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Results for “Thermal acclimation”

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PubMed1999

Heterologous acclimation: a novel approach to the study of thermal acclimation in the crab Cancer pagurus.

The control of the attainment of acclimation in Cancer pagurus has been studied. Homologous (8 or 22 degrees C) and heterologous acclimation [central nervous system (CNS) and periphery of crabs simultaneously held at 8 or 22 degrees C] were used. The dependence of electrophysiological parameters of dactylopodite closer muscles of walking legs on nerve stimulation was determined between 6 and 26 degrees C. Muscle resting potential (RP) hyperpolarized linearly with increasing measurement temperatures and showed a 69% compensation between 8 and 22 degrees C on homologous acclimation. With the CNS temperature constant at 8 degrees C, the leg muscle RP showed a 72% compensation on heterologous acclimation to 8 and 22 degrees C; when CNS temperature was constant at 22 degrees C, leg muscle RP showed a 48% compensation on heterologous acclimation to 8 and 22 degrees C. In homologous acclimation, the shape of the excitatory junction potential vs. temperature relationship was characteristic of acclimation temperature. In heterologous acclimation, the shape of this plot was related to the temperature experienced by the leg and not by the CNS. Thus acclimation was principally dependent on local tissue temperature and was relatively independent of CNS or hormonal influences.

Acclimatization↗

PubMed2003

Thermal acclimation and the dynamic response of plant respiration to temperature.

Temperature-mediated changes in plant respiration (R) are now accepted as an important component of the biosphere's response to global climate change. Here we discuss the underlying mechanisms responsible for the dynamic response of plant respiration to short and long-term temperature changes. The Q(10) is often assumed to be 2.0 (i.e. R doubles per 10 degrees C rise in temperature); however, the Q(10) is not constant (e.g. it declines near-linearly with increasing temperature). The temperature dependence of Q(10) is linked to shifts in the control exerted by maximum enzyme activity at low temperature and substrate limitations at high temperature. In the long term, acclimation of R to temperature is common, in effect reducing the temperature sensitivity of R to changes in thermal environment, with the temperature during plant development setting the maximal thermal acclimation of R.

Acclimatization↗

PubMed1986

Muscle myoglobin as determined by electrophoresis in thermally acclimated rat.

Quantitative analysis of myoglobin (Mb) was established using the sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis in order to determine the influence of thermal acclimation on Mb levels in muscles. Myoglobin was measured in the red and white parts of quadriceps, soleus, diaphragm and heart of young adult male rats (11 weeks old). It was higher in the red muscle (0.92 +/- 0.043 mg/g fresh weight) than in the white muscle (0.08 +/- 0.007), and similar in the red muscle and soleus (1.17 +/- 0.117). Heart showed the highest level (1.52 +/- 0.073) among the tissues studied. The level in diaphragm (0.74 +/- 0.039) was intermediate between red muscle and heart. Cold acclimation (5 degrees C for 4 weeks, 11 weeks old) caused significant increases in Mb levels in white muscle (0.27 +/- 0.031, p less than 0.001), heart (1.95 +/- 0.094, p less than 0.01), and diaphragm (1.01 +/- 0.060, p less than 0.01), but not in red muscle and soleus. The rats reared in cold for many generations (20 generations at 5 degrees C, 11 weeks old) manifested significant increases in Mb levels of all tissues (p less than 0.05-0.001) examined. Heat acclimation (33 degrees C for 4 weeks, 11 weeks old) did not influence Mb levels of the tissues. The above findings suggest that skeletal muscle Mb may be partly involved in an enhanced thermogenesis in cold acclimation by favouring an oxidative capacity of muscles.

Acclimatization↗

PubMed1977

Turnover of cytochrome C in skeletal muscle of green sunfish (Lepomis cyanellus, R.) during thermal acclimation.

