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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate the combined use of an interactive racecar simulator and heat acclimation on psychomotor (driving) performance, eight rally drivers underwent 4 days of repeated heat (50 degrees C) exposure (1 h x day(-1)) during which they performed a simulated rally drive (3x12-min stages each separated by a 2-min break), after first cycling for 15 min at 125 W to induce some degree of fatigue and heat storage prior to beginning the rally. During the rally stages, a generic set of pace notes were read to the subject by a co-driver. In each simulation, sweat loss, heart rate, core (rectal) and skin temperatures were recorded and driving and psychomotor performance were assessed by recording stage times and time to complete a psychomotor test. Levels of physiological and perceived thermal strain were also recorded. Significant decreases in rally stage times (88 s; P<0.005), psychomotor test time (18 s; P<0.01), final core (0.25 degrees C; P<0.001) and skin (0.44 degrees C; P<0.005) temperatures, heart rate (16 beats x min(-1); P<0.05) and physiological (15 W x m(-2); P<0.005) and perceived thermal (3.7 units; P<0.01) strain were evident by the end of the final simulation, and a significant (P<0.05) increase in sweat sensitivity (+0.33 g x h(-1) x degrees C(-1)) was also recorded. These results suggest that both heat acclimation and race simulation can improve the psychomotor performance of rally drivers, although the relative contribution of each factor was not determined here. However, in a practical setting, these factors would not be used in isolation. After performing the acclimation and simulation protocol prior to an actual rally, drivers subjectively reported improvements in tolerating a high thermal load and in their ability to control the rally vehicle.
Comp Biochem Physiol A Mol Integr Physiol 2001 Apr
PMID:Performance enhancement in rally car drivers via heat acclimation and race simulation. 1128 14

Cold exposure facilitates body heat loss which can reduce body temperature, unless mitigated by enhanced heat conservation or increased heat production. When behavioral strategies inadequately defend body temperature, vasomotor and thermogenic responses are elicited, both of which are modulated if not mediated by sympathetic nervous activation. Both exercise and shivering increase metabolic heat production which helps offset body heat losses in the cold. However, exercise also increases peripheral blood flow, in turn facilitating heat loss, an effect that can persist for some time after exercise ceases. Whether exercise alleviates or exacerbates heat debt during cold exposure depends on the heat transfer coefficient of the environment, mode of activity and exercise intensity. Prolonged exhaustive exercise leading to energy substrate depletion could compromise maintenance of thermal balance in the cold simply by precluding continuation of further exercise and the associated thermogenesis. Hypoglycemia impairs shivering, but this appears to be centrally mediated, rather than a limitation to peripheral energy metabolism. Research is equivocal regarding the importance of muscle glycogen depletion in explaining shivering impairments. Recent research suggests that when acute exercise leads to fatigue without depleting energy stores, vasoconstrictor responses to cold are impaired, thus body heat conservation becomes degraded. Fatigue that was induced by chronic overexertion sustained over many weeks, appeared to delay the onset of shivering until body temperature fell lower than when subjects were rested, as well as impair vasoconstrictor responses. When heavy physical activity is coupled with underfeeding for prolonged periods, the resulting negative energy balance leads to loss of body mass, and the corresponding reduction in tissue insulation, in turn, compromises thermal balance by facilitating conductive transfer of body heat from core to shell. The possibility that impairments in thermoregulatory responses to cold associated with exertional fatigue are mediated by blunted sympathetic nervous responsiveness to cold is suggested by some experimental observations and merits further study.
Comp Biochem Physiol A Mol Integr Physiol 2001 Apr
PMID:Exertion-induced fatigue and thermoregulation in the cold. 1128 20

Males and females both express estrogen receptor (ER) in white adipose tissue (WAT), and estrogens appear to play an important role in regulating WAT in females. However, the role of ER in male WAT was unclear. In this review, we describe our work, which used wild type (WT) and ERalpha-knockout (alphaERKO) male and female mice to determine the role of ERalpha in regulating WAT and brown adipose tissue (BAT). There were progressive increases in WAT with advancing age in alphaERKO compared with WT males; weights of various WAT depots in alphaERKO males were increased by more than 100% compared with WT controls during adulthood. Conversely, BAT weight was similar in alphaERKO and WT males at all ages. Adipocyte areas and numbers were also increased in WAT from alphaERKO compared with WT males. Compared with WT controls, alphaERKO females also had increases in WAT. The alphaERKO mice also had insulin resistance and impaired glucose tolerance, similar to humans lacking ERalpha or aromatase. The obesity in alphaERKO males appeared to involve decreased energy expenditure rather than hyperphagia. In summary, ERalpha absence causes adipocyte hyperplasia and hypertrophy in WAT, but not BAT, and is accompanied by insulin resistance and glucose intolerance in both males and females. These results are the first evidence that the estrogen/ERalpha signaling system is critical in female and male WAT deposition, and may have clinical implications.
Mol Cell Endocrinol 2001 Jun 10
PMID:The role of estrogen and estrogen receptor-alpha in male adipose tissue. 1140 4

