Growth of Mycobacterium tuberculosis at acidic pH depends on lipid assimilation and is accompanied by reduced GAPDH activity.

Acidic pH arrests the growth of Mycobacterium tuberculosis in vitro (pH < 5.8) and is thought to significantly contribute to the ability of macrophages to control M. tuberculosis replication. However, this pathogen has been shown to survive and even slowly replicate within macrophage phagolysosomes (pH 4.5 to 5) [M. S. Gomes et al., Infect. Immun. 67, 3199-3206 (1999)] [S. Levitte et al., Cell Host Microbe 20, 250-258 (2016)]. Here, we demonstrate that M. tuberculosis can grow at acidic pH, as low as pH 4.5, in the presence of host-relevant lipids. We show that lack of phosphoenolpyruvate carboxykinase and isocitrate lyase, two enzymes necessary for lipid assimilation, is cidal to M. tuberculosis in the presence of oleic acid at acidic pH. Metabolomic analysis revealed that M. tuberculosis responds to acidic pH by altering its metabolism to preferentially assimilate lipids such as oleic acid over carbohydrates such as glycerol. We show that the activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is impaired in acid-exposed M. tuberculosis likely contributing to a reduction in glycolytic flux. The generation of endogenous reactive oxygen species at acidic pH is consistent with the inhibition of GAPDH, an enzyme well-known to be sensitive to oxidation. This work shows that M. tuberculosis alters its carbon diet in response to pH and provides a greater understanding of the physiology of this pathogen during acid stress.

Sulfur Availability Impacts Accumulation of the 2-Thiouridine tRNA Modification in Bacillus subtilis.

Posttranscriptional modifications to tRNA are critical elements for the folding and functionality of these adaptor molecules. Sulfur modifications in tRNA are installed by specialized enzymes that act on cognate tRNA substrates at specific locations. Most studied organisms contain a general cysteine desulfurase to mobilize sulfur for the synthesis of S-tRNA and other thio-cofactors. Bacillus subtilis and other Gram-positive bacteria encode multiple cysteine desulfurases that partner with specific sulfur acceptors in the biosynthesis of thio-cofactors. This metabolic layout suggests an alternate mode of regulation in these biosynthetic pathways. In this study, tRNA modifications were exploited as a readout for the functionality of pathways involving cysteine desulfurases. These analyses showed that the relative abundance of 2-thiouridine-modified tRNA (s2U) responds to sulfur availability in the growth medium in a dose-dependent manner. This study found that low sulfur concentrations lead to decreased levels of the s2U cysteine desulfurase YrvO and thiouridylase MnmA, without altering the levels of other cysteine desulfurases, SufS, NifS, and NifZ. Analysis of pathway metabolites that depend on the activity of cysteine desulfurases indicates that sulfur nutrient availability specifically impacts s2U accumulation while having no effect on the levels of other S-modified tRNA or activity levels of Fe-S enzymes. Collectively, these results support a model in which s2U tRNA serves as a marker for sulfur availability in B. subtilis. IMPORTANCE The 2-thiouridine (s2U) tRNA modification is found ubiquitously across all domains of life. YrvO and MnmA, the enzymes involved in this modification, are essential in B. subtilis, confirming the well-established role of s2U in maintaining translational efficiency and, consequently, cellular viability. Herein, we show that in the model Gram-positive organism Bacillus subtilis, the levels of s2U are responsive to sulfur availability. Downregulation of the s2U biosynthetic components leads to lower s2U levels, which may serve as a signal for the slowing of the translational apparatus during cellular nutrient insufficiency. Our findings provide the basis for the identification of a potential bacterial mode of regulation during S-metabolite depletion that may use s2U as a marker of suboptimal metabolic status.

