T cells (thymic rebound), restoration of the diversity of the T-cell–receptor (TCR) repertoire and the response to vaccinations with tetanus toxoid (TT). Repopulation by CD4+CD45RA+RO− thymic emigrants varied among patients, starting at approximately 6 months after transplantation. Young patients reconstituted swiftly, whereas in older patients, the recovery of normal numbers of naive CD4+ T cells could take several years. Restoration of TCR diversity was correlated with the number of naive CD4+CD45RA+RO− T cells. Moreover, the extent of the thymic rebound correlated with the patient's capacity to respond to vaccinations. Patients without a significant thymic rebound at the moment of vaccination (CD4+CD45RA+RO− T cells less than 30 μL) did not respond, or responded only marginally even after 3 boosts with TT. We conclude that during the first year after transplantation, the absence of an immune response is due mainly to the loss of an adequate T-cell repertoire. Restoration of the repertoire can come only from a thymic rebound that can be monitored by measuring the increase of CD4+CD45RA+RO−naive T cells. This will allow postponing revaccinations to a moment when the patient will be able to respond more effectively. This may be particularly useful in the elderly patient who, owing to low thymic activity, might not yet be able to respond 1 year after transplant when revaccinations are usually scheduled.

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34

Roux, Etienne, Florence Dumont-Girard, Michel Starobinski, Claire-Anne Siegrist, Claudine Helg, Bernard Chapuis y Eddy Roosnek. "Recovery of immune reactivity after T-cell–depleted bone marrow transplantation depends on thymic activity". Blood 96, n.º 6 (15 de septiembre de 2000): 2299–303. http://dx.doi.org/10.1182/blood.v96.6.2299.h8002299_2299_2303.

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To evaluate the importance of the thymus for the reconstitution of immunity in recipients of a T-cell–depleted bone marrow, we measured the appearance of CD4+CD45RA+RO−naive T cells (thymic rebound), restoration of the diversity of the T-cell–receptor (TCR) repertoire and the response to vaccinations with tetanus toxoid (TT). Repopulation by CD4+CD45RA+RO− thymic emigrants varied among patients, starting at approximately 6 months after transplantation. Young patients reconstituted swiftly, whereas in older patients, the recovery of normal numbers of naive CD4+ T cells could take several years. Restoration of TCR diversity was correlated with the number of naive CD4+CD45RA+RO− T cells. Moreover, the extent of the thymic rebound correlated with the patient's capacity to respond to vaccinations. Patients without a significant thymic rebound at the moment of vaccination (CD4+CD45RA+RO− T cells less than 30 μL) did not respond, or responded only marginally even after 3 boosts with TT. We conclude that during the first year after transplantation, the absence of an immune response is due mainly to the loss of an adequate T-cell repertoire. Restoration of the repertoire can come only from a thymic rebound that can be monitored by measuring the increase of CD4+CD45RA+RO−naive T cells. This will allow postponing revaccinations to a moment when the patient will be able to respond more effectively. This may be particularly useful in the elderly patient who, owing to low thymic activity, might not yet be able to respond 1 year after transplant when revaccinations are usually scheduled.

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35

Cui, Yongzhi, Haven Garber, Masahiro Onozawa, Haiying Qin, Terry J. Fry, Peter Aplan y Crystal L. Mackall. "T Cell Lymphoblastic Lymphoma Resulting From Expression of Self-Reactive TCRs During Early Thymopoiesis". Blood 118, n.º 21 (18 de noviembre de 2011): 2057. http://dx.doi.org/10.1182/blood.v118.21.2057.2057.

