Erythrocyte metabolism

Our aim is to present an updated overview of the erythrocyte metabolism highlighting its richness and complexity. We have manually collected and connected the available biochemical pathways and integrated them into a functional metabolic map. The focus of this map is on the main biochemical pathways consisting of glycolysis, the pentose phosphate pathway, redox metabolism, oxygen metabolism, purine/nucleoside metabolism, and membrane transport. Other recently emerging pathways are also curated, like the methionine salvage pathway, the glyoxalase system, carnitine metabolism, and the lands cycle, as well as remnants of the carboxylic acid metabolism. An additional goal of this review is to present the dynamics of erythrocyte metabolism, providing key numbers used to perform basic quantitative analyses. By synthesizing experimental and computational data, we conclude that glycolysis, pentose phosphate pathway, and redox metabolism are the foundations of erythrocyte metabolism. Additionally, the erythrocyte can sense oxygen levels and oxidative stress adjusting its mechanics, metabolism, and function. In conclusion, fine-tuning of erythrocyte metabolism controls one of the most important biological processes, that is, oxygen loading, transport, and delivery.

Short-Term L-Citrulline Supplementation Does Not Affect Blood Pressure, Pulse Wave Reflection, or Arterial Stiffness at Rest and during Isometric Exercise in Older Males

Hypertension and arterial stiffness are significant factors contributing to cardiovascular disease. L-citrulline, a nitric oxide precursor, has been proposed as a nutritional, non-pharmacological blood pressure-lowering intervention. This study aimed to investigate the impact of L-citrulline on central and peripheral blood pressure, pulse wave reflection, and central arterial stiffness at rest and during an isometric knee extension exercise protocol. Twelve older males received 6 g of L-citrulline or a placebo for six days using a double-blind crossover design. Blood hemodynamics parameters (i.e., aortic and brachial systolic and diastolic blood pressure, mean arterial pressure, pulse pressure, heart rate), pulse wave reflection (i.e., augmented pressure, augmentation index, forward/backward wave pressure), and arterial stiffness (i.e., carotid-femoral pulse wave velocity) were measured at baseline, post-supplementation, and during isometric exercise. No significant effects of L-citrulline supplementation were observed at rest or during exercise on blood pressure, pulse wave reflection, or arterial stiffness. Both central and peripheral blood pressure were increased during the exercise, which is consistent with isometric contractions. The results of the present study do not support any blood pressure-lowering effect of short-term L-citrulline at rest or during low-intensity isometric exercise compared to the pre-exercise values in older males.

Inter-individual variability in redox and performance responses after antioxidant supplementation: A randomized double blind crossover study

AIM

We aimed to investigate the inter-individual variability in redox and physiological responses of antioxidant-deficient subjects after antioxidant supplementation.

METHODS

Two hundred individuals were sorted by plasma vitamin C levels. A low vitamin C group (n = 22) and a control group (n = 22) were compared in terms of oxidative stress and performance. Subsequently, the low vitamin C group received for 30 days vitamin C (1 g) or placebo, in randomized, double-blind, crossover fashion, and the effects were examined through a mixed-effects model, while individual responses were calculated.

RESULTS

The low vitamin C group exhibited lower vitamin C (-25 μmol/L; 95%CI[-31.7, -18.3]; p < 0.001), higher F2 -isoprostanes (+17.1 pg/mL; 95%CI[6.5, 27.7]; p = 0.002), impaired VO2max (-8.2 mL/kg/min; 95%CI[-12.8, -3.6]; p < 0.001) and lower isometric peak torque (-41.5 Nm; 95%CI[-61.8, -21.2]; p < 0.001) compared to the control group. Regarding antioxidant supplementation, a significant treatment effect was found in vitamin C (+11.6 μmol/L; 95%CI[6.8, 17.1], p < 0.001), F2 -isoprostanes (-13.7 pg/mL; 95%CI[-18.9, -8.4], p < 0.001), VO2max (+5.4 mL/kg/min; 95%CI[2.7, 8.2], p = 0.001) and isometric peak torque (+18.7; 95%CI[11.8, 25.7 Nm], p < 0.001). The standard deviation for individual responses (SDir) was greater than the smallest worthwhile change (SWC) for all variables indicating meaningful inter-individual variability. When a minimal clinically important difference (MCID) was set, inter-individual variability remained for VO2max , but not for isometric peak torque.

CONCLUSION

The proportion of response was generally high after supplementation (82.9%-95.3%); however, a few participants did not benefit from the treatment. This underlines the potential need for personalized nutritional interventions in an exercise physiology context.

Short-Term L-Citrulline Supplementation Does Not Affect Inspiratory Muscle Oxygenation and Respiratory Performance in Older Adults

In sports nutrition, nitric oxide (NO^•) precursors such as L-citrulline are widely used to enhance NO^• bioavailability, which is considered an ergogenic aid. Our study aimed to examine the effect of short-term L-citrulline supplementation on respiratory muscles' performance, fatigue, and oxygenation in older adults. Fourteen healthy older males took 6 g of L-citrulline or a placebo for seven days in a double-blind crossover design. Pulmonary function via spirometry (i.e., forced expired volume in 1 s (FEV₁), forced vital capacity (FVC), and their ratio)), fractional exhaled nitric oxide (NO^•), maximal inspiratory pressure (MIP), rate of perceived exertion, and sternocleidomastoid muscle oxygenation (i.e., oxyhemoglobin (Δ[O₂Hb]) and de-oxyhemoglobin (Δ[HHb]), total hemoglobin concentration (Δ[tHb]), and tissue saturation index (TSI%)) were evaluated at baseline, after seven days of L-citrulline supplementation, and after incremental resistive breathing to task failure of the respiratory muscles. The exhaled NO^• value was only significantly increased after the supplementation (26% p < 0.001) in the L-citrulline condition. Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation. In the present study, although short-term L-citrulline supplementation increased exhaled NO^•, no ergogenic aids were found on the examined parameters at rest and after resistive breathing to task failure in older adults.

The effects of chronic concentric and eccentric training on position sense and joint reaction angle of the knee extensors

The aim of the present study was to compare the effect of chronic concentric or eccentric training on position sense and joint reaction angle, in healthy, untrained young men. Twenty-four men were randomly assigned into a pure concentric (CT) or a pure eccentric (ET) group and performed for 8 weeks, one training session/week, 75 maximal knee extensors contractions. Before and 48 h after the first (W1) and the last (W8) training sessions, knee joint position sense and joint reaction angle were assessed at three different knee angles (i.e. 30°, 45° and 60°). At the same time points, indirect indices of exercise-induced muscle damage (EIMD) were evaluated (i.e. range of motion [ROM], optimal angle, maximum isometric, concentric and eccentric torques, delayed onset muscle soreness [DOMS] and blood creatine kinase concentrations [CK]). Forty-eight hours post W1, position sense, reaction angle and all EIMD indices were significantly changed for both groups (p < 0.05; η²: 0.125-0.618), however, greater alterations were observed after ET. Significant correlations were found, in both groups, between the training-induced changes of position sense, reaction angles and the changes of EIMD biomarkers (r: -0.855-0.825; p < 0.005). No significant changes were found 48 h post W8 for position sense, reaction angle and EIMD indices (p > 0.285) for both CT or ET groups. In conclusion, exercise-induced changes in position sense and reaction angle, were related to the magnitude of EIMD, and not by the type of muscle contraction per se. HighlightsExercise induced changes in position sense and reaction angle, were related to the magnitude of EIMD, and not by the type of muscle contraction per se.After the 1st training session eccentric exercise caused greater disturbances, compared to concentric exercise, in EIMD indices which caused concomitant disturbances to position sense and knee reaction angle.8 weeks of either eccentric or concentric training leads to preservation of position sense and knee reaction angle 48 h after maximal intensity exercise of either types of muscle contraction.

