摘要:

PALMER, W. K. Introduction to the symposium: cyclic AMP regulation of fuel metabolism during exercise.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 523–524, 1988. The actions of a number of hormones on cells are mediated through the plasma membranes that produce intracellular “second” messengers. The physiological functions of one of these messengers, cyclic AMP, have been well characterized in a variety of cell types. Since cyclic AMP mediates the action of β-adrenergic hormones, hormones thought to play a significant role during exercise, this symposium is directed toward summarizing what is known about the role of cyclic AMP in fuel metabolism during exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

PALMER, W. K. Effect of exercise on cardiac cyclic AMP.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 525–530, 1988. The effect of one bout of intense swimming caused significant increases in the cyclic AMP content of fast-twitch white skeletal muscle, liver, and heart. Further investigation of the exercise-induced increase in myocardial cyclic AMP indicates that the nucleotide content remained elevated long after (24 h) termination of exercise. This increase in cyclic AMP was time dependent, with the level increasing gradually throughout the work bout. The increase in cardiac cyclic AMP seemed to be independent of work intensity, provided that work time was of sufficient duration (≥30 min). Increases in cardiac cyclic AMP were also seen when rats were exposed to 2°C for 1–7 d. The increases in cyclic AMP seen following exercise and cold exposure were accompanied by an increase in cardiac cyclic AMP phosphodiesterase (PDE) activity. Our working hypothesis was that prolonged elevations in cyclic AMP produced an induction and/or activation of one or more of the PDE isozymes. When we administered dibutyryl cyclic AMP to rats, cardiac PDE activity was increased. This increase was inhibited by cycloheximide, suggesting that the elevated enzyme activity is mediated by the synthesis of new protein. These data support the concept that cyclic AMP is involved in the regulation of its own metabolism during physiological stress.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

SHEPHERD, R. E. and M. D. BAH. Cyclic AMP regulation of fuel metabolism during exercise: regulation of adipose tissue lipolysis during exercise.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 531–538, 1988. Adipocytes from trained rats release more free fatty acids in response to hormonal challenge compared to fat cells from sedentary rats. Lipolysis results from increased triglyceride hydrolysis that is catalyzed by a hormone-sensitive lipase, which, in turn, is activated by a phosphorylation mechanism involving cyclic AMP-dependent protein kinase. Cyclic AMP levels within the fat cell are regulated by beta-adrenergic receptor/adenylate cyclase interactions and cyclic AMP phosphodiesterase activity. This review focuses on cyclic AMP regulation of lipolysis in adipocytes from trained and sedentary animals. Although lipolysis is elevated in fat cells from trained rats, no differences are found in beta-adrenergic receptor number or affinity, adenylate cyclase activity, protein kinase activity, or partially purified hormone-sensitive lipase activity when compared to sedentary rats. The major lipolytic alteration induced by exercise training appears to occur at a site distal to hormonal regulation of the beta-adrenergic receptor.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

OSCAI, L. B., J. GORSKI, W. C. MILLER, and W. K. PALMER. Role of the alkaline TG lipase in regulating intramuscular TG content.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 539–544, 1988. Three TG lipases have been identified in muscle (i.e., acid, neutral, and alkaline), but as yet we do not know which enzyme is responsible for tissue TG hydrolysis. Over the past 8 yr, work in our laboratory has focused on intracellular lipoprotein lipase (LPL). The results show that this lipase is regulated by the classical cAMP cascade and that the activity of this enzyme is inversely related to endogenous TG concentration. Using these results as a foundation we plan to examine molecular mechanisms involved in the synthesis, compartmentalization, and transport of the alkaline TG lipase. Further, the evidence suggests that this enzyme may be regulated by protein phosphorylation mediated by cyclic AMP-dependent protein kinase. We plan to test this possibility

