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PubMed1977

Thermal tolerance and repair of thermal damage by cultured cells.

Exposure of hamster cells to 42.5 degrees C for long periods leads to the development of thermal tolerance; the slope of the survival curve become shallower after about 3.5 to 4 hours. If two 4-hour exposures at 42.5 degrees C are separated by various periods of time, thermal tolerance is eliminated by 20 hours. Prolonged exposure at 42.5 degrees C offers considerable protection from subsequent treatments to acute hyperthermia at 45 degrees C indicate or in conditioned medium or balanced salt solution failed to reveal any evidence of repair of potentially lethal damage.

Animals↗

PubMed1986

Lack of association between glutathione content and development of thermal tolerance in human fibroblasts.

Thermal tolerance is a transient state of heat resistance occurring in cells and tissues after exposure to sublethal heat or certain chemicals. Although the mechanism of such resistance is unknown, it has been recently shown that preceding its development, cellular glutathione (GSH) levels rise. We have used a glutathione synthetase-deficient [GSH(-)] human fibroblast line to study the relationship between glutathione content and thermal tolerance. The GSH(-) cells had approximately 6% as much GSH as normal fibroblasts. Normal and GSH(-) fibroblasts showed similar survival after exposure to 45 degrees C. Exposure of normal fibroblasts to heat (45 degrees C for 15 min) led to a prompt rise in cellular GSH content as well as development of transient thermal tolerance. Similar treatment of GSH(-) fibroblasts produced no change in the very low GSH levels but was associated with a degree of thermal tolerance similar to that of normal cells. Thermal tolerance decayed more rapidly in GSH(-) cells than in normal fibroblasts. We conclude that the development of thermal tolerance in human fibroblasts is independent of GSH content.

Child, Preschool↗

PubMed2005

Ontogenetic shifts in thermal tolerance, selected body temperature and thermal dependence of food assimilation and locomotor performance in a lacertid lizard, Eremias brenchleyi.

We used Eremias brenchleyi as a model animal to examine differences in thermal tolerance, selected body temperature, and the thermal dependence of food assimilation and locomotor performance between juvenile and adult lizards. Adults selected higher body temperatures (33.5 vs. 31.7 degrees C) and were able to tolerate a wider range of body temperatures (3.4-43.6 vs. 5.1-40.8 degrees C) than juveniles. Within the body temperature range of 26-38 degrees C, adults overall ate more than juveniles, and food passage rate was faster in adults than juveniles. Apparent digestive coefficient (ADC) and assimilation efficiency (AE) varied among temperature treatments but no clear temperature associated patterns could be discerned for these two variables. At each test temperature ADC and AE were both higher in adults than in juveniles. Sprint speed increased with increase in body temperature at lower body temperatures, but decreased at higher body temperatures. At each test temperature adults ran faster than did juveniles, and the range of body temperatures where lizards maintained 90% of maximum speed differed between adults (27-34 degrees C) and juveniles (29-37 degrees C). Optimal temperatures and thermal sensitivities differed between food assimilation and sprint speed. Our results not only show strong patterns of ontogenetic variation in thermal tolerance, selected body temperature and thermal dependence of food assimilation and locomotor performance in E. brenchleyi, but also add support for the multiple optima hypothesis for the thermal dependence of behavioral and physiological variables in reptiles.

Adaptation, Physiological↗

PubMed1983

Thermal tolerance to whole body hyperthermia.

Thermal tolerance, that is, a reduced sensitivity to a succeeding heat treatment, has been noted in vitro and following local hyperthermia in normal tissues and malignant tumors. However, information is sparse concerning thermal tolerance following systemic hyperthermia, thereby limiting our ability to design optimally fractionated systemic hyperthermia treatment protocols. A technique for reproducibly inducing systemic hyperthermia in the rat is described, and the survival curve for rats exposed at 42.5 degrees C for periods of up to 75 minutes is presented. Using this system, increased survival of rats to systemic hyperthermia at 42.5 degrees C was demonstrated 30 hours after an initial sublethal conditioning exposure (41.8 degrees C for 1 hour). The LD50 (the time of exposure lethal to 50% of the rats) at 42.5 degrees C was increased by a factor of approximately 2 in the animals exposed to the sublethal conditioning. This increase in LD50 demonstrates the development of thermal tolerance to killing by whole body hyperthermia.

