Mechanisms of modified LDL-induced pericyte loss and retinal injury in diabetic retinopathy

Aims/hypothesis: In previous studies we have shown that extravasated, modified LDL is associated with pericyte loss, an early feature of diabetic retinopathy (DR). Here we sought to determine detailed mechanisms of this LDLinduced pericyte loss.

Methods: Human retinal capillary pericytes (HRCP) were exposed to ‘highly-oxidised glycated’ LDL (HOG-LDL) (a model of extravasated and modified LDL) and to 4-hydroxynonenal or 7-ketocholesterol (components of oxidised LDL), or to native LDL for 1 to 24 h with or without 1 h of pretreatment with inhibitors of the following: (1) the scavenger receptor (polyinosinic acid); (2) oxidative stress (N-acetyl cysteine); (3) endoplasmic reticulum (ER) stress (4-phenyl butyric acid); and (4) mitochondrial dysfunction (cyclosporin A). Oxidative stress, ER stress, mitochondrial dysfunction, apoptosis and autophagy were assessed using techniques including western blotting, immunofluorescence, RT-PCR, flow cytometry and TUNEL assay. To assess the relevance of the results in vivo, immunohistochemistry was used to detect the ER stress chaperon, 78 kDa glucose-regulated protein, and the ER sensor, activating transcription factor 6, in retinas from a mouse model of DR that mimics exposure of the retina to elevated glucose and elevated LDL levels, and in retinas from human participants with and without diabetes and DR.

Results: Compared with native LDL, HOG-LDL activated oxidative and ER stress in HRCP, resulting in mitochondrial dysfunction, apoptosis and autophagy. In a mouse model of diabetes and hyperlipidaemia (vs mouse models of either condition alone), retinal ER stress was enhanced. ER stress was also enhanced in diabetic human retina and correlated with the severity of DR.

Conclusions/interpretation: Cell culture, animal, and human data suggest that oxidative stress and ER stress are induced by modified LDL, and are implicated in pericyte loss in DR.

Introduction Special Section on David Clarke's Archaeology: the Loss of Innocence 25 years after:with Simon Stoddart

Malone, C.A.T. and S.K.F. Stoddart, Special Section. Introduction. David Clarke's 'Archaeology: the loss of Innocence' (1973) 25 years after.

Selective loss of vascular smooth muscle cells in the retinal microcirculation of diabetic dogs

This study was undertaken to further characterise the fine structural changes occurring in the retinal circulation in early diabetes. The eyes of eight alloxan/streptozotocin and three spontaneously diabetic dogs were examined by trypsin digest and electron microscopy after durations of diabetes of between 1 and 7 years. Basement membrane (BM) thickening in the retinal capillaries was the only obvious fine structural change identified during the first 3 years of diabetes and was established within 1 year of induction. Widespread pericyte loss was noted after 4 years of diabetes and was paralleled by loss of smooth muscle (SM) cells, in the retinal arterioles. SM cell loss was most obvious in the smaller arterioles of the central retina. No microaneurysms were noted in the experimental diabetic dogs with up to 5 years' duration of diabetes but were widespread in a spontaneously diabetic animal at 7 years. This study has shown that SM cell loss, a hitherto unrecognised feature of diabetic microangiopathy, accompanies pericyte loss in the retinal circulation of diabetic dogs.

Ultrastructural findings in solar retinopathy

This study documents the ultrastructural findings in a case of solar retinopathy, 6 days after sungazing. A malignant melanoma of the choroid was diagnosed in a 65-year-old man. On fundoscopy, the macula was normal. The patient agreed to stare at the sun prior to enucleation. A typical solar retinopathy developed, characterised by a small, reddish, sharply circumscribed depression in the foveal area. Structural examination of the fovea and parafovea revealed a spectrum of cone and rod outer segment changes including vesiculation and fragmentation of the photoreceptor lamellae and the presence of discrete 100-120 nm whorls within the disc membranes. Many photoreceptor cells, particularly the parafoveal rods, also demonstrated mitochondrial swelling and nuclear pyknosis. Scattered retinal pigment epithelial cells in the fovea and parafovea showed a degeneration characterised by loss of plasma membrane specialisations, swelling of the smooth endoplasmic reticulum and changes in the fine structure of the lipofuscin granules. The good visual prognosis in solar retinopathy was attributed to the resistance of the foveal cone cells to photochemical damage.