Endothelial-Specific Loss of Sphingosine-1-Phosphate Receptor 1 Increases Vascular Permeability and Exacerbates Bleomycin-induced Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease which leads to significant morbidity and mortality from respiratory failure. The two drugs currently approved for clinical use slow the rate of decline in lung function but have not been shown to halt disease progression or reverse established fibrosis. Thus, new therapeutic targets are needed. Endothelial injury and the resultant vascular permeability are critical components in the response to tissue injury and are present in patients with IPF. However, it remains unclear how vascular permeability affects lung repair and fibrosis following injury. Lipid mediators such as sphingosine-1-phosphate (S1P) are known to regulate multiple homeostatic processes in the lung including vascular permeability. We demonstrate that endothelial cell-(EC) specific deletion of the S1P receptor 1 (S1PR1) in mice (EC-S1pr1-/-) results in increased lung vascular permeability at baseline. Following a low-dose intratracheal bleomycin challenge, EC-S1pr1-/- mice had increased and persistent vascular permeability compared with wild-type mice, which was strongly correlated with the amount and localization of resulting pulmonary fibrosis. EC-S1pr1-/- mice also had increased immune cell infiltration and activation of the coagulation cascade within the lung. However, increased circulating S1P ligand in ApoM-overexpressing mice was insufficient to protect against bleomycin-induced pulmonary fibrosis. Overall, these data demonstrate that endothelial cell S1PR1 controls vascular permeability in the lung, is associated with changes in immune cell infiltration and extravascular coagulation, and modulates the fibrotic response to lung injury.

Pediatric Liver Transplant Survival in Alagille Syndrome Is Comparable to Biliary Atresia-A Linked Database Analysis.

OBJECTIVES: This study aims to report liver transplantation (LT) outcomes and cardiac disease manifestations in children with Alagille Syndrome (ALGS) in a contemporary cohort. METHODS: This project used a novel linkage between the Scientific Registry of Transplant Recipients and Pediatric Health Information System databases. All children ≤21 years undergoing a first LT were identified (2002-2018). The presence of ALGS was identified using Scientific Registry of Transplant Recipients diagnosis coding. Subjects with ALGS were age-matched 1:2 to LT recipients with biliary atresia (BA). The Kaplan-Meier method and log-rank test were used to compare patient and graft survival between groups. RESULTS: A total of 156 LT recipients with ALGS were identified and matched to a control group of 312 LT recipients with BA. Children with ALGS were more likely to have an associated diagnosis of congenital heart disease (80.7% vs 16.4%; P = 0.001) compared with children with BA with 40 (25.6%) children with AGS requiring cardiac intervention (catheter or surgical) either before or after LT. Those patients with ALGS had a higher creatinine, laboratory MELD, and PELD scores before LT. No difference was observed regarding patient or graft survival between children with ALGS and children with BA ( P = 0.08 and P = 0.27, respectively). CONCLUSIONS: Despite increased rate of congenital heart defects and cardiac interventions, higher creatinine, and higher laboratory MELD/PELD scores at time of transplant, this study demonstrates that there is no difference in either patient or graft survival between patients with ALGS and BA.

Bacillus subtilis PgcA moonlights as a phosphoglucosamine mutase in support of peptidoglycan synthesis.

Phosphohexomutase superfamily enzymes catalyze the reversible intramolecular transfer of a phosphoryl moiety on hexose sugars. Bacillus subtilis phosphoglucomutase PgcA catalyzes the reversible interconversion of glucose 6-phosphate (Glc-6-P) and glucose 1-phosphate (Glc-1-P), a precursor of UDP-glucose (UDP-Glc). B. subtilis phosphoglucosamine mutase (GlmM) is a member of the same enzyme superfamily that converts glucosamine 6-phosphate (GlcN-6-P) to glucosamine 1-phosphate (GlcN-1-P), a precursor of the amino sugar moiety of peptidoglycan. Here, we present evidence that B. subtilis PgcA possesses activity as a phosphoglucosamine mutase that contributes to peptidoglycan biosynthesis. This activity was made genetically apparent by the synthetic lethality of pgcA with glmR, a positive regulator of amino sugar biosynthesis, which can be specifically suppressed by overproduction of GlmM. A gain-of-function mutation in a substrate binding loop (PgcA G47S) increases this secondary activity and suppresses a glmR mutant. Our results demonstrate that bacterial phosphoglucomutases may possess secondary phosphoglucosamine mutase activity, and that this dual activity may provide some level of functional redundancy for the essential peptidoglycan biosynthesis pathway.

