It has been suggested that the Y chromosome of DBA/1Bg mice makes an incremental contribution to their aggressive behavior and to that of the C57BL/10 female X DBA/1 male F1 hybrids. To test this hypothesis, a congenic stock of C57BL/10 with the DBA/1 Y chromosome was developed by the backcross system of breeding; the stock is designated C57BL/10-Y1. There were no significant differences in aggressive behavior between the congenic C57BL/10 and C57BL/10-Y1. However, the hybrid B10D1 F1 and D1B10-Y1 F1 had identical aggression scores, and both of these were more aggressive than the hybrid D1B10 F1. These findings support the hypothesis that there is an interaction between DBA/1 Y chromosomes and autosomes in the development of intermale aggression of these mice.
Effects of fostering on behavior were studied in DBA/1Bg and C57BL/10Bg mice. Two-day-old pups were either infostered to mothers of their own strain, crossfostered to mothers of the other strain, or left as controls with their own mothers. Body weight, latency of emergence into an open field, open-field activity, defecation in an open field, spontaneous alternation, passive avoidance learning, and active escape learning were measured when the mice were 22 and 43 days old. Strain differences were observed for each trait except for spontaneous alternation. Fostering per se affected open-field activity and active escape learning. Similar effects of fostering per se on aggressive behavior have been reported by others. These may involve a role of ovarian cytoplasm, X-chromosomal genes, or uterine environment.
Among children who have difficulty inhibiting gross motor activity and focusing on learning tasks requiring them to do this, some are helped by central nervous system stimulants such as amphetamine, while others with identical symptoms are not. Similar variations in response to pharmacological agents are seen in other syndromes, suggesting that multiple biological mechanisms are involved and that these are selectively responsive to pharmacological manipulations. Diagnosis, therefore, involves not only the identification of the condition, but knowledge of the mechanisms by means of which it can be brought about, as well as some means of identify ing these. Since such variations often have a genetic basis, their identification and characterization by genetic and pharmacogenetic approaches permit the investigator to avoid confounding biological variation with statistical error and, ultimately, to suit the treatment to the mechanism when there is no final common path permitting a single intervention specific to a given syndrome. Because such researches are difficult with human patients, we have been attempting to identify animal models with analogous symptoms to human conditions and homologous mechanisms underlying these. The present paper is one in a series describing a dog model for hyperkinesis.
(1968). DifJerential Htttftesi Handling and the Development of Agonistic Behavior in Basenji and Shetland Sheep Dogs. DEVELOPMENTAL PSYCHOBIOLOGY, I@): 133-140. This experiment tested the hypothesis that differential treatment will increase the amount of aggressive interactions between young puppies. Litters of Shetland sheepdogs and African basenjis were weaned at 4 weeks of age and reared in pairs. In one pair, one pup was favored through playful interaction by a human experimenter, while the other pup was ignored. In a second pair, both pups were ignored. Significantly greater amounts of aggressive behavior occurred in the differentially treated pairs, both during and imniediately after the treatment periods. This behavior carried over into competitive situations involving a food or hone and was still present 9 weeks after treatment had been discontinued. Breed differences were observed in almost all nieasurenients taken. In particular, shelties learned to inhibit their behavior much more rapidly than basenjis. Such differences are comparable to what might be expected from genetic differences between individuals in human subjects. T h e experiment is not comparable to sibling rivalry in haman families, where differential treatment is iniposed because of difference in ages, but the results support the hypothesis that lessening of differential treatment should reduce the occurrence of quarrels between siblings. agonistic behavior, development in dogs dog, differential handling and agonistic behavior sibling aggression, dogs HE TYPES AND AMOUNTS of aggressive behavior dis-T played by mammals are influenced by a wide variety of biological factors at every level of organization (Scott, 1958).
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