Figure 5

Selective overabundance of essential (a) and ‘conditionally essential’ (b) amino acids in pup serum relative to maternal serum. Relative abundance in the sera of pups with time after birth expressed as a ratio with the concentration in their individual mothers’ sera (ratio of pup/mother; mean + SE). Conditionally essential amino acids are classed as such because their synthesis can be limited under certain pathophysiological conditions, such as prematurity in an infant or in individuals in severe catabolic distress. The days after birth labelled 18 are a combination of samples taken at 17, 18, or 19 days. The horizontal dotted lines indicate equivalence between levels in mothers and pups. Isoleucine (essential) and cysteine (conditionally essential) are not included because they are not resolved in our analytical system. Some amino acids occurred in modified form, such as N6-Methyl-L-lysine, which had overabundance levels in pup:mother ratios of 37.7, 41.5, 84.8, and 83.3 on days 2, 7, 13, and 18, respectively (for clarity, not included in graph – see Supplementary Figure S9). Only threonine, and valine did not show differences between days by ANOVA with Tukey’s test at the 0.05 level or below, or by two-sample t-test between days for deviation from unity. More detailed box and whisker plots with individual ratio values of the data are given in Supplementary Figure S9. Supplementary Table S1 provides statistical analysis of where significant differences were found between the days for each of the compounds.