Seasonal changes in the critical arousal temperature of the marsupialSminthopsis crassicaudata correlate with the thermal transition in mitochondrial respiration

Summary During periods of torporSminthopsis crassicaudata, a dasyurid marsupial, regulated its body temperature above about 16.3°C in summer and 13.0°C in winter. Animals with lower body temperatures were unable to arouse. Liver, heart and brain mitohondrial succinate:cytochrome c reductase showed a thermal transition at 16°C in summer and at 12.5°C in winter. Thus the lowest regulated body temperature was just above the temperature where changes were detected in mitochondrial respiration.Acknowledgments. This work was supported by a Flinders University Research Scholarship Award to F. Geiser. We thank Prof. J. H. Bennett for the supply of animals and M. O'Driscoll for the animal maintenance.     

Photoperiod-induced changes in temperature-metabolism curve,shivering threshold and body temperature in the pigeon

Summary A short photphase combined with cold-acclimation changed the shivering threshold of the pigeon from 21 to 14 °C. The change of critical temperature was also found in the temperature-metabolism curve. A long photophase both alone and combined with warm-acclimation induced a reduction of body temperature to a lower level (about 2°C) at all ambient temperatures, ranging from 5 40°C.     

Effect of water temperature on the motility ofPelagia noctiluca (Forksal)

Summary Laboratory tests have been performed, on the behavior of the jellyfishPelagia noctiluca as a function of the water temperature. It has been found that the usual contractions of the umbrella are almost completely missing at 6°C; they begin to appear at about 7–8°C and they reach frequencies of about 10 and 40 per min at 11 and 15°C respectively. An ambient temperature of about 11°C appears to be a threshold value below which this kind of medusa ceases to move actively and sinks, while at higher temperatures it gradually begins to shift, showing a positive thermotropism in the presence of temperature gradients greater than about 0.01 °C/cm.This work was supported by grant No. 80.00748.88 from the National Research Coucil of Italy (CNR).     

Temperature dependence of neurotransmitter release in the antarctic fishPagothenia borchgrevinki

Summary The quantal contents of endplate potentials from extraocular muscles of an antarctic fishPagothenia borchgrevinki were measured over a range of temperatures. Quantal release was maximal at about 5°C but showed little dependence on temperature between –2°C and 10°C. Above 10°C quantal content declined until release ceased about 18°C. In view of the fact that the ambient temperature at which these fish live is constant at –1.9°C, the results suggest thatPagothenia borchgrevinki is only partially adapted to its environment despite 25 million years acclimatization.The authors wish to thank the staff of New Zealand's Scott Base, Antarctica, without whose cooperation the work would have been impossible. Mr J. Quinn of the Auckland University Physiology Department gave invaluable assistance with computing and electronics and the Antarctic Division of the New Zealand Department of Scientific and Industrial Research provided transportation and logistic support. The project was financially supported by the New Zealand University Grants Committee and the Auckland University Research Committee. S.P. was a Senior Fellow of the N.Z. Medical Research Council.     

Die Wirkung der Temperatur auf das Verhalten der Gewebsatmung poikilothermer und homoiothermer Tiere unter dem Einfluss von 4,6-Dinitro-o-kresol

Summary (1) The liver respirationin vitro of mice and toads was studied under the influence of 4,6-Dinitro-o-cresol at temperatures varying from 17,5 to 42,5°C.(2) The percentage activity of the oxygen uptake of the mouse liver decreased progressively under dinitrocresol with rising temperatures, whereas the respiration of the toad liver showed inhibition at low temperatures and activation at higher temperature.(3) The results were interpreted following the theory of inhibitory types ofJohnson.     

Antifreeze agents in the body fluid of winter active insects and spiders

Summary Insects and spiders which are active at subzero temperatures on snow in winter are found to be protected against internal freezing by antifreeze agents present in their body fluid. The body fluid has a melting point of about –1 °C, but the antifreeze agents prevent growth of ice crystals at temperatures down to –6 to –7 °C.Acknowledgment. We would like to thank Anne Lohrman for her kind help in collecting insects and spiders.     

Heat shock enhances thermotolerance of infective juvenile insect-parasitic nematodesHeterorhabditis bacteriophora (Rhabditida: Heterorhabditidae)

Insect-parasitic nematodes possess many of the attributes of ideal biological control agents, but intolerance to extreme temperatures can restrict their use. We examined whether heat-shock treatments could improve nematode survival and infectivity at temperatures that normally inhibit their activity (35 and 40°C). Nematodes exposed to a sub-lethal temperature (35°C) for 3 h with a latency period of 1–2 h at 25°C killed insects at 35 and 40°C. Correlative evidence was obtained between increased thermotolerance and the synthesis of 70-kDa heat-shock proteins (hsps). These results provide the first evidence of hsp synthesis in the development of thermotolerance and biological activity in the non-feeding, developmentally arrested, infective juvenile nematodes.     

