Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lizard skeletal muscle fiber types were investigated in the iliofibularis (IF) muscle of the desert iguana (Dipsosaurus dorsalis). Three fiber types were identified based on histochemical staining for myosin ATPase (mATPase), succinic dehydrogenase (SDH), and alphaglycerophosphate dehydrogenase (alphaGPDH) activity. The pale region of the IF contains exclusively fast-twitch-glycolytic (FG) fibers, which stain dark for mATPase and alphaGPDH, light SDH. The red region of the IF contains fast-twitch-oxidative-glycolytic (FOG) fibers, which stain dark for all three enzymes, and tonic fibers, which stain light for mATPase, dark for SDH, and moderate for alphaGPDH. Enzymatic activities of myofibrillar ATPase, citrate synthase, and alphaGPDH confirm these histochemical interpretations. Lizard FG and FOG fibers possess twitch contraction times and resistance to fatigue comparable to analogous fibers in mammals, but are one-half as oxidative and several times as glycolytic as analogous fibers in rats. Lizard tonic fibers demonstrate the acetylcholine sensitivity common to other vertebrate tonic fibers.
 ...
PMID:Histochemical, enzymatic, and contractile properties of skeletal muscle fibers in the lizard Dipsosaurus dorsalis. 645 26

The present study examines the use of photographic densitometry combined with atomic absorption spectrophotometry for the quantitation of enzyme activities (SDH and ATPase) in fresh frozen sections of rat tibialis anterior muscles. The technique eliminates some difficulties which are inherent in other methods. The reliability of the technique was found to be in the 98% range; the results were precise for all samples studied. The use of SDH to separate muscle fibers into "types" was found to be totally inaccurate since a full spectrum of activities was observed. ATPase activities could separate easily into two groups, but a continuum of ATPase activities was observed in the fast-twitch fibers. The simultaneous use of both enzymes was capable of separating the FG, FOG and SO fibers; however, variation within a single type was considerable and a great deal of information was lost when using any classification system. The continuum of SDH activities indicates the motor units are arranged as a spectrum of fatigue-resistant contractile units. The range of ATPase activities observed is comparable to ranges of motor unit contraction times emphasizing the importance of this enzyme in the regulation of contraction speed.
 ...
PMID:Alternative method for quantitative enzyme histochemistry of muscle fibers. Application of photographic densitometry combined with atomic absorption spectrophotometry. 646 18

This review describes muscle fiber types based on their histochemical, ultrastructural, biochemical, and physiologic properties. Reportedly the speed of muscle fiber contraction is directly proportional to relative myosin ATPase activity (at pH 9.4) while fatigability relates to relative oxidative capacity. Type I fibers have low ATPase activity (at pH 9.4), are slow twitch, have high oxidative and low glycolytic capacity, and are relatively resistant to fatigue. Type IIA fibers have high myosin ATPase activity (pH 9.4), are fast twitch, have high oxidative and glycolytic capacity, and are relatively resistant to fatigue. Type IIB fibers have high myosin ATPase activity (pH 9.4), are fast twitch, have low oxidative and high glycolytic capacity, and fatigue rapidly.
 ...
PMID:Muscle fiber types. 646 27

Motor units of the medial gastrocnemius (MG) and the single lateral gastrocnemius/soleus (LG/S) muscles of the opossum (Didelphis virginiana) were found to have uniformly slow contraction times relative to homologous muscles of the cat. Though a broad range of peak tetanic tensions was found among motor units from both muscles, most of the motor units were quite large relative to tension of the whole muscle. Comparison of the relative sizes of motor units showed that those of LG/S are significantly larger and slower than the units of MG. This suggests that the motor units of the two muscles may be differentially recruited during different behaviors. All of the MG and LG/S motor units were highly or moderately resistant to fatigue. Histochemical staining for NADH-diaphorase activity indicated consistently high levels of the enzyme in all of the fibers of both muscles. Apparently, all of the fast motor units consist of fast oxidative/glycolytic (FOG)-type muscle fibers. Our data provide functional evidence that the types of myofibrillar ATPase demonstrated by Brooke and Kaiser ('70), are not necessarily correlated to physiological classification of fiber types as slow oxidative (SO), fast oxidative/glycolytic (FOG), and fast glycolytic (FG) (Peter et al., '72). Perhaps compartmentalization of muscle fiber types may be a first step in the separation of muscles into multiple heads during the evolution of specialization to diverse locomotor habits among the mammals.
 ...
PMID:Motor units of the primary ankle extensor muscles of the opossum (Didelphis virginiana): functional properties and fiber types. 648 10

