Thermohaemolysis of human erythrocytes in sucrose containing isotonic media

1. 1.|The thermohaemolysis of human erythrocytes in NaCl/sucrose isotonic media can be best accounted for in terms of the colloid-osmotic theory of haemolysis.

2. 2.|The thermohaemolysis in NaCl saline was preceded by leakage of K⁺ and cell swelling. If the inner oncotic osmoactivity was balanced with external sucrose the cells progressively shrinked losing K⁺, but the haemolysis was strongly reduced.

3. 3.|Time dependence of the shrinking of cells and one-step resealed ghosts suspended in isotonic 60 mOsm NaCl/sucrose media was studied between 50 and 58°C.

4. 4.|After a lag period for cells only, this shrinking proceeded with apparently constant rate for cells and ghosts.

5. 5.|The rate constant of shrinking for cells and ghosts obeys the Arrhenius relation, giving the value of 250 ± 15 kJ/mol for the activation energy of shrinking in both cases. This is also the case for the activation energy of the membrane ion permeability constant.

6. 6.|These results are consistent with the thermal inactivation of membrane associated protein(s) acting as a trigger for the ion permeability barrier disturbance.

7. 7.|The mid-point temperature for these membrane events was about 61°C.

Hyperthermia-induced changes in the morphology of CHO-K1 and their refractile inclusions

1. 1.|Chinese hamster ovary cells (CHO-K1) were heated at temperatures of 42°C and above.

2. 2.|Cells were cultured in microcapillaries to eliminate handling stress, and morphological changes were observed by light microscopy.

3. 3.|Increased incidence of membrane blebbing was noted between 1 and 2 h and few cells were viable after 2 h at 43°C.

4. 4.|Morphological changes, including the appearance of potocytotic blebs, were recorded by cinemicroscopy of microcapillary cultures on a heated microscope stage.

5. 5.|Lipid-rich refractile cell inclusions changed shape before blebbing occurred.

6. 6.|Cell retraction and rearrangement of organelles seen at 1 h at 43°C are the reverse of those seen in spreading post-trypsinized cells and suggest a thermal effect on the cytoskeleton.

Temperature acclimation of axonal functions in the crayfish Astacus astacus L.

1. 1.|Crayfish (Astacus astacus L.) were acclimated for 1–3 weeks at 5 and 20°C. The effects of temperature on the functions of the unicellular medial giant axon were studied.

2. 2.|The resting membrane potential of the giant axon increased slightly with the experimental temperature from 2 to 32°C. The temperature dependence of the resting membrane potential could be described by two lines, which intersected at about 12°C in cold-acclimated crayfish and at about 16°C in the warm-acclimated.

3. 3.|The amplitude of the action potential was stable at temperatures from 4 to 26°C. It decreased at temperatures above 26°C in both acclimation groups.

4. 4.|The duration of the falling phase of action potential was highly temperature dependent at low temperatures. A break in the slope of the dependence was found at about 14°C in cold-acclimated crayfish and at about 17°C in the warm-acclimated.

The effect of temperature on caecal fermentation processes in a poikilothermic mammal, Heterocephalus glaber

1. 1.|The effect of temperature on caecal function was examined in the naked mole-rat Heterocephalus glaber, a poikilothermic mammal, which consumes a high proportion of fibre in its natural diet.

2. 2.|The temperature of optimal caecal function was determined from fermentation data measure at three specifically chosen temperatures (28, 33 and 40°C).

3. 3.|There was no significant difference between gas production at 33 and 40°C, however, gas production was significantly lower at 28°C.

4. 4.|The relative proportions of the gases produced were markedly different at 33 and 40°C (P ≤ 0.01). More methane and hydrogen were produced at 33°C than at 40°C.

5. 5.|These data suggest that microbial organisms within the caecum were active and functioning more effectively at 33°C (the preferred body temperature of the naked mole-rat) than at the other two temperatures.

Employment of a turbidimetric assay system to measure heat-induced protein aggregation

1. 1.|We developed a turbidimetric assay system for quantitation of heat-induced protein aggregation which is presumably caused by protein denaturation.

2. 2.|Rhodanese in 6 M guanidinium chloride was employed in the assay system, because this protein recognizes hydrophobic sites on denatured proteins and aggregates.

3. 3.|Turbidity caused by protein-rhodanase aggregation was recorded at 320 nm by using a u.v./VIS spectrophotometer.

4. 4.|When heated, alcohol dehydrogenase (ADH) aggregates with rhodanese. The increase of ADH-rhodanese aggregation was correlated with the loss of enzymatic activity.

