Plasma matrix metalloproteinases, low density lipoprotein oxidisability and soluble adhesion molecules after a glucose load in Type 2 diabetes

Background

Type 2 diabetes mellitus (DM-2) is one of the most prevalent chronic diseases of the aged and contributes to a significant amount of cardiovascular disease morbidity and mortality. Exercise training may be beneficial in attenuating the cardiovascular maladaptations associated with DM-2. The purpose of this study was to examine the effects of exercise training on left ventricular (LV) and vascular function in a sample of postmenopausal women with DM-2.

Methods

Twenty-eight postmenopausal women with DM-2 (age: 59 ± 7 yrs) were assigned to either an exercise training (ET) (n = 17) or control group (CT) (n = 7). Cardiorespiratory fitness ( ), LV filling dynamics and arterial compliance were assessed at baseline in all participants. The ET group performed a supervised aerobic and resistance training intervention three days per week for a period of 10 weeks, while the CT group continued normal activities of daily living.

Results

Body mass index, , age and duration of diabetes were similar between the ET and CT groups at baseline. (21.3 ± 3.3 to 24.5 ± 4.2 ml·kg^-1·min^-1, p < 0.05) and large artery compliance (1.0 ± 0.4 to 1.2 ± 0.4 mL·mmHg^-1, p < 0.05), increased significantly in the ET group following training despite no change in LV filling dynamics, blood pressure, lipid profile or insulin sensitivity. All variables remained unchanged in the CT group.

Conclusions

Exercise training improves large artery compliance and cardiorespiratory fitness in postmenopausal women with DM-2, without any appreciable changes in LV filling dynamics or conventional risk factors for cardiovascular disease.     

Aerobic fitness and performance in elite female futsal players

Despite its growing popularity, few studies have investigated specific physiological demands for elite female futsal. The aim of this study was to determine aerobic fitness in elite female futsal players using laboratory and field testing. Fourteen female futsal players from the Venezuelan National team (age =21.2±4.0 years; body mass =58.6±5.6 kg; height =161±5.0 cm) performed a progressive maximal treadmill test under laboratory conditions. Players also performed a progressive intermittent futsal-specific field test for endurance, the Futsal Intermittent Endurance Test (FIET), until volitional fatigue. Outcome variables were exercise heart rate (HR), VO₂, post-exercise blood lactate concentrations ([La]b) and running speeds (km · h^-1). During the treadmill test, VO₂max, maximal aerobic speed (MAS), HR and peak [La]b were 45.3±5.6 ml · kg^-1 · min^-1, 12.5±1.77 km · h^-1, 197±8 beats · min^-1 and 11.3±1.4 mmol · l^-1, respectively. The FIET total distance, peak running velocity, peak HR and [La]b were 1125.0±121.0 m, 15.2±0.5 km · h^-1, 199±8 beats · min^-1 and 12.5±2.2 mmol · l^-1, respectively. The FIET distance and peak speed were strongly associated (r= 0.85-87, p < 0.0001) with VO₂max and MAS, respectively. Peak HR and [La]b were not significantly different between tests. Elite female futsal players possess moderate aerobic fitness. Furthermore, the FIET can be considered as a valid field test to determine aerobic fitness in elite level female futsal players.     

Exercise- and methylcholine-induced sweating responses in older and younger men: effect of heat acclimation and aerobic fitness

 The purpose of this investigation was to examine the effects of aging and aerobic fitness on exercise- and methylcholine-induced sweating responses during heat acclimation. Five younger [Y group – age: 23±1 (SEM) years; maximal oxygen consumption (V.O_2max): 47±3 ml·kg^–1·min^–1], four highly fit older (HO group – 63±3 years; 48±4 ml·kg^–1·min^–1) and five normally fit older men (NO group – 67±3 years; 30±1 ml·kg^–1·min^–1) who were matched for height, body mass and percentage fat, were heat acclimated by daily cycle exercise (≈35% V.O_2max for 90 min) in a hot (43°C, 30% RH) environment for 8 days. The heat acclimation regimen increased performance time, lowered final rectal temperature (T _re) and percentage maximal heart rate (%HR_max), improved thermal comfort and decreased sweat sodium concentration similarly in all groups. Although total body sweating rates (M._sw) during acclimation were significantly greater in the Y and HO groups than in the NO group (P<0.01) (because of the lower absolute workload in the NO group), the M._sw did not change in all groups with the acclimation sessions. Neither were local sweating rates (m. _sw) on chest, back, forearm and thigh changed in all groups by the acclimation. The HO group presented greater forearm m. _sw (30–90 min) values and the Y group had greater back and thigh m. _sw (early in exercise) values, compared to the other groups (P<0.001). In a methylcholine injection test on days immediately before and after the acclimation, the order of sweat output per gland (SGO) on chest, back and thigh was Y>HO>NO, and on the forearm Y=HO>NO. No group differences were observed for activated sweat gland density at any site. The SGO at the respective sites increased in the post-acclimation test regardless of group (P<0.01), but on the thigh the magnitude of the increase was lower in the NO (P<0.02) and HO (P=0.07) groups than in the Y group. These findings suggest that heat tolerance and the improvement with acclimation are little impaired not only in highly fit older but also normally fit older men, when the subjects exercised at the same relative exercise intensity. Furthermore, the changes induced by acclimation appear associated with an age-related decrease in V.O_2max. However methylcholine-activated SGO and the magnitude of improvement of SGO with acclimation are related not only to V.O_2max but also to aging, suggesting that sensitivity to cholinergic stimulation decreases with aging. Received: 8 May 1998/Accepted: 5 October 1998     