The concentration of cytochrome c in the skeletal muscle of the green sunfish (Lepomis cyanellus) increases with decreasing temperature of acclimation: 1.51 +/- 0.09, 1.17 +/- 0.03, and 0.98 +/- 0.07 nanomoles per gram wet weight from muscle of animals acclimated to 5 degrees, 15 degrees, and 25 degrees C, respectively. The roles of synthesis and degradation of cytochrome c during thermal acclimation were investigated by measurement of loss of specific radioactivity from cytochrome c and from total mitochondrial heme protein, and by analysis of the rate of change in concentration of cytochrome c. The radioisotope used was 14C-delta-aminolevulinic acid, a non-reutilizable heme precursor. At 25 degrees C, the half-life of cytochrome c was 7.1 days based on radioactivity measurements and 5.6 days based on change in concentration. Statistical analysis showed no significant difference in half-lives obtained by the two methods. The half-life of total mitochondrial heme protein was determined to be 5.7 days on the basis of radioactivity data, under the same conditions. No significant difference was found between the rate of turnover of the heme protein pool from mitochondria and either measurement for cytochrome c at 25 degrees C. At an acclimation temperature of 5 degrees C, the half-life of cytochrome c from skeletal muscle was 13.7 days based upon changes in concentration. At low acclimation temperature, radioactive label was retained in acid-soluble form by fish for many days, precluding measurement of half-life by this technique. Transfer of fish from 25 degrees to 5 degrees C resulted in a rapid decrease of approximately 40% in rates in synthesis of skeletal muscle cytochrome c, and a concomitant decrease in the degradation rate constant for this molecule of approximately 60%. The disproportionality in temperature-sensitivities of these two processes leads to an approximately 50% net increase in the concentration of cytochrome c during acclimation. In transfer from 5 degrees to 25 degrees C, the converse, rapid readjustments in synthetic and degradative parameters occur, resulting in the observed decrease in cytochrome c content.

Acclimatization↗

PubMed2007

Changes in mitochondrial oxidative capacities during thermal acclimation of rainbow trout Oncorhynchus mykiss: roles of membrane proteins, phospholipids and their fatty acid compositions.

Changes in the properties of mitochondria from oxidative muscle of rainbow trout Oncorhynchus mykiss were examined during warm (5 degrees C to 15 degrees C) acclimation. Trout were studied shortly after the initial thermal change and after 8 weeks acclimation to 15 degrees C. To identify potential mechanisms by which oxidative capacities change, the modifications of phospholipid composition, membrane proteins and functional capacities of red muscle mitochondria were examined. Marked functional changes of isolated muscle mitochondria during warm acclimation of rainbow trout were reflected by a host of modifications in phospholipid composition, but by few shifts in protein components. Shortly after transfer of trout from 5 degrees C to 15 degrees C, the maximal oxidative capacity of mitochondria measured at 15 degrees C increased slightly, but rates at both assay temperatures (5 degrees C and 15 degrees C) decreased markedly after warm acclimation. The increase in capacity in short-term warm exposed trout was most pronounced when rates at 15 degrees C were expressed relative to cytochrome a and c(1) levels. Non-phosphorylating (State 4) rates of oxygen uptake increased with short-term warm exposure before returning to initial levels after warm acclimation. Cytochrome c oxidase (CCO) activity in the mitochondrial preparations decreased with warm acclimation. The thermal sensitivity of the ADP affinity was markedly modified during short-term warm exposure, when the ADP/O ratio increased, but warm acclimation returned these values to those observed initially. ADP affinity increased after warm acclimation. Changes in the mitochondrial content of cytochromes and adenine nucleotide translocase (ANT) could not explain these patterns. On the other hand, changes in the proportions of the lipid classes and in the acyl chain composition of certain phospholipid classes mirror the modifications in functional properties. Short-term exposure to 15 degrees C decreased the ratio of diacylphosphatidylethanolamine/diacylphosphatidylcholine (diacylPE/diacylPC), whereas warm acclimation led to restructuring of fatty acids (FA) and to increases of plasmalogen forms of PE and PC. Modification of overall membrane unsaturation did not appear to be the primary aim of restructuring membrane FA during warm acclimation, as total mitochondrial phospholipids and the major phospholipid classes only showed slight shifts of their acyl composition with warm acclimation. On the other hand, natural lysophosphatidylcholine (LysoPC) showed dramatic changes in FA content, as 16:0 and 18:1n-9 doubled whereas 22:6n-3 decreased from around 50% to 32% in warm acclimated trout. Similarly, in cardiolipin (CL), the levels of 16:0 and 18:1n-7 halved while 18:2n-6 increased to over 20% of the FA with warm acclimation. Given the central role of CL in modulating the activity of CCO, F(0)F(1)-ATPase and ANT, these changes suggest that specific compositional changes in CL are important modulators of mitochondrial capacities. The many structural changes in membrane lipids contrast with the limited modifications of the membrane protein components examined and support the concept of lipid structure modulating mitochondrial capacities.

Acclimatization↗

PubMed1994

Myosin subfragment-1 isoforms having different heavy chain structures from fast skeletal muscle of thermally acclimated carp.