Loss-of-Mains Detection by Internet Based ROCOF

This paper considers the enhancement of loss-of-mains detection by use of a differential rate-of-change-of-frequency relay to reduce nuisance tripping and improve sensitivity to small excursions in frequency. The telecommunications media which might carry the differential ROCOF signal are reviewed with a focus on channel latency, bandwidth and security.

Internet Based Loss-of-Mains Detection for Distributed Generation

This paper discusses methods of using the Internet as a communications media between distributed generator sites to provide new forms of loss-of-mains protection. An analysis of the quality of the communications channels between several nodes on the network was carried out experimentally. It is shown that Internet connections in urban environments are already capable of providing real-time power system protection, whilst rural Internet connections are borderline suitable but could not yet be recommended as a primary method of protection. Two strategies of providing loss-of-mains across Internet protocol are considered, broadcast of a reference frequency or phasor representing the utility and an Internet based inter-tripping scheme.

Prescribing for weight loss in primary care: evidence from a population based study

Background Taking antiobesity medication can be a cost effective way to lose weight. Uptake is determined in part by a General Practitioner's decision to prescribe weight loss medication and, in part, by patient preference. It is probable that the latter may indicate a patient's readiness to lose weight.


Methods Analysis of cross-sectional data (from February 2003 to March 2011) from a population based prescribing database (~1.75 million people) using an adjusted Poisson regression.


Results The number of antiobesity medications increased from 23.4 per 1000 population in 2004 to 30.7 per 1000 population in 2010 and was three times higher in female than in male subjects. Against this background, a marked seasonal variation in the number of antiobesity medications dispensed was evident (p<0.001), peaking in June/July with a trough in December/January (±8.0% peak to trough). The seasonal component was stronger in female subjects, ±11.2% peak to trough, compared with ±3.5% for male subjects.


Conclusions Obese patients, particularly women, increase their uptake of weight loss medication in the months leading up to the summer holiday period. The period prior to the summer may represent a time that health professionals could promote increased participation of obese patients in weight loss programmes.

Counselling for sight loss: Using systematic case study research to build a client informed practice model

There is compelling evidence to suggest that acquired sight loss negatively impacts on emotional well-being. Despite increasing recognition of the need to provide emotional support for people with sight loss, we still do not fully understand what counselling interventions help and why they help. The aim of this study was to examine the process and outcome of counselling for a 70-year-old client who had experienced complete, irreversible, post-operative sight loss in order to gain a deeper understanding of client-defined helpful aspects of therapy. A Hermeneutic Single-Case Efficacy Design study was undertaken having received ethical approval from the University's Research Ethics Committee. The client received six sessions of counselling from a vision-impaired counsellor working within a pluralistic framework. Measures were completed by the client at every session, as well as at pre-and post-counselling. All sessions were recorded and transcribed. The client also participated in pre-and post-counselling interviews. Data formed a rich case record that was analysed by a quasi-judicial enquiry team. Results suggested that this was a successful outcome case. Client-defined helpful aspects of therapy were (1) feeling understood; (2) being able to express emotions around the loss of sight; (3) finding a new identity; (4) finding ways to cope with fear, loss, dependency, and other people's perceptions; (5) exploring the possibility of a positive future without sight; (6) making sense of things; and (7) finding ways to become more socially connected. Relevant therapeutic tasks are proposed, and four key aspects of therapy are identified, which may have implications for the development of a practice model.

