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PubMed1975

New data on the hereditary adaptive increase in thermostability in the forked mutant of Drosophila melanogaster under repeated thermal shock.

It was confirmed that forked mutants of D. melanogaster strain C(I)RM developing after a single intrauterine heating of oocytes in females at 39 degrees for 30 and 45 min exhibited changes in the average number of anomalous thoracic macrochaetae on females: heating for 30 min caused a decrease (normalization of the phenotype), while heating for 45 min caused an increase (intensification of mutation expression). It was established that these changes are inherited maternally, in the same manner as long-term Jollos modifications. Evaluation of the number of anomalous thoracic macrochaetae in parallel strains of flies after heating of the oocytes during the critical periods of macrochaeta development (seven days before egg laying), i.e., the stage of oocyte formation in the germarium. Heating of oocytes in F2t1 females "preliminarily heated in the F1 generation showed that the stability curve for the oocytes after "preliminary" heating during the critical developmental period exhibited an abrupt decrease rather than the anticipated rise, which can only be attributed to an adaptive increase in oocyte thermostability as a result of preliminary heating.

Adaptation, Biological↗

PubMed1977

The dynamic response of warm units in human skin nerves.

Electrophysiological recordings were made from 12 specific warm receptors in the sensory nerves of human hairy skin. In all cases examined, single warm fibers were spontaneously active at normal skin temperature from about 32 degrees C upwards, while touch, stretching, vibration or pricking the skin did not elicit any response within the receptive fields of warm units. Moderate warming of the skin using linear temperature rates from 0.5 degrees C/s to 1.5 degrees C/s caused a transient overshoot in the frequency of discharge with peak frequencies depending on the rate of change of temperature (dT/dt), the magnitude of thermal increment (deltaT) and the adapting temperature (TA). Cooling the skin caused a transient inhibition of discharge.

Adult↗

PubMed1978

Evolutionary adaptation of membranes to temperature.

The "fluidity" of brain synaptosomal membrane preparations of arctic and hot-springs fish species, two temperature water fish species acclimated to different seasonal temperatures, and two mammals was estimated using the fluorescence polarization technique. At all measurement temperatures, the fluidity decreased in the order: arctic sculpin, 5 degrees-acclimated goldfish, 25 degrees-acclimated goldfish, desert pupfish, and rat. This correlated with increasing adaptation or body (i.e., cellular) temperatures of 0 degrees, 5 degrees, 25 degrees, 34 degrees, and 37 degrees and suggested a partial compensation of membrane fluidity for environmental temperature that occurs over the evolutionary time period as well as during laboratory (seasonal) acclimation. Evolutionary adaptation of relatively stenothermal species to constant thermal environments resulted in a more complete compensation than laboratory (seasonal) acclimation. Each compensation is accompanied by differences in the saturation of membrane phosphoglycerides. At increased cellular temperatures the proportion of saturated fatty acids increased and the unsaturation index decreased; the correlation between these indices and the measured expression of membrane dynamic structure was highly significant. It is concluded that the homeoviscous compensation of synaptic membrane function is an important component of temperature adaptation.

Adaptation, Physiological↗

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↗

PubMed2026

Maternal and developmental temperature modulate adult response to temperature in Drosophila melanogaster.

Beyond inherited genes and environmentally induced changes in gene expression, phenotypes can also be shaped by parental effects-an effect from a parental phenotype that causes modifications in offspring traits, which cannot be solely explained by the parental or offspring genomes. Such effects may prepare offspring for future environmental conditions and contribute to phenotypic plasticity, including responses to temperature. While temperature-induced plasticity has been extensively studied, the relative contributions of parental versus direct environmental cues remain poorly understood. The fruit fly Drosophila melanogaster is a powerful model for studying physiological and behavioral adaptation to temperature. Flies inhabit environments spanning broad thermal ranges and show evidence of parental effects, such as increased heat tolerance in offspring from warm-reared parents. Here, we exposed mothers to two experimental temperatures and split their broods between the same two temperatures to estimate the relative importance of maternal and developmental effects on adult physiological and developmental responses to temperature. We find that the reaction norms of locomotor activity under gradually increasing temperatures, responses to heat-shock and cold-shock, and fecundity are mostly governed by direct plastic responses to developmental environment. We detected comparatively weak maternal effects in the response to heat-shock, fecundity, and grand-offspring survival where matched environments counteracted the effects of direct offspring experience. We conclude that thermal experience during development is the primary determinant of phenotypic plasticity in D. melanogaster, while maternal experience contributes a small but non-negligible component.

