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  • 1
    Electronic Resource
    Electronic Resource
    In vivo insulin resistance during pregnancy in the rat (1980)
    Springer
    Diabetologia 19 (1980), S. 521-528 
    Details
    ISSN: 1432-0428
    Keywords: Pregnant rat ; insulin resistance ; glucose tolerance ; glucose production ; glucose utilization ; glucose turnover ; insulin sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The glucose disappearance rate measured after IV glucose injection (1 g/kg body wt) remained unchanged between 12 and 21 day of gestation in the rat. In contrast, insulin secretion in response to IV glucose was markedly increased on day 19 and 21 of pregnancy, suggesting resistance to endogenous insulin. Glucose kinetics (glucose production, utilization and clearance) in response to various doses of IV insulin have been studied in anaesthetised postabsorbtive 19 day pregnant and virgin rats using 6-3H glucose. With the supramaximal dose of insulin (4 U/kg body wt) no differences in glucose kinetics were found between pregnant and virgin rats. In contrast, with the two lower doses of insulin (0.15 and 0.05 U/kg body wt) glucose production was inhibited by 36±3% and 13±2% (Mean±SEM) respectively in virgin rats, but was not decreased in pregnant rats. When the effect of insulin on glucose clearance was expressed as % of the maximal effect obtained with 4 U/kg body weight, the rise in glucose clearance in response to the two lower doses of insulin (0.15 and 0.05 U/kg body wt) was lower in pregnant (57.5±6 and 27.4±4%) than in virgin rats (73.3±6 and 42.2±7%). These results suggest that a decreased sensitivity to insulin appears in late pregnancy in the rat and could involve both liver and skeletal muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253179
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of GABA-transaminase inhibition on brain metabolism and amino-acid compartmentation: an in vivo study by 2D 1H-NMR spectroscopy coupled with microdialysis (1999)
    Springer
    Experimental brain research 127 (1999), S. 321-327 
    Details
    ISSN: 1432-1106
    Keywords: Key words Gabaculine ; NMR spectroscopy ; Microdialysis ; Amino acids ; Compartmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The aim of this work was to study the neurochemical effects in the brain of GABA-transaminase inhibition by systemic administration of gabaculine (100 mg/kg, i.a.) in the rat. In order to investigate neurotransmitter and related amino-acid compartmentation and metabolism, we have developed an original tool: the coupling, in vivo, on the same animal, of 2D COSY 1H-NMR spectroscopy with intracerebral microdialysis. The main result is a continuous increase in GABA levels, both in the intracellular compartment (up to 3000±450%; P〈0.001) and extracellular compartment (up to 808±82%; P〈0.01) at the sixth hour. The intracellular increase in GABA level became significant at the first hour following gabaculine administration, whereas the extracellular level increased as of the second hour, probably indicating that accumulation of GABA in nerve endings precedes its release in synaptic clefts. Moreover, the levels of the excitatory amino acids, glutamate and aspartate, were decreased both in the intra- and extracellular compartments, thus enhancing sedative effects of the drug. We also observed a decrease in the global energetic creatine-phosphocreatine pool, which also could be related to the sedative properties of gabaculine, measurable by the diminution of cortical electrical activity and mean arterial blood pressure. Finally, the coupling between 2D 1H-NMR spectroscopy and intracerebral microdialysis appears to be an original tool for investigating the cerebral metabolic effects induced by pharmacological agents, in situ, in living animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050802
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  • 3
    Electronic Resource
    Electronic Resource
    Post-exercise glycogen resynthesis in trained high-protein or high-fat-fed rats after glucose feeding (1989)
    Springer
    European journal of applied physiology 58 (1989), S. 591-595 
    Details
    ISSN: 1439-6327