Über die Funktion der Lorenzinischen Ampullen der Selachier

Summary The afferent impulses from the ampullae ofLorenzini ofScyllium show, both in the intact animal and in the isolated preparation, a steady discharge at constant temperature with a frequency reaching a maximum at an average of 20° and decreasing continuously at higher and lower temperatures. The discharge stops between 5° and 30° on the average. Rapid cooling causes a temporary rise in frequency, while rapid warming causes a temporary drop in frequency. While the ampullae are not sensitive to a mechanical stimulus, they react definitely to a change in temperature of 0.05°C. The ampullae thus behave like the cold receptors of the homoiotherms.     

Body temperatures of lambs and their mothers measured by radio-telemetry during parturition

Using temperature-sensitive radio-telemeters chronically implanted in the abdomens of 8 fetal lambs and their mothers, we measured body temperature changes induced by parturition. Maternal body temperature rose at 0.70±0.06 °C/hour (mean±SEM) in the final stages of labour. Fetal body temperature also rose, but at a significantly lower rate, 0.45±0.06 °C/hour (p<0.05). The fetus appears to be protected from excessive hyperthermia during the birth process.     

Growth ofEchinococcus multilocularis in gerbils exposed to different environmnntal temperature

Summary Gerbils kept at high (35°C) temperature harbored a significantly largerEchinococcus multilocularis cyst biomass than those kept at room (21°C) and low (5°C) temperature. Parasite induced adrenomegaly was observed in all temperature groups.Acknowledgments. I am indebted to Miss Marianne Hardy and Mr Terry Durham for their excellent technical assistance.     

Diurnal variations in cholinesterase activities in the slug,Laevicaulis alte

Summary Cyclical variations in acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) levels in foot muscle (FM) and AChE activity in central nervous system (CNS) ofLaevicaulis, during 24-h-day, were maximal at 04.00 h and minimal at 12.00 h. But BuChE activity was 180°C out of phase with AChE in CNS. The rhythmic trend of AChE in CNS might be due to true cholinesterase activity.Acknowledgements. The Senior Fellowship (CSIR) awarded to TPK is thankfully acknowledged.     

Hypothermia induced in mice by enzyme-mediated depletion of serotonin

Summary Injection of a purified serotonin (and tryptophan)-degrading enzyme into mice produced a pronounced hypothermia when the mice were maintained at 22°C, but not at 30°C. Brain levels of serotonin and tryptophan were strikingly depleted, but concentrations of norepinephrine and dopamine remained unchanged.This investigation was supported by grants CA-18844 and CA-08748 awarded by the National Cancer Institute, DHEW. We thank Barbara Morelli and Margaret Costello for their technical assistance.     

Temperature-dependent activity of mosquito larvicidal factor(s) present inBacillus sphaericus 1593–4 and 1691

Summary The larvicidal factor(s) ofBacillus sphaericus 1593–4 and 1691 was more active at high temperature (33–35 °C) as compared to low temperature (23–25 °C) for the larvae ofCulex fatigans andAnopheles subpictus.     

Influence of posttreatment temperature on the toxicity of pyrethroid insecticides to susceptible and resistant larvae of the Egyptian cotton leafworm,Spodoptera littoralis (Boisd.)

Summary The organophosphorus insecticides chlorpyrifos, leptophos, and phosfolan and the carbamate methomyl was found to be more toxic to larvae of a susceptible strain ofSpodoptera littoralis (Boisd.) when the posttreatment temperature was increased from 20 to 35°C. In contrast, the pyrethroids permethrin, fenvalerate, deltamethrin, cypermethrin, and flucythrinate were more toxic at 20°C than at 35°C. This effect was more pronounced in the pyrethroid-resistant strains. Evidently, resistance levels were reduced at low temperature. However, the application of piperonyl butoxide or DEF in combinations with the tested pyrethroids on R-strains resulted in reducing the effect of temperature.     

Environmental temperature and the growth ofTaenia crassiceps cysticerci in mice

Summary Mice kept at low (5±1 °C) and high (35±1 °C) temperature harboured significantly lessTaenia crassiceps cysticerci than controls kept at 21±1 °C. This effect was more pronounced in heat-stressed than in cold-stressed animals and more in males than in females.     

