We used proton magnetic resonance (MR) spectroscopic imaging to determine the serial changes in MR signals from choline, creatine, lactate, and N-acetylaspartate in and around a large demyelinating lesion followed over a period of 8 months. Elevated lactate and choline signals were observed at the first examination 3 days after the onset of symptoms. Reduced N-acetylaspartate signals were observed a few days afterward. The abnormal metabolite signals varied in different regions of the lesion and extended beyond the borders of abnormal signal intensity seen on conventional MR imaging (MRI). On the last examination at 8 months when the lesion appeared much smaller on MRI, choline signals from the center of the lesion were still high, but were falling. Choline signals outside the lesion on MRI had returned to normal as had lactate signals everywhere. Importantly, there was no recovery of N-acetylaspartate signals in or adjacent to the lesion on MRI. This serial study demonstrates the potential of MR spectroscopic imaging for characterizing the chemical pathological evolution of demyelinating lesions in ways that conventional MRI cannot. We propose that abnormal signals from choline can indicate recent regional demyelination, while persistent abnormal signals from N-acetylaspartate can provide an index of irreversible damage in the nervous system.

Eighty-nine soldiers performed a maximal effort 20-km road march, carrying a total load of 46 kg. Compared to pre-march values, post-march marksmanship accuracy decreased 26% for number of target hits and 33% for distance from the centroid of the target. Maximal grenade throw distance decreased 9%, but there was no change in maximal vertical jump height. The Profile of Mood States questionnaire revealed an 82% increase in self-reported fatigue and 38% decrease in vigor. Significant decrements in some aspects of military performance occur when soldiers march rapidly with heavy loads over long distances.

IntroductionC-peptide and insulin measurements in blood provide useful information regarding endogenous insulin secretion. Conflicting evidence on sample stability and handling procedures continue to limit the widespread clinical use of these tests. We assessed the factors that altered the stability of insulin and C-peptide in blood.MethodsWe investigated the impact of preservative type, time to centrifugation, storage conditions and duration of storage on the stability of C-peptide and insulin on three different analytical platforms.ResultsC-peptide was stable for at least 24 hours at room temperature in both centrifuged and whole blood collected in K+-EDTA and serum gel tubes, with the exception of whole blood serum gel, which decreased to 78% of baseline at 24 hours, (p = 0.008). Insulin was stable at room temperature for 24 hours in both centrifuged and whole blood collected in K+-EDTA tubes. In contrast insulin levels decreased in serum gel tubes both centrifuged and whole blood (66% of baseline, p = 0.01 and 76% of baseline p = 0.01, by 24 hours respectively). C-peptide and insulin remained stable after 6 freeze-thaw cycles.ConclusionsThe stability of C-peptide and insulin in whole blood K+-EDTA tubes negates the need to conform to strict sample handling procedures for these assays, greatly increasing their clinical utility.