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Results for “Thermal acclimation”

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PubMed2003

Plasma membrane rafts of rainbow trout are subject to thermal acclimation.

Rafts are cholesterol- and sphingolipid-enriched microdomains of the plasma membrane (PM) that organize many signal transduction pathways. Interactions between cholesterol and saturated lipids lead to patches of liquid-ordered membrane (rafts) phase-separating from the remaining PM. Phase behavior is temperature sensitive, and acute changes in temperature experienced by poikilotherms would be expected to perturb raft structure, necessitating an acclimatory response. Therefore, with thermal acclimation, we would expect compositional changes in the raft directed to offset this perturbation. Using differential and density gradient centrifugation, we separated PM from the livers of rainbow trout acclimated to 5 degrees C and 20 degrees C into raft-enriched (raft) and raft-depleted PM (RDPM). Compared with RDPM, the raft fractions were enriched in cholesterol, the beta(2)-adrenergic receptor and adenylyl cyclase, which are commonly used markers for this microdomain. Furthermore, cholesterol was enriched in all fractions from warm-compared with cold-acclimated animals, but this increase was 3.4 times greater in raft than in PM. We developed a novel approach for measuring membrane molecular interaction strength (and thus the tendency to stabilize raft structure) based on the susceptibility of membranes to detergent. Specifically, studies with model vesicles demonstrated that the capacity of a membrane to accommodate detergent prior to solubilization (saturation point) was a good index of this property. The saturation point of the isolated membrane preparations was temperature sensitive and was significantly different in 5 degrees C- and 20 degrees C-acclimated RDPM when assayed at 5 degrees C and 20 degrees C, respectively. By contrast, this comparison in rafts was not significantly different, suggesting compensation of this property. These data suggest that compositional changes made in the PM during thermal acclimation act to offset thermal perturbation of the raft but not the RDPM structural integrity.

Acclimatization↗

PubMed2004

Partitioning of evaporative water loss in white-winged doves: plasticity in response to short-term thermal acclimation.

We investigated changes in the relative contributions of respiratory evaporative water loss (REWL) and cutaneous evaporative water loss (CEWL) to total evaporative water loss (TEWL) in response to short-term thermal acclimation in western white-winged doves Zenaida asiatica mearnsii. We measured REWL, CEWL, oxygen consumption and carbon dioxide production in a partitioned chamber using flow-through respirometry. In doves housed for 2-4 weeks in a room heated to ca. 43 degrees C during the day, TEWL increased from 5.5+/-1.3 mg g(-1) h(-1) at an air temperature (T(a)) of 35 degrees C to 19.3+/-2.5 mg g(-1) h(-1) at T(a)=45 degrees C. In doves housed at room temperature for the same period, TEWL increased from 4.6+/-1.1 mg g(-1) h(-1) at T(a)=35 degrees C to 16.1+/-4.6 mg g(-1) h(-1) at T(a)=45 degrees C. The CEWL of heat-acclimated doves increased from 3.6+/-1.2 mg g(-1) h(-1) (64% of TEWL) at 35 degrees C to 15.0+/-2.1 mg g(-1) h(-1) (78% of TEWL) at T(a)=45 degrees C. Cool-acclimated doves exhibited more modest increases in CEWL, from 2.7+/-0.7 mg g(-1) h(-1) at T(a)=35 degrees C to 7.8+/-3.4 mg g(-1) h(-1) at T(a)=45 degrees C, with the contribution of CEWL to TEWL averaging 53% over this T(a) range. Cool-acclimated doves became mildly hyperthermic (body temperature T(b)=42.9+/-0.4 degrees C) and expended 35% more energy relative to heat-acclimated doves (T(b)=41.9+/-0.6 degrees C) at T(a)=45 degrees C, even though TEWL in the two groups was similar. In each of the two groups, metabolic rate did not vary with T(a), and averaged 7.1+/-0.5 mW g(-1) in cool-acclimated doves and 6.3+/-0.8 mW g(-1) in heat-acclimated doves. The differences in TEWL partitioning we observed between the two experimental groups resulted from a consistently lower skin water vapour diffusion resistance (r(v)) in the heat-acclimated doves. At T(a)=45 degrees C, r(v) in the cool-acclimated doves was 120+/-81 s cm(-1), whereas r(v) in the heat-acclimated doves was 38+/-8 s cm(-1). Our data reveal that in Z. a. mearnsii, TEWL partitioning varies in response to short-term thermal acclimation.