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

CHASIOTIS, D. Role of cyclic AMP and inorganic phosphate in the regulation of muscle glycogenolysis during exercise.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 545–550, 1988. The roles of cAMP and inorganic phosphate (Pi) in the regulation of muscle glycogenolysis during exercise have been investigated in humans using the needle biopsy technique. The fraction of phosphorylaseain resting muscle was as a mean 23%, but the rate of glycogenolysis was extremely low. Epinephrine infusion increased cAMP in muscle by 3-fold and transformed 80% of phosphorylase to theaform. Despite this, the rate of glycogenolysis was only 5–10% of the maximum rate of phosphorylaseaWINDER, W. W. Role of cyclic AMP in regulation of hepatic glucose production during exercise.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 551–560,1988. Cyclic AMP increases in liver during exercise, the magnitude of the increase being dependent on duration and intensity of the exercise. Within limits, the increase in cAMP is closely correlated with the rate of glycogenolysis and with the exercise intensity. It is unlikely that epinephrine is involved in determining cAMP concentration in liver during exercise. Adrenodemedullated rats show no impairment in exercise-induced liver glycogenolysis or in the increase in cAMP. When epinephrine is infused at different rates into exercising rats, liver cAMP appears to be unrelated to plasma epinephrine. The rise in plasma glucagon is likely responsible for the increase in hepatic cAMP during exercise. The increase in cAMP is apparently necessary for maintaining low levels of fructose-2,6-bisphosphate (the activator of PFK-1 and inhibitor of fructose-1,6-bisphosphate) in liver. The low fructose-2,6-bisphosphate concentration would be expected to result in an increase rate of gluconeogenesis during exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

WINDER, W. W. Role of cyclic AMP in regulation of hepatic glucose production during exercise.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 551–560,1988. Cyclic AMP increases in liver during exercise, the magnitude of the increase being dependent on duration and intensity of the exercise. Within limits, the increase in cAMP is closely correlated with the rate of glycogenolysis and with the exercise intensity. It is unlikely that epinephrine is involved in determining cAMP concentration in liver during exercise. Adrenodemedullated rats show no impairment in exercise-induced liver glycogenolysis or in the increase in cAMP. When epinephrine is infused at different rates into exercising rats, liver cAMP appears to be unrelated to plasma epinephrine. The rise in plasma glucagon is likely responsible for the increase in hepatic cAMP during exercise. The increase in cAMP is apparently necessary for maintaining low levels of fructose-2,6-bisphosphate (the activator of PFK-1 and inhibitor of fructose-1,6-bisphosphate) in liver. The low fructose-2,6-bisphosphate concentration would be expected to result in an increase rate of gluconeogenesis during exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

HAMILTON, L. H., J. BROOKS-GUNN, M. P. WARREN, and W. G. HAMILTON. The role of selectivity in the pathogenesis of eating problems in ballet dancers.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 560–565, 1988. Forty-nine dancers from four national ballet companies in America (N= 32) and the People's Republic of China (N= 17) were surveyed (mean age, 24.6 ± 4.18) from highly and moderately selective dance companies. The less selected American dancers reported significantly more eating problems (46% vs 11%;P< 0.05), anorectic behaviors (2.77 vs 1.11;P< 0.05), and familial obesity (42% vs 5%;P< 0.05) than the Americans chosen from a company school. Differences were not found on these variables between the highly selected American and Chinese dancers. All of the groups reported a delay in menarche and weighed approximately 14% below their ideal weight for height. These data suggest that dancers who have survived a stringent process of early selection may be more naturally suited to the thin body image demanded by ballet and so less at risk for the development of eating problems. In addition, delayed menarche is typical of the majority of national dancers and probably is reflective of genetic and environmental factors.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

HORSWILL, C. A., D. L. COSTILL, W. J. FINK, M. G. FLYNN, J. P. KIRWAN, J. B. MITCHELL, and J. A. HOUMARD. Influence of sodium bicarbonate on sprint performance: relationship to dosage.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 566–569, 1988. The purpose of this investigation was to determine the minimum oral dosage of bicarbonate needed to significantly elevate blood bicarbonate and the influence of induced alkalosis on performance in high-intensity, short-duration exercise. Nine endurance-trained cyclists performed four 2-min sprints on separate occasions using an isokinetic cycle ergometer (Fitron, Cybex, Inc.). One hour before each test, the cyclists consumed either a placebo (A), a solution of 0.10 g NaHCO3·kg-1body weight (B), a solution of 0.15 g NaHCO3·kg-1body weight (C), or a solution of 0.20 g NaHCO3·kg-1body weight (D) in random order. Arterialized venous blood was taken before (PRE) and after (POST) ingestion, and 1, 3, 5, 10, and 15 min following the 2-min bike sprint. The results showed a significant increase in POST blood bicarbonate, and the elevation was incrementally related to the dosage. There was, however, no significant improvement in performance. Total work (mean ± SE) for each treatment (N·m per 2 min) were: A, 47,267(±2,472); B, 47,004(± 3,094); C, 46,312(±2,964); and D, 47,190(±2,621). The results of this study show that incremental doses of NaHCO3of 0.20 g·kg-1and below produce incremental elevations in blood bicarbonate but do not produce improvements in performance for a sprint bout lasting 2 min.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

