Human PKD1 sequences form R-loop structures in vitro.

Autosomal dominant polycystic kidney disease results from the loss of the PKD1 gene product, polycystin 1. Regulatory mechanisms are unresolved, but an apparent G/C sequence bias in the gene is consistent with co-transcriptional R-loop formation. R-loops regulate gene expression and stability, and they form when newly synthesized RNA extensively pairs with the template DNA to displace the non-template strand. In this study, we tested two human PKD1 sequences for co-transcriptional R-loop formation in vitro. We observed RNase H-sensitive R-loop formation in intron 1 and 22 sequences, but only in one transcriptional orientation. Therefore, R-loops may participate in PKD1 expression or stability.

Evaluating Surgical Cervical Arthrodesis With a Novel MRI Grading Score.

STUDY DESIGN: This was a single-institution retrospective study. OBJECTIVE: Evaluate a magnetic resonance imaging (MRI)-scoring system to differentiate arthrodesis from pseudoarthrosis following anterior cervical discectomy and fusion. SUMMARY OF BACKGROUND DATA: Diagnostic workup following fusion surgery often includes MRI to evaluate neural structures and computed tomography (CT) and/or dynamic x-rays to evaluate instrumentation and arthrodesis. The use of MRI alone for these evaluations would protect patients from harmful CT and x-ray ionizing radiation. METHODS: Neurosurgical attending evaluated CTs for arthrodesis or pseudoarthrosis. Blinded neuroradiology attending and neurosurgery senior resident evaluated independent T1 and T2 region of interest (ROI) signal intensity over instrumented disk space. Cerebral spinal fluid (CSF) at the cisterna magnum and distal adjacent uninstrumented vertebral body (VB) were also calculated. ROI interspace /ROI CSF and ROI interspace /ROI VB quotients were used to create T1- and T2-interspace interbody scores (IIS). RESULTS: Study population (n=64 patients, 50% female) with a mean age of 51.72 years and 109 instrumented levels with 45 fused levels (41.3%) were included. T1-weighted MRI, median T1-IIS CSF for arthrodesis was 176.20 versus 130.92 for pseudoarthrosis ( P <0.0001), T1-IIS VB for arthrodesis was 68.52 and pseudoarthrosis was 52.71 ( P <0.0001). T2-weighted MRI, median T2-IIS CSF for arthrodesis was 27.72 and 14.21 for pseudoarthrosis ( P <0.0001), while T2-IIS VB for arthrodesis was 67.90 and 41.02 for pseudoarthrosis ( P <0.0001). The greatest univariable discriminative capability for arthrodesis via AUROC was T1-IIS VB (0.7743). CONCLUSION: We describe a novel MRI scoring system that may help determine arthrodesis versus pseudoarthrosis following anterior cervical discectomy and fusion. Postoperative symptomatic patients may only require MRI, which would protect patients from ionizing radiation. LEVEL OF EVIDENCE: Level IV.

Defining the Clival Recess Surgical Corridor and Clival Classification System for Approach to Sellar Pathology.

BACKGROUND: Sellar masses within the pars intermedius, bordered anteriorly by normal pituitary gland/stalk, and/or with ectatic cavernous carotid anatomy are challenging and high risk when approached through the endonasal standard direct/anterior sellar approach. This approach portends itself to a higher risk of pituitary gland/stalk injury and subtotal resection with the aforementioned anatomic variants. OBJECTIVE: To describe the indirect clival recess corridor approach to sellar lesions. This corridor is a "silent" point of access to lesions in this region endoscopically. While skull base teams may have used this approach to some degree, it has not yet been described in the literature to our knowledge. METHODS: We defined the clival recess surgical corridor with skull base craniometric measurements and use a case example with aberrant anatomy to illustrate the approach. We cross-sectionally reviewed 42 patients with sellar and suprasellar masses. To describe the approach's anatomy, we devised and defined the terms dorsum sella plumb line, anatomic corridor, angle of osseous, and operative corridor. RESULTS: Created novel clival aeration grade informing surgical planning. Classified clival aeration as Grade 1 (100%-75% aeration), Grade 2 (75%-50% aeration), Grade 3 (50%-25% aeration), and Grade 4 (25%-0% aeration). This classification system determines extent of drilling of the clivus required to optimize the clival recess corridor approach and its limitations. CONCLUSION: The clival recess surgical corridor is effective for accessing pituitary lesions within the sella. Consider the indirect approach when a standard direct/anterior sellar approach has high risk for vascular injury and/or endocrinological dysfunction.