Seasonal thaw and landscape position determine foliar functional traits and whole-plant water use in tall shrubs on the low arctic tundra.

Climate warming is driving tundra shrub expansion with implications for ecosystem function and regional climate. Understanding associations between shrub ecophysiological function, distribution and environment is necessary for predicting consequences of expansion. We evaluated the role of topographic gradients on upland shrub productivity to understand potential constraints on shrub expansion. At a low arctic tundra site near Inuvik, Northwest Territories, Canada, we measured sap flow, stem water potential and productivity-related functional traits in green alder, and environmental predictors (water and nutrient availability and seasonal thaw depth) across a toposequence in alder patches. Seasonal thaw reduced stem sap flow whereas topographic position predicted stem water potential and productivity-related functional traits. Upslope shrubs were more water-limited than those downslope. Shrubs in drainage channels had traits associated with greater productivity than those on the tops of slopes. The effect of thaw depth on sap flow has implications for seasonal water-use patterns and warming impacts on tundra ecohydrology. Topographic variation in functional traits corresponds with observed spatial patterns of tundra shrub expansion along floodplains and concave hillslopes rather than in upland areas. Green alder is expanding rapidly across the low arctic tundra in northwestern North America; thus, anticipating the implications of its expansion is essential for predicting tundra function.

Associations of accelerometer-measured sedentary time, sedentary bouts, and physical activity with adiposity and fitness in children.

Sedentary time (ST) has been inconsistently associated with adiposity and cardiorespiratory fitness in children in previous studies. We studied cross-sectional associations of ST, light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) with fat mass index (FMI) and cardiorespiratory fitness (estimated VO2max). Associations were evaluated with and without considering pattern of ST by bout length. We measured ST and activity by a wrist-worn accelerometer, FMI by bioelectrical impedance, and VO2max by Pacer test in 443 children (51.2% girls, 10.2 ± 0.6 years). Isotemporal substitution regression models estimated the effects of substituting ST, LPA, and MVPA on FMI and VO2max. Further models repeated analyses separating ST into short (<10 min) and long (≥10 min) bouts. Only replacing ST or LPA with MVPA was consistently associated with lower FMI and greater VO2max. When separated by bout length, only one unique association was found where replacing long ST bouts with short ST bouts was associated with lower FMI in girls only. In conclusion, activity pattern is associated with adiposity in girls and fitness in boys and girls. Separating ST into long and short ST bouts may be of minimal importance when assessing associations with adiposity and fitness using wrist-worn accelerometry in children.

The Thioredoxin System Reduces Protein Persulfide Intermediates Formed during the Synthesis of Thio-Cofactors in Bacillus subtilis.

The biosynthesis of Fe-S clusters and other thio-cofactors requires the participation of redox agents. A shared feature in these pathways is the formation of transient protein persulfides, which are susceptible to reduction by artificial reducing agents commonly used in reactions in vitro. These agents modulate the reactivity and catalytic efficiency of biosynthetic reactions and, in some cases, skew the enzymes' kinetic behavior, bypassing sulfur acceptors known to be critical for the functionality of these pathways in vivo. Here, we provide kinetic evidence for the selective reactivity of the Bacillus subtilis Trx (thioredoxin) system toward protein-bound persulfide intermediates. Our results demonstrate that the redox flux of the Trx system modulates the rate of sulfide production in cysteine desulfurase assays. Likewise, the activity of the Trx system is dependent on the rate of persulfide formation, suggesting the occurrence of coupled reaction schemes between both enzymatic systems in vitro. Inactivation of TrxA (thioredoxin) or TrxR (thioredoxin reductase) impairs the activity of Fe-S enzymes in B. subtilis, indicating the involvement of the Trx system in Fe-S cluster metabolism. Surprisingly, biochemical characterization of TrxA reveals that this enzyme is able to coordinate Fe-S species, resulting in the loss of its reductase activity. The inactivation of TrxA through the coordination of a labile cluster, combined with its proposed role as a physiological reducing agent in sulfur transfer pathways, suggests a model for redox regulation. These findings provide a potential link between redox regulation and Fe-S metabolism.