Three heavy chain isoforms of chymotryptic myosin subfragment-1 (S1) with different molecular sizes of 96 kDa (H1), 94 kDa (H2), and 92 kDa (H3), were detected in the fast skeletal muscle from thermally acclimated carp. In total, six S1 isoforms were present, including two S1 isoforms for each heavy chain due to associated A1 and A2 light chains. H1 heavy chain was dominant in the 10 degrees C-acclimated carp and responsible for high acto-S1 Mg(2+)-ATPase activity and low thermostability. In contrast, H3 heavy chain predominating in the 30 degrees C-acclimated carp showed low acto-S1 Mg(2+)-ATPase activity and high thermostability. H2 heavy chain was found in the 10- and 20 degrees C-acclimated fish. H3 heavy chain featured three tryptic fragments with normal molecular masses of 25, 50, and 20 kDa in order from the N-terminus. However, H1 heavy chain contained an unusual, longer "20 kDa" peptide whose molecular size was estimated to be about 23 kDa.

Adenosine Triphosphatases↗

PubMed2002

Thermal acclimation changes DNA-binding activity of heat shock factor 1 (HSF1) in the goby Gillichthys mirabilis: implications for plasticity in the heat-shock response in natural populations.

The intracellular build-up of thermally damaged proteins following exposure to heat stress results in the synthesis of a family of evolutionarily conserved proteins called heat shock proteins (Hsps) that act as molecular chaperones, protecting the cell against the aggregation of denatured proteins. The transcriptional regulation of heat shock genes by heat shock factor 1 (HSF1) has been extensively studied in model systems, but little research has focused on the role HSF1 plays in Hsp gene expression in eurythermal organisms from broadly fluctuating thermal environments. The threshold temperature for Hsp induction in these organisms shifts with the recent thermal history of the individual but the mechanism by which this plasticity in Hsp induction temperature is achieved is unknown. We examined the effect of thermal acclimation on the heat-activation of HSF1 in the eurythermal teleost Gillichthys mirabilis. After a 5-week acclimation period (at 13, 21 or 28 degrees C) the temperature of HSF1 activation was positively correlated with acclimation temperature. HSF1 activation peaked at 27 degrees C in fish acclimated to 13 degrees C, at 33 degrees C in the 21 degrees C group, and at 36 degrees C in the 28 degrees C group. Concentrations of both HSF1 and Hsp70 in the 28 degrees C group were significantly higher than in the colder acclimated fish. Plasticity in HSF1 activation may be important to the adjustable nature of the heat shock response in eurythermal organisms and the environmental control of Hsp gene expression.

Acclimatization↗

PubMed1998

Effects of temperature on cuticular lipids and water balance in a desert Drosophila: is thermal acclimation beneficial?

The desert fruit fly Drosophila mojavensis experiences environmental conditions of high temperature and low humidity. To understand the physiological mechanisms allowing these small insects to survive in such stressful conditions, we studied the effects of thermal acclimation on cuticular lipids and rates of water loss of adult D. mojavensis. Mean hydrocarbon chain length increased at higher temperatures, but cuticular lipid melting temperature (Tm) did not. Lipid quantity doubled in the first 14 days of adult life, but was unaffected by acclimation temperature. Despite these changes in cuticular properties, organismal rates of water loss were unaffected by either acclimation temperature or age. Owing to the smaller body size of warm-acclimated flies, D. mojavensis reared for 14 days at 33 degrees C lost water more rapidly on a mass-specific basis than flies acclimated to 25 degrees C or 17 degrees C. Thus, apparently adaptive changes in cuticular lipids do not necessarily result in reduced rates of water loss. Avoidance of high temperatures and desiccating conditions is more likely to contribute to survival in nature than changes in water balance mediated by surface lipids.

Acclimatization↗

PubMed1988

Acylation of lysophosphatidylcholine in liver microsomes of thermally acclimated trout.

