Bok Soon Kang

Sprouting of sympathetic nerve fibers into the dorsal root ganglion following peripheral nerve injury depends on the injury site.

Peripheral nerve injury often induces sympathetic nerve fiber sprouting in the dorsal root ganglion (DRG) and injured nerve. Presently, the underlying mechanism and functional significance of the sprouting are unknown. This study was performed to see whether the degree of the sprouting in the DRG was a function of the distance between the DRG and injury site. To this aim, we compared two groups of rats with respect to the sympathetic nerve fibers sprouting in the S1-3 DRG; one group was subjected to unilateral inferior and superior caudal trunk transections at the level between the S3 and S4 spinal nerves (S34 group) and the other group at the levels between the S1 and S2, between S2 and S3 and between S3 and S4 spinal nerves (S123 group). The transections in both groups equally eliminated the inputs from the tail to the S1-3 DRG, but the distance from the S1/S2 DRG to the injury site was different between the two groups. Immunohistochemical staining with tyrosine hydroxylase (TH) antibody of the S1-3 DRG removed from rats a week after the injury revealed that the degree of penetration of TH-positive fibers into the S1 and S2 DRG was much more extensive in the S123 group than in the S34 group, whereas that into the S3 DRG was not significantly different between the two groups. These results suggest that the extent of the sympathetic nerve fiber sprouting in the DRG following peripheral nerve injury is inversely related to the distance between the DRG and injury site.

Organic‐Templating Approach to Synthesis of Nanoporous Silica Composite Membranes (II): MTES‐Templating and CO2 Separation

Nanoporous silica composite membranes for gas separation have been synthesized by dip-coating the tetrapropylammonium (TPA)-templating silica sols on tubular alumina supports (pore size 2.8–100 nm), followed by eliminating the template via heat-treating at 550–600°C. The NMR spectroscopy of TPABr-silica hybrid composites obtained from the templated silica sols confirmed that TPA molecules (i.e., final pores) were uniformly distributed in the silica matrix. The average pore size and the specific surface area of an unsupported membrane prepared by firing the TPABr (6 wt%)-silica hybrid composite at 600°C were below 18 Å and 830 m2/g, respectively. Any defects such as cracks or pin-holes on the surface of amorphous silica composite membranes were not observed. The CO2/N2 separation factor of their composite membranes varied from 3.2 to 10.3 and their gas permeability from 10−8 to 10−9 mol/m2 · s · Pa depending on the microstructure of aluminar supports.