Acute L-Citrulline Supplementation Increases Nitric Oxide Bioavailability but Not Inspiratory Muscle Oxygenation and Respiratory Performance

The present study aimed to investigate whether acute L-citrulline supplementation would affect inspiratory muscle oxygenation and respiratory performance. Twelve healthy males received 6 g of L-citrulline or placebo in a double-blind crossover design. Pulmonary function (i.e., forced expired volume in 1 s, forced vital capacity and their ratio), maximal inspiratory pressure (MIP), fractional exhaled nitric oxide (NO^•), and sternocleidomastoid muscle oxygenation were measured at baseline, one hour post supplementation, and after an incremental resistive breathing protocol to task failure of the respiratory muscles. The resistive breathing task consisted of 30 inspirations at 70% and 80% of MIP followed by continuous inspirations at 90% of MIP until task failure. Sternocleidomastoid muscle oxygenation was assessed using near-infrared spectroscopy. One-hour post-L-citrulline supplementation, exhaled NO^• was significantly increased (19.2%; p < 0.05), and this increase was preserved until the end of the resistive breathing (16.4%; p < 0.05). In contrast, no difference was observed in the placebo condition. Pulmonary function and MIP were not affected by the L-citrulline supplementation. During resistive breathing, sternocleidomastoid muscle oxygenation was significantly reduced, with no difference noted between the two supplementation conditions. In conclusion, a single ingestion of 6 g L-citrulline increased NO^• bioavailability but not the respiratory performance and inspiratory muscle oxygenation.

The redox signal: A physiological perspective

A signal in biology is any kind of coded message sent from one place in an organism to another place. Biology is rich in claims that reactive oxygen and nitrogen species transmit signals. Therefore, we define a "redox signal as an increase/decrease in the level of reactive species". First, as in most biology disciplines, to analyze a redox signal you need first to deconstruct it. The essential components that constitute a redox signal and should be characterized are: (i) the reactivity of the specific reactive species, (ii) the magnitude of change, (iii) the temporal pattern of change, and (iv) the antioxidant condition. Second, to be able to translate the physiological fate of a redox signal you need to apply novel and bioplausible methodological strategies. Important considerations that should be taken into account when designing an experiment is to (i) assure that redox and physiological measurements are at the same or similar level of biological organization and (ii) focus on molecules that are at the highest level of the redox hierarchy. Third, to reconstruct the redox signal and make sense of the chaotic nature of redox processes, it is essential to apply mathematical and computational modeling. The aim of the present study was to collectively present, for the first time, those elements that essentially affect the redox signal as well as to emphasize that the deconstructing, decoding and reconstructing of a redox signal should be acknowledged as central to design better studies and to advance our understanding on its physiological effects.

Eccentric exercise per se does not affect muscle damage biomarkers: early and late phase adaptations

PURPOSE

Acute high-intensity unaccustomed eccentric exercise performed by naive subjects is accompanied by disturbances in muscle damage biomarkers. The aim of the study was to investigate whether a causal relationship indeed exists between eccentric exercise and muscle damage.

METHODS

Twenty-four men randomly assigned into a concentric only or an eccentric-only training group and performed 10 weeks of isokinetic resistance exercise (one session/week of 75 maximal knee extensors actions). Physiological markers of muscle function and damage (i.e., range of motion, delayed onset muscle soreness, isometric, concentric and eccentric peak torque) were assessed prior to and 1-3 and 5 days post each session. Biochemical markers of muscle damage (creatine kinase) and inflammation (C-reactive protein) were measured prior and 2 days post each session.

RESULTS

After the first bout, eccentric exercise induced greater muscle damage compared to concentric exercise; however, during the nine following sessions, this effect progressively diminished, while after the 10th week of training, no alterations in muscle damage biomarkers were observed after either exercise protocol. Additionally, strength gains at the end of the training period were comparable between the two groups and were mode-specific.

CONCLUSION

(1) eccentric exercise per se does not affect muscle damage biomarkers; (2) muscle damage occurs as a result of muscle unaccustomedness to this action type; (3) exercise-induced muscle damage is not a prerequisite for increased muscle strength. Collectively, we believe that muscle unaccustomedness to high-intensity eccentric exercise, and not eccentric exercise per se, is the trigger for muscle damage as indicated by muscle damage biomarkers.

Dietary Cysteine Intake is Associated with Blood Glutathione Levels and Isometric Strength

Glutathione is the most abundant cellular antioxidant and regulates redox homeostasis. Healthy individuals with certain antioxidant inadequacies/deficiencies exhibit impairments in physiological functions. The aim was to investigate whether low levels of dietary cysteine intake are associated with a) lower erythrocyte glutathione, b) increased plasma F₂-isoprostanes, and c) impaired muscle function. Towards this aim, we recorded the dietary intake of the three amino acids that synthesize glutathione (i. e., glutamic acid, cysteine, and glycine) in forty-one healthy individuals, and subsequently measured erythrocyte glutathione levels. Maximal isometric strength and fatigue index were also assessed using an electronic handgrip dynamometer. Our findings indicate that dietary cysteine intake was positively correlated with glutathione levels (r=0.765, p<0.001). In addition, glutathione levels were negatively correlated with F₂-isoprostanes (r=- 0.311, p=0.048). An interesting finding was that glutathione levels and cysteine intake were positively correlated with maximal handgrip strength (r=0.416, p=0.007 and r=0.343, p=0.028, respectively). In conclusion, glutathione concentration is associated with cysteine intake, while adequate cysteine levels were important for optimal redox status and muscle function. This highlights the importance of proper nutritional intake and biochemical screening with the goal of personalized nutrition.

Antioxidant supplementation, redox deficiencies and exercise performance: A falsification design

The aim of the present study was to validate the idea of personalized redox supplementation by subjecting individuals to targeted and non-targeted antioxidant supplementation schemes. Seventy-three volunteers were screened for plasma vitamin C and erythrocyte glutathione levels. Three groups were formed: i) the "low vitamin C″ group (12 individuals with the lowest vitamin C levels; Low VitC), ii) the "low glutathione" group (12 individuals with the lowest glutathione levels; Low GSH) and iii) a control group (12 individuals with moderate vitamin C and glutathione levels). The three groups received 1 g of vitamin C or 1.2 g of NAC daily for 30 days in a crossover design with a wash-out period of 30 days. Both antioxidant treatments reduced the increased resting systemic oxidative stress levels, assessed via urine F₂-isoprostanes, in the Low VitC and Low GSH groups (P < .05). A significant group × time interaction (P < .05) was found for VO₂max and isometric peak torque after both treatments, with the Low VitC and Low GSH groups exhibiting improved performance only after the targeted treatment (vitamin C and NAC, respectively). A significant group × time interaction (P < .05) was found for fatigue index after NAC treatment, but not after vitamin C treatment. No interaction was found for the Wingate test after both treatments. Most of the evidence verifies the idea that antioxidant supplementation increases performance when a particular deficiency is reversed. This indicates that the presence of oxidative stress per se does not rationalize the use of antioxidants and emphasizes the need to identify "responsive" phenotypes.

