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PubMed1994

THE EFFECTS OF ACCLIMATION TEMPERATURE ON THE DYNAMICS OF CATECHOLAMINE RELEASE DURING ACUTE HYPOXIA IN THE RAINBOW TROUT ONCORHYNCHUS MYKISS

The response of cannulated rainbow trout (Oncorhynchus mykiss) to acute hypoxia was studied in fish acclimated to two temperatures (5 and 15 °C). Blood/water respiratory variables and plasma catecholamine levels were measured before and 15 min after exposure to hypoxic water varying between 4.0 and 10.7 kPa (3080 mmHg) oxygen partial pressure (PwO2). Arterial blood PO2 (PaO2) and oxygen content (CaO2) fell during hypoxia in a similar manner at both temperatures, although the changes in CaO2 were often more pronounced in the fish acclimated to 15 °C. Regardless of acclimation temperature, plasma catecholamine levels were consistently elevated at PwO2 values below 8.0 kPa (60 mmHg); the largest increases in plasma catecholamine levels occurred below PwO2=5.3 kPa (40 mmHg). Adrenaline was the predominant catecholamine released into the circulation. Adrenaline was released at PwO2 values of 8.0 kPa or below, whereas noradrenaline was released at PwO2 values of 6.7 kPa or below. The construction of in vivo oxygen dissociation curves demonstrated an obvious effect of acclimation temperature on haemoglobin (Hb) oxygen-affinity; the P50 values at 15 °C and 5 °C were 3.6 kPa (26.7 mmHg) and 1.9 kPa (14.0 mmHg), respectively. At 15 °C, catecholamines were released into the circulation abruptly at a PaO2 threshold of 4.6 kPa (34.5 mmHg) while at 5 °C the catecholamine release threshold was lowered to 3.3 kPa (24.5 mmHg). The difference in the PaO2 catecholamine release thresholds was roughly equivalent to the difference in the P50 values at the two distinct temperatures. Catecholamine release thresholds, calculated on the basis of arterial blood oxygen-saturation (expressed as CaO2/[Hb]), were similar at both temperatures and were approximately equal to 5355 % Hb O2-saturation. The results support the contention that the lowering of blood oxygen content/saturation rather than PO2 per se is the proximate stimulus/signal causing catecholamine release in rainbow trout during acute hypoxia.

Journal Article↗

PubMed1997

The two essential light chains of carp fast skeletal myosin, LC1 and LC3, are encoded by distinct genes and change their molar ratio following temperature acclimation.

cDNA libraries were constructed from fast skeletal muscles of carp acclimated to 10 and 30 degrees C for a minimum of 5 weeks and were screened for myosin alkali light chains, LC1 and LC3, using an anti-skipjack LC1 polyclonal antibody. Two types of LC1 cDNA clone were isolated and termed LC1a and LC1b: their nucleotide sequences showed 92% homology. The ratio of LC1a to LC1b cDNA clones isolated was approximately 3:1, showing no apparent changes following temperature acclimation. The occurrence of the two isoforms was further confirmed by N-terminal amino acid sequencing of purified LC1. No isoform was, however, detected for LC3, while homology in the overlapping region between LC1a and LC3 cDNAs was only 65% even after the most probable alignment. Southern blot analyses probed with cDNA clones specific to LC1a and LC3 showed different hybridization patterns from each other, demonstrating that carp LC1 and LC3 are encoded by different genes. These results are in marked contrast to those from higher vertebrates which express LC1 and LC3 from a single gene by alternative RNA transcription and two modes of splicing. Northern blot analysis showed that the ratios of LC3/LC1 mRNAs were significantly higher (3.93) in 30 degrees C-acclimated than in 10 degrees C-acclimated (3.10) carp.

