Biochemistry and Morphology of Fragmented Sarcoplasmic Reticulum

1970 ◽  
Vol 28 ◽  
pp. 90-91 ◽  
Author(s):  
J. B. Peter ◽  
W. Fiehn ◽  
Robert F. Dunn
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Relaxation Cycle ◽  
Calcium Accumulation ◽  
Maximal Amount ◽  
Slow Twitch ◽  
Vesicle Protein ◽  
Fast Twitch ◽  
Kinetics Of

The function of the sarcoplasmic reticulum (SR) is well defined, but much confusion exists about the role of the SR in the contraction-relaxation cycle of slow-twitch muscles. Fragmented SR (FSR) was isolated from different guinea pig muscles. The muscles were classified as fast-twitch-red, fast-twitch-white or slow-twitch-intermediate according to their contractionrelaxation times and the histochemical characteristics of the component fibers.The kinetics of calcium accumulation showed no difference between FSR from fast-twitch-red or fast-twitch-white muscles, and the yield of FSR (expressed as mg vesicle protein per gram of muscle) was the same. By contrast the amount of FSR obtained per gram of slow-twitch-intermediate muscle was only half as high. Likewise, the maximal amount of calcium that could be stored in the presence of oxalate by FSR from slow-twitch-intermediate muscles was only half that of FSR from fast-twitch muscles.

scholarly journals The Functional Role of Calcineurin in Hypertrophy, Regeneration, and Disorders of Skeletal Muscle

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Kunihiro Sakuma ◽  
Akihiko Yamaguchi
Keyword(s):  
Skeletal Muscle ◽  
Functional Role ◽  
Muscular Hypertrophy ◽  
Growth And Remodeling ◽  
Muscular Disorders ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Calcineurin Activity ◽  
Muscle Remodeling

Skeletal muscle uses calcium as a second messenger to respond and adapt to environmental stimuli. Elevations in intracellular calcium levels activate calcineurin, a serine/threonine phosphatase, resulting in the expression of a set of genes involved in the maintenance, growth, and remodeling of skeletal muscle. In this review, we discuss the effects of calcineurin activity on hypertrophy, regeneration, and disorders of skeletal muscle. Calcineurin is a potent regulator of muscle remodeling, enhancing the differentiation through upregulation of myogenin or MEF2A and downregulation of the Id1 family and myostatin. Foxo may also be a downstream candidate for a calcineurin signaling molecule during muscle regeneration. The strategy of controlling the amount of calcineurin may be effective for the treatment of muscular disorders such as DMD, UCMD, and LGMD. Activation of calcineurin produces muscular hypertrophy of the slow-twitch soleus muscle but not fast-twitch muscles.

Guinea pig soleus and gastrocnemius electromyograms at varying speeds, grades, and loads

1982 ◽  
Vol 52 (2) ◽  
pp. 451-457 ◽  
Author(s):  
K. R. Gardiner ◽  
P. F. Gardiner ◽  
V. R. Edgerton
Keyword(s):  
Guinea Pig ◽  
Work Load ◽  
Burst Duration ◽  
Lateral Gastrocnemius ◽  
Biochemical Alterations ◽  
Hindlimb Muscles ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Grade Increase ◽  
Emg Electrodes

The purpose of the study was to describe changes that occur in the usage of fast-twitch and slow-twitch guinea pig hindlimb muscles, as estimated using chronically implanted electromyogram (EMG) electrodes, during voluntary locomotion under various conditions. Guinea pigs, in which fine wire electrodes were implanted in soleus (SOL) and lateral gastrocnemius (LG) muscles, were exercised at various speeds (13.4, 26.8, 40.2 m/min), grades (0–30%) and in some conditions loads (50–150 g) on a motor-driven treadmill. Bipolar EMG signals were rectified-averaged (RA-EMG) and analyzed for burst duration, amplitude, and the integral of each burst (IEMG). For each condition and muscle, total IEMG/min (IEMG/step x steps/min) was calculated and expressed as a percent of the maximum IEMG recorded. With increasing speed at 0% grade, the ratio of LG to SOL IEMG, each expressed as percent of maximum, remained constant at about 0.82. An increased stepping rate of 150 (at 13.4 m/min) to 225 (at 40.2 m/min) steps/min was accompanied by a 37% decrease in burst duration in LG and SOL. When the treadmill belt speed was increased from 13.4 to 4.02 m/min at 30% grade, the LG/SOL ratio increased from 0.83 to 1.03, whereas burst duration decreased by 49% (SOL) and 51% (LG). Soleus IEMG did not change significantly with increases in speed or grade; LG IEMG increased significantly with speed at 10% grade and with grade increase at the highest speed (40.2 m/min). These data provide some insight into how modifications of work load on a treadmill affect overall muscle activity and may assist in the interpretation of training-induced muscle biochemical alterations previously noted by other investigators.

scholarly journals A combination of MEF3 and NFI proteins activates transcription in a subset of fast-twitch muscles.