Rapid decreases of key antioxidant molecules in critically ill patients: A personalized approach

BACKGROUND & AIMS

Oxidative stress is regarded a key component of critical illness and has been associated with poor prognosis in Intensive Care Unit (ICU) patients. Diverse antioxidant treatments have been applied to combat oxidative stress in ICU, yet the results were typically disappointing. An explanation for this failure is that all studies utilized antioxidants indiscriminately and did not take into account the antioxidant profile of the patients. The aim of the present study was to investigate whether critically ill patients experience different insufficiencies in three major antioxidants with a "recycling" redox relationship (vitamin C, vitamin E and glutathione) and in the central reductant molecule of many enzymatic antioxidants (NADPH).

METHODS

Sixty mechanically-ventilated adult medical critically ill patients (age: 63.5 ± 17.1; APACHE II score: 21.2 ± 7.4; Glasgow Coma Scale: 6.2 ± 1.9) were enrolled in the study, while 20 healthy age-matched volunteers served as control group. The antioxidant profile and the level of systemic oxidative stress (F₂-isoprostanes) were measured at ICU admission and at days 1 and 7.

RESULTS

The majority of the ICU patients developed rapid and severe antioxidant insufficiencies (by exhibiting less than 50% of the control values) in one (22/60), two (7/60) or three (2/60) of the antioxidants measured, despite the almost similar levels of oxidative stress.

CONCLUSIONS

The wide heterogeneity in antioxidant decreases in response to ICU stay highlights the importance of patient stratification when planning to apply antioxidant treatments and indicates that the successful delivery of personalized clinical nutrition may depend on our ability to identify "responsive" phenotypes.

Effect of body composition on redox homeostasis at rest and in response to exercise: The case of underfat women

Underfat individuals have been neglected as a malnourished population in terms of redox homeostasis. The aim of the present study was to evaluate the effect of body composition on redox homeostasis at rest and in response to exercise. Underfat, lean and overfat women, classified according to their BMI and body fat percentage, participated in the study and were subjected to an acute session of eccentric exercise. With regard to muscle function and damage, a significant group × time interaction was found for range of motion (P < .01), isometric peak torque at 90° (P < .01), delayed onset muscle soreness (P < .01) and creatine kinase (P < .05), with the lean group generally exhibiting faster recovery compared to the underfat and overfat groups. With regard to redox homeostasis, a significant group × time interaction was found for F₂-isoprostanes, protein carbonyls and glutathione (P < .01 for all biomarkers), with the underfat and overfat groups exhibiting increased resting oxidative stress levels and lower exercise-induced reactive species production . In conclusively, our data underline the importance of normal body composition for redox homeostasis, since underfat and overfat women demonstrate a similar pattern of redox disturbances both at rest and in response to exercise.

Antioxidants in Personalized Nutrition and Exercise

The present review highlights the idea that antioxidant supplementation can be optimized when tailored to the precise antioxidant status of each individual. A novel methodologic approach involving personalized nutrition, the mechanisms by which antioxidant status regulates human metabolism and performance, and similarities between antioxidants and other nutritional supplements are described. The usefulness of higher-level phenotypes for data-driven personalized treatments is also explained. We conclude that personally tailored antioxidant interventions based on specific antioxidant inadequacies or deficiencies could result in improved exercise performance accompanied by consistent alterations in redox profile.

Nicotinamide riboside supplementation dysregulates redox and energy metabolism in rats: Implications for exercise performance

NEW FINDINGS

What is the central question of this study? The aim was to investigate the potential metabolic and redox mechanisms that impaired exercise performance after 21 days of supplementation with 300 mg (kg body weight)^-1 of nicotinamide riboside in rats. What is the main finding and its importance? Nicotinamide riboside disturbed energy and redox metabolism and impaired exercise performance in heathy rats. Exogenously administered redox agents in heathy populations might lead to adverse effects.

ABSTRACT

Nicotinamide riboside is a recently discovered form of vitamin B₃ that can increase NAD(P) levels. NAD(P) plays key roles in energy metabolism, and its main function is the transfer of electrons in various cellular reactions. Research in aged or diseased mice reported that nicotinamide riboside increases NAD(H) levels, reduces morbidity and improves health and muscle function. We have recently shown that in healthy young rats, chronic administration of nicotinamide riboside marginally non-significantly decreased exercise performance by 35% (P = 0.071). As a follow-up to this finding, we analysed samples from these animals, in an attempt to reveal the potential mechanisms driving this adverse effect, focusing on redox homeostasis and bioenergetics. Thirty-eight Wistar rats were divided into four groups: control (n = 10), exercise (n = 9), nicotinamide riboside (n = 10) and exercise plus nicotinamide riboside (n = 9). Nicotinamide riboside was administered for 21 days [300 mg (kg body weight)^-1 daily]. At the end of administration, the exercise and the exercise plus nicotinamide riboside groups performed an incremental swimming performance test until exhaustion. Nicotinamide riboside supplementation increased the levels of NADPH in the liver (P = 0.050), increased the levels of F₂ -isoprostanes in plasma (P = 0.047), decreased the activity of glutathione peroxidase (P = 0.017), glutathione reductase (P < 0.001) and catalase (P = 0.024) in erythrocytes, increased the level of glycogen in the liver (P < 0.001) and decreased the concentration of glucose (P = 0.016) and maximal lactate accumulation in plasma (P = 0.084). These findings support the prevailing idea that exogenously administered redox agents in heathy populations might lead to adverse effects and not necessarily to beneficial or neutral effects.

N-acetylcysteine supplementation increases exercise performance and reduces oxidative stress only in individuals with low levels of glutathione

Most of the evidence indicates that chronic antioxidant supplementation induces negative effects in healthy individuals. However, it is currently unknown whether specific redox deficiencies exist and whether targeted antioxidant interventions in deficient individuals can induce positive effects. We hypothesized that the effectiveness of antioxidant supplements to decrease oxidative stress and promote exercise performance depends on the redox status of the individuals that receive the antioxidant treatment. To this aim, we investigated whether N-acetylcysteine (NAC) supplementation would enhance exercise performance by increasing glutathione concentration and by reducing oxidative stress only in individuals with low resting levels of glutathione. We screened 100 individuals for glutathione levels and formed three groups with low, moderate and high levels (N = 36, 12 per group). After by-passing the regression to the mean artifact, by performing a second glutathione measurement, the individuals were supplemented with NAC (2 × 600mg, twice daily, for 30 days) or placebo using a double-blind cross-over design. We performed three whole-body performance tests (VO₂max, time trial and Wingate), measured two systemic oxidative stress biomarkers (F₂-isoprostanes and protein carbonyls) and assessed glutathione-dependent redox metabolism in erythrocytes (glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase and NADPH). The low glutathione group improved after NAC supplementation in VO₂max, time trial and Wingate by 13.6%, 15.4% and 11.4%, respectively. Thirty days of NAC supplementation were sufficient to restore baseline glutathione concentration, reduce systemic oxidative stress and improve erythrocyte glutathione metabolism in the low glutathione group. On the contrary, the 30-day supplementation period did not affect performance and redox state of the moderate and high glutathione groups, although few both beneficial and detrimental effects in performance were observed. In conclusion, individuals with low glutathione levels were linked with decreased physical performance, increased oxidative stress and impaired redox metabolism of erythrocytes. NAC supplementation restored both performance and redox homeostasis.