Porcine Bladder Replacement with a Bilayer Silk Fibroin Enhanced Prosthetic Reservoir: A Feasibility Study.

Introduction: The creation of synthetic reservoirs for bladder replacement has been limited by challenges of interfacing synthetic materials and native tissue. We sought to overcome this challenge by utilizing a novel bilayer silk fibroin scaffold (BLSF) as an intermediary toward the development of an acellular prosthetic reservoir. Methods: Under institutionally approved protocols, 3D-printed reservoirs were implanted in six juvenile female pigs after cystectomy. BLSF was attached to the in situ prosthetic reservoir serving as an intermediary to native ureteral and urethral tissue anastomoses. Our first protocol allowed four pigs to be survived up to 7 days, and the second protocol allowed two pigs to be survived for up to 1 year. At the first sign of functional decline or the end of the study period, the animals were euthanized, and kidneys, ureters, prosthetic bladder, and urethra were harvested en bloc for histopathology analysis. Results: The first two pigs had anastomotic urine leaks because of design flaws resulting in early termination. The third pig had acute renal failure resulting in early termination. The artificial bladder design was modified in subsequent iterations. The fourth pig survived for 7 days and, upon autopsy, had intact urethral and ureteral anastomoses. The fifth and sixth pigs survived for 11 and 12 weeks, respectively, before they were sacrificed because of failure to thrive. One animal developed an enteric fistula. The other animal had an intact anastomosis, and the BLFS was identified at the ureteral and urethral anastomoses on histopathologic analysis. Conclusions: Replacing the porcine bladder with a prosthetic bladder was achieved for up to 3 months, the second longest survival period for a nonbiologic bladder alternative. BLSF was used for the first time to create an interface between synthetic material and biologic tissue by allowing ingrowth of urothelium onto the acellular alloplastic bladder.

A Method of Intraoperative Registration Verification to Prevent Accuracy Errors in Robot-Assisted Stereotactic Electroencephalography Electrode Placement.

BACKGROUND: Robotic-assisted stereotactic electroencephalography (sEEG) electrode placement is increasingly common at specialized epilepsy centers. High accuracy and low complication rates are essential to realizing the benefits of sEEG surgery. The aim of this study was to describe for the first time in the literature a method for a stereotactic registration checkpoint to verify intraoperative accuracy during robotic-assisted sEEG and to report our institutional experience with this technique. METHODS: All cases performed with this technique since the adoption of robotic-assisted sEEG at our institution were retrospectively reviewed. RESULTS: In 4 of 111 consecutive sEEG operations, use of the checkpoint detected an intraoperative registration error, which was addressed before completion of sEEG electrode placement. CONCLUSIONS: The use of a registration checkpoint in robotic-assisted sEEG surgery is a simple technique that can prevent electrode misplacement and improve the safety profile of this procedure.

Rare Case of Pediatric Disseminated Choroid Plexus Papilloma: Literature Review and Call for Reclassification.

INTRODUCTION: Choroid plexus tumors are rare neuroectodermal tumors that arise from the choroid plexus. Choroid plexus papillomas (CPPs) represent the lowest grade of these types of tumors and have a WHO grade I designation. Despite their typical low grade, some CPPs can exhibit aggressive behaviors including parenchymal invasion and dissemination throughout the neuro-axis. Due to their association with the choroid plexus, patients with CPP commonly present with signs and symptoms of hydrocephalus and increased intracranial pressure. CASE PRESENTATION: A 2-year-old male presented in extremis with acute hydrocephalus and seizure. He was found to have a large left intraventricular mass with innumerable intraparenchymal and extra-axial cysts throughout his neuro-axis. A literature review revealed five similar disseminated CPP cases with innumerable lesions. This is the youngest reported patient with disseminated CPP and the first with multiple compressive lesions. Following cranial resection and thoracic decompression, the patient's lesions have remained stable (2 years of follow-up). A literature search of the PubMed/Medline databases was performed using the search terms ["disseminated choroid plexus papilloma" OR "choroid plexus papilloma" OR "metastatic choroid plexus papilloma"] up to March 2021. Articles were then screened for similar patient radiographic presentation and histological diagnosis. To mitigate publication bias, referenced articles were utilized to identify other case reports and case series. DISCUSSION/CONCLUSION: We describe a rare case of a lateral ventricle CPP with widespread leptomeningeal dissemination causing acute obstructive hydrocephalus and compressive myelopathy requiring cerebrospinal fluid diversion and intracranial resection followed by thoracic spine decompression. This case report serves to broaden knowledge of disseminated CPP and to encourage complete neuro-axis imaging for choroid plexus tumors. Additionally, we propose a naming paradigm refinement that includes radiographic characteristics.

