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At least 19 recordsLinked to original sources
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↗
PubMed1979

The interaction of thermal tolerance with drug cytotoxicity in vitro.

The effect of preheating EMT6 cells in vitro on their response to cytotoxic agents of either 43 degrees C or 37 degrees C has been investigated. Preheating for 3 h at 40 degrees C produced measurable protection (thermal tolerance) to subsequent treatment for 1 h at 43 degrees C. This preheat treatment was further found to reduce cell killing by BLM and BCNU (drug tolerance) present during 1 h at 43 degrees C. In contrast, no such heat-induced drug tolerance was seen with ADR. An additional effect with ADR was the apparent elimination of heat-induced thermal tolerance at toxic drug doses. However, preheating under these conditions had no effect on the subsequent cytotoxicity of any of these drugs at 37 degrees C. Also, preheating for 1 h at 43 degrees C was found to sensitize cells to BLM and BCNU toxicity at 37 degrees C but to protect against ADR toxicity. The results are discussed in relation to known mechanisms of cell killing by heat and of thermal tolerance.

Animals↗
PubMed2026

Long-term heat exposure reshapes muscle molecular regulation and enhances thermal tolerance in Clarias fuscus.

Rapid fluctuations in water temperature driven by global warming have become a major abiotic stressor affecting muscle function in teleost fish. This study examined the effects of long-term thermal conditions on heat tolerance in Clarias fuscus. Fish were maintained for 90 days at either a normal temperature group (NT, 26 °C) or a high-temperature group (HT, 34 °C). Subsequently, muscle histology, and transcriptomic profiles were observed following acute high-temperature exposure (34 °C) and after temperature recovery (26 °C). Histological analysis showed that fish from the NT under acute high-temperature stress exhibited severe muscle damage (atrophy, myofilament disruption, and myolysis), whereas fish from the HT displayed markedly reduced lesions. RNA-seq profiling revealed 5769 differentially expressed genes (DEGs) in the NT and 3292 DEGs in the HT following acute temperature challenges. Functional enrichment indicated that, in the HT, modulation of key cell cycle regulators (e.g., ccna, ccnb, cdk1, cdk2) contributed to alleviating muscle damage caused by temperature fluctuations. In the NT, genes associated with ribosome biogenesis (e.g., nop56, riok2, riok1) were up-regulated and then down-regulated during temperature fluctuation, whereas p53 in the cell cycle pathway showed the opposite expression pattern. These findings demonstrate long-term heat exposure reshapes molecular expression and regulatory mechanisms in the muscle of C. fuscus, thereby enhancing thermal tolerance and adaptability, and providing a theoretical basis for breeding heat-resistant, high-quality aquaculture strains.

Animals↗
PubMed2026

Quantifying the evolutionary potential for Delta Smelt persistence in a warming habitat.

Long-term persistence of managed species will depend, in part, on whether the species harbors the physiological or genetic potential to adjust to warming temperatures, and whether relevant genetic variation is modified by management practices. The critically endangered Delta Smelt (Hypomesus transpacificus) is intensively managed, but little is known about the presence of genetic variation for resistance to elevated temperature, which will be important to maintain for their persistence in a rapidly warming future. Using a pedigree and whole genome sequencing data, we characterized the genetic variation and genomic architecture for CTMax (as a metric of upper thermal tolerance) across control and elevated rearing temperatures, alongside covarying traits (body size, degree of hatchery ancestry). Warmer rearing temperatures increased CTMax through acclimation but also resulted in reduced additive genetic variation for the trait, which could constrain adaptation under thermal stress. We found that larger fish had reduced CTMax, although this effect was diminished at elevated temperatures. We observed modest heritability for CTMax at rearing temperatures of 15°C and 18°C (0.26 and 0.16, respectively), but only a limited number of loci were identified that had consistent effects on CTMax across rearing temperatures. Instead, the genomic basis of thermal tolerance was highly dependent on rearing temperature (many loci detected with a GxE effect). The influence of domestication selection was indicated by changes in allele frequency, and divergence in upper thermal tolerance and plasticity, between low and high hatchery ancestry groups. Minimal overlap between loci associated with domestication and CTMax suggests that these traits possess separate genetic underpinnings. Knowledge of genetic variation supporting ecologically relevant physiological variation may be useful for refuge management and may inform supplementation in an ever-warming environment.

conservation physiology↗
PubMed2026

Quantifying the Evolutionary Potential for Delta Smelt Persistence in a Warming Habitat.