Acclimatization↗

PubMed1982

The effect of chronic and acute heat conditioning on the development of thermal tolerance.

Survival studies with Chinese hamster ovary cells showed that thermal tolerance, which developed during chronic heating (treatment times greater than or equal to 1 hr) or after acute heating (treatment times less than 1 hr) involves similar mechanisms. For example, cells that expressed thermal tolerance during a 6-14 hr chronic heat treatment at 41.5 degrees C or 42 degrees C also expressed thermal tolerance to a subsequent acute treatment at 45.5 degrees C. Also, cells heated acutely for 10 min at 45.5 degrees C and incubated at 37 degrees C for 12 hr showed tolerance to both 45.5 degrees C acute and 42 degrees C chronic hyperthermia. Finally, thermal tolerance developed between fractionated acute heat treatment at 45.5 degrees C and fractionated chronic heat treatments at 42.5 degrees C. These data indicate that when cells are tolerant to chronic hyperthermia they are also tolerant to acute hyperthermia and that the reverse is also true.

Adaptation, Physiological↗

PubMed2004

Upper thermal tolerance and oxygen limitation in terrestrial arthropods.

The hypothesis of oxygen limitation of thermal tolerance proposes that critical temperatures are set by a transition to anaerobic metabolism, and that upper and lower tolerances are therefore coupled. Moreover, this hypothesis has been dubbed a unifying general principle and extended from marine to terrestrial ectotherms. By contrast, in insects the upper and lower limits are decoupled, suggesting that the oxygen limitation hypothesis might not be as general as proposed. However, no direct tests of this hypothesis or its predictions have been undertaken in terrestrial species. We use a terrestrial isopod (Armadillidium vulgare) and a tenebrionid beetle (Gonocephalum simplex) to test the prediction that thermal tolerance should vary with oxygen partial pressure. Whilst in the isopod critical thermal maximum declined with declining oxygen concentration, this was not the case in the beetle. Efficient oxygen delivery via a tracheal system makes oxygen limitation of thermal tolerance, at a whole organism level, unlikely in insects. By contrast, oxygen limitation of thermal tolerances is expected to apply to species, like the isopod, in which the circulatory system contributes significantly to oxygen delivery. Because insects dominate terrestrial systems, oxygen limitation of thermal tolerance cannot be considered pervasive in this habitat, although it is a characteristic of marine species.

Adaptation, Physiological↗

PubMedDate not supplied

A comparative analysis of the upper thermal tolerance limits of eastern Pacific porcelain crabs, genus Petrolisthes: influences of latitude, vertical zonation, acclimation, and phylogeny.

Marine intertidal organisms are subjected to a variety of abiotic stresses, including aerial exposure and wide ranges of temperature. Intertidal species generally have higher thermal tolerance limits than do subtidal species, and tropical species have higher thermal tolerance limits than do temperate species. The adaptive significance of upper thermal tolerance limits of intertidal organisms, however, has not been examined within a comparative context. Here, we present a comparative analysis of the adaptive significance of upper thermal tolerance limits in 20 congeneric species of porcelain crabs, genus Petrolisthes, from intertidal and subtidal habitats throughout the eastern Pacific. Upper thermal tolerance limits are positively correlated with surface water temperatures and with maximal microhabitat temperatures. Analysis of phylogenetically independent contrasts (from a phylogenetic tree on the basis of the 16s rDNA gene sequence) suggests that upper thermal tolerance limits have evolved in response to maximal microhabitat temperatures. Upper thermal tolerance limits increased during thermal acclimation at elevated temperatures, the amount of increase being greater for subtidal than for intertidal species. This result suggests that the upper thermal tolerance limits of some intertidal species may be near current habitat temperature maxima, and global warming thus may affect the distribution limits of intertidal species to a greater extent than for subtidal species.

Acclimatization↗

PubMed2002

[Thermal tolerance, diel variation of body temperature, and thermal dependence of locomotor performance of hatchling soft-shelled turtles, Trionyx sinensis].

