Evolving Improved Sampling Protocols for Dose-Response Modelling Using Genetic Algorithms with a Profile-Likelihood Metric.

Practical limitations of quality and quantity of data can limit the precision of parameter identification in mathematical models. Model-based experimental design approaches have been developed to minimise parameter uncertainty, but the majority of these approaches have relied on first-order approximations of model sensitivity at a local point in parameter space. Practical identifiability approaches such as profile-likelihood have shown potential for quantifying parameter uncertainty beyond linear approximations. This research presents a genetic algorithm approach to optimise sample timing across various parameterisations of a demonstrative PK-PD model with the goal of aiding experimental design. The optimisation relies on a chosen metric of parameter uncertainty that is based on the profile-likelihood method. Additionally, the approach considers cases where multiple parameter scenarios may require simultaneous optimisation. The genetic algorithm approach was able to locate near-optimal sampling protocols for a wide range of sample number (n = 3-20), and it reduced the parameter variance metric by 33-37% on average. The profile-likelihood metric also correlated well with an existing Monte Carlo-based metric (with a worst-case r > 0.89), while reducing computational cost by an order of magnitude. The combination of the new profile-likelihood metric and the genetic algorithm demonstrate the feasibility of considering the nonlinear nature of models in optimal experimental design at a reasonable computational cost. The outputs of such a process could allow for experimenters to either improve parameter certainty given a fixed number of samples, or reduce sample quantity while retaining the same level of parameter certainty.

Adducin Regulates Sarcomere Disassembly During Cardiomyocyte Mitosis.

BACKGROUND: Recent interest in understanding cardiomyocyte cell cycle has been driven by potential therapeutic applications in cardiomyopathy. However, despite recent advances, cardiomyocyte mitosis remains a poorly understood process. For example, it is unclear how sarcomeres are disassembled during mitosis to allow the abscission of daughter cardiomyocytes. METHODS: Here, we use a proteomics screen to identify adducin, an actin capping protein previously not studied in cardiomyocytes, as a regulator of sarcomere disassembly. We generated many adeno-associated viruses and cardiomyocyte-specific genetic gain-of-function models to examine the role of adducin in neonatal and adult cardiomyocytes in vitro and in vivo. RESULTS: We identify adducin as a regulator of sarcomere disassembly during mammalian cardiomyocyte mitosis. α/γ-adducins are selectively expressed in neonatal mitotic cardiomyocytes, and their levels decline precipitously thereafter. Cardiomyocyte-specific overexpression of various splice isoforms and phospho-isoforms of α-adducin in identified Thr445/Thr480 phosphorylation of a short isoform of α-adducin as a potent inducer of neonatal cardiomyocyte sarcomere disassembly. Concomitant overexpression of this α-adducin variant along with γ-adducin resulted in stabilization of the adducin complex and persistent sarcomere disassembly in adult mice, which is mediated by interaction with α-actinin. CONCLUSIONS: These results highlight an important mechanism for coordinating cytoskeletal morphological changes during cardiomyocyte mitosis.

Household Air Pollution Interventions to Improve Health in Low- and Middle-Income Countries: An Official American Thoracic Society Research Statement.

Background: An estimated 3 billion people, largely in low- and middle-income countries, rely on unclean fuels for cooking, heating, and lighting to meet household energy needs. The resulting exposure to household air pollution (HAP) is a leading cause of pneumonia, chronic lung disease, and other adverse health effects. In the last decade, randomized controlled trials of clean cooking interventions to reduce HAP have been conducted. We aim to provide guidance on how to interpret the findings of these trials and how they should inform policy makers and practitioners.Methods: We assembled a multidisciplinary working group of international researchers, public health practitioners, and policymakers with expertise in household air pollution from within academia, the American Thoracic Society, funders, nongovernmental organizations, and global organizations, including the World Bank and the World Health Organization. We performed a literature search, convened four sessions via web conference, and developed consensus conclusions and recommendations via the Delphi method.Results: The committee reached consensus on 14 conclusions and recommendations. Although some trials using cleaner-burning biomass stoves or cleaner-cooking fuels have reduced HAP exposure, the committee was divided (with 55% saying no and 45% saying yes) on whether the studied interventions improved measured health outcomes.Conclusions: HAP is associated with adverse health effects in observational studies. However, it remains unclear which household energy interventions reduce exposure, improve health, can be scaled, and are sustainable. Researchers should engage with policy makers and practitioners working to scale cleaner energy solutions to understand and address their information needs.

