Variability in subthalamic nucleus targeting for deep brain stimulation with 3 and 7 Tesla magnetic resonance imaging

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective surgical treatment for Parkinson's disease (PD). Side-effects may, however, be induced when the DBS lead is placed suboptimally. Currently, lower field magnetic resonance imaging (MRI) at 1.5 or 3 Tesla (T) is used for targeting. Ultra-high-field MRI (7 T and above) can obtain superior anatomical information and might therefore be better suited for targeting. This study aims to test whether optimized 7 T imaging protocols result in less variable targeting of the STN for DBS compared to clinically utilized 3 T images. Three DBS-experienced neurosurgeons determined the optimal STN DBS target site on three repetitions of 3 T-T2, 7 T-T2*, 7 T-R2* and 7 T-QSM images for five PD patients. The distance in millimetres between the three repetitive coordinates was used as an index of targeting variability and was compared between field strength, MRI contrast and repetition with a Bayesian ANOVA. Further, the target coordinates were registered to MNI space, and anatomical coordinates were compared between field strength, MRI contrast and repetition using a Bayesian ANOVA. The results indicate that the neurosurgeons are stable in selecting the DBS target site across MRI field strength, MRI contrast and repetitions. The analysis of the coordinates in MNI space however revealed that the actual selected location of the electrode is seemingly more ventral when using the 3 T scan compared to the 7 T scans

Dust and grit matter: abrasives of different size lead to opposing dental microwear textures in experimentally fed sheep (Ovis aries)

External abrasives ingested along with the herbivore diet are considered main contributors to dental wear, though how the different sizes and concentrations of these abrasives influence wear remains unclear. Dental microwear texture analysis (DMTA) is an establishedmethod for dietary reconstructionwhich describes a tooth’s surface topography on a micrometre scale. The method has yielded conflicting results as to the effect of external abrasives. In the present study, a feeding experiment was performed on sheep (Ovis aries) fed seven diets of different abrasiveness. Our aim was to discern the individual effects of size (4, 50 and 130 μm) and concentration (0%,4% and 8% of dry matter) of abrasives on dental wear, applying DMTA to four tooth positions. Microwear textures differed between individual teeth, but surprisingly, showed no gradient along the molar tooth row, and the strongest differentiation of experimental groups was achieved when combining data of all maxillary molars. Overall, a pattern of increasing height, volume and complexity of the tooth’s microscopic surface appeared with increasing size of dietary abrasives, and when compared with the control, the small abrasive diets showed a polishing effect. The results indicate that the size of dietary abrasives is more important for dental microwear texture traces than their concentration, and that different sizes can have opposing effects on the dietary signal. The latter finding possibly explains conflicting evidence from previous experimental DMTA applications. Further exploration is required to understand whether and how microscopic traces created by abrasives translate quantitatively to tissue loss

Clinical effectiveness of unilateral deep brain stimulation in Tourette syndrome

Dysfunctional basal ganglia loops are thought to underlie the clinical picture of Tourette syndrome (TS). By altering dopaminergic activity in the affected neural structures, bilateral deep brain stimulation is assumed to have a modulatory effect on dopamine transmission resulting in an amelioration of tics. While the majority of published case reports deals with the application of bilateral stimulation, the present study aims at informing about the high effectiveness of unilateral stimulation of pallidal and nigral thalamic territories in TS. Potential implications and gains of the unilateral approach are discussed

Low-dose glucocorticoid treatment affects multiple aspects of intermediary metabolism in healthy humans: a randomised controlled trial

