Physiological and muscle histochemical assessment of men and women 10 km runners matched for race performance or training volume.

Women have a disadvantage for performance in long-distance running compared with men. To elaborate on inherent characteristics, 12 subelite women were matched with 12 men for training volume (M-Tm) (56.6 ± 18 vs. 55.7 ± 17 km/wk). The women were also matched to other men for a 10 km staged outdoor time trial (M-Pm) (42:36 min:s) to determine which factors could explain equal running performance. Anthropometry and treadmill tests were done. Fiber type (% Type I and Type IIA) and citrate synthase activities were analyzed in muscle biopsy samples. Consistent sex differences for both comparisons included height, weight, % body fat (P < 0.01), and hematocrit (P < 0.05). Women had lower V̇o2max and peak treadmill speed (PTS) compared with both M-Tm and M-Pm (P < 0.01). Training matched pairs had no sex difference in % PTS at race pace but compared with M-Pm women ran at a higher % PTS (P < 0.05) and %HRmax (P < 0.01) at race pace. On average, the women trained 22.9 km/wk more than M-Pm (+67.5%, P < 0.01). This training was not associated with higher V̇o2max or better running economy. Muscle morphology and oxidative capacity did not differ between groups. Percentage body fat remained significantly higher in women. In conclusion, women matched to men for training volume had slower 10 km performance (-10.5% P < 0.05). Higher training volume, more high-intensity sessions/wk, and time spent training in the 95%-100% HRmax zone may explain the higher % PTS and %HRmax at race pace in women compared with performance-matched men.NEW & NOTEWORTHY When subelite women 10 km runners were matched with male counterparts for 10 km race performance, inherent differences in % body fat, V̇o2max, Hct, and peak treadmill speed were counteracted by significantly higher training volume, more time training at higher %HRmax and consequently, higher %HRmax and %PTS at race pace. Citrate synthase activity and muscle fiber types did not differ. When women and men matched for training, 10 km performance of men was 10.5% faster.

Mechanistic assessment of tolerance to iron deficiency mediated by Trichoderma harzianum in soybean roots.

AIMS: Iron (Fe) deficiency in soil is a continuing problem for soybean (Glycine max L.) production, partly as a result of continuing climate change. This study elucidates how Trichoderma harzianum strain T22 (TH) mitigates growth retardation associated with Fe-deficiency in a highly sensitive soybean cultivar. METHODS AND RESULTS: Soil TH supplementation led to mycelial colonization and the presence of UAOX1 gene in roots that caused substantial improvement in chlorophyll score, photosynthetic efficiency and morphological parameters, indicating a positive influence on soybean health. Although rhizosphere acidification was found to be a common feature of Fe-deficient soybean, the upregulation of Fe-reductase activity (GmFRO2) and total phenol secretion were two of the mechanisms that substantially increased the Fe availability by TH. Heat-killed TH applied to soil caused no improvement in photosynthetic attributes and Fe-reductase activity, confirming the active role of TH in mitigating Fe-deficiency. Consistent increases in tissue Fe content and increased Fe-transporter (GmIRT1, GmNRAMP2a, GmNRAMP2b and GmNRAMP7) mRNA levels in roots following TH supplementation were observed only under Fe-deprivation. Root cell death, electrolyte leakage, superoxide (O2 •- ) and hydrogen peroxide (H2 O2 ) substantially declined due to TH in Fe-deprived plants. Further, the elevation of citrate and malate concentration along with the expression of citrate synthase (GmCs) and malate synthase (GmMs) caused by TH suggest improved chelation of Fe in Fe-deficient plants. Results also suggest that TH has a role in triggering antioxidant defence by increasing the activity of glutathione reductase (GR) along with elevated S-metabolites (glutathione and methionine) to stabilize redox status under Fe-deficiency. CONCLUSIONS: TH increases the availability and mobilization of Fe by inducing Fe-uptake pathways, which appears to help provide resistance to oxidative stress associated with Fe-shortage in soybean. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings indicate that while Fe deficiency does not affect the rate or degree of TH hyphal association in soybean roots, the beneficial effects of TH alone may be Fe deficiency-dependent.

