Solving the conundrum of intra-specific variation in metabolic rate: A multidisciplinary conceptual and methodological toolkit: New technical developments are opening the door to an understanding of why metabolic rate varies among individual animals of a species: New technical developments are opening the door to an understanding of why metabolic rate varies among individual animals of a species.

Researchers from diverse disciplines, including organismal and cellular physiology, sports science, human nutrition, evolution and ecology, have sought to understand the causes and consequences of the surprising variation in metabolic rate found among and within individual animals of the same species. Research in this area has been hampered by differences in approach, terminology and methodology, and the context in which measurements are made. Recent advances provide important opportunities to identify and address the key questions in the field. By bringing together researchers from different areas of biology and biomedicine, we describe and evaluate these developments and the insights they could yield, highlighting the need for more standardisation across disciplines. We conclude with a list of important questions that can now be addressed by developing a common conceptual and methodological toolkit for studies on metabolic variation in animals.

Consistent changes in muscle phenotype and mitochondrial abundance underlie dive performance across multiple lineages of diving ducks.

Diving animals must sustain high muscle activity with finite oxygen (O2) to forage underwater. Studies have shown that some diving mammals exhibit changes in the metabolic phenotype of locomotory muscles compared with non-divers, but the pervasiveness of such changes across diving animals is unclear, particularly among diving birds. Here, we examined whether changes in muscle phenotype and mitochondrial abundance are associated with dive capacity across 17 species of ducks from three distinct evolutionary clades (tribes) in the subfamily Anatinae: the longest diving sea ducks, the mid-tier diving pochards and the non-diving dabblers. In the gastrocnemius (the primary swimming and diving muscle), mitochondrial volume density in both oxidative and glycolytic fiber types was 70% and 30% higher in sea ducks compared with dabblers, respectively. These differences were associated with preferential proliferation of the subsarcolemmal subfraction, the mitochondria adjacent to the cell membrane and nearest to capillaries, relative to the intermyofibrillar subfraction. Capillary density and capillary-to-fiber ratio were positively correlated with mitochondrial volume density, with no variation in the density of oxidative fiber types across tribes. In the pectoralis, sea ducks had greater abundance of oxidative fiber types than dabblers, whereas pochards were intermediate between the two. These data suggest that skeletal muscles of sea ducks have a heightened capacity for aerobic metabolism and an enhanced ability to utilize O2 stores in the blood and muscle while diving.

Consistent changes in muscle metabolism underlie dive performance across multiple lineages of diving ducks.

Diving animals must sustain high activity with limited O2 stores to successfully capture prey. Studies suggest that increasing body O2 stores supports breath-hold diving, but less is known about metabolic specializations that underlie underwater locomotion. We measured maximal activities of 10 key enzymes in locomotory muscles (gastrocnemius and pectoralis) to identify biochemical changes associated with diving in pathways of oxidative and substrate-level phosphorylation and compared them across three groups of ducks-the longest diving sea ducks (eight spp.), the mid-tier diving pochards (three spp.) and the non-diving dabblers (five spp.). Relative to dabblers, both diving groups had increased activities of succinate dehydrogenase and cytochrome c oxidase, and sea ducks further showed increases in citrate synthase (CS) and hydroxyacyl-CoA dehydrogenase (HOAD). Both diving groups had relative decreases in capacity for anaerobic metabolism (lower ratio of lactate dehydrogenase to CS), with sea ducks also showing a greater capacity for oxidative phosphorylation and lipid oxidation (lower ratio of pyruvate kinase to CS, higher ratio of HOAD to hexokinase). These data suggest that the locomotory muscles of diving ducks are specialized for sustaining high rates of aerobic metabolism, emphasizing the importance of body O2 stores for dive performance in these species.

Adaptive increases in respiratory capacity and O2 affinity of subsarcolemmal mitochondria from skeletal muscle of high-altitude deer mice.