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Abstract Abstract 2057 Survivin has been considered a potential tumor antigen due to high expression in most cancers and limited expression in normal tissues. To explore the potential for survivin reactive TCRs to mediate antitumor effects in mice, we generated several founders of TCR transgenic (Tg) mice with specificity for the H-2b restricted immunodominant epitope of survivin. In survivin TCR Tg mice, survivin reactive T cells were predominantly CD8+ and mediated specific immune reactivity toward survivin peptide pulsed targets. Some antitumor reactivity was observed, but it was not potent, and the survivin reactive transgenic T cells were unable to mediate objective tumor regression of survivin bearing tumors in vivo. Surprisingly, spontaneous T cell acute lymphoblastic leukemia (T-ALL) was observed beginning at 4–6 months of age in both survivin TCR+Rag+/− and survivin TCR+Rag−/− mice. By one year of age, all mice had succumbed to T-cell ALL. The leukemic cells were CD3+, survivin TCR+, and CD8+ or CD4−/CD8−. Analysis of alpha gene rearrangements in tumor tissues revealed oligoclonality but the cells were malignant since they grew continuously in vitro without growth factors and induced tumors in C57BL/6 immunocompetent recipients. The occurrence of T-ALL in 3 founders suggests that the transgene itself, rather than insertional mutagenesis, is causative. We postulate that the survivin reactive TCR serves as an oncogene via recognition of survivin peptides within the thymus, leading to expansion of early thymic progenitors. In support of this, survivin itself is expressed in thymic tissue and premalignant survivin TCR Tg+ thymi show expanded frequencies and absolute numbers of CD4−CD8−CD44−CD25− thymocytes and increased BrdU incorporation within this subset compared to controls. Subsequent to the premalignant phase characterized by expansion of early thymic progenitors, surviving TCR Tg+ cells acquired NOTCH mutations and upregulated CD25, consistent with NOTCH signaling as a 2nd hit in this oncogenic process. At least one NOTCH1 mutation was found in all leukemias, with mutations in the PEST domain being most common (8/8), but 5' deletions (19/25) and mutations in the heterodimerization domain were also observed. Interestingly, T cell acute lymphoblastic leukemia with NOTCH mutations were also observed, albeit at reduced frequencies, in TCR Tg mice with specificity to WT1 and gp100. We propose a 2-hit model of oncogenesis for self-reactive TCR expression in the thymus. Early thymic expression of TCRs recognizing self antigens expressed in the thymus induces proliferation of early thymocytes, followed by acquisition of NOTCH mutations and ultimately lymphoblastic leukemia. We conclude that genetic engineering aimed at endowing hematopoietic or T lymphoid progenitors with the capacity to recognize tumor antigens expressed in the thymus could pose a risk for neoplasia, independent of insertional mutagenesis. Disclosures: No relevant conflicts of interest to declare.

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36

Dargél, Aroldo A., Ophelia Godin, Bruno Etain, Vânia Hirakata, Jean-Michel Azorin, Katia M’Bailara, Frank Bellivier et al. "Emotional reactivity, functioning, and C-reactive protein alterations in remitted bipolar patients: Clinical relevance of a dimensional approach". Australian & New Zealand Journal of Psychiatry 51, n.º 8 (4 de abril de 2017): 788–98. http://dx.doi.org/10.1177/0004867417691850.

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Objectives: Inter-episode mood instability has increasingly been considered in bipolar disorder. This study aimed to investigate emotional reactivity as a major dimension for better characterizing remitted bipolar patients with subthreshold mood symptoms and functional status. This study also aimed to investigate whether high-sensitivity C-reactive protein, a marker of low-grade inflammation, could be a biological marker of emotional dysregulation in bipolar disorder (BD). Methods: Cross-sectional study of 613 subjects who met Diagnostic and Statistical Manual of Mental Disorders–Fourth Edition criteria for BD recruited from the FondaMental Advanced Centers of Expertise in Bipolar Disorders cohort from 2009 to 2014. All patients had been in remission for at least 3 months before assessment. Patients were classified into three groups according to levels of emotional reactivity. Emotional reactivity was assessed by using the Multidimensional Assessment of Thymic States, and functional status was assessed by the Functioning Assessment Short Test. Clinical characteristics and blood sample were collected from all patients. Results: In total, 415 (68%) patients had abnormal emotional reactivity. Independent of potential confounders, including age, gender and subthreshold mood symptoms, serum levels of high-sensitivity C-reactive protein were significantly higher in patients with emotional hyper-reactivity (median = 4.0 mg/L, interquartile range = 2.7–5.6), and with emotional hypo-reactivity (median = 3.0 mg/L, interquartile range = 1–4) compared with patients with normal emotional reactivity (median = 0.95 mg/L, interquartile range = 0.4–1.9, p < 0.001). Patients with emotional hyper-reactivity showed significant cognitive functioning impairment ( p < 0.001). Conclusions: Emotional reactivity appears to be a relevant dimension for better characterizing remitted bipolar patients with subthreshold mood symptoms. Levels of high-sensitivity C-reactive protein may be an objective marker of emotional dysregulation in BD. Further studies are needed to confirm our findings.

