Kari Y. H. Lagerspetz

Temperature acclimation and the nervous system.

1. The conduction velocity of the compound action potential of peripheral nerves shows compensatory acclimation to temperature in a fish, a snail, a crab, and probably also in the frog. The heat and cold tolerances of peripheral conduction are probably both increased by cold acclimation in the frog.

Thermal behaviour of crustaceans.

Specific thermoreceptors or putative multimodal thermoreceptors are not known in Crustacea. However, behavioural studies on thermal avoidance and preference and on the effects of temperature on motor activity indicate that the thermosensitivity of crustaceans may be in the range 0.2–2°C. Work on planktonic crustaceans suggests that they respond particularly to changes in temperature by klinokinesis and orthokinesis. The thermal behaviour of crustaceans is modified by thermal acclimation among other factors. The acclimation of the critical maximum temperature is an example of resistance acclimation, while the acclimation of preference behaviour may be classified as capacity acclimation of some other function. In crustaceans, the use of the concepts stenothermy and eurythermy at the species level is questionable, and it is not possible to divide crustacean species into thermal guilds as suggested for fishes. Thermal preference behaviour contributes to fitness in different ways in different species, often by maximising the aerobic metabolic scope for activity. In crustaceans the peripheral nervous system seems to have retained the capacity for thermosensitivity and thermal acclimation independently of the central nervous system control of behaviour.

Phagocyte activity in the frog Rana temporaria: whole blood chemiluminescence method and the effects of temperature and thermal acclimation.

The respiratory burst activity of phagocytes was measured as zymosan induced, luminol-enhanced chemiluminescence (CL) emission in the whole blood of the frog Rana temporaria. The effect of thermal acclimation on phagocyte activity was studied by acclimating adult frogs for 14-18 days to 5 and 24 degrees C. The phagocyte CL was measured at seven temperatures ranging from 5 to 37 degrees C. Clear signs of resistance acclimation were seen both in CL reaction kinetics at 5 degrees C (P < 0.0001) and in intensities at 37 degrees C (P < 0.003). Thermal adaptation was also seen as a 1-5 degrees C shift in the temperature response curve of CL intensity towards the acclimation temperature (P < 0.03). The highest CL intensities were seen at 30 degrees C and they were of the same magnitude in both acclimation groups. The phagocyte activation enhanced progressively at temperatures ranging from 5 to 30 degrees C, showing that migration to a warmer environment would increase the phagocyte activity of frogs. The possible relation to behavioral fever is discussed.

Thermal avoidance and preference in Daphnia magna.

Abstract 1. Water fleas (Daphnia magna) bred at 23°C were non-responsive to temperatures between 13 and 25°C. 2. At the lower (11°C) and upper limits (30°C) their klinokinetic avoidance behaviour showed a larger intraindividual than interindividual variation. 3. Thermal sensitivity for avoidance responses in D. magna was about 1.5°C. 4. For D. magna bred for one parthenogenetic generation at 14°C heat avoidance temperature was about 8°C lower, and cold avoidance temperature was about 1°C higher than in D. magna from 23°C. 5. In group experiments the animals showed some preference for the acclimation temperature. 6. Cold induced stenothermy and warm induced eurythermy in D. magna were related to the mode of reproduction.

Bacterial endotoxin and infection cause behavioural hypothermia in infant mice

1. When placed in a temperature gradient, 3-10 day old mice injected with living Escherichia coli or with E. coli endotoxin, select 2-3 degrees C lower temperatures than their litter-mate controls injected with saline. 2. At the lower selected temperature (32 degrees C) young mouse pups resist bacterial infection for longer and tolerate higher doses of endotoxin than at the temperature selected by the controls (35 degrees C). 3. It is possible that a controlled hypothermic state, here called cryexia, is in small mammals an alternative strategy to fever for coping with infections.

Heat shock response and thermal acclimation in Asellus aquaticus

Abstract 1. 1. Three methods were used to assess the heat tolerance of adult Asellus aquaticus : critical thermal maximum (CTMax, loss of the righting reflex), temperature for the loss of pleopod movements (LTMax), and the time at 33°C for the loss of pleopod activity (LT). All these measures are affected by heat shock and by thermal acclimation. 2. 2. Heat shock (60 min at 28°C) increased heat tolerance only for a period of 6–7 h after the shock. One h after the shock CTMax was increased by 2.2°C, LTMax by 1.1°C, and LT by 2.2 times on average. 3. 3. Thermal acclimation after the transfer of animals from 10°C to 23°C caused an increase of thermal tolerance (distinct from the effects of heat shock) which began about 6 h after the transfer. This change continues for several days until a new steady level of heat tolerance has been acquired. Especially increased is CTMax; this depends on changes in the nervous function. 4. 4. The heat shock used in this study induced the synthesis of about 50 kDa protein for at least 6 h. 5. 5. The effects of heat shock are rapid and transient, the effects of thermal acclimation slow and cumulative. They are distinct phenomena with at least in part different mechanisms.

The expression of the genes of aggressiveness in mice: The effect of androgen on aggression and sexual behavior in females

Female mice of strains selectively bred for aggressiveness or nonaggressiveness were injected with testosterone propionate (TF′) at the age of 2 days and as adults, or they were injected as adults only. Aggressive and sexual behavior was then tested with female, receptive female, and male partners before, during, and after the latter TP treatment. The females that had received both TP treatments displayed as much or as little aggression as males of the same strain, leading to the conclusion that aggressiveness genes are not linked with the male sex chromosome, even though they depend on it for their expression. The sexual behavior of the females of both strains that had received both TP treatments was altered to the male type. In the females of the aggressive strain even adult treatment alone was sufficient for this change. Aggressiveness and male sexual behavior would seem to be determined separately, although aggressiveness facilitates the display of male sexual behavior.