Chronic Eccentric Exercise and Antioxidant Supplementation: Effects on Lipid Profile and Insulin Sensitivity

Eccentric exercise has been shown to exert beneficial effects in both lipid profile and insulin sensitivity. Antioxidant supplementation during chronic exercise is controversial as it may prevent the physiological training-induced adaptations. The aim of this study was to investigate: 1) the minimum duration of the eccentric exercise training required before changes on metabolic parameters are observed and 2) whether antioxidant supplementation during training would interfere with these adaptations. Sixteen young healthy men were randomized into the Vit group (1 g of vitamin C and 400 IU vitamin E daily) and the placebo (PL) group. Subjects received the supplementation for 9 weeks. During weeks 5-9 all participants went through an eccentric exercise training protocol consisting of two exercise sessions (5 sets of 15 eccentric maximal voluntary contractions) per week. Plasma triglycerides (TG), total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), apolipoproteins (Apo A1, Apo B and Lpa) and insulin sensitivity (HOMA) were assessed before the supplementation (week 0), at weeks 5, 6, 7, 8 and 9. TG, TC and LDL were significantly lower compared to pre supplementation at both weeks 8 and 9 (P<0.05) in both groups. HDL was significantly elevated after 4 weeks of training (p < 0.005) in both groups. There was no effect of the antioxidant supplementation in any of the variables. There was no effect of either the training or the supplementation protocol in apolipoproteins levels and insulin sensitivity. A minimum duration of 3 weeks of eccentric exercise training is required before beneficial effects in lipid profile can be observed in healthy young men. Concomitant antioxidant supplementation does not interfere with the training-induced adaptations.

Experimental verification of regression to the mean in redox biology: differential responses to exercise

An important methodological threat when selecting individuals based on initial values for a given trait is the "regression to the mean" artifact. This artifact appears when a group with an extreme mean value during a first measurement tends to obtain a less extreme value (i.e. tends toward the mean) on a subsequent measurement. The main aim was to experimentally confirm the presence of this artifact in the responses of the reference oxidative stress biomarker (F₂-isoprostanes) after exercise. Urine samples were collected before and immediately following acute exercise in order to determine the level of exercise-induced oxidative stress. Afterwards, participants were arranged into three groups based on their levels of exercise-induced oxidative stress (low, moderate and high oxidative stress groups; n = 12 per group). In order to verify the existence of the regression to the mean artifact, the three groups were subjected to a second exercise trial one week after the first trial. This study confirmed the regression to the mean artifact in a redox biology context and showed that this artifact can be minimized by performing a duplicate pretreatment measurement after completing a nonrandom sorting based on the first assessment. This study also indicated that different individuals experience high oxidative stress or reductive stress (or no stress) to the same exercise stimulus even after adjusting for regression to the mean. This finding substantiates the methodological choice to divide individuals based on their degree of exercise-induced oxidative stress in future experiments to investigate the role of reactive species in exercise adaptations.

Going retro: Oxidative stress biomarkers in modern redox biology

The field of redox biology is inherently intertwined with oxidative stress biomarkers. Oxidative stress biomarkers have been utilized for many different objectives. Our analysis indicates that oxidative stress biomarkers have several salient applications: (1) diagnosing oxidative stress, (2) pinpointing likely redox components in a physiological or pathological process and (3) estimating the severity, progression and/or regression of a disease. On the contrary, oxidative stress biomarkers do not report on redox signaling. Alternative approaches to gain more mechanistic insights are: (1) measuring molecules that are integrated in pathways linking redox biochemistry with physiology, (2) using the exomarker approach and (3) exploiting -omics techniques. More sophisticated approaches and large trials are needed to establish oxidative stress biomarkers in the clinical setting.

Muscle damage and inflammation after eccentric exercise: can the repeated bout effect be removed?

The current consensus in exercise physiology is that the repeated bout effect always appears after few eccentric exercise sessions. This is the first attempt to challenge this tenet, by exploiting specificity in muscle plasticity. More specifically, we examined whether the opposing adaptations in muscle induced after concentric and eccentric exercise can attenuate and/or remove the repeated bout effect. Seventeen young men were randomly assigned into one of the following groups: (1) the alternating eccentric‐concentric exercise group; and (2) the eccentric‐only exercise group. Both groups performed 8 weeks of resistance exercise using the knee extensors of both legs on an isokinetic dynamometer. The alternating eccentric‐concentric exercise group performed an alternating exercise protocol, switching between eccentric‐only and concentric‐only exercise every 4 weeks, while the eccentric‐only group performed eccentric exercise. Evaluation of muscle damage using physiological (isometric torque, delayed onset muscle soreness, and range of movement) and biochemical (creatine kinase) markers and inflammation (C‐reactive protein) was performed at weeks 1, 5, and 10. Baseline isometric peak torque was also evaluated at week 14 after another cycle (4 weeks) of alternating or eccentric‐only exercise training. In the alternating eccentric‐concentric exercise group, the concentric exercise training performed prior to eccentric exercise reduced dramatically the repeated bout effect by reversing muscle back to its unaccustomed state. On the contrary, the eccentric‐only exercise group exhibited a typical manifestation of the repeated bout effect. Interestingly, muscle strength was elevated similarly for both alternating and eccentric‐only exercise groups after 13 weeks of training. The alternating eccentric‐concentric exercise scheme, implemented in the present study, has for the first time successfully overcame the repeated bout effect. The similarity in muscle strength measurements following the two protocols is against the notion that inflammation plays an important role in exercise‐induced adaptations in muscle.

Acute and Chronic Whole-Body Vibration Exercise does not Induce Health-Promoting Effects on The Blood Profile

Whole-body vibration (WBV) exercise is an alternative, popular and easy exercise that can be followed by general public. Therefore, the aim of the present study was to investigate the influence of acute and chronic WBV exercise on health-related parameters. Twenty-eight women were allocated into a control group (n=11, mean ±SEM: age, 43.5 ±1.5 yr; body mass, 66.1 ±3.1 kg; height, 160.6 ±1.5 cm) and a vibration group (n=17, mean ±SEM: age, 44.0 ±1.0 yr; body mass, 67.1 ±2.2 kg; height, 162.5 ±1.5 cm). After baseline assessments, participants of the experimental group performed WBV training 3 times/week for 8 weeks. Before and after the chronic WBV exercise, the participants of the vibration group performed one session of acute WBV exercise. Blood chemistry measurements (hematology, creatine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, C-reactive protein, glucose, insulin, triacylglycerols, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein A1, apolipoprotein B and lipoprotein, thiobarbituric-acid reactive substances, protein carbonyls, total antioxidant capacity, uric acid, albumin and bilirubin) were assessed pre-exercise and post-exercise at the first and eighth week of WBV exercise in both control and vibration groups. The results failed to support any effect of both acute and chronic WBV exercise on biochemical health-related parameters. However, it seems that WBV exercise is a safe way of training without a negative impact on muscle and liver functionality.

