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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mechanical and histochemical characteristics of the lateral gastrocnemius (LG) muscle of the rat were examined 21 days after capsaicin injection into the LG muscle. The capsaicin caused a decrease in generation rate of twitch and tetanic tension and an increase in fatigue resistance of LG muscle. The histochemical muscle fiber profile evaluated by myosin adenosine triphosphatase and reduced nicotinamide adenine dinucleotide tetrazolium reductase methods showed an increase of type I and IIC fibers and a decrease of the type IIB in whole muscle, and a decrease of the IIA, IIX fibers in the red part accompanied by their increase in the white part. Therefore the capsaicin treatment, which selectively eliminated fibers belonging to the III and IV groups of muscle afferents, induced muscle fiber transformation from fast contracting fatiguing fibers to slowly contracting nonfatiguing ones.
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PMID:Partial transformation from fast to slow muscle fibers induced by deafferentation of capsaicin-sensitive muscle afferents. 934 57

The extensor carpi radialis muscle of the horse is deceptive at first appearance. It has a fusiform shape similar to other forearm extensor muscles. The fiber arrangement also appears long and relatively parallel. However, it may contain two or more compartments that correlate with differing functional roles. Histochemical and immunocytochemical analysis of proximal and distal regions of the muscle (n = 9) demonstrate that the proximal portion of the muscle is composed of a mean of 13% type I, presumed slow twitch, and 61% type IIb, presumed fast twitch fibers. In contrast, the distal compartment is composed of a mean of about 43% type I and only 22% type IIB fibers. The type I and IIa fibers are all highly aerobic based on nicotinamide dinucleotide tetrazolium reductase reactions. Correlative data regarding the myosin isoforms has been obtained with 4% SDS-PAGE analysis of myosin heavy chain isoforms which demonstrate isoforms migrating at rates similar to rat type I, IIa, and IIx. The latter has been referred to as type IIB/X in a study of the horse's gluteus medius muscle. We propose that the in-series 'compartmentalization' of the muscle, while not conforming strictly to the definitions of neuromuscular compartments, relates to the insertion of the lacertus fibrosus, a distal slip of the biceps brachii, upon the extensor carpi radialis. Earlier studies demonstrated a high proportion of type I fibers in the equine lateral biceps brachii which were thought to stabilize the shoulder during long periods of quiet standing. Because of action imposed on the distal compartment by the biceps brachii, slow and fatigue-resistant functions are part of the limb's passive stay apparatus to effect long-term standing by the horse. Thus, the fatigue-resistant compartments of biceps brachii and extensor carpi radialis may constitute an in-series arrangement of the two muscles. The proximal compartment is suited to provide powerful, more fatigable contractions during locomotion and likely affects stress or strain within the distal postural compartment.
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PMID:Architecture and the division of labor in the extensor carpi radialis muscle of horses. 957 63

Low-frequency fatigue was investigated in nine female and one male adult pigtail monkeys (Macaca nemestrina) with a mean weight of 5.3 kg (range 4.3 to 6.5 kg). After sedation and anesthesia, silver electrodes were inserted into the anterior and posterior parts of the right masseter muscle. The contralateral muscle was used as a control. The masseter muscles were stimulated for 3 minutes (4 Hz, 2 ms, 100 V). After a 5-minute rest period, the stimulation was repeated with the same duration and voltage but at a higher frequency of 8 Hz. Bite forces were measured, and muscle biopsies were obtained from the central part of the right masseter and immediately frozen in liquid nitrogen. After freeze-drying, a fluorometric analysis that used enzymatic methods for measuring levels of glycogen, glucose, lactate, pyruvate, creatine phosphate, nicotinamide-adenine dinucleotide (NAD), and reduced NAD (NADH) was performed. The bite force decreased by 12% after the initial 3 minutes of work. After the second contraction the bite force decreased to 56%. Prominent substrate depletion was observed. The precontraction levels of glycogen, glucose, and phosphocreatine were all reduced. The NADH and the NAD concentrations increased. An accumulation of metabolites was evident. The pyruvate increased by 32% and lactate levels increased by a factor of 3. The male measurements were comparable to the nine female measures for each assessment. The substantial substrate depletion in combination with a prominent accumulation of metabolites may contribute to the development of low-frequency fatigue.
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PMID:Frequency-dependent fatigue development during electrical stimulation in the masseter muscle of pigtail monkeys. 1042 74