Postnatal development of thermoregulation in laboratory mice

KurzfassungLaboratoriumsmäuse sind bis zum 7. Tag nach der Geburt beinahe völlig poikilotherm. Diese Periode ist durch starke Kälteresistenz, beträchtliches relatives Gewicht und hohe Sukzinodehydrogenase-Aktivität des braunen Fettgewebes und Thermo-Orthokinese charakterisiert. Möglicherweise ist bereits die Nebennierenrinde an der noch schlecht entwickelten Thermoregulation funktionell beteiligt. Die Zunahme der Wärmeproduktion in der Zeit vom 7. bis 15. Tag nach der Geburt führt zu Homoiothermie bei Außentemperaturen von 20° bis 30° C. Gleichzeitig nimmt die Sukzinodehydrogenase-Aktivität des Lebergewebes zu. Dieser Sachverhalt ist wahrscheinlich durch die Zunahme der Schilddrüsenaktivität bedingt, welche auch die Beeinflussung des Sauerstoffverbrauchs durch Adrenalin verursacht. Das Muskelzittern in der Kälte erreicht im Alter von 15 bis 17 Tagen die Werte der adulten Tiere. Die Catecholamine des Nebennierenmarks nehmen während des Wachstums allmählich zu. Wahrscheinlich sind die Bedingungen für die Thermoregulation durch das Nebennierenmark im Alter von etwa drei Wochen bereits entwickelt. Vergleichend physiologische Befunde an Goldhamstern und Lemmingen werden mitgeteilt. Die Ausbildung des Zentralnervensystems und die darauf folgende Aktivierung des Endokriniums sind wahrscheinlich die wichtigsten kausalen Faktoren in der Entwicklung der Thermogenese.Summary1.Laboratory mice exhibit nearly complete poikilothermia up to 7 days after birth. This period is characterized by high cold resistance, high relative weight and succinic dehydrogenase activity of the brown fat and thermo-orthokinesis. It is possible that the adrenal cortex already at this age also participates in thermoregulation.2.Increase in the heat production between ages of 7 and 15 days, which allows for homoiothermy at ambient temperatures of 20° to 30° C, is accompanied with an increase in the succinic dehydrogenase activity in the liver. This is probably caused by the increase in the thyroid activity which also makes the oxygen consumption sensitive to adrenaline.3.Muscle shivering reaches the adult level at the age of 15 to 17 days.4. Catecholamine stores in the adrenal medulla increase steadily during the growth. It is probably that the conditions for adrenomedullary thermoregulation attain the functional level found in adults at the age of about three weeks.5.Comparative data on the golden hamster and on the Norwegian lemming are presented.6.Maturation of the central nervous system and subsequent activation of the endocrines are probably the main factors responsible for the development of thermogenesis.7.The developmental approach seems to be a suitable method for the analysis of complex cybernetic systems in higher animals.

Variation in heat tolerance in individual Asellus aquaticus during thermal acclimation

Abstract 1. 1.|The thermal tolerance of adult Asellus aquaticus was determined during acclimation from 10 to 20°C and 20 to 10°C. 2. 2.|Thermal tolerance was established by imposing a temperature rise of 12°C/h. The temperature at which righting reflex was lost was considered to be the critical thermal maximum (CTMax). 3. 3.|This parameter can be determined repeatedly in the same individual, reliably and with constancy over time. 4. 4.|The CTMax increased by 4–5°C by acclimation at 20°C as compared with the same animals at 10°C, a change that was fully reversible by acclimation to 10°C. The rate of attainment of acclimation was faster from 10 to 20°C than from 20 to 10°C. 5. 5.|No narrowing of the range of interindividual variation was found in the thermal acclimation of CTMax during the process of the gain or loss of acclimation. 6. 6.|No evidence was found to support the proposal [Ushakov B. P. and Pashkova I. M. (1984) J. therm. Biol. 1–6] that a negative correlation occurred between the individual value of CTMax and the extent of its change during the process of acclimation.

Direct adaptation of cells to temperature: Membrane fluidity of goldfish cells cultured in vitro at different temperatures

Abstract 1. 1. Membrane fluidity (reciprocal of structural order) of crude membrane preparations of CAF cells from goldfish fin cultured at different temperatures was measured by the steady-state fluorescence polarization technique at 10–30°C using l,6-diphenyl-l,3,5-hexatriene (DPH) as the fluorophore. 2. 2. The polarization value was statistically significantly higher (the fluidity was lower) in preparations from log phase cells cultured at 36°C for more than 2 years than in those cultured at 24°C, showing 52% compensation. 3. 3. The cells cultured at 14°C for 3–6 months showed lower polarization values (higher fluidity) corresponding to 34% compensation, although those cultured at the same temperature for more than 2 years showed only 19% compensation (statistically not significant). 4. 4. The extent of partial compensations observed in cells cultured in vitro is comparable to that reported in tissues of thermally acclimated fishes and frogs, suggesting that the homeoviscous adaptation of cell membranes of poikilothermic vertebrates exemplifies the “direct adaptation” (Precht, 1973) where information on environmental temperature need not be mediated by nervous or hormonal regulatory systems of the whole animal.