The specificity of acyl-coenzyme A (CoA): lysophosphatidylcholine acyltransferase (LPCAT; EC 2.3.1.23) was determined for a range for acyl-CoA substrates differing with respect to chain length and degree of unsaturation in liver microsomes of thermally acclimated (5 and 20 degrees C) rainbow trout, Salmo gairdneri. Absolute levels of oleate incorporation into phosphatidylcholine (PC) were determined at substrate concentrations in the physiological range (12 microM) and higher (64 microM). The specificity of LPCAT was determined by the extent to which competing substrates decreased the incorporation of oleate. LPCAT specificity was significantly influenced by both assay and acclimation temperature at total substrate concentrations of both 72 and 256 microM. A clear preference for 14- and 16-carbon monoenes was exhibited by LPCAT from 20 but not 5 degrees C-acclimated trout. Furthermore, LPCAT from 5 degrees C-acclimated trout preferentially incorporated long chain and polyunsaturated fatty acids (eicosadienoyl, arachidonoyl, erucoyl) and excluded 18-carbon unsaturates at an assay temperature of 5 degrees C compared with 20 degrees C; at 20 degrees C, 18-carbon unsaturates were incorporated more readily than 20-carbon species. Linolenic acid (18:3N3) was generally excluded from incorporation, reflecting a possible mechanism by which this precursor of docasahexaenoic acid (22:6N3, n - 3) remains available for modification. These results indicate that trout liver LPCAT preferentially incorporates fatty acids into PC on the basis of both chain length and degree of unsaturation in a manner consistent with the temperature-induced restructuring of membrane phospholipids.

Acclimatization↗

PubMed1978

Carbonic anhydrase (acetazolamide-sensitive esterase) activity in the blood, gill and kidney of the thermally acclimated rainbow trout, Salmo gairdneri.

1. Gill, kidney and blood levels of acetazolamide-sensitive esterase (carbonic anhydrase) activity were estimated at acclimation temperature and at a common temperature (25 degrees C) in rainbow trout acclimated to 2, 10 and 18 degrees C. Plasma levels of sodium, potassium and chloride were also examined for possible acclimatory variations. 2. Plasma sodium and chloride levels, and the sodium:chloride ratio were unaffected by thermal acclimation; potassium concentrations were significantly elevated at 18 degrees C. 3. Significant, but modest changes in renal and branchial carbonic anhydrase activity were observed under physiologically realistic incubation temperature conditions. Blood carbonic anhydrase activity was sharply elevated at higher acclimation temperatures. 4. The data are discussed in relation to the hypothesis that carbonic anhydrase in this relatively stenothermal freshwater salmonid, through its intimate association with the coupled HCO-3/CL- and H+ +NH+4/Na+ exchange systems may provide for relatively thermostable basal rates of sodium and chloride uptake from the medium and recovery from urine. The renal, and more notably the branchial (Na+/K+)-stimulated ATPase systems, and erythrocytic carbonic anhydrase may then serve primarily as high-temperature amplifiers of sodium and chloride recruitment respectively.

Acclimatization↗

PubMed1994

THERMAL ACCLIMATION, NEUROMUSCULAR SYNAPTIC DELAY AND MINIATURE END-PLATE CURRENT DECAY IN THE FROG RANA TEMPORARIA

1. The effects of 1 or 23 weeks of acclimation to 4 °C and 24 °C of overwintering grass frogs (Rana temporaria) on the synaptic delay and on the time constant of the decay phase (tau) of miniature end-plate currents (MEPCs) in the neuromuscular junction of sartorius muscle were studied. In order to equalize the possible effects of differential starvation, the animals were usually cross-acclimated to the two temperatures. 2. Synaptic delay was not affected by temperature acclimation but was slightly prolonged by the more profound starvation at the higher temperature when the cross-acclimation procedure was not used. The average Q10 of synaptic delay between 4 and 24 °C was 2.60 and of minimum synaptic delays, 2.64. The corresponding values for apparent activation energy (Ea) were 65.79 and 66.48 kJ mol-1. 3. The time constant of the decay phase of MEPCs was not affected by temperature acclimation. The average Q10 between 4 and 24 °C was 2.27. The corresponding Ea value was 56.02 kJ mol-1. 4. The function of peripheral neuromuscular synapses is well regulated and changes in its time relationships do not appear to be involved in the thermal acclimation of frogs.

Journal Article↗

PubMed1981

Temperature adaptation of biological membranes. Compensation of the molar activity of cytochrome c oxidase in the mitochondrial energy-transducing membrane during thermal acclimation of the carp (Cyprinus carpio L.).