The thermal tolerance, body temperature, and influence of temperature on locomotor performance of hatchling soft-shelled turtles (Trionyx sinensis) were studied under dry and wet conditions, and the selected body temperature of hatchlings was 28.0 and 30.3 degrees C, respectively. Under wet condition, the critical thermal maximum and minimum averaged 40.9 and 7.8 degrees C, respectively. In the environments without thermal gradients, the diel variation of body temperature was highly consistent with the variation of both air and water temperatures, and the body temperature was more directly affected by water temperature than by air temperature, which implied that the physiological thermoregulation of hatchling T. sinensis was very weak. In the environments with thermal gradients, hatchling turtles could maintain relatively high and constant body temperatures, primarily through behavioral thermoregulation. The locomotor performance of hatchling turtles was highly dependent on their body temperature. Within a certain range, the locomotor performance increased with increasing body temperature. In our study, the optimal body temperature for locomotor performance was 31.5 degrees C, under which, the maximum continuous running distance, running distance per minute, and number of stops per minute averaged 1.87 m, 4.92 m.min-1, and 6.2 times.min-1, respectively. The correspondent values at 33.0 degrees C averaged 1.30 m, 4.28 m.min-1, and 7.7 times.min-1, respectively, which indicated that the locomotor performance of hatchling turtles was impaired at 33.0 degrees C. Therefore, extremely high body temperatures might have an adverse effect on locomotor performance of hatchling turtles.

Animals↗

PubMed2002

The 70-kDa heat shock protein response in two intertidal sculpins, Oligocottus maculosus and O. snyderi: relationship of hsp70 and thermal tolerance.

The role that hsp70 plays in influencing thermal tolerance of a whole animal is not clearly understood. We explored this question by examining liver hsp70 response in the tidepool sculpin (Oligocottus maculosus) and fluffy sculpin (O. snyderi), which have distinct distribution patterns in the intertidal zone. The tidepool sculpin is in upper and lower tidepools, while the fluffy sculpin is exclusively in lower tidepools during a low tide. We conducted experiments in order to investigate: (1) habitat water temperatures; (2) upper thermal tolerance limits; (3) the cellular hsp70 response to changes in water temperature in nature; (4) induction temperatures for hepatic hsp70 and hsp70 mRNA; and (5) effects of long-term heat stress on liver hsp70 levels, in these sculpins. Accordingly, we found: (1) the tidepool sculpin was exposed to a wider temperature range in nature; (2) the tidepool sculpin had higher lethal and induction temperatures for hsp70; (3) the liver hsp70 level of the tidepool sculpin was less sensitive to changes in water temperatures; and (4) the tidepool sculpin had higher constitutive hsp70 levels in nature, compared with the fluffy sculpin. From these results, we proposed that the less thermally sensitive tidepool sculpin may enhance its thermal tolerance by having a large pool of cellular hsp70, thus allowing it to inhabit the upper intertidal zone with relatively large and unpredictable fluctuations in environmental variables.

Adaptation, Physiological↗

PubMed1987

Heat shock protein induction and induced thermal tolerance are independent in adult salamanders.

Ectothermic vertebrates become thermally tolerant (heat hardened) after exposure to heat shock. Eukaryotic cells show a similar response. Cellular thermal tolerance is correlated with the induction of heat shock proteins (hsps). We have investigated the relationship between heat hardening in salamanders and the induction of hsps in the tissues of these organisms. Although the synthesis of hsps can be induced in these animals by sublethal heat shocks, conditions required for hsp induction and heat hardening often do not coincide. We conclude that induced thermal tolerance in adult salamanders is independent of hsp induction in their tissues.

Acclimatization↗

PubMed2005

Intraspecific differences in thermal tolerance of the diamondback watersnake (Nerodia rhombifer): effects of ontogeny, latitude, and sex.

