Aggression and sociometric status among peers: do gender and type of aggression matter?

The connections between the use of different types of aggression (direct physical, direct verbal, and indirect) and sociometric status among same-sex and opposite-sex peers were studied. The subjects were 209 ninth-grade adolescents. Although an adolescent's aggression in general was related to being rejected by peers, a different picture emerged when the shared variance between types of aggression was controlled: The partial correlations showed that when the level of direct (physical and verbal) aggression was kept constant, increases in indirect aggression did not explain variance in peer rejection scores. On the contrary, the use of indirect aggression contributed (especially among boys) to social acceptance by peers. The direct (physical and verbal) forms of aggression were unrelated to adolescents' social acceptance scores. No clear differences were detected between girls' and boys' acceptance or rejection of their aggressive peers, despite the finding that boys seemed to tolerate indirect aggression better than girls did.

Effects of thermal acclimation on nervous conduction and muscle contraction in the frog Rana temporaria.

The effects of season and acclimation temperature on the latency of the leg withdrawal reflex and three of its components have been studied: conduction velocity in the sciatic nerve, spinal conduction time, and contraction time of gastrocnemius muscle. The latency of the leg withdrawal reflex was markedly shortened by cold acclimation: the reaction times were at 6 degrees C 1.54 s in 4 degrees C acclimated and 3.97 s in 24 degrees C acclimated winter frogs. Also, the temperature dependence of the reflex latency was reduced by cold acclimation. Thus, frogs acclimated to cold responded to external stimuli in cold more rapidly than warm-acclimated ones. This cold adaptation of the reflex could not be explained by changes in its studied components. These made up only one-tenth of the reflex response time, and either did not show significant cold acclimation (muscle contraction and spinal conduction times in summer) or showed inverse acclimation, especially when measured at high temperatures (i.e. conduction velocities were reduced by acclimation to cold). Thus, the cold acclimation of the reflex response probably resides in the sensory component of the response. The inverse temperature adaptation response of conduction velocities may reflect a reduced ion permeability across cellular membranes in cold which decreases metabolic energy expenditure during inactive periods.

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.

Effects of testosterone exposure and fighting experience on the aggressive behavior of female and male mice selectively bred for intermale aggression.

Exposure of female mice to testosterone resulted in aggressive behavior as a function of breeding line in two lines of mice selectively bred for high (Turku Aggressive, TA) and low (Turku Nonaggressive, TNA) levels of aggressiveness. Female TA mice that received a single injection of testosterone propionate (TP) (1 mg in 0.05 ml peanut oil) on the second day of life, and starting at 120 days of age received daily injections for seven consecutive days, displayed aggressive behavior on a level comparable to that of socially isolated males of the same line, whereas control TA females (injected with 0.05 ml peanut oil) and TP-exposed TNA females were totally nonaggressive. The level of aggressiveness was assessed by means of dyadic tests against intact male opponents. Early and adult exposure to TP did not lead to increased aggressiveness in male TNA mice. Fighting experience in combination with prolonged TP treatment changed the aggressiveness of the TP-exposed TA females, leading to decreased aggressiveness in defeated animals. The genetically correlated low level of aggressiveness of TNA male and female mice was unaffected by any combination of TP exposure, learning and social isolation. It is concluded that differences in testosterone reactivity of target organs, other than those which are Y chromosome determined, i.e., the testes, are responsible for the aggressiveness in the strains studied.

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.

Changes in cell membrane fluidity affect the sodium transport across frog skin and its sensitivity to amiloride.

1. 1-5 mM n-hexanol added to the outer (mucosal) medium of isolated skin of the frog Rana temporaria increases the short circuit current (Isc) across it. 2. This effect shows a saturable dependency on the outer sodium concentration, also when NaCl is replaced by Na2SO4. 3. n-Hexanol at a concentration of 1 mM, and cold acclimation of the frogs, which increases the fluidity of epidermal cell membranes, do not affect the sensitivity of Isc to the inhibiting effect of amiloride. 4. n-Hexanol at a concentration (5 mM) which causes a fluidization of cell membrane preparations from isolated frog epidermis also increases the sensitivity of Isc to amiloride. 5. The effects of low concentrations of n-hexanol and of cold acclimation probably depend on an increase of the permeability of apical membranes of epidermal cells to sodium caused by membrane fluidization. At higher concentrations of n-hexanol, a further disordering of the membrane structure occurs with a better access of amiloride to its action sites.