AIM/HYPOTHESIS: To assess whether low-dose glucocorticoid treatment induces adverse metabolic effects, as is evident for high glucocorticoid doses. METHODS: In a randomised placebo-controlled double-blind (participants and the investigators who performed the studies and assessed the outcomes were blinded) dose-response intervention study, 32 healthy men (age 22 +/- 3 years; BMI 22.4 +/- 1.7 kg/m(2)) were allocated to prednisolone 7.5 mg once daily (n = 12), prednisolone 30 mg once daily (n = 12), or placebo (n = 8) for 2 weeks using block randomisation. Main outcome measures were glucose, lipid and protein metabolism, measured by stable isotopes, before and at 2 weeks of treatment, in the fasted state and during a two-step hyperinsulinaemic clamp conducted in the Clinical Research Unit of the Academic Medical Centre, Amsterdam, the Netherlands RESULTS: Prednisolone, compared with placebo, dose dependently and significantly increased fasting plasma glucose levels, whereas only prednisolone 30 mg increased fasting insulin levels (29 +/- 15 pmol/l). Prednisolone 7.5 mg and prednisolone 30 mg decreased the ability of insulin to suppress endogenous glucose production (by 17 +/- 6% and 46 +/- 7%, respectively, vs placebo). Peripheral glucose uptake was not reduced by prednisolone 7.5 mg, but was decreased by prednisolone 30 mg by 34 +/- 6% (p < 0.0001). Compared with placebo, prednisolone treatment tended to decrease lipolysis in the fasted state (p = 0.062), but both prednisolone 7.5 mg and prednisolone 30 mg decreased insulin-mediated suppression of lipolysis by 11 +/- 5% and 34 +/- 6%, respectively. Finally, prednisolone treatment increased whole-body proteolysis during hyperinsulinaemia, which tended to be driven by prednisolone 30 mg (5 +/- 2%; p = 0.06). No side effects were reported by the study participants. All participants completed the study and were analysed. CONCLUSIONS/INTERPRETATION: Not only at high doses but also at low doses, glucocorticoid therapy impaired intermediary metabolism by interfering with the metabolic actions of insulin on liver and adipose tissue. These data indicate that even low-dose glucocorticoids may impair glucose tolerance when administered chronically. TRIAL REGISTRATION: ISRCTN83991850

Finite temperature mobility of a particle coupled to a fermion environment

We study numerically the finite temperature and frequency mobility of a particle coupled by a local interaction to a system of spinless fermions in one dimension. We find that when the model is integrable (particle mass equal to the mass of fermions) the static mobility diverges. Further, an enhanced mobility is observed over a finite parameter range away from the integrable point. We present a novel analysis of the finite temperature static mobility based on a random matrix theory description of the many-body Hamiltonian.Comment: 11 pages (RevTeX), 5 Postscript files, compressed using uufile

Age-related differences in drop-jump performance are eliminated by matching triceps surae muscle strength and Achilles tendon stiffness.

INTRODUCTION Reduced leg-extensor muscle strength and tendon stiffness in old age have been associated with changes in locomotor performance and motor task execution strategy (Karamanidis and Arampatzis, 2005; Kulmala et al., 2014). However, if leg-extensor muscle-tendon unit (MTU) mechanical properties are the only primary drivers of these alterations seen with ageing remains unclear. Therefore, we examined if matching triceps surae (TS) muscle strength and Achilles tendon (AT) stiffness eliminates potential age-related differences in drop jump (DJ) performance and motor task execution strategy in younger and middle-aged adults

Matching Participants for Triceps Surae Muscle Strength and Tendon Stiffness Does Not Eliminate Age-Related Differences in Mechanical Power Output During Jumping

Reductions in muscular power output and performance during multi-joint motor tasks with aging have often been associated with muscle weakness. This study aimed to examine if matching younger and middle-aged adults for triceps surae (TS) muscle strength and tendon stiffness eliminates age-related differences in muscular power production during drop jump. The maximal ankle plantar flexion moment and gastrocnemius medialis tendon stiffness of 29 middle-aged (40–67 years) and 26 younger (18–30 years) healthy physically active male adults were assessed during isometric voluntary ankle plantar flexion contractions using simultaneous dynamometry and ultrasonography. The elongation of the tendon during the loading phase was assessed by digitizing the myotendinous junction of the gastrocnemius medialis muscle. Eight younger (23 ± 3 years) and eight middle-aged (54 ± 7 years) adults from the larger subject pool were matched for TS muscle strength and tendon stiffness (plantar flexion moment young: 3.1 ± 0.4 Nm/kg; middle-aged: 3.2 ± 0.5 Nm/kg; tendon stiffness: 553 ± 97 vs. 572 ± 100 N/mm) and then performed series of drop jumps from different box heights (13, 23, 33, and 39 cm) onto a force plate (sampling frequency 1000 Hz). The matched young and middle-aged adults showed similar drop jump heights for all conditions (from lowest to highest box height: 18.0 ± 3.7 vs. 19.7 ± 4.8 cm; 22.6 ± 4.2 vs. 22.9 ± 4.9 cm; 24.8 ± 3.8 vs. 23.5 ± 4.9 cm; 25.2 ± 6.2 vs. 22.7 ± 5.0 cm). However, middle-aged adults showed longer ground contact times (on average 36%), lower vertical ground reaction forces (36%) and hence lower average mechanical power (from lowest to highest box height: 2266 ± 563 vs. 1498 ± 545 W; 3563 ± 774 vs. 2222 ± 320 W; 4360 ± 658 vs. 2475 ± 528 W; 5008 ± 919 vs. 3034 ± 435 W) independent of box height. Further, leg stiffness was lower (48%) in middle-aged compared to younger adults for all jumping conditions and we found significant correlations between average mechanical power and leg stiffness (0.70 ≤ r ≤ 0.83; p < 0.01). Thus, while jumping performance appears to be unaffected when leg extensor muscle strength and tendon stiffness are maintained, the reduced muscular power output during lower limb multi-joint tasks seen with aging may be due to age-related changes in motor task execution strategy rather than due to muscle weakness