1997 ◽  
Vol 17 (2) ◽  
pp. 656-666 ◽  
Author(s):  
F Spitz ◽  
M Salminen ◽  
J Demignon ◽  
A Kahn ◽  
D Daegelen ◽  
...  
Keyword(s):  
Regulatory Elements ◽  
Specific Expression ◽  
Transgenic Lines ◽  
Slow Twitch ◽  
Myogenic Factors ◽  
Fast Twitch ◽  
Restricted Pattern ◽  
Aldolase A ◽  
Drive Reporter Gene Expression

The human aldolase A pM promoter is active in fast-twitch muscles. To understand the role of the different transcription factors which bind to this promoter and determine which ones are responsible for its restricted pattern of expression, we analyzed several transgenic lines harboring different combinations of pM regulatory elements. We show that muscle-specific expression can be achieved without any binding sites for the myogenic factors MyoD and MEF2 and that a 64-bp fragment comprising a MEF3 motif and an NFI binding site is sufficient to drive reporter gene expression in some but, interestingly, not all fast-twitch muscles. A result related to this pattern of expression is that some isoforms of NFI proteins accumulate differentially in fast- and slow-twitch muscles and in distinct fast-twitch muscles. We propose that these isoforms of NFI proteins might provide a molecular basis for skeletal muscle diversity.

Expression of sarcoplasmic reticulum Ca(2+)-ATPase isoforms in marlin and swordfish muscle and heater cells

1996 ◽  
Vol 271 (1) ◽  
pp. R262-R275 ◽  
Author(s):  
A. Tullis ◽  
B. A. Block
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Fiber Type ◽  
Direct Sequencing ◽  
Rectus Muscle ◽  
Superior Rectus ◽  
Cardiac Muscles ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Sarcoplasmic Reticulum Calcium ◽  
Superior Rectus Muscle

The superior rectus muscles of marlin, swordfish, sailfish, and spearfish are modified for generating heat rather than force. This study focuses on the sarcoplasmic reticulum calcium-adenosinetriphosphatase (SR Ca(2+)-ATPase) to gain further insight into the muscle fiber type origin of the billfish “heater cell.” Direct sequencing and immunolocalization demonstrated that marlin and swordfish epaxial swimming muscles express two forms of the SR Ca(2+)-ATPase in a fiber type-specific manner; red slow-twitch skeletal and cardiac muscles express the same SERCA2 message, whereas white fast-twitch skeletal muscles express a SERCA1 message. Thus the expression pattern of the SR Ca2+ pump is similar in both billfish and tetrapod muscles. Molecular and immunological studies revealed that billfish heater tissue and superior rectus muscle express both fast and slow SR Ca2+ pump isoforms. Immunohistochemical results suggest that heater cells and most extraocular muscle fibers express the fast SR Ca2+ pump. Expression of the fast SR Ca(2+)-ATPase by heater cells has implications for heater cell origin and thermogenic control.

Effects of diabetes on protein synthesis in fast- and slow-twitch rat skeletal muscle

1980 ◽  
Vol 239 (1) ◽  
pp. E88-E95 ◽  
Author(s):  
K. E. Flaim ◽  
M. E. Copenhaver ◽  
L. S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Peptide Chain ◽  
Fiber Types ◽  
Chain Initiation ◽  
Rapid Reversal ◽  
Slow Twitch ◽  
Fast Twitch

The effects of acute (2-day) and long-term (7-day) diabetes on rates of protein synthesis, peptide-chain initiation, and levels of RNA were examined in rat skeletal muscles that are known to have differing proportions of the three fiber types: fast-twitch white, fast-twitch red, and slow-twitch red. Short-term diabetes resulted in a 15% reduction in the level of RNA in all the muscles studied and an impairment in peptide-chain initiation in muscles with mixed fast-twitch fibers. In contrast, the soleus, a skeletal muscle with high proportions of slow-twitch red fibers, showed little impairment in initiation. When the muscles were perfused as a part of the hemicorpus preparation, addition of insulin to the medium caused a rapid reversal of the block in initiation in mixed fast-twitch muscles but had no effect in the soleus. The possible role of fatty acids in accounting for these differences is discussed. Long-term diabetes caused no further reduction in RNA, but resulted in the development of an additional impairment to protein synthesis that also affected the soleus and that was not corrected by perfusion with insulin. The defect resulting from long-term diabetes may involve elongation or termination reactions.

Diazepam reveals different rate-limiting processes in rat skeletal muscle contraction

1987 ◽  
Vol 65 (2) ◽  
pp. 272-273 ◽  
Author(s):  
Michael Chua ◽  
Angela F. Dulhunty
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Binding ◽  
Extensor Digitorum Longus ◽  
Calcium Uptake ◽  
Rat Skeletal Muscle ◽  
Skeletal Muscle Contraction ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Rate Limiting

The action of the tranquilizer diazepam on rat skeletal muscle showed that relaxation of isometric twitches is controlled by different processes in extensor digitorum longus (fast-twitch) and soleus (slow-twitch) muscles. Diazepam caused an increase in the amplitude of twitches in fibres from both muscles but increased the twitch duration only in soleus. The amplitude of fused tetani were reduced in both muscles and the rate of relaxation after the tetanus slowed by as much as 34% when the amplitude of the tetanus was reduced by only 11%. The slower tetanic relaxation indicated that calcium uptake by the sarcoplasmic reticulum was slower than normal in slow- and fast-twitch fibres. We conclude therefore that calcium uptake by the sarcoplasmic reticulum is rate limiting for twitch relaxation in slow-twitch but not fast-twitch fibres and suggest that calcium binding to parvalbumin controls relaxation in the fast fibres.

scholarly journals Calcium accumulation by the sarcoplasmic reticulum in two populations of chemically skinned human muscle fibers. Effects of calcium and cyclic AMP.