The acclimation temperature of carp does not affect the amount of cytochrome c oxidase per mg mitochondrial protein as revealed from the reduced-minus-oxidized difference spectra of red muscle mitochondria from cold- and warm-acclimated carp. There are no differences between cold- and warm-acclimated fish in the substrate binding properties of the enzyme as judged from the Km values for cytochrome c at 30 degrees C (3.34 +/- 0.ee microM, acclimation temperature 10 degrees C and 3.55 +/- 0.31 microM, acclimation temperature 30 degrees C). The molar activities of the enzyme, however, differ for both acclimation temperatures: when intercalated in the 10 degrees C-acclimated mitochondrial membrane, the enzyme can catalyze the oxidation of 117.6 +/- 17.2 mol ferrocytochrome c/s per mol heme a as compared with 85.6 +/- 17.2 in the 30 degrees C-acclimated membrane (experimental temperature 30 degrees C). Correspondingly, higher specific activities of the succinate oxidase system are observed in mitochondria from cold-acclimated carp as compared with those obtained from warm-acclimated carp. The results indicate that cold acclimation of the eurythermic carp is accompanied by a partial compensation of the acute effect of decreasing temperature on the activity of cytochrome c oxidase in red muscle mitochondria. Based on the temperature-induced lipid adaptation reported for carp red muscle mitochondria (Wodtke, E. (1980) Biochim. Biophys. Acta 640, 698--709), it is concluded that during thermal acclimation the molar activity of cytochrome c oxidase is controlled by viscotropic regulation. The results fit to the conception that cardiolipin constitutes a lipid shell (annulus) surrounding the oxidase within the native membrane, but that it is the bilayer fluidity and not the annular fluidity which determines the activity of cytochrome c oxidase.

Acclimatization↗

PubMed1979

Significance of the variation in isozymes of liver lactate dehydrogenase with thermal acclimation in goldfish--II. Effect of pH.

1. Effect of pH on liver lactate dehydrogenase (LDH) and its isozymes was examined in the goldfish acclimated to different temperatures and some purification of the LDH was attempted. 2. The optimal pH and the Km value at 30 degrees C of the enzyme were independent of acclimation temperature. 3. the optimal pH of isozyme was more basic in the order of LDH-1, LDH-2, LDH-3, LDH-4 and LDH-5. Km values of isozymes at 30 degrees C were higher in the order of LDH-1, LDH-3 and LDH-5. 4. There was no change in the enzyme activity during thermal acclimation.

Acclimatization↗

PubMed1999

Contractile properties of atrial and ventricular myocardium of the heart of rainbow trout oncorhynchus mykiss: effects of thermal acclimation

Atrial and ventricular myocardium perform different tasks in the pumping work of the vertebrate heart, which are reflected in their contractile properties. Although atrial contraction is assumed to have an important role in the function of fish heart, the contractile properties of atrial and ventricular myocardium have not been directly compared in any fish species. The objective of this study was to clarify any contractile differences in the heart of teleost fish and, in particular, to elucidate the contribution of myofibrillar ATPase and intracellular Ca(2+) stores to the characteristics of atrial and ventricular contraction. Experiments were conducted on thermally acclimated rainbow trout Oncorhynchus mykiss to determine whether the effects of temperature adaptation are the same in atrial and ventricular tissue. It was shown that the rate of isometric contraction is much faster in atrial than in ventricular tissue of the fish heart and that acclimation to cold increases the rate of contraction in both cardiac compartments. The rapid contraction kinetics of the atrial tissue were associated with higher myofibrillar ATPase activity and faster Ca(2+) uptake rate of the sarcoplasmic reticulum (SR) compared with ventricular tissue. Similarly, the faster kinetics of contraction following cold acclimation could be attributed to enhancement of the myofibrillar and/or SR function. The atrio-ventricular and temperature-induced differences were also expressed in the recovery of force from inactivation, i.e. in the mechanical restitution. The refractory period and the rate constant of force restitution were shorter in atrial than in ventricular muscle tissue. Similar differences also existed between the tissues of cold-acclimated (CA, 4 degrees C) and warm-acclimated (WA, 17 degrees C) fish. The fast recovery of force from inactivation in the heart of the CA trout was, at least in part, due to more active SR. Furthermore, it was shown that the force of atrial contraction in the CA trout is sensitive to ryanodine (10 (&mgr;)mol l(-)(1)), a Ca(2+)-release channel blocker of SR, at physiological body temperature (4 degrees C) and at a physiological pacing rate (0.6 Hz). This finding indicates that the Ca(2+) stores of SR contribute to activation of cardiac contraction in the fish heart, and that the SR of fish heart is able to retain its Ca(2+) load at low body temperatures, i.e. the Ca(2+ )release channels of SR are not leaky in the cold. The present data show that in the atrial tissue of CA trout, the SR directly contributes to the cytosolic Ca(2+) and that in the atrium and ventricle of CA trout, the SR significantly accelerates the recovery of contractility from inactivation. The fast recovery from inactivation allows relatively high heart rates and therefore adequate cardiac outputs at low environmental temperatures for the cold-active rainbow trout.