Long-term persistence of managed species will depend, in part, on whether the species harbors the physiological or genetic potential to adjust to warming temperatures, and whether relevant genetic variation is modified by management practices. The critically endangered Delta Smelt (Hypomesus transpacificus) is intensively managed, but little is known about the presence of genetic variation for resistance to elevated temperature. Using a pedigree and whole genome sequencing data, we characterized the genetic basis of CTMax (as a metric of upper thermal tolerance) across control and elevated rearing temperatures, alongside covarying traits (body size and degree of hatchery ancestry). Warmer rearing temperatures increased CTMax through acclimation but also resulted in reduced additive genetic variation for the trait. We observed modest heritability for CTMax at rearing temperatures of 15°C and 18°C (0.26 and 0.16, respectively), but only a limited number of loci were identified that had consistent effects on CTMax across rearing temperatures. Instead, the genomic basis of thermal tolerance was highly dependent on rearing temperature (i.e., many loci detected with a GxE effect). This temperature-dependent genomic architecture is consistent with our finding that additive genetic variation for CTMax was reduced under warmer rearing conditions, indicating a potential constraint on adaptive evolutionary change. The influence of domestication selection was indicated by changes in allele frequency, and divergence in upper thermal tolerance and plasticity, between low and high hatchery ancestry groups. Minimal overlap between loci associated with domestication and CTMax suggests that these traits possess separate genetic underpinnings. Knowledge of genetic variation supporting ecologically relevant physiological variation may be useful for captive management and may inform supplementation of fish to the wild in an ever-warming environment.

conservation physiology↗
PubMed2026

DeepLabCut-based automated system reveals diverse temperature tolerance among medaka strains and related Oryzias species.

Temperature is a critical environmental factor influencing the physiology and behavior of ectothermic animals, yet conventional methods for evaluating thermal tolerance in fish rely on subjective manual observation of loss of equilibrium (LOE), limiting experimental throughput and introducing observer bias. Here, we developed an automated temperature tolerance evaluation system integrating DeepLabCut-based pose estimation with custom image processing algorithms to objectively quantify the timing of LOE during thermal stress tests. Our system incorporated region partitioning and color transformation preprocessing to improve keypoint detection accuracy, followed by a classification model combining ResNet34-based frame features with keypoint coordinates to objectively determine the timing of LOE without manual observation. Validation against manual annotation showed that the automated system achieved an accuracy comparable to the natural variability between trained investigators, and outperformed naive human observers, supporting its validity as an objective and reproducible alternative to manual scoring. Using this system, we characterized cold and heat tolerance across six medaka strains (Oryzias latipes: d-rR/TOKYO, HB11A, OK-Cab, HO5 and HdrR-II1; O. sakaizumii: HNI-II). Cold and heat tolerance assessment revealed inter-strain variation, with HdrR-II1 among the most cold- and heat-tolerant strains and HNI-II the least tolerant of both cold and heat stress. We further evaluated cold tolerance in medaka-related species (O. sinensis, O. cabaranensis, O. curvinotus, O. luzonensis, O. celebensis, and O. javanicus) and zebrafish (Danio rerio), revealing substantial interspecific variation that broadly corresponded with latitudinal distribution. O. latipes, distributed at the highest latitudes among the tested species, exhibited the greatest cold tolerance, whereas O. celebensis, O. javanicus, and other tropical or low-latitude species showed comparatively low cold tolerance. Our automated system provides a robust, high-throughput platform for thermal tolerance evaluation and, combined with the genetic and genomic resources available in medaka, establishes a foundation for elucidating the molecular mechanisms underlying temperature adaptation in fish.

Animals↗
PubMed2026

Endozoicomonas acroporae enhances coral thermal resilience through host-microbe coordination.