1982 ◽  
Vol 79 (4) ◽  
pp. 603-632 ◽  
Author(s):  
G Salviati ◽  
M M Sorenson ◽  
A B Eastwood
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cyclic Amp ◽  
Muscle Fibers ◽  
Human Muscle ◽  
Wide Range ◽  
Ca Uptake ◽  
Human Muscles ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

In previous efforts to characterize sarcoplasmic reticulum function in human muscles, it has not been possible to distinguish the relative contributions of fast-twitch and slow-twitch fibers. In this study, we have used light scattering and 45Ca to monitor Ca accumulation by the sarcoplasmic reticulum of isolated, chemically skinned human muscle fibers in the presence and absence of oxalate. Oxalate (5 mM) increased the capacity for Ca accumulation by a factor of 35 and made it possible to assess both rate of Ca uptake and relative sarcoplasmic reticulum volume in individual fibers. At a fixed ionized Ca concentration, the rate and maximal capacity (an index of sarcoplasmic reticulum volume) both varied over a wide range, but fibers fell into two distinct groups (fast and slow). Between the two groups, there was a 2- to 2.5-fold difference in oxalate-supported Ca uptake rates, but no difference in average sarcoplasmic reticulum volumes. Intrinsic differences in sarcoplasmic reticulum function (Vmax, K0.5, and n) were sought to account for the distinction between fast and slow groups. In both groups, rate of Ca accumulation increased sigmoidally as [Ca++] was increased from 0.1 to 1 microM. Apparent affinities for Ca++ (K0.5) were similar in the two groups, but slow fibers had a lower Vmax and larger n values. Slow fibers also differed from fast fibers in responding with enhanced Ca uptake upon addition of cyclic AMP (10(-6) M, alone or with protein kinase). Acceleration by cyclic AMP was adequate to account for adrenaline-induced increases in relaxation rates previously observed in human muscles containing mixtures in fast-twitch and slow-twitch fibers.

scholarly journals Patterns of sarcomere activation, temperature dependence, and effect of ryanodine in chemically skinned cardiac fibers.

1986 ◽  
Vol 87 (6) ◽  
pp. 885-905 ◽  
Author(s):  
A Lundblad ◽  
H Gonzalez-Serratos ◽  
G Inesi ◽  
J Swanson ◽  
P Paolini
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Temperature Dependence ◽  
Calcium Release ◽  
Contractile Activity ◽  
The Other ◽  
Calcium Blockers ◽  
Calcium Accumulation ◽  
Contractile Activation

Functionally skinned and electrochemically shunted myocytes were prepared by perfusing rat hearts with collagenase in order to obtain a technically improved measurement of sarcomere dynamics and to evaluate the role of sarcoplasmic reticulum in situ with respect to contractile activation. In the presence of micromolar calcium, the myocytes exhibited phasic and propagated contraction waves beginning at one end and proceeding along the myocyte. Beating rates, the propagation velocity of the activation wave, and single sarcomere shortening and relaxation velocities were obtained by manual or automated analysis of 16-mm film recorded at 170 frames/s from a camera attached to a microscope that was equipped with a temperature-controlled stage. In parallel experiments, calcium accumulation by the sarcoplasmic reticulum of the myocytes in situ was measured by direct isotopic tracer methods. The frequency (10-38 min-1) of spontaneous contractions, the velocity (1.9-7.4 microns . s-1) of sarcomere shortening, and the velocity (1.7-6.8 microns . s-1) of sarcomere relaxation displayed identical temperature dependences (Q10 = 2.2), which are similar to that of the calcium pump of sarcoplasmic reticulum and are consistent with a rate limit imposed by enzyme-catalyzed mechanisms on all these parameters. On the other hand, the velocity (77-159 microns . s-1) of sequential sarcomere activation displayed a lower temperature dependence (Q10 = 1.5), which is consistent with a diffusion-limited and self-propagating release of calcium from one sarcomere to the other. The phasic contractile activity of the dissociated myocytes was inhibited by 10(-8)-10(6) M ryanodine (and not by myolemmal calcium blockers) under conditions in which calcium accumulation by sarcoplasmic reticulum in situ was demonstrated to proceed optimally. The effect of ryanodine is attributed to an interaction of this drug with sarcotubular structures, producing inhibition of calcium release from the sarcoplasmic reticulum. The consequent lack of sarcomere activation underlines the role of sarcoplasmic reticulum uptake and release in the phasic contractile activation of the electrochemically shunted myocytes.

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