Preliminary evaluation of dynamic glucose enhanced MRI of the human placenta during glucose tolerance test.

BACKGROUND: To investigate dynamic glucose enhanced (DGE) chemical exchange saturation transfer (CEST) MRI as a means to non-invasively image glucose transport in the human placenta. METHODS: Continuous wave (CW) CEST MRI was performed at 3.0 Tesla. The glucose contrast enhancement (GCE) was calculated based on the magnetization transfer asymmetry (MTRasym), and the DGE was calculated with the positive side of Z-spectra in reference to the first time point. The glucose CEST (GlucoCEST) was optimized using a glucose solution phantom. Glucose solution perfused ex vivo placenta tissue was used to demonstrate GlucoCEST MRI effect. The vascular density of ex vivo placental tissue was evaluated with yellow dye after MRI scans. Finally, we preliminarily demonstrated GlucoCEST MRI in five pregnant subjects who received a glucose tolerance test. For human studies, the dynamic R2* change was captured with T2*-weighted echo planar imaging (EPI). RESULTS: The GCE effect peaks at a saturation B1 field of about 2 µT, and the GlucoCEST effect increases linearly with the glucose concentration between 4-20 mM. In ex vivo tissue, the GlucoCEST MRI was sensitive to the glucose perfusate and the placenta vascular density. Although the in vivo GCE baseline was sensitive to field inhomogeneity and motion artifacts, the temporal evolution of the GlucoCEST effect showed a consistent and positive response after oral glucose tolerance drink. CONCLUSIONS: Despite the challenges of placental motion and field inhomogeneity, our study demonstrated the feasibility of DGE placenta MRI at 3.0 Tesla.

Evaluating the efficacy of wood shreds for mitigating erosion.

An erosion control product made by shredding on-site woody materials was evaluated for mitigating erosion through a series of rainfall simulations. Tests were conducted on bare soil and soil with 30, 50, and 70% cover on a coarse and a fine-grained soil. Results indicated that the wood product known as wood shreds reduced runoff and soil loss from both soil types. Erosion mitigation ranged from 60 to nearly 100% depending on the soil type and amount of concentrated flow and wood shred cover. Wood shreds appear to be a viable alternative to agricultural straw. A wood shred cover of 50% appears optimal, but the appropriate coverage rate will depend on the amount of expected concentrated flow and soil type.

Transdermal selegiline: targeted effects on monoamine oxidases in the brain.

BACKGROUND: The oral administration of monoamine oxidase (MAO) inhibitors has the potential to cause a hypertensive reaction after the ingestion of tyramine-containing compounds. Because transdermal drug administration bypasses gastrointestinal absorption, it is possible that inhibition of MAO-A in brain may be achieved without enzyme inhibition in the gastrointestinal system, thereby eliminating the possibility of this drug interaction. These studies determined whether the transdermal administration of selegiline has differential effects on MAOs in brain versus the gastrointestinal system. METHODS: Rats were exposed to various doses of selegiline via a transdermal patch for up to 30 days, and MAO-A and MAO-B activities were determined in brain regions and gastrointestinal tissue. RESULTS: In all brain regions, transdermal selegiline, at doses that produced maximal MAO-B inhibition, led to a dose- and time-dependent MAO-A inhibition. The inhibition of MAOs in gastrointestinal tissue was less than that in brain, and doses that produced maximal MAO-A inhibition in brain inhibited MAO-A in gastrointestinal tissue by only 30%-40%. CONCLUSIONS: Results suggest that transdermal selegiline preferentially inhibits MAO-A in brain relative to the gastrointestinal system. As a consequence, transdermal selegiline should be devoid of the potential to cause a hypertensive reaction after the ingestion of tyramine-containing compounds.