Acclimatization↗

PubMed1996

Differences in protein patterns of gill epithelial cells of the fish Gillichthys mirabilis after osmotic and thermal acclimation.

Different protein patterns in gill epithelium of a euryhaline and eurythermal teleost fish (Gillichthys mirabilis, Family Gobiidae) in response to long-term (2 months) osmotic and thermal acclimation were found for the first time. Gill epithelial cells were isolated to remove extracellular proteins and quantify specialized cell types. Chloride cells were identified on the basis of size (> 10 microns) and bright appearance after [2-(p-dimethylaminostyryl)-1-methyl-pyridinium-iodine] staining. Small mitochondria-rich cells were < 5 microns in diameter and showed intermediate fluorescence. Abundance of chloride cells and small mitochondria-rich cells was significantly influenced by osmotic but not thermal acclimation (dilute seawater/25 degrees C: 1.4 +/- 0.2% chloride cells, 11.9 +/- 4.6% small mitochondria-rich cells; seawater/25 degrees C: 2.4 +/- 0.6% chloride cells, 2.2 +/- 1.3% small mitochondria-rich cells; seawater/10 degrees C: 2.9 +/- 0.3% chloride cells, 1.2 +/- 0.7% small mitochondria-rich cells). Pavement cells, identified by low fluorescence and intermediate size (5-10 microns), largely predominated under all conditions (> 85% of cells). Thus, they represented the major protein source in gill epithelium. Differences in protein patterns were detectable using two-dimensional but not one-dimensional electrophoresis. Of 602 proteins identified by charge and molecular weight properties, only two were induced by high temperature (25 degrees C) and three in response to cold acclimation (10 degrees C). Nine proteins were induced in diluted seawater-acclimated fish, whereas no seawater-induced proteins were found. We hypothesize that proteins induced under dilute seawater conditions are important for the function of pavement cells in gills of hyper-osmoregulating G. mirabilis.

Acclimatization↗

PubMed1984

Temperature-dependent deacylation of molecular species of phosphatidylcholine by microsomal phospholipase A2 of thermally acclimated rainbow trout, Salmo gairdneri.

Using the ratios of kinetic parameters, V/Km, the deacylation of different molecular species of 1-palmitoyl,2-acyl phosphatidylcholine via microsomal phospholipase A2 (PLA2) was studied in liver tissue of thermally acclimated rainbow trout (Salmo gairdneri). In general, PLA2 from fish acclimated to cold temperatures showed an order of preference for the acyl moieties of 18:1 greater than 18:2 greater than 18:0. Trout acclimated to warm temperatures generally preferred 18:0 PC, but the actual order of preference depended on the temperature of the assays and the presence of endogenous lipids in the enzyme preparation. At 5 C, the particulate (microsomal) enzyme preferred 18:0 greater than 18:2 greater than 18:1, but a lipid-free preparation of the enzyme preferred 18:2 greater than 18:0 greater than 18:1. At 20 C, particulate enzyme preferred 18:1 greater than 18:0 greater than 18:2 but purified enzyme preferred 18:0 greater than 18:2 greater than 18:1. Thus, assay temperature and the presence of microsomal lipids had a greater effect on PLA2 from fish acclimated to warm temperatures than fish acclimated to cold temperatures. The substrate preference of PLA2 is discussed with reference to the previously observed changes in membrane fatty acid composition that occur with thermal acclimation in rainbow trout.

Acclimatization↗

PubMed1998

Thermal acclimation of phase behavior in plasma membrane lipids of rainbow trout hepatocytes.