Influence of short-term aerobic training and hydration status on tolerance during uncompensable heat stress

The purpose of the present study was to determine the separate and combined effects of a short-term aerobic training program and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40°C, 30% relative humidity). Males of moderate fitness [<50 ml · kg⁻¹ · min⁻¹ maximal O₂ consumption (V˙O_{2 max} )] were tested while euhydrated or hypohydrated by ≈2% of body weight through exercise and fluid restriction the day preceding the trials. Tests were conducted before and after either a 2-week program of daily aerobic training (1 h treadmill exercise at 65% V˙O_{2 max} for 12 days; n = 8) or a control period (n = 7), which had no effect on any measured variable. The training increased V˙O_{2 max} by 6.5%, while heart rate (f _c) and the rectal temperature (T _re) rise decreased during exercise in a thermoneutral environment. In the heat, training resulted in a decreased skin temperature and increased sweat rate, but did not affect f _c, T _re or tolerance time (TT). In both training and control groups, hypohydration significantly increased T _re and f _c and decreased the TT. It was concluded that the short-term aerobic training program had no benefit on exercise-heat tolerance in this uncompensable heat stress environment. Accepted: 12 November 1997     

Heart rate as an indicator of stress during the critical swimming speed test of farmed Atlantic salmon (Salmo salar L.)

A swim tunnel is to fish as a treadmill is to humans, and is a device used for indirect measuring of the metabolic rate. This study aims to explore the fish stress (if any) during the critical swimming test routines (fish handling, confinement, and swimming) using heart rate (f_H, heartbeat per minute) bio-loggers in farmed Atlantic salmon (Salmo salar L.). In addition, the recovery dynamics of exercised fish using f_H were explored for 48 h post swim tests. Continuous f_H data were acquired following the surgical implantation and throughout the trials, such as during fish handling, swim tests (critical swimming speed, U_crit), and 48 h post swim tests. After 3 weeks of surgical recovery, f_H stabilized at 46.20 ± 1.26 beats min⁻¹, equalizing a ~38% reduction in f_H recorded post-surgical tachycardia (74.13 ± 1.44 beats min⁻¹). Interestingly, f_H was elevated by ~200% compared to baseline levels not only due to the U_crit (92.04 ± 0.23 beats min⁻¹) but also due to fish handling and confinement in the swim tunnel, which was 66% above the baseline levels (77.48 ± 0.34 beats min⁻¹), suggesting fish stress. Moreover, significantly higher plasma cortisol levels (199.56 ± 77.17 ng mL⁻¹) corresponding to a ~300% increase compared to baseline levels (47.92 ± 27.70 ng mL⁻¹) were identified after U_crit, predicting post-swim test stress (physiological exhaustion). These findings reinforce the importance of fish acclimation in the swim tunnel prior to the swimming tests. However, f_H dropped over the course of the 48-h post-swim test, but remained comparatively higher than the basal levels, suggesting fish should be given at least 48 h to recover from handling stress for better fish welfare. This study further explored the influence of fish tagging on U_crit, which resulted in reduced swimming capabilities of tagged fish (1.95 ± 0.37 body lengths s⁻¹) compared to untagged fish (2.54 ± 0.42 body length s⁻¹), although this was not significant (p = 0.06), and therefore future tagging studies are warranted.     