Hypoxia-induced stabilization of HIF2A promotes cardiomyocyte proliferation by attenuating DNA damage.

Introduction: Gradual exposure to a chronic hypoxic environment leads to cardiomyocyte proliferation and improved cardiac function in mouse models through a reduction in oxidative DNA damage. However, the upstream transcriptional events that link chronic hypoxia to DNA damage have remained obscure. Aim: We sought to determine whether hypoxia signaling mediated by the hypoxia-inducible factor 1 or 2 (HIF1A or HIF2A) underlies the proliferation phenotype that is induced by chronic hypoxia. Methods and Results: We used genetic loss-of-function models using cardiomyocyte-specific HIF1A and HIF2A gene deletions in chronic hypoxia. We additionally characterized a cardiomyocyte-specific HIF2A overexpression mouse model in normoxia during aging and upon injury. We performed transcriptional profiling with RNA-sequencing on cardiac tissue, from which we verified candidates at the protein level. We find that HIF2A - rather than HIF1A - mediates hypoxia-induced cardiomyocyte proliferation. Ectopic, oxygen-insensitive HIF2A expression in cardiomyocytes reveals the cell-autonomous role of HIF2A in cardiomyocyte proliferation. HIF2A overexpression in cardiomyocytes elicits cardiac regeneration and improvement in systolic function after myocardial infarction in adult mice. RNA-sequencing reveals that ectopic HIF2A expression attenuates DNA damage pathways, which was confirmed with immunoblot and immunofluorescence. Conclusion: Our study provides mechanistic insights about a new approach to induce cardiomyocyte renewal and mitigate cardiac injury in the adult mammalian heart. In light of evidence that DNA damage accrues in cardiomyocytes with aging, these findings may help to usher in a new therapeutic approach to overcome such age-related changes and achieve regeneration.

"If you have light, your heart will be at peace": A qualitative study of household lighting and social integration in southwestern Uganda.

Background: Expanding electrification and access to other clean and affordable energy, such as solar energy, is a critical component of the Sustainable Development Goals, particularly in sub-Saharan Africa where 70% of people are energy insecure. Intervention trials related to access or less polluting household energy alternatives have typically focused on air quality and biological outcomes rather than on how an intervention affects the end user's lived experiences, a key determinant of uptake and adoption outside of a research setting. We explored perceptions of and experiences with a household solar lighting intervention in rural Uganda. Methods: In 2019, we completed a one-year parallel group, randomized wait-list controlled trial of indoor solar lighting systems (ClinicalTrials.gov NCT03351504) in rural Uganda where participants are largely relying on kerosene and other fuel-based lighting received household indoor solar lighting systems. In this qualitative sub-study, we conducted one-on-one, in-depth qualitative interviews with all 80 female participants enrolled in the trial. Interviews explored how solar lighting and illumination impacted participants' lives. We applied a theoretical model linking social integration and health to analyse dynamic interactions across aspects of study participants' lived experiences. Sensors were used to measure daily lighting use before and after receipt of the intervention solar lighting system. Results: Introduction of the solar lighting system increased daily household lighting use by 6.02 (95% confidence intervals (CI) = 4.05-8.00) hours a day. The solar lighting intervention had far-reaching social implications with improved social integration and, consequently, social health. Participants felt that lighting improved their social status, mitigated the stigma of poverty, and increased the duration and frequency of social interactions. Household relationships improved with access to lighting because of reduced conflicts over light rationing. Participants also described a communal benefit of lighting due to improved feelings of safety. At the individual-level, many reported improved self-esteem, sense of well-being, and reduced stress. Conclusion: Improved access to lighting and illumination had far reaching implications for participants, including improved social integration. More empirical research, particularly in the light and household energy field, is needed that emphasizes the impacts of interventions on social health. Registration: ClinicalTrials.gov No. NCT03351504.

Field assessment of straw pellet combustion in improved heating stoves in rural Northeast China.