A randomized controlled trial of a video intervention shows evidence of increasing COVID-19 vaccination intention.

Increasing acceptance of COVID-19 vaccines is imperative for public health. Previous research on educational interventions to overcome vaccine hesitancy have shown mixed effects in increasing vaccination intention, although much of this work has focused on parental attitudes toward childhood vaccination. In this study, we conducted a randomized controlled trial to investigate whether vaccination intention changes after viewing an animated YouTube video explaining how COVID-19 mRNA vaccines work. We exposed participants to one of four interventions-watching the video with a male narrator, watching the same video with a female narrator, reading the text of the transcript of the video, or receiving no information (control group). We found that participants who watched the version of the video with a male narrator expressed statistically significant increased vaccination intention compared to the control group. The video with a female narrator had more variation in results. As a whole, there was a non-significant increased vaccination intention when analyzing all participants who saw the video with a female narrator; however, for politically conservative participants there was decreased vaccination intention for this intervention compared to the control group at a threshold between being currently undecided and expressing probable interest. These results are encouraging for the ability of interventions as simple as YouTube videos to increase vaccination propensity, although the inconsistent response to the video with a female narrator demonstrates the potential for bias to affect how certain groups respond to different messengers.

Neurological emergency from rare spinal metalloma: Case report and literature review.

Metallosis is a rare and poorly understood long-term complication of instrumented surgery that can result in an inflammatory pseudotumor termed metalloma. We describe a particularly unique case and compare it to 6 analogous cases identified by PubMed and/or Medline search through July 2020. A 79-year-old male with multiple prior spinal lumbar fusion procedures presented with progressive weakness and pain. Imaging revealed a large mass surrounding the right-sided paraspinal rod with extension into the spinal canal, neural foramina, extraforaminal spaces, psoas muscle, marrow spaces, and right sided pedicles. The case presented is a unique example of a unilateral metalloma with mixed-metal instrumentation that created a progressive neurologic deficit without infection, pseudoarthrosis, or hardware failure. This case highlights the lack of understanding regarding the pathophysiology of metallosis and metalloma in spinal instrumentation. We highlight the imaging findings of metalloma to encourage early identification for removal and decompression.

Minimally Invasive Posterior Cervical Diskectomy: Operative Video.

Cervical disk protrusion is a common pathology. Anterior diskectomy and fusion is considered the gold standard of treatment, although anterior arthroplasty has gained some acceptance in the past decade as an alternative. Posterior cervical minimally invasive diskectomy is a rarely used technique, and there is less literature discussing this procedure. We have found this technique to be useful in lateral, soft disk herniations not ventral to the cord or mineralized. This avoids an anterior approach with risk to the cervical viscera, the dysphagia associated with an anterior approach, the need for expensive implanted instrumentation, and the need for prolonged activity restrictions after an anterior approach. We include a Video 1 documenting the technique of minimally invasive posterior cervical diskectomy (anatomic landmarks of interest are labeled at several points during the video). This is achieved prone on an OSI Jackson table (Mizuho OSI, Union City, California, USA) without skeletal fixation. A stepwise technique is used to advance an 18-mm tube retractor into contact with the facet and lateral lamina. A 5-mm smooth diamond drill is used to perform a foraminotomy. To avoid nerve root or spinal cord manipulation, it is often necessary to remove some of the rostral aspect of the inferior pedicle to gain access to the axilla and disk protrusion. The procedure is rapid, well tolerated, and performed as outpatient, and it results in a rapid return to normal activity.

