Low plasma glutamine in combination with high glutamate levels indicate risk for loss of body cell mass in healthy individuals: the effect of N-acetyl-cysteine

Skeletal muscle catabolism, low plasma glutamine, and high venous glutamate levels are common among patients with cancer or human immunodeficiency virus infection. In addition, a high glycolytic activity is commonly found in muscle tissue of cachectic cancer patients, suggesting insufficient mitochondrial energy metabolism. We therefore investigated (a) whether an anaerobic physical exercise program causes similar changes in plasma amino acid levels, and (b) whether low plasma glutamine or high glutamate levels are risk factors for loss of body cell mass (BCM) in healthy human subjects, i.e., in the absence of a tumor or virus infection. Longitudinal measurements from healthy subjects over longer periods suggest that the age-related loss of BCM occur mainly during episodes with high venous glutamate levels, indicative of decreased muscular transport activity for glutamate. A significant increase in venous glutamate levels from 25 to about 40 M was seen after a program of anaerobic physical exercise. This was associated with changes in T lymphocyte numbers. Under these conditions persons with low baseline levels of plasma glutamine, arginine, and cystine levels also showed a loss of BCM. This loss of BCM was correlated not only with the amino acid levels at baseline examination, but also with an increase in plasma glutamine, arginine, and cystine levels during the observation period, suggesting that a loss of BCM in healthy individuals terminates itself by adjusting these amino acids to higher levels that stabilize BCM. To test a possible regulatory role of cysteine in this context we determined the effect of N-acetyl-cysteine on BCM in a group of subjects with relatively low glutamine levels. The placebo group of this study showed a loss of BCM and an increase in body fat, suggesting that body protein had been converted into other forms of chemical energy. The decrease in mean BCM/body fat ratios was prevented by N-acetyl-cysteine, indicating that cysteine indeed plays a regulatory role in the physiological control of BCM.Abbreviations BCM Body cell mass - HIV Human immunodeficiency virus type 1 - NAC N-Acetyl-cysteine     

Effect of different types of high carbohydrate diets on glycogen metabolism in liver and skeletal muscle of endurance-trained rats

Male Wistar rats were fed ad libitum four different diets containing fructose, sucrose, maltodextrins or starch as the source of carbohydrate (CH). One group was subjected to moderate physical training on a motor-driven treadmill for 10 weeks (trained rats). A second group received no training and acted as a control (sedentary rats). Glycogen metabolism was studied in the liver and skeletal muscle of these animals. In the sedentary rats, liver glycogen concentrations increased by 60%–90% with the administration of simple CH diets compared with complex CH diets, whereas skeletal muscle glycogen stores were not significantly affected by the diet. Physical training induced a marked decrease in the glycogen content in liver (20%–30% of the sedentary rats) and skeletal muscle (50%–80% of the sedentary rats) in animals fed simple (but not complex) CH diets. In liver this was accompanied by a two-fold increase of triacylglycerol concentrations. Compared with simple CH diets, complex CH feeding increased by 50%–150% glycogen synthase (GS) activity in liver, whereas only a slight increase in GS activity was observed in skeletal muscle. In all the animal groups, a direct relationship existed between tissue glucose 6-phosphate concentration and glycogen content (r = 0.9911 in liver, r = 0.7177 in skeletal muscle). In contrast, no relationship was evident between glycogen concentrations and either glycogen phosphorylase activity or adenosine 5-monophosphate tissue concentration. The results from this study thus suggest that for trained rats diets containing complex CH (compared with diets containing simple CH) improve the glycogenic capacity of liver and skeletal muscle, thus enabling the adequate regeneration of glycogen stores in these two tissues.     

Effect of previous supramaximal work on lacticaemia during supra-anaerobic threshold exercise

