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In order to investigate poly(N-vinyl pyrrolidone) as an alternative to poly(ethylene glycol) in preparing a biomedical polymer, we synthesized a series of reverse thermogelling poly(N-vinyl pyrrolidoneb-alanine) (PVP-PA). The amphiphilic polymers consisting of the hydrophilic PVP block and the hydrophobic PA block formed micelles in water and the micelles aggregated as the temperature increased. FTIR spectroscopy, circular dichrosim spectroscopy, and 13 C NMR spectroscopy showed that the aggregation behavior accompanied a change in PA conformation as well as a decrease in the molecular motion of PVP-PA. The sol-to-gel transition temperature decreased as the PA block length increased, PVP block length decreased, and L-alanine/DL-alanine ratio of PA increased. This paper suggests that PVP can be a promising alternative to poly(ethylene glycol) in designing a reverse thermogelling biomaterial.

Moderate blood loss was associated with a decline in mean SI that was clearly detectable with impedance cardiography. However, as a test for moderate blood loss in this controlled setting, neither SI nor triangle up SI performed better than traditional vital signs.

BackgroundThe ability to explore the anatomy has improved our appreciation of the brachial anatomy and the quality of regional anesthesia. Using real-time ultrasonography, we investigated the cross-sectional anatomy of the brachial plexus and of vessels at the axillary fossa in Koreans.MethodsOne hundred and thirty-one patients scheduled to undergo surgery in the region below the elbow were enrolled after giving their informed written consent. Using the 5-12 MHz linear probe of an ultrasound system, we examined cross-sectional images of the brachial plexus in the supine position with the arm abducted by 90°, the shoulder externally rotated, and the forearm flexed by 90° at the axillary fossa. The results of the nerve positions were expressed on a 12-section pie chart and the numbers of arteries and veins were reported.ResultsApplying gentle pressure to prevent vein collapse, the positions of the nerves changed easily and showed a clockwise order around the axillary artery (AA). The most frequent positions were observed in the 10-11 section (79.2%) for the median, 1-2 section (79.3%) for the ulnar, 3-5 section (78.4%) for the radial, and 8-9 section (86.9%) for the musculocutaneous nerve. We also noted anatomical variations consisting of double arteries (9.2%) and multiple axillary veins (87%).ConclusionsUsing real-time ultrasonography, we found that the anatomical pattern of the major nerves in Koreans was about 80% of the frequent position of individual nerves, 90.8% of the single AA, and 87% of multiple veins around the AA.

Background Thermosensitive micelles with rigid cores that exhibit a reversible lower critical solution temperature at 30–35 °C can be applied for drug delivery. Method Hydrophilic monomethoxy poly(ethylene glycol) was conjugated to hydrophobic deoxycholic acid to prepare monomethoxy poly(ethylene glycol)-deoxycholic acid (mPEG-DC). Micelle formation and thermosensitive solution behavior were studied using various methods, including hydrophobic dye solubilization, transmission electron microscopy, dynamic light scattering, turbidity measurement, microcalorimetry, and 1H-NMR spectroscopy. Drug release from the thermosensitive micelles was demonstrated using estradiol, a model drug. Results The mPEG-DC formed micelles with a critical micelle concentration of 0.05 wt.% and an average size of 15 nm. Aqueous mPEG-DC solutions exhibit a lower critical solution temperature (LCST) that is independent of concentration and reversible over heating and cooling cycles. The LCST transition is an entropically driven process involving dehydration of the PEG shell. The thermosensitive mPEG-DC micelles with rigid DC cores were applied as an estradiol delivery system in which estradiol was released, without initial burst, over the 16 days in a diffusion-controlled manner. Conclusions This study suggests that mPEG-DCs form thermosensitive micelles with rigid cores that can function as an excellent diffusion-controlled hydrophobic drug delivery system without initial burst release. Graphical Abstract Thermosensitive core-rigid micelles of monomethoxy poly(ethylene glycol)-deoxy cholic acid