Characterization of the intermediate MSUD murine model. A, Survival analysis of transgenic rescue lines. Presented are percentages of mice alive at weaning from each transgenic line tested that had the rescue genotype (i.e., homozygous for knockout of endogenous E2 and positive for both the LAP-tTA and TRE-E2 transgenes). Also plotted is the theoretical maximum frequency at which this genotype is expected in this population of animals. The numbers on the bars indicates the numbers of observations for each line. B, Ratio of total BCAA to alanine in blood of mice from controls and Lines A and 525A. Total BCAA represent the sum of leucine, isoleucine, and valine. BCAA/alanine values were significantly greater for Lines A and 525A compared to controls at all ages tested. The numbers on the bars indicates the numbers of samples analyzed. *, P ≤ 0.01; **, P < 0.005. C, BCKDH enzyme activity in liver of control and Lines A and 525A mice. *, P ≤ 0.001; **, P ≤ 0.0001. D, Survival curves for mice from Lines A and 525A. Rescue mice alive at weaning were monitored until they were moribund and subsequently sacrificed or were found dead in their cages.