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  • 1
    Electronic Resource
    Electronic Resource
    Peripheral and central short-term effects of fusaric acid, a DBH inhibitor, on tryptophan and serotonin metabolism in the rat (1986)
    Springer
    Journal of neural transmission 65 (1986), S. 219-232 
    Details
    ISSN: 1435-1463
    Keywords: Fusaric acid ; dopamineΒ-hydroxylase ; tryptophan ; serotonin ; 5-hydroxyindoleacetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fusaric acid (FA) administration to the rats promoted one hour later a large decrease in plasma total tryptophan (TRP), without affecting either plasma free TRP or lipolysis, as measured by plasma non esterified fatty acid concentration. The previous change was associated with hypoinsulinemia, hyperglycemia and increased plasma corticosterone level. Regression analysis revealed a significant correlation between brain TRP and the percentage of plasma TRP which was free (i.e. unbound to albumin), both increased by FA injection. The increase in brain TRP promoted an increased brain serotonin synthesis, as measured by the enhanced brain and CSF 5-HIAA levels. Valine pretreatment, which blocks TRP entry into the brain, completely prevented FA-induced brain TRP and brain 5-HIAA increases. These results suggest that the increased brain serotonergic turnover following FA treatment was due to a peripheral action of the drug upon TRP disposition. The latter effect may be caused (i) byin vivo peripheral alterations in catecholaminergic metabolism and (ii) by FA chemical structure sincein vitro experiments revealed that FA was able to displace TRP binding to albumin, thus increasing the plasma free TRP pool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01249084
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolic effects of testosterone during prolonged physical exercise and fasting (1984)
    Springer
    European journal of applied physiology 52 (1984), S. 300-304 
    Details
    ISSN: 1439-6327
    Keywords: Prolonged physical exercise ; Fasting ; Testosterone ; Proteolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous studies have shown a decrease in plasma testosterone during prolonged physical exercise and 72 h fasting in rats. To determine whether this hormonal change has an influence upon energy metabolism, two experiments were carried out, in which the plasma levels of testosterone were elevated during prolonged physical exercise and fasting in male wistar rats. The effects of acute and chronic increases in the levels of circulating testosterone were studied, on the one hand after human chorionic gonadotropin (H.C.G.) injection, and on the other by prolonged testosterone perfusion with an osmotic minipump. Blood and tissue sampling were performed to evaluate blood glucose, alanine, and lactate, and tissue glycogen. The results in fed and rest control rats showed no changes in blood parameters under the effect of hypertestosteronemia but there was an increase in muscle glycogen after testosterone perfusion. In 72 h fasted rats both types of hypertestosteronemia were associated with a decrease in blood alanine and lactate ranging from 25% to 35%. Only testosterone perfusion was associated with higher concentrations of muscle glycogen. After 7 h of treadmill running, testosterone perfusion and H.C.G. injection induced a 35% decrease in blood alanine and a slight decrease in blood glucose, with no change in other parameters. Whereas an elevation in the level of testosterone can induce muscle glycogen compensation in the fed resting state, it cannot counteract the exhaustion of muscle glycogen during running.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01015214
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  • 3
    Electronic Resource
    Electronic Resource
    Muscle damage induced by running training during recovery from hindlimb suspension: the effect of dantrolene sodium (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 421-427 
    Details
    ISSN: 1439-6327
    Keywords: Key words Unloading ; Degeneration ; Muscle regeneration ; Myosin heavy chain ; Calcium antagonist ; Running recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined the extent of morphological alterations and the myosin heavy chain (MHC) distribution in the rat soleus muscle after a 4-week period of spontaneous recovery or retraining after hindlimb suspension (HS). Moreover, we tested the hypothesis that dantrolene sodium, which affects the flux of calcium over the sarcoplasmic reticulum membrane, was able to attenuate muscle damage. Three groups of rats were submitted to 3 weeks of HS, followed by either 4 weeks of unrestricted cage activity (HC, n = 7), or running training for the same period and were compared to age-matched animals (C, n = 8). Trained rats were treated with either placebo or dantrolene sodium (HTP, HTD, n = 8 each, respectively). Four weeks after HS recovery, the percentage of myofibres with internal