Matching triceps surae muscle strength and tendon stiffness eliminates age-related differences in drop-jump performance

INTRODUCTION: Age-related changes in locomotor performance and motor task execution strategy have been associated with reduced leg-extensor muscle-tendon unit capacities in old age (Karamanidis & Arampatzis, 2005; Kulmala et al., 2014). However, it remains unclear if leg-extensor muscle strength and tendon stiffness are the primary drivers of these alterations seen with ageing, or if other factors also play a role. We aimed to determine if potential age-related differences in drop jump (DJ) performance and motor task execution strategy would be eliminated in a group of younger and middle-aged adults when triceps surae (TS) muscle strength and Achilles tendon (AT) stiffness were matched. METHODS: Ankle plantarflexion moments and AT stiffness of both legs were assessed in 12 younger (20-30y) and 12 middle-aged (50-65y) adults during isometric plantarflexion contractions using dynamometry and ultrasonography synchronously. Tendon elongation during the loading phase was assessed by visualising the myotendinous junction of the gastrocnemius medialis muscle and stiffness of the AT was determined in the linear region of the force-length relationship. There were no significant differences between the matched young and middle-aged adults in maximal ankle plantarflexion moment (young: 3.2±0.4; middle-aged: 3.1±0.5 Nm/kg) and AT stiffness (580.3±121.8 vs. 590.2±108.4 N/mm). On a second occasion, the matched participants performed a series of DJs from different starting heights (13, 23, 33 and 39 cm) onto a force plate. A two-way ANOVA (factors: age, starting height) was performed in order to detect any age or starting height effects on DJ height and motor task execution strategy. The effect of TS muscle strength and AT stiffness on DJ height was investigated by using Pearson’s product-moment correlation coefficient. RESULTS: There was no significant age effect for DJ performance, meaning that matched younger and middle-aged adults achieved similar DJ heights, independent of starting height (Fig. 1). Concerning DJ mechanics, there were significant age effects (p<.05) on ground contact time, maximum vertical ground reaction force and mechanical power, with the middle-aged adults showing higher ground contact times (Fig. 2A), but lower forces (Fig. 2B) and lower mechanical power (Fig. 2C) for all starting heights. Significant correlations were found between DJ performance and TS muscle strength and AT stiffness (.41≤r≤.81; p<.05) for all starting heights. DISCUSSION: The results of the current study demonstrate that matching younger and middle-aged adults for TS muscle strength and AT stiffness eliminates age-related differences in the performance of a jumping task, independent of starting height and hence, task demand. However, the age groups used different motor task execution strategies, as measured by ground contact time, ground reaction forces and mechanical power for all starting heights, indicating that while changes in leg extensor muscle strength and tendon stiffness may be the primary drivers of deteriorated locomotor performance in older age, they may not be major contributors to motor task execution strategy during jumping. CONCLUSION: Jumping performance appears to be unaffected when leg extensor muscle strength and tendon stiffness are maintained with age and therefore, countering the degeneration of these properties may help prevent the decline in locomotor performance seen with ageing. REFERENCES: Karamanidis, K., & Arampatzis, A. (2005). Mechanical and morphological properties of different muscle-tendon units in the lower extremity and running mechanics: effect of aging and physical activity. The Journal of Experimental Biology, 208, 3907–23. Kulmala, J.-P., Korhonen, M. T., Kuitunen, S., Suominen, H., Heinonen, A., Mikkola, A., & Avela, J. (2014). Which muscles compromise human locomotor performance with age? Journal of The Royal Society Interface, 11, 20140858