scholarly journals Masses of inositol phosphates in resting and tetanically stimulated vertebrate skeletal muscles

1991 ◽  
Vol 280 (3) ◽  
pp. 631-640 ◽  
Author(s):  
G W Mayr ◽  
R Thieleczek
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Time Course ◽  
Inositol Phosphates ◽  
Energy Charge ◽  
Cell Types ◽  
Free Concentration ◽  
Rate Of Increase ◽  
The Masses

The masses of inositol phosphates have been determined in isolated skeletal muscles from Xenopus laevis (sartorius, tibialis anterior and iliofibularis) and rat (gastrocnemius and soleus) which were quick-frozen in the resting state and at different stages of an isometric (Xenopus) or isotonic (rat) tetanus. The isomeric spectrum of inositol phosphates detected was similar to that in other tissues and cell types. The total sarcoplasmic concentrations of the isomers Ins-(1,4,5,6)P4/Ins(3,4,5,6)P4 (0.2-0.9 microM), Ins(1,3,4,6)P4 (not detectable), Ins(1,3,4,5,6)P5 (about 1 microM) and InsP6 (3.2-4.6 microM) were lower than in other cell types. Variations in these concentrations were due to the muscle type rather than to the donor species. The putative second messenger Ins(1,4,5)P3, as well as its dephosphorylation product Ins(1,4)P2, were present at surprisingly high total myoplasmic resting concentrations, ranging from 1.2 to 2.5 microM and 3.5 to 6.9 microM respectively. Upon tetanic stimulation these two inositol phosphates in particular exhibited significantly increased total sarcoplasmic concentrations, up to 4.2 microM and 11.3 microM respectively, with a time scale of seconds. From the initial rate of increase in the total sarcoplasmic concentrations of Ins(1,4,5)P3 and its rapidly formed metabolic products, a minimal phosphoinositidase C (PIC) activity in tetanically activated Xenopus skeletal muscle of about 1.7-2.6 microM/s can be estimated. This PIC activity observed in vivo seems to be far too low to account for a functional role for Ins(1,4,5)P3 as a chemical transmitter in the fast excitation-contraction coupling (ECC) process in skeletal muscle. The presence of Ins(1,3,4,5)P4 in all muscle types is indicative of a Ca(2+)-activated Ins(1,4,5)P3 3-kinase activity. The rapid transient increases in Ins(1,3,4)P3 and Ins(1,3)P2 in isometrically contracting Xenopus muscles suggest that corresponding Ins(1,3,4,5)P4 phosphatases are operating in skeletal muscle as well. In all muscles investigated except rat soleus, the fructose 1,6-bisphosphate [Fru(1,6)P2] concentration increased substantially during a tetanus, up to about 2 mM. This increase is correlated with a simultaneous decrease in phosphocreatine, whereas the energy charge of the muscles was essentially unaffected by the applied tetani. The time course of the rise in Fru(1,6)P2 was used to model changes in the free concentrations of high-affinity aldolase-binding inositol phosphates during the course of a tetanus. These calculations demonstrate that the free concentration of Ins(1,4,5)P3 and other aldolase-bound inositol phosphates can increase much faster and to a larger extent than the corresponding total concentrations as a result of their competitive displacement from aldolase-binding sites by the rapidly rising concentration of Fru(1,6)P2.

In vivo expression patterns of MyoD, p21, and Rb proteins in myonuclei and satellite cells of denervated rat skeletal muscle

2004 ◽  
Vol 287 (2) ◽  
pp. C484-C493 ◽  
Author(s):  
Minenori Ishido ◽  
Katsuya Kami ◽  
Mitsuhiko Masuhara
Keyword(s):  
Skeletal Muscle ◽  
Satellite Cell ◽  
Time Course ◽  
Kinase Inhibitor ◽  
Expression Patterns ◽  
Cell Types ◽  
Cell Nuclei ◽  
Myogenic Regulatory Factor