Hepcidin as a Prospective Individualized Biomarker for Individuals at Risk of Low Energy Availability.

Hepcidin, a peptide hormone with an acknowledged evolutionary function in iron homeostasis, was discovered at the turn of the 21st century. Since then, the implications of increased hepcidin activity have been investigated as a potential advocate for the increased risk of iron deficiency in various health settings. Such implications are particularly relevant in the sporting community where peaks in hepcidin postexercise (∼3-6 hr) are suggested to reduce iron absorption and recycling, and contribute to the development of exercise-induced iron deficiency in athletes. Over the last decade, hepcidin research in sport has focused on acute and chronic hepcidin activity following single and repeated training blocks. This research has led to investigations examining possible methods to attenuate postexercise hepcidin expression through dietary interventions. The majority of macronutrient dietary interventions have focused on manipulating the carbohydrate content of the diet in an attempt to determine the health of athletes adopting the low-carbohydrate or ketogenic diets, a practice that is a growing trend among endurance athletes. During the process of these macronutrient dietary intervention studies, an observable coincidence of increased cumulative hepcidin activity to low energy availability has emerged. Therefore, this review aims to summarize the existing literature on nutritional interventions on hepcidin activity, thus, highlighting the link of hepcidin to energy availability, while also making a case for the use of hepcidin as an individualized biomarker for low energy availability in males and females.

Body Image Among Elite Rugby Union Players.

Gibson, C, Hindle, C, McLay-Cooke, R, Slater, J, Brown, R, Smith, B, Baker, D, Healey, P, and Black, K. Body image among elite rugby union players. J Strength Cond Res 33(8): 2217-2222, 2019-There is limited information on the risk of eating disorders (EDs) and body image of elite male athletes. However, research studies suggest that there are some athletes who have poor body image and they may be at increased risk of developing EDs. Therefore, the current study investigated risk of EDs, body image, and the relationship with age, in elite rugby union players during their preseason training period. This cross-sectional study was undertaken at the start of the preseason among elite rugby union players in New Zealand. Twenty-six professional rugby union players completed a 49-item questionnaire on body image and disordered eating. A "body image score" was calculated from questionnaire subscales including "drive for thinness," "bulimia," and "body dissatisfaction," with total scores above 20 indicative of poor body image. Body image scores varied from 8 to 39 out of a possible 0-100. Disordered eating behaviors were reported, including binge eating at least once a week (15%, n = 4/26), pathogenic weight control use (4%, n = 1/26), and avoidance of certain foods (77%, n = 20/26). There was a statistically significant inverse association between the bulimia subscale and age (p = 0.034). At the start of the preseason training period, many elite rugby union players experience disturbances in body image. The prevalence of disordered eating behaviors is of concern, and needs to be minimized due to the negative impact on health and performance. A focus on assessment and education of younger male rugby players may be required to reduce disordered eating patterns.

Sleep timing is associated with diet and physical activity levels in 9-11-year-old children from Dunedin, New Zealand: the PEDALS study.

It is well documented that short sleep duration is associated with excess body weight and poor food intake in children. It has been suggested that sleep timing behaviour may also be an important predictor of weight and other related behaviours, independent of sleep duration; however, there is a lack of research investigating these relationships. The present study investigated sleep timing in association with diet and physical activity levels in 439 children aged 9-11 years old from New Zealand. Sleep and physical activity data were collected using accelerometry, and food choice using a short food-frequency questionnaire. Participants were classified into one of four sleep timing behaviour categories using the median split for sleep-onset and -offset times. Differences between sleep timing groups for weekly consumption frequency of selected food groups, dietary pattern scores and minutes of moderate-to-vigorous physical activity were examined. Children in the late sleep/late wake category had a lower 'Fruit & Vegetables' pattern score [mean difference (95% CI): -0.3 (-0.5, -0.1)], a lower consumption frequency of fruit and vegetables [mean weekly difference (95% CI): -2.9 (-4.9, -0.9)] and a higher consumption frequency of sweetened beverages [mean weekly difference (95% CI): 1.8 (0.2, 3.3)] compared with those in the early sleep/early wake category. Additionally, children in the late sleep/late wake category accumulated fewer minutes of moderate-to-vigorous physical activity per day compared with those in the early sleep/early wake category [mean difference (95% CI): -9.4 (-15.3, -3.5)]. These findings indicate that sleep timing, even after controlling for sleep duration, was associated with both food consumption and physical activity.

