Automated brain tissue and myelin volumetry based on quantitative MR imaging with various in-plane resolutions

BACKGROUND AND PURPOSE

Segmented brain tissue and myelin volumes can now be automatically calculated using dedicated software (SyMRI), which is based on quantification of R₁ and R₂ relaxation rates and proton density. The aim of this study was to determine the validity of SyMRI brain tissue and myelin volumetry using various in-plane resolutions.

METHODS

We scanned 10 healthy subjects on a 1.5T MR scanner with in-plane resolutions of 0.8, 2.0 and 3.0mm. Two scans were performed for each resolution. The acquisition time was 7-min and 24-sec for 0.8mm, 3-min and 9-sec for 2.0mm and 1-min and 56-sec for 3.0mm resolutions. The volumes of white matter (WM), gray matter (GM), cerebrospinal fluid (CSF), non-WM/GM/CSF (NoN), brain parenchymal volume (BPV), intracranial volume (ICV) and myelin were compared between in-plane resolutions. Repeatability for each resolution was then analyzed.

RESULTS

No significant differences in volumes measured were found between the different in-plane resolutions, except for NoN between 0.8mm and 2.0mm and between 2.0mm and 3.0mm. The repeatability error value for the WM, GM, CSF, NoN, BPV and myelin volumes relative to ICV was 0.97%, 1.01%, 0.65%, 0.86%, 1.06% and 0.25% in 0.8mm; 1.22%, 1.36%, 0.73%, 0.37%, 1.18% and 0.35% in 2.0mm and 1.18%, 1.02%, 0.96%, 0.45%, 1.36%, and 0.28% in 3.0mm resolutions.

CONCLUSION

SyMRI brain tissue and myelin volumetry with low in-plane resolution and short acquisition times is robust and has a good repeatability so could be useful for follow-up studies.

Ionic Liquid Based Nanocarriers for Topical and Transdermal Drug Delivery

In the pharmaceutical industry, there are challenges in topical and transdermal administration of drugs, which are sparingly soluble in water and most organic solvents. Ionic liquids (ILs) have been found to be very effective for dissolution of sparingly soluble drugs. However, hydrophilic IL-borne drugs cannot penetrate into or across the skin because of the highly hydrophobic barrier function of the outer skin. In this chapter we report a novel IL-in-oil (IL/o) microemulsion (ME) that is able to dissolve a significant amount of sparingly soluble drug, acyclovir, in the IL core while the continuous oil phase can provide the desired features for topical/transdermal transport through the skin. The ME is composed of a blend of the nonionic surfactants polyoxyethylene sorbitan monooleate (Tween 80) and sorbitan laurate (Span 20), isopropyl myristate (IPM) as an oil phase, and the IL [C1mim][(MeO)2PO2] (dimethylimidazolium dimethylphosphate) as a dispersed phase. The size and size distribution of the aggregates in the MEs were characterized by dynamic light scattering, showing formation of the nanocarrier in the size range 8–34 nm. In vitro drug permeation studies into and across the skin showed that the IL/o ME increased drug administration compared with other formulations. The safety profile of the new carrier was evaluated using a cytotoxicity assay on the human epidermal model LabCyte. We believe that these IL-assisted nonaqueous MEs can serve as a versatile and efficient nanodelivery system for sparingly soluble drug molecules.

Dual Regulation of Gluconeogenesis by Insulin and Glucose in the Proximal Tubules of the Kidney

Growing attention has been focused on the roles of the proximal tubules (PTs) of the kidney in glucose metabolism, including the mechanism of regulation of gluconeogenesis. In this study, we found that PT-specific insulin receptor substrate 1/2 double-knockout mice, established by using the newly generated sodium-glucose cotransporter 2 (SGLT2)-Cre transgenic mice, exhibited impaired insulin signaling and upregulated gluconeogenic gene expression and renal gluconeogenesis, resulting in systemic insulin resistance. In contrast, in streptozotocin-treated mice, although insulin action was impaired in the PTs, the gluconeogenic gene expression was unexpectedly downregulated in the renal cortex, which was restored by administration of an SGLT1/2 inhibitor. In the HK-2 cells, the gluconeogenic gene expression was suppressed by insulin, accompanied by phosphorylation and inactivation of forkhead box transcription factor 1 (FoxO1). In contrast, glucose deacetylated peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α), a coactivator of FoxO1, via sirtuin 1, suppressing the gluconeogenic gene expression, which was reversed by inhibition of glucose reabsorption. These data suggest that both insulin signaling and glucose reabsorption suppress the gluconeogenic gene expression by inactivation of FoxO1 and PGC1α, respectively, providing insight into novel mechanisms underlying the regulation of gluconeogenesis in the PTs.