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71.
Kovarik A Dadejova M Lim YK Chase MW Clarkson JJ Knapp S Leitch AR 《Annals of botany》2008,101(6):815-823
Background: The evolution and biology of rDNA have interested biologistsfor many years, in part, because of two intriguing processes:(1) nucleolar dominance and (2) sequence homogenization. Wereview patterns of evolution in rDNA in the angiosperm genusNicotiana to determine consequences of allopolyploidy on theseprocesses. Scope: Allopolyploid species of Nicotiana are ideal for studying rDNAevolution because phylogenetic reconstruction of DNA sequenceshas revealed patterns of species divergence and their parents.From these studies we also know that polyploids formed overwidely different timeframes (thousands to millions of years),enabling comparative and temporal studies of rDNA structure,activity and chromosomal distribution. In addition studies onsynthetic polyploids enable the consequences of de novo polyploidyon rDNA activity to be determined. Conclusions: We propose that rDNA epigenetic expression patterns establishedeven in F1 hybrids have a material influence on the likely patternsof divergence of rDNA. It is the active rDNA units that arevulnerable to homogenization, which probably acts to reducemutational load across the active array. Those rDNA units thatare epigenetically silenced may be less vulnerable to sequencehomogenization. Selection cannot act on these silenced genes,and they are likely to accumulate mutations and eventually beeliminated from the genome. It is likely that whole silencedarrays will be deleted in polyploids of 1 million years of ageand older. 相似文献
72.
The study was designed to examine the gender-related differences in maximum mechanical power output in various short-burst activities during growth. The subject sample consisted of four subgroups: 9 boys (14.11 +/- 0.6 yr), 9 boys (10.67 +/- 0.71 yr), 7 girls (14.29 +/- 0.49 yr), 7 girls (10.57 +/- 0.54 yr). We measured peak power (PP), mean power (MP), fatigue index (FI) during 30-s WAnT, squat jump height (SJH) and power (SJP), and counter movement jump height (CMJH) and power (CMJP), maximum speed over 20-metre distance (S20). Lactation concentration was measured in the 3rd and 5th minutes after the WAnT Ratio normalisation and ANCOVA were used to remove the influence of the differences in muscle (MM) and body mass (BM). Male adolescents had higher absolute values of PP (P < 0.05), MP (P < 0.05) than female. Ratio normalisation showed that boys had higher PP/BM (P < 0.05), PP/MM (P < 0.05), MP/BM (P < 0.05), MP/MM (P < 0.06) than girls. The ANCOVA adjustment for MM showed differences between genders in PP (P < 0.001), MP (P < 0.001), SJH (P < 0.05), SJP (P < 0.05) and CMJP (P < 0.001), whereas the ANCOVA adjustment for BM showed differences only in PP (P < 0.001), MP (P < 0.001). Prepubertal boys had higher absolute values only in SJP (P < 0.05). We concluded that variations in body composition could not be the only key to gender-related differences in power output in short-burst activities. 相似文献
73.
74.
Tercelj M Ales A Rott T Sever N Prodnik L Erzen J Primic-Zakelj M Rylander R 《Acta cytologica》2008,52(5):584-590
OBJECTIVE: To measure cell nuclei characteristics, previously reported to express probability for lung cancer, in subjects with different forms ofpulmonary disease and those without disease. STUDY DESIGN: Sputum and buccal cell samples were obtained from 846 patients without pulmonary disease, with nonmalignant disease, chronic obstructive pulmonary disease, asbestosis and lung cancer, stained for DNA, scanned by cytometer and scored. This was related to specificity and sensitivity for lung cancer. At score 4.5 sensitivity was 53.8% and specificity 70.9%. This score and higher were defined as high scores (HS) and used to compare groups with lung cancer and other pulmonary disease. RESULTS: Among subjects without disease, 21.1% had HS in sputum cells. Among those with nonmalignant pulmonary disease, 31.7% had HS, and among subjects with lung cancer, 53.8% had it. Repeated evaluations showed that about one third of those with HS on the first occasion were normal on repeat sampling. Among subjects without lung cancer, 33.8% of never-smokers had sputum cell HS compared to 22.7.2% among smokers. CONCLUSION: Results demonstrate that the DNA cellular characteristics on cytometry were more frequent among subjects with lung cancer but also among subjects with other pulmonary disease compared to subjects witbout pulmonary disease. 相似文献
75.