Passive smoking reduces and vitamin C increases exercise-induced oxidative stress: does this make passive smoking an anti-oxidant and vitamin C a pro-oxidant stimulus?

The current interpretative framework states that, for a certain experimental treatment (usually a chemical substance) to be classified as "anti-oxidant", it must possess the property of reducing (or even nullifying) exercise-induced oxidative stress. The aim of the study was to compare side by side, in the same experimental setup, redox biomarkers responses to an identical acute eccentric exercise session, before and after chronic passive smoking (considered a pro-oxidant stimulus) or vitamin C supplementation (considered an anti-oxidant stimulus). Twenty men were randomly assigned into either passive smoking or vitamin C group. All participants performed two acute eccentric exercise sessions, one before and one after either exposure to passive smoking or vitamin C supplementation for 12 days. Vitamin C, oxidant biomarkers (F2-isoprostanes and protein carbonyls) and the non-enzymatic antioxidant (glutathione) were measured, before and after passive smoking, vitamin C supplementation or exercise. It was found that chronic exposure to passive smoking increased the level of F2-isoprostanes and decreased the level of glutathione at rest, resulting in minimal increase or absence of oxidative stress after exercise. Conversely, chronic supplementation with vitamin C decreased the level of F2-isoprostanes and increased the level of glutathione at rest, resulting in marked exercise-induced oxidative stress. Contrary to the current scientific consensus, our results show that, when a pro-oxidant stimulus is chronically delivered, it is more likely that oxidative stress induced by subsequent exercise is decreased and not increased. Reversely, it is more likely to find greater exercise-induced oxidative stress after previous exposure to an anti-oxidant stimulus. We believe that the proposed framework will be a useful tool to reach more pragmatic explanations of redox biology phenomena.

The effects of eccentric exercise on muscle function and proprioception of individuals being overweight and underweight

The aim of this study was to estimate the effect of being overweight or underweight on proprioception at rest and after muscle damaging eccentric exercise. Twelve lean, 12 overweight, and 8 underweight female participants performed an eccentric exercise session using the knee extensor muscles of the dominant leg. Muscle damage indices and proprioception were assessed up to 3 days postexercise. The results indicated that proprioception at baseline of the lean individuals was superior to that of the other 2 groups. The overweight individuals exhibited a smaller knee joint reaction angle to release than did the lean group, whereas the underweight individuals exhibited a larger reaction angle to release than did the lean group. After eccentric exercise, proprioception was affected more in the overweight and the underweight groups than in the lean group. The greater exercise-induced muscle damage appeared in the overweight group, and the deficient muscle mass of the underweight participants could explain in part the greater disturbances that appeared in proprioception in these 2 groups than for the lean counterparts. In conclusion, deviating from the normal body mass is associated with significant disturbances in the proprioception of the legs at rest and after participation in activities involving eccentric actions.

Reductive stress after exercise: The issue of redox individuality

Exercise has been consistently used as an oxidant stimulus in redox biology studies. However, previous studies have focused on group differences and did not examine individual differences. As a result, it remains untested whether all individuals experience oxidative stress after acute exercise. Therefore, the main aim of the present study was to investigate whether some individuals exhibit unexpected responses after an acute eccentric (i.e., muscle-damaging) exercise session. Ninety eight (N = 98) young men performed an isokinetic eccentric exercise bout with the knee extensors. Plasma, erythrocytes and urine samples were collected immediately before and 2 days post-exercise. Three commonly used redox biomarkers (F₂-isoprostanes, protein carbonyls and glutathione) were assayed. As expected, the two oxidant biomarkers (F₂-isoprostanes and protein carbonyls) significantly increased 2 days after exercise (46% and 61%, respectively); whereas a significant decrease in glutathione levels (by −21%) was observed after exercise. A considerable number of the participants exhibited changes in the levels of biomarkers in the opposite, unexpected direction than the group average. More specifically, 13% of the participants exhibited a decrease in F₂-isoprostanes and protein carbonyls and 10% of the participants exhibited an increase in glutathione levels. Furthermore, more than 1 out of 3 individuals exhibited either unexpected or negligible (from 0% to ± 5%) responses to exercise in at least one redox biomarker. It was also observed that the initial values of redox biomarkers are important predictors of the responses to exercise. In conclusion, although exercise induces oxidative stress in the majority of individuals, it can induce reductive stress or negligible stress in a considerable number of people. The data presented herein emphasize that the mean response to a redox stimulus can be very misleading. We believe that the wide variability (including the cases of reductive stress) described is not limited to the oxidant stimulus used and the biomarkers selected.

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Exercise may induce reductive stress instead of the expected oxidative stress.

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The initial values of biomarkers are major predictors of the responses to exercise.

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The mean response of a group to a redox stimulus can be misleading.

Stair descending exercise increases muscle strength in elderly males with chronic heart failure

BACKGROUND

Previous studies from our group have shown that "pure" eccentric exercise performed on an isokinetic dynamometer can induce health-promoting effects that may improve quality of life. In order to investigate whether the benefits of "pure" eccentric exercise can be transferred to daily activities, a new and friendlier way to perform eccentric exercise had to be invented. To this end, we have proceeded to the design and construction of an automatic escalator, offering both stair descending (eccentric-biased) and stair ascending (concentric-biased) exercise.

FINDINGS

Twelve elderly males (60-70 yr) with chronic heart failure participated in the present study. Participants carried out six weeks of stair descending or ascending training on the novel SmartEscalator device. Muscle damage and performance indices were evaluated before and at day 2 post exercise at the first and sixth week of training. Both training regimes increased, albeit not significantly in some cases, eccentric, concentric and isometric torque. After six weeks of stair descending exercise, eccentric, concentric and isometric peak torque increased 12.3%, 7.7% and 8.8%, respectively, whereas after stair ascending exercise eccentric, concentric and isometric peak torque increased 7.1%, 9.6% and 5.9%, respectively.

CONCLUSIONS

Stair descending exercise appears to be a pleasant and mild activity that can be easily followed by the elderly. Compared to the more demanding stair ascending exercise, changes in muscle strength are similar or even greater. Elderly or people with impaired endurance wishing to increase their muscle strength may be benefited by participating in activities with strong eccentric component, such as stair descending.