Straw pellets are widely promoted and expected to be a cleaner alternative fuel to unprocessed crop residues and raw coal in rural China. However, the effectiveness of these dissemination programs is not well evaluated. In this field study, emission characteristics of burning straw pellets, raw coal, and unprocessed corn cobs in heating stoves were investigated in a pilot village in Northeast China. Emission measurements covering the whole combustion cycle (ignition, flaming, and smoldering phases) shows the promotion of improved heating stoves and straw pellets could reduce pollutant emissions (e.g., SO2 and CO), but increase NOX and PM2.5 emissions compared to the initial stove-fuel use pattern in the studied area. There is a significant variance in emission characteristics between different combustion phases. The normalized emission concentrations of the different stove-fuel combinations were higher than the limits in the Chinese national standard for heating stoves, indicating that the standard is not met for real-world emissions. Coal consumption was lower than official data. Household surveys were conducted to identify the barriers to fuel and stove access associated with existing promotion strategies, management, and policies. The pilot program was of the typical "subsidy-and-policy-dependence" pattern and was unlikely to be implemented on a large scale. Technological innovation, operational optimization, and proper policies considering the local socioeconomic factors are needed to sustain the promotion of biomass straw pellets and stoves.

Use, cost-effectiveness, and end user perspectives of a home solar lighting intervention in rural Uganda: a mixed methods, randomized controlled trial.

Energy poverty is prevalent in resource-limited settings, leading households to use inefficient fuels and appliances that contribute to household air pollution. Randomized controlled trials of household energy interventions in low and middle income countries have largely focused on cooking services. Less is known about the adoption and impact of clean lighting interventions. We conducted an explanatory sequential mixed methods study as part of a randomized controlled trial of home solar lighting systems in rural Uganda in order to identify contextual factors determining the use and impact of the solar lighting intervention. We used sensors to track usage, longitudinally assessed household lighting expenditures and health-related quality of life, and performed cost-effectiveness analyses. Qualitative interviews were conducted with all 80 trial participants and coded using reflexive thematic analysis. Uptake of the intervention solar lighting system was high with daily use averaging 8.23 ± 5.30 hours per day. The intervention solar lighting system increased the EQ5D index by 0.025 [95% CI 0.002 - 0.048] and led to an average monthly reduction in household lighting costs by -1.28 [-2.52, -0.85] US dollars, with higher savings in users of fuel-based lighting. The incremental cost-effectiveness ratio for the solar lighting intervention was $2025.72 US dollars per quality adjusted life year (QALY) gained making the intervention cost-effective when benchmarked against the gross domestic product (GDP) per capita in Uganda. Thematic analysis of qualitative data from individual interviews showed that solar lighting was transformative and associated with numerous benefits that fit within a Social Determinants of Health (SDOH) framework. The benefits included improved household finances, improved educational performance of children, increased household safety, improved family and community cohesion, and improved perceived household health. Our findings suggest that household solar lighting interventions may be a cost-effective approach to improve health-related quality of life by addressing SDOH.

Effect of a solar lighting intervention on fuel-based lighting use and exposure to household air pollution in rural Uganda: A randomized controlled trial.

Solar lighting is an alternative to polluting kerosene and other fuel-based lighting devices relied upon by millions of families in resource-limited settings. Whether solar lighting provides sustained displacement of fuel-based lighting sources and reductions in personal exposure to fine particulate matter (PM2 .5 ) and black carbon (BC) has not been examined in randomized controlled trials. Eighty adult women living in rural Uganda who utilized fuel-based (candles and kerosene lamps) and/or clean (solar, grid, and battery-powered devices) lighting were randomized in a 1:1 ratio to receive a home solar lighting system at no cost to study participants (ClinicalTrials.gov NCT03351504). Among intervention group participants, kerosene lamps were completely displaced in 92% of households using them. The intervention led to an average exposure reduction of 36.1 µg/m3 (95% CI -70.3 to -2.0) in PM2 .5 and 10.8 µg/m3 (95% CI -17.6 to -4.1) in BC, corresponding to a reduction from baseline of 37% and 91%, respectively. Reductions were greatest among participants using kerosene lamps. Displacement of kerosene lamps and personal exposure reductions were sustained over 12 months of follow-up. Solar lighting presents an immediate opportunity for achieving sustained reductions in personal exposure to PM2.5 and BC and should be considered in household air pollution intervention packages.

The Effects of Additional Local-Mixing Compartments in the DISST Model-Based Assessment of Insulin Sensitivity.