Aerobic energy demands have led to the evolution of complex mitochondrial reticula in highly oxidative muscles, but the extent to which metabolic challenges can be met with adaptive changes in physiology of specific mitochondrial fractions remains unresolved. We examined mitochondrial mechanisms supporting adaptive increases in aerobic performance in deer mice (Peromyscus maniculatus) adapted to the hypoxic environment at high altitude. High-altitude and low-altitude mice were born and raised in captivity, and exposed as adults to normoxia or hypobaric hypoxia (12 kPa O2 for 6-8 weeks). Subsarcolemmal and intermyofibrillar mitochondria were isolated from the gastrocnemius, and a comprehensive substrate titration protocol was used to examine mitochondrial physiology and O2  kinetics by high-resolution respirometry and fluorometry. High-altitude mice had greater yield, respiratory capacity for oxidative phosphorylation, and O2 affinity (lower P50 ) of subsarcolemmal mitochondria compared to low-altitude mice across environments, but there were no species difference in these traits in intermyofibrillar mitochondria. High-altitude mice also had greater capacities of complex II relative to complexes I + II and higher succinate dehydrogenase activities in both mitochondrial fractions. Exposure to chronic hypoxia reduced reactive oxygen species (ROS) emission in high-altitude mice but not in low-altitude mice. Our findings suggest that functional changes in subsarcolemmal mitochondria contribute to improving aerobic performance in hypoxia in high-altitude deer mice. Therefore, physiological variation in specific mitochondrial fractions can help overcome the metabolic challenges of life at high altitude.

Inter-individual variation in mitochondrial phosphorylation efficiency predicts growth rates in ectotherms at high temperatures.

There is increasing evidence that aquatic ectotherms are especially vulnerable to global warming since their metabolic demands increase with ambient temperature while water-oxygen content decreases. The possible role of shrinking aerobic scope in limiting performance has been much discussed; however, less attention has been given to whether tissue-level changes in the efficiency of oxygen usage occur at elevated temperatures. Here, we show that this varies widely among individuals, with consequences for performance. We examined the inter-individual variation in growth rate and mitochondrial function from white muscle and liver of brown trout (Salmo trutta) acclimated to either high (19.5°C) or near-optimal temperature (12°C). Liver (but not muscle) mitochondria showed a positive relationship between growth rate and maximal oxidative phosphorylation at both temperatures, and a negative relationship between growth rate and ROS release. There was a positive correlation in both tissues between individual mitochondrial phosphorylation efficiency and growth rate, but only at 19.5°C. In this representative of aquatic ectotherms, an individual's liver mitochondrial efficiency thus seems to dictate its capacity to grow at elevated temperatures. This suggests that individual heterogeneity in cellular function may cause variation in the thermal limits of aquatic ectotherms and could adversely affect wild populations in warming environments.

Avian red blood cell mitochondria produce more heat in winter than in autumn.

Endotherms in cold regions improve heat-producing capacity when preparing for winter. We know comparatively little about how this change is fueled by seasonal adaptation in cellular respiration. Thus, we studied the changes of mitochondrial function in red blood cells in sympatric Coal (Periparus ater), Blue (Cyanistes caeruleus), and Great (Parus major) tits between autumn and winter. These species differ more than twofold in body mass and in several aspects of their foraging ecology and social dominance, which could require differential seasonal adaptation of energy expenditure. Coal and Great tits in particular upregulated the mitochondrial respiration rate and mitochondrial volume in winter. This was not directed toward ATP synthesis, instead reflecting increased uncoupling of electron transport from ATP production. Because uncoupling is exothermic, this increased heat-producing capacity at the sub-cellular level in winter. This previously unexplored the route of thermogenesis in birds should be addressed in future work.

Measurement of mitochondrial respiration in permeabilized fish gills.

Physiological investigations of fish gills have traditionally centred on the two principal functions of the gills: gas exchange and ion regulation. Mitochondrion-rich cells (MRCs) are primarily found within the gill filaments of fish, and are thought to proliferate in order to increase the ionoregulatory capacity of the gill in response to environmentally induced osmotic challenges. However, surprisingly little attention has been paid to the metabolic function of mitochondria within fish gills. Here, we describe and validate a simple protocol for the permeabilization of fish gills and subsequent measurement of mitochondrial respiration rates in vitro Our protocol requires only small tissue samples (8 mg), exploits the natural structure of fish gills, does not require mechanical separation of the gill tissue (so is relatively quick to perform), and yields accurate and highly reproducible measurements of respiration rates. It offers great potential for the study of mitochondrial function in gills over a wide range of fish sizes and species.

Cardiovascular responses to progressive hypoxia in ducks native to high altitude in the Andes.