No Association between Vitamin D and Acute Respiratory Tract Infections Amongst Elite New Zealand Rugby Players and Rowers.

Upper respiratory tract infections are the most common infections reported by elite athletes. Low vitamin D status has been associated with an increased risk of upper respiratory tract infections. The aim of this study was to investigate associations between serum 25-hydroxyvitamin D (25(OH)D), salivary immunoglobulin A (S-IgA) concentrations, and acute respiratory tract infections (colds/flu) (ARI) in elite rowers and rugby players. A total of 53 (23 rugby players, 30 rowers) elite New Zealand athletes volunteered to participate in an interview, and to provide a blood and a saliva sample. Testing occurred twice, 6 months apart. Athletes' serum 25(OH)D concentrations and s-IgA levels were both significantly higher in summer, 108.9 (CI 102.8, 115.4) nmol/L, than in winter, 86.8 (CI 81.8, 92.1) nmol/L (p < 0.01, p = 0.028). The occurrence of an acute respiratory tract infection did not differ significantly between the time points (p = 0.322). However, ARI duration was significantly longer in winter than in summer (6.9 ± 4.3 days vs 4.8 ± 3.0 days; p = 0.044). There were no significant correlations between athletes' 25(OH)D levels and their s-IgA levels (p > 0.05) nor with acute respiratory tract infection occurrence (p > 0.05) nor duration (p > 0.05) in summer or winter. These findings suggest there may not be any associations between serum 25(OH)D concentrations and acute respiratory tract infections in this population. However, this null finding may be attributed to the high vitamin D concentrations seen in these athletes.

Macronutrient Intakes of Male Rugby Union Players: A Review.

Rugby is a worldwide intermittent team sport. Players tend to be heavier than the majority of similar team sport athletes on whom the dietary guidelines have been developed. Therefore, the aim of the current review was to describe the intakes of rugby union players. Article databases were searched up to February 2017 and were included if they were published in English and reported dietary intakes of male rugby union players. Of the research articles identified, energy intakes were lower than two of three studies that reported intakes and expenditure, which would suggest the players were losing weight that is somewhat supported by the decreases in skinfolds seen during preseason. However, it should also be noted that there are errors in both the measurement of energy intakes and expenditure. Carbohydrate intakes ranged from 2.6 to 6.5 g·kg-1·day-1, which is lower than the current relative to body mass recommendations; however, this would not be classed as a low-carbohydrate diet. The consistently low intakes of carbohydrate suggest that these intake levels maybe sufficient for performance, given the players greater body mass or there are errors in the measurements. However, there is currently no evidence for the carbohydrate needs of rugby union players in terms of performance. The lower intakes than expenditure would suggest the players were losing weight. Previous research shows that rugby union players lose body fat during preseason training.

Low Energy Availability, Plasma Lipids, and Hormonal Profiles of Recreational Athletes.