BACKGROUND: The identification of insulin sensitivity in glycemic modelling can be heavily obstructed by the presence of outlying data or unmodelled effects. The effect of data indicative of local mixing is especially problematic with models assuming rapid mixing of compartments. Methods such as manual removal of data and outlier detection methods have been used to improve parameter ID in these cases, but modelling data with more compartments is another potential approach. METHODS: This research compares a mixing model with local depot site compartments with an existing, clinically validated insulin sensitivity test model. The Levenberg-Marquardt (LM) parameter identification method was implemented alongside a modified version (aLM) capable of operator-independent omission of outlier data in accordance with the 3 standard deviation rule. Three cases were tested: LM where data points suspected to be affected by incomplete mixing at the depot site were removed, aLM, and LM with the more complex mixing model. RESULTS: While insulin parameters identified in the mixing model differed greatly from those in the DISST model, there were strong Spearman correlations of approximately 0.93 for the insulin sensitivity values identified across all 3 methods. The 2 models also showed comparable identification stability in insulin sensitivity estimation through a Monte Carlo analysis. However, the mixing model required modifications to the identification process to improve convergence, and still failed to converge to feasible parameters on 5 of the 212 trials. CONCLUSIONS: The mixing compartment model effectively captured the dynamics of mixing behavior, but with no significant improvement in insulin sensitivity identification.

Mitochondrial fatty acid utilization increases chromatin oxidative stress in cardiomyocytes.

The inability of adult mammalian cardiomyocytes to proliferate underpins the development of heart failure following myocardial injury. Although the newborn mammalian heart can spontaneously regenerate for a short period of time after birth, this ability is lost within the first week after birth in mice, partly due to increased mitochondrial reactive oxygen species (ROS) production which results in oxidative DNA damage and activation of DNA damage response. This increase in ROS levels coincides with a postnatal switch from anaerobic glycolysis to fatty acid (FA) oxidation by cardiac mitochondria. However, to date, a direct link between mitochondrial substrate utilization and oxidative DNA damage is lacking. Here, we generated ROS-sensitive fluorescent sensors targeted to different subnuclear compartments (chromatin, heterochromatin, telomeres, and nuclear lamin) in neonatal rat ventricular cardiomyocytes, which allowed us to determine the spatial localization of ROS in cardiomyocyte nuclei upon manipulation of mitochondrial respiration. Our results demonstrate that FA utilization by the mitochondria induces a significant increase in ROS detection at the chromatin level compared to other nuclear compartments. These results indicate that mitochondrial metabolic perturbations directly alter the nuclear redox status and that the chromatin appears to be particularly sensitive to the prooxidant effect of FA utilization by the mitochondria.

Mitochondrial Substrate Utilization Regulates Cardiomyocyte Cell Cycle Progression.

The neonatal mammalian heart is capable of regeneration for a brief window of time after birth. However, this regenerative capacity is lost within the first week of life, which coincides with a postnatal shift from anaerobic glycolysis to mitochondrial oxidative phosphorylation, particularly towards fatty-acid utilization. Despite the energy advantage of fatty-acid beta-oxidation, cardiac mitochondria produce elevated rates of reactive oxygen species when utilizing fatty acids, which is thought to play a role in cardiomyocyte cell-cycle arrest through induction of DNA damage and activation of DNA-damage response (DDR) pathway. Here we show that inhibiting fatty-acid utilization promotes cardiomyocyte proliferation in the postnatatal heart. First, neonatal mice fed fatty-acid deficient milk showed prolongation of the postnatal cardiomyocyte proliferative window, however cell cycle arrest eventually ensued. Next, we generated a tamoxifen-inducible cardiomyocyte-specific, pyruvate dehydrogenase kinase 4 (PDK4) knockout mouse model to selectively enhance oxidation of glycolytically derived pyruvate in cardiomyocytes. Conditional PDK4 deletion resulted in an increase in pyruvate dehydrogenase activity and consequently an increase in glucose relative to fatty-acid oxidation. Loss of PDK4 also resulted in decreased cardiomyocyte size, decreased DNA damage and expression of DDR markers and an increase in cardiomyocyte proliferation. Following myocardial infarction, inducible deletion of PDK4 improved left ventricular function and decreased remodelling. Collectively, inhibition of fatty-acid utilization in cardiomyocytes promotes proliferation, and may be a viable target for cardiac regenerative therapies.