The cardiovascular system is critical for delivering O2 to tissues. Here we examine the cardiovascular responses to progressive hypoxia in four high-altitude Andean duck species compared to four related low-altitude populations in North America, tested at their native altitude. Ducks were exposed to stepwise decreases in inspired partial pressure of O2 while we monitored heart rate, O2 consumption rate, blood O2 saturation, haematocrit (Hct), and blood haemoglobin concentration [Hb]. We calculated O2 pulse (the product of stroke volume and the arterial-venous O2 content difference), blood O2 concentration, and heart rate variability. Regardless of altitude, all eight populations maintained O2 consumption rate with minimal change in heart rate or O2 pulse, indicating that O2 consumption was maintained by either a constant arterial-venous O2 content difference (an increase in the relative O2 extracted from arterial blood) or by a combination of changes in stroke volume and the arterial-venous O2 content difference. Three high-altitude taxa (yellow-billed pintails, cinnamon teal, and speckled teal) had higher Hct and [Hb], increasing the O2 content of arterial blood, and potentially providing a greater reserve for enhancing O2 delivery during hypoxia. Hct and [Hb] between low- and high-altitude populations of ruddy duck were similar, representing a potential adaptation to diving life. Heart rate variability was generally lower in high-altitude ducks, concurrent with similar or lower heart rates than low-altitude ducks, suggesting a reduction in vagal and sympathetic tone. These unique features of the Andean ducks differ from previous observations in both Andean geese and bar-headed geese, neither of which exhibit significant elevations in Hct or [Hb] compared to their low-altitude relatives, revealing yet another avian strategy for coping with high altitude.

Cardiovascular responses to progressive hypoxia in ducks native to high altitude in the Andes.

The cardiovascular system is critical for delivering O2 to tissues. Here, we examined the cardiovascular responses to progressive hypoxia in four high-altitude Andean duck species compared with four related low-altitude populations in North America, tested at their native altitude. Ducks were exposed to stepwise decreases in inspired partial pressure of O2 while we monitored heart rate, O2 consumption rate, blood O2 saturation, haematocrit (Hct) and blood haemoglobin (Hb) concentration. We calculated O2 pulse (the product of stroke volume and the arterial-venous O2 content difference), blood O2 concentration and heart rate variability. Regardless of altitude, all eight populations maintained O2 consumption rate with minimal change in heart rate or O2 pulse, indicating that O2 consumption was maintained by either a constant arterial-venous O2 content difference (an increase in the relative O2 extracted from arterial blood) or by a combination of changes in stroke volume and the arterial-venous O2 content difference. Three high-altitude taxa (yellow-billed pintails, cinnamon teal and speckled teal) had higher Hct and Hb concentration, increasing the O2 content of arterial blood, and potentially providing a greater reserve for enhancing O2 delivery during hypoxia. Hct and Hb concentration between low- and high-altitude populations of ruddy duck were similar, representing a potential adaptation to diving life. Heart rate variability was generally lower in high-altitude ducks, concurrent with similar or lower heart rates than low-altitude ducks, suggesting a reduction in vagal and sympathetic tone. These unique features of the Andean ducks differ from previous observations in both Andean geese and bar-headed geese, neither of which exhibit significant elevations in Hct or Hb concentration compared with their low-altitude relatives, revealing yet another avian strategy for coping with high altitude.

Control of breathing and respiratory gas exchange in high-altitude ducks native to the Andes.

We examined the control of breathing and respiratory gas exchange in six species of high-altitude duck that independently colonized the high Andes. We compared ducks from high-altitude populations in Peru (Lake Titicaca at ∼3800 m above sea level; Chancay River at ∼3000-4100 m) with closely related populations or species from low altitude. Hypoxic ventilatory responses were measured shortly after capture at the native altitude. In general, ducks responded to acute hypoxia with robust increases in total ventilation and pulmonary O2 extraction. O2 consumption rates were maintained or increased slightly in acute hypoxia, despite ∼1-2°C reductions in body temperature in most species. Two high-altitude taxa - yellow-billed pintail and torrent duck - exhibited higher total ventilation than their low-altitude counterparts, and yellow-billed pintail exhibited greater increases in pulmonary O2 extraction in severe hypoxia. In contrast, three other high-altitude taxa - Andean ruddy duck, Andean cinnamon teal and speckled teal - had similar or slightly reduced total ventilation and pulmonary O2 extraction compared with low-altitude relatives. Arterial O2 saturation (SaO2 ) was elevated in yellow-billed pintails at moderate levels of hypoxia, but there were no differences in SaO2  in other high-altitude taxa compared with their close relatives. This finding suggests that improvements in SaO2  in hypoxia can require increases in both breathing and haemoglobin-O2 affinity, because the yellow-billed pintail was the only high-altitude duck with concurrent increases in both traits compared with its low-altitude relative. Overall, our results suggest that distinct physiological strategies for coping with hypoxia can exist across different high-altitude lineages, even among those inhabiting very similar high-altitude habitats.