Amino Acid Sequence↗

PubMed1997

Release of atrial natriuretic factor prohormone peptides 1-30, 31-67 and 99-126 from freshwater- and seawater-acclimated perfused trout (Oncorhynchus mykiss) hearts

Atrial natriuretic factor (ANF), a 28-amino-acid peptide hormone produced in the heart, circulates in both freshwater and seawater rainbow trout. In mammals, two other peptide hormones, proANF 1-30 and proANF 31-67, derived from the same 126-amino-acid prohormone as ANF (amino acids 99&shyp;126), circulate and have natriuretic and diuretic properties. It has never been determined whether these peptides circulate in fish. The present investigation was designed to determine (1) whether proANF 1-30 and/or proANF 31-67 circulate in perfused hearts from freshwater- and seawater-acclimated rainbow trout (Oncorhynchus mykiss) in situ, and (2) if they do, to determine whether increasing the filling pressure of the heart causes their release in trout as it does in mammals. High-performance gel-permeation chromatography of fish plasma revealed that both proANF 1-30 and 31-67 circulate in freshwater- and seawater-acclimated trout plasma at threefold higher concentrations than does ANF. The basal rates of release of ANF and proANF 1-30 and 31-67 were similar in both freshwater and seawater trout, with the rate of release of proANF 1-30 being 10 times higher and that of proANF 31-67 20 times higher than that of ANF. When the filling pressure was increased to the peak of the Starling curve (max), the rate of release of ANF and proANFs 1-30 and 31-67 increased fivefold for each peptide in the freshwater trout, while in seawater trout the rates of release increased six- to ninefold. We conclude that proANF 1-30 and 31-67, as well as ANF, circulate in both freshwater-and seawater-acclimated trout and do so at concentrations higher than that of ANF. Increasing the filling pressure to the trout heart was found to cause a similar increase in the release rates for each of these peptides, but the maximal increase was higher in the seawater-acclimated trout, apparently because they showed a larger increase in cardiac output.

Journal Article↗

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↗

PubMed2000

A cold acclimation protein with refolding activity on frozen denatured enzymes.

We found that a cold acclimation protein from an ice-nucleating bacterium, Patoea ananas KUIN-3, has refolding activity on frozen denatured protein. Based on a SDS-PAGE analysis, we confirmed that the cold shock-treated cells of strain KUIN-3 could produce some cold acclimation proteins that inhibit their syntheses by the addition of chloramphenicol during the cold acclimation. Among such proteins, Hsc25 had refolding activity similar to GroELS. Hsc25 was purified to apparent homogeneity by (NH4)2SO4 precipitation and some chromatographies. The purified Hsc25 was composed of 8 subunits of 25,000 each with a molecular mass of 200,000 and had refolding activity against denatured enzymes, which were denatured by heat-treatment at 100 degrees C, cryopreservation at -20 degrees C, or guanidine hydrochloride, in a manner similar to GroELS. The N-terminal sequence of Hsc25 was Met-Arg-Ala-Ser-Thr-Tyr-His-Ala-Ala-Arg-. Furthermore, Hsc25 had a high level of activity at low temperature (12 degrees C). Also, the dissociation constants, KD (M) as the binding specificity for enolase, mutarotase, isocitrate dehydrogenase, and lactate dehydrogenase were 1.82x10(-10), 4.35x10(-9), 8.98x10(-12), and 3.05x10(-11), respectively. The affinity of Hsc25 for frozen danatured enzymes was higher than the affinity for heat denatured enzymes when compared with the affinity of GroEL. These results are the first report on the characterization of a purified chaperon that was induced by cold acclimation.

Adaptation, Physiological↗

PubMedDate not supplied

Mechanical and metabolic performance of the rat heart: effects of combined stress of heat acclimation and swimming training.

Although the individual effects of heat acclimation and swimming exercise on cardiovascular reserve and efficiency have been studied, the relative and cumulative effects of these interventions have not. Myocardial developed force, coronary flow (CF), and oxygen consumption during baseline conditions and during pacing-induced tachycardia were therefore studied in isolated perfused hearts from four groups of rats: normothermic sedentary (C), heat acclimated sedentary (AC), normothermic swimmers (CS), and heat acclimated swimmers (ACS). Normothermic temperature was 24 degrees C. Heat acclimation was attained by continuous exposure to 34 degrees C for one and two months. Swimmers had two daily 75 minute sessions for five days a week with water temperatures of 33-35 degrees C and 36-38 degrees C for CS and ACS rats, respectively. After one month AC animals showed a remarkable decrease in O2 consumption. In contrast, ACS increased both O2 consumption and the maximal isometric force generated. After two months, O2 consumption of AC rats continued to be low. The heart failed to restitute the force developed at high pacing frequency. In these rats CF was remarkably low and remained unchanged with increased pacing. In contrast ACS maintained the ability to develop force at all pacing rates at a level similar to that of the normothermic C and ACS rat hearts, but at high oxygen cost. The data suggest that the AC heart is more efficient but cannot meet demands at high pacing rates. In contrast, swimming in the heat improved performance of ACS temporarily, without decreasing the metabolic rate.