Summary Twelve male and female subjects (eight trained, four untrained) exercised for 30 min on a treadmill at an intensity of maximal O₂ consumption (% O_2max) 90.0%, SD 4.7 greater than the anaerobic threshold of 4 mmol ·1^–1 (Th_an =83.6% O_2max, SD 8.9). Time-dependent changes in blood lactate concentration ([la_b]) during exercise occurred in two phases: the oxygen uptake ( O₂) transient phase (from 0 to 4 min) and the O₂ steady-state phase (4–30 min). During the transient phase, [la_b] increased markedly (l.30 mmol · l ^–1 · min ^–1, SD 0.13). During the steady-state phase, [la_b] increased slightly (0.02 mmol · 1^–1 · min^–1, SD 0.06) and when individual values were considered, it was seen that there were no time-dependent increases in [la_b] in half of the subjects. Following hyperlacticaemia (8.8 mmol -l^–1, SD 2.0) induced by a previous 2 min of supramaximal exercise (120% O_2max), [la_b] decreased during the O₂ transient (–0.118 mmol · 1^–1 · min^–1, SD 0.209) and steady-state (–0.088 mmol · 1^–1 · min ^–1, SD 0.103) phases of 30 min exercise (91.4% O_2max, SD 4.8). In conclusion, it was not possible from the Th_an to determine the maximal [la_b] steady state for each subject. In addition, lactate accumulated during previous supramaximal exercise was eliminated during the O₂ transient phase of exercise performed at an intensity above the Th_an. This effect is probably largely explained by the reduction in oxygen deficit during the transient phase. Under these conditions, the time-course of changes in [la_b] during the O₂ steady state was also affected.     

Potentiation and restitution of heart muscle contraction in rats adapted to exercise

The original amplitude of contraction of strips of myocardium determined the inotropic response to paired stimulation. The higher the initial amplitude, the lower the degree of potentiation and the higher the degree of restitution of contraction. For equal amplitude, the degree of potentiation of myocardial contraction of exercise-adapted rats was greater and the degree of restitution smaller than in the control. These changes probably reflect changes in the ion transport system of the myocardial cells.Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 7, pp. 780–782, July, 1976.     

The effect of a high calory diet on hormonal changes in young men during prolonged physical strain and sleep deprivation

Summary Major changes occur in the serum level of several hormones during 5 days of heavy and continuous physical activities, with less than a total of 2 h of sleep. The present investigation was designed to evaluate the importance of caloric deficiency, energy requirement being about 8,000–10,000 kcal/24 h. A comparison between well fed subjects and those with food deprivation revealed significantly higher levels of (T₃) triiodothyronin, insulin and thyroid stimulating hormone (TSH) in the well-fed subjects, who also had lower levels of growth hormone (hGH) and cortisol, whereas no difference was found between the two groups for thyroxin (T₄). Increased levels were found for T₃ and T₄ in both groups during the first day of activity, with a concomitant decrease in TSH and a subsequent decrease of T₄ during the next 2 days. T₃ decreased only in the low-calory group whereas increased levels were found in the iso-calory group throughout the course. The resting levels of insulin decreased during the course in the low-calory group whereas it increased in the iso-calory group. High levels were maintained throughout the course for hGH. Cortisol showed high levels just before the start of the course and then decreased from day 2 to day 4. No difference was found between the morning and evening levels for cortisol, indicating disappearance of the circadian rhythm. The present investigation has shown that energy deficiency during prolonged physical strain is responsible for the decreased serum levels of T₃ and insulin and may contribute to the decrease in TSH and the increase in hGH and cortisol.     

Physiological effects of dynamic work on a bicycle ergometer combined with different types of static contraction

Summary The effects on heart rate, oxygen uptake, and pulmonary ventilation of muscular exercises, including both dynamic contractions, either simple or combined, were studied in 4 male subjects, aged 21 to 23 years. The dynamic work consisted in cycling on an ergometric bicycle at three power levels: 40, 80, and 100 W. The static work consisted in pushing against, pulling and holding with the arms a 6, 9, 12, or 18 kg load. The physiological effects are expressed as cardiac cost (HR), oxygen cost (VO₂) and ventilation cost (V). The physiological cost of the combined work increases according to the cycling power and to the isometric load developed. A statistical analysis shows that the costs of combined work are not different from the sum of the costs of the static and dynamic contractions measured separately. Thus, the physiological responses to the combinations investigated are of an additive type.     

人参二醇组皂甙及游泳训练对大鼠股四头肌α-肌动蛋白mRNA表达的影响

目的:观察大鼠7周大负荷游泳训练及人参二醇组皂甙(PDS)对大鼠股四头肌α-肌动蛋白mRNA表达的影响。方法:采用Northernblot分析7周大负荷游泳训练后恢复期大鼠股四头肌α-肌动蛋白mRNA表达水平及PDS对其影响。结果:α-肌动蛋白mRNA杂交信号的扫描积分光密度值(A),运动·盐水组较安静组略强;运动·PDS,扫描积分光密度值(A)显著强于运动·盐水组和安静组,运动·甲睾组与运动·盐水组表达无明显差异。结论:PDS可提高长期耐力运动大鼠股四头肌α-肌动蛋白mRNA表达,从而提高耐力运动能力;长期应用外源性雄激素对耐力训练大鼠股四头肌α-肌动蛋白无明显提高,这可能与外源睾酮对内源性睾酮分泌的抑制有关。     

