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  • 1
    Publication Date: 2018-02-17
    Description: tRNA maturation and quality control are crucial for proper functioning of these transcripts in translation. In several organisms, defective tRNAs were shown to be tagged by poly(A) or CCACCA tails and subsequently degraded by 3'-exonucleases. In a deep-sequencing analysis of tRNA 3'-ends, we detected the CCACCA tag also in Escherichia coli . However, this tag closely resembles several 3'-trailers of tRNA precursors targeted for maturation and not for degradation. Here, we investigate the ability of two important exonucleases, RNase R and RNase T, to distinguish tRNA precursors with a native 3'-trailer from tRNAs with a CCACCA tag. Our results show that the degrading enzyme RNase R breaks down both tRNAs primed for degradation as well as precursor transcripts, indicating that it is a rather nonspecific RNase. RNase T, a main processing exonuclease involved in trimming of 3'-trailers, is very inefficient in converting the CCACCA-tagged tRNA into a mature transcript. Hence, while both RNases compete for trailer-containing tRNA precursors, the inability of RNase T to process CCACCA tails ensures that defective tRNAs cannot reenter the functional tRNA pool, representing a safeguard to avoid detrimental effects of tRNAs with erroneous integrity on protein synthesis. Furthermore, these data indicate that the RNase T-mediated end turnover of the CCA sequence represents a means to deliver a tRNA to a repeated quality control performed by the CCA-adding enzyme. Hence, originally described as a futile side reaction, the tRNA end turnover seems to fulfill an important function in the maintenance of the tRNA pool in the cell.
    Print ISSN: 1355-8382
    Electronic ISSN: 1469-9001
    Topics: Biology , Medicine
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  • 2
    Publication Date: 2012-08-28
    Description: Plants possess arrays of functionally diverse specialized metabolites, many of which are distributed taxonomically. Here, we describe the evolution of a class of substituted alpha-pyrone metabolites in Arabidopsis, which we have named arabidopyrones. The biosynthesis of arabidopyrones requires a cytochrome P450 enzyme (CYP84A4) to generate the catechol-substituted substrate for an extradiol ring-cleavage dioxygenase (AtLigB). Unlike other ring-cleavage-derived plant metabolites made from tyrosine, arabidopyrones are instead derived from phenylalanine through the early steps of phenylpropanoid metabolism. Whereas CYP84A4, an Arabidopsis-specific paralog of the lignin-biosynthetic enzyme CYP84A1, has neofunctionalized relative to its ancestor, AtLigB homologs are widespread among land plants and many bacteria. This study exemplifies the rapid evolution of a biochemical pathway formed by the addition of a new biological activity into an existing metabolic infrastructure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weng, Jing-Ke -- Li, Yi -- Mo, Huaping -- Chapple, Clint -- New York, N.Y. -- Science. 2012 Aug 24;337(6097):960-4. doi: 10.1126/science.1221614.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22923580" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Arabidopsis/enzymology/genetics/*metabolism ; Arabidopsis Proteins/chemistry/genetics/*metabolism ; Base Sequence ; Biosynthetic Pathways ; Catalytic Domain ; Cytochrome P-450 Enzyme System/chemistry/genetics/*metabolism ; Dioxygenases/genetics/metabolism ; Evolution, Molecular ; Gene Duplication ; Genome, Plant ; Models, Molecular ; Molecular Sequence Data ; Mutation ; Phenylalanine/metabolism ; Phylogeny ; Plant Stems/metabolism ; Plants, Genetically Modified ; Pyrones/chemistry/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    ISSN: 1432-1084
    Keywords: Key words: Contrast medium ; Iopentol ; Metrizoate ; Haemodynamics ; Left ventricular function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of the study was to evaluate and compare the hemodynamic and electrocardiographic effects following injection of the non-ionic, low- osmolar contrast medium iopentol (Imagopaque® 350, Nycomed Imaging AS, Oslo, Norway) and the ionic, hyper-osmolar contrast medium metrizoate meglumine-Na-Ca (Isopaque® Coronar 370, Nycomed Imaging AS, Oslo, Norway) when used for left ventricular angiography. The study was performed in a double-blind, randomized manner in 82 patients with severe coronary heart disease. The patients who received iopentol experienced less adverse events and subjective discomfort of lesser intensity than those who received metrizoate (p = 0.0001). Both contrast media induced a biphasic change in left ventricular (LV) systolic pressure, with an initial fall followed by a prolonged rise, but the alterations were statistically significantly more pronounced with metrizoate than with iopentol. The changes in LV end-diastolic pressure (p = 0.023), and LV negative dP/dt (p = 0.002) were significantly more pronounced with metrizoate than with iopentol. Cardiac output and heart rate increased more with metrizoate, while stroke volume was equally increased by both agents. A prolonged increase in the QT-interval, throughout the 10-min observation period, was seen only after injection of metrizoate (p = 0.0006 for comparison between contrast media). Conclusion: Iopentol was well tolerated and induced markedly less severe hemodynamic and electrocardiographic alterations than did metrizoate in patients with severe coronary heart disease.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Dopamine-β-hydroxylase (DβH) activity was measured in sera from ten healthy male students after 2 and 3 days fasting which is associated with increased circulating noradrenaline.2. Circulating DβH remained essentially unchanged throughout the fasting period, although ‘stress parameters’ like plasma glycerol and free fatty acid concentrations were elevated by a factor of about two from first to second and third day of fasting (P〈.0.01).3. Serum DβH activity is not a sensitive index of increased sympathoadrenal activity in fasting man.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1277-1279 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A screen printing method has been used to deposit superconducting films of Y-Ba-Cu-O materials on Al2O3 substrates. The electrical resistivity, microstructure, and adhesion of these films are highly sensitive to the post-printing heat treatment. Films heat treated at 950 °C and below are poorly adherent, whereas those annealed above 1000 °C undergo phase separation to Y2Cu2O5 and BaCuO2 and also react with the substrate. Nearly single phase, highly adherent, and smooth films showing a zero resistance state at 79 K have been synthesized by optimizing the annealing conditions.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0022-2828