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37

San Pedro, Joanna Maria N. y Marc M. Greenberg. "Photochemical Generation and Reactivity of the Major Hydroxyl Radical Adduct of Thymidine". Organic Letters 14, n.º 11 (22 de mayo de 2012): 2866–69. http://dx.doi.org/10.1021/ol301109z.

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38

Hemmers, Saskia, Michail Schizas, Elham Azizi, Stanislav Dikiy, Yi Zhong, Yongqiang Feng, Grégoire Altan-Bonnet y Alexander Y. Rudensky. "IL-2 production by self-reactive CD4 thymocytes scales regulatory T cell generation in the thymus". Journal of Experimental Medicine 216, n.º 11 (21 de agosto de 2019): 2466–78. http://dx.doi.org/10.1084/jem.20190993.

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Regulatory T (T reg) cells, a specialized subset of CD4+ T cells, are essential to prevent fatal autoimmunity. Expression of the T reg lineage-defining transcription factor Foxp3, and therefore their differentiation in the thymus, is dependent upon T cell receptor (TCR) and interleukin-2 (IL-2) signaling. Here, we report that the majority of IL-2–producing cells in the thymus are mature CD4 single-positive (CD4SP) thymocytes and that continuous IL-2 production sustained thymic T reg cell generation and control of systemic immune activation. Furthermore, single-cell RNA sequencing analysis of CD4 thymocyte subsets revealed that IL-2 was expressed in self-reactive CD4SP thymocytes, which also contain T reg precursor cells. Thus, our results suggest that the thymic T reg cell pool size is scaled by a key niche factor, IL-2, produced by self-reactive CD4SP thymocytes. This IL-2–dependent scaling of thymic T reg cell generation by overall self-reactivity of a mature post-selection thymic precursor pool may likely ensure adequate control of autoimmunity.

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39

Chen, Shun-Hua, W. James Cook, Kristie L. Grove y Donald M. Coen. "Human Thymidine Kinase Can Functionally Replace Herpes Simplex Virus Type 1 Thymidine Kinase for Viral Replication in Mouse Sensory Ganglia and Reactivation from Latency upon Explant". Journal of Virology 72, n.º 8 (1 de agosto de 1998): 6710–15. http://dx.doi.org/10.1128/jvi.72.8.6710-6715.1998.

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ABSTRACT Herpes simplex virus type 1 thymidine kinase exhibits a strikingly broad substrate specificity. It is capable of phosphorylating deoxythymidine and deoxyuridine as does human thymidine kinase, deoxycytidine as does human deoxycytidine kinase, the cytosolic kinase whose amino acid sequence it most closely resembles, and thymidylate as does human thymidylate kinase. Following peripheral inoculation of mice, viral thymidine kinase is ordinarily required for viral replication in ganglia and for reactivation from latency following ganglionic explant. To determine which activity of the viral kinase is important for replication and reactivation in mouse ganglia, recombinant viruses lacking viral thymidine kinase but expressing individual human kinases were constructed. Each recombinant virus expressed the appropriate kinase activity with early kinetics following infection of cultured cells. The virus expressing human thymidine kinase exhibited thymidine phosphorylation activity equivalent to ∼5% of that of wild-type virus in a quantitative plaque autoradiography assay. Nevertheless, it was competent for ganglionic replication and reactivation following corneal inoculation of mice. The virus expressing human thymidylate kinase was partially competent for these activities despite failing to express detectable thymidine kinase activity. The virus expressing human deoxycytidine kinase failed to replicate acutely in neurons or to reactivate from latency. Therefore, it appears that low levels of thymidine phosphorylation suffice to fulfill the role of the viral enzyme in ganglia and that this role can be partially fulfilled by thymidylate kinase activity alone.

