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1.
Steinberg H.; Das D. K.; Cerreta J. M.; Cantor J. D. 《Journal of applied physiology》1986,61(2):775-779
Hyperoxic injury results in an influx of polymorphonuclear leukocytes (PMN) into the lung. To better understand the role of the PMN in this injury, kinetic studies were used to assess the survival of PMNs in the circulation. The rate of deposition of PMNs in the lungs of rabbits exposed to hyperoxia was also examined. The half-lives (T1/2) of [3H]thymidine-labeled PMNs in the circulation in rabbits exposed to air or to 95% O2 for less than or equal to 48 h varied between 3.9 and 4.5 h. After 72 h of hyperoxic exposure, T1/2 fell to 2.2 h, the marginal and circulating PMN pool increased and 3H deposition in the lung increased 10-fold. Autoradiographs confirmed that [3H]thymidine was initially nuclear- and cellular-associated but, with time, [3H]thymidine dispersed throughout the lung, suggesting PMN disintegration. These PMN events seem to occur in the later phases of O2 toxicity, and because PMNs are an additional source of oxyradicals, they may further amplify oxidant injury. 相似文献
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The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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