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Biomedical subjects

K Nazar

Publications and source records attributed to K Nazar.

At least 19 recordsLinked to original sources
PubMed1997

Physiological characteristics and hormonal profile of young normotensive men with exaggerated blood pressure response to exercise.

Exaggerated blood pressure (BP) response to exercise in normotensive subjects is considered as a predictor of future hypertension. The aim of the study was to find out whether elevated BP response to exercise is associated with any other haemodynamic, metabolic or hormonal abnormalities. Abnormal BP response to exercise, i.e. systolic BP (SBP) > 200 mmHg at 150 W or lower workload, was found in 37 out of 180 normotensive, male students, aged 20-24 years. Fifteen students with elevated exercise BP (group E) volunteered for further examinations. Their resting and ambulatory BP showed high normal values. Eight of them had a family history of hypertension. Four subjects met the criteria of cardiac hypertrophy. Significant correlations were found between exercise SBP and left ventricular mass index, average 24 h and daytime SBP recordings. In comparison with normal subjects of the same age (group N, n = 13), those from group E did not differ in body mass index, plasma lipid profile, fasting glucose, insulin and catecholamine (CA) concentrations, but had increased erythrocyte sodium content, slightly elevated plasma renin activity and cortisol level. During exercise, E subjects showed greater cardiac output (CO) increases with normal heart rate, total peripheral resistance (TPR) and plasma CA. There were no significant differences between groups in haemodynamic and plasma CA responses to posture change from supine to standing. Glucose ingestion (75 g) caused smaller increases in CO and smaller decreases in TPR in E than in N subjects without differences in BP, blood glucose plasma insulin and CA. It is concluded that young normotensive men with exaggerated BP response to exercise show some other characteristics that may be considered as markers of predisposition to hypertension or factors promoting the development of hypertension.

Adult↗
PubMed1996

Threshold increases in plasma growth hormone in relation to plasma catecholamine and blood lactate concentrations during progressive exercise in endurance-trained athletes.

Plasma human growth hormone ([HGH]), adrenaline ([A]), noradrenaline ([NA]) and blood lactate ([La-](b)) concentrations were measured during progressive, multistage exercise on a cycle ergometer in 12 endurance-trained athletes [aged 32.0 (SEM 2.0) years]. Exercise intensities (3 min each) were increased by 50 W until the subjects felt exhausted. Venous blood samples were taken after each intensity. The [HGH] and catecholamine concentrations increased negligibly during exercise of low to moderate intensities revealing an abrupt rise at the load corresponding to the lactate threshold ([La-]-T). Close correlations (P <0.001) were found between [La-]b and plasma [HGH] (r = 0.64), [A] (r = 0.71) and [NA] (r = 0.81). The mean threshold exercise intensities for [HGH], [A] and [NA], detected by log-log transformation, [154 (SEM 19) W, 162 (SEM 15) W and 160 (SEM 17) W, respectively] were not significantly different from the [La-]-T [161 (SEM 12) W]. The results indicated that the threshold rise in plasma [HGH] followed the patterns of plasma catecholamine and blood lactate accumulation during progressive exercise in the endurance-trained athletes.

Adult↗
PubMed1996

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.

Animals↗
PubMed1996

Triacylglycerol synthesis in the different skeletal muscle fiber sections of the rat.