Neurotrophin-4 (NT-4) is produced by slow muscle fibers in an activity-dependent manner and promotes growth and remodeling of adult motorneuron innervation. However, both muscle fibers and motor neurons express NT-4 receptors, suggesting bidirectional NT-4 signaling at the neuromuscular junction. Mice lacking NT-4 displayed enlarged and fragmented neuromuscular junctions with disassembled postsynaptic acetylcholine receptor (AChR) clusters, reduced AChR binding, and acetylcholinesterase activity. Electromyographic responses, posttetanic potentiation, and action potential amplitude were also significantly reduced in muscle fibers from NT-4 knock-out mice. Slow-twitch soleus muscles from these mice fatigued twice as rapidly as those from wild-type mice during repeated tetanic stimulation. Thus, muscle-derived NT-4 is required for maintenance of postsynaptic AChR regions, normal muscular electrophysiological responses, and resistance to muscle fatigue. This neurotrophin may therefore be a key component of an activity-dependent feedback mechanism regulating maintenance of neuromuscular connections and muscular performance.
Mol Cell Neurosci 2001 Jul
PMID:Neuromuscular junction disassembly and muscle fatigue in mice lacking neurotrophin-4. 1146 Nov 53

Recent evidence indicates that hypoxia enhances the generation of oxidants. Little is known about the role of free radicals in contractility of the rat diaphragm during hypoxia. We hypothesized that antioxidants improve contractility of the hypoxic rat diaphragm and that xanthine oxidase (XO) is an important source of free radicals in the hypoxic diaphragm. The effects of N-acetylcysteine (NAC; 18 mM), Tiron (10 mM), and the XO inhibitor allopurinol (250 microM) were studied on isometric and isotonic force generation during hypoxia (PO(2) approximately 7 kPa). NAC and Tiron decreased maximal force generation, slowed the shortening velocity, and decreased the power output. Fatigue rate was decreased in the presence of either NAC or Tiron. Allopurinol did not alter the contractility or fatigability of the diaphragm. During hyperoxia (PO(2) approximately 85 kPa), neither NAC nor allopurinol affected the contractility or fatigability of the diaphragm. Thus free radicals play a significant role in diaphragm contractility during hypoxia. Whether antioxidants exert a beneficial or harmful effect on muscle performance depends on the contraction pattern of the muscle. Free radicals generated by XO do not play a role in diaphragm contractility during either hypoxia or hyperoxia.
Am J Physiol Lung Cell Mol Physiol 2001 Dec
PMID:Free radicals in hypoxic rat diaphragm contractility: no role for xanthine oxidase. 1170 36

Critical swimming speed (U(crit)) is a standard measurement to assess swimming capabilities of fishes. To conduct this measurement a fish is introduced into a water tunnel in which the current velocity can be controlled by the investigator. At the beginning of the measurement water velocity is low, approximately 1 body length (BL) s(-1), and is then incrementally increased at prescribed intervals. Fishes tend to maintain their position in the water tunnel against the current until fatigue sets in. The time and velocity at which the fish fatigue are used to calculate the critical swimming speed. This procedure is widely used to assess the effects of environmental conditions and pollutants on fish performance. Since the procedure is conducted in conditions that are far from representing most natural environment experienced by fishes, doubts have been raised about its ecological and ecophysiological relevance. Few studies examined correlations between critical swimming speed and traits that seem to be more ecologically relevant. Positive correlations were found between U(crit) and routine activity, metabolic rates and body size of open water, planktivorous fishes, metabolic rates and body size. These data indirectly suggest ecological relevancy of U(crit), but direct measurements relating U(crit) to reproductive success or survival are required to assess such relevancy.
Comp Biochem Physiol A Mol Integr Physiol 2001 Dec
PMID:Critical swimming speed: its ecological relevance. 1173 65

