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A hypomorphic variant of choroideremia is associated with a novel intronic mutation that leads to exon skipping.
INTRODUCTION: Molecular confirmation of pathogenic sequence variants in the CHM gene is required prior to enrolment in retinal gene therapy clinical trials for choroideremia. Individuals with mild choroideremia have been reported. The molecular basis of genotype-phenotype associations is of clinical relevance since it may impact on selection for retinal gene therapy. METHODS AND MATERIALS: Genetic testing and RNA analysis were undertaken in a patient with mild choroideremia to confirm the pathogenicity of a novel intronic variant in CHM and to explore the mechanism underlying the mild clinical phenotype. RESULTS: A 42-year-old male presented with visual field loss. Fundoscopy and autofluorescence imaging demonstrated mild choroideremia for his age. Genetic analysis revealed a variant at a splice acceptor site in the CHM gene (c.1350-3C > G). RNA analysis demonstrated two out-of-frame transcripts, suggesting pathogenicity, without any detectable wildtype transcripts. One of the two out-of-frame transcripts is present in very low levels in healthy controls. DISCUSSION: Mild choroideremia may result from +3 or -3 splice site variants in CHM. It is presumed that the resulting mRNA transcripts may be partly functional, thereby preventing the development of the null phenotype. Choroideremia patients with such variants may present challenges for gene therapy since there may be residual transcript activity which could result in long-lasting visual function which is atypical for this disease.
PTCH1-mutant human cerebellar organoids exhibit altered neural development and recapitulate early medulloblastoma tumorigenesis
ABSTRACT Patched 1 (PTCH1) is the primary receptor for the sonic hedgehog (SHH) ligand and negatively regulates SHH signalling, an essential pathway in human embryogenesis. Loss-of-function mutations in PTCH1 are associated with altered neuronal development and the malignant brain tumour medulloblastoma. As a result of differences between murine and human development, molecular and cellular perturbations that arise from human PTCH1 mutations remain poorly understood. Here, we used cerebellar organoids differentiated from human induced pluripotent stem cells combined with CRISPR/Cas9 gene editing to investigate the earliest molecular and cellular consequences of PTCH1 mutations on human cerebellar development. Our findings demonstrate that developmental mechanisms in cerebellar organoids reflect in vivo processes of regionalisation and SHH signalling, and offer new insights into early pathophysiological events of medulloblastoma tumorigenesis without the use of animal models.
The effect of single-component sleep restriction therapy on depressive symptoms: A systematic review and meta-analysis.
Sleep restriction therapy is a behavioural component within cognitive behavioural therapy for insomnia and is an effective standalone treatment for insomnia, but its effect on depressive symptoms remains unclear. This review aimed to synthesise and evaluate the impact of single-component sleep restriction therapy on depressive symptoms relative to a control intervention. We searched electronic databases and sleep-related journals for randomised controlled trials and uncontrolled clinical trials, published from 1 January 1986 until 19 August 2023, that delivered sleep restriction therapy to adults with insomnia. Random-effects meta-analysis of standardised mean differences and Cochrane risk of bias assessment were performed on randomised controlled trials, while uncontrolled clinical trials were discussed narratively. The meta-analysis was pre-registered on PROSPERO (ID: CRD42020191803). We identified seven randomised controlled trials (N = 1102) and two uncontrolled clinical trials (N = 22). Findings suggest that sleep restriction therapy is associated with a medium effect for improvement in depressive symptoms at post-treatment (Nc = 6, g = -0.45 [95% confidence interval = -0.70 to -0.21], p
Modelling the economic constraints and consequences of anaesthesia associate expansion in the UK National Health Service: a narrative review.
Shortages in the physician anaesthesia workforce have led to proposals to introduce new staff groups, notably in the UK National Health Service (NHS) Anaesthesia Associates (AAs) who have shorter training periods than doctors and could potentially contribute to workflow efficiencies in several ways. We analysed the economic viability of the most efficient staffing model, previously endorsed by both the UK Royal College of Anaesthetists and the Association of Anaesthetists, wherein one physician supervises two AAs across two operating lists (1:2 model). For this model to be economically rational (something which neither national organisation considered), the employment cost of the two AAs should be equal to or less than that of a single supervisor physician (i.e. AAs should be paid <50% of the supervisor's salary). As the supervisor can be an autonomous specialty and specialist (SAS) doctor, this sets the economically viable AA salary envelope at less than £40,000 per year. However, we report that actual advertised AA salaries greatly exceed this, with even student AAs paid up to £48,472. Economically, one way to justify such salaries is for AAs to become autonomous such that they eventually replace SAS doctors at a lower cost. We discuss some other options that might increase AA productivity to justify these salaries (e.g. ≥1:3 staffing ratios), but the medico-political consequences of each of them are also profound. Alternatively, the AA programme should be terminated as economically nonviable. These results have implications for any country seeking to introduce new models of working in anaesthesia.