5. 5.|These results indicated that the aggregation was proportional to the extent of ADH denaturation which assumingly caused the loss of ADH activity during heating at 45.5°C.

6. 6.|Similar results were observed when cytosolic proteins from CHO cells were heated at 45.5°C. Heated cytosolic proteins promoted aggregation by complex formation with rhodanese. The aggregation increased with increasing heat dose.

7. 7.|Therefore, the rhodanese assay system can be employed usefully to quantitate the protein aggregation after heat stress.

Effect of temperature on growth and bioenergetics of a tropical moth

1. 1.|Larval development and metamorphosis of Achaea junta were prolonged at 22°C, compared to 27, 32 and 35°C.

2. 2.|Overall rates of consumption, assimilation, production and metabolism of the larvae increased with temperature.

3. 3.|Efficiencies of assimilation and conversion of the digested food were significantly altered by life stage and temperature.

4. 4.|About 60% of the pupal energy was transferred to the imago at the tested temperatures.

Exercise in the heat: Effects of dinitrophenol administration

1. 1.|Dinitrophenol (DNP) was administered to rats in two equal dosages (20 mg/kg, 30 min interval); the second injection was followed immediately by exercise (9.14 m/min) in the heat (30°C) or at room temperature (21°C).

2. 2.|At 21°C control (saline-treated) rats manifested a mean endurance of 94 min which was reduced to 32 min among DNP-treated animals.

3. 3.|At 30°C, control rats ran for 65 min (δT_re/min = 0.05°C) while DNP-treated animals had a mean endurance of only 12 min (δT_re/min = 0.22°C).

4. 4.|DNP-treated rats (30°C) manifested no decrements in tail-skin heat loss (δT_sk/min = 0.17°C vs 0.10°C) or saliva secretion (0.78 g/min, DNP vs. 0.19 g/min, control) for their brief treadmill duration.

5. 5.|The increased metabolic heat production of DNP severely reduced performance.

Some effects of thyroidectomy on growth, heat production and the thermoregulatory ability of the immature fowl (Gallus domesticus)

1. 1.|The effect of thyroidectomy at 12 days of age on weight gain, and on heat production and thermoregulatory ability of 4- to 5-week-old chickens at temperatures within and below the thermo-neutral zone was investigated.

2. 2.|Despit the absence of thyroid tissue, as demonstrated with radioiodine, a small amount of thyroxine was found in the plasma of some thyroidectomized (TX) birds.

3. 3.|Thyroidectomy depressed weight gain; pair-fed controls grew significantly faster than TX birds.

4. 4.|Resting heat production of TX birds at thermoneutrality (30°C) was depressed by 18% (P < 0.001) and body temperature by 0.4°C (P < 0.001).

5. 5.|At 12°C heat production of TX birds was similar to that of controls but the body temperature of TX birds was 0.7°C lower (P < 0.001).

6. 6.|Thyroidectomized birds were unable to regulate body temperature at 5°C even if thyroxine was provided on the day before and at the time of cold-exposure. This inability to thermoregulate was probably due to inadequate insulation and poor nutritional status.

Muscle temperature and muscle metabolism during short-term exercise in the goat

1. 1.|External heat exchangers acting on lower aortal blood temperature were used to dissociate hindleg muscle temperature (T_hlm) from general internal temperature (T_int) during short-term exercise of moderate intensity.

2. 2.|In series 1 39°C T_hlm was combined with 40.6°C T_int, and in series II 42°C T_hlm was combined with 39.8°C T_int.

3. 3.|At constant work rates, the 3°C difference in muscle temperature did not result in significantly different concentrations of muscle metabolites.

4. 4.|It is concluded that high local muscle temperature without general hyperthermia does not influence muscle metabolism during short-term moderate excercise.

Effect of temperature on the electrical activity of the rat epididymis in vitro

1. 1.|Regional differences in the frequency of electrical activity in rat epididymis were maintained at all temperatures below 39°C.

2. 2.|The change in frequency per deg C increased with temperature and was highest in the temperature region of 34–39°C and the Arrhenius plots of the frequency were linear and parallel in all parts of the epididymis.

3. 3.|The Q₁₀ of the frequency varied between 2.2.–4.3.

4. 4.|The conduction velocity at the cauda epididymis was highest (2.8 mm/s) at 37°C. The Q₁₀ of the conduction velocity was 2.3 in the temperature region of 24–37°C.