In infectious diseases and during inflammation, anorexia, loss of body weight, malaise, fatigue and depression are induced. These symptoms are correctively called 'sickness behaviors', and the central actions of cytokines play a role in their induction. The loss of body weight in cancer cachexia is also a result of development of sickness behaviors. It has been reported that the administration of NSAID ibuprofen to patients with cancer cachexia improves the loss in body weight. We studied the effect of NSAID on the loss of body weight by using rodent sickness behavior models. We have reported that sickness behaviors such as anorexia, decrease in body weight, and loss of locomotor activity are induced in concanavalin A (Con A)-induced mouse hepatitis and carbon tetrachloride-induced rat hepatitis. Zaltoprofen is a non-steroidal anti-inflammatory drug (NSAID) causes potent inhibition of cyclooxygenase-2 with fewer side effects on the gastrointestinal tract. Zaltoprofen improves the loss in body weight in both Con A-treated mice and carbon tetrachloride-treated rats. These results suggest the possible application of zaltoprofen for the treatment of sickness behaviors including loss of body weight occurring in cancer cachexia.
Int J Mol Med 2002 Apr
PMID:NSAID zaltoprofen improves the decrease in body weight in rodent sickness behavior models: proposed new applications of NSAIDs (Review). 1189 29

Muscle responses to tetanic electrical stimulation were detected by the non-invasive tensiomyographic (TMG) measuring method. The main objective of this study was to find out whether the TMG measuring method is suitable for monitoring the unfused tetanus (stimulation frequencies ranging from 1 Hz to the fusion frequency (ff)--the frequency at which tetanus occurs), and whether this monitoring provides any information on skeletal muscles' structural or functional changes. The muscle adaptation process was observed in damped unfused tetanus (DUT). The measured results in the clinical environment as well as on the sports field indicate that DUT is caused by a type II muscle fibres fatigue process. Separate observation of type II muscle fibres enables more efficient treatment and observation of pathological changes, and helps professional athletes and their trainers to better understand the influence of training stimuli on the training process.
Cell Mol Biol Lett 2002
PMID:The muscle adaptation process as a result of pathological changes or specific training procedures. 1209 88

The aim of this study was to test a hypothesis that a longer duration of isometric contraction is related to an increased oxygenation status of the muscle. A group of trained rock climbers and untrained subjects performed 15 kp sustained isometric contraction until fatigue set in. The oxygenation status was assessed using near infrared spectroscopy (ISS, USA). The results support the hypothesis. The concentration of relative oxygenated hemoglobin was higher in the rock climbers than in the untrained subjects. The relative total hemoglobin did not differentiate the two groups enough to show that blood volume also strongly influences contraction time.
Cell Mol Biol Lett 2002
PMID:Differences in the oxygenation of the forearm muscle during isometric contraction in trained and untrained subjects. 1209 90

Many similarities exist between the key characteristics of muscular metabolism in marine invertebrates and those found in vertebrate striated muscle, even though there are important phosphagens and glycolytic end products that differ between groups. Lifestyles and modes of locomotion also vary extremely among invertebrates thereby shaping the pattern of exercise metabolism. In accordance with the limited availability of integrated ecological and physiological information the present paper reports recent progress in the exercise physiology of cephalopods, which are characterized by high rates of aerobic and anaerobic energy turnover during high velocity hunts or escapes in their pelagic environment, and a sipunculid worm, which mostly uses anaerobic resources during extended marathon-like digging excursions in the hypoxic marine sediment. Particular attention is paid to how lifestyle and oxygen availability in various marine environments shapes the use and rates of aerobic and anaerobic metabolism and acidosis as they depend on activity levels and energy saving strategies. Whereas aerobic scope and, accordingly, use of ambient oxygen by blood oxygen transport and skin respiration is maximized in some squids, aerobic scope is very small in the worm and anaerobic metabolism readily used upon muscular activity. Until recently, it was widely accepted that the glycolytic end product octopine, produced in the musculature of these invertebrates, acted as a weak acid and so did not compromise acid-base balance. However, it has now been demonstrated that octopine does cause acidosis. Concomitant study of tissue energy and acid-base status allows to evaluate the contribution of glycolysis, pH and free ADP accumulation to the use of the phosphagen and to the delayed drop in the Gibb's free energy change of ATP hydrolysis. The analysis reveals species specific capacities of these mechanisms to support exercise beyond the anaerobic threshold. During high intensity anaerobic exercise observed in squid, the levels of ATP free energy change finally fall to critical minimum levels contributing to fatigue. Maintenance of sufficiently high energy levels is found at low but extended rates of anaerobic metabolism as observed in the long term digging sipunculid worm. The greatest aerobic and anaerobic performance levels are seen in squid inhabiting the open ocean and appear to be made possible by the uniform and stable physicochemical parameters (esp. high O(2) and low CO(2) levels) that characterize such an environment. It is suggested that at least some squid operate at their functional and environmental limits. In extremely different environments, both the worm and the squids display a tradeoff between oxygen availability, temperature, performance level and also, body size.
Comp Biochem Physiol A Mol Integr Physiol 2002 Oct
PMID:Environmental and functional limits to muscular exercise and body size in marine invertebrate athletes. 1220 2


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