Animals↗

PubMed1979

A review of selected biological effects and dosimetric data useful for development of radiofrequency safety standards for human exposure.

This report examines the bases for developing radiofrequency exposure standards which can be related to the thermogenic properties of electromagnetic fields. A review of selected biological effects, including dosimetric data and simulation of human thermodyanmic characteristics that are pertinent to standards development, is presented. Based on the analogy of thermal-stress standards that have been developed for hot industrial environments, limits on increases of body temperature are proposed as criteria for limiting exposure to radiofrequency fields, i.e., occupational exposures involving deep heating of the whole body should not increase core temperature in excess of 1 degree C. Since energy deposition from exposure to some RF fields is likely to be non-uniform and may be high in tissues that are not adapted to high rates of absorption or dissipation of thermalizing energy, means are needed to adjust focal thermal loading against the whole-body averages. A limit on core temperature is inadequate when focal elevations of temperature are close to the limits for protein denaturation, as may well occur even though the core temperature may rise less than 1 degree C. Safety limits for the general population are also discussed and here the permissible thermal load should be low enough to cause no more than an insignificant increase in core temperature. Areas needing further research to reduce the uncertainties in developing safe exposure limits for man are delineated. Even in highly adverse environmental conditions the gross thermal load and consequential heat stress from exposure to radiofrequency fields at the 10 mW/cm2 level will be small compared with that generated by any physical effort. On the basis of available data, it is concluded that the safe value for continuous exposure to 10 mW/cm2, widely used in Western countries, appears to provide an adequate margin of safety for both occupational and environmental exposure for frequencies above about 1 GHz. This limit may well be too high (perhaps by an order of magnitude) for some frequencies below 1 GHz where body resonances cause a significant increase in energy deposition and where local temperature rises occur. At the same time the present averaging period of 0.1 h seems unjustifiably short.

Animals↗

PubMed1977

Human skin burns induced by defibrillator default current: a mathematical simulation model.

A preliminary model was prepared for the development of superficial burns which can result from the interaction of faulty defibrillator and other electrical operating room equipment. A thermal model previously used to predict retinal coagulation was adapted to give temperature rise history of the skin. Skin resistance is assumed to decrease rapidly due to the instability of a small volume near the surface. Heating due to dissipation of the defibrillator capacitor energy in this skin volume is shown to be high enough to cause burns. A sensitivity analysis is included to isolate the dominant input parameters. Recommendations are made for future research.

Burns, Electric↗

PubMed1977

Lability of the prolonged depolarizing afterpotential in Balanus photoreceptors.

A large cell to cell variability of the prolonged depolarizing afterpotential (PDA) decay time constant (tau) has been measured in Balanus eberneus lateral ocelli. While 25% of the cells had PDA's of long duration, tau greater than 10 min. 45% of the cells tested showed either weak (tau less than 60 s) PDA or none at all. The variability was not reflected in the late receptor potential. All the cells showed normal light-coincident responses. The variability was not due to some alteration of the thermal stability of the pigment states, since after monochromatic adaptation the amplitude of the early receptor potential remained unchanged for at least 30 min. In addition, in some cells that initially showed PDAs of long duration, the decay time was either shortened or abolished after exposure to anoxia. Again, the late receptor potential and the stability of the pigments remained unaffected. These results indicate that the mechanisms which give rise to the PDA are not always tightly coupled to the direct chain of events that lead to the light-coincident response.