Journal Article↗

PubMed1990

Thermal acclimation and muscle contractile properties in cyprinid fish.

After several weeks of cold acclimation, the swimming performance of some fish is increased at low temperatures and decreased at high temperatures. The temperature compensation of locomotory activity involves changes in central patterns of muscle fiber recruitment and in the properties of the peripheral nervous system and muscle tissues. In some freshwater fish belonging to the family Cyprinidae, including the goldfish (Carassius auratus), the common carp (Cyprinus carpio), and the roach (Rutilus rutilus), the intrinsic contractile properties of muscles are modified by thermal acclimation. Parameters that can be altered by temperature acclimation in both fast and slow muscle fibers include isometric twitch contraction time, maximum force production, and unloaded shortening speed. The molecular mechanisms responsible for these changes in contractility are discussed.

Acclimatization↗

PubMed1986

Primary Role of the Cytoplasmic Membrane in Thermal Acclimation Evidenced in Nitrate-Starved Cells of the Blue-Green Alga, Anacystis nidulans.

The lipid phase transition of the cytoplasmic membrane and the chilling susceptibility were studied in nitrate-starved Anacystis nidulans cells. Nitrate starvation resulted in the disappearance of the thylakoid membrane system, without any effect on chilling susceptibility. The chilling susceptibility of the algal cells depended on the growth temperature. Temperatures of lipid phase transitions of the cytoplasmic membranes were detected by chilling-induced spectral changes in the carotenoid region, in vivo. These values were identical to those of cultures containing intact thylakoid systems. Our results suggest that cytoplasmic membrane plays a determinative role in the thermal acclimation of the alga cells.

Journal Article↗

PubMed2004

Thermal acclimation and seasonal variations of erythrocyte size in the Andean mouse Phyllotis xanthopygus rupestris.

Seasonal hematological adjustments in small mammals may include changes in the number and size of the red cells or changes in other linked blood parameters. The direction and magnitude of these changes vary in different species. We hypothesized that the observed variations of the red cell adjustments could be directly related to the magnitude of the seasonal temperature differential, and predicted that the annual red cell size variation in rodents from environments with marked seasonal changes would tend to disappear, if the animals were raised under milder and constant environments. To test this idea, we got field blood samples from the Andean species Phyllotis xanthopygus rupestris enduring a winter-summer thermal differential of at least 20 degrees C. These animals had significantly smaller erythrocytes during the winter. Contrary to our prediction, their offspring born and raised under constant temperature conditions showed a similar trend. Unless the effective environmental cue differed from the one we used, these results favor the idea of a genetically determined annual red cell size variation that occurs independent of thermal acclimation and acclimatization.

Acclimatization↗

PubMed2002

Thermal acclimation and stress in the American lobster, Homarus americanus: equivalent temperature shifts elicit unique gene expression patterns for molecular chaperones and polyubiquitin.

Using homologous molecular probes, we examined the influence of equivalent temperature shifts on the in vivo expression of genes coding for a constitutive heat shock protein (Hsc70), heat shock proteins (Hsps) (Hsp70 and Hsp90), and polyubiquitin, after acclimation in the American lobster, Homarus americanus. We acclimated sibling, intermolt, juvenile male lobsters to thermal regimes experienced during overwintering conditions (0.4 +/- 0.3 degrees C), and to ambient Pacific Ocean temperatures (13.6 +/- 1.2 degrees C), for 4-5 weeks. Both groups were subjected to an acute thermal stress of 13.0 degrees C, a temperature shift previously found to elicit a robust heat shock response in ambient-acclimated lobsters. Animals were examined after several durations of acute heat shock (0.25-2 hours) and after several recovery periods (2-48 hours) at the previous acclimation temperature, following a 2-hour heat shock. Significant inductions in Hsp70, Hsp90, and polyubiquitin messenger RNA (mRNA) levels were found for the ambient-acclimated group. Alternatively, for the cold-acclimated group, an acute thermal stress over an equivalent interval resulted in no induction in mRNA levels for any of the genes examined. For the ambient-acclimated group, measurements of polyubiquitin mRNA levels showed that hepatopancreas, a digestive tissue, incurred greater irreversible protein damage relative to the abdominal muscle, a tissue possessing superior stability over the thermal intervals tested.

Animals↗