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40

Takeoka, Yuichi, Shao-Yuan Chen, Richard L. Boyd, Koichi Tsuneyama, Nobuhisa Taguchi, Shinji Morita, Hisashi Yago et al. "A Comparative Analysis of the Murine Thymic Microenvironment in Normal, Autoimmune, and Immunodeficiency States". Developmental Immunology 5, n.º 2 (1997): 79–89. http://dx.doi.org/10.1155/1997/69270.

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It is widely accepted that the thymic microenvironment regulates normal thymopoiesis through a highly coordinated and complex series of cellular and cytokine interactions. A direct corollary of this is that abnormalities within the microenvironment could be of etiologic significance in T-cell-based diseases. Our laboratory has developed a large panel of monoclonal antibodies (mAbs) that react specifically with epithelial or nonepithelial markers in the thymus. We have taken advantage of these reagents to characterize the thymic microenvironment of several genetic strains of mice, including BALB/cJ, C57BL/6J, NZB/BlnJ, SM/J, NOD/Ltz, NOD/Ltz-scid/sz, C57BL/6J-Hcphme/Hcphme, and ALY/NscJcl-aly/alymice, and littermate control animals. We report herein that control mice, including strains of several backgrounds, have a very consistent phenotypic profile with this panel of monoclonal antibodies, including reactivity with thymic epithelial cells in the cortex, the medulla and the corticomedullary junction, and the extracellular matrix. In contrast, the disease-prone strains studied have unique, abnormal staining of thymic cortex and medulla at both the structural and cellular levels. These phenotypic data suggest that abnormalities in interactions between developing thymocytes and stromal cells characterize disease-prone mice.

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41

Chen, M. C., A. T. Lee, W. E. Karnes, D. Avedian, M. Martin, J. M. Sorvillo y A. H. Soll. "Paracrine control of gastric epithelial cell growth in culture by transforming growth factor-alpha". American Journal of Physiology-Gastrointestinal and Liver Physiology 264, n.º 2 (1 de febrero de 1993): G390—G396. http://dx.doi.org/10.1152/ajpgi.1993.264.2.g390.

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Studying primary cultures of replicating canine oxyntic mucosal cells, we found evidence for modulation of cell growth by endogenous factors. [3H]thymidine incorporation into DNA was rapid with cells cultured in medium free of serum or added growth factors, and growth rates of these cultures were markedly dependent on plating density, indicating mitogenic control by soluble endogenous growth factors. Data indicated that endogenous transforming growth factor-alpha (TGF-alpha) exerted mitogenic control under the following conditions. 1) TGF-alpha was detected in the cultured cells by radioimmunoassay and immunohistochemistry. 2) TGF-alpha-like immunoreactivity and receptor reactivity were present in the medium in concentrations sufficient to exert mitogenic control. 3) Receptors for TGF-alpha and epidermal growth factor (EGF) were present in the cultures. 4) Immunoabsorption by a TGF-alpha-specific antisera reduced [3H]thymidine incorporation. TGF-alpha was localized to parietal cells by immunohistochemistry and cell separation. In contrast, combined [3H]thymidine autoradiography and immunohistochemistry with anti-TGF-alpha did not detect TGF-alpha in dividing cells. We conclude that parietal cell TGF-alpha exerts paracrine control of mucosal cell growth in vitro, and we speculate that this is an important paracrine mechanism in vivo.

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42

Griffiths, Anthony, Shun-Hua Chen, Brian C. Horsburgh y Donald M. Coen. "Translational Compensation of a Frameshift Mutation Affecting Herpes Simplex Virus Thymidine Kinase Is Sufficient To Permit Reactivation from Latency". Journal of Virology 77, n.º 8 (15 de abril de 2003): 4703–9. http://dx.doi.org/10.1128/jvi.77.8.4703-4709.2003.

