Volume osmotic flows of non-homogeneous electrolyte solutions through horizontally mounted membrane.

Results of an experimental study of volume osmotic flows in a single-membrane osmotic-diffusive cell, which contains a horizontal, microporous, symmetrical polymer membrane separating water and binary or ternary electrolyte solutions are presented. In the experimental set-up, water was placed on one side of the membrane. The opposite side of the membrane was exposed to binary or ternary solutions. As binary solutions, aqueous potassium chloride or ammonia solutions were used, whereas potassium chloride in 0.25 mol x l(-1) aqueous ammonia solution or ammonia in 0.1 mol x l(-1) aqueous potassium chloride solution were used as ternary solutions. Two (A and B) configurations of a single-membrane osmotic-diffusive cell in a gravitational field were studied. In configuration A, water was placed in a compartment above the membrane and the solution below the membrane. In configuration B the position of water and solution was reversed. Furthermore, the effect of amplification of volume osmotic flows of electrolyte solutions in the single-membrane osmotic-diffusive electrochemical cell was demonstrated. The thermodynamic models of the flux graviosmotic and amplification effects were developed, and the volume flux graviosmotic effect for configurations A and B of a single-membrane osmotic-diffusive cell was calculated. The results were interpreted within the conventional instability category, increasing the diffusion permeability coefficient value for the system: concentration boundary layer/membrane/concentration boundary layer.

Anaerobic power, creatine kinase activity, lactate concentration, and acid-base equilibrium changes following bouts of exhaustive strength exercises.

The study was conducted on 10 male bodybuilders and powerlifters who performed highly exhaustive strength exercises for both the upper and lower limbs. They included 10 progressive sets of squats for the lower limbs and 10 progressive sets of the bench press for the upper limbs. Anaerobic power was evaluated by the 30-second Wingate test 3 times: after a 2-day rest period, and 10 minutes and 24 hours after the cessation of exhaustive strength exercises. Blood samples were drawn at rest, 5 minutes, and 24 hours after the strength exercise for the evaluation of creatine kinase (CK) activity, lactate (LA) concentration, and changes in acid-base equilibrium. Relative external work (Wt) evaluated immediately after the cessation of strength exercises decreased significantly for both the lower and upper limbs, whereas relative maximal power (Pmax) did not change significantly throughout the protocol. The return of Pmax and Wt to initial levels within 24 hours occurred in the upper and lower limbs for Pmax and only in the upper limbs for Wt. Postexercise LA concentration was nearly 3 times as high for the lower limbs in comparison to upper limbs, and it remained slightly elevated 24 hours after the cessation of exercise in comparison to resting values. CK activity increased significantly 10 minutes after the intense strength exercises and rose to significantly higher levels 24 hours after the cessation of exercise. The level of serum CK may not be related to the amount of muscle mass utilized in strength exercises. Acid-base equilibrium variable changes were significantly different immediately after the end of the exercise session and returned to resting values 24 hours after the exhaustive exercise protocol. The 2 analyzed anaerobic power indices (Pmax and Wt) were significantly different for the upper and lower limbs under initial circumstances, 5 minutes, and 24 hours after exhaustive exercise, whereas blood variables (LA, CK, pH, and base excess) differed significantly only immediately after the strength protocol.

Effect of sustained adrenergic receptors stimulation and blockade on lactate threshold in rats.

