Effect of high-intensity interval exercise on lipid oxidation during postexercise recovery.

PURPOSE: The aim of this study was to examine whether lipid oxidation predominates during 3 h of postexercise recovery in high-intensity interval exercise as compared with moderate-intensity continuous exercise on a cycle ergometer in fit young men (n = 12; 24.6 +/- 0.6 yr). METHODS: The energy substrate partitioning was evaluated during and after high-intensity submaximal interval exercise (INT, 1-min intervals at 80% of maximal aerobic power output [Wmax] with an intervening 1 min of active recovery at 40% Wmax) and 60-min moderate-intensity continuous exercise at 45% of maximal oxygen uptake (C45%) as well as a time-matched resting control trial (CON). Exercise bouts were matched for mechanical work output. RESULTS: During exercise, a significantly greater contribution of CHO and a lower contribution of lipid to energy expenditure were found in INT (512.7 +/- 26.6 and 41.0 +/- 14.0 kcal, respectively) than in C45% (406.3 +/- 21.2 and 170.3 +/- 24.0 kcal, respectively; P < 0.001) despite similar overall energy expenditure in both exercise trials (P = 0.13). During recovery, there were no significant differences between INT and C45% in substrate turnover and oxidation (P > 0.05). On the other hand, the mean contribution of lipids to energy yield was significantly higher after exercise trials (C45% = 61.3 +/- 4.2 kcal; INT = 66.7 +/- 4.7 kcal) than after CON (51.5 +/- 3.4 kcal; P < 0.05). CONCLUSIONS: These findings show that lipid oxidation during postexercise recovery was increased by a similar amount on two isoenergetic exercise bouts of different forms and intensities compared with the time-matched no-exercise control trial.

Effect of an overground walking training on gait performance in healthy 65- to 80-year-olds.

The aim of this study was to examine the effect of an individualized overground walking interval training on gait performance [i.e., speed and energy cost (C(w))] in healthy elderly individuals. Twenty-two older adults were assigned to either a training group (TG; n=12, 73.4+/-3.9yr) or a non-training control group (CG; n=10, 70.9+/-9.6yr). TG participated in a 7-week individualized walking interval training at intensities progressing from 50 to 100% of ventilatory threshold (T (VE)). Aerobic fitness [maximal oxygen uptake (V O(2max)) and T (VE)], preferred walking speed (PWS), gross and net C(w) (GC(w) and NC(w), respectively) and relative effort (%V O(2max)) at PWS measured before training (PWS(1)) were assessed prior and following the intervention. All outcomes were measured on a treadmill. Significant improvements in GC(w) (-8%; P=0.007), NC(w) (-12%; P=0.003), relative effort (%V O(2max): -12%; P<0.001) and PWS (+12%; P<0.001) were observed in TG but not in CG (P>0.71). V O(2max) and T (VE) remained unchanged in both groups (P>0.57). Changes in GC(w) at PWS(1) (difference between GC(w) at PWS(1) measured pre and post intervention) were inversely correlated with changes in PWS (difference between pre and post PWS; r=-0.67; P=0.02). The decreased C(w) at PWS(1), with no concomitant improvement in aerobic fitness, represents the main contributing factor for the reduction of the relative effort at this speed. This also allows elderly people to increase their PWS post training. Therefore, the present walking training may be an effective way to improve walking performance and delay mobility impairment in older adults.

Cardio-pulmonary interaction in premature newborn with nasal continuous positive airways pressure (n-CPAP) respiratory assistance evaluated with echocardiography