MyoD, a myogenic regulatory factor, is rapidly expressed in adult skeletal muscles in response to denervation. However, the function(s) of MyoD expressed in denervated muscle has not been adequately elucidated. In vitro, it directly transactivates cyclin-dependent kinase inhibitor p21 (p21) and retinoblastoma protein (Rb), a downstream target of p21. These factors then act to regulate cell cycle withdrawal and antiapoptotic cell death. Using immunohistochemical approaches, we characterized cell types expressing MyoD, p21, and Rb and the relationship among these factors in the myonucleus of denervated muscles. In addition, we quantitatively examined the time course changes and expression patterns among distinct myofiber types of MyoD, p21, and Rb during denervation. Denervation induced MyoD expression in myonuclei and satellite cell nuclei, whereas p21 and Rb were found only in myonuclei. Furthermore, coexpression of MyoD, p21, and Rb was induced in the myonucleus, and quantitative analysis of these factors determined that there was no difference among the three myofiber types. These observations suggest that MyoD may function in myonuclei in response to denervation to protect against denervation-induced apoptosis via perhaps the activation of p21 and Rb, and function of MyoD expressed in satellite cell nuclei may be negatively regulated. The present study provides a molecular basis to further understand the function of MyoD expressed in the myonuclei and satellite cell nuclei of denervated skeletal muscle.

scholarly journals Proteins containing peptide sequences related to Lys-Phe-Glu-Arg-Gln are selectively depleted in liver and heart, but not skeletal muscle, of fasted rats

1991 ◽  
Vol 275 (1) ◽  
pp. 165-169 ◽  
Author(s):  
S S Wing ◽  
H L Chiang ◽  
A L Goldberg ◽  
J F Dice
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Time Course ◽  
Polyclonal Antibodies ◽  
Protein Loss ◽  
Cultured Fibroblasts ◽  
Cytosolic Proteins ◽  
Mammalian Tissues ◽  
Fasted Rats

In response to serum withdrawal, when overall rates of proteolysis increase in cultured fibroblasts, proteins containing peptide regions similar to Lys-Phe-Gln-Arg-Gln (KFERQ) are targeted to lysosomes for degradation, and the intracellular concentrations of these proteins decline [Chiang & Dice (1988) J. Biol. Chem. 263, 6797-6805]. To test whether such proteins are also selectively depleted in mammalian tissues in vivo, we have used affinity-purified polyclonal antibodies to KFERQ to detect proteins containing such sequences in tissues of fed and fasted rats. Immunoreactive cytosolic proteins were partially depleted from liver and heart of fasted rats, but the time course differed for these two tissues. Immunoreactive proteins in liver were lost during days 2 and 3 of fasting, whereas such proteins in heart were depleted within day 1 of fasting. In the same fasted rats, levels of immunoreactive cytosolic proteins did not change in two skeletal muscles, the dark soleus and the pale extensor digitorum longus. Immunoreactive proteins in a myofibrillar fraction were also partially depleted in heart, but not in skeletal muscles, of fasted rats. The most likely explanation for these results is that the protein loss in different tissues upon fasting results from selective activation of different proteolytic pathways. The increased proteolysis in liver and heart of fasted animals includes activation of the KFERQ-selective lysosomal pathway, whereas increased proteolysis in skeletal muscle does not.

Potassium depletion increases potassium clearance capacity in skeletal muscles in vivo during acute repletion

2002 ◽  
Vol 283 (4) ◽  
pp. C1163-C1170 ◽  
Author(s):  
Henning Bundgaard ◽  
Keld Kjeldsen
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Ouabain Binding ◽  
K Uptake ◽  
Rate Of Increase ◽  
Increased Risk ◽  
Gastrocnemius Muscles ◽  
K Depletion

Muscular K uptake depends on skeletal muscle Na-K-ATPase concentration and activity. Reduced K uptake is observed in vitro in K-depleted rats. We evaluated skeletal muscle K clearance capacity in vivo in rats K depleted for 14 days. [3H]ouabain binding, α1 and α2 Na-K-ATPase isoform abundance, and K, Na, and Mg content were measured in skeletal muscles. Skeletal muscle K, Na, and Mg and plasma K were measured in relation to intravenous KCl infusion that continued until animals died, i.e., maximum KCl dose was administered. In soleus, extensor digitorum longus (EDL), and gastrocnemius muscles K depletion significantly reduced K content by 18%, 15%, and 19%, [3H]ouabain binding by 36%, 41%, and 68%, and α2 isoform abundance by 34%, 44%, and 70%, respectively. No significant change was observed in α1 isoform abundance. In EDL and gastrocnemius muscles K depletion significantly increased Na (48% and 59%) and Mg (10% and 17%) content, but only tendencies to increase were observed in soleus muscle. K-depleted rats tolerated up to a fourfold higher KCl dose. This was associated with a reduced rate of increase in plasma K and increases in soleus, EDL, and gastrocnemius muscle K of 56%, 42%, and 41%, respectively, but only tendencies to increase in controls. However, whereas K uptake was highest in K-depleted animals, the K uptake rate was highest in controls. In vivo K depletion is associated with markedly increased K tolerance and K clearance despite significantly reduced skeletal muscle Na-K-ATPase concentration. The concern of an increased risk for K intoxication during K repletion seems unwarranted.