Triacylglycerol (TG) synthesis rates of low-oxidative fast-twitch white and high-oxidative fast- and slow-twitch red skeletal muscle fiber sections of adult rats were measured by the incorporation of perfusate-derived palmitate into the neutral lipid fraction by use of a perfused hindquarter preparation under high-flow conditions. The perfusion medium consisted of 95% O2-5% CO2 Krebs-Henseleit buffer, pH 7.4, containing 5 g/100 ml bovine serum albumin, 100 microU/ml insulin, 5 mmol/l glucose, amino acids, and added fatty acids (FA), including 0.1 microCi/ml [3H]palmitate. FA incorporation was linear with time. TG synthesis rates correlated (r > or = 0.90) with the oxidative capacity of each of the different fiber type sections and increased in proportion to the perfusate FA concentration (0.25, 0.5, 1.0, 1.5, and 2.0 mmol/l). TG synthesis rates among different muscle fiber sections were related (r > or = 0.90) to perfusate flow during high-flow conditions; however, this was not causal, because TG synthesis rates within each muscle fiber section were independent of flow rate when experimentally varied over an approximately threefold range. Thus the relatively high TG synthesis rates observed in the high-oxidative muscle sections are not uniquely related to their high-flow capacities but are inherent to the TG synthesis process, probably events associated with FA uptake and/or capacity of the TG synthesis pathway.

Animals↗
PubMed1996

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.

3-Hydroxybutyric Acid↗
PubMed1996

Phosphate supplementation prevents a decrease of triiodothyronine and increases resting metabolic rate during low energy diet.

Thirty overweight women participated in 8 week slimming program consisting of a self-controlled low-energy diet (4.2 MJ/day) supplemented with highly viscous fibres and mineral tablets containing calcium, potassium and sodium phosphates (Redusan Combi, Biokraft Pharma AB, Sweden). Half of the patients received in double blind manner mineral tablets during first 4 weeks and placebo (without phosphates) during next 4 weeks (group 1) while the remaining patients were treated (cross-over) with placebo first and mineral tablets in the final period (group 2). The rate of weight loss was similar in groups 1 and 2 (4.7 vs 5.2 kg during the first 4 weeks and 2.7 vs 3.0 kg in the further 4 weeks). During periods of phosphate supplementation, the resting metabolic rate (RMR) increased by approx. 12% (p < 0.05) in group 1 and 19% (p < 0.05) in group 2. Phosphate supplementation ameliorated also a decrease in plasma triiodothyronine level and a decrease in thyroxine to triiodothyronine ratio. There were no differences between groups in the plasma insulin, catecholamine, growth hormone, cortisol and testosterone levels. Phosphate supplementation did not affect plasma lipids or blood glucose concentration. It is concluded that phosphate supplementation in obese patients on a low-energy diet enhances RMR irrespectively of the rate of weight loss. This effect seems to be, at least partly, due to an influence of phosphates on peripheral metabolism of thyroid hormones.

Adult↗
PubMed1996

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.

Animals↗
PubMed1995

Low ambient temperature and neuroendocrine response to hypoglycemia in men.

Nutritional factors, such as an excess or a deficiency of glucose, play an important role in neuroendocrine regulations. Hormonal and metabolic responses to hypoglycemia were examined in healthy non-obese volunteers under conditions of low ambient temperature. Hypoglycemia was induced by intravenous injection of insulin in two randomized trials performed at room temperature and at 4 degrees C. At room temperature, the typical neuroendocrine response to hypoglycemia was established. The increases of ACTH, beta-endorphin, growth hormone and cortisol in response to insulin hypoglycemia failed to be modified by low ambient temperature. Acute cold exposure significantly reduced epinephrine and totally inhibited prolactin response to insulin-induced hypoglycemia. In spite of significant changes in epinephrine response to hypoglycemia at low ambient temperature, no striking differences in plasma glucose levels compared to those measured at room temperature were observed. However, under conditions of low temperature the reestablishment of normoglycemia was delayed. No changes in free fatty acids were found under our experimental conditions. The presented data show that low ambient temperature exerts selective effects on some neuroendocrine and metabolic parameters.

Adrenocorticotropic Hormone↗
PubMed1995

Glucose infusion into exercising dogs after confinement: rectal and active muscle temperatures.