A calcineurin-Hoxb13 axis regulates growth mode of mammalian cardiomyocytes.

A major factor in the progression to heart failure in humans is the inability of the adult heart to repair itself after injury. We recently demonstrated that the early postnatal mammalian heart is capable of regeneration following injury through proliferation of preexisting cardiomyocytes1,2 and that Meis1, a three amino acid loop extension (TALE) family homeodomain transcription factor, translocates to cardiomyocyte nuclei shortly after birth and mediates postnatal cell cycle arrest3. Here we report that Hoxb13 acts as a cofactor of Meis1 in postnatal cardiomyocytes. Cardiomyocyte-specific deletion of Hoxb13 can extend the postnatal window of cardiomyocyte proliferation and reactivate the cardiomyocyte cell cycle in the adult heart. Moreover, adult Meis1-Hoxb13 double-knockout hearts display widespread cardiomyocyte mitosis, sarcomere disassembly and improved left ventricular systolic function following myocardial infarction, as demonstrated by echocardiography and magnetic resonance imaging. Chromatin immunoprecipitation with sequencing demonstrates that Meis1 and Hoxb13 act cooperatively to regulate cardiomyocyte maturation and cell cycle. Finally, we show that the calcium-activated protein phosphatase calcineurin dephosphorylates Hoxb13 at serine-204, resulting in its nuclear localization and cell cycle arrest. These results demonstrate that Meis1 and Hoxb13 act cooperatively to regulate cardiomyocyte maturation and proliferation and provide mechanistic insights into the link between hyperplastic and hypertrophic growth of cardiomyocytes.

Mechanism of Eccentric Cardiomyocyte Hypertrophy Secondary to Severe Mitral Regurgitation.

BACKGROUND: Primary valvular heart disease is a prevalent cause of morbidity and mortality in both industrialized and developing countries. Although the primary consequence of valvular heart disease is myocardial dysfunction, treatment of valvular heart diseases centers around valve repair or replacement rather than prevention or reversal of myocardial dysfunction. This is particularly evident in primary mitral regurgitation (MR), which invariably results in eccentric hypertrophy and left ventricular (LV) failure in the absence of timely valve repair or replacement. The mechanism of LV dysfunction in primary severe MR is entirely unknown. METHODS: Here, we developed the first mouse model of severe MR. Valvular damage was achieved by severing the mitral valve leaflets and chords with iridectomy scissors, and MR was confirmed by echocardiography. Serial echocardiography was performed to follow up LV morphology and systolic function. Analysis of cardiac tissues was subsequently performed to evaluate valve deformation, cardiomyocyte morphology, LV fibrosis, and cell death. Finally, dysregulated pathways were assessed by RNA-sequencing analysis and immunofluorescence. RESULTS: In the ensuing 15 weeks after the induction of MR, gradual LV dilatation and dysfunction occurred, resulting in severe systolic dysfunction. Further analysis revealed that severe MR resulted in a marked increase in cardiac mass and increased cardiomyocyte length but not width, with electron microscopic evidence of sarcomere disarray and the development of sarcomere disruption. From a mechanistic standpoint, severe MR resulted in activation of multiple components of both the mammalian target of rapamycin and calcineurin pathways. Inhibition of mammalian target of rapamycin signaling preserved sarcomeric structure and prevented LV remodeling and systolic dysfunction. Immunohistochemical analysis uncovered a differential pattern of expression of the cell polarity regulator Crb2 (crumbs homolog 2) along the longitudinal axis of cardiomyocytes and close to the intercalated disks in the MR hearts. Electron microscopy images demonstrated a significant increase in polysome localization in close proximity to the intercalated disks and some areas along the longitudinal axis in the MR hearts. CONCLUSIONS: These results indicate that LV dysfunction in response to severe MR is a form of maladaptive eccentric cardiomyocyte hypertrophy and outline the link between cell polarity regulation and spatial localization protein synthesis as a pathway for directional cardiomyocyte growth.

Household fuel use and pulmonary tuberculosis in western Nepal: A case-control study.

