The Acute Effect of Fast and Slow Stepping Cadence on Regional Vascular Function.

The aim of this study was to determine if stepping cadence when controlling for total steps has a differential impact on regional vascular function. 16 young adults (21±2 years) performed fast (125 steps per min) and slow (80 steps per min) walking for a total of 3 000 steps on separate days. Doppler ultrasound was used to measure compliance, blood flow and shear rate of the common carotid artery and superficial femoral artery before walking and at 30 and 60 min after walking. Carotid compliance was significantly (p<0.05) elevated 60 min after fast (17.1±25.9%) and slow (24.1±27.3%) walking with no difference between cadences. Both fast and slow walking failed to increase femoral compliance, despite significant (p<0.05) dilation in the femoral artery that was observed at 30 (4.2±3.9%) and 60 min (3.9±5.4%) after fast walking. Consistent with this latter finding, femoral blood flow and shear rate were significantly (p<0.05) increased at 30 min after fast walking. These results indicate that a single bout of walking at a fast or slow stepping cadence increases compliance of large elastic arteries but has no acute effect on compliance of peripheral (leg) arteries.

Types, levels and patterns of low-copy DNA sequence divergence, and phylogenetic implications, for Gossypium genome types.

To explore types, levels and patterns of genetic divergence among diploid Gossypium (cotton) genomes, 780 cDNA, genomic DNA and simple sequence repeat (SSR) loci were re-sequenced in Gossypium herbaceum (A1 genome), G. arboreum (A2), G. raimondii (D5), G. trilobum (D8), G. sturtianum (C1) and an outgroup, Gossypioides kirkii. Divergence among these genomes ranged from 7.32 polymorphic base pairs per 100 between G. kirkii and G. herbaceum (A1) to only 1.44 between G. herbaceum (A1) and G. arboreum (A2). SSR loci are least conserved with 12.71 polymorphic base pairs and 3.77 polymorphic sites per 100 base pairs, whereas expressed sequence tags are most conserved with 3.96 polymorphic base pairs and 2.06 sites. SSR loci also exhibit the highest percentage of 'extended polymorphisms' (spanning multiple consecutive nucleotides). The A genome lineage was particularly rapidly evolving, with the D genome also showing accelerated evolution relative to the C genome. Unexpected asymmetry in mutation rates was found, with much more transition than transversion mutation in the D genome after its divergence from a common ancestor shared with the A genome. This large quantity of orthologous DNA sequence strongly supports a phylogeny in which A-C divergence is more recent than A-D divergence, a subject that is of much importance in view of A-D polyploid formation being key to the evolution of the most productive and finest-quality cottons. Loci that are monomorphic within A or D genome types, but polymorphic between genome types, may be of practical importance for identifying locus-specific DNA markers in tetraploid cottons including leading cultivars.