丁酸梭菌替代金霉素对肉鸡腿肌肉品质和抗氧化功能的影响

丁酸梭菌(Clostridium butyricum)是一种产丁酸等短链脂肪酸的有益菌,添加到饲料中可改善动物的生产性能、提高饲料利用率和机体的抗氧化功能.[目的]本文研究了丁酸梭菌替代金霉素添加到肉鸡日粮中,对肉鸡腿肌肉品质和抗氧化功能的影响.[方法]随机选取1日龄健康艾拔益加(AA)肉仔鸡360只,分为3组,每组8...     

Effects of 12 weeks of aerobic exercise plus dietary restriction on body composition, resting energy expenditure and aerobic fitness in mildly obese middle-aged women

This study investigated the effects of 12 weeks of aerobic exercise plus voluntary food restriction on the body composition, resting metabolic rate (RMR) and aerobic fitness of mildly obese middle-aged women. The subjects were randomly assigned to exercise/diet (n = 17) or control (n = 15) groups. The exercise/diet group participated in an aerobic training programme, 45–60 min · day ^–1 at 50%–60% of maximal oxygen uptake (VO_2max), 3–4 days · week^–1, and also adopted a self-regulated energy deficit relative to predicted energy requirements (–1.05 MJ · day ^–1 to –1.14 MJ · day ^–1 ). After the regimen had been followed for 12 weeks, the body mass of the subjects had decreased by an average of 4.5 kg, due mainly to fat loss, with little change of fat free mass (m _ff). The absolute RMR did not change, but the experimental group showed significant increases in the RMR per unit of body mass (10%) and the RMR per unit of m _ff (4%). The increase in RMR/m _ff was not correlated with any increase in VO_2max/m _ff. The resting heat production per unit of essential body mass increased by an average of 21%, but the resting heat production rate per unit of fat tissue mass remained unchanged. We concluded that aerobic exercise enhances the effect of moderate dietary restriction by augmenting the metabolic activity of lean tissue.     

Effects of attachment substrates on the growth and differentiation of LLC-PK1 cells

Summary The growth and differentiation of an established renal epithelial cell line, LLC-PK₁, on membrane bound mussel adhesive protein (MAP), collagen, and extracellular matrix (ECM) in serum-containing medium was studied. Cell attachment and growth on uncoated- vs. protein-coated cellulose nitrate and acetate membranes did not differ significantly, and confluence was achieved on all membranes. However, cells remained in a single monolayer only when plated on collagen or ECM. LLC-PK₁ monolayers grown on ECM-coated membranes displayed the highest transepitheliald-glucose transport (333 ± 22 ng·cm⁻²·min⁻¹) whereas cells plated on collagen-coated membranes displayed the lowest (94 ± 23 ng·cm⁻²·min⁻¹). Glucose flux values increased with age of the culture, reaching a plateau at 28 d postseeding. These results indicate that the underlying substratum and cell age can affect differentiation of renal epithelial cells in vitro.     

Stroke volume response to progressive exercise in athletes engaged in different types of training

Using the impedance cardiography method, heart rate ( _c) matched changes on indexed stroke volume (SI) and cardiac output (CI) were compared in subjects engaged in different types of training. The subjects consisted of untrained controls (C), volleyball players (VB) who spent about half of their training time (360 min · week^–1) doing anaerobic conditioning exercises and who had a maximal oxygen uptake ( ) 41% higher than the controls, and distance runners (D) who spent all their training time (366 min·week^–1) doing aerobic conditioning exercises and who had a 26% higher than VB. The subjects performed progressive submaximal cycle ergometer exercise (10 W·min^–1) up to _c of 150 beats·min^–1. In group C, SI had increased significantly (P<0.05) at _c of 90 beats·min^–1 ( + 32%) and maintained this difference up to 110 beats·min^–1, only to return to resting values on reaching 130 beats·min^–1 with no further changes. In group VB, SI peaked (+ 54%) at _c of 110 beats·min^–1, reaching a value significantly higher than that of group C, but decreased progressively to 22010 of the resting value on reaching 150 beats·min^–1. In group D, SI peaked at _c of 130 beats·min^–1 (+ 54%), reaching a value significantly higher than that of group VB, and showed no significant reduction with respect to this peak value on reaching 150 beats·min^–1. As a consequence, the mean CI increase per _c unit was progressively higher in VB than in C (+46%) and in D than in VB (+ 105%). It was concluded that thef _c value at which SI ceased to increase during incremental exercise was closely related to the endurance component in the training programme.     

Modelling the lactate response to short-term all out exercise

Background

The maximum post exercise blood lactate concentration (BLC_max) has been positively correlated with maximal short-term exercise (MSE) performance. However, the moment when BLC_max occurs (TBLC_max) is rather unpredictable and interpretation of BLC response to MSE is therefore difficult.

