scholarly journals Fructose 2,6-bisphosphate in rat skeletal muscle during contraction

1984 ◽  
Vol 223 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Y Minatogawa ◽  
L Hue
Keyword(s):  
Extensor Digitorum Longus ◽  
Fold Increase ◽  
Rat Skeletal Muscle ◽  
Low Frequencies ◽  
Contracting Muscle ◽  
Glycolytic Intermediates ◽  
Fructose 1,6 Bisphosphate ◽  
Frequency Of Stimulation ◽  
Stimulation Of

Fructose 2,6-bisphosphate and several glycolytic intermediates were measured in two rat muscles, extensor digitorum longus and gastrocnemius, which were electrically stimulated in situ. Both the duration and the frequency of stimulation were varied to obtain different rates of glycolysis. There was no relationship between fructose 2,6-bisphosphate content and the increase in tissue lactate in contracting muscle. However, in gastrocnemius stimulated at low frequencies (less than or equal to 5 Hz), there was a 2-fold increase in fructose 2,6-bisphosphate at 10s, followed by a return to basal values, whereas lactate increased only after 1 min of contraction. The concentrations of hexose 6-phosphates, fructose 1,6-bisphosphate and triose phosphates were all increased during the 3 min stimulation. During tetanus (frequencies greater than or equal to 10 Hz) fructose 2,6-bisphosphate was not increased, whereas glycolysis was maximally stimulated and resulted in an accumulation of tissue lactate, mostly from glycogen. The concentrations of hexose 6-phosphate increased continuously during the 1 min tetanus, whereas fructose 1,6-bisphosphate was increased at 10s and then decreased progressively. It therefore appears that fructose 2,6-bisphosphate does not play a role in the stimulation of glycolysis during tetanus; it may, however, be involved in the control of glycolysis when the muscles are stimulated at low frequencies for short periods of time.

The release of catecholamines from the adrenal medulla and its modulation by α2-adrenoceptors in the anaesthetized dog

1987 ◽  
Vol 65 (4) ◽  
pp. 550-557 ◽  
Author(s):  
Sylvain Foucart ◽  
Réginald Nadeau ◽  
Jacques de Champlain
Keyword(s):  
Electrical Stimulation ◽  
Adrenal Medulla ◽  
Plasma Concentrations ◽  
Splanchnic Nerve ◽  
Feedback Mechanism ◽  
Adrenal Vein ◽  
Low Frequencies ◽  
Negative Feedback Mechanism ◽  
Frequency Of Stimulation ◽  
Stimulation Of

The adrenal nerve of anaesthetized and vagotomized dogs was electrically stimulated (10 V pulses of 2 ms duration for 10 min) at frequencies of 1, 3, 10, and 25 Hz. There was a correlation between the frequency of stimulation and the plasma concentrations of epinephrine, norepinephrine, and dopamine in the adrenal vein, mainly after the 1st min of stimulation and the maximal concentration was reached sooner with higher frequencies of stimulation. Moreover, the relative percentage of catecholamines released in response to the electrical stimulation was not changed by the frequency of stimulation. To test the hypothesis that a local negative feedback mechanism mediated by α2-adrenoceptors exists in the adrenal medulla, the effects of the systemic administration of clonidine (α2-agonist) and yohimbine (α2-antagonist) on the concentrations of catecholamines in the adrenal vein were evaluated during the electrical stimulation of the adrenal nerve (5 V pulses of 2 ms duration for 3 min) at 3 Hz. Moreover, the effects of the systemic injections of more specific α2-agonist and antagonist (oxymetazoline and idazoxan) were tested on the release of catecholamines in the adrenal vein in response to electrical stimulation of the splanchnic nerve at 1 and 3 Hz frequencies. The injection of 0.5 mg/kg of yohimbine caused a significant increase in the concentrations of epinephrine and norepinephrine in the adrenal vein induced by the electrical stimulation of the adrenal nerve and the injection of 15 μg/kg of clonidine had no effects. In the second series of experiments, the injection of 2 μg/kg of oxymetazoline caused a significant decrease in the release of epinephrine and norepinephrine at 1 Hz, but similarly to clonidine, there were no changes at 3 Hz. In contrast, the release of epinephrine and dopamine in response to electrical stimulation of the splanchnic nerve was increased at 3 Hz after the injection of idazoxan, but not at 1 Hz. It is concluded that the adrenal medulla catecholamines secretion appears to be partly modulated by a presynaptic inhibitory mechanism that involves α2-adrenoceptors. The observation that agonists appear to be more efficient at low frequencies of stimulation while antagonists appear to be more efficient at higher frequencies could be explained by the possibility that adrenal medullary α2-receptors would be saturated at higher frequencies of stimulation.

scholarly journals The effects of myomodulin and structurally related neuropeptides on skeletal neuromuscular transmission in the locust.