JILKA, S. M., M. J. JOYNER, J. M. NITTOLO, J. K. KALIS, J. A. TAYLOR, T. G. LOHMAN, and J. H. WILMORE. Maximal exercise responses to acute and chronic beta-adrenergic blockade in healthy male subjects.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 570–573, 1988. Conflicting data on the alterations in the maximal exercise response to beta blockade (BB) may be the result of differences in the length of time the subject has been on medication, i.e., hours vs days. The purpose of this study was to examine maximal exercise responses during acute and chronic administration of BB. Twenty-eight healthy males, 14 untrained (UT) and 14 involved in a personal training regimen (TR), performed maximal treadmill tests after 1 d and 9 d under three double-blind, randomized conditions: a placebo (PLAC), propranolol (PROP) 80 mg b.i.d., and atenolol (ATEN) 100 mg o.d. Maximal heart rate (HR), oxygen consumption (&OV0312;O2), ventilation (&OV0312;E), and treadmill time were significantly reduced by PROP and ATEN after an acute and chronic dose when compared to PLAC (P< 0.05) in both groups of subjects. Maximal HR was decreased more after 1 d of BB than after 9 d of BB with both PROP and ATEN in the UT subjects and with PROP only in the TR group. &OV0312;O2max, &OV0312;Emaxand treadmill time were also less attenuated after 9 d of BB; however, this trend did not reach statistical significance. The nonselective beta blocker, PROP, caused greater reductions in &OV0312;O2maxcompared to the selective beta blocker, ATEN, in both groups of subjects. These data indicate that, other than a small change in maximal HR, there is no difference in the exercise response to acute and chronic BB in normal and highly conditioned individuals.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

MAHLER, D. A. and A. HARVER. Prediction of peak oxygen consumption in obstructive airway disease.Med. Sci. Sports Exerc., Vol. 20, No. 6, pp. 574–578, 1988. The hypothesis of this study was that non-exercise variables can be used to reliably predict peak oxygen consumption (&OV0312;O2) in patients with obstructive airway disease (OAD). We also evaluated the impact of symptoms on exercise capacity. Selected predictor variables included age, lung function, respiratory muscle strength, gas exchange, and the Baseline Dyspnea Index (BDI). In 40 patients peak &OV0312;O2was 19.9 ± 8.7 (mean ± SD) ml·kg-1min-1during progressive, incremental exercise until limited by symptoms on a cycle ergometer. Multiple regression analysis yielded three significant predictors: forced expiratory volume in one second (FEV1), age, and BDI. Peak &OV0312;O2(ml·kg-1·min-1) = 5.5 (FEV1)-0.3 (age) + 0.8 (BDI) + 19.3 (R2= 0.79; SEE: 4.2 ml·kg-1min-1). Comparisons between patients who stopped exercise because of breathlessness (N= 14) and those who stopped because of leg fatigue (N= 18) showed that lung function, inspiratory muscle strength, and peak &OV0312;O2were significantly reduced in the former group compared to the latter. Peak exercise ventilation (&OV0312;E)/MW ratio was similar in the breathless (95.3 ± 23.8%) and leg fatigue (86.8 ± 20.3) groups, but peak heart rate (HR)/pred. HRmaxratio was significantly higher in the leg fatigue group (86.8 ± 12.6%) than in the breathless group (75.1 ± 8.6%) (P= 0.006). We conclude that lung function, age, and the clinical rating of breathlessness reliably predict peak &OV0312;O2in patients with symptomatic OAD. Moreover, peak exercise performance in OAD appears to be affected by different physiological factors which may be distinguished by the major symptom limiting exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID