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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Whole-organism oxygen uptake rate and its temperature sensitivity (determined using regression analyses and estimates of Q10) were examined in six closely related weevil species (Palirhoeus eatoni, Bothrometopus randi, Bothrometopus elongatus, Bothrometopus parvulus, Ectemnorhinus similis, and Ectemnorhinus marioni) from sub-Antarctic Marion Island over a short time period and using the same methods. Bothrometopus elongatus, B. parvulus, and the two Ectemnorhinus species have populations at both high and low elevations, and pairwise comparisons of these species were made. Regressions of the log of oxygen uptake rate on temperature and Q10 values revealed that the Ectemnorhinus species have a significantly greater thermal sensitivity than do species in the genera Bothrometopus and Palirhoeus. This may be considered an adaptation of the former to their moist lowland habitats and the requirements of angiosperm-feeding in E. similis. It is argued that elevated oxygen uptake rates and reduced slopes of the regression of the log of oxygen uptake rate on temperature in species and populations from high altitudes compared with those from low elevations provide evidence for metabolic cold adaptation. In addition, it seems likely that elevated oxygen uptake rates and their reduced thermal sensitivity within the genera Bothrometopus and Palirhoeus are an adaptation to the cold Neogene environments they evolved in. However, because data on the more basal taxa in the Ectemnorhinus group of weevils are not available, this temperature compensation could not be attributed conclusively to adaptation. Q10's of the lowland populations of all the species were negatively correlated with body water content, and it is suggested that the low temperature sensitivity of metabolism in P. eatoni and the Bothrometopus species may also be due to constraints imposed on them by their dry habitats.
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PMID:The influence of habitat and altitude on oxygen uptake in sub-Antarctic weevils. 923 83

The heart rate of crustaceans changes with variations in ambient temperature within the normal environmental range (Maynard, 1960). The temperature coefficient (Q10) of the heart rate of crabs over the range 4­19 °C is about 2 (Florey and Kriebel, 1974). There are few studies of the heart response to a rapid change in temperature, although aquatic crustaceans often meet with warm or cold water masses (Spaargaren and Achituv, 1977). Electromechanical coupling of muscle fibres becomes less effective with decreasing temperature (Dudel and Ruedel, 1968), but a mechanism has been described that compensates for the tonus effect during leg muscle activity (Fischer and Florey, 1981). Compensatory mechanisms may also exist for heart muscle, and I have recently found that myocardial cells of a marine lobster begin to produce large action potentials in response to cooling. Lobster myocardial fibres develop tension in response to excitatory junction potentials (EJPs) generated by impulse activity of motor neurones in the cardiac ganglion (Van der Kloot, 1970; Anderson and Cooke, 1971; Kuramoto and Kuwasawa, 1980; Kuramoto and Ebara, 1984a). The heart tension produced is fed back to the cardiac ganglion because the cardiac neurones are sensitive to filling pressure (Maynard, 1960; Kuramoto and Ebara, 1984a, 1885, 1988, 1991). Thus, the responses of the isolated heart to cooling will result from the combined activities of the cardiac ganglion and the muscle cells. This report focuses on the development of a spiking response by the myocardial cells when the heart is cooled. The spikes produced correspond to enhanced contractions of the myocardium, suggesting that the myocardial cells may use this as a mechanism to compensate for the reduced efficacy of excitation­contraction coupling that occurs with falling temperature. Lobsters (Panulirus japonicus Von Siebolt, both sexes, approximately 200 g, N=25) were reared in an indoor aquarium continuously supplied with fresh natural sea water. Seasonal changes of aquarium temperature ranged from 15 to 25 °C. The isolated hearts were subjected to cooling experiments. The rate of cooling ranged from 1 to 3 °C min-1, the magnitude from 1 to 6 °C and the duration from 5 to 6 min. The methods for perfusing and recording from the isolated hearts were substantially the same as those used previously (Kuramoto and Ebara, 1984a, 1985, 1988, 1991). The perfusion saline was switched to warm or cold. Bath temperature near the heart was monitored with a platinum sensor (1 k omega at 0 °C). Myocardial membrane potentials were measured with glass microelectrodes (3 mol l-1 KCl, 10­30 M omega). Muscle tension was recorded using a strain gauge.
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PMID:SPIKING INDUCED BY COOLING IN THE MYOCARDIUM OF THE LOBSTER PANULIRUS JAPONICUS 931 43

Short-horned sculpin Myoxocephalus scorpius were acclimated to 5 and 15 °C to evaluate the impact of thermal acclimation upon maximal rates of substrate oxidation by mitochondria and upon the thermal sensitivity of their ADP affinity. Cold acclimation virtually doubled maximal rates of pyruvate oxidation at all experimental temperatures (2.5, 7.5, 12.5 and 20 °C). Rates of palmitoyl carnitine oxidation were also enhanced by cold acclimation, but to a lesser degree. At their respective acclimation temperatures, the mitochondria attained similar rates of pyruvate oxidation. For warm-acclimated sculpin, the Q10 values for mitochondrial pyruvate and palmitoyl carnitine oxidation were higher between 2.5 and 7.5 °C than between 7.5 and 12.5 °C or between 12.5 and 20 °C. In contrast, for cold-acclimated fish, the Q10 values did not differ over these thermal ranges. The Arrhenius activation energy for pyruvate oxidation was reduced by cold acclimation (from 70 to 55 kJ mol-1), whereas that for palmitoyl carnitine oxidation was unchanged (approximately 75 kJ mol-1). Cold acclimation did not alter the ADP affinity of mitochondria at low temperatures but markedly increased the apparent Km for ADP (Km,app) at 12.5 and 20 °C. At the acclimation temperatures, mitochondrial ADP Km,app values did not differ. The loss of ADP affinity at higher temperatures may represent a cost of the enhanced maximal oxidative capacity achieved during cold acclimation.
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PMID:Plasticity of fish muscle mitochondria with thermal acclimation 931 87

The effects of temperature on transmission through the voltage-sensitive giant motor synapse (GMS) were investigated in crayfish both experimentally and in computer simulation. The GMS is part of the fast reflex escape pathway of the crayfish and mediates activation from the lateral giant (LG) command neurone to the motor giant (MoG) flexor motoneurone. The investigation was motivated by an apparent mismatch between the temperature sensitivity of the activation time constant of the GMS, with a Q10 reported to be close to 11, and that of the active membrane properties of LG and MoG, which are thought to have Q10 values close to 3. Our initial hypothesis was that at cold temperatures the very slow activation of the GMS conductance would reduce the effectiveness of transmission compared with higher temperatures. However, the reverse was found to be the case. Effective transmission through the GMS was reliable at low temperatures, but failed at an upper temperature limit that varied between 12 degrees C and 25 degrees C in isolated nerve cord preparations. The upper limit was extended above 30 degrees C in semi-intact preparations where the GMS was less disturbed by dissection. The results of experiments and simulations both indicate that transmission becomes more reliable at low temperatures because the longer-duration presynaptic spikes are able to drive more current through the GMS into the MoG, which is more excitable at low temperatures. Conversely, effective transmission is difficult at high temperatures because the transfer of charge through the GMS is reduced and because the input resistance of MoG is lowered as its current threshold is increased. The effect of the high Q10 of the GMS activation is to help preserve effective transmission through the synapse at high temperatures and so extend the temperature range for effective operation of the escape circuit.
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PMID:Effect of temperature on a voltage-sensitive electrical synapse in crayfish. 943 26

This study was designed to determine whether the metabolic adaptations developed by frogs to tolerate natural events of hypothermic hypoxia would precondition its liver for ex vivo organ storage. The metabolic responses of the frog, Rana castabiena, were compared to those of a mammalian system (rat) throughout a prolonged period of organ storage. Livers from rats and frogs were flushed and stored in UW solution at 5 degrees C for periods of 24-96 h. In frog livers, ATP was maintained high and constant over the first 24 h of storage; values ranged from 2.7 to 3.0 micro mol/g. Even after 96 h cold storage, ATP remained > 1.0 micro mol/g. In contrast, ATP levels in stored rat livers dropped rapidly, and by 4 h ATP was 1.2 micro mol/g. In terms of anaerobic endproduct accumulation, lactate levels rose 5.8 micro mol/g in frog liver (over 96 h) and by 8.6 micro mol/g in rat liver (over 24 h). This difference in flux through glycolysis was also reflected in relative rates of carbohydrate catabolism (i.e., glucose + lactate production). The rate of carbohydrate catabolism for frog liver was 0.74 micro mol/g/h compared to 2.26 micro mol/g/h for rat liver; a Q10 value of 6.2 was estimated for livers from R. castabiena. An assessment of glycolytic enzyme activities revealed that key differences in the responsiveness of pyruvate kinase to allosteric modifiers may have been responsible for the marked drop in the rate of anaerobic energy production in frog tissues. Although the concept of depressed metabolism in a lower vertebrate is not new, the data presented in this study demonstrate that a depressed metabolic state can be achieved in isolated livers from R. castabiena simply through cold exposure. With respect to clinical relevance, the results of this study indicate that energetics of stored livers can be maintained effectively through an efficient reduction in energy use in combination with a slow, yet continuous, rate of energy production facilitated by glycolysis.
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PMID:Metabolic adaptations of a lower vertebrate to long-term hypothermic hypoxia provide clues to successful clinical liver preservation. 952 71

