Tracking cerebral white matter changes across the lifespan: insights from diffusion tensor imaging studies

Delineating the normal development of brain white matter (WM) over the human lifespan is crucial to improved understanding of underlying WM pathology in neuropsychiatric and neurological conditions. We review the extant literature concerning diffusion tensor imaging studies of brain WM development in healthy individuals available until October 2012, summarise trends of normal development of human brain WM and suggest possible future research directions. Temporally, brain WM maturation follows a curvilinear pattern with an increase in fractional anisotropy (FA) from newborn to adolescence, decelerating in adulthood till a plateau around mid-adulthood, and a more rapid decrease of FA from old age onwards. Spatially, brain WM tracts develop from central to peripheral regions, with evidence of anterior-to-posterior maturation in commissural and projection fibres. The corpus callosum and fornix develop first and decline earlier, whilst fronto-temporal WM tracts like cingulum and uncinate fasciculus have protracted maturation and decline later. Prefrontal WM is most vulnerable with greater age-related FA reduction compared with posterior WM. Future large scale studies adopting longitudinal design will better clarify human brain WM changes over time.     

Effects of Physical Exercise Interventions on Stereotyped Motor Behaviours in Children with ASD: A Meta-Analysis

Journal of Autism and Developmental Disorders - Studies have reported that physical exercise reduces maladaptive stereotyped motor behaviours (SMB) in children with ASD, but these intervention...     

Use of telbivudine in kidney transplant recipients with chronic hepatitis B virus infection: A preliminary experience

Telbivudine is a relatively novel oral nucleoside analogue with favourable efficacy and tolerability in treatment‐naïve chronic hepatitis B virus (HBV) infection, but its data in kidney transplant recipients (KTRs) was lacking. The efficacy and tolerability of telbivudine in four treatment‐naïve HBsAg‐positive KTRs were reviewed (treatment duration 54 (36–72) months) HBV DNA declined from 2.6 × 10⁵(7.8 × 10³–1.5 × 10⁷) copies/mL at baseline to 170 (0.0–3.2 × 10⁴) copies/mL at 12 months, and became undetectable at 24 and 36 months (P = 0.060, 0.118 and 0.005 compared with baseline). Alanine aminotransferase levels dropped from 46.5 (30–48) IU/mL at baseline to 28 (13–45) IU/mL, 34.5 (15–71) IU/mL and 26 (12–41) IU/mL at 12, 24 and 36 months, respectively (P = 0.109, 0.715 and 0.068 compared with baseline). Serum creatinine level and estimated glomerular filtration rate (eGFR) remained stable after 36 months of treatment (P all > 0.05 compared with baseline). No virological breakthrough, cirrhosis or hepatocellular carcinoma occurred. Our pilot data suggests that telbivudine has favourable efficacy and renal safety profiles in HBsAg‐positive KTRs.     

Extinction in the developing rat: an examination of renewal effects

In the present series of experiments the context-specificity of extinction was examined from a developmental perspective. For postnatal day (PN) 23 rats, renewal of freezing to an aversive odor conditioned stimulus (CS) was observed when rats were conditioned in Context A, extinguished in Context B, and tested in Context A (i.e., ABA renewal). This effect was not observed in PN16 rats, which is consistent with previous studies suggesting that rats < approximately PN20 are impaired in encoding contextual information [i.e., Carew and Rudy [1991]. Developmental Psychobiology, 24, 191-209]. Subsequent experiments demonstrated that for rats conditioned at PN16 and tested at PN23, contextual regulation of extinction performance depended on the age at which extinction occurred. Specifically, ABA renewal was observed in rats given extinction training at PN22 but not in rats given extinction training at PN17. These latter results show that whether or not context regulates the expression of an ambiguous memory is determined by the animal's age when the memory becomes ambiguous.     

Occlusion and periodontal disease--where is the link?

The effect of occlusion on the periodontium has been the subject of much debate. Interest on this subject has decreased over the years but has been renewed with the popularity of implant dentistry. This paper reviews the literature and explores the relationship between trauma from occlusion with periodontal disease and peri-implant bone loss. With regards to periodontal disease, there are two schools of thought on the effect that trauma from occlusion has on the periodontium. One believes that trauma from occlusion is a co-destructive factor in the initiation and progression of periodontal disease. The other believes that it is not. Up till now, there are no conclusive explanations on the association between trauma from occlusion and periodontal disease. For dental implants, current literature suggests that there is an association between occlusal overloading and peri-implant bone loss even in the absence of inflammation. However, there is a need for more randomized clinical trials to validate this relationship.     

Physicomechanical evaluation of low-shrinkage dental nanocomposites based on silsesquioxane cores

This study aimed to determine the modulus, hardness, and polymerization shrinkage of novel silsesquioxane (SSQ)-based nanocomposites synthesized for dental applications. Four novel SSQ materials were developed and mixed with control monomers in 5, 10, 20, and 50 wt% SSQ nanocomposite ratios and were evaluated for use as potential low-shrinkage composite restoratives. The postgel polymerization shrinkage of the hybrid materials was then investigated and compared with unfilled 1:1 (control) bisphenol A glycerolate (1 glycerol/phenol) dimethacrylate/tri(ethylene glycol) dimethacrylate (Bis-GMA/TEGDMA) materials using a strain-monitoring device and test configuration. Mechanical properties, such as hardness and modulus, were determined using the depth-sensing microindentation approach. All samples investigated were polymerized using a dental light-curing unit (BISCO VIP) at 500 mW cm(-2) for 40 s. The results obtained were analyzed using analysis of variance/Scheffe's posthoc test at a significance level of 0.05. At 60 min postlight polymerization, postgel shrinkage associated with the control was found to be significantly higher than for all control/SSQ mixtures. Hardness and modulus were found to decrease with increased amount of SSQ monomers added, indicating that the incorporation of SSQ monomers into the control generally helps to reduce both the rigidity and the polymerization shrinkage. Therefore, in the correct formulation, SSQ materials have great potential to be used as low-shrinkage composite restoratives.     

Delayed Gastric Emptying After Sleeve Gastrectomy Is Associated with Poor Weight Loss

Obesity Surgery - Intermediate to long-term weight regain is a major challenge following sleeve gastrectomy (SG). Physiological changes that mediate the extent of weight loss remain unclear. We...