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ABSTRACT Herpes simplex virus thymidine kinase is important for reactivation of virus from its latent state and is a target for the antiviral drug acyclovir. Most acyclovir-resistant isolates have mutations in the thymidine kinase gene; however, how these mutations confer clinically relevant resistance is unclear. Reactivation from explanted mouse ganglia was previously observed with a patient-derived drug-resistant isolate carrying a single guanine insertion within a run of guanines in the thymidine kinase gene. Despite this mutation, low levels of active enzyme were synthesized following an unusual ribosomal frameshift. Here we report that a virus, generated from a pretherapy isolate from the same patient, engineered to lack thymidine kinase activity, was competent for reactivation. This suggested that the clinical isolate contains alleles of other genes that permit reactivation in the absence of thymidine kinase. Therefore, to establish whether thymidine kinase synthesized via a ribosomal frameshift was sufficient for reactivation under conditions where reactivation requires this enzyme, we introduced the mutation into the well-characterized strain KOS. This mutant virus reactivated from latency, albeit less efficiently than KOS. Plaque autoradiography revealed three phenotypes of reactivating viruses: uniformly low thymidine kinase activity, mixed high and low activity, and uniformly high activity. We generated a recombinant thymidine kinase-null virus from a reactivating virus expressing uniformly low activity. This virus did not reactivate, confirming that mutations in other genes that would influence reactivation had not arisen. Therefore, in strains that require thymidine kinase for reactivation from latency, low levels of enzyme synthesized via a ribosomal frameshift can suffice.

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43

Rombouts, Elwin J., Evert-Jan Wils, Irene Van Mourik, Nicolas Legrand, Hergen Spits y Jan J. Cornelissen. "Stem Cell Factor (SCF) Improves Thymopoiesis After Experimental Hematopoietic Stem Cell Transplantation In Both a Murine BMT Model and In “human Immune system” (HIS) Mice, Receiving a Human Stem Cell Graft." Blood 116, n.º 21 (19 de noviembre de 2010): 3725. http://dx.doi.org/10.1182/blood.v116.21.3725.3725.

