In mammals, helping is preferentially provided to members of one’s own group. Yet, it remains unclear how social experience shapes pro-social motivation. We found that rats helped trapped strangers by releasing them from a restrainer, just as they did cagemates. However, rats did not help strangers of a different strain, unless previously housed with the trapped rat. Moreover, pair-housing with one rat of a different strain prompted rats to help strangers of that strain, evidence that rats expand pro-social motivation from one individual to phenotypically similar others. To test if genetic relatedness alone can motivate helping, rats were fostered from birth with another strain and were not exposed to their own strain. As adults, fostered rats helped strangers of the fostering strain but not rats of their own strain. Thus, strain familiarity, even to one’s own strain, is required for the expression of pro-social behavior.DOI: http://dx.doi.org/10.7554/eLife.01385.001

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The present study was undertaken to determine if in vitro exposure to mercuric chloride produces reactive oxygen species (ROS) in the synaptosomes prepared from various regions of rat brain. The effects of in vivo exposure to mercury on antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in different regions of rat brain were also investigated. Adult male Sprague-Dawley (CD) rats were dosed with 0, 1, 2.0 or 4.0 mg HgCl2/kg body weight, for 7 days. One week after the last dose, animals were sacrificed by decapitation, their brains were removed and dissected and frozen in dry ice prior to measuring the activities of these enzymes. The results demonstrated that in vitro exposure to mercury produced a concentration-dependent increase of ROS in different regions of the rat brain. In vivo exposure to mercury produced a significant decrease of total SOD, Cu, Zn-SOD and Mn-SOD activities in the cerebellum of rats treated with different doses of mercury. SOD activity did not vary significantly in cerebral cortex and brain stem. GPx activity declined in a dose-dependent manner in the cerebellum with a significant reduction in animals receiving the 4 mg HgCl2/kg body weight. The activity of GPx increased in the brain stem while unchanged in the cerebral cortex. The results demonstrate that inorganic mercury decreased SOD activity significantly in the cerebellum while GPx activity was affected in both cerebellum and brain stem. Therefore, it can be concluded that oxidative stress may contribute to the development of neurodegenerative disorders caused by mercury intoxication.

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Pie-to postoperative changes in couples electing vasectomy are discussed. High satisfaction with the operation is found, along with apparently desirable changes in attitudes toward child rearing and views of self and spouse. There is, however, concurrent evidence (both on psychometric scales and on clinical ratings) of adverse psychological changes in both husband and wife and of reduced marital satisfaction as compared with similarly studied couples using ovulation-suppression contraception. The "therapeutic" effect of the study itself is presumed to have reduced some of the more apparent adverse effects reported in other studies. Hypotheses are discussed concerning the presumed challenge posed by vasectomy to a man's "masculinity," various ways in which this challenge is apparently met, and the implications of postoperatively modified behavior patterns for psychological functioning of both spouses and for the equilibrium of the marriages. JL N RECENT YEARS, voluntary male sterilization (vasectomy) has become an increasingly common method of contraception. This trend is especially evident in the Western United States, where, in 1960, approximately 7% of the husbands From the Scripps Clinic and Research Foundation, La Jolla, Calif.