Methods

We compared a 3- and a 4-parameter model for the analysis of the dynamics of BLC response to MSEs lasting 10 (MSE10) and 30 s (MSE30) in eleven males (24.6 ± 2.3 yrs; 182.4 ± 6.8 cm; 75.1 ± 9.4 kg). The 3-parameter model uses BLC at MSE-start, extra-vascular increase (A) and rate constants of BLC appearance (k₁) and disappearance (k₂). The 4-parameter model includes BLC at MSE termination and amplitudes and rate constants of increase (A₁, y₁) and decrease (A₂, y₂) of post MSE-BLC.

Results

Both models consistently explained 93.69 % or more of the variance of individual BLC responses. Reduction of the number of parameters decreased (p < 0.05) the goodness of the fit in every MSE10 and in 3 MSE30. A (9.1 ± 2.1 vs. 15.3 ± 2.1 mmol l^-1) and A₁ (7.1 ± 1.6 vs. 10.9 ± 2.0 mmol l^-1) were lower (p < 0.05) in MSE10 than in MSE30. k₁ (0.610 ± 0.119 vs. 0.505 ± 0.107 min^-1), k₂ (4.21 10^-2 ± 1.06 10^-2 vs. 2.45 10^-2 ± 1.04 10^-2 min^-1), and A₂ (-563.8 ± 370.8 vs. -1412.6 ± 868.8 mmol l^-1), and y₁ (0.579 ± 0.137 vs. 0.489 ± 0.076 min^-1) were higher (p < 0.05) in MSE10 than in MSE30. No corresponding difference in y₂ (0.41 10^-2 ± 0.82 10^-2 vs. 0.15 10^-2 ± 0.42 10^-2 min^-1) was found.

Conclusion

The 3-parameter model estimates of lactate appearance and disappearance were sensitive to differences in test duration and support an interrelation between BLC level and halftime of lactate elimination previously found. The 4-parameter model results support the 3-parameter model findings about lactate appearance; however, parameter estimates for lactate disappearance were unrealistic in the 4-parameter model. The 3-parameter model provides useful information about the dynamics of the lactate response to MSE.

     

Reliability and Responsiveness of Cardiopulmonary Exercise Testing in Fatigued Persons with Multiple Sclerosis and Low to Mild Disability

Background

Peak oxygen uptake (VO₂peak) via cardiopulmonary exercise testing is considered the gold standard for testing aerobic capacity in healthy participants and people with various medical conditions. The reliability and responsiveness of cardiopulmonary exercise testing outcomes in persons with MS (PwMS) have not been extensively studied.

Objective

(1) to investigate the reliability of cardiopulmonary exercise parameters in PwMS; (2) to determine the responsiveness, in terms of the smallest detectable change (SDC), for each parameter.

Design

Two repeated measurements of cardiopulmonary exercise outcomes were obtained, with a median time interval of 16 days.

Methods

Thirty-two PwMS suffering from subjective fatigue performed cardiopulmonary exercise tests on a cycle ergometer, to voluntary exhaustion. We calculated the reliability, in terms of the intra-class correlation coefficient (ICC [2,k]; absolute agreement), and the measurement error, in terms of standard error of measurement (SEM) and SDC at individual (SDC_individual) and group level (SDC_group).

Results

The ICC for VO₂peak was 0.951, with an SEM of 0.131 L∙min⁻¹ and an SDC_individual of 0.364 L∙min⁻¹. When corrected for bodyweight, the ICC of VO₂peak was 0.933, with an SEM of 1.7 mL∙kg⁻¹∙min⁻¹ and in an SDC_individual of 4.6 mL∙kg⁻¹∙min⁻¹.

Limitations

Generalization of our study results is restricted to fatigued PwMS with a low to mild level of disability.

Conclusions

At individual level, cardiopulmonary exercise testing can be used reliably to assess physical fitness in terms of VO₂peak, but less so to determine significant changes. At group level, VO₂peak can be reliably used to determine physical fitness status and establish change over time.     