Variation of the prevalence of pediatric polypharmacy: A scoping review.

PURPOSE: To examine the range of prevalence of pediatric polypharmacy in literature through a scoping review, focusing on factors that contribute to its heterogeneity in order to improve the design and reporting of quality improvement, pharmacovigilance, and research studies. METHODS: We searched Ovid Medline, PubMed, EMBASE, CINAHL, Ovid PsycINFO, Cochrane CENTRAL, and Web of Science Core Collection databases for studies with concepts of children and polypharmacy, along with a hand search of the bibliographies of six reviews and 30 included studies. We extracted information regarding study design, disease conditions, and prevalence of polypharmacy. RESULTS: Two hundred eighty-four studies reported prevalence of polypharmacy. They were more likely to be conducted in North America (37.7%), published after 2010 (44.4%), cross-sectional (67.3%), in outpatient settings (59.5%). Prevalence ranged from 0.9% to 98.4%, median 39.7% (interquartile range [IQR] 22.0%-54.0%). Studies from Asia reported the highest median prevalence of 45.4% (IQR 27.3%-61.0%) while studies from North America reported the lowest median prevalence of 30.4% (IQR 14.7%-50.2%). Prevalence decreased over time: median 45.6% before 2001, 38.1% during 2001 to 2010, and 34% during 2011 to 2017. Studies involving children under 12 years had a higher median prevalence (46.9%) than adolescent studies (33.7%). Inpatient setting studies had a higher median prevalence (50.3%) than studies in outpatient settings (38.8%). Community level samples, higher number and duration of medications defining polypharmacy, and psychotropic medications were associated with lower prevalence. CONCLUSIONS: The prevalence of pediatric polypharmacy is high and variable. Studies reporting pediatric polypharmacy should account for context, design, polypharmacy definition, and medications evaluated.

Functional health status of adults with serious mental illness and diabetes mellitus: A latent profile analysis.

OBJECTIVE: Adults with serious mental illness are at increased risk for diabetes mellitus and diabetes-related complications. This article classifies subgroups among people with serious mental illness and comorbid diabetes with respect to functional status and examines differences among those groups. METHODS: This analysis used a baseline sample of 157 adults with serious mental illness and diabetes mellitus enrolled in a National Institute of Health-funded research study. Latent profile analysis was used to distinguish health status profiles and investigate how these subgroups differed across assessment domains. RESULTS: Participants with depression, schizophrenia, and bipolar disorder (n = 157) were included in the study. Mean age was 52.9 years (standard deviation = 9.8), and 62 (40%) were African American. From the latent profile analysis, a three-class model appeared to provide the best fit. Class 1 (34.9%) had a very low functional health status approximately two standard deviations below the general population mean. Class 2 (43.7%) had a low functional status approximately one standard deviation below the general mean. Class 3 (21.4%) had moderate functional status with scores near population mean. Groups differed on measures of personal characteristics, clinical status and symptom severity, self-care behaviors, and environmental characteristics. CONCLUSIONS: Although individuals with schizophrenia generally have poor prognosis once they develop diabetes, latent profile analysis identified distinct health status subgroups. Although all three groups demonstrated illness burden, the pattern of differences between these groups across measures may suggest the need for different interventions for highly diverse adults who received care within safety-net primary care.

Outcome measures in pediatric polypharmacy research: a scoping review.