1994 ◽  
Vol 190 (1) ◽  
pp. 253-264 ◽  
Author(s):  
P D Evans
Keyword(s):  
Nervous System ◽  
Relaxation Rate ◽  
Neuromuscular Transmission ◽  
Contraction Rate ◽  
Low Frequencies ◽  
Consistent Effect ◽  
Frequency Of Stimulation ◽  
Stimulation Of

1. The modulatory actions of myomodulin A on tension generated in the extensortibiae muscle of the locust hindleg by stimulation of the slow excitatory motoneurone (SETi) depend upon the frequency of stimulation. Myomodulin A has no consistent effect on the tension induced by the fast extensor motoneurone (FETi) or upon the myogenic rhythm present in the extensor. The effects of a range of structurally related neuropeptides have also been assessed. 2. At low frequencies of SETi stimulation (1 Hz and below), the predominant modulatory effects are increases in the amplitude, contraction rate and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), these effects are superimposed upon an increase of maintained tension. 3. The modulatory actions of myomodulin-like peptides show some similarities to and some differences from the modulatory actions of octopamine, proctolin and FMRFamide-like neuropeptides in this preparation, but are likely to be mediated via a distinct set of receptors. 4. The results of the present study, taken together with the localization of myomodulin-like immunoreactivity in specific sets of neurones in the locust nervous system, suggest the presence of a novel modulatory system in insects that uses myomodulin-like neuropeptides. It also indicates that myomodulins, which were first identified in molluscs, may represent another interphyletic family of neuropeptides.

scholarly journals Phorbol ester only partially mimics the effects of insulin on glucose transport and glucose-transporter distribution in 3T3-L1 adipocytes

1991 ◽  
Vol 275 (1) ◽  
pp. 145-150 ◽  
Author(s):  
E M Gibbs ◽  
D M Calderhead ◽  
G D Holman ◽  
G W Gould
Keyword(s):  
Plasma Membrane ◽  
Phorbol Ester ◽  
Glucose Transporter ◽  
Fold Increase ◽  
Hexose Transport ◽  
Glut 1 ◽  
Glut 4 ◽  
Glucose Analogue ◽  
Stimulation Of

We examined the effects of the phorbol ester phorbol 12-myristate 13-acetate (PMA) on the rate of hexose transport into 3T3-L1 adipocytes. Exposure of adipocytes to PMA (1 microM) for 60 min results in a 1.7-2.5-fold increase in the rate of hexose transport. This effect was mediated by translocation of two isoforms of glucose transporters to the plasma membrane, as determined by labelling in situ, photoaffinity labelling with a membrane-impermeant glucose analogue, and by immunoblotting of subcellular fractions. The PMA-induced stimulation of both transport and transporter translocation was substantially less than that induced by insulin in this cell line; the PMA-induced increase in plasma-membrane GLUT 1 and GLUT 4 transporter isoforms was only about 40% and 10% respectively of that induced by insulin. We suggest that the stimulation of transport by insulin and PMA occurs via different mechanisms, which is manifested by the ability of insulin to induce a much greater increase in the plasma-membrane content of GLUT 4 compared with the phorbol ester.

scholarly journals Insulin stimulation of glucose transport activity in rat skeletal muscle: increase in cell surface GLUT4 as assessed by photolabelling

1994 ◽  
Vol 299 (3) ◽  
pp. 755-759 ◽  
Author(s):  
C M Wilson ◽  
S W Cushman
Keyword(s):  
Skeletal Muscle ◽  
Cell Surface ◽  
Glucose Transport ◽  
Fold Increase ◽  
Transport Activity ◽  
Insulin Stimulation ◽  
Rat Skeletal Muscle ◽  
Photoaffinity Label ◽  
Isolated Rat ◽  
Stimulation Of

We have used a photoaffinity label to quantify cell surface GLUT4 glucose transporters in isolated rat soleus muscles. In this system, insulin stimulated an 8.6-fold increase in 3-O-methylglucose glucose transport, while photolabelled GLUT4 increased 8-fold. These results demonstrate that the insulin-stimulated increase in glucose transport activity in skeletal muscle can be accounted for by an increase in surface-accessible GLUT4 content.