Pulsatile Pressure and Flow in the Skeletal Muscle Microcirculation

1990 ◽  
Vol 112 (4) ◽  
pp. 437-443 ◽  
Author(s):  
Shou-Yan Lee ◽  
G. W. Schmid-Scho¨nbein
Keyword(s):  
Skeletal Muscle ◽  
Arterial Pressure ◽  
Time Course ◽  
Venous Pressure ◽  
Time Dependent ◽  
Physiological Importance ◽  
Pulsatile Pressure ◽  
Theoretical Predictions ◽  
Skeletal Muscle Microcirculation

Although blood flow in the microcirculation of the rat skeletal muscle has negligible inertia forces with very low Reynolds number and Womersley parameter, time-dependent pressure and flow variations can be observed. Such phenomena include, for example, arterial flow overshoot following a step arterial pressure, a gradual arterial pressure reduction for a step flow, or hysteresis between pressure and flow when a pulsatile pressure is applied. Arterial and venous flows do not follow the same time course during such transients. A theoretical analysis is presented for these phenomena using a microvessel with distensible viscoelastic walls and purely viscous flow subject to time variant arterial pressures. The results indicate that the vessel distensibility plays an important role in such time-dependent microvascular flow and the effects are of central physiological importance during normal muscle perfusion. In-vivo whole organ pressure-flow data in the dilated rat gracilis muscle agree in the time course with the theoretical predictions. Hemodynamic impedances of the skeletal muscle microcirculation are investigated for small arterial and venous pressure amplitudes superimposed on an initial steady flow and pressure drop along the vessel.

scholarly journals Inhibiting myosin-ATPase reveals a dynamic range of mitochondrial respiratory control in skeletal muscle

2011 ◽  
Vol 437 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Christopher G. R. Perry ◽  
Daniel A. Kane ◽  
Chien-Te Lin ◽  
Rachel Kozy ◽  
Brook L. Cathey ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Dynamic Range ◽  
Energy Charge ◽  
Respiratory Control ◽  
Basic Research ◽  
Dependent Manner ◽  
Atpase Inhibitor ◽  
Wide Range ◽  
The Impact

Assessment of mitochondrial ADP-stimulated respiratory kinetics in PmFBs (permeabilized fibre bundles) is increasingly used in clinical diagnostic and basic research settings. However, estimates of the Km for ADP vary considerably (~20–300 μM) and tend to overestimate respiration at rest. Noting that PmFBs spontaneously contract during respiration experiments, we systematically determined the impact of contraction, temperature and oxygenation on ADP-stimulated respiratory kinetics. BLEB (blebbistatin), a myosin II ATPase inhibitor, blocked contraction under all conditions and yielded high Km values for ADP of >~250 and ~80 μM in red and white rat PmFBs respectively. In the absence of BLEB, PmFBs contracted and the Km for ADP decreased ~2–10-fold in a temperature-dependent manner. PmFBs were sensitive to hyperoxia (increased Km) in the absence of BLEB (contracted) at 30 °C but not 37 °C. In PmFBs from humans, contraction elicited high sensitivity to ADP (Km<100 μM), whereas blocking contraction (+BLEB) and including a phosphocreatine/creatine ratio of 2:1 to mimic the resting energetic state yielded a Km for ADP of ~1560 μM, consistent with estimates of in vivo resting respiratory rates of <1% maximum. These results demonstrate that the sensitivity of muscle to ADP varies over a wide range in relation to contractile state and cellular energy charge, providing evidence that enzymatic coupling of energy transfer within skeletal muscle becomes more efficient in the working state.

scholarly journals Inhibition of mTOR during a postnatal critical sensitive window rescues deficits in GABAergic PV cell connectivity and social behavior caused by loss of TSC1

2020 ◽  
Author(s):  
Mayukh Choudhury ◽  
Clara A. Amegandjin ◽  
Vidya Jadhav ◽  
Josianne Nunes Carriço ◽  
Ariane Quintal ◽  
...  
Keyword(s):  
Social Behavior ◽  
Time Course ◽  
Cell Types ◽  
Developmental Time ◽  
Adult Mice ◽  
Mtorc1 Signaling ◽  
Pv Cell ◽  
Mechanistic Basis