Reflex bradycardia does not influence oxygen consumption during hypoxia in the European eel (Anguilla anguilla)

Most teleost fish reduce heart rate when exposed to acute hypoxia. This hypoxic bradycardia has been characterised for many fish species, but it remains uncertain whether this reflex contributes to the maintenance of oxygen uptake in hypoxia. Here we describe the effects of inhibiting the bradycardia on oxygen consumption (MO₂), standard metabolic rate (SMR) and the critical oxygen partial pressure for regulation of SMR in hypoxia (Pcrit) in European eels Anguilla anguilla (mean ± SEM mass 528 ± 36 g; n = 14). Eels were instrumented with a Transonic flow probe around the ventral aorta to measure cardiac output (Q) and heart rate (f _H). MO₂ was then measured by intermittent closed respirometry during sequential exposure to various levels of increasing hypoxia, to determine Pcrit. Each fish was studied before and after abolition of reflex bradycardia by intraperitoneal injection of the muscarinic antagonist atropine (5 mg kg⁻¹). In the untreated eels, f _H fell from 39.0 ± 4.3 min⁻¹ in normoxia to 14.8 ± 5.2 min⁻¹ at the deepest level of hypoxia (2 kPa), and this was associated with a decline in Q, from 7.5 ± 0.8 mL min⁻¹ kg⁻¹ to 3.3 ± 0.7 mL min⁻¹ kg⁻¹ in normoxia versus deepest hypoxia, respectively. Atropine had no effect on SMR, which was 16.0 ± 1.8 μmol O₂ kg⁻¹ min⁻¹ in control versus 16.8 ± 0.8 μmol O₂ kg⁻¹ min⁻¹ following treatment with atropine. Atropine also had no significant effect on normoxic f _H or Q in the eel, but completely abolished the bradycardia and associated decline in Q during progressive hypoxia. This pharmacological inhibition of the cardiac responses to hypoxia was, however, without affect on Pcrit, which was 11.7 ± 1.3 versus 12.5 ± 1.5 kPa in control versus atropinised eels, respectively. These results indicate, therefore, that reflex bradycardia does not contribute to maintenance of MO₂ and regulation of SMR by the European eel in hypoxia.     

Maximal oxygen uptake, anaerobic threshold and running economy in women and men with similar performances level in marathons

Sex differences in running economy (gross oxygen cost of running, C_R), maximal oxygen uptake (VO_2max), anaerobic threshold (Th_an), percentage utilization of aerobic power (% VO_2max), and Th_an during running were investigated. There were six men and six women aged 20–30 years with a performance time of 2 h 40 min over the marathon distance. The VO_2max, Th_an, and CR were measured during controlled running on a treadmill at 1° and 3° gradient. From each subject's recorded time of running in the marathon, the average speed (v _M) was calculated and maintained during the treadmill running for 11 min. The VO_{2 max} was inversely related to body mass (m _b), there were no sex differences, and the mean values of the reduced exponent were 0.65 for women and 0.81 for men. These results indicate that for running the unit ml·kg^–0.75·min^–1 is convenient when comparing individuals with different m _b. The VO_2max was about 10% (23 ml·kg^–0.75·min^–1) higher in the men than in the women. The women had on the average 10–12 ml·kg^–0.75·min^–1 lower VO₂ than the men when running at comparable velocities. Disregarding sex, the mean value of C_R was 0.211 (SEM 0.005) ml·kg^–1·m^–1 (resting included), and was independent of treadmill speed. No sex differences in Th_an expressed as % VO_2max or percentage maximal heart rate were found, but Than expressed as VO₂ in ml·kg^–0.75·min^–1 was significantly higher in the men compared to the women. The percentage utilization of f _emax and concentration of blood lactate at v _M was higher for the female runners. The women ran 2 days more each week than the men over the first 4 months during the half year preceding the marathon race. It was concluded that the higher VO_2max and Th_an in the men was compensated for by more running, superior C_R, and a higher exercise intensity during the race in the performance-matched female marathon runners.     

Role of the left aortic arch and blood flows in embryonic American alligator (<Emphasis Type="Italic">Alligator mississippiensis</Emphasis>)