Mitochondrial Mass Assessment in a Selected Cell Line under Different Metabolic Conditions.

Changes of quantity and/or morphology of cell mitochondria are often associated with metabolic modulation, pathology, and apoptosis. Exogenous fluorescent probes used to investigate changes in mitochondrial content and dynamics are strongly dependent, for their internalization, on the mitochondrial membrane potential and composition, thus limiting the reliability of measurements. To overcome this limitation, genetically encoded recombinant fluorescent proteins, targeted to different cellular districts, were used as reporters. Here, we explored the potential use of mitochondrially targeted red fluorescent probe (mtRFP) to quantify, by flow cytometry, mitochondrial mass changes in cells exposed to different experimental conditions. We first demonstrated that the mtRFP fluorescence intensity is stable during cell culture and it is related with the citrate synthase activity, an established marker of the mitochondrial mass. Incidentally, the expression of mtRFP inside mitochondria did not alter the oxygen consumption rate under both state 3 and 4 respiration conditions. In addition, using this method, we showed for the first time that different inducers of mitochondrial mass change, such as hypoxia exposure or resveratrol treatment of cells, could be consistently detected. We suggest that transfection and selection of stable clones expressing mtRFP is a reliable method to monitor mitochondrial mass changes, particularly when pathophysiological or experimental conditions change ΔΨm, as it occurs during mitochondrial uncoupling or hypoxia/anoxia conditions.

Assessment of muscular energy metabolism and heat shock response of the green abalone Haliotis fulgens (Gastropoda: Philipi) at extreme temperatures combined with acute hypoxia and hypercapnia.

The interaction between ocean warming, hypoxia and hypercapnia, suggested by climate projections, may push an organism earlier to the limits of its thermal tolerance window. In a previous study on juveniles of green abalone (Haliotis fulgens), combined exposure to hypoxia and hypercapnia during heat stress induced a lowered critical thermal maximum (CTmax), indicated by constrained oxygen consumption, muscular spams and loss of attachment. Thus, the present study investigated the cell physiology in foot muscle of H. fulgens juveniles exposed to acute warming (18 °C to 32 °C at +3 °C day-1) under hypoxia (50% air saturation) and hypercapnia (~1000 µatm PCO2), alone and in combination, to decipher the mechanisms leading to functional loss in this tissue. Under exposure to either hypoxia or hypercapnia, citrate synthase (CS) activity decreased with initial warming, in line with thermal compensation, but returned to control levels at 32 °C. The anaerobic enzymes lactate and tauropine dehydrogenase increased only under hypoxia at 32 °C. Under the combined treatment, CS overcame thermal compensation and remained stable overall, indicating active mitochondrial regulation under these conditions. Limited accumulation of anaerobic metabolites indicates unchanged mode of energy production. In all treatments, upregulation of Hsp70 mRNA was observed already at 30 °C. However, lack of evidence for Hsp70 protein accumulation provides only limited support to thermal denaturation of proteins. We conclude that under combined hypoxia and hypercapnia, metabolic depression allowed the H. fulgens musculature to retain an aerobic mode of metabolism in response to warming but may have contributed to functional loss.

Differential response of hexaploid and tetraploid wheat to interactive effects of elevated [CO2] and low phosphorus.