The present study was conducted on vocal muscles removed at autopsy from adult individuals (10 men and 8 women, ages ranging from 48 to 78 years) with no laryngeal disease. Histologic analysis was performed with hematoxylin and eosin staining, and histochemical analysis was performed by nicotinamide-adenine-dinucleotide tetrazolium reductase, succinate dehydrogenase, and acid and alkaline myofibrillar adenosine triphosphatase reactions. The histochemical reactions showed that the muscle consists of slow-twitch oxidative (SO), fast-twitch glycolytic (FG), and fast-twitch glycolytic oxidative (FOG) fibers distributed in mosaic form. The frequencies of SO, FOG, and FG fibers were 40.50%, 54.75%, and 4.75%, respectively. The higher frequency of SO and FOG oxidative fibers characterizes the muscle as having aerobic metabolism, resistance to fatigue, and fast contraction. The mean minimum diameters were 31.37 microm for SO fibers and 36.46 microm for FOG and FG fibers.
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PMID:Morphometric and histochemical study of the human vocal muscle. 1065 16

The distribution of Fos-immunoreactive (Fos-ir) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d)-reactive neurons in the rat lumbar spinal cord was examined following muscle fatigue caused by intermittent high-rate (100 s(-1)) electrical stimulation of the triceps surae muscle or the ventral root L5 (VRL5) for 30 min. Following both types of stimulation, the fatigue-related c-fos gene expression was more extensive in the L2-L5 segments on the stimulated side, and the majority of Fos-ir neurons were concentrated in the dorsal horn. After direct muscle stimulation, the highest number of Fos-ir neurons were detected in two regions: layer 5, and superficial layers (1 and 2(o)), although many labeled cells were also found in layers 3, 4, 6, and 7. In response to VRL5 stimulation, the maximal density of Fos-ir neurons was detected in the middle and lateral parts of layers 1 and 2(o), the zone of termination of high-threshold muscle afferents(.) Statistically significant prevalence of Fos-ir cell number was also found in layers 5 and 7 on the stimulated side. A few Fos-ir neurons were detected in the ventral horn (layer 8 and area 10) on both sides. The lamellar distribution of NADPH-d-reactive neurons was similar over all experimental groups of animals. In the L3-L6 segments, such reactive cells were arranged in two distinct regions: dorsal horn (layers 2(i), 3, and 5) and area 10; in the L1 and L2 segments, an additional cluster of NADPH-d positive cells was found in the intermediolateral cell column (IML). Double-labeled cells were not detected. We suggest that c-fos expression in response to muscle fatigue reveals activity of functionally different types of spinal neurons which could operate together with NOS-containing cells in pre-motoneuronal networks to modulate the motoneuron output.
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PMID:c-fos Expression and NADPH-d reactivity in spinal neurons after fatiguing stimulation of hindlimb muscles in the rat. 1174 76

In Alzheimer's disease (AD) brain increased lipid peroxidation and decreased energy utilization are found. Mitochondria membranes contain a significant amount of arachidonic and linoleic acids, precursors of lipid peroxidation products, 4-hydroxynonenal (HNE) and 2-propen-1-al (acrolein), that are extremely reactive. Both alkenals are increased in AD brain. In this study, we examined the effects of nanomolar levels of acrolein on the activities of pyruvate dehydrogenase (PDH) and Alpha-ketoglutarate dehydrogenase (KGDH), both reduced nicotinamide adenine dinucleotide (NADH)-linked mitochondrial enzymes. Acrolein decreased PDH and KGDH activities significantly in a dose-dependent manner. Using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS), acrolein was found to bind lipoic acid, a component in both the PDH and KGDH complexes, most likely explaining the loss of enzyme activity. Acrolein also interacted with oxidized nicotinamide adenine dinucleotide (NAD(+)) in such a way as to decrease the production of NADH. Acrolein, which is increased in AD brain, may be partially responsible for the dysfunction of mitochondria and loss of energy found in AD brain by inhibition of PDH and KGDH activities, potentially contributing to the neurodegeneration in this disorder.
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PMID:Acrolein inhibits NADH-linked mitochondrial enzyme activity: implications for Alzheimer's disease. 1471 35