Introduction: Nasal continuous positive airways pressure (n-CPAP) is an effective treatment in premature infants with respiratory distress. The cardio-pulmonary interactions secondary to n-CPAP are well studied in adults, but less well described in premature infants. We postulated that there could be important interactions with regard to the patent ductus arteriosus (PDA). Methods: Prospective study, approved by the local ethic committee. Premature infants less than 32 weeks gestation, _7 days-old, needing n-CPAP for respiratory distress, but without the need of additional oxygen were included in the study. Every patient had a first echocardiography with n-CPAP and then n-CPAP was retrieved. 3 hours later the echocardiography was repeated by the same investigator and then the patient replaced on n-CPAP. Results: 14 premature newborn were included, mean gestational age of 28 _ 2 weeks, mean weight 1.1 _ 0.3 Kg and height 39 _ 3 cm. Echocardiographic measurements are depicted in Table 1. Significant finding were observed between measurement on n- CPAP or without n-CPAP: on end diastolic left ventricular diameter (12.8 _ 1.6 mm vs. 13.5 _ 2 mm), on end systolic left ventricular diameter (8.4 _ 1.3 mm vs. 9.1 _ 1.5 mm), left atrium diameter (8.9 _ 2.2 mm vs. 10.4 _ 2.5 mm), maximal velocity on tricuspid valve (46 _ 10 cm/s vs. 51 _ 9 cm/s), calculated Qp (3.7 _ 0.8 L/min/m2 vs. 4.3 _ 0.8 L/min/m2). Only three patients have demonstrated a PDA during the study. Conclusion: Positive end expiratory pressure (Peep) has hemodynamic effects which are: reduction of systemic and pulmonary venous return as shown by the changes on tricuspid valve inflow,on the calculated Qp and finally on the diameter of the left atrium and left ventricle.We found in premature infants the same hemodynamic effects than those described in adults but with lower Peep values. This could be due to the particular elasticity and weakness of the thoracic wall of premature infants. Interestingly the flow through a PDA seems also to be diminished with Peep, but the number of patients is insufficient to conclude. Further investigation will be needed to better understand these interactions. Table 1. Echocardiographic measurement (mean (SD)). With n-CPAP Without n-CPAP p value RV ED diameter (mm) 6.3 (1.7) 6.04 (1.1) NS LV ED diameter (mm) 12.8 (1.6) 13.5 (2.0) _0.05 LV ES diameter (mm) 8.4 (1.3) 9.1 (1.5) _0.05 SF (%) 34 (5) 33 (6) NS Ao valve diameter (mm) 7.4 (1.3) 7.4 (1.2) NS LA diameter (mm) 8.9 (2.2) 10.4 (2.5) _0.05 Vmax Ao (cm/s) 70 (16) 71 (18) NS Vmax PV (cm/s) 69 (15) 72 (16) NS Vmax TV (cm/s) 46 (10) 51 (9) _0.05 Vmax MV (cm/s) 53 (17) 54 (18) NS Qp (L/min/m2) 3.7 (0.8) 4.3 (0.8) _0.05 Qs (L/min/m2) 4.0 (0.8) 4.0 (0.7) NS Qp/Qs 0.92 (0.14) 1.09 (0.23) _0.05 RV: right ventricle, LV: left ventricle, ED: end diastolic, ES: end systolic, SF: shortening fraction,Ao: aortic valve, LA: left atrium,Vmax: maximum Doppler Velocity, Qp: pulmonary output, Qs: systemic output, NS: non significant.

Clinical and hormonal effects of the new angiotensin II receptor antagonist LRB081.

The renin-angiotensin system is a major contributor to the pathophysiology of cardiovascular diseases such as congestive heart failure and hypertension. Antagonizing angiotensin (Ang) II at the receptor site may produce fewer side effects than inhibition of the promiscuous converting enzyme. The present study was designed to assess in healthy human subjects the effect of LRB081, a new orally active AT1-receptor antagonist, on the pressor action of exogenous Ang II. At the same time, plasma hormones and drug levels were monitored. At 1-week intervals and in a double-blind randomized fashion, 8 male volunteers received three doses of LRB081 (10, 40, and 80 mg) and placebo. Blood pressure (BP) was measured at a finger by photoplethysmograph. The peak BP response to intravenous injection of a standard dose of Ang II was determined before and for < or = 24 h after administration of an oral dose of LRB081 or placebo. After drug administration, the blood BP response to Ang II was expressed in percent of the response before drug administration. At the same time, plasma renin activity (PRA), Ang II, aldosterone, catecholamine (radioassays), and drug levels (by high-performance liquid chromatography) were monitored. After LRB081 administration, a dose dependent inhibition of the BP response to Ang II was observed. Maximal inhibition of the systolic BP response was 54 +/- 3 (mean +/- SEM), 63 +/- 2, and 93 +/- 1% with 10, 40, and 80 mg LRB081, respectively. The time to peak was 3 h for 6 subjects and 4 and 6 h for 2 others. Preliminary plasma half-life (t1/2) was calculated at 2 h. With the highest dose, the inhibition remained significant for 24 h (31 +/- 5%, p < 0.05). Maximal BP-blocking effect and maximal plasma drug level coincided, suggesting that the unmetabolized LRB081 is responsible for the antagonistic effect. PRA and Ang II increased dose dependently after LRB081 intake. Aldosterone, epinephrine, and norepinephrine concentrations remained unchanged. No clinically significant adverse reaction was observed during the study. LRB081 is a well-tolerated, orally active, potent, and long-acting Ang II receptor antagonist. Unlike in the case of losartan, no active metabolite of LRB081 has been shown to be responsible for the main effects.