Instantaneous fuel usage at 5 degreesC or 15 degreesC was assessed by measurement of rates of O2 consumption (O2), CO2 excretion (CO2) and nitrogenous waste excretion (nitrogen =ammonia-N + urea-N) in juvenile rainbow trout (Oncorhynchus mykiss) at rest and during swimming at 45 % and 75 % of aerobic capacity (Ucrit). After 2 weeks of training at approximately 1 body length s-1 (BL s-1), critical swimming speeds (approximately 3.0 BL s-1) and whole-body energy stores (total protein, lipids and carbohydrates) were identical in fish acclimated to 5 degreesC or 15 degreesC. O2 and CO2 increased with swimming speed at both temperatures and were higher at 15 degreesC than at 5 degreesC at all speeds, but the overall Q10 values (1.23-1.48) were low in these long-term (6 weeks) acclimated fish. The respiratory quotient (CO2/O2, approximately 0.85) was independent of both temperature and swimming speed. In contrast to O2 and CO2, the rate of ammonia excretion was independent of swimming speed, but more strongly influenced by temperature (Q10 1. 4-2.8). Urea excretion accounted for 15-20 % of nitrogen, was unaffected by swimming speed and showed a tendency (P<0.07) to be positively influenced by temperature at one speed only (45 % Ucrit). Nitrogen quotients (NQ nitrogen/O2) were generally higher in warm-acclimated fish, remaining independent of swimming speed at 15 degreesC (0.08), but decreased from about 0.08 at rest to 0.04 during swimming at 5 degreesC. Instantaneous aerobic fuel use calculations based on standard respirometric theory showed that both acclimation temperature and swimming speed markedly influenced the relative and absolute use of carbohydrates, lipids and proteins by trout. At rest, cold-acclimated trout used similar proportions of carbohydrates and lipids and only 27 % protein. During swimming, protein use decreased to 15 % at both speeds while the relative contributions of both lipid and carbohydrate increased (to more than 40 %). On an absolute basis, carbohydrate was the most important fuel for fish swimming at 5 degreesC. In contrast, resting fish acclimated to 15 degreesC utilized 55 % lipid, 30 % protein and only 15 % carbohydrate. However, as swimming speed increased, the relative contribution of carbohydrate increased to 25 %, while the protein contribution remained unchanged at approximately 30 %, and lipid use decreased slightly (to 45 %). On an absolute basis, lipid remained the most important fuel in fish swimming at 15 degreesC. These results support the concept that lipids are a major fuel of aerobic exercise in fish, but demonstrate that the contribution of protein oxidation is much smaller than commonly believed, while that of carbohydrate oxidation is much larger, especially at higher swimming speeds and colder temperature.
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PMID:A respirometric analysis of fuel use during aerobic swimming at different temperatures in rainbow trout (Oncorhynchus mykiss) 978 32

Arctic woollybear caterpillars, Gynaephora groenlandica, had the capacity to rapidly and dramatically increase respiration rates up to fourfold within 12-24 h of feeding and exhibited similar decreases in respiration of 60-85 % in as little as 12 h of starvation. At the peak of their feeding season, the respiration rates of caterpillars also increased significantly with temperature from 0.5 to 22 degreesC for both fed and starved caterpillars (Q10=1-5). Indicative of diapause, late season caterpillars had depressed respiration rates which were less sensitive to temperature changes (Q10 approximately 1.5), while respiration rates for caterpillars that had spun hibernacula were even lower. G. groenlandica did not appear to demonstrate metabolic cold adaptation compared with other temperate lepidopteran larvae. The seasonal capacity to adjust metabolic rate rapidly in response to food consumption and temperature (which can be elevated by basking) may promote the efficient acquisition of energy during the brief (1 month) summer growing and feeding season, while conserving energy by entering diapause when conditions are less favorable. These adaptations, along with their long 15-20 year life cycle and the retention of freeze tolerance year-round, promote the survival of G. groenlandica in this harsh polar environment.
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PMID:Metabolic opportunists: feeding and temperature influence the rate and pattern of respiration in the high arctic woollybear caterpillar gynaephora groenlandica (Lymantriidae) 984 94