Drug-Induced Seizures: Considerations for Underlying Molecular Mechanisms.

A broad spectrum of chemical entities have been associated with drug-induced seizure (DIS), emphasizing the importance of this potential liability across various drug classes (e.g., antidepressants, antipsychotics, antibiotics, and analgesics among others). Despite its importance within drug safety testing, an understanding of the molecular mechanisms associated with DIS is often lacking. The etiology of DIS is understood to be a result of either a deficit in inhibitory (e.g., gamma aminobutyric acid) or an elevated excitatory (e.g., glutamate) signaling, leading to synchronous neuronal depolarization affecting various brain regions and impairing normal neurological functions. How this altered neuronal signaling occurs and how these changes interact with other non-brain receptor driven DIS-associated changes such as metabolic disturbances, electrolyte imbalances, altered drug metabolism, and withdrawal effects are poorly understood. Herein, we discuss important molecular mechanisms identified in DIS for several drugs and/or drug classes. With a better understanding of the molecular mechanisms associated with DIS, in vivo or in vitro models may be applied to characterize and mitigate DIS risk during drug development. Susceptibility stratification for DIS presents species differences in the following order beagle dogs > rodents and cynomolgus monkeys > Göttingen minipigs with a more than 2-fold difference between canines and minipigs, which is important to consider during non-clinical species selection. While clinical signs such as myoclonus, severe muscle jerks, or convulsions are often associated with abnormal epileptiform EEG activity, tremors are most of the time physiological and rarely observed with concurrent epileptiform EEG activity which need to be considered during DIS risk evaluation.

Characterization of long G4-rich enhancer-associated genomic regions engaging in a novel loop:loop 'G4 Kissing' interaction.

Mammalian antibody switch regions (∼1500 bp) are composed of a series of closely neighboring G4-capable sequences. Whereas numerous structural and genome-wide analyses of roles for minimal G4s in transcriptional regulation have been reported, Long G4-capable regions (LG4s)-like those at antibody switch regions-remain virtually unexplored. Using a novel computational approach we have identified 301 LG4s in the human genome and find LG4s prone to mutation and significantly associated with chromosomal rearrangements in malignancy. Strikingly, 217 LG4s overlap annotated enhancers, and we find the promoters regulated by these enhancers markedly enriched in G4-capable sequences suggesting G4s facilitate promoter-enhancer interactions. Finally, and much to our surprise, we also find single-stranded loops of minimal G4s within individual LG4 loci are frequently highly complementary to one another with 178 LG4 loci averaging >35 internal loop:loop complements of >8 bp. As such, we hypothesized (then experimentally confirmed) that G4 loops within individual LG4 loci directly basepair with one another (similar to characterized stem-loop kissing interactions) forming a hitherto undescribed, higher-order, G4-based secondary structure we term a 'G4 Kiss or G4K'. In conclusion, LG4s adopt novel, higher-order, composite G4 structures directly contributing to the inherent instability, regulatory capacity, and maintenance of these conspicuous genomic regions.

Nitric Oxide Signaling Strengthens Inhibitory Synapses of Cerebellar Molecular Layer Interneurons through a GABARAP-Dependent Mechanism.

Nitric oxide (NO) is an important signaling molecule that fulfills diverse functional roles as a neurotransmitter or diffusible second messenger in the developing and adult CNS. Although the impact of NO on different behaviors such as movement, sleep, learning, and memory has been well documented, the identity of its molecular and cellular targets is still an area of ongoing investigation. Here, we identify a novel role for NO in strengthening inhibitory GABAA receptor-mediated transmission in molecular layer interneurons of the mouse cerebellum. NO levels are elevated by the activity of neuronal NO synthase (nNOS) following Ca2+ entry through extrasynaptic NMDA-type ionotropic glutamate receptors (NMDARs). NO activates protein kinase G with the subsequent production of cGMP, which prompts the stimulation of NADPH oxidase and protein kinase C (PKC). The activation of PKC promotes the selective strengthening of α3-containing GABAARs synapses through a GΑΒΑ receptor-associated protein-dependent mechanism. Given the widespread but cell type-specific expression of the NMDAR/nNOS complex in the mammalian brain, our data suggest that NMDARs may uniquely strengthen inhibitory GABAergic transmission in these cells through a novel NO-mediated pathway.SIGNIFICANCE STATEMENT Long-term changes in the efficacy of GABAergic transmission is mediated by multiple presynaptic and postsynaptic mechanisms. A prominent pathway involves crosstalk between excitatory and inhibitory synapses whereby Ca2+-entering through postsynaptic NMDARs promotes the recruitment and strengthening of GABAA receptor synapses via Ca2+/calmodulin-dependent protein kinase II. Although Ca2+ transport by NMDARs is also tightly coupled to nNOS activity and NO production, it has yet to be determined whether this pathway affects inhibitory synapses. Here, we show that activation of NMDARs trigger a NO-dependent pathway that strengthens inhibitory GABAergic synapses of cerebellar molecular layer interneurons. Given the widespread expression of NMDARs and nNOS in the mammalian brain, we speculate that NO control of GABAergic synapse efficacy may be more widespread than has been appreciated.