nuclei (%in) was determined by histological staining with hematoxylin and eosin. %in was affected by the individual rat (P 〈 0.001), and was higher in the mid-belly region of the muscle (P 〈 0.05). Muscle damage, as estimated by %in, was more extensive in trained rats (i.e. HTP and HTD) than in HC animals (23% and 12%, respectively). Moreover, dantrolene sodium tended to exert a protective effect on training-induced muscle injury. A 12% increase in type I MHC was observed in both HTP and HTD rats, in comparison with group C animals (P 〈 0.001). The relative proportion of type-I MHC was inversely correlated with %in (r = −0.65, P 〈 0.001). Running recovery led to an increased citrate synthase activity in comparison with that of C or HC rats. In conclusion, the present findings demonstrate that running recovery from HS increases the incidence of muscle damage, and that dantrolene sodium administration has only limited protective effects against exercise-induced muscle injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050271
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of prolonged physical exercise and fasting upon plasma testosterone level in rats (1982)
    Springer
    European journal of applied physiology 49 (1982), S. 159-168 
    Details
    ISSN: 1439-6327
    Keywords: Prolonged physical exercise ; Fasting ; Plasma steroids ; Glycogen stores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Prolonged physical exercise and fasting in male rats were studied to determine the effect of these two treatments on plasma testosterone level. Blood and tissue samples were drawn after 1 h, 3 h, 5 h, and 7 h treadmill running, and after 24 h, 48 h, and 72 h of fasting. Both treatments resulted in a significant fall in plasma testosterone, plasma luteinizing hormone (LH), plasma Insulin (IRI) and in liver and muscle glycogen stores. In the course of these two treatments the injection of a supra maximal dose of Human Chorionic Gonadotropin (HCG) produced a rise in plasma testosterone similar to that in control rats. This indicates that the decrease of plasma LH may be responsible for the decrease in plasma testosterone, which is time-related with the decrease in glycogen stores. The possible metabolic role of the decrease in plasma testosterone is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02334064
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  • 5
    Electronic Resource
    Electronic Resource
    Hormonal and metabolic response to physical exercise, fasting and cold exposure in the rat (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 114-119 
    Details
    ISSN: 1439-6327
    Keywords: Prolonged physical exercise ; Fasting ; Cold exposure ; Ketogenesis ; Pancreatic hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four groups of rats were subjected to the following conditions: (1) 48 h fasting, (2) 48 h of 4°C cold exposure, (3) 5 h treadmill running, (4) 48 h fasting with 4°C cold exposure. The groups were compared to fed control rats in order to study hormonal and metabolic responses in blood and tissue samples. Isolated hepatocytes were used to evaluate the rate of ketogenesis. Decreases in liver glycogen and increases in blood free fatty acids (FFA) confirmed that glycogenolysis and lipolysis occur in these situations of metabolic stress. Increases in the glucagon/insulin plasma ratio were also noted. Plasma catecholamine levels were only enhanced after running and after cold exposure. Production of blood ketone bodies was stimulated more by running and by fasting than by cold exposure. The low ketone body production observed after cold exposure seems to be linked to increases liver glycogen levels and decreased FFA availability. Liver cells isolated after cold exposure exhibited higher ketogenesis than these isolated after running. This difference in ketogenic capacity could result both from the longer hormonal stimulation by high glucagon/insulin plasma ratios and from the metabolic state of the liver.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00691249
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of Growth hormone on rat skeletal muscle after hindlimb suspension (1994)
    Springer
    European journal of applied physiology 69 (1994), S. 337-343 
    Details
    ISSN: 1439-6327