BACKGROUND: Whether cooking with solid fuels, as occurs widely in developing countries, including Nepal, is a risk factor for pulmonary tuberculosis (PTB) is uncertain. Epidemiologic studies have produced variable results. This case-control study sought to resolve this issue with a large sample size and a population-based control group. METHODS: PTB cases (N = 581), aged 18-70 were recruited from diagnostic centers in Kaski and neighboring districts of Nepal. Population-based controls (N = 1226) were recruited. Persons who had previously been diagnosed with TB were excluded. Questionnaires were administered at participants' homes. RESULTS: Using liquefied petroleum gas (LPG) as the cookstove reference fuel, for women the odds ratio (OR) for having a primary cookstove that used wood was 0.21 (95% CI: 0.08,0.52); for men the corresponding OR was 0.80 (0.37, 1.74). For biogas, the OR for women was 0.24 (0.06,0.87) and for men, 1.41 (0.61, 3.23). CONCLUSIONS: The unexpected finding of a higher risk for women using LPG cookstoves, relative to wood or biogas-burning cookstoves, may be attributable to excluding persons with prior TB. A possible explanation is that emissions, such as ultrafine particles, formed during LPG combustion promote PTB manifestation in infected people who have not previously had PTB. The damage from the initial PTB leaves them susceptible to the PTB-promoting effects of smoke from wood fires. Further studies, excluding participants who have previously had TB are needed to confirm these findings. Use of exhaust hoods to the outdoors for all stoves, well-ventilated kitchens, and gas stoves raised above ground would reduce exposures.

Neonatal Heart Regeneration: Comprehensive Literature Review.

BACKGROUND: The adult mammalian heart is incapable of meaningful functional recovery after injury, and thus promoting heart regeneration is 1 of the most important therapeutic targets in cardiovascular medicine. In contrast to the adult mammalian heart, the neonatal mammalian heart is capable of regeneration after various types of injury. Since the first report in 2011, a number of groups have reported their findings on neonatal heart regeneration. The current review provides a comprehensive analysis of heart regeneration studies in neonatal mammals conducted to date, outlines lessons learned, and poses unanswered questions. METHODS: We performed a PubMed search using the keywords "neonatal" and "heart" and "regeneration." In addition, we assessed all publications that cited the first neonatal heart regeneration reports: Porrello et al, Science, Feb 2011 for apical resection injury; Porrello et al, PNAS, Dec 2012 for coronary ligation injury; and Mahmoud et al, Nature Methods, Jan 2014 for surgical methodology. Publications were examined for surgical models used, timing of surgery, and postinjury assessment including anatomic, histological, and functional assessment, as well as conclusions drawn. RESULTS: We found 30 publications that performed neonatal apical resection, 19 publications that performed neonatal myocardial infarction by coronary artery ligation, and 6 publications that performed cryoinjury using liquid nitrogen-cooled metal probes. Both apical resection and ischemic infarction injury in neonatal mice result in a robust regenerative response, mediated by cardiomyocyte proliferation. On the other hand, several reports have demonstrated that cryoinjury is associated with incomplete heart regeneration in neonatal mice. Not surprisingly, several studies suggest that injury size, as well as surgical and histological techniques, can strongly influence the observed regenerative response and final conclusions. Studies have utilized these neonatal cardiac injury models to identify factors that either inhibit or stimulate heart regeneration. CONCLUSIONS: Overall, there is consensus that both apical resection and coronary ligation injuries during the first 2 days of life result in heart regeneration in neonatal mammals, whereas cryoinjury was not associated with a similar regenerative response. This regenerative response is mediated by proliferation of preexisting cardiomyocytes, and is modifiable by injury size and surgical technique, as well as metabolic, immunologic, genetic, and environmental factors.

Small, Smart, Fast, and Cheap: Microchip-Based Sensors to Estimate Air Pollution Exposures in Rural Households.

Over the last 20 years, the Kirk R. Smith research group at the University of California Berkeley-in collaboration with Electronically Monitored Ecosystems, Berkeley Air Monitoring Group, and other academic institutions-has developed a suite of relatively inexpensive, rugged, battery-operated, microchip-based devices to quantify parameters related to household air pollution. These devices include two generations of particle monitors; data-logging temperature sensors to assess time of use of household energy devices; a time-activity monitoring system using ultrasound; and a CO2-based tracer-decay system to assess ventilation rates. Development of each system involved numerous iterations of custom hardware, software, and data processing and visualization routines along with both lab and field validation. The devices have been used in hundreds of studies globally and have greatly enhanced our understanding of heterogeneous household air pollution (HAP) concentrations and exposures and factors influencing them.

Chronic Sciatic Neuropathy in Rat Reduces Voluntary Wheel-Running Activity With Concurrent Chronic Mechanical Allodynia.

BACKGROUND: Animal models of peripheral neuropathy produced by a number of manipulations are assessed for the presence of pathologic pain states such as allodynia. Although stimulus-induced behavioral assays are frequently used and important to examine allodynia (ie, sensitivity to light mechanical touch; von Frey fiber test), other measures of behavior that reflect overall function are not only complementary to stimulus-induced responsive measures, but are also critical to gain a complete understanding of the effects of the pain model on quality of life, a clinically relevant aspect of pain on general function. Voluntary wheel-running activity in rodent models of inflammatory and muscle pain is emerging as a reliable index of general function that extends beyond stimulus-induced behavioral assays. Clinically, reports of increased pain intensity occur at night, a period typically characterized with reduced activity during the diurnal cycle. We therefore examined in rats whether alterations in wheel-running activity were more robust during the inactive phase compared with the active phase of their diurnal cycle in a widely used rodent model of chronic peripheral neuropathic pain, the sciatic nerve chronic constriction injury (CCI) model. METHODS: In adult male Sprague Dawley rats, baseline (BL) hindpaw threshold responses to light mechanical touch were assessed using the von Frey test before measuring BL activity levels using freely accessible running wheels (1 hour/day for 7 sequential days) to quantify the distance traveled. Running wheel activity BL values are expressed as total distance traveled (m). The overall experimental design was after BL measures, rats underwent either sham or CCI surgery followed by repeated behavioral reassessment of hindpaw thresholds and wheel-running activity levels for up to 18 days after surgery. Specifically, separate groups of rats were assessed for wheel-running activity levels (1 hour total/trial) during the onset (within first 2 hours) of either the (1) inactive (n = 8/group) or (2) active (n = 8/group) phase of the diurnal cycle. An additional group of CCI-treated rats (n = 8/group) was exposed to a locked running wheel to control for the potential effects of wheel-running exercise on allodynia. The 1-hour running wheel trial period was further examined at discrete 20-minute intervals to identify possible pattern differences in activity during the first, middle, and last portions of the 1-hour trial. The effect of neuropathy on activity levels was assessed by measuring the change from their respective BLs to distance traveled in the running wheels. RESULTS: Although wheel-running distances between groups were not different at BL from rats examined during either the inactive phase of the diurnal cycle or active phase of the diurnal cycle, sciatic nerve CCI reduced running wheel activity levels compared with sham-operated controls during the inactive phase. In addition, compared with sham controls, bilateral low-threshold mechanical allodynia was observed at all time points after surgical induction of neuropathy in rats with free-wheel and locked-wheel access. Allodynia in CCI compared with shams was replicated in rats whose running wheel activity was examined during the active phase of the diurnal cycle. Conversely, no significant reduction in wheel-running activity was observed in CCI-treated rats compared with sham controls at any time point when activity levels were examined during the active diurnal phase. Finally, running wheel activity patterns within the 1-hour trial period during the inactive phase of the diurnal cycle were relatively consistent throughout each 20-minute phase. CONCLUSIONS: Compared with nonneuropathic sham controls, a profound and stable reduction of running wheel activity was observed in CCI rats during the inactive phase of the diurnal cycle. A concurrent robust allodynia persisted in all rats regardless of when wheel-running activity was examined or whether they ran on wheels, suggesting that acute wheel-running activity does not alter chronic low-intensity mechanical allodynia as measured using the von Frey fiber test. Overall, these data support that acute wheel-running exercise with limited repeated exposures does not itself alter allodynia and offers a behavioral assay complementary to stimulus-induced measures of neuropathic pain.

Redox Regulation of Heart Regeneration: An Evolutionary Tradeoff.