Ontogenetic shifts in microhabitat use are widespread among taxa and can result in drastic shifts in thermal habitat among age classes. Likewise, geographic variation in climate along latitudinal gradients can cause differences in thermal environments among populations of a species. Using a common garden design, we examined four populations of a single species of semi-aquatic snake, Nerodia rhombifer, to determine whether ontogenetic shifts in habitat use (and/or body size) and latitudinal differences in ambient temperature have resulted in evolutionary changes in thermal tolerance. We found ontogenetic differences in thermal tolerance for all populations, with neonates tolerating temperatures 2 degrees C higher than adults, a pattern that is consistent with ontogenetic shifts in body size and microhabitat use in this species. There were differences in thermal tolerance among latitudes in neonates, suggesting genetic differences among populations, but adults showed no latitudinal differences. In combination, the increased thermal tolerance of neonates and the age-specific response to latitude suggest individuals may be most sensitive to selection on thermal tolerance as neonates. Although latitudinal differences exist in neonates, their tolerances were not ranked according to latitude, suggesting the effects of some other local factor (e.g., microclimate) may be important. Lastly, among neonates, females tolerate higher temperatures than males.

Adaptation, Physiological↗

PubMed1989

Heat shock protein synthesis and thermal tolerance in wheat.

Plants respond to high temperature stress by the synthesis of an assortment of heat shock proteins that have been correlated with an acquired thermal tolerance to otherwise lethal temperatures. This study was conducted to determine whether genotypic differences in acquired thermal tolerance were associated with changes in the pattern of heat shock protein synthesis. The pattern of heat shock protein synthesis was analyzed by (35)S-methionine incorporation in wheat (Triticum aestivum L.) varieties exhibiting distinct levels of acquired thermal tolerance. Significant quantitative differences between the cultivars Mustang and Sturdy were observed in the HSP exhibiting apparent molecular weights of 16, 17, 22, 26, 33, and 42 Kilodaltons. Genotypic differences in the synthesis of the small subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase were observed at 34 degrees C. Two-dimensional electrophoretic analysis revealed unique proteins (16, 17, and 26 kilodaltons) in the thermal tolerant variety Mustang that were absent in the more thermal sensitive variety Sturdy. These results provide a correlation between the synthesis of specific low molecular weight heat shock proteins and the degree of thermal tolerance expressed following exposure to elevated temperatures.

Journal Article↗

PubMed1990

Thermal sensitivity and thermal tolerance of human B-lineage acute lymphoblastic leukemia (ALL) cells.

The thermal sensitivities of four B-cell precursor acute lymphoblastic (ALL) cell lines (REH and KM-3 = pre pre B-ALL; NALM-6 and HPB-NULL = pre B-ALL), and 1 B-cell ALL (NAMALWA) cell line were studied and compared to the thermal sensitivity of the T-lineage ALL cell line MOLT-3 using an in vitro clonogenic assay system by limiting dilution. B-lineage ALL cells were as sensitive to hyperthermia as were T-lineage ALL cells. D0 values at 42 degrees C ranged from 44.9 min (NALM-6) to 85.6 min (NAMALWA), D0 values at 43 degrees C ranged from 15.3 min (NALM-6) to 35.7 min (KM-3), and D0 values at 44 degrees C ranged from 11.1 min (NALM-6) to 23.8 min (HPB-NULL). By comparison, the D0 values of MOLT-3 cells were 95.1 min at 42 degrees C, 23.8 min at 43 degrees C, and 14.7 min at 44 degrees C. The maximum log kill values which were observed ranged from 0.8 log (KM-3 and HPB-NULL) to 1.3 logs (NALM-6) at 42 degrees C, from 1.4 logs (KM-3) to 4.2 logs (NALM-6) at 43 degrees C, and from 3.8 logs (HPB-NULL) to 4.8 logs (NALM-6) at 44 degrees C. A thermal tolerant plateau was observed in the hyperthermia survival curves of REH, NALM-6, and HPB-NULL cells, providing circumstantial evidence that thermal tolerance may develop in some B-cell precursor ALL cells after 90-120 min of continuous heating. In contrast, no thermal tolerant plateau was observed in the hyperthermia survival curves of pre-pre-B-ALL/KM-3 B-cell ALL/NAMALWA or T-lineage ALL/MOLT-3 cells. The kinetics of development and decay of thermotolerance was studied for NALM-6 cells. Thermotolerance after a priming heat exposure to 42 degrees C for 30 min was maximum at 8 hr with a maximum thermotolerance ratio of 2.0, and it decayed by 24 hr. These findings extend previous studies on the thermal sensitivity of human leukemia cells and provide new information on the thermal sensitivity and thermotolerance of B-lineage ALL cells.