Black, K, Slater, J, Brown, RC, and Cooke, R. Low energy availability, plasma lipids, and hormonal profiles of recreational athletes. J Strength Cond Res 32(10): 2816-2824, 2018-It has been postulated that low energy availability (LEA) impacts bone health, hormonal concentrations, and cardiovascular function. This study describes the lipid levels, hormonal profiles, and nutrient intakes of recreationally active adults at risk of LEA compared with those not at risk. Thirty-eight women who meet or exceed the New Zealand guidelines for physical activity participated. Each participant completed an online questionnaire including the Low Energy Availability in Females questionnaire (LEAF-Q), demographic questions, and daily exercise to determine energy expenditure. Participants also provided a weighed 3-day diet record, a blood sample analyzed for total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and cortisol, and a saliva sample analyzed for testosterone. Body composition was assessed using bioelectrical impedance. Those classed as at risk of LEA according to the LEAF-Q showed very likely lower energy availability (at risk: mean, 36.3 [95% confidence interval, 30.8-41.7] kcal·kg·FFMd vs. not at risk: mean, 47.5 [95% CI, 39.5-55.4] kcal·kg·FFMd) and lower calcium intakes (mean, 847 [95% CI, 695-998] mg, vs. mean, 1488 [95% CI, 690-2,286] mg). Those at risk also had a likely small lower T3 concentration of 1.78 (SD: 0.36) nmol·L compared with 2.01 (SD: 0.53) nmol·L for those not at risk. These data suggest that recreationally active female subjects classed as at risk of LEA according to the LEAF-Q also have lower energy availability as determined by diet records and exercise diaries. The results also suggests that those at risk of LEA have reductions in T3, and their low energy intake, in addition to a low calcium intake, could put them at an increased risk of poor bone health.

ß-Hydroxy ß-Methylbutyrate (HMB) Supplementation Effects on Body Mass and Performance in Elite Male Rugby Union Players.

McIntosh, ND, Love, TD, Haszard, J, Osborne, H, and Black, KE. ß-hydroxy ß-methylbutyrate (HMB) supplementation effects on body mass and performance in elite male rugby union players. J Strength Cond Res 32(1): 19-26, 2018-Preseason is characterized by high training volumes with short recovery periods ß-hydroxy ß-methylbutyrate (HMB) has been postulated to assist with recovery. ß-hydroxy ß-methylbutyrate has been shown to improve strength and body composition among untrained groups; the benefits of HMB among trained populations are unclear because of the methodologies employed. This randomized control trail determined the effects of 11 weeks HMB supplementation on body mass and performance measures in 27 elite rugby players. ß-hydroxy ß-methylbutyrate group (n = 13), mean ± SD age 20.3 ± 1.2 years, body mass 99.6 ± 9.1 kg; placebo group (n = 14), age 21.9 ± 2.8 years body mass 99.4 ± 13.9 kg for placebo. During the supplementation period, body mass increased with HMB 0.57 ± 2.60 kg but decreased with placebo 1.39 ± 2.02 kg (p = 0.029). There were no significant differences in any of the 4 strength variables (p > 0.05). However, on the yo-yo intermittent recovery test (YoYo IR-1), the placebo group improved 4.0 ± 2.8 levels but HMB decreased 2.0 ± 3.0 levels (p = 0.003). The results of this study suggest that HMB could be beneficial for gaining or maintaining body mass during periods of increased training load. However, it appears that HMB may be detrimental to intermittent running ability in this group although further research is required before firm conclusions can be made. Only 6 participants on HMB managed to complete both YoYo IR-1 tests because of injury, a larger sample size is required to fully investigate this potentially negative effect. Further, the mechanisms behind this decrement in performance cannot be fully explained and requires further biochemical and psychological investigation.

Physiological responses to a five-day adventure race: Continuous blood glucose, hemodynamics and metabolites the 2012 GODZone field-study.