Abstract. Morphological (size and shape) and functional (growth, reproduction and phenology) attributes are used to characterize 42 annual species of Mediterranean grasslands according to their strategy. Principal component analysis of the matrix of 42 species x 9 attributes shows that the main trend of variation is related to plant size. Larger species have larger seeds, lower relative growth rates and lower reproductive output. The second and third trends of variation are related to plant shape. Ordination of species shows differences in shape between taxa and growth forms (grasses, legumes, forbs). The relative abundance of species with different attributes vary with the level of stress (water and nutrient availability) and disturbance (grazing and ploughing). Size is related to stress, with larger plants dominating in productive habitats and smaller ones in the most unproductive. Disturbance is related to shape and phenology, since grazing favours species with low canopies and ploughing favours species with shorter life cycles, that are usually small in size. Relations between plant attributes and habitat characteristics are examined within the more general framework of plant strategy theory. 相似文献
76.
D Stoiber P Kovarik S Cohney J A Johnston P Steinlein T Decker 《Journal of immunology (Baltimore, Md. : 1950)》1999,163(5):2640-2647
77.
Ales Tichopad Craig Roberts Igor Gembula Petr Hajek Anna Skoczynska Waleria Hryniewicz Karina Jahnz-Rozyk Roman Prymula Ivan Solovi? Vitězslav Kolek 《PloS one》2013,8(8)
We estimate and describe the incidence rates, mortality, and cost of CAP (community-acquired pneumonia), in both inpatient and outpatient settings, in the Czech Republic (CZ), Slovakia (SK), Poland (PL), and Hungary (HU). A retrospective analysis was conducted on administrative data from the health ministry and insurance reimbursement claims with a primary diagnosis of pneumonia in 2009 to determine hospitalization rates, costs, and mortality in adults ≥50 years of age. Patient chart reviews were conducted to estimate the number of outpatient cases. Among all adults ≥50 years, the incidence of hospitalized CAP per 100,000 person years was: 456.6 (CZ), 504.6 (SK), 363.9 (PL), and 845.3 (HU). The average fatality rate for all adults ≥50 is 19.1%, and for each country; 21.7% (CZ), 20.9% (SK), 18.6% (PL), 17.8% (HU). Incidence, fatality, and likelihood of hospitalization increased with advancing age. Total healthcare costs of CAP in EUR was 12,579,543 (CZ); 9,160,774 (SK); 22,409,085 (PL); and 18,298,449 (HU); with hospitalization representing over 90% of the direct costs of treatment. The burden of CAP increases with advancing age in four CEE countries, with hospitalizations driving the costs of CAP upwards in the elderly population. Mortality rates are generally higher than reported in Western EU countries. 相似文献
78.
Ales Cvekl Kv ta Horsk Karel ebesta Ivan Rosenberg Antoní n Holý 《Biocatalysis and Biotransformation》1988,1(4):275-281
The effect of divalent Mg2+ and Mn2+ cations on the elongation of ApU, UpA and their 3'-O- and 5'-O-phosphonylmethyl analogues by RNA polymerase holoenzyme to the corresponding trinucleo-tides on a poly(dA-dT) template was investigated. In contrast to Mgz+ ions, Mn2+ ions enhance abortive trinucleotide synthesis. This effect is more pronounced with phosphonylmethyl analogues. The core enzyme cannot catalyze the elongation of either (2'-5') UpA or phosphonylmethyl analogues. The localization of the divalent cation activator, as well as the role of the σ subunit at the catalytic centre of the holoenzyme, is discussed. 相似文献
79.
80.
J. -Y. Fann A. Kovarik V. Hemleben N. I. Tsirekidze T. G. Beridze 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(6-7):1068-1073
Highly repeated satellite DNA (stDNA) of citric plants was characterized by cloning and sequencing 10–14 repeats of each plant
(Citrus limon, C. sinensis, C. ichangensis, Poncirus trifoliata). The monomers are mostly 181 bp in length with a GC-content between 60% and 68% (significantly higher than the average GC-content
of the citrus group genomes). Similarity among the repeats indicates that they belong to a satellite family that underwent
species-specific modifications, which are reflected in the phylogenetic relationships. Curvature provoked by dA-stretches
of the repeats analyzed by gel shifts revealed structural conservation, even though the nucleotide sequences vary among species,
thereby probably supporting the heterochromatic structure of stDNA. We show that the species-specific modification of the
satellite consensus involves changes in the position and number of dA tracts. The molecule shapes of satellite oligomeres
predicted by computer modelling indicate a superhelical structure of the tandem repeats which is in a good agreement with
the satellite sequence dendrogram. The contribution of DNA bending elements to the evolution of plant satellite repeats is
discussed.
Received: 27 November 2000 / Accepted: 12 January 2001 相似文献