BACKGROUND: Intravenous glucose infusion into ambulatory dogs results in attenuation of exercise-induced increase of both rectal and thigh muscle temperatures. HYPOTHESIS: That glucose (Glu) infusion attenuates excessive increase in body temperature from restricted activity during confinement deconditioning. METHODS: Rectal (Tre) and quadriceps femoris muscle (Tmu) temperatures, metabolic rate, and blood samples were taken before and after 90 min of moderate treadmill exercise (mean = 3.1 +/- SE 0.2 W.kg-1) at Tdb = 21 +/- 1 degrees C and 45-60% rh from 7 male mongrel dogs (19.6 +/- SD 3.0 kg) with i.v. infusion of 40% Glu in 0.9% NaCl (0.07 ml.kg-1.min-1) or 0.9% NaCl (0.07 mg.g-1.min-1) both before and after 8 weeks of cage confinement. RESULTS: Mean (+/- SE) delta Tre (90-0 min) were: NaCl.after = 1.8 +/- 0.4 degrees C vs. 1.4 +/- 0.3 degrees C (NS) before confinement; Glu.after = 1.3 +/- 0.2 degrees C vs. 0.9 +/- 0.3 degrees C (p < 0.02) before confinement. Comparable delta Tmu (90-0 min) data were: NaCl.after = 2.5 +/- 0.4 degrees C vs. 1.9 +/- 0.4 degrees C (NS) before; Glu.after = 1.6 +/- 0.2 degrees C vs. 1.4 +/- 0.4 degrees C (NS) before. Glucose infusion significantly attenuated the rise of Tmu (1.9 degrees vs. 1.4 degrees C) only before confinement, but attenuated the rise of Tre both before (1.4 degrees vs. 0.9 degrees C) and after (1.8 degrees vs. 1.3 degrees C) confinement. Body temperature attenuation was not related to change in plasma volume, osmolality, [Glu], [lactate], [cortisol], or heat production with constant VO2. CONCLUSION: Intravenous glucose infusion attenuates the rise in exercise core temperature in deconditioned dogs by a yet undefined mechanism.

Animals↗
PubMed1994

Choice reaction time during graded exercise in relation to blood lactate and plasma catecholamine thresholds.

Twenty-two male soccer players (mean age 21.3 yrs) performed an incremental, multistage bicycle ergometer exercise test with work load increasing by 50 W, until volitional exhaustion. The exercise stages lasted 3 min and were separated by 1 min resting periods. Before exercise and during each load an audio-visual five-choice reaction task was administered to assess subjects' psychomotor performance. During resting intervals venous blood samples were taken for lactate (LA), adrenaline (A) and noradrenaline (NA) determinations. It was found that reaction time (RT) decreased gradually during exercise reaching its minimum (approx. 87% of pre-exercise value) at load 236 W (approx. 75% VO2max, HR 164 beats/min). Then, it increased rapidly, exceeding the resting level by 18%. The work load and heart rate (HR) associated with the minimal RT were higher (p < 0.001) than work load and HR associated with the LA threshold (by 46 W and 17 beats/min, respectively). Plasma A and NA showed an exponential increase during exercise with thresholds at 204 and 208 W, respectively (HR 149 and 154 beats/min). Work load at which plasma NA threshold occurred was significantly higher than the LA threshold but it did not differ from the work load associated with the minimal RT. Conversely, plasma A threshold was lower than the load of the minimal RT but did not differ significantly from LA threshold. It is concluded that young athletes continue to improve their psychomotor performance during exercise even at heavy work loads exceeding anaerobic, and plasma adrenaline thresholds. A relationship between reaction time and plasma catecholamines fits the U-shape curve.

Adult↗
PubMed1994

Effect of mild psychological stress on physiological responses to exercise in men.