1. This report describes selected histochemical and physiological properties of the motor units of adult cat soleus muscle approximately one year after self- and cross-reinnervation with the nerve of the heterogenous flexor hallucis longus (f.h.l.). Self-reinnervated f.h.l. motor units are also considered. Whole muscles were tested for fibre reaction to alkaline pre-incubated ATPase, alpha-glycerophosphate dehydrogenase (alpha-GPD) and reduced nicotinamide adenine dinucleotide diaphorase (NADH-D). Motor units were isolated and studied by splitting the ventral root in acute preparations.2. The histochemical fibre type profile in the self-reinnervated muscle was comparable to normal muscle as was mean twitch contraction time, twitch-tetanus ratio and fatigue index. The mean tetanic tension of the soleus self- and cross-reinnervated motor units appeared close to a normal soleus whereas the mean tetanic tension of the f.h.l. self-reinnervated units was significantly less than a normal f.h.l.3. An average of 14% of the fibres of the soleus cross-reinnervated muscles had high ATPase and a alpha-GPD staining intensity in contrast to normal and self-reinnervated soleus in which such fibres are absent. Thus alkaline lability of myofibrillar ATPase increased in some fibres of what was originally a homogeneous population. The small increase in the number of densely staining fibres for ATPase at an alkaline pH (14%) was associated with a 73% decrease in (mean) contraction time (41 +/- 11 ms) of the thirty-three cross-reinnervated muscle units studied, with no unit's contraction time greater than 60 ms. Mean contraction times for the self-reinnervated soleus and f.h.l. muscles were 78 +/- 31 ms and 27 +/- 8 ms respectively.4. All fibres of the soleus cross-reinnervated muscles showed intense reaction to NADH-D, as was true of self-reinnervated soleus. This staining pattern is typical of normal soleus. In concordance, these motor units consistently demonstrated a high resistance to fatigue when stimulated for a four-minute period.5. These results suggest that in the adult self-and cross-reinnervated soleus muscle, there is some active mechanism which regulates the eventual size of motor units as reflected by tetanic tension.6. Change in contraction time from that typical for a soleus unit to that similar to an f.h.l. unit remains incomplete one year after cross-reinnervation. Within this time this partial change in single motor units reflects incomplete neural control of this property rather than a mixture of self- and foreign-innervation.7. A greater degree of independence from neural control to conversion of the histochemically demonstrated myofibrillar ATPase activity exists than is the case for contraction time.
 ...
PMID:Histochemical and physiological properties of cat motor units after self-and cross-reinnervation. 715 31

Muscle fiber type and isokinetic strength and fatigue were examined in nine highly trained canoe and kayak paddlers. Needle biopsies were taken from the right vastus lateralis and biceps brachii muscles and the samples stained for myofibrillar ATPase. Baseline elbow flexion and knee extension isometric (0 degrees . s-1) and isokinetic (60 degrees . s-1 or 1.05 rad . s-1 and 180 degrees . s-1 or 3.14 rad . s-1) peak torques were determined. Each subject then performed two series of 50 isokinetic contractions at an angular velocity of 180 degrees . s-1: elbow flexion and knee extension series, separated by 3 h. The percentage of slow twitch fibers was similar in the biceps brachii (43.9%) and the vastus lateralis (43.3%). The fast twitch/slow twitch fiber area ratio was significantly higher in the more highly trained biceps brachii due to larger FT fibers. No relationship was found between fiber type composition and baseline peak torques or decline in peak torque due to the fatigue regimens. Baseline peak torque correlated with initial strength level, body weight, and limb girth. The results suggested that for these paddlers muscle strength and the decline in strength induced by repetitive isokinetic contractions were more dependent on characteristics of body size than on fiber type composition.
 ...
PMID:Isokinetic strength, endurance, and fiber type composition in elite American paddlers. 719 55

A comparison of the anatomy, fiber type profiles, and contractile properties of the wrist flexor muscles was undertaken in the cat. Isometric contractile characteristics were measured for each muscle. Three muscle fiber types, FG, FOG, and SO, were differentiated by staining cross sections of each muscle for ATPase, NADH diaphorase, SDH, and alpha-GPD activities. The wrist flexor muscles ranged from less than 1% to 49% SO fiber content; with two of the five heads of the flexor digitorium profundus (FDP) having 1% or less SO fibers (FDP1-1.07%, FDP5-0.81%) and the humeral head of the flexor carpi ulnaris muscle (FCUh) having the greatest content of SO fibers. The mean contraction time (CT) plus one-half relaxation time for an isometric twitch was correlated with the percentage of SO fibers and ranged from 40.5 to 111.8 ms. Except for the FCU (37ms), the CT was less than 25 ms for the wrist flexor muscles. The uniarticular wrist flexor muscles, the flexor carpi radialis (FCR), and the FCU had the highest percentage of SO fibers and were more fatigue-resistant that the multiarticular muscles. Considerable differences exist in muscle structure, fiber type proportions, and contractile properties between the FCR and FCU, which may be related to functional differences between the two sides of the wrist that may exist during the placement of the foot during locomotion.
 ...
PMID:Morphological organization and contractile properties of the wrist flexor muscles in the cat. 725 81

