Myelin is composed primarily of lipids and diseases affecting myelin are associated with alterations in its lipid composition. However, correlation of the spatial (in situ) distribution of lipids with the disease-associated compositional and morphological changes is not well defined. Herein we applied high resolution matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS), immunohistochemistry (IHC), and liquid chromatography–electrospray ionization–mass spectrometry (LC-ESI-MS) to evaluate brain lipid alterations in the dysmyelinating shiverer (Shi) mouse and cuprizone (Cz) mouse model of reversible demyelination. MALDI-IMS revealed a decrease in the spatial distribution of sulfatide (SHexCer) species, SHexCer (d42:2), and a phosphatidylcholine (PC) species, PC (36:1), in white matter regions like corpus callosum (CC) both in the Shi mouse and Cz mouse model. Changes in these lipid species were restored albeit not entirely upon spontaneous remyelination after demyelination in the Cz mouse model. Lipid distribution changes correlated with the local morphological changes as confirmed by IHC. LC-ESI-MS analyses of CC extracts confirmed the MALDI-IMS derived reductions in SHexCer and PC species. These findings highlight the role of SHexCer and PC in preserving the normal myelin architecture and our experimental approaches provide a morphological basis to define lipid abnormalities relevant to myelin diseases.

Studying the causes and reproductive consequences of social variation can provide insight into the evolutionary basis of sociality. Individuals are expected to behave adaptively to maximize reproductive success, but reproductive outcomes can also depend on group structure. Degus (Octodon degus) are plurally breeding rodents, in which females allonurse indiscriminately. However, communal rearing does not appear to enhance female reproductive success, and larger group sizes are correlated with decreasing per capita pup production. To further investigate mechanisms underlying these patterns, we asked how differences in sex, season and average group reproductive success are related to degu association networks. We hypothesized that if reproductive differences mirror social relationships, then females (core group members) should show stronger and more stable associations than males, and female association strength should be strongest during lactation. We also hypothesized that, at the group level, social cohesion would increase reproductive output, while social conflict would decrease it. Females did have higher association strength and more preferred partners than males, but only during lactation, when overall female associations increased. Females also had more stable preferred social partnerships between seasons. A measure of social cohesion (average association strength) was not related to per capita pup production of female group members, but potential social conflict (heterogeneity of association strengths) was negatively related to per capita pup production of female group members. Our results highlight temporal and multilevel patterns of social structure that may reflect reproductive costs and benefits to females.