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0022-2828
    Keywords: FFA ; Lipid droplets ; Microspheres ; Morphometric analysis ; Myocardial infarction ; NEFA ; Plasma fatty acids
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1971
    Keywords: Right ventricle ; Echocardiography ; Angiography ; Atrial septal defect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A comparative study of right ventricular (RV) function, assessed by echocardiography and angiography, undertaken in 20 patients, 10 of whom had atrial septal defects (ASDs) and 10 had various other heart diseases. All of the measured echocardiographic variables of RV size, apart from RV length, were larger in the patients with ASD. When assessed by multiple regression analysis, the RV M-mode dimension was an independent variable of RV angiographic end-diastolic volume (EDV) in patients without RV volume load (R=0.92,R 2=0.85,p〈0.001). In the patients with ASD, echocardiographic RV end-diastolic area was an independent variable of angiographic RVEDV (R=0.75,R 2=0.55,p〈0.05), whereas M-mode dimension had a weaker correlation (r=0.29). The agreement between RV ejection fraction (RVEF) obtained by echocardiography and angiography was moderate in both patient groups. However, fractional area change and fractional length change could not estimate RVEF better. Thus care should be taken to use single measurements and derivatives as the only parameters of RV size and function.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1439-0973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Pharmakokinetik von Tabletten mit einer Kombination von Sulphadiazin (SDZ) und Trimethoprim (TMP-Co-trimazin) und von Tabletten mit Sulphamethoxazol (SMZ) und TMP (Co-trimoxazol) wurde bei Patienten mit unterschiedlicher Nierenfunktion verglichen. Bei normaler Nierenfunktion gleicht die Pharmakokinetik von SMZ mehr der von TMP als bei Nierenfunktionsstörungen. Obwohl die Serumhalbwertzeit (t1/2) sowohl von aktivem wie vom Gesamt-SDZ derjenigen von TMP ähnlich bleibt, wird der t1/2 Wert des SMZ bei Nierenfunktionsstörungen um ein Mehrfaches höher als der von TMP. Das unveränderte SMZ behält annähernd dieselbe Eliminationsgeschwindigkeit bei eingeschränkter wie bei normaler Nierenfunktion. Folglich sammeln sich bei Co-trimoxazol SMZ Metaboliten an, die nur zur Toxizität von Co-trimoxazol beitragen können, während die Co-trimazin Komponenten bei Nierenfunktionsstörungen t1/2 Werte im gleichen Bereich behalten. Die Verteilungsvolumina von SDZ, SMZ oder TMP sind dieselben, unabhängig von der Nierenfunktion. Jedoch liegt das Verteilungsvolumen von SDZ näher bei dem, von TMP, das heißt, es ist größer als das von SMZ. Sowohl bei normaler als auch bei eingeschränkter Nierenfunktion wird mehr aktives SDZ als SMZ ausgeschieden. In vieler Hinsicht ist Co-trimazin neben seinen Vorteilen beim normalen Patienten eindeutig besser für Patienten mit Nierenfunktionsstörungen. Auf der Basis der pharmakokinetischen Eigenschaften werden Dosierungen vorgeschlagen, die unabhängig von der Nierenfunktion annähernd dieselben Plasmaspiegel erzielen.
    Notes: Summary The pharmacokinetics of tablets containing combinations of sulphadiazine (SDZ) and trimethoprim (TMP) (co-trimazine) and tablets with sulphamethoxazole (SMZ) and TMP (co-trimoxazole) were compared in patients with different renal functions. In normal renal function, SMZ is more similar to TMP than in renal impairment. In renal impairment although the serum half-life (t1/2) of both active and total SDZ remains similar to that of TMP, the t1/2 of total SMZ becomes several times higher than the t1/2 of TMP. The unchanged SMZ maintains approximately the same elimination velocity in reduced as in normal renal function. Consequently, for co-trimoxazole there is a buildup of SMZ metabolites which can only contribute to toxicity for co-trimoxazole, whereas the co-trimazine components have t1/2 values of the same order, also in renal dysfunction. The distribution volumes of SDZ, SMZ or TMP are the same regardless of renal function. However, the distribution volume of SDZ is closer to that of TMP, i. e. higher than the SMZ values. More active SDZ is excreted in the urine than SMZ both in normal and in reduced renal function. Thus co-trimazine, in addition to having some advantages in the normal individual, is in many respects distinctly more suitable in patients with renal functional impairment. On the basis of the pharmacokinetic properties, dosage schedules are suggested that will give approximately the same plasma levels regardless of renal function.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 137 (1987), S. 225-231 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A simulation of accretion of a string loop has been done. It shows that aspherical accretion is essential for large-scale loops. All configurations found in the distribution of galaxies, such as filaments, pancakes, bubbles, and voids, can be formed by the accretion of cosmic strings.
    Type of Medium: Electronic Resource
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