Fatigue, a common symptom among persons living with HIV/AIDS, is often underreported and undertreated. However, given fatigue's pervasive effects on well-being and functioning, the identification of its physiologic and psychological causes and strategies to alleviate it are important to patients' quality of life. As part of a study to understand better how HIV-positive middle-aged and older adults (50+) manage common symptoms, 49 participants discussed in depth their experience with fatigue. Most engaged in both self-care activities and sought the assistance of a health care professional. Frequent strategies included dietary changes, vitamins, modification of routines, rest, exercise, and prescribed medications for anemia, Vitamin B(12) deficiency, or testosterone deficiency. Complementary and alternative medicine (e.g., acupuncture, massage, herbal remedies, special juices) was also commonly used. Participants often used multiple strategies to alleviate their fatigue, possibly because of their tendency to attribute it to multiple causes. These HIV-positive older adults were also apt to view fatigue as an indirect indicator of their overall health status and immune functioning. This may explain why many of the coping strategies they used could be considered approaches to improving their overall health status as a means to increasing their energy levels. Health care professionals can play an important role in helping HIV-positive individuals manage their fatigue. The majority of participants tried to implement the coping suggestions offered by health care professionals, as well as those from family, friends, and support group members.
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PMID:Strategies for coping with fatigue among HIV-positive individuals fifty years and older. 1518 11

This study addressed the effects of nandrolone decanoate (ND) on contractile properties and muscle fiber characteristics of rats submitted to swimming. Male Wistar rats were grouped in sedentary (S), swimming (Sw), sedentary+ND (SND), and swimming+ND (SwND), six animals per group. ND (3 mg/kg) was injected (subcutaneously) 5 days/week, for 4 weeks. Swimming consisted of 60-min sessions (load 2%), 5 days/week, for 4 weeks. After this period, the sciatic nerve extensor digitorum longus (EDL) muscle was isolated for myographic recordings. Fatigue resistance was assessed by the percent (%) decline of 180 direct tetanic contractions (30 Hz). Safety margin of synaptic transmission was determined from the resistance to the blockade of indirectly evoked twitches (0.5 Hz) induced by pancuronium (5 to 9x10(-7) M). EDL muscles were also submitted to histological and histochemical analysis (haematoxylin-eosin (HE); nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR)). Significant differences were detected by two-way ANOVA (p<0.05). ND did not change body mass, fatigue resistance or kinetic properties of indirect twitches in either sedentary or swimming rats. In contrast, ND reduced the safety margin of synaptic transmission in sedentary animals (SND=53.3+/-4.7% vs. S=75.7+/-2.0%), but did not affect the safety margin in the swimming rats (SwND=75.81+/-3.1% vs. Sw=71.0+/-4.0%). No significant difference in fiber type proportions or diameters was observed in EDL muscle of any experimental group. These results indicate that ND does not act as an ergogenic reinforcement in rats submitted to 4 weeks of swimming. On the other hand, this study revealed an important toxic effect of ND, that it reduces the safety margin of synaptic transmission in sedentary animals. Such an effect is masked when associated with physical exercise.
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PMID:Effects of nandrolone decanoate on the neuromuscular junction of rats submitted to swimming. 1568 30

Combining nutritional supplements to achieve synergistic benefit is a common practice in the nutraceutical industry. However, establishing added health benefit from a combination of natural ingredients is often assumed, untested and without regard to the principle of metabolic competition between the active components. Here, we report on the combination of a cat's claw water extract (C-Med-100, carboxy alkyl esters = active ingredients) + medicinal mushroom extracts (Cordyceps sinensis, Grifola blazei, Grifolafrondosa, Trametes versicolor and Ganoderma lucidum, polysaccharides = active ingredients) + nicotinamide + zinc into a formulation designed to optimize different modes of immunostimulatory action, and yet that would avoid metabolic antioxidant competition yielding less than expected efficacious effects. Isobole curve analyses of these two active classes of ingredients determined by growth inhibition of HL-60 human leukemic cells in vitro confirmed they were indeed synergistic when in combination, and not metabolically competitive. Furthermore, an in vivo study showed significant health benefit for 14 subjects treated for 4 weeks with the unique C-Med-100/mushroom extract formulation in that they had reduced pain, reduced fatigue, weight loss and a reduced presence of DNA damage in peripheral blood assessed by (8-OH) guanine DNA adducts and elevation in serum protein thiols. Because this broad-based panel of clinical parameters indicating clinical efficacy has never been demonstrated before for either of the active ingredients evaluated alone in humans, these data were taken as strong evidence that the combination of C-Med-100 + mushroom extracts + nicotinamide + zinc gave additive or synergistic effects to health benefit, and thus supported no efficacious limits from metabolic competition regarding this particular formulation.
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PMID:Formulation and in vitro/in vivo evaluation of combining DNA repair and immune enhancing nutritional supplements. 1589 2