Local Competition, Inbreeding, and the Evolution of Sex-Biased Dispersal.

Using game theory, we developed a kin-selection model to investigate the consequences of local competition and inbreeding depression on the evolution of natal dispersal. Mating systems have the potential to favor strong sex biases in dispersal because sex differences in potential reproductive success affect the balance between local resource competition and local mate competition. No bias is expected when local competition equally affects males and females, as happens in monogamous systems and also in polygynous or promiscuous ones as long as female fitness is limited by extrinsic factors (breeding resources). In contrast, a male-biased dispersal is predicted when local mate competition exceeds local resource competition, as happens under polygyny/promiscuity when female fitness is limited by intrinsic factors (maximal rate of processing resources rather than resources themselves). This bias is reinforced by among-sex interactions: female philopatry enhances breeding opportunities for related males, while male dispersal decreases the chances that related females will inbreed. These results meet empirical patterns in mammals: polygynous/promiscuous species usually display a male-biased dispersal, while both sexes disperse in monogamous species. A parallel is drawn with sex-ratio theory, which also predicts biases toward the sex that suffers less from local competition. Optimal sex ratios and optimal sex-specific dispersal show mutual dependence, which argues for the development of coevolution models.

Fish oil after abdominal aorta aneurysm surgery

OBJECTIVE: Fish oil (FO) may attenuate the inflammatory response after major surgery such as abdominal aortic aneurysm (AAA) surgery. We aimed at evaluating the clinical impact and safety aspects of a FO containing parenteral nutrition (PN) after AAA surgery. METHODS: Intervention consisted in 4 days of either standard (STD: Lipofundin medium-chain triglyceride (MCT): long-chain triglyceride (LCT)50%-MCT50%) or FO containing PN (FO: Lipoplus: LCT40%-MCT50%-FO10%). Energy target were set at 1.3 times the preoperative resting energy expenditure by indirect calorimetry. Blood sampling on days 0, 2, 3 and 4. Glucose turnover by the (2)H(2)-glucose method. Muscle microdialysis. Clinical data: maximal daily T degrees, intensive care unit (ICU) and hospital stay. RESULTS: Both solutions were clinically well tolerated, without any differences in laboratory safety parameters, inflammatory, metabolic data, or in organ failures. Plasma tocopherol increased similarly; with FO, docosahexaenoic and eicosapentaenoic acid increased significantly by day 4 versus baseline or STD. To increased postoperatively, with a trend to lower values in FO group (P=0.09). After FO, a trend toward shorter ICU stay (1.6+/-0.4 versus 2.3+/-0.4), and hospital stay (9.9+/-2.4 versus 11.3+/-2.7 days: P=0.19) was observed. CONCLUSIONS: Both lipid emulsions were well tolerated. FO-PN enhanced the plasma n-3 polyunsaturated fatty acid content, and was associated with trends to lower body temperature and shorter length of stay.

Impaired glucose metabolism in the heart of obese Zucker rats after treatment with phorbol ester.