Ozone-induced enhancement of airway hyperreactivity in rhesus macaques: Effects of antioxidant treatment.

BACKGROUND: Ozone (O3) inhalation elicits airway inflammation and impairs treatment responsiveness in asthmatic patients. The underlying immune mechanisms have been difficult to study because of the lack of relevant experimental models. Rhesus macaques spontaneously have asthma and have a similar immune system to human subjects. OBJECTIVES: We sought to investigate mucosal immune changes after O3 inhalation in a clinically relevant nonhuman primate asthma model and to study the effects of an antioxidant synthetic lignan (synthetic secoisolariciresinol diglucoside [LGM2605]). METHODS: A cohort of macaques (n = 17) previously characterized with airway hyperreactivity (AHR) to methacholine was assessed (day 1). Macaques were treated (orally) with LGM2605 (25 mg/kg) or placebo twice per day for 7 days, exposed to 0.3 ppm O3 or air for 6 hours (on day 7), and studied 12 hours later (day 8). Lung function, blood and bronchoalveolar lavage (BAL) fluid immune cell profile, and bronchial brushing and blood cell mRNA expression were assessed. RESULTS: O3 induced significant BAL fluid neutrophilia and eosinophilia and increased AHR and expression of IL6 and IL25 mRNA in the airway epithelium together with increased BAL fluid group 2 innate lymphoid cell (ILC2s), CD1c+ myeloid dendritic cell, and CD4+ T-cell counts and diminished surfactant protein D expression. Although LGM2605 attenuated some of the immune and inflammatory changes, it completely abolished O3-induced AHR. CONCLUSION: ILC2s, CD1c+ myeloid dendritic cells, and CD4+ T cells are selectively involved in O3-induced asthma exacerbation. The inflammatory changes were partially prevented by antioxidant pretreatment with LGM2605, which had an unexpectedly disproportionate protective effect on AHR.

Preload Sensitivity with TORVAD Counterpulse Support Prevents Suction and Overpumping.

PURPOSE: This study compares preload sensitivity of continuous flow (CF) VAD support to counterpulsation using the Windmill toroidal VAD (TORVAD). The TORVAD is a two-piston rotary pump that ejects 30 mL in early diastole, which increases cardiac output while preserving aortic valve flow. METHODS: Preload sensitivity was compared for CF vs. TORVAD counterpulse support using two lumped parameter models of the cardiovascular system: (1) an open-loop model of the systemic circulation was used to obtain ventricular function curves by isolating the systemic circulation and prescribing preload and afterload boundary conditions, and (2) a closed-loop model was used to test the physiological response to changes in pulmonary vascular resistance, systemic vascular resistance, heart rate, inotropic state, and blood volume. In the open-loop model, ventricular function curves (cardiac output vs left ventricular preload) are used to assess preload sensitivity. In the closed-loop model, left ventricular end systolic volume is used to assess the risk of left ventricular suction. RESULTS: At low preloads of 5 mmHg, CF support overpumps the circulation compared to TORVAD counterpulse support (cardiac output of 3.3 L/min for the healthy heart, 4.7 with CF support, and 3.5 with TORVAD counterpulse support) and has much less sensitivity than counterpulse support (0.342 L/min/mmHg for the healthy heart, 0.092 with CF support, and 0.306 with TORVAD counterpulse support). In the closed-loop model, when PVR is increased beyond 0.035 mmHg s/mL, CF support overpumps the circulation and causes ventricular suction events, but TORVAD counterpulse support maintains sufficient ventricular volume and does not cause suction. CONCLUSIONS: Counterpulse support with the TORVAD preserves aortic valve flow and provides physiological sensitivity across all preload conditions. This should prevent overpumping and minimize the risk of suction.