B-Lymphocytes↗

PubMed2001

Quantitative trait loci for upper thermal tolerance in outbred strains of rainbow trout (Oncorhynchus mykiss).

The expression of three putative QTL for upper thermal tolerance (UTT) was examined in two strains of outbred rainbow trout unselected for this trait using simple-sequence repeat (SSR; microsatellite) markers associated with UTT in backcrosses of lines selected on this trait. Two-way diallel lots in the third generation of an outbred pedigree were exposed to an acute thermal challenge. QTL detection was performed separately by each second-generation parent within each diallel lot, incorporating the effects of full sib families and correlated traits. Inheritance of different alleles at the SSR Ssa20.19NUIG from the sire 93-32-1 was strongly associated with the thermal tolerance of his half sib progeny, explaining 7.5% of their phenotypic variance in this trait. A hierarchical linear model incorporating allelic inheritance from all four grandsires of the experimental diallels (in addition to family specific and covariate trait effects) was also used to detect associations between the SSR and thermal tolerance in their third-generation grandprogeny. Ssa20.19NUIG was strongly associated with thermal tolerance in the grandprogeny of the grandsire G(0)SVM2. The generally stronger marker-trait associations found in male parents may be partially due to reduced chromosomal recombination rates in male salmonids compared to females. These results indicate the effects of a QTL on a fitness-related trait in unselected populations of rainbow trout.

Alleles↗

PubMed2000

Effects of growth at low water activity on the thermal tolerance of Staphylococcus aureus.

Staphylococcus aureus is the most osmotolerant foodborne pathogen, and outbreaks of staphylococcal food poisoning are often linked to foods of reduced water activity (a(w)) values. While it is generally known that the thermal tolerance of microorganisms increases as the a(w) of the heating menstruum is decreased, surprisingly little research has examined the influence of growth medium a(w) on microbial thermal tolerance. In the present study, we show that growth of S. aureus at an a(w) value of 0.94 leads to the development of dramatically enhanced thermal tolerance (i.e., less than 1 log reduction after heating for 20 min at 60 degrees C). We further show that the identity of the accumulated compatible solute within cells grown at low a(w) can also influence the overall level of thermal tolerance of S. aureus. Finally, we provide evidence that the synthesis of general stress and/or osmotic stress proteins is required for the development of enhanced thermal tolerance of S. aureus at low a(w).

Heat-Shock Proteins↗

PubMed1982

Induced thermal tolerance and heat shock protein synthesis in Chinese hamster ovary cells.

We have performed experiments to determine the kinetics of induction of thermal tolerance in Chinese hamster HA-1 cells, and the effects of heat treatments on the recovery of protein synthesis, with particular attention to whether heat induces specific proteins, perhaps the heat shock proteins (HSP). The kinetics of the development of thermal tolerance were measured by increases in cellular survival. In parallel experiments, the effects of heat treatment on the recovery of protein synthesis in HA-1 cells were examined. After heating (45 degrees, 20 minutes), some of these cells were immediately labeled with 35S-methionine (10 microCi/ml) for 1 hour at 37 degrees, while the others were incubated at 37 degrees for 1-8 hours and then labeled. The cell samples were prepared for electrophoresis on a gradient SDS gel. The incorporation of label into HA-1 cell proteins was drastically inhibited by the 45 degrees heat treatment, but recovered gradually during the 8-hour incubation period at 37 degrees C. A comparison of the proteins synthesized following heat shock with those synthesized by non-heated cells showed that the levels of synthesis of certain proteins were greatly enhanced following the 45 degrees treatment. By 8 hours, it was qualitatively apparent that three proteins, with molecular weights of 59K, 70K and 87K, were synthesized in greater amounts than in untreated cells. The kinetics of HSP synthesis were compared to the kinetics of thermal tolerance; these showed good correlation. Overall protein synthesis also increased during this time, although at a rate slower than the synthesis of the HSP. The question of whether the HSP play a causative role in the development of thermal tolerance and if so, what role might be, has not been answered.

Adaptation, Physiological↗

PubMed2006

Intraspecific variation in thermal tolerance and heat shock protein gene expression in common killifish, Fundulus heteroclitus.