All embryonic and fetal amniotes possess a ductus(i) arteriosus(i) that allows blood to bypass the pulmonary circulation and the non-functional lungs. The central hemodynamic of embryonic reptiles are unique, given the additional systemic aorta that allows pulmonary circulatory bypass, the left aorta (LAo). The LAo exits in the right ventricle or ‘pulmonary side’ of reptilian hearts in both embryos and adults, but its functional significance in ovo is unknown. This study investigated the role of the LAo in embryonic American alligators by surgically occluding the LAo and measuring oxygen consumption and, in addition, measured hemodynamic responses to hypoxia in embryonic alligators. We measured systemic cardiac output and primary chorioallantoic membrane (CAM) artery blood flow for normoxic and hypoxic-incubated (10% O₂) American alligator embryos (Alligator mississippiensis). Chronic blood flow (1–124 h) in the primary CAM artery for hypoxic-incubated embryos (92 ± 26 ml min⁻¹ kg⁻¹) was elevated when compared with normoxic-incubated embryos (29 ± 14 ml min⁻¹ kg⁻¹, N = 6; P = 0.039). For hypoxic-incubated embryos, acute LAo blood flow (49.6 ± 24.4 ml min⁻¹ kg⁻¹) was equivalent to the combined flow of the three systemic great vessels that arise from the left ventricle, the right aorta, common carotid and subclavian arteries (43.6 ± 21.5 ml min⁻¹ kg⁻¹, N = 5). Similarly, for normoxic-incubated embryos, LAo blood flow (27.3 ± 6.6 ml min⁻¹ kg⁻¹) did not statistically differ from the other three vessels (18.4 ± 4.9 ml min⁻¹ kg⁻¹, N = 5). This study contains the first direct test of LAo function and the first measurements of blood flow in an embryonic reptile. These data support the hypotheses that embryonic alligators utilize the LAo to divert a significant amount of right ventricular blood into the systemic circulation, and that CAM blood flow increases following chronic hypoxic conditions. However, surgical occlusion of the LAo did not affect egg [(V)\dot]_\textO2, \dot{V}_{{\text{O}}_{2}}, supporting the hypothesis that the LAo of reptiles is not critical to maintain in ovo oxygen consumption.     

Cardiac Autonomic Modulation Is Determined by Gender and Is Independent of Aerobic Physical Capacity in Healthy Subjects

Background

Aerobic physical capacity plays an important role in reducing morbidity and mortality rates in subjects with cardiovascular diseases. This action is often related to an improvement in the autonomic modulation of heart rate variability (HRV). However, controversies remain regarding the effects of physical training on cardiac autonomic control in healthy subjects. Therefore, our objective was to investigate whether aerobic capacity interferes with the autonomic modulation of HRV and whether gender differences exist.

Methods

Healthy men and women (N=96) were divided into groups according to aerobic capacity: low (VO₂: 22-38 ml/kg^-1 min^-1), moderate (VO₂: 38-48 ml/kg^-1 min^-1) and high (VO₂ >48 ml/kg^-1 min^-1.) We evaluated the hemodynamic parameters and body composition. The autonomic modulation of HRV was investigated using spectral analysis. This procedure decomposes the heart rate oscillatory signal into frequency bands: low frequency (LF=0.04-0.15Hz) is mainly related to sympathetic modulation, and high frequency (HF=0.15-0.5Hz) corresponds to vagal modulation.

Results

Aerobic capacity, regardless of gender, determined lower values of body fat percentage, blood pressure and heart rate. In turn, the spectral analysis of HRV showed that this parameter did not differ when aerobic capacity was considered. However, when the genders were compared, women had lower LF values and higher HF values than the respective groups of men.

Conclusion

The results suggest that aerobic physical capacity does not interfere with HRV modulation; however, the cardiac modulatory balance differs between genders and is characterized by a greater influence of the autonomic vagal component in women and by the sympathetic component in men.     

The Effect of Neoadjuvant Chemoradiotherapy on Whole-Body Physical Fitness and Skeletal Muscle Mitochondrial Oxidative Phosphorylation In Vivo in Locally Advanced Rectal Cancer Patients – An Observational Pilot Study

Background

In the United Kingdom, patients with locally advanced rectal cancer routinely receive neoadjuvant chemoradiotherapy. However, the effects of this on physical fitness are unclear. This pilot study is aimed to investigate the effect of neoadjuvant chemoradiotherapy on objectively measured in vivo muscle mitochondrial function and whole-body physical fitness.

Methods

We prospectively studied 12 patients with rectal cancer who completed standardized neoadjuvant chemoradiotherapy, recruited from a large tertiary cancer centre, between October 2012 and July 2013. All patients underwent a cardiopulmonary exercise test and a phosphorus magnetic resonance spectroscopy quadriceps muscle exercise-recovery study before and after neoadjuvant chemoradiotherapy. Data were analysed and reported blind to patient identity and clinical course. Primary variables of interest were the two physical fitness measures; oxygen uptake at estimated anaerobic threshold and oxygen uptake at Peak exercise (ml.kg⁻¹.min⁻¹), and the post-exercise phosphocreatine recovery rate constant (min⁻¹), a measure of muscle mitochondrial capacity in vivo.