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Abstract Abstract 3725 Deficient thymopoiesis, due to epithelial injury by chemo- and/or radiotherapy, age-associated thymic involution and by graft-versus-host disease, is an important determinant of the impaired immune competence following allogeneic transplantation. Therefore, strategies to improve thymopoiesis are considered pivotal to improve T cell recovery and immune competence after transplantation. As SCF is a cytokine produced by thymic stroma and its receptor, c-kit, is expressed by the earliest thymocytes, we evaluated whether SCF administration would improve thymic recovery following stem cell transplantation in immuno-deficient mice receiving: (1) a T-cell depleted bone marrow (BM) graft of congenic mice, or (2) a CD34+CD38low-selected xenogenic hematopoietic stem cell (HSC) graft of human fetal liver origin (HIS) mice model). In the mouse-mouse model, 10–12 week old rag-1−/− mice were 3 Gy irradiated (137Cs -source) and received 2×105 T-cell depleted C57Bl/6 (CD45.1) congeneic bone marrow cells intravenously. Recipient mice received either PBS or recombinat rat SCF (Amgen, USA, 100μg/kg per injection) by subcutaneous injection 3 times a week from day 1 until the end of the experiment. In this model, SCF enhanced thymopoiesis and peripheral T-cell recovery. BM lymphoid progenitor recovery was not affected. Median thymic cellularity increased from 0.9 in PBS- to 266 × 104/thymus in SCF-treated mice (p=0.05), which increase was similarly distributed over the thymocyte subsets of double negative (DN), double positive (DP), and CD4+, CD8+ single positive thymocytes. Next, we assessed whether SCF-induced improved thymic recovery also translated into improved T-cell recovery in the periphery. Absolute numbers of donor-derived newly developed CD4+ and CD8+ T-cells were quantified in peripheral blood, spleen and lymph nodes at weeks 4 and 6 post-transplantation. T-cell numbers were low at 4 weeks after transplantation and did not differ between PBS or SCF treated animals. However, at 6 weeks T-cell numbers were significantly increased in spleen and lymph nodes of SCF treated animals (p<0.05). Next, we studied the effect of recombinant human (rh) SCF in our HIS mouse model. In short, newborn (days 3–7) Rag-2−/−gc−/− mice were 3.5 Gy irradiated and transplanted with 5–10 × 104 CD34+CD38low human fetal liver (FL) cells intra-hepatically. CD34+CD38low cells were isolated via a two step procedure. CD34+− FL cells were isolated using a CD34 human progenitor cell-isolation kit and further sorted as CD38low using a FACS Aria (BD biosciences). In HIS mice, PBS or rhSCF (Amgen, USA) 100μg/kg per injection) was administered intraperitoneally (i.p.) 3 times weekly as of day 14 following transplantation. Similar to the murine BMT model, a higher thymic cellularity was observed in SCF treated mice (Fig. 1) in the HIS model. DN and early DP thymocyte subsets were enhanced, albeit not significantly. In contrast, lateDP, CD4SP and CD8SP thymocyte subset recovery was significantly enhanced in thymi of SCF-treated HIS mice. As the HIS model remains a hybrid human–mouse system with limited cytokine cross reactivity and in which MHC-HLA mismatch compromises peripheral T-cell survival (Legrand et al J IMMUNOL 2009), the model did not allow us to study the effect of SCF on T-cells in the peripheral lymphoid organs. Figure 1: SCF improves thymic recovery following human SCT in an HIS mouse model. Newborn rag-2−/− γc−/− mice were 3.5 Gy irradiated and received 5–10 × 104 CD34+CD38low human fetal liver cells intra-hepatically and were treated with PBS or SCF. At indicated times post transplantation, thymi were harvested analyzed for the human thymocyte subsets: TN (CD3-CD4-CD8-), early DP (CD3- CD4+CD8+), late DP (CD3+CD4+CD8+), CD4SP and CD8SP (CD3+CD4-CD8+). Figure 1:. SCF improves thymic recovery following human SCT in an HIS mouse model. Newborn rag-2−/− γc−/− mice were 3.5 Gy irradiated and received 5–10 × 104 CD34+CD38low human fetal liver cells intra-hepatically and were treated with PBS or SCF. At indicated times post transplantation, thymi were harvested analyzed for the human thymocyte subsets: TN (CD3-CD4-CD8-), early DP (CD3- CD4+CD8+), late DP (CD3+CD4+CD8+), CD4SP and CD8SP (CD3+CD4-CD8+). Collectively, these results show that SCF may significantly improve post-transplant thymopoiesis after both experimental murine BMT and human fetal liver HSC transplantation in HIS mice. While peripheral T-cell recovery was significantly enhanced in the murine BMT model, it remains to be established whether improved human thymopoiesis will also translate into better peripheral T-cell recovery and enhanced immune competence towards opportunistic infections as well as a better recovery of regulatory T cells. These studies now set the stage for studying SCF, either alone or combined with other thymopoietic cytokines, in a larger pre-clinical animal model. Disclosures: No relevant conflicts of interest to declare.

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Chao, Dennis L, Miles P Davenport, Stephanie Forrest y Alan S Perelson. "The effects of thymic selection on the range of T cell cross-reactivity". European Journal of Immunology 35, n.º 12 (diciembre de 2005): 3452–59. http://dx.doi.org/10.1002/eji.200535098.

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Misiura, Konrad. "Synthesis and chemical and enzymatic reactivity of thymidine 3′-O- and 5′-O-phosphorofluoridothioates". Chemical Communications, n.º 4 (1998): 515–16. http://dx.doi.org/10.1039/a706636h.

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46

Aboud, Said, Charlotta Nilsson, Katarina Karlén, Mary Marovich, Britta Wahren, Eric Sandström, Hans Gaines, Gunnel Biberfeld y Karina Godoy-Ramirez. "Strong HIV-Specific CD4+ and CD8+ T-Lymphocyte Proliferative Responses in Healthy Individuals Immunized with an HIV-1 DNA Vaccine and Boosted with Recombinant Modified Vaccinia Virus Ankara Expressing HIV-1 Genes". Clinical and Vaccine Immunology 17, n.º 7 (12 de mayo de 2010): 1124–31. http://dx.doi.org/10.1128/cvi.00008-10.