ABSTRACTMutations in regulators of the Mechanistic Target Of Rapamycin Complex 1 (mTORC1), such as Tsc1/2, lead to neurodevelopmental disorders associated with autism, intellectual disabilities and epilepsy. Whereas the effects of mTORC1 signaling dysfunction within diverse cell types are likely critical for the onset of the diverse neurological symptoms associated with mutations in mTORC1 regulators, they are not well understood. In particular, the effects of mTORC1 dys-regulation in specific types of inhibitory interneurons are unclear.Here, we showed that Tsc1 haploinsufficiency in parvalbumin (PV)-positive GABAergic interneurons either in cortical organotypic cultures or in vivo caused a premature increase in their perisomatic innervations, followed by a striking loss in adult mice. This effects were accompanied by alterations of AMPK-dependent autophagy in pre-adolescent but not adult mice. PV cell-restricted Tsc1 mutant mice showed deficits in social behavior. Treatment with the mTOR inhibitor Rapamycin restricted to the third postnatal week was sufficient to permanently rescue deficits in both PV cell innervation and social behavior in adult conditional haploinsufficient mice. All together, these findings identify a novel role of Tsc1-mTORC1 signaling in the regulation of the developmental time course and maintenance of cortical PV cell connectivity and provide a mechanistic basis for the targeted rescue of autism-related behaviors in disorders associated with deregulated mTORC1 signaling.

Thymocyte/stromal cell chimaerism in allothymus-grafted Xenopus: developmental studies using the X. borealis fluorescence marker

Development ◽  
1987 ◽  
Vol 100 (1) ◽  
pp. 107-117
Author(s):  
J.D. Horton ◽  
J.H. Russ ◽  
P. Aitchison ◽  
T.L. Horton
Keyword(s):  
Stromal Cell ◽  
Time Course ◽  
Adult Life ◽  
Cell Types ◽  
Lymphoid Cells ◽  
Host Cells ◽  
Developmental Studies ◽  
Stage Of Development ◽  
Time Course Study

These experiments employ the X. borealis (quinacrine-fluorescence) cell marker to illustrate that froglet (normal or in vivo-irradiated) thymuses, alloimplanted to 4- to 6-week-old, 7-day-thymectomized hosts, become filled with host lymphoid cells, while a range of thymic stromal cell types (e.g. epithelial derivatives and reticuloendothelial cells) remain donor derived. A time-course study of 4 micron historesin-embedded sections reveals that for normal thymus implants, host cells begin to immigrate in good number only after metamorphosis. In contrast, 3000 rad-irradiated thymus implants begin to be repopulated with host lymphocytes within 2 weeks postimplantation, when hosts are still at a late larval stage of development. Despite rapid colonization by host lymphoid cells, irradiated thymuses remain small and often disappear in early adult life. Donor-derived lymphocytes frequent the blood and both the red pulp and perifollicular regions of the spleen following normal thymus implantation, whereas such thymic emigrants were not seen in the periphery of thymectomized hosts grafted with irradiated thymus glands.

Expression of steroidogenic enzymes and synthesis of sex steroid hormones from DHEA in skeletal muscle of rats

2007 ◽  
Vol 292 (2) ◽  
pp. E577-E584 ◽  
Author(s):  
Katsuji Aizawa ◽  
Motoyuki Iemitsu ◽  
Seiji Maeda ◽  
Subrina Jesmin ◽  
Takeshi Otsuki ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Steroid Hormones ◽  
Skeletal Muscles ◽  
Muscle Cells ◽  
Sex Steroid Hormones ◽  
Sex Steroid ◽  
Dependent Manner ◽  
Steroidogenic Enzymes

The functional importance of sex steroid hormones (testosterone and estrogens), derived from extragonadal tissues, has recently gained significant appreciation. Circulating dehydroepiandrosterone (DHEA) is peripherally taken up and converted to testosterone by 3β-hydroxysteroid dehydrogenase (HSD) and 17β-HSD, and testosterone in turn is irreversibly converted to estrogens by aromatase cytochrome P-450 (P450arom). Although sex steroid hormones have been implicated in skeletal muscle regulation and adaptation, it is unclear whether skeletal muscles have a local steroidogenic enzymatic machinery capable of metabolizing circulating DHEA. Thus, here, we investigate whether the three key steroidogenic enzymes (3β-HSD, 17β-HSD, and P450arom) are present in the skeletal muscle and are capable of generating sex steroid hormones. Consistent with our hypothesis, the present study demonstrates mRNA and protein expression of these enzymes in the skeletal muscle cells of rats both in vivo and in culture (in vitro). Importantly, we also show an intracellular formation of testosterone and estradiol from DHEA or testosterone in cultured muscle cells in a dose-dependent manner. These findings are novel and important in that they provide the first evidence showing that skeletal muscles are capable of locally synthesizing sex steroid hormones from circulating DHEA or testosterone.