INTRODUCTION: Various methods have been used to interpret the reports of pediatric polypharmacy across the literature. This is the first scoping review that explores outcome measures in pediatric polypharmacy research. OBJECTIVES: The aim of our study was to describe outcome measures assessed in pediatric polypharmacy research. METHODS: A search of electronic databases was conducted in July 2017, including Ovid Medline, PubMed, Elsevier Embase, Wiley Cochrane Central Register of Controlled Trials (CENTRAL), EBSCO CINAHL, Ovid PsyclNFO, Web of Science Core Collection, ProQuest Dissertations and Thesis A&I. Data were extracted about study characteristics and outcome measures, and also synthesized by harms or benefits mentioned. RESULTS: The search strategy initially identified 8169 titles and screened 4398 using the inclusion criteria after de-duplicating. After the primary screening, a total of 363 studies were extracted for the data analysis. Polypharmacy (prevalence) was identified as an outcome in 31.4% of the studies, prognosis-related outcomes in 25.6%, and adverse drug reactions in 16.5%. A total of 265 articles (73.0%) mentioned harms, including adverse drug reactions (26.4%), side effects (24.2%), and drug-drug interactions (20.9%). A total of 83 studies (22.9%) mentioned any benefit, 48.2% of which identified combination for efficacy, 24.1% combination for treatment of complex diseases, and 19.3% combination for treatment augmentation. Thirty-eight studies reported adverse drug reaction as an outcome, where polypharmacy was a predictor, with various designs. CONCLUSIONS: Most studies of pediatric polypharmacy evaluate prevalence, prognosis, or adverse drug reaction-related out-comes, and underscore harms related to polypharmacy. Clinicians should carefully weigh benefits and harms when introducing medications to treatment regimens.

A transdisciplinary team approach to scoping reviews: the case of pediatric polypharmacy.

BACKGROUND: Polypharmacy can be either beneficial or harmful to children. We conducted a scoping review to examine the concept of pediatric polypharmacy: its definition, prevalence, extent and gaps in research. In this manuscript, we report our transdisciplinary scoping review methodology. METHODS: After establishing a transdisciplinary team, we iteratively developed standard operating procedures for the study's search strategy, inclusion/exclusion criteria, screening, and data extraction. We searched eight bibliographic databases, screened abstracts and full text articles, and extracted data from included studies using standardized forms. We held regular team meetings and performed ongoing internal validity measurements to maintain consistent and quality outputs. RESULTS: With the aid of EPPI Reviewer collaborative software, our transdisciplinary team of nine members performed dual reviews of 363 included studies after dual screening of 4398 abstracts and 1082 full text articles. We achieved overall agreement of 85% and a kappa coefficient of 0.71 (95% CI 0.68-0.74) while screening full text articles. The screening and review processes required about seven hours per extracted study. The two pharmacists, an epidemiologist, a neurologist, and a librarian on the review team provided internal consultation in these key disciplines. A stakeholder group of 10 members with expertise in evidence synthesis, research implementation, pediatrics, mental health, epilepsy, pharmacoepidemiology, and pharmaceutical outcomes were periodically consulted to further characterize pediatric polypharmacy. CONCLUSIONS: A transdisciplinary approach to scoping reviews, including internal and external consultation, should be considered when addressing complex cross-disciplinary questions.

Accuracy of Cardiovascular Risk Prediction Varies by Neighborhood Socioeconomic Position: A Retrospective Cohort Study.

BACKGROUND: Inequality in health outcomes in relation to Americans' socioeconomic position is rising. OBJECTIVE: First, to evaluate the spatial relationship between neighborhood disadvantage and major atherosclerotic cardiovascular disease (ASCVD)-related events; second, to evaluate the relative extent to which neighborhood disadvantage and physiologic risk account for neighborhood-level variation in ASCVD event rates. DESIGN: Observational cohort analysis of geocoded longitudinal electronic health records. SETTING: A single academic health center and surrounding neighborhoods in northeastern Ohio. PATIENTS: 109 793 patients from the Cleveland Clinic Health System (CCHS) who had an outpatient lipid panel drawn between 2007 and 2010. The date of the first qualifying lipid panel served as the study baseline. MEASUREMENTS: Time from baseline to the first occurrence of a major ASCVD event (myocardial infarction, stroke, or cardiovascular death) within 5 years, modeled as a function of a locally derived neighborhood disadvantage index (NDI) and the predicted 5-year ASCVD event rate from the Pooled Cohort Equations Risk Model (PCERM) of the American College of Cardiology and American Heart Association. Outcome data were censored if no CCHS encounters occurred for 2 consecutive years or when state death data were no longer available (that is, from 2014 onward). RESULTS: The PCERM systematically underpredicted ASCVD event risk among patients from disadvantaged communities. Model discrimination was poorer among these patients (concordance index [C], 0.70 [95% CI, 0.67 to 0.74]) than those from the most affluent communities (C, 0.80 [CI, 0.78 to 0.81]). The NDI alone accounted for 32.0% of census tract-level variation in ASCVD event rates, compared with 10.0% accounted for by the PCERM. LIMITATIONS: Patients from affluent communities were overrepresented. Outcomes of patients who received treatment for cardiovascular disease at Cleveland Clinic were assumed to be independent of whether the patients came from a disadvantaged or an affluent neighborhood. CONCLUSION: Neighborhood disadvantage may be a powerful regulator of ASCVD event risk. In addition to supplemental risk models and clinical screening criteria, population-based solutions are needed to ameliorate the deleterious effects of neighborhood disadvantage on health outcomes. PRIMARY FUNDING SOURCE: The Clinical and Translational Science Collaborative of Cleveland and National Institutes of Health.