The fluorescent probes laurdan (6-dodecanoyl-2-dimethylaminonapthalene) and N-[7-nitrobenz-2-oxa-1, 3-diazol-4-yl] dipalmitoyl-L-alpha-phosphatidylethanolamine (NBD-PE) in addition to Fourier transform infrared spectroscopy (FTIR) were employed to measure the phase behavior and physical properties of hepatocyte plasma membranes isolated from the livers of thermally acclimated (5 and 20 degreesC) rainbow trout (Oncorhynchus mykiss). The primary objective was to determine the extent to which the phase behavior of membrane lipids is conserved at different growth temperatures. Arrhenius plots of laurdan-generalized polarization revealed a single discontinuity believed to reflect either the onset of the gel-fluid phase transition or the formation of gel phase microdomains, and this discontinuity occurred at significantly higher temperatures in membranes of 20 degrees C (13.2 +/- 0.7 degrees C)- than 5 degrees C (7.2 +/- 0.1 degrees C)-acclimated trout. Similarly, acclimation from 5 to 20 degrees C increased both the onset temperature (from 2.0 +/- 0.3 to 7.2 +/- 0.6 degrees C) and the thermal range (from 10.9 +/- 0.5 to 16.0 +/- 1.0) of the gel-fluid transition as assessed by FTIR. The gel-fluid transition midpoint (approximately -2 degrees C) and completion temperatures (-9 degrees C) were unchanged by thermal acclimation. The anisotropy of NBD-PE fluorescence displayed a distinct minimum in membranes of both warm- and cold-acclimated trout (reflecting alterations in lipid packing that in pure lipid membranes ultimately lead to the formation of nonlamellar phases) in the range of 56-58 degrees C; only membranes of 5 degrees C-acclimated trout displayed an additional minimum at significantly lower temperatures (24.5 +/- 1.7 degrees C). Collectively, these data suggest that the regulation of both the temperature at which gel phase lipids begin to form in response to cooling as well as the propensity of membrane lipids to form nonlamellar phases at higher temperatures may be key features of membrane organization subject to adaptive regulation.

2-Naphthylamine↗

PubMed1996

Plasticity of fish muscle mitochondria with thermal acclimation

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.

Journal Article↗

PubMed2003

Influences of thermal acclimation and acute temperature change on the motility of epithelial wound-healing cells (keratocytes) of tropical, temperate and Antarctic fish.

The ability to heal superficial wounds is an important element in an organism's repertoire of adaptive responses to environmental stress. In fish, motile cells termed keratocytes are thought to play important roles in the wound-healing process. Keratocyte motility, like other physiological rate processes, is likely to be dependent on temperature and to show adaptive variation among differently thermally adapted species. We have quantified the effects of acute temperature change and thermal acclimation on actin-based keratocyte movement in primary cultures of keratocytes from four species of teleost fish adapted to widely different thermal conditions: two eurythermal species, the longjaw mudsucker Gillichthys mirabilis (environmental temperature range of approximately 10-37 degrees C) and a desert pupfish, Cyprinodon salinus (10-40 degrees C), and two species from stable thermal environments, an Antarctic notothenioid, Trematomus bernacchii (-1.86 degrees C), and a tropical clownfish, Amphiprion percula (26-30 degrees C). For all species, keratocyte speed increased with increasing temperature. G. mirabilis and C. salinus keratocytes reached maximal speeds at 25 degrees C and 35 degrees C, respectively, temperatures within the species' normal thermal ranges. Keratocytes of the stenothermal species continued to increase in speed as temperature increased above the species' normal temperature ranges. The thermal limits of keratocyte motility appear to exceed those of whole-organism thermal tolerance, notably in the case of T. bernacchii. Keratocytes of T. bernacchii survived supercooling to -6 degrees C and retained motility at temperatures as high as 20 degrees C. Mean keratocyte speed was conserved at physiological temperatures for the three temperate and tropical species, which suggests that a certain rate of motility is advantageous for wound healing. However, there was no temperature compensation in speed of movement for keratocytes of the Antarctic fish, which have extremely slow rates of movement at physiological temperatures. Keratocytes from all species moved in a persistent, unidirectional manner at low temperatures but at higher temperatures began to take more circular or less-persistent paths. Thermal acclimation affected the persistence and turning magnitude of keratocytes, with warmer acclimations generally yielding more persistent cells that followed straighter paths. However, acclimation did not alter the effect of experimental temperature on cellular speed. These findings suggest that more than one temperature-sensitive mechanism may govern cell motility: the rate-limiting process(es) responsible for speed is distinct from the mechanism(s) underlying directionality and persistence. Keratocytes represent a useful study system for evaluating the effects of temperature at the cellular level and for studying adaptive variation in actin-based cellular movement and capacity for wound healing.