There is growing evidence that the amyloid beta-peptide (beta 1-40) is involved in the aetiology of Alzheimer's disease also implicating an altered calcium homeostasis of affected cells. Beta 1-40 has been proposed to form calcium channels in synthetic bilayer membranes [1]. We wanted to investigate in the present study whether beta 1-40 (or fragments thereof) could act as ionophores in a biological membrane like the one in human erythrocytes. Incubation of the cells for 2 h and 4 h at 37 degrees C together with 6 mumol L-1 of beta 1-40 or of fragments beta 1-28 and beta 25-35, resulted in a significantly decreased energy charge qualitatively similar to the one obtained by a known calcium ionophore (A 23187, 0.05 mumol L-1). Moreover, beta 1-40 and its two fragments induced a significant alteration of 45Ca permeability in human red blood cells of the same type as the one achieved by the calcium ionophore. The ionophoric action of beta 1-40 and its two fragments may lead to an increase of the intracellular calcium ion concentration, in turn resulting in enhanced Ca(2+)-ATPase activity and a decrease in energy charge. This may be valid also for neuronal plasma membranes and could, therefore, be a possible aetiological mechanism in Alzheimer's disease.
 ...
PMID:Alzheimer amyloid beta-peptides exhibit ionophore-like properties in human erythrocytes. 755 64

To re-establish anal function in fecally incontinent patients it may be feasible to transpose the gracilis muscle around the anal canal, using electrical stimulation to trigger contraction. However, because the fast-twitching gracilis muscle is incapable of prolonged contraction without fatigue, it is necessary to convert it to a slow-twitching, fatigue-resistant muscle. We demonstrated this conversion by longterm electrical stimulation at low frequencies using a rabbit model. The nerve to the gracilis muscle was continuously stimulated at 2 Hz, 5 Hz, and 10 Hz for 2, 4, or 6 weeks. In the 6-week conditioning group, the percentage of type I fibers, identified by ATPase staining, increased as the conditioning frequency became higher, but the twitch contraction speed reduced with conditioning at a frequency of more than 5 Hz. The fatigue resistance improved by conditioning at 10 Hz, and conversion occurred in 6 weeks. Thus, we concluded that conditioning at 10 Hz for 6 weeks can convert rabbit gracilis muscle to a slow-twitching, fatigue-resistant muscle suitable for use as a neoanal sphincter.
 ...
PMID:Conversion of the rabbit gracilis muscle for transposition as a neoanal sphincter by electrical stimulation. 764 Apr 52

A broadly held opinion is that fatigue is not due to an insufficient supply of ATP to the energy consuming mechanisms because tissue [ATP] always remains at least one order of magnitude higher than Km for ATP of any ATPase. In general these findings also suggest that ATP consumption is well balanced with ATP regeneration even in the fatigued muscles. This balance is achieved by down-regulation of ATP consumption. Potentially this down-regulation could be accomplished by any product of the ATPase reaction and the role of Pi and H+ accumulation in this regulation has been discussed in the literature. The purpose of this paper is to describe known compartmentalization of ATP regeneration systems in muscle cell, their importance in the regulation of [adenine nucleotide] in the vicinity of ATPases and how such local ATP regeneration maybe important in the etiology of muscle fatigue. Available experimental evidence suggests that the binding of creatine kinase and glycolytic enzymes in the vicinity of sites where ATP is hydrolyzed and functional coupling between these ATP regenerating mechanisms and ATPase can generate ATPase microenvironments that have an important role in the regulation of ATPase function. Main function of this ATP regeneration is to keep the local ADP/ATP ratios favorable for ATPase function, which seems to be especially important when ATPase turnover is high. Unfortunately, the maximum rate of local ATP regeneration relative to that of ATP hydrolysis in vivo is not known, mainly because in vitro determinations underestimate this value due to a decrease in the fractional of loosely abound enzyme to the preparation during isolation procedure.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The importance of ATPase microenvironment in muscle fatigue: a hypothesis. 764 8


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>