Patchiness of ion-exchanged mica revealed by DNA binding dynamics at short length scales

The binding of double-stranded (ds) DNA to mica can be controlled through ion-exchanging the mica with divalent cations. Measurements of the end-to-end distance of linear DNA molecules discriminate whether the binding mechanism occurs through 2D surface equilibration or kinetic trapping. A range of linear dsDNA fragments have been used to investigate length dependences of binding. Mica, ion-exchanged with Ni(II) usually gives rise to kinetically trapped DNA molecules, however, short linear fragments (<800 bp) are seen to deviate from the expected behaviour. This indicates that ion-exchanged mica is heterogeneous, and contains patches or domains, separating different ionic species. These results correlate with imaging of dsDNA under aqueous buffer on Ni(II)-mica and indicate that binding domains are of the order of 100 nm in diameter. Shorter DNA fragments behave intermediate to the two extreme cases of 2D equilibration and kinetic trapping. Increasing the incubation time of Ni(II) on mica, from minutes to hours, brings the conformations of the shorter DNA fragments closer to the theoretical value for kinetic trapping, indicating that long timescale kinetics play a role in ion-exchange. X-ray photoelectron spectroscopy (XPS) was used to confirm that the relative abundance of Ni(II) ions on the mica surface increases with time. These findings can be used to enhance spatial control of binding of DNA to inorganic surfaces with a view to patterning high densities arrays.

Feasibility of catheter-based renal nerve ablation and effects on sympathetic nerve activity and blood pressure in patients with end-stage renal disease

BACKGROUND AND OBJECTIVES

Sympathetic activation is a hallmark of ESRD and adversely affects cardiovascular prognosis. Efferent sympathetic outflow and afferent neural signalling from the failing native kidneys are key mediators and can be targeted by renal denervation (RDN). Whether this is feasible and effective in ESRD is not known.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

In an initial safety and proof-of-concept study we attempted to perform RDN in 12 patients with ESRD and uncontrolled blood pressure (BP). Standardized BP measurements were obtained in all patients on dialysis free days at baseline and follow up. Measures of renal noradrenaline spillover and muscle sympathetic nerve activity were available from 5 patients at baseline and from 2 patients at 12 month follow up and beyond.

RESULTS

Average office BP was 170.8 ± 16.9/89.2 ± 12.1 mmHg despite the use of 3.8 ± 1.4 antihypertensive drugs. All 5 patients in whom muscle sympathetic nerve activity and noradrenaline spillover was assessed at baseline displayed substantially elevated levels. Three out of 12 patients could not undergo RDN due to atrophic renal arteries. Compared to baseline, office systolic BP was significantly reduced at 3, 6, and 12 months after RDN (from 166 ± 16.0 to 148 ± 11, 150 ± 14, and 138 ± 17 mmHg, respectively), whereas no change was evident in the 3 non-treated patients. Sympathetic nerve activity was substantially reduced in 2 patients who underwent repeat assessment.

CONCLUSIONS

RDN is feasible in patients with ESRD and associated with a sustained reduction in systolic office BP. Atrophic renal arteries may pose a problem for application of this technology in some patients with ESRD.

Contextual risk, maternal parenting and adolescent externalizing behaviour problems: the role of emotion regulation

BACKGROUND

The objective of this study was to test if emotion regulation mediates the association between mothers' parenting and adolescents' externalizing behaviour problems (conduct problems and hyperactivity). The parenting dimensions were warmth, psychological control and behavioural control (measured with knowledge, monitoring and discipline). Adjustment was made for contextual risk (measured with the number of proximal adverse life events experienced), gender, age and English as an additional language.

METHOD

Data were from a UK community sample of adolescents aged 11-18 from a comprehensive school in a disadvantaged area.

RESULTS

At the multivariate level, none of the parenting variables predicted hyperactivity, which was associated only with difficulties in emotion regulation, contextual risk and English as a first language. The parenting variables predicting conduct problems at the multivariate level were warmth and knowledge. Knowledge did not predict emotion regulation. However, warmth predicted emotion regulation, which was negatively associated with conduct problems. Contextual risk was a significant predictor of both difficulties in emotion regulation and externalizing behaviour problems. Its effect on conduct problems was independent of parenting and was not via its association with difficulties in emotion regulation.

CONCLUSIONS

The findings add to the evidence for the importance of maternal warmth and contextual risk for both regulated emotion and regulated behaviour. The small maternal control effects on both emotion regulation and externalizing behaviour could suggest the importance of paternal control for adolescent outcomes.