UNLABELLED: To find out whether a negative shift in subject's mood alters cardio-respiratory and endocrine responses to exercise, 20 young men performed a graded bicycle ergometer test (50, 100, 150 W): 1) when they experienced a mixed emotional and cognitive stress before exercise (1st session), 2) when they were familiarized with the laboratory and rested quietly before exercise (2nd session). The subjects' mood was assessed by the Profile of Mood State (POMS) questionnaire. In the 1st session the subjects started exercise with significantly higher scores of tension, anger, depression, confusion and global mood in comparison with the 2-nd session. They also had slightly elevated systolic blood pressure, blood lactate, plasma cortisol and noradrenaline concentrations. During exercise performed in the 1st session only plasma free and total noradrenaline and cortisol levels were higher than those in the 2nd session. IN CONCLUSION: a mild psychological stress, causing the mood worsening before standard exercise test, does not evoke pronounced alterations in cardio-respiratory responses to exercise in healthy men, but it does affect the magnitude of exercise-induced changes in both plasma free and total noradrenaline concentrations.

Adult↗
PubMed1993

Electrical stimulation partly reverses the muscle insulin resistance caused by tenotomy.

It was shown that 15-min electrical stimulation of the rat sciatic nerve greatly increases the in vitro measured sensitivity of lactate formation, glucose transport, and glycogen synthesis to insulin, impaired by previous tenotomy. The insulin sensitivity of all these processes was, however, still below that found in the stimulated intact soleus muscle. Extending the stimulation up to 30 min did not cause any further changes in insulin sensitivity either in tenotomized or in intact muscles.

Achilles Tendon↗
PubMed1993

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.

Anaerobic Threshold↗
PubMed1993

Effect of phosphate supplementation on metabolic and neuroendocrine responses to exercise and oral glucose load in obese women during weight reduction.

Thirty six obese women (BMI 29.5 to 44.0 kg m-2, aged 27 to 45 yrs) participated in the 4- week weight reducing program. All of them have prescribed low fat diet of approx. 4.2 MJ (1000 kcal per day) with high viscous fibre capsules as a basic supplement. In addition 18 women (group 1) received Redusan mineral tablets containing mainly calcium and potassium phosphates while the remaining subjects (group 2) were given Placebo instead of mineral tablets. Before energy restriction and after 4 weeks on the diet, half of the women from each group performed 30 min--bicycle ergometer exercise (30-50 W; HR approx. 110 beats.min-1). The remaining subjects were submitted to oral glucose (75 g) tolerance test (OGTT). Weight loss during energy restriction was not affected by phosphate supplementation (4.6 +/- 0.4 and 5.2 +/- 0.5 kg in group 1 and 2, respectively). Phosphates caused a significant increase (p < 0.05) in the resting metabolic rate (RMR). Net energy cost of work, resting and post-exercise blood glucose, lactate, plasma FFA, adrenalin, cortisol, growth hormone, insulin and testosterone did not differ between the groups receiving phosphates and placebo while respiratory exchange ratio was slightly higher (p < 0.05), and the plasma beta-hydroxybutyrate concentration lower (p < 0.05) than without phosphate supplementation. Post-exercise plasma noradrenaline was significantly lowered after 4 weeks of energy restriction in group 2 (on Placebo). Neither blood glucose, plasma insulin and noradrenaline responses to oral glucose ingestion nor the glucose induced thermogenesis were significantly affected by phosphate supplementation, whilst blood pressure increases following glucose load were reduced (p < 0.05). In conclusion, the present study confirmed a potential usefulness of phosphate supplementation during energy restriction in obese patients due to its effect on resting metabolic rate. The results did not, however, reveal any major alterations in the metabolic and hormonal responses to exercise or to glucose ingestion in comparison with placebo treatment.

Adult↗
PubMed1993

Muscle mitochondrial density after exhaustive exercise in dogs: prolonged restricted activity and retraining.