The tricarboxylic acid (TCA) cycle is the major final common pathway for oxidation of carbohydrates, lipids and some amino acids, which produces reducing equivalents in the form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide that result in production of large amounts of adenosine triphosphate (ATP) via oxidative phosphorylation. Although regulated primarily by the products of ATP hydrolysis, in particular adenosine diphosphate, the rate of delivery of reducing equivalents to the electron transport chain is also a potential regulatory step of oxidative phosphorylation. The TCA cycle is responsible for the generation of approximately 67% of all reducing equivalents per molecule of glucose, hence factors that influence TCA cycle flux will be of critical importance for oxidative phosphorylation. TCA cycle flux is dependent upon the supply of acetyl units, activation of the three non-equilibrium reactions within the TCA cycle, and it has been suggested that an increase in the total concentration of the TCA cycle intermediates (TCAi) is also necessary to augment and maintain TCA cycle flux during exercise. This article reviews the evidence of the functional importance of the TCAi pool size for oxidative metabolism in exercising human skeletal muscle. In parallel with increased oxidative metabolism and TCA cycle flux during exercise, there is an exercise intensity-dependent 4- to 5-fold increase in the concentration of the TCAi. TCAi concentration reaches a peak after 10-15 minutes of exercise, and thereafter tends to decline. This seems to support the suggestion that the concentration of TCAi may be of functional importance for oxidative phosphorylation. However, researchers have been able to induce dissociations between TCAi pool size and oxidative energy provision using a variety of nutritional, pharmacological and exercise interventions. Brief periods of endurance training (5 days or 7 weeks) have been found to result in reduced TCAi pool expansion at the start of exercise (same absolute work intensity) in parallel with either equivalent or increased oxidative energy provision. Cycloserine inhibits alanine aminotransferase, which catalyses the predominant anaplerotic reaction in exercising human muscle. When infused into contracting rat hindlimb muscle, TCAi pool expansion was reduced by 25% with no significant change in oxidative energy provision or power output. Glutamine supplementation has been shown to enhance TCAi pool expansion at the start of exercise with no increase in oxidative energy provision. In summary, there is a consistent dissociation between the extent of TCAi pool expansion at the onset of exercise and oxidative energy provision. At the other end of the spectrum, the parallel loss of TCAi, glycogen and adenine nucleotides and accumulation of inosine monophosphate during prolonged exercise has led to the suggestion that there is a link between muscle glycogen depletion, reduced TCA cycle flux and the development of fatigue. However, analysis of serial biopsies during prolonged exercise demonstrated dissociation between muscle TCAi content and both muscle glycogen content and muscle oxygen uptake. In addition, the delay in fatigue development achieved through increased carbohydrate availability does not attenuate TCAi reduction during prolonged exercise. Therefore, TCAi concentration in whole muscle homogenate does not seem to be of functional importance. However, TCAi content can currently only be measured in whole muscle homogenate rather than the mitochondrial subfraction where TCA cycle reactions occur. In addition, anaplerotic flux rather than TCAi content per se is likely to be of greater importance in determining TCA cycle flux, since TCAi content is probably merely reflective of anaplerotic substrate concentration. Methodological advances are required to allow researchers to address the questions of whether oxidative phosphorylation is limited by mitochondrial TCAi content and/or anaplerotic flux.
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PMID:Tricarboxylic acid cycle intermediate pool size: functional importance for oxidative metabolism in exercising human skeletal muscle. 1802 94


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