Muscle oxygenation during incremental arm and leg exercise in men and women

The purpose of this study was to compare the rates of muscle deoxygenation in the exercising muscles during incremental arm cranking and leg cycling exercise in healthy men and women. Fifteen men and 10 women completed arm cranking and leg cycling tests to exhaustion in separate sessions in a counterbalanced order. Cardiorespiratory measurements were monitored using an automated metabolic cart interfaced with an electrocardiogram. Tissue absorbency was recorded continuously at 760 nm and 850 nm during incremental exercise and 6 min of recovery, with a near infrared spectrometer interfaced with a computer. Muscle oxygenation was calculated from the tissue absorbency measurements at 30%, 45%, 60%, 75% and 90% of peak oxygen uptake (VO2) during each exercise mode and is expressed as a percentage of the maximal range observed during exercise and recovery (%Mox). Exponential regression analysis indicated significant inverse relationships (P < 0.01) between %Mox and absolute VO2 during arm cranking and leg cycling in men (multiple R = -0.96 and -0.99, respectively) and women (R = -0.94 and -0.99, respectively). No significant interaction was observed for the %Mox between the two exercise modes and between the two genders. The rate of muscle deoxygenation per litre of VO2 was 31.1% and 26.4% during arm cranking and leg cycling, respectively, in men, and 26.3% and 37.4% respectively, in women. It was concluded that the rate of decline in %Mox for a given increase in VO2 between 30% and 90% of the peak VO2 was independent of exercise mode and gender.     

Muscle oxygenation trends during constant work rate cycle exercise in men and women

Chronic bacterial colonization of the lungs, with an excessive inflammatory response, is the major cause of morbidity and mortality in cystic fibrosis. Lung surfactant exhibits a spectrum of potential immunomodulatory properties: phospholipid components inhibit cellular inflammatory responses, whereas the hydrophilic surfactant proteins A (SP-A) and D (SP-D) are integral components of the innate host defense response of the lungs against bacterial infection. Consequently, alteration to the relative proportions of lung surfactant components may alter the susceptibility of the lungs to bacterial colonization. In this study, bronchoalveolar lavage (BAL) samples were collected at diagnostic fiberoptic bronchoscopy from 11 control children, 13 children with cystic fibrosis, and 11 children with acute lung infection. Electrospray ionization mass spectrometry analysis demonstrated negligible changes to the molecular species or total BAL concentrations of phosphatidylcholine, phosphatidylglycerol, or phosphatidylinositol among the three subject groups. In contrast, median SP-A concentration was decreased (P < 0.001) in the cystic fibrosis group (2.65 microg/ml) compared with control (12.35 microg/ml) and infection (9.76 microg/ml) groups. Median SP-D was also decreased (P < 0.05) in the infection (12.17 ng/ml) compared with the control group (641 ng/ml), and was below assay limits for the majority of cystic fibrosis children (P < 0. 001). This dramatic decrease of hydrophilic surfactant proteins in the presence of normal surfactant phospholipid may be one mechanism underlying the relative ineffectiveness of the cellular inflammatory response in killing invading bacteria in the lungs of patients with cystic fibrosis.     

Physiological responses of men and women during exercise in hot environments with equivalent WBGT

Eight Japanese men and women participated in this study. They were randomly exposed to two environments: hot-dry; HD (Ta = 40 degrees C, rh 30%, wet bulb globe temperature (WBGT) = 32 degrees C) and hot-wet; HW (Ta = 31 degrees C, rh = 80%, WBGT = 32 degrees C) for 110 min. During the exposure, they rested on a bicycle ergometer for 20 min during rest and 30 min during recovery, then they pedaled it with an intensity of 40% VO2 max for 60 min. Tre, Tsk, and HR were recorded every minute. Total sweat loss and dripping were measured by independent bed balances which was connected to a computer processing with an accuracy of 1 g throughout the experiment. Sweat sodium concentration at forearm and back sites were collected by sweat capsule technique. These results showed that delta Tre, Tsk, evaporated sweat, dripping sweat, body heat storage of both sexes in HD were significantly higher than these in HW during exercise. HR of men in HD at the end of recovery was slightly higher than that of women. Whereas the sweat sodium concentration at forearm and back sites in both sexes remained unchanged either in HD or HW environment, it was found that HD was more stressful than HW environment under equivalent WBGT.     

