Performance of renin assays in selecting fludrocortisone dose in children with adrenal disorders.

Children with salt-wasting adrenal insufficiency are managed with glucocorticoid and mineralocorticoid replacement. Measurement of renin activity or concentration alongside blood electrolyte levels is used to monitor the adequacy of mineralocorticoid replacement. Our unit changed from using renin activity to renin concentration and carried out a service review to assess whether this influenced decision-making for fludrocortisone dosing. In total, 50 measurements of plasma renin activity and 50 of renin concentration were analysed on separate cohorts before and after the assay change, with values standardised to multiples of the upper limit of normal (MoU) to allow comparison between assays. We were more likely to increase the fludrocortisone dose for a raised renin concentration than a raised renin activity. The renin concentration MoU was more strongly related to plasma sodium (negatively) and 17α-hydroxyprogesterone (17α-OHP) (positively) than the renin activity MoU. Using a MoU cut-off of 1.5, a decision to increase the dose of fludrocortisone was more likely to be made when using the renin concentration assay compared with the activity assay. Using a cut-off of 40 nmol/L for 17α-OHP, a decision not to change the fludrocortisone dose when 17α-OHP was <40 was more likely when using the renin concentration assay. For both assays, a plasma sodium <140 mmol/L was more likely to lead to a fludrocortisone dose increase, and most likely for the renin concentration assay. Overall, the decision to adjust fludrocortisone dose in this cohort of children with adrenal insufficiency was better supported by the biochemical parameters when based on renin concentration results and clinical status.

Informal peer-assisted learning amongst medical students: A qualitative perspective.

PURPOSE: Peer-assisted learning (PAL) can occur informally as part of a medical programme and complements the formal curriculum. However, little is known about the mechanisms and processes of how informal peer-assisted learning (IPAL) is enacted. MATERIALS AND METHODS: This paper presents data from an ethnographic and semi-structured interview study with Year 1 and 2 undergraduate medical students at a UK university. RESULTS: Peers were observed assisting each other informally: a process that developed as part of the integrated, group-based approach to undergraduate medical education at a UK university. IPAL took place both within and outside of formal teaching sessions and included explanation/clarification of particular points, sharing resources, guiding pronunciation and demonstrating skills. Students placed a high value on IPAL and believed that it was beneficial. When IPAL broke down, this led to negative emotions that presented obstacles to learning, such as resentment. CONCLUSIONS: IPAL is an important part of academic support for medical students, and this work shows both its scope, extending from formal to informal teaching, and how it is enacted. This understanding can help educators situate IPAL within student education.

Reducing Metabolic Bone Disease Burden in Intestinal Failure Children on Home Parenteral Nutrition.

Objective: To determine the prevalence of secondary hyperparathyroidism in a cohort of pediatric patients receiving home parenteral nutrition. Methods: For a service review, a population-based cohort of 37 pediatric intestinal failure patients receiving long-term parenteral nutrition that underwent serial biochemical monitoring during a study period of approximately 4 years were examined. Following the production of an algorithm, a follow-up audit was carried out (n = 33) after approximately 6 months. Results: Of the 37 patients examined in the initial service review, 22 (59%) were found to have an elevated parathyroid hormone (PTH) during the period of monitoring and 5 (14%) had a persistently elevated PTH. In the follow-up audit following the implementation of an algorithm, the number with elevated PTH reduced to 6 (18%) and no patients had persistently high levels. Conclusion: Elevated PTH is a common biochemical finding in pediatric intestinal failure patients receiving home parenteral nutrition and its presence should alert clinicians to the need to optimize nutritional parameters such as calcium to phosphate molar ratio and vitamin D status; failure to do so may increase the future burden of metabolic bone disease in such patients. We propose that an algorithm may help in this endeavor.

First stellar photons for an integrated optics discrete beam combiner at the William Herschel Telescope.

We present the first on-sky results of a four-telescope integrated optics discrete beam combiner (DBC) tested at the 4.2 m William Herschel Telescope. The device consists of a four-input pupil remapper followed by a DBC and a 23-output reformatter. The whole device was written monolithically in a single alumino-borosilicate substrate using ultrafast laser inscription. The device was operated at astronomical H-band (1.6 µm), and a deformable mirror along with a microlens array was used to inject stellar photons into the device. We report the measured visibility amplitudes and closure phases obtained on Vega and Altair that are retrieved using the calibrated transfer matrix of the device. While the coherence function can be reconstructed, the on-sky results show significant dispersion from the expected values. Based on the analysis of comparable simulations, we find that such dispersion is largely caused by the limited signal-to-noise ratio of our observations. This constitutes a first step toward an improved validation of the DBC as a possible beam combination scheme for long-baseline interferometry.

Compact, modular and in-plane AOSLO for high-resolution retinal imaging.

The adaptive optics scanning laser ophthalmoscope (AOSLO) was first developed in 2002 and since then the technology has been adopted in several laboratories around the world, for both clinical and psychophysical research. There have been a few major design implementations of the AOSLO. The first used on-axis tilted spherical mirrors in a planar arrangement, and the second minimized the build up of astigmatism present in the first design by using a non-planar arrangement. Other designs have avoided astigmatism by using custom-made toroidal mirrors or by using lenses on-axis, rather than mirrors. We present a new design implementation for an AOSLO that maintains a planar optical alignment without the build up astigmatism using compact, reconfigurable modules based on an Offner relay system. We additionally use an off-the-shelf digital oscilloscope for data capture and custom-written Python code for generating and analyzing the retinal images. This design results in a compact system that is simple to align and, being composed of modular relays, has the potential for additional components to be added. We show that this system maintains diffraction-limited image quality across the field of view and that cones are clearly resolved in the central retina. The modular relay design is generally applicable to any system requiring one or more components in the pupil conjugate plane. This is likely to be useful for any point-scanned system, such as a standard scanning laser ophthalmoscope or non-ophthalmic confocal imaging system.