    Keywords: Fat and protein feeding ; Glucose feeding ; Glycogen resynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study examined the effect on glycogen resynthesis during recovery from exercise of feeding glucose orally to physically trained rats which had been fed for 5 weeks on high-protein low fat (HP), high-protein/long-chain triglyceride (LCT) or high carbohydrate (CHO) diets. Muscle glycogen remained low and hepatic gluconeogenesis was stimulated by long-term fat or high-protein diets. The trained rats received, via a stomach tube, 3 ml of a 34% glucose solution immediately after exercise (2 h at 20 m · min−1), followed by 1ml portions at hourly intervals until the end of the experiments. When fed glucose soleus muscle glycogen overcompensation occurred rapidly in the rats fed all three diets following prolonged exercise. In LCT- and CHO-fed rats, glucose feeding appeared more effective for soleus muscle repletion than in HP-fed rats. The liver demonstrated no appreciable glycogen overcompensation. A complete restoration of liver glycogen occurred within a 2- to 4-h recovery period in the rats fed HP-diet, while the liver glycogen store had been restored by only 67% in CHO-fed rats and 84% in LCT-fed rats within a 6-h recovery period. This coincides with low gluconeogenesis efficiency in these animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418504
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  • 4
    Electronic Resource
    Electronic Resource
    Physical performance and metabolic changes induced by combined prolonged exercise and different energy intakes in humans (1994)
    Springer
    European journal of applied physiology 68 (1994), S. 525-530 
    Details
    ISSN: 1439-6327
    Keywords: Diet ; Prolonged exercise ; Physical performance ; Metabolism ; Undereating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to evaluate the effects on physical performance of three levels of energy intake during a 5-day period of prolonged physical exercise and relative sleep deprivation. A group of 27 male soldiers were randomly assigned to three groups receiving either 1800 kcal · 24 h−1 (7560 kJ, LC), 3200 kcal · 24h−1 (13440 kJ, MC) or 4200 kcal-24h−1 (17640 kJ, HC). They took part in a 5-day combat course (CC) of heavy and continuous physical activities, with less than 4 h sleep per day. Performance capacity was tested just before and at the end of CC. Maximal oxygen uptake ( $$\dot V$$ O2max) was determined during an exhausting incremental exercise test on a cycle ergometer. Anaerobic performance was measured from the time during which exercise could be maintained at supra maximal loads on a cycle ergometer. After CC, the subjects receiving LC exhibited a 14% decrease in power output at exhaustion in the incremental exercise test [from 325 (SEM 8) to 278 (SEM 9) W,P 〈 0.001] and a significant decrease in $$\dot V$$ O2max of 8% [from 3.74 (SEM 0.06) to 3.45 (SEM 0.05) l · min−1,P〈0.05]. The remaining two experimental groups demonstrated the same mechanical and metabolic performances on days 1 and 5. Anaerobic performance was not influenced by energy intake and the field course. Blood samples were obtained at rest on days 1 and 5. At the end of CC, the data demonstrated a significant decrease in blood glucose concentrated ion (P〈0.01) for LC diet only. Plasma free fatty acid, blood glycerol and β-OH butyrate were significantly increased in all groups, from day 1, but the values observed for LC were higher than those for the MC and HC diets. The concentrations of the anabolic hormones, insulin and testosterone, decreased in the three groups, the lowest values being observed in the LG group (P 〈 0.05). In conclusion, we found that only a severe energy deficit decreased physical performance during submaximal exercise. A moderate deficit between energy intake and expenditure did not affect performance. Supramaximal exercise did not appear to be influenced by energy intake and CC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00599524
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  • 5
    Electronic Resource
    Electronic Resource
    Metabolic effects of glucose, medium chain triglyceride and long chain triglyceride feeding before prolonged exercise in rats (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 126-131 
    Details
    ISSN: 1439-6327