Adaptive strategies used by surgical teams under pressure: an interview study among senior healthcare professionals in four major hospitals in the United Kingdom
Abstract Background Healthcare systems are operating under substantial pressures, and often simply cannot provide the standard of care they aspire to within the available resources. Organisations, managers, and individual clinicians make constant adaptations in response to these pressures, which are typically improvised, highly variable and not coordinated across clinical teams. The purpose of this study was to identify and describe the types of everyday pressures experienced by surgical teams and the adaptive strategies they use to respond to these pressures. Methods We conducted interviews with 20 senior multidisciplinary healthcare professionals from surgical teams in four major hospitals in the United Kingdom. The interviews explored the types of everyday pressures staff were experiencing, the strategies they use to adapt, and how these strategies might be taught to others. Results The primary pressures described by senior clinicians in surgery were increased numbers and complexity of patients alongside shortages in staff, theatre space and post-surgical beds. These pressures led to more difficult working conditions (e.g. high workloads) and problems with system functioning such as patient flow and cancellation of lists. Strategies for responding to these pressures were categorised into increasing or flexing resources, controlling and prioritising patient demand and strategies for managing the workload (scheduling for efficiency, communication and coordination, leadership, and teamwork strategies). Conclusions Teams are deploying a range of strategies and making adaptations to the way care is delivered. These findings could be used as the basis for training programmes for surgical teams to develop coordinated strategies for adapting under pressure and to assess the impact of different combinations of strategies on patient safety and surgical outcomes.
A systematic review of the performance of actigraphy in measuring sleep stages.
The accuracy of actigraphy for sleep staging is assumed to be poor, but examination is limited. This systematic review aimed to assess the performance of actigraphy in sleep stage classification of adults. A systematic search was performed using MEDLINE, Web of Science, Google Scholar, and Embase databases. We identified eight studies that compared sleep architecture estimates between wrist-worn actigraphy and polysomnography. Large heterogeneity was found with respect to how sleep stages were grouped, and the choice of metrics used to evaluate performance. Quantitative synthesis was not possible, so we performed a narrative synthesis of the literature. From the limited number of studies, we found that actigraphy-based sleep staging had some ability to classify different sleep stages compared with polysomnography.
Effects of the COVID-19 Pandemic on Everyday Neurosurgical Practice in Alsace, France: Lessons Learned, Current Perspectives, and Future Challenges—Preliminary Results of a Longitudinal Multicentric Study Registry
Background and Objectives: The global outbreak caused by the SARS-CoV-2 pandemic disrupted healthcare worldwide, impacting the organization of intensive care units and surgical care units. This study aimed to document the daily neurosurgical activity in Alsace, France, one of the European epicenters of the pandemic, and provide evidence of the adaptive strategies deployed during such a critical time for healthcare services. Materials and Methods: The multicentric longitudinal study was based on a prospective cohort of patients requiring neurosurgical care in the Neurosurgical Departments of Alsace, France, between March 2020 and March 2022. Surgical activity was compared with pre-pandemic performances through data obtained from electronic patient records. Results: A total of 3842 patients benefited from care in a neurosurgical unit during the period of interest; 2352 of them underwent surgeries with a wide range of pathologies treated. Surgeries were initially limited to neurosurgical emergencies only, then urgent cases were slowly reinstated; however, a significant drop in surgical volume and case mix was noticed during lockdown (March–May 2020). The crisis continued to impact surgical activity until March 2022; functional procedures were postponed, though some spine surgeries could progressively be performed starting in October 2021. Various social factors, such as increased alcohol consumption during the pandemic, influenced the severity of traumatic pathologies. The progressive return to the usual profile of surgical activity was characterized by a rebound of oncological interventions. Deferrable procedures for elective spinal and functional pathologies were the most affected, with unexpected medical and social impacts. Conclusions: The task shifting and task sharing approaches implemented during the first wave of the pandemic supported the reorganization of neurosurgical care in its aftermath and enabled the safe and timely execution of a broad spectrum of surgeries. Despite the substantial disruption to routine practices, marked by a significant reduction in elective surgical volumes, comprehensive records demonstrate the successful management of the full range of neurosurgical pathologies. This underscores the efficacy of adaptive strategies in navigating the challenges imposed by the largest healthcare crisis in recent history. Those lessons will continue to provide valuable insights and guidance for health and care managers to prepare for future unpredictable scenarios.