OBJECTIVE: To investigate the influence of obesity on the regulation of myocardial glucose metabolism following protein kinase C (PKC) activation in obese (fa/fa) and lean (Fa/?) Zucker rats. DESIGN: Isolated hearts obtained from 17-week-old lean and obese Zucker rats were perfused with 200 nM phorbol 12-myristate 13-acetate (PMA) for different time periods prior to the evaluation of PKC and GLUT-4 translocation. For metabolic studies isolated hearts from 48 h starved Zucker rats were perfused with an erythrocytes-enriched buffer containing increased concentrations (10-100 nM) of PMA. MEASUREMENTS: Immunodetectable PKC isozymes and GLUT-4 were determined by Western blots. Glucose oxidation and glycolysis were evaluated by measuring the myocardial release of 14CO2 and 3H2O from [U-14C]glucose and [5-3H]glucose, respectively. RESULTS: PMA (200 nM) induced maximal translocation of ventricular PKCalpha from the cytosol to the membranes within 10 min. This translocation was 2-fold lower in the heart from obese rats when compared to lean rats. PMA also induced a significant translocation of ventricular GLUT-4 from the microsomal to the sarcolemmal fraction within 60 min in lean but not in obese rats. Rates of basal cardiac glucose oxidation and glycolysis in obese rats were approximately 2-fold lower than those of lean rats. Perfusion with increasing concentrations of PMA (10-100 nM) led to a significant decrease of cardiac glucose oxidation in lean but not in obese rats. CONCLUSION: Our results show that in the heart of the genetically obese Zucker rat, the impairment in PKCalpha activation is in line with a diminished activation of GLUT-4 as well as with the lack of PMA effect on glucose oxidation.

Selective distribution of lactate dehydrogenase isoenzymes in neurons and astrocytes of human brain.

In vertebrates, the interconversion of lactate and pyruvate is catalyzed by the enzyme lactate dehydrogenase. Two distinct subunits combine to form the five tetrameric isoenzymes of lactate dehydrogenase. The LDH-5 subunit (muscle type) has higher maximal velocity (Vmax) and is present in glycolytic tissues, favoring the formation of lactate from pyruvate. The LDH-1 subunit (heart type) is inhibited by pyruvate and therefore preferentially drives the reaction toward the production of pyruvate. There is mounting evidence indicating that during activation the brain resorts to the transient glycolytic processing of glucose. Indeed, transient lactate formation during physiological stimulation has been shown by 1H-magnetic resonance spectroscopy. However, since whole-brain arteriovenous studies under basal conditions indicate a virtually complete oxidation of glucose, the vast proportion of the lactate transiently formed during activation is likely to be oxidized. These in vivo data suggest that lactate may be formed in certain cells and oxidized in others. We therefore set out to determine whether the two isoforms of lactate dehydrogenase are localized to selective cell types in the human brain. We report here the production and characterization of two rat antisera, specific for the LDH-5 and LDH-1 subunits of lactate dehydrogenase, respectively. Immunohistochemical, immunodot, and western-blot analyses show that these antisera specifically recognize their homologous antigens. Immunohistochemistry on 10 control cases demonstrated a differential cellular distribution between both subunits in the hippocampus and occipital cortex: neurons are exclusively stained with the anti-LDH1 subunit while astrocytes are stained by both antibodies. These observations support the notion of a regulated lactate flux between astrocytes and neurons.

Subject-based steroid profiling and the determination of novel biomarkers for DHT and DHEA misuse in sports.

Doping with natural steroids can be detected by evaluating the urinary concentrations and ratios of several endogenous steroids. Since these biomarkers of steroid doping are known to present large inter-individual variations, monitoring of individual steroid profiles over time allows switching from population-based towards subject-based reference ranges for improved detection. In an Athlete Biological Passport (ABP), biomarkers data are collated throughout the athlete's sporting career and individual thresholds defined adaptively. For now, this approach has been validated on a limited number of markers of steroid doping, such as the testosterone (T) over epitestosterone (E) ratio to detect T misuse in athletes. Additional markers are required for other endogenous steroids like dihydrotestosterone (DHT) and dehydroepiandrosterone (DHEA). By combining comprehensive steroid profiles composed of 24 steroid concentrations with Bayesian inference techniques for longitudinal profiling, a selection was made for the detection of DHT and DHEA misuse. The biomarkers found were rated according to relative response, parameter stability, discriminative power, and maximal detection time. This analysis revealed DHT/E, DHT/5β-androstane-3α,17β-diol and 5α-androstane-3α,17β-diol/5β-androstane-3α,17β-diol as best biomarkers for DHT administration and DHEA/E, 16α-hydroxydehydroepiandrosterone/E, 7β-hydroxydehydroepiandrosterone/E and 5β-androstane-3α,17β-diol/5α-androstane-3α,17β-diol for DHEA. The selected biomarkers were found suitable for individual referencing. A drastic overall increase in sensitivity was obtained. The use of multiple markers as formalized in an Athlete Steroidal Passport (ASP) can provide firm evidence of doping with endogenous steroids.

