A Dimension-Adaptive Multi-Index Monte Carlo Method Applied to a Model of a Heat Exchanger

We present an adaptive version of the Multi-Index Monte Carlo method, introduced by Haji-Ali, Nobile and Tempone (2016), for simulating PDEs with coefficients that are random fields. A classical technique for sampling from these random fields is the Karhunen-Lo\`eve expansion. Our adaptive algorithm is based on the adaptive algorithm used in sparse grid cubature as introduced by Gerstner and Griebel (2003), and automatically chooses the number of terms needed in this expansion, as well as the required spatial discretizations of the PDE model. We apply the method to a simplified model of a heat exchanger with random insulator material, where the stochastic characteristics are modeled as a lognormal random field, and we show consistent computational savings

Autoimmune and autoinflammatory mechanisms in uveitis

The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of Treg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8(+) T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders

Adalimumab in Patients with Active Noninfectious Uveitis

BACKGROUND: Patients with noninfectious uveitis are at risk for long-term complications of uncontrolled inflammation, as well as for the adverse effects of long-term glucocorticoid therapy. We conducted a trial to assess the efficacy and safety of adalimumab as a glucocorticoid-sparing agent for the treatment of noninfectious uveitis. METHODS: This multinational phase 3 trial involved adults who had active noninfectious intermediate uveitis, posterior uveitis, or panuveitis despite having received prednisone treatment for 2 or more weeks. Investigators and patients were unaware of the study-group assignments. Patients were randomly assigned in a 1:1 ratio to receive adalimumab (a loading dose of 80 mg followed by a dose of 40 mg every 2 weeks) or matched placebo. All patients received a mandatory prednisone burst followed by tapering of prednisone over the course of 15 weeks. The primary efficacy end point was the time to treatment failure occurring at or after week 6. Treatment failure was a multicomponent outcome that was based on assessment of new inflammatory lesions, best corrected visual acuity, anterior chamber cell grade, and vitreous haze grade. Nine ranked secondary efficacy end points were assessed, and adverse events were reported. RESULTS: The median time to treatment failure was 24 weeks in the adalimumab group and 13 weeks in the placebo group. Among the 217 patients in the intention-to-treat population, those receiving adalimumab were less likely than those in the placebo group to have treatment failure (hazard ratio, 0.50; 95% confidence interval, 0.36 to 0.70; P<0.001). Outcomes with regard to three secondary end points (change in anterior chamber cell grade, change in vitreous haze grade, and change in best corrected visual acuity) were significantly better in the adalimumab group than in the placebo group. Adverse events and serious adverse events were reported more frequently among patients who received adalimumab (1052.4 vs. 971.7 adverse events and 28.8 vs. 13.6 serious adverse events per 100 person-years). CONCLUSIONS: In our trial, adalimumab was found to be associated with a lower risk of uveitic flare or visual impairment and with more adverse events and serious adverse events than was placebo

Doyne lecture 2016:intraocular health and the many faces of inflammation

Dogma for reasons of immune privilege including sequestration (sic) of ocular antigen, lack of lymphatic and immune competent cells in the vital tissues of the eye has long evaporated. Maintaining tissue and cellular health to preserve vision requires active immune responses to prevent damage and respond to danger. A priori the eye must contain immune competent cells, undergo immune surveillance to ensure homoeostasis as well as an ability to promote inflammation. By interrogating immune responses in non-infectious uveitis and compare with age-related macular degeneration (AMD), new concepts of intraocular immune health emerge. The role of macrophage polarisation in the two disorders is a tractable start. TNF-alpha regulation of macrophage responses in uveitis has a pivotal role, supported via experimental evidence and validated by recent trial data. Contrast this with the slow, insidious degeneration in atrophic AMD or in neovasular AMD, with the compelling genetic association with innate immunity and complement, highlights an ability to attenuate pathogenic immune responses and despite known inflammasome activation. Yolk sac-derived microglia maintains tissue immune health. The result of immune cell activation is environmentally dependent, for example, on retinal cell bioenergetics status, autophagy and oxidative stress, and alterations that skew interaction between macrophages and retinal pigment epithelium (RPE). For example, dead RPE eliciting macrophage VEGF secretion but exogenous IL-4 liberates an anti-angiogenic macrophage sFLT-1 response. Impaired autophagy or oxidative stress drives inflammasome activation, increases cytotoxicity, and accentuation of neovascular responses, yet exogenous inflammasome-derived cytokines, such as IL-18 and IL-33, attenuate responses

Deletion of the gabra2 gene results in hypersensitivity to the acute effects of ethanol but does not alter ethanol self administration