KEY MESSAGE: Hexaploid wheat is more responsive than tetraploid to the interactive effects of elevated [CO2] and low P in terms of carboxylate efflux, enzyme activity and gene expression (TaPT1 and TaPAP). Availability of mineral nutrients to plants under changing climate has become a serious challenge to food security and economic development. An understanding of how elevated [CO2] influences phosphorus (P) acquisition processes at the whole-plant level would be critical in selecting cultivars as well as to maintain optimum yield in limited-P conditions. Wheat (Triticum aestivum and T. durum) grown hydroponically with sufficient and low P concentration were exposed to elevated and ambient [CO2]. Improved dry matter partitioning towards root resulted in increased root-to-shoot ratio, root length, volume, surface area, root hair length and density at elevated [CO2] with low P. Interaction of low P and [CO2] induced activity of enzymes (phosphoenolpyruvate carboxylase, malate dehydrogenase and citrate synthase) in root tissue resulting in twofold increase in carboxylates and acid phosphatase exudation. Physiological absorption capacity of roots showed that plants alter their uptake kinetics by increasing affinity (low Km) in response to elevated [CO2] under low P supply. Increased relative expression of genes, purple acid phosphatase (TaPAP) and high-affinity Pi transporter (TaPT1) in roots induced by elevated [CO2] and low P supported our physiological observations. Hexaploid wheat (PBW-396) being more responsive to elevated [CO2] at low P supply as compared to tetraploid (PDW-233) necessitates the ploidy effect to be explored further which might be advantageous under changing climate.

Non-invasive assessment of hepatic mitochondrial metabolism by positional isotopomer NMR tracer analysis (PINTA).

Hepatic mitochondria play a central role in the regulation of intermediary metabolism and maintenance of normoglycemia, and there is great interest in assessing rates of hepatic mitochondrial citrate synthase flux (V CS) and pyruvate carboxylase flux (V PC) in vivo. Here, we show that a positional isotopomer NMR tracer analysis (PINTA) method can be used to non-invasively assess rates of V CS and V PC fluxes using a combined NMR/gas chromatography-mass spectrometry analysis of plasma following infusion of [3-13C]lactate and glucose tracer. PINTA measures V CS and V PC fluxes over a wide range of physiological conditions with minimal pyruvate cycling and detects increased hepatic V CS following treatment with a liver-targeted mitochondrial uncoupler. Finally, validation studies in humans demonstrate that the V PC/V CS ratio measured by PINTA is similar to that determined by in vivo NMR spectroscopy. This method will provide investigators with a relatively simple tool to non-invasively examine the role of altered hepatic mitochondrial metabolism.Liver mitochondrial metabolism plays an important role for glucose and lipid homeostasis and its alterations contribute to metabolic disorders, including fatty liver and diabetes. Here Perry et al. develop a method for the measurement of hepatic fluxes by using lactate and glucose tracers in combination with NMR spectroscopy.

Energy expenditure and oxygen consumption as novel biomarkers of obesity-induced cardiac disease in rats.

The purpose of the present study was to determine calorimetric parameters to predict obesity adverse effects on oxidative stress and cardiac energy metabolism. Male Wistar 24 rats were divided into three groups (n = 8): given standard chow and water (C), receiving standard chow and 30% sucrose in its drinking water (S), and given sucrose-rich diet and water (SRD). After 45 days, both S and SRD rats had obesity, serum oxidative stress, and dyslipidemic profile, but the body weight gain and feed efficiency (FE) were higher in SRD than in S, whereas the obesity-related oxidative stress, myocardial triacylglycerol accumulation, and enhanced cardiac lactate dehydrogenase (LDH) activity were higher in S than in SRD rats. Myocardial beta-hydroxyacyl coenzyme-A-dehydrogenase was lower in SRD and in S than in C, whereas glycogen was only depleted in S rats. Myocardial pyruvate dehydrogenase (PDH) was lowest in S rats indicating depressed glucose oxidation. There was higher myocardial LDH/citrate synthase (CS) ratio and lower adenosine triphosphate (ATP)-synthetase indicating delayed aerobic metabolism in S rats than in the others. Cardiac ATP-synthetase was positively correlated with energy expenditure, namely resting metabolic rate (RMR), and with oxygen consumption per body weight (VO(2)/body weight). Myocardial lipid hydroperoxide (LH)/ total antioxidant substances (TAS) ratio and triacylglycerol accumulation were negatively correlated with RMR and with VO(2)/body weight. In conclusion, the present study brought new insights into obesity because the study demonstrated for the first time that reduced energy expenditure and oxygen consumption may provide novel risk factors of obesity-induced reduced energy generation for myocardial contractile function. The results serve to highlight the role of calorimetric changes as novel biomarkers of risk to obesity-induced cardiac effects.