Acclimatization↗

PubMed1990

The effect of thermal acclimation on the activity of arylhydrocarbon hydroxylase in rainbow trout (Oncorhynchus mykiss).

1. The possibility that temperature acclimation (to 10 or 18 degrees C for 28 days) would alter the cytochromes P-450 of rainbow trout was addressed. 2. The specific content of LM4b (P-450 IA1), the trout isozyme responsible for activation of polynuclear aromatic hydrocarbons, was lower in 18 degrees C fish than it was in 10 degrees C fish. 3. Kinetic analysis of aryl hydrocarbon hydroxylase indicated that, while thermal acclimation caused no change in Vmax, it lowered the apparent Km of this enzyme for benzo[a]pyrene when assayed at acutely shifted temperatures. 4. Thermal acclimation of fish may have significance when feral populations are subjected to acute temperature shifts.

Acclimatization↗

PubMed2000

Inability of adult Limnodynastes peronii (Amphibia: Anura) to thermally acclimate locomotor performance.

Despite several studies on adult amphibians, only larvae of the striped marsh frog (Limnodynastes peronii) have been reported to possess the ability to compensate for the effects of cool temperature on locomotor performance by thermal acclimation. In this study, we investigated whether this thermal acclimatory ability is shared by adult L. peronii. We exposed adult L. peronii to either 18 or 30 degrees C for 8 weeks and tested their swimming and jumping performance at six temperatures between 8 and 35 degrees C. Acute changes in temperature affected both maximum swimming and jumping performance, however there was no difference between the two treatment groups in locomotor performance between 8 and 30 degrees C. Maximum swimming velocity of both groups increased from 0.62+/-0.02 at 8 degrees C to 1.02+/-0.03 m s(-1) at 30 degrees C, while maximum jump distance increased from approximately 20 to >60 cm over the same temperature range. Although adult L. peronii acclimated to 18 degrees C failed to produce a locomotor response at 35 degrees C, this most likely reflected a change in thermal tolerance limits with acclimation rather than modifications in the locomotor system. As all adult amphibians studied to date are incapable of thermally acclimating locomotor performance, including adults of L. peronii, this acclimatory capacity appears to be absent from the adult stage of development.

Adaptation, Physiological↗

PubMed1989

Thermal Acclimation of Photosynthetic Electron Transport Activity by Thylakoids of Saxifraga cernua.

Thermal acclimation by Saxifraga cernua to low temperatures results in a change in the optimum temperature for gross photosynthetic activity and may directly involve the photosynthetic apparatus. In order to test this hypothesis photosynthetic electron transport activity of S. cernua thylakoids acclimated to growth temperatures of 20 degrees C and 10 degrees C was measured in vitro. Both populations exhibited optimum temperatures for whole chain and PSII electron transport activity at temperatures close to those at which the plants were grown. Chlorophyll a fluorescence transients from 10 degrees C-acclimated leaves showed higher rates in the rise and subsequent quenching of variable fluorescence at low measuring temperatures; 20 degrees C-acclimated leaves showed higher rates of fluorescence rise at higher measuring temperatures. At these higher temperatures, fluorescence quenching rates were similar in both populations. The kinetics of State 1-State 2 transitions in 20 degrees C- and 10 degrees C-acclimated leaf discs were measured as changes in the magnitude of the fluorescence emission maxima measured at 77K. Leaves acclimated at 10 degrees C showed a larger F730/F695 ratio at low temperatures, while at higher temperatures, 20 degrees C-acclimated leaves showed a higher F730/F695 ratio after the establishment of State 2. High incubation temperatures also resulted in a decrease in the F695/F685 ratio for 10 degrees C-acclimated leaves, suggesting a reduction in the excitation transfer from the light-harvesting complex of photosystem II to photosystem II reaction centers. The relative amounts of chlorophyll-protein complexes and thylakoid polypeptides separated electro-phoretically were similar for both 20 degrees C- and 10 degrees C-acclimated leaves. Thus, photosynthetic acclimation to low temperatures by S. cernua is correlated with an increase in photosynthetic electron transport activity but does not appear to be accompanied by major structural changes or different relative amounts in thylakoid protein composition.