    Keywords: Glucose and fat feeding ; Glycogen sparing ; Ketone bodies ; Insulin ; Lipolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to test the hypothesis that oral ingestion of lipids could increase endurance by slowing the rate of glycogen depletion. Trained rats were killed after a 2 h run on a rodent treadmill, following an intragastric infusion of water, glucose, medium chain triglycerides (MCT) or long chain triglycerides (LCT). Glucose and triglycerides were administered in equicaloric concentrations (50 kJ). The results show that oral ingestion of lipids (MCT or LCT) did not reduce glycogen depletion in liver, heart or skeletal muscle after exercise whereas the fat diet increased muscle and heart glycogen stores in resting conditions. In contrast, glucose feeding induced a significant sparing effect on endogenous carbohydrate utilization and reduced physical exercise lipolysis. These data indicated, firstly, that enhanced lipid availability induced by a single lipid meal before exercise was not able to modify the glycogen depletion occuring after exercise and, secondly, that the glucose/fatty acid cycle was not effective in these conditions. The comparison between lipids indicated that the effect on glycogen use of MCT did not differ from that of LCT, and did not seem to be of any particular importance during physical exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00691251
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of long-term feeding of high-protein or high-fat diets on the response to exercise in the rat (1989)
    Springer
    European journal of applied physiology 58 (1989), S. 583-590 
    Details
    ISSN: 1439-6327
    Keywords: Fat feeding ; Exercise ; Glycogen ; Gluconeogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this work was to find by which mechanisms an increased availability of plasma free fatty acids (FFA) reduced carbohydrate utilization during exercise. Rats were fed high-protein medium-chain triglycerides (MCT), high-protein long-chain triglycerides (LCT), carbohydrate (CHO) or high-protein low-fat (HP) diets for 5 weeks, and liver and muscle glycogen, gluconeogenesis and FFA oxidation were studied in rested and trained runner rats. In the rested state the hepatic glycogen store was decreased by fat and protein feeding, whereas soleus muscle glycogen concentration was only affected by high-protein diets. The percentage decrease in liver and muscle glycogen stores, after running, was similar in fat-fed, high-protein and CHO-fed rats. The fact that plasma glucose did not drastically change during exercise could be explained by a stimulation of hepatic gluconeogenesis: the activity of phosphoenolpyruvate carboxykinase (PEPCK) and liver phosphoenolpyruvate (PEP) concentration increased as well as cyclic adenosine monophosphate (AMPc) while liver fructose 2,6-bisphosphate decreased and plasma FFA rose. In contrast, the stimulation of gluconeogenesis in rested HP-, MCT- and LCT-fed rats appears to be independent of cyclic AMP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418503
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of protein supplementation during prolonged exercise at moderate altitude on performance and plasma amino acid pattern (1993)
    Springer
    European journal of applied physiology 66 (1993), S. 5-10 
    Details
    ISSN: 1439-6327
    Keywords: Repeated endurance exercise ; Moderate altitude ; Protein ; Free amino acids ; Protein supplementation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of two levels of protein intake on muscle performance and energy metabolism were studied in humans submitted to repeated daily sessions of prolonged exercise at moderate altitude. For this purpose, 29 healthy males, were exposed to seven successive stages of ski-mountaineering at altitudes between 2500 and 3 800 m, and to an isocaloric diet (4000 kcal·day−1, 16760 kJ·day−1) with either 1.5g·kg−1·day−1 (C group,n =14), or 2.5 g·kg−1·day−1 (PR group,n =15) protein intake. Measurements made after the ski-mountaineering programme did not show any change in body mass. The peak torque during maximal isometric voluntary contraction (MVC) of the quadriceps muscle was unaffected by the repeated exercises, whereas the endurance time at 50% MVC was decreased in PR subjects (−26.8%,P〈0.001). Increased levels of both free fatty acids (+147%,P〈0.001) and glycerol (+170%,P〈0.001) observed in C subjects would suggest that lipolysis was enhanced after the repeated exercise. The plasma amino acid pattern was altered after completion of the ski-mountaineering programme; the plasma concentration of the three branched-chain amino acids (BCAA) was significantly decreased in C subjects, whereas the higher level of protein intake (PR group) greatly minimized the exercise-induced decrease in serum BCAA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863392
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