BACKGROUND: This study examined the hypothesis that prolonged (12 hrs) stimulation of adrenergic receptors by adrenaline and their blockade by regitine (alpha-blockade) or propranolol (beta-blockade) affect lactate thresh-old (T(LA)) and exercise tolerance in rats. METHODS: Twenty-four untrained male Wistar rats performed a multistage running test on a treadmill with an intensity increased from 13 m/min to the maximum speed. After a control exercise test the animals were devided into three groups implanted s.c. with: 1) adrenaline; 2) propranolol and 3) regitine tablets. Twelve hours after the tablet implantation the exercise was repeated. Both before the exercise test and at the end of each 2-min loads blood lactate [LA] was measured to evaluate T(LA). RESULTS: Prolonged adrenaline excess resulted in reduced maximal running speed and shifted T(LA) towards lower exercise intensities than in the control test. Both alpha- and beta-adrenergic blockade reduced the work load at which T(LA) occurred, without changing the maximum running speed and maximal blood LA concentration. Blood [LA] at the lactate threshold ([LA] at T(LA)) was significantly higher in hyperadrenalinemic than in control rats, whilst under beta-blockade it was lowered in comparison with control values. Alpha-adrenergic blockade had no effect on [LA] at T(LA), but at the higher exercise intensities blood [LA] exceeded the respective control values. CONCLUSIONS: The present study demonstrated that prolonged excess of adrenaline reduces the maximum power output and T(LA). The former effect seems to be a result of simultaneous stimulation of both types of adrenergic receptors.

[Physical fitness of children after cardiosurgical correction of an atrial septal defect type II]. / Wydolnosc fizyczna dzieci po leczeniu kardiochirurgicznym ubytku w przegrodzie miedzyprzedsionkowej serca typu II.

Physical fitness of 17 children aged 8-12 years being 4-7 years after cardiosurgical correction of interatrial defect of the heart (ASD II) was studied. The results were compared with the ones obtained in 14 healthy children of the same age. The parameters of gas exchange, gasometry, heart rate, ECG, arterial blood pressure were determined during supervised physical fitness test. The power of the children and so called anaerobic threshold (according to Beavers method) were evaluated during the exercise test performed on mechanical treadmill, as well. No significant differences of the studied classical physical fitness parameters between both studied groups were observed. On the other hand, the use of a log-log transformation method indicated that the children after cardiosurgical correction achieved the anaerobic threshold at lower exercise intensity. This fact is connected with lower physical performance of these children as compared to the control group.

The effect of a low-carbohydrate diet on performance, hormonal and metabolic responses to a 30-s bout of supramaximal exercise.

The aim of this study was to find out whether a low-carbohydrate diet (L-CHO) affects: (1) the capacity for all-out anaerobic exercise, and (2) hormonal and metabolic responses to this type of exercise. To this purpose, eight healthy subjects underwent a 30-s bicycle Wingate test preceded by either 3 days of a controlled mixed diet (130 kJ/kg of body mass daily, 50% carbohydrate, 30% fat, 20% protein) or 3 days of an isoenergetic L-CHO diet (up to 5% carbohydrate, 50% fat, 45% protein) in a randomized order. Before and during 1 h after the exercise venous blood samples were taken for measurement of blood lactate (LA), beta-hydroxybutyrate (beta-HB), glucose, adrenaline (A), noradrenaline (NA) and insulin levels. Oxygen consumption (VO2) was also determined. It was found that the L-CHO diet diminished the mean power output during the 30-s exercise bout [533 (7) W vs 581 (7) W, P < 0.05] without changing the maximal power attained during the first or second 5-s interval of the exercise. In comparison with the data obtained after the consumption of a mixed diet, after the consumption of a L-CHO diet resting plasma concentrations of beta-HB [2.38 (0.18) vs 0.23 (0.01) mmol x l(-1), P < 0.001] and NA [4.81 (0.68) vs 2.2 (0.31) nmol x l(-1), P < 0.05] were higher, while glucose [4.6 (0.1) vs 5.7 (0.2) mmol x l(-1), P < 0.05] and insulin concentrations [11.9 (0.9) vs 21.8 (1.8) mU x l(-1)] were lower. The 1-h post-exercise excess of VO2 [9.1 (0.25) vs 10.6 (0.25) 1, P < 0.05], and blood LA measured 3 min after the exercise [9.5 (0.4) vs 10.6 (0.5) mmol x l(-1), P < 0.05] were lower following the L-CHO treatment, whilst plasma NA and A concentrations reached higher values [2.24 (0.40) vs 1.21 (0.13) nmol x l(-1) and 14.30 (1.41) vs 8.20 (1.31) nmol x l(-1), P < 0.01, respectively]. In subjects on the L-CHO diet, the plasma beta-HB concentration decreased quickly after exercise, attaining approximately 30% of the pre-exercise value within 60 min, while insulin and glucose levels were elevated. The main conclusions of this study are: (1) a L-CHO diet is detrimental to anaerobic work capacity, possibly because of a reduced muscle glycogen store and decreased rate of glycolysis; (2) reduced carbohydrate intake for 3 days enhances activity of the sympathoadrenal system at rest and after exercise.

Effect of various types of exercise training on 5'-nucleotidase and adenosine deaminase activities in rat heart: influence of a single bout of endurance exercise.

The aim of the present study was to find out whether activities of the enzymes controlling adenosine metabolism, 5'-nucleotidase (5NT) and adenosine deaminase (ADA), in the left ventricle of the rat's heart change after 6 weeks of endurance or sprint training. Additionally, an influence of a single bout of endurance exercise till exhaustion on activities of these enzymes was investigated in sedentary and trained rats. The rats were divided into three groups: (1) sedentary controls (C), (2) endurance-trained (ET), and (3) sprint-trained (ST). It was shown that both types of training increased 5NT, but did not change ADA activity in the rat heart. Acute exercise till exhaustion did not affect 5NT activity in the heart taken from C and ST rats, but decreased its activity in the ET group. The heart ADA activity after exhaustive exercise increased in C and in ET group, but decreased in ST animals. It is concluded that physical training affects cardiac adenosine metabolism and the type of training may exert an influence on purine nucleotides metabolism in the heart during exhaustive exercise.

Influence of thyroid hormones on exercise tolerance and lactate threshold in rats.

Effects of thyroid hormone deficit, and triiodothyronine (T3) treatment on exercise performance, blood lactate (LA) concentrations and LA threshold (TLA) were studied in trained and untrained rats. Fourteen rats were thyroidectomized and then treated with propylthiouracil for 30 days (THY + PTU group). Fourteen sham operated rats served as controls. In each group there were 7 sedentary and 7 endurance-trained animals. Six weeks after thyroidectomy or sham operation the rats were subjected to a multistage running test with speed increasing from 13 m/min at 10 degrees treadmill inclination till maximum. Blood samples for LA were taken from the rats' tail after each 3-min exercise stage. During 3 days following this test rats from all groups were injected (i.p.) with 75 micrograms/100 g of triiodothyronine (T3), and 24 hrs afterwards the second exercise test was performed. In THY + PTU rats maximal running speed (RSmax) and the speed at which TLA occurred were markedly decreased in comparison with control group. The level of LA at the maximal speed (LAmax) and that corresponding to TLA were higher in THY + PTU rats than in controls. T3 injection to control animals diminished their RSmax and TLA, whereas in THY + PTU rats it increased RSmax and shifted TLA to a higher speed. Both in THY + PTU and control animals T3 elevated LAmax and the threshold LA concentration. Endurance training in control and THY + PTU animals markedly enhanced RSmax and TLA. This was accompanied by increases in LAmax and concentration of LA at TLA only in control group. After T3 injection to control trained rats RSmax and TLA were diminished, whereas in THY + PTU trained group RSmax was unchanged and TLA was elevated. Maximal blood LA increased only in THY + PTU trained rats whilst the threshold blood LA was elevated in both groups. It is concluded, that both the T3 deficiency and its excess reduce maximal exercise performance and shift TLA to lower workloads. Enduarance training or administration of T3 to hypothyroid rats markedly improve their exercise performance and elevate TLA, however, T3 treatment markedly increases maximal and submaximal LA levels.

Effect of low-carbohydrate-ketogenic diet on metabolic and hormonal responses to graded exercise in men.

Maximal oxygen uptake (VO2 max) and lactate threshold (LT) were measured during graded, incremental exercise in 8 healthy, untrained volunteers (aged 22 +/- 0.9 yrs) following 3 days on a control, mixed diet, or a ketogenic (50% fat, 45% protein and 5% carbohydrates) diet of equal energy content. Before and after exercise tests acid base balance, plasma beta-hydroxybutyrate (beta-HB), free fatty acid (FFA), and some hormone concentrations were determined. In comparison with the normal diet, the ketogenic diet resulted in: an increased VO2 max, decreased respiratory exchange ratio an a shift of LT towards higher exercise loads. Blood LA concentrations were lower before, during and after exercise. Post exercise blood pH, as well as pre-and post exercise base excess and bicarbonates were reduced. Resting beta-HB concentration was elevated to approx. 2.0 mM, and FFA to approx. 1.0 mM. During a 1 h recovery period beta-HB decreased to 0.85 mM (p < 0.01) after the ketogenic diet, while plasma FFA did not change after exercise under either conditions. Both the pre-and post-exercise levels of adrenaline, noradrenaline, and cortisol were enhanced, whilst plasma insulin concentration was decreased on the ketogenic diet. It is concluded that the short-term ketogenic diet does not impair aerobic exercise capacity, as indicated by elevated VO2 max and LT. This may be due to increased utilization of beta-HB and FFA when carbohydrate stores are diminished. Stimulation of the sympatho-adrenal system, and cortisol secretion with reduced plasma insulin concentration seem to be of importance for preservation of working capacity.

Effect of sustained hyperadrenalinemia on exercise performance and lactate threshold in rats.

The effect of prolonged elevation of blood adrenaline concentration (sustained up to 60 h) on exercise performance and lactate threshold (TLA) was investigated in 24 rats on the basis of a incremental, multistage treadmill exercise test, performed before and after subcutaneous implantation of retard adrenaline tablets (15 mg), which release adrenaline at a constant rate of approx. 1.6 micrograms min-1. Blood samples for lactate (LA) determinations were taken from the rats' tails after each exercise stage. The results obtained indicate that hyperadrenalinemia within the physiologic range, sustained for 6 or 12 h, decreases exercise performance, measured as the maximal speed of running, increases blood LA concentration during submaximal and maximal exercise, and shifts TLA toward lower exercise intensities than in control or sham-operated rats. When adrenaline excess was maintained for 60 h the maximal running speed was still reduced, and exercise blood LA was even higher than during earlier stages of hyperadrenalinemia, but TLA returned to control values. In the rat, a moderate excess of circulating adrenaline, sustained up to 60 h, reduces maximal exercise performance, and causes marked elevations in submaximal and maximal blood lactate concentration. However, this is accompanied by lowering of TLA only in the early stages of hyperadrenalinemia (6 and 12 h), which suggests that shifts of TLA may occur independently of absolute levels of blood lactate during graded exercise.

Effect of a low-carbohydrate diet on plasma and sweat ammonia concentrations during prolonged nonexhausting exercise.

The purpose of this investigation was to examine the effect of low body glycogen stores on plasma ammonia concentration and sweat ammonia excretion during prolonged, nonexhausting exercise of moderate intensity. On two occasions seven healthy untrained men pedalled on a cycle ergometer for 60 min at 50% of their predetermined maximal O2 uptakes (VO2max) firstly, following 3 days on a normal mixed diet (N-diet) (60% carbohydrates, 25% fat and 15% protein) and secondly, following 3 days on a low-carbohydrate diet (LC-diet) (less than 5% carbohydrates, 50% fat and 45% protein) of equal energy content. Blood was collected from the antecubital vein immediately before, at 30th and at 60th min of exercise. Sweat was collected from the hypogastric region using gauze pads. It was shown that plasma ammonia concentrations after the LC-diet were higher than after the N-diet at both the 30th and 60th min of exercise. Sweat ammonia concentration and total ammonia loss through the sweat were also higher after the LC-diet. The higher ammonia concentrations in plasma and sweat after the LC-diet would seem to indicate an increased ammonia production, which may be related to reduced initial carbohydrate stores.

Anaerobic threshold in rats.

1. The aim of this study was to find out whether the anaerobic threshold (AT) can be estimated in rats running at increasing speed and if so what is the reproducibility of the measurements. 2. Lactate (LA) concentrations in blood taken from 11 rats were determined during a discontinued, multistage treadmill exercise test repeated four times in each animal. 3. It was found that blood LA changes vs speed have an exponential pattern with a distinct, rapid rise at the speed above 25 m/min which corresponds to blood LA of approx. 4 mmol/l. 4. The variation coefficient of the speed at which AT occurred in individual animals ranged between 10 and 20%. 5. These results offer a potential application of AT determination in the animal studies concerning mechanisms controlling exercise metabolism.

Dynamics of metabolic responses to prolonged elevation of circulating adrenaline in resting and exercising rats.

The purpose of this study was to follow the time course of metabolic responses to hyperadrenalinemia sustained up to 3 days. Hyperadrenalinemia was produced in rats by s.c. implantation of tablets releasing adrenaline (A) at a constant rate (1.6 micrograms x min-1). After 6, 12, 24 and 72 h of hyperadrenalinemia and 3 days after the tablet removal rats were sacrificed and liver, 3 types of muscles and blood samples were taken. Each time 14 rats were used: 7 of them were sedentary and 7 performed treadmill endurance exercise before decapitation. Sham operated animals served as controls. In preliminary experiments working ability was examined in 10 hyperadrenalinemic and 10 control rats. Duration of exercise until exhaustion was reduced in hyperadrenalinemic rats on the average by 40%. In sedentary rats, hyperglycemia, marked depletion of liver glycogen (by approx. 80%) and muscle glycogen (by 60-80%) as well as an elevation (2-4 times) of muscle lactate (LA) were found only during the first day after A-tablet implantation. At the end of the experiment these values approached the control ones. Muscle contents of ATP and creatine phosphate (CrP) were decreased by approx. 20% and 30-60%, respectively. Plasma FFA were markedly enhanced, varying in the time-course of the experiment from 0.8 to 1.4 mmol x l-1. Post-exercise values for blood glucose, liver and muscle glycogen were always lower in hyperadrenalinemic rats than in controls sacrificed after time-matched exercise (30 min). Circulating FFA decreased during exercise at all time points following A-tablet implantation, but they were still above the post-exercise levels in sham-operated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma lactate dehydrogenase and creatine kinase after anaerobic exercise.

Eight untrained men performed 15-s and 60-s high-intensity exercise on a bicycle ergometer. Activities of the creatine kinase (CK) and lactate dehydrogenase (LDH) were measured in blood 3 min and 2, 6, and 24 h after cessation of exercise. The results indicate that anaerobic exercise induces a transient increase in plasma LDH activity and a more prolonged elevation in plasma CK activity. A negative correlation was found between CK activity measured before and 3 min after exercise and mean power, and total external work performed in both test types. A similar correlation was ascertained between pre- and post-exercise CK activity and maximal power output measured in the 60-s test. After the 15-s exercise test, only post-exercise plasma CK activity was negatively correlated with the maximal power output.

Prolonged hyperadrenalinemia impairs exercise ability in rats.

This study was performed on rats with sustained (24 h) hyperadrenalinemia produced by sc implantation of retard adrenaline (A) tablets. Comparing with control, sham-operated animals, in A-treated rats duration of endurance exercise until exhaustion was shortened by approx. 40%. This was accompanied by: significant decreases of the pre-exercise muscle glycogen and creatine phosphate values in both "slow twitching" (soleus) and "fast twitching" (white portion of gastrocnemius) muscles, and of ATP content in soleus. Muscle lactate and pyruvate contents as well as blood glucose and FFA levels were elevated. After exercise muscle substrate and metabolite contents were similar in both groups in spite of the difference in exercise duration. It is concluded that prolonged hyperadrenalinemia diminishes the intramuscular energy substrate content, thereby reducing endurance capacity of rats.