Stair descending exercise using a novel automatic escalator: effects on muscle performance and health-related parameters

A novel automatic escalator was designed, constructed and used in the present investigation. The aim of the present investigation was to compare the effect of two repeated sessions of stair descending versus stair ascending exercise on muscle performance and health-related parameters in young healthy men. Twenty males participated and were randomly divided into two equal-sized groups: a stair descending group (muscle-damaging group) and a stair ascending group (non-muscle-damaging group). Each group performed two sessions of stair descending or stair ascending exercise on the automatic escalator while a three week period was elapsed between the two exercise sessions. Indices of muscle function, insulin sensitivity, blood lipid profile and redox status were assessed before and immediately after, as well as at day 2 and day 4 after both exercise sessions. It was found that the first bout of stair descending exercise caused muscle damage, induced insulin resistance and oxidative stress as well as affected positively blood lipid profile. However, after the second bout of stair descending exercise the alterations in all parameters were diminished or abolished. On the other hand, the stair ascending exercise induced only minor effects on muscle function and health-related parameters after both exercise bouts. The results of the present investigation indicate that stair descending exercise seems to be a promising way of exercise that can provoke positive effects on blood lipid profile and antioxidant status.

Exercise as a model to study redox homeostasis in blood: the effect of protocol and sampling point

Twenty males ran either on a level treadmill (nonmuscle-damaging condition) or on a downhill treadmill (muscle-damaging condition). Blood and urine samples were collected before and after exercise (immediately after, 1h, 4h, 24h, 48h, and 96h). The following assays were performed: F(2)-isoprostanes in urine, protein carbonyls in plasma, glutathione, superoxide dismutase, glutathione peroxidase, and catalase in erythrocytes. The main finding was that monophasic redox responses were detected after nonmuscle-damaging exercise compared to the biphasic responses detected after muscle-damaging exercise. Based on these findings, muscle-damaging exercise may be a more appropriate experimental model to induce physiological oxidative stress.

Redox biology of exercise: an integrative and comparative consideration of some overlooked issues

The central aim of this review is to address the highly multidisciplinary topic of redox biology as related to exercise using an integrative and comparative approach rather than focusing on blood, skeletal muscle or humans. An attempt is also made to re-define ‘oxidative stress’ as well as to introduce the term ‘alterations in redox homeostasis’ to describe changes in redox homeostasis indicating oxidative stress, reductive stress or both. The literature analysis shows that the effects of non-muscle-damaging exercise and muscle-damaging exercise on redox homeostasis are completely different. Non-muscle-damaging exercise induces alterations in redox homeostasis that last a few hours post exercise, whereas muscle-damaging exercise causes alterations in redox homeostasis that may persist for and/or appear several days post exercise. Both exhaustive maximal exercise lasting only 30 s and isometric exercise lasting 1–3 min (the latter activating in addition a small muscle mass) induce systemic oxidative stress. With the necessary modifications, exercise is capable of inducing redox homeostasis alterations in all fluids, cells, tissues and organs studied so far, irrespective of strains and species. More importantly, ‘exercise-induced oxidative stress’ is not an ‘oddity’ associated with a particular type of exercise, tissue or species. Rather, oxidative stress constitutes a ubiquitous fundamental biological response to the alteration of redox homeostasis imposed by exercise. The hormesis concept could provide an interpretative framework to reconcile differences that emerge among studies in the field of exercise redox biology. Integrative and comparative approaches can help determine the interactions of key redox responses at multiple levels of biological organization.

No adverse effects of statins on muscle function and health-related parameters in the elderly: an exercise study

The aim of the present study was to investigate the effects of a repeated bout of eccentric exercise on health-related parameters and muscle performance on subjects undergoing atorvastatin therapy. Twenty-eight elderly men participated in the investigation and were assigned either in a control (n = 14) or in a statin therapy group (n = 14). All participants performed two isokinetic eccentric exercise bouts separated by 3 weeks. Muscle damage indices, resting energy expenditure, substrate metabolism, lipid and lipoprotein profile, as well as insulin sensitivity, were evaluated before and after eccentric. No differences in muscle function were observed between the two groups either at rest or after exercise. Eccentric exercise increased resting energy expenditure, increased fat oxidation, improved lipid profile, and increased insulin resistance 2 days after both eccentric exercise bouts. However, these changes appeared to lesser extent after the second bout. No differences were observed in the responses in the health-related parameters in the control and in the statin therapy group. Eccentric exercise affected similarly the control and the atorvastatin-treated individuals. The present results indicate that atorvastatin-treated elderly individuals may participate in various physical activities, even high-intensity muscle-damaging activities, without negative impact on muscle function and adaptation.

Isokinetic knee joint evaluation in track and field events

The purpose of this study was to evaluate maximal torque of the knee flexors and extensors, flexor/extensor ratios, and maximal torque differences between the 2 lower extremities in young track and field athletes. Forty male track and field athletes 13-17 years old and 20 male nonathletes of the same age participated in the study. Athletes were divided into 4 groups according to their age and event (12 runners and 10 jumpers 13-15 years old, 12 runners and 6 jumpers 16-17 years old) and nonathletes into 2 groups of the same age. Maximal torque evaluation of knee flexors and extensors was performed on an isokinetic dynamometer at 60°·s(-1). At the age of 16-17 years, jumpers exhibited higher strength values at extension than did runners and nonathletes, whereas at the age of 13-15 years, no significant differences were found between events. Younger athletes were weaker than older athletes at flexion. Runners and jumpers were stronger than nonathletes in all relative peak torque parameters. Nonathletes exhibited a higher flexor/extensor ratio compared with runners and jumpers. Strength imbalance in athletes was found between the 2 lower extremities in knee flexors and extensors and also at flexor/extensor ratio of the same extremity. Young track and field athletes exhibit strength imbalances that could reduce their athletic performance, and specific strength training for the weak extremity may be needed.

No effect of antioxidant supplementation on muscle performance and blood redox status adaptations to eccentric training

BACKGROUND

It was recently reported that antioxidant supplementation decreases training efficiency and prevents cellular adaptations to chronic exercise.

OBJECTIVE

This study aimed to investigate the effects of vitamin C and vitamin E supplementation on muscle performance, blood and muscle redox status biomarkers, and hemolysis in trained and untrained men after acute and chronic exercise. A specific type of exercise was applied (eccentric) to produce long-lasting and extensive changes in redox status biomarkers and to examine more easily the potential effects of antioxidant supplementation.

DESIGN

In a double-blinded fashion, men received either a daily oral supplement of vitamin C and vitamin E (n = 14) or placebo (n = 14) for 11 wk (started 4 wk before the pretraining exercise testing and continued until the posttraining exercise testing). After baseline testing, the subjects performed an eccentric exercise session 2 times/wk for 4 wk. Before and after the chronic eccentric exercise, the subjects underwent one session of acute eccentric exercise, physiologic measurements were performed, and blood samples and muscle biopsy samples (from 4 men) were collected.

RESULTS

The results failed to support any effect of antioxidant supplementation. Eccentric exercise similarly modified muscle damage and performance, blood redox status biomarkers, and hemolysis in both the supplemented and nonsupplemented groups. This occurred despite the fact that eccentric exercise induced marked changes in muscle damage and performance and in redox status after exercise.

CONCLUSION

The complete lack of any effect on the physiologic and biochemical outcome measures used raises questions about the validity of using oral antioxidant supplementation as a redox modulator of muscle and redox status in healthy humans.