Probiotics hold promise for enhancing coral resilience under climate-driven thermal stress, yet their mechanisms remain poorly understood. Although the bacterial genus Endozoicomonas has been proposed to benefit corals, in vivo evidence of beneficial effects on the host remains limited. Here, we establish Endozoicomonas acroporae Acr-14T as a coral probiotic and characterize its effects on the reef-building coral Stylophora pistillata. We show that E. acroporae Acr-14T enhances host thermal tolerance, colonizes coral tissues, and forms coral-associated microbial aggregates. Microbial profiling indicates that probiotic treatment is associated with reduced relative abundances of opportunistic microbes and enrichment of putatively beneficial taxa. To support transcriptomic analyses, we assembled a chromosome-level genome of S. pistillata clade 1 (Pacific lineage) and found that E. acroporae Acr-14T treatment mitigates heat-induced protein-folding stress and apoptotic signaling. Single-cell transcriptomics further revealed altered expression of genes involved in S-adenosylmethionine (SAMe) metabolism and pro-survival signaling in gastrodermal cells of probiotic-treated corals. Together, our results provide a cell-type-resolved view of host responses linked to Endozoicomonas-mediated coral thermal resilience and offer insight into molecular mechanisms implicated in host-microbe interactions under environmental stress.

Animals↗
PubMed1979

Relationships among training, heat acclimation, and heat tolerance in men and women: the controversy revisited.

For more than a decade there has been a controversy over the beneficial effects of physical training in a cool environment on exercise-heat tolerance. The issues include (a) inadequate controls regarding the physical characteristics of subjects, (b) marked variability in the conditions of the standard heat tolerance tests and (c) differences in the intensity and duration of the training programs employed. Intense training in a cool environment cannot serve as a substitute for exercise in the heat if acclimation is desired within a 2 week period. However, a substantial improvement (50%) in heat tolerance can be derived from 8-11 weeks of training under temperate conditions (21 degrees C) and thermal equilibrium can be maintained for at least 4 hours during mild work (200 W/m2) in dry or wet heat by endurance runners. These adjustments occur in both men and women and appear to be independent of aerobic capacity. The key to improved thermal tolerance with training in a cool environment is maintenance of an elevated core temperature for a sufficient duration of time to produce an adaptive response.

Acclimatization↗
PubMed1976

A transient thermotolerant survival response produced by single thermal doses in HeLa cells.

Continuous exposure of HeLa cells in culture to elevated temperatures (41-45 degrees) results in cell killing which increases exponentially as the time at the elevated temperature increases linearly. When cells are returned to 37 degrees after an initial thermal dose, cellular sensitivity to subsequent hyperthermic doses is reduced. Cell inactivation rates for cultures previously treated with 44 degrees for either 0.5 or 1 hr followed by incubation at 37 degrees for 2 hr, showed D0's of 1.1 and 1.5 hr, respectively, for subsequent thermal treatments at 44 degrees. Cultures receiving no prior hyperthermic dose had a D0 of 0.5 hr for treatments at 44 degrees for up to 3.5 hr. The viable progeny of cells treated with 44 degrees for 1 hr, however, had the same sensitivity to thermal doses at 44 degrees as did previously unheated cells. These results and others demonstrate that (a) single thermal dose produce a state of thermotolerance in HeLa cells to subsequent hyperthermic doses; (b) the degree of thermotolerance produced is dependent on the magnitude (i.e., temperature and time at the elevated temperature) of the first thermal dose; (cy thermotolerance does not develop at the elevated temperature but requires a return of culture temperatures to 37 degrees; (d) cellular acquisition of thermal tolerance is dependent on cell metabolism, as demonstrated by an inhibition of the effect at 0 degrees; and (e) this effect is a transient phenomenon which is lost as cells divide following the first thermal dose.

Cell Division↗
PubMed2026

Epitranscriptomic erasers in bivalves: Evolutionary divergence and species-specific transcriptional plasticity of the ALKBH family under acute thermal stress.

The AlkB homolog (ALKBH) family of Fe(II)/α-ketoglutarate-dependent dioxygenases mediates nucleic acid demethylation, thereby governing RNA metabolism and genomic stability. Despite their pivotal roles in epitranscriptomic regulation across vertebrates, the evolutionary dynamics and functional significance of ALKBH proteins in bivalve mollusks remain largely unexplored. Here, we present a comprehensive phylogenomic analysis of 210 ALKBH genes identified across 35 bivalve species. Our analyses reveal a distinct evolutionary trajectory characterized by the lineage-specific loss of ALKBH4 and the restricted distribution of ALKBH5 to the Mytilidae family, contrasting sharply with vertebrate repertoires. Using the noble scallop (Chlamys nobilis) and Pacific oyster (Crassostrea gigas) as model systems, we demonstrate that ALKBH genes exhibit conserved spatiotemporal expression patterns, with pronounced enrichment in gonadal tissues and during metamorphic transitions, implicating these enzymes in gametogenesis and larval development. Furthermore, comparative thermal stress experiments reveal divergent transcriptional plasticity: the subtropical scallop C. nobilis mounts rapid, transient induction of ALKBH1/2/6 under heat shock, whereas the eurythermal oyster C. gigas maintains sustained ALKBH3 expression, potentially underpinning its superior thermal tolerance. Conversely, cold stress elicits bimodal regulation in C. nobilis, with ALKBH1/2 upregulation contrasting with ALKBH6/7/8 suppression. These findings illuminate the functional diversification of bivalve ALKBH genes and their potential utility as molecular biomarkers for assessing developmental competence and thermal resilience in shellfish aquaculture.