Heart failure is a costly and deadly disease, affecting over 23 million patients worldwide, half of which die within 5 years of diagnosis. The pathophysiological basis of heart failure is the inability of the adult heart to regenerate lost or damaged myocardium. Although limited myocyte turnover does occur in the adult heart, it is insufficient for restoration of contractile function (Nadal-Ginard, 2001; Laflamme et al., 2002; Quaini et al., 2002; Hsieh et al., 2007; Bergmann et al., 2009, 2012). In contrast to lower vertebrates (Poss et al., 2002; Poss, 2007; Jopling et al., 2010; Kikuchi et al., 2010; Chablais et al., 2011; González-Rosa et al., 2011; Heallen et al., 2011), adult mammalian heart cardiomyogenesis following injury is very limited (Nadal-Ginard, 2001; Laflamme et al., 2002; Quaini et al., 2002; Bergmann et al., 2009, 2012) and is insufficient to restore normal cardiac function. Studies in the late 90s elegantly mapped the DNA synthesis and cell cycle dynamics of the mammalian heart during development and following birth (Soonpaa et al., 1996; Soonpaa and Field, 1997, 1998), where they showed that DNA synthesis drops significantly around birth with low-level DNA synthesis few days after birth. Around P5 to P7, cardiomyocytes undergo a final round of DNA synthesis without cytokinesis, and the majority become binucleated and exit the cell cycle permanently. Therefore, due to the similarities between the immature mammalian heart and lower vertebrates (Poss, 2007; Walsh et al., 2010), it became important to determine whether they have similar regenerative abilities. Recently, we demonstrated that removal of up to 15% of the apex of the left ventricle of postnatal day 1 (P1) mice results in complete regeneration within 3 weeks without any measurable fibrosis and cardiac dysfunction (Porrello et al., 2011). This response is characterized by robust cardiomyocyte proliferation with gradual restoration of normal cardiac morphology. In addition to the histological evidence of proliferating myocytes, genetic fate-mapping studies confirmed that the majority of newly formed cardiomyocytes are derived from proliferation of preexisting cardiomyocytes (Porrello et al., 2011). More recently, we established an ischemic injury model where the left anterior descending coronary artery was ligated in P1 neonates (Porrello et al., 2013). The injury response was similar to the resection model, with robust cardiomyocyte proliferation throughout the myocardium, as well as restoration of normal morphology by 21 days. However, this regenerative capacity is lost by P7, after which injury results in the typical cardiomyocyte hypertrophy and scar-formation characteristic of the adult mammalian heart. Not surprisingly, the loss of this regenerative capacity coincides with binucleation and cell cycle exit of cardiomyocytes (Soonpaa et al., 1996; Walsh et al., 2010). An important approach toward a deeper understanding the loss of cardiac regenerative capacity in mammals is to first consider why , and not only how , this happens. Regeneration of the early postnatal heart following resection or ischemic infarction involves replacement of lost myocardium and vasculature with restoration of normal myocardial thickness and architecture, with long-term normalization of systolic function. Why would the heart permanently forego such a remarkable regenerative program shortly after birth? The answer may lie in within the fundamental principal of evolutionary tradeoff.

A Randomized Double-Blinded Trial on the Effects of Ultrasound Transducer Orientation on Teaching and Learning Ultrasound-Guided Regional Anesthesia.

OBJECTIVES: Learning ultrasound-guided regional anesthesia skills, especially needle/ beam alignment, can be especially difficulty for trainees, who can often become frustrated. We hypothesized that teaching novices to orient the transducer and needle perpendicular to their shoulders will improve performance on a standardized task, compared to holding the transducer and needle parallel to the shoulders. METHODS: This study compared the effects of transducer orientation on trainees' ability to complete a standardized ultrasound-guided nerve block simulation. The time to task completion and percentage of the attempt time without adequate needle visualization were measured. Participants were right-handed healthy adults with no previous ultrasound experience and were randomly assigned to training in either transducer and needle alignment in a coronal plane, parallel to the shoulders (parallel group) or transducer and needle alignment in a sagittal plane, perpendicular to the shoulders (perpendicular group). Participants used ultrasound to direct a needle to 3 targets in a standardized gelatin phantom and repeated this task 3 times. Their efforts were timed and evaluated by an assessor, who was blinded to group assignment. RESULTS: Data were analyzed on 28 participants. The perpendicular group was able to complete the task more quickly (P < .001) and with a smaller proportion of time lost to inadequate needle visualization (P < .001). CONCLUSIONS: Ultrasound-guided regional anesthesia trainees complete a standardized task more quickly and efficiently when instructed to hold the transducer and needle in an orientation perpendicular to their shoulders.