Results

Median age was 67 years (IQR 64–75). Differences (95%CI) in all three primary variables were significantly negative post-NACRT: Oxygen uptake at estimated anaerobic threshold −2.4 ml.kg⁻¹.min⁻¹ (−3.8, −0.9), p = 0.004; Oxygen uptake at Peak −4.0 ml.kg⁻¹.min⁻¹ (−6.8, −1.1), p = 0.011; and post-exercise phosphocreatine recovery rate constant −0.34 min⁻¹ (−0.51, −0.17), p<0.001.

Conclusion

The significant decrease in both whole-body physical fitness and in vivo muscle mitochondrial function raises the possibility that muscle mitochondrial mechanisms, no doubt multifactorial, may be important in deterioration of physical fitness following neoadjuvant chemoradiotherapy. This may have implications for targeted interventions to improve physical fitness pre-surgery.

Trial Registration

Clinicaltrials.gov registration {"type":"clinical-trial","attrs":{"text":"NCT01859442","term_id":"NCT01859442"}}NCT01859442     

Effects of hypercapnia on blood-gas and acid-base status in the white sturgeon, Acipenser transmontanus

The effect of environmental hypercapnia on respiratory and acid-base variables was studied in white sturgeon, Acipenser transmontanus. Blood PCO₂, PO₂, pH, hemoglobin concentration, and plasma lactate, glucose, catecholamines and cortisol were measured first under normocapnia (water PCO₂ < 0.5 Torr, 1 Torr = 133.32 Pa), then under hypercapnia (25–35 Torr) and a final return to normocapnia at 19 ± 0.5 °C. Acute (≤ 2h) hypercapnia significantly increased arterial PCO₂ (8-fold increase), ventilation frequency (2-fold increase), plasma HCO₃ ⁻ (2.3-fold) and decreased arterial pH (to 7.15 ± 0.02). After 24 h, norepinephrine, epinephrine and cortisol, were significantly increased, and arterial pH reached its nadir (7.10 ± 0.03). During the 72- and 96-h-periods, arterial PCO₂ (24 ± 4.4 Torr) and ventilatory frequency (105 ± 5 breaths min⁻¹) stabilized, HCO₃ ⁻ reached its apparent maximum (23.6 ± 0.0 mmol⁻¹), glucose decreased by 32%, and pH increased significantly to 7.31 + 0.03. The return to normocapnia completely restored arterial PCO₂ (2.5 ± 0.14 Torr), HCO₃ ⁻ (7.4 ± 0.59 mmol · l⁻¹), ventilation frequency (71 ± 7 breaths · min⁻¹), and pH (7.75 ± 0.04). Overall, hypercapnia produced a respiratory acidosis, hyperventilation, a transient norepinephrine “spike”, and increased plasma catecholamines, cortisol, and arterial PO₂. The respiratory acidosis was only partially compensated (35% pH restoration) 96 h after the onset of hypercapnia and resulted in a significantly decreased blood-O₂ affinity (Bohr effect), as determined by construction of in vitro blood O₂ equilibrium curves at 15 °C and 20 °C. Prolonged exposure to hypercapnia may lead to acid-base disturbances and negatively affect growth of white sturgeon. Accepted: 17 August 1997     

The Antarctic notothenioid fish <Emphasis Type="Italic">Pagothenia borchgrevinki</Emphasis> is thermally flexible: acclimation changes oxygen consumption

Antarctic marine organisms are considered to have extremely limited ability to respond to environmental temperature change. However, here we show that the Antarctic notothenioid fish Pagothenia borchgrevinki is an exception to this theory. P. borchgrevinki was able to acclimate its resting metabolic rate and resting ventilation frequency after a 5°C rise in temperature. Acute exposure to 4°C resulted in an elevation in metabolic rate (57.8 ± 4.79 mg O₂ kg⁻¹ h⁻¹) and resting ventilation rate (40.38 ± 1.61 breaths min⁻¹) compared with fish at −1°C (metabolic rate 34.45 ± 3.12 mg O₂ kg⁻¹ h⁻¹; ventilation rate 29.88 ± 3.72 breaths min⁻¹). However, after a 1-month acclimation period, there was no significant difference in the metabolic rate (cold fish 29.52 ± 3.01; warm fish 31.13 ± 2.30 mg O₂ kg⁻¹ h⁻¹), or the resting ventilation rate (cold fish 28.75 ± 0.98; warm fish 34.25 ± 2.28 breaths min⁻¹) of cold and warm acclimated fish. Acclimation changes to the rate of oxygen consumption following exhaustive exercise were complex. The pattern of oxygen consumption during recovery from exhaustive exercise was not significantly different in either cold or warm acclimated fish.     

