Use of the embedded peritoneal dialysis catheter.

Introduction The use of embedded peritoneal dialysis (PD) catheters is purported to offer numerous benefits over standard placement. However, the optimum period of embedment and the effect of prolonged embedment on subsequent catheter function remain unclear. Methods This retrospective observational study looked at adult patients undergoing embedded PD catheter insertion in a large tertiary referral centre in the UK. Possible predictors for catheter non-function at externalisation were investigated. These included patient factors (age, sex, diabetic status, body mass index, ethnicity, smoking status, previous surgery, estimated glomerular filtration rate), procedural factors (modality of surgery, concurrent surgical procedure), duration of catheter embedment and catheter damage at externalisation. Outcomes examined were proportion of catheters functioning after externalisation, futile placement rate, surgical reintervention rate, infectious complication rate and proportion of externalised catheters lost owing to malfunction. Results Sixty-six catheters were embedded and two-thirds (n=47, 63.6%) were externalised after a median embedment period of 39.4 weeks. Of these, 25 (53.2%) functioned on externalisation. Fourteen (63.6%) of the 22 non-functioning catheters were salvaged. The overall utilisation of PD was 34/47 (72.3%) and the futile placement rate was 12.1%. Over half of the externalised catheters (n=27, 57.4%) were lost directly as a result of catheter related complications, with a median survival time of 39.4 weeks. In adjusted analysis, increasing embedment duration was significantly predictive of catheter non-function at externalisation (adjusted odds ratio: 0.957, 95% confidence interval [CI]: 0.929-0.985, p=0.003) while subsequent catheter loss was highly dependent on catheter function at externalisation (hazard ratio: 0.258, 95% CI: 0.112-0.594, p=0.001). Conclusions Prolonged embedment of PD catheters is associated with a significantly higher likelihood of catheter dysfunction following externalisation, which is in turn associated with subsequent catheter loss. We have discontinued the use of this technique in our unit.

Openspritzer: an open hardware pressure ejection system for reliably delivering picolitre volumes.

The ability to reliably and precisely deliver picolitre volumes is an important component of biological research. Here we describe a high-performance, low-cost, open hardware pressure ejection system (Openspritzer), which can be constructed from off the shelf components. The device is capable of delivering minute doses of reagents to a wide range of biological and chemical systems. In this work, we characterise the performance of the device and compare it to a popular commercial system using two-photon fluorescence microscopy. We found that Openspritzer provides the same level of control over delivered reagent dose as the commercial system. Next, we demonstrate the utility of Openspritzer in a series of standard neurobiological applications. First, we used Openspritzer to deliver precise amounts of reagents to hippocampal neurons to elicit time- and dose-precise responses on neuronal voltage. Second, we used Openspritzer to deliver infectious viral and bacterial agents to living tissue. This included viral transfection of hippocampal interneurons with channelrhodopsin for the optogenetic manipulation of hippocampal circuitry with light. We anticipate that due to its high performance and low cost Openspritzer will be of interest to a broad range of researchers working in the life and physical sciences.

Probing the location of displayed cytochrome b562 on amyloid by scanning tunnelling microscopy.

Amyloid fibres displaying cytochrome b562 were probed using scanning tunnelling microscopy (STM) in vacuo. The cytochromes are electron transfer proteins containing a haem cofactor and could, in principle, mediate electron transfer between the tip and the gold substrate. If the core fibres were insulating and electron transfer within the 3D haem network was detected, then the electron transport properties of the fibre could be controlled by genetic engineering. Three kinds of STM images were obtained. At a low bias (<1.5 V) the fibres appeared as regions of low conductivity with no evidence of cytochrome mediated electron transfer. At a high bias, stable peaks in tunnelling current were observed for all three fibre species containing haem and one species of fibre that did not contain haem. In images of this kind, some of the current peaks were collinear and spaced around 10 nm apart over ranges longer than 100 nm, but background monomers complicate interpretation. Images of the third kind were rare (1 in 150 fibres); in these, fully conducting structures with the approximate dimensions of fibres were observed, suggesting the possibility of an intermittent conduction mechanism, for which a precedent exists in DNA. To test the conductivity, some fibres were immobilized with sputtered gold, and no evidence of conduction between the grains of gold was seen. In control experiments, a variation of monomeric cytochrome b562 was not detected by STM, which was attributed to low adhesion, whereas a monomeric multi-haem protein, GSU1996, was readily imaged. We conclude that the fibre superstructure may be intermittently conducting, that the cytochromes have been seen within the fibres and that they are too far apart for detectable current flow between sites to occur. We predict that GSU1996, being 10 nm long, is more likely to mediate successful electron transfer along the fibre as well as being more readily detectable when displayed from amyloid.