Physiological and performance adaptations of elite Greco-Roman wrestlers during a one-day tournament

The aim of this study was to determine the effects of a simulated one-day Greco-Roman wrestling tournament on selected performance and inflammatory status indices. Twelve competitive wrestlers (22.1 ± 1.3 years) completed five matches according to the official Olympic wrestling tournament regulations following a ~6% weight loss. Performance measurements, muscle damage assessment, and blood sampling were performed before and following each match. Performance and inflammatory markers were not affected by weight loss. Mean wrestling heart rate reached ~85% of maximal and lactate concentration exceeded 17 mM. Fatigue rating demonstrated a progressive rise (P < 0.05) throughout the tournament, peaking in match 4. Performance demonstrated a progressive deterioration (P < 0.05) throughout the tournament, especially in the last two matches (P < 0.05), with upper-body measures exhibiting a greater decline (P < 0.05) and remaining below baseline (P < 0.05) until the end of the tournament. Muscle damage markers increased during the course of the tournament with upper limbs affected more. Creatine kinase activity, CRP levels, IL-6 concentration, and leukocyte counts increased (P < 0.05) progressively throughout the tournament, peaking in the last two matches. Cortisol, epinephrine and norepinephrine increased (P < 0.05) after each match, but testosterone declined (P < 0.05) progressively, reaching a nadir before the last match. This inflammatory response was accompanied by a marked increase (p < 0.05) in lipid peroxidation, protein oxidation, and antioxidant status markers indicating the development of oxidative stress. These results suggest that a one-day wrestling tournament may induce significant physiological demands on wrestlers that may adversely affect their performance and inflammatory status especially during the later stages of the tournament.

Eccentric exercise affects the upper limbs more than the lower limbs in position sense and reaction angle

In this study, we investigated the effect of eccentric exercise on position sense and reaction angle of the elbow and knee flexors. Twelve males underwent two eccentric exercise sessions involving a randomized crossover design. In the first session participants used their elbow flexors and in the other session their knee flexors. Muscle damage indices, position sense, and joint reaction angle to release of the elbow and knee flexors were measured before, immediately after, and up to 7 days after exercise. Exercise induced greater muscle damage in the elbow flexors than knee flexors. Exercise disturbed position sense of the elbow and knee joint. For both limbs, the participants adopted a more extended position than the reference angle. The elbow and knee joint reaction angles to release increased after exercise for both the elbow and knee flexors. The disturbances in position sense and reaction angle after exercise were greater in the elbow flexors than knee flexors. The elbow flexors remained more accurate and faster than the knee flexors at all time points. These results may be explained by the higher density of muscle spindles and the lower innervation ratio of the elbow flexors compared with the knee flexors, as well as the fact that the arms are more accustomed than the legs to perform fast and accurate movements.

Beneficial changes in energy expenditure and lipid profile after eccentric exercise in overweight and lean women

The aim was to compare lean and overweight females in regard to the effects of eccentric exercise on muscle damage indices, resting energy expenditure (REE) and respiratory quotient (RQ) as well as blood lipid and lipoprotein profile. Lean and overweight females (deviated by their body mass index) performed an eccentric exercise session. Muscle damage, energy cost and lipid profile were assessed pre-exercise and up to 72 h post-exercise. After eccentric exercise (i) muscle damage indices were affected more in the overweight subjects compared with the lean subjects; (ii) the elevation of absolute and relative REE was larger and more prolonged in the overweight group compared with the lean group; (iii) after 24 h, RQ had significantly declined, with the overweight subjects exhibiting a larger reduction compared with the lean group; and (iv) the blood lipid profile was favorably modified, with the overweight group exhibiting more favorable responses compared with the lean group. The differences between the lean and the overweight subjects may be partly due to the fact that overweight individuals experienced greater muscle damage than lean individuals. Eccentric exercise may be a promising lifestyle factor to combat obesity and dyslipidemias.

Favorable and prolonged changes in blood lipid profile after muscle-damaging exercise

PURPOSE

To examine the effect of repeated muscle-damaging exercise on the time-course changes in blood lipid and lipoprotein profile and compare them with changes in indices of muscle function and damage.

METHODS

Twelve women underwent an isokinetic exercise session consisting of 75 eccentric knee flexions, which was repeated after 3 wk. Triacylglycerols (TG), total cholesterol (TC), and high-density lipoprotein cholesterol (HDLC) in plasma were measured before, immediately, 1, 2, 3, 4, and 7 d after muscle-damaging exercise. Low-density lipoprotein cholesterol (LDLC) and TC/HDLC were also calculated.

RESULTS

The largest changes in TG and lipoproteins appeared 3 d after exercise, returning toward baseline thereafter. The magnitudes of these changes at 3 d compared with rest were -18% and -8% for TG, -14% and -10% for TC, 8% and 7% for HDLC, -25% and -18% for LDLC, and -20% and -15% for TC/HDLC after sessions 1 and 2, respectively. In addition, the incremental or decremental area under the curve for the TG and lipoproteins measured after the first session was higher than that after the second session--except for HDLC concentration.

CONCLUSION

These findings reveal that lipid and lipoprotein profile was favorably affected by both sessions of muscle-damaging exercise but relatively less so after a repeated session of muscle-damaging exercise.

Coccidioidomycosis in adolescents with lupus nephritis

Coccidioidomycosis, a fungal infection endemic in the southwestern United States, can cause life-threatening infections in immunosuppressed patients. We report the contrasting cases of two adolescents with lupus nephritis, treated with intravenous pulse cyclophosphamide and daily oral corticosteroids, who developed pulmonary coccidioidomycosis. One patient developed a fatal form of fulminant disseminated coccidioidomycosis, while the other patient developed a solitary pulmonary Coccidioides immitis abscess which was responsive to intravenous liposomal amphotericin and fluconazole therapy. Because serologies and initial X-ray studies can be negative, definitive diagnostic studies including bronchoaveolar lavage and needle aspiration should be performed when there is clinical suspicion of coccidioidomycosis in an immunocompromised patient. Immunosuppressed patients with coccidioidomycosis should receive early intravenous amphotericin therapy and may benefit from long-term suppressive antifungal therapy to prevent relapse.

Concurrent centrifugation plasmapheresis and continuous venovenous hemodiafiltration

Continuous venovenous hemofiltration/hemodiafiltration (CVVH/D) is commonly used to provide renal replacement therapy for critically ill patients who are hemodynamically unstable. Occasionally, the addition of plasmapheresis therapy is necessary for some conditions, including immune-mediated acute renal failure, sepsis, fulminant hepatic failure, and thrombotic thrombocytopenic purpura/hemolytic uremic syndrome. Most tertiary care facilities provide centrifugation plasmapheresis instead of membrane plasmapheresis, because of the requirement for both therapeutic plasma exchange and pheresis of cellular blood products. We report a new technique where centrifugation plasmapheresis and CVVHD (P-CVVHD) are combined and used concurrently. Blood from the patient was concurrently filtered utilizing a Hospal BSM 22 machine with a Multiflow 60 hemofilter and a Cobe Spectra continuous cell separator in a parallel configuration. P-CVVHD is technically possible and can be used for long periods of time with limited risks. There may be advantages to P-CVVHD compared with discontinuous combined CVVH/D and plasmapheresis therapy.