Human genetic studies have suggested that polymorphisms of the GABRA2 gene encoding the GABA(A) α2-subunit are associated with ethanol dependence. Variations in this gene also convey sensitivity to the subjective effects of ethanol, indicating a role in mediating ethanol-related behaviours. We therefore investigated the consequences of deleting the α2-subunit on the ataxic and rewarding properties of ethanol in mice. Ataxic and sedative effects of ethanol were explored in GABA(A) α2-subunit wildtype (WT) and knockout (KO) mice using a Rotarod apparatus, wire hang and the duration of loss of righting reflex. Following training, KO mice showed shorter latencies to fall than WT littermates under ethanol (2 g/kg i.p.) in both Rotarod and wire hang tests. After administration of ethanol (3.5 g/kg i.p.), KO mice took longer to regain the righting reflex than WT mice. To ensure the acute effects are not due to the gabra2 deletion affecting pharmacokinetics, blood ethanol concentrations were measured at 20 minute intervals after acute administration (2 g/kg i.p.), and did not differ between genotypes. To investigate ethanol's rewarding properties, WT and KO mice were trained to lever press to receive increasing concentrations of ethanol on an FR4 schedule of reinforcement. Both WT and KO mice self-administered ethanol at similar rates, with no differences in the numbers of reinforcers earned. These data indicate a protective role for α2-subunits, against the acute sedative and ataxic effects of ethanol. However, no change was observed in ethanol self administration, suggesting the rewarding effects of ethanol remain unchange

Exotendons for assistance of human locomotion

BACKGROUND: Powered robotic exoskeletons for assistance of human locomotion are currently under development for military and medical applications. The energy requirements for such devices are excessive, and this has become a major obstacle for practical applications. Legged locomotion in many animals, however, is very energy efficient. We propose that poly-articular elastic mechanisms are a major contributor to the economy of locomotion in such specialized animals. Consequently, it should be possible to design unpowered assistive devices that make effective use of similar mechanisms. METHODS: A passive assistive technology is presented, based on long elastic cords attached to an exoskeleton and guided by pulleys placed at the joints. A general optimization procedure is described for finding the best geometrical arrangement of such "exotendons" for assisting a specific movement. Optimality is defined either as minimal residual joint moment or as minimal residual joint power. Four specific exotendon systems with increasing complexity are considered. Representative human gait data were used to optimize each of these four systems to achieve maximal assistance for normal walking. RESULTS: The most complex exotendon system, with twelve pulleys per limb, was able to reduce the joint moments required for normal walking by 71% and joint power by 74%. A simpler system, with only three pulleys per limb, could reduce joint moments by 46% and joint power by 47%. CONCLUSION: It is concluded that unpowered passive elastic devices can substantially reduce the muscle forces and the metabolic energy needed for walking, without requiring a change in movement. When optimally designed, such devices may allow independent locomotion in patients with large deficits in muscle function

Adalimumab in Active and Inactive, Non-Infectious Uveitis: Global Results from the VISUAL I and VISUAL II Trials

PURPOSE: Report global adalimumab safety and efficacy outcomes in patients with non-infectious uveitis. METHODS: Adults with non-infectious intermediate, posterior, or panuveitis were randomized 1:1 to receive placebo or adalimumab in the VISUAL I (active uveitis) or VISUAL II (inactive uveitis) trials. Integrated global and Japan substudy results are reported. The primary endpoint was time to treatment failure (TF). RESULTS: In the integrated studies, TF risk was significantly reduced (hazard ratio [95% CI]) with adalimumab versus placebo (VISUAL I: HR = 0.56 [0.40-0.76], p < 0.001; VISUAL II: HR = 0.52 [0.37-0.74], p < 0.001). In Japan substudies, no consistent trends were observed between groups (VISUAL I: HR = 1.20 [0.41-3.54]; VISUAL II: HR = 0.45 [0.20-1.03]). Adverse event rates were similar between treatment groups in both studies (854 to 1063 events/100 participant-years). CONCLUSIONS: Adalimumab lowered time to TF versus placebo in the integrated population; no consistent trends were observed in Japan substudies. Safety results were consistent between studies

Safety and Efficacy of Adalimumab in Patients with Noninfectious Uveitis in an Ongoing Open-Label Study: VISUAL III