Populations of common killifish, Fundulus heteroclitus, are distributed along the Atlantic coast of North America through a steep latitudinal thermal gradient. We examined intraspecific variation in whole-animal thermal tolerance and its relationship to the heat shock response in killifish from the northern and southern extremes of the species range. Critical thermal maxima were significantly higher in southern than in northern fish by approximately 1.5 degrees C at a wide range of acclimation temperatures (from 2-34 degrees C), and critical thermal minima differed by approximately 1.5 degrees C at acclimation temperatures above 22 degrees C, converging on the freezing point of brackish water at lower acclimation temperatures. To determine whether these differences in whole-organism thermal tolerance were reflected in differences in either the sequence or regulation of the heat shock protein genes (hsps) we obtained complete cDNA sequences for hsc70, hsp70-1 and hsp70-2, and partial sequences of hsp90alpha and hsp90beta. There were no fixed differences in amino acid sequence between populations in either hsp70-1 or hsp70-2, and only a single conservative substitution between populations in hsc70. By contrast, there were significant differences between populations in the expression of many, but not all, of these genes. Both northern and southern killifish significantly increased hsp70-2 levels above control values (T(on)) at a heat shock temperature of 33 degrees C, but the magnitude of this induction was greater in northern fish, suggesting that northern fish may be more susceptible to thermal damage than are southern fish. In contrast, hsp70-1 mRNA levels increased gradually and to the same extent in response to heat shock in both populations. Hsc70 mRNA levels were significantly elevated by heat shock in southern fish, but not in northern fish. Similarly, the more thermotolerant southern killifish had a T(on) for hsp90alpha of 30 degrees C, 2 degrees C lower than that of northern fish. This observation combined with the ability of southern killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance. These data highlight the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole-organism traits such as thermal tolerance.

Acclimatization↗

PubMed1984

Fluorescence-activated cell sorting analysis of the induction and expression of acute thermal tolerance within the cell cycle.

We have examined the cell cycle specificity of 45.5 degrees heat-induced toxicity and the induction and expression of thermal tolerance. Ultrapure populations of G1-, S-, and G2-M-phase cells were obtained through sequential centrifugal elutriation and flow cytometric cell sorting of Hoechst 33342-stained cells. We found no interaction of Hoechst 33342 with hyperthermia under staining conditions that gave good cytometric resolution of DNA distributions. Single dose-response survival curves indicated that S phase was the most sensitive to 45.5 degrees hyperthermia (Do = 1.97, 1.26, and 1.95 min for G1, S, and G2-M, respectively). Both S and G2-M phases exhibited a decreased ability from G1 to accumulate sublethal heat lesions as evidenced by decreased heat survival curve shoulders (Dq) = 13.7, 9.51, and 8.39 min for G1, S, and G2-M, respectively). Thermal tolerance, as measured by the decreased inactivation slope of the split-dose treatment, could be induced and expressed in G1, S, and G2-M phases. However, both the magnitude and temporal expression of tolerance were dependent on the position of the cell within the cell cycle at the time of the initial heat treatment. S-phase cells exhibited slightly less thermal tolerance as compared to G1 cells given isosurvival thermal induction doses as measured by the split-dose inactivation rate constants (heated/control = 8.37 and 5.62 for G1 cells at 12 and 24 hr and 7.68 and 5.27 for S-phase cells at 12 and 28 hr). Also, split-dose survival curves for cells heated in G2-M indicated a near total inability to accumulate heat-induced sublethal damage. Simultaneous bivariate (90 degrees light scatter and DNA content) progression analysis of heated replicates indicated that tolerance could probably be expressed in those cells which moved into other cycle compartments following the initial heat treatment. For instance, G1-phase cells preheated for 20 min began progression into normally heat-sensitive S phase between 24 and 28 hr after the heat treatment. This corresponded to approximately the time of maximal thermal tolerance expression. [3H]Thymidine suicide experiments also indicated that the ultimately clonogenic cells began movement into S phase at or near the time of maximal tolerance. In this case then, tolerance expression appeared to supersede the S-phase acute heat sensitivity. Heated S-phase cells began progression into G2-M between 4 and 12 hr, which corresponded temporally to large amounts of tolerance expression4 +

Animals↗