Acclimatization↗

PubMed2001

Changes in heart rate variability following acclimation to heat.

We studied the sympatho-vagal balance during acclimation to heat in eight healthy individuals. The subjects, dressed in shorts and tennis shoes, underwent a 10 d procedure of acclimation. Daily exposure lasted 115 min--5 min rest followed by 2 bouts of 50 min exercise (walking on a treadmill at a work load of approximately 350 watt) separated by 10 min rest-at 40 degrees C and 40% relative humidity. We analyzed the time and frequency domains of 256 R-R intervals, toward the end of the second bout of exercise, on the first and tenth days of acclimation. Typical changes for heat acclimation (a reduction in rectal temperature and heart rate, an increase in sweat rate) were observed. Concomitant to a decrease in the final heart rate on the tenth day, sympathetic tone increased. We suggest that, except for the chronotropic response, changes in the sympatho-vagal balance may reflect several adaptive mechanisms of the cardiovascular system. Peripheral factors rather than intrinsic cardiac factors are of relatively greater importance in the direct control of cardiac function.

Acclimatization↗

PubMed2000

Changes in lactate dehydrogenase and malate dehydrogenase activities during hypoxia and after temperature acclimation in the armored fish, Rhinelepis strigosa (Siluriformes, Loricariidae).

Lactate (LDH) and malate dehydrogenase (MDH) of white skeletal muscle of fishes acclimated to 20, 25 and 30 degrees C and thereafter submitted to hypoxia were studied in different substrate concentrations. Significant differences for LDH and MDH of white muscle enzyme activities are described here for the first time in Rhinelepis strigosa of fishes acclimated to 20 degrees C and submitted to hypoxia for six hours. LDH presented a significant decrease in enzyme affinity for pyruvate in acute hypoxia, for fishes acclimated to 20 degrees C and an increase for fishes acclimated to 30 degrees C.

Acclimatization↗

PubMed2006

Comparison of two types of inocula during acclimation and stable operation for nitrophenol biodegradation in an anaerobic-aerobic SBR.

This work presents a comparison of two inocula used for the acclimation of two anaerobic-aerobic sequencing batch bioreactors used for toxic wastewater treatment. The bioreactors were acclimated with different types of sludge: one coming from an anaerobic wastewater treatment plant and the other one from a conventional aerobic activated sludge plant. The model toxic compound was p-nitrophenol, which is reduced to p-aminophenol during the initial anaerobic phase of the reaction, and later mineralized during a posterior aerated reaction phase. Biodegradation of the compounds was monitored using UV/Vis spectrophotometry. After acclimation stabilization of the sludge and of the process was also monitored. Results show that there is no significant difference in acclimation times and stability of the process between the two employed inocula, and thus an originally anaerobic inoculum presents no apparent advantage over a more easily accessible aerobic one.

Aerobiosis↗

PubMed1982

Thermogenic response to glucagon in cold-acclimated mice.

Heat production after injection of glucagon and norepinephrine was measured in warm- and cold-acclimated mice. Glucagon and norepinephrine in a dose of 100 microgram/100 g caused a marked increase in oxygen consumption. Heat production after administration of glucagon and norepinephrine was significantly potentiated by cold acclimation. A significant positive correlation was observed between the increase in oxygen consumption after injection of glucagon or norepinephrine and the weight of brown adipose tissue in warm- and cold-acclimated mice. These findings indicate that glucagon is a calorigenic hormone in mice and its effect is potentiated by cold acclimation possibly due to an activation of thermogenic mechanism(s) in brown adipose tissue.

Acclimatization↗

PubMed1983

Effects of glucagon and noradrenaline on the blood flow through brown adipose tissue in temperature-acclimated rats.