Effect on Physical Activity of a Randomized Afterschool Intervention for Inner City Children in 3rd to 5th Grade

Background

Less than 45% of U.S. children meet the 60 min^.d^-1 physical activity (PA) guideline. Structured after-school PA programing is one approach to help increase activity levels. This study aimed to evaluate the feasibility and short-term impact of a supervised after-school PA and nutrition education program on activity levels.

Methods

Forty-two 3^rd-5^th graders from an inner-city school in Boston, MA were randomly assigned to a 10-wk after-school program of either: 1) weekly nutrition education, or 2) weekly nutrition education plus supervised PA 3 d^.wk^-1 at a community-based center. At baseline and follow-up, PA was measured using accelerometry and fitness (VO_2max) was estimated using the PACER 15-m shuttle run. Additional measures obtained were non-fasting finger stick total cholesterol (TC) and glucose levels, waist circumference (WC), body mass index (BMI), percent body fat (%BF), and blood pressure (BP). Values are presented as mean±SE, unless noted otherwise.

Results

Thirty-six participants completed the study (mean±SD; age 9.7±0.9 years). Participants attended >80% of the sessions. After adjusting for accelerometer wear time and other design factors, light and moderate-to-vigorous PA (MVPA) increased in the nutrition+PA group (+21.5±14.5 and +8.6±8.0 min^.d^-1, respectively) and decreased in the nutrition only group (-35.2±16.3 and -16.0±9.0 min^.d^-1, respectively); mean difference between groups of 56.8±21.7 min^.d^-1 (light PA, p = 0.01) and 24.5±12.0 min^.d^-1 (MVPA, p = 0.04). Time spent in sedentary behaviors declined in the nutrition+PA group (-14.8±20.7 min^.d^-1) and increased in the nutrition only group (+55.4±23.2 min^.d^-1); mean difference between groups of -70.2±30.9 min^.d^-1 (p = 0.02). Neither group showed changes in TC, BP, WC, %BF, BMI percentile, or fitness (p>0.05).

Conclusions

The supervised afterschool community-based nutrition and PA program was well accepted and had high attendance. The changes in light PA and MVPA has potential to promote weight maintenance in inner-city elementary school children, however longer term studies with larger samples are needed.

Trial Registration

ClinicalTrials.gov NCT01104038     

Oxygen uptake during moderate intensity running: response following a single bout of interval training

Eight male endurance runners [mean ± (SD): age 25 (6) years; height 1.79 (0.06) m; body mass 70.5 (6.0) kg; % body fat 12.5 (3.2); maximal oxygen consumption (V˙O_2max 62.9 (1.7) ml · kg⁻¹ · min⁻¹] performed an interval training session, preceded immediately by test 1, followed after 1 h by test 2, and after 72 h by test 3. The training session was six 800-m intervals at 1 km · h⁻¹ below the velocity achieved at V˙O_2max with 3 min of recovery between each interval. Tests 1, 2 and 3 were identical, and included collection of expired gas, measurement of ventilatory frequency (f _v ), heart rate (f _c), rate of perceived exertion (RPE), and blood lactate concentration ([La⁻]_B) during the final 5 min of 15 min of running at 50% of the velocity achieved at V˙O_2max (50% −V˙O_2max).␣Oxygen uptake (V˙O₂), ventilation (V˙ _E ), and respiratory exchange ratio (R) were subsequently determined from duplicate expired gas collections. Body mass and plasma volume changes were measured preceding and immediately following the training session, and before tests 1–3. Subjects ingested water immediately following the training session, the volume of which was determined from the loss of body mass during the session. Repeated measures analysis of variance with multiple comparison (Tukey) was used to test differences between results. No significant differences in body mass or plasma volume existed between the three test stages, indicating that the differences recorded for the measured parameters could not be attributed to changes in body mass or plasma volume between tests, and that rehydration after the interval training session was successful. A significant (P < 0.05) increase was found from test 1 to test 2 [mean (SD)] for V˙O₂ [2.128 (0.147) to 2.200 (0.140) 1 · min⁻¹], f _c [125 (17) to 132 (16) beats · min⁻¹], and RPE [9 (2) to 11 (2)]. A significant (P < 0.05) decrease was found for submaximal R [0.89 (0.03) to 0.85 (0.04)]. These results suggest that alterations in V˙O₂ during moderate-intensity, constant-velocity running do occur following heavy-intensity endurance running training, and that this is due to factors in addition to changed substrate metabolism towards greater fat utilisation, which could explain only 31% of the increase in V˙O₂. Accepted: 8 December 1997