Epigenetic patterns in Atlantic herring (Clupea harengus): Temperature and photoperiod as environmental stressors during larval development

Understanding the molecular mechanisms underlying individual responses to environmental changes is crucial for species conservation and management. Pelagic fishes including Atlantic herring (Clupea harengus) are of particular interest because of their key ecological and economic roles and their susceptibility to a changing ocean from global warming. Temperature and photoperiod have been linked with spawning time and location in adult herring, but no study has thus far investigated the role of environmental factors on gene regulation during the vulnerable early developmental stages. Here, we examine DNA methylation patterns of larval herring bred under two temperatures (11°C and 13°C) and photoperiod (6 and 12 h) regimes in a 2 × 2 factorial design. We found consistently high levels of global methylation across all individuals and a decline in global methylation with increased developmental stage that was more pronounced at 13°C (p ≤ 0.007) than at 11°C (p ≥ 0.21). Most of the differentially methylated sites were in exon and promoter regions for genes linked to metabolism and development, some of which were hypermethylated at higher temperature. These results demonstrate the important role of DNA methylation during larval development and suggest that this molecular mechanism might be key in regulating early-stage responses to environmental stressors in Atlantic herring.

Argininosuccinate lyase deficiency causes blood-brain barrier disruption via nitric oxide-mediated dysregulation of claudin expression

Nitric oxide (NO) is a critical signaling molecule that has been implicated in the pathogenesis of neurocognitive diseases. Both excessive and insufficient NO production have been linked to pathology. Previously, we have shown that argininosuccinate lyase deficiency (ASLD) is a novel model system to investigate cell-autonomous, nitric oxide synthase-dependent NO deficiency. Humans with ASLD are at increased risk for developing hyperammonemia due to a block in ureagenesis. However, natural history studies have shown that individuals with ASLD have multisystem disease including neurocognitive deficits that can be independent of ammonia. Here, using ASLD as a model of NO deficiency, we investigated the effects of NO on brain endothelial cells in vitro and the blood-brain barrier (BBB) in vivo. Knockdown of ASL in human brain microvascular endothelial cells (HBMECs) led to decreased transendothelial electrical resistance, indicative of increased cell permeability. Mechanistically, treatment with an NO donor or inhibition of Claudin-1 improved barrier integrity in ASL-deficient HBMECs. Furthermore, in vivo assessment of a hypomorphic mouse model of ASLD showed increased BBB leakage, which was partially rescued by NO supplementation. Our results suggest that ASL-mediated NO synthesis is required for proper maintenance of brain microvascular endothelial cell functions as well as BBB integrity.

775 Role of Inversion Imaging in the Diagnoses of Neck of Femur Fractures

Aim

The objective of this study was to assess whether inversion of grey scale radiograph images has any impact on the diagnostic sensitivity and inter-observer reliability in diagnosing neck of femur fractures.

Method

We performed a retrospective, single centre study, using 50 randomly selected AP pelvis radiographs. The images included a combination of normal, intracapsular and extracapsular neck of femur fractures, which had been confirmed on CT, MRI and/or subsequent surgery.

Four independent observers (two orthopaedic specialists, one registrar and one SHO in orthopaedics) reviewed the images and graded each radiograph image using the Likert scale in response to the statement “there is a fracture”. Following this, the same radiographs were inverted to grey scale images and sent for a second review using the same method. RAND correlation was used for statistical analysis.

Results

Overall, observers appeared to have similar accuracy and equivocal rates with normal and inversion radiographic imaging.

One of the T&O Consultant's had much higher equivocal rate when analysing inverted radiographs compared to conventional digital radiographs but had slightly higher accuracy with inversion (95.35% compared to 93.88%) as well as the Registrar (83.33% compared to 81.63%). The second Trauma and Orthopaedics Consultant had slightly more accuracy with conventional digital radiographs (89.58% compared with 87.50%).

Conclusions

Inversion of digital radiographs did not affect the diagnostic sensitivity of neck of femur fractures in our study, and similarly did to not have a statistically significant impact in clinician confidence in diagnosing neck of femur fractures.