Temperature effects on different organization levels in animals.

One of the central concepts in present biology is the recognition of different organization levels and their hierarchical array. Complex multicellular animals are constituted of organ systems, the organs of cells, the cells of organelles, membranes, and molecules. The primary effects of many environmental factors (e.g. light, concentrations of ions and molecules) can be delimited mainly to one level. Temperature, being the macroscopic physical measure of the random motion of smallest material particles, affects directly the animal life at all organization levels. The special physical nature of temperature means also, that during the history of life, organisms have always been subjected to temperature variations. Many different ways to evade the pervasive effects of temperature have been evolved during the course of evolution. The study of the temperature relations of organisms can therefore give models for other branches of environmental biology. The temperature limits and relations of an animal cannot be explained by the temperature relations and limits of its cells without taking into account such interactions between different types of cells, which are found only through the study of the organs. Also, the temperature limits and relations of animal cells cannot be explained just through the study of the constituent molecules. The possible interactions of the molecules (e.g. lipids and proteins in a cell membrane) are so manifold and complex that in order to ascertain the relative importance of them in the temperature relations of the cells we must rely in part on studies done on organelles (e.g. on the plasma membrane). The study of the thermal biology of animal cells thus exemplifies the situation often found in biology: the attainment of a reductive explanation is not always a one-way deduction, but it may involve modifications of the lower level concepts according to the knowledge derivable only from studies of the higher level systems.

Children'S experience of three types of cartoon at two age levels.

Three cartoons were shown to 87 children at two age levels: 5-6 years, and 9 years. The children's experience was assessed in interviews. The younger children experienced the cartoons in a fragmentary manner and not as a continuous story, understood less of the cartoons, and tended to base their moral judgements of a character's behaviour on whether or not they identified with that character. Six months later, the younger children remembered best those scenes that had made them the most anxious earlier. A subgroup of children with abundant aggressive fantasies had a lower level of moral reasoning than the other children, preferred violent scenes, became less anxious while watching them and tended to give illogical explanations for the behaviour of the cartoon characters. The degree of anxiety provoked by a cartoon depended not on the amount of explicit violence shown but on the way the violence was presented. One cartoon, which contained no explicit violence, was considered the most frightening one due to its sound effects.

Comparative psychopharmacology.

Studies of the effects of psychoactive drugs and neurotransmitters on the behavior of invertebrates and poikilothermic vertebrates are reviewed. Dangers of reductive explanations are pointed out. Results and suggestions are given concerning the use of poikilothermic animals (1) in the development of screening tests, (2) in experiments on the action mechanisms of psychopharmaca, and (3) in the use of psychoactive drugs in the study of the mechanisms of animal behavior.

Temperature compensation of sodium transport and ATPase activity in frog skin.

Na+ transport across frog skin, measured as short-circuit current (SCC) shows perfect temperature compensation in frogs acclimated to 6 degrees, 12 degrees, and 23 degrees C as SCC values observed at the acclimation temperatures are equal (about 13 muA/cm2). Reacclimation experiments show that this is not a starvation effect. While very little temperature compensation is seen in the activity of Na+, K+-ATPase in epidermal homogenates from frog skins, the activity of Mg2+-ATPase shows inverse compensation at assay temperatures from 4 degrees to 48 degrees C. This ATPase is apparently activated either by Mg2+ or by Ca2+ and it probably controls the passive permeability of epidermal cells. It is suggested that the inverse temperature compensation in the activity of this enzyme is the main mechanism by which the observed perfect temperature compensation of Na+ transport across frog skin occurs.

ATPase stimulated by Na+ or K+ in gills of the freshwater mussel Anodonta.

1. Microsomal preparations from the gills of the freshwater mussel anodonta cygnea cellensis show Mg2+ -dependent Na+ - or K+ -stimulated ATPase activity, which is not inhibited by ouabain. 2. Na+ - or Ka+ -ATPase activity is decreased by Ca2+, acetylcholine, choline, and tetramethylammonium, but slightly increased by ethyl alcohol. 3. It is tentatively suggested that Na+ - or K+ -ATPase is involved in the mechanism of active monovalent cation uptake through the gills of freshwater mussels.