Journal Article↗

PubMed2000

Thermal acclimation of locomotor performance in tadpoles and adults of the aquatic frog Xenopus laevis.

Among amphibians, the ability to compensate for the effects of temperature on the locomotor system by thermal acclimation has only been reported in larvae of a single species of anuran. All other analyses have examined predominantly terrestrial adult life stages of amphibians and found no evidence of thermal acclimatory capacity. We examined the ability of both tadpoles and adults of the fully aquatic amphibian Xenopus laevis to acclimate their locomotor system to different temperatures. Tadpoles were acclimated to either 12 degrees C or 30 degrees C for 4 weeks and their burst swimming performance was assessed at four temperatures between 5 degrees C and 30 degrees C. Adult X. laevis were acclimated to either 10 degrees C or 25 degrees C for 6 weeks and their burst swimming performance and isolated muscle performance was determined at six temperatures between 5 degrees C and 30 degrees C. Maximum swimming performance of cold-acclimated X. laevis tadpoles was greater at cool temperatures and lower at the highest temperature in comparison with the warm-acclimated animals. At the test temperature of 12 degrees C, maximum swimming velocity of tadpoles acclimated to 12 degrees C was 38% higher than the 30 degrees C-acclimation group, while at 30 degrees C, maximum swimming velocity of the 30 degrees C-acclimation group was 41% faster than the 12 degrees C-acclimation group. Maximum swimming performance of adult X. laevis acclimated to 10 degrees C was also higher at the lower temperatures than the 25 degrees C acclimated animals, but there was no difference between the treatment groups at higher temperatures. When tested at 10 degrees C, maximum swimming velocity of the 10 degrees C-acclimation group was 67% faster than the 25 degrees C group. Isolated gastrocnemius muscle fibres from adult X. laevis acclimated to 10 degrees C produced higher relative tetanic tensions and decreased relaxation times at 10 degrees C in comparison with animals acclimated to 25 degrees C. This is only the second species of amphibian, and the first adult life stage, reported to have the capacity to thermally acclimate locomotor performance.

Acclimatization↗

PubMed2006

Energetics of lizard embryos are not canalized by thermal acclimation.

In some species of ectotherms, temperature has little or no effect on the amount of energy expended during embryonic development. This phenomenon can result from either of two mechanisms: (1) a shorter incubation period at higher temperatures, which offsets the expected increase in metabolic rate, or (2) a compensatory decrease in the rate at which embryos expend energy for maintenance. To distinguish the relative importance of these two mechanisms, we quantified the acute and chronic effects of temperature on embryonic metabolism in the eastern fence lizard (Sceloporus undulatus). First, we measured metabolic rates of individual embryos at 27 degrees, 31 degrees, and 34 degrees C. Second, we examined the capacity for thermal acclimation by measuring the metabolic rates of embryos at 30 degrees C, after a period of incubation at either 28 degrees or 32 degrees C. As with adult reptiles, the metabolic rates of embryos increased with an acute increase in temperature; the Q(10) of metabolic rate from 27 degrees to 34 degrees C was 2.1 (+/-0.2). No evidence of thermal acclimation was observed either early or late in development. In S. undulatus, a shorter incubation period at higher temperatures appears to play the primary role in canalizing the energy budget of an embryo, but a reduction in the cost of growth could play a secondary role.

Acclimatization↗

PubMed1985

A model of thermal acclimation in cattle.