Cisapride poisoning

A MEDLINE search from 1966-1996 revealed no reports of cisapride poisoning. An 8-mo-old, 8.9 kg girl received 8 mL of cisapride (Propulsid Suspension, 1 mg/mL, Janssen Pharmaceutica, Titusville, NJ) rather than the usual dose of 0.8 mL, resulting in an inadvertent, 10-fold, iatrogenic, dosing error. She developed emesis, hyperactive bowel sounds, abnormal behavior, mild hyperthermia, tachycardia, hypertension, and thrombocytosis. This is the first published report of poisoning with cisapride.

Propylene glycol-induced proximal renal tubular cell injury

Propylene glycol is a solvent that is used in many oral, injectable, and topical medications. Although uncommon, acute renal failure has been attributed to propylene glycol. The mechanism of propylene glycol-mediated renal injury is unknown. We report a case of acute renal failure in a 16-year-old boy given large doses of pentobarbital and phenobarbital, both of which are solubilized with propylene glycol. A renal biopsy showed proximal renal tubular cell swelling and vacuole formation. The data from this case suggest that the reversible acute renal failure caused by propylene glycol is attributable to proximal renal tubular cell injury.

Local fibrinolysis in cerebral venous thrombosis

Extensive cerebral venous sinus thrombosis may cause death or severe neurologic sequelae. A minimally responsive 10-year-old boy with thrombosis of the superior sagittal sinus, left transverse and left sigmoid sinus, torcular, vein of Galen, and straight sinus underwent fibrinolytic therapy with urokinase during transfemoral venous angiography. He improved dramatically during the procedure as antegrade venous flow was re-established. Local thrombolytic therapy may be beneficial for other patients with rapid neurologic deterioration caused by extensive thrombosis of superficial and deep venous structures.

Role of adenosine triphosphate and adenosine in oxygen-induced pulmonary vasodilation in fetal lambs

We investigated the hypothesis that purine nucleotides, ATP and adenosine, mediate the pulmonary vasodilation that occurs at birth in response to an increase in arterial O2 pressure (PaO2). We studied 20 fetal lambs 1 to 3 d after placement of intravascular catheters and a flow transducer around left pulmonary artery. In 16 lambs, we investigated the effects of 1) an increase in fetal PaO2 on ATP levels in pulmonary circulation and 2) 8-phenyl-theophylline (8-PT) and cibacron blue, antagonists of receptors for adenosine and ATP, on pulmonary vasodilation caused by increased PaO2. In four other lambs, we investigated the specificity of 8-PT and cibacron blue for purine receptors by investigating their effects on pulmonary vasodilation caused by acetylcholine, bradykinin, and nitroprusside. The fetal PaO2 increased by 7 +/- 2 during administration of 100% O2 to the pregnant ewe, resulting in a 3-fold decrease in PVR and increase in pulmonary blood flow. Blood and plasma concentrations of ATP in fetal pulmonary artery and left atrium increased significantly during the increase in fetal PaO2. 8-PT and cibacron blue caused increases in baseline pulmonary and systemic vascular pressures and pulmonary vascular resistance and inhibited the pulmonary vasodilation caused by O2. 8-PT and cibacron blue did not alter the pulmonary vascular effects of acetylcholine, bradykinin, and nitroprusside. An increase in baseline pulmonary vascular resistance caused by infusion of U46619 (in four lambs) did not alter the pulmonary vasodilation caused by O2. In summary, O2-induced pulmonary vasodilation is accompanied by increased ATP levels in pulmonary circulation and is attenuated by antagonists of purine receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine triphosphate and adenosine increase the pulmonary blood flow to postnatal levels in fetal lambs

We investigated the hypothesis that purine nucleotides may mediate the pulmonary vasodilation that occurs at birth in fetal lambs. We studied nine fetal lambs 3 d after placement of intravascular catheters, a flow transducer around the left pulmonary artery, and an inflatable vascular occluder around the ductus arteriosus. The pressure-flow relationship of left lung during a brief occlusion of the ductus arteriosus was studied as an index of pulmonary vascular resistance. We investigated the pulmonary vascular effects of adenosine, ATP, or saline (control) in doses of 0.01-2.50 mumol/kg/min infused into the right atrial line, and measured blood adenosine and ATP levels in samples from the pulmonary artery and left atrium. We also investigated the mechanism of pulmonary vascular effects of adenosine and ATP. Adenosine and ATP caused significant decreases in pulmonary vascular resistance and increases in pulmonary blood flow in doses of 0.08-2.5 mumol/kg/min. The pulmonary blood flow increased to levels seen in postnatal lambs at doses of 1.2 and 2.5 mumol/kg/min of adenosine and ATP. The baseline blood adenosine and ATP levels in fetus were 8 and 70% of levels in postnatal lambs. ATP concentrations increased to postnatal levels and adenosine levels increased to 20% of postnatal levels at infusion rates of 1.2 and 2.5 mumol/kg/min. The pulmonary vasodilation caused by adenosine and ATP was attenuated by 8-phenyltheophylline and cibacron blue, respectively, but not by indomethacin. We conclude that adenosine and ATP are pulmonary vasodilators and increase the fetal pulmonary flow to postnatal levels in doses that increase their blood concentrations to less than or equal to postnatal levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Limitations of the Glasgow Coma Scale in predicting outcome in children with traumatic brain injury

OBJECTIVE

To study the hypothesis that, in the absence of an ischemic-hypoxic state, children with severe traumatic brain injury and with unfavorable Glasgow Coma Scale scores may have good recovery.

DESIGN

Retrospective, observational, cross-sectional study with factorial design.

SETTING

Inpatient population in a university hospital.

PATIENTS

Seventy-nine children with traumatic brain injury admitted to the intensive care unit.

INTERVENTIONS

All patients received close monitoring and strict control of intracranial pressure (less than 20 mm Hg) and cerebral perfusion pressure (greater than 60 mm Hg).

MEASUREMENTS AND RESULTS

Admission Glasgow Coma Scale score, survival, need for cardiopulmonary resuscitation, presence of shock, peak intracranial pressure, duration of coma, Glasgow Outcome Scale score, and the results of neuropsychologic tests were analyzed. Of 79 children, 70 (89%) survived. Although the mortality rate was higher among patients with Glasgow Coma Scale scores of 3 to 5, 14 (64%) of 22 of these children survived. Nonsurvivors had a significantly higher incidence of shock and need for cardiopulmonary resuscitation. Except for two patients who had prolonged hypoxemia, all children, including those with Glasgow Coma Scale scores of 3 to 5, had a satisfactory outcome (Glasgow Outcome Scale scores of 4 or 5). Neuropsychologic outcome was not significantly different in the survivors with Glasgow Coma Scale scores of 3 to 5 and those with Glasgow Coma Scale scores of 6 or more.

CONCLUSIONS

A low Glasgow Coma Scale score does not always accurately predict the outcome of severe traumatic brain injury; in the absence of hypoxic-ischemic injury, children with traumatic brain injury and Glasgow Coma Scale scores of 3 to 5 can recover independent function.