After 30 min infusion of glucagon or noradrenaline, blood flow through brown adipose tissue (BAT) from various sites was investigated with the aid of 113Sn-labeled microspheres under hexobarbital anesthesia in cold-acclimated (CA), heat-acclimated (HA), and warm control (WC) rats. Glucagon increased cardiac output in both CA and HA, while noradrenaline increased it in HA but not in CA. Blood flow through BAT as well as the fractional distribution of cardiac output to BAT increased by glucagon dose-dependently and reached a maximum level in a dose of 2 micrograms/min. These glucagon-induced responses were significantly higher in CA and smaller in HA as compared with WC. Noradrenaline in a dose of 2 microgram/min caused larger responses than glucagon in all groups. Glucagon- or noradrenaline-induced blood flow per unit weight of BAT increased or tended to increase by cold acclimation. These results suggest that an in vivo enhanced glucagon-induced thermogenesis in cold-acclimated BAT is partly due to an increased blood flow through this tissue.

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↗

PubMed1986

Metyrapone-induced thermogenesis in cold- and heat-acclimated rats.

Metyrapone caused significant increase of VO2 in cold-acclimated rats, but not in warm controls and heat-acclimated rats. Plasma FFA decreased, while plasma glycerol increased in all groups. Glycerol increase was less in heat-acclimated rats than in other groups. FFA/glycerol molar ratio decreased most in cold-acclimated rats.

Acclimatization↗

PubMed1987

Enhanced formation of cyclic AMP after cold acclimation in the rat.

Plasma cAMP response to glucagon was enhanced after cold acclimation. Cold-acclimated rats also showed an enhanced production of hepatic cAMP in response to glucagon. In both brown and white fat tissues, cAMP contents increased after cold acclimation. Enhancement of cAMP formation in the liver and fat tissues may partly contribute to an enhanced nonshivering thermogenesis during cold acclimation.

Acclimatization↗

PubMed1988

Effect of facial cooling during heat acclimation process on adaptive changes in sweating activity.

On assumptions that tympanic temperature (Tty) reflects brain temperature and that the latter can be lowered by cooling of the face, effect of facial cooling during acclimation process on adaptive changes in sweating activity was examined, in comparison with the results of our previous studies on heat acclimation with controlled hyperthermia. Face fanning, by which Tty was clamped at approximately 37.1 degrees C, was combined with either of the following 9-day acclimation procedures: 90-min heating in a "Sauna box," keeping mean skin temperature slightly above 40 C, or 90-min exercise on a bicycle, clamping rectal temperature (Tre) at approximately 38 degrees C. Each procedure was imposed on the same four male subjects on different occasions, two of whom had participated in our previous experiments. Sweat tests, carried out before and immediately after the completion of the procedure, consisted of measurements of local sweat rates, whole body sweat rate, Tre, Tty, and skin temperatures on 5 areas, and of calculations of mean body temperature (Tb) and the rate of sweat expulsions (Fsw, as an indicator of central sudomotor activity). No or only a slight increase in sweating activity was observed following the acclimation procedures with face fanning, whereas similar procedures without face fanning had resulted in substantial enhancement of sweating activity in most of the cases, which had been attributed mainly to adaptive changes in central sudomotor activity (as indicated by a shift of the regression line relating Fsw to Tb). Similar results were obtained in an additional series of experiments, where the effects of 9-day 90-min exercise in heat, clamping Tre at approximately 38.2 degrees C, with and without facial cooling, were compared with each other in a subject. From the above results it is inferred that Tty reflects brain temperature and that enhancement of sweating activity induced by repeated heat load is strongly impeded, if not accompanied, by an elevation of brain temperature.

Acclimatization↗

PubMed1990

Changes in fasting-induced adrenocortical secretion of cold-acclimated rats.

Effect of cold acclimation on fasting-induced adrenocortical and metabolic responses was studied in rats. The animals were acclimated to cold by exposure to 5 degrees C for 4 weeks. The warm control animals were kept at 25 degrees C for the same period. Fasting for 48 h decreased the body weight to the same extent in warm controls (WC) and cold-acclimated rats (CA). Plasma free fatty acids concentration increased by fasting, but the degree of increase did not differ between WC and CA. Plasma glucose level decreased in WC, while it increased in CA by fasting. Plasma corticosterone level was significantly higher in CA than in WC. Fasting increased the level in both groups, and the extent of increase as assessed by 95% confidence interval was significantly greater in CA as compared with that in WC. The present results indicate that fasting-induced glucocorticoid secretion is potentiated by cold acclimation, suggesting a possible role of this hormone in some metabolic changes in fasting.