Influence of hip-flexion angle on hamstrings isokinetic activity in sprinters.

CONTEXT: Hamstrings strains are common and debilitating injuries in many sports. Most hamstrings exercises are performed at an inadequately low hip-flexion angle because this angle surpasses 70° at the end of the sprinting leg's swing phase, when most injuries occur. OBJECTIVE: To evaluate the influence of various hip-flexion angles on peak torques of knee flexors in isometric, concentric, and eccentric contractions and on the hamstrings-to-quadriceps ratio. DESIGN: Descriptive laboratory study. SETTING: Research laboratory. Patients and Other Participants: Ten national-level sprinters (5 men, 5 women; age = 21.2 ± 3.6 years, height = 175 ± 6 cm, mass = 63.8 ± 9.9 kg). Intervention(s): For each hip position (0°, 30°, 60°, and 90° of flexion), participants used the right leg to perform (1) 5 seconds of maximal isometric hamstrings contraction at 45° of knee flexion, (2) 5 maximal concentric knee flexion-extensions at 60° per second, (3) 5 maximal eccentric knee flexion-extensions at 60° per second, and (4) 5 maximal eccentric knee flexionextensions at 150° per second. Main Outcome Measure(s): Hamstrings and quadriceps peak torque, hamstrings-to-quadriceps ratio, lateral and medial hamstrings root mean square. RESULTS: We found no difference in quadriceps peak torque for any condition across all hip-flexion angles, whereas hamstrings peak torque was lower at 0° of hip flexion than at any other angle (P < .001) and greater at 90° of hip flexion than at 30° and 60° (P < .05), especially in eccentric conditions. As hip flexion increased, the hamstrings-to-quadriceps ratio increased. No difference in lateral or medial hamstrings root mean square was found for any condition across all hip-flexion angles (P > .05). CONCLUSIONS: Hip-flexion angle influenced hamstrings peak torque in all muscular contraction types; as hip flexion increased, hamstrings peak torque increased. Researchers should investigate further whether an eccentric resistance training program at sprint-specific hip-flexion angles (70° to 80°) could help prevent hamstrings injuries in sprinters. Moreover, hamstrings-to-quadriceps ratio assessment should be standardized at 80° of hip flexion.

Influence of initial foot dorsal flexion on vertical jump and running performance.

Several studies (on an inclined platform or with special shoes) have reported improved jump performance when the ankle was in a dorsiflexion (DF) position. The present study aims to test whether shoes inducing moderate DF modify vertical jump performance and energy cost. Twenty-one young, healthy female subjects (30 +/- 6 yr, 58 +/- 6 kg, O2max 45 +/- 3 mLxkg-1xmin-1, mean +/- SD) participated in the study. Jump performance was tested with subjects either wearing 4 degrees DF or standard (S) shoes. The jump tests (performed on a force platform) consisted of squat jump (SJ), countermovement jump (CMJ), and continuous jumps (CJ) during 15 seconds. Measured parameters were jump height, speed at take off, and maximal and average power. Oxygen uptake was measured on a treadmill while subjects ran at 95% of the anaerobic threshold during a 7-minute steady-state period. As compared with S shoes, DF shoes significantly improved the height of SJ (31 +/- 4 cm vs. 34 +/- 4 cm, p = 0.0001), CMJ (32 +/- 4 cm vs. 34 +/- 4 cm, p = 0.0004), and CJ (17.5 +/- 4.2 cm vs. 22.0 +/- 6.0 cm, p = 0.0001). Speed at take off was also significantly higher. Mean power significantly increased in SJ and CJ but not in CMJ. Oxygen uptake was not different between conditions (p = 0.40). Dorsiflexion shoes induce a significant increase in jump performance. These results are in accordance with the concept that a DF of the ankle may induce an increase of the length and strength of the triceps surae (higher torque). However, wearing DF shoes did not require more energy during running. Dorsiflexion shoes could be used to increase jump performance in several sports such as volleyball in which jump height is essential.