The effect of acclimation temperature and the removal of peripheral temperature receptors on body temperature preference in the cockroach, Periplaneta americana

1. 1.|Body temperature preferences were compared between cockroaches acclimated to different ambient temperatures and between 25°C acclimated cockroaches and cockroaches deprived of their peripheral temperature receptors.

2. 2.|Acclimation to 35°C resulted in a significantly higher mean body temperature and low body temperature selected compared with 25°C acclimated cockroaches.

3. 3.|Cockroaches deprived of their peripheral temperature receptors showed a significantly higher mean high body temperature selected when compared to normal 25°C acclimated cockroaches.

4. 4.|It is concluded that cockroach temperature regulation is more precise than expected and that central temperature receptors are the primary sensing elements for cockroach thermoregulation.

Alteration of heat sensitivity by treatment with nonpermissive temperature or cycloheximide in temperature-sensitive CHO mutant tsH1 cell

1. 1.|The temperature-sensitive mutant CHO-tsH1 and wild type (CHO-SC) cells became thermal resistant when cells were treated for either 2 h at 39.5°C before heating at 43°C or 2 h with 10 μg/ml cycloheximide (CHM) before and during heating at 43°C.

2. 2.|There was a 2000-fold increase in survival after 2.5 h at 43°C by preincubation at 39.5°C in both cell types. There was also a 200- or 700-fold increase in survival after 2.5 h at 43°C by treatment with CHM in tsH1 or SC cell type respectively.

3. 3.|In contrast to the effects at 43°C, at 41.8°C these protective effects were not evident in tsH1 cells. In wild type, however, there was an 800- or 1800-fold increase in survival after 8 h at 41.8°C by preincubation at the temperature of 39.5°C or treatment with CHM, respectively.

4. 4.|Therefore, these results suggest that killing of tsH1 at low temperature hyperthermia (41.8°C) is probably due to denaturation of thermolabile leucyl-tRNA synthetase.

5. 5.|The denaturation of this enzyme may not be protected by inhibition of protein synthesis by preincubation at the nonpermissive temperature of 39.5°C or by CHM.

Temperature effects on evoked potentials of hippocampal slices from noncold-acclimated, cold-acclimated and hibernating hamsters

1. 1.|Neural activity was recorded in hippocampal slices from noncold-acclimated, cold-acclimated and hibernating hamsters.

2. 2.|Action potentials from a population of hippocampal pyramidal neurons were evoked by stimulating an afferent fiber tract, the Schaffer collaterals. The temperature of the artificial cerebrospinal fluid bathing the slice was varied by controlling the temperature of a water chamber jacketing the recording chamber.

3. 3.|The temperature just below that at which a population spike could be evoked, T_t, was 15.8 ± 0.9°C (mean ± SEM) for noncold-acclimated hamsters, 13.9 ± 0.3°C for cold-acclimated hamsters and 12.3 ± 0.3°C for hibernating hamsters.

4. 4.|These thresholds for evoked activity were significantly different in noncold-acclimated, cold-acclimated and hibernating hamsters, and may reflect acclimation of hippocampal neurons to cold.

Autonomic thermoregulatory effects of electrical stimulation of the hypothalamus in the sheep (Ovis aries)

1. 1.|The effects of electrical stimulation of the preoptic region, on autonomic thermoregulatory responses, were studied in conscious sheep at ambient temperatures of 5, 20, and 40°C.

2. 2.|Stimulation of the dorsal preoptic region elicited co-ordinated thermoregulatory responses characterized by increased respiratory frequency (RF), vasodilation of the ears and lowered body temperature. Stimulation inhibited shivering in cold environments.

3. 3.|The thermoregulatory responses were greater at 5°C in unshorn than in shorn sheep. Increased RF, induced at 20 and 40°C, persisted several minutes after stimulation ceased.

4. 4.|Intraventricular injection of noradrenaline reduced both normal and electrically-induced panting.

5. 5.|Sheep would press panels to electrically stimulate the preoptic region and this “self-stimulation” activated heat-loss mechanisms.

The effect of incubation temperatuer on oxygen consumption and organ growth in domestic-fowl embryos

1. 1.|Oxygen consumption and organ growth were measured in domestic-fowl embryos incubated at different temperatures (36, 38 and 40°C).

2. 2.|Embryonic oxygen consumption was highest at an incubation temperature of 40°C and lowest at 36°C. These differences were ascribed largely to variations in embryo size at different incubation temperatures.

3. 3.|At incubation temperatuers of 40 and 38°C, there was a plateau in oxygen consumption late in incubation, but this was not apparent at 36°C.