A model of temperature effects on cattle daily feed intake has been developed that takes into account (1) time course of thermal acclimation and (2) behavioral responses to short-term thermal stress (STTS). The key difference between this model and the classical intake-temperature model is its consideration of the acclimation state of the animal. Time course of physiological acclimation is represented by a running average temperature. The STTS is defined as the difference between the current acclimated temperature [Tacci(L)] and current daily mean temperature (Ti). Ruminants were postulated as decreasing activity in response to STTS. An empirical relationship between daily feed intake (I) and environmental temperature was derived as: I = 100% - b'[Ti - Tacci(L)]2. Length of the acclimation period, L, and value of the behavioral response coefficient, b', were determined for grazing time of free-roaming cattle and feed intake of five breeds of feedlot cattle. Cattle breeds displayed apparent differences in L but no significant differences in b'. Feeding situation (feedlot vs free-roaming) had a significant effect on b' in cattle, but not on L. Because of explicit treatment of acclimation and stress, two-dimensional representation of thermal environment may be a more meaningful expression of effective environmental temperature in fluctuating environments than mean daily temperature alone. This model may have value in the interpretation of laboratory studies, as well as field studies, because the time frame of experiments will influence the results obtained, depending upon the acclimation state of the animal.

Acclimatization↗

PubMed1995

The thermal acclimation of burst escape performance in fish: an integrated study of molecular and cellular physiology and organismal performance

Goldfish (Family Cyprinidae, Carassius auratus) and killifish (Family Cyprinodontidae, Fundulus heteroclitus) were acclimated to 10, 20 and 35 °C for 4 weeks. The thermal acclimation of C-start (escape swimming) performance and the physiological properties of fast twitch muscle fibres that underlie it were investigated in these species at the molecular (myosin isoform expression), biochemical (myofibrillar ATPase activity), cellular (contractile kinetics) and organismal levels of organisation. Peptide maps were obtained for fast muscle myosin heavy chains, isolated from 10 °C- and 35 °C-acclimated fish. Different myosin heavy chain isoforms were expressed in response to a change in acclimation temperature in goldfish, but myosin heavy chain isoform expression was unaffected by acclimation temperature in killifish. Compared with fish acclimated to 35 °C, acclimation to 10 °C increased the activity of fast muscle myofibrillar ATPase assayed at 10 °C fivefold in goldfish and only 50 % in killifish. Muscle twitch contraction time at 10 °C decreased significantly in response to acclimation to 10 °C in both species; however, the magnitude of this response was much greater in goldfish (100 %) than in killifish (30 % or less). In goldfish, these changes in the physiological properties of fast twitch fibres during 10 °C acclimation resulted in a six- to eightfold increase in the speed and turning velocity of fish performing C-starts at 10 °C. By comparison, the somewhat smaller acclimatory response of killifish fast muscle properties was accompanied by only a minor (50 % or less) adjustment in locomotor performance. Thermal acclimatory responses of fast muscle at the molecular, biochemical and cellular levels of organisation are clearly reflected in alterations in organismal escape performance.

Journal Article↗

PubMed1985

Rapid changes in the phospholipid composition of gill membranes during thermal acclimation of the rainbow trout, Salmo gairdneri.

The phospholipid composition of gill tissue was determined in rainbow trout (Salmo gairdneri) undergoing thermal acclimation between 5 degrees C and 20 degrees C for a period of up to 28 days. Proportions of phosphatidylethanolamine (PE) and cardiolipin (CL) increased during cold acclimation and decreased during warm acclimation; proportions of phosphatidylcholine (PC) changed in the opposite direction (i.e., decreased during cold acclimation). In contrast, levels of phosphatidylserine, -inositol, and sphingomyelin did not vary significantly. Thermal modulation of headgroup composition occurred rapidly as reflected by changes in the ratio of PC-to-PE, which rose significantly from 2.40 +/- 0.09 to 2.92 +/- 0.09 within 72 h of transfer from 5 to 20 degrees C; adaptation to 5 degrees C was equally rapid. Proportions of PE changed more rapidly than those of PC during cold adaptation, whereas the opposite was true during warm acclimation. Both the time course and the direction of the observed changes in phospholipid composition suggest that such adjustments may contribute to the homeoviscous regulation of membrane properties, particularly during the initial stages of thermal adaptation.

Acclimatization↗

PubMed1998

Ca2+-ATPase activity and Ca2+ uptake by sarcoplasmic reticulum in fish heart: effects of thermal acclimation.