Melanopsin retinal ganglion cells and the maintenance of circadian and pupillary responses to light in aged rodless/coneless (rd/rd cl) mice
AbstractMelanopsin‐expressing ganglion cells have been proposed as the photoreceptors mediating non‐rod, non‐cone ocular responses to light. Here we use the aged (approximately 2 years) rodless and coneless (rd/rd cl) mouse to assess the impact of progressive inner retinal cell loss on melanopsin expression, circadian entrainment and pupillary constriction. Aged rd/rd cl mice show substantial transneuronal retinal degeneration leaving only the ganglion cell layer and little of the inner nuclear layer. Despite this loss, quantitative reverse transcriptase‐polymerase chain reaction showed normal levels of melanopsin expression, and immunocytochemistry demonstrated both the presence and normal cellular appearance of these cells. Furthermore, the optic nerves of the two genotypes (rd/rd cl and +/+) were not obviously different in animals older than 2 years. However, this massive level of retinal degeneration left both pupillary and circadian responses to light intact, even in rd/rd cl mice older than 2 years. Our data provide the first positive correlation between the persistence of melanopsin‐expressing cells and the maintenance of both circadian and pupillary responses to light in the absence of rods and cones. These findings, together with recent studies on melanopsin knockout mice, are consistent with the hypothesis that melanopsin‐expressing ganglion cells are photosensitive and mediate a range of irradiance‐detection tasks.
Melanopsin (Opn4) positive cells in the cat retina are randomly distributed across the ganglion cell layer
A rare type of rodent retinal ganglion cell expresses melanopsin (Opn4), the majority of which project to the suprachiasmatic nuclei. Many of these cells are directly light sensitive and appear to regulate the circadian system in the absence of rod and cone photoreceptors. However, the rodent retina contains no overt regions of specialization, and the different ganglion cell types are hard to distinguish. Consequently, attempts to distinguish the distribution of melanopsin ganglion cells in relation to regions of retinal specialization or subtype have proved problematic. Retinal cells with a common function tend to be regularly distributed. In this study, we isolate cat melanopsin and label melanopsin expressing cells usingin situhybridization. The labelled cells were all confined to the ganglion cell layer, their density was low, and their distribution was random. Melanopsin containing cells showed no clear center-to-periphery gradient in their distribution and were comprised of a relatively uniform cellular population.
Impact of age and retinal degeneration on the light input to circadian brain structures
Aging causes anatomical and functional changes in visual and circadian systems. In wild type mice rods, cones, and photosensitive retinal ganglion cells (pRGCs) decline with age. In rd/rd cl mice, the early loss of rods and cones is followed by protracted transneuronal loss of inner retinal neurons as well as the pRGCs. Here we use Fos induction to study the light input pathway to the suprachiasmatic nuclei (SCN), the intergeniculate leaflets (IGL) and ventral lateral geniculate nuclei (vLGN) of old (~700 days) and young (~150 days) wild type and rd/rd cl mice. Cholera toxin tracing was used in parallel to study the anatomy of this pathway. We find that aging rather than retinal degeneration is a more important factor in reducing light input to the SCN, causing both a reduction in Fos expression and retinal afferents. Furthermore, we show light-induced Fos within the vLGN and IGL is predominantly subserved by rods and cones, and once again aging reduces the amplitude of this response. © 2012 Elsevier Inc.
Eel visual pigments revisited: The fate of retinal cones during metamorphosis
During their complex life history, anguilliform eels go through a major metamorphosis when developing from a fresh water yellow eel into a deep-sea silver eel. In addition to major changes in body morphology, the visual system also adapts from a fresh water teleost duplex retina with rods and cones, to a specialized deep-sea retina containing only rods. The history of the rods is well documented with an initial switch from a porphyropsin to a rhodopsin (P5232to P5011) and then a total change in gene expression with the down regulation of a “freshwater” opsin and its concomitant replacement by the expression of a typical “deep-sea” opsin (P5011to P4821). Yellow eels possess only two spectral classes of single cones, one sensitive in the green presumably expressing an RH2 opsin gene and the second sensitive in the blue expressing an SWS2 opsin gene. In immature glass eels, entering into rivers from the sea, the cones contain mixtures of rhodopsins and porphyropsins, whereas the fully freshwater yellow eels have cone pigments that are almost pure porphyropsins with peak sensitivities at about 540–545 nm and 435–440 nm, respectively. However, during the early stages of metamorphosis, the pigments switch to rhodopsins with the maximum sensitivity of the “green”-sensitive cone shifting to about 525 nm, somewhat paralleling, but preceding the change in rods. During metamorphosis, the cones are almost completely lost.