At the low temperatures of the overwintering environment of the frog Rana temporaria, small changes in ambient temperature have large effects on metabolism and behaviour, especially since Q10 values are often greatly elevated in the cold. How the overwintering aquatic frog copes with variable thermal environments in terms of its overall activity metabolism and recovery from pursuit by predators is poorly understood, as is the role of behavioural thermoregulation in furthering recovery from intense activity. Exhaustive exercise was chosen as the method of evaluating activity capacity (defined by time to exhaustion, total distance swum and number of leg contractions before exhaustion) and was determined at 1.5 and 7 degreesC. Other cohorts of frogs were examined at both temperatures to determine the metabolic (acid-base, lactate, glucose, ATP and creatine phosphate) and respiratory responses to exercise in cold-submerged frogs. Finally, temperature preference before and after exercise was determined in a thermal gradient to define the importance of behavioural thermoregulation on the recovery rates of relevant metabolic and respiratory processes. Activity capacity was significantly reduced in frogs exercised at 1.5 versus 7 degreesC, although similar levels of tissue acid-base metabolites and lactate were reached. Blood pH, plasma PCO2 and lactate levels recovered more rapidly at 1.5 degreesC than at 7 degreesC; however, intracellular pH and the recovery of tissue metabolite levels were independent of temperature. Resting aerobic metabolic rates were strongly affected by temperature (Q10=3.82); however, rates determined immediately after exercise showed a reduced temperature sensitivity (Q10=1.67) and, therefore, a reduced factorial aerobic scope. Excess oxygen consumption recovered to resting values after 5-6.25 h, and 67 % recovery times tended to be slightly faster at the lower temperatures. Exercise in the cold, therefore, provided an immediately higher factorial scope, which could be involved in the faster rate of recovery of blood lactate levels in the colder frogs. In addition, exercise significantly lowered the preferred temperature of the frogs from 6.7 to 3.6 degreesC for nearly 7 h, after which they returned to their normal, unstressed preferred temperatures. Thus, a transient behavioural hypothermia in the skin-breathing, overwintering frog may be an important strategy for minimising post-exercise stress and maintaining aerobic metabolism during recovery from intense activity.
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PMID:Does behavioural hypothermia promote post-exercise recovery in cold-submerged frogs? 992 62

Sudden infant death syndrome has been associated with winter climates, infection, and overwrapping of babies. The hypothesis has been tested in this laboratory that two different causes of increased metabolic rate, high core temperature (via the van't Hoff or 'Q10' effect) and face-cooling, might synergistically induce hyperthermia. This proved not to be the case. We now report on a 'febrile' state adding Salmonella abortus equi pyrogens. The combination of face-cooling and pyrogen administration to 14 already hot piglets produced an increase in oxygen consumption of 47% in 6 of the animals (19% overall). Face-cooling alone caused a 6.5% fall in oxygen consumption, and injection of pyrogens alone had no effect on oxygen consumption. We conclude that there may be a danger of life-threatening hyperthermia in the combination of a cold face and febrile state.
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PMID:The effect of cold stimulation to the face on the metabolic rate of the febrile piglet. 1072 21

The two species of isopods, Idotea baltica (Pallas) and Idotea emarginata (Fabricius), co-occur frequently near Helgoland, North Sea, occupying different ecological niches. Respiration rates and kinetic properties of citrate synthase (CS) were compared in these species in order to identify possible mechanisms of temperature adaptation. Specimens were acclimated to 5 and 15 degrees C prior to further investigations. Respiration rates were measured under normoxic conditions at 5, 10 and 15 degrees C. CS was partly purified chromatographically and influences of temperature, pH, substrate saturation and ATP-concentration on enzyme activity were examined. In both species, rising temperatures led to linearly increasing oxygen consumption, with estimated Q10 values between 3.2 and 4.2. Only I. baltica showed an effect of short term acclimation: warm adapted animals had always higher respiration rates than cold adapted ones. In I. emarginata, the acclimation temperature had no effect on oxygen consumption. Furthermore, its CS slightly indicates higher affinity to oxaloacetic acid when specimens were adapted to 15 degrees C compared to those maintained at 5 degrees C. Any effect of the experimental temperature on CS in I. baltica was negligible. The results are discussed in view of the different habitats occupied by the species compared.
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PMID:Effects of temperature on the respiration rates and the kinetics of citrate synthase in two species of Idotea (Isopoda, Crustacea). 1084 Jun 43


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