Side by Side Treadmill Walking With Intentionally Desynchronized Gait

Humans demonstrate an innate desire to synchronize stepping when walking side by side. This behavior requires modification of each person’s gait, which may increase for pairings with very different walking patterns. The purpose of this study was to compare locomotor behavior for conditions in which partners exhibited similar and substantially different walking patterns. Twenty-six unimpaired subjects walked on a motorized treadmill at their preferred walking speed for three trials: by themselves (SOLO), next to someone on an adjacent treadmill (PAIRED), and next to someone who purposely avoided synchronization by altering stride times and/or lengths (DeSYNC). Means, coefficients of variance, approximate entropy (ApEn), rate of autocorrelation decay (α), and estimates of maximal Lyapunov exponents (λ*) were calculated for several dependent variables taken from sagittal plane kinematic data. Few differences in behavior were noted when the PAIRED condition was compared to the SOLO condition. However, the DeSYNC condition resulted in several alterations in ApEn, α, and λ*. These results suggest that greater differences in walking pattern between partners will facilitate greater modification to an individual’s gait. Additional study of side by side walking may hold implications for understanding the control of gait in humans and may have application in a clinical setting

13C Pyruvate Transport Across the Blood-Brain Barrier in Preclinical Hyperpolarised MRI.

Hyperpolarised MRI with Dynamic Nuclear Polarisation overcomes the fundamental thermodynamic limitations of conventional magnetic resonance, and is translating to human studies with several early-phase clinical trials in progress including early reports that demonstrate the utility of the technique to observe lactate production in human brain cancer patients. Owing to the fundamental coupling of metabolism and tissue function, metabolic neuroimaging with hyperpolarised [1-13C]pyruvate has the potential to be revolutionary in numerous neurological disorders (e.g. brain tumour, ischemic stroke, and multiple sclerosis). Through the use of [1-13C]pyruvate and ethyl-[1-13C]pyruvate in naïve brain, a rodent model of metastasis to the brain, or porcine brain subjected to mannitol osmotic shock, we show that pyruvate transport across the blood-brain barrier of anaesthetised animals is rate-limiting. We show through use of a well-characterised rat model of brain metastasis that the appearance of hyperpolarized [1-13C]lactate production corresponds to the point of blood-brain barrier breakdown in the disease. With the more lipophilic ethyl-[1-13C]pyruvate, we observe pyruvate production endogenously throughout the entire brain and lactate production only in the region of disease. In the in vivo porcine brain we show that mannitol shock permeabilises the blood-brain barrier sufficiently for a dramatic 90-fold increase in pyruvate transport and conversion to lactate in the brain, which is otherwise not resolvable. This suggests that earlier reports of whole-brain metabolism in anaesthetised animals may be confounded by partial volume effects and not informative enough for translational studies. Issues relating to pyruvate transport and partial volume effects must therefore be considered in pre-clinical studies investigating neuro-metabolism in anaesthetised animals, and we additionally note that these same techniques may provide a distinct biomarker of blood-brain barrier permeability in future studies