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ABSTRACT We investigated HIV-1 vaccine-induced lymphoproliferative responses in healthy volunteers immunized intradermally or intramuscularly (with or without adjuvant granulocyte-macrophage colony-stimulating factor [GM-CSF] protein) with DNA expressing HIV-1 gag, env, rev, and rt at months 0, 1, and 3 using a Biojector and boosted at 9 months with modified vaccinia virus Ankara (MVA) expressing heterologous HIV-1 gag, env, and pol (HIV-MVA). Lymphoproliferative responses to aldrithiol-2 (AT-2)-inactivated-HIV-1 antigen were tested by a [3H]thymidine uptake assay and a flow-cytometric assay of specific cell-mediated immune response in activated whole blood (FASCIA-WB) 2 weeks after the HIV-MVA boost (n = 38). A FASCIA using peripheral blood mononuclear cells (FASCIA-PBMC) was also employed (n = 14). Thirty-five of 38 (92%) vaccinees were reactive by the [3H]thymidine uptake assay. Thirty-two of 38 (84%) vaccinees were reactive by the CD4+ T-cell FASCIA-WB, and 7 of 38 (18%) also exhibited CD8+ T-cell responses. There was strong correlation between the proliferative responses measured by the [3H]thymidine uptake assay and CD4+ T-cell FASCIA-WB (r = 0.68; P < 0.01). Fourteen vaccinees were analyzed using all three assays. Ten of 14 (71%) and 11/14 (79%) demonstrated CD4+ T-cell responses in FASCIA-WB and FASCIA-PBMC, respectively. CD8+ T-cell reactivity was observed in 3/14 (21%) and 7/14 (50%) using the FASCIA-WB and FASCIA-PBMC, respectively. All 14 were reactive by the [3H]thymidine uptake assay. The overall HIV-specific T-cell proliferative response in the vaccinees employing any of the assays was 100% (38/38). A standardized FASCIA-PBMC, which allows simultaneous phenotyping, may be an option to the [3H]thymidine uptake assay for assessment of vaccine-induced T-cell proliferation, especially in isotope-restricted settings.

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47

Alfadil, Sara, Kim Mi-Jeong, Marcos Iglesias Lozano, Byoung Chol Oh, W. P. Andrew Lee, Gerald Brandacher, Thomas Serworld y Giorgio Raimondi. "2558: Optimization of intra-thymic transplantation of donor-derived thymic epithelial cells to promote lasting regulation of anti-donor reactivity". Vascularized Composite Allotransplantation 3, n.º 1-2 (10 de octubre de 2016): 46. http://dx.doi.org/10.1080/23723505.2016.1234206.

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48

Hassler, Tobias, Emanuel Urmann, Sebastian Teschner, Christine Federle, Thamotharampillai Dileepan, Kilian Schober, Marc K. Jenkins, Dirk H. Busch, Maria Hinterberger y Ludger Klein. "Inventories of naive and tolerant mouse CD4 T cell repertoires reveal a hierarchy of deleted and diverted T cell receptors". Proceedings of the National Academy of Sciences 116, n.º 37 (26 de agosto de 2019): 18537–43. http://dx.doi.org/10.1073/pnas.1907615116.

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Deletion or Tregcell differentiation are alternative fates of autoreactive MHCII-restricted thymocytes. How these different modes of tolerance determine the size and composition of polyclonal cohorts of autoreactive T cells with shared specificity is poorly understood. We addressed how tolerance to a naturally expressed autoantigen of the central nervous system shapes the CD4 T cell repertoire. Specific cells in the tolerant peripheral repertoire either were Foxp3+or displayed anergy hallmarks and, surprisingly, were at least as frequent as in the nontolerant repertoire. Despite this apparent lack of deletional tolerance, repertoire inventories uncovered that some T cell receptors (TCRs) were lost from the CD4 T cell pool, whereas others mediated Tregcell differentiation. The antigen responsiveness of these TCRs supported an affinity model of central tolerance. Importantly, the contribution of different diverter TCRs to the nascent thymic Tregcell population reflected their antigen reactivity rather than their frequency among precursors. This reveals a multilayered TCR hierarchy in CD4 T cell tolerance that separates deleted and diverted TCRs and assures that the Tregcell compartment is filled with cells of maximal permissive antigen reactivity.