Functional Recovery Induced by Satellite Cell Grafts in Irreversibly Injured Muscles

1994 ◽  
Vol 3 (1) ◽  
pp. 3-14 ◽  
Author(s):  
H.S. Alameddine ◽  
J.P. Louboutin ◽  
M. Dehaupas ◽  
A. Sébille ◽  
M. Fardeau
Keyword(s):  
Fold Increase ◽  
Functional Improvement ◽  
Muscle Response ◽  
Cell Grafting ◽  
Contractile Parameters ◽  
The Mean ◽  
Edl Muscle ◽  
Tetanic Tension ◽  
Stimulation Of

Grafting autologous cultured satellite cells in irreversibly injured rat extensor digitorum longus EDL muscle leads to myofiber regeneration at the grafting site. In this study, we investigated whether cell grafts induced functional improvement and correlated mechanophysiological findings with histological observations. In cell grafted muscles, the number of myofibers did not differ significantly between 2 wk and 3 mo, whereas no regenerating myofibers were observed in ungrafted controls. During this period, the total number of myofibers in the cell grafted muscles represented 48.2-51.9% of that in normal muscles. The mean diameter of regenerated myofibers increased with time, reaching a maximum (32 μm) at the second mo and remained smaller than that of normal myofibers (47 μm). Muscle function was measured by mechanophysiological recordings of muscle response to supramaximal electrical stimulation of the nerve in situ. Cell grafted muscles exhibited a progressive improvement of all contractile parameters. After 3 mo, a 4-fold increase in absolute values of twitch and tetanic tension outputs was measured in cell grafted muscles when compared to ungrafted controls. However, these parameters remained much lower than in normal muscles (23.4% and 22.3% of control, respectively). This study showed that myogenic cell grafts replace degenerated myofibers and form functional myofibers. Functional improvement observed, between 2 wk and 3 mo after cell grafting, correlated with the development, differentiation, and maturation of the regenerated myofibers rather than with an increase in the number of regenerated myofibers.

Effects of thyroid hormones on calcium contents and 45Ca exchange in rat skeletal muscle

1986 ◽  
Vol 251 (3) ◽  
pp. E258-E265 ◽  
Author(s):  
M. E. Everts ◽  
T. Clausen
Keyword(s):  
Extensor Digitorum Longus ◽  
Lactate Production ◽  
Calcium Content ◽  
Metabolic Effects ◽  
Rat Skeletal Muscle ◽  
45Ca Uptake ◽  
Old Rats ◽  
Slow Twitch ◽  
Edl Muscle ◽  
Stimulation Of

In 4-wk-old rats, pretreatment with L-triiodothyronine (T3) increased calcium content by 100% and the 30-min 45Ca uptake by 64% in the soleus, whereas the extensor digitorum longus (EDL) muscle showed no significant change. The stimulation of 45Ca uptake was resistant to dantrolene and methoxyverapamil (D600) and could not be attributed to altered permeability of the plasma membrane to calcium, but appears to reflect increased net accumulation of calcium in intracellular pools. The stimulating effect of high K0 (20 mM) on 45Ca uptake was more pronounced in soleus than in EDL and could be suppressed by dantrolene and D600. The results indicate that the effects of T3 on calcium content and 45Ca exchange are primarily exerted on muscles containing a large proportion of slow-twitch, oxidative fibers. In soleus muscle from hyperthyroid rats the stimulating effects of high K0 on 45Ca uptake and lactate production were, respectively, 3.4 and 4.5 times larger than in those obtained from controls. These observations further support the earlier proposed idea [C. van Hardeveld and T. Clausen. Am. J. Physiol. 247 (Endocrinol. Metab. 10): E421-E430, 1984] that the metabolic effects of thyroid hormone depend on the availability of cellular as well as extracellular calcium.

scholarly journals Changes in glucose 1,6-bisphosphate content in rat skeletal muscle during contraction

1986 ◽  
Vol 240 (3) ◽  
pp. 747-751 ◽  
Author(s):  
A M Bassols ◽  
J Carreras ◽  
R Cussó
Keyword(s):  
Skeletal Muscle ◽  
Sciatic Nerve ◽  
Muscle Contraction ◽  
Gastrocnemius Muscle ◽  
Lactate Concentration ◽  
Glycolytic Flux ◽  
Rat Skeletal Muscle ◽  
Contracting Muscle ◽  
Apparent Relationship

Glucose 1,6-bisphosphate, fructose 2,6-bisphosphate, glycogen, lactate and other glycolytic metabolites were measured in rat gastrocnemius muscle, which was electrically stimulated in situ via the sciatic nerve. Both the frequency and the duration of stimulation were varied to obtain different rates of glycolysis. There was no apparent relationship between fructose 2,6-bisphosphate content and lactate accumulation in contracting muscle. In contrast, glucose 1,6-bisphosphate content increased with lactate concentration during contraction. It is suggested that the increase in glucose 1,6-bisphosphate could play a role in phosphofructokinase stimulation and in the activation of the glycolytic flux during muscle contraction.