PURPOSE: To evaluate safety and efficacy of adalimumab in patients with noninfectious intermediate, posterior, or panuveitis. DESIGN: Phase 3, open-label, multicenter clinical trial extension (VISUAL III). PARTICIPANTS: Adults meeting treatment failure (TF) criteria or who completed VISUAL I or II (phase 3, randomized, double-masked, placebo-controlled) without TF. METHODS: Patients received adalimumab 40 mg every other week. Interim follow-up data were described from VISUAL III weeks 0 through 78. MAIN OUTCOME MEASURES: Disease quiescence, steroid-free quiescence, active inflammatory chorioretinal/retinal vascular lesions, anterior chamber cell grade, vitreous haze grade, best-corrected visual acuity (BCVA), and corticosteroid dose. Binary data were reported using nonresponder imputation (NRI), continuous data using last observation carried forward and as-observed analysis, and corticosteroid dose using observed-case analysis. Adverse events (AEs) were reported from first adalimumab dose in VISUAL III through interim cutoff. RESULTS: Of 424 patients enrolled, 371 were included in intent-to-treat analysis. At study entry, 242 of 371 (65%) patients had active uveitis; 60% (145/242, NRI) achieved quiescence at week 78, and 66% (95/143, as-observed) of those were corticosteroid free. At study entry, 129 of 371 (35%) patients had inactive uveitis; 74% (96/129, NRI) achieved quiescence at week 78, and 93% (89/96, as-observed) of those were corticosteroid free. Inflammatory lesions, anterior chamber grade, and vitreous haze grade showed initial improvement followed by decline in patients with active uveitis and remained stable in patients with inactive uveitis. BCVA improved in patients with active uveitis from weeks 0 to 78 (0.27 to 0.14 logMAR; left and right eyes; as-observed) and remained stable in patients with inactive uveitis. Mean corticosteroid dose decreased from 13.6 mg/day (week 0) to 2.6 mg/day (week 78) in patients with active uveitis and remained stable in those with inactive uveitis (1.5-1.2 mg/day). AEs (424 events/100 patient-years) and serious AEs (16.5 events/100 patient-years) were comparable with previous VISUAL trials. CONCLUSIONS: Patients with active uveitis at study entry who received adalimumab therapy were likely to achieve quiescence, improve visual acuity, and reduce their daily uveitis-related systemic corticosteroid use. Most patients with inactive uveitis at study entry sustained quiescence without a systemic corticosteroid dose increase. No new safety signals were identified

Allometric Scaling of the Active Hematopoietic Stem Cell Pool across Mammals

BACKGROUND: Many biological processes are characterized by allometric relations of the type Y = Y (0) M(b) between an observable Y and body mass M, which pervade at multiple levels of organization. In what regards the hematopoietic stem cell pool, there is experimental evidence that the size of the hematopoietic stem cell pool is conserved in mammals. However, demands for blood cell formation vary across mammals and thus the size of the active stem cell compartment could vary across species. METHODOLOGY/PRINCIPLE FINDINGS: Here we investigate the allometric scaling of the hematopoietic system in a large group of mammalian species using reticulocyte counts as a marker of the active stem cell pool. Our model predicts that the total number of active stem cells, in an adult mammal, scales with body mass with the exponent ¾. CONCLUSION/SIGNIFICANCE: The scaling predicted here provides an intuitive justification of the Hayflick hypothesis and supports the current view of a small active stem cell pool supported by a large, quiescent reserve. The present scaling shows excellent agreement with the available (indirect) data for smaller mammals. The small size of the active stem cell pool enhances the role of stochastic effects in the overall dynamics of the hematopoietic system

Long-Term Safety and Efficacy of Adalimumab in Patients With Noninfectious Intermediate Uveitis, Posterior Uveitis, or Panuveitis

PURPOSE: To evaluate long-term efficacy and safety of extended treatment with adalimumab in patients with noninfectious intermediate, posterior, or panuveitis. DESIGN: Open-label, multicenter, phase 3 extension study (VISUAL III). PARTICIPANTS: Adults who had completed a randomized, placebo-controlled phase 3 parent trial (VISUAL I or II) without treatment failure (inactive uveitis) or discontinued after meeting treatment failure criteria (active uveitis). METHODS: Patients received subcutaneous adalimumab 40 mg every other week. Data were collected for ≤362 weeks. Adverse events (AEs) were recorded until 70 days after the last dose of study drug. MAIN OUTCOME MEASURES: Main outcome measures were long-term safety and quiescence; other efficacy variables included inflammatory lesions, anterior chamber cell and vitreous haze grade, macular edema, visual acuity, and dose of uveitis-related corticosteroids. RESULTS: Of 424 patients enrolled, 67% (283/424) had active uveitis and 33% (141/424) had inactive uveitis at study entry; 60 patients subsequently met exclusion criteria, and 364 patients were included in the intent-to-treat analysis. Efficacy variables were analyzed through week 150 when approximately 50% of patients (214/424) remained in the study. The percentage of patients in quiescence increased from 34% (122/364) at week 0 to 85% (153/180) at week 150. Corticosteroid-free quiescence was achieved by 54% (66/123) and 89% (51/57) of patients with active or inactive uveitis at study entry, respectively, by week 150. Mean daily dose of corticosteroids was reduced from 9.4±17.1 mg/day at week 0 (n=359) to 1.5±3.9 mg/day at week 150 (n=181). The percentage of patients who achieved other efficacy variables increased over time for those with active uveitis at study entry and was maintained for those with inactive uveitis. The most frequently reported treatment-emergent AEs of special interest for adalimumab were infections (n=275; 78.7 events/100 patient-years); AEs and serious AEs occurred at a rate of 396 events/100 patient-years and 15 events/100 patient-years, respectively. CONCLUSIONS: Long-term treatment with adalimumab led to quiescence and reduced corticosteroid use for patients who entered VISUAL III with active uveitis and maintenance of quiescence for those with inactive uveitis. AEs were comparable to those reported in the parent trials and consistent with the known safety profile of adalimumab