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Sommariva, Roberto, Louisa J. Kramer, Leigh R. Crilley, Mohammed S. Alam y William J. Bloss. "An instrument for in situ measurement of total ozone reactivity". Atmospheric Measurement Techniques 13, n.º 3 (2 de abril de 2020): 1655–70. http://dx.doi.org/10.5194/amt-13-1655-2020.

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Abstract. We present an instrument for the measurement of total ozone reactivity – the reciprocal of the chemical lifetime of ozone (O3) – in the troposphere. The Total Ozone Reactivity System (TORS) was developed with the objective to study the role of biogenic volatile organic compounds (BVOCs) as chemical sinks of tropospheric ozone. The instrument was extensively characterized and tested in the laboratory using individual BVOCs and small plants (lemon thyme, Thymus citriodorus) in a Teflon bag and proved able to measure reactivities corresponding to >4.5×10-5 s−1 (at 5 min averaging time), with an estimated total uncertainty of ∼32%. Such reactivities correspond to >20 ppb of α-pinene or >150 ppb of isoprene in isolation – larger than typical ambient levels but observable in environmental chamber and enclosure experiments as well as in BVOC-rich environments. The functionality of TORS was demonstrated in quasi-ambient conditions with a deployment in a horticultural glasshouse containing a range of aromatic plants. The measurements of total ozone reactivity made in the glasshouse showed a clear diurnal pattern, following the emissions of BVOCs, and are consistent with mixing ratios of tens of parts per billion of monoterpenes and several parts per billion of sesquiterpenes.

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Freysdottir, Jona y Mary A. Ritter. "Antibodies to Human Thymic Epithelium Form Part of the Murine Autoreactive Repertoire". Developmental Immunology 8, n.º 2 (2001): 75–93. http://dx.doi.org/10.1155/2001/59678.

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Monoclonal antibody (mAb) MR6 recognises a 200 kDa glycoprotein, gp200-MR6, which is expressed at high levels on the surface of human thymic cortical epithelium. In order to produce further mAbs against the gp200-MR6 molecule, mice were immunised with purified human gp200-MR6, hybridomas produced and supernatants screened for MR6-like reactivity on human thymic sections. Surprisingly this conventional hybridoma technique failed to produce stable hybridoma cells producing MR6-like antibodies. However, antibodies with specificitie other than MR6-like were obtained. Three such antibodies (1B2, 3A3 and 4B3) were analysed further. Expression of 1B2-antigen, 3A3-antigen and 4B3-antigen was analysed on skin, tonsil and thymic sections, on cultured thymic epithelial cells (TEC), thymocytes and peripheral blood mononuclear cells (PBMC), and found to be expressed by both lymphocytes and epithelial cell populations. Furthermore, the antigens were also expressed on mouse thymic, epithelial cells. The regulation of expression of these antigens was analysed following mitogen or cytokine stimulation of PBMC and cultured TEC, respectively. Expression on T cells was clearly affected by mitogens that mimic activation through the T cell receptor and expression on cultured TEC was affected by T cell-derived cytokines. Thus, the shared epithelial- lymphocyte molecules identified in this study may play a role in the cross-talk between the developing thymocytes and their epithelial microenvironment. The production of mAbs with specificities other than that of purified gp200-MR6 indicates that a wide range of B cells with specificity for components of the human thymic microenvironment exist in the normal mouse. These may detect epitopes that are shared with common pathogens to which the animals are exposed. Alternatively, they may be autoreactive B cells that are normally silent in the absence of T cell help. This help may be provided by T cells specific for human gp200-MR6, or nonspecifically by polyclonal activation induced by the adjuvant.

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