Acclimatization↗

PubMed1996

Fatty acid profiles of phospholipids in brown adipose tissue from rats during cold acclimation and repetitive intermittent immobilization: with special reference to docosahexaenoic acid.

The effects of cold acclimation and repetitive intermittent immobilization were examined on fatty acid (FA) compositions in phospholipids of rat interscapular brown adipose tissue (BAT) and plasma. As previously reported, cold acclimation and intermittent immobilization increased the degree of unsaturation as a whole in FAs of BAT but not in plasma. N-3 polyunsaturated docosahexaenoic acid (22-6; DHA) decreased in cold acclimation but increased in intermittent immobilization in phospholipids of BAT. DHA was decreased in phospholipids of plasma in both groups. Considering our previous findings that the in vitro thermogenic response of BAT was suppressed in cold acclimation and enhanced in intermittent immobilization, it was inferred that DHA in BAT is involved in the regulation of thermogenic function of this tissue.

Acclimatization↗

PubMed2006

Acclimation to high ambient temperature in Large White and Caribbean Creole growing pigs.

The effect of breed [Creole (CR) vs. Large White (LW)] on performance and physiological responses during acclimation to high ambient temperature was studied in 2 experiments involving 24 (12/breed) growing pigs each. Pigs were exposed to 24 degrees C for 10 d (d -10 to -1) and thereafter to a constant temperature of 31 degrees C for 16 d (d 1 to d 16) in Exp. 1 and for 20 d (d 1 to d 20) in Exp. 2. For both experiments, the temperature change was achieved over 4 h on d 0. The first experiment began at 105 d of age, and the average BW of CR and LW pigs was 36.6 +/- 2.5 kg and 51.7 +/- 3.0 kg, respectively. The second experiment was designed to compare both breeds at a similar BW (about 52 kg on d 0). Pigs were individually housed and given ad libitum access to feed. At 24 degrees C, ADG was lower (P < 0.01) in CR than in LW (602 vs. 913 g/d and 605 vs. 862 g/d in Exp. 1 and 2, respectively), but the ADFI was not affected by breed (190 and 221 g x d(-1) x kg(-0.60) in Exp. 1 and 2, respectively). Short-term thermoregulatory responses during the 4-h transition from 24 to 31 degrees C (d 0) were analyzed according to a linear plateau model to determine the break point temperature, above which rectal temperature (RT), cutaneous temperature (CT), and respiratory rate (RR) began to change. The CT increased linearly with temperature increase (0.22 degrees C/ degrees C) and was less (P < 0.05) in CR than in LW (by -0.3 degrees C on average). In both experiments, the break point temperature for RT was not affected by breed (27.6 degrees C on average), whereas for RR it was greater (P < 0.05) in CR than in LW (27.5 vs. 25.5 degrees C, P < 0.01). On average, ADFI declined by about 50 g x d(-1) x kg(-0.60) from d -1 to d 1 (P < 0.01), and thereafter at 31 degrees C, it gradually increased (23 g x d(-1) x kg(-0.60); P < 0.05), suggesting an acclimation to high exposure. This response was not influenced by breed. After the day that marked the beginning of the acclimation response (i.e., the threshold day), RR, CT, and RT declined over the duration of exposure to 31 degrees C (P < 0.05) in both experiments. During this period, RT and CT were less in CR than in LW pigs (39.6 vs. 39.9 degrees C and 37.9 vs. 38.2 degrees C, respectively; P < 0.05), whereas RR was not affected by breed. The threshold day at which RT began to decline was less in CR than in LW pigs (0.18 vs. 1.17 d and 0.39 vs. 0.93 d in Exp. 1 and 2, respectively; P < 0.05). In conclusion, this study suggests that short- and long-term physiological reactions during heat acclimation differed when CR and LW pigs were compared at the same age or BW.

Acclimatization↗