Player position in American football influences the magnitude of mechanical strains produced in the location of chronic traumatic encephalopathy pathology: A computational modelling study.

American football players are frequently exposed to head impacts, which can cause concussions and may lead to neurodegenerative diseases such as chronic traumatic encephalopathy (CTE). Player position appears to influence the risk of concussion but there is limited work on its effect on the risk of CTE. Computational modelling has shown that large brain deformations during head impacts co-localise with CTE pathology in sulci. Here we test whether player position has an effect on brain deformation within the sulci, a possible biomechanical trigger for CTE. We physically reconstructed 148 head impact events from video footage of American Football games. Players were separated into 3 different position profiles based on the magnitude and frequency of impacts. A detailed finite element model of TBI was then used to predict Green-Lagrange strain and strain rate across the brain and in sulci. Using a one-way ANOVA, we found that in positions where players were exposed to large magnitude and low frequency impacts (e.g. defensive back and wide receiver), strain and strain rate across the brain and in sulci were highest. We also found that rotational head motion is a key determinant in producing large strains and strain rates in the sulci. Our results suggest that player position has a significant effect on impact kinematics, influencing the magnitude of deformations within sulci, which spatially corresponds to where CTE pathology is observed. This work can inform future studies investigating different player-position risks for concussion and CTE and guide design of prevention systems.

Copper-controllable gene expression system for whole plants.

We describe a system for gene expression in plants based on the regulation mechanism of the yeast metallothionein (MT) gene. The system consists of two elements: (i) the yeast ace1 (activating copper-MT expression) gene encoding a transcription factor under control of the cauliflower mosaic virus (CaMV) 35S RNA promoter, and (ii) a gene of interest under control of a chimeric promoter consisting of the 90-base-pair domain A of the CaMV 35S RNA promoter linked to the ACE1 transcription factor-binding site. At elevated copper ion concentrations, the ACE1 protein changes conformation, binds to, and activates transcription from the chimeric promoter. To test the functioning of the system in plants, a construct containing the beta-glucuronidase (GUS) reporter gene under control of the chimeric promoter was prepared, and transgenic tobacco plants were produced. It was shown that GUS activity in the leaves of transgenic plants increased up to 50-fold, either after addition of 50 microM CuSO4 to the nutrient solution or after application of 0.5 microM CuSO4 to the plants in a foliar spray. This GUS expression was repressed after the removal of copper ions. The results show that the activity of the described chimeric promoter directly depends on copper ion concentration and that this system can be used in experiments that demand precise timing of expression.

A system for tissue-specific copper-controllable gene expression in transgenic plants: nodule-specific antisense of aspartate aminotransferase-P2.

A vector system, based on copper controllable gene expression, has been developed to give control over place as well as time of expression of an introduced gene. This system consists of two elements: (1) the yeast ace1 gene encoding a metallo-regulatory transcription factor, ACE1, under control of either an organ-specific or a constitutive promoter; and (2) a gene of interest under control of a chimaeric promoter consisting of the 46 bp TATA fragment of the CaMV 35S RNA promoter linked to four repeats of the ACE1 binding site. The functioning of the system in an organ-specific manner was tested in nodulated Lotus corniculatus plants which consisted of non-transformed shoots plus transformed hairy root tissue 'wild-type tops/transgenic roots'. After addition of copper ions to the plant nutrient solution, beta-glucuronidase (GUS) expression was visualized either specifically in nodules or in both roots and nodules when the ace1 gene was placed under control of the nod45 promoter or the CaMV 35S RNA promoter, respectively. The nodule-specific system was used to express antisense constructs of aspartate aminotransferase-P2 in transgenic Lotus corniculatus plants. When expression was induced by the addition of copper ions to the plant nutrient solution aspartate aminotransferase-P2 activity declined dramatically, and a decrease of up to 90% was observed in nodule asparagine concentration.