General cognitive ability can be highly heritable in some species, but at the same time, is very malleable. This apparent paradox could potentially be explained by gene-environment interactions and correlations that remain hidden due to experimental limitations on human research and blind spots in animal research. Here, we shed light on this issue by combining the design of a sibling study with an environmental intervention administered to laboratory mice. The analysis included 58 litters of four full-sibling genetically heterogeneous CD-1 male mice, for a total of 232 mice. We separated the mice into two subsets of siblings: a control group (maintained in standard laboratory conditions) and an environmental-enrichment group (which had access to continuous physical exercise and daily exposure to novel environments). We found that general cognitive ability in mice has substantial heritability (24% for all mice) and is also malleable. The mice that experienced the enriched environment had a mean intelligence score that was 0.44 standard deviations higher than their siblings in the control group (equivalent to gains of 6.6 IQ points in humans). We also found that the estimate of heritability changed between groups (55% in the control group compared with non-significant 15% in the enrichment group), analogous to findings in humans across socio-economic status. Unexpectedly, no evidence of gene-environment interaction was detected, and so the change in heritability might be best explained by higher environmental variance in the enrichment group. Our findings, as well as the 'sibling intervention procedure' for mice, may be valuable to future research on the heritability, mechanisms and evolution of cognition.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.
The peak force required to separate pieces of meat at a binding junction was measured with the In&on Universal Testing Machine. These measurements were used to study the effects of salt, phosphate, pH, cooking temperature and. protein concentration on the ability of crude myosin to bind meat pieces. Results showed salt and phosphate to linearly increase the ability of myosin to bind meat pieces primarily by solubilizing the protein. Temperature and the level of protein had increasing effects on binding ability in the range 45-80°C and O-8%, respectively. Scanning electron micrographs of the ultrastructure of gels formed by myosin showed a three dimensional network of overlapping fibers in the presence of salt and phosphate and a sponge-like network in their absence. Since the ultrastructure of the gel formed by myosin heavy chains was comparable to that of myosin, it was concluded that the heavy chain core of the myosin molecule plays an important role in the heatinduced gelation of myosin. The relationship between the formation of a three dimensional network of fibers by the heavy chains of myosin and the mechanism of binding meat pieces was discussed.
A model system designed for the Instron Universal Testing Machine to record the peak force required to separate pieces of meat at a binding junction was used to measure the ability of various muscle protein fractions to bond meat pieces. The binding abilities of crude myosin preparations were found to be significantly greater than the binding ability of either a muscle homogenate free of fat and sarcoplasmic proteins, a total muscle homogenate or a nonprotein control consisting of salt, phosphate and water. Crude myosin fractions extracted from pre-and post-rigor bovine muscle over short and long extraction times with three extracting solutions, GubaStraub, Hasselbach-Schneider and Weber-Edsall, were measured for binding ability, yield and mole ratio of myosin to actin by scanning SDS-PAGE gels. Results showed that the HasselbachSchneider myosin was superior to the GubaStraub and Weber-Edsall myosins in both binding ability and yield. Comparisons of mole ratios with binding abilities showed that when the same extracting conditions were present the higher proportion of myosin resulted in a higher binding ability. However, when different extracting conditions were present, the higher proportion of myosin did not always give a higher binding ability. These results imply that ionic interactions are inculpated in the binding phenomenon.
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