Associations among comorbid anxiety, psychiatric symptomatology, and diabetic control in a population with serious mental illness and diabetes: Findings from an interventional randomized controlled trial.

Objective Serious mental illness and type II diabetes mellitus have a high comorbidity, and both have a higher prevalence of anxiety disorders compared to the general population. Targeted Training in Illness Management is a group-based self-management training approach which targets serious mental illness and type II diabetes mellitus concurrently. This analysis examines data from a randomized controlled trial of Targeted Training in Illness Management intervention to examine the impact of comorbid anxiety on baseline psychiatric symptomatology and diabetic control, and on longitudinal treatment outcomes. Methods We conducted secondary analyses on data from a prospective, 60-week, randomized controlled trial testing Targeted Training in Illness Management versus treatment as usual in 200 individuals with serious mental illness and diabetes. Primary outcomes included measures related to serious mental illness symptoms, functional status, general health status, and diabetes control. Measures were compared between those participants with anxiety disorders versus those without anxiety at baseline as well as over time using linear mixed effects analyses. Results Forty seven percent of the participants had one or more anxiety disorders. At baseline, those with an anxiety diagnosis had higher illness severity, depressive, and other psychiatric symptomatology and disability. Diabetic control (HbA1c) was not significantly different at baseline. In the longitudinal analyses, no significant mean slope differences over time (group-by-time interaction effect) between those with anxiety diagnoses and those without in treatment as usual group were found for primary outcomes. Within the Targeted Training in Illness Management arm, those with anxiety disorders had significantly greater improvement in mental health functioning. Those with anxiety comorbidity in the Targeted Training in Illness Management group demonstrated significantly lower HbA1c levels compared to no anxiety comorbidity and also demonstrated a greater improvement in HbA1c over the first 30 weeks compared to those without anxiety comorbidity. Conclusion Comorbid anxiety in serious mental illness and type II diabetes mellitus population is associated with increased psychiatric symptomatology and greater disability. Individuals from this population appear to experience greater improvement in functioning from baseline with the Targeted Training in Illness Management intervention. Anxiety comorbidity in the serious mental illness and type II diabetes mellitus population does not appear to have a negative impact on diabetic control. These complex relationships need further study. Clinical Trials Registration ClinicalTrials.gov: Improving outcomes for individuals with serious mental illness and diabetes (NCT01410357).

What Works in a Nurse Led Self-Management Program for Patients with Serious Mental Illness (SMI) and Diabetes (DM).

OBJECTIVE: To develop a deeper understanding of "how" a nurse led self-management intervention in a successful randomized controlled trial (RCT) for individuals with both serious mental illness (SMI) and diabetes (DM) influenced health outcomes and the lives of the participants. METHODS: In depth interviews, were conducted with a sample of 10 participants who received the self-management intervention in the RCT. Interviews were audiotaped, transcribed verbatim, and analyzed using content analysis, with an emphasis on dominant themes. RESULTS: The mean age of the respondents was 53.9years (SD=5.6); 6 (60%) were women and the mean level of education was 12.4years (SD=2.4). Transcript based analysis generated 3 major mechanisms of action that led to improved self-management of their SMI and DM: (Colton & Manderscheid, 2006) positive group experience, (Osborn et al., 2008) increased health knowledge, and (Newcomer, 2005) increased self- confidence. CONCLUSIONS: Developing complex interventions for testing in RCTs of individuals with SMI and other comorbid conditions is of increasing importance in healthcare planning for this vulnerable population. Using qualitative methods to explore mechanisms of action underlying quantitative outcomes, can enrich our understanding of processes relevant for individuals with SMI and comorbid conditions.

