Biomedical subjects

Young S Lee

Publications and source records attributed to Young S Lee.

3 recordsLinked to original sources

PubMed2005

Spin chirality on a two-dimensional frustrated lattice.

The collective behaviour of interacting magnetic moments can be strongly influenced by the topology of the underlying lattice. In geometrically frustrated spin systems, interesting chiral correlations may develop that are related to the spin arrangement on triangular plaquettes. We report a study of the spin chirality on a two-dimensional geometrically frustrated lattice. Our new chemical synthesis methods allow us to produce large single-crystal samples of KFe3(OH)6(SO4)2, an ideal Kagomé lattice antiferromagnet. Combined thermodynamic and neutron scattering measurements reveal that the phase transition to the ordered ground-state is unusual. At low temperatures, application of a magnetic field induces a transition between states with different non-trivial spin-textures.

Beryllium↗

PubMed2003

Suppression of tumor necrosis factor-alpha and inducible nitric oxide synthase gene expression by THI 52, a new synthetic naphthyl-benzylisoquinoline alkaloid.

The effects of THI 52 (1-naphthylethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) on (a) inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) expression in RAW 264.7 cells stimulated by lipopolysaccharide (LPS)/interferon gamma (IFN-gamma), (b) plasma nitrate concentration as well as iNOS protein expression (lung) in vivo in LPS-treated rats, and (c) the restoration of vascular contractility to vasoconstrictor agents in LPS-treated vessels in vitro were investigated. THI 52 concentration-dependently reduced not only nitric oxide (NO) production (IC(50) value, 12.5 microM) but also the expression of TNF-alpha and iNOS mRNA in RAW 264.7 cells. Incubation of rat endothelium-denuded thoracic aorta with LPS (300 ng/mL) in vitro for 8 hr resulted in the suppression of vasoconstrictor effects to phenylephrine (PE), effects that were restored by co-incubation with THI 52. Administration of THI 52 (10 and 20mg/kg, i.p.) 30 min before injection of LPS (10mg/kg, i.p.) resulted in a significant reduction of the expression of iNOS protein in rat lung tissue and in the plasma nitrite/nitrate (NOx) level. Addition of THI 52-treated macrophage-conditioned medium to a TNF-sensitive L929 fibroblast cell line (CCL1) increased cell viability, depending on the concentration of THI 52. Finally, THI 52 inhibited the activation of nuclear factor kappaB (NF-kappaB) by inhibition of IkappaB degradation through the prevention of IkappaB phosphorylation. Collectively, these results strongly suggest that THI 52 suppresses both TNF-alpha and iNOS gene expression by inhibiting NF-kappaB. Thus, THI 52, a new synthetic isoquinoline alkaloid, may be beneficial in inflammatory disorders where the overproduction of NO and TNF-alpha is a matter of concern.

Alkaloids↗

PubMedDate not supplied

Effect of suturing on latrogenic keratectasia after laser in situ keratomileusis.

PURPOSE: To evaluate the influence of corneal suturing on the clinical course of iatrogenic keratectasia after laser in situ keratomileusis (LASIK), in order to improve quality of vision and to avoid progressive deterioration of visual acuity. METHODS: Three patients (four eyes) who had a perforation during LASIK or became keratectatic after LASIK received corneal suturing with 10-0 nylon immediately or up to 11 days after LASIK. Sutures were left in place for 1 to 4 months. Patients were followed for 20 to 23 months after suturing. RESULTS: All eyes had a significant improvement in uncorrected and best spectacle-corrected visual acuity after suturing. The improvements in visual acuity for all patients remained unchanged after suture removal. In patient 1, keratectatic changes were not detected in the sutured eye although they were detected in the contralateral unsutured eye. In patient 2, both eyes were sutured, one immediately and the other 11 days after LASIK; no keratectatic changes were noted in either eye. Slight progression of corneal protrusion was observed in patient 3, who had corneal suturing after development of prominent keratectasia 2 weeks after LASIK. This eye showed stable but moderate keratectatic change 9 months after suture removal. CONCLUSIONS: Flap suturing in patients during the course of keratectasia after LASIK improved both aided and unaided visual acuity. Prompt suturing seemed to provide a means of preventive management for iatrogenic keratectasia in anticipation of keratoplasty.

Adult↗