Non-linear cardiac output dynamics during ramp-incremental cycle ergometry

Published literature asserts that cardiac output (=O₂×1/C_(a-v)O₂) increases as a linear function of oxygen uptake with a slope of approximately 5–6 during constant work rate exercise. However, we have previously demonstrated that C_(a-v)O₂ has a linear relationship as a function of O₂ during progressively increasing work rate incremental exercise. Therefore, we hypothesized that may indeed have a non-linear relationship with respect to O₂ during incremental, non-steady state exercise. To investigate this hypothesis, we performed five maximal progressive work rate exercise studies in healthy human subjects. was determined every minute during exercise using measured breath-by-breath O₂, and arterial and pulmonary artery measurements of PO₂, hemoglobin saturation, and content. was plotted as a function of O₂ and the linear and non-linear (first order exponential and hyperbolic) fits determined for each subject. Tests for linearity were performed by assessing the significance of the quadratic terms added to the linear relation using least squares estimation in linear regression. Linearity was inadequate in all cases (group P<0.0001). We conclude that cardiac output is a non-linear function of O₂ during ramp-incremental exercise; the pattern of non-linearity suggests that while the kinetics of are faster than those of O₂ they progressively slow as work rate (and O₂) increases.     

Aerobic exercise performance correlates with post-ischemic flow-mediated dilation of the brachial artery in young healthy men

In older healthy men, aerobic exercise capacity is related to postischemic flow-mediated dilation of the brachial artery (FMD), but corresponding data in a younger population is not available. In addition, whether submaximal aerobic exercise performance also correlates with this kind of vasomotor reactivity is not known. Therefore, in 15 nonsmoking young healthy men [age 27 (5) years; body mass index: 24 (2) kg/m²; mean (SD)] with different levels of ordinary physical activity, but not performing upper-extremity training, we measured FMD at 1 min after reactive hyperemia, and pulmonary oxygen uptake (O₂) at ventilatory anaerobic threshold (O₂AT) and at peak effort (peak O₂) during an incremental exercise on a treadmill. In our participants, FMD was 9.1 (3.4)%, O₂AT was 40.72 (5.92) ml/kg per min, and peak O₂ was 52.95 (8.13) ml/kg per min. Using bivariate Pearsons correlation, and in separate multivariate regression analyses, O₂AT and peak VO₂ showed a significant and reasonably good correlation with FMD (r=0.84, P<0.001 and r=0.77, P=0.001, respectively), independent of age, body mass index and serum total cholesterol (=0.77, P<0.001, R² of the overall model=0.79 and =0.70, P<0.005, R² of the overall model=0.69, respectively). Our data provide evidence suggesting that in young healthy men a higher submaximal and maximal aerobic exercise performance is associated with a greater FMD of peripheral conduit arteries.     

Local injection of a mixture of beta-aminopropionitril fumarate and sodium hyaluronate together with controlled exercise for treatment of subacute superficial digital flexor tendonitis in horses

Local injection of a mixture of beta-aminopropionitril fumarate (BAPN-f) and sodium hyaluronate (NaH⁺) together with controlled exercise were evaluated for treatment of superficial digital flexor tendon (SDFT) injuries in horses. Fourteen mixed breed horses with subacute SDF tendon injuries in forelimbs were randomly assigned to two groups. One group received BAPN-f (0.7 mg/ml) and the other received NaH⁺ (10 mg/ml) all by intratendinous injection. Controlled exercise started during the first week after intratendinous treatment and continued for 12 weeks. Cross-sectional area (CSA) of the SDFT, diameter of the SDFT, and relative area of the lesion (presence of CSA) were measured by ultrasonographic examination. Lesions were semiquantitatively graded for echogenicity on a scale of 0 to 4. The lesion severity in CSA was significantly reduced by BAPN and NaH compared to those horses treated by BAPN only (p < 0.05). Lesion echogenicity score was significantly higher in horses treated with BAPN and NaH⁺ at day 0 compared to horses treated with BAPN (p < 0.05). At the end of the study, lesion echogenicity score was significantly reduced in the horses treated with BAPN and NaH⁺ compared to horses treated by BAPN only (p < 0.05). According to the results of the present study, a combination of BAPN-f and NaH⁺ has a greater beneficial effect on tendon healing and remodeling in horses, as assessed by sonographic examination, compared to treatment with single drugs.