Response of Sulfolobus solfataricus Dpo4 polymerase in vitro to a DNA G-quadruplex.

Repetitive DNA sequences support the formation of structures that can interrupt replication and repair, leading to breaks and mutagenesis. One particularly stable structure is G-quadruplex (G4) DNA, which is four-stranded and formed from tandemly repetitive guanine bases. When folded within a template, G4 interferes with DNA synthesis. Similar to non-duplex structures, DNA base lesions can also halt an advancing replication fork, but the Y-family polymerases solve this problem by bypassing the damage. In order to better understand how guanine-rich DNA is replicated, we have investigated the activity of the model Y-family polymerase, Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4), on guanine-rich templates in vitro. We find that Dpo4 progression on templates containing either a single GC-rich hairpin or a G4 DNA structure is greatly reduced and synthesis stalls at the structure. Human polymerase eta (hPol eta) showed the same pattern of stalling at G4; however, and in contrast to Klenow, hPol eta and Dpo4 partially synthesise into the guanine repeat. Substitution of the nucleotide selectivity residue in Dpo4 with alanine permitted ribonucleotide incorporation on unstructured templates, but this further reduced the ability of Dpo4 to synthesise across from the guanine repeats. The advancement of Dpo4 on G4 templates was highest when the reaction was supplied with only deoxycytidine triphosphate, suggesting that high-fidelity synthesis is favoured over misincorporation. Our results are consistent with a model where the Y-family polymerases pause upon encountering G4 structures but have an ability to negotiate some synthesis through tetrad-associated guanines. This suggests that the Y-family polymerases reduce mutagenesis by catalysing the accurate replication of repetitive DNA sequences, but most likely in concert with additional replication and structure resolution activities.

A Novel Toroidal-Flow Left Ventricular Assist Device Minimizes Blood Trauma: Implications of Improved Ventricular Assist Device Hemocompatibility.

BACKGROUND: Continuous-flow left ventricular assist devices (LVADs) cause blood trauma that includes von Willebrand factor degradation, platelet activation, and subclinical hemolysis. Blood trauma contributes to bleeding, thrombosis, and stroke, which cause significant morbidity and mortality. The TORVAD (Windmill Cardiovascular Systems, Inc, Austin, TX) is a first-of-its kind, toroidal-flow LVAD designed to minimize blood trauma. We tested the hypothesis that the TORVAD causes less blood trauma than the HeartMate II (Abbott Laboratories, Pleasanton, CA) LVAD. METHODS: Whole human blood was circulated for 6 hours in ex vivo circulatory loops with a HeartMate II (n = 8; 10,000 rpm, 70 ± 6 mm Hg, 4.0 ± 0.1 L/min) or TORVAD (n = 6; 144 rpm, 72 ± 0.0 mm Hg, 4.3 ± 0.0 L/min). von Willebrand factor degradation was quantified with electrophoresis and immunoblotting. Platelet activation was quantified by cluster of differentiation (CD) 41/61 enzyme-linked immunosorbent assay (ELISA). Hemolysis was quantified by plasma free hemoglobin ELISA. RESULTS: The TORVAD caused significantly less degradation of high-molecular-weight von Willebrand factor multimers (-10% ± 1% vs -21% ± 1%, p < 0.0001), accumulation of low-molecular-weight von Willebrand factor multimers (22% ± 2% vs 45% ± 2%, p < 0.0001), and accumulation of von Willebrand factor degradation fragments (7% ± 1% vs 25% ± 6%, p < 0.05) than the HeartMate II. The TORVAD did not activate platelets, whereas the HeartMate II caused significant platelet activation (CD 41/61: 645 ± 20 ng/mL vs 1,581 ± 150 ng/mL, p < 0.001; normal human CD 41/61, 593 ng/mL; range, 400 to 800 ng/mL). Similarly, the TORVAD caused minimal hemolysis, whereas the HeartMate II caused significant hemolysis (plasma free hemoglobin: 11 ± 2 vs 109 ± 10 mg/dL, p < 0.0001; normal human plasma free hemoglobin <4 mg/dL). CONCLUSIONS: The TORVAD design, with markedly lower shear stress and pulsatile flow, caused significantly less blood trauma than the HeartMate II. LVADs with reduced blood trauma are likely to improve clinical outcomes and expand LVAD therapy into patients with less advanced heart failure.

Oxidative damage of SP-D abolishes control of eosinophil extracellular DNA trap formation.

The asthmatic airways are highly susceptible to inflammatory injury by air pollutants such as ozone (O3 ), characterized by enhanced activation of eosinophilic granulocytes and a failure of immune protective mechanisms. Eosinophil activation during asthma exacerbation contributes to the proinflammatory oxidative stress by high levels of nitric oxide (NO) production and extracellular DNA release. Surfactant protein-D (SP-D), an epithelial cell product of the airways, is a critical immune regulatory molecule with a multimeric structure susceptible to oxidative modifications. Using recombinant proteins and confocal imaging, we demonstrate here that SP-D directly bound to the membrane and inhibited extracellular DNA trap formation by human and murine eosinophils in a concentration and carbohydrate-dependent manner. Combined allergic airway sensitization and O3 exposure heightened eosinophilia and nos2 mRNA (iNOS) activation in the lung tissue and S-nitrosylation related de-oligomerisation of SP-D in the airways. In vitro reproduction of the iNOS action led to similar effects on SP-D. Importantly, S-nitrosylation abolished the ability of SP-D to block extracellular DNA trap formation. Thus, the homeostatic negative regulatory feedback between SP-D and eosinophils is destroyed by the NO-rich oxidative lung tissue environment in asthma exacerbations.

Scaling the Low-Shear Pulsatile TORVAD for Pediatric Heart Failure.

This article provides an overview of the design challenges associated with scaling the low-shear pulsatile TORVAD ventricular assist device (VAD) for treating pediatric heart failure. A cardiovascular system model was used to determine that a 15 ml stroke volume device with a maximum flow rate of 4 L/min can provide full support to pediatric patients with body surface areas between 0.6 and 1.5 m. Low-shear stress in the blood is preserved as the device is scaled down and remains at least two orders of magnitude less than continuous flow VADs. A new magnetic linkage coupling the rotor and piston has been optimized using a finite element model (FEM) resulting in increased heat transfer to the blood while reducing the overall size of TORVAD. Motor FEM has also been used to reduce motor size and improve motor efficiency and heat transfer. FEM analysis predicts no more than 1°C temperature rise on any blood or tissue contacting surface of the device. The iterative computational approach established provides a methodology for developing a TORVAD platform technology with various device sizes for supporting the circulation of infants to adults.

G-quadruplex DNA structures can interfere with uracil glycosylase activity in vitro.

Genome sequences that contain tandem repeats of guanine can form stable four-stranded structures known as G-quadruplex, or G4 DNA. While the molecular mechanisms are not fully defined, such guanine-rich loci are prone to mutagenesis and recombination. Various repair pathways function to reduce the potential for genome instability by correcting base damage and replication errors; however, it is not yet fully defined how well these processes function at G4 DNA. One frequent form of base damage occurs from cytidine deamination, resulting in deoxyuracil and UG mismatches. In duplex and single-stranded DNA, uracil bases are recognised and excised by uracil glycosylases. Here, we tested the efficiency of uracil glycosylase activity in vitro on uracil bases located directly adjacent to guanine repeats and G4 DNA. We show that uracil excision by bacterial UDG and human hUNG2 is reduced at uracils positioned directly 5' or 3' of a guanine tetrad. Control reactions using oligonucleotides disrupted for G4 formation or reaction conditions that do not favour G4 formation resulted in full uracil excision activity. Based on these in vitro results, we suggest that folding of guanine-rich DNA into G4 DNA results in a DNA conformation that is resistant to uracil glycosylase-initiated repair and this has the potential to increase the risk of instability at guanine repeats in the genome.