This study was designed to compare the activities of sarcoplasmic (SR) Ca2+-ATPase and Ca2+ uptake in fish and mammalian hearts and to determine whether thermal acclimation has any effect on the function of the cardiac SR in fish. To this end, we measured thapsigargin-sensitive Ca2+-ATPase activity and thapsigargin-inhibitable Ca2+ uptake velocity in crude cardiac homogenates of newborn and adult rats and of two teleost fish (crucian carp and rainbow trout) acclimated to low (4 degrees C) and high (17 degrees C and 24 degrees C for trout and carp, respectively) ambient temperatures. The TG-sensitive Ca2+-ATPase activity was highest in adult rat, and the corresponding activities of cold-acclimated trout, warm-acclimated trout, warm-acclimated carp, cold-acclimated carp and newborn rat were 76, 58, 43, 28 and 23 %, respectively, of that of the adult rat at 25 degrees C. SR Ca2+ uptake velocity, measured using Fura-2 at room temperature (approximately 22 degrees C), was highest in cold-acclimated trout, and the values for adult rat, warm-acclimated trout, newborn rat, warm-acclimated carp and cold-acclimated carp were 93, 56, 24, 21 and 14 % of the uptake velocity of cold-acclimated trout, respectively. When corrected to the body temperature of the animal, the relative rates of SR Ca2+ uptake were 100, 26, 19, 18, 11 and 2 % for adult rat, newborn rat, cold-acclimated trout, warm-acclimated trout, warm-acclimated carp and cold-acclimated carp, respectively. These findings show that SR Ca2+ uptake is slower in fish than in mammalian hearts and that marked species-specific differences exist among teleost fish in this respect. Furthermore, acclimation to cold increases the Ca2+ uptake rate of trout cardiac SR (complete thermal compensation) but decreases the SR Ca2+ uptake rate of crucian carp heart. This difference in acclimation response probably reflects the different activity patterns of the two species in their natural habitat during the cold season.

Adaptation, Physiological↗

PubMed1988

Membrane lipid composition and overwintering strategy in thermally acclimated crayfish.

The membrane lipid composition of hepatopancreas tissue was analyzed from two phylogenetically related species of crayfish after thermal acclimation to either 5 or 20 degrees C. One species overwinters in a quiescent state (Orconectes propinquus) and the other remains active throughout the winter (Cambarus bartoni). Both species significantly decreased the level of saturates in the major phosphatides, phosphatidylcholine (PC) and phosphatidylethanolamine (PE; difference not significant in C. bartoni), and both winter-active and winter-quiescent animals tended to be enriched in n-3 acids in PC. Orconectes animals tended to be enriched in n - 3 acids in PC. Orconectes accumulated n - 6 acids in PE at low temperature, whereas Cambarus lost n - 6 acids in this lipid, a change that was offset by the accumulation of monoenes. Cardiolipin became more saturated with cold acclimation in both species. The fatty acid content of the triacylglycerol fraction showed little change with acclimation history, although O. propinquus did accumulate n - 3 acids in triglycerides at low temperature. In O. propinquus, head-group composition was not significantly altered by temperature, but in C. bartoni, cold temperature increased the relative amounts of PE, sphingomyelin, and phosphatidylinositol at the expense of PC. Adaptations to temperature in membrane composition of poikilotherms are related to the overwintering strategy of the animal.

Acclimatization↗

PubMed1995

Phagocyte activity in the frog Rana temporaria: whole blood chemiluminescence method and the effects of temperature and thermal acclimation.

The respiratory burst activity of phagocytes was measured as zymosan induced, luminol-enhanced chemiluminescence (CL) emission in the whole blood of the frog Rana temporaria. The effect of thermal acclimation on phagocyte activity was studied by acclimating adult frogs for 14-18 days to 5 and 24 degrees C. The phagocyte CL was measured at seven temperatures ranging from 5 to 37 degrees C. Clear signs of resistance acclimation were seen both in CL reaction kinetics at 5 degrees C (P < 0.0001) and in intensities at 37 degrees C (P < 0.003). Thermal adaptation was also seen as a 1-5 degrees C shift in the temperature response curve of CL intensity towards the acclimation temperature (P < 0.03). The highest CL intensities were seen at 30 degrees C and they were of the same magnitude in both acclimation groups. The phagocyte activation enhanced progressively at temperatures ranging from 5 to 30 degrees C, showing that migration to a warmer environment would increase the phagocyte activity of frogs. The possible relation to behavioral fever is discussed.

Animals↗