BACKGROUND/OBJECTIVE: Adventure racing is an ultra-endurance activity that imposes a unique multifaceted stress on the human body. The purpose of this field study was to examine the physiological responses to a 5-day adventure race. METHODS: Eight competitors, two teams (1 female each) in the 2012 GODZone adventure race volunteered. Competitors trekked, cycled and paddled ∼326 km in ∼116 hours. Continuous glucose was measured the day before and throughout. Body mass, urinary solutes, and blood pressure and heart rate during resting, standing, and repeated squat-stand conditions, were assessed pre and post. RESULTS: Despite no changes in mean blood glucose levels, there was increased glycemic variability (Standard deviation glucose; Pre: 0.5 ±â€¯0.1 vs Race: 1.0 ±â€¯0.2 mmol/L, p = 0.02) and periods of hypoglycemia (i.e., Min glucose Pre: 4.1 ±â€¯0.3 vs Race: 3.6 ±â€¯0.5 mmol/L, p = 0.05) during the race. After the race, the blood pressure during resting, standing and squat-stand conditions was significantly lower, by 14 ±â€¯14 mmHg, 16 ±â€¯15 mmHg and 18 ±â€¯15 mmHg (all p < 0.05), respectively, with no change in heart rate. During five-days of adventure racing there is increased glycemic variability and more frequent periods of low blood glucose levels. Additionally, following the race pronounced hypotension is observed in competitors. CONCLUSION: We observed more frequent glucose fluctuations, lower glucose levels and significant perturbations in blood pressure control. Further research is warranted to examine the long-term impact of adventure racing on metabolic and cardiovascular function.

Hemodynamic Effects of Lipid-Based Oxygen Microbubbles via Rapid Intravenous Injection in Rodents.

PURPOSE: Low oxygen levels, or hypoxemia, is a common cause of morbidity and mortality in critically ill patients. Hypoxemia is typically addressed by increasing the fraction of inspired oxygen, the use of mechanical ventilation, or more invasive measures. Recently, the injection of oxygen gas directly into the bloodstream by packaging it within lipid-based oxygen microbubbles (LOMs) has been explored. The purpose of this work is to examine the acute hemodynamic effects of intravenous injections of LOMs. METHODS: LOMs composed of 1,2-distearoyl-sn-glycero-3-phosphocoline and cholesterol were manufactured using a process of shear homogenization under an oxygen headspace. A 5 mL aliquot of either PlasmaLyte A, or low (37%) or high (55%) concentration LOMs (n = 10 per group) was injected over a 1 min period into Sprague Dawley rats instrumented for measurement of cardiac index and pulmonary (PVR) and systemic (SVR) vascular resistance during a 60 min observation period. Hemodynamics were compared between groups by linear mixed modeling. RESULTS: Approximately 1011 LOMs with mean diameter 3.77 ± 1.19 µm were injected over the 1 min period. Relative to controls, rodents treated with high concentration LOMs exhibited a higher pulmonary artery pressure (20 ± 0.4 mmHg vs 18 ± 0.4 mmHg, P < 0.001) and higher PVR (0.31 ± 0.01 vs 0.23 ± 0.01 mmHg/mL*min*kg, P < 0.001. Despite a stable cardiac index (62.2 ± 3.5 vs 62.3 ± 3.4 mL/min*kg, P < 0.001), mean arterial blood pressure decreased significantly in LOM-treated animals (46 ± 2 vs 60 ± 2 mmHg, P < 0.001) due to a decrease in SVR. Injections with aged LOM emulsions (>48 h since manufacture) resulted in a higher incidence of hemodynamic collapse during the observation period (P = 0.02). CONCLUSIONS: LOMs may be injected in quantities sufficient to deliver clinically meaningful volumes of oxygen but cause significant decrements in blood pressure and elevations in PVR.

Shared-intermediates in the biosynthesis of thio-cofactors: Mechanism and functions of cysteine desulfurases and sulfur acceptors.

Cysteine desulfurases utilize a PLP-dependent mechanism to catalyze the first step of sulfur mobilization in the biosynthesis of sulfur-containing cofactors. Sulfur activation and integration into thiocofactors involve complex mechanisms and intricate biosynthetic schemes. Cysteine desulfurases catalyze sulfur-transfer reactions from l-cysteine to sulfur acceptor molecules participating in the biosynthesis of thio-cofactors, including Fe-S clusters, thionucleosides, thiamin, biotin, and molybdenum cofactor. The proposed mechanism of cysteine desulfurases involves the PLP-dependent cleavage of the C-S bond from l-cysteine via the formation of a persulfide enzyme intermediate, which is considered the hallmark step in sulfur mobilization. The subsequent sulfur transfer reaction varies with the class of cysteine desulfurase and sulfur acceptor. IscS serves as a mecca for sulfur incorporation into a network of intertwined pathways for the biosynthesis of thio-cofactors. The involvement of a single enzyme interacting with multiple acceptors, the recruitment of shared-intermediates partaking roles in multiple pathways, and the participation of Fe-S enzymes denote the interconnectivity of pathways involving sulfur trafficking. In Bacillus subtilis, the occurrence of multiple cysteine desulfurases partnering with dedicated sulfur acceptors partially deconvolutes the routes of sulfur trafficking and assigns specific roles for these enzymes. Understanding the roles of promiscuous vs. dedicated cysteine desulfurases and their partnership with shared-intermediates in the biosynthesis of thio-cofactors will help to map sulfur transfer events across interconnected pathways and to provide insight into the hierarchy of sulfur incorporation into biomolecules. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.