Glucose kinetics during exercise in trained men

The effects of a novel bradycardic agent Zeneca ZM 227189 (4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) triazinium iodide) were tested on the inward rectifying properties of guinea-pig substantia nigra pas compacta (SNC) and guinea-pig olfactory cortical cells recorded in vitro. In SNC neurones, ZM 227189 (10-100 microM) produced a dose-dependent block of the slow anomalous rectifier; under voltage clamp, a clear reduction was seen in the amplitude of the slow inward current (Ih) relaxation evoked by negative voltage commands from a holding potential of -60 mV. ZM 227189 (50-100 microM) induced an irreversible block of the Ih current after 10-15 min exposure. A similar block of Ih was observed following application of 5 mM Cs+. ZM 227189 had little effect on other membrane properties. By contrast, in olfactory cortical neurones, ZM 227189 (100 microM) induced an increase in the input resistance (approximately 20%) and cell excitability, accompanied by a small (< 2 mV) hyperpolarization; these effects were also not reversible. Activation of the fast (K(+)-mediated) inward rectifier at negative membrane potentials remained unaffected. Lower concentrations (1-10 microM) of ZM 227189 had no obvious effect on cortical cell properties. Our data indicate that ZM 227189 is a potent and apparently selective blocker of Ih in substantia nigra neurones, but has no effect on the fast-type inward rectifier in olfactory cortical cells.     

Gender and exercise behavior among women and men with osteoarthritis

The purposes of this study were to determine differences between women and men with osteoarthritis in (1) amount and type of exercise behavior; (2) the demographic, psychosocial, health status, and personality correlates of exercise behavior; and (3) the relationship between exercise and health care utilization. Participants were 70 male and 126 female members of a large health maintenance organization who were 60 years of age or older and had osteoarthritis. Results indicated fewer women than men exercised, but among those who exercised, no significant differences in the [amount and type of exercise] behavior were found. Walking was the most frequently reported form of exercise among both women and men. To clarify which variables were related to exercise within each gender, regression analyses were performed separately on the total sample first, and then on women and men separately. In the total sample, age, quality of well-being, and extroversion were significantly related to exercise. Extroversion was significantly related to exercise among men. Helplessness and quality of well-being were significantly related to exercise among women. Exercise was not significantly related to health care service utilization. Results in this study underscore the importance of separating women and men in examination of variables related to exercise behavior.     

Left ventricular function during exercise in athletes and in sedentary men

Galactose-1-phosphate uridyltransferase (GALT) is a key enzyme in the metabolism of galactose. GALT activates the galactose-glucose interconversion and enables the synthesis of glucose-1-phosphate and UDP-galactose (UDP-Gal). UDP-Gal is the galactosyl donor for the incorporation of galactose into complex oligosaccharides, glycoproteins and glycolipids. The expression of GALT was characterized both in vivo and in vitro during late embryonic and postnatal development of the brain and peripheral nerve of the rat. Assays of GALT mRNA and protein showed that it is weakly expressed during late embryonic development with a second peak of expression concomitant with myelinogenesis. GALT was prominently expressed in myelinating Schwann cells in a rat dorsal root ganglia culture system. GALT deficiency in humans results in galactosemia, a disease characterized by long-term intellectual impairment, and probably dysmyelination. The developmentally regulated pattern of GALT expression during maturation of the nervous system may provide a molecular basis for these neurological complications which seriously compromise the outcome of many galactosemic patients.     