Paradoxical opsin expressing cells in the inner retina that are augmented following retinal degeneration
AbstractHere we reveal a population of cells that express cone photoreceptor opsins that are located in the inner retina, distant from outer retinal photoreceptors. These cells are present in rodents and human. They also express a range of key proteins critical in the cone phototransduction cascade and make contact with other retinal neurons. Their opsins are not generally confined to cellular specialized regions but are present throughout the plasma membrane, although their nuclear configurations are similar to those of outer retinal cones. This population is distinct from the ganglion cells that contain melanopsin and which are known to be inner retinal irradiance detectors regulating circadian behaviour. Surprisingly, the size of the population of short wavelength opsin positive cells in the ganglion cell layer is plastic. In normal animals their number declines with age. However, their numbers increase significantly in response to outer retinal photoreceptor loss, probably by drawing on a pool of inner retinal cells that express cone specific markers, but not opsins.
Survival and remodeling of melanopsin cells during retinal dystrophy
AbstractThe melanopsin positive, intrinsically photosensitive retinal ganglion cells (ipRGCs) of the inner retina have been shown to send wide-ranging projections throughout the brain. To investigate the response of this important cell type during retinal dystrophy, we use the Royal College of Surgeons (RCS) dystrophic rat, a major model of retinal degeneration. We find that ipRGCs exhibit a distinctive molecular profile that remains unaltered during early stages of outer retinal pathology (15 weeks of age). In particular, these cells express βIII tubulin, α-acetylated tubulin, and microtubule-associated proteins (MAPs), while remaining negative for other RGC markers such as neurofilaments, calretinin, and parvalbumin. By 14 months of age, melanopsin positive fibers invade ectopic locations in the dystrophic retina and ipRGC axons/dendrites become distorted (a process that may involve vascular remodeling). The morphological abnormalities in melanopsin processes are associated with elevated immunoreactivity for MAP1b and a reduction in α-acetylated tubulin. Quantification of ipRGCs in whole mounts reveals reduced melanopsin cell number with increasing age. Focusing on the retinal periphery, we find a significant decline in melanopsin cell density contrasted by a stability of melanopsin positive processes. In addition to these findings, we describe for the first time, a distinct plexus of melanopsin processes in the far peripheral retina, a structure that is coincident with a short wavelength opsin cone-enriched rim. We conclude that some ipRGCs are lost in RCS dystrophic rats as the disease progresses and that this loss may involve vascular remodeling. However, a significant number of melanopsin positive cells survive into advanced stages of retinal degeneration and show indications of remodeling in response to pathology. Our findings underline the importance of early intervention in human retinal disease in order to preserve integrity of the inner retinal photoreceptive network.
Oxygen modulates cell death in the proliferating retina
AbstractMany factors probably regulate the process of natural cell death during development. It is present in both the early undifferentiated retina and later following differentiation. Melanin production plays a role in regulating retinal development and when it is absent, cell proliferation and death are enhanced. Here we examine the effects of hyperoxia on this process, as oxygen has been shown to reduce cell death among differentiated photoreceptors late in development. However, in this study we examine its effects much earlier in pigmented and albino pigmentation phenotypes, when most cells are still actively dividing and are not committed to a specific fate. Newborn mice were exposed to high oxygen levels for 24 h and then returned to normal air for varying periods and their retinae examined. Hyperoxia had a dramatic effect on the number of dying cells, reducing them by almost 60% in pigmented animals and by over 80% in albinos. Following the return to normal air there was a gradual increase in their number over 360 min back to normal levels in pigmented mice; however, in albinos there was a complete rebound in levels of cell death within 40 min, reflecting the increased metabolic stress present in albino retinae due to their abnormal levels of proliferation. These results highlight the important role played by oxygen during early natural cell death in the retina and reveal the different developmental conditions present in the retinae of the two pigmentation phenotypes examined.