    Keywords: Growth hormone ; Hindlimb suspension ; Muscle atrophy ; Pituitary-intact rats ; Soleus muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To examine the effects of growth hormone (GH) on the preferential atrophy of the soleus muscle (SOL) occurring after hindlimb suspension (HS), two groups of male rats received daily injections of 2 IU · kg −1 body mass of recombinant human growth hormone (rhGH). Rats were either suspended by the tail for 21 days (HS-GH, n = 5) or nonsuspended (CGH, n=5). The effects of rhGH treatment on SOL and extensor digitorum longus muscles (EDL) were compared in two groups of animals receiving daily injections of saline, either suspended by the tail (HS-SA, n = 5) or nonsuspended (C-SA, n = 5). The results showed that the SOL hypertrophy in response to rhGH administration was mostly observed in C rats (+33%, P〈0.01). This increase in muscle mass was correlated with a concomitant increase in the size of type I fibres (+21%, P〈0.05). Although SOL mass decreased during HS in rhGH treated animals (−44%, P〈0.001), the mean normalized mass of this muscle did not significantly differ between C-SA and HS-GH groups. A statistically significant increase in the absolute mass of EDL occurred with rhGH treatment in CGH (+12%, P〈0.05). The HS-induced decrease in the percentage distribution of type I fibres in SOL was unaffected by the rhGH treatment. In addition, a decrease in the citrate synthase activity in the whole SOL was observed in the two groups of tail-suspended rats (−31%, P〈0.05; −21%, P〈0.05 in SA and GH animals, respectively). The activity of 3-hydroxyacyl coenzyme A dehydrogenase was enhanced by the rhGH treatment (P〈0.05) with similar magnitude in both C (+25%) and HS rats (+24%). Therefore, GH prevented only slightly the atrophy of SOL, occurring after 21 days of HS. The effects of rhGH treatment appeared most effective in C rats, suggesting that HS impaired the growth-promoting effects of this hormone on skeletal muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392040
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of chronic low frequency stimulation on structural and metabolic properties of hindlimb suspended rat soleus muscle (1995)
    Springer
    European journal of applied physiology 70 (1995), S. 528-535 
    Details
    ISSN: 1439-6327
    Keywords: Hindlimb suspension ; Chronic low ; frequency stimulation ; Fibre type composition ; Immunohistochemistry ; Biochemical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The use of chronic low frequency stimulations (CLFS, 10 Hz bipolar current 8 h · day−1) as a countermeasure against unweighting-induced muscle alterations was investigated in rat soleus muscle during 21 days of hindlimb suspension (HS). It was shown that CLFS was able to minimize the soleus muscle atrophy induced by suspension (−29% in stimulated muscles compared to −56% in the non-stimulated soleus muscle). In parallel, CLFS partly prevented the HS-induced decreases in the cross-sectional area of type I fibres and in the total and myofibril protein contents. Stimulation at low frequency reduced the increase in the fast-myosin expression recorded with unweighting. Moreover, the HS-induced increase in glycolytic capacity was counteracted to a considerable extent by CLFS. In conclusion, the results of this study showed that CLFS can only partly prevent the HS-induced modifications in the soleus muscle. However, the limited effectiveness of CLFS to prevent muscle atrophy emphasized the critical role of reduced load bearing in the induction of solens muscle atrophy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634382
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative assessment of degenerative changes in soleus muscle after hindlimb suspension and recovery (1997)
    Springer
    European journal of applied physiology 75 (1997), S. 380-387 
    Details
    ISSN: 1439-6327
    Keywords: Key words Unloading  ;  Degeneration  ;  Muscle regeneration  ;  Muscle fibre necrosis  ;  Myosin heavy chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to quantify the degenerative and regenerative changes in rat soleus muscle resulting from 3-week hindlimb suspension at 45° tilt (HS group, n = 8) and 4-week normal cage recovery (HS-R group, n = 7). Degenerative changes were quantified by microscope examination of muscle cross sections, and the myosin heavy chain (MHC) composition of soleus muscles was studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis. At the end of 3-week hindlimb suspension, histological signs of muscle degenerative changes were detected in soleus muscles. There was a significant variability in the percentage of fibres referred to as degenerating (%dg) in individual animals in the HS group [%dg = 8.41 (SEM 0.5)%, range 4.66%–14.08%]. Moreover, %dg varied significantly along the length of the soleus muscle. The percentage of fibres with internal nuclei was less than %dg in HS-soleus muscles [4.12 (SEM 0.3)%, range 1.24%–8.86%]. In 4-week recovery rats, the greater part of the fibres that were not referred to as normal, retained central nuclei [15.8 (SEM 2.2)%, range 6.2%–21.1%]. A significant increase in the slow isoform of MHC was recorded in the HS-R rats, compared to muscles from age-matched rats (P 〈 0.01). These results would suggest that a cycle of myofibre degeneration-regeneration occurred during HS and passive recovery, and that the increased accumulation of slow MHC observed in soleus muscles after recovery from HS could be related to the prevalence of newly formed fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050176
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