Hypervolemia in men from fluid ingestion at rest and during exercise

BACKGROUND: Plasma osmolality (Osm) is important for controlling and maintaining plasma volume (PV) and body water. The effect of oral rehydration fluids for ameliorating dehydration is well-established; but optimal composition and Osm of fluids for hyperhydrating normally hydrated subjects is less clear. METHODS: Six treatments were used without and with oral fluids of varying ionic and constituent concentrations for hyperhydrating six previously euhydrated men (30 +/- SD 8 yr, 76.84 +/- 16.19 kg, 73 +/- 12 ml.kg-1 PV, 40 +/- 10 ml.min-1.kg-1 peak VO2) sitting at rest for 90 min (VO2 = 0.39 +/- SE 0.02 L.min-1) and during subsequent 70 min of submaximal exercise (VO2 = 2.08 +/- SE 0.33 L.min-1, 70 +/- 7% peak VO2). The hypothesis was that the fluid composition is more important than plasma Osm for increasing PV in euhydrated subjects at rest and maintaining it during exercise. Drink formulation compositions, given at 10 ml.kg-1 body wt, (mean = 768 ml), for the sitting period were: Performance 1 (P1; 55 mEq Na+, 365 mOsm.kg H2O-1), P2 (97 mEq Na+, 791 mOsm.kg-1), P2G (113 mEq Na+, 4% glycerol, 1382 mOsm.kg-1), AstroAde (AA; 164 mEq Na+, 253 mOsm.kg-1), and 01 and 02 (no drinking). The exercise drink (10 ml.kg-1, 768 ml) was P1 for all treatments except 02 (no drinking); thus, drink designations were: P1/P1, P2/P1, P2G/P1, AA/P1, 0/P1, and 0/0. RESULTS: PV at rest increased (p < 0.05) by 4.7% with P1 and by 7.9% with AA. Percent change in PV during exercise was +1% to +3% (NS) with AA/P1; -6% to 0% (NS) with P1/P1, P2/P1, P2G/P1, and 0/P1; and -8% to -5% (p < 0.05) with 0/0. AA, with the lowest Osm of 253 mOsm.kg-1, increased PV at rest (as did P1) and maintained it during exercise, whereas the other drinks with lower Na+ and higher Osm of 365-1382 mOsm.kg-1 did not. CONCLUSION: Drink composition appears to be more important than its Osm for increasing PV at rest and for maintaining it during exercise in previously euhydrated subjects.     

Thermoregulatory effects of caffeine ingestion during submaximal exercise in men

BACKGROUND: The exclusive effect of caffeine ingestion on exercise thermoregulation is unclear; data indicate that caffeine may have a positive effect, a negative effect, or no effect. METHODS: Rectal (TRE) and mean skin (TSK) temperatures, skin heat conductance (HSK), and sweat rate (MSW) were measured during 30 min of rest and subsequent 70 min of submaximal cycle-ergometer exercise (67% VO2PEAK) in 11 aerobically conditioned men (mean +/- SD 29 +/- 6 yr, 49 +/- 6 mL x min(-1) x kg(-1) VO2PEAK) under two conditions: a caffeine (10 mg x kg(-1) ingestion (CI) session and a noncaffeine ingestion (NCI) control session. RESULTS: There were no significant differences in physiological or thermoregulatory parameters during exercise: X (+/-SE) end exercise levels for the NCI and CI sessions, respectively, were VO2 = 2.50 +/- 0.09 vs. 2.55 +/- 0.09 L x min(-1); heart rate = 145 +/- 7 vs. 145 +/- 5 bpm; HSK = 30 +/- 3 vs. 28 +/- 3 kcal x m(-2) x h(-1) x degrees C(-1); MSW = 393 +/- 35 vs. 378 +/- 36 g x m(-2) x h(-1); and TRE = 38.3 +/- 0.2 vs. 38.4 +/- 0.1 degrees C. Control TSK was lower than that for CI by 0.4 to 0.5 degrees C at rest and during exercise. CONCLUSION: Ingestion of a high level (10 mg x kg(-1) of caffeine has no effect on skin heat conductance, sweating, or the rate of increase and final level of rectal temperature during moderate, submaximal leg exercise.     

Gender and fat metabolism during exercise: a review

We examined the evidence for greater fat utilization by women during exercise and the potential gender differences in specific cellular processes. Results from well-controlled studies show that, compared to men, women oxidize more fat during submaximal exercise, resulting in the relative sparing of muscle glycogen. Mature female rats use less muscle glycogen during running and can run longer than male counterparts. Circulating estrogen is critical to these observations, as shown by studies where male rats were treated with estrogen. Estrogen-treated male rats use less muscle glycogen during exercise and can run longer than untreated males. The cellular mechanisms and factors underlying these findings are unknown and certainly multifactorial. We offer some information that, unfortunately, does not lead to any natural conclusion. However, this area is certainly ripe for research.     

Creatine supplementation and age influence muscle metabolism during exercise

Young [n = 5, 30 +/- 5 (SD) yr] and middle-aged (n = 4, 58 +/- 4 yr) men and women performed single-leg knee-extension exercise inside a whole body magnetic resonance system. Two trials were performed 7 days apart and consisted of two 2-min bouts and a third bout continued to exhaustion, all separated by 3 min of recovery. 31P spectra were used to determine pH and relative concentrations of Pi, phosphocreatine (PCr), and beta-ATP every 10 s. The subjects consumed 0.3 g . kg-1 . day-1 of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. During the placebo trial, the middle-aged group had a lower resting PCr compared with the young group (35.0 +/- 5.2 vs. 39.5 +/- 5.1 mmol/kg, P < 0.05) and a lower mean initial PCr resynthesis rate (18.1 +/- 3.5 vs. 23.2 +/- 6.0 mmol . kg-1 . min-1, P < 0.05). After creatine supplementation, resting PCr increased 15% (P < 0.05) in the young group and 30% (P < 0.05) in the middle-aged group to 45.7 +/- 7.5 vs. 45.7 +/- 5.5 mmol/kg, respectively. Mean initial PCr resynthesis rate also increased in the middle-aged group (P < 0.05) to a level not different from the young group (24.3 +/- 3.8 vs. 24.2 +/- 3.2 mmol . kg-1 . min-1). Time to exhaustion was increased in both groups combined after creatine supplementation (118 +/- 34 vs. 154 +/- 70 s, P < 0.05). In conclusion, creatine supplementation has a greater effect on PCr availability and resynthesis rate in middle-aged compared with younger persons.     

Voluntary food intake during prolonged exercise in obese women

The effect of 57 days of moderate physical activity on the energy intake and balance of three obese women (187% of ideal weight) was investigated in a metabolic balance study. Food was offered in extra quantity, prepared in a palatable but simple fashion, and intake was covertly monitored. Expenditure was measured using the factorial method and indirect calorimetry done every 3 to 4 days. After a 5-day evaluation phase which no exercise was done, individual treadmill assignments were given to subjects to increase daily expenditure to 125% of sedentary levels. Mean dialy intake (1903 kcal/day) and expenditure (2882 kcal/day) did not change with time. As a result, negative energy balance was obtained and sustained. A consistent rate of weight loss (0.12 kg/day) at a reasonable cost (8200 kcal/kg)occurred. Therefore, obese women doing long-term moderate exercise do not compensate by an increase in caloric intake. This can produce a negative caloric balance when exercise is coupled with ad libitum selection of ordinary foods.     

Effect of theophylline on substrate metabolism during exercise

We tested the hypothesis that adenosine is involved in regulating substrate metabolism during exercise. Seven trained cyclists were studied during 30 minutes of exercise at approximately 75% maximal oxygen uptake (VO2max). Lipid metabolism was evaluated by infusing [2H5]glycerol and [1-13C]palmitate, and glucose kinetics were evaluated by infusing [6,6-2H]glucose. Fat and carbohydrate oxidation were also measured by indirect calorimetry. The same subjects performed two identical exercise tests, but in one trial theophylline, a potent adenosine receptor antagonist, was infused for 1 hour before and throughout exercise. Theophylline did not increase whole-body lipolysis (glycerol rate of appearance [Ra]) or free fatty acid (FFA) release during exercise, but fat oxidation was lower than control values (9.5 +/- 3.0 v 18.0 +/- 4.2 micromol x min(-1) x kg(-1), P < .01). Glucose Ra was not affected by theophylline infusion, but glucose uptake was lower (31.6 +/- 4.1 v 40.4 +/- 5.0 micromol x min(-1) x kg(-1), P < .05) and glucose concentration was higher (6.4 +/- 0.6 v 5.8 +/- 0.4 mmol/L, P < .05) than in the control trial. Total carbohydrate oxidation (302.3 +/- 26.2 v 265.5 +/- 11.7 micromol x min(-1) x kg(-1), P < .06), estimated muscle glycogenolysis (270.7 +/- 23.1 v 225.1 +/- 9.7 micromol x min(-1) x kg(-1), P < .05), and plasma lactate concentration (7.9 +/- 1.6 v 5.9 +/- 1.1 mmol/L, P < .001) were also higher during the theophylline trial. These data suggest that adenosine may play a role in stimulating glucose uptake and restraining glycogenolysis but not in limiting lipolysis during exercise.     

Effect of epinephrine on muscle glycogenolysis during exercise in trained men

To test the hypothesis that an elevation in circulating epinephrine increases intramuscular glycogen utilization, six endurance-trained men performed two 40-min cycling trials at 71 +/- 2% of peak oxygen uptake in 20-22 degrees C conditions. On the first occasion, subjects were infused with saline throughout exercise (Con). One week later, after determination of plasma epinephrine levels in Con, subjects performed the second trial (Epi) with an epinephrine infusion, which resulted in a twofold higher (P < 0.01) plasma epinephrine concentration in Epi compared with Con. Although oxygen uptake was not different when the two trials were compared, respiratory exchange ratio was higher throughout exercise in Epi compared with Con (0.93 +/- 0.01 vs. 0.89 +/- 0.01; P < 0.05). Muscle glycogen concentration was not different when the trials were compared preexercise, but the postexercise value was lower (P < 0.01) in Epi compared with Con. Thus net muscle glycogen utilization was greater during exercise with epinephrine infusion (224 +/- 37 vs. 303 +/- 30 mmol/kg for Con and Epi, respectively; P < 0.01). In addition, both muscle and plasma lactate and plasma glucose concentrations were higher (P < 0.05) in Epi compared with Con. These data indicate that intramuscular glycogen utilization, glycolysis, and carbohydrate oxidation are augmented by elevated epinephrine during submaximal exercise in trained men.     

Improvements in blood pressure, glucose metabolism, and lipoprotein lipids after aerobic exercise plus weight loss in obese, hypertensive middle-aged men

Peroxynitrite, a cytotoxic oxidant formed in the reaction of superoxide and nitric oxide is known to cause programmed cell death. However, the mechanisms of peroxynitrite-induced apoptosis are poorly defined. The present study was designed to characterize the molecular mechanisms by which peroxynitrite induces apoptosis in HL-60 cells, with special emphasis on the role of caspases. Peroxynitrite induced the activation of apopain/caspase-3, but not ICE/caspase-1 as measured by the cleavage of fluorogenic peptides. Considering the short half-life of peroxynitrite and the kinetics of caspase-3 activation (starting 3-4 h after peroxynitrite treatment), the enzyme is not likely to become activated directly by the oxidant. Caspase-3 activation proved to be essential for DNA fragmentation, because pretreatment of the cells with the specific tetrapeptide inhibitor DEVD-fmk completely blocked peroxynitrite-induced DNA fragmentation. Peroxynitrite-induced cytotoxicity was also significantly altered by the inhibition of caspase-3, whereas phosphatidylserine exposure was unaffected by DEVD-fmk treatment. Because many of the effects of peroxynitrite are mediated by poly(ADP-ribose) synthetase (PARS) activation, we have also investigated the effect of PARS-inhibition on peroxynitrite-induced apoptosis. We have found that PARS-inhibition modulates peroxynitrite-induced apoptotic DNA fragmentation in the HL-60 cells. The effect of the PARS inhibitors, 3-aminobenzamide and 5-iodo-6-amino-1,2-benzopyrone were dependent on the concentration of peroxynitrite used. While PARS-inhibition resulted in increased DNA-fragmentation at low doses (15 microM) of peroxynitrite, a decreased DNA-fragmentation was found at high doses (60 microM) of peroxynitrite. PARS inhibition negatively affected viability as determined by flow cytometry. These data demonstrate the crucial role of caspase-3 in mediating apoptotic DNA fragmentation in HL-60 cells exposed to peroxynitrite.     

Modulation of whole body protein metabolism, during and after exercise, by variation of dietary protein

The aim of this study was to investigate dietary protein-induced changes in whole body leucine turnover and oxidation and in skeletal muscle branched chain 2-oxo acid dehydrogenase (BCOADH) activity, at rest and during exercise. Postabsorptive subjects received a primed constant infusion of L-[1-13C,15N]leucine for 6 h, after previous consumption of a high- (HP; 1.8 g . kg-1 . day-1, n = 8) or a low-protein diet (LP; 0.7 g . kg-1 . day-1, n = 8) for 7 days. The subjects were studied at rest for 2 h, during 2-h exercise at 60% maximum oxygen consumption, then again for 2 h at rest. Exercise induced a doubling of both leucine oxidation from 20 micromol . kg-1 . h-1 and BCOADH percent activation from 7% in all subjects. Leucine oxidation was greater before (+46%) and during (+40%, P < 0.05) the first hour of exercise in subjects consuming the HP rather than the LP diet, but there was no additional change in muscle BCOADH activity. The results suggest that leucine oxidation was increased by previous ingestion of an HP diet, attributable to an increase in leucine availability rather than to a stimulation of the skeletal muscle BCOADH activity.     

Red blood cell metabolism in men during long term bed rest

In typhoid-endemic areas the results obtained from the laboratory are important in confirming the clinical diagnosis of typhoid and may also contribute to decisions made on the management and treatment of typhoid cases. Isolation of Salmonella typhi remains the gold standard, with culture from bone marrow aspirate or a combination of specimens from other body sites resulting in the greatest sensitivity. Antibody detection techniques may still provide valuable information, but only if the results are interpreted in the context of the background antibody levels in the local population. None of the available antigen detection techniques have been consistently demonstrated to be of diagnostic value and a recently developed polymerase chain reaction (PCR) for the detection of Salmonella typhi has yet to undergo a full-scale clinical evaluation. The initial identification of chronic typhoid carriers relies upon the detection of elevated Vi capsular antibody levels, but seeking out chronic carriers will be of limited value in controlling the spread of typhoid in areas where transmission is principally mediated by convalescent excretors. Whilst resistance of Salmonella typhi to antibiotics has emerged as an increasing problem in some areas of the world, it is still uncommon in isolates from Papua New Guinea. However, monitoring of antibiotic susceptibility patterns will ensure that signs of developing resistance are detected early and that the appropriate action is taken.     

Acylcarnitine metabolism during fasting and after refeeding

Carnitine metabolism during starvation and just after refeeding was studied by the measurement of acylcarnitine (ACR) and total carnitine (TCR) concentration in the serum and liver of mice. Starvation caused marked increases in the concentration of serum ACR, and of acid-soluble ACR in the liver. The refeeding caused the quick decrement of serum ACR with a concomitant marked increase in the level of acid-soluble TCR in the liver. Through the use of positron emission tomography in a rhesus monkey, a marked increase in [2-11C]acetyl-L-carnitine uptake in the liver was observed after the administration of glucose accompanying the decrease of serum ACR. From this study, it is clear that the mammalian liver can salvage and conserve the unused ACR when the state of energy metabolism is improved.