Uptake and re-use of sympathetic transmitter in the cat’s spleen

1969 ◽  
Vol 174 (1034) ◽  
pp. 51-68 ◽  
Keyword(s):  
Sympathetic Nerve ◽  
Present Method ◽  
Sympathetic Nerves ◽  
Homologous Blood ◽  
Progressive Decline ◽  
The Relationship ◽  
Frequency Of Stimulation ◽  
Sympathetic Transmitter ◽  
Stimulation Of

The output of transmitter resulting from stimulation of the sympathetic nerves of the cat’s spleen, perfused with homologous blood, is described and compared with similar results obtained from the spleen in situ . Transmitter overflows are somewhat lower in the spleen perfused by the present method, but the relationship between overflow and frequency of stimulation is the same as in the spleen in situ . Noradrenaline added to the perfusate at rates as high as 6 μ g/min is taken up by the spleen which shows no sign of saturation even at these high levels of presentation. Loss of transmitter from the spleen causes a progressive decline in the overflow of transmitter produced by successive trains of stimuli. Evidence is presented to support the hypothesis that the continued effectiveness of a sympathetic nerve depends upon the uptake and re-use of the transmitter that it liberates.

Insulin does not hyperpolarize rat muscle by means of a ouabain-inhibitable process

1981 ◽  
Vol 241 (3) ◽  
pp. C145-C149 ◽  
Author(s):  
K. Zierler ◽  
E. Rogus
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Electrogenic Pump ◽  
Rat Skeletal Muscle ◽  
Rat Muscle ◽  
Longus Muscle ◽  
Stimulation Of

Experiments were designed to test the hypothesis that insulin-induced hyperpolarization of rat skeletal muscle is mediated by stimulation of a ouabain-inhibitable electrogenic pump. Parallel experiments were carried out on rat caudofemoralis with isoproterenol, known to hyperpolarize rat skeletal muscle by stimulation of such a pump. Ouabain (10(-5) M) completely inhibited isoproterenol-induced hyperpolarization within 15 min but had no effect on half-maximal insulin-induced hyperpolarization. Ouabain (10(-6) M) inhibited isoproterenol effect by 60% during a period of 5–15 min. Ouabain (10(-4) M) had no effect on insulin-induced hyperpolarization within 10 min but depolarized during the next 10 min. In a separate series of studies in rat extensor digitorum longus muscle, 10(-5) M ouabain increased intracellular Na+ within 14 min. It is concluded that in rat caudofemoralis muscle, insulin-induced hyperpolarization is not mediated by a ouabain-inhibitable electrogenic pump.

scholarly journals The Modulatory Actions of FMRFamide and Related Peptides on Locust Skeletal Muscle

1986 ◽  
Vol 126 (1) ◽  
pp. 403-422 ◽  
Author(s):  
PETER D. EVANS ◽  
CAMILLA M. MYERS
Keyword(s):  
Slow Muscle ◽  
Motor Neurone ◽  
Muscle Fibres ◽  
Relaxation Rates ◽  
Receptor System ◽  
Low Frequencies ◽  
Slow Muscle Fibres ◽  
Slow Twitch ◽  
Frequency Of Stimulation ◽  
Stimulation Of

1. The modulatory actions of FMRFamide and related peptides on tension generated in the extensor-tibiae muscle of the locust hindleg by stimulation of the slow excitatory motor neurone (SETi) depend upon the frequency of stimulation of SETi. They have no effect on the tension induced by the fast motor neurone (FETi) or upon the myogenic rhythm present in this muscle. 2. At low frequencies of SETi stimulation (1Hz and below) the predominant modulatory effects are increases in the amplitude, contraction rates and relaxation rates of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz) these effects are superimposed upon an increase of maintained tension. 3. FMRFamide increases the amplitude and relaxation rate of slow twitch tension by different amounts in different regions of the extensor muscle. It is likely that the effects of FMRFamide are restricted to slow muscle fibres that are innervated by SETi but not FETi. 4. The modulatory actions of FMRFamide on SETi-induced tension are additive to, but do not potentiate, the modulatory actions of octopamine and proctolin in this muscle. The actions of FMRFamide show some similarities with the modulatory actions of octopamine in this preparation but they are mediated by an independent receptor system that does not change cyclic nucleotide levels. Other actions of FMRFamide are similar to the actions of proctolin.

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