Ultrasound assessment of the hamstrings complex of athletes with MRI correlation

Due to anatomical complexity, ultrasound examination of the hamstring muscles is challenging, resulting in potential diagnostic uncertainty and under-confidence in the technique. This leads to a subsequent tendency to favour magnetic resonance imaging (MRI) evaluation, which can delay diagnosis and potential intervention. This article describes a comprehensive technique of ultrasound evaluation of the hamstrings complex, using key anatomical landmarks. A direct comparison of the sonographic landmarks with corresponding MRI appearances is also provided. If these landmarks can be identified successfully, the complex anatomy can be unlocked, thus improving the time and sensitivity of diagnosis of acute injuries, as well as providing a reliable framework for monitoring injury progress and helping to identify candidates for potential intervention. Many of the anatomical landmarks discussed are common areas of injury in elite athletes, encountered frequently in clinical practice.

Development, evaluation and validation of machine learning algorithms to detect atypical and asymptomatic presentations of Covid-19 in hospital practice

BACKGROUND

Diagnostic methods for Covid-19 have improved, both in speed and availability. Because of atypical and asymptomatic carriage of the virus and nosocomial spread within institutions, timely diagnosis remains a challenge. Machine learning models trained on blood test results have shown promise in identifying cases of Covid-19.

AIMS

To train and validate a machine learning model capable of differentiating Covid-19 positive from negative patients using routine blood tests and assess the model's accuracy against atypical and asymptomatic presentations.

DESIGN AND METHODS

We conducted a retrospective analysis of medical admissions to our institution during March and April 2020. Participants were categorized into Covid-19 positive or negative groups based on clinical, radiological features or nasopharyngeal swab. A machine learning model was trained on laboratory parameters and validated for accuracy, sensitivity and specificity and externally validated at an unconnected establishment.

RESULTS

An Ensemble Bagged Tree model was trained on data collected from 405 patients (212 Covid-19 positive) producing an accuracy of 81.79% (95% confidence interval (CI) 77.53-85.55%), the sensitivity of 85.85% (CI 80.42-90.24%) and specificity of 76.65% (CI 69.49-82.84%). Accuracy was preserved for atypical and asymptomatic subgroups. Using an external data set for 226 patients (141 Covid-19 positive) accuracy of 76.82% (CI 70.87-82.08%), sensitivity of 78.38% (CI 70.87-84.72%) and specificity of 74.12% (CI 63.48-83.01%) was achieved.

CONCLUSION

A machine learning model using routine laboratory parameters can detect atypical and asymptomatic presentations of Covid-19 and might be an adjunct to existing screening measures.

1547 An Alternative Approach to High-Risk Resternotomy

Introduction

Resternotomies are associated with substantial perioperative morbidity and mortality. Strategies described in literature mostly involve peripheral cannulation pre-sternotomy. Disadvantages of this technique relate to prolonged systemic heparinisation and cardiopulmonary bypass (CPB) time and the sequelae of hypothermic circulatory arrest. We describe a two-stage approach that potentially reduces the complications associated with high-risk resternotomy.

Method

3 high-risk patients (from pre-operative CT images) were referred for redo complex aortic surgery. A right mini-thoracotomy incision was first made in the 4th or 5th intercostal space. The right lung was isolated and careful blunt dissection was carried out to mobilise the heart and great vessels attached to the sternum. Once these structures were free, thoracotomy incision was closed. A standard median sternotomy was then performed and central cannulation carried out after systemic heparinisation. Rest of the surgery was performed routinely. In one patient, aortic aneurysm was heavily adherent and attempts to mobilise it fully proved impossible. Resultantly, systemic heparinisation was administered and the patient was cannulated in the right superficial femoral artery and right atrium (via mini-thoracotomy). CPB was instituted and the patient cooled to 28 °C. Right superior pulmonary vein vent was introduced to prevent left ventricular distension from hypothermic ventricular fibrillation. Once the heart and aneurysm were decompressed on full CPB, complete mobilisation was performed safely. All 3 patients survived surgery without major complications.

Conclusions

Meticulous preoperative planning is key to management of high-risk resternotomy. We describe a novel technique which we believe minimises risk of morbidity and mortality in these complex cases.

Birmingham Intervention Tent Technique (BITT): A Technical Note

Objective We describe a novel and safe CT biopsy technique that we have termed the “Birmingham intervention tent technique (BITT).” This technique is ideal for biopsying osseous lesions where a direct approach is not possible due to difficult positioning.

Methods The BITT uses a plastic surgical forceps clamp attached at an angle to the biopsy needle, creating a tent shape. The finger rings of the forceps is stabilized on the table.

Results In our institution, we have already used the BITT successfully in over 10 cases.

Conclusion The BITT is an inexpensive and reproducible technique.

Nitric oxide modulates bone anabolism through regulation of osteoblast glycolysis and differentiation

Previous studies have shown that nitric oxide (NO) supplements may prevent bone loss and fractures in preclinical models of estrogen deficiency. However, the mechanisms by which NO modulates bone anabolism remain largely unclear. Argininosuccinate lyase (ASL) is the only mammalian enzyme capable of synthesizing arginine, the sole precursor for nitric oxide synthase-dependent (NOS-dependent) NO synthesis. Moreover, ASL is also required for channeling extracellular arginine to NOS for NO production. ASL deficiency (ASLD) is thus a model to study cell-autonomous, NOS-dependent NO deficiency. Here, we report that loss of ASL led to decreased NO production and impairment of osteoblast differentiation. Mechanistically, the bone phenotype was at least in part driven by the loss of NO-mediated activation of the glycolysis pathway in osteoblasts that led to decreased osteoblast differentiation and function. Heterozygous deletion of caveolin 1, a negative regulator of NO synthesis, restored NO production, osteoblast differentiation, glycolysis, and bone mass in a hypomorphic mouse model of ASLD. The translational significance of these preclinical studies was further reiterated by studies conducted in induced pluripotent stem cells from an individual with ASLD. Taken together, our findings suggest that ASLD is a unique genetic model for studying NO-dependent osteoblast function and that the NO/glycolysis pathway may be a new target to modulate bone anabolism.

Hamstring origin-anatomy, angle of origin and its possible clinical implications

INTRODUCTION

The posterior compartment of the thigh is composed of three major muscles collectively known as the hamstring muscles. These consist of the biceps femoris short and long head, semimembranosus and semitendinosus. Excluding the short head of biceps femoris, the hamstrings contribute to the movement of the hip and the knee joints as they span across both joints. Our hypothesis is that the nature of the conjoint tendon -ischial angle predisposes to an increased risk of tearing in this hamstring component. We therefore aim to look at the anatomy of the hamstring origin at the ischial tuberosity and spatial relationship between the long head of biceps, semitendinosus and semimembranosus in the form of vector angles.

MATERIAL AND METHODS

100 consecutive pelvic MRIs in patients under the age of 40 years were reviewed by musculoskeletal radiology fellow and a consultant musculoskeletal radiologist with more than 10 years' experience in musculoskeletal radiology and measured the angle of origin of conjoined tendon and semimembranosus at its ischial origin. P value using a paired t-test was less than 0.0001 confirming that the difference in the vector angle of the different hamstring components was statistically significant.

RESULTS

The median angle of origin of conjoined tendon was 12° and for semimembranosus was 6°. Applying the concept of Newton's second law to the angles calculated we demonstrated that an increase of 9% force applied to the conjoint tendon origin when compared to the semimembranosus tendon.

CONCLUSION

We hypothesis that the difference in the angle of origin of the components of hamstrings might be one of the reasons for the difference in the incidence and patterns of the injuries of the various muscles of the hamstrings.

MRI assessment of anatomy and pathology of the iliofemoral ligament

The iliofemoral ligament is strongest ligament of the body. We review the magnetic resonance imaging (MRI) appearances of the iliofemoral ligament, and discuss the disease entities that may affect this region.

Anatomy and pathology of facet joint

Facet joints are the only synovial joints in the spine and can be involved in a large number of pathological processes including arthropathy, infection, inflammation, trauma and tumour. In this review article, we present a spectrum of pathologies that arise from or involve facet joints that we have encountered in our tertiary orthopaedic and spinal centre. The objective of this review is to create an aide memoire for the general radiologist who may encounter facet joint pathology, which they may not be familiar with.

Argininosuccinate Lyase Deficiency Causes an Endothelial-Dependent Form of Hypertension

Primary hypertension is a major risk factor for ischemic heart disease, stroke, and chronic kidney disease. Insights obtained from the study of rare Mendelian forms of hypertension have been invaluable in elucidating the mechanisms causing primary hypertension and development of antihypertensive therapies. Endothelial cells play a key role in the regulation of blood pressure; however, a Mendelian form of hypertension that is primarily due to endothelial dysfunction has not yet been described. Here, we show that the urea cycle disorder, argininosuccinate lyase deficiency (ASLD), can manifest as a Mendelian form of endothelial-dependent hypertension. Using data from a human clinical study, a mouse model with endothelial-specific deletion of argininosuccinate lyase (Asl), and in vitro studies in human aortic endothelial cells and induced pluripotent stem cell-derived endothelial cells from individuals with ASLD, we show that loss of ASL in endothelial cells leads to endothelial-dependent vascular dysfunction with reduced nitric oxide (NO) production, increased oxidative stress, and impaired angiogenesis. Our findings show that ASLD is a unique model for studying NO-dependent endothelial dysfunction in human hypertension.

Abstract 050: Loss of Argininosuccinate Lyase Leads to Nitric Oxide Deficiency, Endothelial Dysfunction, Impaired Angiogenesis, and Hypertension

Nitric oxide (NO) is an important mediator of vascular homeostasis and its deficiency in murine models results in hypertension. However, there are few monogenic causes of NO deficiency in humans and the effects of such genetic forms of NO deficiency on vasculature are not well-studied. We have recently shown that argininosuccinate lyase (ASL), a urea cycle enzyme, is necessary for synthesis of NO. ASL deficiency results in decreased production of NO and hypertension in humans and mice. To investigate whether loss of Asl-mediated NO synthesis in the vascular endothelium alone can cause hypertension, we generated a mouse model with endothelial-specific deletion of Asl (VE-Cadherin Cre(tg/+); Asl(flox/flox), or cKO). Asl cKO mice developed hypertension and had higher mean arterial pressure compared to control littermates (102.2± 2.9 vs. 89.8±3.6 mmHg, p<0.05). This hypertension was secondary to endothelial-specific NO deficiency as demonstrated by abnormal relaxation of aortic rings and correction with treatment with an NOS-independent NO supplement (MAP in sodium nitrite treated Asl cKO 97.7±3.8 vs. 97.6±7.3 mmHg in untreated control mice). To evaluate the human relevance of these findings, we developed human cell-based models from patients with ASL deficiency. Human induced pluripotent stem cells (hiPSCs) were generated and differentiated into endothelial cells. Interestingly, ASL-deficient hiPSCs differentiated less efficiently into endothelial cells as compared to control hiPSCs (9.7±4.0 vs. 20.8±3.7 % of CD144+; CD31+ cells, p<0.01). Furthermore, ASL-deficient hiPSCs-derived endothelial cells had a significantly reduced capacity to form capillary-like structures on Matrigel. Our study using a novel mouse model and hiPSCs-derived endothelial cells from patients with a rare Mendelian form of hypertension supports the hypothesis that structural and functional abnormalities in endothelial cells contribute to pathogenesis of hypertension. Our study is the first to use hiPSC-derived endothelial cells as a model system to study hypertension and highlights the utility of this technology in exploring the pathogenesis of other vascular diseases.

Construction of a novel expression cassette for increasing transgene expression in vivo in endothelial cells of large blood vessels

The success of gene therapy hinges on achievement of adequate transgene expression. To ensure high transgene expression, many gene-therapy vectors include highly active virus-derived transcriptional elements. Other vectors include tissue-specific eukaryotic transcriptional elements, intended to limit transgene expression to specific cell types, avoid toxicity and prevent immune responses. Unfortunately, tissue specificity is often accompanied by lower transgene expression. Here, we use eukaryotic (murine) transcriptional elements and a virus-derived posttranscriptional element to build cassettes designed to express a potentially therapeutic gene (interleukin (IL)-10) in large-vessel endothelial cells (ECs) at levels as high as obtained with the cytomegalovirus (CMV) immediate early promoter, while retaining EC specificity. The cassettes were tested by incorporation into helper-dependent adenoviral vectors, and transduction into bovine aortic EC in vitro and rabbit carotid EC in vivo. The murine endothelin-1 promoter showed EC specificity, but expressed only 3% as much IL-10 mRNA as CMV. Inclusion of precisely four copies of an EC-specific enhancer and a posttranscriptional regulatory element increased IL-10 expression to a level at or above the CMV promoter in vivo, while retaining--and possibly enhancing--EC specificity, as measured in vitro. The cassette reported here will likely be useful for maximizing transgene expression in large-vessel EC, while minimizing systemic effects.

Digital measurement of torsional eye movement due to postural change and its effect on reading performance

PURPOSE

Posture induced torsional eye movements have rarely been investigated. The current study made use of digital imaging technology to measure the cycloduction resulting from postural change. The effect of cycloduction on reading performance was also investigated.

METHODS

Thirty subjects were recruited and pictures of the right eye were captured using a digital camera at three postures, i.e. sitting, 90 degrees tilted to the right and 90 degrees tilted to the left. With the identification of a conjunctival landmark, torsional eye movement was measured. The subjects were then required to read a custom designed near chart while in those three postures, the reading card being rotated 90 degrees clockwise or 90 degrees anti-clockwise, to match with the tilting of the head. The reproducibility of the torsional eye movement and reading performance measure was determined in 12 of those 30 subjects.

RESULTS

Incycloduction was induced when tilting to the right and excycloduction when tilting to the left. This method was found to be reproducible with the 95% confidence limits of 0.80 degrees between visits. The mean incycloduction induced was 6.50 degrees (SD 1.51 degrees ) and 6.41 degrees (SD 1.46 degrees ) for excycloduction. No significant difference in amount was demonstrated (paired t-test: t = 0.624, P = 0.538). No significant difference was found in the reading scores at various postures (Repeated measures ANOVA: df = 2, F = 1.881, P = 0.162).

CONCLUSIONS

The results presented here demonstrate that we have developed an objective and instantaneous method with good precision, which could be applied in other studies that require the measurement of torsional eye movements. The induced cycloduction did not affect the reading performance.

Confirmation of the hierarchical folding of RNase H: a protein engineering study

The kinetic intermediate of RNase H is structured in a core region of the protein. To probe the role of this intermediate in the folding of RNase H, the folding kinetics of mutant proteins with altered native state stabilities were investigated. Mutations within the folding core destabilize the kinetic intermediate and slow refolding in a manner consistent with an obligatory intermediate model. Mutations outside of the folding core, however, do not affect the stability of the kinetic intermediate but do perturb the native state and transition state. These results indicate that interactions formed in the intermediate persist in the transition and native states and that RNase H folds through a hierarchical mechanism.

Fine needle aspiration cytology of benign adrenal cortical nodules. A comparison of cytologic findings with those of primary and metastatic adrenal malignancies

OBJECTIVE

To determine the specific cytomorphologic criteria for diagnosing benign adrenal cortical nodule (BACN) by fine needle aspiration (FNA).

STUDY DESIGN

The smears from 162 adrenal FNA biopsies were reviewed. A diagnosis of BACN was rendered in 50 cases (31%). The cytologic features of BACN were compared to those of primary and metastatic malignant tumors of the adrenal gland, and the size of BACN as measured by computed tomography was recorded.

RESULTS

Bubbly, vacuolated, lipid background; large, cohesive tissue fragments with a syncytial nesting arrangement admixed with sinusoidal endothelial cells; and abundant oval, round, bare nuclei are the three cytomorphologic features most often seen in BACN. The combination of these three features was observed in 40 cases (89%) of BACN and was seen in 4 cases of metastatic carcinoma (6%) in which there was also coexisting adrenal cortical hyperplasia. None of the other primary or metastatic malignancies showed this combination of cytomorphologic features. The mean size of BACN was 2.5 cm, with a standard deviation of 1 cm and a range of 1-5 cm. The sizes of the four metastatic carcinomas with coexisting adrenal cortical hyperplasia were 6.5, 6, 5 and 1.5 cm, respectively (mean, 4.8).

CONCLUSION

Our data suggest that combined cytologic features of bare nuclei; bubbly, vacuolated background; and large, cohesive tissue fragments with sinusoidal endothelial cells in a small adrenal nodule (< 3.5 cm) are highly specific to FNA diagnosis of BACN.

Composite pleomorphic xanthoastrocytoma and ganglioglioma: report of four cases and review of the literature

Composite pleomorphic xanthoastrocytoma (PXA)-ganglioglioma (GG) is a rare recently described entity. Only three examples have been documented, one of which showed evidence of malignant transformation. We report an additional four cases and update the literature. With the exception of an 82-year-old man, all patients have been under 30 years of age. The temporal lobe was involved in three cases and cerebellum in another three. Radiologic features were those common to PXA and GG. Histologically, all were "collision tumors" composed of abutting, although spatially distinct, PXA and GG components. In two cases, the second element was only recognized at reexcision or recurrence. Histologic anaplasia, always in the PXA component, was evident as brisk mitotic activity and/or necrosis in five cases. Of the seven patients, one died of disease 17 years after the onset of seizures and after multiple recurrences, the last of which largely resembled glioblastoma. We conclude that the composite PXA-GG is a rare neoplasm that shares many features of its individual components. In addition to its temporal lobe predilection, the cerebellum is frequently affected. As when it occurs in isolation, the PXA component of composite PXA-GG possesses the potential for malignant transformation.