Action Potentials↗

PubMed1979

Changes in hypothalamic noradrenaline and 5-hydroxytryptamine levels during the development of warm- and cold-adaptation in the rat.

Hypothalamic 5-hydroxytryptamine (5-HT) and noradrenaline (NA) as well as plasma corticosterone levels were studied in male rats after 1, 2, 4 and 6 weeks of exposure to 4--7 or 30--31 degrees C. An increase of the NA concentration and a decrease of the 5-HT level was observed after the first week in both cold and warm environment together with an increase of plasma corticosterone levels in both groups. NA, 5-HT and plasma corticosterone levels returned to normal in cold-exposed animals by the 6th week whereas in warm-acclimated rats NA and corticosterone levels regained their initial values and 5-HT concentrations remained low. Changes by the end of the first week of exposure may result from the thermal stress. The low 5-HT levels of warm-adapted animals at the end of the 6th week were probably secondary to the process of adaptation.

Adaptation, Physiological↗

PubMed1977

Thermoregulatory behaviour after repetitive cooling of the preoptic area and of the spinal cord in the rat.

The thermoregulatory behaviour of 6 rats was studied during exposure to cold and warm ambient temperatures after either the preoptic area or the cervical spinal cord had been intermittently cooled for an average of 130 h. The precooled animals worked more for heat in cold environments and for cool air in a warm environment than the control animals. This behaviour, probably due to a decreased ability of the precooled animals to retain heat, suggested that the precooled animals were not fully adapted to cold. 1974) will learn to press a lever to modify their thermal environment, and this paper describes the thermoregulatory behaviour of rats after prolonged cooling of the preoptic area, and of the spinal cord. The thermoregulatory behaviour of cold exposed and cold adapted animals has already been studied in several species (Carlton and Marks, 1958; Laties and Weiss, 1960; Revusky, 1966; balwin and Ingram, 1967).

Adaptation, Physiological↗

PubMed1976

[Multiplicity of the molecular forms of acetylcholinesterase and thermal acclimatization in Carassius auratus].

Multiple forms of acetylcholinesterase have been studied in Goldfish adapted to 15 degrees C and 25 degrees C. Three forms of enzyme (sedimenting at 18S, 12S and 5S) could be distinguished by sucrose gradient centrifugation. Their molecular and enzymatic properties did not vary with environmental temperature. It was noted that the relative proportion of the three forms differed between brain and muscle extracts, the 18S forms predominating in muscle (about 75 per cent) the 12S forms being more abundant in the brain, suggesting a physiological differentiation between these forms. The latter form varied from 48 per cent to 70 per cent in Goldfish adapted to 15 degrees and 25 degrees C respectively. The relative efficiency of saline buffer solubilization for each form also depended on the tissue used and in all cases decreased with rising environmental temperature. These two facts are taken to reflect interactions between acetylcholinesterase and membrane that depend on the nature of the membrane and probably involve the aliphatic chains of its phospholipids. The greater case of solubilization found in the low temperature adapted fish may be a function of the increased fluidity of the cellular membranes formed at lower temperatures.

Animals↗

PubMed1979

A low temperature investigation of the intermediates of the photocycle of light-adapted bacteriorhodopsin. Optical absorption and fluorescence measurements.