Loss of Synaptic Connectivity, Particularly in Second Order Neurons Is a Key Feature of Diabetic Retinal Neuropathy in the Ins2Akita Mouse

Retinal neurodegeneration is a key component of diabetic retinopathy (DR), although the detailed neuronal damage remains ill-defined. Recent evidence suggests that in addition to amacrine and ganglion cell, diabetes may also impact on other retinal neurons. In this study, we examined retinal degenerative changes in Ins2^Akita diabetic mice. In scotopic electroretinograms (ERG), b-wave and oscillatory potentials were severely impaired in 9-month old Ins2^Akita mice. Despite no obvious pathology in fundoscopic examination, optical coherence tomography (OCT) revealed a progressive thinning of the retina from 3 months onwards. Cone but not rod photoreceptor loss was observed in 3-month-old diabetic mice. Severe impairment of synaptic connectivity at the outer plexiform layer (OPL) was detected in 9-month old Ins2Akita mice. Specifically, photoreceptor presynaptic ribbons were reduced by 25% and postsynaptic boutons by 70%, although the density of horizontal, rod- and cone-bipolar cells remained similar to non-diabetic controls. Significant reductions in GABAergic and glycinergic amacrine cells and Brn3a+ retinal ganglion cells were also observed in 9-month old Ins2^Akita mice. In conclusion, the Ins2^Akita mouse develops cone photoreceptor degeneration and the impairment of synaptic connectivity at the OPL, predominately resulting from the loss of postsynaptic terminal boutons. Our findings suggest that the Ins2^Akita mouse is a good model to study diabetic retinal neuropathy.

Polarization retention loss in PbTiO3 ferroelectric films due to leakage currents

The relationship between retention loss in single crystal PbTiO3 ferroelectric thin films and leakage currents is demonstrated by piezoresponse and conductive atomic force microscopy measurements. It was found that the polarization reversal in the absence of an electric field followed a stretched exponential behavior 1-exp[-(t/k)(d)] with exponent d>1, which is distinct from a dispersive random walk process with d <. The latter has been observed in polycrystalline films for which retention loss was associated with grain boundaries. The leakage current indicates power law scaling at short length scales, which strongly depends on the applied electric field. Additional information of the microstructure, which contributes to an explanation of the presence of leakage currents, is presented with high resolution transmission electron microscopy analysis.

Loss-of-Mains Protection System by Application of Phasor Measurement Unit Technology with Experimentally Assessed Threshold Settings

Loss-of-mains protection is an important component of the protection systems of embedded generation. The role of loss-of-mains is to disconnect the embedded generator from the utility grid in the event that connection to utility dispatched generation is lost. This is necessary for a number of reasons, including the safety of personnel during fault restoration and the protection of plant against out-of-synchronism reclosure to the mains supply. The incumbent methods of loss-of-mains protection were designed when the installed capacity of embedded generation was low, and known problems with nuisance tripping of the devices were considered acceptable because of the insignificant consequence to system operation. With the dramatic increase in the installed capacity of embedded generation over the last decade, the limitations of current islanding detection methods are no longer acceptable. This study describes a new method of loss-of-mains protection based on phasor measurement unit (PMU) technology, specifically using a low cost PMU device of the authors' design which has been developed for distribution network applications. The proposed method addresses the limitations of the incumbent methods, providing a solution that is free of nuisance tripping and has a zero non-detection zone. This system has been tested experimentally and is shown to be practical, feasible and effective. Threshold settings for the new method are recommended based on data acquired from both the Great Britain and Ireland power systems.

Electron-induced hydrogen loss in uracil in a water cluster environment

Low-energy electron-impact hydrogen loss due to dissociative electron attachment (DEA) to the uracil and thymine molecules in a water cluster environment is investigated theoretically. Only the A'-resonance contribution, describing the near-threshold behavior of DEA, is incorporated. Calculations are based on the nonlocal complex potential theory and the multiple scattering theory, and are performed for a model target with basic properties of uracil and thymine, surrounded by five water molecules. The DEA cross section is strongly enhanced when the attaching molecule is embedded in a water cluster. This growth is due to two effects: the increase of the resonance lifetime and the negative shift in the resonance position due to interaction of the intermediate negative ion with the surrounding water molecules. A similar effect was earlier found in DEA to chlorofluorocarbons.