A hydrogen peroxide safety valve: The reversible phosphorylation of catalase from the freeze-tolerant North American wood frog, Rana sylvatica.

BACKGROUND: The North American wood frog, Rana sylvatica, endures whole body freezing while wintering on land and has developed multiple biochemical adaptations to elude cell/tissue damage and optimize its freeze tolerance. Blood flow is halted in the frozen state, imparting both ischemic and oxidative stress on cells. A potential build-up of H2O2 may occur due to increased superoxide dismutase activity previously discovered. The effect of freezing on catalase (CAT), which catalyzes the breakdown of H2O2 into molecular oxygen and water, was investigated as a result. METHODS: The present study investigated the purification and kinetic profile of CAT in relation to the phosphorylation state of CAT from the skeletal muscle of control and frozen R. sylvatica. RESULTS: Catalase from skeletal muscle of frozen wood frogs showed a significantly higher Vmax (1.48 fold) and significantly lower Km for H2O2 (0.64 fold) in comparison to CAT from control frogs (5°C acclimated). CAT from frozen frogs also showed higher overall phosphorylation (1.73 fold) and significantly higher levels of phosphoserine (1.60 fold) and phosphotyrosine (1.27 fold) compared to control animals. Phosphorylation via protein kinase A or the AMP-activated protein kinase significantly decreased the Km for H2O2 of CAT, whereas protein phosphatase 2B or 2C action significantly increased the Km. CONCLUSION: The physiological consequence of freeze-induced CAT phosphorylation appears to improve CAT function to alleviate H2O2 build-up in freezing frogs. GENERAL SIGNIFICANCE: Augmented CAT activity via reversible phosphorylation may increase the ability of R. sylvatica to overcome oxidative stress associated with ischemia.

Passive regeneration of glutathione: glutathione reductase regulation in the freeze-tolerant North American wood frog, Rana sylvatica.

Wood frogs inhabit a broad range across North America, extending from the southern tip of the Appalachian Mountains to the northern boreal forest. Remarkably, they can survive the winter in a frozen state, where as much as 70% of their body water is converted into ice. Whilst in the frozen state, their hearts cease to pump blood, causing their cells to experience ischemia, which can dramatically increase the production of reactive oxygen species within the cell. To overcome this, wood frogs have elevated levels of glutathione, a primary antioxidant. We examined the regulation of glutathione reductase, the enzyme involved in recycling glutathione, in both the frozen and unfrozen (control) state. Glutathione reductase activity from both the control and frozen state showed a dramatic reduction in substrate specificity (Km) for oxidized glutathione (50%) when measured in the presence of glucose (300 mmol l-1) and a increase (157%) when measured in the presence of levels of urea (75 mmol l-1) encountered in the frozen state. However, when we tested the synergistic effect of urea and glucose simultaneously, we observed a substantial reduction in the Km for oxidized glutathione (43%) to a value similar to that with glucose alone. In fact, we found no observable differences in the kinetic and structural properties of glutathione reductase between the two states. Therefore, a significant increase in the affinity for oxidized glutathione in the presence of endogenous levels of glucose suggests that increased glutathione recycling may occur as a result of passive regulation of glutathione reductase by rising levels of glucose during freezing.

Respiratory mechanics of eleven avian species resident at high and low altitude.

The metabolic cost of breathing at rest has never been successfully measured in birds, but has been hypothesized to be higher than in mammals of a similar size because of the rocking motion of the avian sternum being encumbered by the pectoral flight muscles. To measure the cost and work of breathing, and to investigate whether species resident at high altitude exhibit morphological or mechanical changes that alter the work of breathing, we studied 11 species of waterfowl: five from high altitudes (>3000 m) in Perú, and six from low altitudes in Oregon, USA. Birds were anesthetized and mechanically ventilated in sternal recumbency with known tidal volumes and breathing frequencies. The work done by the ventilator was measured, and these values were applied to the combinations of tidal volumes and breathing frequencies used by the birds to breathe at rest. We found the respiratory system of high-altitude species to be of a similar size, but consistently more compliant than that of low-altitude sister taxa, although this did not translate to a significantly reduced work of breathing. The metabolic cost of breathing was estimated to be between 1 and 3% of basal metabolic rate, as low or lower than estimates for other groups of tetrapods.