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Annemarie MM Vlaar Angela EP Bouwmans Marinus JPG van Kroonenburgh Werner H Mess Selma C Tromp Piet GWM Wuisman Alfons GH Kessels Ania Winogrodzka Wim EJ Weber 《BMC neurology》2007,7(1):28
Background
Parkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD. 相似文献4.
The identity of the histidine specific transfer RNA (tRNAHis) is largely determined by a unique guanosine residue at position −1. In eukaryotes and archaea, the tRNAHis guanylyltransferase (Thg1) catalyzes 3′-5′ addition of G to the 5′-terminus of tRNAHis. Here, we show that Thg1 also occurs in bacteria. We demonstrate in vitro Thg1 activity for recombinant enzymes from the two bacteria Bacillus thuringiensis and Myxococcus xanthus and provide a closer investigation of several archaeal Thg1. The reaction mechanism of prokaryotic Thg1 differs from eukaryotic enzymes, as it does not require ATP. Complementation of a yeast thg1 knockout strain with bacterial Thg1 verified in vivo activity and suggests a relaxed recognition of the discriminator base in bacteria. 相似文献
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Escherichia coli UvrD is an SF1A (superfamily 1 type A) helicase/translocase that functions in several DNA repair pathways. A UvrD monomer is a rapid and processive single-stranded DNA (ssDNA) translocase but is unable to unwind DNA processively in vitro. Based on data at saturating ATP (500?μM), we proposed a nonuniform stepping mechanism in which a UvrD monomer translocates with biased (3' to 5') directionality while hydrolyzing 1 ATP per DNA base translocated, but with a kinetic step size of 4-5?nt/step, suggesting that a pause occurs every 4-5?nt translocated. To further test this mechanism, we examined UvrD translocation over a range of lower ATP concentrations (10-500?μM ATP), using transient kinetic approaches. We find a constant ATP coupling stoichiometry of ~1 ATP/DNA base translocated even at the lowest ATP concentration examined (10?μM), indicating that ATP hydrolysis is tightly coupled to forward translocation of a UvrD monomer along ssDNA with little slippage or futile ATP hydrolysis during translocation. The translocation kinetic step size remains constant at 4-5?nt/step down to 50?μM ATP but increases to ~7?nt/step at 10?μM ATP. These results suggest that UvrD pauses more frequently during translocation at low ATP but with little futile ATP hydrolysis. 相似文献
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We have developed eight high-quality microsatellite DNA loci for the saltmarsh sharp-tailed sparrow and one additional locus with evidence of null alleles. In a sample of 250-350 individuals, the average number of alleles per locus was 14.7 and average observed heterozygosity was 0.80. These loci were tested in three additional species of emberizid sparrows, indicating that more than half of the loci could be useful in other sparrows. 相似文献
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Abstract. Woodland colonization on wetlands is considered to have a detrimental effect on their ecological value, even though detailed analysis of this process is lacking. This paper provides an evaluation of the ecological changes resulting from succession of poor fen (base‐poor mire) to willow wet woodland on Goss Moor NNR in Cornwall, UK. Different ages of willow carr were associated with eight understorey communities. During willow colonization, in the ground flora, there was a progressive decrease in poor fen species and an associated increase in woodland species, which appeared to be related to an increase in canopy cover and therefore shade. The most diverse community was found to be the most recent willow and was dominated by poor fen species. The oldest willow was the second most diverse and was associated with a reduction in poor fen species and an increase in woodland species. Architectural features were used successfully to assess the general condition and structure of willow. Tree height and DBH were identified as useful parameters to accurately assess willow age in the field. The implications of active intervention to remove willow in order to conserve the full range of communities within the hydrosere are discussed. 相似文献
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BŁAŻEJ BERKOWSKI CHRISTIAN KLUG 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2012,45(1):24-33
Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa. 相似文献
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Annemarie MM Vlaar Marinus JPG van Kroonenburgh Alfons GH Kessels Wim EJ Weber 《BMC neurology》2007,7(1):27