The effect of Me2SO overexposure during cryopreservation on HOS TE85 and hMSC viability, growth and quality.

With the cell therapy industry continuing to grow, the ability to preserve clinical grade cells, including mesenchymal stem cells (MSCs), whilst retaining cell viability and function remains critical for the generation of off-the-shelf therapies. Cryopreservation of MSCs, using slow freezing, is an established process at lab scale. However, the cytotoxicity of cryoprotectants, like Me2SO, raises questions about the impact of prolonged cell exposure to cryoprotectant at temperatures >0 °C during processing of large cell batches for allogenic therapies prior to rapid cooling in a controlled rate freezer or in the clinic prior to administration. Here we show that exposure of human bone marrow derived MSCs to Me2SO for ≥1 h before freezing, or after thawing, degrades membrane integrity, short-term cell attachment efficiency and alters cell immunophenotype. After 2 h's exposure to Me2SO at 37 °C post-thaw, membrane integrity dropped to ∼70% and only ∼50% of cells retained the ability to adhere to tissue culture plastic. Furthermore, only 70% of the recovered MSCs retained an immunophenotype consistent with the ISCT minimal criteria after exposure. We also saw a similar loss of membrane integrity and attachment efficiency after exposing osteoblast (HOS TE85) cells to Me2SO before, and after, cryopreservation. Overall, these results show that freezing medium exposure is a critical determinant of product quality as process scale increases. Defining and reporting cell sensitivity to freezing medium exposure, both before and after cryopreservation, enables a fair judgement of how scalable a particular cryopreservation process can be, and consequently whether the therapy has commercial feasibility.

Assessing the stability of an ALPAO deformable mirror for feed-forward operation.

A deformable mirror (DM) is a mirror whose surface can be deformed in order to correct for optical aberrations. If a DM is used in a feed-forward operation (i.e. without feed-back, also known as open-loop) it is, among other requirements, crucial that a set of actuator commands repeatedly results in the same surface shape. We have tested an ALPAO DM against this criterion, by repeatedly applying a set of actuator commands over hours and monitoring the DM shape with an interferometer. We found that if the surface shape was held to shape A for several hours, then changed to a second shape, ℬ, the DM surface will drift from this new shape over the course of several hours. During this period the root-mean-square (RMS) of the deviation from shape ℬ can exceed 30% of the RMS of the difference between shapes A and ℬ. This can correspond to a surface deviation with RMS of several hundred nanometers, and would severely impact the resulting performance of an AO system using such a DM in a feed-forward operation. We have developed a model to correct for the time-varying surface shape in software by continuously adapting the actuator commands over the stabilization period. Application of the stabilisation procedure allows the surface to remain stable to within 4 nm RMS after a period of 6 minutes. We also provide a suggestion on how to improve the repeatability of surface response to different sets of actuator commands, which can be affected by the surface drift.

Amphipathic polymer-mediated uptake of trehalose for dimethyl sulfoxide-free human cell cryopreservation.

For stem cell therapy to become a routine reality, one of the major challenges to overcome is their storage and transportation. Currently this is achieved by cryopreserving cells utilising the cryoprotectant dimethyl sulfoxide (Me2SO). Me2SO is toxic to cells, leads to loss of cell functionality, and can produce severe side effects in patients. Potentially, cells could be frozen using the cryoprotectant trehalose if it could be delivered into the cells at a sufficient concentration. The novel amphipathic membrane permeabilising agent PP-50 has previously been shown to enhance trehalose uptake by erythrocytes, resulting in increased cryosurvival. Here, this work was extended to the nucleated human cell line SAOS-2. Using the optimum PP-50 concentration and media osmolarity, cell viability post-thaw was 60 ± 2%. In addition, the number of metabolically active cells 24h post-thaw, normalised to that before freezing, was found to be between 103 ± 4% and 91 ± 5%. This was found to be comparable to cells frozen using Me2SO. Although reduced (by 22 ± 2%, p=0.09), the doubling time was found not to be statistically different to the non-frozen control. This was in contrast to cells frozen using Me2SO, where the doubling time was significantly reduced (by 41 ± 4%, p=0.004). PP-50 mediated trehalose delivery into cells could represent an alternative cryopreservation protocol, suitable for research and therapeutic applications.

Expression of Aedes trypsin-modulating oostatic factor on the virion of TMV: A potential larvicide.

We report the engineering of the surface of the tobacco mosaic virus (TMV) virion with a mosquito decapeptide hormone, trypsin-modulating oostatic factor (TMOF). The TMV coat protein (CP) was fused to TMOF at the C terminus by using a read-through, leaky stop codon that facilitated expression of CP and chimeric CP-TMOF (20:1 ratio) that were coassembled into virus particles in infected Nicotiana tabacum. Plants that were infected with the hybrid TMV RNA accumulated TMOF to levels of 1.3% of total soluble protein. Infected tobacco leaf discs that were fed to Heliothis virescens fourth-instar larvae stunted their growth and inhibited trypsin and chymotrypsin activity in their midgut. Purified CP-TMOF virions fed to mosquito larvae stopped larval growth and caused death. Because TMV has a wide host range, expressing TMV-TMOF in plants can be used as a general method to protect them against agricultural insect pests and to control vector mosquitoes.