The effect of exhaustive treadmill exercise on mitochondrial density (MD) and ultrastructural changes in quadriceps femoris muscle was studied in 7 normal, healthy, male mongrel dogs (2-4 years, 15-20 kg) before and after restricted activity (RA) (2 months for 5 dogs, 5 months for 2 dogs), and following a subsequent 2-month exercise retraining period (2-months group). Mean (+/- S.E.) time to exhaustion in the 2-month group decreased from 177 +/- 11 min before to 90 +/- 16 min (delta = -49%, p < 0.05) after RA; retraining increased tolerance to 219 +/- 36 min (delta = +24%, p < 0.05) above the pre-RA and 143% (p < 0.05) above the post-RA time. Post-RA exhaustion time in the 5-months group was 25 and 45 min (35 +/- 10 min). Muscle samples taken after RA showed abnormalities indicative of degeneration, which were reversed by retraining. Resting MD decreased (p < 0.05) from a control level of 27.8% to 14.7% (2 months) and 16.3% (5 months), and was restored to 27.1% (NS) after retraining. Exhaustive exercise caused an increase in MD under control conditions and after RA, but not following retraining. Disruption of mitochondria after exercise was evident after 5-months confinement. Factors causing mitochondrial changes and eventually their disruption during exercise after restricted activity are not related as much to the state of fatigue as to the pre-exercise quality of the muscle modified by disease or training.

Animals↗
PubMed1992

Metabolic, body temperature and hormonal responses to repeated periods of prolonged cycle-ergometer exercise in men.

This study was designed to find out whether rest intervals and prevention of dehydration during prolonged exercise inhibit a drift in metabolic rate, body temperature and hormonal response typically occurring during continuous work. For this purpose in ten healthy men the heart rate (fc), rectal temperature (Tre), oxygen uptake (VO2), as well as blood metabolite and some hormone concentrations were measured during 2-h exercise at approximately 50% maximal oxygen uptake split into four equal parts by 30-min rest intervals during which body water losses were replaced. During each 30-min exercise period there was a rapid change in Tre and fc superimposed on which, these values increased progressively in consecutive exercise periods (slow drift). The VO2 showed similar changes but there were no significant differences in the respiratory exchange ratio, pulmonary ventilation, mechanical efficiency and plasma osmolality between successive periods of exercise. Blood glucose, insulin and C-peptide concentrations decreased in consecutive exercise periods, whereas plasma free fatty acid, glycerol, catecholamine, growth hormone and glucagon concentrations increased. Blood lactate concentrations did not show any regular drift and the plasma cortisol concentration decreased during the first two exercise periods and then increased. In conclusion, in spite of the relatively long rest intervals between the periods of prolonged exercise and the prevention of dehydration several physiological and hormonal variables showed a distinct drift with time. It is suggested that the slow drift in metabolic rate could have been attributable in the main to the increased concentrations of heat liberating hormones.

Adult↗
PubMed1992

Relationship between plasma ammonia and blood lactate concentrations after maximal treadmill exercise in circumpubertal girls and boys.

The purpose of the study was to define a relationship between plasma ammonia [NH3]pl and blood lactate concentrations [la-]b after exercise in children and to find out whether the [NH3]pl, determined during laboratory treadmill tests, may be useful as a predictor of the children's sprint running ability. A group of 20 girls and 14 boys trained in athletics or swimming and 8 untrained boys, aged 13.2 to 13.7 years, participated in the study. Their [NH3]pl and [la-]b were measured before and after incremental maximal treadmill exercise. In addition, the subjects' running performance was tested in 30-, 60- and 600- or 1000-m runs under field conditions. The [NH3]pl during the treadmill runs increased by 20.1 (SD 17.3), 24 (SD 16.7) and 10 (SD 4.3) mumol.l-1 in the girls, the trained boys and the untrained boys, respectively. The postexercise [NH3]pl correlated positively with [la-]b (r = 0.565 in the girls and 0.812 in the boys) and treadmill speed attained during the test (r = 0.489 in the girls and 0.490 in the boys). Significant correlations were also found between [NH3]pl obtained during the treadmill test and the times of 30- and 60-m runs (r = -0.676 and -0.648, respectively) in the boys but not in the girls. A comparison of the present data with those reported previously in adults showed that increases in [NH3]pl during maximal exercise in children would seem to be lower than in adult subjects both in absolute values and in relation to [la-]b.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