The effect of chronic heat stress on cortisol levels in the antarctic fishPagothenia borchgrevinki

Radioimmunoassay was used to determine levels of the stress-inducible glucocorticoid, cortisol, circulating in the plasma of the extremely stenothermal Antarctic fishPagothenia borchgrevinki at rest and after heat stress. Fish sampled immediately after capture (–1.9°C) had low cortisol levels (10.4±1.4 ng ml^–1, mean±SEM) as did fish which were laboratory rested for 3 days. Sudden exposure to 5°C (48h) resulted in a peak cortisol value after 3 h (69.9±6.8 ng ml^–1) whereas exposure to 8°C (6h) resulted in a peak value after 1 h (73.5±8.0 ng ml^–1). At both temperatures levels remained significantly elevated (p<0.05) for the entire period of exposure. Increased temperature also resulted in a significant change in haemoglobin, haematocrit and mean cell haemoglobin concentration (MCHC) (p<0.05). Plasma lactate was significantly elevated only after exposure to 8°C (p<0.05). Plasma cortisol levels fromP. borchgrevinki are reported here for the first time and show this cryopelagic Antarctic species to have an unusual hormonal stress profile.     

Internal interactions within the human circadian system: the masking effect

Summary In the realm of human circadian rhythms, the masking effect is defined as the change in the course of deep body temperature induced by changes in the degree of physical activity, or by the alteration between sleep and wake. This effect is particularly obvious during internal desynchronization where the rhythms of deep body temperature, and the sleep-wake sleep-wake sleep cycle — i.e. one of the masking factors — run with different periods.Every sleep onset is accompanied by a rapid drop, and wake onset by a rapid rise in deep body temperature, each one with an overshoot of about 50% of the steady state variations. When rhythms are calculated, with the dominant temperature period as the screening period, exclusively from data obtained during sleep episodes, on the one hand, and from those obtained exclusively during wake, on the other, two average cycles emerge: the sleep temperature curve and the wake temperature curve. Both run in parallel but are separated by the masking effcct. As derived from many experiments, the mean masking effect amounts to 0.28±0.06°C. The masking effect also depends to some extent on the phase of the temperature rhtthm; it is larger than average around the temperature maximum and during the descending phase of the temperature cycle, where the alertness commonly is highest and the probability to sleep, in general, and the REM sleep propensity, in particular, are smaller than average. This also can be interpreted to indicate that the sleep temperature curve is phase advanced relative to the wake temperature curve; this, on the average, by 0.9±0.3 h.If the individually determined amount of masking is added to the temperature data obtained during sleep, or substracted from the temperature data obtained during wake, a temperature curve emerges that can be though of as being purified of the masking effect. Analyses of this artificial curve allow estimation of that part of the internal interactions uninfluenced by the masking effect. On the average, about half of the amount of interaction between the rhythm of sleep-wake and that of deep body temperature is explained by the masking effect, whereas the other half is oscillatory interaction. Both types of interaction are inherent and inseparable parts of the circadian clock mechanism, as can be deduced from model considerations.     

Photoperiodic summation is temperature-dependent inPyrrhocoris apterus (L.) (Heteroptera)

Summary InPyrrhocoris apterus, a low temperature, 15°C, prevented the termination of diapause by long days and, unexpectedly, also the induction of diapause by short days. Both responses were enabled at a higher temperature, 26°C. In contrast to current concepts, it was proved that the summation of photoperiodic signals was temperature-dependent, since the morphogenetic development was prevented by starvation.     

Sleep in an Amazonian manatee,Trichechus inunguis

For the first time, sleep was studied in a representative of the order of Sirenia. Slow wave sleep occupied 27%, and paradoxical sleep 1% of the total recording time in the Amazonian manatee,Trichechus inunguis. The circadian rhythmicity of sleep was pronounced. During the sleep period, the manatee woke up for a short time for each respiratory act. Interhemispheric asynchrony of the electrocortical slow wave activity was found.     

Temperature-controlled alternative respiration and outgrowth rate from conidia ofNeurospora crassa

Summary Incubation of conidia of wild typeNeurospora crassa at temperatures ranging from 25 to 46°C modulates their respiratory type. Between 37 and 41°C, the transient activity of the cyanide-insensitive respiratory pathway parallels, with a maximal extrusion of protons into the medium, the optimal rate of germ tube outgrowth.We are grateful to Mrs Arlette Cattaneo for her competent technical assistance.