scholarly journals In Vivo Activation of STAT3 Signaling in Satellite Cells and Myofibers in Regenerating Rat Skeletal Muscles

2002 ◽  
Vol 50 (12) ◽  
pp. 1579-1589 ◽  
Author(s):  
Katsuya Kami ◽  
Emiko Senba
Keyword(s):  
Skeletal Muscle ◽  
Satellite Cells ◽  
Muscle Regeneration ◽  
Intracellular Signaling ◽  
Skeletal Muscles ◽  
Early Stage ◽  
Skeletal Muscle Regeneration ◽  
Stat3 Signaling

Although growth factors and cytokines play critical roles in skeletal muscle regeneration, intracellular signaling molecules that are activated by these factors in regenerating muscles have been not elucidated. Several lines of evidence suggest that leukemia inhibitory factor (LIF) is an important cytokine for the proliferation and survival of myoblasts in vitro and acceleration of skeletal muscle regeneration. To elucidate the role of LIF signaling in regenerative responses of skeletal muscles, we examined the spatial and temporal activation patterns of an LIF-associated signaling molecule, the signal transducer and activator transcription 3 (STAT3) proteins in regenerating rat skeletal muscles induced by crush injury. At the early stage of regeneration, activated STAT3 proteins were first detected in the nuclei of activated satellite cells and then continued to be activated in proliferating myoblasts expressing both PCNA and MyoD proteins. When muscle regeneration progressed, STAT3 signaling was no longer activated in differentiated myoblasts and myotubes. In addition, activation of STAT3 was also detected in myonuclei within intact sarcolemmas of surviving myofibers that did not show signs of necrosis. These findings suggest that activation of STAT3 signaling is an important molecular event that induces the successful regeneration of injured skeletal muscles.

Regional differences in constitutive and induced ICAM-1 expression in vivo

1995 ◽  
Vol 269 (6) ◽  
pp. H1955-H1964 ◽  
Author(s):  
J. Panes ◽  
M. A. Perry ◽  
D. C. Anderson ◽  
A. Manning ◽  
B. Leone ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Regional Differences ◽  
Time Course ◽  
Intercellular Adhesion Molecule ◽  
Intercellular Adhesion Molecule 1 ◽  
Fourfold Increase ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Higher Doses

The aim of the present study was to characterize and compare the expression of intercellular adhesion molecule 1 (ICAM-1) on unstimulated and endotoxin-challenged endothelial cells in different tissues of the rat. ICAM-1 expression was measured using 125I-labeled anti-rat ICAM-1 monoclonal antibody (MAb) and an isotype-matched control MAb labeled with 131I (to correct for nonspecific accumulation of the binding MAb). Under baseline conditions, ICAM-1 MAb binding was observed in all organs. The binding of 125I-ICAM-1 MAb varied widely among organs, with the largest accumulation (per g tissue) in the lung, followed by heart (1/30th of lung activity), splanchnic organs (1/50th of lung activity), thymus (1/100th of lung activity), testes (1/300th of lung activity), and skeletal muscle (1/800th of lung activity). Endotoxin induced an increase in ICAM-1 MAb binding in all organs except the spleen. Endotoxin-induced upregulation of ICAM-1 was greatest in heart and skeletal muscle (5- to 10-fold), whereas the remaining organs exhibited a two- to fourfold increase in ICAM-1 expression. Maximal upregulation of ICAM-1 occurred at 9-12 h after endotoxin administration. A dose-dependent increase in ICAM-1 expression was elicited by 0.1-10 microgram/kg, with higher doses (up to 5 mg/kg) producing no further increment. Induction of ICAM-1 mRNA after endotoxin was observed in all tissues examined (lung, heart, intestine), peaked at 3 h, and then rapidly returned to control levels. These findings indicate that ICAM-1 is constitutively expressed on vascular endothelium in all organs of the rat and that there are significant regional differences in the magnitude and time course of endotoxin-induced ICAM-1 expression.

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