4. 4.|At 36°C, some tissues (e.g. eyeballs) were “spared” the repression of growth that characterized the embryo as a whole, while other tissues (e.g. stomach) incurred a much greater growth reduction. Similarly, at 40°C, stomach growth exceeded that of the embryo as a whole, while the eyeballs were largely spared the enhanced growth.

5. 5.|A simple index of tissue age revealed that, in general, there were consensual changes in tissue maturity and growth at different temperatures but that there were some disparities between growth and maturity in individual organs.

Hatching of freshwater sponge gemmules after low temperature exposure: Ephydatia mülleri (Porifera: Spongillidae)

1. 1.|Gemmules of Ephydatia mülleri can withstand exposure to temperatures down to −80°C for 63 days without loss of hatchability.

2. 2.|Hatching is slowed following exposure to temperatures below −27°C.

3. 3.|There is a slight but significant relationship between gemmule size and the time to hatch.

4. 4.|This species can withstand long-term exposure to winter air temperatures occurring within its known geographic range.

Threshold temperature responses of thermosensitive neurons in guinea-pig hypothalamic slices

1. 1.|Neuronal activity in slices of the preoptic and anterior hypothalamic area of guinea-pigs during slow low-amplitude temperature changes analogous to temperature changes in the brain of endothermic animals, was extracellularly recorded.

2. 2.|42% of neurons showed threshold temperature responses. The threshold of response averaged 37.4°C for warm-sensitive neurons during warming and 37.0°C for cold-sensitive neurons during cooling.

3. 3.|The thresholds differed, on average, by 0.1°C in the same neuron at repeated temperature changes.

4. 4.|With temperatures 0.8°C above threshold on average (0.2°C in some units) neuronal activity reached a new high level that did not change either during a further exceeding of the threshold or prolonged maintenance of suprathreshold temperature.

5. 5.|The characteristics of the threshold temperature response of a hypothalamic neuron meet the criteria of thermoinduced structural rearrangements of cell membranes, caused by phase transitions of lipids, changes in protein conformation and cytoskeletal activity.

Compensation limits of fish muscle myofibrillar ATPase enzyme to environmental temperature

1. 1.|Goldfish acclimated to a range of temperatures between 5 and 35°C were found to only compensate the specific activity of their myofibrillar ATPase enzyme between 10 and 30°C.

2. 2.|The preferred temperatures of goldfish acclimated to 5°C and to 30°C were determined to be about 10 and 26°C respectively.

3. 3.|It is conlcuded that goldfish are only able to acclimate their myofibrillar ATPase system to temperatures between 10 and 30°C, but acclimation to these temperatures enables them to tolerate extremes.

Daphnia development and reproduction: Responses to temperature

1. 1.|The development times and reproduction were measured for Daphnia pulex and Daphnia magna from 5 to 30°C at 5°C increments.

2. 2.|The general trends for D. pulex and D. magna were for the duration of all juvenile instars to be less than that of adults and for the last juvenile (or adolescent) instar to be longer than all previous juvenile instars.

3. 3.|The number of juvenile instars both species pass through before adulthood is influenced by temperature with increasing numbers occurring at temperature extremes.

4. 4.|Duration of development time decreased over the entire range of increasing temperatures measured for D. pulex but increased for D. magna at 30°C in relation to 25°C.

5. 5.|Quadratic models were less desirable than simple linear logarithmic transformations of the form ln Y = ln a + b ln X for describing the temperature/development relationship.

6. 6.|The greatest young production occurs at 15 and 20°C with significant decreases occurring at temperatures above and below these.

7. 7.|The observed temperature-dependent phenomena an the ecological relationships for the two species are discussed.

Stereological analysis of mitochondria from brains of temperature acclimated goldfish, Carassius auratus L. (5 and 30°C)

1. 1.|The mitochondrial population in hypothalamic and hypophysial brain tissue from warm (30°C) and cold (5°C) acclimated goldfish (Carassius auralus L.) was analyzed using sterological techniques.

2. 2.|It was revealed that there is a significantly larger volume density (Vv) in the cold acclimated tissue, with no significant difference in either of the surface densities (Svext and Svint) from either of the brain areas.

3. 3.|The hypothalamic brain tissue has a significantly lower specific surface (S/V) in the cold acclimated tissue but there is not a significant difference in this parameter for the hypophysial brain tissue.

4. 4.|The values for these three parameters (Vv, Svext and SVint, and S/V) indicate that mitochondria from acclimated brain tissue undergo shape changes in response to thermal stress.

5. 5.|We suggest that the shape changes may be related to the change in the phospholipid composition of the inner mitochondrial membrane with acclimation temperature.