One-legged bicycling as an assessment tool for patients with stroke.

OBJECTIVE: To assess whether one-legged bicycling correlates with muscle strength and thereby could work as an outcome measure for persons with stroke. METHODS: The study comprised 29 men (age 35-65) with a first occurrence of stroke 6-35 months earlier. Each leg was evaluated separately. A ramp protocol was used (10 W/min), with continuous recording of the ventilatory uptake (Vo(2)) and heart rate. An isokinetic dynamometer was used to assess strength and endurance. Enzyme assays were performed on muscle biopsy samples. RESULTS: The peak isometric strength and isokinetic strength of the paretic leg correlated with the max. W on the bicycle. The oxidative enzyme citrate synthase correlated with the workload for both legs on the bicycle and lactate dehydrogenase correlated with peak isometric strength in both legs. CONCLUSIONS: The one-legged bicycle exercise test can be used to assess endurance in persons with a previous stroke as it correlates with dynamometer testing and muscle biopsies.

Brown fat mediates increased energy expenditure of cold-exposed overfed neonatal rats.

Genetically lean rat pups, overfed by being raised in small litters of three from day 1 postpartum, rapidly become obese compared with pups raised in standard sized litters of eight. Because of the rapid onset of their obesity, we expected that overfed pups would exhibit defective brown fat thermogenesis as is seen in neonatal genetically obese rodents. O2 consumption (VO2) was measured in 2-, 4-, 6-, and 8-day-old homozygous lean (Fa/Fa) Zucker pups from each treatment. We determined minimum rate of VO2 at thermoneutrality and maximum VO2 in response to progressively colder ambient temperatures. Overfed pups were fatter than standard-fed pups (P less than 0.001). But contrary to our prediction, overfed pups had a significantly increased maximum VO2 in response to acute cold exposure. To test the hypothesis that brown fat mediated the increased VO2 in the overfed pups, scapular brown fat lipectomies were performed on a new group of overfed pups at 2 days of age and compared with sham-operated littermate controls. On day 8, no differences in minimum VO2 were seen at thermoneutrality when brown fat is turned off. But maximum VO2 in response to cold, when brown fat is turned on maximally, was significantly reduced in the lipectomized overfed pups compared with sham-operated overfed littermates. These data suggest that manipulations of diet, accomplished by raising pups in small litters, can increase brown fat thermogenic function. The results of the lipectomy experiment imply that brown adipose tissue is a primary mediator of the increased energy expenditure in response to acute cold exposure in the overfed pups.

Assessment of mineralocorticoid activity in the rabbit colon.

Analyses of [3H]corticosteroid binding sites in distal colon indicated high-affinity binding sites or receptors for both [3H]aldosterone (Type I, Kd = 6.5 X 10(-9) M) and [3H]dexamethasone (Type II, Kd = 5.5 X 10(-8) M). The relative affinity of dexamethasone (D) was 1/20 that of aldosterone (A) for Type I sites and the affinity of A for Type II sites was 1/50 that of D at 37 degrees C. Citrate synthase (CS) activity was assayed and found to be reduced in enterocytes harvested from adrenalectomized (ADX) vs. normal colon segments (0.24 vs. 0.44 U/mg protein, P less than 0.025). Aldosterone (10 micrograms/kg body wt) increased CS at 2 h to a level intermediate between normal and ADX animals and thus not significantly different from either group, but was significantly increased over ADX + D values. Transmural potential difference was increased by 10(-8) M A but not by 10(-8) M D. Since both steroids enhanced short-circuit current at this concentration, the dichotomy of the glucocorticoid vs. mineralocorticoid results can be best explained by the pronounced effect of D on resistance (R) across the tissue (R at 4 h + D was 50% that of paired controls). These findings would suggest that the rabbit distal colon is a target segment for both mineralocorticoids and glucocorticoids. Furthermore, as in the kidney, the two steroids may play coordinated but, perhaps in some way, unique roles in the regulation of transport.