Fig. 7.

Examples of ¹³C NMR spectra of brain microdialysates from patients who received 1,2-¹³C₂ glucose (4 mM) perfused via the microdialysis catheter (Jalloh et al., unpublished data). Uninjured brain is normal-appearing brain in a patient operated on for a benign tumour elsewhere in the brain. TBI brain is from a traumatic brain injury patient with diffuse injury. The part of the spectrum illustrated in each case is for the C3 carbon of lactate. Also present in this part of the spectrum is one of the signals due to the internal standard DSS (2,2-dimethyl-2-silapentane-5-sulfonate sodium salt). The remainder of the spectrum, including the main DSS signal (at 0 ppm) is not shown. The C3 doublet indicated by red stars represents lactate doubly labelled with ¹³C, produced by glycolysis; the C3 signal for ¹³C is split into 2 peaks by coupling to ¹³C also present at the neighbouring C2 position within the same molecule. The C3 singlet indicated by green stars represents lactate singly labelled with ¹³C, produced via the PPP; the singlet also contains a contribution from endogenous lactate due to the natural abundance background of ¹³C (1.1% of all carbon atoms).