A novel pediatric biventricular assist device: in vitro test results.

Most ventricular assist devices (VADs) currently used in infants are extracorporeal. These VADs require long-term anticoagulation therapy and extensive surgery, and two devices are needed for biventricular support. We designed a biventricular assist device based on shape memory alloy that reproduces the hemodynamic effects of cardiomyoplasty, supporting the heart with a compressing movement, and evaluated its performance in a dedicated mockup system. Nitinol fibers are the device's key component. Ejection fraction (EF), cardiac output (CO), and generated systolic pressure were measured on a test bench. Our test bench settings were a preload range of 0-15 mm Hg, an afterload range of 0-160 mm Hg, and a heart rate (HR) of 20, 30, 40, and 60 beats/min. A power supply of 15 volts and 3.5 amperes was necessary. The EF range went from 34.4% to 1.2% as the afterload and HR increased, along with a CO from 180 to 6 ml/min. The device generated a maximal systolic pressure of 25 mm Hg. Cardiac compression for biventricular assistance in child-sized heart using shape memory alloy is technically feasible. Further testing remains necessary to assess this VAD's in vivo performance range and its reliability.

Epidermal growth factor (EGF) stimulation of cultured brain cells. I. Enhancement of the developmental increase in glial enzymatic activity.

Serum-free aggregating cell cultures of fetal rat telencephalon grown in the presence of 3 ng/ml (5 X 10(-10) M) epidermal growth factor (EGF) until day 12 showed 2- to 3-fold increased activities in the two glial enzymes, glutamine synthetase (GLU-S) and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase). This effect was concentration-dependent, with maximal stimulation in cultures treated daily with 3 ng/ml EGF. Addition of EGF during the first 10 culture days was sufficient to produce a maximal stimulation of both GLU-S and CNPase on day 19, whereas treatments starting on day 12 were ineffective. The stimulation of GLU-S preceded that of CNPase. The EGF-induced increase in GLU-S activity was not directly dependent on the presence of insulin, triiodothyronine, or hydrocortisone in the medium, whereas insulin was required for the stimulation of CNPase. A single dose of 5 ng/ml EGF on day 2 caused a slight but significant decrease in DNA synthesis after day 6. The present results indicate that in serum-free aggregating cell cultures of fetal rat telencephalon EGF partially inhibits DNA synthesis, and stimulates an early step in glial differentiation.

Role of Particle Shape on the Stress Propagation in Granular Packings

We present an experimental and numerical study on the influence that particle aspect ratio has on the mechanical and structural properties of granular packings. For grains with maximal symmetry (squares), the stress propagation in the packing localizes forming chainlike forces analogous to the ones observed for spherical grains. This scenario can be understood in terms of stochastic models of aggregation and random multiplicative processes. As the grains elongate, the stress propagation is strongly affected. The interparticle normal force distribution tends toward a Gaussian, and, correspondingly, the force chains spread leading to a more uniform stress distribution reminiscent of the hydrostatic profiles known for standard liquids

A new paradigm of neuromuscular electrical stimulation for the quadriceps femoris muscle.

PURPOSE: Neuromuscular electrical stimulation (NMES) with large electrodes and multiple current pathways (m-NMES) has recently been proposed as a valid alternative to conventional NMES (c-NMES) for quadriceps muscle (re)training. The main aim of this study was to compare discomfort, evoked force and fatigue between m-NMES and c-NMES of the quadriceps femoris muscle in healthy subjects. METHODS: Ten healthy subjects completed two experimental sessions (c-NMES and m-NMES), that were randomly presented in a cross-over design. Maximal electrically evoked force at pain threshold, self-reported discomfort at different levels of evoked force, and fatigue-induced force declines during and following a series of 20 NMES contractions were compared between c-NMES and m-NMES. RESULTS: m-NMES resulted in greater evoked force (P < 0.05) and lower discomfort in comparison to c-NMES (P < 0.05-0.001), but fatigue time course and magnitude did not differ between the two conditions. CONCLUSIONS: The use of quadriceps m-NMES appears legitimate for (re)training purposes because it generated stronger contractions and was less discomfortable than c-NMES (due to multiple current pathways and/or lower current density with larger electrodes).