Optical absorption and emission measurements have been made on samples of light-adapted purple membrane of Halobacterium halobium at temperatures ranging from 77 K to room temperature. As a result of these experiments a set of equations is given which described thermal and photochemical reactions interrelating various intermediates of the reaction cycle of the chromophore of light-adapted bacteriorhodopsin (BR). Further some specific problems connected to these intermediates have been investigated. Thus the room temperature emission spectrum of bacteriorhodopsin has been found to exhibit a Stokes shift of 3430 cm-1 only, if low excitation intensities are used. The recently detected intermiediate P-BR can be shown to convert thermally into bacteriorhodopsin following a first-order decay with the activation energy delta E = 2.4 +/- 0.2 kcal/mol. The thermal decay of K-BR consists of two exponentials if measured on purple membrane suspensions in a mixture of H2O and glycerol (1 : 1, v/v). A simple procedure is given for trapping the intermediate L-BR at 170 K in a very pure form. M-BR is shown to consist of two species, MI-BR and MII-BR. They are characterized by similar optical absorption spectra but different thermal stability. Further the oscillator strengths corresponding to the long wavelength absorption bands of the intermediates bacteriorhodopsin, K-, L, MI- and MII-BR have been calculated. They have been discussed with respect to the question which of the corresponding absorption spectra show the characteristics of isomerism of the chromophore or simply solvatochromism.

Bacteriorhodopsins↗

PubMed1978

Adaptation of biological membranes to temperature. The lack of homeoviscous adaptation in the sarcoplasmic reticulum.

Temperature adaptation of biological membranes was examined by comparing the fragmented sarcoplasmic reticulum preparation of goldfish acclimated to different temperatures. Membrane fluidity was estimated using the fluorescence polarization technique. There was considerable variation between preparations, but no consistent differences in fluidity were observed between 5- and 25 degrees C-acclimated goldfish, fish species adapted over an evolutionary period to arctic or desert temperatures, and rat. The fatty acid composition of the sarcoplamic reticulum preparations of differently acclimated goldfish showed differences in the proportion of mono- and polyunsaturated fatty acids while the proportion of saturated fatty acids remained relatively constant. However, the fatty acid composition of sarcoplasmic reticulum phosphoglycerides became more unsaturated in the order rat, desert pupfish, arctic sculpin, which correlates with their respective environmental or body temperature. It is concluded that differences in membrane components other than fatty acids are important in determining membrane dynamic structure. The inability to demonstrate homeoviscous adaptation in sarcoplasmic reticulum is supported by other evidence suggesting that functions of the sarcoplasmic reticulum that are measured in vitro are not affected by such modifications of their phosphoglyceride fatty acid composition as occur during thermal acclimation.

Adaptation, Biological↗

PubMed1979

[Brain and kidney, Na, K-ATPase activation in the rat in adaptation to cold].

The activity of Na,K-ATPase of the rat brain and kidney is 1.5--2-fold as increased during intermittent and prolonged (16 weeks) adaptation to cold, without changes in the enzyme affinity to ATP. It is suggested that adaptive increase in the power of the Na pump, triidothyronine-dependent in the kidneys and triiodothyronine-independent in the brain, ensures elevation in thermal production to body cooling.

Adaptation, Physiological↗

PubMed1977

Rhodopsin photoproducts and rod sensitivity in the skate retina.

The late photoproducts that result from the isomerization of rhodopsin have been identified in the isolated all-rod retina of the skate by means of rapid spectrophotometry. The sequence in which these intermediates form and decay could be described by a scheme that incorporates two pathways for the degradation of metarhodopsin II (MII) to retinol: one via metarhodopsin III (MIII) and the other (which bypasses MIII) through retinal. Computer simulation of the model yielded rate constants and spectral absorbance coefficients for the late photoproducts which fit experimental data obtained at temperatures ranging from 7 degrees C to 27 degrees C. Comparing the kinetics of the thermal reactions with the changes in rod threshold that occur during dark adaptation indicated that the decay of MII and the fall in receptor thresholds exhibit similarities with regard to their temperature dependence. However, the addition of 2 mM hydroxylamine to a perfusate bathing the retina greatly accelerated the photochemical reactions, but had no significant effect on the rate of recovery of rod sensitivity. It appears, therefore, that the late bleaching intermediates do not control the sensitivities of skate rods during dark adaptation.

Animals↗

PubMed1976

Cold-adaptive modifications in man induced by repeated short-term cold-exposures and during a 10-day and-night cold-exposure.