Cardiorespiratory fitness is positively associated with a healthy dietary pattern in New Zealand adolescents.

OBJECTIVE: To examine the association between cardiorespiratory fitness and dietary patterns in adolescents. DESIGN: Food choice was assessed using the validated New Zealand Adolescent FFQ. Principal components analysis was used to determine dietary patterns. Trained research assistants measured participants' height and body mass. Cardiorespiratory fitness was assessed in a subset of participants using the multistage 20 m shuttle run. The level and stage were recorded, and the corresponding VO2max was calculated. Differences in mean VO2max according to sex and BMI were assessed using t tests, while associations between cardiorespiratory fitness and dietary patterns were examined using linear regression analyses adjusted for age, sex, school attended, socio-economic deprivation and BMI. SETTING: Secondary schools in Otago, New Zealand. SUBJECTS: Students (n 279) aged 14-18 years who completed an online lifestyle survey during a class period. RESULTS: Principal components analysis produced three dietary patterns: 'Treat Foods', 'Fruits and Vegetables' and 'Basic Foods'. The 279 participants who provided questionnaire data and completed cardiorespiratory fitness testing had a mean age of 15·7 (sd 0·9) years. Mean VO2max was 45·8 (sd 6·9) ml/kg per min. The 'Fruits and Vegetables' pattern was positively associated with VO2max in the total sample (ß=0·04; 95%CI 0·02, 0·07), girls (ß=0·06; 95% CI 0·03, 0·10) and boys (ß=0·03; 95% CI 0·01, 0·05). CONCLUSIONS: These results indicate that increase in cardiorespiratory fitness was associated with a healthier dietary pattern, suggesting both should be targeted as part of a global lifestyle approach. Longitudinal studies are needed to confirm this association in relation to health outcomes in New Zealand adolescents.

Female Recreational Exercisers at Risk for Low Energy Availability.

Low energy availability (LEA) describes the disruption in normal physiological function existent when insufficient energy intake is combined with exercise. To conserve energy a range of endocrine adaptations occur, impairing health and athletic performance. The prevalence of LEA has not been fully established especially among recreational exercisers. Determining recreational exercisers at risk of LEA may help to maximize prevention, early diagnosis and treatment. The design of this study was a cross-sectional online survey. One-hundred and nine female recreational exercisers, with a mean age of 23.8 (SD 6.9) years were recruited via gyms and fitness centers throughout NZ. Participants completed an online questionnaire including questions from the LEAF-Q (Low Energy Availability in Females Questionnaire). A total of 45.0% (CI, 35.4%, 54.8%) of participants were classified as "at risk" of LEA. For every extra hour of exercise per week the odds of being at risk of LEA were 1.13 times greater (CI 1.02, 1.25, p = .016). All participants reporting previous stress fracture injuries (n = 4) were classified as at risk for LEA. Significantly more subjects participating in an individual sport were classified as at risk for LEA (69.6%, CI 24.3%, 54.8%) compared with team sports (34.8%, CI 18.7%, 40.5%) (p = .006). The high prevalence of female recreational exercisers at risk of LEA is of concern, emphasizing the importance of increasing awareness of the issue, and promoting prevention and early detection strategies, so treatment can be implemented before health is severely compromised.