Oral Tyrosine Supplementation Facilitates Conditions for the Preferential Transport of Tyrosine Across the Blood-Brain Barrier in Anorexia Nervosa: a Case Study Series

Background: Anorexia nervosa is a severe and complex illness associated with a lack of efficacious treatment. Ongoing tyrosine administration has been proposed as a possible treatment through increasing blood tyrosine sufficiently to facilitate brain catecholamine synthesis. Saturation with the noradrenergic precursor tyrosine could alleviate noradrenergic dysregulation with subsequent reduction in dietary restraint and eating, weight and shape concern. The effects of tyrosine supplementation in adolescents with anorexia nervosa remain to be tested. This feasibility study aimed to explore whether an oral tyrosine dosage raises plasma tyrosine sufficiently in adolescents with anorexia nervosa and healthy peers and is sustained over time to allow conditions for the preferential transport across the blood-brain barrier. Case Presentation: The first stage of this study explored the pharmacological response to a single, oral tyrosine load in adolescents (aged 12-15 years) with anorexia nervosa (n=2) and healthy peers (n=2). The second stage explored the pharmacological and psychological response to ongoing tyrosine administration in adolescents with anorexia nervosa. Peak tyrosine levels occurred at approximately two-three hours and approached baseline levels by eight hours. Blood tyrosine elevation was maintained over time in participants with anorexia nervosa. Some improvements in participant psychological tests were evident. There were no measured side effects. Conclusions: The considerable blood tyrosine increase appeared sufficient to facilitate conditions for the preferential transport of tyrosine across the blood-brain barrier which has the potential to improve noradrenergic brain function in people with anorexia nervosa. Further exploration of tyrosine as an adjunct treatment in anorexia nervosa is warranted.

Effects of influent concentration and different valence cations on solute preferential transport in inter-tidal zone of Yellow River Estuary

The migration of land-based pollutants in tidal flat sediments has an important impact on the marine ecological environment. The effects of three influent concentrations and two cation valence states on the preferential transport of NO3-N in the sediments of the Yellow River Estuary were studied by soil column experiments. Results showed that the preferential flow and solute transport were more obvious with the increase of influent concentration; The solute potential was increased in the process of solute transport, which led to the rapid flow, shortened the total time, and facilitated the solute transport speed in the soil; The cation in the sediment of the Yellow River Estuary has little effect on the transport of nitrate nitrogen, and the initial penetration time of the penetration curve using Ca (NO3)2 as tracer was a little later than that using KNO3 as tracer, but it is not obvious.

Effect of preferential transport and coherent denitrification on leaching of nitrate to drainage

To protect the quality of the aquatic environment, it is imperative to be able to assess the leaching of nitrate through various hydrogeological settings. Numerical model concepts have been developed in order to describe this leaching and possible routes of nitrogen at field scale, often without being evaluated in regard to their ability to account for dominant preferential transport and coherent denitrification, which is the rule rather than the exception in soils. This study evaluates whether it is possible to describe 10-years of nitrate concentrations, measured in drainage from a tile-drained agricultural clay till field in Denmark, by applying the soil-plant-atmosphere model DAISY, capable of accounting for preferential transport and denitrification. A DAISY model concept, including macropores capable of capturing the water and bromide balance of the field within this specific timeframe, was able to predict the water transport to drainage, dry matter and N-yield of the harvested crops, while it was unable, with the standard default denitrification model, to predict dynamics and quantity of N-loss to drainage. This was caused by a fast saturation of the plow layer, where nitrate seemed to be denitrified almost instantly, and no surplus nitrate remained to be transported to the drainage. To circumvent this and describe the measured N-loss, modification to the water reduction function affecting denitrification was conducted. The denitrification had to be reduced by approximately 50 % from a seasonal average of 75 kg N ha−1 to 35 kg N ha−1 while 48 % to 80 % of the total N-loss to drainage had to be preferentially transported from the plow layer. This study, therefore, reveals that, by not accounting for preferential transport and coherent denitrification, there is a high risk of underestimating leaching of nitrate to the aquatic environment.