Animals↗
PubMed1979

Effects of chronic cadmium exposure on crayfish survival, growth, and tolerance to elevated temperatures.

Crayfish Cambarus latimanus were subjected over a 5-month period to 0.02, 5, and 10 microgram Cd/L in a continuous flow system at ambient winter temperatures. Uptake of cadmium, growth, and mortality were measured. One-half of the surviving crayfish were analyzed for Cd after completion of the 5-month experiment, while the remaining half were removed from the contaminated water and subjected in a static laboratory experiment to stepwise, daily increases in temperature. The results indicated that (1) the rate of Cd uptake in crayfish was positively related to external concentration, (2) mortality increased significantly with higher Cd concentrations, and (3) neither growth nor thermal tolerance was significantly related to the Cd concentration in the crayfish tissues. The importance of chronic, low-level studies is discussed.

Animals↗
PubMed2026

Hidden genomic structure and widespread structural polymorphism across environmental gradients in the spiny sea star Marthasterias glacialis.

Genomic regions of reduced recombination can preserve linkage among co-adapted alleles, facilitating local adaptation despite high connectivity. Such regions-often generated by chromosomal inversions-may be especially important in highly dispersive marine taxa yet remain poorly documented in echinoderms. Here, we combined a chromosome-level reference genome with genome-wide ddRAD-seq from 296 Marthasterias glacialis individuals across 19 Atlantic-Mediterranean locations to quantify population structure and scan for recombination-suppressed haploblocks. Genome-wide neutral markers showed significant population differentiation together with evidence of high connectivity, revealed by the presence of inter-ecoregion migrants. Additionally, we identified 16 polymorphic haploblocks with patterns consistent with putative chromosomal inversions spanning 18.6% of the genome. Haploblock haplotypes were strongly environmentally and geographically structured and contained genes with key functions in stress response, osmoregulation and thermal tolerance. Haplotype distributions also paralleled previously described mitochondrial lineages despite nuclear gene flow, consistent with a model of ancient divergence followed by secondary contact. Overall, our results suggest a role for widespread structural polymorphism in adaptive differentiation in Echinodermata, providing a framework for linking echinoderm genome rearrangements to ecological divergence. Marthasterias glacialis thus emerges as a promising system to explore how structural variation contributes to adaptation and genome evolution in highly dispersive organisms.

Animals↗
PubMed1979

Fractionation and characterization of cystine aminopeptidase (oxytocinase) and arylamidase of the human placenta.

Three activity peaks hydrolysing L-cystine-di-beta-naphthylamide (CysNA) and two activities hydrolysing L-leucine-beta-naphthylamide (LeuNA) were separated by gel filtration on Sepharose 6B from human placental tissue. The enzyme activities in the void volume and the solubilized enzyme activities with both substrates apparently are bound and free forms of the same enzymes (I) since detergent treatment caused a total disappearance of the activities in the void volume. The second distinct enzyme (II) was highly soluble and detected only with CysNA. The particle-bound enzyme(s) had a pH optimum at 6.5 with CysNA and at about 7.5 with LeuNA. They were highly sensitive to EDTA, could be reactivated by Co2+ and Zn2+ and were more sensitive to Ni2+ and L-methionine than the soluble enzyme II. The former enzyme(s) tolerated thermal treatment better than the soluble enzyme II. The solubilized free enzyme(s) I had a molecular weight of about 309,000. The soluble enzyme II was resistant to EDTA. Its optimum was at pH 6.0 and an estimate of 76,000 for the molecular weight was obtained.

2,2'-Dipyridyl↗