Two types of cold exposures were carried out in humans. A. Fourteen subjects were exposed 4-7 times within 2 weeks to the following conditions: ambient temperature was decreased from 28 degrees C to between plus and minus 5 degrees C; the subjects wore a bathing suit and remained in a resting position during the exposure which lasted for 1h. B. Nine conscripts were studied before and after a 10-day exercise, during which they were exposed to moderately cold conditions during day and night. The exercise did not require increased physical activity. In two thirds of the subjects A, metabolic reactions and shivering threshold were shifted to a lower weighted mean body temperature as well as a lower esophageal temperature ("hypothermic" type of adaptation). This modification in the thermoregulatory system was linked with a reduction in thermal discomfort and cold sensation. No change was found in the resting metabolic rate nor was there any indication of the development of non-shivering thermogenesis. Similar modifications were found in 4 of the 9 soldiers (study B). These 4, however, had particularly high shivering thresholds before the 10-day exercise and the values found thereafter were no lower than those found in the remaining five and in the subjects of group A before the cold-exposure regimen.

Acclimatization↗

PubMedDate not supplied

[Perception of chemical and temperature stimuli by the ampullae of Lorenzini in in skates].

Recording impulse activity in single nervous fibers, studies have been made on the effect of chemical and thermal stimuli on the activity of Lorenzini ampullae in the rays Dasyatis pastinaca and Raja clavata. Application of the diluted sea water to the opening of ampullary canal increases the discharge rate of the receptors resulting into subsequent adaptation, whereas the increase in water salinity causes opposite changes. Threshold changes in the salinity of sea water amount 1--2%. Thermal transient in the sea water at the vicinity of the opening of ampullary canal did not affect the activity of the receptors. A decrease in temperature at the vicinity of receptor cells resulted in a transient rise of the firing rate of the receptors, while the increase of temperature decreased the activity of the receptors.

Adaptation, Physiological↗

PubMed1976

The effects of temperature and thermal acclimation upon the osmotic properties and nonelectrolyte permeability of liver and gill mitochondria from rainbow trout (Salmo gairdneri).

Thermal acclimation of rainbow trout (Salmo gairdneri) taken from 20 degrees C to 7 degrees C resulted in adaptation of mitochondrial function, as evidenced by increases in the specific activities of NADH- and succinate-cytochrome c reductase of 1.93- and 2.7-fold respectively. Mitochondria from both gill and liver obeyed the Boyle-van't Hoff relationship in the range from 400 to 60 mosM. Thermal acclimation had no effect on the osmotic properties of liver mitochondria, whereas gill mitochondria from cold-acclimated trout were more sensitive to osmotic swelling than mitochondria from warm-acclimated individuals. The non-electrolyte permeability of liver mitochondria was assessed by optically monitoring mitochondrial swelling rates in isosmotic solutions of urea, glycerol, mannitol and glucose. Two parameters of mitochondrial swelling were determined: (a) initial swelling rates, d(1/A)dt, and (b) swelling constants, ks, derived from the time required to swell a fixed volume. Regardless of the assay temperature or the permeant employed, liver mitochondria from cold-acclimated trout exhibited greater initial swelling rates than mitochondria from warm-acclimated trout, indicating properties of temperature-compensated permeability. The apparent ranking of nonelectrolyte permeabilities was urea greater than glycerol greater than mannitol greater than glucose. ks values for urea and glycerol from cold-acclimated trout were greater than values typical of warm-acclimated populations; however ks values for glucose and mannitol were not influenced by thermal acclimation. Regardless of the permeant considered, activation energies for ks values were 3- to 5-fold greater than those for initial swelling rates. The time course of mitochondrial swelling consists of two components, an initial rapid swelling phase characterized by a half-life of 3-12 seconds, and a slower swelling phase characterized by a half life of 1-6 minutes. Initial swelling rates, which approximate the rapid swelling component, are considered to be the least ambiguous index of permeability, whereas ks values are more complex and strongly influenced by the slower swelling component.

Acclimatization↗